QUALITY EVALUATION METHOD FOR PEARL AND ITS DEVICE

PURPOSE:To precisely measure thickness of pearl wrapping without depending on any experienced appraiser by finding a quality estimate value of a pearl on the basis of a reflection wave of an ultrasonic wave incident on the pearl. CONSTITUTION:A pearl S to be measured is positioned (5), while a transmission signal from a transmitter 1 is converted into an ultrasonic wave by a transducer 3 so as to be propagated in a sound lens 4, and the ultrasonic wave is incident toward the center of the pearl S having a double structure of a core and wrapping. The ultrasonic wave is reflected on a pearl S surface and an interface between the wrapping and the core so as to be individually turned into a surface reflection wave and a boundary surface reflection wave, which are converted into receiving signals, and then, the signals are inputted in a signal cutting unit 7. In this process, durations t1, t2 from the generation (9) of a transmission trigger to arrival of the surface reflection wave and the boundary surface reflection wave to a gate circuit 12 are set (13), and the circuit 12 is opened (closed) at the time t1 (t2), and each reflection wave form signal is inputted (8). T his input is converted into reflection wave form data by an A/D converter 14 so as to be stored (15) and displayed (16). On the other hand, a computer 17 reads the reflection wave form data so as to carry out measurement of the thickness of wrapping and quality evaluation computing.