Multiple curved transducers providing extended depth of field

Apparatus for focussing ultrasonic waves over a large field comprising the following transducers and lens located in order along an axis:

• an acoustical lens,
• a flat transducer whose ultrasonic waves are focussed by said acoustical lens, and
• a curved transducer, and
• means for coupling the acoustical lens to the flat transducer, and the flat transducer to the curved transducer so that ultrasound can travel efficiently from the acoustical lens, to the flat transducer, and to the curved transducer, the flat and curved transducers focussing upon adjacent fields forming a composite, extended field, and the flat transducer being large enough to intersect substantially all forward, focussed waves transmitted by the curved transducer.

Apparatus for focussing ultrasonic waves over a large field comprising the following transducers and lens located in order along an axis:

• a curved transducer,
• an acoustical lens, and
• a flat transducer whose ultrasonic waves are focussed by said acoustical lens, and
• means for coupling the curved transducer to the acoustical lens, and the acoustical lens to the flat transducer so that ultrasound can travel efficiently from the curved transducer, to the acoustical lens, and to the flat transducer, the curved and flat transducers focussing upon adjacent fields forming a composite, extended field, and the curved transducer being large enough to intersect substantially all forward, focussed waves transmitted by the flat transducer.