A device for measuring movement of an object (15) and the device relative to each other. The device comprises a laser (3) for generating a measuring beam (13), which is converged by a lens (10) in an action plane. Radiation reflected by the object (15) is converged to re-enter the laser cavity to generate a self-mixing effect in the laser (3). Measuring means (4) are provided to receive the reflected measuring beam radiation and enable the frequency difference between the measuring beam (13) and the reflected measuring beam radiation to be determined, which is representative of the relative movement.