Focus-based automated alignment for laser direct writing

We aim to integrate two-photon polymerization (TPP) in a fully digitalized and automated workflow for micro- and nanooptics production. This requires linking the coordinate system of the writing laser scanner to the geometry of the sample or previously fabricated structures on the sample. We developed a fast layer detection algorithm, which determines the axial position and the tilt angles of both interface planes of the photosensitive material using the integrated microscope camera of the TPP system. Furthermore, we identify the shear angles between the camera and the lateral scanner axes. The individual measurement results are stored and accessible via direct-written identification QR code on the sample itself. This is an important step towards an individualized automatic workflow based on digital twins.