Patents by Inventor David C. Hempstead

David C. Hempstead 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: 4956640
    Abstract: This invention provides a method and apparatus for controlling the type of information displayed at each display pixel on the video monitor of a video display system. A number of video RAMs are provided which number is at least equal to the number of different types of information. A bitmap is stored for each type of information in the video RAMs in interspersed fashion, a selected number of bits for select display pixels of the bitmap for a given type of information being simultaneously stored in said RAMs, followed for each RAM by the selected number of bits for the same selected display pixels for the bitmap of at least one other information type. No more than one bitmap bit for a given display pixel is stored in any video RAM. The addressing of the RAMs for read out of the bitmap is shifted so that bits for the same display pixels for all of the bitmaps are simultaneously read out from the RAMs.
    Type: Grant
    Filed: November 28, 1988
    Date of Patent: September 11, 1990
    Assignee: Hewlett-Packard Company
    Inventors: Richard H. Jundanian, David C. Hempstead