Abstract: A composite disc in which a pattern of spaced glue dots is sandwiched between two disc halves. One of the disc halves is a dummy disc, and the other is a recordable optical disc. The pair of disc halves are joined together by depositing a pattern of spaced glue dots on the upper surface of one of the discs, positioning the second disc over the first, and contacting the lower surface of the second disc with the pattern of spaced glue dots. Preferably, the material of the glue dots is an ultraviolet curable contact cement, and, subsequent to the application of the pattern of dots on the dummy disc, and prior to joining the two disc halves, the glue dots are cured by being exposed to a source of ultraviolet light.

Abstract: An optical storage media and information storage system and method for optically recording information in optically readable form. The DRAW recording medium of the present invention consists of a three layer structure: a transparent substrate; a uniform layer of a dielectric light-responsive material having a threshold energy level at which a physical change in the material occurs; and a highly electrically conductive and highly reflective overcoating on the opposite side of the light-responsive layer from the substrate. The recording method and system allow the concentration of the writing energy to a well defined volume within the thickness of the energy responsive layer or the uniform distribution of the energy throughout the layer by setting up a standing wave within the energy responsive layer by use of the electrically conductive reflecting layer.

Abstract: An optical storage media. The DRAW recording medium of the present invention consists of a three layer structure: a transparent substrate; a uniform layer of a dielectric light-responsive material having a threshold energy level at which a physical change in the material occurs; and a highly electrically conductive and highly reflective overcoating on the opposite side of the light-responsive layer from the substrate. The invention provides a DRAW recording medium which is capable of recording information immediately readable in accordance with the International Electrotechnical Commission optical disc standard for videodiscs.

Abstract: Apparatus and method for monitoring the optical recording of information on an information storage member using a first beam of light for writing the information and a second beam of light for reading the information. Both the writing beam and the reading beam are focused on the storage member by a single objective lens. The input information signal which is used for modulating the writing beam is also directed to a delaying circuit, and the delayed information signal is compared with the playback signal derived from the reading beam.

Abstract: Method and apparatus for optically recording information on a moving information storage member and for reading the information immediately after it is written. An intensity modulated writing beam and a separate reading beam of light are simultaneously focused by a single objective lens. The reading beam impinges the medium at a point trailing the point of impingement of the writing beam by a prescribed amount. The reading beam is reflected by the moving medium in accordance with the recorded information. The modulated reflected light is collected by the objective lens, and the intensity of the reflected light is sensed for generating a playback signal. The quality of the playback signal may be monitored to allow control of the intensity of the writing beam.

Abstract: An optical disc structure including two resilient disc members which are bonded together adjacent their outer peripheries and which include an air channel allowing communication between the chamber formed between the discs and the atmosphere. An information layer is formed on the inner surface of at least one of the members. When the members are spun, a pressure differential is caused tending to push the two members apart, thereby assuring that one member will not contact the information layer formed on the other member and that the two members will not be close enough together to cause optical interference.

Abstract: Apparatus and process for writing information using a laser light writing beam focused on a light sensitive layer having a threshold power level above which the layer reacts to the laser write beam. The intensity of the writing beam is adjusted relative to the threshold power level. In one embodiment, the peak intensity of the writing beam is adjusted so that one-half of the peak intensity is equal to the threshold power level. In a second embodiment, the average intensity of the writing beam is adjusted to equal the threshold power level.

Abstract: A system for recovering information from a movable information storage medium by scanning with a beam of radiation, the system including a movable lens for focusing the beam of radiation. The movable information storage medium includes a plurality of substantially parallel information tracks containing a pilot signal having a phase angle aligned with the phase angle of the pilot signal recorded on adjacent tracks. The movement of the lens to acquire focus of the beam is controlled such that the lens is retracted until the pilot signal is no longer detected. When detection of the pilot signal ceases, the retraction of the lens also ceases. The lens is subsequently advanced until focus is achieved. Defining the limits of retraction of the lens based on the limits of detection of the pilot signal minimize the range over which the lens must be moved for initial acquisition of focus.

Abstract: Electro-optical focus detection apparatus for providing a signal indicative of the magnitude and polarity of focus error in a light beam impinging on a surface, such as a recording surface in a recording or playback system. The detector includes a beam splitter for dividing the beam reflected from the recording surface into two reflected beams of equal power, and includes an aperture placed in the path of the two reflected beams. The first reflected beam converges at a focal point before encountering the aperture and the second reflected beam converges at a focal point after encountering the aperture, both beams thereafter impinging upon separate photodetector elements. The aperture reduces the light incident on the photodetectors from both reflected beams, and the apparatus is so configured that the powers of the reflected beams incident on the photodetector elements are identical when the original beam is in focus on the recording surface.

Abstract: Method and apparatus for recovering information from an information storage medium, such as a disc-shaped record carrier, and for correcting time base variations in the recovered information. 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 a variable delay for correcting time base variations of the recovered information.

Abstract: A recording medium, such as a light-reflective video disc, having a plurality of substantially parallel information tracks, each track formed by a succession of spaced, information-bearing indicia having reduced reflectivity. Each track records both a modulated carrier signal and a pilot signal, the pilot signal having a prescribed frequency substantially lower than a substantial portion of the modulated carrier signal. The duty cycle of the spaced indicia forming each track varies in accordance with the phase angle of the recorded pilot signal, and the pilot signal's phase angle is aligned with itself on adjacent tracks.

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 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: 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: Apparatus and process for writing upon a video record and for reading the video information from the video record after the writing is complete, and the video disc structure so written. The apparatus includes a laser and an optical system which directs the laser beam to a prepared rotating disc. The disc has a very thin metallic coating. A first lens acts to diverge the laser beam so as to fill a miscroscope objective lens which focuses the beam to a small spot of approximately 1 .mu.m in diameter. The spot contains sufficient energy to melt the metallic surface coating on the disc. The surface tension of the molten metal makes it draw back leaving a hole.Video information in the form suitable for display with a T.V. monitor is applied to an F.M. modulator for forming an F.M. signal. The F.M. signal intensity modulates a laser beam passing through a Pockels cell--Glan prism combination. The series of holes forming the coating of the disc represent the F.M. signal. Since an F.M.

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.