A telecentric lens is a compound lens which has its entrance or exit pupil at infinity; in the prior case, this produces an orthographic view of the subject. The simplest way to make a lens telecentric is to put the aperture stop at one of the lens's focal points. An entrance pupil at infinity makes the lens object-space telecentric. Such lenses are used in machine vision systems because image magnification is independent of the object's distance or position in the field of view.