Design and discussion of off-axis reflective double-pass optical systems

In most off-axis reflective optical systems, light beams only pass each optical element once. A double-pass structure can increase the number of beam reflections while using the same number of elements as conventional systems, which can be advantageous for some optical systems, with benefits that include high system compactness and cost-friendliness. In this paper, a design method for off-axis reflective double-pass optical systems is proposed that enables effective control of the overlap of a beam that passes through the double-pass surface twice. Furthermore, we designed and analyzed various geometric folding structure double-pass optical systems that include three-mirror reflections to explore their optimization potential and volume control capabilities. Subsequently, the effect of the double-pass structure on the optical system's performance is investigated using the system volume as an indicator. The results obtained show that when a system inherently requires a longer total optical length to enable better aberration correction, a double-pass structure may reduce the system volume. Finally, we discuss the impact of the double-pass configuration on the optical system's position sensitivity and surface shape sensitivity.