Optics: measuring and testing – Crystal or gem examination
Patent
1983-03-22
1985-08-13
Evans, F. L.
Optics: measuring and testing
Crystal or gem examination
356421, G01J 352, G01N 2187
Patent
active
045346445
ABSTRACT:
Guides to facilitate color grading of faceted gemstones such as rubies and sapphires. Each guide has a series of simulated standards thereon representing a range of grades for a particular class of colored stones and serving as reference points for comparing an unknown therewith in a standardized lighting environment. The guide is constituted by a strip of reflective metal, foil or metallized film sandwiched between a back panel and a top panel having a row of port holes therein, each exposing a reflective zone on the strip. The zone is embossed to create a radial array of wedge-shaped segments, each of which is serrated to define a series of prism-like steps that run from the apex to the base of the segment to provide a pattern simulating the reflective properties of a step-cut faceted stone. Interposed between each zone and its associated hole is a planar optical filter whose coloration is such that in combination with the underlying reflective zone, it creates a respective color grade in the range thereof. In making a color judgment, the observer seeks the closest match between the unknown being examined and one of the simulated standards on the guide, thereby obviating the need for actual stone standards.
REFERENCES:
patent: 1597830 (1926-08-01), Rueger
patent: 1612791 (1927-01-01), Ames et al.
patent: 1617024 (1927-02-01), Munsell et al.
patent: 2007264 (1935-07-01), Allen
patent: 2058073 (1936-10-01), Fritzsching
patent: 3898869 (1975-08-01), Reneer
"Color Comparators," Magnuson Engineers, Inc.
Ebert Michael
Evans F. L.
Harringa Joel L.
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