Abstract: A system for automatically controlling a lawn watering system responsive to the moisture content of the soil includes at least one moisture sensor which supplies a signal to a moisture controller to actuate a water supply valve. The moisture sensor has a casing containing two electrodes and an insulating body of synthetic fibers which provide a path to transfer water from the soil to the electrodes.

Abstract: A method and apparatus for stabilizing the frequency at which a laser cavity oscillates comprising a passive system which provides a plurality or continuum of optical paths of differing lengths. The various paths correspond to differences in mode parameters in the cavity, and involve compensating changes in polarization, beam direction, beam divergence, and the like, in exchange for a constant optical path length in the laser cavity. The unchanging optical path length results in a stable frequency of oscillation despite physical changes in the cavity which might otherwise alter that path length.

Abstract: A device for steering a wavefront of electromagnetic radiation comprising a pumping means for coherently pumping a plurality of phase conjugate mirrors with a monochromatic coherent beam having a wavelength substantially the same as the wavelength of the wavefront. The device further comprises an array of phase conjugate mirrors wherein the acceptance of each phase conjugate mirror, for conjugate reflection of the wavefront, is pointing in substantially the same direction, and the phase conjugate mirrors are composed of material responsive to the beam wavelength. The device further comprises a Fourier transform lens, a control reflector positioned such that the reflected beam from the reflector back to the lens is within the acceptance angle of the ray, and a beam splitter positioned between the array and the control reflector for extracting a steered beam. Each phase conjugate mirror may provide amplification of the wavefront, or amplifying lasers may be used.

Abstract: The treatment of biological tissue is effected by a pulsed electric field induced by a time changing magnetic field produced by a magnetic coil or a plurality of magnetic coils. These magnetic coils are arranged in the area of desired treatment and respond to a driving current to induce the pulsed electric field into the localized treatment area. The driving current and concomitant magnetic field generates an electric field waveform that has a first pulse in a positive direction having a selected value followed by a second pulse in a negative direction having a larger value than the first pulse, and in turn followed by a third pulse in the positive direction having a value on the order of the first pulse. The apparatus for applying the driving current includes switching circuitry for energizing the magnetic coils in pairs to induce a symmetrical distribution of the magnetic and electric fields in the treatment area.

Abstract: In an optical radar system a coherent signal is transmitted at a variable position and the return signal, that is, the reflected portion of the coherent signal is received and coherently detected. The transmitter utilizes a scanning laser having an electron beam that impinges upon a variable reflectance mirror that terminates one end of an optical cavity. An oscillating mode is generated within the resonant cavity when the electron beam locally heats the surface of the variable reflectance mirror to create a pixel that reflects light in a diffracted pattern. The receiver utilizes a stable single mode laser to illuminate a variable reflectance surface. A receiver electron beam generates a plurality of receiver pixels at various positions. The diffracted light from each pixel generates a plurality of variable angle local oscillator beams that are summed with the return signal at a beamsplitter. The output of the beamsplitter is applied to the surface of a detector array.

Abstract: A method and apparatus for generating a plurality of secondary directional modes within the resonant cavity of a scanning laser oscillator. A first directional mode is generated by directing an electron beam on a variable reflectance end reflector to create a variable position pixel. A pattern of fixed reflectance material is positioned on the surface of the variable reflectance end reflector to generate the secondary directional modes within the resonant cavity. The oscillation threshold for the secondary directional modes is higher than the first directional mode, thereby allowing the first directional mode to have priority over the second directional modes. The second directional modes occupy the regions of the active laser medium of the resonant cavity not occupied by the first directional mode thereby suppressing the gain of the laser medium therein.

Abstract: A high-energy laser (22) carried in an aircraft (10) directs a laser beam (16) downward to a point (18) on the earth's surface beneath the aircraft (10). The intensity of the laser beam (16) is such that the material at the point (18) of contact is vaporized and thereby caused to emit atomic emission spectra characteristic of the material. A spectrometer (28) carried in the aircraft (10) collects the resulting spectra which is analyzed to determine the type and quantity of chemical elements present in the vaporzied sample. The laser beam (16) is directed at the point (18) on the surface with sufficient energy and for a period of time so as to penetrate the surface layer and vaporize the underlying material more representative of the overall mineral composition present in the region of the sample. A second laser beam from laser (29) is directed to the point (18) of contact to generate radiation for Raman and fluorescence spectrometry.

Abstract: A method and apparatus are disclosed for drilling gas, oil or geothermal wells in geological formations and for "fracing" the pay zones of such wells to increase recovery, using a laser beam projected into the well bore along a beam guide so as to make available laser energy adequate to melt or vaporize the formation under down-hole conditions. Fluid circulation is established via the beam guide to keep the beam path adequately free of contaminants to permit drilling. A novel orifice window is provided to allow transmitting the high energy beam from the surface into a high-pressure, down-hole environment.

Abstract: A regenerative laser device having remotely located optical components. A resonant cavity having a plurality of transverse modes is defined at one end by a highly reflective retrodirective member and at the other end by a retrodirective member formed of a converging lens and a highly transmissive mirror. A body of laser material is located within the resonant cavity, and there are provided means for exciting the material to create a loop gain of the device that is substantially equal to unity. A collimating lens receives light transmitted through the mirror. An energy source supplies additional energy into the resonant cavity through the collimating lens and mirror to increase the radiation, in at least one of the transverse modes, in the resonant cavity.