| 摘要 |
PROBLEM TO BE SOLVED: To shorten the time required over the entire part of cutting by spirally cutting a stamper. SOLUTION: Cutting of the reverse type of saw tooth-shaped grooves is executed toward the center from the outermost periphery. Namely, the cutting of a Fresnel surface is executed. In such a case, a Fresnel angle and the depth of cut change continuously from the outermost periphery toward the center and, therefore, the cutting is executed while the face (a) of a cutting tool for working the Fresnel face is aligned to the prescribed Fresnel angle in its position from the outermost periphery toward the center in such a manner that the prescribed depth of cut is attained in this position. Further, the cutting tool is arranged again in the cutting start position and the similar spiral cutting is executed while the depth of cut is increased in such a manner that the depth of cut of the Fresnel surface attains the prescribed quantity. The cutting tool is then arranged in the prescribed position and the cutting of the rise face is executed. The face (b) of the cutting tool for working the rise face is aligned to the prescribed rise angle in the position from the outermost periphery toward the center and the cutting is executed until the prescribed depth of cut is attained in this position. |
