Browsing by Author "Kumar, Ravi"

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3D incoherent imaging using an ensemble of sparse self-rotating beams
(Optics Express, 2023) Bleahu, Andrei-ioan; Gopinath, Shivasubramanian; Kahro, Tauno; Angamuthu, Praveen Periyasamy; Rajeswary, Aravind Simon John Francis; Prabhakar, Shashi; Kumar, Ravi; Salla, Gangi Reddy; Singh, Ravindra P.; Kukli, Kaupo; Tamm, Aile; Rosen, Joseph; Anand, Vijayakumar
Interferenceless coded aperture correlation holography (I-COACH) is one of the simplest incoherent holography techniques. In I-COACH, the light from an object is modulated by a coded mask, and the resulting intensity distribution is recorded. The 3D image of the object is reconstructed by processing the object intensity distribution with the pre-recorded 3D point spread intensity distributions. The first version of I-COACH was implemented using a scattering phase mask, which makes its implementation challenging in light-sensitive experiments. The I-COACH technique gradually evolved with the advancement in the engineering of coded phase masks that retain randomness but improve the concentration of light in smaller areas in the image sensor. In this direction, I-COACH was demonstrated using weakly scattered intensity patterns, dot patterns and recently using accelerating Airy patterns, and the case with accelerating Airy patterns exhibited the highest SNR. In this study, we propose and demonstrate I-COACH with an ensemble of self-rotating beams. Unlike accelerating Airy beams, self-rotating beams exhibit a better energy concentration. In the case of self-rotating beams, the uniqueness of the intensity distributions with depth is attributed to the rotation of the intensity pattern as opposed to the shifts of the Airy patterns, making the intensity distribution stable along depths. A significant improvement in SNR was observed in optical experiments.
3D single shot lensless incoherent optical imaging using coded phase aperture system with point response of scattered airy beams
(Scientific Reports, 2023) Kumar, Ravi; Anand, Vijayakumar; Rosen, Joseph
Interferenceless coded aperture correlation holography (I-COACH) techniques have revolutionized the field of incoherent imaging, offering multidimensional imaging capabilities with a high temporal resolution in a simple optical configuration and at a low cost. The I-COACH method uses phase modulators (PMs) between the object and the image sensor, which encode the 3D location information of a point into a unique spatial intensity distribution. The system usually requires a one-time calibration procedure in which the point spread functions (PSFs) at different depths and/or wavelengths are recorded. When an object is recorded under identical conditions as the PSF, the multidimensional image of the object is reconstructed by processing the object intensity with the PSFs. In the previous versions of I-COACH, the PM mapped every object point to a scattered intensity distribution or random dot array pattern. The scattered intensity distribution results in a low SNR compared to a direct imaging system due to optical power dilution. Due to the limited focal depth, the dot pattern reduces the imaging resolution beyond the depth of focus if further multiplexing of phase masks is not performed. In this study, I-COACH has been realized using a PM that maps every object point into a sparse random array of Airy beams. Airy beams during propagation exhibit a relatively high focal depth with sharp intensity maxima that shift laterally following a curved path in 3D space. Therefore, sparse, randomly distributed diverse Airy beams exhibit random shifts with respect to one another during propagation, generating unique intensity distributions at different distances while retaining optical power concentrations in small areas on the detector. The phase-only mask displayed on the modulator was designed by random phase multiplexing of Airy beam generators. The simulation and experimental results obtained for the proposed method are significantly better in SNR than in the previous versions of I-COACH.
4D imaging using accelerating airy beams and nonlinear reconstruction
(2023) Bleahu, Andrei; Gopinath, Shivasubramanian; Anand, Vijayakumar; Rosen, Joseph; Juodkazis, Saulius; Tamm, Aile; Kukli, Kaupo; Rajeswary, Aravind Simon John Francis; Katkus, Tomas; Pristy, Agnes; Ng, Soon Hock; Praveen, P. A.; Kahro, Tauno; Smith, Daniel; Arokiaraj, Francis Gracy; Kumar, Ravi
Enhanced design of multiplexed coded masks for Fresnel incoherent correlation holography
(Scientific Reports, 2023) Gopinath, Shivasubramanian; Bleahu, Andrei; Kahro, Tauno; Rajeswary, Aravind Simon John Francis; Kumar, Ravi; Kukli, Kaupo; Tamm, Aile; Rosen, Joseph; Anand, Vijayakumar
Fresnel incoherent correlation holography (FINCH) is a well-established incoherent digital holography technique. In FINCH, light from an object point splits into two, differently modulated using two diffractive lenses with different focal distances and interfered to form a self-interference hologram. The hologram numerically back propagates to reconstruct the image of the object at different depths. FINCH, in the inline configuration, requires at least three camera shots with different phase shifts between the two interfering beams followed by superposition to obtain a complex hologram that can be used to reconstruct an object’s image without the twin image and bias terms. In general, FINCH is implemented using an active device, such as a spatial light modulator, to display the diffractive lenses. The first version of FINCH used a phase mask generated by random multiplexing of two diffractive lenses, which resulted in high reconstruction noise. Therefore, a polarization multiplexing method was later developed to suppress the reconstruction noise at the expense of some power loss. In this study, a novel computational algorithm based on the Gerchberg-Saxton algorithm (GSA) called transport of amplitude into phase (TAP-GSA) was developed for FINCH to design multiplexed phase masks with high light throughput and low reconstruction noise. The simulation and optical experiments demonstrate a power efficiency improvement of ~ 150 and ~ 200% in the new method in comparison to random multiplexing and polarization multiplexing, respectively. The SNR of the proposed method is better than that of random multiplexing in all tested cases but lower than that of the polarization multiplexing method.
Enhanced design of pure phase greyscale diffractive optical elements by phase-retrieval-assisted multiplexing of complex functions
(2023) Gopinath, Shivasubramanian; Bleahu, Andrei; Kahro, Tauno; Rajeswary, Aravind Simon John Francis; Kumar, Ravi; Kukli, Kaupo; Tamm, Aile; Rosen, Joseph; Anand, Vijayakumar
Enhanced design of pure phase greyscale diffractive optical elements by phase-retrieval-assisted multiplexing of complex functions
(Society of Photo-Optical Instrumentation Engineers (SPIE), 2023) Gopinath, Shivasubramanian; Bleahu, Andrei; Kahro, Tauno; Rajeswary, Aravind Simon John Francis; Kumar, Ravi
Incoherent Digital Holography using Spiral Rotating Point Spread Functions Created by Double-helix Beams
(Digital Holography and 3-D Imaging 2022, 2022) Dubey, Nitin; Anand, Vijayakumar; Khonina, Svetlana; Kumar, Ravi; Reddy, Andra Naresh Kumar; Rosen, Joseph
A new incoherent 3D imaging system with a rotating point spread function has been developed. Different computational reconstruction methods such as non-linear reconstruction and the Lucy-Richardson-Rosen algorithm were tested, and their performances were compared.
Nonlinear Reconstruction of Images from Patterns Generated by Deterministic or Random Optical Masks—Concepts and Review of Research
(Journal of Imaging, 2022) Smith, Daniel; Gopinath, Shivasubramanian; Arockiaraj, Francis Gracy; Reddy, Andra Naresh Kumar; Balasubramani, Vinoth; Kumar, Ravi; Dubey, Nitin; Ng, Soon Hock; Katkus, Tomas; Selva, Shakina Jothi; Renganathan, Dhanalakshmi; Kamalam, Manueldoss Beaula Ruby; Rajeswary, Aravind Simon John Francis; Navaneethakrishnan, Srinivasan; Inbanathan, Stephen Rajkumar; Valdma, Sandhra-Mirella; Praveen, Periyasamy Angamuthu; Amudhavel, Jayavel; Kumar, Manoj; Ganeev, Rashid A.; Magistretti, Pierre J.; Depeursinge, Christian; Juodkazis, Saulius; Rosen, Joseph; Anand, Vijayakumar
Indirect-imaging methods involve at least two steps, namely optical recording and computational reconstruction. The optical-recording process uses an optical modulator that transforms the light from the object into a typical intensity distribution. This distribution is numerically processed to reconstruct the object’s image corresponding to different spatial and spectral dimensions. There have been numerous optical-modulation functions and reconstruction methods developed in the past few years for different applications. In most cases, a compatible pair of the optical-modulation function and reconstruction method gives optimal performance. A new reconstruction method, termed nonlinear reconstruction (NLR), was developed in 2017 to reconstruct the object image in the case of optical-scattering modulators. Over the years, it has been revealed that the NLR can reconstruct an object’s image modulated by an axicons, bifocal lenses and even exotic spiral diffractive elements, which generate deterministic optical fields. Apparently, NLR seems to be a universal reconstruction method for indirect imaging. In this review, the performance of NLR is investigated for many deterministic and stochastic optical fields. Simulation and experimental results for different cases are presented and discussed
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.
Statement of Peer Review
(2023) Anand, Vijayakumar; Jayavel, Amudhavel; Palm, Viktor; Gopinath, Shivasubramanian; Bleahu, Andrei; Rajeswary, Aravind Simon John Francis; Kukli, Kaupo; Balasubramani, Vinoth; Kumar, Ravi; Smith, Daniel; Ng, Soon Hock; Juodkazis, Saulius