CN1791231A - Chromatic display unit white field homogeneity testing method and system - Google Patents

Abstract

The invention discloses a homogeneity test method for homogeneity of color display, which comprises: collecting image with image collector, filtering with mean value average filter device, partitioning image with image partition device, calculating lightness and colority and homogeneity of white field by opposite device. This invention decides the homogeneity of white field for whole screen with uniform standard instead of manual decision to avoid test error and ensure consistency.

Description

Method and system for testing white field uniformity of color display device

Technical Field

The invention relates to the field of detection of color display devices, in particular to a method and a system for testing white field uniformity of a color display device.

Background

The white field uniformity of a color display is an important parameter for evaluating the quality of a color display device, and comprises the evaluation of color and brightness uniformity, and currently, a single-probe colorimeter point-by-point test method is mostly adopted or an experienced tester judges the color display device by naked eyes. Both of these judgment methods have drawbacks. The single-probe colorimeter point-by-point testing method can only test one point at a time, so that the performance of the whole screen cannot be integrally evaluated, and a manual judgment method is adopted, and a unified standard cannot be formed because errors exist in naked eye judgment of each person.

Therefore, there is a need for a method and system for determining the uniformity of the white field of the whole screen, which can avoid the test error caused by the difference of the visual characteristics of each person without depending on manual determination, thereby ensuring the consistency of the determination standard.

Disclosure of Invention

The invention aims to provide a method and a system for testing the white field uniformity of a color display device, which can judge the white field uniformity of the whole screen according to a uniform standard.

According to an aspect of the present invention, there is provided a method for testing white field uniformity of a color display device, the method comprising the steps of:

an image acquisition step, namely imaging the color image on a photoelectric detector, and acquiring the image through a graphic acquisition card to obtain R, G, B values of a full-screen white field image of the color display device;

filtering, namely filtering R, G, B values of the acquired image by adopting a median average filtering method, sequencing R, G, B values of each frame, deleting the maximum and minimum parts, and accumulating the rest values to be an arithmetic average;

an image blocking step of blocking the image processed in the above step;

calculating the brightness and the chromaticity, namely calculating the brightness, the chromaticity and x and y values of the brightness and the chromaticity of each image block to obtain the relation and distribution of the brightness and the chromaticity on the whole screen;

and calculating the uniformity of the white field, namely calculating the uniformity of the white field of the color display device according to the obtained relation and distribution of the brightness and the chromaticity on the screen.

According to another aspect of the present invention, there is provided a system for testing white field uniformity of a color display device, comprising:

the image acquisition device is connected with the color display device and acquires an image of the color display device to obtain an R, G, B value of a full-screen white field image of the color display device;

a median average filter connected with the output of the image acquisition device, filtering R, G, B values of the acquired image by adopting a median average filter method, sorting R, G, B values of each frame, deleting the maximum and minimum parts, and accumulating the rest values to be an arithmetic average;

the image blocking device is connected with the output of the median average filtering device and blocks the image output by the median average filtering device;

the device for calculating the brightness and the chroma is connected with the image blocking device, and the brightness, the chroma and the x and y values of each image block are calculated to obtain the relation and the distribution of the brightness and the chroma on the whole screen;

and the device for calculating the uniformity of the white field calculates the uniformity of the white field of the color display device according to the obtained relation and distribution of the brightness and the chromaticity on the screen.

After the technical scheme is adopted, the white field uniformity testing method and the white field uniformity testing system for the color display device can judge the white field uniformity of the whole screen according to a uniform standard without depending on manual judgment, so that testing errors caused by different visual characteristics of everyone are avoided, and the consistency of the judgment standard is ensured.

Drawings

The above and other features and advantages of the present invention will become more apparent from the following description of the embodiments taken in conjunction with the accompanying drawings in which like reference characters identify like features throughout and wherein:

FIG. 1 is a flow chart of a white field uniformity testing method of a color display device according to the present invention;

FIG. 2 is a graph of a color picture tube under a white field signal;

FIG. 3 is test result data;

FIG. 4 is a three-dimensional graph of luminance uniformity distribution;

FIG. 5 is a three-dimensional view of Yc considering only the chromaticity uniformity distribution;

FIG. 6 is a three-dimensional map of CLD taking into account both luminance and chrominance uniformity distributions;

FIG. 7 is a three-dimensional plot of color difference analysis Δ E taking into account both luminance and chrominance;

FIG. 8 is a block diagram of a system for testing white field uniformity of a color display device according to the present invention.

Detailed Description

The technical scheme of the invention is further explained by combining the drawings and the embodiment.

FIG. 1 is a flow chart of a method for testing the uniformity of the white field of a color display device according to the present invention. Referring to fig. 1, the method for testing the white field uniformity of a color display device of the present invention comprises the following steps:

s11, an image acquisition step, namely imaging the color image on a photoelectric detector, and acquiring the image through a graphic acquisition card to obtain R, G, B values of a full-screen white field image of the color display device. Generally, the complete acquisition of the display screen image by the photo detector (CCD) will result in at least 5 consecutive frames of image acquisition. The form of the acquired image is shown in fig. 2, which is an example of the pattern of a color picture tube under a white field signal.

S12, filtering R, G, B values of the acquired image by adopting a median average filtering method, sequencing R, G, B values of each frame, deleting the maximum and minimum parts, and accumulating the rest values to be arithmetically averaged. Because of the spike interference phenomenon, the method of the invention adopts a median average filtering method to eliminate the spike interference.

And S13, an image blocking step, namely blocking the image processed in the step. The number of the divided image blocks is minimum 3 × 3 blocks and maximum 100 × 100 blocks, and the number of the image blocks can be adjusted according to the size of the actual image.

And S14, calculating the brightness and the chromaticity, namely calculating the brightness, the chromaticity and x and y values of each image block to obtain the relation and distribution of the brightness and the chromaticity on the whole screen. In this embodiment, generating a distribution map of chroma versus relative luma based on luma, chroma, and their x, y values is also included. Fig. 4 shows an example of a three-dimensional graph of the luminance uniformity distribution, which is generated based on the luminance values and the coordinate values of x and y.

And S15, calculating the uniformity of the white field, namely calculating the uniformity of the white field of the color display device according to the obtained relation and distribution of the brightness and the chromaticity on the screen. The main three parameters that represent the uniformity of the white field, Δ E, Yc and CLD, are calculated in this example according to the following formula:

calculating Δ E:

$L^{*}=116f\left(\frac{Y}{Y_0}\right)-16;$

u^*＝13L^*(u′-u₀′)；

v^*＝13L^*(v′-v₀′)；(3)

wherein

$f\left(x\right)=\left\{\begin{array}{cc}{x}^{1/3}& x>0.008856\\ 7.787x+16/116& \mathrm{otherwise}\end{array}\right.;---\left(4\right)$

<math> <mrow> <msup> <mi>u</mi> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>4</mn> <mi>X</mi> </mrow> <mrow> <mi>X</mi> <mo>+</mo> <mn>15</mn> <mi>Y</mi> <mo>+</mo> <mn>3</mn> <mi>Z</mi> </mrow> </mfrac> <msup> <mrow> <mo>,</mo> <mi>v</mi> </mrow> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>9</mn> <mi>Y</mi> </mrow> <mrow> <mi>X</mi> <mo>+</mo> <mn>15</mn> <mi>Y</mi> <mo>+</mo> <mn>3</mn> <mi>Z</mi> </mrow> </mfrac> </mrow> </math>

<math> <mrow> <msup> <msub> <mi>u</mi> <mn>0</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>4</mn> <msub> <mi>X</mi> <mn>0</mn> </msub> </mrow> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>15</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>Z</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>,</mo> <msup> <msub> <mi>v</mi> <mn>0</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>9</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> </mrow> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>15</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>Z</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>5</mn> <mo>)</mo> </mrow> </mrow> </math>

Wherein (X)₀，Y₀，Z₀) For reference white point, L^*Representing the coordinates of the luminance signal, it and u^*And v^*Coordinates are orthogonal to each other, in CIELUV space, two colors (L)₁ ^*，u₁ ^*，v₁ ^*) And (L)₂ ^*，u₂ ^*，v₂ ^*) The difference between these can be expressed in terms of Euclidean distance,

<math> <mrow> <msub> <mi>&Delta;E</mi> <mi>Luv</mi> </msub> <mo>=</mo> <msqrt> <msup> <mrow> <mo>(</mo> <msup> <mi>&Delta;L</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msup> <mi>&Delta;u</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <msup> <mi>&Delta;v</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>6</mn> <mo>)</mo> </mrow> </mrow> </math>

wherein Δ L^*＝L^* ₁-L^* ₂；Δu^*And Δ v^*Similarly. In image processing, the amount of color difference Δ E_LuvIs widely used to measure the difference between two colors.

The formula for calculating Yc:

$Y_c=\frac{\sqrt[2]{{(u_c-u_m)}^2+{(v_c-v_m)}^2}}{0.00384}$ unit JND (7)

Wherein,

$u_c=\frac{{4x}_c}{{-2x}_c+{12y}_c+3}$

$u_m=\frac{{4x}_m}{{-2x}_m+{12y}_m+3}$

$v_c=\frac{{6y}_c}{{-2x}_c+{12y}_c+3}$

$v_m=\frac{{6y}_m}{{-2x}_m+{12y}_m+3}---\left(8\right)$

the formula for calculating CLD:

<math> <mrow> <mi>CLD</mi> <mo>=</mo> <msqrt> <msup> <mrow> <mn>1.56</mn> <mi>&Delta;x</mi> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mn>1.2</mn> <mi>&Delta;x&Delta;y</mi> <mo>+</mo> <msup> <mrow> <mn>0.44</mn> <mi>&Delta;y</mi> </mrow> <mn>2</mn> </msup> <mo>+</mo> <mn>500</mn> <msup> <mrow> <mo>(</mo> <mi>&Delta;Y</mi> <mo>/</mo> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mrow> </math>

in the formula: delta x and delta y are chromaticity differences of the test point and the central point; Δ Y is the difference in brightness between the test point and the center point, and Y₀Is the center point brightness.

After the test results are obtained by the method, the invention further provides various ways for displaying the test results, one of which is to use the form of a graph, as shown in fig. 3, and fig. 3 displays the test result data in the form of a graph. Another way is to generate a three-dimensional distribution map of the white field uniformity parameter. For example, in this embodiment, a Yc three-dimensional map considering only the chromaticity uniformity distribution as shown in fig. 5, a CLD three-dimensional map considering both the luminance and chromaticity uniformity distributions as shown in fig. 6, and a color difference analysis Δ E three-dimensional map considering both the luminance and chromaticity as shown in fig. 7 can be generated.

The present invention also provides a system 100 for testing white field uniformity of a color display device, as shown in fig. 8, the system includes:

and the image acquisition device 104 is connected to the color display device 102 and acquires the image of the color display device 102 to obtain R, G, B values of a full-screen white field image of the color display device. In this embodiment, the image acquisition device 104 includes two components, a photodetector 106 and a graphics capture card 108. Wherein the photodetector 106 is connected to the color display device 102 and the color image of the color display device 102 is imaged onto the photodetector 106. The image acquisition card 108 is connected to the photodetector 106 for acquiring images. Also, in this embodiment, the image capture device 104 captures at least 5 consecutive frames of images.

A median average filtering device 110 connected to the output of the image capturing device 104, filtering R, G, B values of the captured image by a median average filtering method, sorting R, G, B values of each frame, deleting the largest and smallest parts, and then adding the rest of the values to make an arithmetic average. The function of the mean average filter 110 is to eliminate the spike interference phenomena encountered.

And an image blocking device 112 connected to the output of the median average filtering device 110 for blocking the image output from the median average filtering device 110. According to this embodiment, the image blocking means 112 divides the number of image blocks into a minimum of 3 × 3 blocks and a maximum of 100 × 100 blocks.

And a device 114 for calculating brightness and chromaticity, connected to the image blocking device 112, for calculating the brightness, chromaticity and x and y values of each image block, so as to obtain the relationship and distribution of brightness and chromaticity on the whole screen. According to this embodiment, the apparatus 114 for calculating luminance and chrominance further comprises a first distribution graph generating apparatus 116 for generating a distribution graph of chrominance and relative luminance according to the luminance, the chrominance and the x and y values thereof. Examples of the figures may refer to fig. 4 described above.

Means 118 for calculating the white field uniformity calculates the white field uniformity of the color display device based on the obtained luminance and chrominance relationship and distribution on the screen. The three parameters, Δ E, Yc and CLD, representing the uniformity of the white field are mainly used in this embodiment to calculate the three parameters Δ E, Yc and CLD respectively by using the means 122 for calculating Δ E, the means 124 for calculating Yc and the means 126 for calculating CLD respectively, and the calculation formulas used in the three means can be referred to as described in the step S15. According to this embodiment, the means 118 for calculating the white field uniformity further comprises a second distribution pattern generating means 120 for generating a three-dimensional distribution pattern of the white field uniformity parameter. Examples of the figures may refer to fig. 5, 6, 7 described above.

When the system is used, the test is preferably carried out in a darkroom environment when the test is required, and the test lens is placed at a distance which is more than 3 times of the diagonal of the display screen, so that the visual angle of the lens is ensured to be less than 2 degrees. The current chroma testing precision of the system is about +/-0.004 averagely, and the brightness testing precision is about +/-5.0 percent averagely.

After the technical scheme is adopted, the white field uniformity testing method and the white field uniformity testing system for the color display device can judge the white field uniformity of the whole screen according to a uniform standard without depending on manual judgment, so that testing errors caused by different visual characteristics of everyone are avoided, and the consistency of the judgment standard is ensured.

The embodiments described above are provided to enable persons skilled in the art to make or use the invention and that modifications or variations can be made to the embodiments described above by persons skilled in the art without departing from the inventive concept of the present invention, so that the scope of protection of the present invention is not limited by the embodiments described above but should be accorded the widest scope consistent with the innovative features set forth in the claims.

Claims (10)

1. A method for testing white field uniformity of a color display device comprises the following steps:

an image acquisition step, namely imaging the color image on a photoelectric detector, and acquiring the image through a graphic acquisition card to obtain R, G, B values of a full-screen white field image of the color display device;

filtering, namely filtering R, G, B values of the acquired image by adopting a median average filtering method, sequencing R, G, B values of each frame, deleting the maximum and minimum parts, and accumulating the rest values to be an arithmetic average;

an image blocking step of blocking the image processed in the above step;

calculating the brightness and the chromaticity, namely calculating the brightness, the chromaticity and x and y values of the brightness and the chromaticity of each image block to obtain the relation and distribution of the brightness and the chromaticity on the whole screen;

and calculating the uniformity of the white field, namely calculating the uniformity of the white field of the color display device according to the obtained relation and distribution of the brightness and the chromaticity on the screen.

2. The method of claim 1, wherein at least 5 frames of images are acquired continuously in the image acquisition step.

3. The method as claimed in claim 1, wherein the number of image blocks in the image blocking step is a minimum of 3 x 3 blocks and a maximum of 100 x 100 blocks.

4. The method of claim 1,

the step of calculating the brightness and the chroma further comprises generating a distribution diagram of the chroma and the relative brightness according to the brightness, the chroma and the x and y values of the brightness and the chroma;

the step of calculating the uniformity of the white field further comprises generating a three-dimensional distribution map of the uniformity parameters of the white field.

5. The method according to claim 1, wherein the step of calculating the white field uniformity specifically uses the following formula:

calculating Δ E:

$L^{*}=116f\left(\frac{Y}{Y_0}\right)-16;$

u^*＝13L*(u′-u₀′)； (3)

v^*＝13L*(v′-v₀′)；

wherein

$f\left(x\right)=\left\{\begin{array}{cc}{x}^{1/3}& x>0.008856\\ 7.787x+16/116& \mathrm{otherwise}\end{array}\right.;$ (4)

<math> <mrow> <msup> <mi>u</mi> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>4</mn> <mi>X</mi> </mrow> <mrow> <mi>X</mi> <mo>+</mo> <mn>15</mn> <mi>Y</mi> <mo>+</mo> <mn>3</mn> <mi>Z</mi> </mrow> </mfrac> </mrow> </math> <math> <mrow> <msup> <mi>v</mi> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>9</mn> <mi>Y</mi> </mrow> <mrow> <mi>X</mi> <mo>+</mo> <mn>15</mn> <mi>Y</mi> <mo>+</mo> <mn>3</mn> <mi>Z</mi> </mrow> </mfrac> </mrow> </math>

<math> <mrow> <msup> <msub> <mi>u</mi> <mn>0</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <msub> <mrow> <mn>4</mn> <mi>X</mi> </mrow> <mn>0</mn> </msub> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>15</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>Z</mi> <mn>0</mn> </msub> </mrow> </mfrac> </mrow> </math> <math> <mrow> <msup> <msub> <mi>v</mi> <mn>0</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>9</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> </mrow> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>15</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>Z</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>;</mo> </mrow> </math> (5)

Wherein (X)₀，Y₀，Z₀) For reference, L^*Representing the coordinates of the luminance signal, it and u^*And v^*Coordinates are orthogonal to each other, in CIELUV space, two colors (L)₁ ^*，u₁ ^*，v₁ ^*) And (L)₂ ^*，u₂ ^*，v₂ ^*) The difference between these can be expressed in terms of Euclidean distance,

<math> <mrow> <mi>&Delta;</mi> <msub> <mi>E</mi> <mi>Luv</mi> </msub> <mo>=</mo> <msqrt> <msup> <mrow> <mo>(</mo> <mi>&Delta;</mi> <msup> <mi>L</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>&Delta;</mi> <msup> <mi>u</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>&Delta;</mi> <msup> <mi>v</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mrow> </math> (6)

wherein Δ L^*＝L^* ₁-L^* ₂；

The formula for calculating Yc:

$Y_c=\frac{2\sqrt{{(u_c-u_m)}^2+{(v_c-v_m)}^2}}{0.00384},$ unit JND (7)

Wherein,

$u_c=\frac{4x_c}{-2x_c+12y_c+3}$

$u_m=\frac{4x_m}{-2x_m+12y_m+3}$

$v_c=\frac{6y_c}{-2x_c+12y_c+3}$

$v_m=\frac{6y_m}{-2x_m+12y_m+3}$ (8)

the formula for calculating CLD:

<math> <mrow> <mi>CLD</mi> <mo>=</mo> <msqrt> <msup> <mrow> <mn>1.56</mn> <mi>&Delta;x</mi> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mn>1.2</mn> <mi>&Delta;x&Delta;y</mi> <mo>+</mo> <mn>0.44</mn> <mi>&Delta;</mi> <msup> <mi>y</mi> <mn>2</mn> </msup> <mo>+</mo> <mn>500</mn> <msup> <mrow> <mo>(</mo> <mi>&Delta;Y</mi> <mo>/</mo> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mrow> </math>

in the formula: delta x and delta y are chromaticity differences of the test point and the central point; Δ Y is the difference in brightness between the test point and the center point, and Y₀Is the center point brightness.

6. A white field uniformity testing system for a color display device, comprising:

the image acquisition device is connected with the color display device and acquires an image of the color display device to obtain an R, G, B value of a full-screen white field image of the color display device;

a median average filter connected with the output of the image acquisition device, filtering R, G, B values of the acquired image by adopting a median average filter method, sorting R, G, B values of each frame, deleting the maximum and minimum parts, and accumulating the rest values to be an arithmetic average;

the image blocking device is connected with the output of the median average filtering device and blocks the image output by the median average filtering device;

the device for calculating the brightness and the chroma is connected with the image blocking device, and the brightness, the chroma and the x and y values of each image block are calculated to obtain the relation and the distribution of the brightness and the chroma on the whole screen;

and the device for calculating the uniformity of the white field calculates the uniformity of the white field of the color display device according to the obtained relation and distribution of the brightness and the chromaticity on the screen.

7. The system of claim 6, wherein the image acquisition device comprises:

the photoelectric detector is connected with the color display device, and a color image of the color display device is imaged on the photoelectric detector;

the image acquisition card is connected to the photoelectric detector and used for acquiring images; and is

The image acquisition device acquires at least 5 continuous frames of images.

8. The system of claim 6, wherein the image blocking means divides the number of image blocks into a minimum of 3 x 3 blocks and a maximum of 100 x 100 blocks.

9. The system of claim 6,

the device for calculating the brightness and the chroma also comprises a first distribution diagram generating device which generates a distribution diagram of the chroma and the relative brightness according to the brightness, the chroma and the x and y values thereof;

the apparatus for calculating the uniformity of the white field further comprises a second distribution pattern generating means for generating a three-dimensional distribution pattern of the uniformity parameter of the white field.

10. The system of claim 6, wherein the means for calculating white field uniformity further comprises:

means for calculating Δ E according to the following equation:

$L^{*}=116f\left(\frac{Y}{Y_0}\right)-16;$

u^*＝13L*(u′-u₀′)； (3)

v^*＝13L*(v′-v₀′)；

wherein

$f\left(x\right)=\left\{\begin{array}{cc}{x}^{1/3}& x>0.008856\\ 7.787x+16/116& \mathrm{otherwise}\end{array}\right.;$ (4)

<math> <mrow> <msup> <mi>u</mi> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>4</mn> <mi>X</mi> </mrow> <mrow> <mi>X</mi> <mo>+</mo> <mn>15</mn> <mi>Y</mi> <mo>+</mo> <mn>3</mn> <mi>Z</mi> </mrow> </mfrac> </mrow> </math> <math> <mrow> <msup> <mi>v</mi> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>9</mn> <mi>Y</mi> </mrow> <mrow> <mi>X</mi> <mo>+</mo> <mn>15</mn> <mi>Y</mi> <mo>+</mo> <mn>3</mn> <mi>Z</mi> </mrow> </mfrac> </mrow> </math>

<math> <mrow> <msup> <msub> <mi>u</mi> <mn>0</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <msub> <mrow> <mn>4</mn> <mi>X</mi> </mrow> <mn>0</mn> </msub> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>15</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>Z</mi> <mn>0</mn> </msub> </mrow> </mfrac> </mrow> </math> <math> <mrow> <msup> <msub> <mi>v</mi> <mn>0</mn> </msub> <mo>&prime;</mo> </msup> <mo>=</mo> <mfrac> <mrow> <mn>9</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> </mrow> <mrow> <msub> <mi>X</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>15</mn> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>Z</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mo>;</mo> </mrow> </math> (5)

Wherein (X)₀，Y₀，Z₀) For reference white point, L^*Representing the coordinates of the luminance signal, it and u^*And v^*Coordinates are orthogonal to each other, in CIELUV space, two colors (L)₁ ^*，u₁ ^*，v₁ ^*) And (L)₂ ^*，u₂ ^*，v₂ ^*) The difference between these can be expressed in terms of Euclidean distance,

<math> <mrow> <mi>&Delta;</mi> <msub> <mi>E</mi> <mi>Luv</mi> </msub> <mo>=</mo> <msqrt> <msup> <mrow> <mo>(</mo> <mi>&Delta;</mi> <msup> <mi>L</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>&Delta;</mi> <msup> <mi>u</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <msup> <mrow> <mo>(</mo> <mi>&Delta;</mi> <msup> <mi>v</mi> <mo>*</mo> </msup> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mrow> </math> (6)

wherein Δ L^*＝L^* ₁-L^* ₂；

Means for calculating Yc according to the following equation:

$Y_c=\frac{2\sqrt{{(u_c-u_m)}^2+{(v_c-v_m)}^2}}{0.00384},$ unit JND (7)

Wherein,

$u_c=\frac{4x_c}{-2x_c+12y_c+3}$

$u_m=\frac{4x_m}{-2x_m+12y_m+3}$

$v_c=\frac{6y_c}{-2x_c+12y_c+3}$

$v_m=\frac{6y_m}{-2x_m+12y_m+3}$ (8)

means for calculating a CLD, the means calculating the CLD according to the formula:

<math> <mrow> <mi>CLD</mi> <mo>=</mo> <msqrt> <msup> <mrow> <mn>1.56</mn> <mi>&Delta;x</mi> </mrow> <mn>2</mn> </msup> <mo>-</mo> <mn>1.2</mn> <mi>&Delta;x&Delta;y</mi> <mo>+</mo> <mn>0.44</mn> <mi>&Delta;</mi> <msup> <mi>y</mi> <mn>2</mn> </msup> <mo>+</mo> <mn>500</mn> <msup> <mrow> <mo>(</mo> <mi>&Delta;Y</mi> <mo>/</mo> <msub> <mi>Y</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> </msqrt> </mrow> </math>

in the formula: delta x and delta y are chromaticity differences of the test point and the central point; Δ Y is the difference in brightness between the test point and the center point, and Y₀Is the center point brightness.

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