JP2011045071A - Image reading device and image reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image reading device excellent in preventing a decrease in image quality caused by fluctuation of accuracy of reading. <P>SOLUTION: The image reading device includes a reading means, a storing means, a generation means, and a correction means. The reading means reads an image. The storing means stores first image data obtained by reading a test image by the reading means, and second image data obtained by reading a target image by the reading means. The generation means generates a correction value for correcting the image data affected by an image reading error by the reading means on the basis of the first image data. The correction means corrects the second image data on the basis of the correction value. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  Embodiments described herein relate generally to an image reading apparatus and an image reading method for reading an image from a document.

  An image reading apparatus such as a multifunction printer (MFP) or a copier may not be able to accurately read an image of a document due to the influence of lens characteristics of the image reading apparatus, carriage vibration, or the like. That is, even when the image reading apparatus reads an image with the same density on the entire surface, the luminance value or density value of the image data as a result of reading may vary (unevenness).

JP 2009-49714 A

  As described above, when there is variation (unevenness) in the reading accuracy of the image reading apparatus, read image data having unevenness different from the actual original image is acquired, or a copy original having unevenness different from the actual original image. Will be output. That is, the quality of the read image data or the output image is degraded due to variations in the reading accuracy of the image reading apparatus.

  An object of the present invention is to provide an image reading apparatus and an image reading method that are excellent in preventing deterioration in image quality due to variations in reading accuracy.

  The image reading apparatus according to the embodiment includes a reading unit, a storage unit, a generation unit, and a correction unit. The reading unit reads an image. The storage means stores first image data acquired by reading a test image by the reading means and second image data acquired by reading a target image by the reading means. The generation unit generates a correction value for correcting image data affected by an image reading error by the reading unit based on the first image data. The correction unit corrects the second image data based on the correction value.

It is a flowchart which shows an example of a correction value calculation process. It is a figure which shows an example of the screen of the operation input part for inputting the execution instruction | indication of brightness in-plane nonuniformity correction. It is a figure which shows an example of the chart for the reader apparatus brightness in-plane nonuniformity correction | amendment of a fixed density. It is a figure which shows an example of the read image data of the correction chart acquired corresponding to the reading of the reading device luminance in-plane unevenness correction chart. It is a figure which shows an example of several rectangular area | region (several blocks) in the read image data of the correction chart. It is a block diagram which shows an example of schematic structure of the image processing system of this embodiment. It is a block which shows an example of the 1st image processing part which comprises an image processing system. It is a block diagram which shows an example of the system part which comprises an image processing system. It is a flowchart which shows an example of an image data correction process. It is a figure for demonstrating an example of the brightness | luminance correction value calculation of an attention pixel. It is a figure for demonstrating an example of the brightness | luminance correction value calculation at the time of use of the reader of a sheet through system.

  Hereinafter, embodiments will be described with reference to the drawings.

  FIG. 6 is a block diagram illustrating an example of a schematic configuration of the image processing system according to the present embodiment. As shown in FIG. 6, the image processing system (hereinafter, “MFP”) includes an image reading unit 1, an image processing unit 2, a printer unit 3, and a system unit 4. The image processing unit 2 includes a first image processing unit 21 and a second image processing unit 22.

  FIG. 7 is a block diagram illustrating an example of the first image processing unit 21. As shown in FIG. 7, the first image processing unit 21 includes a pixel correction value calculation unit 211, a block correction value setting unit 212, a correction processing unit 213, an in-block luminance average value calculation unit 214, a selector 215, and a scan data image. A processing unit 216 is provided.

  FIG. 8 is a block diagram illustrating an example of the system unit 4. As shown in FIG. 8, the system unit 4 includes a controller 41, an operation input unit 42, a page memory controller 43, a page memory 44, and a hard disk drive (HDD) 45.

  The operation, function, and the like of each unit constituting the MFP will be described sequentially.

  The MFP shown in FIG. 6 executes a correction process for correcting the read image data in response to an image reading error (variation in reading accuracy (unevenness in luminance)) of the image reading apparatus, and prevents deterioration in quality of the read image data. can do.

  For example, the image reading unit 1 reads a test image, the system unit 4 stores the first image data acquired by reading the test image in the page memory 44, and the image processing unit 2 (first image processing unit). 21) generates a correction value for correcting the image data affected by the image reading error of the image reading unit 1 based on the first image data, and is obtained by reading the target image based on the correction value. The second image data can be corrected.

  For example, the image processing unit 2 is affected by the unevenness in luminance of image reading of the image reading unit 1 based on each image block data (block luminance value of each image block data) constituting the first image data. Each correction value for correcting each image block data constituting the second image data is generated, and the second image data is corrected based on the correction value.

  Specifically, the image processing unit 2 performs each correction based on the block luminance average value of each image block data constituting the first image data (the luminance maximum value among the block luminance average values of each image block data). Generate a value. For example, the image processing unit 2 generates each correction value based on the difference value between the maximum luminance value and the block luminance average value of each image block data constituting the first image data.

  Alternatively, the image processing unit 2 calculates each correction value based on the block luminance average value of each image block data constituting the first image data (the overall luminance average value obtained from the block luminance average value of each image block data). Generate. For example, the image processing unit 2 generates each correction value based on the difference value between the overall luminance average value and the block luminance average value of each image block data.

  The image processing unit 2 corrects the pixel-of-interest data among the plurality of pixel data constituting the second image data based on the correction value corresponding to the image block data including the pixel-of-interest data. For example, the image processing unit 2 uses the first correction value corresponding to the first image block data including the target pixel data, the first correction value corresponding to the target pixel data among the plurality of pixel data constituting the second image data, and the first Is corrected based on the second correction value corresponding to the second image block data adjacent to the image block data.

  Hereinafter, the above correction process will be described in detail. For example, the correction process described above includes a correction value calculation process and an image data correction process.

  In the correction value calculation process, a luminance in-plane non-uniformity correction chart (test image) is used to detect luminance in-plane non-uniformity in the first image data obtained by reading the chart, and the luminance in-plane is calculated. This is processing for generating a correction value for correcting unevenness. The image data correction process is a process for correcting the luminance in-plane unevenness included in the second image data acquired by reading the target image based on the correction value.

  FIG. 1 is a flowchart illustrating an example of correction value calculation processing. FIG. 9 is a flowchart illustrating an example of the image data correction process.

  First, an example of the correction value calculation process will be described with reference to FIG.

  For example, a user or a service person can input an instruction to execute luminance in-plane unevenness correction via the operation input unit 42 of the system unit 4 of the MFP. FIG. 2 is a diagram illustrating an example of a screen of the operation input unit 42 for inputting an instruction to execute luminance in-plane unevenness correction.

  The controller 41 detects a luminance in-plane unevenness correction execution instruction input via the operation input unit 42 and controls execution of the correction value calculation process and the image data correction process.

  After the user or serviceman inputs an instruction to perform luminance in-plane unevenness correction, a reading device in-plane unevenness correction chart (test image) having a constant density is set on the entire surface, and the reading device in-plane unevenness correction chart is set. Instructs reading of. FIG. 3 is a diagram illustrating an example of a reading device luminance in-plane unevenness correction chart. In response to the reading instruction, the image reading device reads the reading device luminance in-plane unevenness correction chart (operation 101). The first image data acquired by reading the reading device luminance in-plane unevenness correction chart is stored in the page memory 44 or the like. For example, as shown in FIG. 4, the first image data is read image data having luminance in-plane unevenness.

  The intra-block luminance average value calculation unit 214 of the first image processing unit 21 converts the first image data as shown in FIG. 4 into a plurality of rectangular areas (a plurality of image block data) as shown in FIG. To divide. For example, one rectangular area (one image block data) is an area of 100 × 100 pixels (10000 pixels). Further, the intra-block luminance average value calculation unit 214 calculates the average luminance value of pixels (100 × 100 = 10000 pixels) in each image block data (hereinafter referred to as a block) (operation 102).

  The intra-block luminance average value calculation unit 214 outputs the average luminance value of the pixels in each block to the system unit 4. The page memory controller 43 of the system unit 4 stores the average luminance value of the pixels in each block in the page memory 44, and the controller 41 stores the average luminance value of the pixels in each block on the hard disk by the HDD 45. To control.

  The controller 41 calculates a corrected target luminance value from the average luminance value in each block stored in the hard disk (operation 103). For example, the controller 41 sets the highest value (MAX value) among the average luminance values of the pixels in all blocks as a corrected target luminance value (hereinafter, corrected target luminance value M). Alternatively, the controller 41 sets the overall luminance average value obtained from the luminance average value of the pixels in each block as the corrected target luminance value.

  For example, the controller 41 calculates the luminance correction value of each block based on the correction target luminance value M (operation 104). The luminance correction value is a correction value for making the luminance value of each block the correction target luminance value, and the luminance correction value of each block is calculated. Specifically, when the average luminance value in the block of the block of interest is a (i, j), M−a (i, j) is the luminance correction value of the block of interest.

  The controller 41 controls to store the brightness correction value of each block in the hard disk (operation 105).

  Next, an example of image data correction processing will be described with reference to FIG.

  During normal use (copying or network scanning), if the MFP operation mode (character mode, photo mode, text photo mode, etc.) is determined before reading the document, the controller 41 corrects the brightness of each block stored in the hard disk. The value M-a (i, j) is set in the block correction value setting unit 212 (operation 201).

  The image reading unit 1 reads an image (target image) of a document designated by the user (operation 202). The page memory 44 stores second image data acquired by reading the target image.

  The pixel correction value calculation unit 211 calculates a luminance correction value e (x, y) for each pixel based on the luminance correction value M a (i, j) of each block (operation 203). The luminance correction value e (x, y) for each pixel is the luminance correction value M−a (i, j) of the target block where the target pixel on which correction processing is performed, and adjacent blocks adjacent to the target block in the upper, lower, left, and right directions. Is calculated based on the luminance correction value M-a (i, j). Specifically, as shown in FIG. 10 and the following equation, calculation based on the ratio of the distance (area) between the pixel of interest and the adjacent block suppresses sudden switching of the luminance correction value at the boundary of each block. , Can prevent sudden changes in image quality. Since the luminance correction value of the target pixel is calculated every time during actual processing, it is not necessary to store the correction value of the target pixel in a hard disk or the like.

e: Brightness correction value of the target pixel
e = {(A x a) + (B x b) + (C x c) + (D x d)} / (Xsize x Ysize)
a to d: luminance correction value in each block A to D: area of each area The correction processing unit 213 calculates the luminance correction value D (x, y) for the target pixel calculated by the pixel correction value calculation unit 211 for the target pixel. The luminance value of the target pixel is corrected by adding to the luminance value of the image data (operation 204). In this way, the correction writing unit 213 corrects the luminance values of the image data of a plurality of pixels constituting the second image data acquired by reading the target image, and outputs corrected image data.

  The scan data image processing unit 216 applies necessary image processing to the corrected image data and outputs the corrected image data (operation 205). The corrected image data is stored in, for example, a hard disk, and is output to an external device as necessary, and the corrected image data is output to the printer unit 3. The printer unit 3 forms an image based on the corrected image data (outputs a copy image).

  As described above, the MFP reduces the influence of variation (unevenness) in the reading accuracy of the image reading apparatus, acquires read image data (corrected image data) that is faithful to the original image, and copies images that are faithful to the original image. Can be output.

  Further, since the luminance correction value is held in units of blocks instead of holding the luminance correction value in units of one pixel, the memory capacity for storing the luminance correction values can be relatively small.

  In addition, the MFP performs the luminance in-plane unevenness correction at the time of image reading or copying using the document table as described above. The luminance value of the read image data can be corrected as follows. That is, the MFP uses an averaged luminance correction value obtained by averaging the luminance correction values of the respective blocks in the sub-scanning direction that is the paper conveyance direction, and uses the luminance correction values of the respective blocks only in the main scanning direction. The luminance value of the read image data can also be corrected (see FIG. 11).

  As described above, the MFP can acquire a high-quality scan image or output a high-quality copy image by correcting the luminance in-plane unevenness. Further, since the MFP has a luminance in-plane unevenness correction function, even if an inexpensive lens that causes in-plane luminance unevenness is applied, a relatively good scan image can be obtained or a high-quality image can be obtained. A copy image can be output.

  In the above-described embodiment, a case has been described in which functions (software) for executing the correction value calculation process and the image data correction process are recorded in advance in the MFP. It may be downloaded to the MFP, or a similar function stored in a recording medium may be installed in the MFP. The recording medium may take any form as long as it can store a program such as a CD-ROM and can be read by the apparatus. In addition, the function obtained by installing or downloading in advance may be realized in cooperation with an OS (operating system) inside the MFP.

  According to the embodiments described above, the following apparatuses, methods, programs, and storage media can be provided.

  (1) a reading apparatus that reads a document, a controller unit that divides the read image data into a plurality of regions, and calculates a feature amount of color information in the divided regions; The target color information is determined from the feature amount of the color information, a correction value for correcting in-plane unevenness of the color information is calculated from the difference between the target color information and the feature amount of the color information of each area, and the reading device An image processing unit that performs correction using the correction value for the read data read in step 1, and after reading the original, eliminates uneven color information in the surface and outputs uniform image data on the entire surface. An image forming apparatus having a function capable of performing the above.

  (2) In addition to the above (1), an image forming apparatus that makes a shape of a rectangular shape when the read image data is divided into a plurality of pieces.

  (3) In addition to the above (1), an image forming apparatus that changes the color information of each area used to luminance information.

  (4) In addition to the above (1), an image forming apparatus that uses color information of each area to be used as density information.

  (5) In addition to the above (1), an image forming apparatus in which color information of each area to be used is L * a * b * space.

  (6) In addition to the above (1), an image forming apparatus that changes color information of each area to be used into an XYZ space.

  (7) In addition to the above (1), an image forming apparatus that sets the feature amount of the color information in the divided area to an average value of the color information.

  (8) In addition to the above (1), an image forming apparatus that uses an average value of the color information feature amount of each region when determining a target from the feature amount of the color information of each region.

  (9) a reading apparatus that reads a document, a controller unit that divides the read image data into a plurality of regions, and calculates a feature amount of color information in the divided regions; The target color information is determined from the feature amount of the color information, a correction value for correcting in-plane unevenness of the color information is calculated from the difference between the target color information and the feature amount of the color information of each area, and the reading device When a sheet-through type device is used, the correction value in the sub-scanning direction is calculated from the correction value of each block, and for the read data read by the sheet-through type reading device, only in the main scanning direction An image processing unit that performs correction using correction values, and has an image processing function capable of eliminating unevenness of color information in a surface after reading a document and outputting uniform image data on the entire surface. Forming apparatus.

  (10) In addition to (9) above, an image forming apparatus that forms a rectangular shape when the read image data is divided into a plurality of pieces.

  (11) In addition to the above (9), an image forming apparatus that changes the color information of each area used to luminance information.

  (12) In addition to the above (9), an image forming apparatus that uses color information of each area to be used as density information.

  (13) In addition to the above (9), an image forming apparatus in which color information of each area to be used is L * a * b * space.

  (14) In addition to the above (9), an image forming apparatus that changes the color information of each area to be used to an XYZ space.

  (15) In addition to the above (9), the image forming apparatus which sets the feature value of the color information in the divided area to the average value of the color information.

  (16) In addition to the above (9), an image forming apparatus that uses an average value of the color information feature amount of each area when determining a target from the feature value of the color information of each area.

  (17) In addition to the above (9), an image forming apparatus that uses an average value of color information feature values of each region when calculating a correction value in the sub-scanning direction when a sheet-through type reading device is used.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Image reading part, 2 ... Image processing part, 3 ... Printer part, 4 ... System part, 21 ... 1st image processing part, 211 ... Pixel correction value calculation part, 212 ... Block correction value setting part, 213 ... Correction Processing unit, 214 ... In-block luminance average value calculation unit, 215 ... Selector, 216 ... Scan data image processing unit

Claims (9)

Reading means for reading an image;
Storage means for storing first image data obtained by reading the test image by the reading means and second image data obtained by reading the target image by the reading means;
Generating means for generating a correction value for correcting image data affected by an image reading error by the reading means, based on the first image data;
Correction means for correcting the second image data based on the correction value;
An image reading apparatus comprising: The generating means determines each image block data constituting the second image data affected by unevenness in luminance of image reading by the reading means based on each image block data constituting the first image data. Generate each correction value to correct,
The image reading apparatus according to claim 1, wherein the correction unit corrects each image block data constituting the second image data based on each correction value.   The image reading apparatus according to claim 2, wherein the generation unit generates each correction value based on a block luminance value of each image block data constituting the first image data.   The image reading apparatus according to claim 3, wherein the generation unit generates each correction value based on a block luminance average value of each image block data constituting the first image data.   The image reading apparatus according to claim 4, wherein the generation unit generates each correction value based on a luminance maximum value among block luminance average values of the respective image block data constituting the first image data.   The image reading apparatus according to claim 5, wherein the generation unit generates each correction value based on a difference value between the maximum luminance value and a block luminance average value of each image block data constituting the first image data. .   The image reading apparatus according to claim 4, wherein the generation unit generates each correction value based on an overall luminance average value obtained from a block luminance average value of each image block data constituting the first image data.   The image reading apparatus according to claim 7, wherein the generation unit generates each correction value based on a difference value between the overall luminance average value and a block luminance average value of each image block data. Scan a test image,
Storing first image data acquired by reading the test image;
Based on the first image data, a correction value for correcting the image data affected by the image reading error is generated,
Scan the target image,
Storing second image data obtained by reading the target image;
An image reading method for correcting the second image data based on the correction value.

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