Phase Shifting Grating-Cross Slit Test Device Utilizing Liquid Crystal Spatial Light Modulator

• Main Authors: Chien-fu Ou, 歐建甫
• Other Authors: Chao-wen Liang
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/3y9ffn

碩士 === 國立中央大學 === 光電科學研究所 === 97 === At a process of making the optics, no matter what manufacturing method we’ve chosen, we have to measure the surface profile of semi-finished goods or finished items. The most usual test method and measurement of optical element surface profile of optics roughly can be classified into two ways: the interferometry of two wavefronts; and the measurement of transverse ray aberration on the focal plane. The former belongs to the application of wave optics, and the latter belongs to the geometry optics. Our dissertation belongs to the testing method of geometry optics. This experiment is by means of the grating-slit test invented by Dr. Liang to measure the transverse ray aberration. The experiment used incoherent light source to irradiate the liquid crystal modulator. And we used liquid crystal modulator to control the brightness of object and reached the function of grating. By using the cross-slit, we can get the Ronchigram on exit pupil plane. Then through four steps of phase-shifting method, we can mathematically calculate the amount of transverse ray aberration. Finally, we reconstruct the wavefront and get the information of surface profile of optics. We already obtained the wavefront result of mirror’s surface profile by grating-cross slit method. Comparing it with the result measured by interferometry, we found the two surface profiles were very similar. By doing so, we can verify the feasibility of our experiment setup.