Varifocal diffractive lenses for multi-depth microscope imaging

Author(s):

Reda, Francesco; Salvatore, Marcella; Borbone, Fabio; Maddalena, Pasqualino; Ambrosio, Antonio & Oscurato, Stefano Luigi

Abstract:

“Flat optical elements enable the realization of ultra-thin devices able to either reproduce or overcome the functionalities of standard bulky components. The fabrication of these elements involves the structuration of material surfaces on the light wavelength scale, whose geometry has to be carefully designed to achieve the desired optical functionality. In addition to the limits imposed by lithographic design-performance compromises, their optical behavior cannot be accurately tuned afterward, making them difficult to integrate in dynamic optical systems. Here we show the realization of fully reconfigurable flat varifocal diffractive lens, which can be in-place realized, erased and reshaped directly on the surface of an azopolymer film by an all-optical holographic process. Integrating the lens in the same optical system used as standard refractive microscope, results in a hybrid microscope capable of multi-depth object imaging. Our approach demonstrates that reshapable flat optics can be a valid choice to integrate, or even substitute, modern optical systems for advanced functionalities.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 30; Number 8; Pages 12695; 2022
DOI: 10.1364/oe.455520

Scalability of all-optical neural networks based on spatial light modulators

Author(s):

Ying Zuo, Zhao Yujun, You-Chiuan Chen, Shengwang Du & Liu, Junwei

Abstract:

“Optical implementation of artificial neural networks has been attracting great attention due to its potential in parallel computation at speed of light. Although all-optical deep neural networks (AODNNs) with a few neurons have been experimentally demonstrated with acceptable errors re- cently, the feasibility of large scale AODNNs remains unknown because error might accumulate inevitably with increasing number of neurons and connections. Here, we demonstrate a scalable AODNN with programmable linear operations and tunable nonlinear activation functions. We ver- ify its scalability by measuring and analyzing errors propagating from a single neuron to the entire network. The feasibility of AODNNs is further confirmed by recognizing handwritten digits and fashions respectively.”

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Publication: Physical Review Applied
Issue/Year: Physical Review Applied, 2021
DOI: https://doi.org/10.1103/PhysRevApplied.15.054034

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

Coded aperture correlation holography (COACH) with a superior lateral resolution of FINCH and axial resolution of conventional direct imaging systems

Author(s):

Bulbul, Angika; Hai, Nathaniel & Rosen, Joseph

Abstract:

“Fresnel incoherent correlation holography (FINCH) is a self-interference incoherent digital holography technique. It possesses a higher lateral resolution than an equivalent incoherent imaging system. However, FINCH has lower axial resolution than the direct imaging systems with the same numerical aperture. A decade after the FINCH invention, a different incoherent holographic method named coded aperture correlation holography (COACH) was developed with improved axial resolution but with the same lateral resolution as direct imaging. In this study, we propose and demonstrate a variant of COACH called coded aperture with FINCH intensity responses (CAFIR) with an improved lateral resolution that is similar to the FINCH system while maintaining its high axial resolution similar to the direct imaging system. CAFIR is implemented with coded phase masks to generate an ensemble of quasi-randomly distributed FINCH-like responses. Point spread holograms and object holograms are recorded under identical conditions, and they are cross-correlated to obtain the image reconstruction. Imaging of a multiplane object is studied to compare the axial resolution of CAFIR with FINCH and direct imaging systems.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 25; Pages 42106; 2021
DOI: 10.1364/oe.446945

Complex-amplitude single-pixel imaging using coherent structured illumination

Author(s):

Hou, Hong-Yun; Zhao, Ya-Nan; Han, Jia-Cheng; Cui, Sheng-Wei; Cao, De-Zhong; Liu, Hong-Chao; Zhang, Su-Heng & Liang, Bao-Lai

Abstract:

“This research presents a coherent structured illumination single-pixel imaging scheme to image objects with complex amplitudes. By utilizing a phase-only spatial light modulator for phase modulation, we can efficiently generate the Hadamard basis structured light and the reference light that interfere with each other to form the coherent structured illumination. Using the 4-step phase-shifting, the spectrum of the object is acquired by detecting the zero-frequency component of the object light with a single-pixel photodetector. The desired complex-amplitude image can be further retrieved by applying an inverse Hadamard transform. The proposed scheme is experimentally demonstrated by imaging two etched glass objects, a dragonfly wing, and a resolution test chart. Benefiting from the phase modulation, this scheme has a high efficiency, a high imaging quality, a high spatial resolution, and a simple and stable configuration to obtain both the phase and amplitude information of the target object. The proposed scheme provides a promising complex-amplitude imaging modality with single-pixel detection. Thus it might find broad applications in optical metrology and biomedical science.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 25; Pages 41827; 2021
DOI: 10.1364/oe.443258

Clustering-based CLEAN algorithm in ghost imaging with sparse spatial frequencies

Author(s):

Chang, Chen; Wu, Guohua; Yang, Dongyue; Yin, Longfei & Luo, Bin

Abstract:

“When insufficient samples in the spatial frequency domain could be effectively compensated by the modified CLEAN algorithm, a novel aperture-synthetic scheme of ghost imaging takes advantage of a superior speed of modulation and an enhancement on the spatial resolution. However, there still exist some imperfections in the modified CLEAN reconstructions, such as the fact that some omitted scatter noise still remains or the object contour may be incomplete. Therefore, we optimize the modified CLEAN algorithm by proposing a density clustering algorithm to overcome these drawbacks and improve the visual quality.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 23; Pages 38841; 2021
DOI: 10.1364/oe.440497

Wide angle holographic video projection display

Author(s):

Chlipała, Maksymilian; a; Kozacki, Tomasz; Yeom, Han-Ju; Martinez-Carranza, Juan; Rafał; Kukołowicz; Kim, Jinwoong; Yang, Jong-Heon; Choi, Ji Hun; Pi, Jae-Eun & Hwang, Chi-Sun

Abstract:

“Holographic projection displays provide high diffraction efficiency. However, they have a limited projection angle. This work proposes a holographic projection display with a wide angle, which gives an image of size 306mm×161mm at 700 mm and reduced speckle noise. The solution uses single Fourier lens imaging with a frequency filter and hologram generation utilizing complex coding and nonparaxial diffraction. The experiment was performed with a 4K phase-only spatial light modulator (SLM) to prove the high efficiency of the developed numerical tools. Optical reconstruction shows high resolution and high image quality achieved from a single frame. Hence, displaying video at a full frame rate of the SLM is possible.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Volume 46; Number 19; Pages 4956; 2021
DOI: 10.1364/ol.430275

Focusing light into scattering media with ultrasound-induced field perturbation

Author(s):

Cheng, Zhongtao & Wang, Lihong V.

Abstract:

“Focusing light into scattering media, although challenging, is highly desirable in many realms. With the invention of time-reversed ultrasonically encoded (TRUE) optical focusing, acousto-optic modulation was demonstrated as a promising guidestar mechanism for achieving noninvasive and addressable optical focusing into scattering media. Here, we report a new ultrasound-assisted technique, ultrasound-induced field perturbation optical focusing, abbreviated as UFP. Unlike in conventional TRUE optical focusing, where only the weak frequency-shifted first-order diffracted photons due to acousto-optic modulation are useful, here UFP leverages the brighter zeroth-order photons diffracted by an ultrasonic guidestar as information carriers to guide optical focusing. We find that the zeroth-order diffracted photons, although not frequency-shifted, do have a field perturbation caused by the existence of the ultrasonic guidestar. By detecting and time-reversing the differential field of the frequency-unshifted photons when the ultrasound is alternately ON and OFF, we can focus light to the position where the field perturbation occurs inside the scattering medium. We demonstrate here that UFP optical focusing has superior performance to conventional TRUE optical focusing, which benefits from the more intense zeroth-order photons. We further show that UFP optical focusing can be easily and flexibly developed into double-shot realization or even single-shot realization, which is desirable for high-speed wavefront shaping. This new method upsets conventional thinking on the utility of an ultrasonic guidestar and broadens the horizon of light control in scattering media. We hope that it provides a more efficient and flexible mechanism for implementing ultrasound-guided wavefront shaping.”

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Publication: Light: Science {&} Applications
Issue/Year: Light: Science {&} Applications, Volume 10; Number 1; 2021
DOI: 10.1038/s41377-021-00605-7

Predicting optical transmission through complex scattering media from reflection patterns with deep neural networks

Author(s):

Skarsoulis, Kyriakos; Kakkava, Eirini & Psaltis, Demetri

Abstract:

“Deep neural networks (DNNs) are used to reconstruct transmission speckle intensity patterns from therespective reflection speckle intensity patterns generated by illuminated parafilm layers. The dependence ofthe reconstruction accuracy on the thickness of the sample is examined for different illumination patterns ofvarious feature sizes. High reconstruction accuracy is obtained even for large parafilm thicknesses, for whichthe memory effect of the sample is vanishingly small. The generalization capability of the DNN is also studiedfor unseen scatterers of the same type.”

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Publication: Optics Communications
Issue/Year: Optics Communications, Volume 492; Pages 126968; 2021
DOI: 10.1016/j.optcom.2021.126968
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