When designing or sizing a high precision positioning system using homodyne laser interferometry or when evaluating a measurement uncertainty of an already designed system, many error sources which can degrade the measurement precision have to be taken into account. Some errors originate from :
the mechanical and electronical integration of the interferometer (mechanical drift, dead path error, resolution limit, noise level, interpolation, cosine error, parasitic rotation, beam alignment and Abbe error, aging error, thermal expansion of the interferometer itself)
from the environment in which the instrument is installed (mechanical vibration, drift of environmental parameters like pressure, temperature, hygrometry, Edlen correction, air turbulence),
from the optical components (mirror shape and roughness, orthogonality error),
from intrinsic errors linked to the principles of interferometry (vacuum wavelength calibration of the laser source used, wavelength stability, calibration of environment sensor used for Edlen correction, nonlinearity errors, differential measurement or not, beam profile quality)
and so on.
The given presentation will review the main errors sources, will quantify and classify them by order of importance and will establish the principle rules to achieve nanometre range precision when measuring displacements by interferometry.