Development of a new automatic gamma control system for mobile LCD applications

This paper presents a new automatic LCD gamma control system using gamma curve optimization for the first time. Since conventional manual method depends on experiences of LCD module developers, it is highly labor intensive and requires several correction steps providing large gamma correction error. Proposed system controls automatically gamma adjustment registers in mobile LCD driver IC to reduce gamma correction error and adjusting time. The proposed gamma system contains module-under-test (MUT, LCD module), PC installed with program, multimedia display tester for measuring luminance, and control board for interface between PC and LCD module. We have developed a new algorithm using 6-point programmable matching technique with reference gamma curve. Developed algorithm and program are generally applicable for most of the LCD modules. It is realized to calibrate gamma values of 1.8, 2.0, 2.2 and 3.0. The control board is designed with DSP and FPGA, and it supports various interfaces such as RGB and CPU. Developed automatic gamma control system showed significantly reduced gamma adjusting time of 4 min. and much less average gamma error of 11% than 42 h and 27% with conventional manual method, respectively. We believe that the proposed system is very useful to provide high-quality LCD and to improve developing process using optimized gamma-curve setting.