Interactive security alert system

A security alert system adapted to be installed in an exhibition hall to exhibit a display content, comprising:

• a light emitting unit adapted to install in the exhibition hall for emitting a light beam consisting of an optical pattern onto a viewer, wherein said optical pattern varies depending on a distance between the viewer and the exhibition/performance activity;
• an image capturing unit adapted to install in the exhibition hall corresponding to said light emitting unit, including an optical lens for capturing images of said optical pattern and the viewer and a photosensitive element coupled with said optical lens for sensing said images;
• a distance arithmetic unit adapted to install in the exhibition hall and coupled electrically with said image capturing unit for receiving said images from said image capturing unit and calculating a distance between the viewer and the exhibition/performance activity based on variation of said images;
• a multimedia player unit adapted to install in the exhibition hall and coupled electrically with said distance arithmetic unit such that when said distance between the viewer and the exhibition/performance activity is smaller than a first threshold, said multimedia player unit displays multimedia information corresponding to said exhibition/performance activity to be seen or heard by said viewer;
• and
• an alarm generating unit adapted to install in the exhibition hall and coupled electrically with said multimedia player unit such that when said distance between the viewer and the exhibition/performance activity is smaller than a second threshold, said alarm generating unit generates an alarm signal to be seen or heard by said viewer, wherein said second threshold is smaller and/or shorter than said first threshold.