Method and apparatus for very low temperature acoustic microscopy

摘要

A method and apparatus for imaging objects utilizing acoustic waves at frequencies above 4.2 Ghz and up to 8 Ghz wherein the transducer and the object imaged by waves or beams from the transducer are both at a temperature no greater 0.2 DEG K. The transducer is driven by pulses generated by a short pulse generator which are stretched and coded by a dispersive filter and inductively coupled to a low temperature coupler to be use to drive the transducer. The frequency returns are carried by the same bidirectional coupler to a low noise amplifier. Both the low noise amplifier and bidirectional coupler are maintained at a temperature of less than 4.2 DEG K. The output of the amplifier is then coupled to a dispersive filter which responds the coding in the first dispersive filter to decode the information and reconstruct the signal. Subsurface defects are detected by heating the object while it is inspected by the acoustic transducer.