Sirvi Autor "Tiwari, Vipin" järgi

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Advances in polarization imaging: Techniques and instrumentation
(2025) Tiwari, Vipin
Polarization imaging has drawn significant attention from the research fraternity for decades due to its prominent imaging capabilities across multidisciplinary fields. Polarization imaging is based on the study of vectorial properties of light and associated vectorial transformations resulting from light-matter interaction. The range of polarization imaging and its applications is so broad that it is very challenging to accommodate all relevant concepts and applications in a single literature. This review article is an attempt in this direction. This paper presents a concise review of polarization imaging from fundamental to advanced level, covering the essential elements, such as historical development, theoretical concepts, and experimental aspects of polarization imaging, followed by a brief introduction to traditional and modern polarization imaging instruments. This review article aims to provide a reference text for readers from various research backgrounds interested in polarization imaging.
Coded Aperture Imaging using Non-Linear Lucy-Richardson Algorithm
(2025) Xavier, Agnes Pristy Ignatius; Kahro, Tauno; Gopinath, Shivasubramanian; Tiwari, Vipin; Smith, Daniel; Kasikov, Aarne; Piirsoo, Helle-Mai; Ng, Soon Hock; Rajeswary, Aravind Simon John Francis; Vongsvivut, Jitraporn; Tamm, Aile; Kukli, Kaupo; Juodkazis, Saulius; Rosen, Joseph; Anand, Vijayakumar
Imaging involves the process of recording and reproducing images as close to reality as possible, encompassing both direct and indirect approaches. In direct imaging, the object is directly recorded. Coded aperture imaging (CAI) is an example of indirect imaging, that utilizes optical recording and computational reconstruction to obtain information about an object. Computational reconstruction can be achieved using different linear, non-linear, iterative, and deep learning algorithms. In this study, we proposed and demonstrated two computational reconstruction algorithms based on the non-linear Lucy-Richardson algorithm (NL-LRA), one for limited support images and another for full-view images based on entropy reduction. The efficacy of these algorithms has been validated through simulations and optical experiments carried out in visible and infrared (IR) light with different coded phase masks. The methods were also tested on a commercial IR microscope with internal Globar™ and synchrotron sources. The results obtained from the two algorithms were compared with those from their parent methods, and a notable improvement in both entropy and the convergence rate was observed. We believe the developed algorithms will drastically improve image reconstruction in incoherent imaging applications
Extending the Depth of Focus of Infrared Microscope Using a Binary Axicon Fabricated on Barium Fluoride
(2024) Han, Molong; Smith, Daniel; Kahro, Tauno; Stonytė, Dominyka; Kasikov, Aarne; Gailevičius, Darius; Tiwari, Vipin; Xavier, Agnes Pristy Ignatius; Gopinath, Shivasubramanian; Ng, Soon Hock; Rajeswary, Aravind Simon John Francis; Tamm, Aile; Kukli, Kaupo
Axial resolution is one of the most important characteristics of a microscope. In all microscopes, a high axial resolution is desired in order to discriminate information efficiently along the longitudinal direction. However, when studying thick samples that do not contain laterally overlapping information, a low axial resolution is desirable, as information from multiple planes can be recorded simultaneously from a single camera shot instead of plane-by-plane mechanical refocusing. In this study, we increased the focal depth of an infrared microscope non-invasively by introducing a binary axicon fabricated on a barium fluoride substrate close to the sample. Preliminary results of imaging the thick and sparse silk fibers showed an improved focal depth with a slight decrease in lateral resolution and an increase in background noise.
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.
Roadmap on computational methods in optical imaging and holography [invited].
(2024) Rosen, Joseph; Alford, Simon; Allan, Blake; Anand, Vijayakumar; Arnon, Shlomi; Arockiaraj, Francis Gracy; Art, Jonathan; Bai, Bijie; Balasubramaniam, Ganesh M.; Birnbaum, Tobias; Bisht, Nandan S.; Blinder, David; Cao, Liangcai; Chen, Qian; Chen, Ziyang; Dubey, Vishesh; Egiazarian, Karen; Ercan, Mert; Forbes, Andrew; Gopakumar, G.; Gao, Yunhui; Gigan, Sylvain; Gocłowski, Paweł; Gopinath, Shivasubramanian; Greenbaum, Alon; Horisaki, Ryoichi; Ierodiaconou, Daniel; Juodkazis, Saulius; Karmakar, Tanushree; Katkovnik, Vladimir; Khonina, Svetlana N.; Kner, Peter; Kravets, Vladislav; Kumar, Ravi; Lai, Yingming; Li, Chen; Li, Jiaji; Li, Shaoheng; Li, Yuzhu; Liang, Jinyang; Manavalan, Gokul; Mandal, Aditya Chandra; Manisha, Manisha; Mann, Christopher; Marzejon, Marcin J.; Moodley, Chané; Morikawa, Junko; Muniraj, Inbarasan; Narbutis, Donatas; Ng, Soon Hock; Nothlawala, Fazilah; Oh, Jeonghun; Ozcan, Aydogan; Park, YongKeun; Porfirev, Alexey P.; Potcoava, Mariana; Prabhakar, Shashi; Pu, Jixiong; Rai, Mani Ratnam; Rogalski, Mikołaj; Ryu, Meguya; Choudhary, Sakshi; Salla, Gangi Reddy; Schelkens, Peter; Şener, Sarp Feykun; Shevkunov, Igor; Shimobaba, Tomoyoshi; Singh, Rakesh K.; Singh, Ravindra P.; Stern, Adrian; Sun, Jiasong; Zhou, Shun; Zuo, Chao; Zurawski, Zack; Tahara, Tatsuki; Tiwari, Vipin; Trusiak, Maciej; Vinu, R. V.; Volotovskiy, Sergey G.; Yılmaz, Hasan; Barbosa De Aguiar, Hilton; Ahluwalia, Balpreet S.; Ahmad, Azeem
Computational methods have been established as cornerstones in optical imaging and holography in recent years. Every year, the dependence of optical imaging and holography on computational methods is increasing significantly to the extent that optical methods and components are being completely and efficiently replaced with computational methods at low cost. This roadmap reviews the current scenario in four major areas namely incoherent digital holography, quantitative phase imaging, imaging through scattering layers, and super-resolution imaging. In addition to registering the perspectives of the modern-day architects of the above research areas, the roadmap also reports some of the latest studies on the topic. Computational codes and pseudocodes are presented for computational methods in a plug-and-play fashion for readers to not only read and understand but also practice the latest algorithms with their data. We believe that this roadmap will be a valuable tool for analyzing the current trends in computational methods to predict and prepare the future of computational methods in optical imaging and holography.
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.
Spatio spectral correlations in interferenceless coded aperture correlation holography with vortex speckles
(2025) Vilardell, Eulàlia Puig; Gopinath, Shivasubramanian; Tiwari, Vipin; Kahro, Tauno; Kasikov, Aarne; Kõiv, Markus; Reddy, Andra Naresh Kumar; Rosen, Joseph; Kukli, Kaupo; Gailevičius, Darius; Juodkazis, Saulius; Anand, Vijayakumar
Interferenceless coded aperture correlation holography (I-COACH) is a computational imaging method that enables three-dimensional information of an object to be obtained without the need for two-beam interference. For the first time, in this study, we propose and demonstrate I-COACH with vortex speckles (I-COACH-VS). The vortex speckle distribution is generated by designing a unique coded mask by combining several spiral phases with different topological charges and linear phases using the transport of the amplitude into the phase based on the Gerchberg-Saxton algorithm (TAP-GSA). The spiral phase generates multiple beams carrying different orbital angular momentum, and the linear phase is used to map the beams at different locations within the image sensor to achieve a random vortex speckle distribution. The recently developed Lucy-Richardson-Rosen algorithm (LRRA) is used for image reconstruction. The theory, simulation studies, design of a coded mask by TAP-GSA, fabrication of coded masks by photolithography, and experimental demonstration of I-COACH-VS are presented. We believe that the developed method will be impactful in fields such as incoherent digital holography and computational imaging.
Super-Resolution Correlating Optical Endoscopy
(2024) Tamm, Oskar; Tiwari, Vipin; Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Singh, Scott Arockia; Rosen, Joseph; Anand, Vijayakumar
Optical endoscopy is a widely used minimally invasive diagnostic tool for imaging internal organs. The imaging resolution is defined by the numerical aperture of the objective lens. In this study, we proposed and demonstrated a Super-resolution Correlating OPtical Endoscopy (SCOPE) system. In SCOPE, modified recording and reconstruction methods are introduced with the existing built-in endoscopy lens. Instead of recording a single image, multiple images of the object are recorded by scanning the tip of the endoscope around the object. The recorded low-resolution images of the object are arranged as sub-matrices in a 2D matrix. Another similar 2D matrix with either recorded or synthesized point spread functions (PSFs) is created. The 2D matrices of the object and the PSF were processed using a deconvolution algorithm to reconstruct a super-resolution image of the object. Both simulation and proof-of-concept experimental studies have been presented. SCOPE neither requires any additional optical element nor any changes in the endoscopy system itself; therefore, it can be easily implemented in commercial endoscopy systems.