Introduction

A dopter is a surface separating two different medium indexes. Apart from those with mirrors or diffracting surfaces, usual optical systems (camera objective lenses, projection lenses, glasses, microscopes) are exclusively made of a number of diopters.

Optical systems generally have a revolution axis and diopters used are generally spherical or plane. The system axis is the line goring through the diopters centers of curvature, it is perpendicular to the diopters planes.

Some optical systems can have optical aspherical surfaces of revolution around the system axis. These aspherisation are necessary for the reduction of aberrations of which the study cannot be treated here. Such a surface will be assimilated to a spherical diopter of which the curvature ray is identical to that of the surface on the optical system axis.