Ultrasonic scanner with enhanced depth resolution focussing - has transmission spectrum with fixed and stepwise-varying bands

摘要

An ultrasonic scanner has a scanning head connected in transmission and receiver circuits. At least the transmission circuit has a system of different frequencies. It pref. also has a depth variation focussing system while the receiver has fitters for different frequencies. The ultrasonic scanner head (1-9) is activated by the transmitter circuit (10.15) so that each transmission/reception cycle covers a selected frequency band. The selected frequency spectrum contains a h.f. band for depths near the surface and a lower frequency band for greater depths increasing step-wise from cycle to cycle. The receiver filters (18-20) are tuned to the selected transmission frequency spectrum.