| 主权项 |
1. A hand held instrument comprising:
a handpiece having a working element to be placed by an operator into contact with a workpiece; a power source for actuating the working element between a rest condition and a fully-operating condition; a laser proximity sensor arrangement carried by the handpiece, the laser proximity sensor arrangement being adapted to sense proximity of the working element to the workpiece; a controller for activating the power source to actuate the working element, the controller being responsive to the laser proximity sensor arrangement for activating the power source to actuate the working element in response to the working element reaching a predetermined proximity to the workpiece, as the working element is moved by the operator toward placement into contact with the workpiece, the predetermined proximity being such that the working element will reach the fully-operating condition prior to contact with the workpiece, whereby the working element will be at the fully-operating condition upon contact with the workpiece; and the laser proximity sensor arrangement comprises at least two laser proximity sensors providing at least two corresponding laser beams converging at a point spaced from the working element, the point being located at a distance corresponding to the predetermined proximity of the working element to the workpiece. |
