| 摘要 |
PURPOSE:To eliminate faults of machining technology by providing a 1st metallic disk made of metal with high reflecting ability by a photoelectroforming method, etc., and a 2nd metallic disk which has plural thin beltlike hollows. CONSTITUTION:The 1st metallic disk 2 is formed by the photoelectroforming method, etc. A center hole 4 is formed in this disk, a fitting hole 6 for a rotary shaft 6 is formed in the center of the metallic disk 2 by the photoelectroforming method, and the 2nd metallic disk 10 which has plural thin beltlike hollows radially around the hole 6 along the outer circumference is formed. A rotary disk R having reflection parts 16 consisting of the thin beltlike hollows rotates in a specific direction together with the rotary shaft 20 inserted fixedly into the fitting hole 6. Extremely high performance is obtained as compared with a conventional rotary disk which uses a glass plate as its substrate without causing faults of the machining technology nor problems such as moment of inertia and a breakage.
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