TESA Gauge Block Interferometer

At METAS, gauge blocks of the highest accuracy classes are calibrated for lengths of up to 100 mm in the vertical position using an automatic NPL-TESA gauge block interferometer. The interferometric measurement is based on determining the fraction of an interference fringe (fringe fraction) using two or three frequency-stabilised He-Ne lasers with different wavelengths. The primary application is the interferometric absolute measurement of gauge blocks made of steel, carbide, ceramics and Zerodur® in the range from 0.5 mm to 100 mm. The central length of the gauge block, its deviation from flatness and its variation in length are measured.