Rca Inc.

Michael J Lurie

Istvan Gorog

Zygmunt Marian Andrevski

Recovery from a record of data recorded in an elongated information track, comprising depressed areas of a given width, a given depth and variable length, alternating along the length of the track with relatively non-depressed areas, is effected by an optical playback system. The playback system employs means for focusing light from a laser source on the information track as a light spot having a diameter which is diffraction limited. The focusing system includes an additional light source (e.g., laser) which impinges on the surface of the record as a circular spot which illuminates a plurality of elongated tracks. The circular spot is imaged by a lens system on a detector plane which is positioned at a plane which is conjugate to the record surface. The focus error signal which is used to adjust the position of the objective lens with respect to the record surface is representative of a measure of the diameter of the circular spot imaged on the detector plane, and, thus, is a measure of the diameter of the circular spot at the record surface. The imaging lens system includes a quasi-zoom lens arrangement that permits adjustment of the correct focus when the surface of the record is at the required position.

Quasi-zoom lens optical focus sensor

Recovery from a record of data recorded in an elongated information track, comprising undulations representative of the data is effected by an optical playback system. In the system, the data is recorded within two substantially different frequency bands. The optical playback system has a dual response characteristic to provide improved response at the two different frequency bands. A modifying means interposed in the light beam path shapes the light beam to effect this dual response characteristic (i.e., two different bandwidth responses).

Multi-bandwidth optical playback apparatus with elongated read spot

A redundant Fraunhofer or Fresnel hologram is recorded by interfering a temporal-information beam with a reference beam of mutually coherent light. The temporal-information beam is intensity-modulated with each of a series of samples of the temporal information signal. The relative phase difference between the two interfering beams is selectively determined for each sample of the series and the effective value of the angular displacement between the two interfering beams is changed for each successive sample of the series. The hologram can be recorded directly from an electronic signal, such as television, without the need for a coherently illuminated object, or an intermediate imaging step, such as transcribing from television to film.

Redundant hologram recording method employing temporal information signal

A holographic recording of a plurality of rows of informational elements, which may represent a binary number, is successively illuminated by each of a plurality of light sources, where the number of light sources equals the number of rows of elements. In response to the successive illumination, a holographic reconstruction of the elements is projected upon photodetectors disposed along a line in a projection plane. The illumination may be instead by a deflected beam having an angle of incidence with the recording which changes at a vertical scan rate. In response to the deflected beam, a holographic reconstruction of horizontal lines of the elements are successively projected upon the photodetectors.

Providing a representation of information stored in a hologram

A mask is used to sequentially illuminate successive elemental areas of an object (by changing the position of the mask) to obtain from each relatively small elemental area a diverging object-information component of coherent wave energy which is passed through a relatively large cross-sectional aperture of imaging and/or recording means. The fact that this cross-sectional aperture is so much larger in area than the area covered by any dust or optical defects of the imaging and/or recording means markedly reduces spurious coherent-wave patterns normally produced by such dust or optical defects. Further, since the illumination is not diffuse, no speckle pattern problem exists.

Coherent wave imaging and/or recording technique for reducing the

The maintenance of a light spot of a chosen dimension on the surface of a rotating disc for optical playback or optical recording of data is effectively accomplished by a hydrostatic bearing apparatus. The apparatus includes: a housing for a lens assembly, which is disposed in the housing with its axis aligned parallel to the path of an incident light beam; a movable frame mounted on a support for movement in a direction substantially parallel to the light path; a pair of leaf springs coupling the housing to the frame for maintaining the axis of the lens assembly parallel to the light path; adjustable means for fixing an operating location for the movable frame; and a pressurized gas source coupled to a hydrostatic pad affixed to the lower portion of the housing, for providing a lubricating film of gas between the housing and the disc of a chosen thickness. The apparatus maintains the dimensions of the light spot focused on successive regions of the surface of the rotating disc independent of variations, if any, in the height of the successive regions.

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East Brunswick, NJ, United States of America

Michael J Lurie