G PHYSICS
G02 OPTICS
G02B OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
G02B27/00 Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
G02B27/09 Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
G02B27/0938 Using specific optical elements
G02B27/095 Refractive optical elements