GB2459374A

GB2459374A - Fire monitor using camera with narrow field of view and using a remote marker

Info

Publication number: GB2459374A
Application number: GB0906858A
Authority: GB
Inventors: Thomas Hanses; Ralph Bergmann; Ulrich Oppelt; Bernd Siber
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2008-04-25
Filing date: 2009-04-21
Publication date: 2009-10-28
Anticipated expiration: 2029-04-21
Also published as: GB2459374B; GB0906858D0

Abstract

A smoke or fire detection device 1 for monitoring region along a monitoring section 2, has a camera device 3, which for generating image data of the monitoring region 2, the image data evaluated by device 6 to detect fire features such as smoke or flames. The camera may have a lens 7 and may be designed so that the monitoring region sector has a maximum viewing angle alpha of less than 5°, preferably less than 3° and in particular less than 1°. Alternatively the evaluation device 6, may define the monitoring region sector to the stated maximum angle. The camera may view a marker image 4 that may be illuminated or projected by optical means 8a near the camera or 8b remote for the camera. The camera 3 and the mark 4 may be separated by up to 20m.

Description

Description Title

Detection device and method of detecting fires along a monitoring section

Background art

The invention relates to a detection device for detecting fires and/or fire features in a monitoring region along a monitoring section, having a camera device, which for generating image data is and/or can be disposed in the monitoring region, having an evaluation device that is designed to detect the fires and/or the fire features in the monitoring region by evaluating the image data, wherein by means of the detection device a monitoring region sector, in which the evaluation is carried out, is selectable and/or selected. The invention further relates to a method of detecting fires and/or fire features.

Fire alarm systems comprise fire detectors in the form of sensor devices for detecting fires, smoke, flames or other fire features and are installed both in public buildings, such as for example schools or museums, and in private buildings. The majority of fire detectors may be divided roughly into two groups, wherein a first group relates to so-called point fire detectors, which are used for example in offices or children's rooms, i.e. in smaller spaces.

The point fire detectors are conventionally fitted on the ceiling and detect a fire or spreading smoke by virtue of optical, thermal or chemical detection at precisely one point. These fire detectors have the advantage that for example smoke rising and accumulating below the ceiling is detected very quickly. The drawback of these fire detectors is that for larger spaces, such as for example warehouses, a plurality of fire detectors have to be installed because otherwise it is impossible to cover the entire area.

An alternative to this is offered by a second group of fire detectors that take the form of video fire recognition devices, wherein use is made of video monitoring systems, which record a video image of a monitoring region by means of commercially available monitoring cameras and evaluate this video image for fires or fire features in a monitoring control centre.

The printed matter DE 10 246 056 Al discloses a smoke detector that comprises an image recorder and a light source. This smoke detector is fitted for example as a ceiling smoke detector and designed so that the focal point of the image recorder is set approximately 10 cm below the housing of the smoke detector. Given inadequate lighting, it is additionally possible to activate a light source that illuminates the focal point. Because of the close focal point, with this smoke detector background images are blurred compared to images from the immediate environment of the focal point.

The printed matter DE 100 114 11 Al, which is probably the closest prior art, relates likewise to a fire detector that uses a video camera or an infrared camera as an image recorder, wherein the image recorder is set in such a way that a large camera lens coverage and a true-to--life representation of the observed scene are provided. Fire detection is effected by means of an object analysis, wherein individual objects of the scene are automatically analyzed, particularly with regard to whether these objects are obscured by smoke, thermal schlieren or fire, and namely in that the actually recorded objects are compared with stored objects.

Disclosure of the invention

The invention relates to a detection device having the features of claim 1 and to a method having the features of claim 10. Advantageous or preferred forms of implementation of the invention emerge from the sub-claims, the following description and the accompanying figures.

The invention refers to a detection device that is suitable and/or designed for the detection of fires and/or fire features, in particular signs of fire, and may also be referred to as a fire detector or fire sensor. The detection is effected along a monitoring section, wherein preferably a monitoring volume developing along the monitoring section is observed.

The detection device comprises a camera device, which comprises as a sensor field for example a matrix or a linear array of sensor elements that is and/or may be aligned in such a way that it senses the monitoring region and/or the monitoring volume along the monitoring section and during operation generates image data of the monitoring region. The camera device and/or the sensor element of the camera device may take the form of any desired UV, VIS and/or NIR camera. In alternative forms of implementation, the camera device or the sensor element may also be realized as an FIR sensor, a thermal imaging camera or a thermopile array.

An evaluation device is used to detect the fires and/or the fire features and/or signs of fire in the monitoring region by evaluating the image data, preferably by means of digital image processing. Alternatively or additionally, an inclusion of analogue image processing steps in the framework of the invention is conceivable. The evaluation is effected also or preferably exclusively in a monitoring region sector or in a plurality of monitoring region sectors, which is/are selectable, selected and/or formed by the detection device.

In the framework of the invention it is proposed that the at least one monitoring region sector lies within a maximum viewing angle of the camera device of less than 50, preferably less than 3° and in particular less than 10.

The maximum viewing angle in this case is the aperture angle of the utilized lens coverage of the detection device and/or of the camera device in precisely one, several or all planes, in which a vector of the main observation direction of the camera device is also situated. The detection device is in particular so designed that the optical resolution in the monitoring region sector is high enough to allow the evaluation in the evaluation device.

At the same time, it is a consideration of the invention that particularly for very spacious areas, such as for example large halls, it is meaningful to use the detection device to monitor a monitoring section that extends for example along the entire length of the spacious area. A particular advantage of an image-supported monitoring of the monitoring section compared to other linear detectors is that disturbances, such as may arise for example as a result of vibrations, may be compensated by suitable image processing algorithms, such as for example image stabilization. For the monitoring of further sections special design-or program-related adaptations to conventional cameras are necessary because camera devices with standard optical systems and/or sensor elements do not provide an adequate optical resolution for the observation of remote objects.

In a preferred option of the invention it is accordingly provided that the camera device has an optical device that limits the recording range of the camera device to the viewing angle. In particular, this optical device takes the form of a telephoto lens and/or zoom lens. With such an optical device it is possible to form a sufficiently large image of the monitoring region sector at the sensor element.

Alternatively or additionally a high-resolution sensor element is used, wherein the evaluation device in terms of programming is designed to limit the sensing range of the sensor element and hence of the camera device to the desired maximum viewing angle. The advantage of this design is that an expensive optical device is not required, while the additional cost of a high-resolution sensor element is nowadays no longer of such great consequence.

The detection device is preferentially aligned so as to monitor the monitoring section over a distance of at least 10 m, in particular of at least 15 m and especially of at least 20 m. In addition, it is preferred that the camera device is set in a sharply focussed manner to the respective selected maximum distance in order to enable a detection of fires and/or fire features at the maximum distance. On the other hand, the entire monitoring section or at least a large part of the monitoring section is to be monitored, so that it is moreover preferred if the depth of focus ranges from the maximum distance to less than 5 m, preferably to less than 3 m, in particular to less than 1 in in the direction of the camera device. Optionally, the monitoring section is designed with one or more convolutions, wherein it is preferably provided that at least one convolution is disposed at a distance of at least I in, preferably of at least 3 m from the camera device. By a convolution is meant a diversion or deflection of the monitoring section for example by means of a mirror.

It is preferentially provided that the detection is carried out by way of or on the basis of abstract features, such as for example texture, structure, colour, intensity etc., in the image data of an object and/or a corresponding structure presented in the monitoring region sector. Fires and/or fire features are detected for example by means of optical emissions, such as for example incandescence or flames, by means of particle emissions, such as for example dense smoke or smoke, or by means of thermal schlieren, which lead to a variation of the abstract features in the image data of the monitoring region sector. For this type of evaluation it is therefore necessary for the object and/or structure to be represented in a sharply focussed manner in the monitoring region sector.

In principle it is possible for the evaluation device to carry out the detection of fires and/or fire features by virtue of the evaluation of any desired object and/or a corresponding structure positioned in the monitoring region sector. In particular, the evaluation may be carried out on the basis of a pre-existing structure in the monitoring environment or of a stationary object, such as for example a door, window, cabinet.

A further development of the invention according to claim 1 or a further development of the invention according to the preamble of claim 1 is provided by a detection device that is notable for the fact that it comprises a marker device, wherein the marker device is designed to generate or represent a mark in the monitoring region sector.

Instead of using a passive mark, i.e. a mark that is already provided by the environment without further measures, it is also possible actively to attach or apply a mark in the monitoring region sector. This actively applied mark has the advantage that its structure is known in advance and/or may be tuned to the intended application.

In a preferred constructional realization, the marker device takes the form of an optical mark, in particular of a target signal. The optical mark may comprise geometrical figures, colour-marked elements and/or other structures, which are preferably so designed that the detection of fires and/or fire features is simplified.

In an alternative form of implementation or development, the marker device comprises or takes the form of a light source, wherein the light source is designed to project a mark and/or the optical mark in the monitoring region sector and/or to illuminate the optical mark. On the one hand, it may be provided that the light source is integrated near or in the camera device, so that these preferably represent a jointly mountable device. As an alternative to this, the light source is disposed in or adjacent to the monitoring region sector, with the result that the distance between light source and monitoring region sector and/or the mark is short, for example less than 3 m, preferably less than 2 m.

In line with the concept of the invention of monitoring an extensive linear monitoring section with the detection devide, it is proposed that the camera device and the mark are spaced apart from one another by at least 10 m, in particular by at least 15 m and especially by at least m. The mark performs the function of a transmitter, with the camera device forming the receiver. In further developments of the invention, the detection device may also be so designed that greater distances are monitored, such as for example distances greater than 50 m or greater than 100 m.

A further advantage of the invention may be achieved in that the data-and the power supply of the detection device, in particular of the camera device and/or of the marker device, are effected via a common two-core or four-core cable. In particular, this cable takes the form of a field bus. This coining of the invention exploits the advantage of the detection device, namely that the detection device requires only a low power input.

In a development of the evaluation device, disturbances in the field of view of the camera device in the region of the monitoring section, such as may occur for example as a result of loading cranes, birds etc., are blanked out during detection. This may be realized for example by means of an object tracking mechanism, wherein a disturbing object is first detected and then tracked. This form of implementation ensures that no false alarms are triggered and/or that the number of false alarms is minimized.

A further subject matter of the invention relates to a method of detecting fires and/or fire features, in particular along a monitoring section, having the features of claim 10. Preferably, for the method a detection device according to one of the preceding claims and/or of the type just described, was used. In the method, in a first step a mark is positioned, selected and/or formed in front of a camera device, wherein the distance between camera device and mark is at least 10 m, preferably at least 15 m and in particular at least 20 rn. In a second step, by virtue of an evaluation of the image data. recorded by the camera device in the region of the mark, fires and/or signs of fire are detected. The detection is effected preferably by means of digital image processing algorithms, with it being alternatively or additionally possible also to use analogue image processing steps.

In a preferred development of the invention, the detection device comprises a light source that generates and/or illuminates the mark, wherein the lighting device is preferably activated only temporarily for example in the event of poor light conditions.

Brief description of the drawings

Further features, advantages and effects of the invention emerge from the following description as well as the figure of a preferred embodiment of the invention. In the present case: Figure 1 shows a highly diagrammatic representation of a detection device for setting up a measuring section along a linear monitoring section as an embodiment of the invention.

Form(s) of implementation of the invention Figure 1 shows in a highly diagrammatic representation a detection device 1 for setting up a monitoring section 2 with a camera device 3, wherein the measuring section 2 takes the form of an extensive, linear monitoring section 2 that is at least 10 m, preferably at least 15 m and in particular at least 20 m long. The detection device 1 is designed to detect fires or fire features along the monitoring section 2 and is used for example in large halls, railway stations or other spacious areas.

Positioned at the start of the monitoring section 2 is the camera device 3, which is oriented towards a mark 4 disposed at the end of the measuring section. The mark 4 performs the role of a signal transmitter and the camera device 3 the role of a signal receiver. In control terms, the monitoring section 2 forms a transmission path, which varies signals generated by the mark 4 in dependence upon the ambient conditions. Compared to the length of the monitoring section 2 the mark 4 is of a small desigr and consequently has for example a maximum diameter smaller than 1 m, preferably smaller than 0.5 m. The length of the measuring section 2 and the maximum diameter of the mark 4 define an effective lens coverage 5 of the camera device 3 that delimits a volume that is monitored along the monitoring section 2 by means of the camera device 3. In order to achieve an adequate security of detection, it is preferred that the depth of focus extends from the mark 4 as far as possible in the direction of the camera device 3, consequently for example up to 2 rn or 1 in in front of the camera device 3. This large depth of focus may be ensured for example by the use of suitable apertures in the camera device 3.

For evaluation of the image data recorded by the camera device 3 in the lens coverage 5 the detection device 1 has an evaluation device 6, which for example takes the form of a digital arithmetic unit. The evaluation device 6 may be disposed integrally in a common housing with the camera device 3 or, as an alternative to this, the evaluation device 6 is positioned at a distance from the camera device 3, wherein the image data of the camera device 3 are transmitted wirelessly or via cables to the evaluation device 6.

The basis of the measuring principle of the detection device 1 is that preferably abstract features of the mark 4, i.e. for example structures, lines, colours and/or intensities are recorded by the camera device 3 and evaluated. In the event of a fire or flames the image of the mark 4 varies, the image being changed as a result of fire features, for example thermal schlieren, the development of smoke or dense smoke, flame-or incandescence emissions. In this case, it is immaterial whether the fire or flames have broken out in the direct vicinity of the mark 4 because the variation of the image of the mark 4 occurs even if the fire features occur in the region of the monitoring section 2 and/or -from a control viewpoint -act upon the transmission path.

In the event of such changes, the detection device 1 transmits an information signal in the sense of a fire alarm signal. Optionally, actual image data may be output for verification purposes for example to a monitoring control centre.

As the monitoring section 2 is very long, it is necessary to design the camera device 3 in such a way that it has, on the one hand, an adequate depth of focus and, on the other hand, an adequate optical resolution for the imaging of the mark 4. In a first constructional alternative, the camera device has a telephoto-and/or zoom lens 7 that reduces the viewing angle alpha of the lens coverage 5 to a value of less than 5°, preferably less than 3° and in particular less than 1°. Alternatively or additionally, the camera device 3 may comprise a high-resolution sensor element (megapixel camera), wherein the limiting of the recording range of the camera device 3 to the lens coverage 5 is effected by programming. In the present case, in a simple manner only the region of the sensor element showing the mark 4 is evaluated.

A further advantage of the measuring method is that disturbances, caused for example by moving objects such as loading cranes in a large hail, may be blanked out.

Equally, the interference susceptibility of the measuring method is very low because disturbing influences regarding the positioning of the mark 4 that are caused for example by vibrations may be compensated with the aid of image processing methods, for example blur correction.

The camera device 3 and/or evaluation device 6 may be designed for example as an embedded hardware solution and may be manufactured at low cost as a result of the advantageous availability of camera modules. Furthermore, the detection device 1 has only a low power consumption, with the result that it is optionally possible to connect the camera device 3 and/or the evaluation device 6 to a two-core field bus that simultaneously enables data transfer and power supply.

In a first possible form of implementation of the invention, the mark 4 takes the form of an existing element in the monitored environment. It is therefore possible to use for example cabinets, door openings or other characteristic features in the monitored region.

Optionally, the mark 4 -in whatever form -may be illuminated by light sources 8a and/or 8b, for example in order to enable detection also at night or in poor light conditions. The light source 8a is positioned at the camera device 3, the light source 8b in the region of the mark 4. Given positioning of the light source 8a in the region of the camera device 3 or in the housing thereof, this has the advantage that only the camera device 3 has to have a signal-and power connection to the light source Ba, the mark 4 on the other hand not requiring any connections.

The use of the light source 8b has the advantage that it is disposed in the immediate vicinity, for example at a distance of less than 5 m, preferably less than 3 m, in particular less than 1 m from the mark 4 so that the required light output is only very low.

In a further form of implementation of the invention, the mark 4 takes the form of a target signal or a target mark, which comprises for example geometrical or colour-marked elements. The target signal may be adapted to the requirements of the evaluation by the evaluation device 6.

In a further possibility, the mark 4 is realized in the form of a light pattern that is generated by the light source Ba and/or 8b. Such a light pattern may for example also be designed so as to vary over time. Naturally, it is also conceivable to combine the various possibilities with one another, thus for example to project a light pattern onto a target signal.

In order further to reduce the power consumption, the camera device 3 and/or the light sources Ba and Sb may be switched on only at intervals, for example at a frequency of less than 15 Hz. It is also possible for the light sources 8a, b to take the form of infrared light sources that emit light outside of the visible range, so that the lighting remains invisible to the human eye. The spectral responsivity of the camera device 3 is adapted to the wavelengths of the light sources 8a, b.

Claims

Claims 1. Detection device (1) for detecting fires and/or fire features in a monitoring region along a monitoring section (2), having a camera device (3), which for generating image data is and/or may be disposed in the monitoring region, having an evaluation device (6) that is designed to detect the fires and/or the fire features in the monitoring region by evaluating the image data, wherein by means of the detection device (1) a monitoring region sector, in which the evaluation is carried out, is selectable and/or selected, characterized in that the detection device (1) is designed so that the monitoring region sector has a maximum viewing angle (alpha) in at least one plane of the lens coverage of the detection device and/or of the camera device of less than 50, preferably less than 3° and in particular less than 1°.
2. Detection device (1) according to claim 1, characterized in that the camera device (3) has an optical device (7) that limits the recording range of the camera device (3) to the maximum viewing angle (alpha), and/or that the detection device (1), in particular the evaluation device (6), in terms of programming is designed to limit the recording range of the camera device (3) to the maximum viewing angle (alpha).
3. Detection device (1) according to one of the preceding claims, characterized in that the camera device (3) is set in a sharply focussed manner to a distance of at least 10 m, in particular at least 15 in and especially of at least 20 in.
4. Detection device (1) according to one of the preceding claims or according to the preamble of claim 1 optionally in conjunction with any desired feature from the sub-claims, characterized by a marker device (4), wherein the marker device (4) is designed to generate and/or represent a mark (4) in the monitoring region sector.
5. Detection device (1) according to claim 4, characterized in that the marker device takes the form of an optical mark (4), in particular with geometrical figures and/or colour-marked elements.
6. Detection device (1) according to claim 4 or 5, characterized in that the marker device (4) takes the form of and/or comprises a light source (8a, b) that is designed to project a mark (4) in the monitoring region sector and/or to illuminate the optical mark (4)
7. Detection device (1) according to claim 6, characterized in that the light source (8a, b) is disposed near and/or integrated in the camera device (3) or is disposed in or near the monitoring region sector.
8. Detection device (1) according to one of the preceding claims, characterized in that the camera device (3) and the mark (4) are spaced apart from one another by at least 10 m, in particular by at least 15 m and in particular by at least 20 m.
9. Detection device (1) according to one of the preceding claims, characterized by an interface for the connection of a two-core cable or a four-core cable, in particular a field bus, for the power-and data supply of the detection device.
10. Method of detecting fires and/or fire features, preferably using the detection device (1) according to one of the preceding claims, characterized in that in a first step a mark (4) is positioned and/or selected in front of a camera device (3), wherein the distance between camera device and mark is at least 10 m, preferably at least 15 rn and in particular at least
11. 20 m, and in a second step an evaluation device (6) detects fires and/or signs of fire by evaluating image data of the mark (4)
12. Method according to claim 10, characterized in that at least one light source (8a, b) generates a mark (4) and/or illuminates the mark (4), wherein the light source (8a, b) is preferably activated only temporarily, for example in poor light conditions.
13. A detection device for detecting fires and/or fire features substantially as herein described with reference to the accompanying drawing.
14. A method of detecting fires and/or fire features substantially as herein described.