US 3739372 A
An intrusion alarm system comprises a pair of light sources which produce overlapping light beams that effectively cover the entire area being protected. When either of the beams is interrupted by an intrusion, an alarm is caused to be actuated. In the embodiment of the invention here described, one of the light sources acts as a master unit directed toward a first array of detectors and the second light source directed at a second array of detectors acts as a transponder unit. When each of the detectors in the first array receives light from the master unit, the second source is turned on. The alarm is actuated whenever one of the second array of detectors fails to receive a light beam from the transponder unit.
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United States Patent Schlisser et al.
OPTICAL INTRUSION ALARM SYSTEM Inventors: Gabor Schlisser, Tenafly; Julius R.
Insler, Bergenfield, both of NJ.
Assignee: Holobeam, Inc., Paramus, NJ.
Filed: Oct. 27, 1971 Appl. No.: 192,926
US. Cl. 340/258 B, 250/221, 340/276 Int. Cl. G08b 13/18 Field of Search 340/258 B, 228 S;
 References Cited UNITED STATES PATENTS 3,235,738 2/1966 Kress et a1 340/258 B Pr imary Examiner-David L. Trafton Attorney-Sandoe, Hopgood & Calimafde [111' as] June 12, 1973  ABSTRACT An intrusion alarm system comprises a pair of light sources which produce overlapping light beams that ef fectively cover the entire area being protected. When either of the beams is interrupted by an intrusion, an alarm is caused to be actuated. In the embodiment of the invention here described, one of the light sources acts as a master unit directed toward a first array of dearray of detectors fails to receive a light beam from the transponder unit.
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INVENTORS GABOR SCHLISSER BY JZ/L/US I? JMSLER m ATIURNEYS l OPTICAL INTRUSION ALARM SYSTEM The present invention relates generally to intrusion warning systems, and more particularly to an optical intrusion alarm system in which an alarm is actuated upon the interruption of a light beam.
The use of optical techniques to provide an indication of an unwarranted intrusion into an area is not a new one. One well-known technique is the provision of a light beam normally incident on a photocell or similar photodetector. When that beam is crossed by an intruder so that the path of the beam to the photocell is interrupted, an electrical circuit is energized to thereby actuate a suitable alarm. I
The known optical or light intrusion alarm systems are, however, able to effect surveillance only over a relatively small area, limited primarily by the area of the light beam employed. To increase the extent of the area which can be accurately monitored for intrusion, the number of beams as well as the number of detectors employed may be increased. The use of additional beam sources, however, results in a system that is relatively complex and costly and less reliable than one employing a lesser number of sources or detectors. In addition, even with a larger number of sources, I gaps through which the intruder may pass unnoticed are often unavoidably present unless an excessive'number of beam sources are employed, and great care is exercised in positioning those beam sources such that the resulting beams scan over the entire area to' be protected.
As a result the known optical intrusion warning systems have heretofore been used only to protect relatively small areas, as no practical optical intrusion system has yet been developed for use in protecting largescale installations such as industrial faciliteis, airports and the like, even though such systems may take the place of conventional structural fences or the like.
It is thus an object of the invention to provide an improved intrusion warning system employing optical techniques.
It is another object of the invention to provide an in trusion warning system capable of covering a greater area than has heretofore been possible.
It is a further object of the invention to provide a warning system of the type described employing only two sources of coherent or incoherent radiation, and which is capable of protecting a relatively large area against unwarranted intrusions.
To these ends, the intrusion warning system of the invention comprises a first beam source located at one boundary of the protected area and directed at a first array of detectors arranged at the opposite boundary of the protected area. Those detectors are coupled through a logic circuit to a second beam source located at the opposite boundary and directed toward a second array of detectors. The beams produced by the two beam sources are each triangular as viewed in a vertical cross-section, and preferably partially overlap one anothe so as to cover the entire area between the two boundaries. The patterns of the two beams result in an overall radiation pattern that constitutes an invisible wall of light energy extending between the bound.- aries. The second detector array is coupled to a second logic circuit which in turn is coupled to an alarm. The alarm is actuated only when one or more of the detectors in the second array fail to receive radiation thereon from the second beam source. If desired, the second array can be located in the same area as the first beam source.
In operation, when all of the detectors in the first detector array receive beam energy from the first beam source, the second beam source is actuated. However, if the radiation path from the first beam source to one or more of the detectors in the first array is interrupted, such as by an intruder through the area, the second beam source is not actuated. As a direct and immediate result, no beam energy is received! by the second array of the detectors, and the alarm is caused to be oper' ated.
Alternatively, if the second beam source is not actuated, that is, if no interruption occurs in the beam radiation to the first detector array, but if an intrusion through the area causes an interruption of beam radiation to the second detector array, the alarm is similarly actuated. If no intrusion occurs anywhere in the protected area, that is, if no interruption occurs in either of the overlapping beams produced by the two beam sources, no alarm indication is produced.
As herein employed in the specification and claims,
' the term light is intended to include coherent and incoherent radiation in both the visible and nonvisible portions of the spectrum including the infrared range.
To the accomplishment of the above and to such further objects as may hereinafter appear, the present invention relates to an optical intrusion alarm substantially as defined in the appended claims, and as described in the following specification taken together with the accompanying drawings in which:
FIG. 1 is a schematic diagram of the intrusion warning system of the invention illustrating the configurations of the light beams that constitute the optical wall;
FIG. 2 is a more detailed schematic diagram in block form of the system of the invention shown in FIG. 1; and
FIG. 3 is a detailed schematic diagram of the signal processor of the system of FIG. 2..
The operating principles of the invention are schematically illustrated in FIG. 1 in which the system of the invention is illustrated for use in protecting against the unwanted intrusion into an area or zone 10 defined by spaced boundaries l2 and 14. The boundaries 12, 14 are spaced transversely by a distance D; and the height of the boundaries is d, so that the area of the protected zone 10 is Dxd.
In accordance with the invention, a first light source 16, which is preferably a source of either coherent or incoherent infrared energy and which is here shown in the form of a laser, is positioned. at the lower end of boundary l2, and a second beam source 18 also herein shown as a laser, is positioned at the upper end of boundary 14. The output light energy of source 16 is conical in form and is thus triangular as viewed in vertical cross-section in the plane of zone 10. That output beam is shaped into a triangular lower beam 20 having a desired area by optical means described below. Beam 20 is directed at a plurality of detectors 22, here shown as five in number, arranged and equidistantly vertically spaced along boundary l4.v The output of source 18 is similarly formed into a triangular upper beam 24 which is directed toward a second array of detectors 26 (also shown as five in number) equidistantly vertically spaced along boundary 12. The base angles a of the two triangular beams 22, 24 is selected to approximately correspond to the angle whose tangent is the ratio d/D.
As shown in FIG. 1, triangular beams 20 and 24 intersect at the central region of zone at region 28 such that beams and 24 cover substantially the entire area of zone 10, thereby forming what may be considered an invisible wall of light extending between the zone-defining boundaries l2 and 14. Any unwarranted intrusion through that wall is detected in a manner to be described, and causes the actuation of an alarm to advise those concerned with the integrity and security of the protected zone, that an intrusion has occurred therethrough.
The operation of the system of the invention may be better understood with reference to the schematic block diagram of the system illustrated in FIG. 2 wherein elements corresponding to those in FIG. 1 are designated by similar reference numerals. As shown in FIG. 2, the system comprises two separate but interrelated units, namely, a master unit which includes laser source 16 and detectors 26, and a transponder unit 32 which includes laser beam transmitter 18 and detectors 22. Master unit 32 further includes a suitable energizing source, here shown as an oscillator 34, which provides the energy necessary to actuate laser source 16 to cause source 16 to produce an output beam in a known manner. That beam is shaped by beam forming optics 36 into beam 20 having the triangular pattern hown in FIG. 1. Optics 36 may consist simply of a lens positioned along the beam axis so as to achieve the desired base angle a with the resulting complete coverage of the zone by the partially overlapping means as described above.
The thus shaped beam produced by laser source 16, in the absence of any intrusion through lower beam 20, is incident upon all of detectors '22. The outputs of detectors 22 re respectively coupled to the inputs of an AND gate 38, the output of which is in turn coupled to the actuating or control portion of laser source 18. As a result, when all of detectors 22 receive light energy from laser source 16, that is, when no intrusion occurs in lower beam 20, all inputs to gate 30 re present and the resulting output of that gate causes laser source 18 to operate and produce an output'beam.
That beam is shaped in beam forming optics which may be similar to beam forming optics 36, to produce upper beam 24 which, as described above, has a segment that overlies or intersects the upper segment of lower beam 20. Beam 24 is directed at detectors 26, and is received by all of those detectors except when beam 24 is interrupted.
The outputs of detectors 26 are applied respectively to the inputs of a second AND gate 42, the output of which is applied to a signal processor 44, which is described in greater detail below with respect to FIG. 3.
g The output of processor 44 is applied to the control terminal of an' alarm or warning indicator 46, which may conveniently be a siren, horn, whistel and/or flashing light.
Indicator 46 is caused to operate whenever processor 44 receives no signal from gate 42. That can occur as a result of an intrusion through beam 20, which will interrupt the beam at one or more of detectors 22, with the result that gate 38 does not produce an operating signal for laser source 18. When this occurs, no input is received at gate 42 from any of detectors 26 since beam 24 is at that time terminated and none of detectors 26 receives radiation thereon.
When intrusion occurs in beam 24, the operation of transponder laser source 18 is unaffected since beam 20 remains undisturbed and each of detectors 22 produces a signal to gate 38 which in turn operates laser source 18. However, the interruption in beam 24 causes at least one of detectors 26 to at least temporarily fail to receive light incident thereon, such that at least one input will be absent at gate 42. As a result, gate 42 produces no output signal and processor 44 accordingly produces a signal to cause the actuation of alarm indicator 46.
Thus, as desired, an interruption in either of beams 20, 24 constituting the invisible light wall that completely covers the protected zone 10, causes alarm indicator 46 to be actuated, thereby immediately calling that intrusion to the attention of the security personnel assigned to monitor the protected area. v
Signal processor 44, which is shown in greater detail in FIG. 3,'receives the output of AND gate 42 at an input terminal 48 coupled in turn to the junction point 50 of a voltage divider consisting of resistors RI and R2, the latter being connected to ground. Point 50 is coupled to one input of a NAND gate 52, the output of which is coupled trough a capacitor C1 to the input of an NAND gate 54 and to ground through a resistor R3.
The output of gate 54 is returned to the other input of gate 52.
Gates 52 and 54 constitute a one-shot multivibrator 55 which upon the receipt of a signal from AND gate 42, indicating that all the detectors in array 26 are receiving radiation from transponder source 18, produces a as gate. To ensure that one-shot multivibrator 55 is triggered on only by an input signal rather than by noise, a reference voltage is established at point 50 by means of a Zener diode CR1 connected to a B+ source 56 through a resistor R4. A capacitor C2 is coupled across diode CR1 and ground.
The output gate produced by the one-shot multivibrator is coupled from the output of gate 52 through a resistor R5 and a diode CR2 to the base of a switching transistor Q1. A resistor R6 is coupled between the. base of transistor Q1 and ground, and the emitter of that transistor is directly connected to ground. The collector of transistor O1 is coupled to gate 2 of a dual gate field effect transistor (FET) Q2, as well as through a resistor R7 to the drain and gate 1 of FET Q2. The drain contact of that transistor is connected to the B+ source. A charging capacitor C3 is coupled across the emitter and collector contacts of transistor Q1.
Capacitor C3 is also coupled to the base of a transistor Q3 which together with transistor Q4 defines a differential amplifier 58 which, when actuated, produces an alarm signal whenever the voltage charged across capacitor C3 exceeds a reference voltage, the latter being established by a Zener diode CR3 connected between the base of transistor Q4 and ground.
A resistor R8 is connected between the emitters of transistors Q3 and Q4 and ground, the collector transistor Q3 is connected to the B-lsource through a resistor R9, the base of transistor Q4 is connected to the B+ source through a resistor R10, and the collector of that transistor is directly connected to the B+ source.
The alarm gate signal produced by the differntial amplifier is coupled from the collector of transistor O3 to the base of an emitter follower consisting of a transistor 64 and 66, point 60 being connected to one input of gate 64. The output of gate 64 is connected to one input of gate 66, and the output of the latter is in turn connected to a second input of the 'former. The state of the latching flip-flop is changed upon the presence of the alarm gate signal at gate 64, and remains at that state until reset by a reset signal applied to the other input of gate 66 through a resistor R12. A capacitor C4 is connected between resistors R12 and ground.
The output of flip-flop 62 is coupled through a resistor R13 and a diode CR5 to the base of an amplifier driver transistor Q6. A resistor R14 is connected between the base of that transistor and ground and its emitter is directly connected to ground. The collector of transistor 06 is coupled to the 13+ source through a resistor R15, and to the gate electrode of a switching field effect transistor (FET) Q7. The source of FET O7 is coupled to the B+ source through a resistor R16, and
, a resistor R17 is connected between the source of that transistor and ground.
The alarm 46 is coupled across the drain and source of PET Q7 as is a diode CR6. Alarm 46 is thus actuated whenever conduction is produced in the source-drain circuit of F ET Q7 as a result of an alarm signal being applied to the gate of that transistor in response to an intrusion in the laser wall. That is, an intrusion in the wall causes, for reasons described above, AND gate 42 not to produce an output signal. As a result, one-shot multivibrator 55 in signal processor 44 fails to produce a 100 as gate such that the voltage across capacitor C3 is permitted to change to a level exceeding the reference voltage of differential amplifier 58. The resulting output of amplifier 58 in turn changes the state of flipflop 62 to a condition rendering FET Q7 conductive thereby actuating alarm 46 as desired. In the absence of an intrusion, the 100 [LS signal produced by one-shot multivibrator 55, when applied to switching transistor O1, is effective to discharge capacitor C3 before the voltage thereon reaches the level at which differential amplifier 58 is actuated.
The system of the invention thus has the capability of detecting the unwanted intrusion through a protected area, and of practically immediately actuating an alarm to provide a warning of that intrusion to security personnel, who are thus able to quickly locate and apprehend the intruder. The system is highly reliable and accurate and yet requires only a minimum number of relatively inexpensive components; gallium-arsenide laser diodes may be used to advantage for laser sources .16 and 18.
Moreover, the system of the invention provides sur- .veillance and protection ofa large area, and thus significantly expands the practical application of optical surveillance techniques. If desired, the system of the invention may be employed in a multiple-segment perimeter protection system of the type disclosed in our copending application Ser. No. 113, 329, filed on Feb. 8,
1971, entitled Segment Locating Intrusion Alarm System with each segment of the perimeter being defined by a single laser wall" as established herein.
As herein disclosed, the alarm indicator 46 is actuated in response to the switching operation of an FET. If desired, the output of driver transistor Q6 may be connected to a relay coil or the like, to actuate the alarm whenever no signal is received by the signal processor as a result of an intrusion in the laser wall. Moreover, as herein shown, a latching flip-flop is provided so that once actuated, the alarm is maintained indefi-. nitely until reset. If desired, that flip-flop may be omitted if only a temporary alarm indication is desired upon the detection of an intrusion.
Thus, while the invention has been herein described with respect to a single particular embodiment thereof, it will be apparent that modifications may be made therein all without departing from the spirit and scope of the invention.
What is claimed is:
1. An intrusion warning system for providing an indication of an intrusion into a protected area, said area being defined by first and second boundaries, said sys tem comprising a first beam source, a first array of detectors located at one of said boundaries and in optical communication with said first beam source, a second beam source, means coupled to said first array of detectors and to said second beam source for disabling the latter whenever radiation from said first beam source is interrupted from one of said first array of detectors, a second array of detectors located at an opposite one of said boundaries and in optical communication with said second beam source, alarm means, and meanscoupled between said second detector array and said alarm means for actuating the: latter whenever radiation from said second beam source to one of said second detector arrays is interrupted.
2. The system of claim 1, further comprising means respectively interposed between said first and second beam sources and said first and second detector arrays for shaping the output of said first and second sources into first and second beams that substantially completely cover said area. 3
3. The system of claim 2, in which said beam shaping means includes means for causing adjacent portions of said first and second beams to overlie one another at the central portion of said area.
4. The system of claim 3, in which said beam shaping means include means for developing the patterns of each of said first and second beams-into an approximate triangular configuration.
S. The system of claim 4, in which said area has a transverse dimension D and a vertical dimension d, the base angle a of said triangular beams beingapproximately equal to tan d/D.
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