JP4552630B2 - Color image forming apparatus - Google Patents

Description

  The present invention relates to a color image forming apparatus that prevents deterioration in image quality due to a change in imaging area in a main scanning direction when forming a color image of a plurality of colors.

  In an image forming apparatus that performs optical writing, a method of providing a scanning optical system as an exposure device and a method of using a light emitting element array are known. For example, Patent Document 1 describes an example of a tandem image forming apparatus that forms a color image of four colors using a light emitting element array in which light emitting elements are integrated on a single substrate.

JP 11-138899 A

  When an optical system such as a light emitting element array is used, an equal-magnification optical system using a rod lens array having a rod lens is generally used as an imaging optical system for the line head. FIG. 11 is an explanatory view showing an example using such a line head. In FIG. 11A, the line head 23 uses a gradient index rod lens array (SLA). Reference numeral 63 denotes a light emitting portion (light emitting element), 51 denotes a plurality of light emitting elements 63 arranged in the main scanning direction, for example, cyan light emitting element lines, and 84 denotes a rod lens.

  C. L is the center line of the SLA, and D is the diameter of the rod lens 84. As shown in FIG. 11B, the light emitted from the light emitting element 63 passes through the rod lens 84 and forms an image in the shape of spots 92 and 93 on the irradiated surface such as an image carrier. Here, the spot 92 has a normal shape with a diameter d, and the spot 93 has a shape with a diameter enlarged to d + a in the main scanning direction.

  The spot 92 corresponds to the surface irradiated by the light emitting element at a position away from the rod lens adjacent to each other, and the spot 93 corresponds to the surface irradiated by the light emitting element near the boundary of the rod lens adjacent to each other. is doing. Thus, even if the light emitting element 2 is the same size, the relative positional relationship between the light emitting element 63 and the rod lens 84, that is, the position in the main scanning direction of the rod lens through which the light emitted from the light emitting element 63 is transmitted. Thus, the spot shape in the main scanning direction is different.

  The reason why the shapes of the spots 92 and 93 are different in the main scanning direction due to the relative positional relationship between the light emitting element 63 and the rod lens 84 as shown in FIG. 11 will be described with reference to the characteristic diagram of FIG. In FIG. 12A, the horizontal axis indicates the distance x, and the vertical axis indicates the width s of the spot in the main scanning direction. D is the diameter of the rod lens 84 as described in FIG. 11, and corresponds to the period of the characteristic G.

  As shown in FIG. 12B, in the valley portion of the characteristic G, the spot 92 has a diameter d. Further, at the peak portion of the characteristic G, the diameter of the spot 93 is enlarged to d + a. That is, the spot shape (light beam spreading shape) in the main scanning direction differs with the pitch of the diameter of the rod lens 84. As described above, the relative positional relationship between the light emitting element 63 and the rod lens 84 causes a difference in the spreading shape of the light beam in the main scanning direction. Similarly, the spot shape (light beam spreading shape) may differ in the main scanning direction at the radius pitch of the rod lens 84.

  FIG. 13 is an explanatory diagram showing an example of a spot shape when forming a color image. In FIG. 13, the spot shape of one line in the main scanning direction of each color of cyan (C), magenta (M), yellow (Y), and black (K) is shown. Reference numeral 92 denotes a spot having a normal size described in FIG. 11, and 93 denotes a spot having a large light spreading shape. In this manner, the spot shape of cyan (C) is formed in different sizes in the main scanning direction.

  In each of the colors magenta (M), yellow (Y), and black (K), spots 94, 96, and 98 having normal sizes and spots 95, 97, and 99 having a large light spreading shape are mixed. As shown in FIG. 13, the positions where the spots 92, 95, 97, and 99 having a large light spreading shape are formed are positions where each color is different in the main scanning direction. For this reason, when the image forming apparatus described in Patent Document 1 performs color superposition to form a plurality of color images, there is a problem in that color unevenness occurs and the image quality deteriorates.

  The present invention has been made in view of the above-described problems of the prior art, and its object is to cause unevenness in the imaging area due to the relative positional relationship between the light emitting element and the lens array in the main scanning direction. Another object of the present invention is to provide a color image forming apparatus that prevents deterioration in image quality when forming a color image of a plurality of colors.

In order to achieve the above object, a color image forming apparatus of the present invention comprises an image carrier,
An image forming station including a charging unit, a line head, a developing unit, and a transfer unit, and each of the charging unit, the line head, the developing unit, and the transfer unit disposed around the image carrier. And
In order to correspond to a plurality of colors, it has a plurality of the image carrier and the image forming station,
A tandem color image forming apparatus in which image formation is performed by a recording medium passing through the plurality of image forming stations,
The line head includes a plurality of light emitting elements arranged in the main scanning direction, and a lens array.
The spot shape at the imaging position of the irradiated surface of the image carrier has a first spot that is a first shape and a second spot that is a second shape different from the first shape. The light emitting element and the lens array are arranged so that the first and second spots overlap each other at the same position in the main scanning direction, and the light emitting element is an organic EL element. It is characterized by. According to this configuration, the relative positional relationship between the light emitting element and the lens array prevents color misregistration that occurs because the position at which the large spot of the light spreading shape in the main scanning direction is different for each color. be able to.
The color image forming apparatus of the present invention is characterized in that the light emitting element is an organic EL element. According to this configuration, since the organic EL element that can be manufactured with good linearity in the process is used as the light emitting element, there is an advantage that the light amount unevenness of the light emitting element itself is smaller than the transmitted light amount unevenness of the lens array.

  In addition, the color image forming apparatus of the present invention includes an intermediate transfer member. According to this configuration, in the color image forming apparatus provided with the intermediate transfer member, it is possible to prevent color misregistration caused by unevenness in the imaging area in the main scanning direction.

  In addition, the color image forming apparatus of the present invention serves as a reference based on imaging means for imaging the spot shape in the main scanning direction of each color at the imaging position of the irradiated surface, and data acquired by the imaging means. First setting means for setting the imaging position of the spot formed in the main scanning direction of the color, and second setting means for setting the imaging position of the spot formed in the main scanning direction for each of the other colors Based on the first setting means and the second setting means, the shape of the spot is compared at each imaging position in the main scanning direction, and the color of the spot color of the reference color is different from that of the imaging position. And a calculation unit that calculates a positional deviation in the main scanning direction from the spot-shaped image formation position, and an adjustment unit that aligns the line head in the main scanning direction based on the calculation result of the calculation unit. . According to this configuration, for each spot formation position in the main scanning direction, the positional deviation is calculated by comparing the spot shapes of the reference color and the other colors, and based on the calculation result, the line head in the main scanning direction of each color line head is calculated. Since the positional deviation is adjusted, it is possible to prevent deterioration in image quality due to uneven imaging area with high accuracy.

  In the color image forming apparatus of the present invention, the spot shape is different depending on a relative position of the light emitting element in the main scanning direction with respect to the lens array, and the spot shape is different in a position in the main scanning direction. Is aligned with each color. According to this configuration, the spread position of the light beam by the light emitting elements arranged at positions near the lens adjacent in the main scanning direction at the pitch of the lens diameter or ½ pitch of the diameter is the same at the imaging position of each color. Thus, image quality deterioration can be prevented.

The color image forming apparatus of the present invention is characterized in that the light-emitting element which arranged plurality in the main scanning direction by one column formed in the sub-scanning direction. According to this structure, the main light emitting element which arranged plurality in the scanning direction is one column formed in the sub-scanning direction, one row lens array in the sub-scanning direction, or in a color image forming device formed two rows, imaging It is possible to prevent color misregistration caused by a difference in position in the main scanning direction in which unevenness in area occurs.

The color image forming apparatus of the present invention is characterized in that the light-emitting element which arranged plurality in the main scanning direction and two rows formed in the sub-scanning direction. According to this structure, the main light emitting element which arranged plurality in the scanning direction is two rows formed in the sub-scanning direction, the lens array is in a color image forming device formed two rows in the sub-scanning direction, resulting unevenness of the imaging area It is possible to prevent image quality degradation caused by the difference in the position in the main scanning direction. The light-emitting element which arranged plurality in the main scanning direction is two rows formed in the sub-scanning direction, the lens array is the same action and effect also in a color image forming apparatus which is one column formed in the sub-scanning direction is obtained.

  The color image forming apparatus of the present invention is characterized in that the lens array is formed in one line in the sub-scanning direction. According to this configuration, when the lens array is formed in one row in the sub-scanning direction, in any color image forming apparatus in which the light-emitting element lines are formed in one or two rows in the sub-scanning direction, the imaging area is uneven. It is possible to prevent image quality degradation caused by the difference in the position of the main scanning direction in which the image is generated.

  The color image forming apparatus of the present invention is characterized in that the lens array is formed in two rows in the sub-scanning direction. According to this configuration, when the lens array is formed in two rows in the sub-scanning direction, in any color image forming apparatus in which the light-emitting element lines are formed in one or two rows in the sub-scanning direction, the imaging area is uneven. It is possible to prevent image quality degradation caused by the difference in the position of the main scanning direction in which the image is generated.

The color image forming apparatus of the present invention is characterized in that the light-emitting element which arranged plurality in the main scanning direction to form the sub-scanning direction in three or more rows. According to this configuration, there is an advantage that image quality deterioration can be prevented and the color image forming apparatus can be applied to various uses.

  The color image forming apparatus of the present invention is characterized in that the light emitting element has a double ring structure. According to this configuration, in a color image forming apparatus using a light emitting element having a double ring structure, unevenness in the imaging area can be reduced and image quality can be improved. In this case, it can be arbitrarily selected whether the number of arrangements of the light emitting element lines and the lens arrays in the sub-scanning direction is one column or two columns. It is also possible to arrange three or more light emitting element lines in the sub-scanning direction.

  According to the color image forming apparatus of the present invention, the line head is positioned so that the spot shape at the imaging position on the irradiated surface is the same for each color in the main scanning direction. With such a configuration, it is possible to reduce color unevenness during color superposition and improve image quality.

  The present invention will be described below with reference to the drawings. FIG. 5 is a longitudinal sectional side view of a color image forming apparatus using a line head whose position is adjusted in the main scanning direction according to the present invention. In this embodiment, an intermediate transfer belt is used as the transfer belt. In FIG. 5, an image forming apparatus 1 according to the present embodiment is mounted on a housing body 2, a first opening / closing member 3 that can be opened and closed on the front surface of the housing body 2, and on an upper surface of the housing body 2. And a second opening / closing member 4 (also serving as a paper discharge tray). Further, the first opening / closing member 3 is provided with an opening / closing lid 3 ′ attached to the front surface of the housing body 2 so as to be freely opened and closed.

  In the housing body 2, an electrical component box 5 containing a power circuit board and a control circuit board, an image forming unit 6, a blower fan 7, a transfer belt unit 9, and a paper feeding unit 10 are disposed. In addition, a secondary transfer unit 11, a fixing unit 12, and a recording medium transport unit 13 are disposed in the first opening / closing member 3.

  The transfer belt unit 9 is disposed below the housing body 2 and is driven to rotate by a drive source (not shown), a driven roller 15 disposed obliquely above the drive roller 14, and the two rollers. An intermediate transfer belt 16 that is stretched between 14 and 15 and driven to circulate in the direction of the arrow shown in the figure, and a cleaning means 17 that comes into contact with and separates from the surface of the intermediate transfer belt 16.

  A primary transfer member 21 composed of a leaf spring electrode is brought into contact with the image carrier 20 of each image forming station Y, M, C, K by its elastic force, and a transfer bias is applied to the primary transfer member 21. ing. A test pattern sensor 18 is installed in the transfer belt unit 9 in the vicinity of the drive roller 14. The image forming unit 6 includes a plurality (four in this embodiment) of image forming stations Y (for yellow), M (for magenta), C (for cyan), and K (for black) that form images of different colors. Each of the image forming stations Y, M, C, and K includes an image carrier 20 including a photosensitive drum, and a charging unit 22 and an image writing unit (line head) disposed around the image carrier 20. ) 23 and developing means 24.

  The image carrier 20 is rotationally driven in the conveyance direction of the intermediate transfer belt 16 as indicated by the arrows in the figure. The charging means 22 is composed of a conductive brush roller connected to a high voltage generation source, and the outer periphery of the brush is opposite to the image bearing member 20 as a photosensitive member at a peripheral speed of 2 to 3 times. The surface of the image carrier 20 is uniformly charged by contact rotation.

  The line head 23 uses an organic EL element array in which organic EL elements are arranged in a line in the axial direction of the image carrier 20. The line head using the organic EL element array has an advantage that the optical path length is shorter and more compact than the laser scanning optical system, can be disposed close to the image carrier 20, and the entire apparatus can be downsized. . In the present embodiment, the image carrier 20, the charging unit 22, and the line head 23 of each image forming station Y, M, C, and K are unitized as one image carrier unit 25.

  Next, details of the developing unit 24 will be described on behalf of the image forming station K. The developing unit 24 includes a toner storage container 26 that stores toner (hatched portion in the drawing), a toner storage part 27 formed in the toner storage container 26, and a toner stirring member disposed in the toner storage part 27. 29, and a partition member 30 that is partitioned and formed on the upper portion of the toner storage portion 27.

  Further, the toner supply roller 31 disposed above the partition member 30, the blade 32 provided on the partition member 30 and in contact with the toner supply roller 31, and the toner supply roller 31 and the image carrier 20 are in contact with each other. And a regulating blade 34 that is in contact with the developing roller 33.

  The paper feed unit 10 includes a paper feed unit including a paper feed cassette 35 in which the recording media P are stacked and held, and a pickup roller 36 that feeds the recording media P from the paper feed cassette 35 one by one. In the first opening / closing member 3, a registration roller pair 37 that regulates the feeding timing of the recording medium P to the secondary transfer portion, and a secondary transfer unit that is pressed against the drive roller 14 and the intermediate transfer belt 16. A secondary transfer unit 11, a fixing unit 12, a recording medium conveyance unit 13, a paper discharge roller pair 39, and a duplex printing conveyance path 40 are provided.

  The fixing unit 12 includes a heating roller 45 that includes a heating element such as a halogen heater and is rotatable, a pressure roller 46 that presses and biases the heating roller 45, and is swingable on the pressure roller 46. A belt tension member 47 and a heat-resistant belt 49 stretched between the pressure roller 45 and the belt tension member 47. The color image secondarily transferred to the recording medium is fixed to the recording medium at a predetermined temperature at a nip formed by the heating roller 45 and the heat-resistant belt 49.

  FIG. 6 is a schematic perspective view showing the line head 23 in an enlarged manner. In FIG. 6, a mechanism for accurately positioning the line head 23 with respect to each image carrier (photosensitive drum) 20 attached to the image carrier unit 25 is shown. The organic EL element array 61 is held in a long housing 60. Positioning pins 69 provided at both ends of the long housing 60 are inserted into facing holes in the case of the line head (not shown). The positioning pins 69 and the positioning holes are fitted with a slight gap in the main scanning direction, and the position of the line head in the main scanning direction is set to be adjustable.

  Each image writing means 23 is fixed at a predetermined position by screwing a fixing screw into a screw hole of the case of the line head through screw insertion holes 68 provided at both ends of the long housing 60. . As will be described later, the housing 60 is fixed to the case after the position adjustment in the main scanning direction is completed.

  The line head 23 is driven by a TFT 71 on which the light emitting portion 63 of the organic EL element array 61 is placed on a glass substrate 62 and formed on the same glass substrate 62. The light emitting unit 63 is connected to a cathode that is a common electrode (not shown). The gradient index rod lens array (SLA) 65 constitutes an imaging optical system, and has a gradient index rod lens 84 arranged in front of the light emitting unit 63.

  60 is the housing, and 67 is a fixed leaf spring. The housing 60 covers the periphery of the glass substrate 62 and the side facing the image carrier 20 is open. In this way, light is emitted from the gradient index rod lens 84 to the image carrier 20. A light-absorbing member (paint) is provided on the surface of the housing 60 that faces the end surface of the glass substrate 62.

  FIG. 7 is a cross-sectional view of the line head 23 in the main scanning direction. The glass substrate 62 covers the light emitting unit 63 using an organic EL element with a cover glass 64. The glass substrate 62 in which the light emitting unit 63 is covered with the cover glass 64 is fixed to the housing 60. The glass substrate 62 is covered with the cover 66 and the cover 66 is fixed with a leaf spring 67. As described with reference to FIG. 6, screw insertion holes 68 a and 68 b and positioning pins 69 a and 69 b are provided at both end portions of the housing 60.

  In the present invention, the spread position of the light beam at the image forming position of each color in the main scanning direction is detected. Then, by using a certain color, for example, cyan (C) as a reference, the spread of light rays at the image forming position of the other color in the main scanning direction is matched to prevent occurrence of color unevenness. Hereinafter, a description will be given of the detection of the position of the spot shape in the main scanning direction, that is, the detection of the spread position of the light beam, and the process of aligning the spread position of the light beam at the image forming position of each color in the main scanning direction.

  FIG. 2 is an explanatory diagram showing an example of detecting the spread position of the light beam at the imaging position. In FIG. 2, reference numeral 62 denotes a glass substrate, which is not shown, but as described in FIG. 7, a plurality of light emitting elements, a cathode as a common electrode of each light emitting element, and a cover glass are formed. Reference numeral 66 denotes a cover for covering the glass substrate 62, 65 denotes an SLA, 60 denotes a housing for holding the SLA 65, 90 denotes a CCD camera, and 91 denotes an irradiated surface such as an image carrier.

  3A and 3B are partial views of FIG. 1, in which FIG. 3A is a cross-sectional view in the main scanning direction, and FIG. 3B is a plan view. As described above, the line head is set to be movable in the main scanning direction (arrow X direction). Next, an example of a processing procedure for detecting the spread position of the light beam and aligning the line head of each color in the main scanning direction will be described with reference to FIGS.

  (1) A cover 66 is attached to the glass substrate 62. (2) Insert the SLA 65 into the housing 60, and place and fix it on the stepped portion 60a. (3) The glass substrate 62 with the cover 66 attached is inserted into the housing 60 and attached to the stepped portion 60b. (4) The housing 60 is attached to the case of the line head (not shown). At this time, the fixing screw is loosened so that the housing 60 can be slightly moved in the main scanning direction.

  (4) The light emitting element is caused to emit light to form one line spot in the main scanning direction on the irradiated surface 91. (5) The irradiated surface 91 is imaged by the CCD camera 90. The captured image at this time is a spot-shaped image for one line in the main scanning direction. The captured image is transmitted to a control unit which will be described later with reference to FIG. 3 and stored in the storage unit. (6) The processes (1) to (5) are sequentially performed for each color.

  (7) The control unit performs the following processing. a) Based on the data acquired by the CCD camera 90, the imaging position of each spot formed in the main scanning direction of a reference color, for example, cyan (C) is set. b) For each of the other colors, the imaging position of each spot formed in the main scanning direction is set. c) The shape of each spot is compared at each imaging position in the main scanning direction based on the setting data of the reference color and other colors. d) A positional deviation in the main scanning direction is calculated with respect to the imaging position that is the spreading position of the light beam of the reference color and the imaging position that is the spreading position of the light beam of the other color.

  (8) Based on the positional deviation information of each color in the main scanning direction with respect to the reference color calculated in the control unit, in this example, cyan (C), the spread positions of the light rays on the irradiated surface 91 of other colors are matched. The housing 60 is moved in the direction of arrow X. At this time, positioning is performed by moving the housing 60 while observing with the CCD camera 90. (9) The positioned housing 60 is fixed to the case of the line head with a screw.

  FIG. 4 is a block diagram illustrating a schematic configuration of the control unit of the line head. In FIG. 4, 101 is a control unit, 102 is a spot shape detection unit, and corresponds to the CCD camera 90. Reference numeral 103 denotes a memory, 104 denotes a control circuit, and 105 denotes a drive circuit composed of TFTs. Reference numeral 106 denotes a light emitting unit in which a plurality of light emitting elements are arranged in one line (main scanning direction). In this example, one light emitting element line is formed in the main scanning direction.

  Reference numeral 100 denotes a main body controller. The main body controller 100 forms print data and transmits it to the control unit 101 of the line head. The spot shape detection unit 102 images the spot shape formed on the irradiated surface 91 as described above. The memory 103 stores image data of each color.

  The control circuit 104 reads the image data of each color from the memory 103, and calculates the positional deviation in the main scanning direction between the light spread position of the reference color and the light spread position of the other colors as described above. Further, the control circuit 104 sends a signal to the drive circuit 105 to control the applied voltage or drive current of the light emitting unit 106.

  As described above, the control unit 101 of the line head shown in FIG. 4 includes an imaging unit (spot shape detection unit 102) that images the spot shape of each color in the main scanning direction at the imaging position of the irradiated surface, and a control circuit. 104 is provided. The control circuit 104 is configured to set a first setting unit for setting an imaging position of a spot formed in the main scanning direction of a reference color based on data acquired by the CCD camera, and main scanning for each of the other colors. Based on the second setting means for setting the imaging position of the spot formed in the direction, and the first setting means and the second setting means, the shape of the spot is determined at each imaging position in the main scanning direction. In contrast, it has a function of a calculation means for calculating a positional deviation in the main scanning direction from a spot shape imaging position of another color with respect to a spot shape imaging position of a reference color.

  FIG. 1 is an explanatory diagram showing an embodiment of the present invention. The same parts as those in FIG. 13 are denoted by the same reference numerals, and detailed description thereof is omitted. In the example of FIG. 1, each color line head indicates a spot shape after the position adjustment in the main scanning direction is completed. When the cyan (C) spot shapes 92 and 93 in the main scanning direction are used as a reference, the normal size spots 94, 96, and magenta (M), yellow (Y), and black (K) are also sized. The position of 98 and the positions of spots 95, 97, and 99 having a large light spreading shape are formed at the same position in the main scanning direction. For this reason, when a plurality of colors are superimposed, the occurrence of color unevenness can be prevented.

  FIG. 8 is an explanatory view showing another embodiment of the present invention. In the line head 23a of FIG. 8, the light emitting element lines 51 are arranged in one column in the sub-scanning direction, and the SLA is arranged in two columns in the sub-scanning direction. 84a and 84b are rod lenses of each SLA. In the example of FIG. 8, the spot shape is large at a pitch of the radius (1/2) D of the rod lens. Also in this case, as described above, by performing the alignment of the spot shape in the main scanning direction of the line head of each color, it is possible to prevent the occurrence of color unevenness when a plurality of colors are overlaid. That is, it is possible to prevent image quality degradation caused by the difference in the position in the main scanning direction where the unevenness of the imaging area occurs.

  FIG. 9 is an explanatory view showing another embodiment of the present invention. In FIG. 9, the light emitting element lines 63 are arranged in one column in the sub-scanning direction, and the SLA is arranged in two columns in the sub-scanning direction. 84a and 84b are rod lenses of each SLA. In FIG. 9, a double ring structure is used as shown by the reference numerals 63a and 63b in a partially enlarged view of the light emitting element. 63a is an example in which the light emitting area is reduced, and 63b is an example in which the light emitting area is increased. Even in the example of FIG. 9, it is possible to prevent the occurrence of color unevenness when a plurality of colors are superimposed.

  FIG. 10 is an explanatory view showing another embodiment of the present invention. In FIG. 10, the light emitting element lines 51 and 52 are arranged in two rows in the sub-scanning direction, and the SLA is arranged in two rows in the sub-scanning direction. 84a and 84b are rod lenses of each SLA, and 64 is a cover glass. Y1 is the length between one side edge of the cover glass 64 and the outer tangent line of the rod lens 84a, and Y2 is the length between the other side edge of the cover glass 64 and the outer tangent line of the rod lens 84b. The configuration of FIG. 10 is applicable to various uses such as multiple exposure because the light emitting element lines 51 and 52 are arranged in a plurality of rows in the sub-scanning direction. Even in such a configuration, it is possible to prevent color unevenness when a plurality of colors are superimposed.

  In the image forming apparatus of the present invention, the light emitting element lines are arranged in one or two rows in the sub-scanning direction. SLA is also arranged in one or two rows in the sub-scanning direction. The combination of the number of light emitting element lines and the number of SLA columns can be arbitrarily selected. It is also possible to arrange light emitting element lines in three or more rows in the sub-scanning direction and to apply to uses such as multiple exposure. When three or more light emitting element lines are arranged in the sub-scanning direction, it is possible to appropriately select the SLA to be arranged in one or two rows in the sub-scanning direction.

  When an organic EL element is used for the light emitting part of the line head, the light emitting pixel column is manufactured using a semiconductor process on a single substrate, and therefore its linearity is extremely high compared to conventional LEDs. It becomes possible to comprise. Furthermore, there is an advantage that the unevenness of the light amount of the light emitting element is smaller than the unevenness of the transmitted light amount of the lens array.

  The image forming apparatus of the present invention has been described based on some embodiments. However, the present invention is not limited to these embodiments, and various modifications can be made.

It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is a vertical side view of a color image forming apparatus. It is a perspective view of a line head. It is sectional drawing of the main scanning direction of a line head. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows embodiment of this invention. It is explanatory drawing which shows a spot shape. It is explanatory drawing which shows the example which a spot shape changes periodically. It is explanatory drawing which shows the example of the spot shape at the time of forming a color image.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Color image forming apparatus, 23 ... Line head, 51, 52 ... Light emitting element line, 60 ... Housing, 61 ... Organic EL element array, 62 ... Glass substrate (transparent substrate) ), 63... Light emitting part, 64... Cover glass, 65... Refractive index distribution type rod lens array (SLA), 84. ~ 99 ... Spot shape

Claims (10)

An image carrier;
An image forming station including a charging unit, a line head, a developing unit, and a transfer unit, and each of the charging unit, the line head, the developing unit, and the transfer unit disposed around the image carrier. And
In order to correspond to a plurality of colors, it has a plurality of the image carrier and the image forming station,
A tandem color image forming apparatus in which image formation is performed by a recording medium passing through the plurality of image forming stations,
The line head includes a plurality of light emitting elements arranged in the main scanning direction, and a lens array.
The spot shape at the imaging position of the irradiated surface of the image carrier has a first spot that is a first shape and a second spot that is a second shape different from the first shape. The light emitting element and the lens array are arranged so that the first and second spots overlap each other at the same position in the main scanning direction, and the light emitting element is an organic EL element. A color image forming apparatus.   The color image forming apparatus according to claim 1, further comprising an intermediate transfer member.   An imaging unit that images the spot shape of each color in the main scanning direction at the imaging position of the irradiated surface, and a spot formed in the main scanning direction of a reference color based on data acquired by the imaging unit A first setting means for setting an imaging position; a second setting means for setting an imaging position of a spot formed in the main scanning direction for each of the other colors; the first setting means and the second setting means; Based on the setting means, the shape of the spot is compared at each imaging position in the main scanning direction, and the main scanning direction with respect to the imaging position of the spot shape of the reference color and the imaging position of the spot shape of the other color 3. The apparatus according to claim 1, further comprising: a calculation unit that calculates a positional deviation of the line head; and an adjustment unit that aligns a line head in a main scanning direction based on a calculation result of the calculation unit. Mosquito Over the image forming apparatus.   The spot shape is different depending on the relative position of the light emitting element in the main scanning direction with respect to the lens array, and the position in the main scanning direction where the spot shape is different is aligned with each color. The optical writing device according to claim 1.   5. The color image forming apparatus according to claim 1, wherein a plurality of light emitting elements arranged in the main scanning direction are formed in one line in the sub scanning direction.   5. The color image forming apparatus according to claim 1, wherein a plurality of light emitting elements arranged in the main scanning direction are formed in two rows in the sub scanning direction.   The color image forming apparatus according to claim 5, wherein the lens array is formed in one row in the sub-scanning direction.   7. The color image forming apparatus according to claim 5, wherein the lens array is formed in two rows in the sub-scanning direction.   9. The color image forming apparatus according to claim 7, wherein a plurality of light emitting elements arranged in the main scanning direction are formed in three or more rows in the sub scanning direction. The color image forming apparatus according to claim 1, wherein the light emitting element has a double ring structure.

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