U.S. Philips Corporation

Kornelis Bulthuis

Bram Johan Derksema

Hendrik Tjalling Dijkstra

Johannes Van Der Wal

Johannes Van De Wal

An optical record carrier having an information track structure on a surface thereof, one or more of the tracks being pre-recorded with standard information pertaining to a particular class of information of common use to an undefined number of users. Portions of one or more tracks which are not so pre-recorded are covered with a layer of optically recordable material, for recording thereon of information of the aforesaid class which completes or updates the standard information in whole or in part.

Optically inscribable record carrier with prerecorded information

A gas-discharge laser having a Brewster window near at least one of the reflectors which is secured directly to the laser tube. The Brewster window is secured to a surface of the laser tube and a normal to the window makes an angle equal to the Brewster angle with the axis of the laser tube. The surface may be a slot in the laser tube or a recessed end face of the laser tube near a reflector. An advantage is that the Brewster window may have any convenient diameter and that the laser tube need not be drilled to form a cavity.

Gas-discharge laser

An apparatus is described for reading a radiation-reflecting record carrier on which information is stored in an optically readable structure. For separating the modulated and the unmodulated read beam, the radiation path from the radiation source to the record carrier includes a beam-splitting element with such a reflection coefficient that only a small part of the modulated read beam returns to the radiation source, while a sufficiently large part of said beam reaches a radiation-sensitive detector.

Apparatus for optically reading a radiation-reflecting record carrier

A gas discharge laser in which a plane parallel transparent plate whose normal encloses an angle with the axis of the laser tube equal to the Brewster angle is arranged in at least one of the ends of the laser tube. The plate is secured to the adjacent reflector so that the plate can easily be replaced.

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Eindhoven, Netherlands

Kornelis Bulthuis