| 摘要 |
An optical cell having an optically active material, for example a liquid crystal is disclosed, the transparency of which is a function of the electrical voltage applied together with a control circuit, wherein said optically active material presents an electrical impedance variable with the frequency of the signal applied and said control circuit has a voltage source and means for controlling the frequency of the signal delivered by said voltage source. The cell has applications in attenuating light, notably in a sun screen or automobile rear-view mirror.
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