Aberration, the deviation of light rays through lenses in optical devices, such as lenses and curved mirrors, causing images of objects to become distorted. Every point on the object in an ideal system would focus on the image to a point of zero size. However, practically every point of the image occupies a volume of finite size and unsymmetrical form, causing some blurring of the entire image. Unlike a plane mirror that creates images free of aberrations, a lens is an imperfect image maker, making it suitable only for rays that pass through its center parallel to the optical axis (a line through the center, perpendicular to the lens surfaces).

READ  What is Apparent Magnitude?

The equations developed for object-image relationships in a lens with spherical surfaces are only approximate and only deal with paraxial rays — that is, rays with the optical axis make only small angles. There are five aberrations to be noticed when light of just a single wavelength is present, called spherical aberration, coma, astigmatism, field curvature, and distortion. A sixth aberration observed in lenses (but not mirrors) — chromatic aberration in particular — occurs when light is not monochromatic (not one wavelength).

READ  What is Antimatter? The Curious Case of Antimatter