JP5041587B2 - Optical scanning apparatus and image forming apparatus - Google Patents

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 a light beam, and an image forming apparatus including the optical scanning apparatus.

  In current optical scanning devices and image forming apparatuses using the same, there are increasing demands for higher image quality, higher image forming speed, lower cost of the device, and the like. Challenges to achieve high image quality include reduction in scan line curvature, reduction in variation in beam spot diameter formed on the surface to be scanned, and reduction in beam spot misalignment by improving constant velocity characteristics. and so on.

  The challenge to achieve higher image formation speed is the realization of an optical scanning device that can simultaneously scan the surface to be scanned with a plurality of light beams. In recent years, various images employing a multi-beam method have been developed. A forming device has arrived. However, in these image forming apparatuses, since the light source that emits the light beam has a certain distance in the sub-scanning direction, the curved shape differs between the scanning lines, and as a result, the image quality is reduced. There is. In particular, in a full-color compatible image forming apparatus, for example, a tandem type image forming apparatus, which scans a scanning surface corresponding to each of a plurality of colors with different scanning optical systems and superimposes toner images corresponding to the respective colors, A major problem is a decrease in image quality caused by color misregistration and differences in image density.

  In addition, it is particularly effective to use a vertical cavity surface emitting laser (hereinafter abbreviated as VCSEL) that can easily form many light emitting points for emitting a light beam on one element as a light source. However, as the number of beams increases, the region where the light emitting points are arranged becomes wider around the optical axis, so the above-described problem becomes significant.

  A problem to achieve cost reduction of the apparatus is to reduce the thickness of a relatively expensive scanning lens among elements constituting the scanning optical system. However, if the scanning lens is made thinner, the degree of freedom in optical design decreases, and it becomes difficult to maintain and improve the optical performances. In addition, in order to reduce the cost of the apparatus, it is very disadvantageous to use a scanning lens made of glass. Therefore, it is indispensable to use a scanning lens made of a resin that is mass-productive and can be manufactured at a low cost. However, since the change in optical characteristics due to moisture absorption and temperature change is larger than that of glass, it is difficult to maintain scanning quality and image quality. Therefore, there is a need for a technique for reducing the cost of the apparatus using a thinned scanning lens while maintaining the performance of the optical characteristics described above.

  For each problem described above, for example, the inventions described in Patent Document 1 and Patent Document 2 have been proposed. In the invention described in Patent Document 1, by setting the intervals between the light emitting points formed adjacent to the light source to be equal intervals, the arrangement density of the light emitting points is reduced while reducing the influence of crosstalk due to heat generated from the light emitting points. It is the one that can be maximized. However, this technique complicates the arrangement of the light emitting points, which increases the memory capacity. In addition, Patent Document 1 does not disclose any reduction in scanning line interval variation.

  The invention described in Patent Document 2 is an invention that combines a light source in which light emitting points are two-dimensionally arranged and a scanning optical system that scans a light beam emitted from the light source. However, Patent Document 2 does not sufficiently disclose a technique for performing light scanning using an array of light emitting points or a light source having several tens of light emitting points.

JP 2001-272615 A JP-A-2005-250319

  The present invention has been made under such circumstances, and a first object of the present invention is to extend the life of a light source in which a light emitting section is two-dimensionally arranged and to reduce deterioration of optical characteristics due to heat generated from the light source. It is an object of the present invention to provide an optical scanning device capable of performing the above.

  A second object of the present invention is to provide an image forming apparatus capable of reducing running costs and forming a high quality image.

According to a first aspect of the present invention, there is provided an optical scanning device that scans a surface to be scanned in a main scanning direction with a plurality of light beams, and the plurality of light emitting units that emit the light beams have a first direction, And a light source two-dimensionally arranged in a plane parallel to a second direction orthogonal to the first direction; a deflector that scans the plurality of light beams in the main scanning direction; A scanning optical system that forms an image of a light beam on the surface to be scanned, and the arrangement intervals of the plurality of light emitting units in the first direction and the arrangement intervals in the second direction are non-uniform, the light source arrangement interval of the light emitting portion in the central portion, both end portions of the first direction, or have become wider than the arrangement interval of the light emitting portion at the both end portions in the second direction the plurality of light emitting unit includes a light emitting portion position for the first direction is the same A scanning device.

According to this, together with the prolong the life of the light source, it is possible to avoid the fluctuation of the optical characteristics due to thermal unevenness.

  According to a second aspect of the present invention, there is provided an image forming apparatus for forming an image by fixing a toner image formed based on a latent image obtained from information relating to an image to a recording medium. An optical scanning device; a photosensitive member on which a latent image is formed by the optical scanning device; a developing unit that visualizes the latent image formed on the surface to be scanned of the photosensitive member; And a transfer unit that fixes the toner image to the recording medium.

  According to this, the image forming apparatus includes the optical scanning device of the present invention. Therefore, it is possible to form a high-quality image on the recording medium while reducing the cost of the apparatus.

  Hereinafter, an embodiment of the present invention will be described with reference to FIGS. FIG. 1 shows a schematic configuration of an image forming apparatus 200 according to the present embodiment.

  The image forming apparatus 200 is a printer that prints an image by transferring a toner image onto plain paper (paper) using a Carlson process. As shown in FIG. 1, the image forming apparatus 200 includes an optical scanning device 100, a photosensitive drum 201, a charging charger 202, a toner cartridge 204, a cleaning case 205, a paper feeding tray 206, a paper feeding roller 207, and a registration roller pair 208. A transfer charger 211, a fixing roller 209, a paper discharge roller 212, a paper discharge tray 210, and a housing 215 for housing them.

  The housing 215 has a substantially rectangular parallelepiped shape, and openings that communicate with the internal space are formed on the side walls on the + X side and the −X side.

  The optical scanning device 100 is disposed above the housing 215 and scans the surface of the photosensitive drum 201 by deflecting a light beam modulated based on image information in the main scanning direction (Y-axis direction in FIG. 1). To do. The configuration of the optical scanning device 100 will be described later.

  The photosensitive drum 201 is a cylindrical member in which a photosensitive layer having a property that becomes conductive when irradiated with a light beam on the surface thereof. The direction is arranged as a longitudinal direction, and is rotated clockwise in FIG. 1 (direction indicated by an arrow in FIG. 1) by a rotation mechanism (not shown). In the vicinity thereof, the charging charger 202 is disposed at the 12 o'clock (upper) position in FIG. 1, the toner cartridge 204 is disposed at the 2 o'clock position, and the transfer charger 211 is disposed at the 6 o'clock position. A cleaning case 205 is disposed at the hour position.

  The charging charger 202 is disposed with a predetermined clearance with respect to the surface of the photosensitive drum 201, and charges the surface of the photosensitive drum 201 with a predetermined voltage.

  The toner cartridge 204 includes a cartridge main body filled with toner, a developing roller charged with a voltage having a polarity opposite to that of the photosensitive drum 201, and the toner charged in the cartridge main body via the developing roller. Supply to the surface.

  The cleaning case 205 includes a rectangular cleaning blade whose longitudinal direction is the Y-axis direction, and is disposed so that one end of the cleaning blade is in contact with the surface of the photosensitive drum 201. The toner adsorbed on the surface of the photosensitive drum 201 is peeled off by the cleaning blade as the photosensitive drum 201 rotates, and is collected in the cleaning case 205.

  The transfer charger 211 is arranged with a predetermined clearance with respect to the surface of the photosensitive drum 201, and a voltage having a polarity opposite to that of the charging charger 202 is applied.

  The paper feed tray 206 is disposed in a state where the + X side end protrudes from an opening formed in the side wall on the + X side of the housing 215 and can accommodate a plurality of sheets 213 supplied from the outside. .

  The sheet feeding roller 207 takes out the sheets 213 one by one from the sheet feeding tray 206, and enters a gap formed by the photosensitive drum 201 and the transfer charger 211 via a registration roller pair 208 including a pair of rotating rollers. To derive.

  The fixing roller 209 is composed of a pair of rotating rollers, overheats and pressurizes the paper 61, and guides it to the paper discharge roller 212.

  The paper discharge roller 212 is composed of a pair of rotating rollers and the like, and with respect to the paper discharge tray 210 disposed with the −X side end protruding from the opening formed in the −X side side wall of the housing 215, The sheets 213 sent from the fixing roller 209 are sequentially stacked.

  Next, the configuration of the optical scanning device 100 will be described. The optical scanning device 100 scans the writing area on the surface of the photosensitive drum 201 with a plurality of laser beams modulated based on the image data, so that points corresponding to pixels on the writing area continuously in the main scanning direction. By forming the device, the device forms a plurality of scanning lines. As shown in FIGS. 2A and 2B, which are schematic diagrams of the optical scanning device 100, the optical scanning device 100 is sequentially arranged on the light source 10 and the + X side of the light source 10. The coupling lens 11, the aperture member 12, the line image forming lens 13, the reflection mirror 14, the polygon mirror 15 disposed on the −Y side of the reflection mirror 14, and the polygon mirror 15 are sequentially disposed on the + X side. A first scanning lens 16 and a second scanning lens 17 are provided.

FIG. 3 is a diagram showing a plurality of VCSELs formed in the light source 10 together with the matrices M _{m and n} . The matrix M _{m, n} is a matrix of 80 rows and 20 columns (m = 1, 2, 3,... 80, n = 1, 2, 3,... 20), and one matrix is formed in the writing area of the photosensitive drum 201. This corresponds to one point constituting the scanning line to be processed. Then, the light source 10, the matrix _{M 1, 13, M 3, 16,} and _{M 5,18, M 7,20} 4 single VCSEL ₁ ~VCSEL ₄ disposed in a position corresponding to the matrix _{M 9,1, M 11,3, M 13,5, M 15,8} , M 17,13, M 19,16, M 21,18, and eight VCSEL ₅ ~VCSEL ₁₂ disposed at a position corresponding to the _{M 23,20} 8 arranged at positions corresponding to the matrix M _25,1 , M _27,3 , M _29,5 , M _31,8 , M _33,13 , M _36,16 , M _37,18 , M _39,20 and One of _VCSEL 13 _{~VCSEL 20,} the matrix _{M 42,1, M 44,3, M 46,5} , M 48,8, M 50,13, M 52,16, M 54,18, corresponding to _{M 56,20} 8 VCSELs ₂₁ to VCSELs arranged at positions ₂₈ and the matrix M _58,1 , M _60,3 , M _62,5 , M _64,8 , M _66,13 , M _68,16 , M _70,18 , M _72,20 and eight _VCSEL 29 ~VCSEL ₃₆ has, the matrix _{M 74,1, M 76,3, M 78,5} , four which are disposed at a position corresponding to the _{M 80, 8 VCSEL} 37 total ~VCSEL _{40 40} amino The VCSEL is formed two-dimensionally. Hereinafter, the 20 VCSEL ₁ ～VCSEL ₂₀ and the first light emission group 10a, as the 20 _VCSEL 21 _{~VCSEL 40} is referred to as a second light emission group 10b. For convenience of explanation, as shown in FIG. 3, yz coordinates having the origin at the center of the surface on which the VCSEL of the light source 10 is arranged are defined.

  The coupling lens 11 is a lens having a focal length of 46.0 mm, and shapes each of the 40 light beams emitted from the light source 10 into substantially parallel light.

  The aperture member 12 has a rectangular or elliptical opening whose size in the Y-axis direction (main scanning direction) is 5.64 mm and whose size in the Z-axis direction (sub-scanning direction) is 2.2 mm, It arrange | positions so that an aperture center may be located in the focus position vicinity of the coupling lens 11. FIG.

  The line image forming lens 13 is a cylindrical lens having a focal length of 104.7 mm, and forms an image of the light beam that has passed through the aperture member 12 in the vicinity of the reflection surface of the polygon mirror 15 in the sub-scanning direction.

  The polygon mirror 15 is a quadrangular prism-shaped member whose upper surface is a square inscribed in a circle having a radius of 7 mm. Deflection surfaces are formed on the four side surfaces of the polygon mirror 15, and are rotated at a constant angular velocity around an axis parallel to the Z axis by a rotation mechanism (not shown). Thereby, the light beam incident on the polygon mirror 15 is scanned in the Y-axis direction.

The first scanning lens 16 and the second scanning lens 17 are arranged such that the distances from the deflection surface to the incident surface of the polygon mirror 15 are 46.3 mm and 149.5 mm. Each of the centers (on the optical axis) has a thickness of 13.5 mm and 3.5 mm, for example, a scanning lens made of resin. These optical surface shapes are expressed by the following equations (1) and (2). ). Where Y is the coordinate in the main scanning direction with the optical axis position as the origin, Rm is the radius of curvature of the lens, a ₀₀ , a ₀₁ , a ₀₂ ,... Are the aspherical coefficients of the main scanning shape, and R _S0 is the curvature on the optical axis in the sub-scanning direction, and b ₀₀ , b ₀₁ , b ₀₂ ,... Are aspherical coefficients of the sub-scanning shape. The values of the coefficients are as shown in Table 1 below.

  FIG. 4A shows a function Cs (Y) for each lens height of the curvature in the sub-scanning direction of the first scanning lens 16 represented by Expression (2), and is shown by a dotted line in FIG. 4A. The curved line indicates the optical surface shape of the entrance surface L1R1, and the curve indicated by the solid line indicates the optical surface shape of the exit surface L1R2. FIG. 4B shows a function Cs (Y) for each lens height of the curvature in the sub-scanning direction of the second scanning lens 17 shown by the equation (2). The dotted line in FIG. The curve indicated by indicates the optical surface shape of the entrance surface L2R1, and the curve indicated by the solid line indicates the optical surface shape of the exit surface L2R2.

  FIG. 5A shows the shape of the first scanning lens 16 in the main scanning section shown by the equation (2), and the curve shown by the dotted line in FIG. 5A is the incident surface L1R1. The optical surface shape is shown, and the curve indicated by the solid line shows the optical surface shape of the exit surface L1R2. FIG. 5B shows the shape of the second scanning lens 17 in the main scanning section, and the curve shown by the dotted line in FIG. 5B shows the optical surface shape of the incident surface L2R1, and is a solid line. The curve shown shows the optical surface shape of the exit surface L2R2. The vertical axis indicates the coordinate X in the optical axis direction, the horizontal axis indicates the lens height, and the center in the sub-scanning direction when Y = 0 in Equation (2) unless otherwise specified. The axis that passes through the point.

  The lateral magnification in the sub-scanning direction of the entire optical system included in the optical scanning device 100 is 2.2 times, and the sub-scanning magnification of only the optical system on the scanning surface side from the polygon mirror 15 is -0.97 times. . In the optical scanning device 100, the aim of the beam spot diameter on the surface to be scanned is set to 52 μm in the main scanning direction and 55 μm in the sub-scanning direction.

  In FIG. 6A, when the surface to be scanned is scanned by the optical scanning device 100, the quadrilateral curvature in the main scanning direction with respect to the image height Y is indicated by a dotted line, and the field curvature in the sub-scanning direction is indicated by a solid line. Has been. In FIG. 6B, the fθ characteristic with respect to the image height Y is indicated by a dotted line, and the linearity is indicated by a solid line. 6A and 6B, the field curvature in the main scanning direction and the sub-scanning direction converges within a range of ± 1 mm, and the fθ characteristic and linearity for all image heights are ± 0. It converges in the range of 5%, and it can be seen that the variation in the beam spot diameter becomes very small even though the thickness is reduced as described above. FIG. 7 also shows the sub-scanning lateral magnification deviation Δβ. From FIG. 7, it can be seen that the sub-scanning lateral magnification deviation Δβ is suppressed to a range of ± 0.5% and is substantially constant.

  Next, the operation of the printer 200 configured as described above will be described. When the image information from the host device is received, the optical scanning device 100 is driven by the modulation data based on the image information, and 40 light beams modulated based on the image information are emitted from the light source 10. When this light beam is condensed on the deflection surface of the polygon mirror 15 by the line image forming lens 13 via the aperture member 12, it is scanned in the Y-axis direction by the polygon mirror 15. The light beam is incident on the first scanning lens 16 and the deflection speed is adjusted, and then the light beam is condensed on the surface of the photosensitive drum 201 via the second scanning lens 17.

  On the other hand, the surface of the photosensitive drum 201 is charged with a predetermined voltage by the charging charger 202, so that charges are distributed with a constant charge density. When the photosensitive drum 201 is scanned by the light beam scanned by the polygon mirror 15, a plurality of scanning lines defined by the charge distribution are formed in the writing area of the photosensitive drum 201. Hereinafter, it will be described in detail with reference to FIGS.

Figure 8 is a writing area 201a formed on the photosensitive drum 201 is a diagram schematically illustrating a beam spot _BS 1 _{to BS 40} of 40 moving on the writing area 201a in the main scanning direction in the first scanning. Each beam spot BS _{1 to} BS ₄₀ is formed by a light beam emitted from each of the VCSEL ₁ to VCSEL ₄₀ formed in the light source 10, and one grid shown in FIG. 8 indicates an area corresponding to one pixel. Is.

Scanning lines to be formed in the writing area, the scanning line L ₁ toward the sub-scanning _direction, L 2, _{L 3, ...} When L _i, in the first scan, the light beam from the first light emission group 10a As the formed 20 beam spots BS _{1 to} BS ₂₀ move in the main scanning direction, as shown in FIG. 8, the odd-numbered scanning lines from the scanning line L ₁ to the scanning line L ₄₀ are shown. Scan lines (L ₁ , L ₃ ,... L ₃₉ ) are formed in the write area 201a. In addition, the 20 beam spots BS _{21 to} BS ₄₀ formed by the light beam from the second light emitting group 10b move in the main scanning direction, so that of the scanning lines from the scanning line L ₄₁ to the scanning line L ₈₂ . , Even-numbered scan lines (L ₄₂ , L ₄₄ ,... L ₈₂ ) are formed in the write area 201a.

Figure 9 is a writing area 201a, a writing area 201a above in the second scan is a diagram schematically showing the 40 beam spots _BS 1 _{to BS 40} that moves in the main scanning direction. In the second scanning, 20 beam spots BS _{1 to} BS ₂₀ formed by the light beam from the first light emitting group 10a move in the main scanning direction, and as shown in FIG. 9, the scanning line L ₄₁ The odd-numbered scanning lines (L ₄₁ , L ₄₃ ,... L ₈₁ ) among the scanning lines from to L ₈₂ are formed in the writing area 201a. In addition, the 20 beam spots BS _{21 to} BS ₄₀ formed by the light beam from the second light emitting group 10b move in the main scanning direction, so that of the scanning lines from the scanning line L ₈₃ to the scanning line L ₁₂₄ , , Even-numbered scanning lines (L ₈₄ , L ₈₆ ,... L ₁₂₄ ) are formed in the writing area 201a.

That is, as can be seen with reference to FIG. 9, the writing area 201a is scanned with the light beam from the second light emitting group 10b and then scanned with the light beam from the first light emitting group 10a. , The scanning lines L _{41 to} L ₈₂ are formed adjacent to each other. Thereafter, third scanning, by repeating the scanning of the fourth, the plurality of scans, the write region 201a, the scanning lines L ₈₃ and subsequent scan lines are formed adjacent the electrostatic latent image based on the image data Is formed.

  When an electrostatic latent image is formed on the surface of the photosensitive drum 201, toner is supplied to the surface of each photosensitive drum 201 by the developing roller of the toner cartridge 203. At this time, since the developing roller of the toner cartridge 203 is charged with a voltage having a polarity opposite to that of the photosensitive drum 201, the toner attached to the developing roller is charged with the same polarity as that of the photosensitive drum 201. Therefore, no toner adheres to the portion of the surface of the photosensitive drum 201 where the electric charges are distributed, and the toner adheres only to the scanned portion, so that the electrostatic latent image is visualized on the surface of the photosensitive drum 201. A toner image is formed. The toner image is attached to the sheet 213 by the transfer charger and then fixed by the fixing roller 209 to form an image on the sheet. The paper 213 on which the image is formed in this manner is discharged by the paper discharge roller 212 and sequentially stacked on the paper discharge tray 210.

As described above, in the optical scanning device 100 according to the present embodiment, the 40 VCSELs formed in the light source 10 have the arrangement interval in the main scanning direction as shown in FIG. It is arranged so as to narrow toward the + y side and the −y side from the vicinity of the intersection of the z-axis). Further, in the sub-scanning direction, the interval between the VCSEL ₂₀ and the VCSEL ₂₁ is larger than the interval between other adjacent VCSELs. Therefore, only the VCSEL arranged at the center of the light source 10 is prevented from becoming high temperature due to thermal interference from other VCSELs, thereby extending the life of the light source and avoiding fluctuations in optical characteristics due to thermal unevenness. It becomes possible.

Further, in terms of optical characteristics, the distance between the VCSEL ₁ and the VCSEL _{40 at} both ends in the main scanning direction, and the VCSEL ₅ , VCSEL ₁₃ , VCSEL ₂₁ , VCSEL ₂₉ , VCSEL ₃₇ and VCSEL ₄ , VCSEL ₁₂ , VCSEL at both ends in the sub-scanning direction. ₂₀ , VCSEL ₂₈ , and VCSEL ₃₆ are preferably as small as possible from the viewpoint of preventing aberrations and reducing the size of the optical element. For this reason, in the periphery of the light source 10 with high cooling efficiency of the VCSEL, the light source 10 can be reduced in size by increasing the arrangement interval of the VCSELs.

In general, the distance between the scanning lines by the light beam from the VCSEL farthest in the main scanning direction is likely to vary greatly due to component manufacturing errors. In the optical scanning apparatus 100 according to this embodiment, adjacent with respect to the z-axis direction (sub scanning direction), the VCSEL ₄ and VCSEL _5, VCSEL ₁₂ and _VCSEL 13, VCSEL ₂₀ that is most distant in the y-axis direction (main scanning direction) Among the five VCSELs of VCSEL ₂₁ , VCSEL ₂₈ and VCSEL ₂₉ , VCSEL ₃₆ and VCSEL ₃₇ , the intervals in the sub-scanning direction of the VCSEL ₄ and VCSEL ₅ and VCSEL ₃₆ and VCSEL ₃₇ of the pair at both ends of the sub-scanning direction are The interval between the VCSEL ₂₀ and the VCSEL _{21 in} the center in the scanning direction is smaller than the interval in the sub-scanning direction. As described above, by reducing the interval in the sub-scanning direction between the pair of VCSELs ₄ and VCSEL ₅ and the VCSEL ₃₆ and VCSEL ₃₇ at both ends in the sub-scanning direction, the variation in the scanning line interval formed in the writing region is reduced. It becomes possible.

The VCSELs located at both ends in the sub-scanning direction are most subject to scanning position fluctuations due to temperature. In particular, this problem becomes significant when the scanning lenses 16 and 17 are made of resin for cost reduction. Therefore, in the optical scanning apparatus 100 according to the present embodiment, the main scanning direction at the farthest pair of VCSEL ₁ and VCSEL _40, by arranging the position closest to the z-axis of the center in the main scanning direction, VCSEL ₁ The light beam from the VCSEL ₄₀ passes through the vicinity of the optical axis of each element of the optical system. As a result, it is possible to reduce the influence of the manufacturing error of the parts and reduce the scanning line interval variation.

  Further, in the optical scanning device 100 according to the present embodiment, every other scanning line is formed by the light beam from the second light emitting group 10b among the scanning lines sequentially formed adjacent to the writing region 201a. Subsequent light beams from the first light emitting group 10a form scanning lines adjacent to the scanning lines formed by the light beams from the second light emitting group 10b. In this case, the interval between the scan lines formed in one scan is twice or more than the interval between the scan lines finally formed in the writing area 201a. Thereby, the arrangement interval of the VCSELs formed in the light source 10 in the sub-scanning direction can be doubled or more as compared with the arrangement interval corresponding to the adjacent scanning lines on the writing area 201a. Therefore, thermal interference between VCSELs can be reduced, and as a result, thermal degradation of the light source 10 can be suppressed.

For example, as shown in FIG. 10A, the scanning line L1 by the light beam from the VCSEL ₁ and the scanning line L40 by the light beam from the VCSEL ₄₀ are caused by temperature fluctuations due to the characteristics of the optical system. However, the scanning line L20 by the light beam from the VCSEL ₂₀ disposed in the vicinity of the optical axis and the scanning line L21 by the light beam from the VCSEL ₂₁ are relatively small in curvature. Therefore, for example, as shown in FIG. 10B, the scanning lines having a large curvature are avoided from being adjacent to each other, and as shown in FIG. 10C, the scanning lines by the light beam from the VCSEL ₁ and By making the scanning line L21 having a small curvature adjacent to the scanning line by the light beam from the VCSEL _40, it is possible to reduce the variation in the scanning line interval formed on the surface to be scanned. .

  In the optical scanning device 100 according to the present embodiment, there are a plurality (five) of VCSELs having the same y coordinate of the light source 10. As a result, the timing of starting and ending writing can be shared, so that the portion that holds the timing information can be reduced, and the cost can be reduced, such as memory capacity reduction.

  In this optical scanning device 100, it is desirable that the line image forming lens 13 is attached so as to be movable in a direction parallel to the sub-scanning direction or is fixed after adjustment. In high-density writing, reduction of sub-scanning beam pitch variation becomes an issue. The sub-scanning beam pitch is generally a value of several tens of μm. When the writing density is high, for example, 600 dpi, it does not pose a big problem on the image. However, for example, at the time of 1200 dpi writing, the scanning line interval is approximately 21 μm, and the above-described sub-scanning beam pitch value causes a large deterioration in image quality.

  In the optical scanning device 100 of this embodiment, FIG. 11A showing a variation in sub-scanning beam pitch due to a manufacturing error and a temperature change (a legend such as 2nd · 1st in the figure is the first scanning line and 2 3 represents the sub-scanning beam pitch between the second scanning lines, the numbers being 1st, 2nd, etc. in order from the + side in the sub-scanning direction according to the enlarged view of the light source in FIG. As can be seen from the above, the optical system of the optical scanning device 100 reduces the difference between the image heights of the sub-scanning lateral magnification (hereinafter referred to as Δβ) as much as possible, so that the sub-scanning beam pitch variation Is still about 13 μm. In 2400 dpi high-density writing, the scanning line interval is 11 μm, and this value causes a problem in image quality.

  FIG. 11B is a diagram showing the sub-scanning beam pitch after adjustment of the line image forming lens. As can be seen from FIG. 11B, the sub-scanning beam pitch is 8.5 μm, which can be effectively reduced to the extent that there is no problem even in high-density writing. As described above, it is effective for the present inventor to perform the Z shift adjustment (position adjustment in the Z-axis direction) of the line image forming optical element with respect to the sub-scanning beam pitch variation reduction, which is limited only by the conventional optical system design. I found out. With respect to these adjustments, the line image forming optical element may be adjusted in a separate process after being movably assembled within a certain range in the optical housing of the optical scanning device, or may be performed at the stage of assembly.

  In order to realize this adjustment mechanism, a line image forming optical element can be provided in the optical housing using an intermediate member. As an example, the line image forming lens 13 of the optical scanning device according to the present embodiment is a set of L-shape formed on a housing 101 such as a casing of the optical scanning device 100 as shown in FIG. Both end portions in the Y-axis direction are supported on the support portion 101a via intermediate members 102 made of a resin material transparent in the ultraviolet region.

  As can be seen from the developed perspective view of FIG. 12B, the set of intermediate members 102 is a rectangular parallelepiped member whose longitudinal direction is the Z-axis direction, and the surfaces on the + Y side and the −Y side are respectively supported. The line image forming lens 13 is bonded to the member 101a, and the + Y side of the −X side surface and the vicinity of the outer edge of the −Y side are bonded to the + X side surface of the intermediate member 102 (hereinafter referred to as an adhesive surface). Thus, it is supported by the support portion 101a. Therefore, when the line image forming lens 13 is supported, the line image forming lens 13 is positioned at an arbitrary position in the Z-axis direction and the X-axis direction by changing the bonding position or the bonding posture of the intermediate member 102. In addition, it is possible to rotate an arbitrary angle around an axis parallel to the Y axis, that is, it is possible to adjust three degrees of freedom, and by rotating the line image forming lens 13 with respect to the intermediate member 102. A rotation around an axis parallel to the X axis is also possible.

  By using the intermediate member 102, adjustment can be performed with many degrees of freedom as described above, and optical performance can be further improved. For example, when the line image forming lens 13 is directly held and fixed to the support portion 101a without using the intermediate member 102, the degree of freedom of rotation adjustment and the degree of freedom of translation are reduced. Cannot compensate for performance degradation. Further, when the line image forming lens 13 is held, since the line image forming lens 13 is not fixed while being tilted with respect to each member, a surface (line image forming lens 13) that is an extension of an optical surface with good flatness accuracy. It is desirable to use the + X side of the surface in contact with the intermediate member 102 for fixing. In that case, in order to adjust the beam waist position in the sub-scanning direction on the surface to be scanned, an intermediate member (102) as shown in FIG. Hereinafter, an actual adjustment method will be described with reference to FIG.

  While holding the line image forming lens 13 with the jig 104 and measuring the optical characteristics of the optical scanning device 100, the line image forming lens 13 is rotated about the Z axis direction, the X axis direction, the Y axis rotation direction, and the X axis rotation. Move in each direction of rotation and adjust to the optimal posture. Here, the optical characteristics are a beam waist position, a beam spot diameter, and a sub-scanning beam pitch. For the sub-scanning beam pitch, the interval between the light beams at both ends in the sub-scanning direction, which is indicated by “40th · 01st” in FIG. That is, the light sources corresponding to these two light beams are turned on, and the beam position in the sub-scanning direction and the distance between them are measured at the image heights at both ends on the surface to be scanned. As shown in FIG. The line image forming lens held by the jig is moved in the sub-scanning direction so that the distance between the side and the minus side becomes substantially the same value. By adjusting in this way, the sub-scanning beam pitch can be optimized, and at that time, the sub-scanning beam pitch for other light beams can be optimized at the same time. Further, the beam waist position is optimized by movement in the X-axis direction, and the beam spot diameter is optimized by rotation around the X-axis, and the beam spot diameter is adjusted to be the smallest on the surface to be scanned. The adjustment is preferably performed in the order of movement in the X-axis direction, rotation around the X-axis, and movement in the sub-scanning direction. However, the adjustment may be performed in any other order or at the same time. You may perform rotation adjustment of. Thereafter, the intermediate member 102 coated with an adhesive, for example, an ultraviolet curable resin, is abutted against both the line image forming lens 13 and the support portion 101a (temporary fixing). Then, the intermediate member 102 is fixed to the line image forming lens 13 and the support portion 101a by irradiating ultraviolet rays. Since the intermediate member 102 is a transparent material, it has a high degree of freedom in ultraviolet irradiation and can be fixed quickly and uniformly. Here, “adjustable” in the present embodiment means that initial adjustment is possible, adjustment after assembly is possible, and that there is no positioning reference. In the present embodiment, the housing and the intermediate member are made of different materials. At this time, since the linear expansion coefficients are different from each other, it is conceivable that the position of the optical element changes due to a temperature change. Therefore, as shown in FIG. 12A, it is desirable that the surface to which the intermediate member 102 of the support portion 101a is bonded is a plane perpendicular to the main scanning direction.

  In the optical scanning device 100 according to the present embodiment, it is desirable that the power of the second scanning lens 17 is larger than that of the first scanning lens 16. By setting in this way, it becomes easy to reduce the difference in magnification, the change in magnification due to temperature can be reduced, and the variation in the sub-scanning beam pitch due to the temperature change can be reduced.

FIG. 14 is a schematic view showing a cross-sectional structure of the VCSEL, and FIG. 15 is an enlarged view around the active layer in FIG. Each VCSEL of the light source 10 according to the present embodiment is a 780 nm band VCSEL. As can be understood from FIG. 14 and FIG. 15, Al ₀ ... Is formed on the n-GaAs substrate 21 on which the n-side electrode 20 is formed _{. An} active layer 24 including a quantum well layer 24 a made of ₁₂ Ga _0.88 As and a barrier layer 24 b made of Al _0.3 Ga _0.7 As, and from the active layer 24 and Al _0.6 Ga _0.4 As A one-wavelength optical thickness resonator region consisting of spacer layers 23 and 25, and 40.5 pairs of n-Al _0.3 Ga _0.7 As high refractive index layers with an optical thickness of each layer λ / 4; A lower reflecting mirror 22 composed of a low refractive index layer of n-Al _0.9 Ga _0.1 As, 24 pairs of p-Al _0.3 Ga _0.7 As high refractive index layer and p-Al _0.9 Ga. Upper reflector 27 made of _0.1 As low refractive index layer It is a composition that is sandwiched between. An AlAs selectively oxidized layer 30 surrounded by the AlxOy current confinement layer 26 is provided on the upper reflecting mirror 27 that is λ / 4 away from the resonator region. Between each layer of the reflecting mirrors 22 and 27, there is included a composition gradient layer (not shown) whose composition gradually changes in order to reduce the resistance value.

  Here, a method for forming a VCSEL provided in the light source 10 will be described. First, each of the above layers is formed by crystal growth using a metal organic chemical vapor deposition method (MOCVD method) or a molecular beam crystal growth method (MBE method).

  Next, a mesa shape is formed by forming a groove having a depth of, for example, 4.5 μm around the region to be an element region by dry etching. In general, the etching bottom surface is provided at least beyond the AlAs selective oxidation layer 30.

Next, the AlAs selectively oxidized layer 30 whose side surface is exposed by the groove forming process by etching is heat-treated in water vapor to oxidize the periphery to an Al _x O _y insulator layer, and the element driving current path is formed at the center. A current confinement structure is formed that limits only to the unoxidized AlAs region.

Next, a SiO ₂ protective layer (not shown) having a thickness of 150 nm, for example, is provided except for the region where the upper electrode 31 is formed on each element region and the light emitting portion 32, and the etched portion is embedded with polyimide 29. Flatten.

Next, the polyimide and SiO ₂ protective layer (not shown) on the upper reflecting mirror having the p contact layer 28 and the light emitting portion in each element region are removed, and the P side other than the light emitting portion 32 on the p contact layer 28 is removed. An individual electrode 31 is formed, and an n-side electrode is formed on the lower surface of the n-GaAs substrate 21.

  In the case of this embodiment, the mesa portion formed by the dry etching method becomes each surface emitting laser element. The method of forming the VCSEL arrangement of the light source 10 can be formed by forming a photomask along the VCSEL arrangement of the present invention, forming an etching mask by a normal photolithography process, and etching. For electrical and spatial separation of each element of the array, it is preferable to provide a groove of about 4 to 5 μm or more between the elements. This is because if it is too narrow, it becomes difficult to control etching. In addition to the circular shape as in the present embodiment, the mesa portion can have any shape such as an ellipse, a square, or a rectangular rectangle. Further, the size (diameter or the like) is preferably about 10 μm or more. This is because if it is too small, heat will be accumulated during device operation and the characteristics will deteriorate.

Note that the above-described surface-emitting laser in the 780 nm band can be manufactured using another material. FIG. 16 shows an enlarged view around the active layer made of another material. As shown in FIG. 16, the active layer has a compressive strain composition and Ga _0.6 In ₀ having a four-layer tensile strain lattice-matched with a three-layer GaInPAs quantum well active layer 24 c having a band gap wavelength of 780 nm. _.4 is composed of a P barrier layer 24d, which is a wide band gap as (spacer layer in this embodiment) cladding layer 23, 25 for confining electrons _{(a l0.7 Ga 0.3) 0.5 in} 0 _.5 P is used. The band gap difference between the cladding layer and the quantum well active layer can be made extremely large as compared with the case where the carrier confinement cladding layer is formed of AlGaAs.

  Table 2 below shows an AlGaAs (spacer layer) / AlGaAs (quantum well active layer) system 780 nm and 850 nm surface emitting semiconductor laser, and an AlGaInP (spacer layer) / GaInPAs (quantum well active layer) system 780 nm surface emitting semiconductor. The band gap difference between the spacer layer and the well layer and the barrier layer and the well layer at the typical material composition of the laser is shown. Note that the spacer layer is a layer between the active layer and the reflecting mirror in the case of a normal configuration, and indicates a layer having a function as a cladding layer for confining carriers.

  As shown in the following Table 2, according to the AlGaInP (spacer layer) / GaInPAs (quantum well active layer) system 780 nm surface emitting semiconductor laser, not only the AlGaAs / AlGaAs system 780 nm surface emitting semiconductor laser but also the AlGaAs / AlGaAs system It can be seen that the band gap difference can be made larger than that of the 850 nm surface emitting semiconductor laser. Specifically, the band gap difference between the cladding layer and the active layer is 767 meV, which is very large, compared to 466 meV (when the Al composition is 0.6) when the cladding layer is formed of AlGaAs. Similarly, the band gap difference between the barrier layer and the active layer also has a dominant difference, resulting in good carrier confinement.

  In addition, since the active layer has compressive strain, the increase in gain is increased by band separation of heavy holes and light holes. Because of these high gains, the output was high at a low threshold. Note that this effect cannot be obtained with a surface-emitting laser having a wavelength of 780 nm or 850 nm manufactured using an AlGaAs system having substantially the same lattice constant as the GaAs substrate. Furthermore, by lowering the threshold by improving carrier confinement and increasing the gain by the strained quantum well active layer, it is possible to reduce the reflectivity of the light extraction side DBR and further increase the output.

  In addition, the active layer and the barrier layer are made of a material that does not contain Al, and are formed as an Al-free active region (a quantum well active layer and a layer adjacent thereto), so that oxygen uptake is reduced. Formation of a non-radiative recombination center can be suppressed, and a long life can be achieved. As a result, the writing unit or the light source unit can be reused.

  Next, a modification of the optical scanning device 100 will be described. Note that the description of the same or equivalent components as those in the above embodiment will be omitted.

  FIGS. 17A and 17B are diagrams showing a schematic configuration of an optical scanning device 100 ′ according to a modification. As shown in FIGS. 17A and 17B, the optical scanning device 100 ′ includes a light source 10, a coupling lens 11, an aperture member 12, and a line image, which are sequentially arranged on the + X side of the light source 10. The forming lens 13, the reflection mirror 14, the polygon mirror 15 disposed on the −Y side of the reflection mirror 14, and the first scanning lens 16 and the second scanning lens 17 sequentially disposed on the + X side of the polygon mirror 15. And.

  The coupling lens 11 is a lens having a focal length of 46.0 mm, and shapes each of the 40 light beams emitted from the light source 10 into substantially parallel light.

  The aperture member 12 has a rectangular or elliptical opening whose size in the Y-axis direction (main scanning direction) is 5.8 mm and whose size in the Z-axis direction (sub-scanning direction) is 1.22 mm. It arrange | positions so that an aperture center may be located in the focus position vicinity of the coupling lens 11. FIG.

  The line image forming lens 13 is a cylindrical lens having a focal length of 58 mm, and forms an image of the light beam that has passed through the aperture member 12 in the vicinity of the reflection surface of the polygon mirror 15 in the sub-scanning direction.

  The polygon mirror 15 is a quadrangular prism-shaped member whose upper surface is a square inscribed in a circle having a radius of 7 mm. Deflection surfaces are formed on the four side surfaces of the polygon mirror 15, and are rotated at a constant angular velocity around an axis parallel to the Z axis by a rotation mechanism (not shown). Thereby, the light beam incident on the polygon mirror 15 is scanned in the Y-axis direction. The light beam is incident on the deflecting surface at an angle of 0.7 degrees with respect to the normal surface of the reflecting surface. In the present modification, the effective diameter of the deflection surface is 6.8 mm in the main scanning direction and 2 mm in the sub-scanning direction.

   The first scanning lens 16 and the second scanning lens 17 are arranged such that the distances from the deflection surface to the incident surface of the polygon mirror 15 are 46.3 mm and 149.5 mm. Each of the centers (on the optical axis) has a thickness of 13.5 mm and 3.5 mm, for example, a resin-made scanning lens, and these optical surface shapes are represented by the following equations (3) to (5). Represented by a function. However, X represents coordinates in the optical axis direction, and Y represents coordinates in the main scanning direction. Cm represents the curvature in the main scanning direction at the center (Y = 0) and is the reciprocal of the radius of curvature Rny, and An to En are aspherical coefficients of the main scanning shape. Cs (Y) is a curvature in the sub-scanning direction with respect to Y. Further, values of each aspheric coefficient and the like are as shown in Table 3 below.

  Further, the main scanning cross-sectional shapes of the first surface and the second surface of the first scanning lens 16 are as indicated by the solid line R1 and the broken line R2 in FIG.

  Further, the curvatures in the main scanning direction of the first surface and the second surface of the first scanning lens 16 are as indicated by the solid line R1 and the broken line R2 in FIG.

  Further, the curvature in the sub-scanning direction of the first surface of the first scanning lens 16 is as indicated by a solid line L1R1 in FIG.

  Further, the curvature in the sub-scanning direction of the second surface of the first scanning lens 16 is as indicated by a solid line L1R2 in FIG. The vertical axis corresponds to tan θ where the tilt angle is θ. The optical axis means an axis passing through a point when Y = 0 and Z = 0 in the expression (3) unless otherwise specified.

  The main scanning cross-sectional shapes of the first surface and the second surface of the second scanning lens 17 are as indicated by the solid line R1 and the broken line R2 in FIG.

  Further, the curvatures in the main scanning direction of the first surface and the second surface of the second scanning lens 17 are as indicated by the solid line R1 and the broken line R2 in FIG.

  Further, the curvature in the sub-scanning direction of the second surface of the second scanning lens 17 is as indicated by a solid line L2R2 in FIG.

  Further, the tilt amount in the sub-scanning direction of the first surface of the second scanning lens 17 is as indicated by the solid line L2R1 in FIG.

  The lateral magnification in the sub-scanning direction of the entire optical system included in the optical scanning device 100 ′ according to the modification is 1.22 times, and the sub-scanning magnification of only the optical system on the scanning surface side from the polygon mirror 15 is −0.97. It has doubled. In the optical scanning device 100 ′, the beam spot diameter on the surface to be scanned is set to 55 μm in the main scanning direction and 55 μm in the sub-scanning direction. The distance from the exit surface of the first scan lens 16 to the entrance surface of the second scan lens 17 is 89.7 mm, and the distance from the exit surface of the second scan lens to the surface to be scanned (the surface of the photosensitive drum 201) is 143.mm. 5 mm.

FIGS. 20A to 21C are diagrams regarding the field curvature and the sub-scanning lateral magnification deviation of the optical scanning device 100 ′, and FIG. 20A illustrates ch01 (VCSEL ₁ ) and ch40 (VCSEL). ₄₀ ) and axial (corresponding to the light emission point at the position of Y = 0 and Z = 0 in FIG. 3). FIG. 20B is a diagram showing the sub-scanning field curvature corresponding to ch01, ch40, and axial. 21A is a diagram showing the linearity characteristic of the optical scanning device 100 ′, FIG. 21B is a diagram showing a sub-scanning lateral magnification deviation, and FIG. 21C is a diagram showing scanning line bending. FIG.

  As shown in FIG. 20A, the optical performance varies depending on the spatial position of ch01 and ch40, but the difference is reduced to the minimum in the optical system of the optical scanning device 100 '. Therefore, the optical performance is stable in all channels, and variations in beam spot diameter variation and scanning line interval variation can be reduced.

  In addition, by using the light source 10 shown in FIG. 3 in the optical scanning device 100 ′, a multi-channel scanning optical system can be configured in a space-saving manner, and high-quality scanning lines can be formed. By adjusting the line image forming lens 13 in this way, it becomes possible to perform scanning with higher definition.

  The reason why the scanning line interval can be adjusted by adjusting the optical elements 13 and 14 to move in the Z direction is that the displacement of the light beam in the sub-scanning direction can be corrected. As the light beam moves away from the optical axis of the optical element, the aberration of the lens increases, so that the light beam becomes a secondary error due to manufacturing errors such as rotation of the reflection mirror 14 and polygon mirror 15 around the Y axis and movement in the Z axis direction. When displaced in the scanning direction, the optical magnification seen from each light beam slightly changes.

  In the conventional resolution, the change was negligible, but when high definition of 2400 dpi or higher, or when scanning with several tens of beams, this becomes the amount perceived as banding. It becomes a problem for. By adjusting the optical elements 13 and 14, the position of the beam can be corrected and the deviation between the image heights can be reduced, and at the same time, the adjustment in the direction of reducing the aberration can be performed. Great effect.

  In addition, it has been known that adjusting the rotation of the light source 10 about the X axis is also effective for adjusting the scanning line interval. However, unlike a conventionally known one-dimensional array LD array or the like, in the case of a two-dimensional array light source, there is a limit to the amount that can be adjusted by rotation around the X axis. In FIG. 22, the VCSEL before adjustment is indicated by a white square, and the VCSEL after adjustment is indicated by a black square. This is because, as can be seen with reference to FIG. 22, there are a pair of light-emitting points where the original interval is widened and a pair of light-emitting points that are narrowed when rotating around the X axis. This does not happen with a one-dimensional array. Therefore, there is no other way to adjust the scanning line interval, and therefore adjustment of the optical elements 13 and 14 in the Z-axis direction is effective.

  The scanning devices 100 and 100 ′ according to the above-described embodiment and the modified example may be a tandem color machine that corresponds to a color image and includes a plurality of photosensitive drums, instead of the single-color image forming apparatus 200.

  Hereinafter, a multicolor image forming apparatus 1000A that corresponds to a color image and includes a plurality of photosensitive drums will be described with reference to FIGS. 23 (A) and 23 (B). The image forming apparatus 1000 </ b> A is an apparatus that visualizes a plurality of color images by scanning and exposing a plurality of scanned surfaces and superimposing the plurality of images to form a color image.

  In image forming apparatus 1000A, photoconductive photoreceptors 1302a to 1302d rotate at a constant speed in a clockwise direction as indicated by arrows in the drawing. The surfaces of the photoreceptors 1302a to 1302d are uniformly charged by the charging device 1305, and the surface of the photoreceptor is scanned by the optical scanning device 1301 similarly to the image forming apparatus 200 described above. The electrostatic latent images formed on the photoreceptors 1302a to 1302d by this scanning are visualized as toner images by the developing device 1303, respectively. Each toner image is transferred in a state of being superimposed on the intermediate transfer belt 1308 by the transfer unit 1306, and the toner image is fixed on the paper S by the transfer unit 1309 and the fixing unit 1307, thereby forming a full color image. Is done.

  The corresponding colors of the photoconductors 1302a to 1302d can be cyan C, magenta M, yellow Y, and black K, and the correspondence with 1302a to 1302d can be freely selected and optimized. For example, in the present embodiment, the colors are configured to correspond to the colors of YMCK in the order of 1302a to 1302d. For optical scanning devices corresponding to positions where it is difficult to improve scanning quality, and optical scanning devices corresponding to photoreceptors that require reduction of adjustment processes, the corresponding colors can be selected according to the level of brightness and visibility. It is desirable to choose. For example, it is desirable to use yellow Y having low visibility or high brightness for a photoreceptor corresponding to an optical system having the worst optical characteristics (large curvature of field, large scanning line curvature, etc.). Also, the stability of the entire apparatus can be improved by setting the durability of the photoconductor that is frequently used, for example, by increasing the size of the photoconductor corresponding to black K, for example. Further, as a modification of the multicolor image forming apparatus 1000A, a system using a plurality of optical scanning devices can be adopted as in the multicolor image forming apparatus 1000B shown in FIG.

  In each of the above embodiments, the case where the optical scanning device of the present invention is used in a printer has been described. However, the image forming device other than the printer, for example, a copier, a facsimile, or a multifunction machine in which these are integrated. Is preferred.

1 is a diagram illustrating a schematic configuration of a printer 200 according to an embodiment of the present invention. 2A and 2B are diagrams (No. 1 and No. 2) illustrating a schematic configuration of the optical scanning device 100. FIG. It is a figure which shows the light source. 4A is a diagram illustrating a function Cs (Y) of the first scanning lens 16 in the sub-scanning direction for each lens height, and FIG. 4B is a diagram illustrating the second scanning lens 17 in the sub-scanning direction. It is a figure showing function Cs (Y) for every lens height of curvature. FIG. 5A is a diagram showing the shape of the first scanning lens 16 in the main scanning section, and FIG. 5B is a diagram showing the shape of the second scanning lens 17 in the main scanning section. FIG. 6A is a diagram showing the ellipsoidal curvature in the main scanning direction and the field curvature in the sub-scanning direction with respect to the image height y, and FIG. 6B is a diagram showing the fθ characteristic and linearity with respect to the image height y. Is It is a figure which shows subscanning horizontal magnification deviation (DELTA) (beta). FIG. 6 is a diagram (part 1) for explaining a scanning method of a writing area 201a; FIG. 10 is a second diagram for explaining the scanning method of the writing area 201a. FIGS. 10A to 10C are diagrams (Nos. 1 to 3) for explaining the variation of the scanning lines formed in the writing region. FIG. 11A and FIG. 11B are diagrams (No. 1 and No. 2) showing the beam pitch in the sub-scanning direction in the writing area. 12A and 12B are views (No. 1 and No. 2) for explaining a method of attaching the line image forming lens 13. FIG. 6 is a third diagram for explaining a method of attaching the line image forming lens 13; 2 is a cross-sectional view of a VCSEL formed in a light source 10. FIG. It is an enlarged view (the 1) of the active layer 24 of VCSEL. It is an enlarged view (the 2) of the active layer 24 of VCSEL. FIGS. 17A and 17B are diagrams (No. 1 and No. 2) illustrating a schematic configuration of the optical scanning device 100 ′. FIG. 18A is a diagram illustrating main scanning cross-sectional shapes of the first surface and the second surface of the first scanning lens 16, and FIG. 18B is a diagram illustrating the first surface and the second surface of the first scanning lens 16. FIG. 18C is a diagram illustrating the curvature of the first surface of the first scanning lens 16 in the sub-scanning direction, and FIG. 18D is a diagram illustrating the curvature of the surface in the main scanning direction. FIG. 6 is a diagram showing a curvature in the sub-scanning direction of the second surface of the scanning lens 16. FIG. 19A is a diagram illustrating main scanning cross-sectional shapes of the first surface and the second surface of the second scanning lens 17, and FIG. 19B is a diagram illustrating the first surface and the second surface of the second scanning lens 17. FIG. 19C is a diagram illustrating the curvature of the first surface of the second scanning lens 17 in the sub-scanning direction, and FIG. 19D is a diagram illustrating the curvature of the surface in the main scanning direction. FIG. 6 is a diagram illustrating a curvature in the sub-scanning direction of the second surface of the scanning lens 17. FIG. 20A is a diagram showing main scanning field curvature corresponding to ch01 (VCSEL ₁ ), ch40 (VCSEL ₄₀ ), and axial (corresponding to the light emission point at the position of Y = 0 and Z = 0 in FIG. 3). FIG. 20B is a diagram illustrating the sub-scanning field curvature corresponding to ch01 (VCSEL ₁ ), ch40 (VCSEL ₄₀ ), and axial. 21A is a diagram showing the linearity characteristic of the optical scanning device 100 ′, FIG. 21B is a diagram showing a sub-scanning lateral magnification deviation, and FIG. 21C is a diagram showing scanning line bending. FIG. It is a figure for demonstrating the adjustment around the X-axis of the light source. FIG. 23A is a diagram illustrating a schematic configuration of the image forming apparatus 1000A, and FIG. 23B is a diagram illustrating a schematic configuration of the image forming apparatus 1000B.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Light source, 11 ... Coupling lens, 12 ... Aperture member, 13 ... Line image formation lens, 14 ... Reflection mirror, 15 ... Polygon mirror, 16 ... 1st scanning lens, 17 ... 2nd scanning lens, 18 ... Reflection mirror , 100, 100 '... optical scanning device, 200 ... image forming device, 201 ... photosensitive drum, 202 ... charging charger, 204 ... toner cartridge, 205 ... cleaning case, 206 ... paper feed tray, 207 ... paper feed roller, 208 ... Registration roller pair, 209... Fixing roller, 210... Discharge tray, 211... Transfer charger, 212.

Claims (13)

An optical scanning device that scans a surface to be scanned in a main scanning direction with a plurality of light beams,
A plurality of light emitting units for emitting the light beams, two-dimensionally arranged in a plane parallel to a first direction and a second direction orthogonal to the first direction;
A deflector that scans the plurality of light beams in the main scanning direction;
A scanning optical system that forms an image of the scanned light beam on the scanned surface;
The arrangement interval of the plurality of light emitting units in the first direction and the arrangement interval in the second direction are non-uniform,
In the light source, the arrangement interval of the light emitting units at the central portion is wider than the arrangement interval of the light emitting units at both end portions in the first direction or both end portions in the second direction. ,
Before Kifuku number of the light emitting portion, the first position with respect to the direction of the same light-emitting portion including a light scanning apparatus.   2. The optical scanning device according to claim 1, wherein the light source has an arrangement interval of the light emitting units that is narrower from a central portion to both end portions in the first direction.   3. The optical scanning device according to claim 1, wherein the light source has an arrangement interval of the light emitting portions that is narrowed from a central portion to both end portions in the second direction. A plurality of sets of two light emitting units adjacent to each other in the second direction and having the widest spacing in the first direction;
Among the plurality of sets, at least the interval in the second direction of the light emitting units of the set farthest from the central portion of the light source in the second direction is the arrangement of the light emitting units in the second direction. The optical scanning device according to claim 1, wherein the optical scanning device is the smallest among the intervals.   5. The light emitting portion that is most spaced apart in the second direction among the plurality of light emitting portions is disposed between the light emitting portions that are furthest apart with respect to the first direction. The optical scanning device according to any one of the above.   6. The light emitting unit that is most separated in the second direction is disposed at a position closest to the center of the light source in the first direction among the plurality of other light emitting units. The optical scanning device according to 1.   The optical scanning apparatus according to claim 1, wherein the surface to be scanned is interlaced and scanned by the plurality of light beams.   8. The light according to claim 7, wherein the scanning lines formed on the surface to be scanned are formed without being adjacent to each other by the light beam from the light emitting portion farthest away in the second direction. Scanning device. The first direction is parallel to the main scanning direction and the second direction is either one of claims 1-8, characterized in that it is parallel to the sub scanning direction orthogonal to the main scanning direction The optical scanning device according to one item. An optical element for condensing the plurality of light beams incident on the deflecting surface of the deflector in the sub-scanning direction, wherein the optical element is adjusted by being translated in the sub-scanning direction; the optical scanning device according to any one of claims 1 to 9, characterized in that it is supported. The optical scanning device according to claim 10 , further comprising: a housing that houses at least the optical element; and an intermediate member that is attached to the housing while holding the optical element. The optical scanning device according to claim 11 , wherein the intermediate member holds at least one end of the optical element in the main scanning direction. An image forming apparatus that forms an image by fixing a toner image formed based on a latent image obtained from information about an image to a recording medium,
An optical scanning device according to any one of claims 1 to 12 , and
A photoreceptor on which a latent image is formed by the optical scanning device;
Developing means for visualizing a latent image formed on the surface to be scanned of the photoreceptor;
An image forming apparatus comprising: a transfer unit that fixes the toner image visualized by the developing unit to the recording medium.

Images