| 摘要 |
<p>An ultrasonic echo phasing circuit which uses a variable delay line having a short delay time as element for constituting a variable focus means having large aperture, and which is capable of accomplishing focusing uniformly from portions very near the surface of the sample to be inspected to deep portions thereof. Each of a plurality of receiving channels forming a maximum aperture in the ultrasonic echo reception is provided with a separately controlled variable attenuator and with a separately controlled variable delay line that has the same maximum delay quantity. A variable aperture is formed by controlling the variable attenuators, delay time distribution for focusing in the aperture is formed by using the variable delay lines only that pertain to the aperture, and the received signals delayed through these variable delay lines are added and synthesized together by the beam steering means.</p> |
