| 摘要 |
PURPOSE:To make signal to noise ratio good by segmenting the electric signals which a piezoelectric element has generated by receiving reflected waves to plural systems by their generation times, passing these to filter circuts of respectively suited characteristics and combining these. CONSTITUTION:The ultrasonic wave pulses generated by a piezoelectric element 1 are reflected by reflectors a-d of different depths of a target 2, and these reflected waves are converted to electric signals by the piezoelectric element 1. These are applied simultaneously to gate circuit groups 61-64, and the gate circuits open one by one for a fixed time only. The outputs thereof a are passed through filters 71-74 of different characteristics having the impulse response waveforms coinciding with the signal waveforms in the respective time sections which are inverted of their time axes. The outputs are next synthesized in a synthesizing circuit 8 and the synthesized signal is applied to and displayed in a display device 5. Hence, the SN ratio and detection efficiency are improved by processing the signals with the filters which are respectively different according to the distances up to the points of reflection. |
