Best-fit Spheres and Conics as an Aid in the Manufacture and Testing of Diamond-turned Aspheric Optics

Abstract

Abstract The development of high-quality and high-accuracy diamond turning has led to an increase in the use of aspheric surfaces in optical systems, especially those operating in the infrared. In the interests of economy it is important to start from a ‘best-fit’ spherical surface, which can be produced by cheaper conventional methods. The testing of these aspheric surfaces also poses a problem, which can often be partially solved by considering the departure of the aspheric from a best-fit conic rather than the more usual sphere. This paper looks at the computation of these best-fit spheres and conies.