GB2323741A

GB2323741A - Transmission cable equalisation in video security/surveillance system

Info

Publication number: GB2323741A
Application number: GB9813118A
Authority: GB
Inventors: Scott Anthony Rhodes; Andrew William Jackson
Original assignee: Maxpro Systems Pty Ltd
Current assignee: Maxpro Systems Pty Ltd
Priority date: 1994-07-26
Filing date: 1995-07-26
Publication date: 1998-09-30
Anticipated expiration: 2015-07-26
Also published as: GB2323740A; GB9813114D0; GB2323739A; GB2323739B; GB2323740B; GB9813118D0; GB2323741B; GB9813117D0

Abstract

The video security system typically has a plurality of video cameras 70 and a plurality of monitors 24 and/or recorders for displaying and/or recording the output of selected ones of the video cameras. The transmission cable equalisation system 16 acts between a video camera selector 42 and a monitor 24 to equalise signal loss of respective transmission cables between the cameras 70 and the selector 42. A control computer 40 provides a conditioning signal input for the equalisation system for a particular transmission signal route between a particular video camera 70 and the selector 42.

Description

2323741 TITLE TRANSMISSION CABLE EQUALISATION. SYSTEM

FIELD OF THE INVENTION

The present invention relates to a transmission cable equalisation system for a video security system particularly, although not exclusively, envisaged for use in the monitoring of a plurality of locations, such as, in a building, for example, a casino.

BACKGROUND OF THE EWENTION

Hereinafter the term "VCR" will be used to denote any form of video signal recording and/or playback device (referred to as a WRD") and may include a video cassette recorder, or any optical or digital recording media suitable for recording video signals.

ID A typical video security system (VSS) includes a plurality of video cameras linked by transmission cables to a plurality of VCRs via a central control system. Because the cameras are at different locations the transmission cables are of various lengths and therefore introduce differing degrees of transmission loss. To overcome this in the prior art VSS equalisation of the video signals must be provided for each video camera. That is, there must be one equalisation unit for each camera.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an equalisation system which does not require a dedicated equalisation unit for each camera in a video security system.

According to the present invention there is provided a transmission cable equalisation system for a video security system having a plurality of video cameras and a video monitor andlor a VRD capable of operation in a record mode, the transmission cable equalisation system comprising:

a selector means connected between the video cameras and the video monitor andlor VRD for selecting video signals from the video cameras to be directed to the video monitor andlor VRD so that the video signal from one video camera is displayed on the video monitor andlor recorded on the VRD at a time; an equaliser means connected between the selector means and the video monitor andlor VRD for equalising the video signal from losses caused by the nature of the connection between each of the video cameras and the selector means; and, a control means connected to the equaliser means and the selector means, the control means having a reference means having data quantifying the losses between each video camera and the selector means, and the control means controlling the equaliser means to compensate for the losses associated with each video camera as its video signal is displayed on the video monitor andlor recorded on the VRD so that the condition of the video signal at the video monitor andlor VRD is equalised substantially independent of the characteristics of the connection between the video camera and the selector means os that only one equalisation means is required per video monitor and/or VRD instead of one equalisation means per video camera.

BRIEF DESCRIEPTION OF THE DRAWINGS An exemplary embodiment of the present invention will now be described with reference to the accompanying drawings in which:

Figure 1.1 is a block diagram of a video security system in which embodiments of the present invention may be used; Figure 1.2 is a set of waveforms showing the nature of insertion of a signal corresponding to text into the video signal; Figure 2 is a block diagram of an automatic VCR management system incorporated in the video security system; Figure 3 is a block diagram of a text insertion system incorporated in the video security system; Figure 4a is a block diagram of a prior art transmission cable equalisation system;

Figure 4b is a block diagram of a transmission cable equalisation system in accordance with an embodiment of the invention; Figure 5 is a block diagram of a video camera substitution system incorporated in the video security system; and, Figure 6 is a perspective view of a PTZ camera incorporated in the video security system shown with part of its housing shown in phantom.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to provide the context of the preferred embodiment a compleie video security system incorporating the preferred embodiment will be described.

Video Security System In Figure 1 there is shown a Video Security System (VSS) 10 comprising an Automatic 0 VCR Management System (AVCRMS) 12, a Text Insertion System (TIS) 14, a Transmission Cable Equalisation System (TCES) 16 and a Video Camera Substitution System (VCSS) 18.

The VSS 10 also comprises a plurality of fixed position cameras 20, a plurality of pantilt cameras 22, a plurality of video monitors 24, a plurality of VCRs 26, one or more standby VCRs 28 and a printer 30.

Typically, the VSS 10 is embodied in a computer system programmed to effect various routines equivalent to the systems 12, 14, 16 and 18 described herein.

Automatic VCR Management System As shown in figure 2 the AVCRMS 12 comprises a controller 40 and a selector 42.

Typically the controller 40 is in the form of a computer programmed to effect certain control functions as described herein. The controller 40 is connected to a remote control input 44 of each of the plurality of VCRs 26 and 28 and to an alarm output 46 of each of the VCRs 26 and 28. The controller 40 being capable of operating each of the VCRs M and 28 via the remote control inputs 44 and also being capable of sensing an alarm condition in each of the VCRs 26 and 28 via the alarm outputs 46. The controller 40 disabling any one of the VCRs 26 and 28 upon the occurTence of an alarm signal at the alarm output 46 of that VCR 26 or 28. The alarm condition becomes active when the VCR 26 or 28 is no longer in a record mode of operation. This can happen due to failure of the VCR 26 or 28, the VCR 26 or 28 being taken out of service such as to change a recording tape or to review a recorded tape or for repairs or the like.

The selector 42 is typically in the form of a matrix video switch in which any of its inputs 48 can be connected to any of its outputs 50, 52 and 54. The output 50 is connected to one of the monitors 24, and the outputs 52 and 54 are connected to record input 56 of two standby VCRs 28. Each of the VCRs 26 and 28 has a play output 58 wWch is connected to one of the video inputs of the selector 42 so that any video signal on any of the VCRs 26 or 28 can be displayed on the moriitor 24. The selector 42 is also connected via its inputs 48 to a plurality a video camera outputs 60.

Typicaffy, when one of the VCRs is detected as no longer being in a record mode of operation the controUer 40 causes an audible tone to be generated and an alarm message is caused to be displayed on the monitor 24. The message identifies which one of the VCRs 26 and 29 requires attention. The-controfler 40 simultaneously selects the next available one of the standby VCRs 28 and sets it to a record mode of operation via the remote control input 44 and controls the selector 42 to direct the video signal from the relevant video camera output 60 to that VCR 28 for recordai. The controller 40 also displays the identity of the video camera and the VCR 28 onto wl&h the video signal is now being recorded. Simultaneously, this information, along with the time and date and any other special messages, are printed out on the printer 30.

Text Insertion System As shown in Figures 2 and 3 the text inserter 14 is connected between the camera outputs 60 and the inputs 56 of the VCRs 26. The text inserter 14 is controlled by the controller 40 for the generation of text to be inserted into the video signal being recorded onto the VCR 26. The controller 40 controls the insertion of the text into the video signal at a location which is not ordinarily part of the visible part of the video screen once displayed. Typically, the text data is inserted into the horizontal line interval portion of the video signal (known as the "back porch" of the video signal).

The text inserter 14, particularly as shown in Figure 3, inserts the text 'generated by the controller 40 into the video signal and is recorded onto the VCR 26 during recording.

Due to the positioning of the text into the video signal the text does not overly the normal viewable portion of the video signal. DurinQ Dlayback of the video signal from the VCR 26 the text inserter extracts the text from the horizontal line interval of the video signal and reinserts it into the visible portion of the video signal so that the text can be seen on the monitor 24.

In the event that the text masks important parts of the video image on the moritor 24 the text inserter 14 can be controlled by the controller 40 to remove the text signal from the visible part of the video signal. Hence, the text recorded with the video image from the video cameras can be removed from the video image seen on the monitor in the event that it masks important parts of the video image.

It is important to note that the text is a data stream and not a video stream.

The recorded information can include time, date, source, equalisation, operator identification number, VCR identification number (since each VCR has its own efFective "fingerprint") and the like. This information is important in the scheme of irrefutably proving that the images recorded by the VCRs are the events which actually took place.

Transmission Cable Equalisation System As shown in Figures 1, 4a and 4b the transmission cable equaliser 16 is connected between the video camera output 60 and the text inserter 14 and is controlled by the controller 40.

The controller 40 has a conditioning signal (such as data).which characterises the nature of the connection between each of a plurality of video cam ems 70 and the selector 42. This conditioning signal takes into account any losses in. the connection between the camera 70 and the selector 42 due to the nature of a connecting cable including its transmission characteristics and its length. The conditioning signal is applied to the equaliser 16 so as to alter the gain of the equaliser 16 to allow for the losses inherent in the cable of each of the cameras 70.

Hence, only one equaliser 16 is required per monitor 24 rather than one equaliser 16 per camera 70. In the event that a new camera 70 is added to the video sewfity system 10 the equalising requirements for that camera 70 are input into the controller 40 for controlling the equaliser 16 when video signals from that camera 70 are being viewed on the monitor 24.

Video Camera Substitution System The cameras 70 in the video security system 10 include fixed position cameras 70a and pan/tilt cameras 70b (herein referred to as PTZ cameras 70b). Typically, a plurality of the fixed position cameras 70a are directed at fixed targets in an area and a lesser number of the PTZ cameras 70b are spread out amorigst the fixed position cameras 70a so that:he PTZ cameras 70b can substantially view the same field as the plurality off fixe.' position cameras 70a and to be used to view moving targets.

1 P The video camera substitution system 18 is a part of the controller 40 and has information concerning the relative positions of the PTZ cameras 70b and the fixed position cameras 70a. The information includes which of the PTZ cameras 70b are capable of covering the viewing areas of each of the fixed position cameras 70a. The controller 40 is connected to the PTZ cameras 70b via a communication control module 74 so that in the event that a particular one of the fixed position cameras 70a ceases to operate the controller can automatically determine which one of the PTZ cameras 70b can be used in its place and then control the PTZ camera 70b via its controller 76 to pan, tilt, zoom and focus to view the target viewed by the camera 70a which failed.

The WSS 18 also has a keyboard 78 connected to the controller 40 for allowing manual operation of the PTZ cameras 70b to view targets at the will of an operator of the keyboard 78. For this purpose the keyboard 78 conveniently includes a joy stick 80.

Multiple Rotation Video Camera The PTZ cameras 70b comprise a conventional camera 100 set on a transport mechanism 102 which is capable of rotating greater than 360 such as about 100T.

The camera 100 has a lens 110 which has a zoom facility and whose iris can be adjusted for changes in lighting levels.

The transport mechanism 102 has a housing 120, a fl-ame 122, a vertical axis drive unit 124, a horizontal axis drive unit 126 and control unit 128.

The housing 120 comprises,a cefling mount 140, a camera mask 142 and a transparent cover 144.

The ceiling mount 140 is typically fixed into a ceiling of a building (although it could be fixed to a wall or the Eke) so that the camera mask 142 and the transparent cover 144 are disposed below the ceding for allowing the camera 100 viewing within a room under the ceding. The ceiling mount 140 is typically made from anodised aluminium and is typicafly cyfindrical in cross section.

The camera mask 142 is attached to the fl-ame 122 and hence is able to rotate with respect to the ceiling mount 140. The camera mask 142 has a slot 150 which is dimensioned to allow the lens 110 to have a clear uninterrupted view through it. The slot 150 extends substantially from a horizontal position with respect to the lens 110 to a vertically downward position with respect to the lens 110. Hence, the lens can be moved from a horizontal.,ic\ving position to a vertically downward viewing posmon in the slot 150. The carnera mask 142 has a plurality of lugs 152 fo-, use in releasably attaching the- canc-,-.

mask 142 to clips 154 of two mask mounts 156 (one of which is shown) of the frame 122.

Typically, the camera mask 142 is coloured black so as to avoid reflecting light from it. The purpose of the camera mask 142 is to rotate with the camera 100 to mask observation of the viewing position of the camera 100. We have discovered that due to the darkness of the camera mask 142 the viewing position of the camera 100 is substantially unobservable.

The transparent cover 144 is attached to the ceiling mount 140 and located outside of the camera mask 142. The Purpose of the transparent cover 144 is to shield the camera 100 and the interior of the transport mechanism 102 from the elements. In this manner the cover 144 can be hermetically sealed to the ceiling mount 140 and the PTZ camera 70b can be located out doors.

The frame 122 comprises a top plate 160, two brackets 162 and 164 and a moveable platform 166. The top plate 160 is disposed horizontally and is able to rotate inside the housing.120. The brackets 162 and 164 are fixed to the top plate 160 and disposed vertically downwardly therefrom. The platform 166 is conveniently substantially U-shaped and pivotably attached to lower ends of the brackets 162 and 164. The pivotable attachment is via a pivot bolt 170 located through the bracket 162 and a pivot axle 172 located through the bracket 164 The platfonn 166 has a plurality of fixing slots 176 for mounting the camera 100 onto it. The fixing slots 176 are typically disposed parallel to the brackets 162 and 164.

The vertical a?ds chive unit 124 comprises a drive motor 180 with a drive cog 182, a toothed cog 184 and a toothed belt 186. The toothed cog 184 is releasably secured to the ceding plate 140, such as by holes (not shown) in a top 188 of the toothed cog 184. The drive motor 180 is attached to the top plate 160 of the frame 122. The drive motor 180 is driven by electrical signals from the control unit 128 for producing rotation of the drive cog 182. Since the toothed cog 184 is stationary with respect to the ceiling mount 140 rotation of the drive cog 182 causes the fi-ame 122 to rotate within the housing 120. The speed of rotation of the fi-ame 122 is dependent upon the speed of the drive cog 182 and the angle of rotation is dependent upon the time for which the drive motor 180 receives signals from the control unit 128.

The horizontal axis drive unit 126 comprises a drive motor 200 with a drive cog 202, a toothed cog 204 and a toothed belt 206. The toothed cog 204 is fixed to the platform 166 so that rotation of the toothed cog 204 produces pivoting of the platform 166. The drive motor 200 is mounted onto the bracket 164 and the drive cog 202 drives the toothed belt 206 for driving the toothed cog 204. The toothed cog 204 has a stop 210 located in it for 35 limiting the pivotable travel of the platform 166 so as to protect the camera 1 dama,,:,,c which may otherwise occur. The drive!-,-oto,- 200 is controlled by signals frorn the control unit 128 for pivoting the lens 110 of the camera 100 in the slot 150 of the camera mask 142 as indicated by arrow 212. Typically, the horizontal drive unit 126 allows pivoting of the platform 166 from substantially horizontal to substantially vertical.

The control unit 128 has a horizontal control unit and a vertical control unit. Each of the horizontal and vertical control units has a position sensor device for detem-dning the position of the toothed cogs 204 and 184 respectively. Typically, the position sensor device is a hole located in the toothed cog 184, 204 and the control unit are able to count up and down from the position of the holes for deterinining the movement of the cogs 184, 204.

We have discovered that in order to quickly move the camera 100 from one viewing position to another, and to keep accurate count of the actual position of the camera 100 there are some physical constraints which must be allowed for. Principally this involves controffing the drive motors 180 and 200 so as not to exceed maximum rates of acceleration and deceleration and not to exceed a maximum speed. Also, and most 15 importantly, we have discovered that the drive motors 180 and 200 need to be controlled so as to have a period of substantially zero acceleration between periods of acceleration and deceleration. This is required because otherwise there is a very large change in the momentum of the transport mechanism 102 required in switching ft6m acceleration to deceleration- The result of such abrupt changes in the acceleration of the transport 20 mechanism is the control unit 128 looses count of the position of the toothed cogs 184 and 204 and thus inaccuracies in the location of the camera 100 are experienced.

Hence, the control unit 128 is programmed to limit the maximum rate of acceleration and deceleration of the drive.motors 180 and 200 and to provide a ininimurn period of substantially zero acceleration between periods of acceleration and deceleration. The control unit 128 then uses these limits to drive the transport mechanism 102 between viewing locations whilst accurately reaching those viewing locations.

The PTZ camera 70b is, in one embodiment, connected to the remainder of the video sennity system 10 by a plurality of cables. The cables carry video signals, control signals and electrical power. In order to allow the transport mechanism 102 to rotate through greater than 36T the cables are arranged in a loop so that they can be twisted three or four times without damage. This allows the vertical axis drive unit 124 to rotate the platform 166 through a total angle of about I OOT.

The control unit 128 has a counter to count up and down depending upon the position and motion of the drive motor 180. Typically, the counter increments the count by 4000 for each 360 of rotation. By such counting the control unit 128 can be aware of how far the transport mechanism 102 is away from its ultimate end of travel. The control unit 128 is programmed such that when the camera 100 is not engaged in tracking a moving event it unwinds to proximate the middle of its 1000 of angular travel. In this way the chances of the transport mechanism 102 reaching its ultimate angular travel is greatly reduced.

In another embodiment slip rings are used for each cable, wich then allows the vertical axis drive unit 124 to rotate the platform 166 through an infinite angle of rotation.

Hence, the PTZ camera 70b can be used to follow a target even where the target travels th.rogh an angle of greater than 360 and hence the chances of the PTZ camera 70b being run up against its firnits of rotation are greatly reduced and the ability to follow a target as it moves through an area is greatly enhanced.

SWITCHING BETWEEN VIEWING LOCATIONS The controller 40 controls the PTZ cameras 70b to move back and forth between a plurality of viewing locations so that the camera can monitor a plurality of fixed locations.

The PTZ camera 70b comprises a video lens 110 and camera 100, a zoom Control, a focus controI, a pan control, a tilt control and a camera position controller (included in the controller unit 128 - Figure 6).

The video lens and camera is settable to view a target. For example, the target could be a person at a gaming table in a casino. The video lens has a machine readable signal corresponding to its zoom and focus setting. The zoom and focus controls allow adjustment of the zoom and focus of the video lens and camera.

The pan and tilt controls control the pan and filt of the video lens and camera about substantially vertical and horizontal axes for viewing targets typically in a region of 360' about the PTZ camera. The pan and flit controls each have a machine readable signal corresponding to their settings.

The camera position controller is coupled to respond to the machine readable signals from the video lens and camera, the zoom and focus controls and the pan and tilt controls. The camera position controller controls the settings of the video lens, the zoom and focus controls and the pan and tilt controls for viewing the targets within the viewing region automatically under the instruction of an operator.

The camera position controller has a first memory register (such as located in a computer) to store the values of the macifine readable signals corresponding to the settings of the video lens and camera, the zoom and focus controls and the pan and tilt controls. The first memory register stores the values of the settings correspondifig to a first location of temporary interest, such as the location of a handbag. The camera position controller also has a second memory register for stonng the values corresponding to a second location o'.

-10 temporary interest, such as the location of a suspected felon who is believed to be about to steal the handbag.

The camera position controller has a toggle button which is operable to cause the values of the settings of the video lens and camera corresponding to the second location to be recalled from the second memory register and loaded into the video lens and camera whilst the values corresponding to the first location are removed from the video lens and camera and stored into the first memory register. The toggle button is also operable to cause the values of the settings to be updated in the event that one of the targets moves or the operator chooses a new target of temporaryinterest. The toggle button also allows for switching viewing between the two locations of temporary interest. By so doing the camera position controller can control the video lens and camera to view between two (or more) desired locations without continual manual re-adjustment of the video lens, the zoom and focus controls or the pan and tilt controls.

In use, an operator can set a desired location of temporary interest to be monitored by the video lens and camera. The video lens 110 and camera 100 can then be manually moved to view another location of temporary interest and the -video lens I 10 and camera 100 can then by toggled between the two viewing locations by the operation of the toggle button.

To achieve this the operator first manually pans and tilts the video lens 110 and camera to view a first target at a first location of temporary interest Then the operator manually adjust the zoom and focus of the video lens 110 and camera 100 for the target.

Ile operator then presses the toggle button to store the values of the settings of the zoom and focus controls and the pan and tilt controls into the first memory register. The operator can then manually control the zoom and focus controls and the pan and tilt controls for setting the video lens 110 and camera 100 to view a second target at a second location of temporary interest. When the operator again presses the toggle button the values of the settings corresponding to the second location are stored into the second memory register and the values of the settings corresponding to the first viewing location are recalled from the first memory register and used to control the video lens 110 and camera 100. Once the values are exchanged the camera position controller controls the zoom and focus controls and the pan and tilt controls to reposition the viewing location of the video lens 110 and camera 100.

The location of the targets can be updated by manually adjusting the zoom and focus controls and the pan and tilt controls for the video lens I 10 and camera 4 00 and pressing the toggle button again to update the values stored in the relevant memory register. That is, when no manual adjustments are made to the settings of the video lens 110 and camera the toggle button causes toggling between the two locations of ternporary interest, but when manual adjustments are made to the settings of the video lens 110 and camera 100 the toggle button causes updating of the values of the settings..

Thus a PTZ camera can be used to monitor two fixed locations within a viewing area, as well as to operate under fully manual control. Hence, the PTZ camera of the present invention is the equivalent of two fixed position cameras which can be set to view locations of temporary interest and which can be set to new locations of temporary interest as desired by an operator. That is, the PTZ camera function as the equivalent of two dynamically positioned fixed cameras. Also, the change tirne in changing between the two viewing locations is about the same as the time involved in changing viewing between two fixed cameras (that is, less than 1 second).

Typically, the camera position controller is configured to set the last viewing position as being any position at wlich the operator stopped for greater than, say, I second.

This facility could be configured into a logical data stack so that the last, say 10, viewing positions could be stored in memory are recalled sequentially (this feature is herein refer-red to as "back up").

Modffications and variations such as would be apparent to a skill addressee are considered within the scope of the present invention. For example, the camera position controller could have a single switch to control toggling between two camera locations. Also, the iris setting of the video lens and camera could also be controlled.

0 a

Claims

CLAIMS:

1. A transmission cable equalisation system for.. a video security system having a plurality of video cameras and a video monitor andlor a VRD capable of operation in a record mode, the transmission cable equalisation system comprising:

a selector means connected between the video cameras and the video monitor andlor VRD for selecting video signals from the video cameras to be directed to the video monitor andlor VRD so that the video signal from one video camera is displayed on the vido monitor andlor recorded on the VRD at a time; an equaliser means connected between the selector means and the video monitor andlor VRD for equalising the video signal from losses caused by the nature of the connection between each of the video cameras and selector means; and, a control means connected to the equaliser means and the selector means, the control means having a reference means having data quantifying the losses between each video camera and the selector means, and. the control means controlling the is equaliser me= to compensate for the losses associated with each video camera as its video signal is displayed on the video monitor andlor recorded on the VRD so that the condition of the video signal at the video monitor andlor VRD is equalised substantially independent of the. characteristics of the connection between the video camera and the selector means so that only one equalisation means is required per video, monitor andfor VRD instead of one equalisation means per video camera.

2. A transmission cable equalisation system substantially as hereinbefore described with reference to and as shown in the accomp4nying drawngs.

3.

Any novel feature or combination of features disclosed herein.