GB2378598A

GB2378598A - Security imaging using illumination.

Info

Publication number: GB2378598A
Application number: GB0114339A
Authority: GB
Inventors: Derek Graham Huff
Original assignee: Integrated Design Ltd
Current assignee: Integrated Design Ltd
Priority date: 2001-06-13
Filing date: 2001-06-13
Publication date: 2003-02-12
Also published as: GB0114339D0

Abstract

A security system comprises a camera 1 and associated imaging processing means 6 arranged to capture images from a region, such as a boundary formed by fence 2, illuminated by a light source 4. The light source 4 may be an infrared source. In the embodiment shown, the light source 4 is set up to illuminate the boundary 2 such that, if an intruder 3 crosses the boundary, processing means 6 senses a change in image, i.e. from moving from a non-illuminated to IR illuminated region. Processing means 6 may sense such changes by, for example, subtraction of successive stored images. In a further modification shown in Figure 2, two illuminating beams may be used to reduce the risk of erroneous processing, such as when a bird 8 crosses a single beam: to be correctly identified, an object must be recorded in both beams in the region 10.

Description

SECURITY SYSTEM This invention relates to security systems. In particular, it relates to security systems utilizing video images.

There currently exist a number of security and other products which use video signals, such as digital video signals. In these types of systems, cameras are connected via various means to signal storage means, which may be VCRs or the like or may more preferably be digital storage. Sometime moving images are stored and sometimes still shots. Within the security industry, there are a range of products aimed at capturing alarm events in picture form and increasingly these products are based upon personal computers (PCs). Often, it is possible to trigger the storage of an image or sequences of images and this triggering may be by means of an external input such as an alarm contact, a timer or other input. This may be actuated by a person crossing a boundary for example which is alarmed or by crossing an infrared or an electromagnetic beam and breaking the beam.

In a number of these products, the triggering for storing and/or displaying images is actually done by analysis of the image itself That it, the image is analysed in successive frames and software is used to determine whether an image (or the outline of an image) appears to be of a type which is considered to be hostile, in which case a trigger signal is sent for the images to begin to be stored and/or displayed. These type of products are sometime known as'move alarms'and the level of processing in them varies from simple changes in overall video level to quite sophisticated shape and movement processing.

One difficulty with such devices is that they are'volumetric'. That is to say, the camera generally has a particular field of view and the size and shape of a target object depends on how far it is from the camera. It is therefore difficult to distinguish between small objects moving close to a camera and large objects moving a further distance away from the camera. For example, a small bird flying very close to a camera may cause a large change in the image to be processed even though it is not a threat at all, whereas a human target in the distance will cause a small change and may not be detected even though this man may present a hostile attack.

Furthermore, in some situations it is desirable to use a video system to detect that a target (such as a man) has crossed from one area to another, such as from an insecure area to a secure area. However, the field of view of the camera may be such that it is not possible to tell accurately on which side of the'security line'the person is standing. It may be, for example, that no person is allowed to approach to within a certain distance of an object, eg a work of art, a military vehicle, and so on (but if he attempts to move closer to the object an alarm is to be raised). This is very difficult to achieve with presently available video alarm systems.

The present invention arose in an attempt to provide an improved video security system.

According to the present invention in a first aspect there is provided security

apparatus comprising a camera ; means for storing and/or displaying images from the camera and a source of electromagnetic radiation modulated in a manner related to the storing of images, whereby the source of radiation is used to selectably illuminate an object and means for processing images including at least the image of the illuminated object and another image to obtain security information.

In an aspect, a system may comprise means for storing at least two time displaced images, and an electromagnetic radiation means adapted to provide a beam at a location which is related to a location or a boundary line to be protected, the apparatus comprising means for storing and comparing an image captured while a target is being illuminated with an image captured before or after the target is illuminated and processing the two images to obtain security related information.

Preferably, the information comprises information derived by subtracting the illuminated images from the unilluminated one so as to detect that a security breach has occurred.

In a further aspect, there is provided a security method in which one or more electromagnetic beams are used to periodically illuminate a line or region and at least two images are captured, one with the line or the region being illuminated and one with the line or region not being illuminated, the images being compared, eg by subtraction or otherwise, to determine whether a security condition has been breached.

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows schematically a security system; and Figure 2 shows an alternative security system.

Referring to Figure 1, a security system is shown, which in this case is for protecting against an unauthorised person passing a boundary. The boundary comprises a fence 2. A camera 1, which is preferably a digital camera and which will generally be a video camera, although it may be a camera which can take a sequence of individual still shots, is positioned so as to be able to view at least part of the boundary line. As shown, the camera lies within a protected site and looks out at the fence line 2 on the perimeter of the site. Members of the public such as a person 3 can legitimately walk along a path 5 on the outside of the fence. However, if they step over the fence an alarm is to be generated.

A source of electromagnetic radiation, most preferably an infrared transmitter 4 is arranged to provide a beam of radiation along the line of the fence. Typically, it is established at, say, waist height, horizontal and parallel, slightly to the inside of the fence line such that anyone stepping over the fence will be illuminated by the beam The advantage of using a currently available video camera having a silicone based charged couple device (CCD) imaging chip is that these are sensitive to, and thereby can see, infrared light which is generally invisible to a human observer. Thus, a target upon which the IR beam impinges will be illuminated by the IR beam and this will be picked up and seen by the camera, although in general the user will not be aware that he has been so illuminated, since he cannot see the IR beam.

The camera 1 is connected to a processing means 6 which will generally include a microprocessor and means for storing at least two frames of digital video and means for comparing the frames.

If the IR beam 4 were not present, then a small movement of the target 3 towards the camera would not significantly alter the image received by the camera. The signal processing in the processing means 6 may therefore not recognise that the target has begun to cross the boundary. However, if the target begins at the position shown where he is not illuminated by the beam and then moves to a position where he is illuminated by the beam, the video image stored where he is illuminated is considerably different, being an illuminated image, to that before the target crosses the beam. The signal processing is therefore assisted in distinguishing between an allowed and an unallowed operation by the person. The signal processing may comprise, for example, a process in which sequential images are subtracted one from another. In this case, the image of the illuminated target minus the image of the target just before it is illuminated will remove most the material except for the illuminated part of the image and therefore the signal processing can tell that an unauthorised act has been made.

If the beam is very strong is comparison to background light levels viewed by the camera, then this will generally be sufficient in itself However, in an optically noisy situation where ambient light levels can change, it may have limited benefit.

To allow for this, in a modification, the beam is turned on or off synchronised to the

storage of images from the camera, ie in one frame the beam is turned off in the next frame (video frame) the beam is turned on and so on. Then, an image stored when the beam is off is subtracted (or compared digitally or by other means) from an image stored when the beam is on. The resulting image contains only objects illuminated by the beam. So if behind the person in the figure is a wood or forested area which remains the same between subsequent illuminated or unilluminated images, then these parts of the image would be the same and so would cancel out and only the part which is actually illuminated by the beam, ie the person as he crosses the border (or just after he crosses the border in this case) would be illuminated.

Figure 2 shows a system in which a plurality of beams (in this case two) are used to create a light plane or planes. Two infrared sources 9a and 9b are used to create beams which intersect. The cross-hatched region 10 is one which is therefore protected. The system may be used to take several pictures of a scene, firstly a picture with just the beam from source 9a on then one with the beam from source 9b on and then one with neither source on. By subtracting or otherwise relatively processing the images, targets which have been moved into the zone 10 and which are therefore illuminated by one or other beams can be detected. False alarms can be reduced significantly by using the approach of having multiple beams since a target such as one of birds shown schematically at 8 in the figure which fly outside the protected zone 10 would be seen by one of the beams, say, beam 9a but not by beam 9b. So, by using an image which is seen by both beams 9a and 9b the chances of false alarms can be reduced.

In other modifications, an infrared, or other electromagnetic, beam may be directed into the air, eg upwards, so that the passage of a flying object can be detected.

The invention may be used in many different security circumstances, for example, but not limited to, the examples described in the introductory portion of this specification.

In general, it will often be useful that the images are taken in quick succession, so that changes in the image due to movement of objects in the field of view are small.. It is possible, for example, by first taking two unilluminated images, to determine which areas of the image were changing due to movement of objects and hence to ignore these areas.

It is also possible to modulate the IR (or other) source so that, for example, successive lines, rather than frames, of a video image can be illuminated and unilluminated., and this modification is within the scope of the present invention- It will be apparent that it is within the scope of the invention that, instead of IR radiation, any alternative radiation may be used, which serves to illuminate a target in a manner which can be detected or viewed by a suitable detector or camera.

Claims

1. Security apparatus comprising: a camera; means for storing and/or displaying images from the camera; a source of electromagnetic radiation modulated in a manner related to the storing of images, whereby the source of radiation is used to selectably illuminate an object; and means for processing images, including at least the image of the illuminated object and another image, to obtain security information.

2. Security apparatus as claimed in claim 1, wherein the camera is a digital camera.

3. Security apparatus as claimed in claim 1, wherein the camera is a video camera.

4. Security apparatus as claimed in claim 3, wherein the video camera includes a charged couple device.

5. Security apparatus as claimed in any preceding claim, wherein the source of electromagnetic radiation is an infra-red radiation source.

6. Security apparatus as claimed in claim 5, wherein the infra-red radiation source emits a beam of infra-red radiation.

7. Security apparatus as claimed in any proceeding claim, wherein the means for processing images includes a microprocessor and means for storing frames of successive

images.

8. Security apparatus as claimed in claim 7, wherein the means for processing images further includes means for comparing the frames of successive images.

9. Security apparatus as claimed in claim 6, wherein the apparatus includes another infra-red radiation source for producing another beam of infra-red radiation that intersects with the beam of infra-red radiation.

10. A security system comprising electromagnetic radiation means adapted to provide a beam at a location which is related to a location or a boundary line to be protected, means for capturing and storing at least two time displaced images, means for comparing a stored image captured while a target is being illuminated with stored image captured before or after the target is illuminated and means processing the two images to obtain security related information.

11. A security system as claimed in claim 10, wherein the information comprises information derived by subtracting the illuminated images from an unilluminated one so as to detect that a security breach has occurred.

12. A security method in which one or more electromagnetic beams are used to periodically illuminate a line or region and at least two images are captured, one with the line or the region being illuminated and one with the line or region not being illuminated,

the images being compared, for example by subtraction or otherwise, to determine whether a security condition has been breached.

13. A security method as claimed in claim 12, wherein a light plane delimiting a zone is formed by the intersection of a plurality of beams in the case where more than one electromagnetic beams are used.

14. A security method as claimed in claim 12 or 13, wherein the or each of the beams are turned on or off in synchronisation with the storage of the images.

15. A security apparatus as hereinbefore described, with reference to, and as illustrated by, the accompanying schematic drawings.

16. A security system as hereinbefore described, with reference to, and as illustrated by, the accompanying schematic drawings.

17. A security method as hereinbefore described, with reference to, and as illustrated by, the accompanying schematic drawings.