Arrangement for spatial monitoring

• US 6,396,534 B1
• Filed: 02/26/1999
• Issued: 05/28/2002
• Est. Priority Date: 02/28/1998
• Status: Expired due to Term

• Current Assignee: Raven Licensing LLC (IP Edge LLC)
• Original Assignee: Siemens Building Technologies AG (Siemens AG)
• Inventors: Mahler, Hansjurg, Rechsteiner, Martin
• Primary Examiner(s): BRITTON, HOWARD W
• Application Number:
  US09/258,731
• Time in Patent Office: 1,187 Days
• Field of Search: 348/143,154,155
• US Class Current: 348/155
• CPC Class Codes: G08B 13/19602 Image analysis to detect motion of the intruder, e.g. by frame subtraction
• CPC Class Codes: G08B 13/19604 involving reference image or background adaptation with time to compensate for changing conditions, e.g. reference image update on detection of light level change
• CPC Class Codes: G08B 13/19697 Arrangements wherein non-video detectors generate an alarm themselves

Abstract

Included in an arrangement for spatial monitoring or surveillance are an image sensor (5), a presence/movement detector (6), and control and evaluation electronics (2) with a processor stage (4) for evaluating signals from the sensor (5) and detector (6) in combination. Imaged objects can be categorized on the basis of their geometry and movement. The signal from the detector (6) can be used in interpreting sensed images.

Claims

1. An arrangement for monitoring a spatial region, comprising:

at least one image sensor for the region;

at least one presence/movement detector for the region; and

control and evaluation electronics connected for receiving respective sensor and detector signals and including processing means for evaluating the sensor and detector signals jointly for an alarm condition.

2. The monitoring arrangement according to claim 1, further comprising means for evaluating the sensor and detector signals separately before evaluating them jointly.

3. The monitoring arrangement according to claim 2, wherein the means for separately evaluating the sensor signal is included with the sensor.

4. The monitoring arrangement according to claim 2, wherein the means for separately evaluating the sensor signal is included with the processing means.

5. The arrangement according to claim 2, wherein the means for separately evaluating the detector signal is included with the detector.

6. The monitoring arrangement according to claim 2, wherein the means for separately evaluating the detector signal is included with the processing means.

7. The monitoring arrangement according to claim 1, wherein the image sensor is a CMOS sensor.

8. The arrangement according to claim 7, wherein the image sensor is an active pixel sensor.

9. The monitoring arrangement according to claim 1, further comprising a memory for storing a critical image which is sensed by the image sensor on the alarm condition.

10. The monitoring arrangement according to claim 9, further comprising an interface for stored-image readout.

11. The monitoring arrangement according to claim 10, wherein the interface is to a PC.

12. The monitoring arrangement according to claim 9, further comprising means for transferring a sensed image to a unit that is spatially separated from the monitoring arrangement.

13. The monitoring arrangement according to claim 9, further comprising a further memory for storing at least one further image sensed by the image sensor before and/or after the critical image.

14. The monitoring arrangement according to claim 13, further comprising an interface for stored-image readout.

15. The monitoring arrangement according to claim 14, wherein the interface is to a PC.

16. The monitoring arrangement according to claim 13, further comprising means for transferring sensed images to a unit that is spatially separated from the monitoring arrangement.

17. The monitoring arrangement according to claim 1, further comprising means for determining distance to an object detected in the region and for communicating the distance to the processing means.

18. The monitoring arrangement according to claim 7, further comprising:

means for evaluating the sensor signals separately before evaluating them jointly with the detector signals; and

means for determining how many pixels have changed as compared with a reference image and/or pixel accumulation and/or pixel distribution over a sensed image.

19. The monitoring arrangement according to claim 1, wherein the control electronics includes means for generating criteria for use in evaluating the sensor and detector signals jointly.

20. An arrangement for monitoring a spatial region, comprising at least one presence/movement detector for the region, control and evaluation electronics connected for receiving sensor and detection signals, and processing means for evaluating the sensor and detector signals jointly for an alarm condition and further wherein the control electronics comprise means for generating criteria for determining average illumination of the region and for weighting the detector signal in an inverse relationship to the average illumination for use in evaluating the sensor and detector signals jointly.

21. The monitoring arrangement according to claim 20, wherein the criteria-generating means further comprises means for comparing the average illumination with a threshold (P₁) below which the alarm condition will be determined based on the detector signal without regard to the sensor signal.

22. The monitoring arrangement according to claim 20, wherein the control and evaluation electronics further comprises:

means for determining whether brightness in the region is sufficient for imaging;

means for comparing, in case brightness is insufficient, the detector signal with a first threshold (P₁);

means for determining, in case brightness is sufficient, a count of how many pixels are different in a sensed image as compared with a reference image and whether the count is low, intermediate or high;

means for comparing, in case the count is low, the detector signal with a second threshold (P₂) which is greater than the first threshold (P₁);

means for determining, in case the count is high, whether there has been a change in illumination of the region; and

means for comparing, in case of a change in illumination, the detector signal with a third threshold (P₃) which is less than the first threshold (P₁).