Image analysis – Histogram processing – For setting a threshold
Patent
1991-04-26
1993-02-09
Boudreau, Leo H.
Image analysis
Histogram processing
For setting a threshold
356359, 356376, G06K 900, G01B 1124, G01B 902
Patent
active
051858100
ABSTRACT:
The optical testing method of the invention permits the reliable elimination of discontinuities, i.e., the determination of the integer values of modulo 2.pi. phase differences, even when the measured data includes seriously noisy signals. The intensity signals from a two-dimensional raster of camera image points are used to compute differences in phase values between adjacent image points in lines, as well as between adjacent image points in columns. The phase differences are summed along a closed path around each of a plurality of partial fields which are delineated by a predetermined set of adjacent image points. A filter (21) searches the vector field of these phase differences; and those partial fields where vortexes exist, i.e., each field for which the sign-correct sum along its closed path is not zero, are masked, thereby creating holes in the image pattern. Additional closed paths are summed around these holes and, by masking further image points between these holes, the masked partial fields are combined until the path integral around each of these combined holes disappears. The final phase value data used for display of a phase map of the sample is calculated by path integration of the unmasked image points; and inconsistent measured values, e.g., due to noisy signals, do not corrupt the phase map.
REFERENCES:
patent: 4768881 (1988-09-01), Juptner et al.
patent: 4791584 (1988-12-01), Greivenkamp
patent: 4832489 (1989-05-01), Wyant et al.
Kazuyoshi Itoh, "Analysis of the Phase Unwrapping Algorithm", Applied Optics, vol. 21, No. 14, p. 2470, 1982.
Dennis C. Ghiglia, et al. "Cellular-automata Method for Phase Unwrapping", Journal of Optical Society of America, vol. 4, No. 1, pp. 267-280, 1987.
Boudreau Leo H.
Carl-Zeiss-Stiftung
Kelley Christopher
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