Optical scanner and image formation apparatus

Abstract

To inhibit generation of jitter images by avoiding the adverse effects of wind caused by rotation of a polygon mirror.SOLUTION: A motor 521 for rotating a rotary shaft 52b of a polygon mirror 52 is mounted to a motor substrate 520. A first photoelectric conversion element 56 detects beam light reflected by each of a plurality of mirror planes 52a. A detection object part is provided on the rotary shaft 52b. An optical sensor 57 is disposed separated from the motor substrate 520, and has a light-emitting part 57a and a second photoelectric conversion element 57b. An amplifier circuit 571 amplifies a detection signal of the second photoelectric conversion element 57b. A controller 86 controls the timing of formation start of an electrostatic latent image, based on the detection signal of the first photoelectric conversion element 56. The controller 86 specifies a scanning plane during scanning of the beam light on the basis of the detection signal of the second photoelectric conversion element 57b amplified by the amplifier circuit 571, and adjusts a pixel pitch of the electrostatic latent image.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to an optical scanning device and an image forming apparatus that control the operation of a beam light source according to the rotation state of a polygon mirror.

Background Art

[0002] An electrophotographic image forming apparatus includes an optical scanning device that scans a photosensitive member with a beam of light. In the optical scanning device, a rotating polygon mirror reflects the beam of light to scan the beam of light on the surface of the photosensitive member (see, for example, Patent Document 1).

[0003] The polygon mirror has a plurality of mirror surfaces arranged in a polygonal shape. The optical scanning device forms an electrostatic latent image on the surface of the photosensitive member by scanning with the beam of light.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, variations in the dimensions or arrangements of the plurality of mirror surfaces in the polygon mirror cause variations in the position and length of each line image along the scanning direction. Therefore, due to variations in the dimensions or the like of the polygon mirror, a jitter image may be output.

[0006] On the other hand, by appropriately controlling the timing of starting to form the electrostatic latent image on the photosensitive member by the beam light source and the pixel pitch of the electrostatic latent image in the scanning direction for each of the plurality of mirror surfaces in the polygon mirror, the generation of the jitter image is suppressed.

[0007] For each of the plurality of mirror surfaces, the timing of the start of formation of the electrostatic latent image is controlled based on the timing at which the beam light scanned by each of the plurality of mirror surfaces is detected at a reference position in the scanning direction.

[0008] The pixel pitch of the electrostatic latent image is individually adjusted for each of the plurality of mirror surfaces by prior adjustment. Therefore, it is necessary to grasp which of the plurality of mirror surfaces the beam light is being scanned by.

[0009] For example, it is conceivable that a reflective optical sensor detects a specific portion provided on the rotation axis of the polygon mirror. The number of times the beam light is detected at the reference position starting from the point in time when the specific portion of the rotation axis is detected by the optical sensor represents one of the plurality of mirror surfaces during which the beam light is being scanned.

[0010] However, if the optical sensor is disposed near the rotation axis of the polygon mirror, the detection signal of the optical sensor may be affected by high-frequency noise generated by the wind generated by the rotation of the polygon mirror colliding with surrounding objects.

[0011] An object of the present invention is to provide an optical scanning device and an image forming device that can prevent the occurrence of a jitter image caused by variations in the dimensions or arrangements of a plurality of mirror surfaces in the polygon mirror while avoiding the adverse effects of wind generated by the rotation of the polygon mirror.

Means for Solving the Problems

[0012] An optical scanning device according to one aspect of the present invention includes a beam light source, a motor substrate, a first photoelectric conversion element, a detection target portion, an optical sensor, an amplification circuit, and a control device. The beam light source emits beam light. The polygon mirror has a plurality of mirror surfaces and a rotation axis, and scans while reflecting the beam light by rotating. The motor substrate is a substrate on which a motor for rotating the rotation axis of the polygon mirror is mounted. The first photoelectric conversion element is disposed away from the motor substrate and detects the beam light reflected by each of the plurality of mirror surfaces of the polygon mirror. The detection target portion is provided on the rotation axis of the polygon mirror and is a portion having different light reflection characteristics compared to other portions in the circumferential direction of the rotation axis. The optical sensor is disposed away from the motor substrate and has a light emitting portion that emits light toward the rotation axis of the polygon mirror and a second photoelectric conversion element that detects the light reflected by the rotation axis of the polygon mirror. The amplification circuit amplifies the detection signal of the second photoelectric conversion element. The control device controls the timing of starting the formation of an electrostatic latent image on a photoreceptor by the beam light source for each of the plurality of mirror surfaces based on the detection signal of the first photoelectric conversion element. The control device identifies the scanning surface on which the beam light is being scanned among the plurality of mirror surfaces based on the detection signal of the second photoelectric conversion element amplified by the amplification circuit, and adjusts the pixel pitch of the electrostatic latent image for each scanning surface.

[0013] An image forming apparatus according to another aspect of the present invention includes a photoreceptor, the optical scanning device, a developing device, and a transfer device. The optical scanning device forms an electrostatic latent image on the surface of the photoreceptor by scanning the surface of the photoreceptor with beam light. The developing device develops the electrostatic latent image on the surface of the photoreceptor with a developer. The transfer device transfers the image of the developer on the surface of the photoreceptor to a sheet.

Advantages of the Invention

[0014] According to the present invention, it is possible to provide an optical scanning device and an image forming apparatus that can prevent the generation of jitter images caused by variations in the dimensions or arrangements of a plurality of mirror surfaces in the polygon mirror while avoiding the adverse effects of wind generated by the rotation of the polygon mirror.

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the following embodiments are an example of embodying the present invention and do not limit the technical scope of the present invention.

[0017] The image forming apparatus 10 according to the embodiment executes print processing by an electrophotographic method. The print processing is a process of forming an image on a sheet 9. The sheet 9 is an image forming medium such as paper or a sheet-like resin member.

[0018] [Configuration of Image Forming Apparatus 10] As shown in FIG. 1, the image forming apparatus 10 includes a sheet conveyance device 3, a printing device 4, and a control device 8.

[0019] The sheet conveyance device 3 includes a sheet feeding mechanism 30 and a plurality of sets of conveyance roller pairs 31. The sheet feeding mechanism 30 feeds the sheet 9 accommodated in the sheet storage unit 2 to the conveyance path 300. The conveyance path 300 is a passage through which the sheet 9 is conveyed.

[0020] The plurality of pairs of conveying rollers 31 are rotationally driven by a motor (not shown). The plurality of pairs of conveying rollers 31 convey the sheet 9 along the conveyance path 300 by rotating, and further discharge the sheet 9 to the discharge tray 1x.

[0021] The printing device 4 executes the printing process by an electrophotographic method. In the example shown in FIG. 1, the image forming apparatus 10 is a tandem type color image forming apparatus.

[0022] The printing device 4 includes a plurality of image forming units 4x corresponding to a plurality of developing colors. Further, the printing device 4 includes an optical scanning device 5, a transfer device 44, and a fixing device 46.

[0023] Each of the image forming units 4x includes a drum-shaped photoreceptor 41, a charging device 42, a developing device 43, a drum cleaning device 45, and the like. That is, the printing device 4 includes a plurality of photoreceptors 41, a plurality of developing devices 43, and a plurality of drum cleaning devices 45 corresponding to a plurality of toner colors.

[0024] In each of the image forming units 4x, the photoreceptor 41 rotates, and the charging device 42 charges the surface of the photoreceptor 41. The optical scanning device 5 scans a plurality of laser beams on the surface of each of the plurality of charged photoreceptors 41. Thereby, the optical scanning device 5 forms an electrostatic latent image on the surface of each of the plurality of photoreceptors 41.

[0025] Each of the laser beams is an example of a beam light scanned on the surface of the photoreceptor 41.

[0026] In each of the image forming units 4x, the developing device 43 develops the electrostatic latent image into a toner image by supplying toner to the surface of the photoreceptor 41. The toner is a granular developer. The photoreceptor 41 is an example of an image carrier that rotates while carrying the toner image.

[0027] In this embodiment, the printing apparatus 4 includes four image forming units 4x corresponding to the toners of four developing colors: yellow, cyan, magenta, and black. Accordingly, the printing apparatus 4 includes four photoreceptors 41, four developing devices 43, and four drum cleaning devices 45.

[0028] The four toner images are formed on the surfaces of the four photoreceptors 41. The transfer device 44 transfers the four toner images from the four photoreceptors 41 to the sheet 9.

[0029] The transfer device 44 includes an intermediate transfer belt 441, four primary transfer devices 442 corresponding to the four image forming units 4x, a secondary transfer device 443, and a belt cleaning device 444.

[0030] The four primary transfer devices 442 transfer the toner images on the surfaces of the four photoreceptors 41 to the surface of the intermediate transfer belt 441. Thereby, a color toner image in which the toner images of the four photoreceptors 41 are combined is formed on the surface of the intermediate transfer belt 441.

[0031] The secondary transfer device 443 transfers the color toner image formed on the intermediate transfer belt 441 to the sheet 9 at the transfer position of the conveyance path 300.

[0032] The fixing device 46 pressurizes the color toner image transferred to the sheet 9 while heating it. Thereby, the fixing device 46 fixes the color toner image to the sheet 9.

[0033] Each of the drum cleaning devices 45 removes the toner remaining on the surface of each photoreceptor 41. The belt cleaning device 444 removes the toner remaining on the intermediate transfer belt 441.

[0034] The control device 8 executes various data processes and controls devices such as the sheet conveyance device 3 and the printing apparatus 4.

[0035] As shown in FIG. 2, the control device 8 includes a CPU (Central Processing Unit) 81 and peripheral devices. The peripheral devices include a RAM (Random Access Memory) 82, a secondary storage device 83, a signal interface 84, and the like.

[0036] Furthermore, the control device 8 includes a communication device 85 and a laser control circuit 86.

[0037] The CPU 81 is a processor that executes various data processes and controls by executing a computer program.

[0038] The RAM 82 is a computer-readable volatile storage device. The RAM 82 primarily stores the computer program executed by the CPU 81 and the data output and referenced during the execution of various processes by the CPU 81.

[0039] The communication device 85 executes communication with other devices such as a host device that transmits a print job to the image forming apparatus 10. The CPU 81 communicates with the other devices through the communication device 85.

[0040] The CPU 81 includes a plurality of processing modules realized by executing the computer program. The plurality of processing modules include a main control unit 8a, a print control unit 8b, and the like.

[0041] The main control unit 8a executes start control and the like to start various processes in response to operations on an operation device (not shown).

[0042] The print control unit 8b controls the sheet conveyance device 3. Furthermore, the print control unit 8b causes the printing device 4 to execute the printing process in synchronization with the conveyance of the sheet 9 by the sheet conveyance device 3.

[0043] The print control unit 8b controls the charging device 42, the developing device 43, the transfer device 44, and the fixing device 46. Further, the print control unit 8b controls the optical scanning device 5 through the signal interface 84 and the laser control circuit 86.

[0044] The secondary storage device 83 is a computer-readable non-volatile storage device. For example, one or both of a flash memory and a hard disk drive are adopted as the secondary storage device 83.

[0045] The signal interface 84 converts the detection signals output by various sensors into digital data and transmits the digital data to the CPU 81. Further, the signal interface 84 converts the control commands output by the CPU 81 into control signals and transmits the control signals to the devices to be controlled.

[0046] The laser control circuit 86 controls the lighting and extinguishing of a plurality of light sources 51 provided in the optical scanning device 5 according to the lighting pattern data supplied from the print control unit 8b. The lighting pattern data represents a plurality of pixels of the electrostatic latent image formed on the surface of the photoreceptor 41.

[0047] The laser control circuit 86 and the print control unit 8b that controls the laser control circuit 86 constitute a part of the optical scanning device 5.

[0048] As shown in FIGS. 3 and 4, the optical scanning device 5 includes a housing 50, a plurality of light sources 51, a polygon mirror 52, and a motor substrate 520. The motor substrate 520 is a substrate on which the polygon motor 521 is mounted.

[0049] Furthermore, the optical scanning device 5 includes a main lens 53, a plurality of long mirrors 54, and a plurality of sub-lenses 55. The housing 50 is a molded member of synthetic resin. The plurality of light sources 51 and the polygon mirror 52 are arranged inside the housing 50.

[0050] The plurality of light sources 51 are laser light sources that each emit laser light. The laser light is an example of beam light. Each of the light sources 51 is an example of a beam light source that emits the beam light.

[0051] The polygon mirror 52 rotates to scan while reflecting the plurality of laser lights emitted from the plurality of light sources 51. The polygon mirror 52 scans the plurality of laser lights along the first direction D1.

[0052] In the example shown in FIGS. 3 and 4, the scanning direction SD1 of the plurality of laser lights is a direction from the first side to the second side of the first direction D1.

[0053] The polygon mirror 52 has a plurality of mirror surfaces 52a arranged in a regular polygon shape in the circumferential direction and a rotation axis 52b. In the example shown in FIG. 3, the polygon mirror 52 has six mirror surfaces 52a arranged in a regular hexagon shape.

[0054] The polygon motor 521 rotates the rotation axis 52b of the polygon mirror 52. Thereby, the polygon mirror 52 rotates about the rotation axis 52b.

[0055] The optical scanning device 5 further includes a cover 523 that covers the polygon mirror 52 (see FIGS. 3 and 4). The cover 523 is formed with a first opening 523a through which the plurality of laser lights pass.

[0056] The plurality of laser lights emitted from the plurality of light sources 51 enter the polygon mirror 52 through the first opening 523a. The plurality of laser lights reflected by the polygon mirror 52 travel toward the main lens 53 through the first opening 523a.

[0057] The cover 523 suppresses the flow of hot air heated by the heat generated by the polygon motor 521 from being deflected by the polygon mirror 52 to a partial area within the housing 50. Thereby, the deviation of the temperature distribution within the housing 50 is suppressed, and the deviation of the distribution of the thermal expansion of the housing 50 and the optical devices within the housing 50 is suppressed. As a result, the deterioration of the scanning accuracy of the plurality of laser beams due to the distribution of the thermal expansion is suppressed.

[0058] The main lens 53, the plurality of long mirrors 54, and the plurality of sub-lenses 55 are each mounted within the housing 50 with the first direction D1 as the longitudinal direction. That is, the main lens 53, the plurality of long mirrors 54, and the plurality of sub-lenses 55 are respectively arranged within the housing 50 along the first direction D1.

[0059] The plurality of long mirrors 54 each reflect the plurality of laser beams. The plurality of laser beams are reflected by the plurality of long mirrors 54 and transmitted through the main lens 53 and the plurality of sub-lenses 55.

[0060] The main lens 53 is an fθ lens common to the four developing colors. In the present embodiment, the optical scanning device 5 includes four sub-lenses 55 respectively corresponding to the four developing colors.

[0061] The plurality of long mirrors 54 include a first mirror 54a corresponding to black, a second mirror 54b and a third mirror 54c corresponding to cyan, a fourth mirror 54d corresponding to magenta, and a fifth mirror 54e corresponding to yellow (see FIGS. 3 and 4).

[0062] The main lens 53 is an fθ lens that transmits all of the plurality of laser beams irradiated to the four photoreceptors 41. The four sub-lenses 55 transmit a part of the plurality of laser beams that are irradiated to the corresponding photoreceptors 41 respectively.

[0063] The four sub-lenses 55 include a first sub-lens 55a corresponding to black, a second sub-lens 55b corresponding to cyan, a third sub-lens 55c corresponding to magenta, and a fourth sub-lens 55d corresponding to yellow (see FIGS. 3 and 4).

[0064] Incidentally, variations in the dimensions or arrangements of the plurality of mirror surfaces 52a in the polygon mirror 52 cause variations in the position and length of each line image along the scanning direction SD1. Therefore, due to variations in the dimensions and the like of the polygon mirror 52, there is a possibility that a jitter image may be output.

[0065] On the other hand, by appropriately controlling the timing of the start of formation of the electrostatic latent image on the photoreceptor 41 by each of the light sources 51 and the pixel pitch of the electrostatic latent image in the scanning direction SD1 for each of the plurality of mirror surfaces 52a in the polygon mirror 52, the generation of the jitter image is suppressed.

[0066] The timing of the start of formation of the electrostatic latent image for each of the plurality of mirror surfaces 52a is controlled based on the timing at which the laser light scanned by each of the plurality of mirror surfaces 52a is detected at the reference position in the scanning direction SD1.

[0067] The pixel pitch of the electrostatic latent image in the scanning direction SD1 is individually adjusted for each of the plurality of mirror surfaces 52a by prior adjustment. Therefore, it is necessary to grasp which of the plurality of mirror surfaces 52a the laser light is being scanned by.

[0068] For example, it is conceivable that a reflective optical sensor detects a specific portion in the circumferential direction on the rotation axis 52b of the polygon mirror 52. The number of times the laser light is detected at the reference position starting from the time when the specific portion of the rotation axis 52b is detected by the optical sensor represents one of the plurality of mirror surfaces 52a through which the laser light is being scanned.

[0069] However, when the optical sensor is disposed near the rotation axis 52b of the polygon mirror 52, the detection signal of the optical sensor may be affected by the high-frequency noise generated by the wind generated by the rotation of the polygon mirror 52 colliding with surrounding objects.

[0070] The optical scanning device 5 is provided with a configuration for preventing the occurrence of the jitter image caused by variations in the dimensions or arrangements of the plurality of mirror surfaces 52a of the polygon mirror 52 while avoiding the adverse effects of the wind generated by the rotation of the polygon mirror 52. The configuration will be described below.

[0071] The optical scanning device 5 further includes a photoelectric conversion element 56, an optical sensor substrate 570, and a detection target portion 52c (see FIGS. 3 and 4). An optical sensor 57, an amplification circuit 571, and a determination circuit 572 are mounted on the optical sensor substrate 570 (see FIG. 3).

[0072] The photoelectric conversion element 56 is disposed away from the motor substrate 520 (see FIG. 3). The photoelectric conversion element 56 detects the laser light reflected by each of the plurality of mirror surfaces 52a of the polygon mirror 52 at the reference position. The reference position is a position upstream of the main lens 53 in the scanning direction SD1.

[0073] The optical sensor substrate 570 is disposed away from the motor substrate 520 (see FIG. 3). The optical sensor 57 is a reflection type sensor having a light emitting portion 57a and a photoelectric conversion element 57b.

[0074] The light emitting portion 57a emits light toward the rotation axis 52b of the polygon mirror 52. The photoelectric conversion element 57b detects the reflected light reflected by the rotation axis 52b of the polygon mirror 52. The photoelectric conversion element 56 is an example of a first photoelectric conversion element, and the photoelectric conversion element 57b is an example of a second photoelectric conversion element.

[0075] The detection target portion 52c is provided on the rotation axis 52b of the polygon mirror 52. The detection target portion 52c has different light reflection characteristics compared to other portions in the circumferential direction of the rotation axis 52b.

[0076] For example, the detection target portion 52c is a mirror surface having a higher light reflectance than other portions in the circumferential direction on the rotation axis 52b. In this case, it is conceivable that the portion other than the detection target portion 52c on the rotation axis 52b is a black surface.

[0077] Alternatively, the detection target portion 52c may be a black surface having a lower light reflectance than other portions in the circumferential direction on the rotation axis 52b. In this case, it is conceivable that the portion other than the detection target portion 52c on the rotation axis 52b is a mirror surface.

[0078] In the present embodiment, the cover 523 of the polygon mirror 52 has a second opening 523b in addition to the first opening 523a (see FIGS. 3 and 4). The reflected light that is reflected by the rotation axis 52b and travels toward the photoelectric conversion element 57b passes through the second opening 523b.

[0079] The amplification circuit 571 amplifies the detection signal of the photoelectric conversion element 57b. The determination circuit 572 determines whether the level of the detection signal of the photoelectric conversion element 57b amplified by the amplification circuit 571 is greater than or less than a reference level, and outputs a determination signal representing the determination result.

[0080] When the detection target portion 52c passes through the position facing the photoelectric conversion element 57b, the determination signal is in an active state, and when the detection target portion 52c is not facing the photoelectric conversion element 57b, the determination signal is in a negative state.

[0081] The laser control circuit 86 controls, based on the detection signal of the photoelectric conversion element 56, the timing of starting the formation of the electrostatic latent image on the photoreceptor 41 by each of the light sources 51 for each of the plurality of mirror surfaces 52a.

[0082] Specifically, the laser control circuit 86 detects, as a line start point, a point in time when a predetermined time has elapsed from the point in time when the level of the detection signal of the photoelectric conversion element 56 exceeds a set level. The line start point is the start point of the formation of the electrostatic latent image in the scanning direction SD1.

[0083] The laser control circuit 86 controls the timing of the start of formation of the electrostatic latent image with reference to the line start point for each line in the scanning direction SD1.

[0084] Furthermore, the laser control circuit 86 counts the number of times the line start point is detected starting from the point in time when the determination signal is in an active state, and identifies the scanning surface according to the count value. The scanning surface is one of the plurality of mirror surfaces 52a on which the laser light is being scanned.

[0085] That is, the laser control circuit 86 identifies the scanning surface based on the detection signal of the photoelectric conversion element 57b amplified by the amplifier circuit 571. Furthermore, the laser control circuit 86 adjusts the pixel pitch of the electrostatic latent image for each scanning surface.

[0086] In the present embodiment, pitch adjustment data DT1 set by equipment adjustment is stored in the secondary storage device 83 (see FIG. 2). The pitch adjustment data DT1 represents a plurality of pixel pitch candidates corresponding to the plurality of mirror surfaces 52a.

[0087] The pitch adjustment data DT1 is supplied to the laser control circuit 86 by the print control unit 8b. The laser control circuit 86 selects a target pixel pitch corresponding to the scanning surface from among the plurality of pixel pitch candidates, and controls the time interval between the blinking of each light source 51 using the target pixel pitch as the pixel pitch of the electrostatic latent image.

[0088] In the optical scanning device 5, the optical sensor 57 is disposed away from the polygon motor 521. Thereby, it is avoided that the wind generated by the rotation of the polygon mirror 52 adversely affects the detection signal of the optical sensor 57.

[0089] Furthermore, a cover 523 covering the polygon mirror 52 prevents the wind generated by the rotation of the polygon mirror 52 from directly hitting the surrounding devices.

[0090] However, since the optical sensor 57 is arranged away from the polygon motor 521, the change in the detection signal according to the detection of light in the optical sensor 57 becomes small. This inhibits the detection of the detection target portion 52c based on the detection signal of the optical sensor 57.

[0091] On the other hand, in the optical scanning device 5, the amplification circuit 571 amplifies the detection signal of the optical sensor 57. Therefore, the determination circuit 572 can surely detect the detection target portion 52c based on the amplified detection signal.

[0092] Therefore, by adopting the optical scanning device 5, it is possible to prevent the occurrence of a jitter image caused by variations in the dimensions or arrangements of the plurality of mirror surfaces 52a in the polygon mirror 52.

Explanation of Reference Numerals

[0093] 4: Printing device 4x: Image forming unit 5: Optical scanning device 8: Control device 10: Image forming apparatus 41: Photoconductor 42: Charging device 43: Developing device 44: Transfer device 51: Light source 52: Polygon mirror 52a: Mirror surface 52b: Rotation axis 52c: Detection target portion 53: Main lens 54: Mirror 55: Sub lens 56: Photoelectric conversion element (first photoelectric conversion element) 57: Optical sensor 57a: Light emitting portion 57b: Photoelectric conversion element (second photoelectric conversion element) 86: Laser control circuit 520: Motor substrate 521: Polygon motor 523: Cover 523a: First opening 523b: Second opening 570: Optical sensor substrate 571: Amplification circuit 572: Judgment circuit

Claims

1. a beam light source that emits a beam of light; a polygon mirror having a plurality of mirror surfaces and a rotation axis, and rotating to reflect and scan the light beam; a motor board on which a motor for rotating the rotation shaft of the polygon mirror is mounted; a first photoelectric conversion element that is disposed away from the motor board and detects the beam of light reflected by each of the plurality of mirror surfaces of the polygon mirror; a detection target portion provided on the rotation shaft of the polygon mirror and having light reflection characteristics different from those of other portions of the rotation shaft in a circumferential direction; an optical sensor disposed away from the motor board, the optical sensor having a light emitting unit that emits light toward the rotation shaft of the polygon mirror and a second photoelectric conversion element that detects light reflected by the rotation shaft of the polygon mirror; an amplifier circuit that amplifies a detection signal from the second photoelectric conversion element; a control device that controls a timing at which the beam light source starts forming an electrostatic latent image on the photoconductor for each of the plurality of mirror surfaces based on a detection signal from the first photoelectric conversion element, The control device identifies a scanning surface among the multiple mirror surfaces that is being scanned with the beam light based on the detection signal of the second photoelectric conversion element amplified by the amplifier circuit, and adjusts the pixel pitch of the electrostatic latent image for each scanning surface.

2. a cover for covering the polygon mirror; The optical scanning device according to claim 1 , wherein the cover has a first opening through which the beam light passes, and a second opening through which light reflected by the rotation shaft and traveling toward the second photoelectric conversion element passes.

3. A photoconductor; an optical scanning device according to claim 1 , wherein an electrostatic latent image is formed on the surface of the photoconductor by scanning a light beam on the surface of the photoconductor; a developing device that develops the electrostatic latent image on the surface of the photoconductor with a developer; a transfer device that transfers the developer image on the surface of the photoconductor onto a sheet.

Images