| 摘要 |
A communications device such as a personal identity card is in the form of a badge or label worn on the outside of the wearer's clothing. The badge includes a first layer of a transparent material having an inner surface that is contoured with a retroreflecting repeating pattern. A second layer also of a transparent material has an inner surface with a reciprocating retroreflecting pattern. Sandwiched between the two layers is a layer of liquid crystal material the refractive index of which can be varied through the application of an electric field. When the refractive index of the layer is close to that of the first and second layers, incident radiation passes through the device with little scattering. However, as the refractive index of the layer is varied by application of an electric field, incident radiation is retroreflected from the contoured interface of the first layer with the layer. The communications device is capable of retroreflecting incident radiation and modulating the radiation, by altering the refractive index of the layer, so that the reflected beam is capable of delivering information to a receiver. In this way information can be delivered in a non-contact environment using a device that requires very little power to operate.
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