Color-temperature calibration method of mixed liquid crystals thermometry

Thermochromic liquid crystals (TLCs) are useful for understanding temperature fields, but their color changes occur over a narrow temperature range. This work aims to expand the applicable temperature range by concurrent use of a combination of liquid crystals with different temperature ranges, but because the correlation between color and temperature becomes complicated, a new deterministic technique is required. As a result of detailed color analysis, it was found that changing the concentration of TLCs in suspension resulted in a remarkable difference in chroma saturation and luminance and was effective for distinction of the TLCs. The color of each TLC was converted into temperature using the values of hue and chroma saturation entered into a database. By using this method, we were able to quantify temperature from the visualization image when two kinds of TLC were used. Also, although the angle of observation also influenced the observed color of TLC, bi-directional light irradiation into a test section minimized this problem.