Acoustic microscope with a control and data capturing device

An acoustic microscope for the examination of a specimen, with a tip fastened to a cantilever, said tip being in the surface-near-zone of the specimen, said microscope comprising an ultrasonic transducer, a scanning device for positioning the specimen relative to the tip, and with a device for control and data acquisition, wherein

• a) the ultrasonic transducer includes a transmitter with means for providing ultrasound coupled to the specimen,
• b) the ultrasound has a frequency which exceeds the lowest resonance frequency of the cantilever with the tip fixed to the cantilever,
• c) the cantilever, a clamp with a resonance frequency lower than the ultrasonic frequency, the scanning device, the transmitter, and the specimen are mechanically rigidly coupled to one another, and
• d) with a detection unit installed which measures the deflections of the tip caused by the topography of the specimen, the deflections being of lower frequency in relation to the ultrasonic frequency in a first detection signal, and the detection unit also measuring high-frequency displacements of the tip caused by the ultrasound in the specimen in a second detection signal, and means for maintaining a constant distance between the tip and the surface of the specimen by utilizing a feedback loop in the control and data acquisition device, the feedback loop serving to average the first detection signal using a time large as compared to the period of the ultrasonic frequency and with a scanning rate small as compared to the ultrasonic frequency, and
• a light beam reflected by the cantilever can be coupled, via optical devices for beam deflection, into a detection unit which comprises a first optical detection unit connected with the feedback loop and a second optical detection unit for generation of the second detection signal, said second detection unit contains a heterodyne time-of-flight interferometer whose long reference arm contains a frequency shifter in order to shift the frequency of the light-beam in the long reference arm.