Fringe projection profilometry in combination with other optical measuring technologies has established itself over the last decades as an essential complement to conventional, tactile measuring devices. The non-contact, holistic reconstruction of complex geometries within fractions of a second in conjunction with the lightweight and transportable sensor design open up many fields of application in production metrology. Furthermore, triangulation-based measuring principles feature good scalability, which has led to 3D scanners for various scale ranges. Innovative and modern production processes, such as sheet-bulk metal forming, thus, utilize fringe projection profilometry in many respects to monitor the process, quantify possible wear and improve production technology. Therefore, it is essential to identify the appropriate 3D scanner for each application and to properly evaluate the acquired data. Through precise knowledge of the measurement volume and the relative uncertainty with respect to the specimen and scanner position, adapted measurement strategies and integrated production concepts can be realized. Although there are extensive industrial standards and guidelines for the quantification of sensor performance, evaluation and tolerancing is mainly global and can, therefore, neither provide assistance in the correct, application-specific positioning and alignment of the sensor nor reflect the local characteristics within the measuring volume. Therefore, this article compares fringe projection systems across various scale ranges by positioning and scanning a calibrated sphere in a high resolution grid.

Systematic deviations due to remaining lubricant on the workpiece have a significant influence on the measurement of sheet-hulk metal formed parts. The expected layer thickness for the workpieces after the forming process is less than 35 mu m. For the determination of the refractive index of the lubricant and thus the effects of the lubricant on optical measurement techniques, a lubricant thin-film thickness standard was developed which represents a continuous measuring range from 6 to 100 mu m. To determine the refractive index, the thin-film thickness standard was measured with a coaxial interferometric measurement system in various thickness ranges. Due to the knowledge of the optical and the geometrical path length, the refractive index can then be determined approximately. In addition, an XY stage was used to scan the entire thin-film area of the standard. The measurement setup in a temperature box allows for determining the effects of temperature changes on the optical properties of the lubricant.