Apparatus and method for ultrasonically inspecting articles for internal

Abstract

A mechanically amplified electroacoustic transducer system comprising an electroacoustic transducer having a vibrating element and an amplifier rod forming a probe extending from the transducer and in acoustically coupling contact with the vibrating element over a relatively small region thereof. The probe has a length which is approximately equal to the quarter wavelength or a multiple of the quarter wavelength of the acoustical energy generated by the transducer, the exact length of the probe being selected to provide optimum output from the system at a selected operation frequency of the transducer. The invention also provides a method for detecting internal defects in an object which comprises placing the object between one or more transmitting electroacoustic transducer systems and a plurality of receiving electroacoustic transducer systems, each transducer system being as described above, bringing the tips of the transducer probes into contact with the object, energizing the or each transmitting transducer, obtaining electrical output signals from the receiving transducers, and determining from the amplitude or phase differences between the output signals the presence or absence of defects. The apparatus and method are especially suited to the detection of 'hollow hearts' in potatoes.