Autofocus method using dual aperture and color filters

摘要

We propose a new autofocus method for digital camerasnbased on the separation of color components from the incoming lightnrays and the measure of their disparity. For separating color com-nponents, we place two apertures with the red and blue color filtersnon them. This enables us to get two monochromatic images thatnhave disparities proportional to the distances of the objects fromnthe camera. We also propose a new measure to find the dispar-nity of these color components because the conventional disparitynmeasures show low accuracy for the pair of different color channelnimages. The measure is based on the observation that the overlap ofnimages with disparity has many weak gradients, whereas the overlapnwith no disparity has a small number of strong gradients. One of twonimages is shifted from left to right, and the measure is computed forneach position. Then, the position with the maximum measure is con-nsidered as the disparity, and the direction and distance of focus arencomputed from the estimated disparity and camera parameters. Thenproposed method is implemented in a commercial compact camera,nand it has been demonstrated that the method finds the focus in anwide range of distance and illumination conditions