A Monochrome Light Emitting Diode Moirأ© Deflectometry Technique for Two Dimensional Temperature Measurement

Abstract

This article develops low cost moirأ© deflectometry for twodimensional temperature measurement in free boundary environment. Experimental setup uses a red monochrome lightemitting diode (LED) lamp with wavelength range of 625–635 nm as light source. In process, the light first runs through the convex lens and then propagates to the parabolic mirror with diameter of 406 mm and f/4.5 for generating the parallel light. The parallel light further propagates to test object and through two gratings both with pitch of 254 lpi which are printed by laser printer. Behind the two gratings, a CCD camera is applied to capture the image, the distorted fringes. Based on the moirأ© deflectometry theory, the twodimensional temperature distribution in free boundary environment can be determined in terms of the captured fringe shift analysis. This work has successfully measured the twodimensional temperature distribution in free boundary environment with heat source models of 40–95 آ°C vertical wall, 60 W light bulb, and burning candle flame. The measured temperature deviations between moirأ© deflectometry and thermocouple thermometer are all less than 5%.