| 摘要 |
PURPOSE:To set accurate dimensional accuracy so as to allow the center of a metal disc to coincide and to enhance the capacity of a rotary disc, by applying processing to the metal disc formed using photoelectroforming. CONSTITUTION:A rotary shaft mount hole 4 is provided to the center of a metal disc 2 formed by a photoelectroforming technique. Reflecting parts 6 each composed of a fine strip like body group are radially formed on the metal disc 2 around the center of said hole 4 along the outer peripheral inner surface of said disc 2 and the upper surface of the metal disc 2 having no reflecting parts 6 formed thereto is set to a non-reflecting part 8 to form a rotary plate R. A reinforcing support plate 10 is mounted on one side surface or both side surfaces of the rotary plate R while the rotary plate R is fixed to a rotary shaft 14 through the support plate 10. A fixed slitted plate 28 is interposed between a light emitting element 22 and a light receiving element 32 along with the rotary plate R and, when the slit 26 of the fixed slitted plate 28 is synchronized to the reflecting parts 6 of the rotary plate R, the light from the light emitting element 22 transmits through the slit 26 and reflected by the reflecting parts 6 of the rotary plate R rotating along with the rotary shaft 14 to be guided to the light receiving element 32 to be subjected to photoelectric conversion.
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