High frequency 16 channel ultrasonic microscope for annular arrays

A 16 channel scanning acoustic microscope for annular arrays is presented. It has 16 independent true channels with variable gain and high precision dynamic pulse delay for high frequencies applications up to 100 MHz. It is connected to a high sampling rate (1 GS/s) AD converter and a real time data processing and acquisition computer system. Annular phased arrays enable dynamical adjustment of the focal area and an extension of the focal range without transducer movement or replacement. Since all channels are excited, the received signal to noise ratio after channel combination and image quality is in the same range as with a one element transducer. The major gain for annular arrays is time, since one scan is sufficient for multiple focus levels. It enables dynamic autofocus and can also be used in sampling phased array mode for synthetic focusing. Due to the high flexibility of the developed multi channel ultrasonic microscope, experiments for new techniques to get more information from sound field properties are possible.