Super-resolution imaging by optical incoherent synthetic aperture with one channel at a time

Author(s):

Bulbul, Angika & Rosen, Joseph

Abstract:

“Imaging with an optical incoherent synthetic aperture (SA) means that the incoherent light from observed objects is processed over time from various points of view to obtain a resolution equivalent to single-shot imaging by the SA larger than the actual physical aperture. The operation of such systems has always been based on two-wave interference where the beams propagate through two separate channels. This limitation of two channels at a time is removed in the present study with the proposed SA where the two beams pass through the same single channel at any given time. The system is based on a newly developed self-interference technique named coded aperture correlation holography. At any given time, the recorded intensity is obtained from interference between two waves co-propagating through the same physical channel. One wave oriented in a particular polarization is modulated by a pseudorandom coded phase mask and the other one oriented orthogonally passes through an open subaperture. Both subapertures are multiplexed at the same physical window. The system is calibrated by a point spread hologram synthesized from the responses of a guide star. All the measurements are digitally processed to achieve a final image with a resolution higher than that obtained by the limited physical aperture. This unique configuration can offer alternatives for the current cumbersome systems composed of far apart optical channels in the large optical astronomical interferometers. Furthermore, the proposed concept paves the way to an SA system with a single less-expensive compact light collector in an incoherent optical regime that may be utilized for future ground-based or space telescopes.”

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Publication: Photonics Research
Issue/Year: Photonics Research, Volume 9; Number 7; Pages 1172; 2021
DOI: 10.1364/prj.422381

Single-shot digital multiplexed holography for the measurement of deep shapes

Author(s):

Kozacki, Tomasz; Mikuła-Zdańkowska, Marta; Martinez-Carranza, Juan & Idicula, Moncy Sajeev

Abstract:

“This work develops a single-shot holographic profilometer that enables shape characterization of discontinuous deep surfaces. This is achieved by combining hologram frequency multiplexing and an illumination technique of complex amplitude in multi-incidence angle profilometer. Object illumination is carried out from seven directions simultaneously, where the radial angular coordinates of illumination plane waves obey the geometric series. It is shown that: (i) the illumination pattern provides the required frequency separation of all object wavefronts in transverse frequency space, which is necessary for hologram demultiplexing, and (ii) numerical generation of longitudinal scanning function (LSF) is possible, which has large measurement range, high axial resolution, and small side lobes. Low side lobes of LSF and the developed multiplexed field dependent aberration compensation method are essential to minimize the negative influence of speckle noise of single-shot capture on the measurement result. The utility of the proposed method is demonstrated with experimental measurement of heights of two step-like objects.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 14; Pages 21965; 2021
DOI: 10.1364/oe.428419

Broadband chromatic dispersion measurements in higher-order modes selectively excited in optical fibers using a spatial light modulator

Author(s):

Zolnacz, Kinga; Szatkowski, Mateusz; Masajada, Jan & Urbanczyk, Waclaw

Abstract:

“We propose an improvement of the interferometric method used up to now to measure the chromatic dispersion in single mode optical fibers, which enables dispersion measurements in higher-order modes over a wide spectral range. To selectively excite a specific mode, a spatial light modulator was used in the reflective configuration to generate an appropriate phase distribution across an input supercontinuum beam. We demonstrate the feasibility of the proposed approach using chromatic dispersion measurements of the six lowest order spatial modes supported by an optical fiber in the spectral range from 450 to 1600 nm. Moreover, we present the results of numerical simulations that confirm sufficient selectivity of higher-order mode excitation.”

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Publication: Optics Express
Issue/Year: Optics Express, Volume 29; Number 9; Pages 13256; 2021
DOI: 10.1364/oe.422736

Phase Compensation of the Non-Uniformity of the Liquid Crystal on Silicon Spatial Light Modulator at Pixel Level

Author(s):

Zeng, Zhen; Li, Zexiao; Fang, Fengzhou & Zhang, Xiaodong

Abstract:

“Phase compensation is a critical step for the optical measuring system using spatial light modulator (SLM). The wavefront distortion from SLM is mainly caused by the phase modulation non-linearity and non-uniformity of SLM’s physical structure and environmental conditions. A phase modulation characteristic calibration and compensation method for liquid crystal on silicon spatial light modulator (LCoS-SLM) with a Twyman-Green interferometer is illustrated in this study. A method using two sequences of phase maps is proposed to calibrate the non-uniformity character over the whole aperture of LCoS-SLM at pixel level. A phase compensation matrix is calculated to correct the actual phase modulation of the LCoS-SLM and ensure that the designed wavefront could be achieved. Compared with previously known compensation methods, the proposed method could obtain the phase modulation characteristic curve of each pixel on the LCoS-SLM, rather than a mono look-up table (LUT) curve or multi-LUT curves corresponding to an array of blocks over the whole aperture of the LCoS-SLM. The experiment results show that the phase compensation precision could reach a peak-valley value of 0.061λ in wavefront and this method can be applied in generating freeform wave front for precise optical performance.”

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Publication: Sensors
Issue/Year: Sensors, Volume 21; Number 3; Pages 967; 2021
DOI: 10.3390/s21030967

Method for single-shot fabrication of chiral woodpile photonic structures using phase-controlled interference lithography

Author(s):

Swagato Sarkar, Krishnendu Samanta, and Joby Joseph

Abstract:

“In this report, we propose a large-area, scalable and reconfigurable single-shot
optical fabrication method using phase-controlled interference lithography (PCIL) to realize
submicrometer chiral woodpile photonic structures. This proposed technique involves a 3 + 3
double-cone geometry with beams originated from a computed phase mask displayed on a single
spatial light modulator. Simulation studies show the filtering response of such structures for
linearly polarized plane wave illumination, with structural features tunable through a single
parameter of interference angle. Further, these single chiral woodpile structures show dual
chirality on illumination with both right circularly and left circularly polarized light through
simulation. Experimentally fabricated patterns on photoresist show resemblance to the desired
chiral woodpile structures.”

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Publication: Optics Express
Issue/Year: Volume 28, Issue 3, pp. 4347-4361
DOI: 10.1364/OE.384987

Velocity measurements with structured light transmitted through a multimode optical fiber using digital optical phase conjugation

Author(s):

Lars Büttner and Martin Thümmler and Jürgen Czarske

Abstract:

“Lensless fiber microendoscopes enable optical diagnostics and therapy with minimal
invasiveness. Because of their small diameters, multimode fibers are ideal candidates, but mode
scrambling hinders the transmission of structured light fields. We present the generation of a
localized fringe system at variable distances from the distal fiber end by exploiting digital optical
phase conjugation. The replayed fringe system was used for quantitative metrology. Velocity
measurements of a microchannel flow in the immediate proximity of the fiber end without the
use of any imaging lenses are shown. Lensless multimode fiber systems are of interest especially
for biomedical imaging and stimulation as well as technical inspection and flow measurements. ”

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Publication: Optics Express
Issue/Year: Vol. 28, Issue 6, pp. 8064-8075
DOI: 10.1364/OE.386047

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

Spectrum and space resolved 4D imaging by coded aperture correlation holography (COACH) with diffractive objective lens

Author(s):

A. Vijayakumar and Joseph Rosen

Abstract:

“In this Letter, we present an advanced optical configuration of coded aperture correlation holography (COACH) with a diffractive objective lens. Four-dimensional imaging of objects at the three spatial dimensions and with an additional spectral dimension is demonstrated. A hologram of three-dimensional objects illuminated by different wavelengths was recorded by the interference of light diffracted from the objects with the light diffracted from the same objects, but through a random-like coded phase mask (CPM). A library of holograms denoted point spread function (PSF) holograms were prerecorded with the same CPM, and under identical conditions, using point objects along different axial locations and for the different illuminating wavelengths. The correlation of the object hologram with the PSF hologram recorded using a particular wavelength, and at a particular axial location, reconstructs only the object corresponding to the particular axial plane and to the specific wavelength. The reconstruction results are compared with regular imaging and with another well-established holographic technique called Fresnel incoherent correlation holography.”

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Publication: Optics Letters
Issue/Year: Optics Letters Vol.42, Issue 5, pp. 947-950 (2017)
DOI: 10.1364/OL.42.000947

Closed-loop adaptive optics with a single element for wavefront sensing and correction

Author(s): Raúl Martínez-Cuenca, Vicente Durán, Justo Arines, Jorge Ares, Zbigniew Jaroszewicz, Salvador Bará, Lluís Martínez-León, and Jesús Lancis

Abstract:

“We propose a closed-loop adaptive optical arrangement based on a single spatial light modulator that simultaneously works as a correction unit and as the key element of a wavefront sensor. This is possible by using a liquid crystal on silicon display whose active area is divided into two halves that are respectively programmed for sensing and correction. We analyze the performance of this architecture to implement an adaptive optical system. Results showing a closed-loop operation are reported, as well as a proof of concept for dealing with aberrations comparable to those typically found in human eyes.”

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Publication: Optics Letters
Issue/Year: Optics Letters, Vol. 36, Issue 18, pp. 3702-3704 (2011)
DOI: 10.1364/OL.36.003702

Estimation and Compensation of aberrations in Spatial Light Modulators

Author(s): Augusto Arias and Roman Castaneda

Abstract:

“The spatial light modulator (SLM) Holoeye LC-R720 is based on LCoS (Liquid Crystal on Silicon) technology. Due to the induced curvatures on the silicon plate by the production process, there are static aberrations in the wave-fronts modified by the SLM. In order to calculate the aberrated wave-front we used phase-shifting interferometry, an optimization algorithm for far field propagation, and the geometric characterization of the focal spot along the caustic. Zernike polynomials were used for expanding and comparing the wave-fronts. The aberration compensation was carried out by displaying the conjugated transmittance on the SLM. The complexity of the experimental setup and the requirements of the digital processing of each estimation method were comparatively analyzed.”

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Publication: Journal of Physics: Conference Series
Issue/Year: J. Phys.: Conf. Ser., Volume 274, 012060, (2011)
DOI: 10.1088/1742-6596/274/1/012060
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