| 摘要 |
PURPOSE:To detect a pinhole with high accuracy without contacting with film by respectively providing an ultrasonic projector and an ultrasonic receiver on the upper and lower surfaces of a film path and detecting the pinhole with passing ultrasonic wave. CONSTITUTION:The ultrasonic projector 10 including an ultrasonic oscillation element 2 is provided at intervals from the film surface on one surface side of the path set for a web or sheet-shaped film 1 and continuously projects the ultrasonic waves to the set width on the film surface. The ultrasonic receiver 11 including an ultrasonic detection element 3 is set on a position symmetric with the array of the element 2 on the other surface side. The element 2 receives a high frequency pulse signal from an oscillator 4 through a pulse shaping unit 5 and generates the ultrasonic wave 6 of the same frequency. When the pinhole 9 of the film 1 coincides with an ultrasonic propagation path which leads to the element 3 from the element 2, the element 3 receives the penetrated component of the ultrasonic wave 6 and generates output voltage so as to perform display 8 through an amplifier 7. |
