LASER SPECKLE PHOTOGRAPHY USED FOR MEASURING TEMPERATURE GRADIENT DISTRIBUTION IN A NATURAL CONVECTION

摘要

Laser speckle photography is an useful optical method for quan-titative measurement of light deflection angles in the phase object field, such as natural convection, combustion, supersonic flow and plasma diagnostics etc. For a stable flow, as a laminar free convection, only a He-Ne laser is required for exposure with a duration of 1 second. The laser beam required for this purpose is not stricted in coherence as used for holographic interferometry. The optical system for speckle photography can be easily constructed with inexpensive optical parts.