Scanning optical device

Abstract

To suppress deviation of an optical element when the optical element receives force from a sheet at the time of thermal expansion.SOLUTION: A scanning optical device 1 includes: a light source (semiconductor laser 10); a polygon mirror 51; a scanning optical system; an optical box 2; and a sheet 3. The polygon mirror 51 deflects beams from the light source. The scanning optical system forms an image of light from the polygon mirror 51 on an image surface. The scanning optical system has a first optical element (first reflection mirror 81Y). The optical box 2 houses the light source, the polygon mirror 51, and the scanning optical system. The optical box 2 has a first projection R1. The first projection R1 surrounds the first optical element, and a tip end face R101 is positioned outside the first optical element. The sheet 3 is a flexible one for covering the first optical element. The sheet 3 is adhered to a tip end face R101 of the first projection R1.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a scanning optical device for exposing a photoreceptor.

Background Art

[0002] Conventionally, as a scanning optical device, there is known one including an optical box having a hole in an outer wall, a lens disposed at a position corresponding to the hole, and a sheet covering the hole from the outside (see Patent Document 1). In this technique, the sheet is attached to the outer wall and the lens.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the prior art, since the sheet is attached to the outer wall and the lens, when the optical box or the like thermally expands, the lens may receive a force from the sheet and the position of the lens may shift.

[0005] Therefore, an object of the present invention is to suppress the optical element from receiving a force from the sheet and shifting during thermal expansion.

Means for Solving the Problems

[0006] To solve the above problems, a scanning optical device according to the present invention includes a light source, a polygon mirror, a scanning optical system, an optical box, and a sheet. The polygon mirror deflects a beam from the light source. The scanning optical system forms an image of light from the polygon mirror on an image plane. The scanning optical system has a first optical element. The optical box houses the light source, the polygon mirror, and the scanning optical system. The optical box has a first protrusion. The first protrusion surrounds the first optical element, and its tip surface is located outside the first optical element. The sheet is a flexible sheet that covers the first optical element. The sheet is adhered to the tip surface of the first protrusion.

[0007] In this configuration, the sheet is bonded to the tip surface of the first protrusion surrounding the first optical element, which is located outside the first optical element, so the sheet does not come into contact with the first optical element. Therefore, it is possible to suppress the displacement of the first optical element caused by the force exerted on it by the sheet during thermal expansion.

[0008] Furthermore, the scanning optical system may further include a second optical element separate from the first optical element, and the optical box may have a second protrusion surrounding the second optical element, with its tip surface located outside the second optical element, and the sheet may be adhered to the tip surface of the second protrusion to cover the second optical element.

[0009] This configuration simplifies the manufacturing process by covering the first and second optical elements with a single sheet.

[0010] Furthermore, the optical box has a third protrusion connecting the first protrusion and the second protrusion, and the tip surface of the third protrusion may be connected to the tip surface of the first protrusion and the tip surface of the second protrusion.

[0011] With this configuration, the sheet can also be supported at the tip surface of the third protrusion, thus ensuring the sheet's height.

[0012] Furthermore, the scanning optical system may further include a third optical element separate from the first and second optical elements, the second protrusion may surround the second and third optical elements, and the sheet may cover the third optical element.

[0013] According to this configuration, the second and third optical elements can be sealed together with a sheet.

[0014] Further, the first optical element may be a reflection mirror that reflects a beam toward an image plane.

[0015] According to this configuration, the reflection mirror can be sealed with a sheet.

[0016] Also, an adhesive may be provided on the entire surface of the sheet on the side of the first optical element.

[0017] According to this configuration, the operation of attaching the sheet to the optical box can be easily performed. Also, since the sheet is separated from the first optical element, the adhesive of the sheet does not adhere to the first optical element. Furthermore, even when dust enters the optical box, the adhesive of the sheet can capture the dust.

[0018] The optical box includes a frame to which the light source, the polygon mirror, and the scanning optical system are fixed, and a cover that covers a part of the frame, and the sheet may be adhered to both the frame and the cover.

[0019] According to this configuration, the gap between the frame and the cover can also be sealed with a sheet.

Effect of the Invention

[0020] According to the present invention, it is possible to suppress the optical element from being displaced by receiving a force from the sheet during thermal expansion.

Brief Description of the Drawings

[0021] [Figure 1] It is a perspective view showing a scanning optical device according to an embodiment. [Figure 2] It is a perspective view showing the scanning optical device disassembled. [Figure 3] It is a perspective view of the frame to which the incident optical system and the like are attached as viewed from the other side in the first direction. [Figure 4] It is a perspective view showing an enlarged incident optical system. [Figure 5] It is a perspective view of a frame to which an incident optical system or the like is attached, seen from one side in the first direction. [Figure 6] It is a sectional view taken along line VI-VI of FIG. 3. [Figure 7] It is a sectional view taken along line VII-VII of FIG. 3. [Figure 8] It is a perspective view of the frame seen from the other side in the first direction. [Figure 9] It is a sectional view showing an enlarged relationship between the sheet and the reflection mirror.

Embodiments for Carrying Out the Invention

[0022] Next, embodiments of the present invention will be described in detail with appropriate reference to the drawings. As shown in FIGS. 1 and 2, the scanning optical device 1 includes an optical box 2 and a sheet 3. The optical box 2 houses an incident optical system Li, a deflector 50, and a scanning optical system Lo, which will be described later. The optical box 2 includes a frame F and a cover C. The cover C includes a first cover C1 and a second cover C2.

[0023] As shown in FIGS. 3 to 5, the scanning optical device 1 further includes an incident optical system Li, a deflector 50, and a scanning optical system Lo. The incident optical system Li, the deflector 50, and the scanning optical system Lo are fixed to the frame F. The scanning optical device 1 is applied to an electrophotographic image forming device. In the following description, the direction along the rotation axis X1 of the polygon mirror 51 shown in FIG. 5 is referred to as the "first direction". Also, the direction orthogonal to the first direction and in which the polygon mirror 51 and the first scanning lens 60 shown in FIG. 5 are arranged is referred to as the "second direction". Also, the direction orthogonal to the first direction and the second direction is referred to as the "third direction". Note that the third direction corresponds to the main scanning direction in the scanning optical system Lo, and the first direction corresponds to the sub-scanning direction. Also, the arrows indicating the respective directions in the drawings shall refer to the "one side" in each direction.

[0024] As shown in Figure 4, the incident optical system Li comprises four semiconductor lasers 10, four coupling lenses 20, an aperture plate 30, and a focusing lens 40 (see Figure 3).

[0025] The semiconductor laser 10 is an example of a light source and is a device that emits light. There are four semiconductor lasers 10, corresponding to the four photosensitive drums 200 (see Figure 7) that the scanning optical device 1 scans and exposes. A toner image of a different color is formed on each photosensitive drum 200.

[0026] 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 the following description, the name of the component corresponding to the first color may be prefixed with "1st", and the code of the component corresponding to the first color may be prefixed with "Y" to distinguish them. Similarly, the components corresponding to the second, third, and fourth colors may be prefixed with "2nd", "3rd", and "4th", and the code may be prefixed with "M", "C", and "K" to distinguish them.

[0027] The first semiconductor laser 10Y is positioned at a distance from the second semiconductor laser 10M in the first direction. The first semiconductor laser 10Y is located on one side of the second semiconductor laser 10M in the first direction.

[0028] The third semiconductor laser 10C is positioned at a distance from the second semiconductor laser 10M in the second direction. The third semiconductor laser 10C is located on the other side of the second direction relative to the second semiconductor laser 10M. The fourth semiconductor laser 10K is positioned at a distance from the third semiconductor laser 10C in the first direction, and at a distance from the first semiconductor laser 10Y in the second direction.

[0029] The coupling lens 20 is a lens that converts light from the semiconductor laser 10 into a beam. Coupling lenses 20Y, 20M, 20C, and 20K corresponding to each color are positioned opposite the corresponding semiconductor lasers 10Y, 10M, 10C, and 10K.

[0030] As shown in Figure 3, the aperture plate 30 is the part that has an aperture diaphragm 31 through which the beam from the coupling lens 20 passes, and is integrally formed with the frame F. The aperture plate 30 is located between the coupling lens 20 and the focusing lens 40.

[0031] The focusing lens 40 is a lens that focuses the beam from the coupling lens 20 onto 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.

[0032] As shown in Figure 5, the deflector 50 includes a polygon mirror 51 and a motor 52. The polygon mirror 51 is a mirror that deflects the beam from the focusing lens 40 in the main scanning direction. The polygon mirror 51 has five mirror surfaces that are equidistant from the rotation axis X1. The motor 52 is a motor that rotates the polygon mirror 51. The motor 52 is fixed to the frame F.

[0033] The scanning optical system Lo is an optical system that forms an image of the beam deflected by the deflector 50 onto the surface of the photosensitive drum 200, which serves as the image plane. The scanning optical system Lo is fixed to the frame F. As shown in Figure 7, the scanning optical system Lo has a first scanning optical system LoY corresponding to yellow, a second scanning optical system LoM corresponding to magenta, a third scanning optical system LoC corresponding to cyan, and a fourth scanning optical system LoK corresponding to black.

[0034] The first scanning optical system LoY and the second scanning optical system LoM are positioned on one side of the polygon mirror 51 in the second direction. The third scanning optical system LoC and the fourth scanning optical system LoK are positioned on the other side of the polygon mirror 51 in the second direction. A beam deflected in the main scanning direction by the polygon mirror 51 is incident on each of the scanning optical systems LoY, LoM, LoC, and LoK.

[0035] The first scanning optical system LoY includes a first scanning lens 60YM, a second scanning lens 70Y, and a first reflective mirror 81Y as an example of a first optical element.

[0036] The first scanning lens 60YM is a lens that refracts the beams BY and BM, which have been deflected by the deflector 50, in the main scanning direction to form an image on the image plane. The first scanning lens 60YM also has an fθ characteristic that causes the light scanned at a constant angular velocity by the deflector 50 to be at a constant velocity on the image plane. The first scanning lens 60YM is the scanning lens in the first scanning optical system LoY that is closest to the polygon mirror 51.

[0037] The first reflection mirror 81Y is a mirror that reflects the beam BY from the first scanning lens 60YM toward the image plane. The second scanning lens 70Y is a lens that refracts the beam BY reflected by the first reflection mirror 81Y in the sub-scanning direction to form an image on the image plane. The second scanning lens 70Y is positioned on one side of the first direction relative to the polygon mirror 51. The second scanning lens 70Y is the scanning lens in the first scanning optical system LoY that is closest to the image plane.

[0038] The second scanning optical system LoM includes a first scanning lens 60YM, a second scanning lens 70M, and a second reflective mirror 81M and a mirror 82M, which are examples of second optical elements.

[0039] The first scanning lens 60YM is shared with the first scanning optical system LoY. The second scanning lens 70M and the second reflecting mirror 81M have the same function as the second scanning lens 70Y and the first reflecting mirror 81Y of the first scanning optical system LoY. Mirror 82M is a mirror that reflects the beam BM from the first scanning lens 60YM to the second reflecting mirror 81M.

[0040] The third scanning optical system LoC has a structure that is roughly symmetrical to the second scanning optical system LoM with respect to the rotation axis X1 of the polygon mirror 51. Specifically, the third scanning optical system LoC has a first scanning lens 60CK, a second scanning lens 70C, and a third reflective mirror 81C and mirror 82C as an example of a third optical element, which have the same functions as the components of the second scanning optical system LoM.

[0041] The fourth 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 fourth scanning optical system LoK has a first scanning lens 60CK, a second scanning lens 70K, and a fourth reflective mirror 81K, which have the same functions as the components of the first scanning optical system LoY.

[0042] As shown in Figure 6, 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.

[0043] As shown in Figure 7, 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 first reflection mirror 81Y, and exits through the second scanning lens 70Y toward the image plane on one side of the first direction. Beam BY exits from the second scanning lens 70Y at a predetermined angle with the first direction. Beam BY is imaged onto the surface of the first photosensitive drum 200Y and scanned in the main scanning direction.

[0044] The beam BM directed towards the second scanning optical system LoM passes through the first scanning lens 60YM, is reflected by mirror 82M and the second reflection mirror 81M, and is emitted through the second scanning lens 70M toward the image plane 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 second photosensitive drum 200M and scanned in the main scanning direction. Similarly, the beams BC and BK are emitted toward the image plane on one side of the first direction by the corresponding scanning optical systems LoC and LoK, are imaged onto the surfaces of the corresponding photosensitive drums 200C and 200K, and scanned in the main scanning direction.

[0045] Frame F is made of resin and is integrally manufactured by molding. Frame F has a first recess CP1 shown in Figure 5 and a second recess CP2 shown in Figure 8. The first recess CP1 opens on one side in the first direction. The second recess CP2 opens on the other side in the first direction. As shown in Figure 7, a deflector 50 and a part of the scanning optical system Lo are arranged inside the first recess CP1. Specifically, all members of the scanning optical system Lo except for each reflective mirror 81 are arranged inside the first recess CP1. As shown in Figure 4, a coupling lens 20, an aperture plate 30, and a condensing lens 40 (see Figure 1) are arranged inside the second recess CP2.

[0046] As shown in Figure 3, frame F has a first base wall Fb1 located at the bottom of the first recess CP1 and a second base wall Fb2 located at the bottom of the second recess CP2.

[0047] The first base wall Fb1 and the second base wall Fb2 are walls that intersect in the first direction. More specifically, the first base wall Fb1 and the second base wall Fb2 are walls whose thickness direction is aligned with the first direction. In other words, the first base wall Fb1 and the second base wall Fb2 are walls that have a plane perpendicular to the first direction. The second base wall Fb2 is located offset to one side in the first direction relative to the first base wall Fb1.

[0048] The reflective mirror 81 is positioned near the first base wall Fb1. When the sheet 3 is not attached to the frame F, the reflective mirror 81 is exposed on the other side in the first direction relative to the first base wall Fb1. In other words, the frame F does not have a portion located on the other side of the reflective mirror 81 in the first direction. As a result, the reflective mirror 81 is exposed on the other side in the first direction and can be attached to the frame F from the other side in the first direction.

[0049] As shown in Figure 8, the frame F has a support surface Fm1 that supports the reflective mirrors 81. The support surface Fm1 is positioned corresponding to each end of the four reflective mirrors 81 in the longitudinal direction. The support surface Fm1 supports the reflective mirrors 81 via a support member Fs shown in Figure 9. The support member Fs has a spherical projection Fs1 that can tiltably support the reflective mirrors 81. The reflective mirrors 81 are angle-adjustable with the projection Fs1 as a pivot point. The reflective mirrors 81 are fixed to the support member Fs by a photocurable resin P. The reflective mirrors 81 and support member Fs, fixed by the photocurable resin, are attached to the frame F by a U-shaped leaf spring SP. Specifically, the reflective mirrors 81 and support member Fs, with the photocurable resin P sandwiched between them, are attached to the support surface Fm1 by the leaf spring SP, the angle of the reflective mirrors 81 is adjusted, and then the photocurable resin P is cured by irradiating it with light, thereby attaching the reflective mirrors 81 and the support member Fs to the frame F.

[0050] As shown in Figure 8, frame F further has a partition wall F1 located between the first recess CP1 and the second recess CP2. Partition wall F1 is connected to the first base wall Fb1 and the second base wall Fb2.

[0051] The partition wall F1 has two first openings F11 and F12 through which beams BY, BM, BC, and BK, which extend from each opening 31 of the diaphragm plate 30 toward the polygon mirror 51, pass. The first openings F11 and F12 are formed as long slits in the first direction, penetrate in the third direction, and open on one side in the first direction. The first opening F11 allows beams BY and BM to pass through. The first opening F12 allows beams BC and BK to pass through.

[0052] As shown in Figures 3 and 8, the frame F further includes a first protrusion R1, a second protrusion R2, a third protrusion R3, a fourth protrusion R4, and a fifth protrusion R5. The first protrusion R1, the second protrusion R2, the third protrusion R3, the fourth protrusion R4, and the fifth protrusion R5 project from the other side of the polygon mirror 51 in the axial direction, more specifically in the first direction.

[0053] The first protrusion R1 is a roughly rectangular, cylindrical rib that surrounds the first reflective mirror 81Y when viewed from a direction along the rotation axis X1. The first protrusion R1 has four ribs R11, R12, R13, and R14. Rib R11 is located on one side of the second direction relative to the first reflective mirror 81Y. Rib R12 is located on the other side of the second direction relative to the first reflective mirror 81Y.

[0054] Rib R13 is located on one side of the third direction relative to the first reflecting mirror 81Y. Rib R13 is connected to ribs R11 and R12. Rib R14 is located on the other side of the third direction relative to the first reflecting mirror 81Y. Rib R14 is connected to ribs R11 and R12.

[0055] The second protrusion R2 is a roughly rectangular, cylindrical rib that surrounds the second reflective mirror 81M and the third reflective mirror 81C when viewed from a direction along the rotation axis X1. The second protrusion R2 has four ribs R21, R22, R23, and 24. Rib R21 is located on one side in the second direction relative to the second reflective mirror 81M. Rib R22 is located on the other side in the second direction relative to the third reflective mirror 81C.

[0056] Rib R23 is located on one side of the third direction relative to the second reflecting mirror 81M. Rib R23 is connected to ribs R21 and R22. Rib R24 is located on the other side of the third direction relative to the second reflecting mirror 81M. Rib R24 is connected to ribs R21 and R22.

[0057] As shown in Figure 9, the first protrusion R1 has a tip surface R101. The tip surface R101 is a roughly rectangular frame-shaped surface that surrounds the first reflective mirror 81Y when viewed from a direction along the rotation axis X1 of the polygon mirror 51. The tip surface R101 is located outside the first reflective mirror 81Y. Here, "outside" refers to the downstream side in the direction from the support surface Fm1 toward the first reflective mirror 81Y. In other words, the tip surface R101 is located further away from the support surface Fm1 than the first reflective mirror 81Y. Also, the plane S1 including the tip surface R101 does not overlap with the first reflective mirror 81Y and is located on the opposite side of the support surface Fm1 with the first reflective mirror 81Y in between.

[0058] The second protrusion R2 has a tip surface R201. The tip surface R201 is a roughly rectangular frame-shaped surface that surrounds the second reflective mirror 81M and the third reflective mirror 81C when viewed from a direction along the rotation axis X1 of the polygon mirror 51. The tip surface R201 is located outside the second reflective mirror 81M and the third reflective mirror 81C (see also Figure 7). Here, "outside" when the two reflective mirrors 81M and 81C are arranged within the frame-shaped tip surface R201 refers to the downstream side in the direction from the two support surfaces Fm1 toward the two reflective mirrors 81M and 81C. In other words, the tip surface R201 is located further away from the two support surfaces Fm1 than the two reflective mirrors 81M and 81C in the direction along the rotation axis X1 of the polygon mirror 51. Furthermore, the plane S2, which includes the tip surface R201, does not overlap with the two reflective mirrors 81M and 81C, and is located on the opposite side of the two support surfaces Fm1, with the two reflective mirrors 81M and 81C in between.

[0059] As shown in Figure 8, the third protrusion R3 is a rib connecting the first protrusion R1 and the second protrusion R2. The third protrusion R3 extends in the second direction. Multiple third protrusions R3 are arranged in the third direction at intervals. The tip surface R301 of the third protrusion R3 is connected to the tip surface R101 of the first protrusion R1 and the tip surface R201 of the second protrusion R2.

[0060] As shown in Figures 3 and 8, the fourth protrusion R4 is a roughly rectangular cylindrical rib that surrounds the fourth reflective mirror 81K when viewed from a direction along the rotation axis X1. The fourth protrusion R4 is roughly symmetrical to the first protrusion R1 with respect to the rotation axis X1 of the polygon mirror 51. The fourth protrusion R4 has a rib R41 corresponding to the rib R11 of the first protrusion R1, a rib R42 corresponding to the rib R12 of the first protrusion R1, a rib R43 corresponding to the rib R13 of the first protrusion R1, and a rib R44 corresponding to the rib R14 of the first protrusion R1.

[0061] The fourth protrusion R4 has a tip surface R401. The relationship between the tip surface R401 and the fourth reflecting mirror 81K is the same as the relationship between the tip surface R101 of the first protrusion R1 and the first reflecting mirror 81Y. In other words, the tip surface R401 is located outside the fourth reflecting mirror 81K.

[0062] The fifth protrusion R5 is a rib that connects the fourth protrusion R4 and the second protrusion R2. The fifth protrusion R5 extends in the second direction. Multiple fifth protrusions R5 are arranged in a row at intervals in the third direction. The tip surface R501 of the fifth protrusion R5 is connected to the tip surface R401 of the fourth protrusion R4 and the tip surface R201 of the second protrusion R2.

[0063] As shown in Figure 2, the first cover C1 is a cover that covers the first recess CP1. The second cover C2 is a cover that covers the second recess CP2. As shown in Figure 1, the second cover C2 is aligned with the second protrusion R2 in the third direction.

[0064] Sheet 3 is a flexible sheet that covers all four reflective mirrors 81. Sheet 3 is made of, for example, polyethylene terephthalate (PET). In this embodiment, Sheet 3 may be light-transmitting or light-blocking.

[0065] Adhesive is applied to the entire surface of sheet 3 on the side facing the reflective mirror 81. Sheet 3 is bonded to the second cover C2 and to the respective tip surfaces R101, R201, R301, R401, and R501 of each of the protrusions R1, R2, R3, R4, and R5 (see also Figure 6).

[0066] As shown in Figure 7, sheet 3 is supported by the tip surface R101 of the first protrusion R1, and is positioned with a space between it and the first reflecting mirror 81Y. Sheet 3 is supported by the tip surface R201 of the second protrusion R2, and is positioned with a space between it and the second reflecting mirror 81M and the third reflecting mirror 81C. Sheet 3 is supported by the tip surface R401 of the fourth protrusion R4, and is positioned with a space between it and the fourth reflecting mirror 81K.

[0067] Based on the above, the following effects can be obtained in this embodiment. Since the sheet 3 is bonded to the tip surfaces R101, R201, and R401 located outside each reflective mirror 81, the sheet 3 does not come into contact with each reflective mirror 81. Therefore, it is possible to suppress the displacement of the reflective mirror 81 due to the force exerted on it by the sheet 3 during thermal expansion.

[0068] Since one sheet 3 covers four reflective mirrors 81, the four reflective mirrors 81 can be sealed together with one sheet 3, and the manufacturing process can be simplified.

[0069] Since the sheet 3 is also supported by the tip surface R301 of the third protrusion R3 and the tip surface R501 of the fifth protrusion R5, the height position of the sheet 3 can be secured.

[0070] Since adhesive is applied to the entire surface of the sheet 3 on the side facing the reflective mirror 81, the sheet 3 can be easily attached to the optical box 2. Also, because the sheet 3 is separated from each reflective mirror 81, the adhesive on the sheet 3 does not adhere to each reflective mirror 81. Furthermore, even if dust enters the optical box 2, the adhesive on the sheet 3 can capture the dust.

[0071] Since sheet 3 is bonded to both frame F and second cover C2, the gap between frame F and second cover C2 can also be sealed with sheet 3.

[0072] The present invention is not limited to the embodiments described above, and can be used in various forms as illustrated below.

[0073] The first optical element, the second optical element, and the third optical element are not limited to the reflective mirror 81, but may be other optical elements that constitute the scanning optical system.

[0074] The adhesive may be applied to only a portion of the sheet, rather than the entire surface.

[0075] The light source may be a semiconductor laser having multiple light-emitting points.

[0076] In the above embodiment, a scanning optical device applied to a color image forming apparatus was illustrated, but the scanning optical device may also be applied to a monochrome image forming apparatus that scans only one beam.

[0077] The elements described in the above embodiments and modifications may be implemented in any combination. [Explanation of Symbols]

[0078] 1. Scanning optical device 2 Optical box 3 sheets 10 Semiconductor lasers 51 Polygon Mirror 81Y First Reflecting Mirror Lo scanning optical system R1 First protrusion R101 Tip surface

Claims

1. Light source and A polygon mirror for deflecting a beam from the light source, comprising a polygon mirror that rotates about a rotation axis along a first direction, A scanning optical system for imaging light from the aforementioned polygon mirror onto an image plane, comprising a lens and a mirror, An optical box housing the light source, the polygon mirror, and the scanning optical system, the optical box having a first protrusion that surrounds a first optical element which is one of the lenses and mirrors constituting the scanning optical system, and whose leading edge surface is located outside the first optical element, The device comprises a flexible sheet that is adhered to the tip surface of the first protrusion and covers the first optical element, The aforementioned optical box is A first recess opening on one side in the first direction, the first recess having the polygon mirror arranged inside, The first base wall is located at the bottom of the first recess, The first optical element is exposed on the other side in the first direction relative to the first base wall, The first protrusion has four ribs that protrude to the other side in the first direction, surrounding only the first optical element, which is one of the lenses and mirrors constituting the scanning optical system, which is a mirror. Two of the four ribs are positioned on one side of the first optical element in the longitudinal direction of the first optical element, and the remaining two ribs are positioned on one side of the first optical element in the short direction of the first optical element. The scanning optical apparatus is characterized in that the sheet seals the space inside the four ribs from the other side in the first direction.

2. The scanning optical system further includes a second optical element, which is a mirror separate from the first optical element. The optical box surrounds the second optical element and has a second protrusion whose tip surface is located outside the second optical element. The second optical element is exposed on the other side in the first direction relative to the first base wall, The second protrusion has four second ribs that surround the second optical element and protrude to the other side in the first direction, Two of the four second ribs are positioned on one side of the second optical element in the longitudinal direction, and the remaining two second ribs are positioned on one side of the second optical element in the short direction. The scanning optical apparatus according to claim 1, characterized in that the sheet is adhered to the tip surface of the second protrusion, covers the second optical element, and seals the space inside the second rib from the other side in the first direction.

3. The optical box has a third protrusion connecting the first protrusion and the second protrusion, The scanning optical apparatus according to claim 2, characterized in that the tip surface of the third protrusion is connected to the tip surface of the first protrusion and the tip surface of the second protrusion.

4. The scanning optical system further includes a third optical element, which is a mirror separate from the first and second optical elements. The third optical element is exposed on the other side in the first direction relative to the first base wall, The second protrusion surrounds only the second optical element and the third optical element, which are two mirrors among the lenses and mirrors that constitute the scanning optical system. The scanning optical apparatus according to claim 2, characterized in that the sheet covers the second optical element and the third optical element and seals the space inside the second rib from the other side in the first direction.

5. The scanning optical apparatus according to any one of claims 1 to 4, characterized in that the first optical element is a reflective mirror that reflects a beam toward the image plane.

6. The scanning optical apparatus according to any one of claims 1 to 4, characterized in that an adhesive is provided over the entire surface of the sheet on the side facing the first optical element.

7. The aforementioned optical box is The frame on which the light source, the polygon mirror, and the scanning optical system are fixed, The frame comprises a cover that covers a part of the frame, The scanning optical apparatus according to any one of claims 1 to 4, characterized in that the sheet is bonded to both the frame and the cover.

Images