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Production sequence of Si-spheres and interferometrical determination of the sphere volume

Interferometry on Material Measures

Department 5.4


The availability of length standards and the ability to measure lengths with high accuracy are of fundamental importance for technologically advanced societies. With increasing demands on accuracy, more and more precise length standards were developed already in the beginning industrial age. In Department 5.4, the connection of the length of measuring standards to the International System of Units (SI) is realized by means length measurements by interferometry. The optical frequency standards recommended by the International Committee for Weights and Measures (CIPM) are used as light sources. Within the scope of intensive research, the methods used are constantly being further developed.

High-precision calibrations of gauge blocks, spheres, line scales, laser interferometers, electronic distance measuring instruments and probes as well as special measurements such as sub-nm measurements of thermal expansion and drift behaviour of materials are carried out on behalf of customers.

On behalf of the conformity assessment body of PTB, type examination certificates according to Module B of Directive 2004/22/EC Annex MI-009 of the European Parliament (MID) are issued and type approval of choirometers, distance measuring instruments and instruments for wood measurement is carried out. Another focus is on the support, assessment and training of external calibration laboratories, especially in the field of gauge blocks.

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