Aspherics

It has long been known that lenses with spherical surfaces are less than ideal for creating optical images, however, the ease of making them has made them ubiquitous. With advances in technology however, aspheres are beginning to see a widespread use. As the name suggests, aspherics have non-spherical surfaces and a single one can replace a multi-lens design. This reduces both the size as well as the back reflections so common in lens systems. The complex surface of an asphere eliminates spherical aberration and reduces other optical aberrations. While smaller aspheres are created from molds, larger ones are made by grinding and polishing. Aspherics that require higher precision are made by single point diamond-turning; a technique that utilizes a CNC lathe with a diamond point to carve the glass to the precise contour of a CAD drawing.

Molded aspherics are usually used in less expensive consumer products.  So, while the initial cost of a mold can be high the large quantities are used to amortize it. Applications for plastic (PMMA, Acrylics) or glass molded lenses come in laser diode collimators, automotive cameras and other consumer areas. Diamond-turned lenses are much more precise and expensive, so they find their application in more expensive product lines, such as night vision systems and other specialty optics. Standard MgF2 AR coatings or metal coatings are often applied.

AgniRoth OPTIK supplies both Molded and Diamond-turned aspherics.

 

Material

Typical Materials: Optical Glass, BK7, Schott, Ohara, Hoya, CDGM
IR Materials: FS, Ge, Si, CaF2, ZnS, ZnSe

Diameter

2mm – 350mm

Dimensional Tolerance

±0.1mm

Aperture Angle

Up to 180º

Form Precision

Up to 0.2 nm p-v

Tangential Error

0.2 mrad

Surface Roughness

< 1nm Rq

 
Agniroth OPTIK 2009