| 摘要 |
PROBLEM TO BE SOLVED: To correctly form a bit pattern to be marked and facilitate changing of the bit pattern by forming a reflecting member beforehand to an entire circumference of a code ring, irradiating laser beams to the reflecting member and forming a non-reflection code, thereby obtaining the bit pattern. SOLUTION: A code ring 10 is subjected to aluminum hot stamping while being butted with a code ring foil over an entire circumference in a rotational direction, whereby an aluminum 24 is attached. A laser beam 25 is irradiated to the attached aluminum 24 to cut the aluminum. As a result, a bit pattern of a reflecting face and a non-reflecting face is formed. When an irradiation output of the laser beam 25 has a duty ratio of 20-30%, the formed bit pattern appears good and a part of the aluminum 24 can be cut beautifully. A size accuracy of each bit can be maintained in a level of not higher than±0.2 mm and the bit pattern can be formed more elaborately than in case of a conventional code ring plate.
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