| 摘要 |
Method for detecting objects or bodies in a liquid by means of ultrasound pulses. In the seas, one is interested in detecting the presence of copepods, water fleas. Water fleas typically have a length of 30-70 microns. Furthermore, one is interested in being able to determine the distribution of the various species of copepods. This is achieved according to the invention by means of ultrasound pulses of a frequency of around 4 MHz. If such an ultrasound pulse hits a copepod, one gets two echoes, the last of which is relatively powerful. This is evidently due to the fact that the copepod acts as a lens and furthermore contains liquid. If the sound wave, however, strikes an air bubble, one gets only one echo. If the sound wave strikes an impurity, one gets two nearly identical echoes. One should therefore be able to filter out irrelevant signals. On the basis of the mutual phase relationship of the reflected pulses, one then determines the types of the reflecting bodies. In an especially advantageous embodiment, the mutual phase relationship of the pulses is determined by means of a phase differentiation circuit consisting of a leading edge filter 1 in conjunction with a delay line 2 with tap. <IMAGE>
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