For other uses, see Lens.

A lens.

Lenses can be used to focus light.
A lens is an optical device which transmits and refracts light, converging or diverging the beam.[citation needed] A simple lens consists of a single optical element. A compound lens is an array of simple lenses (elements) with a common axis; the use of multiple elements allows more optical aberrations to be corrected than is possible with a single element. Lenses are typically made of glass or transparent plastic. Elements which refract electromagnetic radiation outside the visual spectrum are also called lenses: for instance, a microwave lens can be made from paraffin wax.
The variant spelling lense is sometimes seen. While it is listed as an alternative spelling in some dictionaries, most mainstream dictionaries do not list it as acceptable.[1][2]
Contents
* 1 History * 2 Construction of simple lenses * 2.1 Types of simple lenses * 2.2 Lensmaker's equation * 2.2.1 Sign convention of lens radii R1 and R2 * 2.2.2 Thin lens equation * 3 Imaging properties * 4 Aberrations * 4.1 Spherical aberration * 4.2 Coma * 4.3 Chromatic aberration * 4.4 Other types of aberration * 4.5 Aperture diffraction * 5 Compound lenses * 6 Other types * 7 Uses * 8 See also * 9 References * 10 Bibliography * 11 External links * 11.1 Simulations
History
| This section requires expansion with: history after 1758. (January 2012) |
See also: History of optics and Camera lens

The Nimrud lens
The word lens comes from the Latin name of the lentil, because a double-convex lens is lentil-shaped. The genus of the lentil plant is Lens, and the most commonly eaten species is Lens culinaris. The lentil plant also gives its name to a geometric figure.
The oldest lens artifact is the Nimrud lens,