| 摘要 |
PURPOSE:To easily and correctly perform centering work when an internal peripheral edge is prepared by the method of photoetching, by providing observational aligning marks concentrically with an internal circle in the vicinity of said circle. CONSTITUTION:There are respectively provided concentrical aligning marks 4 in the vicinity of an internal circle 2 and small circles 5, used as the hole of a bolt fixed to a spread frame, in the peripheral edge of an external circle 3. These aligning marks 4 are observed by a microscope, then the correct work of centering can be performed. |
