Abstract: A coating comprised of a broadband transparent binder and multilayer thin film particles is applied to the surface of an object. Each particle has a flat principal surface and the dimensions of the particles are selected so that the flat surface of essentially every particle will align parallel to the nearest portion of the object surface to the particle. There is a leafing or an overlap of the particles parallel to the object surface. The particles form a continuous conformal coating over the object surface. It is preferred that the maximum dimension of the principal surface of each particle be at least 30 microns and, for best results the maximum dimension should exceed 50 microns. Metallic flakes and/or flakes or particles comprised of organic dyes may be included in the coating to further tailor its spectral characteristics. It is preferred that the weight of the particles equals 20 to 40% of the weight of the combination of the particles and the binder.

Abstract: A nonlinear tunable optical bandpass filter of the Fabry-Perot type is disclosed comprising an optically transparent substrate and a plurality of multilayer coatings deposited on a facing side of the substrate. One of the coating layers comprises a spacer being a nonlinear optical coating material having an externally-variable refractive index. The spacer is bounded on two ends by structures of multilayer stacks being alternating thin films of transparent, physically compatible materials. The filter of the invention can be tuned to pass various transmittance wavelengths through the application of external activation apparatus, such as heating by a laser acting on the spacer.

Abstract: An optical system for determining if a target object is an object of a first kind, including means for illuminating the target object along an incident path with coherent light of a selected nature means, for retro-reflecting coherent light from an object of a first kind, means for detecting the nature of light reflected from at least a portion of the target object, means for comparing the nature of the detected light to the selected nature, and means for indicating that said target object is an object of a first kind if the nature of said detected light is the same as the selected nature. Alternative embodiments include encoding interrogating and retro-reflected light signals at both the interrogating station and target stations, and the use of a verification signal directed at the target object prior to illumination of the target object with an interrogating beam.

Abstract: Thermal energy is deposited within the body of an infrared transparent material. The thermal energy heats a radiating material which is opaque and strongly emitting over infrared wavelengths. An infrared image is then radiated from the radiating material. The thermal energy is deposited within the infrared transparent material preferably by providing a reticulated surface and scanning across an exposed portion of the thermal conductor with an electron beam or a laser.

Abstract: A tunable Fabry-Perot filter device including at least three low index substrates having a refractive index less than 2.4 and mounted in parallel relationship so as to present two pairs of facing sides to each other in an optical path and a high index, non-metallic or non-absorbing coating having a refractive index of at least 4.0, the high index coating being placed on the facing sides of each of said low index substrates with the thickness of the coating on at least one of the pairs of facing sides being less than the thickness of the coating on the other of the pairs of facing sides, and spacer means for mounting said low index substrates and adjusting the distance between said facing sides. Preferred substrates are potassium halides, cesium halides, and zinc selenide. High index, non-metallic or non-absorbing coatings are preferably from the group of lead telluride, bismuth telluride, germanium telluride and germanium.

Abstract: A tunable Fabry-Perot filter for transmitting light in the wavelength range from 3-40 microns is disclosed wherein a pair of low index substrates of refractive index less than 2.4 and positioned between an adjustable spacer means have, on their facing sides, a non-metallic coating of refractive index of at least 4.0 and of optical thickness less than one-half the minimum wavelength to be transmitted. Preferred substrates are potassium halides, cesium halides, and zinc selenide, and preferred high index coatings are from the group of lead telluride, bismuth telluride, germanium telluride and germanium.

Abstract: A Fabry-Perot filter device comprising a pair of low index substrates having a refractive index of less than 2.4 and mounted in parallel relationship so as to present facing sides to each other in an optical path. A coating is placed on the facing sides of each of said low index substrates, the coating having an increasing index of refraction away from the sides from about that of the substrate to above 4.0 such that the index increases in increments of from at least 2 steps to continuously. The total coating thickness is on the order of the light wavelength or more. Means are also provided to adjust the distance between the two faces, at least from a distance of from substantially less than a desired wavelength to at least one-half of the desired wavelength.