Optics Sign Conventions -- from Eric Weisstein's World of Physics

There are a number of different conventions used for keeping track of the orientations of images in optics. The "Cartesian" convention is used by Schroeder (1987). It is similar to that of Born and Wolf (1999) and Longhurst (1967). In this convention, distances to the left of the vertex are negative, and distances to the right are positive. Distances from the optical axis are positive if measured upwards. Primes are used to denote the image, whereas unprimed quantities denote the object. This convention allows the treatment of reflected rays by letting . The "positive" convention is used by Hecht. In this convention, the subscripts i and o are used to denote object and image. furthermore, and are positive if left of the vertex, is positive if left of , and are positive is right of the vertex, is positive if right of , R is positive if the center of curvature is to the right of the vertex, and and are positive if measured above the optical axis.

Optical Sign

References