CN109920356B - Fitting method for evaluating threshold curve of black matrix and evaluation method of black matrix - Google Patents
Fitting method for evaluating threshold curve of black matrix and evaluation method of black matrix Download PDFInfo
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Abstract
The embodiment of the invention provides a fitting method for evaluating a threshold value curve of a black matrix and an evaluation method for the black matrix, relates to the technical field of display, and can improve the accuracy of evaluating the black matrix. A fitting method for evaluating a threshold value curve of a black matrix comprises obtaining a contrast sensitivity value from the width of a plurality of light shielding bars and the width of sub-pixels, wherein the light shielding bars extend along the length direction or the width direction of each sample, and the black matrix of each sample comprises; the shading strips have N widths, and N is more than or equal to 2; the width of the light shielding strips in at least part of the samples is not completely equal to the width of the light shielding strips in other samples; obtaining space frequency values corresponding to the samples at different observation distances; marking the visible or invisible condition of each sample dark line under the same environment brightness and corresponding observation distance in a coordinate system with the spatial frequency as an abscissa and the contrast sensitivity value as an ordinate; and fitting a threshold curve to enable coordinate points of the visible or invisible condition to be respectively positioned at two sides of the threshold curve.
Description
Technical Field
The invention relates to the technical field of display, in particular to a fitting method for evaluating a threshold value curve of a black matrix and an evaluation method for the black matrix.
Background
In order to increase the aperture ratio of the display panel, the black matrix between different sub-pixels is designed to have at least two different widths, and is repeated periodically. However, the various black matrix widths may cause a visual macroscopic effect such that alternating dark and light lines appear on the display panel. Therefore, when designing the layout of the display panel, the risk of the occurrence of the dark line needs to be evaluated.
Disclosure of Invention
The embodiment of the invention provides a fitting method for evaluating a threshold value curve of a black matrix and an evaluation method for the black matrix, which can improve the accuracy of evaluating the black matrix.
In order to achieve the above purpose, the embodiment of the invention adopts the following technical scheme:
in a first aspect, a fitting method for evaluating a threshold curve of a black matrix is provided, including: calculating the contrast sensitivity value of each sample according to the widths of a plurality of light shading strips extending along a first direction and the widths of sub-pixels included in the black matrix of each sample in a plurality of sample display panels; wherein the light shielding strips extending along the first direction in the plurality of samples have N kinds of widths, and N is more than or equal to 2; the width of the light-shielding strip in at least part of the samples is not completely equal to the width of the light-shielding strip in other samples; the first direction is a length direction of each of the samples, or the first direction is a width direction of each of the samples; calculating to obtain space frequency values corresponding to the samples at different observation distances according to the plurality of samples and different observation distances; for each sample, marking the visible or invisible condition of the dark line of the sample observed by human eyes under the same environment brightness and corresponding observation distance in a coordinate system taking the spatial frequency as the abscissa and the contrast sensitivity value as the ordinate; and fitting a threshold curve, wherein the coordinate points for identifying the visible condition and the coordinate points for identifying the invisible condition are respectively positioned on two sides of the threshold curve.
Optionally, calculating a contrast sensitivity value of each sample according to widths of a plurality of light-shielding strips extending along the first direction and widths of the sub-pixels included in the black matrix of each sample, including:
for each sample, obtaining a continuous brightness distribution curve corresponding to the sample according to the width of the light shielding strips extending along the first direction and the width of the sub-pixels included in the black matrix of the sample, and the brightness ratio of the sub-pixels of different colors in the sample; the abscissa of the brightness distribution curve is width, and the ordinate is brightness; obtaining a frequency domain spectrum corresponding to the sample according to the brightness distribution curve; calculating to obtain a contrast sensitivity value of the sample according to a component spectrum value of absolute spatial frequency corresponding to a dark line period in the frequency domain spectrum of the sample and a direct current component spectrum value; wherein the contrast sensitivity value is (component spectrum value/direct current component spectrum value of absolute spatial frequency corresponding to a dark line period in the frequency domain spectrum of the sample) × 2 × 100%.
On this basis, optionally, obtaining a luminance distribution curve corresponding to the sample according to the widths of the plurality of light-shielding strips extending along the first direction, the widths of the sub-pixels, and the luminance ratios of the sub-pixels of different colors in the sample, where the black matrix of the sample includes: obtaining an integer ratio of the widths of the light-shielding bars extending along the first direction and the widths of the sub-pixels included in the black matrix of the sample according to the widths of the light-shielding bars extending along the first direction and the widths of the sub-pixels included in the black matrix of the sample; and obtaining a brightness distribution curve corresponding to the sample according to the integral ratio of the widths of the light shielding strips and the widths of the sub-pixels which extend along the first direction and the brightness ratio of the sub-pixels with different colors in the sample, wherein the black matrix of the sample comprises a plurality of light shielding strips.
Optionally, the different colors include a first color, a second color and a third color, and the first color, the second color and the third color are three primary colors; the brightness ratio of the sub-pixels with different colors in the sample is obtained by testing the brightness value of the sample under the conditions that the monochrome first color is used, the gray scale is the middle gray scale, the monochrome second color is used, the gray scale is the middle gray scale, the monochrome third color is used, and the gray scale is the middle gray scale.
Optionally, obtaining a frequency domain spectrum corresponding to the sample according to the brightness distribution curve includes: sampling the brightness distribution curve, and taking the absolute spatial frequency corresponding to the sampling interval as the sampling frequency; and calling a fast Fourier transform function to perform fast Fourier transform to obtain a frequency domain spectrum corresponding to the sample.
Optionally, for each of said samples, according to the formula
Calculating to obtain a spatial frequency value of the sample under the corresponding observation distance; and CPD is the spatial frequency value, l is the product of the number of the dark lines of the sample observed by human eyes at the observation distance and the distance between the dark lines, t is the distance between the adjacent dark lines, and d is the observation distance.
In a second aspect, a method for evaluating a black matrix is provided, including: calculating to obtain a contrast sensitivity value of the display panel to be evaluated according to the widths of a plurality of shading strips extending along a first direction and the widths of sub-pixels included in a black matrix of the display panel to be evaluated; marking the contrast sensitivity value of the display panel to be evaluated as a vertical coordinate and the spatial frequency value most sensitive to human eyes as a coordinate point of a horizontal coordinate in a coordinate system where a threshold curve is obtained by the method for fitting the threshold curve for evaluating the black matrix as claimed in any one of claims 1 to 5; the light-shielding strips of the display panel to be evaluated, which extend along the first direction, and the light-shielding strips, which extend along the first direction, in the sample corresponding to the threshold curve all have N widths; if the coordinate point is located below the threshold curve, a dark line of the display panel to be evaluated is visible; and if the coordinate point is positioned above the threshold curve, the dark line of the display panel to be evaluated is invisible.
Optionally, the evaluation method of the black matrix further includes: according to
Obtaining the spatial frequency value which is most sensitive to human eyes; wherein CPD is the spatial frequency and Af is the sensitivity function of human eyes.
In a third aspect, a product design method is provided, which includes the evaluation method of the black matrix.
In a fourth aspect, a computer-readable medium is provided, on which a computer program is stored, which, when executed, implements the above-described fitting method for evaluating a threshold curve of a black matrix, or implements the above-described evaluation method for a black matrix.
In a fifth aspect, an electronic device is provided, comprising: a processor, a memory; the memory is used for storing one or more programs; the one or more programs, when executed by the processor, implement the fitting method for evaluating a threshold curve of a black matrix described above, or implement the evaluation method for a black matrix described above.
The embodiment of the invention provides a fitting method for a threshold value curve for evaluating a black matrix and an evaluation method for the black matrix. Therefore, the theory of sensitivity of human eyes to spatial frequency and an actual observation result are fitted, the difference of the widths of the black matrixes can be accurately reflected, whether dark stripes are visible or not is more practical, and the accuracy of evaluation is improved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1a is a schematic top view of a black matrix according to an embodiment of the present invention;
fig. 1b is a schematic top view of another black matrix according to an embodiment of the present invention;
fig. 2 is a schematic flowchart of a fitting method for evaluating a threshold curve of a black matrix according to an embodiment of the present invention;
FIG. 3 is a diagram illustrating a threshold curve of a fitting black matrix according to an embodiment of the present invention;
FIG. 4 is a schematic flow chart of another fitting method for evaluating a threshold curve of a black matrix according to an embodiment of the present invention;
FIG. 5a is a graph illustrating a luminance distribution curve of a sample according to an embodiment of the present invention;
FIG. 5b is a graph illustrating a luminance distribution curve of another sample according to an embodiment of the present invention;
FIG. 6 is a schematic flowchart of another fitting method for evaluating a threshold curve of a black matrix according to an embodiment of the present invention;
FIG. 7 is a schematic flowchart of another fitting method for evaluating a threshold curve of a black matrix according to an embodiment of the present disclosure;
FIG. 8a is a schematic diagram of a frequency domain spectrum of a sample luminance distribution curve according to an embodiment of the present invention;
FIG. 8b is a schematic frequency domain spectrum of another sample luminance distribution curve according to an embodiment of the present invention;
FIG. 9 is a schematic view of a sample observation provided by an embodiment of the present invention;
fig. 10 is a flowchart illustrating an evaluation method of a black matrix according to an embodiment of the present invention;
fig. 11 is a schematic diagram of a sensitivity function of a human eye according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1, the display panel includes a plurality of sub-pixels 10, and a black matrix is disposed between any adjacent sub-pixels 10 to prevent light emitted between the sub-pixels 10 from interfering with each other and to prevent light leakage.
For example, as shown in fig. 1a and 1b, the black matrix is in a grid shape as a whole, and an area surrounded by each small grid is an area where one sub-pixel 10 is located.
In order to increase the aperture ratio, for example, as shown in fig. 1a and 1b, the light-shielding bars 201 extending along the first direction X in the black matrix are provided with two widths, and the two widths are periodically repeated. It should be noted that fig. 1a and 1b illustrate only the example where the light-shielding bars 201 extending in the first direction X have two widths, but the light-shielding bars 201 extending in the first direction X may have two or more widths. The first direction X may be a length direction of the display panel, or the first direction X may be a width direction of the display panel.
However, such a design may cause the display panel to have alternating dark and dark lines arranged in the horizontal or vertical direction.
Based on this, embodiments of the present invention provide a fitting method for a threshold curve used for evaluating a black matrix, by which the black matrix can be evaluated.
As shown in fig. 2, the fitting method of the threshold curve includes the following steps:
s11, calculating the contrast sensitivity value of each sample according to the widths of a plurality of light shielding strips extending along the first direction X and the widths of sub-pixels included in the black matrix of each sample in a plurality of sample display panels; wherein, the shading strips extending along the first direction X in the plurality of samples have N kinds of widths, and N is more than or equal to 2; the width of the masking strip in at least some of the samples was not exactly equal to the width of the masking strip in other samples.
Wherein the first direction X is a length direction of each sample, or the first direction X is a width direction of each sample.
The contrast sensitivity is the reciprocal of a contrast threshold which can be perceived by a human eye visual system, and if the contrast threshold is low, the contrast sensitivity is high and the visual function is good. At a certain spatial frequency, the visual system has a certain contrast sensitivity, and at the same contrast sensitivity, the visual system has a certain spatial frequency resolution.
It should be noted that the light-shielding bars in the embodiments of the present invention are all light-shielding bars extending along the first direction X.
The light-shielding strips with two widths are used as an example for the above samples. Under the same environmental brightness and observation distance, the dark line of the sample is actually observed, and the observation results shown in table 1 below are obtained.
TABLE 1
Where, o represents no dark stripes, Δ represents light dark stripes, a-tangle represents severe dark stripes, and the shading strip width difference value ═ (difference of two shading strip widths/2) × sub-pixel width × 100%.
It can be obtained that at a certain observation distance, the severity of dark fringes is increased along with the increase of the width difference of the sample shading strip, and the dark fringes are positively correlated. Furthermore, dark streak severity also correlates negatively with sample PPI (Pixel Per inc), i.e., dark streak severity decreases with increasing sample PPI.
It can be seen that the visibility of the dark fringes of the sample is related to the width of the light-shielding bars and the width of the sub-pixels of the sample.
S12, calculating space frequency values corresponding to the samples at different observation distances according to the multiple samples and different observation distances; for each sample, the visible or invisible condition of the dark line of the sample observed by human eyes under the same environment brightness and corresponding observation distance is marked in a coordinate system taking the spatial frequency as the abscissa and the contrast sensitivity value as the ordinate.
The spatial frequency value of the sample is related to the sample and the observation distance of the sample, and the spatial frequency value of the same sample is different when the observation distance of the tester to the sample is different.
According to the perception of human vision on brightness, the ambient brightness can be divided into photopic vision, scotopic vision and mesopic vision. And the plurality of samples can be observed by changing the observation distance under the same photopic vision environment brightness, the same scotopic vision environment brightness and the same mesopic vision environment brightness respectively. When a threshold curve under the brightness of the photopic vision environment needs to be obtained, a plurality of samples can be observed at the same brightness of the photopic vision environment by changing the observation distance. When the threshold curve under the dark vision environment brightness needs to be obtained, a plurality of samples can be observed at the same dark vision environment brightness by changing the observation distance. When a threshold curve under the mesopic vision environment brightness needs to be obtained, a plurality of samples can be observed at the same mesopic vision environment brightness by changing the observation distance
The example is still given with the light-shielding bars of the above samples having two widths. The sample size selected was 23.6 inches with a resolution of HD1366 x 768. The actual observation of the dark lines of the sample at different observation distances was performed under the same ambient brightness (e.g., photopic vision), and the observation results are shown in table 2 below. In table 2, only the observed results of 4 samples observed at different observation distances in an environment with a brightness of 127 gray levels are listed.
TABLE 2
Where o stands for no dark stripes, Δ stands for slight dark stripes, a for severe dark stripes, shading strip width difference value ═ the difference of two shading strip widths/2 x sub-pixel width x 100%.
As can be seen from table 2, the dark stripes become severe as the value of the difference in width of the shade strip increases. Moreover, when the observation distance is short, that is, the distance between the human eye and the sample is small, the human eye sees the sub-pixels of the sample, and cannot see dark stripes. When the observation distance is long, namely the distance between the human eyes and the sample is large, the dark fringes cannot be distinguished by the human eyes. Therefore, there is an optimum observation distance when observing dark streaks.
If, according to the above observation results, for each sample, a dark streak of the sample at the corresponding observation distance is visible, then, in the above coordinate system with the spatial frequency as the abscissa and the contrast sensitivity value as the ordinate, at the coordinate point determined by the spatial frequency of the sample and the contrast sensitivity value of the sample at the corresponding observation distance, for example, the coordinate point is marked by Δ. If the dark streak of the sample is not visible at the respective observation distance, then, in the above-mentioned coordinate system, at the coordinate points determined by the spatial frequency of the sample and the contrast sensitivity value of the sample at the corresponding observation distance, for example, the mark o is given.
According to the method, all samples are marked in a coordinate system with spatial frequency as abscissa and contrast sensitivity value as ordinate one by one in different observation distances and actual observation results of observed dark lines under the same environmental brightness, for example, as shown in fig. 3.
S13, fitting a threshold curve, wherein the coordinate points for identifying the visible condition and the coordinate points for identifying the invisible condition are respectively located at two sides of the threshold curve (as shown in fig. 3).
It should be noted that, as the above N is different, the skilled person should understand that different threshold curves need to be fitted. For example, on the premise of determining the ambient brightness, when N is 2, threshold curve fitting is performed on a sample having light-shielding bars of two widths. When N is 3, threshold curve fitting is performed on samples having three widths of masking strips.
Furthermore, those skilled in the art will appreciate that coordinate points further from the threshold curve may be optionally ignored in fitting the threshold curve to reduce errors.
According to the embodiment of the invention, under the same environment brightness and different observation distances, the visible or invisible condition of the dark line of the sample is actually observed by human eyes, the visible or invisible condition is marked in a coordinate system with the spatial frequency as a horizontal coordinate and the contrast sensitivity value as a vertical coordinate, and a threshold curve is obtained by fitting. Therefore, the theory of sensitivity of human eyes to spatial frequency and an actual observation result are fitted, the difference of the widths of the black matrixes can be accurately reflected, whether dark stripes are visible or not is more practical, and the accuracy of evaluation is improved.
Alternatively, as shown in fig. 4, calculating a contrast sensitivity value of each sample according to widths of a plurality of light-shielding bars extending along the first direction X and widths of sub-pixels included in the black matrix of each sample includes:
s111, aiming at each sample, obtaining a continuous brightness distribution curve corresponding to the sample according to the width of a plurality of light shielding strips extending along the first direction X and the width of sub-pixels included in the black matrix of the sample and the brightness ratio of the sub-pixels with different colors in the sample; the abscissa of the luminance distribution curve is the width and the ordinate is the luminance.
In order to improve the resolution of the frequency domain spectrum in the subsequent step, when obtaining the brightness distribution curve, the minimum repetition period of the pixels can be selected according to the sample, and the period length of more than two pixels can be selected. The more cycles, the higher the spectrum resolution, thereby improving the accuracy of the calculation result. For example, for a sample with two widths of light-shielding bars and a difference value of 11.0%, a brightness distribution curve of four periods can be selected (as shown in fig. 5 b).
For example, the widths of the plurality of light-shielding bars extending in the first direction X, the widths of the sub-pixels included in the black matrix of the sample, and the luminance ratios of the sub-pixels of different colors in the sample may be input to Matlab to establish a plurality of periodic luminance distribution curves. When the brightness distribution curve is established, according to the information (the width of a plurality of shading strips extending along the same direction and the width of sub-pixels included in the black matrix, and the brightness ratio of the sub-pixels with different colors in the sample), linear connection is performed to obtain the brightness distribution curve corresponding to each sample.
And S112, obtaining a frequency domain spectrum corresponding to the sample according to the brightness distribution curve.
For example, for a sample with a shade bar having one width (i.e. a shade bar width difference value of 0%), the luminance profile is shown in fig. 5a, and the corresponding frequency domain spectrum is shown in fig. 8 a. For the samples with two widths of light bars and the difference value between the widths of the light bars is 11.0%, the luminance distribution curve is shown in fig. 5b, and the corresponding frequency domain spectrum is shown in fig. 8 b.
S113, calculating to obtain a contrast sensitivity value of the sample according to a component spectrum value of absolute spatial frequency corresponding to a dark line period in a frequency domain spectrum of the sample and a direct current component spectrum value; wherein, the contrast sensitivity value is (component spectrum value/direct current component spectrum value of absolute spatial frequency corresponding to the dark line period in the frequency domain spectrum of the sample) × 2 × 100%.
In practical observation, the brightness curve of the alternate bright and dark stripes is generally a sine wave curve. The contrast sensitivity represents the contrast of the brightness and the darkness of the bright and dark alternate stripes relative to the average brightness value, and the higher the contrast sensitivity value, the easier the human eye can distinguish the stripes.
The contrast sensitivity value is defined as (luminance maximum-luminance minimum)/(luminance maximum + luminance minimum) x 100%. In the frequency domain spectrum, the contrast sensitivity value may be converted into a contrast sensitivity value (component spectrum value of absolute spatial frequency corresponding to a dark line period in the frequency domain spectrum of the sample/direct current component spectrum value) × 2 × 100%, where the direct current component spectrum value is the component spectrum value corresponding to a frequency of zero in the frequency domain spectrum.
The absolute spatial frequency is defined as the number of periods of a sinusoidal quantitative variation per unit length. Here, the absolute spatial frequency corresponding to the dark line period is the number of dark line periods per unit length. Taking a sample of a light-shielding bar with two widths as an example, the dark line period is two pixel widths, and the absolute spatial frequency corresponding to the dark line period is 1/(two pixel widths).
On this basis, optionally, as shown in fig. 6, obtaining a luminance distribution curve corresponding to the sample according to the width of the plurality of parallel light-shielding bars extending in the first direction X included in the black matrix of the sample, the width of the sub-pixels, and the luminance ratio of the sub-pixels of different colors in the sample includes:
s1111, obtaining the integer ratio of the widths of the parallel light-shielding strips extending along the same direction and the widths of the sub-pixels according to the widths of the parallel light-shielding strips extending along the first direction X and the widths of the sub-pixels included in the black matrix of the sample; and obtaining a brightness distribution curve corresponding to the sample according to the widths of a plurality of parallel light shielding strips extending along the first direction X and the integer ratio of the widths of the sub-pixels and the brightness ratio of the sub-pixels with different colors in the sample.
The ratio of the widths of the light-shielding strips extending along the first direction X and the widths of the sub-pixels included in the black matrix of the sample is taken as an integer, so that the calculation is simpler, and the calculation time is shortened when the brightness distribution curve corresponding to the sample is obtained.
Optionally, the different colors include a first color, a second color and a third color, and the first color, the second color and the third color are three primary colors.
Based on the above, the luminance ratio of the sub-pixels with different colors in the sample is obtained by testing the luminance value of the sample under the conditions that the monochrome first color is used, the gray scale is the intermediate gray scale, the monochrome second color is used, the gray scale is the intermediate gray scale, and the monochrome third color is used, and the gray scale is the intermediate gray scale. For example, the middle gray level of a monochrome 8-bit screen is 127 gray levels, and the middle gray level of a monochrome 10-bit screen is 512 gray levels.
Taking red, green and blue three primary colors as an example, the brightness values of the samples are respectively tested under a red picture with a monochromatic gray scale of 127, a green picture with a monochromatic gray scale of 127 and a blue picture with a monochromatic gray scale of 127. In the case of ignoring the difference of the aperture ratios of the three sub-pixels of red, green and blue, the luminance ratio of the three sub-pixels of red, green and blue can be equal to the luminance ratio of the sample of the monochrome picture of the three colors of red, green and blue, for example, the luminance ratio can be red: green: blue 10:39: 7.
When the dark line of the sample is evaluated to be visible, the spatial frequency corresponding to the dark line of the sample needs to be obtained, and the spatial frequency has no relation with the absolute magnitude of the luminance values of the sub-pixels with different colors, so that the luminance ratio of the sub-pixels with different colors in the sample can also be an integer ratio, and the calculation is simplified.
Because the brightness gray scale is selected as the obvious intermediate gray scale, the situation that the observation difficulty of human eyes on dark fringes is high under the condition that the brightness gray scale of the sample is too high or too low can be avoided, and the human eyes can observe the dark fringes conveniently.
Optionally, as shown in fig. 7, obtaining a frequency domain spectrum corresponding to the sample according to the brightness distribution curve includes:
s1121, sampling the brightness distribution curve, and taking the absolute spatial frequency corresponding to the sampling interval as the sampling frequency; and calling a fast Fourier transform function to perform fast Fourier transform to obtain a frequency domain spectrum corresponding to the sample.
It can be understood that the luminance distribution curve appears as a rectangular wave in the time domain spectrum as shown in fig. 5a and 5b, and after the luminance distribution curve is transformed from the time domain to the frequency domain by the fast fourier transform, a frequency domain spectrum of the luminance distribution curve is obtained (as shown in fig. 8a and 8 b), wherein the horizontal axis in the frequency domain spectrum is frequency and the vertical axis in the frequency domain spectrum is amplitude. As can be seen from the frequency domain spectrum, the square wave in the time domain is formed by superimposing sine waves of a plurality of frequencies.
After the fast fourier transform, each sample point in the time domain spectrum corresponds to a frequency point in the frequency domain spectrum, and the spectral value of each sample point in the time domain spectrum is the amplitude characteristic of the point in the corresponding frequency domain spectrum. The corresponding spectrum value of the first sampling point in the frequency domain spectrum is the above-mentioned direct current component spectrum value.
When the N is changed, the component spectrum value corresponding to the dark fringe period in the frequency domain spectrum of the sample is also changed. For example, for a sample with two widths of light-shielding bars and a light-shielding bar width difference value of 11.0%, the component spectrum value at the absolute spatial frequency (e.g., 1 ×) corresponding to the dark line period in the frequency domain spectrum (as shown in fig. 8 b) is significantly different from the component spectrum value at the absolute spatial frequency corresponding to the dark line period in the frequency domain spectrum (as shown in fig. 8 a) corresponding to the sample with one width (i.e., a light-shielding bar width difference value of 0%).
And calling a fast Fourier transform function through calculation software such as Matlab to perform fast Fourier transform to obtain a component spectrum value of absolute spatial frequency and a direct-current component spectrum value corresponding to a dark line period in a frequency domain spectrum, so that the calculated amount of the contrast sensitivity value of the sample is reduced, and the operation time is shortened.
Optionally, for each sample, according to the formula
Calculating to obtain a spatial frequency value of the sample at the corresponding observation distance; therein, as shown in FIG. 9CPD is a spatial frequency value, l is the product of the number of dark lines of the sample which can be observed by human eyes at the observation distance and the distance between the dark lines, t is the distance between adjacent dark lines, and d is the observation distance.
Spatial frequency refers to the number of cycles of sinusoidal modulation of the intensity of an image or stimulus pattern per degree of view, i.e., the number of cycles of dark fringes of a sample per degree of view. The range of the visual angle theta of an observation sample is different under different observation distances, the obtained periodicity of the dark fringes is also different, and for the same sample, the larger the observation distance d is, the larger the spatial frequency is.
An embodiment of the present invention further provides a method for evaluating a black matrix, as shown in fig. 10, including the following steps:
s21, calculating the contrast sensitivity value of the display panel to be evaluated according to the width of a plurality of light shielding strips extending along the first direction X and the width of the sub-pixels included in the black matrix of the display panel to be evaluated.
It can be understood that the light-shielding bars extending in the first direction X in the black matrix of the display panel to be evaluated have N kinds of widths.
S22, marking the contrast sensitivity value of the display panel to be evaluated as a vertical coordinate and the spatial frequency value most sensitive to human eyes as a coordinate point of a horizontal coordinate in a coordinate system where the threshold curve is obtained by the fitting method of the threshold curve for evaluating the black matrix; the light-shielding strips of the display panel to be evaluated, which extend along the first direction X, and the light-shielding strips of the sample corresponding to the threshold curve, which extend along the first direction X, have N widths.
S23, if the coordinate point is located below the threshold curve, a dark line of the display panel to be evaluated is visible; and if the coordinate point is positioned above the threshold curve, the dark line of the display panel to be evaluated is invisible.
It should be noted that, when the light-shielding bars extending along the first direction X in the black matrix of the display panel to be evaluated have N widths, comparison needs to be performed according to the threshold curves obtained by the samples of the black matrix of the light-shielding bars having M widths to determine whether the dark lines of the display panel to be evaluated are visible. M is more than or equal to N. For example, if the black matrix of the display panel to be evaluated has two widths of the light-shielding bars extending in the first direction X, the dark line visibility evaluation needs to be performed according to the threshold curve obtained from the sample of the black matrix of the light-shielding bars having the two widths.
For example, for a display panel to be evaluated having light-shielding bars with two widths, the contrast sensitivity value of the display panel to be evaluated may be taken as the ordinate, the spatial frequency value most sensitive to human eyes may be taken as the coordinate point of the abscissa, and the threshold curve obtained by fitting the sample of the black matrix having light-shielding bars with two widths may be compared. Judging whether the coordinate point is positioned above or below the threshold curve, and if the coordinate point is positioned below the threshold curve, the dark line of the display panel to be evaluated is visible; and if the coordinate point is positioned above the threshold curve, the dark line of the display panel to be evaluated is invisible.
Therefore, the embodiment of the invention establishes a relation between the display panel to be evaluated and the actual observation data of the sample, and combines the sensitivity theory of human eyes to spatial frequency and the actual observation result, so that the evaluation result is more practical, and the accuracy of evaluation is improved.
Optionally, according to
Obtaining the spatial frequency value which is most sensitive to human eyes; wherein CPD is the spatial frequency and Af is the sensitivity function of human eyes. As shown in fig. 11, the sensitivity function Af to the human eye is logarithmically scaled, and the spatial frequency value most sensitive to the human eye is obtained, and CPD is 9.18.
The samples described above are exemplified by light-shielding bars having two widths. A sample having a size of 23.6 inches, a resolution of HD1366 × 768, and a pixel width of 381.75 μm was selected, and the display screen of the sample was changed under the same ambient brightness, and the dark line thereof was actually observed, as shown in table 3 below.
TABLE 3
| Display screen | Optimum observation distance (cm) |
| Pure white picture with 127 gray scale brightness | ≈40 |
| Pure white picture with 255 gray levels of brightness | ≈40 |
| Pure yellow picture with 255 gray levels of brightness | ≈37 |
As can be seen from Table 3, the optimal observation distance of the dark line is about 40cm regardless of the change of the display image of the sample, and the spatial frequency at this time is 9.14, which is close to the spatial frequency value 9.18 to which the human eye is most sensitive. Therefore, the spatial frequency value which is most sensitive to human eyes is selected for evaluation, and the best observation effect of the human eyes on the dark line is met.
When the display panel to be evaluated is marked in the coordinate system where the threshold curve obtained by the fitting method for evaluating the threshold curve of the black matrix is located, the spatial frequency value 9.18 most sensitive to human eyes is used as the abscissa, and the contrast sensitivity value of the display panel to be evaluated is used as the ordinate, so that the relation between the spatial frequency and the human eye sensitivity is established, the evaluation result is more practical, and the evaluation accuracy is improved.
The embodiment of the invention also provides a product design method, which comprises the evaluation method of the black matrix, has the same effect as the evaluation method of the black matrix, and is not repeated herein.
Embodiments of the present invention also provide a computer-readable medium having stored thereon a computer program that, when executed, implements the above-described fitting method for evaluating a threshold curve of a black matrix or implements the above-described evaluation method for a black matrix.
An embodiment of the present invention further provides an electronic device, including: a processor, a memory; the memory is used for storing one or more programs; the one or more programs, when executed by the processor, implement the fitting method for evaluating the threshold curve of the black matrix described above, or implement the evaluation method of the black matrix described above.
Those of ordinary skill in the art will understand that: all or part of the steps of implementing the method embodiments may be implemented by hardware related to program instructions, and the program may be stored in a computer-readable storage medium, and when executed, executes the steps including the method embodiments; and the aforementioned storage medium includes: various media that can store program codes, such as ROM, RAM, magnetic or optical disks.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A fitting method for evaluating a threshold curve of a black matrix, comprising:
calculating the contrast sensitivity value of each sample according to the widths of a plurality of light shading strips extending along a first direction and the widths of sub-pixels included in the black matrix of each sample in a plurality of sample display panels; wherein the light shielding strips extending along the first direction in the plurality of samples have N kinds of widths, and N is more than or equal to 2; the width of the light-shielding strip in at least part of the samples is not completely equal to the width of the light-shielding strip in other samples; the first direction is a length direction of each of the samples, or the first direction is a width direction of each of the samples;
calculating to obtain space frequency values corresponding to the samples at different observation distances according to the plurality of samples and different observation distances; for each sample, marking the visible or invisible condition of the dark line of the sample observed by human eyes under the same environment brightness and corresponding observation distance in a coordinate system taking the spatial frequency as the abscissa and the contrast sensitivity value as the ordinate;
fitting a threshold curve, wherein coordinate points for identifying visible conditions and coordinate points for identifying invisible conditions are respectively positioned on two sides of the threshold curve;
wherein, calculating the contrast sensitivity value of each sample according to the widths of the light shielding strips and the widths of the sub-pixels, which are included in the black matrix of each sample and extend along the first direction, comprises:
for each sample, obtaining a continuous brightness distribution curve corresponding to the sample according to the width of the light shielding strips extending along the first direction and the width of the sub-pixels included in the black matrix of the sample, and the brightness ratio of the sub-pixels of different colors in the sample; the abscissa of the brightness distribution curve is width, and the ordinate is brightness;
obtaining a frequency domain spectrum corresponding to the sample according to the brightness distribution curve;
calculating to obtain a contrast sensitivity value of the sample according to a component spectrum value of an absolute spatial frequency corresponding to a dark line period in the frequency domain spectrum of the sample and a direct current component spectrum value;
wherein the contrast sensitivity value is (component spectrum value/direct current component spectrum value of absolute spatial frequency corresponding to a dark line period in the frequency domain spectrum of the sample) × 2 × 100%.
2. The fitting method of the threshold value curve for evaluating a black matrix according to claim 1, wherein obtaining the luminance distribution curve corresponding to the sample based on widths of a plurality of light-shielding bars extending in the first direction, widths of sub-pixels included in the black matrix of the sample, and luminance ratios of the sub-pixels of different colors in the sample comprises:
obtaining an integer ratio of the widths of the light-shielding bars extending along the first direction and the widths of the sub-pixels included in the black matrix of the sample according to the widths of the light-shielding bars extending along the first direction and the widths of the sub-pixels included in the black matrix of the sample;
and obtaining a brightness distribution curve corresponding to the sample according to the integral ratio of the widths of the shading strips and the widths of the sub-pixels which extend along the first direction and the brightness ratio of the sub-pixels with different colors in the sample, wherein the black matrix of the sample comprises the shading strips and the sub-pixels.
3. The fitting method for evaluating a threshold value curve of a black matrix according to claim 1 or 2, wherein the different colors include a first color, a second color, and a third color, and the first color, the second color, and the third color are three primary colors;
the brightness ratio of the sub-pixels with different colors in the sample is obtained by testing the brightness value of the sample under the conditions that the monochrome first color is used, the gray scale is the middle gray scale, the monochrome second color is used, the gray scale is the middle gray scale, the monochrome third color is used, and the gray scale is the middle gray scale.
4. The fitting method of the threshold value curve for evaluating the black matrix according to claim 1 or 2, wherein obtaining the frequency domain spectrum corresponding to the sample from the luminance distribution curve comprises:
sampling the brightness distribution curve, and taking the absolute spatial frequency corresponding to the sampling interval as the sampling frequency;
and calling a fast Fourier transform function to perform fast Fourier transform to obtain a frequency domain spectrum corresponding to the sample.
5. The fitting method for evaluating a threshold value curve of a black matrix according to claim 1,
for each of said samples, according to the formula
Calculating to obtain a spatial frequency value of the sample under the corresponding observation distance;
and CPD is the spatial frequency value, l is the product of the number of the dark lines of the sample observed by human eyes at the observation distance and the distance between the dark lines, t is the distance between the adjacent dark lines, and d is the observation distance.
6. A method for evaluating a black matrix, comprising:
calculating to obtain a contrast sensitivity value of the display panel to be evaluated according to the widths of a plurality of shading strips extending along a first direction and the widths of sub-pixels included in a black matrix of the display panel to be evaluated;
marking the contrast sensitivity value of the display panel to be evaluated as a vertical coordinate, a spatial frequency value which is most sensitive to human eyes as a coordinate point of a horizontal coordinate in a coordinate system where a threshold curve is obtained by the method for fitting the threshold curve for evaluating the black matrix according to any one of claims 1 to 5; the light-shielding strips of the display panel to be evaluated, which extend along the first direction, and the light-shielding strips, which extend along the first direction, in the sample corresponding to the threshold curve all have N widths;
if the coordinate point is located below the threshold curve, a dark line of the display panel to be evaluated is visible; and if the coordinate point is positioned above the threshold curve, the dark line of the display panel to be evaluated is invisible.
7. The method of evaluating a black matrix according to claim 6, further comprising: according to
Obtaining the spatial frequency value which is most sensitive to human eyes; wherein CPD is the spatial frequency and Af is the sensitivity function of human eyes.
8. A method for designing a product, comprising the method for evaluating a black matrix according to claim 6 or 7.
9. A computer-readable medium, on which a computer program is stored, which, when being executed, carries out the fitting method of the threshold curve for evaluating a black matrix according to any one of claims 1 to 5, or the evaluation method of a black matrix according to claim 6 or 7.
10. An electronic device, comprising: a processor, a memory; the memory is used for storing one or more programs;
the one or more programs, when executed by the processor, implement the fitting method for evaluating a threshold curve of a black matrix according to any one of claims 1 to 5, or implement the evaluation method of a black matrix according to claim 6 or 7.
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