Abstract: The present invention relates to a head-worn display device carried for displaying an image in accordance with at least two projection reference frames, comprising: an image acquisition module configured to separately acquire an image stream for each of the at least two projection reference frames and/or to extract from a single input stream an image stream for each of the at least two projection reference frames; for each projection reference frame, a spatial processing module configured to adapt the corresponding image stream to a display reference frame; a mixing module configured to generate a resulting stream; a projection module configured to project the resulting stream onto a display surface in accordance with the display reference frame.

Abstract: A head-up display or helmet-mounted display device includes at least one image source configured to emit a first image in at least two different spectral bands. A relay optics includes at least one first optical element for reflecting the two spectral bands and a semi-reflecting second optical element. The relay optics and the semi-reflecting second optical element are arranged so as to give, from the first image emitted by the image source, a second image at infinity.

Abstract: The disclosure relates to a compact optical device, intended for use in a night vision telescope, that includes an objective, a standard light intensifier that rotates the image through 180° between its entry and its exit, an eyepiece, and four optical deflections, one in the objective and three in the eyepiece. The eyepiece, producing a single intermediate image between its entry and its exit, includes a combiner whose deflection angle ? depends on its optical index n and the half-field ? of the device. The field width of the device is at least 40°. The invention is applicable notably to night vision binoculars for aircraft or helicopter pilots.

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 head-up sight for an aircraft having a curved windshield. The windshield is external to the sight, which can project at infinity a symbology intended to be superimposed onto an external scene. The head-up sight includes a combination of optical elements bent at an angle to a folding mirror, the folding mirror having a curved shape adapted to correct the parallax associated with the optical power of the windshield. The head-up sight is especially applicable to aircraft having a cylindrical or conical windshield.

Abstract: A head-up display including a combiner and a relay optics formed from a combination of optical elements and forming an intermediate image projected to infinity by the combiner of a symbology emitted in a given spectral band by an image source. The combiner forms an off-axis convergent mirror in the spectral band, and an angle of inclination of the off-axis convergent mirror is adjustable for a given type of equipment as a function of a position of the image source and in a given angular range that depends on the type of equipment. The relay optics is modular and includes a first module with at least one optical element fixed regardless of the type of equipment and a second module with at least one optical element for which a position is predefined as a function of an angular position of the combiner.

Abstract: An optical device for a system presenting collimated images through an off-axis spherical concave mirror. An image can be presented to a user with correction of eccentric distortion caused by the off-axis spherical concave mirror without altering the quality of the image. A diffractive mirror is set in the neighborhood of an intermediate image, and preferably a second intermediate image. The extent of the neighborhood is limited by image resolution and, in the neighborhood, the correction by the diffractive mirror does not alter the resolution. The diffractive mirror may include a hologram which may be digital or made of a photosensitive material. A hologram substrate is preferably not planar to operate partly upon the correction, the residual correction being carried out by the hologram. Such a device may find application to an aircraft pilot's visor.

Abstract: A compact optical architecture for a wide-field helmet-mounted display includes a one-piece visor and optical relay to convey said the image between an image source and the visor. The visor is formed by a surface generated by revolution having an axis of revolution (&Dgr;) parallel to the ocular axis (&Dgr;oc) and substantially contained in the sagittal plane of the pilot, at the level of the forehead. The optical relay includes a forehead-mounted mirror that is not planar, having an axis of revolution (&Dgr;) that is the same as the axis of revolution (&Dgr;) of the visor, its geometrical parameters being computed in such a way that the envelope of the useful beams propagated between the forehead-mounted mirror and the first beam-formation device of the optical relay upstream from the forehead-mounted mirror are substantially contained in a cylinder with a section substantially equal to the useful surface of the mirror.

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 with a liquid crystal cell including a layer of twisted nematic liquid crystal placed between two polarizers and including, between the liquid crystal layer and each of the polarizers, a structure for compensating for cell contrast variations according to the observation angle which has an orientation in the plane of the cell. The pass directions of the polarizers are separated by an angle of 90+A degrees, in which A is not zero, and the orientations of the two compensation structures are separated by an angle of 90+B degrees, in which B is not zero. Such a structure may find particular application to a liquid crystal screen, especially for avionics.

Abstract: The present invention relates to a display device with a liquid-crystal cell comprising a twisted nematic liquid-crystal layer (40) placed between two crossed polarizers (46, 48) and comprising, between the liquid-crystal layer and at least one of the polarizers, a structure for compensating for the variations in contrast of the cell according to the angle of observation. This structure comprises at least two superposed negative uniaxial media such that the extraordinary optical axis of one medium (44, 42) is parallel to the normal to the cell and that of the other medium (43, 41) is inclined with respect to this normal on the one hand and with respect to the plane of the cell on the other. This compensating structure includes an additional layer (50, 49) of a positive uniaxial birefringent material.

Abstract: The invention relates to the field of head-up sights for an aircraft having a curved windshield.

Abstract: The invention relates to an optical device for a system for presenting collimated images including an off-axis spherical mirror. The device has an additional aspherical mirror whose surface forms, in the plane of symmetry of the unfolded optical system, a curve whose radius of curvature is variable. The surface provides for correction of the image of a pupil of an eye given by the spherical mirror and the pupil image is rectified on the optical axis. The surface may be a paraboloid, an ellipsoid and it may exhibit symmetry of revolution.

Abstract: A compact optical architecture for a wide-field helmet-mounted display comprises especially a one-piece visor, an optical relay to convey said image between an image source and the visor. The visor is formed by a surface generated by revolution having an axis of revolution (&Dgr;) parallel to the ocular axis (&Dgr;oc) and substantially contained in the sagittal plane of the pilot, at the level of the forehead. The optic relay comprises a forehead-mounted mirror that is not plane, having an axis of revolution (&Dgr;) that is the same as said axis of revolution (&Dgr;) of the visor, its geometrical parameters being computed in such a way that the envelope of the useful beams propagated between said forehead-mounted mirror and the first beam-formation means of the optical relay upstream from the forehead-mounted mirror are substantially contained in a cylinder with a section substantially equal to the useful surface of said mirror.

Abstract: The invention relates to a head-up display adaptable to different equipments of a given type, for example aircraft type, land vehicle type or helmets type. The display is used to project a symbology emitted within a given spectral range by an image source to infinity, and which is intended to be superposed on the outside surroundings observed by a pilot, by means of a convergent combiner and a relay optics.

Abstract: An optical device for a system presenting collimated images using a spherical mirror. The optical device makes it possible to present the user with an image corrected of off-centring distortion of a second kind due to an off-axis spherical mirror. In order to do this the optical device includes a tubular mirror whose optical characteristics ensure a high-quality image and correction of the off-centering distortion. The tubular mirror has a surface generated by the translation of a plane curve (a circular arc) along another plane curve (also a circular arc). The optical device is especially applicable to helmet sights for an aircraft pilot.

Abstract: An optical device for a system for the presentation of collimated images by a non-plane mirror, which makes it possible to present a user with an image corrected of distortion due to a non-plane mirror and exhibiting good resolution. To do this, the device includes a Mangin type mirror whose optical characteristics ensure good image quality of correction of off-centering distortion and good image sharpness. The Mangin type mirror has a reflecting surface and a layer of refracting material defining a refracting surface. One surface may be spherical, and the other aspherical. The surfaces may also be aspherical. One aspherical surface may be a paraboloid, an ellipsoid, or a torus. The refracting material can exhibit an optical index varying according to the position on the surface of the mirror. The device may be applied in particular to a system for the presentation of collimated images by a spherical mirror inclined with respect to the direction from which it is observed.

Abstract: An optical system for presenting an image to a user. The system includes an image source and an optical channel transmitting the image to the user's eye. It also includes an illumination of the ocular fundus and an imaging of the illuminated ocular fundus, both using part of the optical channel. The system enables an analysis of the eye retina observing an image. It also enables depending on the eye position, an adaptation of the visual image presented. If the system is partially mounted in a headset, it enables the presentation of the image to a mobile user.

Abstract: A display panel having compensation using holographic birefringent films. Due to the natural birefringence of liquid crystals, contrast suffers when a liquid crystal cell is viewed at an oblique incident angle. Compensation devices made of birefringent media are used to correct this deficiency. The compensation devices include at least one film, the birefringence of which is induced by the recording of a volume hologram consisting of parallel fringes. The choice of the optical birefringent axes depends only on the orientation of the fringes so that it is easy to achieve compensation using uniaxial films which are inclined with respect to the plane of the film.