achromatic lens

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achromatic lens

(ak-rŏ-mat -ik) (achromat) A two-element lens – a doublet – that greatly reduces chromatic aberration in an optical system. The components, one converging and the other diverging in action, are of different types of glass (i.e. they have different refractive indices); the combination focuses two selected colors, say red and blue, at a common image plane with a small spread in focal length for other colors. The difference in optical power (reciprocal of focal length) for the two colors in one element must cancel that in the other element. By a suitable choice of glasses and surface curvatures, the doublet can be aplanatic as well as achromatic, so that three major aberrations are minimized (see aplanatic system).

Residual color effects in an achromat can be further reduced by using a compound lens of three or more elements – an apochromatic lens; each element has an appropriate shape and dispersive power so that three or more colors can be focused in the same image plane.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

achromatic lens

[¦a·krə¦mad·ik ′lenz]
(optics)
A combination of two or more lenses having a focal length that is the same for two quite different wavelengths, thereby removing a major portion of chromatic aberration. Also known as achromat.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.
References in periodicals archive ?
This study aims to develop an achromatic lens design that combines the advantages of Fresnel lenses (high efficiency, reduced thickness, and lightweight construction) along with the stability and lack of spectrum aberrations of achromatic lenses. The achromatic doublet design will be carried out by means of a parametric analysis to reject the less efficient configurations, thus leading to a set of optimal solutions that will be compared in terms of efficiency, stability flux distribution, uniformity, and so forth.
The blackening service is available off-the-shelf for most of Edmund's TECH-SPEC VIS 0[degrees] achromatic lenses. It is also available for all transmissive components through the Edmund Optics' Quik Mod program which allows rapid turnaround of modified catalog components in small quantities.
However it was not until the 19th century when the use of achromatic lenses were implemented to reduce distortion that the telescope came into its own right, and became a popular scientific instrument.