| 摘要 |
PURPOSE:To correctly install a cross section measuring instrument from a reference laser beam, and also, to simply detect its position by reflecting the reference laser beam at a right angle against its optical axis, and determining the installed position of the cross section measuring instrument so that a prescribed part of the cross section measuring instrument is irradiated by its reflected light. CONSTITUTION:A reflecting device 10 which is provided with a mirror and reflects a reference laser beam l so that an angle of reflection goes to a right angle against its optical axis, and a cross section measuring instrument 1 provided with a measuring instrument body 2 which is installed in a prescribed position in a tunnel and executes a measurement and a measuring head 3 are used. The reflecting device 10 is provided so that its movement can be adjusted in the vertical direction and the horizontal direction by a supporting leg 12, and also, it can turn centering around the vertical axis and the horizontal axis, respectively. The measuring head 3 is rotatable against the measuring instrument body 2, the reference laser beam whose optical axis is reflected at a right angle by the reflecting device 10 is adjusted by using collimating plates 7, 8, and the installed position of the cross section measuring instrument 1 is determined. In such a way, a rotation axis of the measuring head 3 and the reference beam l, namely, a tunnel axis become parallel to each other. |
