Optodynamic measurement of a non-stationary temperature field in air by multiple laser-beam deflection

A new method for non-stationary temperature-field measurement is presented. Optoacoustic generation is used to emit short acoustic transients within the observed field. The transient deflects a probe laser beam, which is folded by two parallel mirrors in such a way that it passes through the observed field several times before it reaches a position-sensitive photo-detector. The timing of the acoustic wavefront transits at several distances from the source is obtained from a single oscilloscope trace of the photo-detector output. By measuring the acoustic wavefront transit times and the distances between the probe-beam segments, the velocity of sound is determined and from this we were able to calculate the local temperature.