Abstract: An ultrasonic echo sounding technique for reducing unwanted echoes from reflectors outside the focal line of a focused ultrasonic field is disclosed. In this technique at least two pulse-defined ultrasonic waves are successively transmitted. The amplitudes of the said waves are functions of an angle .phi. which is generated about the axis of the source of ultrasound. Echoes from the reflected waves are received from reflectors both on and outside the focal line and multiplied by an amplitude factor which is a function of the above mentioned angle .phi.. Echo signals associated with echoes having the same transit time are then added together.

Abstract: An improved method and apparatus for reducing the echoes from reflectors disposed outside the focal line in an echo-sounding process using an ultrasonic field focusing in a focal line. A pulsed ultrasonic wave is transmitted having a cross-sectional area corresponding to one or more annularly arranged transducer segments having a total azimuth angle of less than 360.degree.. Echoes of the transmitted wave are received from the spatial region corresponding to at least a part of other annular transducer segments, which complement the annular segments of the cross-sectional area of the transmitted ultrasonic pulse to form a complete ring. The radiation or receiving surfaces of the transducer segments forming the transducer ring are inclined toward the axis of the ring.

Abstract: An apparatus for focusing ultrasonic waves in a focal line by an ultrasonic optical system having at least one rotation-symmetrical, non-spherical acoustical reflection surface which together with an ultrasonic transducer element transmits an at least partially convergent ultrasonic field having an annular cross-section.