Abstract

Noise reduction is one of the most exciting problems in automatic fringe processing. We propose a two-dimensional (2-D) envelope transform for normalization of fringe patterns, coupled with spin filtering, to construct so-called noise-free normalized fringe patterns. The 2-D envelope transform uses correct fringe intensity envelopes for normalization of fringe patterns, i.e., for making the fringe background and amplitude constant over the whole field. Spin filtering is applied to fringe patterns for removal of random noise taking into account fringe flow. With spin filtering and the 2-D envelope transform, a noise-free normalized fringe pattern is constructed for postprocessing. Based on this improved fringe pattern, two local pixel transforms for strain extraction from a single moiré pattern are developed, in which the digital pure secondary moiré method is improved and the strain-field image method with division is developed.

© 1996 Optical Society of America

Digital pure shear-strain moiré patterns

Qifeng Yu, K. Andresen, and Dongsheng Zhang
Appl. Opt. 31(11) 1813-1817 (1992)

New spin filters for interferometric fringe patterns and grating patterns

Qifeng Yu, Xiaolin Liu, and Klaus Andresen
Appl. Opt. 33(17) 3705-3711 (1994)

Generalized spin filtering and an improved derivative-sign binary image method for the extraction of fringe skeletons

Qifeng Yu, Xiaolin Liu, and Xiangyi Sun
Appl. Opt. 37(20) 4504-4509 (1998)

Spin filtering with curve windows for interferometric fringe patterns

Qifeng Yu, Xiangyi Sun, Xiaolin Liu, and Zhiqiang Qiu
Appl. Opt. 41(14) 2650-2654 (2002)

Fringe-orientation maps and fringe skeleton extraction by the two-dimensional derivative-sign binary-fringe method

Qifeng Yu and Klaus Andresen
Appl. Opt. 33(29) 6873-6878 (1994)