Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
1999-04-30
2001-02-13
Wu, Daniel J. (Department: 2736)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S556000, C340S552000
Reexamination Certificate
active
06188319
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to an intruder detector system and, in particular, it concerns a system which scans an area with a laser beam and then analyzes the reflected light to determine if an intruder has entered the area.
Security is becoming an increasingly complicated issue in today's world. Even one of the most basic threats, that of an intruder attempting to gain access to a building or other protected area, has become much more difficult to counter. As the technology to protect these secure areas has become more sophisticated, so have those criminal individuals who wish to subvert it. Thus, there is an increasing need for sophisticated systems to detect the presence of these intruders in protected areas.
One example of an attempt to solve this problem is a method of intruder detection which is disclosed in U.S. Pat. No. 4,949,074. In this method, a beam of infrared radiation is projected and the reflected radiation is measured. However, this method does not include the ability to scan a large area or to track a moving intruder. Indeed, the figures and examples in U.S. Pat. No. 4,949,074 show only narrow rectangular corridors, rather than wide, irregularly shaped areas. Furthermore, the range of an infrared beam is also relatively short. Thus, the method of U.S. Pat. No. 4,949,074 is highly limited in potential applications.
Similarly, U.S. Pat. No. 3,715,953 disclosed an serial surveillance and fire-control system which includes a laser rangefinder. However, the rangefinder is used only to aim at a target, and does not actively scan the area under surveillance.
Clearly, being able to scan an entire area would enable intruder detection systems to survey much larger, wider or irregularly shaped areas. Such scanners are also called rangefinders, since they measure the distance between the object and the rangefinder itself. U.S. Pat. No. 4,939,379 discloses a system for actively scanning the surface of an object and measuring its contours. However, this system is designed to be used to scan stationary objects, and has no provisions for detecting or tracking moving objects.
Another example of a range finder is disclosed in U.S. Pat. No. 4,788,441. This range finder includes a light source at a first location, a retroreflector attached to the target at a second location and a photoreceptor. A beam from the light source can be scanned along a path and is then reflected back by the retroreflector. The photoreceptor receives the reflected light. The distance between the light source and the retroreflector is then determined. Without the retroreflector, the device in inoperable. The range finder of U.S. Pat. No. 4,788,441 is thus limited to those situations where a retroreflector can be attached to the target.
However, such a limitation implies the compliance of the target, or of the individual operating the target, with being monitored, Certainly, such compliance would not be available from an intruder attempting to gain access to a protected area, since theses individuals are actually attempting to avoid detection. Thus, clearly a system is required which can also scan a light beam from a light source along a path, collect the reflected light and then analyze it, without requiring a retroreflector. Such a system would be able to detect and analyze light reflected from any objects in the area to be scanned, including human beings.
There is therefore a need for, and it would be highly useful to have, a system for detecting the presence of an intruder in a protected area, which scans the area with alight beam and then analyzes the reflected light to determine if such an individual is present.
SUMMARY OF THE INVENTION
According to the teachings of the present invention, there is provided an intruder detection system for detecting a presence of an intruder in an area to be protected, the system including: (a) a light source for emitting a light beam for scanning the area to be protected and for reflecting from a target, such that the light beam becomes reflected light beam; (b) a detector for receiving the reflected light beam; and (c) an signal processor for determining an intensity of the reflected light beam and a distance of the light source from the target, and for comparing the intensity and the distance to previously stored values of the intensity and the distance, such that a change in a value of the intensity or alternatively of the distance indicates the presence of the intruder.
According to another embodiment of the present invention, there is provided a method of detecting an intruder in an area to be protected, comprising the steps of: (a) scanning the area with a beam of light; (b) collecting light reflected from a target; (c) determining an intensity of the light and a distance to the target; (d) repeating steps (a) to (c) at least once to determine at least a first and a second distance, and a first and second intensity; and (e) analyzing the first distance and the second distance, and the first and the second intensity to determine if the target is the intruder.
According to preferred embodiments of the present invention, the light source is a laser. Also preferably, the previously stored values of the distance and the intensity are obtained by scanning the area to be protected with the light beam. Preferably, the signal processor includes a computer and an algorithm for converting the intensity of light and the period of time required for the reflected light to return to the detector into the distance of the light source from the target. Preferably, the computer further includes an algorithm for tracking the target.
According to another preferred embodiment of the present invention, the intruder detection system further includes an apparatus for visual identification of the target substantially only if the target is the intruder. Also preferably, the apparatus for visual identification is a video camera, and a movement of the video camera is controlled according to the tracking of the target. Alternately and preferably, the system further includes an alarm for being activated substantially only if the target is the intruder.
According to yet another embodiment of the present invention, the intruder detection system further includes a mirror for bending the light beam and a motor for rotating the mirror, such that substantially the entirely of the area to be protected is contacted by the light beam. Alternately and preferably, the system further includes a motor for rotating the detector and the light source, such that substantially the entirety of the area to be protected is contacted by the light beam.
According to still another embodiment of the present invention, there is provided a detection device for detecting a target in an area, comprising: (a) a light source for emitting a light beam; (b) a mirror for bending the light beam; (c) a motor for rotating the mirror, such that the light beam is able to contact substantially the entirety of the area and is able to reflect from the target, such that the light beam becomes a reflected light beam; (d) a detector for receiving the reflected light beam; and (e) an signal processor for determining a value selected from the group consisting of an intensity of the reflected light beam and a distance of the light source from the target.
Hereinafter the term “scanning” refers to the process of moving the light beam around the area to be protected such that reflected light is received from more than one point in that area. Hereinafter the phrase “bending the light beam ” refers to reflecting the light beam by a mirror such that the path of the beam is substantially changed.
DESCRIPTION OF THE INVENTION
The present invention is of a device and a method for detecting the presence of an intruder by scanning an area to be protected with a light beam, and then measuring both the intensity of the reflected light and the apparent distance from the device to a reflective object. Methods are disclosed for reducing the number of false alarms by evaluating any change in either the appar
Knobbe Martens Olson & Bear LLP
Laser Guard Ltd.
Nguyen Tai T.
Wu Daniel J.
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