Method and apparatus for detecting moving objects, particularly intrusions

• US 20020044054A1
• Filed: 06/05/2001
• Published: 04/18/2002
• Est. Priority Date: 06/09/1999
• Status: Active Grant

• Current Assignee: Electronics Line 3000 Limited (Risco Ltd.)
• Original Assignee: Electronics Line 3000 Limited (Risco Ltd.)
• Inventors: Yagoda, Eyal, Krubiner, Dan, Strauss, Bar
• Granted Patent: US 6,774,791 B2
• Time in Patent Office: Days
• US Class Current: 340/545.3
• CPC Class Codes: G08B 13/191 using pyroelectric sensor means
• CPC Class Codes: G08B 29/18 Prevention or correction of operating errors G08B29/02, G08B29/12 take precedence

Abstract

A method and apparatus for detecting movement of an infrared-radiating object within a monitored space is provided. The method of includes exposing the monitored space to a passive infrared sensor having a first sensor element generating a first polarity signal when its field of view senses an infrared-radiating moving object, and a second sensor element generating a second polarity signal when its field of view senses an infrared-radiating moving object and determining the direction of movement of the detected object from the relative sequential order of the first and second polarity signals, for example for detecting intrusions in the monitored space to determine whether the movement direction is a hostile direction or a friendly direction.

Claims

1. A method of detecting intrusions with respect to a monitored space, comprising:

exposing said monitored space to at least one passive infrared sensor, each passive infrared sensor having a first sensor element generating a positive polarity signal when its field of view senses an infrared-radiating moving object, and a second sensor element generating a negative polarity signal when its field of view senses an infrared-radiating moving object;

generating a movement signal constituted of at least one positive polarity signal and at least one negative polarity signal when both have been generated within a first time interval such as to indicate the movement of an object within the monitored space;

determining from the relative sequential order of the at least one positive polarity signal and at least one negative polarity signal in said movement signal the direction of movement of the detected object, and particularly whether the movement direction is a hostile direction or a friendly direction; and

actuating an alarm when the direction of movement of the movement signal is determined to be in the hostile direction, but not when it is determined to be in the friendly direction.

2. The method according to claim 1, wherein said method further comprises disabling the actuation of said alarm during a second time interval after a generated movement signal has been determined to be in the friendly direction.

3. The method according to claim 2, wherein said disabling of the actuation of the alarm is effected by applying each movement signal, after a short time delay, to restart said second time interval during which the actuation of the alarm is disabled.

4. The method according to claim 3, wherein said first time interval is measured in seconds, said second time interval is measured in tens of seconds or minutes, and said short time delay is measured in a small fraction of a second.

5. The method according to claim 1, wherein said method further comprises determining whether the temperature of the monitored space is above or below body temperature (approximately 36°

C.), and utilizing said latter determination to determine from said sequential order of positive and negative polarity signals, the direction of movement of the body generating said movement signal.

6. The method according to claim 1, wherein the monitored space is a door or window of an enclosure and said hostile direction is from the door or window into the interior of the enclosure.

7. The method according to claim 6, wherein only the space within, and at one side of, the enclosure in the region of the door or window, is exposed to the passive infrared sensor.

8. A method of detecting movement of an infrared-radiating object in a predetermined direction within a monitored space, comprising:

exposing said monitored space to at least one passive infrared sensor, each passive infrared sensor having a first sensor element generating a positive polarity signal when its field of view senses an infrared-radiating moving object, and a second sensor element generating a negative polarity signal when its field of view senses an infrared-radiating moving object;

generating a movement signal comprising at least one positive polarity signal and at least one negative polarity signal when both have been generated within a first time interval such as to indicate the movement of an object within the monitored space; and

determining from the relative sequential order of the at least one positive polarity signal and the at least one negative polarity signal in said movement signal the direction of movement of the detected object.

9. The method according to claim 8, wherein said method further comprises determining whether the temperature of the monitored space is above or below body temperature (approximately 36°

C.), and utilizing said latter determination to determine the direction of movement of the body generating said movement signal.

10. The method according to claim 8, wherein the monitored space is a door or window of an enclosure, and the passive infrared sensor is mounted to monitor only the space within, and at one side of, the enclosure in the region of the door or window.

11. Apparatus for detecting moving infrared-radiating objects in a monitored space, comprising:

at least one passive infrared sensor to be mounted to view said monitored space, said at least one passive infrared sensor having a first sensor element generating a positive polarity signal when its field of view senses an infrared-radiating moving object, and a second sensor element generating a negative polarity signal when its field of view senses an infrared-radiating moving object;

a time window circuit for receiving the generated positive polarity signals and negative polarity signals and for generating a movement signal when a positive polarity signal and negative polarity signal have both been generated within a first time interval such as to indicate the movement of an object within the monitored space; and

a direction-determining circuit for determining, from the relative sequential order of the positive and negative polarity signals in said movement signal, the direction of movement of the detected object.

12. The apparatus according to claim 11, particularly useful for detecting intrusions in said monitored space, wherein said apparatus further comprises:

an alarm; and

an alarm actuating circuit which actuates the alarm when the direction of movement of the movement signal is determined to be in a hostile direction, but not when it is determined to be in a friendly direction.

13. The apparatus according to claim 12, wherein said apparatus further comprises:

a disabling circuit for disabling the actuation of said alarm during a second time interval after a generated movement signal has been determined to be in the friendly direction.

14. The apparatus according to claim 13, wherein said apparatus further comprises:

a delay circuit for receiving each movement signal and, after a short time delay, for applying said movement signal to said disabling circuit to restart said second time interval.

15. The apparatus according to claim 14, wherein said first time interval is measured in seconds, said second time interval is measured in tens of seconds or minutes, and said short time delay is measured in a small fraction of a second.

16. The apparatus according to claim 11, wherein said apparatus further comprises a temperature sensor for sensing the temperature of the monitored space, and for utilizing said sensed temperature to determine from said sequential order of positive and negative polarity signals, the direction of movement of the body generating said movement signal.

17. The apparatus according to claim 11, wherein said first and second sensor elements are mounted on a base enclosed within a housing having a lens defining said fields of view;

said base being shifted laterally with respect to said lens such that the mid-line between said first and second sensor elements passes obliquely through the transverse optical axis of the lens, to thereby produce fields of view of the sensor elements which are non-symmetrical with respect to the lens.

18. The apparatus according to claim 17, wherein the distance between said first and second sensor elements and said lens is 10-30 mm, and said lateral shift is 0.5-3 mm.

19. The apparatus according to claim 17, wherein said at least one passive infrared sensor is mounted on one side of a door or window of an enclosure so as to monitor only the space within, and at one side of, the enclosure in the region of the door or window.

20. The apparatus according to claim 18, wherein said at least one passive infrared sensor is mounted on one side of a door or window of an enclosure so as to monitor only the space within, and at one side of, the enclosure in the region of the door or window.

21. A method of detecting movement of an infrared-radiating object in a predetermined direction within a monitored space, comprising:

exposing said monitored space to at least one passive infrared sensor, each passive infrared sensor having a first sensor element generating a first polarity signal when its field of view senses an infrared-radiating moving object, and a second sensor element generating a second polarity signal when its field of view senses an infrared-radiating moving object; and

determining from the relative sequential order of said first polarity signal and said second polarity signal the direction of movement of the detected object, and particularly whether the movement direction is a hostile direction or a friendly direction.

22. The method of detecting movement according to claim 21 further comprising the step of:

counting the number of persons moving in at least one direction.

23. The method according to claim 21, further comprising the step of:

generating a movement signal constituted of said first polarity signal and said second polarity signal when both have been generated within a first time interval such as to indicate the movement of an object within the monitored space.

24. The method according to claim 21 particularly useful for detecting intrusions in said monitored space further comprising the step of:

actuating an alarm when the direction of movement of the movement signal is determined to be in the hostile direction, but not when it is determined to be in the friendly direction.

25. The method according to claim 24, wherein said disabling of the actuation of the alarm is effected by applying each movement signal, after a short time delay, to restart said second time interval during which the actuation of the alarm is disabled.

27. The apparatus according to claim 26, particularly useful for detecting intrusions in said monitored space, wherein said apparatus further comprises:

a time window circuit for receiving the generated first polarity signals and second polarity signals and for generating a movement signal when a positive polarity signal and negative polarity signal have both been generated within a first time interval such as to indicate the movement of an object within the monitored space;

an alarm; and

an alarm actuating circuit which actuates the alarm when the direction of movement of the movement signal is determined to be in a hostile direction, but not when it is determined to be in a friendly direction.

28. The apparatus according to claim 27, wherein said apparatus further comprises:

a disabling circuit for disabling the actuation of said alarm during a second time interval after a generated movement signal has been determined to be in the friendly direction.

29. The apparatus according to claim 26, wherein said apparatus further comprises:

a delay circuit for receiving each movement signal and, after a short time delay, for applying said movement signal to said disabling circuit to restart said second time interval.

26. Apparatus for detecting moving infrared-radiating objects in a monitored space, comprising:

at least one passive infrared sensor to be mounted to view said monitored space, said at least one passive infrared sensor having a first sensor element generating a first polarity signal when its field of view senses an infrared-radiating moving object, and a second sensor element generating a second polarity signal when its field of view senses an infrared-radiating moving object; and

a direction-determining circuit for determining, from the relative sequential order of the first and second polarity signals in said movement signal, the direction of movement of the detected object.