Abstract: A fiber optic liquid level sensor for measuring the level of multiple immiscible liquids in a container (20). An end of an optical fiber (24) is immersed in the liquids in the container (20). Light is injected into the other end of the fiber. The ratio of transmitted to the reflected light is dependent on the evanescent mode losses to the liquids in the container. The levels of the liquids are derived from the losses, since the absorption per unit length of the fiber is different for each liquid. The relative amounts of liquids in the container are obtained from the amount of absorption.

Abstract: An optical fiber having an index of refraction less than that conventionally available. The low index of refraction fiber 10 of the present invention includes a fiber core 20 of a first index of refraction. The fiber core 20 circumscribes a longitudinal axis, and is surrounded by a cladding layer 30 having a second index of refraction less than the first index of refraction. Included within the cladding layer 30 are a plurality of tube structures 40 arranged about the fiber core 20. The tube structures 40 create a plurality of channels 42 within the cladding layer 20, thereby engendering a low index of refraction therein.

Abstract: A shaft rotation rate sensor for turbine engines. A reflective radial grating on the surface of the turbine shaft is employed in conjunction with an electromagnetic wave source and beam combining elements to mix two beams of frequency f and f.+-..DELTA.f, where .DELTA.f is proportional to the rotation rate of the grating. The source energy is reflected off the grating, and the zero-th and first order transmission from the grating are mixed to give the beat frequency proportional to the rotation rate. The sensor has no moving parts.

Abstract: A speed sensor for a moving vehicle. A transmissive grating is used in conjunction with an electromagnetic wave source and beam combining waveguide to mix two beams of frequency f and f+.DELTA.f, where .DELTA.f is proportional to the speed of the grating relative to the ground. The source energy is reflected off the road to the grating. The zeroth and first order transmission from the grating are mixed to give the beat frequency .DELTA.f proportional to the ground speed. The sensor has no moving parts, and is independent of any gear ratios.

Abstract: Latent fingerprints are detected by upconverting infrared radiation provided by a special dusting powder and digitally imaging the upconverted radiation. In accordance with the principles of the present invention, a real time image of latent fingerprints is obtained by first "dusting" the print with a powdered upconversion material. The print is then illuminated with 1.55 .mu.m infrared radiation using a fiber optic bundle in the form of a probe. The 1.55 .mu.m infrared radiation is converted into several reradiated wavelength bands by the powdered upconversion material. A charge coupled device or diode matrix detector array converts the image of the fingerprint to digital format for real time display and/or transmission over airwaves. The system is a portable latent fingerprint acquisition system that permits rapid fingerprint evaluation and comparison. A method of detecting fingerprints is also disclosed.

Abstract: A fiber optic fuel or liquid level gauge is disclosed which determines the liquid level by measuring the amount of light loss due to evanescent transfer to the fuel or liquid. An optical fiber is supported in the fuel or liquid tank, with a first end adjacent the highest possible liquid level to be measured with a reflector at the first end. The optical fiber extends downwardly through the tank, and its second end is connected to a light source for injecting light into the fiber. The intensity of the input light is compared to the intensity of light reflected from the first fiber end, and the liquid level is calculated from the light loss. The gauge has very high reliability since it has no moving mechanical parts.

Abstract: A precision liquid leak detector 10 free of mechanical moving parts is disclosed herein. The liquid leak detector 10 of the present invention is disposed to measure the rate of change of the volume of a liquid within a container 14. The leak detector 10 includes a light guide 16, implemented as an optical fiber, which is disposed within the container 14 and at least partially immersed in the liquid. The optical fiber 16 includes a fiber core circumscribed by a fiber cladding selected such that evanescent wave loss occurs as a result of immersion of the cladding within the liquid. The optical fiber 16 is positioned in optical alignment with a laser source 26, which injects optical energy therein. The leak detector 10 of the present invention further includes an arrangement 24 for measuring the decrease in the intensity of the injected optical energy occurring over a length of the fiber 16 immersed in the liquid.

Abstract: An optical fiber is constructed by selecting a first material for a core of the optical fiber. The first material has a known coefficient of thermal expansion, .alpha..sub.1, and a known temperature dependent rate of change, dn/dT, of an index of refraction, n. A second material (cladding) has a predetermined coefficient of thermal expansion, .alpha..sub.2, and a radius, R.sub.2, about the axis of the fiber. The radius, R.sub.2, of the cladding is determined such that an effective coefficient of thermal expansion for the fiber is substantially equal to the negative of the product of the reciprocal of the index of refraction of the first material and the temperature dependent rate of change of the index of refraction of the first material, i.e. .alpha.=(-1/n)dn/dT.

Abstract: A .gamma.-ray detector that comprises a dislocation-free single crystal. Typical crystals include silicon and germanium, for example. The crystal is surrounded by an active shield that functions as an anticoincidence counter and a .gamma.-ray detector is disposed adjacent the crystal in order to detect received -65 -rays. The .gamma.-ray detector comprises an imaging proportional counter, scintillation counter, or a .gamma.-ray detecting charge coupled device, for example. The .gamma.-ray detector of the present invention is based on the Bormann effect, which is the anomalous transmission of .gamma.-rays through dislocation free single crystals at the Bragg angle. For extended sources, data processing is provided to separate the directional and wavelength dependence of the intensity variation. The .gamma.-ray detector has angular resolution of at least one arc second and may have an effective aperture of several square meters.

Abstract: A fiber-optic interferometric chemical sensor for detecting chemical vapors in the air. The chemical sensor 10 includes a light source 12 which outputs an optical signal to a first beam splitter 14. The first beam splitter 14 splits the optical signal into first and second components and transfers the optical signal over sensor and reference optical fibers 20 and 22 respectively. The optical fibers 20 and 22 are bonded to the sensor and reference magnetostrictive substrates 24 and 26, which oscillate in response to an oscillating electromagnetic field generated by a coil 28 circumscribing the substrates 24 and 26. The sensor substrate 24 is further coated with a substance to facilitate collection thereon of molecules associated with the chemical vapor being detected. The optical outputs of the optical fibers bonded to the substrates 24 and 26 are then output to second and third beam splitters 16 and 18 respectively, and first and second beam combiners 32 and 34 respectively.

Abstract: A system for detecting the presence of known materials in a body or container. The system incorporates a gamma or X-ray source for irradiating the body with gamma rays to produce X-ray fluorescence of materials contained therein. A directionally discriminate X-ray detector is positioned to intercept X-rays emitted from the body and is adapted to pass only those X-rays having a predetermined wavelength and incident from a specific direction that are characteristic of a material of interest contained in the body. The detector includes a dislocation free single crystal having substantially parallel input and output surfaces. A second crystal aligned parallel to the first crystal may be disposed at a position offset from the first crystal to receive the X-rays transmitted by the first crystal in order to discriminate between materials fluorescing within the body. In a specific embodiment of the invention, the first detector comprises an elongated crystal which pass X-rays in accordance with the Borrmann effect.

Abstract: A stimulated Brillouin scattering (SBS) ring laser gyroscope. The SBS laser gyroscope is fabricated from a single-mode optical fiber waveguide and is optically coupled to a laser to accommodate being pumped in two directions by laser radiation having sufficient energy to induce stimulated Brillouin scattering radiation (SBS). The apparatus includes means for extracting a portion of each of the SBS radiation from the single-mode optical fiber waveguide and superimposing the extracted portions to permit detection of a beat frequency therebetween. The beat frequency detected is indicative of the rate of angular rotation of the area circumscribed by the single-mode optical fiber waveguide. Means are provided to accommodate a significant reduction in the required laser pumping power.

Abstract: An X-ray and Gamma ray waveguide, cavity, and method for directing electromagnetic radiation of the X-ray, Gamma ray, and extreme ultraviolet wavelengths. A hollow fiber is used as the waveguide and is manufactured from a material having an index of refraction less than unity for these wavelengths. The internal diameter of the hollow fiber waveguide and the radius of curvature for the waveguide are selectively predetermined in light of the wavelength of the transmitted radiation to minimize losses. The electromagnetic radiation is obtained from any suitable source and upon introduction into the waveguide is transmitted along a curvilinear path. The waveguide may be formed as a closed loop to create a cavity or may be used to direct the electromagnetic radiation to a utilization site.

Abstract: A laser gyroscope for determining rotation of an area circumscribed by two closely adjacent optical fiber waveguides which serve as double laser cavities. Laser oscillation is restricted to one direction only in each optical fiber waveguide with the direction of oscillation in each waveguide being opposite to that in the adjacent optical fiber waveguide. Fractional parts of the laser radiation from the laser oscillation in each optical fiber waveguide are superimposed to develop a beat frequency therebetween which is proportional to the angular rotation of the area circumscribed by the two optical fiber waveguides.

Abstract: An apparatus for determining rotation of an area including optical apparatus for optically circumscribing the area and to guide laser radiation counter-directionally around the circumscribed area. Differences that develop between the clockwise and counterclockwise laser radiation as a function of the rotation of the area are detected to determine the rotation of the area. The optical apparatus includes an optical fiber waveguide which may function as a laser cavity or a ring inferometer path. The ring inferometer may also be provided by at least three reflective surfaces.