Optical scanning device

Abstract

An optical scanning apparatus is disclosed. There is provided a light scanning apparatus including: a deflection unit that deflects a light beam from a light source to scan a surface to be scanned in a main scanning direction; an imaging optical system including at least one optical element that guides the light beam deflected by the deflecting surface of the deflecting unit to a surface to be scanned; and a reflecting element that reflects the light beam. On an optical path of the light beam from the deflection unit to the surface to be scanned, the reflection element is arranged between the deflection unit and an optical element closest to the deflection unit among at least one optical element included in the imaging optical system. An optical path length between an on-axis deflection point of the deflection surface on an optical axis of the imaging optical system and the surface to be scanned is equal to or less than a distance between an outermost off-axis image height on the surface to be scanned.

Description

Technical Field

[0001] The present disclosure relates to an optical scanning device, for example, an optical scanning device suitable for an image forming device such as a laser beam printer, a digital copying machine, or a multifunctional printer. Background Art

[0002] Hitherto, as disclosed in, for example, Japanese Patent Application Laid-Open No. 2008-145717, an optical scanning device is known in which miniaturization is achieved by arranging a reflection element between the deflection unit and the optical element closest to the deflection unit among at least one optical element included in the imaging optical system.

[0003] However, in the optical scanning device disclosed in Japanese Patent Application Laid-Open No. 2008-145717, no discussion is made regarding the optical path length between the deflection unit and the scanned surface, and the miniaturization is insufficient. Summary of the Invention

[0004] In view of the above circumstances, an object of the present disclosure is to provide an optical scanning device that is sufficiently miniaturized.

[0005] According to an embodiment, there is provided an optical scanning device including: a deflection unit configured to deflect a first light beam from a first light source to scan a first scanned surface in a main scanning direction; a first imaging optical system including at least one optical element configured to guide the first light beam deflected by a first deflection surface of the deflection unit to the first scanned surface; and a first reflection element configured to reflect the first light beam. On an optical path of the first light beam from the deflection unit to the first scanned surface, the first reflection element is arranged between the deflection unit and a first optical element closest to the deflection unit among the at least one optical element included in the first imaging optical system. A first optical path length between a first on-axis deflection point of the first deflection surface on an optical axis of the first imaging optical system and the first scanned surface is equal to or less than a first distance between outermost off-axis image heights on the first scanned surface.

[0006] Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the accompanying drawings. Brief Description of the Drawings

[0007] Figure 1A is a schematic unfolded view in a main scanning cross section of an optical scanning device according to a first embodiment of the present invention.

[0008] Figure 1B is a schematic partial sub-scanning cross-sectional view of the optical scanning device according to the first embodiment.

[0009] Figure 1C is a schematic partial sub-scanning cross-sectional view of the optical scanning device according to the first embodiment.

[0010] Figure 2 is a graph for illustrating partial magnification deviation at each image height in the light scanning device according to the first embodiment.

[0011] Figure 3A : is a graph for illustrating the image height dependency of the depth center position in the main scanning direction LSF on the scanned surface in the light scanning device according to the first embodiment.

[0012] Figure 3B : is a graph for illustrating the image height dependency of the depth center position in the sub scanning direction LSF on the scanned surface in the light scanning device according to the first embodiment.

[0013] Figure 4A 1 is a schematic development view in the main scanning section of an optical scanning device according to a second embodiment of the present invention.

[0014] Figure 4B is a schematic partial sub-scanning cross-sectional view of the optical scanning device according to the second embodiment.

[0015] Figure 4C is a schematic partial sub-scanning cross-sectional view of the optical scanning device according to the second embodiment.

[0016] Figure 5 is a graph for illustrating local magnification deviation at each image height in the light scanning device according to the second embodiment.

[0017] Fig. 6A : is a graph for illustrating the image height dependency of the depth center position in the main scanning direction LSF on the first scanned surface in the light scanning device according to the second embodiment.

[0018] Figure 6B : is a graph for illustrating the image height dependency of the depth center position in the sub scanning direction LSF on the first scanned surface in the light scanning device according to the second embodiment.

[0019] Fig. 7A 1 is a schematic development view in main scanning section of an optical scanning device according to a third embodiment of the present invention.

[0020] Figure 7B is a schematic partial sub-scanning cross-sectional view of the optical scanning device according to the third embodiment.

[0021] Figure 7Cis a schematic partial sub-scanning cross-sectional view of the optical scanning device according to the third embodiment.

[0022] Figure 8 is a graph for illustrating local magnification deviation at each image height in the light scanning device according to the third embodiment.

[0023] Fig. 9A : is a graph for illustrating the image height dependency of the depth center position in the main scanning direction LSF on the scanned surface in the light scanning device according to the third embodiment.

[0024] Fig. 9B : is a graph for illustrating the image height dependency of the depth center position in the sub scanning direction LSF on the scanned surface in the optical scanning device according to the third embodiment.

[0025] Fig.10 is a sub-scanning cross-sectional view of a main portion of the image forming apparatus according to the present embodiment. DETAILED DESCRIPTION

[0026] The optical scanning device according to the present embodiment is described in detail below with reference to the accompanying drawings. In order to make the present disclosure more easily understood, some of the drawings referred to below may be drawn at a scale different from the actual scale.

[0027] In the following description, the main scanning direction refers to a direction perpendicular to the rotation axis of the deflection element 104 and perpendicular to the optical axis of the imaging optical system 85 (the direction in which the light beam is deflected by the deflection element 104 ), and the sub-scanning direction refers to a direction parallel to the rotation axis of the deflection element 104 .

[0028] Furthermore, a main-scanning cross section refers to a cross section perpendicular to a sub-scanning direction, and a sub-scanning cross section refers to a cross section perpendicular to the main-scanning direction.

[0029] Hereinafter, a direction parallel to the optical axis of the imaging optical system 85 , a main scanning direction, and a sub-scanning direction are defined as an X direction, a Y direction, and a Z direction, respectively.

[0030] [First embodiment]

[0031] Hitherto, in order to miniaturize a product such as an image forming apparatus mounted with a light scanning device, a configuration has been used in the light scanning device in which the optical path of a light beam deflected by a deflection unit is folded by a folding mirror.

[0032] In addition, various techniques for miniaturizing the housing itself have also been proposed, in which each optical element forming the light scanning device is accommodated by arranging a folding mirror between a deflection unit and an optical element (imaging optical element) closest to the deflection unit.

[0033] However, in the prior art optical scanning device in which the folding mirror is arranged between the deflection unit and the optical element closest to the deflection unit, no discussion is made about the optical path length between the deflection unit and the scanned surface - that is, the optical path length of the imaging optical system, resulting in insufficient miniaturization.

[0034] In view of the above, the present embodiment has an object to provide an optical scanning device that can achieve sufficient miniaturization by reducing the optical path length in an imaging optical system.

[0035] Figure 1A A schematic development diagram of the optical scanning device 100 according to the first embodiment of the present invention in a main scanning section is shown.

[0036] also, Figure 1B and Figure 1C , each showing a schematic partial sub-scanning cross-sectional view of the light scanning device 100 according to the first embodiment.

[0037] According to the present embodiment, the optical scanning device 100 includes a housing 10, a deflection element unit 12 (deflection unit), a light source 101 (first light source), an aperture 102, an incident optical element 103 (first incident optical element), a folding mirror 105 (first reflecting element), and an optical element 106.

[0038] In the light scanning device 100 according to the present embodiment, the stop 102 and the incident optical element 103 form the incident optical system 75 (first incident optical system), and the optical element 106 forms the imaging optical system 85 (first imaging optical system).

[0039] Furthermore, in the optical scanning device 100 according to the present embodiment, the folding mirror 105 forms the reflective optical system 95 (first reflective optical system).

[0040] That is, in the light scanning device 100 according to the present embodiment, the imaging optical system 85 is composed of only the optical element 106 , in other words, is formed of the single optical element 106 .

[0041] However, the present invention is not limited thereto. In the light scanning device 100 according to the present embodiment, the imaging optical system 85 may be formed of at least one optical element.

[0042] Furthermore, in the optical scanning device 100 according to the present embodiment, the reflection optical system 95 for reflecting the light beam deflected by the deflection element unit 12 is composed of only the folding mirror 105 , in other words, is formed of a single folding mirror 105 .

[0043] That is, in the optical scanning device 100 according to the present embodiment, a folding mirror other than the folding mirror 105 is prevented from being arranged on the optical path of the light beam from the deflection element unit 12 to the scanned surface 107 .

[0044] The housing 10 accommodates the above-mentioned optical elements forming the light scanning device 100 according to the present embodiment.

[0045] For example, a semiconductor laser may be used as the light source 101 , and the number of light emitting parts of the light source 101 may be one, and may be two or more.

[0046] The stop 102 includes an elliptical aperture portion, and limits the beam width in each of the main scanning direction and the sub-scanning direction of the light beam (first light beam) emitted from the light source 101 .

[0047] The incident optical element 103 has a positive refractive power in the main scanning section, and converts the light beam having passed through the aperture 102 into a convergent light beam in the main scanning section.

[0048] As described above, by converting the light beam emitted from the light source 101 into a convergent light beam in the main scanning section, both a short optical path and optical performance can be achieved with good balance in the imaging optical system 85 formed of only the single optical element 106 .

[0049] Furthermore, the incident optical element 103 has a positive refractive power in the sub-scan section and converges the light beam having passed through the aperture 102 near the deflection surface 104a of the deflection element 104 so that a line image long in the main scanning direction is formed near the deflection surface 104a.

[0050] In the light scanning device 100 according to the present embodiment, in the main scanning section, the beam width of the light beam when entering the deflecting element 104 is smaller than the width of the deflecting surface 104 a of the deflecting element 104 .

[0051] The deflection element unit 12 includes a deflection element 104, a motor 104b (driving unit), and a motor substrate 104c (driving unit). The deflection element 104 includes a plurality of deflection surfaces 104a. The motor 104b and the motor substrate 104c are required to rotate the deflection element 104 around a rotation axis.

[0052] In addition, in the deflection element unit 12 , the motor 104 b rotates the deflection element 104 at a constant speed.

[0053] Folding mirror 105 is, for example, a plane mirror. In addition, folding mirror 105 is arranged on the optical path of the light beam deflected by deflection element unit 12 , between deflection element unit 12 and optical element 106 closest to deflection element unit 12 among at least one optical element included in imaging optical system 85 .

[0054] The folding mirror 105 reflects the light beam deflected by the deflection surface 104a of the deflection element 104 toward the optical element 106 without changing the convergence degree.

[0055] In the optical scanning device 100 according to the present embodiment, the folding mirror 105 folds the optical path of the light beam deflected by the deflecting surface 104 a of the deflecting element 104 by 90 degrees in the sub-scan section.

[0056] In other words, in the optical scanning device 100 according to the present embodiment, the incident angle of the light beam to the reflecting surface of the folding mirror 105 (the angle formed by the incident direction of the light beam with respect to the normal line of the reflecting surface) is 45 degrees.

[0057] The optical element 106 includes two optical surfaces (lens surfaces) of an incident surface (first surface) and an exit surface (second surface), and has a positive refractive power in each of a main-scan section and a sub-scan section.

[0058] With this configuration, the light beam that has been incident on the optical element 106 is converged in both the main scanning section and the sub-scanning section, and thus a point-like image is formed in the vicinity of the scanned surface 107 (first scanned surface).

[0059] In addition, the optical element 106 is configured so that the light beam deflected by the deflection surface 104 a of the deflection element 104 in the main scanning section scans the scanned surface 107 with desired scanning characteristics.

[0060] Furthermore, the optical element 106 allows an optical conjugate relationship to be set between the vicinity of the deflecting surface 104 a of the deflecting element 104 and the vicinity of the scanned surface 107 in the sub-scan section.

[0061] This arrangement allows so-called optical surface angle error compensation that reduces the deviation of the scanning position in the sub-scanning direction on the scanned surface 107 when the deflecting surface 104 a is tilted.

[0062] In the light scanning device 100 according to the present embodiment, the light beam emitted from the light source 101 is guided to the deflecting surface 104 a (first deflecting surface) of the deflecting element 104 by the incident optical system 75 .

[0063] Next, the light beam deflected by the deflection surface 104 a of the deflection element 104 is reflected by the folding mirror 105 , and then guided (converged) onto the scanned surface 107 by the optical element 106 .

[0064] In addition, the motor 104b rotates the deflection element 104 at a constant speed so that the light beam scans the scanned surface 107 in the direction of the arrow Sc. Thus, an electrostatic latent image is formed on the scanned surface 107.

[0065] In the optical scanning device 100 according to the present embodiment, the angle between the optical axis of the incident optical system 75 and the optical axis of the imaging optical system 85 in the main scanning section is 90 degrees.

[0066] As described above, in the light scanning device 100 according to the present embodiment, the folding mirror 105 is arranged on the upstream side of the optical element 106 on the optical path of the light beam deflected by the deflecting surface 104 a of the deflecting element 104 .

[0067] In this way, compared with a general configuration in which the folding mirror 105 is arranged on the downstream side of the optical element 106 on the optical path, the optical path length between the deflecting surface 104 a and the reflecting surface of the folding mirror 105 can be reduced.

[0068] That is, miniaturization of the housing 10 can be achieved by reducing the size in the main scanning section of the optical scanning device 100 according to the present embodiment.

[0069] Furthermore, in the optical scanning device 100 according to the present embodiment, as Figure 1C As shown in FIG. 1 , the folding mirror 105 reflects the incident light beam toward the lower side in the sub-scanning direction, that is, toward the side where the motor 104 b and the motor substrate 104 c are arranged with respect to the deflection element 104 .

[0070] In this way, the optical element 106 can be arranged in an inefficient space in the deflection element unit 12 that is formed by the motor 104 b and the motor substrate 104 c rather than by the deflection element 104 .

[0071] That is, further miniaturization of the housing 10 can also be achieved by reducing the size in the sub-scanning cross section of the optical scanning device 100 according to the present embodiment.

[0072] Furthermore, in the optical scanning device 100 according to the present embodiment, the light beam deflected at a predetermined scanning angle by the deflection surface 104a of the deflection element 104 is guided to the synchronization detection sensor by a synchronization detection optical system (not shown). Thus, a synchronization detection signal is generated.

[0073] In addition, based on the generated synchronization detection signal, the rotation speed of the deflection element 104 is controlled to be constant.

[0074] A plastic molded lens formed by injection molding is used as each of the incident optical element 103 and the optical element 106 provided in the light scanning device 100 of the present embodiment, but the present invention is not limited thereto. A glass molded lens may be used instead.

[0075] It is easy to form an aspherical shape on a molded lens, and the molded lens is suitable for mass production. Therefore, the use of the molded lens as the incident optical element 103 and the optical element 106 can improve productivity and optical performance.

[0076] Furthermore, the folding mirror 105 provided in the optical scanning device 100 according to the present embodiment is formed by forming a film as a reflective surface on a general long glass sheet, but the present invention is not limited thereto.

[0077] That is, the folding mirror 105 can be formed by forming a film as a reflective surface on a member formed by plastic molding or by performing mirror finishing on a metal such as aluminum.

[0078] Furthermore, the reflection surface of the folding mirror 105 is formed to have a planar shape, but may be formed to have a spherical surface or other shapes.

[0079] Next, the following Tables 1, 2, and 3 respectively show specification values ​​of the light scanning device 100 according to the present embodiment, the refractive index and surface interval of each optical element, and the lens surface shapes of the incident optical element 103 and the optical element 106.

[0080] Table 1

[0081]

[0082]

[0083] Table 2

[0084]

[0085]

[0086] Table 3

[0087]

[0088]

[0089]

[0090] The incident optical element 103 provided in the light scanning device 100 according to the present embodiment has an incident surface which is a diffraction surface having a diffraction grating formed therein.

[0091] In addition, the incident optical element 103 is formed by injection molding using a plastic material. Therefore, the light scanning device 100 adopts a so-called temperature compensation optical system in which changes in refractive power due to environmental changes are compensated by changes in diffraction power accompanying changes in the wavelength of the semiconductor laser.

[0092] Specifically, the diffraction surface formed on the incident surface of the incident optical element 103 is defined by a phase function represented by the following expression (1).

[0093]

[0094] In Expression (1), φ represents a phase function and M represents a diffraction order, and since the optical scanning device 1 according to the present embodiment uses first-order diffracted light, the diffraction order M is 1.

[0095] Furthermore, λ is the wavelength of the light beam emitted from the light source 101 , and in the light scanning device 100 according to the present embodiment, the wavelength λ is 790 nm.

[0096] In addition, the optical element 106 provided in the light scanning device 100 according to the present embodiment has an incident surface and an exit surface, each of which has a shape (meridian shape) in the main scanning section as follows: the shape is a non-spherical shape defined by a tenth-order polynomial function expressed by the following expression (2).

[0097]

[0098] In expression (2), the intersection between each optical surface of the optical element 106 and the optical axis is set as the origin, the direction parallel to the optical axis is set as the X direction, and the position perpendicular to the optical axis in the main scanning section is set as the Y direction.

[0099] Furthermore, in Expression (2), R represents the radius of curvature of the meridian, K represents the eccentricity, and B 1 To B 10 represents the aspheric coefficient.

[0100] In addition, the aspheric coefficient B 1 To B 10 , coefficients having different values ​​between the light source side (positive side in the Y direction) and the opposite light source side (negative side in the Y direction) are represented by the values ​​of the respective sides.

[0101] Furthermore, the shapes (sagittal shapes) in the sub-scan section of the incident surface and the exit surface of the optical element 106 provided in the light scanning device 100 according to the present embodiment are expressed by the following expression (3) below.

[0102]

[0103] In Expression (3), S represents a shape (sagittal shape) in a cross section including a normal line to a meridian at a predetermined position in the main scanning direction and perpendicular to the main scanning cross section.

[0104] Furthermore, the curvature radius r' (curvature radius of the sagittal line) in the sub-scan section at a position spaced apart from the optical axis by Y in the main-scan direction is expressed by the following expression (4):

[0105]

[0106] In expression (4), "r" represents the radius of curvature of the sagittal line on the optical axis, and E 1 To E 10 represents the coefficient of variation of the sagittal line.

[0107] As shown in Expression (4), the curvature radius of the sagittal line r' changes depending on the position Y in the main scanning direction.

[0108] In the light scanning device 100 according to the present embodiment, the shape of the optical surface of each optical element is defined by the functions represented by the above expressions (1) to (4), but is not limited thereto and may be defined by other functions.

[0109] Next, scanning at a non-constant speed in the optical scanning device 100 according to the present embodiment is described.

[0110] The scanning characteristic of the imaging optical system 85 provided in the light scanning device 100 according to the present embodiment is expressed by the following expression (5).

[0111] Y=KK·θ+α·θ 3 …(5)

[0112] In Expression (5), θ represents the scanning angle of the deflection element 104, and Y represents the coordinates in the main scanning direction (image height) of the convergence position on the scanned surface 107 of the light beam deflected at the scanning angle θ.

[0113] Furthermore, in Expression (5), KK represents an imaging coefficient at an on-axis image height, and α represents a scanning characteristic coefficient for determining the scanning characteristic of the imaging optical system 85 .

[0114] In the light scanning device 100 according to the present embodiment, the on-axis image height is the image height (Y=0) on the optical axis of the imaging optical system 85 , and corresponds to the scanning angle θ=0.

[0115] Furthermore, the off-axis image height is the image height other than the on-axis image height (Y≠0), and corresponds to a scan angle θ≠0. Additionally, the outermost off-axis image height is the image height given when the scan angle θ is maximum.

[0116] Furthermore, the imaging coefficient KK corresponds to the coefficient “f” in the scanning characteristic (fθ characteristic) Y=fθ when a completely parallel light beam is incident on the imaging optical system 85 .

[0117] That is, the imaging coefficient KK is a coefficient for establishing a proportional relationship between the image height Y and the scanning angle θ, similar to the fθ characteristic when a light beam other than a completely parallel light beam is incident on the imaging optical system 85 .

[0118] In the optical scanning device 100 according to the present embodiment, the convergent beam in the main scanning section is made incident on the imaging optical system 85, and the imaging coefficient KK in the scanning characteristics of the imaging optical system 85 is set depending on the incidence of the convergent beam.

[0119] Furthermore, in the light scanning device 100 according to the present embodiment, the scanning characteristic coefficient α is set to a positive value.

[0120] For example, when the value of the scanning characteristic coefficient α is 0, Expression (5) is expressed as Y=KK·θ, and thus the scanning characteristic of the imaging optical system 85 is the same as the scanning characteristic Y=fθ of a general imaging optical system.

[0121] Furthermore, when both sides of Expression (5) are differentiated with respect to the scanning angle θ, the scanning speed of the light beam at a predetermined image height on the scanned surface 107 corresponding to the predetermined scanning angle θ is obtained as represented by the following Expression (6).

[0122]

[0123] In addition, when both sides of Expression (6) are divided by the scanning speed dY / dθ=KK at the on-axis image height, the following Expression (7) is obtained.

[0124]

[0125] The right side of expression (7) represents the deviation of the scanning speed at each off-axis image height relative to the scanning speed at the on-axis image height. In other words, the deviation of the local magnification at each off-axis image height relative to the local magnification at the on-axis image height, that is, the local magnification deviation.

[0126] Therefore, as in the imaging optical system 85 provided in the light scanning device 100 according to the present embodiment, when the value of the scanning characteristic coefficient α is other than 0, the scanning speed of the light beam differs between the on-axis image height and the off-axis image height.

[0127] In addition, in the light scanning device 100 according to the present embodiment, the imaging optical system 85 is provided so as to have a scanning characteristic in which the value of the scanning characteristic coefficient α is not 0. Therefore, the optical path of the imaging optical system 85 is reduced.

[0128] Figure 2The local magnification deviation at each image height in the light scanning device 100 according to the present embodiment is shown.

[0129] Specifically, Figure 2 The values ​​of the ratio of the local magnification at each off-axis image height to the local magnification at the on-axis image height are shown.

[0130] like Figure 2 As shown in , in the optical scanning device 100 according to the present embodiment, the largest local magnification deviation is caused at the outermost off-axis image height, specifically, a local magnification deviation of about 130.6%.

[0131] That is, in the light scanning device 100 according to the present embodiment, the scanning characteristics of the imaging optical system 85 are set so that the scanning speed at each off-axis image height becomes greater than the scanning speed at the on-axis image height.

[0132] In other words, in the light scanning device 100 according to the present embodiment, the scanning speed of the light beam on the scanned surface 107 increases monotonically from the on-axis image height toward the outermost off-axis image height.

[0133] As described above, in the light scanning device 100 according to the present embodiment, the incident optical element 103 has a positive refractive power in the main scanning section, and converts the incident light beam into a convergent light beam in the main scanning section.

[0134] Specifically, in the optical scanning device 100 according to the present embodiment, when the imaging optical system 85 is not virtually provided, the optical path length D between the on-axis deflection point (the first on-axis deflection point) and the position where the on-axis light beam naturally converges in the main scanning section is m About 229mm.

[0135] In this case, the on-axis beam refers to a beam for scanning the on-axis image height on the scanned surface 107 , and the on-axis deflection point refers to the deflection point of the principal ray of the on-axis beam on the deflection surface 104 a of the deflection element 104 .

[0136] In the optical scanning device 100 according to the present embodiment, the convergence in the main scanning section of the light beam realized by the incident optical element 103 is set to be stronger than that in the prior art. Therefore, even in the case of a short optical path, even when the optical element 106 is arranged to be spaced apart from the deflection element 104, the optical performance can be satisfactorily maintained.

[0137] Figure 3A and Figure 3B The image height dependencies of the main scanning direction line spread function (LSF) depth center position and the sub-scanning direction LSF depth center position on the scanned surface 107 in the optical scanning device 100 according to the present embodiment are respectively shown.

[0138] Here, the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position refer to the center positions of the areas where the LSF widths in the main scanning direction and the sub-scanning direction are equal to or smaller than the slice level when defocusing is performed in the optical axis direction near the scanned surface 107.

[0139] In the light scanning device 100 according to the present embodiment, the slice level is set to 120 μm over the entire image height in both the main scanning direction and the sub-scanning direction.

[0140] The LSF width in the main scanning direction and the LSF width in the sub-scanning direction refer to the width of a slice of the light quantity distribution obtained by integrating the light spot distribution at each image height in the sub-scanning direction and the main scanning direction respectively when the light quantity distribution is sliced ​​at a position of 13.5% of the maximum value.

[0141] like Figure 3A and Figure 3B As shown in , the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position fall within ±1 mm at all image heights, which shows that excellent imaging performance is achieved in the optical scanning device 100 according to the present embodiment.

[0142] In the optical scanning device 100 according to the present embodiment, as shown in Table 1, the optical path length T between the on-axis deflection point on the deflection surface 104a of the deflection element 104 and the scanned surface 107 along the optical axis of the imaging optical system 85 is c (first optical path length) is equal to or less than the scanning width in the main scanning direction on the scanned surface 107, in other words, the distance "h" (first distance) between the outermost off-axis image heights of the scanned surface 107.

[0143] In this way, sufficient miniaturization can be achieved in the optical scanning device 100 according to the present embodiment.

[0144] Furthermore, in the optical scanning device 100 according to the present embodiment, it is preferable that the following inequality (8) is satisfied.

[0145]

[0146] When T c When / h exceeds the upper limit value in inequality (8), the optical path length of imaging optical system 85 becomes larger than the distance between the outermost off-axis image heights of scanned surface 107, and thus it becomes difficult to sufficiently miniaturize optical scanning device 100 according to the present embodiment.

[0147] At the same time, when T cWhen / h is lower than the lower limit value in inequality (8), the optical path length of the imaging optical system 85 becomes much smaller than the distance between the outermost off-axis image heights of the scanned surface 107, and it becomes difficult to satisfactorily maintain the imaging performance in the optical scanning device 100 of this embodiment.

[0148] In the optical scanning device 100 according to the present embodiment, the following inequality (8a) is more preferably satisfied.

[0149]

[0150] Furthermore, in the optical scanning device 100 according to the present embodiment, it is preferable that the following inequalities (9), (10), and (11) are satisfied.

[0151]

[0152] In inequality (9), D m Indicates the optical path length between the position (natural convergence point, first convergence point) at which the on-axis light beam deflected by the deflection surface 104a of the deflection element 104 converges in the main scanning section and the on-axis deflection point when the imaging optical system 85 is not provided.

[0153] When D m / T c When the upper limit value in inequality (9) is exceeded or the lower limit value in inequality (9) is fallen below, it becomes difficult to maintain the balance for sharing the refractive power in the imaging optical system 85, and it becomes difficult to satisfactorily maintain the imaging performance.

[0154] In addition, when D m / T c If the lower limit value in the inequality (9) is not reached, there is also a problem of increased sensitivity to irradiation position deviation in the main scanning direction due to an installation error of the deflection element 104 .

[0155] In addition, in inequality (10), “f s ” and “f m ” respectively represent the focal lengths in the sub-scan section and the main-scan section on the optical axis of the imaging optical system 85.

[0156] When f s / f m When the upper limit value in inequality (10) is exceeded or the lower limit value in inequality (10) is fallen below, it becomes difficult to achieve such a shape that is balanced with the optical performance of each of the main scanning section and the sub-scanning section of the optical element 106 forming the imaging optical system 85.

[0157] In addition, in inequality (11), D R2φ represents the optical path length between the on-axis deflection point of the deflection element 104 and the exit surface of the optical element 106 along the optical axis of the imaging optical system 85 .

[0158] When D R2 / T c When the upper limit value in the inequality (11) is exceeded, the optical element 106 is excessively spaced apart from the deflection element 104 , and thus it becomes difficult to sufficiently miniaturize the optical scanning device 100 according to the present embodiment.

[0159] At the same time, when D R2 / T c When the lower limit value of the inequality (11) is exceeded, the optical element 106 is too close to the deflection element 104, and thus it becomes difficult to arrange the folding mirror 105.

[0160] In the optical scanning device 100 according to the present embodiment, the following inequalities (9a), (10a), and (11a) are more preferably satisfied.

[0161]

[0162] Furthermore, in the optical scanning device 100 according to the present embodiment, the following inequality (12) is preferably satisfied.

[0163] 110.0≤|ΔY|≤140.0…(12) In inequality (12), ΔY (%) represents the ratio of the local magnification at the outermost off-axis image height to the local magnification at the on-axis image height.

[0164] In the optical scanning device 100 according to the present embodiment, the following inequality (12a) is more preferably satisfied.

[0165] 120.0≤|ΔY|≤135.0…(12a)

[0166] In the optical scanning device 100 according to the present embodiment, T c / h=0.58、D m / T c =1.83 and f s / f m =0.11, thus satisfying inequalities (8), (8a), (9), (9a), (10) and (10a).

[0167] In addition, in the optical scanning device 100 according to the present embodiment, D R2 / T c =0.23 and |ΔY|=130.6%, thereby satisfying inequalities (11), (11a), (12) and (12a).

[0168] As described above, in the light scanning device 100 according to the present embodiment, the folding mirror 105 is arranged between the deflection element unit 12 and the optical element 106 closest to the deflection element unit 12 in the imaging optical system 85 , and the inequality (8) is satisfied.

[0169] In this way, it is possible to provide the light scanning device 100 which is sufficiently miniaturized by reducing the optical path.

[0170] In the light scanning device 100 according to the present embodiment, a coupling lens and a cylindrical lens may be provided instead of the incident optical element 103 .

[0171] [Second embodiment]

[0172] Figure 4A A schematic development diagram of a light scanning device 200 according to a second embodiment of the present invention in a main scanning section is shown.

[0173] also, Figure 4B and Figure 4C , each showing a schematic partial sub-scanning cross-sectional view of the light scanning device 200 according to the second embodiment.

[0174] Hereinafter, description of the same configuration as that of the light scanning device 100 according to the first embodiment is omitted.

[0175] The optical scanning device 200 according to the present embodiment includes a housing 10 , a deflection element unit 12 , first and second light sources 101 a and 101 b , and first and second apertures 102 a and 102 b .

[0176] Furthermore, the light scanning device 200 according to the present embodiment includes first and second incident optical elements 103a and 103b, first and second folding mirrors 105a and 105b, and first and second optical elements 106a and 106b.

[0177] In the light scanning device 200 according to the present embodiment, the first aperture 102a and the first incident optical element 103a form a first incident optical system, and the second aperture 102b and the second incident optical element 103b form a second incident optical system.

[0178] Furthermore, in the light scanning device 200 according to the present embodiment, the first optical element 106 a forms a first imaging optical system, and the second optical element 106 b (third optical element) forms a second imaging optical system.

[0179] Furthermore, in the light scanning device 200 according to the present embodiment, the first folding mirror 105 a forms a first reflecting optical system, and the second folding mirror 105 b (second reflecting element) forms a second reflecting optical system.

[0180] For example, a semiconductor laser may be used as each of the first light source 101a and the second light source 101b, and the number of light emitting parts of each of the first light source 101a and the second light source 101b may be one, and may be two or more.

[0181] Each of the first and second apertures 102a and 102b has an elliptical aperture portion and limits the beam width in each of the main scanning direction and the sub-scanning direction of each of the first and second light beams emitted from the corresponding first and second light sources 101a and 101b.

[0182] The first incident optical element 103a and the second incident optical element 103b each have a positive refractive power in the main scanning section, and convert the first light beam and the second light beam having passed through the first aperture 102a and the second aperture 102b into convergent light beams in the main scanning section.

[0183] In this way, in the first imaging optical system and the second imaging optical system respectively formed of the single first optical element 106 a and the second optical element 106 b , both a short optical path and optical performance can be achieved with good balance.

[0184] Furthermore, the first incident optical element 103a and the second incident optical element 103b each have a positive refractive power in the sub-scan section.

[0185] Therefore, the first light beam and the second light beam having passed through the respective first aperture 102 a and second aperture 102 b are condensed near the first deflecting surface 104 a 1 and the second deflecting surface 104 a 2 of the deflecting element 104 .

[0186] In this way, a line image that is long in the main scanning direction is formed near the first deflecting surface 104 a 1 and the second deflecting surface 104 a 2 .

[0187] In the light scanning device 200 according to the present embodiment, in the main scanning section, the beam widths of the first and second beams entering the deflecting element 104 are smaller than the respective widths of the first and second deflecting surfaces 104a1 and 104a2 of the deflecting element 104 .

[0188] Each of the first folding mirror 105a and the second folding mirror 105b is, for example, a plane mirror. In addition, the first folding mirror 105a and the second folding mirror 105b reflect the corresponding first and second light beams deflected by the first deflection surface 104a1 and the second deflection surface 104a2 of the deflection element 104 toward the corresponding first optical element 106a and the second optical element 106b without changing the convergence.

[0189] The first folding mirror 105 a and the second folding mirror 105 b fold the respective optical paths of the first light beam and the second light beam deflected by the first deflecting surface 104 a 1 and the second deflecting surface 104 a 2 of the deflecting element 104 by 90° in the sub-scanning section.

[0190] The first optical element 106a and the second optical element 106b each include two optical surfaces (lens surfaces) of an incident surface (first surface) and an exit surface (second surface), and each have a positive refractive power in each of the main scanning section and the sub-scanning section.

[0191] In this way, the first and second light beams having been incident on the respective first and second optical elements 106a and 106b are converged in both the main scanning section and the sub-scanning section, thereby forming point images near the first and second scanned surfaces 107a and 107b.

[0192] In addition, the first optical element 106a and the second optical element 106b are configured so that the first and second light beams deflected by the respective first and second deflecting surfaces 104a1 and 104a2 scan the respective first and second scanned surfaces 107a and 107b with desired scanning characteristics.

[0193] Furthermore, the first optical element 106a and the second optical element 106b allow an optical conjugate relationship to be set between the vicinity of the first deflecting surface 104a1 and the second deflecting surface 104a2 of the deflecting element 104 and the vicinity of the first scanned surface 107a and the second scanned surface 107b in the sub-scan section.

[0194] This arrangement allows so-called optical surface angle error compensation that reduces deviation of scanning positions in the sub-scanning direction on the first scanned surface 107a and the second scanned surface 107b when the first deflecting surface 104a1 and the second deflecting surface 104a2 are tilted.

[0195] In the light scanning device 200 according to the present embodiment, the first light beam emitted from the first light source 101 a is guided to the first deflecting surface 104 a 1 of the deflecting element 104 by the first incident optical system.

[0196] Next, the first light beam deflected by the first deflecting surface 104a1 of the deflecting element 104 is reflected by the first folding mirror 105a, and then guided (converged) by the first optical element 106a onto the first scanned surface 107a.

[0197] In addition, the motor 104b rotates the deflection element 104 at a constant speed so that the first light beam scans the first scanned surface 107a in the direction of the arrow Sc. Thus, an electrostatic latent image is formed on the first scanned surface 107a.

[0198] In the light scanning device 200 according to the present embodiment, the second light beam emitted from the second light source 101 b is guided to the second deflecting surface 104 a 2 of the deflecting element 104 by the second incident optical system.

[0199] Next, the second light beam deflected by the second deflecting surface 104a2 of the deflecting element 104 is reflected by the second folding mirror 105b, and then guided (converged) onto the second scanned surface 107b by the second optical element 106b.

[0200] In addition, the motor 104b rotates the deflection element 104 at a constant speed so that the second light beam scans the second scanned surface 107b in the direction of the arrow Sc'. Thus, an electrostatic latent image is formed on the second scanned surface 107b.

[0201] As described above, the optical scanning device 200 according to the present embodiment adopts a so-called opposed (two-side) scanning system, in which the first light beam and the second light beam scan the corresponding first scanned surface 107a and the second scanned surface 107b provided on the sides opposite to each other (different from each other) relative to the deflection element unit 12.

[0202] Next, the following Tables 4, 5, and 6 respectively show the specification values ​​of the light scanning device 200 according to the present embodiment, the refractive index and surface interval of each optical element, and the lens surface shapes of the first incident optical element 103a and the first optical element 106a.

[0203] In the light scanning device 200 according to the present embodiment, the first incident optical system and the second incident optical system are arranged symmetrically with respect to the deflection element 104 , and the first imaging optical system and the second imaging optical system are arranged symmetrically with respect to the deflection element 104 .

[0204] Therefore, Tables 4 to 6 show only the configurations of the first incident optical system and the first imaging optical system, and the configurations of the second incident optical system and the second imaging optical system are omitted.

[0205] Even when the configurations of the first incident optical system and the second incident optical system are asymmetric to each other and the configurations of the first imaging optical system and the second imaging optical system are asymmetric to each other, the effects of the present embodiment described below can be obtained.

[0206] Table 4

[0207]

[0208]

[0209] Table 5

[0210]

[0211]

[0212] Table 6

[0213]

[0214]

[0215] In the optical scanning device 200 according to the present embodiment, the first folding mirror 105a and the second folding mirror 105b reflect the corresponding incident first and second light beams toward the upper side in the sub-scanning direction, that is, toward the side where the motor 104b and the motor substrate 104c are not arranged relative to the deflection element 104.

[0216] As described above, when the optical element 106 is arranged on the upper side in the sub-scanning direction with respect to the folding mirror 105 , mounting of each optical element in the housing 10 is facilitated.

[0217] Specifically, from the perspective of, for example, the width in the main scanning direction of the effective area of ​​each optical element and the configuration of the supporting portion when each optical element is installed from the upper side (opening portion) of the housing 10, the housing 10 can be easily miniaturized in the main scanning section.

[0218] Figure 5 The local magnification deviation at each image height in the light scanning device 200 according to the present embodiment is shown.

[0219] like Figure 5 As shown in , in the optical scanning device 200 according to the present embodiment, the maximum local magnification deviation is caused at the outermost off-axis image height, specifically, a local magnification deviation of about 130.6%.

[0220] That is, in the optical scanning device 200 according to the present embodiment, similar to the optical scanning device 100 according to the first embodiment, the scanning characteristics of the imaging optical system 85 are set so that the scanning speed at each off-axis image height becomes greater than the scanning speed at the on-axis image height.

[0221] As described above, in the light scanning device 200 according to the present embodiment, the first incident optical element 103a and the second incident optical element 103b each have a positive refractive power in the main scanning section and convert the corresponding incident first and second light beams into convergent light beams in the main scanning section.

[0222] Specifically, in the optical scanning device 200 according to the present embodiment, when the first imaging optical system and the second imaging optical system are not virtually provided, the optical path length D between the on-axis deflection point and the position where the on-axis light beam naturally converges in the main scanning section is m About 241.8mm.

[0223] Fig. 6A and Figure 6B The image height dependencies of the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position on the first scanned surface 107a in the light scanning device 200 according to the present embodiment are respectively shown.

[0224] like Fig. 6A and Figure 6B As shown in , the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position fall within ±1 mm at all image heights, which shows that excellent imaging performance is achieved in the optical scanning device 200 according to the present embodiment.

[0225] In the optical scanning device 200 according to the present embodiment, as shown in Table 4, the optical path length T between the on-axis deflection point on the first deflecting surface 104a1 of the deflecting element 104 and the first scanned surface 107a along the optical axis of the first imaging optical system is c1 (first optical path length) is equal to or less than the scanning width in the main scanning direction on the first scanned surface 107a, in other words, the distance "h" between the outermost off-axis image heights of the first scanned surface 107a. 1 ” (First distance).

[0226] In addition, the optical path length T between the on-axis deflection point on the second deflecting surface 104a2 of the deflecting element 104 and the second scanned surface 107b along the optical axis of the second imaging optical system is c2 (the second optical path length) is equal to or less than the scanning width in the main scanning direction on the second scanned surface 107b, in other words, the distance "h" between the outermost off-axis image heights of the second scanned surface 107b. 2 ” (Second distance).

[0227] In this way, sufficient miniaturization can be achieved in the light scanning device 200 according to the present embodiment.

[0228] Furthermore, in the optical scanning device 200 according to the present embodiment, it is preferable that the following inequalities (8′) and (8″) corresponding to the above-mentioned inequality (8) are satisfied.

[0229]

[0230] In the optical scanning device 200 according to the present embodiment, it is more preferred that the following inequalities (8a′) and (8a″) are satisfied.

[0231]

[0232] In addition, in the optical scanning device 200 according to the present embodiment, the following inequalities (9') and (9") corresponding to the above inequality (9) and the following inequalities (10') and (10") corresponding to the above inequality (10) are preferably satisfied.

[0233] Furthermore, in the optical scanning device 200 according to the present embodiment, the following inequalities (11′) and (11″) corresponding to the above-mentioned inequality (11) are preferably satisfied.

[0234]

[0235] In inequality (9'), D m1 represents the optical path length between the position (first convergence point) at which the first light beam deflected by the first deflecting surface 104a1 converges in the main scanning section when the first imaging optical system is not provided and the on-axis deflection point on the first deflecting surface 104a1.

[0236] In addition, in inequality (9"), D m2 represents the optical path length between the position (second convergence point) at which the second light beam deflected by the second deflecting surface 104a2 converges in the main scanning section when the second imaging optical system is not provided and the on-axis deflection point on the second deflecting surface 104a2.

[0237] In addition, in inequality (10'), f s1 and f m1 Respectively represent the focal lengths in the sub-scan section and the main-scan section of the first imaging optical system.

[0238] In addition, in inequality (10"), f s2 and f m2 Respectively represent the focal lengths in the sub-scan section and the main-scan section of the second imaging optical system.

[0239] In addition, in inequality (11'), D R2_1 It represents the optical path length between the on-axis deflection point on the first deflecting surface 104a1 on the optical axis of the first imaging optical system and the exit surface of a predetermined optical element (second optical element).

[0240] The predetermined optical element referred to here is an optical element which is farthest from the deflection element unit 12 among at least one optical element included in the first imaging optical system on the optical path of the first light beam deflected by the first deflecting surface 104a1.

[0241] That is, in the light scanning device 200 according to the present embodiment, the predetermined optical element is the first optical element 106a.

[0242] In addition, in inequality (11"), D R2_2 It represents the optical path length between the on-axis deflection point on the second deflecting surface 104a2 on the optical axis of the second imaging optical system and the exit surface of a predetermined optical element (second optical element).

[0243] The predetermined optical element referred to here is an optical element which is farthest from the deflection element unit 12 among at least one optical element included in the second imaging optical system on the optical path of the second light beam deflected by the second deflecting surface 104a2.

[0244] That is, in the light scanning device 200 according to the present embodiment, the predetermined optical element is the second optical element 106b.

[0245] In the optical scanning device 200 according to the present embodiment, it is more preferred that the following inequalities (9a'), (9a"), (10a'), (10a"), (11a'), and (11a") are satisfied.

[0246]

[0247] Furthermore, in the optical scanning device 200 according to the present embodiment, the following inequalities (12′) and (12″) corresponding to the above-mentioned inequality (12) are preferably satisfied.

[0248] 110.00≤|ΔY 1 |≤140.0…(12′)

[0249] 110.0≤|ΔY2|≤140.0…(12”)

[0250] In inequality (12'), ΔY 1 (%) represents the ratio value of the local magnification at the outermost off-axis image height on the first scanned surface 107a to the local magnification at the on-axis image height.

[0251] In inequality (12"), ΔY 2 (%) represents the ratio value of the local magnification at the outermost off-axis image height to the local magnification at the on-axis image height on the second scanned surface 107b.

[0252] In the optical scanning device 200 according to the present embodiment, it is more preferred that the following inequalities (12a′) and (12a″) are satisfied.

[0253] 120.0≤|ΔY 1|≤135.0…(12a′)

[0254] 120.0≤|ΔY 2 |≤135.0…(12a")

[0255] In the optical scanning device 200 according to the present embodiment, T c1 / h 1 =T c2 / h 2 =0.65, thus satisfying inequalities (8′), (8a′), (8″) and (8a″).

[0256] In addition, in the optical scanning device 200 according to the present embodiment, D m1 / T c1 =D m2 / T c2 =1.73, thus satisfying inequalities (9′), (9a′), (9″) and (9a″).

[0257] In addition, in the optical scanning device 200 according to the present embodiment, f s1 / f m1 =f s2 / f m2 =0.15, thus satisfying inequalities (10′), (10a′), (10″) and (10a″).

[0258] In addition, in the optical scanning device 200 according to the present embodiment, D R2_1 / Tc 1 =D R2_2 / T c2 =0.30, thus satisfying inequalities (11′), (11a′), (11″) and (11a″).

[0259] Furthermore, in the optical scanning device 200 according to the present embodiment, |ΔY 1 |=|ΔY 2 |=130.6%, thus satisfying inequalities (12′), (12a′), (12″) and (12a″).

[0260] As described above, in the light scanning device 200 according to the present embodiment, the first folding mirror 105 a is arranged between the deflection element unit 12 and the first optical element 106 a closest to the deflection element unit 12 in the first imaging optical system.

[0261] Furthermore, the second folding mirror 105b is arranged between the deflection element unit 12 and the second optical element 106b closest to the deflection element unit 12 in the second imaging optical system, and thus inequalities (8') and (8") are satisfied.

[0262] In this way, it is possible to provide the light scanning device 200 which is sufficiently miniaturized by reducing the optical path of each of the first light beam and the second light beam scanning both sides across the deflection element unit 12 .

[0263] [Third embodiment]

[0264] Fig. 7A A schematic development diagram of a main scanning cross-sectional view of an optical scanning device 300 according to a third embodiment of the present invention is shown.

[0265] Figure 7B and Figure 7C , each showing a schematic partial sub-scanning cross-sectional view of the light scanning device 300 according to the third embodiment.

[0266] The light scanning device 300 according to the present embodiment has the same configuration as that of the light scanning device 100 according to the first embodiment except for the difference in specification values. Therefore, the same components are denoted by the same reference numerals, and description thereof is omitted.

[0267] Tables 7, 8, and 9 below respectively show specification values ​​of the optical scanning device 300 according to the present embodiment, the refractive index and surface spacing of each optical element, and the lens surface shapes of the incident optical element 103 and the optical element 106.

[0268] Table 7

[0269]

[0270]

[0271] Table 8

[0272]

[0273]

[0274] Table 9

[0275]

[0276]

[0277]

[0278] In the optical scanning device 300 according to this embodiment, as Figure 7C As shown in FIG. 1 , the folding mirror 105 reflects the incident light beam toward the lower side in the sub-scanning direction, that is, toward the side where the motor 104 b and the motor substrate 104 c are arranged with respect to the deflection element 104 .

[0279] In this way, the optical element 106 can be arranged in an inefficient space in the deflection element unit 12 that is formed by the motor 104 b and the motor substrate 104 c rather than by the deflection element 104 b.

[0280] That is, the optical scanning device 300 according to the present embodiment can be miniaturized in the sub-scan section.

[0281] Figure 8 The local magnification deviation at each image height in the light scanning device 300 according to the present embodiment is shown.

[0282] like Figure 8 As shown in , in the optical scanning device 300 according to the present embodiment, the maximum local magnification deviation is caused at the outermost off-axis image height, specifically, a local magnification deviation of about 130.9%.

[0283] That is, in the optical scanning device 300 according to the present embodiment, similar to the optical scanning device 100 according to the first embodiment, the scanning characteristics of the imaging optical system 85 are set so that the scanning speed at each off-axis image height becomes greater than the scanning speed at the on-axis image height.

[0284] As described above, in the light scanning device 300 according to the present embodiment, the incident optical element 103 has a positive refractive power in the main scanning section, and converts the incident light beam into a convergent light beam in the main scanning section.

[0285] Specifically, in the optical scanning device 300 according to the present embodiment, when the imaging optical system 85 is virtually not provided, the optical path length D between the on-axis deflection point and the position where the on-axis light beam naturally converges in the main scanning section is m About 157.8mm.

[0286] Fig. 9A and Fig. 9B The image height dependencies of the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position on the scanned surface 107 in the optical scanning device 300 according to the present embodiment are respectively shown.

[0287] like Fig. 9A and Fig. 9B As shown in , the main scanning direction LSF depth center position and the sub-scanning direction LSF depth center position fall within ±1 mm at all image heights, which shows that excellent imaging performance is achieved in the optical scanning device 300 according to the present embodiment.

[0288] In the optical scanning device 300 according to the present embodiment, as shown in Table 7, the optical path length T between the on-axis deflection point on the deflection surface 104a of the deflection element 104 and the scanned surface 107 along the optical axis of the imaging optical system 85 isc (The first optical path length) is equal to or less than the scanning width in the main scanning direction on the scanned surface 107, in other words, the distance "h" (the first distance) between the outermost off-axis image heights of the scanned surface 107.

[0289] In this way, sufficient miniaturization can be achieved in the optical scanning device 300 according to the present embodiment.

[0290] In addition, in the optical scanning device 300 according to the present embodiment, T is satisfied c / h = 0.58, D m / T c = 1.26 and f s / f m = 0.08, so the inequalities (8), (8a), (9), (9a), (10), and (10a) are satisfied.

[0291] In addition, in the optical scanning device 300 according to the present embodiment, D is satisfied R2 / T c = 0.32 and |ΔY| = 130.9%, thus satisfying the inequalities (11), (11a), (12), and (12a).

[0292] As described above, in the optical scanning device 300 according to the present embodiment, the folding mirror 105 is arranged between the deflection element unit 12 and the optical element 106 closest to the deflection element unit 12 in the imaging optical system 85, and the inequality (8) is satisfied.

[0293] In this way, an optical scanning device 300 that is sufficiently miniaturized by reducing the optical path can be provided.

[0294] Table 10 below shows the values corresponding to the respective inequalities in each of the optical scanning devices according to the first to third embodiments.

[0295] Table 10

[0296]

[0297]

[0298] The exemplary embodiments have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made thereto without departing from its gist.

[0299] According to the present embodiment, an optical scanning device that is sufficiently miniaturized can be provided.

[0300] [Image forming device]

[0301] Fig.10 ​A sub-scanning cross-sectional view showing a main portion of an image forming apparatus 90 including an optical scanning apparatus according to any one of the first to third embodiments of the present invention.

[0302] The image forming apparatus 90 is a tandem type color image forming apparatus in which the light scanning unit 11 records image information on surfaces of a plurality of photosensitive drums each serving as an image bearing member.

[0303] The image forming apparatus 90 includes a light scanning unit 11 , developing units 15 , 16 , 17 , and 18 , photosensitive drums 23 , 24 , 25 , and 26 , a conveying belt 91 , a printer controller 93 , and a fixing unit 94 .

[0304] The light scanning unit 11 may include, for example, four light scanning devices according to the first embodiment or the third embodiment, or two light scanning devices according to the second embodiment.

[0305] like Fig.10 As shown in , color signals 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 .

[0306] Then, these input color signals are converted into image data (dot data) of C (cyan), M (magenta), Y (yellow), and K (black) by a printer controller 93 included in the image forming apparatus 90 .

[0307] Then, the image data generated by the conversion is input to the light scanning unit 11 .

[0308] Light beams 19 , 20 , 21 and 22 modulated based on corresponding image data are emitted from the light scanning unit 11 , and photosensitive surfaces of the photosensitive drums 23 , 24 , 25 and 26 are scanned in the main scanning direction with the corresponding light beams 19 , 20 , 21 and 22 .

[0309] A charging roller (not shown) is provided for uniformly charging the respective surfaces of the photosensitive drums 23, 24, 25 and 26 so as to abut against these surfaces. In addition, the light scanning unit 11 irradiates the respective surfaces of the photosensitive drums 23, 24, 25 and 26 charged by the charging roller with light beams 19, 20, 21 and 22.

[0310] As described above, the light beams 19, 20, 21, and 22 have been modulated based on the image data of the corresponding colors, and electrostatic latent images are formed on the corresponding surfaces of the photosensitive drums 23, 24, 25, and 26 by irradiating the corresponding surfaces with the light beams 19, 20, 21, and 22. The formed electrostatic latent images are developed into toner images by the developing units 15, 16, 17, and 18 arranged to abut against the photosensitive drums 23, 24, 25, and 26, respectively.

[0311] The toner images developed by the developing units 15, 16, 17, and 18 are transferred in a superimposed manner onto a sheet (transfer material) (not shown) conveyed on the conveyor belt 91 by transfer rollers (transfer units) (not shown) arranged opposite to the photosensitive drums 23, 24, 25, and 26. Thus, a full-color image is formed on the sheet.

[0312] In the above-described manner, the sheet to which the unfixed toner image is transferred is further conveyed to the rear side ( Fig.10 ) on the left side of the fixing unit 94.

[0313] The fixing unit 94 includes a fixing roller including a fixing heater (not shown) therein and a pressure roller arranged to be in pressure contact with the fixing roller. Under the pressure applied from the pressure contact portion between the fixing roller and the pressure roller, the unfixed toner image on the sheet conveyed from the transfer portion is fixed by heating. A discharge roller (not shown) is also provided on the rear side of the fixing roller, and discharges the sheet to which the toner image is fixed to the outside of the image forming device 90.

[0314] 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.

[0315] 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 interpretation so as to encompass all such modifications and equivalent structures and functions.

Claims

1. An optical scanning device, comprising: a deflection unit configured to deflect the first light beam from the first light source to scan the first scanned surface in a main scanning direction; a first imaging optical system including at least one optical element configured to guide the first light beam deflected by the first deflection surface of the deflection unit to the first scanned surface; as well as a first reflecting element configured to reflect the first light beam, wherein, on an optical path of the first light beam from the deflection unit to the first scanned surface, the first reflecting element is arranged between the deflection unit and a first optical element closest to the deflection unit among the at least one optical element included in the first imaging optical system, and Wherein, a first optical path length between a first on-axis deflection point of the first deflection surface on the optical axis of the first imaging optical system and the first scanned surface is equal to or less than a first distance between the outermost off-axis image heights on the first scanned surface.

2. The optical scanning device according to claim 1, wherein: The following conditions are met: 0.50≤T c1 / h1≤1.00, Among them, T c1 denotes the first optical path length and h1 denotes the first distance. 3 . The light scanning device according to claim 1 , further comprising a first incident optical system configured to convert the first light beam from the first light source into a convergent light beam in a main scanning section so that the convergent light beam is incident on the first deflecting surface.

4. The optical scanning device according to claim 3, wherein: The first incident optical system includes a first incident optical element configured to convert the first light beam from the first light source into the convergent light beam in a main scanning section and converge the first light beam in a sub-scanning section.

5. The optical scanning device according to claim 1, wherein: The following conditions are met: 0.50≤D m1 / T c1 ≤2.50, Among them, D m1 Indicates the optical path length between a first convergence point where the first light beam deflected by the first deflecting surface converges in a main-scan section and the first on-axis deflection point when the first imaging optical system is not provided.

6. The optical scanning device according to claim 1, wherein: The following conditions are met: 0.05≤f s1 / f m1 ≤0.25, Among them, f s1 and f m1 Respectively represent the focal lengths in the sub-scan section and the main-scan section of the first imaging optical system.

7. The optical scanning device according to claim 1, wherein: The following conditions are met: 0.15≤D R2_1 / T c1 ≤0.50, Among them, D R2_1 Represents the optical path length between the first on-axis deflection point on the optical axis of the first imaging optical system and the exit surface of the second optical element farthest from the deflection unit among the at least one optical element included in the first imaging optical system.

8. The optical scanning device according to claim 1, wherein: A scanning speed of the first light beam on the first scanning surface increases monotonically from an on-axis image height toward the outermost off-axis image height.

9. The optical scanning device according to claim 8, wherein: The following conditions are met: 110.0≤ΔY1≤140.0, Wherein ΔY1 (%) represents the ratio of the local magnification at the outermost off-axis image height to the local magnification at the on-axis image height.

10. The optical scanning device according to claim 1, further comprising: a second imaging optical system including at least one optical element configured to guide the second light beam deflected by the second deflection surface of the deflection unit to a second scanned surface; as well as a second reflecting element configured to reflect the second light beam, wherein, on an optical path of the second light beam from the deflection unit to the second scanned surface, the second reflecting element is arranged between the deflection unit and a third optical element closest to the deflection unit among the at least one optical element included in the second imaging optical system, wherein the deflection unit is configured to deflect the second light beam from the second light source to scan the second scanned surface in a main scanning direction, and Wherein, a second optical path length between a second on-axis deflection point of the second deflection surface on the optical axis of the second imaging optical system and the second scanned surface is equal to or less than a second distance between the outermost off-axis image heights on the second scanned surface.

11. The optical scanning device according to claim 10, wherein: The following conditions are met: 0.50≤T c2 / h2≤1.00, Among them, T c2 denotes the second optical path length and h2 denotes the second distance.

12. The optical scanning device according to claim 1, in, The deflection unit comprises a deflection element having a plurality of deflection surfaces, and a drive unit configured to rotate the deflection element around a rotation axis, and The first light beam deflected by the first deflecting surface is reflected by the first reflecting element to a side of the sub-scanning direction where the driving unit is arranged relative to the deflecting element.

13. The optical scanning device according to claim 1, wherein: The first imaging optical system is composed of the first optical element.

14. The optical scanning device according to claim 1, wherein: Any reflecting element other than the first reflecting element is not arranged on an optical path of the first light beam from the deflecting unit to the first scanned surface.

15. An image forming apparatus, comprising: The optical scanning device according to any one of claims 1 to 14; a developing unit configured to develop the electrostatic latent image formed by the light scanning device on the first scanned surface into a toner image; a transfer unit configured to transfer the developed toner image onto a transfer material; as well as The fixing unit is configured to fix the transferred toner image onto the transfer material.

16. An image forming device, comprising: The optical scanning device according to any one of claims 1 to 14; as well as The printer 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.

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