Micro-optical components are of growing interest and used in very different applications such as displays,
biophotonics, optical-data communication... More in particular, refractive microlenses and refractive microlens
arrays are widely used. The fabrication of these components has been extensively investigated and today
different technologies are already commercially available such as thermal reflow, laser ablation, reactive ion
etching, microject printing... These technologies allow the fabrication of high-quality microlenses in different
materials, however these fabrication methods are often too expensive and too time-consuming for prototyping.
In our facilities, we implemented Deep Proton Writing (DPW) as a rapid prototyping technology to fabricate
plastic refractive microlenses and microlens arrays. To reduce the calibration time and minimize the influence of uncontrollable external parameters we built a transmission Mach-Zehnder interferometer allowing to monitor in situ and in real-time the growing of the refractive microlenses. This means that we can stop the growing process of the microlenses as soon as the predefined specifications are reached. Additionally we can determine out of this interferometric data the geometrical properties and optical quality of each of the microlenses. We have studied the precision and accuracy of our interferometer for the characterization of the latter components. In this paper, we will present the latest results showing the performance of our set-up and the resulting enhancements of our technology.