CIPHR - ERA Chair for Computational Imaging and Processing in High Resolution
Permanent URI for this collectionhttps://hdl.handle.net/10062/91302
In the project, the Centre of Photonics and Computational Imaging is established at the UT. The combined application of photonics and computationally intensive data processing allows to enhance the image quality, resolution or add spatial dimension to the image beyond the physical or technical limits of the imaging system. By nature, the research is interdisciplinary and embraces the extensive competence of the University of Tartu in optics, spectroscopy, mathematics, computer science and their applications.
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Item Incoherent nonlinear deconvolution using an iterative algorithm for recovering limited-support images from blurred digital photographs(2024) Rosen, Joseph; Anand, VijayakumarRecovering original images from blurred images is a challenging task. We propose a new deconvolution method termed incoherent nonlinear deconvolution using an iterative algorithm (INDIA). Two inputs are introduced into the algorithm: one is a random or engineered point spread function of the scattering system, and the other is a blurred or distorted image of some object produced from this system. The two functions are Fourier transformed, and their phase distributions are processed independently of their magnitude. The algorithm yields the image of the original object with reduced blurring effects. The results of the new method are compared to two linear and two nonlinear algorithms under various types of blurs. The root mean square error and structural similarity between the original and recovered images are chosen as the comparison criteria between the five different algorithms. The simulation and experimental results confirm the superior performance of INDIA compared to the other tested deblurring methods.Item Optimizing the temporal and spatial resolutions and light throughput of Fresnel incoherent correlation holography in the framework of coded aperture imaging(2024) Arockiaraj, Francis Gracy; Xavier, Agnes Pristy Ignatius; Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Juodkazis, Saulius; Anand, VijayakumarFresnel incoherent correlation holography (FINCH) is a well-established digital holography technique for 3D imaging of objects illuminated by spatially incoherent light. FINCH has a higher lateral resolution of 1.5 times that of direct imaging systems with the same numerical aperture. However, the other imaging characteristics of FINCH, such as axial resolution, temporal resolution, light throughput, and signal-to-noise ratio (SNR), are lower than those of direct imaging systems. Different techniques were developed by researchers around the world to improve the imaging characteristics of FINCH while retaining the inherent higher lateral resolution of FINCH. However, most of the solutions developed to improve FINCH presented additional challenges. In this study, we optimized FINCH in the framework of coded aperture imaging. Two recently developed computational methods, such as transport of amplitude into phase based on the Gerchberg Saxton algorithm and Lucy–Richardson–Rosen algorithm, were applied to improve light throughput and image reconstruction, respectively. The above implementation improved the axial resolution, temporal resolution, and SNR of FINCH and moved them closer to those of direct imaging while retaining the high lateral resolution. A point spread function (PSF) engineering technique has been implemented to prevent the low lateral resolution problem associated with the PSF recorded using pinholes with a large diameter. We believe that the above developments are beyond the state-of-the-art of existing FINCH-scopes.Item 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, KaupoAxial 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.Item Super-Resolution Correlating Optical Endoscopy(2024) Tamm, Oskar; Tiwari, Vipin; Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Singh, Scott Arockia; Rosen, Joseph; Anand, VijayakumarOptical 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.Item 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, AzeemComputational 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.Item Post-ensemble generation with Airy beams for spatial and spectral switching in incoherent imaging(Optica Publishing Group, 2024) Gopinath, Shivasubramanian; Anand, VijayakumarSpatial, temporal, and spectral resolutions and field-of-view are important characteristics of any imaging system. In most, if not all, it is impossible to change the above characteristics after recording a digital picture, video, or hologram. In recent years, there have been investigations on the possibilities to change the above characteristics post-recording. In this Letter, for the first time, to the best of our knowledge, we report novel recording and reconstruction methods built upon the principles of coded aperture imaging that allow changing the axial and spectral resolutions post-recording. We named this method—post-ensemble generation with Airy beams for spatial and spectral switching (PEGASASS). In PEGASASS, light from an object point is converted into Airy beams and recorded such that every recording has a unique Airy pattern. An ensemble of Airy patterns is constructed post-recording and the axial and spectral resolutions are tuned by controlling the chaos in the ensemble. The above tunability is achieved without adversely affecting the lateral resolution. Proof-of-concept experimental results of PEGASASS in 3D in both (x,y,z) and (x,y,λ) and 4D in (x,y,z,λ) are presented. We believe that PEGASASS has the potential to revolutionize the field of imaging and holography.Item Engineering axial resolution realtime and postrecording of incoherent holograms using hybridization techniques(2024) Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Anand, VijayakumarItem Holographic solution to a fundamental problem in diffractive optics: resolution beyond diffraction and lithography limits(2023) Bleahu, Andrei; Gopinath, Shivasubramanian; Xavier, Agnes Pristy Ignatius; Kahro, Tauno; Reddy, Andra Naresh Kumar; Arockiaraj, Francis Gracy; Smith, Daniel; Ng, Soon Hock; Katkus, Tomas; Rajeswary, Aravind Simon John Francis; Angamuthu, Praveen Periyasami; Pikker, Siim; Kukli, Kaupo; Tamm, Aile; Juodkazis, Saulius; Rosen, Joseph; Anand, VijayakumarItem 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, VijayakumarItem Realizing large-area diffractive lens using multiple subaperture diffractive lenses and computational reconstruction(2023) Gopinath, Shivasubramanian; Xavier, Agnes Pristy Ignatius; Angamuthu, Praveen Periyasamy; Kahro, Tauno; Tamm, Oskar; Bleahu, Andrei; Arockiaraj, Francis Gracy; Smith, Daniel; Ng, Soon Hock; Juodkazis, Saulius; Kukli, Kaupo; Tamm, Aile; Anand, VijayakumarItem Fresnel incoherent correlation holography with Lucy-Richardson-Rosen algorithm and modified Gerchberg-Saxton algorithm(2023) Anand, Vijayakumar; Juodkazis, Saulius; Rajeswary, Aravind Simon John Francis; Arockiaraj, Francis Gracy; Gopinath, Shivasubramanian; Bleahu, AndreiItem Roadmap of incoherent digital holography(2022) Tahara, Tatsuki; Zhang, Yaping; Rosen, Joseph; Anand, Vijayakumar; Cao, Liangcai; Wu, Jiachen; Koujin, Takako; Matsuda, Atsushi; Ishii, Ayumi; Kozawa, Yuichi; Okamoto, Ryo; Oi, Ryutaro; Nobukawa, Teruyoshi; Choi, Kihong; Imbe, Masatoshi; Poon, Ting‑ChungItem Interferenceless coded aperture correlation holography: history, development, and applications(2023) Rosen, Joseph; Anand, VijayakumarItem Three-dimensional phase imaging with near infrared synchrotron beam using phase-retrieval algorithm(2023) Han, Molong; Anand, Vijayakumar; Juodkazis, Saulius; Vongsvivut, Jitraporn; Tobin, Mark J.; Praveen, Periyasamy Angamuthu; Rajeswary, Aravind Simon John Francis; Katkus, Tomas A.; Ng, Soon Hock; Smith, DanielItem Computational three-dimensional imaging with near infrared synchrotron beam using Fresnel zone apertures fabricated on barium fluoride windows using femtosecond laser ablation(2023) Smith, Daniel; Han, Molong; Ng, Soon Hock; Katkus, Tomas; Rajeswary, Aravind Simon John Francis; Tobin, Mark J.; Vongsvivut, Jitraporn; Juodkazis, Saulius; Anand, VijayakumarItem 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, RaviItem White Light Correlation Holography Using a Random Lens for Astronomical Imaging Applications(2022 Photonics & Electromagnetics Research Symposium (PIERS), 2022) Anand, V.; Ng, S. H.; Katkus, T.; Juodkazis, S.Item Simultaneous Detection of Modal Composition and Wavelength of OAM Fields Using a Hexagonal Vortex Filter(2022 Photonics & Electromagnetics Research Symposium (PIERS), 2022) Reddy, Andra Naresh Kumar; Anand, Vijayakumar; Podlipnov, Vladimir V.; Khonina, Svetlana Nikolaevna; Juodkazis, SauliusItem Sculpting axial characteristics of incoherent imagers by hybridization methods(2024) Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Anand, VijayakumarAxial resolving power (ARP) is one of the cornerstones of imaging systems. In conventional imaging systems, changing ARP by changing the numerical aperture affects also lateral resolving power (LRP). It is highly desirable to change ARP independent of LRP. Recently, incoherent digital holography (IDH) techniques were developed using sparse ensembles of Bessel, Airy and self-rotating beams that allow tuning ARP independent of LRP. In the above studies, the ARP was tuned by controlling the randomness which resulted in noisy reconstructions. In this study, we proposed and demonstrated two INCoherent Hybrid Imaging Systems (INCHIS) using a Bessel and spherical beam to change the ARP between the limits of Bessel and spherical beam independent of LRP. The first hybridization technique INCHIS-H1 requires pre-engineering of multifunctional phase masks using a recently developed modified Gerchberg-Saxton algorithm and an active device such as a spatial light modulator. The second hybridization technique INCHIS-H2 can be implemented using both active as well as passive optical elements with lens and axicon functions and the ARP is changed digitally after optical recording. While INCHIS-H1 requires pre-engineering of phase masks to change ARP like any conventional imaging system, the capability in INCHIS-H2 to change ARP post-recording opens a new pathway in imaging technology. Simulation results and proof-of-concept experimental results are presented. A recently developed Lucy-Richardson-Rosen algorithm has been used for image reconstruction for the above cases. We believe that the developed hybridization methods will revolutionize the field of IDH, computational imaging, computer vision and microscopy.Item Fraxicon for Optical Applications with Aperture ∼1 mm: Characterisation Study(2023) Mu, Haoran; Smith, Daniel; Ng, Soon Hock; Anand, Vijayakumar; Le, Nguyen Hoai An; Dharmavarapu, Raghu; Khajehsaeidimahabadi, Zahra; Richardson, Rachael T.; Ruther, Patrick; Stoddart, Paul R.; Gricius, Henrikas; Baravykas, Tomas; Gailevicius, Darius; Seniutinas, Gediminas; Katkus, Tomas; Juodkazis, SauliusEmerging applications of optical technologies are driving the development of miniaturised light sources, which in turn require the fabrication of matching micro-optical elements with sub-1 mm cross-sections and high optical quality. This is particularly challenging for spatially constrained biomedical applications where reduced dimensionality is required, such as endoscopy, optogenetics, or optical implants. Planarisation of a lens by the Fresnel lens approach was adapted for a conical lens (axicon) and was made by direct femtosecond 780 nm/100 fs laser writing in the SZ2080™ polymer with a photo-initiator. Optical characterisation of the positive and negative fraxicons is presented. Numerical modelling of fraxicon optical performance under illumination by incoherent and spatially extended light sources is compared with the ideal case of plane-wave illumination. Considering the potential for rapid replication in soft polymers and resists, this approach holds great promise for the most demanding technological applications.