Igor Shevkunov

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• PhD optics
• Senior Researcher at Tampere University

This paper addresses the challenge of regularization in lens-less single-shot phase retrieval (PR) by noise suppression. Due to the unique aspects of the PR algorithm, the noise is spatially correlated with a non-stationary level and distribution, which complicates PR's reconstruction and convergence. To address this problem, We propose an algorith...

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...

In this paper, we propose an approach that combines wavefront encoding and convolutional neuronal network (CNN)-based decoding for quantitative phase imaging (QPI). Encoding is realized by defocusing, and decoding by CNN trained on simulated datasets. We have demonstrated that based on the proposed approach of creating the dataset, it is possible t...

The race for miniature color cameras using flat meta-optics has rapidly developed the end-to-end design framework using neural networks. Although a large body of work has shown the potential of this methodology, the reported performance is still limited due to fundamental limitations coming from meta-optics, mismatch between simulated and resultant...

We propose a hyperspectral broadband phase retrieval technique with spectrally varying object and modulation phase masks. The technique is based on a complex domain version of the alternating direction method of multipliers (ADMM) and the Spectral Proximity Operators derived for Gaussian and Poisson intensity observations, which are considered as a...

The hyperspectral broadband phase retrieval is developed for a scenario where both object and modulation phase masks are spectrally varying. The proposed iterative algorithm is based on a complex domain version of the alternating direction method of multipliers (ADMM) and the novel Spectral Proximity Operators derived for Gaussian and Poissonian mu...

Phase retrieval in optical imaging refers to the recovery of a complex signal from phaseless data acquired in the form of its diffraction patterns. These patterns are acquired through a system with a coherent light source that employs a diffractive optical element (DOE) to modulate the scene, resulting in coded diffraction patterns (CDPs) at the se...

In the considered hybrid diffractive imaging system, a refractive lens is arranged simultaneously with a multilevel phase mask (MPM) as a diffractive optical element (DOE). Extended depth-of-field (EDoF) imaging and low chromatic aberrations are the two potential advantages of the proposed hybrid setup. To make use of these advantages, this paper p...

The hyperspectral broadband phase retrieval is developed for a scenario where both object and modulation phase masks are spectrally varying. The proposed iterative algorithm is based on a complex domain version of the alternating direction method of multipliers (ADMM) and the novel Spectral Proximity Operators derived for Gaussian and Poissonian mu...

In this paper, we adopt a complex-domain cube filter (CCF) developed for hyperspectral 3D complex domain images for noise suppression of 3D complex-valued data in optical diffraction tomography. CCF is based on two processing steps: singular value decomposition (SVD) and complex-domain sparsity-based filter (CDID). SVD provides data compression and...

End-to-end optimization of diffractive optical elements (DOEs) profile through a digital differentiable model combined with computational imaging have gained an increasing attention in emerging applications due to the compactness of resultant physical setups. Despite recent works have shown the potential of this methodology to design optics, its pe...

In this paper, we adopt a complex-domain cube filter (CCF) developed for hyperspectral 3D complex domain images for noise suppression of 3D complex-valued data in optical diffraction tomography. CCF is based on two processing steps: singular value decomposition (SVD) and complex-domain sparsity-based filter (CDID). SVD provides data compression and...

A hybrid imaging system is a simultaneous physical arrangement of a refractive lens and a multilevel phase mask (MPM) as a diffractive optical element (DOE). The favorable properties of the hybrid setup are improved extended-depth-of-field (EDoF) imaging and low chromatic aberrations. We built a fully differentiable image formation model in order t...

A hybrid imaging system is a simultaneous physical arrangement of a refractive lens and a multilevel phase mask (MPM) as a diffractive optical element (DOE). The favorable properties of the hybrid setup are improved extended-depth-of-field (EDoF) imaging and low chromatic aberrations. We built a fully differentiable image formation model in order t...

End-to-end optimization of diffractive optical elements (DOEs) profile through a digital differentiable model combined with computational imaging have gained an increasing attention in emerging applications due to the compactness of resultant physical setups. Despite recent works have shown the potential of this methodology to design optics, its pe...

In this paper, we detail a phase-shift implementation in a rotated plane-parallel plate (PPP). Considering the phase-shifting digital holography application, we provide a more precise phase-shift estimation based on PPP thickness, rotation, and mutual inclination of reference and object wavefronts. We show that phase retardation uncertainty impleme...

We report on the application of time-resolved inline digital holography in the study of the nonlinear optical properties of quantum dots deposited onto sample glass. The Fresnel diffraction patterns of the probe pulse due to noncollinear degenerate phase modulation induced by a femtosecond pump pulse were extracted from the set of inline digital ho...

Phase retrieval in optical imaging refers to the recovery of a complex signal from phaseless data acquired in the form of its diffraction patterns. These patterns are acquired through a system with a coherent light source that employs a diffractive optical element (DOE) to modulate the scene resulting in coded diffraction patterns at the sensor. Re...

We report on the application of time-resolved inline digital holography to study the nonlinear optical properties of quantum dots deposited onto the sample glass. Fresnel diffraction patterns of the probe pulse due to noncollinear degenerate phase modulation induced by the femtosecond pump pulse were extracted from the set of inline digital hologra...

We propose a novel approach for lensless single-shot phase retrieval, which provides pixel super-resolution phase imaging. The approach is based on a computational separation of carrying and object wavefronts. The imaging task is to reconstruct the object wavefront, while the carrying wavefront corrects the discrepancies between the computational m...

A power-balanced hybrid optical imaging system has a diffractive computational camera, introduced in this paper, with image formation by a refractive lens and multilevel phase mask (MPM). This system provides a long focal depth with low chromatic aberrations thanks to MPM and a high energy light concentration due to the refractive lens. We introduc...

We propose a novel approach and algorithm based on two preliminary tests of the optical system elements to enhance the super-resolved complex-valued imaging. The approach is developed for inverse phase imaging in a single-shot lensless optical setup. Imaging is based on wavefront modulation by a single binary phase mask. The preliminary tests compe...

We propose a new ptychographic algorithm where the object scanning is performed by the complex-valued probe function, formed in the setup of independent amplitude-phase modulation. The results of numerical experiments demonstrate the effectiveness of the proposed approach.

Algorithm enhancements are proposed for single-shot phase retrieval to reduce loss from ill-conditioning. The approach is based on prior observations, improved diffraction pattern up-sampling, and updated filters. High-quality super-resolved reconstructions are demonstrated in simulation.

A novel formulation of the hyperspectral broadband phase retrieval is developed for the scenario where both object and modulation phase masks are spectrally varying. The proposed algorithm is based on a complex domain version of the alternating direction method of multipliers (ADMM) and Spectral Proximity Operators (SPO) derived for Gaussian and Po...

The power-balanced hybrid optical imaging system is a special design of a computational camera, introduced in this paper, with image formation by a refractive lens and Multilevel Phase Mask (MPM) as a diffractive optical element (DoE). This system provides a long focal depth and low chromatic aberrations thanks to MPM, and a high energy light conce...

In this paper, we employ a deep convolutional neural network for the solution of the phase retrieval problem in a lensless optical system from a single observation. We utilize U-net-like structured DCNN to reconstruct phase from the amplitude images at the sensor plane, and after applying computational backpropagation, the complex objects’ amplitud...

Time-resolved inline digital holography was validated during study of nonlinear optical properties of graphene microparticles on the sample glass. A set of probe pulse inline digital holograms were recorded and compared with numerically simulated data.

https://sigport.org/documents/broadband-hyperspectral-phase-retrieval-noisy-data Hyperspectral (HS) imaging retrieves information from data obtained across a wide spectral range of spectral channels. The object to reconstruct is a 3D cube, where two coordinates are spatial and the third one is spectral. We assume that this cube is complex-valued,...

Hyperspectral (HS) imaging retrieves information from data obtained across a wide spectral range of spectral channels. The object to reconstruct is a 3D cube, where two coordinates are spatial and third one is spectral. We assume that this cube is complex-valued, i.e. characterized spatially-frequency varying amplitude and phase. The observations a...

Time-resolved inline digital holography is a promising technique for the measurement of optical nonlinear properties of materials. Here we adapt it for the study samples with inhomogeneities in the spatial distribution of the nonlinear refractive index.

A novel phase retrieval algorithm for broadband hyperspectral phase imaging from noisy intensity observations is proposed. It utilizes advantages of the Fourier transform spectroscopy in the self-referencing optical setup and provides additional, beyond spectral intensity distribution, reconstruction of the investigated object’s phase. The noise am...

A novel algorithm for reconstruction of hyperspectral 3D complex domain images (phase/amplitude) from noisy complex domain observations has been developed and studied. This algorithm starts from the SVD (singular value decomposition) analysis of the observed complex-valued data and looks for the optimal low dimension eigenspace. These eigenspace im...

A novel phase retrieval algorithm for broadband hyperspectral noisy data is proposed. It utilizes the advantages of the Fourier Transform spectroscopy in a self-referencing optical setup and additionally beyond the spectral information provides a reconstruction of the investigated object's phase. The noise multiplicative Fellgett's disadvantage is...

Design and optimization of lensless phase-retrieval optical system with phase modulation of free-space propagation wavefront is proposed for subpixel imaging to achieve super-resolution reconstruction. Contrary to the traditional super-resolution phase-retrieval, the method in this paper requires a single observation only and uses the advanced Supe...

We consider hyperspectral phase/amplitude imaging from hyperspectral complex-valued noisy observations. Block-matching and grouping of similar patches are main instruments of the proposed algorithms. The search neighborhood for similar patches spans both the spectral and 2D spatial dimensions. SVD analysis of 3D grouped patches is used for design o...

A digital holographic approach is used for calibrating the phase modulation in every pixel of the spatial light modulator (SLM). The phase reconstruction method involves a variational algorithm based on the local least square technique.

In this paper, we have applied a recently developed complex-domain hyperspectral denoiser for the object recognition task, which is performed by the correlation analysis of investigated objects’ spectra with the fingerprint spectra from the same object. Extensive experiments carried out on noisy data from digital hyperspectral holography demonstrat...

Broadband hyperspectral digital holography and Fourier transform spectroscopy are important instruments in various science and application fields. In the digital hyperspectral holography and spectroscopy the variable of interest are obtained as inverse discrete cosine transforms of observed diffractive intensity patterns. In these notes, we provide...

A new denoising algorithm for hyperspectral complex domain data has been developed and studied. This algorithm is based on the complex domain block-matching 3D filter including the 3D Wiener filtering stage. The developed algorithm is applied and tuned to work in the singular value decomposition (SVD) eigenspace of reduced dimension. The accuracy a...

We investigate the possibilities of the time-resolved inline digital holography to study local optical nonlinear properties. Proposed approach includes the registration, processing and simulation of the diffraction patterns and enables to distinguish local nonlinear responses.

The paper is devoted to a computational super-resolution microscopy. A complex-valued wavefront of a transparent biological cellular specimen is restored from multiple intensity diffraction patterns registered with noise. For this problem, the recently developed lensless super-resolution phase retrieval algorithm [Optica, 4(7), 786 (2017)] is modif...

We propose an algorithm for absolute phase retrieval from multiwavelength noisy phase coded diffraction patterns. A lensless optical system is considered with a set of successive single wavelength experiments (wavelength-division setup). The phase masks are applied for modulation of the multiwavelength object wavefronts. The algorithm uses the forw...

Recent works demonstrated that digital time-resolved holography is the prospective approach to study nonlinear light–matter interaction processes. In this Letter, we present a straightforward inline holographic approach for studying degenerate phase modulation induced by an inclined collimated pump beam in the isotropic sample. The method is based...

We study the problem of multiwavelength absolute phase retrieval from noisy diffraction patterns. The system is lensless with multiwavelength coherent input light beams and random phase masks applied for wavefront modulation. The light beams are formed by light sources radiating all wavelengths simultaneously. A sensor equipped by a Color Filter Ar...

The topography of surface relief gratings was studied by digital holographic microscopy. The applicability of the method for quantitative measurements of surface microstructure at nanoscale was demonstrated. The method for wavefront reconstruction of surface relief from a digital hologram recorded in off-axis configuration was also applied. The mai...

Surface relief gratings and refractive index gratings are formed by direct holographic recording in amorphous chalcogenide nanomultilayer structures As 2 S 3 − Se and thin films As 2 S 3 . The evolution of the grating parameters, such as the modulation of refractive index and relief depth in dependence of the holographic exposure, is investigated....

The topography of surface relief gratings patterned on As2S3–Se nanomultilayers was investigated by digital holographic microscopy. For the high-accuracy phase reconstruction of the topography we used the sparse wavefront modeling. Experimental results are presented.

In this paper, we consider computational super-resolution inverse diffraction phase retrieval. The optical setup is lensless, with a spatial light modulator for aperture phase coding. The paper is focused on experimental tests of the super-resolution sparse phase amplitude retrieval algorithm. We start from simulations and proceed to physical exper...

A variational algorithm to object wavefront reconstruction from noisy intensity observations is developed for the off-axis holography scenario with imaging in the acquisition plane. The algorithm is based on the local least square technique proposed in paper [J. Opt. Soc. Am. A 21, 367 (2004)]. First, multiple reconstructions of the wavefront are p...

This work is devoted to an elimination of the phase discontinuities problem of the reconstructed object wavefront. Novel robust phase unwrapping method is proposed. It is based on the phase shift implementation of the reconstructed wavefront. The unwrapped phase field of the amplitude-phase object is presented. Comparison with another known methods...

Time-resolved inline digital holography technique for investigation of optical nonlinear interaction of high-energy pump with probe pulse in transparent samples is presented. The observed inline hologram in the Fresnel diffraction zone depends on variation of refractive index and allows one to analyze some properties of the nonlinear media.

Color digital holography allows to numerical and optical reconstruction of 2D and 3D-scenes in colored vision. In this paper, we consider the opposite problem, namely, using of color digital holograms simultaneously recorded on several wavelengths for the reconstruction of monochromatic images. Special feature of the procedure of monochromatic imag...

A novel advanced algorithm is based on the sparsity hypothesis forphase and amplitude modeling.

The topic of sparse representations (SR) of images has attracted tremendous interest from the research community in the last ten years. This interest stems from the fundamental role that the low dimensional models play in many signal and image processing areas, i.e., real world images can be well approximated by a linear combination of a small numb...

This work presents the new method for wavefront reconstruction from a digital hologram recorded in off-axis configuration. The main feature of the proposed algorithm is a good ability for noise filtration due to the original formulation of the problem taking into account the presence of noise in the recorded intensity distribution and the sparse ph...

Представлено экспериментальное сравнение четырех методов восстановления волнового фронта. Рассмотрены два итерационных и два голографических метода, отличающихся математической моделью и алгоритмами восстановления. Первые два из рассматриваемых методов не используют опорную волну в схеме записи, что снижает требования к стабильности установки. Осно...

An experimental comparison of four methods of wavefront reconstruction is presented. We considered two iterative and two holographic methods with differences in mathematical models and reconstruction algorithms. The first two of these methods do not use the reference wave in the recording scheme that reduces the need of setup stability. A set of sp...

Performance of the three phase retrieval methods that use spatial intensity distributions was investigated in dealing with a task of reconstruction of the amplitude characteristics of the test object. These methods differ both by mathematical models and order of iteration execution. The single-beam multiple-intensity reconstruction method showed th...

Multiphoton and electron-impact ionization of a gas-dynamic beam of xenon atoms are compared in order to determine the effective multiphoton ionization cross sections. The three-photon ionization cross section of the xenon atom is determined.

The two photon resonant, three photon ionization spectra of ArXe were recorded in the spectral region of 88 500-90 100 cm(-1). Seven new molecular band progressions dissociating to ArXe(∗) → Ar(1)S0 + Xe(∗) 7p[1∕2]0, Xe(∗) 7p[3∕2]2, Xe(∗) 6p'[3∕2]2, Xe(∗) 6p'[1∕2]1, Xe(∗) 6p'[1∕2]0 have been selected and analyzed. The molecular constants for the ex...

Electronic spectra of the Xe2 molecules in the energy range of 77700–89300 cm−1 are recorded. The method of resonance enhanced multiphoton ionization of molecules in a supersonic molecular beam was used, in which excitation of the molecules by three photons was followed by ionization caused by a fourth photon (the (3+1) REMPI method). Analysis of t...

The electronic spectra of ArXe molecules in the 80 300–89 500 cm−1 region were recorded by (2 + n) and (3 + n) REMPI methods. The vibrational progressions attributed to transitions of molecules from the ground state to the bounded excited state and wide unstructured bands related to transitions to the continuous upper state were obtained. The molec...

The excited electronic states of ArXe molecules in the region 77 000-80 200 cm-1 were studied using the (2+1) and (3+1) resonance-enhanced multiphoton ionization methods. The use of different methods of multi-photon excitation and Ar+ ion registration allowed us to obtain some new data. Molecular constants were obtained for previously unknown excit...

The electronic spectra of XeNe molecules in the range of 77100-90100 cm-1 are measured by the method of laser resonance multiphoton ionization in a supersonic jet. The photoionization spectra are obtained upon two- and three-photon excitations of molecules and their ionization by the next photon. In the range of 80300-90100 cm-1 near Xe*(5 d, 6 p',...

The excitation cross-sections of the OH-radical band A2Σ+ → X2 (v' = 0 → v'' = 0, v' = 1 → v'' = 1) were measured. OH-radicals were formed during dissociation of water molecules by electron impact in the conditions of crossing of supersonic molecular and electron beams in the energy range 10–120 eV. Measurements were conducted at temperatures of 50...

Data on excited states of XeKr molecules in the energy range 78280–77600 cm−1 are obtained. Using the method of multiphoton laser photoionization of molecules in a supersonic jet, five vibrational progressions of XeKr molecules are obtained, which are attributed to five electronic-vibrational transitions from the ground state of the XeKr molecule o...