Absolute Fringe Order Determination in Digital Photoelasticity
Pichet PINIT** and Eisaku UMEZAKI***
**King Mongkut's University of Technology Thonburi
126 Prachautid, Bangmod, Thungkru, Bangkok 10140, Thailand
*** Nippon Institute of Technology
4-1 Gakuendai, Miyashiro, Saitama 345-8501, Japan
An improvement of the already proposed phase unwrapping algorithm for directly processing the triangular-typed wrapped phase map of the isochromatic parameter, photoelastically generated by an arccosine function based on
the well-known technique of phase-shifting, is presented. In phase unwrapping algorithm, at any pixel, a three-dimensional plane and its normal vector are generated using three fractional (relative) fringe order values. Its generated plane is then adjusted using the orthogonal projection associated with the reference plane. Such point is unwrapped on the basis of regularization. The quality guide map is used to guide phase unwrapping and to mask out the conflictive regions such that they are lastly processed. The circular disk under compression demonstrated the performance of the improved algorithm. Results showed the accuracy improvement in such conflictive regions with reasonable agreement to theory.