Abstract: A first ultrasonic transducer (e.g. for wave reception) is mounted at the open bottom of a probe housing. One or more lenses are disposed around the first transducer and have a sloping surface or surfaces on which at least two second ultrasonic transducers (e.g. for transmission) are mounted. The second ultrasonic transducers provide paths of ultrasonic wave propagation extending through the lens or lenses and crossing each other at a point just below the first transducer. In an alternate embodiment the first transducer is made adjustably movable up and down relative to the lens or lenses, and an elastic coupling is provided through which the first transducer is held against an irregularly shaped object to be inspected.