Fire detection device for detecting a fire and method for detecting a fire with the fire detection device

Abstract

Fire detection device (1) for detecting a fire (2) in a monitored area (3) with a surveillance camera (9) for monitoring the surveillance area (3) and for outputting first and second image data, wherein the surveillance area (3) is shown in a first illumination state in the first image data, with an evaluation unit (11) for evaluating the initial image data and for generating a fire warning based on the evaluation, with a control device (12), wherein the control device (12) has a control interface (13) for transmitting control commands to a lighting status control device (14), wherein the control device (12) is configured to issue control commands to the lighting state control device (14) to set a second lighting state in response to the fire warning via the control interface (13), characterized by that the evaluation device (11) is designed to evaluate the second image data, wherein the monitoring area (3) is shown in the second illumination state in the second image data, to verify the fire indication and, in the event of positive verification, to issue a fire alarm, and that the evaluation device (11) is designed for flame detection, wherein the second illumination state is designed as a dimming state of the monitoring area (3).

Description

State of the art

[0001] The invention relates to a fire detection device for detecting a fire in a monitored area, comprising a surveillance camera for monitoring the monitored area and for outputting first and second image data, wherein the first image data depicts the monitored area in a first illumination state, and an evaluation unit for evaluating the first image data and generating a fire indication based on the evaluation. The invention further relates to a method for detecting a fire with this fire detection device.

[0002] Video-based methods are frequently used for fire detection. In these methods, cameras monitor the areas to be observed, and the images output by the cameras are analyzed using digital image processing to check for the presence of fire characteristics, such as flames, smoke plumes, etc. From a systems engineering perspective, these video-based fire detection systems are easy to implement, as they essentially only require a camera and a corresponding evaluation unit to be operational.

[0003] Such a video-based system is described, for example, in DE 10 2008 001 391 A1.

[0004] A method for detecting smoke and / or flames is known from DE 10 2009 043 080 A1. Disclosure of the invention

[0005] The invention proposes a fire detection device with the features of claim 1 and a method for detecting a fire with the features of claim 9. Preferred or advantageous embodiments of the invention are described in the dependent claims, the following description, and the accompanying figures.

[0006] The invention relates to a fire detection device suitable and / or designed for detecting a fire in a monitored area. The monitored area can be an open area, such as a parking lot or container storage area, or an enclosed area, such as rooms or halls within a building. In particular, the monitored area is configured as a room or space within the building. The fire can be a raging fire with visually detectable flames or a smoldering fire with low luminous emissions but smoke development. In the most general embodiment, any type of fire can be detected by the fire detection device.

[0007] The fire detection device comprises at least one surveillance camera, which is arranged or can be arranged within the monitored area such that the camera's field of view overlaps with the monitored area. In particular, the surveillance camera monitors the monitored area. The surveillance camera can be a black and white camera or a color camera, in particular a CMOS or CCD camera. The surveillance camera is designed to output digital image data, and can output, for example, individual images or image sequences, in particular videos, as image data.

[0008] When the monitored area is in an initial lighting state, the surveillance camera outputs initial image data.

[0009] Thus, the initial image data refers to the monitored area in its first illumination state. The illumination state of the monitored area specifically refers to the brightness distribution within the monitored area, which is generated by natural and / or artificial light sources. Therefore, in this first illumination state, the artificial and / or natural light sources are in their initial state of illumination.

[0010] The fire detection device includes an evaluation unit designed to analyze the initial image data and, if necessary, subsequent image data, as well as to generate a fire indication based on this analysis. The analysis primarily involves digital image processing of the image data. Specifically, the analysis searches for fire characteristics within the image data. These fire characteristics could be, for example, flames depicted in the image data. Alternatively or additionally, they could also include smoke or smoke-related objects depicted in the image data.

[0011] If the evaluation unit detects fire characteristics in the initial image data during its analysis, it is configured to issue a fire alert. For example, the evaluation unit may be a digital data processing unit or may include one. If no fire characteristics are detected, no fire alert or a neutral signal is issued. Specifically, the fire alert is designed as a pre-alarm. Such a pre-alarm can be processed exclusively internally, i.e., within the fire detection device, or alternatively or optionally, it can also be transmitted and forwarded, for example, to a monitoring center, particularly a private monitoring center or a public monitoring center such as a fire department, police station, etc.

[0012] Within the scope of the invention, it is proposed that the fire detection device includes a control unit which has a control interface for communication with a lighting status control unit. The control interface is specifically designed for transmitting control commands to the lighting status control unit. In one possible embodiment, the lighting status control unit is configured separately for each of the light sources. Alternatively, it can be a central lighting status control unit.

[0013] The control interface can be wired or wireless. At a minimum, the control interface must be configured to allow control commands to be sent from the control unit to the lighting status control unit. Optionally, the control interface can also be configured for bidirectional communication between the control unit and the lighting status control unit. The control unit is specifically designed as a digital data processing unit.

[0014] The control unit is specifically designed, in terms of programming and / or circuitry, to issue control commands to the lighting control unit via the control interface in response to a fire alarm, thereby setting a second lighting state in the monitored area. These control commands can, for example, be implemented as digital messages. In particular, the first and second lighting states differ with regard to the brightness distribution within the monitored area. Specifically, the natural and / or artificial light sources assume a second illumination state in the second lighting state, with the first and second illumination states being configured differently.

[0015] The surveillance camera implements or continues the monitoring of the monitored area and outputs second image data, in which the monitored area is shown in the second lighting condition.

[0016] The evaluation unit is designed to analyze the second set of image data to verify the fire indication and, if the verification is successful, to trigger a fire alarm. Verification is achieved primarily by checking whether the fire characteristics found in the first set of image data are also present in the second set. Alternatively, different fire characteristics are searched for in the second set of image data, meaning that different methods are used to search for fire characteristics in the first and second sets of image data.

[0017] The evaluation unit is designed to trigger a fire alarm upon successful verification. Specifically, the fire alarm is transmitted to a private or public monitoring center. Following the initial pre-alarm, the fire alarm thus constitutes a main alarm. In response to the fire alarm, the monitoring center can initiate countermeasures, warning measures, and / or rescue operations, etc.

[0018] One aspect of the invention is that a two-stage fire alarm generation process can increase the significance of the triggered fire alarm and, in particular, prevent false alarms. The invention is based on the observation that some lighting conditions are unsuitable or at least not optimal for fire detection in the monitored area. Rather, the lighting conditions are set for the users of the monitored area. To maintain a user-friendly lighting condition for as long as possible, video-based fire detection is performed in a first stage under a specific lighting condition of the monitored area. This first lighting condition corresponds, in particular, to the normal lighting conditions for using the monitored area.

[0019] As soon as a fire warning is issued as a pre-alarm during monitoring, the control unit changes the lighting state from the first to the second lighting state. The second lighting state is specifically tailored to the requirements of video-based fire detection. It no longer serves to illuminate the monitored area in a user-friendly way, but rather to illuminate it in a way that is particularly conducive to effective monitoring. Thus, a fundamental aspect of the invention is that, after the fire warning is triggered as a pre-alarm, the lighting of the monitored area is automatically adjusted to create more suitable conditions for video-based fire detection. This approach achieves greater reliability in alarm verification.

[0020] In a preferred embodiment of the invention, the control device is configured to output control commands for artificial light sources in the monitored area via the control interface. In particular, the control commands are transmitted to the lighting state control device and executed by it. In this way, it is possible to change the lighting state of the artificial light sources.

[0021] In an alternative or further development of the invention, the control device for transmitting control commands to the lighting status control device is configured to control shading devices for natural light sources. These shading devices can be, in particular, roller shutters, awnings, window tinting devices, etc. The shading devices are designed to dim the natural light sources present in the monitored area. Dimming is achieved, for example, by closing a roller shutter acting as a shading device on a window that serves as a natural light source. In a further development or alternative, such a shading device can be configured as an automatic door to block light entering through the doorway. In this way, it is possible to change the illumination level of the natural light sources.

[0022] In a preferred embodiment of the invention, the lighting status control device is designed as a building automation system. Preferably, the building automation system includes a central server that communicates with the artificial light sources and / or the shading devices via a network. Suitable networks include, for example, KNX, EIB, DALI, LON, SMI, EnOcean, ZigBee, Z-Wave, or other networks. Such a building automation system is typically present in larger buildings or building complexes, allowing changes to the lighting status to be implemented by controlling the existing building automation system. This saves on installation costs and simultaneously adds new functions to existing systems.

[0023] According to the invention, the evaluation unit is designed for flame detection. Flame detection uses digital image processing to search for self-illuminating objects, such as flames, but also embers, etc., as a fire indicator. Flame detection is negatively affected by other luminous objects in the monitored area. Therefore, the second illumination state is designed as a dimming state of the monitored area. In particular, the second illumination state is significantly darker than the first. For example, some or all artificial light sources are deactivated and / or some or all dimming devices for natural light sources are activated. This deactivates the remaining luminous objects, so that the remaining luminous objects are highly likely to be flames or embers.

[0024] In an alternative configuration or another operating mode of the fire detection device, the evaluation unit is designed for smoke detection. Smoke detection is preferably based on the reflection of light from the smoke towards the surveillance camera. Smoke is particularly easy to detect when illuminated from the side or from the camera's viewing direction. Against this background, it is particularly preferred that the second illumination state be configured as a contrast state, with a first part of the monitored area facing the surveillance camera in an illumination state and a more distant part of the monitored area in a dimming state. This increases the probability that any smoke will be clearly distinguishable for the evaluation unit by the illumination from the illumination state.In contrast, a rear part of the monitoring area is darkened by setting it to the partial darkening state, so that the background for smoke detection is darkened.

[0025] In a possible further development of the invention, the evaluation unit is configured to determine the position of a smoke object within the monitored area when evaluating the first image data. For example, the smoke object could be a column of smoke. The control unit is configured to establish a transition between the illumination and dimming phases at the position of the smoke object in the contrast state. This sets a boundary in the second illumination phase such that the smoke object is illuminated from the front with respect to the viewing direction of the surveillance camera and is positioned against a dark or at least dimmed background. In this way, video-based smoke detection can be carried out with particular reliability.

[0026] In a possible further development of the invention, the control unit is configured to control additional lighting states. These additional lighting states can differ, in particular, in the brightness levels of the artificial light sources and / or the natural light sources or the shading device. The evaluation unit is configured to perform verification based on additional image data, wherein the monitored area is depicted in the additional lighting states in the additional image data. A fire alarm can be triggered upon successful verification. In this embodiment, the fire detection device is configured to cycle through multiple lighting states and thus multiple lighting scenarios. This makes it possible to optimize several fire detection strategies by changing the lighting states.

[0027] However, it is particularly preferred that the second illumination state be selected depending on the evaluation of the first image data. For example, if a flame object is detected in the first image data, the darkening state is selected as the second illumination state. Conversely, if a smoke object is detected during the evaluation of the first image data, the contrast state is selected as the second illumination state.

[0028] From a design perspective, it is preferred that the fire detection device includes the lighting status control device. Optionally, the fire detection device may also include the artificial light sources and / or the dimmer devices for the natural light sources.

[0029] The invention also includes a use of the fire detection device for detecting a fire.

[0030] A further aspect of the invention relates to a method for detecting a fire, preferably using the fire detection device as previously described. The method involves evaluating initial image data showing a monitored area in a first illumination state and generating a fire alert based on this evaluation. In a subsequent step, the illumination state in the monitored area is changed in response to the fire alert, transitioning from the first illumination state to a second illumination state. Next, image data is acquired again as a second set of images of the monitored area, this time in the second illumination state. This second set of images is then evaluated to verify the fire alert. If the verification is successful, a fire alarm is triggered. If the verification is unsuccessful, the fire alert is identified as a false alarm.

[0031] Further features, advantages, and effects of the invention will become apparent from the following description of a preferred embodiment of the invention and the accompanying figures. These figures show: Fig. 1 a schematic block diagram of a fire detection device as an embodiment of the invention; Fig. 2 a flowchart to illustrate a method for detecting a fire, in particular with the fire detection device.

[0032] The Fig. Figure 1 shows a highly schematic representation of a fire detection device 1 for detecting a fire 2 in a monitoring area 3. In the exemplary embodiment, the monitoring area 3 is located in the Fig. 1 is designed as an interior space bounded by walls and the floor. Systematically, the fire 2 can be divided into a flame object 4 and a smoke object 5, with the smoke object 5 being located above the flame object 4.

[0033] In monitoring area 3, artificial light sources in the form of ceiling lamps 6a, b and a natural light source in the form of a window 7, through which outside light penetrates, are arranged. A roller shutter 8 is arranged in front of window 7 as a blackout device, which can darken the window 7 or completely block out light.

[0034] The fire detection device 1 comprises a surveillance camera 9, the field of view of which 10 is directed into the surveillance area 3. It may be provided that the artificial light sources, i.e., the ceiling lights 6a, b and / or the natural light sources, i.e., the window 7, are located within the field of view 10 or only illuminate the portion of the surveillance area 3 that is captured by the field of view 10 of the surveillance camera 9.

[0035] The fire detection device 1 comprises an evaluation unit 11, which, for example, uses digital image processing to evaluate image data from the surveillance camera 9 and searches for or detects fire features in the image data. For example, in a first operating mode, the evaluation unit 11 can perform flame detection, so that the flame object 4 is detected as a fire feature. Alternatively or additionally, in a second operating mode, the evaluation unit 11 can perform smoke detection, thereby detecting the smoke object 5.

[0036] The fire detection device 1 comprises a control unit 12, which has a control interface 13 for outputting control commands. The control interface 13, and thus the control unit 12, is connected to a lighting status control unit 14 via signaling, so that the control commands are transmitted from the control unit 12 to the lighting status control unit 14. The lighting status control unit 14 is connected via signaling to the artificial light sources, in particular the ceiling lights 6a, b, and to the blackout device in the form of the roller shutter 8, and can control them. In the system configuration, the control unit 12 and the lighting status control unit 14 can be integrated into the fire detection device 1.Alternatively, the lighting status control device 14 can be designed as a building automation device that also performs other functions, such as heating control, etc. In yet another embodiment, several lighting status control devices 14 can be provided, which are arranged locally and decentrally at the artificial light sources, i.e., at the ceiling lights 6a, b and / or at the shading devices, in particular at the roller shutter 8.

[0037] In normal operation, monitoring area 3 is in an initial lighting state. This initial lighting state can be controlled, for example, by the lighting state control device 14, but it can also be a lighting state set by users through manual operation of light switches, etc. In particular, the initial lighting state is designed to be user-friendly or user-oriented.

[0038] The surveillance camera 9 transmits initial image data from the monitored area 3, captured under the initial lighting conditions, to the evaluation unit 11. This unit checks the initial image data for signs of fire. If fire signs are detected in the initial image data, the evaluation unit 11 generates a fire alert, specifically a pre-alarm, and sends it to the control unit 12. If no fire signs are detected, the monitoring continues, for example, by checking new initial image data at a later time.

[0039] In response to the fire warning and / or pre-alarm, the control unit 12 sends control commands via the control interface 13 to the lighting status control unit(s) 14, indicating that the monitoring area 3 is set to a second lighting status. This second lighting status is optimized for video-based fire detection. The lighting status control unit 14 executes the control commands and controls the artificial light sources, in particular the ceiling lights 6 a, b, and the natural light sources via the shading device, in particular the roller shutter 8, according to the control commands.

[0040] After the monitoring area 3 has been set to the second illumination state, a second set of image data is captured by the monitoring camera 9 and transmitted to the evaluation unit 11. The evaluation unit 11 evaluates the second set of image data from the monitoring area 3 in the second illumination state and verifies or rejects the fire indication, in particular the pre-alarm, depending on the result of the verification. If the fire indication is confirmed and thus positively verified, the evaluation unit 11 is configured to output a fire alarm, in particular a verified fire alarm, via an alarm interface 15.

[0041] The second lighting state is adjusted depending on the fire detection performed. Two examples are given below: First example: Flame detection

[0042] In the event that flame detection, specifically detection of self-illuminating objects and object areas in the image data, is performed in the evaluation unit 11, it is provided that in the second illumination state, light sources located in or shining into the monitoring area 3 are deactivated. To implement the second illumination state as a dimming state, all light sources are thus switched to a second illumination state. The artificial light sources, i.e., the ceiling lamps 6a and 6b, are deactivated so that they emit no light. The natural light source, in particular the window 7, is deactivated by lowering the roller shutter 8 as a blackout device, so that little or no light can enter the monitoring area 3.Once the light sources have reached the second illumination state, the surveillance camera 9 generates the second image data and transmits it to the evaluation unit 11. After all self-illuminating light sources have been deactivated, the evaluation unit 11 can concentrate on the remaining light sources as flame objects 4 and detect them with a high degree of certainty in order to verify the fire indication. Second example: smoke detection

[0043] In the case of smoke detection, the surveillance camera 9 records, in particular, reflected light from the direction of the surveillance camera 9 in the image data. Against this background, it is preferred that in the second illumination state, as a contrast state, the part of the monitoring area 3 which is located behind the fire 2 with respect to the position of the surveillance camera 9 or with respect to the field of view 10, is converted into a darkening partial state, and conversely, the part of the monitoring area 3 which is located in front of the fire 2 in the line of sight of the surveillance camera 9 is set into an illumination partial state.In this example, ceiling light 6a is activated to illuminate the front part of the monitoring area 3 in front of fire 2, and to darken the rear part of the monitoring area behind fire 2 by deactivating ceiling light 6b and closing the roller shutter 8. This ensures that the second set of image data is optimized for smoke detection.

[0044] The Fig. Figure 2 shows a schematic flowchart of the procedure for detecting a fire using the fire detection device 1 in the Fig. 1.

[0045] In step 100, video-based fire monitoring of monitoring area 3 is performed using evaluation unit 11, based on the initial image data showing monitoring area 3 in its initial lighting state. In step 200, the initial image data is analyzed for fire characteristics using digital image processing. If sufficient fire characteristics are detected, a fire alert is generated in step 300. Otherwise, the video-based fire monitoring continues as described in step 100.

[0046] The fire warning is passed from the evaluation unit 11 to the control unit 12, so that in step 400 the latter implements a change or adjustment of the lighting state, in particular the activation of the second lighting state, via the control interface 13.

[0047] After setting the second lighting state and capturing second image data under this second lighting state, the evaluation unit 11 checks the second image data for fire characteristics, specifically for the same fire characteristics, in step 500. If fire characteristics are detected, a fire alarm is triggered in step 600. If no fire characteristics are detected and the fire alert cannot be verified, the lighting state is reset in step 700, specifically from the second lighting state back to the first lighting state. Subsequently, the fire alert is canceled in step 800, and video-based fire monitoring resumes in step 100 under the first lighting state.

Claims

[1] Fire detection device (1) for detecting a fire (2) in a monitored area (3) with a surveillance camera (9) for monitoring the surveillance area (3) and for outputting first and second image data, wherein the surveillance area (3) is shown in a first illumination state in the first image data, with an evaluation unit (11) for evaluating the initial image data and for generating a fire warning based on the evaluation, with a control device (12), wherein the control device (12) has a control interface (13) for transmitting control commands to a lighting status control device (14), wherein the control device (12) is configured to issue control commands to the lighting state control device (14) to set a second lighting state in response to the fire warning via the control interface (13), characterized by , that the evaluation device (11) is designed to evaluate the second image data, wherein the monitoring area (3) is shown in the second illumination state in the second image data, to verify the fire indication and, in the event of positive verification, to issue a fire alarm, and that the evaluation device (11) is designed for flame detection, wherein the second illumination state is designed as a dimming state of the monitoring area (3). [2] Fire detection device (1) according to claim 1, characterized by , that the control device (12) is designed to output control commands via the control interface (13) for controlling artificial light sources (6a,b) in the monitoring area (3). [3] Fire detection device (1) according to claim 1 or 2, characterized by, that the control device (12) is designed to issue control commands for controlling shading devices (8) for natural light sources (7). [4] Fire detection device (1) according to any one of the preceding claims, characterized by , that the lighting status control device (14) is designed as a building automation device. [5] Fire detection device (1) according to any one of the preceding claims, characterized by , that the evaluation device (11) is designed for smoke detection, wherein the second illumination state is designed as a contrast state, wherein a first part of the monitoring area (3) facing the monitoring camera (9) is set to an illumination partial state and a more distant part of the monitoring area (3) is set to a darkening partial state. [6] Fire detection device (1) according to claim 5, characterized by, that the evaluation device (11) is designed to determine the position of a smoke object (5) in the monitoring area (3), wherein the control device (12) is designed to set a transition between the illumination partial state and the darkening partial state at a position of the smoke object (5). [7] Fire detection device (1) according to any one of the preceding claims, characterized by , that the control device (12) is designed to control further lighting states, wherein the evaluation device (11) is designed to carry out the verification on the basis of further image data, wherein in the further image data the monitoring area (3) is shown in the further lighting states and, in the event of positive verification, to issue the fire alarm. [8] Fire detection device (1) according to any one of the preceding claims, characterized by, that this includes the lighting state control device (14) as well as the artificial light sources (6a,b) and / or the shading devices (8) for the natural light sources (7). [9] Method for detecting a fire, in particular with a fire detection device (1) according to one of the preceding claims, wherein first image data showing a monitoring area (3) in a first illumination state are evaluated and a fire indication is generated on the basis of the evaluation, wherein in a subsequent step, in response to the fire indication, the illumination state in the monitoring area (3) is changed, wherein the change is made from the first illumination state to a second illumination state, wherein image data are subsequently recorded as second image data from the monitoring area (3), but in the second illumination state, characterized by , that the second set of image data will subsequently be evaluated to verify the fire indication, whereby a fire alarm will be triggered if verification is positive, and that flames are detected, the second illumination state being designed as a dimming state of the monitoring area (3).

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