Method for testing brightness uniformity of direct type backlight display screen

Abstract

The invention discloses a method for testing the brightness uniformity of a direct type backlight display screen. The method comprises the following steps of: shooting the brightness distribution of the whole surface of a display screen to be tested by using a brightness meter or a colorimeter to obtain a brightness distribution diagram; on the basis of the obtained brightness distribution diagram, on the basis of the original data, shrinking inwards by 1 / 4 to obtain an effective value range as shown in figure 3; identifying the minimum value and the maximum value of the brightness in the determined effective value range, and calculating the ratio of the minimum value and the maximum value to evaluate the brightness uniformity of the display screen; in the effective value range, dividing the brightness distribution diagram into a plurality of partitions according to the partition number, the arrangement mode and the screen resolution of the backlight source of the display screen, and calculating the length and the width of each partition; a plurality of vertical and horizontal sectioning lines are drawn according to the number and the arrangement mode of the partitions, as shown in figure 4, the brightness value of each point on the lines is measured, a brightness distribution curve is drawn, and then the characteristic parameters of the curve, namely the wave height, the half-wave width and the wavelength, are calculated so as to evaluate the severity of the lamp shadow effect. Compared with an existing uniformity testing method, the method has the advantages that the uniformity of the display screen can be directly revealed from the data level, and the defects of a mainstream testing method that errors are increased and testing objectivity is reduced due to the fact that the mainstream method cannot directly reflect the uniformity only through numerical values and depends on human eye observation and subjective judgment are effectively overcome. According to the method, the accuracy and reliability of the brightness uniformity test of the display screen are remarkably improved by reducing the intervention of human factors.

Description

Technical Field

[0001] The present invention relates to the technical field of display testing, and particularly to a method for testing the brightness uniformity of a direct-lit backlight display screen. Background Art

[0002] Brightness uniformity testing is a key indicator for evaluating the quality of a display screen. It can help identify potential defects, faults, and poor performance issues, so as to repair or replace them in a timely manner to ensure the stable operation of the display screen. For a display screen using a direct-lit backlight, the LEDs at the center position have better brightness uniformity due to the light compensation effect of the surrounding LEDs. However, the LEDs at the edge lack this compensation, resulting in a decrease in uniformity. In addition, in a direct-lit backlight, the LED light source is directly located behind the liquid crystal panel, and the light directly propagates from the light source to the panel. Due to the light-emitting characteristics of the LED light source, the closer the distance is to the center position of the light source, the greater the intensity of the light; the farther the distance is from the center position, the weaker the intensity of the light. When the number of LED light sources arranged in the backlight module is small, the distance between two LED light sources will become larger, resulting in a problem of the light-emitting angle of the light emitted by the LED light sources. Part of the light directly irradiates the diffusion plate, and part of the light projects onto the reflectors on the rear and surrounding sides. After one or more reflections by the reflectors, it finally irradiates the diffusion plate. During the actual working process, the light projected to the rear by the LED light sources will form light spots (regions with relatively high visible brightness to the naked eye) on the reflectors installed on the bottom surface of the backplane. Since the light intensity in the light spot region is high, the light intensity reflected to the diffusion plate is also high, resulting in a high brightness in this region; while the light projected outside the light spot region has a weak intensity, so after being reflected by the reflector, the intensity projected onto the diffusion plate is also weak, thus forming an uneven bright and dark "lantern" phenomenon on the liquid crystal panel, that is, the lamp shadow problem will occur.

[0003] Currently, there are mainly two common methods for testing the brightness uniformity of a display screen:

[0004] Point measurement method: As Figure 1 shown, by selecting 5 or 9 points on the screen for testing, these points are arranged in a 3x3 or 5x3 array, the edge points are located at a position 1 / 10 of the screen width away from the screen edge, and the middle points are located between the edge points. Since this method only tests a limited number of points and cannot comprehensively cover the edge region and the lamp shadow region, it cannot accurately reflect the uniformity of the edge and the impact of the lamp shadow on the overall uniformity.

[0005] Full-screen scanning method: Use a brightness and chrominance meter to photograph the brightness distribution of the entire screen. According to the resolution and pixel size of the display screen, appropriately narrow the value range to exclude edge pixels, and then calculate the ratio of the minimum brightness value to the maximum brightness value to determine the uniformity. Although this method can obtain the brightness distribution data of the entire screen, if the edge uniformity is extremely poor while the middle area performs well, the calculated uniformity value may be too low, thus losing its reference value. At the same time, since the lamp shadow is just a dark spot with little difference in brightness from the surrounding area, the full-screen scanning method is also difficult to accurately reflect the impact of the lamp shadow on the uniformity.

[0006] In summary, both methods have their limitations. The point measurement method cannot fully cover the screen, and the full-screen scanning method also has deficiencies in dealing with edge and lamp shadow problems. Summary of the Invention

[0007] The present invention provides a test method that can improve the test results of the brightness uniformity of a display screen.

[0008] The method for testing the brightness uniformity of a direct-lit backlight display screen according to the present invention includes the following steps: S1. Use a brightness meter or a chrominance meter to photograph the brightness distribution of the entire surface of the display screen to be tested to obtain a brightness distribution map; S2. Based on the obtained brightness distribution map, shrink inward by 1 / 4 on the basis of the original data to obtain an effective value range; S3. Within the determined effective value range, identify the minimum and maximum brightness values and calculate the ratio of the two to evaluate the brightness uniformity of the display screen; S4. Within the effective value range, divide the brightness distribution map into several partitions according to the number of partitions, arrangement pattern of the backlight sources of the display screen, and the screen resolution, and calculate the length and width of each partition; S5. According to the number of partitions and the arrangement pattern, draw multiple vertical and horizontal cutting lines, measure the brightness values of each point on these lines, draw a brightness distribution curve, and then calculate the characteristic parameters of the curve: wave height, half-wave width, and wavelength, to evaluate the severity of the lamp shadow effect.

[0009] The described method for testing the brightness uniformity of a direct - type backlight display screen uses a high - precision luminance meter or colorimeter device to measure the display screen, records the luminance values of each pixel point, and thus generates a luminance distribution map of the entire display screen, providing a detailed data basis for subsequent analysis. To exclude the influence of edge effects, based on the original luminance distribution data, the measurement range is shrunk inward by 1 / 4 to determine a more accurate effective measurement area. Within the effective measurement area, by comparing the luminance values of all measurement points, the minimum and maximum luminance values are found. Then, the ratio of these two values is calculated and used as an index to measure the brightness uniformity of the display screen. According to the specific zoning and arrangement of the backlight source of the display screen and the resolution of the screen, the luminance distribution map is divided into several zones, and the length and width of each zone are accurately calculated for more detailed analysis. Within the effective measurement area, multiple vertical and horizontal cutting lines are drawn according to the layout of the zones, the luminance values of the points on these lines are measured, and the luminance distribution curves are drawn. By analyzing these curves, characteristic parameters such as wave height, half - wave width, and wavelength are calculated. These parameters can quantify the light - shadow effect on the display screen and provide an important basis for evaluating the overall quality of the display screen. In summary, compared with the existing uniformity testing methods, this method can directly reveal the uniformity of the display screen from the data level, effectively overcoming the deficiencies of the mainstream testing methods: the mainstream methods often cannot directly reflect the uniformity only through numerical values and rely on human eye observation and subjective judgment, which not only increases errors but also reduces the objectivity of the test. This method significantly improves the accuracy and reliability of the brightness uniformity test of the display screen by reducing the intervention of human factors. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 It is a schematic diagram of the existing point - measurement method.

[0011] Figure 2 It is a flowchart of a method for testing the brightness uniformity of a direct - type backlight display screen.

[0012] Figure 3 It is a schematic diagram of the inward contraction of the luminance distribution map in step S2.

[0013] Figure 4 It is a schematic diagram of the cutting line in step S4.

[0014] Figure 5 It is a schematic diagram of the luminance distribution curve in step S5.

[0015] Figure 6 It is a schematic diagram of reading luminance values.

[0016] Figure 7 It is a schematic diagram of the luminance curve of a straight line.

[0017] Figure 8 It is a schematic diagram of the luminance distribution curve.

[0018] Figure 9 Schematic diagram for measuring curve characteristic values such as wavelength, wave height, and half-wave width on a curve.

[0019] Figure 10 Schematic diagram where the lamp shadow can be clearly seen by the human eye.

[0020] Figure 11 Schematic diagram where the human eye needs to look closely to see the lamp shadow.

[0021] Figure 12 Schematic diagram where it is almost difficult for the human eye to see the lamp shadow. Detailed implementation manner

[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all the structures.

[0023] As Figure 2 shown, a method for testing the brightness uniformity of a direct-lit backlight display screen includes the following steps: S1. Use a luminance meter or a colorimeter to photograph the brightness distribution of the entire surface of the display screen to be tested to obtain a brightness distribution map; S2. Based on the obtained brightness distribution map, shrink inward by 1 / 4 on the basis of the original data to obtain an effective value range, as Figure 3 shown; S3. In the determined effective value range, identify the minimum and maximum values of the brightness, and calculate the ratio of the two to evaluate the brightness uniformity of the display screen; S4. In the effective value range, divide the brightness distribution map into several partitions according to the number of partitions, arrangement mode, and screen resolution of the backlight source of the display screen, and calculate the length and width of each partition; S5. According to the number of partitions and the arrangement mode, draw multiple vertical and horizontal cutting lines, as Figure 4 shown, and measure the brightness values of each point on these lines, draw a brightness distribution curve, and then calculate the characteristic parameters of the curve: wave height, half-wave width, and wavelength, to evaluate the severity of the lamp shadow effect.

[0024] The described method for testing the brightness uniformity of a direct - type backlight display screen uses a high - precision luminance meter or colorimeter device to measure the display screen, records the brightness values of each pixel point, and thus generates a brightness distribution map of the entire display screen, providing a detailed data basis for subsequent analysis. To exclude the influence of edge effects, on the basis of the original brightness distribution data, the measurement range is shrunk inward by 1 / 4, thereby determining a more accurate effective measurement area. Within the effective measurement area, by comparing the brightness values of all measurement points, the minimum and maximum brightness values are found. Then, the ratio of these two values is calculated and used as an index to measure the brightness uniformity of the display screen. According to the specific zoning and arrangement of the backlight source of the display screen and the resolution of the screen, the brightness distribution map is divided into several zones, and the length and width of each zone are accurately calculated for more detailed analysis. Within the effective measurement area, multiple vertical and horizontal cutting lines are drawn according to the layout of the zones, the brightness values of the points on these lines are measured, and the brightness distribution curves are drawn. By analyzing these curves, characteristic parameters such as wave height, half - wave width, and wavelength are calculated. These parameters can quantify the light - shadow effect on the display screen and provide an important basis for evaluating the overall quality of the display screen. In summary, compared with the existing uniformity testing methods, this method can directly reveal the uniformity of the display screen from the data level, effectively overcoming the deficiencies of the mainstream testing methods: the mainstream methods often cannot directly reflect the uniformity only through numerical values and rely on human eye observation and subjective judgment, which not only increases errors but also reduces the objectivity of the test. This method significantly improves the accuracy and reliability of the brightness uniformity test of the display screen by reducing the intervention of human factors.

[0025] Further, in step S2, the length of the long side is shrunk by 1 / 4 of its length, and the width of the short side is shrunk by 1 / 4 of its width, that is, on the long side and the short side, 1 / 4 of the length and width are removed to reduce the influence of edge effects on the measurement results, as Figure 3 shown.

[0026] Further, in step S4, the calculation values of the length and width of each zone are as follows: Where: LEDzones represents an LED lamp zone, LEDzones(H) represents the horizontal - direction length of an LED lamp zone, LEDzones(V) represents the vertical - direction length of an LED lamp zone, Resolution represents the resolution, Resolution(H) represents the horizontal - direction resolution of the display screen, Resolution(V) represents the vertical - direction resolution of the display screen, LEDnumber represents the number of LEDs, LEDnumber(H) represents the number of LEDs in the horizontal direction, and LEDnumber(V) represents the number of LEDs in the horizontal direction.

[0027] Further, in step S5, the wave height is the brightness peak, the half-wave width is the width at half of the brightness peak, and the wavelength is the distance between two adjacent peaks, such as Figure 5 shown.

[0028] Specifically, use the common brightness test instrument on the market, the imaging brightness meter, to collect the test surface of the display screen to obtain the following brightness distribution diagram, from which the brightness value can be directly read. If you click the middle point with the mouse, you can get the brightness value L (cd / m 2 ),like Figure 6 shown.

[0029] To further illustrate, after obtaining the brightness distribution diagram, you can use the instrument's own software to draw a straight line, such as Figure 7 As shown, the instrument software will read the brightness value of each point on this line, and then use drawing software (such as origin, etc.) to draw the brightness distribution curve of each point along the line according to the brightness value of each point on the line, and obtain the brightness curve of one of the drawing lines, such as Figure 8 shown.

[0030] Use drawing software to obtain the brightness distribution curve of each point along the line, and then measure the wavelength, wave height, half-wave width and other values ​​representing the characteristics of the curve on the curve, such as Figure 9 As shown, the wave height unit is expressed in brightness unit cd / m2, and the wavelength and half-wave width unit is expressed in pixel unit pixel.

[0031] The following is the test data, which is summarized through multiple tests. Figure 10 As shown in the figure, the human eye can clearly see the problem of light shadow: at this time, the wave height is ≥25cd / m2, the wave width is ≥35pixel, and the wavelength is ≥50pixel. Figure 11 As shown, the human eye needs to look carefully to see the problem of light shadow: at this time 10cd / m2<wave height<25cd / m2, 15pixel<half-wave width<35pixel, 20pixel<wavelength<50pixel. Figure 12 As shown, it is almost difficult to see the light shadow problem: at this time the wave height is less than 10cd / m2, the half-wave width is less than 15pixel, and the wavelength is less than 20pixel.

[0032] The above are only the preferred embodiments of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in more detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, it may also include more other equivalent embodiments, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for testing brightness uniformity of a direct-lit backlight display screen, characterized in that: The following steps are involved: S1. Use a brightness meter or a colorimeter to photograph the brightness distribution of the entire display screen to be tested to obtain a brightness distribution diagram; S2, based on the acquired brightness distribution map, shrink the original data by 1 / 4 to obtain the effective value range; S3. Within the determined valid value range, identify the minimum and maximum values ​​of the brightness, and calculate the ratio between the two to evaluate the brightness uniformity of the display screen; S4. Within the valid value range, according to the number of partitions, arrangement mode and screen resolution of the display backlight source, divide the brightness distribution map into several partitions, and calculate the length and width of each partition; S5. Draw multiple vertical and horizontal section lines according to the number and arrangement of partitions, measure the brightness value of each point on these lines, draw a brightness distribution curve, and then calculate the characteristic parameters of the curve: wave height, half-wave width and wavelength, to evaluate the severity of the light shadow effect.

2. The method for testing brightness uniformity of a direct-lit display screen according to claim 1, characterized in that: In step S2, the long side is shrunk by 1 / 4 of the length, and the wide side is shrunk by 1 / 4 of the width.

3. The method for testing brightness uniformity of a direct-lit display screen according to claim 1, characterized in that: In step S4, the length and width of each partition are calculated as: Wherein: LEDzones represents an LED light zone, LEDzones(H) represents the horizontal length of an LED light zone, LEDzones(V) represents the vertical length of an LED light zone, Resolution represents the resolution, Resolution(H) represents the horizontal resolution of the display screen, Resolution(V) represents the vertical resolution of the display screen, LEDnumber represents the number of LEDs, LEDnumber(H) represents the number of LEDs in the horizontal direction, and LEDnumber(V) represents the number of LEDs in the horizontal direction.

4. The method for testing brightness uniformity of a direct-lit backlight display screen according to claim 1, characterized in that: In step S5, the wave height is the brightness peak, the half-wave width is the width at half of the brightness peak, and the wavelength is the distance between two adjacent peaks.

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