Conference Agenda

The flexible and efficient production of precise optical free-form surfaces requires advanced kinematic operating principles. Due to the complex surface geometries, polishing processes with point or linear contact are used. These generally result in longer polishing times due to the smaller footprint compared to large-area polishing tools. The creation of a high precision, polishable surface in the shaping steps of the process chain is therefore of great importance. This applies in particular to minimising the roughness, but also the depth of SSD (sub-surface damage) and the mid-spatial frequency errors before the polishing process. The article describes selected process chains for the production of free-form optics and presents options for optimising the required polishing steps.

A new concept for polishing pads for flat and spherical surfaces is introduced which comprises additive manufactured polishing pads made of cerium oxide. By using additive manufacturing technologies in polishing processes with polishing slurry, those processes can be substituted with tools containing bonded grain. The bonded polishing pads can be fabricated using rolling processes. The pad geometries can be adjusted by using laser cutting. Furthermore, surface modifications of the pad can be applied with laser processes as well to favour quality and economic factors of polishing processes. First results from the experimental setup are showing, that lapped surface with a roughness Rq of ~500 nm can be polished to approx. 30 nm roughness Rq by polishing with pads using bonded grain cerium oxide foils.

Different Light-based techniques for 3D printing have been developed such as SLA and DLP that use single photon absorption and direct writing by scanning a focused spot using two photon absorption. These techniques employ a layered approach using incoherent imaging. Herein, we propose a layerless approach using coherent holographic projection which is based on Tomographic Volumetric Additive Manufacturing (TVAM). We demonstrated this concept by implementing a volumetric printer using a Digital Micromirror Device (DMD) in a Fourier configuration and showing its capabilities by printing a micrometric scale object. The use of the Lee holograms method allows us to use the DMD as a fast phase modulator, and the combination of tiling holograms with Point Spread Function (PSF) modifications allows us to reduce speckle noise and provide three-dimensional control of the projections. We use these holographic projections to fabricate millimetric 3D objects in less than a minute.

We here present our research into application-adapted laser beam shaping which enables the generation of tailored light volumes, explicit optimization of the temperature distribution within a work piece and high-fidelity beam shaping in combination with optical amplifiers.