Optical scanning apparatus and image forming apparatus having the same

Abstract

The present invention provides an optical scanning device that allows for easy adjustment of the relative positions of multiple light sources and multiple light guide units. [Solution] The optical scanning device according to the present invention comprises a deflector having a first deflection surface that deflects first and second luminous beams from first and second light sources to scan first and second scan surfaces in the main scanning direction, and first and second light guides that guide first and second luminous beams from first and second light sources to the first deflection surface, wherein the optical path of the first luminous beam in the first light guide includes a straight line connecting the first light source and the first deflection surface, and the optical path of the second luminous beam in the second light guide does not include a straight line connecting the second light source and the first deflection surface.

Description

[Technical Field]

[0001] The present invention relates to an optical scanning device, and more particularly to an optical scanning device suitably used in image forming apparatus such as a laser beam printer or a multifunction printer having an electrophotographic process. [Background technology]

[0002] Patent Document 1 discloses an optical scanning device that enables adjustment of the relative position between each collimator lens and multiple light sources by arranging multiple collimator lenses so that they can be gripped from the same direction during manufacturing. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-83744 [Overview of the project] [Problems that the invention aims to solve]

[0004] Specifically, the optical scanning apparatus disclosed in Patent Document 1 does not adequately simplify the adjustment of the relative positions between multiple light sources and multiple collimator lenses.

[0005] Therefore, the present invention aims to provide an optical scanning device that can easily adjust the relative positions of multiple light sources and multiple light guide units. [Means for solving the problem]

[0006] The optical scanning apparatus according to the present invention comprises a deflector having a first deflection surface that deflects first and second luminous beams from first and second light sources to scan first and second surfaces to be scanned in the main scanning direction, and first and second light guides that guide first and second luminous beams from first and second light sources to the first deflection surface, wherein the optical path of the first luminous beam in the first light guide includes a straight line connecting the first light source and the first deflection surface, and the optical path of the second luminous beam in the second light guide does not include a straight line connecting the second light source and the first deflection surface. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an optical scanning device that can easily adjust the relative positions of multiple light sources and multiple light guide units. [Brief explanation of the drawing]

[0008] [Figure 1] A partially unfolded view of the main scanning cross-section of the optical scanning apparatus according to the first embodiment. [Figure 2] A partial sub-scanning cross-sectional view of the optical scanning apparatus according to the first embodiment. [Figure 3] An optical scanning device according to the first embodiment and a partially enlarged perspective view of the optical scanning device according to a modified example of the first embodiment. [Figure 4] A partially enlarged perspective view of an optical scanning apparatus according to the first embodiment and an optical scanning apparatus according to a comparative example. [Figure 5] A partially unfolded view of the main scanning cross section of the optical scanning apparatus according to the second embodiment. [Figure 6] A partial sub-scanning cross-sectional view of the optical scanning apparatus according to the second embodiment. [Figure 7] A partially enlarged perspective view of the optical scanning device according to the second embodiment. [Figure 8] A partial unfolded view of the main scanning cross-section of the optical scanning apparatus according to the third embodiment. [Figure 9] A partial sub-scanning cross-sectional view of the optical scanning apparatus according to the third embodiment. [Figure 10] A partially enlarged perspective view of the optical scanning device according to the third embodiment. [Figure 11] A sub-scanning cross-sectional view of the main part of a color image forming apparatus according to an embodiment. [Figure 12] A partially enlarged perspective view of the optical scanning device disclosed in Patent Document 1. MODE FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, the optical scanning device according to the present embodiment will be described in detail with reference to the accompanying drawings. Note that the drawings shown below may be drawn at a scale different from the actual scale to facilitate understanding of the present embodiment. In the following description, the main scanning direction is a direction perpendicular to the rotation axis 55 of the deflector 5 and the optical axes of the first to fourth imaging optical systems (the direction in which the first to fourth light beams are deflected by the deflector 5), and the sub-scanning direction is a direction parallel to the rotation axis 55 of the deflector 5.

[0010] Further, the main scanning cross-section is a cross-section perpendicular to the sub-scanning direction, and the sub-scanning cross-section is a cross-section perpendicular to the main scanning direction. Hereinafter, the direction parallel to the optical axes of the first to fourth imaging optical systems, the main scanning direction, and the sub-scanning direction are defined as an X direction, a Y direction, and a Z direction, respectively.

[0011] [First Embodiment] Conventionally, an optical scanning device has been used as an exposure device mounted in an image forming apparatus such as a laser beam printer using an electrophotographic process.

[0012] Specifically, in an optical scanning device, a light beam modulated and emitted from a light source means in accordance with an image signal from a personal computer is guided by an incident optical system to a deflector such as a polygon mirror (rotating polygonal mirror), and then deflected by a deflection surface of the deflector. The deflected light beam is then focused in a spot shape onto the photosensitive surface of a photosensitive drum serving as a scanned surface by an imaging optical system, and the focused light beam scans the photosensitive surface, whereby exposure recording of image information is performed. Various color image forming apparatuses that form a color image by scanning the photosensitive surfaces of a plurality of photosensitive drums using an optical scanning device have also been proposed.

[0013] Figure 12 shows a partially enlarged schematic perspective view of an optical scanning device 500 used in a color image forming apparatus disclosed in Patent Document 1. As shown in Figure 12, in the optical scanning device 500, multiple light beams emitted from multiple semiconductor laser elements 10Y, 10M, 10C, and 10K are focused by multiple collimator lenses, including collimator lenses 20Y and 20K, respectively, and then guided to a deflector. The multiple light beams deflected by the deflector are then guided by the corresponding imaging optical system onto the photosensitive surface of the photosensitive drum, which serves as the corresponding scanning surface, and are scanned on that corresponding photosensitive surface.

[0014] Patent Document 1 discloses a technique for obtaining predetermined optical performance in the above-mentioned optical scanning device 500 by finely adjusting the relative positions between multiple semiconductor laser elements and multiple collimator lenses. On the other hand, the technology disclosed in Patent Document 1 has the following problems.

[0015] Specifically, in the technology disclosed in Patent Document 1, the positions of the collimator lenses 20Y and 20K, corresponding to the semiconductor laser elements 10Y and 10K, are first adjusted while being held by a jig. Next, after the adjustment is made, the collimator lenses 20Y and 20K are fixed in place by the photocurable resin P applied to the gaps between them and the seating surfaces Hf1 and H12 of the laser holder H11, respectively, and the lens holder H2 is attached by screw fastening.

[0016] Subsequently, the positions of the collimator lenses (not shown) corresponding to the semiconductor laser elements 10M and 10C are adjusted while being held by a jig. After the adjustment is made, the collimator lens is fixed in place by the photocurable resin P applied to the gaps between it and the seating surfaces Hf21 and Hf22 of the lens holder H2.

[0017] As described above, the technology disclosed in Patent Document 1 requires several steps, including positioning and fixing of collimator lenses 20Y and 20K, mounting of lens holder H2, and positioning and fixing of the remaining collimator lenses. In other words, performing these multiple processes increases the cycle time, and also necessitates the installation of components such as the lens holder H2, resulting in higher costs. Therefore, the objective of this embodiment is to provide an optical scanning device that is cost-effective, compact, and lightweight by providing multiple light sources and multiple incident optical systems, which allow for easy arrangement adjustment and assembly when installed in a small space.

[0018] Figures 1(a) and 1(b) show a partially schematic unfolded view of the main scanning cross section of the optical scanning apparatus 100 according to the first embodiment. Figure 2 shows a partially schematic sub-scanning cross-sectional view of the optical scanning apparatus 100 according to the first embodiment.

[0019] The optical scanning device 100 according to this embodiment includes first, second, third, and fourth light sources 11, 21, 31, and 41, and first, second, third, and fourth apertures 12, 22, 32, and 42. Furthermore, the optical scanning device 100 according to this embodiment includes first, second, third, and fourth incident optical elements 13, 23, 33, and 43 (first, second, third, and fourth light guides) and a deflector 5. Furthermore, the optical scanning device 100 according to this embodiment includes first scanning imaging elements 161 and 361, and second scanning imaging elements 162, 262, 362 and 462.

[0020] In the optical scanning device 100 according to this embodiment, a first incident optical system is formed by a first aperture 12 and a first incident optical element 13 that guides a first light beam from a first light source 11 to a deflector 5. Furthermore, the second aperture 22 and the second incident optical element 23 form a second incident optical system that guides the second light beam from the second light source 21 to the deflector 5. Furthermore, a third incident optical system is formed by the third aperture 32 and the third incident optical element 33, which guides the third light beam from the third light source 31 to the deflector 5. Furthermore, the fourth aperture 42 and the fourth incident optical element 43 form a fourth incident optical system that guides the fourth light beam from the fourth light source 41 to the deflector 5.

[0021] Furthermore, in the optical scanning device 100 according to this embodiment, a first imaging optical system (first optical system) is formed which guides the first light beam deflected by the deflector 5 to the first scanned surface 17 using the first scanning imaging element 161 and the second scanning imaging element 162. Furthermore, a second imaging optical system (second optical system) is formed by the first scanning imaging element 161 and the second scanning imaging element 262 to guide the second light beam, which has been deflected by the deflector 5, to the second scanning surface 27. Furthermore, a third imaging optical system (third optical system) is formed by the first scanning imaging element 361 and the second scanning imaging element 362 to guide the third light beam, which has been deflected by the deflector 5, to the third scanning surface 37. Furthermore, a fourth imaging optical system (fourth optical system) is formed by the first scanning imaging element 361 and the second scanning imaging element 462 to guide the fourth light beam, which has been deflected by the deflector 5, to the fourth scanning surface 47.

[0022] As shown in Figures 1(a) and (b), in the optical scanning apparatus 100 according to this embodiment, the first and second imaging optical systems and the third and fourth imaging optical systems are arranged on opposite sides of the deflector 5 within the main scanning cross-section. The first and second light beams emitted from the first and second light sources 11 and 21 are then guided to the first and second scanning surfaces 17 and 27, respectively, by the first and second incident optical systems and the first and second imaging optical systems, which are provided on the first and second optical paths. Furthermore, the third and fourth light beams emitted from the third and fourth light sources 31 and 41 are guided to the third and fourth scanning surfaces 37 and 47, respectively, by the third and fourth incident optical systems and the third and fourth imaging optical systems, which are provided on the third and fourth optical paths.

[0023] Furthermore, as shown in Figure 2, the optical scanning device 100 according to this embodiment employs a so-called sub-scanning oblique incidence system, in which the first to fourth light beams emitted from the first to fourth light sources 11 to 41 are obliquely incident on the deflector 5 by the first to fourth incident optical systems, respectively. In other words, the first and second light beams from the first and second incident optical elements 13 and 23 are obliquely incident on the first deflection surface 5a of the deflector 5 in the sub-scan cross-section. Furthermore, the third and fourth light beams from the third and fourth incident optical elements 33 and 43 are obliquely incident on the second deflection surface 5b of the deflector 5 in the sub-scan cross-section. The first and second light beams, deflected by the first deflection surface 5a of the deflector 5 (Figure 3(a)), are then guided to the first and second scanning surfaces 17 and 27 by the first and second imaging optical systems.

[0024] Furthermore, the third and fourth light beams deflected by the second deflection surface 5b of the deflector 5 (Figure 3(a)) are guided to the third and fourth scanning surfaces 37 and 47 by the third and fourth imaging optical systems. Furthermore, the first to fourth luminous beams deflected by the first deflection surface 5a or the second deflection surface 5b of the deflector 5 are each reflected by a folding mirror (not shown). Furthermore, in the optical scanning device 100 according to this embodiment, a portion of the light beam deflected by the deflector 5 is guided to a synchronization detection light receiving element (not shown) by a synchronization detection optical system (not shown).

[0025] Each of the first to fourth light sources 11 to 41 is formed by a semiconductor laser element, has at least one light-emitting point, and is mounted on a common substrate (not shown). The first to fourth apertures 12 to 42 each regulate the beam width of the first to fourth light beams emitted from the first to fourth light sources 11 to 41 in both the main scanning direction and the sub-scanning direction.

[0026] In the optical scanning device 100 according to this embodiment, instead of the first to fourth apertures 12 to 42, a main scanning aperture that restricts the beam width of the first to fourth light beams in the main scanning direction and a sub-scanning aperture that restricts the beam width of the first to fourth light beams in the sub-scanning direction may be provided. In this case, by positioning the main scanning aperture near the deflector 5, the generation of jitter can be suppressed in the case of a monolithic multibeam where each of the first to fourth light sources 11 to 41 has multiple light emission points.

[0027] The first to fourth incident optical elements 13 to 43 each concentrate the first to fourth light beams that have passed through the first to fourth apertures 12 to 42 into parallel light beams in the main scanning plane and into converged light beams in the sub-scanning plane. Here, the term "parallel beam" includes not only strictly parallel beams but also approximate parallel beams such as weakly diverging beams and weakly converging beams.

[0028] Specifically, the first to fourth incident optical elements 13 to 43 each have different powers in the main scanning direction and the sub-scanning direction, and have the function of coupling the first to fourth light beams from the first to fourth light sources 11 to 41. The specific shapes of the first to fourth incident optical elements 13 to 43 will be described later.

[0029] The deflector 5 has four deflection surfaces, each arranged on the sides of a square within the main scanning cross-section, and is a tetrahedral polygon mirror (rotating polyhedron mirror) that rotates around the rotation axis 55. In the optical scanning device 100 according to this embodiment, the rotation axis 55 of the deflector 5 is positioned at the center of the inscribed circle that is inscribed in each of the four deflection surfaces, or at the center of the circumscribed circle that passes through the corner between adjacent deflection surfaces. Furthermore, the deflector 5 can be formed, for example, by cutting a metal block or by molding a base material using a mold, and then applying a vapor-deposited film to each deflection surface of the base material.

[0030] The first scanning imaging elements 161 and 361 and the second scanning imaging elements 162 to 462 are scanning lenses whose incident and exit surfaces are formed by predetermined free-form surfaces, and can be formed by molding optical resin using a mold. In the optical scanning device 100 according to this embodiment, the first to fourth imaging optical systems each have a constant velocity characteristic Y=Fθ, scanning the first to fourth scanning surfaces 17 to 47 at a constant velocity.

[0031] However, the process is not limited to this; the first to fourth imaging optical systems may each have non-uniform velocity characteristics such as Y=tanθ. Furthermore, in the optical scanning device 100 according to this embodiment, the first to fourth imaging optical systems are each formed by two scanning imaging elements, namely the first scanning imaging elements 161 and 361 and the second scanning imaging elements 162 to 462, but the invention is not limited to this.

[0032] In other words, each of the first to fourth imaging optical systems may be formed by a single scanning imaging element to reduce costs, or it may be formed by three or more scanning imaging elements to further improve optical performance. Furthermore, in the optical scanning device 100 according to this embodiment, each of the first to fourth imaging optical systems has a second scanning imaging element 162 to 462. On the other hand, the first scanning imaging element 161 is shared in the first and second imaging optical systems, and the first scanning imaging element 361 is shared in the third and fourth imaging optical systems.

[0033] The first to fourth light beams deflected by the deflector 5 are each focused by the first to fourth imaging optical systems so that beam spots are formed on the first to fourth scanning surfaces 17 to 47. As the deflector 5 rotates, the beam spot formed on each of the first to fourth scanned surfaces 17 to 47 scans a printing range from the off-axis image height on the side where the first to fourth light sources 11 to 41 are located to the off-axis image height on the opposite side.

[0034] Next, the specifications of the optical scanning device 100 according to this embodiment are shown in Table 1 below. Furthermore, the arrangement of the first incident optical system and the first imaging optical system provided in the optical scanning device 100 according to this embodiment is shown in Table 2 below, and the arrangement of the second incident optical system and the second imaging optical system is shown in Table 3 below.

[0035] Furthermore, the shapes of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 100 according to this embodiment are shown in Table 4 below. Furthermore, Table 5 below shows the shapes of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the second scanning imaging elements 162 to 462, respectively, which are provided in the optical scanning device 100 according to this embodiment.

[0036] [Table 1] [Table 2] [Table 3] [Table 4] [Table 5]

[0037] In Tables 4 and 5, "EX" is 10 -X It means that.

[0038] Furthermore, the arrangement of the third incident optical system and the third imaging optical system provided in the optical scanning device 100 according to this embodiment can be changed by converting the values ​​shown in Table 2 so that they are symmetrical with respect to a plane that includes the rotation axis 55 of the deflector 5 and is parallel to the Y and Z directions. Similarly, for the arrangement of the fourth incident optical system and the fourth imaging optical system provided in the optical scanning device 100 according to the present embodiment, the values shown in Table 3 may be converted so as to be symmetric with respect to a plane that includes the rotation shaft 55 of the deflector 5 and is parallel to the Y direction and the Z direction.

[0039] The shape (generatrix shape) in the main scanning section of each of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 100 according to the present embodiment is represented by the following formula (1). Further, the shapes in the main scanning section of each of the incident surfaces and exit surfaces of the first scanning imaging elements 161 and 361, and the incident surfaces and exit surfaces of the second scanning imaging elements 162 to 462 provided in the optical scanning device 100 according to the present embodiment are also represented by the following formula (1).

Math

[0040] In formula (1), R Y is the radius of curvature, K Y is the eccentricity, and B i (i=1,2,3,4,5,6,7,8,9,10,11,12) are aspheric coefficients. Further, in formula (1), when the aspheric coefficient B i is different between the plus side and the minus side with respect to Y, as shown in Tables 4 and 5, a suffix u is added to the coefficient on the plus side (i.e., B iu ), and a suffix l is added to the coefficient on the minus side (i.e., B il ). This also applies to the coefficient M jk in the following formula (2) and E j in the following formula (3).

[0041] Further, the shape (creatrix shape) in the sub-scanning section of each of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 100 according to the present embodiment is represented by the following formula (2). Furthermore, the shapes within the sub-scan cross-section of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the incident and exit surfaces of the second scanning imaging elements 162 to 462, which are provided in the optical scanning device 100 according to this embodiment, are also represented by the following equation (2).

number

[0042] In equation (2), S represents the surface shape within a cross-section perpendicular to the main scanning cross-section, including the surface normal on the generatrix at each position in the main scanning direction, and M jk (j=0,1,2,3,4,5,6,7,k=1) are the aspherical coefficients. Also, the r shown in equation (2) Z ' represents the radius of curvature (sub-line radius of curvature) in the sub-scan cross-section at a position Y away from the optical axis in the main scanning direction, and changes continuously according to the magnitude of Y, as shown in equation (3) below.

[0043]

number

[0044] Next, the characteristic configuration of the optical scanning device 100 according to this embodiment will be described. Figure 3(a) shows a partially enlarged schematic perspective view of the optical scanning device 100 according to this embodiment.

[0045] As shown in Figure 3(a), in the optical scanning device 100 according to this embodiment, the first to fourth incident optical elements 13 to 43 are integrally formed with each other as a compound eye optical element. Furthermore, the incident surfaces 131, 231, 331, and 431 of the first to fourth incident optical elements 13 to 43 each have a spherical shape that is rotationally symmetric with respect to the optical axis.

[0046] As a result, the first to fourth light beams incident on the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are converted into parallel light beams in both the main scanning cross-section and the sub-scanning cross-section. Furthermore, the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 may each have an aspherical shape, not limited to those described above.

[0047] Furthermore, the exit surfaces 134, 234, 334, and 434 of the first to fourth incident optical elements 13 to 43 are anamorphic surfaces that have power in the sub-scan cross-section, i.e., they have a cylindrical shape. The exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 each converge the parallel light beams from the incident surfaces 131 to 431 within the sub-scanning cross-section. In this way, the first to fourth luminous beams are focused within the sub-scanning cross-section by the respective emission surfaces 134 to 434, thereby forming line images in the vicinity of the first and second deflection surfaces 5a and 5b of the deflector 5.

[0048] As shown in Figure 3(a), the second incident optical element 23 has first and second reflective surfaces 232 and 233 (first and second reflective surfaces), and the fourth incident optical element 43 has first and second reflective surfaces 432 and 433 (third and fourth reflective surfaces). In other words, in the first incident optical element 13, the first light beam incident from the incident surface 131 (first optical surface, first incident surface) exits from the exit surface 134 (second optical surface, first exit surface). On the other hand, in the second incident optical element 23, the second light beam incident from the incident surface 231 (third optical surface, second incident surface) is reflected by the first and second reflective surfaces 232 and 233, respectively, and then exits from the exit surface 234 (fourth optical surface, second exit surface). Furthermore, in the third incident optical element 33, the third luminous beam incident from the incident surface 331 (the fifth optical surface, the third incident surface) exits from the exit surface 334 (the sixth optical surface, the third exit surface). On the other hand, in the fourth incident optical element 43, the fourth light beam incident from the incident surface 431 (seventh optical surface, fourth incident surface) is reflected by the first and second reflective surfaces 432 and 433, respectively, and then exits from the exit surface 434 (eighth optical surface, fourth exit surface).

[0049] In other words, in the optical scanning device 100 according to this embodiment, the optical paths of the first and third light beams in the first and third incident optical elements 13 and 33, respectively, are linear. In other words, in the optical scanning device 100 according to this embodiment, the optical paths of the first and third light beams between the first and third light sources 11 and 31 and the first and second deflection surfaces 5a and 5b of the deflector 5 are straight lines. To put it another way, the optical paths of the first and third light beams in the first and third incident optical elements 13 and 33 include straight lines connecting the first and third light sources 11 and 31 and the first and second deflection surfaces 5a and 5b of the deflector 5.

[0050] On the other hand, in the optical scanning device 100 according to this embodiment, the optical paths of the second and fourth light beams in the second and fourth incident optical elements 23 and 43, respectively, are not linear. In other words, in the optical scanning device 100 according to this embodiment, the optical paths of the second and fourth light beams between the second and fourth light sources 21 and 41 and the first and second deflection surfaces 5a and 5b of the deflector 5 are not straight lines. To put it another way, the optical paths of the second and fourth light beams in the second and fourth incident optical elements 23 and 43 do not include the straight line connecting the second and fourth light sources 21 and 41 and the first and second deflection surfaces 5a and 5b of the deflector 5. Furthermore, it is preferable that the first and second reflective surfaces 232 and 233 provided on the second incident optical element 23, and the first and second reflective surfaces 432 and 433 provided on the fourth incident optical element 43, are all reflective surfaces. Furthermore, the number of reflective surfaces formed on the second and fourth incident optical elements 23 and 43, respectively, provided in the optical scanning device 100 according to this embodiment is not limited to the above.

[0051] Furthermore, in the optical scanning device 100 according to this embodiment, the oblique incidence angles that the propagation directions of the first and third light beams emitted from the first and third light sources 11 and 31 make with respect to the main scanning cross-section are the same for all of them within the sub-scanning cross-section. Furthermore, within the sub-scanning cross-section, the oblique incidence angles of the second and fourth light beams emitted from the second and fourth light sources 21 and 41 with respect to the main scanning cross-section are the same for all of them. On the other hand, the oblique incidence angles of the first and third luminous beams and the oblique incidence angles of the second and fourth luminous beams are different from each other.

[0052] The first to fourth incident optical elements 13 to 43 are each formed by molding a resin material using a mold in order to reduce costs and facilitate manufacturing. In this case, since the refractive index of the resin material fluctuates with respect to the ambient temperature, the degree of focusing of the first to fourth light beams by the first to fourth incident optical elements 13 to 43 may change with respect to the ambient temperature.

[0053] Therefore, a temperature-compensated optical system may be adopted by forming a diffraction grating on the incident surface 131 to 431 or the exit surface 134 to 434. Furthermore, in the second and fourth incident optical elements 23 and 43, a temperature-compensated optical system may be adopted by forming a diffraction grating on the first reflective surfaces 232 and 432 or the second reflective surfaces 233 and 433, respectively.

[0054] Furthermore, as shown in Figure 3(a), in the optical scanning device 100 according to this embodiment, the principal rays of the first and second light beams immediately before they enter the first deflection surface 5a of the deflector 5 are each located in a predetermined plane 58 parallel to the sub-scanning direction. In other words, in the optical scanning device 100 according to this embodiment, the first and second light beams emitted from the first and second light sources 11 and 21 are incident on the first deflection surface 5a of the deflector 5 by the first and second incident optical systems.

[0055] Furthermore, the principal rays of the third and fourth luminous beams immediately before they enter the second deflection surface 5b of the deflector 5 are each located within a predetermined plane 59 parallel to the sub-scanning direction. In other words, in the optical scanning device 100 according to this embodiment, the third and fourth light beams emitted from the third and fourth light sources 31 and 41 are incident on the second deflection surface 5b of the deflector 5 by the third and fourth incident optical systems.

[0056] Furthermore, as shown in Figure 3(a), the straight line (the first straight line) passing through the centers of the light-emitting surfaces of the first and second light sources 11 and 21 (the first center and the second center) is twisted with respect to the rotation axis 55 of the deflector 5 and is non-parallel to the sub-scanning direction. Furthermore, the straight line (the second straight line) passing through the centers of the light-emitting surfaces of the third and fourth light sources 31 and 41 (the center of the third and the center of the fourth) is twisted with respect to the rotation axis 55 of the deflector 5, that is, it is non-parallel to the sub-scanning direction. Here, the center of the light-emitting surface of a light source is defined as the position of a single light-emitting point if the light source has a single light-emitting point, and as the midpoint between two light-emitting points located at both ends if the light source has multiple light-emitting points arranged on a predetermined straight line.

[0057] The center of each of the first to fourth light sources 11 to 41 is positioned on a predetermined trapezoidal corner within a predetermined plane. In other words, the signs of the angles that the lines passing through the centers of the light-emitting surfaces of the first and second light sources 11 and 21 make with respect to the sub-scanning direction are different from those of the lines passing through the centers of the light-emitting surfaces of the third and fourth light sources 31 and 41. Since the centers of the light-emitting surfaces of the first to fourth light sources 11 to 41 are positioned on the predetermined plane, the first to fourth light sources 11 to 41 are each driven to emit light by a common light-emitting substrate (not shown).

[0058] Specifically, in the optical scanning device 100 according to this embodiment, it is preferable that the absolute value |φ1|(°) of the angle (first angle) between the straight line passing through the center of the light-emitting surfaces of the first and second light sources 11 and 21 and the straight line parallel to the sub-scanning direction satisfies the following condition (4). Furthermore, it is preferable that the absolute value |φ2|(°) of the angle (second angle) between the line passing through the center of the light-emitting surface of the third and fourth light sources 31 and 41 and the line parallel to the sub-scanning direction satisfies the following condition (5). 30.0 ≤ |φ1| ≤ 60.0 ···(4) 30.0 ≤ |φ2| ≤ 60.0 ···(5)

[0059] Furthermore, in the optical scanning device 100 according to this embodiment, it is more preferable that the following conditions (4a) and (5a) are satisfied instead of conditions (4) and (5). 33.0 ≤ |φ1| ≤ 56.0 ···(4) 33.0 ≤ |φ2| ≤ 56.0 ···(5) Specifically, in the optical scanning device 100 according to this embodiment, |φ1|=|φ2|=33.8, so conditions (4), (4a), (5), and (5a) are satisfied.

[0060] Furthermore, as shown in Figures 1(a) and (b), in the optical scanning device 100 according to this embodiment, the optical path lengths from the center of the light-emitting surfaces of the first to fourth light sources 11 to 41 to the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are the same for all of them. Furthermore, the optical path lengths from the exit surfaces 134 and 234 of the first and second incident optical elements 13 and 23 to the on-axial deflection point of the first deflection surface 5a, and the optical path lengths from the exit surfaces 334 and 434 of the third and fourth incident optical elements 33 and 43 to the on-axial deflection point of the second deflection surface 5b are all the same.

[0061] Furthermore, the optical path lengths in the first and third incident optical elements 13 and 33 are the same, and the optical path lengths in the second and fourth incident optical elements 23 and 43 are also the same. On the other hand, the optical path lengths in the first and third incident optical elements 13 and 33 are different from those in the second and fourth incident optical elements 23 and 43, with the latter being larger than the former.

[0062] Therefore, the optical path lengths from the centers of the light-emitting surfaces of the first and third light sources 11 and 31 to the on-axial deflection points of the first and second deflection surfaces 5a and 5b of the deflector 5 are the same. Furthermore, the optical path lengths from the center of the light-emitting surfaces of the second and fourth light sources 21 and 41 to the on-axial deflection points of the first and second deflection surfaces 5a and 5b of the deflector 5 are the same. On the other hand, the optical path lengths from the center of the light-emitting surfaces of the first and second light sources 11 and 21 to the on-axial deflection point (first on-axial deflection point) of the first deflection surface 5a of the deflector 5 are different from each other. Furthermore, the optical path lengths from the center of the light-emitting surfaces of the third and fourth light sources 31 and 41 to the on-axial deflection point (second on-axial deflection point) of the second deflection surface 5b of the deflector 5 are different from each other.

[0063] In the optical scanning device 100 according to this embodiment, the first to fourth luminous beams are converted into parallel luminous beams between the incident surfaces 131 to 431 and the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43. Therefore, by making the shapes of the incident surfaces 131 to 431 identical and the shapes of the exit surfaces 134 to 434 identical, the arrangement and magnification of each optical surface in the first to fourth incident optical systems can be made to match.

[0064] On the other hand, if it is difficult to convert the first to fourth luminous beams into parallel luminous beams between the incident surfaces 131 to 431 and the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43, the following can be done. In other words, in the second and fourth incident optical elements 23 and 43, the first reflective surfaces 232 and 432 and the second reflective surfaces 233 and 433 should each be formed to have power.

[0065] This makes it possible to make the shapes of the incident surfaces 131 to 431 and the exit surfaces 134 to 434 identical in the first to fourth incident optical elements 13 to 43. Therefore, the arrangement and magnification of each optical surface in the first to fourth incident optical systems can be made to match each other. However, in this case, the number of optical surfaces with power increases, so tolerances must be carefully considered.

[0066] As described above, in the optical scanning device 100 according to this embodiment, it is preferable to convert the first to fourth luminous beams into parallel luminous beams between the incident surfaces 131 to 431 and the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43. Therefore, it is preferable that the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 each have a shape that is rotationally symmetric with respect to the optical axis. In other words, it is preferable that the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are each formed as refractive or diffracting surfaces that are rotationally symmetric with respect to the optical axis.

[0067] In conventional optical scanning devices, when using rotationally symmetric coupling lenses, the incident surface is generally formed as a flat or gently spherical surface, while the exit surface is formed as a spherical surface with power, in order to suppress the occurrence of spherical aberration. On the other hand, the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 100 according to this embodiment each have a spherical shape that is rotationally symmetric with respect to the optical axis, as described above. Therefore, it is important to note that spherical aberration occurs in the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 100 according to this embodiment.

[0068] In addition, in order to suppress the occurrence of spherical aberration in the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 100 according to this embodiment, each of the incident surfaces 131 to 431 may be formed to have an aspherical shape that is rotationally symmetric with respect to the optical axis. Alternatively, the occurrence of spherical aberration may be suppressed by forming each of the exit surfaces 134 to 434 such that a higher-order aspherical amount is added to the anamorphic surface.

[0069] Figures 4(a) and 4(b) show partially enlarged schematic perspective views of the optical scanning device 100 according to this embodiment and the optical scanning device 150 according to a comparative example, respectively. The optical scanning device 150 in the comparative example has the same configuration as the optical scanning device 100 in this embodiment, except for the different arrangement of the optical elements. Therefore, the same reference numerals are used for the same components, and their descriptions are omitted.

[0070] Specifically, in the optical scanning apparatus 150 relating to the comparative example, as shown in Figure 4(b), the first and second light sources 11 and 21 are arranged at the same position within the main scanning cross-section, and the third and fourth light sources 31 and 41 are also arranged at the same position. Therefore, in the comparative example optical scanning device 150, the first and second incident optical elements 13 and 23 are arranged at the same position within the main scanning cross-section, and the third and fourth incident optical elements 33 and 43 are also arranged at the same position.

[0071] Therefore, in the comparative example optical scanning device 150, as indicated by the arrows in Figure 4(b), it is difficult to secure sufficient space for positioning the jig when adjusting the position of each of the first to fourth light sources 11 to 41 by gripping them with the jig from above and below in the sub-scanning direction. In other words, in the optical scanning device 150 of the comparative example, it is not easy to adjust the relative positional relationship between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0072] On the other hand, in the optical scanning apparatus 150 according to the comparative example, if the first and second light sources 11 and 21 are spaced far apart from each other in the sub-scanning direction, and the third and fourth light sources 31 and 41 are also spaced far apart from each other, the height increases. Therefore, in the optical scanning device 100 according to this embodiment, as shown in Figures 3(a) and 4(a), the first and second light sources 11 and 21 are arranged at different positions within the main scanning cross-section, and the third and fourth light sources 31 and 41 are also arranged at different positions.

[0073] This optimizes the arrangement of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems. In other words, as indicated by the arrows in Figure 4(a), each of the first to fourth light sources 11 to 41 can be easily gripped by a jig from above and below in the sub-scanning direction. This makes it possible to easily adjust the relative position between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0074] Furthermore, in the optical scanning device 100 according to this embodiment, all of the first to fourth light sources 11 to 41 can be simultaneously grasped and their positions adjusted using a jig, thus reducing the time required to assemble and adjust the optical scanning device 100 according to this embodiment. Furthermore, the number of parts required to assemble and adjust the optical scanning device 100 according to this embodiment can be reduced, as can the man-hours required for such assembly and adjustment.

[0075] Furthermore, in the optical scanning device 100 according to this embodiment, since each optical element is housed and fixed within the optical housing, it is preferable that no structures are provided above or below in the sub-scanning direction for each of the first to fourth light sources 11 to 41 so that a jig can directly access them. Then, after adjusting the relative position of each of the first to fourth light sources 11 to 41 with respect to the first to fourth incident optical elements 13 to 43 while gripping each of them with a jig, it is preferable that each optical element is adhesively fixed to the optical housing in order to reduce costs. In the optical scanning device 100 according to this embodiment, instead of gripping each of the first to fourth light sources 11 to 41 with a jig, a holding member for each of the first to fourth light sources 11 to 41 may be provided, and the holding member may be gripped by a jig.

[0076] Furthermore, |α1|(°) and |α2|(°) are defined as the absolute values ​​of the angles within the main scanning cross-section between the propagation direction of the principal rays of the first and second light beams immediately before they enter the first deflection surface 5a of the deflector 5 and the optical axes of the first and second imaging optical systems. Furthermore, |α3|(°) and |α4|(°) are defined as the absolute values ​​of the angles within the main scanning cross-section between the propagation direction of the principal rays of the third and fourth light beams immediately before they enter the second deflection surface 5b of the deflector 5 and the optical axes of the third and fourth imaging optical systems.

[0077] In this embodiment, it is preferable that at least one of the following conditions (6) and (7) is satisfied in the optical scanning device 100. -10≦|α3|-|α1|≦10 ···(6) -10≦|α4|-|α2|≦10 ···(7)

[0078] By satisfying at least one of conditions (6) and (7), interference between the first to fourth light sources 11 to 41 can be suppressed, and the size of the first to fourth incident optical elements 13 to 43, which are integrally formed with each other, can be suppressed. Specifically, in the optical scanning device 100 according to this embodiment, |α1|, |α2|, |α3|, and |α4| are each 90°, so conditions (6) and (7) are satisfied.

[0079] Furthermore, in the optical scanning device 100 according to this embodiment, it is preferable that the following condition (8) is satisfied when the number of deflection surfaces of the deflector 5 is N. 3 <N≦6 ···(8)

[0080] If the upper limit of condition (8) is exceeded, the scanning angle of each deflection surface will decrease, and the size of each deflection surface will also decrease. Therefore, it becomes difficult to suppress interference between the first to fourth light sources 11 to 41, and to suppress the enlargement of the first to fourth incident optical elements 13 to 43, which are integrally formed with each other. In the optical scanning device 100 according to this embodiment, the number of deflection surfaces N of the deflector 5 is 4, so condition (8) is satisfied.

[0081] Figure 3(b) shows a partially enlarged schematic perspective view of an optical scanning device 101 according to a modified example of this embodiment. The optical scanning device 101 according to a modified example of this embodiment has the same configuration as the optical scanning device 100 according to this embodiment, except that the configuration of the first to fourth incident optical systems is different. Therefore, the same reference numerals are used for the same components, and their descriptions are omitted.

[0082] Specifically, in the optical scanning device 101 according to a modified example of this embodiment, first, second, third, and fourth collimator lenses 135, 235, 335, and 435, first and second prisms 236 and 436, and first and second cylinder lenses 337 and 338 are provided. In other words, in the optical scanning device 101 according to a modified example of this embodiment, the first light guide is formed by the first collimator lens 135 and the first cylinder lens 337. Furthermore, a second light guide is formed by the second collimator lens 235, the first prism 236, and the second cylinder lens 338, while a third light guide is formed by the third collimator lens 335 and the first cylinder lens 337.

[0083] Furthermore, a fourth light guide is formed by a fourth collimator lens 435, a second prism 436, and a second cylinder lens 338. The first and second cylinder lenses 337 and 338 are integrally formed with each other as a compound eye optical element.

[0084] The first to fourth collimator lenses 135 to 435 each have an optical surface that is rotationally symmetric with respect to the optical axis. The first to fourth collimator lenses 135 to 435 each convert the first and fourth light beams, which are emitted from the first to fourth light sources 11 to 41 and have passed through the first to fourth apertures 12 to 42, into parallel light beams within the main scanning cross-section.

[0085] The first and second prisms 236 and 436 reflect the light beams of the second and fourth light beams that have passed through the second and fourth collimator lenses 235 and 435, respectively, in a manner that bends their optical paths, and then guide the light to the second cylinder lens 338. On the other hand, the first and third light beams that have passed through the first and third collimator lenses 135 and 335 proceed to the first cylinder lens 337 without passing through optical elements such as the first and second prisms 236 and 436.

[0086] Furthermore, the first and second cylinder lenses 337 and 338 each possess power within the sub-scanning cross-section. The first cylinder lens 337 then guides the first and third light beams that have passed through the first and third collimator lenses 135 and 335 to the first and second deflection surfaces 5a and 5b of the deflector 5, respectively, while focusing them within the sub-scan cross-section. Furthermore, the second cylinder lens 338 guides the second and fourth light beams that have passed through the first and second prisms 236 and 436 to the first and second deflection surfaces 5a and 5b of the deflector 5, respectively, while focusing them within the sub-scanning cross-section.

[0087] In the modified optical scanning device 101 of this embodiment, instead of adjusting the position of each of the first to fourth light sources 11 to 41 by gripping them with a jig, the position of each of the first to fourth collimator lenses 135 to 435 can be adjusted by gripping them with a jig from above and below in the sub-scanning direction. In other words, in the modified optical scanning device 101 of this embodiment, all of the first to fourth collimator lenses 135 to 435 can be simultaneously gripped and their positions adjusted using a jig. This makes it easy to adjust the relative position between the first to fourth light sources 11 to 41 and the first to fourth collimator lenses 135 to 435.

[0088] In another modified optical scanning device according to this embodiment, the first and third collimator lenses 135 and 335 and the first cylindrical lens 337 may be integrally formed with each other as anamorphic optical elements having a spherical incident surface and a cylindrical exit surface. Furthermore, in the optical scanning device, the second and fourth collimator lenses 235 and 435, the first and second prisms 236 and 436, and the second cylinder lens 338 may be integrally formed with each other. In this case, a composite anamorphic optical element is formed, which is a prism having a spherical incident surface and a cylindrical exit surface.

[0089] As described above, in the optical scanning apparatus 100 according to this embodiment, the configurations of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems are optimized so that the first to fourth light sources 11 to 41 do not overlap with each other when projected into the main scanning cross-section. This allows the position of each of the first to fourth light sources 11 to 41 to be easily adjusted by gripping them with a jig from above and below in the sub-scanning direction, thus enabling simple adjustment of the relative position between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0090] Furthermore, in the optical scanning device 100 according to this embodiment, all of the first to fourth light sources 11 to 41 can be simultaneously grasped and their positions adjusted using a jig, thus reducing the time required to assemble and adjust the optical scanning device 100 according to this embodiment. Furthermore, the number of parts required to assemble and adjust the optical scanning device 100 according to this embodiment can be reduced, as can the man-hours required for such assembly and adjustment.

[0091] In addition, in the optical scanning device 100 according to this embodiment, the first to fourth light sources 11 to 41 are appropriately arranged as described above, so that the first to fourth light sources 11 to 41 can be driven to emit light by a common drive circuit board. This makes it possible to miniaturize and reduce the cost of the optical scanning device 100 according to this embodiment.

[0092] Therefore, by providing first to fourth light sources 11 to 41 and first to fourth incident optical systems, it is possible to provide an optical scanning device 100 that is cost-effective, compact, and lightweight, in order to facilitate arrangement adjustment and assembly when installed in a small space. Ultimately, this makes it possible to provide a compact optical scanning device 100 suitable for high-quality image recording, and an image forming apparatus equipped with the optical scanning device 100.

[0093] [Second Embodiment] Figures 5(a) and (b) show a partially schematic unfolded view of the main scanning cross section of the optical scanning apparatus 200 according to the second embodiment. Figure 6 shows a partially schematic sub-scanning cross-sectional view of the optical scanning apparatus 200 according to the second embodiment. Since the optical scanning device 200 according to this embodiment has the same configuration as the optical scanning device 100 according to the first embodiment, except that the shapes of the first to fourth incident optical elements 13 to 43 are different, the same reference numerals are used for the same components and their descriptions are omitted.

[0094] Furthermore, the specifications of the optical scanning device 200 according to this embodiment are shown in Table 6 below. Furthermore, the arrangement of the first incident optical system and the first imaging optical system provided in the optical scanning device 200 according to this embodiment is shown in Table 7 below, and the arrangement of the second incident optical system and the second imaging optical system is shown in Table 8 below.

[0095] Furthermore, the shapes of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 200 according to this embodiment are shown in Table 9 below. Furthermore, Table 10 below shows the shapes of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the second scanning imaging elements 162 to 462, respectively, which are provided in the optical scanning device 200 according to this embodiment.

[0096] [Table 6] [Table 7] [Table 8] [Table 9] [Table 10]

[0097] Note that in Tables 9 and 10, "EX" is 10 -X It means that.

[0098] Furthermore, the arrangement of the third incident optical system provided in the optical scanning device 200 according to this embodiment can be changed by transforming the values ​​shown in Table 8 so that they are 180 degrees rotationally symmetric with respect to a straight line parallel to the Y direction passing through the origin. Furthermore, the arrangement of the fourth incident optical system provided in the optical scanning device 200 according to this embodiment can be changed by transforming the values ​​shown in Table 7 so that they are 180 degrees rotationally symmetric with respect to a straight line parallel to the Y direction passing through the origin. Furthermore, the arrangement of the third and fourth imaging optical systems provided in the optical scanning device 200 according to this embodiment can be modified by converting the values ​​shown in Tables 7 and 8 so that they are symmetrical with respect to a plane that includes the rotation axis 55 of the deflector 5 and is parallel to the Y and Z directions.

[0099] The shape (generatrix shape) of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 200 according to this embodiment within the main scanning cross-section is represented by the above formula (1). Furthermore, the shapes of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the incident and exit surfaces of the second scanning imaging elements 162 to 462, respectively, within the main scanning cross-section, are also represented by the above formula (1).

[0100] Furthermore, the shapes (sub-line shapes) within the sub-scanning cross-sections of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 200 according to this embodiment are represented by the above equations (2) and (3). Furthermore, the shapes within the sub-scan cross-section of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the incident and exit surfaces of the second scanning imaging elements 162 to 462, which are provided in the optical scanning device 200 according to this embodiment, are also represented by the above equations (2) and (3).

[0101] Figure 7 shows a partially enlarged schematic perspective view of the optical scanning device 200 according to this embodiment. As shown in Figure 7, in the optical scanning device 200 according to this embodiment, the first and second incident optical elements 13 and 23 are integrally formed with each other as the first compound eye optical element.

[0102] Furthermore, the third and fourth incident optical elements 33 and 43 are integrally formed with each other as a second compound eye optical element. The first and second compound eye optical elements have the same shape as each other, but are arranged to be 180 degrees rotationally symmetrical with respect to a line parallel to the Y direction passing through the origin.

[0103] The incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 each have a spherical shape that is rotationally symmetric with respect to the optical axis. As a result, the first to fourth light beams incident on the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are converted into parallel light beams in both the main scanning cross-section and the sub-scanning cross-section. Furthermore, the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 may each have an aspherical shape, not limited to those described above.

[0104] Furthermore, the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 are each anamorphic surfaces that have power within the sub-scanning cross-section, i.e., they have a cylindrical shape. The exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 each converge the parallel light beams from the incident surfaces 131 to 431 within the sub-scanning cross-section. In this way, the first to fourth luminous beams are focused within the sub-scanning cross-section by the respective emission surfaces 134 to 434, thereby forming line images in the vicinity of the first and second deflection surfaces 5a and 5b of the deflector 5.

[0105] As shown in Figure 7, the first incident optical element 13 has first and second reflective surfaces 132 and 133, and the fourth incident optical element 43 has first and second reflective surfaces 432 and 433. In other words, in the first incident optical element 13, the first light beam incident from the incident surface 131 is reflected by the first and second reflective surfaces 132 and 133, respectively, and then exits from the exit surface 134. Furthermore, in the fourth incident optical element 43, the fourth light beam incident from the incident surface 431 is reflected by the first and second reflective surfaces 432 and 433, respectively, and then exits from the exit surface 434.

[0106] In other words, in the optical scanning device 200 according to this embodiment, the optical paths of the second and third light beams (first and third light beams) in the second and third incident optical elements 23 and 33, respectively, are straight lines. On the other hand, the optical paths of the first and fourth light beams (second and fourth light beams) in the first and fourth incident optical elements 13 and 43, respectively, are not straight lines. It is preferable that the first and second reflective surfaces 132 and 133 provided on the first incident optical element 13, and the first and second reflective surfaces 432 and 433 provided on the fourth incident optical element 43, are all reflective surfaces.

[0107] Furthermore, as shown in Figure 7, in the optical scanning device 200 according to this embodiment, the principal rays of the first and second light beams immediately before they enter the first deflection surface 5a of the deflector 5 are each located in a predetermined plane 58 parallel to the sub-scanning direction. In other words, in the optical scanning device 200 according to this embodiment, the first and second light beams emitted from the first and second light sources 11 and 21 are incident on the first deflection surface 5a of the deflector 5 by the first and second incident optical systems.

[0108] Furthermore, the principal rays of the third and fourth luminous beams immediately before they enter the second deflection surface 5b of the deflector 5 are each located within a predetermined plane 59 parallel to the sub-scanning direction. In other words, in the optical scanning device 200 according to this embodiment, the third and fourth light beams emitted from the third and fourth light sources 31 and 41 are incident on the second deflection surface 5b of the deflector 5 by the third and fourth incident optical systems.

[0109] Furthermore, as shown in Figure 7, in the optical scanning device 200 according to this embodiment, the straight line passing through the center of the light-emitting surfaces of the first and second light sources 11 and 21 is in a twisted relationship with respect to the rotation axis 55 of the deflector 5, that is, it is non-parallel to the sub-scanning direction. Furthermore, the straight lines passing through the centers of the light-emitting surfaces of the third and fourth light sources 31 and 41 are also in a twisted relationship with respect to the rotation axis 55 of the deflector 5, that is, they are not parallel to the sub-scanning direction.

[0110] On the other hand, the straight lines passing through the centers of the light-emitting surfaces of the first and second light sources 11 and 21, respectively, and the straight lines passing through the centers of the light-emitting surfaces of the third and fourth light sources 31 and 41, respectively, are parallel to each other. In other words, the signs of the angles that the lines passing through the centers of the light-emitting surfaces of the first and second light sources 11 and 21 make with respect to the sub-scanning direction are the same for both the lines passing through the centers of the light-emitting surfaces of the third and fourth light sources 31 and 41. Since the centers of the light-emitting surfaces of the first to fourth light sources 11 to 41 are positioned on a predetermined plane, the first to fourth light sources 11 to 41 are each driven to emit light by a common light-emitting substrate (not shown).

[0111] Furthermore, as shown in Figures 5(a) and (b), in the optical scanning device 200 according to this embodiment, the optical path lengths from the center of the light-emitting surfaces of the first to fourth light sources 11 to 41 to the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are the same for all of them. Furthermore, the optical path lengths from the exit surfaces 134 and 234 of the first and second incident optical elements 13 and 23 to the on-axial deflection point of the first deflection surface 5a, and the optical path lengths from the exit surfaces 334 and 434 of the third and fourth incident optical elements 33 and 43 to the on-axial deflection point of the second deflection surface 5b are all the same.

[0112] Furthermore, the optical path lengths in the first and fourth incident optical elements 13 and 43 are the same, and the optical path lengths in the second and third incident optical elements 23 and 33 are also the same. On the other hand, the optical path lengths in the first and fourth incident optical elements 13 and 43 are different from those in the second and third incident optical elements 23 and 33, with the latter being smaller than the former.

[0113] Therefore, the optical path lengths from the center of the light-emitting surfaces of the first and fourth light sources 11 and 41 to the on-axial deflection points of the first and second deflection surfaces 5a and 5b of the deflector 5 are the same. Furthermore, the optical path lengths from the center of the light-emitting surfaces of the second and third light sources 21 and 31 to the on-axial deflection points of the first and second deflection surfaces 5a and 5b of the deflector 5 are the same. On the other hand, the optical path lengths from the center of the light-emitting surfaces of the first and second light sources 11 and 21 to the on-axial deflection point of the first deflection surface 5a of the deflector 5 are different from each other. Furthermore, the optical path lengths from the center of the light-emitting surfaces of the third and fourth light sources 31 and 41 to the on-axial deflection point of the second deflection surface 5b of the deflector 5 are different from each other.

[0114] Furthermore, as shown in Figure 7, in the optical scanning device 200 according to this embodiment, the first and second light sources 11 and 21 are arranged at different positions within the main scanning cross-section, and the third and fourth light sources 31 and 41 are also arranged at different positions. This optimizes the arrangement of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems.

[0115] In other words, each of the first to fourth light sources 11 to 41 can be easily gripped by a jig from above and below in the sub-scanning direction. This makes it possible to easily adjust the relative position between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0116] Furthermore, in the optical scanning device 200 according to this embodiment, all of the first to fourth light sources 11 to 41 can be simultaneously grasped and their positions adjusted using a jig, thus reducing the time required to assemble and adjust the optical scanning device 200 according to this embodiment. Furthermore, the number of parts required to assemble and adjust the optical scanning device 200 according to this embodiment can be reduced, as can the man-hours required for such assembly and adjustment.

[0117] Furthermore, in the optical scanning device 200 according to this embodiment, |φ1|=|φ2|=42.2°, so conditions (4), (4a), (5), and (5a) are satisfied. Furthermore, in the optical scanning device 200 according to this embodiment, |α1|, |α2|, |α3|, and |α4| are each 90°, so conditions (6) and (7) are satisfied. Furthermore, in the optical scanning device 200 according to this embodiment, N is 4, so condition (8) is satisfied.

[0118] As described above, in the optical scanning apparatus 200 according to this embodiment, the configurations of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems are optimized so that the first to fourth light sources 11 to 41 do not overlap with each other when projected into the main scanning cross-section. This allows the position of each of the first to fourth light sources 11 to 41 to be easily adjusted by gripping them with a jig from above and below in the sub-scanning direction, thus enabling simple adjustment of the relative position between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0119] Furthermore, in the optical scanning device 200 according to this embodiment, all of the first to fourth light sources 11 to 41 can be simultaneously grasped and their positions adjusted using a jig, thus reducing the time required to assemble and adjust the optical scanning device 200 according to this embodiment. Furthermore, the number of parts required to assemble and adjust the optical scanning device 200 according to this embodiment can be reduced, as can the man-hours required for such assembly and adjustment.

[0120] In addition, in the optical scanning device 200 according to this embodiment, the first to fourth light sources 11 to 41 are appropriately arranged as described above, so that the first to fourth light sources 11 to 41 can be driven to emit light by a common drive circuit board. This makes it possible to miniaturize and reduce the cost of the optical scanning device 200 according to this embodiment.

[0121] Therefore, by providing first to fourth light sources 11 to 41 and first to fourth incident optical systems, it is possible to provide an optical scanning device 200 that is cost-effective, compact, and lightweight, in order to facilitate arrangement adjustment and assembly when installed in a small space. Ultimately, this makes it possible to provide a compact optical scanning device 200 suitable for high-quality image recording, and an image forming apparatus equipped with the optical scanning device 200.

[0122] [Third Embodiment] Figures 8(a) and (b) show a partially schematic unfolded view of the main scanning cross section of the optical scanning device 300 according to the third embodiment. Figure 9 shows a partially schematic sub-scanning cross-sectional view of the optical scanning apparatus 300 according to the third embodiment.

[0123] In this embodiment, the optical scanning device 300 is provided with first and second deflectors 51 and 52 instead of the deflector 5, compared to the optical scanning device 100 according to the first embodiment. Furthermore, in the optical scanning device 300 according to this embodiment, the shapes of the first to fourth incident optical elements 13 to 43 are different from those of the optical scanning device 100 according to the first embodiment, and the arrangement of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems is also different. The other configurations of the optical scanning device 300 according to this embodiment are the same as those of the optical scanning device 100 according to the first embodiment; therefore, the same reference numerals are used for the same components, and their descriptions are omitted.

[0124] Specifically, in the optical scanning device 300 according to this embodiment, first and second deflectors 51 and 52 are provided, which are arranged in the sub-scanning direction so as to be positioned at the same location when projected within the main scanning cross-section, and which rotate around a common rotation axis 55. The first and second luminous beams emitted from the first and second light sources 11 and 21 are then incident on the first deflection surfaces 51a and 52a of the first and second deflectors 51 and 52, respectively, by the first and second incident optical systems (Figure 10).

[0125] Furthermore, the third and fourth luminous beams emitted from the third and fourth light sources 31 and 41 are incident on the second deflection surfaces 51b and 52b of the first and second deflectors 51 and 52, respectively, by the third and fourth incident optical systems (Figure 10). In the optical scanning device 300 according to this embodiment, the first and third light beams emitted from the first and third light sources 11 and 31 are incident on the first and second deflection surfaces 51a and 51b of the first deflector 51 parallel to the main scanning cross-section by the first and third incident optical systems, respectively. Furthermore, in the optical scanning device 300 according to this embodiment, the second and fourth light beams emitted from the second and fourth light sources 21 and 41 are incident on the first and second deflection surfaces 52a and 52b of the second deflector 52 parallel to the main scanning cross-section by the second and fourth incident optical systems, respectively.

[0126] The first and second light beams, deflected by the first deflection surfaces 51a and 52a of the first and second deflectors 51 and 52, are then guided to the first and second scanning surfaces 17 and 27 by the first and second imaging optical systems. Furthermore, the third and fourth light beams deflected by the second deflection surfaces 51b and 52b of the first and second deflectors 51 and 52 are guided to the third and fourth scanning surfaces 37 and 47 by the third and fourth imaging optical systems.

[0127] Furthermore, the specifications of the optical scanning device 300 according to this embodiment are shown in Table 11 below. Furthermore, the arrangement of the first incident optical system and the first imaging optical system provided in the optical scanning device 300 according to this embodiment is shown in Table 12 below, and the arrangement of the second incident optical system and the second imaging optical system is shown in Table 13 below.

[0128] Furthermore, the shapes of the incident surfaces 131 to 431 and the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 300 according to this embodiment are shown in Table 14 below. Furthermore, the shapes of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the second scanning imaging elements 162 to 462, respectively, provided in the optical scanning device 300 according to this embodiment are shown in Table 15 below.

[0129] [Table 11]

[0130] [Table 12]

[0131] [Table 13]

[0132] [Table 14]

[0133] [Table 15]

[0134] Note that in Tables 14 and 15, "EX" is 10 -X It means that.

[0135] Furthermore, the arrangement of the third incident optical system and the third imaging optical system provided in the optical scanning device 300 according to this embodiment can be changed so that the values ​​in Table 12 are symmetrical with respect to a plane that includes the rotation axes 55 of the first and second deflectors 51 and 52 and is parallel to the Y and Z directions. Similarly, the arrangement of the fourth incident optical system and the fourth imaging optical system provided in the optical scanning device 300 according to this embodiment can be changed so that the values ​​in Table 13 are symmetrical with respect to a plane that includes the rotation axes 55 of the first and second deflectors 51 and 52 and is parallel to the Y and Z directions.

[0136] The incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 300 according to this embodiment each have an aspherical shape that is rotationally symmetric with respect to the optical axis, as represented by the following formula (9).

number

[0137] In equation (9), h is the height in the direction perpendicular to the optical axis, R is the radius of curvature, K is the eccentricity, and C i (i=2,4,6) are the aspherical coefficients. Furthermore, the shape (generatrix shape) of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 300 according to this embodiment within the main scanning cross-section is represented by the above formula (1). Furthermore, the shapes of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the incident and exit surfaces of the second scanning imaging elements 162 to 462, respectively, within the main scanning cross-section, are also represented by the above formula (1).

[0138] Furthermore, the shapes (sub-line shapes) within the sub-scanning cross-sections of the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 provided in the optical scanning device 300 according to this embodiment are represented by the above equations (2) and (3). Furthermore, the shapes within the sub-scan cross-section of the incident and exit surfaces of the first scanning imaging elements 161 and 361 and the incident and exit surfaces of the second scanning imaging elements 162 to 462, which are provided in the optical scanning device 300 according to this embodiment, are also represented by the above equations (2) and (3).

[0139] Figure 10 shows a partially enlarged schematic perspective view of the optical scanning device 300 according to this embodiment. As shown in Figure 10, in the optical scanning device 300 according to this embodiment, the first to fourth incident optical elements 13 to 43 are integrally formed with each other as a compound eye optical element.

[0140] Furthermore, the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 each have an aspherical shape that is rotationally symmetric with respect to the optical axis. As a result, the first to fourth light beams incident on the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are converted into parallel light beams in both the main scanning cross-section and the sub-scanning cross-section.

[0141] Furthermore, the exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 are each anamorphic surfaces that have power within the sub-scanning cross-section, i.e., they have a cylindrical shape. The exit surfaces 134 to 434 of the first to fourth incident optical elements 13 to 43 each converge the parallel light beams from the incident surfaces 131 to 431 within the sub-scanning cross-section.

[0142] In this way, the first and second light beams are focused within the sub-scanning cross-section by the exit surfaces 134 and 234 of the first and second incident optical elements 13 and 23, so that line images are formed near the first deflection surfaces 51a and 52a of the first and second deflectors 51 and 52. Furthermore, the third and fourth light beams are focused within the sub-scanning cross-section by the exit surfaces 334 and 434 of the third and fourth incident optical elements 33 and 43, respectively, so that line images are formed near the second deflection surfaces 51b and 52b of the first and second deflectors 51 and 52.

[0143] As shown in Figure 10, the second incident optical element 23 has first and second reflective surfaces 232 and 233, and the fourth incident optical element 43 has first and second reflective surfaces 432 and 433. In other words, in the second incident optical element 23, the second light beam incident from the incident surface 231 is reflected by the first and second reflective surfaces 232 and 233, respectively, and then exits from the exit surface 234. Furthermore, in the fourth incident optical element 43, the fourth light beam incident from the incident surface 431 is reflected by the first and second reflective surfaces 432 and 433, respectively, and then exits from the exit surface 434.

[0144] In other words, in the optical scanning device 300 according to this embodiment, the optical paths of the first and third light beams in the first and third incident optical elements 13 and 33, respectively, are linear. On the other hand, the optical paths of the second and fourth light beams in the second and fourth incident optical elements 23 and 43, respectively, are not straight lines. Furthermore, it is preferable that the first and second reflective surfaces 232 and 233 provided on the second incident optical element 23, and the first and second reflective surfaces 432 and 433 provided on the fourth incident optical element 43, are all reflective surfaces.

[0145] As shown in Figure 10, in the optical scanning device 300 according to this embodiment, the principal rays of the first and second luminous beams immediately before they enter the first deflection surfaces 51a and 52a of the first and second deflectors 51 and 52 are each located in a predetermined plane 58 parallel to the sub-scanning direction. Furthermore, the principal rays of the third and fourth luminous beams immediately before they enter the second deflection surfaces 51b and 52b of the first and second deflectors 51 and 52 are each located within a predetermined plane 59 parallel to the sub-scanning direction.

[0146] Furthermore, as shown in Figure 10, the straight line passing through the center of the light-emitting surfaces of the first and second light sources 11 and 21 is twisted with respect to the rotation axis 55 of the first and second deflectors 51 and 52, that is, it is non-parallel to the sub-scanning direction. Furthermore, the straight line passing through the center of the light-emitting surfaces of the third and fourth light sources 31 and 41 is also in a twisted relationship with respect to the rotation axis 55 of the first and second deflectors 51 and 52, that is, it is non-parallel to the sub-scanning direction.

[0147] The center of each of the first to fourth light sources 11 to 41 is positioned on a predetermined trapezoidal corner within a predetermined plane. In other words, the signs of the angles that the lines passing through the centers of the light-emitting surfaces of the first and second light sources 11 and 21 make with respect to the sub-scanning direction are different from those of the lines passing through the centers of the light-emitting surfaces of the third and fourth light sources 31 and 41. Since the centers of the light-emitting surfaces of the first to fourth light sources 11 to 41 are positioned on the predetermined plane, the first to fourth light sources 11 to 41 are each driven to emit light by a common light-emitting substrate (not shown).

[0148] Furthermore, as shown in Figures 8(a) and (b), in the optical scanning device 300 according to this embodiment, the optical path lengths from the center of the light-emitting surfaces of the first to fourth light sources 11 to 41 to the incident surfaces 131 to 431 of the first to fourth incident optical elements 13 to 43 are the same for all of them. Furthermore, the optical path lengths from the exit surfaces 134 and 234 of the first and second incident optical elements 13 and 23 to the on-axial deflection points of the first deflection surfaces 51a and 52a are the same. Furthermore, the optical path lengths from the exit surfaces 334 and 434 of the third and fourth incident optical elements 33 and 43 to the on-axial deflection points of the second deflection surfaces 51b and 52b are the same to each other, and are also the same as the optical path lengths mentioned above.

[0149] Furthermore, the optical path lengths in the first and third incident optical elements 13 and 33 are the same, and the optical path lengths in the second and fourth incident optical elements 23 and 43 are also the same. On the other hand, the optical path lengths in the first and third incident optical elements 13 and 33 are different from those in the second and fourth incident optical elements 23 and 43, with the latter being larger than the former.

[0150] Therefore, the optical path lengths from the center of the light-emitting surfaces of the first and third light sources 11 and 31 to the on-axial deflection points of the first and second deflection surfaces 51a and 51b of the first deflector 51 are the same. Furthermore, the optical path lengths from the center of the light-emitting surfaces of the second and fourth light sources 21 and 41 to the on-axial deflection points of the first and second deflection surfaces 52a and 52b of the second deflector 52 are the same.

[0151] On the other hand, the optical path lengths from the center of the light-emitting surfaces of the first and second light sources 11 and 21 to the on-axial deflection points of the first deflection surfaces 51a and 52a of the first and second deflectors 51 and 52 are different from each other. Furthermore, the optical path lengths from the center of the light-emitting surfaces of the third and fourth light sources 31 and 41 to the on-axial deflection points of the second deflection surfaces 51b and 52b of the first and second deflectors 51 and 52 are also different from each other.

[0152] Furthermore, as shown in Figure 10, in the optical scanning device 300 according to this embodiment, the first and second light sources 11 and 21 are arranged at different positions within the main scanning cross-section, and the third and fourth light sources 31 and 41 are also arranged at different positions. This optimizes the arrangement of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems.

[0153] In other words, each of the first to fourth light sources 11 to 41 can be easily gripped by a jig from above and below in the sub-scanning direction. This makes it possible to easily adjust the relative position between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0154] Furthermore, in the optical scanning device 300 according to this embodiment, all of the first to fourth light sources 11 to 41 can be simultaneously grasped and their positions adjusted using a jig, thus reducing the time required to assemble and adjust the optical scanning device 300 according to this embodiment. Furthermore, the number of parts required to assemble and adjust the optical scanning device 300 according to this embodiment can be reduced, as can the man-hours required for such assembly and adjustment.

[0155] Furthermore, in the optical scanning device 300 according to this embodiment, |φ1|=|φ2|=45.5°, so conditions (4), (4a), (5), and (5a) are satisfied. Furthermore, in the optical scanning device 300 according to this embodiment, |α1|, |α2|, |α3|, and |α4| are each 90°, so conditions (6) and (7) are satisfied. Furthermore, in the optical scanning device 300 according to this embodiment, N is 4, so condition (8) is satisfied.

[0156] As described above, in the optical scanning apparatus 300 according to this embodiment, the configuration of the first to fourth light sources 11 to 41 and the first to fourth incident optical systems is optimized so that the first to fourth light sources 11 to 41 do not overlap with each other when projected into the main scanning cross-section. This allows the position of each of the first to fourth light sources 11 to 41 to be easily adjusted by gripping them with a jig from above and below in the sub-scanning direction, thus enabling simple adjustment of the relative position between the first to fourth light sources 11 to 41 and the first to fourth incident optical elements 13 to 43.

[0157] Furthermore, in the optical scanning device 300 according to this embodiment, all of the first to fourth light sources 11 to 41 can be simultaneously grasped and their positions adjusted using a jig, thus reducing the time required to assemble and adjust the optical scanning device 300 according to this embodiment. Furthermore, the number of parts required to assemble and adjust the optical scanning device 300 according to this embodiment can be reduced, as can the man-hours required for such assembly and adjustment.

[0158] In addition, in the optical scanning device 300 according to this embodiment, since the first to fourth light sources 11 to 41 are appropriately arranged as described above, the first to fourth light sources 11 to 41 can be driven to emit light by a common drive circuit board. This makes it possible to miniaturize and reduce the cost of the optical scanning device 300 according to this embodiment.

[0159] Therefore, by providing first to fourth light sources 11 to 41 and first to fourth incident optical systems, it is possible to provide an optical scanning device 300 that is cost-effective, compact, and lightweight, in order to facilitate arrangement adjustment and assembly when installed in a small space. Ultimately, this makes it possible to provide a compact optical scanning device 300 suitable for high-quality image recording, and an image forming apparatus equipped with the optical scanning device 300.

[0160] [Image forming apparatus] Figure 11 shows a sub-scanning cross-sectional view of the main part of an image forming apparatus 90 equipped with an optical scanning device 111 according to any of the first to third embodiments.

[0161] The image forming apparatus 90 is a tandem-type color image forming apparatus that records image information on each photosensitive drum surface, which is an image carrier, using an optical scanning device 111 according to any of the first to third embodiments. The image forming apparatus 90 comprises an optical scanning apparatus 111 according to any of the first to third embodiments, photosensitive drums (photoreceptors) 73, 74, 75, and 76 as image carriers, and developing units 65, 66, 67, and 68. The image forming apparatus 90 also includes a conveyor belt 91, a printer controller 93, and a fuser 94.

[0162] The image forming apparatus 90 receives R (red), G (green), and B (blue) color signals (code data) output from an external device 92 such as a personal computer. Next, the input color signal is converted by the printer controller 93 in the image forming apparatus 90 into image data (dot data) of C (cyan), M (magenta), Y (yellow), and K (black).

[0163] The converted image data is then input to the optical scanning device 111, and from the optical scanning device 111, modulated optical beams 69, 70, 71, and 72 are emitted according to each image data. As a result, the photosensitive surfaces of the photosensitive drums 73 to 76 are exposed by the light beams 69 to 72, respectively.

[0164] In the image forming apparatus 90, charging rollers (not shown) are provided so as to contact the surface of the photosensitive drums 73 to 76, which uniformly charge the surface of the drums. Then, the photosensitive drums 73 to 76, which have been charged by the charging roller, are irradiated with light beams 69 to 72 by the optical scanning device 111.

[0165] As described above, the light beams 69 to 72 are each modulated based on image data of each color, and an electrostatic latent image is formed on the surface of each of the photosensitive drums 73 to 76 by irradiating with the light beams 69 to 72. The formed electrostatic latent image is developed as a toner image by developing units 65 to 68, which are arranged to come into contact with the photosensitive drums 73 to 76.

[0166] The toner image developed by the developing units 65 to 68 is then transferred in multiple layers onto a sheet of paper (transfer material) (not shown) being transported on a transport belt 91 by a transfer roller (transfer unit) (not shown) positioned opposite the photosensitive drums 73 to 76. This forms a single full-color image. The paper onto which the unfixed toner image has been transferred as described above is then transported to the fuser 94 located behind the photosensitive drums 73 to 76 (on the left side in Figure 11).

[0167] The fuser 94 is formed by a fuser roller having a fuser heater (not shown) inside and a pressure roller disposed to press against the fuser roller. The paper transported from the transfer section is then heated under pressure at the contact point between the fixing roller and the pressure roller, thereby fixing the unfixed toner image on the paper.

[0168] Furthermore, a paper discharge roller (not shown) is located behind the fuser 94, and this paper discharge roller ejects the fixed paper to the outside of the image forming apparatus 90. The image forming apparatus 90 uses an optical scanning device 111 to record image signals (image information) on the photosensitive surfaces of each of the photosensitive drums 73 to 76, corresponding to the C, M, Y, and K colors, and prints color images at high speed.

[0169] As the external device 92, for example, a color image reading device equipped with a CCD sensor may be used. In this case, a color digital copier is formed by the color image reading device and the image forming apparatus 90. Although preferred embodiments have been described above, the invention is not limited to these embodiments, and various modifications and changes are possible within the scope of its essence.

[0170] This embodiment includes the following configuration. (Configuration 1) An optical scanning device comprising: a deflector having a first deflection surface that deflects first and second luminous beams from first and second light sources to scan first and second scan surfaces in the main scanning direction; and first and second light guides that guide first and second luminous beams from first and second light sources to the first deflection surface, wherein the optical path of the first luminous beam in the first light guide includes a straight line connecting the first light source and the first deflection surface, and the optical path of the second luminous beam in the second light guide does not include a straight line connecting the second light source and the first deflection surface. (Configuration 2) An optical scanning device comprising: a deflector having a first deflection surface that deflects first and second luminous beams from first and second light sources to scan first and second scan surfaces in the main scanning direction; and first and second light guides that guide first and second luminous beams from first and second light sources to the first deflection surface, wherein the optical path of the first luminous beam in the first light guide includes a straight line connecting the first light source and the first deflection surface, and the first straight line passing through the centers of the respective light-emitting surfaces of the first and second light sources is non-parallel to the sub-scanning direction. (Configuration 3) The optical scanning apparatus according to Configuration 2, characterized in that when the first angle that the first straight line makes with respect to the sub-scanning direction is φ1(°), the condition 30.0 ≤ |φ1| ≤ 60.0 is satisfied. (Configuration 4) The optical scanning device according to any one of Configurations 1 to 3, characterized in that the second light guide has first and second reflective surfaces that reflect the second light beam. (Configuration 5) The optical scanning device according to Configuration 4, characterized in that the first light guide has a first incident surface into which a first light beam from a first light source is incident and a first exit surface from which the first light beam from the first incident surface exits, and the second light guide has a second incident surface into which a second light beam from a second light source is incident and a second exit surface from which the second light beam reflected by the first and second reflective surfaces exits. (Configuration 6) The optical scanning apparatus according to Configuration 5, characterized in that the optical path length of the principal ray of the first luminous beam from the first incident surface to the first exit surface and the optical path length of the principal ray of the second luminous beam from the second incident surface to the second exit surface are different from each other. (Configuration 7) The optical scanning device according to Configuration 6, characterized in that the optical path length of the principal ray of the first luminous beam from the first light source to the first incident surface and the optical path length of the principal ray of the second luminous beam from the second light source to the second incident surface are the same. (Configuration 8) The optical scanning device according to Configuration 7, characterized in that the optical path length of the principal ray of the first luminous beam from the first emission surface to the first on-axial deflection point of the first deflection surface and the optical path length of the principal ray of the second luminous beam from the second emission surface to the first on-axial deflection point are the same. (Configuration 9) An optical scanning apparatus according to any one of Configurations 5 to 8, characterized in that the first and second incident surfaces are aspherical surfaces that are rotationally symmetric with respect to the optical axis. (Configuration 10) The optical scanning apparatus according to any one of Configurations 1 to 9, characterized in that the first and second light guide units are integral with each other. (Configuration 11) The optical scanning device according to any one of Configurations 1 to 10, wherein the deflector has a second deflection surface that deflects the third and fourth luminous beams from the third and fourth light sources to scan the third and fourth scanned surfaces in the main scanning direction, and the optical scanning device comprises third and fourth light guides that guide the third and fourth luminous beams from the third and fourth light sources to the second deflection surface, the optical path of the third luminous beam in the third light guide includes a straight line connecting the third light source and the second deflection surface, and the optical path of the fourth luminous beam in the fourth light guide does not include a straight line connecting the fourth light source and the second deflection surface. (Configuration 12) The optical scanning apparatus according to any one of Configurations 1 to 10, wherein the deflector has a second deflection surface that deflects the third and fourth luminous beams from the third and fourth light sources to scan the third and fourth scanned surfaces in the main scanning direction, and the optical scanning apparatus comprises third and fourth light guides that guide the third and fourth luminous beams from the third and fourth light sources to the second deflection surface, the optical path of the third luminous beam in the third light guide includes a straight line connecting the third light source and the second deflection surface, and the second straight line passing through the centers of the respective light-emitting surfaces of the third and fourth light sources is non-parallel to the sub-scanning direction. (Configuration 13) The optical scanning apparatus according to Configuration 12, characterized in that when the first angle made by the first straight line with respect to the sub-scanning direction is φ1(°) and the second angle made by the second straight line with respect to the sub-scanning direction is φ2(°), the conditions 30.0≦|φ1|≦60.0 and 30.0≦|φ2|≦60.0 are satisfied. (Configuration 14) The optical scanning device according to any one of Configurations 11 to 13, characterized in that the fourth light guide has third and fourth reflective surfaces that reflect the fourth light beam. (Configuration 15) The optical scanning device according to Configuration 14, wherein the third light guide has a third incident surface into which a third light beam from a third light source is incident and a third exit surface from which the third light beam from the third incident surface exits, and the fourth light guide has a fourth incident surface into which a fourth light beam from a fourth light source is incident and a fourth exit surface from which the fourth light beam reflected by the third and fourth reflecting surfaces exits, and the optical path length of the principal ray of the third light beam from the third incident surface to the third exit surface and the optical path length of the principal ray of the fourth light beam from the fourth incident surface to the fourth exit surface are different from each other. (Configuration 16) The optical scanning apparatus according to Configuration 15, characterized in that the optical path length of the principal ray of the third luminous beam from the third light source to the third incident surface is the same as the optical path length of the principal ray of the fourth luminous beam from the fourth light source to the fourth incident surface, and the optical path length of the principal ray of the third luminous beam from the third exit surface to the second on-axial deflection point of the second deflection surface is the same as the optical path length of the principal ray of the fourth luminous beam from the fourth exit surface to the second on-axial deflection point. (Configuration 17) An optical scanning device according to any one of Configurations 11 to 16, characterized in that the first to fourth light guides are integral with one another. (Configuration 18) An optical scanning device comprising: first and second deflectors having first and second deflection surfaces for deflecting first and second luminous beams from first and second light sources to scan first and second scanned surfaces in the main scanning direction; and first and second light guides for guiding first and second luminous beams from first and second light sources to the first and second deflection surfaces, wherein the first and second on-axial deflection points of the first and second deflection surfaces are on a plane parallel to the sub-scanning direction, the optical path of the first luminous beam in the first light guide includes a straight line connecting the first light source and the first deflection surface, and the optical path of the second luminous beam in the second light guide does not include a straight line connecting the second light source and the second deflection surface. (Configuration 19) An image forming apparatus comprising an optical scanning device described in any one of Configurations 1 to 18, and a developing device for developing electrostatic latent images formed on first and second scanned surfaces by the optical scanning device. (Configuration 20) An image forming apparatus comprising an optical scanning device described in any one of Configurations 1 to 18, and a controller that converts a signal output from an external device into image data and inputs it to the optical scanning device. [Explanation of Symbols]

[0171] 5 Deflector 5a First deflection surface 11, 21 First and second light sources 13, 23 First and second incident optical elements (first and second light guides) 17, 27 First and second scanned surfaces 100 Optical scanning device

Claims

1. A deflector having a first deflection surface that deflects first and second luminous beams from first and second light sources to scan first and second scanned surfaces in the main scanning direction, The system comprises first and second light guides that guide the first and second light beams from the first and second light sources to the first deflection surface, The optical path of the first light beam in the first light guide includes a straight line connecting the first light source and the first deflection surface. The optical scanning device is characterized in that the optical path of the second light beam in the second light guide does not include a straight line connecting the second light source and the first deflection surface.

2. A deflector having a first deflection surface that deflects first and second luminous beams from first and second light sources to scan first and second scanned surfaces in the main scanning direction, The system comprises first and second light guides that guide the first and second light beams from the first and second light sources to the first deflection surface, The optical path of the first light beam in the first light guide includes a straight line connecting the first light source and the first deflection surface. An optical scanning apparatus characterized in that the first straight line passing through the centers of the respective light-emitting surfaces of the first and second light sources is non-parallel to the sub-scanning direction.

3. The first angle that the first straight line makes with respect to the sub-scanning direction is φ. １ When we consider (°), 30.0≦|φ １ |≦60.0 The optical scanning apparatus according to claim 2, characterized in that it satisfies the following conditions.

4. The optical scanning apparatus according to claim 1, characterized in that the second light guide portion has first and second reflective surfaces that reflect the second light beam.

5. The first light guide portion has a first incident surface into which the first light beam from the first light source is incident, and a first exit surface from which the first light beam from the first incident surface exits. The optical scanning apparatus according to claim 4, characterized in that the second light guide has a second incident surface into which the second light beam from the second light source is incident, and a second exit surface into which the second light beam reflected by the first and second reflective surfaces is emitted.

6. The optical scanning apparatus according to claim 5, characterized in that the optical path length of the principal ray of the first luminous beam from the first incident surface to the first exit surface and the optical path length of the principal ray of the second luminous beam from the second incident surface to the second exit surface are different from each other.

7. The optical scanning apparatus according to claim 6, characterized in that the optical path length of the principal ray of the first luminous beam from the first light source to the first incident surface and the optical path length of the principal ray of the second luminous beam from the second light source to the second incident surface are the same as each other.

8. The optical scanning apparatus according to claim 7, characterized in that the optical path length of the principal ray of the first luminous beam from the first emission surface to the first on-axial deflection point of the first deflection surface and the optical path length of the principal ray of the second luminous beam from the second emission surface to the first on-axial deflection point are the same as each other.

9. The optical scanning apparatus according to claim 5, characterized in that the first and second incident surfaces are aspherical surfaces that are rotationally symmetric with respect to the optical axis.

10. The optical scanning apparatus according to claim 1, characterized in that the first and second light guides are integral with each other.

11. The deflector has a second deflection surface that deflects the third and fourth luminous beams from the third and fourth light sources to scan the third and fourth scanned surfaces in the main scanning direction. The optical scanning device includes third and fourth light guides that guide the third and fourth light beams from the third and fourth light sources to the second deflection surface. The optical path of the third light beam in the third light guide includes a straight line connecting the third light source and the second deflection surface. The optical scanning apparatus according to claim 1, characterized in that the optical path of the fourth light beam in the fourth light guide does not include a straight line connecting the fourth light source and the second deflection surface.

12. The deflector has a second deflection surface that deflects the third and fourth luminous beams from the third and fourth light sources to scan the third and fourth scanned surfaces in the main scanning direction. The optical scanning device includes third and fourth light guides that guide the third and fourth light beams from the third and fourth light sources to the second deflection surface. The optical path of the third light beam in the third light guide includes a straight line connecting the third light source and the second deflection surface. The optical scanning apparatus according to claim 2, characterized in that the second straight line passing through the center of the respective light-emitting surfaces of the third and fourth light sources is non-parallel to the sub-scanning direction.

13. The first angle that the first straight line makes with respect to the sub-scanning direction is φ. １ (°), the second angle that the second line makes with respect to the sub-scanning direction is φ ２ When we consider (°), 30.0≦|φ １ |≦60.0 30.0≦|φ ２ |≦60.0 The optical scanning apparatus according to claim 12, characterized in that it satisfies the following conditions.

14. The optical scanning apparatus according to claim 11, characterized in that the fourth light guide portion has third and fourth reflective surfaces that reflect the fourth light beam.

15. The third light guide portion has a third incident surface into which the third light beam from the third light source is incident, and a third exit surface from which the third light beam from the third incident surface exits. The fourth light guide has a fourth incident surface into which the fourth light beam from the fourth light source is incident, and a fourth exit surface into which the fourth light beam reflected by the third and fourth reflective surfaces is emitted. The optical scanning apparatus according to claim 14, characterized in that the optical path length of the principal ray of the third luminous beam from the third incident surface to the third exit surface and the optical path length of the principal ray of the fourth luminous beam from the fourth incident surface to the fourth exit surface are different from each other.

16. The optical path length of the principal ray of the third luminous beam from the third light source to the third incident surface and the optical path length of the principal ray of the fourth luminous beam from the fourth light source to the fourth incident surface are the same. The optical scanning apparatus according to claim 15, characterized in that the optical path length of the principal ray of the third luminous beam from the third emission surface to the second on-axial deflection point of the second deflection surface and the optical path length of the principal ray of the fourth luminous beam from the fourth emission surface to the second on-axial deflection point are the same as each other.

17. The optical scanning apparatus according to claim 11, characterized in that the first to fourth light guides are integral with one another.

18. First and second deflectors having first and second deflection surfaces for deflecting first and second luminous beams from first and second light sources to scan first and second scanned surfaces in the main scanning direction, The system comprises first and second light guides that guide the first and second light beams from the first and second light sources to the first and second deflection surfaces, The first and second axial deflection points of the first and second deflection surfaces are located on a plane parallel to the sub-scanning direction. The optical path of the first light beam in the first light guide includes a straight line connecting the first light source and the first deflection surface. The optical scanning device is characterized in that the optical path of the second light beam in the second light guide does not include a straight line connecting the second light source and the second deflection surface.

19. An image forming apparatus comprising an optical scanning apparatus according to any one of claims 1 to 18, and a developer for developing electrostatic latent images formed on the first and second scanned surfaces by the optical scanning apparatus.

20. An image forming apparatus comprising an optical scanning device according to any one of claims 1 to 18, and a controller that converts a signal output from an external device into image data and inputs it to the optical scanning device.

Images