Method and device for measuring optical axis and gap of lens group by differential confocal internal focusing method

The invention relates to method and device for measuring an optical axis and a gap of a lens group by a differential confocal internal focusing method, belonging to the technical field of optical precision measurement. The method comprises the following steps of: firstly accurately regulating the optical axis of the measured lens group by combining an internal focusing objective with an autocollimation method; then realizing the high-accuracy positioning of each surface of the measured lens group by utilizing a differential confocal focus-fixing principle, and acquiring a numerical aperture angle of a differential confocal light cone positioned on each positioning point; finally sequentially calculating each gap of the measured lens group by utilizing a ray tracing recursion formula, and also leading an annular optical pupil into a measuring optical path to form a hollow measuring light cone so as to reduce the influence of astigmation on a measurement result. The invention combines a differential confocal te