Abstract: A measuring device comprises a light source with a wide spectrum feeding an optical sensor through an optical fiber. The sensor comprises an interferometer adjusted to a dull tint and an optical component sensitive to a measured parameter, which may be either a pressure, a measured displacement or an index of refraction of a fluid, a readout device includes the photodetector, a processing unit and an optical wedge for producing fringes, whose lateral positions, in contrast, are representative of the spectrum of the flux leaving the interferometer and analyzed by the photodetector. The processing unit measures the lateral position of the fringe and converts it into a value of the parameter P.

Abstract: The invention relates to a fiber optic measuring device in which the variation in a measured parameter engenders a phase difference between two waves. It comprises a SAGNAC ring interferometer (2) in which two counter-propagating waves propagate; a polarization splitter (6) spatially splits the two polarizations which will propagate in the interferometer (2), interferometer (2) comprises a polarization conserving birefringent fiber (7) having two ends having neutral birefringence axes, each of the ends of the polarization conserving fiber (7) being connected to one of the gates (6b) and (6c) of the polarization splitter (6). It comprises a birefringent component, placed ahead of the polarization splitter (6) and introducing a path difference greater than the coherence length of the source (1) between the two polarized waves.

Abstract: A fiber optic measuring device can be used, for example, as a rate gyro. Variation in a measured parameters engenders a phase difference between two waves. The measuring device includes a light source 1, a SAGNAC ring interferometer 2, a detector 3, a phase modulator 4, and a electronic unit 7. The electronic unit 7 includes a processing system 9 which furnishes a signal that is a function of the measured parameter and an electronic sub-unit 12 for controlling the phase modulator 4. The control signal for the modulator is a superposition of a first, periodic gating, bias signal .PHI..sub.b (t) with period 2.tau. and amplitude .PHI..sub.bm, and of a second, staircase, negative-feedback signal .PHI..sub.m (t) synchronized with .PHI..sub.b (t), each step of which has a duration equal to .tau. or to one of its sub-multiples, and an amplitude .PHI..sub.s, which is a function of the value of the measured parameter and which falls back to zero when its amplitude exceeds a predetermined value .PHI..sub.mm . .PHI..

Abstract: The invention relates to a fibre optic measuring device of the type in which the change in a measured parameter generates a phase difference between two waves in a SAGNAC ring interferometer (2). Electronic means (7) comprise a processing system (9) delivering a signal depending on the measured parameter and electronic means (12) controlling the phase modulator (4). The electronic means (12) produce a control signal for the modulator determined in such a way that the phase difference .delta..PHI..sub.m which it produces between the counter-propagating waves periodically takes the following four successive values: ##EQU1## where .PHI..sub.o is a constant phase shift and it depends on a, and a is a positive constant satisfying the condition: cos .PHI..sub.o =cos a.PHI..sub.o.

Abstract: The invention relates to improvements to methods and devices for determining the contact angle of a drop of liquid placed on a substrate. The device comprises: a support 12 for a substrate 11 which receives a drop of liquid 9; a light source 1; optical means, formed for example by a plate with parallel faces 21 rotatable about its axis 22 and whose inclination with respect to the axis may be modified, with a reflecting prism 5a, for forming a primary beam 6a, advantageously annular, striking the interface 8 between drop and substrate; a receiving surface 13a, 13b formed by a reflection diffusing surface; a reflecting surface 17; and a camera C.

Abstract: Active chemical sensor with optical fiber and its production process.The chemical sensor according to the invention makes it possible to measure a given quantity or magnitude of a fluid. It has a chemical reagent suitable for the measurement and for reacting with the fluid, a support means (20a, 28) for the reagent and a single optical fiber (20) for supplying light to the reagent and recovering the light reflected by the reagent, said sensor being characterized in that the support means incorporates a vinyl imidazole polymer or copolymer film (28) in which the reagent is immobilized, said polymer being in particular directly grafted on to one of the ends (20a) of the optical fiber (20).

Abstract: A method of positioning an object relative to a plane, and apparatus therefor. According to the method, the plane is swept by the axis of a light-beam between a source assembly and a detection assembly, and the object is translated approximately perpendicularly to the plane, the detection assembly emitting a signal representative of the light received and therefore, the position of the object relative to the plane. The signal emitted by the detection assembly is measured as a function of time, the translation of the object being halted when the signal has a particular form. The particular form of the signal corresponds to the position of the object in which the shoulder masks a predetermined fixed part of the light-beam during part of its sweep.

Abstract: A measuring method and device are provided based on the analysis of a channelled light spectrum, particularly for measuring a low amplitude movement of a mobile surface, possibly representative of the variation of a physical magnitude convertible into such a movement.

Abstract: An optical-fiber detection device which involves testing for correct operation is provided with at least one sensor having a sensing element which operates by light reflection at the end of an optical fiber and with a line for transmission of light by optical fibers. The transmission line connects the sensor to a source of periodic light pulses and to an electronic signal detection and processing unit. The sensor includes an optical fiber segment of predetermined length between the sensing element and an intermediate connection which produces a state pulse by reflection. The sensing element produces a measurement pulse which is separated from the state pulse by an elementary time interval. The electronic unit serves to detect the state of operation of the sensor by means of the presence or absence of the state pulse or reference pulse in the signals.

Abstract: A vibration detection device is provided having multimode optical fiber as sensitive element; a coherent light source; photodetecting means; means for analyzing the output of the photodetector means; a monomode optical fiber disposed between the coherent light source and the first end of the multimode optical fiber forming the input face thereof; and at least one optical fiber, whose core diameter is smaller than that of the multimode optical fiber, disposed between the other end of the multimode optical fiber, forming the output face thereof and on which a speckle appears, and the photodetector means.

Abstract: In an optical fiber sensor, the fiber has a sensitive zone which cooperates with a retroreflecting surface through the agency of an optical couplant. The function of the retroreflecting surface is to return into the optical fiber all light losses which escape from the fiber in the sensitive zone.