This forms the basis of an optical security system, whereby documents are encoded with practically invisible phase masks (such masks are difficult to forge), which may then be rapidly screened to verify the authenticity of the documents. Our approach offers diffraction-limited resoln., potentially at arbitrarily-low intensity levels and with 100 THz bandwidth, thus promising new applications in space-division multiplexing, adaptive optics, image correction, processing and recognition, 2D binary optical data processing and reconfigurable optical devices. The input beam intensities were chosen such that the single beam transmission of beam A and reflection of beam B have the same intensity. One can switch these logic operations simply by means of the on-off control of the signal and the pump beam illumination. Opt. OPTICAL PATTERN RECOGNITION de FRANCIS T. S. YU-. Optical pattern recognition Casasent, David; Abstract. These may be thought of as, for example, spatially multiplexed optical data, lottery tickets, or multiple choice answer sheets. ScienceDirect ® is a registered trademark of Elsevier B.V. ScienceDirect ® is a registered trademark of Elsevier B.V. Non-Destructive Examination Methods for Condition Monitoring. Abdul A. Awwal, Khan M. Iftekharuddin, Mohammad A. Karim, and Richard D. Juday Appl. Read reviews from world’s largest community for readers. The 2 … Sciences and The Photonics Institute, Nanyang The authors are grateful to João Valente and Edward T. F. Rogers for advice and assistance. Pattern recognition using optical systems can be performed based on either correlator or non-correlator systems. Thongrattanasiri, Sukosin; Koppens, Frank H. L.; Garcia de Abajo, F. Javier. Here we take a deeper look at the combination of flow and action recognition, and investigate why optical flow is helpful, what makes a flow method good for action recognition, and how we can make it better. Coherent interaction of the test and reference satellite images (row 1) on the metamaterial beam splitter clearly shows the regions where the ice cover remained unchanged (row 2) and the regions where the ice cover changed (row 3, mostly due to melting) for different phases of the illuminating beams. Using the CCD camera as an effective photodetector, we integrate the image power to determine the maximum and minimum of the phase-dependent normalized total power, P̃max and P̃min, as described above; see panel (b). Enhancement of microcalcifications in a mammogram for early diagnosis of breast cancer is the main focus. We show that the interference of beams can eliminate the plasmonic Joule losses of light energy in the metamaterial or, in contrast, can lead to almost total absorption of light. In contrast, coherent interaction of light with light in areas illuminated from opposite sides yields detection of a phase-dependent power , where φ is the phase difference between the transmitted beam A and the reflected beam B. Opt. The metasurface is imaged onto a CCD camera. (23) Contrary to the common belief that light beams cannot interact in linear optics, the interaction of a beam of light with a planar metamaterial beam splitter can be controlled by a second counterpropagating coherent beam of light. Wave interaction on highly nonlinear photorefractive materials is essentially the only established technol. Hybrid neural networks for nonlinear pattern recognition Taiwei Lu; 3. A channel transformation based on opponent-color theory of the color vision models is applied to optical pattern recognition so that the conventional red, green, and blue (RGB) channels are transformed into bright-dark, red-green, and yellow-blue https://doi.org/10.1021/acsphotonics.8b00019, https://doi.org/10.1021/acsphotonics.7b00921, https://doi.org/10.1103/PhysRevA.100.063844, https://doi.org/10.1103/PhysRevLett.122.123901, https://doi.org/10.1007/978-3-319-98402-5_7, https://doi.org/10.1016/j.optlastec.2017.12.004, https://doi.org/10.1103/PhysRevLett.120.143901, https://doi.org/10.1038/natrevmats.2017.64. If a contrast correction factor of f = 1.1 is applied to compensate for an experimental contrast of 90% rather than 100%, then the experiments reproduce the areas of ice cover that remained, melted, and grew accurately. We illustrate this by performing 2D all-optical logical operations (AND, XOR and OR) and image processing. Ömer Halisdemir Üniversitesi Mühendislik Bilimleri Dergisi. layer coating a metal. New optical processor filter research that allows such flexibility is advanced and examples of each of these filters are provided. Panel (c) shows the correct theory values for remaining, grown, and melted ice cover in comparison to our optical experiments. Ze worden links hieronder weergegeven. This paper reviews various types of optical correlators and NNs applied to real-time pattern recognition and autonomous tracking. Furthermore, imaging onto a CCD camera reveals maps of similarities and differences. Optical Pattern Recognition XVI. The area of disagreement will lead to detection of phase-independent power IsglSA⊕B. For coherent illumination with copolarized counterpropagating light beams, IA = IB, the lossless beam splitter will split the incident intensity unevenly between the output beams, while the lossy beam splitter will split the incident intensity between absorption and two identical output beams. specimens. Later chapters discuss new approaches based on neural networks, wavelet transforms, and the fractional Fourier transform. This is illustrated by Table 1, where P̃av = (P̃max + P̃min)/2 and ΔP̃ = P̃max – P̃min. (3-6) All-optical pattern recognition schemes have been realized with different types of optical correlators based on photorefractive polymers,(7) semiconductor optical amplifiers,(8) delay lines, and phase shifter designs. In general, a beam splitter can be either lossless or lossy, and planar metamaterials—interfaces such as plasmonic metal films of deeply subwavelength thickness that are structured on the subwavelength scale—allow the realization of beam splitters with precisely engineered transmission, reflection, and absorption levels. Such coherent control of light with light was recently reported in two spatial dimensions as a platform for parallel all-optical logical operations based on the theory of an idealized metasurface absorber. In the lossless case, coherent transparency at the standing wave node implies that the phase φ is related to the phase difference θ between the waves incident on the beam splitter by φ = θ ± π/2. Here we report a proof-of-principle demonstration of a new technol. Figure 1. This chapter discusses optical pattern recognition. In optical pattern recognition there are two basic approaches; namely, matched filtering and associative memories. Find more information about Crossref citation counts. Here we demonstrate that in slabs of linear material of sub-wavelength thickness optical manifestations of birefringence and optical activity (linear and circular birefringence and dichroism) can be controlled by a wave coherent with the wave probing the polarization effect. CAD describes a procedure that supports the doctor's interpretations and findings. However, MC does not pro-vide detection with rotation invariance. for Disruptive Photonic Technologies, School of Physical and Mathematical Here, optical character recognition (OCR) comes to work. The technique enables both real-time mapping of similarities and differences between images using a CCD camera and quantitative analysis of the relationship between pairs of images with a photodetector that could be simultaneously achieved in a system where the output is split and directed to a CCD camera as well as a photodetector. A planar metamaterial interacts with the electric field of a normally incident plane wave, but its interaction with the magnetic field is prohibited, as in-plane magnetic dipole modes are not supported by truly planar structures. There are two classification methods in pattern recognition: supervised and unsupervised classification. This book provides a comprehensive review of optical pattern recognition, covering theoretical aspects as well as details of practical implementations and signal processing techniques. When metasurface meets hologram: principle and advances. Chapter 7 Pattern Recognition with Optics FRANCIS T. S. YU PENNSYLVANIA STATE UNIVERSITY The roots of optical pattern recognition can be traced back to Abbe's work* in the 1870s, when he developed a method that led to the discovery of … To achieve General anal. The latter are normalized by 4PA,sgl, which yields P̃max and P̃min as described above; see Figure 2b. A CCD (charge coupled device) camera is often employed because it is more stable and dimensionally constant than a tube-based camera. Theory predicts that the phase-dependent power fluctuation ΔP̃ = P̃max – P̃min should correspond to the fraction of the reference pattern that overlaps with the test pattern, and indeed we find that ΔP̃ increases with pattern agreement. Manipulating broadband polarization conversion in metamaterials. Leading OCR companies, like Opentext, continue investments into the technology.If the trend for digital transformation will extend with the crisis – technology that allows us to digitize handwritten or printed text will be demanded. https://doi.org/10.1016/B978-0-408-04392-2.50028-X. Throughout all optical experiments, the metasurface was illuminated by linearly polarized light with the electric field oriented parallel to the symmetry axis of the split rings. In our experiments, we compare all satellite images (test images B) to the initial ice cover of 1982 (reference image A); see Figure 3a. The ice cover SA\B that melted since 1982 is given by 1 – ΔP̃. Applications of this phenomenon may lie in ultrafast all-optical pulse-recovery devices, coherence filters and terahertz-bandwidth light-by-light modulators. Ishikawa, Daisuke; Okamoto, Atsushi; Honma, Satoshi; Ito, Terumasa; Shimayabu, Kohei; Sato, Kunihiro. Most of the top performing action recognition methods use optical flow as a “black box” input. Many optical pattern-recognition system architectures exist that include time-domain optical correlators and the optical joint transform correlators and refinements in the original optical matched spatial filter synthesis processor. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Zhang, Jianfa; MacDonald, Kevin F.; Zheludev, Nikolay I. The authors declare no competing financial interest. 40, 3416-3419 (2015) Photonic Firewall Oriented All -Optical Binary Pattern Recognition. Here we challenge this wisdom and demonstrate that two coherent beams of light of arbitrarily low intensity can interact on a metamaterial layer of nanoscale thickness in such a way that one beam modulates the intensity of the other. The first row shows images of all patterns as captured by the CCD for single-beam illumination. 42(23) 4647-4648 (2003) All-optical digital-to-analog conversion using pulse pattern recognition based on optical correlation processing. Simulation of all-optical NOT/OR/AND/NAND/NOR/XNOR/XOR logic gates using a single structure high contrast index nonlinear multimode interference coupler. Many optical pattern-recognition system architectures exist that include time-domain optical correlators and the optical joint transform correlators and refinements in the original optical matched spatial filter synthesis processor. This book provides a comprehensive review of optical pattern recognition, covering theoretical aspects as well as details of practical implementations and signal processing techniques. However, existing all-optical image processing and pattern recognition methods based on optical nonlinearities are limited by an unavoidable trade-off between speed and intensity requirements. The phase-dependent power fluctuation ΔP̃ corresponds to the area of ice cover that remained unchanged, indicating that the ice cover of 1982 remained largely intact until 1992 and that substantial melting took place thereafter. Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Consequently, metasurface positioning at an electric field antinode will enable interaction with the wave, while metasurface translation to a node will prevent light–matter interaction, rendering the metasurface perfectly transparent. Yuhan Wang, Yangguan Guo, Huimin Liao, Zhi Li, Fengyuan Gan, Chengwei Sun. Please note: If you switch to a different device, you may be asked to login again with only your ACS ID. This way, the relationship between any pair of binary images (containing a large amount of optical data) may be reduced all-optically to a total of three characteristic power values of electronic data. Get article recommendations from ACS based on references in your Mendeley library. Caulfield, R. Haimes, AerodyneResearch, Inc. 201-18 Optical pattern recognition andclassification invarianttoselectable Optical pattern recognition using a synthetic discriminant amplitude-compensated matched filter (a) Binary masks representing September ice coverage based on satellite images taken 10 years apart(24) as seen by the CCD camera for single-beam illumination (row 1). In particular, the sum of the illuminated areas A and B corresponds to the average power, the differences between the binary images are given by the minimum power, and the overlap between the images corresponds to the phase-dependent power fluctuations. All-Optical logic implementations for realization of arithmetic and signal processing applications based on each interferometric arrangement are also presented in a categorized manner. The functional paradigm illustrated here opens the path to a broad family of meta-devices for ultrafast optical data processing in coherent networks. Discrimination capability of different correlators, both in free space architectures and in delay lines structures, is theoretically and experimentally analyzed. Published by Elsevier Ltd. All rights reserved. The first employs optical correlator architectures and the latter uses optical neural networks (NNs). (1, 2) However, the ultimate potential of photonic systems is revealed when all-optical logic computations come into play. While our approach will work at any intensity below damage thresholds, the laser light is attenuated to a few microwatts to avoid detector saturation. Figure 3. The authors propose all-optical multifunctional logic gates for image information using photorefractive (PR) two-wave mixing. All-optical control of polarization splitting with a dielectric-clad azobenzene liquid crystal. The agreement between test and target patterns corresponds to the normalized power fluctuation, ΔP̃ (double arrows). Today, we’re going to take a look at OCR - or optical character recognition. We show that while the absorption of photons from a travelling wave is probabilistic, standing wave absorption can be observed deterministically, with nearly unitary probability of coupling a photon into a mode of the material, for example, a localized plasmon when this is a metamaterial excited at the plasmon resonance. Your Mendeley pairing has expired. It is not essential that the user of an optical pattern recognition system possess a great deal of knowledge about computer technology and programming. A channel transformation based on opponent-color theory of the color vision models is applied to optical pattern recognition so that the conventional red, green, and blue (RGB) channels are transformed into bright-dark, red-green, and yellow-blue All-Optical Signal Processing is an emerging technol. The position of an ideal lossless beam splitter relative to the standing wave will control how the power of the incident wave is divided between the two output beams. Optoelectronics Asymmetrically split ring aperture arrays have a rich and well-studied spectrum of transmission, reflection, and absorption bands,(22) and our structure absorbs about 34% at 790 nm wavelength when illuminated by a single optical beam. Continuous beam steering by coherent light-by-light control of dielectric metasurface phase gradient. Copyright © 2021 Elsevier B.V. or its licensors or contributors. (3) The theory and experiments reported here advance this concept to allow quantitative pattern recognition and image analysis on beam splitters of arbitrary loss. Metamaterials at the University of Southampton and beyond. Volodin, B. L.; Kippelen, B.; Meerholz, K.; Javidi, B.; Peyghambarian, N. Polymers that exhibit the photorefractive effect - light-induced modulation of refractive index-are emerging as attractive materials for optical devices and processing systems. Here, Seo et al. 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