JP2013154542A - Method of generating exposure unevenness correction table, light emitting device for exposure, and image forming apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology for accurately correcting the light quantity of light emitting elements while suppressing a memory from increasing.SOLUTION: A method of generating a correction table for correcting exposure unevenness caused by variation in the light quantity among a plurality of light emitting elements, includes: a step (S10) of setting a correction range for correcting a parameter value of driving signals which light each light emitting element so that each light emitting element can obtain the target exposure light quantity by correcting the light quantity of each light emitting element; a step (S20) of setting a first reference value of the parameter value in the set correction range; a step (S30) of setting the correction sectioning number to be applied to a group of light emitting elements with the exposure light quantity larger than the target exposure light quantity when lighting each light emitting element using the first reference value to be the correction sectioning number or more to be applied to a group of light emitting elements with the exposure light quantity smaller than the target exposure light quantity; and a step (S50) of generating the correction table by associating the correction amount of the parameter value with each set correction section.

Description

  The present invention relates to an exposure unevenness correction table creation method, an exposure light emitting device, and an image forming apparatus, and more particularly to a technique for correcting exposure unevenness due to light emitting elements in an image forming apparatus.

  Conventionally, as a technique for correcting exposure unevenness due to light emitting elements in an image forming apparatus, for example, a technique described in Patent Document 1 is known. In that prior art document, correction data for correcting variations in the amount of exposure light of the beam emitted from the LED caused by individual differences of LED (light emitting diode) elements as light emitting elements is stored in advance in a nonvolatile memory, A technique for reading correction data from a non-volatile memory at the time of drawing and obtaining a desired light amount is disclosed.

JP 2000-351232 A

  However, the LED element that needs to be corrected so that the exposure light quantity is larger than the target exposure light quantity and the lighting time is shortened is generally an LED element that has high light intensity or high imaging efficiency, that is, a large change rate in exposure light quantity. Therefore, when the gradation of the LED element is changed with a single correction section width, the change in the amount of light is when the gradation of a standard light emitting element that does not require correction is changed with a single correction section width. Greater than the light intensity change.

  On the other hand, the LED element that needs to be corrected so that the exposure light amount is smaller than the target exposure light amount and the lighting time is lengthened is an LED element that has a generally low light intensity or low imaging efficiency, that is, a small change rate of the exposure light amount, Therefore, when the gradation of the LED element is also changed with a single correction section width, the change in the light amount is caused by changing the gradation of a standard light emitting element that does not require correction with a single correction section width. It is smaller than the light intensity change at the time.

  Therefore, if the same lighting time width is set as the single correction section width (gradation section width), the exposure light amount change corresponding to one correction section (one gradation) that shortens the lighting time Is larger than the change in exposure light intensity corresponding to one section of the correction that lengthens the lighting time, and even if the same one section is changed, the change in the print density is larger in the correction that shortens the lighting time, and the influence of the correction error is also Easy to come out.

  On the other hand, if the single correction division width (gradation width) can be set finely, the correction error between the correction for shortening the lighting time and the correction for increasing the lighting time can be reduced, but the number of classifications (number of gradations) is small. There is a risk that the memory becomes larger and the memory increases.

  The present invention provides a technique for accurately correcting exposure light amounts of a plurality of light emitting elements used in image formation while suppressing an increase in memory.

  The method for creating an exposure unevenness correction table disclosed in this specification is a method for creating a correction table for correcting exposure unevenness between light emitting elements in an exposure light emitting device in which a plurality of light emitting elements are arranged in a predetermined arrangement. A correction range setting step for setting a correction range for correcting a parameter value of a drive signal for lighting each light emitting element so that the light amount of each light emitting element is corrected to obtain a substantially target exposure light amount. A reference value setting step of setting a first reference value of the parameter value within the set correction range, and when the light emitting elements are turned on using the set first reference value, the target The number of correction categories applied to a light emitting element group having a larger exposure light amount than the exposure light amount is set to be greater than the number of correction categories applied to a light emitting element group having a smaller exposure light amount than the target exposure light amount. To include a division setting step, and a table generation step of generating a correction table in correspondence with the correction amount of the parameter values in the correction sections is set.

  According to this configuration, when each light emitting element is turned on using the reference value, a light emitting element group having a larger exposure light amount than the target exposure light amount, that is, a light emitting element group having a large exposure light amount change rate, uses the reference value. When each light emitting element is turned on, more correction opportunities are set by setting the number of correction classifications for the light emitting element group whose exposure light quantity is smaller than the target exposure light quantity, that is, the light emitting element group whose exposure light quantity change rate is small. Blessed.

  In the section setting step, the light emitting element group having a large exposure light amount change rate has a large light amount change in one correction section. Therefore, the light amount correction is performed by finely dividing the correction section width, while light emission having a small exposure light amount change rate is performed. In the element group, since the change in the light amount in one correction section is small, the light amount is corrected with a large correction section width. Accordingly, an increase in the number of correction sections in the correction range can be suppressed, and more appropriate light amount correction can be performed. That is, it is possible to accurately correct the light amounts of the plurality of light emitting elements used at the time of image formation while suppressing an increase in memory.

  According to this configuration, by changing the correction section width according to the exposure light amount change rate, it is possible to reduce the difference in the light amount change with respect to one correction section, and to correct each light emitting element with high accuracy.

In the exposure unevenness correction table creation method, in the reference value setting step, in the adjustable light amount range, the range on the side to increase the light amount and the range on the side to decrease the light amount are substantially the same. One reference value may be set.
According to this configuration, the adjustable light amount range is optimized, so that manufacturing variations can be absorbed and more light emitting elements, for example, LEDs can be used.

The exposure unevenness correction table creation method further includes a reference value resetting step of setting a second reference value of the parameter value within a correction range divided by the first reference value, In the correction range in which the second reference value is set, the number of sections is set for the second reference value, and the correction setting section width is set for the second reference value. You may be made to be.
In this case, even when light emitting elements having greatly different light intensity changes are mixed, the light quantities can be more accurately aligned.

Further, in the reference value resetting step, a new reference value of the parameter value is set within a correction range divided by the reference value of the parameter value set previously, and in the classification setting step, the new reference value is set. In the correction range in which a reference value is set, the number of sections is set for the new reference value, and the correction setting section width is set for the new reference value. It may be repeated more than once.
In this case, it is possible to align the light amounts with higher accuracy.

  In the exposure unevenness correction table creation method, the parameter value of the drive signal may be a drive time for lighting each light emitting element.

  In this case, since the light amount of the light emitting element depends on the lighting time, the light amount control of the light emitting element can be suitably performed by the driving time of the light emitting element which is the time for lighting the light emitting element.

Further, the light emitting device for exposure disclosed in this specification includes a plurality of light emitting elements arranged in a predetermined array and a drive signal generated based on the correction table created by any one of the above correction table creating methods. And a driving circuit for driving the plurality of light emitting elements.
The exposure light-emitting device may include the correction table.

  Further, an image forming apparatus disclosed in this specification includes a photoconductor and the above-described light-emitting device for exposure as an exposure device that exposes the photoconductor.

  According to the present invention, it is possible to accurately correct the light amounts of a plurality of light emitting elements used during image formation while suppressing an increase in memory.

FIG. 3 is a side sectional view of a main part of the color printer according to the first embodiment. Enlarged view of LED unit and process cartridge Block diagram of light emission control unit and control device Graph showing the concept of exposure unevenness correction 6 is a flowchart schematically showing exposure unevenness correction table creation processing according to the first embodiment. The graph which shows the correction range of a drive signal (drive time) and the reference value of drive time in Embodiment 1. The graph which shows roughly the correction gradation division number and correction gradation division width in Embodiment 1. Table showing the relationship between the number of corrected gradation sections and the corrected gradation section width in the first embodiment 7 is a flowchart schematically showing exposure unevenness correction table creation processing according to the second embodiment. The graph which shows roughly the correction gradation division number and correction gradation division width in Embodiment 2 A table showing the relationship between the number of corrected gradation sections and the corrected gradation section width in the second embodiment

<Embodiment 1>
The first embodiment will be described with reference to FIGS. 1 to 8.

1. Overall Configuration of Color Printer FIG. 1 is a side sectional view schematically showing a main part of an electrophotographic color printer according to a first embodiment. The color printer 1 is an example of an image forming apparatus. As shown in FIG. 1, the color printer 1 includes a main body housing 10 in which a paper feeding unit 20 that supplies paper S, an image forming unit 30 that forms an image on the fed paper S, and an image are formed. A paper discharge unit 90 that discharges the printed paper S, and a control device 100 that controls the operation of each unit.

  In the following description, the direction will be described with reference to the user when using the color printer. That is, in FIG. 1, the left side toward the paper surface is “front side”, the right side toward the paper surface is “rear side”, the rear side toward the paper surface is “left side”, and the front side toward the paper surface is “right side”. To do. In addition, the vertical direction toward the page is defined as the “vertical direction”. Further, the image forming apparatus is not limited to the color printer 1 and may be, for example, a monochrome printer, a multifunction machine having a copy function and a FAX function.

  An openable and closable upper cover 12 is provided on the upper portion of the main body casing 10. The 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, which is an example of a light emitting device for exposure, is provided below. Light emission of the LED print head 41 as an exposure head included in the LED unit 40 is controlled by the control device 100 and the light emission control unit 110 (see FIG. 3).

  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 sheet feeding unit 20 configured as described above, the sheets S in the sheet feeding tray 21 are separated one by one and sent upward, and are turned backward through the conveyance path 28, and the image forming unit 30. To be supplied.

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

  The process cartridges 50K to 50C are arranged side by side in the front-rear direction between the upper cover 12 and the paper feeding unit 20, and are detachably attached to the drum unit 51 as shown in FIG. Development unit 61. The process cartridge 50 supports the photosensitive drum 53. The process cartridges 50K to 50C have 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 includes a photosensitive drum 53 as an example of a photosensitive member, and a scorotron charger 54.

  The developing unit 61 includes a developing roller 63, a supply roller 64, and a toner storage chamber 66 that stores toner. The developing unit 61 is mounted on the drum unit 51, thereby forming an exposure hole 55 that faces the photosensitive drum 53 from above, as shown in FIG. The LED unit 40 holding the LED print head 41 is inserted into the lower end of the exposure hole 55. Details of the LED print head 41 will be described later.

  Further, a cartridge drawer 15 that detachably accommodates each process cartridge 50 is provided in the main body housing 10.

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

  A conveying belt 73 is stretched between the driving roller 71 and the driven roller 72. 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 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 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 print head 41. It is exposed by the 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 on the conveyor belt 73 passes between each photosensitive drum 53 and each transfer roller 74, so that the toner image formed on each photosensitive drum 53 is on the sheet S. Transcribed. 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 heat-fixed paper S is discharged to the outside of the main body housing 10 via the paper discharge unit 90 and accumulated in the paper discharge tray 13.

2. 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 and an EEPROM 100B configured by a CPU and the like.

  The light emission control unit 110 controls the light emission of each light emitting element P of the LED print head 41 in cooperation with the control device 100. The LED print head 41 has a plurality of LEDs (light emitting diodes) as light emitting elements P arranged in the main scanning direction orthogonal to the paper transport direction. A lens (not shown) such as a microlens that collects light from the LED is provided on the output side of each LED print head 41.

  The light emission control unit 110 includes a RAM 120, an ASIC 130, and an oscillation circuit 140 as shown in FIG. Four LED print heads 41K, 41Y, 41M, and 41C are commonly connected to the light emission control unit 110, and the light emission control unit 110 controls the light emission of the four LED print heads 41 at once. Here, the control device 100, the light emission control unit 110, and the LED unit 40 constitute a light emitting device for exposure. The printer 1 includes the exposure light-emitting device as an exposure device that exposes the photosensitive drum 53.

  Each LED print head 41 is provided with an EEPROM 43, for example. In the EEPROM 43, light emission data necessary for the light emission control unit 110 to perform light emission control of each light emitting element P is written. More specifically, the EEPROM 43 stores drive signal data corrected for each light emitting element P. The drive signal data is drive signal data generated in advance based on an exposure unevenness correction table created by an exposure unevenness correction table creation method described below. That is, the drive signal data is data in which the drive time (lighting time) of each light emitting element P is corrected based on the correction amount S so that each light emitting element P obtains the target exposure light amount PLo (see FIG. 8). ). When an image is formed by the color printer 1, a drive signal corresponding to each light emitting element P based on the drive signal data stored in the EEPROM 43, specifically, a drive time (an example of parameter value) Dt corresponding to each light emitting element P is set. Drive signal is generated, and each light emitting element P emits light during the corresponding drive time Dt.

  The parameter value of the drive signal corresponding to each correction amount S, that is, the parameter value of the drive signal to be corrected is not limited to the drive time Dt, and may be, for example, the drive current value of each light emitting element P. .

  The EEPROM 43 may store an exposure unevenness correction table (see FIG. 8 and the like) itself. In this configuration, drive signal data corresponding to each light emitting element P when causing each light emitting element P to emit light is generated with reference to the correction table. In this case, the exposure amount can be adjusted on the color printer 1.

  Further, the correction data memory in which the correction data is stored is not limited to the EEPROM 43 provided in each LED print head 41. For example, the EEPROM 43 may not be provided in each LED print head 41, and the correction data memory may be provided in the light emission control unit 110.

3. Exposure unevenness correction table creation processing Next, the exposure unevenness correction table creation processing of the LED print head 41 will be described with reference to FIGS. FIG. 4 is a graph for explaining the concept of exposure unevenness correction in the present embodiment, and FIG. 5 is a flowchart schematically showing an exposure unevenness correction table creation process. FIG. 6 is a graph showing a correction range of the drive signal (drive time) and a reference value of the drive time. FIG. 7 is a graph schematically showing the number of corrected gradation sections and the corrected gradation section width, and FIG. 8 is a table showing the relationship between the number of corrected gradation sections and the corrected gradation section width. .

  As shown in FIG. 4, the exposure curve (light emission characteristic) EC by each light emitting element P varies, and therefore, exposure by each light emitting element P before correction at a correction gradation C which is a predetermined reference value for correction. The light quantity PL varies (see pre-correction distribution Bb). Therefore, in the exposure unevenness correction in the present embodiment, for the light emitting element P in the light amount range Rup on the side where the light amount is increased, the correction gradation (drive time) is increased and the light amount range Rdw on the side where the light amount is decreased. The light emitting element P is corrected so as to reduce the correction gradation (driving time) C. Then, the exposure light quantity PL by each light emitting element P is set within a predetermined allowable range (between the allowable lower limit value PLdw and the allowable upper limit value PLup) as shown in the corrected distribution Ba in FIG.

  In this embodiment, the exposure unevenness correction table creation process (hereinafter referred to as “table creation process”) is performed by a predetermined correction table generation device (not shown) at the manufacturing stage of the color printer 1. The correction table generation device processes, for example, a light emission control unit similar to the light emission control unit 110, a light receiving sensor that receives light from each light emitting element P near the image plane, and light reception data from the light receiving sensor, as shown in FIG. A data processing unit that generates a correction table indicating the relationship between the gradation and the correction amount S is included. The correction table obtained by the table creation process is stored in the EEPROM 43 at the time of manufacture. At the time of image formation, a drive signal having a corresponding drive time (lighting time) Dt is generated based on the correction amount S of the correction table in each EEPROM 43, and the LED print heads 41K to 41C emit light by the drive signal. The

  In the table creation process, first, a correction range Hs for correcting the drive time Dt of the drive signal is set (step S10). The correction range Hs is determined in consideration of the variation in the exposure curve EC of each light emitting element P, the yield, and the like. Preferably, the correction is set to a range in which most of the light emitting elements P can emit light with the target exposure light amount PLo. The correction range Hs is between the minimum value L and the maximum value H of the drive time Dt.

  Next, the reference value C (corresponding to the first reference value) of the drive time Dt is set within the set correction range Hs (step S20). Here, the reference value C is approximately the center value of the correction range Hs as shown in FIG. That is, reference value C−minimum value L≈maximum value H−reference value C.

  Next, the L-C section divided by the reference value C and the number of correction gradations (the number of correction sections) in the C-H section are set (step S30). Here, the L-C section corresponds to a correction section applied to a light emitting element group having an exposure light amount larger than the target exposure light amount PLo when each light emitting element P is turned on using the set reference value C. . On the other hand, the C-H section corresponds to a correction section applied to a light emitting element group in which the exposure light quantity PL is smaller than the target exposure light quantity PLo when each light emitting element P is turned on using the reference value C.

  Here, the number of correction sections in the LC section is set to be greater than or equal to the number of correction sections in the CH section. That is, when each light emitting element P is turned on using the reference value C, the number of correction categories applied to the light emitting element group having a larger exposure light amount than the target exposure light amount PLo is set so that the exposure light amount is larger than the target exposure light amount PLo. It is set to be equal to or greater than the number of correction categories applied to a small light emitting element group. Specifically, as shown in FIGS. 7 and 8, for example, the number of correction sections in the LC section is set to “4”, and the number of correction sections in the CH section is set to “2”. .

  Next, the correction section width (correction gradation width: correction amount for one gradation) is set in accordance with the setting of the number of correction sections (correction gradation number) in the LC section and the CH section (step S40). ). At this time, the correction section width of the LC section is set smaller than the correction section width of the CH section. That is, the correction classification width applied to the light emitting element group having the exposure light quantity PL larger than the target exposure light quantity PLo is larger than the correction classification width applied to the light emitting element group having the exposure light quantity PL smaller than the target exposure light quantity PLo. Set small. Specifically, as shown in FIGS. 7 and 8, for example, the correction section width of the LC section is set to “3”, and the correction section width of the CH section is set to “6”. .

  Next, a correction table as shown in FIG. 8 is generated by associating the set correction category (correction gradation) with the correction amount S of the driving time (step S50). Then, with reference to the correction table, drive signal data for generating a drive signal having a drive time Dt corresponding to each light emitting element P is generated, and each drive signal data is stored in each EEPROM 43. When each light emitting element P is turned on, a drive signal is generated based on the drive signal data stored in each EEPROM 43. Thereby, the amount of exposure light from each light emitting element P can be kept within a predetermined allowable range shown in the corrected distribution Ba in FIG.

4). Effects of Embodiment 1 When each light emitting element P is turned on using the reference value C, a light emitting element group having a larger exposure light quantity than the target exposure light quantity PLo, that is, a light emitting element group having a large exposure light quantity change rate is corrected. Since the change in the amount of light in the section is large, the amount of light is corrected by finely dividing the correction section. On the other hand, when each light emitting element P is turned on using the reference value C, a light emitting element group having an exposure light amount smaller than the target exposure light amount PLo, that is, a light emitting element group having a small exposure light amount change rate, is classified into one category (one Since the change in the amount of light in the correction gradation) is small, the amount of light is corrected with a large correction section. That is, the number of correction sections is set according to the light emission characteristics of the light emitting element P. Accordingly, the number of correction sections in the correction adjustable range can be reduced, and more appropriate light amount adjustment can be performed. That is, it is possible to accurately correct the light amounts of the plurality of light emitting elements P used during image formation while suppressing an increase in memory.

  Further, the correction section width (correction amount for one gradation) in the LC section is set smaller than the correction section width in the CH section. That is, the light amount change per correction gradation (unit correction drive time) is reduced for a light emitting element group with a large exposure light amount change rate, and the unit correction drive time for a light emitting element group with a small exposure light amount change rate. The change in the amount of light per hit can be increased. In this way, by changing the correction section width according to the exposure light quantity change rate, the difference in the light quantity change with respect to one correction section (for one gradation) can be reduced, and each light emitting element P can be accurately corrected. it can.

<Embodiment 2>
A second embodiment will be described with reference to FIGS. 9 to 11. FIG. 9 is a flowchart schematically showing an exposure unevenness correction table creation process according to the second embodiment. FIG. 10 is a graph schematically showing the number of corrected gradation sections and the corrected gradation section width of the second embodiment, and FIG. 11 is a relationship between the number of corrected gradation sections and the corrected gradation section width of the second embodiment. It is a table | surface which shows.

  The second embodiment differs from the first embodiment in that a plurality of reference values C are set in the exposure unevenness correction table creation process. Therefore, only differences from the first embodiment will be described below. Therefore, the same component numbers as those of the first embodiment are denoted by the same member numbers, the same step numbers are denoted by the same processes, and the description thereof is omitted.

  In the second embodiment, as shown in FIG. 9, after step S40, the same method as step S20 in the correction range (LC section) Hs1 divided by the reference value C (first reference value). Thus, the reference value C1 (corresponding to the second reference value) is further set. And the process of step S30 and step S40 is performed with respect to the newly set reference value C1 (step S45). That is, in the correction range Hs1 in which the reference value C1 is set, the number of sections is set for the reference value C1, and the correction section width is set for the reference value C1.

  Specifically, as shown in FIGS. 10 and 11, the correction gradation “−3” is set as a new reference value C1, and the correction range Hs1 is set to the L-C1 section by the correction gradation “−3”. , Divided into C1-C sections. Then, the number of correction gradations (the number of correction sections) in the L-C1 section and the C1-C section is set to, for example, “4” and “3”, respectively. That is, the number of correction sections in the L-C1 section is set to be greater than or equal to the number of correction sections in the C1-C section.

  Further, the correction section width of the L-C1 section is set to “1.5”, for example, and the correction section width of the C1-C section is set to “2”, for example. That is, the correction section width of the L-C1 section is set smaller than the correction section width of the C1-C section. For example, a correction table as shown in FIG. 11 is generated by associating the correction amount S of the driving time with each correction category (correction gradation) set in this way (step S50).

  In step S45, the same processing as that of the correction range (LC section) may be performed on the correction range (CH section) divided by the reference value C. Further, step S45 may be further repeated at least once. That is, a further reference value C2 for further dividing the L-C1 section may be provided, and the number of correction sections and the correction section width may be set for the section divided by the reference value C2.

In other words, in step S45 (corresponding to the reference value resetting step), a new reference value of the parameter value is set within the correction range divided by the reference value of the previously set parameter value. In step S45, a new reference value is set. In the correction range in which the reference value is set, the number of sections is set for the new reference value (step S30: section setting step), and the correction setting section width is set for the new reference value. This process (step S40: classification setting process) may be repeated once more.
As described above, as the number of divisions for dividing the correction range Hs by the plurality of reference values C is set, the light amount change per correction gradation can be made more uniform. Thereby, the adjustment accuracy of the exposure light amount of the light emitting element P can be improved. Ultimately, the correction range Hs can be divided up to the set number of gradations.

5. Effects of Second Embodiment In the second embodiment, a reference value C1 is further provided in the further divided correction range (LC section) Hs1, and the correction gradation is set more finely in the correction range Hs1. Therefore, for a light emitting element group having a large exposure light amount change rate, the light amount change per correction gradation (unit correction drive time) can be further reduced, and the light amount change per correction gradation can be made uniform. For this reason, even when light emitting elements P having greatly different light intensity changes are mixed, the light quantities can be more accurately aligned.

<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 embodiments, the reference values C and C1 are set to substantially the center values of the correction ranges Hs and Hs1, but the present invention is not limited to this. For example, for the adjustable light quantity range, the reference value C may be set so that the range Rup on the light quantity increasing side and the range Rdw on the light quantity reducing side are substantially the same. Alternatively, the light emitting element P that can obtain the target exposure light amount Plo when turned on with a drive signal having a predetermined drive time is selected as the reference light emitting element, and the drive time of the reference light emitting element is set to the reference value C. Good.

  DESCRIPTION OF SYMBOLS 1 ... Printer, 40 ... LED unit, 41 ... LED print head, 53 ... Photosensitive drum, 100 ... Control apparatus, 110 ... Light emission control part, P ... Light emitting element

Claims (9)

In an exposure light-emitting device in which a plurality of light-emitting elements are arranged in a predetermined arrangement, a method for creating a correction table for correcting exposure unevenness between the light-emitting elements,
A correction range setting step for setting a correction range for correcting a parameter value of a drive signal for lighting each light emitting element so that each light emitting element can substantially obtain a target exposure light amount by correcting the light quantity of each light emitting element;
Within the set correction range, a reference value setting step for setting a first reference value of the parameter value, and when each of the light emitting elements is turned on using the set first reference value, And a category setting step for setting the number of correction categories applied to the light emitting element group having a large exposure light amount to be equal to or greater than the number of correction categories applied to the light emitting element group having an exposure light amount smaller than the target exposure light amount,
And a table generation step of generating a correction table by associating the correction amount of the parameter value with each set correction category. In the exposure unevenness correction table creation method according to claim 1,
In the category setting step, the correction category width applied to the light emitting element group having the exposure light amount larger than the target exposure light amount is the correction category applied to the light emitting element group having the exposure light amount smaller than the target exposure light amount. An exposure unevenness correction table creation method that is set smaller than the width. In the exposure unevenness correction table creation method according to claim 2,
In the reference value setting step, in the adjustable light quantity range, the first reference value is set such that the range on the light intensity increasing side and the range on the light intensity reducing side are substantially the same. Method for creating an unevenness correction table. In the exposure unevenness correction table creation method according to claim 2,
A reference value resetting step of setting a second reference value of the parameter value within a correction range divided by the first reference value;
In the category setting step,
In the correction range in which the second reference value is set, the number of sections is set for the second reference value, and the correction setting section width is set for the second reference value. , Exposure unevenness correction table creation method. In the exposure unevenness correction table creation method according to claim 4,
In the reference value resetting step, a new reference value of the parameter value is set within a correction range divided by the reference value of the parameter value set previously, and in the classification setting step, the new reference value is set. In the correction range in which is set, the number of sections is set for the new reference value, and the correction setting section width is set for the new reference value more than once. An exposure unevenness correction table creation method that is repeated. In the exposure unevenness correction table creation method according to any one of claims 1 to 5,
The exposure unevenness correction table creation method, wherein the parameter value of the drive signal is a drive time for lighting each light emitting element. A plurality of light emitting elements arranged in a predetermined arrangement;
A drive circuit that drives the plurality of light emitting elements using a drive signal generated based on a correction table created by the correction table creation method according to any one of claims 1 to 6.
A light emitting device for exposure, comprising: The light-emitting device for exposure according to claim 7,
An exposure light-emitting device comprising the correction table. A photoreceptor,
The light-emitting device for exposure according to claim 7 or 8, as an exposure device that exposes the photoreceptor.
An image forming apparatus comprising:

Images