Abstract: A positive unit magnification reflective head is used to back-reflect a primary light beam, for storing reflection microholograms at the coincident foci of the primary and reflected beams. Imaging the primary beam focus onto itself at positive unit magnification allows increasing system tolerance to tilts and transverse misalignments between the primary and reflective heads. Holograms are stored at multiple depths in a holographic storage medium. Tunable-focus primary and reflective heads are positioned on opposite sides of the storage medium. The reflective head images each storage location onto itself at positive unit magnification. Suitable reflective heads include: two lenses in an f-2f-f configuration and a planar mirror; a lens and a corner cube; a thin lens and a thick lens with a coated reflective back surface; and a thin lens and a back-coated gradient-index (GRIN) lens.

Abstract: A focus error signal generator device including first and second optical lenses disposed in the respective paths of first and second light beams derived from the return read beam wherein the first and second optical lens have corresponding points of focus, and first and second detectors disposed in the corresponding paths of the first and second light beams located after the points of focus. First and second pinholes are disposed in the corresponding paths of the first and second light beams after the corresponding optical lens and before the corresponding detector, and an electrical differencing circuit having inputs to the first and second detectors and an output to an optical head servo system.

Abstract: The holographic storage and retrieval system according to the present invention comprises one convex reflector and one concave reflector having the same optical axis. The reflective surfaces of the two reflectors are opposite each other. The concave reflector is normally larger than the convex reflector. The holographic storage medium is positioned at the focal surface of the concave reflector. The spherical reflector system according to the present invention has nearly ideal performance off-axis: high bandwidth, low aberration imaging is permitted at a number of radial and axial locations. Thus, multiple SLM/CCD pairs can be placed off-axis to access the same storage medium and implement multiple interconnects.

Abstract: Two lenses separated by an air gap provide spherical aberration compensation and focusing of a light beam to a focal point inside a data storage medium. The thickness of the air gap determines the amount of spherical aberration compensation provided. The distance between the lens pair and storage medium determines the depth of the focal point within the storage medium. The internal surfaces of the lenses which define the air gap are preferably planar. The external surfaces of the lenses are aspheric to provide accurate focusing and positive spherical aberration. The air gap between the lenses may also be formed by curved internal surfaces, in which case it is best for the focus lens to have a concave internal surface. The apparatus and method of the present invention reduces the number of optical components required for an optical data reading/writing device.

Abstract: An optical access device for a moving optical data storage media having a flying lens near an outer surface of the media, and an objective lens spaced from the flying lens, with the flying lens and objective lens co-operating to substantially offset a variable range of negative spherical aberration occurring in the media by forming a positive spherical aberration which substantially cancels the negative spherical aberration.

Abstract: Digital data bits are stored as discrete-level reflection microholograms in a multi-depth digital optical data storage system. Reference and signal beams are incident in a counterpropagating geometry on opposite faces of a tape. The reflection microholograms are stored at the coinciding focus of the reference and signal beams. The holograms are stored at the diffraction limit of high-N.A. optics, and have relatively high grating frequencies and small sizes. Dynamic aberration compensators correct for the depth-varying spherical aberration imparted to the beams by the medium. Multiple mutually-incoherent lasers are used for parallel storage and retrieval to increase data transfer rates. Achievable densities and signal-to-noise ratios are substantially higher than for index-perturbation or transmission hologram storage methods.

Abstract: A head-up display for vehicle including a windshield having first and second opposing air interfaces for partially reflecting imaging illumination at a predetermined air interface to produce a primary virtual image viewable by the operator of the vehicle, and a half-wave retarder interposed between the first and second air interfaces of the windshield for rotating the linear polarization of illumination transmitted therethrough. An imaging illumination source provides linearly polarized imaging illumination to the first air interface of the windshield at an angle which is selected to enhance the reflection of S-polarized light and the transmission of P-polarized light, with the polarization being selected so as to provide S-polarized imaging illumination at the predetermined beam splitting air interface.

Abstract: A display having a linearly polarized image source, a quarter-wave retarder for transforming the linearly polarized illumination to circularly polarized illumination, imaging elements responsive to the circularly polarized illumination for producing viewable circularly polarized imaging illumination, and a circular imaging illumination to viewable linearly polarized imaging illumination. The circular polarizer includes a quarter-wave retarder for transforming the circular light to linearly polarized light, and a linear polarizer configured to transmit the linearly polarized imaging illumination. Contrast enhancement is achieved by the circular polarizer which functions to block ambient light reflected from the front element of the imaging elements as a result of transmission through the circular polarizer.

Abstract: A head-up vehicle instrument display system that includes an imaging illumination source located in a recess in the vehicle dashboard or on the dashboard, and a combiner/retarder element embedded in a vehicle windshield. The combiner/retarder element includes a reflection hologram and one or more half-wave retarders, and optionally the inside surface of the vehicle windshield.