摘要:
A rotating body has paired anchoring projections and small projections projectingly disposed on one side thereof. On a shutter plate are formed guide holes in which the paired anchoring projections and small projections inserted in the shutter plate are slidable within a predetermined allowance angle range. When rotation input to a handle is broken during rotation input, the shutter plate is rotated respective to the rotating body in a direction opposite to the rotation direction of the rotating body within the allowance angle range, and the light transmission paths are closed by the shutter plate.