Effective Denoising with Non-local Means Filter for Reliable Unwrapping of Digital Holographic Interferometric Fringes
01 Jan 2018-pp 13-24
TL;DR: This paper proposes a preprocessing technique that removes the noise from the interference field, thereby improving the performance of naive unwrapping algorithms and validates the applicability of proposed approach for processing the noisy interference field.
Abstract: Estimation of phase from the complex interference field has become an emerging area of research for last few decades. The phase values obtained by using arctan function are limited to the interval \((-\pi , \pi ]\). Such phase map is known as wrapped phase. The unwrapping process, which produces continuous phase map from the wrapped phase, becomes tedious in presence of noise. In this paper, we propose a preprocessing technique that removes the noise from the interference field, thereby improving the performance of naive unwrapping algorithms. For de-noising of the complex field, real part and imaginary parts of the field are processed separately. Real-valued images (real and imaginary parts) are processed using non-local means filter with non-Euclidian distance measure. The de-noised real and imaginary parts are then combined to form a clean interference field. MATLAB’s unwrap function is used as unwrapping algorithm to get the continuous phase from the cleaned interference field. Comparison with the Frost’s filter validates the applicability of proposed approach for processing the noisy interference field.
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TL;DR: In this article, a fast Fourier transform method of topography and interferometry is proposed to discriminate between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour generation techniques.
Abstract: A fast-Fourier-transform method of topography and interferometry is proposed. By computer processing of a noncontour type of fringe pattern, automatic discrimination is achieved between elevation and depression of the object or wave-front form, which has not been possible by the fringe-contour-generation techniques. The method has advantages over moire topography and conventional fringe-contour interferometry in both accuracy and sensitivity. Unlike fringe-scanning techniques, the method is easy to apply because it uses no moving components.
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TL;DR: The proposed approach provides accurate phase estimation from a single record of the interference field; it avoids cumbersome and error-prone filtering and 2D unwrapping procedures; and it paves the way to adapt well-established PPS analysis tools available in signal processing literature for the phase estimation in holographic interferometry.
Abstract: This paper proposes a new approach for the analysis of reconstructed interference fields in digital holographic interferometry. In the proposed approach the interference phase to be estimated is conceived as a piecewise polynomial signal; consequently, each segment of the reconstructed interference field is modeled as a polynomial phase signal (PPS) with constant or slowly varying amplitude. The unwrapped phase distribution is then directly computed using the maximum likelihood estimation. Salient features of the proposed approach are: it provides accurate phase estimation from a single record of the interference field; it avoids cumbersome and error-prone filtering and 2D unwrapping procedures; and it paves the way to adapt well-established PPS analysis tools available in signal processing literature for the phase estimation in holographic interferometry.
27 citations
TL;DR: A local histogram-data-orientated filtering algorithm is proposed to remove noise from the deformation phase map obtained by a phase stepping electronic speckle pattern interferometry (ESPI) and can successfully eliminate any speckled residues of a real dislocation free map.
Abstract: A local histogram-data-orientated filtering algorithm is proposed to remove noise from the deformation phase map obtained by a phase stepping electronic speckle pattern interferometry (ESPI). The proposed filter can successfully eliminate any speckle-generated residues of a real dislocation free map. Since the filtered result is totally free from any phase inconsistency, a simple unwrapping rule, like Macy's method, can be applied for the correct phase retrieval. The motivation and theory of the proposed method is described. A simulated noisy wrapped map is employed to detail its implementation. An intercomparison of the present study and two well-known methods is performed to present the performance of the proposed method. In addition, several ESPI experiments are conducted to provide successful filtering of practical phase maps and to prove the effectiveness of the proposed method.
14 citations
TL;DR: A path-following phase unwrapping algorithm and a phase unwRApping algorithm based on discrete cosine transform (DCT) which accelerates the Computation and suppresses the propagation of noise are described.
14 citations
01 Aug 2015
TL;DR: This paper discusses a Fourier transform based phase unwrapping method that is highly robust to noise and performs better even at lower SNR values (5-10dB) with a very less value of RMS error.
Abstract: Phase information recovered through interferometric techniques is mathematically wrapped in the interval (−π, π). Obtaining the original unwrapped phase is very important in numerous number of applications. This paper discusses a Fourier transform based phase unwrapping method. Kalman filter is proposed for denoising in post processing step to restore the unwrapped phase without any noise. The proposed method is highly robust to noise and performs better even at lower SNR values (5–10dB) with a very less value of RMS error. Also, the time taken for execution is very less compared to the many available methods in the literature.
10 citations