Abstract:
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.
Abstract:
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.
Abstract:
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.
Abstract:
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.
Abstract:
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.
Abstract:
A liquid-level measuring device including, in effect, two similar elongate members each adapted to be partially submerged in a liquid, the two elongate members being displaced lengthwise relative to one another by an odd number of quarter wavelengths of a predetermined wavelength of a chosen flexurally resonant mode of the elongate members. Each elongate member has flexure wave transmitting elements in contact therewith for launching flexure waves along the member and flexure wave receiving elements in contact with the member for receiving flexure waves launched by the transmitting elements. Also, associated with each elongate member is a phase detection arrangement connected both to the transmitting elements and to the receiving elements for detecting and comparing the phase of the flexure waves at the transmitting elements with the phase at the receiving elements so as to obtain a phase difference measurement, the magnitude of which provides an indication of the resonance frequency of the elongate member. An operating unit is connected to the respective outputs of the two phase detection arrangements so as to provide an indication of the extent to which the elongate members are immersed in the liquid.
Abstract:
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.
Abstract:
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.
Abstract:
A device for measuring the mass flow of a fluid consists of a body which is arranged to resonate under the influence of a travelling flexure wave. Various embodiments of the invention are described. In certain embodiments in which the resonating body is in the form of a cylinder, the frequency of resonance is related to the mass of fluid flowing over the surface of the cylinder. In other embodiments, the wave velocity of the flexure wave is modified by a fluid flowing over the surface of the cylinder and amplitude modulation is introduced into the resonating flexure wave. The amplitude modulation is related to the mass of fluid flowing and an output indicative of the mass flow is produced. In further embodiments the body is in the form of a flat vane. The wave velocity of the flexure wave is modified by the fluid over the surface of the vane, and the wave velocity is monitored by comparing the relative phases of the flexure wave at different points along the vane. The phase difference is related to the mass of fluid flowing and an output indicative of the mass flow is produced.
Abstract:
A liquid level sensing device consists of an elongate member in which flexure waves are induced. By partially submerging the elongate member in a fluid the depth of immersion can be determined from characteristics of the flexure waves. In one mode of operation the transit time for a flexure wave to travel along the elongate member is measured, and in another mode the nature of resonant modes in the flexure wave is determined.