Abstract: Windshear detector using Rayleigh-backscattered light and a molecular filter for optical discrimination, and frequency locking of a laser, to detect windshear. The windshear detector has a pulsed ring laser that transmits a signal out of the detector and receives reflected backscatter of the transmitted signal. The ring laser is driven with an injection laser. Both lasers are ultimately keyed to the molecular transmission or absorption filter with locking electronics. The received reflected backscatter is detected and processed into a signal that indicates whether there is windshear or turbulence.

Abstract: A solid-block homodyne Doppler interferometer utilizing continuous-wave or pulse-wave light beam technology. A pulse-wave light beam version of the homodyne interferometer compares the pulse-wave return signal with a continuous-wave local oscillator signal, thereby permitting the interferometer to be utilized over a wide range of distances.

Abstract: A laser illuminated helmet mounted sight that determines helmet or sight position from an externally mounted light source. The electronics, including light sources and detectors, are on the helmet. Also, no electrical cables or mechanical linkage is connected to the helmet. The helmet only has passive reflectors for reflecting light beams from a laser source. The return times and directions of the returning light beams processed by off-helmet electronics, result in a position indication of the helmet.

Abstract: A scanning laser helmet mounted sight that determines helmet or sight position from externally mounted light sources and detectors. No electronics, including light sources and detectors, are on the helmet. Also, no electrical cables or mechanical linkage is connected to the helmet. The helmet has passive reflectors for reflecting a scanning light beam from a laser source. The return times and directions of the returning light beam relative to a return of a light beam from a reference point, processed by the off-helmet electronics, result in a position indication of the helmet.

Abstract: A Doppler velocimeter having a semiconductor laser which sends a laser beam through a polarization beam splitter onto an fractional-wavelength plate. The plate both reflects the beam back to the polarization beam splitter and sends the beam on through the beam expander to the target. The beam is returned by the target. The returned beam passes through the fractional-wavelength plate to the polarization beam splitter. The returned and reflected beams are directed by the splitter to a detector. The detector mixes the beams and sends a signal to a spectrum analyzer on which the velocity of the target can be accurately determined.

Abstract: Apparatus is provided for rapidly switching among discrete wavelengths within the output spectrum of a gas laser. A portion of the radiation in a primary optical cavity of a laser is transmitted by a partially reflective surface into a secondary cavity which includes a reflector element and one or more Bragg deflector cells. The Bragg cells are positioned between the primary cavity and reflector element, and frequency shift radiation passing between the primary cavity and reflector element. Each Bragg cell is selectably driven by an RF driver to enhance radiation of a predetermined wavelength within the range of the laser spectrum. Consequently, radiation injected back into the primary cavity from the secondary cavity is essentially of the predetermined wavelength.

Abstract: An optical fiber is processed by ablating cladding material with an intense electromagnetic energy source. The intensity of another beam directed along the propagation axis of the fiber is monitored to detect near exposure of the fiber core. The ablating electromagnetic energy source is preferably circularly polarized. Apparatus for performing this process is disclosed. Fibers produced by this process are used to form optical couplers or, when a metallic layer is provided over the nearly exposed core region, an optical polarizer.

Abstract: Method and means are disclosed for rapidly tuning a laser over a large number of wavelengths. The means of the present invention includes first and second reflecting means which define the optical resonating cavity of a laser, and further includes a dispersive means adapted to sequentially select and direct one and only one of the wavelengths of light from the beam emitted by a laser's amplifying medium along a path back through the laser's amplifying medium as one of the reflecting means is continuously rotated. One embodiment of the present invention forms the rotating reflecting means as a faceted polygonal solid with at least one face thereof being a Littrow reflective grating. A pulsed laser is adapted to tune to a different wavelength of light each time some or all of the grating faces of the polygonal solid are rotated to intercept the longitudinal axis of the laser.

Abstract: Pulse stability is provided to a pulsed gas filled electrical discharge device by an electrical circuit including first and second electrical energy storage means, with the energy stored in the first storage means being substantially greater than the energy stored in the second storage means. A first voltage corresponding to the energy stored on the first storage means is applied to the input of the gas filled device. A second voltage corresponding to the energy stored on the second storage means is periodically switched to combine with the first voltage and be input to the gas filled device. The period for switching is precisely controlled, preferably with a piezoelectric crystal, and is selected to combine the first and second voltages just before the first voltage reaches the natural breakdown voltage of the gas within the gas filled device.

Abstract: A laser Doppler homodyne detection system includes transmitting-receiver optics including a roof reflector and a twin off-axis Cassegrain reflector system.BACKGROUND OF THE INVENTIONWith the development of laser sources with good frequency stability, optical systems for Doppler homodyne detection have become possible. Laser Doppler systems are especially useful for flow measurement, true air speed measurement, vortex detection, moving target indication, and remote atmospheric measurements.In a typical laser Doppler homodyne system, the laser beam is expanded in diameter and is directed at a target. The radiation back reflected and scattered by the target is received by receiver optics and directed to a detector. A portion of the laser beam is split off prior to transmission and forms the local oscillator beam. This local oscillator beam is also directed to the detector to produce Doppler homodyne signal.One form of laser Doppler system is shown in R. Munoz et al., Applied Optics, 13, 2890 (Dec, 1974).