Short range ultrasonic rangefinder

摘要

The present invention provides a short-range ultrasonic distance sensor configured to reduce the adverse effect of ringing that occurs when detecting a nearby obstacle within about 10 inches. In one embodiment antiphase ultrasound is introduced into the circuit 245, while in another embodiment, the strain sensor 232 introduces a negative feedback to cancel the ringing 147. Finally, in the third embodiment, both negative feed back and anti-phase methods are employed for optimal results.