Scanning optical apparatus and image forming apparatus

Abstract

To prevent stray light from entering the holes in the substrate. [Solution] The scanning optical device comprises a deflector, a first optical sensor 108, a frame F, and a substrate 100. The first optical sensor 108 has a first light-receiving surface 108A that detects a first beam BY deflected by the deflector. The frame F has a side wall (second side wall F12) surrounding the deflector. The substrate 100 is located outside the side wall. The first optical sensor 108 is fixed to the substrate 100. The side wall has a first frame hole H1 through which the first beam BY deflected by the deflector passes. The substrate 100 has a first substrate hole 118 facing the first frame hole H1. The first light-receiving surface 108A is placed in the first substrate hole 118. In the scanning direction of the first beam BY at the position of the first frame hole H1, one end 118A of the first substrate hole 118 is located outside the range of the first frame hole H1, and the other end 118B of the first substrate hole 118 is located within the range of the first frame hole H1.

Description

Technical Field

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[0001] The present disclosure relates to a scanning optical device and an image forming device.

Background Art

[0002] Conventionally, as a scanning optical device, one including an optical sensor that detects light scanned by a polygon mirror, a substrate that supports the optical sensor, and a frame that surrounds the polygon mirror is known (see Patent Document 1). The substrate has holes for guiding light to the optical sensor.

Prior Art Document

Patent Document

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, when the substrate is installed outside the frame, it is necessary to form holes for allowing light to pass through in the outer wall of the frame. However, if the holes in the frame are large, stray light from the inner surface of the holes in the frame is likely to enter the holes in the substrate, which may cause false detection by the optical sensor.

[0005] Therefore, an object of the present disclosure is to suppress the entry of stray light into the holes in the substrate.

Means for Solving the Problems

[0006] The scanning optical device of the present disclosure includes a first semiconductor laser, a first coupling lens, a deflector, a first optical sensor, a scanning optical system, a frame, and a substrate. The first coupling lens converts the light from the first semiconductor laser into a first beam. The deflector has a polygon mirror. The polygon mirror deflects the first beam from the first coupling lens in the main scanning direction. The first light sensor has a first light-receiving surface that detects the first beam deflected by the deflector. The scanning optical system images the first beam from the deflector onto the surface to be scanned. The frame has side walls that enclose the deflector and scanning optical system. The substrate is located on the outside of the side wall. The first light sensor is fixed to the substrate. The side wall has a first frame hole through which the first beam, deflected by the deflector, passes. The substrate has a first substrate hole facing the first frame hole. The first light-receiving surface is placed in the first substrate hole. In the scanning direction of the first beam at the position of the first frame hole, one end of the first substrate hole is located outside the range of the first frame hole, and the other end of the first substrate hole is located within the range of the first frame hole.

[0007] In the scanning direction of the first beam, by configuring the first substrate hole so that one end is outside the range of the first frame hole and the other end of the first substrate hole is within the range of the first frame hole, a portion of the opening of the first substrate hole on the first frame hole side can be covered by the frame, thereby suppressing stray light from the first frame hole from entering the first substrate hole.

[0008] Furthermore, the first light sensor may have a package that transmits the first beam. The package encloses the components that make up the first light sensor. The first light-receiving surface is offset to one side from the center of the package in the scanning direction, and also offset to one side from the center of the first substrate hole in the scanning direction.

[0009] Furthermore, the first light-receiving surface may be offset upstream from the center of the package in the scanning direction.

[0010] By configuring the first light-receiving surface to be offset upstream of the center of the package in the scanning direction, reflection of the first beam within the portion of the package upstream of the first light-receiving surface can be reduced, thereby suppressing stray light from entering the first light-receiving surface.

[0011] Furthermore, the first light sensor may have terminals extending from the package. The terminals are connected to the side of the circuit board opposite the frame.

[0012] By configuring the terminals of the first light sensor to be connected to the side of the circuit board opposite to the frame, it is not necessary to place the terminals of the first light sensor between the circuit board and the frame, thereby suppressing interference between the terminals and the frame when the circuit board is mounted to the frame.

[0013] Furthermore, the dimension of the first frame hole in the direction through which the first beam passes may be larger than the dimension in the scanning direction.

[0014] By configuring the first frame opening in the direction of the first beam's passage to be larger than the opening in the scanning direction, it is possible to suppress dust from entering the frame through the first frame opening.

[0015] Furthermore, the first beam may be incident on the first light-receiving surface at approximately perpendicular angles.

[0016] By configuring the first beam to be incident approximately perpendicular to the first light-receiving surface, the size of the first frame hole and the first substrate hole can be reduced.

[0017] The scanning optical device may also further include a first lens that focuses the first beam, which has been deflected by a deflector, onto a first light sensor. The distance of the optical path from the first lens to the first light sensor may be smaller than the distance of the optical path from the first lens to the deflector.

[0018] By configuring the distance of the optical path from the first lens to the first optical sensor to be smaller than the distance of the optical path from the first lens to the deflector, the magnification of the optical system from the first semiconductor laser to the first optical sensor can be reduced, so that the influence of errors of the components constituting the optical system on the imaging state can be mitigated.

[0019] Further, the scanning optical device may further include a second semiconductor laser, a second coupling lens, and a second optical sensor. The second coupling lens converts the light from the second semiconductor laser into a second beam. The second optical sensor has a second light receiving surface for detecting the second beam deflected by the deflector. The side wall has a second frame hole through which the second beam deflected by the deflector passes. The substrate is a second substrate hole facing the second frame hole, and has a second substrate hole into which the second light receiving surface enters. In the scanning direction of the second beam, one end of the second substrate hole is located outside the range of the second frame hole, and the other end of the second substrate hole is located inside the range of the second frame hole.

[0020] By configuring such that in the scanning direction of the second beam, one end of the second substrate hole is located outside the range of the second frame hole and the other end of the second substrate hole is located inside the range of the second frame hole, a part of the opening on the second frame hole side of the second substrate hole can be covered with the frame, so that stray light from the second frame hole entering the second substrate hole can be suppressed.

[0021] Also, in the scanning direction, the center of the first frame hole may be located within the range of the first light receiving surface.

[0022] Further, the image forming apparatus of the present disclosure includes a scanning optical device and a control device that controls the scanning optical device. The scanning optical device includes the first frame hole, the first substrate hole, and the first optical sensor described above. The first optical sensor has a first light receiving surface that is shifted upstream from the center of the package in the scanning direction. The control device determines that the first beam has been incident on the first light-receiving surface when the amount of light from the first beam received by the first light-receiving surface first exceeds a threshold value in a period shorter than the time it takes for the first beam to scan from one end to the other of the surface being scanned.

[0023] By configuring the control device to determine that the first beam has been incident on the first light-receiving surface when the light intensity of the first beam first exceeds a threshold in a short period of time, false detections by the first light sensor can be suppressed even if the light intensity of the first beam exceeds the threshold multiple times in a short period of time. Specifically, because the first light-receiving surface is shifted upstream in the scanning direction from the center of the package, reflection of the first beam within the part of the package upstream of the first light-receiving surface can be reduced. Therefore, the amount of light received on the first light-receiving surface is below the threshold before the first beam is incident on the first light-receiving surface, and the amount of light received first exceeds the threshold when the first beam is incident on the first light-receiving surface. After that, even if the amount of light received exceeds the threshold due to reflection of the first beam within the part of the package downstream of the first light-receiving surface, false detections can be suppressed because the incident determination by the control device has been completed. [Effects of the Invention]

[0024] This can suppress stray light from entering the holes in the substrate. [Brief explanation of the drawing]

[0025] [Figure 1] This is a perspective view of the scanning optical device from the other side of the first direction. [Figure 2] This is a perspective view of the scanning optical device from one side in the first direction. [Figure 3] This is a cross-sectional view taken along line III-III in Figure 1. [Figure 4] This is a cross-sectional view taken along line IV-IV in Figure 1. [Figure 5] This is a perspective view of the substrate from the other side in the third direction. [Figure 6] (a) is a view of the substrate from one side in the third direction, (b) is a magnified view of the structure around the first light sensor, and (c) is a magnified view of the structure around the second light sensor. [Figure 7]This diagram shows the optical components that guide the beam from the deflector to the light sensor. [Figure 8] (a) is a cross-sectional view showing an enlarged view of the relationship between the first frame hole and the first substrate hole, and (b) is a cross-sectional view showing an enlarged view of the relationship between the second frame hole and the second substrate hole. [Figure 9] This figure shows the waveform of the amount of light incident on the light-receiving surface when a beam scans a light sensor. [Figure 10] This is a flowchart showing the operation of the control device. [Figure 11] Figure (a) shows the state in which the first beam is located in the part of the package upstream of the first light-receiving surface, and Figure (b) shows the state in which the first beam is located in the part of the package downstream of the first light-receiving surface. [Modes for carrying out the invention]

[0026] As shown in Figures 1 and 2, the scanning optical device 1 comprises a frame F, an incident optical system Li, a deflector 50, a scanning optical system Lo, a substrate 100, a first photosensor 108, and a second photosensor 109. In this embodiment, the scanning optical device 1 is applied to an electrophotographic image forming apparatus. As shown in Figure 4, the image forming apparatus comprises four photosensitive drums 200, the scanning optical device 1, and a control device 300 that controls the scanning optical device 1.

[0027] In the following explanation, the direction parallel to the rotation axis X1 of the polygon mirror 51, which will be described later, will be referred to as the "first direction." The direction perpendicular to the first direction, in which the polygon mirror 51 and the first scanning lens 60 are aligned, will be referred to as the "second direction." The direction perpendicular to both the first and second directions will be referred to as the "third direction." The third direction corresponds to the main scanning direction, and the first direction corresponds to the sub-scanning direction of the incident optical system Li. The arrows indicating each direction in the drawings will point to one side in each direction.

[0028] As shown in Figures 1 and 2, the incident optical system Li comprises a first semiconductor laser 10Y, 10M, a second semiconductor laser 10C, 10K, a first coupling lens 20Y, 20M, a second coupling lens 20C, 20K, an aperture plate 30, and a focusing lens 40.

[0029] The semiconductor laser 10 is a device that emits light. There are four semiconductor lasers 10, corresponding to the four photosensitive drums 200 that the scanning optical device 1 scans and exposes. A toner image of a different color is formed on each photosensitive drum 200.

[0030] In this embodiment, the first color is "yellow (Y)", the second color is "magenta (M)", the third color is "cyan (C)", and the fourth color is "black (K)". In this embodiment, the letters "Y", "M", "C", and "K" may be added to the end of the component code corresponding to each color to distinguish them.

[0031] The semiconductor laser 10 has two first semiconductor lasers 10Y and 10M corresponding to yellow and magenta, and two second semiconductor lasers 10C and 10K corresponding to cyan and black. The two first semiconductor lasers 10Y and 10M are spaced apart in a first direction. The first semiconductor laser 10Y is located on one side of the first semiconductor laser 10M in the first direction.

[0032] The second semiconductor laser 10C is positioned at a distance from the first semiconductor laser 10M in the second direction. The second semiconductor laser 10C is located on the other side of the second direction relative to the first semiconductor laser 10M. The second semiconductor laser 10K is positioned at a distance from the second semiconductor laser 10C in the first direction, and at a distance from the first semiconductor laser 10Y in the second direction.

[0033] The first coupling lenses 20Y, 20M and the second coupling lenses 20C, 20K are positioned opposite the corresponding semiconductor lasers 10Y, 10M, 10C, 10K. The first coupling lenses 20Y, 20M convert the light from the first semiconductor laser 10Y, 10M into the first beam BY, BM. The second coupling lenses 20C, 20K convert the light from the second semiconductor laser 10C, 10K into the second beam BC, BK.

[0034] The aperture plate 30 has an aperture diaphragm 31 through which the beam from the coupling lens 20 passes. In this embodiment, the aperture plate 30 is integrally formed with the frame F. The aperture plate 30 is located between the coupling lens 20 and the focusing lens 40. Four aperture diaphragms 31 are provided, corresponding to the four semiconductor lasers 10 and the coupling lens 20.

[0035] The focusing lens 40 is a lens that focuses the beam from the coupling lens 20 onto the mirror surface of the polygon mirror 51 in the sub-scanning direction. The focusing lens 40 is located on the opposite side of the aperture plate 30 from the coupling lens 20.

[0036] As shown in Figure 3, the deflector 50 is a device that deflects the beam from the coupling lens 20 in the main scanning direction (third direction), and includes a polygon mirror 51, a polygon motor 52, and a motor substrate 53. The polygon mirror 51 rotates to deflect the first beams BY and BM from the first coupling lenses 20Y and 20M and the second beams BC and BK from the second coupling lenses 20C and 20K in the main scanning direction. The polygon mirror 51 has five mirror surfaces provided at equidistant from the rotation axis X1. The polygon motor 52 is a motor that rotates the polygon mirror 51. The motor substrate 53 has the polygon motor 52 and is fixed to the frame F. In other words, the deflector 50 is fixed to the frame F.

[0037] As shown in Figure 4, the scanning optical system Lo is an optical system that images the beam deflected by the deflector 50 onto the surface of the photosensitive drum 200, which is the surface to be scanned. Each component constituting the scanning optical system Lo is fixed to the frame F. The scanning optical system Lo has a first scanning optical system LoY,LoM corresponding to yellow and magenta, and a second scanning optical system LoC,LoK corresponding to cyan and black. The first scanning optical system LoY,LoM images the first beams BY,BM onto the surface to be scanned. The second scanning optical system LoC,LoK images the second beams BC,BK onto the surface to be scanned.

[0038] The first scanning optical systems LoY and LoM are positioned on one side of the polygon mirror 51 in the second direction. The second scanning optical systems LoC and LoK are positioned on the other side of the polygon mirror 51 in the second direction. That is, the deflector 50 is located between the first scanning optical systems LoY and LoM and the second scanning optical systems LoC and LoK. The beam from the deflector 50 is incident on each of the scanning optical systems LoY, LoM, LoC, and LoK.

[0039] The first scanning optical system LoY comprises a first scanning lens 60YM, a second scanning lens 70Y, and a reflective mirror 81Y. The first scanning lens 60YM is the optical component closest to the deflector 50 among the optical components constituting the first scanning optical system LoY. More specifically, in the first scanning optical system LoY, the first scanning lens 60YM is the optical component closest to the deflector 50 when viewed in terms of the distance along the optical path of the beam passing through the center of the main scanning direction.

[0040] The first scanning lens 60YM is a lens that refracts the first beams BY and BM, which have been deflected by the deflector 50, in the main scanning direction to form images on the photosensitive drums 200Y and 200M. The first scanning lens 60YM also has an fθ characteristic that causes the first beams BY and BM, which have been scanned at a constant angular velocity by the deflector 50, to move at a constant velocity on the photosensitive drums 200Y and 200M.

[0041] The reflective mirror 81Y is a mirror that reflects the first beam BY from the first scanning lens 60YM toward the photosensitive drum 200Y.

[0042] The second scanning lens 70Y is a lens that refracts the first beam BY, reflected by the reflection mirror 81Y, in the sub-scanning direction to form an image on the photosensitive drum 200Y. In the scanning optical system Lo, the sub-scanning direction corresponds to the direction perpendicular to the main scanning direction and the beam propagation direction. The second scanning lens 70Y is positioned on one side of the first direction relative to the polygon mirror 51.

[0043] The first scanning optical system LoM includes a first scanning lens 60YM, a second scanning lens 70M, a reflective mirror 81M, and a mirror 82M. The first scanning lens 60YM is the optical component closest to the deflector 50 among the optical components constituting the first scanning optical system LoM.

[0044] The first scanning lens 60YM is shared with the first scanning optical system LoY. Mirror 82M is a mirror that reflects the beam BM from the first scanning lens 60YM to the reflection mirror 81M. The second scanning lens 70M and the reflection mirror 81M have the same function as the second scanning lens 70Y and the reflection mirror 81Y of the first scanning optical system LoY. That is, the reflection mirror 81M reflects the beam BM reflected by mirror 82M toward the photosensitive drum 200M, and the second scanning lens 70M refracts the beam BM reflected by the reflection mirror 81M in the sub-scanning direction to image it onto the photosensitive drum 200M.

[0045] The second scanning optical system LoC has a structure that is roughly symmetrical to the first scanning optical system LoM with respect to the rotation axis X1 of the polygon mirror 51. Specifically, the second scanning optical system LoC has a first scanning lens 60CK, a second scanning lens 70C, a reflective mirror 81C, and a mirror 82C, which have the same functions as the components of the first scanning optical system LoM. The first scanning lens 60CK is the optical component that is closest to the deflector 50 among the optical components that make up the second scanning optical system LoC.

[0046] The first scanning lens 60CK refracts the beams BC and BK deflected by the deflector 50 in the main scanning direction and images them onto the photosensitive drums 200C and 200K. The mirror 82C reflects the beam BC from the first scanning lens 60CK to the reflective mirror 81C, and the reflective mirror 81C reflects the beam BC reflected by the mirror 82C towards the photosensitive drum 200C. The second scanning lens 70C refracts the beam BC reflected by the reflective mirror 81C in the sub-scanning direction and images it onto the photosensitive drum 200C.

[0047] The second scanning optical system LoK has a structure that is roughly symmetrical to the first scanning optical system LoY with respect to the rotation axis X1 of the polygon mirror 51. Specifically, the second scanning optical system LoK has a first scanning lens 60CK, a second scanning lens 70K, and a reflective mirror 81K, which have the same functions as the components of the first scanning optical system LoY. The first scanning lens 60CK is the optical component that is closest to the deflector 50 among the optical components that make up the second scanning optical system LoK.

[0048] The reflective mirror 81K reflects the beam BK from the first scanning lens 60CK toward the photosensitive drum 200K, and the second scanning lens 70K refracts the beam BK reflected by the reflective mirror 81K in the sub-scanning direction to form an image on the photosensitive drum 200K.

[0049] As shown in Figure 3, the light emitted from each semiconductor laser 10Y, 10M, 10C, and 10K is converted into beams BY, BM, BC, and BK by passing through the corresponding coupling lenses 20Y, 20M, 20C, and 20K. The beams BY, BM, BC, and BK then pass through the corresponding aperture diaphragms 31Y, 31M, 31C, and 31K of the aperture plate 30, and then pass through the focusing lens 40 before being incident on the polygon mirror 51. The focusing lens 40 is a lens through which the beams BY, BM, BC, and BK pass in common, and its incident surface is a cylindrical surface, while its exit surface is a flat surface.

[0050] As shown in Figure 4, the polygon mirror 51 deflects beams BY, BM, BC, and BK toward the corresponding scanning optical systems LoY, LoM, LoC, and LoK. Beam BY toward the first scanning optical system LoY passes through the first scanning lens 60YM, is reflected by the reflection mirror 81Y, and is emitted through the second scanning lens 70Y toward the photosensitive drum 200Y on one side of the first direction. Beam BY is emitted from the second scanning lens 70Y at a predetermined angle with the first direction. Beam BY is imaged onto the surface of the photosensitive drum 200Y and scanned in the main scanning direction.

[0051] The beam BM directed towards the first scanning optical system LoM passes through the first scanning lens 60YM, is reflected by mirror 82M and reflection mirror 81M, and is emitted through the second scanning lens 70M toward the photosensitive drum 200M on one side of the first direction. The beam BM is emitted from the second scanning lens 70M at a predetermined angle with the first direction. The beam BM is imaged onto the surface of the photosensitive drum 200M and scanned in the main scanning direction. Similarly, the beams BC and BK are emitted toward the photosensitive drums 200C and 200K on one side of the first direction by the corresponding second scanning optical systems LoC and LoK, are imaged onto the surface of the corresponding photosensitive drums 200C and 200K, and scanned in the main scanning direction.

[0052] As shown in Figure 1, the frame F is made of resin and is integrally manufactured by molding. The frame F has side walls F1 that surround the deflector 50 and the scanning optical system Lo.

[0053] The side wall F1 is formed in the shape of a roughly rectangular frame. The side wall F1 has a first side wall F11, a second side wall F12, a third side wall F13, and a fourth side wall F14.

[0054] The first side wall F11 is located at one end of frame F in the third direction. The second side wall F12 is located at the other end of frame F in the third direction. The third side wall F3 is located at one end of frame F in the second direction. The fourth side wall F4 is located at the other end of frame F in the second direction.

[0055] The substrate 100 is located outside the second side wall F12. In other words, the substrate 100 is located on the other side in the third direction relative to the second side wall F12. The substrate 100 has a rectangular shape with the second direction as its longer side.

[0056] As shown in Figure 5, the substrate 100 has a first semiconductor laser 10Y, 10M, a second semiconductor laser 10C, 10K, a first optical sensor 108, and a second optical sensor 109 fixed to it. In other words, in this embodiment, the first semiconductor laser 10Y, 10M, the second semiconductor laser 10C, 10K, the first optical sensor 108, and the second optical sensor 109 mounted on the substrate 100.

[0057] The first light sensor 108 is a sensor that detects the first beam BY which has been deflected by the deflector 50. The first light sensor 108 detects the first beam BY which corresponds to yellow among the first beam BY and BM.

[0058] The second optical sensor 109 is a sensor that detects the second beam BK which has been deflected by the deflector 50. The second optical sensor 109 detects the second beam BK which corresponds to black among the second beams BC and BK.

[0059] The first light sensor 108 is located at one end of the substrate 100 in the second direction. The second light sensor 109 is located at the other end of the substrate 100 in the second direction.

[0060] As shown in Figures 6(a) to (c), the first light sensor 108 has a first light-receiving surface 108A for detecting the first beam BY. The second light sensor 109 has a second light-receiving surface 109A for detecting the second beam BK.

[0061] The substrate 100 has a first substrate hole 118 for exposing the first light-receiving surface 108A to the frame F side, and a second substrate hole 119 for exposing the second light-receiving surface 109A to the frame F side. The first light-receiving surface 108A is located in the first substrate hole 118. The second light-receiving surface 109A is located in the second substrate hole 119.

[0062] As shown in Figure 7, the scanning optical device 1 further comprises a first mirror 411, a second mirror 412, a first lens 421, and a second lens 422.

[0063] The first mirror 411 is provided on the frame F and reflects the first beam BY, which has been deflected by the deflector 50, and directs it to the first lens 421. In the third direction, the first mirror 411 is located between the polygon mirror 51 and the first light sensor 108. The first mirror 111 is positioned so as to overlap with the first light sensor 108 when viewed from the third direction.

[0064] The first lens 421 is a lens that focuses the first beam BY from the deflector 50, which has been reflected by the first mirror 411, onto the first photosensor 108. The first lens 421 has a spherical surface on one side and a cylindrical surface on the other. The distance of the optical path from the first lens 421 to the first photosensor 108 is smaller than the distance of the optical path from the first lens 421 to the deflector 50.

[0065] The second mirror 412 is provided on the frame F and reflects the second beam BK, which has been deflected by the deflector 50, and guides it to the second lens 422. In the third direction, the second mirror 412 is located between the polygon mirror 51 and the second light sensor 109. When viewed from the third direction, the second mirror 412 is positioned to overlap with the second light sensor 109.

[0066] The second lens 422 is a lens that focuses the second beam BK from the deflector 50, which has been reflected by the second mirror 412, onto the second photosensor 109. The second lens 422 has a spherical surface on one side and a cylindrical surface on the other. The distance of the optical path from the second lens 422 to the second photosensor 109 is smaller than the distance of the optical path from the second lens 422 to the deflector 50.

[0067] As shown in Figures 7 and 8(a) and 8(b), the second side wall F12 has a first frame hole H1 and a second frame hole H2. The first frame hole H1 and the second frame hole H2 are square holes.

[0068] As shown in Figure 8(a), the first frame hole H1 is a hole through which the first beam BY, deflected by the deflector 50, passes. The first frame hole H1 is opposite the first substrate hole 118.

[0069] In the scanning direction D1 of the first beam BY at the position of the first frame hole H1, one end 118A of the first substrate hole 118 is located outside the range of the first frame hole H1. Also, in the scanning direction D1, the other end 118B of the first substrate hole 118 is located within the range of the first frame hole H1.

[0070] One end 118A of the first substrate hole 118 is located downstream of the other end 118B in the scanning direction D1. One end 118A of the first substrate hole 118 is located downstream of the first frame hole H1 in the scanning direction D1.

[0071] The dimension of the first frame hole H1 is larger in the direction through which the first beam BY passes than in the scanning direction D1. In other words, the dimension of the first frame hole H1 is larger in the third direction than in the second direction.

[0072] The first light sensor 108 further comprises a package 108B and terminals 108C extending from the package 108B.

[0073] Package 108B is made of a resin that transmits the first beam BY. Package 108B encapsulates the components that make up the first light sensor 108. Specifically, package 108B encapsulates a light-receiving element having a first light-receiving surface 108A, a lead frame having terminals 108C, and a circuit element having an amplifier and a comparator.

[0074] Terminal 108C is connected to the side of the substrate 100 opposite to the frame F. The first beam BY is incident on the first light-receiving surface 108A approximately perpendicular to it.

[0075] The first light-receiving surface 108A is offset to one side from the center C1 of the package 108B in the scanning direction D1, and also offset to one side from the center C2 of the first substrate hole 118 in the scanning direction D1. In this embodiment, the center C1 of the package 108B and the center C2 of the first substrate hole 118 are assumed to be at the same position in the scanning direction D1.

[0076] More specifically, the first light-receiving surface 108A is offset upstream from the center C1 of the package 108B in the scanning direction D1. Furthermore, the first light-receiving surface 108A is offset upstream from the center C2 of the first substrate hole 118 in the scanning direction D1.

[0077] Furthermore, in the scanning direction D1, the center C3 of the first frame hole H1 is located within the range of the first light-receiving surface 108A.

[0078] As shown in Figure 8(b), the second frame hole H2 is the hole through which the second beam BK, deflected by the deflector 50, passes. The second frame hole H2 is opposite the second substrate hole 119.

[0079] In the scanning direction D2 of the second beam BK at the position of the second frame hole H2, one end 119A of the second substrate hole 119 is located outside the range of the second frame hole H2. Also, in the scanning direction D2, the other end 119B of the second substrate hole 119 is located within the range of the second frame hole H2.

[0080] One end 119A of the second substrate hole 119 is located downstream of the other end 119B in the scanning direction D2. One end 119A of the second substrate hole 119 is located downstream of the second frame hole H2 in the scanning direction D2.

[0081] The dimension of the second frame hole H2 is larger in the direction through which the second beam BK passes than in the scanning direction D2. In other words, the dimension of the second frame hole H2 is larger in the third direction than in the second direction.

[0082] The second light sensor 109 further comprises a package 109B and terminals 109C extending from the package 109B.

[0083] Package 109B is made of a resin that transmits the second beam BK. Package 109B encapsulates the components that make up the second light sensor 109. Specifically, package 109B encapsulates a light-receiving element having a second light-receiving surface 109A, a lead frame having terminals 109C, and a circuit element having an amplifier and a comparator.

[0084] Terminal 109C is connected to the side of the substrate 100 opposite to the frame F. The second beam BK is incident on the second light-receiving surface 109A at approximately perpendicular angles.

[0085] The second light-receiving surface 109A is offset to one side from the center C4 of the package 109B in the scanning direction D2, and also offset to one side from the center C5 of the second substrate hole 119 in the scanning direction D2. In this embodiment, the center C4 of the package 109B and the center C5 of the second substrate hole 119 are assumed to be in the same position in the scanning direction D2.

[0086] More specifically, the second light-receiving surface 109A is offset upstream from the center C4 of the package 109B in the scanning direction D2. Furthermore, the second light-receiving surface 109A is offset upstream from the center C5 of the second substrate hole 119 in the scanning direction D2.

[0087] Furthermore, in the scanning direction D2, the center C6 of the second frame hole H2 is located within the range of the second light-receiving surface 109A.

[0088] The control device 300 is configured with, for example, a CPU, RAM, ROM, input / output circuits, etc. As shown in Figure 7, the polygon mirror 51 rotates clockwise as shown in the figure, scanning the beams BY, BM, BC, and BK. The control device 300 has a function to determine the timing to start scanning exposure, in which the scanned surface is exposed by beams BY, BM, BC, and BK, based on the signal from the second photosensor 109 detecting the second beam BK. The control device 300 also detects the timing after the scanning exposure, in which the scanned surface is exposed by the first beam BY on the photosensitive drum 200, has finished, based on the signal from the first photosensor 108 detecting the first beam BY. Here, the scanned surface refers to the portion of the surface of the photosensitive drum 200 that is within the beam scanning range.

[0089] As shown in Figure 9, the control device 300 determines that the first beam BY has been incident on the first light-receiving surface 108A if the amount of light from the first beam BY received by the first light-receiving surface 108A exceeds the threshold TH during a period T1 shorter than the period it takes for the first beam BY to scan from one end to the other of the surface being scanned. Furthermore, the control device 300 determines that the second beam BK has been incident on the second light-receiving surface 109A if the amount of light from the second beam BK received by the second light-receiving surface 109A exceeds the threshold TH during a period T1 shorter than the period it takes for the second beam BK to scan from one end to the other of the surface being scanned.

[0090] Period T1 is the period after the period during which the first beam BY exposes the scanned surface. For example, it can be the time from when the first beam BY reaches the upstream end of the first frame hole H1 in the scanning direction until it reaches the downstream end of the first frame hole H1. Period T1 is also the period before the period during which the second beam BK exposes the scanned surface. For example, it can be the time from when the second beam BK reaches the upstream end of the second frame hole H2 in the scanning direction until it reaches the downstream end of the second frame hole H2.

[0091] Next, the operation of the control device 300 will be described. In the following description, the period during which the beam scans from one end to the other of the surface to be scanned will also be referred to as the "scanning period".

[0092] The control device 300 constantly performs the light reception determination process shown in Figure 10. Since the light reception determination process for the first beam BY and the second beam BK are the same, the following explanation will describe the light reception determination process for the first beam BY as representative.

[0093] In the light reception determination process, the control device 300 first determines whether the amount of light received by the first light receiving surface 108A is equal to or greater than the threshold TH (S1). If it is determined in step S1 that the amount of light is not equal to or greater than the threshold TH (No), the control device 300 terminates this process.

[0094] If the control device 300 determines in step S1 that the light intensity is equal to or greater than the threshold TH (Yes), then the control device 300 determines that the first beam BY has been detected by the first light-receiving surface 108A of the first light sensor 108 (S2). Specifically, in step S2, the control device 300 determines the time in step S1 when it was determined that the light intensity is equal to or greater than the threshold TH as the time when the first beam BY was detected by the first light-receiving surface 108A.

[0095] After step S2, the control device 300 determines whether the scanning cycle has elapsed (S3). The control device 300 repeats the process of step S3 until the scanning cycle has elapsed (No), and if it determines that the scanning cycle has elapsed (Yes), it terminates this process.

[0096] Next, we will explain the effects of detecting the first beam BY with the first optical sensor 108. Experiments have confirmed that scanning the first photosensor 108 with the first beam BY yields the signal shown in Figure 9. The following are possible reasons for obtaining such a signal.

[0097] As shown in Figure 11(a), because the first light-receiving surface 108A is located upstream of the center C1 of the package 108B, the scanning length of the first portion P1 is small, and the time during which the first beam BY scans the first portion P1 is short. Therefore, the probability of large amounts of stray light occurring within the first portion P1 during scanning is low, and it is considered that the amount of light received by the first light-receiving surface 108A does not exceed the threshold TH during the period T2 shown in Figure 9.

[0098] As shown in Figure 8(a), when the first beam BY is incident on the first light-receiving surface 108A, the amount of light received by the first light-receiving surface 108A becomes greater than or equal to the threshold TH during the period T3 shown in Figure 9. As shown in Figure 11(b), because the first light-receiving surface 108A is located upstream of the center C1 of the package 108B, the scanning length of the second portion P2 is large, resulting in a long scanning time for the first beam BY over the second portion P2. In addition, elements such as a lead frame supporting the first light-receiving surface 108A and an amplifier are mounted on the second portion P2 of the first light sensor 108, and stray light may be generated due to these elements. Therefore, the probability of large amounts of stray light occurring within the second portion P2 increases during scanning, and it is thought that the light intensity exceeded the threshold TH during the period T4 shown in Figure 9.

[0099] In this embodiment, the control device 300 determines that the first beam BY has been incident on the first light-receiving surface 108A when the light intensity first exceeds the threshold TH within the period T1. Therefore, even if the light intensity exceeds the threshold TH in period T4 due to stray light generated in the second portion P2, the result for period T4 can be ignored, and the timing of the incidence of the first beam BY on the first light-receiving surface 108A can be determined with high accuracy. Alternatively, the first semiconductor laser 10Y may be controlled to turn off the first beam BY based on the determination that the first beam BY has been incident on the first light-receiving surface 108A. Note that the effects of detecting the second beam BK with the second light sensor 109 are the same as those of detecting the first beam BY, so a detailed explanation is omitted.

[0100] As described above, the following effects can be obtained according to this embodiment. In the scanning direction D1 of the first beam BY, by configuring the first substrate hole 118 such that one end 118A is located outside the range of the first frame hole H1 and the other end 118B is located within the range of the first frame hole H1, a portion of the opening of the first substrate hole 118 on the first frame hole H1 side can be covered by the frame F, thereby suppressing stray light from the first frame hole H1 from entering the first substrate hole 118.

[0101] By configuring the first light-receiving surface 108A to be shifted upstream of the scanning direction D1 from the center C1 of the package 108B, the reflection of the first beam BY within the first portion P1 upstream of the first light-receiving surface 108A in the package 108B can be reduced, thereby suppressing stray light from entering the first light-receiving surface 108A.

[0102] By configuring the terminal 108C of the first light sensor 108 to be connected to the side of the circuit board 100 opposite to the frame F, it is not necessary to place the terminal 108C of the first light sensor 108 between the circuit board 100 and the frame F, thereby suppressing interference between the terminal 108C and the frame F when the circuit board 100 is attached to the frame F.

[0103] By configuring the first frame hole H1 in the direction of passage of the first beam BY to be larger than the dimension in the scanning direction D1, it is possible to suppress dust from entering the frame F through the first frame hole H1.

[0104] By configuring the first beam BY to be incident on the first light-receiving surface 108A at approximately orthogonal angles, the sizes of the first frame hole H1 and the first substrate hole 118 can be reduced.

[0105] By configuring the optical path distance from the first lens 421 to the first optical sensor 108 to be smaller than the optical path distance from the first lens 421 to the deflector 50, the magnification of the optical system from the first semiconductor laser 10Y to the first optical sensor 108 can be reduced, thereby mitigating the influence of errors in the components constituting the optical system on the imaging state.

[0106] In the scanning direction D2 of the second beam BK, by configuring the second substrate hole 119 such that one end 119A is located outside the range of the second frame hole H2 and the other end 119B of the second substrate hole 119 is located within the range of the second frame hole H2, a portion of the opening of the second substrate hole 119 on the second frame hole H2 side can be covered by the frame F, thereby suppressing stray light from the second frame hole H2 from entering the second substrate hole 119.

[0107] The control device 300 is configured to determine that the first beam BY has been incident on the first light-receiving surface 108A when the light intensity of the first beam BY first exceeds the threshold TH during a short period T1. This configuration suppresses false detections by the first light sensor 108 even if the light intensity of the first beam BY exceeds the threshold TH multiple times during a short period T1. Specifically, because the first light-receiving surface 108A is shifted upstream of the center C1 of the package 108B in the scanning direction D1, the reflection of the first beam BY within the first portion P1 of the package 108B upstream of the first light-receiving surface 108A is reduced. Therefore, before the first beam BY is incident on the first light-receiving surface 108A, the amount of light received on the first light-receiving surface 108A is less than the threshold TH, and the amount of light received first exceeds the threshold TH when the first beam BY is incident on the first light-receiving surface 108A. Subsequently, even if the amount of light received exceeds the threshold TH due to reflection of the first beam BY within the second portion P2 downstream of the first light-receiving surface 108A in package 108B, the incident detection by the control device 300 is completed, thus suppressing false detections.

[0108] This disclosure is not limited to the embodiments described above and can be used in various forms as illustrated below.

[0109] In the scanning direction, the upstream end of the first substrate hole may be located outside the range of the first frame hole, and the downstream end of the first substrate hole may be located within the range of the first frame hole. In the scanning direction, the upstream end of the second substrate hole may be located outside the range of the second frame hole, and the downstream end of the second substrate hole may be located within the range of the second frame hole.

[0110] In the scanning direction, the center of the first frame hole may be located outside the range of the first light-receiving surface.

[0111] The image forming apparatus is not limited to printers; it may also be a copier or a multifunction device, for example.

[0112] The elements described in the above embodiments and modifications may be implemented in any combination. [Explanation of Symbols]

[0113] 1. Scanning optical device 10Y First Semiconductor Laser 20Y First Coupling Lens 50 Deflector 51 Polygon Mirror 100 circuit boards 108 First Optical Sensor 108A 1st light receiving surface 118 1st board hole 118A One end 118B Other end F Frame F1 side wall F12 2nd side wall H1 First frame hole Lo scanning optical system

Claims

1. The first semiconductor laser and A first coupling lens that converts light from the first semiconductor laser into a first beam, A deflector having a polygon mirror that deflects the first beam from the first coupling lens in the main scanning direction, A first light sensor having a first light-receiving surface for detecting the first beam deflected by the deflector, A scanning optical system that images the first beam from the deflector onto the surface to be scanned, A frame having side walls surrounding the deflector and the scanning optical system, The system comprises a substrate located on the outside of the side wall to which the first light sensor is fixed, The side wall has a first frame hole through which the first beam deflected by the deflector passes. The substrate has a first substrate hole facing the first frame hole, the first substrate hole into which the first light-receiving surface is inserted. In the scanning direction of the first beam at the position of the first frame hole, One end of the first substrate hole is located outside the range of the first frame hole, A scanning optical apparatus characterized in that the other end of the first substrate hole is located within the range of the first frame hole.

2. The first optical sensor is The package has a first beam that transmits through it and seals the components constituting the first light sensor, The scanning optical apparatus according to claim 1, characterized in that the first light-receiving surface is offset to one side from the center of the package in the scanning direction, and offset to one side from the center of the first substrate hole in the scanning direction.

3. The scanning optical apparatus according to claim 2, characterized in that the first light-receiving surface is offset upstream from the center of the package in the scanning direction.

4. The first light sensor has terminals extending from the package, The scanning optical apparatus according to claim 2, characterized in that the terminal is connected to the side of the substrate opposite to the frame.

5. The scanning optical apparatus according to claim 1, characterized in that the dimension of the first frame hole in the direction through which the first beam passes is larger than the dimension in the scanning direction.

6. The scanning optical apparatus according to claim 1, characterized in that the first beam is incident on the first light-receiving surface substantially perpendicular to it.

7. The system further comprises a first lens that focuses the first beam, which has been deflected by the deflector, onto the first light sensor. The scanning optical apparatus according to claim 1, characterized in that the distance of the optical path from the first lens to the first light sensor is smaller than the distance of the optical path from the first lens to the deflector.

8. The second semiconductor laser, A second coupling lens that converts light from the second semiconductor laser into a second beam, The system further comprises a second photosensor having a second light-receiving surface for detecting the second beam deflected by the deflector, The side wall has a second frame hole through which the second beam deflected by the deflector passes. The substrate has a second substrate hole facing the second frame hole, in which the second light-receiving surface is inserted. In the scanning direction of the second beam, One end of the second substrate hole is located outside the range of the second frame hole, The scanning optical apparatus according to claim 1, characterized in that the other end of the second substrate hole is located within the range of the second frame hole.

9. The scanning optical apparatus according to claim 1, characterized in that, in the scanning direction, the center of the first frame hole is located within the range of the first light-receiving surface.

10. The scanning optical apparatus according to claim 3, An image forming apparatus comprising a control device for controlling the scanning optical device, The control device is An image forming apparatus characterized in that it determines that the first beam has been incident on the first light-receiving surface when the amount of light of the first beam received on the first light-receiving surface first exceeds a threshold value in a period shorter than the period during which the first beam scans the surface to be scanned from one end to the other.

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