SEEING BEHIND THE SCENE - ANALYSIS OF PHOTOMETRIC PROPERTIES OF OCCLUDING EDGES BY THE REVERSED PROJECTION BLURRING MODEL

This paper analyzes photometric properties of occluding edges and prov es that an object surface behind a nearer object is partially observab le beyond the occluding edges. We first discuss a limitation of the im age blurring model using the convolution, and then present an optical flux based blurring model named the reversed projection blurring (RPB) model. Unlike the multicomponent blurring model proposed by Nguyen et al., the RPB model enables us to explore the optical phenomena caused by a shift-variant point spread function that appears at a depth disc ontinuity. Using the RPB model, theoretical analysis of occluding edge properties are given and two characteristic phenomena are shown: (1) a blurred occluding edge produces the same brightness profiles as woul d be predicted for a surface edge on the occluding object when the occ luded surface radiance is uniform and (2) a non-monotonic brightness t ransition would be observed in blurred occluding edge profiles when th e occluded object has a surface edge. Experimental results using real images have demonstrated the validity of the RPB model as well as the observability of the characteristic phenomena of blurred occluding edg es.