3D-shape measurement of rough surface using wavelength shift interferometer under unavoidable random changes of optical path differences

We propose a 3D-shape measurement technique of a rough surface using speckle interferograms captured under ramdom changes of optical path differences. Amounts of the phase shifts between captured interferograms are calculated through Max & Min light intensities searchings at two different pixels in frames and twin normalizations of their intensity changes. The calculated phase shifts which involve random changes over 2π are used to extract phase distribution of a speckle interferogram. After capturing 175 specklegrams which consist of 25 specklegrams at wavelengths of around 778,20 Inm, 778.2I7nm, 778.258nm 778.366nm, 778.623nm, 779.151 nm and 780.260nm, phase distributions are extracted regarding the first captured interferogram in each wavelength. These distributions normally involve uncertain offsets due to random shifts. After canceling these offsets with the phase data at a base-height pixel selected arbitrarily, the ratios of phase change against wavelength change are extracted at all the pixels. 3D shape is calculated from the extracted ratios.