Figure 4
From: A closed form unwrapping method for a spherical omnidirectional view sensor
Projection of sphere on image plane. When a sphere is projected onto an image plane, a circular feature is obtained. The parameter R describes the spherical mirror’s radius while h is the distance between the spherical mirror and the centre of projection, C. However, the radius of the circular feature does not represent an equivalent radius of the sphere due to the viewing angle, ζ.