Research Of Image Acquisition And Multi-stable Liquid Crystal Display Technology Based On DSP

Multi-stable liquid crystal is a special kind of liquid crystal,in which the arrangement of molecules shows multiple stable states.Therefore a Multi-stable Liquid Crystal Display(hereinafter referred to as MLCD)can preserve its screen content permanently.It is a key technology for multi-gradation and full-color display of electronic paper.There are many types of multi-stable liquid crystals,among which cholesteric liquid crystal is the most common one.In this thesis,the display and drive principle of cholesteric liquid crystal display(Ch-LCD)was studied and a driving scheme was proposed.In addition,a set of hardware and software was designed to light a 54×54 matrix Ch-LCD to display static image and dynamic video in multi-gray level.Based on consulting a lot of relevant literature,the following work has been finished in this thesis:(1)Studied the structural and electro-optic characteristics of cholesteric liquid crystal material,as well as drive scheme of its display device.At the same time,the continuum theory of liquid crystal and the phase transition of cholesteric liquid crystal induced by electric field has also been discussed.Based on the characteristics of Ch-LCD,accumulative drive scheme combined with P-state-refreshing was designed.(2)Analyzed the common scheme for embedded image acquisition and its related theoretical basis,compared the advantages and disadvantages of image acquisition systems based on FPGA,DSP or general-purpose processor respectively.Considering the demands of the project,a image acquisition system based on DSP was proposed.(3)According to the working principle of image acquisition system and the drive scheme of Ch-LCD,a image acquisition and display system was designed based on DSPTMS320DM642 and MCU C8051F120 to drive a Ch-LCD to display image.In this system,TMS320DM642 was used to image acquisition and data processing;C8051F120 was used toregulating the driving waveform,and a FIFO was used as a bridge for data transmission between them.In addition,A upper-computer software was also designed for the convenience of parameters-setting and states-observing of the display system real-timely.(4)Image processing and Ch-LCD driving software was programed.Image acquisition and display on Ch-LCD was achieved.Besides this,the display effect has also been analyzed.By massive experiments and tests,BT.656 format video image acquisition was finally realized,and a certain display effect was achieved:the graylevel achieved 16 levels,the dynamic display speed achieved 19fps.