Optical measurement of temperature using TLC (thermochromic liquid crystal) and interferential filters

This paper describes a new, simple and accurate optical method which can be used to determine the temperatures in a TLC field using interferential filters. Also, it provides detailed information on the experimental rig which was used to calibrate the TLC film employed in this study. The radiation effects of the light source on the temperatures are also investigated. The experimental rig was comprised of a horizontal solid aluminium rod at the centre of which was embedded nine thermocouples for temperature measurement. The two ends of the cylinder were kept at different constant temperatures. The surface of the cylinder was covered with a TLC film. The TLC colour responses were recorded by a frame grabber, a black and white CCD camera and a set of interferential filters. Commercially available software was used for image processing. The deduced temperatures from the filtered images were compared with the thermocouple readings. Good agreement between the two sets of data was found.