We present a fabrication technology for the creation of high-aperture polymer microlenses and their optical characterization both as single lenses and mounted in a micro-objective. The microlenses are made by the LIGA process (x-ray lithography, electroforming and moulding techniques), which is modified by an additional x-ray irradiation step and a melting process. The spherical lenses are realized by melting of PMMA micro-cylinders, which have been flood exposed in the additional synchrotron irradiation step. For the cost-effective replication by hot embossing a moulding tool is made out of the primary PMMA lenses. As the focus of interest is the development of a micro-objective for medical applications, we concentrated on lenses which have a front focal length of 700 and and an equal outer diameter of , which is achieved by an additional lateral structuring.