Building structured lighting applications using low-cost cameras

Structured lighting is a computer vision technique that projects illumination patterns onto the scene to facilitate feature extraction from the captured images. The use of low-cost cameras is avoided not only due to their low image quality but mostly due to the lack of a synchronization mechanism for the illuminators. In this paper we propose a method to synchronize low-cost cameras and illuminators based on the dynamic estimation of the camera sensor exposure and number of lines. At the same time, the use of structured stroboscopic lighting is used to enhance the image quality. Starting with a coarse estimation of the sensor parameters, we developed computer vision algorithms that detect image artifacts created by the structured lighting when the illuminators are not correctly synchronized with the camera frames. The detected artifacts are used to refine the estimation of the sensor parameters and to adjust the firing of the illuminators until a clear picture is obtained. Our technique requires a simple external circuit to control the firing of the illuminators, that is adjusted by software, and allows virtually any modern digital camera to be used in structured lighting applications. We demonstrate the use of this technique in a fast 187 fps robust pupil detector that can be used for gaze interaction applications. (AU)