JP2011129999A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image forming apparatus mounted with a color reader and another reader other than the color reader at the same device, and capable of correcting a difference between data read by each reader to reduce difference in the quality of an image. <P>SOLUTION: The image forming apparatus includes a color reader for reading a manuscript in color and another reader different from the color reader. A method for correcting a difference between data read by each reader, comprising the steps of: determining whether the manuscript is colored or non-colored; based on the decision results, automatically determining whether image forming of the manuscript should be performed in color or in monochrome; comparing data read by the color reader with data read by another reader; based on the results of the comparison, calculating the difference between the data read by the color reader and the data read by another reader; generating data for correction; and correcting the difference between the data read by the color reader and the data read by another reader, using the generated data for correction. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus having a color reading unit and other reading units as means for reading a document.

  Currently, in the case of MFP (Multi Function Peripheral, especially low-end MFP), an increasing number of machines adopt a 4-line CCD (Charged Coupled Device) for cost reduction. The 4-line CCD is provided with, for example, a Bk (Black) sensor dedicated to monochrome reading as another sensor in addition to an RGB (Red Green Blue) sensor for color reading. In an image forming apparatus equipped with this 4-line CCD, color (RGB) reading is transferred with one CCD shift register for each RGB channel, but CCD shift is applied to a Bk sensor for monochrome (Bk) reading. A technique using two registers for even pixels and odd pixels is known. As a result, since the data transfer speed can be increased, the reading linear speed can be increased with respect to reading at the same resolution, and high productivity of monochrome copying can be ensured.

  However, until now, no image forming apparatus equipped with a 4-line CCD has been developed that has an automatic color determination (Auto Color Select) function. Since the ACS function automatically determines whether the document is color or monochrome, it is necessary to use RGB data for the read data. Therefore, when the ACS function is selected, color reading is performed even with a 4-line CCD. On the other hand, in 4-line CCD monochrome copying, the original is read by another sensor (Bk sensor). Therefore, there is a problem that a difference occurs in the image because there is a difference in read data between the monochrome copy image when the ACS function is selected and the monochrome copy image when the monochrome copy is selected.

  Patent Document 1 (Japanese Patent Laid-Open No. 2002-262007) aims to solve the problem that it is difficult for a user to manage a test chart used for scanner adjustment so as not to deteriorate. Is read with a plurality of scanners, target reference data is created from the read data, and each read data is corrected so as to approach the reference data.

  Since the technique of Patent Document 1 corrects a difference (variation) in read data between different devices, reference data must be generated from the read data of a plurality of devices. Therefore, it is impossible to correct a difference in read data between different read sensors provided in the same apparatus. That is, the technique of Patent Document 1 cannot be applied to the correction of the difference between read data of each sensor in an image forming apparatus equipped with a 4-line CCD having an RGB sensor (color reading unit) and a Bk sensor (monochrome reading unit). . In Patent Document 1, reference data is generated from a plurality of read data, but a calculation method and a specific generation method of a correction table are not disclosed.

  The present invention has been made in view of the above circumstances, and in an image forming apparatus in which a color reading unit and other reading units are mounted in the same device, image quality is corrected by correcting a difference in reading data of each reading unit. An object of the present invention is to provide an image forming apparatus capable of reducing the difference between the two.

  In order to achieve this object, the image forming apparatus of the present invention is read by a color reading unit in an image forming apparatus having a color reading unit for reading an original in color and another reading unit different from the color reading unit. Based on the data, the chromatic / achromatic determination means that determines whether the original is chromatic or achromatic, and the determination result of the chromatic / achromatic determination means. Based on the comparison result of the automatic color determination means for automatically determining whether to perform, the data comparison means for comparing the data read by the color reading section with the data read by another reading section, and the comparison result of the data comparison means The difference calculation means for calculating the difference between the data read by the color reading section and the data read by another reading section and generating correction data, and the correction data generated by the difference calculation means Using , And having a read by the color reading unit data, and the line sensor correction means for correcting the difference between the data read by another read unit.

  In the image forming apparatus of the present invention, the other reading unit is a monochrome read-only sensor.

  In the image forming apparatus of the present invention, when correcting the difference between the data read by the color reading unit and the data read by another reading unit, each of red, green, and blue used depending on the density region It is characterized by changing the data.

  In the image forming apparatus of the present invention, the difference calculation means calculates the difference by performing calculation based on the red, green, and blue data read by the color reading unit, and generates correction data. Features.

  The image forming apparatus of the present invention is characterized in that when the data read by the color reading unit is corrected to data read by another reading unit, the calculation method is switched according to the density region.

  The image forming apparatus according to the present invention includes a test pattern generation unit that outputs a test pattern for correction.

  In the image forming apparatus of the present invention, the correction test pattern is gray scale.

  The image forming apparatus of the present invention is characterized in that at least one test pattern having a different black ratio is provided in the gray scale portion of the test pattern for correction.

  In the image forming apparatus of the present invention, when a difference correction is performed using test patterns having different black rates, the black rate test pattern to be used can be changed according to the image quality mode selected by the user. It is characterized by that.

  In the image forming apparatus of the present invention, when the difference correction is performed using the test patterns having different black ratios, the black ink used for each specific area in the page according to the image area separation result of the original image. The rate test pattern can be changed.

  In the image forming apparatus of the present invention, when a difference correction is performed using test patterns having different black ratios, the user can arbitrarily change the output destination of the test pattern used for the correction. .

  In the image forming apparatus of the present invention, when a monochrome image is formed from cyan, magenta, and yellow color materials using test patterns having different black ratios, the spectral characteristics of the color reading unit and the characteristics of the color materials are taken into account. The ratio of the cyan, magenta, and yellow color materials is not uniform.

  According to the present invention, in an image forming apparatus in which a color reading unit and other reading units are mounted in the same device, a difference in image quality can be reduced by correcting a difference in reading data of each reading unit.

1 is a block diagram illustrating an example of the overall configuration of an image forming apparatus according to an embodiment of the present invention. It is a figure explaining a 4 line CCD module. (1) is a graph showing the spectral characteristics of a 4-line CCD Bk line sensor, and (2) is a graph showing the spectral characteristics of each RGB line sensor. 6 is a flowchart illustrating an example (Example 1) of a processing flow of the image forming apparatus according to the embodiment of the present disclosure. (1) is a diagram showing a gray gradation patch (photographic paper), and (2) to (4) are graphs showing data when the gray gradation patch (photographic paper) is read by a certain four-line CCD. It is. 6 is a graph showing read data when an RGB read value is optimized to a Bk read value from the data shown in FIGS. 5 (2) to (4). (1) is a diagram representing a gray gradation patch (halftone dot), and (2) to (4) represent data when the gray gradation patch (halftone dot) is read by a certain 4-line CCD. It is a graph. It is a graph showing the read data when the RGB read value is optimized to the Bk read value from the data shown in FIGS. 7 (2) to (4). (1) to (3) are graphs showing data when a gray gradation patch (3C gray patch) is read by a certain 4-line CCD. FIG. 10 is a graph showing read data when an RGB read value is optimized to a Bk read value from the data shown in FIGS. FIG. 10 is a diagram illustrating an example (Example 2) of a processing flow of the image forming apparatus according to the embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example (Example 3) of a processing flow of the image forming apparatus according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example (Example 4) of a processing flow of the image forming apparatus according to an embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example (Example 5) of a processing flow of the image forming apparatus according to the embodiment of the present disclosure. FIG. 10 is a diagram illustrating an example (Example 6) of a processing flow of the image forming apparatus according to the embodiment of the present disclosure. FIG. 3 is a diagram illustrating an example of a document on which image area separation is performed in the image forming apparatus according to the embodiment of the present invention. FIG. 10 is a diagram illustrating an example (Example 7) of a processing flow of the image forming apparatus according to an embodiment of the present disclosure. FIG. 7 is a diagram visually showing a flow of line sensor correction operation of the image forming apparatus according to the embodiment of the present invention. FIG. 3 is a diagram illustrating an example of a test pattern used for correction of the image forming apparatus according to an embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments (embodiments) for carrying out the present invention will be described in detail.

  First, an outline of the present embodiment will be described. Specifically, the image forming apparatus according to the present embodiment performs the following when performing image processing for reducing a difference between a monochrome copy image when the ACS function is selected and a monochrome copy image when the monochrome copy is selected. Has characteristics. In short, the image forming apparatus of the present embodiment continuously reads a specific gradation pattern by each of the RGB sensor and the Bk sensor, and corrects the data difference from the difference between the read data (RGB data and Bk data) ( The feature is that the data read by the RGB sensor is close to the data read by the Bk sensor).

  In the image forming apparatus of the present embodiment, when RGB data is matched with Bk data, the RGB to be used depends on the density of the document and the type of document (halftone dot or non-halftone dot / monochrome Bk or 3C gray or 4C gray). It is also characterized by optimizing the read data.

  Hereinafter, the features of the image forming apparatus of the present embodiment described above will be specifically described with reference to the accompanying drawings. First, the overall configuration of the image forming apparatus of the present embodiment will be described with reference to FIG.

  In the image forming apparatus of the present embodiment, a reading unit (scanner) 12, an engine 15, an operation unit 16, a CPU (Central Processing Unit) 19, a memory (storage unit) 112, and an image processing unit 113 are connected to a data bus 11. ing.

  In addition to the RGB reading means 13, the reading means 12 has a Bk reading means 14 dedicated to Bk reading. An example of the reading means 12 is a 4-line CCD. For example, the RGB reading unit 13 is an RGB line sensor (color reading unit) for color reading, and the Bk reading unit 14 is a Bk line sensor (monochrome reading unit) for monochrome reading.

  The CPU 19 includes a data comparison unit 110 and a difference calculation unit 111. The data comparison unit 110 compares the image data read by the reading unit 12 (which may be image data stored in the memory 112 after reading). The difference calculation unit 111 outputs (calculates) a difference from the data difference that is the comparison result of the data comparison unit 110, and generates γ data for correction.

  The image processing unit 113 is a unit that processes the read data read by the reading unit 12 (or the read data stored in the memory 112). The image processing unit 113 includes a line sensor correction unit 115 that approximates the Bk data from the RGB data read by the RGB reading unit 13, and reflects the γ data generated by the difference calculation unit 111 of the CPU 19. Execute image quality correction.

  In addition to the line sensor correction unit 115, the image processing unit 113 includes a scanner γ correction unit 114, an image area separation unit 116 (automatic color determination unit 117, chromatic / achromatic determination unit 118), a filter processing unit 119, A color correction unit 121, a gradation processing unit 119, a printer γ correction unit 122, and a test pattern generation unit 123 are provided. These units will be described later.

  Next, a 4-line CCD module will be described with reference to FIG.

  The 3-line CCD has only three line sensors for RGB. As shown in FIG. 2, the 4-line CCD has a Bk line sensor for Bk reading (color reading unit) in addition to each line sensor for RGB reading (color reading unit). One monochrome reading unit). Further, in FIG. 2, each RGB line sensor has only one CCD analog shift register, but the Bk line sensor has two CCD analog shift registers for odd columns and even columns. . As a result, the transfer rate can be doubled. Therefore, with the configuration shown in FIG. 2, the Bk line sensor can double the linear velocity even when the resolution is the same as that of the RGB line sensor. With such a configuration, productivity at the time of monochrome copying can be improved.

  Here, the spectral characteristics of each line sensor will be described with reference to FIG.

  FIG. 3 (1) shows the spectral characteristics of a 4-line CCD Bk line sensor, and FIG. 3 (2) shows the spectral characteristics of each RGB line sensor. As shown in FIG. 3B, each RGB line sensor also has a peak for a specific wavelength. On the other hand, the Bk line sensor does not have a large peak at a specific wavelength like the RGB line sensor, as shown in FIG. 3 (1), but has a high relative sensitivity as a whole.

  Next, a processing flow example (example 1) in the image forming apparatus of the present embodiment will be described with reference to the flowchart of FIG.

  First, when copying is performed, it is confirmed whether or not the user has selected the automatic color mode (S1). In the automatic color mode, the image forming device automatically determines the color (chromatic or achromatic) of the document to be copied, and determines whether to perform color copying or monochrome copying based on the determination result. This is the mode to select. Whether the original is chromatic or achromatic is determined by the chromatic / achromatic determination means 118 of the image area separation means 116 of the image processing unit 113 shown in FIG. Whether to perform color copying or monochrome copying is determined by the automatic color determination unit 117 of the image area separation unit 116 of the image processing unit 113 shown in FIG.

  If a mode other than the automatic color mode is selected (S1 / NO), image processing is executed according to the color mode (color copy or monochrome copy) selected by the user. That is, when color copy is selected (S9 / YES), RGB reading is performed by the RGB line sensor (S10), and color image forming processing is performed by each means of the image processing unit 113 (S8). On the other hand, when monochrome copy is selected (S9 / NO), Bk reading is performed by the Bk line sensor (S11), and monochrome image forming processing is performed in each unit of the image processing unit 113 (S7).

  When the automatic color mode is selected by the user (S1 / YES), the original is read by the RGB line sensor (S2), and image data (read data) for one page is accumulated in the memory 112 (S3). . The accumulation of S3 may be omitted. Then, the chromatic / achromatic determining means 118 determines whether the original is a color original or a monochrome original (S4). Note that the determination by the chromatic / achromatic determination means 118 is a technique that is generally performed in the related art, and thus the description thereof is omitted.

  If the determination result is a color original, the automatic color determination unit 117 determines that color copying is to be executed (S5 / NO). Therefore, the same image forming process as when color copy is selected in the color mode is performed (S8).

  On the other hand, if the determination result is a monochrome document, the automatic color determination unit 117 determines that monochrome copying is to be executed (S5 / YES). Then, the line sensor correction unit 115 performs a line sensor correction process on the read data (S6). This process corrects, for example, the difference between the read value (RGB data) from the RGB line sensor and the read value (Bk data) from the Bk line sensor. After this process is performed, the same image forming process as that when the monochrome copy is selected is performed (S7). Details of the monochrome image forming process (S7) will be described later.

  Next, a correction method using a gray photographic paper gradation patch will be described with reference to FIGS. In FIG. 5, the data is white 255.

  FIG. 5A illustrates a gray gradation patch (printing paper). Each gray patch (printing paper) has an actual gradation. 5 (2) to 5 (4) are diagrams showing data when a gray gradation patch (printing paper type patch) is read by a certain 4-line CCD (RGB sensor + Bk sensor). FIG. 6 is a diagram showing read data when the RGB read value is optimized to the Bk read value from the data of FIGS. 5 (2) to (4).

  Conventionally, the G signal was extracted as the closest data to the monochrome sensor and used for monochrome copying. However, since the line sensor itself has a difference in color sensitivity as shown in FIG. 3, FIGS. ) Will occur. From these data, it is understood that it is not necessary to simply use only the G signal in order to bring RGB read data close to Bk read data.

  For example, in a highlight portion (a portion with a low input density, a portion with a small number in the X-axis direction in FIG. 5), the read data of the B signal is closest to the read value of the Bk sensor. Similarly, in the middle part (intermediate density part), the G signal read data is closest to the Bk sensor read value, and in the shadow part (high input density part), the R signal read data is closest to the Bk sensor read value. .

  From the above data, the optimum RGB data as Bk data differs depending on each input density, and it must be taken into account.

  FIG. 6 shows data that takes this into account. Using the formula: (xR + yG + zB) / (x + y + z), the values of x, y, z were optimized in the highlight part, middle part, and shadow part (in this example, The highlight part (patch No. 1-6) is x = 0, y = 0, z = 1, the middle part (patch No.7-10) is x = 0, y = 1, z = 0, shadow (Patch Nos. 11 to 15) x = 1, y = 0, z = 0).

  The content described above is only an example. This is because the values of x, y, and z differ depending on the line sensor used. Also, since the highlight, middle, and shadow separation points depend on the line sensor used, it is clear that the optimum value varies depending on the sensor used.

  Next, a correction method using a gray halftone patch will be described with reference to FIGS. In FIG. 7, the data is 255 for white.

  FIG. 7A shows a gray gradation patch (halftone dot). The difference from the gray gradation patch (printing paper) in FIG. 5 (1) is that the printing paper actually has a gradation, whereas the halftone dots are obtained by changing the area ratio of the black data in the patch. This is a pseudo gradation. 7 (2) to 7 (4) are diagrams showing data when a gray gradation patch (halftone patch) is read by a certain 4-line CCD (RGB sensor + Bk sensor). 8 optimizes the RGB read value to the Bk read value from the data of FIGS. 7 (2) to (4) (in this characteristic 4-line CCD, patch Nos. 0 to 6 are set as x = 0, y = (1), (z = 0), patches Nos. 7 to 13 are set to x = 0, y = 0, z = 1).

  Compared with the characteristics of the gray scale patch shown in FIG. 5, the reading characteristics of the halftone patch shown in FIG. 7 are different. This is because, in the gradation patch of photographic paper (FIG. 5 (1)), all density patches are configured with a uniform density, whereas the gradation patch of halftone dots has a density difference (gradation of halftone dots). This is because the characteristics of the reflected light when light is irradiated are different, and as a result, the amount of light input to the line sensor is different. Because of these factors, it can be seen that the values of x, y, and z for optimizing the Bk read value differ depending on the document type.

  Next, a correction method using the 3C gray gradation patch will be described with reference to FIGS. In FIG. 9, the data is 255 for white.

  The gray gradation patch (3C gray patch) is a patch generated from three colors of cyan, magenta, and yellow. 9 (1) to 9 (3) are diagrams showing data when a gray gradation patch (3C gray patch) is read by a certain 4-line CCD (RGB sensor + Bk sensor). 3C gray is not a gradation patch drawn in Bk single color but Bk expressed in CMY. 10 optimizes the RGB reading value to the Bk reading value from the data of FIGS. 9 (1) to 9 (3) (patch numbers 0 to 6 are set to x = 0, y = 1 in the 4-line CCD having this characteristic. , Z = 0, patch Nos. 7 to 13 are set to x = 1, y = 1, and z = 1).

  Even if the same halftone document is used, the single color Bk color material is used in Fig. 7, whereas the 3C gray patch uses the Bk color material of the three primary colors cyan, magenta, and yellow. It is composed by doing. Such a patch looks black to the human eye, but in terms of pixels, it is an image in which dots of cyan, magenta, and yellow are arranged. Therefore, in addition to the fact that the reflection when irradiated with light is different from Bk single color, color information is read in pixel units, so when RGB reading is performed, the difference in color sensitivity of each RGB line sensor Therefore, a difference in read data occurs. Therefore, compared with the characteristics shown in FIGS. 5 and 7, the reading characteristics of the 3C gray patch are different. Also, 4C gray (cyan, magenta, yellow plus Bk color material) differs from 3C gray, which is composed of only cyan, magenta, and yellow color materials, and the inking rate. It is clear that there is a difference in the read data depending on (how much Bk color material is mixed in 4C gray). Therefore, it is clear that the values of x, y, and z for optimizing the Bk reading value are different.

  Next, an example (Example 2) of an image processing flow of the image forming apparatus according to the present exemplary embodiment will be described with reference to FIG. Each process shown in FIG. 11 is executed by means having the same reference numerals in the image processing unit 113 shown in FIG.

  When the normal color mode is set, image processing is performed through the R / G / B data paths in FIG. When the monochrome mode is set, the Bk data passes through the G path and image processing is performed. After the color correction process (color correction means) 121, the process is performed as K data.

  Next, an image processing flow when automatic color determination (ACS) is set will be described. Image data read by the scanner (reading means) 12 is input to a scanner γ process (scanner γ correction means) 114 and an image area separation process (image area separation means) 116. Although the reflection of the scanner γ 114 and the image area separation processing 116 are performed in parallel, a processing delay occurs (the image area separation processing 116 takes processing time), so that one page of image data after the scanner γ processing 114 is processed. Once stored in the memory 112.

  Thereafter, the image data (read data), the chromatic / achromatic determination result, and the image quality mode setting information set by the user are input to the line sensor correction process (line sensor correction means) 115. The image quality mode setting information is information (for example, a character mode, a photo mode, a character photo mode, etc.) that is set so that image processing suitable for a document is performed when the user uses a copy function, a scanner function, or the like. . The image quality mode setting is set by the operation unit 16 (command input means 17). The chromatic / achromatic determination result indicates a result of the chromatic / achromatic determination unit 118 determining whether the input image data is chromatic or achromatic.

  When it is determined that the color is achromatic, the line sensor correction process 115 reflects γ for correcting the difference between the R / G / B line sensor and the Bk line sensor in the image data in accordance with the image quality mode. Let the corrected image data be Bk ′. Bk ′ is transferred to the filter processing (filter processing means) 119 using the G data path, and is subjected to color correction processing (color correction means) 121, gradation processing (gradation processing means) 120, printer γ processing (printer). Image processing is performed by each (γ correction means) 122 and then output to the engine 15. On the other hand, if it is determined that the color is chromatic, the line sensor correction process 115 performs the image processing in the same manner as described above in the same R / G / B data path as that of a normal color copy without correcting the image data. Is done.

  Next, an example (Example 3) of an image processing flow of the image forming apparatus according to the present embodiment will be described with reference to FIG. Each process shown in FIG. 12 is executed by means having the same reference numerals in the image processing unit 113 shown in FIG.

  In FIG. 12, R / G / B is read data (scanner data) read by each R / G / B sensor, and Bk is read data (scanner data) read by the Bk sensor. Bk ′ is data used for ACS achromatic determination, and the generation method will be described below.

  In this example, the line sensor correction process 115 in the automatic color selection (ACS) mode will be described.

  When the ACS mode is selected, image data for one page of R / G / B is temporarily stored in the memory 112. The R / G / B data flows to the line sensor correction γ 130 of the line sensor correction process 115. At this time, R / G / B data flows to the data selector 131 in parallel. The R / G / B data sent to the line sensor correction γ 130 reflects the line sensor correction γ data corresponding to the currently set image quality mode setting information, and is generated as Bk ′ data. This Bk ′ data is sent to the data selector 131. The data selector 131 selects necessary data from R / G / B / BK ′ based on the result of automatic color determination (ACS).

  If it is determined to be chromatic, R / G / B data is selected by the data selector 131, and the selected R / G / B data is based on the same parameter settings as the color copy, and each image after the filter processing 119 is processed. Processing is performed (filter processing 119 and subsequent steps are the same as in FIG. 11). If it is determined that the color is achromatic, Bk ′ data is selected by the data selector 131, and the image processing after the filter processing 119 is performed based on the same parameter setting as the monochrome copy (the processing after the filter processing 119 is the same as that in FIG. 11). .

  Next, an example (Example 4) of an image processing flow of the image forming apparatus according to the present embodiment will be described with reference to FIG. The fourth example is a detailed description of the line sensor correction processing 115 in FIGS.

  In the flow of FIG. 13, each determination of S41 to S49 is performed based on the above-described image quality mode setting information. That is, depending on the image quality mode set by the user, the data to be used and the calculation method can be changed so that the document to be used can be predicted and the document can be optimally corrected. In the example of FIG. 13, in S41 to S49, it is determined whether the character mode, the print photo mode, the photographic paper photo mode, the copy photo mode, the character photo mode, the highlighter mode, and the map mode are set.

  For example, if the character mode is selected (S41 / YES), it can be expected that the document has many characters. In addition, since this image processing path flows only in monochrome documents, it can be assumed that there are many black characters. For this reason, it can be predicted that there is a high possibility that the Bk single color is formed, so that the correction method (Processing A) with the Bk single color patch and the solid image can be expected to be optimal.

  Next, an example (Example 5) of an image processing flow of the image forming apparatus of the present embodiment will be described with reference to FIG. Each process shown in FIG. 14 is executed by means having the same reference numerals in the image processing unit 113 shown in FIG.

  When the normal color mode is set, image processing is performed through the R / G / B data paths in FIG. When the monochrome mode is set, the Bk data passes through the G path and image processing is performed. After the color correction process (color correction means) 121, the process is performed as K data.

  Next, an image processing flow when automatic color determination (ACS) is set will be described. Image data read by the scanner (reading means) 12 is input to a scanner γ process (scanner γ correction means) 114 and an image area separation process (image area separation means) 116. Although the reflection of the scanner γ 114 and the image area separation processing 116 are performed in parallel, a processing delay occurs (the image area separation processing 116 takes processing time), so that one page of image data after the scanner γ processing 114 is processed. Once stored in the memory 112.

  Thereafter, image data (read data), a chromatic / achromatic determination result, and image area separation information are input to the line sensor correction process (line sensor correction means) 115. The image area separation information is information indicating a character area or a photograph area in the read data. The chromatic / achromatic determination result indicates a result of the chromatic / achromatic determination unit 118 determining whether the input image data is chromatic or achromatic.

  When it is determined that the color is achromatic, in the line sensor correction process 115, line sensor correction γ for correcting the difference between the R / G / B line sensor and the Bk line sensor based on the image area separation information is reflected in the image data. Let the corrected data be Bk ′. Bk ′ is transferred to the filter processing (filter processing means) 119 using the G data path, and is subjected to color correction processing (color correction means) 121, gradation processing (gradation processing means) 120, printer γ processing (printer). Image processing is performed by each (γ correction means) 122 and then output to the engine 15. On the other hand, if it is determined that the color is chromatic, the line sensor correction process 115 performs the image processing in the same manner as described above in the same R / G / B data path as that of a normal color copy without correcting the image data. Is done.

  Next, an example (Example 6) of an image processing flow of the image forming apparatus of the present embodiment will be described with reference to FIG. Each process shown in FIG. 15 is executed by means having the same reference numerals in the image processing unit 113 shown in FIG.

  In FIG. 15, R / G / B is read data (scanner data) read by each R / G / B sensor, and Bk is read data (scanner data) read by the Bk sensor. Bk ′ is data used for ACS achromatic determination, and the generation method will be described below.

  In this example, the line sensor correction process 115 in the automatic color selection (ACS) mode will be described.

  When the ACS mode is selected, image data for one page of R / G / B is temporarily stored in the memory 112. The R / G / B data flows to the line sensor correction γ 130 of the line sensor correction process 115. At this time, R / G / B data flows to the data selector 131 in parallel. In the R / G / B data sent to the line sensor correction γ130, the line sensor correction γ data corresponding to the image area separation determination result is reflected for each pixel, and Bk ′ data is generated. This Bk ′ data is sent to the data selector 131. The data selector 131 selects necessary data from R / G / B / BK ′ based on the result of automatic color determination (ACS).

  If it is determined to be chromatic, R / G / B data is selected by the data selector 131, and the selected R / G / B data is based on the same parameter settings as the color copy, and each image after the filter processing 119 is processed. Processing is performed (filter processing 119 and subsequent steps are the same as in FIG. 14). If it is determined to be achromatic, Bk ′ data is selected by the data selector 131, and each image process after the filter process 119 is performed based on the same parameter setting as the monochrome copy (the process after the filter process 119 is the same as in FIG. ).

  Next, an example in which processing is changed in combination with image area separation information will be described with reference to FIG. As shown on the left side of FIG. 16, it is assumed that there is a document in which characters and photographs are mixed. When this is copied in the automatic color determination mode and monochrome determination is made, as shown in the center of FIG. 16, it is separated into a character portion and a photograph portion by an image area separation means. Further, regarding the photographic part, as shown on the right side of FIG. 16, it is separated whether it is a halftone image or a photographic paper image. Appropriate line sensor correction is performed on different determination portions such as a character portion, a halftone dot portion, and a photographic paper portion in one image.

  Next, an example (Example 7) of an image processing flow of the image forming apparatus according to the present embodiment will be described with reference to FIG. Here, the flow of the RGB data correction method (calibration operation) will be described.

  When the line sensor correction is performed by the line sensor correction unit 115 in response to a user instruction (S21 / YES), a test pattern for correction is output (printed) by the test pattern generation unit 123 (S22).

  The user sets the output test pattern on the contact glass or ADF (Auto Document Feeder). When a reading start execution instruction is received from the user (S23 / YES), RGB scanning is started after scanner calibration (S24).

  After acquiring the RGB data (S25), the scanner calibration is performed again, and reading with the Bk sensor is started (S26). If a test pattern is installed on the ADF, the same document must be set on the ADF again.

  After obtaining the Bk data (S27), the CPU 19 calculates the difference between the RGB read data and the Bk read data (for example, closes the RGB data to the Bk data. S28), and generates γ for correcting the difference (S29). The generated γ is reflected in the image processing in the image processing unit 113 (S30).

  In the flow of FIG. 17, the resolution of RGB reading and Bk reading is not particularly limited, but it is recommended that the two readings have the same resolution and the same resolution as in the copy operation.

  Next, an embodiment of the line sensor correction operation will be described with reference to FIG. The user selects execution of the line sensor correction (“execute” button) from the operation panel (an example of the command input unit 17 of the operation unit 16).

  When the “execute” button is pressed, the image forming apparatus prints a specific test pattern. The user places the test pattern on the contact glass or ADF, and presses the “Execute” button again.

  During reading (RGB reading & Bk reading), the image forming apparatus displays on the operation panel (an example of the display unit 18 of the operation unit 16, LCD) that reading is in progress. In addition, when the test pattern is set in the ADF by the user, the image forming apparatus displays a message to set the document again in the ADF after the first scan, and after the setting, the user presses the “execute” button again. Have it pressed. When the two scans (RGB scan and Bk scan) are completed, the image forming apparatus compares the two read data with the CPU, generates (calculates) a line sensor correction γ that corrects the difference, and generates an image processing unit. The correction completion message is displayed on the operation panel.

Next, a test pattern used for correction will be described with reference to FIG. As the correction requirement this time, since the original is a monochrome case, a plurality of monochrome test patterns are prepared for correction. Also, since there is a difference in color sensitivity between single color Bk and 3C gray and 4C gray, for example, the following gradation patches are prepared.
a: gradation patch generated with monochrome Bk b: gradation patch generated with 66% black (4C gray) c: gradation patch generated with 33% black (4C gray) d: black 0 Tone patch generated in% (3C gray) e: a is rotated 180 °.
f: b is rotated 180 °.
g: c is rotated 180 °.
h: d is rotated 180 °.

  The pattern rotated 180 ° is a pattern for reducing the fluctuation of the scanner light source (lamp). Basically, it is assumed that such a test pattern is output by the device itself. However, if there is paper or printer that the user uses frequently and uses the same electronic data, this test pattern is often used. It is also possible to output using a paper / printer and perform line sensor correction using the output as a test pattern.

  In addition, although automatic color determination is performed in 3C gray and 4C gray, the automatic color determination performance may be determined as an achromatic color even if it is not completely black (for example, the CMY ratio is 1: 1: 1). Exists. In such a case, since the black is slightly colored, the reading characteristics also change. Therefore, it is possible to further improve the correction accuracy (correspondence capability) by using and correcting the test pattern of the CMY ratio that becomes the limit point of the monochrome determination of the automatic color determination.

  In addition, for the sake of explanation, the black rate, the number of gradations, the number of patterns with different black rates, the arrangement of patches, the rotation angle, the position of the pattern, etc. are only described as described above. It is not the intention to do.

  As described above, according to the present embodiment, a specific test pattern is printed and output in an image forming apparatus equipped with an RGB sensor (color reading unit) and a Bk sensor (monochrome reading unit) in the same device. The read image is continuously read by the RGB sensor and the Bk sensor, and the difference between the two read data is corrected (closer to one of the data). Thereby, the difference in image quality between the monochrome copy image when the ACS function is selected and the monochrome copy image when the monochrome copy is selected can be reduced.

  As described above, this embodiment can reduce the difference in image quality of output images caused by reading with different sensors in the same device. Here, the difference from ACC (Auto Color Calibration) will be described. To do. ACC performs correction by using a scanner as a measuring device, linking the read value of the output pattern and the output density, and matching the output density to a certain target. On the other hand, in the present embodiment, in a configuration in which different sensors coexist in the same device, the same document is continuously read by different sensors, and correction for matching the reading difference between the sensors with the reading data of either sensor is performed. Realized. Therefore, in the present embodiment, unlike ACC, the test pattern to be used is not limited, and a manuscript that is always managed, such as scanner difference correction, is not required. This embodiment is characterized in that correction is performed without using a specific test chart.

  Further, in the conventional correction of read data, it is necessary to use a document that is managed so that the document does not change in any application. Although this embodiment is a specific application, it is also characterized in that correction is performed not using such managed data but using an image output by the device being used or other printing machine. It is.

  Note that the configuration of this embodiment is not merely a design matter. In the correction of read data, even if parameters are prepared in advance, the correction data can be optimized in real time because there are fluctuations in the environment (temperature / humidity) of the scanner characteristics and fluctuations over time (including fluctuations in the light source). is necessary. For this reason, the above-described embodiment cannot be handled by changing the design item of increasing one parameter for the correction.

  As mentioned above, although embodiment of this invention was described, it is not limited to the said embodiment, A various deformation | transformation is possible in the range which does not deviate from the summary.

  For example, the operation in the above-described embodiment can be executed by hardware, software, or a combined configuration of both.

  When executing processing by software, a program in which a processing sequence is recorded may be installed and executed in a memory in a computer incorporated in dedicated hardware. Or you may install and run a program in the general purpose computer which can perform various processes.

  For example, the program can be recorded in advance on a hard disk or a ROM (Read Only Memory) as a recording medium. Alternatively, the program is temporarily or permanently stored on a removable recording medium such as a CD-ROM (Compact Disc Read Only Memory), an MO (Magneto optical) disc, a DVD (Digital Versatile Disc), a magnetic disc, or a semiconductor memory. It can be stored (recorded). Such a removable recording medium can be provided as so-called package software.

  The program may be wirelessly transferred from the download site to the computer in addition to being installed on the computer from the removable recording medium as described above. Or you may wire-transfer to a computer via networks, such as LAN (Local Area Network) and the internet. The computer can receive the transferred program and install it on a recording medium such as a built-in hard disk.

  In addition to being executed in time series in accordance with the processing operations described in the above embodiment, the processing capability of the apparatus that executes the processing, or a configuration to execute in parallel or individually as necessary Is also possible.

  The present invention can be applied not only to an image forming apparatus but also to an apparatus, system, method, and program for performing image processing.

12 Reading means (scanner)
13 RGB reading means (color reading unit, eg RGB line sensor)
14 BK reading means (monochrome reading unit, eg Bk line sensor)
DESCRIPTION OF SYMBOLS 15 Engine 16 Operation part 17 Command input means 18 Display means 19 CPU
DESCRIPTION OF SYMBOLS 110 Data comparison means 111 Difference calculation means 112 Memory 113 Image processing part 114 Scanner gamma correction means 115 Line sensor correction means 116 Image area separation means 117 Automatic color determination means 118 Chromatic / achromatic determination means 119 Filter processing means 120 Gradation processing Means 121 Color correction means 122 Printer γ correction means 123 Test pattern generation means 130 Line sensor correction γ
131 Data selector

JP 2002-262007 A

Claims (12)

In an image forming apparatus having a color reading unit for reading a document in color and another reading unit different from the color reading unit,
Chromatic / achromatic determination means for determining whether the original is chromatic or achromatic based on the data read by the color reading unit;
Automatic color determination means for automatically determining whether image formation of the document is performed in color or monochrome based on the determination result of the chromatic / achromatic determination means;
Data comparison means for comparing the data read by the color reading unit with the data read by the other reading unit;
A difference calculating means for calculating a difference between the data read by the color reading unit and the data read by the other reading unit based on the comparison result of the data comparing unit, and generating correction data; ,
A line sensor correction unit that corrects a difference between the data read by the color reading unit and the data read by the other reading unit, using the correction data generated by the difference calculation unit;
An image forming apparatus comprising:   The image forming apparatus according to claim 1, wherein the other reading unit is a monochrome reading-only sensor.   When correcting the difference between the data read by the color reading unit and the data read by the other reading unit, the red, green, and blue data to be used are changed according to the density region. The image forming apparatus according to claim 1, wherein the image forming apparatus is an image forming apparatus.   The difference calculation means calculates the difference by performing calculation based on red, green, and blue data read by the color reading unit, and generates the correction data. Item 4. The image forming apparatus according to any one of Items 1 to 3.   5. The method according to claim 1, wherein when the data read by the color reading unit is corrected to data read by the other reading unit, the calculation method is switched according to the density region. The image forming apparatus described in the item.   6. The image forming apparatus according to claim 1, further comprising test pattern generation means for outputting a test pattern for correction.   The image forming apparatus according to claim 6, wherein the correction test pattern is a gray scale.   8. The image forming apparatus according to claim 6, wherein at least one test pattern having a different black ratio is provided in a gray scale portion of the correction test pattern.   The black pattern test pattern to be used can be changed according to an image quality mode selected by a user when the difference correction is performed using the test patterns having different black ratios. Item 9. The image forming apparatus according to Item 8.   When the difference correction is performed using the test patterns having different black ratios, the black ratio test pattern to be used for each specific area in the page is determined according to the image area separation result of the original image. The image forming apparatus according to claim 8, wherein the image forming apparatus is changeable.   9. The image according to claim 8, wherein when the difference correction is performed using the test patterns having different black ratios, a user can arbitrarily change an output destination of the test pattern used for the correction. Forming equipment.   When a monochrome image is formed from cyan, magenta, and yellow color materials using the test patterns having different black ratios, cyan, magenta, and yellow colors are added in consideration of spectral characteristics and color material characteristics of the color reading unit. The image forming apparatus according to any one of claims 8 to 11, wherein a ratio of mixing the respective color materials is not uniform.

Images