As a mainstream display device, LCD is widely used in various fields. Under the current production technology, LCD products produced by factories have display unevenness defects (Mura), which affects their display quality. The flat panel display industry calls the method of eliminating Mura as Demura, and the use of Demura system equipment can improve the display quality of the product, and thus improve the competitiveness of the product. The existing Demura system equipment in China has problems such as slow operation speed and poor display correction, which are difficult to meet the current production requirements.
In this paper, we investigate the method of display uniformity correction, and design and implement Demura system to solve the above problems.
The main work is as follows：
1) A polynomial-gamma segmented electro-optical response model based LCD luminance uniformity correction method is proposed. The method uses polynomial and gamma functions to represent the electro-optical response model of LCD at low and high luminance respectively, estimates the parameters of the electro-optical response model by the LCD display luminance sample data collected by CCD camera, and applies the estimated model parameters to achieve the luminance uniformity correction. The model can accurately estimate the response model of the LCD under a small amount of sample data, reducing the correction time. From the experiments, the method solves the problem of poor correction effect of low luminance display signal area of LCD, and the correction effect reaches the requirement of industrial technical index of luminance uniformity correction of display.
2) Based on the luminance uniformity correction, a chromaticity uniformity correction method based on the taylor series expansion of the local LCD color response model is proposed. The response model of local LCD color change is established by taylor series expansion, which reduces the difficulty of establishing color response model. A CCD color camera is used to measure the display sample data to estimate the model parameters, and the estimated model parameters are applied to achieve chromaticity uniformity correction. From the experiments, the method of this paper can effectively solve the problem of chromaticity display unevenness, and the correction effect reaches the general industrial index requirements.
3) Based on the brightness and chromaticity uniformity correction method in this paper, the color Demura system based on CCD color camera is designed and implemented by applying GPU general-purpose parallel computing method. The designed system was installed on the purchased hardware equipment, and a complete Color Demura system was built and tested in the factory. The test results show that the system designed in this paper is fast and meets the requirements of the technical specifications for LCD industrial production.
In summary, the brightness chromaticity uniformity correction method researched in this paper can effectively solve the LCD display unevenness problem, and the designed and implemented system can meet the current LCD production requirements.
