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1. (WO2002031474) SYSTEMS AND METHODS FOR EVALUATING THE APPEARANCE OF A GEMSTONE

Pub. No.:    WO/2002/031474    International Application No.:    PCT/US2001/032177
Publication Date: Fri Apr 19 01:59:59 CEST 2002 International Filing Date: Fri Oct 12 01:59:59 CEST 2001
IPC: G01N 21/87
Applicants: GEMOLOGICAL INSTITUTE OF AMERICA, INC.
Inventors: REINITZ, Ilene, M.
JOHNSON, Mary, L.
SHIGLEY, James, E.
HEMPHILL, Thomas, S.
Title: SYSTEMS AND METHODS FOR EVALUATING THE APPEARANCE OF A GEMSTONE
Abstract:
Of the 'four C's,' cut has historically been the most complex to understand and assess. This application presents a three-dimensional mathematical model to study the interaction of light with a fully faceted, colorless, symmetrical round-brilliant-cut diamond. With this model, one can analyze how various appearance factors (brilliance, fire, and scintillation) depend on proportions. The model generates images and a numerical measurement of the optical efficiency of the round brilliant-called DCLR - which approximates overall fire. DCLR values change with variations in cut proportions, in particular crown angle, pavilion angle, table size, star facet length, culet size, and lower girdle facet length. The invention describes many combinations of proportions with equal or higher DCLR than 'Ideal' cuts, and these DCLR ratings may be balanced with other factors such as brilliance and scintillation to provide a cut grade for an existing diamond or a cut analysis for prospective cut of diamond rough.