Abstract: In a device for switching a light beam, the conditions of propagation of the beam are modified locally under electric control by interposing on the beam path a fluid which modifies the conditions of refraction of the medium traversed by the beam.

Abstract: Device for memory-storage of a coherent image in a multimode optical cavity. A coherent light source generates a signal wave and a reference wave and provides these waves to optical guiding devices. These optical guiding devices form a closed loop in which the signal wave circulates. The guiding devices form a multimode optical cavity having a Fourier plane. An amplifying interactive medium is disposed within the cavity on the path of the signal wave and at the Fourier plane. Within the interactive medium, the signal wave interferes with the reference wave in order to create a diffraction grating. Each signal wave thus receives energy from the reference wave with which it interferes. A semi-transparent beam splitter is disposed within the cavity on the path of the signal wave in order to extract a portion of the energy from the optical cavity.

Abstract: Display device in which an interferometric hologram corresponding to the vibrations of the object is recorded in a photosensitive electrooptical material. The corresponding interferogram is collected on the directly transmitted object beam by the recording material.

Abstract: A multiple bulk optical storage device capable of storing information by the photovoltaic effect is disclosed wherein a thick photosensitive electro-optic material is illuminated by a reference beam incident on one face thereof and an object beam, without a zero order stop, is incident on a different face thereof. Transparent electrodes are attached to all of the faces of the crystal and electrically short circuited to one another.

Abstract: A correlation system providing the correlation function of two objects illuminated with coherent light by using the principle of double diffraction.The correlation system of the invention is essentially characterized in that it uses as recording medium a plate of recyclable material, i.e. inscribable and erasable at will, such as bismuth-silicon oxide. The recording provided in the plate by superimposition of the beams illuminating the objects is read by a beam undergoing angular sweeping so as to optimize the diffraction efficiency for all the correlation peaks in the observation plane.

Abstract: The arrangement for displaying deformations of deformable structures by holographic interferometry, in which the interferogramme of the object is obtained by double exposure for an object subjected to periodic deformation or by prolonged exposure by comparison with the period of vibration for a vibrating object, comprises a recording electro-optical, photoconductive crystal to which is applied an electrical field substantially orthogonal to the mean direction of the fringes. The interferogramme is viewed in an image plane or recorded in a memory tube where it is desired to memorize the information because readout destroys the information. The arrangement can be made compact by integration of the displaying means in an enclosure. In that case, the source furnishes a reference beam and an object beam which are respectively directed towards the enclosure and the object by optic cables.

Abstract: The invention relates to the acousto-optical imagery of objects transmitting ultrasonic waves; an optical image diffracted by the action of an ultrasonic wave is detected by coherent detection in an electro-optical and photoconductive holographic recording material under an applied field by holographic recording of the interferences between the diffracted order to be imaged formed by the optical wave of pulsation .omega..sub.o +.omega..sub.s (or .omega..sub.o -.omega..sub.S) and an optical reference wave having the same pulsations. Imagery is effected in real time by restoration of the object wave by a reading wave having the same pulsation as the reference wave.

Abstract: A holographic storage cell for storing volume holograms wherein a plate of either Bi.sub.12 SiO.sub.20 or Bi.sub.12 GeO.sub.20 is provided with electrodes producing an electric field transversed to the plate. These electrodes may be on opposite ends of the plate, or in the form of interdigitated combs. In one embodiment, such a cell is utilized as a holographic memory wherein the modulation of the object beam and the deflection of the reference and object beams are controlled electronically. The cell may also be utilized to perform calculations by superpositioning data to perform addition and substraction.

Abstract: The present invention relates to a holographic optical storage device utilizing a material in which the transfer of photo-induced charges is orientated along the cristallographic axis C of the material. On the faces of the material perpendicular to said axis, two transparent electrodes connected together are arranged so that the field developed between said two faces is zero whatever the uniform illumination superimposed upon the modulation. The selective erasing of a first induced spatial variation in refractive index is achieved by recording a second spatial variation which is the complement of the first, the number of successive record-erase cycles being unlimited.