Patents by Inventor Dennis Vanderwerf

Dennis Vanderwerf 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).

  • Telephoto lens assembly for overhead projector
    Patent number: 4744641
    Abstract: The invention consists of a four-element telephoto projection lens for use in conventional overhead projectors, which lens assembly affords an extended projection distance from the lens to the projection screen while retaining the same back focus as conventional two-element projection lenses for overhead projectors.
    Type: Grant
    Filed: June 1, 1987
    Date of Patent: May 17, 1988
    Assignee: Minnesota Mining and Manufacturing Company
    Inventor: Dennis Vanderwerf