Position measurement in standing wave interferometer for metrology of length

We present techniques oriented to improvement of precision in incremental interferometric measurements of displacements over a limited displacement range. The wavelength of the coherent laser source is here directly stabilized to a mechanical reference and not to a reference of any optical frequency. This may represent a reduction of uncertainty linking the laser wavelength not to indirectly evaluated refractive index but to the setup mechanics which cannot be completely eliminated. Here we suggest an approach where the traditional interferometers are replaced by a passive Fabry-Perot cavity with position sensing using an intracavity transparent photodetector.