Metrology

Traceable Measuring Equipment for Nanomeasuring Technology

PI qualifies its products with external measuring equipment. These are calibrated in part and traceable to a national standard.

In the simplest of cases, measuring sensors are used for length measurement. However, PI also has available a number of high-resolution interferometers from leading manufacturers of metrology equipment.

Measuring equipmentDescriptionResolution / DPMIAccuracy
5 x Laser interferometerZYGO ZMI10001.24 nm2.4 nm
2 x Laser interferometerZYGO ZMI20000.31 nm2 nm
3 x Laser interferometerZYGO ZMI40000.151 to 0.019 nm2 nm
1 x Laser interferometerSIOS SP120d1.24 nm-

 

 

 

Metrology Measuring Equipment at PI

Using the PIOne incremental encoder and capacitive sensors, PI manufactures own metrology for inclusion in PI products. This measuring equipment is also employed in manufacturing and qualification devices to measure subnanometer resolution, but is not calibrated.

PI also has available 3-D coordinate measuring machines and a 6-D laser tracker for the qualification of hexapod systems.

Depending on the angle range, angle measurements are conducted with autocollimators (7 units in total, 4 of which are calibrated), inclinometers, incremental rotary encoders, or the interferometers.

As PI also conducts materials research in the field of piezo technology and piezomotors, the range of equipment at PI also includes two white light interferometers.

Vibrometers measure the velocity and vibration properties of positioning systems up to max. 25 kHz.

Metrology Standards

The qualification of the PI products is based on:

  • DIN ISO 230-2
    Test code for machine tools 
    Part 2: Determination of accuracy and repeatability of positioning numerically controlled axes

    However, deviating from the standard, the repeatability of the positioning stages is given with a scatter of 1-Sigma instead of 3-Sigma.

  • VDI/DGQ 3441 
    Statistical Testing of the Operational and Positional Accuracy of Machine Tools

Both standards are strongly focused on the specification of machine tools. They do not take into account any specifics relating to precision positioning technology in the nanometer range, for example, for products offered by PI.

PI and other leading manufacturers of precision positioning equipment have recognized this deficiency. Together with the National Institute of Standards and Technology a project was launched to address this specific class of positioners ("Methods for Performance Evaluation of Single Axis Positioning Systems: A New Standard").

Absence of Standards in Nanopositioning Technology:

The term "resolution" is subject to various interpretations, depending on the supplier – from the smallest possible step width to ridiculously small values in the picometer range resulting from mathematical transformation in the frequency domain which are absolutely irrelevant for the actual use of the stages.


Nanometrology Rooms

Every manufacturing fractal at PI has its own metrology equipment. Next to the measuring equipment this also includes vibration-damped honeycomb tables.

Long-term measurements to confirm positional stability over several hours, as well as measurements less than one nanometer, are conducted in special, climate stable measuring rooms.

The seismic, electromagnetic, and thermal isolation of the test laboratories guarantees a stable temperature better than 0.25 °C over 24 hours. Measuring accuracies down to picometer range set standards in the measurement of nanopositioning equipment.