Passive range sensor using multi-focus images

A focus-based passive range sensor is presented. As a basic principle this range sensor uses Asada et al´s method (1993), which models the blurring of an ideal linear step edge and calculates edge depth by fitting this model to multi-focus images. However the applicability of their method to a real scene is open, because the assumption of an ideal linear step edge is not always true, especially in real scenes. In order to deal with this problem, we first detect a resolution level focused edge position without any specific model. Then using the fact that edge point intensity is focal invariant, we adaptively select the proper focal scope within which the linear step edge model can be applied by changing a focus parameter sequentially around a resolution level focused edge position. The experiments show that the prototype range sensor can estimate depth of a general edge including centers at a distance of 2.5 m with 0.43% accuracy