Novel surface temperature distribution measurement using ratios of scattered light intensity from thermochromic liquid crystals

• Temperature measurement method using the intensity ratio of scattered light from TLC. • Temperature distribution measurement using Scheimpflug camera configuration. • Realization of temperature measurement accuracy comparable to that of thermocouples. • Significant extension of the range of the measurable temperature of the TLC. This study develops a novel method for measurement of two-dimensional temperature distribution using the ratios of scattered light intensities from thermochromic liquid crystals (TLCs). The proposed method involves analyzing the ratio of spectral intensities at two specific wavelengths using two cameras equipped with narrow bandpass optical filters configured in a Scheimpflug arrangement. As the intensity of scattered light from the TLC surface varies with camera elevation angle, we first examined the dependence of measurable temperature range and resolution on elevation angle. Results demonstrated that, with a temperature resolution of <0.05 °C, a measurable range of 17–39 °C could be achieved at elevation angles of 35–55°, using scattered wavelengths of 405 nm and 420 nm. Based on these findings, an elevation angle of 50° was selected to measure the temperature distribution of a two-dimensional field with a constant temperature gradient, using a multi-point calibration method for accuracy. The results indicated that the temperature distribution achieved high accuracy, with measurement errors comparable to those of thermocouples ( < 0.05 °C).