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Surface Profiling and Aberration Analysis for the Microoptical Components
|關鍵字:||像差分析;aberration analysis;雷射顯微干涉;白光顯微干涉;Zernike多項式;laser microscopic interferometry;white-light microscopic interferometry;Zernike polynomial||出版社:||機械工程學系||摘要:||
In this study, the measurement techniques of microscopic interferometry have been combined with the optical aberration analysis. First, we used the laser microscopic interferometry to measure the surface profiles of microoptical components. According to the general structures of microscopic interferometry at present, we proposed a modified simple configuration that adopted the phase-measurement analysis method for attaining the purpose of surface profile measurement. The phase-measurement analysis method composed of two sections. One was to get the wrapped phase and the other was to unwrap its phase. We acquired four different pieces of intensity pictures by using piezoelectric transducer (PZT) to shift phase four times. Then, after using the four-frame technique to compute the intensity pictures, a saw-toothed wrapped phase picture could be obtained. After that, we applied the reliability analysis method to unwrap the phase. This method calculated the reliability of every pixel and unwrapped the phase from the edge with maximum reliability. When the variation between two pixels was greater than π, we corrected their phases by multiples of 2π and set them into a single block. After merging all the blocks, we could obtain the unwrapped phase. However, the experimental results showed that the laser microscopic interferometry had some limitations on measuring the samples with high depth structure. Therefore, we furthermore proposed the white-light microscopic interferometry for solving this problem.
The white-light microscopic interferometry measured the profiles of microoptical components in vertical scanning by the use of PZT. With the feature that a maximum signal will be generated while there is zero phase difference between the reference light and the testing light, we can record the intensity change of every pixel and obtain the shape of the test surface. Because of scanning vertically, there are no limitations on high depth structure samples. Therefore, the difficulties of the laser microscopic interferometry could be solved. After obtaining the shape of the test surface, we started to analyze the distribution of its optical aberrations. In this study, we adopted the least square method to fit the shape and get the shape equation. Then, by using the Zernike polynomials, the shape equation could be well represented. Finally, we got each optical aberration from the corresponding coefficient of the Zernike polynomials and achieved the purpose of integrating the microscopic interferometry measurement with optical aberration analysis.
|Appears in Collections:||機械工程學系所|
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