Scanning acoustic Doppler microscopy and scanning acoustic correlation microscopy

Acoustic microscopy with vector contrast at 100 MHz in a fluid with immersed particles is used to detect the flow profile in front of a microscopic orifice. The velocity profile concerning the component in axial direction of the focused beam is derived from the phase contrast. Possibilities to resolve the flow profile also for the components in normal direction with respect to the axis are demonstrated. The methods concerning measurement techniques and data evaluation for scanning acoustic Doppler microscopy are presented. For scanning acoustic correlation microscopy the time dependent phase and amplitude signals resulting from sound waves scattered by the immersed particles (aluminium flakes with a typical diameter of 10 μm) have been analysed by correlation procedures. From the obtained autocorrelation functions the velocity distribution can be derived. Both methods can be applied simultaneously. Data analysis is based on the information contained in the originally obtained images in vector contrast derived from temporal and spatial resolved analogue and digital processing of the acoustic signals.