Aspheric lens Totally Explained

Everything about Aspheric Lens totally explained

An aspheric lens or asphere is a lens whose surfaces have a profile that's neither a portion of a sphere nor of a circular cylinder. In photography, a lens assembly that includes an aspheric element is often called an aspherical lens. The asphere's more complex surface profile can eliminate spherical aberration and reduce other optical aberrations compared to a simple lens. A single aspheric lens can often replace a much more complex multi-lens system. The resulting device is smaller and lighter, and possibly cheaper than the multi-lens design.
Aspheric lenses are also sometimes used for eyeglasses. These are typically designed to give a thinner lens, and also distort the viewer's eyes less as seen by other people, producing better aesthetic appearance. In a prescription for the farsighted, the lens curve flattens toward the edge of the glass, and in the nearsighted, the surface becomes steeper toward the lens edge. Aspheric eyeglass lenses typically don't provide better vision than standard "best form" lenses, but rather allow a thinner, flatter lens to be made without compromising the optical performance. which he used to work out the shapes of anaclastic lenses that focus light with no geometric aberrations.
Early attempts at making aspheric lenses to correct spherical aberration were made by René Descartes in the 1620s, and by Constantijn Huygens in the 1630s. The Visby lenses produced by Vikings on the island of Gotland in the 10th or 11th century are also aspheric, but there's no evidence that the science behind the technique was known, they were 'simply' produced by craftsmen working from experience of what worked. Francis Smethwick ground the first high-quality aspheric lenses and presented them to the Royal Society on February 27, 1667/8. A telescope containing four aspheric elements was judged superior to a "common, yet very good" telescope used for comparison, and aspheric reading and burning glasses also outdid their spherical equivalents. Moritz von Rohr is usually credited with the design of the first aspheric lenses for eyeglasses. He invented the eyeglass lens designs that became the Zeiss Punktal lenses.

Non-optical advantages of aspheric eyeglass lenses

High minus lenses, especially finished in a plastic resin lens, have dangerously curved edges that don't bevel off sufficiently to protect the eye from injury. Serious injury to the eye is often seen from blunt trauma, when the edge of a thick lens has been mounted in a poorly fit frame. Bi-concave lens design is different from the usual plus four base curvature ordered in thin lens prescriptions, but by splitting the curvature in thirds or so, a thinner lens is developed, although costing more, and more difficult to mount into a frame.

Testing of aspheric lens systems

The optical quality of a lens system can be tested in an optics or physics laboratory using bench apertures, optic tubes, lenses, and a source. Refractive and reflective optical properties can be tabulated as a function of wavelength, to approximate system performances; tolerances and errors can also be evaluated. In addition to focal integrity, aspheric lens systems can be tested for aberrations before being deployed.

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