| 摘要 |
<p>The ultrasonic detection device comprising a transducer (10) for emitting and receiving a sequence of ultrasonic pulses in the width of a window and for producing an echo signal (40, 50) representative of the reflected pulse trains, an amplifier (23) for amplifying the echo signals (40, 50), an integrator (26) for integrating the echo signals (40, 50) over a selected period (62, 63) so as to produce an integral value, amplification control means (27, 28) for measuring the integral value and for selecting the gain of the amplifier so as to keep the integral value at a steady-state value, and means (29) for measuring the time shift of the integral value with respect to the steady-state value and for determining whether the time shift is greater than a predetermined threshold. The invention can be used for detecting the presence of water on a windscreen. <IMAGE></p> |
