Optical device with dielectric heating

Claim 1

In an optical device containing dielectric material in which the device is switchable between an inactive relatively opaque state and an activated relatively transparent state in response to the application of a driving electric field of sufficiently low frequency wherein the switching time between the inactive-opaque state and the activated-transparent state is increased and/or the light transmissivity in the activated-transparent state is decreased when the device is at a relatively low temperature, and in which a heating electric field is applied to the device sufficiently high frequency as to heat the dielectric material while not switching the device to the activated-transparent state thereby raising the temperature of the device to decrease the switching time between the inactive-opaque state and the activated-transparent state and/or to increase the light transmissivity in the activated-transparent state, the improvement comprising: a first electrode located on one side of the device, second and third interdigitated electrodes located on an opposite side of the device, means for applying the driving electric field between the first electrode and one of the second and third electrodes, means for applying the heating electric field between the second and third electrodes, and low pass filter means connected between the second and third electrodes for effectively connecting the electrodes together at the low frequency of the driving electric field and for effectively disconnecting the electrodes one from the other at the high frequency of the heating electric field.