Common path two-wavelength homodyne counting interferometer development

The linearity of displacement measurement is an important parameter in nanometrology. The development of the common path two-wavelength (633 nm and 532 nm) homodyne counting interferometer within the Nanotrace project is described. These two differential interferometers are also designed for the elimination of optical path drifts and fluctuations. Their short-term instability is projected to be in the order of tens of pm in the single wavelength path difference and below 10 pm in the difference of these two wavelength path differences. This solution enables better real-time validation of interferometer fringe interpolation. The whole system could be transportable and measure displacements up to 100 µm under ambient air conditions under cover. Refractive index compensation will also be included