Abstract: Apparatus and method are disclosed for providing an improved variable lens and birefringence compensator envisioned for use within the resonator cavity of a laser which is capable of continuous operation. A pair of cylindrical bodies of optical material (12A, B) having a temperature dependent index of refraction are thermally coupled to heat exchange means (14A, B) surrounded by potting material (16) which adds heat to or extracts heat from the exterior surfaces of the cylindrical bodies in order to establish radially dependent thermal and stress gradients within the bodies. The heat exchange means (14A, B) is supplied power through leads (20A, B) and infuses or removes heat in order to establish a thermal gradient which is used to create a dynamic lens of opposite power to that of the laser rod which corrects beam divergence in the lased output. The stress gradient causes the compensator body to behave like a birefringent substance.

Abstract: Gigahertz test jig apparatus (10) is disclosed for providing accurate and reliable evaluation of a wide variety of test devices which propagate signals having frequencies in excess of one gigahertz over a broad range of temperatures. A circular ground wall (12) encloses a multi-layer arrangement of disc-shaped dielectric layers (18, 22) which both enclose and are attached to a conductive ground plane (20). Plated-through holes (26) are deployed at the periphery of each of the discs (18, 20, 22) in order to electrically coupled upper and lower ground rings (24, 25) to the ground wall (12) and the ground plane (20). External jig connectors (16) are mounted in connector holes (14) formed in the ground wall (12). Conductive signal traces (30A, 30B) are etched on the exterior faces of the dielectric discs (18, 22) and are joined to the external jig connectors (16) and test device pin terminals (28) which are arranged to receive and hold a test device (36) such as an integrated circuit.

Abstract: A laser radar system employing a linear FM chirp laser followed by post detection pulse compression by a surface acoustic wave (SAW) device. The system includes an FM chirp modulator that provides the needed tuning range and linearity for pulse compression. This modulation is accomplished by using a high-pressure CO.sub.2 laser with an intracavity electro-optic modulator of CdTe. The frequency of the transmitter laser is accurately controlled through the application of high linearity, high frequency, sawtooth voltages to the two plates of the CdTe crystal, with the voltage waveform applied to one plate being out of phase with that applied to the other crystal plate. With the performance the system offers, absolute radar ranges can be measured to 0.22 m and velocities to 0.37 m/sec.

Abstract: A video signal processing technique for detection and correction of the video signal from a bad video channel is disclosed for use with a video imaging system having a plurality of video channels for providing a video signal for a plurality of video scan lines.

Abstract: Circuitry for using the statistical properties of detected radiation in the time domain to discriminate between stimuli from fire and non-fire sources. Statistical discriminators for fire sensing may be combined with other types of sensors operating in the frequency domain for developing improved sensitivity with better security against false alarms. Such other types of sensors may include peak detectors, zero crossing detectors, second derivative-equal-to-zero detectors, for example. The invention determines the mean or average, the variance or standard deviation, the mean deviation, and the Kurtosis of sampled data in statistical analysis to discriminate between fires and non-fires.

Abstract: A laser radar system employing a linear FM chirp laser followed by post detection pulse compression by a surface acoustic wave (SAW) device. The heart of the invention is the FM chirp modulator that provides the needed tuning range and linearity for pulse compression. This modulation is accomplished by using a high pressure CO.sub.2 laser with an intracavity electric-optic modulator of CdTe. The frequency of the laser is controlled through the voltage applied to the crystal. With the performance the system offers, absolute radar ranges can be measured to 0.22 m and velocities to 0.37m/sec.

Abstract: Feed-through vias (38) of 8 mil and smaller diameter are placed on 25 mil centers or smaller so that the feed-through vias serve only as electrical connections and do not block channels between conductors (24a and 42a). The method for forming such feed-through vias and interconnections utilizes metallic resist (36 and 40) which covers the feed-through vias so that the metallic resist, along with conventional photoresist material, prevent undesired etching of the feed-through vias even in the event of misregistration of the photoresist material.

Abstract: An improved method and apparatus for measuring the aberrated wave slope of an optical beam. The apparatus includes a shearing interferometer having a reference mirror 14 and a steerable mirror 16 mounted perpendicularly to one another with a beam splitter 10 disposed at a 45.degree. angle to each. The beam splitter 10 directs a portion of the incident beam to the reference mirror to form a reference beam 20 and transmits a portion 22 of the incident beam to the steerable mirror. The steerable mirror 16 is pivoted about two mutually perpendicular axes to form a shearing interference pattern at a detector array 24 when a portion of the incident beam is reflected off the steerable mirror 16 and combines with the reference beam 20 reflected off the reference mirror. The reference mirror 14 is periodically displaced to modulate the reference beam 20.

Abstract: A chirp laser system includes an intracavity electro-optical crystal modulated at a relatively high frequency, for example 250 kilohertz, to sweep the frequency of the transmitter laser above and below its nominal center frequency. One of the mirrors of the laser transmitter is adjustable to vary the length of the cavity and to shift the frequency of the transmitter laser. When the frequency of the transmitter laser is shifted, the output amplitude of the laser changes. With the center frequency of the laser at a maximum gain point, the amplitude of the output signals during positive and negative frequency excursions of the transmitter laser will be substantially symmetrical. However, if thermal or other effects cause the frequency of the laser to shift away from the maximum gain point, the output during positive and negative excursions will be asymmetrical.

Abstract: A hot air leak sensor for sensing jet engine bleed air leaks in an aircraft. Infrared detectors are combined with thermal re-radiating elements which are installed in air passages adjacent to the bleed air ducts and downstream of the region where a bleed air leak may occur. The elements are approximately 50% transmissive and 50% absorptive to infrared radiation with wavelengths within the range of approximately 4 to 20 micrometers. Incident radiation within the field of view of the detector is both transmitted and absorbed for re-radiation to the detector. If no incident radiation within the sensor field of view is available, the re-radiating element still responds to the increased airstream temperature resulting from the bleed air leak and supplies radiation to the detector to provide detection of the leak.

Abstract: Optical projection apparatus is disclosed for generating a planar light beam of substantially uniform intensity from a nonplanar multi-element light source projecting a beam having a generally Gaussian intensity distribution. In the preferred embodiment, an optical integrator rod having a faceted end face is used to essentially invert the cross-sectional intensity of the beam entering the entrance face so that when the beam leaves the exit face it has a generally uniform intensity. The body of the integrator rod serves to homogenize the nonplanar source into an exiting beam having substantially planar characteristics.

Abstract: A transverse gas flow RF pumped waveguide laser has been developed utilizing RF discharge waveguide technology in several infrared lasers. Two potential applications have been identified; the pulsed chemical laser and the CW CO.sub.2 laser. In the chemical laser, the flowing gas device provides rapid gas replenishment to maintain high electrical efficiency at high repetition rates. In the CW CO.sub.2 laser, the flowing gas provides efficient cooling so that high output power per unit gain length can be achieved.

Abstract: A fire sensor apparatus of the type having a discriminating fire sensor portion for detecting radiation in at least two different spectral bands associated with a fire and for providing an output signal in response to predetermined amounts of radiation in those spectral bands associated with a particular size and type of fire to be detected. A novel heat sensor channel is provided, which provides a further output signal in response to an amount of detected heat radiation greater than that associated with the fire of the type and size to be detected. A heat override function is thereby provided to permit the generation of an output signal even when contaminants block the action of the discriminating fire sensor portion.

Abstract: A cross-correlation fire sensor circuit includes detectors responsive to heat and light radiation, respectively. Electrical signals from the detectors are processed in two distinct channels through low pass filters and samplers. The sampled signals from the two channels are multipled together and the products are summed over a selected interval to provide a correlation function. This function is compared with an adjustable threshold to provide an indication of fire sensing. The circuit is also included as an adjunct to an existing system to provide improved sensitivity for fire sensing in the presence of noise and enhanced discrimination against false alarms. A ratio window detector circuit is disclosed as an alternative cross-correlator for detected radiation.

Abstract: A HgCdTe photodiode array for detecting mid-wavelength infrared radiation has a laminated structure consisting of a substrate, a heavily doped wide bandgap buffer layer, and a more lightly doped narrow bandgap base layer. Two sets of a orthogonally disposed U-shaped grooves are etched completely through the base layer and partially through the buffer layer, thereby forming a plurality of mesa-shaped structures. Overlying the portion of base layer contained within each mesa is a capping layer of opposite conductivity. The junction of the base and capping layer within each mesa forms a photodiode. In contact with each capping layer is a metalization area for connection of the underlying diode to a readout device. In contact with the buffer layer is another metalization layer for making a common electrical connection to the array of photodiodes. Overlying the mesa surfaces is a layer of passivation which contains a fixed positive charge.

Abstract: A fire detection system incorporating fiber optics and having a selectively energizable light source for applying light pulses to a fiber optics path and a one way light transmitting element, such as a dichroic mirror, at the remote end of the fiber optics path for reflecting the pulses back to the detection portion of the system, thus providing a Built In Test Equipment (BITE) test capability in the system. Instead of a dichroic mirror, a bandpass filter may be used as the light transmitting member. The bandpass filter is selected to transmit light with wavelengths in the range from about 1.3 to 1.5 microns, in which case the light source is a light emitting diode (LED) emitting light at a wavelength of approximately 0.9 microns. The fiber optics path includes a branch which is coupled to the light source. This branch may comprise one fiber of a multi-fiber bundle or it may be an auxiliary fiber of a commercially available fiber optics combiner.

Abstract: In a power supply having transformer coupling for regulation of voltage by a pulsing of primary current, a control circuit integrates the output voltage to obtain a measure of flux and primary current. A comparator monitors the integrated voltage to terminate a pulse of primary current prior to saturation of a core of the transformer. This insures linear operation and efficient transfer of energy from the primary to the secondary windings of the transformer. A sensor of secondary current initiates a new pulse of primary current when the secondary current has decayed to a fractional value of the peak secondary current.

Abstract: A method and apparatus associated therewith for acquiring and maintaining a high quality communication by communication means of the type that includes a detector and focusing means for directing encoded incoming radiation to said detector. Means are provided for determining the location of said radiation upon said detector and for generating an electrical signal responsive to said location. Said electrical signal is applied to electroluminescent means so that there is produced for the user a pattern of illumination indicating the degree of alignment of said communication means with the incoming radiation.

Abstract: A transresistance amplifier particularly adapted for use in a radiation detection system. The amplifier includes a feedback gain stage with a switched capacitor load. The amplifier is arranged to provide an average detector voltage approximating zero thus substantially reducing detector noise and also providing a low equivalent input impedance for increasing injection efficiency. A switched capacitor output load is also provided which allows the total transresistance to be determined by simply selecting an appropriate capacitance value.

Abstract: In this disclosure there is described a novel method for using electrochemical etching to finely polish the surface of a (Hg,Cd)Te substrate resulting in a defect-free infrared detector with enhanced electronic properties. The fine surface polishing is obtained by etching at optimal levels of current density and electrolyte agitation.