A5073275636- Digital Holography and Microscopy
- Orbital Angular Momentum in Optics
- Advanced X-ray Imaging Techniques
- Optical measurement and interference techniques
- Random lasers and scattering media
- Neutrino Physics Research
- Optical Polarization and Ellipsometry
- Radiation Detection and Scintillator Technologies
- Retinal Imaging and Analysis
- Advanced Optical Imaging Technologies
- Particle physics theoretical and experimental studies
- Quasicrystal Structures and Properties
- Advanced Measurement and Metrology Techniques
- Photonic and Optical Devices
- Glaucoma and retinal disorders
- Optical Coherence Tomography Applications
- Advanced Optical Sensing Technologies
- Adaptive optics and wavefront sensing
- Dark Matter and Cosmic Phenomena
- Retinal Diseases and Treatments
- Advanced optical system design
- Diffusion and Search Dynamics
- Ferroelectric and Negative Capacitance Devices
- Nanocluster Synthesis and Applications
- Vehicle Routing Optimization Methods
Rice University
2019-2024
Indian Institute of Technology Delhi
1974-2022
University of Alberta
2020-2021
Manipal University Jaipur
2021
STMicroelectronics (India)
2019
Northwestern University
2015-2017
Indian Institute of Technology Indore
1975-2014
Kansas City VA Medical Center
2004
University of Kansas Medical Center
2003
Synthetic aperture radar is a well-known technique for improving resolution in radio imaging. Extending these synthetic techniques to the visible light domain not straightforward because optical receivers cannot measure phase information. We propose use macroscopic Fourier ptychography (FP) as practical means of creating imaging achieve subdiffraction-limited resolution. demonstrate first working prototype FP reflection geometry that capable optically rough objects. In addition, novel image...
In this work, we propose using camera arrays coupled with coherent illumination as an effective method of improving spatial resolution in long distance images by a factor often and beyond. Recent advances ptychography have demonstrated that one can image beyond the diffraction limit objective lens microscope. We demonstrate similar imaging system to range imaging. emulate array single attached XY translation stage. show appropriate phase retrieval based reconstruction algorithm be used...
Abstract Wavefront sensing is the simultaneous measurement of amplitude and phase an incoming optical field. Traditional wavefront sensors such as Shack-Hartmann sensor (SHWFS) suffer from a fundamental tradeoff between spatial resolution estimation consequently can only achieve few thousand pixels. To break this tradeoff, we present novel computational-imaging-based technique, namely, Imaging Sensor with High (WISH). We replace microlens array in SHWFS light modulator (SLM) use...
Diffraction-limited optical imaging through scattering media has the potential to transform many applications such as airborne and space-based (through atmosphere), bioimaging skin human tissue), fiber-based fiber bundles). Existing wavefront shaping methods can image other obscurants by optically correcting aberrations using high-resolution spatial light modulators-but these generally require (i) guidestars, (ii) controlled illumination, (iii) point scanning, and/or (iv) statics scenes...
Purpose: It is difficult to determine the position of a preferred retinal locus (PRL) relative fovea in scanning laser ophthalmoscope (SLO) images as result disease-related morphologic changes that obscure fovea. To overcome this problem, we developed method for determining foveal based on normal fixation optic disk. The measurements can then be used estimate distance between PRL and Methods: Using SLO, was determined 50 subjects by measuring disk undistorted SLO images. resulting area...
A transmission matrix describes the input-output relationship of a complex wavefront as it passes through/reflects off multiple-scattering medium, such frosted glass or painted wall. Knowing medium's enables one to image through send signals even use medium lens. The double phase retrieval method is recently proposed technique learn that avoids difficult-to-capture interferometric measurements. Unfortunately, perform high resolution imaging, existing methods require (1) large number...
In optical image processing, selective edge enhancement is important when it preferable to emphasize some edges of an object more than others. We propose a new method for amplitude objects using the anisotropic vortex phase mask by introducing anisotropy in conventional with help sine function. The capable region and required direction changing power offset angle, respectively,
A method of mapping the retinal location text during reading is described in which position plotted cumulatively on scanning laser ophthalmoscope images. Retinal locations that contain most often are brightest cumulative plot, and least darkest. In this way, area contains determined. Text maps were for eight control subjects without vision loss with central scotomas from macular degeneration. Control subjects' showed fovea contained often. five they used same peripheral to scan fixate. other...
We demonstrate that the two-dimensional quadrature transform property of a spiral-phase filter may be utilized for addressing noninterferometric iterative phase imaging problem. Two intensity measurements an unknown input object are performed in back focal (Fourier transform) plane lens with and without mask aperture. It is shown two along aperture support constraint can used estimating algorithm. Numerical simulations presented comparison new diversity technique more standard...
When a narrowband coherent wavefront passes through or reflects off of scattering medium, the input and output relationship incident field is linear so can be described by transmission matrix (TM). If TM for given medium known, one computationally "invert" process image medium. In this paper, we investigate effect broadband illumination, i.e., what happens when only partially coherent? Can still measure scattering? To accomplish task, TMs using double-phase retrieval technique, method that...
In both lensless Fourier transform holography (FTH) and coherent diffraction imaging (CDI), a beamstop is used to block strong intensities which exceed the limited dynamic range of sensor, causing loss in low-frequency information, making high quality reconstructions difficult or even impossible. this paper, we show that an image can be recovered from high-frequencies alone, thereby overcoming problem FTH CDI. The only requirement object sparse known basis, common property most natural...
Diffractals are electromagnetic waves diffracted by a fractal aperture. In an earlier paper, we reported important property of Cantor diffractals, that redundancy [R. Verma et. al., Opt. Express 20, 8250 (2012)]. this report another property, robustness. The question address is: How much disorder in the grating can be accommodated diffractals to continue yield faithfully its dimension and generator? This answer is consequence number physical problems involving architecture.
Aperiodic and fractal optical elements are proving to be promising candidates in image-forming devices. In this paper, we analyze the diffraction patterns of Fibonacci gratings (FbGs), which prototypical examples aperiodicity. They exhibit novel characteristics such as redundancy robustness that keep their imaging intact even when there is significant loss information. FbGs also contain signatures characterized by a dimension. Our study suggests aperiodic may better than counterparts...
We consider the transformation properties of density operator as well its diagonal coherent-state representation when a plane monochromatic light is passed through compensator followed by rotator. Special cases unpolarized and polarized are considered general form determined.
A new technique to generate a spatially varying coherence field, such as comb using Dammann grating, is proposed and experimentally demonstrated. The principle of the lies with vectorial van Cittert-Zernike theorem, which connects source structure coherence-polarization light. grating encoded into one polarization components light shape and, consequently, Experimental results on generation spatial by are presented for different orders.
SNO+ is a large-scale liquid scintillator experiment with the primary goal of searching for neutrinoless double beta decay, and located approximately 2 km underground in SNOLAB, Sudbury, Canada. The detector acquired data two years as pure water Cherenkov detector, starting May 2017. During this period, optical properties were measured situ using deployed light diffusing sphere, improving model energy response systematic uncertainties. parameters included attenuation coefficients, effective...
Purpose. The Rodenstock scanning laser ophthalmoscope (SLO) is useful for mapping retinal function and developing evaluating visual rehabilitation methods. It essential to know the angle subtended by stimuli in SLO laser-beam raster accurately measure angular distances between objects final image. To accomplish this, extent of must be calibrated. Methods. We developed a simple method apparatus calibrating used it repeated calibrations during 3-month period. Results. quite stable shape size,...
This talk describes our recently-developed guidestar-free approach to imaging through scattering and other optical aberrations; neural wavefront shaping (NeuWS). NeuWS integrates maximum likelihood estimation, measurement modulation, signal representations reconstruct diffraction-limited images strong static dynamic media without guidestars, sparse targets, controlled illumination, nor specialized image sensors. We experimentally demonstrate guidestar-free, wide field-of-view,...