Multiple wavelength interferometry is a technique used in mechanical metrology laboratories throughout the world for the absolute measurement of length of gauge blocks and length bars.
Current instruments use cadmium and mercury gas discharge lamps to provide the measurement wavelengths. They present the disadvantage however of low intensity which limits the performance of this kind of calibration both in terms of speed and maximum length capability.
The objective of the project is to develop a compact laser source, based on available He Ne lasers, stabilized at 543 nm and possibly at 594 or 612 nm.
The project studied the stabilization of newly available green and yellow helium-neon lasers. The stabilization was tested on lasers from three manufacturers.
In each case, the adjustment must be slightly different and the lasers must be calibrated individually. The results are nevertheless very satisfactory as in the worst case observed, there is a drift of only 3 1E8 for 1000 hours operation.
The stabilized two-colour laser is already used by the firm TESA on an equipment designed for the automatic calibration of gauge blocks in metrology laboratories.