Off-axis mirror system design with a dual-level self-updating surface description

Freeform surfaces offer more degrees of freedom (DOF) in off-axis optical system design, showing its advantages in achieving compact systems and improving system performance. Various types of freeform descriptions have been put forward and have shown their effectiveness in optical design. However, conventional surfaces focus on mathematics and their function is limited to ray tracing. In this study, we propose a novel description method for optical surfaces, where the surface contains the mathematic core and a surface manipulation encirclement, and its key ray tracing results is dynamically updated as surface coefficients. With its two-level construction, the DOF in surface representation can be extended, and with the self-updating capability, pseudo-paraxial ray tracing data can be obtained and even controlled in the optimization process. The description is fulfilled with user-defined surface type and is compatible with commercial lens design software. Two design examples are introduced, and the design results reveal that the flexibility and DOF of the proposed surface can facilitate the design process.