Chromatic Modelling in Liquid Crystal Films for Ultrasonic Thermography

Several methods for the acquisition of bidimensional thermal images in acoustic fields produced by ultrasonic transducers for therapy have been described. A low cost technique used for the characterisation of ultrasonic therapy equipment consists in placing a thermochromic liquid crystal (TLC) film in a cross-section of the ultrasonic beam, forming a colorful image of the temperature distribution. This method gives information about the whole thermal pattern, which is related to intensity of ultrasound, offering a qualitative measurement. The present paper describes the acquisition of a sequence of thermal images in TLC films for the temperature range from 35degC to 40degC and digital image processing (DIP) used in order to get the mathematical model of the monotonic relation between temperature and color to get the quantitative measurement of the rise in temperature for future application in ultrasonic thermography.