Computer-aided alignment technology for freeform off-axis four-mirror optical systems

Compared to traditional spherical and aspherical surfaces, freeform surfaces offer extensive design freedom, which can be fully utilized to correct and balance asymmetric aberrations, achieving system parameters, structures, and functions that are difficult to realize with conventional optical systems. This has made freeform surfaces a research hotspot in the fields of optical detection and imaging. Currently, freeform surface off-axis reflective systems are widely used in space detection and extreme ultraviolet lithography objective lenses due to their advantages of no obstruction, no ghost images, and a large field of view. This paper focuses on a four-mirror off-axis optical system, studying the alignment methods for such systems. By deeply investigating the relationship between aberration characteristics and misalignment, the aim is to address issues of blind alignment and long assembly cycles associated with traditional methods, thereby providing more precise technical support for optical system assembly.