JP3610294B2 - Multi-beam scanning optical system and image forming apparatus using the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-beam scanning optical system and an image forming apparatus using the same, and particularly suitable for an image forming apparatus such as a laser beam printer or a digital copying machine capable of high-quality printing at a high speed with a relatively simple configuration. It is a thing.
[0002]
[Prior art]
Conventionally, a scanning optical system used in an image forming apparatus such as a laser beam printer or a digital copying machine guides a light beam emitted from a light source to a deflecting unit by an incident optical unit, and the light beam deflected by the deflecting unit. The image is formed in a spot shape on the surface of the photosensitive drum, which is the surface to be scanned, by the scanning optical means, and the surface of the photosensitive drum is optically scanned with the luminous flux.
[0003]
In recent years, as the performance and functionality of image forming apparatuses have increased, the demand for higher speed has increased. In order to meet this demand, the use of a plurality of light sources has been studied. For example, Japanese Patent Laid-Open No. 9-54263 proposes a multi-beam scanning optical system using a multi-beam laser chip that emits a plurality of laser beams arranged in a straight line from a single chip as a light source.
[0004]
[Problems to be solved by the invention]
(Problem 1)
In such a multi-beam scanning optical system, in order to accurately control the image writing position, it is common to provide synchronization detection optical means (BD optical system) immediately before writing the image signal.
[0005]
FIG. 22 is a sectional view (main scanning sectional view) of the main part in the main scanning direction of the conventional multi-beam scanning optical system. In the figure, reference numeral 51 denotes a light source unit, which has two light emitting portions (light sources) made of, for example, a semiconductor laser. The two light emitting units are arranged separately from each other in the main scanning direction and the sub scanning direction. Reference numeral 52 denotes an aperture stop, which shapes the light beam emitted from each light emitting section into a desired optimum beam shape. A collimator lens 53 converts the light beam that has passed through the aperture stop 52 into a substantially parallel light beam. A cylindrical lens 54 has a predetermined refractive power only in the sub-scanning direction. Each element such as the aperture stop 52, the collimator lens 53, and the cylindrical lens 54 constitutes one element of the incident optical means 62.
[0006]
Denoted at 55 is a deflecting means, which is composed of, for example, a rotating polygon mirror, and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor. Reference numeral 56 denotes scanning optical means having fθ characteristics, which has first and second fθ lenses. The scanning optical means 56 has a tilt correction function by making a conjugate relationship between the vicinity of the deflecting surface 55a of the optical deflector 55 and the vicinity of the photosensitive drum surface 57 as the surface to be scanned in the sub-scan section.
[0007]
Reference numeral 58 denotes a folding mirror (hereinafter referred to as a “BD mirror”), and a plurality of synchronization signal detection light beams (BD light beams) for adjusting the timing of the scanning start position on the photosensitive drum surface 57 are synchronized as described later. Reflected toward the detection element 61 side. Reference numeral 59 denotes a slit (hereinafter referred to as “BD slit”), which is arranged at a position equivalent to the photosensitive drum surface 57. Reference numeral 60 denotes an imaging lens (hereinafter referred to as a “BD lens”) for making the BD mirror 58 and the synchronous detection element 61 in a conjugate relationship, and correcting the surface tilt of the BD mirror 58. Yes. Reference numeral 61 denotes an optical sensor (hereinafter referred to as “BD sensor”) as a synchronization detecting element. Each element such as the folding mirror 58, the BD slit 59, the BD lens 60, and the BD sensor 61 constitutes one element of the synchronous detection optical means (BD optical system).
[0008]
In the figure, BD detection is performed for each BD light beam, and the timing of the scanning start position of image recording on the photosensitive drum surface 57 is adjusted for each BD light beam using the output from the BD sensor 61.
[0009]
By the way, in a multi-beam optical scanning optical system having a plurality of light emitting sections (light sources), an image to be printed is deteriorated when the interval in the main scanning direction of each light source is changed for scanning for various reasons. Further, even if the interval in the main scanning direction between the light emitting units does not change during scanning, if the writing position is shifted between the light emitting units, the printed image is deteriorated.
[0010]
One possible cause of the above phenomenon is that there is a difference between the focus position deviation amount of the BD light beam on the BD slit surface and the focus position deviation amount of the scanning light beam on the scanned surface.
[0011]
Hereinafter, description will be made with reference to FIGS. Note that marginal rays are omitted in FIGS. 17A, 18A, 20A, and 21A in order to prevent the figure from becoming difficult to see.
[0012]
FIG. 16A shows a state where each light beam (here, A and B light rays) is condensed at one end on the BD slit in the main scanning direction. The A light beam scanned from the left to the right in the figure enters the BD sensor for the first time just when it reaches the right end of the BD slit, and at this time, the BD sensor outputs a signal notifying that the A light beam is incident. Next, the B light beam scanned from left to right enters the BD sensor for the first time just like the A light beam when it comes to the right end of the BD slit, and the BD sensor outputs a signal notifying that the B light beam has been incident. By detecting the timing of these two signals, the timing of the writing start positions of the A and B rays is adjusted.
[0013]
However, when the focus positions of the A and B rays in the main scanning section passing through the BD optical system are shifted toward the front side, that is, the deflecting means side by δM as shown in FIG. 17A, the following phenomenon occurs. The writing positions of the rising A and B rays are shifted. If there is no focus shift, light is condensed at the right end of the BD slit, and finally the A light beam at the timing of starting to enter the BD sensor is already on the BD sensor surface due to the focus shift (the broken line on the right side in the figure). Actually, it begins to enter the BD sensor when the A ray comes to the right solid line in the figure, and the writing timing of the A ray is accelerated by the amount of deviation from the broken line and the solid line. Conversely, the B ray should be incident on the BD sensor at the left broken line because it is out of focus, but cannot enter the BD sensor until it reaches the left solid line position. The B light writing timing is delayed by the amount of deviation. As a result, the writing positions of the A and B rays are shifted by the distance of two broken lines on the BD slit surface.
[0014]
Further, the writing position deviation amount δY of the A and B rays is determined from the focusing deviation amount δM and the incident angle θ [rad] (a state parallel to the optical axis of the BD optical system is 0 [rad]), and is approximately as follows. Can be described in
[0015]
δY = δM × θ (1)
Similarly, the maximum deviation amount δYtotal of the writing position between the light emitting units is assumed that the maximum angle difference of the incident angles is θmax [rad].
δYtotal = δM × θmax (2)
Determined by.
[0016]
Therefore, if the maximum value of the allowable write deviation determined from δYmax and δYmax is δMmax, the maximum value of the write start position shift between the scanning lines is δMmax, the focus shift amount δM is
| ΔM | ≦ δMmax = δYmax / θmax (3)
It is necessary to configure the multi-beam scanning optical system to satisfy the above.
[0017]
Further, δYmax is preferably about half or less of the resolution in the sub-scanning direction. If it seems to exceed this, the adjacent horizontal lines will start to appear shifted, and the printed result will be very difficult to see.
[0018]
Incidentally, if δYmax = 10 μm (corresponding to half a dot of 1200 dpi) and θmax = 0.5 [rad]
δMmax = 1.15mm
It becomes.
[0019]
However, the above formulas (1) to (3) hold when only the BD optical system is defocused, and the same amount of defocus as the BD optical system is in the same direction on the scanned surface (see FIG. 17 occurs on the deflecting means side), the A and B ray writing position deviations called dot deviation hardly occur. It is assumed that the focus positions of the A and B rays in the main scanning section passing through the BD optical system are shifted by δM toward the front side, that is, the deflection means side as shown in FIG. At this time, as described above, dot displacement occurs between the A and B light rays, but if the focal position is uniformly displaced by δM on the surface to be scanned, dots are displaced at the location where δM displacement occurs as shown in FIG. Deviation will occur.
[0020]
However, the ideal image plane (scanned surface) is at the back by δM, and when the A and B rays enter the ideal image plane (scanned surface), the distance between the A and B rays almost disappears. FIG. 18C depicts the positional relationship of light rays in the vicinity of the axis, but a triangle having the principal rays of the A and B rays as the hypotenuse and the straight line at the position δM from the scanned surface as the base, and FIG. It can be seen that there is no dot displacement because the triangles with the original A and B rays indicated by broken lines in FIG. However, in such a case, the best spot position and the position on the surface to be scanned are shifted. However, if the focus position is within the allowable depth range, the image quality is hardly affected.
[0021]
In the above description, the focus position has shifted to the front of the BD slit. However, even if the focus position has shifted to the back of the BD slit, the same can be said as can be seen from FIGS. .
[0022]
If the above explanation is viewed from the reverse side, it can be seen that when the focus position is uniformly deviated on the surface to be scanned, the image is deteriorated if the focus position in the BD optical system is not similarly deviated. In addition, when the focus position shift amount on the surface to be scanned and the focus position shift amount in the BD optical system are individually standardized, if each focus position shift occurs in the opposite direction, a large dot shift may occur. I can expect. Furthermore, if the image surface is greatly curved on the surface to be scanned, it can be easily predicted that the interval between the light beams will change according to the curvature. Therefore, the focus position deviation amount δX of each image height on the surface to be scanned is obtained from Equation (3)
| ΔX−δM | ≦ δMmax = δYmax / θmax (4)
It can be seen that the multi-beam scanning optical system needs to be configured to satisfy the above.
[0023]
Of course, when the incident angles of the light beams on the scanned surface are exactly the same, the writing position shift between the scanning lines is uniformly the same, and the writing position shifts with respect to each light emitting section only by shifting the writing position as a whole. Absent.
[0024]
However, in order to achieve the above-described state, the arrangement of the light emitting units is not shifted in the main scanning direction, that is, when the light emitting units are arranged in a line in the sub-scanning direction, or the principal ray of each light beam using a relay optical system. This is only possible when crossing on the polygon mirror surface. Regarding the former, when each light emitting part is arranged in this way, the distance between the light emitting parts is usually too short, from several μm to several tens of μm (usually commercially available), particularly when the sub-scanning direction is configured as an enlargement system. The distance between the light emitting parts of the multi-laser used is about 100 μm), crosstalk occurs, and stable oscillation cannot be achieved because the light quantity of each light emitting part is different, and the life is likely to be shortened. Further, regarding the latter, if a relay optical system is used, the number of required optical elements increases, which is not preferable in terms of space and cost.
[0025]
In the case of a multi-beam scanning optical system having no BD slit in the BD optical system, as a result, the edge portion of the BD sensor plays the role of the BD slit, the right end of the BD slit is the left end of the BD sensor effective portion, and the BD slit surface is the BD slit. You can replace it with the light receiving surface of the sensor.
[0026]
In the description so far, the scanning direction is the left direction to the right direction in the figure. However, even if the scanning direction is reversed, the BD slit that determines the writing timing is the right BD slit that is not shown in the figure from the right end. The same can be said except that it changes to the left end of.
(Problem 2)
In the multi-beam scanning optical system that performs BD detection for each BD light beam as shown in FIG. 22, the focus position of the BD light beam is not on the BD slit surface due to lens manufacturing error, assembly error, lens focus error, etc. (In the following, it will be difficult to understand when considering the timing of the BD with a light beam having a width, so the following will be represented by the principal ray of each light beam) Except for the case where it is incident parallel to the optical axis of the BD optical system, There is a problem in that the timing at which the principal ray of each BD light beam grazes the edge of the BD slit is different from that before defocusing, and the image writing position is deviated.
[0027]
FIGS. 29A, 29B, and 29C are main part schematic views showing the positional relationship of principal rays of a part of light beams (BD light beams) emitted from two light emitting units (light sources). It is. FIG. 4A shows the positional relationship of the principal rays of each light emitting unit when the BD light beam is ideally out of focus, and FIG. 4B shows each light emission when the BD light beam is out of focus. FIG. 3C shows the positional relationship of the chief rays of the respective light emitting portions when the condensing state on the BD slit surface is improved by some method.
[0028]
Originally, as shown in FIG. 6A, the writing position on the surface to be scanned is timed by a light beam that grabs one end of the BD slit. However, as shown in FIG. When this occurs, the original ray (shown by a solid line in the figure) of the A ray is shielded by the BD slit, and the actual writing position of the A ray is determined by the ray shown by the broken line. That is, the writing position of the A ray is shifted by the amount that the state of the A ray changes from the solid line to the broken line. The same applies to the B ray, and the writing position is advanced by the amount of deviation between the solid line and the broken line. Therefore, the deviation of the writing position between the A and B rays is shifted by the width of the solid line on the BD slit surface.
[0029]
Further, the writing position deviation amount δY of the A and B rays is the amount of focus deviation δM and the incident angle θ.
(The state parallel to the optical axis of the BD optical system is 0 °), and can be described approximately as follows.
[0030]
δY = δM · tan (θ) (5)
Similarly, the total write position deviation amount δY total is calculated by assuming that the maximum angle difference of the incident angles is θmax.
δY total = δM · tan (θmax) (6)
Determined by.
[0031]
Therefore, if the maximum value of the allowable write deviation between each scanning line is δYmax and the maximum allowable focus shift determined from δYmax is δMmax, the focus shift amount δM is
| ΔM | ≦ δMmax = δYmax / tan (θmax) (7)
It is necessary to configure the multi-beam scanning optical system to satisfy the above.
[0032]
Incidentally, if δYmax = 11 μm and θmax = 0.5 °, then δMmax = 1.26 mm.
[0033]
Of course, when the incident angles of the respective light beams on the scanning surface are exactly the same, the writing position deviation between the scanning lines is uniformly the same, and the writing position is not shifted as a whole, and the writing position does not shift. .
[0034]
An object of the present invention is to provide a multi-beam scanning optical system capable of realizing high-quality printing at a high speed with a relatively simple configuration, and an image forming apparatus using the same.
[0035]
[Means for Solving the Problems]
The multi-beam scanning optical system of the invention of claim 1 comprises: at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means for controlling the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The following conditional expression
| ΔM1 | ≦ δYmax / tan (θmax)
(However,
δM1: focus position shift amount in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. And a correction means for shifting the focus position of the light beam guided to the synchronization detecting element in the main scanning section in the optical axis direction of the optical means for synchronization detection relative to the slit.
[0036]
The multi-beam scanning optical system of the invention of claim 2 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means for controlling the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The following conditional expression
| ΔM1 | ≦ δYmax / tan (θmax)
(However,
δM1: focus position shift amount in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. And a correction means for moving the position of the slit or the unit including the slit with respect to the optical axis direction of the optical means for synchronization detection.
[0037]
The multi-beam scanning optical system according to the invention of claim 3 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means for controlling the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The following conditional expression
| ΔM1 | ≦ δYmax / tan (θmax)
(However,
δM1: focus position shift amount in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. The lens unit is provided in an optical path between the deflecting unit and the slit, and includes a correcting unit that moves the lens unit with respect to the optical axis direction of the synchronization detecting optical unit. .
[0038]
A multi-beam scanning optical system according to a fourth aspect of the present invention comprises: at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means for controlling the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The following conditional expression
| ΔM1 | ≦ δYmax / tan (θmax)
(However,
δM1: focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element as seen from the slit
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. At least a part of the lenses constituting the lens unit is integrated with the scanning optical unit, and at least a part of the lens unit not integrated with the scanning optical unit and the slit are used for the synchronous detection. A correction means for moving the optical means in the optical axis direction is provided.
[0039]
The multi-beam scanning optical system according to the invention of claim 5 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means for controlling the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The following conditional expression
| ΔM1 | ≦ δYmax / tan (θmax)
(However,
δM1: focus position shift amount in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. The lens unit is integrated with the scanning optical means, and at least a part of the optical elements of the scanning optical means is moved in the optical axis direction of the scanning optical means, and the slits are light of the optical means for synchronization detection. A correction means for moving in the axial direction is provided.
[0040]
The multi-beam scanning optical system according to the invention of claim 6 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means for controlling the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The following conditional expression
| ΔM1 | ≦ δYmax / tan (θmax)
(However,
δM1: focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element as seen from the slit
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. And at least a part of the lenses constituting the lens unit is integrated with the scanning optical means, and includes a correcting means for moving at least a part of the lenses constituting the scanning optical means in the main scanning direction. Yes.
[0041]
The multi-beam scanning optical system of the invention of claim 7 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned And a scanning optical unit that forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element,
A dot position deviation for each scanning line on the surface to be scanned, which is generated by having a focus position deviation amount δM1 in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit, is corrected. A correction means, wherein the dot position deviation amount is less than or equal to 1/2 of the resolution in the sub-scanning direction, and the slit is inclined in the sub-scanning direction according to the dot position deviation amount for each scanning line on the scanned surface It is characterized by that.
[0042]
The multi-beam scanning optical system of the invention of claim 8 is at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned And a scanning optical unit that forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element,
A dot position deviation for each scanning line on the surface to be scanned, which is generated by having a focus position deviation amount δM1 in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit, is corrected. A correction means, wherein the dot position deviation amount is ½ or less of the resolution in the sub-scanning direction, and the slit or the unit including the slit is adapted to the dot position deviation amount for each scanning line on the scanned surface. And rotating means for rotating around the optical axis of the optical means for synchronization detection.
[0043]
A multi-beam scanning optical system according to claim 9 is provided. at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is guided to the synchronization detection element by the lens unit, and a signal from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using
The following conditional expression
| ΔM2 | ≦ δYmax / tan (θmax)
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element as viewed from the light receiving surface of the synchronization detection element
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the light receiving surface)
Satisfying and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the focus position in the main scanning section of the light beam guided to the synchronization detecting element is determined. The present invention is characterized by comprising correction means for shifting the optical axis of the optical means for detecting synchronization relative to the light receiving surface of the synchronous detecting element.
[0044]
The multi-beam scanning optical system according to the invention of claim 10 comprises: at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is guided to the synchronization detection element by the lens unit, and a signal from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using
The following conditional expression
| ΔM2 | ≦ δYmax / tan (θmax)
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element as viewed from the light receiving surface of the synchronization detection element
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the position of the synchronization detecting element or the unit including the synchronization detecting element is determined as the synchronization detecting optical. It is characterized by comprising correction means for moving the means relative to the optical axis direction.
[0045]
The multi-beam scanning optical system according to claim 11 is provided. at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is guided to the synchronization detection element by the lens unit, and a signal from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using
The following conditional expression
| ΔM2 | ≦ δYmax / tan (θmax)
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element as viewed from the light receiving surface of the synchronization detection element
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the light receiving surface
Satisfactory, the permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens unit is provided in the optical path between the deflecting means and the synchronization detecting element. And a correction means for moving the lens portion with respect to the optical axis direction of the synchronization detecting optical means.
[0046]
The multi-beam scanning optical system according to the invention of claim 12 is at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is guided to the synchronization detection element by the lens unit, and a signal from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using
The following conditional expression
| ΔM2 | ≦ δYmax / tan (θmax)
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element as viewed from the light receiving surface of the synchronization detection element
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the light receiving surface)
Satisfactory, the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and at least some of the lenses constituting the lens unit are integrated with the scanning optical means. And a correction unit that moves at least a part of the lenses of the lens unit that is not integrated with the scanning optical unit in the optical axis direction of the synchronization detection optical unit.
[0047]
The multi-beam scanning optical system according to the invention of claim 13 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is guided to the synchronization detection element by the lens unit, and a signal from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using
The following conditional expression
| ΔM2 | ≦ δYmax / tan (θmax)
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element as viewed from the light receiving surface of the synchronization detection element
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, the lens unit is integrated with the scanning optical means, and at least one of the scanning optical means The optical element is provided with correction means for moving the optical element in the optical axis direction of the scanning optical means.
[0048]
The multi-beam scanning optical system according to the invention of claim 14 comprises: at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detection element by the lens unit, and a signal from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using
The following conditional expression
| ΔM2 | ≦ δYmax / tan (θmax)
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element as viewed from the light receiving surface of the synchronization detection element
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the light receiving surface)
Satisfactory and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and at least some of the lenses constituting the lens unit are integrated with the scanning optical means. Further, the present invention is characterized by comprising correction means for moving at least a part of the lenses constituting the scanning optical means in the main scanning direction.
[0049]
The multi-beam scanning optical system according to the invention of claim 15 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflection means, and a plurality of light beams deflected by the deflection means on the surface to be scanned Scanning optical means for forming an image on the light beam, and condensing a part of a plurality of light beams deflected by the deflecting means on the slit surface by the lens unit, and then guiding the light to the synchronization detection element. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface using a signal,
When the focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit is δM1, and the focus position shift amount of each image height on the scanned surface is δX, Conditional expression
| ΔX−δM1 | ≦ δYmax / θmax
(However,
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference of the incident angle of each light beam used for synchronous detection to the slit surface)
Satisfying and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the focus position in the main scanning section of the light beam guided to the synchronization detecting element is determined. It is characterized by comprising a correcting means that shifts relative to the optical axis direction of the synchronization detecting optical means from the slit.
[0050]
The multi-beam scanning optical system according to the invention of claim 16 comprises: at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting portions arranged apart from the main scanning direction to the deflection means, and a plurality of light beams deflected by the deflection means on the surface to be scanned Scanning optical means for forming an image on the light beam, and condensing a part of a plurality of light beams deflected by the deflecting means on the slit surface by the lens unit, and then guiding the light to the synchronization detection element. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface using a signal,
When the focal position deviation amount in the main scanning section of the light beam guided to the synchronous detection element viewed from the slit is δM1, and the focal position deviation amount of each image height on the scanned surface is δX, Conditional expression
| ΔX−δM1 | ≦ δYmax / θmax
(However,
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the slit surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the position of the slit or the unit including the slit is defined as the optical axis of the optical means for synchronization detection. It is characterized by comprising correction means for moving relative to the direction.
[0051]
The multi-beam scanning optical system according to the invention of claim 17 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned Scanning optical means for forming an image on the light beam, and condensing a part of a plurality of light beams deflected by the deflecting means on the slit surface by the lens unit, and then guiding the light to the synchronization detection element. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface using a signal,
When the focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit is δM1, and the focus position shift amount of each image height on the scanned surface is δX, Conditional expression
| ΔX−δM1 | ≦ δYmax / θmax
(However,
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the slit surface)
Satisfactory, the permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens unit is provided in the optical path between the deflecting means and the slit, The lens unit includes a correcting unit that moves the lens unit with respect to the optical axis direction of the synchronization detecting optical unit.
[0052]
The multi-beam scanning optical system according to the invention of claim 18 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned And a scanning optical unit that forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. And a multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element.
When the focal position deviation amount in the main scanning section of the light beam guided to the synchronous detection element viewed from the slit is δM1, and the focal position deviation amount of each image height on the scanned surface is δX, both Correction means for correcting the dot position deviation for each scanning line on the surface to be scanned that is generated when there is a difference between the focus position deviation amounts δM1 and δX, and the dot position deviation amount has a resolution in the sub-scanning direction. The slit is inclined in the sub-scanning direction according to the amount of dot position deviation for each scanning line on the surface to be scanned.
[0053]
A multi-beam scanning optical system according to claim 19 is provided. at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned And a scanning optical unit that forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. And a multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element.
When the focal position deviation amount in the main scanning section of the light beam guided to the synchronous detection element viewed from the slit is δM1, and the focal position deviation amount of each image height on the scanned surface is δX, both Correction means for correcting the dot position deviation for each scanning line on the surface to be scanned that is generated when there is a difference between the focus position deviation amounts δM1 and δX, and the dot position deviation amount has a resolution in the sub-scanning direction. Rotating means for rotating the slit or the unit including the slit around the optical axis of the optical means for synchronization detection according to the amount of dot position deviation for each scanning line on the scanned surface. It is characterized by that.
[0054]
The multi-beam scanning optical system according to the invention of claim 20 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned A scanning optical means for forming an image on the surface, and a part of a plurality of light beams deflected by the deflecting means is guided to the synchronization detecting element by the lens unit, and a signal from the synchronization detecting element is used on the surface to be scanned A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position,
The amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element is δM2, and the amount of focus position deviation of each image height on the surface to be scanned is δX. The following conditional expression
| ΔX−δM2 | ≦ δYmax / θmax
(However,
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the focus position in the main scanning direction of the light beam guided to the synchronization detection element is synchronized. It is characterized by comprising a correcting means for shifting in the optical axis direction of the synchronous detecting optical means relative to the light receiving surface of the detecting element.
[0055]
The multi-beam scanning optical system according to the invention of claim 21 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned A scanning optical means for forming an image on the surface, and a part of a plurality of light beams deflected by the deflecting means is guided to the synchronization detecting element by the lens unit, and a signal from the synchronization detecting element is used on the surface to be scanned A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position,
The amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element is δM2, and the amount of focus position deviation of each image height on the surface to be scanned is δX. The following conditional expression
| ΔX−δM2 | ≦ δYmax / θmax
(However,
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of the light beams used for synchronous detection on the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the position of the synchronization detecting element or the unit including the synchronization detecting element is determined as the synchronization detecting optical. It is characterized by comprising correction means for moving the means relative to the optical axis direction.
[0056]
The multi-beam scanning optical system according to the invention of claim 22 at least Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means on the surface to be scanned A scanning optical means for forming an image on the surface, and a part of a plurality of light beams deflected by the deflecting means is guided to the synchronization detecting element by the lens unit, and a signal from the synchronization detecting element is used on the surface to be scanned A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position,
The amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element is δM2, and the amount of focus position deviation of each image height on the surface to be scanned is δX. The following conditional expression
| ΔX−δM2 | ≦ δYmax / θmax
(However,
δYmax: allowable dot position deviation amount for each scanning line
θmax: the maximum angle difference between the incident angles of each light beam used for synchronous detection on the light receiving surface)
Satisfactory and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens portion is provided in the optical path between the deflecting means and the synchronization detecting element. And a correction means for moving the lens portion with respect to the optical axis direction of the synchronization detecting optical means.
[0077]
DETAILED DESCRIPTION OF THE INVENTION
[Embodiment 1]
FIG. 1 is a sectional view (main scanning sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system according to the first embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP).
[0078]
In this specification, the surface formed by the optical axis of the scanning optical means and the light beam deflected by the optical deflector is the main scanning section, and the surface including the optical axis of the scanning optical means and perpendicular to the main scanning section is sub-scanned. It is defined as a cross section.
[0079]
In the figure, reference numeral 1 denotes a light source unit (light source means), which has two light emitting portions (light sources) 1a and 1b made of, for example, a semiconductor laser. Three or more light emitting units may be used. As shown in FIG. 2, the two light emitting units 1a and 1b are arranged apart from each other in the main scanning direction and the sub scanning direction. As shown in FIG. 2, the distance between the light emitting units is longer in the main scanning direction than in the sub scanning direction. This is because the actual distance between the light-emitting parts is longer than the distance between the light-emitting parts in the sub-scanning direction actually required, and the light source unit 1 having the two light-emitting parts 1a and 1b is rotated. This is because the distance between the light emitting parts is set to a desired value. Reference numeral 3 denotes an aperture stop, which shapes the light beams emitted from the light emitting units 1a and 1b into a desired optimum beam shape. Reference numeral 2 denotes a collimator lens, which converts a light beam that has passed through the aperture stop 3 into a substantially parallel light beam. A cylindrical lens 4 has a predetermined refractive power only in the sub-scanning direction. Each element such as the aperture stop 3, the collimator lens 2, and the cylindrical lens 4 constitutes one element of the incident optical means 14.
[0080]
Reference numeral 5 denotes an optical deflector as a deflecting means, which is composed of, for example, a rotating polygon mirror, and is rotated at a constant speed in the direction of arrow A in the figure by a driving means (not shown) such as a motor. Reference numeral 6 denotes scanning optical means having fθ characteristics, which includes first and second optical elements (fθ lenses) 6a and 6b, and an optical deflector. 5 Multiple deflected by (Two) The beam to be scanned 7 A plurality of scanning lines are formed by forming a spot image on the top. The scanning optical means 6 has a tilt correction function by providing a conjugate relationship between the vicinity of the deflecting surface 5a of the optical deflector 5 and the vicinity of the photosensitive drum surface 7 in the sub-scan section.
[0081]
Reference numeral 8 denotes a synchronization detection lens unit which forms (condenses) a plurality of synchronization signal detection light beams (BD light beams) on a slit 9 surface provided in the vicinity of a synchronization detection element 10 described later. Although the lens unit 8 in the present embodiment is configured integrally with the scanning optical means 6, it may be provided independently. Reference numeral 12 denotes a folding mirror (hereinafter referred to as “BD mirror”), which reflects a plurality of BD light beams for adjusting the timing of the scanning start position on the photosensitive drum surface 7 toward the synchronization detecting element 10 described later. Yes. The BD mirror 12 is located on the incident optical means 14 side with the optical axis L of the scanning optical means 6 interposed therebetween. Reference numeral 9 denotes a slit for synchronization detection (hereinafter referred to as “BD slit”), which is arranged at a position equivalent to the photosensitive drum surface 7 and determines an image writing position. Reference numeral 11 denotes an imaging lens (hereinafter referred to as a “BD lens”) for making the BD mirror 12 and the synchronization detecting element 10 in a conjugate relationship, and correcting the surface tilt of the BD mirror 12. Yes. Reference numeral 10 denotes an optical sensor (hereinafter referred to as “BD sensor”) as a synchronization detection element. In this embodiment, a synchronization signal (BD signal) obtained by detecting an output signal from the BD sensor 10 is used. Thus, the timing of the scanning start position of image recording on the photosensitive drum surface 7 is adjusted for each BD light beam.
[0082]
Each element such as the lens unit 8, the BD mirror 12, the BD slit 9, the BD lens 11, and the BD sensor 10 constitutes one element of the synchronous detection optical means (BD optical system).
[0083]
In the present embodiment, the two light beams that are light-modulated and emitted from the light source unit 1 according to image information are limited in size by the aperture stop 3 and converted into a substantially parallel light beam by the collimator lens 2. 4 is incident. Of the light beam incident on the cylindrical lens 4, the light beam is emitted as it is in the main scanning section. In the sub-scan section, the light beam converges and forms a substantially linear image (a linear image extending in the main scanning direction) on the deflecting surface 5a of the optical deflector 5. Then, the two light beams reflected and deflected by the deflecting surface 5a of the optical deflector 5 are imaged in a spot shape on the photosensitive drum surface 7 by the scanning optical means 6, and the optical deflector 5 is rotated in the direction of arrow A by rotating it. The photosensitive drum surface 7 is optically scanned at an equal speed in the direction of arrow B (main scanning direction). As a result, an image is recorded on the photosensitive drum surface 7 as a recording medium.
[0084]
At this time, in order to adjust the timing of the scanning start position on the photosensitive drum surface 7 before optical scanning on the photosensitive drum surface 7, a part of the two light beams reflected and deflected by the optical deflector 5 is used as the lens unit 8. Is condensed on the surface of the BD slit 9 via the BD mirror 12 and then guided to the BD sensor 10 via the BD lens 11. Then, the timing of the scanning start position of image recording on the photosensitive drum surface 7 is adjusted for each BD light beam using a synchronization signal (BD signal) obtained by detecting the output signal from the BD sensor 10.
[0085]
At this time, if the focus position of the BD light beam on the surface of the BD slit 9 and the focus position of the light beam for scanning on the scanned surface 7 are deviated from each other for various reasons as described above, the write positions of the A and B light beams are changed as described above. There arises a problem that the printed image is deteriorated due to deviation or a change in the main scanning direction interval of the A and B light rays during scanning.
[0086]
Therefore, in this embodiment, each element is set so as to satisfy the following conditional expression (A). That is, the amount of focus position deviation of the BD light beam guided to the BD sensor 10 viewed from the BD slit 9 within the main scanning section is δM, and the amount of focus position deviation of each image height on the scanned surface 7 is δX. When
| ΔX−δM | ≦ δYmax / θmax (A)
(However,
δYmax: allowable dot shift amount
θmax: Maximum angle difference [rad] of the incident angle of the BD light beam with respect to the BD slit when the BD light beam corresponding to each light emitting unit starts to enter the BD sensor)
Satisfy the following conditions.
[0087]
Specifically, the resolution in the sub-scanning direction is 1200 dpi, δYmax = 10 μm, θmax = 0.5 [rad], and the maximum value of | δX−δM | is 1.15 mm. Thereby, in this embodiment, high-speed and high-quality printing is realized. In this embodiment, the allowable dot shift amount (write position shift amount between each scanning line) δYmax is set to be ½ or less of the resolution in the sub-scanning direction.
[0088]
In the present embodiment, each light beam emitted from the light source unit 1 is converted into a substantially parallel light beam by the collimator lens 2. However, the present invention is not limited to this. For example, the same effect can be obtained by converting into a convergent light beam or a divergent light beam. Can be obtained.
[0089]
Next, the reason why the allowable dot position deviation amount for each scanning line is preferably ½ or less of the resolution in the sub-scanning direction will be described below.
If it is assumed that the number of light sources is two and the amount of dot deviation is one dot, the image one dot before or after is printed at the original print location, and it is not necessary to print it. It may happen that printing is performed or, on the contrary, printing is not performed at a place where printing is to be performed, and the printing state becomes very difficult to see.
[0090]
Considering the phenomenon as described above, it is desirable that the amount of dot shift is 0, but it is very difficult to actually carry out. Further, if the amount is as small as 1/2 dot (about 10 μm at 1200 dpi) or less, it will not be difficult to see even if the actually printed image is viewed. On the other hand, when a dot shift exceeding 1/2 dot occurs, although it depends on the actually printed image, it can be recognized gradually with the naked eye and cannot be said to be in a good printing state.
[0091]
In the above description, the number of light sources is limited to two so as not to complicate the story. However, since such a phenomenon occurs regardless of the number of light sources, the maximum value of the dot shift amount is ½ dot or less. It is necessary to.
[0092]
In this embodiment, the A light beam enters the BD sensor 10, and the time interval from when the output signal is generated from the BD sensor 10 to when printing is started on the photosensitive drum 7 and the B light beam enter the BD sensor 10. The time interval from when the output signal is generated from the BD sensor 10 to when printing is started on the photosensitive drum 7 is assumed to be equal.
[0093]
Further, although the case where two laser beams are used has been described, the number of laser beams may be three or more.
Next, an image forming apparatus applied to the present invention will be described.
[0094]
FIG. 31 is a cross-sectional view of the main part in the sub-scanning direction showing the embodiment of the image forming apparatus of the present invention. In FIG. 31, reference numeral 104 denotes an image forming apparatus. Code data Dc is input to the image forming apparatus 104 from an external device 117 such as a personal computer. The code data Dc is converted into image data (dot data) Di by a printer controller 111 in the apparatus. The image data Di is input to the optical scanning unit 100 having the configuration shown in the first embodiment. The light scanning unit 100 emits a light beam 103 modulated according to the image data Di, and the light beam 103 scans the photosensitive surface of the photosensitive drum 101 in the main scanning direction.
[0095]
The photosensitive drum 101 serving as an electrostatic latent image carrier (photoconductor) is rotated clockwise by a motor 115. With this rotation, the photosensitive surface of the photosensitive drum 101 moves in the sub-scanning direction perpendicular to the main scanning direction with respect to the light beam 103. Above the photosensitive drum 101, a charging roller 102 for uniformly charging the surface of the photosensitive drum 101 is provided so as to contact the surface. The surface of the photosensitive drum 101 charged by the charging roller 102 is irradiated with the light beam 103 scanned by the optical scanning unit 100.
[0096]
As described above, the light beam 103 is modulated based on the image data Di, and by irradiating the light beam 103, an electrostatic latent image is formed on the surface of the photosensitive drum 101. The electrostatic latent image is developed as a toner image by a developing unit 107 disposed so as to contact the photosensitive drum 101 further downstream in the rotation direction of the photosensitive drum 101 than the irradiation position of the light beam 103.
[0097]
The toner image developed by the developing unit 107 is transferred onto a sheet 112 as a transfer material by a transfer roller 108 disposed below the photosensitive drum 101 so as to face the photosensitive drum 101. The paper 112 is stored in the paper cassette 109 in front of the photosensitive drum 101 (on the right side in FIG. 31), but can be fed manually. A paper feed roller 110 is provided at the end of the paper cassette 109, and feeds the paper 112 in the paper cassette 109 into the transport path.
[0098]
As described above, the sheet 112 on which the unfixed toner image has been transferred is further conveyed to a fixing device behind the photosensitive drum 101 (left side in FIG. 31). The fixing device includes a fixing roller 113 having a fixing heater (not shown) therein, and a pressure roller 114 disposed so as to be in pressure contact with the fixing roller 113, and the sheet conveyed from the transfer unit. The unfixed toner image on the paper 112 is fixed by heating 112 while applying pressure at the pressure contact portion between the fixing roller 113 and the pressure roller 114. Further, a paper discharge roller 116 is disposed behind the fixing roller 113, and the fixed paper 112 is discharged out of the image forming apparatus.
[0099]
Although not shown in FIG. 31, the print controller 111 will be described first. did In addition to data conversion, control is performed for each unit in the image forming apparatus including the motor 115 and a polygon motor in an optical scanning unit described later.
[0100]
[Embodiment 2]
FIG. 3 is a sectional view (main scanning sectional view) of the main scanning direction when the multi-beam scanning optical system according to the second embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0101]
This embodiment is different from the first embodiment described above in that the focus position of the BD light beam guided to the BD sensor 10 in the main scanning section is shifted from the BD slit 9 in the optical axis direction of the BD optical system. This satisfies the conditional expression (A). Other configurations and optical actions are substantially the same as those of the first embodiment, and the same effects are obtained.
[0102]
That is, the degree of curvature of field of the scanning optical means 6 is considerably stable for each product, and if the BD slit 9 is disposed at the focus position, the difference value | δX−δM | In this case, as shown in FIG. 3, the conditional expression (A) is satisfied by shifting the BD slit 9 from the focus position in the optical axis direction of the BD optical system by adjusting means (FIG. 30) from the beginning. This achieves high-speed and high-quality printing.
[0103]
Next, the dot misalignment adjusting means applied to the present invention will be described.
[0104]
The BD slit 9 can be moved and adjusted in the optical axis direction of the BD lens 11 by the adjusting means 220 constituting the multi-beam scanning optical system of the present invention. That is, as shown in FIG. 30, the BD slit 9 is fixed to the support body 221 by adhesion or the like. The support body 221 is fitted to the guide 222 and is movable in the optical axis direction. The holding body 223 is fixed in the image forming apparatus.
[0105]
The guide 222 is fixed to a “U-shaped” holding body 223 fixed to a stationary member of the apparatus. A compressible spring 224 is interposed between the holding body 223 and the support body 221, and an elastic force directed to the left in the drawing is applied to the support body 221. The adjustment screw 225 screwed to the holding body 223 abuts the tip of the adjustment screw 225 from the right side to stop the movement of the support body due to the elastic force of the spring 224. Therefore, if the adjustment screw 225 is sent, the support 221 can be displaced to the right side of the figure, and if the adjustment screw 225 is loosened, the support 221 can be displaced to the left side. Is moved and adjusted in the optical axis direction so as to satisfy the conditional expression (A).
[0106]
[Embodiment 3]
FIG. 4 is a sectional view (main scanning sectional view) of the main scanning direction when the multi-beam scanning optical system according to the third embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0107]
This embodiment differs from the first embodiment described above in that the conditional expression (A) is satisfied by moving the unit 13 including the BD slit 9 in the optical axis direction of the BD optical system, and the rotation of the optical deflector. That is, the direction is rotated in the reverse direction (arrow C direction in the figure). Other configurations and optical actions are substantially the same as those of the first embodiment, and the same effects are obtained.
[0108]
That is, in the present embodiment, the optical deflector 5 is rotated at a constant speed in the direction of arrow C in the figure opposite to the rotation direction of the first embodiment by a driving means (not shown) such as a motor. This is because the synchronization detection optical means (BD optical system) cannot be disposed between the scanning optical means 6 and the incident optical means 14 due to space problems.
[0109]
At this time, as in the first embodiment, if the focus position of each BD light beam on the surface of the BD slit 9 and the focus position of the scanning light beam on the scanned surface 7 are shifted, as described above, the A and B light beams There arises a problem that the print image is deteriorated due to a shift in the writing position or a change in the main scanning direction interval of the A and B light rays during scanning.
[0110]
In particular, in the present embodiment, in order to achieve high image quality, δY max = 6 μm and θmax = 0.5 [rad] are set. Therefore, the difference value | δX−δM | of the conditional expression (A) is set to 0.69 mm or less. Therefore, it is very difficult to stably configure a multi-beam scanning optical system having such optical performance without adjustment.
[0111]
Therefore, in this embodiment, the unit 13 including the BD slit 9 is moved in the optical axis direction of the BD optical system as indicated by an arrow D shown in FIG. The condensing state in the main scanning section is adjusted, and for example, the state shown in FIG. 17B is improved to the state shown in FIG. As a result, the above specification, that is, conditional expression (A) is satisfied, and high-quality printing is realized at high speed.
[0112]
[Embodiment 4]
FIG. 5 is a sectional view (main scanning sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system according to the fourth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0113]
In the present embodiment, the difference from the above-described third embodiment is that the BD slit 9 and the unit 13 including the BD slit 9 are fixed, and the first and second optical elements (fθ lenses) 6a constituting the scanning optical means 6 are provided. In order to shorten the shape of 6b in the main scanning direction, the lens unit 8 is provided independently without being integrated with the scanning optical means 6, and the lens unit 8 is moved in the direction of the optical axis of the BD optical system. A) is satisfied. Other configurations and optical actions are substantially the same as those of the third embodiment, and the same effects are obtained.
[0114]
That is, in this embodiment, the BD slit 9 and the unit 13 including the BD slit 9 are fixed, and the lens unit 8 having a single lens is configured separately from the scanning optical means 6 without being integrated. Yes. At this time, as in the first embodiment, if the focus position of each BD light beam on the surface of the BD slit 9 and the focus position of the scanning light beam on the scanned surface 7 are shifted, as described above, the A and B light beams There arises a problem that the print image is deteriorated due to a shift in the writing position or a change in the main scanning direction interval of the A and B light rays during scanning.
Therefore, in the present embodiment, the lens unit 8 is moved in the optical axis direction of the BD optical system by the adjusting means (FIG. 30) as indicated by an arrow F in the figure, so that the main scanning section of the BD light beam on the BD slit 9 surface. Thus, the above conditional expression (A) is satisfied, and high-quality printing is realized.
[0115]
In this embodiment, the degree of curvature of field of the scanning optical means 6 is considerably stable for each product, and the difference value | δX−δM | of the conditional expression (A) is ignored when the BD slit 9 is disposed at the focus position. If the value cannot be obtained, the position of the lens unit 8 is shifted in advance on the optical axis to change the focus position in the main scanning section, thereby satisfying the conditional expression (A).
[0116]
[Embodiment 5]
FIG. 6 is a sectional view (main scanning sectional view) of the main scanning direction when the multi-beam scanning optical system according to the fifth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0117]
In this embodiment, the amount of focus position deviation δM in the main scanning section of the BD light beam guided to the BD sensor 10 viewed from the BD slit 9 and the amount of focus position deviation δX of each image height on the scanned surface 7. The BD slit 9 or the unit 16 including the BD slit 9 is detected by the angle adjusting unit 15 as a correcting unit shown in FIG. Correction is performed by adjusting the rotation around the optical axis of the BD optical system.
[0118]
That is, in the light source unit 1 in this embodiment, as shown in FIG. 2, the light emitting portions 1a and 1b are arranged apart from each other also in the sub-scanning direction. The A and B rays corresponding to the portions 1a and 1b are different.
[0119]
Therefore, in this embodiment, the angle adjusting means 15 rotates the BD slit 9 as shown in FIGS. 8A and 8B and FIGS. The timing at which the light enters the BD sensor 10 is changed. FIG. 8 is an explanatory diagram showing the inclination of the BD slit 9 and the printing position (before adjustment) of each light beam, and FIG. 9 is an explanatory diagram showing the inclination of the BD slit 9 and the printing position of each light beam (after adjustment).
[0120]
Thus, in the present embodiment, as described above, the focus position shift amount δM in the main scanning section of each BD light beam guided to the BD sensor 10 and the focus position shift amount δX of each image height on the scanned surface 7. As a result, there is a difference between the two focus position deviation amounts δM and δX, so that the dot deviation that should have occurred is corrected (cancelled) by rotating and adjusting the BD slit 9 using the angle adjusting means 15. . This achieves high-speed and high-quality printing.
[0121]
In this embodiment, the optical action for forming an image using the multi-beam scanning optical system is substantially the same as that of the first embodiment.
[0122]
[Embodiment 6]
FIG. 10 is a sectional view (main scanning sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system according to the sixth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). It is a principal part perspective view of BD slit 9 of FIG. 10 and 11, the same elements as those shown in FIG. 6 are denoted by the same reference numerals.
[0123]
In this embodiment, the difference from the above-described fifth embodiment is that there is no angle adjusting means, and the dot deviation is corrected (cancelled) by inclining the BD slit 9 or the unit 16 including the BD slit 9 from the beginning in the sub-scanning direction. ) Other configurations and optical actions are substantially the same as those of the fifth embodiment, and the same effects are obtained.
[0124]
That is, the degree of curvature of field of the scanning optical means 6 is considerably stable for each product, and if the BD slit 9 is arranged at the focus position, the difference value | δX−δM | of the conditional expression (A) has a value that cannot be ignored. In such a case, the dot deviation is corrected (cancelled) by inclining the BD slit 9 in the sub-scanning direction from the beginning as shown in FIGS. This achieves high-speed and high-quality printing.
[0125]
[Embodiments 7, 8, 9, 10]
12, 13, 14, and 15 are respectively main components when the multi-beam scanning optical system according to the seventh, eighth, ninth, and tenth embodiments of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). It is principal part sectional drawing (main scanning sectional drawing) of a scanning direction. 12, 13, 14, and 15, the same elements as those shown in FIGS. 1, 3, 4, and 5 are denoted by the same reference numerals.
[0126]
The seventh embodiment corresponds to the first embodiment, the eighth embodiment corresponds to the second embodiment, the ninth embodiment corresponds to the third embodiment, and the tenth embodiment corresponds to the fourth embodiment. The difference between the seventh, eighth, ninth, and tenth embodiments in common with the first, second, third, and fourth embodiments is that the BD slit 9 is used to simplify and reduce the cost of the entire apparatus. And it is having constituted without using BD lens 11. Other configurations and optical actions are substantially the same as those of the corresponding first, second, third, and fourth embodiments, thereby obtaining the same effects.
[0127]
That is, in each of the seventh, eighth, ninth, and tenth embodiments, the effective end of the BD sensor 10 has an action corresponding to the BD slit 9 in each of the corresponding first, second, third, and fourth embodiments. Therefore, in each of the seventh, eighth, ninth, and tenth embodiments, the contents of the corresponding first, second, third, and fourth embodiments are implemented by replacing the BD slit 9 surface with the light receiving surface of the BD sensor 10. Thereby, the same effects as those of the corresponding embodiments described above are obtained.
[0128]
As described above, each of the seventh, eighth, ninth, and tenth embodiments is configured without using the BD slit and the BD lens, so that the entire apparatus can be simplified and reduced in cost, and the high speed can be achieved with a relatively simple configuration. Achieves quality printing.
[0129]
[Embodiment 11]
FIG. 11 is a sectional view (main scanning sectional view) of a main part in the main scanning direction when the multi-beam scanning optical system according to the eleventh embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP).
[0130]
At this time, when the focus position of each BD light beam is shifted and not on the surface of the BD slit 9 due to an assembly error, a lens focus error, etc. as described above, each light emission as shown in FIG. Since the parts 1a and 1b are also separated in the main scanning direction, the timing at which the principal ray of each BD light beam grazes the edge of the BD slit 9 is different from that before the focus shift, and image writing to the light emitting parts 1a and 1b is performed. The position will shift.
[0131]
Therefore, in this embodiment, the following conditional expression (B)
| ΔM | ≦ δYmax / tan (θmax) (B)
(However,
δM: Distance in the optical axis direction of the BD optical system from the BD slit surface to the condensing point of the BD light beam used for synchronous detection in the main scanning section
δYmax: Allowable writing position deviation amount (dot deviation amount) between each scanning line θmax: Maximum angle difference of incident angle of each BD light beam used for synchronization detection to the BD slit surface)
Each element is configured to satisfy.
[0132]
As specific values, δYmax = 11 μm, θmax = 0.5 °, and | δM | = δMmax = 1.26 mm. Thereby, in this embodiment, high-quality printing is realized at high speed.
[0133]
In this embodiment, the allowable dot deviation amount δYmax is set to be ½ or less of the resolution in the sub-scanning direction.
[0134]
In the present embodiment, each light beam emitted from the light source unit 1 is converted into a substantially parallel light beam by the collimator lens 2. However, the present invention is not limited to this. For example, the same effect can be obtained by converting into a convergent light beam or a divergent light beam. Can be obtained.
[0135]
[Embodiment 12]
FIG. 23 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction when the multi-beam scanning optical system according to the twelfth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0136]
In this embodiment, the optical deflector 5 is rotated at a constant speed in the direction of the arrow C in the figure opposite to the rotation direction of the first embodiment by a driving means (not shown) such as a motor. This is because the synchronization detection optical means (BD optical system) cannot be disposed between the scanning optical means 6 and the incident optical means 14 due to space problems.
[0137]
At this time, as described in the eleventh embodiment, when the focus position of each BD light beam is shifted and not on the surface of the BD slit 9, the light emitting units 1 a and 1 b are mainly scanned as shown in FIG. Since they are also separated in the direction, the timing at which the principal ray of each BD light beam grazes the edge of the BD slit 9 is different from that before defocusing, and the image writing position for each light emitting section 1a, 1b is shifted. In the present embodiment, further improvement in image quality is demanded, and therefore the above-described writing start position shift becomes a problem.
[0138]
Therefore, in this embodiment, the BD slit 9 is moved in the optical axis direction of the BD optical system by the adjusting means (FIG. 30) as indicated by the arrow D shown in FIG. By adjusting the condensing state in the scanning section and thereby improving from the state shown in FIG. 29B to the state shown in FIG. 29C, high-quality printing is realized at high speed.
[0139]
Further, in the present embodiment, each element is set so as to satisfy the above-described conditional expression (B). As specific numerical values, δYmax = 7 μm, θmax = 0.5 °, | δM | = δMmax = 0 .80 mm.
[0140]
In this embodiment, the optical action for forming an image using the multi-beam scanning optical system is substantially the same as that of the above-described eleventh embodiment.
[0141]
Next, the dot misalignment adjusting means applied to the present invention will be described.
[0142]
The BD slit 9 can be moved and adjusted in the optical axis direction of the BD lens 11 by the adjusting means 220 constituting the multi-beam scanning optical system of the present invention. That is, as shown in FIG. 30, the BD slit 9 is fixed to the support body 221 by adhesion or the like. The support body 221 is fitted to the guide 222 and is movable in the optical axis direction. The holding body 223 is fixed in the image forming apparatus.
[0143]
The guide 222 is fixed to a “U-shaped” holding body 223 fixed to a stationary member of the apparatus. A compressible spring 224 is interposed between the holding body 223 and the support body 221, and an elastic force directed to the left in the drawing is applied to the support body 221. The adjustment screw 225 screwed to the holding body 223 abuts the tip of the adjustment screw 225 from the right side to stop the movement of the support body due to the elastic force of the spring 224. Therefore, if the adjustment screw 225 is sent, the support 221 can be displaced to the right side of the figure, and if the adjustment screw 225 is loosened, the support 221 can be displaced to the left side. Is moved and adjusted in the optical axis direction so as to satisfy the conditional expression (B).
[0144]
[Embodiment 13]
FIG. 24 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction when the multi-beam scanning optical system according to the thirteenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0145]
This embodiment differs from the above-described embodiment 12 in that the BD slit 9, the optical element (BD lens) 11 disposed between the BD slit 9 and the BD sensor 10, and the BD sensor 10 are held by the same holding member 13. Then, by moving the holding member 13 in the optical axis direction of the BD optical system by the adjusting means, it is possible to adjust the condensing state in the main scanning section of each BD light beam on the BD slit 9 surface. It is. Other configurations and optical actions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.
[0146]
That is, in the present embodiment, as described in the above-described eleventh embodiment, the BD lens 11 is disposed behind the BD slit 9 so that a conjugate relationship exists between the vicinity of the reflecting surface of the BD mirror 12 and the vicinity of the BD sensor 10. Therefore, it has a fall correction function. However, in order to obtain the above-described tilt correction function, it is particularly important to obtain the distance between the BD lens 11 and the BD sensor 10 with high accuracy. This is because if the distance between the BD mirror 12 and the BD lens 11 is S and the distance between the BD lens 11 and the BD sensor 10 is T, the distance K from the BD mirror 12 to the BD sensor 10 is K = S + T.
[0147]
On the other hand, if the holding member 13 is moved by δS to the BD sensor 10 side in order to adjust the condensing state of the BD light beam on the BD slit 9 surface, the distance K ′ from the BD mirror 12 to the BD sensor 10. Is
K ′ = S + T + (1−f ² / (S-f) ² * ΔS
It becomes. Here, f is the focal length of the BD lens 11.
[0148]
In general, the focal length f of the BD lens 11 is very small with respect to the distance S between the BD mirror 12 and the BD lens 11, so the distance K ′ is
K′≈S + T + δS
Thus, the distance T between the BD lens 11 and the BD sensor 10 hardly changes. Therefore, it is necessary to always keep the original distance in order to obtain the tilt correction function. In addition, if the position of the BD slit 9 is shifted and the writing position of the scanning line is shifted, the phenomenon described so far occurs, which is not good. In addition, since the distance from the BD slit 9 to the BD sensor 10 is practically negligible, the BD slit 9, the BD lens 11, and the BD sensor 10 are incorporated in the same holding member 13 in order to obtain positional accuracy. Become advantageous.
[0149]
Therefore, in the present embodiment, as described above, the BD slit 9, the BD lens 11, and the BD sensor 10 are held by the same holding member 13, and the holding member 13 is adjusted as shown by an arrow E in FIG. By moving in the optical axis direction of the BD optical system, the condensing state in the main scanning section of each BD light beam on the surface of the BD slit 9 is adjusted. This achieves high-speed and high-quality printing.
[0150]
[Embodiment 14]
FIG. 25 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction when the multi-beam scanning optical system according to the fourteenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0151]
This embodiment is different from the above-described embodiment 12 in that the lens portion 8 is provided independently without being integrated with the scanning optical means 6, and the BD slit 9 is fixed, and the lens portion 8 is adjusted by the adjusting means. By moving in the optical axis direction of the BD optical system, the condensing state of each BD light beam on the surface of the BD slit 9 within the main scanning section can be adjusted. Other configurations and optical actions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.
[0152]
That is, in the present embodiment, the lens unit 8 having a single lens is arranged separately from the scanning optical unit 6 without being integrated with the scanning optical unit 6, and the lens unit 8 is adjusted by the adjusting unit (FIG. 30) to the arrow shown in FIG. By moving in the optical axis direction of the BD optical system as in F, the condensing state of each BD light beam on the surface of the BD slit 9 in the main scanning section is adjusted. As a result, the state shown in FIG. 29B is improved to the state shown in FIG.
[0153]
[Embodiment 15]
FIG. 26 is a main part sectional view (main scanning sectional view) in the main scanning direction when the multi-beam scanning optical system according to the fifteenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0154]
The present embodiment is different from the above-described embodiment 12 in that at least a part of the lens constituting the lens unit 8 is integrated with the scanning optical unit 6, and at least the lens unit 8 not integrated with the scanning optical unit 6 is used. By adjusting some of the lenses 8a and the BD slit 9 in the optical axis direction of the BD optical system by adjusting means, the condensing state in the main scanning section of each BD light beam on the surface of the BD slit 9 is adjusted. It is possible. Other configurations and optical actions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.
[0155]
That is, in the present embodiment, at least a part of the lenses constituting the lens unit 8 is integrated with the scanning optical unit 6, and a part of the lenses 8a of the lens unit 8 that is not integrated with the scanning optical unit 6 and the BD. By moving the slit 9 in the optical axis direction of the BD optical system by adjusting means (FIG. 30), the condensing state of each BD light beam on the surface of the BD slit 9 in the main scanning section is adjusted. As a result, the state shown in FIG. 29B is improved to the state shown in FIG.
[0156]
In the present embodiment, both the lens 8a and the BD slit 9 of the lens unit 8 are moved, but the present invention can be applied in the same manner as in the fifth embodiment described above.
[0157]
[Embodiment 16]
FIG. 27 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction when the multi-beam scanning optical system according to the sixteenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0158]
This embodiment is different from the above-described embodiment 12 in that at least a part of the optical elements (fθ lens) of the scanning optical means 6 integrated with the lens unit 8 is adjusted in the optical axis direction of the scanning optical means 6 by the adjusting means. By moving and moving the BD slit 9 in the optical axis direction of the BD optical system, it is possible to adjust the condensing state in the main scanning section of each BD light beam on the surface of the BD slit 9. . Other configurations and optical actions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.
[0159]
In other words, in the present embodiment, the first optical element (fθ lens) 6a constituting the scanning optical means 6 is adjusted by the adjusting means (FIG. 30) as long as the spot shape on the scanned surface 7 does not change much. Each BD light beam on the surface of the BD slit 9 is moved in the G direction (the optical axis direction of the scanning optical means 6) and the BD slit 9 is moved in the arrow D direction (the optical axis direction of the BD optical system) in the figure. The light condensing state in the main scanning section is adjusted. As a result, the state shown in FIG. 29B is improved to the state shown in FIG.
[0160]
In this embodiment, the first optical element 6a is moved, but the second optical element (fθ lens) 6b may be moved, or both the first and second optical elements 6a and 6b are moved. It may be moved.
[0161]
In the present embodiment, both the first optical element 6a and the BD slit 9 are moved. However, the present invention can be applied in the same manner as in the above-described sixth embodiment with only one of them.
[0162]
[Embodiment 17]
FIG. 28 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction when the multi-beam scanning optical system according to the seventeenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). In the figure, the same elements as those shown in FIG.
[0163]
In this embodiment, the difference from the above-described embodiment 12 is that the BD slit 9 is fixed, and at least a part of the optical elements (fθ lens) constituting the scanning optical means 6 integrated with the lens unit 8 are arranged in the main scanning direction. By moving the light, it is possible to adjust the condensing state of each BD light beam on the surface of the BD slit 9 in the main scanning section, and the rotation direction of the optical deflector is reversed (the direction of arrow A in the figure). It is configured. Other configurations and optical actions are substantially the same as those of the twelfth embodiment, and the same effects are obtained.
[0164]
That is, in this embodiment, the BD slit 9 is fixed, and among the plurality of lenses constituting the scanning optical means 6 formed integrally with the lens unit 8, the local curvature in the main scanning direction is sharp especially in the periphery. Each moving first optical element 6a is moved in the main scanning direction as shown by an arrow H in the drawing by the adjusting means (FIG. 30) within a range where the spot shape on the scanned surface 7 does not change so much. The vertical magnification of the BD light beam in the main scanning direction is changed to adjust the condensing state of each BD light beam in the main scanning section on the BD slit 9 surface. As a result, the state shown in FIG. 29B is improved to the state shown in FIG.
[0165]
In the present embodiment, the first optical element 6a is moved in the main scanning direction, but the second optical element (fθ lens) 6b may be moved, or the first and second optical elements 6a, 6a, Both of 6b may be moved.
[0166]
[Embodiment 18]
In the eighteenth embodiment, the dot deviation on the surface to be scanned, which is caused by having the focus position deviation amount δX in the main scanning section of the BD light beam guided to the BD sensor 10 viewed from the BD slit 9, is shown in FIG. 7 is corrected by rotationally adjusting the BD slit 9 or the unit 16 including the BD slit 9 around the optical axis of the BD optical system.
[0167]
That is, in the light source unit 1 in this embodiment, as shown in FIG. 2, the light emitting portions 1a and 1b are arranged apart from each other also in the sub-scanning direction. The A and B rays corresponding to the portions 1a and 1b are different.
[0168]
Therefore, in this embodiment, the angle adjusting means 15 rotates the BD slit 9 as shown in FIGS. 8A and 8B and FIGS. The timing at which the light enters the BD sensor 10 is changed. FIG. 8 is an explanatory diagram showing the inclination of the BD slit 9 and the printing position (before adjustment) of each light beam, and FIG. 9 is an explanatory diagram showing the inclination of the BD slit 9 and the printing position of each light beam (after adjustment).
[0169]
As described above, in the present embodiment, as described above, there are dots on the surface to be scanned that should be generated due to the amount of focus position deviation δX in the main scanning section of each BD light beam guided to the BD sensor 10. The deviation is corrected (cancelled) by rotationally adjusting the BD slit 9 using the angle adjusting means 15. This achieves high-speed and high-quality printing.
[0170]
In this embodiment, the optical action for forming an image using the multi-beam scanning optical system is substantially the same as that of the above-described eleventh embodiment.
[0171]
[Embodiment 19]
FIG. 10 is a sectional view (main scanning sectional view) of the principal part in the main scanning direction when the multi-beam scanning optical system according to the nineteenth embodiment of the present invention is applied to an image forming apparatus such as a laser beam printer (LBP). It is a principal part perspective view of BD slit 9 of FIG. 10 and 11, the same elements as those shown in FIG. 6 are denoted by the same reference numerals.
[0172]
In the present embodiment, the difference from the above-described eighteenth embodiment is that there is no angle adjusting means, and the BD slit 9 or the unit 16 including the BD slit 9 is tilted in the sub-scanning direction from the beginning to form dots on the surface to be scanned. This is to correct (cancel) the deviation. Other configurations and optical actions are substantially the same as those in the eighteenth embodiment, and the same effects are obtained.
[0173]
That is, the degree of curvature of field of the scanning optical means 6 is considerably stable for each product, and the difference value | δX | of the conditional expression (B) has a value that cannot be ignored when the BD slit 9 is arranged at the focus position. As shown in FIGS. 10 and 11, the BD slit 9 is tilted in the sub-scanning direction from the beginning to correct (cancel) dot deviation on the surface to be scanned. This achieves high-speed and high-quality printing.
[0174]
[Embodiments 20, 21, 22, 23, 24, 25, 26]
Embodiments 20, 21, 22, 23, 24, 25, and 26 correspond to Embodiments 11, 12, 13, 14, 15, 16, and 17, respectively. , 23, 24, 25, and 26 are different from the above-described Embodiments 11, 12, 13, 14, 15, 16, and 17 in that the BD slit 9 and the BD slit 9 are simplified in order to simplify the entire apparatus and reduce the cost. That is, it is configured without using the BD lens 11. Other configurations and optical actions are substantially the same as those of the corresponding Embodiments 11, 12, 13, 14, 15, 16, and 17, thereby obtaining the same effects.
[0175]
That is, in each of the embodiments 20, 21, 22, 23, 24, 25, and 26, the effective end of the BD sensor 10 is the BD slit 9 in each of the corresponding embodiments 11, 12, 13, 14, 15, 16, and 17 described above. Acts equivalent to Therefore, in each of Embodiments 20, 21, 22, 23, 24, 25, and 26, the contents of the corresponding Embodiments 11, 12, 13, 14, 15, 16, and 17 are replaced with the BD slit 9 surface and the BD sensor 10. This is implemented by replacing the light receiving surface. Thereby, the same effects as those of the corresponding embodiments described above are obtained.
[0176]
As described above, each of the embodiments 20, 21, 22, 23, 24, 25, and 26 is configured without using the BD slit and the BD lens, so that the entire apparatus can be simplified and reduced in cost while being relatively simple. High-quality printing is achieved at high speed with this simple configuration.
[0177]
【The invention's effect】
According to the present invention, as described above, the amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detecting element viewed from the BD slit (in the case of not having the BD slit, the light receiving surface of the synchronization detecting element). Is set to δM, and the focus position shift amount of each image height on the scanned surface is set to δX. By setting each element so that the focus position shift amount δX satisfies the conditional expression (A), it is relatively easy. With this configuration, it is possible to achieve a multi-beam scanning optical system that can realize high-quality printing at high speed and an image forming apparatus using the same.
[0178]
Further, according to the present invention, as described above, the focus position shift amount δM in the main scanning section of the light beam guided to the synchronization detecting element viewed from the BD slit and the focus position shift of each image height on the scanned surface 7. By correcting the dot shift generated by the difference between the focus position shift amounts δM and δX of the two and the amount δX by the correction means, high-quality printing can be realized at a high speed with a relatively simple configuration. A multi-beam scanning optical system and an image forming apparatus using the same can be achieved.
[0179]
According to the present invention, as described above, the incident optical means for causing the light beams emitted from the light source means having the plurality of light emitting portions to enter the deflecting means, and the light beams deflected by the deflecting means are coupled on the surface to be scanned. A scanning optical means for forming an image and forming a plurality of scanning lines; and a part of a plurality of light beams deflected by the deflecting means is condensed on the slit surface by a lens portion via a folding mirror, and then a synchronous detection element In a multi-beam scanning optical system having synchronization detecting optical means that controls the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. By setting each element so as to satisfy the conditional expression (B), or by making it possible to adjust the condensing state of the plurality of light beams in the main scanning section on the slit surface, it is relatively easy. Structure It is possible to achieve an image forming apparatus using a multibeam scanning optical system and it is possible to realize high-quality printing at high speed by.
[Brief description of the drawings]
FIG. 1 is a main scanning sectional view of a first embodiment of the present invention.
FIG. 2 is an explanatory diagram showing the arrangement of light emitting units.
FIG. 3 is a main scanning sectional view of Embodiment 2 of the present invention.
FIG. 4 is a main scanning sectional view of Embodiment 3 of the present invention.
FIG. 5 is a main scanning sectional view of Embodiment 4 of the present invention.
FIG. 6 is a main scanning sectional view of Embodiment 5 of the present invention.
FIG. 7 is an angle adjustment unit according to a fifth embodiment of the present invention.
FIG. 8 is an explanatory view showing the inclination of the slit and the printing position (before adjustment) of each light beam according to the fifth embodiment of the present invention.
FIG. 9 is an explanatory view showing the inclination of the slit and the printing position (after adjustment) of each light beam according to the fifth embodiment of the present invention.
FIG. 10 is a main scanning sectional view of Embodiment 6 of the present invention.
FIG. 11 is a perspective view of main parts of a slit according to a sixth embodiment of the present invention.
FIG. 12 is a main scanning sectional view of Embodiment 7 of the present invention;
FIG. 13 is a main scanning sectional view of Embodiment 8 of the present invention.
FIG. 14 is a main scanning sectional view of Embodiment 9 of the present invention.
FIG. 15 is a main scanning sectional view of Embodiment 10 of the present invention.
FIG. 16 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the near side (deflecting means).
FIG. 17 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the near side (deflecting means).
FIG. 18 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the near side (deflection means).
FIG. 19 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the back (anti-deflection means) side.
FIG. 20 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the back (anti-deflection means) side.
FIG. 21 is an explanatory diagram showing the positional relationship of each light beam when the focus is shifted to the back (anti-deflection means) side.
FIG. 22 is a main scanning sectional view of a conventional multi-beam scanning optical system.
FIG. 23 is a main scanning sectional view of Embodiment 12 of the present invention.
FIG. 24 is a main scanning sectional view of Embodiment 13 of the present invention.
FIG. 25 is a main scanning sectional view of Embodiment 14 of the present invention;
FIG. 26 is a main scanning sectional view of Embodiment 15 of the present invention.
FIG. 27 is a main scanning sectional view of Embodiment 16 of the present invention.
FIG. 28 is a main scanning sectional view of Embodiment 17 of the present invention.
FIG. 29 is an explanatory diagram showing the relationship between the focus shift and each principal ray.
FIG. 30 is an explanatory diagram of adjusting means according to the present invention.
FIG. 31 is a schematic view of an image forming apparatus of the present invention.
[Explanation of symbols]
1a, 1b light emitting part (semiconductor laser)
1 Light source unit
2 Collimator lens
3 Aperture stop
4 Cylindrical lens
5 Deflection means (optical deflector)
5a Deflection surface
6 Scanning optical means
6a First optical element
6b Second optical element
7 Scanned surface (photosensitive drum surface)
8 Lens part
9 Slit
10 Sync detector
11 Imaging lens
12 Folding mirror
13 units
14 Incident optical means

Claims (24)

Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then the synchronous detection element. A multi-beam scanning optical system comprising: a synchronization detection optical unit that guides light and controls a timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detection element. And
The following conditional expression is expressed as | δM1 | ≦ δYmax / tan (θmax).
(However,
δM1: Focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit δYmax: Allowable dot position deviation amount θmax for each scanning line: Each light beam used for synchronization detection The maximum allowable angle difference of the incident angle to the slit surface) and the allowable dot position deviation amount δYmax for each scanning line is equal to or less than ½ of the resolution in the sub-scanning direction, and is guided to the synchronization detecting element. A multi-beam scanning optical system comprising correction means for shifting the focus position of the luminous flux in the main scanning section relative to the optical axis direction of the synchronization detecting optical means from the slit. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by a lens unit, and then the synchronous detection element. A multi-beam scanning optical system comprising: a synchronization detecting optical unit that guides light and controls a timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element. And
The following conditional expression is expressed as | δM1 | ≦ δYmax / tan (θmax).
(However,
δM1: focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit δYmax: allowable dot position deviation amount θmax for each scanning line: each light beam used for synchronization detection Satisfying the maximum angle difference of the incident angle to the slit surface), the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the slit or the unit including the slit A multi-beam scanning optical system comprising correction means for moving the position of the optical axis relative to the optical axis direction of the synchronization detecting optical means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then the synchronous detection element. A multi-beam scanning optical system comprising: a synchronization detection optical unit that guides light and controls a timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detection element. And
The following conditional expression is expressed as | δM1 | ≦ δYmax / tan (θmax).
(However,
δM1: Focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit δYmax: Allowable dot position deviation amount θmax for each scanning line: Each light beam used for synchronization detection The maximum allowable angle difference of the incident angle to the slit surface) is satisfied, and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. A multi-beam scanning optical system comprising correction means provided in an optical path between the slit and moving the lens unit with respect to the optical axis direction of the synchronization detecting optical means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then the synchronous detection element. A multi-beam scanning optical system comprising: a synchronization detection optical unit that guides light and controls a timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detection element. And
The following conditional expression is expressed as | δM1 | ≦ δYmax / tan (θmax).
(However,
δM1: Focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit δYmax: Allowable dot position deviation amount θmax for each scanning line: Each light beam used for synchronization detection The maximum allowable angle difference of the incident angle to the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. The lens of the unit is integrated with the scanning optical unit, and at least a part of the lens unit that is not integrated with the scanning optical unit and the slit are moved in the optical axis direction of the optical unit for synchronization detection. A multi-beam scanning optical system comprising correction means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by a lens unit, and then the synchronous detection element. A multi-beam scanning optical system comprising: a synchronization detecting optical unit that guides light and controls a timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element. And
The following conditional expression is expressed as | δM1 | ≦ δYmax / tan (θmax).
(However,
δM1: focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit δYmax: allowable dot position deviation amount θmax for each scanning line: each light beam used for synchronization detection The maximum angle difference of the incident angle to the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens unit is the scanning optical means. And a correction means for moving at least a part of the optical elements of the scanning optical means in the optical axis direction of the scanning optical means, and for moving the slit in the optical axis direction of the synchronization detecting optical means. A multi-beam scanning optical system. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of a plurality of light beams deflected by the deflecting unit is condensed on the slit surface by a lens unit, and then the synchronous detection element. A multi-beam scanning optical system comprising: a synchronization detecting optical unit that guides light and controls a timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detecting element. And
The following conditional expression is expressed as | δM1 | ≦ δYmax / tan (θmax).
(However,
δM1: Focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit δYmax: Allowable dot position deviation amount θmax for each scanning line: Each light beam used for synchronization detection The maximum allowable angle difference of the incident angle to the slit surface), and the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction. The multi-beam scanning optical system is characterized in that the lens of the unit is integrated with the scanning optical means, and includes correction means for moving at least a part of the lenses constituting the scanning optical means in the main scanning direction. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means that controls the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The dot position deviation for each scanning line on the surface to be scanned, which is generated by having a focus position deviation amount δM1 in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit, is corrected. A correction unit, wherein the dot position deviation amount is less than or equal to half of the resolution in the sub-scanning direction, and the slit is inclined in the sub-scanning direction according to the dot position deviation amount for each scanning line on the scanned surface A multi-beam scanning optical system. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: synchronization detecting optical means that controls the timing of the scanning start position on the surface to be scanned for each of the plurality of light beams using a signal from the synchronization detecting element. ,
The dot position deviation for each scanning line on the surface to be scanned, which is generated by having a focus position deviation amount δM1 in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit, is corrected. A correction unit, wherein the dot position deviation amount is ½ or less of the resolution in the sub-scanning direction, and the slit or the unit including the slit is set according to the dot position deviation amount for each scanning line on the scanned surface. And a rotating means for rotating the optical means for synchronizing detection around the optical axis. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detecting element by the lens unit, A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal,
The following conditional expression is expressed as | δM2 | ≦ δYmax / tan (θmax).
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element δYmax: An allowable dot position deviation amount θmax for each scanning line: Synchronization detection The maximum angle difference of the incident angle of each light beam used for the light receiving surface)
Satisfying and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the focus position in the main scanning section of the light beam guided to the synchronization detecting element is determined. A multi-beam scanning optical system comprising correction means for shifting relative to the optical axis direction of the synchronization detection optical means relative to the light receiving surface of the synchronization detection element. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detecting element by the lens unit, A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal,
The following conditional expression is expressed as | δM2 | ≦ δYmax / tan (θmax).
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element δYmax: An allowable dot position deviation amount θmax for each scanning line: Synchronization detection The maximum angle difference of the incident angle of each light beam used for the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the position of the synchronization detection element or the unit including the synchronization detection element A multi-beam scanning optical system comprising correction means for moving relative to the optical axis direction of the means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detecting element by the lens unit, A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal,
The following conditional expression is expressed as | δM2 | ≦ δYmax / tan (θmax).
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element δYmax: An allowable dot position deviation amount θmax for each scanning line: Synchronization detection The maximum angle difference of the incident angle of each light beam used for the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens portion is provided in the optical path between the deflecting means and the synchronization detecting element. And a correction means for moving the lens section with respect to the optical axis direction of the synchronization detecting optical means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detecting element by the lens unit, A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal,
The following conditional expression is expressed as | δM2 | ≦ δYmax / tan (θmax).
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element δYmax: An allowable dot position deviation amount θmax for each scanning line: Synchronization detection The maximum angle difference of the incident angle of each light beam used for the light receiving surface)
Satisfactory and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and at least some of the lenses constituting the lens unit are integrated with the scanning optical means. A multi-beam scanning optical system comprising correction means for moving at least a part of the lenses of the lens unit not integrated with the scanning optical means in the optical axis direction of the synchronization detecting optical means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detecting element by the lens unit, A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal,
The following conditional expression is expressed as | δM2 | ≦ δYmax / tan (θmax).
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element δYmax: An allowable dot position deviation amount θmax for each scanning line: Synchronization detection The maximum angle difference of the incident angle of each light beam used for the light receiving surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, the lens unit is integrated with the scanning optical means, and at least one of the scanning optical means A multi-beam scanning optical system comprising correction means for moving the optical elements in the optical axis direction of the scanning optical means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on a surface and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit are guided to the synchronization detecting element by the lens unit, A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface for each of the plurality of light beams using a signal,
The following conditional expression is expressed as | δM2 | ≦ δYmax / tan (θmax).
(However,
δM2: A focus position deviation amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element δYmax: An allowable dot position deviation amount θmax for each scanning line: Synchronization detection The maximum angle difference of the incident angle of each light beam used for the light receiving surface)
Satisfactory and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and at least a part of the lenses constituting the lens unit is integrated with the scanning optical means. A multi-beam scanning optical system comprising correction means for moving at least a part of the lenses constituting the scanning optical means in the main scanning direction. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the surface, and a part of a plurality of light beams deflected by the deflecting unit are condensed on the slit surface by the lens unit, and then guided to the synchronization detection element, from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface using the signal of
When the focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit is δM1, and the focus position shift amount of each image height on the scanned surface is δX, The conditional expression of | δX−δM1 | ≦ δYmax / θmax
(However,
δYmax: Permissible dot position deviation amount θmax for each scanning line: Maximum angle difference of incident angle of each light beam used for synchronization detection to slit surface)
Satisfying and allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the focus position in the main scanning section of the light beam guided to the synchronization detecting element is determined. A multi-beam scanning optical system comprising correction means for shifting relative to the optical axis direction of the synchronization detection optical means from the slit. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the surface, and a part of a plurality of light beams deflected by the deflecting unit are condensed on the slit surface by the lens unit, and then guided to the synchronization detection element, from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface using the signal of
When the focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit is δM1, and the focus position shift amount of each image height on the scanned surface is δX, The conditional expression of | δX−δM1 | ≦ δYmax / θmax
(However,
δYmax: Permissible dot position deviation amount θmax for each scanning line: Maximum angle difference of incident angle of each light beam used for synchronization detection to slit surface)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the position of the slit or the unit including the slit is defined as the optical axis of the optical means for synchronization detection. A multi-beam scanning optical system comprising correction means for moving relative to a direction. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the surface, and a part of a plurality of light beams deflected by the deflecting unit are condensed on the slit surface by the lens unit, and then guided to the synchronization detection element, from the synchronization detection element A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position on the scanned surface using the signal of
When the focus position shift amount in the main scanning section of the light beam guided to the synchronization detection element viewed from the slit is δM1, and the focus position shift amount of each image height on the scanned surface is δX, The conditional expression of | δX−δM1 | ≦ δYmax / θmax
(However,
δYmax: Permissible dot position deviation amount θmax for each scanning line: Maximum angle difference of incident angle of each light beam used for synchronization detection to slit surface)
Satisfactory, the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens unit is provided in the optical path between the deflecting means and the slit, A multi-beam scanning optical system comprising correction means for moving the lens portion with respect to the optical axis direction of the synchronization detecting optical means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: a synchronization detection optical unit configured to control the timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detection element;
When the focal position deviation amount in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit is δM1, and the focal position deviation amount of each image height on the scanned surface is δX, both Correction means for correcting the dot position deviation for each scanning line on the surface to be scanned that is generated when there is a difference between the focus position deviation amounts δM1 and δX, and the dot position deviation amount has a resolution in the sub-scanning direction. A multi-beam scanning optical system, wherein the slit is inclined in the sub-scanning direction according to the amount of dot position deviation for each scanning line on the surface to be scanned. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical unit that forms an image on the top and forms a plurality of scanning lines, and a part of the plurality of light beams deflected by the deflecting unit is condensed on the slit surface by the lens unit, and then guided to the synchronization detecting element. A multi-beam scanning optical system comprising: a synchronization detection optical unit configured to control the timing of a scanning start position on the scanned surface for each of the plurality of light beams using a signal from the synchronization detection element;
When the focal position deviation amount in the main scanning section of the light beam guided to the synchronization detecting element viewed from the slit is δM1, and the focal position deviation amount of each image height on the scanned surface is δX, both Correction means for correcting the dot position deviation for each scanning line on the surface to be scanned, which is generated when there is a difference between the focus position deviation amounts δM1 and δX, and the dot position deviation amount has a resolution in the sub-scanning direction. Rotating means for rotating the slit or the unit including the slit around the optical axis of the optical means for synchronization detection according to the amount of dot position deviation for each scanning line on the scanned surface. A multi-beam scanning optical system. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical means that forms an image on the surface, and a part of a plurality of light beams deflected by the deflecting means are guided to the synchronization detecting element by the lens unit, and the signal from the synchronization detecting element is used on the surface to be scanned. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position of
The amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element is δM2, and the amount of focus position deviation of each image height on the surface to be scanned is δX. Where | δX−δM2 | ≦ δYmax / θmax
(However,
δYmax: Permissible dot position deviation amount θmax for each scanning line: Maximum angle difference of incident angles of light beams on the light receiving surface used for synchronization detection)
Satisfactory, the allowable dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the focus position in the main scanning direction of the light beam guided to the synchronization detecting element is A multi-beam scanning optical system comprising correction means for shifting relative to the optical axis direction of the optical means for synchronization detection from a light receiving surface of a detection element. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical means that forms an image on the surface, and a part of a plurality of light beams deflected by the deflecting means are guided to the synchronization detecting element by the lens unit, and the signal from the synchronization detecting element is used on the surface to be scanned. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position of
The amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element is δM2, and the amount of focus position deviation of each image height on the surface to be scanned is δX. Where | δX−δM2 | ≦ δYmax / θmax
(However,
δYmax: Permissible dot position deviation amount θmax for each scanning line: Maximum angle difference of incident angles of light beams on the light receiving surface used for synchronization detection)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the position of the synchronization detecting element or the unit including the synchronization detecting element is determined as the synchronization detecting optical. A multi-beam scanning optical system comprising correction means for moving the optical axis in the optical axis direction of the means. Incident optical means for guiding a plurality of light beams emitted from a light source means having a plurality of light emitting units arranged at least apart from the main scanning direction to the deflecting means, and a plurality of light beams deflected by the deflecting means to be scanned A scanning optical means that forms an image on the surface, and a part of a plurality of light beams deflected by the deflecting means are guided to the synchronization detecting element by the lens unit, and the signal from the synchronization detecting element is used on the surface to be scanned. A multi-beam scanning optical system having synchronization detecting optical means for controlling the timing of the scanning start position of
The amount of focus position deviation in the main scanning section of the light beam guided to the synchronization detection element viewed from the light receiving surface of the synchronization detection element is δM2, and the amount of focus position deviation of each image height on the surface to be scanned is δX. Where | δX−δM2 | ≦ δYmax / θmax
(However,
δYmax: Permissible dot position deviation amount θmax for each scanning line: Maximum angle difference of incident angles of light beams on the light receiving surface used for synchronization detection)
Satisfactory and permissible dot position deviation amount δYmax for each scanning line is ½ or less of the resolution in the sub-scanning direction, and the lens portion is provided in the optical path between the deflection means and the synchronization detection element. And a correction means for moving the lens section with respect to the optical axis direction of the synchronization detecting optical means. 23. The multi-beam scanning optical system according to any one of claims 1 to 22, a photosensitive member disposed on the surface to be scanned, and a light beam scanned by the multi-beam scanning optical system. A developing unit that develops the developed electrostatic latent image as a toner image, a transfer unit that transfers the developed toner image to a transfer material, and a fixing unit that fixes the transferred toner image to the transfer material. Image forming apparatus. 23. Image formation comprising the multi-beam scanning optical system according to claim 1 and a printer controller that converts code data input from an external device into an image signal and inputs the image signal to the multi-beam scanning optical system. apparatus.

Images