JP2006014214A - Image reading apparatus, image forming apparatus, and image reading method - Google Patents

Abstract

An object of the present invention is to accurately associate shading data of each primary color component with an image signal of each primary color component of a document at any timing.
In the sheet-through method, an original is read when the original passes over the carriage, and the output order of the image signals is B image → G image → R image. When the reference white board is read, the order is R image → G image → B image, so the first image path switching unit 310 replaces the R image output first from the CCD and the B image output last. Then, the CCD line correction unit (integer unit) 311 performs CCD line correction, and the third image path switching unit 312 restores the image path before passing the image to the shading correction unit 313. After the shading correction, the image path is replaced again by the fourth image path switching unit 314, and the decimal part is corrected between the CCD lines. Finally, the second image path switching unit 316 performs the image path switching.
[Selection] Figure 4

Description

  BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus installed in a color scanner that reads a color original, and more particularly, an image reading apparatus that performs shading correction using data read from a reference white plate, and a color digital copy provided with the image reading apparatus The present invention relates to an image forming apparatus such as an image forming apparatus or a digital multifunction peripheral, and an image reading method for performing shading correction.

  When performing shading correction, color image shading data is created for each RGB from the color image signal of each primary color component (in this case, RGB) read from the reference white board, and then the original color image signal of each primary color component is read. On the other hand, correction is performed for each RGB based on color image shading data. Therefore, color image shading data for each primary color component is required. As a CCD for reading a color image, one in which line sensors for each primary color component are arranged at regular intervals is generally used. When an image is read with such a CCD, the primary color components are shifted at regular intervals. Will be read. This shift is corrected by storing the positions of the reading lines for the respective colors of the CCD in the subsequent block by the necessary lines using a field memory and delaying them.

  Further, the reading order of each primary color component is determined by the order of the line sensors and the reading direction of the carriage or document. For example, when an image is read in a format in which a conventional flatbed type image reading unit moves, a carriage is moved to read a color image of a document placed on a reference white plate and a platen platen. The reading order at this time is read out with a shift of R → G → B as shown in FIG. However, when an image is read in a form in which a sheet-through type document is moved, the document is moved and read. Therefore, when the CCD line layout does not change, the order of B → G → R as shown in FIG. Are read out of position.

As related techniques, for example, the inventions disclosed in Patent Documents 1 to 3 are known. Of these, Patent Document 1 discloses a shading correction method in a sheet-through type image reading apparatus, Patent Document 2 discloses a technique relating to a method for recording shading data for color images, and Patent Document 3 discloses. A technique relating to a method for creating shading data is disclosed.
JP 2000-358160 A JP 2000-295486 A JP 2002-152510 A

  As described above, in the flat bed type reading, reading is performed with a shift from R → G → B, and in the sheet through reading, the reading is performed with a shift in the order of B → G → R. When reading, the image path of the color read first and the color read last is switched, and the deviation is corrected by the CCD line correction memory.

  However, when the sheet-through type DF is used, the document moves when the document is read, and the carriage moves when the reference white plate is read, and the order of the images when reading the document and the reference white plate is different. . For this reason, shading correction may be applied without the shading data of each primary color component and the image signal of each primary color component of the original being coincident. Further, when the line sensors are replaced with different CCDs, if the image paths are fixed, it is difficult to associate the image paths.

  The present invention has been made in view of the situation of the prior art as described above, and its purpose is to accurately associate the shading data of each primary color component with the image signal of each primary color component of the document at any timing. There is to do.

  In order to achieve the above object, the first means reads the document and converts it into a color image signal of each primary color component, reads the reference white plate in color by the reading means, creates shading correction data, In an image reading apparatus having correction means for performing shading correction on image data obtained by reading a document based on the created shading correction data, each color image signal of each primary color component read from the document and each reference white plate Means is provided for accurately associating the primary color component with the color image shading data.

  The second means is characterized in that, in the first means, storage means for storing the shading correction data for each primary color component is provided.

  The third means is the second means, wherein the correction means refers to the shading correction data stored in the storage means and performs shading correction on the image data sent through each image path. It is characterized by giving.

  The fourth means is characterized in that, in any one of the first to third means, the means for accurately taking the correspondence comprises an image path changing means for changing an image path between a preceding stage and a subsequent stage of the correcting means. To do.

  A fifth means is the fourth means, wherein the image path changing means changes the image path according to whether the reading means reads a document by a flat bed method or when reading a document by a sheet through method. It is characterized by that.

  The sixth means is the shading correction applied to the image path for each color of the image data inputted to the correction means by the means for accurately taking the correspondence in any one of the first to third means. It is characterized by exchanging data.

  A seventh means is the sixth means, wherein the replacement is characterized in that the image path is changed depending on whether the reading means reads a document by a flat bed method or when a document is read by a sheet through method. .

  The eighth means comprises any one of the third to seventh means, wherein the reading means includes a reading element provided in a line shape so as to be orthogonal to the sub-scanning direction corresponding to each color of RGB. The replacement is performed between an image path corresponding to the reading element array positioned at the frontmost part in the sub-scanning direction and an image path corresponding to the reading element array positioned at the rearmost part.

  A ninth means is characterized in that, in the eighth means, the reading element comprises a three-line CCD.

  A tenth means is the eighth means, wherein the reading element comprises a contact image sensor.

  The eleventh means is characterized in that, in any of the fifth to seventh means, among the image path replacement means, the last stage replacement means arbitrarily selects an image path of each primary color component.

  According to a twelfth means, in the first means, the means for accurately taking the moving direction when reading the reference white plate is different when the original is read by the flat bed method and when the original is read by the sheet through method. The reading means is moved so as to coincide with each other.

  A thirteenth means is characterized in that the image forming apparatus includes an image reading apparatus according to any one of the first to eleventh means and an image forming means for visualizing an image read by the image reading apparatus. To do.

  The fourteenth means reads a document and converts the color image signal of each primary color component into a reference white plate in color, creates shading correction data, and reads the document based on the created shading correction data. In an image reading method that performs shading correction on image data, when reading a document using the flatbed method, the color image signal of each primary color component scanned from the document and the color image shading data of each primary color component scanned from the reference whiteboard In addition, it is characterized in that the correspondence between the read data and the shading data is obtained by switching the image path between when reading a document by the sheet-through method.

  According to a fifteenth aspect, in the fourteenth aspect, the replacement includes an image path corresponding to a reading element array positioned at the foremost portion in the sub-scanning direction and an image path corresponding to a reading element array positioned at the rearmost. It is characterized by being performed between.

  The sixteenth means reads a document and converts it into color image signals of each primary color component, reads a reference white plate in color, creates shading correction data, and reads the document based on the created shading correction data. In an image reading method that performs shading correction on image data, when reading a document using the flatbed method, the color image signal of each primary color component scanned from the document and the color image shading data of each primary color component scanned from the reference whiteboard And the shading data to be applied by changing the shading data applied in the case of reading a document by the sheet-through method.

  In a seventeenth means according to the sixteenth means, the change includes an image path corresponding to a reading element array positioned at the foremost part in the sub-scanning direction and an image path corresponding to a reading element array positioned at the rearmost part. It is characterized by being performed between.

  According to the present invention, it is possible to accurately associate the shading data of each primary color component with the image signal of each primary color component of the document at any timing by switching the image path or changing the shading data to be applied.

  Embodiments of the present invention will be described below with reference to the drawings.

  There are two operations of the image reading unit of the image processing apparatus. One is an operation performed by placing a document on the platen platen (flatbed method), and the other is an operation performed by sheet-through using DF (sheet-through method). FIG. 1 is a diagram showing a reading configuration of a flat bed method, and FIG. 2 is a diagram showing a reading configuration of a sheet through method. In an image reading apparatus equipped with a sheet through DF, a flat bed method (hereinafter referred to as a pressure plate mode in operation) is shown. In general, the two modes of the sheet-through method (hereinafter also referred to as the sheet-through mode in operation) are used in accordance with the state of the document.

  In FIG. 1, when reading an image in the pressure plate mode, the carriage on which the original is placed on the platen platen and the reading unit is placed is moved in the sub-scanning direction from the position of the home position to the end of the original through the reference white plate. Is configured to read an image on the original surface.

  That is, a document 2 placed on a platen document (contact glass) 1 is irradiated by a light source 4 mounted on the first carriage 3, and the second and third mirrors are also mounted on the first carriage 3 from the first mirror 5. Read to the image plane of the 3-line CCD sensor 7 by the imaging lens 6 from the second and third mirrors mounted on the second carriage (not shown) through the first carriage 3 mounted with the third mirror. The light is guided and read by the 3-line CCD sensor 7. At that time, first, after reading the reference white plate 8, the original is read. At this time, since the CCD images 7R, 7G, and 7B of the respective colors are arranged at the d interval as described above, the original image is incident on the CCDs 7R, 7G, and 7B of the respective colors in the order of R → G → B.

  On the other hand, in the sheet-through mode, a document placed on the document tray 9 is fed by a conveyance roller 10 and a discharge roller 11 and is guided along a reflection guide plate in the middle of the conveyance path 12 on the platen platen. 1 is read by a reading optical system through a slit glass (reading window) 14 provided on 1, and when reading an original using a sheet through DF, a reading position is fixed under the slit glass 14. In this way, the carriage 3 is fixed, and the original passes through the carriage 3, whereby the image on the original surface is read. As the optical system components such as the light source 4, the first mirror 5, the imaging lens 6, and the 3-line CCD 7, those used for reading in the flat bed system are used as they are.

Since the present invention relates to the shading correction and the interline correction, the shading correction / interline correction unit 300 will be described in more detail.
The shading correction method in the two reading operations is as follows. In the pressure plate mode, reading of the reference white plate 8 for creating shading data is performed simultaneously with a scanning operation for reading a document. When reading the reference white plate 8 and the document 2, the carriage (the first carriage 3 and the second carriage (not shown) that moves at half the speed of the first carriage) moves, so the order of the read image signals is as shown in FIG. Thus, the R image is output first, and the G image and B image data at the same pixel position are output at intervals of d. This is determined by the arrangement of the three line sensors 7 of the CCD. Further, in an apparatus that realizes zooming by changing the moving speeds of the first carriage 3 and the second carriage, the value of d changes depending on the zooming ratio.

  The first carriage 3 moves from the home position, and the SHGATE signal indicating the position of the reference white plate 8 in FIG. 8 generates shading data for each RGB in the shading correction unit 300 during the effective period, and each memory (shading data memory) 313R. , 313G, 313B. At this time, as shown in FIG. 3, the image path is not replaced. FIG. 3 is a diagram showing an image path for reading a pressure platen, reading a reference white plate in pressure plate reading, and reading a reference white plate in sheet-through reading. While the carriage 3 is further moved and the SFGATE signal indicating the effective range of the document is in an effective period, the RGB image signals read from the CCD 7 are output from the shading data memory 313R, G, B for R image, G image, B Image shading data is read and shading correction is performed. At this time, since it is not necessary to replace the image path of the original color image signal, the R image shading data is accurately associated with the R image. The same applies to the G image and the B image. In FIG. 3, the outputs from the CCDs 7R, G, and B are the first image path switching unit 310, the CCD interline correction unit (integer unit) 311 and the third image path. The RGB data is output through the replacement unit 312, the shading correction unit 313, the fourth image path replacement unit 314, the inter-CCD line correction unit (decimal part) 315, and the second image path replacement unit 316. The second image path switching unit 316 corresponding to the last stage has a selector for selecting one image from each RGB image for each RGB. This is because when the order of images output from the CCD changes, such as when the type of CCD is changed, the correspondence of the image path is absorbed in this replacement part so that the image path such as the next stage filter is not affected. It is to do.

  In the sheet-through mode, the reading operation of the reference white plate 8 cannot be performed at the same time as the scanning operation of the original reading, and is a separate operation. The reason is that the reading of the reference white plate 8 requires the carriage 3 to move, so that the operation first activates the sheet-through DF operation. That is, as can be seen from the timing chart of FIG. 9, the SDF_ON signal is validated when the sensor detects that a document is placed on the document tray 9. Next, the carriage 3 is moved to read the reference white plate 8. As shown in FIG. 9, even when the SDF_ON signal is valid, the PATH_SEL signal is invalidated during the SHGATE valid period, and the image path is not replaced. After reading the reference white plate and creating shading data for each RGB, the carriage 3 is fixed at a position below the slit glass 14 and the original is read.

  Reading of the document 2 is performed when the document 2 passes over the carriage 3, but the output order of the image signals is B image → G image → R image as shown in FIG. In order to correct the position of the shifted line, it is necessary to perform correction between the CCD lines. However, the image path delayed by the correction between the lines is different between when reading the pressure plate and when reading the document with the sheet through DF. . If the image path is not exchanged, the positions of the RGB images will not be more aligned when the document is read with the sheet-through DF. Therefore, the R image output first from the CCD 7 and the B image output last are replaced by the first image path switching unit 310, and the CCD line correction unit (integer part) 311 performs CCD line correction to perform line correction. Correct the position. Next, before passing the image to the shading correction unit 313, the third image path switching unit 312 restores the image path. As shown in FIG. 4, if the image path is not replaced at this position, the correspondence between the shading data and the image signal cannot be obtained, and the seeding correction cannot be performed accurately. After the shading correction, the image path is switched again by the fourth image path switching unit 314, and the inter-line correction is performed by the CCD line correction (decimal part) 315. This is because when the magnification is changed, the decimal part is corrected when the shift between the lines does not become an integral multiple. The CCD line inter-line correction units 311 and 315 are constituted by delay circuits.

  Then, after performing line-to-line correction, the second image path replacement unit 316 performs the last image path replacement. This is to eliminate the fact that the first image path replacement unit 310 first performed the image path replacement for the inter-line correction of the integer part. Image path replacement is performed during a period in which the SFGATE signal is valid while the SDF_ON signal is valid. With this configuration, the RGB data output from the CCD 7 and the RGB data processed by the shading correction unit 313 and the interline correction units 311 and 315 are appropriate even in the sheet through DF, and the seeding data and the original color image signal are obtained. It is possible to perform shading correction corresponding to and accurately.

  In this embodiment, a 3-line CCD is taken as an example, but the same applies to a 3-line contact image sensor.

  In the above-described embodiment, in the case of sheet-through DF, the third image path switching unit 312 and the fourth image path switching unit 4 are provided in the preceding stage and the subsequent stage of the shading correction unit 313 in the document reading image path, respectively. In this second embodiment, the reference of the shading data is replaced without performing the replacement of the image path before and after the shading correction during the document reading with the sheet-through DF. So that shading correction is performed. This prevents an increase in selectors and signal lines due to image path replacement.

  FIG. 5 is a diagram showing a state of an image path when the reference white plate and the original are read in the pressure plate mode. Note that the same reference numerals are given to the same components as those in the first embodiment, and duplicate descriptions are omitted as appropriate.

  In the example shown in FIG. 5, a three-line CCD 7 (7R, 7G, 7B), a first image path switching unit 310, a CCD line correction unit (integer part) 311, a shading correction unit 313, a CCD line correction unit ( (Fractional part) 315 and a second image path switching unit 316. During the period when the SHGATE signal indicating the position of the reference white plate 8 in FIG. 8 is valid, the shading correction unit 300 creates shading data for each RGB and records them in the respective memories (shading data memories) 313R, 313G, and 313B. Then, the image data is transferred from the second image path switching unit 2 to the subsequent stage.

  When reading the original, the RGB data read by the CCD 7 for each color is not changed, and the line correction is performed by the CCD inter-line correction unit (integer unit) 311, and the reference pressure plate 8 is read by the shading correction unit 313. The shading data is read from the shading data memories 313R, 313G, and 313B, shading correction is executed based on this data, and the CCD inter-line correction (decimal part) unit 315 further performs inter-line correction if necessary to perform the second line correction. Image data is output from the image path switching unit without switching the image path.

  On the other hand, in the sheet-through mode, as shown in FIG. 6 showing the state of the image path at the time of reading the reference white plate, RGB shading data is created by the shading correction unit 313 when the original pressure plate 8 is read, and the shading data for each color is generated. The data is stored in the memories 313R, 313G, and 313B, and the image data is transferred from the second image path switching unit 316 to the subsequent stage.

  After the shading correction data is stored in the memory memories 313R, 313G, and 313B in this way, the original is read in the sheet through mode. At this time, as can be seen from the image path state at the time of reading the reference white plate in the sheet-through mode in FIG. 7, the RGB image data read for each color by the CCD 7 is converted into R and B by the first image path switching unit 310. And the image data B and G are delayed by the CCD line inter-line correction unit 311 to perform inter-line correction. The BGR image data subjected to the interline correction is switched between the shading data memories 313R, 313G, and 313B read by the shading correction unit, and the shading correction is performed on the respective image data RGB, and the CCD interline correction unit (decimal) Part) 315 corrects the deviation below the decimal, returns to the original path by the second image path switching part 316, and passes the image data RGB to the subsequent stage.

  With this configuration, the third and fourth image path switching units 312 and 314 in the first embodiment are not necessary, and the number of selectors and signal lines can be minimized.

  In addition, each part which is not demonstrated especially is comprised equivalent to 1st Embodiment, and functions equivalently.

  As shown in FIG. 10, the image forming apparatus 100 has a configuration in which an engine unit 110 that performs image formation and a controller 120 that controls the entire image forming apparatus are connected by a bus 140. The engine unit 110 includes a CPU 111 that controls the engine unit 110, an image reading unit 112 that includes a scanner that reads a document, an image recording unit 113 that includes a plotter that forms an image on a transfer material, image processing, and CPU I / O. ASIC-E114 (image processing unit) for controller incorporating F, PCIII / F and the like is provided. The ASIC-E 114 serves as an interface between the image processing unit (scanner image processing unit 115 and printer image processing unit 116) that performs shading correction, MTF correction, γ correction, and the like on the image data from the image reading unit 112 and the bus 140. The image I / F unit 117 functions. The CPU 111 controls an instruction to replace an image path or switching a shading data memory to be referred to.

  The controller 120 includes an operation unit 121 that performs processing and operation settings of the image forming apparatus, an HDD 122 that accumulates image data, a CPU 123 that controls the entire image forming apparatus, an operation unit I / F, a CPU I / F, a PCI II / F, a memory The controller ASIC-C 124 with a built-in controller, a local memory (MEM-C) 127 and (MEM-P) 129, and an interface (AGP) 141 NB 128 connected to the ASIC-C 124, etc. The ASIC-C 124 is also provided with a rotator 125 that rotates image data to a desired angle and an editor 126 that performs image composition, scaling, and the like. The controller 120 is further provided with a communication ASIC 130 for capturing image information from the outside, options 131 and 132, SB 133, ROM 134, and the like.

  FIG. 11 is a diagram showing a schematic configuration of an image forming apparatus provided with the image processing apparatus. The image forming apparatus main body 400 and an automatic original which is provided on the upper portion of the image forming apparatus main body 400 and conveys an original to a reading position. It is composed of a feeding device 500, and a sorter having a tray for storing paper on which images have been formed and a bin for sorting the paper. A contact glass 401 is disposed on the upper part of the image forming apparatus main body 400, and a reading optical system for reading a document placed on the contact glass 401 or a document fed by the automatic document feeder 500 at a fixed position is provided. Yes. The reading optical system reads a document by a so-called flatbed method or sheet-through method, and the read image data is stored in the HDD 122.

  When forming an image, the stored image data is read out and optically written onto the photosensitive drum 402 by a writing optical system (not shown), and an image forming element (not shown) provided along the outer periphery of the photosensitive drum 402 is read. With the function, the latent image formed on the surface of the photosensitive drum 402 is developed with toner, and is transferred to a sheet fed from the first or second sheet feeding tray by a transfer unit to form an image on the sheet. The formed image is sent to the fixing unit by the conveyance belt 403, fixed by heating and pressure fixing, sent to the sorter, and discharged to a bin or a tray according to the mode set by the controller 120. Since the configuration of the image forming apparatus itself is known, detailed description thereof is omitted.

  FIG. 12 is a block diagram showing details of the engine unit 110 of FIG. In the figure, the image processing unit includes a scanner image processing unit 115 and a printer image processing unit 116. The scanner image processing unit 115 receives RGB read data from the CCD 200, converts the data into CMYK data, and converts the image I / O into image data. The data is output from the F unit 117 to the ASIC-C of the controller 120. On the other hand, CMYK print data read from the HDD 122 and subjected to rotation processing and editing processing is input to the printer image processing unit 116 from the ASIC-C 124 of the controller 120, and the CMYK color image data is input to the printer image processing unit 116. Are subjected to gradation processing and output to the LDBs 210, 211, 212, and 213, and the LDBs 210, 211, 212, and 213 perform laser writing for each color on the surface of the photosensitive drum 402 to form a latent image.

  FIG. 13 is a block diagram illustrating a functional configuration of the image processing unit of the image reading apparatus. In the figure, the image processing unit 115 includes a shading correction / interline correction unit 300, a picture / character separation unit 301, a filter processing unit 302, a color correction unit 303, and a scaling unit 304. The shading correction / interline correction unit 300 performs shading correction on each of the RGB image data read by the optical system, and delays a shift between lines caused by a shift in reading timing of each CCD 7R, G, B by a delay circuit. To correct. A picture / character separating unit 301 separates a halftone image region of a picture or photo from a binary image region of characters, and causes the filter processing unit 302 to perform filtering based on the image region information, and the color correction unit 304 performs RGB processing. The data is converted into YMCK data, and the scaling unit performs scaling processing as necessary to output YMCK data.

  As described above, according to the above-described embodiment, the correspondence between the color image signal of each primary color component read from the document and the color image shading data of each primary color component read from the reference white plate is switched, and Since the image path of the color image signal of the primary color component can be switched, the correspondence between the seeding data and the original color image signal can be accurately taken even when the original is read in the sheet through mode, and appropriate shading correction is performed. The abnormal image is not output.

  In addition, it is possible to prevent an increase in selectors and signal lines due to image path replacement by replacing shading data reference and performing shading correction without replacing image paths before and after shading correction.

  Furthermore, since the image path replacement at the final stage has a selector for selecting an image from each primary color component for each primary color component, the order of images output from the CCD, such as when the CCD type is changed, is changed. When a change occurs, the correspondence of the image path can be absorbed by this replacement portion so that the image path such as the next-stage filter is not affected.

It is a figure which shows the reading structure of a flat bed system. It is a figure which shows the reading structure of a sheet through system. FIG. 6 is a diagram illustrating image paths when reading a pressure platen in the case of switching image paths, reading a reference white plate during pressure plate reading, and reading a reference white plate during sheet-through reading. FIG. 6 is a diagram illustrating an image path at the time of reading a document in the sheet-through method when the image path is replaced. It is a figure which shows the state of an image path when reading the standard white board and original in a flat bed system in the case of changing the shading correction data to refer. It is a figure which shows the state of the image path at the time of the reference white board reading by the sheet through method in the case of changing the shading correction data to refer. FIG. 5 is a diagram illustrating a state of an image path when reading a document in the sheet-through method when changing shading correction data to be referred to. It is a timing chart which shows the timing at the time of reading by a flat bed system. It is a timing chart which shows the timing at the time of reading by a sheet through system. It is a block diagram which shows the function structure of the image process part of an image reading apparatus. 1 is a diagram illustrating a schematic configuration of an image forming apparatus according to an embodiment of the present invention. It is a block diagram which shows the function structure of the engine part of the image processing apparatus of FIG. It is a block diagram which shows the function structure of the scanner image process part of the engine part of FIG.

Explanation of symbols

7 3-line CCD
7R, 7G, 7B CCD
8 reference white plate 100 image forming apparatus 110 engine unit 111 CPU
112 Image reading unit 113 Image recording unit 114 ASIC-E for controller (image processing unit)
115 Scanner Image Processing Unit 116 Printer Image Processing Unit 120 Controller 121 Operation Unit 122 HDD
123 CPU
124 ASIC-C for controller
310 First image path switching unit 311 CCD line correction unit (integer part)
312 Third image path switching unit 313 Shading correction unit 313R, 313G, 313B Shading data memory 314 Fourth image path switching unit 315 CCD line correction unit (decimal part)
316 Second image path switching unit

Claims (17)

Reading means for reading a document and converting it into a color image signal of each primary color component;
Correction means for reading a reference white plate in color by the reading means, creating shading correction data, and performing shading correction on image data obtained by reading a document based on the created shading correction data;
In an image reading apparatus having
An image reading apparatus comprising means for accurately matching the color image signal of each primary color component read from an original and the color image shading data of each primary color component read from a reference white plate.   2. The image reading apparatus according to claim 1, further comprising storage means for storing the shading correction data for each primary color component.   3. The correction unit according to claim 2, wherein the correction unit refers to the shading correction data stored in the storage unit and performs shading correction on the image data sent through each image path. Image reading device.   4. The image reading apparatus according to claim 1, wherein the means for accurately taking the correspondence comprises image path switching means for switching image paths between a front stage and a rear stage of the correction means.   5. The image reading according to claim 4, wherein the image path switching unit performs image path switching according to whether the reading unit reads a document by a flat bed method or when reading a document by a sheet through method. apparatus.   The means for accurately taking the correspondence replaces the shading correction data applied to the image path for each color of the image data input to the correction means. The image reading apparatus according to item.   7. The image reading apparatus according to claim 6, wherein in the replacement, the image path is switched according to whether the reading unit reads a document by a flat bed method or when reading a document by a sheet through method.   The reading means includes reading elements arranged in a line so as to be orthogonal to the sub-scanning direction corresponding to each color of RGB, and the replacement of the image path is performed on a reading element array positioned at the forefront with respect to the sub-scanning direction. The image reading apparatus according to claim 3, wherein the image reading apparatus is performed between a corresponding image path and an image path corresponding to a reading element array located at the rearmost part.   9. The image reading apparatus according to claim 8, wherein the reading element is a three-line CCD.   9. The image reading apparatus according to claim 8, wherein the reading element comprises a contact image sensor.   8. The image reading apparatus according to claim 5, wherein, among the image path replacement means, the last-stage replacement means arbitrarily selects an image path of each primary color component. 9.   The means for accurately taking the reading means moves the reading means by matching the moving direction when reading the reference white plate when reading the original by the flat bed method and when reading the original by the sheet-through method. The image reading apparatus according to claim 1. An image reading apparatus according to any one of claims 1 to 11,
An image forming means for visualizing an image read by the image reading device;
An image forming apparatus comprising: When a document is read and converted into color image signals for each primary color component, the reference white plate is read in color, shading correction data is created, and shading is performed on the image data that has been read based on the created shading correction data. In the image reading method for correction,
Image path when reading the original with the flatbed method and when reading the original with the sheet-through method, the color image signal of each primary color component that read the original and the color image shading data of each primary color component that read the reference white plate An image reading method characterized in that the correspondence between the read data and the shading data is obtained by replacing   The replacement is performed between an image path corresponding to a reading element array positioned at the foremost part in the sub-scanning direction and an image path corresponding to a reading element array positioned at the rearmost part. Item 15. The image reading method according to Item 14. When a document is read and converted into color image signals for each primary color component, the reference white plate is read in color, shading correction data is created, and shading is performed on the image data that has been read based on the created shading correction data. In the image reading method for correction,
Applicable when reading a document using the flatbed method and when reading a document using the sheet-through method, the color image signal of each primary color component scanned from the document and the color image shading data of each primary color component scanned from the reference white plate An image reading method, wherein the shading data is changed to take a correspondence between the read data and the shading data.   The change is performed between an image path corresponding to a reading element array positioned at the foremost part in the sub-scanning direction and an image path corresponding to a reading element array positioned at the rearmost part. Item 17. The image reading method according to Item 16.

Images