| 摘要 |
PURPOSE:To obtain an ultrasonic tomographic image of high resolution for a wide range and distance, simplified in operation with a driving circuit having a simplified structure by a method wherein, a group of acoustic lens converging ultrasonic waves emitted from an opening corresponding to a plurality electrodes of electroacoustic converting element, on a central axis of an ultrasonic radiation, on positions different from each other by each element, is provided. CONSTITUTION:An electroacoustic convertion element 1 has a structure in which, a common electrode 3 is provided in front of a sheet of piezoelectric plate 2, while ring-shaped electrodes 5, 6, 7 positioned in sequence concentrically on the outer periphery of the back surface of the plates 2 together with a central circular electrode 4. On the front surface of the electroacoustic conversion element 1, an acoustic lens group 14-17 is formed unitarily on the side opposite to each electrodes 5, 6, 7. A driving voltage is applied on electrodes 3-6 through leadwires 8-12, ultrasonic waves are emitted from openings corresponding to each electrodes 4-7 caused by the excitation of the piezoelectric plate 2. These ultrasonic waves can be converged on the points different from each other on an ultrasonic radiation central axis 18 by the function of acoustic lenses 14-17. Accordingly, by applying the same phase voltage (without delay), a high resolution ultrasonic tomographic image ranging widely converging near to far distances of a body to be detected can be obtained. |
