CN100587781C - Method for on-line brightness correction and color gamut optimization of full-color LED display screen - Google Patents

Abstract

The invention discloses a method for online brightness correction and color gamut optimization of a full-color LED display screen. The method comprises the following specific steps: shooting white balance pictures and RGB (red, green and blue) tricolor pictures of the full-color LED display screen to obtain a planar light image; reading planar light image information; determining and storing the number of pixels and the position coordinates of each pixel; measuring and storing the white light and tricolor brightness values and color coordinate values of the selected pixel; calculating and storing pixel brightness and color coordinate average values; comparing the white light brightness value of the pixel with a standard brightness value, judging whether the difference value exceeds the standard, finishing correction if the difference value does not exceed the standard, and performing the following steps if the difference value exceeds the standard; calculating and storing the tricolor brightness distribution value of the selected pixel; calculating color coordinate values G (x, y), R (x, y) and B (x, y) of the three primary colors after light distribution and judging whether the three primary colors are in a standard color gamut or not; repeating the steps g and h when the color is not in the standard color gamut; in the standard color gamut, the brightness correction parameters are output to correct the brightness of the selected pixel LED.

Description

Method for online brightness correction and color gamut optimization of full-color LED display

Technical field:

The invention relates to a method for calibrating the brightness of a full-color LED display, in particular to an online brightness calibrating method for a full-color LED display that can correct brightness attenuation and ensure optimization of the color gamut space during delivery and use of the full-color LED display And the method of color gamut optimization.

Background technique:

The full-color LED display is a flat light composed of RGB three-color LED chips. Generally, the brightness of the RGB three-color LED chips is calibrated according to the standard value before leaving the factory. Due to different manufacturing processes, LED chips have discreteness in terms of wavelength and brightness. Especially in the process of use, due to the different brightness attenuation coefficients of RGB three-color LED chips, the color gamut space is deformed, resulting in mottled and dirty LED displays. screen phenomenon, it is difficult to maintain a high-quality, high-uniform picture for a long time. During maintenance, the full-color LED display can only be disassembled and returned to the factory for inspection and calibration, which not only affects the normal operation of the display, but also wastes a lot of manpower and material resources.

Invention content:

The present invention aims to solve the problem of brightness attenuation and deformation of color gamut space existing in the prior art, and provides a full-color LED display that can correct brightness attenuation and ensure color gamut space optimization during use. A method for online brightness correction and color gamut optimization of color LED displays.

The technical solution of the present invention is: a method for online brightness correction and color gamut optimization of a full-color LED display, which is characterized in that the following steps are repeated:

a. Take full-color LED display white balance screen, RGB tri-color screen to obtain plane light image;

b. Read the plane light image information;

c. Determine and store the number of pixels and the position coordinates of each pixel;

d. Measure and store the white light luminance value, three primary color luminance values and color coordinate values of the selected pixels;

e. Calculate and store the average value of pixel white light brightness, the average brightness of three primary colors and the average value of color coordinates;

f. Compare the brightness value of the pixel white light with the standard brightness value of white light to determine whether the difference exceeds the standard, and if it does not exceed the standard, end the calibration, and if it exceeds the standard, proceed to the following steps;

g. Calculate and store the brightness and light distribution values of the three primary colors of the selected pixels;

h. Calculate the color coordinate values G(x, y), R(x, y), and B(x, y) of the three primary colors after light distribution and compare the standard color coordinate values to determine whether they are within the standard color gamut;

i. Not within the standard color gamut, repeat steps g and h;

j. In the standard color gamut, output brightness correction parameters to correct the LED brightness of the selected pixel.

The g step is to compare the brightness of the original color with the standard brightness value of the original color in accordance with the order of green, red, and blue colors in units of pixels, and the difference is filled in proportion by the other two colors of light: the brightness difference of green light is determined by the red Light compensation 30-35%, blue light compensation 65-70%; red light brightness difference is 38-42% by green light compensation, blue light compensation 58-62%; blue light brightness difference is 82-85% by red light compensation , Green light compensation 15 to 18%.

The present invention can also detect and correct the brightness attenuation of pixels during use (online) except when the full-color LED display leaves the factory. The phenomenon of mottled and dirty screens caused by different brightness attenuation coefficients of different color LED chips and color gamut deformation saves a lot of manpower and material resources. In particular, the supplementary light method used can not only correct the brightness attenuation, but also optimize the color gamut space, ensuring the fidelity effect of the display screen, so that the LED display screen can always maintain bright colors and uniform brightness during use.

Description of drawings:

Fig. 1 is a flowchart of an embodiment of the present invention.

Detailed ways:

The specific implementation manner of the present invention will be described below with reference to the accompanying drawings. The equipment used in the present invention includes: a CCD camera, an image processing module, an image recording module, a calculation module, adjustment parameters, and an LED control circuit.

CCD camera: It is used to shoot white light and RGB three-primary color pictures of LED display, and obtain corresponding plane light images.

Image processing module: perform image processing on each pixel of the obtained plane image to obtain the number of screen pixels and position coordinates; measure and calculate the brightness value of white light, the brightness value of three primary colors, and the color coordinates Cx and Cy for each selected pixel .

Calculation module: Calculate the average value of pixel white light brightness, the average brightness of RGB three primary colors and the average value of color coordinates.

Image recording module: record the number of pixels, position coordinates, brightness and color coordinates of LEDs of each color and the average value.

Adjust the parameter output module, and adjust the output parameter to a PWM signal that modulates the gray scale of the LED.

The LED control circuit is installed in the LED display control system.

Described image processing module, calculation module, image recording module and adjustment parameter output module can be completed by general-purpose computer, and described CCD camera is to be connected with computer by USB interface, and computer can be connected with LED by USB, ethernet or serial interface. connected to the control system.

Example 1:

a. Use a CCD camera with two-dimensional test photometer and colorimeter function to shoot full-color LED display white balance screen and RGB three primary color screen to obtain plane light image;

b. The computer reads the plane light image information through the USB interface;

c. The computer determines and stores the number of pixels and the position coordinates of each pixel, and the selected pixels can be each pixel or set according to needs;

d. Measure and store the white light luminance value, three primary color luminance values and color coordinate values of the selected pixels;

e. Calculate and store the average value of pixel white light brightness, the average brightness of three primary colors and the average value of color coordinates;

f. Compare the brightness value of the pixel white light with the standard white light brightness value, and judge whether the difference exceeds the standard, that is, whether it exceeds ±5% of the standard brightness value. ;

The standard luminance value of the white light may be a luminance value designed at the factory, or a luminance value that is corrected and formulated based on the average value of the white light luminance.

g. Calculate and store the light distribution value required for the brightness of the three primary colors of the selected pixel according to the standard brightness value designed by the factory;

h. Calculate the color coordinates G(x, y), R(x, y), B(x, y) of the three primary colors after light distribution and judge whether they are within the standard color gamut;

i. Not within the standard color gamut, repeat steps g and h;

j. In the standard color gamut, output the brightness correction parameters, that is, output the PWM signal that modulates the gray level of the LED, and control the brightness of the LED by the LED control circuit through the USB, Ethernet or serial interface.

Due to the difference of pixels, the calculated values of brightness and color coordinates are gradually approaching the target value, so it is necessary to repeat a and the following steps until the brightness difference does not exceed the standard.

The standard color coordinate value shall be determined according to the difference between the average value of the color coordinate and the color coordinate value designed by the factory. If the difference is within ±20%, the color coordinate value designed by the factory shall be used as the standard color coordinate value; if the difference is within Within ±20% to ±30%, the color coordinate value of the factory design needs to be corrected, that is, the color coordinate value of the factory design is reduced by 3 to 5% as the standard color coordinate value. In general, if the brightness and color coordinate difference exceeds ±30%, it can no longer be corrected.

Example 2:

Except g step, other steps are with embodiment 1.

Step g is to compare the brightness of the original color with the standard brightness value of the original color in the order of green, red, and blue in units of pixels. 30～35%, blue light compensation 65～70%; red light brightness difference is compensated by green light compensation 38～42%, blue light compensation 58～62%; blue light brightness difference is compensated by red light compensation 82～85%, blue light compensation Shade supplement 15-18%.

For example, the color coordinates obtained from the photographed plane light are X1, Y1, the white light luminance value Y11 of the pixel is 1.096cd/m ² , and the luminance values of the three primary colors are R11=324mcd/m ² ; G11=668mcd/m ² ; B11= 104mcd/m ² , while the standard value of brightness of white light (the brightness design value at the factory) Y＝1.18cd/m ² , the standard value of brightness of three primary colors R＝354mcd/m ² , G＝708mcd/m ² , B＝118mcd/m ² . Therefore, the fill light value is as follows:

According to the CIE1931XYZ chromaticity diagram method, the color coordinate value of the three primary colors of each pixel after light supplement is calculated and compared with the standard color coordinate value.

The change of color coordinates of pixels after lighting is as follows:

Three primary colors and white light R G B white light Before fill light X 0.678 0.165 0.132 0.31 Before fill light Y 0.252 0.714 0.065 0.293 Target value X 0.64 0.2 0.142 0.32 Target value Y 0.33 0.62 0.1 0.33 After fill light X 0.639 0.202 0.142 0.319 After fill light Y 0.331 0.619 0.099 0.332

It can be seen from the comparison that if the color coordinate value is within the standard color gamut after light supplementation, proceed to step j. If the difference between the color coordinate value after light supplement and the standard color coordinate value is large, it is necessary to continue to adjust within the light supplement range, so that the adjusted color coordinate value is within the standard color gamut, and then proceed to step j.

Repeat steps a to f, the coordinates are the white light luminance value of X1 and Y1 pixels after brightness adjustment Y11'=1152mcd/m ² ; R11'=361mcd/m ² ; G11'=681mcd/m ² ; B11'=110mcd/m ^2. Compared with the brightness standard value designed by the factory, if it does not exceed the standard value, the adjustment will end.

Claims (1)

1. the method for online gamma correction of full-color LED display screen and color gamut optimizing is characterized in that repeating following steps:

A. take full-color LED display screen white balance picture, RGB tricolor frame, obtain the planar light image;

B. read the planar light image information;

C. determine and storage pixel quantity and each location of pixels coordinate;

D. measure and store white brightness value, three primary colours brightness value and the chromaticity coordinates value of selected pixel;

E. calculate and storage pixel white brightness mean value, three primary colours average brightness and chromaticity coordinates mean value;

F. with pixel white brightness value and the contrast of white light normal brightness value, judge whether difference exceeds standard, do not exceed standard and finish to proofread and correct, exceed standard and carry out the following step;

G. calculate and store selected pixel three primary colours brightness luminous intensity distribution value;

H. calculate three primary colours behind the luminous intensity distribution chromaticity coordinates value G (x, y), R (x, y), B (x, y) and with the contrast of standard colors coordinate figure, judge whether in the standard colour gamut;

I. not in the standard colour gamut, repeat g, h step;

J. in the standard colour gamut, the output brightness correction parameter is proofreaied and correct selected pixel LED brightness,

Described g step is to be unit with the pixel, according to green, red, Lan Sanse order, with the contrast of true qualities luminance brightness and true qualities light standard brightness value, difference is by other two color light light filling in proportion: the green light luminance difference by red light mend 30～35%, blue light mends 65～70%; The red light luminance difference mends 58～62% by green light benefit 38～42%, blue light; The blue light luminance difference mends 15～18% by red light benefit 82～85%, green light.

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