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Abstract

A noncontacting method of measuring periodic surface heating is described. The perturbation of an externally generated acoustic wave is measured. The acoustic wave is generated in the air above a sample to be studied. The acoustic wave is directed onto the sample surface, coincident with a modulated light beam. Absorption of the light beam results in the periodic heating of the sample, at and near the sample surface. The air in contact with the sample surface is in turn heated, and produces a periodic phase shift in the reflected acoustic wave. This phase shift is detected and gives a direct measure of the periodic heating of the sample surface. An acoustic microscope may generate the acoustic wave. The sample is placed in water. An acoustic microscope lens produces an acoustic wave in the water, which focuses onto the sample surface, coincident with a modulated laser beam. The light beam is guided onto the sample using an optical fiber. Heating in the water directly above the illuminated sample produces a phase perturbation in the acoustic wave reflecting off the sample surface. This embodiment of the present invention allows surface heating to be measured with very high spatial resolution.

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First Claim