JP2008074052A - Line head and image forming apparatus using line head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a line head which attains improvement of an image quality by preventing ghost from being visible, and to provide an image forming apparatus using a line head. <P>SOLUTION: A side face 2972 of a light guide hole 2971 is formed to have a sectional width spread from one face 2973 to the other face 2974. An angle θ1 of incidence and an angle θ2 of reflection to the side face 2972 of a light beam are reduced consequently. A position I0X of irradiation of a face 211 to be scanned of a reflected light passed through an imaging lens approaches an intersection I0 which is the position of a spot of a direct light. The ghost caused by irradiation with the reflected light can be prevented from being visible because the position I0X of irradiation with the reflected light and the intersection I0 as the position of the spot of the direct light come close to each other. Improvement of the image quality can be attained accordingly. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a line head that scans a surface to be scanned with a light beam and an image forming apparatus using the line head.

  As a light emitting element having an optical lens that can be used in this type of line head, for example, a light emitting element described in Patent Document 1 has been proposed. In the light emitting element described in Patent Document 1, the light emitting element is formed in the opening on one surface of the substrate on which the light guide hole that is a through hole is formed, and the imaging lens that is an optical lens is bonded to the opening on the other surface. Has been. Here, the width of the light guide hole on the cross section is substantially constant from one surface to the other surface. In the above-described line head using the light emitting element, the light beam emitted from the light emitting element is guided to the imaging lens by the light guide hole, and the light beam guided to the lens is imaged by the imaging lens to be scanned on the surface to be scanned. A spot is formed.

JP 2002-170662 A (pages 6-7, FIG. 8)

  In a line head using a light emitting element as described above, only the light beam directly incident on the imaging lens (hereinafter referred to as direct light) among the light beams emitted from the light emitting element is imaged by the imaging lens. Thus, it is preferable that a spot of light is directly formed on the surface to be scanned. However, in such a line head, a part of the light beam emitted from the light emitting element becomes a light beam reflected by the side surface of the light guide hole (hereinafter referred to as reflected light), passes through the imaging lens, and is scanned. Irradiate. In the light beam from the same light emitting element, the incident light incident on the imaging lens is different between direct light and reflected light, so that different positions on the surface to be scanned are irradiated. Irradiation on the surface to be scanned causes a so-called ghost. This causes a problem of image quality degradation due to a clearly visible ghost in the image. SUMMARY An advantage of some aspects of the invention is that it provides a line head and an image forming apparatus using the line head that improve image quality by making it difficult to visually recognize a ghost.

  In order to solve the above problems, the line head of the present invention is a line head that forms a spot by forming an image of a light beam on a surface to be scanned that is conveyed in a sub-scanning direction that is substantially perpendicular to the main scanning direction, A plurality of light emitting element groups each having a transparent substrate capable of transmitting the light beam and a plurality of light emitting elements formed on the back surface side of the transparent substrate, each of which is arranged discretely on the back surface side of the transparent substrate The light beams emitted from the plurality of light emitting elements belonging to the opposing light emitting element groups are arranged in a one-to-one correspondence with the plurality of light emitting element groups, respectively. A plurality of imaging lenses that form an image on the surface of the transparent substrate, the other surface of the imaging lenses facing the surface of the transparent substrate, and the other surface of the imaging lenses. A light-shielding member having a plurality of light guide holes penetrating from the one surface to the other surface in a one-to-one correspondence with the optical element group, and the light guide holes from the one surface It is formed so that it may spread toward the said other surface.

  According to this invention, the light guide hole is formed so as to expand from one surface to the other surface. Here, a part of the light beam is reflected by the side surface of the light guide hole, passes through the imaging lens as reflected light, and irradiates the surface to be scanned. The other light beams that are not involved in the side surface of the light guide hole are imaged as direct light by the imaging lens, and a spot of direct light is formed on the surface to be scanned. Compared to the side surface of the light guide hole in which the cross-sectional width is almost constant from one surface to the other surface as described in the background art, the side surface of the present invention has a cross-sectional width from one surface to the other surface. It is formed to spread. For this reason, the incident angle and the reflection angle on the side surface of the light beam are reduced, and the position of irradiation of the reflected light that has passed through the imaging lens onto the surface to be scanned approaches the position of the direct light spot. By approaching the position of the reflected light irradiation and the position of the direct light spot, it is possible to make it difficult to visually recognize a ghost caused by the irradiation of the reflected light. Therefore, it is possible to improve the image quality.

  In this invention, it is preferable that the said light emitting element of the said light emitting element group is an organic EL element.

  In this invention, the light emitting element of the light emitting element group is an organic EL element. The organic EL element is not formed by fixing individual completed products as light emitting elements on the back side of the same transparent substrate, but sequentially forming each component of the organic EL element on the back side of the same transparent substrate. By doing so, a plurality of completed bodies are obtained in a lump, so that the dimensional accuracy between the organic EL elements or between the organic EL element groups is excellent. Since the dimensional accuracy of the organic EL element and the organic EL element group is excellent in the assembly of the transparent substrate on which the organic EL element and the organic EL element group are formed and the light shielding member, the organic EL element and the organic EL element group and the light shielding member The positional accuracy with respect to the light guide hole can also be excellent. Therefore, since the position accuracy is poor and the organic EL element or the organic EL element group has approached the light guide hole, the optical intensity of the reflected light irradiation is increased, and the ghost caused by the reflected light irradiation is clearly visually recognized. It is possible to avoid this. Therefore, it is possible to further improve the image quality.

  In the present invention, the light emitting element group includes a plurality of light emitting element arrays having the plurality of light emitting elements arranged in the main scanning direction in the sub scanning direction, and the plurality of light emitting elements in the main scanning direction. The element interval is constant, the column interval of the plurality of light emitting element rows is substantially equal to the element interval, the number of the plurality of light emitting elements is larger than the number of the plurality of light emitting element columns, and the light guide hole An opening formed on one side of the track includes a region formed by an intersection of the light beam that is directly incident on the imaging lens and the one surface, and a track that is long in the main scanning direction in contact with the outer periphery of the region or It preferably has an oval shape.

  In the present invention, the element spacing in the main scanning direction of the plurality of light emitting elements is constant, the column spacing of the plurality of light emitting element rows is substantially equal to the element spacing, and the number of the plurality of light emitting elements is the number of the plurality of light emitting element rows. Larger than the number, the opening on one side of the light guide hole includes a region formed by the intersection of the light beam directly incident on the imaging lens and the one surface, and in the main scanning direction in contact with the outer periphery of the region Long track or oval shape. As a result, direct light is incident on the imaging lens without being shielded at all, and a part of the light beam that does not become direct light is shielded on one side, thereby suppressing reflected light incident on the imaging lens. It is possible. Therefore, since the optical intensity of the reflected light is weakened without reducing the optical intensity of the spot of direct light formed on the surface to be scanned, it is difficult to visually recognize the ghost caused by the irradiation of the reflected light. It is possible. Therefore, it is possible to further improve the image quality.

  In the present invention, the light emitting element group includes a plurality of light emitting element arrays having a plurality of light emitting elements in the main scanning direction in the sub scanning direction, and an element interval in the main scanning direction of the plurality of light emitting elements is set. The column spacing of the plurality of light emitting element rows is substantially equal to the element spacing, the number of the plurality of light emitting elements and the number of the plurality of light emitting element rows are the same, It is preferable that the opening on one side includes a region formed by an intersection of the light beam that is directly incident on the imaging lens and the one surface, and has a circular shape that touches the outer periphery of the region. .

  In this invention, the element spacing in the main scanning direction of the plurality of light emitting elements is constant, the column spacing of the plurality of light emitting element arrays is substantially equal to the element spacing, and the number of the plurality of light emitting elements and the number of the plurality of light emitting element arrays The number of openings is equal to the number, and the opening on one side of the light guide hole includes a region formed by the intersection of the light beam directly incident on the imaging lens and one side, and a circle in contact with the outer periphery of the region Shape. As a result, direct light is incident on the imaging lens without being shielded at all, and a part of the light beam that does not become direct light is shielded on one side, thereby suppressing reflected light incident on the imaging lens. It is possible. Therefore, since the optical intensity of the reflected light is weakened without reducing the optical intensity of the spot of direct light formed on the surface to be scanned, it is difficult to visually recognize the ghost caused by the irradiation of the reflected light. It is possible. Therefore, it is possible to further improve the image quality.

  In the image forming apparatus of the present invention, the latent image carrier having a scanned surface conveyed in the sub-scanning direction substantially orthogonal to the main scanning direction, and spots are formed on the scanned surface of the latent image carrier. An exposure means having the same configuration as the line head according to any one of 1 to 4 is provided.

  According to the present invention, the direct light that is part of the light beam emitted from the light emitting element is incident on the imaging lens without being shielded at all, and the part of the light beam that is not directly light is shielded on one side. Therefore, the reflected light incident on the imaging lens is suppressed. The position of irradiation of the scanned surface of the reflected light is closer to the position of the direct light spot. Therefore, without reducing the optical intensity of the spot of direct light on the surface to be scanned, the optical intensity of irradiation of the reflected light is weakened, and the position of irradiation of the reflected light and the position of the spot of direct light are closer, It is possible to execute image formation in which a ghost caused by irradiation of reflected light is difficult to visually recognize. Therefore, it is possible to provide an image forming apparatus that can further improve image quality.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram showing an electrical configuration of the image forming apparatus of FIG. The image forming apparatus 1 includes a color mode in which four color toners of black (K), cyan (C), magenta (M), and yellow (Y) are superimposed to form a color image, and black (K) toner. This is an image forming apparatus 1 that can selectively execute a monochrome mode in which a monochrome image is formed using only a monochrome image. FIG. 1 is a diagram corresponding to the execution of the color mode. As shown in FIG. 2, in this image forming apparatus 1, when an image forming command is given from an external device such as a host computer to a main controller MC having a CPU, a memory, etc., the main controller MC sends a control signal to the engine controller EC. And the video data VD corresponding to the image formation command is supplied to the head controller HC. The head controller HC controls the line head 29 for each color based on the video data VD from the main controller MC, the vertical synchronization signal Vsync from the engine controller EC, and parameter values. As a result, the engine unit EG executes a predetermined image forming operation, and forms an image corresponding to the image forming command on a sheet such as copy paper, transfer paper, paper, and an OHP transparent sheet.

  As shown in FIG. 1, an electrical component box 5 containing a power circuit board, a main controller MC, an engine controller EC, and a head controller HC is provided in a housing body 3 included in the image forming apparatus 1 according to the present embodiment. ing. An image forming unit 7, a transfer belt unit 8, and a paper feeding unit 11 are also disposed in the housing body 3. In FIG. 1, a secondary transfer unit 12, a fixing unit 13, and a sheet guide member 15 are disposed on the right side in the housing body 3. The paper feeding unit 11 is configured to be detachable from the image forming apparatus 1. The sheet feeding unit 11 and the transfer belt unit 8 can be removed and repaired or replaced.

  The image forming unit 7 includes four image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form a plurality of images of different colors. Further, each image forming station Y, M, C, K is provided with a latent image carrier 21 on which the respective color toner images are formed. Each latent image carrier 21 is connected to a dedicated drive motor and is driven to rotate at a predetermined speed in the direction of arrow D21 in the figure. As a result, the surface of the latent image carrier 21 is conveyed in the sub-scanning direction. In addition, around the latent image carrier 21, a charging unit 23, a line head 29, a developing unit 25, and a photoconductor cleaner 27 are disposed along the rotation direction. Then, a charging operation, a latent image forming operation, and a toner developing operation are executed by these functional units. Therefore, when the color mode is executed, the toner images formed at all the image forming stations Y, M, C, and K are superimposed on the transfer belt 81 of the transfer belt unit 8 to form a color image, and the monochrome mode is executed. In some cases, a monochrome image is formed using only the toner image formed at the image forming station K. In FIG. 1, the image forming stations of the image forming unit 7 have the same configuration, and therefore, for convenience of illustration, only some image forming stations are denoted by reference numerals, and the other image forming stations are omitted. .

  The charging unit 23 includes a charging roller whose surface is made of elastic rubber. This charging roller is configured to abut on the surface of the latent image carrier 21 at the charging position so as to be driven to rotate, and in a driven direction with respect to the latent image carrier 21 as the latent image carrier 21 rotates. Driven at peripheral speed. The charging roller is connected to a charging bias generator (not shown), and is supplied with a charging bias from the charging bias generator, and the latent image is charged at a charging position where the charging unit 23 and the latent image carrier 21 come into contact with each other. The surface of the carrier 21 is charged.

  The line head 29 includes a plurality of light emitting elements arranged in the axial direction of the latent image carrier 21 (direction perpendicular to the paper surface of FIG. 1), and is spaced from the latent image carrier 21. From these light emitting elements, the surface of the latent image carrier 21 charged by the charging unit 23 is irradiated with light to form a latent image on the surface. In this embodiment, as shown in FIG. 2, a head controller HC is provided to control the line heads 29 for each color, and based on video data VD from the main controller MC and signals from the engine controller EC. Each line head 29 is controlled. That is, in this embodiment, the image data included in the image formation command is input to the image processing unit 51 of the main controller MC. Various image processing is performed on the image data to create video data VD for each color, and the video data VD is given to the head controller HC via the main-side communication module 52. In the head controller HC, the video data VD is given to the head control module 54 via the head side communication module 53. As described above, the head controller module 54 is supplied with the signal indicating the parameter value related to the latent image formation and the vertical synchronization signal Vsync from the engine controller EC. Based on these signals, video data VD, and the like, the head controller HC creates a signal for controlling element driving for the line head 29 of each color and outputs the signal to each line head 29. Thus, the operation of the light emitting elements is appropriately controlled in each line head 29, and a latent image corresponding to the image formation command is formed.

  In this embodiment, the latent image carrier 21, the charging unit 23, the developing unit 25, and the photoconductor cleaner 27 of each image forming station Y, M, C, and K are unitized as a photoconductor cartridge. Each photoconductor cartridge is provided with a nonvolatile memory for storing information related to the photoconductor cartridge. Then, wireless communication is performed between the engine controller EC and each photoconductor cartridge. In this way, information on each photoconductor cartridge is transmitted to the engine controller EC, and information in each memory is updated and stored.

  The developing unit 25 has a developing roller 251 on which toner is carried. Then, charging is performed at a developing position where the developing roller 251 and the latent image carrier 21 come into contact with each other by a developing bias applied to the developing roller 251 from a developing bias generator (not shown) electrically connected to the developing roller 251. The toner moves from the developing roller 251 to the latent image carrier 21, and the electrostatic latent image formed by the line head 29 becomes obvious.

  The toner image that has been made visible at the development position in this manner is conveyed in the rotation direction D21 of the latent image carrier 21, and then the primary transfer in which the transfer belt 81 and the latent image carrier 21 described later contact each other. Primary transfer is performed on the transfer belt 81 at a position TR1.

  In this embodiment, the photoreceptor cleaner 27 is in contact with the surface of the latent image carrier 21 on the downstream side of the primary transfer position TR1 in the rotation direction D21 of the latent image carrier 21 and on the upstream side of the charging unit 23. Is provided. The photoconductor cleaner 27 abuts on the surface of the latent image carrier 21 to remove the toner remaining on the surface of the latent image carrier 21 after the primary transfer.

  The transfer belt unit 8 includes a driving roller 82, a driven roller 83 (blade facing roller) disposed on the left side of the driving roller 82 in FIG. 1, and stretched around these rollers in a direction indicated by an arrow D81 (conveying direction). And a transfer belt 81 that is driven to circulate. Further, the transfer belt unit 8 is disposed on the inner side of the transfer belt 81 so as to be opposed to each of the latent image carriers 21 included in the image forming stations Y, M, C, and K when the photosensitive cartridge is mounted. Four primary transfer rollers 85Y, 85M, 85C, and 85K are provided. Each of these primary transfer rollers 85 is electrically connected to a primary transfer bias generator (not shown). As will be described in detail later, when the color mode is executed, as shown in FIG. 1, all the primary transfer rollers 85Y, 85M, 85C, and 85K are positioned on the image forming stations Y, M, C, and K side. Then, the transfer belt 81 is pushed and brought into contact with the latent image carrier 21 included in each of the image forming stations Y, M, C, and K so that the primary transfer position is between each latent image carrier 21 and the transfer belt 81. TR1 is formed. Then, by applying a primary transfer bias from the primary transfer bias generating unit to the primary transfer roller 85 at an appropriate timing, the toner images formed on the surface of each latent image carrier 21 are respectively corresponding. A color image is formed by transferring to the surface of the transfer belt 81 at the primary transfer position TR1.

  On the other hand, when the monochrome mode is executed, among the four primary transfer rollers 85, the color primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations Y, M, and C facing each other, and the monochrome primary transfer is performed. By bringing only the roller 85K into contact with the image forming station K, only the monochrome image forming station K is brought into contact with the transfer belt 81. As a result, the primary transfer position TR1 is formed only between the monochrome primary transfer roller 85K and the image forming station K. Then, by applying a primary transfer bias from the primary transfer bias generator to the monochrome primary transfer roller 85K at an appropriate timing, the toner image formed on the surface of the latent image carrier 21 is subjected to primary transfer. At the position TR1, the image is transferred onto the surface of the transfer belt 81 to form a monochrome image.

  Further, the transfer belt unit 8 includes a downstream guide roller 86 disposed downstream of the monochrome primary transfer roller 85K and upstream of the driving roller 82. Further, the downstream guide roller 86 includes the primary transfer roller 85K and the latent image carrier 21 at the primary transfer position TR1 formed by the monochrome primary transfer roller 85K being in contact with the latent image carrier 21 of the image forming station K. Are in contact with the transfer belt 81 on a common inscribed line.

  The drive roller 82 circulates and drives the transfer belt 81 in the direction of the arrow D81 in the figure, and also serves as a backup roller for the secondary transfer roller 121. A rubber layer having a thickness of about 3 mm and a volume resistivity of 1000 kΩ · cm or less is formed on the peripheral surface of the drive roller 82, and secondary transfer is omitted by grounding through a metal shaft. The conductive path of the secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 121 is used. When the rubber layer having high friction and shock absorption is provided on the driving roller 82 in this way, the sheet enters the contact portion (secondary transfer position TR2) between the driving roller 82 and the secondary transfer roller 121. Is difficult to be transmitted to the transfer belt 81, and image quality deterioration can be prevented.

  The paper feed unit 11 includes a paper feed unit having a paper feed cassette 77 capable of stacking and holding sheets and a pickup roller 79 for feeding sheets one by one from the paper feed cassette 77. The sheet fed from the sheet feeding unit by the pickup roller 79 is fed to the secondary transfer position TR2 along the sheet guide member 15 after the sheet feeding timing is adjusted by the registration roller pair 80.

  The secondary transfer roller 121 is provided so as to be able to come into contact with and separate from the transfer belt 81 and is driven to come into contact with and separate from a secondary transfer roller drive mechanism (not shown). The fixing unit 13 includes a heating roller 131 that includes a heating element such as a halogen heater and is rotatable, and a pressure unit 132 that presses and biases the heating roller 131. The sheet on which the image has been secondarily transferred is guided to a nip formed by the heating roller 131 and the pressure belt 1323 of the pressure unit 132 by the sheet guide member 15, and in the nip, a predetermined value is formed. The image is heat-fixed at temperature. The pressure unit 132 includes two rollers 1321 and 1322 and a pressure belt 1323 stretched between them. A nip portion formed by the heating roller 131 and the pressure belt 1323 is formed by pressing the belt tension surface stretched by the two rollers 1321 and 1322 out of the surface of the pressure belt 1323 against the peripheral surface of the heating roller 131. Is configured to be widely taken. Further, the sheet thus subjected to the fixing process is conveyed to a paper discharge tray 4 provided on the upper surface portion of the housing body 3.

  In the image forming apparatus 1, a cleaner unit 71 is disposed to face the blade facing roller 83. The cleaner unit 71 includes a cleaner blade 711 and a waste toner box 713. The cleaner blade 711 removes foreign matters such as toner and paper dust remaining on the transfer belt 81 after the secondary transfer by bringing the tip of the cleaner blade 711 into contact with the blade facing roller 83 via the transfer belt 81. The foreign matter removed in this way is collected in a waste toner box 713. Further, the cleaner blade 711 and the waste toner box 713 are integrally formed with the blade facing roller 83. Therefore, when the blade facing roller 83 moves as will be described below, the cleaner blade 711 and the waste toner box 713 also move together with the blade facing roller 83.

  FIG. 3 is a perspective view showing an outline of an embodiment of a line head (exposure means) according to the present invention. FIG. 4 is a sectional view in the sub-scanning direction of an embodiment of the line head (exposure means) according to the present invention. The line head 29 according to the present embodiment includes a case 291 whose longitudinal direction is the main scanning direction XX, and positioning pins 2911 and screw insertion holes 2912 are provided at both ends of the case 291. Then, the positioning pin 2911 is fitted into a positioning hole (not shown) provided in the photoreceptor cover (not shown) that covers the latent image carrier 21 and is positioned with respect to the latent image carrier 21. The line head 29 is positioned with respect to the latent image carrier 21. Further, the line head 29 is positioned and fixed with respect to the latent image carrier 21 by screwing and fixing a fixing screw into a screw hole (not shown) of the photoreceptor cover via the screw insertion hole 2912.

  The case 291 holds the microlens array 299 at a position facing the surface to be scanned 211 that is the surface of the latent image carrier 21, and includes a light shielding member 297 and a transparent substrate in the order close to the microlens array 299. The glass substrate 293 is provided. A plurality of light emitting element groups 295 are provided on the back side of the glass substrate 293 (the side opposite to the microlens array 299 side of the two surfaces of the glass substrate 293). That is, the plurality of light emitting element groups 295 are two-dimensionally arranged on the back side of the glass substrate 293 and spaced apart from each other by a predetermined distance in the main scanning direction XX and the sub-scanning direction YY. Here, each of the light emitting element groups 295 is configured by two-dimensionally arranging a plurality of light emitting elements. In the present embodiment, an organic EL (Electro-Luminescence) element is used as the light emitting element. That is, in this embodiment, the organic EL element is disposed as a light emitting element on the back surface side of the glass substrate 293. A light beam emitted from each of the plurality of light emitting elements toward the latent image carrier 21 is directed to the light shielding member 297 through the glass substrate 293. Here, the light-emitting element group 295 of organic EL elements has a plurality of light-emitting elements formed on the back side of the same transparent substrate by utilizing techniques such as thin film formation, photolithography, and precision etching. Since the light emitting element groups 295 are discretely arranged on the back surface side of the glass substrate 293, the light emitting element groups 295 are excellent in dimensional accuracy between organic EL elements and between organic EL element groups.

  A plurality of light guide holes 2971 are formed in the light shielding member 297 on a one-to-one basis with respect to the plurality of light emitting element groups 295. The light guide hole 2971 is formed as a hole penetrating the light shielding member 297 with a line parallel to the normal line of the glass substrate 293 as a central axis. Here, light emitted from the light emitting elements belonging to the light emitting element group 295 is guided to the microlens array 299 through the light guide hole 2971 corresponding to the light emitting element group 295. Then, the light beam that has passed through the light guide hole 2971 formed in the light shielding member 297 is imaged as a spot on the surface of the latent image carrier 21 by the microlens array 299. The light shielding member 297 can be formed of metal such as carbon steel or titanium, but is formed of carbon steel in this embodiment.

  As shown in FIG. 4, the back cover 2913 is pressed against the case 291 through the glass substrate 2913 by the fixing device 2914. In other words, the fixing device 2914 has an elastic force that presses the back cover 293 toward the case 291, and presses the back cover with the elastic force, thereby making the inside of the case 291 light-tight (that is, from the inside of the case 291. It is sealed so that light does not leak and so that light does not enter from the outside of the case 291. Note that a plurality of fixing devices 2914 are provided in the longitudinal direction of the case 291. The light emitting element group 295 is covered with a sealing member 294.

  FIG. 5 is a perspective view schematically showing the microlens array. FIG. 6 is a cross-sectional view of the microlens array in the main scanning direction. The microlens array 299 includes a glass substrate 2991 and a plurality of lens pairs each including two lenses 2993A and 2993B arranged one-on-one so as to sandwich the glass substrate 2991. These lenses 2993A and 2993B can be formed of resin.

  That is, a plurality of lenses 2993A are arranged on the front surface 2991A of the glass substrate 2991, and a plurality of lenses 2993B are arranged on the back surface 2991B of the glass substrate 2991 so as to correspond one-to-one to the plurality of lenses 2993A. Further, the two lenses 2993A and 2993B constituting the lens pair share a common optical axis OA. The plurality of lens pairs are arranged one-on-one in the plurality of light emitting element groups 295. In this specification, an optical system including lenses 2993A and 2993B forming a one-to-one pair and a glass substrate 2991 sandwiched between the lens pairs is referred to as “microlens ML”. The plurality of lens pairs (microlenses ML) are two-dimensionally arranged at predetermined intervals in the main scanning direction XX and the sub-scanning direction YY, corresponding to the arrangement of the light emitting element groups 295.

  FIG. 7 is a diagram illustrating an arrangement of a plurality of light emitting element groups. In the present embodiment, two light emitting element arrays L2951 configured by arranging four light emitting elements 2951 in the main scanning direction XX at predetermined intervals are arranged in the sub-scanning direction YY at two predetermined intervals. A group 295 is formed. That is, eight light emitting elements 2951 corresponding to the microlens ML indicated by the two-dot chain line in FIG. Here, the element interval SS and the column interval LL are intervals having substantially the same length. The plurality of light emitting element groups 295 are arranged as follows.

  That is, two light emitting element groups 295 are arranged such that three light emitting element group rows L295 (group rows) configured by arranging a predetermined number (two or more) of light emitting element groups 295 in the main scanning direction XX are arranged in the sub scanning direction YY. Dimensionally arranged. Further, all the light emitting element groups 295 are arranged at different main scanning direction positions. Further, the plurality of light emitting element groups 295 are arranged so that the sub scanning direction positions of the light emitting element groups (for example, the light emitting element group 295C1 and the light emitting element group 295B1) whose main scanning direction positions are adjacent to each other are different. Note that in this specification, the geometric center of gravity of the light emitting element 2951 is defined as the position of the light emitting element 2951. Therefore, the distance between the two light emitting elements means the distance between the geometric centers of gravity of the respective light emitting elements. Further, in this specification, the “geometric centroid of light emitting element group” means the geometric centroid of all light emitting element positions belonging to the same light emitting element group 295. In addition, the main scanning direction position and the sub scanning direction position mean the main scanning direction component and the sub scanning direction component at the position of interest, respectively.

  Corresponding to the arrangement of the light emitting element groups 295, a light guide hole 2971 is formed in the light shielding member 297, and a lens pair including lenses 2993A and 2993B is arranged. That is, in the present embodiment, the gravity center position of the light emitting element group 295, the central axis of the light guide hole 2971, and the optical axis OA of the lens pair configured by the lenses 2993A and 2993B are configured to substantially coincide. ing. Then, the light beam emitted from the light emitting element 2951 of the light emitting element group 295 enters the microlens array 299 through the corresponding light guide hole 2971 and is spotted on the surface of the latent image carrier 21 by the microlens array 299. Is imaged.

  FIG. 8 is a diagram showing an imaging state of direct light of the microlens array in the present embodiment. Also, in the figure, in order to show the imaging characteristics of the microlens array 299, the geometric center of gravity E0 of the light emitting element group 295 and the positions E1, which are both ends in the left-right direction of the figure separated from the geometric center of gravity E0 by a predetermined interval. The locus of the light beam emitted from E2 is indicated by a two-dot chain line. As shown by the locus, the light beam emitted from each position and directly becomes light enters from the back surface side of the glass substrate 293, passes through the glass substrate 293, and is emitted from the front surface side. The light beam emitted from the surface of the glass substrate 293 reaches the surface (scanned surface 211) of the latent image carrier 21 via the microlens array 299.

  As shown in FIGS. 6 and 8, the light beam emitted from the geometric center of gravity E0 of the light emitting element group forms an image at an intersection I0 between the surface of the latent image carrier 21 and the optical axis OA of the lenses 2993A and 2993B. . As described above, this is because, in the present embodiment, the geometric gravity center position E0 (the position of the light emitting element group 295) of the light emitting element group 295 is on the optical axis OA of the lenses 2993A and 2993B. . The light beams emitted from the positions E1 and E2 are imaged at positions I1 and I2 on the surface of the latent image carrier 21, respectively. That is, the light beam emitted from the position E1 is imaged at the position I1 on the opposite side across the optical axis OA of the lenses 2993A and 2993B in the main scanning direction XX, and the light beam emitted from the position E2 is In the main scanning direction XX, an image is formed at a position I2 on the opposite side across the optical axis OA of the lenses 2993A and 2993B. That is, an imaging lens composed of a lens pair composed of lenses 2993A and 2993B having a common optical axis and a glass substrate 2991 sandwiched between the lens pairs is a so-called reversal optical system having reversal characteristics.

  Further, as shown in FIG. 8, the distance between the position I1 where the light beam is imaged and the intersection point I0 is longer than the distance between the position E1 and the geometric gravity center E0. That is, the absolute value of the magnification (optical magnification) of the optical system in the present embodiment is greater than 1. That is, the optical system in the present embodiment is a so-called magnifying optical system having magnifying characteristics. As described above, in the present embodiment, the microlens ML that is an optical system including the lens pair including the lenses 2993A and 2993B having the same optical axis and the glass base member 2991 sandwiched between the lens pairs is the present invention. It functions as an “imaging lens”.

  FIG. 9 is a diagram illustrating an example of trajectories of direct light and reflected light. As shown in the figure, a plurality of light emitting element groups 295 are discretely arranged on the back side of the glass substrate 293. A plurality of microlenses ML (imaging lenses) are arranged in one-to-one correspondence with the plurality of light emitting element groups 295. Further, the light shielding member 297 is disposed so that one surface 2993 faces the surface of the glass substrate 293 and the other surface 2974 faces the plurality of imaging lenses. In the light shielding member 297, a plurality of light guide holes 2971 are formed by penetrating from one surface 2773 to the other surface 2974 of the light shielding member 297 on a one-to-one basis with respect to the plurality of light emitting element groups 295. The plurality of light guide holes 2971 are formed so as to be axisymmetric with respect to the optical axis OA of the corresponding microlens ML. The light guide hole 2971 is formed in a tapered shape so as to expand from the one surface 2973 toward the other surface 2974. Further, a latent image carrier 21 is disposed above the microlens ML in the drawing in the extending direction of the optical axis OA.

  As shown in FIG. 9, the line head 29 in the present embodiment includes a light shielding member 297 having a plurality of light guide holes 2971 formed one-on-one with respect to the plurality of microlenses ML. 2971 is formed so as to spread from one surface 2973 toward the other surface 2974. Therefore, the light beam emitted from the light emitting element group 295 through the glass substrate 293 is guided to the opposing microlens ML (imaging lens) by the light guide hole 2971 formed in the light shielding member 297, and the microlens. The surface of the latent image carrier 21 (scanned surface 211) is reached via the array 299. The direct light that is part of the light beam emitted from the geometric center of gravity E0 of the light emitting element group 295 and the positions E1 and E2 that are both ends in the left-right direction in FIG. The surface of the latent image carrier 21 (scanned surface 211) is reached by a locus represented by a chain line. The reaching positions are the intersection point I0, the position I1, and the position I2 corresponding to E0, E1, and E2. That is, the direct light from all the light emitting elements belonging to the light emitting element group 295 in the range from the positions E1 to E2 which are both ends in the left-right direction in the figure is the position of the surface of the latent image carrier 21. A range from I1 to I2 is reached to form a spot.

  Further, as shown in FIG. 9, the other light beam is reflected by the side surface 2972 of the light guide hole 2971. As an example, the locus of the light beam emitted from the geometric center of gravity E0 of the light emitting element group 295 is indicated by a thick broken line. The light beam is reflected by the side surface 2972 of the light guide hole 2971, and irradiates the position I0X on the surface (scanned surface 211) of the latent image carrier 21 through the microlens array 299 as reflected light. Here, the case where the light guide hole 2971 has a temporary side wall 2972Y in which the width on the cross section of the light guide hole 2971 is substantially constant from the one surface 2973 toward the other surface 2974 will be considered. The locus of the light beam emitted from the geometric center of gravity E0 of the light emitting element group 295 described above is indicated by a thick broken line and a thin solid line up to the side wall 2972Y, and only after the reflection at the side wall 2972Y, is a thin solid line. The light beam is reflected by the side surface 2972Y, and irradiates the position I0Y of the surface (scanned surface 211) of the latent image carrier 21 through the microlens array 299 as reflected light. Since the incident angle θ1 and the reflection angle θ2 of the light beam on the side surface 2972 are smaller than the incident angle θ3 and the reflection angle θ4 of the light beam on the side surface 2972Y, the reflected light on the side surface 2972 is irradiated on the scanned surface 211. The position I0X is closer to the intersection point I0, which is the position of the direct light spot, than the position I0Y of irradiation of the reflected light on the side surface 2972Y to the scanned surface 211.

  FIG. 10A is a diagram schematically showing a glass substrate on which a light emitting element group is arranged and a light shielding member, where FIG. 10A is a partial plan view, and FIG. 10B is a diagram of one surface side of FIG. (C) is an enlarged sectional view taken along line AA of (a), and (c) also clearly shows the surface of the microlens and the trajectory of the light beam. 10A, 10B, and 10C, the arrangement of the plurality of light emitting element groups 295 arranged on the glass substrate 293 is the same as the arrangement of the plurality of light emitting element groups 295 shown in FIG. The configuration of the plurality of light emitting elements 2951 belonging to the light emitting element group 295 is the same as the configuration of the plurality of light emitting elements 2951 shown in FIG. Further, the arrangement of the light shielding member 297 having the light guide holes 2971 corresponding to the arrangement of the light emitting element groups 295 and the micro lens ML is also the same as the arrangement of the light shielding member 297 and the micro lens ML shown in FIG. It is the same way. A typical direct light trajectory is represented by a two-dot chain line. Here, two light emitting element rows L2951 are arranged in the sub-scanning direction YY of one light emitting element group 295, and four light emitting elements 2951 belong to the light emitting element row L2951 in the main scanning direction XX. The light emitting element group 295 has a long shape in the main scanning direction. The opening on one side of the light guide hole 2971 is an opening 2971A, and the opening on the other side is an opening 2971B.

  Next, in FIGS. 10A, 10 </ b> B, and 10 </ b> C, the intersection of the direct light trajectory and the one surface 2973 will be considered. Here, the combination of the light emitting elements 2951A and 2951B, and the combinations of the light emitting elements 2951C and 2951D are the light emitting elements 2951 belonging to the light emitting element group 295 that have the longest distance between the light emitting elements. In one combination of the light emitting element 2951A and the light emitting element 2951B, the locus OL1 from the left end of the light emitting element 2951A to the outer diameter of the microlens ML closest to the light emitting element 2951A and the right end of the light emitting element 2951B in the drawing. The trajectory of direct light is drawn in the range from the trajectory OL2 to the outer diameter of the microlens ML closest to the light emitting element 2951B. A region SQ1 formed by the intersection of the direct light and the one surface 2973 is a range of an intersection CP1 of the locus OL1 and the one surface 2773, and an intersection CP2 of the locus OL2 and the one surface 2993. The shape of the track that includes the region SQ1 and is long in the main scanning direction XX in contact with the outer periphery OC1 of the region SQ1 is the shape of the opening 2971A on the one surface side of the light guide hole 2971. Accordingly, the direct light is incident on the microlens ML without being shielded at all, and as an example, a part of the light beam represented by the locus OL3 is shielded by the one surface 2993 and does not reach the microlens ML. Note that the direction of the linear portion of the track is the same as the main scanning direction.

  FIG. 11A is a diagram schematically showing a glass substrate on which a light emitting element group is arranged and a light shielding member, where FIG. 11A is a partial plan view, and FIG. 11B is an opening on one surface side of FIG. (C) is an enlarged sectional view taken along the line BB of (a), and clearly shows the surface of the microlens and the locus of the light beam. 11A, 11B, and 11C, the arrangement of the plurality of light emitting element groups 295 arranged on the glass substrate 293 is the same as the arrangement of the plurality of light emitting element groups 295 shown in FIG. Although the method is the same, the configuration of the plurality of light emitting elements 2951 belonging to the light emitting element group 295 is different from the configuration of the plurality of light emitting elements 2951 shown in FIG. Next, the light guide hole 2971 is formed corresponding to the arrangement of the light emitting element group 295, and the arrangement of the light shielding member 297 and the microlens ML is described in the arrangement of the light shielding member 297 and the microlens ML shown in FIG. It is the same way. A typical direct light trajectory is represented by a two-dot chain line. The configuration of the plurality of light emitting elements 2951 belonging to the different light emitting element groups 295 is only the arrangement of the three light emitting element rows L2951 in the sub-scanning direction YY of one light emitting element group 295. Here, since the four light emitting elements 2951 in the main scanning direction XX in the light emitting element row L2951 belong, the lengths of the light emitting element groups 295 in the main scanning direction and the sub scanning direction are substantially equal. The opening on one side of the light guide hole 2971 is an opening 2971C, and the opening on the other side is an opening 2971D.

  Next, in FIG. 11A, FIG. 11B, and FIG. 11C, the intersection of the direct light trajectory and the one surface 2973 will be considered. Here, the combination of the light emitting elements having the longest distance between the light emitting elements among the light emitting elements 2951 belonging to the light emitting element group 295 is a combination of the light emitting elements 2951E and 2951F and the light emitting elements 2951G and 2951H. In the light emitting element 2951E and the light emitting element 2951F which is one combination, the locus OL4 from the left end portion of the light emitting element 2951E to the outer diameter of the microlens ML closest to the light emitting element 2951E and the right end portion of the light emitting element 2951F in the drawing. The trajectory of direct light is drawn in the range from the trajectory OL5 to the outer diameter of the microlens ML closest to the light emitting element 2951F. A region SQ2 formed by the intersection of the direct light and the one surface 2973 is a range of the intersection CP3 of the locus OL4 and the one surface 2773 and the intersection CP4 of the locus OL5 and the one surface 2993. The shape of the circle including the region SQ2 and in contact with the outer periphery OC2 of the region SQ2 is the shape of the opening 2971C on the one surface side of the light guide hole 2971. Accordingly, the direct light is incident on the microlens ML without being shielded at all, and as an example, a part of the light beam represented by the locus OL6 is shielded by the one surface 2993 and does not reach the microlens ML.

  FIG. 12 is a diagram showing a spot forming operation by the above-described line head. Hereinafter, the spot forming operation by the line head in this embodiment will be described with reference to FIGS. 2, 7, and 12. In order to facilitate understanding of the invention, here, a case where a plurality of spots are formed side by side on a straight line extending in the main scanning direction XX will be described. In the present embodiment, a plurality of light emitting elements are caused to emit light at a predetermined timing by the head control module 54 while transporting the surface (scanned surface 211) of the latent image carrier 21 in the sub-scanning direction YY. A plurality of spots are formed side by side on a straight line extending to XX.

  That is, in the line head of this embodiment, six light emitting element rows L2951 are arranged side by side in the sub-scanning direction YY corresponding to each position of the sub-scanning direction positions Y1 to Y6 (FIG. 7). Therefore, in this embodiment, the light emitting element rows L2951 at the same sub-scanning direction position emit light at substantially the same timing, and the light emitting element rows L2951 at different sub-scanning direction positions emit light at different timings. More specifically, the light emitting element rows L2951 are caused to emit light in the order of the sub-scanning direction positions Y1 to Y6. Then, while the surface of the latent image carrier 21 (scanned surface 211) is conveyed in the sub-scanning direction YY, the light-emitting element array L2951 emits light in the above-described order, so that the surface extends in the main scanning direction XX. A plurality of spots are formed side by side.

  Such an operation will be described with reference to FIGS. First, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y1 belonging to the most upstream light emitting element groups 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted and imaged on the surface of the latent image carrier 21 by the “imaging lens” having the above-described inversion magnification characteristics. That is, a spot is formed at the position of the “first” hatching pattern in FIG. In the figure, white circles represent spots that have not yet been formed and are to be formed in the future. In the same figure, the spots labeled with reference numerals 295C1, 295B1, 295A1, and 295C2 indicate spots formed by the light emitting element groups 295 corresponding to the reference numerals assigned thereto.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y2 belonging to the same light emitting element group 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emission operation are expanded while being inverted by the “imaging lens” having the above-described inversion enlarging characteristics, and are connected to the surface of the latent image carrier 21 (scanned surface 211). Imaged. That is, a spot is formed at the position of the “second” hatching pattern in FIG. Here, while the transport direction of the surface of the latent image carrier 21 (scanned surface 211) is the sub-scanning direction YY, the light emitting element array L2951 on the upstream side in the sub-scanning direction YY is sequentially (that is, the sub-scanning direction 211). The reason for emitting light (in the order of the scanning direction positions Y1, Y2) is to respond to the “imaging lens” having the reversal characteristics.

  Next, the light emitting elements 2951 of the light emitting element array L2951 in the sub scanning direction position Y3 belonging to the second light emitting element groups 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted and imaged on the surface of the latent image carrier 21 by the “imaging lens” having the above-described inversion magnification characteristics. That is, a spot is formed at the position of the “third” hatching pattern in FIG.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y4 belonging to the light emitting element groups 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted and imaged on the surface of the latent image carrier 21 by the “imaging lens” having the above-described inversion magnification characteristics. That is, a spot is formed at the position of the “fourth” hatching pattern in FIG.

  Next, the light emitting elements 2951 of the light emitting element row L2951 in the sub scanning direction position Y5 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted and imaged on the surface of the latent image carrier 21 by the “imaging lens” having the above-described inversion magnification characteristics. That is, a spot is formed at the position of the “fifth” hatching pattern in FIG.

  Finally, the light emitting elements 2951 of the light emitting element row L2951 in the sub-scanning direction position Y6 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emission operation are enlarged while being inverted and imaged on the surface of the latent image carrier 21 by the “imaging lens” having the above-described inversion magnification characteristics. That is, a spot is formed at the position of the “sixth” hatching pattern in FIG. In this way, by performing the first to sixth light emitting operations, a plurality of spots are formed side by side on a straight line extending in the main scanning direction XX.

In the above-described embodiment, the following effects can be obtained.
(1) The light guide hole 2971 is formed so as to expand from the one surface 2973 toward the other surface 2974. Here, a part of the light beam is reflected by the side surface 2972 of the light guide hole 2971, passes through the imaging lens as reflected light, and irradiates the scanned surface 211. The other light beams not involved in the side surface 2972 of the light guide hole 2971 are imaged as direct light by the imaging lens, and a spot of direct light is formed on the scanned surface 211. Compared to the side surface of the light guide hole in which the width on the cross section is substantially constant from one surface to the other surface as described in the background art, the side surface 2972 of the present embodiment has a width on the cross section from the one surface 2993 to the other surface. It is formed so as to expand toward the direction 2974. Therefore, the incident angle θ1 and the reflection angle θ2 of the light beam on the side surface 2972 are reduced, and the irradiation position I0X of the reflected light that has passed through the imaging lens to the scanned surface 211 is the position of the direct light spot. It approaches a certain intersection I0. When the reflected light irradiation position I0X approaches the intersection point I0 which is the position of the direct light spot, it is possible to make it difficult to visually recognize a ghost caused by the reflected light irradiation. Accordingly, the image quality can be improved.

  (2) The light emitting element 2951 of the light emitting element group 295 is an organic EL element. The organic EL element is not formed by fixing individual completed bodies as the light emitting elements 2951 to the back side of the glass substrate 293 that is the same transparent substrate, but the back side of the glass substrate 293 that is the same transparent substrate. In addition, since the constituent members of the organic EL elements are sequentially formed to form a plurality of completed bodies, the dimensional accuracy between the organic EL elements and between the organic EL element groups is excellent. In the assembly of the glass substrate 293, which is a transparent substrate on which the organic EL element and the organic EL element group are formed, and the light shielding member 297, the organic EL element and the organic EL element group are excellent in dimensional accuracy. The positional accuracy between the element group and the light guide hole 2971 of the light shielding member 297 can also be excellent. Therefore, since the position accuracy is poor and the organic EL element or the organic EL element group approaches the light guide hole 2971, the optical intensity of the reflected light irradiation is increased, and the ghost caused by the reflected light irradiation is clearly visually recognized. Can be avoided. Therefore, the image quality can be further improved.

  (3) The element spacing SS in the main scanning direction XX of the plurality of light emitting elements 2951 is constant, the row spacing LL of the plurality of light emitting element rows L2951 is substantially equal to the element spacing SS, and the number of the plurality of light emitting elements 2951 is The opening 2971A on one surface side of the light guide hole 2971 is larger than the number of the plurality of light emitting element rows L2951 and includes a region formed by the intersection of the light beam directly incident on the imaging lens and the one surface 2993. The shape of the track or ellipse is long in the main scanning direction in contact with the outer periphery of the region. As a result, direct light is incident on the imaging lens without being shielded at all, and a portion of the light beam that does not become direct light is shielded by the one surface 2993, thereby suppressing reflected light incident on the imaging lens. can do. Therefore, since the optical intensity of the reflected light irradiation is weakened without reducing the optical intensity of the spot of direct light on the scanned surface 211, it is difficult to visually recognize the ghost caused by the irradiation of the reflected light. it can. Therefore, the image quality can be further improved.

  (4) The element spacing SS in the main scanning direction XX of the plurality of light emitting elements 2951 is constant, the column spacing LL of the plurality of light emitting element rows L2951 is substantially equal to the element spacing SS, and the number of the plurality of light emitting elements 2951 The number of the plurality of light emitting element rows L2951 is the same, and the opening 2971A on one surface side of the light guide hole 2971 is formed by the intersection of the light beam directly incident on the imaging lens and the one surface 2993 And a circular shape in contact with the outer periphery of the region. As a result, direct light is incident on the imaging lens without being shielded at all, and a portion of the light beam that does not become direct light is shielded by the one surface 2993, thereby suppressing reflected light incident on the imaging lens. can do. Therefore, since the optical intensity of the reflected light irradiation is weakened without reducing the optical intensity of the spot of direct light on the scanned surface 211, it is difficult to visually recognize the ghost caused by the irradiation of the reflected light. it can. Therefore, the image quality can be further improved.

  (5) Direct light, which is a part of the light beam emitted from the light emitting element 2951, is incident on the imaging lens without being shielded at all, and a part of the light beam that does not become direct light is shielded by the one surface 2993. Therefore, the reflected light incident on the imaging lens is suppressed. The position of irradiation of the reflected light onto the surface to be scanned 211 is closer to the position of the direct light spot. Therefore, the optical intensity of the spot of direct light on the surface to be scanned 211 is not weakened, the optical intensity of the spot of reflected light is weakened, and the position of the reflected light irradiation and the position of the spot of direct light are closer. Thus, it is possible to perform image formation in which a ghost caused by irradiation of reflected light is difficult to visually recognize. Accordingly, it is possible to provide an image forming apparatus capable of further improving the image quality.

  The present invention is not limited to the above-described embodiment, and various modifications other than those described above can be made without departing from the spirit of the present invention. That is, in the said embodiment, although the transparent substrate is comprised with glass, it cannot be overemphasized that the material of a transparent substrate is not restricted to glass. That is, the transparent substrate can be made of a material that can transmit a light beam.

  Moreover, in the said embodiment, as shown in FIG.7, FIG.10 (a), FIG.10 (b), FIG.11 (a), and FIG.11 (b), the several light emitting element group is arrange | positioned. That is, in FIG. 7, FIG. 10A and FIG. 10B, a light emitting element array L2951 configured by arranging four light emitting elements 2951 in the main scanning direction XX at a predetermined constant interval in the sub scanning direction YY. Two light emitting element groups 295 are configured by arranging two at predetermined intervals. Further, in FIG. 11A and FIG. 11B, a light emitting element array L2951 configured by arranging four light emitting elements 2951 in the main scanning direction XX at a predetermined constant interval is arranged at predetermined constant intervals in the sub-scanning direction YY. Three light emitting element groups 295 are formed side by side. However, the number of the light emitting elements 2951 constituting the light emitting element group 295, the number of the light emitting element rows L2951, and the arrangement method of the plurality of light emitting elements 2951 and the plurality of light emitting element rows L2951 are not limited thereto, and may be appropriately changed. Is possible. However, as described above, the arrangement of the plurality of light emitting elements 2951 is preferable in that a favorable spot formation can be easily realized by adopting the above-described symmetrical arrangement.

  Further, in the above embodiment, light emission is performed so that three light emitting element group rows L295 (group row) configured by arranging a predetermined number (two or more) of light emitting element groups 295 in the main scanning direction XX are arranged in the sub scanning direction YY. The element group 295 is arranged two-dimensionally. However, the arrangement of the plurality of light emitting element groups 295 is not limited to this, and can be changed as appropriate.

  In the above embodiment, the magnifying optical system is adopted as the imaging lens, but this is not an essential requirement for the present invention. That is, a reduction optical system having a magnification (optical magnification) of less than 1 or a 1 × optical system having a magnification of approximately 1 may be used as the imaging lens.

  In the above embodiment, the opening 2971A on one side shown in FIGS. 10 (a) and 10 (b) has a track shape long in the main scanning direction XX, and FIGS. 11 (a) and 11 (b). The opening portion 2971C on the one surface side shown in FIG. 5 is formed in a circular shape, but is not limited to this, and includes a region formed by the intersection of the light beam directly incident on the imaging lens and the one surface 2993, Any shape that contacts the outer periphery of the region may be used. Therefore, as an example, the opening 2971A on one surface side may have an elliptical shape that is long in the main scanning direction XX.

  In the above embodiment, the line head 29 according to the present invention is used to form a plurality of spots in a straight line in the main scanning direction XX as shown in FIG. However, the spot forming operation is an example of the operation of the line head according to the present invention, and the operation that can be performed by the line head 29 is not limited to this. That is, the formed spots do not need to be formed in a straight line along the main scanning direction XX. For example, the spots may be formed side by side with a predetermined angle in the main scanning direction XX, You may form in a waveform.

  In the above-described embodiment, the present invention is applied to the image forming apparatus 1 for forming a color image. However, the application target of the present invention is not limited to this, and the monochrome image forming for forming a so-called monochromatic image is not limited thereto. The present invention can also be applied to an image forming apparatus.

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an electrical configuration of the image forming apparatus in FIG. 1. 1 is a perspective view schematically showing an embodiment of a line head according to the present invention. FIG. 3 is a cross-sectional view in the sub-scanning direction of one embodiment of the line head according to the invention. The perspective view which shows the outline of a microlens array. The main scanning direction sectional view of a micro lens array. The figure which shows arrangement | positioning of a several light emitting element group. The figure which shows the imaging state of the direct light of a micro lens array. The figure which shows an example of the locus | trajectory of direct light and reflected light. It is a figure which shows typically the glass substrate and light-shielding member in which the light emitting element group is arrange | positioned, (a) is a partial top view, (b) is the enlarged view of the vicinity of the opening part of the one surface side of (a), (C) is an expanded sectional view of the AA line of (a). It is a figure which shows typically the glass substrate and light-shielding member in which the light emitting element group is arrange | positioned, (a) is a partial top view, (b) is the vicinity enlarged view of the opening part of the one surface side of (a), c) Enlarged sectional view taken along line BB in (a). The figure which shows the spot formation operation | movement by a line head.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 21 ... Latent image carrier, 211 ... Scanned surface, 29 ... Line head (exposure means), 293 ... Glass substrate as transparent substrate, 295 ... Light emitting element group, 2951 ... Light emitting element, L2951 ... Light emitting element row, SS: element spacing, LL: row spacing, ML: microlens (imaging lens), 297 ... light shielding member, 2971 ... light guide hole, 2773 ... one side, 2974 ... other side, 2971A, 2971C ... one Directional openings, CP1, CP2, CP3, CP4 ... intersections, SQ1, SQ2 ... area, OC1, OC2 ... outer periphery, XX ... main scanning direction, YY ... sub-scanning direction.

Claims (5)

A line head that forms a spot by forming an image of a light beam on a surface to be scanned conveyed in a sub-scanning direction substantially orthogonal to the main-scanning direction;
A transparent substrate capable of transmitting the light beam;
A plurality of light emitting elements formed on the back side of the transparent substrate, and a plurality of light emitting element groups each arranged discretely on the back side of the transparent substrate;
The light emitting elements are arranged in one-to-one correspondence with the plurality of light emitting element groups, and each of the light beams emitted from the plurality of light emitting elements belonging to the opposing light emitting element group is coupled to the scanned surface. A plurality of imaging lenses for imaging;
The one surface is disposed so that one surface faces the surface of the transparent substrate and the other surface faces the plurality of imaging lenses, and further, the one surface corresponds to the plurality of light emitting element groups on a one-to-one basis. A light-shielding member having a plurality of light-guiding holes drilled through the other surface from
The line head, wherein the light guide hole is formed so as to expand from the one surface toward the other surface. The line head according to claim 1, wherein
The line head according to claim 1, wherein the light emitting element of the light emitting element group is an organic EL element. The line head according to claim 1 or 2,
The light emitting element group has a plurality of light emitting element rows having a plurality of the light emitting elements arranged in the main scanning direction in the sub scanning direction,
The element spacing in the main scanning direction of the plurality of light emitting elements is constant, the column spacing of the plurality of light emitting element rows is substantially equal to the element spacing, and the number of the plurality of light emitting elements is the plurality of light emitting elements. Greater than the number of columns,
The main scanning direction in which the opening on one surface side of the light guide hole includes a region formed by the intersection of the light beam that is directly incident on the imaging lens and the one surface, and is in contact with the outer periphery of the region A line head characterized by having a long track or elliptical shape. In the line head according to any one of claims 1 to 3,
The light emitting element group has a plurality of light emitting element rows having a plurality of light emitting elements in the main scanning direction in the sub scanning direction,
The element spacing in the main scanning direction of the plurality of light emitting elements is constant, the column spacing of the plurality of light emitting element rows is substantially equal to the element spacing, and the number of the plurality of light emitting elements and the plurality of light emitting elements The number of columns is the same,
A shape of a circle in contact with the outer periphery of the region, wherein the opening on one surface side of the light guide hole includes a region formed by an intersection of the light beam and the one surface directly incident on the imaging lens A line head characterized by comprising: A latent image carrier having a scanned surface conveyed in the sub-scanning direction substantially orthogonal to the main scanning direction;
An image forming apparatus comprising: an exposure unit having the same configuration as the line head according to claim 1, wherein a spot is formed on the surface to be scanned of the latent image carrier.

Images