Depth from projector's defocus based on multiple focus pattern projection

For 3D active measurement methods using video projector, there is the implicit limitation that the projected patterns must be in focus on the target object. Such limitation set a severe constraints on possible range of the depth for reconstruction. In order to overcome the problem, Depth from Defocus (DfD) method using multiple patterns with different in-focus depth is proposed to expand the depth range in the paper. With the method, not only the range of the depth is extended, but also the shape can be recovered even if there is an obstacle between the projector and the target, because of the large aperture of the projector. Furthermore, thanks to the advantage of DfD which does not require baseline between the cameras and the projector, occlusion does not occur with the method. In order to verify the effectiveness of the method, several experiments using the actual system was conducted to estimate the depth of several objects.