An automatic temperature measurement by holographic inferferometry with compensation for the error due to light deflection

The deflection characteristics of the measuring beam ray in holographic interferometry are theoretically analyzed for the forced laminar convection over a heated flat plate, and the additional fringe order shift, ▵S_di, and fringe position displacement, ▵Z_T, are numerically calculated. A computer-programmed method is established to automatically compensate the light deflection effect of the taken real interferogram. The average Nusselt number estimated from the interferogram with the present compensation for ▵S_di and ▵Z_T agrees well with the exact one measured by the energy balance, and the present computer-programmed compensation procedure is found to be reasonable and effective for estimating the real fringes with a good accuracy. Therefore, the compensation for ▵S_di and ▵Z_T should be made in essence to minimize the measurement error