Rigid endoscopic relay systems: a comparative study.

Relay systems in rigid endoscopes can compensate for aberrations in the objective and the eyepiece. Five classes of rigid relay systems are examined: conventional; glass Hopkins; plastic lens, glass-rod Hopkins; modified Hopkins; and gradient index. First-order theory, including achromatization, is developed for these systems. Design results are presented, and aberration, vignetting, and system length trade-offs are analyzed.