Spectral, polar and spectral-polar imagers for use in space situational awareness
An imager for imaging a plurality of images of a single scene over a plurality of disparate electromagnetic wavelength sets includes front-end optics for outputting a polychromatic, collimated image beam of the scene; a beam displacer configured for splitting the collimated image beam into spatially displaced, mutually parallel beams, and an imaging-sensor array configured for registration of the spatially displaced wavelength sets at disparate locations along the imaging-sensor array. In alternative versions, the beam displacer displaces constituent light beams based on at least one of wavelength and polarization. In various implementations, a back-end focusing element focuses each constituent beam onto a predetermined location along the imaging-sensor array. The imaging-sensor array is optimally configured for simultaneous sampling of the plural images focused thereupon by the back-end focusing elements.
1. An imager for imaging a plurality of spatially-correlated images of a single scene over a plurality of disparate electromagnetic wavelength sets representing correspondingly disparate color bands, the apparatus comprising:
front-end optics configured for outputting a polychromatic, collimated image of a selected scene;
a first optically-dispersive element spatially situated for receiving the collimated image and dispersing disparate constituent wavelength sets within the received collimated image such that the disparate constituent wavelength sets mutually angularly diverge away from the first optically-dispersive element, wherein the mutual angular divergence of the electromagnetic wavelength sets results from the optical phenomenon of dispersion in which the phase velocity of a wave depends on its frequency such that the paths of the constituent wavelength sets within the received collimated image are bent by the first optically-dispersive element to different angles and the colors represented by the disparate constituent wavelength sets are mutually angularly separated;
a second optically-dispersive element spatially situated for receiving the wavelength sets dispersed by the first optically-dispersive element and reducing the degree of mutual angular divergence, while maintaining mutual spatial displacement, among the wavelength sets, wherein the reduction in mutual angular divergence imparted by the second optically-dispersive element also results from the optical phenomenon of dispersion; and
an imaging-sensor array configured for registration of the spatially displaced wavelength sets at disparate locations along the imaging-sensor array.
2. The imager of claim 1 further comprising a plurality of back-end optical focusing elements, each focusing element aligned for focusing upon a corresponding location on the imaging-sensor array the electromagnetic wavelengths associated with one of the spatially displaced wavelength sets.
3. The imager of claim 2 further comprising an optical polarizer for displacing the collimated light based on polarization.
4. The imager of claim 1 wherein
(i) the front-end optics have associated therewith an exit pupil;
(ii) each optical focusing element has associated therewith a focusing-element entrance aperture; and
(iii) the focusing-element entrance aperture of each optical focusing element is at least as large as the exit pupil of the front-end optics.
5. An imager for imaging a plurality of spatially-correlated images of a single scene over a plurality of disparate electromagnetic wavelength sets representing correspondingly disparate color bands, the apparatus comprising:
front-end optics configured for outputting a polychromatic, collimated image of a selected scene;
a first optically-dispersive element spatially situated for receiving the collimated image and dispersing disparate constituent wavelength sets within the received collimated image such that the disparate constituent wavelength sets mutually angularly diverge away from the first optically-dispersive element, wherein the mutual angular divergence of the electromagnetic wavelength sets results from the optical phenomenon of dispersion in which the phase velocity of a wave depends on its frequency such that the paths of the constituent wavelength sets within the received collimated image are bent by the first optically-dispersive element to different angles and the colors represented by the disparate constituent wavelength sets are mutually angularly separated;
a second optically-dispersive element spatially situated and oriented for receiving the wavelength sets dispersed by the first optically-dispersive element and canceling the mutual angular divergence, while maintaining mutual spatial displacement, among the wavelength sets, wherein the cancellation of the mutual angular divergence imparted by the second optically-dispersive element also results from the optical phenomenon of dispersion; and
an imaging-sensor array configured for registration of the spatially displaced wavelength sets at disparate locations along the imaging-sensor array.
6. The imager of claim 5 further comprising a plurality of back-end optical focusing elements, each focusing element aligned for focusing upon a corresponding location on the imaging-sensor array the electromagnetic wavelengths associated with one of the spatially displaced wavelength sets.
7. The imager of claim 6 further comprising an optical polarizer for displacing the collimated light based on polarization.
8. The imager of claim 5 wherein
(i) the front-end optics have associated therewith an exit pupil;
(ii) each optical focusing element has associated therewith a focusing-element entrance aperture; and
(iii) the focusing-element entrance aperture of each optical focusing element is at least as large as the exit pupil of the front-end optics.