| 摘要 |
PCT No. PCT/GB85/00542 Sec. 371 Date Sep. 23, 1986 Sec. 102(e) Date Sep. 23, 1986 PCT Filed Nov. 26, 1985 PCT Pub. No. WO86/03247 PCT Pub. Date Jun. 5, 1986.A security device comprises a guide (21) provided with two polarizing screens (22) between which are placed a plurality of stacked, movable elements. Each element contains means for causing the plane of polarization of incident light passing therethrough to be rotated, the amount of rotation depending on the position of the means for rotating relative to the other elements. Setting the stacked elements to various positions results in a particular pattern of colors when light is shown through the device. This pattern can be used as an output indicator to control access to an apparatus.
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