| 摘要 |
A temporary line projection system designed to be grasped by hand and moved, by a single human operator, into a desired location as, for example, along the sidelines of a football field adjacent to where a first down line is to be projected. The system comprises a movable structure that is dimensioned and arranged to be supported by and project upwardly from an athletic field surface. A laser source is supported by the movable structure and is maintained by the movable structure at an elevated location relative to the athletic field surface. This allows the laser source to direct optical energy downward upon the field while the movable structure is maintained substantially in a first orientation relative to the athletic field surface. A sensing arrangement is operative to determine when the movable structure is no longer maintained substantially in the first orientation and a switch is operative to disable the laser source when the movable structure is no longer maintained substantially in the first orientation. |
