JP2008141532A - Reading characteristic compensation device, image formation system, calibration method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To highly precisely calibrate a printer without performing a complicated arithmetic operation or the like. <P>SOLUTION: A chart CA for scanner in which the respective color reference images of yellow (Y), magenta (M), cyan (C), black (K), orange (OR), green are formed is read as a color image of red (R), green (G), blue (B) with the scanner 10, scanner compensation LUTs of each color are created from relation between image colors and complementary color components based on reading results of the reference images of each color. Then, a test chart CB in which test images of each color is formed by a printer 20 is read as a color image of RGB by the scanner 10 and printer compensation LUTs of each color in the printer 20 are created based on results by compensating reading results of test images of each color by the scanner compensation LUTs of each color. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a reading characteristic correction apparatus, an image forming system, and a calibration method.

  In a color printer that forms a color image using a color material such as toner or ink, the reproducibility of the output color changes as the members constituting the color printer change with time or change in environment. Therefore, a setup operation called printer calibration is performed for the purpose of keeping the color reproducibility in the color printer constant.

  As such a printer calibration method, for example, a test pattern created using each color toner is output by a target color printer, the test pattern is read by a scanner, and correction for each color is performed based on the read result. What determines a table (tone correction profile) is known. Then, when creating the correction table, for example, by changing the conversion parameter when converting the test pattern reading result by the scanner into a standard color space signal to a profile corresponding to the scanner used for reading, the scanner-specific reading characteristics A technique for reducing the influence of the above has been proposed (see, for example, Patent Document 1).

JP 2000-253268 A

  The present invention has been made against the background of the above-described technology, and an object of the present invention is to realize accurate printer calibration without performing complicated calculations.

  For this purpose, the reading characteristic correction apparatus to which the present invention is applied includes reading means for reading a reference chart on which reference images of yellow, magenta, and cyan are formed as red, green, and blue color images. Based on the result obtained by reading the reference chart by the reading means, the first characteristic that associates the density of the yellow reference image and the blue read output, the density of the magenta reference image and the green read output, A grasping means for grasping a second characteristic associated with each other and a third characteristic associated with the density of the cyan reference image and the red read output; and the density of the yellow image and the blue color from the first characteristic A first correction characteristic for correcting the relationship with the reading output is determined, and a second correction for correcting the relationship between the density of the magenta image and the green reading output from the second characteristic. And characterized, and a third determining means for determining a correction characteristic for correcting the relationship between the concentration and red reading output of the third characteristic from the cyan image.

  In such a reading characteristic correcting apparatus, the first standard characteristic indicating the standard relationship between the density of the yellow image and the blue reading output, and the standard relation between the density of the magenta image and the green reading output are obtained. And a standard characteristic storage means for storing a second standard characteristic indicating a third standard characteristic indicating a standard relationship between the density of the cyan image and the red read output, and the determining means includes the first characteristic The first correction characteristic is determined from the first standard characteristic, the second correction characteristic is determined from the second characteristic and the second standard characteristic, and the third correction characteristic is determined from the third characteristic and the third standard characteristic. The correction characteristic may be determined. The reference chart further includes a black reference image in addition to yellow, magenta, and cyan, and the grasping means determines the density and red color of the black reference image based on the result obtained by reading the reference chart with the reading means. And determining the relationship between the density of the black image and the read output of red, green, or blue based on the fourth characteristic. A fourth correction characteristic for correction may be further determined. The reference chart further includes reference images of spot colors other than yellow, magenta, cyan, and black, and the grasping means is based on the result obtained by reading the reference chart by the reading means and the reference image of the spot color and the red color. And determining the relationship between the density of the spot color image and the read output of red, green, and blue from the fifth characteristic. A fifth correction characteristic for correction may be further determined. In this case, the grasping means determines any one of red, green, and blue as the key color, and associates the read output of the key color with the read output of the two colors other than the key color, and the fifth characteristic. It can be characterized by grasping. Further, the grasping means may be characterized in that the fifth characteristic is grasped by weighting each read output of red, green, and blue with respect to the reference image of the spot color.

  From another viewpoint, an image forming system to which the present invention is applied includes a scanner that reads an image of a document as a color image, a printer that forms a color image using a plurality of color materials as recording materials, From the first chart on which a reference image of the same color as the color materials of a plurality of colors is formed and the first color image data obtained by reading the first chart with a scanner, the density of each color and each color constituting the reference image A scanner correction characteristic setting unit for acquiring a scanner input / output characteristic corresponding to a read output corresponding to a complementary color of the image, and setting a scanner correction characteristic for correcting the scanner input / output characteristic, and a plurality of color materials in the printer The second chart created using the second color image data obtained by reading the second chart with the scanner and the scanner set in the scanner correction characteristic setting unit. Based on Na correction characteristic, and a printer correction characteristic setting unit that sets the printer correction characteristic for correcting the printer output characteristics of the printer.

  In such an image forming system, the scanner reads in the red, green, and blue wavelength regions, and the printer uses yellow, magenta, and cyan color materials as a plurality of color materials. It can be characterized by using. In this case, the scanner correction characteristic setting unit associates the density of the yellow reference image with the blue read output obtained by reading the yellow reference image as the scanner input / output characteristic, The green read output obtained by reading the magenta reference image is associated, and the density of the cyan reference image is associated with the red read output obtained by reading the cyan reference image. it can. The printer further uses a black color material as a color material of a plurality of colors, and the scanner correction characteristic setting unit, as a scanner input / output characteristic, reads the black reference image density and the red reference image obtained by reading the black reference image. , Green, or blue reading output can be associated with each other. Further, the printer further uses special color materials other than yellow, magenta, cyan, and black as the color materials of the plurality of colors, and the scanner correction characteristic setting unit sets the density and special color of the special color reference image as the scanner input / output characteristics. And the read output of the complementary color component of the special color obtained by combining the red, green, and blue read outputs obtained by reading the reference image. In this case, the scanner correction characteristic setting unit outputs, as a scanner input / output characteristic, a read output corresponding to a density change of the special color reference image among red, green, and blue read outputs obtained by reading the special color reference image. It is characterized in that a color that is most sensitive to change is determined as a feature color, and a readout output of a complementary color component of a special color is created by associating the readout output of the feature color with the readout output of two colors other than the feature color. it can.

  Furthermore, from another viewpoint, the calibration method to which the present invention is applied includes a step of reading a first chart on which a reference image having the same color as a plurality of color materials is formed as a color image with a scanner, From the first color image data obtained by reading one chart, scanner input / output characteristics are obtained by associating the density of each color constituting the reference image with the read output corresponding to the complementary color of each color, and scanner input / output characteristics A step of setting a scanner correction characteristic for correcting the characteristic, a step of forming a second chart using a plurality of color materials by a printer, and a step of reading the second chart as a color image by the scanner Based on the second color image data obtained by reading the second chart and the set scanner correction characteristics, And a step of setting the printer correction characteristic for correcting the data input-output characteristics.

According to the first aspect of the invention, the correction characteristics for the yellow image, the magenta image, and the cyan image are obtained based on the relationship between yellow and blue, the relationship between magenta and green, and the relationship between cyan and red. Therefore, it is possible to realize accurate printer calibration without performing complicated calculations such as color conversion to the standard color space.
According to the second aspect of the present invention, each correction characteristic can be obtained from the relationship with each standard characteristic.
According to the third aspect of the present invention, the correction characteristic for the black image can be obtained based on the relationship between black and any one of red, green, and blue.
According to the fourth aspect of the present invention, it is possible to obtain the correction characteristic for the spot color image based on the relationship between the spot color and red, green, and blue.
According to the fifth aspect of the present invention, as for the special colors, red, green, and blue can be combined into one around the key color.
According to the sixth aspect of the present invention, it is possible to more accurately synthesize the color of the complementary color component for the spot color.
According to the seventh aspect of the invention, since the scanner calibration and the printer calibration are performed based on the relationship between the color of the image and its complementary color, the accuracy is high without performing complicated calculations. Printer calibration can be realized.
According to the invention described in claim 8, scanner calibration and printer calibration can be performed without using a special printer or scanner.
According to the ninth aspect of the invention, the correction characteristics for the yellow image, the magenta image, and the cyan image are obtained based on the relationship between yellow and blue, the relationship between magenta and green, and the relationship between cyan and red. Is possible.
According to the tenth aspect of the present invention, it is possible to perform scanner calibration and printer calibration for a black image.
According to the eleventh aspect of the present invention, it is possible to execute scanner calibration and printer calibration for a spot color image.
According to the twelfth aspect of the present invention, red, green, and blue can be combined into one with the characteristic color as the center.
According to the invention described in claim 13, since the calibration of the scanner and the calibration of the printer are performed based on the relationship between the color of the image and its complementary color, it is possible to achieve high accuracy without performing complicated calculations. Printer calibration can be realized.

The best mode for carrying out the present invention (hereinafter referred to as an embodiment) will be described below in detail with reference to the accompanying drawings.
FIG. 1 shows an example of the configuration of a print system to which the present embodiment is applied. This printing system includes a copying machine 1 and a computer terminal 2, and these copying machine 1 and computer terminal 2 are connected via a network 3. The copying machine 1 also includes a scanner 10 that reads an image formed on a document and a printer 20 that forms an image on a sheet. The scanner 10 and the printer 20 are connected via an internal network (not shown). Here, the scanner 10 has a configuration capable of reading an image of a document in color, that is, red (R), green (G), and blue (B). The printer 20 also has a configuration capable of forming a color image on paper. In particular, in this embodiment, the printer 20 uses orange (Y), magenta (M), cyan (C), and black (K), which are commonly used for forming full-color images, as a special color, orange ( OR) and green (GR) are added so that six-color printing can be performed.

  In this printing system, for example, based on the image data output from the computer terminal 2, the printer 20 of the copying machine 1 can perform a printing operation for executing image formation. Further, in the copying machine 1, based on the image data obtained by reading the original with the scanner 10, the printer 20 can perform a copying operation for executing image formation.

  Furthermore, in this printing system, in order to maintain the color reproducibility of the image output from the printer 20, the input / output characteristics of the printer 20 are corrected as necessary (hereinafter referred to as printer calibration). Can be executed. In the printer calibration, a predetermined test chart CB is output by the printer 20, and the input / output characteristics of each color in the printer 20 are corrected based on the reading result obtained by reading the test chart CB with the scanner 10.

  In this embodiment, input / output characteristic correction (referred to as scanner calibration in the following description) in the scanner 10 can be executed prior to execution of such printer calibration. In the scanner calibration, the input / output characteristics of each color in the scanner 10 are corrected based on the reading result obtained by reading the scanner adjustment chart CA created for the scanner calibration with the scanner 10.

FIG. 2A shows a configuration example of a scanner adjustment chart CA as a reference chart or a first chart.
The scanner adjustment chart CA has reference images SY, SM, SC, SK, SOR, and SGR recorded at eight levels for each of Y, M, C, K, OR, and GR colors. Here, the density of each image in the reference image of each color is lower on the left side and higher on the right side in the figure. In the following description, the reference images of the respective colors are classified into yellow reference image (yellow reference image) SY, magenta reference image (magenta reference image) SM, cyan reference image (cyan reference image) SC, as necessary. They are referred to as a black reference image (black reference image) SK, an orange reference image (special color reference image) SOR, and a green reference image (special color reference image) SGR. This scanner adjustment chart CA can be created by a printing machine other than the printer 20, for example, and the density value of each image in the reference image of each color is known (for example, 1%, 7%, 15%, 30%, 50%, 80%, 90%, 100%).

On the other hand, FIG. 2B shows a configuration example of a test chart CB as a second chart.
The test chart CB has test images TY, TM, TC, TK, TOR, and TGR, which are formed with 24 levels of density for each color of Y, M, C, K, OR, and GR using the printer 20. ing. Here, in the test chart CB, 12 patch images of each color are formed in two rows in each test image, and the density of each image constituting the test image of each color is lower on the left side and higher on the right side in the figure. In the figure, the upper side is low and the lower side is high. In the following description, the test images of each color are referred to as a yellow test image TY, a magenta test image TM, a cyan test image TC, a black test image TK, an orange test image TOR, and a green test image TGR as necessary. To. The test chart CB is created by the printer 20 with a predetermined gradation value common to each color (for example, in increments of 4 to 5%), but the actual density value of each patch image in the test image of each color is unknown. It is.
Details of printer calibration and scanner calibration will be described later.

FIG. 3 is a block diagram illustrating a configuration example of the scanner 10 illustrated in FIG. 1.
The scanner 10 includes a sensor 11 that reads an image of a document and a signal processing unit 12. The sensor 11 that functions as a reading unit includes an R sensor 11R, a G sensor 11G, and a B sensor 11B.
Here, each of the R sensor 11R, the G sensor 11G, and the B sensor 11B is provided with a color filter for transmitting different wavelength components, and each of them is a color sensor for red, green, and blue. It is functioning. The scanner 10 irradiates the reading surface of the document with white light by a light source (not shown), for example, and receives reflected light from the document by the R sensor 11R, the G sensor 11G, and the B sensor 11B. Yes.

  The signal processing unit 12 converts the R signal output from the R sensor 11R, the G signal output from the G sensor 11G, and the B signal output from the B sensor 11B, such as A / D conversion and shading correction. Various processing is performed. Then, the signal processing unit 12 outputs an RGB signal (referred to as scanner output data S (R, G, B) in the following description) obtained by performing these various processes. In the following description, the output of each color constituting the scanner output data S is referred to as output IR, output IG, and output IB, respectively. The output IR, output IG, and output IB are composed of, for example, 8-bit, that is, 256 gradation data.

FIG. 4 is a block diagram illustrating a configuration example of the printer 20 illustrated in FIG. The printer 20 is a digital color printer that forms each color toner image on a sheet by electrophotography.
The printer 20 includes a color conversion unit 21, a gradation correction unit 22, an image forming unit 23, a scanner correction LUT setting unit 24, and a printer correction LUT setting unit 25. The image forming unit 23 includes a Y image forming unit 23Y, an M image forming unit 23M, a C image forming unit 23C, a K image forming unit 23K, an OR image forming unit 23OR, and a GR image forming unit 23GR.

  The color conversion unit 21 receives input image data D from the computer terminal 2 or the scanner 10. Here, as the input image data D, RGB data D (R, G, B) including color signals of RGB colors, YMC data D (Y, M, C) including color signals of YMC colors, and further each color of YMCK YMCK data D (Y, M, C, K) including the color signal of the color. When performing a copying operation, the scanner output data S (R, G, B) output from the scanner 10 becomes the RGB data D (R, G, B) as it is. Then, the color conversion unit 21 performs color conversion processing on the input image data D, and color signals of each color of Y, M, C, K, OR, GR, that is, yellow data Y1, magenta data M1, cyan data C1, black Output as data K1, orange data OR1, and green data GR1. Here, the data of each color is composed of, for example, 8-bit, that is, gradation data of 256 gradations.

  The gradation correction unit 22 is obtained by performing gradation correction processing on the gradation data of each color input from the color conversion unit 21 in order to correct the nonlinearity of the density of the image output by the image forming unit 23. The corrected yellow data Y2, the corrected magenta data M2, the corrected cyan data C2, the corrected black data K2, the corrected orange data OR2, and the corrected green data GR2 are formed with corresponding colors. To the unit 23. That is, the tone correction unit 22 corrects input / output characteristics in the printer 20. Each color data output from the gradation correction unit 22 is also 8-bit gradation data. The gradation correction unit 22 performs gradation correction of each color data using a one-dimensional LUT (Look Up Table) set for each color. Each color LUT (referred to as printer correction LUT in the following description) has a profile corresponding to the corresponding color, and is created by the printer correction LUT setting unit 25 when printer calibration is executed.

  The image forming unit 23, that is, the Y image forming unit 23Y, the M image forming unit 23M, the C image forming unit 23C, the K image forming unit 23K, the OR image forming unit 23OR, and the GR image forming unit 23GR are respectively supplied from the gradation correction unit 22. Based on the corrected yellow data Y2, corrected magenta data M2, corrected cyan data C2, corrected black data K2, corrected orange data OR2, and corrected green data GR2, the corresponding color A toner image is formed on a sheet using toner as a coloring material. For example, the Y image forming unit 23Y executes image formation using yellow toner based on the corrected yellow data Y2.

  The scanner correction LUT setting unit 24 functioning as a scanner correction characteristic setting unit is a first color which is a reading result of the scanner adjustment chart CA input from the scanner 10 in scanner calibration performed prior to execution of printer calibration. Input of scanner output data S (R, G, B) as image data is accepted. Further, the scanner correction LUT setting unit 24 uses the Y, M, C, K, OR, and GR colors used by the printer correction LUT setting unit 25 when performing printer calibration based on the reading result of the scanner adjustment chart CA. A scanner correction LUT (scanner correction characteristic) is created and stored.

  The printer correction LUT setting unit 25 that functions as a printer correction characteristic setting unit scans the output data S (R, R, R) as second color image data that is the result of reading the test chart CB input from the scanner 10 in printer calibration. G, B) is received. The printer correction LUT setting unit 25 uses the scanner correction LUT for each color Y, M, C, K, OR, and GR set by the scanner correction LUT setting unit 24 based on the reading result of the test chart CB. A printer correction LUT (printer correction characteristic) for each color Y, M, C, K, OR, and GR used in the gradation correction unit 22 is created and stored.

FIG. 5 is a block diagram illustrating a configuration example of the scanner correction LUT setting unit 24 illustrated in FIG.
The scanner correction LUT setting unit 24 includes a data distribution unit 31, a current characteristic grasping unit 32, a scanner correction LUT determination unit 33, a scanner correction LUT storage unit 34, and a standard characteristic storage unit 35.

  The data distribution unit 31 obtains six pieces of data Y (B), M (G), C from the scanner output data S (R, G, B), which is the result of reading the scanner adjustment chart CA input from the scanner 10. (R), K (G), OR (R, G, B), GR (R, G, B) are extracted and distributed. In the following description, these are referred to as yellow reference data Y (B), magenta reference data M (G), cyan reference data C (R), black reference data K (G), orange reference data OR (R, G, B) and green reference data GR (R, G, B).

FIG. 6 schematically shows scanner output data S (R, G, B) when the scanner adjustment chart CA shown in FIG. 6A illustrates the output IR of the R sensor 11R, FIG. 6B illustrates the output IG of the G sensor 11G, and FIG. 6C illustrates the output IB of the B sensor 11B. .
As shown in FIG. 6, the yellow reference data Y (B) is the result of reading the yellow reference image SY by the B sensor 11B, the magenta reference data M (G) is the result of reading the magenta reference image SM by the G sensor 11G, and the cyan reference. Data C (R) is a result of reading the cyan reference image SC by the R sensor. The black reference data K (G) is a result of reading the black reference image SK by the G sensor 11G. Further, the orange reference data OR (R, G, B) is obtained by combining the reading results of the orange reference image SOR by the R sensor 11R, the G sensor 11G, and the B sensor 11B. Furthermore, the green reference data GR (R, G, B) is obtained by combining the reading results of the green reference image SGR by the R sensor 11R, the G sensor 11G, and the B sensor 11B.

  Further, as shown in FIG. 5, the current characteristic grasping unit 32 functioning as a grasping unit is based on the reference data for each color of Y, M, C, K, OR, and GR input from the data sorting unit 31. The current characteristics that are the current input / output characteristics of the scanner 10 for each color of M, C, K, OR, and GR are grasped. Further, the current state grasping unit 32 obtains the obtained yellow current state characteristic (first current state characteristic) YB, magenta current state characteristic (second current state characteristic) MG, cyan current state characteristic (third current state characteristic). CR, black current characteristics (fourth current characteristics) KG, orange current characteristics (fifth current characteristics) OR-ΔEOR, green current characteristics (fifth current characteristics) GR-ΔEGR are output.

  Here, FIG. 7 is a diagram illustrating a configuration example of the current characteristic grasping unit 32. The current characteristic grasping unit 32 includes a YB characteristic obtaining unit 41, an MG characteristic obtaining unit 42, a CR characteristic obtaining unit 43, a KG characteristic obtaining unit 44, an OR-ΔEOR characteristic obtaining unit 45, and a GR- A ΔEGR characteristic acquisition unit 46 and a reference value storage unit 47 are provided.

FIG. 8 illustrates the reference values for each color Y, M, C, K, OR, and GR stored in the reference value storage unit 47. The reference value storage unit 47 stores, for each color of Y, M, C, and K, the density of each image constituting the reference image of each color. More specifically, the reference value storage unit 47 includes the densities DY1 to DY8 (first standard characteristics) of the eight images constituting the yellow reference image SY and the densities of the eight images constituting the magenta reference image SM. DM1 to DM8 (second standard characteristics), the densities DC1 to DC8 (third standard characteristics) of the eight images constituting the cyan reference image SC, and the densities DK1 of the eight images constituting the black reference image SK. ~ DK8 are stored. Further, the reference value storage unit 47, for each color of OR and GR, the color difference between each image constituting the reference image of each color and blank paper (distance ΔE between two colors in the CIE-L ^* a ^* b ^* color space). Is stored. More specifically, the reference value storage unit 47 has a color difference ΔEOR1 to ΔEOR8 between the eight images constituting the orange reference image SOR and the blank paper, and a color difference ΔEGR1 between the eight images constituting the green reference image SGR and the blank paper. ~ EGR8 are stored. In FIG. 8, the larger the image number value in each reference image, the higher the image density (or the greater the color difference from the blank paper).

  The Y-B characteristic acquisition unit 41 determines the relationship between the density DY1 to DY8 of the yellow reference image SY and the output IB of the B sensor 11B corresponding to the yellow reference image SY based on the input yellow reference data Y (B). Output as current characteristics Y-B. Here, Y and B have a complementary color relationship, and the output IB of the B sensor 11B changes most sensitively among the RGB colors with respect to the density change of the yellow image.

  Based on the input magenta reference data M (G), the MG characteristic acquisition unit 42 determines the relationship between the densities DM1 to DM8 of the magenta reference image SM and the output IG of the G sensor 11G corresponding to the magenta reference image SM. Output as current characteristics MG. Here, M and G are in a complementary color relationship, and the output IG of the G sensor 11G among the RGB colors changes most sensitively to the density change of the magenta image.

  The CR characteristic acquisition unit 43 determines the relationship between the densities DC1 to DC8 of the cyan reference image SC and the output IR of the R sensor 11R corresponding to the cyan reference image SC based on the input cyan reference data C (R). Output as current characteristics CR. Here, C and R are in a complementary color relationship, and the output IR of the R sensor 11R among the RGB colors changes most sensitively to the change in density of the cyan image.

  Based on the input black reference data K (G), the KG characteristic acquisition unit 44 determines the relationship between the density DK1 to DK8 of the black reference image SK and the output IG of the G sensor 11G corresponding to the black reference image SK as black. Output as current characteristics KG. Note that the outputs of the R sensor 11R, the G sensor 11G, and the B sensor 11B all change sensitively with respect to the density change of the black image, but in the present embodiment, the G sensor 11G corresponding to the RGB center wavelength. The output IG is used.

  FIG. 9A shows a configuration example of the OR-ΔEOR characteristic acquisition unit 45 shown in FIG. The OR-ΔEOR characteristic acquisition unit 45 includes a ΔEOR association unit 51, an OR output calculation unit 52, and an OR weighting coefficient storage unit 53.

  The ΔEOR association unit 51 includes an output IR of the R sensor 11R, an output IG of the G sensor 11G, an output IB of the B sensor 11B, and a reference value storage unit that constitute the input orange reference data OR (R, G, B). The color difference ΔEOR (ΔEOR1 to ΔEOR8) input from 47 is received. The ΔEOR associating unit 51 associates these outputs IR, IG, and IB with the color differences ΔEOR1 to ΔEOR8, respectively, and obtains the obtained orange R current characteristic IR-ΔEOR, orange G current characteristic IG-ΔEOR, and orange B current condition. The characteristic IB-ΔEOR is output.

  The OR output calculation unit 52 includes an orange R current characteristic IR-ΔEOR, an orange G current characteristic IG-ΔEOR, an orange B current characteristic IB-ΔEOR, and a weighting coefficient W corresponding to each RGB color read from the OR weighting coefficient storage unit 53. And the obtained orange current state characteristic OR-ΔEOR is output.

  As shown in FIG. 9B, the OR weighting coefficient storage unit 53 stores three weighting coefficients WROR, WGOR, and WBOR corresponding to RGB colors. In the following description, each coefficient is referred to as an orange R coefficient WROR, an orange G coefficient WGOR, and an orange B coefficient WBOR. Here, since RGB colors are not complementary colors to OR, the outputs IR, IG, and IB of the R sensor 11R, G sensor 11G, and B sensor 11B change with respect to the density change of the orange image. However, among these, the output IG of the G sensor 11G changes most sensitively. Therefore, in the present embodiment, an output IG that is a result of reading the orange reference image SOR by the G sensor 11G is set as a key color (characteristic color), and the orange R coefficient WROR, orange G coefficient WGOR, An LUT (Look Up Table) is used with the orange B coefficient WBOR on the vertical axis. Each coefficient is determined so that WROR + WGOR + WBOR = 1 at each gradation of the output IG.

Then, in the OR output calculation unit 52, based on the output IG in the orange reference data OR (R, G, B), the corresponding orange R coefficient WROR, orange G coefficient WGOR, orange B coefficient WBOR from FIG. 9B. And the orange complementary color output IOR in the orange current state characteristic OR-ΔEOR is obtained using the following calculation formula.
IOR = WROR × IR + WGOR × IG + WBOR × IB (1)

  FIG. 10A shows a configuration example of the GR-ΔEGR characteristic acquisition unit 46 shown in FIG. The GR-ΔEGR characteristic acquisition unit 46 includes a ΔEGR association unit 61, a GR output calculation unit 62, and a GR weighting coefficient storage unit 63.

  The ΔEGR association unit 61 includes an output IR of the R sensor 11R, an output IG of the G sensor 11G, an output IB of the B sensor 11B, and a reference value storage unit that constitute the input green reference data GR (R, G, B). The color difference ΔEGR (ΔEGR1 to ΔEGR8) input from 47 is received. The ΔEGR associating unit 61 associates these outputs IR, IG, and IB with the color differences ΔEGR1 to ΔEGR8, respectively, and obtains the obtained green R current characteristics IR-ΔEGR, green G current characteristics IG-ΔEGR, and green B current conditions. The characteristic IB-ΔEGR is output.

  The GR output calculation unit 62 includes a green R current characteristic IR-ΔEGR, a green G current characteristic IG-ΔEGR, a green B current characteristic IB-ΔEGR, and a weighting coefficient W corresponding to each RGB color read from the GR weighting coefficient storage unit 63. And the obtained green current characteristic GR−ΔEGR is output.

  As shown in FIG. 10B, the GR weighting coefficient storage unit 63 stores three weighting coefficients WRGR, WGGR, and WBGR corresponding to RGB colors. In the following description, each coefficient is referred to as a green R coefficient WRGR, a green G coefficient WGGR, and a green B coefficient WBGR. Here, since each RGB color is not a complementary color to GR, the outputs IR, IG, and IB of the R sensor 11R, G sensor 11G, and B sensor 11B are respectively applied to the density change of the green image as in the case of the orange image. Change. However, among these, the output IR of the R sensor 11R changes most sensitively. Therefore, in the present embodiment, the output IR, which is the result of reading the green reference image SGR by the R sensor 11R, is used as a key color (characteristic color), and the green R coefficient WRGR, the green G coefficient WGGR, The LUT (Look Up Table) is used with the green B coefficient WBGR on the vertical axis. Each coefficient is determined so that WRGR + WGGR + WBGR = 1 at each gradation of the output IR.

Then, in the GR output calculation unit 62, based on the output IR of the green reference data GR (R, G, B), the corresponding green R coefficient WRGR, green G coefficient WGGR, green B coefficient WBGR from FIG. And the green complementary color output IGR in the current green characteristic GR−ΔEGR is obtained using the following calculation formula.
IGR = WRGR × IR + WGGR × IG + WBGR × IB (2)

  Further, as shown in FIG. 5, the scanner correction LUT determination unit 33 receives the current characteristics of each color Y, M, C, K, OR, and GR input from the current characteristic grasping unit 32 and the standard characteristic storage unit 35. Based on the read standard characteristics of the colors Y, M, C, K, OR, and GR, a scanner correction LUT (scanner correction profile) for each of the colors Y, M, C, K, OR, and GR is determined. The scanner correction LUT determination unit 33 outputs the obtained Y scanner correction profile YLS, M scanner correction profile MLS, C scanner correction profile CLS, K scanner correction profile KLS, OR scanner correction profile ORLS, and GR scanner correction profile GRLS. To do. Note that the scanner correction profiles for each color of Y, M, C, K, OR, and GR are configured by a one-dimensional LUT.

  The scanner correction LUT storage unit 34 stores scanner correction profiles for each color Y, M, C, K, OR, and GR input from the scanner correction LUT determination unit 33. Further, when requested by the printer correction LUT setting unit 25, the scanner correction LUT storage unit 34 outputs the scanner correction profiles for these colors Y, M, C, K, OR, and GR.

The standard characteristic storage unit 35 functioning as standard characteristic storage means stores yellow standard characteristics YS, magenta standard characteristics MS, cyan standard characteristics CS, black standard characteristics KS, orange standard characteristics ORS, and green standard characteristics GRS.
Here, the yellow standard characteristic YS indicates the density of the yellow reference image SY and the output IB of the B sensor 11B for the yellow reference image SY when the yellow reference image SY is read by the scanner 10 having the target sensitivity characteristic. It is a correspondence. The magenta standard characteristic MS associates each density of the magenta reference image SM with the output IG of the G sensor 11G with respect to the magenta reference image SM when the scanner 10 having the target sensitivity characteristic reads the magenta reference image SM. Is. The cyan standard characteristic CS associates each density of the cyan reference image SC with the output IR of the R sensor 11R with respect to the cyan reference image SC when the scanner 10 having the target sensitivity characteristic is read. Is. The black standard characteristic KS correlates each density of the black reference image SK and the output IG of the G sensor 11G with respect to the black reference image SK when the black reference image SK is read by the scanner 10 having the target sensitivity characteristic. Is. The orange standard characteristic ORS is an R sensor 11R and a G sensor 11G corresponding to the orange reference image SOR, each color difference of the blank paper, and the orange reference image SOR when the orange reference image SOR is read by the scanner 10 having a target sensitivity characteristic. The output IR, IG, and IB of each of the B sensors 11B are associated with the orange complementary color output IOR obtained by performing the weighting calculation with the respective weighting coefficients W shown in FIG. 9B. The green standard characteristic GRS is an R sensor 11R and a G sensor 11G corresponding to the green reference image SGR and each color difference of the green reference image SGR and the green reference image SGR when the green reference image SGR is read by the scanner 10 having a target sensitivity characteristic. , The output of each of the B sensors 11B is associated with the green complementary color output IGR obtained by performing the weighting calculation with each weighting coefficient W shown in FIG. 10B.

  FIG. 11 is a diagram illustrating a configuration example of the scanner correction LUT determination unit 33 that functions as a determination unit. The scanner correction LUT determination unit 33 includes a Y scanner correction LUT determination unit 71, an M scanner correction LUT determination unit 72, a C scanner correction LUT determination unit 73, a K scanner correction LUT determination unit 74, an OR scanner correction LUT determination unit 75, and A GR scanner correction LUT determination unit 76 is provided.

  The Y scanner correction LUT determination unit 71 determines a Y scanner correction profile YLS as a first correction characteristic based on the input yellow current characteristic Y-B and the yellow standard characteristic YS. The M scanner correction LUT determination unit 72 determines the M scanner correction profile MLS as the second correction characteristic based on the input magenta current characteristic MG and the magenta standard characteristic MS. The C scanner correction LUT determination unit 73 determines a C scanner correction profile CLS as a third correction characteristic based on the input cyan current characteristic CR and the cyan standard characteristic CS. The K scanner correction LUT determination unit 74 determines a K scanner correction profile KLS as a fourth correction characteristic based on the input black current characteristic KG and the black standard characteristic KS. The OR scanner correction LUT determination unit 75 determines an OR scanner correction profile ORLS as a fifth correction characteristic based on the input orange current characteristic OR-ΔEOR and the orange standard characteristic ORS. The GR scanner correction LUT determination unit 76 determines the GR scanner correction profile GRLS as the fifth correction characteristic based on the input green current characteristic GR−ΔEGR and the green standard characteristic GRS.

FIG. 12 is a block diagram illustrating a configuration example of the printer correction LUT setting unit 25 illustrated in FIG.
The printer correction LUT setting unit 25 includes a data selection unit 81, a printer correction LUT determination unit 82, and a printer correction LUT storage unit 83.

  The data selection unit 81 uses six pieces of data B (Y), G (M), R (C) from the scanner output data S (R, G, B) that is the result of reading the test chart CB input from the scanner 10. ), G (K), R, G, B (OR), R, G, B (GR) are selected and output. In the following description, these are yellow test data B (Y), magenta test data G (M), cyan test data R (C), black test data G (K), orange test data R, G, B, respectively. (OR), referred to as green test data R, G, B (GR).

FIG. 13 schematically shows scanner output data S (R, G, B) when the scanner 10 reads the test chart CB shown in FIG. 13A illustrates the output IR of the R sensor 11R, FIG. 13B illustrates the output IG of the G sensor 11G, and FIG. 13C illustrates the output IB of the B sensor 11B. .
As shown in FIG. 13, yellow test data B (Y) is the result of reading the yellow test image TY by the B sensor 11B, and magenta test data G (M) is the result of reading the magenta test image TM by the G sensor 11G. Data R (C) is a reading result of the cyan test image TC by the R sensor 11R. The black test data G (K) is a result of reading the black test image TK by the G sensor 11G. Further, the orange test data R, G, B (OR) is a result of reading the orange test image TOR by the R sensor 11R, the G sensor 11G, and the B sensor 11B. Furthermore, the green test data R, G, B (GR) is a result of reading the green test image TGR by the R sensor 11R, the G sensor 11G, and the B sensor 11B.

  Also, as shown in FIG. 12, the printer correction LUT determination unit 82 receives test data for each color Y, M, C, K, OR, and GR input from the data selection unit 81, and the scanner correction LUT setting unit 24. Printer correction LUT for each color of Y, M, C, K, OR, GR is determined based on the scanner correction profile of each color of Y, M, C, K, OR, GR read from the scanner correction LUT storage unit 34 To do. The printer correction LUT determination unit 82 outputs the obtained Y printer correction profile YLP, M printer correction profile MLP, C printer correction profile CLP, K printer correction profile KLP, OR printer correction profile ORLP, and GR printer correction profile GRLP. To do. The printer correction profiles for each color of Y, M, C, K, OR, and GR are each configured with a one-dimensional LUT.

  The printer correction LUT storage unit 83 stores Y, M, C, K, OR, and GR printer correction profiles input from the printer correction LUT determination unit 82. The printer correction LUT storage unit 83 outputs printer correction profiles for these colors Y, M, C, K, OR, and GR when requested by the gradation correction unit 22.

  FIG. 14 is a diagram illustrating a configuration example of the printer correction LUT determination unit 82. The printer correction LUT determination unit 82 includes a Y printer correction LUT determination unit 91, an M printer correction LUT determination unit 92, a C printer correction LUT determination unit 93, a K printer correction LUT determination unit 94, an OR printer correction LUT determination unit 95, and a GR. A printer correction LUT determination unit 96 and a created gradation storage unit 97 are provided.

  The creation gradation storage unit 97 sets the creation gradation of each image when creating a test image of each color of Y, M, C, K, OR, and GR when creating the test chart CB shown in FIG. I remember it. In this embodiment, the printer 20 can form an image with 8 bits, that is, 256 gradations, and the gradation steps of the images constituting the test images of the respective colors are set in common. For this reason, the created gradation storage unit 97 stores 24 gradation data common to each color.

  The Y printer correction LUT determination unit 91 creates a Y printer correction profile YLP based on the input yellow test data B (Y) and the like. The Y printer correction LUT determination unit 91 includes a Y association unit 91a, a Y data correction unit 91b, and a Y-LUT determination unit 91c. The Y association unit 91a associates the input yellow test data B (Y) with the gradation data read from the created gradation storage unit 97, and outputs the obtained yellow data YD1. The Y data correction unit 91b corrects the input yellow data YD1 using the Y scanner correction profile YLS read from the scanner correction LUT storage unit 34, and outputs the corrected yellow data YD2. The Y-LUT determination unit 91c creates and outputs a Y printer correction profile YLP based on the input corrected yellow data YD2.

  The M printer correction LUT determination unit 92 creates an M printer correction profile MLP based on the input magenta test data G (M) and the like. The M printer correction LUT determination unit 92 includes an M association unit 92a, an M data correction unit 92b, and an M-LUT determination unit 92c. The M association unit 92a associates the input magenta test data G (M) with the gradation data read from the created gradation storage unit 97, and outputs the obtained magenta data MD1. The M data correction unit 92b corrects the input magenta data MD1 using the M scanner correction profile MLS read from the scanner correction LUT storage unit 34, and outputs the corrected magenta data MD2. The M-LUT determination unit 92c creates and outputs an M printer correction profile YLP based on the input corrected magenta data MD2.

  The C printer correction LUT determination unit 93 creates a C printer correction profile CLP based on the input cyan test data R (C) and the like. The C printer correction LUT determination unit 93 includes a C association unit 93a, a C data correction unit 93b, and a C-LUT determination unit 93c. The C association unit 93a associates the input cyan test data R (C) with the gradation data read from the created gradation storage unit 97, and outputs the obtained cyan data CD1. The C data correction unit 93b corrects the input cyan data CD1 using the C scanner correction profile CLS read from the scanner correction LUT storage unit 34, and outputs corrected cyan data CD2. The C-LUT determination unit 93c creates and outputs a C printer correction profile CLP based on the input cyan data CD2 after correction.

  The K printer correction LUT determination unit 94 creates a K printer correction profile KLP based on the input black test data G (K) or the like. The K printer correction LUT determination unit 94 includes a K association unit 94a, a K data correction unit 94b, and a K-LUT determination unit 94c. The K association unit 94a associates the input black test data G (K) with the gradation data read from the created gradation storage unit 97, and outputs the obtained black data KD1. The K data correction unit 94b corrects the input black data KD1 using the K scanner correction profile KLS read from the scanner correction LUT storage unit 34, and outputs corrected black data KD2. The K-LUT determination unit 94c creates and outputs a K printer correction profile KLP based on the input corrected black data KD2.

  The OR printer correction LUT determination unit 95 creates an OR printer correction profile ORLP based on the input orange test data R, G, B (OR) or the like. The OR printer correction LUT determination unit 95 includes an OR association unit 95a, an OR data correction unit 95b, and an OR-LUT determination unit 95c. The OR association unit 95a associates the input orange test data R, G, B (OR) with the gradation data read from the created gradation storage unit 97, and outputs the obtained orange data ORD1. The OR data correction unit 95b corrects the input orange data ORD1 using the OR scanner correction profile ORLS read from the scanner correction LUT storage unit 34, and outputs corrected orange data ORD2. The OR-LUT determination unit 95c creates and outputs an OR printer correction profile ORLP based on the input corrected orange data ORD2.

  The GR printer correction LUT determination unit 96 creates a GR printer correction profile GRLP based on the input green test data R, G, B (GR) and the like. The GR printer correction LUT determination unit 96 includes a GR association unit 96a, a GR data correction unit 96b, and a GR-LUT determination unit 96c. The GR association unit 96a associates the input green test data R, G, B (GR) with the gradation data read from the created gradation storage unit 97, and outputs the obtained green data GRD1. The GR data correction unit 96b corrects the input green data GRD1 using the GR scanner correction profile GRLS read from the scanner correction LUT storage unit 34, and outputs the corrected green data GRD2. The GR-LUT determination unit 96c creates and outputs a GR printer correction profile GRLP based on the input corrected green data GRD2.

  Note that the functions of the units constituting the scanner correction LUT setting unit 24 and the printer correction LUT setting unit 25 are realized by cooperation of software and hardware resources. That is, a CPU (Central Processing Unit) (not shown) provided in the printer 20 loads a program for realizing the functions of the scanner correction LUT setting unit 24 and the printer correction LUT setting unit 25 from a storage device such as a hard disk to the main memory. To implement each of these functions.

Now, scanner calibration performed before printer calibration will be described in detail.
FIG. 15 is a flowchart showing the flow of processing in scanner calibration.
In the printing system of the present embodiment, when a scanner calibration execution instruction is given from a UI (user interface) provided in the copying machine 1 or the computer terminal 2, the following processing is performed.
In the copying machine 1, first, the scanner adjustment chart CA is set in the scanner 10. Then, the scanner 10 reads the scanner adjustment chart CA using the R sensor 11R, the G sensor 11G, and the B sensor 11B (step 101). Scanner output data S (R, G, B) obtained by reading the scanner adjustment chart CA is input to the scanner correction LUT setting unit 24 of the printer 20. The data distribution unit 31 distributes the scanner output data S (R, G, B) to reference data for each color of Y, M, C, K, OR, and GR (step 102).

  Next, the reference data for each color of Y, M, C, K, OR, and GR is input to the current characteristic grasping unit 32. Then, the current characteristic grasping unit 32 grasps the current characteristic of the scanner 10 for each color of Y, M, C, K, OR, and GR based on the reference data of each color of Y, M, C, K, OR, and GR (step) 103).

  Next, the scanner correction LUT determination unit 33 acquires the standard characteristics of the scanner 10 for each color of Y, M, C, K, OR, and GR from the standard characteristic storage unit 35 (step 104). Then, the scanner correction LUT determination unit 33 uses the current characteristics of the colors Y, M, C, K, OR, and GR input from the current characteristics grasping section 32 and the corresponding standard characteristics of the colors, Y, M , C, K, OR, and GR color scanner correction profiles are created (step 105). Thereafter, the scanner correction LUT storage unit 34 stores the obtained scanner correction profiles for Y, M, C, K, OR, and GR colors (step 106), and completes a series of processing.

Now, the processing of each unit in the above-described scanner calibration will be described more specifically.
FIG. 16 is a diagram for explaining the processing executed by the current characteristic grasping unit 32 of the scanner correction LUT setting unit 24 in step 103. Here, FIG. 16A shows the yellow current state characteristic YB output from the YB characteristic acquisition unit 41, and FIG. 16B shows the magenta current state characteristic M- output from the MG characteristic acquisition unit 42. FIG. 16C shows the cyan current characteristic CR output from the CR characteristic acquisition unit 43, and FIG. 16D shows the black current characteristic K- output from the KG characteristic acquisition unit 44. Each G is illustrated.

  The Y-B characteristic acquisition unit 41 corresponds to the densities DY1 to DY8 (Y density) of the eight yellow reference images constituting the yellow reference image SY read from the reference value storage unit 47 and the yellow reference image SY by the B sensor 11B. Eight output IBs (B outputs) are associated with each other. Next, the Y-B characteristic acquisition unit 41 creates a curve that passes through a plurality of intersections between the density of the paired Y image and the B output, and obtains the yellow current characteristic Y-B shown in FIG. . In the yellow current characteristic Y-B, the B output is high in the region where the Y density is low, and the B output is low in the region where the Y density is high.

  The MG characteristic acquisition unit 42 applies the density DM1 to DM8 (M density) of the eight magenta reference images constituting the magenta reference image SM read from the reference value storage unit 47 and the magenta reference image SM by the G sensor 11G. 8 outputs IG (G output) are associated. Next, the MG characteristic acquisition unit 42 creates a curve that passes through a plurality of intersections between the density of the paired M image and the G output, and obtains the magenta current state characteristic MG shown in FIG. . In the magenta current characteristic MG, the G output is high in a region where the M density is low, and the G output is low in a region where the M density is high.

  The C-R characteristic acquisition unit 43 performs the density DC1 to DC8 (C density) of the eight cyan reference images constituting the cyan reference image SC read from the reference value storage unit 47 and the cyan reference image SC by the R sensor 11R. Eight outputs IR (R output) are associated. Next, the CR characteristic acquisition unit 43 creates a curve that passes through a plurality of intersections of the density of the paired C image and the R output, and obtains the cyan current characteristic CR shown in FIG. . Note that in the cyan current characteristics CR, the R output is high in a region where the C density is low, and the R output is low in a region where the C density is high.

  The KG characteristic acquisition unit 44 applies the density DK1 to DK8 (K density) of the eight black reference images constituting the black reference image SK read from the reference value storage unit 47 and the black reference image SK by the G sensor 11G. 8 outputs IG (G output) are associated. Next, the KG characteristic acquisition unit 44 creates a curve that passes through a plurality of intersections between the density of the paired K image and the G output, and obtains the black current characteristic KG shown in FIG. . In the black current characteristic KG, the G output is high in a region where the K density is low, and the G output is low in a region where the K density is high.

  FIG. 17 is a diagram for explaining the process executed by the OR-ΔEOR characteristic acquisition unit 45 of the current characteristic grasping unit 32 in step 103. Here, FIG. 17A is a chart showing the relationship between the orange reference image SOR, the sensor output in the orange reference data OR (R, G, B), and the corresponding weighting coefficient W, and FIG. The orange current characteristic OR-ΔEOR output from the −ΔEOR characteristic acquisition unit 45 is illustrated.

  The ΔEOR associating unit 51 of the OR-ΔEOR characteristic acquiring unit 45 includes color differences ΔEOR1 to ΔEOR8 (OR color differences) between the eight images constituting the orange reference image SOR read from the reference value storage unit 47 and blank paper, and an R sensor. Eight output IRs (specifically, IROR1 to IROR8: R output) with respect to the orange reference image SOR by 11R are associated with each other to obtain the orange R current characteristic IR-ΔEOR. Further, the ΔEOR association unit 51 associates the color differences ΔEOR1 to ΔEOR8 with the eight output IGs (specifically, IGOR1 to IGOR8: G output) for the orange reference image SOR by the G sensor 11G, and the orange G current state A characteristic IG-ΔEOR is obtained. Further, the ΔEOR associating unit 51 associates the color differences ΔEOR1 to ΔEOR8 with eight outputs IB (specifically, IBOR1 to IBOR8: B output) for the orange reference image SOR by the B sensor 11B. The characteristic IB-ΔEOR is obtained. The orange R current characteristic IR-ΔEOR, the orange G current characteristic IG-ΔEOR, and the orange B current characteristic IB-ΔEOR each have eight pairs of data.

  Next, the OR output calculation unit 52 of the OR-ΔEOR characteristic acquisition unit 45 calculates an orange complementary color output IOR for each image number (for each color difference ΔEOR) of the orange reference image SOR. More specifically, for example, in the case of image number 1 (color difference ΔEOR1), the OR output calculation unit 52 receives the orange R coefficient WROR (WROR1) and orange G corresponding to the sensor output IG = IROR1 from the OR weighting coefficient storage unit 53. The coefficient WGOR (WGOR1) and the orange B coefficient WBOR (WBOR1) are read out. Then, the OR output calculation unit 52 calculates an orange complementary color output IOR for the color difference ΔEOR1 according to the equation (1). The OR output calculation unit 52 calculates the orange complementary color output IOR using the same method for the other image numbers 2 to 8 (color differences ΔEOR2 to ΔEOR8).

  Then, the OR output calculation unit 52 associates the eight color differences ΔEOR1 to ΔEOR8 with the eight orange complementary color outputs IOR obtained by the above calculation. Next, the OR output calculation unit 52 creates a curve that passes through a plurality of intersections between the color difference (OR color difference) of the paired OR image with the blank sheet and the orange complementary color output IOR, and the orange shown in FIG. The current characteristic OR-ΔEOR is obtained. In the orange current characteristic OR-ΔEOR, the OR complementary color output is high in the region where the OR color difference is small, and the OR complementary color output is low in the region where the OR color difference is large.

  Further, FIG. 18 is a diagram for explaining the processing executed by the GR-ΔEGR characteristic acquisition unit 46 of the current characteristic grasping unit 32 in step 103. Here, FIG. 18A is a chart showing the relationship between the green reference image SGR, the sensor output in the green reference data GR (R, G, B), and the corresponding weighting coefficient W, and FIG. 18B is the GR. The green present state characteristic GR−ΔEGR output from the −ΔEGR characteristic acquisition unit 46 is illustrated.

  The ΔEGR association unit 61 of the GR-ΔEGR characteristic acquisition unit 46 includes color differences ΔEGR1 to ΔEGR8 (GR color difference) between the eight images constituting the green reference image SGR read from the reference value storage unit 47 and blank paper, and an R sensor. The green R current characteristic IR-ΔEGR is obtained by associating eight output IRs (specifically, IRGR1 to IRGR8: R output) with respect to the green reference image SGR by 11R. Further, the ΔEGR associating unit 61 associates the color differences ΔEGR1 to ΔEGR8 with eight output IGs (specifically, IGGR1 to IGGR8: G output) for the green reference image SGR by the G sensor 11G. A characteristic IG-ΔEGR is obtained. Further, the ΔEGR associating unit 61 associates the color differences ΔEGR1 to ΔEGR8 with the eight outputs IB (specifically, IBGR1 to IBGR8: B output) for the green reference image SGR by the B sensor 11B, and the current state of Green B The characteristic IB-ΔEGR is obtained. The green R current characteristic IR-ΔEGR, the green G current characteristic IG-ΔEGR, and the green B current characteristic IB-ΔEGR each have eight sets of paired data.

  Next, the GR output calculation unit 62 of the GR-ΔEGR characteristic acquisition unit 46 calculates a green complementary color output IGR for each image number (for each color difference ΔEGR) of the green reference image SGR. More specifically, for example, in the case of image number 1 (color difference ΔEGR1), the GR output calculation unit 62 receives, from the GR weighting coefficient storage unit 63, a green R coefficient WRGR (WRGR1), green G corresponding to sensor output IR = IRGR1. The coefficient WGGR (WGGR1) and the green B coefficient WBGR (WBGR1) are read out. Then, the GR output calculation unit 62 calculates a green complementary color output IGR for the color difference ΔEGR1 according to the equation (2). The GR output calculation unit 62 calculates the green complementary color output IGR using the same method for the other image numbers 2 to 8 (color differences ΔEGR2 to ΔEGR8).

  Then, the GR output calculation unit 62 associates the eight color differences ΔEGR1 to ΔEGR8 with the eight green complementary color outputs IGR obtained by the above calculation. Next, the GR output calculation unit 62 creates a curve passing through a plurality of intersections between the color difference (GR color difference) of the paired GR image with the blank sheet and the green complementary color output IGR, and the green shown in FIG. The current characteristic GR-ΔEGR is obtained. Note that, in the green current characteristic GR−ΔEGR, the GR complementary color output is high in a region where the GR color difference is small, and the GR complementary color output is low in a region where the GR color difference is large.

  FIGS. 19 and 20 are diagrams for explaining processing executed by the scanner correction LUT determination unit 33 of the scanner correction LUT setting unit 24 in steps 104 and 105 described above. 19A is executed by the Y scanner correction LUT determination unit 71, FIG. 19B is executed by the M scanner correction LUT determination unit 72, and FIG. 19C is executed by the C scanner correction LUT determination unit 73. The process to be performed is illustrated. 20A is executed by the K scanner correction LUT determination unit 74, FIG. 20B is executed by the OR scanner correction LUT determination unit 75, and FIG. 20C is executed by the GR scanner correction LUT determination unit 76. The process is illustrated.

  To the Y scanner correction LUT determination unit 71, the current yellow property Y-B shown in FIGS. 19A and 19A is input from the current property grasping unit 32. Further, the yellow standard characteristic YS shown in FIGS. 19A and 19B is also input from the standard characteristic storage unit 35 to the Y scanner correction LUT determination unit 71. Then, based on both of these, the Y scanner correction LUT determination unit 71 associates the input / output characteristics with each other so that the yellow current characteristic YB matches the yellow standard characteristic YS, and Y shown in FIGS. A scanner correction profile YLS is created. The Y scanner correction profile YLS is a one-dimensional LUT in which the yellow input gradation (Y input gradation) and the output gradation (Y output gradation) in the scanner 10 are associated one-to-one.

  The magenta current characteristic MG shown in FIGS. 19 (b) and (1) is input to the M scanner correction LUT determination unit 72 from the current characteristic grasping unit 32. Further, the M scanner correction LUT determination unit 72 also receives the magenta standard characteristic MS shown in FIGS. 19B and 19B from the standard characteristic storage unit 35. Then, based on both of these, the M scanner correction LUT determination unit 72 associates the input / output characteristics so that the magenta current characteristic MG matches the magenta standard characteristic MS, and M shown in FIGS. A scanner correction profile MLS is created. The M scanner correction profile MLS is a one-dimensional LUT in which the magenta input gradation (M input gradation) and the output gradation (M output gradation) of the scanner 10 are associated one-to-one.

  The cyan current characteristic CR shown in FIGS. 19C and 19C is input to the C scanner correction LUT determination unit 73 from the current characteristic grasping unit 32. Further, the cyan standard characteristic CS shown in FIGS. 19C and 19B is also input to the C scanner correction LUT determination unit 73 from the standard characteristic storage unit 35. Then, based on both of these, the C scanner correction LUT determination unit 73 associates the input / output characteristics with each other so that the cyan current characteristic CR matches the cyan standard characteristic CS, and the C scanner correction LUT determination unit 73 performs C shown in FIGS. A scanner correction profile CLS is created. The C scanner correction profile CLS is a one-dimensional LUT in which the cyan input gradation (C input gradation) and the output gradation (C output gradation) in the scanner 10 are associated one-to-one.

  The black current characteristic KG shown in FIGS. 20A and 20A is input to the K scanner correction LUT determination unit 74 from the current characteristic grasping unit 32. Further, the black standard characteristic KS shown in FIGS. 20A and 20B is also input from the standard characteristic storage unit 35 to the K scanner correction LUT determination unit 74. Then, the K scanner correction LUT determination unit 74 associates the input / output characteristics with each other so that the black current characteristic KG matches the black standard characteristic KS based on both of them, and K shown in FIGS. A scanner correction profile KLS is created. The K scanner correction profile KLS is a one-dimensional LUT in which the black input gradation (K input gradation) and the output gradation (K output gradation) in the scanner 10 are associated one-to-one.

  The orange current state characteristic OR-ΔEOR shown in FIGS. 20B and 20A is input to the OR scanner correction LUT determination unit 75 from the current characteristic grasping unit 32. Further, the orange standard characteristic ORS shown in FIGS. 20B and 20B is also input from the standard characteristic storage unit 35 to the OR scanner correction LUT determination unit 75. Based on these, the OR scanner correction LUT determination unit 75 associates the input / output characteristics with each other so that the orange current characteristic OR-ΔEOR matches the orange standard characteristic ORS, and the OR shown in FIGS. A scanner correction profile ORLS is created. The OR scanner correction profile ORLS is a one-dimensional LUT in which the orange input gradation (OR input gradation) and the output gradation (OR output gradation) in the scanner 10 are associated one-to-one.

  The green current characteristic GR-ΔEGR shown in FIGS. 20C and 20C is input to the GR scanner correction LUT determination unit 76 from the current characteristic grasping unit 32. Further, the green standard characteristic GRS shown in FIGS. 20C and 20B is also input from the standard characteristic storage unit 35 to the GR scanner correction LUT determination unit 76. Then, based on both of these, the GR scanner correction LUT determination unit 76 associates the input / output characteristics with each other so that the green current characteristic GR-ΔEGR matches the green standard characteristic GRS, and the GR shown in FIGS. A scanner correction profile GRLS is created. Note that the GR scanner correction profile GRLS is a one-dimensional LUT in which the input gradation (GR input gradation) and the output gradation (GR output gradation) of the scanner 10 are associated one-to-one.

Next, printer calibration performed after the above-described scanner calibration will be described in detail.
FIG. 21 is a flowchart showing the flow of processing in printer calibration.
In the printing system, when an output instruction of the test chart CB is issued from the UI provided in the copying machine 1 or the computer terminal 2, the printer 20 uses the image forming unit 23 to print Y, M, C, K, A test chart CB on which a test image of each color of OR and GR is formed is output (step 201). Next, the output test chart CB is set in the scanner 10. Then, the scanner 10 reads the test chart CB using the R sensor 11R, the G sensor 11G, and the B sensor 11B (step 202). Scanner output data S (R, G, B) obtained by reading the test chart CB is input to the printer correction LUT setting unit 25 of the printer 20. The data selection unit 81 selects test data for each color of Y, M, C, K, OR, and GR from the scanner output data S (R, G, B) (step 203).

  Next, the printer correction LUT determination unit 82 acquires scanner correction profiles for each color of Y, M, C, K, OR, and GR from the scanner correction LUT storage unit 34 (step 204). Further, the printer correction LUT determination unit 82 uses the test data for each color Y, M, C, K, OR, and GR input from the data selection unit 81 and the scanner correction profile for the corresponding color to generate Y, A printer correction profile for each color of M, C, K, OR, and GR is created (step 205). Thereafter, the printer correction LUT storage unit 83 stores the obtained printer correction profiles of Y, M, C, K, OR, and GR colors (step 206), and completes a series of processes.

Now, the processing in printer calibration will be described more specifically.
FIGS. 22 and 23 are diagrams for explaining the processing executed by the printer correction LUT determination unit 82 of the printer correction LUT setting unit 25 in steps 203 and 204 described above. Here, FIG. 22A is executed by the Y printer correction LUT determination unit 91, FIG. 22B is executed by the M printer correction LUT determination unit 92, and FIG. 22C is executed by the C printer correction LUT determination unit 93. The process to be performed is illustrated. 23A is executed by the K printer correction LUT determination unit 94, FIG. 23B is executed by the OR printer correction LUT determination unit 95, and FIG. 23C is executed by the GR printer correction LUT determination unit 96. The process is illustrated.

  In the Y printer correction LUT determination unit 91, yellow test data B (Y) corresponding to 24 yellow test images TY is input from the data selection unit 81 to the Y association unit 91a. In addition, the created gradation storage unit 97 also receives the created gradations (24) of the yellow test image TY from the created gradation storage unit 97. Then, the Y association unit 91a associates the two and executes a complementing process to create yellow data YD1 shown in FIGS.

Further, the Y data correction unit 91b receives the yellow data YD1 shown in FIGS. 22A and 22A from the Y association unit 91a and the Y scanner shown in FIGS. 22A and 22B from the scanner correction LUT storage unit 34. A correction profile YLS is input. Then, the Y data correction unit 91b performs output correction of the yellow data YD1 using the Y scanner correction profile YLS, and creates corrected yellow data YD2 shown in FIGS.
After that, the Y-LUT determination unit 91c performs an operation so that the relationship between the Y input gradation and the B output becomes linear in the corrected yellow data YD2 input from the Y data correction unit 91b, and FIG. a) A Y printer correction profile YLP shown in (4) is created. The Y printer correction profile YLP is a one-dimensional LUT in which the Y input gradation that is the yellow input gradation and the Y output gradation that is the output gradation in the printer 20 are associated one-to-one.

  In the M printer correction LUT determination unit 92, magenta test data G (M) corresponding to 24 magenta test images TM is input from the data selection unit 81 to the M association unit 92a. In addition, the M associating unit 92a also receives the created gradations (24) of the magenta test image TM from the created gradation storage unit 97. Then, the M associating unit 92a associates the two and executes complement processing to create magenta data MD1 shown in FIGS.

Further, the M data correction unit 92b receives the magenta data MD1 shown in FIGS. 22B and 22A from the M association unit 92a and the M scanner shown in FIGS. 22B and 22B from the scanner correction LUT storage unit 34. A correction profile MLS is input respectively. Then, the M data correction unit 92b performs output correction of the magenta data MD1 using the M scanner correction profile MLS, and generates the corrected magenta data MD2 shown in FIGS.
After that, the M-LUT determination unit 92c performs an operation so that the relationship between the M input gradation and the G output is linear in the corrected magenta data MD2 input from the M data correction unit 92b, as shown in FIG. b) Create an M printer correction profile MLP shown in (4). The M printer correction profile MLP is a one-dimensional LUT in which the M input gradation, which is the magenta input gradation in the printer 20, and the M output gradation, which is the output gradation, are associated one-to-one.

  In the C printer correction LUT determination unit 93, cyan test data R (C) corresponding to 24 cyan test images TC is input from the data selection unit 81 to the C association unit 93a. In addition, the C gradation unit 93 a also receives the created gradations (24) of the cyan test image TC from the created gradation storage unit 97. Then, the C associating unit 93a associates the two and executes complement processing to create cyan data CD1 shown in FIGS. 22 (c) and (1).

Also, the C data correction unit 93b receives the cyan data CD1 shown in FIGS. 22C and 22C from the C association unit 93a and the C scanner shown in FIGS. 22C and 22B from the scanner correction LUT storage unit 34. A correction profile CLS is input respectively. Then, the C data correction unit 93b performs output correction of the cyan data CD1 using the C scanner correction profile CLS, and generates corrected cyan data CD2 shown in FIGS.
Thereafter, the C-LUT determination unit 93c performs an operation so that the relationship between the C input gradation and the R output is linear in the corrected cyan data CD2 input from the C data correction unit 93b, as shown in FIG. c) A C printer correction profile CLP shown in (4) is created. The C printer correction profile CLP is a one-dimensional LUT in which the C input gradation that is the cyan input gradation and the C output gradation that is the output gradation in the printer 20 are associated one-to-one.

  In the K printer correction LUT determination unit 94, black test data G (K) corresponding to 24 black test images TK is input from the data selection unit 81 to the K association unit 94a. In addition, the K gradation unit 94a also receives the generation gradations (24) of the black test image TK from the generation gradation storage unit 97. Then, the K associating unit 94a associates the two and executes a complementing process to create black data KD1 shown in FIGS. 23 (a) and (1).

The K data correction unit 94b receives black data KD1 shown in FIGS. 23 (a) and (1) from the K association unit 94a, and the K scanner shown in FIGS. 23 (a) and (2) from the scanner correction LUT storage unit 34. The correction profiles KLS are input respectively. Then, the K data correction unit 94b performs output correction of the black data KD1 using the K scanner correction profile KLS, and generates corrected black data KD2 shown in FIGS.
After that, the K-LUT determination unit 94c performs an operation so that the relationship between the K input gradation and the G output becomes linear in the corrected black data KD2 input from the K data correction unit 94b, as shown in FIG. a) A K printer correction profile KLP shown in (4) is created. The K printer correction profile KLP is a one-dimensional LUT in which the K input gradation that is the black input gradation and the K output gradation that is the output gradation in the printer 20 are associated one-to-one.

  In the OR printer correction LUT determination unit 95, orange test data R, G, B (OR) corresponding to 24 orange test images TOR is input from the data selection unit 81 to the OR association unit 95a. Further, the created gradations (24) of the orange test image TOR are also input to the OR association unit 95a from the created gradation storage unit 97. Then, the OR association unit 95a associates the two and executes complement processing to create orange data ORD1 shown in FIGS.

Further, the OR data correction unit 95b receives the orange data ORD1 shown in FIGS. 23 (b) (1) from the OR association unit 95a, and the OR scanner shown in FIGS. 23 (b) (2) from the scanner correction LUT storage unit 34. The correction profiles ORLS are input respectively. Then, the OR data correction unit 95b performs output correction of the orange data ORD1 using the OR scanner correction profile ORLS, and generates corrected orange data ORD2 shown in FIGS.
Thereafter, the OR-LUT determination unit 95c makes the relationship between the OR input gradation and each of the R output, the G output, and the B output linear in the corrected orange data ORD2 input from the OR data correction unit 95b. An arithmetic operation is performed to create an OR printer correction profile ORLP shown in FIGS. The OR printer correction profile ORLP is a one-dimensional LUT in which the OR input gradation, which is the OR input gradation in the printer 20, and the OR output gradation, which is the output gradation, are associated one-to-one.

  In the GR printer correction LUT determination unit 96, green test data R, G, B (GR) corresponding to 24 green test images TGR are input from the data selection unit 81 to the GR association unit 96a. Also, the created gradation storage unit 97 receives the created gradations (24) of the green test image TGR from the created gradation storage unit 97. Then, the GR associating unit 96a associates the two and executes complement processing to create green data GRD1 shown in FIGS. 23 (c) and (1).

Further, the GR data correction unit 95b receives the green data GRD1 shown in FIGS. 23C and 23A from the GR association unit 96a, and the GR scanner shown in FIGS. 23C and 23B from the scanner correction LUT storage unit 34. The correction profiles GRLS are input respectively. Then, the GR data correction unit 96b performs output correction of the green data GRD1 using the GR scanner correction profile GRLS, and generates corrected green data GRD2 shown in FIGS.
Thereafter, the GR-LUT determination unit 96c makes the relationship between the GR input gradation and each of the R output, the G output, and the B output linear in the corrected green data GRD2 input from the GR data correction unit 96b. The calculation is performed to create a GR printer correction profile GRLP shown in FIGS. The GR printer correction profile GRLP is a one-dimensional LUT in which the GR input gradation that is the GR input gradation in the printer 20 and the GR output gradation that is the output gradation are associated one-to-one.

  The printer correction profiles for each color Y, M, C, K, OR, and GR created in this way and stored in the printer correction LUT storage unit 83 are subjected to gradation correction when an image forming operation is performed in the printer 20. Is read by the unit 22. Then, the gradation correction unit 22 uses the printer correction profile for each color to generate a gradation for the input yellow data Y1, magenta data M1, cyan data C1, black data K1, orange data OR1, and green data GR1. Performs tone correction and outputs. Thereby, it is possible to correct the non-linearity of the density of the image output by the image forming unit 23.

  In this embodiment, the scanner 20 for each color and the printer correction LUT for each color are created in the printer 20 of the copying machine 1. However, the present invention is not limited to this. You may make it create.

1 is a diagram illustrating a configuration example of a print system to which the exemplary embodiment is applied. (A) is a figure which shows the structural example of the chart for scanner adjustment, (b) is a figure which shows the structural example of a test chart, respectively. It is a block diagram which shows the structural example of a scanner. 2 is a block diagram illustrating a configuration example of a printer. FIG. It is a block diagram which shows the structural example of a scanner correction | amendment LUT setting part. (A)-(c) is the figure which showed typically the scanner output data at the time of reading the scanner adjustment chart with a scanner. It is a figure which shows the structural example of a present condition grasping | ascertainment part. It is the figure which illustrated the reference value of each color stored in a reference value storage part. (A) is a figure which shows the structural example of an OR-deltaEOR characteristic acquisition part, (b) is a figure for demonstrating an orange R coefficient, an orange G coefficient, and an orange B coefficient. (A) is a figure which shows the structural example of a GR- (DELTA) EGR characteristic acquisition part, (b) is a figure for demonstrating a green R coefficient, a green G coefficient, and a green B coefficient. It is a figure which shows the structural example of a scanner correction LUT determination part. 6 is a block diagram illustrating a configuration example of a printer correction LUT setting unit. FIG. (A)-(c) is a figure which shows typically the scanner output data at the time of reading a test chart with a scanner. It is a figure which shows the structural example of a printer correction LUT determination part. It is a flowchart which shows the flow of a process in scanner calibration. It is a figure for demonstrating the process performed in the present condition grasping | ascertainment part of a scanner correction | amendment LUT setting part. It is a figure for demonstrating the process performed in the OR-deltaEOR characteristic acquisition part of a present condition characteristic grasping | ascertainment part. It is a figure for demonstrating the process performed by the GR- (DELTA) EGR characteristic acquisition part of a present condition grasping | ascertainment part. FIG. 10 is a diagram (No. 1) for describing processing executed by a scanner correction LUT determination unit of a scanner correction LUT setting unit; FIG. 10 is a diagram (No. 2) for explaining the process executed by the scanner correction LUT determination unit of the scanner correction LUT setting unit. 6 is a flowchart illustrating a processing flow in printer calibration. FIG. 10 is a diagram (No. 1) for describing processing executed by a printer correction LUT determination unit of a printer correction LUT setting unit; FIG. 10 is a diagram (No. 2) for explaining the process executed by the printer correction LUT determination unit of the printer correction LUT setting unit;

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Copy machine, 2 ... Computer terminal, 3 ... Network, 10 ... Scanner, 20 ... Printer, 21 ... Color conversion part, 22 ... Tone correction part, 23 ... Image formation part, 24 ... Scanner correction LUT setting part, 25 ... Printer correction LUT setting section

Claims (13)

Reading means for reading a reference chart on which reference images of yellow, magenta, and cyan are formed as red, green, and blue color images;
Based on the result obtained by reading the reference chart with the reading means, a first characteristic that associates the density of the yellow reference image with the blue read output, the density of the magenta reference image and the green read output A grasping means for grasping a second characteristic that associates the density of the cyan reference image and a third characteristic that associates the density of the cyan reference image with the red read output;
A first correction characteristic for correcting the relationship between the density of the yellow image and the blue reading output is determined from the first characteristic, and the density of the magenta image and the green reading output are determined from the second characteristic. Determining means for determining a second correction characteristic for correcting the relationship between the density of the cyan image and a red read output based on the third characteristic; And a reading characteristic correcting device. A first standard characteristic indicating a standard relationship between the density of the yellow image and the blue read output, a second standard characteristic indicating a standard relationship between the density of the magenta image and the green read output, and cyan A standard characteristic storage means for storing a third standard characteristic indicating a standard relationship between the image density and the red read output;
The determining means determines the first correction characteristic from the first characteristic and the first standard characteristic, and determines the second correction characteristic from the second characteristic and the second standard characteristic. 2. The reading characteristic correction apparatus according to claim 1, wherein the third correction characteristic is determined from the third characteristic and the third standard characteristic. The reference chart further includes a black reference image in addition to yellow, magenta, and cyan,
The grasping means further has a fourth characteristic in which the density of the black reference image is associated with the read output of red, green, or blue based on the result obtained by reading the reference chart by the reading means. Grasp,
The determination means further determines a fourth correction characteristic for correcting a relationship between a density of a black image and a read output of red, green, or blue from the fourth characteristic. The reading characteristic correction apparatus according to 1. The reference chart further includes reference images of spot colors other than yellow, magenta, cyan, and black,
The grasping means further grasps a fifth characteristic in which the reference image of the spot color is associated with the read output of red, green, and blue based on the result obtained by reading the reference chart by the reading means. ,
The determination means further determines a fifth correction characteristic for correcting the relationship between the density of the spot color image and the read output of red, green, and blue from the fifth characteristic. The reading characteristic correction apparatus according to 1. The grasping means determines any one of red, green, and blue as a key color, associates the read output of the key color with the read output of two colors other than the key color, and the fifth characteristic. The reading characteristic correcting apparatus according to claim 4, wherein 5. The reading characteristic correcting apparatus according to claim 4, wherein the grasping unit grasps the fifth characteristic by weighting each read output of red, green, and blue with respect to the reference image of the spot color. A scanner that reads the original image as a color image;
A printer for forming a color image using a plurality of color materials as a recording material;
A first chart in which a reference image of the same color as the color materials of the plurality of colors is formed;
Scanner input / output characteristics in which the density of each color constituting the reference image and the read output corresponding to the complementary color of each color are associated with each other from the first color image data obtained by reading the first chart with the scanner. And a scanner correction characteristic setting unit for setting a scanner correction characteristic for correcting the scanner input / output characteristic,
A second chart created by the printer using the color materials of the plurality of colors;
In order to correct printer input / output characteristics in the printer based on the second color image data obtained by reading the second chart with the scanner and the scanner correction characteristics set by the scanner correction characteristic setting unit. An image forming system including a printer correction characteristic setting unit that sets the printer correction characteristic of the printer. The scanner reads in the red, green, and blue wavelength regions,
The image forming system according to claim 7, wherein the printer uses a yellow color material, a magenta color material, and a cyan color material as the color materials of the plurality of colors.   The scanner correction characteristic setting unit associates the density of the yellow reference image with the blue read output obtained by reading the yellow reference image as the scanner input / output characteristic, A green read output obtained by reading a magenta reference image is associated, and a density of a cyan reference image is associated with a red read output obtained by reading the cyan reference image. Item 9. The image forming system according to Item 8. The printer further uses a black color material as the color material of the plurality of colors,
The scanner correction characteristic setting unit, as the scanner input / output characteristic, associates a density of a black reference image with a red, green, or blue read output obtained by reading the black reference image. The image forming system according to claim 8. The printer further uses color materials of special colors other than yellow, magenta, cyan, and black as the color materials of the plurality of colors,
The scanner correction characteristic setting unit, as the scanner input / output characteristic, is obtained by combining the density of the reference image of the special color and the read output of red, green, and blue obtained by reading the reference image of the special color. 9. The image forming system according to claim 8, wherein the reading output of the complementary color component of the spot color is associated.   The scanner correction characteristic setting unit, as the scanner input / output characteristic, includes a read output corresponding to a density change of the reference image of the spot color among red, green, and blue read outputs obtained by reading the reference image of the spot color. Determining the color most sensitive to change as a feature color, and creating a read output of a complementary color component of the spot color by associating the read output of the feature color with the read output of two colors other than the feature color The image forming system according to claim 11. Reading a first chart on which a reference image of the same color as a plurality of color materials is formed as a color image with a scanner;
From the first color image data obtained by reading the first chart, a scanner input / output characteristic in which the density of each color constituting the reference image is associated with the read output corresponding to the complementary color of each color is acquired. Setting a scanner correction characteristic for correcting the scanner input / output characteristic;
Forming a second chart with a printer using the color materials of the plurality of colors;
Reading the second chart as a color image with the scanner;
Setting printer correction characteristics for correcting printer input / output characteristics in the printer based on the second color image data obtained by reading the second chart and the set scanner correction characteristics. Calibration method.

Images