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Applied Optics

Applied Optics


  • Vol. 15, Iss. 10 — Oct. 1, 1976
  • pp: 2394–2399

Equidensitometry by coherent optical filtering

H. K. Liu, J. W. Goodman, and J. L-H. Chan  »View Author Affiliations

Applied Optics, Vol. 15, Issue 10, pp. 2394-2399 (1976)

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A new and simple method has been developed for fabrication of multilevel halftone screens that have proved useful for generation of equidensity contours by means of coherent optical filtering. Up to ten contours of constant brightness have been generated on a picture by coherent optical filtering of a single halftone copy of that picture. The possible application of this method to optical analog-to-digital conversion using a single halftone photograph is discussed.

© 1976 Optical Society of America

Original Manuscript: February 23, 1976
Published: October 1, 1976

H. K. Liu, J. W. Goodman, and J. L-H. Chan, "Equidensitometry by coherent optical filtering," Appl. Opt. 15, 2394-2399 (1976)

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  1. H. Kato, J. W. Goodman, Opt. Commun. 8, 378 (1973).
  2. H. Kato, J. W. Goodman, J. Opt. Soc. Am. 63, 1306A (1973).
  3. A. A. Sawchuk, S. R. Dashiell, in Proc. IEEE Int. Computing Conf. (April1975), p. 173; also Opt. Commun. 15, 66 (1975).
  4. T. C. Strand, Opt. Commun. 15, 60 (1975).
  5. S. R. Dashiell, U. Southern California; private communication.
  6. A. Lohmann, T. C. Strand, “Analog-to-Digital Conversion by Optical Means,” in Proceedings of the 1975 Electro-Optical Systems Design Conference, Anaheim, California.
  7. The exact levels Tn(n = 1,2,…,7) required depend on the photographic gamma of the input transparency, assuming that it is the original exposure distribution of this transparency that is to be digitized.
  8. Strictly speaking, no hard-clipping detector is required for the seventh-order image, since the output emerges already in binary form.
  9. Hua-Kuang Liu, Joseph W. Goodman, Nouv, Rev. Optique, Sept. (1976).

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