Optical Lenses

COE Optics' optical lenses are designed to meet the demanding requirements of laser electro-optic applications, and all of our BK7 material is from annealed optical glass and are polished to tight tolerances using master test plates to ensure minimum wavefront distortion.

An optical lens is an optical device that focuses on or disperses a light beam by means of refraction. A simple optical lens consists of a single piece of optical material while a compound lens consists of several simple lenses (elements), usually arranged along a common axis. COE Optics optical Lenses are mainly made from materials such as sapphire, optical glass, fused silicon and IR material: Silicon and Germanium.   A lens can focus light to form an image, unlike a prism, which refracts light without focusing.

Optical lenses are classified by the curvature of the two optical surfaces. An optical lense is biconvex (or double convex, or just convex) if both surfaces are convex. If both surfaces have the same radius of curvature, the lens is bi-convex. A lens with two concave surfaces is biconcave (or just concave). If one of the surfaces is flat, the lens is Plano-convex or Plano-concave depending on the curvature of the other surface. A lens with one convex and one concave side is convex-concave or meniscus. It is this type of lens that is most commonly used in corrective lenses.

If the optical lens is biconvex or Plano-convex, a collimated beam of light passing through the optical lens converges to a spot (a focus) behind the lens. In this case, the lens is called a positive or converging lens. For a thin lens in air, the distance from the lens to the spot is the focal length of the lens, which is commonly represented by f in diagrams and equations. An extended hemispherical lens is a special type of Plano-convex lens, in which the lens's curved surface is a full hemisphere and the lens is much thicker than the radius of curvature.

If the optical lens is biconcave or Plano-concave, a collimated beam of light passing through the optical lens is diverged (spread); the lens is thus called a negative or diverging lens. The beam, after passing through the lens, appears to emanate from a particular point on the axis in front of the lens. For a thin lens in air, the distance from this point to the lens is the focal length, though it is negative with respect to the focal length of a converging lens.
Convex-concave (meniscus) lenses can be either positive or negative, depending on the relative curvatures of the two surfaces. A negative meniscus lens has a steeper concave surface and is thinner at the centre than at the periphery. Conversely, a positive meniscus lens has a steeper convex surface and is thicker at the centre than at the periphery. An ideal thin lens with two surfaces of equal curvature would have zero optical power, meaning that it would neither converge nor diverge light. All real lenses have nonzero thickness, however, which makes a real lens with identical curved surfaces slightly positive. To obtain exactly zero optical power, a meniscus lens must have slightly unequal curvatures to account for the effect of the lens' thickness.