JP2009051194A - Linehead and imaging apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical write linehead comprising a plurality of light emitter devices in rows located in association with each of a plurality positive lenses lined up in array form and designed such that even when the surface of the linehead with light emitter devices lined up on it and the write surface thereof fluctuate in the optical axis direction, there is no variation from misalignments of light-emission dots. <P>SOLUTION: The linehead comprises a light emitter array 1 including a plurality of light emitter blocks 4 located at least in the main scan direction at intervals. Each light emitter block 4 includes at least one row of a plurality of light emitter devices lined up in array form in the main scan direction. A lens array is located on the exit side of the light emitter array 1 such that one each positive lens system 5 is in alignment with each light emitter block 4 and it is located in parallel with the light emitter array 1. A write surface 41 is located on the imaging side of the lens array in parallel. Each positive lens system 5 forming a part of the lens array comprises a telephoto optical system having confocally located two positive lens groups L1 and L2 with an aperture stop 30 located at the confocal plane of the telephoto optical system. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a line head and an image forming apparatus using the line head, and more particularly to a line head that forms an imaging spot row by projecting a light emitting element row onto an irradiated surface using a microlens array. The present invention relates to an image forming apparatus.

  Conventionally, a plurality of LED array chips are arranged in the direction of the LED array, and enlarged and projected onto a photosensitive member with a positive lens in which the LED arrays of the respective LED array chips are arranged correspondingly, and the ends of adjacent LED array chips on the photosensitive member. An optical writing line head that forms images adjacent to each other at the same pitch as the pitch between the light emitting dots of the same LED array chip, and an optical reading line head with the optical path reversed. This is proposed in Japanese Patent Application Laid-Open No. H10-228707.

  Further, Patent Document 2 proposes that the positive lens is composed of two lenses in the arrangement as in Patent Document 1, and the depth of focus is made deep so that the projected light approaches the parallel light.

In addition, the LED array chips are arranged in two rows with a gap, the repetition phase is shifted by a half cycle, and the positive lens array is arranged in two rows with each LED array chip corresponding to each positive lens. Patent Document 3 proposes an optical writing line head in which images of light emitting dot arrays are arranged in a line.
Japanese Patent Laid-Open No. 2-4546 JP-A-6-344596 JP-A-6-278314

  In these conventional techniques, even if the images of the light emitting dot arrays are aligned at an equal pitch on the ideal image plane, if the image plane moves back and forth in the optical axis direction of the lens due to the shake of the photoconductor, the photoconductor As a result, the light emitting dots are displaced from each other, and the light emitting dot array moves relatively in the sub-scanning direction to cause unevenness in the pitch between scanning lines (pitch unevenness in the main scanning direction).

  Further, as the angle of view of each positive lens increases, the peripheral light amount decrease increases according to the cos 4 law (shading). In order to prevent density unevenness of the printed image due to this shading, it is necessary to make the light amount of each pixel (light emitting dot image) on the image plane constant. To do this, the light amount of the light source (light emitting dot) is changed for each light emitting dot. Shading must be corrected. However, since the light emission intensity of the light source pixel (light emitting dot) affects the life characteristics, if the shading of the optical system is increased, even if the light amount is adjusted for each light emitting dot and a uniform image surface light amount is initially obtained. The light amount unevenness of the light emitting dot pitch occurs with time, and the image density unevenness occurs.

  The present invention has been made in view of such problems of the prior art, and an object thereof is to arrange a plurality of light emitting elements in a row corresponding to each lens of a plurality of positive lenses arranged in an array. In the optical writing line head thus formed, even if the light emitting element array surface and the writing surface fluctuate in the optical axis direction, unevenness based on the positional deviation of the light emitting dot image is reduced. Another object of the present invention is to reduce density unevenness due to shading between imaging spots formed by the respective lenses. Still another object of the present invention is to reduce the influence of a change in the distance in the optical axis direction based on the curvature of a drum-shaped photoconductor.

  Another object of the present invention is to provide an image forming apparatus using such an optical writing line head and an optical reading line head in which the optical path is reversed.

  In the line head of the present invention that achieves the above object, a light emitter block including at least one light emitting element row in which a plurality of light emitting elements are arranged in a row in a first direction is spaced at least in the first direction. A plurality of arranged light emitter arrays, and a lens array in which one positive lens system is arranged corresponding to each light emitter block is arranged on the emission side, and the imaging side of the lens array The positive lens system constituting the lens array comprises a telephoto optical system in which two positive lens groups are arranged at a confocal point, and an aperture is formed in the confocal surface of the telephoto optical system. A diaphragm is arranged.

  With this configuration, even if one or both of the position of the writing surface and the light emitting element placement surface is displaced in the optical axis direction, the position of the imaging spot does not occur, and the density between the imaging spots does not occur. Unevenness does not occur and deterioration of the formed image can be prevented.

  Further, the positive lens system can be composed of two positive lenses.

  Such a configuration not only facilitates the production of individual lens arrays, but also facilitates aberration correction.

  It is desirable that all positive lens systems constituting the lens array are the same.

  With this configuration, it is possible to make the intervals between the imaging spots, which are images of the light emitting elements in the first direction (main scanning direction) uniform, and to easily manufacture the lens array.

  The writing surface may be a flat surface.

  With this configuration, even when a plurality of light emitter blocks are arranged in the sub-scanning direction (second direction), writing can be performed in the same state in all columns, and uneven density between imaging spots does not occur. Deterioration of the formed image can be prevented.

  The writing surface may be a cylindrical surface.

  With this configuration, a line head suitable for an exposure head of an image forming apparatus that uses a drum-shaped photoconductor is obtained.

  It is desirable that at least the image side surface of the positive lens group on the image side of the positive lens system is a flat surface.

  With this configuration, the exit surface of the lens closest to the image plane can be made flat, and foreign matters such as dust and toner adhering to the exit surface can be easily cleaned, improving the cleaning performance. To do.

  Further, it is desirable that the shape of the aperture stop is a shape that limits at least the aperture diameter in the first direction.

  With this configuration, it is possible to cope with at least the main scanning direction (first direction) in which the positional deviation of the off-axis imaging spot becomes a problem.

  In addition, it is preferable that the light emitter block includes a plurality of the light emitting element rows arranged in a second direction (sub scanning direction) orthogonal to the first direction.

  With this configuration, it is possible to cope with image formation with a high density of imaging spots.

  Further, it is desirable that a plurality of the light emitter blocks are arranged in a second direction orthogonal to the first direction.

  With this configuration, it is possible to cope with image formation with a high density of imaging spots.

  Moreover, it is desirable that the light emitting element is an organic EL element.

  By configuring in this way, it is possible to cope with in-plane uniform image formation.

  The light emitting device may be an LED.

  By configuring in this way, it is possible to cope with a line head using an LED array.

  In addition, at least two or more image forming stations in which image forming units including a charging unit, a line head as described above, a developing unit, and a transfer unit are arranged around the image carrier are provided. By passing through the station, an image forming apparatus that forms an image by a tandem method can be configured.

  With this configuration, it is possible to configure an image forming apparatus such as a printer that is small in size and has high resolution and little image deterioration.

  The present invention relates to a photoreceptor array in which a plurality of photoreceptor blocks each including at least one light receiving element array in which a plurality of light receiving elements are arranged in a row in a first direction are arranged at least in the first direction. A lens array in which one positive lens system is arranged to correspond to each photoreceptor block, and a reading surface is disposed on the object side of the lens array, Each positive lens system constituting the lens array includes a telephoto optical system in which two positive lens groups are disposed at a confocal point, and an aperture stop is disposed on a confocal surface of the telephoto optical system. The line head is also included.

  With this configuration, even in the optical reading line head, even if one or both of the reading surface and the light receiving element arrangement surface are shifted in the optical axis direction, the position of the reading spot does not occur. It is possible to prevent deterioration of the read image by preventing the density unevenness between them.

  Before describing the optical system of the line head of the present invention in detail, the arrangement of the light emitting elements and the light emission timing will be briefly described.

  FIG. 4 is an explanatory diagram showing a correspondence relationship between the light emitter array 1 according to the embodiment of the present invention and the microlens 5 having a negative optical magnification. In the line head of this embodiment, two rows of light emitting elements correspond to one microlens 5. However, since the microlens 5 is an imaging element having a negative optical magnification (inverted imaging), the position of the light emitting element is reversed in the main scanning direction and the sub-scanning direction. That is, in the configuration of FIG. 1, even-numbered light emitting elements (8, 6, 4, 2) are arranged on the upstream side (first row) in the moving direction of the image carrier, and on the downstream side (second row). Are arranged with odd-numbered light emitting elements (7, 5, 3, 1). In addition, a light emitting element having a large number is arranged on the head side in the main scanning direction.

  1 to 3 are perspective views of a portion corresponding to one microlens of the line head of this embodiment. As shown in FIG. 2, the image spot 8a of the image carrier 41 corresponding to the odd-numbered light emitting elements 2 arranged on the downstream side of the image carrier 41 is formed at a position reversed in the main scanning direction. The R is the moving direction of the image carrier 41. Further, as shown in FIG. 3, the imaging spot 8b of the image carrier 41 corresponding to the even-numbered light emitting elements 2 arranged on the upstream side (first row) of the image carrier 41 is in the sub-scanning direction. It is formed at the inverted downstream position. However, in the main scanning direction, the positions of the imaging spots from the head side correspond to the light emitting elements 1 to 8 in order. Therefore, in this example, it is understood that the imaging spots can be formed in the same row in the main scanning direction by adjusting the timing of forming the imaging spots in the sub scanning direction of the image carrier.

  FIG. 5 is an explanatory diagram showing an example of the memory table 10 of the line buffer in which image data is stored. The memory table 10 in FIG. 5 is stored with being inverted in the main scanning direction with respect to the light emitting element numbers in FIG. 4. In FIG. 5, among the image data stored in the memory table 10 of the line buffer, first image data (1, 3, 5, 5) corresponding to the light emitting elements on the upstream side (first row) of the image carrier 41 first. 7) to read out the light emitting element. Next, after T time, the second image data (2, 4, 6, 8) corresponding to the light emitting elements on the downstream side (second row) of the image carrier 41 stored in the memory address is read and emitted. Let In this way, as indicated by the position 8 in FIG. 6, the first row of imaging spots on the image carrier is formed in the same row as the second row of imaging spots in the main scanning direction.

  FIG. 1 is a perspective view conceptually showing an example in which image data is read out at the timing of FIG. 5 to form an imaging spot. As described with reference to FIG. 5, the light emitting element on the upstream side (first row) of the image carrier 41 is first caused to emit light, thereby forming an imaging spot on the image carrier 41. Next, after a predetermined timing T has elapsed, the odd-numbered light emitting elements on the downstream side (second row) of the image carrier 41 are caused to emit light, thereby forming an imaging spot on the image carrier. At this time, the imaging spot formed by the odd-numbered light emitting elements is not formed at the position 8a described in FIG. 2, but is formed at the position 8 in the same row in the main scanning direction as shown in FIG. become.

  FIG. 7 is a schematic explanatory diagram showing an example of a light emitter array used as a line head. In FIG. 7, in the light emitter array 1, a light emitter block 4 (see FIG. 4) is formed by providing a plurality of light emitting element rows 3 in which a plurality of light emitting elements 2 are arranged in the main scanning direction. In the example of FIG. 7, the light emitter block 4 forms two light emitting element rows 3 in which four light emitting elements 2 are arranged in the main scanning direction in the sub scanning direction (see FIG. 4). A large number of the light emitter blocks 4 are arranged in the light emitter array 1, and each light emitter block 4 is arranged corresponding to the microlens 5.

  A plurality of microlenses 5 are provided in the main scanning direction and the sub-scanning direction of the light emitter array 1 to form a microlens array (MLA) 6. The MLA 6 is arranged with the leading position in the main scanning direction shifted in the sub-scanning direction. Such an arrangement of the MLA 6 corresponds to a case where the light emitting elements 1 are provided in a staggered manner in the light emitter array 1. In the example of FIG. 7, three rows of MLA 6 are arranged in the sub-scanning direction. However, for convenience of explanation, the unit blocks 4 corresponding to the respective positions of the three rows of MLA 6 in the sub-scanning direction are group A and group B. And group C.

  As described above, when the plurality of light emitting elements 2 are arranged in the microlens 5 having a negative optical magnification and the lenses are arranged in a plurality of rows in the sub-scanning direction, the main body of the image carrier 41 is used. In order to form imaging spots arranged in a line in the scanning direction, the following image data control is required. (1) Inversion in the sub-scanning direction, (2) Inversion in the main scanning direction, (3) Adjustment of light emission timing of a plurality of rows of light emitting elements in the lens, and (4) Adjustment of light emission timing of the light emitting elements between groups.

  FIG. 8 is an explanatory diagram showing an imaging position when the exposure surface of the image carrier is irradiated through the microlens 5 with the output light of each light emitting element 2 in the configuration of FIG. In FIG. 8, as described with reference to FIG. 7, the light emitter array 1 has unit blocks 4 divided into group A, group B, and group C. The light-emitting element rows of the unit blocks 4 of group A, group B, and group C are divided into the upstream side (first row) and the downstream side (second row) of the image carrier 41, and even-numbered light emission in the first row Elements are assigned, and odd-numbered light emitting elements are assigned to the second column.

  For group A, by operating each light emitting element 2 as described with reference to FIGS. 1 to 3, an image spot is formed on the image carrier 41 at a position reversed in the main scanning direction and the sub scanning direction. . In this manner, imaging spots are formed on the image carrier 41 in the order of 1 to 8 in the same row in the main scanning direction. Thereafter, the image carrier 41 is moved in the sub-scanning direction for a predetermined time, and the processing of the group B is similarly executed. Further, by moving the image carrier 41 in the sub-scanning direction for a predetermined time and executing the processing of group C, it is based on the input image data in the order of 1 to 24... In the same column in the main scanning direction. An imaging spot is formed.

  FIG. 9 is an explanatory diagram showing a state of forming an imaging spot in the sub-scanning direction in FIG. S is the moving speed of the image carrier 41, d1 is the distance between the first and second light emitting elements in group A, and d2 is the second light emitting element in group A and the second light emission in group B. The element spacing, d3 is the distance between the light emitting elements in the second row of group B and the light emitting elements in the second row of group C, and T1 is the light emitting element in the first row after the light emission of the light emitting elements in the second row of group A. T2 is the time required for the image forming position of the light emitting elements in the second row of group A to move to the image forming position of the light emitting elements in the second row of group B, and T3 is the light emitting elements in the second row of group A Is the time required for the imaging position to move to the imaging position of the light-emitting elements in the second row of group C.

  T1 can be obtained as follows. T2 and T3 can be similarly obtained by replacing d1 with d2 and d3.

T1 = | (d1 × β) / S |
Here, each parameter is as follows.
d1: Distance in the sub-scanning direction of the light emitting elements S: Moving speed of the imaging surface (image carrier) β: Lens magnification In FIG. 9, T2 hours after the time when the light emitting elements in the second row of group A emit light. The light emitting elements in the second row of group B are caused to emit light. Furthermore, the light emitting elements in the second row of group C are caused to emit light after T2 to T3 hours. The first row of light emitting elements in each group emits light after T1 time after the second row of light emitting elements emits light. By performing such processing, as shown in FIG. 8, the imaging spots formed by the light emitters arranged two-dimensionally on the light emitter array 1 can be formed in a line on the image carrier. It becomes possible. FIG. 10 is an explanatory diagram showing an example in which an imaging spot is formed by inverting in the main scanning direction of the image carrier when a plurality of microlenses 5 are arranged.

  An image forming apparatus can be configured using the line head as described above. In the embodiment, a tandem color printer (exposed to four photoconductors with four line heads, simultaneously forms four color images, and transfers them to one endless intermediate transfer belt (intermediate transfer medium)). The line head as described above can be used in the image forming apparatus. FIG. 11 is a vertical side view showing an example of a tandem image forming apparatus using an organic EL element as a light emitting element. This image forming apparatus includes four line heads 101K, 101C, 101M, and 101Y having the same configuration, and corresponding four photosensitive drums (image carriers) 41K, 41C, 41M, and 41Y having the same configuration. These are respectively arranged at exposure positions, and are configured as a tandem image forming apparatus.

  As shown in FIG. 11, this image forming apparatus is provided with a driving roller 51, a driven roller 52, and a tension roller 53. The tension roller 53 applies tension to the image forming apparatus and stretches it in the direction indicated by the arrow (counterclockwise). ) Is circulated to the intermediate transfer belt (intermediate transfer medium) 50. Photosensitive members 41K, 41C, 41M, and 41Y having photosensitive layers are arranged on the outer peripheral surface as four image carriers arranged at predetermined intervals with respect to the intermediate transfer belt 50.

  K, C, M, and Y added after the above symbols mean black, cyan, magenta, and yellow, respectively, and indicate that the photoconductors are black, cyan, magenta, and yellow, respectively. The same applies to other members. The photoreceptors 41K, 41C, 41M, and 41Y are rotationally driven in the direction indicated by the arrow (clockwise) in synchronization with the driving of the intermediate transfer belt 50. Around each photoconductor 41 (K, C, M, Y), charging means (corona charger) 42 (K) for uniformly charging the outer peripheral surface of the photoconductor 41 (K, C, M, Y), respectively. , C, M, Y) and the outer peripheral surface uniformly charged by the charging means 42 (K, C, M, Y) are synchronized with the rotation of the photoconductor 41 (K, C, M, Y). Thus, the above-described line head 101 (K, C, M, Y) of the present invention for sequentially scanning the line is provided.

  Further, a developing device 44 (K, C, and M) that applies a toner as a developer to the electrostatic latent image formed by the line head 101 (K, C, M, and Y) to form a visible image (toner image). M, Y) and a primary transfer roller 45 (K, Y) as transfer means for sequentially transferring the toner image developed by the developing device 44 (K, C, M, Y) to the intermediate transfer belt 50 as a primary transfer target. C, M, Y) and a cleaning device 46 (K, C, M, Y) as a cleaning means for removing the toner remaining on the surface of the photoreceptor 41 (K, C, M, Y) after being transferred. ).

  Here, in each line head 101 (K, C, M, Y), the array direction of the line head 101 (K, C, M, Y) is set to the bus of the photosensitive drum 41 (K, C, M, Y). It is installed along. The emission energy peak wavelength of each line head 101 (K, C, M, Y) and the sensitivity peak wavelength of the photoconductor 41 (K, C, M, Y) are set to substantially coincide.

  The developing device 44 (K, C, M, Y) uses, for example, a non-magnetic one-component toner as a developer, and the one-component developer is conveyed to the developing roller by a supply roller, for example, and adhered to the developing roller surface. The film thickness of the developed developer is regulated by a regulating blade, and the developing roller is brought into contact with or increased in thickness by the photosensitive body 41 (K, C, M, Y), whereby the photosensitive body 41 (K, C, M, Y). The toner is developed as a toner image by attaching a developer according to the potential level.

  The black, cyan, magenta, and yellow toner images formed by the four-color single-color toner image forming station are intermediated by the primary transfer bias applied to the primary transfer roller 45 (K, C, M, Y). The toner image, which is sequentially primary transferred onto the transfer belt 50 and sequentially superposed on the intermediate transfer belt 50 to become a full color, is secondarily transferred to a recording medium P such as paper by a secondary transfer roller 66, and serves as a fixing unit. The toner is fixed on the recording medium P by passing through the fixing roller pair 61, and is discharged onto a paper discharge tray 68 formed in the upper part of the apparatus by a paper discharge roller pair 62.

  In FIG. 11, reference numeral 63 denotes a paper feed cassette in which a large number of recording media P are stacked and held, 64 denotes a pickup roller for feeding the recording media P from the paper feed cassette 63 one by one, and 65 denotes a secondary transfer roller. A pair of gate rollers for defining the supply timing of the recording medium P to the secondary transfer portion 66, a secondary transfer roller 66 as a secondary transfer means for forming a secondary transfer portion with the intermediate transfer belt 50, 67 Is a cleaning blade as a cleaning means for removing the toner remaining on the surface of the intermediate transfer belt 50 after the secondary transfer.

  The present invention relates to the optical system of the above-described line head (optical writing line head). First, the principle will be described.

  FIG. 12 is a diagram for explaining the principle of the present invention. FIG. 12 shows an end light emitting element 2x of a light emitting element array arranged in a line on the light emitting element arrangement surface 55 of the light emitter array 1 in the line head, a microlens 5 for projecting the light emitting element array, and the light emitting element array projected. 4A and 4B are diagrams showing a relationship with a photosensitive member (image carrier) 41, in which FIG. 5A shows the case of the present invention, and FIG. In the conventional example of FIG. 12B, since the opening of the microlens 5 is generally defined by its outer shape, the imaging spot 8x that is an image of the end light emitting element 2x on the photoreceptor 41 is the end light emitting element. Since the image is formed on a straight line passing through 2x and the center of the microlens 5, the surface of the photoconductor 41, which is an image surface, is moved back and forth in the lens optical axis OO ′ direction due to the shake of the photoconductor. Is moved to the position 41 ', the position of the imaging spot 8x on the photoconductor 41 becomes the position 8x' on the straight line, the position of the imaging spot is shifted, and the imaging spot 8x is relatively sub-positioned. Unevenness occurs in the pitch between the scanning lines drawn by moving in the scanning direction (unevenness of the imaging spot in the main scanning direction).

  Similarly, when the light emitting element arrangement surface 55 that is the object plane moves back and forth in the direction of the lens optical axis OO ′ due to the attachment of the light emitter array 1 or the like and moves to the position 55 ′ in FIG. The position of the imaging spot 8x, which is an image of the end light emitting element 2x, is a position 8x ″ on a straight line passing through the center of the end light emitting element 2x and the microlens 5, and the positional deviation of the imaging spot occurs. The imaging spot 8x moves relatively in the sub-scanning direction, causing unevenness in the pitch between the scanning lines drawn (unevenness of the imaging spot in the main scanning direction).

  Therefore, in the present invention, as shown in FIG. 12A, a combination of the first positive lens L1 and the second positive lens L2 in order from the object side in which the microlens 5 is arranged coaxially with the optical axis OO ′. A telephoto lens system in which the image side (rear side) focal point of the first positive lens L1 and the object side (front side) focal point of the second positive lens L2 coincide at a point (confocal) F, and It is assumed that the aperture stop 11 is arranged coaxially with the optical axis OO ′ at the position of the confocal point F. In this way, when the microlens 5 is configured by a telephoto lens system including two positive lenses L1 and L2, and the aperture stop 11 is disposed at the confocal point F, the microlens 5 exits from the end light emitting element 2x and the aperture stop 11 is disposed. The principal ray 12 passing through the center travels in parallel with the optical axis OO ′ until reaching the first positive lens L1, is refracted by the first positive lens L1, passes through the center of the aperture stop 11, and enters the second positive lens L2. Refracted and travels in parallel with the optical axis OO ′, and even if the photosensitive member 41 moves to the position 41 ′ in the optical axis OO ′ direction, the imaging spot 8x on the photosensitive member 41 Is the position 8x ′ of the principal ray 12 after being refracted by the microlens 5, and even if the position of the photosensitive member 41 is moved back and forth, the position of the imaging spot 8x does not shift.

  Similarly, even if the light emitting element arrangement surface 55 moves to the position 55 ′ in the direction of the lens optical axis OO ′, the position of the imaging spot 8x on the photoconductor 41 remains at the principal ray 12 refracted by the microlens 5. Even if the position of the light emitting element arrangement surface 55 is moved back and forth, the position of the imaging spot 8x does not shift.

  If a telephoto lens system comprising the confocal two positive lenses L1 and L2 and the aperture stop 11 disposed at the confocal point F is used as the microlens 5 as described above, the light emitting element arrangement surface 55 is used. The solid angle of divergence Ω from the light emitting element 2 of the light beam coming out of the light emitting element 2 at an arbitrary upper position and passing through the aperture of the aperture stop 11 (in FIG. 12A, the divergence solid angle Ω from the end light emitting element 2x is shown. Is the same at any position on the light emitting element arrangement surface 55, and the central ray of the divergent light beam is a light ray perpendicular to the light emitting element arrangement surface 55. Therefore, the peripheral light amount decreases according to the cos 4 law of the lens. Therefore, the density of the imaging spot 8 on the photoconductor 41 of any of the light emitting elements 2 in the light emitting element array arranged in a line on the light emitting element array 1 is the density of the light emitting elements 2. Same light intensity As long as it is the same, it is the same, and uneven density does not occur.

  Therefore, when the optical system of the above-described line head according to the present invention is used for an optical writing line head, the unevenness of the pitch of the imaging spot 8 in the main scanning direction does not occur as in the prior art, and the imaging spot 8 moves in the sub-scanning direction. Thus, there is no unevenness in the pitch between the scanning lines drawn.

  Further, the density unevenness between the imaging spots 8 due to the shading of the microlens 5 as in the prior art does not occur, and the density unevenness between the scanning lines drawn by moving the imaging spot 8 in the sub-scanning direction does not occur.

  That is, according to the present invention, a plurality of light emitting elements are arranged in a row in the main scanning direction, a single positive lens system is arranged corresponding to the plurality of light emitting elements, and an image of the row of the light emitting elements (image formation). In a line head that forms an image by projecting an array of spots onto a projection surface (photoreceptor), the projection optical system has a telecentric configuration on both sides, so that the position of the projection surface (photoreceptor) Even if one or both of the light emitting element arrangement surfaces are displaced in the optical axis direction, the position of the imaging spot does not shift, and density unevenness between the imaging spots does not occur. This is to prevent deterioration.

  The function of the aperture stop 11 may be any shape as long as it has a shape that limits the aperture diameter in a direction (main scanning direction) at least where the positional deviation of the off-axis imaging spot is a problem. When an array of light emitting elements in one row is arranged for one positive lens system as in 3), it may be a shape that only limits the aperture diameter in the main scanning direction. Further, even when two rows of arrays are arranged in close proximity in the sub-scanning direction as in the above embodiment of the present invention (FIG. 4), the shape may limit the aperture diameter in the main scanning direction. It is good also as a shape which restrict | limits the opening diameter of a direction. For that purpose, any opening shape of a circle, an ellipse or a rectangle may be used.

  In the description of FIG. 12, each of the positive lenses L1 and L2 constituting the microlens 5 is composed of one lens. However, each lens has a positive refractive power formed by coaxially arranging two or more lenses. It may consist of a lens system.

  The optical system of the optical writing line head has been described so far. A plurality of light receiving elements are arranged in a row in the main scanning direction with the optical path reversed, and one light receiving element is provided corresponding to the plurality of light receiving elements. Even in the case of an optical reading line head that has a positive lens and reads the image by back projecting the image of the array of light receiving elements (array of reading spots) onto the reading surface, the projection optical system has a telecentric configuration on both sides. Or by using a telephoto lens system comprising two confocal positive lenses and an aperture stop arranged at the confocal position, either one of the reading surface and the light receiving element arrangement surface or Even if both are shifted in the direction of the optical axis, the position of the reading spot does not occur and density unevenness between the reading spots does not occur to prevent deterioration of the scanned image. It can also be adapted to. In this case, in FIG. 12A, reference numeral 41 denotes a reading surface, reference numeral 2x denotes an end light receiving element, and the principle is the same as that of the optical system of the optical writing line head.

  Next, an optical writing line head according to one embodiment to which the principle of the present invention is applied will be described.

  13 is a partially broken perspective view showing the configuration of the optical writing line head of this embodiment, FIG. 14 is a partially enlarged perspective view thereof, and FIG. 15 is a sectional view of the optical writing line head in the sub-scanning direction. (The center of the microlenses 5 in each row is not in the same plane in the sub-scanning direction, but in FIG. 15, the cross-section in the sub-scanning direction passes through the center of the microlenses in each row. The same applies hereinafter.) FIG. 16 is a plan view showing the arrangement of the light emitter array and the microlens array in this case. Further, FIG. 17 is a diagram showing a correspondence relationship between one microlens and a corresponding light emitter block.

  In this embodiment, as in the case of FIGS. 4 and 7, four light emitting element rows 3 in which four light emitting elements 2 made of organic EL elements are arranged in the main scanning direction are formed in the sub scanning direction. Thus, one light emitter block 4 is provided, and a plurality of the light emitter blocks 4 are provided in the main scanning direction and the sub scanning direction to form the light emitter array 1. The light emitter block 4 is in the main scanning direction in the sub scanning direction. They are arranged in a staggered pattern by shifting the top position of. In the example of FIG. 16, the light emitter blocks 4 are arranged in three rows in the sub-scanning direction. Such a light emitter array 1 is formed on the back surface of the glass substrate 20 and is driven by a drive circuit formed on the back surface of the same glass substrate 20. The organic EL element (light emitting element 2) on the back surface of the glass substrate 20 is sealed with a sealing member 27.

  The glass substrate 20 is fitted into a receiving hole 22 provided in a long case 21, covered with a back cover 23, and fixed by a fixing bracket 24. The positioning pins 25 provided at both ends of the long case 21 are fitted into the positioning holes of the opposing image forming apparatus main body, and the fixing screws are inserted through the screw insertion holes 26 provided at both ends of the long case 21. The optical writing line head 101 is fixed at a predetermined position by being screwed into the screw hole.

  The positive lens L1 is arranged on the surface side of the glass substrate 20 of the case 21 via the first spacer 71 so that the center of each light emitter block 4 of the light emitter array 1 and the positive lens L1 are aligned. The first microlens array 61 is arranged, and the openings 31 (FIGS. 18 and 19) are arranged on the first microlens array 61 via the second spacer 72 so as to align with the centers of the respective light emitter blocks 4 of the light emitter array 1. The aperture plate 30 provided is disposed, and the positive lens L2 is configured as a constituent element so that the center of each light emitter block 4 of the light emitter array 1 and the positive lens L2 are aligned via the third spacer 73 thereon. The second microlens array 62 is fixed.

  As described above, the lens array of the microlens 5 that projects the light emitting element array of each light emitter block 4 includes a combination of the first microlens array 61 and the second microlens array 62.

  Then, according to the present invention, the image side (rear side) focal point of the positive lens L1 constituting the first microlens array 61 and the object side (front side) focal point of the positive lens L2 constituting the second microlens array 62 coincide with each other. The thicknesses of the second spacer 72 and the third spacer 73 are set so that the diaphragm plate 30 is disposed on the coincident surface. Details of the diaphragm plate 30 are shown in FIGS. FIG. 18 is a plan view of the diaphragm plate 30 arranged corresponding to the light emitter block 4 of the light emitter array 1, and FIG. 19 is a view showing the opening 31 of the diaphragm plate 30 with respect to one light emitter block 4. . The aperture plate 30 is provided with openings 31 aligned with the center (optical axis) of each of the microlenses 5 including the positive lens L1 and the positive lens L2 and the center of the light emitter block 4. In this embodiment, each opening is provided. The shape of 31 is configured to be a substantially elliptical shape that limits the opening diameter in the main scanning direction to be larger than the subscanning direction, but may be a circular, elliptical, rectangular, or other opening shape as described above. (It is shown as a circle in FIGS. 13 and 14).

  13 and 14 show light rays that come out of the center of the light emitter block 4 and reach the image plane (photosensitive member 41), the light emitter block 4 in this example has the light emitting element 2 at the center thereof. Since they are not arranged (FIG. 17), the light rays emitted from the center of the light emitter block 4 are virtual. In FIG. 14, the light beam that is adjacent to the light beam that exits from the center is the light beam that exits from the light emitting elements 2 at both ends of the light emitter block 4.

  The above embodiment is an optical writing line head 101 having a so-called bottom emission arrangement using an organic EL element provided on the back surface of the glass substrate 20 as the light emitting element 2 and using light emitted on the front surface side of the glass substrate 20. However, an EL element or LED in which the light emitting element 2 is arranged on the surface side of the substrate may be used.

  In the above embodiment, as is apparent from FIG. 16, the light emitter blocks 4 of the light emitter array 1 are arranged in three rows in the sub-scanning direction by shifting the head position in the main scanning direction, and the micro lens 5 Similarly, this array is also configured by shifting the head position in the main scanning direction and arranging three columns in the sub-scanning direction. The number of rows of the light emitter blocks 4 arranged in a row in the main scanning direction is not limited to three, and may be any number of two or more. FIG. 20 shows a diagram similar to FIG. 16 when two rows are arranged, and FIG. 21 shows a diagram similar to FIG. 16 when four rows are arranged. In these, the array of microlenses 5 is similarly configured by arranging two or four rows of microlenses 5 arranged in a row in the main scanning direction in the subscanning direction.

  Further, in the example of FIG. 16, one light emitter block 4 is configured by arranging two light emitting element rows 3 oriented in the main scanning direction in the sub scanning direction. The number of rows is not limited to two and may be one or more. FIG. 22 is a view similar to FIG. 16 when three light emitting element rows 3 are arranged, and FIG. 23 is a view similar to FIG. 16 when four light emitting element rows 3 are arranged (of the light emitter block 4). The same applies when the number of columns is other than three.)

  By the way, in the above example, as shown in FIG. 15, the image plane 41 is assumed to be a plane parallel to the surface of the light emitter array 1 and the surface of the array of microlenses 5, and all the microlenses 5 have the same characteristics. Was supposed to be. However, the microlens 5 according to the present invention has a telecentric configuration on both sides as described above, and the distance from the microlens 5 of the image plane 41 is arranged for each row aligned in the main scanning direction of the microlens 5. Even if they are slightly different, there is no positional deviation of the imaging spots, and there is no uneven density between the imaging spots. Therefore, even when the photoconductor 41 constituting the image surface has a curved surface shape such as a drum shape (FIGS. 9 to 11) or the optical writing line head 101 of the present invention, the light emitter block 4 on the photoconductor 41 is used. The image formation spot is not shifted in position and density unevenness is not generated for each column, and is uniform.

FIG. 24 is a cross-sectional view taken along the sub-scanning direction showing the relationship between the optical system of the optical writing line head 101 and the photosensitive drum 41 when the photosensitive member 41 has a drum shape. In this case, the light emitter block 4 has three rows, the light emitter blocks 4 in the _first , _second , and third rows are 4 ₁ , 4 ₂ , and 4 ₃ , respectively, and the corresponding microlenses 5 are 5 ₁ , respectively. 5 ₂ , 5 ₃ . The microlenses 5 ₁ , 5 ₂ , and 5 ₃ have the same configuration, and all have the same object side distance from the light emitter blocks 4 ₁ , 4 ₂ , and 4 ₃ , but the photoconductor 41 has a bus line in the main scanning direction. for a cylindrical shape having, for example, the microlens 5 ₂ in the optical axis of the center by setting so as to pass through the axis of the photosensitive drum 41, on both sides of the microlens 5 _1, 5 ₃ image-side distance is slightly different. However, as described above, the microlenses 5 ₁ , 5 ₂ , and 5 ₃ are telecentric on both sides, and the imaging magnification is the same even if the image side distance is slightly different, and the position of the imaging spot Deviation does not occur, and density unevenness between imaging spots does not occur for the above reason.

  By the way, the microlens arrays 61 and 61 used in the optical writing line head 101 of the present invention can be of any conventionally known configuration. FIG. 25 shows the first microlens array 61 and the second microlens array. 62 is a cross-sectional view taken along the main scanning direction when an array of microlenses 5 is configured by combining 62 so that the microlenses L1 and L2 are coaxially aligned (FIGS. 13 and 15). In this example, the microlens L1 and L2 are formed by integrally molding a lens surface portion 35 made of a transparent resin in alignment with one side (object side) of the glass substrate 34 of each of the microlens arrays 61 and 62. is there. In this case, by setting the image side surface of the second microlens array 62 to be a flat surface, for example, when used as a microlens array of a line head of an image forming apparatus, the toner of the developer scatters and the flat surface of the microlens array. Even if it adheres to the surface, it can be easily cleaned and the cleaning performance is improved.

Next, specific numerical examples of the optical system used in the above examples are shown as Examples 1 to 4. Examples 1 to 3 are examples of each microlens 5 when the image surface 41 is a flat surface, and Example 4 is a microlens 5 ₁ , 5 ₂ , 5 when the photosensitive drum 41 is used as the image surface 41. _{3 is} an example.

  26A and 26B are cross-sectional views of the optical system corresponding to one microlens 5 of Example 1 in the main scanning direction and the sub-scanning direction, respectively, and a glass substrate is provided on the emission side of the light emitting element 2. The microlens 5 is a telephoto lens system including a confocal convex positive lens L1 and a convex flat positive lens L2, and the diaphragm plate 30 is a confocal plane (convex) between the convex flat positive lens L1 and the convex flat positive lens L2. This is an example in which the image side (rear side) focal point of the flat positive lens L1 and the object side (front side) focal point of the convex flat positive lens L2 are arranged.

Numerical data of this example are shown below. In order from the light emitter block 4 side to the photoconductor (image surface) 41 side, r ₁ , r _2, ... Are curvature radii (mm), d ₁ , d of each optical surface. ₂ ... Is the distance (mm) between the optical surfaces, n _d1 , n _d2 ... Is the refractive index of the d-line of each transparent medium, and ν _d1 , ν _d2 . Here, r ₁ , r ₂ ... Also represent optical surfaces, the optical surface r ₁ is the light emitter block (object surface) 4, the optical surfaces r ₂ and r ₃ are the object side surface and the image side of the convex positive lens L 1. , The optical surface r ₄ is the aperture 31 of the aperture plate 30, the optical surfaces r ₅ and r ₆ are the object side surface, the image side surface, and the optical surface r ₇ is the photoconductor (image surface) 41. It is. The full width of the image plane pixel group is a width in the main scanning direction of the image on the image plane of the light emitter block 4 that is an object (the same applies hereinafter).

  27A and 27B are cross-sectional views of the optical system corresponding to one microlens 5 of Example 2 in the main scanning direction and the sub-scanning direction, respectively, and a glass substrate is provided on the emission side of the light emitting element 2. The microlens 5 is a telephoto lens system including a convex flat positive lens L1 and a convex flat positive lens L2, and the diaphragm plate 30 is a confocal plane between the convex flat positive lens L1 and the convex flat positive lens L2 (convex positive positive lens L1). The image side (rear side) focal point and the object side (front side) focal point of the convex positive lens L2 are arranged on the same surface).

Numerical data of this example are shown below. In order from the light emitter block 4 side to the photoconductor (image surface) 41 side, r ₁ , r _2, ... Are curvature radii (mm), d ₁ , d of each optical surface. ₂ ... Is the distance (mm) between the optical surfaces, n _d1 , n _d2 ... Is the refractive index of the d-line of each transparent medium, and ν _d1 , ν _d2 . Here, r ₁ , r ₂ ... Also represent optical surfaces, the optical surface r ₁ is the light emitter block (object surface) 4, the optical surfaces r ₂ and r ₃ are the object side surface and the image side of the convex positive lens L 1. , The optical surface r ₄ is the aperture 31 of the aperture plate 30, the optical surfaces r ₅ and r ₆ are the object side surface, the image side surface, and the optical surface r ₇ is the photoconductor (image surface) 41. It is. Further, both the object-side surface of the convex flat lens L1 and the object-side surface of the convex flat lens L2 are aspherical surfaces, but the aspherical shape has a distance from the optical axis as r.
cr ² / [1 + √ {1- (1 + K) c ² r ² }]
It is represented by Where c is the curvature on the optical axis (1 / r), and K is the conic coefficient. In the following numerical data, K ₂ is the conic coefficient of the object side surface of the convex flat positive lens L1, and K ₅ is the conic coefficient of the object side surface of the convex flat positive lens L2.

  28A and 28B are sectional views of the optical system corresponding to one microlens 5 of Example 3 in the main scanning direction and the sub-scanning direction, respectively, and a glass substrate is provided on the emission side of the light emitting element 2. The microlens 5 is a telephoto lens system composed of a biconvex positive lens L1 and a convex planopositive lens L2, and the diaphragm plate 30 is a confocal plane (biconvex between the biconvex positive lens L1 and the convex planopositive lens L2). This is an example in which the image side (rear side) focal point of the positive lens L1 and the object side (front side) focal point of the convex flat lens L2 are arranged.

Numerical data of this example are shown below. In order from the light emitter block 4 side to the photoconductor (image surface) 41 side, r ₁ , r _2, ... Are curvature radii (mm), d ₁ , d of each optical surface. ₂ ... Is the distance (mm) between the optical surfaces, n _d1 , n _d2 ... Is the refractive index of the d-line of each transparent medium, and ν _d1 , ν _d2 . Here, r ₁ , r ₂ ... Also represent optical surfaces, the optical surface r ₁ is the light emitter block (object surface) 4, the optical surfaces r ₂ and r ₃ are the object-side surfaces and images of the biconvex positive lens L 1. The optical surface r ₄ is the aperture 31 of the diaphragm plate 30, the optical surfaces r ₅ and r ₆ are the object side surface, the image side surface, and the optical surface r ₇ is the photoconductor (image surface). 41. Further, both the object side surface of the biconvex positive lens L1 and the object side surface of the convex plano positive lens L2 are aspherical surfaces, but the aspherical shape has a distance from the optical axis as r.
cr ² / [1 + √ {1- (1 + K) c ² r ² }]
It is represented by Where c is the curvature on the optical axis (1 / r), and K is the conic coefficient. During the numerical data below, K ₂ is the object side surface of the conic coefficient of the double-convex positive lens L1, K ₅ are each conic coefficient of the object-side surface of the plano-convex positive lens L2.

FIG. 29 is a sectional view in the sub-scanning direction of the optical system corresponding to the three rows of microlenses 5 ₁ , 5 ₂ , and 5 ₃ of Embodiment 4, and FIG. 30 shows the light emitter array 1 and the microlens array of this embodiment. The required dimensions (mm) and angles are entered in each figure. The lenses L1, L2 constituting the microlenses 5 ₁ , 5 ₂ , 5 ₃ in this embodiment have the same shape, the distance between the lenses L1, L2, the position of the diaphragm plate 30, the light emitter block (object surface). ) The distance between 4 ₁ , 4 ₂ , 4 ₃ and the lens L1 is the same, and only the distance between the lens L2 and the photosensitive member (image surface) 41 and the inclination of the photosensitive member (image surface) 41 are different. radius of curvature of each optical surface only the microlens _{5 1, (mm) r 1} , r 2 ..., there is shown a distance d _1, d ₂ ... between the optical surfaces.

In the microlenses 5 ₁ , 5 ₂ , and 5 ₃ of this embodiment, a glass substrate is not disposed on the emission side of the light emitting element 2 and the microlens 5 is a telephoto lens composed of a convex flat positive lens L1 and a convex flat positive lens L2. The diaphragm plate 30 has a confocal plane between the convex flat lens L1 and the convex flat lens L2 (the image side (rear side) focal point of the convex flat lens L1 and the object side (front side) focal point of the convex flat lens L2 coincide. It is an example arrange | positioned on the surface to carry out.

The optical axes of the microlenses 5 ₁ , 5 ₂ , and 5 ₃ are parallel to each other. In addition, as described above, the first, second, and third rows of microlenses 5 ₁ , 5 ₂ , and 5 ₃ use lenses having the same configuration, and the lens L 2 and the photoconductor (image surface) 41. Only the interval differs depending on the curvature (radius 20 mm) of the photoconductor 41. Microlenses 5 ₁ of the first and third columns of both sides of the microlens 5 ₂ in the second column of the center, ₃ of the lens L2 and the photosensitive member interval (image plane) 41 is larger by 32μm (FIG. 29). The inclination α of the image plane 41 with respect to the optical axis is 0.0 ° for the _second microlens 52 in the center, and 3.24 ° for the _first and _third microlenses 5 ₁ and 5 ₃ on both sides. (FIG. 29). The cylindrical photoreceptor 41 has a diameter of 40 mm (FIG. 29), and the pitch between the rows of the microlenses 5 ₁ , 5 ₂ , 5 ₃ is 1.13137 mm (FIG. 30).

Numerical data of the microlenses 5 ₁ , 5 ₂ , and 5 ₃ of this embodiment are shown below. R ₁ , r ₂ ... Are optical surfaces in order from the light emitter block 4 side to the photoreceptor (image surface) 41 side. radius of curvature _{(mm), d 1, d} 2 ... the spacing between the respective optical surfaces _{(mm), n d1, n} d2 ... d-line refractive index of each transparent medium, ν _d1, ν _d2 ... each transparent The Abbe number of the medium. Here, r ₁ , r ₂ ... Also represent optical surfaces, the optical surface r ₁ is the light emitter block (object surface) 4, the optical surfaces r ₂ and r ₃ are the object side surface and the image side of the convex positive lens L 1. , The optical surface r ₄ is the aperture 31 of the aperture plate 30, the optical surfaces r ₅ and r ₆ are the object side surface, the image side surface, and the optical surface r ₇ is the photoconductor (image surface) 41. It is. Further, the object-side surface of the convex positive lens L1 and the object-side surface of the convex flat lens L2 are both aspherical surfaces, but the aspherical shape has a distance from the optical axis as r.
cr ² / [1 + √ {1- (1 + K) c ² r ² }]
It is represented by Where c is the curvature on the optical axis (1 / r), and K is the conic coefficient. In the following numerical data, K ₂ is the conic coefficient of the object side surface of the convex flat positive lens L1, and K ₅ is the conic coefficient of the object side surface of the convex flat positive lens L2. Note that the inclination of the image plane is indicated by α ₇ .

Example 1
r ₁ = ∞ (object surface) d ₁ = 3.2325
r ₂ = 1.5993 d ₂ = 0.7000 n _d1 = 1.5168 ν _d1 = 64.2
r ₃ = ∞ d ₃ = 2.6200 r ₄ = ∞ (aperture) d ₄ = 1.5106
r ₅ = 0.8003 d ₅ = 0.7000 n _d2 = 1.5168 ν _d2 = 64.2
r ₆ = ∞ d ₆ = 1.0000
r ₇ = ∞ (image plane)
Use wavelength 632.5nm
Optical magnification β -0.5
Total width of image plane pixel group 0.2mm
Object side numerical aperture 0.08.

Example 2
r ₁ = ∞ (object plane) d ₁ = 1.7324
r ₂ = 1.030207 d ₂ = 0.7000 n _d1 = 1.5168 ν _d1 = 64.2
K ₂ = -1.4132
r ₃ = ∞ d ₃ = 1.5380 r ₄ = ∞ (aperture) d ₄ = 2.0000
r ₅ = 1.030207 d ₅ = 0.7000 n _d2 = 1.5168 ν _d2 = 64.2
K ₅ = -0.97399
r ₆ = ∞ d ₆ = 1.7892
r ₇ = ∞ (image plane)
Use wavelength 632.5nm
Optical magnification β -1.0
Total width of image plane pixel group 0.4mm
Object side numerical aperture 0.16.

Example 3
r ₁ = ∞ (object plane) d ₁ = 0.9621
r ₂ = 2.3131 d ₂ = 0.7000 n _d1 = 1.5168 ν _d1 = 64.2
K ₂ = -38.3122
r ₃ = -1.0438 d ₃ = 1.3482 r ₄ = ∞ (aperture) d ₄ = 2.0000
r ₅ = 1.5453 d ₅ = 0.7000 n _d2 = 1.5168 ν _d2 = 64.2
K ₅ = -1.1520
r ₆ = ∞ d ₆ = 3.3375
r ₇ = ∞ (image plane)
Use wavelength 632.5nm
Optical magnification β -2.0
Image surface pixel group overall width 0.6mm
Object side numerical aperture 0.16.

Example 4
r ₁ = ∞ (object plane) d ₁ = 1.7324
r ₂ = 1.0302 d ₂ = 0.7000 n _d1 = 1.5168 ν _d1 = 64.2
K ₂ = -1.41329
r ₃ = ∞ d ₃ = 1.538 r ₄ = ∞ (aperture) d ₄ = 2.000
r ₅ = 1.0302 d ₅ = 0.7000 n _d2 = 1.5168 ν _d2 = 64.2
K ₅ = -0.97399
r ₆ = ∞ d ₆ = 1.7572 (second row)
1.7892 (first and third rows)
r ₇ = ∞ (main scanning direction) α ₇ = 0.0 ° (second row)
20.0 (sub-scanning direction) 3.24 ° (first and third rows)
(Image plane: Cylindrical surface)
Use wavelength 632.5nm
Optical magnification β -1.0
Total width of image plane pixel group 0.4mm
Object side numerical aperture 0.16.

  As described above, the line head and the image forming apparatus using the same according to the present invention have been described based on the principle and the embodiments, but the present invention is not limited to these embodiments and can be variously modified.

It is a perspective view of the part corresponding to one micro lens of the line head concerning one embodiment of the present invention. It is a perspective view of the part corresponding to one micro lens of the line head concerning one embodiment of the present invention. It is a perspective view of the part corresponding to one micro lens of the line head concerning one embodiment of the present invention. It is explanatory drawing which shows the correspondence of the light-emitting body array which concerns on one Embodiment of this invention, and the micro lens with minus optical magnification. It is explanatory drawing which shows the example of the memory table of the line buffer in which image data is stored. It is explanatory drawing which shows a mode that the imaging spot by the light emitting element of an odd number and an even number is formed in the same row in the main scanning direction. It is explanatory drawing of the outline which shows the example of the light-emitting body array used as a line head. It is explanatory drawing which shows the image formation position at the time of irradiating the exposure surface of an image carrier through a micro lens with the output light of each light emitting element by the structure of FIG. FIG. 9 is an explanatory diagram illustrating a state of forming an imaging spot in the sub-scanning direction in FIG. 8. It is explanatory drawing which shows the example in which an imaging spot is reversed and formed in the main scanning direction of an image carrier when a plurality of microlenses are arranged. 1 is a schematic cross-sectional view illustrating an overall configuration of an embodiment of an image forming apparatus using an electrophotographic process according to the present invention. It is a figure for demonstrating the principle of this invention. It is the perspective view which fractured | ruptured a part which shows the structure of the optical writing line head of one Example of this invention. FIG. 14 is a partially enlarged perspective view of FIG. 13. It is sectional drawing taken along the subscanning direction of FIG. It is a top view which shows arrangement | positioning of the light-emitting body array in the case of FIG. 13, and a micro lens array. It is a figure which shows the correspondence of one micro lens and the light-emitting body block corresponding to it. It is a top view of the aperture plate arrange | positioned corresponding to the light-emitting body block of a light-emitting body array. It is a figure which shows opening of the aperture plate with respect to one light-emitting body block. FIG. 17 is a view similar to FIG. 16 when two rows of light emitter blocks are arranged. FIG. 17 is a view similar to FIG. 16 in the case where four rows of light emitter blocks are arranged. FIG. 17 is a view similar to FIG. 16 when three light emitting element rows are arranged. FIG. 17 is a view similar to FIG. 16 when four light emitting element rows are arranged. FIG. 6 is a cross-sectional view taken along the sub-scanning direction showing the relationship between the optical system of the optical writing line head and the photosensitive drum when the photosensitive member is drum-shaped. It is sectional drawing taken along the main scanning direction in the case of comprising a microlens array with two microlens arrays. 2 is a cross-sectional view of an optical system corresponding to one microlens of Example 1 in a main scanning direction and a sub-scanning direction. FIG. 6 is a cross-sectional view of an optical system corresponding to one microlens of Example 2 in a main scanning direction and a sub-scanning direction. FIG. 6 is a cross-sectional view of an optical system corresponding to one microlens of Example 3 in a main scanning direction and a sub scanning direction. FIG. FIG. 6 is a cross-sectional view in the sub-scanning direction of an optical system corresponding to three rows of microlenses in Example 4. FIG. 6 is a plan view showing an arrangement of a light emitter array and a microlens array of Example 4.

Explanation of symbols

OO ′: lens optical axis, F: front focal point of microlens, 1 ... light emitter array, 2 ... light emitting element, 2x ... edge light emitting element or edge light receiving element, 3 ... light emitting element array, 4, 4 ₁ 4 ₂ , 4 ₃ ... luminous body block, 5, 5 ₁ , 5 ₂ , 5 ₃ ... micro lens, 6 ... micro lens array, 8, 8a, 8b ... imaging spot, 8x ... imaging of edge light emitting element Spot, 8x ′: the position of the imaging spot of the end light emitting element when the photoconductor is displaced, 8x ″: the position of the imaging spot of the end light emitting element when the light emitting element arrangement surface is displaced, 10: memory table DESCRIPTION OF SYMBOLS 11 ... Aperture stop, 12 ... Main ray, 20 ... Glass substrate, 21 ... Long case, 22 ... Receiving hole, 23 ... Back cover, 24 ... Fixing metal fitting, 25 ... Positioning pin, 26 ... Insertion hole, 27 ... Sealing member, 30 ... aperture plate, 31 ... aperture plate aperture, 34 ... glass substrate, 5 ... Lens surface portion, 41 ... Photoconductor (image carrier) or reading surface, 41 '... Position of displacement of photoconductor (image carrier), 41 (K, C, M, Y) ... Photoconductor drum (image carrier) ), 42 (K, C, M, Y) ... charging means (corona charger), 44 (K, C, M, Y) ... developing device, 45 (K, C, M, Y) ... primary transfer roller, DESCRIPTION OF SYMBOLS 50 ... Intermediate transfer belt, 51 ... Drive roller, 52 ... Driven roller, 53 ... Tension roller, 55 ... Light emitting element arrangement surface, 55 '... Displacement position of light emitting element arrangement surface, 61 ... First micro lens array, 62 ... First 2 microlens array, 66 ... secondary transfer roller, 71 ... first spacer, 72 ... second spacer, 73 ... third spacer, 101, 101K, 101C, 101M, 101Y ... line head (optical writing line head), L1 ... first lens, L2 ... second Lens

Claims (13)

A light emitter block including one or more light emitting element rows in which a plurality of light emitting elements are arranged in an array in the first direction is at least on the emission side of the light emitter array in which a plurality of light emitter blocks are arranged at intervals in the first direction. A lens array in which one positive lens system is arranged corresponding to each light emitter block, a writing surface is arranged on the image forming side of the lens array, and a positive lens constituting the lens array A line head characterized in that the system comprises a telephoto optical system in which two positive lens groups are arranged confocally, and an aperture stop is arranged on the confocal surface of the telephoto optical system. The line head according to claim 1, wherein the positive lens system includes two positive lenses. 3. The line head according to claim 1, wherein the positive lens systems constituting the lens array are all the same. 4. The line head according to claim 1, wherein the writing surface is a flat surface. 4. The line head according to claim 1, wherein the writing surface is a cylindrical surface. 6. The line head according to claim 1, wherein at least the image side surface of the positive lens group on the image side of the positive lens system is a flat surface. The line head according to any one of claims 1 to 6, wherein the shape of the aperture stop is a shape that limits at least an aperture diameter in the first direction. 8. The line head according to claim 1, wherein the light emitter block includes a plurality of the light emitting element rows arranged in a second direction orthogonal to the first direction. 9. The line head according to any one of claims 1 to 7, wherein a plurality of the light emitter blocks are arranged in a second direction orthogonal to the first direction. The line head according to claim 1, wherein the light emitting element is an organic EL element. The line head according to claim 1, wherein the light emitting element is an LED. 12. At least two or more image forming stations in which image forming units including a charging unit, a line head according to any one of claims 1 to 11, a developing unit, and a transfer unit are arranged around an image carrier. An image forming apparatus characterized in that an image is formed by a tandem method when the transfer medium passes through each station. A light receiving block including at least one light receiving element array in which a plurality of light receiving elements are arranged in a row in a first direction is at least on the incident side of a light receiving array in which a plurality of light receiving blocks are arranged at intervals in the first direction. A lens array in which one positive lens system is arranged to correspond to each photoreceptor block, a reading surface is arranged on the object side of the lens array, and the lens array Each of the constituent positive lens systems comprises a telephoto optical system in which two positive lens groups are arranged at a confocal point, and an aperture stop is arranged on a confocal surface of the telephoto optical system. .

Images