| 摘要 |
PURPOSE:To detect a microdefect in micron unit by forming both internal and external surfaces of the bottom of a case to a spot convergence type acoustic lens which swells spherically to its internal surface side. CONSTITUTION:When a pulse is applied from an ultrasonic wave oscillator to a vertical probe 11, an emitted ultrasonic wave passes through the liquid in the case 8 and reaches the acoustic lens 8. In this case, a plane wave arrives at the internal surface 9a of the lens 9 and the wave enters the lens 9 except a reflected wave and is refracted and diffused in the lens 9. The ultrasonic wave which is diffused to pass through the lens 9 reaches the external surface 9b of the lens 9 and reflected and converged as determined by each acoustic velocity in the liquid 10 in the tank and the radius of curvature of the external surface 9b of the lens 9, so that the wave is focused. Then an ultrasonic wave beam when entering the liquid 10 in the tank from the external surface 9b of the lens 9 operates as well as the use of a large-diameter vibrator as the probe 11 because the plane wave emitted by the probe 11 is diffused by the internal surface 9a of the lens 9, and the focal length is also shortened at the same time. |
