JP2010271644A - Optical scanner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical scanner in which the deterioration of an image due to temperature variation is suppressed and an SOS (Start Of Scan) synchronization signal is accurately generated. <P>SOLUTION: The optical scanner 10a is used for an image forming apparatus including a photoreceptor drum. A light emission element 12Y emits a beam BY. A deflector 20 deflects the beam BY. A scanning lens 22 images the beam BY deflected with the deflector 20 onto the photoreceptor drum. A sensor 32 detects a beam BYa which does not pass through the scanning lens 22 and a beam BYb which passes through the point P1 on the scanning lens 22. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical scanning device, and more particularly to an optical scanning device that irradiates a photoconductor with a beam to form an electrostatic ray image on the photoconductor.

  As a conventional optical scanning device, for example, an optical scanning device of an image forming apparatus described in Patent Document 1 is known. The optical scanning device will be described below with reference to the drawings. FIG. 10 is a configuration diagram of the optical scanning device 500 described in Patent Document 1. In FIG.

  The optical scanning device 500 includes a light source 502, a deflector 504, a scanning lens 506, mirrors 508a and 508b, and sensors 510a and 510b. The optical scanning device 500 is a device that irradiates the photosensitive drum 550 with the beam B and forms an electrostatic ray image on the peripheral surface of the photosensitive drum 550.

  The light source 502 emits a beam B. The deflector 504 includes a polygon mirror having a plurality of reflecting surfaces, and deflects the beam B from the lower side to the upper side in FIG. The scanning lens 506 is provided on the right side of the deflector 504 and corrects the aberration of the deflected beam B. The beam B that has passed through the scanning lens 506 is scanned on the photosensitive drum 550.

  The mirror 508a reflects and guides the beam B passing through the vicinity of the upstream end of the scanning lens 506 in the scanning direction to the sensor 510a. The mirror 508b reflects and guides the beam B passing through the vicinity of the downstream end of the scanning lens 506 in the scanning direction to the sensor 510b. The sensors 510a and 510b detect the beam B reflected by the mirrors 508a and 508b, respectively.

  In the optical scanning device 500 as described above, the shape / refractive index of the scanning lens 506 changes due to temperature changes. This causes a magnification error in the main scanning direction of the scanning lens 506, making it difficult to obtain a high-quality image. Here, when the shape / refractive index of the scanning lens 506 changes, the time required for the beam B to scan the scanning lens 506 varies. Therefore, in the optical scanning device 500, a control unit (not shown) measures the time difference between signals output from the sensors 510a and 510b. The control unit corrects the magnification error in the main scanning direction based on the time difference. Thereby, the optical scanning device 500 suppresses the occurrence of image quality degradation.

  However, as described below, the optical scanning device 500 has a problem that it is difficult to accurately generate an SOS (Start Of Scan) synchronization signal for determining the timing of starting writing to the photosensitive drum 550. Have In the optical scanning device 500, for example, it is conceivable to generate the SOS synchronization signal using the output of the sensor 510a. However, the beam B incident on the sensor 510 a is a beam that has passed through the scanning lens 506. Therefore, when the shape / refractive index of the scanning lens 506 is changed due to a temperature change, the timing at which the beam B is incident on the sensor 510a deviates from the original timing. As a result, the timing at which the pulse of the SOS synchronization signal rises also shifts.

  In the optical scanning device 500, it is conceivable that the control unit corrects the SOS synchronization signal using the time difference between the signals output from the sensors 510a and 510b. However, in this case, since it is necessary to cause the control unit to perform calculation for correction, the operation of the control unit becomes complicated.

JP 2002-29085 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an optical scanning device that can suppress degradation of image quality due to temperature change and can accurately generate an SOS synchronization signal.

  An optical scanning device according to an aspect of the present invention is an optical scanning device used in an image forming apparatus including a photosensitive member, and a first light source that emits a first beam, and the first beam is deflected. Deflecting means, a first scanning optical element for imaging the first beam deflected by the deflecting means on the photoconductor, the first beam not passing through the first scanning optical element, And first detection means for detecting the first beam that has passed through a first predetermined position of the first scanning optical element.

  According to the present invention, it is possible to suppress degradation of image quality due to a temperature change and to accurately generate an SOS synchronization signal.

1 is a configuration diagram of an optical scanning device according to a first embodiment. 1 is a configuration diagram of an optical scanning device according to a first embodiment. FIG. 2 is a waveform diagram of a control signal output from a sensor of the optical scanning device in FIG. 1. FIG. 4 is a diagram showing one line of an electrostatic latent image formed on a photosensitive drum. It is a block diagram of the optical scanning device which concerns on a 1st modification. It is a figure when the mirror and sensor of the optical scanning device concerning the 1st modification are planarly viewed from the y-axis direction. It is a block diagram of the optical scanning device which concerns on a 2nd modification. It is a block diagram of the optical scanning device which concerns on 2nd Embodiment. It is a figure for demonstrating that a color shift can be suppressed in the optical scanning device which concerns on 2nd Embodiment. 1 is a configuration diagram of an optical scanning device described in Patent Document 1. FIG.

  Hereinafter, an optical scanning device according to an embodiment of the present invention will be described with reference to the drawings.

(First embodiment)
The optical scanning device according to the first embodiment will be described below with reference to the drawings. 1 and 2 are configuration diagrams of the optical scanning device 10a according to the first embodiment. 1 and 2, the main scanning direction (referred to as the scanning direction in FIG. 1) is defined as the y-axis direction, and the sub-scanning direction is defined as the z-axis direction. A direction orthogonal to the y-axis direction and the z-axis direction is defined as an x-axis direction. Therefore, FIG. 1 is a plan view of the optical scanning device 10a from the z-axis direction, and FIG. 2 is a plan view of the optical scanning device 10a from the y-axis direction.

  As shown in FIGS. 1 and 2, the optical scanning device 10a includes a housing 11, a light emitting element 12 (12Y, 12M, 12C, 12K), a collimator lens 14 (14Y, 14M, 14C, 14K), and a mirror 16 (16M). , 16C, 16K), cylindrical lens 18, deflector 20, scanning lenses 22, 24, 26 (26Y, 26M, 26C, 26K), mirrors 28, 30, sensor 32, mirror 34 (34Y, 34M, 34C, 34K). , 36 (36Y, 36M, 36C), 38C and dustproof glass 40 (40Y, 40M, 40C, 40K). The optical scanning device 10a is used in an image forming apparatus provided with a photosensitive drum 50 (50Y, 50M, 50C, 50K), and each of the photosensitive drum 50 (50Y, 50M, 50C, 50K) shown in FIG. Then, the beam B (BY, BM, BC, BK) is irradiated to form an electrostatic line image on the peripheral surface of the photosensitive drum 50.

  The housing 11 includes a light emitting element 12, a collimator lens 14, a mirror 16, a cylindrical lens 18, a deflector 20, scanning lenses 22, 24 and 26, mirrors 28 and 30, a sensor 32, mirrors 34, 36, and 38C, and a dustproof glass 40. Is stored.

  The light emitting element 12 is constituted by a laser diode, for example, and emits a beam B. The light emitting elements 12Y, 12M, 12C, and 12K form one light source. The collimator lens 14 shapes the beam B emitted from the light emitting element 12 into substantially parallel light in the xy plane.

  As shown in FIG. 1, the mirror 16M reflects the beam BM that has passed through the collimator lens 14M toward the deflector 20, and combines it with the beam BY. Thereby, the beam BY and the beam BM overlap when viewed in plan from the z-axis direction. As shown in FIG. 1, the mirror 16C reflects the beam BC that has passed through the collimator lens 14C toward the deflector 20, and combines it with the beams BY and BM. Thereby, the beam BC and the beams BY and BM overlap when viewed in plan from the z-axis direction. As shown in FIG. 1, the mirror 16K reflects the beam BK that has passed through the collimator lens 14K toward the deflector 20, and combines it with the beams BY, BM, and BC. Thereby, the beam BK and the beams BY, BM, BC overlap when viewed in plan from the z-axis direction. However, the beams BY, BM, BC, and BK are slightly shifted in the z-axis direction when viewed in plan from the y-axis direction. The cylindrical lens 18 condenses the beams BY, BM, BC, and BK in the z-axis direction.

  As shown in FIG. 1, the deflector 20 includes a polygon mirror having a plurality of reflecting surfaces, and a motor (not shown) that rotates the polygon mirror clockwise. The deflector 20 deflects the beams BY, BM, BC, and BK.

  The scanning lenses 22, 24, and 26 are lenses through which the beam B deflected by the deflector 20 passes, and form an image of the beam B on the photosensitive drum 50. Thereby, the beam B is scanned at a constant speed toward the positive side in the y-axis direction, as shown in FIG. Further, as shown in FIGS. 1 and 2, the scanning lenses 22, 24, and 26 are provided on the positive side in the x-axis direction with respect to the deflector 20 when viewed in plan from the z-axis direction, and y It has a longitudinal direction in the axial direction.

  As shown in FIG. 2, the mirrors 34Y and 36Y reflect the beam BY that has passed through the scanning lenses 22 and 24 and guide it to the photosensitive drum 50Y. The scanning lens 26Y is provided between the mirrors 34Y and 36Y. The mirrors 34M and 36M reflect the beam BM that has passed through the scanning lenses 22 and 24 and guide it to the photosensitive drum 50M. The scanning lens 26M is provided between the mirrors 34M and 36M. The mirrors 34C, 36C, and 38C reflect the beam BC that has passed through the scanning lenses 22 and 24 and guide it to the photosensitive drum 50C. The scanning lens 26C is provided between the mirrors 36C and 38C. The mirror 34K reflects the beam BK that has passed through the scanning lenses 22 and 24 and guides it to the photosensitive drum 50K. The scanning lens 26K is provided in front of the mirror 34K.

  The dustproof glass 40 is provided on the bottom surface (surface on the negative side in the z-axis direction) of the housing 11 and prevents dust and the like from entering the housing 11. The beam B passes through the dust-proof glass 40 and forms an image on the peripheral surface of the photosensitive drum 50.

  The photosensitive drum 50 is rotationally driven at a predetermined speed. A two-dimensional electrostatic latent image is formed by the main scanning by the beam B and the sub scanning by the rotation of the photosensitive drum 50.

  The mirror 28 reflects the beam BY (hereinafter referred to as the beam BYa) that has been deflected by the deflector 20 and has not passed through the scanning lenses 22 and 24, and guides it to the sensor 32. Therefore, as shown in FIG. 1, the mirror 28 is provided on the negative side of the scanning lens 22 in the y-axis direction. That is, the mirror 28 is provided on the upstream side in the scanning direction of the beam B with respect to the scanning lens 22. The sensor 32 detects the beam BYa that passes through the negative direction side in the y-axis direction from the scanning lenses 22, 24 without passing through the scanning lenses 22, 24 and is reflected by the mirror 28. Is generated.

  The mirror 30 reflects the beam BY deflected by the deflector 20 and passes through the point P1 of the scanning lens 22 and the scanning lens 24 (hereinafter referred to as a beam BYb) and guides it to the sensor 32. The point P1 is a point located on the negative side in the y-axis direction (upstream in the scanning direction of the beam BY) from the image forming area A1 of the scanning lens 22. The image forming area A1 is an area corresponding to an area where an electrostatic ray image is formed on the photosensitive drum 50Y in the scanning lens 22. That is, the image forming area A1 is an area through which the beam BY passes through the scanning lens 22 while an electrostatic ray image is formed on the photosensitive drum 50Y. The sensor 32 generates a control signal by detecting the point BY of the scanning lens 22 and the beam BYb that has passed through the scanning lens 24.

  Here, the control signal will be described with reference to the drawings. FIG. 3 is a waveform diagram of a control signal output from the sensor 32 of the optical scanning device 10a. FIG. 4 is a diagram showing one line of the electrostatic latent image formed on the photosensitive drum 50. FIG. 4 shows an electrostatic latent image when the operation of the image forming apparatus starts, when the temperature rises, and after correction.

  The control signal generated by the sensor 32 includes two pulses Q1 and Q2, as shown in FIG. The pulse Q1 is generated when the beam BYa enters the sensor 32. The pulse Q2 is generated when the beam BYb is incident on the sensor 32.

  Here, in the optical scanning device 10a, when the temperature inside the device rises due to use, the scanning lenses 22, 24, and 26 expand. As a result, as shown in FIG. 4, an error occurs in the magnification in the main scanning direction of the scanning lenses 22, 24, and 26 (hereinafter referred to as magnification error) (the magnification in the main scanning direction increases). Since the beam BYa does not pass through the scanning lenses 22, 24, and 26, the timing at which the beam BYa enters the sensor 32 hardly changes as shown in FIG. On the other hand, since the beam BYb passes through the scanning lenses 22, 24 and 26, the timing at which the beam BYb enters the sensor 32 is delayed as shown in FIG. As a result, as shown in FIG. 3, the interval t2 between the pulse Q1 and the pulse Q2 when the temperature rises becomes larger than the interval t1 between the pulse Q1 and the pulse Q2 at the start of operation.

  Therefore, a control unit (not shown) of the image forming apparatus measures the intervals t1 and t2 between the pulse Q1 and the pulse Q2 of the control signal, and calculates the magnification error of the scanning lenses 22, 24, and 26. Then, as shown in FIG. 4, the control unit emits light so that an electrostatic latent image is formed between the same writing start position and writing end position even when the temperature rises. The operation of the element 12 is corrected.

  The control signal pulse Q1 is also used as an SOS synchronization signal. Specifically, the control unit detects the rising edge of the pulse Q1 of the control signal, and starts writing the electrostatic ray image after a predetermined time has elapsed.

(effect)
According to the optical scanning device 10a, as will be described below with reference to the drawings, it is possible to suppress deterioration in image quality due to temperature changes. More specifically, in the optical scanning device 10a, the sensor 32 detects the beams BYa and BYb. Since the beam BYa does not pass through the scanning lenses 22 and 24, the timing at which the beam BYa enters the sensor 32 hardly varies as shown in FIG. 3 even if the temperature rises. Therefore, the timing at which the pulse Q1 generated by the beam BYa rises hardly changes. On the other hand, the timing at which the beam BYb enters the sensor 32 is delayed as shown in FIG. 3 when the temperature rises because the beam BYb passes through the scanning lenses 22 and 24. Therefore, the timing at which the pulse Q2 generated by the beam BYb rises is also delayed. Accordingly, in the optical scanning device 10a, when the temperature rises, as shown in FIG. 3, the interval t2 between the pulse Q1 and the pulse Q2 becomes larger than the interval t1 between the pulse Q1 and the pulse Q2 at the start of operation.

  Therefore, the optical scanning device 10a calculates magnification errors occurring in the scanning lenses 22, 24, and 26 by measuring the intervals t1 and t2 between the pulses Q1 and Q2. The control unit corrects the operation of the light emitting element 12 using the magnification error. Therefore, according to the optical scanning device 10a, it is possible to suppress deterioration in image quality due to temperature changes.

  Further, according to the optical scanning device 10a, as described below, the SOS synchronization signal can be generated accurately. More specifically, in the conventional optical scanning device 500 shown in FIG. 10, for example, it is conceivable to generate an SOS synchronization signal using the output of the sensor 510a. However, the beam B incident on the sensor 510 a is a beam that has passed through the scanning lens 506. Therefore, when the shape / refractive index of the scanning lens 506 is changed due to temperature change, the timing at which the beam B is incident on the sensor 510a deviates from the original timing. As a result, the timing at which the pulse of the SOS synchronization signal rises also shifts.

  On the other hand, in the optical scanning device 10a, the pulse Q1 generated by the beam BYa is used as the SOS synchronization signal. The beam BYa does not pass through the scanning lenses 22, 24, and 26. Therefore, even when the scanning lenses 22, 24, and 26 expand due to temperature changes, the timing at which the beam BYa enters the sensor 32 does not change, and the timing at which the pulse Q1 rises does not change. As a result, the optical scanning device 10a can generate the SOS synchronization signal more accurately than the optical scanning device 500.

  Further, the optical scanning device 10a can be downsized as described below. More specifically, the beam BYa passes through the negative side of the scanning lens 22 in the y-axis direction, and the beam BYb passes through a point P1 on the negative side of the image forming area A1 of the scanning lens 22 in the y-axis direction. ing. Therefore, the beams BYa and BYb pass through positions relatively close to each other. Therefore, the optical scanning device 10a can be reduced in size as compared with the optical scanning device in which the beams BYa and BYb pass apart.

(Modification)
The optical scanning device according to the first modification will be described below with reference to the drawings. FIG. 5 is a configuration diagram of an optical scanning device 10b according to the first modification. FIG. 6 is a diagram when the mirrors 28 and 30 and the sensor 32 of the optical scanning device 10b according to the first modification are viewed in plan from the y-axis direction.

  In the optical scanning device 10a, the beam B reflected by the mirrors 28 and 30 is the beam BY emitted from the same light emitting element 12Y. On the other hand, in the optical scanning device 10b, the beam B reflected by the mirror 28 and the beam B reflected by the mirror 30 are beams emitted by different light emitting elements 12. Specifically, as shown in FIGS. 5 and 6, the beam B reflected by the mirror 28 is a beam BK emitted by the light emitting element 12K. Hereinafter, the beam BK reflected by the mirror 28 is referred to as a beam BKa. The beam B reflected by the mirror 30 is the beam BY emitted from the light emitting element 12Y. Hereinafter, the beam BY reflected by the mirror 30 is referred to as a beam BYb.

  Here, as shown in FIG. 6, the beam BY and the beam BK pass through different positions in the z-axis direction when viewed in plan from the y-axis direction. Therefore, as shown in FIG. 5, the beam BYb and the beam BKa can be overlapped when viewed in plan from the z-axis direction. Thereby, when viewed in plan from the z-axis direction, the area of the optical scanning device 10b can be made smaller than the area of the optical scanning device 10a.

  Next, an optical scanning device according to a second modification will be described with reference to the drawings. FIG. 7 is a configuration diagram of an optical scanning device 10c according to the second modification.

  The optical scanning device 10c is different from the optical scanning device 10b in that a mirror 52 is provided. The mirror 52 reflects the beam BY deflected by the deflector 20 and passes through the point P2 of the scanning lens 22 and the scanning lens 24 (hereinafter referred to as a beam BYc) and guides it to the sensor 32. The point P2 is a point located on the positive side in the y-axis direction from the image forming area A1 of the scanning lens 22. The sensor 32 generates a control signal by detecting the beam BYc.

  In the optical scanning device 10c, the sensor 32 detects a beam BY (hereinafter referred to as a beam BYb) reflected by the mirror 30, a beam BYc, and a beam BK (hereinafter referred to as a beam BKa) reflected by the mirror 28. is doing. The beam BYb passes through a point P1 located at the end of the scanning lens 22 on the negative side in the y-axis direction, and the beam BYc is a point P2 located at the end of the scanning lens 22 on the positive side in the y-axis direction. Is going through. Therefore, the optical scanning device 10c can calculate the magnification error more accurately than the optical scanning devices 10a and 10b by calculating the magnification error using these beams BYa and BYc. Furthermore, in the optical scanning device 10c, by using the beam BKa, the SOS synchronization signal can be accurately generated as in the optical scanning device 10a.

  In the optical scanning device 10 c, the beam B reflected by the mirror 28 may be the same beam BY as the beam B reflected by the mirror 30 and the beam B reflected by the mirror 52.

(Second Embodiment)
The optical scanning device according to the second embodiment will be described below with reference to the drawings. FIG. 8 is a configuration diagram of an optical scanning device 10d according to the second embodiment. In FIG. 8, the main scanning direction is defined as the y-axis direction, and the sub-scanning direction is defined as the z-axis direction. A direction orthogonal to the y-axis direction and the z-axis direction is defined as an x-axis direction. Accordingly, FIG. 8 is a plan view of the optical scanning device 10d from the z-axis direction.

  As shown in FIGS. 1 and 2, the optical scanning device 10d includes a housing 11, a light emitting element 12 (12Y, 12M, 12C, 12K), a collimator lens 14 (14Y, 14M, 14C, 14K), and a mirror 16 (16M). , 16K), cylindrical lens 18 (18YM, 18CK), deflector 20, scanning lenses 22 (22YM, 22CK), 24 (24YM, 24CK), mirrors 28 (28a, 28b), 30 (30a, 30b), sensor 32 (32a, 32b). The optical scanning device 10d is used in an image forming apparatus including four photosensitive drums (not shown), and irradiates the beam B (BY, BM, BC, BK) to each of the four photosensitive drums. Then, electrostatic ray images are formed on the peripheral surfaces of the four photosensitive drums.

  The housing 11 stores the light emitting element 12, the collimator lens 14, the mirror 16, the cylindrical lens 18, the deflector 20, the scanning lenses 22 and 24, the mirrors 28 and 30, and the sensor 32.

  The light emitting element 12 is constituted by a laser diode, for example, and emits a beam B. The light emitting elements 12Y and 12M form a first light source. The light emitting elements 12C and 12K form a second light source. The collimator lens 14 shapes the beam B emitted from the light emitting element 12 into substantially parallel light in the xy plane.

  As shown in FIG. 8, the mirror 16M reflects the beam BM that has passed through the collimator lens 14M toward the deflector 20, and combines it with the beam BY. Thereby, the beam BY and the beam BM overlap when viewed in plan from the z-axis direction. The cylindrical lens 18YM condenses the beams BY and BM in the z-axis direction.

  As shown in FIG. 8, the mirror 16K reflects the beam BK that has passed through the collimator lens 14K toward the deflector 20, and combines it with the beams BC and BK. Thereby, the beam BC and the beam BK overlap when viewed in plan from the z-axis direction. The cylindrical lens 18CK collects the beams BC and BK in the z-axis direction.

  As shown in FIG. 8, the deflector 20 includes a polygon mirror having a plurality of reflecting surfaces and a motor (not shown) that rotates the polygon mirror clockwise. The deflector 20 deflects the beams BY and BM and the beams BC and BK using different reflecting surfaces. Specifically, the deflector 20 deflects the beams BY and BM using a reflecting surface relatively positioned on the positive direction side in the x-axis direction and relatively moves toward the negative direction side in the x-axis direction. The beams BC and BK are deflected using the reflection surface located.

  The scanning lenses 22YM and 24YM are provided on the positive side in the x-axis direction with respect to the deflector 20. The scanning lenses 22YM and 24YM are lenses through which the beams BY and BM pass, and form images of the beams BY and BM on the photosensitive drum. Thereby, the beams BY and BM are scanned at a constant speed toward the positive direction side in the y-axis direction, as shown in FIG. The scanning lenses 22CK and 24CK are provided on the negative direction side in the x-axis direction with respect to the deflector 20. The scanning lenses 22CK and 24CK are lenses through which the beams BC and BK pass, and form images of the beams BC and BK on the photosensitive drum. As a result, the beams BC and BK are scanned at a constant speed toward the negative side in the y-axis direction, as shown in FIG. Further, as shown in FIG. 8, the scanning lenses 22 and 24 have a longitudinal direction in the y-axis direction when viewed in plan from the z-axis direction.

  The mirror 28a reflects the beam BM deflected by the deflector 20 and does not pass through the scanning lenses 22YM and 24YM (hereinafter referred to as beam BMa) and guides it to the sensor 32a. Therefore, the mirror 28a is provided on the negative direction side of the scanning lens 22YM in the y-axis direction, as shown in FIG. That is, the mirror 28a is provided on the upstream side in the scanning direction of the beam B with respect to the scanning lens 22YM. The sensor 32a detects the beam BMa that does not pass through the scanning lenses 22YM and 24YM but passes through the negative direction side in the y-axis direction from the scanning lenses 22YM and 24YM and is reflected by the mirror 28a. Control signal is generated.

  The mirror 30a reflects the beam BY (hereinafter referred to as the beam BYb) deflected by the deflector 20 and passed through the point P1 of the scanning lens 22YM and the scanning lens 24YM, and guides it to the sensor 32a. Point P1 is a point located on the negative side in the y-axis direction with respect to image forming area A1 of scanning lens 22YM. The image forming area A1 is an area corresponding to an area where an electrostatic line image is formed on the photosensitive drum in the scanning lens 22YM. That is, the image forming area A1 is an area through which the beam BY passes through the scanning lens 22YM while an electrostatic ray image is formed on the photosensitive drum. The sensor 32a generates the first control signal by detecting the beam BYb that has passed through the point P1 of the scanning lens 22YM and the scanning lens 24YM.

  The mirror 28b reflects the beam BK deflected by the deflector 20 and does not pass through the scanning lenses 22CK and 24CK (hereinafter referred to as beam BKb) and guides it to the sensor 32b. Therefore, the mirror 28b is provided on the positive direction side in the y-axis direction of the scanning lens 22CK, as shown in FIG. That is, the mirror 28b is provided on the upstream side in the scanning direction of the beam B with respect to the scanning lens 22CK. The sensor 32b detects the beam BKb that passes through the positive side in the y-axis direction from the scanning lenses 22CK and 24CK without passing through the scanning lenses 22CK and 24CK and is reflected by the mirror 28b. Control signal is generated.

  The mirror 30b reflects the beam BC (hereinafter referred to as the beam BCa) deflected by the deflector 20 and passed through the point P2 of the scanning lens 22CK and the scanning lens 24CK, and guides it to the sensor 32b. Point P3 is a point located on the positive side in the y-axis direction from image forming area A2 of scanning lens 22CK. The image forming area A2 is an area corresponding to an area where an electrostatic line image is formed on the photosensitive drum in the scanning lens 22CK. That is, the image forming area A2 is an area through which the beam BC passes through the scanning lens 22CK while an electrostatic ray image is formed on the photosensitive drum. The sensor 32b generates the second control signal by detecting the beam BCa that has passed through the point P3 of the scanning lens 22CK and the scanning lens 24CK.

  A control unit (not shown) corrects the operations of the light emitting elements 12Y and 12M using the first control signal. In addition, the control unit corrects the operation of the light emitting elements 12C and 12K using the second control signal. The details of the correction of the light emitting element 12 are the same as the correction of the light emitting element 12 in the optical scanning device 10a, and thus the description thereof is omitted.

  Further, the control unit uses the first control signal as the SOS synchronization signal used when starting the writing of the electrostatic ray image by the beams BY and BM. Further, the control unit uses the second control signal as the SOS synchronization signal used when starting the writing of the electrostatic ray image by the beams BC and BK. However, in the optical scanning device 10d, using the first control signal and the second control signal as the SOS synchronization signal is the same as using the control signal as the SOS synchronization signal in the optical scanning device 10a. The above description is omitted.

(effect)
According to the optical scanning device 10d, it is possible to suppress deterioration in image quality due to a temperature change for the same reason as the optical scanning device 10a. Further, the SOS synchronization signal can be generated accurately for the same reason as the optical scanning device 10a.

  Further, according to the optical scanning device 10d, it is possible to suppress color misregistration between the electrostatic latent image by the beams BC and BK and the electrostatic latent image by the beams BY and BM as described below. FIG. 9 is a diagram for explaining that color misregistration can be suppressed in the optical scanning device 10d according to the second embodiment. FIG. 9A shows an optical scanning device 600 according to a comparative example, and FIG. 9B shows an optical scanning device 10d according to the second embodiment.

  In the optical scanning device 600 shown in FIG. 9A, the SOS synchronization signal is generated by the beam B that has passed through the scanning lenses 622YM and 622CK. In this case, as shown in FIG. 9A, even if the temperature rises, the relative relationship between the SOS synchronization signal generation position and the electrostatic latent image writing start position hardly changes. This is because both the beam B for detecting the SOS synchronization signal and the beam B for forming the electrostatic latent image are displaced by the deformation of the scanning lenses 622YM and 622CK, and the relative positional relationship between them is almost changed. It is because it does not. However, the scanning directions of the beams BC and BK and the scanning directions of the beams BY and BM are opposite to each other. Therefore, when the temperature rises, the electrostatic latent image by the beams BY and BM extends downward from the upper end of FIG. 9A. On the other hand, the electrostatic latent image by the beams BC and BK extends upward from the lower end of FIG. As a result, a deviation occurs between the electrostatic latent image by the beams BC and BK and the electrostatic latent image by the beams BY and BM.

  On the other hand, in the optical scanning device 10d shown in FIG. 9B, the SOS synchronization signal is generated by the beam B that has not passed through the scanning lenses 22YM and 22CK. Therefore, even if the temperature rises, the position of the beam B for detecting the SOS synchronization signal does not change. On the other hand, since the beam B for forming the electrostatic latent image is deformed as the lens is deformed, the electrostatic latent image extends in the vertical direction as shown in FIG. 9B. For this reason, the generation position of the SOS synchronization signal and the position of the electrostatic latent image change. As a result, the occurrence of a shift between the electrostatic latent image by the beams BC and BK and the electrostatic latent image by the beams BY and BM is suppressed. That is, color misregistration between the electrostatic latent images by the beams BC and BK and the electrostatic latent images by the beams BY and BM can be suppressed.

  In FIG. 9, it is assumed that the scanning lenses 22YM and 22CK are fixed at the center in the longitudinal direction. However, the scanning lenses 22YM and 22CK may have one end fixed in the longitudinal direction. Even in this case, color misregistration between the electrostatic latent image by the beams BC and BK and the electrostatic latent image by the beams BY and BM can be suppressed.

  The present invention is useful for an optical scanning device, and is particularly excellent in that it can suppress deterioration in image quality due to a temperature change and can accurately generate an SOS synchronization signal.

A1, A2 Image forming area BY, BM, BC, BK, BYa, BYb, BYc, BMa, BKa, BKb, BCa
Beam 10a to 10d Optical scanning device 12Y, 12M, 12C, 12K Light emitting element 20 Deflector 22, 22YM, 22CK, 24, 24YM, 24CK, 26Y, 26M, 26C, 26K Scanning lens 32, 32a, 32b Sensor

Claims (6)

An optical scanning device used in an image forming apparatus provided with a photoconductor,
A first light source emitting a first beam;
Deflecting means for deflecting the first beam;
A first scanning optical element for imaging the first beam deflected by the deflecting unit on the photosensitive member;
First detection means for detecting the first beam not passing through the first scanning optical element and the first beam passing through a first predetermined position of the first scanning optical element; ,
Having
An optical scanning device characterized by the above. The first beam that has not passed through the first scanning optical element passes upstream of the first scanning optical element in the scanning direction of the first beam;
The first predetermined position is located on the upstream side in the scanning direction of the first beam with respect to an image forming area corresponding to an area where an electrostatic ray image is formed on the photosensitive member in the first scanning optical element. Doing things,
The optical scanning device according to claim 1. The first beam that has not passed through the first scanning optical element passes upstream of the first scanning optical element in the scanning direction of the first beam;
The first predetermined position is located on the downstream side in the scanning direction of the first beam with respect to the image forming area corresponding to the area where an electrostatic ray image is formed on the photosensitive member in the first scanning optical element. Doing things,
The optical scanning device according to claim 1. The first light source includes a plurality of light emitting elements,
The first beam that has not passed through the first scanning optical element and the first beam that has passed through the first predetermined position are emitted from different light emitting elements;
The optical scanning device according to claim 1, wherein: The first light source includes a plurality of light emitting elements,
The first beam that has not passed through the first scanning optical element and the first beam that has passed through the first predetermined position are emitted from the same light emitting element;
The optical scanning device according to claim 1, wherein: The optical scanning device includes:
A second light source emitting a second beam;
In addition,
The deflection means has a plurality of reflection surfaces, and deflects the first beam and the second beam using different reflection surfaces,
The optical scanning device includes:
A second scanning optical element for imaging the second beam deflected by the deflecting means on the photosensitive member;
Second detection means for detecting the second beam that has not passed through the second scanning optical element and the second beam that has passed through a second predetermined position of the second scanning optical element; ,
Further comprising
The optical scanning device according to claim 1, wherein:

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