Flexible Robot-Based In-Line Measurement System for High-Precision Optical Surface Inspection

Advances in industrial manufacturing and an increasing trend towards direct integration of measurement systems in the production line require flexible, fast, precise and robust systems. This paper presents the development and evaluation of a fully automated robot-based in-line measurement system, suitable for applications incorporating process variability and uncertainty, however, requiring single micrometer resolution and low instrumentation effort. The system utilizes laser triangulation in combination with mechanical 2D-scanning for fast and precise measurements. Lissajous trajectories and a computer vision algorithm based on edge detection are used to locate relevant features within the scan area. This allows alignment of the measurement tool, by using plane fits, to optimally utilize the measurement range of the sensor system for a high resolution scan, applied to a refined area, providing robustness and flexibility. For a scan area of 25×25mm the measurement uncertainty equals 6.4μm at 2σ. The system accuracy is evaluated to 2.2μm. The combined standard uncertainty of reference sample measurements equals 1.2μm.