Crime preventive door viewer

Details Crime preventive door viewer Crime preventive door viewer

1980-04-01

1982-09-07

Corbin, John K.

350 69, G02B 2504

Patent

active

043480837

ABSTRACT:
A crime preventive optical door viewer having an assembled optical system with a field of vision of about 160 degrees is set through a door to enable viewing of the outerside from the inside of the door. The optical system includes first and second objectives having the same shape but arranged with a curvature on opposite surfaces, an eyepiece, a focus length keeper or focus length cylindrical sleeve which is put between the second objective and the eyepiece, and a colored filter placed at an appropriate location. The lenses are arranged on the optical axis and are assembled in parallel into an inner tube from one end thereof, then the inner tube is screwed and set into an outer tube.

REFERENCES:
patent: 4116529 (1978-09-01), Yamaguchi
patent: 4172636 (1979-10-01), Yanagimachi
patent: 4175824 (1979-11-01), Daley

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