JP2013067142A - Image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make streaks of images inconspicuous.SOLUTION: The image forming apparatus includes a light emitting array 41 which is composed of a plurality of light emitting chips CH disposed by forming a plurality of light emitting elements P on a semiconductor substrate and arranging them in a main scanning direction, and a light emission control device 100 which makes the light emitting elements P of the light emitting array 41 form a dither pattern Z indicative of an image tone. The light emission control device 100 controls lighting timing of the light emitting element P so as to bend an end of at least either one end of a pair of ends corresponding to a connection C of the light emitting chips in a direction to loosen an inclination with respect to the main scanning direction in each of segments of sets LL and LR formed by the light emitting chips CH of the light emitting array 41 when a distance between two light emitting elements located on a joint line of the light emitting chips is larger than a reference value.

Description

  The present invention relates to a technique for making an image stripe inconspicuous.

  Japanese Patent Application Laid-Open No. 2004-133620 discloses a technique for making white stripes inconspicuous by correcting the light amount of the light emitting element at the boundary according to the distance between the LED array chips. Patent Document 2 below proposes a technique in which the gradation of an image is represented by a dither pattern composed of a repetitive pattern of diagonal lines.

JP 2001-080111 A JP 2004-364084 A

  In order to improve the image quality, it is preferable to make the streaks such as white streaks as inconspicuous as possible, and further improvement has been demanded.

  The present invention has been completed based on the above-described circumstances, and an object thereof is to make an image streak inconspicuous.

  An image forming apparatus disclosed in the present specification includes a light emitting array formed of a plurality of light emitting chips arranged in a main scanning direction by forming a plurality of light emitting elements on a semiconductor substrate, and a photosensitive exposed by the light emitting array. An image forming unit that forms an image on a recording medium using an electrostatic latent image formed on the photosensitive member, and the light emitting elements of the light emitting array indicate the gradation of the image in one direction. A light emission control device that forms a dither pattern in which a collection line composed of an aggregate of dots having inclined regularity is repeated in the sub-scanning direction, and the light emission control device is located at a joint between the light emitting chips. When the distance between the two light emitting elements is larger than a reference value, among the pair of end portions corresponding to the joint between the light emitting chips in each assembly line segment formed by each light emitting chip of the light emitting array, Also either side of the end portion, the main as bent inclined to become loose direction with respect to the scanning direction, performs timing control for controlling lighting timing of the light emitting elements corresponding to said end portion. The “arranged in the main scanning direction” includes a pattern in which the light emitting chips are arranged in a line in the main scanning direction and a pattern in which the light emitting chips are arranged in a staggered pattern in the main scanning direction.

  In the image forming apparatus disclosed in this specification, the seam portion can be made to look natural by bending the end portions of the collective line segments. As a result, white lines can be made inconspicuous.

  An image forming apparatus disclosed in the present specification includes a light emitting array formed of a plurality of light emitting chips arranged in a main scanning direction by forming a plurality of light emitting elements on a semiconductor substrate, and a photosensitive exposed by the light emitting array. An image forming unit that forms an image on a recording medium using an electrostatic latent image formed on the photosensitive member, and the light emitting elements of the light emitting array indicate the gradation of the image in one direction. A light emission control device that forms a dither pattern in which a collection line composed of an aggregate of dots having inclined regularity is repeated in the sub-scanning direction, and the light emission control device is located at a joint between the light emitting chips. When a distance between two light emitting elements is smaller than a reference value, among a pair of end portions corresponding to a joint between the light emitting chips in each assembly line segment formed by each light emitting chip of the light emitting array, there are few The ends of both or one side, the main as bent in the direction of inclination steeper with respect to the scanning direction, performs timing control for controlling lighting timing of the light emitting elements corresponding to said end portion.

  In the image forming apparatus disclosed in this specification, the seam portion can be made to look natural by bending the end portions of the collective line segments. Therefore, the color streak can be made inconspicuous.

In the image forming apparatus, the following is preferable.
The light emission control device is configured to bend the both ends of the pair of end portions in a direction in which the inclination with respect to the main scanning direction becomes gentle or in a direction in which the inclination becomes steep, the light emitting elements corresponding to the pair of end portions. Control the lighting timing.

-The said light emission control apparatus controls the lighting timing of the light emitting element corresponding to a pair of said edge part so that the said bent pair of edge part may become a straight line.

-The said light emission control apparatus performs the control of the said lighting timing in the control unit which consists of a several light emitting element by which lighting timing is controlled uniformly.

The light emission control device controls the lighting timing of the light emitting element at the boundary portion so that the boundary portion between the aggregate line segment and the end portion is smoothly connected.

The light emission control device is configured to control the lighting timing of the light emitting element corresponding to the end corresponding to the joint between the light emitting chips, and the light amount of the light emitting element located at the joint between the light emitting chips. It is used in combination with the light amount control that is corrected according to the distance between them.

  According to the present invention, it is possible to make an image streak inconspicuous.

1 is a side sectional view of a main part of a color printer according to an embodiment. Enlarged view of LED unit and process cartridge LED unit viewed from the exposure side Block diagram of light emission control unit and control device Diagram showing the white stripe suppression principle Diagram showing the suppression principle of color streaking Enlarged view of the joints between the line segments (before and after end bending) The figure which shows the lighting timing of the light emitting element The figure which shows the lighting timing of the light emitting element Diagram showing the effect of bending Enlarged view of the joints between the line segments (before and after end bending) Diagram showing the principle of light intensity correction Diagram showing correction value data Diagram showing correction table The flowchart figure which shows the flow of the process performed at the time of print data reception A diagram with curved lines connecting the corners between the line and the end The figure which shows the lighting timing of the light emitting element

<Embodiment>
An embodiment will be described with reference to FIGS.
1. As shown in FIG. 1, an electrophotographic color printer 1 is fed into a main body housing 10 with a paper feeding unit 20 that feeds paper S, which is an example of a recording medium, and the paper is fed. An image forming unit 30 that forms an image on the sheet S, a sheet discharge unit 90 that discharges the sheet S on which the image is formed, and a control device 100 that controls the operation of each unit are provided. In the following description, a direction (right and left direction in FIG. 7) orthogonal to the feeding direction of the paper S is a main scanning direction, and a feeding direction (up and down direction in FIG. 7) is a sub-scanning direction.

  An upper cover 12 that can be opened and closed relative to the main body housing 10 is provided on the upper portion of the main body housing 10 so as to be rotatable up and down around a hinge 12A provided on the rear side. An upper surface of the upper cover 12 serves as a paper discharge tray 13 for accumulating the paper S discharged from the main body housing 10, and an LED unit 40 serving as an exposure device is provided below the upper cover 12.

  Further, a cartridge drawer 15 that detachably accommodates each process cartridge 50 is provided in the main body housing 10. The cartridge drawer 15 is provided with a pair of metal side plates 15A (only one side is shown) provided on the left and right and a cross member 15B connecting the pair of side plates 15A on the front and rear. The side plates 15A are members that are disposed on both sides of the LED array 41 as the exposure head of the LED unit 40 in the left-right direction, and directly or indirectly support and position the photosensitive drum 53. Light emission of the LED array 41 is controlled by the control device 100 and the light emission control unit 110. The control device 100 and the light emission control unit 110 are examples of the light emission control device of the present invention. The photosensitive drum 31 is an example of the photosensitive member of the present invention.

  The paper feeding unit 20 is provided in the lower part of the main body housing 10, and is a paper feeding tray 21 that is detachably attached to the main body housing 10, and a paper that conveys the paper S from the paper feeding tray 21 to the image forming unit 30. A supply mechanism 22 is mainly provided. The paper supply mechanism 22 is provided on the front side of the paper feed tray 21 and mainly includes a paper feed roller 23 and a separation roller 24.

  In the paper feed unit 20 configured as described above, the paper S in the paper feed tray 21 is separated one by one and sent upward, and is turned backward through the transport path 28 to the image forming unit 30. Supplied.

  The image forming unit 30 includes four LED units 40, four process cartridges 50, a transfer unit 70, and a fixing unit 80. The four LED units 40 and the four process cartridges 50 correspond to four colors of black, yellow, magenta, and cyan.

  The process cartridge 50 is arranged side by side in the front-rear direction between the upper cover 12 and the paper feeding unit 20, and as shown in FIG. 2, the drum unit 51 and the developing unit 61 that is detachably attached to the drum unit 51. And. The side plate 15 </ b> A supports the process cartridge 50, and the process cartridge 50 supports the photosensitive drum 53. Each process cartridge 50 has the same configuration except that the color of the toner stored in the toner storage chamber 66 of the developing unit 61 is different.

  The drum unit 51 mainly includes a drum frame 52, a photosensitive drum 53 as an example of a photosensitive member rotatably supported by the drum frame 52, and a scorotron charger 54.

  The developing unit 61 includes a developing frame 62, a developing roller 63 and a supply roller 64 that are rotatably supported by the developing frame 62, and includes a toner storage chamber 66 that stores toner. In the process cartridge 50, the developing unit 61 is mounted on the drum unit 51, whereby an exposure hole 55 is formed between the developing frame 62 and the drum frame 52 so as to face the photosensitive drum 53 from above. The LED unit 40 holding the LED array 41 at the lower end is inserted into the exposure hole 55. Details of the LED array 41 will be described later.

  As shown in FIG. 1, the transfer unit 70 is provided between the paper feeding unit 20 and each process cartridge 50, and mainly includes a drive roller 71, a driven roller 72, a conveyance belt 73, and a transfer roller 74.

  The driving roller 71 and the driven roller 72 are spaced apart and arranged in parallel in the front-rear direction, and a conveyor belt 73 is stretched therebetween. The outer surface of the conveyor belt 73 is in contact with each photosensitive drum 53. In addition, four transfer rollers 74 that sandwich the conveyor belt 73 between the photosensitive drums 53 are arranged inside the conveyor belt 73 so as to face the photosensitive drums 53. A transfer bias is applied to the transfer roller 74 by constant current control during transfer.

  The fixing unit 80 is disposed on the back side of each process cartridge 50 and the transfer unit 70, and includes a heating roller 81 and a pressure roller 82 that is disposed to face the heating roller 81 and presses the heating roller 81.

  In the image forming unit 30 configured as described above, first, the surface (photosensitive surface 53A) of each photosensitive drum 53 is uniformly charged by the scorotron charger 54 and then irradiated from each LED array 41. It is exposed by LED light. As a result, the potential of the exposed portion is lowered, and an electrostatic latent image based on the image data is formed on each photosensitive drum 53.

  Further, the toner in the toner storage chamber 66 is supplied and carried on the developing roller 63 by the rotation of the supply roller 64. The toner carried on the developing roller 63 is supplied to the electrostatic latent image formed on the photosensitive drum 53 when the developing roller 63 comes into contact with the photosensitive drum 53. As a result, the toner is selectively carried on the photosensitive drum 53 to visualize the electrostatic latent image, and a toner image is formed by reversal development.

  Next, the sheet S supplied onto the conveyance belt 73 passes between each photosensitive drum 53 and each transfer roller 74 disposed inside the conveyance belt 73, thereby forming on each photosensitive drum 53. The toner image thus transferred is transferred onto the paper S. Then, as the sheet S passes between the heating roller 81 and the pressure roller 82, the toner image transferred onto the sheet S is thermally fixed.

  The paper discharge unit 90 mainly includes a paper discharge side transport path 91 formed so as to extend upward from the exit of the fixing unit 80 and to be reversed to the front side, and a plurality of pairs of transport rollers 92 that transport the paper S. I have. The sheet S on which the toner image has been transferred and heat-fixed is transported along a paper discharge side transport path 91 by a transport roller 92, discharged outside the main body housing 10, and accumulated in the paper discharge tray 13.

2. Configuration of LED Array As shown in FIG. 3, the LED array 41 has a plurality of light emitting elements P arranged in the main scanning direction orthogonal to the paper feeding direction (vertical direction in FIG. 3). Specifically, 20 LED array chips CH are arranged in a staggered pattern on the circuit board CB. Each LED array chip CH is obtained by forming a plurality of light emitting diodes as light emitting elements P on a semiconductor substrate by a semiconductor process. The LED array 41 receives a light emission signal from a light emission control unit 110 to be described later, so that the scanning start side (for example, the left side in FIG. 3) in the main scanning direction to the scanning end side (for example, the right side in FIG. 3). The light is emitted toward the light and the photosensitive drum 53 is exposed. In this embodiment, each light emitting element P constituting the LED array 41 has its light emission timing controlled by the control unit in the LED array chip CH.

  In this example, as shown in FIG. 3, each LED array chip CH is staggered in the sub-scanning direction orthogonal to the main scanning direction on the circuit board CB. This is because the chip cannot be formed up to the chip edge. That is, the staggered arrangement allows the distance Dx between the light emitting elements at the joint C between the chips CH to coincide with the reference pitch.

3. Description of Control Device 100 and Light Emission Control Unit 110 The control device 100 controls the entire color printer 1, and includes an arithmetic control unit 100A including a CPU, a RAM 100B, and a ROM 100C. . The light emission control unit 110 controls lighting of the light emitting elements P of the LED array 41 together with the control device 100. The light emission control unit 110 includes an ASIC 120 as shown in FIG. Four sets of LED arrays 41 are commonly connected to the light emission control unit 110, and the ASIC 120 of the light emission control unit 110 is configured to control lighting of the four sets of LED arrays 41.

  Each LED array 41 is provided with an EEPROM 43 as a nonvolatile storage means. The EEPROM 43 and the ROM 100C store the following data necessary for performing the lighting timing correction and the light amount correction described below.

Data on the pitch “Dx” in the main scanning direction between the light emitting elements at the joint portion between the chips (see FIG. 3: stored in EEPEOM)).
Correction value data X, correction value table (see FIGS. 13 and 14: stored in EEPROM)
The data of the angle “θ” of the dither pattern Z of each color (stored in the ROM 100C).

4). Correction of lighting timing The light emitting elements P on the LED array 41 are arranged at a constant reference pitch Dp in the main scanning direction, specifically, at a pitch of 42 μm when the resolution of the image is 600 dpi. And also about the joint C of each LED array chip CH, the LED array chip CH is arranged so that the distance Dx in the main scanning direction between the light emitting elements becomes the reference pitch Dp. The distance in the sub-scanning direction of the joint portion is 52.3 μm. The reference pitch Dp is an example of the “reference value” in the present invention.

  However, when each LED array chip CH is mounted on the circuit board CB, the mounting position may deviate from the normal position. At the joint C between the LED array chips, a one-dot chain line (A part, B part in FIG. , The distance Dx between the light emitting elements may increase or decrease with respect to the reference pitch Dp. When the distance Dx between the light emitting elements increases or decreases with respect to the reference pitch Dp, as shown in FIG. 5 and FIG. 6, repeated oblique lines L that are formed by dots formed by the respective light emitting elements P and are inclined with respect to the main scanning direction. When the image is printed using the dither pattern Z, the image is likely to be streaked.

  That is, when the distance Dx between the light emitting elements coincides with the reference pitch Dp (in the case of A portion in FIG. 3), as shown in the left hand of FIG. 5 and FIG. Absent. However, when the distance Dx between the light emitting elements is larger than the reference pitch Dp (in the case of B portion in FIG. 3), as shown in the center of FIG. Further, when the distance Dx between the light emitting elements is smaller than the reference pitch Dp (in the case of C portion in FIG. 3), as shown in the center of FIG.

  Therefore, in the present embodiment, when the distance Dx between the light emitting elements at the joint C of each LED array chip CH deviates from the reference pitch Dp, the end portions of the line segments LL and LR constituting the oblique line L of the dither pattern Z Is bent to suppress the occurrence of color streaks and white streaks appearing in the dither pattern Z. The oblique line L is an example of an assembly line made up of an assembly of dots having regularity inclined in one direction of the present invention, and each line segment LL, LR of the oblique line L is an example of the assembly line segment of the present invention. .

  The dither pattern Z is a repetitive pattern of oblique lines L, and is used when a gradation is added to an image (that is, the shade of the print color). In the present embodiment, four patterns, that is, four types of dither patterns Z having different oblique line angles θ with respect to the main scanning direction are provided corresponding to the four color toners. Specifically, there are four dither patterns Z in which the angle θ of the oblique line L is “+ 27 °”, “−27 °”, “+ 63 °”, and “−63 °”. The dither pattern Z is changed for each color so that the dither patterns Z do not overlap each other.

  Hereinafter, the method for suppressing the stripes generated in the image is as follows: when the distance Dx between the light emitting elements is larger than the reference pitch Dp, that is, when the white stripe occurs, and when the distance Dx between the light emitting elements is smaller than the reference pitch Dp, A case where color streaks occur will be described separately.

<When the distance Dx between the light emitting elements is larger than the reference pitch Dp>
When the distance Dx between the light emitting elements is larger than the reference pitch Dp, a blank N is formed between the two line segments LL and LR constituting the dither pattern Z as shown in FIG. In the present embodiment, among the two line segments LL and LR, the end portion T on the joint C side of each line segment LL and LR is bent in a direction in which the inclination with respect to the main scanning direction becomes gentle.

  Hereinafter, the bending of the line segments LL and LR will be described using correction straight lines. The correction straight line is a straight line that passes through the center point between the two line segments LL and LR and has an inclination angle smaller than the oblique line L by a certain value. In the upper part of FIG. It is shown. The correction straight line 1 is a straight line whose angle is 15 degrees loose with respect to the oblique line L, and the correction straight line 2 is a straight line whose angle is 30 degrees loose with respect to the oblique line L.

  For example, when the correction straight line 1 is used, the end T of the line segment LL, LR ahead of the intersection S with the correction straight line 1 is bent so as to coincide with the correction straight line 1. As a result, the end T from the intersection S is bent by 15 degrees, so that the two line segments LL and LR have the lower shape in FIG.

  In this way, the seam C of the two line segments LL and LR is a straight line between the two line segments LL and LR, although the space N remains between the two lines even after bending. Therefore, since the seam C looks natural, the white stripes are not noticeable.

  In order to bend the end portions T of the line segments LL and LR as shown in FIG. 7, the dots formed by the light emitting elements P correct the lighting timing of the light emitting elements P corresponding to the end portions T of the line segments LL and LR. What is necessary is just to correct | amend so that it may be located on a straight line.

  For example, in the case of the left array chip CHL shown in FIG. 5, the time corresponding to the angle for correcting the lighting timing of the light emitting element PT1 corresponding to the end T with respect to the normal lighting timing as shown in FIG. What is necessary is just to make it early by t1. In the case of the right array chip CHR shown in FIG. 5, the time corresponding to the angle for correcting the lighting timing of the light emitting element PT2 corresponding to the end T with respect to the normal lighting timing as shown in FIG. What is necessary is just to delay by t2.

  The regular lighting timing means the lighting timing when the line segments LL and LR constituting the dither pattern Z are not bent, that is, the timing at which each light emitting element P emits light at equal intervals.

  In the above description, the reason why the white streaks are inconspicuous is described as the point where the seam is close to a straight line, but the gap between the two line segments LL and LR adjacent to each other in the sub-scanning direction is narrowed by bending the end. It can also be mentioned. That is, in the example of FIG. 10, the gap D between LL3 and LR2 is narrowed.

<When the distance Dx between the light emitting elements is smaller than the reference pitch Dp>
When the distance Dx between the light emitting elements is smaller than the reference pitch Dp, as shown in FIG. 11, among the two line segments LL and LR constituting the dither pattern Z, the end portion T on the joint C side of each line segment LL and LR. Are bent in a direction in which the inclination with respect to the main scanning direction becomes steep. In the upper part of FIG. 11, when the angle is steeped by 15 degrees, the correction straight line 3 is shown, and when the angle is steeped by 30 degrees, the correction straight line 4 shows.

  In this example, the end C of each line segment LL, LR on the joint C side is bent so as to coincide with the correction straight line 3, and after bending, the two line segments LL, LR are in the lower part of FIG. The shape, that is, the joint C of the two line segments LL and LR is a straight line. Therefore, since the seam C looks natural, the color streak becomes inconspicuous.

  In order to bend the end portion T on the joint C side of each line segment LL, LR, two LED array chips corresponding to each line segment LL, LR, as in the case where the distance Dx between the light emitting elements is larger than the reference pitch Dp. What is necessary is just to correct | amend the lighting timing of the light emitting element corresponding to the edge part T among CHL and CHR so that the dot which the light emitting element P makes may be located on a correction straight line.

<Number of light-emitting elements that require correction of lighting timing>
When the angle θ of the oblique line L constituting the dither pattern Z is the same, if the bending angle of the end portion T is reduced (for example, the correction straight line 1 or the correction straight line 3), the bending length becomes longer, so the lighting timing The number of light emitting elements that need to be corrected increases. On the other hand, when the bending angle is increased (for example, the correction straight line 2 or the correction straight line 4), the bending length is shortened, so that the number of light emitting elements that need to be corrected for the lighting timing is reduced.

  In order to make the joint C of the line segments LL and LR appear naturally, it is preferable to set the bending angle of the end T small. However, if the angle is reduced, as described above, the number of light emitting elements that need to be corrected for lighting timing increases, and the control becomes complicated. Therefore, it is preferable to set the bending angle of the line segments LL and LR to be small within a range where the control is not complicated.

  In addition, the number of light emitting elements that need to be corrected for the lighting timing varies depending on the magnitude of the error amount of the distance Dx with respect to the reference pitch Dp and the angle θ of the oblique line L constituting the dither pattern Z with respect to the main scanning direction. The bending angle needs to be set in consideration of these error amounts and the angles of the line segments LL and LR.

<Control unit of light emitting element>
Each light emitting element P constituting each LED array chip CH of the LED array 41 has a large number of elements, and controlling these lighting timings individually makes the control complicated. Therefore, in the present embodiment, a plurality of light emitting elements (four light emitting elements as an example) are set as one control unit, and the lighting timing of the light emitting elements P is uniformly controlled in each control unit for each LED array chip CH. And it is preferable that the above-described correction of the lighting timing is performed in a unit of control.

  Specifically, for example, when the number of light-emitting elements that need to be corrected for lighting timing is calculated as nine, it corresponds to two units when converted to a control unit, so that the lighting timing is uniformly corrected for eight light-emitting elements. Good. The timing charts shown in FIG. 8 and FIG. 9 show the lighting timing of the control unit, with the light emitting element Pu in the figure corresponding to one control unit.

5. In the present embodiment, the effect of suppressing color streaks and white streaks is enhanced by using both the above-described lighting timing correction and light amount correction in combination.
The light amount correction is to correct the light amount of the light emitting element P at the joint C of each LED array chip CH according to the distance Dx between the light emitting elements. By performing this light amount correction, the color streaks and white streaks are corrected. Generation can be suppressed. For example, as shown in FIG. 12, when the distance Dx between the light emitting elements is larger than the reference pitch Dp, the correction is performed to increase the light amount by extending the light emission time for the two light emitting elements Pa and Pb at the center of the joint. Do. As a result, after the light amount correction, as shown on the right side of FIG. 12, the center portion of the joint is in a state where the lines are connected, and the white streak is less noticeable than in the case where the correction is not performed.

  Contrary to the example of FIG. 12, when the distance Dx between the light emitting elements is smaller than the reference pitch Dp, the light emission time is shortened and the amount of light is reduced for the two light emitting elements Pa and Pb at the center of the joint. Make corrections. Thereby, after the light amount correction, the light amount difference between the central portion of the seam and the peripheral portion is reduced, so that the color streak becomes inconspicuous compared with the case where the correction is not performed.

  The light emission time of each light emitting element P is determined by correction value data X described below, and the set values are different. This is because each light emitting element P of the LED array 41 has a luminance variation, and when the light emitting time and the current value are lit uniformly with the same conditions such as the light emitting time and the current value, a difference in the amount of light occurs, resulting in uneven exposure and image quality. Affects. Therefore, by changing the light emission time according to the luminance value of each light emitting element P, the luminance variation is compensated and the light quantity is made uniform.

  The correction value data X shown in FIG. 13 defines the correspondence relationship of which grade of correction gradation is applied to each light emitting element P on the LED array. The numbers in the frame of FIG. 14, for example, “2”, “1”, “3”, etc., indicate the grade of the correction gradation. On the other hand, the correspondence between the correction gradation grade and the light emission time (specifically, the clock count) is defined in the correction value table of FIG.

  Therefore, the light emission time of each light emitting element can be obtained by referring to the correction value table. In the case of the light emitting element P1 shown in FIG. 13, the correction value data X is “2”. In this case, the grade of the correction gradation is “2”, and the clock count is “29” times, that is, the light emission time is 112.4 sec according to the correction value table. In the case of the light emitting element Pn, the correction value data X is “4”. In this case, the grade of the correction gradation is “4”, and the clock count is “31” times, that is, the light emission time is 120.1 sec according to the correction value table. Here, the clock cycle of the clock for measuring the light emission time is set to “3.875” ns.

  The correction value data “X1” shown in FIG. 13 is obtained by incorporating a light amount correction for suppressing the generation of color streaks and white streaks into the correction value data X, and is positioned at the center of the seam with respect to the correction value data “X”. The correction gradation grade of the two light emitting elements Pa and Pb is changed.

6). Lighting Control Next, a lighting control example of each light emitting element P constituting the LED array 41 will be described with reference to FIG. Upon receiving the print data, the arithmetic control unit 100A of the control device 100 first reads out the data of the pitch “Dx” of the light emitting elements P at the joint C between the chips for each LED array 41 from the EEPROM 43 of each LED array 41. (S10 to S20).

  Thereafter, the arithmetic control unit 100A determines the light emitting elements P for correcting the lighting timing so that the color stripes and white stripes of the dither pattern Z are reduced for the LED array chip CH of each LED array 41 (S30). . Specifically, the light emitting elements P whose lighting timing is to be corrected are determined based on the data of the pitch “Dx” of the light emitting elements P at the joint portion between the chips.

  Next, the arithmetic control unit 100A reads the correction value data “X” from the EEPROM 43 of each LED array 41 and creates correction value data “X1” from the read correction value data “X”. Specifically, based on the data of the pitch “Dx” of the light emitting elements P at the joint portion between the chips, correction for adjusting the light emission time of the two light emitting elements Pa and Pb at the center of the joint is performed.

  Thereafter, the arithmetic control unit 100A determines the print pattern. Specifically, it is determined whether or not the dither pattern Z is used for the image to be printed (S50).

  If the dither pattern Z is used for the image to be printed, a YES determination is made in S50. If YES is determined in S50, the process proceeds to S60. In S60, the printing process A is executed.

  Specifically, the data of the light emitting element P for correcting the lighting timing for each LED array chip CH of each LED array 41 and the correction value data X1 are sent to the light emission control unit 110 together with the print data. Then, the ASIC 120 of the light emission control unit 110 that has received the data corrects the lighting timing of the light emitting element P specified for each LED array chip CH of each LED array 41, and each light emitting element P mounted on the LED array 41. Is controlled according to the correction value data X1.

  Thus, at the joint portion of the LED array chip CH, the end portions T of the line segments LL and LR are bent so as to be in a straight line, the light amount of the light emitting element P is further adjusted, and the dots formed by each light emitting element P are changed. It becomes close to the state of regular connection. Accordingly, white stripes and color stripes are not noticeable in the dither pattern Z.

  On the other hand, if the dither pattern Z is not used for the image to be printed, NO is determined in S50. If NO is determined in S50, the process proceeds to S70. In S70, the printing process B is executed. In the case of the printing process B, the correction value data X is sent to the light emission control unit 110 together with the print data. Therefore, the ASIC 120 of the light emission control unit 110 controls the lighting timing of the light emitting element P for each LED array chip CH of each LED array 41 with the normal lighting timing, and the light emission of each light emitting element P mounted on the LED array 41. The time is controlled according to the correction value data X. That is, when the dither pattern Z is not used, the lighting timing correction and the light amount correction of the light emitting element where the end T is located are not executed.

  As described above, in the present embodiment, the end T on the line segment LL side and the end T on the line segment LR side are bent along the same correction straight line. Therefore, after bending, the two end portions T become the same straight line, so that the seam C can be seen naturally. Therefore, white stripes and color stripes can be made inconspicuous.

  In addition, in this embodiment, since the lighting timing is controlled by a control unit including a plurality of light emitting elements whose lighting timing is uniformly controlled, there is an advantage that the lighting timing control is not complicated.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.

  (1) In the above embodiment, an LED array using a light emitting diode as a light emitting element is illustrated as an example of the light emitting array. However, an organic EL array using an organic EL (electroluminescence) element as the light emitting element may be used. Is possible.

  (2) In the above embodiment, an example in which the generation of color streaks and white streaks is suppressed by bending both end portions T on the line segment LL side and the line segment LR side is shown, but only the end portion T on one side is shown. It may be bent. Further, even when both end portions T are bent, it is sufficient that the end portions T are close to a straight line after the bending, and the end portions T of each line segment are bent using correction straight lines having different angles. Is also possible.

  (3) In the above-described embodiment, an example in which the end T is bent so as to form a corner with respect to the line segment LL and the line segment LR has been shown. For example, as illustrated in FIG. You may make it connect a corner with the curve R so that the boundary part of a part may connect smoothly. When corners are connected by the curve R, the lighting timing of the light emitting elements P constituting the LED array chip CH may be set so that the dots formed by the light emitting elements P are on the curve R. Specifically, as shown in FIG. 17, the lighting timing correction amount with respect to the regular lighting timing may be set to change greatly in steps or to be changed in steps.

1. Printer (an example of the “image forming apparatus” of the present invention)
DESCRIPTION OF SYMBOLS 30 ... Image formation part 40 ... LED unit 41 ... LED array (an example of "light emitting array" of this invention)
53. Photosensitive drum (an example of the “photosensitive member” of the present invention)
100... Control device (an example of the “light emission control device” of the present invention)
110... Light emission control unit (an example of the “light emission control device” of the present invention)
C: Seam CH: LED array chip (an example of the “light emitting chip” of the present invention)
P: Light emitting element L: Diagonal line (an example of “an assembly line composed of an assembly of dots having regularity inclined in one direction” in the present invention)
LL ... line segment (an example of the “set line segment” of the present invention)
LR ... line segment (an example of the “collective line segment” of the present invention)
Z ... Dither pattern

Claims (7)

A plurality of light emitting elements formed on a semiconductor substrate, and a light emitting array comprising a plurality of light emitting chips arranged in the main scanning direction;
A photoreceptor exposed by the light emitting array;
An image forming unit that forms an image on a recording medium using an electrostatic latent image formed on the photoreceptor;
A light-emission control device that forms a dither pattern in which light-emitting elements of the light-emitting array repeat a repeating line in the sub-scanning direction, which is a collection of dots having regularity inclined in one direction, indicating the gradation of the image And
When the distance between the two light emitting elements located at the joint between the light emitting chips is larger than a reference value, the light emission control device,
In each assembly line segment formed by each light emitting chip of the light emitting array, at least one of the pair of end portions corresponding to the joint between the light emitting chips is gently inclined with respect to the main scanning direction. An image forming apparatus that performs timing control for controlling lighting timing of a light emitting element corresponding to the end portion so as to be bent in a direction. A plurality of light emitting elements formed on a semiconductor substrate, and a light emitting array comprising a plurality of light emitting chips arranged in the main scanning direction;
A photoreceptor exposed by the light emitting array;
An image forming unit that forms an image on a recording medium using an electrostatic latent image formed on the photoreceptor;
A light-emission control device that forms a dither pattern in which light-emitting elements of the light-emitting array repeat a repeating line in the sub-scanning direction, which is a collection of dots having regularity inclined in one direction, indicating the gradation of the image And
When the distance between the two light emitting elements located at the joint between the light emitting chips is smaller than a reference value, the light emission control device,
In each assembly line segment formed by each light emitting chip of the light emitting array, at least one of the pair of end portions corresponding to the joint between the light emitting chips is steeply inclined with respect to the main scanning direction. An image forming apparatus that performs timing control to control the lighting timing of the light emitting element corresponding to the end portion so as to be bent in the direction to be.   The light emission control device turns on the light emitting elements corresponding to the pair of end portions so that both of the pair of end portions are bent in a direction in which the inclination with respect to the main scanning direction becomes gentle or in a direction in which the inclination becomes steep. 3. The image forming apparatus according to claim 1, wherein the timing is controlled.   The image forming apparatus according to claim 3, wherein the light emission control device controls lighting timings of light emitting elements corresponding to the pair of end portions so that the pair of bent end portions are in a straight line.   The image forming apparatus according to claim 1, wherein the light emission control device executes the control of the lighting timing in a control unit including a plurality of light emitting elements whose lighting timing is uniformly controlled.   3. The image forming apparatus according to claim 1, wherein the light emission control device controls a lighting timing of a light emitting element at the boundary portion so that the boundary portion between the aggregate line segment and the end portion is smoothly connected. The light emission control device includes:
The timing control for controlling the lighting timing of the light emitting element corresponding to the end corresponding to the joint between the light emitting chips,
The image forming apparatus according to any one of claims 1 to 6, wherein a light amount control for correcting a light amount of a light emitting element located at a joint between the light emitting chips according to a distance between the light emitting elements is used in combination.

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