Image analysis – Histogram processing – For setting a threshold
Patent
1993-04-08
1994-11-01
Moore, David K.
Image analysis
Histogram processing
For setting a threshold
382 48, 356358, 324 7677, G06K 900
Patent
active
053613120
ABSTRACT:
The invention relates to measuring a phase-modulated signal 5. The signal is measured along at least five different steps (P1-P5) corresponding to preselected phase angles of the carrier wave 4. From the associated sets of measured values, at least three sets of measured values are formulated in a manner that from each of the sets a phase value [.phi..sub.i =arctan (Z.sub.i /N.sub.i) where i is equal to or greater than 3] can be calculated. The same correct phase value is computed based upon these three sets for a signal with the frequency of the carrier wave. The essence of the invention is finding that linear combinations of a.sub.i Z.sub.i and a.sub.i N.sub.i can be used for the computation of an accurate phase measurement where the factors a.sub.i are selected so that the phase error, as a function of the preselected phase steps, has at least three zero positions among the measured phase steps (P1-P5). As a result, the systemic errors that normally accompany phase measuring are significantly reduced. The invention is particularly suitable for the evaluation of bar pattern images and multiple-bar pattern images.
REFERENCES:
patent: 4506333 (1985-03-01), Porrot et al.
patent: 4744659 (1988-05-01), Kitabayashi
patent: 4872755 (1989-10-01), Kuchel
Patent Abstracts of Japan, unexamined applications, Aug. 4, 1988, P Field, vol. 12, No. 284, The Patent Office Japanese Government, Method and Device for Analyzing Interference Fringe, No. 63-61925 (18 Mar. 1988).
"Interferometric Phase Measurement Using Spatial Synchronous Detection", by K. H. Womack, Optical Engineering, vol. 23, No. 4, pp. 391-395 (1984).
"Digital Wave-Front Measuring Interferometry: Some Systematic Error Sources", by J. Schwider et al., Applied Optics, vol. 22, No. 21, pp. 3421-3432 (1983).
Carl-Zeiss-Stiftung
Johns Andrew W.
Moore David K.
Ottesen Walter
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