Highly accurate imaging based position measurement using holographic point replication

Abstract

The experimental approach of a highly accurate imaging based stereo measurement setup with a total measurement volume of 140 mm × 100 mm × 50 mm is presented. The system can detect the position of multiple target points (LEDs) in a calibrated volume of 100 mm × 75 mm × 24 mm with an accuracy of σx=0.367μm, σy=0.373μm and σz=0.437μm. This high accuracy is reached by holographically replicating each point light source to a predefined pattern (cluster) of spots on the camera sensor and averaging the center positions of all spots. We present a detailed description of the principle, the process and results of calibration including deformation compensation and stability measurements, as well as the results of two- and three-dimensional trajectory measurements. To validate the performance and accuracy of the measurement setup, interferometers are employed as reference sensors. The residual error of a two-dimensional trajectory of distance D=277μm is σd=0.242μm and for a three-dimensional trajectory of distance D=57.2 mm it is σd = 0.674 μm.