Aspheric Lenses

The most notable benefit of aspheric lenses is their ability to correct for spherical aberration, an optical effect which causes incident light rays to focus at different points when forming an image, creating a blur. Spherical aberration is commonly seen in spherical lenses, such as plano-convex or double-convex lens shapes, but aspheric lenses focus light to a small point, creating comparatively no blur and improving image quality. Spherical aberration is inherent in the basic shape of a spherical surface and is independent of alignment or manufacturing errors; in other words, a perfectly designed and manufactured spherical lens will still inherently exhibit spherical aberration. An aspheric lens can be designed to minimize aberration by adjusting the conic constant and aspheric coefficients of the curved surface of the lens.

Aspheric lenses allow optical designers to correct aberrations using fewer elements than conventional spherical optics because the former gives them more aberration correction than multiple surfaces of the latter. For example, in zoom lenses where ten or more lens elements are typically used, two aspheric lenses can be substituted for a handful of spherical lenses in order to achieve similar or better optical results, while reducing system size and potentially reducing the overall cost of production.

The term asphere encompasses any lens with surfaces that are not portions of a sphere. However, when we use the term here we are specifically talking about the subset of aspheres that are rotationally symmetric optics with a radius of curvature that varies radially from the center of the lens. As discussed earlier, aspheric lenses improve image quality and reduce the number of required optical elements. From smart phones and laser-enabled devices to high-end microscope objectives and surgical equipment, aspheric lenses are increasingly critical to every facet of the optics, imaging, and photonics industries due to the distinct advantages that they offer compared to traditional spherical optics.