Hybrid optics for the visible produced by bulk casting of sol-gel glass using diamond-turned molds

摘要

Recent combinations of diffractive and refractive functions in the same optical component allow designers additional opportunities to make systems more compact and enhance performance. This paper describes a research program for fabricating hybrid refractive/diffractive components from diamond-turned molds using the bulk casting of sol-gel silica glass. We use the complementary dispersive nature of refractive and diffractive optics to render two-color correction in a single hybrid optical element. Since diamond turning has matured as a deterministic manufacturing technology, techniques previoulsy suitable only in the infrared are now being applied to components used at visible wavelengths. Thus, the marriage of diamond turning and sol-gel processes offers a cost-effective method for producing highly customized and specialized optical components in high quality silica glass. With the sol-gel casting method of replication, diamond-turned mold costs can be shared over many pieces. Diamond turning takes advantage of all of the available degrees of freedom in a single hybrid optical element: aspheric surface to elimiate spherical aberration, kinoform surface for control of primary chromatic aberration, and the flexibility to place the kinoform on nonplanar surfaces for maximum design flexibility. We will discuss the critical issues involved in designing the hybrid element, single point diamond-turning the mold, and fabrication in glass using the sol-gel process.