PROPERTY PROTECTION SYSTEM EMPLOYING LASER LIGHT

• US 3,688,298 A
• Filed: 05/13/1970
• Issued: 08/29/1972
• Est. Priority Date: 05/13/1970
• Status: Expired due to Term

• Current Assignee: Charles Call, Peter Miller
• Original Assignee: Charles Call, Peter Miller
• Inventors: Call, Charles G., Miller, Peter
• Primary Examiner(s): Caldwell, John W.
• Assistant Examiner(s): Curtis, Marshall M.
• Application Number:
  US05/036,899
• Time in Patent Office: 839 Days
• Field of Search: 340/258B,228S,276 250/221,222,209,205,217 352/16LR
• US Class Current: 340/557
• CPC Class Codes: G08B 13/184 using radiation reflectors

Abstract

A system for protecting an area employing a laser light source. A monochromatic coherent beam of light from the laser light source is directed around the perimeter of the area to be protected in a series of paths. A photo cell is stationed at the end of the path of laser light for deactivating the laser and actuating an alarm signal when the beam of light is broken by an object such as an intruder moving through the beam. The laser is deactivated in order to safeguard the intruder, innocent or otherwise, and a reset device is provided for initiating the operation of the laser.

Claims

1. A property protection system for protecting an outside area comprising, in combination:

means for emitting a coherent monochromatic beam of electromagnetic energy, to be deflected around the perimeter of the area to be protected;

beam responsive means for actuating an alarm signal when said beam is broken by an object moving therethrough such that said alarm is activated whenever an intruder passes through a portion of said beam;

safeguard means for instantaneously terminating generation of said beam when said beam is broken by an object moving therethrough;

a generator for operating said means for emitting the beam wherein said means for actuating the alarm comprises a photosensitive element having conducting electrodes and a power supply;

said safeguard means comprising in series said conducting electrodes, power supply and generator, and an electrically actuated alarm having substantially greater impedance than said generator in shunt connection across said power supply such that when said beam is broken by an object moving therethrough, current from said power supply normally conducted across said electrodes to said generator is shunted through said alarm for actuating said alarm.

2. The system of claim 1 including a reset switch in shunt connection with said electrodes such that closure of said switch delivers power to said generator for reactivating said means for emitting the beam.