Lighting device with ambient light sensor

1. A lighting device comprising:

a light source adapted to project light;

a sensor adapted to provide illumination measurements based on ambient light detected by the sensor including at least a reflected portion of the projected light;

a memory adapted to store the illumination measurements as hysteresis data; and

a controller adapted to:

select a range of illumination levels,

process the hysteresis data to provide processed illumination measurements,

adjust the projected light based on the processed illumination measurements to transition the projected light through a plurality of projected light levels until at least a first one of the processed illumination measurements is within the range of illumination levels while the projected light exhibits a current projected light level, and

maintain the projected light at the current projected light level until at least a second one of the processed illumination measurements is outside the range of illumination levels.

2. The lighting device of claim 1 , wherein:

the sensor is adapted to provide an initial illumination measurement based on initial ambient light detected by the sensor while the light source is not projecting light; and

the controller is adapted to select the range of illumination levels from a plurality of ranges based on the initial illumination measurement.

3. The lighting device of claim 2 , wherein the controller is adapted to determine, prior to the light being projected by the light source, an initial projected light level for the light source, wherein a combined level of the initial ambient light and the initial projected light level is within the selected range of illumination levels.

4. The lighting device of claim 1 ,

wherein the processed illumination measurements comprise averaged hysteresis data.

5. The lighting device of claim 1 , wherein the controller is adapted to interrupt adjustment of the projected light in response to an override condition.

6. The lighting device of claim 1 , wherein the controller is adapted to:

transition the projected light through decreasing projected light levels at a first rate;

transition the projected light through increasing projected light levels at a second rate; and

wherein the first rate is greater than the second rate to reduce glare perceived by a user of the lighting device.

7. The lighting device of claim 1 , wherein the controller is adapted to:

determine a difference between at least one of the processed illumination measurements and at least one of the illumination levels within the range;

transition the projected light through the projected light levels at a rate based on the determined difference; and

wherein the rate is greater for greater determined differences.

8. The lighting device of claim 1 , wherein the range of illumination levels corresponds to a single illumination level.

9. The lighting device of claim 1 , wherein the controller is adapted to adjust the projected light in accordance with a proportional-integral-derivative (PID) controller process.

10. The lighting device of claim 1 , further comprising:

a filter adapted to limit the ambient light and the reflected portion of the projected light detected by the sensor to substantially only visible light; and

wherein the lighting device is a flashlight.

11. A method of operating a lighting device, the method comprising:

selecting a range of illumination levels;

projecting light from a light source of the lighting device;

providing, by a sensor of the lighting device, illumination measurements based on ambient light detected by the sensor including at least a reflected portion of the projected light;

storing the illumination measurements as hysteresis data;

processing the hysteresis data to provide processed illumination measurements;

adjusting the projected light based on the processed illumination measurements to transition the projected light through a plurality of projected light levels until at least a first one of the processed illumination measurements is within the range of illumination levels while the projected light exhibits a current projected light level; and

maintaining the projected light at the current projected light level until at least a second one of the processed illumination measurements is outside the range of illumination levels.

12. The method of claim 11 , wherein the selecting comprises:

providing, by the sensor, an initial illumination measurement based on initial ambient light detected by the sensor while the light source is not projecting light; and

selecting the range of illumination levels from a plurality of ranges based on the initial illumination measurement.

13. The method of claim 12 , wherein the method further comprises:

determining, prior to the projecting, an initial projected light level for the light source; and

wherein a combined level of the initial ambient light and the initial projected light level is within the selected range of illumination levels.

14. The method of claim 11 ,

wherein the processed illumination measurements comprise averaged hysteresis data.

15. The method of claim 11 , further comprising interrupting the adjusting in response to an override condition.

16. The method of claim 11 , wherein:

the projected light transitions through decreasing projected light levels at a first rate;

the projected light transitions through increasing projected light levels at a second rate;

wherein the first rate is greater than the second rate to reduce glare perceived by a user of the lighting device.

17. The method of claim 11 , further comprising:

determining a difference between at least one of the processed illumination measurements and at least one of the illumination levels within the range;

wherein the adjusting comprises transitioning the projected light through the projected light levels at a rate based on the determined difference; and

wherein the rate is greater for greater determined differences.

18. The method of claim 11 , wherein the range of illumination levels corresponds to a single illumination level.

19. The method of claim 11 , wherein the adjusting comprises performing a proportional-integral-derivative (PID) controller process.

20. The method of claim 11 , further comprising:

filtering the sensor to detect substantially only visible light; and

wherein the lighting device is a flashlight.