An aspheric lens or asphere is a lens whose surfaces have a profile that is 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. A lens. ... A sphere is a perfectly symmetrical geometrical object. ... A right circular cylinder An elliptic cylinder In mathematics, a cylinder is a quadric surface, with the following equation in Cartesian coordinates: This equation is for an elliptic cylinder, a generalization of the ordinary, circular cylinder (a = b). ... Photography [fәtɑgrәfi:],[foʊtɑgrәfi:] is the process of recording pictures by means of capturing light on a light-sensitive medium, such as a film or sensor. ...

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. Focal plane Longitudinal sections In optics, spherical aberration is an image imperfection that occurs due to the increased refraction of light rays that occurs when rays strike a lens or mirror near its edge, in comparison with those that strike nearer the center. ... This article or section is in need of attention from an expert on the subject. ... A simple lens is a lens consisting of a single simple element. ...

Aspheric lenses are also sometimes used for eyeglasses. These provide clearer vision and a wider unaberrated field of view than conventional eyeglass lenses, and also distort the viewer's eyes less as seen by other people, producing better aesthetic appearance. The complex front surface curves from the center of the lens to the edge. With a prescription for the farsighted, the lens curve flattens toward the edge of the glass, and in the nearsighted, the surface becomes steeper to the lens edge, which offers vision superior to a conventional lens. Glasses, spectacles, or eyeglasses are frames bearing lenses worn in front of the eyes, sometimes for purely aesthetic reasons but normally for vision correction or eye protection. ... The field of view is the part of the observable world that is seen at any given moment. ... Farsighted has two meanings: In vision it is a specific defect of image focusing called farsightedness (Hypermetropia). ... Normal vision for a achromatopsic colour-blind person. ...

Aesthetic Curvature Combinations In An Aspheric Lens Prescription

High minus lenses, especially finished in a plastic resin lens, have dangerously curved edges that do not bevel off sufficiently to protect the orbit from contusion. 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. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ...

As defined by the adjective, an aspheric lens does not have a spherical curvature, but let me describe it to you as a series of pseudo-spherical curvatures blended together on each others carrier curvature. An aspheric lens design that I have worn for over 25 years is actually a lens constructed from a lens blank used for thicker, larger eye sizes. By grinding down the edges of the lens with a flatter curvature, lower power, and the polishing a blend of curvature successively into the back surface, not only am I able to use aesthetically pleasing front base curvatures, but also larger frames for a diversified fit, including frames with sweat bars, key-hole bridges, and even rim-less.

Ray Tracing Techniques For Finding The Change Of Aspheric Lens Focal Lengths

Beginning at a point source of light, diverging rays are refracted through an aspheric lens. Emerging from imaginary space, the collimated light passes through a ring aperature having an open ring center a given radius from the optical center of the aspheric lens. This blocks light rays that are out of focus, but allows the rays of light passing through the correct curvature gradient of the aspheric lens to be refracted with the correct power of diopters. Also see diopter Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... A dioptre (also diopter) is a unit of curvature equal to one per metre; that is, inverse metres, or 1/(metres). ...

Manufacture

Small glass or plastic aspheric lenses can be made by molding, which allows cheap mass production. Due to their low cost and good performance, molded aspheres are commonly used in inexpensive consumer cameras, camera phones, and CD players. They are also commonly used for laser diode collimation, and for coupling light into and out of optical fibers. Large format camera lens. ... A packaged laser diode with penny for scale. ... Optical fibers An optical fiber (or fibre) is a glass or plastic fiber designed to guide light along its length by confining as much light as possible in a propagating form. ...

Larger aspheres can be made by diamond turning, a process in which a computer-controlled lathe directly cuts the desired profile into a piece of glass or another optical material. This is a slow process. A faster and newer technology is deterministic microgrinding, where computer-controlled grinding wheels are used to shape the aspheric profile which is then polished to the final shape. Lenses produced by these techniques are used in telescopes, projection TVs, missile guidance systems, and scientific research instruments. Diamond turning is a process of mechanical machining of precision elements using Computer Numerical Control (CNC) lathes equipped with natural or synthetic diamond-tipped cutting elements. ... Conventional metalworking lathe In woodturning, metalworking, metal spinning, and glassworking, a lathe is a machine tool which spins a block of material so that when abrasive, cutting, or deformation tools are applied to the block, it can be shaped to produce an object which has rotational symmetry about an axis... This article does not cite any references or sources. ... For other uses, see Television (disambiguation). ...

Another method for producing aspheric lenses is by depositing op]]tical resin onto a spherical lens to form a composite lens of aspherical shape. Plasma ablation has also been proposed, such as by RAPT Industries.

As defined by the adjective, an aspheric lens does not have a spherical curvature. Carrier curvatures are blended from a spherical, into an aspherical curvature by grinding the curvatures off-axis. Dual rotating axis grinding can be used for high index glass that isn't easily spin molded like the CR-39 resin lens is.

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History

In 984, Ibn Sahl first discovered the law of refraction, usually called Snell's law,^[1][2] which he used to work out the shapes of anaclastic lenses that focus light with no geometric aberrations. Events End of the reign of Emperor Enyu of Japan Emperor Kazan ascends to the throne of Japan Births Deaths Categories: 984 ... Ibn Sahl - Wikipedia, the free encyclopedia /**/ @import /skins-1. ... The straw seems to be broken, due to refraction of light as it emerges into the air. ... Refraction of light at the interface between two media of different refractive indices, with n2 > n1. ...

Francis Smethwick ground the first high-quality aspheric lenses and presented them to the Royal Society on February 27, 1667/8.^[3] A telescope containing four aspheric elements was judged superior to a "common, yet very good" telescope used for comparison, and aspherical reading and burning glasses also outdid their spherical equivalents. The premises of The Royal Society in London (first four properties only). ... Old Style or O.S. is a designation indicating that a date conforms to the Julian calendar, formerly in use in many countries, rather than the Gregorian calendar, currently in use in most countries. ...

References

1. ^ K. B. Wolf, "Geometry and dynamics in refracting systems", European Journal of Physics 16, p. 14-20, 1995.
2. ^ R. Rashed, "A pioneer in anaclastics: Ibn Sahl on burning mirrors and lenses", Isis 81, p. 464–491, 1990.
3. ^ (1668) "An Account of the Invention of Grinding Optick and Burning-Glasses, of a Figure Not-Spherical, Produced before the Royal Society" (PDF). Philisophical Transactions of the Royal Society 3: 631. Retrieved on 2006-11-03.