| 摘要 |
PURPOSE:To prevent the occurrence of slackening of support of a length-measuring mirror and the strain thereof and thereby to enable the realization of measurement of high accuracy by a method wherein the mirror is fixed at the center to a moving bed by a clamp member and further it is supported at pots being apart by prescribed distances from the center through the intermediary of a vibration damping material. CONSTITUTION:A length-measuring mirror 2 is fixed at the center to a moving bed 1 by a clamp member 3, and it is supported at positions being apart by prescribed distances from said fixed position by vibration damping units 5. Each of the vibration damping units 5 is constructed of a horizontal plate member 5b having a presser pawl 5a and of a vertical vibration damping plate member 5c, and the mirror 2 is fixed to the horizontal plate member 5b by the presser pawl 5a and a fixing screw 5e, while the vertical vibration damping plate member 5c is inserted into a concavity wherein a vibration damping material 6 is impounded. Therefore, the mirror 2 does not slacken even when the moving bed 1 moves at high speed, and no strain occurs since a difference in expansion due to a change in temperature between the moving bed 1 and the mirror 2 is absorbed by the vibration damping material 6. Thus, measurement of high accuracy can be realized.
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