New manufacturing approaches for the fabrication of aspheres has increased opportunities for using aspheres in a wider range of optical systems. If manufacturability is considered early in the optical design process, the short and long term costs of the aspheric surface can be greatly reduced without sacrificing performance.
The optical designer must learn how to select optimum materials for aspheres. Using non-staining glasses, higher index glass types, and softer glass types can help reduce production costs. If the optical designer understands what range of aspheric surfaces can be manufactured, they can constrain the aspheric surface during optimization. The steepness of the aspheric departure (the slope of the aspheric departure) often has a larger impact on manufacturing difficulty than the amplitude of the asphere or the steepness of the base radius. Tolerancing can increase the difficulty without measurably improving optical performance. Finally, the asphere can be designed for ease of metrology. Understanding the options that are available for aspheric metrology will allow the engineer to control tooling and fixturing that is required for testing.
"Designing and specifying aspheres for manufacturability; Technical Digest", Proc. SPIE 10315, Optifab 2005: Technical Digest, 103150K (2 May 2005); doi: 10.1117/12.601079; https://doi.org/10.1117/12.601079