Achromats

Part of speech: noun

Definitions

1. A type of optical device designed to bring multiple wavelengths of light into focus at the same point, correcting chromatic aberration
2. Instruments that consist of a combination of lenses made to minimize color distortions in images produced
3. Optical systems specifically engineered to prevent color fringing by ensuring different colors converge accurately at the same focal plane

Etymology: "Achromats" is the plural of "achromat," a noun that was formed by shortening "achromatic." The longer adjective is built from the Greek prefix "a-," meaning "without," and "chroma," meaning "colour," so the word literally describes something free of colour. In optics, the term names lenses or lens combinations designed to bring different colours of light to a common focus, which removes the coloured fringes that plain lenses produce around bright objects. The plural form refers to these instruments collectively, as in telescopes or microscopes fitted with several such lens pairs. Because the noun is a clipping of the adjective, its meaning comes straight from the sense of "without colour" applied to a lens that has been corrected so that colour no longer distorts the image.