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: Single stage tracking actuator apparatus for an optical or magneto-optical disk drive system in which a read/write head is suspended by parallel flexures between mutually isolated magnetic circuits disposed on opposite sides of the head, one of the magnetic circuits being nested in the span between the parallel flexures. The flexure suspension provides friction-free translatable motion of the head in the longitudinal direction parallel to a radial line relative to the information storage disk. An electromagnetic coil provided with tracking actuator signals is formed about the head axially concentric with and transverse to the longitudinal center line of the head and is centrally positioned on the head between the points at which the free ends of the flexures are attached to the ends of the head. The end turn segments of the coil are disposed transversely of magnetic flux lines in elongated air gaps formed in the magnetic circuits to provide the driving force for the actuator.

Abstract: A method and apparatus for anamorphically shaping a beam of radiation and for deflecting such beam by 90.degree. independently of beam wavelength shifts within a predetermined wavelength range. The apparatus of the invention comprises an achromatic prism comprising a pair of prism elements of different optical materials. The prism elements are joined together to define a complex prism having four faces which interact with an incident beam to achieve a desired beam shaping and deflection. Two of such faces are parallel, one face being in a plane parallel to the direction of propagation of an incident beam, and the other being in a plane perpendicular to the beam exiting the prism.

Abstract: Apparatus for playing-back information on a magneto-optic recording element includes a diffraction grating for splitting a read beam reflected from the recording element and modified by the recorded information into three beams. Two of such beams (i.e., the upper and lower first order diffracted beams) are used in a differential detection scheme to recover the recorded information, and the third beam (i.e., the zero order beam) is used to provide focus and/or tracking information.

Abstract: During the arrival phase of long seeks, e.g. the last six tracks of a seek, and during the entirety of relatively short seeks, e.g. seeks of less than 256 tracks, position mode servo control is employed by locking an actual tracking error feedback signal to a microprocessor-synthesized reference tracking error signal. The position mode servo feedback loop employs a parallel combination of a synchronous demodulator and a phase-frequency detector to achieve good locking performance over the entire frequency spectrum of the synthesized reference tracking error signal.

Abstract: A method and apparatus for anamorphically shaping a beam of radiation and for deflecting such beam by 90.degree.. The apparatus consists of a prism having at least four faces, two of such faces being parallel. The prism is arranged to receive a beam at the Brewster angle .THETA..sub.B, and is adapted to deflect the beam by 90.degree. by refraction and double internal reflection. The prism faces define four internal angles of .THETA..sub.B, 90.degree.+.THETA..sub.B, 90.degree.-.THETA..sub.B and 180.degree.-.THETA..sub.B.

Abstract: An optical memory with a storage plate and an optical write/read unit, with which during a relative movement the storage plate is illuminated pointwise for writing and reading of information, the storage plate and the optical write/read unit each being positioned in a coordinate with the aid of electromagnetic mechanical positioning means for addressing storage elements.