| 摘要 |
PURPOSE:To suppress the deterioration of image quality generated by the refraction of beam at the boundary of the coupling solution in an ultrasonic probe and a living body to the min. degree, by bringing the contact surface of an acoustic window with a medium to be measured to nearly level. CONSTITUTION:When the radius of curvature of the wave front shift of the equivalent radius of curvature of a convex annular array transducer is set to r2, the radius of curvature of an acoustic window is set to r1, the sonic velocity of the coupling solution sealed in the acoustic window is set to c1 and the sonic velocity in a medium to be measured is set to c2, ultrasonic waves are converged to the position separated by r2 from the transducer at the time of c1=c2. The shift DELTAr of the converging point generated at the time of c1=c2 is approximately represented by formula (wherein DELTAc=c2-c1). In this formula, the relation between DELTAr and r1 can be rewritten as DELTAr=K(1+r2/r1) (wherein K is a constant). From this formula, it is understood that DELTAr becomes min. at the time of r1=infinity , that is, the shape of the window is planar with respect to a living body. When an annular array ultrasonic probe provided with the acoustic window having the above-mentioned shape is used, the shift of the ultrasonic beam converging point generated by that of the sonic velocity of the coupling solution in the probe is different from that of the living body can be suppressed to the min. degree. |
