| 摘要 |
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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