Topographic Imaging by Wavelet Correlation Method

在非相干光源干涉测量中，干涉条纹只在干涉仪两臂光程差为零的部分产生。在相干干涉测量中，由于波长的不确定性，通常无法确定孤立点的位置。散射种子的绝对位置可以从参考反射镜的位置测量，在参考反射镜的位置处，样品和移动的参考反射镜产生干涉条纹。利用这种低相干光源的干涉方法被称为波前相关法。为了进一步提高测量精度，对相干干涉测量中常用的相移法进行了研究。分析了将该方法应用于非相干光源干涉法时的注意事项，并将其应用于测量块规的绝对高度。并将所得数据与采用多波长光源的分数阶技术的结果进行了比较，并对误差进行了评价。对于活体样品，由于干涉条纹的信噪比很小，本文分析了小波变换、去频谱变换和相关法等技术，并探讨了用半导体激光器作光源的可能性。我们在Littoman排列的系统中实现了约50nm波长的移动。使用该光源，可以通过实时扫描波长来实现更精确的测量。

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.