One-way peephole
First Claim
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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Accused Products
Abstract
A door-mounted security peephole providing an undistorted view over a relatively large area by use of a beam splitter optical system. The peephole comprises a door-mounted housing containing a beam splitter and light source arranged so that light is reflected from the beam splitter and toward the area exterior of the door. An observer behind the door may view the door exterior area including a visitor at the door entrance. The visitor, however, cannot see the observer through the beam splitter, because of the light reflected therefrom, thus increasing the overall security aspect. The design exploits the contrast sensitivity of the human eye as a function of field brightness.
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Citations
20 Claims
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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:
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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. - View Dependent Claims (2, 3, 4, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16)
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5. The optical system of claim i wherein said beam splitter means comprises a curved glass surface coated with a thin semi-reflective layer on one side.
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17. A method of viewing an area exterior to a barrier from within comprising the steps of:
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providing an optical system having an observation port for allowing a view of the barrier exterior area through a beam splitter; and generating light in said optical system for incidence on a surface of said beam splitter, a reflected portion of said incident light illuminating the barrier exterior area, the light received at said observation port being passed to a barrier interior area through the other side of sad light beam splitter, said barrier interior area being substantially non-visible through said observation port concurrent with the exit therefrom of said reflected light portion. - View Dependent Claims (18, 19, 20)
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Specification