Method for measuring the axial runout of a plane surface of a workpiece with respect to an axis of rotation, and corresponding measuring assembly

A method for measuring the axial runout or orthogonality error of a plane surface of a workpiece with respect to an axis of rotation via an optoelectronic probe provided with a linear image sensor oriented parallel to a plane perpendicular to the axis of rotation, the method comprising:

• performing, via the optoelectronic probe, a first optical scanning of the workpiece standing at a certain angular position, via a relative translation between the workpiece and the optoelectronic probe along a direction parallel to the axis of rotation to obtain a first light intensity trend of at least one pixel of the linear image sensor as the relative position between the workpiece and the optoelectronic probe along said direction varies;
• determining a relative position of the plane surface of the workpiece as an intermediate position in a position range in which the first light intensity trend has a monotonic trend;
• performing a second optical scanning of the workpiece via the optoelectronic probe in the relative position of the plane surface of the workpiece while the workpiece rotates with respect to the axis of rotation to obtain a second light intensity trend of said at least one pixel as the angular position of the workpiece around the axis of rotation varies;
• obtaining at least two light intensity values from the second light intensity trend;
• in the first light intensity trend, selecting at least two position values corresponding to said at least two light intensity values;
• on the basis of said at least two position values, determining a maximum position value and a minimum position value from the first light intensity trend;
• and
• calculating said axial runout as the difference between the maximum position value and the minimum position value.