Phase unwrapping is one of the key steps of optical interferogram analysis.However,implementing phase-unwrapping algorithm(PUA) can be challenging,and the accuracy may be low when it is used to handle fringe patterns containing complicated singularities, such as noise, shadow, shears and surface discontinuity. When weighted least-squares unwrapping approach is adopted to unwrap the phase,the weighting coefficients are designed and defined to distinguish the singularities regions and normal regions in wrapped phase patterns.The weighting coefficients corresponding to the singularities are given zero-weighted, the singularities will not affect the unwrapping.But weighted least-squares unwrapping approach has the smooth effect on the final phase map.In view of this problem, a Robust Weighted leastsquares phase-unwrapping algorithm is proposed in this paper, which is based on combining the phase correction operation and weighted least-squares(WLS) method.In our method, Two partial derivatives of the wrapped phase are obtained from the fringe patterns. The phase singularities are determined using reliability, and the weighting coefficient is obtained from the binary mask from the reliability mask generated by thresholding method. The Weighted leastsquares phase-unwrapping was solved using the preconditioned conjugate gradient (PCG) method,The result of WLS is used to estimate the fringe order directly.The spatial phase unwrapping algorithm is applied to correct the phase with residual wraps by. Experiments are conducted to prove the validity of the proposed method. Results are analyzed and compared with the other least-squares methods, The experimental results demonstrate that the performance of proposed method.
Digital holography is a powerful tool for noncontact quantitative phase imaging. According to the relative incident angle between the object beam and the reference beam, digital holography is grouped into on-axis and off-axis digital holography, The measurable area is narrow in off-axis digital holography, on-axis digital holography suffers from image blurring. Phase-shifting technique is usually used to obtain the high-quality object image. However, the phase shifting technique requires to record multiple phase-shifted holograms. The most conventional holography configuration requires a separately generated reference and object beams that result in a low stability. The paper presents an One-shot common-path phase-shifting holography based on micro polarizer camera and large-shearing Wollaston Prism. The system employs a commercial micro polarizer camera and a doubly-refractive prism with large shearing. The Wollaston prism separates the incoming beam into two orthogonally polarized components ,brings the reference and object from the two-windows to overlap at the lateral shearing region. The two light beams transmit through the quarter wave plate(QWP) and pixelated micro polarizer array(PMA) camera, QWP is used to transform the orthogonally polarized light into orthogonal circular components, The circular polarizations interfere at CCD after passing through the micro polarizer array. The data captured by PMA camera can be parsed into four phase shifting fringe images corresponding to each direction of the four polarizations. The interpolation method is used to obtain the same resolution as the original image. The phase distribution of the specimen can be retrieved using the four-step algorithm. Finally, experiments are conducted to prove the validity of the proposed method. The results demonstrate the capability and applicability of the system .