JP2008062468A - Line head and image forming apparatus using the line head - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technique which enables achievement of good spot formation by suppressing a reduction in quantity of light of light beams related to the formation of spots corresponding to an outermost element. <P>SOLUTION: The line head comprises a transparent substrate which can pass the light beams, a plurality of light emitting element groups each with a plurality of light emitting elements formed on a rear face of the transparent substrate, and a plurality of imaging lenses formed on the front face of the transparent substrate correspondingly by one to one to the plurality of light emitting element groups. For each of the plurality of light emitting element groups, when the light emitting element most separated from an optical axis of the imaging lens is defined as the outermost element, and a region of the front face of the transparent substrate where the light beam ejected from the outermost element can pass without being totally reflected at the front face is defined as an outermost pass region, a radius of the imaging lens is larger than a distance between the optical axis and a position most separated from the optical axis of the imaging lens of the outermost pass region. <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 this type of line head, for example, as described in Patent Document 1, a head using a light emitting element group (a “light emitting element array” in the same patent document) configured by arranging a plurality of light emitting elements is proposed. ing. Furthermore, in the line head described in Patent Document 1, a plurality of light emitting element groups are arranged side by side, and a plurality of imaging lenses are arranged in one-to-one correspondence with the plurality of light emitting element groups. Then, the light beams emitted from the light emitting elements of the light emitting element group are imaged by the imaging lens facing the light emitting element group, and a spot is formed on the surface to be scanned.

JP 2000-158705 A

  In the above-described line head, it is preferable that the light beam emitted from the light emitting element is incident on the corresponding imaging lens as much as possible from the viewpoint of forming a spot with as much light as possible. However, among the light emitting elements belonging to the light emitting element group, the following problem may occur with respect to the light emitting element (outermost element) that is located farthest from the optical axis of the corresponding imaging lens. That is, the relationship between the outermost element and the diameter of the imaging lens corresponding to the outermost element is not appropriate, so that the amount of the light beam incident on the imaging lens among the light beams emitted from the outermost element is reduced. There was a case. As a result, the light amount of the light beam related to the formation of the spot corresponding to the outermost element is reduced, and it may be impossible to realize good spot formation.

  The present invention has been made in view of the above problems. In a line head that forms an image of a light beam emitted from a plurality of light emitting elements on a surface to be scanned by an imaging lens corresponding to the plurality of light emitting elements. It is an object of the present invention to provide a technique that makes it possible to realize good spot formation by suppressing a decrease in the amount of light beams associated with spot formation corresponding to an outer element.

  A line head according to 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, and in order to achieve the above object, a transparent substrate that can transmit the light beam, and each transparent substrate A plurality of light emitting element groups having a plurality of light emitting elements formed on the back surface of the substrate, and a plurality of light emitting element groups formed on the front surface of the transparent substrate in a one-to-one correspondence with each other, and each corresponding light emitting element group And a plurality of imaging lenses that form images of light beams emitted from the plurality of light emitting elements belonging to the scanning surface on the surface to be scanned, and for each of the plurality of light emitting element groups, the light emitting element among the light emitting elements belonging to the light emitting element group The light emitting element that is farthest from the optical axis of the imaging lens corresponding to the group is defined as the outermost element, and the light beam emitted from the outermost element on the surface of the transparent substrate is When an area that can pass without being totally reflected on the surface is defined as an outermost passing area, the radius of the imaging lens corresponding to the light emitting element group is the light of the imaging lens in the outermost passing area. It is characterized by being larger than the distance between the position farthest from the axis and the optical axis.

  The line head configured in this way is configured such that the radius of the imaging lens is larger than the distance between the optical axis of the outermost passing region and the position farthest from the optical axis of the imaging lens. ing. However, the outermost passing region is the light emitting element belonging to the light emitting element group, and the light emitting element farthest from the optical axis of the imaging lens corresponding to the light emitting element group is defined as the outermost element. A region of the surface where the light beam emitted from the outermost element can pass without being totally reflected on the surface. In other words, in the line head according to the present invention, the corresponding imaging lens covers the outermost passing region in which the light beam emitted from the outermost element of the surface of the transparent substrate can pass without being totally reflected. The relationship between the outermost element and the diameter of the imaging lens corresponding to the outermost element is defined. Therefore, substantially all of the light beam that passes through the outermost passage region can be incident on the imaging lens, and a reduction in the amount of light of the light beam incident on the imaging lens from the outermost element can be suppressed. As a result, it is possible to realize a good spot formation by suppressing a decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element.

を満たすように、ラインヘッドを構成しても良い。このように構成されたラインヘッドでは、透明基板の表面のうち最外素子から射出された光ビームが全反射されること無く通過可能である最外通過領域を対応する結像レンズが覆うこととなる。よって、最外素子に対応するスポットの形成に関わる光ビームの光量の減少を抑制して、良好なスポット形成の実現が可能となる。 A line head having a transparent substrate thickness t and a refractive index n may be configured as follows. That is, for each of a plurality of light emitting element groups, when the distance between the outermost element and the optical axis of the imaging lens corresponding to the light emitting element group to which the outermost element belongs is a, and the radius of the imaging lens is R ,

The line head may be configured to satisfy the above. In the line head configured as described above, the corresponding imaging lens covers the outermost passage region in which the light beam emitted from the outermost element can pass without being totally reflected on the surface of the transparent substrate. Become. Therefore, it is possible to realize a favorable spot formation by suppressing a decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element.

  Further, for each of the plurality of light emitting element groups, the line head may be configured such that the plurality of light emitting elements are arranged symmetrically with respect to the optical axis of the imaging lens. This is because the distance a takes the minimum value due to the symmetrical arrangement, and acts advantageously to satisfy the above inequality.

  Further, a line head in which a plurality of imaging lenses are arranged so as to form a lens array in which imaging lenses are arranged at a predetermined lens interval LS in the main scanning direction may be configured as follows. good. That is, the line head may be configured such that the radius R of the imaging lens is smaller than half of the lens interval LS. This is because it is preferable because it is possible to suppress overlapping of imaging lenses adjacent in the main scanning direction.

  A line in which a plurality of imaging lenses are arranged so that lens rows are arranged in m (m is a natural number of 2 or more) rows in the sub-scanning direction substantially orthogonal to the main scanning direction, and the respective positions in the main scanning direction are different from each other. The head may be configured as follows. That is, the line head may be configured such that the positions of the two imaging lenses adjacent in the main scanning direction are different in the sub scanning direction. If this is the case, it is possible to increase the distance between the imaging lenses adjacent in the main scanning direction, and “the radius R of the imaging lens is smaller than half the lens interval LS”. This is because it works advantageously to satisfy the conditions.

  From the viewpoint of satisfying the above conditions, the following configuration may be adopted. That is, the line head may be configured so that two imaging lenses adjacent in the main scanning direction position belong to different lens rows. This is because with such a configuration, the positions of the two imaging lenses adjacent in the main scanning direction are different from each other in the sub-scanning direction, which is advantageous for satisfying the above conditions. .

を満たすようにラインヘッドを構成しても良い。このように構成することで、主走査方向位置が隣り合う２個の発光素子グループそれぞれにより形成されるスポットの主走査方向への配列が良好となり好適である。 In the line head configured as described above, the main scanning direction distance between two imaging lenses whose adjacent positions in the main scanning direction are adjacent to each other is substantially equal to LS / m. The number of light emitting elements included in each light emitting element group is k, and the main scanning direction between two light emitting elements located at both ends in the main scanning direction among the k light emitting elements included in each of the plurality of light emitting element groups. When the distance is b and the absolute value of the optical magnification of each of the plurality of imaging lenses is h, the following formula

The line head may be configured to satisfy the above. Such a configuration is preferable because the arrangement in the main scanning direction of the spots formed by each of the two light emitting element groups adjacent in the main scanning direction is favorable.

  In order to achieve the above object, the image forming apparatus according to the present invention has a latent image carrier whose surface is conveyed in the sub-scanning direction, and the latent image carrier with the surface of the latent image carrier as the surface to be scanned. And an exposure unit having the same configuration as that of the line head for forming spots on the body surface. Accordingly, it is possible to suppress a decrease in the light amount of the light beam incident on the imaging lens from the outermost element. As a result, it is possible to suppress a decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element, and it is possible to realize image formation with a good spot.

  FIG. 1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a view showing the arrangement of image forming stations in the image forming apparatus of FIG. FIG. 3 is a diagram showing an electrical configuration of the image forming apparatus of FIG. This apparatus uses a color mode in which four color toners of yellow (Y), magenta (M), cyan (C) and black (K) are superimposed to form a color image, and only black (K) toner. Thus, the image forming apparatus can selectively execute a monochrome mode for forming a monochrome image. In this image forming apparatus, 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 and the like, the main controller MC gives a control signal to the engine controller EC, and based on this, the engine controller EC The controller EC controls each part of the device such as the engine unit EG and the head controller HC to execute a predetermined image forming operation, and responds to an image forming command on a sheet as a recording material such as a copy sheet, a transfer sheet, a sheet, and an OHP transparent sheet. The image to be formed is formed.

  In the housing main body 3 of the image forming apparatus according to this embodiment, an electrical component box 5 is provided that incorporates a power circuit board, a main controller MC, an engine controller EC, and a head controller HC. An image forming unit 2, a transfer belt unit 8, and a paper feed unit 7 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 feed unit 7 is configured to be detachable from the housing body 3. The paper feeding unit 7 and the transfer belt unit 8 can be removed and repaired or exchanged.

  The image forming unit 2 includes four image forming stations 2Y (for yellow), 2M (for magenta), 2C (for cyan) and 2K (for black) that form a plurality of images of different colors. In FIG. 1, since the image forming stations of the image forming unit 2 have the same configuration, only some of the image forming stations are denoted by reference numerals for convenience of illustration, and the reference numerals are omitted for other image forming stations. To do.

  Each image forming station 2Y, 2M, 2C, and 2K is provided with a photosensitive drum 21 on which a toner image of each color is formed. Each photosensitive drum 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. A charging unit 23, a line head 29, a developing unit 25, and a photoconductor cleaner 27 are disposed around the photoconductive drum 21 along the rotation direction thereof. Then, a charging operation, a latent image forming operation, and a toner developing operation are executed by these functional units. When the color mode is executed, the toner images formed by all the image forming stations 2Y, 2M, 2C, and 2K are superimposed on the transfer belt 81 provided in the transfer belt unit 8 to form a color image. When the monochrome mode is executed, only the image forming station 2K is operated to form a black monochrome image.

  The charging unit 23 includes a charging roller whose surface is made of elastic rubber. The charging roller is configured to rotate in contact with the surface of the photosensitive drum 21 at the charging position, and is driven to rotate as the photosensitive drum 21 rotates. The charging roller is connected to a charging bias generator (not shown). The charging roller is supplied with the charging bias from the charging bias generator and is charged at the charging position where the charging unit 23 and the photosensitive drum 21 come into contact with each other. The surface of 21 is charged to a predetermined surface potential.

  The line head 29 includes a plurality of light emitting elements arranged in the axial direction of the photosensitive drum 21 (a direction perpendicular to the paper surface of FIG. 1), and is disposed to face the photosensitive drum 21. Then, light is emitted from these light emitting elements toward the surface of the photosensitive drum 21 charged by the charging unit 23 to form an electrostatic latent image on the surface.

  The developing unit 25 has a developing roller 251 on which toner is carried. The charged toner is developed at a developing position where the developing roller 251 and the photosensitive drum 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. Moves from the developing roller 251 to the photosensitive drum 21, and the electrostatic latent image formed on the surface thereof is visualized.

  The toner image made visible at the developing position is conveyed in the rotational direction D21 of the photosensitive drum 21, and then is transferred to the transfer belt 81 at a primary transfer position TR1 where the photosensitive belt 21 comes into contact with the transfer belt 81 described later in detail. Primary transcription.

  A photoreceptor cleaner 27 is provided in contact with the surface of the photoreceptor drum 21 on the downstream side of the primary transfer position TR1 in the rotation direction D21 of the photoreceptor drum 21 and on the upstream side of the charging unit 23. The photoconductor cleaner 27 abuts on the surface of the photoconductor drum to remove the toner remaining on the surface of the photoconductor drum 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 an arrow D81 illustrated in FIG. And a transfer belt 81 that is circulated in the direction (conveyance direction). Further, four transfer belt units 8 are arranged on the inner side of the transfer belt 81 so as to be opposed to each of the photosensitive drums 21 included in the image forming stations 2Y, 2M, 2C, and 2K when the cartridge is mounted. Primary transfer rollers 85Y, 85M, 85C and 85K. Each of these primary transfer rollers is electrically connected to a primary transfer bias generator (not shown).

  When the color mode is executed, as shown in FIGS. 1 and 2, all the primary transfer rollers 85Y, 85M, 85C, and 85K are positioned on the image forming stations 2Y, 2M, 2C, and 2K, so that the transfer belt 81 is imaged. A primary transfer position TR1 is formed between each photosensitive drum 21 and the transfer belt 81 by being pushed and brought into contact with the photosensitive drum 21 included in each of the forming stations 2Y, 2M, 2C, and 2K. Then, by applying a primary transfer bias from the primary transfer bias generating unit to the primary transfer roller 85Y or the like at an appropriate timing, the toner images formed on the surface of each photosensitive drum 21 are respectively transferred to the corresponding primary transfer positions. Transfer is performed on the surface of the transfer belt 81 in TR1. That is, in the color mode, the single color toner images of the respective colors are superimposed on the transfer belt 81 to form a color image.

  In the so-called tandem image forming apparatus, the primary transfer position where the toner image is primarily transferred from the photosensitive drum 21 to the transfer belt 81 is different for each image forming station. In this embodiment, the yellow image forming station 2Y, the magenta image forming station 2M, the cyan image forming station 2C, and the black image forming station 2K are arranged in this order along the moving direction of the transfer belt 81. . Accordingly, the yellow primary transfer position TR1y and the magenta primary transfer position TR1m are the distance Lym, the magenta primary transfer position TR1m and the cyan primary transfer position TR1c are the distance Lmc, and the cyan primary transfer position TR1c and the black primary transfer position TR1k are only the distance Lck. Separated.

  On the other hand, when executing the monochrome mode, among the four primary transfer rollers, the primary transfer rollers 85Y, 85M, and 85C are separated from the image forming stations 2Y, 2M, and 2C that face each other, and the primary transfer rollers corresponding to the black color are used. By bringing only 85K into contact with the image forming station 2K, only the monochrome image forming station 2K is brought into contact with the transfer belt 81. As a result, the primary transfer position TR1k is formed only between the primary transfer roller 85K and the image forming station 2K. Then, by applying a primary transfer bias to the primary transfer roller 85K from the primary transfer bias generator at an appropriate timing, a black toner image formed on the surface of the photosensitive drum 21 provided in the image forming station 2K is obtained. A monochrome image is formed by transferring to the surface of the transfer belt 81 at the primary transfer position TR1k.

  Further, the transfer belt unit 8 includes a downstream guide roller 86 disposed on the downstream side of the black primary transfer roller 85K and on the upstream side of the driving roller 82. The downstream guide roller 86 is common to the primary transfer roller 85K and the black photosensitive drum 21 (K) at the primary transfer position TR1 formed by the primary transfer roller 85K contacting the photosensitive drum 21 of the image forming station 2K. It is configured to contact the transfer belt 81 on the tangent line.

  A patch sensor 89 is provided opposite to the surface of the transfer belt 81 wound around the downstream guide roller 86. The patch sensor 89 is composed of, for example, a reflection type photosensor, and optically detects a change in the reflectance of the surface of the transfer belt 81, so that the position and density of the patch image formed on the transfer belt 81 as necessary. Is detected.

  The sheet feeding unit 7 includes a sheet feeding unit having a sheet feeding cassette 77 capable of stacking and holding sheets and a pickup roller 79 that feeds sheets one by one from the sheet feeding cassette 77. The sheet fed from the sheet feeding unit by the pickup roller 79 is adjusted in sheet feeding timing by the registration roller pair 80, and then the drive roller 82 and the secondary transfer roller 121 abut along the sheet guide member 15. Paper is fed to the secondary transfer position TR2.

  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 is secondarily transferred is guided to the 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.

  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. A conductive path of a secondary transfer bias supplied from the bias generation unit via the secondary transfer roller 121 is used. Thus, by providing the driving roller 82 with a rubber layer having high friction and shock absorption, image quality deterioration caused by transmission of the impact to the transfer belt 81 when the sheet enters the secondary transfer position TR2. Can be prevented.

  Further, in this apparatus, a cleaner portion 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.

  In this embodiment, the photosensitive drum 21, the charging unit 23, the developing unit 25, and the photosensitive cleaner 27 of each of the image forming stations 2Y, 2M, 2C, and 2K are unitized as a unit. The cartridge is configured to be detachable from the apparatus main body. Each cartridge is provided with a nonvolatile memory for storing information related to the cartridge. Then, wireless communication is performed between the engine controller EC and each cartridge. Thus, information about each cartridge is transmitted to the engine controller EC, and information in each memory is updated and stored. Based on these pieces of information, the usage history of each cartridge and the lifetime of consumables are managed.

  FIG. 4 is a perspective view schematically showing an embodiment of the line head according to the present invention. FIG. 5 is a cross-sectional view in the sub-scanning direction of one embodiment of the line head according to the present invention. The line head 29 (exposure means) in the present embodiment includes a case 291 whose longitudinal direction is the main scanning direction MD, and positioning pins 2911 and screw insertion holes 2912 are provided at both ends of the case 291. Then, the positioning pin 2911 covers the photosensitive drum 21 and is fitted into a positioning hole (not shown) formed in a photosensitive cover (not shown) positioned with respect to the photosensitive drum 21, thereby The head 29 is positioned with respect to the photosensitive drum 21. Further, the line head 29 is positioned and fixed with respect to the photosensitive drum 21 by screwing and fixing a fixing screw into a screw hole (not shown) of the photosensitive member cover through the screw insertion hole 2912.

  The case 291 has a glass substrate 293 therein. A microlens array 299 is formed on the surface of the glass substrate 293 so as to face the surface of the photosensitive drum 21. In addition, a plurality of light emitting element groups 295 are provided on the back surface of the glass substrate 293 (the surface opposite to the surface on which the microlens array 299 is formed among 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 surface of the glass substrate 293 so as to be separated from each other by a predetermined distance in the main scanning direction MD and the sub scanning direction SD. Here, each of the plurality of light emitting element groups 295 is configured by two-dimensionally arranging a plurality of light emitting elements. In the present embodiment, organic EL (Electro-Luminescence) is used as the light emitting element. That is, in the present embodiment, the organic EL is disposed as a light emitting element on the back surface of the glass substrate 293. A light beam emitted from each of the plurality of light emitting elements toward the photosensitive drum 21 is directed to the microlens array 299 through the glass substrate 293 (transparent substrate). Then, the light beam incident on the microlens array 299 is imaged as a spot on the surface of the photosensitive drum 21.

  As shown in FIG. 5, the back cover 2913 is pressed against the case 291 through the glass substrate 293 by the fixing device 2914. That is, the fixing device 2914 has an elastic force that presses the back cover 2913 toward the case 291, and presses the back cover 2913 with the elastic force, so that the inside of the case 291 is light-tight (that is, inside the case 291). From the outside of the case 291 so that no light leaks from 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. 6 is a perspective view schematically showing the microlens array. FIG. 7 is a cross-sectional view of the microlens and the glass substrate 293. The microlens array 299 is formed on the surface of a glass substrate 293 (transparent substrate). More specifically, the microlens array 299 includes a plurality of microlenses ML formed on the surface of the glass substrate 293. Such microlenses ML can be directly formed on the surface of the glass substrate 293 by resin. The plurality of microlenses ML are two-dimensionally arranged at a predetermined distance from each other in the main scanning direction MD and the sub-scanning direction SD corresponding to the arrangement of the light emitting element groups 295.

  Each of the plurality of microlenses ML forms an image of the light beam from the light emitting element 2951 of the corresponding light emitting element group 295 on the surface of the photosensitive drum 21 with a predetermined optical magnification. At this time, the light beam emitted from the light emitting element 2951 rotates 180 ° with respect to the optical axis OA of the microlens ML and forms an image on the surface of the photosensitive drum 21. That is, a spot is formed as an inverted image of the light emitting element 2951 on the surface of the photosensitive drum 21. In this specification, the characteristic of the microlens ML that forms an image inverted with respect to the optical axis OA on the surface of the photosensitive drum 21 is referred to as “inversion characteristic” in this specification.

  FIG. 8 is a diagram showing the arrangement of light emitting element groups and microlenses. As shown in the figure, in the present embodiment, a plurality of light emitting element groups 295 are two-dimensionally arranged at a predetermined interval from each other in the main scanning direction MD and the sub-scanning direction SD. A plurality of microlenses ML (imaging lenses) are arranged in one-to-one correspondence with the plurality of light emitting element groups 295. As shown in the figure, the plurality of microlenses ML are arranged so as to form a lens row RML in which the microlenses ML are arranged in the main scanning direction MD at a lens interval LS. The lens rows RML are arranged in three rows in the sub-scanning direction SD, and the plurality of microlenses ML are arranged so that their positions in the main scanning direction are different. The plurality of microlenses ML are arranged such that the positions of the two microlenses ML adjacent in the main scanning direction are different from each other in the subscanning direction. That is, two microlenses ML adjacent in the main scanning direction position belong to different lens rows RML, and the main scanning direction distance between the two microlenses ML is substantially equal to LS / m. A plurality of microlenses ML are arranged. Here, the value m is the number of lens rows RML arranged in the sub-scanning direction SD, and in this embodiment, m = 3. The radius R of the microlens ML is set to be smaller than half the lens interval LS.

  FIG. 9 is a diagram showing the relationship between the light emitting element and the diameter of the microlens. As shown in the figure, in the present embodiment, the light emitting element group 295 is configured by eight light emitting elements 2951 arranged two-dimensionally. Further, these eight light emitting elements 2951 are disposed symmetrically with respect to the optical axis OA of the microlens ML. And the diameter of the micro lens ML is comprised as follows with respect to the outermost element OM2951 which is a light emitting element most distant from the optical axis OA of the microlens ML among the eight light emitting elements 2951. That is, the radius R of the microlens ML is determined from the distance I between the optical axis OA and the position farthest from the optical axis OA of the microlens ML in the outermost passing region OMTA (the region surrounded by the broken line in FIG. 9). Is also set larger. Here, the outermost passing region OMTA is a region through which the light beam emitted from the outermost element OM2951 can pass without being totally reflected on the surface of the glass substrate 293.

で与えられる。この理由について説明する。 The relationship between the glass substrate 293 (transparent substrate) and the outermost passage region OMTA will be described with reference to FIG. When the thickness of the glass substrate 293 (transparent substrate) is t and the refractive index is n, the radius r of the outermost passage region OMTA is

Given in. The reason for this will be described.

が成立する。 On the boundary line of the outermost passing region OMTA, the light beam emitted from the outermost element OM2951 is totally reflected. That is, the light beam emitted from the outermost element OM2951 is totally reflected at the point P which is the right end portion of the outermost passage region OMTA in the figure. Therefore, when the angle formed between the normal line of the surface of the glass substrate 293 and the light beam from the outermost element OM2951 toward the point P is θ,

Is established.

が成立することを利用すると、数４は次式のように変形できる。 here

4 can be transformed as shown in the following equation.

が導かれる。 And solving Equation 6 for radius r,

Is guided.

で与えられることとなる。ここで、値ａは、最外素子ＯＭ２９５１と該最外素子ＯＭ２９５１が属する発光素子グループ２９５に対応するマイクロレンズＭＬの光軸ＯＡとの距離である。 Therefore, in this embodiment, as shown in FIG.

Will be given. Here, the value a is the distance between the outermost element OM2951 and the optical axis OA of the microlens ML corresponding to the light emitting element group 295 to which the outermost element OM2951 belongs.

を満たすことで、マイクロレンズＭＬの半径Ｒが距離Ｉよりも大きくなるように構成されている。 That is, in this embodiment, the radius R of the microlens ML (imaging lens) is expressed by the following equation.

By satisfying the above, the radius R of the microlens ML is configured to be larger than the distance I.

が成立するように、レンズ間隔ＬＳを設定している。また、上述の通り、マイクロレンズＭＬの半径Ｒは、レンズ間隔ＬＳの半分よりも小さく設定されている。 In the present embodiment, the lens interval LS is set as follows. That is, the number of the light emitting elements 2951 included in each of the light emitting element groups 295 is k (in this embodiment, k = 8), and among the k light emitting elements 2951 included in the light emitting element group 295, both ends in the main scanning direction MD. When the distance in the main scanning direction between the two light emitting elements 2951 positioned at 2 is b (FIG. 9) and the absolute value of the optical magnification of the microlens ML is h,

The lens interval LS is set so that. Further, as described above, the radius R of the microlens ML is set to be smaller than half of the lens interval LS.

を満たすこととなる。なお、レンズ間隔ＬＳを上記のように設定する理由については後述する。 Therefore, in this embodiment, the radius R of the microlens ML is expressed by the following inequality.

Will be satisfied. The reason for setting the lens interval LS as described above will be described later.

  10 and 11 are explanatory diagrams of the operation of the line head in the present embodiment. Hereinafter, the spot forming operation by the line head 29 in this embodiment will be described with reference to FIGS. 3, 10, and 11. In order to facilitate understanding of the invention, here, a case where a plurality of spots are formed side by side at equal intervals on a straight line extending in the main scanning direction MD will be described. In the present embodiment, a plurality of light emitting elements 2951 are caused to emit light at a predetermined timing by the head control module 54 while transporting the surface (scanned surface) of the photosensitive drum 21 (latent image carrier) in the sub scanning direction SD. Thus, a plurality of spots are formed side by side on a straight line extending in the main scanning direction MD.

  That is, in the line head 29 of the present embodiment, six light emitting element rows R2951 are arranged side by side in the sub-scanning direction SD corresponding to each position of the sub-scanning direction positions SD1 to SD6 (FIG. 10). Therefore, in this embodiment, the light emitting element rows R2951 at the same sub-scanning direction position emit light at substantially the same timing, and the light emitting element rows R2951 at different sub-scanning direction positions emit light at different timings. More specifically, the light emitting element array R2951 is caused to emit light in the order of the sub scanning direction positions SD1 to SD6. A plurality of spots are formed side by side on a straight line extending in the main scanning direction MD on the surface by causing the light emitting element array R2951 to emit light in the order described above while transporting the surface of the photosensitive drum 21 in the sub scanning direction SD. To do.

  Such an operation will be described with reference to FIGS. First, the light emitting elements 2951 of the light emitting element row R2951 in the sub scanning direction position SD1 belonging to the most upstream light emitting element groups 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emission operation are reversed and imaged on the surface of the photosensitive drum by the microlens ML having the above reversal 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 R2951 in the sub scanning direction position SD2 belonging to the light emitting element groups 295A1, 295A2, 295A3,. The plurality of light beams emitted by the light emission operation are reversed and imaged on the surface of the photosensitive drum by the microlens ML having the above reversal characteristics. That is, a spot is formed at the position of the “second” hatching pattern in FIG. Here, while the conveyance direction of the surface of the photosensitive drum 21 is the sub-scanning direction SD, the light emitting element rows R2951 on the downstream side in the sub-scanning direction SD are sequentially (that is, at the sub-scanning direction positions SD1 and SD2). The reason why the light is emitted in order is that the microlens ML has a reversal characteristic.

  Next, the light emitting elements 2951 of the light emitting element row R2951 in the sub scanning direction position SD3 belonging to the second light emitting element group 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emission operation are reversed and imaged on the surface of the photosensitive drum by the microlens ML having the above reversal 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 R2951 in the sub scanning direction position SD4 belonging to the light emitting element groups 295B1, 295B2, 295B3,. The plurality of light beams emitted by the light emission operation are reversed and imaged on the surface of the photosensitive drum by the microlens ML having the above reversal 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 R2951 in the sub scanning direction position SD5 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emission operation are reversed and imaged on the surface of the photosensitive drum by the microlens ML having the above reversal 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 R2951 in the sub scanning direction position SD6 belonging to the light emitting element groups 295C1, 295C2, 295C3,. The plurality of light beams emitted by the light emission operation are reversed and imaged on the surface of the photosensitive drum by the microlens ML having the above reversal 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 MD.

を満たすように構成されている。そして、このように構成することで、マイクロレンズＭＬ（結像レンズ）の半径Ｒが、最外通過領域ＯＭＴＡのうち該マイクロレンズＭＬの光軸ＯＡから最も離れた位置と該光軸との距離Ｉよりも大きくなる。つまり、本実施形態におけるラインヘッド２９では、ガラス基板２９３（透明基板）の表面のうち最外素子ＯＭ２９５１から射出された光ビームが全反射されること無く通過可能である最外通過領域ＯＭＴＡを対応するマイクロレンズＭＬが覆うように、最外素子ＯＭ２９５１と該最外素子ＯＭ２９５１に対応するマイクロレンズＭＬの径との関係が規定されている。よって、最外通過領域ＯＭＴＡを通過する光ビームの略全てをマイクロレンズＭＬに入射させて、最外素子ＯＭ２９５１からマイクロレンズＭＬに入射する光ビームの光量の減少を抑制することが可能となる。そして、その結果、最外素子ＯＭ２９５１に対応するスポットの形成に関わる光ビームの光量の減少を抑制して、良好なスポット形成の実現が可能となっている。 Thus, in the line head 29 in the present embodiment, the radius R of the microlens ML is expressed by the following equation.

It is configured to satisfy. With this configuration, the radius R of the micro lens ML (imaging lens) is the distance between the optical axis and the position farthest from the optical axis OA of the micro lens ML in the outermost passage region OMTA. Larger than I. That is, the line head 29 in the present embodiment corresponds to the outermost passing region OMTA in which the light beam emitted from the outermost element OM2951 can pass without being totally reflected on the surface of the glass substrate 293 (transparent substrate). The relationship between the outermost element OM2951 and the diameter of the microlens ML corresponding to the outermost element OM2951 is defined so as to cover the microlens ML. Therefore, almost all of the light beam that passes through the outermost passage region OMTA can be incident on the microlens ML, and the decrease in the amount of light of the light beam incident on the microlens ML from the outermost element OM2951 can be suppressed. As a result, it is possible to suppress the decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element OM2951, and to realize good spot formation.

  In the line head 29 in the present embodiment, a plurality of light emitting elements 2951 are preferably arranged symmetrically with respect to the optical axis OA of the corresponding microlens ML. This is because the distance a takes a local minimum value, which is advantageous for satisfying the equation (1).

  Further, the line head 29 in the present embodiment is preferably configured so that the radius R of the microlens ML is smaller than half the lens interval LS. This is because it is possible to suppress overlapping of the microlenses ML adjacent in the main scanning direction MD.

  In the present embodiment, the line head 29 is configured such that two microlenses ML whose positions in the main scanning direction are adjacent belong to different lens rows RML. Therefore, the sub-scanning direction positions of the two microlenses ML adjacent in the main scanning direction position are different from each other, which is preferable. If this is the case, it is possible to increase the distance between the adjacent microlenses ML in the main scanning direction MD. “The radius R of the microlens ML is smaller than half the lens interval LS. This is because it advantageously works to satisfy the condition "

を満たすようにラインヘッド２９を構成している。よって、主走査方向位置が隣り合う２個の発光素子グループ２９５それぞれにより形成されるスポットの主走査方向ＭＤへの配列が良好となり好適である。この理由を次に説明する。 In the present embodiment, the main scanning direction distance between two microlenses ML adjacent in the main scanning direction position is substantially equal to LS / m, and each of the plurality of light emitting element groups 295 is further configured. The number of the light emitting elements 2951 included in each of the plurality of light emitting element groups 295 and the k light emitting elements 2951 included in each of the plurality of light emitting element groups 295 is the main scanning direction between the two light emitting elements 2951 positioned at both ends in the main scanning direction. When the distance is b and the absolute value of the optical magnification of each of the plurality of microlenses ML (imaging lens) is h,

The line head 29 is configured to satisfy the above. Therefore, the arrangement in the main scanning direction MD of the spots formed by each of the two light emitting element groups 295 whose main scanning direction positions are adjacent to each other is favorable. The reason for this will be described next.

  FIG. 12 is a diagram illustrating spot formation by two light emitting element groups whose positions in the main scanning direction are adjacent to each other. That is, the figure shows spots formed side by side in the main scanning direction MD on the surface to be scanned by the light emitting element groups 295A and 295B whose positions in the main scanning direction are adjacent to each other. In the present embodiment, m lens rows RML are arranged in the sub-scanning direction SD, and the lens interval between the microlenses ML adjacent to each other in the main scanning direction MD in one lens row is LS. The lens interval LS is equal to the interval between the light emitting element groups 295 adjacent in the main scanning direction MD. Therefore, the interval between the light emitting element groups 295A and 295B adjacent to each other in the main scanning direction is LS / m.

で与えられる。つまり、同図に示すように、主走査方向位置が隣り合う２個の発光素子グループ２９５Ａ，２９５Ｂにより、長さが数１０で与えられるスポット列が２個並べて形成されることとなる。 The number of light emitting elements 2951 included in one light emitting element group 295 is k (in this embodiment, k = 8). Accordingly, a spot row in which k spots are arranged in the main scanning direction MD is formed on the surface to be scanned by one light emitting element group 295. Here, in this specification, k spots formed by arranging one light emitting element group in the main scanning direction MD are referred to as a spot row. By the way, the distance between two spots positioned at the end of the spot row in the main scanning direction is given by h · b. Therefore, considering that the distance h · b corresponds to the length of (k−1) spots, the length of the spot row in the main scanning direction is given by

Given in. That is, as shown in the figure, two spot rows having a length of several 10 are formed side by side by two light emitting element groups 295A and 295B whose positions in the main scanning direction are adjacent to each other.

を満たすように、ラインヘッド２９を構成している。このように構成した場合、１つのスポット列におけるスポット間隔と、主走査方向に隣り合うスポット列の間隔とが等しくなる。よって、主走査方向位置が隣り合う２個の発光素子グループ２９５Ａ，２９５Ｂにより、主走査方向ＭＤに並んで形成される複数のスポットのスポット間隔が全て等しくなる。したがって、主走査方向位置が隣り合う２個の発光素子グループ２９５それぞれにより形成されるスポットの主走査方向ＭＤへの配列が良好となり好適である。 Therefore, in the present embodiment, the distance LS / m between the light emitting element groups 295A and 295B is equal to the value given by Equation 10, that is, the lens distance LS is expressed by the following equation.

The line head 29 is configured to satisfy the above. When configured in this manner, the spot interval in one spot row is equal to the interval between adjacent spot rows in the main scanning direction. Therefore, the two light emitting element groups 295A and 295B whose positions in the main scanning direction are adjacent to each other make the spot intervals of a plurality of spots formed side by side in the main scanning direction MD all equal. Therefore, the arrangement of the spots formed by the two light emitting element groups 295 adjacent in the main scanning direction position in the main scanning direction MD is favorable.

  The image forming apparatus according to the present embodiment includes the line head 29 as an exposure unit that forms spots with the surface of the photosensitive drum 21 (latent image carrier) as a surface to be scanned. Therefore, it is possible to suppress a decrease in the light amount of the light beam incident on the microlens ML from the outermost element OM2951. As a result, it is possible to suppress a decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element OM2951, and it is possible to realize image formation with a good spot.

  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. In other words, in the above-described embodiment, the light emitting element group 295 is configured by arranging two light emitting element rows R2951 configured by arranging four light emitting elements 2951 in the main scanning direction MD in the sub scanning direction SD (FIGS. 9 and 10). ). However, the configuration of the light emitting element group 295 is not limited to this, and may be configured as follows.

  FIG. 13 is a diagram showing another embodiment of the line head according to the present invention. As shown in FIG. 13, in another embodiment, a light emitting element group 295 is configured by arranging three light emitting element rows R2951 arranged in the main scanning direction MD in the sub scanning direction SD. More specifically, in the embodiment shown in FIG. 13, a light emitting element row R2951 configured by arranging five light emitting elements 2951 in the main scanning direction MD is arranged in the upper stage and the lower stage of the figure, and in the middle stage of the figure. A light emitting element row R2951 configured by arranging six light emitting elements 2951 in the main scanning direction MD is arranged. That is, in the embodiment illustrated in FIG. 13, the light emitting element group 295 is configured by 16 light emitting elements 2951. That is, in the embodiment shown in FIG. 13, the number k of light emitting elements in one light emitting element group 295 is set to 16.

を満たすように構成されている。そして、このように構成することで、マイクロレンズＭＬ（結像レンズ）の半径Ｒが、最外通過領域ＯＭＴＡのうち該マイクロレンズＭＬの光軸ＯＡから最も離れた位置と該光軸との距離Ｉよりも大きくなる。つまり、図１３に示す実施形態においても、最外通過領域ＯＭＴＡを対応するマイクロレンズＭＬが覆うように、最外素子ＯＭ２９５１と該最外素子ＯＭ２９５１に対応するマイクロレンズＭＬの径との関係が規定されている。よって、最外通過領域ＯＭＴＡを通過する光ビームの略全てをマイクロレンズＭＬに入射させて、最外素子ＯＭ２９５１からマイクロレンズＭＬに入射する光ビームの光量の減少を抑制することが可能となる。そして、その結果、最外素子ＯＭ２９５１に対応するスポットの形成に関わる光ビームの光量の減少を抑制して、良好なスポット形成の実現が可能となっている。 Also in the embodiment shown in FIG. 13, the radius R of the microlens ML is given by

It is configured to satisfy. With this configuration, the radius R of the micro lens ML (imaging lens) is the distance between the optical axis and the position farthest from the optical axis OA of the micro lens ML in the outermost passage region OMTA. Larger than I. That is, also in the embodiment shown in FIG. 13, the relationship between the outermost element OM2951 and the diameter of the microlens ML corresponding to the outermost element OM2951 is defined so that the corresponding microlens ML covers the outermost passage area OMTA. Has been. Therefore, almost all of the light beam that passes through the outermost passage region OMTA can be incident on the microlens ML, and the decrease in the amount of light of the light beam incident on the microlens ML from the outermost element OM2951 can be suppressed. As a result, it is possible to suppress the decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element OM2951, and to realize good spot formation.

  Also in the embodiment shown in FIG. 13, a plurality of light emitting elements 2951 are preferably arranged symmetrically with respect to the optical axis OA of the corresponding microlens ML. This is because the distance a takes a local minimum value, which is advantageous for satisfying the equation (1).

  In the embodiment shown in FIG. 13, b defines the distance in the main scanning direction between two light emitting elements 2951 located at both ends of the main scanning direction MD among the k light emitting elements 2951 included in the light emitting element group. it can. Therefore, by arranging the microlens ML so as to satisfy Equation 2 as in the embodiments shown in FIGS. 8, 9, 10, etc., the positions in the main scanning direction are formed by two adjacent light emitting element groups 295, respectively. This is preferable because the arrangement of the spots in the main scanning direction MD is favorable.

  Moreover, 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.

  In the above embodiment, the k light emitting elements 2951 belonging to the light emitting element group 295 are arranged symmetrically with respect to the optical axis OA. However, such arrangement is not an essential requirement for the present invention. However, by arranging in this way, the distance a becomes the minimum value, which advantageously works to satisfy the inequality represented by the above formula 1, and as a result, good spot formation is easily realized. It is suitable.

  In the above embodiment, three lens rows RML are arranged in the sub-scanning direction SD, but the number of lens rows RML is not limited to this, and can be changed as necessary. That is, the number of lens rows RML may be one or two, or three or more.

  Moreover, in the said embodiment, although comprised so that the lens space | interval LS might satisfy | fill several 2, it is not an essential requirement for this invention that the lens space | interval LS satisfy | fills several 2. However, in the case of such a configuration, the arrangement in the main scanning direction MD of the spots formed by the two light emitting element groups 295 whose positions in the main scanning direction are adjacent to each other is favorable and is preferable as described above. It is.

  In the above embodiment, the line head according to the present invention is used to form a plurality of spots arranged in a straight line at equal intervals in the main scanning direction MD 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 executed by the line head is not limited thereto. That is, regardless of the specific operation of the line head 29, the relationship between the outermost element OM2951 and the diameter of the microlens ML corresponding to the outermost element OM2951 so that the corresponding microlens ML covers the outermost passage area OMTA. By defining the above, it is possible to achieve the effect of the present invention that realizes favorable spot formation by suppressing the decrease in the light amount of the light beam related to the formation of the spot corresponding to the outermost element OM2951.

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

1 is a diagram showing an embodiment of an image forming apparatus according to the present invention. FIG. 2 is a diagram illustrating an arrangement of image forming stations in the image forming apparatus of FIG. 1. 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. Sectional drawing of the subscanning direction of one Embodiment of the line head concerning this invention. The perspective view which shows the outline of a microlens array. Sectional drawing of a microlens and a glass substrate (transparent substrate). The figure which shows arrangement | positioning of a light emitting element group and a micro lens. The figure which shows the relationship between the diameter of a light emitting element and a micro lens. FIG. 6 is an operation explanatory diagram of the line head in the embodiment. FIG. 6 is an operation explanatory diagram of the line head in the embodiment. The figure which shows the spot formation by the light emitting element group where the main scanning direction position is adjacent. The figure which shows another embodiment of the line head concerning this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 21 ... Photosensitive drum (latent image carrier), 29 ... Line head (exposure means), 295 ... Light emitting element group, 2951 ... Light emitting element, OM2951 ... Outermost element, 293 ... Glass substrate (transparent substrate), 299 ... Micro Lens array, ML: Microlens (imaging lens), OMTA ... Outermost pass region, OA ... Optical axis, RML ... Lens array, MD ... Main scanning direction, SD ... Sub-scanning direction, t ... Thickness of transparent substrate, n: refractive index of transparent substrate, a: distance between outermost element and optical axis, R: radius of micro lens, LS: lens interval, m: number of lens rows, k: number of light emitting elements, h: micro Absolute value of optical magnification of lens, r: radius of outermost passage region, P: point at end of outermost passage region, θ: normal of surface of glass substrate (transparent substrate) and point P from outermost element Light toward Angle formed by the over-time

Claims (8)

In a line head that forms a spot by imaging a light beam on a surface to be scanned,
A transparent substrate capable of transmitting a light beam;
A plurality of light emitting element groups each having a plurality of light emitting elements formed on the back surface of the transparent substrate;
A light beam emitted from a plurality of light emitting elements belonging to the corresponding light emitting element group is formed on the surface of the transparent substrate in a one-to-one correspondence with the plurality of light emitting element groups. And a plurality of imaging lenses for imaging
For each of the plurality of light emitting element groups, out of the light emitting elements belonging to the light emitting element group, the light emitting element farthest from the optical axis of the imaging lens corresponding to the light emitting element group is defined as the outermost element, and the transparent substrate The imaging lens corresponding to the light emitting element group is defined as an outermost passing region where a light beam emitted from the outermost element can pass through the surface without being totally reflected on the surface. The line head is characterized in that the radius is larger than the distance between the optical axis of the outermost passing region and the position farthest from the optical axis of the imaging lens. The line head according to claim 1, wherein the transparent substrate has a thickness t and a refractive index n.
For each of the plurality of light emitting element groups, a represents the distance between the outermost element and the optical axis of the imaging lens corresponding to the light emitting element group to which the outermost element belongs, and R represents the radius of the imaging lens. When

Meet the line head.   3. The line head according to claim 1, wherein, for each of the plurality of light emitting element groups, the plurality of light emitting elements are arranged symmetrically with respect to an optical axis of the imaging lens. The line head according to any one of claims 1 to 3, wherein the plurality of imaging lenses are arranged so as to form a lens array in which the imaging lenses are arranged at a predetermined lens interval LS in the main scanning direction. And
A line head in which a radius R of the imaging lens is smaller than half of the lens interval LS. The lens arrays are arranged in m (m is a natural number of 2 or more) in the sub-scanning direction substantially orthogonal to the main scanning direction, and the plurality of imaging lenses are arranged so that the positions in the main scanning direction are different from each other. The line head according to claim 4,
Line heads in which the positions of two imaging lenses adjacent in the main scanning direction are different in the sub scanning direction.   The line head according to claim 5, wherein two imaging lenses adjacent in a main scanning direction position belong to different lens rows. The line head according to claim 5 or 6, wherein a distance in the main scanning direction between two imaging lenses having adjacent positions in the main scanning direction is substantially equal to LS / m,
The number of the light emitting elements included in each of the plurality of light emitting element groups is k, and two light emitting elements positioned at both ends in the main scanning direction among the k light emitting elements included in each of the plurality of light emitting element groups. Where b is the distance in the main scanning direction and h is the absolute value of the optical magnification of each of the plurality of imaging lenses.

Meet the line head. A latent image carrier whose surface is conveyed in the sub-scanning direction;
An exposure unit having the same configuration as the line head according to claim 1, wherein spots are formed on the surface of the latent image carrier using the surface of the latent image carrier as a surface to be scanned. Image forming apparatus.

Images