Aspheric Surface Metrology - Where Do We Go From Here?

The routine testing of aspheric optical components remains an elusive goal for the optical engineer. While significant improvements in the art of aspheric testing (especially in the use computer-generated diffractive nulls) have occurred over the last several years, the usual aspheric test situation still requires specialized null optics with relatively long lead times and added cost. As a result, the use of precision aspherics have been limited to situations that can afford or amortize these costs: large programs such as telescopes, high-volume products, or very specialized instruments. The irony is that these limitations are occurring at a time when manufacturing technology is capable of producing an ever-increasing variety of surface types and specifications, and sometimes these surfaces can be fabricated economically even in small quantities.