Method and photo sensor assembly for sensing rotational positions of a camera module, and surveillance camera having the assembly

A surveillance camera comprising:

• a motor configured to generate a driving power;
• a transmission device configured to transfer the driving power generated by the motor;
• a rotator configured to rotate together with a camera module according to the transferred driving power;
• a plurality of first photo interrupter bars disposed at a same interval along a first circumference on the rotator;
• a second photo interrupter bar disposed at a second circumference on the rotator, the second circumference being coaxially arranged with the first circumference;
• a first photo sensor disposed closer to the first circumference than to the first circumference, and configured to detect a first light-blocking pattern generated from the plurality of first photo interrupter bars;
• a second photo sensor disposed closer to the second circumference than to the first circumference, and configured to detect a second light-blocking pattern generated from the second photo interrupter bar;
• and
• a processor configured to estimate an initial position of the rotator based on the second light-blocking pattern, and estimate a rotational angle from the initial position of rotator based on the first light-blocking pattern,
• wherein a position of the second photo interrupter bar does not overlap a position of any of the plurality of first photo interrupter bars in a circumferential direction of the rotator, and the second light-blocking pattern is obtained at an idle interval between a plurality of pulses that form the first light-blocking pattern.

A method for estimating angular positions of a camera module by a photo sensor assembly, the method comprising:

• rotating a rotator on which the camera module is mounted, the rotator comprising a plurality of first photo interrupter bars disposed at a same interval along a first circumference on the rotator, and a second photo interrupter bar disposed at a second circumference on the rotator, the second circumference being coaxially arranged with the first circumference;
• detecting by a first photo sensor, a first light-blocking pattern generated from the plurality of first photo interrupter bars;
• detecting by a second photo sensor, a second light-blocking pattern generated from the second photo interrupter bar;
• estimating an initial position of the rotator based on the second light-blocking pattern;
• and
• estimating a rotational angle from the initial position of the rotator based on the first light-blocking pattern,
• wherein a position of the second photo interrupter bar does not overlap a position of any of the plurality of first photo interrupter bars in a circumferential direction of the rotator, and the second light-blocking pattern is obtained at an idle interval between a plurality of pulses that form the first light-blocking pattern.