Method for measuring the oscillation amplitude of a scanner mirror in a projection system of a motor vehicle headlight, wherein a laser beam generated by a laser source is directed onto and reflected by the scanner mirror the latter, the laser beam thus reflected arriving on a detector device, wherein a detector device is used, comprising several photodetector elements (Q1, Q2, Q3, Q4) arranged adjacent to one another about a centre thereof, the laser beam describing a curve across the photodetector elements by virtue of the oscillating movement of the scanner mirror, said curve being bordered within a rectangular light distribution, characterised in that, with respect to at least one detector region (R X, R Y) formed each by a detector element or a group of directly adjacent detector elements and corresponding either to the negative or the positive range of a coordinate, - the centre point of the light distribution generated by the laser source and the scanner mirror is displaced by an offset value (x offset, y offset) from the centre of the detector device along the coordinate associated with the specific detector region (R X, R Y); - the time period (t ON,X, t ON,Y) during which the curve passes through the specific detector region (R X, R Y) is determined; - using the ratio of the time period (t ON,X, t ON,Y) thus determined to the total duration of an oscillation period and using the offset value (x offset, y offset), a value of the oscillation amplitude (x p, y p) is determined. wherein a detector device is used, comprising several photodetector elements (Q1, Q2, Q3, Q4) arranged adjacent to one another about a centre thereof, the laser beam describing a curve across the photodetector elements by virtue of the oscillating movement of the scanner mirror, said curve being bordered within a rectangular light distribution, characterised in that, with respect to at least one detector region (R X, R Y) formed each by a detector element or a group of directly adjacent detector elements and corresponding either to the negative or the positive range of a coordinate, - the centre point of the light distribution generated by the laser source and the scanner mirror is displaced by an offset value (x offset, y offset) from the centre of the detector device along the coordinate associated with the specific detector region (R X, R Y); - the time period (t ON,X, t ON,Y) during which the curve passes through the specific detector region (R X, R Y) is determined; - using the ratio of the time period (t ON,X, t ON,Y) thus determined to the total duration of an oscillation period and using the offset value (x offset, y offset), a value of the oscillation amplitude (x p, y p) is determined. - the centre point of the light distribution generated by the laser source and the scanner mirror is displaced by an offset value (x offset, y offset) from the centre of the detector device along the coordinate associated with the specific detector region (R X, R Y); - the time period (t ON,X, t ON,Y) during which the curve passes through the specific detector region (R X, R Y) is determined; - using the ratio of the time period (t ON,X, t ON,Y) thus determined to the total duration of an oscillation period and using the offset value (x offset, y offset), a value of the oscillation amplitude (x p, y p) is determined.