Patent ID: 7068438

Claim:
A lens arrangement ( 100 ) for transforming a divergent, generally astigmatic laser beam from a diode laser ( 110 ) into a beam having a high degree of rotational symmetry, comprising in series: a first cylindrical gradient index lens ( 101 ) arranged with its principal axes parallel to the principal axes of the astigmatic laser beam for converging the fast axis of the astigmatic laser beam; a second cylindrical gradient index lens ( 102 ) arranged with its principal axes parallel to the principal axes of the astigmatic laser beam for converging the slow axis of the astigmatic laser beam; and a third cylindrical gradient index lens ( 103 ) arranged with its principal axes rotated 45 degrees with respect to the principal axes of the astigmatic laser beam for twisting the converged astigmatic laser beam into a beam having a high degree of rotational symmetry, wherein the first and the second gradient index lenses have such refractive powers that both the fast and the slow axis of the astigmatic laser beam are converged to a focus inside the third gradient index lens.