Abstract: The positions of a plurality of targets (26) are located using three or more sensors (20, 22, 24) such as radars which sense only the bearing angle of the targets. The intersecting bearing lines (30) form triangles (28) representing both true targets (26) and false targets (28). The false target triangles (28) are separated from the true target triangles by analyzing the size and position of each triangle. Bearing data defining the triangles is first ordered and then sequentially examined in a manner such that a first group of false targets (28) is eliminated from consideration. The bearing data defining the remaining triangles is processed through coarse and fine gates to eliminate second and third groups of false targets (28). A fourth group of false targets (28) is eliminated by using a global maximum likelihood procedure, in which a likelihood function is maximized through the use of discrete optimization techniques.

Abstract: In a laser, a gaseous mixture is suitably heated to a first temperature and at a first pressure to provide a large energy content. The gaseous mixture comprises a polyatomic gas such as carbon dioxide having an upper level, ground state, and intermediate level. It also comprises at least one auxiliary gas such as nitrogen, having an energy level substantially resonant with one of the above-mentioned levels and a relaxation time operative to increase the ratio of the relaxation time of the upper level to that of the lower level. A chamber receives the mixture via a supersonic nozzle proportioned to provide a flow time short compared to the relaxation time of the upper level and long compared to the relaxation time of the lower level and the gas is throttled to a relative low second gas temperature and pressure, whereby population inversion exists in the chamber. An optical resonator defines a light path beam through the gaseous medium in the chamber.

Abstract: A multibeam laser amplifier system is disclosed wherein a plurality of laser beams may be amplified to high power with high efficiency. The beams may then be directed upon a target such as a nuclear fusion fuel element, as in a laser fusion reactor. The system is made up of an array of dual, active mirror laser amplifier units. The laser beams are reflected between successively disposed ones of these units. The units are optically pumped by flash lamps which are arranged in close proximity to the reflective sides of the laser bodies in each unit.

Abstract: An intrinsic safety barrier for use in combination with electromagnetic transducers which are intended to generate alternating current signals in hazardous zones and to transmit such alternating signals out of the hazardous zone to remote signal-responsive installations. The intrinsic safety barrier permits transmission of alternating current signals without significant distortion and yet precludes introduction of surges of electrical energy into the hazardous area.

Abstract: A land surface seismic prospecting cable which can be towed on the surface of the earth along seismic survey lines. The cable is used to transport, position, protect, house, or attach sensors used for making geophysical and environmental measurements. The cable apparatus may comprise a plurality of segments each interconnected by an electrical connector and each segment having a plurality of sensors associated therewith. The outputs of the signals from the sensors are carried by way of a multiconductor wire cable within the seismic cable to a seismic recorder. After an acoustic disturbance is produced and the seismic information is recorded, the towed land cable or land streamer is towed intact to the next shooting site which saves a great deal of time and allows greater areas to be covered in a predetermined time period.

Abstract: An elongated seismic source for use in marine seismic explorations consisting of individual seismic sources with one or more sources being grouped in an array. A number of arrays are used with each array being individually supported in the water and coupled by a separate cable to a vessel. The cables are arranged for towing the arrays in a straight line while the vessel contains means for individually controlling the length of the cables.

Abstract: A modulator for monochromatic beam of radiation, such as a laser beam, consists of a semiconductor crystal body. A sufficient potential is applied to the body to produce a moving zone of resistivity and potential gradient varying from the remainder of the body. The zone may result, for example, from the Gunn effect or the piezoelectric effect. The zone also has optical properties differing from the remainder of the body, so that a beam directed at the crystal can be modulated by the moving zone.

Abstract: Seismic exploration method applicable to marine surveys. It involves making a dual spread of detectors which are spaced apart vertically. The signals received at the uppermost spread are delayed sufficiently to make downgoing energy signals in time coincidence with downgoing energy signals from the lower spread. Then the signals from both spreads are algebraically combined so as to cancel downgoing energy signals only.

Abstract: An optical amplifier particularly for use in a high data-rate fibre-optics communication link utilizing a body of a dielectric substance transparent to signal light of a given band of wavelengths and transparent also to pumping light of a different band of wavelengths, a smooth continuous surface along the length of the body having as amplifying component a layer of laser material adhered contiguous to the surface. Both signal light and pumping light are introduced into an end face of the body, which may be a passive dielectric fibre core such as glass, or a passive dielectric slab with parallel side walls, utilising mode order converting holograms. By the phenomenon of penetration by light of both frequencies within a thin layer of the adhered material as the light beams undergo multiple total internal reflections at the interface between the body and the laser material, atoms of active material, e.g. Nd.sup..sup.

Abstract: In the method and means disclosed, an energy source applies energy of varying magnitude, to a substance being tested, and in a sufficient amount to produce detectable variations in a surrounding fluid. The frequency of the energy is varied. A pickup in the vicinity of the sample responds to the detectable variations and produces electrical signals corresponding to the detected variations. A display indicates the intensity of the electrical signals at the different energy frequencies.

Abstract: An electrically conductive product generally comprised of a substrate or web coated with or impregnated with an electrically conductive thermally stable material which includes a special polymeric binder and conductive particles to produce the final conductive sheet.

Abstract: A system for maintaining a continuous log of activity in and around an underground mine wherein seismic energy in the area is continually monitored, processed and classified into meaningful relative data indications; and which system further includes selectively deployable seismic energy monitoring equipment providing more specific data in the event of mine catastrophy. This system utilizes permanently disposed seismic energy detectors and/or emergency detectors placed in accordance with the particular exigency, and detected seismic energy return is continually processed to maintain a data log indicative of general type and location of mine activity, with particular capability for isolation of unusual seismic events by comparison with statistical data constraints of predetermined character.

Abstract: An optical intermediate amplifier intended for a system of communications transmission by means of light waves through optical wave guides employs an optical amplifier for amplifying the light waves on the laser principle. The amplifier is provided with rectangular cross sectional areas traversed by the light waves which correspond in size with the cross-sectional areas of the core zones of the wave guides with which the amplifier is serially coupled, the rectangular cross sectional areas having heights of 0.1 to 10 .mu.m and widths of 100 to 300 .mu.m.

Abstract: An intermediate amplifier for a transmission system intended for communications transmission applications using light waves in optical wave guides employs an optical amplifier for amplifying the light waves on the laser principle, wherein an optical filter is provided to restrict the frequency band of the optical amplifier to the frequency band of the pulses being transmitted. The filter comprises a dielectric multi-layer system arranged upon an inclined surface of the optical amplifier through which the signal light passes in one embodiment. In another embodiment the filter is a zone of the output wave guide of the amplifier which has an absorption characteristic outside of the frequency band of the light pulses which are to be transmitted.

Abstract: A method and apparatus for seismic geophysical exploration including a seismic energy source, a control means, a plurality of geophones, and a plurality of geophone monitoring means, all located in a selected survey area. Each geophone monitoring means is positioned in relatively close physical proximity and electrically coupled to one or more of the geophones forming a set of geophones. The control means is utilized to generate electrical signals containing data initiating the operation of the seismic energy source and the plurality of geophone monitoring means. The electrical signals generated by the various geophones in a set responsive to a particular shot of the seismic energy source are received by the associated geophone monitoring means. Apparatus contained within the associated geophone monitoring means samples such geophone signals and produces representative data in digital form. The digitized data is stored in a memory device contained within the geophone monitoring means.

Abstract: A laser system for producing short optical pulses with higher energy and controllable shape from a high power solid state laser system. The system includes two gratings at the output with an adjustable interferometer between the laser source and an amplifier element. Thus, the output pulse may be tailored to a particular shape.

Abstract: A laser mirror resistant to thermal distortions produced by radiative heating and/or heating by other processes associated with high power CW lasers. A plurality of rods connect a flexible face portion to a stiff base portion to define an "elastic" arrangement which permits free lateral expansion but resists if not prevents distortion in the form of bending of the face portion. The face portion may be formed1. from a block of heat conductive material which has been deeply slotted from its rear end to define an effectively thin face portion attached to a middle portion of high heat capacity, or2. from a thin plate of heat conductive material cooled from the rear face by either forced convection to, or by nucleate boiling of, a flowing heat transfer media in the middle portion.

Abstract: Either of two beams of coherent light has components which are phase shifted and/or attenuated; the phase shifting is alternatively provided in different embodiments by (a) transmitting the coherent light through a phase plate (which may be of variable opacity); (b) processing the coherent light in a second laser-acoustic delay line through which an acoustic wave has been transmitted, or (c) providing in the laser acoustic delay line two acoustic traveling waves, one of which interacts at the Bragg angle with the coherent light. An interaction at the Bragg angle between either of the light beams and a traveling wave generated in a laseracoustic delay line by an electrical rf signal provides a diffracted light beam having a frequency equal to the sum of the light beam frequency and that of the rf signal. A photodetector heterodynes the two light beams thereby providing a modulated rf signal with phase or amplitude modulation in accordance with the phase shift or attenuation of either of the light beams.

Abstract: An optical power amplifier system for extracting high power radiation from a basic active laser media. The system includes a plurality of basically confocal mirrors so positioned that radiation output from a laser is amplified, that no power is absorbed in the supporting structure and it has no feedback from the secondary mirror. In the system, the laser beam passes through the active laser media region at least four times which increases the output power.

Abstract: Near surface anomalies in common depth point seismic surveying are identified by divergence between two records which are obtained by (1) wherein generating a set of common depth point traces with full or partial fold coverage by combining traces containing energy reflected from common depth points and detected in all or a first fraction of the surface detector spread; and (2) generating a further set of common depth point traces with partial fold coverage by combining traces containing energy reflected from the same common depth points but detected in a second fraction of the surface detector spread. The first and second fractions will not be common. Similarly, this technique is used in verifying the accuracy of static corrections applied in seismic processing since erroneous corrections give rise to anomalies which can be identified.