CIPHR - ERA Chair for Computational Imaging and Processing in High Resolution

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https://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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Now showing 1 - 20 of 57

Engineering axial resolution realtime and postrecording of incoherent holograms using hybridization techniques
(2024) Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Anand, Vijayakumar
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, Vijayakumar
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
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, Vijayakumar
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, Andrei
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‑Chung
Interferenceless coded aperture correlation holography: history, development, and applications
(2023) Rosen, Joseph; Anand, Vijayakumar
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, Daniel
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, Vijayakumar
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
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.
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, Saulius
Sculpting axial characteristics of incoherent imagers by hybridization methods
(2024) Gopinath, Shivasubramanian; Rajeswary, Aravind Simon John Francis; Anand, Vijayakumar
Axial 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.
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, Saulius
Emerging 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.
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
Preface: International Conference on Holography Meets Advanced Manufacturing (HMAM2)
(2023) Anand, Vijayakumar; Jayavel, Amudhavel; Palm, Viktor; Gopinath, Shivasubramanian; Bleahu, Andrei; Rajeswary, Aravind Simon John Francis; Kukli, Kaupo; Balasubramani, Vinoth; Smith, Daniel; Ng, Soon Hock; Juodkazis, Saulius
The CIPHR group, Institute of Physics, University of Tartu, Estonia, and Optical Sciences Center, Swinburne University of Technology, Australia, jointly organized the interdisciplinary online conference “Holography Meets Advanced Manufacturing” during 20–22 February 2023.
Incoherent nonlinear deconvolution using an iterative algorithm for recovering limited-support images from blurred digital photographs
(Optics Express, 2024) Rosen, Joseph; Anand, Vijayakumar
Recovering 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.
Computational Imaging at the Infrared Beamline of the Australian Synchrotron Using the Lucy–Richardson–Rosen Algorithm
(2023) Ng, Soon Hock; Anand, Vijayakumar; Han, Molong; Smith, Daniel; Maksimovic, Jovan; Katkus, Tomas; Klein, Annaleise; Bambery, Keith; Tobin, Mark J.; Vongsvivut, Jitraporn; Juodkazis, Saulius
The Fourier transform infrared microspectroscopy (FTIRm) system of the Australian Synchrotron has a unique optical configuration with a peculiar beam profile consisting of two parallel lines. The beam is tightly focused using a 36× Schwarzschild objective to a point on the sample and the sample is scanned pixel by pixel to record an image of a single plane using a single pixel mercury cadmium telluride detector. A computational stitching procedure is used to obtain a 2D image of the sample. However, if the imaging condition is not satisfied, then the recorded object’s information is distorted. Unlike commonly observed blurring, the case with a Schwarzschild objective is unique, with a donut like intensity distribution with three distinct lobes. Consequently, commonly used deblurring methods are not efficient for image reconstruction. In this study, we have applied a recently developed computational reconstruction method called the Lucy–Richardson–Rosen algorithm (LRRA) in the online FTIRm system for the first time. The method involves two steps: training step and imaging step. In the training step, the point spread function (PSF) library is recorded by temporal summation of intensity patterns obtained by scanning the pinhole in the x-y directions across the path of the beam using the single pixel detector along the z direction. In the imaging step, the process is repeated for a complicated object along only a single plane. This new technique is named coded aperture scanning holography. Different types of samples, such as two pinholes; a number 3 USAF object; a cross shaped object on a barium fluoride substrate; and a silk sample are used for the demonstration of both image recovery and 3D imaging applications.
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.
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

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