Concurrent engineering of a next-generation freeform telescope: optical design

The latest generation of optical sensing hardware comprise optical surfaces without rotational symmetry, commonly known as freeform optics. Whether the goal is obtaining more information by using a larger aperture and/or field of view or to decrease the overall footprint of the system, freeform optics have demonstrated unique capabilities to enable these advancements. However, it is critical to use concurrent engineering practices between design, fabrication, and testing to ensure that the final system meets the required design specifications after applying manufacturing tolerances, can be fabricated, and is able to be tested using the available technologies, all while staying within the budget for the project. Here, we describe the collaborative effort between two universities, specifically as it relates to optical design, to create a 250 mm aperture-class telescope that operates at F/3 over a full field of view of 3 degrees along the diagonal. The optical system utilizes all reflective surfaces whose surface shapes are freeforms described by orthogonal polynomials. The freeform benefit was realized in the package size of the system, which was minimized to the extent possible (40 liters) while maintaining diffraction-limited optical performance over the full field-of-view in the visible spectrum.