Patents by Inventor Antonius Adrianus Marius VAN Alem

Antonius Adrianus Marius VAN Alem has filed for patents to protect the following inventions. This listing includes patent applications that are pending as well as patents that have already been granted by the United States Patent and Trademark Office (USPTO).

  • Apparatus for reading a record carrier with an optical information structure
    Patent number: 3969576
    Abstract: In an apparatus for reading a record carrier on which information is stored in an optically readable structure, the radiation which is supplied by the radiation source is split into a read beam and an auxiliary beam for determining the focussing of the read beam on the record carrier. Said auxiliary beam is intercepted by two radiation-sensitive detectors. By disposing a radiation-absorbing knife between the radiation source and the Wollaston prism a part of the auxiliary beam is blocked. Thus, an accurate indication can be obtained of the magnitude and the direction of a focussing error.
    Type: Grant
    Filed: January 22, 1975
    Date of Patent: July 13, 1976
    Assignee: U.S. Philips Corporation
    Inventors: Lieuwe Boonstra, Antonius Adrianus Marius VAN Alem