gradient index lens
gradient index lens[′grād·ē·ənt ¦in‚deks ‚lenz]
An optical element within which the refractive index is a smooth, but not constant, function of position and, as a result, the ray paths are curved. Also known as graded index lens.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.