A lens is a transparent optical element with curved surfaces that refracts light in order to form an image. Lenses are made from materials such as glass, plastic, and quartz, and are used in a variety of optical devices, including cameras, eyeglasses, microscopes, and telescopes.
There are two main types of lenses: convex lenses and concave lenses. Convex lenses are thicker at the edges than at the center, and cause light to converge (i.e., come together). Concave lenses are thinner at the edges than at the center, and cause light to diverge (i.e., spread out). Lenses can also be categorized by their shape: spherical lenses have a curved surface that is part of a sphere; aspheric lenses have a curved surface that is not part of a sphere; and cylindrical lenses have one or more flat surfaces with cylindrical curvature.
The focal length of a lens is the distance from the lens to the point where parallel rays of light converge (for a converging lens) or diverge (for a diverging lens). The power of a lens is measured in diopters (D), which is the inverse of the focal length in meters (−1/focal length in meters). A higher-powered lens will have a shorter focal length and vice versa. The most common type of eyeglass prescription is for plus or minus four diopters (-4D to +4D), which corresponds to focal lengths ranging from 0.25 m to 2 m.
Lenses can be used singly (simple lenses) or in combination (compound lenses). Compound lenses consist of two or more simple lenses arranged along what is known as an optical axis. The simplest type of compound lens is the bi-convex lens, which consists of two convex surfaces facing each other; this type of lens converges light regardless of where on theLens it strikes because both sides curve outward equally. More complicated compound designs include meniscus lenses (one concave surface paired with one convex surface), plano-convex/plano-concave doublets (two simple Lens elements cemented together), bestform Doublets(a single positive element combined with either another positive or negative element having different curvatures), Fresnel lenselementary prisms(a series Of triangular prismatic facets designed so that parallel incoming beams emerge parallel after passing through them.), etcetera..
A great dealOf research has gone into designing aspheric optics because they offer many advantages over traditional spherical optics: they can correct for aberrations over wider fieldsOf view, they require fewer elements to achieve high levels Of performance,, etcetera… Aspherical optics are now commonplace in consumer electronics such as digital camerasAnd camcorders.. In addition To their use In commercial products,, aspheric optics are also used In scientific applications suchAs space telescopes And particle accelerators..