JPS5950936B

PURPOSE:To decrease the attenuation or reflection of the ultrasonic wave and thus obtain a high-resolution picture by producing the sample holding plate with the sapphire or the like which features a small propagation loss of the ultrasonic wave and also securing an integer-fold of the half wavelength of the ultrasonic wave for the thickness of the holding plate. CONSTITUTION:Sample holding plate 11 is produced with the material like the sapphire or the like featuring a small propagation loss of the ultrasonic wave, and the thickness of the holding plate is set to an integer-fold of 1/2 the wavelength of the ultrasonic wave. The crystal, ruby and the like can also be used for plate 11. In such constitution, the attenuation of the ultrasonic wave can be decreased for plate 11, and at the same time the acoustic impedance viewed from the sound field medium is set equivalent to the intrinsic acoustic impedance of the acoustic medium. Thus the reflection loss can be reduced down to zero substantially. Also silcon dioxide layer 12 featuring the thickness set to the 1/4 odd-fold of the wavelength of the ultrasonic beam can be formed on both surfaces of plate 11 the thickness of which is prescribed as mentioned above.