FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

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specialized applications such as microscopy, a probing area of the order of
that produced by a conventional transducer is desirable. In this paper, the
techniques for the detection of ultrasound based on optical interferometry are
reviewed and discussed, especially their potential for application in the
industry. We will also present some experimental results obtained by
generating and detecting ultrasound at distances over 1 meter (both).
First, it is important to understand how the ultrasonic vibration of a surface
affects the light which impinges on it. It is well known that the surface
motion shifts the frequency of the reflected or scattered light by the Doppler
effect, but it is also useful to see the phenomenon in a different way.
Let us assume that the surface moves by S(t) at a location where a light field
Eo cos ut is incident,