Optical system including focal plane array compensation technique for focusing and periodically defocusing a beam
AssigneeRaytheon Company
InventorsRobert A. Eckel, Jr., Gordon C. MacKenzie, Joseph C. Ottney
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Abstract
An imaging optical system is described including an array of photodetectors, each photodetector having a surface, and a focusing system for focusing a beam of electromagnetic infrared energy on the surface of at least one of the photodetectors. The focusing system further includes a technique for periodically defocusing the beam of electromagnetic infrared energy on the surface of at least one of the photodetectors. With such an arrangement, a scanning and focusing system is provided wherein fixed pattern noise can be decreased.
Claims8
An imaging optical system comprising:
- (a) an array of photodetectors, each photodetector having a surface;
- (b) means for focusing and periodically defocussing a beam of electromagnetic energy on the surface of at least one of the photodetectors, said focusing and periodically defocussing means comprising:
- (i) a primary mirror and a secondary mirror disposed in a catadioptric telescope arrangement and a plurality of relay lenses disposed within the beam of the electromagnetic energy;
- and
- (ii) means for dithering the secondary mirror for defocusing the beam of electromagnetic energy upon the surface of at least one of the photodetectors.
An imaging optical system for receiving a beam of electromagnetic energy comprising:
- (a) an optics assembly disposed within the beam of electromagnetic energy comprising a plurality of lenses disposed within the beam of electromagnetic energy to focus an image at an image plane;
- (b) a detector array disposed within the beam of the electromagnetic energy at the image plane to detect the electromagnetic energy;
- and
- (c) means for dithering one of the plurality of lenses for defocusing the image at the image plane.
A method of operating an imaging optical system comprising the steps of:
- (a) focusing a beam of infrared energy with a plurality of lenses on an array of photodetectors and forming an in-focus image comprising an array of pixels, each pixel represented by a digital word;
- (b) periodically defocusing the beam of infrared energy by dithering one of the plurality of lenses on the array of photodetectors and forming an out-of-focus image comprising an array of pixels, each pixel represented by a digital word;
- and
- (c) differencing the digital word of each pixel of the out-of-focus image with the digital word of a corresponding pixel of the in-focus image to provide a difference image comprising an array of pixels, each pixel represented by a digital word indicative of a limited field of view of the optical radar system.
Dependencies are inferred from the claim text.