1 Introduction
In recent years, flat panel display technology represented by LED display has developed rapidly and has been widely used in various fields of production and life. In particular, the emergence and continuous development of new technologies such as point-by-point correction technology and color gamut correction technology have greatly improved the consistency of display brightness and chromaticity, and obtained superior image display quality. Although LEDs have outstanding advantages over other light sources, the attenuation of light intensity and the drift of color coordinates are inevitable in the case of long-term operation. In order to further understand the attenuation and drift of LED full-color screen for a long time, this paper made a preliminary monitoring experiment.
2, LED display color consistency
Colorimetry is a comprehensive discipline based on the fields of physical optics, visual physiology and visual psychology developed in the last century. It goes beyond the scope of physics in the usual sense, but it does belong to the field of physics. There are many phenomena in scientific research, production, and life that are often associated with the discipline. These phenomena are a mixture of physical processes and physiological processes [2].
The ultimate goal of the LED full color screen is to present a good visual effect. The consistency of the brightness and color is an important aspect. In the range of chromaticity, it includes two aspects of color uniformity and color fidelity. Color uniformity refers to the color difference consistency when displaying the same color between each pixel, module and module on the same screen; color fidelity refers to the color reproduction between the image on the display screen and the source image or source scene. The degree of fit. With the continuous improvement of the technical level, the mainstream LED full-color screen on the market has achieved high color fidelity with its 14-bit or higher color performance, but at the same time, the color uniformity is not high. The problem of low level of consistency is becoming more apparent.
By correcting the difference in chromaticity by the point-by-point correction technique, a better visual effect can be achieved. However, as time goes by, LED full color screen will show different degrees of brightness uniformity and chromaticity difference. In order to understand the trend of this difference, guide the determination of the relevant parameters of the LED full color screen and the secondary correction in the later maintenance stage to provide reliable correction data, and make the change of the brightness and chromaticity related parameters of the LED full color screen with time. In-depth research and a more accurate understanding of the decay of long-term work have become a very necessary task. There are many factors to evaluate the color consistency of LED full color screen. Here, this paper focuses on the study of the drift of the primary color coordinates.
3. Test model
3.1 Test plan
In this paper, a 64*32 pixel Changchun Xida Electronic Technology Co., Ltd. P7.62 dot-pitch module indoor LED full color screen is selected as the test object. In order to simulate the actual use of the screen as much as possible, a white field of 50% brightness is used in the daily decay process for 24 hours a day. In order to simulate the attenuation of the display screen after being delivered to the user, the full-color LED of the test module is fully aged, as the starting zero point of the decay test time, in the darkroom condition, every 6 hours (12 hours at night), The test screen is collected according to the change of the chromaticity parameter of the module. The measuring instrument selects the BM-7 color luminance meter of Yuanfang Photoelectric Information Co., Ltd.
Figure 1 is a schematic diagram of the system of this test.
Fig.1 Schematic diagram of LED full color screen attenuation and color coordinate drift test system
The first module of the screen is lit, the relevant data is collected by the data acquisition system; the computer extracts the data and saves it; then the next module of the control system is illuminated to perform the measurement, and the chromaticity parameters of the screen at that time are obtained step by step. .
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