Lens cleaning method for a surveillance camera
A cleaning method for a surveillance camera uses a capacitive sensor to determine whether rain, ice, dirt, debris or other foreign objects are present on the camera lens substrate. A determination is made whether the sensed capacitance is greater than a first threshold indicative of the presence of a foreign object on the lens. If a foreign object is indicated, the lens is sprayed with a sprayer and then a wiper is activated. If a foreign object is not indicated, a determination is made whether ice is present by comparing the sensed capacitance to a second threshold that is less than the first threshold. If ice is present, wiper and lens defrosters are activated, and a wiper is then turned on. The cleaning method may include a temperature sensor and power management for the defrosters.
1. A method for cleaning a lens of a surveillance camera, comprising:
sensing, with a capacitance sensor, a sensed capacitance of the lens of the surveillance camera, the sensed capacitance indicating the type of foreign object detected on the lens;
converting, with a capacitive to digital converter, the sensed capacitance to a digital capacitance value;
activating, with a controller, a first device when the digital capacitance value exceeds a first threshold value that is greater than a second threshold value, wherein the first device is at least one of a lens wiper, a lens defroster and a lens sprayer;
cleaning the lens with the first device;
activating, with the controller, a second device when the digital capacitance value is less than the first threshold value and greater than the second threshold value, wherein the second device is at least one of the lens wiper, the lens defroster and the lens sprayer; and
cleaning the lens with the second device, wherein the second device is not the same as the first device.
2. The method of claim 1 , further comprising:
activating, with the controller, a third device when the digital capacitance value is less than the second threshold value and exceeds a third threshold value that is less than the second threshold value, wherein the third device is at least one of the lens wiper, the lens defroster and the lens sprayer; and
cleaning the lens with the third device.
3. The method of claim 1 , wherein activating the first device includes activating the lens defroster, and wherein activating the second device includes activating the lens wiper, the method further comprising:
defrosting the lens with the lens defroster after the lens defroster is activated; and
wiping the lens with the lens wiper after the lens wiper is activated.
4. The method of claim 1 , further comprising:
sensing, with a temperature sensor, a temperature of the lens,
wherein activating the first device includes activating the first device when the sensed temperature exceeds a temperature threshold; and
cleaning the lens with the first device.
5. The method of claim 2 , wherein activating the first device includes activating the lens defroster, wherein activating the second device includes activating the lens sprayer, and wherein activating the third device includes activating the lens wiper, and wherein the method further comprises:
defrosting the lens with the lens defroster after the lens defroster is activated;
spraying the lens with the lens sprayer after the lens sprayer is activated; and
wiping the lens with the lens wiper after the lens wiper is activated.
6. The method of claim 4 , further comprising:
controlling power to the lens defroster to maintain the power of the lens defroster below a power threshold, including turning on the power to the lens defroster for a first time period and then turning off the power to the lens defroster for a second time period.
7. The method of claim 5 , further comprising:
sensing, with a temperature sensor, a temperature of the lens,
wherein activating the first device includes activating the lens defroster when the sensed temperature exceeds a temperature threshold; and
defrosting the lens with the lens defroster.
8. The method of claim 7 , further comprising:
controlling power to the lens defroster to maintain the power of the lens defroster below a power threshold, including turning on the power to the lens defroster for a first time period and then turning off the power to the lens defroster for a second time period.
9. A method for cleaning a lens of a surveillance camera, comprising:
sensing, with a capacitance sensor, a sensed capacitance of the lens of a surveillance camera, the sensed capacitance indicating the type of foreign object detected on the lens;
converting, with a capacitive to digital converter, the sensed capacitance to a first digital capacitance value;
activating, with a controller, a first device when the first digital capacitance value exceeds a first threshold value that is greater than a second threshold value, wherein the first device is at least one of a lens wiper, a lens defroster and a lens sprayer;
cleaning the lens with the first device;
activating, with the controller, a second device when the first digital capacitance value is less than the first threshold value and greater than the second threshold value, wherein the second device is at least one of the lens wiper, the lens defroster and the lens sprayer;
cleaning the lens with the second device, wherein the second device is not the same as the first device;
sensing, with the capacitance sensor, a second sensed capacitance of the lens;
converting, with the capacitive to digital converter, the second sensed capacitance to a second digital capacitance value;
activating, with the controller, the first device when the second digital capacitance value exceeds the first threshold value;
cleaning the lens with the first device;
activating, with the controller, the second device when the second digital capacitance value is less than the first threshold value and greater than the second threshold value; and
cleaning the lens with the second device.
10. The method of claim 9 , further comprising:
sensing, with a temperature sensor, a temperature of the lens; and
controlling power to at least one of the first device and the second device when the sensed temperature exceeds a temperature threshold, including turning on the power to the at least one of the first device and the second device for a first time period and then turning off the power to the at least one of the first device and the second device for a second time period.
11. The method of claim 9 , further comprising:
controlling power to at least one of the first device and the second device to maintain power to the at least one of the first device and the second device below a power threshold, including turning on the power to the at least of the first device and the second device for a first time period and then turning off the power to the at least one of the first device and the second device for a second time period.