Ultrasonic system

Claim 1

An ultrasonic system for ultrasonic imaging, comprising: an array defining an axis and including a plurality of flat annular transducer elements arranged contiguously in concentric relation and in a common plane for transmitting ultrasonic sound waves to an object in a medium and for receiving ultrasonic sound waves reflected therefrom, each of said transducer elements having substantially the same area; pulse generating means for applying high frequency electrical pulses to said transducer elements of said array; control means for successively energizing said transducer elements so as to create a focus of focal maximum intensity having a predetermined ultrasonic sound beam profile at a predetermined point in a predetermined region of said medium, comprising means for varying a relative time delay between the pulses applied to said transducer elements to minimize error of delay time of ultrasonic energy transmission and reception in each individual transducer element and to equalize errors in delay time between adjacent transducer elements; means for summing the plurality of received ultrasonic signals from said array; and means for displaying ultrasonic image in correspondence with the summed signals; wherein the radius of the i-th transducer element as measured from the axis of the array is given in accordance with the relation: r.sub.i =(i/N).sup.1/2 r.sub.N wherein N is the number of coaxial annular transducer elements and r N is the outer radius of the outermost annular transducer element; and wherein the relative time delay T of energization of the i-th annular transducer element is determined by the means for varying a relative time delay according to the following relationships: T.sub.i =f/c[{1+(r.sub.N /f).sup.2 }.sup.1/2 -{1+(x.sub.i /f).sup.2 }.sup.1/2 ] x.sub.i ={(i-1/2)1/N}.sup.1/2 r.sub.N where f is the focal length along the axis of the array, and c is the velocity of the ultrasonic sound wave.