Abstract: Disclosed is a video surveillance technique for performing automated surveillance through intelligent video recognition. A distance between two persons is measured from an image captured by a camera. When the measured distance is less than or equal to a reference value, a proximity event occurs. In an embodiment, feet of two persons are detected from an image captured by a camera and a distance between the two persons is calculated using a distance between positions on the ground at which the feet are placed by using camera parameters. In another embodiment, heads of two persons are detected from an image captured by a camera and a distance between the two persons is calculated using a distance between positions of the heads on a plane corresponding to an average height.

Abstract: A technique for counting the number of occupants is provided. An occupancy control apparatus may be part of an access control apparatus or a security system for identifying visitors. The number of occupants is calculated from the difference between a count of people entering a space and a count of people exiting the space, and entering the space is restricted when the difference is greater than a reference value. A current counter value may be corrected in real time by counting a fractional error rate per count of each counter. An entrance may be blocked when the number of occupants is greater than the reference value, and the blocking of the entrance may be released when the number of occupants is restored to another reference value or less. An error rate per count of each counter may be calculated in units of devices or time slots.

Abstract: Provided is a current sensor having variable tuning precision capability depending on an amount of a current to be measured, a system state and the like. In the present disclosure, the current measurement apparatus having variable tuning precision capability does not separately require a current sensor measuring a small current with high precision and a current sensor stably measuring a large current without saturation. In the present disclosure, a single current measurement apparatus may vary current measurement precision depending on a current magnitude and the like, and may thus measure the small current with the high precision and stably measure the large current without saturation.