Abstract: A catadioptric optical imaging system comprises a dioptric assembly (20) and a catoptric assembly (21), which are positioned with respect to each other to form an imaging system of long focal length. The dioptric assembly (20) comprises two confocal paraboloidal mirrors (22, 23) arranged to form a telescope of the Mersenne type. The catoptric assembly (21) comprises lens elements arranged in two groups, viz., a field group (25) and a relay group (26), which are coaxially disposed with respect to the dioptric assembly (20). Only two different optical materials, viz., calcium fluoride crystal and Hoya LAC7 glass, are used in making the lens elements of the dioptric assembly (20). The dioptric assembly (20) is color-corrected at five wavelengths and has only negligible secondary and higher-order spectra in a wavelength band extending from the ultraviolet region to the near infrared region of the optical spectrum.

Abstract: An apochromatic lens triplet consists of a liquid lens element contained between two glass lens elements, where the two glass lens elements are made of the same material and are geometrically identical to each other but oriented in opposite directions along the optic axis of the triplet.

Abstract: A modified Petzval-type optical objective is provided, whose design form has a long focal length (i.e., 1000 mm) at a large relative aperture (i.e., f/2) over a field of view of 4.2.degree. without vignetting, which is well-corrected for both monochromatic and chromatic aberrations, and which is color-corrected at four wavelengths over a spectral band extending from the visible to the near-infrared regions of the electromagnetic spectrum. The optical objective is made from only two different optical glasses. The design form can be scaled up or down from the 1000 mm focal length by using an appropriate scaling factor.

Abstract: A radio-frequency reflective surface is made of a fabric woven from a yarn having an effective coefficient of thermal expansion of substantially zero over a useful temperature range. The yarn comprises a metallic filament around which non-metallic rovings are wound. The coefficients of thermal expansion of the filament and the roving material are related to each other so that mechanical strain thermally induced in the filament by changes in temperature is counteracted by mechanical strain theremally induced in the rovings. Intermodulation products at yarn intersections of the fabric are substantially zero.

Abstract: An ice shaving system for domestic purposes is formed by coupling the shaft on which a rotary blade of a food processor is mounted to the drive shaft of the motor of garbage disposal unit located under a kitchen sink.

Abstract: An apochromatic lens triplet comprises a liquid lens element contained between two glass lens elements. where the two glass lens elements are geometrically identical to each other but face in opposite directions along an optic axis. Inwardly facing surfaces of the two glass lens elements, which are in contact with the liquid lens element, are spherical. Outwardly facing surfaces of the two glass lens elements are aspherical to optimize performance.

Abstract: An apochromatic lens system consisting of three identical glass lens elements and a liquid lens element is disclosed. The glass lens elements are made from an inexpensive and readily available optical glass, and the liquid lens element is made from a commercially available immersion oil. The lens elements coact to focus optical radiation passing through the system onto a focal surface with a change in focus of less than one-quarter wavelength over a wavelength range from 0.48 micron to 0.72 micron.

Abstract: A lens triplet consisting of two identical aspherical acrylic lens elements and a liquid lens element is well-corrected for chromatic aberration and for spherochromatism, and is diffraction limited over the visible spectrum. The liquid lens element is made of an optical liquid selected because of its compatibility with acrylic for achieving paraxial color correction with negligible chromatic variation of spherical aberration. One surface of each acrylic lens element is aspherized to minimize spherical aberration.

Abstract: A two-phase closed-loop heat transfer system comprises a capillary-type evaporator 10, a condenser 11 (preferably also of the capillary-type), and a vapor conduit 17 through which heat-laden working fluid in vapor phase is driven adiabatically from the evaporator 10 to the condenser 11. The evaporator 10 comprises a plurality of tubes 12 connected in parallel. A helically threaded capillary channel 39 is formed on the cylindrical interior surface of each tube 12, and a wick assembly 33 is positioned longitudinally within each tube 12. Each wick assembly 33 comprises a high-permeability wick 36 within which are embedded a first tubule 34 and a second tubule 35. The first and second tubules 34 and 35 are of low permeability, and have one closed end and one open end. The open end of the first tubule 34 is connected to a feed line 16 through which liquid-phase working fluid is delivered into the first tubule 34.

Abstract: A liquid-propellant tank for a spacecraft is symmetric about a longitudinal axis, and has a transverse partition (15) and a truncated conical partition (16), which divide the interior of the tank into a remote chamber (20), a proximate peripheral chamber (21) and a proximate axial chamber (22). Communication between the remote chamber (20) and the proximate peripheral chamber (21) is provided by a port structure (23), and communication between the proximate peripheral chamber (21) and the proximate axial chamber (22) is provided by a port structure (24). As liquid propellant is withdrawn from the tank, pressurant gas in the remote chamber (20) causes liquid propellant to pass from the remote chamber (20) into the proximate peripheral chamber (21) to replace liquid propellant thereby forced from the proximate peripheral chamber (21) into the proximate axial chamber (22), which replaces the liquid propellant withdrawn from the tank.

Abstract: A two-phase closed-loop heat transfer system comprises a capillary-type evaporator 10, a condenser 11 (preferably also of the capillary type), and a vapor conduit 17 through which heat-laden working fluid in vapor phase is driven adiabatically from the evaporator 10 to the condenser 11. The evaporator 10 comprises a plurality of tubes 12 connected in parallel. A helically threaded capillary channel 39 is formed on the cylindrical interior surface of each tube 12, and a wick assembly 33 is positioned longitudinally within each tube 12. Each wick assembly 33 comprises a high-permeability wick 36 within which are embedded a first tubule 34 and a second tubule 35. The first and second tubules 34 and 35 are of low permeability, and have one closed end and one open end. The open end of the first tubule 34 is connected to a feed line 16 through which liquid-phase working fluid is delivered into the first tubule 34.

Abstract: A radio-frequency reflective surface is made of a fabric woven from a yarn having an effective coefficient of thermal expansion of substantially zero over a useful temperature range. The yarn comprises a metallic filament around which non-metallic rovings are wound. The coefficients of thermal expansion of the filament and the roving material are related to each other so that mechanical strain thermally induced in the filament by changes in temperature is counteracted by mechanical strain thermally induced in the rovings. Intermodulation products at yarn intersections of the fabric are substantially zero.

Abstract: An aircraft velocimeter comprises means for projecting three pairs of independently generated ribbon-shaped laser beams to a measurement volume located at a predetermined distance from the aircraft with a predetermined separation being maintained between the two ribbon-shaped laser beams of each pair at the measurement volume. The times of flight of atmospheric aerosol particles between the two ribbon-shaped laser beams of corresponding pairs of laser beams are measured as the aerosol particles pass through the measurement volume. From the predetermined distance between the two ribbon-shaped laser beams of each pair and the measured time of flight of an aerosol particle across that predetermined distance, a component of velocity of the aerosol particle relative to the aircraft is calculated for each pair of ribbon-shaped laser beams.

Abstract: Two optical beams of different frequencies are focussed as concentric spots, one spot being larger than the other, on a reflective surface whose roughness is to be measured. The smaller spot has a maximum dimension that is smaller than any significant deviation of the profile of the surface from spatial uniformity, and the larger spot has a minimum dimension that is larger than any significant deviation of the surface profile from spatial uniformity. The two beams are reflected from the surface along a common path with a phase difference that is measured by a heterodyne interferometric technique. The phase difference measurement is indicative of the roughness of the surface, and is substantially insensitive to vibration of the surface.

Abstract: A catadioptric optical imaging system comprises a dioptric assembly (20) and a catoptric asembly (21), which are positioned with respect to each other to form an imaging system of long focal length. The dioptric assembly (20) comprises two confocal paraboloidal mirrors (22, 23) arranged to form a telescope of the Mersenne type. The catoptric assembly (21) comprises lens elements arranged in two groups, viz., a field group (25) and a relay group (26), which are coaxially disposed with respect to the dioptric assembly (20). Only two different optical materials, viz., calcium fluoride crystal and Hoya LAC7 glass, are used in making the lens elements of the dioptric assembly (20). The dioptric assembly (20) is color-corrected at five wavelengths and has only negligible secondary and higher-order spectra in a wavelength band extending from the ultraviolet region to the near infrared region of the optical spectrum.

Abstract: A catadioptric optical imaging system comprises a dioptric assembly (20) and a catoptric assembly (21), which are positioned with respect to each other to form an imaging system of long focal length. The dioptric assembly (20) comprises two confocal paraboloidal mirrors (22, 23) arranged to form a telescope of the Mersenne type. The catoptric assembly (21) comprises lens elements arranged in two groups, viz., a field group (25) and a relay group (26), which are coaxially disposed with respect to the dioptric assembly (20). Only two different optical materials, viz., calcium fluoride crystal and Hoya LAC7 glass, are used in making the lens elements of the dioptric assembly (20). The dioptric assembly (20) is color-corrected at five wavelengths and has only negligible secondary and higher-order spectra in a wavelength band extending from the ultraviolet region to the near infrared region of the optical spectrum.

Abstract: Design forms for wide-field mapping lenses are disclosed wherein limitations on resolving power attributable to monochromatic aberrations have been minimized, wherein chromatic aberration has been minimized over a broad wavelength band and has been reduced to zero for paraxial marginal rays at three discrete wavelengths, and wherein chromatic variations of the monochromatic aberrations (particularly chromatic variation of coma) have been substantially eliminated. Each of the lenses disclosed has an aperture diameter in the range from 10 to 15 inches, a focal length in the range from 200 to 300 inches, and a circular field of view in the range from 40.degree. to 60.degree.. Further, each lens is diffraction limited in a spectral range from 0.50 to 0.80 micron over the entire field of view. The focal surface for each lens disclosed is curved, so that illumination fall-off from the center to the edge of the focal surface varies by a factor of only about cos.sup.1.5 .theta., where .theta.

Abstract: A self-aligned metal gate is formed on a semiconductor substrate surface between a source region and a drain region of the substrate. Precise alignment of the boundaries of the gate with the boundaries of the source and drain regions is obtained by shadowing a photoresist coating over metal deposited onto the substrate surface, while photochemically dissociating the photoresist over metal deposited onto an oxide layer formed over the source and drain regions of the substrate. The developed photoresist is removed, and the undeveloped photoresist is hard-baked to serve as a protective coating for the metal between the source and drain regions. The metal over the source and drain regions is etched away, leaving the metal between the source and drain regions to function as an electronic gate.

Abstract: An inflation-controlled parachute comprises a canopy (10) for providing an aerodynamic drag-producing surface, and an inflation-control line (21) for controlling the rate at which the canopy (10) unfolds from a stowed configuration to an inflated configuration. The inflation-control line (21) is threaded through an anti-fouling tube (20) attached to the canopy (10). When the canopy (10) is in the stowed configuration, the inflation-control line (21) overlaps itself within the anti-fouling tube (20). As the canopy (10) unfolds to the inflated configuration, overlapping portions of the inflation-control line (21) slide against each other and against an inner surface of the anti-fouling tube (20). Frictional engagement of the overlapping portions of the inflation-control line (21) with each other and with the inner surface of the anti-fouling tube (20) provides resistance to the unfolding of the canopy (10), thereby controlling the rate of inflation of the canopy (10).

Abstract: An optical effects device which is adaptable as a container is disclosed. The device is a hollow, elongated structure having a viewing port at one end and an opaque wall at the other. The opaque wall has an apertured portion of predetermined design to admit light. The interior of the device is bounded by a plurality of substantially planar interior walls that are light reflective and extend from one end of the hollow structure to the other. Light passing through the apertured portion of the end wall is reflected by the interior walls to form corresponding images of the aperture in a generally annular arrangement around the apertured portion of the end, wall when a viewer looks into the interior of the hollow structure through the viewing port.