JP2009211100A - Optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device that scans with a plurality of beams, that is large in size to be usable for a high-speed color printer device, and that has high degree of freedom in an image forming section. <P>SOLUTION: The exposure device 1 includes an imaging system 9 constituted of three first to third glass-made imaging lenses 23, 25 and 27 having Abbes number ν of ≥60, ≤28 and ≤65, respectively, and laser beams L (Y, M, C and B) passing through the respective lenses form their optical paths to cross one another in the rotating axis direction of the polygon mirror of a deflector 5 between the polygon mirror and the first imaging lens 23, consequently, the machining cost is reduced, and the degree of freedom in the optical path related to the shape required as the image forming section is enhanced, and a variation in beam diameter of the laser beam at the imaging position and a variation in the imaging position are reduced. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention is used in a multi-drum type color printer device or color copying device, a multi-color color printer device or color copying device, and a single color high-speed laser printer or high-speed digital copying device using a plurality of exposure beams. The present invention relates to an optical apparatus that performs exposure scanning collectively.

  For example, in an image forming apparatus such as a color printer apparatus or a color copying apparatus using an image forming unit including a plurality of photosensitive drums, a plurality of image data corresponding to color components that have undergone color separation, that is, at least the number of image forming units. An exposure apparatus that provides a plurality of equal light beams is used.

  This type of exposure apparatus includes a plurality of semiconductor laser elements that emit a predetermined number of light beams corresponding to color-separated image data for each color component, and a sectional beam diameter of each light beam emitted from each semiconductor laser element. A first lens group that is narrowed to a predetermined size and shape, and a light beam group that has been narrowed to a predetermined size and shape by the first lens group is continuously reflected in a direction perpendicular to the direction in which the recording medium is conveyed. And a second lens group that forms an image of the light beam deflected by the deflecting device at a predetermined position of the recording medium.

  The above-described exposure apparatus includes an example using a plurality of exposure apparatuses corresponding to each of the image forming units in accordance with the image forming apparatus to be applied, and a multi-beam exposure apparatus capable of providing a plurality of light beams with one exposure apparatus. It is classified into the example using. Today, in order to increase the image forming speed and improve the resolution, a high-speed printer apparatus capable of forming an image at a high speed by exposing image data of the same color in parallel has been proposed.

  For example, Japanese Patent Application Laid-Open No. 7-256926 discloses four sets of image forming units corresponding to color components that have undergone color separation, and image data for four colors for each image forming unit using a single exposure device. An example of exposure is disclosed. JP-A-3-53213 discloses an exposure apparatus including four sets of light sources and two sets of imaging lens systems separated in two directions.

  Incidentally, it is known that the exposure apparatus disclosed in Japanese Patent Application Laid-Open No. 3-53213 is large in size as a single exposure apparatus, and as a result, increases in the size of the image forming apparatus. On the other hand, the exposure apparatus disclosed in Japanese Patent Application Laid-Open No. 7-256926 has only one set of imaging lens system provided between the deflection apparatus and the image surface (photosensitive drum). In addition, the image forming apparatus is configured to be compact.

  However, in today's color image forming apparatuses, it is required to increase the number of black-only images that can be output. This can be easily achieved, for example, by increasing the amount of toner contained in the developing device. However, with respect to the imaging lens system of the exposure device, the imaging lens system for black images and the imaging lens other than for black images are used. Due to the difference in optical characteristics required for the system, there is a problem that the size of the exposure apparatus becomes large.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a large-sized exposure apparatus having a high degree of freedom in an image forming unit that can be used in a high-speed color printer apparatus.

  The present invention has been made on the basis of the above-described problems, and is converted into substantially parallel light by the light source, the first lens that converts light emitted from the light source into substantially parallel light, and the first lens. An optical member that is given a positive power only in the first direction to further converge the light with respect to the first direction in a plane orthogonal to the direction in which the light travels; Each of the first direction and the direction in which the light travels has light that has a reflecting surface formed so as to be rotatable, and has converged light at least in the first direction by the first optical means. A deflection unit that deflects in an orthogonal direction and a plurality of lenses, and is positioned at a position farthest from the deflection unit and a lens surface on the deflection unit side of a lens disposed closest to the deflection unit. Said deflection means of the lens The lenses on the far side are toric surfaces each having a rotationally symmetric axis extending along the first direction parallel to a rotation axis that is a rotation center of the deflection unit, and the reflection of the deflection unit Correcting the influence of the deviation of the angle between the surface and the rotation axis, and the light deflected by the deflecting means at the position of the predetermined distance at the position of the rotation angle of the reflecting surface and the position of the predetermined distance. And an optical device comprising: a second optical unit including a lens that makes a distance in a second direction orthogonal to the first direction proportional to the first direction.

  The exposure apparatus according to the present invention relates to fluctuations in the imaging position of the laser beam caused by an increase in the ambient temperature, and changes in the imaging position caused by each optical element arranged on the rear stage (image plane side) of the collimator lens. Can be canceled by the fluctuation amount of the imaging position caused by the semiconductor laser element and the collimator lens alone, and the fluctuation of the beam diameter on the image plane can be reduced.

  In addition, the exposure apparatus of the present invention can ensure a wide angle of view in each of the sub-scanning direction and the main scanning direction, and has an improved degree of freedom in selecting an optical path. In addition, the black toner capacity can be increased.

  Furthermore, in the exposure apparatus of the present invention, among the three lenses of the post-deflection optical system (imaging optical system), the lens surface closest to the deflection apparatus is formed by molding each of the entrance surface and the exit surface. Since it is configured with a suitable free-form surface, the manufacturing cost of a single lens is reduced.

  Still further, the exposure apparatus of the present invention has a lens surface that faces each laser beam toward the deflection device side of the lens closest to the deflection device in the imaging optical system (post-deflection optical system) with the polygon mirror of the deflection device. Therefore, the distance between the laser beams in the vicinity of the conjugate imaging position can be reduced, and the thickness of the polygon mirror of the deflecting device can be reduced. This reduces the cost of the polygon mirror of the deflecting device.

  Therefore, the manufacturing cost and assembly cost of the exposure apparatus are reduced, and the cost of the image forming apparatus is also reduced.

  In addition, since the degree of freedom in selecting the optical path of the laser beam is high, the optical path of the specific laser beam can be easily changed in accordance with the request on the image forming apparatus side. As a result, it is possible to apply to a printer or a color copying apparatus capable of forming a large and high-speed image.

1 is a schematic diagram showing an example of an image forming apparatus in which an exposure apparatus as an embodiment of the present invention is incorporated. FIG. 2 is a schematic diagram illustrating a state where an optical path of an exposure apparatus incorporated in the image forming apparatus illustrated in FIG. 1 is viewed from a plane direction. FIG. 3 is a schematic cross-sectional view of the exposure apparatus shown in FIG. 2 cut along a sub-scanning cross section including a reflection point (a position where the deflection angle is 0 °) on the reflection surface of the deflection apparatus. FIG. 4 is a schematic diagram illustrating elements for optimizing the shape of each lens surface of the first to third imaging lenses in the exposure apparatus shown in FIGS. 2 and 3. FIG. 4 is a schematic diagram for explaining a state of a light beam in the vicinity of a reflecting surface of a deflecting device of the exposure apparatus shown in FIGS. 2 and 3. 5 is a graph for explaining the imaging position in the main scanning direction of the light beam for magenta when using the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 5 in the exposure apparatus shown in FIGS. 5 is a graph for explaining the imaging position in the main scanning direction of the cyan light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 are used in the exposure apparatus shown in FIGS. In the exposure apparatus shown in FIGS. 2 and 3, the arrangement of the optical elements capable of providing the characteristics shown in FIG. 5 and the configuration of the optical beam for yellow and the light beam for black are used in the main scanning direction. The graph explaining an image position. FIG. 4 is a graph for explaining an imaging position in a sub-scanning direction of a light beam for magenta when using the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 5 in the exposure apparatus shown in FIGS. FIG. 4 is a graph for explaining an imaging position in the sub-scanning direction of a cyan light beam when using the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 5 in the exposure apparatus shown in FIGS. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 are used, the yellow light beam and the black light beam are connected in the sub-scanning direction. The graph explaining an image position. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 is used, the polygon mirror surface of the magenta light beam is tilted at 1 minute. The graph explaining the variation | change_quantity of a beam position. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 are used, the polygon mirror surface of the cyan light beam is tilted at 1 minute. The graph explaining the variation | change_quantity of a beam position. In the exposure apparatus shown in FIGS. 2 and 3, the polygon mirror surfaces of the yellow light beam and the black light beam are tilted when the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 5 are used. The graph explaining the variation | change_quantity of the beam position by the plane fall at the time of 1 minute. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 is used, the polygon swing angle of the cyan light beam of the magenta light beam is 0 degree. The graph explaining the relationship of the subscanning direction relative position with respect to the position at normal temperature. In the exposure apparatus shown in FIG. 2 and FIG. 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. The graph explaining the relationship of the subscanning direction relative position with respect to the position at normal temperature. In the exposure apparatus shown in FIGS. 2 and 3, the cyan light beam of the yellow light beam and the black light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 are used. 6 is a graph for explaining the relationship of the relative position in the sub-scanning direction with respect to the position at the normal temperature of the polygon swing angle of 0 degree. In the exposure apparatus shown in FIGS. 2 and 3, the main scanning direction with respect to the same temperature of the cyan light beam of the magenta light beam when using the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. The graph explaining the relationship of a relative position. In the exposure apparatus shown in FIGS. 2 and 3, the cyan light beam of the yellow light beam and the black light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 are used. The graph explaining the relationship of the main scanning direction relative position with respect to the same temperature. 5 is a graph for explaining a deviation amount from the fθ characteristic of the light beam for magenta when using the arrangement and configuration of each optical element capable of providing the characteristic shown in FIG. 5 in the exposure apparatus shown in FIGS. FIG. 4 is a graph for explaining an amount of deviation from the fθ characteristic of a cyan light beam when the arrangement and configuration of optical elements capable of providing the characteristic shown in FIG. 5 are used in the exposure apparatus shown in FIGS. 2 and 3. In the exposure apparatus shown in FIGS. 2 and 3, from the respective fθ characteristics of the yellow light beam and the black light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 5 are used. The graph explaining the relationship of deviation | shift amount. Implementation of arrangement and configuration of optical elements that can provide different characteristics from the example shown in FIG. 5 in the state of the light beam in the vicinity of the reflecting surface of the deflecting device of the exposure apparatus shown in FIGS. Schematic explaining the form of. FIG. 24 is a graph for explaining the imaging position in the main scanning direction of the light beam for magenta when using the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 in the exposure apparatus shown in FIGS. FIG. 24 is a graph for explaining an imaging position in the main scanning direction of a cyan light beam when using the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 23 in the exposure apparatus shown in FIGS. In the exposure apparatus shown in FIG. 2 and FIG. 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 are used, each of the yellow light beam and the black light beam is connected in the main scanning direction. The graph explaining an image position. FIG. 24 is a graph for explaining an imaging position in a sub-scanning direction of a light beam for magenta when using the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 23 in the exposure apparatus shown in FIGS. FIG. 24 is a graph for explaining an imaging position in the sub-scanning direction of a cyan light beam when using the arrangement and configuration of optical elements capable of providing the characteristics shown in FIG. 23 in the exposure apparatus shown in FIGS. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 are used, the yellow light beam and the black light beam are connected in the sub-scanning direction. The graph explaining an image position. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 is used, the polygon mirror surface of the magenta light beam is tilted at 1 minute. The graph explaining the variation | change_quantity of a beam position. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 is used, the polygon mirror surface of the cyan light beam is tilted at 1 minute. The graph explaining the variation | change_quantity of a beam position. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 are used, the respective polygon mirror surfaces of the yellow light beam and the black light beam are tilted. The graph explaining the relationship of the variation | change_quantity of the beam position by the surface inclination at the time of 1 minute. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 is used, the polygon swing angle of the cyan light beam of the magenta light beam is 0 degree, The graph explaining the relationship of the subscanning direction relative position with respect to the position at normal temperature. In the exposure apparatus shown in FIGS. 2 and 3, when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 is used, the polygon swing angle of the cyan light beam of the cyan light beam is 0 degree. The graph explaining the relationship of the subscanning direction relative position with respect to the position at normal temperature. In the exposure apparatus shown in FIGS. 2 and 3, the cyan light beam of the yellow light beam and the black light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 are used. 6 is a graph for explaining the relationship of the relative position in the sub-scanning direction with respect to the position at the normal temperature of the polygon swing angle of 0 degree. In the exposure apparatus shown in FIGS. 2 and 3, the main scanning direction with respect to the same temperature of the cyan light beam of the magenta light beam when using the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. The graph explaining the relationship of a relative position. In the exposure apparatus shown in FIGS. 2 and 3, the cyan light beam of the yellow light beam and the black light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 are used. The graph explaining the relationship of showing the main scanning direction relative position with respect to the same temperature. FIG. 24 is a graph for explaining a deviation amount from the fθ characteristic of the light beam for magenta when using the arrangement and configuration of each optical element capable of providing the characteristic shown in FIG. 23 in the exposure apparatus shown in FIGS. FIG. 24 is a graph for explaining an amount of deviation from the fθ characteristic of a cyan light beam when using the arrangement and configuration of optical elements capable of providing the characteristic shown in FIG. 23 in the exposure apparatus shown in FIGS. In the exposure apparatus shown in FIG. 2 and FIG. 3, from the respective fθ characteristics of the yellow light beam and the black light beam when the arrangement and configuration of each optical element capable of providing the characteristics shown in FIG. 23 are used. The graph explaining deviation | shift amount.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a color image forming apparatus using an exposure apparatus according to an embodiment of the present invention. In this type of color image forming apparatus, a color image is formed using subtractive color mixing. Therefore, usually Y, yellow (yellow), M, magenta (crimson), C, cyan (blue purple), and B That is, there are four types of image data that are color-separated into black (for black and inking) color components and various apparatuses that form images for each color component corresponding to Y, M, C, and B, respectively. Since each set is used, in the following description, Y, M, C, and B are added to the reference symbols to identify the image data for each color component and the corresponding device. .

  As shown in FIG. 1, the image forming apparatus 100 includes first to fourth image forming units 50Y, 50M, 50M, which form images corresponding to color components separated based on a known subtractive color mixing method. 50C and 50B.

  For each image forming unit 50 (Y, M, C and B, hereinafter, all of the first to fourth image forming units and the elements constituting each image forming unit, a reference symbol “*” is used as a reference symbol. The first mirror 33B used for exposure of a black image in the exposure apparatus 1 described later with reference to FIGS. 2 and 5, yellow, magenta 50Y at positions corresponding to each of the four sets of laser beams L * as image light emitted from the exposure apparatus 1 to the outside by the third mirrors 37Y, 37M and 37C used for exposure of the respective images of cyan and cyan , 50M, 50C and 50B are arranged in series.

  Laser beams L * guided to the respective photosensitive drums 58 * by the mirrors 37Y, 37M, 37C and 33B of the exposure apparatus 1 are emitted from eight semiconductor laser elements which will be described in detail later with reference to FIG. A predetermined position on the outer peripheral surface of each photoreceptor drum 58 * corresponding to each mirror 37Y, 37M, 37C and 33B is irradiated from between each charging device 60 * and each developing device 62 *.

  The laser beam L * irradiated to each photosensitive drum 58 *, that is, image information separated into color components, is supplied with toner from a developing device 62 * arranged in combination with each photosensitive drum 58. A belt driving roller 56 which is visualized and rotated in the direction of an arrow by a motor (not shown) through a paper feeding roller 72 and an aligning roller 74 from a paper cassette 70 or from an unillustrated manual feed portion through an aligning roller 74; The transfer device 64 * sequentially applies the recording paper P, which is a transfer material, that is electrostatically attracted to the conveyance belt 52 stretched around the tension roller 54 by the electric field applied by the charging roller 76 and moved together with the conveyance belt. Transcribed. The untransferred toner remaining on each photosensitive drum 58 * is removed by a cleaner 66 *. Further, the residual potential remaining on each photoconductive drum 58 * is removed by the static eliminator 68 *.

  In this way, the four-color (or black one-color) image visualized by each developing device 64 * and transferred to the paper P conveyed by the conveying belt 52 is thermally fixed on the paper P by the fixing device 80. The

  The black developing device 62B combined with the black image forming device 50B is formed so as to accommodate more toner than the other developing devices in consideration of the frequency with which a black non-color image is formed.

  Next, an exposure apparatus used in the image forming apparatus shown in FIG. 1 will be described in detail.

  2 shows a state in which the optical path of the exposure apparatus 1 incorporated in the image forming apparatus 100 shown in FIG. 1 is developed and seen from the plane direction (a direction orthogonal to the rotation axis of the deflection apparatus described below). Is an optical member arranged between the reflection point of the deflecting device and the imaging position (image plane) in a direction orthogonal to the plane direction shown in FIG. 2 (a direction parallel to the rotation axis of the deflecting device). With respect to the light beam passing therethrough, the state when the deflection angle by the deflecting device is viewed at 0 ° is shown.

  The exposure apparatus 1 corresponds to the image data for four colors corresponding to the image for each color component subjected to the color separation formed by each of the four image forming units 50 * of the image forming apparatus 100 shown in FIG. 2 × 4 colors for generating laser beams = 8 laser elements 3Ya and 3Yb, 3Ma and 3Mb, 3Ca and 3Cb, 3Ba and 3Bb, and a plurality of reflecting surfaces 5a formed in a rotatable manner, each reflecting By rotating the surface 5a at a predetermined speed, the laser beams emitted from the respective laser elements are image surfaces provided at predetermined positions, that is, the four photosensitive members of the four image forming units 50 * shown in FIG. A deflecting device 5 that deflects toward the body drum 58 * at a predetermined linear velocity is provided between the laser devices 3 * a and 3 * b and the deflecting device 5, and each of the laser beams L * a and L * b That The laser beam deflected (reflected) by the pre-deflection optical system 7 * which arranges each laser beam as a group of 2 × 4 laser beams, and the deflecting device 5 is arranged. It has a post-deflection optical system 9 that forms an image on the photosensitive drum 58 *. In many cases, the direction in which each laser beam is deflected (continuously reflected linearly) by the deflecting device 5 is the main scanning direction (the direction parallel to the direction in which the reflecting surface 5a is rotated). A direction orthogonal to the scanning direction and parallel to the axial direction of the rotation axis when the reflecting surface 5a of the deflecting device 5 is rotated is called a sub-scanning direction.

  Eight laser beams emitted from the respective laser elements are converted into eight collimator lenses 11Ya, 11Yb, 11Ma, 11Mb, 11Ca, 11Cb, 11Ba, and 11Bb provided in the vicinity of the respective laser elements (pre-deflection optical system). 7 *). Note that all the collimator lenses may be replaced with finite focal lenses by appropriately selecting the lenses of the post-deflection optical system 9. Further, as will be described later with reference to Tables 3 and 4, each collimator lens exhibits characteristics similar to those of a finite focus lens.

  The eight laser beams collimated by the respective collimator lenses are given predetermined cross-sectional beam shapes by the diaphragms 13Ya, 13Yb, 13Ma, 13Mb, 13Ca, 13Cb, 13Ba, and 13Bb (pre-deflection optical system 7 *), respectively. Two laser beams LYa and LYb, LMa and LMb, LCa and LCb, LBa and LBb, which are paired with each other by the mirrors 15Y, 15M, 15C and 15B (pre-deflection optical system 7 *), are deflected by the deflecting device 5. Are aligned at a predetermined interval with respect to the sub-scanning direction, which is a direction orthogonal to the direction of scanning.

  Here, when the number of laser elements and the number of color components are arranged, the number of color components is “M”, and the number of laser elements for each color component is “Ni (i is a positive integer and the maximum value is M)”. Then, N1 (Y) = N2 (M) = N3 (C) = N4 (B) 2 × M sets (M is a positive integer, M = 4). That is, the eight laser beams are aligned by the half mirror 15 *, so that they can be handled as four sets (two each) of ΣNi laser beams as viewed from the main scanning direction.

  The two laser beams LYa and LYb aligned at a predetermined interval in the sub-scanning direction by the half mirror 15Y are converged at least in the sub-scanning direction side by the cylinder lens 17Y (pre-deflection optical system 7Y) and then laser The light is reflected by the combining mirror 19Y (pre-deflection optical system 7Y) and guided to the reflecting surface 5a of the deflecting device 5.

  Similarly, the two laser beams LMa and LMb aligned at a predetermined interval in the sub-scanning direction by the half mirror 15M are converged at least on the sub-scanning direction side by the cylinder lens 17M (pre-deflection optical system 7M). After that, the laser beams LYa and LYb reflected by the laser combining mirror 19M (pre-deflection optical system 7M) and turned back by the laser combining mirror 19Y almost overlap with the laser beams LYa and LYb as viewed from the main scanning direction, and viewed from the sub scanning direction. In this state, the laser beams are aligned so as to pass through the inside of the laser beams LYa and LYb (near the center of the length of the reflecting surface 5a of the deflecting device 5 in the sub-scanning direction), and are guided to the reflecting surface 5a of the deflecting device 5 through the half mirror 19Y. Is done.

  In addition, the two laser beams LCa and LCb aligned at a predetermined interval in the sub-scanning direction by the half mirror 15C are converged at least on the sub-scanning direction side by the cylinder lens 17C (pre-deflection optical system 7C). After that, the laser combining mirror 19C (pre-deflection optical system 7C) reflects the laser beams LMa and LMb reflected by the laser combining mirror 19M so that the laser beams LMa and LMb are substantially overlapped when viewed from the main scanning direction. 19M and 19Y are guided to the reflecting surface 5a of the deflecting device 5 through an optical path shifted in the sub-scanning direction.

  Further, the two laser beams LBa and LBb aligned at a predetermined interval in the sub-scanning direction by the half mirror 15B are converged at least on the sub-scanning direction side by the cylinder lens 17B (pre-deflection optical system 7B). After that, the laser beam LCa, LCb reflected by the folding mirror 19B (pre-deflection optical system 7B) and folded by the laser combining mirror 19C is substantially overlapped when viewed from the main scanning direction and viewed from the sub scanning direction. Thus, the laser beam is aligned with the laser beam LYa and LYb so as to be axially symmetric with respect to the center of the sub-scanning direction length of the reflection surface 5a of the deflecting device 5 outside the laser beams LCa and LCb. 19C, 19M, and 19Y are sequentially guided to the reflecting surface 5a of the deflecting device 5 through a space shifted in the sub-scanning direction. It is.

  The laser elements 3 * a to 3 * b, the collimator lenses 11 * a to 11 * b, and the apertures 13 * a to 13 * are integrated into a lens holder (not shown), and are made of, for example, an aluminum alloy. It is formed to be movable along the optical axis direction on the formed holding member 21. Each half mirror 15 * is provided with a mirror holder (not shown) with a reflecting surface angle adjusting mechanism, each cylinder lens 17 * is provided with a lens mount (not shown) with a focal length adjusting mechanism, and each laser combining mirror mirror 19 * is adjusted with an angle. The mirror mounts with a mechanism (not shown) are independently held and are integrally disposed at a predetermined position of the holding member 21.

  The eight (four sets) laser beams sequentially deflected by the rotation of the reflecting surfaces 5a of the deflecting device 5 are first to third imaging lenses 23 in which the direction parallel to the main scanning direction is formed in an arc shape. , 25 and 27 (post-deflection optical system 9) in order, each lens is provided with predetermined imaging characteristics, and the imaging state (focal position deviation in the optical axis direction) and imaging position ( The focal position in the main scanning direction and the sub-scanning direction), the cross-sectional beam diameter and its shape, the aberration state, etc. are optimally set and guided to the image plane (the outer peripheral surface of the photosensitive drum 58 *). A part of the laser beam that has passed through a predetermined region of the third imaging lens 27 that can reach a portion corresponding to the non-image region of each photoconductive drum 58 * generates a horizontal synchronization signal. In order to obtain it, it is bent toward the horizontal synchronization detector 31 by the horizontal synchronization mirror 29. Further, as is apparent from FIG. 1, each laser beam guided to the image plane (excluding black laser beams LBa and LBb) has first to third mirrors 33Y, 35Y and 37Y, 33M, 35M and 37M, 33C, 35C and 37C (post-deflection optical system 9) are sequentially bent (the laser beams LBa and LBb for black are bent only on the first mirror 33B), and the dustproof filter 39 * (post-deflection optical system) 9) The image plane is irradiated through.

  The laser beams L * a and L * b for each color component irradiated on the image surface, that is, the photosensitive drum 58 * of each image forming unit 50 * correspond to the respective photosensitive drums 58 as described above. The surface potential (of the photosensitive drum 58 *) charged in advance by the charging device 60 * is selectively changed. This change in the surface potential is maintained as an electrostatic latent image for a predetermined time, and is visualized (developed) when toner as a developer is supplied from the corresponding developing device 62 *.

  In this way, image data, that is, toner images copied using four sets (eight) of laser beams as a medium are fed from the cassette 70, and are transferred from the first image forming unit 50Y side by the conveyor belt 52 to the fourth image data. The images are sequentially transferred onto the paper P conveyed toward the image forming unit 50 </ b> B, and are fixed on the paper P by the fixing device 84.

  At this time, the four color toner images (toners) formed by the developing devices 62 of the respective image forming units 50 * are melted by the heat supplied from the fixing device 84. The intermediate color and the light and shade (black) generated by mixing the toners are optimally reproduced to form a color (black) image.

  Hereinafter, the paper P on which the color (black) image is fixed is sequentially discharged out of the image forming apparatus 100 and stocked.

  Next, the optical characteristics of the optical elements included in each of the pre-deflection optical system 7 and the post-deflection optical system 9 will be described in detail. The optical characteristics of each lens or optical element are as shown in the subsequent stage using Tables 1 to 3.

  Each of the collimator lenses 11Ya, 11Yb, 11Ma, 11Mb, 11Ca, 11Cb, 11Ba and 11Bb is a glass aspherical lens. Each collimator lens has the same optical characteristics as a single unit, and the focal length is, for example, 57.06 mm. Further, the glass material is preferably FK5, SF60, FSK1, or the like as the lens material.

  Each of the apertures 13Ya, 13Yb, 13Ma, 13Mb, 13Ca, 13Cb, 13Ba and 13Bb is a thin plate of stainless steel having a thickness of 0.1 mm, and an opening having a predetermined size and shape. Even when a mounting error occurs, the rear focal point of the collimator lens is arranged so that the light amount fluctuation is minimized.

  Each of the half mirrors 15Y, 15M, 15C, and 15B has a predetermined thickness so that the transmittance is 51.5% on at least one surface of a parallel plate made of glass having a thickness of 5 mm and a transmittance of 97%. The metal thin film is deposited by vapor deposition, for example, and transmits laser beams emitted from the laser elements 3Ya, 3Ma, 3Ca and 3Ba, and lasers emitted from the laser elements 3Yb, 3Mb, 3Cb and 3Bb. By reflecting the beams, the two laser beams corresponding to the respective color components are combined at a predetermined interval in the sub-scanning direction.

  Each of the cylinder lenses 17Y, 17M, 17C and 17B has a sub-scanning direction (the X-axis is the direction in which the laser beam travels, the Y-axis is the main scanning direction in the plane perpendicular to the direction in which the laser beam travels), and the main scanning direction. When the orthogonal sub-scanning direction is shown as the Z-axis, the glass lens is provided with power (0.02338 in curvature display) only in the Z-axis direction. Note that BK7 or the like is preferably used as the glass material.

  Each of the laser combining mirrors 19Y, 19M, 19C, and 19B is formed of, for example, a metal thin film having a predetermined thickness so that the reflectance is 85% or more on at least one surface of a glass parallel plate having a thickness of 5 mm. Laser beam LY deposited by vapor deposition, synthesized into four sets by each of half mirrors 15Y, 15M, 15C and 15B, and given a predetermined cross-sectional beam diameter through cylinder lenses 17Y, 17M, 17C and 17B , LM, LC, and LB can be regarded as substantially one laser beam in the sub-scanning direction at a predetermined interval (the interval at which the laser beams do not contact each other is determined at a predetermined location, for example, the combining mirror 19 , Which is further combined so that the separation mirror 33 * can be secured) and folded toward the deflecting device 5. A.

  The deflecting device 5 rotates, for example, eight reflecting surfaces provided on the outer peripheral surface of the rotatable polygonal mirror along the main scanning direction at a predetermined speed, thereby combining the laser combining mirrors 19Y, 19M, and 19C. Each of the laser beams combined together by each of these is sequentially incident on a post-deflection optical system 9 described below.

  The first to third imaging lenses 23, 25, and 27 are each formed of glass, and in the sub-scanning direction, the convergence given by the three lenses is synthesized, thereby combining the image plane, that is, each photoconductor. The laser beam having a predetermined shape and a cross-sectional beam diameter is provided at a predetermined position on the outer peripheral surface of the drum 58 * by separating the four sets of laser beams and color components from each laser element in correspondence with each other. In addition, in the main scanning direction, each lens is combined with the convergence provided by the three lenses, so that each laser beam and each color are placed at predetermined positions on the outer peripheral surface of each photosensitive drum 58 *. A laser beam having a predetermined shape and a cross-sectional beam diameter is provided while making the components correspond to each other and making the position of each photosensitive drum 58 * in the longitudinal (axial) direction proportional to the rotation angle of each reflecting surface 5a of the deflecting device 5 To do. Each lens is a glass lens, and the lens surface is usually formed by polishing. However, only the first imaging lens 23 is molded as described in detail later. It is formed by.

  In each of the first to third mirrors 33Y, 33M, 33C, 33B, 35Y, 35M, 35C, 37Y, 37M, and 37C, a metal layer constituting a reflective surface is formed on one surface of a normal float glass. It is formed to a predetermined thickness by vapor deposition. Each mirror is formed by a mirror holding member (not described in detail) so that the position and angle can be adjusted independently with respect to the main scanning direction, the sub-scanning direction, and the optical axis direction in which the laser beam travels.

  Each of the dustproof filters 39 * is, for example, float glass having a thickness of 2 mm, and may be colored in an arbitrary color as necessary. In order to avoid the self-fusion of the toner floating inside the image forming apparatus 100, a resin material is avoided.

  By the way, as already explained, when an exposure apparatus such as that disclosed in Japanese Patent Laid-Open No. 7-256926 is used, for example, when it is required to increase the number of black-only images that can be output, it is for black images. However, the size of the exposure apparatus is increased in order to accommodate a large amount of toner. In the exposure apparatus disclosed in Japanese Patent Application Laid-Open No. 7-256926, since the distance between the deflecting device 5 and the image surface is short, it is difficult to increase the toner storage amount.

  Hereinafter, the configuration of the imaging optical system that can increase the toner storage capacity of the developing device without increasing the size of the exposure device will be described.

  FIG. 4 is a schematic diagram for explaining an example of optimizing how to give the conditions of the first to third imaging lenses 23, 25 and 27 of the imaging optical system 9.

  Since the first to third imaging lenses 23, 25, and 27 of the imaging optical system 9 have two lens surfaces, an entrance surface and an exit surface, respectively, from the side close to the deflecting device 5, the first surface to the second surface. The names of the six surfaces are given, and the shape of each lens surface, the direction of the processing axis (rotation symmetry axis) during processing, and the material of the lens will be described in detail.

  The first imaging lens 23 is defined as a free-form surface that is not processed with only a specific rotational symmetry axis on the side facing the deflecting device 5, that is, the incident surface (first surface) is a toric surface, and the exit surface (second surface) is a specific rotational symmetry axis. Lens. In addition, the direction of curvature is concave on the deflection device 5 side in each of the first surface and the second surface in both the main scanning direction and the sub-scanning direction. Note that the direction of the rotationally symmetric axis (processing axis during processing) on the first surface coincides with the sub-scanning direction. Further, the center of the arc of the generatrix of the first surface is defined on the deflection device 5 side. The lens material is, for example, optical glass (BK7) having an Abbe number “νd” of νd = 64.2.

  The second imaging lens 25 is a cylindrical surface having a rotational symmetry axis defined in the sub-scanning direction on the side facing the first imaging lens 23 (deflection device 5), that is, the incident surface (third surface). A lens whose surface (fourth surface) is defined as a plane. The lens material is, for example, optical glass (SF60) with νd = 25.46.

  The third imaging lens 27 is defined such that the side facing the second imaging lens 25 (deflection device 5), that is, the incident surface (fifth surface) is a cylindrical surface, and the emission surface (sixth surface) is a toric surface. Lens. As for the direction of curvature, the fifth surface is convex toward the deflecting device 5 and the sixth surface is concave toward the deflecting device 5. Note that the directions of the rotational symmetry axes of the fifth surface and the sixth surface are both defined in the sub-scanning direction. The material of the lens is optical glass (BK7) with νd = 64.2.

  As shown in FIG. 4, the shape of each lens surface, the direction of the processing axis (rotation symmetry axis) at the time of processing, and the lens material have minimum evaluation functions described below for various combinations of conditions. This is one of the conditions derived from the result of considering the processing cost and the time required for processing.

  That is, the amount of defocus in the main scanning direction, the amount of defocus in the sub-scanning direction, surface tilt (deviation of the reflection angle of the laser beam in the sub-scanning direction due to an error in the angle of each reflecting surface of the deflecting device) The deviation from the target value (reference value) with respect to the relative displacement in the main scanning direction, the relative displacement in the sub-scanning direction of each laser beam, the amount of displacement due to the fθ characteristic and the wavelength variation of the emission wavelength of the laser element. The first to sixth lens surfaces (the lens surfaces of the first to third imaging lenses) are optimized by obtaining a condition that minimizes the evaluation function using the square sum of the deviation as an evaluation function. it can. The incident surface of the first imaging lens 23 is a first lens surface, and the exit surface of the third imaging lens 27 is a sixth lens surface. Therefore, the second lens surface is the exit surface of the first imaging lens 23, the third lens surface is the incident surface of the second imaging lens 25, and the fourth lens surface is the second imaging surface. The exit surface and the fifth lens surface of the lens 25 correspond to the entrance surface of the third imaging lens 27, respectively.

Specifically, the first to sixth lens surfaces are
4: Free curved surface without rotational symmetry axis
cv: Main scanning and sub-scanning direction sectional shapes are both arc surfaces
Defines each of the entrance and exit surfaces
Lens ("cv" 2 sides)
(F is an identifier indicating optimization of the lens surface)
In order of the first to sixth lens surfaces, as shown in FIG. 4A as the lens surface configuration,
44 cvcv (11)
cvcv44 (12)
cv44cv (13)
cvcvcv (14)
When the lens position (lens surface number) where a free-form surface having no rotational symmetry axis is to be arranged is optimized while changing the conditions, each lens surface (first lens) of the first imaging lens 23 shown in (11) is obtained. In the example in which each of the first lens surface and the second lens surface is a free-form surface, it is recognized that there is a condition with a small numerical value of the evaluation function. As shown in FIG. 4 (a), the fact that the lens surfaces on which free curved surfaces are to be arranged is defined as the first lens surface and the second lens surface is small in size and is not suitable for processing by polishing. This is advantageous for the processing of the imaging lens 23, that is, the molding process, and the cycle time required for the molding process can be shortened.

  FIG. 4B shows a free curved surface in which the entrance surface and the exit surface of the first imaging lens 23 have already been described in the optimal lens surface arrangement obtained from the conditions shown in FIG. In this example, the shapes of the third to sixth lens surfaces of the third imaging lenses 25 and 27 are further optimized.

That is, the third lens surface that is the entrance surface of the second imaging lens 25, the fourth lens surface that is the exit surface of the second imaging lens 25, and the entrance surface of the third imaging lens 27. For each of the fifth lens surface and the sixth lens surface that is the exit surface of the third imaging lens 27,
d: cylindrical surface with rotational symmetry axis defined in the sub-scanning direction
c: Cylindrical surface with rotational symmetry axis defined in main scanning direction
s: spherical surface
u: A rotational symmetry axis is defined in the sub-scanning direction
The toric surface has a generatrix with an arc shape
In the same way as shown in FIG. 4A, in order of the first to sixth lens surfaces,
4-4-dc-du (21)
4-4-dd-du (22)
4-4-dc-su ... (23)
4-4-ddsu (24)
4-4-dc-c-u (25)
4-4-d-d-c-u (26)
When the shape of each of the third lens surface to the sixth lens surface is optimized while changing the conditions, the numerical value of the evaluation function is small in the examples (5) and (6) or (7). It is recognized that a condition exists. Note that the size of the evaluation function is different from that in the example of FIG.

  That is, as shown in FIG. 4B, at least the third lens surface (incident surface of the second imaging lens) is preferably a cylindrical surface having a rotational symmetry axis defined in the sub-scanning direction. For the lens surface 5 (incident surface of the third imaging lens), it is recognized that either a toric surface or a spherical surface in which the shape of the generatrix is an arc and the axis of rotational symmetry is defined in the sub-scanning direction is preferable.

FIG. 4 (c) shows the conditions of the first and second lens surfaces that have already been obtained, while taking the conditions of the third and fifth lens surfaces obtained by FIG. 4 (b) into consideration. The result of considering whether it is possible to change to a different condition in terms of easiness, and regarding either one of the first or second lens surface
t: A rotational symmetry axis is defined in the main scanning direction
The toric surface has a generatrix with an arc shape
p: plane
In the order of the first to sixth lens surfaces, as shown in FIG.
u-4-dc-du (31)
u-4-d-d-d-u (32)
4-4-dc-su "SF10"
(33)
u-4-d-p-d-u (34)
4-4-dc-du (35)
t-4-dc-su ... (36)
u-4-dc-su ... (37)
t-4-dc-du (38)
d-4-dc-su ... (3a)
s-4-dc-su ... (3b)
c-4-d-c-su (3c)
4-t-d-c-d-u (3d)
u-4-d-p-c-u (3e)
u-4-d-p-s-u (3f)
u-4-d-d-p-u (3g)
u-4-dppu (3h)
When the shape of each of the third lens surface to the sixth lens surface is optimized while changing the conditions, there is a condition that the numerical value of the evaluation function becomes small in the examples (31) to (33). Is allowed to do. Since the size of the evaluation function is different from that in the example of FIG. 4A or 4B, comparison using only the numerical value of the evaluation function is not possible.

  By the way, although the numerical value of the evaluation function is larger than that in the example of (31), the shape of the generatrix on the first or second lens surface is an arc and the rotational symmetry axis is defined in the main scanning direction. Even in the example (38) or (3d) using the toric surface, a slight significance is recognized, for example, in terms of ease of manufacturing. That is, each of the incident surface (first lens surface) of the first imaging lens 23 and the emission surface (sixth lens surface) of the third imaging lens 27 has a spherical shape and a rotationally symmetric axis. If a toric surface made of glass whose surface is oriented in the sub-scanning direction is used, the size of the evaluation function becomes small. In this condition, the optical characteristics can be further improved by making the first lens surface a free-form surface, but the mold cost for molding the first imaging lens 23 increases. The lens surface is a toric surface. Accordingly, the incident surface (first surface) of the first imaging lens 23 is processed as a toric surface, the output surface (second surface) is a free-form surface, and the incident surface (third surface) of the second imaging lens 25 is processed. The cylindrical surface and the outgoing surface (fourth surface) are flat, the incident surface (fifth surface) of the third imaging lens 27 is the cylindrical surface, and the outgoing surface (sixth surface) is the toric surface. As a result, required optical characteristics can be obtained while ensuring cost and ease of manufacture. Regarding the third imaging lens 27, as the shape of the incident surface (fifth surface), it is possible to set a convex, concave, or flat condition toward the deflecting device 5 in the sub-scanning direction. The main scanning direction needs to be convex toward the deflecting device 5. Here, if the shape in the sub-scanning direction is concave toward the deflecting device 5, it is recognized that the evaluation function increases (deteriorates) by about 50%. For this reason, the shape of the sixth surface (the exit surface of the third imaging lens 27) is oriented in the sub-scanning direction in which the direction of the rotational symmetry axis is parallel to the direction of the rotational axis of the reflecting surface of the deflecting device 5. By making the shape in the sub-scanning direction of the fifth surface (incident surface of the third imaging lens 27) as a toric surface convex toward the deflecting device 5, the size of the evaluation function can be reduced.

FIG. 4D shows the result of further optimization by changing the lens material in the configuration of the lens surface including the “flat surface” obtained by FIG. 4C. The “SF10” used in FIG.
u-4-d-p-d-u "SF6"
(41)
u-4-d-p-d-u "SF60"
(42)
u-4-d-p-d-u "SF11"
(43)
u-4-d-p-d-u "SF14"
(44)
u-4-d-p-d-u "SF13"
(45)
When “SF60” or “SF6” is used, it is recognized that there is a condition that the numerical value of the evaluation function becomes smaller (see Table 4).

  More specifically, as a result of examining by changing the Abbe number “νd” of the glass material used for each lens, νd in the basic “SF10” is νd = 28.83, whereas νd = 27.76. By using each glass material of SF13, νd = 2.46, SF6, νd = 2.46, SF60, νd = 2.70, SF12, νd = 26.55, SF14 Even if the emission wavelength of the laser beam emitted from the laser element fluctuates by about 15 nm at the maximum, for example, the fluctuation amount of the position where the laser beam reaches (beam arrival position) on the image plane can be suppressed to 10 μm or less. Needless to say, when “SF6” and “SF60” are used as described above, the effect becomes more remarkable.

  Thereby, when actually assembling the exposure apparatus, it is not necessary to consider the amount of fluctuation in the emission wavelength of the laser element caused by the temperature change.

As described above, the shapes of the entrance and exit surfaces of the first to third imaging lenses 23, 25 and 27 of the post-deflection optical system 9 are as follows.
First surface (incident surface of first imaging lens 23) →
A toric surface in which the shape of the generatrix in the main scanning direction is concave toward the deflecting device 5, the direction of the rotational symmetry axis is the sub-scanning direction, and the center of rotation is near the deflecting device 5,
Second surface (the exit surface of the first imaging lens 23) →
A free-form surface in which the shape of the bus in the main scanning direction is concave toward the deflecting device 5 and the cross-sectional shape in the sub-scanning direction is concave toward the deflecting device 5;
Third surface (incident surface of second imaging lens 25) →
A cylindrical surface in which the shape of the generatrix in the main scanning direction is concave toward the deflecting device 5, the direction of the rotational symmetry axis is the sub-scanning direction, and the center of rotation is near the deflecting device 5,
Fourth surface (outgoing surface of the second imaging lens 25) → plane,
Fifth surface (incident surface of third imaging lens 27) →
A cylindrical surface whose main scanning direction has a convex shape toward the deflecting device 5 and whose rotational symmetry axis is in the sub-scanning direction and whose rotation center is closer to the image plane;
Sixth surface (the exit surface of the third imaging lens 27) →
A toric surface in which the shape of the generatrix in the main scanning direction is concave toward the deflecting device 5, the direction of the rotational symmetry axis is the sub-scanning direction, and the center of rotation is near the deflecting device 5,
By defining all the imaging lenses of the post-deflection optical system 9 as glass lenses, it is possible to provide an exposure apparatus capable of allowing an increase in the size of the developing device or the toner containing portion.

Tables 1 to 3 show optical numerical data of optical elements in the first embodiment of the pre-deflection optical system 7 * and the post-deflection optical system 9 * described above. Table 1 shows the shapes of the lens surfaces (the respective curvatures in the Y-axis direction and the Z-axis direction) of the first to third imaging lenses 23, 25, and 27 of the post-deflection optical system 9, and the distance between the lenses. Table 2 shows the curvature of the exit surface of the first lens 23 (surface on the side far from the deflecting device 5 (free curved surface)). Table 3 shows the collimator lens or the finite focal lens 13 when the glass material is changed.

Table 3 shows the result of changing the glass material of the collimator lens or the finite focus lens in the first embodiment described in Table 1. For each glass material, 20 ° C. and When the temperature goes up and down by 40 ° C,
s1 (object point-object point side principal point distance),
s2 (image plane side principal point-image plane distance),
φ (Lens power at 20 ° C),
n (including change in refractive index due to change in temperature, wavelength variation of laser element),
The linear expansion coefficient of the glass material,
d (lens thickness),
c1 (the paraxial curvature of the incident surface),
c2 (the curvature of the exit surface on the paraxial axis),
φ ′ (lens power at each temperature),
s1h (incident surface-object point side principal point distance),
s2h ′ (distance between the exit surface and the image surface side principal point), and the distance between the cylinder lens incident surface and the image surface,
And the value of the expression (A) described below.

In Table 3, ADC12, which is the most common aluminum die-cast material, is assumed as a member for holding a collimator lens or a finite focal lens, and the linear expansion coefficient of ADC12 is 2.1 × 10 ⁻⁵ . is there.

  Further, it is preferable that the value of the cylinder lens incident surface-image surface position shown in Table 1 matches the notation of the second value from the right in Table 3 (column of the distance between the cylinder lens incident surface and the image surface). .

  More specifically, as is clear from Table 3, when the glass material is FK5, SF60, or FSK1, the defocus is moved (shifted) in the direction opposite to the defocus tendency by the post-deflection optical system. In other words, the optical performance is improved by combining the collimator lens or the finite focus lens and the post-deflection optical system. However, with BK7, which is a commonly used glass material, when the temperature rises, the distance between the principal point on the image plane side and the imaging plane decreases, consistent with the defocusing tendency by the post-deflection optical system. Therefore, the defocus as a whole is added to the larger side.

Considering this from the viewpoint of the material and characteristics of the lens, for example, as disclosed in Japanese Patent Laid-Open No. 3-179420, when a single lens is used, even if the temperature rises, it is close to the image plane. The condition that the axial imaging point distance does not change is
Lo ² / fo × [{1 / (1-no)} ×
{(∂no / ∂t) + (∂no / ∂λ) × (∂λ / ∂t) + αo}]
-Α1 × Lo = 0 (A)
t; temperature,
L1: Distance between the principal point on the image plane side and the imaging point,
Lo: Distance between object point and object side principal point,
f0: paraxial focal length of the lens,
no: Refractive index of the lens,
∂no / ∂t: Rate of change in refractive index of the lens material due to temperature rise,
∂no / ∂λ: Rate of change in refractive index of the lens material due to wavelength change,
∂λ / ∂t; wavelength change rate due to temperature change of the light source,
αo: the coefficient of linear expansion of the lens material,
α1; coefficient of linear expansion of the material of the holding member,
Can be represented by

  In this case, in the post-deflection optical system, if the image point movement occurs due to temperature change, the movement cannot be reduced.

  Further, as described above with reference to FIG. 4, it has been found that the post-deflection optical system is configured to shift the imaging point toward the deflecting device when the temperature rises. Therefore, in order to cancel this, it is necessary for the lens alone to have a characteristic that the imaging point moves farther when the temperature rises.

For this reason, when the values of the formula (A) are calculated as shown in Tables 3 and 4, and the desired values are compared, the left side of the formula (A) is as shown below.
7.4 × 10 ⁻⁴ > Lo ² / fo × [{1 / (1-no)} ×
{(∂no / ∂t) + (∂no / ∂λ) × (∂λ / ∂t) + αo}]
-Α1 × Lo> 8 × 10 ⁻⁵
It has been found that favorable results are obtained when values in the range are satisfied.

  In addition, when the exposure apparatus 1 having the optical characteristics described above with reference to FIG. 4, that is, when the ambient temperature rises, that is, as described using Tables 3 and 4, the material of the glass of each lens is specified, A configuration in which the distance from the principal point on the emission surface side of each collimator lens 11 * to the position (photosensitive drum) where each laser beam is converged when only each collimator lens is used increases as the temperature rises. In a known exposure apparatus, when the temperature rises, the refractive index of each lens apparently decreases due to the increase in the wavelength of the laser beam emitted from each semiconductor laser element and the expansion of each lens. The position where each laser beam L * is imaged is changed by the distance between each lens being changed by the expansion of the housing and supporting member for holding each lens. With respect to the phenomenon that the ram 58 * is moved to the deflecting device 5 side with respect to the outer peripheral surface of the ram 58 *, the influence of the temperature rise can be canceled, and the fluctuation of the beam spot diameter of each laser beam L * on the photosensitive drum 58 * can be suppressed. Can do.

  Further, by optimizing the shape of the lens surface of the imaging lens (three post-deflection optical systems 9) according to the design procedure shown in FIG. 4, the optical characteristics can be corrected over a wide range in the sub-scanning direction. This increases the degree of freedom in designing the optical path of the laser beam from each laser element toward the photosensitive drum. For example, in order to increase the amount of toner supplied to the black developing device 64B that is frequently used, the black developing device 64B. The space around can be increased. Further, it is possible to provide a color exposure device using the same exposure device while increasing the amount of toner set for the black developing device 64B.

Furthermore, the Abbe numbers of the first to third imaging lenses 23, 25 and 27 of the post-deflection optical system 9 are set as νd1, νd2 and νd3 in order from the first imaging lens.
60 <νd1, νd2 <28 and νd3 <65
Therefore, even if the wavelength varies within a range of about 15 nm due to individual differences between arbitrary semiconductor laser elements, the variation amount of the position where each laser beam is imaged is set to about 10 μm. Can be deterred.

  Furthermore, according to the imaging lenses 23, 25 and 27 (post-deflection optical system 9) shown in FIGS. 2, 3 and Tables 1 and 4, each imaging lens can be shifted to the deflecting device side. As a result, it is possible to correct optical characteristics in the main scanning direction in a wide range. Thus, for example, the space around the black developing device 64B can be increased in order to increase the amount of toner supplied to the black developing device 64B that is frequently used. This simultaneously enables application to a large exposure apparatus capable of high-speed exposure with a large angle of view and a high-speed large digital copying apparatus or printer apparatus using the exposure apparatus.

  Note that the combination of the lens surfaces of the imaging lenses 23, 25, and 27 described above is difficult to process by polishing as compared with other lenses, and in many cases, a lens near the deflecting device formed by molding. This is useful for the processing of the (first imaging lens 23). For this reason, it is possible to reduce the cycle time at the time of molding the first imaging lens 23 and the costs associated therewith.

  FIG. 5 is a schematic diagram showing the characteristics in the sub-scanning direction of the laser beam L * passing between the deflecting device 5 and the image plane. FIG. 5 is a schematic diagram enlarged along the axis line in the sub-scanning direction in order to clarify the characteristics. In FIG. 5, the horizontal axis represents the optical path length, the point O represents the reflection point on the polygonal mirror 5a of the deflecting device 5, and LY, LM, LC, and LB represent the corresponding photosensitive drum 58 *. LYp, LMp, LCp, and LBp represent the chief rays that are the centers of the laser beams.

  As shown in FIG. 5, 2 × 4 sets = 8 laser beams L * reflected by an arbitrary reflecting surface of the polygon mirror 5a of the deflecting device 5 are connected to an arbitrary reflecting surface with respect to the cross section in the sub-scanning direction. The first imaging lens 23 is crossed with each other and guided to the image plane.

  Specifically, in FIG. 5, the optical axis of the exposure apparatus 1 system (the position of each laser beam L * in the sub-scanning direction is directed from the pre-deflection optical system to the image plane with reflection from the pre-deflection optical system. Criteria for definition) If the left side of the paper is the pre-deflection optical system, the right side of the paper is the image plane, and the vertical axis is the arbitrary reflecting surface of the deflecting device 5, for example, the system The laser beam incident from above the optical axis (on the (+) side of the vertical axis) intersects the optical axis of the system in the vicinity of the reflecting surface and then the lower end side of the first imaging lens 23 in the sub-scanning direction. Is incident on. Similarly, for example, a laser beam incident on an arbitrary reflecting surface of the deflecting device 5 from below the optical axis of the system (on the (−) side of the vertical axis) intersects the optical axis of the system near the reflecting surface. After that, it enters the upper end side of the first imaging lens 23 in the sub-scanning direction. Further, as shown in FIG. 5, each laser beam guided to the reflecting surface of the deflecting device 5 is configured such that the positions of the respective light emitting points of the laser elements 3 * a and * b are optimally set. For example, black (LB), cyan (LC), magenta (LM), and yellow (LY) are aligned in this order from the axis (+) side in the sub-scanning direction, that is, the vertical direction. The order of incidence on one imaging lens 23 is yellow (LY), magenta (LM), cyan (LC), and black (LB) from the vertical axis (+) side.

  As shown in FIG. 5, the position where each laser beam intersects the optical axis of the system is defined between the first imaging lens 23 and the reflecting surface of the deflecting device 5, so that the photosensitive drum Each laser beam L * directed to each of 58 * is guided to a predetermined position of the photosensitive drum 58 * while being converged for each laser beam. That is, the interval between the laser beams in the sub-scanning direction at the imaging position (predetermined image plane) assuming that the photosensitive drums 58 * are on the same plane can be reduced. This indicates that the distance in the sub-scanning direction of each laser beam L * is small between the conjugate position, that is, between the first imaging lens 23 and the reflecting surface of the deflecting device 5. As a result, It shows that the thickness (height in the sub-scanning direction) of the reflecting surface of the deflecting device 5 can be reduced.

  Thereby, when forming the polygonal mirror 5a of the deflecting device 5, the number of the polygonal mirrors 5a that can be processed in the same process in a state where a plurality of the polygonal mirrors 5a are stacked in the direction of the rotation axis can be increased, and the cost of the deflecting device can be increased. Is reduced. Further, the loss of windage (loss of rotational force due to air resistance during rotation) can be reduced by reducing the thickness of the polygon mirror 5a. When a mirror motor having the same power is used, power consumption and heat generation are reduced. Can be suppressed. On the other hand, the mirror motor can be reduced in size, and in this case, the cost of the motor drive circuit can be reduced.

  6 to 22 show various imagings obtained by the exposure apparatus 1 capable of providing each laser beam L * intersecting between the first imaging lens 23 and the deflecting device 5 described with reference to FIG. It is a graph which shows a characteristic. In each of FIGS. 6 to 22, a curve a (solid line) indicates that the ambient temperature is 20 ° C., a curve b (broken line) indicates that the ambient temperature is 70 ° C., and a curve c (dashed line). Indicates the respective characteristics when the ambient temperature is −30 ° C. (normal temperature = 20 ° C. ± 40 ° C. explained using Tables 3 and 4). In each figure, the horizontal axis indicates the distance in the main scanning direction.

  6 to 8 show fluctuations in the imaging position of each laser beam in the main scanning direction. FIG. 6 shows a magenta laser beam, FIG. 7 shows a cyan laser beam, and FIG. 8 shows a yellow laser beam. It corresponds to the black laser beam.

  From FIG. 6 to FIG. 8, under all temperature conditions, the main scanning direction is almost the same in the main scanning direction (in the range of −160 mm to 160 mm because printing is possible in the short side direction of A3 size paper). It can be seen that the fluctuation amount of the focus amount can be suppressed within the range of 250 μm to −300 μm.

  9 to 11 show fluctuations in the imaging position of each laser beam in the sub-scanning direction. FIG. 9 shows a magenta laser beam, FIG. 10 shows a cyan laser beam, and FIG. 11 shows a yellow laser beam. It corresponds to the black laser beam.

  From FIG. 9 to FIG. 11, under all temperature conditions, in the main scanning direction (printing is possible in the short side direction of A3 size paper, the range of −160 mm to 160 mm), the data in the sub scanning direction is displayed. It can be seen that the fluctuation amount of the focus amount can be suppressed within the range of 500 μm to −400 μm.

  12 to 14 show the extent to which the position where each laser beam is imaged is corrected when the variation in angular accuracy (surface tilt) of each reflecting surface of the polygonal mirror 5a of the deflecting device 5 is 1 minute. 12 corresponds to a magenta laser beam, FIG. 13 corresponds to a cyan laser beam, and FIG. 14 corresponds to a yellow laser beam and a black laser beam.

  As shown in FIGS. 12 to 14, it is recognized that the influence of the surface tilt is suppressed to 1 μm or less in all regions in the main scanning direction under all temperature conditions.

  FIGS. 15 to 17 show normal temperatures (20 ° C.) when the angle at which each laser beam is reflected by the polygon mirror 5a of the deflecting device 5 (the swing angle of the polygon mirror 5a) is 0 °. FIG. 15 shows a magenta laser beam, FIG. 16 shows a cyan laser beam, and FIG. 17 shows a yellow laser beam and a black laser beam, respectively. Corresponding.

  From FIG. 15 to FIG. 17, the amount of color misregistration in the sub-scanning direction when a color image is exposed by the exposure apparatus 1 shown in FIG. 2 and FIG. In addition, it is recognized that each color component is corrected to a maximum of 24 μm or less.

  18 and 19 show the relative positions of the laser beams in the main scanning direction under the conditions shown in FIGS. 15 to 17, FIG. 18 shows the magenta laser beam, and FIG. 19 shows the yellow laser beam and the black laser beam. Corresponding to each of the laser beams.

  As apparent from FIGS. 18 and 19, the color shift amount in the main scanning direction when the color image is exposed by the exposure apparatus 1 shown in FIGS. 2 and 3 is independent for each color component under all temperature conditions. It can be seen that the maximum correction is made to 1 μm or less and between each color component to 10 μm or less.

  20 to 22 show deviations from the reference value of the fθ characteristic of each laser beam. FIG. 20 shows a magenta laser beam, FIG. 21 shows a cyan laser beam, and FIG. 22 shows a yellow laser beam and a black laser beam. It corresponds to the laser beam for use.

  As shown in FIGS. 20 to 22, it can be seen that the deviation of the fθ characteristic is suppressed within ± 150 μm in all the regions in the main scanning direction under all temperature conditions.

Tables 4, 5 and 6 show optical numerical data of optical elements in the second embodiment of the pre-deflection optical system 7 * and the post-deflection optical system 9 * described above. Table 5 shows the shapes of the lens surfaces (the respective curvatures in the Y-axis direction and the Z-axis direction) of the first to third imaging lenses 23, 25, and 27 of the post-deflection optical system 9, and the distance between the lenses. Table 6 shows the curvature of the exit surface of the first lens 23 (surface on the side far from the deflecting device 5 (free curved surface)). Table 4 shows the results obtained by examining the material of the glass when selecting the optimum collimator lens or finite focus lens for the post-deflection optical system shown in Table 5, and substantially shows The same result as that of the first embodiment shown in FIG. 3 is obtained.

  In the second embodiment of the exposure apparatus 1 specified by the optical numerical data shown in Tables 5 and 6, the first imaging lens 23 of the imaging optical system (post-deflection optical system) 9 * is used. The feature is that the surface facing the deflecting device 5 is a toric surface in which the direction of the rotational symmetry axis is directed in the sub-scanning direction, and the surface facing the image surface (photosensitive drum) does not have a rotational symmetry axis. It is a free-form surface. Further, the direction of the unevenness of the lens surface (the direction in which the center of the arc defining the generatrix is convex) is the surface facing the deflecting device 5 and the surface facing the image surface (photosensitive drum) side. Are concave with respect to the deflecting device in both the main scanning direction and the sub-scanning direction. As a material of the lens, BK7 having an Abbe number νd of 64.2 is used.

  The second imaging lens 25 is characterized in that the surface facing the deflecting device 5 is a cylindrical surface with the rotational symmetry axis directed in the sub-scanning direction, and the surface facing the image surface is the rotational symmetry axis. Is a cylindrical surface oriented in the main scanning direction. The concave and convex directions of the lens surface are concave on the deflecting device side for the surface on the deflecting device 5 side and straight on the deflecting device side for the surface facing the image surface (photosensitive drum) side. As the lens material, SF6 having an Abbe number νd of 25.46 is used.

  On the other hand, the third imaging lens 27 is characterized in that the surface facing the deflecting device is a spherical surface, and the surface facing the image surface is a toric surface with the axis of rotational symmetry directed in the sub-scanning direction. The shape in the main scanning direction of the surface facing the deflecting device 5 (the direction of the concave and convex portions of the bus) is convex toward the deflecting device 5, and the direction of the rotationally symmetric axis of the surface facing the image surface side is the deflecting device. On the side, the center of the arc of the bus is also on the deflection means side. The lens material is BK7 having an Abbe number νd of 64.2.

  FIG. 23 is a schematic diagram showing characteristics in the sub-scanning direction of the laser beam L * passing between the deflecting device 5 and the image plane in the second embodiment shown in Tables 5 and 6. Note that FIG. 23 is a schematic diagram enlarged along the axis in the sub-scanning direction, similarly to FIG. 5, in order to clarify the characteristics. In FIG. 23, the horizontal axis indicates the optical path length, the point O indicates the reflection point on the polygon mirror 5a of the deflecting device 5, and LY, LM, LC, and LB indicate the corresponding photosensitive drum 58 *. LYp, LMp, LCp, and LBp represent the chief rays that are the centers of the laser beams.

  As shown in FIG. 23, 2 × 4 sets = 8 laser beams L * reflected by an arbitrary reflecting surface of the polygonal mirror 5a of the deflecting device 5 have an arbitrary reflecting surface with respect to the cross section in the sub-scanning direction. The first imaging lens 23 is crossed with each other and guided to the image plane.

  Specifically, in FIG. 23, the optical axis of the system of the exposure apparatus 1 (the position of each laser beam L * in the sub-scanning direction) is directed toward the image plane from the pre-deflection optical system with reflection by the deflecting device. Criteria for definition) If the left side of the paper is the pre-deflection optical system, the right side of the paper is the image plane, and the vertical axis is the arbitrary reflecting surface of the deflecting device 5, for example, the system The laser beam incident from above the optical axis (on the (+) side of the vertical axis) intersects the optical axis of the system in the vicinity of the reflecting surface and then the lower end side of the first imaging lens 23 in the sub-scanning direction. Is incident on. Similarly, for example, a laser beam incident on an arbitrary reflecting surface of the deflecting device 5 from below the optical axis of the system (on the (−) side of the vertical axis) intersects the optical axis of the system near the reflecting surface. After that, it enters the upper end side of the first imaging lens 23 in the sub-scanning direction. Further, as shown in FIG. 23, each laser beam guided to the reflecting surface of the deflecting device 5 has the optimum positions of the light emitting points of the laser elements 3 * a and * b, For example, black (LB), cyan (LC), magenta (LM), and yellow (LY) are aligned in this order from the axis (+) side in the sub-scanning direction, that is, the vertical direction. The order of incidence on one imaging lens 23 is yellow (LY), magenta (LM), cyan (LC), and black (LB) from the vertical axis (+) side.

  As shown in FIG. 23, the position where each laser beam intersects the optical axis of the system is defined between the first imaging lens 23 and the reflecting surface of the deflecting device 5, so that the photosensitive drum Each laser beam L * directed to each of 58 * is guided to a predetermined position of the photosensitive drum 58 * while being converged for each laser beam. That is, the interval between the laser beams in the sub-scanning direction at the imaging position (predetermined image plane) assuming that the photosensitive drums 58 * are on the same plane can be reduced. This indicates that the distance in the sub-scanning direction of each laser beam L * is small between the conjugate position, that is, between the first imaging lens 23 and the reflecting surface of the deflecting device 5. As a result, It shows that the thickness (height in the sub-scanning direction) of the reflecting surface of the deflecting device 5 can be reduced.

  Thereby, when forming the polygonal mirror 5a of the deflecting device 5, the number of the polygonal mirrors 5a that can be processed in the same process in a state where a plurality of the polygonal mirrors 5a are stacked in the direction of the rotation axis can be increased, and the cost of the deflecting device can be increased. Is reduced. Further, the loss of windage (loss of rotational force due to air resistance during rotation) can be reduced by reducing the thickness of the polygon mirror 5a. When a mirror motor having the same power is used, power consumption and heat generation are reduced. Can be suppressed. On the other hand, the mirror motor can be reduced in size, and in this case, the cost of the motor drive circuit can be reduced.

  24 to 40 show various imagings obtained by the exposure apparatus 1 that can provide each laser beam L * intersecting between the first imaging lens 23 and the deflecting device 5 described with reference to FIG. It is a graph which shows a characteristic. In each of FIGS. 24 to 40, a curve a (solid line) indicates that the ambient temperature is 20 ° C., a curve b (broken line) indicates that the ambient temperature is 70 ° C., and a curve c (dashed line). Indicates the respective characteristics when the ambient temperature is −30 ° C. In each figure, the horizontal axis indicates the distance in the main scanning direction.

  24 to 26 show fluctuations in the imaging position of each laser beam in the main scanning direction. FIG. 24 shows a magenta laser beam, FIG. 25 shows a cyan laser beam, and FIG. 26 shows a yellow laser beam. It corresponds to the black laser beam.

  From FIG. 24 to FIG. 26, it can be seen that the fluctuation amount of the defocus amount in the main scanning direction is suppressed within the range of 250 μm to −300 μm at almost all positions in the main scanning direction under all temperature conditions.

  27 to 29 show fluctuations in the imaging position of each laser beam in the sub-scanning direction. FIG. 27 shows a magenta laser beam, FIG. 28 shows a cyan laser beam, and FIG. 29 shows a yellow laser beam. It corresponds to the black laser beam.

  From FIG. 27 to FIG. 29, it is recognized that the variation amount of the defocus amount in the sub-scanning direction is suppressed within the range of 500 μm to −400 μm at almost all positions in the main scanning direction under all temperature conditions.

  30 to 32 show the extent to which the position at which each laser beam is imaged is corrected when the variation in angular accuracy (surface tilt) of each reflecting surface of the polygonal mirror 5a of the deflecting device 5 is 1 minute. 30 corresponds to a magenta laser beam, FIG. 31 corresponds to a cyan laser beam, and FIG. 32 corresponds to a yellow laser beam and a black laser beam.

  As shown in FIG. 30 to FIG. 32, it is recognized that the influence of surface tilt is suppressed to 1 μm or less in all regions in the main scanning direction under all temperature conditions.

  33 to 35 show normal temperatures (20 ° C.) when the angle at which each laser beam is reflected by the polygon mirror 5a of the deflecting device 5 (the swing angle of the polygon mirror 5a) is 0 °. FIG. 33 shows a magenta laser beam, FIG. 34 shows a cyan laser beam, and FIG. 35 shows a yellow laser beam and a black laser beam, respectively. Corresponding.

  From FIG. 33 to FIG. 35, the color misregistration amount in the sub-scanning direction when the color image is exposed by the exposure apparatus 1 provided with the optical characteristics shown in Tables 5 and 6 is the same for all color components. It can be seen that correction is made to a maximum of 12 μm or less and between each color component to a maximum of 24 μm or less.

  36 and 37 show the relative positions of the respective laser beams in the main scanning direction under the conditions shown in FIGS. 33 to 35. FIG. 36 shows the magenta laser beam, and FIG. 37 shows the yellow laser beam and the black laser beam. Corresponding to each of the laser beams.

  As is apparent from FIGS. 36 and 37, the amount of color misregistration in the main scanning direction when a color image is exposed by the exposure apparatus 1 to which the above-described second embodiment is applied is the same for each color component alone. It is recognized that the correction is made to a maximum of 1 μm or less under the temperature condition and to a maximum of 10 μm or less between the color components.

  38 to 40 show deviations from the reference value of the fθ characteristic of each laser beam. FIG. 38 shows a magenta laser beam, FIG. 39 shows a cyan laser beam, and FIG. 40 shows a yellow laser beam and a black laser beam. It corresponds to the laser beam for use.

  As shown in FIGS. 38 to 40, it can be seen that the deviation of the fθ characteristic is suppressed within ± 150 μm in all regions in the main scanning direction under all temperature conditions.

  As described above, the exposure apparatus of the present invention is more effective than the collimator lens in the case where the imaging position of the laser beam by the many optical elements arranged downstream of the collimator lens changes due to the increase in the ambient temperature. It is possible to cancel the fluctuation amount of the imaging position caused by each optical element arranged in the subsequent stage and the fluctuation amount of the imaging position caused by the laser element and the collimator lens alone, and reduce the fluctuation of the beam diameter on the image plane. .

  In addition, the exposure apparatus of the present invention can ensure a wide angle of view in each of the sub-scanning direction and the main scanning direction, and has an improved degree of freedom in selecting an optical path. In addition, the black toner capacity can be increased.

  Furthermore, in the exposure apparatus of the present invention, the Abbe numbers of the three imaging lenses of the post-deflection optical system are 60, 28, and 65 in order from the side close to the deflection apparatus. Even when there is an individual difference within a predetermined range (about 15 nm) in the wavelength of each laser beam, the fluctuation of the position where each individual laser beam converges to a predetermined beam diameter can be suppressed to 10 μm or less.

  As described above, the exposure apparatus of the present invention relates to fluctuations in the imaging position of the laser beam that occur as the ambient temperature rises, and results from the optical elements arranged at the rear stage (image plane side) of the collimator lens. The fluctuation amount of the image position can be canceled by the fluctuation amount of the imaging position caused by the semiconductor laser element and the collimator lens alone, and the fluctuation of the beam diameter on the image plane can be reduced.

  In addition, the exposure apparatus of the present invention can ensure a wide angle of view in each of the sub-scanning direction and the main scanning direction, and has an improved degree of freedom in selecting an optical path. In addition, the black toner capacity can be increased.

1 ... exposure apparatus,
5 ... Deflection device,
7: Pre-deflection optical system,
9: Post-deflection optical system,
11: Collimator lens,
13 ・ ・ ・ Aperture,
15 ・ ・ ・ Half mirror,
17 ... Cylinder lens,
19 ... Synthetic mirror,
21 ... Holding member,
23... First imaging lens,
25... Second imaging lens,
27 ... Third imaging lens,
29 ・ ・ ・ Horizontal synchronous mirror,
31 ・ ・ ・ Horizontal synchronization detector,
33 ・ ・ ・ first mirror,
35 ... second mirror,
37 ... the third mirror,
39 ..Dustproof filter,
100 Image forming apparatus.

Claims (5)

A light source, a first lens that converts light emitted from the light source into substantially parallel light, and light that has been converted into substantially parallel light by the first lens in a plane orthogonal to the direction in which the light travels. First optical means comprising: an optical member provided with positive power only in said first direction for further convergence with respect to one direction;
Light having a reflecting surface formed so as to be rotatable and having converged light at least in the first direction by the first optical means is orthogonal to each of the first direction and the direction in which the light travels. Deflection means for deflecting in the direction of
A lens that includes a plurality of lenses and that is located closest to the deflecting means, a lens surface on the deflecting means side, and a lens that is located farthest from the deflecting means and that is farthest from the deflecting means Are toric surfaces each having a rotationally symmetric axis extending along the first direction parallel to the rotational axis that is the rotational center of the deflecting means, the reflective surface of the deflecting means and the rotational axis. The light deflected by the deflecting means is orthogonal to the first direction at the predetermined distance and the rotation angle of the reflecting surface at the predetermined distance. A second optical means comprising a lens for proportioning the distance in the second direction;
An optical device comprising: A light source, a first lens that converts light emitted from the light source into substantially parallel light, and light that has been converted into substantially parallel light by the first lens in a plane orthogonal to the direction in which the light travels. First optical means comprising: an optical member provided with positive power only in said first direction for further convergence with respect to one direction;
Light having a reflecting surface formed so as to be rotatable and having converged light at least in the first direction by the first optical means is orthogonal to each of the first direction and the direction in which the light travels. Deflection means for deflecting in the direction of
The shape of the lens surface on the deflection means side of the lens that includes a plurality of lenses and is arranged at the position farthest from the deflection means is convex toward the deflection means and far from the deflection means The lens surface on the side is formed on a toric surface whose rotational symmetry axis is defined in parallel with the rotation axis that is the rotation center of the deflection means, and the deviation of the angle formed by the reflection surface of the deflection means and the rotation axis is In addition to correcting the influence, the light deflected by the deflecting means is rotated at a predetermined distance to the rotation angle of the reflecting surface and the distance in the second direction orthogonal to the first direction at the predetermined distance. A second optical means comprising a proportional lens;
An optical device comprising: ΣNi (N1 + N2 +... + NM, M is an integer of 2 or more, and each of Ni is an integer of 1 or more), and a plurality of light beams emitted from the ΣNi light sources are converted into convergent light or parallel light. Light converted into convergent light or parallel light by the finite focus lens or collimator lens and the plurality of finite focus lenses and collimator lenses, or converted into convergent light or parallel light by the finite focus lens or collimator lens, First optical means including M sets of optical members that are given positive power only in the first direction for further convergence with respect to the first direction in a plane orthogonal to the direction in which the light travels;
The first optical means has a reflecting surface formed so as to be rotatable, and is converged at least in the first direction by the first optical means, or the light converted into parallel light is converted into the first direction and the light. Deflection means for deflecting in a direction orthogonal to each of the traveling directions;
The .SIGMA.Ni light deflected by the deflecting means and the light deflected by the deflecting means are orthogonal to the first direction at the predetermined distance and the rotation angle of the reflecting surface at a predetermined distance. And a lens having a function of forming an image at the predetermined distance while making the distance in the direction of 2 proportional and correcting the influence of the deviation of the angle between the reflecting surface of the deflecting means and the rotation axis. A second optical means;
Have
Each of the M groups of light is configured to intersect each other between the reflecting surface of the deflecting unit and a lens located closest to the deflecting unit among the lenses of the second optical unit. Optical device characterized. ΣNi (N1 + N2 +... + NM, M is an integer of 2 or more, and each of Ni is an integer of 1 or more), and a plurality of light beams emitted from the ΣNi light sources are converted into convergent light or parallel light. The light converted into convergent light or parallel light by either the finite focus lens or the collimator lens and the plurality of finite focus lenses and the collimator lens is further related to a first direction in a plane orthogonal to the light traveling direction. First optical means including M sets of optical members that are given positive power only in the first direction for convergence;
Light having a reflecting surface formed so as to be rotatable and having converged light at least in the first direction by the first optical means is orthogonal to each of the first direction and the direction in which the light travels. Deflection means for deflecting in the direction of
The .SIGMA.Ni beams deflected by the deflecting means are orthogonal to the first direction at the position of the predetermined distance and the rotation angle of the reflecting surface at the position of the light deflected by the deflecting means. A second lens including a lens that forms an image at the predetermined distance so as to make the distance in the second direction proportional and to correct the influence of the deviation of the angle between the reflecting surface of the deflecting means and the rotation axis; Optical means,
Have
The optical apparatus, wherein the principal rays of the light of the M group are close to each other in the first direction while being directed to the position of the predetermined distance from the second optical means. ΣNi (N1 + N2 +... + NM, M is an integer greater than or equal to 1 and each Ni is an integer greater than or equal to 1), and a plurality of light beams emitted from the ΣNi light sources are converted into convergent light or parallel light. The light converted into convergent light or parallel light by either the finite focus lens or the collimator lens and the plurality of finite focus lenses and the collimator lens is further related to a first direction in a plane orthogonal to the light traveling direction. First optical means including M sets of optical members that are given positive power only in the first direction for convergence;
Light having a reflecting surface formed so as to be rotatable and having converged light at least in the first direction by the first optical means is orthogonal to each of the first direction and the direction in which the light travels. Deflection means for deflecting in the direction of
A lens composed of three lenses and arranged closest to the deflection means includes a surface that does not include a rotational symmetry axis, and deflects the ΣNi beams deflected by the deflection means by the deflection means. The rotation angle of the reflecting surface at a predetermined distance and the distance in the second direction orthogonal to the first direction at the predetermined distance, and the reflecting surface of the deflecting means A second optical means including a lens that forms an image at a position of the predetermined distance so as to correct an influence of a deviation of an angle with the rotation axis;
An optical device comprising:

Images