Fig. 5
From: Design of a 65-degree collimating lens for lightguide-based AR glasses

When a flat glass plate is placed in front of the aperture of the collimating lens: (a) the chief ray tracing showing a diagram of the maximum field angle relationship between position of the entrance pupil and aperture stop; (b) the marginal ray tracing of the maximum field angle, demonstrating that the size of the entrance pupil remains unchanged despite the change in its position.