| 摘要 |
PROBLEM TO BE SOLVED: To solve a problem that, in a prior art, the accurate alignment of an optical axis angle to a helix angle is difficult and an exact projection image of a thread part is hardly obtained.SOLUTION: A projection image of a thread part 5 is photographed by a camera SB using irradiation light from a light source lamp SA while changing an optical axis angle α which is an angle formed by an optical axis Lax of an optical type sensor S to a plane orthogonal to a screw shaft 11, and the optical axis angle α is aligned to a helix angle &thetas; of the thread by adjusting the optical axis angle α so that a transition region between light and shade forming an edge boundary part of a flank surface of the photographed projection image becomes minimum. |
