Optical scanner and image forming apparatus

Abstract

To provide an optical scanner downsized with a simple configuration.SOLUTION: An optical scanner includes: a deflector that deflects a first light flux from a first light source to scan a first scanned surface in a main scanning direction; a first imaging optical system and a reflecting optical element that guide the first light flux deflected by the deflector to the first scanned surface; an optical element that guides the first light flux emitted from the first light source to the deflector; and a holding member that holds the deflector, the first imaging optical system, the reflecting optical element, and the optical element. The holding member has a common protrusion that protrudes in a sub-scanning direction and abuts on both the optical element and the reflecting optical element in the main scanning direction.SELECTED DRAWING: Figure 5

Description

[Technical field]

[0001] The present invention relates to an optical scanning device, and more particularly to an optical scanning device suitable for use in image forming apparatuses such as laser beam printers, digital copiers, and multifunction printers. [Background technology]

[0002] 2. Description of the Related Art Conventionally, there has been known an optical scanning device that is miniaturized by arranging a plurality of optical elements close to each other through ingenious arrangement between a plurality of holding portions each holding an optical element. Patent document 1 discloses an optical scanning device that has been made smaller by devising an arrangement between a holding part that holds a collimator lens that converts the light beam emitted from a light source into a parallel light beam, and a holding part that holds a reflective mirror that bends the optical path of the light beam deflected by a deflector.

[0003] Specifically, in the optical scanning device disclosed in Patent Document 1, a reflecting mirror for bending the optical path of the light beam deflected by the deflector is held by a holding portion that is integrally formed on the housing. On the other hand, a collimator lens that converts the light beam emitted from the light source into a parallel light beam is held by a light source unit that holds the light source, and the light source unit is fixed to the housing by a fixing screw. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2016-133777 A Summary of the Invention [Problem to be solved by the invention]

[0005] In the optical scanning device disclosed in Patent Document 1, a collimator lens that converts the light beam emitted from the light source into a parallel light beam is held by a light source unit that is separate from the housing, and the light source unit is fixed to the housing by fixing screws, making the device large and complex. SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide an optical scanning device that has a simple configuration and is compact. [Means for solving the problem]

[0006] The optical scanning device of the present invention comprises a deflector that deflects a first light beam from a first light source to scan a first scanned surface in a main scanning direction, a first imaging optical system and a reflective optical element that guide the first light beam deflected by the deflector to the first scanned surface, an optical element that guides the first light beam emitted from the first light source to the deflector, and a holding member that holds the deflector, the first imaging optical system, the reflective optical element, and the optical element, and the holding member is characterized in that it protrudes in the sub-scanning direction and has a common protrusion that abuts both the optical element and the reflective optical element in the main scanning direction. Effect of the Invention

[0007] According to the present invention, it is possible to provide an optical scanning device that has a simple configuration and is compact. [Brief description of the drawings]

[0008] [Figure 1] 1A is a development view in a main scanning section and a partial sub-scanning section of an optical scanning device according to a first embodiment. [Diagram 2] 3 is a sub-scanning sectional view of a first imaging optical element included in the optical scanning device according to the first embodiment. [Diagram 3] 2 is a partial main-scan sectional projection view of the optical scanning device according to the first embodiment. FIG. [Figure 4] 3A and 3B are a front view and a side view of a first incident optical element included in the optical scanning device according to the first embodiment. [Diagram 5] 3A to 3C are diagrams illustrating the vicinity of a first incident optical element of the optical scanning device according to the first embodiment as viewed in the optical axis direction, the main scanning direction, and the sub-scanning direction. [Figure 6] 5A and 5B are diagrams showing the image height dependence of the LSF depth center position on each scanned surface in the optical scanning device according to the first embodiment. [Figure 7] 2 is a partial main-scan sectional projection view of the optical scanning device according to the first embodiment. FIG. [Figure 8] 11A and 11B are a main-scanning sectional development view and a partial sub-scanning sectional view of an optical scanning device according to a second embodiment. [Figure 9] FIG. 11 is a partial main-scan sectional projection view of an optical scanning device according to a second embodiment. [Figure 10] 13A and 13B are diagrams showing the image height dependence of the LSF depth center position on each scanned surface in the optical scanning device according to the second embodiment. [Figure 11] 13A and 13B are a main-scanning sectional development view and a partial sub-scanning sectional view of an optical scanning device according to a third embodiment. [Figure 12] FIG. 11 is a partial main-scan sectional projection view of an optical scanning device according to a third embodiment. [Figure 13] 13A and 13B are diagrams showing the image height dependence of the LSF depth center position on each scanned surface in the optical scanning device according to the third embodiment. [Figure 14] 2 is a sub-scanning sectional view of a main part of the image forming apparatus according to the embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an optical scanning device according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings shown below may be drawn at a scale different from the actual scale in order to facilitate understanding of the present embodiment.

[0010] In the following description, the main scanning direction is a direction perpendicular to the rotation axis of the deflector 50 and the optical axes of the first to fourth imaging optical systems (the direction in which the light beam is deflected by the deflector 50). The sub-scanning direction is a direction parallel to the rotation axis of the deflector 50, the main scanning section is a section perpendicular to the sub-scanning direction, and the sub-scanning section is a section perpendicular to the main scanning direction.

[0011] In the following description, the optical axis direction of the first to fourth imaging optical systems is defined as the X direction, the main scanning direction as the Y direction, and the sub-scanning direction as the Z direction. The X direction can also be defined as a direction (first direction) parallel to a straight line passing through a first intersection point of the optical axis of the first scanned surface 100a and the first imaging optical system and a second intersection point of the optical axis of the second scanned surface 100b and the second imaging optical system.

[0012] [First embodiment] 1(a) and (b) respectively show a development view in a main scanning section and a partial sub-scanning section of an optical scanning device 1 according to the first embodiment. In FIG. 1(a), the first reflecting optical elements 70a, 70b, 70c, and 70d and the second reflecting optical elements 90a and 90b are indicated by dashed lines.

[0013] The optical scanning device 1 of this embodiment includes a housing 2 (holding member), first, second, third and fourth light sources 10a, 10b, 10c and 10d, and first and second incident optical elements 20a and 20b (refractive optical elements). The optical scanning device 1 according to this embodiment also includes first and second sub-scanning diaphragms 30a and 30b, first and second main-scanning diaphragms 40a and 40b, and a deflector 50. The optical scanning device 1 of this embodiment also includes first imaging optical elements 60a and 60b, first reflecting optical elements 70a to 70d, second imaging optical elements 80a, 80b, 80c and 80d, and second reflecting optical elements 90a and 90b.

[0014] The housing 2 is configured to hold and house each of the optical elements provided in the optical scanning device 1 according to this embodiment. Each of the first to fourth light sources 10a to 10d is a light source having two light emitting points, such as a semiconductor laser, etc. That is, the optical scanning device 1 according to this embodiment is provided with a total of eight light emitting points. Furthermore, the first light source 10a and the second light source 10b are disposed at the same position in the main scanning cross section, but are disposed at different positions in the sub-scanning direction. Furthermore, the third light source 10c and the fourth light source 10d are disposed at the same position in the main scanning cross section, but are disposed at different positions in the sub-scanning direction.

[0015] The first and second incident optical elements 20a and 20b are formed of anamorphic lenses having different refractive powers in the main scanning section and the sub-scanning section. The first incident optical element 20a converts the convergence of the first and second light beams LA and LB emitted from the first and second light sources 10a and 10b into parallel beams in the main scanning direction. Similarly, the second incident optical element 20b converts the convergence of the third and fourth light beams LC and LD emitted from the third and fourth light sources 10c and 10d into parallel beams in the main scanning direction. In this case, the parallel light beam includes not only a strictly parallel light beam but also an approximately parallel light beam such as a weakly divergent light beam or a weakly convergent light beam.

[0016] The first incident optical element 20a also condenses the first and second light beams LA and LB emitted from the first and second light sources 10a and 10b toward the deflector 50 in the sub-scanning direction. Similarly, the second incident optical element 20b condenses the third and fourth light beams LC and LD emitted from the third and fourth light sources 10c and 10d toward the deflector 50 in the sub-scanning direction. The detailed configurations of the first entrance optical element 20a and the second entrance optical element 20b will be described later.

[0017] The first sub-scanning aperture 30a has a rectangular lower opening 30al (first opening) and an upper opening 30au (second opening) for respectively regulating the beam width in the sub-scanning direction of the first and second beams LA and LB that have passed through the first incident optical element 20a. Similarly, the second sub-scanning diaphragm 30b has two rectangular openings for restricting the beam widths in the sub-scanning direction of the third and fourth beams LC and LD that have passed through the second incident optical element 20b.

[0018] The first main scanning diaphragm 40a has a single rectangular opening for restricting the beam width in the main scanning direction of the first and second beams LA and LB that have passed through the first sub-scanning diaphragm 30a. Similarly, the second main scanning diaphragm 40b has a single rectangular opening for restricting the beam width in the main scanning direction of the third and fourth beams LC and LD that have passed through the second sub-scanning diaphragm 30b.

[0019] The deflector 50 is a polygon mirror (rotating polygonal mirror) having four deflection surfaces, and is rotated at a constant speed in the direction of arrow R shown in FIG. 1(a) by a driving means such as a motor (not shown). The first imaging optical elements 60a and 60b and the second imaging optical elements 80a to 80d are each an fθ lens (scanning lens) having fθ characteristics.

[0020] The first imaging optical element 60a and the second imaging optical element 80a focus (guide) the first light beam LA deflected by the deflector 50 onto a scanning area (image forming area) of the first scanned surface 100a, thereby forming a spot image on the scanning area. In addition, the first imaging optical element 60a and the second imaging optical element 80b focus (guide) the second light beam LB deflected by the deflector 50 onto the scanning area of ​​the second scanned surface 100b, thereby forming a spot image on the scanning area.

[0021] In addition, the first imaging optical element 60b and the second imaging optical element 80c focus (guide) the third light beam LC deflected by the deflector 50 onto the scanning area of ​​the third scanned surface 100c, thereby forming a spot image on the scanning area. In addition, the first imaging optical element 60b and the second imaging optical element 80d focus (guide) the fourth light beam LD deflected by the deflector 50 onto the scanning area of ​​the fourth scanned surface 100d, thereby forming a spot image on the scanning area. The first reflective optical elements 70a to 70d and the second reflective optical elements 90a and 90b are long mirrors without refractive power that bend the optical paths of the first to fourth light beams LA to LD deflected by the deflector 50 in the sub-scanning cross section.

[0022] The first and second incident optical elements 20a and 20b provided in the optical scanning device 1 according to this embodiment are molded lenses formed by injection molding a plastic material (resin material). Similarly, the first imaging optical elements 60a and 60b and the second imaging optical elements 80a to 80d are each a molded lens formed by injection molding a plastic material (resin material).

[0023] However, the present invention is not limited to this, and these may be molded lenses formed by injection molding a glass material. In the optical scanning device 1 according to this embodiment, it is easy to form an optical surface having an aspheric shape, and by using a molded lens that is suitable for mass production, it is possible to improve productivity and optical performance.

[0024] In addition, the first reflective optical elements 70a to 70d and the second reflective optical elements 90a and 90b provided in the optical scanning device 1 of this embodiment are long mirrors formed by depositing a reflective surface on a typical long piece of glass, but are not limited to this. That is, it may be a long mirror formed by forming a reflective surface on a member formed by injection molding a plastic material, or by performing mirror finishing on a metal member such as aluminum. In addition, in the optical scanning device 1 according to this embodiment, the reflecting surfaces of these are formed in a planar shape without refractive power, but are not limited to this and may be formed in a curved shape such as a spherical surface.

[0025] The first and second light beams LA and LB emitted from the first and second light sources 10a and 10b are converted into parallel light beams in the main scanning cross section by the first incident optical element 20a, and are condensed in the sub-scanning cross section. The first and second light beams LA and LB that pass through the first incident optical element 20a pass through the first sub-scanning aperture 30a and the first main-scanning aperture 40a, and are then guided to the first deflecting surface 50a of the deflector 50. As a result, the widths of the first and second light beams LA and LB in the main scanning direction and the sub-scanning direction are restricted, and the first and second light beams LA and LB are focused in the sub-scanning direction so that a long line image in the main scanning direction is formed near the first deflection surface 50a of the deflector 50.

[0026] The third and fourth light beams LC and LD emitted from the third and fourth light sources 10c and 10d are converted into parallel light beams in the main scanning cross section by the second incident optical element 20b, and are condensed in the sub-scanning cross section. The third and fourth light beams LC and LD that have passed through the second incident optical element 20b pass through the second sub-scanning aperture 30b and the second main-scanning aperture 40b, and are then guided to the second deflecting surface 50b of the deflector 50. As a result, the third and fourth light beams LC and LD have their light beam widths restricted in the main scanning direction and the sub-scanning direction, and are focused in the sub-scanning direction so as to form a long line image in the main scanning direction near the second deflection surface 50b of the deflector 50.

[0027] In the optical scanning device 1 of this embodiment, the first and second light beams LA and LB emitted from the first and second light sources 10a and 10b are obliquely incident on the first deflection surface 50a of the deflector 50 at different angles relative to the main scanning section in the sub-scanning section. Specifically, the first and second light beams LA and LB are obliquely incident on the first deflecting surface 50a of the deflector 50 at angles of −2.70 degrees and +2.70 degrees with respect to the main-scan cross section, respectively.

[0028] Moreover, the third and fourth light beams LC and LD emitted from the third and fourth light sources 10c and 10d are obliquely incident on the second deflecting surface 50b of the deflector 50 at different angles in the sub-scanning section with respect to the main-scanning section. Specifically, the third and fourth light beams LC and LD are obliquely incident on the second deflecting surface 50b of the deflector 50 at angles of −2.70 degrees and +2.70 degrees with respect to the main-scan cross section, respectively.

[0029] Next, the first and second light beams LA and LB deflected by the first deflection surface 50a of the deflector 50 are focused onto the first and second scanned surfaces 100a and 100b by the first imaging optical element 60a and the second imaging optical elements 80a and 80b. In addition, the third and fourth light beams LC and LD deflected by the second deflection surface 50b of the deflector 50 are focused on the third and fourth scanned surfaces 100c and 100d by the first imaging optical element 60b and the second imaging optical elements 80c and 80d.

[0030] As the deflector 50 rotates, the first to fourth light beams LA to LD optically scan the first to fourth scanned surfaces 100a to 100d in the main scanning direction at a uniform speed, thereby enabling image recording on the first to fourth scanned surfaces 100a to 100d. Furthermore, in the optical scanning device 1 according to this embodiment, a synchronous detection optical system (not shown) is provided to determine the write timing for starting optical scanning on the first to fourth scanned surfaces 100a to 100d.

[0031] Specifically, a predetermined light beam deflected in a predetermined direction by the deflector 50 is guided to a synchronization detection sensor (not shown) by a synchronization detection lens (not shown). Then, the light emission timing of each of the first to fourth light sources 10a to 10d is determined using a synchronization signal (Beam Detection (BD) signal) acquired by detecting the signal output from the synchronization detection sensor.

[0032] In the optical scanning device 1 of this embodiment, a first incident optical system is formed by the lower portion 21al (first refractive optical part) in the sub-scanning direction of the first incident optical element 20a, the lower opening 30al of the first sub-scanning aperture 30a, and the opening of the first main scanning aperture 40a. Further, a second incident optical system is formed by an upper portion 21au (second refractive optical portion) in the sub-scanning direction of the first incident optical element 20a, an upper opening 30au of the first sub-scanning aperture 30a, and an opening of the first main-scanning aperture 40a. Furthermore, a third incident optical system is formed by a lower portion in the sub-scanning direction of the second incident optical element 20b, the lower opening of the second sub-scanning aperture 30b, and the opening of the second main-scanning aperture 40b. Furthermore, a fourth incident optical system is formed by an upper portion in the sub-scanning direction of the second incident optical element 20b, an upper opening of the second sub-scanning aperture 30b, and an opening of the second main-scanning aperture 40b.

[0033] In the optical scanning device 1 according to this embodiment, a first imaging optical system is formed by the upper portion in the sub-scanning direction of the first imaging optical element 60a and the second imaging optical element 80a. Furthermore, a second imaging optical system is formed by a lower portion in the sub-scanning direction of the first imaging optical element 60a and the second imaging optical element 80b. Furthermore, an upper portion of the first imaging optical element 60b in the sub-scanning direction and the second imaging optical element 80c form a third imaging optical system. Furthermore, a fourth imaging optical system is formed by a lower portion in the sub-scanning direction of the first imaging optical element 60b and the second imaging optical element 80d.

[0034] Next, the specifications of the optical scanning device 1 according to this embodiment, the refractive index and coordinates of each optical element, and the shape of the optical surface of each optical element are respectively shown in the following Tables 1, 2, 3-1, and 3-2. It should be noted that Tables 2, 3-1 and 3-2 only show the first and second incident optical systems and the first and second imaging optical systems. That is, in Table 2, Table 3-1, and Table 3-2, the third and fourth incident optical systems and the third and fourth imaging optical systems are omitted.

[0035] [Table 1]

[0036] [Table 2]

[0037] [Table 3-1] [Table 3-2]

[0038] In addition, the respective incident surfaces of the upper part 21au and the lower part 21al of the first incident optical element 20a and the upper part and the lower part of the second incident optical element 20b provided in the optical scanning device 1 of this embodiment are diffractive surfaces on which a diffraction grating is formed. The first and second incident optical elements 20a and 20b are formed by injection molding using a plastic material as described above.

[0039] For this reason, a so-called temperature compensation optical system is adopted in which the change in the refractive power of the first and second incident optical elements 20a and 20b due to environmental fluctuations is compensated for by the change in the diffractive power of the diffractive surface associated with the change in wavelength of the first to fourth light beams LA to LD in the first to fourth light sources 10a to 10d. Specifically, the diffraction surfaces formed on the respective incident surfaces of the upper part 21au and the lower part 21al of the first incident optical element 20a and the upper part and the lower part of the second incident optical element 20b are defined by a phase function expressed by the following equation (1).

number

[0040] In equation (1), φ is the phase function, M is the diffraction order, and λ is the design wavelength. Since the optical scanning device 1 according to this embodiment uses first-order diffracted light, M is 1 and λ is 790 nm.

[0041] In addition, the shapes (general line shapes) of the entrance surfaces and exit surfaces of the first imaging optical elements 60a and 60b and the second imaging optical elements 80a to 80d provided in the optical scanning device 1 of this embodiment in the main scanning cross section have aspheric shapes expressed by a 10th order polynomial function. Specifically, the points of intersection (surface vertices) between the optical axis and the optical surfaces of the first imaging optical elements 60a and 60b and the second imaging optical elements 80a to 80d are set as the origin.

[0042] The direction parallel to the optical axis of each optical surface is defined as the X-axis, the axis perpendicular to the optical axis in the main-scanning section is defined as the Y-axis, and the axis perpendicular to the optical axis in the sub-scanning section is defined as the Z-axis. In this case, the aspheric shapes of the entrance surfaces and exit surfaces of the first imaging optical elements 60a and 60b and the second imaging optical elements 80a to 80d in the main scanning cross section are expressed by the following formula (2).

number

[0043] In formula (2), R is the radius of curvature in the main scanning section (generatrix radius of curvature), K is the eccentricity, B i are the aspheric coefficients. The shapes (sagittal shapes) of the entrance surfaces and exit surfaces of the first imaging optical elements 60a and 60b and the second imaging optical elements 80a to 80d in the sub-scanning cross section are expressed by the following formula (3).

number

[0044] In formula (3), S is the shape (sagittal shape) in a cross section perpendicular to the main scanning cross section, including the normal to the generatrix at a given position in the main scanning direction, and M ij are the aspheric coefficients. Further, the radius of curvature (sagittal radius of curvature) r′ in the sub-scanning cross section at a position spaced apart by Y from the optical axis in the main scanning direction is expressed by the following formula (4).

number

[0045] In equation (4), r is the radius of curvature of the sagittal line on the optical axis, E i is the sagittal variation coefficient. In the optical scanning device 1 according to this embodiment, the shape of the optical surface of each optical element is defined by the functions expressed by the above formulas (1) to (4), but the definition is not limited to this and may be by another function.

[0046] As shown in Figures 1(a) and (b), in the optical scanning device 1 of this embodiment, the first and second light beams LA and LB pass through a common first imaging optical element 60a, and the third and fourth light beams LC and LD pass through a common first imaging optical element 60b. Specifically, the first and second light beams LA and LB pass through an upper portion 61a and a lower portion 62a, respectively, of the first imaging optical element 60a in the sub-scanning direction.

[0047] Moreover, the third and fourth light beams LC and LD pass through the upper and lower portions, respectively, of the first imaging optical element 60b in the sub-scanning direction. The upper and lower portions in the sub-scanning direction referred to here can also be referred to as the opposite sides of the scanned surface in the sub-scanning direction, that is, the anti-scanned surface side portion and the scanned surface side portion, respectively.

[0048] As shown in Tables 3-1 and 3-2, the shape of the exit surface of the first imaging optical element 60a is defined to be different between the upper portion 61a through which the first light beam LA passes and the lower portion 62a through which the second light beam LB passes. That is, while the first imaging optical element 60a is a single optical element, it is formed as a multi-stage structure in which the shape of the exit surface differs between an upper portion 61a and a lower portion 62a in the sub-scanning direction, and the first imaging optical element 60b has a similar configuration.

[0049] FIG. 2 shows a sub-scanning sectional view of a first imaging optical element 60a provided in the optical scanning device 1 according to this embodiment. As shown in FIG. 2, the first imaging optical element 60a has an upper portion 61a through which the first light beam LA passes, and a lower portion 62a through which the second light beam LB passes, on either side of a center line indicated by a dashed line in the sub-scanning direction.

[0050] The upper portion 61a and the lower portion 62a of the first imaging optical element 60a each have an exit surface formed in the shape shown in Tables 3-1 and 3-2. This makes it possible to efficiently collect both the first and second light beams LA and LB emitted from the first and second light sources 10a and 10b, respectively, by the first imaging optical element 60a.

[0051] FIG. 3 is a partial projection view of the optical scanning device 1 according to this embodiment in the main scanning section. Specifically, FIG. 3 shows a second incident optical system that forms the optical path of the second light flux LB, a second imaging optical system, a first reflecting optical element 70b, and a second reflecting optical element 90a.

[0052] In the optical scanning device 1 of this embodiment, by using multiple reflective optical elements to fold back the optical paths of the first to fourth light beams LA to LD within the sub-scanning cross section, it is possible to reduce the size of the housing 2 and the distance (drum pitch) between adjacent scanned surfaces. As a result, when projected in the main scanning cross section as shown in FIG. 3, the first incident optical element 20a and one end of the second reflecting optical element 90a in the longitudinal direction are positioned very close to each other. In other words, the first incident optical element 20a and the second reflective optical element 90a are arranged in a first region and a second region in the X direction, respectively, and at least a portion of the first region and at least a portion of the second region overlap each other. In other words, when projected within the main scanning cross section, the first entrance optical element 20a is disposed on an extension line in the extending direction (Y direction) of the second reflecting optical element 90a.

[0053] Such an arrangement in which a plurality of optical elements are too close to one another is not preferable in consideration of the outer shape of each optical element and the space required to form the holders for holding each optical element. On the other hand, in the optical scanning device 1 according to this embodiment, the first incident optical element 20a is advantageously positioned from the viewpoints of the optical performance and error sensitivity of the entire device, and therefore the optical arrangement shown in FIG. 3 is optically preferable.

[0054] Next, the specific shapes of the first and second incident optical elements 20a and 20b provided in the optical scanning device 1 according to this embodiment will be described. 4(a) and (b) respectively show a front view and a side view of the first incident optical element 20a provided in the optical scanning device 1 according to this embodiment.

[0055] Note that the two arrows shown in Figure 4(b) indicate the directions of travel of the first and second light beams LA and LB, respectively, and the dashed lines shown in Figure 4(b) diagrammatically indicate the shapes of each optical surface in the sub-scanning cross section. Moreover, since the first and second incident optical elements 20a and 20b have the same shape, only the shape of the first incident optical element 20a will be described below.

[0056] As shown in Figures 4(a) and (b), the first incident optical element 20a provided in the optical scanning device 1 of this embodiment is a so-called twin lens formed of an upper portion 21au and a lower portion 21al arranged at different positions from each other in the sub-scanning direction. That is, in the first entrance optical element 20a, the upper portion 21au and the lower portion 21al are formed integrally with each other. The first and second light beams LA and LB emitted from the first and second light sources 10a and 10b can be collected by the lower portion 21al and the upper portion 21au, respectively.

[0057] The first incident optical element 20a is provided with a plurality of reference surfaces 221a, 222a, and 223a (a second group of convex portions) for positioning the first incident optical element 20a in the optical axis direction. Specifically, each of the multiple reference surfaces 221a to 223a is formed as a convex portion protruding outward from the outer surface 22ae on the exit surface side of the non-effective area around the upper portion 21au and the lower portion 21al, through which the first and second light beams LA and LB do not pass. As will be described later, a plurality of reference surfaces 221a to 223a come into contact with a protrusion 2p provided on the housing 2, so that the position of the first entrance optical element 20a in the optical axis direction is determined.

[0058] As described above, the first incident optical element 20a is formed by injection molding the plastic material injected through the gate portion 24a. Therefore, as shown in FIG. 4(a), the first incident optical element 20a is provided with a plurality of pressing surfaces 231a, 232a, 233a, 234a, 235a, and 236a that are pressed by ejector pins when the first incident optical element 20a is released from the mold.

[0059] Specifically, the pressing surfaces 231a to 236a (third convex group) are formed as convex portions protruding outward from the outer surface 22ae, similar to the reference surfaces 221a to 223a. On the other hand, the protrusion amount of each of the plurality of pressing surfaces 231a to 236a is smaller than the protrusion amount of each of the plurality of reference surfaces 221a to 223. In other words, the multiple pressing surfaces 231a to 236a do not contribute to the positioning of the first entrance optical element 20a in the optical axis direction.

[0060] In the first incident optical element 20a, some of the pressing surfaces 231a to 236a, specifically the pressing surfaces 231a, 233a, 234a and 236a, are formed outside the reference surfaces 221a to 223a in the sub-scanning direction. In this manner, by forming the multiple pressing surfaces 231a, 233a, 234a, and 236a outside the multiple reference surfaces 221a to 223a in the sub-scanning direction, it is possible to suppress changes in shape that could lead to molding defects when the first incident optical element 20a is released from the mold.

[0061] Next, the holding of the first incident optical element 20a and the second reflecting optical element 90a in the optical scanning device 1 according to this embodiment will be described. Figures 5(a), (b), and (c) respectively show a view of the vicinity of the first incident optical element 20a (optical element) of the optical scanning device 1 of this embodiment from the optical axis direction, a view of the vicinity from the main scanning direction, and a view of the vicinity from the sub-scanning direction.

[0062] In the optical scanning device 1 of this embodiment, as shown in Figures 5(a) to (c), a protrusion 2p that protrudes in the sub-scanning direction and is integrated with the first sub-scanning aperture 30a is integrally formed in the housing 2. In other words, the housing 2 includes a box portion having an internal space in which each optical element is arranged, and a lid portion covering the internal space, and the protrusion 2p protrudes in the sub-scanning direction from a predetermined position on the bottom surface of the box portion. In other words, the protrusion 2p is made of the same material as the other parts of the housing 2.

[0063] A plurality of reference surfaces 221a to 223a formed on an outer surface 22ae on the emission surface side of the first incident optical element 20a abuts against the protrusion 2p. Specifically, two convex portions 2a and 2b extending in the sub-scanning direction on the surface (first surface) of the protrusion 2p perpendicular to the optical axis of the first incident optical system are formed on both sides in the main scanning direction of the upper opening 30au and the lower opening 30al of the first sub-scanning aperture 30a. The multiple reference surfaces 221a to 223a are in contact with the two protrusions 2a and 2b (first protrusion group).

[0064] As shown in Figures 5(a) and (b), the first incident optical element 20a is urged toward the convex portions 2a and 2b of the protrusion 2p by the urging portions 2c and 2d that are integrally formed with the housing 2. In this manner, the first incident optical element 20a is urged in the optical axis direction toward the convex portions 2a and 2b of the protrusion 2p by the urging portions 2c and 2d, thereby determining the position of the first incident optical element 20a in the optical axis direction. That is, in the optical scanning device 1 according to this embodiment, the first incident optical element 20a is held by the protrusion 2p and the biasing portions 2c and 2d.

[0065] Further, the second reflecting optical element 90a (reflecting optical element) also abuts against the protruding portion 2p as shown in FIGS. 5(a) to (c). Specifically, the second reflective optical element 90a is placed on a recess formed on a surface (second surface) of the protrusion 2p parallel to the optical axis of the first incident optical system, and is urged toward the recess by a urging member not shown. That is, in the optical scanning device 1 according to this embodiment, the second reflecting optical element 90a is held by the protrusion 2p and the biasing member.

[0066] In the optical scanning device 1 of this embodiment, by adopting the above-mentioned configuration, it is possible to hold the first incident optical element 20a even if the first incident optical element 20a and the second reflective optical element 90a are close to each other in the main scanning cross section. That is, in the optical scanning device 1 according to this embodiment, the first incident optical element 20a can be supported so as to be fixed, without providing a separate support member for supporting the first incident optical element 20a.

[0067] In the optical scanning device 1 of this embodiment, as shown in Figures 5(a) to (c), a common protrusion 2p can be used to hold both the first incident optical element 20a and the second reflective optical element 90a in the main scanning direction. Therefore, the shape of the housing 2 can be simplified compared to a case in which the holding portion for holding the first incident optical element 20a and the holding portion for holding the second reflecting optical element 90a are formed apart from each other.

[0068] In addition, in the optical scanning device 1 of this embodiment, as shown in Figures 5(a) and (c), a holding portion that holds the first incident optical element 20a, a holding portion that holds the second reflective optical element 90a, and the first sub-scanning aperture 30a are integrally formed as a protrusion 2p. Therefore, in the optical scanning device 1 according to this embodiment, the shape of the housing 2 can be simplified.

[0069] 6(a) and (b) respectively show the image height dependence of the main scanning direction LSF (Line Spread Function) depth center position and the sub-scanning direction LSF depth center position on each scanned surface in the optical scanning device 1 according to this embodiment. Note that the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position referred to here respectively refer to the center positions of an area where the LSF widths in the main scanning direction and sub-scanning direction are equal to or less than the slice level when defocused in the optical axis direction near a specified scanned surface.

[0070] In the optical scanning device 1 according to this embodiment, the slice level is set to 120 μm over the entire image height range in both the main scanning direction and the sub-scanning direction. In addition, the LSF width in the main scanning direction and the LSF width in the sub-scanning direction respectively refer to the widths when the light quantity profile obtained by integrating the spot profile at each image height in the sub-scanning direction and the main scanning direction is sliced ​​at a position that is 13.5% of the maximum value. As shown in Figures 6(a) and (b), both the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position are within ±1 mm over the entire image height, which shows that the optical scanning device 1 of this embodiment achieves good imaging performance.

[0071] FIG. 7 is a partial projection view in the main scanning section for explaining each conditional expression in the optical scanning device 1 according to this embodiment. First, the distance in the X direction between the on-axis deflection point C0 on the first deflection surface 50a of the deflector 50 and the center of the outer surface 22ae on which the multiple reference surfaces 221a to 223a of the first input optical element 20a are formed is defined as L. X Let us assume that.

[0072] Here, the on-axis deflection point C0 is the deflection point on the first deflection surface 50a of the chief rays of the first and second light beams LA and LB deflected by the deflector 50 so as to scan the axial image heights on the first and second scanned surfaces 100a and 100b. Moreover, the distance in the X direction between the on-axis deflection point C0 and the center of the reflecting surface of the second reflecting optical element 90a is M X Let us assume that.

[0073] At this time, in the optical scanning device 1 according to this embodiment, it is preferable that the following conditional expression (5) be satisfied. 0.500 <M X / L X <1.500 ···(5)

[0074] If the upper limit value of conditional expression (5) is exceeded, the second reflective optical element 90a will be too far away from the deflector 50 in the main scanning cross section, which is undesirable because it will make it difficult to reduce the distance between adjacent scanned surfaces, i.e., to miniaturize the optical scanning device 1 in this embodiment. On the other hand, if the lower limit of conditional expression (5) is not reached, the second reflective optical element 90a will be too close to the deflector 50 in the main-scanning cross section. Therefore, there is a risk that the second reflective optical element 90a will interfere with at least one optical element provided in the third and fourth imaging optical systems on the opposite side to the deflector 50. Furthermore, if the second reflective optical element 90a and the at least one optical element are separated from each other in the sub-scanning direction in order to suppress such interference, the optical scanning device 1 according to this embodiment would become larger in size in the sub-scanning direction, which is not preferable.

[0075] In the optical scanning device 1 according to this embodiment, it is more preferable that the following conditional formula (5a) be satisfied. 0.700 <M X / L X <1.400 ···(5a)

[0076] The distance in the Y direction between the on-axis deflection point C0 and the center of the outer surface 22ae on which the multiple reference surfaces 221a to 223a of the first incident optical element 20a are formed is defined as L. Y Let us assume that. The distance in the Y direction between the on-axis deflection point C0 and the end of the second reflecting optical element 90a that is closest to the first incident optical element 20a is defined as M. Y Let us assume that.

[0077] At this time, in the optical scanning device 1 according to this embodiment, it is preferable that the following conditional expression (6) be satisfied. 0.9000 <M Y / L Y <0.9700 ···(6)

[0078] If the upper limit value of conditional expression (6) is exceeded, the first entrance optical element 20a and the second reflecting optical element 90a may be too close to each other and may interfere with each other, which is undesirable. On the other hand, if the lower limit of conditional formula (6) is not reached, the first incident optical element 20a and the second reflecting optical element 90a are too far apart from each other, which undesirably increases the size of the optical scanning device 1 according to this embodiment. Furthermore, if the lower limit of conditional formula (6) is exceeded, it will be necessary to provide a holding portion for holding the first incident optical element 20a and a holding portion for holding the second reflective optical element 90a at a distance from each other, instead of a single protrusion 2p, which will complicate the structure of the housing 2, and this is not preferable.

[0079] In the optical scanning device 1 according to this embodiment, it is more preferable that the following conditional formula (6a) be satisfied. 0.9300 <M Y / L Y <0.9700 (6a)

[0080] The distance in the main scanning section (XY section) between the axial deflection point C0 and the center of the outer surface 22ae on which the multiple reference surfaces 221a to 223a of the first incident optical element 20a are formed is defined as L t Let us assume that. The distance between the first and second light sources 10a and 10b and the on-axis deflection point C0 in the optical axis direction of the first and second incident optical systems is defined as L i Let us assume that.

[0081] At this time, in the optical scanning device 1 according to this embodiment, it is preferable that the following conditional expression (7) be satisfied. 0.70 <L t / L i <0.90 ···(7)

[0082] If the upper limit value of conditional formula (7) is exceeded, the first incident optical element 20a and the second reflecting optical element 90a will be too far apart from each other, and therefore, instead of a single protrusion 2p, it will be necessary to provide a holding portion for holding the first incident optical element 20a and a holding portion for holding the second reflecting optical element 90a at a distance from each other, which will complicate the structure of the housing 2, and is therefore undesirable. On the other hand, falling below the lower limit of conditional expression (7) is undesirable because it reduces the optical efficiency of the optical scanning device 1 of this embodiment, specifically, reduces the amount of light of the first and second light beams LA and LB when they reach the first and second scanned surfaces 100a and 100b.

[0083] In the optical scanning device 1 according to this embodiment, it is more preferable that the following conditional formula (7a) be satisfied. 0.75 <L t / L i <0.85 (7a)

[0084] In the optical scanning device 1 according to this embodiment, as shown in Table 1 and Table 10 described later, the conditional expressions (5), (5a), (6), (6a), (7) and (7a) are satisfied.

[0085] As described above, in the optical scanning device 1 according to this embodiment, the first incident optical element 20a and the second reflecting optical element 90a are held by the protrusions 2p that are integrally formed with the housing 2. This makes it possible to hold both the first incident optical element 20a and the second reflecting optical element 90a with a simple configuration when the first incident optical element 20a and the second reflecting optical element 90a are placed close to each other to achieve miniaturization. In other words, in the optical scanning device 1 of this embodiment, the first incident optical element 20a and the second reflective optical element 90a are each held using the protrusion 2p that is integrally formed on the housing 2 without using a separate holding member, thereby reducing the number of components.

[0086] [Second embodiment] 8(a) and (b) respectively show a development view in the main scanning section (corresponding to FIG. 1(a)) and a partial sub-scanning section (corresponding to FIG. 1(b)) of an optical scanning device 201 according to the second embodiment.

[0087] FIG. 9 is a partial projection view (corresponding to FIG. 3) of an optical scanning device 201 according to the second embodiment in the main scanning section. The optical scanning device 201 according to this embodiment has the same configuration as the optical scanning device 1 according to the first embodiment except for various different numerical values, so the same components are given the same reference numerals and descriptions thereof are omitted.

[0088] Moreover, the specification values ​​of the optical scanning device 201 according to this embodiment, the refractive index and coordinates of each optical element, and the shape of the optical surface of each optical element are respectively shown in the following Tables 4, 5, 6-1, and 6-2. It should be noted that Tables 5, 6-1 and 6-2 only show the first and second incident optical systems and the first and second imaging optical systems. That is, in Tables 5, 6-1 and 6-2, the third and fourth incident optical systems and the third and fourth imaging optical systems are omitted.

[0089] [Table 4]

[0090] [Table 5]

[0091] [Table 6-1] [Table 6-2]

[0092] 10A and 10B respectively show the image height dependence of the LSF depth center position in the main scanning direction and the LSF depth center position in the sub-scanning direction on each scanned surface in the optical scanning device 201 according to this embodiment. As shown in FIG. 10(a), the central position of the LSF depth in the main scanning direction falls within ±1 mm over the entire image height.

[0093] Furthermore, as shown in FIG. 10(b), the LSF depth center position in the sub-scanning direction falls within ±1 mm except for some image heights. From the above, it can be seen that the optical scanning device 201 according to this embodiment achieves good imaging performance.

[0094] As described above, in the optical scanning device 201 according to this embodiment, the first incident optical element 20a and the second reflecting optical element 90a are held by the protrusions 2p that are integrally formed with the housing 2. This makes it possible to hold both the first incident optical element 20a and the second reflecting optical element 90a with a simple configuration when the first incident optical element 20a and the second reflecting optical element 90a are placed close to each other to achieve miniaturization.

[0095] [Third embodiment] 11(a) and (b) respectively show a development view in the main-scanning section (corresponding to FIG. 1(a)) and a partial sub-scanning section (corresponding to FIG. 1(b)) of an optical scanning device 301 according to the third embodiment.

[0096] FIG. 12 is a partial projection view (corresponding to FIG. 3) of an optical scanning device 301 according to the third embodiment in the main scanning section. The optical scanning device 301 according to this embodiment has the same configuration as the optical scanning device 1 according to the first embodiment except for various different numerical values, so the same components are given the same reference numerals and descriptions thereof are omitted.

[0097] Moreover, the specifications of the optical scanning device 301 according to this embodiment, the refractive index and coordinates of each optical element, and the shape of the optical surface of each optical element are respectively shown in the following Tables 7, 8, 9-1, and 9-2. It should be noted that Tables 8, 9-1 and 9-2 only show the first and second incident optical systems and the first and second imaging optical systems. That is, in Tables 8, 9-1 and 9-2, the third and fourth incident optical systems and the third and fourth imaging optical systems are omitted.

[0098] [Table 7]

[0099] [Table 8]

[0100] [Table 9-1] [Table 9-2]

[0101] 13A and 13B respectively show the image height dependence of the LSF depth center position in the main scanning direction and the LSF depth center position in the sub-scanning direction on each scanned surface in the optical scanning device 301 according to this embodiment. As shown in FIG. 13(a), the central position of the LSF depth in the main scanning direction falls within ±1 mm over the entire image height.

[0102] As shown in FIG. 13(b), the LSF depth center position in the sub-scanning direction falls within ±1 mm except for some image heights. From the above, it can be seen that the optical scanning device 301 according to this embodiment achieves good imaging performance.

[0103] As described above, in the optical scanning device 301 according to this embodiment, the first incident optical element 20a and the second reflecting optical element 90a are held by the protrusions 2p that are integrally formed with the housing 2. This makes it possible to hold both the first incident optical element 20a and the second reflecting optical element 90a with a simple configuration when the first incident optical element 20a and the second reflecting optical element 90a are placed close to each other to achieve miniaturization.

[0104] The relationships between the various values ​​and the respective conditional expressions in the optical scanning devices according to the first to third embodiments are shown in Table 10 below.

[0105] [Table 10]

[0106] [Image forming equipment] FIG. 14 is a sub-scanning sectional view of a main part of an image forming apparatus 99 including an optical scanning device 1 according to any one of the first to third embodiments.

[0107] The image forming apparatus 99 is a tandem type color image forming apparatus in which an optical scanning device 1 according to any one of the first to third embodiments records image information on the surfaces (scanned surfaces) of four photosensitive drums, each of which is an image carrier. The image forming apparatus 99 includes the optical scanning device 1 according to any one of the first to third embodiments, and first, second, third and fourth photosensitive drums 100a, 100b, 100c and 100d as image carriers. The image forming apparatus 99 also includes first, second, third and fourth developing units 15, 16, 17 and 18, a conveyor belt 91, a printer controller 93 and a fixing unit 94.

[0108] As shown in FIG. 14, an image forming apparatus 99 receives R (red), G (green), and B (blue) color signals output from an external device 92 such as a personal computer. The input color signals are then converted by a printer controller 93 within the device into image data (dot data) for each of C (cyan), M (magenta), Y (yellow), and K (black).

[0109] Next, each converted image data is input to the optical scanning device 1 according to any one of the first to third embodiments. Then, the photosensitive surfaces of the first to fourth photosensitive drums 100a to 100d are scanned in the main scanning direction by the first, second, third and fourth light beams LA, LB, LC and LD, respectively, which are modulated and emitted from the optical scanning device 1 according to each image data.

[0110] A charging roller (not shown) for uniformly charging the photosensitive surface of each of the first to fourth photosensitive drums 100a to 100d is provided in contact with the photosensitive surface. Then, the optical scanning device 1 irradiates the first to fourth light beams LA to LD onto the photosensitive surfaces of the first to fourth photosensitive drums 100a to 100d that have been charged by the charging rollers.

[0111] As described above, the first to fourth light beams LA to LD are modulated based on image data of each color, and electrostatic latent images are formed on the photosensitive surfaces of the first to fourth photosensitive drums 100a to 100d, respectively, by irradiating the first to fourth light beams LA to LD. The formed electrostatic latent images are then developed into toner images by first to fourth developing devices 15 to 18 arranged so as to come into contact with the first to fourth photosensitive drums 100a to 100d, respectively.

[0112] Next, the developed toner images are transferred in multiple layers onto a sheet of paper (transfer material) (not shown) conveyed on a conveyor belt 91 by transfer rollers (transfer devices) (not shown) arranged to face the first to fourth photosensitive drums 100a to 100d. As a result, a full-color image is formed on the sheet of paper. Then, the paper onto which the unfixed toner image has been transferred is further transported by the transport belt 91 to a fixing device 94 provided behind (on the left side in FIG. 14) the first to fourth photosensitive drums 100a to 100d.

[0113] The fixing unit 94 has a fixing roller having an internal fixing heater (not shown) and a pressure roller disposed so as to be in pressure contact with the fixing roller. The paper conveyed by the conveyor belt 91 is heated and pressed by the pressure contact portion between the fixing roller and the pressure roller, whereby the unfixed toner image on the paper is fixed. Furthermore, a paper discharge roller (not shown) is disposed behind the fixing unit 94 , and the paper discharge roller discharges the paper on which the toner image has been fixed to the outside of the image forming apparatus 99 .

[0114] In the image forming apparatus 99, an image signal (image information) is recorded on the photosensitive surfaces of first to fourth photosensitive drums 100a to 100d, each of which corresponds to one of the colors C (cyan), M (magenta), Y (yellow), and K (black), by the optical scanning device 1. This makes it possible to print a color image at high speed.

[0115] The external device 92 may be, for example, a color image reading device equipped with a CCD sensor. In this case, the color image reading device and the image forming device 99 form a color digital copying machine.

[0116] Although the preferred embodiments have been described above, the present invention is not limited to these embodiments, and various modifications and changes are possible within the scope of the gist thereof.

[0117] The disclosure of this embodiment includes the following configuration. (Configuration 1) An optical scanning device comprising: a deflector that deflects a first light beam from a first light source to scan a first scanned surface in a main scanning direction; a first imaging optical system and a reflective optical element that guide the first light beam deflected by the deflector to the first scanned surface; an optical element that guides the first light beam emitted from the first light source to the deflector; and a holding member that holds the deflector, the first imaging optical system, the reflective optical element, and the optical element, wherein the holding member protrudes in the sub-scanning direction and has a common protrusion that abuts both the optical element and the reflective optical element in the main scanning direction. (Configuration 2) The optical scanning device according to configuration 1, wherein, when projected onto a main scanning cross section, the optical element is disposed on an extension line in the extending direction of the reflective optical element. (Configuration 3) In the optical scanning device according to configuration 1 or 2, the protruding portion has a first opening that restricts the width of the first light beam in the sub-scanning direction. (Structure 4) An optical scanning device described in any one of structures 1 to 3, characterized in that the protrusion has a first group of convex portions that abut on the outer surface of the exit surface side of the optical element on both sides in the main scanning direction relative to the optical axis of the optical element on a first surface perpendicular to the optical axis of the optical element. (Configuration 5) An optical scanning device according to configuration 4, characterized in that the holding member has a biasing portion that biases the optical element, and the optical element is held by being biased by the biasing portion toward the first group of convex portions. (Configuration 6) The optical scanning device according to configuration 4 or 5, wherein the optical element has a second group of convex portions that contacts the first group of convex portions on the outer surface. (Configuration 7) An optical scanning device described in any one of configurations 1 to 6, characterized in that the optical element is a refractive optical element that converts the convergence of the first light beam in the main scanning cross section and focuses the first light beam in the sub-scanning cross section. (Configuration 8) An optical scanning device described in any one of configurations 1 to 7, further comprising a second imaging optical system that guides the second light beam deflected by the deflector to a second scanned surface, the deflector deflects a first light beam from a first light source and a second light beam from a second light source by a first deflection surface to scan the first scanned surface and the second scanned surface in the main scanning direction, and the optical element is a refractive optical element having a first refractive optical unit that converts the convergence of the first light beam in the main scanning cross section and focuses the first light beam in the sub-scanning cross section, and a second refractive optical unit that converts the convergence of the second light beam in the main scanning cross section and focuses the second light beam in the sub-scanning cross section. (Configuration 9) In the optical scanning device according to configuration 8, the protrusion has first and second openings that regulate the widths of the first and second light beams in the sub-scanning direction. (Configuration 10) An optical scanning device according to any one of configurations 1 to 9, wherein the reflective optical element is placed on a second surface of a protrusion parallel to the optical axis of the optical element. (Configuration 11) The optical scanning device according to configuration 10, wherein the reflective optical element is held by being biased toward the second surface. (Configuration 12) An optical scanning device described in any one of configurations 1 to 11, characterized in that the holding member includes a box portion having an internal space in which a deflector, a first imaging optical system, a reflective optical element, and an optical element are arranged, and a lid portion covering the internal space, and the protrusion portion protrudes in the sub-scanning direction from a predetermined position on the bottom surface of the box portion. (Configuration 13) An optical scanning device described in any one of configurations 1 to 12, comprising a first incident optical system including an optical element and causing a first light beam to be incident on a deflector, wherein the optical element is a refractive optical element among the refractive optical elements included in the first incident optical system that is closest to the deflector on the optical path of the first light beam. (Configuration 14) A second imaging optical system is provided which guides the second light beam deflected by the deflector to a second scanned surface, the deflector deflects the first light beam from the first light source and the second light beam from the second light source by a first deflection surface to scan the first scanned surface and the second scanned surface in the main scanning direction, and defines a distance between an on-axis deflection point on the first deflection surface of the deflector and a center of an outer surface abutting on a protruding portion of the optical element in a first direction parallel to a straight line passing through a first intersection point of the optical axes of the first scanned surface and the first imaging optical system and a second intersection point of the optical axes of the second scanned surface and the second imaging optical system as L. X , the distance between the on-axis deflection point in the first direction and the center of the reflecting surface of the reflecting optical element is M X When we set it to 0.500, <M X / L X 14. The optical scanning device according to any one of claims 1 to 13, wherein the optical scanning device satisfies the condition: (Configuration 15) The deflector deflects the first light beam by a first deflection surface, and defines a distance in the main scanning direction between an on-axis deflection point on the first deflection surface of the deflector and a center of an outer surface abutting the protrusion of the optical element as L. Y , the distance in the main scanning direction between the on-axis deflection point and the end of the reflecting optical element closest to the optical element is M Y When we set it to 0.9000, <M Y / L Y 15. The optical scanning device according to any one of configurations 1 to 14, wherein the optical scanning device satisfies the condition: <0.9700. (Configuration 16) A first incident optical system including an optical element is provided, which causes a first light beam to be incident on a deflector. The deflector deflects the first light beam by a first deflection surface, and defines a distance in a main scanning cross section between an on-axis deflection point on the first deflection surface of the deflector and a center of an outer surface that abuts on a protruding portion of the optical element as L. t , the distance between the first light source and the on-axis deflection point in a direction parallel to the optical axis of the first incident optical system is L i When we set it as 0.70 <L t / L i 16. The optical scanning device according to any one of configurations 1 to 15, wherein the optical scanning device satisfies the condition: (Configuration 17) The optical scanning device according to any one of configurations 1 to 16, wherein the optical element is an optical element formed by injection molding a resin material. (Configuration 18) In the optical scanning device according to configuration 17, the optical element has a third group of protrusions on the outer surface on the emission surface side that are pressed when the optical element is released from the mold. (Configuration 19) An optical scanning device according to any one of configurations 1 to 18, wherein the entrance surface of the optical element is a diffractive surface. (Configuration 20) An optical scanning device described in any one of configurations 1 to 19, comprising second, third and fourth imaging optical systems which guide the second, third and fourth light beams deflected by a deflector to the second, third and fourth scanned surfaces, the deflector deflects the second, third and fourth light beams to scan the second, third and fourth scanned surfaces in the main scanning direction, the first and second light beams are obliquely incident on a first deflection surface of the deflector at different angles relative to the main scanning cross section in the sub-scanning cross section, and the third and fourth light beams are obliquely incident on a second deflection surface of the deflector at different angles relative to the main scanning cross section in the sub-scanning cross section. (Configuration 21) An image forming apparatus comprising an optical scanning device according to any one of configurations 1 to 20, a developing unit which develops an electrostatic latent image formed on a first scanned surface by the optical scanning device into a toner image, a transfer unit which transfers the developed toner image to a transfer material, and a fixing unit which fixes the transferred toner image to the transfer material. (Configuration 22) An image forming apparatus comprising: an optical scanning device according to any one of configurations 1 to 20; and a printer controller that converts a signal output from an external device into image data and inputs the image data to the optical scanning device. [Explanation of symbols]

[0118] 1 Optical scanning device 2 Housing (holding member) 2p protrusion 10a First light source 20a First incident optical element (optical element) 50 Deflector 90a Second reflecting optical element (reflecting optical element) 100a: First scanned surface LA First beam

Claims

1. a deflector that deflects a first light beam from a first light source to scan a first scanned surface in a main scanning direction; a first imaging optical system and a reflecting optical element that guide the first light beam deflected by the deflector to the first scanned surface; an optical element that guides the first light flux emitted from the first light source to the deflector; the deflector, the first imaging optical system, the reflecting optical element, and a holding member that holds the optical element, The optical scanning device according to claim 1, wherein the holding member has a common protrusion that protrudes in a sub-scanning direction and abuts against both the optical element and the reflective optical element in a main scanning direction.

2. 2. The optical scanning device according to claim 1, wherein, when projected onto a main scanning cross section, the optical element is disposed on an extension line in an extending direction of the reflective optical element.

3. 2. The optical scanning device according to claim 1, wherein the protrusion has a first opening that limits a width of the first light beam in the sub-scanning direction.

4. The optical scanning device according to claim 1, characterized in that the protrusion has a first group of convex portions that abut on the outer surface of the exit surface side of the optical element on both sides of the main scanning direction relative to the optical axis of the optical element on a first surface perpendicular to the optical axis of the optical element.

5. the holding member has a biasing portion that biases the optical element, 5. The optical scanning device according to claim 4, wherein the optical element is held by being biased toward the first group of convex portions by the biasing portion.

6. 5. The optical scanning device according to claim 4, wherein the optical element has a second group of protrusions that contacts the first group of protrusions on the outer surface.

7. 2. The optical scanning device according to claim 1, wherein the optical element is a refractive optical element that converts a convergence degree of the first light beam in a main scanning cross section and condenses the first light beam in a sub-scanning cross section.

8. a second imaging optical system that guides the second light beam deflected by the deflector to a second scanned surface; the deflector deflects the first light beam from the first light source and the second light beam from the second light source by a first deflection surface to scan the first scanned surface and the second scanned surface in a main scanning direction; The optical scanning device according to claim 1, characterized in that the optical element is a refractive optical element having a first refractive optical section that converts the convergence of the first light beam in the main scanning cross section and focuses the first light beam in the sub-scanning cross section, and a second refractive optical section that converts the convergence of the second light beam in the main scanning cross section and focuses the second light beam in the sub-scanning cross section.

9. 9. The optical scanning device according to claim 8, wherein the protrusion has first and second openings for restricting the width of the first and second light beams in the sub-scanning direction.

10. 2. The optical scanning device according to claim 1, wherein the reflective optical element is placed on a second surface of the protrusion that is parallel to an optical axis of the optical element.

11. The optical scanning device according to claim 10 , wherein the reflective optical element is held by being biased toward the second surface.

12. the holding member includes a box portion having an internal space in which the deflector, the first imaging optical system, the reflecting optical element, and the optical element are disposed, and a lid portion covering the internal space, 2. The optical scanning device according to claim 1, wherein the protrusion protrudes in the sub-scanning direction from a predetermined position on the bottom surface of the box.

13. a first incident optical system including the optical element and causing the first light flux to be incident on the deflector; 2. The optical scanning device according to claim 1, wherein the optical element is a refractive optical element that is closest to the deflector on the optical path of the first light beam among the refractive optical elements included in the first incident optical system.

14. a second imaging optical system that guides the second light beam deflected by the deflector to a second scanned surface; the deflector deflects the first light beam from the first light source and the second light beam from the second light source by a first deflection surface to scan the first scanned surface and the second scanned surface in a main scanning direction; The distance between an on-axis deflection point on the first deflection surface of the deflector and the center of an outer surface abutting the protrusion of the optical element in a first direction parallel to a straight line passing through a first intersection point of the optical axis of the first scanned surface and the first imaging optical system and a second intersection point of the optical axis of the second scanned surface and the second imaging optical system is defined as L. Ｘ , the distance between the on-axis deflection point and the center of the reflecting surface of the reflecting optical element in the first direction is M Ｘ When 0.500<M Ｘ / L Ｘ <1.500 2. The optical scanning device according to claim 1, wherein the following conditions are satisfied:

15. The deflector deflects the first light beam by a first deflection surface, The distance in the main scanning direction between the axial deflection point on the first deflection surface of the deflector and the center of the outer surface of the optical element that abuts on the protrusion is defined as L. Ｙ , the distance in the main scanning direction between the on-axis deflection point and the end of the reflecting optical element closest to the optical element is M Ｙ When 0.9000<M Ｙ / L Ｙ <0.9700 2. The optical scanning device according to claim 1, wherein the following conditions are satisfied:

16. a first incident optical system including the optical element and causing the first light flux to be incident on the deflector; The deflector deflects the first light beam by a first deflection surface, The distance in the main scanning section between the axial deflection point on the first deflection surface of the deflector and the center of the outer surface of the optical element that abuts on the protrusion is defined as L. ｔ , the distance between the first light source and the on-axis deflection point in a direction parallel to the optical axis of the first incident optical system is defined as L ｉ When 0.70<L ｔ / L ｉ <0.90 2. The optical scanning device according to claim 1, wherein the following conditions are satisfied:

17. 2. The optical scanning device according to claim 1, wherein the optical element is formed by injection molding a resin material.

18. 18. The optical scanning device according to claim 17, wherein the optical element has a third group of protrusions on an outer surface on the light exit side, the third group of protrusions being pressed when the optical element is released from a mold.

19. 2. The optical scanning device according to claim 1, wherein the incidence surface of the optical element is a diffractive surface.

20. a second, third, and fourth imaging optical system for guiding the second, third, and fourth light beams deflected by the deflector to second, third, and fourth scanned surfaces, the deflector deflects the second, third, and fourth light beams to scan the second, third, and fourth scanned surfaces in a main scanning direction; the first and second light beams are obliquely incident on a first deflecting surface of the deflector at angles different from each other in a sub-scanning cross section with respect to a main-scanning cross section, 2. The optical scanning device according to claim 1, wherein the third and fourth light beams are obliquely incident on the second deflecting surface of the deflector at mutually different angles in the sub-scanning cross section with respect to the main-scanning cross section.

21. 21. An image forming apparatus comprising: an optical scanning device according to claim 1; a developing unit which develops an electrostatic latent image formed on the first scanned surface by the optical scanning device into a toner image; a transfer unit which transfers the developed toner image onto a transfer material; and a fixing unit which fixes the transferred toner image onto the transfer material.

22. 21. An image forming apparatus comprising: the optical scanning device according to claim 1; and a printer controller that converts a signal output from an external device into image data and inputs the image data to the optical scanning device.

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