Method for the manufacture of ultrasonic transducers

A method for the manufacture of ultrasonic transducers with at least one ultrasonic transducer whose active surface exhibits recesses and whose sound radiation field is to be prescribable in terms of focal distance, focal width and angle of aperture in connection with the focus and ultrasonic frequency, characterized by the following steps:

• (a) for the two focal magnitudes of focal width (F.sub.B) and focal distance (F.sub.A) to be prescribed, there is first determined for one of the two focal magnitudes (for example, F.sub.B) either its outer dimension (2a.sub.O) as a function of the radius of curvature (R) of the ultrasonic transducer (1;
• 5) or its radius of curvature (R) as a function of the outer dimension (2a.sub.O);
• (b) given the outer dimension determined in that manner or the radius of curvature determined in that manner, the magnitude radius of curvature or, respectively, outer dimension not yet determined for the other of the two prescribable focal magnitudes (for example, F.sub.A) is determined.
• (c) finally, the maximum value of the angle of aperture of the sound radiation field behind the focus deriving for the outer dimensiom (2a.sub.O) and radius of curvature (R) according to steps (a) and (b) is limited by means of the introduction of a recess (2:
• 8, 9) in the active surface of the ultrasonic transducer (1;
• 5) of such size (2a.sub.i) that the optimum relationship between the angle of aperture and side lobes of the sound radiation field ensue. PG,39