Abstract: A device nematic liquid crystal display device has two stable states corresponding to two liquid crystal molecule textures whose torsion differs by 150° to 180° in terms of absolute value. The device includes two polarizers (10, 40), one (10) of which is placed on the observer side, the other (40) being placed on the opposite side of the liquid crystal cell. The orientation of the two polarizers is offset by a value which is equal to the rotatory power of the cell+/??/2, the rotatory power corresponding to the most twisted texture effect.

Abstract: The application relates to a single-polarizer reflective bistable twisted nematic (BTN) liquid crystal display device comprising a liquid crystal layer of thickness d, birefringence ?n and retardation ?nd, said liquid crystal layer being situated between two substrates and between a polarizer and a reflector, said liquid crystal layer in the absence of an applied electric field having two stable uniformly twisted textures, the twists of the two stable textures differing by an angle being equal mainly to 180°, and at least one compensation layer positioned between said polarizer and said reflector, said compensation layer being composed of at least one birefringent film, said birefringent film having an optical anisotropy defined by three characteristic refractive indices nx, ny, nz, along three corresponding axis x, y, z of index ellipsoid, x and y being situated inside the substrates plane, nx and ny being called in plane indices, with nx?ny, x being called slow axis, and z being perpendicular to the substra

Abstract: A device nematic liquid crystal display device has two stable states corresponding to two liquid crystal molecule textures whose torsion differs by 150° to 180° in terms of absolute value. The device includes two polarizers (10, 40), one (10) of which is placed on the observer side, the other (40) being placed on the opposite side of the liquid crystal cell. The orientation of the two polarizers is offset by a value which is equal to the rotatory power of the cell±n/2, the rotatory power corresponding to the most twisted texture effect.

Abstract: A document includes at least one drawing or data produced, for example, by printing. In addition, this document includes a hologram representing part of the document. The hologram of this document is recorded using a system including a prerecorded or electrically controllable optical modulator in which the image of at least part of the document is recorded. This modulator is designed to be combined with a layer of photosensitive material. A first reference wave illuminates the layer of photosensitive material. A second wave incident on the modulator and giving rise to a third object wave is also transmitted to the layer of photosensitive material in order to interfere with the reference wave in this layer.

Abstract: A display device comprising a liquid-crystal cell element (20) placed between two polarizers (23, 28) comprising at least one optical structure for compensating for the variations in birefringence of said liquid crystal according to the viewing angle. The optical compensation structure comprises at least one oblique-axis film (25, 26) of polymerized liquid-crystal type suitable for at least partly compensating for the undesirable effects of the natural birefringence of the liquid crystal, combined with a volume hologram (24, 27) of small retardation suitable for improving the compensatability of said film.

Abstract: A display device including an illuminating source which emits radiation and a spatial light modulator illuminated by the radiation. The modulator includes a matrix of N.times.M elementary pixels (X.sub.i,j) of dimensions d.sub.N .times.d.sub.M, the pixels X.sub.i,j and X.sub.1+i,j being separated by a spacing p.sub.N. The radiation is collimated in each pixel. The spacing p.sub.N is greater by at least an order of magnitude than the dimension d.sub.M. The display may be used as a flat television screen.

Abstract: An illumination device comprises a light source coupled to a waveguide. the waveguide comprises a diffracting element capable of diffracting emergent light rays coming from the source, in a direction substantially perpendicular to the surface of the waveguide. A device of this kind is particularly well-suited to transmissive display screens of the liquid crystal display screen type. It can generate a highly collimated, polarized light.

Abstract: Invention concerning the therapeutic use of tetracyclic derivatives and their pharmaceutically acceptable salts having the following general formula: ##STR1## in which, independently of the other: X is a carbon or nitrogen atom,T is a carbon or nitrogen atom,L is an oxygen atom or ketone functional protective group,R.sub.1 is an atom of hydrogen, an atom of halogen, or a C.sub.1 to C.sub.5 alkyl radical,R.sub.2 is a hydrogen atom, a halogen atom, a nitro radical, or a C.sub.1 to C.sub.5 alkyl radical,n and m are equal to 0 or to 1, but not independently of the other, so that if n is equal to 1, then m is equal to 0, and if n is equal to 0, then m is equal to 1.

Abstract: This optical filtering device includes a dichroic separator on the path of a light beam to be processed. According to the invention, it also includes a holographic filtering device situated in series with the separator on the path of the same beam. The holographic device can be oriented so as to adjust the angle of incidence of the beam and hence adjust its range of filtering wavelengths.

Abstract: The color display device includes at least a light source which emits at least two primary wavelengths and an array of holographic lenses (HL). Also included is a spatial light modulator (LCD) which includes one picture element (pixel) for each holographic lens with each pixel including one subpixel for each wavelength to be displayed. Each of the holographic lenses disperses the various wavelength and focuses each of them into one of the subpixels. The structure allows for a single lens structure for the various wavelengths.

Abstract: The invention relates to a color display device comprising a chromatic dispersive grating and an active matrix possibly of liquid crystal type. This device moreover comprises a matrix of spherical microlenses, the shape of the cross section of the microlenses being such that it makes it possible to compensate for the spreading of the R G B colored beams by virtue of the use of a dispersive grating, and hence to make best use of the circular aperture of projection objectives.

Abstract: A back projection device comprises an image generator (GI), an onward reflection mirror (MR) and at least one optical component (OM) capable of reflecting certain types of light beams almost entirely and reflecting certain other types of light beams almost entirely, said component being located in the proximity of a screen (E). The selection of optical behavior of the component (OM) may be done as a function of the polarization of the light beam, or else also as a function of its orientation with respect to said component (OM). Application: displays.

Abstract: This invention concerns chromatic light separators, and is particularly intended to reduce their dimensions. A chromatic separator in accordance with the invention contains at least two selective wave length mirrors. According to one characteristic of the invention, the two selective mirrors are nested holographic mirrors. The invention is particularly suitable for three-color rear-projection type picture projectors using liquid crystal screens.

Abstract: A three-color image projector, of the type using several colored light beams with primary colors, with improved luminous efficiency. The projector employs spatial rather than temporal beam modulation. The projector includes a generator producing light in the three spectral bands corresponding to the primary colors (red, green, blue). The generator has at least two light sources (S1, S2), one of which produces multi-spectral band light, and the other is a monochromatic source. By comparison with the prior art, where the white light is produced by a single source, this arrangement avoids, in particular, the elimination of a significant quantity of lumens in the excess primary color.

Abstract: A color display device comprises a source of light simultaneously emitting several ranges of chromatic components and a spatial light modulator comprising several dots, each dot comprising at least one sub-pixel per range of chromatic component to be displayed. Between the light source and the spatial light modulator there are provided at least one chromatic separator angularly separating the light of the different chromatic range along different directions, a lens focusing the light of the different chromatic ranges at distinct points or along distinct lines contained in a determined plane, at least one spatial filter located along this determined plane and selectively filtering the light of the different chromatic ranges, and an array of lenses, each enabling the focusing of the light of each chromatic range substantially on a sub-pixel.

Abstract: Disclosed is a separator of polarizations comprising a Bragg grating gripped between two plates comprising input and output faces in the form of steps. The advantages of the device are that it is light and compact.