Browsing by Author "Almeida, S. P."

Now showing 1 - 7 of 7
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    Coherent spatial-filtering with simulated input
    Fujii, H.; Almeida, S. P. (Optical Society of America, 1979-11)
    A disadvantage of a well-tuned matched filter is partly overcome in recognizing biological species, i.e., algae. A simplified input pattern is prepared which simulates a given species. The matched spatial filter for this pattern can identify various diatoms in the species with considerably less size and orientation dependence. In addition, the filter still retains a high degree of pattern discrimination against other species.
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    Fourier-transform differences and averaged similarities in diatoms
    Almeida, S. P.; Fujii, H. (Optical Society of America, 1979)
    Phase contrast photographs of diatoms are characterized from their Fourier transform taken through an optical diffractometer. The system output is placed on line to a PDP11/40 providing digital subtraction of two output spectral distributions due to different species. Differences obtained in this manner are used for characterizing various species. An average Fourier transform taken through coherent additions is also analyzed to find common features in a given set of diatoms.
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    Multispectral size-averaged incoherent spatial filtering
    Almeida, S. P.; Case, S. K.; Dallas, W. J. (Optical Society of America, 1979-08)
    A method of 2-D size-averaged incoherent recognition filtering is described. White light input illumination is used to multiplex chromatically a continuum of inputs differing in their spatial Fourier spectral magnifications. A two-grating dichromated-gelatin lateral-dispersion compensating device is inserted to correct chromatic dispersion introduced by a computer-generated hologram filter. The resulting registered recognition patterns are added to form a single effective filter size-averaged recognition peak. Using high efficiency compensating gratings and a bleached binary hologram allow the use of a relatively low-power light source.
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    Optical Fourier-transform characterization of fish scale age
    Almeida, S. P.; Wygant, R. W.; Jearld, A.; Penttila, J. A. (Optical Society of America, 1987-04)
    Optical Fourier transforms of haddock fish scales were made for fish taken from two different bodies of water. The scales in each group varied in age from 2 to 10 yr. A comparison of the image processed digitized Fourier transforms for the scales was made on a personal computer. Statistical correlation studies of these transforms were performed, and the results show a fairly good age discrimination between the scales in each age group.
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    Rotational matched spatial filter for biological pattern recognition
    Fujii, H.; Almeida, S. P.; Dowling, J. E. (Optical Society of America, 1980-06)
    Randomly oriented microbiological patterns are recognized by rotating a matched spatial filter with an optical wedge prism. The filter is made from a composite input pattern with various sized objects to cover wider ranges of size variation in a species to be identified.
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    Surface inspection via projection interferometry
    Wygant, R. W.; Almeida, S. P.; Soares, O. D. D. (Optical Society of America, 1988-05)
    Projection fringe interferometry provides a useful technique for nondestructive surface analysis. Two beam interferometric fringes were projected onto a block of aluminum whose surface had various types of grooves cut into it. The fringes were digitized and analyzed via an automatic fringe tracking algorithm. Three-dimensional topographical maps of the surface's microstructure are presented together with a statistical analysis of surface parameters including average roughness, height distributions, and the autocorrelation function.
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    Water-pollution monitoring using matched spatial filters
    Almeida, S. P.; Eu, J. K. T. (Optical Society of America, 1976-02)
    Presented are some results obtained from the application of matched spatial filtering techniques to the identification of biological specimens called diatoms (i.e., water algae). A prototype semiautomatic optical processor has been developed that utilizes the Vander Lugt type complex spatial filters. We describe the optical filter averaging technique employed and discuss our semi in situ developing method for the filters. The advantage of this method with regards to the critical position requirements for time sharing optical filters is also presented. The filter holder is mounted on X, Y stages and precision positioned under the control of a PDP-11-40 computer.