Affordable aspheric lens machine set to improve optics manufacture

A new, low-cost table-top machine that promises the manufacture of high-quality aspheric lenses in small to medium batches has been developed by a University of Cambridge researcher.

The simple machine, which was created by Dr Roderick Willstrop, of the University’s Institute of Astronomy, is suitable for producing batches of aspheric lenses for a range of optics applications, at lower cost than on conventional computer numerical control (CNC) machines.

High quality optics are in demand and have many uses – from camera lenses to defence applications. The machine is built to normal mechanical engineering tolerances. And while it can form aspheric lens surfaces to a high precision, it does not use laser interferometers or any computer control.

Using the skills I have acquired in producing and testing mirrors for astronomy meant I had insight into how to construct a machine for the grinding and polishing of aspheric lenses.

Dr Roderick Willstrop

Willstrop developed the machine in order to solve a lens problem at the University. “The solution was to use a small batch of aspheric lenses but the cost per lens was prohibitively high,” Willstrop said. The machine he developed solves that problem. The machine’s patented non-CNC mechanical arrangement causes the grinding or polishing tool to follow an aspheric path determined by bespoke templates. The machine can produce convex lenses up to around 175mm diameter and 30-300mm radius of curvature, and a more limited range of concaves. The end product quality is comparable to CNC. With a suitable grinding tool, rms surface irregularity better than 120 nm have been attained, ready for polishing. “Astronomy requires high quality optics that can help the astronomer to see the tiniest speck in the sky millions of light years away,” Willstrop said. “Using the skills I have acquired in producing and testing mirrors for astronomy meant I had insight into how to construct a machine for the grinding and polishing of aspheric lenses.” Photo credit: Monocular Telescope by gnuckx via Flickr

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