Apparatus and method for assessing optical quality of gemstones
AssigneeGemological Institute of America, Inc. (GIA)
InventorHiroshi TAKAHASHI
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Abstract
Provided herein is an apparatus for assessing a color characteristic of a gemstone. The apparatus comprises an optically opaque platform for supporting a sample gemstone to be assessed, a daylight-approximating light source to provide uniform illumination to the gemstone, an image capturing component, and a telecentric lens positioned to provide an image of the illuminated gemstone to the image capturing component. Also provided are methods of color analysis based on images collected using such an apparatus.
Claims21
1-20. (canceled)
A method of assessing a color characteristic of a sample gemstone, comprising:
- (i) determining a proportion or shape characteristic of a sample gemstone based on a plurality of color images, wherein each image of the plurality of color images includes a full image of the sample gemstone, is taken at a unique image angle, and comprises a plurality of pixels;
- (ii) selecting a defined area corresponding to the proportion or shape characteristic for further color analysis, wherein the defined area is within the full image of the sample gemstone in each image of the plurality of color images;
- (iii) quantifying individual color components in each pixel in the defined area in each image of the plurality of color images, thereby converting values for individual color components to one or more parameters representing the color characteristic of each pixel;
- (iv) determining an average value for each of the one or more parameters for all pixels in the defined area in all images of the plurality of color image;
- (v) calculating one or more color scores of a sample gemstone based on the average values of the one or more parameters of all pixels in the defined area in all images of the plurality of color images;
- and
- (vi) assessing the color characteristic of the sample gemstone by comparing the one or more color scores to values of corresponding color scores of one or more control gemstones classified to be in the pre-determined category;
- thereby assigning a color grade to the sample stone.
Dependencies are inferred from the claim text.