Imaging apparatus including spatial-spectral interferometer
First Claim
1. A split aperture radiation sensor having an entrance aperture of area A comprising at least two apertures separated by a distance B,a detector array comprising plural transducers arranged to receive focused radiation from said entrance aperture,relay means located between said entrance aperture and said detector array for redirecting and focusing radiation received within said entrance area A onto said detector array,wherein the improvement comprises,phase adjusting means included in said relay means for adjusting the phasing of radiation traversing said relay means from said split aperture as a function of time to produce a time varying diffraction pattern at said detector array, said time varying diffraction pattern having frequency components related to spatial frequencies of radiation incident on said split aperture.
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Abstract
Imaging apparatus for producing the image of a radiating object which exists in a noise-producing background, includes an optical transducer including a focal plane array or radiation detectors. Light collected by a partially filled entrance aperture is relayed to a partially filled focal plane array by relay optics which include one or more variable phase retardation devices. For example, two movable mirrors per dimension driven in push-pull by piezoelectric drives operate as phase shifters. Interference of incident light from separated parts of the entrance pupil at a series of path differences allows the initially distorted image to be dissected into a series of constituent images at several narrow wavelength intervals. The arrangement of the instrument is so chosen that each constituent image carries information about a different region of spatial frequencies. The set of constituent images carries a complete set of spatial frequencies out to a limit much larger than the area of the entrance pupil would ordinarily provide. The detectors in the focal plane are chosen to have a sufficiently wide spectral response to accept all these data. The detectors are arranged at spacings which sample the constituent images adequately for reconstruction. The data collected by the instrument are analyzed by Fourier transformation with respect to imposed path difference by interpolation of detect or samples and by weighting and summing of constituent images.
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Citations
32 Claims
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1. A split aperture radiation sensor having an entrance aperture of area A comprising at least two apertures separated by a distance B,
a detector array comprising plural transducers arranged to receive focused radiation from said entrance aperture, relay means located between said entrance aperture and said detector array for redirecting and focusing radiation received within said entrance area A onto said detector array, wherein the improvement comprises, phase adjusting means included in said relay means for adjusting the phasing of radiation traversing said relay means from said split aperture as a function of time to produce a time varying diffraction pattern at said detector array, said time varying diffraction pattern having frequency components related to spatial frequencies of radiation incident on said split aperture.
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20. A split aperture radiation sensor of aperture area A distributed in a larger area B wherein the aperture area A is separated into pairs of aperture elements which are capable of angular resolution exceeding that associated with the aperture area A and approaching that associated with the area B, said sensor further comprising,
an array of detectors, relay means for redirecting and focusing radiation received at said split aperture onto said detector array, said relay means including phase means for varying paths lengths as a function of time from aperture elements to the detector array to produce a time varying diffraction pattern at said detector array having frequency components related to plural spatial frequencies of radiation incident on said aperture area.
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31. A method of increasing the angular resolution of a radiation sensor of given aperture area A comprising the steps of:
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separating said aperture area A into plural distinct aperture elements separated by distances devoid of aperture elements, providing a detector array, providing relay optics for redirecting and focusing radiation received within said aperture elements onto said detector array, providing phase adjustment means in said relay optics to produce, at said detector array, a time varying diffraction pattern having frequency components related to the spatial frequency of radiation incident on said aperture area, operating said phase adjustment means to cyclically adjust the phase of radiation between maximum and minimum limits, sampling said array as a function of phase adjustment to provide separate sampled arrays, and processing said sampled arrays produced by said sampling to increase the angular resolution of said detector. - View Dependent Claims (32)
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Specification