JP7779117B2 - Scanning Optical Device - Google Patents

Description

The present invention relates to a scanning optical device equipped with a coupling lens and a deflector.

Conventionally, a known scanning optical device includes a coupling lens that converts light from a semiconductor laser into a beam, a deflector with a polygon mirror that deflects the beam from the coupling lens, a scanning optical system that focuses the beam deflected by the deflector on an image plane, and a frame that holds the coupling lens, deflector, and scanning optical system (see Patent Document 1). In this technology, the frame has a first recess that opens toward one side of the rotation axis of the polygon mirror, and a second recess that opens toward the other side of the rotation axis. The coupling lens and deflector are located in the first recess, and the scanning optical system is located in the second recess.

JP 2015-206910 A

However, in conventional technology, the coupling lens and deflector are in the same space and are not separated, so there is a risk that dust near the coupling lens will move toward the polygon mirror and adhere to it.

The present invention therefore aims to prevent dust near the coupling lens from moving toward the polygon mirror and adhering to it.

In order to solve the above problem, the scanning optical device of the present invention comprises a semiconductor laser that emits light, a coupling lens that converts the light from the semiconductor laser into a beam, a condensing lens that condenses the beam from the coupling lens in the sub-scanning direction, a deflector having a polygon mirror that deflects the beam from the condensing lens in the main scanning direction, a scanning optical system that focuses the light from the deflector on an image plane, a frame to which the deflector and the scanning optical system are fixed, and a cover that covers at least the portion of the frame where the deflector is located.
The frame has a first wall with a first opening through which the beam directed toward the polygon mirror passes.
The condenser lens closes the first opening.

With this configuration, the first opening through which the beam travels from the coupling lens to the polygon mirror is blocked by the condenser lens, preventing dust near the coupling lens from moving toward the polygon mirror and adhering to it.

The cover may also have a first rib that overlaps with the first wall when viewed from the direction of travel of the beam incident on the condenser lens.

This configuration improves the sealing performance between the first wall and the cover.

Furthermore, the frame may have an aperture plate located between the coupling lens and the condenser lens and having an aperture stop through which the beam passes, and the condenser lens may be sandwiched between the first wall and the aperture plate.

With this configuration, by sandwiching the condenser lens between the first wall and the aperture plate, the condenser lens can be brought into close contact with the first wall, improving airtightness.

Furthermore, the frame may have a second wall having a second opening through which the beam reflected by the polygon mirror passes, and the scanning lens in the scanning optical system that is closest to the polygon mirror may cover the second opening.

This configuration prevents dust near the scanning optical system from moving toward the polygon mirror and adhering to it.

The scanning optical device may further include a sealing member positioned between the scanning lens and the cover.

This configuration improves the seal between the scanning lens and the cover.

The cover may also have a second rib that overlaps with the second wall when viewed from the direction of travel of the beam incident on the scanning lens.

This configuration improves the sealing between the cover and the second wall.

Furthermore, the scanning optical system may be arranged on one side of the polygon mirror in a second direction perpendicular to a first direction along the rotation axis of the polygon mirror, and a beam deflected in the main scanning direction perpendicular to the first and second directions may be incident thereon, the scanning optical device may further include a first screw and a second screw for fixing the cover to the frame, and the rotation axis may be located between the first screw and the second screw in the main scanning direction.

This configuration improves the airtightness of the part of the frame where the deflector is located.

Furthermore, the device may include a plurality of semiconductor lasers and coupling lenses, and two of the beams emitted from the plurality of coupling lenses may be spaced apart in the second direction, and the first screw may be positioned between the optical paths of the two beams.

The cover may also cover the deflector and at least a portion of the scanning optical system.

With this configuration, the cover that covers the deflector can also seal the scanning optical system.

The frame may also have a first base wall that intersects with a first direction along the rotation axis of the polygon mirror and to which the deflector is attached, and a second base wall that intersects with the first direction and is positioned offset to one side of the first direction relative to the first base wall, and the deflector may be positioned to one side of the first direction relative to the first base wall, and the coupling lens may be positioned to the other side of the first direction relative to the second base wall.

Furthermore, the semiconductor laser may include a first semiconductor laser and a second semiconductor laser arranged at a position spaced apart from the first semiconductor laser in the sub-scanning direction, the coupling lens may include a first coupling lens that converts light from the first semiconductor laser into a beam and a second coupling lens that converts light from the second semiconductor laser into a beam, and the condenser lens may condense the beam from the first coupling lens and the beam from the second coupling lens in the sub-scanning direction.

With this configuration, the first opening through which multiple beams pass can be blocked with a single focusing lens.

Furthermore, the semiconductor laser may include a first semiconductor laser and a third semiconductor laser arranged at a distance from the first semiconductor laser in a direction perpendicular to the sub-scanning direction and the traveling direction of the beam incident on the condenser lens, and the coupling lens may include a first coupling lens that converts light from the first semiconductor laser into a beam and a third coupling lens that converts light from the third semiconductor laser into a beam, and the condenser lens may condense the beam from the first coupling lens and the beam from the third coupling lens in the sub-scanning direction.

With this configuration, the first opening through which multiple beams pass can be blocked with a single focusing lens.

The focusing lens may also have a rib that protrudes in the direction of travel of the beam incident on the focusing lens and contacts the first wall.

With this configuration, the first opening can be sealed with the collecting lens without the optical surface of the collecting lens coming into contact with the first wall.

This invention makes it possible to prevent dust near the coupling lens from moving toward the polygon mirror and adhering to the polygon mirror.

FIG. 2 is a perspective view of the scanning optical device according to the embodiment, as viewed from the other side in the first direction. FIG. 2 is a perspective view showing the structure around a coupling lens. FIG. 2 is a perspective view of the scanning optical device as seen from one side in a first direction. FIG. 4 is a cross-sectional view taken along line IV-IV of FIG. 2 is a cross-sectional view taken along the line VV in FIG. 1. FIG. 10 is a perspective view of the frame as seen from the other side in the first direction. FIG. 2 is a perspective view of the frame as seen from one side in a first direction. FIG. 10 is a cross-sectional view showing a structure for attaching the reflecting mirror to a frame. FIG. 2 is an exploded perspective view showing a frame, a first cover, and a second cover. FIG. 2 is a plan view of the frame as seen from one side in the first direction. FIG. 2 is a plan view of a frame to which a first cover is attached, viewed from one side in a first direction. FIG. 10 is a cross-sectional view showing a second rib of the first cover. FIG. 4 is a cross-sectional view showing a seal member between a first cover and a first scanning lens. FIG. 4 is a perspective view of the second cover as viewed from one side in the first direction. FIG. 4 is a cross-sectional view showing the relationship between the first wall and a first rib of the second cover.

As shown in Figures 1 to 3, the scanning optical device 1 includes a frame F, an incident optical system Li, a deflector 50, and a scanning optical system Lo. The scanning optical device 1 is applied to an electrophotographic image forming apparatus. In the following description, the direction along the rotation axis X1 of the polygon mirror 51 shown in Figure 3 is referred to as the "first direction." Furthermore, the direction perpendicular to the first direction, in which the polygon mirror 51 and the first scanning lens 60 shown in Figure 3 are aligned, is referred to as the "second direction." Furthermore, the direction perpendicular to the first and second directions 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. Furthermore, the arrows indicating each direction in the drawings will refer to "one side" in that direction.

As shown in Figure 2, the incident optical system Li includes four semiconductor lasers 10, four coupling lenses 20, an aperture plate 30, and a condenser lens 40 (see Figure 1).

The semiconductor laser 10 is a device that emits light. Four semiconductor lasers 10 are provided, corresponding to the four photosensitive drums 200 (see Figure 5) that are scanned and exposed by the scanning optical device 1. A toner image of a different color is formed on each photosensitive drum 200.

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, parts corresponding to the first color may be distinguished by adding "first" to the beginning of their names and adding "Y" to the end of their reference numerals. Similarly, parts corresponding to the second, third, and fourth colors may be distinguished by adding "second," "third," and "fourth" to the beginning of their names and adding "M," "C," and "K" to the end of their reference numerals.

The first semiconductor laser 10Y is arranged with a gap in the first direction relative to the second semiconductor laser 10M. The first semiconductor laser 10Y is located on one side of the second semiconductor laser 10M in the first direction.

The third semiconductor laser 10C is aligned with the second semiconductor laser 10M at a distance in the second direction. The third semiconductor laser 10C is located on the other side of the second semiconductor laser 10M in the second direction. The fourth semiconductor laser 10K is aligned with the third semiconductor laser 10C at a distance in the first direction, and is aligned with the first semiconductor laser 10Y at a distance in the second direction.

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

As shown in FIG. 1, the aperture plate 30 is a part that has an aperture stop 31 through which the beam from the coupling lens 20 passes, and is formed integrally with the frame F. The aperture plate 30 is located between the coupling lens 20 and the condenser lens 40.

The condenser lens 40 is a lens that condenses the beam from the coupling lens 20 onto the polygon mirror 51 in the sub-scanning direction. The condenser lens 40 is located on the opposite side of the diaphragm plate 30 from the coupling lens 20.

As shown in FIG. 3, the deflector 50 has a polygon mirror 51 and a motor 52. The polygon mirror 51 is a mirror that deflects the beam from the condenser 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 rotates the polygon mirror 51. The motor 52 is fixed to the frame F.

The scanning optical system Lo is an optical system that focuses the beam deflected by the deflector 50 onto the surface of the photosensitive drum 200, which serves as an image plane. The scanning optical system Lo is fixed to the frame F. As shown in FIG. 5, 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.

The first scanning optical system LoY and the second scanning optical system LoM are arranged 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 arranged 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.

The first scanning optical system LoY has a first scanning lens 60YM, a second scanning lens 70Y, and a reflecting mirror 81Y.

The first scanning lens 60YM is a lens that refracts the beams BY and BM 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 move 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.

The reflecting 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 reflecting mirror 81Y in the sub-scanning direction to form an image on the image plane. The second scanning lens 70Y is disposed on one side in the first direction with respect 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.

The second scanning optical system LoM has a first scanning lens 60YM, a second scanning lens 70M, a reflecting mirror 81M, and a mirror 82M.

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

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, a reflecting mirror 81C, and a mirror 82C, which have the same functions as the respective components of the second scanning optical system LoM.

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 reflecting mirror 81K, which have the same functions as the respective components of the first scanning optical system LoY.

As shown in Figure 4, 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. After passing through the corresponding aperture stops 31Y, 31M, 31C, and 31K of the diaphragm plate 30, the beams BY, BM, BC, and BK pass through the condenser lens 40 and are incident on the polygon mirror 51. The condenser lens 40 is a lens through which all beams BY, BM, BC, and BK pass, and has a cylindrical entrance surface and a flat exit surface.

As shown in FIG. 5, polygon mirror 51 deflects beams BY, BM, BC, and BK toward the corresponding scanning optical systems LoY, LoM, LoC, and LoK. Beam BY toward first scanning optical system LoY passes through first scanning lens 60YM, is reflected by reflecting mirror 81Y, and passes through second scanning lens 70Y to be emitted toward an image plane on one side of the first direction. Beam BY is emitted from second scanning lens 70Y at a predetermined angle with respect to the first direction. Beam BY is focused on the surface of first photosensitive drum 200Y and scanned in the main scanning direction.

Beam BM heading toward the second scanning optical system LoM passes through the first scanning lens 60YM, is reflected by mirror 82M and reflecting mirror 81M, and passes through the second scanning lens 70M to be emitted toward an image plane on one side in the first direction. Beam BM is emitted from the second scanning lens 70M at a predetermined angle with respect to the first direction. Beam BM is imaged on the surface of the second photosensitive drum 200M and scanned in the main scanning direction. Similarly, beams BC and BK are emitted toward an image plane on one side in the first direction by the corresponding scanning optical systems LoC and LoK, are imaged on the surfaces of the corresponding photosensitive drums 200C and 200K, and are scanned in the main scanning direction.

The frame F is made of resin and is integrally molded. The frame F has a first recess CP1 shown in FIG. 7 and a second recess CP2 shown in FIG. 6. The first recess CP1 opens to one side in the first direction. The second recess CP2 opens to the other side in the first direction. As shown in FIG. 5, the deflector 50 and part of the scanning optical system Lo are disposed within the first recess CP1. Specifically, all components of the scanning optical system Lo except for the reflecting mirrors 81 are disposed within the first recess CP1. As shown in FIG. 2, the coupling lens 20, diaphragm plate 30, and condenser lens 40 (see FIG. 1) are disposed within the second recess CP2.

As shown in Figures 6 and 7, the 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.

The first base wall Fb1 and the second base wall Fb2 are walls that intersect with the first direction. More specifically, the first base wall Fb1 and the second base wall Fb2 are walls whose thickness direction is along the first direction. In other words, the first base wall Fb1 and the second base wall Fb2 are walls having a plane that is perpendicular to the first direction.

The second base wall Fb2 is positioned offset to one side in the first direction relative to the first base wall Fb1. As shown in FIG. 5, the deflector 50 is attached to the first base wall Fb1. Specifically, the circuit board constituting the motor 52 is fixed to the first base wall Fb1 with screws from one side in the first direction. Furthermore, the aforementioned portion of the scanning optical system Lo is attached to one side in the first direction on the first base wall Fb1. Specifically, as shown in FIG. 7, the first scanning lenses 60YM and 60CK are attached to a first seating surface B1, which is part of the first base wall Fb1. The first seating surface B1 is a surface offset to one side in the first direction from the portion of the first base wall Fb1 where the deflector 50 is attached. Furthermore, the second scanning lenses 70Y, 70M, 70C, and 70K are attached to a second seating surface B2 that protrudes from the first base wall Fb1 to one side in the first direction. Mirrors 82M and 82C are attached to a third seating surface B3 that protrudes from the first base wall Fb1 toward one side in the first direction. The portion of the first base wall Fb1 that overlaps with the mirrors 82M and 82C in the first direction is a surface that is shifted toward one side in the first direction from the portion of the first base wall Fb1 where the deflector 50 is attached. Therefore, the deflector 50 and a portion of the scanning optical system Lo are located on one side in the first direction relative to the first base wall Fb1. As shown in FIG. 2, the semiconductor laser 10, coupling lens 20, and aperture plate 30 are located on the other side in the first direction relative to the second base wall Fb2. Also, as shown in FIG. 1, the condenser lens 40 and reflecting mirror 81 are also located on the other side in the first direction relative to the second base wall Fb2.

The reflecting mirror 81 is positioned near the first base wall Fb1 and is exposed on the other side in the first direction relative to the first base wall Fb1. In other words, the first base wall Fb1 does not have a portion located on the other side in the first direction of the reflecting mirror 81. As a result, the reflecting mirror 81 is exposed on the other side in the first direction without being hidden by the first base wall Fb1, and can be attached to the frame F from the other side in the first direction.

As shown in FIG. 6, the frame F further has a first wall F1 located between the first recess CP1 and the second recess CP2. The first wall F1 is connected to the first base wall Fb1 and the second base wall Fb2 (see also FIG. 7). The first wall F1 protrudes from the second base wall Fb2 to the other side in the first direction and protrudes from the first base wall Fb1 to one side in the first direction.

The first wall F1 has two first openings F11 and F12 through which the beams BY, BM, BC, and BK pass from the aperture stops 31 of the diaphragm plate 30 toward the polygon mirror 51. The first openings F11 and F12 are formed as slits that are long in the first direction, penetrate in the third direction, and open to one side in the first direction (see Figure 7). The first opening F11 passes the beams BY and BM. The first opening F12 passes the beams BC and BK.

As shown in FIG. 1, the condenser lens 40 is positioned to block the first openings F11 and F12 shown in FIG. 6. The condenser lens 40 is sandwiched between the first wall F1 and the aperture plate 30. As shown in FIG. 15, the condenser lens 40 has a rib 40A that protrudes from the exit surface to one side in the third direction, and the rib 40A contacts the first wall F1. The condenser lens 40 also has a rib 40B that protrudes from the entrance surface to the other side in the third direction, and the rib 40B contacts the aperture plate 30. More specifically, each end of the rib 40B in the second direction contacts the aperture plate 30 (see FIG. 1). The ribs 40A and 40B are configured to surround the periphery of the exit surface and entrance surface, which are optical surfaces of the condenser lens 40. This allows the condenser lens 40 to block the first openings F11 and F12 without the optical surfaces of the condenser lens 40 directly contacting the first wall F1 and the aperture plate 30.

As shown in Figures 3 and 7, the frame F further has two second walls F2 located on either side of the polygon mirror 51 (see Figure 3) in the second direction. The second wall F2 on one side in the second direction has a second opening F21 through which the beams BY and BM reflected by the polygon mirror 51 pass. The second wall F2 on the other side in the second direction has a second opening F22 through which the beams BC and BK reflected by the polygon mirror 51 pass. Each of the second openings F21 and F22 penetrates in the second direction and opens to one side in the first direction.

Each second wall F2 protrudes from the first base wall Fb1 to one side in the first direction. Each second wall F2 is connected to the first wall F1 and a first side wall F41, which will be described later. As a result, the first base wall Fb1, the first wall F1, each second wall F2, and the first side wall F41 form a storage recess CP3 for storing the polygon mirror 51.

The first scanning lens 60YM is positioned so as to block a portion of the second opening F21. The first scanning lens 60CK is positioned so as to block a portion of the second opening F22.

The frame F further has a first side wall F41, a second side wall F42, a third side wall F43, and a fourth side wall F44 that form a substantially rectangular frame surrounding each recess CP1, CP2.

The first side wall F41 is located on the opposite side of the deflector 50 from the semiconductor laser 10. The first side wall F41 protrudes from the first base wall Fb1 to one side in the first direction.

The second side wall F42 is located on the opposite side of the deflector 50 from the first side wall F41. More specifically, the second side wall F42 is located on the opposite side of the coupling lens 20 from the deflector 50. The second side wall F42 protrudes from the second base wall Fb2 to the other side in the first direction.

The third side wall F43 is located on the opposite side of the deflector 50 from the first scanning lens 60YM. The third side wall F43 is connected to one end of the first side wall F41, the first base wall Fb1, the second base wall Fb2, and the second side wall F42 in the second direction. A portion of the third side wall F43 protrudes from the first base wall Fb1 to one side in the first direction, and another portion protrudes from the second base wall Fb2 to the other side in the first direction.

The fourth side wall F44 is located on the opposite side of the deflector 50 from the first scanning lens 60CK. The fourth side wall F44 is connected to the other ends in the second direction of the first side wall F41, the first base wall Fb1, the second base wall Fb2, and the second side wall F42. A portion of the fourth side wall F44 protrudes from the first base wall Fb1 to one side in the first direction, and another portion protrudes from the second base wall Fb2 to the other side in the first direction.

As shown in FIG. 8 , the scanning optical device 1 further includes a support member Fs that can be detached from the frame F, which includes the first recess CP1 and second recess CP2 described above. The support member Fs supports the reflecting mirror 81. The support member Fs has a seat FsZ that supports the reflecting mirror 81 and allows the angle to be adjusted. The seat FsZ has a spherical protrusion Fs1 that can tiltably support the reflecting mirror 81. The protrusion Fs1 protrudes toward the reflecting mirror 81 and comes into contact with the reflecting mirror 81 to serve as a fulcrum when adjusting the orientation of the reflecting mirror 81. The orientation of the reflecting mirror 81 relative to the seat FsZ is fixed by photocurable resin P. The photocurable resin P can be, for example, an ultraviolet-curable resin. The reflecting mirror 81 and support member Fs, fixed by the photocurable resin P, are attached to the frame F by a U-shaped leaf spring SP.

One support member Fs and one leaf spring SP are arranged at each longitudinal end of each reflecting mirror 81. A pair of support members Fs and a pair of leaf springs SP corresponding to one reflecting mirror 81 are provided for each of the four reflecting mirrors 81.

The frame F has a support surface Fm1 that supports the support member Fs. The support surface Fm1 is positioned at a position corresponding to each longitudinal end of the four reflecting mirrors 81 (see Figure 6).

To attach the reflecting mirror 81 to the frame F, photocurable resin P is applied to both sides of the protrusion Fs1 of the support member Fs, and the support member Fs is attached to the support surface Fm1. The first reflecting mirror 81 is then brought into contact with the protrusion Fs1 of the support member Fs. At this time, the photocurable resin P is positioned in contact with both the support member Fs and the first reflecting mirror 81. A leaf spring SP is then attached, and the first reflecting mirror 81 and the support member Fs are pressed toward the frame F. Next, with light emitted from the semiconductor laser 10, the first reflecting mirror 81 is tilted from the protrusion Fs1 as a starting point, thereby adjusting the angle of the first reflecting mirror 81 while monitoring the beam position on the image plane. To adjust the angle, an arm (not shown) is pressed against the first reflecting mirror 81 to move it. After the angle adjustment is complete, the first reflecting mirror 81 is fixed to the support member Fs by irradiating the photocurable resin P with light.

As shown in FIG. 2, the scanning optical device 1 further includes a first laser holder H11, a second laser holder H12, a first lens holder H21, and a second lens holder H22.

The first laser holder H11 is an L-shaped member in cross section that holds the first semiconductor laser 10Y, the second semiconductor laser 10M, and the first coupling lens 20Y. The first coupling lens 20Y is fixed to the first laser holder H11 with a photocurable resin. The first coupling lens 20Y can be attached to the first laser holder H11 from the other side in the first direction. The first laser holder H11 is fixed to the frame F. Note that the second laser holder H12 is configured similarly to the first laser holder H11 except for the object that it holds, so a description of it will be omitted.

The first lens holder H21 is a member that holds the second coupling lens 20M in a position aligned with the first coupling lens 20Y in the first direction. The first lens holder H21 has a cylindrical portion into which the second coupling lens 20M is fitted. The first lens holder H21 is fixed to the first laser holder H11 with photocurable resin. The first lens holder H21 can be attached to the first laser holder H11 from the other side in the first direction. Note that the second lens holder H22 is configured in the same way as the first lens holder H21 except that the object it holds and the fixed destination are changed to the second laser holder H12, and therefore a description thereof will be omitted.

When attaching the coupling lens 20 to the frame, first, each laser holder H11, H12 is fixed to the frame F. Then, photocurable resin is applied to the first coupling lens 20Y or the first laser holder H11, and the position of the first coupling lens 20Y is adjusted relative to the first semiconductor laser 10Y. After adjusting the position, the first coupling lens 20Y is fixed to the first laser holder H11 by irradiating the photocurable resin with light. The fourth coupling lens 20K is also fixed to the second laser holder H12 using the same method as the first coupling lens 20Y.

After that, photocurable resin is applied to the first lens holder H21 or the first laser holder H11, which is holding the second coupling lens 20M, and the position of the second coupling lens 20M is adjusted relative to the second semiconductor laser 10M. After adjusting the position, the first lens holder H21 is fixed to the first laser holder H11 by shining light onto the photocurable resin. The third coupling lens 20C is also fixed to the second laser holder H12 via the second lens holder H22 using the same method as the second coupling lens 20M.

As shown in FIG. 9, the scanning optical device 1 further includes a cover C. The cover C has a first cover C1 and a second cover C2.

The first cover C1 covers the deflector 50 and the first base wall Fb1 from one side in the first direction. Specifically, the first cover C1 covers the first recess CP1.

The second cover C2 covers the coupling lens 20 and the second base wall Fb2 from the other side in the first direction. More specifically, the second cover C2 covers the second recess CP2.

The scanning optical device 1 further includes a first screw N1, a second screw N2, and two third screws N3. The first screw N1 and the second screw N2 are screws that secure the first cover C1 to the frame F. Each third screw N3 is a screw that secures the second cover C2 to the frame F.

As shown in FIG. 10, the frame F has a first boss F51 to which the first screw N1 is fastened and a second boss F52 to which the second screw N2 is fastened. The first boss F51, the rotation axis X1 of the polygon mirror 51, and the second boss F52 are aligned in the third direction. Specifically, the first boss F51 and the second boss F52 are located on a straight line LN that extends in the third direction and passes through the rotation axis X1. The rotation axis X1 is located between the first boss F51 and the second boss F52 in the third direction. Furthermore, the first boss F51 is located between the optical paths of two beams, for example, beams BY and BK, that are spaced apart in the second direction.

As a result, as shown in FIG. 11, when the first cover C1 is attached to the frame F, the rotation axis X1 is located between the first screw N1 and the second screw N2 in the third direction. The first screw N1 and the second screw N2 are also located on the aforementioned straight line LN. Furthermore, the first screw N1 is located between the optical paths of the two beams BY and BK, which are spaced apart in the second direction.

As shown in FIG. 12, the first cover C1 has two second ribs R21, R22. Each second rib R21, R22 overlaps with the second wall F2 when viewed in the direction of travel of the beam incident on the first scanning lens 60YM (see FIG. 13), specifically, when viewed from the second direction. Each second rib R21, R22 extends in the third direction. The distance between each second rib R21, R22 and the second wall F2 in the second direction is smaller than the thickness of the second wall F2. The two second ribs R21, R22 sandwich the second wall F2 in the second direction. The second rib R21, which is farther from the polygon mirror 51, protrudes further toward the first base wall Fb1 than the second rib R22, which is closer. Note that two second ribs R21, R22 are also provided on the second wall F2 on the other side of the polygon mirror 51 in the second direction.

As shown in FIG. 13, the scanning optical device 1 further includes a seal member SL located between the first scanning lens 60YM and the second rib R21 of the first cover C1. The seal member SL is made of an elastic material such as sponge. The seal member SL, together with the first scanning lens 60YM, closes the second opening F21 (see FIG. 3) in the second wall F2. A similar seal member SL is also provided for the first scanning lens 60CK located on the other side of the polygon mirror 51 in the second direction.

As shown in FIG. 14, the second cover C2 has a first rib R1 and two third ribs R3. The first rib R1 extends in the second direction. The two third ribs R3 are arranged at a distance in the second direction at the center of the first rib R1 in the second direction. Each third rib R3 protrudes further toward the second base wall Fb2 than the first rib R1 (see FIG. 15).

As shown in FIG. 15, the first rib R1 overlaps the first wall F1 when viewed in the direction of travel of the beam incident on the condenser lens 40, specifically, when viewed from the third direction. The distance in the third direction between the first rib R1 and the first wall F1 is equal to or less than the thickness of the first wall F1.

As shown in FIG. 4, the third rib R3 overlaps the first wall F1 when viewed from the third direction. The distance in the third direction between the third rib R3 and the first wall F1 is smaller than the thickness of the first wall F1. The third rib R3 sandwiches the condenser lens 40 between itself and the frame F.

Next, the operation of adjusting the positions and orientations of the members of the scanning optical device 1 will be described.
1 and 2, when adjusting the position of the coupling lens 20, the jig that holds the coupling lens 20 or the lens holders H21 and H22 is inserted into the second recess CP2 from the other side in the first direction. Therefore, the position adjustment device is disposed on the other side in the first direction of the frame F.

Furthermore, when performing an inspection to detect the beam incident on the polygon mirror 51, the inspection device is inserted into the first recess CP1 from one side in the first direction. Therefore, the inspection device is positioned on one side of the frame F in the first direction.

When adjusting the angle of the reflecting mirror 81, the jig holding the reflecting mirror 81 is brought into contact with the reflecting mirror 81 from the other side in the first direction. Therefore, the angle adjustment device is placed on the other side of the frame F in the first direction. At this time, the beam is detected by an inspection device placed on one side of the second scanning lens 70 in the first direction. The beam detection device can be placed on one side of the frame F in the first direction, and the device for adjusting the position of the coupling lens 20 and the device for adjusting the angle of the reflecting mirror 81 can be placed on the other side of the frame F in the first direction. Because the detection device and the adjustment device can be placed on opposite sides of the frame F, structural constraints on the manufacturing equipment can be alleviated. This also makes it possible to continuously adjust the position of the coupling lens 20 and the angle of the reflecting mirror 81 while the frame F is fixed to the manufacturing equipment.

As described above, the following effects can be obtained in this embodiment.
Since a device for adjusting the position of the coupling lens 20 can be placed on the other side of the frame F in the first direction, and a device for detecting light incident on the polygon mirror 51 can be placed on one side of the frame F in the first direction, constraints on the structure of the equipment can be relaxed.

By arranging the deflector 50 and part of the scanning optical system Lo on the same side of the first base wall Fb1, the mounting directions of the deflector 50 and part of the scanning optical system Lo are the same, allowing the scanning optical system Lo to be positioned with precision.

Since the beam from the scanning optical system Lo is configured to be emitted to one side in the first direction, the beam emitted from the scanning optical system Lo can be measured from the opposite side of the device for adjusting the position of the coupling lens 20.

Since the reflecting mirror 81 is exposed on the other side of the first base wall Fb1 in the first direction, the coupling lens 20 and reflecting mirror 81 that require adjustment can be adjusted from the same side.

The first cover C1 is provided to cover the deflector 50 and the first base wall Fb1 from one side in the first direction, so the first cover C1 can prevent dust from adhering to the deflector 50.

A second cover C2 is provided to cover the coupling lens 20 and second base wall Fb2 from the other side in the first direction, so the second cover C2 can prevent dust from adhering to the coupling lens 20.

Since the rotation axis X1 of the polygon mirror 51 is located between the first screw N1 and the second screw N2 in the main scanning direction, the airtightness of the portion of the frame F where the deflector 50 is located can be improved.

The first openings F11 and F12 through which the beam traveling from the coupling lens 20 to the polygon mirror 51 passes are blocked by the condenser lens 40, preventing dust near the coupling lens 20 from moving toward the polygon mirror 51 and adhering to the polygon mirror 51.

The second cover C2 has a first rib R1 that overlaps with the first wall F1 when viewed from the third direction, thereby improving the airtightness between the first wall F1 and the second cover C2.

The condenser lens 40 is sandwiched between the first wall F1 and the aperture plate 30, allowing the condenser lens 40 to be tightly attached to the first wall F1, improving airtightness.

The second openings F21, F22 through which the beam reflected by the polygon mirror 51 passes are blocked by the first scanning lenses 60YM, 60CK, preventing dust near the scanning optical system Lo from moving toward the polygon mirror 51 and adhering to the polygon mirror 51.

By providing a seal member SL between the first scanning lenses 60YM, 60CK and the first cover C1, it is possible to improve the sealing performance between the first scanning lenses 60YM, 60CK and the first cover C1.

The first cover C1 has second ribs R21, R22 that overlap with the second wall F2 when viewed from the second direction, thereby improving the airtightness between the first cover C1 and the second wall F2.

The cover may also cover the deflector and at least a portion of the scanning optical system.

The first cover C1 covers the deflector 50 and part of the scanning optical system Lo, so that the deflector 50 and part of the scanning optical system Lo can be sealed together by the first cover C1.

The present invention is not limited to the above-described embodiment and can be used in various forms, as exemplified below.

In the above embodiment, part of the scanning optical system Lo is attached to one side of the first base wall Fb1 in the first direction, but the present invention is not limited to this. For example, the entire scanning optical system may be attached to one side of the first base wall in the first direction.

In the above embodiment, the first side wall F41, second side wall F42, third side wall F43, and fourth side wall F44 are provided on the frame F, but the present invention is not limited to this, and at least one of the four side walls may be provided on the cover.

The cover only needs to cover at least the portion of the frame where the deflector is located. For example, the cover that covers the deflector and the cover that covers part of the scanning optical system may be separate. The cover may also cover the entire scanning optical system. For example, if the entire scanning optical system is housed in the first recess, the cover may cover the entire scanning optical system.

The number of first ribs and second ribs is not limited to that in the above embodiment and may be any number. Also, two first ribs may be provided, with the first wall sandwiched between the two first ribs.

In the above embodiment, the support member Fs having the seat surface FsZ is constructed from a member separate from the frame F, but the seat surface FsZ may also be integrally formed with the frame F.

The semiconductor laser 10 may be configured to have multiple light-emitting points. This allows multiple light beams from the semiconductor laser 10 to be converted into multiple beams by a single coupling lens 20, and the multiple beams to be imaged on the surface of the photosensitive drum 200 by the corresponding scanning optical system Lo. In this configuration, the beams BY, BM, BC, and BK in the above embodiment each include multiple beams.

In the above embodiment, a scanning optical device applied to a color image forming device was exemplified, but the scanning optical device may also be applied to a monochrome image forming device that scans with only one beam.

The elements described in the above embodiments and variations may be implemented in any combination.

REFERENCE SIGNS LIST 1 scanning optical device 10 semiconductor laser 20 coupling lens 40 condenser lens 50 deflector 51 polygon mirror C cover F frame F1 first wall F11 first opening F12 first opening Lo scanning optical system

Claims (12)

a semiconductor laser that emits light;
a coupling lens that converts light from the semiconductor laser into a beam;
a condenser lens that condenses the beam from the coupling lens in a sub-scanning direction;
a deflector having a polygon mirror that deflects the beam from the condenser lens in a main scanning direction;
a scanning optical system that forms an image of the light from the deflector on an image plane;
a resin frame to which the deflector and the scanning optical system are fixed;
an aperture plate located between the coupling lens and the condenser lens and having an aperture stop through which the beam passes, the aperture plate being integrally formed with the frame;
a cover that covers at least a portion of the frame where the deflector is disposed,
the frame has a first wall having a first opening through which a beam directed to the polygon mirror passes;
a focusing lens that covers the first opening and is sandwiched between the first wall and the aperture plate while being in contact with both the first wall and the aperture plate ; The frame is
a third wall that is located on one side of the condenser lens in an orthogonal direction that is orthogonal to the sub-scanning direction and the traveling direction of the beam incident on the condenser lens, and that connects the first wall and the diaphragm plate;
2. The scanning optical device according to claim 1, further comprising a fourth wall located on the other side of the condenser lens in the orthogonal direction and connecting the first wall and the diaphragm plate. the semiconductor lasers include a first semiconductor laser, a second semiconductor laser arranged at a position spaced apart from the first semiconductor laser in the sub-scanning direction, a third semiconductor laser arranged at a position spaced apart from the first semiconductor laser in an orthogonal direction orthogonal to the sub-scanning direction and the traveling direction of the beam incident on the condenser lens, and a fourth semiconductor laser arranged at a position spaced apart from the third semiconductor laser in the sub-scanning direction ,
the coupling lens includes a first coupling lens that converts the light from the first semiconductor laser into a beam, a second coupling lens that converts the light from the second semiconductor laser into a beam, a third coupling lens that converts the light from the third semiconductor laser into a beam, and a fourth coupling lens that converts the light from the fourth semiconductor laser into a beam ;
the condensing lens condenses the beam from the first coupling lens, the beam from the second coupling lens, the beam from the third coupling lens, and the beam from the fourth coupling lens in the sub-scanning direction ,
the first wall has two first openings spaced apart in the orthogonal direction;
3. The scanning optical device according to claim 1, wherein one of the two first apertures passes the beam from the first coupling lens and the beam from the second coupling lens, and the other first aperture passes the beam from the third coupling lens and the beam from the fourth coupling lens . The cover is
4. The scanning optical device according to claim 1, further comprising a first rib that overlaps with the first wall when viewed from the traveling direction of the beam incident on the condenser lens. the frame has a second wall having a second opening through which the beam reflected by the polygon mirror passes;
5. The scanning optical device according to claim 1 , wherein a scanning lens of the scanning optical system that is closest to the polygon mirror closes the second opening. 6. The scanning optical device according to claim 5 , further comprising a seal member positioned between the scanning lens and the cover. The cover is
7. The scanning optical device according to claim 5 , further comprising a second rib that overlaps with the second wall when viewed from the traveling direction of the beam incident on the scanning lens. the scanning optical system is disposed on one side of the polygon mirror in a second direction perpendicular to a first direction along a rotation axis of the polygon mirror, and a beam deflected in the main scanning direction perpendicular to the first direction and the second direction is incident on the scanning optical system;
the scanning optical device further includes a first screw and a second screw that fix the cover to the frame;
8. The scanning optical device according to claim 1 , wherein the rotation axis is located between the first screw and the second screw in the main scanning direction. a plurality of the semiconductor lasers and the coupling lenses;
two beams among the plurality of beams emitted from the coupling lenses are spaced apart in the second direction;
the first screw is located between the optical paths of the two beams ;
9. The scanning optical device according to claim 8 , wherein the condenser lens condenses the two beams separated in the second direction in the sub-scanning direction . 10. The scanning optical device according to claim 1, wherein the cover covers the deflector and at least a part of the scanning optical system. The frame is
a first base wall that intersects with a first direction along a rotation axis of the polygon mirror and to which the deflector is attached;
a second base wall that intersects with the first direction and is positioned at a position shifted to one side in the first direction relative to the first base wall,
the deflector is located on one side of the first base wall in the first direction,
11. The scanning optical device according to claim 1, wherein the coupling lens is located on the other side of the second base wall in the first direction. The condenser lens is
an exit-side rib that protrudes from the exit surface in the traveling direction of the beam incident on the condenser lens and contacts the first wall ;
13. The scanning optical device according to claim 1, further comprising an incident-side rib that protrudes from the incident surface in a direction opposite to the traveling direction and that contacts the diaphragm plate .