U.S. Philips Corporation

Carel Arthur Simons

Gijsbertus Bouwhuis

Jacobus P Heemskerk

Adrianus J Franken

Kornelis A Immink

Hendrik Renes

Hendrik' T Lam

Everardus A Van Megen

Eduard W Moen

An optical read unit is described for scanning a record carrier with a radiation-reflecting trackwise-arranged information structure. The read unit utilizes a diode laser which generates the read beam and also detects the information stored on the record carrier. The read unit is also provided with an opto-electronic system for detecting the position of the read spot relative to a track to be read and the position of the plane of focussing. The diode is mounted in a housing and the unit includes electromechanical apparatus for moving the housing in two perpendicular directions so as to correct the position of the read spot. The objective system for the formation of the read spot is of simple construction.

Optic read unit for scanning a record carrier having a

A focussing error detection system is described for determining deviations between the plane of imaging of an objective system in an optical arrangement and the radiation-reflecting surface in said system. The apparatus comprises an optical element by means of which a radiation beam coming from the radiation reflecting surface is both rendered astigmatic and separated from a radiation beam which is directed to the radiation-reflecting surface. By the use of this element the number of components of the focussing-error detection system can be minimized and a compact construction of said system can be obtained.

Optical focussing-error detection system

An apparatus is described for reading a record carrier on which information is stored in an optically readable information structure, which apparatus includes a radiation source which supplies a read beam of great coherence length. By including a radiation attenuating element in the radiation path of the read beam, preferably nearest to the radiation source, random intensity modulations in the read beam, which modulations may be caused by undesired reflections in the radiation path, can be substantially reduced.

Device for preventing unwanted reflections from an optical system to a

An apparatus is described for reading a radiation-reflecting record carrier on which information is stored in an optically readable track-shaped phase structure. The apparatus inter alia includes a radiation source, an objective system and a radiation-sensitive detection system. By a suitable arrangement and a suitable choice of the power of a cylindrical lens, which lens in conjunction with a four-quadrant detector supplies a focussing signal, it is possible to detect centering-errors with the aid of only two additional detectors in the plane of the four-quadrant detector.

Apparatus for reading an optically readable reflecting information

An apparatus is described for reading a record carrier on which information is stored in an optically readable structure. Between a radiation source and an objective system a mirror system is disposed, by means of which the entrance pupil of the objective lens can be imaged onto beam-controlling elements which deflect the read beam over the information structure.

Videodisc reader with concave mirror elements

An apparatus is described for reading a record carrier on which information is stored in an optically readable structure. Between a radiation source and an objective system, a polarization-sensitive beam splitter and a .lambda./4 plate are disposed. The optic axis of the .lambda./4 plate is perpendicular to the end faces, so that the plate may be thick and may be rotated in its own plane.

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Eindhoven, Netherlands

Carel Arthur Simons