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 o 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.

1 . A method for providing a cut grade for a gemstone comprising: 
 illuminating a gemstone model with a modeled light source from infinite distance;    evaluating the fire of the gemstone model using a metric.    
     
     
         2 . The method of  claim 1  further comprising refracting light elements through the gemstone model.  
     
     
         3 . The method of  claim 2 , wherein the evaluating of fire uses a metric that considers the total number of light elements, the length distribution of light elements and the angular distribution of the light elements for the gemstone model.  
     
     
         4 . The method of  claim 3  wherein the evaluating of fire using said metric further comprises setting a power density threshold for said light elements.  
     
     
         5 . A method for providing a cut grade for a gemstone comprising: 
 illuminating a gemstone model with a point light source at infinite distance;    refracting light elements, originating from the point light source, through the gemstone model;    evaluating the fire of the gemstone model using a metric.    
     
     
         6 . The method of  claim 5 , further comprising evaluating the fire of the gemstone comprises recording light elements that appear to refract out of the crown of the gemstone model from the perspective of a hemispherical observer.  
     
     
         7 . The method of  claim 6 , wherein said hemispherical observer is at an infinite distance from the gemstone model.  
     
     
         8 - 22 . (canceled)  
     
     
         23 . The method of claim  15 , wherein the grade combines an evaluation of fire and scintillation.  
     
     
         24 . The method of claim  15 , wherein the grade combines an evaluation of fire, brilliance and scintillation.  
     
     
         25 - 110 . (canceled)