Patent US 4,136,954

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.