Abstract
An optical proximity sensor which measures a distance of an object from 0 mm to 50 mm is developed. The sensor uses a driving mechanism to cast a light repetitively to the object. A cylinder driven by the driving mechanism is located around a point source of light and is provided with a linear or curved slit. Since light radially coming from the light source passes through the rotating slit, the object is illuminated with a cycle of the cylinder's rotation repetitively. A photodiode detects a reflected light from the object. By differentiating the light signal of the photodiode, the time period when the light illuminates the surface of the object facing the front of the photodiode is obtained. The time period is utilized to calculate the distance based on a simple triangulation. The sensor has such merits that the measurement covers the range greater than 180°and is not affected by the environmental illumination, orientation and reflectivity of the object. Measurement principle and experimental results are given to show how the sensor works and the measurement is achieved without setting specific conditions.
