| 摘要 |
<p>A security device comprises a guide (21) provided with two polarizing screens (22) between which are placed a plurality of movable elements (11). The movable elements (11) are divided into a plurality of zones and in one arrangement the screens extend across a plurality of zones. Each zone rotates the plane of polarization of light passing through it by a given amount. The security device is set by moving the elements relative to each other and the screens to a selected relative position and a light is shone through the screens and the elements. The rotation of the planes of polarization of the light passing between the screens will cause different colours to be viewed at the different zones covered by the screens. This combination of colours can be used as an output indicator, for example to control access to apparatus. In another aspect, the invention provides a method of controlling access to apparatus by generating a random number and feeding input data into a security device, such as the one already described, in response to the random number, feeding output data from said security device (the colours as described above when the security device is as described above) to a control device, and generating reference information in response to the random number generated. Access to the apparatus is allowed when the output data corresponds to the reference data.</p> |
