**1. Introduction**

The increasing technical and economical requirements for components have led to mono material bulk metal components reaching the limits of their performance due to the material used. To extend those limits, the use of hybrid components is the subject of current research [1,2]. A high technological potential lays in hybrid bulk metal components that are first joined and then further processed. In the collaborative research center 1153 "Tailored Forming", such a process chain has been developed [3], following the concept "Put the right material in the right place". Due to the use of novel material combinations in hot bulk metal forming processes, the development of new evaluation techniques also needs to be considered, e.g., to validate new simulation models [4] for cross-wedge rolling [5]. The distortion induced by the combination of cooling and materials with different thermal expansion coefficients needs to be considered for the analysis of such processes. Therefore, the evaluation of the forming process by analyzing the component after cooling down to room temperature is not sufficient. Instead, the component and especially its geometry need to be measured while in the hot state directly after leaving the forming process. To this end, an optical 3D geometry measurement system based on triangulation can be used [6–8]. However, the hot object is surrounded by an inhomogeneous refractive index field, deflecting the measurement light from its linear path [9]. There have been attempts to

estimate the effect [10] and methods to compensate its impact on triangulation measurements [11]. However, there are currently no in-line or close-to-line measurement systems that take the light deflection into account or compensate for it. The system presented in this paper aims to close that gap by adding a suppression device for the light deflection effect based on formed and forced air flow to an optical 3D geometry measurement system. The design, setup, and analysis of such a system is described in this paper.
