High Speed High Accuracy Multilateration System Based on Tracking Interferometers

The use of tracking interferometers has gained industrial application for the testing and the calibration of measuring and production machines. The concept is based on sequential multilateration [1] and can realize calibration uncertainties in the sub-micron order. Another application for tracking interferometers is the real-time multilateration for accurate and highly dynamic measurement of 3D motion. This paper presents the characteristics of a high speed high accuracy multilateration system based on interferometric displacement measurements. Introduction Laser interferometer based multilateration systems have been discussed as a solution to accurate determination of 3D position since the 1970s. A proof of principle has been demonstrated 2000 by Hughes et.al. [2]. Also the Physikalisch-Technische Bundesanstalt (PTB) has developed a system based on commercial available components [3]. An interferometric multilateration system has the following characteristics: Direct traceability to the laser wave length Highest accuracy due to incorporated Abbe principle Self calibration capability Now a multilateration system has been developed and tested, that combines the previously demonstrated benefits with high dynamic measurement capabilities. This paper describes the system, presents results and reviews possible applications. The principle of multilateration The multilateration principle is based on spatial length measurement between a target point and at least three reference points with known coordinates. The multilateration principle is used e.g. in the Global Positioning System (GPS) based on microwave time-of-flight measurement. If four reference points are available, an incremental displacement measurement is sufficient to perform a self calibration of the system [2,3]. The high resolution of an interferometer can be used to realize the displacement measurement in such a system. In the system described here, stable reference points have been realized by the so called Lasertracers [3]. 10th IMEKO TC14 Symposium on Laser Metrology for Precision Measurement and Inspection in Industry Braunschweig, GERMANY, 2011, September 12-14