Patent ID: 7164108

Claim:
An apparatus for circularizing a laser beam and directing the beam into an optical system, said laser beam having an ellipticity defined by orthogonal beam diameters along X and Y axes, said apparatus comprising: beam shaping optics through which the laser beam passes, said optics being adjustable to control the ellipticity of the beam by varying the relative X and Y diameters of the beam, said beam shaping optics including at least one cylindrical lens, the position of which is adjustable along the propagation axis of the laser beam to vary the ellipticity of the beam; a beam splitter for separating the beam into first and second portions, the first portion being directed into the optical system; a quadrant detector positioned to receive the second portion of the beam, with each quadrant generating an output signal, said quadrant detector being oriented so that the axes dividing the quadrants are positioned at a 45 degree angle with respect to the X and Y axes of the beam; and a controller receiving the output signals from the detector and generating control signals which are supplied to the beam shaping optics in order to vary the relative diameters of the beam in order to minimize the ellipticity thereof.