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  • 1
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    Optical recognition of statistical patterns (1981)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Optical implementation of the Fukunaga-Koontz transform (FKT) and the Least-Squares Linear Mapping Technique (LSLMT) is described. The FKT is a linear transformation which performs image feature extraction for a two-class image classification problem. The LSLMT performs a transform from large dimensional feature space to small dimensional decision space for separating multiple image classes by maximizing the interclass differences while minimizing the intraclass variations. The FKT and the LSLMT were optically implemented by utilizing a coded phase optical processor. The transform was used for classifying birds and fish. After the F-K basis functions were calculated, those most useful for classification were incorporated into a computer generated hologram. The output of the optical processor, consisting of the squared magnitude of the F-K coefficients, was detected by a T.V. camera, digitized, and fed into a micro-computer for classification. A simple linear classifier based on only two F-K coefficients was able to separate the images into two classes, indicating that the F-K transform had chosen good features. Two advantages of optically implementing the FKT and LSLMT are parallel and real time processing.
    Keywords: OPTICS
    Type: NASA. Langley Research Center Opt. Inform. Process. for Aerospace Appl.; p 145-166
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    Optically activated switch/modulator using a photoconductor and two channel waveguides (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: An optically activated switch was fabricated on LiNbO3 substrate by deposition of photoconductor-metal electrode structure on two channel waveguides obtained by the outdiffusion process. One waveguide was overcoated with a CdS film, and served as a light detector which converted the optical signal in that waveguide into an electric signal. Utilizing the electrooptic effect, this electric signal modulated the light propagating in the second waveguide by changing the refractive index, and the cutoff condition, of the waveguiding channel between two metal electrodes. The waveguides in the optically controlled switch can be either single or multimode. The length of the device can be short in comparison with other switching schemes. When binary optical signals are applied to the two waveguides, the switch can perform logic AND, NEGATION, OR and pseudo-amplification operations.
    Keywords: OPTICS
    Type: Radio Science; 12; July-Aug
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    Studies in optical parallel processing (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Threshold and A/D devices for converting a gray scale image into a binary one were investigated for all-optical and opto-electronic approaches to parallel processing. Integrated optical logic circuits (IOC) and optical parallel logic devices (OPA) were studied as an approach to processing optical binary signals. In the IOC logic scheme, a single row of an optical image is coupled into the IOC substrate at a time through an array of optical fibers. Parallel processing is carried out out, on each image element of these rows, in the IOC substrate and the resulting output exits via a second array of optical fibers. The OPAL system for parallel processing which uses a Fabry-Perot interferometer for image thresholding and analog-to-digital conversion, achieves a higher degree of parallel processing than is possible with IOC.
    Keywords: OPTICS
    Type: NASA-CR-158237
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 4
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    Method and apparatus for producing an image from a transparent object (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The contrast produced from a photographic transparency is controlled by placing the transparency between a pair of partially reflecting mirrors forming walls of an optical cavity. Mirrors trap a collimated laser beam illuminating the transparency so that at least a portion of the beam energy is passed through the transparency plural times. The distance that the light beam travels between the mirrors is controlled as a function of the wavelength of the beam energy to control the phase of light interference in the beam passing through the transparency, thereby controlling the intensity of the beam derived from the mirror downstream of the transparency.
    Keywords: OPTICS
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  • 5
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    Optical digital logic operations by two-beam coupling in photorefractive material (1986)
    In:  Other Sources
    Details
    Publication Date: 2019-07-12
    Description: The nonlinear phenomena of signal beam saturation, pump beam depletion, and optically controlled coupling coefficient of two-beam interaction in photorefractive materials are analyzed. Applications of these phenomena to digital logic operations is discussed and supported by experimental results obtained in photorefractive BaTiO3.
    Keywords: OPTICS
    Type: Applied Optics (ISSN 0003-6935); 25; 1598-160
    Format: text
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