摘要 |
A CPU first detects a position of a stationary laser beam using a beam position detection sensor, and then determines a target position of a movable laser beam relative to the stationary laser beam. The CPU effects a control to approach the movable laser beam to the target position in predetermined steps. When the CPU moves the movable laser beam, it checks whether the movable laser beam has moved to the target position. If the movable laser beam has not moved to the target position, the CPU performs a control once again to perform the first detection of the position of the stationary laser beam.
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