Differential phase contrast acoustic microscopy

The acoustic counterpart of the Nomarski differential-phase optical microscope is described and demonstrated at 50 MHz. A phase sensitivity of 190 mV/degree with a noise floor at 10 mV in a 1 kHz bandwidth was measured for this instrument. This suggests that the minimum measurable height with this system is 22 AA. A variety of images obtained from metal surfaces and composite materials is presented.<
>