JP2010094822A - Image forming apparatus and method of controlling light amount - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely and efficiently correct a light amount while suppressing a correction data amount which determines the laser light amount to a suitable amount. <P>SOLUTION: A dividing part divides an axis of the ordinate of a correction light amount curve in steps of setting light amount units A by a dividing line parallel to a main scan direction (step S12) and undergoes block division by a block sectioning line which passes an intersection between the dividing line and the correction light amount curve and is perpendicular to the dividing line (step S13). When the number of the blocks is smaller than a permissible range (step S14; YES), the dividing part subtracts a predetermined value x from the setting light amount unit A (step S15) and undergoes block division again. If the number of the blocks exceeds the permissible range (step S16; YES), the dividing part adds the predetermined value x to the setting light amount unit A (step S17) and undergoes block division again. A light amount control part controls the light amount of a light source according to a representative value of each block (step S20). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile, and a printer, and more particularly to a laser type image forming apparatus and a light amount control method.

  In a laser type image forming apparatus, in order to make the density of the output image constant, it is necessary to make the charge amount of the photosensitive drum constant. Therefore, APC (Auto Power Control) control is performed by the laser drive circuit, and the exposure amount of the photosensitive drum is made constant by keeping the light quantity of the laser beam constant during the scanning period.

  However, unevenness in charge amount (sensitivity unevenness) occurs due to unevenness in the thickness of the photosensitive layer of the photosensitive drum, and this causes density unevenness. In addition, in a scanning optical device having a laser light source, laser scanning is performed by emitting laser light to a polygon mirror (rotary reflection mirror). For this reason, the amount of laser light reaching the photosensitive drum becomes lower at the end of the photosensitive drum where the angle change of the reflecting surface becomes larger than near the center of the photosensitive drum where the angle change of the reflecting surface becomes small. . In addition, since the reflectance varies depending on the incident angle to the f-θ lens and the mirror, a difference occurs in the amount of laser light reaching the photosensitive drum. In order to satisfy the recent demand for higher image quality, it is necessary to suppress the uneven sensitivity of the photosensitive drum caused by these causes.

Therefore, in order to suppress the sensitivity unevenness of the photosensitive drum, the charged state of the photosensitive drum and the laser light amount during one main scanning are measured, and the laser light amount of each block obtained by equally dividing the main scanning direction by an arbitrary number is charged. Conventionally, a method of making the charge amount of the photosensitive drum uniform by correcting according to the above has been performed. Further, Patent Document 1 discloses that the potential unevenness of the photosensitive drum is divided into a high frequency component and a low frequency component, the high frequency component is PWM control of the laser light amount, and the low frequency component is corrected by correcting the light amount by changing the light amount of the laser light. A method for suppressing unevenness is described.
JP 2005-234043 A

  However, it is conceivable to increase the number of blocks in the main scanning direction in order to perform highly accurate correction using the conventional method described above or the method described in Patent Document 1. However, if the number of blocks is increased, the amount of correction data for the laser light amount also increases, so it is necessary to increase the memory capacity for storing the correction data. Furthermore, as the correction data increases, it is necessary to increase the transfer speed for transferring the correction data to the light amount control unit that controls the light source. Such an increase in memory capacity and an increase in transfer speed lead to an increase in the cost of the apparatus.

  The present invention has been made to solve the above-described problem, and an image forming apparatus and light amount correction that realize high-precision and efficient light amount correction while suppressing the correction data amount for determining the laser light amount to an appropriate amount. It is intended to provide a method.

  The image forming apparatus according to the first aspect of the present invention includes a light source that irradiates light to a photoconductor, a generation unit that generates a corrected light amount curve by correcting the emitted light amount of the light source for each position in the main scanning direction, and The generated correction light amount curve is divided by a dividing line parallel to the main scanning direction for each set light amount unit, and passes through the intersection of the correction light amount curve and the dividing line and is perpendicular to the dividing line. A dividing means for dividing the correction light quantity curve into blocks, and when the number of blocks generated by the division exceeds a predetermined allowable range, the set light quantity unit is set larger by a predetermined amount, and the block Is less than the allowable range, the set light quantity unit is set to be smaller by a predetermined amount, and the block is divided with respect to the dividing means until the number of blocks falls within the allowable range. Split control means for repeatedly performing splitting, specifying means for specifying a representative value of each block with respect to a correction light amount curve in which the number of blocks is within the allowable range, and representative values of the specified blocks And a light quantity control means for performing control to switch the emitted light quantity in the main scanning direction according to the stored representative value of each block.

  According to a seventh aspect of the present invention, there is provided a light amount control method for generating a corrected light amount curve by correcting an emitted light amount of a light source for irradiating light on a photosensitive member for each position in a main scanning direction, and the generation step. The corrected light amount curve is divided for each set light amount unit by a dividing line parallel to the main scanning direction, and the block light dividing line passing through the intersection of the corrected light amount curve and the dividing line and perpendicular to the dividing line is used. A step of dividing the correction light amount curve into blocks, and when the number of blocks generated by the division exceeds a predetermined allowable range, the set light amount unit is set larger by a predetermined amount, When the number of blocks is less than the allowable range, the set light quantity unit is set small by a predetermined amount, and the dividing means is set until the number of blocks falls within the allowable range. A step of repeatedly performing block division and specifying a representative value of each block with respect to a correction light amount curve in which the number of blocks is within the allowable range; and a storage unit storing the representative value of each specified block A storage step for storing, and a light amount control step for performing control to switch the emitted light amount in the main scanning direction in accordance with the stored representative value of each block.

  According to this configuration, by keeping the number of blocks within a predetermined allowable range, it is possible to efficiently generate a value used for light amount correction (representative value of each block) within the conditions of the apparatus performance. Further, by dividing the correction light amount curve by the block dividing line that passes through the intersection of the correction light amount curve and the dividing line and is perpendicular to the dividing line, the block is finely divided in the region where the fluctuation of the correction light amount curve is intense, Block division can be roughly performed in a region where fluctuation is moderate. That is, the representative value of each block can be a value that appropriately corresponds to the fluctuation of the correction light amount curve.

  According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the permissible range stores the representative value of each block for each scan of light irradiation to the photosensitive member by the light source. The number of representative values that can be transferred when transferring from the storage means to the light quantity control means, or the transfer speed when transferring the representative value of each block from the storage means to the light quantity control means for each scan, or This is based on the memory capacity of the storage means or the number of blocks arbitrarily set by the designer according to the device specifications.

  According to this configuration, by using the range set as described above as the allowable range, it is possible to efficiently generate a value (representative value of each block) used for light amount correction within the conditions of the apparatus performance.

  Further, the invention according to claim 3 is the image forming apparatus according to claim 1 or 2, wherein the division control unit is a target section in the main scanning direction of the correction light amount curve that satisfies a predetermined condition. Determining means for determining, if the number of blocks exceeds the allowable range, the set light quantity unit of the section other than the target section is set larger by a predetermined amount, the number of blocks is If it falls below the allowable range, the set light quantity unit of the target section is set smaller by a predetermined amount, and block division is repeatedly performed on the dividing means until the number of blocks falls within the allowable range. It is something to make.

  According to this configuration, when the number of blocks does not satisfy the permissible range, the block division can be performed by changing the set light quantity unit and limiting the section in which the block division is performed again. In other words, since block division can be performed in different set light quantity units in the target section and sections other than the target section, for example, block division can be performed by changing the set light quantity unit according to the state (variation) of the correction light quantity curve. it can.

  According to a fourth aspect of the present invention, in the image forming apparatus according to the third aspect, the determining unit includes a predetermined number or more of the block dividing lines in the main scanning direction of the corrected light amount curve. To be determined as the target section.

  It can be said that the section with many block delimiters is a section where the variation of the correction light quantity curve is large. According to this configuration, since the determining unit sets a section where the variation of the correction light amount curve is large as the target section, if the number of blocks is below the allowable range, the block is further divided into the target sections (that is, sections where the variation is large). To increase the number of blocks, and conversely, if the number of blocks exceeds the allowable range, the number of blocks can be reduced by roughly dividing blocks in a section other than the target section (that is, a section with small fluctuations). Thereby, the representative value of each block becomes a value appropriately corresponding to the fluctuation of the correction light amount curve, and a value (representative value of each block) used for light amount correction can be efficiently generated within the conditions of the apparatus performance.

  According to a fifth aspect of the present invention, in the image forming apparatus according to the third aspect of the invention, the determining means determines that the difference between the maximum value and the minimum value of the correction light amount in the main scanning direction of the correction light amount curve. A section that is equal to or greater than a predetermined value is determined as the target section.

  According to this configuration, since the determining unit sets a section where the variation of the correction light amount curve is large as the target section, if the number of blocks is below the allowable range, the block is further divided into the target sections (that is, sections where the variation is large). To increase the number of blocks, and conversely, if the number of blocks exceeds the allowable range, the number of blocks can be reduced by roughly dividing blocks in a section other than the target section (that is, a section with small fluctuations). Thereby, the representative value of each block becomes a value appropriately corresponding to the fluctuation of the correction light amount curve, and a value (representative value of each block) used for light amount correction can be efficiently generated within the conditions of the apparatus performance.

  The invention according to claim 6 is the image forming apparatus according to any one of claims 1 to 5, wherein the specifying unit sets a predetermined light amount level as a reference value, and The offset value from the reference value is specified as the representative value of each block.

  According to this configuration, by using the representative value as the offset value, the size of data indicating the representative value of each block can be reduced as compared with the value from the 0 level. Accordingly, the memory capacity of the storage unit can be reduced, and the amount of data transferred from the storage unit to the light amount control unit during the light amount control can be reduced.

  According to the present invention, the value used for the light amount correction (representative value of each block) is obtained by changing the set light amount unit and repeatedly adjusting the block division to keep the number of blocks within a predetermined block number allowable range. ) Can be efficiently generated within the conditions of the apparatus performance. Further, by dividing the correction light amount curve by the block dividing line that passes through the intersection of the correction light amount curve and the dividing line and is perpendicular to the dividing line, the block is finely divided in the region where the fluctuation of the correction light amount curve is severe, Block division can be roughly performed in a region where fluctuation is moderate. That is, the representative value of each block appropriately corresponds to the fluctuation of the corrected light amount curve, and a value (representative value of each block) used for light amount correction can be efficiently generated within the conditions of the apparatus performance.

  Hereinafter, an image forming apparatus and a light amount control method according to an embodiment of the present invention will be described with reference to the drawings. In this embodiment, a copying machine is described as an example of the image forming apparatus, but the present invention can also be applied to printers, facsimiles, multifunction machines, and the like that employ a laser system.

[First Embodiment]
FIG. 1 is a schematic side view mainly showing a mechanical configuration of the copying machine 1 according to the present embodiment. The copying machine 1 includes a main unit 20, a sheet post-processing unit 300 disposed on the left side of the main unit 20, an input operation unit 400 for a user to input various operation commands and the like, and an upper part of the main unit 20. The document reading unit 500 disposed in the document reading unit 500 and the document feeding unit 600 disposed above the document reading unit 500.

  The input operation unit 400 includes an operation panel 401, a start key 402, a numeric keypad 403, and the like. The operation panel 401 displays various operation screens and various operation buttons for the user to input various operation commands. The start key 402 is used for the user to input a print execution command and the like, and the ten key 403 is used for inputting the number of copies to be printed.

  The document feeding unit 600 includes a document placement unit 601, a document discharge unit 602, a paper feed roller 603, a document transport unit 604, a contact glass 605, and the like, and the document reading unit 500 includes a scanner 501 and the like. The paper feed roller 603 feeds out the original set on the original placement unit 601, and the original transport unit 604 transports the fed originals one by one on the scanner 501. The scanner 501 includes a CCD (Charge Coupled Device) sensor, a CMOS (Complementary Metal Oxide Semiconductor) sensor, an exposure lamp, and the like. The scanner 501 sequentially reads a conveyed document and outputs image data. The read original is discharged to the original discharge unit 602. Further, when reading a document placed on the contact glass 605, the scanner 501 is slid in the A direction by a driving unit (not shown) to read the document.

  The main body 20 includes a plurality of paper feed cassettes 201, a plurality of paper feed rollers 202, a transfer roller 203, a photosensitive drum 204, an exposure device 205, a developing device 206, a fixing roller 208, a discharge port 209, and a discharge tray 210. .

  The photosensitive drum 204 is uniformly charged by a charging device (not shown) while rotating in the direction of the arrow. The exposure device 205 converts the modulation signal generated based on the image data of the document read by the document reading unit 500 into a laser beam and outputs it, and forms an electrostatic latent image on the photosensitive drum 204. The developing device 206 supplies a developer to the photosensitive drum 204 to form a toner image. Here, the exposure apparatus 205 includes a light source that outputs laser light, a polygon mirror that scans the laser light output from the light source in the main scanning direction, which is the longitudinal direction of the photosensitive drum 204, and the like, and forms an original image. The light source is driven in accordance with a PWM signal having a pulse width corresponding to the gradation value of each pixel, and the photosensitive drum 204 is exposed.

  On the other hand, the paper feeding roller 202 pulls out the recording paper from the paper feeding cassette 201 in which the recording paper is stored, and conveys the drawn recording paper to the transfer roller 203. The transfer roller 203 transfers the toner image on the photosensitive drum 204 to the conveyed recording paper. The recording paper to which the toner image has been transferred is conveyed to the fixing roller 208, and the fixing roller 208 heats and transfers the transferred toner image to the recording paper. Thereafter, the recording paper is conveyed to the discharge port 209 and carried into the paper post-processing unit 300. The recording paper is also discharged to the discharge tray 210 as necessary.

  The paper post-processing unit 300 includes a carry-in port 301, a recording paper transport unit 302, a carry-out port 303, a stack tray 304, and the like. The recording paper transport unit 302 sequentially transports the recording paper carried into the carry-in port 301 from the discharge port 209 and finally ejects the recording paper from the carry-out port 303 to the stack tray 304. The stack tray 304 is configured to move up and down in the direction of the arrow in accordance with the number of recording sheets stacked from the carry-out port 303.

  FIG. 2 is a functional block diagram showing an electrical configuration of the copying machine 1 according to the present embodiment. The copying machine 1 includes a control unit 100, a storage unit 110, a document reading unit 500, an image memory 120, an image processing unit 130, an image forming unit 140, a sheet post-processing unit 300, an input operation unit 400, and a network I / F unit 150. It is prepared for. The same components as those of the copying machine 1 described with reference to FIG.

  The control unit 100 is configured by a CPU (Central Processing Unit) or the like, reads a program stored in the storage unit 110 in accordance with an input instruction signal or the like, executes a process, and sends the processing to each functional unit. The copier 1 is comprehensively controlled by outputting an instruction signal, transferring data, and the like. The control unit 100 includes a corrected light amount curve generating unit 101, a dividing unit 102, a representative value specifying unit 103, and a light amount control unit 104.

  The corrected light amount curve generation unit 101 generates a corrected light amount curve obtained by correcting the light amount of the laser light emitted from the light source 141 based on various measurement results. FIG. 3 is a diagram illustrating an example of the corrected light amount curve G. As illustrated in FIG. The corrected light amount curve generation unit 101 generates a corrected light amount curve G based on measurement results such as the charged state of the photosensitive drum 204 and the light amount of laser light emitted from the light source 141 during one scan. That is, the corrected light amount curve generation unit 101 generates a corrected light amount curve in which adjustment (correction) of the laser light amount to be exposed to the photosensitive drum 204 is performed for each position in the main scanning direction so as not to generate density unevenness. Since this light amount correction curve calculation method uses a well-known technique that has been conventionally used, a description thereof will be omitted.

  The dividing unit 102 divides the corrected light amount curve G by a dividing line parallel to the main scanning direction for each set light amount unit, and passes through the intersection of the dividing line and the corrected light amount curve G and is a block delimiter perpendicular to the dividing line. The correction light quantity curve G is divided into blocks by lines.

  This will be specifically described. First, the dividing unit 102 sets the initial value of the set light quantity unit to A, and divides the vertical axis of the corrected light quantity curve G in increments of the set light quantity unit A as shown in FIG. That is, the dividing unit 102 sets the dividing line a parallel to the main scanning direction on the corrected light amount curve G in increments of the set light amount unit A. Next, as illustrated in FIG. 5, the dividing unit 102 divides the corrected light amount curve G into blocks by a block dividing line b that passes through the intersection of the corrected light amount curve G and the dividing line a and is perpendicular to the dividing line a. . Here, in the case of FIG. 5, the number of blocks generated by the division by the dividing unit 102 is 13.

  The representative value specifying unit 103 specifies a representative value of each block of the corrected light amount curve G in which the number of blocks satisfies a preset allowable range. It should be noted that block division is repeatedly performed while the set light quantity unit A is varied by control by the control unit 100 until the number of blocks falls within an allowable range. This repeated process will be described in detail later.

  The representative value specifying unit 103 specifies one of the upstream end point and the downstream end point in the main scanning direction of each block as the representative value of the block. Referring to FIG. 6 in detail, for the third block counted from the upstream side in the main scanning direction, the representative value specifying unit 103 specifies L1 which is the value of the upstream end point P31 as the representative value of the block. To do. Further, for the tenth block, the representative value specifying unit 103 specifies L2 that is the value of the upstream end point P101 as the representative value of the block. In the present embodiment, the upstream end points (for example, end points P31 and P101) of each block in the main scanning direction are described as representative values. However, the downstream end points (for example, end points P32 and P102) are described. ) May be specified as a representative value.

  The light amount control unit 103 measures the length in the main scanning direction of each block of the correction light amount curve G using a clock signal generated by a clock circuit (not shown) included in the control unit 100, and represents a representative value at the measured timing. The representative value specified by the specifying unit 103 is read from a representative value storage unit 112 described later, and control for switching the amount of light emitted from the light source 141 is performed.

  The storage unit 110 stores programs, data, and the like for realizing various functions provided in the copying machine 1. In the present embodiment, the storage unit 110 stores a light amount control program 111 and functions as the representative value storage unit 112. The light amount control program 111 generates a corrected light amount curve of laser light based on the laser light amount of the light source 141 and the charged state of the photosensitive drum 204, and after dividing the corrected light amount curve into an appropriate number of blocks in the main scanning direction, This is a program for specifying a representative value of a block and controlling the amount of laser light emitted from the light source 141 according to this representative value. The representative value storage unit 112 stores the representative value of each block specified by the representative value specifying unit 103.

  The image memory 120 temporarily stores image data transmitted from an external device via the network I / F unit 150. The image processing unit 130 performs image processing such as image correction and enlargement / reduction on the image data stored in the image memory 120. The image forming unit 140 forms an image on a sheet based on the image data output from the image memory 120, and includes the photosensitive drum 204, the exposure device 205, the developing device 206, and the like illustrated in FIG. The exposure apparatus 205 has a light source 141 that emits laser light. The network I / F unit 150 includes a communication module such as a LAN board, and transmits / receives various data to / from an external device via a network (not shown) connected to the network I / F unit 150.

  FIG. 7 is a flowchart showing the flow of the light amount control process executed when the control unit 100 reads the light amount control program 111 in the present embodiment. Hereinafter, the flow of the light amount control process will be described in detail with reference to the drawings.

  First, the corrected light amount curve generation unit 101 generates a corrected light amount curve G as shown in FIG. 3, for example (step S11). Next, the dividing unit 102 sets an initial value A as a set light quantity unit, and divides the vertical axis of the corrected light quantity curve G in increments of the set light quantity unit A as shown in FIG. The correction light quantity curve G is divided into blocks by a block dividing line b passing through the intersection of G and the dividing line a and perpendicular to the dividing line a (step S13).

  Then, the control unit 100 determines whether or not the number of blocks generated by the block division is within a predetermined allowable range. The allowable range of the number of blocks is, for example, the number of transferable representative values (transfer speed) and the representative value when the representative value of each block is transferred from the representative value storage unit 112 to the light amount control unit 104 for each scan. This is set based on the memory capacity of the storage unit 112 or the number of blocks arbitrarily set by the designer.

  For example, when the allowable range of the number of blocks is 14 to 17, since the number of blocks shown in FIG. 5 is 13, the control unit 100 determines that the number of blocks is below the allowable range (step S14; YES) ), The set light quantity unit is updated to a value obtained by subtracting the predetermined value x from A (step S15), and the process proceeds to step S12. Here, a value obtained by subtracting a predetermined value x from the set light quantity unit A is defined as A2.

  Subsequently, as shown in FIG. 8, the dividing unit 102 divides the vertical axis of the corrected light amount curve G in increments of the set light amount unit A2 (step S12), passes through the intersection of the corrected light amount curve G and the dividing line a, and The correction light quantity curve G is divided into blocks by a block dividing line b perpendicular to the dividing line a (step S13). Then, the control unit 100 determines whether or not the number of blocks generated by block division is within an allowable range. Since the number of blocks of the correction light quantity curve G shown in FIG. 8 is 16, and the allowable range of the number of blocks is 14 to 17, the control unit 100 determines that the allowable range is satisfied. In other words, when the number of blocks is below the allowable range, the set light quantity unit is set to a smaller value in order to increase the number of blocks, and block division is performed again. The control unit 100 repeats this process until the number of blocks falls within the allowable range.

  On the other hand, for example, when the allowable range of the number of blocks is 9 to 12, since the number of blocks shown in FIG. 5 is 13, the control unit 100 determines that the number of blocks exceeds the allowable range (step S16; (YES), the set light quantity unit is updated to a value obtained by adding A to the predetermined value x (step S17), and the process proceeds to step S12. Here, a value obtained by adding the predetermined value x from the set light quantity unit A is defined as A1.

  Subsequently, as shown in FIG. 9, the dividing unit 102 divides the vertical axis of the corrected light amount curve G in increments of the set light amount unit A1 (step S12), passes through the intersection of the corrected light amount curve G and the dividing line a, and The correction light quantity curve G is divided into blocks by a block dividing line b perpendicular to the dividing line a (step S13). Then, the control unit 100 determines whether or not the number of blocks is within a predetermined allowable range. Since the number of blocks of the corrected light amount curve G shown in FIG. 9 is 10 and the allowable range of the number of blocks is 9 to 12, the control unit 100 determines that the allowable range is satisfied. That is, when the number of blocks exceeds the allowable range, the set light quantity unit is set to a larger value in order to reduce the number of blocks, and block division is performed again. The control unit 100 repeats this process until the number of blocks falls within the allowable range.

  Then, the representative value specifying unit 103 specifies the representative value of each block in the corrected light amount curve G (step S18), and for example, associates the number of each block with the representative value and stores them in the representative value storage unit 112 (step S19). ). Thereafter, the light amount control unit 104 measures the length of each block of the corrected light amount curve G in the main scanning direction, and emits the light source 141 according to the representative value of each block stored in the representative value storage unit 112 at the measured timing. The light amount is controlled by switching the light amount (step S20).

  As described above, the number of blocks of the corrected light amount curve G is, for example, the representative value that can be transferred when the representative value of each block is transferred from the representative value storage unit 112 to the light amount control unit 104 for each scan. The amount of light (correction rate), the memory capacity of the representative value storage unit 112, or the amount of blocks arbitrarily set by the designer is adjusted by repeatedly adjusting the block division so as to be within the allowable range, thereby correcting the light amount. Can be efficiently generated within the conditions of the device performance.

  Further, by dividing the correction light amount curve G by the block dividing line b that passes through the intersection of the correction light amount curve G and the dividing line a and is perpendicular to the dividing line a, in an area where the correction light amount curve G varies greatly. Block division can be performed finely, and rough division can be performed in a region where the fluctuation is moderate. That is, the representative value of each block appropriately corresponds to the fluctuation of the corrected light amount curve G, and a value (representative value of each block) used for light amount correction can be efficiently generated within the conditions of the apparatus performance.

  The present invention is not limited to the configuration of the above embodiment, and various modifications can be made. For example, in the present embodiment, the vertical axis of the corrected light amount curve G has been described as being divided in increments of the set light amount unit A, but the vertical axis of the corrected light amount curve G may be divided by a predetermined number at equal intervals. In this case, the dividing unit 102 first performs block division by a predetermined number N, and when the control unit 100 determines that the number of blocks exceeds the allowable range, the dividing unit 102 subtracts, for example, 1 from N and blocks again. Split. If it is determined that the number of blocks is below the allowable range, the dividing unit 102 adds 1 to N, for example, and performs block division again.

  The representative value specifying unit 103 has been described as specifying the value from 0 of either the upstream end point or the downstream end point in the main scanning direction of each block as the representative value of each block. A value may be set, and an offset value from this reference value may be specified as a representative value.

  This will be described in detail with reference to FIG. The representative value specifying unit 103 sets the reference value L for the corrected light amount curve G in which the number of blocks is within the allowable range. Then, an offset value (a value expressed by a difference from the reference value L) of the upstream or downstream end point from the reference value L is specified for each block. Then, the representative value storage unit 112 stores this offset value as a representative value of each block. As described above, since the representative value of each block is not set to the value from the 0 level but is set to the offset value, the representative value can be made small, so that the size of the data indicating the representative value can be reduced. Therefore, the memory capacity of the representative value storage unit 112 can be reduced, and the amount of data transferred from the representative value storage unit 112 to the light amount control unit 104 during light amount control can be reduced.

[Second Embodiment]
In the first embodiment, when the number of blocks after block division is not within the allowable range, the block division is repeatedly performed by changing the set light quantity unit over the entire region in the main scanning direction. In the second embodiment, a target section in the main scanning direction is set, and when the number of blocks is not within an allowable range, block division is performed by changing the set light quantity unit in the target section or in a section other than the target section. The case where it repeats is demonstrated. The mechanical configuration and electrical configuration of the copying machine 1 according to the present embodiment are the same as those shown in FIGS. 1 and 2 shown in the first embodiment, and thus description thereof will be omitted. Only different portions will be described.

  FIG. 11 is a flowchart showing the flow of light amount control processing executed when the control unit 100 reads the light amount control program 111 in the present embodiment. The same processing steps as those in the flowchart described with reference to FIG. 7 in the first embodiment are denoted by the same reference numerals, and only different portions of the processing steps will be described.

  First, it is assumed that the dividing unit 102 divides the correction light amount curve G into blocks in the set light amount unit A every step in the main scanning direction as shown in FIG. 5 (step S12). When the allowable range of the number of blocks is 14 to 17, since the number of blocks shown in FIG. 5 is 13, the control unit 100 determines that the number is below the allowable range (step S16; YES). Then, as illustrated in FIG. 12, the control unit 100 sets, as the target section, a section including, for example, a predetermined number or more of block delimiters b in the main scanning direction of the corrected light amount curve G.

  Specifically, when a predetermined number of block dividing lines b are included in a predetermined width in the main scanning direction, the control unit 100 sets the width (section) as a target section. In addition, the main scanning direction may be divided into equally spaced sections, and a section including a predetermined number or more of block delimiting lines b may be set as a target section. Further, when the difference between the maximum value and the minimum value in a continuous block is equal to or larger than a predetermined value, the continuous block may be set as a target section. That is, the method of setting the target section may be a method in which a section in which the value variation of the corrected light amount curve G is large is set as the target section.

  Subsequently, the dividing unit 102 updates the set light quantity unit to a value (A2) obtained by adding a predetermined value x to A, and as shown in FIG. 12, the vertical axis of the corrected light quantity curve G is set in increments of the set light quantity unit A2 only for the target section. (Step S32). Further, the dividing unit 102 divides the corrected light amount curve G into blocks by the block dividing line b that passes through the intersection of the corrected light amount curve G and the dividing line a and is perpendicular to the dividing line a (step S13).

  Then, the control unit 100 determines whether or not the number of blocks generated by block division is within an allowable range. Since the number of blocks of the corrected light amount curve G shown in FIG. 12 is 14 and the allowable range of the number of blocks is 14 to 17, the control unit 100 determines that the allowable range is satisfied.

  On the other hand, as shown in FIG. 5, the dividing unit 102 divides the corrected light amount curve G into blocks in the main scanning direction in increments of the set light amount unit A (step S12), and when the allowable number of blocks is 9 to 12, Since the number of blocks shown in FIG. 5 is 13, the control unit 100 determines that the allowable range is exceeded (step S14; YES). The dividing unit 102 updates the set light quantity unit to a value (A1) obtained by subtracting a predetermined value x from A, and as shown in FIG. 13, the vertical axis of the corrected light quantity curve G is set in increments of the set light quantity unit A1 only in the sections other than the target section. (Step S31). Further, the dividing unit 102 divides the corrected light amount curve G into blocks by the block dividing line b that passes through the intersection of the corrected light amount curve G and the dividing line a and is perpendicular to the dividing line a (step S13).

  Then, the control unit 100 determines whether or not the number of blocks generated by block division is within an allowable range. Since the number of blocks of the corrected light quantity curve G shown in FIG. 13 is 12 and the allowable range of the number of blocks is 9 to 12, the control unit 100 determines that the allowable range is satisfied.

  Then, the representative value specifying unit 103 specifies the representative value of each block in the corrected light amount curve G in which the number of blocks satisfies the allowable range (step S18), and associates the number of each block with the representative value, for example. It memorize | stores in the memory | storage part 112 (step S19). Thereafter, the light amount control unit 104 measures the length of each block of the corrected light amount curve G in the main scanning direction, and emits the light source 141 according to the representative value of each block stored in the representative value storage unit 112 at the measured timing. The light amount is controlled by switching the light amount (step S20).

  In this way, when the number of blocks is below the allowable range, by changing the set light quantity unit to a smaller value only for the section where the fluctuation of the correction light quantity curve is large and performing block division again, Finely divided into blocks. On the other hand, if the number of blocks exceeds the permissible range, the set light quantity unit is set to a larger value only for the section where the fluctuation of the correction light quantity curve is small, and the block division is performed again. Divided. Therefore, the representative value of each block can be a value appropriately corresponding to the fluctuation of the corrected light amount curve, and the value (representative value of each block) used for light amount correction can be efficiently generated within the conditions of the apparatus performance. Can do.

1 is a schematic side view mainly showing a mechanical configuration of a copying machine. FIG. 2 is a functional block diagram showing an electrical configuration of a copying machine. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The flowchart which shows the flow of the light quantity correction process in 1st Embodiment. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The figure for demonstrating an offset value. The flowchart which shows the flow of the light quantity correction process in 2nd Embodiment. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve. The figure for demonstrating the block division | segmentation of a correction | amendment light quantity curve.

Explanation of symbols

1 Copying machine 100 control unit (division control means, determination means)
101 correction light quantity curve generation unit (generation means)
102 Dividing unit (dividing means)
103 representative value specifying part (specifying means)
104 Light quantity control unit (light quantity control means)
110 Storage Unit 111 Light Control Program 112 Representative Value Storage Unit (Storage Unit)
500 Document Reading Unit 120 Image Memory 130 Image Processing Unit 140 Image Forming Unit 141 Light Source 300 Paper Post-Processing Unit 400 Input Operation Unit 150 Network I / F Unit

Claims (7)

A light source for irradiating the photoreceptor with light;
Generating means for correcting the emitted light amount of the light source for each position in the main scanning direction to generate a corrected light amount curve;
The generated correction light amount curve is divided by a dividing line parallel to the main scanning direction for each set light amount unit, and passes through the intersection of the correction light amount curve and the dividing line and is perpendicular to the dividing line. Dividing means for dividing the correction light quantity curve into blocks;
When the number of blocks generated by the division exceeds a predetermined allowable range, the set light quantity unit is set larger by a predetermined amount, and when the number of blocks falls below the allowable range, the setting A division control unit that sets a light quantity unit small by a predetermined amount and causes the division unit to repeatedly perform block division until the number of blocks falls within the allowable range;
Specifying means for specifying a representative value of each block with respect to a correction light amount curve in which the number of the blocks is within the allowable range;
Storage means for storing a representative value of each identified block;
A light amount control means for performing control for switching the emitted light amount in the main scanning direction according to the stored representative value of each block;
An image forming apparatus.   The permissible range is the number of representative values that can be transferred when the representative value of each block is transferred from the storage means to the light amount control means for each scan of light irradiation to the photosensitive member by the light source, or the 1 The transfer value when transferring the representative value of each block from the storage means to the light amount control means for each scan, the memory capacity of the storage means, or the number of blocks arbitrarily set by the designer according to the device specifications The image forming apparatus according to claim 1, which is based on the image forming apparatus.   The division control unit further includes a determination unit that determines a target section in the main scanning direction of the correction light amount curve that satisfies a predetermined condition, and when the number of blocks exceeds the allowable range, other than the target section If the set light quantity unit in the section is set larger by a predetermined amount, and the number of blocks is below the allowable range, the set light quantity unit in the target section is set smaller by a predetermined amount. The image forming apparatus according to claim 1, wherein the dividing unit repeatedly performs block division until the number of blocks falls within the allowable range.   The image forming apparatus according to claim 3, wherein the determination unit determines a section including the block dividing lines in a main scanning direction of the correction light quantity curve as a target section.   The determination unit is configured to determine, as the target section, a section in which a difference between a maximum value and a minimum value of the correction light amount is a predetermined value or more in a main scanning direction of the correction light amount curve. Image forming apparatus.   The said specifying means sets a predetermined light quantity level as a reference value, and specifies an offset value from the reference value as a representative value of each block. Image forming apparatus. A generation step of generating a corrected light amount curve by correcting the emitted light amount of the light source that irradiates light to the photoreceptor for each position in the main scanning direction;
The generated correction light amount curve is divided by a dividing line parallel to the main scanning direction for each set light amount unit, and passes through the intersection of the correction light amount curve and the dividing line and is perpendicular to the dividing line. A dividing step of dividing the correction light quantity curve into blocks;
And when the number of blocks generated by the division exceeds a predetermined allowable range, the set light quantity unit is set larger by a predetermined amount, and the number of blocks is below the allowable range , By setting the set light quantity unit small by a predetermined amount, and repeatedly performing block division on the dividing means until the number of blocks falls within the allowable range,
A specifying step of specifying a representative value of each block with respect to a correction light amount curve in which the number of the blocks is within the allowable range;
A storage step of storing a representative value of each identified block in a storage means;
A light amount control step for controlling the emitted light amount of the light source according to the stored representative value of each block;
A light amount control method comprising:

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