Optical scanning device

Abstract

To provide an optical scanner in which a hole provided in a holding part and through which a luminous flux passes can be made small and which is excellent in dustproof performance.SOLUTION: The housing of the optical scanning device includes a holding portion that holds at least one of the scanning lens and the reflection mirror at an end portion in a main scanning direction that is a rotation direction of the rotary polygon mirror, and among the holding portions, the holding portion on a side close to the light source in the main scanning direction has a side wall extending from a bottom portion of the housing in an axial direction of a rotation axis of the rotary polygon mirror, and the side wall is provided with a regulation hole that regulates an incident light beam from the light source to the rotary polygon mirror.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present invention relates to an optical scanning device mounted in an electrophotographic image forming apparatus such as a laser beam printer (LBP) or a digital copying machine. [Background technology]

[0002] An optical scanning device (laser scanner) installed in a laser beam printer or the like has a light source that emits a laser beam in response to an image signal, a deflector that deflects the laser beam, and an imaging lens (scanning lens) and a reflecting mirror that focus the deflected laser beam on a photosensitive drum. The deflector, imaging lens, and reflecting mirror are all mounted in a housing.

[0003] Incidentally, an image forming apparatus for forming a full-color image includes an in-line image forming apparatus in which multiple photosensitive drums corresponding to each color are arranged in a line. When designing such an image forming apparatus to be compact, the distance between the multiple photosensitive drums is often shortened. As the distance between the multiple photosensitive drums becomes shorter, various optical components in the optical scanning device are also arranged closer to each other. For example, as disclosed in Patent Document 1, an imaging lens and a reflecting mirror may be arranged near a deflector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-26038 Summary of the Invention [Problem to be solved by the invention]

[0005] When an imaging lens or a reflecting mirror is placed near the deflector, a holder for the imaging lens or the reflecting mirror provided in the housing may be placed on the optical path from the light source to the deflector. In this case, it is necessary to provide an opening in the holder of the housing to allow the laser beam to pass through.

[0006] On the other hand, for reasons of cost, housings are often manufactured by injection molding of resin, and in this case, they are generally molded using a mold structure known as a cavity-core. With a cavity-core structure, the mold can only be opened and closed in one direction when releasing the molded product. Therefore, if an opening is to be formed in the holding section, the opening widens in the mold opening and closing direction, resulting in a large opening size. A larger opening size poses the problem of dust easily entering the housing from the outside. As a result, dust adhesion to the optical components can cause a decrease in image quality.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to provide an optical scanning device that can reduce the size of the hole provided in the holder through which the light beam passes and has excellent dustproof performance. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, the present invention provides an optical scanning device comprising a light source, a rotating polygon mirror that deflects a light beam emitted from the light source, a scanning lens through which the light beam deflected by the rotating polygon mirror passes, a reflecting mirror that reflects the light beam deflected by the rotating polygon mirror and guides it to a surface to be scanned, and a housing that holds the light source, the rotating polygon mirror, the scanning lens, and the reflecting mirror, wherein the housing has a holding portion that holds at least one of the scanning lens and the reflecting mirror at an end in the main scanning direction, which is the rotation direction of the rotating polygon mirror, and the holding portion on the side closer to the light source in the main scanning direction has a side wall that extends from the bottom of the housing in the axial direction of the rotation axis of the rotating polygon mirror, and the side wall is provided with a regulating hole that regulates the light beam incident from the light source to the rotating polygon mirror. [Effects of the Invention]

[0009] According to the present invention, the hole provided in the holder through which the light beam passes can be made small, and an optical scanning device with excellent dust-proof performance can be provided. [Brief explanation of the drawings]

[0010] [Figure 1]1 is a cross-sectional view of an image forming apparatus according to an embodiment of the present invention; [Figure 2] 1 is a plan view of an optical scanning device according to the present embodiment; [Figure 3] 1 is a cross-sectional view of an incident optical system in an optical scanning device according to the present embodiment. [Figure 4] 1 is a cross-sectional view of an optical scanning system in an optical scanning device according to the present embodiment. [Figure 5] 1 is a perspective view of a reflecting mirror holding portion of the present embodiment; [Figure 6] 1 is a perspective view of a holding portion of the present embodiment; [Figure 7] 1 is a schematic diagram of a mold structure for forming the aperture stop of this embodiment. [Figure 8] 1 is a perspective view of a holding portion of a comparative example; [Figure 9] Schematic diagram showing a mold structure when forming an opening shape of a comparative example. [Figure 10] 1 is a schematic diagram illustrating an air flow in the optical scanning device of the present embodiment. [Figure 11] Schematic diagram showing air flow in the incident optical system of this embodiment. [Figure 12] Schematic diagram showing the effect of different aperture stop positions in the main scanning direction on performance [Figure 13] 1 is a perspective view of an optical scanning device according to a modified example of the present embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] (Example) (Image forming device) 1 is a schematic cross-sectional view of an image forming apparatus 1. The image forming apparatus 1 of this embodiment is a printer that uses electrophotographic recording technology, and is a color printer that forms a full-color image by superimposing images of four colors: yellow, cyan, magenta, and black.

[0012] Next, the image formation process will be described. The process cartridges PY, PM, PC, and PK, each corresponding to a color, are equipped with photosensitive drums 11a, 11b, 11c, and 11d, charging rollers 12a, 12b, 12c, and 12d, and developing rollers 13a, 13b, 13c, and 13d. The photosensitive drums (scanned surfaces) 11a, 11b, 11c, and 11d, which are pre-charged by the charging rollers 12a, 12b, 12c, and 12d, are scanned with laser beams Ly, Lm, Lc, and Lk emitted from an optical scanning device 2, which serves as an exposure device. As a result, electrostatic latent images corresponding to image information are formed on the surfaces of the respective photosensitive drums. These electrostatic latent images are converted into toner images by the developing rollers 13a, 13b, 13c, and 13d, and then transferred onto an intermediate transfer belt 21 by primary transfer rollers 22a, 22b, 22c, and 22d. Meanwhile, recording material P placed in paper cassette 31 arranged below intermediate transfer belt 21 is picked up by pickup roller 32 in synchronization with the above-mentioned image formation process. Thereafter, the four-color toner image on intermediate transfer belt 21 is transferred to recording material P by secondary transfer roller 33. Recording material P with the transferred toner image is fixed by fuser 34 and then discharged by discharge rollers 35 and 36 to discharge tray 37 outside image forming apparatus 1. Note that the direction of arrow X in FIG. 1 is the arrangement direction of photosensitive drums 11a, 11b, 11c, and 11d, and the direction Z in the figure is perpendicular to the X direction. The direction of arrow Y in FIG. 2 is the direction perpendicular to the X and Z directions.

[0013] (Optical scanning device) Next, the overall configuration of the optical scanning device 2 according to this embodiment will be described with reference to FIGS. 2 to 4. FIG. 2 is a plan view of the optical scanning device 2 as viewed from the +Z direction from the process cartridges PY, PM, PC, and PK side of FIG. 1. FIG. 3(a) is a cross-sectional view of the optical scanning device 2 as viewed in the direction A shown in FIG. 2, and FIG. 3(b) is a cross-sectional view of the optical scanning device 2 as viewed in the direction B shown in FIG. 2. For ease of explanation, these figures are views in which a cover member, which is a component for covering an opening of the optical scanning device 2, has been removed. FIG. 4 is a cross-sectional view of the optical scanning device 2 as viewed in the direction C shown in FIG. 2, and also shows the photosensitive drums 11a, 11b, 11c, and 11d, which are components of the image forming apparatus 1, for ease of explanation.

[0014] First, the ray path up to the rotating polygon mirror 105, referred to as the incident optical system in Figures 2, 3(a), and 3(b), will be described. Laser incident beams ILy, ILm, ILc, and ILk emitted from light sources 101y, 101m, 101c, and 101k pass through anamorphic lenses 102ym and 102ck. The beam widths of the laser incident beams ILy, ILm, ILc, and ILk are restricted by sub-scanning aperture stops 103y, 103m, 103c, and 103k (shown by hidden lines in Figure 2) and main-scanning aperture stops 104ym and 104ck. Furthermore, the laser incident beams ILy, ILm, ILc, and ILk are focused as line images with a certain width on the deflecting reflecting surface of the rotating polygon mirror 105. Sub-scanning aperture stops 103y, 103m, 103c, and 103k are shaped so that they can also restrict the light beam width in the main scanning direction, which is the rotation direction of the rotating polygon mirror. However, it is main scanning aperture stops 104ym and 104ck that ultimately restrict the light beam width in the main scanning direction on rotating polygon mirror 105. Rotating rotating polygon mirror 105 deflects the incident laser light beam.

[0015] The optical scanning device 2 uses an anamorphic lens that has two functions: a collimator lens that converts the laser light beam into parallel light, and a cylinder lens that converges the laser light beam in one direction, but the collimator lens and cylinder lens may be arranged separately.

[0016] 3(a) and 3(b), the light source and anamorphic lens are arranged so that the incident laser beams ILy and ILm and the incident laser beams ILc and ILk are at angles of ±θ° with respect to the scanning plane S of the rotating polygon mirror 105. This arrangement is called a sub-scanning oblique incidence optical system among the incident optical systems, and makes it possible to deflect and scan the incident laser beams of four colors simultaneously with a single rotating polygon mirror.

[0017] Next, using Figure 4, we will explain the light ray paths from the rotating polygon mirror 105, known as the optical scanning system, to the photosensitive drums 11a, 11b, 11c, and 11d. The incident laser beams ILy, ILm, ILc, and ILk are deflected and scanned by the rotating polygon mirror 105, resulting in laser beams Ly, Lm, Lc, and Lk. The incident laser beams and the laser beams correspond to each other: ILy and Ly, ILm and Lm, ILc and Lc, and ILk and Lk. The rotating polygon mirror 105 reflects the laser beams Ly and Lc in the -Z direction, and the laser beams Lm and Lk in the +Z direction. The laser beams Ly and Lm then enter a first imaging lens (first scanning lens) 116ym, and the laser beams Lc and Lk enter a first imaging lens (first scanning lens) 116ck.

[0018] The subsequent light path will be explained using the laser beams Lk and Lc, since the laser beams Ly and Lk are similar to each other, and the laser beams Lm and Lc are similar to each other.

[0019] The laser beam Lk passes through a second imaging lens (second scanning lens) 119k and a first reflecting mirror 120k to form an image on the photosensitive drum 11d, and the laser beam Lc passes through a first reflecting mirror 117c, a second imaging lens (second scanning lens) 119c, and a second reflecting mirror 118c to form an image on the photosensitive drum 11c. The spot sizes of the laser beams Lc and Lk formed on the photosensitive drums 11c and 11d are determined by the various lenses described above, the main scanning aperture stop 104ck, and the sub scanning aperture stops 103c and 103k.

[0020] As shown in FIG. 4, due to limitations on the layout of the main body, the laser beams Ly, Lm, Lc, and Lk are incident obliquely at an angle α to the photosensitive drums 11a, 11b, 11c, and 11d. Furthermore, due to device miniaturization, the distance between the photosensitive drums 11a, 11b, 11c, and 11d in the X direction is narrow. For these reasons, the distance between the rotary polygon mirror 105 and the photosensitive drum 11c in the X direction is narrow. As a result, the distance between the second reflecting mirror 118c and the rotary polygon mirror 105 in the X direction is also narrow, and as shown in region P in FIG. 2, the edge of the second reflecting mirror 118c overlaps with the incident laser beam ILc in the XY plane (scanning plane S). Each imaging lens is fixed to the housing 100 with a UV adhesive, and each reflecting mirror is fixed to the housing with a biasing member.

[0021] (holding part) Next, how the second reflecting mirror 118c is held in the housing 100 will be described. FIG. 5 is a perspective view of region P shown in FIG. 2. As shown in FIG. 5, the second reflecting mirror 118c is held by a holder 150 (not shown in FIG. 5; will be described in FIG. 6) having a side wall 151 provided on the housing 100. The second reflecting mirror 118c is pressed and held by a mirror presser spring 160. Note that FIG. 5 shows a holding form for the end of the reflecting mirror that is closer to the light source in the longitudinal direction of the second reflecting mirror 118c, but the other end is also held in a similar configuration. As shown in FIG. 5, the thickness direction of the second reflecting mirror 118c is defined as Md, and the height direction thereof is defined as Mh.

[0022] Next, the details of the holder 150 will be described using FIG. 6. FIG. 6 is a diagram of FIG. 5 excluding the second reflection mirror 118c and the pressure spring 160. The holder 150 has a sidewall 151 extending from the bottom 149 of the housing 100 in the axial direction of the rotation axis of the rotary polygon mirror 105 (the -Z direction). The holder 150 further has an abutment surface 152 that abuts against the second reflection mirror 118c in the Mh direction and an abutment surface 153 that abuts against the second reflection mirror 118c in the Md direction. The sidewall 151 is provided with sub-scanning aperture stops 103c and 103k. The sub-scanning aperture stops 103c and 103k are restricting holes (apertures) that restrict the incident laser beam to a desired shape in the sub-scanning direction. By providing the sub-scanning aperture stops 103c and 103k on the sidewall 151, the aperture size for passing the incident laser beam in the holder 150 can be reduced.

[0023] (Mold structure for aperture stop molding) To provide the sub-scanning aperture stops 103c and 103k on the side wall 151, a mold structure known as a tilted core is required in addition to the typical cavity-core mold structure. Therefore, using FIGS. 7(a) and 7(b), the operation of the mold when providing the sub-scanning aperture stops 103c and 103k on the holder 150 will be described. FIG. 7(a) shows the mold position during molding of the sub-scanning aperture stops 103c and 103k, and FIG. 7(b) shows the mold position during mold release. For ease of explanation, only the mold necessary for explanation is shown. The shape of the +Z direction side of the housing 100 is formed by the cavity 500, which is the fixed side of the mold, and the shape of the -Z direction side is formed by the core 501, which is the movable side of the mold. If the mold structure only included the cavity 500 and the core 501, the sub-scanning aperture stops 103c and 103k would have an undercut shape that would prevent them from being released from the mold when opening and closing. Therefore, the sub-scanning aperture stops 103c and 103k are formed by the tilted core 502.

[0024] 7(b), during mold release, the position of the cavity 500 is fixed, and the molded product, the housing 100 and the core 501, move in the -Z direction in the figure relative to the cavity 500. As the core 501 moves, the inclined core 502 moves in the +Y direction in the figure, while also moving in the -Z direction, thereby eliminating the undercut and enabling mold release.

[0025] (Comparative example of mold structure for forming opening shape) 8 and 9, we will explain the shape around the holding part when molding is performed using only a cavity-core, which is a general mold structure, without using a tilted core. Fig. 8 is a perspective view of housing 300, with the reflective mirror and pressure spring removed for ease of explanation. Fig. 9 is a schematic diagram showing the mold when housing 300 is released from the mold.

[0026] The housing 100 of this embodiment is structured so that the sub-scanning aperture stops 103c and 103k are provided in the holder 150. In contrast, the housing 300 of the comparative example is structured so that the holder 150 is not provided with a sub-scanning aperture stop. A large opening 303 through which the incident laser beam passes is provided in the holder 150. The sub-scanning aperture stops 1034c and 1034k are provided in a portion 300S that extends from the bottom of the housing 300, separate from the holder 350. The sub-scanning aperture stops 1034c and 1034k also function as main-scanning aperture stops.

[0027] The holding portion 350 has a shape for holding the second reflecting mirror arranged in the same manner as the optical scanning device 2. As shown in Fig. 8, the holding portion 350 has a side wall 351, an abutment surface 352 that abuts against the second reflecting mirror in the Mh direction, and an abutment surface 353 that abuts against the second reflecting mirror in the Md direction, and the side wall 351 has an opening 303.

[0028] 9, the shape around holding portion 350 provided in housing 300 is formed by cavity 503 and core 504. Cavity 503 forms opening 303. Opening 303 needs to have a shape that allows cavity 503 and core 504 to be demolded, and opening 303 cannot have a shape in the +Z direction, which is the opening and closing direction of the mold. Therefore, as shown in FIG. 8, side wall 351 of holding portion 350 has a hole extending in the Z direction.

[0029] As described above, in this embodiment, the aperture size can be reduced by providing sub-scanning aperture stops 103c and 103k on the side wall of holding unit 150. In particular, in the configuration of this embodiment, multiple light sources are arranged side by side in the Z direction, so the effect of reducing the aperture size of sub-scanning aperture stops 103c and 103k is greater than that of aperture 303 in the comparative example.

[0030] (Explanation of dustproof effect) Next, the reason why the dustproof performance of the optical scanning device 2 is improved by reducing the aperture size will be explained with reference to FIGS.

[0031] FIG. 10 is a perspective view of the optical scanning device 2. The rotating polygon mirror 105 rotates in the CW direction indicated by the arrow in the figure, generating an internal airflow as it rotates. The first imaging lenses 116ym and 116ck and the light-shielding walls 161 and 162 of the housing 100 are arranged around the rotating polygon mirror along the Y direction, restricting the direction of the airflow, causing the internal airflow to flow in the ±Y direction as shown in the figure. Meanwhile, the internal airflow flowing in the -Y direction, where the light source is located, hits the wall 163 on which the main scanning aperture stops 104ym and 104ck are located. When a fluid hits a wall, its flow velocity decreases, resulting in an increase in air pressure. This increases the air pressure around the wall 163. Because the wall 163 is located near the incident laser beams ILc and ILk, an area of ​​higher pressure than the surrounding area is generated above the incident laser beams ILc and ILk.

[0032] FIG. 11, like FIG. 3(a), illustrates the airflow in the incident system using a cross-sectional view of the optical scanning device 2 viewed in the direction A in FIG. 2. As explained in FIG. 10, if an area with higher pressure than the surroundings occurs above the incident laser beams ILc and ILk, the airflow flows from the high-pressure area to the low-pressure area, generating an external airflow toward the outside of the optical scanning device 2. The external airflow passes through the sub-scanning aperture stops 103c and 103k provided in the holder as an outflow route. As explained above, the small aperture size reduces the outflow amount. Reducing the outflow amount also reduces the inflow amount from other openings in the optical scanning device 2. These other openings vary depending on the configuration of the optical scanning device, but they can include passage holes for passing the laser beam from the optical scanning device toward the photosensitive drum and mold cutout holes provided in the housing. Mold cutout holes are holes that ensure the movement trajectory of the mold to form the desired shape. They are necessary when, for example, a claw shape is required to secure a lens or spring to the housing. Since dust such as toner and paper powder exists outside the optical scanning device 2, reducing the amount of dust entering from the outside reduces the amount of dust entering the optical scanning device, improving the dustproof performance of the optical scanning device 2.

[0033] 10 and 11 is not limited to the configuration of the optical scanning device 2, and a similar effect can be obtained in a configuration in which the holder is arranged above the incident laser beam, as will be explained below. First, the internal airflow generated in the ±Y directions from the rotating polygon mirror will be a similar airflow in a typical optical scanning device in which the first imaging lens is located near the rotating polygon mirror and arranged along the Y direction. Next, with regard to the wall shape that generates an area of ​​high pressure when the airflow hits it, in this embodiment the wall provided with the main scanning aperture stop performed this function. However, even if such a wall is not present, a side wall is required in a configuration in which the holder is arranged above the incident laser beam, and the internal airflow hitting that side wall will generate an area of ​​high pressure.

[0034] That is, in a general optical scanning device where the holding part is arranged on the laser incident light beam, since the air flow is similar to that of this embodiment, a dust-proof effect can be obtained by reducing the opening size of the holding part.

[0035] (Modification example) In this embodiment, as the light source, a multi-beam element that emits a plurality of laser light beams from one light source was assumed, so the aperture stops for the main scanning and the sub-scanning were arranged at different positions. This is because in the case of a multi-beam element, the optical performance can be ensured by arranging the main scanning aperture stop closer to the rotating polygon mirror side 105. Details will be described using FIG. 12. FIG. 12 is a schematic diagram showing the influence of the position of the main scanning aperture stop on the performance when using a multi-beam element. For convenience of explanation, the arrangement of each component is simplified. The multi-beam element 600 emits two laser light beams from one element. The difference in the imaging state on the rotating polygon mirror 602 will be described when the optical path of the two laser light beams is determined by the main scanning aperture stop 601a located far from the rotating polygon mirror 602 via the collimator lens 603 and when the optical path is determined by the main scanning aperture stop 601b located close to the rotating polygon mirror 602. Actually, the beam width of the laser light beam is also determined by the width of the main scanning aperture stop, but for the sake of explanation only about the optical path, the laser light beam only shows the central axis of the laser light beam.

[0036] The two laser light beams LD1a and LD2a whose optical paths are determined by the main scanning aperture stop 601a are separated by a distance fa in the reflection point distance on the rotating polygon mirror 602. On the other hand, the two laser light beams LD1b and LD2b determined by the main scanning aperture stop 601b are separated by a distance fb in the reflection point distance on the rotating polygon mirror 602, and fb < fa. Since a smaller reflection point distance between the lasers on the rotating polygon mirror 602 can reduce the deviation of the laser interval in the main scanning direction when the imaging position on the photosensitive drum varies, in this embodiment, the main scanning aperture stop is arranged closer to the rotating polygon mirror 105 than the sub-scanning aperture stop.

[0037] If deviation in the laser spacing on the photosensitive drum can be tolerated, or if a single-beam element is used in which only one laser beam is emitted from one light source, the main-scanning aperture stop may be located at the position of the sub-scanning aperture stop, which has the advantage of increasing the degree of freedom in arranging optical components.

[0038] In this modified example, an optical scanning device in which a main scanning aperture stop is arranged at the position of the sub-scanning aperture stop is shown using Fig. 13. Note that, apart from the housing, the components are the same as those of the optical scanning device 2, and therefore a description of each component will be omitted. Fig. 13 is a perspective view of a position similar to that of region P of the optical scanning device 2 shown in Fig. 2.

[0039] The holder 250 is shaped to hold the second reflecting mirror 118c, which is arranged in the same manner as in the optical scanning device 2. FIG. 13 is a view excluding the second reflecting mirror and the pressure spring. The holder 250 has a side wall 251 extending from the bottom of the housing 200, an abutment surface 252 that abuts against the second reflecting mirror 118c in the Mh direction, and an abutment surface 253 that abuts against the second reflecting mirror 118c in the Md direction. The side wall 251 is provided with elliptical aperture stops 203c and 203k, which restrict the light beam widths on the rotating polygon mirror 105 in the main scanning direction and the sub-scanning direction.

[0040] In this modified example, the aperture shape is elliptical, but it may be rectangular, for example, as long as it can regulate the light beam width in both the main scanning and sub-scanning directions.

[0041] Furthermore, in this modification, the multi-beam element is a two-beam laser element that emits two laser beams from one element, but it may be a laser element that emits three or more laser beams from one element.

[0042] In this embodiment, a color image forming apparatus has been described, but the present invention is not limited to this. A similar effect can also be obtained in a monochrome image forming apparatus in which the holding portion is positioned on the laser incident light beam and an opening is required in the holding portion to allow the incident light beam to pass through.

[0043] Furthermore, the component held by the holder is a reflecting mirror, but this is not limiting, and a similar effect can be obtained even when the holder of the imaging lens is positioned on the incident laser beam. [Explanation of symbols]

[0044] 2 Optical scanning device 100 Housing 103y, 103m, 103c, 103k Sub-scanning aperture stop 104ym, 104ck Main scanning aperture stop 105 Rotating polygonal mirror 118y, 118m, 118c, 118k reflecting mirror 150 Holding part 151 Side wall ILy, ILm, ILc, ILk Laser incident beam

Claims

1. a light source; and a rotating polygonal mirror that deflects a light beam emitted from the light source. a scanning lens through which the light beam deflected by the rotating polygon mirror passes; a reflecting mirror that reflects the light beam deflected by the rotary polygon mirror and guides it to a surface to be scanned; a housing for holding the light source, the rotating polygonal mirror, the scanning lens, and the reflecting mirror; In an optical scanning device comprising: the housing includes a holder that holds at least one of the scanning lens and the reflecting mirror at an end in a main scanning direction, which is a rotation direction of the rotary polygon mirror; the holding portion on the side closer to the light source in the main scanning direction has a sidewall extending from a bottom of the housing in an axial direction of a rotation axis of the rotary polygon mirror, The optical scanning device is characterized in that the side wall is provided with a restricting hole for restricting the incident light beam from the light source onto the rotary polygon mirror.

2. 2. The optical scanning device according to claim 1, wherein the restricting hole restricts the width in the sub-scanning direction of the light beam that forms an image on the surface to be scanned.

3. 3. The optical scanning device according to claim 2, wherein a restriction hole is provided between the restriction hole and the rotary polygon mirror for restricting the width in the main scanning direction of the light beam that forms an image on the scanned surface.

Images