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Speckle Reduction Using Multiple Tones of Illumination

George, Nicholas and Jain, Atul (1973) Speckle Reduction Using Multiple Tones of Illumination. Applied Optics, 12 (6). pp. 1202-1212. ISSN 0003-6935. doi:10.1364/AO.12.001202.

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The occurrence and smoothing of speckle are studied as a function of the line width for a highly collimated illuminating source. A general theory is presented for speckling in the image of a partially diffuse, phase type of object, which has a variable number of random scattering centers per resolution element. Then, an expression is derived for the wavelength spacing required to decouple the speckle patterns arising from two monochromatic tones in an imaging system, thereby establishing that it is feasible to smooth speckle using multicolor illumination. This theory is verified in a series of experiments using both laser illumination and band-limited light from a carbon arc. With highly collimated sources, we show that speckle appears laserlike for an imaged diffuser even up to line widths of 5 Å. Then, smoothing of speckle is demonstrated in the imaging of a diffuser and for a section of an optic nerve when the illumination is provided by six narrow lines spread over 1500 Å. Since with color-blind, panchromatic viewing the speckle smooths, a direct extension of this method to holographic microscopy, using a multitone laser, should permit one to record and reconstruct holograms of diffraction-limited resolution that are essentially speckle-free.

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Additional Information:© 1973 Optical Society of America. Received 25 September 1972. This work was supported by the Air Force Office of Scientific Research. We acknowledge that J. H. Wayland's and R. J. Bing's interest in making holograms of microcirculatory blood vessels first stimulated our interest in speckle-free holographic microscopy; also we are pleased to acknowledge helpful discussions with D. MacQuigg and R. B. MacAnally as well as the enthusiastic participation of Francois Bertiere in the first series of experiments with the laser sources.
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Air Force Office of Scientific Research (AFOSR)UNSPECIFIED
Issue or Number:6
Record Number:CaltechAUTHORS:20120802-092625932
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Official Citation:Nicholas George and Atul Jain, "Speckle Reduction Using Multiple Tones of Illumination," Appl. Opt. 12, 1202-1212 (1973)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:32870
Deposited On:02 Aug 2012 16:41
Last Modified:09 Nov 2021 21:30

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