Method of maintaining tilt angle, method of controlling tilting, and surveillance camera

A method of controlling tilting of a surveillance camera having an acceleration sensor and being controllable by a processor to tilt the camera to a command tilt-angle and to control an actual tilt-angle to conform to the command tilt-angle, the method comprising the steps of:

• (a) tilting the camera to the command tilt-angle while monitoring whether the operation of tilting to the command tilt-angle is performed by using a photo-interrupt sensor;
• (b) after moving the surveillance camera to the predetermined command tilt-angle in response to a signal from the processor, periodically calculating in the processor estimated tilt-angles by using acceleration values in at least one axis of the acceleration sensor;
• (c) calculating a difference between an estimated tilt-angle of a current period and an estimated tilt-angle of a previous period;
• and
• (d) when the difference between the estimated tilt-angles exceeds a set limit value, moving the camera to another position for correcting the tilt-angle according to the difference calculated in step (c).

A surveillance camera system comprising:

• a surveillance camera having an acceleration sensor;
• a processor to generate signals to rotate the camera to a predetermined tilt angle, wherein the processor is configured to:
• (a) after the surveillance camera is moved, tilt to a predetermined command tilt-angle in response to a signal from the processor, periodically calculate in the processor estimated tilt-angles by using acceleration values in at least one axis of the acceleration sensor;
• (b) calculate a difference between an estimated tilt-angle of a current period and an estimated tilt-angle of a previous period;
• and
• (c) when the difference between the estimated tilt-angles exceeds a set limit value, generate a signal to move the camera to another position for correcting the tilt angle according to the difference calculated in step (b).