ULTRASONIC RANGEFINDER - EDGE-DETECTION AND ENHANCEMENT METHOD

A new ultrasonic rangefinding technique has been developed which impro ves accuracy substantially when it is used as an edge scanner. Distanc e is measured by calculating the relative phase angle between a contin uously transmitted signal and the received (reflected) signals from bo th the top and bottom of the edge. The use of continuous emission wave s and reflections from different surfaces, such as the top and bottom of a step, give rise to interference between the received signals resu lting in phase adding or cancelling. By varying the transmitted freque ncy used for scanning, it appears that both signals are coming either from the top or the bottom of the step, thus reducing interference. Th eoretical and experimental results reveal the extent of interference a nd show the improvement achieved by the application of the new method.