Low-noise ultrasonic wave focusing apparatus

An ultrasonic wave focusing apparatus comprising:

• a transducer array having a plurality of ultrasonic transducers;
• and
• a control device to which position coordinates within a space are inputted, the control device causing the ultrasonic transducers to generate ultrasonic waves having phases based on the position coordinates in such a manner that the ultrasonic waves of the ultrasonic transducers form a focal point at the position coordinates,
• wherein, when the inputted position coordinates within the space are changed discretely in a trajectory from a first position to a second position that is adjacent to the first position, the control device calculates a target value for each target phase necessary for the ultrasonic waves outputted from the ultrasonic transducers to form a focal point at the second position, locates an ultrasonic transducer whose current value for a current phase of an outputted ultrasonic wave is different from the target value, and changes a phase of an ultrasonic wave outputted from the ultrasonic transducer to its target phase in multiple steps.