| 摘要 |
An electro-optical device for switching between transparent and opaque states, comprises a polarizer (5) and an analyzer (6) and, between them, an active slab of strips (10) of an electrically biasable birefringent material, each strip (10) being situated between a pair of electrodes (13), the device being transparent to light in register with said strips (10) while the material of the strips (10) is electrically biased, the device further comprising at least one tab (4) of a photoconductive material placed on at least a portion of the periphery of the active slab, the material of each tab (4), when struck by a sufficient quantity of light, generating sufficient electrons to increase its conductivity and, very quickly, induce a drop of the electric field across the material of the strips (10), thereby inducing a change to its birefringence, with the device then becoming opaque to light. The device can be used in eye protection against lasers.
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