CN104658461A - Method for testing light emission uniformity of display - Google Patents

Abstract

The invention discloses a method for testing the luminous uniformity of a display. Spot pixels and background pixels; a selection window array arranged by a plurality of identical selection windows is set in the image test area, so that each selection window in the selection window array is set on the image test area corresponding to each luminescence of the display Outside the edge of the unit; read and calculate the ratio of the bright spot pixels in each selection window image on the image test area to the bright spot pixels of the selection window of all pixels, and the average gray level of each selection window pixel, thereby calculating the display. Uniformity of light emission. This method can remove the influence of the part outside the area of the light-emitting unit on the evaluation of the light-emitting unit, and can objectively detect and evaluate the uniformity of light emission of the light-emitting unit of the display.

Description

Test method for luminous uniformity of displays

technical field

The invention relates to the technical field of display manufacturing and computer application, in particular to a method for detecting the luminous performance of a display by using a computer.

Background technique

Display refers to a collection of multiple active light-emitting points arranged in rows and columns. The device types of its light source include liquid crystal display (LCD), light-emitting diode display (LED), field emission display (FED) and plasma display (PDP). )wait. With the rapid development of information technology, displays have been widely used in terminals of various multimedia devices. It can be used as a lighting source and backlight, and can also be used for screens that display various information such as characters, graphics, and videos. The brightness uniformity of a display is an important factor affecting its lighting or display performance, so it is very necessary to propose an effective test method for the brightness uniformity of a light source to provide guidance for the production and development of related devices.

At present, the test method mainly uses a luminance meter to randomly select several sampling points of the display to test its luminance value, and then obtains the final evaluation result through a certain algorithm. This method is one-sided, and each measurement can only obtain the data of one sampling point. The test results require multiple adjustments to the test instrument, which takes a lot of time. It is reported that the luminance information of dot matrix pixels is obtained by the sensor, combined with image processing technology and statistical principles, the gray histogram of the pixel is fitted to a normal distribution curve, and the standard deviation is used to evaluate the luminance uniformity. It is also reported that the brightness image obtained by the sensor is divided into several sub-regions, and the brightness feature factors, spatial position factors and texture detail factors based on HVS (human visual characteristics) of each sub-region are calculated, and the characteristics of these factors are used as sub-regions. The evaluation parameters of each sub-area are used to evaluate the brightness uniformity of the light source by the value of the discrete degree of each sub-region parameter. However, the above methods are all directly testing the acquired images, without correcting the geometric distortion of the image caused by shooting; nor distinguishing between luminous points and non-luminous areas, and including those non-luminous areas that should not participate in the evaluation are also included in the evaluation scope; and , or only test the uniformity of brightness, or only test the uniformity of distribution, which is one-sided and does not comprehensively evaluate the uniformity of light emission; the above deficiencies lead to inaccurate evaluation of the uniformity of light emission of the display.

Contents of the invention

The problem to be solved by the present invention is to provide a method for testing the luminous uniformity of a display, which can objectively detect and evaluate the luminous uniformity of a luminous unit of a display.

In order to solve the above problems, the technical solution of the present invention is: the method for testing the luminous uniformity of this display comprises the following steps:

a. Take an image of the part that needs to be detected to obtain a full-brightness display;

b. The acquired image is displayed by computer, and a test area is selected in the image;

c. Read the gray value of each pixel in the image test area, and segment bright spot pixels and background pixels according to the set gray threshold;

d. A selection window array composed of a plurality of identical selection windows is set in the image test area, and the shape, size and array parameters of the selection windows in the selection window array are adjusted, so that each selection window in the selection window array is nested The above-mentioned image test area represents the position of each light-emitting unit in the corresponding part of the display;

e. Read and calculate the ratio of the bright spot pixels in each selection window image on the image test area to the bright spot pixels of the selection window of all pixels, and the average gray level of each selection window pixel, from each selection window in the image test area The brightness uniformity of the display is calculated by the ratio of bright spot pixels and the average value of pixel grayscale.

In the above method for testing the luminous uniformity of a display, when there is lens distortion in the captured image, distortion correction may be performed on the captured image for the deformation caused in the shooting before entering step c.

Due to the adoption of the above technical scheme, the present invention has the following beneficial effects compared with the prior art: the light-emitting unit part and the non-light-emitting unit part in the representative display can be separated, and only the light-emitting unit part that should emit light can be tested, which can be more accurate. Objectively evaluate the luminous uniformity of the luminous part of the display.

Detailed ways

Below in conjunction with example the present invention is described in further detail.

Example 1——Test method for the uniformity of light emission in the central part of the field emission display screen:

Step 1: Use a camera to shoot a video image of the central part of the field emission display in a fully bright state, and capture one of the frames in the computer as a sample image for evaluating the uniformity of the central part of the field emission display;

Prepare an evaluation program applied to a computer, the evaluation program has the following functions:

Open and display the image in the computer, read the gray value of each pixel of the displayed image, and segment bright spot pixels and background pixels according to the set gray threshold;

Generate a vector graphic with multiple selection windows arranged in an array in the computer. The array parameters of the selection windows are adjustable, and the shape and size of each selection window are the same. The selection window can be set as an adjustable circle or ellipse by selecting different parameters. shape, square or rectangle;

Composite vector graphics to the displayed image, read the gray value of each pixel in each selection window, calculate the ratio of bright spot pixels in the selection window, and distinguish the selection window according to the bright spot pixel ratio parameter settings in each selection window Whether it is an effective light-emitting unit, and calculate the number of effective light-emitting units and the distribution uniformity value of the effective light-emitting unit according to the proportion and distribution of effective light-emitting units; calculate the gray value of the selected area window by calculating the gray value of each selected area window, and calculate the gray value of the selected area window. Window grayscale value tolerance and uniformity of grayscale.

Step 2: Run the above evaluation program in the computer, open and display the obtained sample image, select a rectangular area with 5 light-emitting units in length and width in the image sample as the test area; The shape of the selection window is circular, and through the adjustment of the parameters of the size of the polygonal selection window and the parameters of the selection window array, each selection window is just framed in the sample image to represent 25 light-emitting units of the field emission display Within the edge of the position; press the calculation key of the evaluation program, the evaluation program first reads and analyzes the gray value of each pixel in the test area in the sample image, and artificially sets the gray value threshold and full brightness value in the evaluation program. The grayscale value is 255, the grayscale value of all black is 0, and the grayscale threshold is set to 150, then the pixels with a grayscale value of 150 and above are judged as bright spot pixels, and the pixels with a grayscale value below 150 are judged as background pixels ; Calculate the proportion of bright spot pixels in each selection window, and the selection window with a proportion of bright spot pixels reaching more than 60% is determined to be an effective light emitting unit of the field emission display screen represented by the selection window, and the bright spot pixel The selection window accounting for less than 60% is judged as the light-emitting unit of the field emission display screen represented by the selection window is an invalid light-emitting unit, and the evaluation program calculates the field emission display represented by the sample image according to the number of effective light-emitting units in the test area The effective light-emitting unit ratio in the central part of the screen; the evaluation program also calculates the average gray value of pixels in each selected window by reading the gray value of each pixel in each selected window, and counts the average gray value of pixels in each selected window. Calculate the gray value tolerance of the effective light emitting unit in the central part of the field emission display screen represented by the sample image, and evaluate the gray value uniformity of the light emitting unit according to the tolerance value.

Example 2——Test method for luminous uniformity in the upper right corner of the field emission display screen

Step 1: Use a camera to take a video image of the upper right corner of the field emission display in a fully bright state, and capture one of the frames in the computer as a sample image for evaluating the luminous uniformity of the upper right corner of the field emission display;

The second step: use image processing software to correct the distortion of the sample image caused by the image deformation during shooting, so that the position between each light-emitting unit reflected in the sample image conforms to the real situation of the position of the corresponding light-emitting unit in the field emission display screen;

Step 3: Run the evaluation program described in Example 1 in the computer, and open and display the sample image after the distortion correction process in the second step, and select a rectangle whose length and width are 5 light-emitting units in the image sample The area is the test area; according to the characteristic that the light-emitting unit of the field emission display screen in the sample image is circular, the shape of the selection window is selected as a circle, and through the adjustment of the parameters of the size of the polygonal selection window and the parameters of the selection window array, each selection window Just within the edge of the sample image representing the 25 light-emitting units of the field emission display; press the calculation key of the evaluation program, the evaluation program first reads and analyzes the gray value of each pixel in the test area in the sample image, Artificially set the grayscale value threshold in the evaluation program, the grayscale value of full brightness is 255, the grayscale value of full black is 0, and the grayscale threshold is set to 150, then the pixels with grayscale value of 150 and above are judged as bright Spot pixels, pixels whose gray value does not reach 150 are determined as background pixels; calculate the proportion of bright spot pixels in each selection window, and the selection window with a proportion of bright spot pixels exceeding 60% is determined as the field represented by the selection window The light-emitting unit of the emission display screen is an effective light-emitting unit, and the selection window whose bright spot pixels account for less than 60% is determined to be an invalid light-emitting unit of the field emission display screen represented by the selection window. The evaluation program is based on the effective light-emitting unit in the test The number of areas in the area is counted to obtain the effective light-emitting unit ratio of the upper right corner of the field emission display represented by the sample image; the evaluation program also calculates the gray value of the pixel in each selection window by reading the gray value of each pixel in each selection window Calculate the average gray value of pixels in each selection window, calculate the gray value tolerance of the effective light-emitting unit at the upper right corner of the field emission display represented by the sample image, and evaluate the gray value of the light-emitting unit according to the tolerance value Degree value uniformity. the

Claims (2)

1. A test method for display luminous uniformity, characterized in that it may further comprise the steps: a. Take an image of the part that needs to be detected to obtain a full-brightness display; b. The acquired image is displayed by computer, and a test area is selected in the image; c. Read the gray value of each pixel in the image test area, and segment bright spot pixels and background pixels according to the set gray threshold; d. A selection window array composed of a plurality of identical selection windows is set in the image test area, and the shape, size and array parameters of the selection windows in the selection window array are adjusted, so that each selection window in the selection window array is nested The above-mentioned image test area represents the position of each light-emitting unit in the corresponding part of the display; e. Read and calculate the ratio of the bright spot pixels in each selection window image on the image test area to the bright spot pixels of the selection window of all pixels, and the average gray level of each selection window pixel, from each selection window in the image test area The brightness uniformity of the display is calculated by the ratio of bright spot pixels and the average value of pixel grayscale. 2. The method for testing the luminous uniformity of a display according to claim 1, characterized in that: before entering step c, deformity correction is carried out to the distortion caused in the shooting of the acquired image.