Patent ID: 6317991
Filing Date: 2001-11-20
Classification: G01B,G03F

Abstract:
A method for determining a correction function K(r.sub.jk) for rectifying the coordinate-dependent measuring errors of a coordinate-measuring machine by selfcalibration, comprising, in a stepwise fashion:a) measuring initial coordinates r.sub.j0 in relation to a number j of reference structures (5) on a rigid, uncalibrated reference object (1) disposed on an object table of the coordinate-measuring machine in an initial orientation k=0 of the reference object (1), and measuring calibration coordinates r.sub.jk in a number k.gtoreq.1 of different calibration orientations produced by rotation from the initial orientation, wherein the calibration orientations are produced by rotations with the aid of rotation functions D.sub.k about a single rotation axis (6) of the reference object (1),b) operating a coordinate dependent correction function K(r.sub.jk) upon the initial coordinates r.sub.j0 and the calibration coordinates r.sub.jk, the coordinate-dependent correction function K(.sub.jk) is described by an approximation ##EQU4##with initially unknown fit parameters a.sub.i and a number N of prescribed, linearly independent fit functions k.sub.i (r.sub.jk);c) performing rotation functions D.sub.k upon the corrected calibration coordinates (r.sub.jk +K(r.sub.jk)); given by the calibration coordinates r.sub.jk operated upon by the correction function K(r.sub.jk) to rotate back the calibration coordinates into the initial orientation;d) calculating fit parameters a.sub.i such that in relation to a reference structure (5) in each case all the corrected and rotated-back calibration coordinates D.sub.k (r.sub.jk +K(r.sub.jk)) and the corrected initial coordinates (r.sub.j0 +K(r.sub.j0)) substantially agree, ande) generating a continuous correction function K(r.sub.jk) to be applied to arbitrary coordinates to be measured wherein, from the fit functions k.sub.i (r.sub.jk), no linear combinations can be formed which go over into themselves for all the rotations D.sub.k carried out.