Quality-guided phase unwrapping algorithm based on reliability evaluation

Abstract

For optical interferometry, a new quality-guided phase unwrapping algorithm based on the reliability evaluation of each pixel of the wrapped phase is proposed. First, the parameters used as quality measures in the past quality-guided algorithms are classified into the reliability measure and the quality measure, and the intensity of the object image belongs to the reliability measure. Then, by computing and applying a threshold to the intensity of the object image, the valid region (i.e., the interference region) is distinguished into the reliable region and the doubtful region. The wrapped phase in the reliable region is subsequently unwrapped by the way of multipaths integration, and different paths are guided by separate quality measures. Finally, starting from the reliable region, the doubtful region is unwrapped by the way that each path takes in the reliable region. Experimental results have shown that the proposed algorithm not only performs well, but also computes efficiently.

A New Quality Map for 2-D Phase Unwrapping Based on Gray Level Co-Occurrence Matrix

“…Fix the distance d and direction θ with the proper value according to specific application; compose all the available P (i, j, d, θ) in the research region, and then we get the matrix in (6), shown at the bottom of the next page. The matrix P is defined as the Gray Level Co-occurrence Matrix.…”

“…The conventional phase unwrapping methods can be divided into two groups. The first group is path following methods [4]- [6], which rely on the integration path; and the second group is minimum-norm methods [7]- [9], which minimize the differences between the gradients of the wrapped and the solution phase. In both of the two groups, the quality maps play a crucial role in obtaining the true phase.…”

An Improved Quality Guided Phase Unwrapping Method and Its Applications to Mri

“…In the field of MRI, phase information is also very useful in various applications such as magnetic field mapping, noise reduction, and correction of spatial distortion, although the final images are conventionally presented in the magnitude modes [6]. In these imaging modalities and applications, the initial phases of the measured data are obtained by a simple operation of arctangent from the raw complex images and are wrapped in the principal interval (−π, π].…”

Analysis of the relationship between fringe angle and three-dimensional profilometry system sensitivity

“…The phase map corresponding to the depth variation of the object being measured has been one of the most important tools for reconstructing the 3D profiles of objects since it was introduced in 1983 [4][5][6]. During the past several decades, phase-based techniques have seen much development due to the contribution of a number of researchers in fringe pattern encoding methods, modified fringe analysis methods, phase unwrapping algorithms, calibration approaches, and so on [7][8][9].…”