Acoustic microscope

: Arnold, W.; Rabe, U.

Abstract
Through the use of an acoustic microscope, it is possible to measure the topography of a sample (11) and at the same time its elasticity characteristics. The deflection of a dial indicator (1) is measured by the deflection of a laser beam (22). The topography is measurable by the fact that the mean deflection of the dial indicator (1) is kept constant by means of a control loop. The control loop consists of a segmented photodiode (24) which supplies a neutral signal at the output of a normalization amplifier (29) at the mean deflection of the dial indicator. Deviations from the neutral signal can be compensated via the z electrode (8) of a piezocrystal. The elasticity characteristics of the sample (11) are measurable by the fact that ultrasound can be injected into the sample (11) by means of a transmitting head (9) and the high-frequency deflection of the dial indicator (11) can be measured by means of a second detection device from a shadowing device and a high-speedphotodiode (37). The second detection device can also be set up from a heterodyne delay interferometer or by purely electronic means from a capacitive detection device.