ABSTRACT
Finite raytracing is used at the stage when the general form of the optical system is known but the aberrations have to be reduced to acceptable tolerance levels. Finite raytracing is essentially an iterative sequence of two operations; one of these, transfer, is simply taking a ray from where it leaves one optical surface to where it meets the next and it thus involves only the geometry of straight lines and surfaces of appropriate shape. The other operation, usually called refraction, is to find the direction of the ray after it has passed through or been reflected or diffracted by the surface; the calculation involves either Snell's law or a generalized form of it appropriate to diffractive optical elements. This chapter deals only with refracting and reflecting surfaces of axial symmetry; toric surfaces and diffractive components. It describes the general raytrace method for spherical surfaces.
