| 摘要 |
PURPOSE:To make it possible to project only a longitudinal wave into an object to be inspected with an oblique incident angle, by providing a vibrator consisting of a damper and a piezoelectric element, a protective plate fixed to the under-surface of the vibrator and a pair of lead wires. CONSTITUTION:When an electric pulse is applied between lead wires 161, 162 after a damper 11 is set to an object 1 to be inspected so as to contact the protective plate 15 thereof with the surface of the object 1 to be inspected, a plurality of vibrators 13... start vibration. Because the vibrators 13... each comprises a piezoelectric element, a stress phase is different by 180 deg. by the direction of applied voltage. When the vibrators 13... are arranged as shown in the drawing, the phase of adjacent vibrators 13... is different by 180 deg. and the phase of generated ultrasonic waves is also different by 180 deg.. Therefore, the synthesized liquid surface 17 of ultrasonic waves generated in the object 1 to be inspected is brought to the direction of the angle theta given by the formula and ultrasonic waves are propagated to said direction. In the formula, lambda is the wavelength of ultrasonic waves and To of the width of the vibrator. In this case, because the vibrators 13... generate longitudinal waves, no transversal wave is generated. In addition, by simultaneously applying a same pulse to the vibrators 13..., only the longitudinal wave can be projected into the object 1 to be inspected. |
