Analyzer for coherent radiation

Apparatus for determining the wavelength of coherent radiation in the presence of incoherent ambient radiation which, in combination, comprises:

• a Fabry-Perot etalon having at least three regions of different thickness, said etalon having a first surface positioned to receive coherent radiation and a second surface, the average distance between said surfaces being such that the radiation path difference between transmitted portions of radiation impinging on said first surface is substantially greater than the coherence length of incoherent radiation but substantially less than the coherence length of the coherent radiation;
• means for detecting radiation transmitted through each of said regions and generating separate first, second and third signals porportional to the intensity of radiation leaving each of said regions;
• and
• means for processing said signals thorough electronic signal processing elements to detect and determine the wavelength of the coherent radiation,
• means for equalizing the radiation intensity between pairs of said detecting means.

Apparatus for detecting a source of coherent radiation in the presence of noncoherent ambient radiation which, in combination, comprises:

• a Fabry-Perot etalon having at least two regions of different thickness, said etalon having a first surface positioned to receive coherent radiation and a second surface, the average distance between said surfaces being such that the optical path difference between transmitted portions of radiation impinging on said first surface is substantially greater than the coherence length of incoherent radiation but substantially less than the coherence length of the coherent radiation;
• common aperture means for directing radiation to said first surface so that the radiation intensities incident on all parts of said surface are substantially the same;
• means for rotating said Fabry-Perot etalon in a predetermined systematic manner;
• and
• means for detecting radiation transmitted through each of said regions and generating separate signals proportional to the intensity of radiation leaving each of said regions;
• means for effectively subtracting said separate signals so that any steady background signal components caused by noncoherent radiation in said separate signals are substantially eliminated from the resulting difference signal, while the variable signal components caused by the coherent radiation are effectively added;
• whereby said variable signal component is of almost periodic form but of gradually increasing frequency as the impinging coherent radiation makes an increasing angle of incidence relative to said etalon.

Apparatus for detecting a source of coherent radiation in the presence of noncoherent ambient radiation which, in combination, comprises;

• a Fabry-Perot etalon having at least two regions of different thickness, said two regions being formed of a plurality of interdigitated steps, said etalon having a first surface positioned to receive coherent radiation and a second surface, the average distance between said surfaces being such that the optical path difference between transmitted portions of radiation impinging on said first surface is substantially greater than the coherence length of incoherent radiation but substantially less than the coherence length of the coherent radiation;
• means for rotating said Fabry-Perot etalon in a predetermined systematic manner;
• two detector means corresponding to the etalon regions, said detector means having a plurality of interdigitated elements corresponding to the interdigitated steps of the etalon which are adjacent or in contact therewith, said detector means serving to detect the radiation transmitted through each of said regions and generate separate signals proportional to the intensity of radiation leaving each of said regions, the width of said elements being preselected so that they are smaller than the atmosphere scintillation spatial structure;
• means for effectively subtracting said separate signals so that steady background signal components caused by noncoherent radiation in said separate signals are substantially eliminated from the resulting difference signal, while the variable signal components caused by the coherent radiation are effectively added;
• whereby said variable signal component is of almost periodic form but of gradually increasing frequency as the impinging coherent radiation makes an increasing angle of incidence relative to said etalon.

Apparatus for determining the wavelength of coherent radiation in the presence of incoherent ambient radiation which comprises;

• a Fabry-Perot etalon having at least three regions of different thickness, said etalon having a first surface positioned to receive coherent radiation and a second surface, the average distance between said surfaces being such that the optical path difference between transmitted portions of radiation impinging on said first surface is substantially greater than the coherence length of incoherent radiation but substantially less than the coherence length of the coherent radiation;
• means for detecting radiation transmitted through each of said regions and generating separate first, second, and third signals proportional to the intensity of radiation leaving each of said regions;
• means for generating a fourth signal proportional to the difference between said first and second signals;
• means for generating a fifth signal proportional to the difference between said second and third signals;
• and
• means for generating an output proportional to the ratio between said fourth and fifth signals.

Apparatus for detecting a source of coherent radiation in the presence of noncoherent ambient radiation which, in combination, comprises;

• a Fabry-Perot etalon having at least three regions of different thickness, said regions being formed of a plurality of interdigitated steps, said etalon having a first surface positioned to receive coherent radiation and a second surface, the average distance between said surfaces being such that the optical path difference between transmitted portions of radiation impinging on said first surface is substantially greater than the coherence length of incoherent radiation but substantially less than the coherence length of the coherent radiation;
• a plurality of detector means corresponding in number to the number of etalon regions, said detector means having a plurality of interdigitated elements corresponding to the interdigitated steps of the etalon which are adjacent or in contact therewith, said detector means serving to detect the radiation transmitted through each of said regions and generate separate signals proportional to the intensity of radiation leaving each of said regions, the width of said elements being preselected so that they are smaller than the atmosphere scintillation spatial structure;
• and
• means for processing said signals through electronic signal processing elements to detect and determine the wavelength of the coherent radiation.

Apparatus for determining the wavelength of coherent radiation in the presence of incoherent ambient radiation which, in combination, comprises;

• a Fabry-Perot etalon having eight regions of different thickness, said etalon having a first surface positioned to receive coherent radiation and a second surface, the average distance between said surfaces being such that the optical path difference between transmitted portions of radiation impinging on said first surface is substantially greater than the coherence length of incoherent radiation but substantially less than the coherence length of the coherent radiation;
• means for detecting radiation transmitted through each of said regions and generating first, second, third, fourth, fifth sixth, seventh and eighth signals proportional to the intensity of radiation leaving each of said regions;
• said first and eighth signals being applied to a first comparator means to determine the polarity thereof, said second and seventh signals being applied to a second comparator means to determine the polarity thereof, said third and sixth signals being applied to a third comparator means to determine the polarity thereof, and said fourth and fifth signals being applied to a fourth comparator means to determine the polarity thereof;
• and
• the outputs from the first and second comparator means being connected to a first coincidence gate means, the outputs from said second and third comparator means being connected to a second coincident gate means, and the outputs from said third and fourth comparator means being connected to a third coincident gate means, said coincident gate means serving to compute a three-bit wavelength code.