By Erin McDonnell, Product Manager (Laser Interferometers), Zygo Corporation
An aspheric lens — sometimes known as an asphere — is a lens that’s not part of a sphere or cylinder and it can depart somewhat from a sphere. The more complex surface profile of an asphere not only reduces or eliminates spherical aberration but can also reduce other optical aberrations such as astigmatism. The result is a lens which creates sharper and clearer images.
Aspheric surfaces are used in a variety of optical systems and are a powerful way of reducing the number of elements required. This simultaneously enhances a system’s performance, and ultimately reduces its size and weight. Manufacturers working in the optics sector are highly concerned with producing aspheres that are both cost-effective and that conform precisely to the design intent. However, testing the accuracy of an asphere’s shape and deviation from its design can be a considerable challenge, as it requires the measurement of the tiniest nanometer deviations in shape.