Abstract: The invention relates to an optical printing device with unity magnification using coherent light and making it possible to significantly reduce speckle on the print.It relates to a printing device comprising a device for illuminating the object, a device receiving the object wave and in real time restoring a wave phase conjugate with the object wave to form a real image of the object. The printing device also comprises a photosensitive support placed in the image plane. The object illuminating device forms on the object to be reprinted a lighting spot which is of small size compared with the object, and the printing device also comprises scanning means for completely scanning the object a number of times by the lighting spot so as to superimpose a large number of images of the same zone having uncorrelated noises on the photosensitive support.The invention, more particularly, finds application in the printing of high resolution masks and large surface areas.

Abstract: The hydrophone has an interferometer structure incorporating a measuring arm in which is provided a very long monomodal optical fibre immersed in the interaction medium in which is propagated the acoustic wave. A phase displacement is induced on the optical wave by the elastooptical effect and said wave is propagated in the fibre by the acoustic wave which creates an acoustic pressure field in the medium. A reference arm establishes a reference optical path and the phase displacement linked with the acoustic wave is detected by interferometry between the two optical waves emerging from the two arms. The optical connections between the source, the optical fibre immersed in the interaction medium, the reference arm and the detector being provided in guided optics in a compact structure.

Abstract: A telecopying process and a transmitter-receiver telecopier employing this process. A cell having a smectic liquid crystal is used for recording by thermo-optically forming an intermediate image of a linear element (column portion or a whole line) of the transmitted document, which image is thereafter projected onto a photosensitive surface. The same optical system permits, when transmitting, the reading of this linear element by a mosaic of detectors and, when receiving, the projection onto the photosensitive surface of the intermediate image recorded in the cell.

Abstract: A system comprising means for emitting an analysis beam and a recording beam, the two beams being deflected by common deflection means. The analysis beam scans the document carrying the image to be analyzed and a detecting photocell provides an electrical signal. The recording beam scans a liquid crystal cell, where it records the image in synchronism with analysis in dependence upon a modulation of the thermo-optical effects induced in the liquid crystal. This modulation is provided by the electrical signal.

Abstract: The invention relates to a compact optical structure comprising a semiconductor emitter junction, a laser or a light emitting diode, coupled to a plane waveguide formed by a layer of photo-polymer deposited on a substrate with a suitable index. A surface layer, of photo-polymer for example, enables the registration of photo-induced diffraction structures performing particular optical functions such as that of a distributed reflector, deflector or lens. Such compact structures are applicable, in particular to the designing of simple, small devices, laser sources with distributed external resonators, interferometric gyrometers, hydrophones, multiplexers or demultiplexers.

Abstract: The invention relates to a semiconductor laser with a distributed reflector comprising a semiconductor junction, one of whose semi-transparent mirrors is a split face of the semiconductor in which is integrated a light emitting junction with epitaxial layers. The active layer of this junction is coupled to a waveguide integrated in a dielectric medium, on one face of which is engraved a grating forming a distributed reflector playing the part of the second mirror. The reflector, when functioning according the second order of counter coupling emits a diffracted wave normal to the waveguide which can easily be coupled to an optical fiber.

Abstract: In a liquid-crystal display device, a smectic liquid-crystal layer and a layer of photoconductive material are placed between two transparent plates. A voltage is applied to the photoconductor by means of electrodes while scanning the photoconductor with a writing light beam. At locations in which the resistance of the photoconductor is reduced under the action of the light beam, the heat generated causes transition of the liquid crystal to the isotropic state. The light-scattering action produced by subsequent cooling of the liquid crystal has the effect of writing the image to be displayed.

Abstract: The interferometric laser gyrometer according to the invention comprises a laser source, a wound monomode optical fibre an a detector, the optical coupling between the source and the two ends of the optical fibre in order that these two ends receive equal parts of the light emitted by the source contro-propagating in the fibre and the optical coupling between these two ends and the detector being effected by wave guides integrated on an electrooptical substrate at which the two ends of the fibre are rigidly coupled.

Abstract: The invention relates to electret bistable systems comprising two fixed electrodes forming a capacitor. A sheet of electret material is inserted for creating holding forces in two rest positions of a moving element located in the capacitor gap. In accordance with the invention, the electret sheet is separated from the corresponding fixed electrode by a layer of dielectric which can be an air gap. As a variant, the charge density of the electret sheet may be concentrated in islands for reducing the holding forces.

Abstract: An electron sensitive resin comprising a random polymer of ethylene glycol methacrylate with triethylene glycol dimethacrylate, randomly crosslinked, and having a degree of polymerization of from 10 to 1000, is described.