JP2007059989A - Image processing method and apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of excluding the effect of a read error of a test pattern image by an image read section. <P>SOLUTION: When the image read section reads a test pattern outputted from an image output section, a paper sheet 300 on which the test pattern image is outputted is set on a platen glass pane 303 of the image read section in a way that a main scanning direction 301 of the image output section at output of the test pattern image is dissident with a main scanning direction 302 of the image read section. Further, applying abnormal value elimination processing and equalization processing or like processing to a plurality of pixels on the test pattern image set and read in this way and arranged in a subscanning direction of the image output section eliminates the effect of stripe-shaped read errors caused in the image read section. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image forming apparatus such as a copying machine, a facsimile machine, and a printer, and more particularly to image processing in the image forming apparatus.

  When an electrophotographic image forming apparatus is used for a long period of time, streaks extending in the sub-scanning direction and density unevenness in the main scanning direction may occur in the output result. Various correction methods for eliminating such streaks and density unevenness have been proposed. In order to ascertain the current streaks / unevenness level of the image forming apparatus, first, a predetermined test pattern is output. . Then, the image of the output test pattern is read by an image reading unit or the like provided in the image forming apparatus, the generation amount of streaks / unevenness is specified based on the read test pattern image, and the specified generation amount is Corresponding streaks / unevenness correction is performed.

  As described above, since the streak / unevenness correction is normally performed based on the test pattern image read by the image reading unit, if a reading error occurs in the image reading unit, appropriate streak / unevenness correction may not be performed. For example, when dirt or dirt adheres to a shading correction reference plate or mirror in an image reading unit that reads a test pattern, a streak reading error along the sub-scanning direction may occur in the image reading unit. In such a case, the read test pattern image includes a streak generated in the image output unit and a streak generated in the image reading unit in a state where it cannot be distinguished. Therefore, if the amount of generation of streaks / unevenness, etc. is specified based on such a test pattern image, and the streak / unevenness correction according to the specified amount of generation is performed, unnecessary correction is performed and a new There are problems such as causing streaks.

In Japanese Patent Laid-Open No. 11-177824, a test pattern is printed out after operating unevenness removing means (LED light emitting surface cleaning member, charger cleaning member, etc.) for removing unevenness of the system after the recording head. An electrophotographic copying machine capable of obtaining a more accurate gamma of the entire system by reading a printed test pattern image and creating correction data for gamma correction based on the read test pattern image It is disclosed.
Japanese Patent Laid-Open No. 11-177824

  An object of the present invention is to be able to eliminate the influence of reading error of a test pattern image in an image reading unit.

  The image processing method according to the present invention reads the test pattern image so that the main scanning direction at the time of outputting the test pattern image does not match the main scanning direction at the time of reading the test pattern image, and A noise component generated at the time of reading is removed from the read test pattern image.

  In this case, the noise component may be removed by performing abnormal value removal processing on a plurality of pixels arranged in the sub-scanning direction when the test pattern image is output. Further, the noise component may be removed by performing an averaging process on a plurality of pixels arranged in the sub-scanning direction when the test pattern image is output.

  In the above case, a correction parameter for correcting the image signal may be calculated based on the test pattern image from which the noise component has been removed. The main scanning direction at the time of reading the test pattern image may not coincide with the sub-scanning direction at the time of outputting the test pattern image, or the main scanning direction at the time of outputting the test pattern image. You may make it orthogonally cross.

  An image processing apparatus according to the present invention is an image processing apparatus that performs image processing on a test pattern image read so that a main scanning direction at the time of output and a main scanning direction at the time of reading do not coincide with each other, The present invention is characterized in that noise removal means for removing noise components generated at the time of reading is provided by performing processing on a plurality of pixels arranged in the sub-scanning direction when outputting a test pattern image.

  In this case, the noise removing unit may remove the noise component by performing an abnormal value removing process on the plurality of pixels. The noise removing unit may remove the noise component by performing an averaging process on the plurality of pixels.

  In the above case, a correction parameter calculation unit that calculates a correction parameter for correcting the image signal based on the test pattern image from which the noise component has been removed may be further provided.

  According to the present invention, it is possible to eliminate the influence of the reading error of the test pattern image in the image reading unit, so that it is possible to prevent an originally unnecessary correction from being performed, and it is possible to accurately eliminate streaks and unevenness that occur during image output. It becomes possible to correct.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a diagram showing a configuration of an image forming apparatus to which the present invention is applied. As shown in the figure, an image forming apparatus 100 to which the present invention is applied includes an image reading unit 110, an image processing unit 120, and an image output unit 130.

  The image reading unit 110 is used to input various images to the image forming apparatus 100. For example, the image reading unit 110 includes a flatbed scanner unit that optically reads document image information and converts it into digital image data. The image reading unit 110 includes, for example, a platen glass (original table), a light source, a mirror, a line sensor (CCD), and the like.

  The image processing unit 120 performs various image processing on the image signal input from the image reading unit 110. For example, the image processing unit 120 performs a color conversion process (for example, conversion into YMCK data) on the image signal (for example, RGB data) input from the image reading unit 110, and then performs a process for each color component. A tone correction process is performed, and an image recording signal to be output by the image output unit 130 is output.

  The image output unit 130 outputs an image generated based on the image recording signal input from the image processing unit 120 to a transfer sheet, and is configured by, for example, an electrophotographic printer unit. The image output unit 130 includes, for example, a photoreceptor, a charging device, an exposure device, a developing device, a fixing device, and a cleaning device.

  Next, streak / unevenness correction in the image forming apparatus 100 having the above configuration will be described. In the present embodiment, the main scanning direction (the rotation axis direction of the photosensitive member) of the image output unit 130 is divided into a plurality of regions, and the image processing unit 120 performs correction parameters (gradations for gradation correction) for each divided region. It is assumed that the tone correction characteristics can be changed according to the position in the main scanning direction by having a correction table storing tone correction results. Then, the correction parameters for gradation correction are updated as appropriate, and the gradation correction characteristics are changed according to the position in the main scanning direction, thereby causing streaks extending in the sub-scanning direction of the image generated in the image output unit 130 and the density in the main scanning direction. Perform unevenness correction.

  FIG. 2 is a diagram illustrating a flow of correction parameter update processing for streak / unevenness correction in the image forming apparatus 100.

  As shown in the figure, when correcting image streaks or unevenness occurring in the image output unit 130, first, the image output unit 130 outputs a predetermined test pattern (S201). Next, the image of the output test pattern is read by the image reading unit 110 (S202).

  FIG. 3 is a diagram showing a test pattern setting state when the test pattern image is read according to the present invention.

  As shown in the figure, at the time of reading a test pattern image according to the present invention, the paper 300 on which the test pattern image is output includes the main scanning direction 301 of the image output unit 130 when the test pattern image is output, and the image reading. It is set on the platen glass 303 of the image reading unit 110 in such a direction that the main scanning direction 302 of the unit 110 does not match.

  FIG. 4 is a diagram showing an example of a test pattern image read by the image reading unit 110 from the paper sheet 300 set as shown in FIG. In the figure, for ease of viewing, the test pattern image is shown rotated so that the longitudinal direction of the strip-shaped patches constituting the test pattern image coincides with the horizontal direction (lateral direction in the figure).

  As shown in the figure, in the test pattern image 400, a plurality of strip-like patches having a uniform density in the main scanning direction of the image output unit 130 are arranged in the sub-scanning direction of the image output unit 130. The test pattern image 400 includes a plurality of patches having the same density, and the patches having the same density are arranged in a plurality of locations.

  Since the test pattern image 400 is read by the image reading unit 110 from the sheet 300 set as shown in FIG. 3, even when a streak reading error occurs in the image reading unit 110, FIG. As shown, the direction of the streaks 401 generated in the image reading unit 110 is deviated from the direction of the streaks 402 generated in the image output unit 130. As a result, it is possible to distinguish the streak 401 generated by the image reading unit 110 from the streak 402 generated by the image output unit 130.

  Next, the test pattern image read as described above is rotated (S203). The rotation of the test pattern image is performed as necessary to facilitate subsequent processing. For example, the sheet 300 is set so that the longitudinal direction of each patch coincides with the main scanning direction 302 of the image reading unit 110. Is set on the platen glass 303 and the test pattern image is rotated so that the orientation of the image coincides with that when the image is read (that is, as shown in FIG. 4).

  Next, noise removal processing is performed on the test pattern image (S204). That is, by performing abnormal value removal processing, averaging processing, and the like on a plurality of pixels arranged in the sub-scanning direction of the image output unit 130, the influence of streak-like reading errors generated in the image reading unit 110 is removed.

  For example, considering the case where there are four patches of the same density in the test pattern, first, the read pixel data corresponding to each patch is averaged in the sub-scanning direction for a predetermined position in the main scanning direction. Average density data of each patch at the position in the scanning direction is obtained. As a result, four pieces of average density data corresponding to patches of the same density are obtained for a predetermined position in the main scanning direction. Excluding the maximum and minimum values of the four average density data and taking the average of the remaining two data, the image reading unit 110 has a diagonal stripe 401 on the image as shown in FIG. Even if it exists, the effect can be excluded. This is because the direction of the streaks 401 generated in the image reading unit 110 and the sub-scanning direction do not coincide with each other, and therefore the image reading unit 110 out of four average density data arranged in the sub-scanning direction at a predetermined main scanning direction position. This is because the influence of the streaks 401 generated in is limited to a part thereof.

  When the noise removal processing of the test pattern image is completed as described above, next, the generation position and generation amount of streaks / unevenness are specified based on the test pattern image from which the noise is removed, and the specified generation position Then, the correction parameters for gradation correction used by the image processing unit 120 are calculated and updated so that the stripe / unevenness correction according to the generation amount is performed (S205).

  Based on the correction parameter updated as described above, the image processing unit 120 performs gradation correction processing of the image signal, thereby preventing streaking and unevenness in the output result from the image output unit 130. It becomes possible.

  As described above, according to the present invention, even when a streak-like reading error occurs in the image reading unit 110, the influence of the reading error can be removed, so that an appropriate correction parameter can be obtained. .

  In the example shown in FIG. 3, the paper 300 is placed so that the main scanning direction 301 of the output image and the main scanning direction 302 of the image reading unit 110 form an acute angle, but the main scanning direction 301 of the output image. The sheet 300 may be placed so that the main scanning direction 302 of the image reading unit 110 and the main scanning direction 302 are orthogonal to each other. In this case, if the test pattern image is output with the longitudinal direction of the paper coinciding with the main scanning direction of the image output unit 130, the main scanning direction of the image reading unit 110 is short when the image is read. Since it coincides with the hand direction, the line sensor of the image reading unit 110 is sufficient according to the length of the paper in the short direction.

1 is a diagram illustrating a configuration of an image forming apparatus to which the present invention is applied. FIG. 5 is a diagram illustrating a flow of correction parameter update processing for line / unevenness correction in the image forming apparatus 100. It is a figure which shows the setting state of the test pattern at the time of the test pattern image reading by this invention. 6 is a diagram illustrating an example of a test pattern image read by an image reading unit 110. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Image forming apparatus 110 Image reading part 120 Image processing part 130 Image output part 300 Paper 301 Main scanning direction of image output part 302 Main scanning direction of image reading part 400 Test pattern image 401,402 streak

Claims (10)

Read the test pattern image so that the main scanning direction at the time of outputting the test pattern image does not match the main scanning direction at the time of reading the test pattern image,
An image processing method, wherein a noise component generated at the time of reading is removed from the read test pattern image. The image processing method according to claim 1, wherein the noise component is removed by performing abnormal value removal processing on a plurality of pixels arranged in a sub-scanning direction when the test pattern image is output. The image processing method according to claim 1, wherein the noise component is removed by performing an averaging process on a plurality of pixels arranged in a sub-scanning direction when the test pattern image is output. The image processing method according to claim 1, wherein a correction parameter for correcting an image signal is calculated based on the test pattern image from which the noise component has been removed. The image processing method according to claim 1, wherein a main scanning direction at the time of reading the test pattern image does not coincide with a sub-scanning direction at the time of outputting the test pattern image. . The image processing method according to claim 1, wherein a main scanning direction at the time of reading the test pattern image is orthogonal to a main scanning direction at the time of outputting the test pattern image. . An image processing apparatus that performs image processing on a test pattern image read so that a main scanning direction at the time of output and a main scanning direction at the time of reading do not coincide with each other,
An image processing apparatus, comprising: a noise removing unit that removes a noise component generated at the time of reading by performing processing on a plurality of pixels arranged in a sub-scanning direction when outputting the test pattern image. The noise removing means is
The image processing apparatus according to claim 7, wherein the noise component is removed by performing an abnormal value removal process on the plurality of pixels. The noise removing means is
The image processing apparatus according to claim 7, wherein the noise component is removed by performing an averaging process on the plurality of pixels. The correction parameter calculation means for calculating a correction parameter for correcting an image signal based on the test pattern image from which the noise component has been removed is further provided. The image processing apparatus described.