JP5532249B2 - Optical scanning apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to an optical scanning device and an image forming apparatus, and more particularly to an optical scanning device that scans a surface to be scanned with light and an image forming apparatus including the optical scanning device.

  In electrophotographic image recording, an image forming apparatus using a laser is widely used. In this case, the image forming apparatus includes an optical scanning device, deflects laser light emitted from a light source using an optical deflector, and rotates the surface of a photosensitive drum (hereinafter referred to as “photosensitive drum”) as an axis. A method of rotating a photosensitive drum while scanning in the direction (main scanning direction) to form a latent image on the surface of the photosensitive drum is common.

  2. Description of the Related Art In recent years, in an image forming apparatus, output images have become multicolored, and a tandem type image forming apparatus having a plurality (usually four) photosensitive drums has become widespread.

  In order to increase the image forming speed in the image forming apparatus, a multi-beam scanning method in which the surface of the photosensitive drum is simultaneously scanned with a plurality of lights has been proposed. In this case, the optical scanning device has a plurality of light sources, and when the plurality of light sources are arranged apart from each other in the sub-scanning direction, the positions of the plurality of cylindrical lenses corresponding to the respective light sources affect the image quality. .

  For example, Patent Document 1 discloses an optical scanning device in which a cylindrical lens is mounted on a housing via an intermediate member.

  Patent Document 2 discloses a scanning optical system in which all of a plurality of cylinder lenses are integrally configured to form a composite imaging element.

  Further, in Patent Document 3, the anamorphic imaging element has an end portion in the main scanning direction and an end portion in the sub-scanning direction, and only the end portion in the weak power direction contacts the base. An optical scanning device fixed to a base at the center is disclosed.

  However, since the optical scanning device disclosed in Patent Document 1 requires an intermediate member in addition to the housing, the number of parts increases, resulting in an increase in cost. In addition, when the environmental temperature changes, the cylindrical lens moves in the optical axis direction due to the expansion / contraction of the adhesive, and the image may be deteriorated due to the change in the beam diameter.

  In the scanning optical system disclosed in Patent Document 2, the position of the plurality of cylinder lenses in the optical axis direction cannot be individually adjusted. Therefore, the curvature error of the scanning lens is directly out of focus on the surface to be scanned. As a result, the image quality is deteriorated.

  Further, even if the cylindrical lens is fixed in the same manner as the anamorphic imaging element of the optical scanning device disclosed in Patent Document 3, it is difficult to hold a plurality of cylindrical lenses separated in the sub-scanning direction. Furthermore, in the embodiment (FIGS. 2a and 3) disclosed in Patent Document 3, only the lower side of the lens is brought into contact with the base with respect to the end portion in the main scanning direction. In such a configuration, the base expands / shrinks due to temperature fluctuation, and there is a possibility that the lens rotates slightly in the direction around the optical axis. When an anamorphic imaging element that is not rotationally symmetric is rotated around the optical axis, wavefront aberration occurs, which causes the beam spot diameter to increase.

  The present invention has been made under such circumstances, and a first object thereof is to provide an optical scanning device capable of stably performing high-precision optical scanning with a plurality of lights.

  A second object of the present invention is to provide an image forming apparatus capable of stably forming a high quality image.

According to a first aspect of the present invention, there is provided an optical scanning device for optically scanning at least two scanned surfaces individually in the main scanning direction, and disposed at different positions with respect to the sub-scanning direction orthogonal to the main scanning direction. At least two light sources; and at least two line-image forming lenses provided corresponding to the at least two light sources and collecting light beams emitted from the light sources in the sub-scanning direction; and the at least two lines. An optical deflector for deflecting a plurality of light beams through an image forming lens; and a scanning optical system for guiding the plurality of light beams deflected by the optical deflector to a corresponding surface to be scanned. forming lens, the main entire one edge of the scanning direction is fixed by the adhesive, the other side of the main scanning direction center of the area where the light beam with respect to the main scanning direction is incident with respect to the center of the optical surface That are offset is an optical scanning apparatus according to claim.

According to this, high-precision optical scanning with a plurality of lights can be stably performed.
From a second viewpoint, the present invention is an optical scanning device that individually scans at least two scanned surfaces in the main scanning direction, and is arranged at different positions with respect to the sub-scanning direction orthogonal to the main scanning direction. At least two light sources; and at least two line-image forming lenses provided corresponding to the at least two light sources and collecting light beams emitted from the light sources in the sub-scanning direction; and the at least two lines. An optical deflector for deflecting a plurality of light beams via an image forming lens; and a scanning optical system for guiding the plurality of light beams deflected by the optical deflector to a corresponding surface to be scanned, wherein the at least two light sources are The at least two line image forming lenses include a first light source and a second light source, and both end surfaces or one side end surfaces in the main scanning direction are fixed with an adhesive, and the first light source and the second light source are fixed. A first line image forming lens corresponding to the light source and a second line image forming lens corresponding to the second light source, wherein the scanning optical system corresponds to the scanned surface corresponding to the light beam from the first light source. And a second optical system for guiding the light beam from the second light source to the corresponding scanned surface, and the number of reflective optical elements in the first optical system is The amount of the adhesive applied to the first line image forming lens is larger than the number of reflection optical elements in the optical system 2 and the amount of the adhesive applied to the second line image forming lens. This is an optical scanning device characterized in that the number of optical scanning devices is larger.
According to this, high-precision optical scanning with a plurality of lights can be stably performed.

From a third aspect , the present invention is a plurality of image carriers; and an optical scanning device of the present invention that optically scans the plurality of image carriers using light modulated according to image information; An image forming apparatus.

  According to this, a high quality image can be stably formed.

1 is a diagram for describing a schematic configuration of a color printer according to an embodiment of the present invention. FIG. FIG. 2 is a diagram (part 1) for describing a configuration of an optical scanning device 2010A in FIG. FIG. 3 is a diagram (No. 2) for describing a configuration of an optical scanning device 2010A in FIG. FIG. 4A to FIG. 4C are diagrams for explaining the LD array included in each light source. It is a figure for demonstrating the shape of each optical surface of a deflector side scanning lens. It is a figure for demonstrating the shape of each optical surface of each image surface side scanning lens. It is a figure for demonstrating the arrangement | positioning state of each image surface side scanning lens. It is a figure for demonstrating the example of arrangement | positioning of the main optical elements. It is a figure for demonstrating the specific example of d1-d9 in FIG. It is a figure for demonstrating the example of arrangement | positioning of a scanning optical system. It is a figure for demonstrating a holding member. It is FIG. (1) for demonstrating the holding state of each cylindrical lens. It is FIG. (2) for demonstrating the holding state of each cylindrical lens. FIG. 14A is a diagram for explaining the bottom surface adhesion of each cylindrical lens, and FIG. 14B is a diagram for explaining the side surface adhesion of each cylindrical lens. It is FIG. (1) for demonstrating the effect of the subscanning position adjustment of a cylindrical lens. FIG. 6 is a second diagram for explaining the effect of adjusting the sub-scanning position of the cylindrical lens. It is FIG. (1) for demonstrating the effect of the side surface adhesion of a cylindrical lens. It is FIG. (2) for demonstrating the effect of the side surface adhesion of a cylindrical lens. FIG. 3 is a diagram (part 1) for describing a configuration of an optical scanning device 2010B in FIG. 1; FIG. 3 is a second diagram for explaining the configuration of the optical scanning device 2010B in FIG. 1; It is a figure for demonstrating the modification of an optical scanning device. It is a figure for demonstrating the both-sides surface adhesion of a cylindrical lens.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a color printer 2000 as an image forming apparatus according to an embodiment.

  The color printer 2000 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes two optical scanning devices (2010A, 2010B), four Photosensitive drums (2030a, 2030b, 2030c, 2030d), four cleaning units (2031a, 2031b, 2031c, 2031d), four charging devices (2032a, 2032b, 2032c, 2032d), and four developing rollers (2033a, 2033b, 2033c, 2033d), four toner cartridges (2034a, 2034b, 2034c, 2034d), transfer belt 2040, transfer roller 2042, fixing device 2050, paper supply roller 2054, registration roller pair 2056, paper discharge low 2058, the paper feed tray 2060, a discharge tray 2070, and a like communication control unit 2080, and a printer control device 2090.

  The communication control device 2080 controls bidirectional communication with a host device (for example, a personal computer) via a network or the like.

  The printer control device 2090 includes a CPU, a ROM described in a program written in code readable by the CPU, various data used when executing the program, a RAM as a working memory, an analog data An AD conversion circuit for converting the signal into digital data. The printer control device 2090 controls each unit in response to a request from the host device, and sends image information from the host device to each optical scanning device.

  The photosensitive drum 2030a, the charging device 2032a, the developing roller 2033a, the toner cartridge 2034a, and the cleaning unit 2031a are used as a set, and form an image forming station (hereinafter also referred to as “K station” for convenience) that forms a black image. Configure.

  The photosensitive drum 2030b, the charging device 2032b, the developing roller 2033b, the toner cartridge 2034b, and the cleaning unit 2031b are used as a set and form an image forming station (hereinafter also referred to as “C station” for convenience) that forms a cyan image. Configure.

  The photosensitive drum 2030c, the charging device 2032c, the developing roller 2033c, the toner cartridge 2034c, and the cleaning unit 2031c are used as a set, and form an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image. Configure.

  The photosensitive drum 2030d, the charging device 2032d, the developing roller 2033d, the toner cartridge 2034d, and the cleaning unit 2031d are used as a set, and form an image forming station (hereinafter also referred to as “Y station” for convenience) that forms a yellow image. Configure.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is a surface to be scanned. Each photosensitive drum is rotated in the direction of the arrow in the plane of FIG. 1 by a rotation mechanism (not shown).

  Each charging device uniformly charges the surface of the corresponding photosensitive drum.

  The optical scanning device 2010A irradiates the surface of the photosensitive drum 2030a charged by the charging device 2032a with a light beam modulated based on the black image information from the printer control device 2090, and also outputs a cyan image from the printer control device 2090. The light beam modulated based on the information is irradiated onto the surface of the photosensitive drum 2030b charged by the charging device 2032b.

  The optical scanning device 2010B irradiates the surface of the photosensitive drum 2030c charged by the charging device 2032c with a light beam modulated based on the magenta image information from the printer control device 2090, and also outputs a yellow image from the printer control device 2090. The light beam modulated based on the information is irradiated onto the surface of the photosensitive drum 2030d charged by the charging device 2032d.

  As a result, on the surface of each photoconductive drum, the charge disappears only in the portion irradiated with light, and a latent image corresponding to the image information is formed on the surface of each photoconductive drum. The latent image formed here moves in the direction of the corresponding developing roller as the photosensitive drum rotates. The configurations of the optical scanning device 2010A and the optical scanning device 2010B will be described later.

  The toner cartridge 2034a stores black toner, and the toner is supplied to the developing roller 2033a. The toner cartridge 2034b stores cyan toner, and the toner is supplied to the developing roller 2033b. The toner cartridge 2034c stores magenta toner, and the toner is supplied to the developing roller 2033c. The toner cartridge 2034d stores yellow toner, and the toner is supplied to the developing roller 2033d.

  As each developing roller rotates, the toner from the corresponding toner cartridge is thinly and uniformly applied to the surface thereof. Then, when the toner on the surface of each developing roller comes into contact with the surface of the corresponding photosensitive drum, the toner moves only to a portion irradiated with light on the surface and adheres to the surface. In other words, each developing roller causes toner to adhere to the latent image formed on the surface of the corresponding photosensitive drum so as to be visualized. Here, the toner-attached image (toner image) moves in the direction of the transfer belt 2040 as the photosensitive drum rotates.

  The yellow, magenta, cyan, and black toner images are sequentially transferred onto the transfer belt 2040 at a predetermined timing, and are superimposed to form a multicolor image.

  Recording paper is stored in the paper feed tray 2060. A paper feed roller 2054 is disposed in the vicinity of the paper feed tray 2060, and the paper feed roller 2054 takes out the recording paper one by one from the paper feed tray 2060 and conveys it to the registration roller pair 2056. The registration roller pair 2056 feeds the recording paper toward the gap between the transfer belt 2040 and the transfer roller 2042 at a predetermined timing. As a result, the color image on the transfer belt 2040 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing device 2050.

  In the fixing device 2050, heat and pressure are applied to the recording paper, thereby fixing the toner on the recording paper. The recording paper fixed here is sent to a paper discharge tray 2070 via a paper discharge roller 2058 and is sequentially stacked on the paper discharge tray 2070.

  Each cleaning unit removes toner (residual toner) remaining on the surface of the corresponding photosensitive drum. The surface of the photosensitive drum from which the residual toner has been removed returns to the position facing the corresponding charging device again.

  Next, the configuration of the optical scanning device 2010A will be described.

  As shown in FIG. 2 and FIG. 3 as an example, the optical scanning device 2010A includes two light sources (2200a, 2200b), two coupling lenses (2201a, 2201b), two aperture plates (2202a, 2202b), 2 Two cylindrical lenses (2204a, 2204b), polygon mirror 2104A, deflector side scanning lens 2105A, three folding mirrors (2106a, 2106b, 2107a), two image plane side scanning lenses (2108a, 2108b), and two dustproofs Glass (2110a, 2110b) and a scanning control device (not shown) are provided. These are assembled at predetermined positions of the optical housing 2300A (not shown in FIG. 2, see FIG. 3).

  Here, in the XYZ three-dimensional orthogonal coordinate system, the direction along the longitudinal direction of each photosensitive drum is described as the Y-axis direction, and the direction parallel to the rotation axis of the polygon mirror 2104A is described as the Z-axis direction.

  In the following, for convenience, the direction corresponding to the main scanning direction is abbreviated as “main scanning corresponding direction”, and the direction corresponding to the sub scanning direction is abbreviated as “sub scanning corresponding direction”.

  The light source 2200a and the light source 2200b are arranged at positions separated from each other in the sub-scanning corresponding direction (here, the Z-axis direction). Each light source includes an LD (Laser Diode) array having two light emitting portions with an oscillation wavelength of 659 nm (see FIG. 4A). The distance d between the two light emitting portions is 30 μm. Further, the divergence angle of the light flux in each light emitting portion is 32 ° (full width at half maximum) in the horizontal direction and 8.5 ° (full width at half maximum) in the vertical direction when the two light emitting portions are arranged horizontally.

  Each light source can be rotated around an axis parallel to the direction toward the polygon mirror 2104A through its substantially center so that the pixel density of the latent image formed on the surface of the photosensitive drum corresponds to 600 dpi, that is, The rotation is adjusted so that the beam interval (beam pitch) in the sub-scanning direction on the surface of the photosensitive drum is about 42.3 μm (see FIG. 4B). Here, the rotation is adjusted so that the line segment connecting the two light emitting portions is inclined by 63.4 ° with respect to the main scanning corresponding direction (see FIG. 4C).

  The coupling lens 2201a is disposed on the optical path of a light beam emitted from the light source 2200a (hereinafter also referred to as “light beam LBa”).

  The coupling lens 2201b is disposed on the optical path of a light beam emitted from the light source 2200b (hereinafter also referred to as “light beam LBb”).

  Each coupling lens is a glass lens having a focal length of 14.5 mm and a refractive index of 1.515 with respect to light having a wavelength of 659 nm, and converts the light beam from the corresponding light source into a substantially parallel light beam.

  The aperture plate 2202a has an aperture and shapes the light beam LBa via the coupling lens 2201a.

  The aperture plate 2202b has an aperture and shapes the light beam LBb via the coupling lens 2201b.

  The opening of each aperture plate is a rectangular or elliptical opening having a length of 2.84 mm in the main scanning direction and a length of 0.90 mm in the sub-scanning direction (here, the Z-axis direction). . Each aperture plate is arranged such that the center of the aperture is located in the vicinity of the focal position of the corresponding coupling lens.

  The cylindrical lens 2204a forms an image of the light beam LBa that has passed through the opening of the aperture plate 2202a in the vicinity of the deflection reflection surface of the polygon mirror 2104A in the Z-axis direction.

  The cylindrical lens 2204b focuses the light beam LBb that has passed through the opening of the aperture plate 2202b in the vicinity of the deflection reflection surface of the polygon mirror 2104A in the Z-axis direction.

  Each cylindrical lens is a glass lens having a focal length of 87.8 mm and a refractive index of 1.514 for light with a wavelength of 659 nm. The cylindrical lenses are arranged close to each other in the sub-scanning corresponding direction.

  An optical system including the coupling lens 2201a, the aperture plate 2202a, and the cylindrical lens 2204a is a pre-deflector optical system of the K station.

  An optical system including the coupling lens 2201b, the aperture plate 2202b, and the cylindrical lens 2204b is a pre-deflector optical system of the C station.

  The polygon mirror 2104A has a six-sided mirror that rotates around an axis parallel to the Z-axis direction, and each mirror serves as a deflection reflection surface. That is, the polygon mirror 2104A has six deflecting reflecting surfaces. The outer shape of the hexahedral mirror is a regular hexagon inscribed in a circle with a radius of 13 mm.

  Here, the light flux from each cylindrical lens is incident on the same deflecting / reflecting surface located on the + X side from the center of rotation.

  The light beam LBa from the cylindrical lens 2204a is incident on the deflecting / reflecting surface from a direction inclined 2.5 ° to the + Z side with respect to a plane (XY plane) orthogonal to the rotation axis of the polygon mirror 2104A. Further, the light beam LBb from the cylindrical lens 2204b is incident on the deflecting / reflecting surface from a direction inclined by 2.5 ° to the −Z side with respect to a plane orthogonal to the rotation axis of the polygon mirror 2104A.

  In the following, when the light beam is incident on the deflecting / reflecting surface, it is referred to as “oblique incidence” to be incident from a direction inclined with respect to the surface orthogonal to the rotation axis of the polygon mirror, and orthogonal to the rotation axis of the polygon mirror. Incident from a direction parallel to the surface to be projected is called “horizontal incidence”.

  The deflector-side scanning lens 2105A is disposed on the optical path of the light beam LBa and the light beam LBb deflected by the polygon mirror 2104A.

  The folding mirror 2106a is disposed on the optical path of the light beam LBa via the deflector-side scanning lens 2105A, and folds the optical path of the light beam LBa in the −X direction.

  The folding mirror 2107a is disposed on the optical path of the light beam LBa via the folding mirror 2106a, and folds the optical path of the light beam LBa in a direction toward the photosensitive drum 2030a.

  The image plane side scanning lens 2108a is disposed on the optical path of the light beam LBa via the folding mirror 2107a.

  Therefore, the light beam LBa deflected by the polygon mirror 2104A is irradiated onto the photosensitive drum 2030a via the deflector side scanning lens 2105A, the folding mirror 2106a, the folding mirror 2107a, the image plane side scanning lens 2108a, and the dustproof glass 2110a. A light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030a as the polygon mirror 2104A rotates. That is, the photosensitive drum 2030a is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030a, and the rotational direction of the photosensitive drum 2030a is the “sub-scanning direction” on the photosensitive drum 2030a.

  The folding mirror 2106b is disposed on the optical path of the light beam LBb via the deflector-side scanning lens 2105A, and folds the optical path of the light beam LBb in a direction toward the photosensitive drum 2030b.

  The image side scanning lens 2108b is disposed on the optical path of the light beam LBb via the folding mirror 2106b.

  Therefore, the light beam LBb deflected by the polygon mirror 2104A is irradiated onto the photosensitive drum 2030b through the deflector side scanning lens 2105A, the folding mirror 2106b, the image plane side scanning lens 2108b, and the dustproof glass 2110b, thereby forming a light spot. Is done. This light spot moves in the longitudinal direction of the photosensitive drum 2030b as the polygon mirror 2104A rotates. That is, the photosensitive drum 2030b is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030b, and the rotational direction of the photosensitive drum 2030b is the “sub-scanning direction” on the photosensitive drum 2030b.

  Incidentally, a scanning area in the main scanning direction in which image information is written on each photosensitive drum is called an “effective scanning area”, an “image forming area”, or an “effective image area”.

  The optical system disposed on the optical path between the polygon mirror 2104A and each photosensitive drum is also called a scanning optical system.

  In the optical scanning device 2010A, a deflecting side scanning lens 2105A, two folding mirrors (2106a, 2107a), an image plane side scanning lens 2108a, and a dustproof glass 2110a constitute a scanning optical system for the K station.

  Further, the scanning optical system of the C station is composed of the deflector side scanning lens 2105A, the folding mirror 2106b, the image plane side scanning lens 2108b, and the dust-proof glass 2110b.

  That is, the deflector side scanning lens 2105A is shared by the two stations.

  The deflector-side scanning lens 2105A is a resin lens having a refractive index of 1.530 with respect to light having a wavelength of 659 nm, and has a center (on the optical axis) thickness of 5.2 mm.

  Each image plane side scanning lens is a resin lens having a refractive index of 1.530 with respect to light having a wavelength of 659 nm, and has a center (on the optical axis) thickness of 3.0 mm.

  The shape of each optical surface (incident optical surface, exit optical surface) of each scanning lens is expressed by the following equations (1) and (2).

  In the above formulas (1) and (2), the distance from the optical axis in the main scanning correspondence direction is y, and the distance from the optical axis in the sub scanning correspondence direction is z. The paraxial radius of curvature in the “main scanning section” that is a section that includes the optical axis and is parallel to the main scanning corresponding direction is Rm (= 1 / Cm), includes the optical axis, and is orthogonal to the main scanning section. The paraxial radius of curvature in the “scan section” is Rz. A, B, C,... Are the aspheric coefficients of the shape in the main scanning correspondence direction, and a, b, c,.

  Specific examples (unit: mm) of Rm, Rz and each coefficient in the deflector side scanning lens 2105A are shown in FIG. FIG. 6 shows specific examples (unit: mm) of Rm, Rz, and each coefficient in each image plane side scanning lens.

  Each image plane side scanning lens has a position shifted from the axis when it is assumed that each light beam is incident on the polygon mirror in a direction approaching a 3.38 mm passing light beam with respect to the sub-scanning corresponding direction. It arrange | positions so that it may become a lens surface vertex (position of z = 0 in said Formula (1)) (refer FIG. 7).

  The sub-scan magnification of only the scanning optical system at each station is -0.85 times. The design value of the size of the light spot on the surface of each photosensitive drum is 65 μm in the main scanning direction and 75 μm in the sub-scanning direction.

  Each dustproof glass is a glass plate having a refractive index of 1.517 and a wall thickness of 1.9 mm for light having a wavelength of 659 nm.

  Further, specific examples of arrangement positions of main optical elements are shown in FIGS. The length of the effective scanning area is 220 mm, the rotation angle of the polygon mirror 2104A when optically scanning the effective scanning area is 17.1 °, and the field angle is 34.2 °. FIG. 8 is a schematic diagram in which the optical path is developed in one direction for the scanning optical system, and the values of d1 to d9 are optical path lengths.

  FIG. 10 shows a specific example of the arrangement position and inclination angle of each optical element in the scanning optical system. The position in FIG. 10 is indicated by the optical path length starting from the reflection position on the deflecting reflection surface. The angle is indicated by an inclination angle with respect to the sub-scanning corresponding direction.

  By the way, two light sources (2200a, 2200b), two coupling lenses (2201a, 2201b), two aperture plates (2202a, 2202b), and two cylindrical lenses (2204a, 2204b) are shown as an example in FIG. As shown, the holding member 10 is held in a predetermined positional relationship and is unitized. Hereinafter, this unitized unit is referred to as a “light source unit”.

  Each light source is inserted and held in a through hole formed in the holding member 10.

  Each coupling lens is coated with an ultraviolet curable adhesive at one end in the sub-scanning corresponding direction, so that the light emitted from the corresponding light source becomes a parallel light beam. After the adjustment of the shaft, the adhesive is irradiated with ultraviolet rays and fixed to the holding member 10.

  Each aperture plate is coated with an ultraviolet curable adhesive at one end in the sub-scanning corresponding direction, and when attached to a predetermined position, the adhesive is irradiated with ultraviolet rays and fixed to the holding member 10.

  In each cylindrical lens, after the light source unit is assembled to the optical housing, an adhesive is applied to the entire one side end surface in the main scanning direction, and the sub-scanning direction due to attachment error of each folding mirror, curvature error of each scanning lens, etc. The position adjustment is performed so as to correct the focus position shift with respect to, the irradiation position shift with respect to the sub-scanning direction, and the like. Then, the adhesive is irradiated with ultraviolet rays and fixed to the side plate of the holding member 10 (see FIG. 12). Hereinafter, for the sake of convenience, one side end surface of the cylindrical lens in the main scanning corresponding direction is also referred to as an “adhesive fixed end surface”, and the other side end surface is also referred to as a “free end surface”. Further, the adjustment of the attachment position of the cylindrical lens in the sub-scanning corresponding direction is abbreviated as “sub-scanning position adjustment”.

  Moreover, each cylindrical lens is attached so that a light beam may be incident substantially vertically. If a light beam is obliquely incident on the cylindrical lens, refraction occurs, and the incident position and the emission position in the sub-scanning corresponding direction are slightly shifted, resulting in deterioration of optical characteristics.

  Each cylindrical lens is set so that the center of the region through which the light beam passes is shifted by 0.5 mm toward the free end surface with respect to the center of the lens in the main scanning direction (see FIG. 13). In this case, even if the position of the incident light beam is shifted or the adhesive is applied more than expected and the adhesive adheres to the optical surface, the light beam can be prevented from entering the adhesive portion.

  By the way, in the optical scanning device 2010A, the scanning optical system of the K station has two folding mirrors, whereas the scanning optical system of the C station has only one folding mirror. The sub-scanning position adjustment of the cylindrical lens has the purpose of absorbing variations in the mounting angle in the folding direction of the folding mirror. Therefore, the amount of sub-scanning position adjustment increases as the number of folding mirrors increases. Specifically, the adjustment width of the sub-scanning position adjustment in the cylindrical lens 2204a is ± 0.6 mm, whereas the adjustment width of the sub-scanning position adjustment in the cylindrical lens 2204b is ± 0.4 mm.

  Therefore, the amount of adhesive applied to the cylindrical lens 2204a is 1 [ml], and the amount of adhesive applied to the cylindrical lens 2204b is 0.8 [ml]. In order to prevent the adhesive from adhering to the optical surface of the lens, it is desirable to reduce the amount of adhesive as much as possible. However, since the adhesive is stretched by adjusting the sub-scanning position after coating, the cylindrical lens is adjusted to its maximum. Even if the width is moved, it is necessary to maintain a sufficient amount of adhesive to be held by the holding member 10. For this reason, the amount of adhesive applied is larger in the cylindrical lens 2204a having a larger adjustment width than in the cylindrical lens 2204b (see FIG. 13).

  When holding the cylindrical lens on the holding member, conventionally, as shown in FIG. 14A as an example, an adhesive is applied to one end surface of the cylindrical lens in the sub-scanning direction and fixed to the holding member. It was. For convenience, such fixation is also referred to as “bottom surface adhesion”. On the other hand, in the optical scanning device 2010A, an adhesive is applied to the entire surface of one side end surface in the main scanning direction of the cylindrical lens, and is fixed to the holding member. For convenience, such fixing is also referred to as “side adhesion”.

  For example, when the adjustment width of the sub-scanning position adjustment in the cylindrical lens is ± 0.5 mm, if the cylindrical lens is bonded to the bottom surface, the thickness of the adhesive layer becomes 1 mm at the maximum. Since the UV curable adhesive has a linear expansion coefficient that is about an order of magnitude larger than that of glass, if the adhesive layer is thick, the cylindrical lens is attached in the sub-scanning direction due to a change in environmental temperature. The position changes greatly. In particular, the cylindrical lens directly receives the wind from the polygon mirror, so the temperature change is larger than the other parts.

  Further, the volume of the ultraviolet curable adhesive changes when irradiated with ultraviolet rays. Therefore, if the thickness of the adhesive layer is large, even if the position of the cylindrical lens is adjusted to the optimum position before irradiating the ultraviolet rays, there is a possibility that the optimum position is shifted after the ultraviolet rays are irradiated. Therefore, in this case, it is necessary to adjust the sub-scanning position of the cylindrical lens in consideration of the positional deviation at the time of curing, and there is a disadvantage that the adjustment becomes complicated.

  When the light is obliquely incident on the deflecting / reflecting surface, the amount of adjustment for adjusting the sub-scanning position in the cylindrical lens is larger than when the light is incident horizontally. This sub-scanning position adjustment is necessary for adjusting the oblique incident angle of the light incident on the deflecting reflecting surface and adjusting the irradiation position in the sub-scanning direction on the surface of the photosensitive drum due to the attachment error of the folding mirror. In particular, in a configuration in which a folding mirror is provided in front of a scanning lens having power in the sub-scanning corresponding direction, the incident position of light on the scanning lens is shifted from a desired position with respect to the sub-scanning corresponding direction due to an attachment error of the folding mirror. End up. The deviation of the incident position causes deterioration of wavefront aberration, and increases in spot diameter in the sub-scanning direction on the surface of the photosensitive drum (hereinafter, abbreviated as “sub-scanning spot diameter increase” for convenience). This also leads to a positional deviation of the light spot in the sub-scanning direction (hereinafter abbreviated as “sub-scanning spot position deviation” for convenience).

  In the optical scanning device 2010A, only the exit optical surface of the image surface side scanning lens has a power in the direction corresponding to the sub-scanning, and the optical characteristic deterioration due to the mounting error of each folding mirror is adjusted to adjust the sub-scanning position of each cylindrical lens. Therefore, good optical characteristics can be obtained.

  Further, in the optical scanning device 2010A, when the environmental temperature changes and the adhesive expands / shrinks, each cylindrical lens is displaced in the main scanning corresponding direction and hardly displaced in the sub scanning corresponding direction. Since each cylindrical lens has no power in the main scanning direction, it has no influence on the optical characteristics. That is, there is no concern about deterioration of optical characteristics due to changes in environmental temperature.

  Note that, in place of each cylindrical lens, for example, even when an elliptical diffractive lens having a function of correcting a focus position shift in the main scanning direction due to a temperature change is used, the power in the main scanning corresponding direction is very small. There is almost no influence on the optical properties.

  15 and 16 show the effect of adjusting the sub-scanning position of the cylindrical lens 2204a in the K station. Here, symbol A is a case where the folding angle of the folding mirror 2106a and the folding mirror 2107a is shifted by 0.33 ° from the design value, and symbol B is that the folding angle of each folding mirror is 0.33 ° from the design value. This is a case where the sub-scanning position adjustment of 0.27 mm is performed in the cylindrical lens 2204a in a shifted state. FIG. 15 is a graph of the data of FIG.

  Since the folding angle of each folding mirror is shifted by only 0.33 °, the peripheral scanning height (near the end of the effective scanning region) results in a sub scanning spot diameter increase of 1 μm or more. This adversely affects the output image. At this time, when the sub-scanning position adjustment of the cylindrical lens 2204a is performed, the amount of increase in the sub-scanning spot diameter is suppressed to 0.1 μm or less at the total image height, and the mounting error of each folding mirror is absorbed, which is favorable. Optical characteristics can be obtained.

  17 and 18 show the effect of side-bonding the cylindrical lens 2204a at the K station. Here, the symbol C is a case where the cylindrical lens 2204a is bonded to the bottom surface, and the symbol D is a case where the cylindrical lens 2204a is bonded to the side surface. In side adhesion, the thickness of the adhesive layer was 1.5 mm, and the amount of expansion / contraction of the adhesive was 5%. At this time, the amount of displacement of the cylindrical lens 2204a in the sub-scanning corresponding direction was set to 0.08 mm, and the amount of increase in sub-scanning spot diameter at each image height position was calculated. In the side adhesion, the amount of displacement of the sub-scanning spot diameter at each image height position was calculated with the displacement amount of the cylindrical lens 2204a in the direction corresponding to the main scanning being 0.08 mm. FIG. 17 is a graph of the data of FIG.

  In the case of side adhesion, since the cylindrical lens 2204a does not have power in the main scanning direction, there is no influence on the optical characteristics even if it is displaced in the main scanning direction.

  Next, the configuration of the optical scanning device 2010B will be described.

  As shown in FIG. 19 and FIG. 20 as an example, the optical scanning device 2010B includes two light sources (2200c, 2200d), two coupling lenses (2201c, 2201d), two aperture plates (2202c, 2202d), 2 Two cylindrical lenses (2204c, 2204d), polygon mirror 2104B, deflector side scanning lens 2105B, three folding mirrors (2106c, 2106d, 2107c), two image plane side scanning lenses (2108c, 2108d), and two dustproofs Glass (2110c, 2110d) and a scanning control device (not shown) are provided. These are assembled at predetermined positions of the optical housing 2300B (not shown in FIG. 19, see FIG. 20).

  That is, the optical scanning device 2010B has the same configuration as the above-described optical scanning device 2010A.

  A light beam emitted from the light source 2200c (hereinafter, also referred to as “light beam LBc”) is obliquely incident on the polygon mirror 2104B through the coupling lens 2201c, the aperture plate 2202c, and the cylindrical lens 2204c.

  A light beam emitted from the light source 2200d (hereinafter, also referred to as “light beam LBd”) is incident obliquely on the polygon mirror 2104B via the coupling lens 2201d, the aperture plate 2202d, and the cylindrical lens 2204d.

  The light beam LBc deflected by the polygon mirror 2104B is irradiated to the photosensitive drum 2030c via the deflector side scanning lens 2105B, the folding mirror 2106c, the folding mirror 2107c, the image plane side scanning lens 2108c, and the dustproof glass 2110c. A light spot is formed. This light spot moves in the longitudinal direction of the photosensitive drum 2030c as the polygon mirror 2104B rotates. That is, the photosensitive drum 2030c is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030c, and the rotational direction of the photosensitive drum 2030c is the “sub-scanning direction” on the photosensitive drum 2030c.

  The light beam LBd deflected by the polygon mirror 2104B is applied to the photosensitive drum 2030d through the deflector-side scanning lens 2105B, the folding mirror 2106d, the image-side scanning lens 2108d, and the dust-proof glass 2110d, thereby forming a light spot. Is done. This light spot moves in the longitudinal direction of the photosensitive drum 2030d as the polygon mirror 2104B rotates. That is, the photosensitive drum 2030d is scanned. The moving direction of the light spot at this time is the “main scanning direction” on the photosensitive drum 2030d, and the rotational direction of the photosensitive drum 2030d is the “sub-scanning direction” on the photosensitive drum 2030d.

  The two light sources (2200c, 2200d), the two coupling lenses (2201c, 2201d), the two aperture plates (2202c, 2202d), and the two cylindrical lenses (2204c, 2204d) have a predetermined positional relationship with the holding member 10. It is held by and unitized.

  The two cylindrical lenses (2204c, 2204d) are side-bonded to the same side plate of the holding member 10.

  Therefore, even if the environmental temperature changes, there is no influence on the optical characteristics.

  As described above, each optical scanning device according to this embodiment includes two light sources, two pre-polarizer optical systems, a polygon mirror 2104A, and two scanning optical systems.

  Each light source and each pre-polarizer optical system are held by the holding member 10 and unitized. Each pre-polarizer optical system includes a cylindrical lens, and each cylindrical lens is side-bonded to the same side plate of the holding member 10.

  In this case, the moving direction of each cylindrical lens when the environmental temperature changes coincides with the main scanning corresponding direction, and the light spot on the surface of the photosensitive drum can be suppressed from being thickened in the sub-scanning direction. That is, even when the environmental temperature changes, it is possible to suppress the deterioration of the optical characteristics.

  In this case, the sub-scanning position adjustment of each cylindrical lens can be easily performed with high accuracy.

  By the way, if the cylindrical lens is bonded and fixed only at a part of one side end surface in the main scanning direction, the cylindrical lens is rotated around the optical axis by expansion / contraction of the adhesive and the optical housing due to temperature fluctuation. May rotate. This rotation around the optical axis leads to an increase in beam spot diameter in the main scanning direction and the sub-scanning direction.

  On the other hand, in the present embodiment, each cylindrical lens is bonded and fixed over the entire one end face in the main scanning direction, so that rotation of the line image forming lens around the optical axis due to temperature fluctuation can be prevented.

  Therefore, it is possible to stably perform high-precision optical scanning with a plurality of lights.

  Further, the light flux from each light source is obliquely incident on the polygon mirror. In this case, the error of the incident angle in the polygon mirror and the scanning lens results in the degradation of wavefront aberration, and the beam spot diameter is more likely to be degraded than in the case of horizontal incidence. The incident angle can be adjusted by adjusting the sub-scanning position of the cylindrical lens. When the cylindrical lens is bonded to the bottom surface as in the past, there is a limit to the adjustment amount of the sub-scanning position adjustment. A large amount of misalignment occurs, leading to deterioration of various optical characteristics. In the present embodiment, since the cylindrical lenses are bonded to the side surfaces, deterioration of wavefront aberration can be suppressed even when light beams from the respective light sources are obliquely incident on the polygon mirror.

  Further, since the light beams from the respective light sources are obliquely incident on the polygon mirror and are deflected by the same reflecting surface of the polygon mirror, the polygon mirror can be reduced in size and cost.

  The two cylindrical lenses are arranged close to each other in the sub-scanning corresponding direction. Therefore, a compact optical scanning device in the sub-scanning direction can be obtained. Furthermore, the oblique incident angle can be reduced, and good optical characteristics can be obtained.

  Further, since the two cylindrical lenses are fixed to the same surface of the holding member, it is easy to adjust the sub-scanning position. In addition, downsizing of the optical scanning device can be promoted. Furthermore, the number of parts can be reduced compared to the case where a dedicated fixed wall is provided.

  Further, since the two light sources and the two pre-deflector optical systems are held by the same holding member, the assembly process and the adjustment process can be simplified.

  The color printer 2000 according to this embodiment includes the optical scanning device 2010A and the optical scanning device 2010B, and as a result, a high-quality image can be stably formed.

  In the above embodiment, instead of the optical scanning device 2010A and the optical scanning device 2010B, four light sources, four pre-polarizer optical systems, one polygon mirror, and four scanning optical systems are provided. An optical scanning device may be used. As an example, as shown in FIG. 21, when the four light sources and the four pre-polarizer optical systems are held in the holding member 20 to form a unit, the four cylindrical lenses (2204 a to 2204 d) Side surfaces are bonded to 20 identical side plates.

  Moreover, although the case where a cylindrical lens was used as a line image formation lens was demonstrated in the said embodiment, it is not limited to this. For example, a lens having a line image forming function equivalent to that of a cylindrical lens and a temperature correcting function may be used.

  Further, in the above-described embodiment, the case where each cylindrical lens is bonded and fixed on the entire one side end surface in the main scanning correspondence direction has been described. However, the present invention is not limited to this, and as illustrated in FIG. Further, it may be fixed by bonding (bonding on both side surfaces) over the entire end surfaces on both sides in the main scanning corresponding direction. In this case, if the thicknesses of the adhesive layers on both side end faces are substantially the same, the stress caused by the expansion / contraction of the adhesive due to temperature fluctuations becomes substantially equal on both side end faces. Compared to the case, the amount of displacement of the cylindrical lens in the main scanning direction can be reduced.

  In the above embodiment, the case where the light flux from each light source is obliquely incident on the polygon mirror has been described. However, the present invention is not limited to this, and the light flux from each light source is horizontally incident on the polygon mirror. Also good.

  In the above embodiment, the toner image is transferred from the photosensitive drum to the recording paper via the transfer belt. However, the present invention is not limited to this and may be directly transferred to the recording paper.

  Moreover, although the said embodiment demonstrated the case where each light source had two light emission parts, it is not limited to this.

  In the above embodiment, the color printer 2000 is described as the image forming apparatus. However, the present invention is not limited to this, and may be, for example, an optical plotter or a digital copying apparatus.

  Further, an image forming apparatus using a silver salt film as the image carrier may be used. In this case, a latent image is formed on the silver salt film by optical scanning, and this latent image can be visualized by a process equivalent to a developing process in a normal silver salt photographic process. Then, it can be transferred to a photographic paper as a transfer object by a process equivalent to a printing process in a normal silver salt photographic process. Such an image forming apparatus can be implemented as an optical plate making apparatus or an optical drawing apparatus that draws a CT scan image or the like.

  Further, an image forming apparatus using a color developing medium (positive photographic paper) that develops color by the heat energy of a beam spot as an image carrier may be used. In this case, a visible image can be directly formed on the image carrier by optical scanning.

  In short, if the image forming apparatus includes the optical scanning device 2010A (or the optical scanning device 2010B), a high-quality image can be stably formed as a result.

  As described above, the optical scanning device according to the present invention is suitable for stably performing high-precision optical scanning with a plurality of lights. The image forming apparatus of the present invention is suitable for stably forming a high quality image.

  DESCRIPTION OF SYMBOLS 10 ... Holding member, 20 ... Holding member, 2000 ... Color printer (image forming apparatus), 2010A, 2010B ... Optical scanning device, 2030a-2030d ... Photosensitive drum (image carrier), 2104A, 2104B ... Polygon mirror (light deflection) 2105A, 2105B ... Polarizer side scanning lenses, 2106a to 2106d ... Folding mirrors, 2107a, 2107c ... Folding mirrors, 2108a to 2108d ... Image side scanning lenses (scanning lenses having power in the sub-scanning direction), 2200a to 2200d... Light source, 2204a to 2204d... Cylindrical lens (line image forming lens).

JP 2006-350251 A Japanese Patent No. 4366074 Japanese Patent No. 4172538

Claims (11)

An optical scanning device that optically scans at least two scanned surfaces individually in the main scanning direction,
At least two light sources arranged at different positions with respect to the sub-scanning direction orthogonal to the main scanning direction;
At least two line-image forming lenses that are provided corresponding to the at least two light sources and collect light beams emitted from the light sources in the sub-scanning direction;
An optical deflector for deflecting a plurality of light beams through the at least two line image forming lenses;
A scanning optical system for guiding a plurality of light beams deflected by the optical deflector to a corresponding scanned surface;
In the at least two line image forming lenses, the entire surface of one end face in the main scanning direction is fixed with an adhesive, and the center of the region where the light beam enters in the main scanning direction is the center of the optical surface with respect to the main scanning direction. An optical scanning device characterized by being shifted to the other side of the direction .   An optical scanning device that optically scans at least two scanned surfaces individually in the main scanning direction,
  At least two light sources arranged at different positions with respect to the sub-scanning direction orthogonal to the main scanning direction;
  At least two line-image forming lenses that are provided corresponding to the at least two light sources and collect light beams emitted from the light sources in the sub-scanning direction;
  An optical deflector for deflecting a plurality of light beams through the at least two line image forming lenses;
  A scanning optical system for guiding a plurality of light beams deflected by the optical deflector to a corresponding scanned surface;
  The at least two light sources include a first light source and a second light source;
  The at least two line image forming lenses include a first line image forming lens corresponding to the first light source and the first line image forming lens, the entire surface of both end faces or one end face in the main scanning direction being fixed with an adhesive. A second line image forming lens corresponding to the two light sources;
  The scanning optical system includes a first optical system that guides a light beam from the first light source to a corresponding scanned surface, and a second optical system that guides a light beam from the second light source to a corresponding scanned surface. Including
  The number of reflective optical elements in the first optical system is greater than the number of reflective optical elements in the second optical system,
  The optical scanning device characterized in that the amount of the adhesive applied to the first line image forming lens is larger than the amount of the adhesive applied to the second line image forming lens. Wherein the plurality of light beams through at least two linear image forming lens, with respect to the sub scanning direction, the optical scanning device according to claim 1 or 2, characterized in that it is obliquely incident on the reflecting surface. 4. The optical scanning device according to claim 1 , wherein the plurality of light beams that pass through the at least two line image forming lenses are deflected by the same reflecting surface of the optical deflector. 5. . It said at least two linear image forming lens includes an optical scanning apparatus according to any one of claims 1 to 4, characterized in that it is disposed close to each other with respect to the sub-scanning direction. A holding member for holding the at least two line image forming lenses;
It said at least two linear image forming lens includes an optical scanning apparatus according to any one of claims 1 to 5, characterized in that it is fixed to the same surface of the holding member. The scanning optical system includes a scanning lens having power in the sub-scanning direction, and a reflective optical element that reflects an optical path of a light beam deflected by the optical deflector in a direction toward the scanning lens. Item 7. The optical scanning device according to any one of Items 1 to 6 . Wherein said at least two light sources at least two linear image forming lens includes an optical scanning apparatus according to any one of claims 1 to 7, characterized in that held in the same holding member. Comprising at least two coupling lenses provided corresponding to the at least two light sources;
The at least two coupling lenses are arranged on an optical path between a corresponding light source and a line image forming lens, respectively, and a light beam emitted from the light source is a substantially parallel light beam,
Said at least two linear image forming lens includes an optical scanning apparatus according to any one of claims 1-8, characterized in that it is fixed to beams respectively incident substantially vertically.   The optical scanning device according to claim 1, wherein the adhesive is an ultraviolet curable adhesive. A plurality of image carriers;
The optical scanning apparatus and according to any one of claims 1 to 10, the optical scanning by using the light modulated in accordance with image information to the plurality of image bearing members; image forming apparatus provided with.

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