What does one image of one ball tell us about the focal length?

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.

Publication year:2015

Keywords:A1 Journal article

BOF-keylabel:yes

Authors from:Higher Education

Accessibility:Closed