| 摘要 |
PROBLEM TO BE SOLVED: To automatically return to a trackable state capable of tracking a retro reflector in short time and with high accuracy when the tracking is disabled because laser light is blocked and the like.SOLUTION: A tracking control part 621 performs a tracking control of a retro reflector 3, using a light reception signal outputted from a laser interferometer 5. An emission direction control part 624 controls a direction of measurement light so that the measurement light is emitted in a direction where the retro reflector 3 exists with reference to a reference of the laser interferometer 5, using a position of the laser interferometer 5, and a position of the retro reflector 3 detected by retro reflector position detection means 7. A control switch part 625 determines whether or not a tracking state is in a trackable state of the retro reflector 3 on the basis of the light reception signal of the laser interferometer 5, and when the state is put into an untrackable state, a control by the tracking control part 621 is switched to a control by the emission direction control part 624, and when the state is put into the trackable state, the control by the emission direction control part 624 is switched to the control by the tracking control part 621. |
