Video surveillance camera refocus
View Patent ↗A method of refocusing a video surveillance camera includes performing a first focusing operation of a camera at a first time, sensing a first temperature of the camera at the first time, sensing a second temperature of the camera at a second time, determining if a change in temperature between the first temperature and the second temperature is greater than a predetermined temperature change, sensing a level of light in a field of view of the camera at the second time, determining if the level of light sensed in the field of view of the camera at the second time is within a predetermined light level range, determining if a period of time between the first time and second time is greater than a predetermined period of time, and performing a focus operation if the change in temperature between the first temperature and the second temperature is greater than the predetermined temperature change, the level of light sensed in the field of view of the camera at the second time is within the predetermined light level range, and the period of time between the first and second time is greater than a predetermined period of time.
1. A method of refocusing a video surveillance camera comprising:
performing a first auto-focus operation of a camera at a first time; sensing a first temperature of the camera at the first time; sensing a second temperature of the camera at a second time; determining if a change in temperature between the first temperature and the second temperature is greater than a predetermined temperature change; sensing a level of light in a field of view of the camera at the second time; determining if the level of light sensed in the field of view of the camera at the second time is within a predetermined light level range; determining if a period of time between the first time and second time is greater than a predetermined period of time; and determining if the camera has changed from either a day mode of operation to a night mode of operation or a night mode of operation to a day mode of operation;
performing an auto-focus operation if the change in temperature between the first temperature and the second temperature is greater than the predetermined temperature change the level of light sensed in the field of view of the camera at the second time is within the predetermined light level range, and the period of time between the first and second time is greater than a predetermined period of time; and
performing an auto-focus operation if the camera has changed from either a day mode of operation to a night mode of operation or a night mode of operation to a day mode of operation.
2. A method as recited in claim 1 wherein sensing the level of light in the field of view of the camera at the second time comprises sensing a gain signal from an automatic gain control device.
3. A video surveillance camera comprising:
a lens; a device for performing an auto-focus operation on the camera; a temperature sensor for sensing the temperature of the camera; a device for sensing a level of light in the field of view of the lens; a mode changing device for changing an operation of the camera from a day mode of operation to a night mode of operation and for changing the operation from a night mode of operation to a day mode of operation and a mode change sensor for determining if the mode changing device has changed from either a day mode of operation to a night mode of operation or a night mode of operation to a day mode of operation; and a processor connected to the device for performing an auto-focus operation, the temperature sensor, the device for sensing a level of light in the field of view of the lens, and the mode change sensor, the processor configured to:
receive a first temperature from the temperature sensor at a first time when the device for performing an auto-focus operation performs a first auto-focus operation, to receive a second temperature at a second time from the temperature sensor, to determine if the temperature difference between the first temperature and the second temperature is greater than a predetermined temperature change, to receive a level of light sensed by the device for sensing a level of light in the field of view of the lens at the second time, to determine if the level of light sensed in the field of view of the camera at the second time is within a predetermined light level range, adapted to determine if a period of time between the first time and second time is greater than a predetermined period of time, to cause the device for performing an auto-focusing operation to perform an auto focus operation if the change in temperature between the first temperature and the second temperature is greater than the predetermined temperature change, the level of light sensed in the field of view of the lens at the second time is within the predetermined light level range, and the period of time between the first and second time is greater than a predetermined period of time; and to cause the device for performing an auto-focus operation to perform an auto-focus operation if the mode change sensor senses that the mode changing device has changed from either a day mode of operation to a night mode of operation or a night mode of operation to a day mode of operation.
4. A video surveillance camera as recited in claim 3 wherein the device for sensing a level of light in a field of view of the lens comprises an automatic gain control providing a gain signal.