Implementation of a Geometric-Error Correction System for Extremely High Probe Position Accuracy in Spherical Near-Field Scanning
Authors:Scott Pierce, James Langston
Publication: AMTA 2004
Copyright Owner: NSI-MI Technologies
In this paper, we describe a new method for improving the true-position accuracy of a very large, spherical near-field measurement system. The mechanical positioning subsystem consists of 10-meter diameter, 180° circular-arc scanner and an MI Technologies MI-51230 azimuth rotator and position controller.
The principle components of the error correction method are the error measurement system, the position correction algorithm, and a pair of very high precision, mechanical error correction stages. Using a tracking laser interferometer, error maps are constructed for radial, planar and elevation errors. A position correction algorithm utilizes these discrete-point error maps to generate error correction terms over the continuous range of the elevation axis. The small position correction motions required in the radial and planar directions are performed using the mechanical correction stages. Corrections to the position of the elevation axis are made using the primary elevation axis drive.
Results are presented that show the geometry of the spherical scanning system before and after error correction. It is observed that the accuracy of the radial, planar and elevation axes can be significantly improved using the error correction system.