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 (P) 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 (P) 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 (T) 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 (P) 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 (P) 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 (T) 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 (P) 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 (T) 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. <EOS>