Optical scanning device and image forming apparatus

Abstract

The invention discloses an optical scanning device and an image forming apparatus. The invention provides an optical scanning device. Wherein the distance between the light source on the optical axis of the incident optical system and the deflection surface of the deflection unit, the distance between the deflection surface on the optical axis of the imaging optical element and the sagittal line inclined surface of the imaging optical element, and the lateral magnification in the sub-scanning cross section of the incident optical system are appropriately set; and an inclination of the sagittal line inclined surface at a position on the sagittal line inclined surface at which a light beam from each light emission point of the light source reaches.

Description

Technical Field

[0001] The present disclosure relates to a light scanning device, and more particularly to a light scanning device suitable for an image forming device such as a laser beam printer (LBP), a digital copier, and a multifunction printer (MFP). Background Art

[0002] Conventionally, there is known a light scanning device that scans a scanned surface to increase speed by using a plurality of light beams emitted from a light source having a plurality of light emission points.

[0003] On the other hand, it is also known that in such an optical scanning device, image quality may be degraded due to variations in the scanning widths (overall magnification) of the plurality of light beams.

[0004] Japanese Patent Application Laid-Open No. H09-197308 discloses an optical scanning device that reduces deviations among scan widths of a plurality of light beams by using deviations among scan widths corresponding to incident angles of the plurality of light beams with respect to a scanned surface. Summary of the Invention

[0005] An optical scanning device according to an embodiment includes: a deflection unit configured to deflect a plurality of light beams from a first light source having a plurality of light emission points to scan a first scanned surface in a main scanning direction; a first optical element having a first optical surface and configured to guide the plurality of light beams deflected by the first deflection surface of the deflection unit to the first scanned surface; and a first incident optical system configured to cause the plurality of light beams from the first light source to be incident on the first deflection surface, wherein the following conditions are satisfied:

[0006]

[0007] Wherein L1 represents the distance between the first light source and the first deflecting surface on the optical axis of the first incident optical system, D1 represents the distance between the first deflecting surface and the first optical surface on the optical axis of the first optical element, β1 represents the lateral magnification in the sub-scan section of the first incident optical system, and M 1i represents the inclination of the first optical surface at a position on the first optical surface where a light beam from the i-th light emission point of the first light source arrives.

[0008] Further features of the present disclosure will become apparent from the following description of exemplary embodiments with reference to the attached drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1Ais a main-scan cross-sectional view of the optical scanning device according to the first embodiment of the present invention.

[0010] Figure 1B is a partial sub-scanning cross-sectional view of the optical scanning device according to the first embodiment.

[0011] Figure 2 1 and 2 are diagrams for explaining the effects of the optical scanning device according to the first embodiment.

[0012] Figure 3A 1 is a diagram showing a state in which a plurality of light rays arrive at respective image heights on a scanned surface in the light scanning device according to the first embodiment.

[0013] Figure 3B 1 is a diagram showing a state in which a plurality of light rays arrive at respective image heights on a scanned surface in the light scanning device according to the first embodiment.

[0014] Figure 4 : is a graph showing the image height dependency of the distance between the arrival positions of light rays on the scanned surface in the light scanning device according to the first embodiment.

[0015] Figure 5A is a main-scan cross-sectional view of an optical scanning device according to a second embodiment of the present invention.

[0016] Figure 5B is a partial sub-scanning cross-sectional view of the optical scanning device according to the second embodiment.

[0017] Figure 6 : is a graph showing the image height dependency of the distance between the arrival positions of light rays on the scanned surface in the light scanning device according to the second embodiment.

[0018] Figure 7A is a main-scan cross-sectional view of an optical scanning device according to a third embodiment of the present invention.

[0019] Figure 7B is a partial sub-scanning cross-sectional view of the optical scanning device according to the third embodiment.

[0020] Figure 8 : is a graph showing the image height dependency of the distance between the arrival positions of light rays on the scanned surface in the light scanning device according to the third embodiment.

[0021] Figure 9A FIG. 4 is a partially developed view of a main scanning section of an optical scanning device according to a fourth embodiment of the present invention.

[0022] Figure 9B FIG. 4 is a partially developed view in the main scanning section of the optical scanning device according to the fourth embodiment.

[0023] Figure 10 FIG. 1 is a partially developed view of a sub-scan section of an optical scanning device according to a fourth embodiment.

[0024] Figure 11 is a partial sub-scanning cross-sectional view of an optical scanning device according to a fourth embodiment.

[0025] Figure 12A : is a graph showing the image height dependency of the distance between the arrival positions of light rays on the scanned surface in the light scanning device according to the fourth embodiment.

[0026] Figure 12B : is a graph showing the image height dependency of the distance between the arrival positions of light rays on the scanned surface in the light scanning device according to the fourth embodiment.

[0027] Figure 13 FIG. 1 is a development view of a main scanning section of an optical scanning device according to a fifth embodiment of the present invention.

[0028] Figure 14 FIG. 1 is a partially developed view of a sub-scan section of an optical scanning device according to a fifth embodiment.

[0029] Figure 15 is a partial sub-scanning cross-sectional view of an optical scanning device according to a fifth embodiment.

[0030] Figure 16 is a sub-scanning cross-sectional view of a main portion of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION

[0031] Hereinafter, the optical scanning device according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that in order to facilitate understanding of the present disclosure, the drawings described below may be drawn in a scale different from the actual scale.

[0032] In the following description, the main scanning direction is the direction perpendicular to the rotation axis of the deflection unit and the optical axis of the optical system. The sub-scanning direction is the direction parallel to the rotation axis of the deflection unit. The main scanning section is the section perpendicular to the sub-scanning direction. The sub-scanning section is the section perpendicular to the main scanning direction.

[0033] Therefore, in the following description, it should be noted that the main scanning direction and the sub-scanning cross section are different between the incident optical system and the imaging optical system.

[0034] [First embodiment]

[0035] Figure 1A and Figure 1B A schematic main-scanning cross-sectional view and a schematic partial sub-scanning cross-sectional view of the light scanning device 110 according to the first embodiment of the present invention are respectively shown.

[0036] The optical scanning device 110 according to this embodiment includes a light source 1101 (first light source), an anamorphic collimating lens 1102, a sub-scanning aperture 1103, a main scanning aperture 1104, a deflection unit 1, a first fθ lens 1106 (first optical element, first imaging optical element) and a second fθ lens 1107.

[0037] On the optical path, the first fθ lens 1106 is arranged between the deflection unit 1 and the second fθ lens 1107 .

[0038] As the light source 1101 , a semiconductor laser (multi-beam laser) having a plurality of light emitting points or the like is used.

[0039] The anamorphic collimator lens 1102 converts the light beam LG emitted from the light source 1101 into a parallel light beam in the main scanning section and converges the light beam LG in the sub-scanning section. The parallel light beam includes not only a strictly parallel light beam but also a substantially parallel light beam such as a weakly divergent light beam or a weakly converging light beam.

[0040] The sub-scanning aperture 1103 limits the beam diameter of the light beam LG having passed through the anamorphic collimator lens 1102 in the sub-scanning direction.

[0041] The main scanning aperture 1104 limits the beam diameter of the light beam LG having passed through the sub-scanning aperture 1103 in the main scanning direction.

[0042] With the above-described configuration, the light beam LG emitted from the light source 1101 is converged in the sub-scanning direction only in the vicinity of the deflecting surface of the deflecting unit 1 , thereby forming a line image elongated in the main scanning direction.

[0043] The deflection unit 1 is driven by a driving unit (not shown) such as a motor. Figure 1A The deflection unit 1 deflects the incident light beam LG while rotating in the direction indicated by the arrow A in FIG. The deflection unit 1 is formed of, for example, a polygon mirror.

[0044] The first fθ lens 1106 and the second fθ lens 1107 are deformable imaging lenses having different powers (refractive powers) between the main scanning section and the sub-scanning section, and converge (guide) the light beam LG deflected by the deflection unit 1 onto the scanned surface 1108 (first scanned surface).

[0045] In the light scanning device 110 according to the present embodiment, the incident optical system 145 a is formed of the anamorphic collimator lens 1102 , the sub-scanning stop 1103 , and the main scanning stop 1104 .

[0046] In addition, in the light scanning device 110 according to the present embodiment, the scanning optical system 145 b (first imaging optical system) is formed of the first fθ lens 1106 and the second fθ lens 1107 .

[0047] Note that the refractive power of the second fθ lens 1107 in the sub-scan section is stronger than the refractive power of the first fθ lens 1106 in the sub-scan section, that is, is strongest in the scanning optical system 145 b .

[0048] The light beams LG emitted from the respective light emission points of the light source 1101 pass through the incident optical system 145 a to be incident on the deflection unit 1 .

[0049] The light beam LG incident on the deflection unit 1 from the light source 1101 is deflected by the deflection unit 1 to be guided onto the scanned surface 1108 by the scanning optical system 145 b , thereby scanning the scanned surface 1108 at a constant speed.

[0050] Since the deflection unit 1 is Figure 1A The light beam LG deflected by the deflection unit 1 rotates in the direction indicated by the arrow A in FIG. Figure 1A The scanned surface 1108 is scanned in the direction indicated by the arrow B in FIG.

[0051] exist Figure 1A and Figure 1B , C0 represents a deflection point (on-axis deflection point) on the deflection surface of the deflection unit 1 for the principal ray of the on-axis light beam. The deflection point C0 serves as a reference point for the scanning optical system 145b.

[0052] In this embodiment, a photosensitive drum 1108 is used as the scanned surface 1108. By rotating the photosensitive drum 1108 in the sub-scanning direction at each main scanning exposure, an exposure distribution in the sub-scanning direction on the photosensitive drum 1108 is formed.

[0053] Next, various characteristics of the incident optical system 145 a and the scanning optical system 145 b provided in the light scanning device 110 according to the present embodiment are shown in Table 1 and Table 2 below, respectively.

[0054] [Table 1]

[0055]

[0056]

[0057]

[0058] [Table 2]

[0059]

[0060]

[0061]

[0062] In Tables 1 and 2, when the intersection between each lens surface and the optical axis is defined as the origin, the optical axis, the axis orthogonal to the optical axis in the main scanning section, and the axis orthogonal to the optical axis in the sub-scanning section are defined as the X-axis, Y-axis, and Z-axis, respectively.

[0063] In Table 2, “Ex” means “×10 -x ”.

[0064] The aspherical surface shape (meridian shape) in the main scanning section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the light scanning device 110 according to the present embodiment is expressed by the following expression (1):

[0065]

[0066] In expression (1), R represents the radius of curvature, k represents the eccentricity, and B i (i=4, 6, 8, 10, and 12) represent aspherical surface coefficients.

[0067] When the coefficient B i When Y is different between the positive side and the negative side, as shown in Table 2, the coefficient on the positive side is added with a subscript u (ie, B iu ), and add the subscript l to the coefficient on the negative side (i.e., B il ).

[0068] The aspherical surface shape (sagittal line shape) in the sub-scan section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the optical scanning device 110 according to the present embodiment is expressed by the following expression (2):

[0069]

[0070] In expression (2), M jk (j=0 to 12, and k=1) represents an aspherical coefficient.

[0071] Note that the sagittal line inclination (sagittal line inclination amount) in this embodiment indicates M 01 Therefore, the sagittal inclined surface refers to M 01 A non-zero surface.

[0072] In addition, the curvature radius r′ in the sub-scan section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the optical scanning device 110 according to the present embodiment continuously changes according to the position in the Y direction, as expressed by the following expression (3):

[0073]

[0074] In expression (3), r represents the radius of curvature on the optical axis, and E i (i=1 to 10) represents the coefficient of variation.

[0075] Furthermore, the anamorphic collimating lens 1102 provided in the optical scanning device 110 according to the present embodiment has an incident surface formed by a diffraction surface defined by an optical path difference function of two variables Y and Z as expressed by the following expression (4):

[0076]

[0077] In expression (4), λ represents the pitch of the diffraction grating, and D ij Represents the phase coefficient.

[0078] Next, the effects of the light scanning device 110 according to the present embodiment will be described.

[0079] Figure 2 A diagram for explaining the effects of the optical scanning device 110 according to the present embodiment is shown.

[0080] exist Figure 2 , among the plurality of light emitting points in the light source 1101, light emitting points 2101a and 2101b located on opposite sides farthest from the center are shown.

[0081] In addition, Figure 2 , an arrow 2102 is shown, which schematically illustrates the focal power of the anamorphic collimating lens 1102, ie, the focal power of the incident optical system 145a.

[0082] also, Figure 2 The positions 2103 of the deflection surface of the deflection unit 1 and the shapes of the exit surfaces (first sagittal tilt surface, first optical surface) of the first fθ lens 1106 are schematically shown, that is, the sagittal tilt coefficient M 01 and a combination 2104 of a straight line and a curve with a curvature radius R.

[0083] Figure 3AThe schematic diagram illustrates the state where light rays 2105a and 2105b emitted from the light emission points 2101a and 2101b of the light source 1101 reach the positive outermost off-axis image height, the on-axis image height and the negative outermost off-axis image height on the scanned surface 1108 when Δx / d=0.

[0084] Figure 3B The schematic diagram illustrates the state in which light rays 2105a and 2105b emitted from the light emission points 2101a and 2101b of the light source 1101 reach the positive outermost off-axis image height, the on-axis image height and the negative outermost off-axis image height on the scanned surface 1108 when Δx / d≠0.

[0085] Here, Δx (mm) represents the distance in a direction parallel to the optical axis between the arrival positions of the light rays 2105a and 2105b on the exit surface of the first fθ lens 1106, and d (mm) represents the interval in the sub-scanning direction between the light emitting points 2101a and 2101b.

[0086] In addition, d1, d2 and d3 respectively represent the distances in the main scanning direction between the arrival positions of light rays 2105a and 2105b at the outermost off-axis image height, the on-axis image height and the outermost off-axis image height on the negative side on the scanned surface 1108 when Δx / d is 0.

[0087] In addition, d4, d5, and d6 respectively represent the distances in the main scanning direction between the arrival positions of light rays 2105a and 2105b at the outermost off-axis image height, the on-axis image height, and the outermost off-axis image height on the negative side on the scanned surface 1108 when Δx / d is not 0.

[0088] like Figure 3A As shown in , when Δx / d is 0, the relationship d1=d2=d3 is satisfied, that is, the width of the image formed by the light ray 2105a and the width of the image formed by the light ray 2105b on the scanned surface 1108 are equal to each other.

[0089] On the other hand, when Δx / d is not 0, the relationship d4≠d5≠d6 is satisfied, that is, the width of the image formed by the light 2105a on the scanned surface 1108 is different from the width of the image formed by the light 2105b.

[0090] In particular, when Δx / d is greater than 0, as Figure 3B As shown in , the relationship d4>d5>d6 is satisfied, that is, the width of the image formed by the light ray 2105a on the scanned surface 1108 is greater than the width of the image formed by the light ray 2105b.

[0091] Here, the distance on the optical axis between the light source 1101 and the deflection surface of the deflection unit 1 is represented by L (mm), and the distance in the sub-scanning direction between the center of the light source 1101 and the light emission point 2101a or the light emission point 2101b is represented by d0 (mm). That is, the relationship d0 = d / 2 is satisfied.

[0092] The position of the light source 1101 on the optical axis can be obtained as an intersection point of a plane including a plurality of light emission points provided in the light source 1101 and the optical axis.

[0093] In addition, an angle formed by a straight line passing through the light emission point 2101 a or the light emission point 2101 b and the center of the anamorphic collimating lens 1102 with respect to the optical axis in the sub-scan section is represented by θ (degrees).

[0094] The lateral magnification of the anamorphic collimator lens 1102 in the sub-scan section, that is, the lateral magnification of the incident optical system 145 a in the sub-scan section, is represented by β.

[0095] At this time, the height of the arrival position of the light ray 2105a or the light ray 2105b on the deflecting surface of the deflecting unit 1 in the sub-scanning direction is represented by -β×d0, thereby obtaining the following expression (5):

[0096]

[0097] Next, the curvature radius of the exit surface of the first fθ lens 1106 on the optical axis in the sub-scan section is represented by R (mm), and the decentering amount of the first fθ lens 1106 in the sub-scan direction is represented by L s (mm).

[0098] At this time, the inclination M at the arrival position of the light ray 2105a or the light ray 2105b on the exit surface of the first fθ lens 1106 can be calculated using the aspheric coefficient M shown in Expression (2) corresponding to the sagittal line inclination amount on the optical axis. 01 It can be approximately expressed by the following expression (6):

[0099]

[0100] The inclination M of the exit surface of the first fθ lens 1106 is defined as the inclination of the normal line of the exit surface of the first fθ lens 1106 with respect to the optical axis.

[0101] In addition, when the distance in the sub-scanning direction between the arrival positions of the light ray 2105a and the light ray 2105b on the exit surface of the first fθ lens 1106 is represented by Δy (mm), the following expression (7) is obtained:

[0102] Δx=M×Δy…(7).

[0103] When the distance on the optical axis between the deflection surface of the deflection unit 1 and the exit surface of the first fθ lens 1106 is represented by D (mm), Δy can be expressed by the following expression (8):

[0104]

[0105] Note that Expression (5) is used when deriving Expression (8).

[0106] Thus, Δx / d can be expressed by the following expression (9) using expressions (7) and (8):

[0107]

[0108] In addition, by using Expression (6), Equation (9) can be rewritten as the following Expression (10):

[0109]

[0110] When the value of Δx / d is small, the difference between the inclination of the light incident on the first fθ lens 1106 and the inclination of the light emitted from the first fθ lens 1106 becomes smaller.

[0111] Therefore, the degree of freedom in arrangement of the second fθ lens 1107 and the photosensitive drum 1108 decreases, and thus it is difficult to achieve sufficient size reduction.

[0112] On the other hand, when the value of Δx / d is large, the light rays 2105a and 2105b emitted from the light emitting points 2101a and 2101b pass through such a first fθ lens 1106, and thus Figure 3B As depicted, the difference between the widths of the images formed by light rays 2105a and 2105b becomes larger.

[0113] Therefore, in the optical scanning device 110 according to the present embodiment, it is desirable to achieve both miniaturization and high definition by satisfying the following inequality (11) with respect to the absolute value of Δx / d.

[0114] In other words, in the light scanning device 110 according to the present embodiment, it is desirable that the following inequality (11) is satisfied for all light emission points of the light source 1101:

[0115]

[0116] In the light scanning device 110 according to the present embodiment, it is preferable that the following inequality (11a) is satisfied for all light emission points of the light source 1101 instead of inequality (11):

[0117]

[0118] In addition, in the optical scanning device 110 according to the present embodiment, it is more preferable that the following inequality (11b) is satisfied instead of inequality (11a) for all light emission points of the light source 1101:

[0119]

[0120] Note that the above-mentioned effect can be obtained when inequalities (11), (11a) and (11b) are satisfied for at least one of the light emission points of the light source 1101, but it is expected that inequalities (11), (11a) and (11b) are satisfied for all the light emission points of the light source 1101.

[0121] Furthermore, as the inclination of the exit surface of the first fθ lens 1106 increases, that is, the sagittal inclination coefficient M 01 As φ increases, the difference between the widths of the images formed by light rays 2105a and 2105b increases.

[0122] Therefore, in the optical scanning device 110 according to this embodiment, it is preferable to satisfy the following inequality (12):

[0123]

[0124] Furthermore, when the exit surface of the first fθ lens 1106 has a curvature, the amounts of inclination at the arrival positions on the exit surface of the light rays emitted from the respective light emission points of the light source 1101 differ from each other.

[0125] Therefore, in the optical scanning device 110 according to this embodiment, it is preferable to satisfy the following inequality (13):

[0126]

[0127] Specifically, in the optical scanning device 110 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is -0.127.

[0128] Thus, the value of each of inequalities (11), (11a), and (11b) is calculated to be 0.589, and thus inequalities (11), (11a), and (11b) are satisfied.

[0129] On the other hand, in the optical scanning device 110 according to the present embodiment, since M 01 It is -0.0918, so the value of inequality (12) is calculated as 0.426, so that inequality (12) is not satisfied.

[0130] In addition, in the light scanning device 110 according to the present embodiment, since Ls is -1.45 mm and R is 41.166 mm, the value of the inequality (13) is calculated to be 0.589, so that the inequality (13) is satisfied.

[0131] The sagittal line inclination amount of the exit surface of the first fθ lens 1106 provided in the optical scanning device 110 according to the present embodiment varies depending on the position in the main scanning direction.

[0132] Then, the absolute value of the sagittal line inclination amount of the exit surface of the first fθ lens 1106 is maximum on the optical axis.

[0133] In addition, the first fθ lens 1106 has positive power in the sub-scan section.

[0134] In addition, the first fθ lens 1106 closest to the deflection unit 1 on the optical path of the light beam LG among the fθ lenses included in the scanning optical system 145b is the fθ lens having the strongest power in the main scanning section among the fθ lenses included in the scanning optical system 145b.

[0135] Figure 4 The distance in the main scanning direction between the arrival positions of the light rays 2105a and 2105b at respective image heights on the scanned surface 1108 in the light scanning device 110 according to the present embodiment is shown.

[0136] That is, the distance includes Figure 3B d4, d5 and d6 shown in the figure, while the distances at the on-axis image height are Figure 4 Indicated as 0 mm.

[0137] like Figure 4 As shown in , in the light scanning device 110 according to the present embodiment, the difference between the maximum value and the minimum value of the distance is 8.0 μm.

[0138] Since this difference corresponds to a deviation of about 9.4% with respect to 300 dpi (ie, a pitch of 84.7 μm), the influence of the deviation of the arrival position of each light ray on the scanned surface 1108 on the image quality can be reduced.

[0139] As described above, in the light scanning device 110 according to the present embodiment, by satisfying the inequality (11), it is possible to suppress the degradation of image quality due to the deviation of the arrival position of each light ray on the scanned surface 1108 .

[0140] Furthermore, in the light scanning device 110 according to the present embodiment, it is possible to achieve miniaturization by forming the exit surface of the first fθ lens 1106 as a sagittal line inclined surface.

[0141] [Second embodiment]

[0142] Figure 5A and Figure 5B A schematic main-scanning cross-sectional view and a schematic partial sub-scanning cross-sectional view of an optical scanning device 310 according to a second embodiment of the present invention are respectively shown.

[0143] The light scanning device 310 according to the present embodiment has the same configuration as the light scanning device 110 according to the first embodiment except for different specification values, so the same components are denoted by the same reference numerals and descriptions thereof are omitted.

[0144] Specifically, various characteristics of the incident optical system 145 a and the scanning optical system 145 b provided in the light scanning device 310 according to the present embodiment are shown in Table 3 and Table 4 below, respectively.

[0145] [Table 3]

[0146]

[0147]

[0148] [Table 4]

[0149]

[0150]

[0151]

[0152]

[0153] In Tables 3 and 4, when the intersection between each lens surface and the optical axis is defined as the origin, the optical axis, the axis orthogonal to the optical axis in the main scanning section, and the axis orthogonal to the optical axis in the sub-scanning section are defined as the X-axis, Y-axis, and Z-axis, respectively.

[0154] In Table 4, “Ex” means “×10 -x ”.

[0155] The aspherical shape (meridian shape) in the main scanning section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the light scanning device 310 according to the present embodiment is expressed by the above-described Expression (1).

[0156] The aspherical shape (sagittal line shape) in the sub-scan section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the optical scanning device 310 according to the present embodiment is expressed by the above-described Expression (2).

[0157] The curvature radius r' in the sub-scan section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the optical scanning device 310 according to the present embodiment continuously changes according to the position in the Y direction as expressed by the above expression (3).

[0158] The anamorphic collimating lens 1102 provided in the optical scanning device 310 according to the present embodiment has an incident surface formed of a diffraction surface defined by an optical path difference function of two variables Y and Z as expressed by the above-mentioned Expression (4).

[0159] In addition, in the optical scanning device 310 according to this embodiment, it is desirable to satisfy inequality (11), preferably inequality (11a), and more preferably inequality (11b).

[0160] In the optical scanning device 310 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0161] Specifically, in the optical scanning device 310 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is -0.0385.

[0162] Therefore, the value of each of inequalities (11), (11a), and (11b) is calculated to be 0.179, so that inequalities (11), (11a), and (11b) are satisfied.

[0163] In addition, in the optical scanning device 310 according to this embodiment, since M 01 is -0.0385, so the value of inequality (12) is calculated to be 0.179, so that inequality (12) is satisfied.

[0164] Furthermore, in the light scanning device 310 according to the present embodiment, since Ls is 0 mm and R is 76.858 mm, the value of the inequality (13) is calculated to be 0.179, so that the inequality (13) is satisfied.

[0165] Figure 6 The distance in the main scanning direction between the arrival positions of the light rays 2105a and 2105b at respective image heights on the scanned surface 1108 in the light scanning device 310 according to the present embodiment is shown.

[0166] That is, the distance includes Figure 3B d4, d5 and d6 shown in , and the distance at the on-axis image height is Figure 6 Indicated as 0 mm.

[0167] like Figure 6As shown in , in the light scanning device 310 according to the present embodiment, the difference between the maximum value and the minimum value of the distance is 5.9 μm.

[0168] Since this difference corresponds to a deviation of about 7.0% with respect to 300 dpi (ie, a pitch of 84.7 μm), the influence of the deviation of the arrival position of each light ray on the scanned surface 1108 on the image quality can be reduced.

[0169] As described above, in the light scanning device 310 according to the present embodiment, by satisfying the inequality (11), it is possible to suppress the degradation of image quality due to the deviation of the arrival position of each light ray on the scanned surface 1108 .

[0170] [Third embodiment]

[0171] Figure 7A and Figure 7B 1 and 2 respectively show a schematic main-scanning cross-sectional view and a schematic partial sub-scanning cross-sectional view of an optical scanning device 510 according to a third embodiment of the present invention.

[0172] The light scanning device 510 according to the present embodiment has the same configuration as the light scanning device 110 according to the first embodiment except for different specification values, so the same components are denoted by the same reference numerals and descriptions thereof are omitted.

[0173] Specifically, various characteristics of the incident optical system 145 a and the scanning optical system 145 b provided in the light scanning device 510 according to the present embodiment are shown in Table 5 and Table 6 below, respectively.

[0174] [Table 5]

[0175]

[0176]

[0177] [Table 6]

[0178]

[0179]

[0180]

[0181] In Tables 5 and 6, when the intersection between each lens surface and the optical axis is defined as the origin, the optical axis, the axis orthogonal to the optical axis in the main scanning section, and the axis orthogonal to the optical axis in the sub-scanning section are defined as the X-axis, Y-axis, and Z-axis, respectively.

[0182] In Table 6, “Ex” means “×10 -x ”.

[0183] The aspherical shape (meridian shape) in the main scanning section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the light scanning device 510 according to the present embodiment is expressed by the above-described Expression (1).

[0184] The aspherical shape (sagittal line shape) in the sub-scan section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the optical scanning device 510 according to the present embodiment is expressed by the above-described Expression (2).

[0185] The curvature radius r' in the sub-scan section of each lens surface of the first fθ lens 1106 and the second fθ lens 1107 provided in the optical scanning device 510 according to the present embodiment continuously changes according to the position in the Y direction as expressed by the above expression (3).

[0186] The anamorphic collimating lens 1102 provided in the optical scanning device 510 according to the present embodiment has an incident surface formed of a diffraction surface defined by an optical path difference function of two variables Y and Z as expressed by the above-mentioned Expression (4).

[0187] In addition, in the optical scanning device 510 according to this embodiment, it is desirable to satisfy inequality (11), preferably inequality (11a), and more preferably inequality (11b).

[0188] In the optical scanning device 510 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0189] Specifically, in the optical scanning device 510 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is -0.0735.

[0190] Therefore, the value of each of inequalities (11), (11a), and (11b) is calculated to be 0.341, and inequalities (11), (11a), and (11b) are satisfied.

[0191] In addition, in the optical scanning device 510 according to this embodiment, since M 01 is -0.0212, so the value of inequality (12) is calculated to be 0.098, so that inequality (12) is satisfied.

[0192] Furthermore, in the light scanning device 510 according to the present embodiment, since Ls is -1.31 mm and R is 25.004 mm, the value of the inequality (13) is calculated to be 0.341, so that the inequality (13) is satisfied.

[0193] Figure 8 1 and 2. The distance in the main scanning direction between the arrival positions of the light rays 2105a and 2105b at respective image heights on the scanned surface 1108 in the light scanning device 510 according to the present embodiment is shown.

[0194] That is, the distance includes Figure 3B d4, d5 and d6 shown in , and the distance at the on-axis image height is Figure 8 Indicated as 0 mm.

[0195] like Figure 8 As shown in , in the light scanning device 510 according to the present embodiment, the difference between the maximum value and the minimum value of the distance is 2.0 μm.

[0196] Then, the difference corresponds to a deviation of about 9.2% with respect to 1200 dpi (ie, a pitch of 21.2 μm) and a deviation of about 2.3% with respect to 300 dpi (ie, a pitch of 84.7 μm).

[0197] Therefore, the influence of the deviation of the arrival position of each light ray on the scanned surface 1108 on the image quality can be reduced.

[0198] As described above, in the light scanning device 510 according to the present embodiment, by satisfying the inequality (11), it is possible to suppress the degradation of image quality due to the deviation of the arrival position of each light ray on the scanned surface 1108 .

[0199] [Fourth embodiment]

[0200] Figure 9A and Figure 9B , each showing a schematic partial expanded view in a main scanning section of an optical scanning device 710 according to a fourth embodiment of the present invention.

[0201] Figure 10 and Figure 11 A schematic partial expanded view and a schematic partial sub-scan cross-sectional view in a sub-scan section of an optical scanning device 710 according to the fourth embodiment are respectively shown.

[0202] The optical scanning device 710 according to the present embodiment includes first and second light sources 101 and 201 , first and second anamorphic collimating lenses 102 and 202 , and first and second sub-scanning apertures 103 and 203 .

[0203] In addition, the light scanning device 710 according to the present embodiment includes the first main scanning diaphragm 104 and the second main scanning diaphragm 204 , the deflection unit 1 , the first fθ lenses 106 and 206 , and the second fθ lenses 107 and 207 .

[0204] On the optical path, the first fθ lens 106 is arranged between the deflection unit 1 and the second fθ lens 107 , and the first fθ lens 206 is arranged between the deflection unit 1 and the second fθ lens 207 .

[0205] As each of the first light source 101 and the second light source 201 , a semiconductor laser (multi-beam laser) having a plurality of light emission points or the like is used.

[0206] The first anamorphic collimator lens 102 and the second anamorphic collimator lens 202 convert the light beams LA and LB emitted from the first light source 101 and the second light source 201 into parallel light beams in the main scanning section, and converge the light beams LA and LB in the sub-scanning section. Parallel light beams include not only strictly parallel light beams but also substantially parallel light beams such as weakly diverging light beams or weakly converging light beams.

[0207] The first sub-scanning stop 103 and the second sub-scanning stop 203 limit the beam diameters in the sub-scanning direction of the light beams LA and LB that have passed through the first anamorphic collimator lens 102 and the second anamorphic collimator lens 202 , respectively.

[0208] The first main scanning diaphragm 104 and the second main scanning diaphragm 204 restrict the beam diameters in the main scanning direction of the light beams LA and LB having passed through the first sub-scanning diaphragm 103 and the second sub-scanning diaphragm 203 , respectively.

[0209] In this manner, the light beams LA and LB emitted from the first and second light sources 101 and 201 converge in the sub-scanning direction only near the first deflecting surface of the deflecting unit 1 , thereby forming a line image elongated in the main scanning direction.

[0210] The deflection unit 1 is driven by a driving unit such as a motor (not shown). Figure 9A and Figure 9B The incident light beams LA and LB are deflected while rotating in the direction indicated by the arrow A. The deflection unit 1 is formed of, for example, a polygon mirror.

[0211] The first fθ lens 106 (first optical element, first imaging optical element) and the second fθ lens 107 are anamorphic imaging lenses having different focal lengths between the main scanning section and the sub-scanning section, and converge (guide) the light beam LA deflected by the first deflection surface of the deflection unit 1 onto the first scanned surface 108.

[0212] The first fθ lens 206 (second optical element, second imaging optical element) and the second fθ lens 207 are deformable imaging lenses with different focal lengths between the main scanning section and the sub-scanning section, and converge (guide) the light beam LB deflected by the first deflection surface of the deflection unit 1 onto the second scanned surface 208.

[0213] In the light scanning device 710 according to the present embodiment, the first incident optical system 45 a is formed by the first anamorphic collimator lens 102 , the first sub-scanning diaphragm 103 , and the first main-scanning diaphragm 104 .

[0214] The second incident optical system 55 a is formed by a second anamorphic collimator lens 202 , a second sub-scanning diaphragm 203 , and a second main scanning diaphragm 204 .

[0215] In addition, in the light scanning device 710 according to the present embodiment, the first scanning optical system 45 b is formed of the first fθ lens 106 and the second fθ lens 107 .

[0216] The second scanning optical system 55 b is formed of a first fθ lens 206 and a second fθ lens 207 .

[0217] Note that the refractive powers in the sub-scan sections of the second fθ lenses 107 and 207 are stronger than those in the sub-scan sections of the first fθ lenses 106 and 206 , respectively, that is, the strongest among the first scanning optical system 45 b and the second scanning optical system 55 b .

[0218] The light LA emitted from each light emission point of the first light source 101 passes through the first incident optical system 45 a to be incident on the first deflecting surface of the deflecting unit 1 .

[0219] Then, the light beam LA incident on the first deflecting surface of the deflecting unit 1 from the first light source 101 is deflected by the first deflecting surface of the deflecting unit 1 to be guided onto the first scanned surface 108 by the first scanning optical system 45b, thereby scanning the first scanned surface 108 at a constant speed.

[0220] The light beams LB emitted from the respective light emission points of the second light source 201 pass through the second incident optical system 55 a to be incident on the first deflecting surface of the deflecting unit 1 .

[0221] Then, the light beam LB incident on the first deflecting surface of the deflecting unit 1 from the second light source 201 is deflected by the first deflecting surface of the deflecting unit 1 to be guided onto the second scanned surface 208 by the second scanning optical system 55b, thereby scanning the second scanned surface 208 at a constant speed.

[0222] Since the deflection unit 1 is Figure 9A and Figure 9B The light beams LA and LB deflected by the deflection unit 1 rotate in the direction indicated by the arrow A in FIG. Figure 9A and Figure 9B The first scanned surface 108 and the second scanned surface 208 are scanned in the direction indicated by the arrow B in FIG.

[0223] exist Figure 9A and Figure 9B , C0 represents a deflection point (on-axis deflection point) on the first deflecting surface of the deflection unit 1 with respect to the principal ray of the on-axis light beam. The deflection point C0 serves as a reference point for the first scanning optical system 45b and the second scanning optical system 55b.

[0224] In the present embodiment, the first photosensitive drum 108 and the second photosensitive drum 208 are used as the first scanned surface 108 and the second scanned surface 208 .

[0225] The exposure distribution in the sub-scanning direction on the first photosensitive drum 108 and the second photosensitive drum 208 is formed by rotating the first photosensitive drum 108 and the second photosensitive drum 208 in the sub-scanning direction at each main scanning exposure.

[0226] Next, various characteristics of the first and second incident optical systems 45a and 55a and the first and second scanning optical systems 45b and 55b provided in the light scanning device 710 according to the present embodiment are shown in Tables 7 to 9 below.

[0227] [Table 7]

[0228]

[0229]

[0230]

[0231] [Table 8]

[0232]

[0233]

[0234]

[0235] [Table 9]

[0236]

[0237]

[0238]

[0239] In Tables 7 to 9, when the intersection between each lens surface and the optical axis is defined as the origin, the optical axis, the axis orthogonal to the optical axis in the main scanning section, and the axis orthogonal to the optical axis in the sub-scanning section are defined as the X-axis, Y-axis, and Z-axis, respectively.

[0240] In Tables 8 and 9, “Ex” means “×10 -x ”.

[0241] The aspherical shape (meridian shape) in the main scanning section of each lens surface of the first fθ lenses 106 and 206 and the second fθ lenses 107 and 207 provided in the light scanning device 710 according to the present embodiment is expressed by the above-described Expression (1).

[0242] The aspherical shape (sagittal line shape) in the sub-scan section of each lens surface of the first fθ lenses 106 and 206 and the second fθ lenses 107 and 207 provided in the optical scanning device 710 according to the present embodiment is expressed by the above-mentioned Expression (2).

[0243] The curvature radius r' in the sub-scan section of each lens surface of the first fθ lenses 106 and 206 and the second fθ lenses 107 and 207 provided in the optical scanning device 710 according to the present embodiment continuously changes according to the position in the Y direction, as expressed by the above expression (3).

[0244] Each of the first anamorphic collimating lens 102 and the second anamorphic collimating lens 202 provided in the optical scanning device 710 according to this embodiment has an incident surface formed by a diffraction surface defined by an optical path difference function of two variables Y and Z as expressed by the above expression (4).

[0245] In addition, it is desirable that the inequality (11) is satisfied in the first incident optical system 45 a and the first scanning optical system 45 b provided in the light scanning device 710 according to the present embodiment.

[0246] In other words, the inclination at the arrival position of the light from the i-th light emission point of the first light source 101 on the exit surface (first sagittal line inclined surface, first optical surface) of the first fθ lens 106 provided in the optical scanning device 710 according to the present embodiment is given by M 1i express.

[0247] The lateral magnification in the sub-scanning section of the first incident optical system 45 a is represented by β1.

[0248] The distance on the optical axis of the first incident optical system 45 a between the first light source 101 provided in the light scanning device 710 according to the present embodiment and the first deflecting surface of the deflecting unit 1 is represented by L1 (mm).

[0249] The distance on the optical axis of the first scanning optical system 45 b between the first deflecting surface of the deflecting unit 1 and the exit surface of the first fθ lens 106 provided in the light scanning device 710 according to the present embodiment is represented by D1 (mm).

[0250] At this time, in the first incident optical system 45a and the first scanning optical system 45b provided in the light scanning device 710 according to the present embodiment, it is desirable to satisfy the following inequality (11c):

[0251]

[0252] In the first incident optical system 45a and the first scanning optical system 45b provided in the light scanning device 710 according to the present embodiment, it is preferable to satisfy the inequality (11a), and it is more preferable to satisfy the inequality (11b).

[0253] In addition, in the first incident optical system 45 a and the first scanning optical system 45 b provided in the light scanning device 710 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0254] In other words, it is preferable to use the aspheric coefficient M of the exit surface of the first fθ lens 106 provided in the light scanning device 710 according to the present embodiment. 01 To satisfy the following inequality (12a):

[0255]

[0256] In other words, the curvature radius in the sub-scan section of the exit surface of the first fθ lens 106 on the optical axis of the first scanning optical system 45b is represented by R (mm), and the decentering amount in the sub-scan direction of the first fθ lens 106 is represented by L. s (mm).

[0257] At this time, it is preferable to satisfy the following inequality (13a):

[0258]

[0259] Specifically, in the first incident optical system 45 a and the first scanning optical system 45 b provided in the light scanning device 710 according to the present embodiment, β is −3.65, D is 34.2 mm, L is 161.7 mm, and M is 0.100.

[0260] Therefore, the value of each of the inequalities (11), (11a), and (11b) is calculated to be 0.465, so that the inequalities (11), (11a), and (11b) are satisfied.

[0261] On the other hand, in the first incident optical system 45a and the first scanning optical system 45b provided in the light scanning device 710 according to the present embodiment, since M 01 is 0.0766, so the value of inequality (12) is calculated as 0.355, so that inequality (12) is not satisfied.

[0262] In addition, in the first incident optical system 45a and the first scanning optical system 45b provided in the light scanning device 710 according to this embodiment, Ls is 1.31 mm and R is 55.261 mm. Therefore, the value of inequality (13) is calculated to be 0.465, so that inequality (13) is satisfied.

[0263] Furthermore, in the second incident optical system 55 a and the second scanning optical system 55 b provided in the light scanning device 710 according to the present embodiment, it is desirable that inequality (11) is satisfied.

[0264] In other words, the inclination at the arrival position of the light from the j-th light emission point of the second light source 201 on the exit surface (second sagittal line inclined surface, second optical surface) of the first fθ lens 206 provided in the optical scanning device 710 according to the present embodiment is given by M 2j express.

[0265] The lateral magnification in the sub-scanning cross section of the second incident optical system 55 a is represented by β2 .

[0266] The distance on the optical axis of the second incident optical system 55 a between the second light source 201 provided in the light scanning device 710 according to the present embodiment and the first deflecting surface of the deflecting unit 1 is represented by L2 (mm).

[0267] The distance on the optical axis of the second scanning optical system 55 b between the first deflecting surface of the deflecting unit 1 and the exit surface of the first fθ lens 206 provided in the light scanning device 710 according to the present embodiment is represented by D2 (mm).

[0268] At this time, in the second incident optical system 55a and the second scanning optical system 55b provided in the light scanning device 710 according to the present embodiment, it is desirable to satisfy the following inequality (11d):

[0269]

[0270] In addition, in the second incident optical system 55a and the second scanning optical system 55b provided in the light scanning device 710 according to the present embodiment, it is preferable that the inequality (11a) is satisfied, and it is more preferable that the inequality (11b) is satisfied.

[0271] Furthermore, in the second incident optical system 55 a and the second scanning optical system 55 b provided in the light scanning device 710 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0272] Specifically, in the second incident optical system 55a and the second scanning optical system 55b provided in the light scanning device 710 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is 0.0735.

[0273] Therefore, the value of each of the inequalities (11), (11a), and (11b) is calculated to be 0.341, so that the inequalities (11), (11a), and (11b) are satisfied.

[0274] In addition, in the second incident optical system 55a and the second scanning optical system 55b provided in the light scanning device 710 according to the present embodiment, since M 01 is 0.0212, so the value of inequality (12) is calculated to be 0.098, so that inequality (12) is satisfied.

[0275] Furthermore, in the second incident optical system 55a and the second scanning optical system 55b provided in the light scanning device 710 according to this embodiment, since Ls is 1.31 mm and R is 25.004 mm, the value of inequality (13) is calculated to be 0.341, so that inequality (13) is satisfied.

[0276] Note that, in the optical scanning device 710 according to the present embodiment, the sagittal line inclination amount M on the optical axis of the exit surface of the first fθ lens 106 is 01 The absolute value of the sagittal tilt M on the optical axis of the exit surface of the first fθ lens 206 01 The absolute values of are different from each other.

[0277] Figure 12A The distance in the main scanning direction between the arrival position of the light 2105a and the arrival position of the light 2105b at each image height on the first scanned surface 108 in the light scanning device 710 according to this embodiment is shown.

[0278] That is, the distance includes Figure 3B d4, d5 and d6 shown in , and the distance at the on-axis image height is Figure 12A Indicated as 0 mm.

[0279] Figure 12B The distance in the main scanning direction between the arrival position of the light ray 2105a and the arrival position of the light ray 2105b at each image height on the second scanned surface 208 in the light scanning device 710 according to this embodiment is shown.

[0280] That is, the distance includes Figure 3B d4, d5 and d6 shown in , and the distance at the on-axis image height is Figure 12B Indicated as 0 mm.

[0281] like Figure 12A As shown in , in the optical scanning device 710 according to the present embodiment, the difference between the maximum value and the minimum value of the distance on the first scanned surface 108 is 6.3 μm.

[0282] Since this difference corresponds to a deviation of about 7.4% with respect to 300 dpi (ie, a pitch of 84.7 μm), the influence of the deviation of the arrival position of each light ray on the first scanned surface 108 on the image quality can be reduced.

[0283] In addition, if Figure 12B As shown in , in the light scanning device 710 according to the present embodiment, the difference between the maximum value and the minimum value of the distance on the second scanned surface 208 is 2.0 μm.

[0284] Since this difference corresponds to a deviation of about 2.3% with respect to 300 dpi (ie, a pitch of 84.7 μm), the influence of the deviation of the arrival position of each light ray on the second scanned surface 208 on the image quality can be reduced.

[0285] As described above, in the light scanning device 710 according to the present embodiment, inequalities (11) and (13) are satisfied for the first incident optical system 45 a and the first scanning optical system 45 b .

[0286] On the other hand, with the second incident optical system 55a and the second scanning optical system 55b, all of inequalities (11), (12), and (13) are satisfied.

[0287] This makes it possible to reduce the distance in the main scanning direction between the arrival position of the light ray 2105a and the arrival position of the light ray 2105b at each image height on the second scanned surface 208 as compared to the first scanned surface 108.

[0288] As described above, in the light scanning device 710 according to this embodiment, inequality (11) is satisfied in the first incident optical system 45a and the first scanning optical system 45b, thereby making it possible to suppress the deterioration of image quality caused by the deviation of the arrival position of each light ray on the first scanned surface 108.

[0289] In addition, in the optical scanning device 710 according to this embodiment, inequality (11) is satisfied in the second incident optical system 55a and the second scanning optical system 55b, thereby making it possible to suppress the deterioration of image quality caused by the deviation of the arrival position of each light ray on the second scanned surface 208.

[0290] [Fifth embodiment]

[0291] Figure 13 A schematic expansion diagram in main scanning section of an optical scanning device 910 according to a fifth embodiment of the present invention is shown.

[0292] Figure 14 and Figure 15 A schematic partial expanded view and a schematic partial sub-scan cross-sectional view in a sub-scan section of the optical scanning device 910 according to the fifth embodiment are respectively shown.

[0293] The optical scanning device 910 according to this embodiment includes first, second, third, and fourth light sources 301, 401, 501, and 601, and first, second, third, and fourth anamorphic collimating lenses 302, 402, 502, and 602.

[0294] In addition, the optical scanning device 910 according to this embodiment includes a first sub-scanning aperture 303, a second sub-scanning aperture 403, a third sub-scanning aperture 503 and a fourth sub-scanning aperture 603, as well as a first main scanning aperture 304, a second main scanning aperture 404, a third main scanning aperture 504 and a fourth main scanning aperture 604.

[0295] Furthermore, the light scanning device 910 according to the present embodiment includes the deflection unit 1 , first fθ lenses 306 , 406 , 506 , and 606 , second fθ lenses 307 , 407 , 507 , and 607 , and folding mirrors 311 , 312 , 411 , 511 , 512 , and 611 .

[0296] On the optical path, the first fθ lens 306 is arranged between the deflection unit 1 and the second fθ lens 307 , and the first fθ lens 406 is arranged between the deflection unit 1 and the second fθ lens 407 .

[0297] On the optical path, the first fθ lens 506 is arranged between the deflection unit 1 and the second fθ lens 507 , and the first fθ lens 606 is arranged between the deflection unit 1 and the second fθ lens 607 .

[0298] As each of the first light source 301 , the second light source 401 , the third light source 501 , and the fourth light source 601 , a semiconductor laser or the like having a plurality of light emission points is used.

[0299] The first deformed collimating lens 302, the second deformed collimating lens 402, the third deformed collimating lens 502 and the fourth deformed collimating lens 602 respectively convert the light beams LC, LD, LE and LF emitted from the first light source 301, the second light source 401, the third light source 501 and the fourth light source 601 into parallel light beams LC, LD, LE and LF in the main scanning section, and converge the light beams LC, LD, LE and LF in the sub-scanning section.

[0300] The parallel light beam includes not only a strictly parallel light beam but also a substantially parallel light beam such as a weakly diverging light beam or a weakly converging light beam.

[0301] The first sub-scanning aperture 303, the second sub-scanning aperture 403, the third sub-scanning aperture 503 and the fourth sub-scanning aperture 603 respectively limit the beam diameters of the light beams LC, LD, LE and LF in the sub-scanning direction that have passed through the first anamorphic collimating lens 302, the second anamorphic collimating lens 402, the third anamorphic collimating lens 502 and the fourth anamorphic collimating lens 602.

[0302] The first main scanning aperture 304, the second main scanning aperture 404, the third main scanning aperture 504 and the fourth main scanning aperture 604 respectively limit the beam diameters of the light beams LC, LD, LE and LF in the main scanning direction that have passed through the first sub-scanning aperture 303, the second sub-scanning aperture 403, the third sub-scanning aperture 503 and the fourth sub-scanning aperture 603.

[0303] In this manner, the light beams LC and LD emitted from the first and second light sources 301 and 401 respectively converge in the sub-scanning direction only near the first deflecting surface of the deflecting unit 1 , so that a line image elongated in the main scanning direction is formed.

[0304] In addition, the light beams LE and LF emitted from the third light source 501 and the fourth light source 601 , respectively, converge in the sub-scanning direction only near the second deflecting surface of the deflecting unit 1 , so that a line image elongated in the main scanning direction is formed.

[0305] The deflection unit 1 is driven by a driving device such as a motor (not shown). Figure 13 The deflection unit 1 deflects the incident light beams LC, LD, LE, and LF while rotating in the direction indicated by the arrow A. The deflection unit 1 is formed of, for example, a polygon mirror.

[0306] The first fθ lens 306 (first optical element, first imaging optical element) and the second fθ lens 307 are deformable imaging lenses having different focal lengths between the main scanning section and the sub-scanning section, and converge (guide) the light beam LC deflected by the first deflection surface of the deflection unit 1 onto the first scanned surface 308.

[0307] The first fθ lens 406 (second optical element, second imaging optical element) and the second fθ lens 407 are deformable imaging lenses with different focal lengths between the main scanning section and the sub-scanning section, and converge (guide) the light beam LD deflected by the first deflection surface of the deflection unit 1 onto the second scanned surface 408.

[0308] The first fθ lens 506 (third optical element, third imaging optical element) and the second fθ lens 507 are anamorphic imaging lenses having different focal lengths between the main scanning section and the sub-scanning section, and converge (guide) the light beam LE deflected by the second deflection surface of the deflection unit 1 onto the third scanned surface 508.

[0309] The first fθ lens 606 (fourth optical element, fourth imaging optical element) and the second fθ lens 607 are deformable imaging lenses with different focal lengths between the main scanning section and the sub-scanning section, and converge (guide) the light beam LF deflected by the second deflection surface of the deflection unit 1 onto the fourth scanned surface 608.

[0310] The folding mirrors 311 and 312 reflect the light beam LC deflected by the first deflecting surface of the deflecting unit 1 to fold the optical path of the light beam LC, and the folding mirror 411 reflects the light beam LD deflected by the first deflecting surface of the deflecting unit 1 to fold the optical path of the light beam LD.

[0311] The folding mirrors 511 and 512 reflect the light beam LE deflected by the second deflecting surface of the deflecting unit 1 to fold the optical path of the light beam LE, and the folding mirror 611 reflects the light beam LF deflected by the second deflecting surface of the deflecting unit 1 to fold the optical path of the light beam LF.

[0312] In the light scanning device 910 according to the present embodiment, the first incident optical system 65 a is formed by the first anamorphic collimator lens 302 , the first sub-scanning diaphragm 303 , and the first main-scanning diaphragm 304 .

[0313] The second incident optical system 75 a is formed by a second anamorphic collimator lens 402 , a second sub-scanning diaphragm 403 , and a second main scanning diaphragm 404 .

[0314] The third incident optical system 85 a is formed by a third anamorphic collimator lens 502 , a third sub-scanning diaphragm 503 , and a third main scanning diaphragm 504 .

[0315] The fourth incident optical system 95 a is formed by a fourth anamorphic collimator lens 602 , a fourth sub-scanning diaphragm 603 , and a fourth main scanning diaphragm 604 .

[0316] In addition, in the light scanning device 910 according to the present embodiment, the first scanning optical system 65 b is formed by the first fθ lens 306 and the second fθ lens 307 , and the second scanning optical system 75 b is formed by the first fθ lens 406 and the second fθ lens 407 .

[0317] The third scanning optical system 85 b is formed of a first fθ lens 506 and a second fθ lens 507 , and the fourth scanning optical system 95 b is formed of a first fθ lens 606 and a second fθ lens 607 .

[0318] The refractive powers of the second fθ lenses 307, 407, 507 and 607 on the sub-scan section are respectively greater than the refractive powers of the first fθ lenses 306, 406, 506 and 606 on the sub-scan section, that is, they are strongest in the first scanning optical system 65b, the second scanning optical system 75b, the third scanning optical system 85b and the fourth scanning optical system 95b.

[0319] The light beams LC emitted from the respective light emission points of the first light source 301 pass through the first incident optical system 65 a to be incident on the first deflecting surface of the deflecting unit 1 .

[0320] Then, the light beam LC incident on the first deflecting surface of the deflecting unit 1 from the first light source 301 is deflected by the first deflecting surface of the deflecting unit 1 so as to be guided onto the first scanned surface 308 by the first scanning optical system 65b, thereby scanning the first scanned surface 308 at a constant speed.

[0321] The light beams LD emitted from the respective light emission points of the second light source 401 pass through the second incident optical system 75 a to be incident on the first deflecting surface of the deflecting unit 1 .

[0322] Then, the light beam LD incident on the first deflecting surface of the deflecting unit 1 from the second light source 401 is deflected by the first deflecting surface of the deflecting unit 1 so as to be guided onto the second scanned surface 408 by the second scanning optical system 75b, thereby scanning the second scanned surface 408 at a constant speed.

[0323] The light beams LE emitted from the respective light emission points of the third light source 501 pass through the third incident optical system 85 a to be incident on the second deflecting surface of the deflecting unit 1 .

[0324] Then, the light beam LE incident on the second deflecting surface of the deflecting unit 1 from the third light source 501 is deflected by the second deflecting surface of the deflecting unit 1 so as to be guided onto the third scanned surface 508 by the third scanning optical system 85b, thereby scanning the third scanned surface 508 at a constant speed.

[0325] The light beams LF emitted from the respective light emission points of the fourth light source 601 pass through the fourth incident optical system 95 a to be incident on the second deflecting surface of the deflecting unit 1 .

[0326] Then, the light beam LF incident on the second deflecting surface of the deflection unit 1 from the fourth light source 601 is deflected by the second deflecting surface of the deflection unit 1 so as to be guided onto the fourth scanned surface 608 by the fourth scanning optical system 95b, thereby scanning the fourth scanned surface 608 at a constant speed.

[0327] Since the deflection unit 1 is Figure 13 The light beams LC, LD, LE and LF deflected by the deflection unit 1 rotate in the direction indicated by the arrow A, respectively. Figure 13 The first scanned surface 308 , the second scanned surface 408 , the third scanned surface 508 , and the fourth scanned surface 608 are scanned in the direction indicated by the middle arrow B.

[0328] exist Figures 13 to 15 , D0 and E0 respectively denote deflection points (on-axis deflection points) on the first deflecting surface and the second deflecting surface of the deflection unit 1 with respect to the principal ray of the on-axis light beam.

[0329] The deflection point D0 serves as a reference point for the first scanning optical system 65b and the second scanning optical system 75b, and the deflection point E0 serves as a reference point for the third scanning optical system 85b and the fourth scanning optical system 95b.

[0330] In the present embodiment, the first photosensitive drum 308 , the second photosensitive drum 408 , the third photosensitive drum 508 , and the fourth photosensitive drum 608 are used as the first scanned surface 308 , the second scanned surface 408 , the third scanned surface 508 , and the fourth scanned surface 608 .

[0331] The exposure distribution in the sub-scanning direction on the first photosensitive drum 308, the second photosensitive drum 408, the third photosensitive drum 508 and the fourth photosensitive drum 608 is respectively formed by rotating the first photosensitive drum 308, the second photosensitive drum 408, the third photosensitive drum 508 and the fourth photosensitive drum 608 in the sub-scanning direction during each main scanning exposure.

[0332] Next, various characteristics of the first incident optical system 65a, the second incident optical system 75a, the third incident optical system 85a and the fourth incident optical system 95a, and the first scanning optical system 65b, the second scanning optical system 75b, the third scanning optical system 85b and the fourth scanning optical system 95b provided in the optical scanning device 910 according to this embodiment are shown in Tables 10 to 12 below.

[0333] [Table 10]

[0334]

[0335]

[0336]

[0337]

[0338] [Table 11]

[0339]

[0340]

[0341]

[0342]

[0343] [Table 12]

[0344]

[0345]

[0346]

[0347] In Tables 10 to 12, when the intersection between each lens surface and the optical axis is defined as the origin, the optical axis, the axis orthogonal to the optical axis in the main scanning section, and the axis orthogonal to the optical axis in the sub-scanning section are defined as the X-axis, Y-axis, and Z-axis, respectively.

[0348] In Tables 11 and 12, “Ex” means “×10 -x ”.

[0349] The aspherical shape (meridian shape) in the main scanning section of each lens surface of the first fθ lenses 306, 406, 506 and 606 and the second fθ lenses 307, 407, 507 and 607 provided in the light scanning device 910 according to the present embodiment is expressed by the above expression (1).

[0350] The aspherical shape (sagittal line shape) in the sub-scan section of each lens surface of the first fθ lenses 306, 406, 506 and 606 and the second fθ lenses 307, 407, 507 and 607 provided in the optical scanning device 910 according to the present embodiment is expressed by the above expression (2).

[0351] The curvature radius r' of the sub-scanning section of each lens surface of the first fθ lenses 306, 406, 506 and 606 and the second fθ lenses 307, 407, 507 and 607 provided in the optical scanning device 910 according to this embodiment continuously changes according to the position in the Y direction, as expressed by the above expression (3).

[0352] Each of the first anamorphic collimating lens 302, the second anamorphic collimating lens 402, the third anamorphic collimating lens 502 and the fourth anamorphic collimating lens 602 provided in the optical scanning device 910 according to this embodiment has an incident surface formed by a diffraction surface defined by an optical path difference function of two variables Y and Z as expressed by the above expression (4).

[0353] In addition, in the first incident optical system 65a and the first scanning optical system 65b provided in the light scanning device 910 according to this embodiment, it is desirable to satisfy inequality (11), preferably inequality (11a), and more preferably inequality (11b).

[0354] Furthermore, in the first incident optical system 65 a and the first scanning optical system 65 b provided in the light scanning device 910 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0355] Specifically, in the first incident optical system 65a and the first scanning optical system 65b provided in the light scanning device 910 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is 0.138.

[0356] Therefore, the value of each of inequalities (11), (11a), and (11b) is calculated to be 0.638, so that inequalities (11) and (11a) are satisfied.

[0357] On the other hand, in the first incident optical system 65a and the first scanning optical system 65b provided in the light scanning device 910 according to the present embodiment, M 01 It is 0.114.

[0358] Therefore, the value of inequality (12) is calculated as 0.527, so that inequality (12) is not satisfied.

[0359] In addition, in the first incident optical system 65 a and the first scanning optical system 65 b provided in the light scanning device 910 according to the present embodiment, Ls is 1.31 mm and R is 54.586 mm.

[0360] Therefore, the value of inequality (13) is calculated to be 0.638, so that inequality (13) is satisfied.

[0361] In the second incident optical system 75a and the second scanning optical system 75b provided in the light scanning device 910 according to the present embodiment, it is desirable to satisfy inequality (11), preferably inequality (11a), and more preferably inequality (11b).

[0362] In addition, in the second incident optical system 75a and the second scanning optical system 75b provided in the light scanning device 910 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0363] Specifically, in the second incident optical system 75a and the second scanning optical system 75b provided in the light scanning device 910 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is 0.103.

[0364] Therefore, the value of each of the inequalities (11), (11a), and (11b) is calculated to be 0.476, so that the inequalities (11), (11a), and (11b) are satisfied.

[0365] In addition, in the second incident optical system 75a and the second scanning optical system 75b provided in the light scanning device 910 according to the present embodiment, M 01 It is 0.0393.

[0366] Therefore, the value of inequality (12) is calculated to be 0.182, so that inequality (12) is satisfied.

[0367] In addition, in the second incident optical system 75 a and the second scanning optical system 75 b provided in the light scanning device 910 according to the present embodiment, Ls is 1.31 mm and R is 20.586 mm.

[0368] Therefore, the value of inequality (13) is calculated to be 0.476, and inequality (13) is satisfied.

[0369] In addition, in the third incident optical system 85a and the third scanning optical system 85b provided in the light scanning device 910 according to the present embodiment, it is desirable that inequality (11) is satisfied.

[0370] In other words, the inclination at the arrival position of the light from the k-th light emission point of the third light source 501 on the exit surface (third sagittal line inclined surface, third optical surface) of the first fθ lens 506 provided in the optical scanning device 910 according to the present embodiment is given by M 3k express.

[0371] The lateral magnification in the sub-scanning section of the third incident optical system 85 a is represented by β3 .

[0372] The distance on the optical axis of the third incident optical system 85 a between the third light source 501 provided in the light scanning device 910 according to the present embodiment and the second deflecting surface of the deflecting unit 1 is represented by L3 (mm).

[0373] The distance on the optical axis of the third scanning optical system 85 b between the second deflecting surface of the deflecting unit 1 and the exit surface of the first fθ lens 506 provided in the light scanning device 910 according to the present embodiment is represented by D3 (mm).

[0374] At this time, in the third incident optical system 85a and the third scanning optical system 85b provided in the light scanning device 910 according to the present embodiment, it is desirable to satisfy the following inequality (11e):

[0375]

[0376] In addition, in the third incident optical system 85a and the third scanning optical system 85b provided in the light scanning device 910 according to the present embodiment, it is preferable to satisfy the inequality (11a), and it is more preferable to satisfy the inequality (11b).

[0377] Furthermore, in the third incident optical system 85a and the third scanning optical system 85b provided in the light scanning device 910 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0378] Specifically, in the third incident optical system 85a and the third scanning optical system 85b provided in the light scanning device 910 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is 0.138.

[0379] Therefore, the value of each of inequalities (11), (11a), and (11b) is calculated to be 0.638, so that inequalities (11) and (11a) are satisfied.

[0380] On the other hand, in the third incident optical system 85a and the third scanning optical system 85b provided in the light scanning device 910 according to the present embodiment, M 01 It is 0.114.

[0381] Therefore, the value of inequality (12) is calculated as 0.527, so that inequality (12) is not satisfied.

[0382] In addition, in the third incident optical system 85 a and the third scanning optical system 85 b provided in the light scanning device 910 according to the present embodiment, Ls is 1.31 mm and R is 54.586 mm.

[0383] Therefore, the value of inequality (13) is calculated to be 0.638, so that inequality (13) is satisfied.

[0384] Furthermore, in the fourth incident optical system 95 a and the fourth scanning optical system 95 b provided in the light scanning device 910 according to the present embodiment, it is desirable that inequality (11) is satisfied.

[0385] In other words, the inclination at the arrival position of the light from the l-th light emission point of the fourth light source 601 on the exit surface (fourth sagittal line inclined surface, fourth optical surface) of the first fθ lens 606 provided in the optical scanning device 910 according to the present embodiment is given by M 4l express.

[0386] The lateral magnification in the sub-scanning section of the fourth incident optical system 95 a is represented by β4.

[0387] The distance on the optical axis of the fourth incident optical system 95 a between the fourth light source 601 provided in the light scanning device 910 according to the present embodiment and the second deflecting surface of the deflecting unit 1 is represented by L4 (mm).

[0388] The distance on the optical axis of the fourth scanning optical system 95 b between the second deflecting surface of the deflecting unit 1 and the exit surface of the first fθ lens 606 provided in the light scanning device 910 according to the present embodiment is represented by D4 (mm).

[0389] At this time, in the fourth incident optical system 95a and the fourth scanning optical system 95b provided in the light scanning device 910 according to the present embodiment, it is desirable to satisfy the following inequality (11f):

[0390]

[0391] In addition, in the fourth incident optical system 95a and the fourth scanning optical system 95b provided in the light scanning device 910 according to the present embodiment, it is preferable to satisfy the inequality (11a), and it is more preferable to satisfy the inequality (11b).

[0392] Furthermore, in the fourth incident optical system 95 a and the fourth scanning optical system 95 b provided in the light scanning device 910 according to the present embodiment, it is preferable that inequalities (12) and (13) are satisfied.

[0393] Specifically, in the fourth incident optical system 95a and the fourth scanning optical system 95b provided in the light scanning device 910 according to the present embodiment, β is -3.65, D is 34.2 mm, L is 161.7 mm, and M is 0.103.

[0394] Therefore, the value of each of the inequalities (11), (11a), and (11b) is calculated to be 0.476, so that the inequalities (11), (11a), and (11b) are satisfied.

[0395] In addition, in the fourth incident optical system 95a and the fourth scanning optical system 95b provided in the light scanning device 910 according to the present embodiment, M 01 It is 0.0393.

[0396] Therefore, the value of inequality (12) is calculated to be 0.182, so that inequality (12) is satisfied.

[0397] Furthermore, in the fourth incident optical system 95 a and the fourth scanning optical system 95 b provided in the light scanning device 910 according to the present embodiment, Ls is 1.31 mm and R is 20.586 mm.

[0398] Therefore, the value of inequality (13) is calculated to be 0.476, and inequality (13) is satisfied.

[0399] As described above, in the optical scanning device 910 according to this embodiment, inequality (11) is satisfied in the first incident optical system 65a and the first scanning optical system 65b, thereby making it possible to suppress the deterioration of image quality caused by the deviation of the arrival position of each light ray on the first scanned surface 308.

[0400] In the light scanning device 910 according to this embodiment, inequality (11) is satisfied in the second incident optical system 75a and the second scanning optical system 75b, thereby making it possible to suppress the deterioration of image quality caused by the deviation of the arrival position of each light ray on the second scanned surface 408.

[0401] In the optical scanning device 910 according to this embodiment, inequality (11) is satisfied in the third incident optical system 85a and the third scanning optical system 85b, thereby making it possible to suppress the deterioration of image quality caused by the deviation of the arrival position of each light ray on the third scanned surface 508.

[0402] In the optical scanning device 910 according to this embodiment, inequality (11) is satisfied in the fourth incident optical system 95a and the fourth scanning optical system 95b, thereby making it possible to suppress the deterioration of image quality caused by the deviation of the arrival position of each light ray on the fourth scanned surface 608.

[0403] The numerical values of the respective inequalities in each of the optical scanning devices according to the first to fifth embodiments described above are shown in Table 13 below.

[0404] [Table 13]

[0405]

[0406]

[0407]

[0408] According to this embodiment, it is possible to provide a light scanning device capable of easily reducing the deviation between the scanning widths of a plurality of light beams.

[0409] Although the preferred embodiments have been described above, the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the gist of the present invention.

[0410] [Image Forming Apparatus]

[0411] Figure 16 A sub-scanning cross-sectional view showing a main portion of an image forming apparatus 90 in which an optical scanning apparatus 910 according to a fifth embodiment of the present invention is mounted.

[0412] The image forming apparatus 90 is a tandem type color image forming apparatus that records image information on the surface of each photosensitive drum as an image carrier by using the light scanning device 910 according to the fifth embodiment.

[0413] The image forming apparatus 90 includes a light scanning device 910 according to the fifth embodiment, developing units 15 , 16 , 17 and 18 , photosensitive drums (photoconductors) 23 , 24 , 25 and 26 , a conveying belt 91 , a printer controller 93 and a fixing unit 94 .

[0414] Color signals (code data) of R (red), G (green), and B (blue) output from an external device 92 such as a personal computer are input to the image forming device 90 .

[0415] The input color signal is converted into image data (dot data) of C (cyan), M (magenta), Y (yellow), and K (black) by the printer controller 93 in the image forming apparatus 90 .

[0416] The converted image data is input to the light scanning device 910 according to the fifth embodiment.

[0417] Light rays 19 , 20 , 21 , and 22 modulated according to respective image data are emitted from the light scanning device 910 according to the fifth embodiment, and the photosensitive surfaces of the photosensitive drums 23 , 24 , 25 , and 26 are exposed to the light rays 19 to 22 .

[0418] In the image forming apparatus 90 , charging rollers (not shown) for uniformly charging the surfaces of the photosensitive drums 23 to 26 are provided so as to abut on the surfaces.

[0419] The surfaces of the photosensitive drums 23 to 26 charged by the charging rollers are irradiated with light rays 19 to 22 from the light scanning device 910 according to the fifth embodiment.

[0420] As described above, the light rays 19 to 22 are modulated based on the image data of the respective colors, and electrostatic latent images are formed on the surfaces of the photosensitive drums 23 to 26 by irradiation with the light rays 19 to 22 .

[0421] The formed electrostatic latent images are developed into toner images by developing units 15 , 16 , 17 , and 18 arranged adjacent to the photosensitive drums 23 to 26 .

[0422] The toner images developed by the developing units 15 to 18 are transferred to a sheet (transferred material) (not shown) conveyed on the conveyor belt 91 by transfer rollers (transfer units) (not shown) arranged to face the photosensitive drums 23 to 26, thereby forming a full-color image.

[0423] Then, the sheet to which the unfixed toner image is transferred is further conveyed to the photosensitive drums 23 to 26 arranged behind ( Figure 16 The fixing unit 94 is on the left side of the image.

[0424] The fixing unit 94 is formed of a fixing roller having a fixing heater (not shown) therein and a pressure roller arranged in pressure contact with the fixing roller.

[0425] Then, the sheet conveyed from the transfer portion is heated while being pressed at a pressure-contact portion of the fixing roller and the pressure roller, thereby fixing the unfixed toner image on the sheet.

[0426] In addition, a sheet discharge roller (not shown) is arranged behind the fixing roller, and the sheet discharge roller discharges the sheet on which the toner image is fixed to the outside of the image forming apparatus 90 .

[0427] The image forming apparatus 90 records image signals (image information) on photosensitive surfaces of photosensitive drums 23 to 26 corresponding to respective colors of C, M, Y, and K by using the light scanning device 910 according to the fifth embodiment, and prints a color image at high speed.

[0428] As the external device 92, for example, a color image reading device including a CCD sensor can be used. In this case, the color image reading device and the image forming device 90 form a color digital copying machine.

[0429] The image forming device 90 may be provided with four light scanning devices according to any one of the first to third embodiments or two light scanning devices 710 according to the fourth embodiment instead of the light scanning device 910 according to the fifth embodiment.

[0430] While embodiments of the present invention have been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest description so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An optical scanning device, comprising: a deflecting unit configured to deflect a plurality of light beams from a first light source having a plurality of light emission points to scan a first scanned surface in a main scanning direction; a first optical element having a first optical surface and configured to guide the plurality of light beams deflected by the first deflecting surface of the deflecting unit to the first scanned surface; as well as a first incident optical system configured to make the plurality of light beams from the first light source incident on the first deflecting surface, Among them, the following conditions are met: Wherein L1 represents the distance between the first light source and the first deflecting surface on the optical axis of the first incident optical system, D1 represents the distance between the first deflecting surface and the first optical surface on the optical axis of the first optical element, β1 represents the lateral magnification in the sub-scan section of the first incident optical system, and M 1i represents the inclination of the first optical surface at a position on the first optical surface where a light beam from the i-th light emission point of the first light source arrives.

2. The optical scanning device according to claim 1, wherein the following conditions are satisfied: Among them, M 01 The sagittal tilt amount of the first optical surface on the optical axis of the first optical element is represented.

3. The optical scanning device according to claim 1 , wherein the following conditions are satisfied: Wherein R represents the curvature radius of the first optical surface in the sub-scan section on the optical axis of the first optical element, L s represents the eccentricity of the first optical element in the sub-scanning direction, and M 01 The sagittal tilt amount of the first optical surface on the optical axis of the first optical element is represented. 4 . The optical scanning device according to claim 1 , wherein a sagittal line inclination amount of the first optical surface varies depending on a position in a main scanning direction. 5 . The optical scanning device according to claim 4 , wherein an absolute value of a sagittal line inclination amount of the first optical surface is maximum on an optical axis of the first optical element. The light scanning device according to claim 1 , wherein the first optical element has positive power in a sub-scanning section.

7. The optical scanning device according to claim 1 , further comprising a first imaging optical system, the first imaging optical system including the first optical element and configured to guide the plurality of light beams deflected by the first deflecting surface to the first scanned surface, Among the at least one optical element included in the first imaging optical system, the optical element closest to the deflection unit on the optical path of the multiple light beams is the optical element with the strongest focal length in the main scanning section among the at least one optical element.

8. The optical scanning device according to claim 1, further comprising: a second optical element having a second optical surface and configured to guide the plurality of light beams of the second light source having the plurality of light emission points deflected by the first deflecting surface to a second scanned surface; as well as a second incident optical system configured to make the plurality of light beams from the second light source incident on the first deflecting surface, wherein the deflection unit is configured to deflect the plurality of light beams from the second light source to scan the second scanned surface in a main scanning direction, and Among them, the following conditions are met: Wherein L2 represents the distance between the second light source and the first deflecting surface on the optical axis of the second incident optical system, D2 represents the distance between the first deflecting surface and the second optical surface on the optical axis of the second optical element, β2 represents the lateral magnification in the sub-scan section of the second incident optical system, and M 2j represents the inclination of the second optical surface at a position on the second optical surface where the light beam from the j-th light emission point of the second light source arrives. 9 . The optical scanning device according to claim 8 , wherein an absolute value of a sagittal tilt amount of the first optical surface on the optical axis of the first optical element and an absolute value of a sagittal tilt amount of the second optical surface on the optical axis of the second optical element are different from each other.

10. The optical scanning device according to claim 8, further comprising: a third optical element having a third optical surface and configured to guide the plurality of light beams of the third light source having the plurality of light emission points deflected by the second deflecting surface of the deflecting unit to a third scanned surface; a fourth optical element having a fourth optical surface and configured to guide the plurality of light beams of a fourth light source having a plurality of light emission points, deflected by the second deflecting surface, to a fourth scanned surface; a third incident optical system configured to make the plurality of light beams from the third light source incident on the second deflecting surface; as well as a fourth incident optical system configured to make the plurality of light beams from the fourth light source incident on the second deflecting surface, wherein the deflection unit is configured to deflect the plurality of light beams from the third light source and the plurality of light beams from the fourth light source to scan the third scanned surface and the fourth scanned surface in a main scanning direction, respectively, Among them, the following conditions are met: Wherein L3 represents the distance between the third light source and the second deflecting surface on the optical axis of the third incident optical system, D3 represents the distance between the second deflecting surface and the third optical surface on the optical axis of the third optical element, β3 represents the lateral magnification in the sub-scan section of the third incident optical system, and M 3k represents the inclination of the third optical surface at a position on the third optical surface where the light beam from the k-th light emission point of the third light source arrives, and Among them, the following conditions are met: Wherein L4 represents the distance between the fourth light source and the second deflecting surface on the optical axis of the fourth incident optical system, D4 represents the distance between the second deflecting surface and the fourth optical surface on the optical axis of the fourth optical element, β4 represents the lateral magnification in the sub-scan section of the fourth incident optical system, and M 4l represents the inclination of the fourth optical surface at a position on the fourth optical surface where the light beam from the lth light emission point of the fourth light source arrives.

11. An optical scanning device, comprising: a deflecting unit configured to deflect a plurality of light beams from a first light source having a plurality of light emission points to scan a first scanned surface in a main scanning direction; a first optical element having a first optical surface and configured to guide the plurality of light beams deflected by the first deflecting surface of the deflecting unit to the first scanned surface; as well as a first incident optical system configured to make the plurality of light beams from the first light source incident on the first deflecting surface, A normal line of the first optical surface on the optical axis of the first optical element is tilted relative to the optical axis.

12. An image forming apparatus comprising: The optical scanning device according to any one of claims 1 to 11; as well as A developing unit is configured to develop the electrostatic latent image formed on the first scanned surface by the light scanning device.

13. An image forming apparatus comprising: The optical scanning device according to any one of claims 1 to 11; as well as A controller is configured to convert a signal output from an external device into image data to input the image data to the light scanning device.

Images