Systems like TESS require specialized components that challenge all involved. These systems consist of many sub-components, but we are focused on the refractive and reflective optical components. One purpose of this talk is to introduce optical system designers to application specific manufacturing processes. We, as manufacturers, need to tailor our processes for the optic’s specific operational environment. In addition, we want to introduce some of our more unique manufacturing capabilities to allow system designers to widen their design space. It is now feasible to manufacture a wide range of sizes, shapes, and materials for many different applications.
When manufacturing precision optical surfaces of relatively larger sizes it is critical to understand the thermal stability of the substrate material. The material properties associated with thermal homogenization are commonly reviewed and soak schedules are created. These schedules ensure a surface under test is in a stable state and is ready for wavefront measurement with an interferometer. However with some materials such as N-BK7, standard soak schedules may not be enough. This paper shows the thermal challenges associated with manufacturing precision optical surfaces when the substrate material is N-BK7, and how the issue can be easily confused with poor metrology. Throughout the manufacturing of precision optical surfaces, the substrates are exposed to varying heat sources and loads. During the manufacturing of lenses greater than 4 inches in diameter we have observed permanent deformation of the optical surface as a result of exposure to temperatures well below the glass strain point. While the reasons why the change occurs is not yet well understood, the result is well documented and was recently observed during the manufacturing of a 15 inch diameter spherical mirror. We use this lens as a case study highlighting the challenges associated with this phenomenon.