Temperature measurement in laminar free convective flow using digital holography

A method for measurement of temperature in laminar free convection flow of water is presented using digital holographic interferometry. The method is relatively simple and fast because the method uses lensless Fourier transform digital holography, for which the reconstruction algorithm is simple and fast, and also the method does not require use of any extra experimental efforts as in phase shifting. The quantitative unwrapped phase difference is calculated experimentally from two digital holograms recorded in two different states of water-one in the quiescent state, the other in the laminar free convection. Unknown temperature in laminar free convection is measured quantitatively using a known value of temperature in the quiescent state from the unwrapped phase difference, where the equation by Tilton and Taylor describing the variation of refractive index of water with temperature is used to connect the phase with temperature. Experiments are also performed to visualize the turbulent free convection flow. (C) 2009 Optical Society of America