Vellore Institute of Technology (VIT) is a private university located in&nbsp;Tamil Nadu, India. Founded in 1984, as Vellore Engineering College, the institution offers 20 undergraduate, 34 postgraduate, four integrated and four research programs. It has campuses in Vellore, Amravati, Bhopal and Chennai.

VIT is one of the top ranked private universities in India according to NIRF, THE and QS Rankings.&nbsp;Govt. of India has recognized&nbsp;VIT, Vellore as an&nbsp;Institution of Eminence. This has allowed VIT to take independent quality initiatives and move up in world ranking.

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VIT University

A compressive sensing (CS) approach is proposed for the complex wave retrieval algorithm from single off-axis digital Fresnel holography to improve the accuracy of quantitative phase measurement. The linear model of non-linear holographic process used in the complex wave retrieval algorithm is utilized to meet the linearity requirement of the proposed CS implementation presented in this paper. The error in object wave reconstruction due to the approximations used in complex wave retrieval algorithm is compensated by combining it with CS approach. A Mach–Zehnder interferometric geometry in transmission and off-axis mode in the Fresnel domain is used to record the digital hologram. The numerical simulations and experimental results are presented to demonstrate and validate the proof of the concept and to compare CS frame work with conventional complex wave retrieval algorithm. The proposed algorithm is tested for the microlens sample characterization by considering the parameters such as height, diameter and radius of curvature. A Haar wavelet based object wave sparsification is used in the experiment for the prudent phase reconstruction in the CS approach. The proposed method enables an improved and accurate object phase reconstruction, with minimal noise such as distortions or speckles with respect to the conventional complex wave retrieval method. © 2020 Elsevier B.V.

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Department of Sensor and Biomedical Technology

School of Electronics Engineering

Vellore Campus

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Fulltext

Optics Communications

Compressive complex wave retrieval from a single off-axis digital Fresnel hologram for quantitative phase imaging and microlens characterization

Nowadays, scarcity of power has been increased at much higher rate due to improper power management. In this paper, the concept of power management is demonstrated with a Webcam and OpenCV tool. OpenCV is used for the implementation of face-detection algorithm. The system is a real-time embedded system product, which is employed with a camera fixed in a room, which detects the faces of the people present in the room using OpenCV software which is a computer vision tool; as soon as the faces of human are detected in the room, the system takes the necessary steps and accordingly controls (turn ON/OFF) the AC/DC loads (like fan and lights) of the room. Thus, in this way, the utilization of the power can be maintained in an efficient way. © Springer Nature Singapore Pte Ltd. 2018.

VIT Unitversity

Lecture Notes in Electrical Engineering Intelligent Embedded Systems

Vision Intelligence System for Power Management Using Human Activity Detection System

The linear relationship between the sample complex object wave and its approximated complex Fresnel field obtained using single shot parallel phase-shifting digital holograms (PPSDH) is used in compressive sensing framework and an accurate phase reconstruction is demonstrated. It is shown that the accuracy of phase reconstruction of this method is better than that of compressive sensing adapted single exposure inline holography (SEOL) method. It is derived that the measurement model of PPSDH method retains both the real and imaginary parts of the Fresnel field but with an approximation noise and the measurement model of SEOL retains only the real part exactly equal to the real part of the complex Fresnel field and its imaginary part is completely not available. Numerical simulation is performed for CS adapted PPSDH and CS adapted SEOL and it is demonstrated that the phase reconstruction is accurate for CS adapted PPSDH and can be used for single shot digital holographic reconstruction. © 2018 Society of Photo-Optical Instrumentation Engineers (SPIE).

Optical Engineering

Phase reconstruction using compressive two-step parallel phase-shifting digital holography

Reconstruction of phase of the object wave from imperfect noisy Fresnel field using compressive sensing is numerically demonstrated. The CS based method yields better reconstruction accuracy of both intensity and phase than the direct method. © OSA 2016.

13th International Conference on Fiber Optics and Photonics

Phase Reconstruction from Noisy Fresnel Field Using Compressive Sensing

Compressive sensing (CS) in digital holography requires only very less number of pixel level detections in hologram plane for accurate image reconstruction and this is achieved by exploiting the sparsity of the object wave. When the input object fields are non-sparse in spatial domain, CS demands a suitable sparsification method like wavelet decomposition. The Fresnelet, a suitable wavelet basis for processing Fresnel digital holograms is an efficient sparsifier for the complex Fresnel field obtained by the Fresnel transform of the object field and minimizes the mutual coherence between sensing and sparsifying matrices involved in CS. The paper demonstrates the merits of Fresnelet based sparsification in compressive digital Fresnel holography over conventional method of sparsifying the input object field. The phase shifting digital Fresnel holography (PSDH) is used to retrieve the complex Fresnel field for the chosen problem. The results are presented from a numerical experiment to show the proof of the concept. © 2014 Elsevier B.V.

Compressive Fresnel digital holography using Fresnelet based sparse representation

Compressive sensing is applied for Digital in-line Holographic Microscopy assuming the object wave is sparse in spatial domain. The reconstructed complex image is free of noise when compared to conventional method of numerical reconstruction. © OSA 2015.

Frontiers in Optics 2015

Compressive Sensing for Digital In-line Holographic Microscopy

Frontiers in Optics 2014

Compressive holography using Fresnelet based sparsification of input complex object field

Digital holography together with double random phase Fresnel plane (input plane and intermediate Fresnel plane) encoding is used for joint encryption and copyright protection of image and audio data. The image is the host data and 2-D sound map created from audio data serves as copyright information. The host image and sound map are encoded as intensity and phase of a complex function respectively and serves as a complex input image for a digital holographic processor. The proposed method can be interpreted as an audio watermarking since both visual and audio perception takes place simultaneously during reconstruction. The tolerance against partial loss of secured information has been analyzed. From a partial segment of jointly protected image-sound complex encrypted Fresnel field, the data can be reconstructed within an acceptable quality to recognize the copyright audio by human subjects. The proof of concept of the proposed method is demonstrated by numerical simulations using position phase shifting digital holography. © Research India Publications.