Abstract
The development of micro machining technologies results in the wide use of optical interference measurement methods to evaluate surface configurations with micro/nanometer scale accuracy. The measurement range in vertical direction of the former optical interferometry with a single-wavelength was limited to the half of the wavelength. Though the phase unwrapping method is applied to expand the range, the usual high-speed phase unwrapping algorithms are sensitive to such noise as digital errors at A/D conversion of the interference fringe brightness. In this paper, we propose a newly algorithm to unwrap the phase after reducing the noise by interpolating the interference fringe images. Then, the performance of proposed algorism is verified through a numerical simulation and experiments using a high precision steel ball. The effective way to measure a high precision surface with deep slope is expanding the measurement range by combining the arctangent operation and the phase wrapping after applying a cubic spline interpolation to the interference fringe images. A portable single-wavelength interferometry measurement system with the developed algorithm is suitable for measuring a smooth surface like a precision steel ball without partial gaps.
