A companion plot of the variation of the individual colors R,G, and B with temperature is shown in Figure 6.4(d).

Figure 6.4(d): Variation of individual colors R,G, and B with temperature.

It is to be observed that hue has a monotonic variation with respect to temperature. The uniform level of intensity is itself an indication of the uniform level of illumination over the test-surface. It confirms the quality of lighting arrangement used for the experiments.

To estimate the spread of H, S, and I within the sample region of the LC image, their variance is shown in Figure 6.5.

Figure 6.5 A typical HSI variance graph of the LC sheet as a function of temperature

Of the three, hue shows the smallest variance, indicating good quality of isothermal conditions within the sample region around the thermocouple and the suitability of hue as a measure of the color-temperature relationship. The in-situ calibration approach is seen to improve the measurement accuracy by eliminating errors that may arise from differences in viewing angle and lighting, going from calibration to the actual experiment.