| 摘要 |
PURPOSE:To achieve a higher S/N ratio of a signal, by arranging an effective vibration surface of a vibrator so as not to be parallel with particle faces in a curvature of an acoustic lens. CONSTITUTION:An ultrasonic pulse wave is generated from a vibrator 2 by a high frequency pulse electric signal applied to terminals 8 and 9 and propagates through an acoustic lens 4 as indicated by the arrows S4-S8 to converge on a lower point in a sample 11 with a curved surface 10 of a lens 4. The reflected ultrasonic wave from an area as converged near a point F of the sample 11 is converted into an electrical signal with the vibrator 2 passing through a path opposite to the arrows S4-S8 to be outputted at the terminals 8 and 9. At this point, any ultrasonic wave generated from the vibrator 2 fails to reach a partial face at a point P of the curved surface 10 of the lens 4 so positioned as to parallel a vibration surface 3 of the vibrator 2. In other words, as the vibrator 2 is formed into a ring with the center thereof removed, no ultrasonic wave transmitted from the vibrator 2 arrives near the point P of the curved surface 10 of the lens 4 so positioned as to parallel the vibration surface 3. This lowers an undesired suprious signal due to the reflected ultrasonic wave from near the point P significantly, thereby achieving a higher S/N ratio.
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