## 1 Introduction  
Micro-optical systems are essential in everyday life and industrial applications. This includes applications such as mobile phone cameras, driving assistance systems, light barriers, endoscopes, optical data storage, motion controllers, inspection systems, illumination units and many more [1; 2; 3; 4; 5; 6]. Optical components are omnipresent, however very unobtrusive due to rapid advances in miniaturization and micro integration, making them non-observable for the user in most cases. However, behind these applications is a very versatile market for optical technologies, which is currently developing at an impressive speed of 6-8% p.a. [1; 7]. Additionally, being a key-enabling technology for the European Union, the funding for developments of innovative, highly integrated optics is a priority [1; 8]. Current developments are more and more based on polymer technologies as the performance of these materials is improving continuously. Tailoring the properties of the materials by the suppliers opens new doors and offers the possibility to unlock untapped potentials for a multitude of innovative applications [9]. At the same time, costs can be reduced compared to glass components due to the methods of mass production for polymers such as injection molding [10; 11; 12; 13]. Furthermore, more degrees of freedom in terms of three-dimensional processing are possible. Many applications already employ injection molding of optical components. In particular, injection molded lenses, microlenses and micro-structured lenslets or arrays made of thermoplastic materials dominate the market due to their wide range of applicability and the availability of well know material [14; 15; 16; 17; 18; 19; 20; 21; 22]. Newer applications with more challenging requirements employ silicones, which require more sophisticated molding processes and have strong limitations in complex hybrid assemblies [22]. Injection molding of thermoset materials is comparable to silicone processing in terms of tool requirements and process flow. However, thermosets offer the advantage of being provided as granulate making storage and molding significantly easier in comparison to silicones, and they are the established standard in electronic packaging and higher-level assemblies for the last decades. Thermoset materials are not very common in the field of optics since non-filled materials with the required transparency have very high shrinkage rates, large coefficients of thermal expansions and the tendency of yellowing at UV light exposure. However, the surfaces of standard package electronic components using thermosets with tailored filler materials are mirror-like. Smallest defects in the mold tool or deviations of the designed mold flow appear as unacceptable defects in the view of a customer, even though these defects do not present any functional limitations and are, in most cases, less severe as non-visible scratches from demolding or joint lines in thermoplastic components. The ability to form such surfaces during the molding process leads to the idea of using thermosets as reflective optical elements, or moreover of integrating micro-optical features in thermoset components, either as stand-alone components or as additional features in electronic packaging. The injection molding process of thermoset materials can be outlined as follows: the molding tool is closed and the injection process starts. The melt is pressed through an opened nozzle into the gate system. A laminar flow with Re \(\leq\) 2300 is to be derived to avoid turbulences without voids being trapped in the melt [23]. The process differs at two distinct characteristics from processing of thermoplastics. The higher difference in temperature of the melt to the tool in thermoplastic injection molding leads to a surface zone, causing solidification effects of the melt at the wall between melt and tool. Thermosets in contrast, have no significant temperature difference between melt and tool preventing the solidification effect.