Tilt adjustment of the stage is a key technology. If the tilt adjustment accuracy of the stage is not high, it will greatly affect the measurement accuracy of the spherical apex eccentricity, APC angle and positioning key angle. Figure 4 is an overview of the relationship between tilt adjustment and spherical vertex eccentricity measurement accuracy. As shown in Figure 4(a), when the tilt adjustment of the stage is complete, the optical axis of the interferometer optical system will be parallel to the central axis of the ferrule of the optical fiber connector to be measured. At this time, when the optical fiber connector to be measured is rotated, the spherical vertex of the end surface of the optical fiber connector (the center of the annular interference fringe such as point A or point B) will rotate around the center point O of the optical fiber, forming a circle with point O as the center. The measured apex eccentricity value OA or OB will be the same as the actual apex eccentricity. In other words, no matter what angle the fiber optic connector is rotated, the measured apex eccentricity value will not change much. On the contrary, as shown in Figure 4(b), when the tilt adjustment of the stage is incomplete, the optical axis of the interferometer optical system will intersect at an angle with the central axis of the ferrule of the optical fiber connector to be measured. At this time, when the optical fiber connector to be measured is rotated, the spherical vertex of the optical fiber connector end surface (the center of the annular interference fringe such as point A, point B, point C or point D) will revolve around a center O that is different from the center O of the optical fiber. *Rotate to form a circle with O* as the center. Obviously, the apex eccentricity value OA, OB or OC measured at different positions will not be the same as the actual apex eccentricity OD. In other words, after rotating the fiber optic connector, the measured apex eccentricity value will change greatly. From this phenomenon, we can also get a method to check whether the tilt adjustment of the stage is complete. That is, rotate the fiber optic connector and measure the apex eccentricity value in sequence. If the measured apex eccentricity value does not change significantly, the stage tilt adjustment is complete. Otherwise, the stage tilt adjustment is incomplete. In order to improve the adjustment accuracy of the stage tilt, Fuji Photo Optical Machinery Co., Ltd. has developed a high-precision, easy-to-operate stage tilt adjustment technology (multinational patents have been applied for) 7, 8, which can achieve much better results than the general adjustment method. adjustment accuracy.