Efficient phase unwrapping algorithm based on cubature information particle filter applied to unwrap noisy continuous phase maps

<p>InSAR become more and more popular technique for monitoring mining excavation influence on terrain surface. Nowadays, research on the accuracy of InSAR measurements focuses on impact of external factors on SAR signal and process of phase unwrapping. SAR interferogram include information about a displacement in wrapped form &#8211; modulo 2&#960;. Demodulation of phase (phase unwrapping) enable to restore true phase values and then correct interpretation of acquired information. Poor quality of data (low coherency) and large surface deformations cause phase discontinuities that make unwrapping process difficult and may generate incorrect results. Underground mining excavation, especially shallow or inducing seismic activity, may lead to large and abrupt surface displacements. Majority of unwrapping algorithms assume that the difference between any two adjacent samples in the continuous phase signal should not exceed a value of &#960;. However, this assumption may be incorrect for large and abrupt surface displacements and lead to errors in the phase unwrapping and then to determination of incorrect values of surface displacements. Studies were conducted for areas where both natural and mining-induced seismic shocks occurred. DInSAR technique was used to create interferograms. Phase unwrapping processes were performed using Statistical-Cost, Network-Flow Algorithm for Phase Unwrapping (SNAPHU) for conventional parameters, modified discontinuity parameters and taking into account theoretical shock models (Mogi model). Research allowed to determine the impact of abrupt, large displacements on the phase unwrapping process.</p>

Download Full-text

A Range Resolution Enhancement Algorithm for Active Millimeter Wave Based on Phase Unwrapping Mechanism

Electronics ◽

10.3390/electronics10141689 ◽

2021 ◽

Vol 10 (14) ◽

pp. 1689

Author(s):

He Zhang ◽

Hua Zong ◽

Jinghui Qiu

Keyword(s):

Millimeter Wave ◽

Phase Distribution ◽

Resolution Enhancement ◽

Continuous Phase ◽

Target Object ◽

Phase Unwrapping ◽

Practical Applications ◽

Range Resolution ◽

Security Inspection ◽

Security Check

Traditional security check technology is mainly based on metal detection by manual inspection. This method is simple and convenient, can detect a few different kinds of contrabands, and also takes into account the safety of inspectors. Because of its strong penetration characteristics, millimeter waves make up for the deficiency of existing security check technologies. Therefore, it is urgent to research and develop millimeter wave holographic imaging technology for human security inspection. In traditional imaging methods, the azimuthal resolution can be improved through various methods of image processing, but the traditional way to improve the range direction resolution is to increase the system bandwidth. However, improvements of the system bandwidth will greatly increase the cost. The bandwidth improvement space is also limited, so it cannot be expanded indefinitely in practical applications. In this study, the interferometric synthetic aperture theory was used to improve the range direction resolution of 3D millimeter wave holographic images without improving the system bandwidth. Phase unwrapping was used to reconstruct the phase information of complex images and restore the continuous phase distribution of the target object so as to achieve improvement of the range direction resolution without increasing the system bandwidth. This work has theoretical guiding significance to improve the range resolution of millimeter wave imaging.

Download Full-text

2-D phase unwrapping and phase aliasing

Geophysics ◽

10.1190/1.1443515 ◽

1993 ◽

Vol 58 (9) ◽

pp. 1324-1334 ◽

Cited By ~ 18

Author(s):

Umberto Spagnolini

Keyword(s):

Error Propagation ◽

Continuous Phase ◽

Phase Unwrapping ◽

Complex Signals ◽

Rapid Phase ◽

One Dimensional ◽

Complete Problem ◽

Phase Variations ◽

Remote System ◽

The One

The phase of complex signals is measured modulo-2π (wrapped phase); continuous‐phase information is obtained by adding properly chosen multiples of 2π shift to the wrapped phase. Unwrapping searches for the 2π combinations that minimize the discontinuity of the unwrapped phase as only the unwrapped phase can be analyzed and interpreted by further processing. The key problem of phase unwrapping is phase aliasing, a condition mainly caused by rapid phase variations. The extension of the one‐dimensional (1-D) phase unwrapping algorithms to a two‐dimensional (2-D) domain by 1-D slicing gives unsatisfactory results even in the presence of low‐phase aliasing, whereas 2-D phase unwrapping deals with the complete problem, overcoming the limitations of 1-D unwrapping. The 2-D unwrapped phase is obtained as the solution of a variational problem that minimizes the differences between the gradients of the wrapped and unwrapped phase. The Euler equation is then integrated using the boundary conditions obtained from the wrapped phase. In addition to determining a unique unwrapped phase, this approach has the advantage that it limits the influence of phase aliasing. It is also more attractive than iterative 1-D unwrapping since it limits the propagation of unwrapping errors. Error propagation in phase unwrapping can strongly influence the result of any phase processing. Examples in this paper apply 2-D phase unwrapping to problems of refraction statics and interferometrical imaging using a remote system (SAR) and demonstrate how limited error propagation allows phase processing.

Download Full-text

InSAR Phase Unwrapping by Means of a Particle Filter

IGARSS 2008 - 2008 IEEE International Geoscience and Remote Sensing Symposium ◽

10.1109/igarss.2008.4779948 ◽

2008 ◽

Author(s):

Juan J. Martinez-Espla ◽

Tomas Martinez-Marin ◽

J. David Ballester-Berman ◽

Juan M. Lopez-Sanchez

Keyword(s):

Particle Filter ◽

Phase Unwrapping

Download Full-text

Multi-Wavelength Digital-Phase-Shifting Moiré Based on Moiré Wavelength

Applied Sciences ◽

10.3390/app9091917 ◽

2019 ◽

Vol 9 (9) ◽

pp. 1917 ◽

Cited By ~ 1

Author(s):

Fatemeh Mohammadi ◽

Jonathan Kofman

Keyword(s):

Continuous Phase ◽

Phase Unwrapping ◽

Phase Shifting ◽

Surface Shape ◽

Digital Phase ◽

Temporal Phase ◽

Single Pattern ◽

Multi Wavelength ◽

Phase Map ◽

Surface Discontinuities

Multi-wavelength digital-phase-shifting moiré was demonstrated using multiple moiré wavelengths determined by system calibration over the full working depth. The method uses the extended noisy phase map as a reference to unwrap the phase map with a shorter wavelength, and thus achieve a less noisy and more accurate continuous phase map. The moiré wavelength calibration determines a moiré-wavelength to height relationship that permits pixelwise refinement of the moiré wavelength and height during 3D reconstruction. Only a single pattern has to be projected and, thus, a single image captured to compute each phase map with a different wavelength to perform digital-phase-shifting moiré temporal phase unwrapping. Only two captured images are required for two-wavelength phase unwrapping and three captured images for three-wavelength phase unwrapping. The method has been demonstrated in the 3D surface-shape measurement of an object with surface discontinuities and spatially isolated objects.

Download Full-text