Topographic Imaging by Wavelet Correlation Method

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In the interferometry using incoherent light source, the interference fringes are generated only at the part of zero optical path difference between two arms of interferometer. Generally, because the indefiniteness of the wavelengths exists in the coherent interferometric measurement, the position of the isolated point is not able to be determined. The absolute position of the scattered seed can be measured from the position of the reference mirror where the interference fringes is generated by the sample and the mobile reference mirror. The interference method by such a low coherence light source is called as a wavefront correlation method.In this study, we made Twyman-Green type interference meter. To improve more precision, it is examined about the phase shift method, that is commonly used in coherent interferometry. We analyzed about the points when applying the method to the interference method which used incoherent light source.As the application of this study, we measured an absolute height of the block gage in the order of the few cm. The data is compared with the result of fractional technique using the numerous wavelength light source, and we evaluated an error. In case of living sample, because of the small S/N ratio of the interference fringes, we analyze the technique of wavelet conversion, sepstrum conversion and/or correlation method We also examined the possibility to use a semiconductor laser as the brighter light source. We performed to move about 50nm wavelength in the system of Littoman arrangement. Using this light source, more accurate measurement may be realized by scanning the wavelength in real-time.