SPECTRAL BASED ESTIMATION OF OPTICAL-PATH DIFFERENCE OF INTERFERENCE COLORS

A spectral intensity distribution of interference colors which is a fu nction of optical path difference (OPD) is represented as a pattern ve ctor on a subspace. A new algorithm to design a color scale on the sub space to estimate OPD Values is proposed. In experiments, interference colors generated by a differential interference microscope (DIM) were examined. A subspace spanned by four orthogonal bases was constructed to make a color scale to determine OPD values in the range between 0 nm and 1000 nm. Estimated OPD values almost coincided with these expec ted. In an experiment on two-dimensional interference colors obtained by a spherical surface of a ballbearing observed by DIM, the resultant OPD distribution coincided well with that expected within a standard deviation of 12.8 nm.