JP2008197187A - Optical scanning apparatus and image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus capable of scanning stably with light rays on a surface to be scanned and forming a high-quality image, at a high speed. <P>SOLUTION: A light beam Bk from a cylinder lens 204a and a light beam Bc from a cylinder lens 204b are set to enter a polygon mirror 104, each being inclined to -Z side relative to a normal line direction RH of a deflecting reflection face of the polygon mirror 104. Also, a light beam Bm from a cylinder lens 204c and a light beam By from a cylinder lens 204d are set to enter the polygon mirror 104 each inclined to +Z side relative to a normal line direction RH of the deflecting reflection face of the polygon mirror 104. In other words, light beams made incident on the -X side and the +Z side of the polygon mirror 104 are inclined opposite to each other, relative to the normal line direction of the polygon mirror 104, at least with respect to a subscanning line. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

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

  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, and forms a latent image by rotating the drum while scanning laser light using a polygon scanner (for example, a polygon mirror) in the axial direction of the photosensitive drum. Is common. In the field of electrophotography, an image forming apparatus is required to increase image density in order to improve image quality and to increase image output speed in order to improve operability.

  One way to achieve both high density and high speed is to rotate the polygon scanner at high speed, but this method increases noise, increases power consumption, and decreases durability in the polygon scanner. It will occur.

  Another method for achieving both high density and high speed is to make light emitted from a light source into multiple beams. As a method for realizing this multi-beam, (1) a method of combining a plurality of edge emitting lasers, (2) a method using a one-dimensional array of edge emitting lasers, and (3) a vertical cavity surface emitting laser (VCSEL). ) Using a two-dimensional array.

  The method (1) is inexpensive because a general-purpose laser can be used, but it is difficult to stably maintain the relative positional relationship between the laser and the coupling lens with a plurality of lights. There is a possibility that the interval between two adjacent scan lines in a plurality of scan lines formed on the surface to be scanned (hereinafter abbreviated as “scan line interval” for convenience) becomes non-uniform. In the method (1), the number of light sources is practically limited, and the density and speed are limited. In the method (2), the scanning line interval can be made uniform, but there is a disadvantage that the power consumption of the element is increased. Further, if the number of light sources is extremely increased, the amount of deviation of the beam from the optical axis of the optical system increases, and so-called optical performance may be deteriorated.

  On the other hand, in the method (3), the power consumption is about an order of magnitude smaller than that of the edge-emitting laser, and more light sources can be easily integrated two-dimensionally.

  For example, Patent Document 1 includes a first substrate that is mounted with a light-emitting element and its drive circuit, and that is attached to a housing fixed to the image forming apparatus body, and a connector that connects a harness from the image forming apparatus body. A second board that is mounted and separated from the first board and is attached to the housing, and an elasticity that electrically connects the terminals of the first board and the terminals of the second board. An optical scanning device having a deformable connecting member is disclosed.

  Patent Document 2 discloses a plurality of sets each including a light source in which a plurality of light-emitting points that can be independently modulated are arranged two-dimensionally, and a coupling lens that couples divergent light emitted from the light source. A light source device configured in combination, an optical scanning device equipped with the light source device, and an image forming device equipped with the optical scanning device are disclosed.

JP 2004-287292 A JP-A-2005-250319

  By the way, normally, in an optical scanning device, the amount of light emitted from a light source is detected by a detector such as a photodiode in order to prevent the amount of light from changing due to changes in temperature and changes over time and causing uneven density on the image. APC (Auto Power Control) is performed to monitor and control the output level based on the result. In this case, in the edge emitting laser, light is emitted in two directions, front and rear. Therefore, if the light emitted forward is used for scanning and the light emitted backward is used for monitoring, the scanning light is used as a light source. Even if it returns, there is little influence on the monitor result. However, since the surface emitting laser emits light in only one direction, it is necessary to divide or branch the emitted light and use one for scanning and the other for monitoring. At this time, the return light to the light source may affect the monitoring result.

  The present invention has been made under such circumstances, and a first object of the invention is to provide an optical scanning device capable of stably scanning a surface to be scanned with light.

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

  According to a first aspect of the present invention, there is provided an optical scanning device that scans a plurality of scanned surfaces with light, wherein at least one light source having a plurality of light emitting units; and deflects light from the at least one light source A deflector having a deflecting and reflecting surface; a plurality of scanning optical systems individually corresponding to the plurality of scanned surfaces and condensing the light deflected by the deflector onto the corresponding scanned surface; And a monitor optical system that monitors the amount of light emitted from one light source, and the light incident on one side of the deflector is tilted with respect to the normal direction of the deflecting reflection surface at least in the sub-scanning direction The optical scanning device is characterized in that it is incident from the above direction.

  In the present specification, regarding the sub-scanning direction, even if the tilting direction with respect to the normal direction of the deflecting reflection surface of the light incident on the deflector is the same, it is different if the tilt direction with respect to the normal direction is different. It shall be an inclination angle.

  According to this, the light incident on one side of the deflector is configured to be incident from a direction inclined with respect to the normal direction of the deflection reflection surface at least in the sub-scanning direction. In this case, the light emitted from the light source and reflected by the deflecting / reflecting surface can be prevented from returning to the light source side, and the amount of light emitted from the light source can be monitored with high accuracy. As a result, the surface to be scanned can be stably scanned with light.

  According to a second aspect of the present invention, there is provided at least one image carrier; and at least one optical scanning device of the present invention that scans the at least one image carrier with light containing image information. An image forming apparatus provided.

  According to this, since at least one optical scanning device of the present invention is provided, as a result, a high-quality image can be formed at high speed.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of a printer 10 according to an embodiment of the present invention. In this specification, the main scanning direction will be described as the Y-axis direction, the sub-scanning direction as the Z-axis direction, and the direction orthogonal to these will be described as the X-axis direction.

  The printer 10 is a tandem multicolor printer that forms a full-color image by superimposing four colors (black, cyan, magenta, and yellow), and includes an optical scanning device 1010, four photosensitive drums (30a, 30a, 30b, 30c, 30d), four charging chargers (32a, 32b, 32c, 32d), four developing rollers (33a, 33b, 33c, 33d), and four toner cartridges (34a, 34b, 34c, 34d). ) Four cleaning cases (31a, 31b, 31c, 31d), transfer belt 40, paper feed tray 60, paper feed roller 54, registration roller pair 56, fixing roller 50, paper discharge tray 70, paper discharge roller 58, A control device (not shown) that controls the above-described units in an integrated manner is provided.

  The photosensitive drum 30a, the charging charger 32a, the developing roller 33a, the toner cartridge 34a, and the cleaning case 31a 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. Constitute.

  The photosensitive drum 30b, the charging charger 32b, the developing roller 33b, the toner cartridge 34b, and the cleaning case 31b 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. Constitute.

  The photosensitive drum 30c, the charging charger 32c, the developing roller 33c, the toner cartridge 34c, and the cleaning case 31c are used as a set, and an image forming station (hereinafter also referred to as “M station” for convenience) that forms a magenta image. Constitute.

  The photosensitive drum 30d, the charging charger 32d, the developing roller 33d, the toner cartridge 34d, and the cleaning case 31d 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. Constitute.

  Each photosensitive drum has a photosensitive layer formed on the surface thereof. That is, the surface of each photoconductive drum is the surface to be scanned. The photosensitive drums are arranged at equal intervals in the X-axis direction with the longitudinal direction as the Y-axis direction. Each photosensitive drum is rotated clockwise (in the direction of the arrow) within the plane in FIG. 1 by a rotation mechanism (not shown).

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

  The optical scanning device 1010, based on multi-color image information (black image information, cyan image information, magenta image information, yellow image information) from a host device (for example, a personal computer), modulates the light modulated for each color. The surface of the corresponding charged photosensitive drum is irradiated. 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 configuration of the optical scanning device 1010 will be described later.

  Black toner is stored in the toner cartridge 34a, and the toner is supplied to the developing roller 33a. The toner cartridge 34b stores cyan toner, and the toner is supplied to the developing roller 33b. Magenta toner is stored in the toner cartridge 34c, and the toner is supplied to the developing roller 33c. Yellow toner is stored in the toner cartridge 34d, and the toner is supplied to the developing roller 33d.

  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 (hereinafter referred to as “toner image” for convenience) moves in the direction of the transfer belt 40 as the photosensitive drum rotates.

  The black, cyan, magenta, and yellow toner images are sequentially transferred onto the transfer belt 40 at a predetermined timing, and are superimposed to form a color image.

  Recording paper is stored in the paper feed tray 60. A paper feed roller 54 is arranged in the vicinity of the paper feed tray 60, and the paper feed roller 54 takes out the recording paper one by one from the paper feed tray 60 and conveys it to the registration roller pair 56. The registration roller pair 56 feeds the recording paper toward the transfer belt 40 at a predetermined timing. As a result, the color image on the transfer belt 40 is transferred to the recording paper. The recording sheet transferred here is sent to the fixing roller 50.

  In the fixing roller 50, heat and pressure are applied to the recording paper, whereby the toner is fixed on the recording paper. The recording paper fixed here is sent to the paper discharge tray 70 via the paper discharge roller 58 and is sequentially stacked on the paper discharge tray 70.

  Each cleaning case 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 of the corresponding charging charger again.

  As shown in FIG. 2 as an example, the optical scanning device 1010 includes two light source units (200a, 200b), two aperture plates (201a, 201b), two light splitting prisms (202a, 202b), Four cylindrical lenses (204a, 204b, 204c, 204d), polygon mirror 104, four fθ lenses (105a, 105b, 105c, 105d), eight folding mirrors (106a, 106b, 106c, 106d, 108a, 108b, 108c, 108d), four toroidal lenses (107a, 107b, 107c, 107d), two converging lenses (156a, 156b), and two light receiving elements (157a, 157b).

  Each light source unit includes a light source having a two-dimensional array of VCSELs (referred to as a two-dimensional array 100) in which 40 light emitting units are formed on one substrate, and a coupling lens.

  As shown in FIG. 3 as an example, the two-dimensional array 100 includes a direction corresponding to the main scanning direction (hereinafter, also referred to as “M direction” for convenience) to a direction corresponding to the sub-scanning direction (hereinafter referred to as “for convenience”. (Also referred to as “S direction”), and has four rows of light emitting unit rows in which 10 light emitting units 101 are arranged at equal intervals along a direction (hereinafter referred to as “T direction” for convenience) forming an inclination angle α. ing. These four light emitting unit rows are arranged at equal intervals in the S direction. That is, the 40 light emitting units 101 are two-dimensionally arranged along the T direction and the S direction, respectively. In the present specification, the “light emitting portion interval” refers to the distance between the centers of two light emitting portions.

  As an example, the interval between the two light emitting units located at both ends in the M direction is 270 μm, and the interval between the two light emitting units located at both ends in the S direction is 135 μm.

  Each light emitting unit 101 is a 780 nm band VCSEL. As shown in FIG. 4 as an example, a lower reflecting mirror 112, a spacer layer 113, an active layer 114, a spacer layer 115, an upper reflection are formed on an n-GaAs substrate 111. A mirror 117 and a semiconductor layer such as a p-contact layer 118 are sequentially stacked. Hereinafter, a structure in which a plurality of these semiconductor layers are stacked is also referred to as a “stacked body” for convenience. An enlarged view of the vicinity of the active layer 114 is shown in FIG.

The lower reflecting mirror 112 includes a low refractive index layer (referred to as a low refractive index layer 112a) made of n-Al _0.9 Ga _0.1 As and a high refractive index layer made of n-Al _0.3 Ga _0.7 As. 40.5 pairs are provided as a pair (with a high refractive index layer 112b). Each refractive index layer is set to have an optical thickness of λ / 4 when the oscillation wavelength is λ. Note that a composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition between the low refractive index layer 112a and the high refractive index layer 112b in order to reduce electrical resistance. Is provided.

The spacer layer 113 is a layer made of Al _0.6 Ga _0.4 As.

As shown in FIG. 5, the active layer 114 has a quantum well layer 114 a made of Al _0.12 Ga _0.88 As and a barrier layer 114 b made of Al _0.3 Ga _0.7 As.

The spacer layer 115 is a layer made of Al _0.6 Ga _0.4 As.

  The portion composed of the spacer layer 113, the active layer 114, and the spacer layer 115 is also called a resonator structure, and is set so that its thickness is an optical thickness of one wavelength (here, wavelength λ = 780 nm). (See FIG. 5).

The upper reflecting mirror 117 includes a low refractive index layer (referred to as a low refractive index layer 117a) made of p-Al _0.9 Ga _0.1 As and a high refractive index layer made of p-Al _0.3 Ga _0.7 As. There are 24 pairs (with high refractive index layer 117b). Each refractive index layer is set to have an optical thickness of λ / 4. A composition gradient layer (not shown) in which the composition is gradually changed from one composition to the other composition in order to reduce electric resistance between the low refractive index layer 117a and the high refractive index layer 117b. Is provided.

  A selective oxidation layer 116 made of AlAs is provided at a position away from the resonator structure in the upper reflecting mirror 117 by λ / 4.

  Next, a method for manufacturing the two-dimensional array 100 will be briefly described.

(1) The laminate is formed by crystal growth using metal organic chemical vapor deposition (MOCVD) or molecular beam crystal growth (MBE).

(2) Grooves are formed by dry etching around each of a plurality of regions, each of which serves as a light emitting portion, to form a so-called mesa portion. Here, the bottom surface of the etching is set so as to reach the lower reflecting mirror 112. Note that the bottom surface of the etching may be at least beyond the selective oxidation layer 116. As a result, the selectively oxidized layer 116 appears on the sidewall of the trench. In addition, the size (diameter) of the mesa portion is preferably 10 μm or more. This is because if it is too small, heat will be trapped during device operation, which may adversely affect the light emission characteristics. Furthermore, the width of the groove is preferably 5 μm or more. This is because if the groove width is too narrow, it becomes difficult to control the etching.

(3) The laminated body in which the groove is formed is heat-treated in water vapor, and selectively oxidizes a part of the selectively oxidized layer 116 in the mesa portion to change to an Al _x O _y insulator layer. At this time, an unoxidized AlAs region in the selectively oxidized layer 116 remains in the central portion of the mesa portion. As a result, a so-called current confinement structure is formed in which the drive current path of the light emitting part is limited to only the central part of the mesa part.

(4) Except for the region where the upper electrode 103 of each mesa part is formed and the light emitting part 102, for example, a 150 nm thick SiO ₂ protective layer 120 is provided, and polyimide 119 is buried in each groove and planarized.

(5) The upper electrode 103 is formed in each mesa portion on the p contact layer 118 except for the light emitting portion 102, and each bonding pad (not shown) is formed around the laminated body. And each wiring (not shown) which connects each upper electrode 103 and the bonding pad corresponding to each is formed.

(6) A lower electrode (n-side common electrode) 110 is formed on the back surface of the laminate.

(7) The laminate is cut into a plurality of chips.

  The coupling lens makes light from the two-dimensional array 100 substantially parallel light.

  Returning to FIG. 2, the aperture plate 201a has an aperture and defines the beam diameter of light from the light source unit 200a. The aperture plate 201b has an aperture and defines the beam diameter of light from the light source unit 200b. Each of the aperture plates is disposed to be inclined with respect to the corresponding light source unit in order to use the light reflected around the aperture for monitoring. In addition, this can prevent light reflected around the opening from returning to the light source unit.

  The light splitting prism 202a splits the light that has passed through the opening of the aperture plate 201a into two lights that are parallel to each other at a predetermined interval in the Z-axis direction. The light splitting prism 202b splits the light that has passed through the opening of the aperture plate 201b into two lights that are parallel to each other at a predetermined interval in the Z-axis direction.

  The cylinder lens 204 a is arranged on the optical path of the −Z side light (hereinafter also referred to as “black light” for convenience) of the two lights from the light splitting prism 202 a, and the black light is disposed near the deflection reflection surface of the polygon mirror 104. Thus, the sub-scanning direction converges.

  The cylinder lens 204 b is disposed on the optical path of + Z side light (hereinafter also referred to as “cyan light” for convenience) of the two lights from the light splitting prism 202 a, and cyan light is disposed near the deflecting reflection surface of the polygon mirror 104. Convergence with respect to the sub-scanning direction.

  The cylinder lens 204 c is arranged on the optical path of + Z side light (hereinafter also referred to as “magenta light” for convenience) of the two lights from the light splitting prism 202 b, and the magenta light is disposed near the deflecting reflection surface of the polygon mirror 104. Convergence with respect to the sub-scanning direction.

  The cylinder lens 204d is disposed on the optical path of the −Z side light (hereinafter also referred to as “yellow light” for convenience) of the two lights from the light splitting prism 202b, and the yellow light is near the deflecting reflection surface of the polygon mirror 104. Thus, the sub-scanning direction converges.

  The polygon mirror 104 has a four-stage mirror having a two-stage structure, and each mirror serves as a deflection reflection surface. The light from the cylinder lens 204a and the light from the cylinder lens 204d are respectively deflected on the first (lower) deflecting / reflecting surface, and the light and cylinder from the cylinder lens 204b are deflected on the second (upper) deflecting / reflecting surface. It arrange | positions so that the light from the lens 204c may be deflected, respectively. Further, the first-stage deflecting / reflecting surface and the second-stage deflecting / reflecting surface rotate with a phase shift of 45 °, and light scanning is alternately performed in the first and second stages.

  The light from the cylinder lens 204 a and the light from the cylinder lens 204 b are parallel to each other and enter the −X side of the polygon mirror 104. The light from the cylinder lens 204c and the light from the cylinder lens 204d are parallel to each other and enter the + X side of the polygon mirror 104.

  The fθ lens 105 a and the fθ lens 105 b are disposed on the −X side of the polygon mirror 104, and the fθ lens 105 c and the fθ lens 105 d are disposed on the + X side of the polygon mirror 104.

  That is, the optical scanning device 1010 is a counter scanning optical scanning device.

  The fθ lens 105a and the fθ lens 105b are stacked in the Z-axis direction, the fθ lens 105a faces the first-stage deflection / reflection surface, and the fθ lens 105b faces the second-stage deflection / reflection surface. Further, the fθ lens 105c and the fθ lens 105d are stacked in the Z-axis direction, the fθ lens 105c faces the second-stage deflection reflection surface, and the fθ lens 105d faces the first-stage deflection reflection surface.

  Therefore, the black light deflected by the polygon mirror 104 enters the fθ lens 105a, the yellow light enters the fθ lens 105d, the cyan light enters the fθ lens 105b, and the magenta light enters the fθ lens 105c.

  In this optical scanning device 1010, as shown in FIG. 6A as an example, both the light Bk from the cylinder lens 204a and the light Bc from the cylinder lens 204b are in the normal direction of the deflection reflection surface of the polygon mirror 104. It is set so as to be incident on the polygon mirror 104 while being inclined to the −Z side with respect to RH. Further, the light Bm from the cylinder lens 204 c and the light By from the cylinder lens 204 d are both inclined to the + Z side with respect to the normal direction RH of the deflecting reflection surface of the polygon mirror 104 so as to enter the polygon mirror 104. Is set. That is, the light incident on the −X side and the light incident on the + X side of the polygon mirror 104 are inclined to the opposite sides with respect to the normal direction of the polygon mirror 104 at least in the sub-scanning direction.

  The inclination angle of the light Bk from the cylinder lens 204a and the inclination angle of the light Bc from the cylinder lens 204b are equal to each other, and the inclination angle of the light Bm from the cylinder lens 204c and the inclination angle of the light By from the cylinder lens 204d are Are equal to each other.

  Further, the inclination angle of the light Bk from the cylinder lens 204a and the light Bc from the cylinder lens 204b is equal to the inclination angle of the light Bm from the cylinder lens 204c and the inclination angle of the light By from the cylinder lens 204d. Here, as an example, the magnitude of the inclination angle is set to 0.7 degrees.

  As an example, as shown in FIG. 6B, the light Bm from the cylinder lens 204c and the light By from the cylinder lens 204d are both − with respect to the normal direction RH of the deflecting reflection surface of the polygon mirror 104. When entering the polygon mirror 104 with an inclination to the Z side, or as shown in FIG. 6C as an example, all the light incident on the polygon mirror 104 is deflected and reflected by the polygon mirror 104 in the sub-scanning direction. In the case where it coincides with the normal direction of the surface, the reflected light from one fθ lens arranged with the polygon mirror 104 interposed therebetween enters the other fθ lens as flare light.

  The black light transmitted through the fθ lens 105a forms a spot image on the photosensitive drum 30a via the folding mirror 106a, the toroidal lens 107a, and the folding mirror 108a (see FIG. 7).

  The cyan light transmitted through the fθ lens 105b forms a spot image on the photosensitive drum 30b via the folding mirror 106b, the toroidal lens 107b, and the folding mirror 108b (see FIG. 7).

  The magenta light transmitted through the fθ lens 105c forms a spot image on the photosensitive drum 30c via the folding mirror 106c, the toroidal lens 107c, and the folding mirror 108c (see FIG. 7).

  The yellow light transmitted through the fθ lens 105d forms a spot image on the photosensitive drum 30d through the folding mirror 106d, the toroidal lens 107d, and the folding mirror 108d (see FIG. 7).

  In other words, the optical scanning device 1010 has four scanning optical systems that individually correspond to the four photosensitive drums and collect a plurality of lights deflected by the polygon mirror 104 on the corresponding photosensitive drums. .

  Further, in this optical scanning device 1010, the number of folding mirrors that bend the optical path of light toward the photosensitive drum 30a, the number of folding mirrors that bend the optical path of light toward the photosensitive drum 30b, and the optical path of light toward the photosensitive drum 30c. The number of folding mirrors for bending and the number of folding mirrors for bending the optical path of light traveling toward the photosensitive drum 30d are two. That is, the difference in the number of folding mirrors provided corresponding to each photosensitive drum is an even number. Thereby, as shown in FIG. 8A as an example, the bending direction of the scanning line in each photosensitive drum becomes the same direction, and the color misregistration can be easily reduced. If the difference between the number of folding mirrors provided corresponding to the photosensitive drum 30d and the number of folding mirrors provided corresponding to the other three photosensitive drums is one, it is illustrated as an example. As shown in FIG. 8B, the scanning line bending direction in the photosensitive drum 30d is reversed, and the color shift increases.

  The converging lens 156a is disposed on the optical path of the light reflected by the aperture plate 201a, and condenses the light reflected by the aperture plate 201a. The converging lens 156b is disposed on the optical path of the light reflected by the aperture plate 201b, and condenses the light reflected by the aperture plate 201b.

  The light receiving element 157a is disposed at the light condensing position via the converging lens 156a, and receives the light via the converging lens 156a. The light receiving element 157b is disposed at a light condensing position via the converging lens 156b, and receives light via the converging lens 156b.

  Each light receiving element outputs a signal (photoelectric conversion signal) corresponding to the amount of received light.

  As is clear from the above description, in the optical scanning device 1010 according to the present embodiment, the monitor optical system is configured by the aperture plate and the converging lens.

  As described above, according to the optical scanning device 1010 according to the present embodiment, two light sources (200a, 200b) having 40 light emitting units and a polygon having a deflecting reflection surface for deflecting light from the two light sources. Four scanning optical systems that individually correspond to the mirror 104 and the four photosensitive drums (30a, 30b, 30c, and 30d) and condense light deflected by the polygon mirror 104 onto the corresponding photosensitive drum; Two monitor optical systems for monitoring the amount of light emitted from each light source, and the light incident on the −X side and the light incident on the + X side of the polygon mirror 104 is at least in the sub-scanning direction. Inclined on the opposite sides to the normal direction of 104. Thereby, it can suppress that the light inject | emitted from each light source unit and reflected by the deflection | deviation reflective surface returns to the light source side. Therefore, the amount of light emitted from each light source can be accurately monitored, and as a result, the surface of the photosensitive drum can be stably scanned with the light.

  In the present embodiment, each of the four scanning optical systems includes two mirrors that bend the optical path of light, and the difference in the number of mirrors in each scanning optical system is zero. Thereby, the occurrence of color misregistration can be suppressed.

  In this embodiment, the light incident on the −X side and the light incident on the + X side of the polygon mirror 104 are inclined to opposite sides with respect to the normal direction of the polygon mirror 104 at least with respect to the sub-scanning direction. Therefore, it is possible to prevent the reflected light from one fθ lens arranged with the polygon mirror 104 interposed therebetween to enter the other fθ lens as flare light.

  By the way, in the method of increasing the writing density in the sub-scanning direction using the multi-beam light source, (1) the optical system provided on the optical path until the light emitted from the light source reaches the scanned surface is used. There are a method of reducing the lateral magnification in the sub-scanning direction and a method of (2) reducing the interval between the light emitting sections in the sub-scanning direction (reference symbol c in FIG. 3). However, in the method (1), it is necessary to reduce the width of the opening in the sub-scanning direction in the aperture plate that defines the beam diameter on the surface to be scanned, resulting in insufficient light quantity. On the other hand, in the method (2), it is difficult to secure the space necessary for the influence of thermal interference between the light emitting units and the wiring from each light emitting unit.

  In the present embodiment, the plurality of light emitting units are two-dimensionally arranged, and the interval between the two light emitting units located at both ends with respect to the direction corresponding to the main scanning direction is 2 located at both ends with respect to the direction corresponding to the sub scanning direction. Since it is larger than the interval between two light emitting units, it is possible to reduce the effect of thermal interference between the respective light emitting units and to reduce the interval between the light emitting units in the sub-scanning direction while securing the space necessary for passing the wiring of each light emitting unit. Can do.

  Further, the printer 10 according to the present embodiment includes the optical scanning device 1010 that can stably scan the surface to be scanned with light, and as a result, a high-quality image can be formed at high speed. It becomes possible.

  In the above-described embodiment, the case where the shape of each mesa portion of the two-dimensional array 100 is circular has been described. However, the shape is not limited to this, and may be any shape such as an elliptical shape, a square shape, or a rectangular shape. .

  Moreover, although the said embodiment demonstrated the case where the number of the light emission parts which comprise one light emission part row | line was 10 pieces, and the number of the light emission part row | line | columns, this invention is not limited to this. In this case, a plurality of light emitting units are two-dimensionally arranged, and an interval between two light emitting units located at both ends with respect to the direction corresponding to the main scanning direction is set at two intervals located at both ends with respect to the direction corresponding to the sub scanning direction. It is preferably larger than the interval between the light emitting portions.

  Moreover, although the said embodiment demonstrated the case where the space | interval of the two light emission parts located in both ends regarding M direction was 270 micrometers, and the space | interval of the two light emission parts located in both ends regarding S direction was 135 micrometers, it is limited to this. It is not a thing. It is preferable that the interval between the two light emitting units located at both ends with respect to the M direction is larger than the interval between the two light emitting units located at both ends with respect to the S direction.

  In the above embodiment, the case where the inclination angle of the light incident on the polygon mirror 104 is 0.7 degrees with respect to the normal direction of the polygon mirror 104 at least in the sub-scanning direction has been described. It is not limited to. However, since the wavefront aberration increases as the tilt angle increases, the tilt angle is preferably in the range of 0.5 to 1.0 degrees.

  In the above-described embodiment, the case where the polygon mirror 104 is configured by a four-stage mirror having a two-stage structure has been described. However, the present invention is not limited thereto. It may be configured. In this case, as shown in FIG. 9 as an example, when the light Bk from the cylinder lens 204a and the light Bc from the cylinder lens 204b are incident on the same position of the deflection reflection surface in the sub-scanning direction, the cylinder lens 204a It is preferable that the inclination angles of the light Bk and the light Bc from the cylinder lens 204b are different from each other. Similarly, when the light Bm from the cylinder lens 204c and the light By from the cylinder lens 204d are incident on the same position of the deflection reflection surface in the sub-scanning direction, the light Bm from the cylinder lens 204c and the light By from the cylinder lens 204d. It is preferable that the inclination angles are different from each other. For example, the inclination angles of the light Bc and the light By may be 0.7 degrees, and the inclination angles of the light Bk and the light Bm may be 1.46 degrees.

  In the above-described embodiment, the case where the optical scanning device 1010 is a counter scanning optical scanning device has been described. However, the present invention is not limited to this, and a so-called one-side scanning optical scanning device may be used. In this case, as shown in FIG. 10 as an example, the light Bk from the cylinder lens 204a, the light Bc from the cylinder lens 204b, the light Bm from the cylinder lens 204c, and the light By from the cylinder lens 204d are Is also incident on one side of the polygon mirror (-X side in FIG. 10). At this time, when each light is incident on a different position of the deflection reflection surface in the sub-scanning direction, the inclination angle of each light can be made the same.

  Moreover, in the said embodiment, as shown in FIGS. 11-13 as an example, it replaces with the said two-dimensional array 100, and the material of the one part semiconductor layer of the said some semiconductor layers of the two-dimensional array 100 is used. A modified two-dimensional array (referred to as a two-dimensional array 200) may be used. In the two-dimensional array 200, the spacer layer 113 in the two-dimensional array 100 is changed to a spacer layer 213, the active layer 114 is changed to an active layer 214, and the spacer layer 115 is changed to a spacer layer 215. is there.

The spacer layer 213 is a layer made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a wide band gap.

As shown in FIG. 12, the active layer 214 has a composition in which compressive strain remains and has a Ga ₀ having a tensile strain of four layers lattice-matched with the three GaInPAs quantum well layers 214a having a band gap wavelength of 780 nm. _.6 In _0.4 P barrier layer 214b.

The spacer layer 215 is a layer made of (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P having a wide band gap.

  A portion composed of the spacer layer 213, the active layer 214, and the spacer layer 215 is called a resonator structure, and the thickness thereof is set to be one wavelength optical thickness (see FIG. 12).

  Since the two-dimensional array 200 uses an AlGaInP-based material for the spacer layer, the band gap difference between the spacer layer and the active layer can be extremely large compared to the two-dimensional array 100 in the above embodiment. it can.

  In FIG. 13, the spacer layer / quantum well layer material is an AlGaAs / AlGaAs-based VCSEL with a wavelength of 780 nm (hereinafter referred to as “VCSEL_A” for convenience), and the spacer layer / quantum well layer material is AlGaInP / GaInPAs. In this system, a VCSEL having a wavelength of 780 nm band (hereinafter referred to as “VCSEL_B” for convenience) and a spacer layer / quantum well layer material is an AlGaAs / GaAs system and a VCSEL having a wavelength of 850 nm band (hereinafter referred to as “ For VCSEL_C "), the band gap difference between the spacer layer and the quantum well layer and the band gap difference between the barrier layer and the quantum well layer in a typical material composition are shown. Note that VCSEL_A corresponds to the VCSEL 101 of the two-dimensional array 100, and VCSEL_B of x = 0.7 corresponds to the VCSEL (referred to as VCSEL 201) in the two-dimensional array 200.

  According to this, it can be seen that VCSEL_B can take a larger band gap difference than VCSEL_C as well as VCSEL_A. Specifically, the band gap difference between the spacer layer and the quantum well layer in VCSEL_B is 767.3 meV, which is extremely larger than 465.9 meV in VCSEL_A. Similarly, the difference in the band gap between the barrier layer and the quantum well layer is superior to VCSEL_B, and better carrier confinement is possible.

  Further, in the VCSEL 201, since the quantum well layer has a compressive strain, the gain increase is large due to the band separation of the heavy hole and the light hole, and the gain becomes high, so that high output is possible with a low threshold. For this reason, the reflectance of the reflecting mirror on the light extraction side (here, the upper reflecting mirror 117) can be reduced, and a further increase in output can be achieved. Furthermore, since the gain can be increased, it is possible to suppress a decrease in light output due to a temperature rise, and it is possible to narrow the interval between the VCSELs in the two-dimensional array.

  In the VCSEL 201, since both the quantum well layer 214a and the barrier layer 214b are made of a material not containing aluminum (Al), the incorporation of oxygen into the active layer 214 is reduced. As a result, formation of a non-radiative recombination center can be suppressed, and the life can be further extended.

  By the way, for example, when a VCSEL two-dimensional array is used for a so-called writing optical unit, the writing optical unit is disposable when the life of the VCSEL is short. However, since the VCSEL 201 has a long life as described above, the writing optical unit using the two-dimensional array 200 can be reused. Therefore, promotion of resource protection and reduction of environmental load can be achieved. This also applies to other devices using a two-dimensional array of VCSELs.

  In the above-described embodiment, the case where the wavelength of the laser light emitted from each light emitting unit is in the 780 nm band has been described. However, the wavelength is not limited to this and may be any wavelength according to the sensitivity characteristic of the photosensitive drum 901. In this case, at least a part of the material constituting each light emitting part or at least a part of the structure of each light emitting part is changed according to the oscillation wavelength.

  In the above embodiment, a light source unit may be provided for each color. That is, four light source units may be provided.

  In the above embodiment, the case of a tandem color printer as the image forming apparatus has been described. However, the present invention is not limited to this. For example, even an image forming apparatus other than a printer (a copier, a facsimile, or a multifunction machine in which these are integrated) can form a high-quality image at a high speed if the image forming apparatus includes the optical scanning device 1010. It becomes possible.

  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 the above embodiment, the case of a multi-color printer is described as the image forming apparatus. However, the present invention is not limited to this, and it is possible to form a high-quality image at high speed even with a single-color image forming apparatus. Become.

  As described above, the optical scanning device of the present invention is suitable for stably scanning the surface to be scanned with light. The image forming apparatus of the present invention is suitable for forming a high quality image at high speed.

1 is a diagram illustrating a schematic configuration of a printer 10 according to an embodiment of the present invention. It is a perspective view which shows the optical scanning device in FIG. It is a figure for demonstrating the arrangement | sequence of each light emission part of the two-dimensional array of VCSEL contained in the light source in FIG. It is a figure for demonstrating the structure of each VCSEL in the two-dimensional array of FIG. It is the figure which expanded a part of VCSEL of FIG. FIGS. 6A to 6C are diagrams for explaining light traveling from the polygon mirror toward each fθ lens. It is a side view which shows the optical scanning device in FIG. FIG. 8A and FIG. 8B are diagrams for explaining the bending of the scanning line. It is a figure for demonstrating the modification of the polygon mirror in FIG. It is a figure for demonstrating the case of the one side scanning system. It is a figure for demonstrating the modification of VCSEL. It is the figure which expanded a part of VCSEL of FIG. It is a figure for demonstrating the characteristic of VCSEL of FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Printer (image forming apparatus), 30a-30d ... Photosensitive drum (image carrier), 104 ... Polygon mirror (deflector), 105a-105d ... f (theta) lens (a part of scanning optical system), 106a-106d ... Folding mirror (part of scanning optical system), 107a to 107d ... Toroidal lens (part of scanning optical system), 108a to 108d ... Folding mirror (part of scanning optical system), 156a, 156b ... Converging lens (monitoring optics) Part of the system), 200a ... light source unit (light source), 200b ... light source unit (light source), 201a, 201b ... aperture plate (part of the monitor optical system), 1010 ... light scanning device.

Claims (10)

An optical scanning device that scans a plurality of scanned surfaces with light,
At least one light source having a plurality of light emitting portions;
A deflector having a deflecting reflecting surface for deflecting light from the at least one light source;
A plurality of scanning optical systems individually corresponding to the plurality of scanned surfaces and condensing the light deflected by the deflector onto the corresponding scanned surfaces;
A monitor optical system for monitoring the amount of light emitted from the at least one light source;
The light scanning apparatus according to claim 1, wherein the light incident on one side of the deflector is incident from a direction inclined with respect to a normal direction of the deflection reflecting surface at least in the sub-scanning direction.   The optical scanning device according to claim 1, wherein the plurality of light emitting units are two-dimensionally arranged.   In the plurality of light emitting units, an interval between two light emitting units located at both ends in a direction corresponding to the sub-scanning direction is smaller than an interval between two light emitting units located at both ends in the direction corresponding to the main scanning direction. The optical scanning device according to claim 2.   4. Each of the plurality of scanning optical systems includes at least one mirror that bends the optical path of light, and the difference in the number of mirrors in each scanning optical system is an even number. The optical scanning device according to Item. The light incident on the deflector further includes light incident on the other side of the deflector,
2. The light incident on the one side and the light incident on the other side are inclined at opposite sides with respect to the normal direction of the deflection reflecting surface at least in the sub-scanning direction. The optical scanning apparatus as described in any one of -4.   6. The optical scanning device according to claim 5, wherein the light incident on the one side and the light incident on the other side have the same inclination with respect to the normal direction of the deflection reflection surface. The light incident on the deflector includes a first light and a second light that are incident on different positions of at least the sub-scanning direction of the same deflecting reflection surface,
The optical scanning device according to claim 1, wherein the first light and the second light have the same inclination angle with respect to a normal direction of the deflection reflection surface. . The light incident on one side of the deflector includes a first light and a second light,
8. The optical scanning device according to claim 1, wherein the first light and the second light have different inclination angles with respect to a normal direction of the deflection reflection surface. 9. At least one image carrier;
An image forming apparatus comprising: at least one optical scanning device according to claim 1 that scans the at least one image carrier with light including image information.   The image forming apparatus according to claim 7, wherein the image information is multicolor image information.

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