Light pattern blur estimation for automatic projector focus control of structured light 3D camera

This paper presents a method of light pattern blur estimation for its application to automatic projector focus control in structured light 3D camera. To overcome shortcoming of the conventional methods for estimating blur of light pattern, we propose to normalise the light pattern image incorporating reference images. Which are made available by a structured light 3D camera. The reference black and white patterns are utilised in such a way as to eliminate the dependence of intensity variation around an edge on surface reflectivity. Then the unknown blur radius is estimated from the first derivative of normalised edge. Experimental results on both synthetic and real images verify that the proposed method is indeed independent of surface reflectivity and is accurate and sensitive enough to the small change of blur. Finally, based on the proposed light pattern blur estimation, a structured light 3D camera that is equipped with automatic multi-stage focus control in a beam projector has been built to demonstrate its capability of capturing the 3D workspace of large depth variations.