Design and fabrication of imaging optical systems with freeform surfaces

Freeform surfaces provide more degrees of freedom for design of optical systems, and enhance the ability of compensation and correction aberrations. Freeform surfaces are of advantage to balance the unsymmetrical aberrations, especially for the wide-field off-axis optical systems. This paper focus on an off-axis reflective optical system, which focal length is 550mm, F# is 6.5 and field of view (FOV) is 76°. The system adopts some freeform surfaces. We discuss the problems we noticed in processes of design, manufacture, measurement and alignment, and the solutions. At last, the periodical research result and the expected performance are given.