Displacement of an object is sensed by a transducer element having light first strips and dark second strips alternating in a direction of object displacement. The first strips are formed as phase gratings having grating lines extending in the direction of displacement and having a width equal to half the grating period and a depth such that the zero-order diffraction beam is suppressed. The lines may be grooves or ribs, separated by lands which are at the same level as the second strips. A device, for measuring displacement of an object on which such an element is fixed, includes an imaging system having an aperture limited such that first and higher-order diffraction beams from the phase grating are not transmitted to a radiation-sensitive pattern detection system.