Sirvi Autor "Joshi, Narmada" järgi

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Coded Aperture-Based Self-wavefront Interference Using Transverse Splitting Holography
(2023 International Conference on Next Generation Electronics (NEleX), 2023) Joshi, Narmada; Xavier, Agnes Pristy Ignatius; Arockiaraj, Francis Gracy; Rajeswary, Aravind Simon John Francis; Juodkazis, Saulius; Rosen, Joseph; Tamm, Aile; Anand, Vijayakumar
Self-wavefront interference transverse splitting holography (SWITSH) is a recently developed holographic technique to solve a fundamental problem in the manufacturing of large-area diffractive lenses. In SWITSH, a low NA diffractive lens modulates the light from an object, and the modulated light is interfered with light from the same object that reaches beyond the aperture of the diffractive lens. The resulting self-interference hologram is processed with the pre-recorded point spread hologram using the Lucy-Richardson-Rosen algorithm. Since the self-interference hologram is formed by collecting light beyond the NA of the diffractive lens, it acquires the object information corresponding to the higher spatial frequencies of the object. Consequently, a higher imaging resolution is obtained in SWITSH compared to that of direct imaging with a diffractive lens. In the proof-of-concept study, a resolution improvement of an order was demonstrated. However, the optical architecture of the first version of SWITSH was not optimal, as the strength of the self-interference signal was weak. In this study, we improve SWITSH using different coded apertures, such as axicon and spiral element. An improvement in the strength of the self-interference signal was noticed with the axicon and spiral element. Simulation and experimental results using a diffractive lens, axicon and spiral element are presented.
Interferenceless coded aperture correlation holography for five-dimensional imaging of 3D space, spectrum and polarization
(2025) Joshi, Narmada; Tiwari, Vipin; Kahro, Tauno; Xavier, Agnes Pristy Ignatius; Tahara, Tatsuki; Kasikov, Aarne; Kukli, Kaupo; Juodkazis, Saulius; Tamm, Aile; Rosen, Joseph; Anand, Vijayakumar
Interferenceless coded aperture correlation holography (I-COACH) is a robust imaging technique for recovering three-dimensional object information using incoherent holography without two-beam interference. In this study, five-dimensional (5D) imaging along 3D space, spectrum and polarization in I-COACH is proposed and experimentally demonstrated for the first time. The proposed technique exploits the polarization-dependent light modulation characteristics of spatial light modulators to record polarization-dependent intensity distributions, which are distinguished by significant blurring between orthogonal polarization states. 5D I-COACH is implemented by inter-connecting all five dimensions in a single frame, and image recovery is attempted from different configurations of recorded point spread intensity distributions and response-to-object intensity distributions along 5D using recently developed deconvolution techniques. The simulation and experimental results confirm the 5D imaging capabilities of I-COACH. The proposed technique can be a useful tool for birefringence microscopy, and functional and structural imaging applications.
Recent Advances in Spatially Incoherent Coded Aperture Imaging Technologies
(2025) Tiwari, Vipin; Gopinath, Shivasubramanian; Kahro, Tauno; Arockiaraj, Francis Gracy; Xavier, Agnes Pristy Ignatius; Joshi, Narmada; Kukli, Kaupo; Tamm, Aile; Juodkazis, Saulius; Rosen, Joseph; Anand, Vijayakumar
Coded aperture imaging (CAI) is a powerful imaging technology that has rapidly developed during the past decade. CAI technology and its integration with incoherent holography have led to the development of several cutting-edge imaging tools, devices, and techniques with widespread interdisciplinary applications, such as in astronomy, biomedical sciences, and computational imaging. In this review, we provide a comprehensive overview of the recently developed CAI techniques in the framework of incoherent digital holography. The review starts with an overview of the milestones in modern CAI technology, such as interferenceless coded aperture correlation holography, followed by a detailed survey of recently developed CAI techniques and system designs in subsequent sections. Each section provides a general description, principles, potential applications, and associated challenges. We believe that this review will act as a reference point for further advancements in CAI technologies.
Single shot polarization resolved coded aperture imaging
(2025) Joshi, Narmada; Tiwari, Vipin; Tamm, Aile; Rosen, Joseph; Anand, Vijayakumar
Coded aperture imaging (CAI) is a well-established indirect imaging technique consisting of two steps, namely optical recording and computational reconstruction. In the recent years, CAI technique has been extended to image along 3D space and also the spectrum with a single camera shot. In this study, we developed CAI for 3D imaging along 2D space and polarization using dual orthogonal polarization phase-modulation (DOPP) technique. DOPP-CAI has been demonstrated for 3D imaging with only one birefringent optical modulator and without any polarization sensitive image sensors. The theory, simulation and proof-of-concept experimental results are presented. The results demonstrate a one-to-one unique intensity-polarization mapping owing to a significant polarization discriminated blur in CAI. We believe that the developed DOPP-CAI can benefit multimodal imaging, birefringent imaging, holography and microscopy.
Spatial Ensemble Mapping for Coded Aperture Imaging—A Tutorial
(2024) Joshi, Narmada; Xavier, Agnes Pristy Ignatius; Gopinath, Shivasubramanian; Tiwari, Vipin; Anand, Vijayakumar
Coded aperture imaging (CAI) is a well-established computational imaging technique consisting of two steps, namely the optical recording of an object using a coded mask, followed by a computational reconstruction using a computational algorithm using a pre-recorded point spread function (PSF). In this tutorial, we introduce a simple yet elegant technique called spatial ensemble mapping (SEM) for CAI that allows us to tune the axial resolution post-recording from a single camera shot recorded using an image sensor. The theory, simulation studies, and proof-of-concept experimental studies of SEM-CAI are presented. We believe that the developed approach will benefit microscopy, holography, and smartphone imaging systems.