Abstract
A modeling approach combining the entropy method and color difference formula is proposed in order to quantitatively evaluate diamond scintillation. The images of 66 diamonds were captured from 0° to 105° rotation at 15° intervals. The color difference of corresponding pixels in adjacent rotation angle images was calculated using a MatLab r2014a program, which indicated the diamond’s color change due to its scintillation. A threshold (10) was determined to divide the color difference into seven color difference intervals, the percentage of which indicated the color-change area. The color difference and the percentage were comprehensively analyzed using the entropy method to evaluate diamond scintillation objectively and quantitatively. Lightness was the main factor affecting the diamond scintillation while chroma and hue also significantly affected it.
Highlights
IntroductionThe diamond has certain indicators in geology [1,2]. Because of their high hardness, high refractive index, and high dispersion, larger and more pure diamonds are often used as gemstones.Diamonds are evaluated in terms of four aspects: carat weight, color, clarity, and cut in various standards
As a mineral, the diamond has certain indicators in geology [1,2]
The larger the N∆E, the easier it is for the human eye to perceive color change
Summary
The diamond has certain indicators in geology [1,2]. Because of their high hardness, high refractive index, and high dispersion, larger and more pure diamonds are often used as gemstones.Diamonds are evaluated in terms of four aspects: carat weight, color, clarity, and cut in various standards. The diamond has certain indicators in geology [1,2]. Because of their high hardness, high refractive index, and high dispersion, larger and more pure diamonds are often used as gemstones. Faceted diamonds can be characterized by scintillation, a dynamic and comprehensive display of fire and brightness. Moses et al [3] defined scintillation as the appearance, or extent, of spots of light seen in a polished diamond when viewed face-up that flash as the diamond, observer, or light source moves (sparkle), as well as the relative size, arrangement, and contrast of bright and dark areas that result from internal and external reflections seen in a polished diamond when viewed face-up while that diamond is either still or moving (pattern). Tolkowsky systematically analyzed the diamond’s optical characteristics and estimated the best proportions for round brilliant cut diamonds, which today’s standards for “ideal-cut” diamonds are based upon with minor changes [4]
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