| 摘要 |
The device comprises a housing having a chamber with a viewing face and a lamina member mounted within the chamber and movable between two positions. In the first position one face of the member is in face-to-face contact with the viewing face and in the second position the face of the member is out of contact with the viewing face and the other face is face-to-face with a rear face of the chamber rearwardly from the viewing face. A drive device produces an attracting or repulsing force between the housing and the member to move the lamina from one position to the other. Pref. the drive device comprises an electromagnetic coil on the housing and a permanent on the lamina member. The chamber is filled with an opaque fluid, the lamina member having zero buoyancy in the fluid. |
