Adaptive Detection of Wave Aberrations Based on the Multichannel Filter

Author(s):

Khorin, Pavel A.; Porfirev, Alexey P. & Khonina, Svetlana N.

Abstract:

“An adaptive method for determining the type and magnitude of aberration in a wide range is proposed on the basis of an optical processing of the analyzed wavefront using a multichannel filter matched to the adjustable Zernike phase functions. The approach is based on an adaptive (or step-by-step) compensation of wavefront aberrations based on a dynamically tunable multichannel filter implemented on a spatial light modulator. For adaptive filter adjustment, a set of criteria is proposed that takes into account not only the magnitude of the correlation peak, but also the maximum intensity, compactness, and orientation of the distribution in each diffraction order. The experimental results have shown the efficiency of the proposed approach for detecting wavefront aberrations in a wide range (from 0.1 λ to λ).”

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Publication: Photonics
Issue/Year: Photonics, Volume 9; Number 3; Pages 204; 2022
DOI: 10.3390/photonics9030204

Lensless Optical Encryption of Multilevel Digital Data Containers Using Spatially Incoherent Illumination

Author(s):

Cheremkhin, Pavel; Evtikhiev, Nikolay; Krasnov, Vitaly; Ryabcev, Ilya; Shifrina, Anna & Starikov, Rostislav

Abstract:

“The necessity of the correction of errors emerging during the optical encryption process ledto the extensive use of data containers such as QR codes. However, due to specifics of optical encryp-tion, QR codes are not very well suited for the task, which results in low error correction capabilitiesin optical experiments mainly due to easily breakable QR code’s service elements and byte datastructure. In this paper, we present optical implementation of information optical encryption systemutilizing new multilevel customizable digital data containers with high data density. The results ofoptical experiments demonstrate efficient error correction capabilities of the new data container.”

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Publication: Applied Sciences
Issue/Year: Applied Sciences, Volume 12; Number 1; Pages 406; 2021
DOI: 10.3390/app12010406

Reconstructing images of two adjacent objects passing through scattering medium via deep learning

Author(s):

Lai, Xuetian; Li, Qiongyao; Chen, Ziyang; Shao, Xiaopeng & Pu, Jixiong

Abstract:

“In this paper, to the best of our knowledge, we first present a deep learning based method for reconstructing the images of two adjacent objects passing through scattering media. We construct an imaging system for imaging of two adjacent objects located at different depths behind the scattering medium. In general, as the light field of two adjacent objects passes through the scattering medium, a speckle pattern is obtained. We employ the designed adversarial network, which is called as YGAN, for reconstructing the two images simultaneously from the speckle. It is shown that based on the trained YGAN, we can reconstruct images of the two adjacent objects with high quality. In addition, the influence of object image types, and the location depths of the two adjacent objects on the imaging fidelity will be studied. Results demonstrate the strong generalization ability and effectiveness of the YGAN. Even in the case where another scattering medium is inserted between the two objects, the YGAN can reconstruct the object images with high fidelity. The technique presented in this paper can be used for applications in areas of medical image analysis, such as medical image classification, segmentation, and studies of multi-object scattering imaging, three-dimensional imaging etc.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 26; Pages 43280; 2021
DOI: 10.1364/oe.446630

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Experimental estimation of the longitudinal component of a highly focused electromagnetic field

Author(s):

Maluenda, David; Aviñoá, Marcos; Ahmadi, Kavan; Martínez-Herrero, Rosario & Carnicer, Artur

Abstract:

“The detection of the longitudinal component of a highly focused electromagnetic beam is not a simple task. Although in recent years several methods have been reported in the literature, this measure is still not routinely performed. This paper describes a method that allows us to estimate and visualize the longitudinal component of the field in a relatively simple way. First, we measure the transverse components of the focused field in several planes normal to the optical axis. Then, we determine the complex amplitude of the two transverse field components: the phase is obtained using a phase recovery algorithm, while the phase difference between the two components is determined from the Stokes parameters. Finally, the longitudinal component is estimated using the Gauss’s theorem. Experimental results show an excellent agreement with theoretical predictions.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports, Volume 11; Number 1; 2021
DOI: 10.1038/s41598-021-97164-z

Holographic contact lens display that provides focusable images for eyes

Author(s):

Sano, Junpei & Takaki, Yasuhiro

Abstract:

“In this paper, we propose a holographic image generation technique for contact lens displays. The proposed technique employs a phase-only spatial light modulator (SLM), a holographic optical element (HOE) backlight, and a polarizer. The proposed holographic technique can generate 3D images apart from the contact lens displays. Therefore, the eyes can focus on the 3D images while simultaneously observing the real scene through the phase-only SLM and the HOE backlight, which provides see-through capability. A bench-top experimental system was constructed to verify the far-distance image generation capability and see-through function.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 7; Pages 10568; 2021
DOI: 10.1364/oe.419604

Single-shot memory-effect video

Author(s):

Xiaohan Li and Andrew Stevens and Joel A. Greenberg and Michael E. Gehm

Abstract:

“Imaging through opaque scattering media is critically important in applications ranging from biological and astronomical imaging to metrology and security. While the random process of scattering in turbid media produces scattered light that appears uninformative to the human eye, a wealth of information is contained in the signal and can be recovered using computational post-processing techniques. Recent studies have shown that statistical correlations present in the scattered light, known as ‘memory effects’, allow for diffraction-limited imaging through opaque media without detailed knowledge of (or access to) the source or scatterer. However, previous methods require that the object and/or scatterer be static during the measurement. We overcome this limitation by combining traditional memory effect imaging with coded-aperture-based computational imaging techniques, which enables us to realize for the first time single-shot video of arbitrary dynamic scenes through dynamic, opaque media. This has important implications for a wide range of real-world imaging scenarios.”

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Publication: Scientific Reports
Issue/Year: Scientific Reports 8, Article number: 13402 (2018)
DOI: 10.1038/s41598-018-31697-8

Adaptive wavefront interferometry for unknown free-form surfaces

Author(s):

Shuai Xue, Shanyong Chen, Zhanbin Fan and Dede Zhai

Abstract:

“The primary problem of conventional wavefront interferometers is limited dynamic range. Unknown free-form surface figure error with large amplitude or slope is not measurable for too dense or invisible fringes. To troubleshoot this problem, we propose adaptive wavefront interferometry (AWI). AWI utilizes a wavefront sensor-less adaptive optics (AO) subsystem to intelligently speculate and compensate the unknown free-form surface figure error. In this subsystem, adaptive null optics is utilized to iteratively generate adaptive wavefronts to compensate the unknown severe surface figure error. The adaptive null optics is close-loop controlled (i.e., wavefront sensor-less optimization algorithms are utilized to control it by real time monitoring the compensation effects to guarantee convergence of the iteration). Ultimately, invisible fringes turn into resolvable ones, and null test is further realized. To demonstrate the feasibility of AWI, we designed one spatial light modulator (SLM) based AWI modality as an example. The system is based on a commercial interferometer and is easy to establish. No other elements are required besides the SLM. Principle, simulation, and experiments for the SLM based AWI are demonstrated. ”

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Publication: Optics Express
Issue/Year: Vol. 26, Issue 17, pp. 21910-21928 (2018)
DOI: 10.1364/OE.26.021910

Reduction of speckle noise in laser energy distribution on the target by means of modified Fourier hologram and incoherent averaging technique

Author(s):

A.G. Derzhypolskyi, O.V. Gnatovskyi and L.A. Derzhypolska

Abstract:

“Presented in this paper is the technique of formation of required laser intensity distribution on the target with a reduced speckle noise. The method is based on the use of modified Fourier hologram adapted to controlled phase modulators. Reduction of the speckle noise in the laser energy profile is obtained using multiple incoherent superposition of synthesized holographic images. Each hologram is synthesized with different random diffuser. The advantages of this method: relative simplicity of hardware; robustness with regard to distortions of any kind in input beam and/or optical path of the scheme; controlled
reduction of the speckle noise in the final energy distribution. ”

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Publication: Semiconductor Physics, Quantum Electronics and Optoelectronics
Issue/Year: Volume: 21 (4), P. 429-433 (2018).
DOI: 10.15407/spqeo21.04.429

Experimental demonstration of tunable refractometer based on orbital angular momentum of longitudinally structured light

Author(s):

Dorrah, Ahmed H and Zamboni-Rached, Michel and Mojahedi, Mo

Abstract:

“The index of refraction plays a decisive role in the design and classification of optical materials and devices; therefore, its proper and accurate determination is essential. In most refractive index (RI) sensing schemes, however, there is a trade-off between providing high-resolution measurements and covering a wide range of RIs. We propose and experimentally demonstrate a novel mechanism for sensing the index of refraction of a medium by utilizing the orbital angular momentum (OAM) of structured light. Using a superposition of co-propagating monochromatic higher order Bessel beams with equally spaced longitudinal wavenumbers, in a comb-like setting, we generate nondiffracting rotating light structures in which the orientation of the beam’s intensity profile is sensitive to the RI of the medium (here, a fluid). In principle, the sensitivity of this scheme can exceed ∼ 2700°/RIU with a resolution of ∼ 10-5 RI unit (RIU). Furthermore, we show how the unbounded degrees of freedom associated with OAM can be deployed to offer a wide dynamic range by generating structured light that evolves into different patterns based on the change in RI. The rotating light structures are generated by a programmable spatial light modulator (SLM). This provides dynamic control over the sensitivity, which can be tuned to perform coarse or fine measurements of the RI in real time. This, in turn, allows high sensitivity and resolution to be achieved simultaneously over a very wide dynamic range, which is a typical trade-off in all RI sensing schemes. We thus envision that this method will open new directions in refractometry and remote sensing.”

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Publication: Light: Science \& Applications
Issue/Year: Light: Science & Applications accepted article preview 18 May 2018
DOI: 10.1038/s41377-018-0034-9

Generation of optical vortex array along arbitrary curvilinear arrangement

Author(s):

Lin Li and Chenliang Chang and Xiangzheng Yuan and Caojin Yuan and Shaotong Feng and Shouping Nie and Jianping Ding

Abstract:

“We propose an approach for creating optical vortex array (OVA) arranged along arbitrary curvilinear path, based on the coaxial interference of two width-controllable component curves calculated by modified holographic beam shaping technique. The two component curve beams have different radial dimensions as well as phase gradients along each beam such that the number of phase singularity in the curvilinear arranged optical vortex array (CA-OVA) is freely tunable on demand. Hybrid CA-OVA that comprises of multiple OVA structures along different respective curves is also discussed and demonstrated. Furthermore, we study the conversion of CA-OVA into vector mode that comprises of polarization vortex array with varied polarization state distribution. Both simulation and experimental results prove the performance of the proposed method of generating a complex structured vortex array, which is of significance for potential applications including multiple trapping of micro-sized particles.”

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Publication: Optics Express
Issue/Year: Optics Express, Vol.26, Issue 8, pp. 9798- 9812 (2018)
DOI: 10.1364/OE.26.009798