Method of assisting sample inclination error adjustment

A method of assisting sample inclination error adjustment for assisting inclination error adjustment of an axis of a ferrule when a curved leading end face of said ferrule as a sample held by a clamping apparatus is observed by an interferometer apparatus, said method comprising the steps of:

• causing said interferometer apparatus to obtain respective interference fringe images of said curved leading end face of said ferrule at three or more rotational positions by rotating said ferrule by a predetermined angle with respect to said clamping apparatus while in a state where said ferrule is held by said clamping apparatus;
• determining respective interference fringe center positions in thus obtained at least three interference fringe images;
• calculating a center position of a circle passing near each of thus determined interference fringe center positions and defining thus calculated center position as a measured center position;
• and
• outputting relative distance information between said measured center position and a position corresponding to a rotational center position of said curved leading end face of said ferrule or said relative distance information and relative directional information thereof as an inclination error adjustment value for said axis of said ferrule.