Comparison and calibration of laser interferometer systems

Abstract

The paper describes the reasons and practical needs for the calibration of laser interferometer systems. The conventional techniques for mechanical, frequency and wavelenght comparison, and the new co-axial displacement comparator for simultaneous concurrent comparison of up to 10 complete laser interferometer systems, are explained. Requirements of the set-up and experimental results are discussed. The new method gives the ordinary user a simple but efficacious measure to calibrate his own complete laser interferometer system and to estimate the effective precision under his own real laboratory or workshop conditions. Even the comparison of uncalibrated systems gives interesting results: eg, about zero drift, warming up, short- and long-term alterations and electrical noise interferences. For absolute calibration, a portable iodine-stabilised laser source and sophisticated methods for wavelenght compensation in ambient air are needed.