JP5303888B2 - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus which reduces a memory area to secure for a displacement correction, and also to provide a supporting member with a light emitter. <P>SOLUTION: The image forming apparatus 1 includes: a photoreceptor 33, a light emitter 85 having an array of a plurality of light emitting elements 30; and a supporting member 87 for supporting the light emitter 85, and is provided with: a plurality of exposure means 23 for exposing the photoreceptor 33; a memory 65; and a correction means 61 for correcting an exposure displacement of the exposure means 23 with respect to a reference line, by using the area of the memory 65. When an exposure position of at least one of the exposure means 23 is corrected, an area for correcting an exposure position displacement in one direction due to inclination of the light emitter 85 to the supporting member 87 in the exposure means 23, is secured in the memory 65, while an area for correcting an exposure displacement in the opposite direction of the one direction is not secured in the memory 65. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to an image forming apparatus.

  An electrophotographic image forming apparatus includes, for example, an LED head in which a plurality of LEDs are arranged in a line, and an electrostatic latent image is formed by forming a scanning line on the photosensitive member by the LED head. There is. In the color image forming apparatus, a plurality of the LED heads are provided corresponding to each color, an electrostatic latent image is individually formed by each LED head, and each color image based on each electrostatic latent image is finally formed on the transferred body. To form a color image.

  Here, it is difficult to completely match the scanning lines of the LED heads of the respective colors, and in actuality, there is a variation in position between the color images, and a color image having a color shift is formed. Therefore, it is necessary to correct this misalignment. Specifically, when the LED heads of the respective colors form one scan line, for example, the light emission timings of the plurality of LEDs are individually corrected so as to cancel the positional deviation with respect to the reference color.

There is also a technique (see Patent Document 1) that attempts to reduce the memory area used for this correction. First, a relative positional deviation amount of each color image or a positional deviation amount of each color image with respect to a predetermined absolute position is detected, and a position passing through the middle point of the two color positions having the largest positional deviation difference is detected. An alignment reference line is separately defined, and misalignment correction is performed based on the alignment reference.
JP 2001-232867 A

By the way, in the conventional configuration, a memory area used for correction processing is secured on the assumption that the image position is shifted in both the positive direction and the negative direction with respect to the reference color or the alignment reference (referred to as “reference color etc.”). It was common to do. Therefore, when the image position is shifted only in the positive direction with respect to the reference color or the like, there is a problem that the memory area secured for correcting the shift amount in the negative direction is wasted.
The present invention was completed based on the above situation, and its object is to provide an image forming apparatus notes that can be reduced in the re area for positional deviation correction.

As means for achieving the above object, an image forming apparatus according to a first invention has a photosensitive member, a light emitter in which a plurality of light emitting elements are arranged, and a support member that supports the light emitter. A plurality of exposure means for exposing the photosensitive member; a memory; and a correction means for correcting a deviation of an exposure position of the exposure means with respect to a reference line using an area of the memory. When correcting the exposure position of at least one exposure means among the plurality of exposure means, an area for correcting the exposure position shifted in one direction due to the inclination of the light emitter with respect to the support member in the exposure means An area for correcting the exposure position shifted in the direction opposite to the one direction is not secured in the memory.
In the exposure means, the light emitter is often inclined with respect to the support member, and this inclination can greatly affect the amount of positional deviation in exposure. Therefore, if this inclination direction (positive direction, negative direction) is taken into consideration in advance, the memory use area can be reduced. That is, according to the present invention, when correcting the deviation of the exposure position in the exposure unit, an area for correcting the exposure position shifted in one direction due to the inclination of the light emitter with respect to the support member of the exposure unit is secured in the memory. . However, since it is an area for correcting the exposure position deviating in the opposite direction to the one direction (hereinafter referred to as an unnecessary area), it is configured not to be secured in the memory.

A second invention is the image forming apparatus according to the first invention, wherein the correction means corrects the exposure position shifted in the reverse direction when correcting the deviation of the exposure position of any exposure means. Are not reserved in the memory.
According to the present invention, the memory use area can be reduced in the correction of the deviation of the exposure position of any exposure means.

A third aspect of the invention is the image forming apparatus according to the second aspect of the invention, wherein the light emitters are inclined in the same direction with respect to the support member.
For example, in the deviation correction for the exposure position shifted in one direction (positive direction) with respect to the reference line and the shift correction for the exposure position shifted in the other direction (negative direction) with respect to the reference line, the above unnecessary area is not secured. The processing method to be corrected is different. Therefore, according to the present invention, since the light emitters are inclined in the same direction with respect to the support member, the plurality of exposure units are also aligned in the same direction in the direction of deviation of the exposure position from the reference line. Therefore, it is possible to share the correction process without securing unnecessary areas in a plurality of exposure units.

A fourth invention is the image forming apparatus of the first or second invention, wherein the reference line is a scanning line formed by a light emitter of one exposure means.
According to the present invention, since the reference line is a scanning line formed by the light emitter of one exposure means, it is possible to reduce the memory area for correcting the deviation of the exposure position of the one exposure means.

A fifth aspect of the invention is the image forming apparatus according to the fourth aspect of the invention, wherein the one exposure unit is an exposure unit that minimizes a variation in arrangement of the plurality of light emitting elements among the plurality of exposure units.
According to the present invention, it is possible to suppress the deviation of the exposure position due to the variation in the arrangement of the light emitting elements for one exposure means.

A sixth invention is the image forming apparatus according to the fourth or fifth invention, wherein the one exposure means exposes an electrostatic latent image of a black image or a yellow image onto the photoconductor.
If one exposure means exposes the electrostatic latent image of a black image onto the photoreceptor, the correction process can be reduced during black monochrome printing. Further, if one exposure means exposes the electrostatic latent image of a yellow image onto the photoconductor, it is difficult to stand out even if there is a slight misalignment.

A seventh invention is the image forming apparatus according to any one of the first to sixth inventions, wherein an inclination of the light emitter with respect to the support member corresponds to a correction direction of an exposure position by the correction means. Determination means for determining whether or not, and notification means for performing a notification operation according to the determination result of the determination means.
For example, in a manufacturing stage or a repair stage, an exposure unit in which the tilt direction of the light emitter with respect to the support member does not correspond to the correction direction of the exposure position by the correction unit may be arranged. Therefore, according to the present invention, the misplacement can be known.

A support member with a light emitter according to an eighth invention is used as an exposure unit, and includes a light emitter in which a plurality of light emitting elements are arranged, and a support member that supports the light emitter, and the light emission to the support member. Body tilt information is attached to the outside.
According to the present invention, since the tilt information of the light emitter with respect to the support member is attached to the outside, the tilt information can be easily grasped visually or using reading means such as a sensor.

An image forming apparatus according to a ninth aspect of the present invention includes a photoconductor, a light emitter in which a plurality of light emitting elements are arranged, and a support member that supports the light emitter, and a plurality of exposure units that expose the photoconductor. And a correcting unit that corrects a deviation of an exposure position of another exposure unit with respect to a scanning line formed by a light emitter of one exposure unit among the plurality of exposure units, and the plurality of exposure units includes the support The light emitter is inclined in the same direction with respect to the member.
According to the present invention, in the plurality of exposure means, the light emitter is inclined in the same direction with respect to the support member, and the exposure position of the other exposure means is corrected with the scanning line by one of the exposure means as a reference line. To do. Therefore, for example, the amount of deviation of the exposure position between one exposure unit and the other exposure unit can be reduced as compared with the configuration in which the one exposure unit and the other exposure unit have different tilt directions of the light emitter with respect to the support member. It is possible to reduce the memory usage area by that amount.

According to the present invention, it is possible to reduce the memory area for correcting misalignment.

<Embodiment 1> Embodiment 1 of this invention is demonstrated with reference to FIGS.
(Entire printer configuration)
FIG. 1 is a side sectional view showing a schematic configuration of an electrophotographic printer 1 of the present embodiment. In the following description, the right side (right side) in FIG. 1 is the front side (front side) of the printer 1.

  As shown in FIG. 1, a printer 1 (an example of an image forming apparatus) is a direct transfer tandem type color LED printer, and includes a casing 3. A supply tray 5 is provided at the bottom of the casing 3, and a recording medium (for example, a sheet material such as paper) 7 is stacked on the supply tray 5.

  The recording medium 7 is pressed toward the pickup roller 13 by the pressing plate 9 and is sent to the registration roller 17 by the rotation of the pickup roller 13. The registration roller 17 corrects the skew of the recording medium 7 and then sends the recording medium 7 onto the belt unit 21 at a predetermined timing.

  The image forming unit 19 includes a belt unit 21 as an example of a conveyance unit, an LED exposure device 23 (an example of an exposure unit), a process unit 25, a fixing device 28, and the like. In the present embodiment, at least the LED exposure device 23 and the process unit 25 constitute an image forming unit.

  The belt unit 21 includes an endless belt 31 provided between a pair of support rollers 27 and 29. The belt 31 circulates in the counterclockwise direction of FIG. 1 when the rear support roller 29 is driven to rotate, for example, and the recording medium 7 is placed on the belt 31 and conveyed backward.

  The LED exposure device 23 includes four LED exposure devices 23 (23K, 23C, 23M, and 23Y) corresponding to black, cyan, magenta, and yellow colors. Each LED exposure device 23 includes a plurality of light emitting diodes 30 (an example of an LED chip light emitting element) arranged in a line along the axial direction of a photosensitive member 33 as an example of a carrier. Based on the color image data, the plurality of light emitting diodes 30 are controlled to be turned on and off to irradiate light onto the surface of the photoconductor 33, thereby forming an electrostatic latent image on the photoconductor 33.

  Four process units 25 are provided corresponding to the respective colors of black, cyan, magenta, and yellow. Each process unit 25 has the same configuration except for the color of toner (an example of a colorant). In the following description, when it is necessary to distinguish each color, subscripts of K (black), C (cyan), M (magenta), and Y (yellow) are attached to the codes of the respective parts, and it is not necessary to distinguish them. In this case, the subscript is omitted.

  Each process unit 25 includes a photoconductor 33, a charger 35, a developing cartridge 37, and the like. The developing cartridge 37 is provided with a toner containing chamber 39, a developing roller 41, and the like, and the toner in the toner containing chamber 39 is supplied onto the developing roller 41.

  The surface of the photoreceptor 33 is uniformly positively charged by the charger 35. Thereafter, the image is exposed to light L from the LED exposure device 23 to form an electrostatic latent image corresponding to each color image to be formed on the recording medium 7.

  Next, the toner carried on the developing roller 41 is supplied to the electrostatic latent image formed on the surface of the photoreceptor 33. As a result, the electrostatic latent image on the photoconductor 33 is visualized as a toner image for each color.

  Thereafter, the toner carried on the surface of each photoconductor 33 while the recording medium 7 conveyed by the belt 31 passes through each transfer position between the photoconductor 33 and the transfer roller 43 (an example of transfer means). The images are sequentially transferred to the recording medium 7 by a negative transfer bias applied to the transfer roller 43. The recording medium 7 onto which the toner image has been transferred in this way is conveyed to the fixing device 28.

  The fixing device 28 fixes the toner image on the recording medium 7 by heating the recording medium 7 carrying the toner image while being conveyed by the heating roller 45 and the pressure roller 47. Then, the heat-fixed recording medium 7 is discharged onto a paper discharge tray 51 by a paper discharge roller 49.

(Electrical configuration of printer)
FIG. 2 is a block diagram showing an electrical configuration of the printer 1 described above.

  The printer 1 includes a CPU 61, a ROM 63, a RAM 65 (an example of a memory), an NVRAM 67, an operation unit 69, a display unit 71, the above-described image forming unit 19, a network interface 73, and the like.

  Various programs for controlling the operation of the printer 1 are recorded in the ROM 63, and the CPU 61 controls the operation of the printer 1 while storing the processing results in the RAM 65 and the NVRAM 67 according to the program read from the ROM 63. .

  The operation unit 69 includes a plurality of buttons, and various input operations such as an instruction to start printing can be performed by the user. The display unit 71 includes a liquid crystal display and a lamp, and can display various setting screens and operation states. The network interface 73 is connected to an external computer (not shown) or the like via a communication line 75, and mutual data communication is possible.

(Specific configuration of LED exposure device and cause of displacement)
Each LED exposure device 23 is provided with an LED head 81 (an example of a support member with a light emitter) shown in FIG. Specifically, the LED head 81 mainly includes a light emitter 85 and a support member 87 to which the light emitter 85 is fixed. The light emitter 85 has a configuration in which the plurality of light emitting diodes 30 are arranged on a long and thin substrate 83. Reference holes 89 </ b> A and 89 </ b> B through which fixing pins (not shown) for fixing in the casing 3 are passed are formed at both ends of the support member 87. Hereinafter, the reference hole 89A will be described as a reference hole located on the left side in FIG. 3, and the reference hole 89B will be described as a reference hole located on the right side in FIG.

Here, the LED head 81 has the following manufacturing errors, and these can cause exposure position deviation and color misregistration.
A. Inclination error in the arrangement direction of the light emitting diodes The inclination error in the arrangement direction of the light emitting diodes 30 (hereinafter referred to as “line inclination error”) refers to a deviation in the arrangement direction of the light emitting diodes 30 from the longitudinal direction of the support member 87. As shown in FIG. 3, the longitudinal direction of the support member 87 is, for example, the above-described reference holes 89A and 89B formed in the support member 87 (specifically, the centers of both reference holes 89A and 89B, or the upper ends or the lower ends). ) Is defined as the direction of the straight line R1. The arrangement direction of the light emitting diodes 30 is defined as, for example, the direction of a straight line R2 connecting the light emitting diodes 30 closest to the reference hole 89A and the light emitting diodes 30 closest to the reference hole 89B.

B. Light emitting diode placement error The light emitting diode 30 placement error refers to each light emitting diode with respect to the straight line R2 connecting the light emitting diode 30 closest to the reference hole 89A and the light emitting diodes 30 closest to the reference hole 89B. 30 misalignment.

  Normally, error information such as the above-described line tilt error (an example of tilt information) and the placement error of the light emitting diode 30 is measured in advance by the manufacturer before shipment of the LED head 81 and is provided on the substrate 83 or the like. Are recorded in a memory (not shown). Therefore, the operator can read out the error information from the predetermined data reader at the manufacturing stage of the printer 1 or the maintenance stage such as replacing the LED head 81. However, as shown in FIG. 3, the error information is converted into, for example, characters, figures, symbols, barcodes, QR codes (registered trademark), etc. outside the LED head 81 (for example, the back surface 87A of the support member 87 as shown in FIG. 3). It is preferable to be able to be read by vision or a sensor. Then, the trouble of reading data from the memory using the data reader can be saved.

  Note that the cause of the exposure position shift (color shift) is not only the line tilt error and the light emitting diode 30 placement error but also the LED head 81 mounting position error relative to the casing 3.

(Exposure position deviation correction)
The process for correcting the deviation of the exposure position is as follows. At this time, the CPU 61 functions as a correction unit. In the present embodiment, for example, the scanning line GK formed on the photosensitive member 33 by the light emitting diode 30 of the black LED exposure device 23 as a reference color is used as a reference line, and another color (cyan) is used as a correction color for the scanning line GK. , Magenta, yellow) of the scanning lines GC, GM, GY. In the RAM 65, a correction buffer area is secured for each correction color.

  When receiving image data from the external computer, the CPU 61 develops the image data into raster data for each color image on the RAM 65. Then, the CPU 61 transfers raster data of each color image to each buffer area one image line at a time. The raster data of the corrected color image is subjected to shift correction on the buffer area. In FIG. 4 described below, in the state where the left ends of the respective straight lines are aligned, the counterclockwise direction on the paper is defined as a positive inclination direction with respect to the dotted line G0. In order to simplify the description, the number of pixels on one scanning line (the number of light emitting diodes 30) is three. The dotted line G0 is a straight line parallel to the straight line R1 described above.

  In this embodiment, as shown in FIG. 4, the inclination error of the reference color line GK is + θ1, and the inclination error of the correction color line GC (GM, GY) is + θ2. That is, the inclination of the reference color line GK and the inclination of the correction color line GC (GM, GY) are the same positive direction inclination. Then, in order to make the correction color line GC (GM, GY) coincide with the reference color line GK, the light emission timing of the light emitting diode 30 needs to be shifted by a maximum of two addresses. Here, “address” determines the light emission timing of each light emitting diode 30, in other words, the formation position of each color image in the sub-scanning direction. Before correction, the addresses of all the light emitting diodes 30 are uniformly “0”, for example. "Is set.

  Then, in order to cancel the positional deviation amount of the correction color line GC (GM, GY) with respect to the reference color line GK, each light emitting diode 30 is based on the light emitting diode 30 positioned at one end (for example, the left end in the present embodiment). The raster data address corresponding to is shifted. Specifically, the raster data address corresponding to the central light emitting diode 30 is set to “+1”, and the raster data address corresponding to the rightmost light emitting diode 30 is set to “+2” (see the hatched portion in FIG. 4). . At this time, the address may be shifted in consideration of the arrangement error of the light emitting diode 30 and the error of the mounting position of the LED head 81.

  Then, the CPU 61 reads each raster data from the buffer area in the order of addresses and transfers them to the image forming unit 19. Accordingly, the image forming unit 19 causes the light emitting diodes 30 of the correction color to emit light at a timing that is delayed as the deviation amount in the positive direction with respect to the reference color line GK increases, thereby correcting the correction color for the reference color line GK. The amount of misalignment of the line GC (GM, GY) is canceled.

  Here, it is assumed that the inclination error of the correction color line GC ′ (GM ′, GY ′) is −θ2. That is, the inclination of the reference color line GK and the inclination of the correction color line GC (GM, GY) are in opposite directions. In this case, in order to cancel the positional deviation amount of the correction color line GC ′ (GM ′, GY ′) with respect to the reference color line GK, the light emitting diode 30 is caused to emit light at a timing earlier than the address “0”. It is necessary to set an address (for example, -1, -2,...) (See the address field indicated by the dotted line in FIG. 4).

  However, in this embodiment, the CPU 61 knows in advance from the error information that the inclination error of the correction color line GC (GM, GY) is + θ2 (positive direction inclination), and the inclination error + θ2 An address area for canceling the resulting positional deviation amount (an area indicated by a solid line in FIG. 4 is an area for correcting an exposure position shifted in one direction due to the inclination of the light emitter with respect to the support member in the exposure means). Only one example) is secured in the buffer area. On the other hand, an address area (an example of an area indicated by a dotted line “an area for correcting an exposure position shifted in the reverse direction” in FIG. 4) for canceling the positional deviation amount caused by the tilt error −θ2 is In the embodiment, it is an unnecessary area and is not secured on the buffer area. Accordingly, it is possible to reduce the use area of the RAM 65 for correcting misalignment.

  In addition, the inclination of the reference color line GK and the inclination of the correction color line GC (GM, GY) are the same positive direction inclination. For this reason, the amount of misregistration with respect to the reference color line GK is smaller than when the inclination error is −θ2, and the number of addresses for offsetting the misregistration amount is reduced by that amount. Use space can be reduced. In addition, it is possible to share the process of correcting the exposure position of each correction color without securing an unnecessary area in the buffer area.

  In the present embodiment, among the LED heads 81 used in the printer 1, the LED head 81 having the smallest line tilt error is used for exposure of the reference color image. For this reason, it is considered that the influence of the positional deviation caused by the line inclination error is not so great, and the positional deviation caused by this is not corrected. In the present embodiment, among the LED heads 81 used in the printer 1, the LED head 81 having the smallest arrangement error of the light emitting diodes 30 is used for exposure of the reference color image. For this reason, it is considered that the influence of the arrangement error of the light emitting diode 30 is not so great, and the positional deviation due to this is not corrected. Therefore, it is possible to reduce a memory use area for correcting misalignment caused by the line tilt error and the light emitting diode 30 placement error.

(LED head placement error notification function)
The CPU 61 has a function of notifying the LED head 81 in the tilt direction as designed in the manufacturing stage of the printer 1 or the maintenance stage such as replacing the LED head 81, for example. At this time, the CPU 61 functions as a determination unit and a notification unit.

  For example, when the printer 1 is turned on, the CPU 61 executes the control shown in FIG. First, in S1, for example, it is determined whether or not the specified inclination information SP is stored in the NVRAM 67. The specified inclination information SP is information indicating the direction (positive direction or negative direction) of the line inclination error of the LED head 81 of each color determined in the design stage of the printer 1, and for correction based on the specified inclination information SP. Arithmetic processing and buffer area are determined. Therefore, when the LED head 81 is arranged in a direction different from the specified inclination information SP, an appropriate correction process cannot be performed.

  If the specified inclination information SP is stored (S1: YES), the head number N is initialized to “1” in S3, and all the flags FG (1), FG (2), FG (3), FG (4 ) Is cleared to zero, and each head tilt information SH (N) is acquired from the memory of each LED head 81 in S5. In S7, it is determined whether or not the head tilt information SH (N) matches the specified tilt information SP. If the head tilt information SH (N) matches (S7: YES), the flag FG (N) remains “0” indicating the match and the process goes to S9. move on. If they do not match (S7: NO), the flag FG (N) is set to “1” indicating mismatch in S11, and the process proceeds to S9.

  If there is still an LED head 81 that has not been checked for tilt direction (S9: NO), “1” is added to the head number N in S13, and the process returns to S5. If there is no remaining head (S9 :: YES), If the head tilt information SH (N) of the LED heads 81 for all colors matches the specified tilt information SP in S15 (S15: YES), it is allowed to shift to a normal operation for performing other processing. On the other hand, if there is a head number N in which the head tilt information SH (N) and the specified tilt information SP do not match (S15: NO), the LED head 81 arranged at the position corresponding to the head number N Is displayed on the display unit 71, for example, to prompt the user to replace the LED head 81 with another LED head 81 having a different head tilt direction. In addition, the structure which emits the said message with an audio | voice may be sufficient, and the structure transmitted to the high-order apparatus of the manufacturing line of the printer 1 by data communication may be sufficient if it is a manufacturing stage.

  If the specified inclination information SP is not stored (S1: NO), the head inclination information SH (1) to SH (4) for all colors is acquired from the memory of each LED head 81 in S19, and those head inclinations are obtained in S21. If the sum of the information SH (1) to SH (4) is 0, “0” indicating the positive direction is set in the specified slope information SP in S23, and the transition to the normal operation is permitted. If the total is 4, in S31, “1” indicating a negative direction is set in the specified inclination information SP, and the transition to the normal operation is permitted.

  If the total is “1”, the LED head 81 having the reverse tilt direction is arranged at the position corresponding to one head number N. Therefore, in S25, “0” indicating the forward direction is added to the specified tilt information SP. Set and return to S1. As a result, error processing (S17) for prompting the LED head 81 for the one head number N is performed.

  If the total is “3”, the LED head 81 having the reverse tilt direction is disposed at the position corresponding to one head number N. Therefore, “1” indicating the negative direction in the specified tilt information SP in S29. Is set, and the process returns to S1. As a result, error processing (S17) for prompting the LED head 81 for the one head number N is performed.

  Further, if the total is “2”, for example, head tilt information SH (1) of bed number 1 is set as the specified tilt information SP in S27, and the process returns to S1. As a result, error processing (S17) for prompting the LED head 81 for the two head numbers N is performed.

<Embodiment 2>
6 and 7 show the second embodiment. The difference from the first embodiment lies in the misplacement processing of the LED head 81, and the other points are the same as in the first embodiment. Therefore, the same reference numerals as those in the first embodiment are given and the redundant description is omitted, and only different points will be described next.

  The misplacement processing of the LED head 81 of this embodiment is shown in FIGS. The process of S41 is added to FIG. 5 of the first embodiment, and the process when the specified inclination information SP is not stored is different. The memory information M (N) is a flag indicating the memory capacity required to correct the positional deviation caused by the line tilt error of each LED head 81. If “1”, α / 2, “0”. If there is, it means α. “Α / 2” means that only an area for correcting the positional deviation in either positive or negative direction with respect to the reference line is secured, and α is a wide buffer area capable of correcting the positional deviation in both positive and negative directions. Means secure.

  For the head number N whose memory information M (N) is “1” (S41: YES), the head tilt information SH (N) and the specified tilt information SP need to match (S7, S11). It is not necessary for the head number N whose memory information M (N) is “0” (S41: NO). Then, error processing is performed when the LED head 81 having the reverse tilt direction is arranged for the head number N having a memory capacity of α / 2 (S17).

  If the specified inclination information SP is not stored (S1: NO), the head number N is initialized to “1” and the total number T is initialized to “0” in S51 of FIG. In S53, it is determined whether or not the memory information M (N) is “1” for the head number N. If it is “1” (S53: YES), the head tilt information SH (N) is acquired in S55, and the sum in S57. After adding the value of the head tilt information SH (N) to the number T, the process proceeds to S59. If the memory information M (N) is “0” (S53: NO), the process proceeds to S59.

  When the processes of S55 and S57 are performed for all head numbers N (S59: YES), the process proceeds to S61. On the other hand, when the processes of S55 and S57 are not performed for all the head numbers N (S59: NO), “1” is added to the head number N in S81 and the process returns to S53. In S61, it is determined whether the total value of the memory information M (N) of each LED head 81 is “2”. If the total value is “2” (S61: YES), the process proceeds to S63. If the total number T is “0”, “0” is set in the specified slope information SP (S65), and the total number T is If it is “2”, “1” is set in the specified inclination information SP (S69), and the normal operation is allowed. On the other hand, if the total number T is “1”, for example, the value of SH (1) is set in the specified slope information SP (S67), and the process returns to S1 to perform error processing.

  If the total value is not “2” in S61 (S61: NO), the process proceeds to S71. If the total number T is “0”, “0” is set in the specified slope information SP (S73), and the total number If T is “3”, “1” is set in the specified inclination information SP (S79), and the normal operation is allowed. If the total number T is “1”, “0” is set in the specified slope information SP (S75), and if the total number T is “2”, “1” is set in the specified slope information SP. (S77) Returning to S1, error processing is performed.

<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, the unnecessary area is reduced for all color images other than the reference color. However, for example, the unnecessary area may be reduced only for a specific color image such as a large amount of displacement. Good.

  (2) In the above embodiment, the inclination of the reference color line GK and the inclination of the correction color line GC (GM, GY) are the same positive inclination, but of course, the inclination errors of all the lines are the same. It may be in the negative direction. In addition, for example, even if the line inclination error of some correction colors in the correction color is in the positive and negative direction with respect to the line inclination error of the reference color, the use area of the memory in consideration of the line inclination error of some correction colors Can be reduced. For example, when the line inclination error of some correction colors is −θ2 as shown in FIG. 4, the area shown by the dotted line is used as the use area and the area shown by the solid line is reduced as the unnecessary area. It is. However, as shown in FIG. 4, when the line tilt error is + θ2, the exposure start of each scanning line is the light emission timing of the leftmost light emitting diode 30, whereas when the line tilt error is −θ2. Since the exposure start of each scanning line is the light emission timing of the light emitting diode 30 at the right end, both cannot be processed by the same arithmetic circuit. Accordingly, it is preferable that the inclination of the reference color line GK and the inclination of the correction color line GC (GM, GY) are the same positive inclination as in the present embodiment.

(3) In the above embodiment, the scanning line GK is the reference line. However, for example, a straight line (for example, the straight line G0) different from the scanning line of any color may be used as the reference line. However, with the configuration of the above embodiment, the memory area for correcting the deviation of the black exposure position can be reduced.

  (4) In the above embodiment, the correction process can be reduced during black monochrome printing by setting the reference color to black. However, the present invention is not limited to this, and if the reference color is a light color system such as yellow, the correction process is not noticeable. It is difficult and less harmful.

  (5) As a method for correcting the deviation of the exposure position, in addition to the method of the above embodiment, raster data for a plurality of lines are collectively transferred to the buffer area, and a plurality of lines are corrected so as to correct the positional deviation of each line. The present invention can also be applied to a method of selecting an address from a raster data group.

1 is a side sectional view showing a schematic configuration of a printer according to Embodiment 1 of the present invention. Block diagram showing the electrical configuration of the printer Schematic diagram of LED head for explaining line tilt error and arrangement error of light emitting diode Schematic diagram showing the relationship between the displacement of the correction color scan line relative to the reference color scan line and the memory area Flow chart showing the contents of correction processing Flowchart showing details of correction processing of embodiment 2 (part 1) Flow chart showing contents of correction processing (part 2)

1: Printer (image forming device)
23: LED exposure device (exposure means)
30: Light emitting diode (light emitting element)
61: CPU (correction means, determination means, notification means)
65: RAM (memory)
81: LED head (support member with light emitter)
85: Light emitter 87: Support member GK: Scanning line (reference line)

Claims (5)

A photoreceptor,
A plurality of light emitters having a plurality of light emitting elements arranged thereon and a support member that supports the light emitters, and exposing the photoconductor to form an electrostatic latent image corresponding to an image formed on a recording medium. Exposure means,
Memory,
Correction means for correcting a deviation of the exposure position of the exposure means with respect to a reference line, which is a reference line when aligning the images formed by exposure of the plurality of exposure means, using the memory area And comprising
The plurality of exposure means are configured such that the light emitter is inclined in the same direction with respect to the support member, and the exposure position is shifted only in one direction with respect to the reference line,
Wherein the correction means, also in correcting the exposure positions of any of the exposure means, a region for correcting the exposure position shifted in the one direction and secured in the memory, the exposure position shifted in a direction opposite to the one direction An image forming apparatus that does not secure an area for correcting the above in the memory. The image forming apparatus according to claim 1,
The image forming apparatus, wherein the reference line is a scanning line formed by a light emitter of one exposure unit. The image forming apparatus according to claim 2 ,
The image forming apparatus according to claim 1, wherein the one exposure unit is an exposure unit that minimizes an arrangement variation of the plurality of light emitting elements among the plurality of exposure units. An image forming apparatus according to claim 2 or claim 4,
The image forming apparatus that exposes the electrostatic latent image of a black image or a yellow image on the photosensitive member. An image forming apparatus according to any one of claims 1 to 4 , wherein
Determining means for determining whether the inclination of the light emitter with respect to the support member corresponds to a correction direction of an exposure position by the correcting means;
An image forming apparatus comprising: a notification unit that performs a notification operation according to a determination result of the determination unit.

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