Contactless Surface Measurement with a New Acoustic Sensor

A standard diamond tip fixed to a micromechanical tuning fork (32 kHz) is guided by piezo-electric actuators in a controlled distance of about 100 nm along the inspected surface. The small acoustic fork oscillation (constantly excited) is (mainly) damped by the air gap between diamond tip and surface. Thus, constant output signal of the high-Q oscillatory circuit indicates that the tip traces the surface roughness in a constant distance. First results carried out at roughness standards, map the profiles obtained mechanically. Difficult materials like laquers, glasses, ceramics were investigated.