Accuracy of Commercially Available Laser Measurement Systems

This paper presents the results of measurements on the accuracy of commercially available laser measurement systems. After a short introduction the set-ups are described for measuring the laser wavelength and for checking the total measurement system. The first part is based on well known heterodyne measurements and the second is carried out by comparison with a well calibrated laser interferometer. Only one moving mirror is used in both measuring beams, so first order (Abbe) errors are avoided. Results show that laser systems using wavelength stabilisation based on Zeeman-splitting are usually more accurate than the manufacturer claims. However, when automatic compensation for index of refraction is used, large errors can occur due to failure in temperature or pressure measurement. Relative errors up to 1.4 × 10−6 were measured in some laser systems using two mode stabilisation, due to a wrong wavelength used in the electronic system. The conclusion night be that laser measurement systems are very accurate length measuring instruments provided systematic errors are avoided by periodic calibration of emitted wavelength and automatic compensation system.