| 摘要 |
A portable, battery powered, self levelling alignment tool (18) for simultaneously indicating level, plumb and square. A projection unit including a laser diode (56), a collimator (58), and an optical system is located in a projection unit which is pendu- lously suspended inside a housing. The optical system divides a collimated beam from the laser diode and the collimator into out- put beams having a generally perpendicular relationship with each other. The projection unit may be balanced such that at least one of the output beams is substantially level and other beams thus indicate plumb or square.
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