Dissertation > Biological Sciences > Physiology > Neurophysiology

The 2D Beam Shift System Based on the Spatial Light Modulator

Author WuFangJie
Tutor HuangZhenLi
School Huazhong University of Science and Technology
Course Biomedical Engineering
Keywords Spatial light modulator Beam shift Grating algorithm
Type Master's thesis
Year 2010
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In biology, especially the nervous system biology, people has always managed to want to observe nerve cell activities, at present, this can be achieved with clear observation of microscopic techniques. The next goal is to observe the response of different nerve cells to external stimulations under the microscope. Thus the study of nerve cells response activities as well as the controlling of nerve cell activity has very important significance. In this regard, the optical stimulation is highly favorable because of its fast speed and high precise.Since the activities of nerve cells is very fast, so a very high time resolution is required in the stimulation of the nerve system, whereas the traditional method of scanning is inadequate to the stimulation laser scanning systems of high-precision, fast response, and high integrity . For this reason, the spatial light modulator has gained much attention.The liquid crystal unit of the liquid crystal spatial light modulator can be applied with external electric field and deforms the liquid crystal molecules to control the equivalent refractive index of the modulator, thereby changes the wave front of the light waves when passing through the liquid crystal devices. As the control process is performed at moderate electrical intensity, which avoids the mechanical inertia, and the modulation is programmable, therefore, it is an effective way to perform inertia-free laser scanning by using liquid crystal spatial light modulator to achieve fast programmable control of the beam wave form.This paper first introduced the beam deflection principle of SLM, described in detail of the principle and structure of several spatial light modulator, compared these methds with traditional mechanical scanning scheme, and illustrated the significance of this research, later, we provided theoretical and experimental basis for further research.For experimental research, we elaborated the algorithm and the formula and built a experimental system. Based on the MATLAB language, we calculated the desired phase distribution for performing SLM modulation of the wave front. After that we carried out the modulation and obtained the random switching of the light spot in 2D plane, the picture of the corresponding light spot was captured. Experimental results showed that SLM does have a good control effect of the light spot. At last we analyzed the problems to prove our theory and mentioned the prospect of our work.

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