JP5984466B2 - Arithmetic processing device and arithmetic processing method - Google Patents

Description

  The present invention relates to a correction coefficient calculation device and a correction coefficient calculation method.

  Conventionally, the display device controls the R subpixel, the G subpixel, and the B subpixel according to the input gradation values (digital values) of Red, Green, and Blue, and uses additive color mixing of light. Many colors are reproduced. In recent years, liquid crystal panels have become higher definition, and the pixel pitch of liquid crystal display elements has become smaller. In the case of a high definition device, as disclosed in Patent Document 1, a very large lateral electric field is generated between two adjacent pixel electrodes. Due to the influence of the lateral electric field, light distribution failure of the liquid crystal molecules occurs and the color reproduction characteristics deteriorate. Will shift).

  In order to realize higher color reproduction characteristics, it is necessary to correct the image signal. As a correction method, there is a method using a lookup table (LUT: Look Up Table) in which pixel values (input values) input to a display device are associated with corrected pixel values (output values). The pixel value is, for example, a combination of a red tone value r, a green tone value g, and a blue tone value b. In order to create an LUT, an actual display color (CIE / XYZ value, etc.) corresponding to each grid point (each input value) of the LUT must be measured. In order to improve color reproduction characteristics, the number of grid points in the LUT may be increased (that is, the number of combinations of input values and output values may be increased). However, when the number of grid points of the LUT is large, the number of display colors necessary for creating the LUT also increases, and the display color measurement time becomes long.

  A conventional technique in view of such a problem is disclosed in Patent Document 2, for example. Specifically, Patent Document 2 discloses a method for estimating a display color from each signal level of a set of digital input signals input to a display device using a correction coefficient that represents an additive color mixing characteristic of the display device. Has been. By using this method, it is not necessary to measure all display colors corresponding to the lattice points of the LUT, and the measurement time can be shortened.

However, in the technique disclosed in Patent Document 2, red, green, and blue monochrome image signals (r, 0, 0), (0, g, 0), (0, 0, b) are displayed, and Gray. Only the additive color mixing characteristic with the display of the color mixture image signal (r, g, b) (r = g = b at this time) is taken into consideration. Therefore, it cannot be accurately estimated depending on the display color.
In addition, when a liquid crystal panel of a driving method that generates a horizontal electric field such as an IPS (In Plane Switching) method is used, it is considered that the display quality is deteriorated (the additive color mixing characteristic is deteriorated) due to the influence of the horizontal electric field. For this reason, the display color cannot be accurately estimated, and the color reproduction characteristics of the monitor may not be improved.

JP 2009-128401 A JP 2002-149143 A

The present invention accurately estimates a correction coefficient for correcting a deviation between a virtual color when an ideal additive color mixture is established in a display device and an actual display color of the display device. Therefore, it is an object to provide a technique capable of accurately estimating the display color.

The arithmetic processing apparatus of the present invention
An arithmetic processing device that calculates a correction coefficient for bringing the display color of the display device closer to the target color,
One pixel of the display device is composed of a plurality of sub-pixels corresponding to a plurality of primary colors,
The arithmetic processing unit includes:
First acquisition means for acquiring, for each of a plurality of single-color image data representing any of the plurality of primary colors, a first measurement value that is a measurement value of a display color of the display device;
Second acquisition means for acquiring a second measurement value that is a measurement value of the display color of the display device for each of a plurality of first color mixture image data representing a color mixture obtained by mixing two or more primary colors;
Calculating means for calculating a correction coefficient of each first mixed-color image data based on the plurality of first measurement values and the plurality of second measurement values;
First determination means for determining a correction coefficient of second color mixture image data representing a color mixture different from the plurality of first color mixture image data from each correction coefficient calculated by the calculation means;
When the pixel of the display device has a structure in which a subpixel of a second primary color different from the first primary color is arranged next to one of the subpixels of the first primary color,
The first determining means includes a correction coefficient for the first primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data, the first mixed color image data, and the second mixed color. and the difference in gray scale value of the second primary color during the image data, based on, characterized that you determine the correction factor for the first primary color of the second color mixture image data.

The arithmetic processing method of the present invention includes:
An arithmetic processing method for calculating a correction coefficient for bringing a display color of a display device close to a target value,
One pixel of the display device is composed of a plurality of sub-pixels corresponding to a plurality of primary colors,
The arithmetic processing method is:
A first acquisition step in which a computer acquires a first measurement value that is a measurement value of a display color of the display device for each of a plurality of single-color image data representing one of the plurality of primary colors;
A second acquisition step in which a computer acquires a second measurement value that is a measurement value of a display color of the display device for each of a plurality of first color image data representing a color mixture obtained by mixing two or more primary colors;
A calculation step in which a computer calculates a correction coefficient of each first mixed color image data based on the plurality of first measurement values and the plurality of second measurement values;
A first determination step of determining a correction coefficient of second mixed color image data representing a mixed color different from the plurality of first mixed color image data from each correction coefficient calculated in the calculation step;
When the pixel of the display device has a structure in which a subpixel of a second primary color different from the first primary color is arranged next to one of the subpixels of the first primary color,
In the first determination step, a correction coefficient for the first primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data, the first mixed color image data, and the second mixed color A correction coefficient for the first primary color of the second mixed color image data is determined based on the difference in gradation value of the second primary color between the image data.

  According to the present invention, a correction coefficient for correcting a deviation between a virtual color when an ideal additive color mixture is established in a display device and an actual display color of the display device is accurately estimated. As a result, the display color can be estimated with high accuracy.

Example of functional configuration of display device and color calibration device according to embodiment Example of pixel configuration Example of LUT grid points Example of functional configuration of estimated XYZ value calculation unit An example of how monochrome tone characteristics are created An example of how mixed tone characteristics are created Example of functional configuration of LUT generation unit Example of LUT An example of the processing flow of the color proofing apparatus according to this embodiment Example of functional configuration of display device according to embodiment

Hereinafter, a correction coefficient calculation apparatus and a correction coefficient calculation method according to the present embodiment will be described with reference to the drawings. However, the following embodiments are merely examples, and the present invention is not limited to the following embodiments. For example, an example in which the input image signal is an RGB signal (input RGB signal) will be described below, but the input image signal may be a signal other than an RGB signal such as a YCrCb signal. In this embodiment, an example in which the color value (color value) is an XYZ tristimulus value will be described. However, the color value is a value other than the XYZ tristimulus value such as L ^* a ^* b ^*. Also good.

FIG. 1 shows an example of the functional configuration of the display device 100 and the color calibration device 101 (correction coefficient calculation device) according to the present embodiment.
The display device 100 is, for example, a liquid crystal display device, a plasma display device, an organic EL display device, or the like. The display device 100 includes a display unit 102 and a ROM (Read Only Memory) 103. The display unit 102 corrects (converts) the input RGB signal based on the LUT stored in the ROM 103 and displays an image based on the corrected RGB signal. Until the LUT is created by the color proofing apparatus 101 (and during creation), the display unit 102 displays an image based on the input RGB signal without correcting the input RGB signal.
One pixel of the display device 100 includes a plurality of subpixels corresponding to a plurality of primary colors. In the present embodiment, it is assumed that one pixel is constituted by three (three primary colors) subpixels of an R (red) subpixel, a G (green) subpixel, and a B (blue) subpixel. Specifically, as shown in FIG. 2, the G subpixel is located right next to the R subpixel, the B subpixel is located right next to the G subpixel, and the R subpixel is located right next to the B subpixel. Assume that each sub-pixel is arranged so that is located. However, the pixel is not limited to this. For example, the pixel may be composed of four (four primary colors) sub-pixels including Y (yellow) sub-pixels.

  The LUT is a correction table used in image processing that changes the actual display color of the display device 100 to a color when an ideal additive color mixture is established. LUT lattice points are pixel values (input values) of the input RGB signal, as shown in FIG. The pixel value is a combination of the gradation value r of the R subpixel, the gradation value g of the G subpixel, and the gradation value b of the B subpixel. The LUT represents a corrected pixel value (output value) for each grid point. FIG. 3 shows an example in which the gradation values are 0, 128, and 255. Therefore, the total number of lattice points is 3 × 3 × 3 = 27. The grid points are not limited to the pixel values shown in FIG. The greater the number of grid points, the higher the accuracy of the image processing.

  The measuring device 104 measures the actual display color of the display device 100 (the color on the screen of the display device 100). In this embodiment, an XYZ value (XYZ tristimulus value) is obtained as a measurement value. The display color measurement value (XYZ value) is used to create the LUT. When creating a LUT for a plurality of display devices, a LUT common to the plurality of display devices may be created using the measurement values of one display device, or for each display device, An LUT for the display device may be created using the measured value. Note that since there are individual differences in the XYZ values (the XYZ values differ for each display device), it is desirable that an LUT for the display device is created for each display device using the measurement value of the display device.

  The color proofing apparatus 101 includes an XYZ value acquisition unit 105, an estimated XYZ value calculation unit 106, and an LUT generation unit 107. The color proofing device 101 is a device that causes the display device 100 to perform a predetermined display and generates an LUT from measured values of the actual display color when the predetermined display is performed. Each function of the color proofing apparatus 101 is realized by a computer reading and executing a program stored in a recording medium such as a memory.

  The XYZ value acquisition unit 105 acquires the XYZ value measured by the measurement device 104. Specifically, the XYZ value acquisition unit 105 acquires a measurement value of an actual display color of the display device 100 for each of a plurality of predetermined single-color image signals that drive only one primary color sub-pixel ( Monochromatic value acquisition). Further, the XYZ value acquisition unit 105 performs an actual display color of the display device 100 for each of a plurality of first mixed color image signals that are a plurality of predetermined mixed color image signals that drive two or more primary color subpixels. The measured value is acquired (mixed color value acquisition).

  As shown in FIG. 4, the estimated XYZ value calculation unit 106 includes a single color gradation characteristic creation unit 301, a mixed color gradation characteristic creation unit 302, an additive color mixture correction coefficient calculation unit 303, and an additive color mixture correction unit 304. The estimated XYZ value calculation unit 106 calculates a correction coefficient for correcting a shift between a virtual color when an ideal additive color mixture is established in the display device and an actual display color of the display device 100. calculate. Then, the estimated XYZ value calculation unit 106 performs actual display of the display device 100 for a second mixed color image signal (arbitrary mixed color image signal) in which the combination of gradation values of each primary color is different from the plurality of first mixed color image signals. An XYZ value representing the color is estimated.

  The monochromatic gradation characteristic creating unit 301 creates a gradation characteristic (monochromatic gradation characteristic) from the XYZ values of the monochromatic image signal acquired by the XYZ value acquiring unit 105. For example, the gradation characteristic of R single color is created from the XYZ values when the input value (r, 0, 0) is displayed. The G single color gradation characteristic is created from the XYZ values when the input value (0, g, 0) is displayed. The gradation characteristics of B single color are created from XYZ values when the input value (0, 0, b) is displayed. FIG. 5 shows how the gradation characteristics are created. FIG. 5 shows an example in which XYZ values are acquired for three gradation values of 0, 128, and 255. The gradation characteristic is, for example, an approximate function obtained from the three measurement values obtained for the three gradation values. Specifically, the tone characteristics are an approximate function obtained from three X values, an approximate function obtained from three Y values, and an approximate function obtained from three Z values.

  The mixed color gradation characteristic creation unit 302 creates a gradation characteristic (mixed gradation characteristic) from the XYZ values of the mixed color image signal acquired by the XYZ value acquisition unit 105 in the same manner as the single color gradation characteristic. For example, a color mixture gradation characteristic as shown in FIG. 6 is created.

Here, XYZ values (X (r, g, b), Y (r, g, b), Z (r, g, b)) corresponding to a certain input value (r, g, b) are as follows: It can be calculated by Equation 1. In Equation 1, R (r, g, b) is the R component value of the display color, G (r, g, b) is the G component value, and B (r, g, b) is the B component value.

The R component value, the G component value, and the B component value of the monochrome image signal can be expressed by the following Expression 2.

When an ideal additive color mixture is established, the R component value, G component value, and B component value of the input value (r, g, b) depend only on the r value, the g value, and the b value, respectively. Therefore, the relationship of the following formula 3 is satisfied.

However, since there is a deviation between the actual display color and the color when an ideal additive color mixture is established, correction coefficients coefR (r, g, b), coefG (r, g, Using b) and coefB (r, g, b), the following equation 4 is established. The correction coefficient coefR (r, g, b) is a correction coefficient for R (for r value) (additive color mixture correction coefficient). The correction coefficient coefG (r, g, b) is a correction coefficient for G (for g value). The correction coefficient coefB (r, g, b) is a correction coefficient for B (for b value).

式５を用いてｒ＝ｉ通り、ｇ＝ｊ通り、ｂ＝ｋ通りの入力値（ｒ，ｇ，ｂ）についての補正係数を得る場合には、ｉ×ｊ×ｋ通りのＸＹＺ値が必要となる。 The additive color mixture correction coefficient calculation unit 303, for each of the plurality of first color image signals, displays a display color measurement value based on the first color image signal and a single color of each primary color having the same gradation value as the first color image signal. A correction coefficient is calculated from the display color measurement value based on the image signal. Specifically, the additive color mixture correction coefficient calculation unit 303 calculates a correction coefficient for each of the plurality of first color mixture image signals using the following Expression 5.

In order to obtain correction coefficients for r = i, g = j, and b = k input values (r, g, b) using Equation 5, i × j × k XYZ values are required. It becomes.

  Further, the additive color mixture correction coefficient calculation unit 303 estimates the correction coefficient of the second color mixture image signal from the correction coefficients of the plurality of first color mixture image signals calculated by Expression 5.

As a result of examining the characteristics of the display device, the inventors have a structure in which a pixel of the display device has a second primary color sub-pixel different from the first primary color arranged next to one of the first primary color sub-pixels. In this case, it has been found that the correction coefficient of the first primary color depends only on the gradation value (input value) of the first primary color and the gradation value (input value) of the second primary color. Specifically, when the G subpixel is located right next to the R subpixel, the B subpixel is located right next to the G subpixel, and the R subpixel is located right next to the B subpixel, It has been found that the relationship of Equation 6 is satisfied.

  In the present embodiment, the additive color mixture correction coefficient calculation unit 303 estimates a correction coefficient for the second color mixture image signal for each primary color based on the relationship of Equation 6. Specifically, the first mixed color image signal has the same gradation value as the first primary color and the first mixed color image signal has the same gradation value as the second primary color image signal. The correction coefficient for the primary color is the correction coefficient for the first primary color of the second mixed color image signal.

  Further, in the present embodiment, the additive color mixture correction coefficient calculation unit 303 applies the first color correction coefficient to the first primary color of the first color image signal having the same gradation value as that of the second color image signal. A correction coefficient for the first primary color of the second mixed color image signal is obtained by making corrections due to the difference in gradation value of the second primary color between the first mixed color image signal and the second mixed color image signal.

This will be specifically described below. In the following, the first primary color gradation value of the second mixed color image signal is a, the second primary color gradation value is b, and the second mixed color image signal and the first primary color gradation value are the same. It is assumed that the gradation value of the second primary color of the mixed color image signal is m.
The additive color mixture correction coefficient calculation unit 303 obtains a correction coefficient p from the correction coefficient C1 (n, b) and the correction coefficient C1 (n, m). C1 (x, y) is a correction coefficient for the first primary color of the first mixed color image signal in which the gradation value of the first primary color is x and the gradation value of the second primary color is y. That is, the correction coefficient C1 (n, b) is a value n different from the first primary color gradation value a, and the second primary color gradation value b is the first primary color of the first mixed color image signal. It is a correction coefficient. The correction coefficient C1 (n, m) is a correction coefficient for the first primary color of the first mixed color image signal in which the gradation value of the first primary color is n and the gradation value of the second primary color is m. p is a correction coefficient due to a difference in gradation value of the second primary color between the first mixed color image signal and the second mixed color image signal.
The inventors have found from experiments that the correction coefficient p can be obtained by the following equation (7). In the present embodiment, the additive color mixture correction coefficient calculation unit 303 obtains the correction coefficient p by the following formula 7. Note that p may be prepared in advance for each combination of gradation values of the second primary color.
p = C1 (n, b) / C1 (n, m) (Expression 7)
Then, the additive color mixture correction coefficient calculation unit 303 obtains a correction coefficient C (a, b) for the first primary color of the second color mixture image signal by the following equation 8.
C (a, b) = C1 (a, m) × p (Equation 8)

ｒａｔｅＩ（ａ，ｍ）、ｒａｔｅＩ（ｎ，ｂ）、ｒａｔｅＩ（ｎ，ｍ）は、式５で算出された補正係数であり、例えば、以下の式１０に示すような補正係数である。なお、式１０はＩ＝Ｒの場合の例である。Ｉ＝Ｇ，Ｂの場合については、同様のため、説明は省略する。

ここで、ｎ，ｍ，ｌは、ｒａｔｅＲ（ｎ，ｍ）＝ｃｏｅｆＲ（ｎ，ｍ，ｌ）＝０とならない値である。例えば、ｎ，ｍ，ｌは、図６に示すように、表示色の測定が行われた入力値（ａ＝０，１２８，２５５、ｂ＝０，１２８，２５５、ｎ＝１２８、ｍ＝１２８、ｌ＝０）である。なお、図６の例では、ｎ（ｇ値）＝ｍ（ｒ値）＝１２８としているが、ｎ＝ｍでなくてもよい。例えば、ｎ＝０、ｍ＝１２８、ｌ＝２５５といったように、ｎ、ｍ、ｌは互いに異なる値であってもよい。なお、ｒａｔｅＲ（ａ，ｍ）とｒａｔｅＲ（ｎ，ｂ）とｒａｔｅＲ（ｎ，ｍ）とでｌの値が互いに異なっていてもよい。 In other words, in the present embodiment, the additive color mixture correction coefficient calculation unit 303 calculates the correction coefficient rateI (a, b) (I = R, G, B) of the second color mixture image signal by the following Expression 9.

rateI (a, m), rateI (n, b), and rateI (n, m) are correction coefficients calculated by Expression 5, for example, correction coefficients as shown in Expression 10 below. Equation 10 is an example in the case of I = R. Since the case of I = G, B is the same, the description is omitted.

Here, n, m, and l are values that do not satisfy rateR (n, m) = coefR (n, m, l) = 0. For example, as shown in FIG. 6, n, m, and l are input values (a = 0, 128, 255, b = 0, 128, 255, n = 128, m = 128) for which display color is measured. , L = 0). In the example of FIG. 6, n (g value) = m (r value) = 128 is set, but n may not be m. For example, n, m, and l may be different from each other, such as n = 0, m = 128, and l = 255. Note that the value of l may be different between rateR (a, m), rateR (n, b), and rateR (n, m).

  By performing the processing described above, the number of patterns of input values for measuring XYZ values can be greatly reduced. For example, when obtaining correction coefficients for r = i, g = j, and b = k input values (r, g, b), at least (i × 2 + j × 2 + k × 2) input values. What is necessary is just to measure an XYZ value. Specifically, when the number of grid points of the LUT is 17 (r value) × 17 (g value) × 17 (b value) = 4193, 17 × 3 = 51 patterns for the monochromatic image signal and about the mixed color image signal. 17 × 2 + 17 × 2 + 17 × 2 = 102 kinds of measurements may be performed. By performing the above estimation, correction coefficients corresponding to 4193 input values can be obtained. In the present embodiment, since the correction coefficients of the plurality of first mixed color image signals are used, the correction coefficient of the second mixed color image signal can be estimated with high accuracy.

  The additive color mixture correcting unit 304 estimates the actual display color of the display device 100 for the second mixed color image signal using the correction coefficient estimated by the additive color mixture correction coefficient calculating unit 303 (display color estimation). Specifically, the additive color mixing correction unit 304 calculates an R component value, a G component value, and a B component value from the estimated correction coefficient (correction coefficient for the second mixed color image signal) using Equation 4. Then, the additive color mixture correcting unit 304 calculates an XYZ value from the calculated R component value, G component value, and B component value using Equation 1. As described above, in the present embodiment, the correction coefficient of the second mixed color image signal can be estimated with high accuracy. Therefore, the display color of the second mixed color image signal can be estimated with high accuracy.

The LUT generation unit 107 includes the XYZ values acquired by the XYZ value acquisition unit 105 (measured values for the single color image signal and measured values for the first mixed color image signal), and the XYZ values estimated by the additive color correction unit 304. Is used to generate an LUT. Specifically, the LUT generation unit 107 calculates correction data corresponding to each grid point based on the XYZ value (actual display color of the display device 100) corresponding to each grid point for each grid point of the LUT. To do. Then, the LUT generation unit 107 calculates a corrected pixel value from the correction data for each grid point. Thereafter, the LUT generation unit 107 associates lattice points with correction data, and generates a table representing pixel values after correction for each lattice point as an LUT.
The LUT generation unit 107 includes, for example, a matrix coefficient calculation unit 701, a target XYZ value calculation unit 702, a target difference value calculation unit 703, an XYZ change amount calculation unit 704, and a gradation correction value calculation unit 705 as illustrated in FIG. Have.

  Hereinafter, a method for calculating correction data corresponding to the lattice points of the LUT will be described. Although a general correction data calculation method will be described below, the correction data may be calculated by other methods. Any method may be used as long as the correction data is calculated from the display color value. Hereinafter, a method of calculating correction data for one grid point will be described. The following processing is performed for the number of grid points in the LUT.

First, the matrix coefficient calculation unit 701 calculates a matrix coefficient represented by Expression 11 as a matrix coefficient for converting the pixel value (r, g, b) of the grid point (to be processed) into an XYZ value. As can be seen from Equation 11, the matrix coefficient is a common coefficient between lattice points. Therefore, this process needs to be performed only once when generating the LUT.

Next, the target XYZ value calculation unit 702 calculates a target XYZ value (m_X, m_Y, m_Z) corresponding to the grid point to be processed using the obtained matrix coefficient. The target XYZ value is a target value of XYZ, and is calculated by the following expression 12.

Then, the target difference value calculation unit 703 calculates a difference value between the target XYZ value of the grid point to be processed and the measured or estimated XYZ value using the following Expression 13.

ここで、ΔＸＲ，ΔＹＲ，ΔＺＲはＸＹＺ値のＲ成分の変化量を表し、ΔＸＧ，ΔＹＧ，ΔＺＧはＸＹＺ値のＧ成分の変化量を表し、ΔＸＢ，ΔＹＢ，ΔＺＢはＸＹＺ値のＢ成分の変化量を表す。また、ｗｉｄｔｈは、処理対象の格子点と、当該格子点近傍の格子点との階調値の差分を表す。例えば、処理対象の格子点が入力値（１２８，１２８，１２８）であり、ｗｉｄｔｈ＝１２８であった場合は、入力値（２５５，０，０）、（０，２５５，０）、（０，０，２５５）、（０，０，０）の４つの格子点のＸＹＺ値を用いて変化量が算出される。なお、ｗｉｄｔｈの値は特に限定されない。ｗｉｄｔｈの値によっては、測定や推定をしていない入力値のＸＹＺ値が必要となる場合があるが、そのような場合には、ＸＹＺ値を別途測定ないしは推定すればよい。 Next, the XYZ change amount calculation unit 704 calculates the change amount of the XYZ value of the lattice point to be processed with respect to the XYZ value of the lattice point near the lattice point, using the following formulas 14 to 16.

Here, ΔXR, ΔYR, ΔZR represent the amount of change in the R component of the XYZ value, ΔXG, ΔYG, ΔZG represent the amount of change in the G component of the XYZ value, and ΔXB, ΔYB, ΔZB represent the change in the B component of the XYZ value. Represents an amount. Also, width represents a difference in gradation value between a grid point to be processed and grid points near the grid point. For example, when the grid point to be processed is an input value (128, 128, 128) and width = 128, the input value (255, 0, 0), (0, 255, 0), (0, The amount of change is calculated using the XYZ values of the four lattice points (0, 255) and (0, 0, 0). The width value is not particularly limited. Depending on the width value, an XYZ value of an input value that is not measured or estimated may be required. In such a case, the XYZ value may be separately measured or estimated.

Then, the gradation correction value calculation unit 705 calculates gradation correction values ΔR (r, g, b), ΔG (r, g, b) as correction data from the obtained change amount (change amount of the XYZ value). , ΔB (r, g, b). The gradation correction value ΔR (r, g, b) is a correction value for correcting the r value, ΔG (r, g, b) is a correction value for correcting the g value, and ΔB (r, g, b). Is a correction value for correcting the b value. The gradation correction values ΔR (r, g, b), ΔG (r, g, b), ΔB (r, g, b) are calculated using the following equations 17 and 18.

Next, the gradation correction value calculation unit 705 calculates the corrected gradation value by adding the corresponding gradation correction value to the gradation value of the primary color at the grid point to be processed for each primary color. . Thereby, the corrected pixel value (output value) corresponding to the grid point (input value) is calculated.
By performing the processing described above for each grid point, a corrected pixel value for each grid point is obtained. Then, by associating the corrected pixel value (output value) with each grid point (pre-correction pixel value; input value), an LUT as shown in FIG. 8 can be created. The created LUT is recorded in the ROM 103 of the display device 100. The LUT may be automatically recorded by a control unit (not shown) or may be recorded according to a recording operation by the user. In this embodiment, the correction data is a value to be added to the pixel value (the difference between the pixel value that is the input value and the pixel value that reproduces the color when additive color mixture is established). The data is not limited to this. For example, the correction data may be a value multiplied by a pixel value (a ratio of a pixel value that reproduces a color when an additive color mixture is established with respect to a pixel value that is an input value).

The display device 100 corrects (converts) the input image signal using the LUT generated in this way, and displays an image based on the corrected image signal. For example, among the pixel values of the input image signal, pixel values corresponding to the grid points in the LUT are replaced with output values (corrected pixel values) corresponding to the grid points. For pixel values for which there is no corresponding grid point in the LUT, corrected pixel values are calculated by interpolation. Then, the pixel value of the input image signal is replaced with the corrected pixel value. Thereby, an image with improved color reproduction characteristics can be displayed. Specifically, an image can be displayed in a color when an ideal additive color mixture is established.
The interpolation method is not particularly limited. For example, the interpolation method is a process of selecting eight grid points close to the pixel value of the input image signal from the grid points in the LUT, and combining the pixel values after correction of the selected eight grid points. There may be. The interpolation method is a process of selecting four grid points close to the pixel value of the input image signal from the grid points in the LUT and weighting and combining the corrected pixel values of the selected four grid points. Also good.
In the present embodiment, the LUT represents the corrected pixel value for each grid point, but the present invention is not limited to this. The LUT may represent correction data for each grid point. In that case, the display device 100 may perform a correction process using the correction data for the pixel value of the input image signal (for example, a process of adding the gradation correction value to the pixel value).

  Hereinafter, a processing flow of the color proofing apparatus 101 according to the present embodiment will be described. FIG. 9 is a flowchart showing an example of the processing flow of the color proofing apparatus 101 according to the present embodiment.

In step S901, the measurement device 104 measures the actual display color for the monochromatic image signal and the actual display color for the mixed color image signal (first mixed color image signal). The measurement value is input to the XYZ value acquisition unit 105.
In step S902, the RGB single color gradation characteristic creating unit 301 calculates the gradation characteristic (monochromatic gradation characteristic) for the single color image signal from the measurement values for the single color image signal among the measurement values obtained in step S901. To do.
In step S <b> 903, the RGB color mixture gradation characteristic creating unit 302 uses the measurement value obtained in step S <b> 901 to determine the gradation characteristic (color mixture gradation) for the first color mixture image signal from the measurement value for the first color mixture image signal. Characteristic).
In step S904, the additive color mixture correction coefficient calculation unit 303 calculates a correction coefficient for the first color mixture image signal, and calculates (estimates) a correction coefficient for the second color mixture image signal using the calculation result.
In step S905, the additive color mixture correction unit 304 calculates the second mixed color image signal from the single color gradation characteristic calculated in step S902 and the correction coefficient (the value calculated in step S904) for the second mixed color image signal. XYZ values (actual display colors before correction) are estimated. By performing the processing in step S905, an XYZ value corresponding to each lattice point of the LUT can be obtained, so that the LUT can be generated by the subsequent processing.

In step S906, the matrix coefficient calculation unit 701 calculates a matrix coefficient for converting the pixel value (r, g, b) into an XYZ value.
In step S907, the target XYZ value calculation unit 702 calculates a target XYZ value from the matrix coefficient calculated in step S906 for each lattice point of the LUT. Since the target XYZ value is calculated using the matrix coefficient of Expression 11, the target XYZ value indicates the color when the additive color mixture is established (the XYZ value of the color to be displayed with respect to the input value).
In step S908, the target difference value calculation unit 703 calculates a difference between the measured or estimated XYZ value and the target XYZ value for each lattice point of the LUT.
In step S909, the XYZ change amount calculation unit 704 calculates, for each LUT lattice point, the amount of change of the XYZ value of the lattice point with respect to the XYZ value (measured or estimated value) of a nearby lattice point.
In step S910, the tone correction value calculation unit 705 converts the XYZ values into pixel values (r, g, b) using the amount of change calculated in step S909 for each lattice point of the LUT. (Matrix coefficient of Expression 15) is calculated. Then, the gradation correction value calculation unit 705 calculates correction data for each lattice point of the LUT from the Δ matrix coefficient and the difference value obtained in step S908 (Formula 16). After that, the gradation correction value calculation unit 705 adds correction data to the grid points (input values; pixel values (r, g, b)) for each grid point of the LUT, and the corrected pixel values (output) Value). Thereby, an LUT in which the input value and the output value are associated is created.

  In step S911, a control unit (not shown) records the LUT created in step S910 in the ROM 103 of the display device 100. After recording the LUT, the display device 100 performs image processing (replacement of each pixel value of the input image signal) using the LUT on the input image signal, and displays an image based on the image signal subjected to the image processing. To do. Thereby, an image with improved color reproduction characteristics is displayed.

  As described above, in the present embodiment, the first mixed color image signal and the correction coefficient for the first primary color of the first mixed color image signal having the same gradation value of the first primary color as the second mixed color image signal A correction coefficient for the first primary color of the second mixed color image signal is obtained by making corrections due to the difference in gradation value of the second primary color between the second mixed color image signals. Accordingly, it is possible to accurately estimate a correction coefficient for correcting a deviation between a virtual color when an ideal additive color mixture is established in the display device and an actual display color of the display device. it can. In the present embodiment, since the display color is estimated using the correction coefficient estimated as described above, the display color can be estimated with high accuracy.

  In the present embodiment, an example in which the display device 100 and the color calibration device 101 are independent devices has been described, but the present invention is not limited to this configuration. For example, as illustrated in FIG. 10, the display device 100 may include the measurement device and the color calibration device illustrated in FIG. 1 as a measurement unit 1001 and a color calibration unit 1002, respectively. When a display device is used, the display color changes due to aging. With the configuration as shown in FIG. 10, since the LUT can be updated by the display device alone, user convenience is improved.

101 Color Calibration Device 105 XYZ Value Acquisition Unit 106 Estimated XYZ Value Calculation Unit

Claims (18)

An arithmetic processing device that calculates a correction coefficient for bringing the display color of the display device closer to the target color,
One pixel of the display device is composed of a plurality of sub-pixels corresponding to a plurality of primary colors,
The arithmetic processing unit includes:
First acquisition means for acquiring, for each of a plurality of single-color image data representing any of the plurality of primary colors, a first measurement value that is a measurement value of a display color of the display device;
Second acquisition means for acquiring a second measurement value that is a measurement value of the display color of the display device for each of a plurality of first color mixture image data representing a color mixture obtained by mixing two or more primary colors;
Calculating means for calculating a correction coefficient of each first mixed-color image data based on the plurality of first measurement values and the plurality of second measurement values;
First determination means for determining a correction coefficient of second color mixture image data representing a color mixture different from the plurality of first color mixture image data from each correction coefficient calculated by the calculation means;
When the pixel of the display device has a structure in which a subpixel of a second primary color different from the first primary color is arranged next to one of the subpixels of the first primary color,
The first determining means includes a correction coefficient for the first primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data, the first mixed color image data, and the second mixed color. and the difference in gray scale value of the second primary color during the image data, based on a central processing unit, characterized that you determine the correction factor for the first primary color of the second color mixture image data. The monochromatic image data is image data for driving one primary color sub-pixel;
The first mixed color image data and the second mixed color image data are image data for driving two or more primary color sub-pixels,
The arithmetic processing apparatus according to claim 1, wherein the second mixed color image data is image data in which a combination of gradation values of each primary color is different from the plurality of first mixed color image data. For each of the plurality of first mixed color image data, the calculating means calculates the second measurement value of the first mixed color image data and the first color image data of each primary color having the same gradation value as the first mixed color image data. The arithmetic processing apparatus according to claim 1, wherein a correction coefficient of the first mixed color image data is calculated from one measurement value. The first determination unit is configured to calculate a correction coefficient for the first primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data, and the second mixed color image data and the second primary color image data. by adding a correction due to the difference of the gradation values of the second primary colors during the color mixture image data, according to claim 1, wherein that you determine the correction factor for the first primary color of the second color mixture image data The arithmetic processing device according to any one of claims. The gradation value of the first primary color of the second mixed color image data is a, and the gradation value of the second primary color is b.
When the gradation value of the second primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data is m,
Wherein the first determination means, the correction coefficient C (a, b) for the first primary color of the second color mixture image data, to any one of claims 1 to 4, characterized that you determined by the following formula The arithmetic processing unit described.
C (a, b) = C1 (a, m) × p
Here, C1 (x, y) is a correction coefficient for the first primary color of the first mixed color image data in which the gradation value of the first primary color is x and the gradation value of the second primary color is y.
p is a correction coefficient due to a difference in gradation value of the second primary color between the first mixed color image data and the second mixed color image data. The first determining means includes
A correction coefficient C1 (n, b) for the first primary color of the first mixed color image data in which the gradation value of the first primary color is a value n different from a and the gradation value of the second primary color is b;
From the correction coefficient C1 (n, m) for the first primary color of the first mixed color image data in which the gradation value of the first primary color is n and the gradation value of the second primary color is m,
Arithmetic processing apparatus according to claim 5, characterized that you determine the correction factor p. Wherein the first determination means, calculation processing device according to the correction coefficient p to claim 6, characterized that you determined by the following equation.
p = C1 (n, b) / C1 (n, m) Using the correction factor determined by said first determining means, one of the claims 1 to 7, further comprising a second determining means for determining the display color of the display device of the second mixed color image data The arithmetic processing unit according to claim 1. Display color of the display device using the first measurement value acquired by the first acquisition unit, the second measurement value acquired by the second acquisition unit, and the display color determined by the second determination unit The arithmetic processing apparatus according to claim 8, further comprising a generation unit that generates a correction table used in image processing for bringing the color closer to a target color. An arithmetic processing method for calculating a correction coefficient for bringing a display color of a display device close to a target value,
One pixel of the display device is composed of a plurality of sub-pixels corresponding to a plurality of primary colors,
The arithmetic processing method is:
A first acquisition step in which a computer acquires a first measurement value that is a measurement value of a display color of the display device for each of a plurality of single-color image data representing one of the plurality of primary colors;
A second acquisition step in which a computer acquires a second measurement value that is a measurement value of a display color of the display device for each of a plurality of first color image data representing a color mixture obtained by mixing two or more primary colors;
A calculation step in which a computer calculates a correction coefficient of each first mixed color image data based on the plurality of first measurement values and the plurality of second measurement values;
A first determination step of determining a correction coefficient of second mixed color image data representing a mixed color different from the plurality of first mixed color image data from each correction coefficient calculated in the calculation step;
When the pixel of the display device has a structure in which a subpixel of a second primary color different from the first primary color is arranged next to one of the subpixels of the first primary color,
In the first determination step, a correction coefficient for the first primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data, the first mixed color image data, and the second mixed color A calculation processing method, wherein a correction coefficient for the first primary color of the second mixed color image data is determined based on a difference in gradation value of the second primary color between the image data. The monochromatic image data is image data for driving one primary color sub-pixel;
The first mixed color image data and the second mixed color image data are image data for driving two or more primary color sub-pixels,
The arithmetic processing method according to claim 10, wherein the second mixed color image data is image data in which a combination of gradation values of each primary color is different from the plurality of first mixed color image data. In the calculating step, for each of the plurality of first mixed color image data, the second measurement value of the first mixed color image data and the first color image data of each primary color having the same gradation value as the first mixed color image data. The calculation processing method according to claim 10 or 11, wherein a correction coefficient of the first mixed-color image data is calculated from one measurement value. In the first determination step, the first mixed color image data and the second second color image data are compared with the second primary mixed color image data and the first primary color of the first primary color image data having the same gradation value as the correction coefficient for the first primary color. 13. The correction coefficient for the first primary color of the second mixed color image data is determined by adding correction due to a difference in gradation value of the second primary color between the mixed color image data. The arithmetic processing method according to any one of claims. The gradation value of the first primary color of the second mixed color image data is a, and the gradation value of the second primary color is b.
When the gradation value of the second primary color of the first mixed color image data having the same gradation value of the first primary color as that of the second mixed color image data is m,
In the first determination step, the correction coefficient C (a, b) for the first primary color of the second color mixture image data, in any one of claims 10-13, wherein Rukoto determined by the following formula The calculation processing method described.
C (a, b) = C1 (a, m) × p
Here, C1 (x, y) is a correction coefficient for the first primary color of the first mixed color image data in which the gradation value of the first primary color is x and the gradation value of the second primary color is y.
p is a correction coefficient due to a difference in gradation value of the second primary color between the first mixed color image data and the second mixed color image data. In the first determination step,
A correction coefficient C1 (n, b) for the first primary color of the first mixed color image data in which the gradation value of the first primary color is a value n different from a and the gradation value of the second primary color is b;
From the correction coefficient C1 (n, m) for the first primary color of the first mixed color image data in which the gradation value of the first primary color is n and the gradation value of the second primary color is m,
Arithmetic processing method according to claim 14, wherein Rukoto the correction coefficient p is determined. In the first decision step, the arithmetic processing method according to claim 15 wherein the correction factor p is characterized by Rukoto determined by the following equation.
p = C1 (n, b) / C1 (n, m) Computer, by using a correction factor determined by the first determination step, claim and further comprising a second determining step of determining a display color of the display device for the second color mixture image data 10 The arithmetic processing method according to any one of 16. The computer uses the first measurement value acquired in the first acquisition step, the second measurement value acquired in the second acquisition step, and the display color determined in the second determination step. The calculation processing method according to claim 17, further comprising a generation step of generating a correction table used in image processing for bringing the display color of the display color closer to a target value.

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