Utilizing freeform optics in dynamic optical configuration designs

A linear field of view (FOV) K-mirror system used for image derotation is presented as a case example for how to leverage freeform surfaces in dynamic optical configuration design. As the K-mirror rotates about the optical axis, points in the FOV sample the surface at distinct locations, allowing for highly local control of the system aberrations. This methodology is distinct from the typical benefits associated with freeform surfaces, and as such broadens the uses of freeform optics into the category of systems that exhibit changing optical configurations. We show that compared to an on-axis or off-axis conic design, the freeform surface has better distortion correction abilities. Furthermore, a real pupil is generated by the K-mirror system and analyzed for uniformity. The design ideas presented for the K-mirror are discussed in the context of astronomical applications, where systems may benefit from these techniques.