achromatic doublet

(noun)

A type of lens made up of two simple lenses paired together designed so that the chromatic aberration of each lens partially offsets the other; in this way light in a range of wavelengths may be brought to the same focus.

Related Terms

Examples of achromatic doublet in the following topics:

  • Combinations of Lenses

    • An achromatic lens or achromat is a lens that is designed to limit the effects of chromatic and spherical aberration.
    • Achromatic lenses are corrected to bring two wavelengths (typically red and blue/violet) into focus in the same plane.
    • The most common type of achromat is the achromatic doublet, which is composed of two individual lenses made from glasses with different amounts of dispersion Typically, one element is a negative (concave) element made out of flint, which has relatively high dispersion, and the other is a positive (convex) element made of crown glass, which has lower dispersion.
    • Negative doublets, in which the negative-power element predominates, are also made.
    • (b) Multiple-lens systems, such as this achromatic doublet, can partially correct chromatic aberrations, but they may require lenses of different materials and add to the expense of optical systems such as cameras.

  • Aberrations

    • A chromatic aberration, also called achromatism or chromatic distortion, is a distortion of colors .

  • The Telescope

    • With the invention of achromatic lenses in 1733, color aberrations were partially corrected, and shorter, more functional refracting telescopes could be constructed.