Individual shape adaptation of microlenses by means of electric fields
Final Report Abstract
Additive manufacturing enables the individualized realization not only of mechanical components, but also of optical components. However, if “standard 3D printing technologies” such as 3D inkjet printing or stereolithography using lasers or projectors are used, there are three major disadvantages: 1. these processes are based on a layer-by-layer deposition of the material (e.g. UV- curable material); 2. the surface of the elements has a high degree of roughness due to the layer-by-layer deposition (e.g. printing a curved surface results in a “staircase structure”); 3. if a DMD projection system is also used for curing, periodic variations in the refractive index occur due to the pixel structure of the projector. The Elektro3D project offers a possible solution to these challenges. The basic idea is to use a dispensing system to accumulate droplets of a liquid UV-curable polymer on a substrate. The result is a liquid, spherical, larger droplet whose radius is determined by the number of “sub-droplets” deposited. This already represents a microlens. Due to the surface tension, this results in a low surface roughness despite the curvature. There are also no individual pressure layers in the droplet that lead to light scattering. If a global UV light source is also used for curing, a homogeneous refractive index distribution is also achieved. However, this droplet exhibits high optical aberrations due to its spherical shape. In order to create an aspherical microlens, the liquid dielectric polymer droplet is therefore deformed in electric fields. The electric field distribution determines the deformation. This deformed droplet is then cured under UV light. In order to obtain a defined deformation of the drop and thus a defined optical performance of the microlens, it is essential to investigate the relationships in a knowledge-oriented manner. The central question here is which electric field distribution under which boundary conditions (e.g. substrate, drop volume etc.) leads to which deformation of the drop and how this can be described. It was precisely these relationships that were worked out in the project. The application of such individualized microlenses can be found both in interior and exterior lighting. As a rule, this is not coordinated with the surface to be illuminated, resulting in socalled “light pollution”. However, light distribution optimized for the surface to be illuminated requires individualized optics, which is made possible by the approach investigated here.
Publications
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Additive manufactured and electrically deformed lenses on optical fibers for improved coupling. Advanced Fabrication Technologies for Micro/Nano Optics and Photonics XVII, 18. SPIE.
Dohmen, Mike; Heinrich, Andreas & Neumann, Cornelius
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Next generation micro optics. Additive Manufacturing of Glass, 235-257. Elsevier.
Dohmen, Mike; Geiß, Marco; Ilhan, Murat-Jakub & Heinrich, Andreas
