A method for adjusting an optical system, and to an adjustment system for use in an optical system where the adjustment system comprises a predetermined reference object having known visible reference object features, a sensor system, a data evaluation module and an image processor. The data evaluation module receives captured image data and determines at least two visible reference object features of the predetermined reference object arranged in a field of view, and determines position data containing a position deviation of an image of the object to be examined or, in the case of a stereoscopic optical system, of a first and second half-image of the object to be examined. The image processor ascertains an optical distortion of the visible reference object features and sets a corresponding geometric rectification of received image data.