Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1997-05-05
2001-05-01
Pascal, Leslie (Department: 2733)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200, C359S885000
Reexamination Certificate
active
06226113
ABSTRACT:
DESCRIPTION
The present invention relates to filters which operate on the spatial coherence properties of radiation and which are referred to herein as coherence filters. The filters provided by the invention operate on the principle that if a source of radiation has a broad spectrum, such as is the case with many optical sources, the spectrum of the light generated by the source changes as it propagates away from it.
The invention provides a system for spatially modifying the field spectrum by controlling spatial coherence of the source spectrum. Filters provided by the invention are therefore called spatial coherence filters. Transmission properties of the filters depend upon the spatial coherence imposed upon the source spectrum, and the transmission properties determine the spectrum which is filtered both temporally and spatially (as in different directions of observation).
It has been discovered and shown experimentally that the spectrum of radiation emitted by a steady state source depends not only on the spectrum of the source but also on its coherence properties. The spectrum, for example, of light emitted by a source may change significantly on propagation, even in free space. The discovery was reported in Wolf, E.,1986
Phys. Rev. Lett
. 56, 1370 and has been mentioned, for example in
Discovery Magazine
, for August 1988 and experimental verification of the discovery was also reported in Wolf, E. and James, D. F. V., 1996
Rep. Progr. Phys
. 59, 771 and Mandel, L. and Wolf, E., 1995, Optical Coherence and Quantum Optics (Cambridge University Press).
The present invention enables correlation-induced spectral changes to be used to produce new types of radiation filters, which might be called spatial-coherence spectral filters (to be occasionally abbreviated as SCSF). Such filters have several properties that are not possessed by conventional filters. Coherence filters in accordance with the invention are obtained because of the discovery that by controlling the spectral degree of coherence of light transmitted via a transmission control system without changing the spectrum of the light in the transmission control system, different filtering properties or characteristics can be provided which manifest themselves in the radiation propagated from the transmission system. The filtering effect is observed in the far field for example, (Franhoffer region), but the distance from the system may be reduced by optical transformation, (e.g. Fourier transformation), using a lens. The filters can, for example, have different prescribed filtering properties in different directions of observation. SCSF, for example may be applied in astronomy (in the search for particular spectral lines) or in optical computing (to develop spectrum-selective optical interconnects). Another area of SCSF applications is cryptography.
Accordingly, it is the principal object of the invention to provide improved systems for filtering radiation using prescribed spatial coherence effects.
It is a further object of the invention to provide improved optical filters and operative in accordance with the principles of spatial coherence (SCSF).
It is a still further object of the invention to provide systems applying SCSF's for applications including spectrometry, optical data processing and cryptography.
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Lukacher Kenneth J.
Lukacher Martin
Pascal Leslie
The University of Rochester
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