Optical system including focus-defocus focal plane array compensation technique using liquid crystal phased array
AssigneeRaytheon Company
InventorL. O. Lambert, Jr.
Life of this patent
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Abstract
An optical system is described including an array of photodetectors, each photodetector having a surface, and a focusing system employing a liquid crystal phased array for focusing a beam of electromagnetic energy on the surface of at least one of the photodetectors. The focusing system further includes a focus-defocus technique for periodically defocusing the beam of electromagnetic energy on the surface of at least one of the photodetectors. With such an arrangement, a focusing system is provided wherein fixed pattern noise can be decreased.
Claims9
An imaging optical system comprising:
- (a) an array of photodetectors, each photodetector having a surface;
- (b) means for focusing and for periodically defocusing a beam of electromagnetic energy on the surface of at least one of the photodetectors, said focusing and periodically defocusing means comprising:
- (i) a forward optics assembly disposed within the beam of infrared energy;
- (ii) a liquid crystal phased array configured to focus or defocus or both having a center and disposed with the center of the liquid crystal phased array within the beam of infrared energy;
- and
- (iii) an aft optics assembly disposed within the beam of infrared energy.
An optical system for receiving a beam of electromagnetic energy comprising:
- (a) a forward optics assembly disposed within the beam of electromagnetic energy comprising a first silicon lens and a first germanium lens, the first silicon lens disposed juxtapositional with the first germanium lens;
- (b) a liquid crystal phased array configured to focus or defocus or both having a center and disposed with the center of the liquid crystal phased array within the beam of electromagnetic energy;
- (c) an aft optics assembly comprising:
- a second silicon lens disposed juxtapositional with the liquid crystal phased array;
- a pair of folding mirrors disposed within the beam of electromagnetic energy to reverse the direction of the beam of electromagnetic energy;
- a third silicon lens and a second germanium lens, the third silicon lens disposed juxtapositional with the second germanium lens with the third silicon lens and the second germanium lens disposed within the beam of electromagnetic energy;
- and
- (d) a detector array disposed within the beam of the electromagnetic energy to detect the electromagnetic energy.
A method of operating an optical system comprising the steps of:
- (a) focusing a beam of infrared energy with a liquid crystal phased array on an array of photodetectors and forming an in-focus image comprising an array of pixel values, each pixel represented by a digital word;
- (b) periodically defocusing the beam of infrared energy with the liquid crystal phased array on the array of photodetectors and forming an out-of-focus image comprising an array of pixel values, each pixel value 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 pixel values, each pixel value represented by a digital word indicative of a limited field of view of the optical radar system.
Dependencies are inferred from the claim text.