JP2005241482A - Optical deflector, and detector and method for detecting resonance frequency of deflection means in optical deflector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a detecting method for observing an operation of a deflection means by providing a detecting means separately from the actuator (deflection means). <P>SOLUTION: This method detects a resonance frequency of the deflection means 202, in an optical deflector having the deflection means 202 for reciprocation-deflecting light 203 from a light source 201, and for scanning polarized light therein. A reflection position of the scanning polarized light is measured on a light receiving element 101 or on the vicinity thereof, in every of different frequencies in an impressed driving signal to the deflection means 202, and the resonance frequency of the deflection means 202 is detected based on the different frequencies and measured information of the reflection position. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a detection apparatus or method for detecting a resonance frequency of a deflecting means for deflecting light in an optical deflector, an optical deflector using the same, and the like.

As an example of a conventional optical deflector, there is a galvanometer mirror shown in FIG. 11 (see Patent Document 1). This is a galvanometer mirror that drives a movable part with electromagnetic force. A mirror is disposed on the movable portion, and the movable portion is configured to be supported from the main body portion by the torsion bar so as to swing around the axis. In FIG. 11, reference numeral 50 denotes a silicon substrate, reference numeral 51 denotes an upper glass substrate, and reference numeral 52 denotes a lower glass substrate. Reference numeral 53 is a movable plate, reference numeral 54 is a torsion bar, reference numeral 55 is a planar coil, reference numeral 56 is a total reflection mirror, reference numeral 57 is an electrode terminal, and reference numerals 60 to 63 are permanent magnets. This optical deflector is of an electromagnetic type that is driven using a Lorentz force with the permanent magnets 60 to 63 by passing a driving current through the planar coil 55. However, the example of Patent Document 1 does not pay attention to the point that the resonance period of the movable plate 53 drifts due to temperature or the like.

On the other hand, there is an electromagnetic actuator that focuses on this point (see Patent Document 2). The resonance cycle of an electromagnetic actuator (movable part) usually drifts with temperature or with age. If a current with a preset resonance frequency is continuously supplied to a planar coil, it can move according to temperature changes and time. The example of Patent Document 2 pays attention to the problem that the deflection angle of the part is not controlled to be constant. This means that the movable part swings due to electromagnetic force, and is the same as the example of Patent Document 1 described above. The electromagnetic actuator of the example of Patent Document 2 also has a total reflection mirror in the movable part. The example of Patent Document 2 provides an electromagnetic actuator or the like that can reciprocally drive an electromagnetic actuator at a resonance period and can control the deflection angle without providing a separate detection means. As a solution to this problem, the coil is used not only for exciting the movable part but also for detecting. For this detection, an induced electromotive voltage or induced electromotive current generated in the coil is used.
JP 07-175005 (page 3-4, FIG. 1) JP 2001-305471 A (page 3-4, FIG. 1)

However, in the example of Patent Document 2, the coil that is the detection means is always used for excitation.

In view of the above problems, a detection apparatus according to the present invention is a detection apparatus that detects a resonance frequency of a deflection means in an optical deflector having a deflection means that reciprocally deflects light from a light source and scans the deflection light. Measuring means for measuring the return position of the deflected scanning light on the light receiving element or its vicinity, and detecting the resonance frequency of the deflecting means from the measurement information of the different frequency and the return position for each different frequency of the drive signal applied to It has the detection means to do.

Further, in view of the above problem, the optical deflector of the present invention has a control unit that controls the frequency of the applied drive signal and the resonance frequency to be close to each other using the detection result of the detection device and the detection unit. Features. The control unit controls the deflection unit to be held in a desired resonance state, or controls the frequency difference between the frequency of the applied drive signal and the resonance frequency to be constant.

In view of the above problems, a one-dimensional or two-dimensional image forming apparatus of the present invention includes the above-described optical deflector, and performs control by the control unit during a non-image forming period. The two-dimensional image forming apparatus of the present invention includes the above-described optical deflector, and the optical deflector includes a light receiving element and has a shielding surface that shields the deflected scanning light to the area other than the effective display area, and is a non-image. During the formation (in the non-image forming region), continuous lighting light is emitted from the light source, and control by the control means is performed.

Further, in view of the above problems, the detection method of the present invention is a detection method for detecting the resonance frequency of the deflecting means in the optical deflector having the deflecting means for reciprocally deflecting the light from the light source and scanning the deflected light, Measuring the return position of the scanning light on the light receiving element or its vicinity for each different frequency of the drive signal applied to the deflection means, and detecting the resonance frequency of the deflection means from the measurement information of the different frequency and the return position. It is characterized by. Such a detection method is implemented by, for example, installing a program for executing the above procedure in a measuring unit or a detecting unit of an optical deflector having a deflecting unit that reciprocally deflects light from a light source and scans the deflected light. Can be realized.

According to the present invention as described above, the concept is different from that of Patent Document 2, and the detection means is separated from the actuator (deflection means), so that even if there is a change in environmental temperature or the like, it is not related to it. The operation of the deflection means can be observed. Based on the detection result, for example, the operation of the deflecting unit can be controlled as desired. In this way, it is possible to realize an optical deflector that can control the operation of the deflecting means as desired without being affected by temperature changes.

(Embodiment of the Invention)
In the present invention, when detecting the resonance frequency of the deflecting means and controlling the deflecting means, for example, as described above, the deflected light deflected by the deflecting means by the reciprocating motion (oscillating motion) of the deflecting means and reciprocally scanned. Focused on using. In the present embodiment, specifically, the folding position of the scanning light on the light receiving element constituting the measuring means or the vicinity thereof is measured for each different frequency of the drive signal applied to the deflecting means, and the different frequencies The resonance frequency of the deflection means is calculated by the detection means from the relationship with the folding position, and the deflection means is controlled via the control means so that the applied frequency and the resonance frequency substantially coincide.

First, the arrangement of the optical deflector according to the present embodiment will be described. FIG. 1 is a cross-sectional view of the optical deflector according to the embodiment of the present invention in a plane including deflected light deflected by deflecting means. In FIG. 1, 201 is a light source, 202 is a deflecting means, 203 is a light beam emitted from the light source 201, 204 and 205 are light beams at a maximum deflection angle deflected by the deflecting means 202, and 206 is a light deflection center of the deflecting means 202. An axis 207 is a scanning locus of the deflected light on a plane P (a plane perpendicular to the optical deflection center axis 206) at a distance L from the deflecting means 202. The light beam 203 emitted from the light source 201 is incident on the deflecting unit 202, where it is deflected and reciprocally scanned on the plane P. As the light source 201, a light source that can be modulated such as a semiconductor laser is used.

The deflecting unit 202 is a resonant galvanometer mirror provided with a reflecting surface (see the configuration of FIG. 11), and when the deflecting unit 202 reciprocally swings, the light beam 203 is combined with the light beam 204 at the maximum deflection angle. It is deflected in the range of 205. The magnitude of this maximum deflection angle is θ. Hereinafter, for the sake of explanation, it is assumed that the reflected light beam when the deflecting means 202 is not oscillated (neutral state) coincides with the optical deflection central axis 206. A periodic drive waveform is applied to the drive means of the deflecting means 202 that reciprocates around the rotation axis.

In the present invention, the resonance frequency of the deflecting means is calculated from the relationship between the different frequency and the return position of the deflected scanning light. First, a method for measuring the return position will be described, and the resonance frequency will be calculated from the relationship. Explain why you can.

A method for measuring the return position when the deflecting means is swung (deflected) in a certain state will be described below. FIG. 2 and FIG. 3 are schematic diagrams showing, along with the trajectory, how the deflected light deflected (reflected) from the deflecting means of the optical deflector according to the embodiment of the present invention reciprocates on the light receiving element. Here, the deflected light is assumed to be light that is always lit (continuous light). In addition, the fact that the reflection angle of the light emitted from the light source changes periodically by oscillating the reflecting surface of the deflecting means is called deflection, and scanning is performed when the deflected light moves on the plane including the light receiving element. Call it. 2 and 3, reference numeral 101 denotes a light receiving element (line sensor), 102 denotes a plurality of light receiving areas, 103 denotes an area in which the deflected light is scanned, and 104 denotes an axis including a trajectory in which the deflected light is scanned on the light receiving element 101. It is.

The description starts from a state in which the deflected light on the plane including the light receiving element 101 is scanned from the left direction to the right direction (the direction of arrow A) in FIG. As the deflected light is scanned from the left to the right, the swinging (deflection) angle of the deflecting means 202 increases. As the swing angle increases, the moving speed of the scanning light decreases. The scanning is temporarily stopped when the swing angle of the deflecting means 202 is maximized (at the maximum deflection angle). Thereafter, scanning starts in the opposite direction (from right to left, in the direction of arrow B). On the light receiving element 101, the position where the deflecting means 202 becomes the maximum swing (deflection) angle and the scanning direction is reversed is called the deflection light return position, and the deflection angle at that time is called the maximum deflection angle. Here, the swing angle and the deflection angle are used in a substantially synonymous manner because they have a proportional relationship, although the coefficient varies depending on how they are defined. Further, since the deflected light has a certain size, the region 103 where the deflected light is scanned has a certain thickness as shown in FIGS.

The light receiving element 101 is divided into a plurality of light receiving regions 102. As shown in FIGS. 2 and 3, the leftmost light receiving region is assumed to be “1”, and numbers are assigned to “N” in order in the right direction. 2A, 2B, 3A, and 3B show the state of the deflected light scanning region 103 on the light receiving element 101 when the maximum deflection angle of the deflecting means 202 is different. Here, it is assumed that the positional relationship among the light source 201, the deflecting unit 202, and the light receiving element 101 is fixed.

At the maximum deflection angle in FIG. 2A, the folding position is in the leftmost light receiving area (here, the rightmost end of the deflected light scanning area 103 is the folding position), so the folding position is detected as “1”. Is done. In FIG. 2B, if the folding position is the p-th position from the left side, “p” is detected. As shown in FIG. 3A, when the folding position passes the light receiving element 101 (when it is located on the right side of the light receiving element 101), the folding position is set to “N + 1”. On the contrary, when the folding position does not reach the light receiving element 101 (when it is located on the left side of the light receiving element 101 as shown in FIG. 3B), the folding position is set to “0”. Thereby, the deflection state (change in the maximum deflection angle) of the deflecting means 202 can be detected by detecting the folding position on the light receiving element 101 or its vicinity.

As described above, the present invention uses the drive characteristics of the deflecting means 202 depending on the frequency of the applied drive signal. Therefore, the deflecting means used in this embodiment will be described here. The deflecting means used in the present embodiment is a deflector that performs resonance vibration. The deflecting unit 202 is supported by a torsion bar (twisted shaft) in one direction, and has, for example, a magnet in addition to the light reflecting surface. By reversing the polarity of the electromagnetic force generated by the electromagnetic force generating means (coil) (not shown) that is arranged apart from the deflecting means, the magnetic flux acts on the deflecting means, and the deflecting means is centered on the torsion axis. Reciprocate. This deflecting means is driven by resonance vibration inherent to the deflector. That is, at the resonance frequency, the oscillation force (torsion angle) is maximized by the electromagnetic force generated from the electromagnetic force generating means, and resonance oscillation occurs. The resonance vibration is characterized in that a large swing angle can be obtained with a small applied energy. A deflecting means that performs resonant vibration is called a resonant deflector.

FIG. 4 shows an example of frequency characteristics of the resonant deflector. The horizontal axis represents the frequency for oscillating the deflection means (frequency of the applied drive signal for oscillating the deflection means), and the vertical axis in FIG. 4A represents the maximum inclination (maximum oscillation) of the deflection means. Angle), the vertical axis of FIG. 4B shows the phase difference of the deflection angle change of the deflection means with respect to the synchronization signal of the applied drive signal. As shown in FIG. 4A, the maximum swing angle of the deflecting unit varies depending on the frequency of the applied signal. In the present specification, the frequency of the applied signal that provides the maximum swing angle is referred to as the resonance frequency fc of the resonance deflector. As shown in FIG. 4A, in this example, the maximum swing angle has a substantially line-symmetric (left-right symmetric) characteristic around the resonance frequency fc. In this embodiment, paying attention to this line-symmetric characteristic, the resonance frequency is calculated from the relationship between the different frequencies and the return position of the deflected scanning light (corresponding to the maximum swing angle). It is.

Also, as shown in FIG. 4B, when the relationship between the frequency of the applied signal and the resonance frequency changes, the timing of the swinging (deflection) of the deflecting means changes greatly. That is, the timing at which the maximum swing (deflection) angle is easily changed. This is a serious problem when the maximum swing angle is detected by an optical sensor that detects the passage timing of the scanning light. Therefore, this detection method is not adopted in the present invention.

On the other hand, if the positional relationship among the light source 201, the deflecting unit 202, and the light receiving element 101 is fixed, the return position of the deflected light is related to the maximum swing angle of the deflecting unit. Therefore, by detecting the folding position on the light receiving element 101 at the frequency of a certain applied signal, information on the maximum deflection angle of the deflecting means relative to the frequency of other applied signals can be obtained. In the present invention, a detection method using this principle is adopted.

In this example, the rightmost end of the scanning region 103 for deflected light is the folding position, but it is different from the folding position of the center point of the actual deflected light. However, since the magnitude of the deflected light is always the same, the relative position of the folding for each frequency of the applied signal does not change, and there is no problem in control.

Next, a method for calculating the resonance frequency based on the above description will be described. The applied frequency of the deflecting means is gradually swept from a low frequency to a high frequency (or vice versa), and the return position at each frequency is measured as described above. At this time, the frequency range to be swept needs to include a frequency range in which the folding position moves on the light receiving element in the right direction and a frequency range in which the return position moves in the left direction. FIG. 5 shows an example in which the folding position is detected by the light receiving element 101 by changing the applied frequency of the deflecting means 202 in this way. The horizontal axis is the applied frequency, and the vertical axis is the folding position. Here, the resonance frequency fc is an axis frequency at which the characteristic of FIG.

Since the characteristic of FIG. 4A is line symmetric about the resonance frequency fc, the characteristic of FIG. 5 is also line symmetric about the resonance frequency fc, and the same folding position (here, the center of the light receiving element 101 in FIG. 5). The frequency obtained by averaging the two frequencies f1 and f2 at which the position N / 2 + 1/2 of the light receiving region 102 becomes) can be calculated as the resonance frequency fc (= (f1 + f2) / 2). Of course, if the characteristics of the deflecting means are asymmetric with respect to the resonance frequency and the ratio of the asymmetry is known, the average is an average weighted by the ratio. Such characteristics may be examined in advance, stored in the detection or calculation means, and the calculation procedure may be programmed.

Based on the calculated resonance frequency, the applied frequency to the deflecting means 202 is set to the resonance frequency, so that the deflecting means is swung (deflected) at the maximum swing (deflection) angle. Or you may give the frequency of the applied signal which shifted arbitrary frequency from the resonant frequency. When controlling the difference between the drive frequency and the resonance frequency to a constant value in this way, the frequency deviation direction can be detected by detecting the change in amplitude when the frequency deviates from the desired frequency. Control becomes easy.

As described above, according to the present embodiment, even when the resonance frequency of the deflecting means changes due to the environment or the like, the resonance frequency can be easily detected, and an arbitrary deflection characteristic can be obtained. In the present embodiment, detection can be performed without being affected by changes in the characteristics of the detection unit due to changes in the environment or the like by using a method in which deflected light is detected by a light receiving element and the return position is directly measured.

In the above configuration, the light receiving element 101 needs to be arranged away from the light deflection center axis 206. This is because when the light receiving element is arranged at the center of light deflection, the bottom part of FIG. 4A is detected, and the width required for the light receiving element is increased and the detection error is increased. . According to this embodiment, detection accuracy can be improved because detection can be performed in a region where the change rate of the maximum swing angle with respect to the frequency of the applied signal is large.

Further, if this embodiment is used, it is not necessary for all the deflected light to enter the light receiving element 101, and it is only necessary to detect the position of the return in the sweep region of a certain frequency. Therefore, the width in the scanning direction of the light receiving element 101 of the present embodiment can be made smaller than the scanning width by the deflected light on the plane where the light receiving element is arranged. That is, a small light receiving element can be used, and a low-cost optical deflector can be realized. In addition, in this embodiment, since the relative position of folding on the light receiving element 101 is used, there is no restriction on the accuracy of the mounting position. In addition, since it is only necessary to fix the positional relationship among the light source 201, the deflecting unit 202, and the light receiving element 101 during the measurement, even if any one of them shifts due to some reason, the relationship is fixed in a shifted state. Can be used without problems.

The light receiving element 101 used in this embodiment needs to be a light receiving element 101 that can detect the return position of the deflected light as position information. In the present embodiment, a line sensor (image sensor) composed of a plurality of light receiving regions 105 is used as the light receiving element 101. In such a configuration, it is necessary to include a light receiving element that is a photoelectric conversion unit, an accumulation unit for photoelectrically converted charges, and a transfer unit for accumulated charges.

In this case, the amount of the deflected light can be detected for each of the plurality of light receiving regions, so that the position of the deflected light on the light receiving element can be easily specified. At this time, it is not necessary to transfer the accumulated charge at a high speed in accordance with the scanning speed, and a slower transfer can be performed after the light receiving element 101 is scanned once or more. Therefore, it is preferable because the return position can be detected even when the scanning speed v on the light receiving surface 101 is increased (for example, even if one cycle of the applied drive waveform is shortened).

If this light receiving element is used, the light amount distribution on the light receiving element 101 of the scanning light is accumulated as electric charges, and is output as position information for each of the plurality of light receiving regions 105. Therefore, even if the scanning (deflection) timing at which the maximum swing (deflection) angle is changed, it is not necessary to detect in synchronization with the scanning (deflection) timing, and the return position can be detected easily and accurately. be able to.

In the present embodiment, a line sensor constituted by a plurality of light receiving regions 105 is described. However, a light receiving region configuration in which the light receiving regions are arranged vertically and horizontally as a light receiving region arranged two-dimensionally, and the light receiving region is formed in a honeycomb shape. , A configuration in which the columns and rows of the light-receiving areas are nested in the scanning trajectory direction or the direction intersecting the trajectory, or the light-receiving areas are circular, parallelogram, triangular, rhombus, trapezoidal, etc. A configuration having a polygonal shape can also be used.

In the present embodiment, the measurement unit uses the deflection scanning light on the light receiving element or the vicinity thereof as continuous lighting light and measures the return position of the deflection scanning light by the light receiving element. In this case, instead of continuous lighting, the lighting timing is shifted little by little, the light source is turned on at a certain time interval, and the position at the end of the light spot is found from a plurality of deflection scans, and the light is turned back at a certain frequency. A method of measuring the position can also be adopted. This eliminates the need to use continuous light.

Hereinafter, more specific examples will be described.
(First embodiment)
In this embodiment, a resonance type optical deflector is used as a one-dimensional deflecting unit, and the deflected light is scanned two-dimensionally on the surface of the photosensitive member by scanning the deflected light in the longitudinal direction of the rotating cylindrical photosensitive member. The present invention relates to an optical deflector applied as an exposure device for a photoreceptor of a so-called electrophotographic image forming apparatus that scans to obtain an electrostatic latent image. The other points are almost the same as the above embodiment.

FIG. 6 is a schematic perspective view showing the apparatus configuration of the present embodiment. In FIG. 6, the light receiving element 101, the light source 201, the deflecting means 202, the light beam 203 emitted from the light source 201, the light beams 204 and 205 at the maximum deflection angle at the resonance frequency fc, the photosensitive drum 220, and scanning on the photosensitive drum. An axis 221 including a locus and a reflection mirror 223 that guides deflected light to the light receiving element 101 are illustrated. Here, part of the deflected light deflected by the deflecting means 202 is reflected by the reflecting mirror 223 and is incident on the light receiving element 101. As the light receiving element, a 1/7 inch CMOS image sensor (CIF specification, monochrome sensor) is used. The light source 201 directly modulates using a semiconductor laser (wavelength λ = 780 nm). The deflecting means 202 uses a resonance type optical deflector as shown in FIG. 11, and the resonance frequency is around 8 kHz (Q value 1000).

  FIG. 7 is a block diagram schematically illustrating the control system for the optical deflector according to the first embodiment. In FIG. 7, a light beam 208 formed by deflecting a light beam 203 from a light source 201 by a deflecting unit 202, a modulation signal generating unit 301 of a light source 201, a modulation signal 305 of a light source 201, and a light receiving element 101 constituting a measuring unit. Resonance frequency calculation means 302 (detection frequency calculation method is included as software), which is a detection means for calculating the resonance frequency based on the frequency of the detection signal 306, the detection signal 306 and the drive signal 309, and calculation of the resonance frequency A signal 307, a control signal generating means 303 as control means, a control signal 308 of the deflecting means 202, a driving means 304 of the deflecting means 202, and a driving signal 309 of the deflecting means 202 are shown.

FIG. 8 is a flowchart relating to the calculation of the resonance frequency and the control of the drive frequency in this embodiment. When the power source of the image forming apparatus is turned on, control is started (S101). First, the light source 201 is completely turned on (S102) by the modulation signal generation unit 301 of the light source 201. Next, the frequency of the applied signal (control signal 308 of the deflecting means 202) is set by the control signal generating means 303 to a preset sweep start frequency (here, 7.9 kHz) (S104). Next, the return position of the deflected light at that frequency is detected using the light receiving element 101 (S105). Thereafter, the control signal generating means 303 changes the frequency (here, 1 Hz step) by a preset sweep step (S104). The frequency change and the detection of the return position are repeated (S104, S105) until the preset sweep end frequency (here, 8.1 kHz) is reached (S103). After exiting the loop, the light source 201 is completely turned on by the modulation signal generator 301 of the light source 201 (S106).

A resonance frequency fc is calculated by the resonance frequency calculation means 302 from the frequency of the applied signal and the information on the folding position obtained from the light receiving element 101 (for example, the relationship as shown in FIG. 5) (S107). Based on the calculation result, the control signal generator 303 changes the frequency of the applied signal to the deflector 202 (control signal 308 of the deflector 202) to the resonance frequency fc (S108). Thereafter, the process proceeds to the next control (S109). Thus, the photoconductor starts rotating, and scanning is performed while modulating the light in the longitudinal direction of the photoconductor (for example, while turning on and off), so that the present optical deflector can be used as an exposure device for the photoconductor. Can do.

According to this embodiment, the scanning characteristic of the deflecting unit 202 can be maintained in a desired state, and a high-quality image forming apparatus can be realized. In addition, the above control can be performed at any time to detect and correct a change in scanning characteristics over time.

(Second embodiment)
The optical deflector according to the present embodiment relates to an optical deflector that projects the deflected light two-dimensionally onto the projection surface. Others are almost the same as the first embodiment. FIG. 9 is a perspective view schematically showing an optical deflector according to the present embodiment.

In FIG. 9, the light receiving element 101, the light source 201, the deflecting means 202, the emitted light 203, the deflected lights 204 and 205, the scanning line 210, the second deflecting means 211, the deflected light 212, the shielding portion 213, the scanning region 214, and the scanning line. The locus 215 and the projection plane 220 are shown. The apparatus in FIG. 9 is a laser display device that displays an image on the projection surface 220 by two-dimensionally scanning light 203 from a light source 201 that is a laser by means of a deflecting unit 202 and a second deflecting unit 211.

The light receiving element 101 uses a 1/7 inch CMOS image sensor (CIF specification, monochrome sensor). The light source 201 directly modulates using a semiconductor laser (λ = 630 nm). The deflecting means 202 uses a resonance type optical deflector as shown in FIG. 11, and the resonance frequency is around 20 kHz (Q value 2000). In this embodiment, the sweep start frequency described in the first embodiment is 19.9 kHz, the sweep step is 1 Hz step, and the sweep end frequency is 20.1 kHz.

FIG. 10 is a schematic diagram showing an effective display area, a light receiving area, and horizontal scanning / vertical scanning. FIG. 10 shows a scanning line locus 215 within the scanning region 214 on the shielding surface 213. In the effective display area 216, the shielding surface 213 does not exist, and the deflected light forms an image on the projection surface 220. In an area other than the effective display area 216, the deflected light is shielded by the shielding surface 213 so that the deflected light does not reach the projection surface 220.

In the control according to the present invention, the resonance frequency is detected by changing the frequency applied to the deflecting means 202, and noise will be generated if the deflected light appears on the projection plane 220 during the detection. The present embodiment is characterized in that the shielding surface 213 is used in order not to generate this noise. The light receiving element 101 is arranged in a portion other than the effective display area 216 on the shielding surface 213, and the deflected light on the light receiving element 101 is made continuous light, and the deflected light in the effective display area 216 is turned off to project at the time of detection. No light beam for detection appears on the surface 220. Therefore, if this embodiment is used, the detection can be controlled without displaying an image on the projection plane 220 (without displaying the noise of the deflected light due to the detection) when the apparatus is activated.

In FIG. 10, when scanning is started from the scanning point S1, the deflected light 212 moves in the horizontal scanning direction X from the forward path to the backward path, and is gradually scanned from the upper part to the lower part in the vertical scanning direction Y. The deflected light scanned up to the scanning point S2 is returned again to the scanning point S1, and the same scanning is repeated. The light receiving element 101 arranged on the scanning line 215 is arranged so that the deflected light 212 passes.

It is a schematic diagram showing a mode that the deflection light deflected (reflected) from the deflection | deviation means of the optical deflector which concerns on embodiment of this invention reciprocates on a light receiving element with the locus | trajectory. It is a figure showing the mode on a light receiving element in case the largest deflection angles of a deflection | deviation means differ. It is a figure showing the mode on a light receiving element in case the largest deflection angles of a deflection | deviation means differ. It is a graph which shows an example of the frequency characteristic of a resonance type deflector. It is a graph which shows an example of the measurement result when changing the application frequency of a deflection | deviation means in embodiment of this invention, and detecting a folding position by a light receiving element. It is a typical perspective view which shows the optical deflector of the 1st Example which projects a deflected light to one dimension. It is a block diagram which shows the control system of a 1st Example. It is a figure which shows the control flow of a 1st Example. It is a typical perspective view which shows the optical deflector of the 2nd Example which projects a deflection | deviation light in two dimensions. It is a schematic diagram which shows an effective display area, a light receiving area, and horizontal scanning / vertical scanning. It is a figure which shows the optical deflector of a prior art example.

Explanation of symbols

101 Light receiving element (measuring means)
201 light source 202 deflecting unit 203 light beam 208 emitted from light source deflected light beam 301 modulation signal generating unit 302 of light source resonance frequency calculating unit (detecting unit)
303 Control signal generating means (control means)
304 Deflection means drive means 305 Light source modulation signal 306 Detection signal 307 from light receiving element Resonance frequency calculation signal 308 Deflection means control signal 309 Deflection means drive signal

Claims (12)

A detection device for detecting a resonance frequency of a deflecting unit in an optical deflector having a deflecting unit that reciprocally deflects light from a light source and scans the deflected light, and receives light at different frequencies of a drive signal applied to the deflecting unit. A detecting device comprising: measuring means for measuring the return position of the deflected scanning light on the element or its vicinity; and detecting means for detecting the resonance frequency of the deflecting means from the measurement information of the different frequency and the return position. . The detection device according to claim 1, wherein the measuring unit uses the deflection scanning light on the light receiving element or the vicinity thereof as continuous lighting light, and measures the return position of the deflection scanning light by the light receiving element. 3. The detection unit according to claim 1, wherein the detection unit detects a plurality of frequencies corresponding to the deflected scanning light that is folded back at the same position in the scanning direction on the light receiving element, and detects a resonance frequency based on the plurality of frequencies. Detection device. The detection device according to claim 3, wherein the detection unit calculates a resonance frequency by averaging the plurality of detected frequencies. The detection device according to claim 1, wherein the light receiving element is provided so that the deflection scanning light detected by the light receiving element does not include the deflection scanning light at the deflection center position of the deflection unit. The light receiving element is composed of a plurality of light receiving regions, means for converting light incident on the light receiving region into electric charges, means for accumulating the generated charges for each region for a certain period, and the accumulated electric charges in the regions. The detection device according to claim 1, wherein the detection device is a light receiving element having means for transferring each time. 7. The optical deflector comprising: the detection device according to claim 1; and a control unit that controls the frequency of the applied drive signal to be close to the resonance frequency using a detection result of the detection unit. . The optical deflector according to claim 7, wherein the control unit controls the deflection unit to be held in a desired resonance state. The optical deflector according to claim 7, wherein the control unit controls the frequency difference between the frequency of the applied drive signal and the resonance frequency to be kept constant. An image forming apparatus comprising the optical deflector according to claim 7, wherein the control unit performs control in a non-image forming area. An optical deflector according to claim 7, wherein the optical deflector includes a light receiving element, has a shielding surface that shields deflected scanning light outside the effective display area, and is used in a non-image forming area. A two-dimensional image forming apparatus characterized in that continuous lighting light is emitted from a light source and controlled by the control means. A detection method for detecting a resonance frequency of a deflecting unit in an optical deflector having a deflecting unit that reciprocally deflects light from a light source and scans the deflected light, and receives light at different frequencies of a drive signal applied to the deflecting unit. A detection method, comprising: measuring a folding position of scanning light on an element or the vicinity thereof; and detecting a resonance frequency of a deflecting unit from the measurement information of the different frequency and the folding position.

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