Knowledge of depth aids greatly in the object recognition task. It is preferable to be able to calculate depth without requiring multiple views, or special light sources. This paper presents a method of calculating depth from a single image in the case where the object is symmetrical about a plane. The algorithm requires the identification of symmetrical locations in the image, thus for each point at which depth is to be computed the corresponding symmetrical point must be visible in the image. The distance for which the camera is focused must also be known. The implementation of this algorithm is discussed and reconstructed shapes computed from real images are presented.
Gaile G. Gordon,
"Shape From Symmetry", Proc. SPIE 1192, Intelligent Robots and Computer Vision VIII: Algorithms and Techniques, (1 March 1990); doi: 10.1117/12.969742; https://doi.org/10.1117/12.969742