JPH10271352A - Color image processor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a color image processor with which plural patterns for color correction at the different levels of lightness can be prepared by performing gamma correction to pattern data for color correction which is composed of the image patterns of different hues concerning certain lightness, based on plural gamma transformation curves. SOLUTION: Assuming that a color correction data storage part 1 holds hue data only concerning one level of lightness, the color correction data storage part 1 holds 6 pieces of data for an RGB data system as a signal system inside the device. For example, when a pattern 4 for color correction at the high level of lightness is required, gamma correction is performed to 6 pieces of pattern data for color correction while using a liquid curve, with which the lightness is improved rather than the actual level, among plural gamma transformation curves generated by a gamma transforming part 2. Then, the light pattern 4 for color correction is prepared by outputting these gamma corrected pattern data for color correction from a recording part 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color image processing apparatus for independently correcting color misregistration.

[0002]

2. Description of the Related Art Conventionally, in an apparatus of this type, a color shift caused by reading and a color shift caused by recording are independently obtained at the time of manufacturing the apparatus by the following method, and a correction coefficient for correcting the color shift is calculated. I was asking. In the case of a facsimile apparatus, a color shift caused by reading occurs when a document is read and transmitted, and a color shift caused by recording occurs when a received document is recorded. When recording read data as in a copy operation, both color shifts occur. In this case, the correction coefficient of the color shift caused by both reading and recording is calculated by multiplying the respective correction coefficients.

The reading unit reads a clear color pattern of the data, compares the digitized data of the read value with the data digitized by a reading device using the same color pattern as a reference in advance, and performs color misregistration. ,
A color correction coefficient for correcting the color shift is calculated.

[0004] In the recording section, reference color numerical data is output on paper, the output result is measured by a color measuring device such as a color difference meter, the color shift is obtained, and correction for correcting the color shift is performed. Calculate the coefficient.

As described above, the color image processing apparatus is shipped in a state where the color misregistration has been corrected. However, the color misregistration is inevitably generated due to a change over time or a variation in the recording medium. For this reason, it is necessary to correct these color shifts, but it is difficult for a user or serviceman to measure the color shifts and calculate the color correction coefficients.

In order to solve such problems, for example, an invention as disclosed in Japanese Patent Application No. 7-305440 has been proposed. According to the present invention, color correction pattern data is stored, the data is output by recording means, and the output is read by reading means to form pattern data, which is compared with the stored color correction pattern data. Then, correction data for correcting the color misregistration is generated.

According to the above-mentioned invention, it is possible to obtain the effect that the color misregistration correction in which the reading means and the recording means are integrated can be obtained.

However, when creating a color correction pattern,
When creating color correction patterns by recording image data corresponding to each pattern in the memory and outputting the data in the recording unit, when creating patterns for multiple lightness in each chromaticity Is
It is necessary to hold the color correction pattern data by the number obtained by multiplying the chromaticity number by the lightness number, and hold the color correction pattern data as the number of color correction patterns increases. It was necessary to increase the memory area for the.

[0009]

As described above, the conventional color image processing apparatus requires a large amount of color correction pattern data, so that the memory capacity must be increased. There is a problem that it takes time to create data in advance.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and the lightness used for auto-calibration can be different without using a large memory capacity for holding color correction pattern data. An object of the present invention is to provide a color image processing apparatus capable of creating a large number of color correction patterns.

[0011]

In order to achieve the above object, according to the first aspect of the present invention, color correction pattern data composed of image pattern data having different hues is gamma-corrected by a plurality of gamma conversion curves. In this way, a configuration for creating a plurality of color correction patterns having different lightness is adopted.

With this configuration, if one set of hue data is provided for a certain lightness, a color correction patch pattern having a plurality of lightnesses can be created only by changing the gamma conversion curve. Therefore, it is not necessary to increase the memory capacity for storing the data, and the memory area can be used effectively.

According to a second aspect of the present invention, in the color image processing apparatus according to the first aspect, color correction is performed by switching a plurality of gamma conversion curves using a gamma conversion unit that adjusts the density of image data. A configuration for gamma-correcting the pattern data for use is adopted.

With such a configuration, an existing gamma conversion curve can be used, so that color correction can be easily performed without providing a new gamma conversion curve for calibration.

According to a third aspect of the present invention, there is provided the color image processing apparatus according to the first or second aspect, wherein the color correction pattern data is gamma-converted to lightness at which the color reproduction range of the recording medium is optimal. In this case, a gamma conversion curve to be corrected is selected.

With such a configuration, even when the optimum brightness of the color correction pattern differs depending on the recording medium, there is no need to prepare a color correction pattern having the optimum brightness in advance according to the recording medium. The capacity can be effectively used, and a color correction patch pattern can be output with optimal brightness for the recording medium.

According to a fourth aspect of the present invention, in the color image processing apparatus of the first to third aspects, the reading marker is recorded on the recording medium simultaneously with the color correction pattern, and the color correction is performed from the recording medium. Read the reading sign with the pattern,
A configuration is adopted in which the reading point of the color correction pattern is recognized based on the reading mark.

With this configuration, the reading point of the color correction pattern can be recognized with reference to the reading marker, so that the calibration can be realized without increasing the reading accuracy of the reading unit more than necessary. it can.

According to a fifth aspect of the present invention, there is provided a storage means for storing color correction pattern data, and a plurality of color correction pattern data having different hues are gamma-corrected by a plurality of gamma conversion curves to thereby provide a plurality of lightness differences. Pattern creating means for creating a color correction pattern, recording means for printing out the created color correction pattern data, reading means for reading the printed color correction pattern, and the read color correction pattern A color correction means for generating correction data for reducing a color difference between the data and the color correction pattern data read from the recording means is employed.

With such a configuration, the apparatus itself can obtain a color shift correction coefficient in which the recording means and the reading means are integrated.

[0021]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a block diagram of a color image processing apparatus having an automatic calibration function according to an embodiment of the present invention. The color correction data storage unit 1 stores color correction pattern data. The gamma conversion section 2 selectively uses a plurality of gamma conversion curves stored in advance to correct the brightness of image data to be printed. The recording unit 3 is a part that records image data to be printed on a recording medium, and outputs color correction pattern data. The image data output by the recording unit 3 is the color correction pattern 4. The reading unit 5 is a unit that reads a document to be read. The reading unit 5 reads the color correction pattern 4 used for auto-calibration and converts it into an electric signal. The color correction coefficient calculating unit 6 calculates a correction coefficient for correcting a color shift between the value of the read color correction pattern 4 and the value of the color correction data stored in the color correction data storage unit 1. The color correction unit 7 holds the color correction coefficients calculated by the color correction coefficient calculation unit 6 and actually performs color correction during a copy operation or the like. The panel 8 receives an operation instruction from the user, and the control unit 9 controls the gamma conversion unit 2 in response to the instruction.

The case where the auto-calibration function is operated in the color image processing apparatus configured as described above will be described. The color correction data storage unit 1 stores a plurality of image data having the same brightness and different hues as color correction patch pattern data. For example, FIG.
As shown in (1), when the hue at one lightness is divided into six, the difference in Hue between the data becomes an interval of 60 degrees, and the data has six hue data.

If the color correction data storage unit 1 holds hue data only for one lightness, the color correction data storage unit 1 stores six data in an RGB data system as a signal system in the apparatus. Will be held.

The creation of the color correction pattern 4 covering a plurality of lightnesses using the above-described six color pattern data is performed as follows. First, when the color correction pattern 4 with high lightness is required, the light curve 10 which is a curve whose lightness is brighter than the actual light among a plurality of gamma conversion curves that can be generated by the gamma conversion unit 2 is used. Gamma correction is performed on the above-described six color correction pattern data. A bright color correction pattern 4 is created by the recording unit 3 outputting the color correction pattern data after the gamma correction.

Next, when outputting the color correction pattern 4 whose brightness is as designed, among the plurality of gamma conversion curves of the gamma conversion unit 2, a normal curve whose brightness is as designed. Using the curve 20, gamma correction is performed on the six color correction pattern data.
The color correction pattern data after the gamma correction is stored in the recording unit 3
Is output, a color correction pattern 4 is created according to the design value.

Finally, when the color correction pattern 4 having a low brightness is required, the dark curve 30, which is a curve in which the brightness becomes darker than the actual brightness, among a plurality of gamma conversion curves of the gamma conversion section 2, is provided. Gamma correction is performed on the above-described six color correction pattern data. After the gamma correction, the recording section 3 outputs the color correction pattern 4 to create the color correction pattern 4 with low brightness.

As described above, by selecting one variable from the plurality of gamma conversion curves held by the gamma conversion unit 2, the color pattern data of a plurality of lightnesses can be stored only by holding the color pattern data of a single lightness. Correction color pattern data can be generated, and color correction patterns 4 having different lightness can be easily created.

For example, as shown in FIG. 2, if gamma correction is performed on a set of six hue data so that the gamma conversion curve becomes L * = 70, the color correction patterns 11 to 16 become L * = 60 if gamma correction is made
If gamma correction is performed on the 26 color correction patterns so that L * = 50, 31 to 36 color correction patterns can be obtained.

The plurality of gamma conversion curves used in the gamma correction are not used only for calibration, but are used by the user to set the density of image data from the panel 8 in a copy operation or the like. The gamma conversion curve generated by the gamma conversion unit of the above can also be used. The configuration of the device can be simplified by using the function of the gamma conversion unit inherently provided in the device for creating a patch pattern for color misregistration correction.

In a color image processing apparatus using a plurality of recording media (plain paper, coated paper, etc.), a color correction patch pattern 4 of lightness is used to optimize the color reproduction range of each recording medium. It is required to calculate a correction coefficient.

According to the present invention, even in such a case, it is not necessary to have separate color correction pattern data for each recording medium. That is, if the color correction data storage unit 1 holds color pattern data of a single brightness,
The gamma conversion section 2 selects an optimum gamma conversion curve for a recording medium and performs gamma correction, whereby a color correction pattern with optimal brightness for each recording medium can be created.

In FIG. 2, reference numerals 8a and 8b denote markers recorded together with the color correction pattern 4 on a recording medium. The marker 8a is long in the same direction as the scanning direction (document feeding direction) in the reading unit 5, and the marker 8b is
Are longer in the direction (sub-scanning direction) orthogonal to the scanning direction. The markers 8a and 8b are used for accurately recognizing the reading points of the color correction pattern 4 when the reading unit 5 reads the color correction pattern 4 output on the recording medium by the recording unit 3. By adding the markers 8a and 8b, the reading unit 5 can correct the point at which the data is obtained by itself even when the document is sent obliquely when reading the color correction pattern, thereby increasing the reading accuracy more than necessary. Calibration can be realized without any need. Here, if the correction range has been exceeded, error information is sent from the panel 8 to the user to prompt the user to perform calibration again.

The color correction pattern 4 output by the recording unit 3 is read by a reading unit 5 and converted into an electric signal. This becomes a read value, and the color correction coefficient calculation unit 6 calculates the color correction coefficient so that the difference between the read value and the data of the same hue held in the color correction data storage unit 1 becomes smaller.

For the calculation of the color correction coefficient, the color correction unit 7
Replaces the value of the lightness component of the color correction pattern 4 read by the reading unit 5 with the lightness component of each hue data held in the color correction data storage unit 1 so that only the chromaticity component is corrected, A method of calculating a color correction coefficient that minimizes the color difference is employed.

According to such a method, the color correction data storage unit can be used for calculating the color correction coefficient without using the normal curve 20 which outputs the designed value in the gamma conversion unit 2 when the color correction pattern 4 is created. Even if the color correction pattern data stored in No. 1 is used, no inconvenience occurs in color correction.

Then, the color correction coefficient obtained by the above method is written in the color correction section 7. For example, when the present invention is applied to a color facsimile apparatus as shown in FIG. 4, color correction coefficients of both a recording unit and a reading unit are written in a color correction unit. Then, when the received image is output from the recording unit, the received image is output after the color misregistration is corrected by the color correction coefficient of the recording unit. When transmitting the transmission original read by the reading unit from the communication unit, the transmission original image is transmitted after the color misregistration of the transmission original image is corrected by the color correction coefficient of the reading unit.

[0037]

As is clear from the above description, according to the present invention, if a set of hue data is provided for a certain lightness, a plurality of color correction patches of a plurality of lightnesses can be obtained simply by changing the gamma conversion curve. Because you can create patterns,
It is not necessary to increase the memory capacity for holding image data, and the memory area can be used effectively.

Further, according to the present invention, since an existing gamma conversion unit can be used, an optimum color correction coefficient can be easily obtained without providing a new gamma conversion unit for calibration. .

Further, according to the present invention, even when the optimum brightness of the color correction pattern differs depending on the recording medium, it is not necessary to prepare a color correction pattern having the optimum brightness in advance according to the recording medium. In addition, the memory capacity can be effectively used, and a color correction patch pattern can be output with optimum brightness for a recording medium.

Further, according to the present invention, since the reading point of the color correction pattern can be recognized with reference to the reading marker, the calibration can be realized without increasing the reading accuracy of the reading unit more than necessary. be able to.

Further, according to the present invention, it is possible to obtain a color shift correction coefficient in which the recording means and the reading means are integrated in the apparatus itself.

[Brief description of the drawings]

FIG. 1 is a block diagram of a color image processing apparatus according to the present invention.

FIG. 2 is a diagram showing a color correction patch pattern;

FIG. 3 is a characteristic diagram showing a gamma conversion curve.

FIG. 4 is a conceptual diagram in which the present invention is applied to a color facsimile machine.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Patch pattern data storage part 2 Gamma conversion part 3 Recording part 4 Patch pattern for color correction 5 Reading part 6 Color correction coefficient calculation part 7 Color correction part

──────────────────────────────────────────────────続 き Continued on front page (51) Int.Cl. ⁶ Identification code FI H04N 1/46 H04N 1/46 Z

Claims (5)

[Claims] 1. A color image, wherein a plurality of color correction patterns having different lightnesses are created by performing gamma correction on color correction pattern data including image pattern data having different hues using a plurality of gamma conversion curves. Processing equipment. 2. The color image according to claim 1, wherein the gamma correction is performed on the color correction pattern data by switching a plurality of gamma conversion curves using a gamma conversion unit that adjusts the shading of the image data. Processing equipment. 3. The color image processing apparatus according to claim 1, wherein a gamma conversion curve for gamma-correcting the color correction pattern data to a brightness at which a color reproduction range of a recording medium is optimal is selected. . 4. A reading marker is recorded on a recording medium simultaneously with the color correction pattern, the reading marker is read together with the color correction pattern from the recording medium, and a reading point of the color correction pattern is recognized based on the reading marker. The color image processing apparatus according to claim 1, wherein 5. A storage means for holding color correction pattern data, and a pattern for creating a plurality of color correction patterns having different lightness by performing gamma correction on the color correction pattern data having different hues using a plurality of gamma conversion curves. Creating means, recording means for printing out the created color correction pattern data, reading means for reading the printed color correction pattern, and reading out the read color correction pattern data and the recording means A color image processing apparatus comprising: a color correction unit configured to generate correction data that reduces a color difference from color correction pattern data.