Ultrasonic irradiation system

An ultrasonic irradiation system comprising:

• a transducer having a generally circular contour and divided into a plurality of transducer elements in a circumferential direction;
• a plurality of drive circuit means for providing each of said transducer elements with respective drive signals which all have the same frequency;
• and
• control circuit means connected with the drive circuits and transducer elements for controlling the phase of each of said drive signals, including means for forming an annular zone of energy concentration on a focal plane without forming a second zone of energy concentration on a second focal plane by supplying to said transducer elements drive signals that have an initial phase distribution which is rotated "n times 360.degree." for one rotation in the circumferential direction on a face of the transducer where "n" is an integer greater than 0.

An ultrasonic irradiation system comprising:

• a transducer having a generally circular contour and divided into a plurality of transducer elements in both circumferential and radial directions;
• drive circuit means for providing said transducer elements with respective drive signals which all have a same frequency;
• and
• control circuit means for controlling the phases of said drive signals so that initial phases of driving signals of respective transducer elements have a phase distribution, said phase distribution including phase differences along radial directions on a face of said transducer so that ultrasonic waves irradiated from said transducer elements for an annular focal zone and further including "n times 360.degree." phase rotations for one rotation in the circumferential direction on said face of said transducer where "n" is an integer greater than 0.