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One-way peephole

  • US 5,078,470 A
  • Filed: 06/22/1990
  • Issued: 01/07/1992
  • Est. Priority Date: 07/11/1989
  • Status: Expired due to Fees
First Claim
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1. An optical system for use in a peephole mounted in a barrier such as a door, wall and the like, said optical system comprising:

  • a housing mounted in the barrier for providing an observation port to an area exterior of the barrier;

    beam splitter means enclosed within said housing and defining an optical axis aligned with said observation port, said barrier exterior area being visible through said observation port and said beam splitter means from a barrier interior area; and

    illumination means for providing a light beam Incident on a surface of said beam splitter means at a first brightness level, such that a portion of said incident light beam is reflected therefrom and exits said housing via said observation port along said optical axis,light at a second brightness level from said barrier interior area being substantially non-visible at said observation port through said beam splitter means concurrent with the reflection therefrom of said incident light beam, when said first exceeds said second brightness level by a predetermined ratio.

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