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High-resolution imaging using integrated optical systems

INTERNATIONAL JOURNAL OF IMAGING SYSTEMS AND TECHNOLOGY 2004年第2期14卷 67-74页

作者： Prasad, S Torgersen, TC Pauca, VP Plemmons, RJ van der Gracht, J Wake Forest Univ Dept Comp Sci Winston Salem NC 27019 USA Wake Forest Univ Dept Math Winston Salem NC 27019 USA Univ New Mexico Ctr Adv Studies Albuquerque NM 87131 USA Wake Forest Univ Dept Comp Sci Winston Salem NC 27109 USA Holospex Inc Columbia MD 21044 USA

Certain optical aberrations, such as defocus, can significantly degrade the signal collected by an imaging system, producing images with low resolution. In images with depth-dependent detail, such degradations are difficult to remove due to their inherent spatially varying nature. In 1995, Dowski and Cathey introduced the concept of wavefront coding to extend the depth of field. They showed that wavefront coding and decoding enables quality control of such images using integrated optical-digital imaging systems. With wavefront coding, a high-resolution image can be efficiently obtained without the need to resort to expensive algorithms for spatially varying restoration. In this article, we discuss a novel and effective multiple-design-parameter approach for optimizing the processes of encoding and decoding the wavefront phase in integrated optical-digital imaging systems. Our approach involves the use of information metrics, such as the Strehl ratio and Fisher information, for determining the optimal pupil-phase distribution for which the resulting image is insensitive to certain aberrations, such as focus errors. The effectiveness of this approach is illustrated with a number of numerical simulation experiments, and applications to the development of iris recognition systems with high-resolution capabilities are briefly discussed. (C) 2004 Wiley Periodicals, Inc.

关键词： integrated imaging wavefront coding pupil-phase engineering Fisher information Strehl ratio focus extension nonlinear optimization image restoration

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Simultaneous Achromatic and Varifocal Imaging with Quartic Metasurfaces in the Visible

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ACS PHOTONICS 2020年第1期7卷 120-127页

作者： Colburn, Shane Majumdar, Arka Univ Washington Dept Elect & Comp Engn Seattle WA 98195 USA Univ Washington Dept Phys Seattle WA 98195 USA

Two key metrics for imaging systems are their magnification and optical bandwidth. While high-quality imaging systems today achieve bandwidths spanning the whole visible spectrum and large changes in magnification via optical zoom, these often entail lens assemblies with bulky elements unfit for size-constrained applications. Metalenses present a methodology for miniaturization, but their strong chromatic aberrations and the lack of a varifocal, achromatic element limit their utility. Although exemplary broadband achromatic metalenses are realizable via dispersion engineering, in practice, these designs are limited to small physical apertures as large area lenses would require phase compensating scatterers with aspect ratios infeasible for fabrication. Many applications, however, necessitate larger areas to collect more photons for better signal-to-noise ratio and furthermore must also operate with unpolarized light. In this paper, we simultaneously achieve achromatic operation at visible wavelengths and varifocal control using a polarization-insensitive, hybrid optical-digital system with area unconstrained by dispersion-engineered scatterers. We derive phase equations for a pair of conjugate metasurfaces that generate a focused accelerating beam for chromatic focal shift control and a wide tunable focal length range of 4.8 mm (a 667-diopter change). Utilizing this conjugate pair, we realize a near spectrally invariant point spread function across the visible regime. We then combine the metasurfaces with a postcapture deconvolution algorithm to image full-color patterns under incoherent white light, demonstrating an achromatic 5x zoom range. Simultaneously achromatic and varifocal metalenses could have applications in various fields including augmented reality, implantable microscopes, and machine vision sensors.

关键词： metasurfaces computational imaging tunable metasurfaces varifocal lens achromatic metasurface wavefront coding

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Optimized Asymmetrical Arcsine Phase Mask for Extending the Depth of Field

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IEEE PHOTONICS TECHNOLOGY LETTERS 2018年第14期30卷 1309-1312页

作者： Wang, Lei Ye, Qing Nie, Jinsong Sun, Xiaoquan Natl Univ Def Technol State Key Lab Pulsed Power Laser Technol Hefei 230037 Anhui Peoples R China

With the development of wavefront coding technique, various x-y separable phase masks have been proposed for the purpose of extending the depth of field. In this letter, a new asymmetrical arcsine phase mask combing the power and arcsine function was proposed to enrich the separable odd symmetrical family of wavefront coding phase masks. Using the simulated annealing algorithm based on Fisher information for optimization, we evaluated the performance of arcsine phase mask with four typical phase masks: the tangent, sinusoidal, improved-2 logarithmic, and cubic phase masks. The comparison results of Fisher information, defocused modulation transfer function, Hilbert space angle, and digital restoration demonstrated that the arcsine phase mask could restore clear and homogeneous images with both high fidelity and high signal to noise ratio along with a wide range of defocus, proving its superiority in extending the depth of field.

关键词： Image restoration optical imaging phase modulation wavefront coding

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wavefront coded light-field imaging system to achieve substantial retroreflection reduction and anti-laser blinding property

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OPTIK 2019年 192卷 162947-000页

作者： Wang, Lei Dou, Xianan Ye, Qing Nie, Jinsong Sun, Xiaoquan State Key Lab Pulsed Power Laser Technol China 460 Huangshan Rd Hefei 230037 Anhui Peoples R China

To achieve a substantial retroreflection reduction accompanied with a superior anti-laser blinding property without suffering significant degradations in imaging quality, we design a novel imaging system based on the wavefront coded light-field rendering. Relevant studies have been carried out around its mechanism in both anti-laser reconnaissance and blinding. According to the Fresnel-Kirchhoff diffraction theory, the laser propagation through the composite imaging system is theoretically modeled. By comparison among the conventional, the wavefront coding, the light-field, and the composite imaging systems with different defocus parameters and phase modulation coefficients, the spot profiles and intensity distributions on both the imaging and observation planes are further studied, according to which the optimization principle is proposed. The results show that compared with the conventional one, the composite imaging system could not only increase the interference and blinding thresholds by nearly one order of magnitude but also attenuate the retroreflection peak intensity and the echo-detector receiving power by even more than one order of magnitude, achieving the superior properties of anti-laser reconnaissance and blinding.

关键词： Imaging system Retroreflection reduction wavefront coding Light-field imaging Laser interference and blinding

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The effect of detector sampling in wavefront-coded imaging systems

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JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS 2009年第5期11卷 054002 (9p-054002 (9p页

作者： Muyo, G. Harvey, A. R. Heriot Watt Univ Sch Engn & Phys Sci Edinburgh EH14 4AS Midlothian Scotland

We present a comprehensive study of the effect of detector sampling on wavefront-coded systems. Two important results are obtained: the spurious response ratios are reduced in wavefront-coded systems with a cubic phase mask and detector sampling does not compromise the restoration of wavefront-coded images with extended depth of field. Rigorous computer simulation of sampled wavefront-coded images shows an increased signal-to-aliased-noise ratio of up to 16% for a cubic phase mask with alpha = 5 lambda.

关键词： wavefront coding detector sampling aliasing digital image processing

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Analyzing wavelength behavior of a cubic phase mask imaging system based on modulation transfer function

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OPTICS COMMUNICATIONS 2012年第6期285卷 1082-1086页

作者： Zhang, Rongfu Zhang, Min Lu, Kang Wang, Tao Wang, Liangliang Zhuang, Songlin Shanghai Univ Sci & Technol Sch Opt Elect & Comp Engn Shanghai 200093 Peoples R China

The wavefront coding technology is an effectively method for extending the depth of field. However, the phase delayed by the phase mask changes with light wavelength, and the chromatic aberration is caused by chromatic dispersion of the optical elements. The modulation transfer function (MTF) of the cubic phase mask (CPM) system is derived with considering the axial chromatic aberration and optical path difference variation with wavelength, and the wavelength behavior of CPM system is analyzed in details. We yield that the MTF is approximately wavelength invariant within a certain frequency bandwidth, and the bandwidth is nearly inverse proportional to wavelength and varies with axial chromatic aberration. The effect induced by dispersion of the CPM material is very weak. If the CPM system is illuminated by wideband spectral light and the ACA exists, then the frequency bandwidth may become narrower than the monochromatic case, and the position of image sensor can be relocated to balance frequency bandwidth among all wavelengths. (C) 2011 Elsevier B.V. All rights reserved.

关键词： wavefront coding Modulation transfer function Cubic phase mask

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Aberration invariant optical/digital incoherent systems

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OPTICAL REVIEW 1996年第6A期3卷 429-432页

作者： Dowski, ER Cathey, WT Bradburn, SC 1) Imaging Systems Laboratory Department of Electrical Engineering University of Colorado Boulder Colorado 80309 USA

We have developed a fundamental technique for control of important known and unknown lens aberrations. Control of lens aberrations through traditional means is very difficult in high-performance optical systems. Minimizing aberrations caused by deterministic design errors as well as statistical fabrication errors has often led to costly systems and fabrication techniques. By employing a special-purpose optical phase mask and digital signal processing we can form imaging systems that are invariant, or substantially insensitive, to a number of important lens aberrations.

关键词： wavefront coding aberrations optical/digital systems imaging systems incoherent imaging

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Increasing the depth of field of imaging systems with numerically optimized phase masks - art. no. 673611

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Conference on Unmanned/Unattended Sensors and Sensor Networks IV

作者： Frauel, Yann Castro, Albertina Univ Nacl Autonoma Mexico Inst Invest Mat Aplicadas & Sist Dept Ciencias Comp Mexico City 04510 DF Mexico

ISBN: (纸本)9780819468949

The depth of field of optical systems can be extended with a phase mask placed in the pupil. We propose to design this phase mask through a heuristic numerical optimization. We describe two different criteria to illustrate the technique. We present the obtained phase profiles and we show that they have good properties regarding the extension of the depth of field.

关键词： depth of field phase masks wavefront coding numerical optimization simulated annealing

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Design and optimization of aberration and error invariant space telescope systems

Design and optimization of aberration and error invariant sp...

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7th Conference on Novel Optical Systems Design and Optimization

作者： Kubala, K Dowski, E Kobus, J Brown, B CDM Opt Boulder CO 80303 USA

ISBN: (纸本)0819454621

Telescope performance is often limited by aberrations, and/or fabrication and alignment errors. Additionally, image formation in large space-based systems is sensitive to changes in physical form parameters such as temperature-related deformations, mirror structure, piston position and detector alignment. Changes in these parameters significantly degrade image quality and often limit the performance of the system. A fundamental new technology called wavefront coding has been successfully demonstrated via simulations for large space-based imaging systems that promise to surpass the performance attained by traditional optical designs. wavefront coding uses specialized aspheric optics and signal processing of the detected image to correct defocus-like aberrations thereby enabling a new paradigm in aberration balancing for telescope systems. wavefront coding can provide dramatic new mission capabilities by allowing space-based imaging systems that are simpler, lighter, and cheaper, while also providing high quality imagery in dynamic environments that are difficult or impossible to image in with traditional imaging systems. As an example two systems are presented that allow the telescope to repoint the boresight through the actuation of the primary segments or through the use of a scan mirror. Traditional systems with the same goal of repointing the boresight historically have not been feasible due to either the increased error space or due to constraints on system cost and complexity.

关键词： telescopes computational imaging aberration theory adaptive optics lens design image formation theory wavefront coding

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Design, fabrication and characterization of Fresnel lens array with spatial filtering for passive infrared motion sensors

Design, fabrication and characterization of Fresnel lens arr...

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International Conference on Applications of Photonic Technology (Photonics North 2006)

作者： Cirino, Giuseppe A. Barcellos, Robson Morato, Spero P. Bereczki, Allan Neto, Luiz G. HoloPhoton Equipamentos Ltda R Alfredo Lopes1717 Sala E-08 BR-13560460 Sao Carlos SP Brazil LaserTools Tecno Ltda BR-05379130 Sao Paulo Brazil EESC Univ Sao Paulo BR-1356097 Sao Carlos SP Brazil

ISBN: (纸本)0819464287

A cubic-phase distribution is applied in the design, fabrication and characterization of inexpensive Fresnel lens arrays for passive infrared motion sensors. The resulting lens array produces a point spread function (PSF) capable of distinguish the presence of humans from pets by the employment of the so-called wavefront coding method. The cubic phase distribution used in the design can also reduce the optical aberrations present in the system. This aberration control allows a high tolerance in the fabrication of the lenses and in the alignment errors of the sensor. In order to proof the principle, a lens was manufactured on amorphous hydrogenated carbon thin film, by well-known micro fabrication process steps. The optical results demonstrates that the optical power falling onto the detector surface is attenuated for targets that present a mass that is horizontally distributed in space (e.g. pets) while the optical power is enhanced for targets that present a mass vertically distributed in space (e.g. humans). Then a mould on steel was fabricated by laser engraving, allowing large-scale production of the lens array in polymeric material. A polymeric lens was injected and its optical transmittance was characterized by Fourier Transform Infrared Spectrometry technique, which has shown an adequate optical transmittance in the 8-14 mu m wavelength range. Finally the performance of the sensor was measured in a climate-controlled test laboratory constructed for this purpose. The results show that the sensor operates normally with a human target, with a 12 meter detection zone and within an angle of 100 degrees. On the other hand, when a small pet runs through a total of 22 different trajectories no sensor trips are observed. The novelty of this work is the fact that the so-called pet immunity function was implemented in a purely optical filtering. As a result, this approach allows the reduction of some hardware parts as well as decreasing the software complexity, once the

关键词： passive infrared sensor pyroelectric detector cubic phase distribution wavefront coding diamondlike carbon (DLC) thin film laser engraving mould

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