A magneto-optical effect distance measuring device and measuring rig incorporating the device. The device can measure the distance separating two members which can be displaced one with respect to the other by the magneto-optical effect. A permanent magnet is fixed on one of the members and an electro-optical device is fixed on the other member. The electro-optical device includes a diode emitting an optical beam. Further, a Faraday-effect magneto-optical film is disposed, on the one hand, between a polarizer and an analyser and, on the other hand, in the magnetic field of the magnet when the two members are in proximity to one another, the optical beam passing through the assembly. A diode receives the optical beam retransmitted by the analyzer so as to transform the luminous intensity of the beam into an electrical signal whose amplitude depends on the distance separating the two members when they are in proximity to one another. Such a device may find particular application to monitoring the closure of aircraft doors.

The present invention relates to a backlighting device, having several brightness levels, for a transmission display screen (12). The device comprises light sources placed in a case (14) between a translucent front wall formed by a diffuser screen (20) and a rear wall (24). The light sources, selected according to the desired brightness level, are mosaics (24, 28) of light-emitting diodes (26, 30) that are placed immediately behind the diffuser screen with, for the highest brightness level, a first mosaic (24) of light-emitting diodes that provides daytime illumination and with, for the lowest brightness level, a second mosaic (28) of light sources that supplies night-time illumination.

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.

An ice detection warning system mountable on board an aircraft for inflight monitoring of the airspace ahead of the aircraft comprises: a first plurality of optical elements configured to direct a pulsed laser beam at a first wavelength from a laser source into the airspace ahead of the aircraft; a second plurality of optical elements configured to separate received backscattering of light from the laser beam into a plurality of predetermined wavelengths; a plurality of light detectors for detecting the light of the separated plurality of wavelengths, respectively, and generating respectively corresponding plurality of electrical signals representative of the light detected thereby; and a processor for processing the plurality of electrical signals to determine if airspace conditions ahead of the aircraft are likely to cause ice accretion on the surface of the aircraft, and for generating a warning indicative thereof. In one embodiment, the warning system includes an optical scanner operative to scan the pulsed laser beam into the airspace ahead of the aircraft with a predetermined scan pattern, the scanner also being operative to receive the backscattering of light from the pulsed laser beam and direct it to the second plurality of optical elements which is configured to separate the received backscattering of light into the plurality of predetermined wavelengths.

An optical system provides information about tangential vibration components of a surface at remote location. The optical system includes a light source assembly that emits first and second beams, each having one or more wavelengths and one or two polarizations. The first and second beams are directed to the interrogated surface. A detector system is positioned to detect a third beam formed by at least a portion of the first and second beams being reflected from the interrogated surface. The first, second and third beams having incident and reflection angles relative to the interrogated surface that do not lay in a same plane. The detector system positioned remotely from the interrogated surface, and providing information on a phase change in the third beam relative to the first and second beam. The phase change is indicative of at least one surface vibration vector component of the interrogated surface. The detector system is a 90 degree optical hybrid balanced detector with four photodiodes.