ABSTRACT
The measurement of vibration of a solid surface is usually achieved with an accelerometer or some other form of surface contacting sensor. There are, however, many cases of engineering interest where this approach is either impossible or impractical such as measurements on hot, light and rotating surfaces. Practical examples of these are engine exhausts, loudspeaker cones and rotating shafts respectively. Figure D2.3.1 shows the vibration velocity contours on the surface of a diamond-impregnated circular saw blade whilst cutting granite [1] and is an excellent example of a difficult measurement problem solved by laser vibrometry. Since the advent of the laser in the early 1960s, optical metrology has provided a means of obtaining remote measurements of vibration which hitherto would have been unobtainable. The methods are based on laser velocimetry which was introduced and discussed in the preceding chapter D2.2.
