| 摘要 |
A mirror (10) comprising a base (11) part, a reflective surface, a member having an external optically active surface, means to mount said optically active surface on said base part (11) for movement relative to the base part (11) and drive means (34) to cause said movement whereby material deposited on said optically active surface is subjected to a force to displace the particles to a peripheral edge of the surface whereat they are discharged from the surface. |
