Optical: systems and elements – Diffraction – Using fourier transform spatial filtering
Patent
1994-05-02
1997-01-14
Callahan, Timothy P.
Optical: systems and elements
Diffraction
Using fourier transform spatial filtering
359 29, 359338, 359339, 359349, G02B 2746, G02B 523
Patent
active
055945864
ABSTRACT:
Limiting quadratic processing and compansion in photorefractive two beam coupling is disclosed. Two-beam coupling in photorefractive barium titanate employs the imaged intensity of the signal to amplify the reference beam while maintaining the phase of the reference beam. The phase distorted signal beam is converted to that of the controlled phase of the reference beam. The high pump limit of amplification in this two-beam coupling device produces an amplitude compressed output to reduce multiplicative noise. Lost contrast of the image is thereafter restored. Beam clean-up of a non-intelligence bearing beam can be carried out by a similar process; a low pass filter consisting of a pinhole plate can be used in place of the second photorefractive crystal in the Fourier plane and only the planar wavefront portion will pass through the pinhole and may be collimated by a lens to provide a cleaned planar output beam.
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Cronin-Golomb Mark
Fu Jack
Khoury Jehad
Woods Charles L.
Callahan Timothy P.
Collier Stanton E.
Nathans Robert L.
Nu Ton My-Trang
The United States of America as represented by the Secretary of
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