Distance measurement with thousands of lasers simultaneously
A laser is frequently applied as a tool for accurate measurement of distance, with the laser wavelength serving as a 'ruler'. Researchers from the Dutch national metrology institute VSL, Delft University of Technology and the FOM Foundation have developed a new technique to exploit the thousands of wavelengths that are present in the spectrum of a femtosecond laser for distance measurement.
The wavelengths of such a 'frequency comb' are locked to an atomic clock for direct traceability to the SI second. Using a spectrometer with an unprecedented resolution, the closely spaced wavelengths are individually resolved. A wealth of information is obtained when measuring a distance with all wavelengths simultaneously. This allows for direct measurement of absolute distances with a measurement uncertainty on the level of 10s of nanometers. In this scheme it is not necessary to generate a displacement and measure incrementally, which is an important advantage compared to the single wavelength scheme. The new method may find applications in setups that require accurate absolute distance measurement that cannot be determined incrementally, like the determination of distances between satellites. The results of their work will be published in the 4 May issue of the Physical Review Letters.
The research is part of EURAMET joint research project 'Absolute Long Distance Measurement in Air'.
The basis of this work has been laid within the FOM IPP 'Metrology with Frequency Comb Lasers'.
Reference
S.A. van den Berg, S.T. Persijn, G.J.P. Kok, M.G. Zeitouny and N. Bhattacharya, 'Many-wavelength interferometry with thousands of lasers for absolute distance measurement', Phys. Rev. Lett. 108, 183901 (2012).
Contact
Dr. Steven van den Berg +31 (0)15 269 15 86
Dr. Nandini Bhattacharya +31 (0)15 278 96 05