JP2014023053A - Image reading apparatus, image forming apparatus and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image reading apparatus and such which can accurately correct reading density difference in a main scanning direction of a receiver, even when a reference image has uneven density.SOLUTION: An image reading apparatus 100 comprises: a light source 110; a CCD sensor 130 for reading a reference image S; moving means 140 for moving the CCD sensor 130 and the reference image S relatively in a main scanning direction; a shading data creation section; and a shading correction section. The shading data creation section comprises a light quantity value acquisition unit for acquiring a light quantity value created by the CCD sensor 130 for each pixel when the CCD sensor 130 is moved by the moving means 140, and a correction coefficient derivation unit for deriving shading data by using whether a part of a light quantity profile obtained from the light quantity value acquired by the light quantity value acquisition unit moves in association with the movement of the CCD sensor 130 when the CCD sensor is moved by the moving means 140.

Description

  The present invention relates to an image reading apparatus, an image forming apparatus, and a program.

In Patent Document 1, a half-moon roll is disposed to face a CIS that reads an image of a document conveyed along a conveyance path. An arc-shaped outer peripheral surface is formed on the outer periphery of the half-moon roll, and a white reference member is attached to a partial region. When reading a document, the half-moon roll is swung to expose the outer peripheral surface on the conveyance path, and when the shading data is acquired, the half-moon roll is swung to expose the white reference member to the conveyance path. At this time, an image reading apparatus is disclosed in which the white reference member is configured so that the white reference surface of the white reference member and the reading position in the optical axis direction of the document coincide with each other.
In Patent Document 2, when the shading correction is performed during the image reading operation by reading the reference plate, the white reference plate is read at the initial position, the read value is compared with the threshold value a, and the read value is smaller than the threshold value a. Then, the provisional first shading correction is performed with the position as the first shading reading position. Then, after performing the first shading correction, the CCD is moved in units of lines, the white reference plate is read from the initial line position c, the read value is compared with the threshold value b, and the read value is continuously from the initial line position c. Then, an image reading apparatus is disclosed in which the center position is set to the second shading reading position when the predetermined number of lines m or more is smaller than the threshold value b.

Japanese Patent Laying-Open No. 2005-167846 JP 2001-285593 A

  Here, when reading an image, if a reading density difference occurs in the main scanning direction, the reading density difference may be corrected. However, if there is uneven density on the reference member such as a reference plate used for correcting the read density difference or if dust or the like adheres, it may be difficult to correct the read density difference.

  According to the first aspect of the present invention, a light source that irradiates light to a predetermined reference image and light reflected by the reference image are received, and the reference image has a predetermined number in the main scanning direction. A light receiving unit that generates a light amount value for each pixel, a moving unit that relatively moves the light receiving unit and the reference image in a main scanning direction, and a light amount value generated by the light receiving unit. The light receiving means using a correction coefficient creating means for deriving a correction coefficient for correcting a reading density difference in the main scanning direction of the light receiving means, and a correction coefficient created by the correction coefficient creating means Reading density correction means for correcting the reading density difference in the main scanning direction, and the correction coefficient creating means relatively moves the light receiving means and the reference image in the main scanning direction by the moving means. sometimes, A light amount value acquisition unit that acquires the light amount value generated by the light receiving unit for each pixel; and the moving unit relatively moves the light receiving unit and the reference image in the main scanning direction. A correction coefficient deriving unit that derives the correction coefficient using whether or not a part of the light amount distribution obtained from the light amount value acquired by the light amount value acquiring unit moves correspondingly. An image reading apparatus.

The invention according to claim 2 is characterized in that the correction coefficient deriving unit derives the correction coefficient for a pixel corresponding to a moving position in the light amount distribution when the reference image is used as a reference. The image reading apparatus according to Item 1.
According to a third aspect of the present invention, the correction coefficient deriving unit includes a unit that performs correction to increase and decrease the light amount value acquired by the light amount value acquiring unit for each predetermined pixel. A plurality of provisional correction units for correcting with a plurality of provisional coefficients, and a plurality of the provisional light amounts obtained respectively when the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit. A coincidence degree determination unit that determines the coincidence degree of each light quantity distribution when corrected by a coefficient, and the coincidence degree determination by the coincidence degree determination unit, one of a plurality of the temporary coefficients for each pixel The provisional coefficient selection unit to be selected, and a correction coefficient determination unit that determines the correction coefficient for each pixel based on the temporary coefficient selected by the temporary coefficient selection unit. The image described in 1 or 2 A reading device.
According to a fourth aspect of the present invention, the light quantity value acquired when the light receiving means and the reference image are relatively moved in the main scanning direction by the moving means is corrected with the temporary coefficient. It further includes an average light amount calculation unit that calculates an average light amount value for each pixel, and the coincidence degree determination unit is a cumulative value of an absolute value of a difference between the light amount value after correction with a temporary coefficient and the average light amount value. The image reading apparatus according to claim 3, wherein the degree of coincidence of the light quantity distribution is obtained by obtaining.

  The invention according to claim 5 includes an image forming unit that forms an image on a recording medium, and a reading unit that reads an image to adjust an image formed on the recording medium by the image forming unit, The reading unit receives a light source that emits light with respect to a predetermined reference image and light reflected by the reference image, and reads the reference image with a predetermined number of pixels in the main scanning direction. A light receiving unit that generates a light amount value for each pixel, a moving unit that relatively moves the light receiving unit and the reference image in a main scanning direction, and a light amount value generated by the light receiving unit, The correction coefficient creating means for deriving a correction coefficient for correcting the reading density difference in the main scanning direction of the light receiving means and the correction coefficient created by the correction coefficient creating means are used in the main scanning direction of the light receiving means. Dark reading A reading density correction unit that corrects the difference, and the correction coefficient generation unit is configured to move the light receiving unit and the reference image relative to each other in the main scanning direction by the moving unit. A light amount value acquisition unit that acquires the generated light amount value for each pixel, and the light amount value acquisition unit when the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit. And a correction coefficient deriving unit for deriving the correction coefficient using whether or not a part of the light amount distribution obtained from the light amount value acquired in step 1 moves correspondingly. is there.

  According to the sixth aspect of the present invention, when the light receiving unit and the reference image are relatively moved in the main scanning direction, the light amount value generated by the light receiving unit is acquired for each pixel of the light receiving unit. A function for correcting the acquired light amount value with a plurality of provisional coefficients including a correction for increasing and decreasing the light amount value for each predetermined pixel, the light receiving means, and the reference image A function for determining the degree of coincidence of the respective light quantity distributions when the light quantity values acquired when the two are moved relative to each other in the main scanning direction with the plurality of provisional coefficients, and the degree of coincidence determination Thus, a function for selecting one of the plurality of provisional coefficients for each pixel and a correction for correcting a reading density difference in the main scanning direction of the light receiving unit based on the selected provisional coefficient. Coefficient Is a program for realizing a function for determining for each.

According to the first aspect of the present invention, compared with the case where the present invention is not adopted, an image reading apparatus capable of accurately correcting the reading density difference in the main scanning direction of the light receiving means even if the reference image has uneven density. Can be provided.
According to the invention of claim 2, it becomes easier to eliminate the influence of the density unevenness of the reference image as compared with the case where the present invention is not adopted.
According to the third aspect of the present invention, it is possible to determine whether the change in the light amount value is caused by the difference in reading density of the light receiving means or the density unevenness of the reference image.
According to the fourth aspect of the present invention, the provisional coefficient can be selected more easily than when the present invention is not adopted.
According to the fifth aspect of the present invention, it is possible to provide an image forming apparatus with less variation in the density of the formed image as compared with the case where this configuration is not adopted.
According to the sixth aspect of the present invention, compared to the case where the present invention is not adopted, the computer has a function capable of accurately correcting the reading density difference in the main scanning direction of the light receiving means even if the reference image has density unevenness. Can be realized.

1 is a diagram illustrating an image forming apparatus to which an image reading apparatus according to an exemplary embodiment is applied. (A)-(b) is a figure explaining the image reading apparatus of this Embodiment. It is the block diagram explaining the functional structure of the image reading apparatus of this Embodiment. (A) is the figure which showed the positional relationship of a reference | standard image when a CCD sensor is moved by a moving means, and a CCD sensor. (B) is the conceptual diagram explaining the light quantity value acquired at this time. (A)-(b) is a figure explaining the case where the acquired light quantity profile is displayed in piles, when a CCD sensor is moved sequentially. It is a figure explaining the example of functional composition of the shading data creation part of this embodiment. It is the flowchart explaining the procedure which produces shading data in a shading data creation part. (A)-(b) is the figure compared before and after combining an edge part about three light quantity profiles used by this Embodiment. It is a figure explaining the profile for correction. (A) shows “modified Profile 1”, “modified Profile 2” when “modified Profile A” in FIG. 9 is applied to “Profile 1”, “Profile 2”, and “Profile 3” in FIG. It is the figure illustrated about "Profile3 after correction". FIG. 10B is an average profile obtained by averaging “after correction Profile1”, “after correction Profile2”, and “after correction Profile3”. (A) shows “modified Profile 1”, “modified Profile 2” when “modified Profile B” in FIG. 9 is applied to “Profile 1”, “Profile 2”, and “Profile 3” in FIG. It is the figure illustrated about "Profile3 after correction". (B) is an average profile obtained by averaging “post-correction Profile1”, “post-correction Profile2”, and “post-correction Profile3” in FIG. (A) shows “modified Profile1”, “modified Profile2” when “modified ProfileC” in FIG. 9 is applied to “Profile1”, “Profile2”, and “Profile3” in FIG. It is the figure illustrated about "Profile3 after correction". (B) is an average profile obtained by averaging “modified Profile1”, “modified Profile2”, and “modified Profile3” in FIG. It is a figure explaining the profile for correction. “Modified Profile1”, “Modified Profile2”, and “Modified Profile3” when “Modified ProfileA” in FIG. 11 is applied to “Profile1”, “Profile2”, and “Profile3” in FIG. FIG. (B) is an average profile obtained by averaging “post-correction Profile1”, “post-correction Profile2”, and “post-correction Profile3” in FIG. (A) shows “modified Profile1”, “modified Profile2” when “modified ProfileB” in FIG. 11 is applied to “Profile1”, “Profile2”, and “Profile3” in FIG. It is the figure illustrated about "Profile3 after correction". FIG. 12B is an average profile obtained by averaging “after correction Profile1”, “after correction Profile2”, and “after correction Profile3” in FIG. FIG. 8A shows “modified profile 1”, “modified profile 2” when “modified profile C” in FIG. 11 is applied to “profile 1”, “profile 2”, and “profile 3” in FIG. It is the figure illustrated about "Profile3 after correction". (B) is an average profile obtained by averaging “modified Profile1”, “modified Profile2”, and “modified Profile3” in FIG.

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.
<Description of Image Forming Apparatus>
FIG. 1 is a diagram illustrating an image forming apparatus 1 to which the image reading apparatus according to the present embodiment is applied.
The image forming apparatus 1 is a so-called “tandem type” color printer. The image forming unit 10 forms an image on a recording medium (paper) based on print data, and the operation control of the entire image forming apparatus 1 or a personal computer (for example) A main control unit 50 that executes communication with a PC), image processing performed on print data, and the like, a user interface (UI) unit 90 that receives operation input from the user and displays various information to the user, An image reading apparatus 100 is provided as an example of a reading unit that reads an image in order to adjust an image formed on a sheet by the image forming unit 10.

<Description of Image Forming Unit>
The image forming unit 10 is a functional unit that forms an image by, for example, electrophotography, and includes four image forming units 11Y, 11M, 11C, and 11K (hereinafter, referred to as toner image forming units arranged in parallel). "Image forming unit 11"), intermediate transfer belt 20 to which each color toner image formed on the photosensitive drum 12 of each image forming unit 11 is transferred, and each color toner image formed by each image forming unit 11 A primary transfer roll 21 that transfers (primary transfer) to the intermediate transfer belt 20. Further, a secondary transfer roll 22 that collectively transfers (secondary transfer) each color toner image transferred and superimposed on the intermediate transfer belt 20 to the sheet, and a fixing that fixes the second color transferred toner image on the sheet. And a fixing unit 60 as an example of a unit (fixing device).

In addition, the image forming unit 10 cools each color toner image fixed on the sheet by the fixing unit 60, and cools the unit 80 as an example of a cooling unit that promotes fixing of each color toner image on the sheet. A curl correction unit 85 that corrects the curl of the paper.
In the image forming apparatus 1 of the present embodiment, the intermediate transfer belt 20, the primary transfer roll 21, and the secondary transfer roll 22 constitute a transfer unit. Further, an area where the secondary transfer roll 22 is disposed and each color toner image on the intermediate transfer belt 20 is secondarily transferred to a sheet is hereinafter referred to as a “secondary transfer area Tr”.

<Description of image forming unit>
Each image forming unit 11 functions as a functional member, for example, a photosensitive drum 12 on which an electrostatic latent image is formed and then each color toner image is formed, and the surface of the photosensitive drum 12 is charged with a predetermined potential. A charger 13 that exposes the photosensitive drum 12 charged by the charger 13 based on print data, and development that develops the electrostatic latent image formed on the photosensitive drum 12 with toner of each color. And a cleaner 16 for cleaning the surface of the photosensitive drum 12 after transfer.
Each developing device 15 of each image forming unit 11 is connected to toner containers 17Y, 17M, 17C, and 17K (hereinafter referred to as “toner container 17”) that store toner of each color by a toner conveyance path (not shown). Each color toner is supplied from the toner container 17 to the developing device 15 by a supply screw (not shown) provided in the toner conveyance path.

  Each of the image forming units 11 is configured in substantially the same manner except for the toner accommodated in the developing device 15, and each of them has Y (yellow), M (magenta), C (cyan), and K (black) colors. A toner image is formed.

<Description of Paper Conveyance System in Image Forming Apparatus>
Further, the image forming unit 10 feeds out a plurality of (two in the present embodiment) sheet storage containers 40A and 40B that store sheets and the sheets stored in the sheet storage containers 40A and 40B as a sheet transport system. Feeding rolls 41A and 41B, a first transport path R1 for transporting paper from the paper storage container 40A, and a second transport path R2 for transporting paper from the paper storage container 40B. Further, the image forming unit 10 includes a third transport path R3 that transports the paper from the paper storage container 40A and the paper storage container 40B toward the secondary transfer region Tr. In addition, the image forming unit 10 conveys the sheet on which the toner image of each color is transferred in the secondary transfer region Tr so as to pass through the fixing unit 60, the cooling unit 80, and the curl correcting unit 85. And a fifth transport path R5 for transporting the sheet from the curl correction unit 85 toward the sheet stacking section 44 provided in the discharge section of the image forming apparatus 1.
From the first conveyance path R1 to the fifth conveyance path R5, conveyance rolls and conveyance belts are arranged along the respective conveyance paths to sequentially convey the fed sheets.

<Description of double-sided conveyance system>
In addition, the image forming unit 10 serves as a double-sided conveyance system in which an intermediate paper storage container 42 that temporarily holds the paper on which the toner images of each color are fixed on the first surface by the fixing unit 60 and the paper from the curl correction unit 85 as intermediate paper. A sixth transport path R6 for transporting toward the storage container 42 and a seventh transport path R7 for transporting the paper stored in the intermediate paper storage container 42 toward the third transport path R3 are provided. Further, the image forming unit 10 is disposed on the downstream side of the curl correction unit 85 in the sheet conveyance direction, and conveys the sheet toward the sheet stacking unit 44 and a sixth conveyance path R5 that conveys the sheet to the intermediate sheet storage container 42. A distribution mechanism unit 43 that selectively distributes the sheet to the path R6 and a feeding roll 45 that feeds the sheet stored in the intermediate sheet storage container 42 toward the seventh transport path R7 are provided.

<Description of image forming operation>
Next, a basic image forming operation in the image forming apparatus 1 according to the present embodiment will be described with reference to FIG.
Each of the image forming units 11 of the image forming unit 10 forms toner images of Y color, M color, C color, and K color by an electrophotographic process using the above functional members. Each color toner image formed by each image forming unit 11 is primary-transferred sequentially on the intermediate transfer belt 20 by the primary transfer roll 21 to form a composite toner image in which the respective color toners are superimposed. The synthetic toner image on the intermediate transfer belt 20 is conveyed to the secondary transfer region Tr in which the secondary transfer roll 22 is disposed as the intermediate transfer belt 20 moves (in the direction of the arrow).

On the other hand, in the paper transport system, the feeding rolls 41A and 41B rotate in synchronization with the image formation start timing in each image forming unit 11, and the UI unit 90, for example, out of the paper storage container 40A and the paper storage container 40B. The designated sheet is fed out by the feeding rolls 41A and 41B. The sheet fed by the feeding rolls 41A and 41B is transported along the first transport path R1 or the second transport path R2 and the third transport path R3, and reaches the secondary transfer region Tr.
In the secondary transfer region Tr, the composite toner image held on the intermediate transfer belt 20 is secondarily transferred collectively onto the paper by the transfer electric field formed by the secondary transfer roll 22.

Thereafter, the sheet on which the composite toner image is transferred is separated from the intermediate transfer belt 20 and conveyed to the fixing unit 60 along the fourth conveyance path R4. The synthesized toner image on the paper transported to the fixing unit 60 is fixed on the paper after being subjected to a fixing process by the fixing unit 60. Then, the sheet on which the fixed image is formed is cooled by the cooling unit 80, and the curl correction unit 85 corrects the bending of the sheet. Thereafter, the paper passing through the curl correction unit 85 is guided by the distribution mechanism unit 43 to the fifth transport path R5 during single-sided printing and transported toward the paper stacking unit 44.
The toner (primary transfer residual toner) adhering to the photosensitive drum 12 after the primary transfer and the toner (secondary transfer residual toner) adhering to the intermediate transfer belt 20 after the secondary transfer are respectively cleaner 16, And removed by the belt cleaner 26.

On the other hand, during double-sided printing, the paper on which the fixed image is formed on the first surface of the paper by the above-described process passes through the curl correction unit 85 and is then guided to the sixth transport path R6 by the distribution mechanism unit 43. The sixth transport path R6 is transported toward the intermediate paper storage container. Again, the feeding roll 45 rotates in accordance with the start timing of image formation on the second surface by each image forming unit 11, and the sheet is fed out from the intermediate sheet storage container 42. The sheet fed by the feed roll 45 is transported along the seventh transport path R7 and the third transport path R3 and reaches the secondary transfer region Tr.
In the secondary transfer region Tr, as in the case of the first surface, the toner images of the respective colors on the second surface held on the intermediate transfer belt 20 are collectively applied to the sheet by the transfer electric field formed by the secondary transfer roll 22. Second transfer is performed.

Then, the paper on which the toner images are transferred on both sides is fixed by the fixing unit 60 as in the case of the first side, cooled by the cooling unit 80, and further corrected by the curl correction unit 85. Is done. Thereafter, the paper that has passed through the curl correction unit 85 is guided to the fifth transport path R5 by the distribution mechanism unit 43 and transported toward the paper stacking unit 44.
In this way, the image forming process in the image forming apparatus 1 is repeatedly executed for the number of printed sheets.

<Description of Image Reading Device>
2A and 2B are diagrams illustrating the image reading apparatus 100 according to the present embodiment. Here, FIG. 2A is a diagram when the image reading apparatus 100 is viewed from the same direction as FIG. 2B is a diagram when the image reading apparatus 100 is viewed from the IIb direction in FIG. FIG. 3 is a block diagram illustrating a functional configuration of the image reading apparatus 100 according to the present embodiment.
The image reading apparatus 100 will be described below with reference to FIGS. 2 (a) to 2 (b) and FIG.

  As shown in the figure, the image reading apparatus 100 includes a light source 110, an optical system 120, a CCD (Charge Coupled Device) sensor 130, a moving unit 140, a control unit 150, a signal processing unit 160, a housing. A body 170.

  The light source 110 irradiates the toner image formed on the intermediate transfer belt 20 with light. The light source 110 includes, for example, a pair of straight tube xenon fluorescent lamps 111a and 111b. Then, the toner image formed on the intermediate transfer belt 20 is irradiated with light to generate reflected light including information on the image formed as the toner image.

  The optical system 120 guides the light reflected by the toner image to the CCD sensor 130. In the present embodiment, the optical system 120 includes a Selfoc lens array (SLA: registered trademark) which is a lens array. Then, mainly diffuse reflected light of the reflected light from the toner image is collected by the Selfoc lens array and formed on the CCD sensor 130.

  The CCD sensor 130 receives the light reflected by the toner image and guided by the optical system 120. Here, the CCD sensor 130 is an example of a light receiving unit that reads a toner image with a predetermined number of pixels in the main scanning direction and generates a light amount value for each pixel. The CCD sensor 130 is provided with a line of CCDs 131 as pixels that receive light reflected from the toner image. In the present embodiment, the CCD 131 corresponding to each color of R (Red), G (Green), and B (Blue) is arranged in three rows, and the toner image can be measured with each color of RGB. . That is, it is a 3-line color CCD. For example, 7488 CCDs are arranged at a pitch of 40 μm for each color of RGB. In other words, a toner image can be read in the main scanning direction with 7488 pixels. The light received by the CCD 131 is photoelectrically converted into a charge, and this charge is transferred to the light quantity value generation unit 132.

  The light quantity value generation unit 132 detects the charge transferred from the CCD 131 and generates an electric signal. This electric signal becomes data of a light amount value which is information for adjusting the image forming unit 11. That is, the light amount value generation unit 132 creates information for adjusting the image from the light received by the CCD 131. Since the CCD 131 is a color CCD of three colors of R (Red), G (Green), and B (Blue), the light amount value generation unit 132 has R signal, which is light amount value data corresponding to each color, G signal and B signal are generated.

  The moving unit 140 moves the CCD sensor 130 in the main scanning direction. As a result, the CCD sensor 130 and the toner image relatively move in the main scanning direction. The moving means 140 includes a driving source such as a motor and a gear for transmitting the driving force generated by the driving source and moving the CCD sensor 130 in the main scanning direction.

  The control unit 150 controls each unit in the image reading operation of the image reading apparatus 100. In the present embodiment, the control unit 150 controls the light source 110, the CCD sensor 130, the moving unit 140, and the signal processing unit 160. That is, the control unit 150 controls the light source 110 to irradiate the toner image with light with a predetermined amount of light. The control unit 150 also controls the CCD sensor 130 to cause the signal processing unit 160 to transmit the R signal, the G signal, and the B signal that are light amount value data generated by the CCD sensor 130. The control unit 150 controls the moving unit 140 to move the CCD sensor 130 to a predetermined position in the main scanning direction. Further, the control unit 150 controls each unit of the signal processing unit 160 to process the R signal, the G signal, and the B signal, and transmits them to the main control unit 50 (see FIG. 1) of the image forming apparatus 1. The main control unit 50 adjusts the image forming unit 11 (see FIG. 1) and the like based on these signals, thereby adjusting the image formed on the sheet.

  The signal processing unit 160 includes a sample hold unit 161, a gain adjustment unit 162, an offset adjustment unit 163, an A / D conversion unit 164, a shading correction unit 165, a color conversion unit 166, and a shading data creation unit 167. Is provided.

The sample hold unit 161 samples the R signal, G signal, and B signal, which are analog image signals output from the CCD sensor 130.
The gain adjustment unit 162 adjusts the voltage output from the CCD sensor 130 to a value close to the maximum input voltage of the A / D conversion unit 164 when the light source 110 is turned on.
The offset adjustment unit 163 performs adjustment so that the voltage output from the CCD sensor 130 is close to the lowest input voltage of the A / D conversion unit 164 when the light source 110 is turned off.
The A / D conversion unit 164 converts the analog image signal output from the offset adjustment unit 163 into a digital image signal.

The shading correction unit 165 is an example of a reading density correction unit. The shading correction unit 165 corrects the reading density difference in the main scanning direction of the CCD sensor 130 using the shading data that is an example of the correction coefficient for the digital image signal output from the A / D conversion unit 164.
The color conversion unit 166 converts the digital image signal output from the shading correction unit 165 based on a predetermined LUT (Look Up Table), and converts the converted digital image signal into the main control unit 50 of the image forming apparatus 1. Output to.

  The shading data creation unit 167 is an example of a correction coefficient creation unit. As will be described in detail later, the shading data creation unit 167 derives shading data for correcting the reading density difference in the main scanning direction of the CCD sensor 130 based on the light amount value generated by the CCD sensor 130.

  Each function performed by the signal processing unit 160 can be realized by providing an application specific integrated circuit (ASIC) or the like.

  The housing 170 is a case for housing the light source 110, the optical system 120, and the CCD sensor 130. As described above, the moving unit 140 has a function of moving the CCD sensor 130 in the main scanning direction, but actually, this operation is performed by moving the housing 170. Therefore, by moving the housing 170 by the moving means 140, the light source 110, the optical system 120, and the CCD sensor 130 all move in the main scanning direction.

<Description of shading correction>
When shading correction is performed in the present embodiment, a predetermined reference image (chart) is formed on the intermediate transfer belt 20 as a toner image. The shading correction is performed based on the light amount value generated by reading the reference image with the CCD sensor 130. Further, in the present embodiment, when the reference image is read by the CCD sensor 130, the CCD sensor 130 is sequentially moved by a predetermined distance by the moving means 140, and the light amount value is acquired by the CCD sensor 130 each time the CCD sensor 130 is moved.

FIG. 4A is a diagram showing a positional relationship between the reference image S and the CCD sensor 130 when the CCD sensor 130 is moved by the moving unit 140. FIG. 4B is a conceptual diagram illustrating the light quantity value acquired at this time.
In the example shown in FIG. 4A, a rectangular ladder pattern is formed on the intermediate transfer belt 20 as a reference image S. The color of the reference image S is not particularly limited, but in the present embodiment, for example, the color is K (black). The image density of the reference image S is not particularly limited. For example, a uniform image with an image area ratio Cin (Input Coverage) = 100% is formed.

FIG. 4B shows a case where the CCD sensor 130 is sequentially moved to the right side in the drawing along the main scanning direction with respect to the reference image S. That is, in this case, the CCD sensor 130 sequentially moves to the position (1), the position (2), and the position (3) each time it moves.
At this time, the light amount profile (light amount distribution) indicating the distribution of the light amount values generated by the CCD 131 of the CCD sensor 130 moves to the opposite side to the moving direction of the CCD sensor 130 as shown in FIG. Become. That is, when the CCD sensor 130 is used as a reference, the reference image S moves to the left side in the figure, so that the light amount profile moves to the left side in the figure as shown in FIG.

  In FIG. 4B, the light amount profile with a constant light amount value obtained for the sake of simplicity has been described. However, the light amount value of the light amount profile that is actually acquired is not constant. As this factor, first, there is a reading density difference in the CCD sensor 130. This is caused by variations in the mounting accuracy of the optical system 120, variations in the light receiving sensitivity of the CCD 131, dust adhering to the CCD sensor 130, and the like. Further, it is difficult to make the density of the reference image S uniform, and density unevenness may occur. Therefore, the light quantity value of the light quantity profile varies due to these factors.

FIGS. 5A and 5B are diagrams illustrating a case where the acquired light amount profiles are displayed in an overlapping manner when the CCD sensor 130 is sequentially moved. As described above, when the CCD sensor 130 is moved, the light amount profile moves, and the position of the light amount profile is shifted.
Here, FIG. 5A shows a case where the images are displayed in an overlapped state with the light amount profile shifted as shown in FIG. 4B. It can be considered that this is a light amount profile when the CCD sensor 130 is used as a reference. FIG. 5B shows a case where the light intensity profiles are displayed in an overlapped state with the end portions thereof aligned. Here, the end portion of the light amount profile corresponds to the portion of the light amount value acquired at the end portion (illustrated by the end portion T1 and the end portion T2 in FIG. 4A) of the reference image S in the main scanning direction. It can be considered that this is a light amount profile when the reference image S is used as a reference.

  In the example shown in FIG. 5A, the peak P1 in the light amount profile exists at a certain location and does not move. On the other hand, the peak P2 moves and the position is shifted. This is determined by the difference between the reading density difference of the CCD sensor 130 or the density unevenness of the reference image S. In other words, when the difference is due to the difference in reading density of the CCD sensor 130, the reading density difference is generated at the same location of the CCD sensor 130, and is not affected by the movement of the CCD sensor 130. Therefore, it can be seen that the peak P1 is caused by the difference in reading density of the CCD sensor 130. On the other hand, when the density is due to the density unevenness of the reference image S, the reference image S moves according to the movement of the CCD sensor 130 when the CCD sensor 130 is used as a reference. Therefore, it can be seen that the peak P2 is caused by the density unevenness of the reference image S.

  Further, when the light amount profiles are overlapped with the end portions aligned as shown in FIG. 5B, the relationship is opposite to the case described with reference to FIG. That is, the peak P1 caused by the difference in reading density of the CCD sensor 130 moves and shifts in the light amount profile. On the other hand, the peak P2 caused by the density unevenness of the reference image S exists at a certain location in the light amount profile.

  As described above, in the present embodiment, it is possible to determine whether the variation in the light amount value of the light amount profile is due to the difference in reading density of the CCD sensor 130 or the unevenness in the density of the reference image S. . Then, if shading data that is a correction coefficient for correcting the change in the light amount value caused by the difference in reading density of the CCD sensor 130 is derived, shading correction can be performed.

<Description of shading data creation>
FIG. 6 is a diagram illustrating a functional configuration example of the shading data creation unit 167 according to the present embodiment.
As shown in the figure, the shading data creation unit 167 includes a light amount value acquisition unit 167-1 and a correction coefficient derivation unit 167-2.

  The light amount acquisition unit 167-1 acquires, for each pixel, the light amount value generated by the CCD sensor 130 when the moving unit 140 relatively moves the CCD sensor 130 and the reference image S in the main scanning direction. . That is, the light quantity value acquisition unit 167-1 sequentially moves the CCD sensor 130, and acquires the light quantity value for each pixel each time the CCD sensor 130 is moved. Thus, one of the light quantity profiles as shown in FIG. 5A can be created every time the CCD sensor 130 is moved.

The correction coefficient deriving unit 167-2 derives the pudding data for performing the shunning correction based on the light amount profile acquired by the light amount value acquiring unit 167-1. In the present embodiment, the correction coefficient deriving unit 167-2 is acquired by the light amount value acquiring unit 167-1 when the moving unit 140 relatively moves the CCD sensor 130 and the reference image S in the main scanning direction. Based on whether or not a part of the light quantity profile obtained from the obtained light quantity value moves correspondingly, the singing data is derived.
The correction coefficient deriving unit 167-2 includes a temporary correction unit 167-21, an average profile creation unit 167-22, a matching degree determination unit 167-23, a temporary coefficient selection unit 167-24, and a correction coefficient determination unit 167. -25.

The temporary correction unit 167-21, the average profile creation unit 167-22, the matching degree determination unit 167-23, the temporary coefficient selection unit 167-24, and the correction coefficient determination unit 167-25 have the following functions, which will be described in detail later. .
The temporary correction unit 167-21 corrects the light amount value for each pixel acquired by the light amount value acquisition unit 167-1 with a plurality of temporary coefficients including those that increase and decrease the light amount value.
The average profile creation unit 167-22 is an example of an average light amount calculation unit. Then, the average light amount value after correcting the light amount value acquired when the CCD sensor 130 and the reference image S are relatively moved in the main scanning direction by the moving unit 140 with the temporary coefficient is calculated for each pixel. To do.
The degree of coincidence determination unit 167-23 corrects the light quantity value acquired when the moving unit 140 relatively moves the CCD sensor 130 and the reference image S in the main scanning direction with a temporary coefficient. The degree of coincidence of each light quantity distribution is determined.
The provisional coefficient selection unit 167-24 selects one of the plurality of provisional coefficients for each pixel by the coincidence degree determination by the coincidence degree determination unit 167-23.
The correction coefficient determination unit 167-25 determines, for each pixel, shading data that is a correction coefficient for performing the shunning correction based on the temporary coefficient selected by the temporary coefficient selection unit 167-24.

FIG. 7 is a flowchart illustrating a procedure for creating shading data in the shading data creation unit 167.
The procedure for creating shading data will be described below with reference to FIGS.

  First, the light from the light source 110 is directly irradiated to a portion on the intermediate transfer belt 20 where the reference image S is not formed, that is, the intermediate transfer belt 20. Then, the CCD sensor 130 reads the light reflected by the intermediate transfer belt 20, and the light amount value acquisition unit 167-1 acquires the generated light amount value (step 101). This can be regarded as a light amount value when the image density is Cin = 0%.

  Next, the light quantity value acquisition part 167-1 acquires the light quantity value when the light from the light source 110 is irradiated to the reference | standard image S and the CCD sensor 130 read (step 102). At this time, the color of the reference image S is, for example, K (black), and the image density is, for example, Cin = 100%.

  Then, the moving means 140 moves the CCD sensor 130 by a predetermined amount (step 103). In the present embodiment, in order to simplify the following description, it is assumed that the CCD sensor 130 is moved along the main scanning direction by one pixel of the CCD sensor 130.

  Subsequently, the light amount acquisition unit 167-1 further acquires a light amount value when the CCD sensor 130 reads the reference image S (step 104).

  Then, the light quantity value acquisition unit 167-1 determines whether or not the light quantity value has been acquired by moving the CCD sensor 130 a predetermined number of times or more (step 105). If the light quantity value has not been acquired more than a predetermined number of times, the process returns to step 103.

  On the other hand, when the CCD sensor 130 has been moved and acquired a light quantity value more than a predetermined number of times, the light quantity value acquisition unit 167-1 creates a light quantity profile for each position of the moved CCD sensor 130. (Step 106). In the present embodiment, this light amount profile is created by subtracting the light amount value when Cin = 0% from the light amount value when Cin = 100% for each pixel of the CCD sensor 130. That is, the light amount value generated by the CCD sensor 130 includes light reflected by the intermediate transfer belt 20. Since this amount of light value can be regarded as a light amount value of Cin = 0%, the amount of light reflected by the reference image S is expressed as “(light amount value when Cin = 100%) − (Cin = “Light amount value at 0%)” is adopted. If this process is not performed, it is difficult to accurately perform shading correction.

  In the present embodiment, it is necessary to create three or more light amount profiles to be created. In this case, convergence of the correction process described later in step 115 occurs. In order to obtain shading data with higher accuracy, it is more preferable to create four or more. However, the following description will be made assuming that three light intensity profiles have been created.

  Further, the light quantity value acquisition unit 167-1 performs processing to match the end of the created light quantity profile as described with reference to FIG. 5B (step 107).

FIGS. 8A to 8B are diagrams comparing the three light quantity profiles used in the present embodiment before and after combining the end portions.
Among these, FIG. 8A is a diagram showing three light quantity profiles before the ends of the light quantity profiles are combined. FIG. 8B is a diagram showing three light quantity profiles after the ends of the light quantity profiles are matched.
As shown in FIG. 8A, the three light intensity profiles indicated as “Profile1”, “Profile2”, and “Profile3” are moved for “pixel 5”, “pixel 6”, and “pixel 7”, respectively. An upward peak is seen. Similarly, a downward peak that does not move is seen at the location of “pixel 10”. As described with reference to FIG. 5, the former upward peak is caused by unevenness in the reference image S, and the latter downward peak is caused by a reading density difference of the CCD sensor 130.
Further, as described in FIG. 5, in the light amount profile after the end portions in FIG. 8B are matched, the former upward peak does not move, and the latter downward peak moves. Thereafter, processing is performed using the light amount profile shown in FIG.

  Returning to FIG. 6 and FIG. 7, “1” is added as the order of the pixels to be subsequently subjected to temporary correction (step 108). Since the initial value of the order of the pixels is “0”, in the present embodiment, first, “pixel 0”, which is the first pixel, is selected as a target to be temporarily corrected.

  Next, in the present embodiment, the temporary correction unit 167-21 performs temporary correction on each light quantity profile of FIG. 8B (step 109). At this time, in this embodiment, three types of profiles shown in FIG. 9 are prepared as correction profiles for provisional correction. In FIG. 9, “Modified Profile A” indicates correction for increasing (increasing) the light amount value for a predetermined pixel. In the case of “corrected Profile B”, the light amount value is not corrected. Further, what is indicated by “corrected Profile C” is for performing correction for lowering (decreasing) the light amount value for a predetermined pixel. In this case, as the temporary coefficient, for example, 1.01 is selected in order to increase the light amount value for a predetermined pixel, and the original light amount value is multiplied by this temporary coefficient. Similarly, when the light amount value is not corrected, 1.00 is selected as a temporary coefficient, and 0.99 is selected, for example, to decrease the light amount value for a predetermined pixel.

Actually, the following processing is performed in the order of pixels from “pixel 0”, but here, processing from “pixel 0” to “pixel 4” is completed, and provisional correction is performed on “pixel 5”. Will be described.
At this time, the temporary correction is performed by applying the correction profile described in FIG. 9 to the position of “pixel 5” in each light quantity profile in FIG.

FIG. 10A shows the “modified Profile 1” and “modified” when the “modified Profile A” in FIG. 9 is applied to each of “Profile 1”, “Profile 2”, and “Profile 3” in FIG. 8B. “After Profile2” and “After correction Profile3” are illustrated.
As a result, as illustrated in FIG. 10A, in “Profile 1 after correction” in which “Profile 1” is applied to “Profile 1”, the upward peak at the position of “pixel 5” becomes large. Also, in “Profile 2 after correction” in which “Modification Profile A” is applied to “Profile 2”, a new upward peak occurs at the location of “pixel 5”. Furthermore, for “Profile 3 after correction” in which “Profile 3” is applied to “Profile 3”, an upward peak is newly generated at the location of “pixel 5”.

  Also, FIG. 10-2 (a) shows “post-correction Profile1”, “Fixed ProfileB” in FIG. 9 applied to “Profile1”, “Profile2”, and “Profile3” in FIG. 8B. The figure shows “Profile2 after correction” and “Profile3 after correction”. Since “Modified Profile B” is not corrected, “Profile 1”, “Profile 2”, “Profile 3” and “After modified Profile 1”, “After modified Profile 2”, and “After modified Profile 3” are the same. Become.

Further, FIG. 10-3 (a) shows “post-correction Profile1”, “post-correction Profile1” when “correction ProfileC” of FIG. 9 is applied to “Profile1”, “Profile2”, and “Profile3” of FIG. The figure shows “Profile2 after correction” and “Profile3 after correction”.
As a result, as illustrated in FIG. 10C, the peak at the position of “pixel 5” disappears in “modified Profile1” in which “modified ProfileC” is applied to “Profile1”. Also, in “Profile 2 after correction” in which “Profile 2” is applied to “Profile 2”, a new downward peak occurs at the location of “pixel 5”. Furthermore, for “Profile 3 after correction” in which “Profile 3” is applied to “Profile 3”, a new downward peak occurs at the location of “pixel 5”.

Next, in the present embodiment, the average profile creation unit 167-22 performs “revision profile 1”, “figure Profile 1”, “10-1 (a), FIG. 10-2 (a), and FIG. The average profile is created by averaging the profile 2 after correction and the profile 3 after correction (step 110). Specifically, the average profile is obtained by calculating the average value of the light amount values for each pixel of “modified Profile 1”, “modified Profile 2”, and “modified Profile 3”.
10-1 (b), FIG. 10-2 (b), and FIG. 10-3 (b) are respectively the same as FIG. 10-1 (a), FIG. 10-2 (a), and FIG. 10-3 (a). This is an average profile obtained by averaging “modified Profile 1”, “modified Profile 2”, and “modified Profile 3”.

  Next, in the present embodiment, the coincidence determination unit 167-23 determines the coincidence of “modified Profile1”, “modified Profile2”, and “modified Profile3” (step 111). Then, the temporary coefficient selection unit 167-24 selects a correction profile having the highest degree of coincidence (step 112). In other words, the provisional coefficient selection unit 167-24 selects one of the plurality of provisional coefficients for each pixel by the coincidence degree determination by the coincidence degree determination unit 167-23.

In the coincidence determination unit 167-23, the average profile obtained in step 110 is used in order to determine the coincidence between “modified Profile 1”, “modified image 2”, and “modified image 3”. Here, the difference between “modified Profile 1”, “modified Profile 2”, and “modified Profile 3” and the average profile is taken, and the absolute value of this difference is accumulated. In other words, the cumulative value of the absolute value of the difference between the light amount value after correction with the provisional coefficient and the average light amount value is obtained.
Then, it is determined that the one with the smallest cumulative value has the highest degree of coincidence of “post-correction Profile1”, “post-correction Profile2”, and “post-correction Profile3”. In the example of FIGS. 10-1 (a), 10-2 (a), and 10-3 (a), “corrected Profile B”, which is a corrected profile that is not subjected to the correction shown in FIG. 10-2 (a). When used, it is determined that the degree of coincidence of “modified Profile 1”, “modified Profile 2”, and “modified Profile 3” is the highest. Therefore, the temporary coefficient selection unit 167-24 selects “Modified Profile B”.

  In the case of a peak caused by the unevenness of the reference image S as described above, a correction profile that is not corrected is selected.

Next, a case where the processing from “pixel 0” to “pixel 9” has been completed and provisional correction is performed on “pixel 10” will be described.
The temporary correction in this case is performed by applying the correction profile shown in FIG. 11 to the position of “pixel 10” in each light quantity profile of FIG. The correction profile shown in FIG. 11 is obtained by changing the pixel to be corrected from “pixel 5” to “pixel 10” with respect to “correction Profile A”, “correction Profile B”, and “correction Profile C” in FIG. Only the difference.

FIG. 12-1 (a) shows “modified Profile 1” and “modified” when “modified Profile A” in FIG. 11 is applied to “Profile 1”, “Profile 2”, and “Profile 3” in FIG. 8 (b). “After Profile2” and “After correction Profile3” are illustrated.
As a result, as illustrated in FIG. 12A, the downward peak of the position of “pixel 10” disappears in “modified Profile1” in which “modified ProfileA” is applied to “Profile1”. Similarly, “Fixed Profile A” applied to “Profile 2” and “Fixed Profile A” applied to “Profile 3” and “Fixed Profile A” applied to “Profile 3” are also directed downwardly at the position of “Pixel 10”. The peak disappears.

  Also, FIG. 12-2 (a) shows “modified Profile1”, “corrected Profile1”, and “Profile1”, “Profile2”, and “Profile3” in FIG. The figure shows “Profile2 after correction” and “Profile3 after correction”. Since “Modified Profile B” is not corrected, “Profile 1”, “Profile 2”, “Profile 3” and “After modified Profile 1”, “After modified Profile 2”, and “After modified Profile 3” are the same. Become.

Further, FIG. 12-3 (a) shows “post-correction Profile1” and “post-correction Profile1” when “correction ProfileC” of FIG. 11 is applied to “Profile1”, “Profile2”, and “Profile3” of FIG. The figure shows “Profile2 after correction” and “Profile3 after correction”.
As a result, as shown in FIG. 12-3 (a), the downward peak of the position of “pixel 10” becomes large in “post-correction Profile1” in which “correction ProfileC” is applied to “Profile1”.
Similarly, “modified Profile C” applied to “Profile 2” and “modified Profile C” applied to “Profile 3” are also newly added to the “pixel 10” position. The downward peak becomes large.

  In this case, the coincidence determination unit 167-23 uses the average profiles shown in FIGS. 12-1 (b), 12-2 (b), and 12-3 (b), and the step 111 is performed. When the degree of coincidence of “modified profile 1”, “modified profile 2”, and “modified profile 3” is determined, “modified profile A” is selected. As described above, “correction Profile A” (temporary coefficient> 1) for performing correction for increasing the light amount value for this pixel is selected for a portion where a downward peak occurs in the light amount profile. On the other hand, for a portion where an upward peak occurs in the light amount profile, “correction ProfileC” (temporary coefficient <1) for performing correction for decreasing the light amount value for this pixel is selected.

  In the case of the peak caused by the difference in reading density of the CCD sensor 130 as described above, the correction profile is selected as the correction profile.

  As described above, in the case of a peak caused by unevenness of the reference image S, a correction profile that is not corrected is selected. In the case of a peak caused by a difference in reading density of the CCD sensor 130, a correction profile is selected as a correction profile. That is, it is possible to distinguish whether the fluctuation of the light amount value of the light amount profile is caused by the difference in reading density of the CCD sensor 130 or the unevenness of the reference image S. Then, when the fluctuation of the light amount value of the light amount profile is caused by a difference in reading density of the CCD sensor 130, a correction profile for correction is selected. That is, for the pixel that needs to be subjected to shading correction, a correction profile for correction is selected. In this way, in the present embodiment, when the reference image S is used as a reference (when the ends of the light amount profile are aligned), shading data is derived by dividing the pixel corresponding to the moving position in the light amount profile. ing.

  In this embodiment, after the correction profile is selected, it is determined whether or not correction profile selection (provisional coefficient selection) has been completed for all pixels (step 113). If not completed (No in step 113), the process returns to step 108. In step 108, as described above, “1” is added as the order of pixels to be temporarily corrected. Therefore, by repeating the processing from step 108 to step 113, the correction profile is selected for all the pixels in the order of “pixel 0” → “pixel 1” → “pixel 2” →. .

  If correction profile selection has been completed for all pixels (Yes in step 113), the initial value of the pixel order is returned to "0" (step 114). Then, it is determined whether or not the correction process has converged (step 115). For example, it is determined that the correction processing has converged when a pixel for which “corrected profile B” is selected as the corrected profile is equal to or greater than a predetermined threshold. That is, in this case, it can be said that it is no longer necessary to correct the light amount profile.

  If it is determined that the correction process has not converged (No in step 115), the process returns to step 108. That is, the process of selecting the above-described correction profile starting from “pixel 0” is started again. This is because the variation of the light amount profile is large, and it is possible to cope with the case where the variation of the light amount profile cannot be corrected by applying the temporary coefficient once. Therefore, in this case, “correction Profile A” and “correction Profile C” for correcting the same pixel are selected many times.

  On the other hand, when it is determined that the correction process has converged (Yes in step 115), the correction coefficient determination unit 167-25 finally derives shading data (step 116). This is obtained for each pixel by obtaining the cumulative value of the number of selected “Correction Profile A” and “Correction Profile C” to be corrected, and shading data is obtained for each pixel from the cumulative value and the value of the temporary coefficient. Derived.

  According to the image reading apparatus 100 described above, the shoeing correction can be performed without using a reference plate such as a white reference plate. Therefore, it is not necessary to consider the density unevenness of the reference plate, the adhesion of dust to the reference plate, the influence of backlight due to the reference plate, and the like. Further, since the toner image formed on the intermediate transfer belt 20 can be used as the reference image S, shading correction can be easily performed. According to the present embodiment, since the influence of density unevenness of the reference image S can be removed, shading correction can be performed even if the reference image S has density unevenness. Note that the image reading apparatus 100 of the present embodiment can also be applied to the case where shading correction is performed using a conventional reference plate such as a white reference plate. That is, the image reading apparatus 100 according to the present embodiment reads the reference plate as the reference image S, thereby performing shading correction. In this case, since the influence of the uneven density of the reference plate can be eliminated, shading correction can be performed even if the reference plate has uneven density.

  In the above-described example, the moving unit 140 moves the CCD sensor 130 for each pixel of the CCD sensor 130. However, in actuality, this moving distance may be arbitrary, and accuracy is not required for this moving distance. In this case as well, shading data can be obtained by the procedure described above. In the present embodiment, the CCD sensor 130 is moved every 2 mm, for example, and a total of 10 light intensity profiles are acquired.

  In the example described above, the CCD sensor 130 is moved in the main scanning direction by the moving means 140, but the present invention is not limited to this. That is, since the sensor of the CCD sensor 130 and the reference image S need only be relatively moved in the main scanning direction, the CCD sensor 130 may be fixed and the intermediate transfer belt 20 may be moved in the main scanning direction.

  Further, in the above-described example, the reference image S is a toner image formed on the intermediate transfer belt 20, but is not limited to this, and the image after being fixed on the sheet by the fixing unit 60 is used as the reference image. S may be read by the image reading apparatus 100. In the above-described example, the image reading apparatus 100 is for adjusting the image formed on the sheet by the image forming unit 10. However, the present invention is not limited to this. A simple scanner or the like may be used.

  Note that the processing performed by the shading data creation unit 167 described above is realized by cooperation between software and hardware resources. That is, a CPU (not shown) in the control computer provided in the signal processing unit 160 provided with the shading data creation unit 167 executes a program that realizes each function of the shading data creation unit 167, and realizes each of these functions. Let

  Therefore, the processing performed by the shading data creation unit 167 is performed by using the light amount value generated by the CCD sensor 130 when the CCD sensor 130 and the reference image S are relatively moved in the main scanning direction. A function of acquiring each of the obtained values, a function of correcting the acquired light quantity value with a plurality of provisional coefficients including correction for increasing and decreasing the light quantity value for each predetermined pixel, CCD sensor 130 and reference A function for determining the degree of coincidence of the respective light quantity distributions when the light quantity values acquired when the image S is relatively moved in the main scanning direction are corrected by a plurality of provisional coefficients; Based on the determination, one of a plurality of temporary coefficients is selected for each pixel, and the CCD sensor 130 reads in the main scanning direction based on the selected temporary coefficient. It can be regarded as a program for realizing a function for determining for each pixel shading data for correcting the density difference.

DESCRIPTION OF SYMBOLS 1 ... Image forming apparatus, 100 ... Image reading apparatus, 110 ... Light source, 130 ... CCD sensor, 131 ... CCD, 140 ... Moving means, 160 ... Signal processing part, 167-1 ... Light quantity value acquisition part, 167-2 ... Correction Coefficient derivation unit, 167-21 ... Temporary correction unit, 167-22 ... Average profile creation unit, 167-23 ... Matching degree determination unit, 167-24 ... Temporary coefficient selection unit, 167-25 ... Correction coefficient determination unit

Claims (6)

A light source that emits light to a predetermined reference image;
Light receiving means for receiving light reflected by the reference image, reading the reference image with a predetermined number of pixels in the main scanning direction, and generating a light amount value for each pixel;
Moving means for relatively moving the light receiving means and the reference image in the main scanning direction;
Correction coefficient creating means for deriving a correction coefficient for correcting a reading density difference in the main scanning direction of the light receiving means based on the light amount value generated by the light receiving means;
A read density correction means for correcting a read density difference in the main scanning direction of the light receiving means using the correction coefficient created by the correction coefficient creation means;
With
The correction coefficient creating means includes
A light amount value acquisition unit that acquires the light amount value generated by the light receiving unit for each pixel when the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit;
When the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit, a part of the light amount distribution obtained from the light amount value acquired by the light amount value acquiring unit moves correspondingly. A correction coefficient deriving unit for deriving the correction coefficient using whether or not
An image reading apparatus comprising:   The image reading apparatus according to claim 1, wherein the correction coefficient deriving unit derives the correction coefficient for a pixel corresponding to a moving position in the light amount distribution when the reference image is used as a reference. The correction coefficient deriving unit
A temporary correction unit that corrects the light amount value acquired by the light amount value acquisition unit with a plurality of temporary coefficients including a correction that increases and decreases the light amount value for each predetermined pixel;
Matching of the respective light quantity distributions when the light quantity values acquired when the light receiving means and the reference image are relatively moved in the main scanning direction by the moving means are corrected by a plurality of the temporary coefficients. A degree-of-match determination unit that determines the degree;
A provisional coefficient selection unit that selects one of the plurality of provisional coefficients for each of the pixels by determining the degree of coincidence by the coincidence degree determination unit;
A correction coefficient determination unit that determines the correction coefficient for each pixel based on the temporary coefficient selected by the temporary coefficient selection unit;
The image reading apparatus according to claim 1, further comprising: For each pixel, an average light amount value obtained by correcting the light amount value acquired when the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit with the provisional coefficient. An average light amount calculation unit for calculating,
4. The coincidence degree determination unit obtains the coincidence degree of the light amount distribution by obtaining a cumulative value of absolute values of differences between the light amount value corrected by the temporary coefficient and the average light amount value. The image reading apparatus described in 1. An image forming unit for forming an image on a recording medium;
A reading unit that reads an image to adjust an image formed on a recording medium by the image forming unit;
With
The reading unit
A light source that emits light to a predetermined reference image;
Light receiving means for receiving light reflected by the reference image, reading the reference image with a predetermined number of pixels in the main scanning direction, and generating a light amount value for each pixel;
Moving means for relatively moving the light receiving means and the reference image in the main scanning direction;
Correction coefficient creating means for deriving a correction coefficient for correcting a reading density difference in the main scanning direction of the light receiving means based on the light amount value generated by the light receiving means;
A read density correction means for correcting a read density difference in the main scanning direction of the light receiving means using the correction coefficient created by the correction coefficient creation means;
With
The correction coefficient creating means includes
A light amount value acquisition unit that acquires the light amount value generated by the light receiving unit for each pixel when the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit;
When the light receiving unit and the reference image are relatively moved in the main scanning direction by the moving unit, a part of the light amount distribution obtained from the light amount value acquired by the light amount value acquiring unit moves correspondingly. A correction coefficient deriving unit for deriving the correction coefficient using whether or not
An image forming apparatus comprising: On the computer,
A function of acquiring a light amount value generated by the light receiving means for each pixel of the light receiving means when the light receiving means and the reference image are relatively moved in the main scanning direction;
A function of correcting the acquired light amount value with a plurality of provisional coefficients including a correction for increasing and decreasing the light amount value for each predetermined pixel;
Determining the degree of coincidence of the respective light quantity distributions when the light quantity values acquired when the light receiving means and the reference image are relatively moved in the main scanning direction are corrected with the plurality of provisional coefficients. Function and
A function of selecting one of the plurality of provisional coefficients for each of the pixels by determining the degree of coincidence;
A function of determining, for each pixel, a correction coefficient for correcting a reading density difference in the main scanning direction of the light receiving unit based on the selected temporary coefficient;
A program that realizes

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