Abstract: A direct-read-after-write optical recording disc having a pair of transparent, disc-shaped members, each being formed with integral inner and outer ring-shaped bosses on one of its sides. A thin recording layer of a light-sensitive material is coated on each disc-shaped member, in a shallow annular recess formed between its two ring-shaped bosses, and the two members are disposed in a coaxial relationship, with their respective bosses in abutment with each other, whereby the two recording layers are located within a sealed, annular chamber.

Abstract: A write and read objective lens for encoding and recovery of information upon a storage member comprising three single lenses and one achromatic doublet for which the working distance is large, flatness of field and resolving power are high and utilizable with a plurality of wavelengths of light.

Abstract: A video disc player assembly is described employing a fixed base member with a pair of fixed rails, and a movable carriage member employing a pair of linear bearing assemblies in engagement with said rails. A stabilization plate is mounted on the movable carriage for movement therewith. A motor and spindle assembly is mounted on the stabilization plate. A portion of the motor and spindle assembly extends through axially aligned apertures in the stabilization plate and carriage and carries a videodisc mounting surface coplanar with the stabilization plate. A centering means is provided to accurately center the disc about the spindle. A releasable clamp rigidly engages the spindle and holds the videodisc against the mounting surface parallel to the stabilization plate. A motor and spindle are mounted on the carriage for rotary driving of the video disc, a centering means is provided to accurately center the disc about the spindle, and a stabilization plate is provided adjacent and parallel to the rotating disc.

Abstract: A substrate carrier assembly is described which employs a frame, a plurality of rollers, a plurality of substrate carrier rings, captively held within the frame and a carrier support track. The substrate carrier assembly provides support and constraint to a plurality of substrate members, while the substrate members are coated with a thin evaporated layer. The physical configuration provided insures that a uniformly thin metal layer is formed over the substrate member.

Abstract: Method and apparatus for controlling the speed of an information storage medium, such as a disc-shaped record carrier, relative to a device for recovering information recorded thereon. The disc includes a plurality of substantially parallel information tracks arranged in a spiral or in concentric circles, and information recorded thereon includes a pilot signal having a predetermined frequency. The apparatus includes means for comparing the phase angle of the recovered pilot signal with the phase angle of a locally generated reference signal, to produce an error signal for controlling the angular velocity of a spindle motor that rotates the disc. The pilot signal includes an equal integral number of cycles on each information track, so its phase angle is aligned on adjacent tracks and the apparatus can continue to operate even when the information recovering device is traversing the disc from one track to another or is not critically positioned with respect to an individual information track.

Abstract: A digital servo system for maintaining a detection device, such as a light beam, centered as closely as possible over an information track, such as an optical track on a video recording disc. The servo system includes circuitry for detecting when the light beam traverses a switching line, which, in the illustrative embodiment, is the track centerline, for applying a constant-magnitude acceleration force to deflect the beam to a corrected position, and for reversing the polarity of the acceleration force when the beam traverses the switching line.

Abstract: A digital servo system for maintaining a detection device, such as a reading beam, as nearly as possible centered with respect to an information track, such as an optical track on a video recording disc. In each of the embodiments disclosed, circuitry is provided to process a signal obtained from the reading beam, to obtain timing signals indicative of transitions of the beam across noncentral switching lines parallel with the track. In one embodiment, a constant-magnitude acceleration signal is applied to a beam position transducer, and is reversed in polarity each time a switching line is crossed after first crossing the centerline. In another embodiment, the polarity of the constant-magnitude acceleration signal is reversed after crossing a switching line a second time and after applying an additional acceleration impulse of relatively short duration.

Abstract: A servo control system for maintaining an information detection device, such as a light beam, centered on a moving information track, such as a spiral recording track on a video disc. The system of the invention includes a dither signal generator, a bandpass filter for deriving an intermediate signal indicative of the effect of dither on the detected signal derived from the information track, and switching circuitry for deriving an error signal from the intermediate signal and the polarity of the dither signal. In one embodiment of the invention, the switching circuitry includes an inverter, and a switch for selecting either the intermediate signal or the inverted intermediate signal, in accordance with the polarity of the dither signal. The error signal thus derived is low-pass filtered and has a positive value when the center position of the beam moves to one side of the track, and a negative value when the center position of the beam moves to the other side.

Abstract: Apparatus, and a related method, for maintaining an incident beam of radiation in alignment with the centerline of a movable, optically-readable information track, wherein the track comprises a succession of light-reflecting and light-scattering regions representative of a frequency modulated carrier and the sides of the track are adapted to scatter incident radiation in predetermined directions. The apparatus includes photodetector means for sensing the amount of radiation scattered by each side of the track and for generating an error signal indicative of the deviation of the incident beam relative to the centerline of the track, along with means responsive to the error signal for controllably moving the incident beam into alignment with the centerline of the track.

Abstract: Method and apparatus for controllably rotating an information storage disc relative to a radially movable optical transducer, whereby information is recorded on the disc in a series of substantially circular and concentrically arranged information tracks. The angular velocity of the disc and the radial velocity of the transducer are controllably adjusted to be inversely proportional to the radius of the particular information track being recorded, whereby the track is moved at a constant linear velocity relative to the transducer and the successive tracks are equally spaced with respect to each other, and whereby a uniform information recording density over the surface of the disc is achieved.

Abstract: Method and apparatus for recovering information at a substantially constant rate from a rotatable information storage disc. The information is stored on the disc in a plurality of substantially circular and concentrically arranged information tracks, with a substantially uniform recording density, and it is recovered by controllably rotating the disc, relative to a transducer, at an angular velocity substantially inversely proportional to the radius of the corresponding track. The apparatus includes a coarse speed control potentiometer for producing a measure of the radius of the particular information track from which information is being recovered, and fine speed control means for comparing the relative phase angles of a periodic signal in the recovered information and a periodic reference signal and for producing a fine speed control signal proportional to the phase difference.

Abstract: Method and apparatus for rotating an information storage disc about its central axis at a prescribed angular velocity that varies according to the radial position of an optical transducer for recording information thereon, whereby a uniformly high density of information can be recorded over the entire disc. The apparatus includes a register for storing a digital measure of the radius of the current track being recorded by the transducer, along with velocity signal circuitry for producing a disc velocity signal having a frequency inversely proportional to the measure of radius, and a spindle motor servo, responsive to the disc velocity signal, for controlling the angular velocity of the information disc, accordingly.

Abstract: An optical transducer having concentric radiant beam detectors for converting a radiant beam to electrical signals including a first axially placed detector with a second detector concentric therewith. In one embodiment, the detectors receive the radiant beam through an amplifying auxiliary lens. Changes in focus differentially affect the magnitude of the beam impinging on the individual detectors, resulting in corresponding changes in the individual detector outputs.A focusing system employing the transducer moves a focusing lens in response to the differential output of the individual detectors. The focusing system can be employed in a video disc reading system so that the video disc scanning beam is always focused precisely at the disc. An electrical difference circuit leading from the photo-detectors generates a driving signal to energize a lens-moving motor for shifting the focusing lens along the axis of the beam.

Abstract: A video signal play back device derives video signals from a track on a video disc using a light source and an optical path to a lens system which is supported by an air bearing at a predetermined spacing from the surface of the disc. The optical path includes a mirror which is articulated for rotational motion about an axis which shifts the point of impingement of the transmitted light beam upon the disc in the radial direction. The returned beam is directed to a single photosensitive pick-up which, provides input signals to a circuit which generates a "fine" servo control signal to drive the articulated mirror. The air bearing member includes apparatus providing a bias force that varies with the radial displacement of the transducer assembly relative to the disc center.