WO2001056294A1

WO2001056294A1 - Closed circuit television system

Info

Publication number: WO2001056294A1
Application number: PCT/GB2001/000124
Authority: WO
Inventors: David Biggins; Alan Roy Franklin
Original assignee: Adt Services Ag
Priority date: 2000-01-28
Filing date: 2001-01-12
Publication date: 2001-08-02
Also published as: GB0001953D0; AU2001225348A1

Abstract

A CCTV system has associated therewith a camera performance supervisor which include a processor (1) which contains an image analysis module (5). The image analysis module (5) receives images from each of the cameras in turn over a communications link (CL2) via image capture and digitising devices (6-1 to 6-n). The received images are processed by the image analysis module in conjunction with stored reference images (4) for each camera. Identified fault conditions can be sent via the communications interface (7) and communications link (CL2) to a maintenance depot to alert maintenance staff to faulty cameras and enable a speedy response to the occurrence of faults.

Description

DESCRIPTION

CLOSED CIRCUIT TELEVISION SYSTEM

The invention relates to closed circuit television (CCTV) systems and to methods of and arrangements for maintaining them The invention further [-9¹3+95 to 3 camera performance supervisor for rπon!toπn^π the ^perfor ance of cameras in CCTV systems

The use of CCTV systems is increasing and in many cases they are used to monitor sensitive areas Consequently, it is desirable to check the system integrity periodically and to check that each camera is operating correctly This has traditionally been a manual task that is usually performed by looking at the picture produced by each camera on a monitor on a regular basis An operator at a control centre, where one or more monitors are located, will perform this function by selecting each camera in turn and viewing the picture produced on the monitor by the selected camera If the viewed picture indicates a system or camera malfunction then the operator will contact a person responsible for repair of the appropriate part of the system The malfunction may be due to a fault in the equipment or to deliberate actions by persons wno wish ⁺o es^cape observation in the 'after case tne

iew may be obscured, for example by spraying the lens with paint, or the camera may be moved on its mount so that it no longer covers the area of interest A further possibility for persons wishing to avoid observation is to sever the communications link between the camera and the control centre These faults may not be immediately apparent to an operator or may not come to the operator s attention promptly For example, a camera that has been moved on its mount may not be recognised as a fault without full attention by the operator, in particular if the operator is not fully familiar with the layout of the monitored site An operator may not notice the severing of a communications link if his/her attention is occupied by an incident being viewed by another camera, perhaps as a deliberately created diversion It is an object of one aspect of the invention to enable an improved monitoring of the correct functioning of a CCTV system It is an object of a further aspect of the invention to enable the provision of an enhanced method of maintaining a CCTV system

Accordin to one aspect of the invention there is ^nrovιded a CCTV system comprising a camera performance supervisor The camera performance supervisor provides automatic monitoring of pictures received from some or all of the cameras To perform this function the camera performance supervisor (CPS) contains reference images that may be compared with images received from the cameras Alternatively, for some faults such as those which result in no picture being received or one with insufficient contrast or being out of focus an image analysis arrangement can provide an indication of malfunction without requiring a reference image for comparison

In one embodiment of the invention a closed circuit television (CCTV) system comprises a plurality of CCTV cameras communicating with a control centre having at least one CCTV monitor, the CCTV system further comprising a camera performance supervisor, wherein the camera performance supervisor comprises at least one image capture device for captuπnc, images from said CCTV cameras, a reference image storage device for storing a plurality of reference images, an image analysis device for analysing captured images and/or comparing them with selected reference images, and an alarm and/or reporting arrangement for raising an alarm and/or reporting a malfunction based on the results of the image analysis and/or comparison

In this way, the necessity for operators to log each camera on a regular basis to ensure its correct operation is reduced as this task can be performed automatically by the camera performance supervisor Conceptually, the CPS can be made capable of automatically building a report on faulty cameras, communication equipment faults and wrong camera views, keeping records and providing statistics Time to correct faults could be one of the parameters that the CPS could log The CPS may be constructed so that it automatically calls the service provider and also be arranged so that external interrogation can be performed

The reference images may be stored in digital form, the image capture device digitising the captured images and the image analysis device operating on the captured digitised images

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maπe^ in diπital memnrv and the analysis and/or comparison of the captured digitised images can be conveniently carried out using digital processing techniques One image capture device may be arranged to capture images from a plurality of cameras in sequence This gives economy of hardware and the images may be captured and analysed in a given sequence as the image analysis capacity provided will, in most cases, be insufficient to analyse pictures from all cameras simultaneously A number of possibilities for malfunction exist both due to equipment malfunction and to deliberate efforts to subvert the system A non-exhaustive list of examples is set forth below,- a) A fixed camera moved out of position, either deliberately or accidentally b) A fixed camera having a partial picture loss ( e g from paint spray or bag placed over the lens) c) A fixed or movable camera deterioration of focus d) A fixed camera change of contrast level over the image - to warn of major lighting changes e) A fixed or movable camera complete loss of picture f) A movable camera not moved for an extended period

Malfunction a) could be detected by comparing a reference picture generated by the camera when first installed or updated later with the picture currently being received Clearly, allowance has to be made for changes in the picture due to movable objects coming into or moving out of view One way of achieving this is to select those parts of the scene which rarely change as reference marks and to use the reference marks for the comparison For example when monitoring a room the top corners of a window or a doorframe might be used as reference marks and an alarm raised if these points changed position in the picture As a precaution against false alarms, for example caused by a window cleaner temporarily obscuring the corners of the window a time delay before recognising a malfunction and raising an alarm may be built jn

Malfunction b) may be detected by the absence of some of the reference marks or by large areas of constant luminance or chrominance Malfunction c) may be detected by a loss of sharpness at the edges of objects

Malfunction d) may be detected by comparing the reference and received image contrast levels either over the whole picture or over selected portions Malfunction e) may be detected at the inputs of the image capture devices since there will be no image to capture and the analogue input level will be constant, the actual level will depend on the nature of the cause of the picture loss i e whether it is a camera fault or a transmission link fault

Malfunction f) may be detected by storing a captured image, comparing the next captured image with the stored image, changing the stored image only if the captured image is different from the stored image, counting the number of successive unchanged captured images, and raising an alarm when the count reaches a given number

In a further aspect of the invention there is provided a camera performance supervisor (CPS) for monitoring the performance of cameras in a CCTV system, comprising means for capturing images from each of the cameras to be monitored, an image analyser for analysing the captured images to determine whether the captured images indicate a faulty operating condition of the camera, and means for indicating a fault condition in dependence on the result of the image analysis

The image capturing means may comprise means for receiving signals from selected camera(s) and at least one image capture and digitising device The CPS may comprise a memory for storing reference images for at least some of the cameras, the image analyser being arranged to determine whether the reference and received images show that the camera has moved position between the generation of the reference image and the current image.

The image analyser may compare the positions of certain marked features in the reference image with the corresponding features in the current imαπo

In a yet further aspect, the invention provides a method of maintaining a closed circuit television (CCTV) system comprising the steps of; providing a camera performance supervisor (CPS) as claimed in any of

Claims 5 to 9, providing a communications network to enable the CPS to monitor images generated by the cameras in the CCTV system, and alerting maintenance staff when the CPS generates an alarm indication representing a suspected faulty camera function.

Maintenance staff may be enabled to view the image that caused the faulty camera function indication. The CPS may store an audit trail of camera faults for a given time period. The CPS may be arranged to monitor cameras in a plurality of separate CCTV systems.

The above and other features and advantages of the invention will be apparent from the following description, by way of example, of an embodiment of the invention with reference to the accompanying drawings, in which:-

Figure 1 shows in block schematic form a plurality of CCTV systems supervised by a camera performance supervisor according to the invention, and

Figure 2 shows in block schematic form an embodiment of a camera performance supervisor according to the invention.

The arrangement shown in Figure 1 comprises first and second closed circuit television systems CCTV1 and CCTV2. Each of the CCTV systems comprises a plurality of cameras Cι to C_n connected to a control centre CC The CCTV systems CCTV1 and CCTV2 may be of conventional form whereby a central control centre comprises a plurality of TV monitors on which pictures captured by the cameras Ci to C_n may be displayed Generally, there will be fewer monitors than cameras and the control centre will include selection means to enable an operator to select a particular camera for viewing. There may be an element of automatic selection whereby if a significant change in tho crαnn iαiA/oH

rt r+nrc than tha πn+πi it frnm that namcirp ι automatically displayed on a given monitor Alternatively, such a change may be used to alert an operator, for example by initiating an audible or visible alarm, so that the operator can then select the appropriate camera for display on a monitor

As shown in Figure 1 the closed circuit television system CCTV1 is connected to a camera performance supervisor CPS via transmission links CL1 and CL3 and a communications network COM. The transmission links may be of any convenient form both wired and wireless while the communication network may be either a private network or part of a public switched network. Similarly the closed circuit television system CCTV2 is connected to the camera performance supervisor CPS via transmission links CL2 and CL£ and the communications network COM. Clearly more than two CCTV systems can be served by the CPS depending on the size of the CCTV systems, the capability provided in the CPS, and the overall performance required from the system. Furthermore, the CPS may be either on the same site as one of the control centres CC or at a remote site depending on the communication facilities provided. In operation, the CPS receives signals via the communication network

COM from each of the cameras in the CCTV systems CCTV1 and CCTV 2 The CPS is arranged to monitor the performance of the cameras so that the operators in the control centres are alerted in the event of a camera malfunction and/or maintenance personnel are alerted so that they can monitor and rectify the conditions causing the camera malfunction. In order to perform this function the CPS contains a number of functional components that are used to determine malfunctions These functional blocks include a memory in which reference images manually selected from each camera are stored Configuration information is associated and stored with these images The configuration information will include marking sensitive areas and key measurement points in the image, setting whether it comes from a fixed or movable camera timing parameters, and which faults are to be detected Timing parameters may include camera selection hold time, retry time for dial-up links, and ho long a movable camera may remain static before an alarm or malfunction indication is generated Alarm thresholds may also be set so that small or short-lived variations do not generate false warnings Depending on the hardware provided in the CPS a number of cameras may be checked simultaneously This depends on the number of video routes and the processing capacity provided In practice, the CPS is likely to monitor more cameras than can be processed in parallel and therefor it will be provided with the capacity to select cameras in sequence The CPS may receive the camera signals as analogue video or as digital data streams and is arranged to capture a picture or sequence of pictures from each camera in turn for comparison with the corresponding stored reference picture The CPS will select the image from the next camera when it is ready to process it The reference image and configuration information are used to select a particular algorithm to detect faults in the selected camera

Common faults which may be monitored and detected by the CPS are - a) A fixed camera moved out of position, either deliberately or accidentally b) A fixed camera having a partial picture loss (e g from paint spray or bag placed over the lens) c) A fixed or movable camera deterioration of focus d) A fixed camera change of contrast level over the image - to warn of major lighting changes e) A fixed or movable camera complete loss of picture f) A movable camera not moved for an extended period

In order to enable the malfunction a) to be detected the CPS may compare the received picture with the stored reference image to detect whether particular points on the two pictures coincide This simplistic arrangement has certain disadvantages in that it might cause an alarm to be raised if a particular point is obscured by an object passing in front of it To minimise this risk it can be arranged that the particular points are in parts of the picture which are rarely obscured, such as the top of a door or window frame Another precaution is to refrain from raising an alarm for a preset period en tha tho fomnnran/ rvrt/e-πnπ nf α παr+iπ ilαr nnint

nι"-ι+ initnfα n plpr If there are no features in the reference image which are suitable for this purpose other algorithms such as MPEG4 object movement vector analysis can be employed This information will be included in the configuration information stored with the reference images for each camera so that the most appropriate algorithm may be chosen for the selected camera In this way the processing time for each camera can be reduced to a minimum

In order to detect malfunction b) a comparison can be made with the reference image and if significant features are not present in the received image or a portion of the image then a fault indication can be raised

In order to detect malfunction c) the received image is analysed to determine the sharpness of the edges of objects within the image Clearly, the edges will lose sharpness when the camera is out of focus Many software image analysis algorithms are known which are capable of determining the sharpress of edges within an image

In order to detect malfunction d) the CPS may compare the received image with the stored reference image either over the whole image or over selected parts of the image to determine whether the average contrast level over the image or that part of the image has changed significantly In addition the CPS may check whether the average luminance has changed significantly In order to detect malfunction e) the CPS merely has to detect that no image is being received from a selected camera There may, of course, be several reasons for this and the CPS may not of itself be able to indicate the cause of the loss of image

In order to detect malfunction f) the CPS may store the last image in memory and compare the next received image with the stored image The number of times the same image is received, which will give an indication of the time during which the camera is stationary, may be used to indicate whether the camera has been stationary for so long that a malfunction should be indicated It may be that a movable camera is arranged to be stationary unless an operator specifically requests a different view, in which case this is part of the information stored with the reference image in the CPS

Figure 2 shows in block schematic form the conceptual elements of a CPS according to the invention It will typically be implemented as a general purpose computer having the appropriate software and communications and control interfaces The CPS comprises a processor 1 to which is connected a keyboard 2 to enable an operator to interact with the processor to control certain functions and a monitor 3 to enable the operator to view the functions currently being performed and records of any malfunctions to be displayed Associated with the processor 1 is a memory 4 that contains the reference images and associated information for each of the cameras monitored by the CPS An image analyser 5, which may be implemented as a software package running on the processor 1 , receives reference images from the memory 4 and instructions from the processor 1 in order to analyse received images from individual cameras in turn When the camera images are received as analogue video signals they are fed to Image capture and digitising devices 6-1 to 6-n The number of these image capture devices 6 which are provided will depend on the nature of the communications network between the cameras and the CPS, the speed at which the analysis can be performed, the time taken to capture and digitise the images, and the allowable time for cycling round the monitored cameras If the cameras produce a digital output then the digitising stage will clearly be unnecessary A camera may transmit individual images on demand rather than a continuous stream of images, in which case the image capture devices would not be necessary

The images from the image capture devices are fed to the image analyser 5 in turn where they are analysed to determine whether any malfunction or fault should be indicated The received image that caused the fault indication may be stored so that maintenance staff can access it to confirm that a fault occurred and the nature of the fault It may also be arranged that the maintenance staff can access the current image being produced by the apparently faulty camera to confirm that a fault condition still exists and so avoid unnecessary visits to a camera site When a fault is detected the current image may be archived or stored as an alarmed image together with associated measurements This can be used to allow a full audit trail over a pre-defined period for example three months

A communications interface 7 receives from the communications network COM signals representing the camera images These may be either serially received or a number of signals may be received in parallel This will depend on the nature of the communications network and the equipment provided in the CPS, for example whether multiple image capture devices are provided The communications interface will also receive control signals from the processor 1 to enable signals from the desired cameras to be received That is to enable communication with one of a number of CCTV systems which may be monitored by the CPS or to send fault indications or reports to a maintenance depot or worker so that a fault can be rectified as quickly as possible

From reading the present disclosure, other modifications will be apparent to persons skilled in the art Such modifications may involve other features which are already known in the design and use of closed circuit television systems and component parts thereof and which may be used instead of or in addition to features already described herein Although claims have been formulated in this application to particular combinations of features, it should be understood that the scope of the disclosure of the present application also includes any novel feature or any novel combination of features disclosed herein either explicitly or implicitly or any generalisation of one or more of those features which would be obvious to persons skilled in the art, whether or not it relates to the same invention as presently claimed in any claim and whether or not it mitigates any or all of the same technical problems as does the present invention The applicants hereby give notice that new claims may be formulated to such features and/or combinations of such features during the prosecution of the present application or of any further application derived therefrom.

Claims

1 A closed circuit television (CCTV) system comprising a plurality of CCT / cameras communicating with a control centre having at least one CCTV monitor, the CCTV system further comprising a camera performance supervisor, wherein the camera performance supervisor comprises at least one image capture device for captuππg images from said CCTV cameras a reference image storage device for storing a plurality of reference images, an image analysis device for analysing captured images and/or comparing them with selected reference images, and an alarm and/or reporting arrangement for raising an alarm and/or reporting a malfunction based on the results of the image analysis and/or comparison

2 A CCTV system as claimed in Claim 1 in which the reference images are stored in digital form, wherein the image capture device digitises the captured images and the image analysis device operates on the captured digitised images

3 A CCTV system as claimed in Claim 1 or Claim 2 in which one image capture device is arranged to capture images from a plurality of cameras in sequence

4 A CCTV system substantially as described herein with reference to the accompanying drawings

5 A camera performance supervisor (CPS) for monitoring the performance of cameras in a CCTV system, comprising means for capturing images from each of the cameras to be monitored, an image analyser for analysing the captured images to determine whether the captured images indicate a faulty operating condition of the camera, and means for indicating a fault condition in dependence on the result of the image analysis

6 A CPS as claimed in Claim 5 in which the image capturing means comprises means for receiving signals from selected camera(s) and at least one image capture and digitising device

7 A CPS as claimed in Claim 5 or Claim 6 comprising a memory for storing reference images for at least some of the cameras, the image analyser hαinn orr__i nrioH +Q rj 9+9 rrri 11-19 uihgfhor f α rofαrαnfα αnrl ror-oiwe-H imonnc c nui that the camera has moved position between the generation of the reference image and the current image

8 A CPS as claimed in Claim 7 in which the image analyser compares the positions of certain marked features in the reference image with the corresponding features in the current image

9 A camera performance monitor substantially as described herein with reference to the accompanying drawings

10 A method of maintaining a closed circuit television (CCTV) system comprising the steps of, providing a camera performance supervisor (CPS) as claimed in any of Claims

5 to 9, providing a communications network to enable the CPS to monitor images generated by the cameras in the CCTV system, and alerting maintenance staff when the CPS generates an alarm indication representing a suspected faulty camera function

1 1 A method as claimed in Claim 10 in which maintenance staff are enabled to view current images from a camera indicated as having a faulty functionality

12 A method as claimed in Claim 1 1 in which maintenance staff are enabled to view the image which caused the faulty camera function indication

13. A method as claimed in any of Claims 10 to 12 in which the CPS stores an audit trail of camera faults for a given time period.

14. A method as claimed in any of Claims 10 to 13 in which the CPS is arranged to monitor cameras in a plurality of separate CCTV systems.

15. A method of maintaining a closed circuit television (CCTV) system substantially as described herein with reference to the accompanying drawings.

16. Any novel feature or novel combination of features disclosed herein either implicitly or explicitly whether or not it relates to the same invention as that claimed in any preceding claim.