Figure 16.

improvements in light efficiency of the effective pupil of the eye-telescope system resulting from extending the exit pupil horizontally. Dashed squares and rectangles represent the exit pupil sizes for with 2 different eye pupil diameters (3 and 4 mm, respectively) using both a square and horizontally extended entrance pupils. The light gain (or actual loss) is equal to the percentage area of the eye pupil covered by the exit pupil, as shown in the diagrams. The benefit of a rectangular objective in terms of light efficiency is shown to increase with increased eye pupil diameter.