Short gauge blocks

VTT MIKES calibrates the ISO 3650 grade 00 and grade 0 short gauge blocks from 0 to 100 (200) mm with a phase-step interferometer (PSIGB). The device is based on the NPL-TESA measurement interferometer from the 1990s, which optics, mechanics and electronics have been updated to enable phase stepping. Gauge blocks are wringed into a steel reference base and, after stabilization, an automatic measurement program performs the measurement: it collects 9 phase images at both 633 nm and 543 nm HeNe laser wavelengths and analyses the mean length and surface flatness of the gauge blocks. During the measurements, the temperature of the gauge blocks deviates less than 50 mK from 20 °C. The phase correction due to surface roughness and phase change in the reflection is determined by means of the so-called a stack method or using an integrating sphere to measure scattered light. The updated VTT MIKES interferometer is described in detail in [1].

Measurement uncertainty of calibration of short gauge blocks.  ​ 

Measuring range Expanded 
uncertainty (k=2)
0.5...200 mm​U = Q[20; 0.3L] nm ​L in millimetres, Q[x; y]=√(x2+y2)

The performance of the VTT MIKES gauge block interferometer is tested by regular participation in international comparisons organized by EURAMET and CCL. The latest comparison is EURAMET.L–K1.2011 [2]. The results of the comparison supported the reported measurement uncertainty of the VTT MIKES PSIGB interferometer.

VTT MIKES also offers other NPL-TESA interferometer users the possibility to upgrade their device to use phase stepping and Windows 10 operation system. For more information, please contact: Antti Lassila.


    TESA.jpg       2_wb.png

VTT MIKES phase stepping gauge block interferometer for short gauge blocks (left), wringing of the gauge blocks is made inside a vertical laminar clean air cabinet (right).

  1. V. Byman, A. Lassila, MIKES’ primary phase stepping gauge block interferometer, Meas. Sci. Technol. 26, 084009 (2015)  
  2. M. Matus et. al, Measurement of gauge blocks by interferometry, Metrologia 53, 04003 (2016).


  • Antti Lassila, Research Team Leader, tel. +358 40 767 8584, email antti.lassila(at)   

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