Passive infrared motion detector and method

• US 6,215,399 B1
• Filed: 11/10/1997
• Issued: 04/10/2001
• Est. Priority Date: 11/10/1997
• Status: Expired due to Term

• Current Assignee: Shmuel Hershkovitz
• Original Assignee: Shmuel Hershkovitz
• Inventors: Shpater, Pinhas
• Primary Examiner(s): SWANN III, GLEN R
• Application Number:
  US08/967,165
• Time in Patent Office: 1,247 Days
• Field of Search: 340/567, 250/340, 250/371, 250/395, 356/51, 356/256
• US Class Current: 340/567
• CPC Class Codes: G08B 13/191 using pyroelectric sensor means
• CPC Class Codes: G08B 13/193 using focusing means
• CPC Class Codes: G08B 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence

Abstract

Zones of a passive infrared (PIR) motion detector lens are staggered at close range to provide for pet immunity. In a dual sensor, dual lens configuration, the sensor signal is acted on to generate an alarm only when the sensor signal is simultaneous, indicating that an infrared emitting object big enough to cross both staggered zones of a zone pair has been detected. To further enhance sensitivity and immunity to noise, two dual element PIR sensors are arranged in opposite polarity with their elements vertically parallel. The sensor output is simultaneous and of opposite polarity, and noise can be suppressed by blocking like-polarity signals.

Claims

1. A method of detecting an intruder using a dual PIR sensor motion detector comprising the steps of:

collecting infrared radiation from first and second arrays of detection zones, said zones each having a predetermined elevation direction with respect to a vertical direction for reaching a predetermined range and having a predetermined azimuth plane with respect to a horizontal direction, wherein;

each one of said zones in said first array corresponds substantially to a respective one of said zones in said second array;

said corresponding zones have substantially the same shape, solid angle and azimuth direction;

ones of said corresponding zones reaching a close range have different said elevation directions to provide zone separation, whereby short infrared emitting objects only cross one of said corresponding zones of said first and second arrays;

ones of said corresponding zones reaching a far range have substantially the same said elevation direction to provide almost no zone separation, whereby small animals crossing said first and second array of zones at a close range do not result in said alarm signal being generated;

detecting said collected radiation using first and second PIR sensors, associated respectively with said first and second arrays, said first PIR sensor outputting a first sensor signal and said second PIR sensor outputting a second sensor signal; and

generating an alarm signal when both said first and second sensor signals simultaneously indicate intruder motion across said corresponding zones, whereby false alarms are reduced.

2. The method as claime in claim 1, wherein said step of collecting comprises providing a single sheet lens and said step of detecting comprises providing said sensors in a common housing supporting said lens.

3.The method as claimed in claim 2, wherein:

said first and said second arrays of zones are staggered at close range such that short infrared emitting objects crossing said zones at a fixed close range will enter only one of said corresponding zones of alternate ones of said first and second arrays;

whereby small animals crossing said first and second array of zones at a close range do no result in said alarm signal being generated.

3. The method as claimed in claim 1, wherein:

said first and said second arrays of zones are staggered at close range such that short infrared emitting objects crossing said zones at a fixed close range will enter only one of said corresponding zones of alternate ones of said first and second arrays;

whereby small animals crossing said first and second array of zones at a close range do not result in said alarm signal being generated.

4. The method as claimed in claim 1, wherein said step of generating comprises suppressing said alarm signal when radiation detected using said first PIR sensor is not substantially simultaneous with radiation detected using said second PIR sensor.

5. An infrared intrusion detector comprising:

first and second PIR sensors arranged vertically one above the other;

first and second lenses arranged vertically one above the other, said first and said second lenses for directing infrared radiation from a first and a second array of zones respectively onto said first and said second sensors respectively, each one of said zones having a predetermined elevation direction with respect to a vertical direction for reaching a predetermined range and having a predetermined azimuth direction, wherein;

each one of said zones in said first array corresponds substantially to a respective one of said zones in said second array;

said corresponding zones have substantially the same shape, solid angle and said azimuth direction, whereby infrared emitting objects cross said corresponding zones simultaneously;

ones of said corresponding zones reaching a close range having different said elevation directions to provide zone separation, whereby short infrared emitting objects only cross one of said corresponding zones of said first and second arrays; and

ones of said corresponding zones reaching a far range having substantially the same said elevation direction to provide almost no zone separation,

whereby said sensors operate simultaneously.

6. The detector as claimed in claim 6, wherein:

said first and said second arrays of zones are staggered at close range such that short infrared emitting objects crossing said zones at close range will cross only one of said corresponding zones of alternate ones of said first and second arrays, whereby at close range said lenses will not direct infrared radiation from small infrared emitting objects onto both said sensors, and said corresponding zones at a far range substantially overlap.

7. The detector as claimed in claim 7, further comprising alarm generating means connected to said sensors for generating an alarm signal, said generating means suppressing said alarm signal when a response of said sensors is indicative of non-simultaneous detection of intruder motion by said PIR sensors, such as occurs at a fixed close range.

8. The detector as claimed in claim 7, wherein said zone separation provides a substantially common height between a bottom of said zones in one of said arrays and a top of said corresponding zones in another of said arrays.

10. The detector as claimed in claim 7, wherein said sensors are arranged along a common axis next to one another, said sensors each generating an output signal and having two oppositely polarized sensing elements, said sensors being arranged with said sensing elements oriented vertically parallel and in an opposite direction, and said lenses are arranged along said axis, whereby said sensors have a simultaneous, reverse polarity response to motion of infrared emitting objects across a field of view of said lenses.

9. The detector as claimed in claim 9, wherein said common height is approximately 80 cm.

11. The detector as claimed in claim 11, further comprising means for suppressing an alarm signal when said output signals from said sensors are simultaneously of like polarity and waveform, whereby RFI noise is canceled.

12. An infrared intrusion detector comprising:

first and second PIR sensors arranged along a common vertical axis next to one another, said sensors each generating an output signal and having two oppositely polarized sensing elements, said sensors being arranged with said sensing elements oriented vertically parallel and in an opposite direction; and

a pair of substantially similar lenses arranged substantially side by side along said axis, said first and said second lenses for directing infrared radiation onto said first and said second sensors respectively,

whereby said sensors have a simultaneous, reverse polarity response to motion of infrared emitting objects across a field of view of said lenses.

13. The detector as claimed in claim 13, further comprising means for suppressing an alarm signal when said output signals from said sensors are simultaneously of like polarity and waveform, whereby RFI noise is canceled.

14. A method of detecting an intruder using a PIR motion detector comprising the steps of:

collecting infrared radiation from an array of detection zones, said zones each having a predetermined elevation direction with respect to a vertical direction for reaching a predetermined range and having a predetermined azimuth plane with respect to a horizontal direction, wherein;

ones of said zones reaching a close range have a different said elevation direction from neighboring ones of said zones at a same close range to provide zone staggering, whereby short infrared emitting objects only cross alternate ones of said zones when moving at said same close range; and

ones of said zones reaching a far range have substantially the same said elevation direction to provide almost no zone staggering;

detecting said collected radiation using a PIR sensor to produce a sensor signal; and

generating an alarm signal when said sensor signal indicates intruder motion across at least two neighboring ones of said zones, whereby small animals crossing said array of zones at close range generate PIR sensor signal from crossing every other zone and do not result in said alarm signal being generated.

15. The method as claimed in claim 15, wherein said step of generating comprises generating an alarm signal if an energy level of said sensor signal over a predetermined window time period is greater than a predetermined threshold.

16. The method as claimed in claim 15, wherein said step of generating comprises generating an alarm signal if said sensor signal indicates motion across one of said zones followed by motion across another of said zones within a predetermined time period.

17. The method as claimed in claim 17, wherein said predetermined time period is a predetermined amount times a pulse width of said sensor signal indicating motion across said one of said zones.

18. An infrared intrusion detector comprising:

a PIR sensor generating a sensor signal;

a lens for directing infrared radiation from an array of zones onto said sensor, each one of said zones having a predetermined elevation direction with respect to a vertical direction for reaching a predetermined range and having a predetermined azimuth plane with respect to a horizontal direction, wherein;

ones of said zones reaching a close range have different said elevation directions from neighboring ones of said zones reaching said same close range to provide zone staggering, whereby short infrared emitting objects only cross alternate ones of said zones when moving at said same close range; and

ones of said zones reaching a far range have substantially the same said elevation direction to provide almost no zone staggering;

whereby small animals crossing said array of zones at a close range generate PIR sensor signal from crossing every other zone and do not result in said alarm signal being generated.

19. The detector as claimed in claim 19, wherein a distance between a bottom of one of said zones and a top of a neighboring one of said zones at said same close range is a substantially common height.

21. The detector as claimed in claim 19, further comprising sensor signal analyzing means for generating an alarm signal in response to said sensor signal when said sensor signal indicates crossing of two neighboring zones and for suppressing an alarm signal when said sensor signal indicates crossing of a zone and missing a neighboring zone.

20. The detector as claimed in claim 20, wherein said common height is approximately 80 cm.