Proximity sensor using a spiral-shaped light-emitting mechanism

A proximity sensor is presented in which light is cast from a source point on an object through a slit cut in a rotating disk. The light passing through the slit is reflected onto the object´s surface. Some of the reflected light is captured by a photodiode with the time period being recorded. The distance is determined from the function of the slit´s shape and the time period when the photodiode captures the reflected light. The light-emitting mechanism makes it possible to measure the distance of an object repetitively. The distance measurement is neither affected by environmental illumination nor by attributes of the object such as diffusibility or reflectivity as far as there is light to reach the photodiode. Two profiles of the slit are discussed. One allows for easy fabrication and the other simplifies signal processing. The validity of the measurement concerning the two profiles is shown by experimental results