CN101534452A - Conversion method for color gamut conversion system of laser television display based on experimental calibration - Google Patents

Abstract

The invention discloses a conversion method of a laser TV display color gamut conversion system based on an experimental calibration method. It can realize the perfect conversion from CRT fluorescent color gamut to laser display color gamut, and the amount of calculation is not large. The method is as follows: 1) the computer outputs two digital RGB signals to the CRT display and the LD display respectively; 2) the spectroradiation spectrometer collects the RGB signals displayed on the CRT display and the LD display screen respectively, and converts them into Lab values, and then sends them to 3) computer utilizes and receives the Lab value of CRT monitor and LD monitor, according to the RGB value of CRT monitor RGB value corresponding to same Lab value and the RGB value of LD monitor respectively, establishes the original RGB value of Lab value, CRT monitor and The LD display originally corresponds to the corresponding relationship database of RGB values to complete the learning process; 4) use the corresponding relationship database to perform color gamut matching; 5) then perform virtual color gamut expansion; 6) finally display on another LD display.

Description

Conversion Method of Color Gamut Conversion System Based on Experimental Calibration Method for Laser TV Display

technical field

The invention belongs to the field of laser TV video display, in particular to a conversion method of a laser TV display color gamut conversion system based on an experimental calibration method for performing color gamut conversion from phosphor three primary colors to laser three primary colors in laser display.

Background technique

Thanks to the support of related technologies such as microelectronics and processing, laser TVs have developed rapidly. Laser TV has broad development prospects due to its bright colors, high brightness, wide color gamut, and highly saturated colors. However, because the existing TV signals are all based on the CRT display system, the color display of the CRT is based on the RGB three-color phosphor, while the laser TV display system uses the RGB three-color laser, and the spectrum of the laser is very different from the spectrum of the phosphor. . According to the basic principles of chromaticity, in the tongue-shaped area, any color corresponding to three points is taken as the primary color, and all the colors formed by mixing these three primary colors are included in the triangle with these three points as vertices. Therefore, there is a big difference in the color gamut between the laser TV display system and the existing CRT fluorescent display system, and it must be converted to display normally.

Most of the currently existing color gamut conversion schemes are based on the color calibration method of pure colorimetry, which is to establish the relationship between the tristimulus value R _c G _c B _c of CRT and the tristimulus value R _l G _l B _l of laser TV in CEIXYZ space. One-to-one correspondence. That is to say, through the platform of CEIXYZ space, a theoretical conversion model is established. This model can find the corresponding three-stimulus value R l G l _B of LD given the stimulus value R _{c G c B} c of CRT _l , so that the colors displayed by the two are theoretically identical. Unfortunately, this space is perceptually non-linear, i.e. they cannot predict colors from relative positions. This shows that the theoretical conclusion is non-linear between the sensory and calculated values, thus causing a certain chromaticity deviation in the images before and after the mapping. The image after the above conversion needs to be processed by related color images to be corrected, which virtually increases the difficulty of signal processing and also brings difficulties to the realization of hardware. Moreover, the color calibration method based on pure colorimetry assumes a purely ideal state of the display, such as: when the input voltage changes, the color coordinates produced by the RGB guns alone remain unchanged, and the RGB guns act on their corresponding phosphor powders respectively. The light output at a given position does not depend on the input at other positions, the response of each RGB gun to a constant input does not change with time, the response of the RGB channel is independent of the screen position, etc., and often the display does not Fully satisfying these assumptions is sometimes far greater than the change in color coordinates corresponding to the chromatic aberration that can be distinguished by the human eye, so the accuracy of using them for quantitative color rendering will be limited by the assumptions of the theoretical model and will not be too high.

Contents of the invention

In order to overcome the defects of the prior art, the present invention provides a conversion method of the color gamut conversion system of laser TV display based on the experimental calibration method, which can realize the perfect conversion from the CRT fluorescent color gamut to the laser display color gamut, and the calculation amount is not large .

To achieve the above object, the present invention adopts the following technical solutions:

A conversion method of a color gamut conversion system based on an experimental calibration method for laser television displays, the steps of which are:

1) The computer outputs two digital RGB signals to the CRT display and LD display respectively;

2) The spectroradiation spectrometer collects the RGB signals displayed in the CRT display and LD display screen respectively, and converts them into Lab values, and then sends them to the computer to save the data;

3) The computer uses the received Lab values of the CRT display and the LD display, and according to the same Lab value corresponding to the RGB values of the CRT display and the RGB values of the LD display, establishes the Lab value, the original RGB value of the CRT display, and the original corresponding RGB value of the LD display. Value correspondence database, complete the learning process;

4) Color gamut matching is performed using the corresponding relational database;

5) Then expand the virtual color gamut;

6) Finally displayed on another LD display.

Described step 2) in, CRT monitor adopts the CRT monitor that meets EBU standard; Test CRT monitor process is: computer changes the data value of RGB three passages of test area successively from 0 to 255, and correspondingly sending out is the true color of 24bit; CRT display, the 24-bit color information, after D/A converter and γ conversion, directly drives the RGB three guns of the CRT display to generate corresponding colors; the spectrophotometer measures the test area to measure the L corresponding to each group of RGB values, The a, b chromaticity values are sent to the computer, and the computer records and stores these L, a, b chromaticity values and the corresponding 24bit values.

In said step 2), the LD display test process is: the computer also directly sends the 24bit true color signal to the laser TV display screen, and the spectrophotometer measures the laser TV display screen, and measures each group of RGB values in the test area The corresponding L, a, b chromaticity values are sent to the computer; the computer records and stores these L, a, b chromaticity values and the corresponding 24bit true color values.

Said step 4) the color gamut matching process is: according to the corresponding relationship database established in step 3), the color with the same Lab value in the Lab space is converted into the corresponding RGB value of the LD from the RGB value of the CRT to complete the color gamut matching.

In said step 5), the virtual color gamut expansion process is: the digital RGB is converted to the XYZ color gamut space by the processor, the white center point in the color gamut map is found, the converted RGB is processed, and the color RGB is calculated. The distance from the center of the white point is then stretched linearly proportional to the distance, and all colors of the fluorescent color gamut are evenly converted into the corresponding laser color gamut.

The calibration device of the CRT of the present invention provides the stimulus value R _c G _c B _c of the CRT, and finds the corresponding three-stimulus value R _l G _l B _l displayed by the laser through self-study in an experimental method, so that the two displayed Color theory is completely consistent. The color gamut matching device performs color gamut mapping based on a fast search algorithm, so that the laser display that receives the three primary color signals of phosphors can obtain correct color reproduction, and achieve the purpose of correct color restoration. The virtual color gamut expansion device stretches the virtual color gamut proportionally, so as to expand the small color gamut of the three primary colors of the phosphor to the large color gamut of the three primary colors of the laser, and realize the color with higher saturation in the laser color gamut outside the fluorescent pink gamut. It is characterized in that the color gamut conversion adopts an experiment-based self-learning method for color gamut calibration, and the calibration is carried out in CIEL*a*b* space. The Lab color model has a wide color gamut and it makes up for the uneven color distribution of the RGB color model. lack of.

The calibration device of CRT, that is, the hardware of the experimental calibration method is:

Color Calibrated CRT Monitors An EBU compliant CRT monitor will be used as the color calibrated model display.

The correction coefficient module adopts the national broadcasting standard; γ=2.3.

Data collection is carried out according to the CIE standard. The calibration data test of the CRT display and laser TV display is carried out in a dark room. Before the test, the CRT display is preheated for 12 hours according to the CIE regulations.

CRT display parameters are set to:

CRT display brightness: 64.24cd/m2 (when the RGB values (0-255) of the three channels are all 255)

LD display brightness: 80cd/m2 (when the RGB values (0-255) of the three channels are all 255)

CRT display white field: x=0.3127, y=0.3290 (D65)

LD display white field: x=0.2824, y=0.2774 (D65)

Display Color Offset: 0

The parameters of the spectrophotometer were set as:

Viewing angle: 1°

Wavelength range: 370-730nm

The color gamut of CRT monitors and laser TV displays is sampled in the manner specified by CIE, and a square with a side length of 9 cm concentric with the center of the monitor is used as the test area. Keep the monitor screen with a black background outside the test area. .

The data collection is as follows: the computer sequentially changes the data value of the RGB three-channel in the test area from 0 to 255, and the corresponding output is 24bit true color. For CRT monitors, the 24-bit color information directly drives the RGB three guns of the CRT monitor after D/A digital-to-analog conversion and gamma conversion to generate corresponding colors. The spectrophotometer measures the test area and measures the L, a, b chromaticity values corresponding to each group of RGB values, and sends them to the computer. The computer records and stores these L, a, b chromaticity values and the corresponding 24bit values.

For the laser TV display, the whole process is similar to CRT, except that the digital color information of RGB three primary colors 24bit sent by the computer is sent to the digital port of the drive circuit, and the drive circuit completes the control of the LCD panel to generate corresponding colors. . In this way, as long as a RGB three-primary color binary driving data is given, a matching L, a, b value can be found, and at the same time, the RGB24bit data value of the driving LD matching the L, a, b value can be found.

In this way, the database is established through learning, and then the stimulus value RcGcBc of the given CRT display can be found by using a quick search to find the corresponding tri-stimulus value R _L G _L B _L of the laser TV display, and the laser TV display Displays the same colors as those displayed on a CRT monitor, and the displayed color range is also consistent with that of a CRT. The above whole process is actually the calibration process from the color displayed on the CRT monitor to the color of the laser TV display screen, and also completes the process of color gamut matching.

After this color gamut matching relationship is established, the video signal of the ordinary CRT reality can be converted into the electrical signal of the laser accordingly, so as to realize the correct reproduction of color, that is, color reproduction. Although the above color gamut matching can ensure that the color display of the two is consistent, it cannot show the advantages of large color gamut and high saturation color displayed by laser. Therefore, the present invention adds a virtual color extension part to realize the three primary colors of phosphor A method of extending the small color gamut to the large color gamut of laser displays. The specific method is as follows:

Convert the received signal of the existing system into the laser RGB system, find the white center point in the color gamut diagram, process the converted laser color system, and calculate the color tristimulus value R _L B _L G _L and the white point center distance, and then stretched in proportion to the distance, so that all colors of the fluorescent color gamut are uniformly converted into the corresponding laser color gamut.

The beneficial effects of the present invention are: small calculation amount, good display effect, and perfect conversion from CRT fluorescent color gamut to laser display color gamut

Detailed ways

The present invention will be further described below in conjunction with embodiment.

A conversion method of a color gamut conversion system based on an experimental calibration method for laser television displays, the steps of which are:

1) The computer outputs two digital RGB signals to the CRT display and LD display respectively;

2) The spectroradiation spectrometer collects the RGB signals displayed in the CRT display and LD display screen respectively, and converts them into Lab values, and then sends them to the computer to save the data;

3) The computer uses the received Lab values of the CRT display and the LD display, and according to the same Lab value corresponding to the RGB values of the CRT display and the RGB values of the LD display, establishes the Lab value, the original RGB value of the CRT display, and the original corresponding RGB value of the LD display. Value correspondence database, complete the learning process;

4) Color gamut matching is performed using the corresponding relational database;

5) Then expand the virtual color gamut;

6) Finally displayed on another LD display.

Described step 2) in, CRT monitor adopts the CRT monitor that meets EBU standard; Test CRT monitor process is: computer changes the data value of RGB three passages of test area successively from 0 to 255, and correspondingly sending out is the true color of 24bit; CRT display, the 24-bit color information, after D/A converter and γ conversion, directly drives the RGB three guns of the CRT display to generate corresponding colors; the spectrophotometer measures the test area to measure the L corresponding to each group of RGB values, The a, b chromaticity values are sent to the computer, and the computer records and stores these L, a, b chromaticity values and the corresponding 24bit values.

In said step 2), the LD display test process is: the computer also directly sends the 24bit true color signal to the laser TV display screen, and the spectrophotometer measures the laser TV display screen, and measures each group of RGB values in the test area The corresponding L, a, b chromaticity values are sent to the computer; the computer records and stores these L, a, b chromaticity values and the corresponding 24bit true color values.

Said step 4) the color gamut matching process is: according to the corresponding relationship database established in step 3), the color with the same Lab value in the Lab space is converted into the corresponding RGB value of the LD from the RGB value of the CRT to complete the color gamut matching.

In said step 5), the virtual color gamut expansion process is: the digital RGB is converted to the XYZ color gamut space by the processor, the white center point in the color gamut map is found, the converted RGB is processed, and the color RGB is calculated. The distance from the center of the white point is then stretched linearly proportional to the distance, and all colors of the fluorescent color gamut are evenly converted into the corresponding laser color gamut.

Claims (5)

1. a conversion method based on the color gamut conversion system of the laser television display of experimental calibration method, it is characterized in that, its steps are: 1) The computer outputs two digital RGB signals to the CRT display and LD display respectively; 2) The spectroradiation spectrometer collects the RGB signals displayed in the CRT display and LD display screen respectively, and converts them into Lab values, and then sends them to the computer to save the data; 3) The computer uses the received Lab values of the CRT display and the LD display, and according to the same Lab value corresponding to the RGB values of the CRT display and the RGB values of the LD display, establishes the Lab value, the original RGB value of the CRT display, and the original corresponding RGB value of the LD display. Value correspondence database, complete the learning process; 4) Color gamut matching is performed using the corresponding relational database; 5) Then expand the virtual color gamut; 6) Finally displayed on another LD display. 2. the conversion method of the color gamut conversion system based on the laser television display of experimental calibration method as claimed in claim 1, it is characterized in that, described step 2) in, CRT display adopts the CRT display meeting EBU standard; Test CRT display The process is: the computer sequentially changes the data values of the RGB three channels in the test area from 0 to 255, and the corresponding 24-bit true color is sent out; Drive the three RGB guns of the CRT display to produce corresponding colors; the spectrophotometer measures the test area to measure the L, a, b chromaticity values corresponding to each group of RGB values, and sends them to the computer, which records and stores these L, a , b chroma value and the corresponding 24bit value. 3. the conversion method of the color gamut conversion system based on the laser TV display of experimental calibration method as claimed in claim 1, it is characterized in that, described step 2) in, the LD display test process is: computer also will 24bit true color The signal is directly sent to the laser TV display screen, and the spectrophotometer measures the laser TV display screen, and the L, a, b chromaticity values corresponding to each group of RGB values are measured in the test area, and sent to the computer; the computer records and stores these L, a, b chromaticity values and the corresponding 24bit true color values. 4. the conversion method of the color gamut conversion system based on the laser television display of experimental calibration method as claimed in claim 1, is characterized in that, described step 4) color gamut matching process is: according to step 3) the corresponding relationship database of setting up , convert the color with the same Lab value in the Lab space from the RGB value of the CRT to the RGB value corresponding to the LD, and complete the color gamut matching. 5. the conversion method of the color gamut conversion system based on the laser television display of experimental calibration method as claimed in claim 1, it is characterized in that, in described step 5), the virtual color gamut expansion process is: by processor digital RGB Convert to the XYZ color gamut space, find the white center point in the color gamut map, process the converted RGB, calculate the center distance between the color RGB and the white point, and then stretch it linearly proportional to the distance, and the fluorescence All colors of the gamut are uniformly converted into the corresponding laser gamut.