Introduction

An optical system is transversely restricted geometrically by the frames of the lenses or mirros and other various mechanical diaphragms.

For a given combination, the pupil is the diaphragm which limits the luminous beam coming from the object. This diaphragm is generally put inside the optical system. We define the exit pupil of the system by the image of this diaphragm through the lenses (or mirrors) which follow it. It is also the image of the entrance pupil through the lenses (or mirrors) which precedes it.

The exit pupil is the image if the entrance pupil in the optical system. The field object is the maximum lateral dimension of the object.

When the object is infinite, the object field expresses in an angular way. The field is usually restricted by a special diaphragm called: “field diaphragm”.

The full light field object is defined by the set of points of the objects for whose the luminous beam crossing the system are restricted only by the opening diaphragm, D.O. It provides a quasi uniform lightning to the full light field. Beyond the full light field, the diaphgragmations provoked by the frames of the lenses extensively reduce the lightning of the image. This reduction of the lightning at the field edge is called vigneting.