GB2381979A

GB2381979A - Intruder tracking and illuminating system

Info

Publication number: GB2381979A
Application number: GB0125010A
Authority: GB
Inventors: Robert William Chandler
Original assignee: Individual
Current assignee: Individual
Priority date: 2001-10-18
Filing date: 2001-10-18
Publication date: 2003-05-14
Also published as: GB0125010D0

Abstract

A security system for alerting an intruder of their surveillance by illuminating the area surrounding them. The system has image capture means 2 for capturing images of an intruder 1, image processing means 6 for processing the images captured and lighting means 7 for illuminating the intruder 1. The guiding means is responsive to the image processing means 6 and guides the lighting means 7 onto the intruder. The guiding means may also shake the lighting means to alert the intruder that he has been detected.

Description

Security System The present invention relates to a security or safety system that alerts an intruder that an electronic monitoring system is active within an area. In particular it is suitable in security or safety systems that use video surveillance equipment.

In recent years video surveillance equipment has entered into widespread use. The uptake has been at least partly due to advances in manufacturing technology and technological developments in video equipment. Consequently, there has been a drop in the cost of video equipment. Increased familiarity of security monitoring systems throughout society has meant a reduction in their deterrent and/or or security effectiveness. Many false or dummy camera systems are installed in highly visible locations to act as a low cost deterrent but are often ineffective. To restore effectiveness, security monitoring systems need to actively alert those under surveillance that they are being monitored, so as to reduce any complacency, say by directly illuminating and/or tracking them with a spot light.

The use of automatic movement detection in video security systems is known. These detection devices are primarily aimed at triggering alarms and or activating video recording equipment using variety of techniques including external microwave or infra red motion detectors. By way of example, US Patent 5,602, 585 discloses a video frame digitising system that samples multiple video frames over time to detect changes and movement and, in response thereto, to trigger an alarm condition.

Similarly the use of lasers and video cameras to track moving objects is known and there are highly complex and expensive military systems that are able to track, aim and fire weapons at moving targets. By way of example US Patent 4,922, 801 discloses a fire control system utilising a video camera mounted on a servo controlled gun which is able to perform this task.

No known prior art system provides cost effective security surveillance that alerts an intruder within the field of view of the system that they have been detected and that video monitoring is active.

The invention provides a security system comprising image capture means for capturing images of an object, image processing means for processing the images captured, lighting means for illuminating the object and guiding means responsive to the image processing means for guiding the lighting means.

There has been devised an improved form of video security and/or safety system that enhances deterrent value over and above prior art systems by illuminating the area around the intruder in order to deter and/or warn them.

The lighting means may compnse a focusable light source. The source may generate visible, invisible, red or infrared light. Preferably, the source comprises a laser or other spot light.

The guiding means preferably comprises servo motor means. The guiding means may comprise means for making the spot light jitter and/or oscillate.

The image capture means may comprise a monochrome or colour video camera or a matrix of light sensitive devices.

The image processing means may comprise digitlsmg means for digitising captured images. The digitising means may comprise an analogue to digital converter. The image processing means may comprise memory means for storing the digitised images. The image processing means may comprise clock means for determining the rate at which digitised images are stored in the memory means.

The system may comprise comparing means for comparing stored images to determine movement of the object or the position of illumination of the lighting means. The system may comprise control means responsive to the comparing means for moving and/or varying the field of view of the image capture means.

The system may further comprise output power means responsive to the image processing means for altering the intensity of the illuminating means.

The image capture means may include infrared sensitive means or image intensifier means.

The processing means may comprise a user interface.

The image capture means, processing means, lighting means and guiding means may be housed together or separately.

The system may comprise playback means for recording the images for subsequent playback.

As will be appreciated by those experienced in the art, the resolution of the captured image frame and the size and intensity of the spot light within the image frame are directly related to each other. For example a low resolution camera means requires a larger and brighter spot light than a low resolution camera. The size and intensity of the spot light also changes with distance and consequently the camera, spot light and size of area covered are interrelated and need to be matched for the present invention to be effective.

In a simple embodiment of the present invention, a stationary low resolution monochrome video camera or a matrix of light sensitive elements can be used to detect motion in an area. When motion is detected within the image frame the servo positioned spot light can

be directed to a specific area within the frame using a pre-recorded look up table and open loop control.

In another embodiment of the invention the control and spot light means can be retrofitted on to an existing installed video security or safety system. These systems often include a plurality of expensive high specification colour or monochrome video cameras that can pan and or zoom in an area of interest and controlled by an operator. In another embodiment of the present invention the motion detector means can be used to control and guide the camera means to automatically direct and zoom in on a moving object. In this embodiment of the invention it gives the added benefit of increasing the resolution of a distant image. In more sophisticated embodiments of the present invention closed loop control of the spot light and or image means can be used. By closed loop control is meant the ability directly to detect the position of the spot light in the image frame and provide feedback information to the processing means. The spot light beam may be a specific shape and or contain a specific frequency (colour) of light to provide improved detection/feedback means.

In more complex embodiments of the present invention a visible or non-visible spot light may be used to mark a specific object within the field of view of the system and then automatically track any movements on the video monitoring system. In this embodiment of the invention the automatic tracking system may also include various pattern recognition technique means including fuzzy logic and or neural networks.

In another alternative embodiment of the present invention a matrix of light sensitive devices forming an image directly in the controller memory provides a low cost alternative to using high speed video signal processing hardware.

A system according to the invention which is particularly useful in low level light conditions.

The invention further provides a method of alerting an intruder of their surveillance or monitoring comprising capturing images of the intruder, processing the captured images to determine the position of the intruder and illuminating the determined position.

The position of the intruder may be detected by comparing successive images.

The position may be illuminated with a focusable light source. Light source position information may be pre-determined and the information may be used to guide the light source. Alternatively, the light source may be guided according to data from the captured images.

The position of the intruder may be determined by comparing successive images.

The invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is an example of an improved surveillance system utilising a servo motor controlled laser spotting device and illustrates the principle of operation of the present invention.

Figure 2 is an example of a digitised picture and image frame means.

Figures 3a, 3b and 3c illustrates the movement detection principle used in Figure 1.

Figures 4a and 4b illustrates the spot light tracking system superimposed over the movement detector means of Fig 3c Figure 5 illustrates a servo motor control system to direct a light source used in Figure 1.

Figure 6 is a block diagram of the control system used in Figure 1.

Referring in detail to figure 1 which represents a typical video monitoring security system according to the invention. The object 1 in a given area is monitored by a 270,000 pixel CCD video camera means 2 of 380 TV lines in a PAL format with a < 0. 1 Lux sensitivity level. A video monitor 4 and/or video recording and playback equipment 5 can have a plurality of video cameras and channels with video switching and selection means in order to monitor many different areas. The video camera 2 output signal 3 feeds through processing means comprising a main control unit 6 where it is digitised in to a memory store to form a sequence of picture frames as shown in more detail in figure 2.

Subsequent video picture frames from the video signal 3 are subtracted over a period of time to detect movement within the picture frame as shown in more detail in figure 3.

Superimposed on the video picture frame information is also illumination position 8 information. Co-ordinates of the spot light and any movement within the field of view of the camera 2 by the object 1 are calculated by the control unit 6. Lighting means constituted by a spot light 7 is guided by servo motor actuators from a known or detected position to the position at which movement of the object is detected.

Figure 2 is a simplified illustration of an object 1 in a single digitised picture frame derived from a video camera 2 of figure 1. The digitised video frame stored in a memory has a horizontal 23 and vertical 22 number of pixels 21 which determine the overall resolution and quality of the system. Furthermore as will be appreciated by people trained in the art, each pixel 21 can be made to generate a colour and or intensity to add richness to the image and improve sensitivity. Clock means (not shown) determines the rate at which frames are stored.

Figures 3a and 3b represent two frames similar to figure 2 but captured a few seconds apart. Fig 3c represents the difference between the two frames of figure 3a and 3b and therefor represents any change in pixels or movement in an object over time. In this example the human object 31 moved an arm to position 32 and the result is shown in

figure 3c. The sensitivity of the system i. e. the trigger thresholds are adjusted by altering the time between the video frame capture and the quantity of pixels changed in the vicinity. Creep and slow ambient light changes can also be adjusted by up dating the reference picture frame periodically.

Figure 4a represent the X co-ordinates 41 and the Y co-ordinates 42 of the spot light in a video picture frame. Calculations for the servo motor controlled spot light 43 are performed and the spot light is adjusted 43 to match the co-ordinated of any movement within the frame as shown in figure 4b 44. In one embodiment of the present invention the video camera orientation is fixed and a calibration cycle is performed on the spot light servo motor mechanism. During the calibration cycle of the system, the X and Y coordinate limits of the spot light 43 within the video frame are found and recorded in memory to provide open loop control. When movement is detected in the video frame the servo system moves the spot light directly to the pre-recorded look-up table position set during the calibration phase. In an alternative embodiment of the present invention closed loop control is achieved by continually checking the spot light position and adjusting the servo to reduce the difference in the two co-ordinates to a minimum 44. In another alternative embodiment of the present invention when the two co-ordinates are matched in the picture frame as shown in figure 4b the spot light is made to jitter and oscillate to attract attention.

Figure 5 illustrates guiding means in the form of a two dimensional servo motor system to control a spot light 43 position and intensity. The horizontal 53 and vertical 52 direction of the light beam 51 is adjusted by main control unit 6 of figure 1. In this embodiment of the present invention, the laser pointer device 50 generates a red spot of light 54 within the picture frame. Red and or infra red light is readily detected in low intensity or image intensifier video cameras that are primarily used at night. In normal operation the light beam 51 divergence is adjusted to prevent eye damage and or cover a larger area in the picture frame for improved detection. In an alternative embodiment of the present invention the light beam is modulated or interlaced on and off between odd and even

frames within the video signal in order to reduce noise and interference from other light sources.

Figure 6 is a block diagram of the control unit 6 that will be understood by those trained in the art and represents the main electronic building blocks of the system. The black and white video signal input from the camera means is digitised by the analogue to digital converter (ADC) and placed in a page of the memory bank in a 380 by 320 matrix with 255 levels of brightness. The timing and control block ensures that different video picture formats can be used for example the European PAL or the North American NCS standard. The video memory bank is also shared with microprocessor system using direct memory access (DMA) techniques. In an alternative embodiment of the present invention a matrix of light sensitive devices can be used to directly form a picture frame type image in the memory store of the control unit.

In Figure 6 differential calculations are performed on the pages of the video memory bank by the microprocessor system in order to derive the co-ordinates of any movement and the spot light position as previously discussed. The results of the calculations performed by the microprocessor adjust the position of the servo motor controlled spot light when movement above pre-set thresholds are detected. In another alternative embodiments of the present invention colour information can also be used to determine the presence and position of the spot light and moving body. Not shown in figure 6 are details of the microprocessor system elements such as the separate peripheral hardware, memory and control software that can be modified or set up by the user interface. In this embodiment of the invention an RS232 link was used with a computer terminal to alter the program settings and instructions within the microprocessor sub system.

In an alternative embodiment of the invention, a pre-recorded video signal can be used to playback the movements of the spot light and generate a light show for entertainment and or test purposes.

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only, and not in any limitative sense, and that various alterations and modifications of the invention are possible without departure from the scope of the invention as defined by the appended claims.

Claims

1. A security system comprising image capture means for capturing images of an object, image processing means for processing the images captured, lighting means for illuminating the object and guiding means responsive to the image processing means for guiding the lighting means.

2. A security system according to claim 1 wherein the lighting means comprises a focusable light source.

3. A security system according to claim 2 wherein the source generates visible, invisible, red or infrared light.

4. A security system according to claim 2 or claim 3 wherein the source comprises a laser or other spot light.

5. A security system according to any of claims 1 to 4 wherein the guiding means comprises servo motor means.

6. A security system according to any of claims 1 to 5 wherein the guiding means comprises means for making the spot light jitter and/or oscillate.

7. A security system according to any of claims 1 to 6 wherein the image capture means comprises a monochrome or colour video camera or a matrix of light sensitive devices.

8. A security system according to any of claims 1 to 7 wherein the image processing means comprises digitising means for digitising captured images.

9. A security system according to claim 8 wherein the digitising means comprises an analogue to digital converter.

10. A security system according to claim 8 or claim 9 wherein the image processing means comprises memory means for storing the digitised images.

11. A security system according to claim 10 wherein the image processing means comprises clock means for determining the rate at which digitised images are stored in the memory means.

12. A security system according to claim 10 or claim 11 comprising means for comparing stored images to determine movement of the object or the position of illumination of the lighting means.

13. A security system according to claim 12 further comprising control means responsive to the comparing means for moving and/or varying the field of view of the image capture means.

14. A security system according to any preceding claim further comprising output power means responsive to the image processing means for altering the intensity of the illuminating means.

15. A security system according to any preceding claim wherein the image capture means includes infrared sensitive means or image intensifier means.

16. A security system according to any preceding claim wherein the processing means comprises a user interface.

17. A security system according to any preceding claim wherein the image capture means, processing means, lighting means and guiding means are housed together or separately.

18. A security system according to any preceding claim comprising playback means for recording the images for subsequent playback.

19. A method of alerting an intruder of their surveillance comprising capturing images of the intruder, processing the captured images to determine the position of the intruder and illuminating the determined position.

20. A method according to claim 19 wherein the position of the intruder is determined by comparing the captured images.

21. A method according to claim 19 or claim 20 wherein the position is illuminated with a focusable light source.

22. A method according to claim 21 wherein light source position information is pre- determined and the information is used to guide the illumination.

23. A method according to claim 22 wherein the light source is guided according to data from the captured images.

24. A method according to claim 23 wherein the light source is guided so as to minimise the distance between the light source position and the determined movement.