| 摘要 |
PURPOSE:To make it possible to arrange an apparatus that is large enough to interfere with the axis of an excavator to a space between optical path changing devices by a method wherein a target is arranged in a first shield main body and a pair of the optical path-changing devices are provided in a second shield main body. CONSTITUTION:A tunnel excavator 10 is constructed of a barrel like first shield main body 12 and a second shield main body 14 that is connected to the rear part of the main body 12. A TV camera 44 and a target 42 that receives ray 40 from a light source 38 provided in a starting shaft are provided in a barrel- like section of the first shield main body 12. A pair of optical path-changing devices 54, 56 that changes the optical path of the ray 40 are arranged in the second shield main body 14, and a pair of reflecting mirrors 58 are provided to each of the optical path-changing devices. When the axis of the excavator 10 is aligned with the projected reference line, the ray 40 is irradiated on the center of the target through the first and second optical path-changing devices 54, 56, and when the axis is misaligned, the ray is irradiated being off the center of the target.
|
