Variable transmittance optical filter and uses thereof

1. A control circuit, comprising:

a variable transmittance optical filter comprising a first and a second electrode and a switching material in contact with the first and second electrodes, wherein the switching material is capable of transitioning from a light state to a dark state on exposure to ultraviolet radiation and from the dark state to the light state with application of an electric voltage across the first and second electrodes;

power control electronics comprising a switch for electrically coupling to a power source, the power control electronics electrically coupled to the first and second electrodes and operable to:

dissipate any charge on the optical filter by shorting the first and second electrodes together, thereby facilitating transition of the switching material from the light state to the dark state upon exposure of the switching material to ultraviolet radiation; and

transition the optical filter from the dark state to the light state by applying a voltage from the power source across the first and second electrodes; and

a DC-DC regulator or a DC-DC converter electrically coupled in series with the power control electronics, wherein the power control electronics receives a DC voltage from the DC-DC regulator or DC-DC converter when the power source is electrically coupled to the power control electronics and the DC-DC regulator or the DC-DC converter matches the DC voltage to a voltage required by the optical filter in order to trigger lightening.

2. The control circuit of claim 1 , further comprising an AC adapter, wherein the DC-DC regulator or the DC-DC converter is electrically coupled in series between the AC adapter and the power control electronics when the power source is electrically coupled to the power control electronics.

3. The control circuit of claim 1 , wherein the power control electronics further comprise a timing circuit and a first user-controlled sensor, and wherein the power control electronics use the timing circuit to apply the voltage across the first and second electrodes for a fixed period of time in response to receiving a signal from the first user-controlled sensor, the fixed period of time preset to be the amount of time required for the optical filter to transition from the dark state to the light state.

4. The control circuit of claim 1 , wherein the switching material comprises part of a window of a building or vehicle or part of a lens.

5. The control circuit of claim 3 , wherein the power control electronics further comprise a second user-controlled sensor and wherein the power control electronics use the timing circuit to apply, in response to receiving a signal from the second user-controlled sensor, the voltage across the first and second electrodes for a period of time longer than the fixed period of time.

6. The control circuit of claim 3 , wherein the power control electronics further comprise a second user-controlled sensor and the power control electronics cease applying the voltage to the switching material in response to receiving a signal from the second user-controlled sensor while the power control electronics are applying the voltage to the first and second electrodes.

7. The control circuit of claim 6 , wherein the power control electronics short the first and second electrodes together in response to receiving the signal from the second user-controlled sensor.

8. The control circuit of claim 1 , wherein the power control electronics further comprise a user-controlled sensor and the power control electronics short the first and second electrodes together in response to receiving a signal from the user-controlled sensor.

9. The control circuit of claim 1 , wherein the power control electronics further comprise a light sensor and the power control electronics short the first and second electrodes together upon receiving a signal from the light sensor indicating a certain level of ambient brightness around the optical filter.

10. The control circuit of claim 1 , wherein the power control electronics further comprise a user-controlled sensor and a light sensor, and wherein the power control electronics maintain the voltage across the first and second electrodes in response to a first signal from the user-controlled sensor in order to maintain the optical filter in the light state when the light sensor indicates a certain level of ambient brightness around the optical filter.

11. The control circuit of claim 10 , wherein the power control electronics shorts the first and the second electrodes together in response to a second signal from the user-controlled sensor that is received after the first signal.

12. The control circuit of claim 1 , wherein the switch comprises a multi-state control device operable to permit a user to select an intermediate transmittance for the optical filter, wherein the power control electronics applies the voltage across the first and second electrodes for a duration sufficient to achieve the intermediate state.

13. The control circuit of claim 1 , wherein the switch comprises a multi-state control device operable to permit a user to select an intermediate transmittance for the optical filter, wherein the power control electronics applies the voltage across the first and second electrodes to achieve the intermediate state based on feedback from one or more light sensors.

14. The control circuit of claim 1 , wherein the power control electronics further comprise a voltage or a current sensor that senses when the switching material has transitioned to the light state, and wherein the power control electronics cease to apply the voltage across the first and second electrodes when the switching material has transitioned to the light state.