ABSTRACT
The final image in a visual instrument is formed at the retina of a human eye. If the eye is emmetropic, i.e., if it does not have any refractive errors, the virtual image provided by the instrument has be located at an infinite distance. The coupling of the visual instrument to the eye is done by locating the eye close to the exit pupil of the instrument. The distance from the last optical surface of the system to the exit pupil is called the eye relief.
