Simultaneous 3D position sensing by means of large-scale spherical aberration of lens and Hough transform technique

We demonstrate a real time 3D position sensing of multiple light sources by capturing their ring images that are transformed by the molecular lens system with large spherical aberration. The ring images change in diameter in accordance with the distance to the light sources, and the ring center positions determine the directions toward them. Therefore, the 3D positions of light sources are calculated by detecting the diameters and center positions of the circles. This time we succeeded to measure 3D positions of multiple light sources simultaneously in real time by extracting and tracking the circle patterns individually. Each circle is extracted by the Hough transform technique that uses not-closely-distributing three edge points to search the primal votes more than threshold, and is tracked by predicting the successive positions by Kalman filter. These processes make it possible to measure the 3D positions of light sources even in the case of overlapped plural circles. In the experiment, we could track several circle patterns measuring the center positions and diameters, namely, measuring the 3D positions of LEDs in real space. Measurement error of 3D positions for a LED was 6.8mm in average for 150 sampling points ranging from 450mm to 950mm in distance.