Optical: systems and elements – Holographic system or element – Using modulated or plural reference beams
Patent
1990-09-21
1991-12-10
Arnold, Bruce Y.
Optical: systems and elements
Holographic system or element
Using modulated or plural reference beams
359 15, 359 28, G03H 104
Patent
active
050712080
ABSTRACT:
Holographic optical elements relatively free of unwanted, secondary fringes are produced by passing the light beam from a laser through a rotating diffusing plate to generate a beam of light having a very limited coherence length and a spatial coherence which changes over a period of time. A photographic emulsion having a mirror supported on its reverse side is illuminated by the beam and interference occurs between this primary illumination and illumination reflected from the mirror, creating fringes. No other interference fringes are formed because of the lack of coherence between secondary reflections and other rays of the incident beam. The rotation of the diffusion plate time averages out speckle patterns which would otherwise occur. Alternatively, the illuminating beam has a high degree of spatial coherence but its temporal coherence is reduced and varied over a period of time by changing the wavelength of a tunable-dye laser. Alternatively to use of the mirror technique the reduced coherence length beam may be divided into two sections which both illuminate the media at an angle after passing through precisely the same path length so that they interfere within the narrow coherence length of the light beams.
REFERENCES:
patent: 4456328 (1984-06-01), Arns et al.
patent: 4458977 (1984-07-01), Arns et al.
patent: 4458978 (1984-07-01), Arns et al.
Siebert, L. D., "Holographic Coherence Length of a Pulse Laser", Applied Optics, vol. 10, No. 3, Mar. 1971, pp. 632-637.
Leith, E. M., and Leon, S., "Construction and Evaluation of HOEs Made in Light of Reduced Coherence", Applied Optics, vol. 23, No. 6, pp. 942-947, Mar. 15, 1984.
Arnold Bruce Y.
Kaiser Optical Systems
Parsons David R.
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