US 4,397,558 A · System for reducing the effects of background radiation

Abstract

A system for reducing the effects of background radiation on a desired signal includes a plurality of physically spaced phase shifters arranged in a two-dimensional array and disposed in the path of the desired signal for cancelling the background radiation while passing the desired signal without substantial attentuation. In a second embodiment, the desired signal is split into two beams which traverse different paths and passed through two complementary two-dimensional arrays of physically spaced attenuators, each array being disposed in one of the paths. A phase shifter is disposed in one or both of the paths and the signals from the two paths are recombined to cancel the background radiation. The two-dimensional arrays of physically spaced phase shifters may be integrated into the beam splitters.

Claims50

Dependent claims

A device for reducing the effects of background radiation comprising:

phase shift means including a plurality of two-dimensionally spaced elements for shifting the phase of a wavefront impinging thereon to produce a wavefront having portions thereof shifted by substantially 180.degree. with respect to each other in a two-dimensional array to thereby produce a diffraction pattern having at least one area of reduced intensity radiation;
means for receiving an incident beam of radiation containing radiation from a source of desired radiation and undesired radiation and focusing said beam such that most of said desired radiation is concentrated on a single one of said elements while the undesired radiation is spread over several of said elements;
and
means for refocusing the phase shifted wavefront emanating from said phase shift means to produce an image of said source of desired radiation superimposed on an area of reduced intensity radiation.

1 more element

A system for reducing the effects of undesired radiation comprising:

a first two-dimensional array of transparent and reflective elements, said transparent and reflective elements being alternated with each other in two dimensions;
first means for directing an incident beam containing desired radiation from a source of desired radiation and undesired radiation onto said first array, said first array being operative to pass a first portion of the incident beam through said transparent elements and to reflect a second portion of the incident beam from said reflective elements;
a second two-dimensional array of transparent and reflective elements, said transparent and reflective elements being alternated with each other in two dimensions;
second means for directing said first portion of the incident beam onto said reflective elements of said second two-dimensional array;
and
third means for directing said second portion of the incident beam onto said transparent elements of said second two-dimensional array, one of said second and third directing means including phase shifting means for shifting the phase of one of said first and second portions of said incident beam with respect to the phase of the other, said second two-dimensional array being operative to combine said first and second portions of said incident beam to thereby generate an interference pattern of said undesired radiation having a two-dimensional array of areas of increased and reduced intensity alternated with each other in two dimensions, said desired radiation being concentrated on one of said reduced intensity areas.

3 more elements

Dependencies are inferred from the claim text.

System for reducing the effects of background radiation

Life of this patent

System for reducing the effects of background radiation

Life of this patent

Abstract

Claims50