MANUFACTURE OF OPTICAL MEMBER

Japanese Patent JP3827377

B2

PROBLEM TO BE SOLVED: To finish a valley part corner in an ideal shape while maintaining vertical surface accuracy of a saw-toothed groove by applying/cutting an inclined face of the saw-toothed groove to/by a front cutting edge of a cutting tool, and sending/cutting a vertical surface of the saw-toothed groove by the cutting edge tip. SOLUTION: A Fresnel lens base board as a workpiece 1 is held by a chuck of a CNC lathe, and is rotated around the rotational axis 11. A diamond cutting tool 2 is arranged in a position opposed to an end surface 1a of this workpiece 1, and a front cutting edge 30 of the cutting tool 2 is set so as to coincide with an inclination C of an inclined face 15a of a saw-toothed groove. The cutting tool 2 is sent, and the inclined face 15a is cut by the front cutting edge 30, and at the same time, a vertical surface 15b is cut by the cutting edge tip 18. Next, after the cutting tool 2 is retreated, a notch quantity is microscopically increased, and cutting work is reperformed on the vertical surface 15b. Afterwards, the cutting tool 2 is sent, and the above-mentioned work is repeated, and a Fresnel lens having a saw-toothed groove close to an ideal shape can be obtained.