Original Publication Date: 1970-Dec-01
Included in the Prior Art Database: 2005-Feb-22
AbstractA three faced prism has totally internal reflecting surfaces to produce a high contrast and image of fingerprints.
A three faced prism has totally internal reflecting surfaces to produce a high contrast and image of fingerprints.
The prism includes an indentation 4 on surface 3 for placement of fingers, a viewing surface 1 and a black coating on surface 2, which provides high contrast background for fingerprint patterns and enhances reflections of light striking surfaces 3 and indentation 4. When light strikes surface 3 or indentation 4 and there is no object in contact with that surface, the light is reflected to the black surface 2 and gives the effect of a dark area. When light rays strike the area where fingertip ridges are in contact with indentation 4, the light rays are not reflected toward the dark area but are reflected back to the viewer through surface 1 giving the effect of a bright area greatly enhancing the fingerprint pattern.