A holographic system is described for forming visible images in real time using holograms sensed with microwave or acoustic waves. Coherent waves are received together with a coherent reference wave at a set of detectors in an antenna array to develop an interference fringe pattern. A visible luminous display of the fringes is produced on a reduced scale by light bulbs driven by the detectors; the light bulbs producing monochromatic, spatially non-coherent visible light. The light from the bulbs is passed through a beam splitter with a portion going through an inverting prism so as to produce an axially symmetric pair of the fringe patterns. A lens delivers the Fourier transform of the double fringes in its focal plane so as to produce a transform which provides the image.
In a microwave holographic device, the main lobe of a microwave antenna is spatially scanned to receive a microwave signal reflected from an object. The received microwave signal is mixed with a reference signal to generate two-dimensional electric information, synchronized with the scanning. The two-dimensional electric information is used to change the optical properties of an electrooptic material, and then the optical property changes are read out to obtain a holographic image.
Described herein are frequency-domain back-projection processes for forming spotlight synthetic aperture radar ("SAR") images that are not corrupted by the effects of multiple-bounce ghosting artifacts. These processes give an approximately exact reconstruction of the multiple bounce reflectivity function (MBRF) .function.(x,y,.gamma.). Specifically, the evaluation of .function.(x,y,.gamma.) in the .gamma.=0 plane gives an approximately exact reconstruction of the true object scattering centers which is uncorrupted by multiple-bounce contributions to the phase history data G(.xi., .theta.). In addition, the non-zero dependence of .function.(x,y,.gamma.) upon the MB coordinate .gamma. can be used to facilitate the identification of features-interest within the imaged region.
Described herein are frequency-domain back-projection processes for forming spotlight synthetic aperture radar ("SAR") images that are not corrupted by the effects of multiple-bounce ghosting artifacts. These processes give an approximately exact reconstruction of the multiple bounce reflectivity function (MBRF) f(x,y,.gamma.). Specifically, the evaluation of f(x,y,.gamma.) in they .gamma.=0 plane gives an approximately exact reconstruction of the true object scattering centers which is uncorrupted by multiple-bounce contributions to the phase history data G(.xi., .theta.). In addition, the non-zero dependence of f(x,y,.gamma.) upon the MB coordinate .gamma. can be used to facilitate the identification of features-interest within the imaged region.
Described herein is an implementation of the IRAMS processing based upon a multi-delay-resolution framework applied to SAR image data measured at different aspect angles. The power of this new embodiment of IRAMS is that it produces a good separation of immediate response scatterer and delayed response scatterer data for the case of anisotropic scattering events, i.e., those in which the scattering intensity depends upon the aspect angle. Two sources of delayed response scattering include multiple reflection scattering events and delayed responses arising from the physical material composition of the scatterer. That is, this multi-delay-resolution IRAMS processing separates immediate response and delayed response scattering for cases in which there exist delayed response scattering data in the original SAR image data at some aspect angles, but the intensity of these delayed response scattering data is weak or non-existent at different aspect angles. Thus, this IRAMS embodiment provides the additional information of the particular aspect angles at which delayed response scattering effects are most important, thereby improving both the estimates of the delayed response scattering data and the immediate response scattering data.
Described herein are frequency-domain back-projection processes for forming spotlight synthetic aperture radar ("SAR") images that are not corrupted by the effects of multiple-bounce ghosting artifacts. These processes give an approximately exact reconstruction of the multiple bounce reflectivity function (MBRF) f(x,y,.gamma.). Specifically, the evaluation of f(x,y,.gamma.) in the .gamma.=0 plane gives an approximately exact reconstruction of the true object scattering centers which is uncorrupted by multiple-bounce contributions to the phase history data G(.xi.,.theta.). In addition, the non-zero dependence of f(x,y,.gamma.) upon the MB coordinate .gamma. can be used to facilitate the identification of features-interest within the imaged region.
