Abstract: An active flat-design video screen is described, having signal line means arranged in lines and columns, these signal line means, at their crossing points, defining picture elements of the video screen, in which case the lines that are arranged in columns are developed as electrodes and the signal line means that are arranged in lines are developed by means of optical waveguides into which, on the input side, a modulated light signal is coupled and which, at each crossing point, have a device for the coupling-out of the respective light signal. In comparison to conventional active flat-design video screens, the video screen according to the invention distinguishes itself particularly by a good picture resolution and a good contrast range, connected with a good regeneration rate.

Abstract: A refractometer comprises a light source (DEL), a prism (P) immersed in a liquid (L) and the entry face of which is a cylinder portion. The exit face (2) of the rays is cut according to an acute angle (.theta.) relative to a diametrical plane (3) of the cylindrical face so that the rays refracted through the prism at two different temperatures, for a liquid of given concentration, however, emerge from the face (2) converging towards a common zone thereby tending to measure the concentration of the liquid independently of the temperature variations.

Abstract: A refractometer comprises a light source, an angle prism and an optical system in a casing so mounted that the optical system focuses an image of a diaphragm at said light source upon a double photodiode located beyond the prism and supported by an oblique surface of the casing. The ratio of the output of one photodiode to the output of the double photodiode is measured to register the index of refraction.

Abstract: An optical fiber disposed between a light source and a photodetector is subjected at a number of points, equispaced along its axis, to a transverse pressure causing a significant attenuation of the transmitted luminous radiation. The optimum spacing of the pressure points is a function of the radius of the fiber core and of the refractive indices of its core and its envelope. These pressure points are formed by turns of a substantially incompressible helix which is wound around the fiber and which may be constituted by an internal or external rib of a surrounding flexible sheath of similarly incompressible material. The pressure may be applied by a piezoelectrical transducer and may be modulated by an electrical signal to be picked up by the photodetector.

Abstract: An optical fiber disposed between a light source and a photodetector is subjected at a number of points, equispaced along its axis, to a transverse pressure causing a significant attenuation of the transmitted luminous radiation. The optimum spacing of the pressure points is a function of the radius of the fiber core and of the refractive indices of its core and its envelope. These pressure points are formed by turns of a substantially incompressible helix which is wound around the fiber and which may be constituted by an internal or external rib of a surrounding flexible sheath of similarly incompressible material. The pressure may be applied by a piezoelectrical transducer and may be modulated by an electrical signal to be picked up by the photodetector.

Abstract: A partly hydrolyzed gelled polysiloxane mass is contacted with a solution of dopant metal compounds which diffuse therein under thermally controlled condition; alternatively, a partly hydrolyzed gelled polysiloxane mass containing distributed therein dopant metal compounds is contacted with a solvent into which said dopant metal compounds will partly diffuse under thermally controlled conditions.

Abstract: A switching device comprises two optical fibres disposed in two respective supports located one in line with the other. One of these supports is articulated about a transverse axis and loaded by a leaf spring which tends to space its free end from the adjacent end of the other support. The adjacent ends of these supports have oblique faces whose angles are supplementary and the movable support has a window exposing a portion of the fibre adjacent to its bevelled end. This fibre is associated with a light-emitting diode and the other fibre with a photodetector. When the adjacent ends of the fibres are spaced apart the light is reflected through the window, and when they are in optical contact the light is transmitted to the photodetector.

Abstract: An apparatus or device for determining the index of refraction of a fluid referred to or reduced to a predetermined reference temperature comprises a light source, light detector and means forming a bent light-conducting path between the source and the detector such that the intensity of the detected illumination represents the refractive index of the fluid surrounding the light-conductive path. According to the invention, the light source comprises an electroluminescent diode, e.g. a light-emitting diode of the LED type which has a temperature coefficient in conjunction with the temperature coefficient of the optical fiber which compensates substantially precisely for veriations in the temperature coefficient of the effective index and the fluid with which both the path and the LED are in thermally conducting relation, e.g. in direct contact.

Abstract: The device comprises two optical probes (51 and 52) consisting of a light conducting body which are designed to be immersed in the liquid by an intermediate section (53, 54) of the body, two light sources (60, 70) illuminating an extremity respectively of one (58) and of the other (68) body of the probes, two photoelectric transducers (61 and 72) located at the other extremity respectively of the first (58) and of the second (68) body of the probes, a member (73) which divides the signals originating from these transistors and a member (74) for the display of the resulting signal originating from that divider member.

Abstract: A two-position switch for the control of a load, e.g. of a channel selector of a television receiver, comprises a transparent or translucent pushbutton with a stem carrying an optical reflector, such as a prism with a metallized surface, in an opaque housing receiving proximal ends of two optical fibers or fiber bundles whose distal ends confront a light source and a photodetector, respectively. In one position, the reflector directs light from the source to an exposed face of the pushbutton as a signal visible to the user while cutting off the illumination of the photodetector; in the other position, the visible light signal disappears while the photodetector is irradiated to operate the load.

Abstract: A device for producing a light signal corresponding to the refractive index of a fluid medium comprises an elongated light-conducting body consisting of an input section and an output section connected to each other by an intermediate curved section adapted for immersion in said fluid. This curved section is provided with a plurality of curvatures arranged successively and bent alternately in opposite directions, whereby light passing by refraction into said fluid undergoes a notably greater variation, as a function of the refractive index of said fluid medium, than can be obtained with a curved section bent in a simple direction. A light signal is thus provided with a high sensitivity. The complex-curved, preferably .OMEGA.-shaped, section can be enclosed in an envelope composed in part of filter material.

Abstract: A device for producing a light signal corresponding to the refractive index of a fluid medium comprises an elongated light-conducting body consisting of an input section and an an output section connected to each other by an intermediate curved section adapted for immersion in said fluid. This curved section is provided with a plurality of curvatures arranged successively and bent alternately in opposite directions, whereby light passing by refraction into said fluid undergoes a notably greater variation, as a function of the refractive index of said fluid medium, than can be obtained with a curved section bent in a simple direction. A light signal is thus provided with a high sensitivity.

Abstract: An apparatus is disclosed for measuring strain in a solid object, wherein the apparatus is arranged to use the deflection of a light guiding structure as a strain responsive element for determining the amount of applied stress to be measured. The apparatus typically comprises a curved light guiding structure including a medium of given refractive index surrounded by a medium of lower refractive index than that of the medium of given refractive index; means for injecting light into the structure and means for analyzing the change in the propagation characteristics of the light emerging from the structure; and, means for attaching and maintaining the light guiding structure to the solid object in such a way that stresses acting upon the object are translated into changes of the curved form of the structure, creating changes in the propagation of the injected light whereby the strain in the object can be determined.