Single point diamond turning is a technique that refers to machines which uses ultra sharp diamond as a cutting tool. Lathes are also used to increase the accuracy to product plastic or metal optics. For example: Lens shape.
The use of special machine tools (Eg: Diamond Lathe) with single-crystal diamond-cutting tools to produce metal optics is called diamond-turning.
The diamond-turning process produces finished surfaces by very accurately cutting away a thin chip or layer of the surface. The resulting surface is often of a high quality mirror finish with a profile that accurately adheres to the desired final product.
The advantages of diamond turning are:
It can produce good optical surfaces clear to the edge of the optical element. This is important in making scanners, polygons, special shaped flats, and when producing parts with interrupted cuts.
It can turn soft ductile materials that are extremely difficult to polish.
It can easily produce off-axis parabolas and other difficult-to-lap a spherical shapes.
It can produce optical elements with a significant cost advantage over conventional lapping and polishing where the relationship of the mounting surface—or other feature—to the optical surface are very critical.