- noun a defect in a lens that causes light of different colours to be refracted differently
- In a CRT, such as that in a TV, a defect in which the focal spot is enlarged and blurred. It may be due, for instance, to differences in electron velocities as they are emitted by an electron gun, and how these are differentially deflected en route to the screen.
- In an optical lens, a defect in which not all colors come to focus at the same point. May be due, for instance, to the physical properties of the lens.