Patents by Inventor Herbert L. Engstrom

Herbert L. Engstrom 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).

  • Patent number: 4973832
    Abstract: A self-focusing optical head of the type used in magneto-optical and optical recording systems for directing a focused laser beam onto a moving recording surface uses a non-achromatized optical path between the laser and recording surface and the laser wavelength (mode) shifts induced by optically coupling reflected laser energy back to the laser cavity to automatically maintain the beam in sharp focus (i.e., self-focus) on the recording surface. A focus servo system including a photodetector positioned in the path of reflected laser energy serves to coarsely position a focusing lens relative to the recording surface. A field lens, used to concentrate reflected laser energy onto the photodetector, is achromatized to compensate for the chromatic aberration between laser and photodetector. Such achromatization allows the focus servo to operate independently of the wavelength (mode) shifts required to achieve self-focusing of the laser beam on the recording surface.
    Type: Grant
    Filed: November 3, 1989
    Date of Patent: November 27, 1990
    Assignee: Eastman Kodak Company
    Inventors: Alan B. Marchant, Herbert L. Engstrom