Spatial Light Modulator Coding effect on Measuring Image Objects over Mach-Zehnder Interferometry

• Main Authors: Shu-YuChen, 陳淑瑀
• Other Authors: Jen-Fa Huang
• Format: Others
• Language: en_US
• Published: 2014
• Online Access: http://ndltd.ncl.edu.tw/handle/40312419256286686236

碩士 === 國立成功大學 === 光電科學與工程學系 === 102 === Mach-Zehnder Interferometer (MZI) can be used to acquire the optical thickness of samples by utilizing the interference of two lights. Recently, some researchers mentioned that if a dispersion element is put in front of the interferometer, the coherence envelope of the signal will be broadened. The reason is that when the light passes the dispersion element, different refractive indices of different wavelengths in the dispersive medium. The intensity of the interference signal will oscillates, which leads to beat effect. As a result, multiple splitting of the partial-coherence interference (PCI) signal will be induced. Although the resolution of measurement decreases, the curve of the results will be smoother. Therefore, the precision of measuring multi-layer structures can be improved. We observe that the similar effect happens when encoding the signal. In this paper, we set up the spatial-light modulator (SLM) at the signal arm of the MZI to measure the optical thickness of the sample. Different coding patterns are used and discussed in this study. When proper encoding scheme is used in SLM, the signal peaks will be broadened. This effect can be utilized to measure multi-layer structures of object samples. When the incident light passes multi-layer structures, the signal is split into multiple peaks. Though the broadening of the signal decreases the resolution, we can acquire the desired peak and the curve becomes smoother. Therefore, the precision of the measurement can be improved. If this effect is combined with image processing, it can be used in medical fields. It can also be used in industry fields to measure the properties of samples.