Projekte

In the production of microstructures using laser direct exposure, a photoresist is exposed with a focused laser beam, which modifies the solubility of the resist in a suitable developer solution. The desired microstructures are finally formed during the subsequent development.

If non-planar surfaces such as optical lenses are to be structured in this way, the focus of the laser beam must be positionable along the vertical axis during the exposure process in order to follow the height profile of the lens.

In practice, errors in guidance of the vertical axis and angluar errors between the exposure plane and the vertical axis lead to incorrect positioning of the laser focus in the exposure plane. This in turn results in undesirable distortions in the microstructure.

As part of this project, a method and a measurement system for characterizing the positioning errors was developed and integrated into a polar coordinate laser direct writing system. The method enables the determination of the altitude-dependent straightness and angular error of the vertical axis, as well as the angular error between the vertical axis and the exposure plane.

A compensation function was implemented in the writing system on the basis of the recorded guiding errors. In this way, the original positioning error in the exposure plane could be reduced from 5.2 µm to 150 nm for a traversing range of the vertical axis of 70 mm.