Investigation into applying self-calibration techniques to measuring large optical components on a CMM

摘要

Any measurement of an artefact on a CMM will include contributions from the systematic errors of the machine, the random errors in the machine and also the actual geometry of the artifact. If an artifact is rotated (or translated) within the CMM measuring volume, such that the chosen measurement points on the artifact continue to map onto the same machine coordinates, then the component of the measurement due to the artifact geometry will rotate, whilst the component due to the machine systematic errors will remain in the same position. In the self-calibration technique, a set of measurements of this type is made, and from these the systematic errors of the machine can be identified. The measurement accuracy of the artifact geometry is then only limited by the random component of the machine error, which is generally smaller than the systematic errors of the machine. This paper reviews self-calibration techniques and assesses their feasibility for improving the uncertainty of form measurement of large optical surfaces on a coordinate measuring machine.