Research And Application Of Contrast Enhancement Of Liquid Crystal Display Images

The liquid crystal display device is a non-self-luminous display device,and backlight module is necessary to provide a light to display an image normally.Since the closed liquid crystal cannot completely block the light emitted by the backlight module,a "light leakage phenomenon" occurs,resulting in a low contrast of the liquid crystal display.Aimed at this problem,many dynamic dimming algorithms has been proposed,which can dynamically change the pixel value and backlight brightness according to the current display image content,to alleviate the light leakage phenomenon and achieve the improvement on contrast of the display image.This thesis first presents a brief overview of liquid crystal display principle and nowadays dynamic dimming algorithms,the simulation was carried out to analysis the advantages and disadvantages.Then two dynamic dimming algorithms were proposed: two-line dynamic dimming algorithm and dynamic dimming algorithm based on visual saliency.Finally,a complete dynamic dimming video drive system was developed to physically test the proposed algorithms.Aiming at the problem of insufficient pixel compensation ability of S-curve dynamic dimming algorithm,this thesis proposes an improved algorithm using two-line control combined with the idea of linear compensation,which can further improve the contrast of display images.Using saliency theory with frequency domain ideas of image processing technology,a dynamic dimming algorithm based on visual saliency is proposed,which can enhance the static contrast of an image as well as detail expression ability.The developed dynamic dimming video driver board has high versatility,which can support a variety of input and output interfaces.Verilog HDL language and the Quartus II platform are used to properly design the module function and implement the dynamic dimming algorithm.The final actual test results confirm the enhancement on the contrast of the liquid crystal display image by algorithms,and verify the effectiveness of the proposed algorithm and the dynamic dimming video driver board developed in this thesis.