Obtaining method and obtaining apparatus for geometric error of rotation axis

The invention provides a method and equipment for acquiring geometric errors of a rotating shaft. The geometric error acquisition method comprises the following steps. An annular encoder is installed on the rotating shaft, and a first optical reading head and a second optical reading head are installed around the annular encoder. The ring-type encoder is rotated by the rotating shaft, and the deviation distance and the azimuth angle of the central point of the ring-type encoder relative to the central axis of the rotating shaft when the rotating shaft rotates by 0 degree are obtained according to the angle value read by the first optical reading head. A first assembly angle deviation of the first optical read head and a second assembly angle deviation of the second optical read head are obtained. And obtaining a rotation angle error when the rotating shaft rotates to each angle. And obtaining the rotation deflection error of the rotating shaft when the rotating shaft rotates to each angle.