Refractive null correctors for aspheric surfaces

Design and use of mass-produced aspheres at Kodak

Aspheric surfaces provide both performance and cost advantages for large-quantity lens production. Aspheres are reviewed from their early application in viewfinders to their use in camera lenses and, most recently, to applications in laser focusing lenses. There are restrictions imposed on the shape or strength of aspheres by either the manufacturing processes or testing techniques that the designer must recognize.

Measurement of steep aspheric surfaces

A method of measuring the shape of high numerical aperture (NA <0.95), convex or concave, aspheric surfaces is described. The aspheric slope may be as large as 1200 waves/rad. The method is applied in two steps. First, a standard measurement is performed to obtain a reference surface. Second, the reproducibility of the fabrication of aspheric surfaces is tested by means of a holographic comparison method. The measuring error is smaller than 0.1 microm.