Different Considerations in Mirror Photogrammetry

Abstract

The self calibration of a non-metric camera without object space information requires an assumption that the interior orientation is unchanged between more than two photographs taken of the same three-dimensional object. However, this criterion may not be valid for many non-metric cameras. On the other hand, it is not very difficult to manufacture high-quality front-surfaced mirrors with practically no undulation. Also, by placing such a plane mirror close to an object so that a non-metric camera can record not only the object directly but also its mirror reflection, the above assumption can be satisfied rigorously between the normal and satellite pictures taken on the same negative. In addition, constraints are generated among the exterior orientation parameters of the stereopair of mirror photographs. Based on both these findings and the potential theory of overlapped photographs (Okamoto [1986]), this paper discusses the self calibration problem of non-metric cameras employing plane mirrors in detail. Further, the constraints regarding the exterior orientation of overlapped mirror photographs prove to be replaced by coplanarity equations and object space information redundantly used. Finally, corrections techniques for mirror distortions are presented.