2-MIRROR UNOBSCURED OPTICAL-SYSTEM FOR RESHAPING THE IRRADIANCE DISTRIBUTION OF A LASER-BEAM

The design of a two-mirror optical system for reshaping the irradiance distribution of a laser beam is presented. The second mirror is decentered relative to the first to eliminate the obscuration inherent in an axially symmetric design. A geometric-optics approach is used to derive a set of equations that describe the surface figures of each of the mirrors. (In general, the mirror surfaces are not rotationally symmetric.) The special case of a system to convert a Gaussian input beam into a uniform output distribution is considered. The expressions for the surface figures are evaluated numerically for several specific systems to provide illustrative examples. It is observed that in some cases rotationally symmetric aspheres may be used to construct the beam-shaping system.