What does one image of one ball tell us about the focal length?
Faculty of Applied Engineering Sciences
Cham :Springer int publishing ag, 2015
Engineering sciences. Technology
Advanced concepts for intelligent vision systems : 16th International Conference, ACIVS 2015, Catania, Italy, October 26-29, 2015, proceedings / Battiato, Sebastiano [edit.]; et al.
Lecture notes in computer science ; 9386
University of Antwerp
We reanimate the (sometimes forgotten) Belgian Theorems, and show how the balls of Dandelin can give us elegant proofs for geometric properties of perspective ball projections. As a consequence, we derive a new formula for computing the focal length by means of 1 image of 1 ball. By means of simulations we show the sensitivity of our formula in function of the ratio of the major axis to the minor axis of the elliptic ball image. This provides a measure of reliability and enables us to select the most appropriate ball image.