JP2017102458A - Optical scanner and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical scanner which can be reduced in thickness by efficiently arranging optical components in an emission optical system from a light deflector to an object to be scanned.SOLUTION: An optical scanner 11a includes: a plurality of light sources 51 for emitting beams BM; a light deflector 52 for deflecting the beams BM emitted from the plurality of light sources 51; and a plurality of reflection mirrors 53 for reflecting the beams BM deflected by the light deflector 52 respectively and guiding the beams BM to a corresponding photoreceptor drum 13. The optical scanner is configured so that when a plane passing through the light deflector 52 is defined as a reference plane BS, two of the beams emitted from the light sources 51 are made incident on the light deflector 52 at a first deflection angle θb1 and a second deflection angle θb2 different from each other with respect to the reference surface BS, and is configured so that the number of reflection mirrors 53 corresponding to a second beam BM2 is larger than the number of reflection mirrors 53 corresponding to a first beam BM1.SELECTED DRAWING: Figure 4

Description

  The present invention relates to an optical scanning device that includes a plurality of light sources that emit beams and an optical deflector that deflects the beams emitted from the plurality of light sources, and each beam scans a plurality of scanned objects. The present invention relates to an image forming apparatus including an optical scanning device.

  Conventionally, in an image forming apparatus, an optical scanning device is used to expose a photosensitive member. In a tandem color laser beam printer, a photoconductor is scanned with a number of beams corresponding to a plurality of photoconductors, and a color image is formed by superimposing colors. As a configuration of such an optical scanning device, a system in which a single optical deflector (rotating polygonal mirror) is shared in an optical scanning unit that scans a plurality of photosensitive members is applied, and the number of optical deflectors is reduced. Therefore, the image forming apparatus is made compact (for example, see Patent Document 1).

  Further, in the configuration in which a plurality of beams are incident on the optical deflector, a method is adopted in which the incident angles of the beams incident on the optical deflector are different in order to separate the optical paths of the respective beams (for example, (See Patent Document 2).

JP 2009-251308 A JP 2011-100007 A

  By the way, in the optical scanning device that irradiates a plurality of beams such as the optical scanning device described in Patent Document 1 and the optical scanning device described in Patent Document 2, a photosensitive member corresponding to the plurality of beams by an optical component such as a folding mirror. However, the optical components must be arranged at a position corresponding to the incident angle of the beam, and a large space is required for the optical components arranged apart from each other. There is a problem that becomes difficult.

  The present invention has been made in order to solve the above-described problems, and is capable of reducing the thickness by efficiently arranging the optical components in the emission optical system from the optical deflector to the scanned body. An object is to provide a scanning device.

  An optical scanning device according to the present invention reflects a plurality of light sources that emit beams, an optical deflector that deflects beams emitted from the plurality of light sources, and a beam deflected by the optical deflector, A plurality of reflecting mirrors that lead to a corresponding scanned object, and each beam scans a plurality of scanned objects, and is orthogonal to the light incident surface of the light deflector, and the light incident surface When a plane passing through the center of the light source is used as a reference plane, two of the beams emitted from the light source have the first deflection angle and the second deflection angle different from the reference plane, respectively. The second deflection angle is set smaller than the first deflection angle, and the number of reflecting mirrors corresponding to the beam incident at the second deflection angle is the first deflection angle. From the number of reflecting mirrors corresponding to the incident beam And said that no.

  In the optical scanning device according to the present invention, the second region corresponds to the beam incident at the first deflection angle in the direction perpendicular to the reference plane, the light source corresponding to the beam incident at the second deflection angle. It is good also as a structure spaced apart from the to-be-scanned body rather than the light source to perform.

  An optical scanning device according to the present invention reflects a plurality of light sources that emit beams, an optical deflector that deflects beams emitted from the plurality of light sources, and a beam deflected by the optical deflector, A plurality of reflecting mirrors that lead to a corresponding scanned object, and each beam scans a plurality of scanned objects, and is orthogonal to the light incident surface of the light deflector, and the light incident surface When a plane passing through the center of the light source is used as a reference plane, two of the beams emitted from the light source have the first deflection angle and the second deflection angle different from the reference plane, respectively. The second deflection angle is set smaller than the first deflection angle, and the light source corresponding to the beam incident at the second deflection angle is in a direction perpendicular to the reference plane, Paired with the beam incident at the first deflection angle Than a light source for, characterized in that apart from the scanning target.

  In the optical scanning device according to the present invention, a space in the housing in which the reflecting mirror is accommodated is divided into a first region and a second region at the reference surface, and the first region is orthogonal to the reference surface. The width in the direction may be set larger than the second area, and the second area may be set on the side facing the scanning target.

  In the optical scanning device according to the present invention, any one of the reflection mirrors corresponding to the beam incident at the second deflection angle may be arranged in the first region.

  In the optical scanning device according to the present invention, after a plurality of beams incident on the optical deflector are deflected by the optical deflector, the angles formed by the incident light and the reflected light at the first reflecting mirror are compared. Then, the beam incident at the second deflection angle may have a smaller angle than the beam incident at the first deflection angle.

  An image forming apparatus according to the present invention includes the optical scanning device according to the present invention.

  According to the present invention, it is possible to reduce the thickness of the optical scanning device by efficiently arranging the optical components in the emission optical system from the optical deflector to the scanned object.

1 is a schematic side view of an image forming apparatus according to an embodiment of the present invention. It is a top view of the optical scanning device concerning Embodiment 1 of the present invention. 1 is a schematic side view of an optical scanning device according to Embodiment 1 of the present invention. It is explanatory drawing which shows the position of the reflective mirror in the optical scanning device concerning Embodiment 1 of this invention. It is explanatory drawing which shows the position of the reflective mirror in a comparative example. FIG. 10 is an explanatory diagram showing the position of a reflecting mirror in Modification 1 of the optical scanning device according to Embodiment 1. It is a top view of the optical scanning device concerning Embodiment 2 of the present invention. It is explanatory drawing which shows the position of the reflective mirror in the optical scanning device concerning Embodiment 2 of this invention. FIG. 10 is an explanatory diagram showing a position of a reflection mirror in a second modification of the optical scanning device according to the second embodiment. It is a top view of the optical scanning device concerning Embodiment 3 of the present invention. It is explanatory drawing which shows the position of the reflective mirror in the optical scanning device concerning Embodiment 3 of this invention. FIG. 10 is an explanatory diagram showing the position of a reflection mirror in Modification 3 of the optical scanning device according to Embodiment 3. FIG. 10 is an explanatory diagram showing the position of a reflecting mirror in Modification 4 of the optical scanning device according to Embodiment 3. 10 is a schematic side view of Modification 5 of the optical scanning device according to Embodiment 1. FIG.

  Hereinafter, an image forming apparatus according to an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic side view of an image forming apparatus according to an embodiment of the present invention.

  The image forming apparatus 1 has a copying function for reading an original and forming an image on a sheet. The image reading apparatus 2, an original conveying apparatus (ADF) 3 provided on the upper side of the image reading apparatus 2, and the image reading apparatus 2. The image forming unit 4, the paper feed cassette 5, and the paper discharge tray 7 provided on the lower side are provided.

  The document conveying device 3 is supported by a hinge (a fulcrum, not shown) on the back side so as to be openable and closable with respect to the image reading device 2, and is opened and closed by raising and lowering the front end. When the document conveying device 3 is opened, the upper part of the image reading device 2 is opened so that the document can be placed manually. The document conveying device 3 automatically conveys the placed document onto the image reading device 2.

  The image reading apparatus 2 is supported by the hinge (fulcrum) 42 on the back side so as to be openable and closable, and is opened and closed by moving the front end portion up and down. The image reading device 2 reads the placed document or the document conveyed from the document conveying device 3 to generate image data.

  In the image forming apparatus 1, image data corresponding to a color image using each color of black (K), cyan (C), magenta (M), and yellow (Y) or a monochrome image using a single color (for example, black). Are treated. The image forming unit 4 is provided with four developing devices 12 for forming four types of toner images, a photosensitive drum 13, a drum cleaning device 14, and four chargers 15, each of which includes black, cyan, magenta, And four image stations Pa, Pb, Pc, and Pd, which are associated with yellow and yellow.

  The drum cleaning device 14 removes and collects residual toner on the surface of the photosensitive drum 13. The charger 15 uniformly charges the surface of the photosensitive drum 13 to a predetermined potential. The optical scanning device 11 exposes the surface of the photosensitive drum 13 to form an electrostatic latent image. The developing device 12 develops the electrostatic latent image on the surface of the photosensitive drum 13 to form a toner image on the surface of the photosensitive drum 13. Through the above-described series of operations, a toner image of each color is formed on the surface of each photosensitive drum 13. The optical scanning device 11 will be described in detail with reference to FIGS. 2 and 3 to be described later.

  An intermediate transfer belt 21 is disposed on the upper side of the photosensitive drum 13. The intermediate transfer belt 21 circulates in the direction of arrow C, the residual toner is removed and collected by the belt cleaning device 25, and the toner images of the respective colors formed on the surfaces of the photosensitive drums 13 are sequentially transferred and superimposed. Thus, a color toner image is formed on the surface of the intermediate transfer belt 21.

  A nip area is formed between the transfer roller 26a of the secondary transfer device 26 and the intermediate transfer belt 21, and the sheet conveyed through the sheet conveyance path R1 is sandwiched and conveyed in the nip area. When the sheet passes through the nip area, the toner image on the surface of the intermediate transfer belt 21 is transferred and conveyed to the fixing device 17.

  The fixing device 17 includes a fixing roller 31 and a pressure roller 32 that rotate with a sheet interposed therebetween. The fixing device 17 sandwiches the recording paper on which the toner image is transferred between the fixing roller 31 and the pressure roller 32 and heats and presses the recording paper to fix the toner image on the recording paper.

  The paper feed cassette 5 is a tray for storing paper used for image formation, and is provided below the optical scanning device 11. The paper is pulled out from the paper feed cassette 5 by the pickup roller 33, transported through the paper transport path R 1, passes through the secondary transfer device 26 and the fixing device 17, and passes through the paper discharge roller 36 to the paper discharge tray 7. It is carried out. In the paper transport path R1, after the paper is temporarily stopped and the leading edges of the paper are aligned, the paper is fed in accordance with the transfer timing of the color toner image in the nip area between the intermediate transfer belt 21 and the transfer roller 26a. A registration roller 34 that starts conveyance, a conveyance roller 35 that facilitates conveyance of a sheet, and a paper discharge roller 36 are arranged.

  When image formation is performed not only on the front side but also on the back side of the paper, the paper is conveyed in the reverse direction from the paper discharge roller 36 to the reverse path Rr, so that the front and back sides of the paper are reversed and the paper is transferred to the registration roller 34 Then, the image is formed on the rear surface in the same manner as the front surface, and the paper is carried out to the paper discharge tray 7.

  Next, the configuration of the optical scanning device according to the first embodiment of the present invention will be described with reference to the drawings.

  2 is a top view of the optical scanning device according to the first embodiment of the present invention, and FIG. 3 is a schematic side view of the optical scanning device according to the first embodiment of the present invention. In FIG. 3, the collimator 61, the guide mirror 62, and the cylindrical lens 63 are omitted for easy viewing.

  The optical scanning device 11a according to Embodiment 1 of the present invention includes a plurality of light sources 51 that emit beams BM and an optical deflector 52 that deflects the beams BM emitted from the plurality of light sources 51, respectively. Beam BM scans a plurality of scanning objects (for example, the photosensitive drum 13). The optical scanning device 11a further reflects a beam BM deflected by the optical deflector 52 and guides it to the corresponding photosensitive drum 13, and a drive unit 55 that rotates the optical deflector 52. It has.

  Specifically, in the present embodiment, it is configured to include four light sources 51. In the following, in order to distinguish each, a first light source 51a, a second light source 51b, a third light source 51c, and a fourth light source These may be referred to as the light source 51 together. In order to distinguish the beam BM emitted from each light source 51, the beam BM emitted from the first light source 51a is called a first beam BM1, and the beam BM emitted from the second light source 51b is called a second beam BM2. The beam BM emitted from the third light source 51c is called a third beam BM3, the beam BM emitted from the fourth light source 51d is called a fourth beam BM4, and these may be collectively called a beam BM. . Further, in order to distinguish the plurality of reflection mirrors 53, the reflection mirror 53 that guides the first beam BM1 is called a first reflection mirror 53a, the reflection mirror 53 that guides the second beam BM2 is called a second reflection mirror 53b, and a third The reflection mirror 53 that guides the beam BM3 may be referred to as a third reflection mirror 53c, the reflection mirror 53 that guides the fourth beam BM4 may be referred to as a fourth reflection mirror 53d, and these may be collectively referred to as the reflection mirror 53.

  The optical scanning device 11a according to the first embodiment of the present invention includes a light source 51, a collimator 61, a guide mirror 62, a cylindrical lens 63, and a light deflection from upstream to downstream in the traveling direction of the beam BM irradiated from the light source 51. And an optical scanning system in which a device 52, a first lens (hereinafter referred to as an fθ lens 56), a reflecting mirror 53, and an auxiliary mirror (first auxiliary mirror 54a or second auxiliary mirror 54b) are arranged in this order. Has been.

  The light source 51 is, for example, a laser diode. A cross section (beam cross section) perpendicular to the optical axis in the beam BM emitted from the light source 51 is circular. The collimator 61 is an optical component that shapes the conical beam BM emitted so as to diffuse from the light source 51 into a parallel beam BM. The guide mirror 62 is an optical component that guides the beam BM emitted from the light source 51 toward the optical deflector 52. It should be noted that any one of the first beam BM1, the second beam BM2, the third beam BM3, and the fourth beam BM4 to be guided by the guide mirror 62 may be appropriately selected. What is necessary is just to change suitably according to arrangement | positioning of 51. FIG. The cylindrical lens 63 is an optical component for converging the beam BM on the deflection surface 52a of the optical deflector 52.

  The optical deflector 52 is a polygon mirror (rotating polygonal mirror) that is disposed in the approximate center of the optical scanning device 11a in a top view (see FIG. 2) and has a plurality of deflecting surfaces 52a formed thereon. It is rotationally driven around 55a. In the present embodiment, the optical deflector 52 includes four deflecting surfaces 52a and has a quadrangular shape when viewed from above, but is not limited thereto, and has a polygonal shape including a plurality of deflecting surfaces 52a. Just do it. Hereinafter, for simplification of description, the direction parallel to the rotation axis 55a is referred to as the rotation axis direction Z, and the side on which the drive unit 55 is disposed is referred to as the lower side with respect to the optical deflector 52 in the rotation axis direction Z. The opposite side of the drive unit 55 is referred to as the upper side. That is, the drive unit 55 is disposed below the optical deflector 52.

  In the present embodiment, the optical scanning device 11a has the photosensitive drum 13 disposed above and the upper surface thereof is open. The beam BM deflected by the optical deflector 52 is guided upward by the reflection mirror 53 and the auxiliary mirror, and irradiated to the corresponding photosensitive drum 13. Specifically, the four photosensitive drums 13 are arranged at a constant distance in the sub-scanning direction X, and each surface is scanned along the main scanning direction Y orthogonal to the sub-scanning direction X. .

  The first lens is an fθ lens 56 that converges the beam BM deflected by the optical deflector 52 onto the surface of the photosensitive drum 13. In the present embodiment, two fθ lenses 56 (a first fθ lens 56a and a second fθ lens 56b) are provided, and are arranged symmetrically about the optical deflector 52 in the sub-scanning direction X. The optical scanning device 11a is configured such that the beam BM is simultaneously incident on a plurality of deflection surfaces 52a. The first beam BM1 and the second beam BM2 are incident on the same deflection surface 52a, and one fθ lens 56 ( The light is deflected to the side on which the first fθ lens 56a) is disposed (left side of the optical deflector 52 in FIG. 2). Further, the third beam BM3 and the fourth beam BM4 are surfaces different from the deflection surface 52a on which the first beam BM1 and the second beam BM2 are incident, and are incident on the same deflection surface 52a and the other fθ. The light is deflected to the side where the lens 56 (second fθ lens 56b) is disposed (on the right side of the optical deflector 52 in FIG. 2).

  The reflection mirror 53, the first auxiliary mirror 54a, and the second auxiliary mirror 54b are optical components that reflect the beam BM. In this specification, the mirror that first reflects the beam BM deflected by the optical deflector 52 is referred to as a reflection mirror 53, and the mirror that reflects the second and subsequent times is an auxiliary mirror (the first auxiliary mirror 54a and the second auxiliary mirror). Called mirror 54b). Specifically, the first auxiliary mirror 54a guides the second beam BM2 reflected by the second reflection mirror 53b to the photosensitive drum 13, and the second auxiliary mirror 54b is reflected by the fourth reflection mirror 53d. The 4-beam BM4 is guided to the photosensitive drum 13. The first reflecting mirror 53a, the second reflecting mirror 53b, and the first auxiliary mirror 54a are arranged on the side where the first fθ lens 56a is arranged with respect to the optical deflector 52 (left side in FIG. 2). . The third reflection mirror 53c, the fourth reflection mirror 53d, and the second auxiliary mirror 54b are disposed on the side (the right side in FIG. 2) where the second fθ lens 56b is disposed with respect to the optical deflector 52. . A specific positional relationship between the reflection mirror 53 and the auxiliary mirror will be described with reference to FIG. 4 described later.

  In this embodiment, the beam BM deflected by the optical deflector 52 is reflected once or twice. However, the present invention is not limited to this, and the number of auxiliary mirrors may be increased and reflected three times or more. Good. In other words, by appropriately adjusting the number of auxiliary mirrors, the number of times the beam BM is reflected can be adjusted, and the direction and position for guiding the beam BM can be adjusted as appropriate.

  As described above, the optical scanning device 11a is configured to include two optical scanning systems arranged symmetrically around the optical deflector 52 in the sub-scanning direction X, and each optical scanning system includes two optical scanning systems. A light source 51 is provided. That is, one optical scanning system includes a first light source 51a, a second light source 51b, an optical deflector 52, a first fθ lens 56a, a first reflection mirror 53a, a second reflection mirror 53b, and a first auxiliary mirror 54a. The first beam BM1 and the second beam BM2 are scanned. The other optical scanning system includes a third light source 51c, a fourth light source 51d, an optical deflector 52, a second fθ lens 56b, a third reflecting mirror 53c, a fourth reflecting mirror 53d, and a second auxiliary mirror 54b. The third beam BM3 and the fourth beam BM4 are scanned. The collimator 61, the guide mirror 62, and the cylindrical lens 63 may be appropriately provided according to the arrangement of the light source 51. In the two optical scanning systems, the same optical deflector 52 is used. The beam BM irradiated from each optical scanning system is incident on different deflection surfaces 52a and dispersed in different directions, thereby reflecting mirrors. The structure is such that optical parts such as 53 are not crowded.

  Next, the positional relationship of the optical components in each optical scanning system will be described with reference to FIGS.

  FIG. 4 is an explanatory view showing the position of the reflection mirror in the optical scanning device according to Embodiment 1 of the present invention, and FIG. 5 is an explanatory view showing the position of the reflection mirror in the comparative example. In FIGS. 4 and 5, the guide mirror 62 is omitted in view of easy viewing. Further, in order to show the first incident angle θa1 and the second incident angle θa2, an auxiliary line parallel to the reference plane BS is drawn.

  FIG. 4 shows the optical path of the beam BM (first beam BM1 and second beam BM2) of the optical scanning system having the first light source 51a and the second light source 51b extracted from FIG. Note that the optical scanning system having the third light source 51c and the fourth light source 51d has the same arrangement as the optical scanning system having the first light source 51a and the second light source 51b in the rotation axis direction Z, and thus the description thereof is omitted. To do. That is, in the optical scanning system having the third light source 51c and the fourth light source 51d, in FIG. 4, the first light source 51a is the third light source 51c, the second light source 51b is the fourth light source 51d, and the first beam BM1 is the first. The third beam BM3, the second beam BM2 to the fourth beam BM4, the first fθ lens 56a to the second fθ lens 56b, the first reflection mirror 53a to the third reflection mirror 53c, and the second reflection mirror 53b to the fourth reflection mirror The first auxiliary mirror 54a corresponds to the second auxiliary mirror 54b. Therefore, the optical scanning system having the third light source 51c and the fourth light source 51d has the same function as the optical scanning system having the first light source 51a and the second light source 51b.

  In the present embodiment, when a plane orthogonal to the rotation axis direction Z and passing through the optical deflector 52 is used as the reference plane BS, the space in the housing in which the drive unit 55 and the reflection mirror 53 are accommodated is rotated by the reference plane BS. The drive unit 55 is arranged in the first area AR1 and is divided into the first area AR1 and the second area AR2 in the axial direction Z. That is, the space below the optical deflector 52 is the first area AR1, and the space above the optical deflector 52 is the second area AR2. In the first area AR1, the width in the rotation axis direction Z (first area width ZL1) is set larger than the width in the rotation axis direction Z of the second area AR2 (second area width ZL2).

  The first light source 51a is disposed in the second area AR2, and the second light source 51b is disposed in the first area AR1. Further, the guide mirror 62 is arranged so that the traveling direction of the beam BM is not changed in the rotation axis direction Z. That is, the beam BM emitted from the light source 51 travels in parallel with the reference surface BS, is tilted with respect to the reference surface BS by the cylindrical lens 63, and travels in the direction toward the optical deflector 52. Be changed.

  The first reflection mirror 53a and the first auxiliary mirror 54a are arranged in the first area AR1, and the second reflection mirror 53b is arranged in the second area AR2. The position of the first fθ lens 56a in the rotation axis direction Z is not particularly limited as long as it is disposed on the optical path of the first beam BM1 and the second beam BM2. The position where the first auxiliary mirror 54a is disposed is not particularly limited, and may be disposed in the second area AR2.

  Hereinafter, for simplification of explanation, the angle at which the first beam BM1 is incident on the optical deflector 52 with respect to the angle at which the beam BM is inclined in the rotation axis direction Z with respect to the reference plane BS is referred to as the first deflection angle θb1. The angle at which the second beam BM2 is incident on the optical deflector 52 is referred to as a second deflection angle θb2, and the angle at which the first beam BM1 is incident on the first reflecting mirror 53a is referred to as a first incident angle θa1. The angle at which the second beam BM2 enters the second reflecting mirror 53b is referred to as a second incident angle θa2.

  Specifically, the first beam BM1 is incident on the deflection surface 52a from above at the first deflection angle θb1. The second beam BM2 is incident on the deflection surface 52a from below at the second deflection angle θb2. Since the first beam BM1 and the second beam BM2 are not deflected in the rotation axis direction Z by the deflection surface 52a and the first fθ lens 56a, they further proceed while maintaining the first deflection angle θb1 and the second deflection angle θb2. The first beam BM1 incident on the optical deflector 52 from above (second region AR2) travels below (first region AR1) after passing the optical deflector 52, and has a first incident angle equal to the first deflection angle θb1. The light enters the first reflection mirror 53a at θa1 and is guided to the photosensitive drum 13. The second beam BM2 that has entered the optical deflector 52 from below (first region AR1) travels upward (second region AR2) after passing the optical deflector 52, and is equal to the second deflection angle θb2. The light enters the second reflecting mirror 53b at an incident angle θa2 and is guided to the photosensitive drum 13 through the first auxiliary mirror 54a.

  In the present embodiment, the first deflection angle θb1 is set larger than the second deflection angle θb2, and the first incident angle θa1 is set larger than the second incident angle θa2. It is necessary to increase the distance to the one reflecting mirror 53a. By the way, since the drive part 55 is arrange | positioned in 1st area | region AR1 and 1st area | region width | variety ZL1 is designed large, sufficient space for arrange | positioning the 1st reflective mirror 53a is ensured. Further, by setting the second incident angle θa2 to be smaller than the first incident angle θa1, the distance from the reference surface BS to the second reflecting mirror 53b can be reduced, and the second region with respect to the first region width ZL1. The width ZL2 can be reduced.

  In addition, it is desirable that the second reflection mirror 53b is disposed at a position closer to the optical deflector 52 than the first reflection mirror 53a. That is, by shortening the distance from the optical deflector 52 to the second reflecting mirror 53b, the distance from the reference surface BS to the second reflecting mirror 53b can be further shortened, and the optical scanning device 11a can be easily thinned. can do.

  FIG. 5 shows an optical path of the beam BM of the conventional optical scanning device 100 as a comparative example. The comparative example has substantially the same configuration as the present embodiment, but the relationship between the first deflection angle θb1, the second deflection angle θb2, the first incident angle θa1, and the second incident angle θa2 is different. In the comparative example, the first deflection angle θb1 and the second deflection angle θb2 are set to the same angle, and the first incident angle θa1 and the second incident angle θa2 are the same angle. As a result, it is necessary to increase the distance from the reference surface BS to the second reflecting mirror 53b, and the width of the second region AR2 in the rotation axis direction Z (comparison width ZL3) increases. Compared to the present embodiment, since the width in the rotation axis direction Z of the second area AR2 is a comparison width ZL3 that is larger than the second area width ZL2, it is difficult to reduce the thickness of the housing. Although the comparison width ZL3 can be reduced by reducing the second incident angle θa2, when the optical path between the first beam BM1 and the second beam BM2 approaches, for example, the first beam BM1 is changed to the second reflecting mirror. Since there is a risk of image formation defects such as a reduction in the amount of light that is reflected by 53b and applied to the photosensitive drum 13, there is a limit to reducing the first incident angle θa1 and the second incident angle θa2. is there.

  As described above, the optical scanning device 11a according to Embodiment 1 of the present invention includes two of the beams BM emitted from the light source 51 (the first light source 51a and the second light source 51b) (the first beam BM1 and the first beam BM1). The two beams BM2) have a reflection mirror 53 (first reflection mirror 53a and second reflection mirror 53b) at a first incident angle θa1 and a second incident angle θa2 that are different in the rotation axis direction Z with respect to the reference plane BS. The beam BM (first beam BM1) incident at a first incident angle θa1 larger than the second incident angle θa2 is configured to be incident on the reflection mirror 53 (first reflection mirror 53a) disposed in the first area AR1. Led to.

  According to this configuration, the optical scanning device 11a can be thinned by efficiently arranging the optical components in the emission optical system from the optical deflector 52 to the scanned body (photosensitive drum 13). That is, in the optical scanning device 11a that rotates and scans by the optical deflector 52, it is necessary to secure a space (first area AR1) for disposing the driving unit 55. Here, since the beam BM (first beam BM1) incident at the maximum angle (first incident angle θa1) greatly spreads in the rotation axis direction Z, the corresponding reflection mirror 53 (first reflection mirror 53a) is moved to the first. By disposing in the area AR1, the first area AR1 having a large space can be used effectively.

  In the present embodiment, a first lens (fθ lens 56) that is disposed between the optical deflector 52 and the reflection mirror 53 and converges the beam BM deflected by the optical deflector 52 is provided. According to this configuration, by converging the beam BM by the fθ lens 56, the beam BM can be condensed on one point of the photosensitive drum 13, and the resolution in image formation can be improved.

  Next, a first modification of the optical scanning device according to the first embodiment will be described.

  FIG. 6 is an explanatory diagram showing the position of the reflecting mirror in the first modification of the optical scanning device according to the first embodiment. In the figure, the guide mirror 62 is omitted in consideration of the visibility of the figure. In addition, an auxiliary line parallel to the reference plane BS is drawn to indicate the first incident angle θa1.

  Modification 1 has substantially the same configuration as that of the first embodiment, and the second incident angle θa2 is different. Specifically, in the first modification, the second incident angle θa2 is 0 degree, and the second deflection angle θb2 is 0 degree. According to this configuration, by emitting one of the plurality of beams BM in parallel with the reference surface BS, the inclination with respect to the reference surface BS can be ignored, and the arrangement in the emission optical system can be easily designed. .

  Note that an acceptable error is set for the second incident angle θa2, and for example, if it is about 0.2 to 0.3 degrees, it can be corrected by the fθ lens 56 or the like.

  The present invention is not limited to this, and the second incident angle θa2 may be changed as long as the first incident angle θa1 is set to be larger than the second incident angle θa2. That is, both the first beam BM1 and the second beam BM2 may be incident on the optical deflector 52 from above, and the second reflecting mirror 53b may be disposed in the first area AR1.

  Next, the configuration of the optical scanning device according to the second embodiment of the present invention will be described with reference to the drawings.

  FIG. 7 is a top view of the optical scanning device according to the second embodiment of the present invention, and FIG. 8 is an explanatory diagram showing the position of the reflecting mirror in the optical scanning device according to the second embodiment of the present invention. . In addition, the same code | symbol is attached | subjected about the component which has the function similar to Embodiment 1, and the description is abbreviate | omitted. Further, in FIG. 8, the guide mirror 62 is omitted in view of easy viewing, and an auxiliary line parallel to the reference plane BS is shown to indicate the first incident angle θa1 and the second incident angle θa2. It is drawn.

  The optical scanning device 11b according to the second embodiment of the present invention differs from the first embodiment in the position where the fθ lens 56 is disposed. In the present embodiment, a plurality of first lenses (fθ lenses 56) that are arranged between the reflection mirror 53 and the scanning target (photosensitive drum 13) and converge the beams BM deflected by the optical deflector 52, respectively. It has. According to this configuration, the fθ lens 56 can focus the beam BM on one point of the photosensitive drum 13 to improve the resolution in image formation. In addition, by providing the fθ lens 56 for each beam BM, it becomes easy to adjust the angle and position for individually irradiating each beam BM.

  Specifically, in the present embodiment, the light source 51, the collimator 61, the guide mirror 62, the cylindrical lens 63, the optical deflector 52, the reflection are directed from upstream to downstream in the traveling direction of the beam BM emitted from the light source 51. The optical scanning system includes a mirror 53, an auxiliary mirror (first auxiliary mirror 54 a or second auxiliary mirror 54 b), and an fθ lens 56 arranged in this order. The optical scanning device 11b includes four fθ lenses 56. The fθ lens 56 is located above the first reflection mirror 53a, the first auxiliary mirror 54a, the third reflection mirror 53c, and the second auxiliary mirror 54b. Each is arranged.

  As shown in FIG. 8, the first beam BM1 is incident on the deflection surface 52a from above with a first deflection angle θb1. The second beam BM2 is incident on the deflection surface 52a from below at the second deflection angle θb2. Since the first beam BM1 and the second beam BM2 are not deflected in the rotation axis direction Z on the deflection surface 52a, the first beam BM1 and the second beam BM2 further travel in a state where the first deflection angle θb1 and the second deflection angle θb2 are maintained. The first beam BM1 incident on the optical deflector 52 from above (second region AR2) travels below (first region AR1) after passing the optical deflector 52, and has a first incident angle equal to the first deflection angle θb1. The light enters the first reflection mirror 53 a at θa 1 and is guided to the photosensitive drum 13 through the fθ lens 56. The second beam BM2 that has entered the optical deflector 52 from below (first region AR1) travels upward (second region AR2) after passing the optical deflector 52, and is equal to the second deflection angle θb2. The light enters the second reflecting mirror 53b at an incident angle θa2 and is guided to the photosensitive drum 13 through the first auxiliary mirror 54a and the fθ lens 56.

  The optical scanning system having the third light source 51c and the fourth light source 51d is arranged in the same manner as the optical scanning system having the first light source 51a and the second light source 51b in the rotation axis direction Z, as in the first embodiment. Therefore, the description is omitted.

  Also in the second embodiment, the second incident angle θa2 can be changed as appropriate. Next, a second modification of the optical scanning device according to the second embodiment will be described.

  FIG. 9 is an explanatory diagram showing the position of the reflecting mirror in the second modification of the optical scanning device according to the second embodiment. In the figure, the guide mirror 62 is omitted in consideration of the visibility of the figure. In addition, an auxiliary line parallel to the reference plane BS is drawn to indicate the first incident angle θa1.

  Modification 2 has substantially the same configuration as that of the second embodiment, and the second incident angle θa2 is different. Specifically, in the second modification, the second incident angle θa2 is 0 degree, and the second deflection angle θb2 is 0 degree.

  Next, the configuration of the optical scanning device according to Embodiment 3 of the present invention will be described with reference to the drawings.

  FIG. 10 is a top view of the optical scanning device according to the third embodiment of the present invention, and FIG. 11 is an explanatory diagram showing the position of the reflecting mirror in the optical scanning device according to the third embodiment of the present invention. . In addition, the same code | symbol is attached | subjected about the component which has the function similar to Embodiment 1 and Embodiment 2, and the description is abbreviate | omitted. In FIG. 11, the guide mirror 62 is omitted in view of easy viewing, and an auxiliary line parallel to the reference plane BS is shown to indicate the first incident angle θa1 and the second incident angle θa2. It is drawn.

  In the optical scanning device 11c according to the third embodiment of the present invention, the second embodiment in which the beam BM deflected by the optical deflector 52 is tilted in the rotation axis direction Z in place of the fθ lens 56 as compared with the first embodiment. A lens 57 is provided.

  The optical scanning device 11c according to the third embodiment includes a light source 51, a collimator 61, a guide mirror 62, a cylindrical lens 63, an optical deflector 52, from upstream to downstream in the traveling direction of the beam BM emitted from the light source 51. The second lens 57, the reflection mirror 53, and the auxiliary mirror (the first auxiliary mirror 54a or the second auxiliary mirror 54b) are configured to include an optical scanning system arranged in order.

  Two second lenses 57 are provided and are arranged at the same position as the fθ lens 56 in the first embodiment, and are arranged symmetrically around the optical deflector 52 in the sub-scanning direction X. The second lens 57 tilts one (first beam BM1) of the two beams BM (first beam BM1 and second beam BM2) deflected by the optical deflector 52 to the first incident angle θa1. A first inclined portion 57a and a second inclined portion 57b that inclines the other (second beam BM2) to the second incident angle θa2 are provided. According to this configuration, the angle of the beam BM is adjusted by the second lens 57, so that the arrangement of the optical components in the incident optical system is not limited. The second lens 57 converges the beam BM on the surface of the photosensitive drum 13 in the same manner as the fθ lens 56.

  As shown in FIG. 11, the first beam BM1 is incident on the deflection surface 52a from above with a first deflection angle θb1. The second beam BM2 is incident on the deflection surface 52a from below at a second deflection angle θb2 equal to the first deflection angle θb1. Since the first beam BM1 and the second beam BM2 are not deflected in the rotation axis direction Z on the deflection surface 52a, the first beam BM1 and the second beam BM2 further travel in a state where the first deflection angle θb1 and the second deflection angle θb2 are maintained. The first beam BM1 incident on the optical deflector 52 from above (second region AR2) travels below (first region AR1) after passing the optical deflector 52, and reaches the first inclined portion 57a of the second lens 57. Incident. In addition, the second beam BM2 that has entered the optical deflector 52 from below (first region AR1) travels upward (second region AR2) after passing through the optical deflector 52, and the second inclined portion of the second lens 57. Incident to 57b.

  In the second lens 57, the first beam BM1 is emitted while maintaining the first deflection angle θb1, and the second beam BM2 is emitted while being inclined to a second incident angle θa2 smaller than the second deflection angle θb2. . As a result, the first beam BM1 is incident on the first reflecting mirror 53a at a first incident angle θa1 equal to the first deflection angle θb1, and the second beam BM2 is at a second incident angle θa2 that is smaller than the first incident angle θa1. The light enters the second reflection mirror 53b. That is, in the second lens 57, the second beam BM2 incident on the second reflection mirror 53b is tilted so that the angle at which the first beam BM1 enters the first reflection mirror 53a is larger than the second incident angle θa2. One incident angle θa1 is set.

  Thereafter, the first beam BM1 is guided to the photosensitive drum 13 by the first reflecting mirror 53a, and the second beam BM2 is guided to the photosensitive drum 13 via the second reflecting mirror 53b and the first auxiliary mirror 54a.

  In the third embodiment, the first deflection angle θb1 and the second deflection angle θb2 are set to the same angle, and the first incident angle θa1 is set to be larger than the second incident angle θa2. In the third embodiment, similarly to the first embodiment, the distance from the reference surface BS to the second reflection mirror 53b can be reduced by setting the second incident angle θa2 to be smaller than the first incident angle θa1. The second region width ZL2 can be made smaller than the first region width ZL1.

  The optical scanning system having the third light source 51c and the fourth light source 51d is the optical scanning having the first light source 51a and the second light source 51b in the rotation axis direction Z in the same manner as in the first and second embodiments. Since the arrangement is the same as that of the system, the description is omitted.

  Also in the third embodiment, the second incident angle θa2 can be changed as appropriate. Next, a third modification of the optical scanning device according to the third embodiment will be described.

  FIG. 12 is an explanatory diagram showing the position of the reflecting mirror in the third modification of the optical scanning device according to the third embodiment. In the figure, the guide mirror 62 is omitted in consideration of the visibility of the figure. In addition, an auxiliary line parallel to the reference plane BS is drawn to indicate the first incident angle θa1.

  Modification 3 has substantially the same configuration as that of Embodiment 3, and the second incident angle θa2 is different. Specifically, in the third modification, the second beam BM2 is inclined by the second inclined portion 57b and the second incident angle θa2 is set to 0 degree. That is, the second beam BM2 is emitted from the second lens 57 in parallel with the reference plane BS.

  In the third embodiment, the first deflection angle θb1 and the second deflection angle θb2 can be changed as appropriate. Next, a fourth modification of the optical scanning device according to the third embodiment will be described.

  FIG. 13 is an explanatory diagram showing the position of the reflecting mirror in Modification 4 of the optical scanning device according to the third embodiment. In the figure, the guide mirror 62 is omitted in consideration of the visibility of the figure. Further, in order to show the first incident angle θa1 and the second incident angle θa2, an auxiliary line parallel to the reference plane BS is drawn.

  In the fourth modification, the first deflection angle θb1 is set smaller than the second deflection angle θb2. Then, the first beam BM1 is emitted by being inclined at a first incident angle θa1 larger than the first deflection angle θb1 by the first inclined portion 57a. Further, the second beam BM2 is emitted by being inclined by the second inclined portion 57b to a second incident angle θa2 that is smaller than the second deflection angle θb2. Here, the first incident angle θa1 is set to be larger than the second incident angle θa2. That is, the second lens 57 is configured to tilt both the first beam BM1 and the second beam BM2.

  Further, the housing 55 may be provided with unevenness to lift the drive unit 55 upward. Next, a fifth modification of the optical scanning device according to the first embodiment will be described.

  FIG. 14 is a schematic side view of Modification 5 of the optical scanning device according to the first embodiment. In FIG. 14, the collimator 61, the guide mirror 62, and the cylindrical lens 63 are omitted for easy viewing.

  In the modification 5, the convex part 11d which protruded upward is provided in the position corresponding to the downward direction of the drive part 55 in a housing | casing. The drive part 55 is lifted upward according to the convex part 11d. The height of the optical deflector 52 is the same as in the first embodiment. That is, in the rotation axis direction Z, the drive unit 55 is closer to the optical deflector 52 than in the first embodiment. Note that the present invention is not limited to this, and for example, a housing provided with a convex portion 11d may be applied to the second and third embodiments.

  It should be noted that the embodiment disclosed herein is illustrative in all respects and does not serve as a basis for limited interpretation. Therefore, the technical scope of the present invention is not interpreted only by the above-described embodiment, but is defined based on the description of the scope of claims. Moreover, all the changes within the meaning and range equivalent to a claim are included.

DESCRIPTION OF SYMBOLS 1 Image forming apparatus 11, 11a, 11b, 11c Optical scanning device 13 Photosensitive drum (an example of to-be-scanned body)
51 light source 51a first light source 51b second light source 51c third light source 51d fourth light source 52 light deflector 53 reflecting mirror 53a first reflecting mirror 53b second reflecting mirror 53c third reflecting mirror 53d fourth reflecting mirror 54a first auxiliary mirror 54b Second auxiliary mirror 55 Drive unit 55a Rotating shaft 56 fθ lens (first lens)
57 second lens 57a first inclined portion 57b second inclined portion 61 collimator 62 guide mirror 63 cylindrical lens AR1 first region AR2 second region BM beam BM1 first beam BM2 second beam BM3 third beam BM4 fourth beam BS reference Surface X Sub-scanning direction Y Main-scanning direction Z Rotational axis direction θa1 First incident angle θa2 Second incident angle θb1 First deflection angle θb2 Second deflection angle

Claims (7)

A plurality of light sources that emit beams, an optical deflector that deflects the beams emitted from the plurality of light sources, and a plurality of beams that reflect the beams deflected by the optical deflectors and guide them to the corresponding scanned object An optical scanning device that includes a reflecting mirror, and each beam scans a plurality of scanned objects,
When a plane perpendicular to the light incident surface of the light deflector and passing through the center of the light incident surface is a reference surface,
Two of the beams emitted from the light source are configured to enter the optical deflector at a first deflection angle and a second deflection angle that are different from each other with respect to the reference plane,
The second deflection angle is set smaller than the first deflection angle;
The number of reflection mirrors corresponding to the beam incident at the second deflection angle is greater than the number of reflection mirrors corresponding to the beam incident at the first deflection angle. The optical scanning device according to claim 1,
The light source corresponding to the beam incident at the second deflection angle is further away from the scanned object than the light source corresponding to the beam incident at the first deflection angle in a direction orthogonal to the reference plane. An optical scanning device. A plurality of light sources that emit beams, an optical deflector that deflects the beams emitted from the plurality of light sources, and a plurality of beams that reflect the beams deflected by the optical deflectors and guide them to the corresponding scanned object An optical scanning device that includes a reflecting mirror, and each beam scans a plurality of scanned objects,
When a plane perpendicular to the light incident surface of the light deflector and passing through the center of the light incident surface is a reference surface,
Two of the beams emitted from the light source are configured to enter the optical deflector at a first deflection angle and a second deflection angle that are different from each other with respect to the reference plane,
The second deflection angle is set smaller than the first deflection angle;
The light source corresponding to the beam incident at the second deflection angle is further away from the scanned object than the light source corresponding to the beam incident at the first deflection angle in a direction orthogonal to the reference plane. An optical scanning device. An optical scanning device according to any one of claims 1 to 3, wherein
A space in the housing in which the reflecting mirror is accommodated is divided into a first region and a second region at the reference plane,
The first region has a width in a direction perpendicular to the reference plane set larger than the second region,
The second region is set on the side facing the body to be scanned. The optical scanning device according to claim 4,
Any one of the reflection mirrors corresponding to the beam incident at the second deflection angle is disposed in the first region. An optical scanning device according to any one of claims 1 to 5, comprising:
A plurality of beams incident on the optical deflector are incident at the second deflection angle by comparing the angles formed by the incident light and the reflected light at the first reflecting mirror after being deflected by the optical deflector. The optical scanning device is characterized in that the angle of the beam is smaller than that of the beam incident at the first deflection angle.   An image forming apparatus comprising the optical scanning device according to claim 1.

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