System for automatic gauge block length measurement optimized for secondary length metrology

This paper presents a contactless system for automatic gauge blocks calibration based on combination of laser interferometry and low-coherence interferometry. In the presented system, the contactless measurement of the absolute gauge block length is done as a single-step operation without any change in optical setup during the measurement. The optical setup is combined with compact gauge block changer with a capacity of 126-ga blocks, which makes the resulting system fully automatic. The paper also presents in detail a set of optimization steps which have been done in order to transform the original experimental setup into the automatic system which meets secondary length metrology requirements. To prove the measurement traceability, we conducted a set of gauge block length measurement comparing data from the optimized system and the established reference systems TESA NPL A.G.I. 300 and TESA–UPC operated in Czech Metrology Institute Laboratory.