The Design Of Backlight System For Color LCD

This article makes the brief introduction to the technology and the status of backlight for LCD. We analyze the advantages and the disadvantages of backlight at present and the trend of its development. The principle, advantages and existing questions of LED Backlight has been mainly discussedLight guide plate, which determines the efficiency and the uniformity of backlight, is a key component of backlight units. Compared with CCFL is line source, LED is a point source, so the scattering netted dots arrangement of which is more difficult, The radial attenuation of light intensity, the interaction of multiple point sources and the emitting angle of single point source must be considered. To solve these problems, we take two edge-light backlight of LEDs for example, set up a model to obtain the rule of scattering netted dots arrangement based on the optical theory. A brief formula for dots arrangement has been deduced, moreover, has been extended to apply to the arrangement of dots with more LEDs. Then, we transformed the formula equivalently, and found a rule of dots arrangement with linear light source. Moreover, the formula is revised in consideration with the emitting angle of source. The design of dot is carried out by programming with AUTOCAD, and examined the effect by using Tracepro. It's highly uniformity and intensity that meet our need.We studied the electro-optical characteristic of liquid crystal light valve in voltage-drive and frequency-drive, and analyzed the transmissivity of tricolor. The electro-optical characteristic of TB3639 liquid crystal light valve in voltage-drive and frequency-drive was measured using spectrophotometer, and the transmissivity of tricolor in the two methods was also analyzed. The result showed that the change of tricolor transmissivity was not identical, and color cast would appear, which would influence the display quality. The change of tricolor transmissivity becomes more obvious with the changes of voltage in voltage-driven, in which the maximum difference was 11% and the minimum is 0. The transmissivity of tricolor had better uniformity in frequency-drive and the difference of transmissivity was relatively small, in which the maximum difference was 4% and the minimum was 2.5%. The color should be adjusted and compensated to get exact hue and color saturation, and this would help to study more in improving the performance of liquid crystal display.Associated with the principles of LED and the effect of color filter, we designed a special backlight for color LCD. According to the design, the light from LED chip excited color converting layer directly, so we could get tricolor light as backlight. There is no color filter, so 2/3 loss of light energy is avoided, and the utilization of light has been improved. Moreover, the lights of environment were also used effectively in this design, and the color LCD had a good performance in strong light. Based on foregoing research results,LCD's electro-optical characteristics were measured by using spectrophotometer in some voltage. Associated with colorimetry theory, we adjusted the chromaticity of LCD and obtained a better color repeatability.Beginning with the displaying principle and driving principle of LCD, we described the flickering phenomenon of LCD and analyzed the reason. We set up a model on the base of theory, simulated the phenomenon in experiment, and analyzed the data from test. We got the law of frequency interference phenomenon. Its essence was the interference of frame frequency and backlight frequency, consequently we showed the corresponding solution.