Abstract: A method uses an infrared imaging system to produce an image of a scene. Actual infrared radiation from the scene is detected to form a biased signal representing the radiances of objects wiithin the scene, and the biased signal is diffracted by causing rays of the radiation to pass through an array of lenslets at angles devitated from their normal path. The array includes an infrared transmissive deformable film which retains a pattern stamped into it, the pattern including a plurality of the diffracting lenslets. The diffracted and defocused radiation is detected to form a reference signal, the reference signal is subtracted from the biased signal to obtain an unbiased signal, and an image is generated and displayed in reponse to the unbiased signal.

Abstract: A chopper and method of making same, the chopper being fabricated by initially generating a photomask in conjunction with software. The software provides the lens design to be finally stamped onto the chopper element. A silicon wafer is then etched by reactive ion etching using the photomask to provide the pattern and resulting in a silicon wafer master of the chopper pattern with regions in the shape of lenslets to be formed of desired dimension. The chopper pattern on the silicon wafer is then replicated with a hard material which can be easily stripped from the silicon wafer without damaging either the wafer or the hard material, preferably deposited nickel. The separated nickel replication is then used in conjunction with a heavy press to stamp out sheets of an infrared transmissive flexible film, preferably polyethylene, with the lens pattern in the replication. The film with the lens pattern thereon is the chopper element.

Abstract: A chopper and method of making same, the chopper being fabricated by initially generating a photomask in conjunction with software. The software provides the lens design to be finally stamped onto the chopper element. A silicon wafer is then etched by reactive ion etching using the photomask to provide the pattern and resulting in a silicon wafer master of the chopper pattern with regions in the shape oflenslets to be formed of desired dimension. The chopper pattern on the silicon wafer is then replicated with a hard material which can be easily stripped from the silicon wafer without damaging either the wafer or the hard material, preferably deposited nickel. The separated nickel replication is then used in conjunction with a heavy press to stamp out sheets of an infrared transmissive flexible film, preferably polyethylene, with the lens pattern in the replication The film with the lens pattern thereon is the chopper element. The system is designed to operate in the 8 to 13.5 micron range.

Abstract: A chopper, in an infrared imaging system, is used to scatter infrared radiation from a viewed scene. This scattered radiation is detected with an infrared detector and used to produce a reference signal, which represents the uniform average radiance of the scene. This reference signal may be substracted from a signal representing the unscattered radiation emitted by the scene, to produce a signal that represents only radiance differences and that is an optimal signal for amplification.

Abstract: An optical flexure joint comprises first and second gimbal mounted lens doublets. The first doublet has a positive surface and the second a negative surface. Each lens doublet consists of two common glasses having index of refractions between about 1.4 and 1.9 that produce the same power as if they were a single lens having an index of refraction of 2.0. The first and second doublets when mounted with the positive and negative surfaces mating and the first doublet rotated with respect to the second form a wedge which has an optical deviation equal to the wedge angle; thus the optical flexure joint allows a small rotary motion to occur in an optical system perpendicular to the optical axis without any perceptable image motion.