JP4986718B2 - Image forming apparatus and image processing method - Google Patents

Description

The present invention relates to an image forming apparatus and an image processing method including a document reading device that reads a document image.

  The mainstream of image forming apparatuses is a composite printer having a scanner unit for reading a document image, an image processing unit as a controller, and a printer unit for forming an image. The scanner unit basically optically reads an image on an original such as a printed matter or a photograph with an image sensor and generates image data. The image processing unit performs predetermined image processing on the image data read by the scanner unit and image data supplied from a PC, a digital camera, and the like, and serves as an exposure condition in the exposure unit for recording an image in the printer unit. Generate image data. In accordance with the image data output from the image processing unit, the printer unit scans and exposes the photosensitive material by, for example, light beam scanning in the exposure unit, records a latent image, and performs development processing on the exposed photosensitive material. And transferred onto a recording material.

  By the way, the scanner unit of the composite printer optically reads an original image by making the reading light incident on the original and reading the reflected light reflected by the original with an image sensor such as a CCD sensor. In the case of a color document, the scanner unit processes the reflected light of the document with red (R), green (G), and blue (B) color filters, thereby converting the document image into the three primary colors R, G, and B. Disassemble and read.

Here, if the scanner unit is within the scanner reading range, the same image signal (image data) must be obtained when the same document is read even if the reading position changes. However, the light source, optical system, color filter, image sensor, etc. attached to the scanner have unevenness (for example, individual differences, sensitivity variations, deterioration over time, etc.), and appropriate density reproduction according to the original document at all positions. There was a problem that could not be obtained. In order to solve this problem, an image forming apparatus that reads a reference document prepared in advance and corrects an image signal is known (see Patent Documents 1 and 2).
JP 2000-092326 A Japanese Patent Laid-Open No. 11-205598

  However, in the above-described conventional image forming apparatus, when the reference document (reference sample) is used, the reference sample is required again when the characteristics of the reading device change (deterioration with time, change with time, etc.). Therefore, it is troublesome to obtain and store the reference sample, and there is a problem that productivity is lowered.

SUMMARY An advantage of some aspects of the invention is that it provides an image forming apparatus and an image processing method capable of correcting reading unevenness without preparing a reference sample in advance.

To achieve the above object, an image forming apparatus of the present invention is provided with a document reading section for reading a document image based on the image signal of the original image read by the document reading section, an image for forming an image on a transfer material An output image forming unit that forms an output image on the transfer material; an output image reading unit that reads an output image formed on the transfer material; and an output image read by the output image reading unit. a first image information obtaining means for obtaining image signal values and the first image information including the position information, the output image orientation is different from 90 degrees with respect to the reading surface, as an original image, read by the original reading portion , the output image of each orientation, the image signal value and the second image information acquisition means for acquiring second image information including the position information, the first image information and before From the second image data, wherein as the image signal values of the original reading unit is equal to the image signal value of the output image reading means as a target, for correcting an image signal of an original image read by the original reading portion and an image signal correction parameter calculating means for calculating for each of a plurality of positions of the image signal read-area correction parameters by using the image signal correction parameters the calculated, the original image read by the original reading portion And correction means for correcting the image signal .

An image processing method of an image forming apparatus according to the present invention includes a document reading unit that reads a document image, an output image forming unit that forms an output image on a transfer material, and an output image reading unit that reads an output image formed on the transfer material. When, by using the image signal correction parameter, an image processing method for an image forming apparatus and a correcting section that corrects the image signal of an original image read by said original reading unit, by the output image reading unit of the read output image, the image signal values and obtains the first image information including the position information, the output image orientation with respect to the reading surface is different by 90 degrees, as an original image, read by the document reading unit, the the direction of the output image from the image signal values and obtains the second image information including the position information, the first image information and said second image information, the document As the image signal value of the isolation portion is equal to the image signal value of the output image reading unit to the target, reading area the image signal correction parameters for correcting the image signal of the original image read by the original reading portion characterized in that you calculated for each of a plurality of positions of the inner.

In the image forming apparatus according to the first aspect of the present invention, an output image is formed on a transfer material, the image signal of the output image read by the output image reading means and its position information, and the output image read by the document reading device. The image signal correction parameter is calculated from the image signal and its position information so that the image signal value of the document reading apparatus is equal to the target image signal value of the output image reading means . Therefore, it is possible to correct reading unevenness without preparing a reference sample in advance.

Embodiments of an image forming apparatus and an image processing method of the present invention will be described with reference to the drawings. The image forming apparatus of this embodiment is applied to a color digital printer.

  FIG. 1 is a cross-sectional view showing a configuration of a color digital printer 1 in the embodiment. The color digital printer 1 has a box-shaped main body. Also, a scanner unit 200 for reading a reflected original is provided as an original reading device on the upper part of the main body. An image processing device 14 (see FIG. 3) is provided inside the main body.

  As will be described later, the read image signal from the scanner unit 200 is input to the image processing device 14 together with the image signal from other image data supply means (for example, a digital camera). Image processing is performed. In the present embodiment, as the output image reading device, one color sensor 3000 is installed on the conveyance path on the downstream side of the fixing device 109 at the center in the main scanning direction.

  The photosensitive drum 101 in the printer 1 is provided with a metal conductive substrate 101b and a photosensitive layer 101a thereon. The charging roller 102 has a metal core 102b. An elastic layer 102a is provided on the surface layer of the metal core 102b, and the photosensitive drum 101 is uniformly charged. The bias power supply 111 applies a voltage to the cored bar 102 b of the charging roller 102.

  On the surface of the charged photosensitive drum 101, a laser beam (exposure light) 103 having an oscillation wavelength of about 700 to 800 nm is irradiated to form an electrostatic latent image. The ON / OFF operation of the laser beam 103 is performed based on data obtained by processing input image data.

  The developing device 104 visualizes the electrostatic latent image on the surface of the photosensitive drum 101, and a developing bias is applied to the developing sleeve 104a by a developing bias power source 112. The transfer roller 105 transfers the toner image visualized on the surface of the photosensitive drum 101 to a transfer material (not shown). A medium resistance elastic layer 105a is provided on the surface layer of the cored bar 105b. The bias power supply 113 applies a voltage to the core bar 105 b of the transfer roller 105.

  The transfer guide 106 guides a transfer material between the transfer roller 105 and the photosensitive drum 101. The cleaner 107 has a cleaning blade 107 a and removes toner, paper dust, and the like remaining on the surface of the photosensitive drum 101.

  After the transfer, the transfer material is sent to the fixing device 109 by the conveyance guide 108. The fixing device 109 includes a fixing roller 109a and a pressure roller 109b. By pressing and heating the transfer material by the fixing device 109, the toner image is fixed on the transfer material.

  Next, the scanner unit 200 will be described in detail. The scanner unit 200 is covered with a box-shaped casing, and a rectangular opening is provided at the center of the upper surface, and a transparent platen glass 202 is fitted therein.

  The platen glass 202 has a function as a flat document placing table, on which a reflective original on which a flat image is recorded is placed. The platen glass 202 is provided with a pressing cover 204 that can be opened and closed. The scanner unit 200 is provided with a scanning unit 208. The scanning unit 208 is controlled by the controller 209.

  The scanning unit 208 includes a reflective original light source unit 210, a first carriage 214, a second carriage 220, and a fixed unit 228. The reflective original light source unit 210 includes a halogen lamp and a reflector that extend in the width direction (main scanning direction) of the original image. A first mirror 212 extending in the width direction of the document image is incorporated in the first carriage 214 together with the light source unit 210 for the reflected document. A second mirror 216 and a third mirror 218 are incorporated in the second carriage 220. The fixed unit 228 includes a diaphragm 222, a filter group 224 including four color adjustment filters and ND filters, and a lens 226 for imaging.

  The first carriage 214 irradiates the original placed on the surface of the platen glass 202 with the light from the light source unit 210 for the reflective original, and the first mirror 212 applies the reflected light (light of the hanging optical axis). It is deflected by 90 ° and guided to the second mirror 216 of the second carriage 220.

  The second carriage 220 is arranged in a state in which the reflection surface of the second mirror 216 is opposed to and parallel to the reflection surface of the first mirror 212, so when receiving light from the first mirror 212, The second mirror 216 deflects 90 °, and the third mirror 218 deflects 90 °. The light finally deflected by the third mirror 218 parallel to the surface of the platen glass 202 passes through the fixed unit 228 and reaches the light receiving portion of the line CCD sensor 230. FIG. 2 is a diagram showing a configuration of the light receiving unit 34 of the line CCD sensor 230. The light receiving unit 34 of the line CCD sensor 230 includes three line sensors 34R, 34G, and 34B that detect the amount of received light independently for each color (RGB).

  In the fixed unit 228, the light amount is adjusted by the diaphragm 222 and the ND filter of the filter group 224, and each color balance is adjusted by the color adjustment filter of the filter group 224. A document image is formed on the light receiving surface of the line CCD sensor 230 by the lens 226. An IR cut film corresponding to the IR cut filter is deposited on the lens surface of the color adjustment filter.

  The second carriage 220 reciprocates in the sub-scanning direction along the document surface below the platen glass 202. At this time, the second carriage 220 moves in the same direction at half the conveying speed of the first carriage 214 in order to keep the optical path length from the document reflection position to the light receiving unit 34 of the line CCD sensor 230 constant at all times. It is supposed to be.

  One reciprocation of the first carriage 214 and the second carriage 220 corresponds to scanning for one image, and image reading is performed during the forward path. Thereby, the original image on the platen glass 202 can be read.

  The scanner is not limited to the one using the slit scanning as described above, and may use a surface exposure that reads the entire image of one frame at a time. In this case, for example, an area CCD sensor is used, and means for inserting R, G, and B color filters between the light sources is provided. This is sequentially performed for each color filter of G and B. That is, the image is separated into three primary colors and sequentially read.

  Further, the result of reading the reflected original image in the scanner unit 200 is sent to the image processing device 14. FIG. 3 is a block diagram showing the internal configuration of the image processing apparatus 14. The image processing apparatus 14 includes an image processing unit 38 and a data conversion unit 40. The image processing unit 38 includes a preprocessing unit 42, a frame memory 44, a processing unit 50, and a condition setting unit 52.

  FIG. 4 is a diagram illustrating a configuration of the preprocessing unit 42. The preprocessing unit 42 includes an A / D conversion unit 36, a data conversion unit 37, an image signal correction unit 38, a log conversion unit 39, and the like. The A / D converter 36 performs A / D (analog / digital) conversion of the input read image signal. The data conversion unit 37 performs data conversion such as adjustment of the dynamic range of the image signal read by the scanner unit 200. The image signal correction unit 38 corrects the luminance value of the image signal that is image data. Details of the image signal correction unit 38 will be described later. The Log conversion unit 39 performs logarithmic conversion amplification.

  The frame memory 44 is composed of R, G, and B frame memories. The processing unit 50 performs various image processing described later. The condition setting unit 52 manages various processing condition settings by the processing unit 50.

  The condition setting unit 52 selects image processing performed by the processing unit 50, sets image processing conditions in the processing unit 50 using image data input from the frame memory 44, and supplies the image processing conditions to the processing unit 50. The processing unit 50 performs various types of conventional image processing.

  FIG. 3 shows only the image processing related part in the image processing apparatus 14. In addition to these, the image processing device 14 is provided with a CPU for controlling and managing the entire color digital printer 1 including the image processing device 14, a memory for storing information necessary for the operation of the color digital printer 1, and the like. Yes. An operation unit (not shown) is connected to each part via the CPU or the like (CPU bus).

  The image processing device 14 stores output image measurement results (including measurement positions and measurement values) by a color sensor 3000 which is an output image reading device to be described later, and reads the measurement results to obtain an image signal correction unit. A storage device 58 to be supplied to 38 is connected. Here, the storage device 58 may be a memory such as a built-in memory or an external memory, or a hard disk device. In addition, a combination of a storage medium such as a magnetic recording medium such as a floppy (registered trademark) disk (FD), a magneto-optical recording medium such as MO, and an optical recording medium such as an optical disk (CD, CD-R), and a driving device thereof. There may be. Here, it is stored in a storage medium for ease of handling, and is read from the drive device to the image signal correction unit 38 as necessary.

  FIG. 5 is a diagram showing the configuration of the color sensor 3000. 2A shows a schematic configuration of the color sensor 3000, and FIG. 2B shows a configuration of the light receiving portion 54b of the light receiving element 54a of the color sensor 3000. The color sensor 3000 is a sensor that reads the toner patch image (output image) 61 after fixing formed on the transfer material 2027 and detects RGB output values.

  The color sensor 3000 includes a light emitting element 53 such as a white LED, a charge storage sensor with an RGB on-chip filter, a light receiving element 54a such as a photodiode (PD) used for a trigger signal, and a holder that accommodates these.

  The color sensor 3000 causes light emitted from the light emitting element (white LED) 53 to enter the transfer material 2027 on which the toner patch image 61 after fixing is formed at an angle of 45 degrees, and diffusely reflected light in the 0 degree direction. The intensity is detected by the light receiving element 54a. As the light receiving element 54a, the above-described charge storage type sensor with an RGB on-chip filter is used. The light receiving portion 54b of the light receiving element 54a has independent R, G, and B pixels.

  The charge storage sensor constituting the light receiving element 54a may be a photodiode. The light receiving element 54a may be configured by arranging several sets of three RGB pixels. The color sensor 3000 may be configured such that the incident angle is 0 degree and the reflection angle is 45 degrees. Furthermore, the color sensor 3000 may be configured by an LED that individually emits three colors of RGB and an unfiltered sensor.

  The color sensor 3000 having such a configuration detects the RGB output value of the toner patch image on the transfer material, and outputs the detection result to the image processing device 14. Various image controls are performed based on the detection result.

  The normal operation of the color digital printer 1 having the above-described configuration is as follows. That is, the image data of the original image read by the scanner unit 200 is subjected to A / D conversion, Log conversion, DC offset correction, shading correction, and the like in the preprocessing unit 42 of the image processing unit 38 in the image processing apparatus 14. Predetermined data processing is performed. Further, image processing to be described later is performed. The image processing apparatus 14 can also input image data supplied from another image data supply source and perform image processing in the same manner as the read image data.

  The image data processed in this way is converted by the data conversion unit 40 into image data corresponding to the print creation (image recording) of the printer 1 described above. The image processing unit 38 performs preprocessing on the image signal supplied from the scanner unit 200 or another image data supply unit, and then the processing unit 50 converts the image signal to a constant density such as dark correction or shading correction. On the other hand, correction (density correction) for obtaining a predetermined image signal is performed. The image data that has undergone predetermined image processing is output to the printer 1 as image data for output corresponding to image recording by the printer 1. The printer 1 exposes the photosensitive member in accordance with the supplied image data to record a latent image, performs predetermined processing such as development, transfer, and fixing, and outputs it as a print.

  The image processing performed by the processing unit 50 is not particularly limited. For example, color balance adjustment, gradation adjustment, density adjustment, saturation adjustment, electronic scaling processing, density dynamic range compression / expansion, A sharpness process may be used. Here, various image processing performed by a known image processing apparatus is illustrated. Each of these processes can be performed by a known means using a process using an LUT, a matrix calculator, a filter, an adder, etc., or an averaging process or an interpolation calculation performed by appropriately combining them. It is.

  Next, an operation for acquiring a scanner in-plane unevenness correction parameter (image signal correction parameter) in the color digital printer 1 will be described. In the present embodiment, the method for correcting in-plane unevenness is shown by taking a reflective original reading scanner unit as a representative example, but the present invention is not limited to this and can be applied to a transparent original scanner. Yes.

  FIG. 6 is a flowchart showing an operation procedure for acquiring scanner in-plane unevenness correction parameters. First, the printer 1 creates image data for obtaining an output image for correcting in-plane unevenness in the image processing apparatus 14, and forms the image (step S1). FIG. 7 is a diagram showing a scanner in-plane unevenness correction image. This scanner in-plane unevenness correction image (output image) is a banded image drawn in the sub-scanning direction with the same level signal at a portion corresponding to the position detected by the color sensor 3000 arranged at the center position in the main scanning direction. It is. That is, this band image is an output image formed in a line shape in the transport direction. Note that the processing in step S1 corresponds to an output image forming unit.

  The printer 1 detects the in-plane unevenness correction image transferred and fixed on the transfer material with the color sensor 3000 disposed on the conveyance path on the downstream side of the fixing device 109 (step S2), and the detected image signal. The value and its position information are stored in the storage device 58 (step S3). The detected image signal value and its position information correspond to the first image information, and the processing in steps S2 and S3 corresponds to the first image information acquisition means. FIG. 8 is a diagram showing the position of the scanner in-plane unevenness correction image placed on the platen glass 202. FIG. 6A shows a state in which the scanner in-plane unevenness correction image is placed so that the main scanning direction and the longitudinal direction are orthogonal, and FIG. 5B shows the scanner so that the main scanning direction and the longitudinal direction are parallel to each other. The state where the in-plane unevenness correction image is placed is shown.

  The printer 1 puts the output transfer material on which the scanner in-plane unevenness correction image is formed on the platen glass 202 while being aligned in the transport direction (see FIG. 8A). It is received via an operation unit (not shown) in the processing device 14 (step S4). The printer 1 performs the reading (step S5). The printer 1 stores the read image signal value and its position information in the storage device 58 (step S6). The read image signal value and its position information correspond to the second image information, and the processing in steps S5 and S6 corresponds to the second image information acquisition means.

  Thereafter, the printer 1 changes the position (orientation) of the scanner in-plane unevenness correction image to determine whether or not the measurement has been completed (step S7). If the measurement has not been completed, the printer 1 rotates the image for correcting in-plane unevenness by 90 ° and repositions the left end portion so as to be aligned with the left back of the platen glass 202 (see FIG. 8B). The data is received via the operation unit in the processing device 14 (step S8), and the process returns to S5. Similarly, the printer 1 performs the reading in step S5, and stores the image signal value and the position information read in step S6 in the storage device 58.

  On the other hand, if the position (orientation) of the scanner in-plane unevenness correction image has been changed in step S7, that is, if the reading operation has been completed, the printer 1 stores these images stored in the storage device 58. Information is read out (step S9). The printer 1 calculates image signal correction parameters from these image information and sets them in the image signal correction unit 38 (step S10). Thereafter, the printer 1 ends this operation. Note that the processing in step S10 corresponds to image signal correction parameter calculation means.

  Here, as an image signal correction parameter, a set of two parameters including a target value I1 and an actual measurement value I2 is set for each position over the entire area in the scanner reading area.

  The target value I1 is an image signal value read by the color sensor 3000, and is associated with the image position of the sample. The actual measurement value I2 is a value obtained by multiplying the image signal value of the two reading results (see S5) of the scanner according to the position, and is associated with the entire position in the two-dimensional scanner reading area. ing. FIG. 9 is a diagram illustrating calculation of the actual measurement value I2 at an arbitrary position in the reading area. For example, the actual measurement value I2 at the point c, which is the position in the reading area shown in FIG. 9, is the difference between the image signal value I2b at the point b on the corresponding main scanning line and the image signal value I2a at the point a on the sub-scanning line. It is obtained from the product (I2a · I2b).

  The target value I1 corresponding to the same output image detection area as the actual measurement value I2 of each position is similarly obtained from the position information of I1 and I2 (position information obtained in S3 and S6). Thereby, the image signal correction parameter is set as a set of the target value I1 and the actual measurement value I2 for each of the positions R1 to RN (see FIG. 9) in the entire area in the scanner reading region. As described above, the characteristics of the image signal value (actually measured value I2) of the scanner corresponding to the image signal value (target value I1) of the color sensor that is read at the same position in the reading area can be obtained at other positions in the reading area. The image signal correction parameters are calculated so as to be equal.

  FIG. 10 is a graph showing image signal correction parameters when converting an image signal. The horizontal axis (IN) indicates the image signal value input to the image signal correction unit 38, and the vertical axis (OUT) indicates the image signal value output from the image signal correction unit 38. The image signal correction unit 38 corrects the luminance value (image signal value) of the image data after A / D conversion using the image signal correction parameter. Here, assuming that the luminance value to be corrected is X, the corrected luminance value Y is obtained by Equations (1) and (2).

When X ≦ I2 Y = (X−A) * (I1−α) / (I2−A) + α (1)
When X> I2 Y = (X−I2) * (β−I1) / (B−I2) + I1 (2)
Here, α, A, β, and B are a target value and an actual value when the input value is the minimum value, and a target value and an actual value when the input value is the maximum value, respectively. These values are adjusted at the time of shipment from the factory and stored in the storage unit 58. By using this image signal correction parameter and correcting the image signal in the entire area, in-plane reading unevenness can be corrected.

  As described above, according to the color digital printer of this embodiment, it is possible to correct reading unevenness without preparing a reference sample in advance. Further, uneven reading can be eliminated over the entire reading area of the scanner. Further, the output image can be formed easily and with a small area. Further, even if the output image is formed with a small area, the image signal correction parameter can be calculated over the entire reading region by reading the output image a plurality of times.

  The present invention is not limited to the configuration of the above-described embodiment, and any configuration can be used as long as the functions shown in the claims or the functions of the configuration of the present embodiment can be achieved. Is also applicable.

  For example, many apparatuses that perform calibration of an image forming apparatus using a document reading device mounted on the main body of the image forming apparatus are known. In the case of such an image forming apparatus, after performing the reading unevenness correction of the document reading device (scanner) as shown in the present embodiment, the calibration using the document reading device is performed, thereby achieving higher accuracy. Calibration is possible.

  In the above embodiment, the image signal correction parameter is a combination of one target value I1 and an actual measurement value I2, as shown in FIG. 10, but is a combination of a plurality of target values and actual measurement values. In other words, the density unevenness can be finely corrected.

  Further, in the above-described embodiment, the output image formed on the transfer material is formed in a line shape in the transport direction and the reading operation is performed twice. However, the output image is a solid image corresponding to the reading area of the scanner. There may be. In this case, the reading operation can be completed only once.

  In the above-described embodiment, an intermediate transfer member is used as the image forming apparatus, and toner images of each color are sequentially transferred onto the intermediate transfer member, and the toner images carried on the intermediate transfer member are collectively transferred to a recording medium. An image forming apparatus to be transferred is illustrated. However, the present invention is not limited to this transfer method, and an image forming apparatus that uses a recording medium carrier and sequentially superimposes and transfers the toner images of each color onto the recording medium carried on the recording medium carrier. Good.

  In addition, the printer is illustrated as an aspect of the image forming apparatus, but the present invention is not limited to this. For example, the image forming apparatus may be another image forming apparatus such as a copying machine or a facsimile apparatus, or a multifunction machine combining these functions. Other image forming apparatuses may be used.

  In addition, the shapes of the component parts described in the above embodiment, the relative arrangement thereof, and the like should be appropriately changed according to the configuration of the apparatus to which the present invention is applied and various conditions, and the scope of the present invention is described above. It is not limited only to what is illustrated.

  In the above embodiment, the case where the printing method of the composite apparatus is an electrophotographic method has been described as an example. However, the present invention is not limited to the electrophotographic method, and an inkjet method, a thermal transfer method, a thermal method, a static method, and the like. It can be applied to various printing methods such as an electric method and a discharge destruction method.

1 is a cross-sectional view illustrating a configuration of a color digital printer 1 according to an embodiment. 2 is a diagram illustrating a configuration of a light receiving unit 34 of a line CCD sensor 230. FIG. 2 is a block diagram showing an internal configuration of an image processing device 14. FIG. FIG. 3 is a diagram illustrating a configuration of a preprocessing unit 42. 2 is a diagram illustrating a configuration of a color sensor 3000. FIG. It is a flowchart which shows the acquisition operation procedure of a scanner in-plane nonuniformity correction parameter. It is a figure which shows the image for scanner in-plane unevenness correction. FIG. 6 is a diagram showing the position of a scanner in-plane unevenness correction image placed on a platen glass 202. It is a figure which shows calculation of the actual measurement value I2 in the arbitrary positions in a reading area | region. It is a graph which shows the image signal correction parameter at the time of converting an image signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Color digital printer 14 Image processing device 38 Image signal correction part 42 Pre-processing part 58 Storage device 61 Toner patch image (output image)
200 Scanner 230 Line CCD sensor 2027 Transfer material 3000 Color sensor

Claims (5)

Includes a document reading unit for reading a document image based on the image signal of the original image read by the document reader, an image forming apparatus for forming an image on the transfer material,
Output image forming means for forming an output image on the transfer material;
Output image reading means for reading the output image formed on the transfer material;
First image information acquisition means for acquiring first image information including an image signal value and position information of an output image read by the output image reading means;
The output image orientation is different from 90 degrees with respect to the reading surface, as an original image, read by the original reading portion, an output image of the orientation, the image signal value and the second to obtain the second image information including the position information Image information acquisition means,
From the first image information and said second image information, so that the image signal values of the original reading unit is equal to the image signal value of the output image reading means as a target document to be read by the document reading unit and an image signal correction parameter calculating means for calculating for each of a plurality of positions of the image signal read-area correction parameters for correcting the image signal of the image,
An image forming apparatus , comprising: a correcting unit that corrects an image signal of an original image read by the original reading unit using the calculated image signal correction parameter .   And a fixing unit for fixing the toner image formed on the transfer material to the transfer material based on an image signal of the original image read by the original reading unit.
  The image forming apparatus according to claim 1, wherein the output image reading unit is arranged on the downstream side of the fixing unit in the conveyance path.   The image forming apparatus according to claim 1, wherein the output image is formed on a line in a transfer direction of the transfer material based on image data of the same level.   4. The output image formed based on the image data at the same level is formed at a position corresponding to the position of the output image reading means in a direction perpendicular to the transfer material transport direction. The image forming apparatus described. A document reading unit that reads a document image, an output image forming unit that forms an output image on a transfer material, an output image reading unit that reads an output image formed on the transfer material, and an image signal correction parameter, the document An image processing method for an image forming apparatus including a correction unit that corrects an image signal of a document image read by a reading unit ,
Obtaining first image information including an image signal value and position information of an output image read by the output image reading unit ;
The output image whose orientation with respect to the reading surface is different by 90 degrees is read as an original image by the original reading unit, and second image information including an image signal value and position information of the output image in each direction is obtained .
From the first image information and said second image information, so that the image signal values of the original reading unit is equal to the image signal value of the output image reading unit to the target, the original to be read by the document reading unit image processing method, wherein you calculated for each of a plurality of positions of the image signal correction parameter reading region for correcting the image signal of the image.

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