Monitoring system employing infrared image

• US 5,133,605 A
• Filed: 12/11/1990
• Issued: 07/28/1992
• Est. Priority Date: 12/11/1989
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Nakamura, Tetsuya
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): BENNETT, GEORGE B
• Application Number:
  US07/625,373
• Time in Patent Office: 595 Days
• Field of Search: 374/129, 374/124, 374/137, 374/133, 374/120, 374/121, 250/330, 250/334, 250/338.1, 250/342, 358/113, 358/81, 358/, 358/82, 358/110, 356/72
• US Class Current: 374/124
• CPC Class Codes: G08B 13/194 using image scanning and comparing systems
• CPC Class Codes: G08B 17/125 by using a video camera to detect fire or smoke

Abstract

An infrared image monitoring system according to the present invention includes an infrared camera and a visible light camera, both viewing the same scene to be monitored. The visible light camera has a threshold means, for example, an optical filter, to attenuate the visible light input to the visible light camera to a level below which the visible light camera can not detect the scene. The output of the visible light camera indicates reflections of the sun light which are brighter than a predetermined threshold level. The output of the visible light camera is superposed over the temperature pattern of the scene measured with the infrared camera, so that the area having the reflection is deleted from the data of the temperature pattern. Thus processed temperature data is further processed with a conventional process so as to judge whether a rise in the temperature data is abnormal or not. The temperature monitoring system is therefore prevented from an erroneous operation caused by a reflection of the sun light in the scene.

Claims

1. A temperature monitoring system for viewing visible and infrared input light from a scene to be monitored, comprising:

a visible light camera having threshold means having a threshold light level, said visible light camera viewing visible input light from the scene to be monitored, said visible light camera outputting a visible light signal including a first plurality of pixels, said visible light signal being at a first logic level for each of the first plurality of pixels having a corresponding visible input light which is less bright than said threshold light level, and said visible light signal being at a second logic level for each of the first plurality of pixels having a corresponding visible input light which is brighter than or as bright as said threshold light level;

an infrared camera for viewing infrared input light from the scene to be monitored, and for outputting a first temperature data for each of a second plurality of pixels which correspond to each of the first plurality of pixels of said visible light camera; and

superposing means for excluding said first temperature data corresponding to each of the first plurality of pixels of the visible light signal having the second logic level, from said first temperature data so that said first temperature data corresponding to each of the first plurality of pixels of the visible light signal being at the first logic level is output from said superposing means as a second temperature data which is processed to determine an abnormal temperature rise state in said scene to be monitored.

2. A temperature monitoring system as recited in claim 1, wherein each of the first and second plurality of pixels is synchronously updated.

3. A temperature monitoring system as recited in claim 1, wherein said threshold means is an optical filter for attenuating the visible input light to said visible light camera.

4. A temperature monitoring system as recited in claim 3, wherein said optical filter attenuates the visible input light to a level at which the visible input light which is brighter than or as bright as said threshold light level is output by the visible light camera as corresponding ones of the first plurality of pixels of the visible light signal at the second logic level.

5. A temperature monitoring system as recited in claim 1, wherein said threshold means is a comparator which outputs said first logic level for the corresponding visible input light which is less bright than the threshold light level.

6. A temperature monitoring system as recited in claim 1, wherein said first logic level is "1" and said second logic level is "0", and said superposing means performs a multiplication operation of each of said first temperature data with corresponding ones of said first plurality of pixels of said visible light signal.

7. A temperature monitoring system as recited in claim 1, further comprising:

abnormality detection means for receiving the second temperature data, and for determining whether an abnormal temperature rise state exists in the scene to be monitored based on the second temperature data.

10. A method as recited in claim 1, further comprising the step of:

d) determining whether the abnormal temperature condition exists in the scene to be monitored based on a second part of the second data which remains after the deleting of said step (c).

8. A method for eliminating a false detection of an abnormal temperature condition in a scene to be monitored by a temperature monitoring system, comprising the steps of:

comparing visible light from the scene to be monitored with a threshold level to provide a result; and

deleting selected bits or data corresponding to infrared light from the scene to be monitored based on the result before determining whether the abnormal temperature condition exists.

9. A method for eliminating a false detection of an abnormal temperature condition in a scene to be monitored, comprising the steps of:

a) generating first data corresponding to visible light from the scene to be monitored having data values greater than or equal to a threshold level;

b) generating second data corresponding to infrared light form the scene to be monitored; and

c) deleting a first part of the second data, corresponding to the first data.

11. A method for eliminating a false detection of an abnormal temperature condition in a scene to be monitored by a monitoring system, comprising the steps of:

a) comparing visible light from the scene to be monitored with a threshold level to provide a result; and

b) disregarding selected bits of data corresponding to infrared light from the scene to be monitored based on the result in determining whether the abnormal temperature condition exists.