Phase Shift Extraction Algorithm Research Articles

High-quality phase imaging by phase-shifting digital holography and deep learning

Quantitative phase imaging (QPI) technology is widely used in biomedical imaging and other fields because it can realize exact imaging for transparent phase-type samples, which is of great research significance. The complex amplitude distribution of the object wave obtained by phase-shifting digital holography (PSDH) reproduction can provide phase information for QPI, but its existence of phase wrapping and other problems limits its practical application. Although the traditional phase unwrapping algorithm provides a solution, it has problems such as low unwrapping accuracy or long time running. To solve these problems in QPI, a high-quality phase imaging (HQPI) method by PSDH and deep learning (DL) is proposed, where QPI is achieved by extracting the unknown phase shift using a generalized non-iterative phase shift extraction algorithm and unwrapping the wrapped phase by a DL network. Both numerical simulations and optical experiments verify the feasibility of the method. By comparing with the traditional phase unwrapping algorithm, it is demonstrated that the DL unwrapping method has higher unwrapping accuracy and more efficiency. The results show that the method of HQPI is capable of realizing comparatively fast and accurate QPI.

Application of Image Denoising Algorithm and Data Mining in Psychological Teaching Quality Evaluation

In order to improve the psychological teaching quality of college students, this paper combines image denoising algorithm and data mining algorithm to construct a psychological teaching quality evaluation system. The denoising algorithm is mainly used to identify the behavior and expressions of the students so as to explore the psychological state of the students. Moreover, this paper combines the data mining algorithm to carry out the quantitative analysis of students’ psychological state and analyzes and introduces the calibration principle of Dirckx method in detail to improve it and then forms a new calibration method. In addition, based on the arctangent function, this paper proposes a new two-frame random phase-shift fringe image phase shift extraction algorithm. The research results show that the image denoising algorithm and data mining proposed in this paper have a good effect in the evaluation method of psychological teaching quality and can play a good role in the improvement of students’ mental health.

Phase-shift extraction of multiple-frame randomly phase-shifted interferograms by analysis of the amplitude of the analytic signal.

We present a powerful phase-shift extraction algorithm for multiple-frame random phase-shifting fringe patterns. The proposed method is based on changing the regularity of the amplitude of a demodulated analytic signal with respect to different phase shifts and a one-dimensional optimization method. Compared with the existing universal phase-reconstruction method, the proposed method is accurate, stable, and efficient. Both numerical simulations and experimental data demonstrate the high accuracy and efficiency of the proposed method.

An accurate phase shift extraction algorithm for phase shifting interferometry

Abstract The accuracy of phase shift extraction has a significant influence on measurement results in surface micro-topography interferometry. Phase shifting errors are mainly caused by nonlinearity of the employed phase shifter, environmental turbulence, camera imperfection and so on. In this paper, a general algorithm based on Lissajous figures and ellipse fitting is proposed for extracting the phase distribution from a set of phase-shifting interferograms with random noise. Two sets of pixels with π ∕ 2 phase difference in all the investigated interferograms are selected and used for ellipse fitting. Both numerical simulations and optical experiments have proven the validity, rapidity, and accuracy of the proposed method. Experiments show that the proposed method is a general phase extraction method, which can work for straight fringe patterns, circle fringes patterns and other anomalous features.

Phase-shift extraction algorithm for blind phase-shifting holography based on the quotient of inner products

This paper presents a phase-shift extraction method for blind phase-shifting holography applications based on the quotient of inner products. The method only requires acquiring three-frame holograms with arbitrary unequal phase-shift values and the intensity of the reference wave, without requiring the object wave intensity. Two phase shift values can be extracted precisely using the algorithm, which can remove the background noise and DC component effects. Both simulated and experimental results have demonstrated the phase step retrieval accuracy and the feasibility of reconstructing the complex amplitude of the object wave.

Three-frame self-calibration phase shift algorithm using the Gram-Schmidt orthonormalization approach.

Affected by the height dependent effects, the phase-shifting shadow moiré can only be implemented in an approximate way. In the technique, a fixed phase step around π/2 rad between two adjacent frames is usually introduced by a grating translation in its own plane. So the method is not flexible in some situations. Additionally, because the shadow moiré fringes have a complex intensity distribution, computing the introduced phase shift from the existing arccosine function or arcsine function-based phase shift extraction algorithm always exhibits instability. To solve it, we developed a Gram-Schmidt orthonormalization approach based on a three-frame self-calibration phase-shifting algorithm with equal but unknown phase steps. The proposed method using the arctangent function is fast and can be implemented robustly in many applications. We also do optical experiments to demonstrate the correction of the proposed method by referring to the result of the conventional five-step phase-shifting shadow moiré. The results show the correctness of the proposed method.

特殊点的两步广义相移干涉相移值提取算法

特殊点的两步广义相移干涉相移值提取算法

Phase-shift extraction from twice-normalized light intensity changes recorded with random phase shifts

A simple phase-shift extraction algorithm is proposed for interferograms recorded with random phase shifts that vary over at least 2π. The phase-shift-dependent changes in the intensity at two pixels having different phases, selected from one frame, are taken out and normalized. The sum and difference of the two normalized changes are calculated, and both the changes are normalized again along the phase shifts. The normalized sum and difference become the cosine and sine of a term including the random phase shift, respectively. Thereby, the phase shifts are extracted from both twice-normalized intensity changes. An experiment using an interference microscope equipped with a piezoelectric-transducer positioner of an objective lens is conducted to estimate the validity of the algorithm. The algorithm is verified to have satisfactory results when the multiple interferograms used have a sample size of more than 15 frames recorded with random phase shifts.

1-Norm character of phase shifting interferograms and its application in phase shift extraction

Aiming at the situation that the fringe number in the interferogram is less than one, a novel phase shift extraction algorithm is proposed. By introducing the 1-norm of a sequence of phase-shifting interferograms and analyzing its character, which changes in the cosine form with the phase shift, the phase shift can be extracted from an arccosine function easily. Specially, so long as the fringe number in the interferogram is less than 0.5, both the simulation calculation and experimental research show that the phase shift with high precision can be obtained directly and rapidly in the proposed algorithm.

Phase shift extraction algorithm based on Euclidean matrix norm

In this Letter, the character of Euclidean matrix norm (EMN) of the intensity difference between phase-shifting interferograms, which changes in sinusoidal form with the phase shifts, is presented. Based on this character, an EMN phase shift extraction algorithm is proposed. Both the simulation calculation and experimental research show that the phase shifts with high precision can be determined with the proposed EMN algorithm easily. Importantly, the proposed EMN algorithm will supply a powerful tool for the rapid calibration of the phase shifts.

Wavefront reconstruction by two-step generalized phase-shifting interferometry

A wavefront reconstruction method by two-step generalized phase-shifting interferometry (GPSI) with blind phase shift extraction algorithm is verified by both the computer simulations and optical experiments. This method can retrieve complex object wave field by using two interferograms, the recorded object and reference wave intensities, and an unknown phase shift without additional processing. The simulations with irregular wavefronts have shown the effectiveness and high accuracy of this method for blind phase-shift extraction and wavefront reconstruction over a wide range of phase-shifts, while the optical experiments for both the direct and indirect objects have yielded satisfactory results with a higher resolution of reconstructed image than those reported recently.