SURVEILLANCE SYSTEM

Abstract: An optical surveillance system for use, e.g. in detecting shoplifting in retail outlets is disclosed, in which a surveillance assembly provided with an optical detector (such as a closed circuit television camera) is mounted on a rail, permitting the optical detector to be selectively positioned, for example to reduce blind spots due to obstacles. The rail may, for example, be ceiling mounted, or may form part of furniture, freezer cabinets, etc. Image signals from the optical detector are carried by at least one electrical conductor along the rail and the system may have provision for transmission of control signals along the rail to the surveillance assembly.

Description: DESCRIPTION SURVEILLANCE SYSTEM The present invention relates to systems for remote optical monitoring, such as closed circuit television (CCTV) systems. It is well known to use electronic cameras connected to TV displays and/or recorders for remotely monitoring a surveillance environment. An example is the CCTV systems used by many major retailers for detection of shoplifting. It is clearly important for the cameras of such systems to afford the best possible view of their environment, and to this end it is well known to provide adjustable camera assemblies with remotely and/or automatically controlled motors for panning, (that is, rotating the line of sight of the camera about a vertical axis) tilting (rotating the line of sight about a horizontal axis) and zooming (magnifying or reducing the image) . Even so, it is very important to place cameras in appropriate positions, since obstacles may create "blind spots" which no adjustment of viewing angle can eliminate. Particular problems are created where obstacles to vision (such as shop furniture and displays) are rearranged in the surveillance environment, which may create new blind spots and make an existing arrangement of cameras inappropriate. An object of the present invention, therefore, is to create a flexible surveillance system which provides for the field of view of cameras to be maximised and for the elimination of blind spots. Since it is necessary for cameras to be securely and rigidly mounted if effects such as camera shake are not to spoil the image, it is a further object of the present invention to provide for such rigid mounting in a flexible surveillance system. The word "cameras" as used herein should be taken to refer to all types of electronic optical surveillance equipment including, for example, charge coupled devices (CCDs). In accordance with a first aspect of the present invention, there is provided an optical surveillance system in which a surveillance assembly having at least one electronic optical detector is mounted on an elongate rail so as to be selectively displaceable therealong to a desired location, the surveillance assembly having at least one electrical contact coupled to said detector which is in sliding engagement with an electrical conductor extending longitudinally of the track for the transference of electrical signals between the detector and said conductor. In accordance with a second aspect of the present invention, there is provided an optical surveillance system comprising: a surveillance assembly including at least one electronic optical detector; an elongate rail provided with at least one longitudinally extending electrical conductor; and means enabling the surveillance assembly to be mounted on said elongate rail such that it can be selectively displaced along the rail to a desired location, the surveillance assembly having at least one electrical contact for forming an electrical connection between said conductor and said optical detector. By mounting the surveillance assembly, including an optical detector, on a rail, the flexibility of the surveillance system is greatly enhanced. In conventional CCTV systems, cameras are typically wall or ceiling mounted using screws or bolts, so that adjustment of their position typically requires considerable labour in the removal of an existing mounting and the associated wiring, the making good of plaster, and the provision of electrical wiring to the camera*s new site and of suitable mounting holes. In the system in accordance with the invention, the camera may simply be moved along the rail, electrical connections being made via the conductor provided at the rail. Preferably, the elongate rail comprises at least one rail part which is provided, at or adjacent at least one of its ends, with means for mechanical and electrical connection to a further rail part. A modular system of rails is thus made possible, in which a number of straight rail parts may be combined to form a rail of a desired length, or straight and curved rail parts may be joined to create a rail which is shaped, for example, to circumnavigate obstacles or to conform to the perimeter of a room. It is even possible, in accordance with the present invention, to produce a branched network of rails. Preferably, the elongate rail comprises a metallic outer section defining an elongate internal space. Still more preferably, the at least one electrical conductor is disposed within the said internal space. In a particularly preferred embodiment of the present invention, the said outer section of the rail comprises a longitudinally extending slot which connects with the said internal space and the means for movably mounting the surveillance assembly on the rail comprise a rider adapted to extend through said slot and to engage with an inner surface of the rail. In this way, provision can be made for rigid but movable mounting of the surveillance assembly on the rail, while in addition the outer section of the rail can screen the elongate conductor from electromagnetic interference and/or can act as a conductor in its own right, completing the relevant circuit(s). It is preferred that at least one surface of the electrical conductor is exposed along a substantial part of the length of the rail. The contact of the surveillance assembly is thus allowed to make electrical connection with the electrical conductor. In a further preferred embodiment of the present invention, the elongate rail is provided with a plurality of electrical conductors which, in use, conduct-control signals to the surveillance assembly and/or image signals away from the surveillance assembly. Control and/or image signals may, in accordance with the invention, be multiplexed. The control signals may cause the optical device of the surveillance assembly to pan and/or tilt and/or zoom. Additionally or alternatively, the surveillance assembly may, in accordance with the present invention be provided with electrical propulsion means, controllable automatically and/or by signals received via the electrical conductor(s) for propulsion of the surveillance assembly along the rail. In accordance with a still further preferred embodiment of the present invention, the surveillance assembly may comprise a substantially hemispherical dome containing an electronic camera. In accordance with another aspect of the present invention, there is provided a display cabinet, freezer cabinet or item of furniture provided with a rail which comprises an electrical conductor and which is adapted to permit movable mounting of a surveillance assembly. In accordance with still another aspect of the present invention, there is provided a suspended ceiling system comprising a rail which has an electrical conductor and is adapted to permit movable mounting of a surveillance assembly. Specific embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawing which is a cross section through a camera assembly mounted on a rail, both forming part of a surveillance system in accordance with the present invention. In the Figure, the rail is labelled 2 while the camera assembly has reference numeral 4. The rail according to the illustrated embodiment of the invention comprises an elongate, hollow, aluminium extrusion which is substantially rectangular in cross section and which serves as a rail outer 5 having two upright walls 6, linked at their upper edges by a horizontal upper wall 8 and meeting, at their lower edges, respective horizontal lower walls 10 which are separated by a longitudinal slot 12. In the present embodiment of the invention, the slot 12 extends the full length of the rail and communicates with an internal space 11 defined by the rail outer 5. Within the rail 2 are a number of elongate conductors, extending the full length of the rail, which are insulated from each other and from the rail outer 5. In the present embodiment, these take the form of three metallic strips 14 embedded in downwardly open slots in an inner plastics extrusion 16. As the Figure shows, the plastics extrusion 16 is (neglecting the slots) rectangular in cross section, its upper surface lying adjacent the lower surface of the upper wall 8 of the rail outer 5. Lower surfaces of the metallic strips 14 are exposed, permitting electrical contact to be made thereto. The rail outer 5 may serve several functions:- i. it permits movement and, at other times, rigid retention of the camera assembly; ii. it can be used to screen signals conducted by the metallic strips 14 from electromagnetic interference. If necessary, e.g. in a high noise environment, the slot 12 may be covered by a metallic strip (not illustrated) to improve screening. Such a strip may be removable to permit motion of the camera assembly; iii. it can also serve as an electrical connection to the camera assembly 4. Thus in the illustrated embodiment, one metallic strip 14 may be used as a common power supply while the other two metallic strips carry image signals from respective cameras. A negative connection is provided through the rail outer 5. The conductors within the rail are terminated, at one end of the rail, in a screened connector such as a din socket, and are thereby connectable to a monitor, control unit or other electronic device. Turning now to the camera assembly 4, this is linked to the rail by a "T" shaped rider 20 formed of an insulating material and comprising an upright 22 projecting through the slot 12 and a cross bar 24 which lies within the rail outer 5 and is supported by upper surfaces of the horizontal lower walls 10 to support the camera assembly. Three upwardly open holes are provided in the upper surface of the cross bar 24, each containing a respective electrical contact piece 26. The positioning and spacing of the said holes is such that each of the electrical contact pieces lies directly below a respective metallic strip 14, and electrical contact between each contact piece/metallic strip pair is ensured by two resilient spacers 28 which are compressed between the lower surfaces of the cross piece 24 and the upper surface of the lower wall 10 of the rail outer 5 to upwardly bias the rider 20. Electrical signals from and, in some embodiments of the present invention, to the camera assembly 4 are conducted via wires 29 disposed within the rider 20 to the contact pieces 26, thence to the metallic strips 14, and so ultimately to control electronics/monitors etc. The camera assembly 4 includes, according to the present embodiment, a hemispherical dome 32, which is at least partly transparent, and a planar, disc shaped cover 34 which is rigidly linked to the lower end of the upright 22 of the rider 20. In the illustrated embodiment, the rider 20 and the cover 34 are integrally formed as a single plastics moulding. To mount the camera assembly 4, the rider 20 is inserted at an open end of the rail 2. Mechanical connection of the disc shaped cover 34 to the dome 32 is achieved by means of upper and lower walls 36,38 provided respectively at and adjacent the edge of the dome 32 and integrally formed therewith, between which the outer periphery of the cover 34 is sandwiched. The dome 32 can therefore be rotated relative to the cover 34. The camera 39 itself is attached to a mounting plate 42 which in turn is rotatably joined, along one edge, to the lower wall 38 of the dome 32. Being contained and enclosed within the dome, the camera is protected from physical damage. In a very simple embodiment of the present invention, the camera is manually movable for panning and/or tilting. In more sophisticated embodiments, stepper motors or other electronically controllable actuators may be provided to permit adjustment of the camera by any combination of panning, tilting and zooming. The necessary control signals may be transmitted via the conductors provided at the rail. Where it is necessary to carry control signals and image signals to and from several rail mounted camera assemblies, the number of conductors may be increased and/or the signals may be multiplexed. In one embodiment of the present invention (not illustrated) the camera assembly is provided with means for propulsion along the rail. This may, for example, take the form of a stepper motor which drives a propulsive wheel which, in turn, contacts a surface of the rail outer 5 to drive the camera assembly. It will be appreciated that the rail mounted camera assembly may take a variety of forms without departing from the scope of the present invention. For instance, in one embodiment it is envisaged that in place of a conventional CCTV camera, there will be provided a small (of the order of 3cm. across) charge coupled device. In this case, the means for adjusting viewing angle and the protective dome may be dispensed with. In one application, small cameras of this type would be used in conjunction with a rail mounted on a supermarket display or cabinet. As well as, or instead of serving as a security device, the invention could thereby be used to study the dynamics of the shopper population - the number of people passing the display, the number pausing to inspect it, etc. In another potential application, a rail would be mounted along the top of the "back to back" type of supermarket display in which goods are displayed on both long faces of an elongate cabinet. A single camera assembly with a panning facility would thereby be able to survey two supermarket aisles. In a particularly advantageous embodiment of the present invention, the rail could be part of a display stand, freezer cabinet etc. This could allow surveillance cameras to be straightforwardly mounted to survey virtually any part of a retail store. In still a further specific embodiment of the present invention (not illustrated) , the rail is mounted on or integrally formed with components of a suspended ceiling system. In particular, a rail may be provided on a downwardly facing surface of the tile spacers used in well known types of ceiling construction. An architect could thus specify that appropriate rails are to be incorporated into a building during installation of the ceiling. The resulting rail system could, if required, form a grid across an entire ceiling, maximising the flexibility of the resulting surveillance system.

Claims: CLAIMS 1. An optical surveillance system in which a surveillance assembly having at least one electronic optical detector is mounted on an elongate rail so as to be selectively displaceable therealong to a desired location, the surveillance assembly having at least one electrical contact coupled to said detector which is in sliding engagement with an electrical conductor extending longitudinally of the track for the transference of electrical signals between the detector and the electrical conductor. 2. An optical surveillance system as claimed in claim 1, wherein the elongate rail comprises at least one rail part which is provided, at or adjacent at least one of its ends, with means for mechanical and electrical connection to a further rail part. 3. An optical surveillance system as claimed in claim 1 or claim 2, wherein the elongate rail comprises a metallic outer section defining an elongate internal space. 4. An optical surveillance system as claimed in claim 3, wherein the electrical conductor is disposed within the internal space. 5. An optical surveillance system as claimed in claim 4, wherein the outer section of the rail comprises a longitudinally extending slot which connects with the internal space and the means for movably mounting the surveillance assembly on the rail comprise a rider adapted to extend through said slot and to engage with an inner surface of the rail. 6. An optical surveillance system as claimed in any preceding claim, wherein the elongate rail is provided with a plurality of electrical conductors which, in use, conduct control signals to the surveillance assembly and/or image signals away from the surveillance assembly. 7. An optical surveillance system as claimed in any preceding claim, wherein control and/or image signals are multiplexed. 8. An optical surveillance system assembly as claimed in any preceding claim, wherein the surveillance assembly is adapted to cause the optical detector to pan and/or tilt and/or zoom in response to control signals transmitted along electrical conductor(s) provided at the rail. 9. An optical surveillance system as claimed in any preceding claim, wherein the surveillance assembly is provided with electrical propulsion means, controllable automatically and/or by signals received via the electrical conductor(s) for propulsion of the assembly along the rail. 10. A display cabinet, freezer cabinet or item of furniture provided with a rail which comprises an electrical conductor and which is adapted to permit movable mounting of a surveillance assembly. 11. A suspended ceiling system comprising a rail which comprises an electrical conductor and is adapted to permit movable mounting of a surveillance assembly. 12. An optical surveillance system substantially as herein described with reference to, and as illustrated in, the accompanying drawings.

Inventors: DEMPSEY MAURICE, DEMPSEY, MAURICE
Applicants: DEMPSEY MAURICE, JON DAVID LIMITED, DEMPSEY, MAURICE
Application year: 1996
Main classification: G08B15
IPC codes: G08B13, G08B15