Infrared intrusion detector and method

• US 6,642,846 B1
• Filed: 12/06/1999
• Issued: 11/04/2003
• Est. Priority Date: 12/06/1998
• Status: Expired due to Fees

• Current Assignee: Electronics Line 3000 Limited (Risco Ltd.)
• Original Assignee: Electronics Line 3000 Limited (Risco Ltd.)
• Inventors: Yagoda, Eyal, Strauss, Bar, Krubiner, Dani
• Primary Examiner(s): Wu, Daniel J.
• Assistant Examiner(s): Nguyen, Tai T.
• Application Number:
  US09/455,002
• Time in Patent Office: 1,429 Days
• Field of Search: 340/545.3, 340/541, 340/567, 340/511, 340/522, 340/578, 250/342, 250/349, 250/347
• US Class Current: 340/545.3
• CPC Class Codes: G08B 13/193 using focusing means
• CPC Class Codes: G08B 29/24 Self-calibration, e.g. compensating for environmental drift or ageing of components

Abstract

An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface is provided. In one embodiment, the intrusion detector includes a housing to be mounted over the surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover, a plurality of lens elements formed in the transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of the protected space and to transmit infrared radiation from said source to the sensor; an alarm; and a control system for receiving the electrical output of the sensor and for outputting an alarm signal to the alarm when an infrared radiation source is detected simultaneously within at least two of the predetermined viewing zones.

Claims

1. An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;

a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;

an alarm; and

a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones,

wherein said lens elements are oriented such that their viewing zones define a plurality of viewing planes at different inclinations with respect to said surface, with the viewing zones in the viewing planes of smallest inclinations detecting moving infrared radiation sources most distant from the sensor, and

wherein each of the lens elements produces approximately the same magnitude of electrical output from said sensor irrespective of the distance of the moving infrared radiation source from the sensor.

2. The detector according to claim 1, wherein said lens elements are designed such that the lens elements having more distant viewing zones have larger optical gains in order to produce approximately the same magnitude of electrical output from the sensor irrespective of the distance of the moving infrared radiation source from the sensor.

3. The detector according to claim 1, wherein said lens elements are arranged according to a rectangular matrix of a plurality of horizontal rows, each defining one of said viewing planes, and a plurality of vertical columns, each defined by one of said lens elements in all said horizontal rows.

4. The detector according to claim 3, wherein the lens elements are of the same effective optical height in each horizontal row, but are of decreasing effective optical height from the uppermost horizontal row to the lowermost horizontal row, such that the lens elements in the uppermost horizontal row have the largest optical gain, and the lens elements in the lowermost horizontal row have the smallest optical gain.

5. The detector according to claim 4, wherein said lens are of equal width in said horizontal rows and of varying widths in said vertical columns.

6. The detector according to claim 3, wherein said lens elements define a rectangular matrix of four horizontal rows and eleven vertical columns.

7. The detector according to claim 1, wherein said infrared radiation sensor has a low transfer function at high frequencies, said control system including an active filter circuit for amplifying the output signal from the sensor at a higher amplification gain for high frequencies than for low frequencies.

8. The detector according to claim 1, wherein said control system generates a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space.

9. The detector according to claim 8, wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes cold average of the sensor outputs for generating said dynamic alarm threshold.

10. The detector according to claim 1, wherein said control system generates said dynamic alarm threshold by adding, to an initial alarm threshold, an environmental noise factor corresponding to the average of said sensor outputs dynamically produced for said predetermined number of samples.

11. The detector according to claim 1, wherein said infrared radiation sensor and control system are mounted on a printed circuit board within said housing, which printed circuit board is adjustable with respect to said transparent window.

12. The detector according to claim 1, wherein said printed circuit board is adjustable with respect to said transparent window by means of a slot formed in the printed circuit board movable with respect to a pin extending through said housing and said slot;

said pin being rotatable to a first position to free the printed circuit board for adjustment along said slot, or to a second position to lock the printed circuit board in its adjusted position.

13. An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;

a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;

an alarm; and

a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones;

wherein said control system generates a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space,

wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold; and

wherein said control system produces an average of said sensor outputs in a dynamic manner for a predetermined number of pulses, by;

inputting the value of each pulse into a shift register having a plurality of storage locations and operating in a FIFO manner to shift said pulse values from the first storage location to and out of the last storage location; and

with each inputted pulse, adding, to each previously produced average, the value of the pulse inputted into the first storage location minus the value of the pulse outputted from the last storage location.

14. The detector according to claim 13, wherein each pulse value inputted into the shift register is the energy of the respective pulse divided by the number of storage locations in the shift register.

15. The detector according to claim 14, wherein said control system inputs a “

0”

value for a pulse when the value of the pulse is less than a predetermined noise threshold for a predetermined time period.

16. The detector according to claim 15, wherein there are 30 storage locations in the shift register, and said predetermined time period is about 2 seconds.

17. The detector according to claim 15, wherein said control system is an analog system.

18. The detector according to claim 15, wherein said control system is digital system.

19. The detector according to claim 15, wherein:

each of said lens elements produces approximately the same magnitude of electrical output from said sensor irrespective of the distance of the moving infrared radiation source from the sensor; and

said control system outputs said alarm signal when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones.

20. An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources and a transparent window thereover;

a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;

an alarm; and

a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is detected within a viewing zone;

said control system generating a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space;

wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold; and

wherein said control system produces an average of said sensor outputs in a dynamic manner for a predetermined number of pulses, by;

inputting the value of each pulse into a shift register having a plurality of storage locations and operating in a FIFO manner to shift said pulse values from the first storage location to and out of the last storage location; and

with each inputted pulse, adding, to each previously produced average, the value of the pulse inputted into the first storage location minus the value of the pulse outputted from the last storage location.

21. The detector according to claim 20, wherein each pulse value inputted into the shift register is the energy of the respective pulse divided by the number of storage locations in the shift register.

22. The detector according to claim 21, wherein said control system inputs a “

0”

value for a pulse when the value of the pulse is less than a predetermined noise threshold for a predetermined time period.

23. The detector according to claim 22, wherein there are 30 storage locations in the shift register, and said predetermined time period is about 2 seconds.

24. The detector according to claim 23, wherein said control system, in generating said dynamic alarm threshold, also subtracts from said dynamic alarm threshold a correction factor constituting a predetermined percentage of the initial noise alarm threshold, but does not allow the dynamic alarm threshold to drop below this initial noise alarm threshold.

25. An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources and a transparent window thereover;

a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;

an alarm; and

a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is detected within a viewing zone;

said control system generating a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the infrared noise level in the monitored space;

wherein said control system periodically samples the output of said sensor to produce a plurality of incoming pulses, produces an average of said sensor outputs for a predetermined number of incoming pulses, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold; and

wherein said control system generates said dynamic alarm threshold by adding, to an initial alarm threshold, an environmental noise factor corresponding to the average of said sensor outputs dynamically produced for said predetermined number of samples.

26. An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;

said transparent window being formed with a plurality of lens elements each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit said radiation to said sensor to cause said sensor to produce an electrical output therefrom;

an alarm; and

a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm;

said infrared radiation sensor and control system being mounted on a printed circuit board within said housing, which printed circuit board is adjustable with respect to said transparent window by means of a slot formed in the printed circuit board movable with respect to a pin extending through said housing and said slot;

said pin being rotatable to a first position to free the printed circuit board for adjustment along said slot, or to a second position to lock the printed circuit board in its adjusted position.

27. The detector according to claim 26, wherein:

each of said lens elements produces approximately the same electrical output from said sensor irrespective of the distance of the moving infrared radiation source from the sensor; and

said control system outputs an alarm signal when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones.

28. The method according to claim 27, wherein said alarm signal is produced according to an alarm threshold which dynamically varies according to the environmental noise conditions in the monitored space.

29. An intrusion detector for detecting an intrusion into a protected space overlying a predetermined surface, comprising:

a housing to be mounted over said surface and including an infrared radiation sensor for sensing moving infrared radiation sources, and a transparent window thereover;

a plurality of lens elements formed in said transparent window each oriented to receive infrared radiation from a moving infrared radiation source within a predetermined viewing zone of said protected space and to transmit infrared radiation from said source to said sensor;

an alarm; and

a control system for receiving the electrical output of said sensor and for outputting an alarm signal to said alarm when a moving infrared radiation source is simultaneously detected within at least two of said predetermined viewing zones;

wherein said control system generates a dynamic alarm threshold for said alarm signal, which alarm threshold dynamically varies according to the environmental noise conditions in the monitored space,

wherein said control system periodically measures the output of said sensor to produce a plurality of incoming measured signals, produces an average of said sensor outputs for a predetermined number of incoming measured signals, and utilizes said average of the sensor outputs for generating said dynamic alarm threshold; and

wherein said control system produces an average of said sensor outputs in a dynamic manner for a predetermined number of measured signals, by;

inputting the value of each measured signal into a delay unit having a plurality of storage locations and operating in a FIFO manner to shift said measured signals from the first storage location to and out of the last storage location; and

with each inputted measured signal, adding, to each previously produced average, the value of the measured signal inputted into the first storage location minus the value of the measured signal outputted from the last storage location.