Method and apparatus for area and perimeter security with reflection counting

An apparatus for detecting disturbance in a protected are or perimeter, said apparatus comprising:

• a transmitter directionally emitting a radiation beam;
• means for rotating said radiation beam to direct said radiation beam along a predetermined path;
• a plurality of beam reflectors disposed within the protected area or perimeter along said predetermined path, whereby each of said plurality of beam reflectors reflects a portion of said radiation beam when said beam makes contact with one of said plurality of beam reflectors;
• a reflected beam detector for receiving said portion of said radiation beam reflected by said plurality of beam reflectors;
• means for determining the number of said plurality of beam reflectors which are unobscured and capable of being contacted by said radiation beam at the time of initiation of said apparatus, said means for detecting comprising:
• means for counting and storing a base number of beam reflections from said unobscured reflectors received by said detector during a complete revolution of said radiation beam along said predetermined path, whereby said base number corresponds to a normal state in said protected area or perimeter, and said base number of beam reflections being dependent upon the number of said plurality of beam reflectors contacted by said radiation beam during said complete revolution of said radiation beam after activation of said apparatus
• means for measuring a counted number of beam reflections received by said detector for each subsequent revolution;
• means for comparing said base number with said counted number of beam reflections for each subsequent revolution, said means for comparing generating a signal when said base number differs from said counted number whereby a disturbance is detected;
• means for triggering an alarm in response to said signal;
• and
• means for resetting said base number after said apparatus is deactivated and reactivated whereby a new normal state is established dependent upon the number of said plurality of beam reflectors which are open to contact by said radiation beam along said predetermined path.