The present invention relates to a method and apparatus for alignment of two mechanical parts. An inventive measuring device has a housing comprising a light source and a detector for detection of light beams. The light source is capable of transmitting a light beam modulated according to a modulation scheme for information transmission. The output of said detector is connected to an interpreter arranged to demodulate a detected light beam and to a signal conditioner arranged to extract the position of impingement of a detected light beam on the detector surface.