An optical lens or system designed to correct color distortion (chromatic aberration) so that different colors of light focus at the same point.
From Greek 'a-' (without) + 'chroma' (color). Coined in the 18th century when optical scientists discovered how to make lenses that didn't split light into rainbows.
Early telescopes and microscopes had a rainbow blur around everything you looked at—scientists solved this by pairing different types of glass together, and this breakthrough made the Hubble Space Telescope quality possible!
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