Abstract: A pulse detector achieves high accuracy over a wide dynamic range in providing accurately spaced pulse edge markers that allow measurement of pulse to pulse time intervals. Received input pulses are transformed to a Gaussian like waveform and a single cycle AC signal having a first polarity initial half cycle is derived therefrom, accomplished by subtracting the Gaussian like waveform from a delayed, but substantially time overlapping, copy of that waveform. Upon completion of that initial half cycle, a pulse edge marker is generated. By measuring the time between the pulse edge marker obtained from one inputted pulse and that of the next, a measurement of the pulse to pulse interval is achieved that is of one nanosecond in accuracy.

Abstract: An active recognition system comprises a transceiver, tracking electronics, an optical processor, and a data handler. The transceiver transmits chirped pulses and receives a series of reflected ?replicas of the chirped pulse! replica pulses from ?features of! an object ?of interest!. The tracking electronics controls the transceiver to determine object range for gating the optical processor. The optical processor includes a "signal" Bragg cell driven by the reflection signal so that ?a! throughgoing light ?beam! is angularly redistributed as a function of the local spatial frequency of the acoustic waveform within the modulation aperture of the signal Bragg cell. At a first focal plane, the light defines a one-dimensional light distribution that includes moving spots that correspond to respective reflection replicas.

Abstract: An apparatus, using two acousto-optical tuned filters for determining the wavelength and angle of approach of a light wave.

Abstract: To screen or test the electrical properties of HEMT-like wafers for their quality, the critical layer qualities of a wafer (16) are evaluated by measuring its conductivity (sigma or s) and mobility (mu or m) at upper and lower temperatures, which need only be sufficiently different as to remove uncertainties in the test data but, in practice, are room and liquid nitrogen temperatures. Novel equations show (1) that the crucial quality or merit factor (n.sub.s) the electron sheet density of two-dimensional electron gas (2DEG), can be determined by measuring the total layer conductivity (sigma or s) at the lower or liquid nitrogen temperature and mobility (mu or m) at the upper or room temperature and (2) by measuring overall layer effective mobility (mu or m) at both room and liquid nitrogen (the upper and lower) temperatures to provide a means to measure the value of the 2DEG density, n.sub.s which has better accuracy then where the temperature of mobility is only made at room temperature.

Abstract: A body resistant to abrasion and transmissive to light is provided which is formed essentially of zinc sulfide or zinc selenide having incorporated therein small amounts of tellurium. The body can form a layer over zinc sulfide, zinc selenide, or a conventional substrate such as glass. The substrate is thereby protected against fracture and erosion by environmental forces, such as high velocity impact with rain or other atmospheric particles, encountered by aircraft at high speed and over extended periods of time.

Abstract: A system and method for optically scanning a scene are disclosed. The system is rotated about a pitch axis and a roll axis to provide the desired scanning capability. The system consists of a primary mirror, a secondary mirror, a tertiary mirror and a fold mirror. The fold mirror is located between the primary and secondary mirrors and reflects the light from the field of view along the pitch axis of the system. The light is reflected by a series of plane fold mirrors to the roll axis and out through an exit aperture. Because the light is reflected along the pitch axis and roll axis, the system can be rotated about these axes while the optical output is maintained as required. Rotation about these axes through internal points between the primary and secondary mirrors minimizes the volume swept out by the system during rotation and maximizes the angles through which the system can be rotated.

Abstract: A method and apparatus for phasing the apertures of a multiple-aperture imaging system is disclosed. An imaging system gathers light in either a scanning or a staring mode from a natural or real scene without artificial light sources. The spatial frequency of the image is sensed. The phase of the apertures is adjusted until the spectral power is maximized within a preselected spatial frequency band. When the spectral power is maximized, the apertures are optimally phased.

Abstract: A tool is disclosed for accurately and rapidly finishing optical surfaces. The tool has a plurality of lapping buttons attached to its face for contacting the optical surface to be finished. The lapping buttons are held to the surface of the workpiece by a suction established between the tool and the workpiece. The suction force existing between the tool and the workpiece is monitored by a controller and may be selectively changed as the tool is moved across the surface of the workpiece during lapping operations. As the tool is moved toward the edge of a workpiece, the vacuum applied to those buttons approaching the edge of the workpiece is increased to achieve desired rate of material removal. The invention permits selective control of the amount of vacuum applied to each lapping button to permit maximum grinding and/or polishing to be achieved. The disclosed tool permits the use of a thinner facesheet in an optical system while permitting a complex surface geometry to be ground into the facesheet.

Abstract: A body resistant to abrasion and transmissive to light is provided which is formed essentially of zinc sulfide or zinc selenide having incorporated therein small amounts of tellurium. The body can form a layer over zinc sulfide, zinc selenide, or a conventional substrate such as glass. The substrate is thereby protected against fracture and erosion by environmental forces, such as high velocity impact with rain or other atmospheric particles, encountered by aircraft at high speed and over extended periods of time.

Abstract: A adaptive flow-control regulator is disclosed for use in controlling the circulation of cooling fluid through in a cooled laser mirror. The adaptive flow-control regulator utilizes a temperature-sensitive spring to control the movement of a plunger with respect to an orifice through which cooling fluid flows. Elongation of the spring is controlled by the temperature of the cooling fluid circulating around the spring. As the temperature of the coolant fluid increases from heating of the laser mirror, the spring contracts moving the plunger away from the orifice and allowing a greater volume of coolant to circulate through the mirror, thereby absorbing a greater amount of heat from the mirror structure. As the mirror is cooled by the circulating cooling fluid, the spring moves the plunger toward the orifice, thereby reducing the volume of cooling fluid circulating through the mirror's structure.

Abstract: A lightweight mirror is disclosed in which the core and backsheet of the mirror are constructed from a single piece of glass. The core is lightweighted by drilling or otherwise forming a series of pockets in the core with the machining process proceeding from the front of the core toward the backsheet. A plurality of walls left between each of the adjacent machined-out areas to provide the core with rigidity and to aid in supporting a facesheet on which a reflecting surface is formed. The facesheet is fastened to the rim of the core and to the walls which remain between the adjacent pockets in the core using a frit bonding process.

Abstract: Hydraulic actuators are disclosed which are useful for controlling the reflecting surface of deformable mirrors or positioning the segments a segmented reflecting mirror. In one embodiment electrodistortive actuators are used to control movement of a piston into or out of a reservoir containing a fluid. The fluid controls movement of a second, smaller piston whose movement may be coupled to a surface whose shape or position it is desired to influence. In a second preferred embodiment two sets of actuators are used to permit the disclosed mechanism to impart movement in two directions to the reflecting surface or optical element whose shape or position it is desired to control.

Abstract: A wavefront correction system is provided which uses an achromatic null lens to correct various aberrations introduced in a spherical wavefront when the wavefront is reflected off a non-spherical surface, particularly a parabola. Chromatic aberration, including spherochromatism, is corrected over a relatively wide bandwidth. When used in conjunction with an interferometer and a variable wavelength source, the wavefront correction system provides adequate means for determining relative position errors of the segments of a segmented mirror. The derivative of the phase error is obtained with wavelength by measuring interference for different wavelengths of light. This allows position errors of greater than one half wavelength to be accurately measured.

Abstract: A protective cover is disclosed for covering material contained on spools, such as solder. The cover includes a plurality of tabs which are contained in a cavity to receive the spool. Each of the protective tabs has a horizontal slot engage a flange of the spool to retain the cover about the spool when the spool is placed in the cavity within the cover. One embodiment of the invention includes an elongated slot in one side of the cover to permit material stored on the spool to be withdrawn without removing the spool from the protective cover.

Abstract: A method of forming an epitaxial layer of an oxidic high T.sub.c superconductor on a substantially lattice matched monocrystalline substrate is described. The film is formed by liquid phase epitaxy utilizing a melt containing a nutriment composed of oxides of each element of the oxidic superconductor and a non-oxidic flux for such oxides. The preferred flux is an alkali halide. The monocrystalline substrate on which the film is dsposited is introduced into the melt and an epitaxial layer of oxidic superconductor is formed on the substrate.

Abstract: A momentum balance-mechanism is disclosed in which a mirror or other object which must be rapidly dithered around tip and tilt axes is supported above a base. The momentum balance-mechanism permits rapid dithering of the mirror or other mechanism while minimizing the reaction forces generated by rotation of the mirror or other object. The mirror which is subject to being dithered and a balance weight are independently supported to permit each to rotate about a common center in opposite directions to achieve a momentum-balanced scanning system. The mirror and balance weight are independently supported by two concentrically-located tripods which terminate in a common support base at one end and in two interface fittings at the other end. One of the interface fittings supports the mirror while the other interface fitting supports the balance weight. The mirror and the balance weight rotate about the virtual intersection of the two sets of tripod legs.

Abstract: A construction for a deformable mirror is disclosed in which each of the electrodistortive actuators used to selectively impart deformations to the mirror's reflecting facesheet are mechanically fastened to the facesheet and may be disengaged from the facesheet by operating a fusible link. In one preferred embodiment the fusible link consists of a layer of thermoplastic material covering an electrical resistive element located between the top of the actuator and the point on the facesheet at which the actuator is mechanically bonded to the facesheet. Heat generated by the resistive element may be used to melt the thermoplastic material fastening the actuator to the facesheet. The second preferred embodiment provides a fusible link consisting of an electrocapacitive layer sandwiched between two electrically-conducting layers.

Abstract: A lightweight cooled mirror is disclosed in which cooling of the mirror's reflecting surface is provided by a two-phase fluid contained in an enclosed chamber behind the reflecting surface. The chamber includes an evaporator section in contact with the reflecting surface and a condenser section spaced apart from the reflecting section. The fluid is capable of existing in both liquid and gaseous states. When in a liquid state, the fluid can absorb heat from the reflecting surface which transforms the liquid into a gas. The gas is transported away from the reflecting surface to a section in the enclosed chamber where it gives up the absorbed heat by condensation and is converted back into a liquid which is reused to absorb additional heat from the reflecting surface. The liquid is transported back toward the reflecting surface by a wicking action to complete the closed loop fluid flow system.

Abstract: Monocrystalline lanthanum orthogallate compositions grown along a predetermined crystallographic direction in the form of a single crystal of a size greater than 1 cm in diameter/width and at least 10 cm in length are described. Such compositions include mixed crystal monocrystalline lanthanum orthogallates wherein a portion of the lanthanum is replaced with a rare earth element of smaller ionic radius than lanthanum and/or a portion of the gallium is replaced with Al, Sc or In. The foregoing monocrystalline compositions are particularly suited as superconductor substrates.

Abstract: A thin film superconducting device is described in which the substrate is a single or mixed single crystal of lanthanum orthogallate grown from a pure melt of lanthanum, gallium and additive oxides. A portion of the gallium single crystal can be replaced by Sc, Al or In and/or a portion of the lanthanum can be replaced by a rare earth element of smaller ionic radius than lanthanum to allow for manipulation of the lattice constant.