Three-Dimensional Proximity Sensing with Simple Circuit Made of General-Purpose Electronic Components

A simple method for three-dimensional proximity sensing with an electronic circuit composed of only general-purpose electronic components is presented. Three detection electrodes are triangularly arranged at regular intervals. Changes in the stray capacitance of each electrode due to the proximity of an object are observed. This method to detect a slight change in capacitance takes advantage of the fact that the transfer characteristics of a circuit comprising three reactance elements has the property of sharp phase changes near the resonance frequency. The position of an object is estimated from the balance of the signals of three channels, and its distance is determined from their magnitude. This method enables the three-dimensional proximity detection of an object. Especially, this method can be used to electronically recognize the gestures of a human hand with low-cost circuitry.