Spectrally-scanned hyperspectral electro-optical sensor for instantaneous situational awareness

An electro-optic (EO) sensor, comprising

• a corrected objective optical system that forms an image along an optical axis from incident optical radiation simultaneously collected within a field of view (FOV), said objective optical system corrected to reduce a separation of spectral components of the incident optical radiation along the optical axis to an axial chromatic aberration of at most f/2,000 where f is a prime focus position;
• a chromatic aberration enhancing device configured to separate the spectral components of the incident optical radiation in the FOV along the optical axis with an axial chromatic aberration of at least f/100, said separation of spectral components by the enhancing device providing a change in spatial image contrast as a function of position along the optical axis;
• a mechanism configured to move the chromatic aberration enhancing device in and out of an optical path along the optical axis;
• a detector spaced along the optical axis that converts the incident optical radiation into an electrical signal representative of an entire image frame;
• and
• a focus cell configured to temporally adjust a relative focus of the objective optical system with respect to said detector to at least two different axial focus positions,
• a processor configured to alternately command the mechanism to move the enhancing device out of the optical path, command the focus cell to adjust the relative focus to the axial focus position and to process the electrical signal to extract a gray-scale image frame, command the mechanism to move the enhancing device into the optical path, command the focus cell to adjust the relative focus to the at least two different axial focus positions and to process the electrical signal, which is temporally encoded by the at least two different axial focus positions and a corresponding image frame, to compute a relative spatial image contrast metric within an image comprising one or more of the image frames as a function of encoded focus cell position and the prime focus position for a component of a spectral distribution of the incident optical radiation.

A method of retrofitting an existing gray-scale electro-optic (EO) sensor to be useful as a hyperspectral EO sensor, said gray-scale EO sensor comprising a corrected objective optical system that forms an image on an optical axis from incident optical radiation simultaneously collected within a field of view (FOV), said objective optical system corrected to reduce a separation of spectral components of the incident optical radiation along the optical axis to an axial chromatic aberration of at most f/2,000 where f is a prime focus position, a broadband detector that converts the incident optical radiation into an electrical signal representative of an entire image frame, and a focus cell configured to adjust a relative focus of the objective optical system with respect to said detector to the prime focus position, the method comprising:

• placing a chromatic aberration enhancing device in an optical path along the optical axis, said chromatic aberration enhancing device configured to separate the spectral components of the incident optical radiation in the FOV along the optical axis with an axial chromatic aberration of at least f/100, said separation of spectral components by the enhancing device providing a change in spatial image contrast as a function of position along the optical axis;
• commanding the focus cell to adjust the relative focus to at least two different axial focus positions;
• generating the electrical signal from the broadband detector, which is temporally encoded by at least two different axial focus positions and a corresponding image frame;
• and
• processing the electrical signal to compute a relative spatial image contrast metric within an image comprising one or more image frames as a function of encoded focus cell position and the prime focus position for a component of a spectral distribution of the incident optical radiation.