Investigation Of The Modulation Characteristics And Applications Of The Liquid Crystal Spatial Light Modulator

With the development of computer technology, the combination of modern opticsand microelectronics is more widely used, so as the requirement of opticalinformation processing to deal with wide bandwidth, high speed and large capacity ofinformation, becomes important. Although traditional optical element has simplestructure, reliable optical performance, fixed single structure, but inconvenient onweight or volume issue and cannot satisfy the demand of the increasingly complexwavefront transformation any more.In recent years, phase-only liquid crystal spatial light modulator (LCOS), as akind of light modulator, can be controled pixel to pixel with the applied voltage, tomodulate optical wavefront, plays an important role in optical information process,and replace the traditional optical elements. Due to its low cost, low powerconsumption, no mechanical inertia, programmability, high resolution, highdiffraction efficiency, LCOS has been widely used in adaptive optics, multi-channelimaging, dynamic holographic optical tweezers, etc.The model of liquid crystal molecules to realize phase modulation was presentedin this paper, the modulation mechanism was analyzed based on the electro-opticbirefringence effect of liquid crystal molecules. The intensity and phase modulationcharacteristics of LCOS named PLUTO-VIS were characterized by usingTwyman-Green interferometer and digital holography. Then the phase modulationprinciple under the condition of oblique incidence was analyzed and the phasemodulation character was obtained based on double holes interference method, thephase modulation characteristic curve as functions of different incident angles anddifferent grey level value were obtained. The experimental results indicated that theincident angle played an important role in the performance of phase modulationcharacterization of LCOS, and the phase depth of LCOS decreased with the increasingangle of incidence. Beside, an images process method to simplify the computationwas proposed.Based on the modulation curves under the different conditions, a phase Fresnellens was introduced onto LCOS. Due to the discretization of LCOS, the sampling issue of the Fresnel lens was analyzed. And the lens which met the samplingrequirement was experimental certificated, including the focal length, diffractionefficiency and imaging quality, respectively. Finally a lensarray and a multiplex lenswere designed and determined in the experiment respectively.