| 摘要 |
PURPOSE:To provide an equipment for automatically adjusting the focal point of an ultrasonic sensor in an ultrasonic spectrum microscope in the vertical direction. CONSTITUTION:The ultrasonic sensor 12 is an independent transmission/reception sensor comprising a flat transducer 12 and a concave transducer 14. Vertical distance DELTAZ between the ultrasonic sensor 12 and the surface 24a of an object 24 to be inspected can be represented by; DELTAz={(Pfref(f)-Pf(f)}/ f).{(V0.costheta)/2pi(1+cos2theta)}. (f: frequency, Pfref(f): reference phase curve when the focal point of ultrasonic sensor is present on the surface of the object, Pf (f): phase curve when the focal point of ultrasonic sensor is present at an arbitrary position, V0: velocity of sound of an ultrasonic propagation medium present between the ultrasonic sensor and the object, theta: incident angle defined between the flat transducer and the surface of the object). An FFT(Fast Fourier Transform) operating unit 34 calculates DELTAZ based on an output from the ultrasonic sensor 12 through a digital oscilloscope 32. |
