Centre National De La Recherche Scientifique

Université Paris—sud

National Research Council of Canada

Université Pierre Et Marie Curie (Paris Vi)

Sfim Industries

Gerald Roosen

Philippe Delaye

Gilles Pauliat

Jean-Pierre Monchalin

Alain Blouin

Jean Thierry Audren

Albert-Claude Boccara

Denis Drolet

Michel Gross

Benoit Claude Forget

Guillaume Maire

Francois Georges Gerard Ramaz

The invention concerns the field of holographic storage units. More particularly, the invention concerns the field of holographic storage units used for bit-by-bit storage of information. It concerns a method for reading data recorded in a holographic material in the form of a hologram obtained by interference of two beams of substantially the same wavelength, and using at least one reflecting layer. The invention is characterized in that it includes the following steps: emitting a light comprising at least said wavelength at said holographic material comprising said hologram; performing a homodyne detection between the signal resulting from the first light diffracted by said hologram and at least one signal selected between the reflected signal and the signal transmitted by said at least one reflecting layer.

Holographic storage with homodyne detection

This invention concerns an acousto-optic imaging method comprising a step which consists in engraving in a dynamic holographic material a complex index array resulting from the interference of the acousto-optic component of the signal wave and a pump wave of frequency equal to the frequency of the acousto-optic component.

Method and installation for acousto-optic imaging

A process for generating a carrier in an interferogram in interferometry device either of the 'real-time holographic interferometry' type or of the 'double-exposure holographic interferometry' type, including recording a first wave front on a hologram, the first wave front coming from an object; generating a second wave front, in which two wave fronts are superimposed orthogonally polarizing said first and second wave fronts, either naturally or by a modification stage; and passing the orthogonally polarized two wave fronts through a birefringent crystal, a polarizer and a detector to make the two wave fronts interfere.

Device for generating a carrier in an interferogram

A gyroscope comprising a source for emitting a light beam, an optical fiber loop in which the light propagates in both directions, a dual phase-conjugate mirror disposed in said loop in such a manner that light reaches said mirror from both sides thereof, recombination means for recombining the light which has propagated round the loop, and detector means for detecting the recombined signal, wherein the loop includes a monomode fiber that does not conserve polarization and wherein depolarization means are disposed between said fiber and the phase-conjugate mirror, on either side thereof.

Gyros having an optical fiber loop and a dual phase-conjugate mirror

A method and apparatus are provided of optically detecting transient motion from the surface of a workpiece. After directing a laser beam onto a surface of a workpiece the beam is reflected from it and then interferes with a pump beam removed from the laser source, inside a real-time holographic material, so as to form a grating diffracting the pump beam into a reference beam, which interferes at the output of the real-time holographic material with the received light beam, so as to produce a signal representative of the surface transient motion. An electric field is applied to the holographic material of sufficient magnitude to increase substantially the intensity of said reference beam and to give to this beam a phase differing substantially from the phase of said received light beam. The electric field is applied prior to the transient motion to be detected, for a time interval sufficiently long so as to capture the transient motion but sufficiently short a duration so as to avoid excessive heating of the real-time holographic material. The pump beam is of sufficiently high intensity so as to cause the response time of the real-time holographic material to be substantially shorter than a characteristic time defined as the time during which the phase of the received light, on average across its spatial distribution or locally, is not substantially changed.

Sensitive and fast response optical detection of transient motion from a

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La Celle les Bordes, France

Gerald Roosen