Research On Gamma Correction Of LCD Based On FPGA

LCD color correction is a common concerned problem for LCD monitor or television manufacturers. Gamma correction is a n ecessary part of the liquid crystal display, and is also a critical factor affecting the image quality of the final display. As the photoelectric characteristics of LCD monitor generally do not meet the characteristics of the human visual properties, it is necessary to correct the nonlinear gamma luminance corresponding to each gray-scale. It is known that most conventional color correction method s use SCM and gamma correction software. The disadvantage is that the devices used are mostly expensive and the adjustment time is long. Therefore it is unable to adapt these methods to the mass correction in industrial production. Considering various factors, this paper has established a liquid crystal display gamma correction system based on FPGA, through which ca n improve the image gray-scale to a certain degree, and make the image colors more layered. The research work done in this paper is as follows:1. By comparing both SCM and gamma correction software implementation methods, this paper discusses the advantages of FPGA-based method and the significance of gamma correction, and traditional implement methods. Domestic and foreign LCD gamma correction research results are analyzed in detail in this paper, laying the foundation for the correction principle in later chapters.2. The working principle and design flow of FPGA, and basis of colorimetry are introduced. By analyzing the TFT LCD photoelectric characteristics and comparing three kinds of correction methods including formula calculation method, segmented curve fitting method and look-up table method, correction principle based on look-up table is proposed.3. The hardware development platform is constructed, with 8-bit gray level image as the object of study by color analyzer, Kintex-7 the FPGA development board, play box, computer and MSTAR analysis software of 8.9-inch TFT LCD for correction, by using the I2 C bus interface for data transmission, to realize correction system in hardware and software collaborative way.4. The software design part is explained in det ail, including the gamma correction module, image dithering module and OSD core transfer module and EEPROM write module. The gray-scale data measured by analyzer are sent to the gamma correction module, by using the correction formula to generate look-up table, with 10-bit RGB data output to improve accuracy. The 10-bit RGB data output need image dithering algorithms processing to meet the 8-bit output depth of display device. Through the OSD module, the related gamma value and image dithering parameters are passed to the correction module to implement correction. After the correction module, the look-up table data are compiled into a EEPROM chip which is written to the gamma data memory of the liquid crystal display module, thus can be used for large-scale processing.