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At least 91 records · Page 5

All sources NASA NTRS DOE OSTI

DOE OSTI2022

Optical authentication of images

Systems and methods performed for generating authentication information for an image using optical computing are provided. When a user takes a photo of an object, an optical authentication system receives light reflected and/or emitted from the object. The system also receives a random key from an authentication server. The system converts the received light to plenoptic data and uploads it to the authentication server. In addition, the system generates an optical hash of the received light using the random key, converts the generated optical hash to a digital optical hash, and uploads the digital optical hash to the authentication server. When the authentication server receives the upload, it verifies whether the time of the upload is within a certain threshold time from the sending of the random key and whether the digital optical hash was generated from the same light as the plenoptic data.

97 MATHEMATICS AND COMPUTING↗

DOE OSTI2023

Optical authentication of images

Murialdo, Maxwell R.↗

NASA NTRS1972

Analysis of a dual-reflector antenna system using physical optics and digital computers

The application of physical-optics diffraction theory to a deployable dual-reflector geometry is discussed. The methods employed are not restricted to the Conical-Gregorian antenna, but apply in a general way to dual and even multiple reflector systems. Complex vector wave methods are used in the Fresnel and Fraunhofer regions of the reflectors. Field amplitude, phase, polarization data, and time average Poynting vectors are obtained via an IBM 360/91 digital computer. Focal region characteristics are plotted with the aid of a CalComp plotter. Comparison between the GSFC Huygens wavelet approach, JPL measurements, and JPL computer results based on the near field spherical wave expansion method are made wherever possible.

Schmidt, R. F.↗

NASA NTRS1990

Fiber optic systems for mobile platforms III; Proceedings of the Meeting, Boston, MA, Sept. 7, 8, 1989

Various papers on fiber optic systems for mobile platforms are presented. Individual topics addressed include: architecture for fiber optic sensors and actuators in aircraft propulsion systems, fiber optic sensor system readiness for aircraft, microphone headset compatible with power by light, wavelength-division-multiplexed fiber optic sensors for aircraft applications, development of fly-by-light systems, fiber-optic-based inertial measurement unit, fault-tolerant architecture for a fly-by-light flight control computer, optically powered sensors for EMI-immune aviation sensing systems, infrared fiber optic fire sensors for space station applications. Papers on shipboard and automotive applications of fiber optic systems are also included.

Lewis, Norris E.↗

NASA NTRS1979

An efficient approach for computing the geometrical optics field reflected from a numerically specified surface

An approach for computing the geometrical optic fields reflected from a numerically specified surface is presented. The approach includes the step of deriving a specular point and begins with computing the reflected rays off the surface at the points where their coordinates, as well as the partial derivatives (or equivalently, the direction of the normal), are numerically specified. Then, a cluster of three adjacent rays are chosen to define a 'mean ray' and the divergence factor associated with this mean ray. Finally, the ampilitude, phase, and vector direction of the reflected field at a given observation point are derived by associating this point with the nearest mean ray and determining its position relative to such a ray.

Mittra, R.↗

DOE OSTI2025

ExtremeMETA: High-speed Lightweight Image Segmentation Model by Remodeling Multi-channel Metamaterial Imagers

Deep neural networks (DNNs) have heavily relied on traditional computational units, such as CPUs and GPUs. However, this conventional approach brings significant computational burden, latency issues, and high power consumption, limiting their effectiveness. This has sparked the need for lightweight networks such as ExtremeC3Net. Meanwhile, there have been notable advancements in optical computational units, particularly with metamaterials, offering the exciting prospect of energy-efficient neural networks operating at the speed of light. Yet, the digital design of metamaterial neural networks (MNNs) faces precision, noise, and bandwidth challenges, limiting their application to intuitive tasks and low-resolution images. In this study, we proposed a large kernel lightweight segmentation model, ExtremeMETA. Based on ExtremeC3Net, our proposed model, ExtremeMETA maximized the ability of the first convolution layer by exploring a larger convolution kernel and multiple processing paths. With the large kernel convolution model, we extended the optic neural network application boundary to the segmentation task. To further lighten the computation burden of the digital processing part, a set of model compression methods was applied to improve model efficiency in the inference stage. The experimental results on three publicly available datasets demonstrated that the optimized efficient design improved segmentation performance from 92.45 to 95.97 on mIoU while reducing computational FLOPs from 461.07 MMacs to 166.03 MMacs. The large kernel lightweight model ExtremeMETA showcased the hybrid design’s ability on complex tasks.

large convolution kernel↗

NASA NTRS1981

Application of Computer Axial Tomography (CAT) to measuring crop canopy geometry

The feasibility of using the principles of computer axial topography (CAT) to quantify the structure of crop canopies was investigated because six variables are needed to describe the position-orientation with time of a small piece of canopy foliage. Several cross sections were cut through the foliage of healthy, green corn and soybean canopies in the dent and full pod development stages, respectively. A photograph of each cross section representing the intersection of a plane with the foliage was enlarged and the air-foliage boundaries delineated by the plane were digitized. A computer program was written and used to reconstruct the cross section of the canopy. The approach used in applying optical computer axial tomography to measuring crop canopy geometry shows promise of being able to provide needed geometric information for input data to canopy reflectance models. The difficulty of using the CAT scanner to measure large canopies of crops like corn is discussed and a solution is proposed involving the measurement of plants one at a time.

Bauer, M. E.↗

NASA NTRS1990

Spatial light modulators and applications III; Proceedings of the Meeting, San Diego, CA, Aug. 7, 8, 1989

Recent advances in the technology and applications of spatial light modulators (SLMs) are discussed in review essays by leading experts. Topics addressed include materials for SLMs, SLM devices and device technology, applications to optical data processing, and applications to artificial neural networks. Particular attention is given to nonlinear optical polymers, liquid crystals, magnetooptic SLMs, multiple-quantum-well SLMs, deformable-mirror SLMs, three-dimensional optical memories, applications of photorefractive devices to optical computing, photonic neurocomputers and learning machines, holographic associative memories, SLMs as parallel memories for optoelectronic neural networks, and coherent-optics implementations of neural-network models.

Efron, Uzi↗

NASA NTRS1987

Optoelectronic analogs of self-programming neural nets - Architecture and methodologies for implementing fast stochastic learning by simulated annealing

Self-organization and learning is a distinctive feature of neural nets and processors that sets them apart from conventional approaches to signal processing. It leads to self-programmability which alleviates the problem of programming complexity in artificial neural nets. In this paper architectures for partitioning an optoelectronic analog of a neural net into distinct layers with prescribed interconnectivity pattern to enable stochastic learning by simulated annealing in the context of a Boltzmann machine are presented. Stochastic learning is of interest because of its relevance to the role of noise in biological neural nets. Practical considerations and methodologies for appreciably accelerating stochastic learning in such a multilayered net are described. These include the use of parallel optical computing of the global energy of the net, the use of fast nonvolatile programmable spatial light modulators to realize fast plasticity, optical generation of random number arrays, and an adaptive noisy thresholding scheme that also makes stochastic learning more biologically plausible. The findings reported predict optoelectronic chips that can be used in the realization of optical learning machines.

Farhat, Nabil H.↗

NASA NTRS1984

Concentrator optical characterization using computer mathematical modelling and point source testing

The optical characteristics of a paraboloidal solar concentrator are analyzed using the intercept factor curve (a format for image data) to describe the results of a mathematical model and to represent reduced data from experimental testing. This procedure makes it possible not only to test an assembled concentrator, but also to evaluate single optical panels or to conduct non-solar tests of an assembled concentrator. The use of three-dimensional ray tracing computer programs to calculate the mathematical model is described. These ray tracing programs can include any type of optical configuration from simple paraboloids to array of spherical facets and can be adapted to microcomputers or larger computers, which can graphically display real-time comparison of calculated and measured data.

Dennison, E. W.↗

NASA NTRS1992

Ferroelectric/Optoelectronic Memory/Processor

Proposed hybrid optoelectronic nonvolatile analog memory and data processor comprises planar array of microscopic photosensitive ferroelectric capacitors performing massively parallel analog computations. Processors overcome electronic crosstalk and limitations on number of input/output contacts inherent in electronic implementations of large interconnection arrays. Used in general optical computing, recognition of patterns, and artificial neural networks.

Thakoor, Sarita↗

NASA NTRS1993

Model of optical scatter from microimpacts on the Hubble Telescope

The investigation and modelling of optical scatter from damaged or contaminated mirrors is of interest to those who wish to estimate the working life cycle of an optical system. A space born telescope faces a threat to its survival from naturally occurring micrometeoroids and man-made debris. High velocity, in the range of 4 to 14 km/s, impacts of small particles, in the range of 1 to 100 microns, will produce small craters on the impacted surface. These microcraters will typically have a size range of 3 to 300 microns for debris impacts and 6 to 600 microns for micrometeoroid impacts. If the microcraters accumulate on a telescope mirror, there will be an increase in optical scatter and a loss of image resolution. The micrometeoroid model of Cour-Palais and the orbital debris model of Kessler have been encoded in a computer program (SPENV) by the author. The output from this program has been matched with previous calculations and compared with impact data on the LDEF satellite. Subsequent work has been done to marry this computer program with an algorithm to compute optical scatter. The optical scatter algorithm employs Mie theory of scatter from small particles.

Crowell, L. B.↗

NASA NTRS1993

Nonlinear optical thin films

A focused approach to development and evaluation of organic polymer films for use in optoelectronics is presented. The issues and challenges that are addressed include: (1) material synthesis, purification, and the tailoring of the material properties; (2) deposition of uniform thin films by a variety of methods; (3) characterization of material physical properties (thermal, electrical, optical, and electro-optical); and (4) device fabrication and testing. Photonic materials, devices, and systems were identified as critical technology areas by the Department of Commerce and the Department of Defense. This approach offers strong integration of basic material issues through engineering applications by the development of materials that can be exploited as the active unit in a variety of polymeric thin film devices. Improved materials were developed with unprecedented purity and stability. The absorptive properties can be tailored and controlled to provide significant improvement in propagation losses and nonlinear performance. Furthermore, the materials were incorporated into polymers that are highly compatible with fabrication and patterning processes for integrated optical devices and circuits. By simultaneously addressing the issues of materials development and characterization, keeping device design and fabrication in mind, many obstacles were overcome for implementation of these polymeric materials and devices into systems. We intend to considerably improve the upper use temperature, poling stability, and compatibility with silicon based devices. The principal device application that was targeted is a linear electro-optic modulation etalon. Organic polymers need to be properly designed and coupled with existing integrated circuit technology to create new photonic devices for optical communication, image processing, other laser applications such as harmonic generation, and eventually optical computing. The progression from microscopic sample to a suitable film-forming material in a working device is a complex, multifaceted endeavor. It requires close attention to maintaining the optical properties of the electro-optic active portion of the polymer while manipulating the polymer structure to obtain the desired secondary polymer properties.

Leslie, Thomas M.↗

NASA NTRS1985

Levitating Furnance for Containerless Processing in Space

The purpose of this project is to design, construct and test a levitator which would function reliably in a radiant heated cold wall furnace in a reduced gravity environment. A prototype levitating/positioning device termed the Sonic Pump Levitator is designed, built and successfully tested in full gravity and in the reduced gravity of the parabolic flight regime of the KC-135. Positioning is achieved by timely and appropriate application of gas momentum from one or more of six sonic pumps. The sonic pumps, which are arranged orthogonally in opposed pairs about the levitation region, are activated by an electro-optical, computer controlled, feedback system. The Sonic Pump Levitator is a promising candidate for containerless processing in microgravity. Being a null point device, it imposes minimal perturbation on the levitated, or positioned, target. Functioning as it does by optical feedback controlled jets of air, it would be expected to be free from disturbance caused by high temperature. This expectation is now being examined experimentally.

Dunn, S. A.↗

NASA NTRS1998

Crystal Growth of ZnSe and Related Ternary Compound Semiconductors by Vapor Transport

Interest in optical devices which can operate in the visible spectrum has motivated research interest in the II-VI wide band gap semiconductor materials. The recent challenge for semiconductor opto-electronics is the development of a laser which can operate at short visible wavelengths, In the past several years, major advances in thin film technology such as molecular beam epitaxy and metal organic chemical vapor deposition have demonstrated the applicability of II-VI materials to important devices such as light-emitting diodes, lasers, and ultraviolet detectors.The demonstration of its optical bistable properties in bulk and thin film forms also make ZnSe a possible candidate material for the building blocks of a digital optical computer. Despite this, developments in the crystal growth of bulk II-VI semiconductor materials has not advanced far enough to provide the low price, high quality substrates needed for the thin film growth technology. The electrical and optical properties of semiconductor materials depend on the native point defects, (the deviation from stoichiometry), and the impurity or dopant distribution. To date, the bulk growth of ZnSe substrates has been plagued with problems related to defects such as non-uniform distributions of native defects, impurities and dopants, lattice strain, dislocations, grain boundaries, and second phase inclusions which greatly effect the device performance. In the bulk crystal growth of some technologically important semiconductors, such as ZnTe, CdS, ZnSe and ZnS, vapor growth techniques have significant advantages over melt growth techniques due to the high melting points of these materials.

Su, Ching-Hua↗

NASA NTRS1993

Calculating potential fields using microchannel spatial light modulators

We describe and present experimental results of the optical calculation of potential field maps suitable for mobile robot navigation. The optical computation employs two write modes of a microchannel spatial light modulator (MSLM). In one mode, written patterns expand spatially, and this characteristic is used to create an extended two dimensional function representing the influence of the goal in a robot's workspace. Distinct obstacle patterns are written in a second, non-expanding, mode. A model of the mechanisms determining MSLM write mode characteristics is developed and used to derive the optical calculation time for full potential field maps. Field calculations at a few hertz are possible with current technology, and calculation time vs. map size scales favorably in comparison to digital electronic computation.

Reid, Max B.↗

NASA NTRS1993

Self-Amplified Optical Pattern Recognizer

Self-amplified optical pattern recognizers developed for use in recognition of patterns, in optical computing, and in optoelectronic neural networks. In recognizer, photorefractive crystal serves as medium in which one holographically records diffraction-grating filter representing pattern with which recognition sought. Apparatus "self-amplified" because signal amplified within filter to many orders of magnitude greater than in prior optical pattern recognizers. Basic principle of operation applicable to many types of correlation filters, including (but not limited to) Vander Lugt matched filters, joint-transform filters, and phase-only filters.

Liu, Hua-Kuang↗

NASA NTRS2000

Airborne Sunphotometer, Airborne in-situ, Space-borne, and Ground-Based Measurements of Troposoheric Aerosol in Ace-2

We report on clear-sky column closure experiments performed in the Canary Islands during the second Aerosol Characterization Experiment (ACE-2) in June/July 1997. We present results obtained by combining airborne sunphotometer and in-situ aerosol measurements taken aboard the Pelican aircraft, space-borne NOAA/AVHRR data and ground-based lidars A wide range of aerosol types was encountered throughout the ACE-2 area, including background Atlantic marine, European pollution-derived, and African mineral dust. During !he two days discussed here, vertical profiles flown in cloud free air masses revealed three distinctly different layers: a marine boundary layer (MBL) with varying pollution levels, an elevated dust layer, and a very clean layer between the MBL and the dust layer. We found that the presence of the elevated dust layer removes the good agreement between satellite and sunphotometer AOD usually found in the absence of the dust layer. Using size-resolved composition information we have computed optical properties of the ambient aerosol from the in-situ measurements and subsequently compared those to the sunphotometer results. In the dust, the agreement in layer aerosol optical depth (380-1060 nm) is 3-8%. In the MBL there is tendency for the in-situ results to be slightly lower than the sunphotometer measurements (10-17% at 525 nm), but these differences are within the combined error bars of the measurements and computations.

Schmid, Beat↗