JP3719637B2 - Optical beam scanning device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light beam scanning apparatus, and more particularly to a light beam scanning apparatus applicable to a laser printer, a digital copying machine, a facsimile machine, and the like.
[0002]
[Prior art]
Conventionally, rotary polygon mirrors and holo scanners are known as means for deflecting a light beam. The rotating polygon mirror deflects a light beam by a plurality of mirror surfaces a plurality of times while the polygon mirror rotates once. On the other hand, a holo scanner deflects a light beam a plurality of times by a plurality of hologram gratings during one rotation of the holo disk. Thus, the rotating polygon mirror and the holo scanner deflect the light beam a plurality of times by a plurality of mirror surfaces or a plurality of hologram gratings.
[0003]
In view of such a problem, there is provided a deflector that tilts a mirror surface with respect to the rotation axis of the deflector, makes a light beam to be deflected incident along the rotation axis, reflects the beam by the mirror surface, and deflects the reflected beam by 360 degrees. Proposed. The mirror surface of this deflector is called a pyramid mirror, and the deflection method using this pyramid mirror deflects the light beam a plurality of times by a plurality of mirror surfaces or a plurality of hologram gratings like the rotary polygon mirror and the holo scanner. Unlike the above, since the light beam is deflected by only one mirror surface, there is no problem of the above-described surface collapse.
[0004]
As described above, the deflection method using the pyramid mirror is such that the light beam to be deflected is incident along the rotation axis of the deflector and is deflected and reflected by the pyramid mirror. Therefore, the light source for emitting the light beam is used as the rotation axis. If the light source is not arranged on a straight line along the rotation axis, a reflection mirror is provided on the straight line along the rotation axis, and the light beam emitted from the light source is reflected on this reflection mirror. The light beam is incident along the rotation axis of the deflector by being refracted and reflected by.
[0005]
[Problems to be solved by the invention]
However, in the configuration in which the light source that emits the light beam is arranged on a straight line along the rotation axis, the space for arranging the light source must be provided in the sub-scanning direction that is orthogonal to the main scanning direction. There is a problem that the whole becomes larger in the sub-scanning direction.
[0006]
On the other hand, if the light source is not arranged on a straight line along the rotation axis, a reflection mirror must be provided on the straight line along the rotation axis, which increases the number of components and the cost. There is.
[0007]
The present invention has been made in order to solve the above-described problems of the prior art, and the rotation shaft of the deflector has a hollow structure, and the hollow portion serves as the optical path of the incident beam toward the imaging lens. An object of the present invention is to provide a light beam scanning apparatus that can reduce the size of the entire apparatus, reduce the number of components, and reduce the cost.
[0008]
[Means for Solving the Problems]
According to the first aspect of the present invention, a beam shaping slit is provided on the optical path on the incident side of the imaging lens in order to form an image of the beam on the surface to be scanned with a required spot diameter necessary for image formation. In the light beam scanning device in which the beam after passing is incident on the pyramid mirror constituting the reflecting surface of the deflector at an angle with respect to the normal direction, and the reflected light is incident on the imaging lens, the deflector rotates. A slit member that has a hollow shaft, arranges a light source on a straight line along the rotation axis, and uses the hollow portion of the deflector as a part of the optical path of the incident beam that is emitted from the light source and directed to the imaging lens. Is integrally provided at the rotating shaft end of the deflector on the incident side of the pyramid mirror, and the rotating shaft provided with the slit member rotates integrally with the deflector .
[0009]
According to a second aspect of the present invention, in the first aspect of the present invention, the diameter of the hollow portion is at least equal to or larger than a required light spot diameter necessary for image formation on the surface to be scanned.
[0010]
According to a third aspect of the invention, in the invention according to the first aspect, the slit member includes a beam diameter in the main scanning direction of the incident beam towards the imaging lens, that Turkey to shaping the beam diameter in the sub-scanning direction Features.
[0011]
According to a fourth aspect of the present invention, in the first aspect of the present invention, the inner surface of the hollow portion is subjected to a process of absorbing a light beam.
[0012]
According to a fifth aspect of the present invention, in the first aspect of the invention, the shape of the light beam incident portion or the light emitting portion of the pyramidal mirror block is a collimator lens shape that makes the light beam diverging light emitted from the light source a parallel light beam. It is characterized by being.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of a light beam scanning apparatus according to the present invention will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a deflector used in the light beam scanning apparatus. The deflector 1 mainly includes a motor 2 and a pyramid mirror block 3 (see FIG. 6) described later.
[0014]
As shown in FIG. 1, the motor 2 includes a rotor part and a stator part in a disc-shaped case 4, and a part of the rotating shaft 5 of the rotor part protrudes from the center of the case 4. Yes. The rotating shaft 5 rotates as the rotor portion rotates relative to the stator portion.
[0015]
One end of the rotating shaft 5 is formed in a step shape, and includes a large diameter portion 6 and a small diameter portion 7 formed at the lower end of the large diameter portion 6. The small diameter portion 7 is formed with a recess 8 and an annular groove 9. The rotating shaft 5 is formed in a hollow structure. More specifically, a hollow portion 10 extending in the axial direction is formed through the center of the large-diameter portion 6 and the small-diameter portion 7 of the rotary shaft 5, and the inside of the hollow portion 10 is shown in FIG. The light beam emitted from the light source 20 shown in FIG. That is, a part of the optical path of the incident beam emitted from the light source 20 and directed to the imaging lens provided on the deflection side of the deflector 1 is formed in the hollow portion 10 of the rotation shaft 5.
[0016]
The diameter of the hollow portion 10 is formed so that the light beam emitted from the light source is at least the required light spot diameter necessary for image formation on the surface to be scanned. Further, the inner surface of the hollow portion 10 is subjected to a treatment for absorbing a light beam, so that the light beam irregularly reflected in the hollow portion 10 can be absorbed. As a result, it is possible to prevent a ghost from occurring on the image and obtain a good image.
[0017]
As shown in FIGS. 1 and 2, a slit member 11 is integrally attached to the tip end of the protruding rotating shaft 5, i.e., the small diameter portion 7, which is positioned on the optical path on the incident side of the imaging lens described later. . The slit member 11 is formed in a cylindrical shape having a bottom surface. On the inner surface of the slit member 11 on the opening side, an annular protrusion 13 that fits into the groove 9 formed in the small diameter portion 7 is formed. Further, at the opening end of the slit member 11, a convex portion 14 that engages with the concave portion 8 formed in the small diameter portion 7 is formed.
[0018]
The slit member 11 can be positioned and attached to the small diameter portion 7 of the rotating shaft 5 by fitting the protrusion 13 into the groove 9 and engaging the convex portion 14 with the concave portion 8. The method of attaching the slit member 11 to the rotating shaft 5 is not limited to the above configuration, and any method such as bonding, press-fitting, screwing, or the like can be used as long as the slit member 11 can be attached to the rotating shaft 5 integrally. Such a method may be used.
[0019]
An elliptical beam shaping slit 12 is formed at the center of the bottom surface of the slit member 11. This slit 12 is for shaping the incident beam emitted from the light source and directed to the imaging lens, more specifically, for shaping the beam diameter in the main scanning direction and the beam diameter in the sub-scanning direction of the incident beam. is there. The incident beam passes through the slit 12 and is shaped into a beam diameter corresponding to the main scanning direction and the sub-scanning direction, and forms an image on the surface to be scanned with a required spot diameter necessary for image formation.
[0020]
Further, when the slit 12 is rotated by an effective scanning field angle (a scanning angle that can ensure an effective writing width to the photosensitive member), the shape of the incident beam is set to exceed at least the size of the slit 12. ing. In particular, when a semiconductor laser is used as the light source, the divergence angle of the light beam emitted from the semiconductor laser differs between the parallel direction and the perpendicular direction with respect to the joint surface, and the beam shape can be obtained even if a lens, prism, or the like is used. Therefore, even if the slit 12 is rotated by an effective scanning angle of view, the shape of the incident beam must be set so as to exceed the size of the slit 12 at least in the range. If the beam diameter is increased, the light utilization efficiency is lowered and the required power cannot be obtained. Therefore, it is better to set the shape of the incident beam to exceed the size of the slit 12 in consideration of this.
[0021]
At the other end of the deflector 1, that is, one end where the large-diameter portion 6 and the small-diameter portion 7 are not formed, as shown in FIG. 6, a pyramid mirror 3a constituting the reflecting surface of the deflector 1 is formed. A pyramid mirror block 3 is integrally attached. The pyramid mirror 3a is provided so as to be inclined so that the light beam that has passed through the hollow portion 10 is incident on the normal direction perpendicular to the optical axis direction.
[0022]
The light beam emitted from the light source passes through the slit 12, passes through the hollow portion 10, enters the pyramid mirror 3a, is deflected and reflected by the pyramid mirror 3a, and is in a normal direction perpendicular to the optical axis direction. The emitted light is incident on an imaging lens described later.
[0023]
As described above, the pyramid mirror block 3 in which the pyramid mirror 3a is formed and the slit member 11 in which the slit 12 is formed are integrally attached to the rotating shaft 5, thereby the deflection reflection direction of the pyramid mirror 3a, The shaping of the light beam by the slit 12 can always be performed synchronously at an effective scanning angle of view.
[0024]
Next, an image forming apparatus using a light beam scanning apparatus to which the deflector 1 is applied will be described. Around the photosensitive drum 30, a charger 31, a developing unit 32, a transfer charger 33, and a cleaning unit 34 are arranged in the order of rotation, and the photosensitive member is positioned between the charger 31 and the developing unit 32. A light beam scanning device 35 is provided so that the light beam emitted from the light source 20 enters the drum 30 and is exposed.
[0025]
The charger 31 and the optical writing position 36 are disposed below the photosensitive drum 30, and the light beam scanning device 35 is provided below the photosensitive drum 30, the developing unit 32, and the cleaning unit 34. Further, the transfer charger 33 is disposed on the upper side of the photosensitive drum 30.
[0026]
A paper feed tray 37 that feeds transfer paper to a transfer portion between the transfer charger 33 and the photosensitive drum 30 is provided below the light beam scanning device 35, and the transfer paper comes into pressure contact with the feed roller 38. Each image is fed out one by one by the friction pad 39, is largely reversed by the side of the developing unit 32, and the image and position formed on the photosensitive drum 30 by the pair of registration rollers 40 and 41 provided above the developing unit 32 are changed. The paper is fed to the transfer unit at the same timing so as to match. A fixing unit 42 is provided in the transfer paper path after transfer, and a paper discharge tray 43 is provided on the discharge side.
[0027]
The light beam emitted from the light source 20 is shaped into a beam diameter corresponding to the main scanning direction and the sub-scanning direction by passing through the slit 12 of the slit member 11, and passes through the hollow portion 10 formed on the rotating shaft 5. After that, the light enters the pyramid mirror 3a and repeatedly deflects within a certain angular range. The light beam deflected and reflected by the pyramid mirror 3a is corrected by the imaging lens (fθ lens) 44 so as to form an image on a straight line at the incident position 36 on the photosensitive drum 30 so that the projection point moves at a constant speed. The light enters the photosensitive drum 30 via the reflection mirror 45 and the toroidal lens 46, and main scanning is performed by deflection of the incident light, and sub scanning is performed by rotation of the photosensitive drum 30, and an image corresponding to the image information signal is displayed. Written to form an electrostatic latent image. The light beam scanning device 35 is directly attached to a base cover 47 of the image forming apparatus.
[0028]
The electrostatic latent image formed on the photosensitive drum 30 is developed by the developing unit 32 to form a toner image, which is transferred to the transfer paper fed by the pair of registration rollers 40 and 41 by the action of the transfer charger 33. Is done. After the transfer, the transfer paper separated from the photosensitive drum 30 is fixed by the fixing unit 42 and discharged to the paper discharge tray 43. The toner remaining on the photosensitive drum 30 after the transfer is cleaned by the cleaning unit 34.
[0029]
According to the above embodiment, the rotating shaft 5 of the deflector 1 has a hollow structure, and the hollow portion 10 is used as the optical path of the incident beam toward the imaging lens. Therefore, the entire apparatus can be reduced in size by this optical path. . Further, when the light source is not arranged on the straight line along the rotation axis, the reflection mirror must be provided on the straight line along the rotation axis. In the above embodiment, the light source is arranged on the straight line along the rotation axis 5. Therefore, it is not necessary to provide the reflection mirror, and the number of parts can be reduced and the cost can be reduced.
[0030]
Further, as shown in FIG. 3, a collimator lens or the like is provided by changing the shape of the light beam incident portion 50 of the pyramidal mirror block 3 to a collimator lens shape that converts the light beam diverging light emitted from the light source into a parallel light flux. There is no need, and the cost can be reduced. 3, the shape of the light beam incident portion of the pyramidal mirror block 3 is a collimator lens shape. However, as shown in FIG. 4, the shape of the light beam emitting portion 51 of the pyramidal mirror block 3 is used. May be in the shape of a collimator lens. 3 and 4 show the slit member 11 omitted.
[0031]
【The invention's effect】
According to the first aspect of the present invention, in order to form an image of the beam on the surface to be scanned with a required spot diameter necessary for image formation, a slit for beam shaping is provided on the optical path on the incident side of the imaging lens, In the light beam scanning apparatus, the beam after passing through the slit is incident on a pyramid mirror constituting the reflecting surface of the deflector at an angle with respect to the normal direction, and the reflected light is incident on the imaging lens. The rotation axis of the lens is hollow, the light source is arranged on a straight line along the rotation axis, the hollow part of the deflector is made part of the optical path of the incident beam that is emitted from the light source and goes to the imaging lens, and the beam is shaped the slit member is provided integrally with the rotating shaft end of Piramidarumira incident side of the deflector, since the rotary shaft slit member is provided is so as to rotate integrally with the deflector, to miniaturize the entire device Door can be. Further, since the light sources are arranged on a straight line along the rotation axis, it is not necessary to provide the reflection mirror, and the number of components can be reduced and the cost can be reduced.
[0032]
According to the invention described in claim 2, in the invention described in claim 1, since the diameter of the hollow portion is at least a required light spot diameter necessary for image formation on the surface to be scanned, A spot diameter can be formed.
[0033]
According to the invention described in claim 3, in the invention described in claim 1, the slit in which the slit for shaping the beam diameter in the main scanning direction and the beam diameter in the sub-scanning direction of the incident beam toward the imaging lens is formed. Since the member is integrally provided at the rotation shaft end of the deflector on the incident side of the pyramid mirror, a change in the beam spot diameter can be prevented, and the image quality can be improved.
[0034]
According to a fourth aspect of the present invention, in the first aspect of the invention, the inner surface of the hollow portion is subjected to a process of absorbing a light beam, so that it is possible to prevent the occurrence of ghost on the image. Can be obtained.
[0035]
According to the invention described in claim 5, in the invention described in claim 1, the shape of the light beam incident portion or the emitting portion of the pyramidal mirror block is a collimator lens shape that converts the light beam divergent light emitted from the light source into a parallel light beam. Therefore, it is not necessary to provide a collimator lens or the like, and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a deflector applicable to a light beam scanning apparatus according to the present invention.
FIG. 2 is a perspective view showing a part of the deflector.
FIG. 3 is a cross-sectional view showing another deflector applicable to the light beam scanning apparatus according to the present invention.
FIG. 4 is a sectional view showing still another deflector applicable to the light beam scanning apparatus according to the present invention.
FIG. 5 is a cross-sectional view showing an image forming apparatus using the light beam scanning apparatus according to the present invention.
FIG. 6 is a perspective view showing a deflector applicable to the light beam scanning apparatus according to the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Deflector 2 Motor 3 Pyramidal mirror block 3a Pyramidal mirror 4 Case 5 Rotating shaft 6 Large diameter part 7 Small diameter part 8 Concave part 9 Groove 10 Hollow part 11 Slit member 12 Slit 13 Protrusion part 14 Convex part
20 light sources 50 light beam incident part 51 light beam emitting part

Claims (5)

In order to form a beam on the surface to be scanned with a required spot diameter necessary for image formation, a slit for beam shaping is provided on the optical path on the incident side of the imaging lens, and the beam after passing through the slit is transmitted to the deflector. In a light beam scanning device that makes a pyramid mirror that constitutes a reflecting surface incident on the pyramid mirror while being inclined with respect to the normal direction, and that makes the reflected light incident on the imaging lens,
The rotating shaft of the deflector has a hollow structure,
Place the light source on a straight line along the rotation axis,
The hollow part of the deflector is part of the optical path of the incident beam that is emitted from the light source and directed to the imaging lens,
A light beam scanning device characterized in that a slit member for shaping a beam is integrally provided at a rotating shaft end of a deflector on the incident side of a pyramid mirror, and the rotating shaft provided with the slit member rotates integrally with the deflector. .   2. The light beam scanning apparatus according to claim 1, wherein the diameter of the hollow portion is at least equal to or larger than a required light spot diameter necessary for image formation on the surface to be scanned.   2. The light beam scanning apparatus according to claim 1, wherein the slit member shapes the beam diameter in the main scanning direction and the beam diameter in the sub scanning direction of the incident beam directed to the imaging lens.   2. The light beam scanning apparatus according to claim 1, wherein the inner surface of the hollow portion is subjected to a process of absorbing a light beam.   2. The light beam scanning device according to claim 1, wherein the shape of the light beam incident portion or the light emitting portion of the pyramidal mirror block is a collimator lens shape for converting the light beam diverging light emitted from the light source into a parallel light beam.

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