The Marconi Company Limited

Gec-marconi Limited

Bae Systems, Inc.

General Electric Company

Gm Global Technolgoy Operations, Inc.

Fisher Controls International LLC

Bae Systems Electronics Limited

Marconi Electronic Systems Limited

Roger Martin Langdon

Edward L Lewis

Andrew Graham McCarthy

Charles R Jarvis

William R McKnight

Cyril Smith

Richard G Kirman

Philip M Watts

Kenneth Firth

George A Macdonald

A method and apparatus for determining gas velocity, which includes generating transmitted radiation having an expected transmission frequency, detecting backscattered radiation, and determining gas velocity in dependence upon any Doppler shift of the frequency of the backscattered radiation, determining a transmission frequency of the transmitted radiation; detecting any difference between the measured transmission frequency and the expected transmission frequency and generating a feedback signal therefrom, and determining gas velocity using said feedback signal.

Gas velocity sensor

An acousto-optic module is provided, including a number of partially coupled optical resonators distributed within a dielectric medium and at least one acoustic transducer mounted on a surface of the dielectric medium for injecting an acoustic wave into the optical resonators so as to diffract light passing therethrough by means of Bragg diffraction. This acousto-optic module has been applied in particular to an improved tuneable optical filter in which an acoustic shear wave is generated and which travels through the acousto-optic module in a direction substantially parallel with a polarized light signal passing therethrough. The acousto-optic module is also applied to an improved optical frequency shifter.

Acousto-optic devices

This invention relates to a gas velocity sensor such as an air velocity sensor for use on an aircraft such that the velocity of the aircraft can be determined. There is provided a gas velocity sensor comprising an electromagnetic radiation source operable to illuminate a gas; a photodetector operable to detect electromagnetic radiation scattered from the gas; an optical path linking the gas to the photodetector; an interferometer positioned on the optical path, the interferometer having an input for receiving electromagnetic radiation scattered by the gas and an output for producing an interference pattern when the interferometer is illuminated; and a spatial filter positioned on the optical path on the output side of the interferometer, the spatial filter having regions that are relatively transparent and relatively opaque that form a structure corresponding to an interference pattern produced by the interferometer.

Apparatus and method for identifying a remote target () is described. The remote target () is illuminated with radiation () generated by a laser () and the radiation scattered by the target () is modulated in phase by the surface () vibrations of the target (). A portion of the scattered radiation is collected by multiple optical receivers () and demodulated by a phase demodulator to generate a signal proportional to the vibrational displacement of the remote target (). The radiation scattered by the remote target () will also include laser 'speckle', generated when radiation is scattered by a rough solid surface. This speckle can generate errors in the signal demodulated, which can in turn cause identification errors. Apparatus is disclosed where the signals generated are substantially unaffected by laser speckle, improving the accuracy of remote target identification.

Method and apparatus for laser vibrometry

Detection of remote acoustic signals is achieved using a pulse to pulse coherent laser beam which is projected from a telescope to a remote region that contains acoustic signals from a nearby source. Light from the beam is scanned in the region and a resultant signal collected by a telescope. The signal and a reference are applied to an interferometer and the resultant interference pattern applied to a photoreceiver. An alternating current is produced across the photoreceiver which corresponds to the scattered light from the beam caused by the periodic movement of acoustic signals through a region. The detector can be used to determine the curvature of an acoustic signal wavefront and to detect the location of a source producing the acoustic signals.

Sound detection

A transmitter (,) is arranged to produce and focus a beam (,) on a remote focal point (,). A small proportion of resultant light (,) is back-scattered from the focal point (,) by particles or aerosols in air flowing through point (,) and returns to a receiver (,) where it is collected A detector combines resultant light (,) and reference light (,), splits the resultant light (,) and reference light (,) equally between two arms and detects which arm leads the other in phase thereby indicating the flow direction of air through focal point (,).

Remote air detection

In a laser radar system, in which pulses from a laser are focused by a telescope onto a target, the back-scattered radiation being deflected by polarizing beam splitter onto a detector in conjunction with a reference beam, the reference beam being produced from pulses derived from the pulse laser by the beam splitter, the pulses making repeated journeys around a cavity and a proportion of the pulse being emitted each time so that each input pulse produces a multiplicity of output pulses to form the reference beam, thereby avoiding the need for a separate laser for the reference beam.

Laser radar with reference beam storage

A receiver-transmitter for a target identification system having a particular but not necessarily an exclusive application for the identification of aircraft which utilizes laser vibrometry and a coherent array receiver including an array of photodetectors adapted to receive signals from different parts of the target and to use a corresponding array of frequency-offset reference beams to provide coherent detection of each of the received signals.

Receiver-transmitter for a target identification system

A sensor, for use in determining physical properties of fluid, comprises a flexible diaphragm having a plane. Two tines depend from the diaphragm substantially at right angles to the plane. First and second substantially planar transducers are each bonded to the diaphragm so that the plane of the transducers are parallel to that of the diaphragm. A first one of the transducers is operative, in use, to flex between in its plane and to couple an alternating driving force into the plane of the diaphragm such that the tines vibrate in an oscillatory motion. Second of the transducers is operative to detect vibrations of the diaphragm.

Sensor apparatus

A holographic objective system (3) produces an intermediate real image (4) of information displayed on an electrically addressable spatial light modulator or SLM (1), the real image (4) being collimated by a powered holographic reflector (5) constructed as part of the visor of a helmet worn by the viewer (9). The SLM (1) is illuminated by laser light from a remote laser (8) via a single optical fibre (6) and beam splitter (2). A diffuser (7) is provided either between the laser and the beam splitter or in the plane of the intermediate image (4). The objective system (3) may alternatively include, or consist entirely of, conventional optical elements.

Helmet mounted display

The orientation of a helmet is monitored by illuminating the cockpit volume by a moving interference pattern produced by three beams. The sensors detect the varying phase to produce outputs which are compared to determine the orientation of the helmet.

Orientation monitoring apparatus

A position measurement system transmits moving interference pattern and these are received by a sensor fixed relative to the transmitter and a mobile sensor, by comparing the phases of the interference pattern at the two sensors the position of the mobile sensor relative to the transmitter can be calculated.

Optical interference position measurement system

A fluxgate magnetometer includes a body of magnetic material, a drive coil and a sensing coil. At least one of the drive coil and the sensing coil is composed of two portions, each of the two portions being disposed in generally parallel planes which are spaced apart and respectively include an electrically insulating substrate and a spiral shaped portion which is electrically conductive supported by the electrically insulating substrate, the two portions being electrically connected such that electric current flows in the respective spiral shaped portions in opposite rotational senses relative to the body of magnetic material.

Magnetometer having coil formed by two spiral shaped conductors

A sensor comprises a beam, e.g. of silicon, which resonates at a frequency dependent on the force imposed on the beam. Light on a line induces resonance of the beam by means of the photothermal effect. The light reflected from the beam is amplitude modulated at the resonance frequency, and returns along the line. It is reflected by a semi-reflecting plane mirror onto a lens which focusses it onto a photodetector. The photodetector produces an output voltage modulated at the oscillation frequency, and is thus representative of the force imposed on beam 1.

Photothermal oscillator force sensor

A flowmeter has a vane which is caused to vibrate at one of its resonant frequencies and a flexure standing wave set up along it. Two piezoelectric sensors are used to monitor characteristics of the standing wave and hence the mass flow rate of a fluid flowing past the vane along a pipe. The vane comprises a ceramic planar member on which a conductive ceramic ink is laid down to form tracks. The ink also bonds a ceramic piezoelectric transducer to the member to drive and maintain it in vibration. A non-conductive layer is laid down on the surface of the member covering the conductive tracks surrounding the transducer. A metal layer forms the external surface of the vane and acts as a ground plane for the transducer.

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Colchester, United Kingdom

Roger Martin Langdon