Papers by Author: Xiang Li

Abstract: According to different light sources and cathodoluminescence (CL) intensity, the performance of color parameters (lightness L^*, chromaticity a^* and b^*, chroma C^*, hue angle h_o) and chromophore contents (Cr³⁺, åFe) are studied to analyze the impact of all these elements on ruby red color. Ruby red under the standard light source D65 (a^*=5.65 ~ 26.97, b^*= -5.43~3.98) is similar with the color under natural sun-light. Purplish red h_o Î (354.14°, 0.7°) with medium-low lightness (L^* = 32 ~ 40) under D65 displays the best visual appearance, showing a relatively high value. Comparing with D65, standard light source A reveals ruby a deep red hue (a^* = 10.61 ~ 37.39, b^* = -6.59 ~ 7.50). Because of the strongest spectrum power distribution in the orange range and fluorescence of light source U30, the hue of orangish tone is mixed in ruby red (a^* = 6.92 ~ 31.23, b^* = 0.31 ~ 9.34). It is illustrated that åFe can inhibit the intensity of CL which is compared in different voltages. Low lightness purplish red is easy to be influenced by CL and always shows strong luminescence correspondingly. It is concluded that ruby purplish red has strong luminescence of CL which is usually supported by a few of åFe and medium-low lightness under D65, which has an excellent visual perception.

Abstract: The correlations between of lightness, chroma, Cr3+ and color index were studied to analyze the impact of all these three elements on ruby red color; and with the color difference research, the lightness difference is testified to be the key affecting color appearance. Based on the uniform color space CIE 1976L*a*b*, the ruby displays the best red color when the content of Cr3+ is within (1555, 5183ppm), L* (32.64, 44.25) and ho  (354.14, 0.7). With the help of partial correlation analysis of color difference, it is illustrated that the correlation between L* and E* (r=0.999) is relatively higher than that between L* and E* (r=0.948); and with high significance level ( = 0.129) of H* and E*, it shows that H* has little impact on E*. It is concluded that the color change of ruby from red to purple are mostly affected by lightness change; lightness difference should be considered as the most important factor when evaluating the red color of ruby, and then followed by the chroma and hue jointly.