R.V. Vinu

National Huaqiao University · College of Information Science and Engineering

Unconventional systems that adopt the concept of ghost schemes have led to advancements in some imaging applications. However, their application in quantitative phase imaging remains a challenge. Here, we introduce a basis for quantitative phase imaging with ghost diffraction and demonstrate ghost diffraction holographic microscopy for complex-valu...

Digital holography assisted with inline phase-shifting methods has the benefit of a large field of view and a high resolution, but it is limited in dynamic imaging due to sequential detection of multiple holograms. Here we propose and experimentally demonstrate a single-shot phase-shifting digital holography system based on a highly stable on-axis...

Quantitative phase microscopy (QPM) has been emerged as an indispensable diagnostic and characterization tool in biomedical imaging with its characteristic nature of label‐free, non‐invasive, and real time imaging modality. The integration of holography to the conventional microscopy opens new advancements in QPM featuring high‐resolution and quant...

The fascinating domain of ghost imaging has been a subject of interest in the fundamental and applied research for the last two decades with its promising applications in various imaging and characterization scenarios. In this chapter, we discuss the recently developed ghost diffraction holography (GDH) system with due emphasis on the capability of...

Correlation optics has evolved into an exceptionally fascinating and promising domain in modern optics and photonics with diverse technological developments ranging from imaging to communication, from astronomy to industrial metrology, etc. In correlation assisted optical techniques, the light fields were visualized in terms of correlation function...

By adopting the polarization phase shifting and space division multiplexing in digital holographic microscopy, a reflectance quantitative phase microscopy system capable of dynamic quantitative phase imaging and depth-resolved imaging is developed. The compact design of on-axis near common-path Fizeau polarization interferometry offers a single-sho...

By adopting the polarization phase shifting and space division multiplexing in digital holographic microscopy, a reflectance quantitative phase microscopy system capable of dynamic quantitative phase imaging and depth‐resolved imaging is developed. The compact design of on‐axis near common‐path Fizeau polarization interferometry offers a single‐sho...

Feedback-based wavefront shaping has been proposed to modulate the speckle field generated by coherent light transmitting through scattering media. Different from a monochromatic light, a colorful speckle pattern is generated when polychromatic light transmits through scattering media. Although single-position spectrum modulation has been realized,...

Quantitative phase imaging (QPI) plays an essential role in exploring properties of objects exemplified by transparent and absorption-free samples. Within the realm of QPI, the holography that records both the amplitude and the phase of optical fields is widely used. However, when the object is obscured by a scattering medium, conventional holograp...

Orbital angular momentum (OAM) of optical vortex beams has been regarded as an independent physical dimension of light with predominant information-carrying potential. However, the presence of scattering environment and turbulent atmosphere scrambles the helical wavefront and destroys the orthogonality of modes in vortex beam propagation. Here, we...

We present a spatial light modulator (SLM) assisted compact holographic method and illustrate its application by imaging through a random scattering medium. The merit of the proposed method is wavefront division multiplexing, i.e. the dual wavefront modulations over a single SLM. Two different wavefront shapes: a reference-light shape and a phase o...

As an object is passing through a static scattering medium, a speckle is formed. We can reconstruct the image from the speckle, based on the principle of optical memory effect. However, when the object passes through a dynamic scattering medium, such as fog, the reconstructed image quality will be degraded even blurred. In this paper, we want to in...

Wepresent a new polarization holographic microscopy technique based on speckle-field illumination with enhanced spatial resolution and controlled coherent noise reduction. The proposed technique employs a spatial light modulator for the generation of a sequential speckle pattern for the illumination of the sample. The developed microscope is capabl...

Imaging through a scattering medium or focusing light through a scattering layer using light in the visible region of the electromagnetic spectrum is a challenging task. When a beam of light enters into a non-absorbing opaque medium such as living tissue, white paint, fog, atmospheric turbulence etc., the constituent photons undergo scattering even...

We present our recent research studies on single-shot complex amplitude information retrieval through a visually opaque scattering layer realized using different architectures based on speckle interferometry, intensity correlation interferogram, phase-retrieval algorithm and digital holography.

We present a technique for polarization holographic imaging that employs the complex speckle pattern (rather than a uniform field) to illuminate the sample and utilizes the randomness of the speckle pattern for image enhancement. The vectorial wave front is recovered by developing a polarization holographic imaging system with the potential of simu...

Quantitative measurement of Jones matrix elements is crucial for the study of light polarization with the wide range of applications. Here, we propose and experimentally demonstrate a novel method of Fourier space sharing to determine spatially resolved all four elements of the Jones matrix from a single-intensity frame. This is achieved by applyin...

Optical imaging through complex scattering media is one of the major technical challenges with important applications in many research fields, ranging from biomedical imaging to astronomical telescopy to spatially multiplexed optical communications. Various approaches for imaging through a turbid layer have been recently proposed that exploit the a...

We propose and demonstrate a compressive sensing(CS) framework for correlation holography. This is accomplished by adopting the principle of compressive sensing and thresholding in the two point intensity correlation. The measurement matrix and the sensing matrix that is required for applying the CS frame work here are systematically extracted from...

We propose and experimentally demonstrate lensless complex amplitude image retrieval through a visually opaque scattering medium from spatially fluctuating fields using intensity measurement and a phase-retrieval algorithm. The complex amplitude information of the hidden object is encoded in the form of a real and nonnegative amplitude function rep...

Measurement of optical activity of anisotropic sample in the visible domain is employed as a routine task in wide range of applications. In this paper, we propose a new scheme to measure anisotropy of the sample using Jones matrix elements. This is implemented by making use of polarization and angular multiplexing. The technique offers retrieval of...

A non-interferometric technique for imaging from laser speckle using speckle autocorrelation assisted with sparsity enhanced iterative phase reconstruction is proposed and demonstrated in this paper. The use of sparsity assisted approach in combination with speckle correlation provides the potential to retrieve the complex correlation function from...

A non-interferometric technique for imaging from laser speckle using speckle autocorrelation assisted with sparsity enhanced iterative phase reconstruction is proposed and demonstrated in this paper. The use of sparsity assisted approach in combination with speckle correlation provides the potential to retrieve the complex correlation function from...

We propose and experimentally demonstrate a technique to quantitatively determine the topological structure of the vortex beam coaxially launched into the random scattering media with another non-vortex beam of the orthogonal polarization component. The proposed technique applies the coherent superposition of the random electromagnetic fields and a...

The main objectives of this thesis are shaping and analysis of laser speckle pattern and the effective utilization of their randomness for optical manipulation and imaging through scattering layers. These imaging techniques have a remarkable achievement in true non-invasive single-shot and depth resolved 3D imaging through complex scattering layers...

Non-invasive and single-shot holographic imaging through complex media is technically challenging due to random light scattering which significantly scrambles optical information. Recently, several methods have been presented to address this issue. However, they require complicated measurements of optical transmission matrices, or existing techniqu...

We propose and experimentally demonstrate a technique, based on polarization modulation, for imaging of the polarization discriminating object hidden behind a scattering medium. This is realized by making use of the relation between the complex correlation function of the randomly scattered orthogonal polarization components in the far field and po...

Optical imaging through complex scattering media is one of the major technical challenges with important applications in many research fields, ranging from biomedical imaging, astronomical telescopy, and spatially multiplex optical communications. Although various approaches for imaging though turbid layer have been recently proposed, they had been...

An experimental technique for the synthesis of statistical properties of a randomly fluctuating polarized field is investigated and experimentally demonstrated. The technique offers the controlled synthesis of coherence and polarization and subsequent analysis of the synthesized field is carried out by making use of two-point intensity correlation...

A new technique to determine generalized Stokes parameters by making use of the speckle holographic technique and the two-point intensity correlation is proposed and experimentally demonstrated. Assuming Gaussian statistics and spatial stationarity, a speckle hologram is generated prior to the fourth-order correlation, i.e., the two-point intensity...

We experimentally demonstrate the generation of two dimensional spatially varying coherence points using Dammann grating. The experimental result is presented for the case of 3×3 array of coherence points. The principle of the technique is based on van Cittert Zernike theorem and the coherence is controlled by using a phase grating.

A method to retrieve complex coherence of the speckle field from two-point intensity correlation is described and experimentally demonstrated. This is carried out by combining two-point intensity correlation and a holographic principle. Experimental results of the complex coherence function of the speckle fields are presented for two different sour...

A new technique to generate spatially varying coherence field, such as coherence comb, by the Dammann grating is proposed and experimentally demonstrated. Principle of the technique lies with the vectorial van Cittert Zernike theorem which connects vectorial source structure with the coherence-polarization of the light. The Dammann grating is encod...

We propose and experimentally demonstrate a technique for the recovery of the wavefront from spatially fluctuating fields using the two point intensity correlation, i.e., fourth order correlation. Assuming spatial ergodicity and Gaussian statistics for the speckle field, we connect the fourth order correlation to the modulus of the corresponding se...

In this paper, generation of the Dammann grating by using the spatial light modulator (SLM) is discussed, and quality of the grating is examined by using the polarization interferometer and Fourier fringe analysis technique.

We discuss here the phenomenon of speckle and speckle memory effect in far-field region. Correlation technique for analyzing memory effect is investigated. Result obtained using cross-correlation technique for measuring the memory effect is discussed. Practical observations of the experiment are described. Speckle pattern gives sample specific fing...

Effect of 60Co γ-ray radiation with 1×1016 γ/cm2 fluence on the ideality factor, saturation current and series resistance for two separate junctions p–i and i–n of p–i–n diode are studied by using temperature dependent current–voltage measurements and β model analysis. After γ-ray irradiation, the resistance of p–i–n diode increases from 858 to 278...