Abstract: A method of optically processing a laser beam for in turn processing a substrate with the processed laser beam is disclosed. The energy of the laser beam is altered so that the substrate can be properly processed even with laser outputs of poor beam quality such as low spatial or temporal coherence or unreproducible multimode structure or poor beam pointing stability. The method uses an optical integrator and appropriate optical elements based on the principles of geometrical optics. The optical elements may be aspherical lenses or mirrors whose surface shapes are derived mathmatically based on the desired energy redistribution and based on working in a region where the interaction of the substrate material and the laser energy is known.