Device for white light interferometry comprising a light source of main emission wavelength .lamda..sub.0 and spectral width .DELTA..lamda. and an evaluating unit with a line sensor of pixel width P for detecting an interference fringe pattern with a fringe spacing F, a mask being placed in front of the line sensor having a periodically modulated light transmittance along said line sensor, characterized in that the period length M of the mask is such as to fulfill the condition.DELTA..times..times..lamda..lamda.<<.times..DELTA..times.- .times..lamda..lamda. ##EQU00001##