Abstract: A device for optically measuring the distance of a target (20) comprising a monomode coherent light source (18) means (18a, 21, 30) for periodically varying the wavelength of the light of the source, a photodetector (19) for detecting the variation in the wavelength between the light from the source (18) and that retroradiated by the target (20), and means (23, 24, 25; 33, 34, 35; 41, 43, 46) for processing the output signal of the photodetector (19) corresponding to the composite optical signal issuing from the cavity of the source of light and resulting from the re-injection into this cavity of the light retroradiated by the target (20), the frequency of the output signal of the photodetector being representative of the distance between the source (18) and the target (20).

Abstract: The discriminating device comprises an optical coupler (4) having at least three ends (5 to 8) to which are connected a semiconductor source of light (1) whose intensity is modulated, a semiconductor photoconductor (2) and an optical probe constituted by a multi-mode optical fibre (3) whose end has a pointed shape. This discriminating device is in particular applicable in a device for measuring the voluminal fraction of at least one fluid of a current of non-mixible fluids.

Abstract: The detector comprises an avalanche photodiode for receiving a light beam, a circuit for measuring the mean current across the avalanche photodiode and a bias voltage source. That source is controlled by the circuit for applying to the photodiode a bias voltage such that the mean current across the diode be substantially equal to an adjustable set value.

Abstract: The present invention relates to a method of and apparatus for enabling the visualization of isometric physical condition maps of a three-dimensional test object, the physical condition being for example the amplitude of vibration of the test object or the contour of the object. The latter is studied by the striation method whereby flat parallel light beams on light on the object forming a system of striations thereon; there is superimposed on the image in a given direction of the illuminated object a corresponding image of a typical comparison object, the resultant superimposed image being a coded representation of the physical condition of the test object. A television camera is used to analyze the successive images of the system of striations formed on the surface of the object.