The Phase-Only Twist Nematic Liquid Crystal Spatial Light Modulator

Liquid crystal phase-only spatial light modulator plays an important role in optical information process, optical correlation and optical interconnections. It can be used in many fields, such as precision measurement, three-dimensional display, digital holography, laser wave front shaping and optical information encryption system. Hence, it is very important to research it. In this paper, firstly, the principle of phase modulation and intensity modulation is introduced. Then the driver circuit board of commercial liquid crystal display panel is modified and designed based on the reference design module. Lastly, the phase modulation characteristic of this LCSLM is investigated by the Mach-Zehnder interferometer. The main points of this thesis are as follows.Based on the optical properties of the liquid crystal material and the structure of twist nematic liquid crystal cell, the term of molecules direction vector and the influential factors of its spatial distribution are introduced. Then the complex transmission and polarization properties of output light are analyzed by the Jones matrix.According to the relationship between signal amplitude and transmittance, the reference driver circuit is modified and a video signal process module is added in order to get rid of the DC voltage which is beneficial for the purpose of intensity modulation. So the drive voltage range can be limited in the phase-only modulation area.After the driver circuit board designed, a SLM system is built by liquid crystal display panel, driver circuit board, polarizer, analyzer and PC. Then the phase modulation characteristic of this LCSLM is investigated by the Mach-Zehnder interferometer and interferograms captured by CCD are treated in order to extract the phase modulation information. In addition, we should adjust the components to satisfy the interference terms perfectly. The experimental setup and method to measure intensity modulation property are also introduced. Lastly, the phase and intensity modulation property are given in charts.