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Applied Optics

Applied Optics


  • Vol. 31, Iss. 1 — Jan. 1, 1992
  • pp: 120–125

Image speckle contrast reduction resulting from integrative synthetic aperture imaging

Louis Sica  »View Author Affiliations

Applied Optics, Vol. 31, Issue 1, pp. 120-125 (1992)

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Reduction of image speckle noise with the use of an integrative synthetic aperture imaging technique is studied. It is found that the Fourier inversion of the mutual intensity estimate [ Appl. Opt. 30, 206– 213 ( 1991)] yields an image intensity that corresponds exactly to the illumination of the object with partially coherent light from source optics imaging a delta-function incoherent source. An expression for the signal-to-noise ratio at an image point is derived for a large rough object with delta-function correlated amplitude reflection. A synthetic aperture system receiver of sufficiently small diameter yields image speckle with a signal-to-noise ratio (SNR) equal to 1. When the receiver and the transmitter diameters are equal, the SNR is 2 for linearly polarized speckle. The SNR continues to increase with receiver size and is linear in the diameter for large receiver-to-transmitter diameter ratios.

© 1992 Optical Society of America

Original Manuscript: November 19, 1990
Published: January 1, 1992

Louis Sica, "Image speckle contrast reduction resulting from integrative synthetic aperture imaging," Appl. Opt. 31, 120-125 (1992)

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  1. L. Sica, “Estimator and signal-to-noise ratio for an integrative synthetic aperture imaging technique,” Appl. Opt. 30, 206–213 (1991). [CrossRef] [PubMed]
  2. N. D. Ustinov, A. V. Anufriev, A. L. Vol’pov, Yu. A. Zimin, A. I. Tolmachev, “Active aperture synthesis in observation of objects via distorting media,” Sov. J. Quantum Electron. 17, 108–110 (1987). [CrossRef]
  3. C. C. Aleksoff, “Synthetic interferometric imaging technique for moving objects,” Appl. Opt. 15, 1923–1929 (1976). [CrossRef] [PubMed]
  4. A. Kozma, C. R. Christensen, “Effects of speckle on resolution,” J. Opt. Soc. Am. 66, 1257–1260 (1976). [CrossRef]
  5. J. W. Goodman, “Statistical properties of laser speckle patterns,” in Laser Speckle and Related Phenomena, J. C. Dainty, ed. (Springer-Verlag, New York, 1984), p. 38.
  6. M. Born, E. Wolf, Principles of Optics, 5th ed., (Pergamon, Oxford, 1975) p. 529.
  7. G. O. Reynolds, D. J. Cronin, “Imaging with optical synthetic apertures (Mills–Cross analog),” J. Opt. Soc. Am. 60, 634–640 (1970). [CrossRef]
  8. M. J. Beran, G. B. Parrent, Theory of Partial Coherence (Prentice-Hall, Englewood Cliffs, N.J., 1964), p. 35.
  9. H. H. Hopkins, “The concept of partial coherence in optics,” Proc. R. Soc. London Ser. A 208, 263–277 (1951). [CrossRef]
  10. A. Papoulis, Probability Random Variables and Stochastic Processes (McGraw-Hill, New York, 1965), p. 325.
  11. Ref. 5, p. 41. Analogously, the far-field statistics of speckle at the receiver depend on the intensity reflectivity and shape of the object. See L. I. Goldfischer, “Autocorrelation function and power spectral density of laser-produced speckle patterns,” J. Opt. Soc. Am. 55, 247–253 (1965). [CrossRef]
  12. J. C. Dainty, “Some statistical properties of random speckle patterns in coherent and partially coherent illumination,” Opt. Acta 17, 761–772 (1970). For reviews of various speckle reduction methods see G. Parry, “Speckle patterns in partially coherent light,” and T. S. McKechnie, “Speckle reduction,” both in Laser Speckle and Related Phenomena, J. C. Dainty, ed. (Springer-Verlag, New York, 1984). [CrossRef]
  13. The square aperture is also of interest because it is advantageous to know the object Fourier transform at points on a square grid for purposes of eventual Fourier inversion by the FFT algorithm.
  14. This plot has the same qualitative character as that given in Dainty’s paper in Ref. 12.

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