| 摘要 |
The procedure for detecting includes a camera (3) mounted above the monitored position. The camera is used to take a point-by-point image of the monitored area which is then stored as a reference image. A further image is taken in real time, and working in parallel the intensities of points within the image are subtracted from those in the reference image and the absolute value of the sum of the differences is determined. The presence or absence a person or object within the field of view is determined by comparing the sum of the differences determined above with a threshold value.
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