Field of Invention

The present invention relates to the field of surveillance systems. Particularly an surveillance system which employs a camera equipped mobile surveillance device and which relies on lighting devices for providing system communication and positioning information via for example visible light communication is proposed. The invention further includes a lighting device and a mobile surveillance device for such a surveillance system.

Background

Systems and devices for application of RF communication, devices integrated with light sources for position detection of mobile devices, for performing control of components of a light system and for communication with mobile and stationary devices are known in the art. Buildings, retail stores, libraries, airport terminals, public building, office building, factories are illuminated by lighting devices which increasingly use light emitting diodes (LEDs) . LED based lighting devices are particular suited for modulation and therefore provide an inherent capability of communicating information by means of visible light communication (VLC) .

Indoor positioning applications relate to systems and methods for estimating a mobile device's position within a confined space, for example a building. Radio wave based indoor positioning applications encounter specific difficulties, which affect the availability and precision of satellite based positioning systems . Ultrasonic based and also light based systems are proposed as specific indoor positioning systems for providing position information to location based applications in the areas of marketing, entertainment, logistics or management. As an example, a retail enterprise may use a VLC based system to alert a customer via his camera equipped mobile device to a particular item in a store and provide a navigation function for guiding the customer through a maze of aisles situated between shelves to the particular item. For a management application in the same retail store, the mobile device of the customer and its location are tracked with time and corresponding data is generated which describes how the customer moves through a store, where they spend their time in the retail store, in order to improve store layout, product arrangement and placement of merchandize displays .

Indoor positioning systems rely advantageously on different technical principles than systems for determining position information such as satellite based positioning systems. Radio waves passing through construction material of walls undergo significant losses and suffer from multi-path propagation effects. Global navigation Satellite systems (GNSS), such as GPS, are generally unsuited for indoor navigation. Techniques using evaluation of received signal strength indication (RSSI) from radio transceiver, for example Bluetooth™ or wireless local area network (WLAN - WiFi™) access points may fill the gap left by traditional GNSS systems and provide a positioning accuracy up to some decimetres. Ultrasonic based techniques which rely on inaudible acoustic waves received by microphones can also be used to estimate an indoor position, nevertheless a limited range and lack for suitable devices requires significant funding in order to implement a positioning system based on ultrasonic communication techniques.

In current buildings multiple infrastructure elements exist in parallel. Besides a lighting system, an emergency lighting system, a wired communication system, a wireless communication system, a fire alarm system, an air conditioning system (heating, ventilation and air conditioning - in the following abbreviated as HVAC) all might be implemented with separate wiring and separate control devices in order to implement their different functions. This may also include security and surveillance systems which link cameras, motion detectors, control devices which are required to cover an entire building and each include their separate communication network to a central control center.

For surveying a building with many corridors and numerous rooms efficiently, large numbers of cameras or sensors need to be installed and linked. Thus high costs are incurred.

Further severe limitations of known security systems originate from their static layout. Cameras and other sensors are installed at fixed positions with a predetermined and limited surveillance area and may at best be installed on a remote controlled moveable platform like an arm of a robot for changing their surveillance coverage. However covering an entire building still requires many sensors. A possible sensor failure can only be taken account of by covering sensible areas with multiple sensors. Moreover the presence of camera sensors even when not in use may raise a feeling of uncertainty with visitors and staff in the building, even when the sensor is not active due to its sheer presence.

Thus temporary surveillance systems for confined spaces may be improved with respect to high cost efficiency on one hand and high adaptability to changing security scenarios on the other hand .

In order to physically install the devices belonging to building infrastructure, a process of commissioning is to be performed. Commissioning is the process of associating a physical position of an installed building technology device with a logical address such as a network address according to a applicable network protocol. It is an essential step during the installation and setup of an intelligent lighting system, for example a light management system. The commissioning step typically requires electric, electronic and/or software expertise by the staff installing the light system. During the commissioning process dedicated software is used to assign an address and/or a geographical position to a building technology device . Commissioning is a costly process during installation due to the needed staff qualification.

For semi-automated commissioning the building technology device to be commissioned generally needs to be equipped with a communication component that is able to communicate with a commissioning tool, usually by means of wireless communication. The commissioning tool can then be used to read or set an address for the building technology device and to read or configure operating parameters. Moreover, the commissioning tool can associate a position with the address of a building technology device.

However, this type of commissioning requires a peer-to-peer- communication between the commissioning tool and each building technology device and also rises extra costs as the building technology device not only needs to be provided with the communication component, but also with additional means to allow control and configuration by a wireless commissioning functionality. A definition of a location of a building technology device, e.g. based on a floor, building or room plan still needs to be performed manually.

The invention aims at resolving these problems and to furthermore improve commissioning of a building technology device .

Summary of the invention The surveillance system according to claim 1 provides an advantageous solution.

A surveillance system for adaptable surveillance comprises at least one lighting device including a communication unit and at least one mobile surveillance device including a mobile communication unit for communicating with the communication unit of the at least one lighting device. The at least one mobile surveillance device is configured to navigate based on data received from the at least one lighting device and including information that allows to determine a current position of the surveillance device.

The mobile surveillance device offers the advantage of moving the surveillance device to different accessible locations in a given surveillance space. The surveillance system dispenses with the need of installing numerous surveillance devices covering the entire surveillance space or even providing key areas with multiple coverage. Not only a large number of static surveillance devices can be reduced to a number or even a simple mobile surveillance device, the cost for dedicated cabling between units of the surveillance system is also reduced. The surveillance system is also capable to react in a flexible manner to different threats and presents a much more challenging task to intruders. Even more advantageous, by reacting to a triggered alarm with moving a mobile surveillance device to verify the reported intrusion, an independent verification of an alarm is provided which under some jurisdictions is a prerequisite for involving public security authorities. The number of false alarms may therefore be reduced by the additional verification capabilities of such flexible surveillance system. A further advantage is that other security infrastructure systems such as emergency lighting, fire alarm can be integrated which further reduces the overall infrastructure cost. By precisely locating the mobile surveillance device, in particular with modulated light, an effective handling of multiple mobile surveillance devices in a confined space and effective collision avoidance with static obstacles in the surveillance space becomes possible. Advantageous embodiments of the autonomous surveillance system are defined in the dependent claims .

The surveillance system of a preferred embodiment comprises the at least one communication unit being configured to use for communicating with the mobile communication unit at least one of visible light communication, infrared light communication, ultraviolet light communication and wireless communication.

The available lighting network for the surveillance provides the system infrastructure for operating with mobile surveillance devices such as autonomously flying aerial vehicles (intelligent flying drones), for example quadrocopters or ducted fan aerial vehicles, robots driving on the ground or robots travelling at rails below the ceiling. The mobile surveillance device can be equipped with camera sensors. The autonomously moving surveillance device relies for navigation and for transmission of acquired surveillance data such as images, videos (image streams), for transmission of control signals, status signals on the lighting device network installed in the space under surveillance. The surveillance system of the invention accordingly has the capability to act independent from external input by an operator in order to react to an intrusion. Thus the surveillance system is capable to autonomously adapt its surveillance coverage to changing surveillance requirements . The term autonomous is to be understood as having the ability to act independently from operator instructions and based on its own set of rules and right.

The surveillance system according to an advantageous embodiment includes the at least one mobile surveillance device further comprising a sensor unit including at least one of an optical sensor, an acoustic sensor, a smoke detector, a gas detector, an humidity sensor, an accelerometer, a magnetometer, a relative pressure sensor and a temperature sensor.

The accelerometer provides in particular the capability to determine an optical sensor viewing point and viewing angle in addition to support stabilizing the mobile surveillance device. The magnetometer may also assist the corresponding tasks as the accelerometer in addition to support determining the actual direction for navigation of the mobile surveillance device. The relative pressure sensor (barometric sensor) assists the mobile surveillance device in determining a relative travel altitude relative to a floor level or a ceiling level of a building on at least a coarse scale. The cited sensor technologies of the sensor unit support fulfilling the surveillance task as well as support navigation of the surveillance device in a surveillance space. The cited and further sensor technologies may assist the mobile surveillance device to navigate back into a coverage area of the at least one lighting device and hence into a zone in which communication via VLC is possible if the mobile surveillance device left the coverage area of the lighting device .

An advantageous surveillance system of an embodiment comprises at least one base station for the mobile surveillance device, The at least one base station is configured to perform at least one of sheltering the mobile surveillance device and charging an energy storage unit of the mobile surveillance device.

The surveillance system of a preferred embodiment further additionally comprises at least one static surveillance device. A static surveillance device may combine the double functions of providing a control of the lighting of the surveillance space and detecting any intruder into the surveillance space, for example by motion detection. A typical example of the at least one static surveillance device may be a motion detector unit used for example for lighting control, air conditioning control or in security systems.

The surveillance system according to an advantageous embodiment further comprises a surveillance control unit which is configured to determine if a motion reported by for example such a static surveillance device is within a predefined time period, and if the reported motion is within the predefined time period, to control the mobile surveillance device to move to a location suitable for investigating the reported motion. Such predetermined time period might be for example non working hours in office buildings, stores or the like. An advantageous surveillance system has the lighting device configured to radiate light in a frequency spectrum outside the visible light spectrum, and the least one sensor unit is configured to obtain light in the frequency spectrum radiated by the lighting device. Thus the communication between the mobile surveillance device and the static elements of the surveillance system will not be perceived by an intruder, at least not without additional technical means.

An embodiment of the inventive surveillance system comprises a data storage device configured to store at least one of map data, lighting device location information and mobile surveillance device position information. The map data for autonomous operation of the mobile surveillance device can be stored centrally on a data storage unit to be readily accessible and updateable, for planning of flight and movement paths for different mobile surveillance devices which avoid interference with other mobile surveillance devices as well as coordinating of individual surveillance mission profiles. The data storage device may be a local server or a remote server such as a cloud server.

An advantageous embodiment of the surveillance system includes the mobile surveillance device including a sensor unit which is configured to optically inspect at least one of an emergency lighting unit and a smoke detector unit, and the surveillance system further comprises a surveillance control unit configured to control the mobile surveillance device to move to a location of the at least one emergency lighting unit or smoke detection unit .

A lighting device (luminaire) for use in a surveillance system for adaptable surveillance comprises a communication unit configured to transmit data including information for determining a current position of a surveillance device for a time period in which the surveillance device is present in an area illuminated by the lighting device. The lighting device of a further embodiment of the surveillance system transmits data including beacon identification information changing with time. The change of beacon identification as well as only transmitting the data including information for determining a current position of a surveillance device for a time period improves the security of the system. Transmitting the data only for a time period when the data is required also reduces negative effects on people suffering from epilepsy or migraine due to intensity modulated lighting, or possible interference with dimming of the lighting device .

A lighting device for use in a surveillance system for adaptable surveillance comprises a communication unit which is configured to transmit data including information for determining a current position of a mobile surveillance device, and to receive surveillance data from the mobile surveillance device. Thus the lighting device provides an interface for a mobile surveillance device to the static backbone of the autonomous surveillance system. A mobile surveillance device for use in a surveillance system for adaptable surveillance comprises a mobile communication unit configured to receive data from a lighting device including information that allows determining a current position of the mobile surveillance device and at least one sensor unit. The mobile communication unit is further configured to transmit data acquired by the sensor unit to the lighting device.

The mobile surveillance device for use in a surveillance system for adaptable surveillance of an advantageous embodiment includes the mobile communication unit configured to receive and transmit the data using at least one of visible light communication, infrared light communication, ultraviolet light communication and wireless communication.

According to a further aspect of the invention, a mobile surveillance device comprises a mobile communication unit configured to receive data from at least one lighting device, the data including identification information for uniquely identifying the lighting device, and a processing unit configured to associate the received identification information with a position information of the mobile surveillance device when receiving the data identification information. The mobile surveillance device significantly improves the configuration phase of a lighting system. The movable surveillance device moves to a location of an installed lighting device, determines the identity of the lighting device and associates the determined identity with the location information. Thus in an indoor as well as in an outdoor environment, the identity of a lighting device, in particular an operation address, a bus address or network address, and the corresponding location can be gathered in convenient and efficient manner.

The features discussed above may be combined within scope of the appended claims which define the invention.

Brief description of the figures

A preferred embodiment of the invention is given in the following detailed description which is supported by the attached figures, in which

Fig. 1 provides a scenario for an autonomous camera surveillance system according to a preferred embodiment employed in an indoor environment, Fig. 2 shows a scenario of a surveillance system in an indoor environment according to prior art,

Fig. 3 provides general steps of employing the autonomous camera surveillance system in a flowchart, and

Fig. 4 shows a block diagram of an autonomous camera surveillance system according to a preferred embodiment.

Detailed description Fig. 1 provides an overview of a scene of an autonomous surveillance system 1 showing some of the structural elements constituting the autonomous surveillance system. The surveillance space 9 depicted in fig. 1 corresponds to a portion of a building. The depicted building interior shows elements of a lighting system including lighting devices 4 mounted in a ceiling and PIR motion detection sensors 6 at suitable locations on the walls . The PIR motion detection sensors 6 are spatially arranged in order to provide motion detection coverage of the interior of the building. At least some of the lighting devices 4 include a communication unit adapted to communicate via visible light communication. The infrastructure of the building further includes "Heating, Ventilation & Air Conditioning" (HVAC) - devices 7 which also may be controlled based on own PIR presence sensors integrated into the HVAC devices 7.

The mobile surveillance device 2 according to an embodiment as shown in fig. 2 may be an aerial vehicle in form of a quadrocopter carrying a sensor unit in form of a camera. The hovering capability of the aerial vehicle and its capability to manoeuvre in the restricted space of a building provide a suitable mobile and highly flexible basis for a camera in the autonomous surveillance system 1.

The invention is described with reference to an autonomous camera surveillance system for a building. The detailed functions for the autonomous surveillance system are manifold. By combining the mobile surveillance devices 2 and the lighting devices 4 for surveillance system backbone connection, the autonomous surveillance system 1 may detect any activity in the surveillance space 9 representing an area of interest and may notify a facility management on any logged event in the surveillance space 9. This function can be fulfilled without need of further infrastructure but using the lighting system which has to be installed anyway.

A further detailed use scenario of the autonomous surveillance system 1 employs a mobile surveillance device 2 using a sensor unit which acquires an extended parameter set including at least one of optical images, humidity values, gas concentration values, temperature values for example. The mobile surveillance device 2 performs scheduled runs through aisles during closing hours of a supermarket, offices, ... to collect respective data. The data collected during the scheduled runs provides information on the state of the doors of refrigerators, in particular if they are properly closed, if the humidity and/or temperature are within specified limits, or if an ethylene concentration in a flower department is within specified concentration limits .

Fig. 2 depicts the view of a surveillance space 9 situated within a building and corresponds to the view as depicted in fig. 1. However, the view of fig. 2 includes devices of known building infrastructure for comparison purposes. The exemplary building might be an office building including lighting infrastructure, HVAC infrastructure and a security alarm infrastructure .

The lighting in the depicted example includes lighting devices 4 mounted at the ceiling which are switched between an ON state and an OFF state by motion detector units 6 which are mounted at the walls of the corridors or rooms.

The air condition infrastructure is also controlled by using signals provided by motion detectors included in the HVAC units 7 mounted high on the walls of rooms which detect the presence of a person in the corresponding room.

Furthermore the depicted exemplary infrastructure also includes a conventional security surveillance system which employs motion detector units 11 for the detection of intruders and employs cameras 12 for acquiring visual images from the monitored surveillance space 9.

In addition to the depicted security surveillance system, air conditioning system and lighting system, further systems such as a fire alarm system, a parallel emergency lighting system could exist with parallel sensor devices and actuating devices and/or information display devices could be installed within the surveillance space 9.

When comparing the required physical infrastructure according to a preferred embodiment of the inventive autonomous surveillance system 1 as shown in fig. 1 with the corresponding scenario shown in fig.2, the advantages of the inventive surveillance system become evident.

Mobile surveillance devices 2 movable to any accessible position in the surveillance space 9 and adapted to monitor the surveillance space 9 from different angles avoid the requirement of fixedly installing a dense network of cameras 12 and the corresponding cabling. The costs for hardware, installation of hardware and maintaining the hardware are significantly reduced. During periods when surveillance can be dispensed with, no cameras 12 are visible and accordingly no discussion of admissibility of surveillance cameras 12 may arise .

The inventive autonomous surveillance system 1 is particularly suited for refitting into existing buildings due to the lower proportion of static installation when compared to conventional surveillance systems and reuse of existing motion detection units 6 for security purposes .

Thus a dedicated motion detector network for controlling the security surveillance system 1 is dispensable, as the lighting systems motion detector units 6 fulfil the motion detection task also.

The lighting devices 4 installed throughout the building of fig. 1 also include a VLC capability and thus are able to provide a communication capability to the autonomous surveillance system 1. Accordingly, a dedicated security system cabling for communicating the surveillance results from the sensor units is not necessary, and furthermore the communication between sensor units and the backbone of the autonomous surveillance system 1 benefits from a more flexible communication network enabling mobile communication and whose layout may more easily be designed to include a second backup communication link. Even more advantageous, an office building equipped with the autonomous surveillance system according to a preferred embodiment can be adapted to changing layout of rooms, for example when changing to another tenant without the respective high costs of changing room layout and changing the fixed infrastructure of a fixedly installed conventional surveillance system at the same time. According to the inventive surveillance system 1 an adaption of map data, drone coordination data may suffice to take account of a different spatial layout of the surveillance space 9 and different security requirements of the new tenant.

Fig. 3 provides a flowchart with general steps of employing the autonomous camera surveillance system 1 according to a preferred embodiment. The autonomous camera surveillance system 1 starts in step 1 with a step of detecting a motion in the monitored surveillance space 9. If for example one of a plurality of PIR motion detectors 6 of the lighting system in the surveillance space 9 detects a motion and issues a corresponding detection report including a movement location to the surveillance control unit 15, the autonomous camera surveillance system 1 proceeds to a next step S2. In the step S2 the surveillance control unit 15 acquires an actual time and compares the acquired actual time with preset time limits. If the acquired actual time is between first time and second time, the surveillance control unit 15 determines that movement in the monitored space is admissible and proceeds to step S3. In step S3 a respective lighting device 4 is switched in order to illuminate the portion of the surveillance space 9 in which at least one of the PIR motion detectors 6 reports a movement. In case the acquired actual time is before the first time limit or after second time limit, the surveillance control unit 15 determines that the detected movement may be due to an intruder violating the surveillance space 9. In the case of determining an intruder invading the surveillance space 9, the surveillance control unit 15 proceeds to a step S4 of investigating the reported movement. In the step S4 the surveillance control unit 15 starts to investigate the reported movement. The step S4 of investigating the reported movement according to the preferred embodiment includes for example issuing a surveillance task to the mobile surveillance device 2 for moving to and reconnoitring the reported movement location. The mobile surveillance device 2, for example an autonomously operating drone equipped with a camera, starts or is summoned from a routine flight pattern, transfers autonomously to a sensing location 5.2 suitable for optically investigating an area around the reported movement location, and uses its camera to search for a possible intruder which might have caused the received detection report. The autonomously operating mobile surveillance device 2 navigates through the surveillance space 9 based on VLC capable lighting devices 4. In particular the present position of the mobile surveillance device 2, a planned movement path 5.1, 5.2, 5.3 of the mobile surveillance device 2 including the sensing location 5.2 with respective imaging directions for the camera are determined using positioning information and direction information determined from VLC signals emitted from the lighting devices 4. Furthermore the mobile surveillance device 2 transmits image information acquired by its camera via VLC to the lighting devices 4. The lighting devices 4 relay the acquired image information to the surveillance control unit 15 for further processing . The surveillance control unit 15 evaluates the received image information and determines if indeed an intruder into the surveillance space 9 is the reason for the motion detection reported in step SI. If in the step S5 an intruder is confirmed, the method proceeds to step S6 and starts a suitable action in response to the detected and confirmed violation of the surveillance space 9. A suitable action may in particular be starting an acoustic alarm, triggering an in depth investigation by security personnel, issuing a security report to a law enforcement authorities, ... If in step S5 of confirming an intruder, the result of the movement investigation step S4 is assessed to be no violation of the surveillance space is to be determined, the method returns to step SI of detecting a motion.

Step S2 is described above to merely compare an actual time if it is within a time period between the first time and the second time. However a more complex evaluation of the detection time, the detection location and a set of rules which define the requirement of investigating in response to a movement report may be executed in step S2. The set of rules may regard office hours in a business building, regular patrol patterns for mobile devices 2, map data. The set of rules can be stored in central data storage unit 23 which can be accessed by the surveillance control unit 15. The central data storage unit 23 may also be implemented as a cloud server or as distributed network of servers .

In the following description of a preferred embodiment, the term 'interface' is used. The term interface describes a shared boundary across which two separate components of the surveillance system exchange information. The information exchange can be between software, hardware, peripheral devices and combinations of these. Hardware interfaces exist in many of the components such as the various buses, storage devices, other I/O devices, etc. A hardware interface is described by the mechanical, electrical and logical signals at the interface and the protocol for sequencing them, often also called signaling .

Fig. 4 shows a block diagram of an autonomous camera surveillance system 1 according to a preferred embodiment. The autonomous camera surveillance system 1 is capable to perform surveillance of the surveillance space 9. The surveillance space 9 includes a lighting system which is controlled based on the signals of numerous PIR motion detector units 6. For sake of simplicity of description a single PIR motion detector unit 6 is depicted in fig. 4. The PIR motion detector unit 6 may directly communicate with a plurality of lighting devices 4.1, 4.2, 4.3 as depicted in fig. 4 or may be linked to a central lighting control unit 19. The PIR motion detector unit 6 according to the preferred embodiment transmits a motion detection report to a lighting control unit 19. The lighting control unit 19 performs the known function of switching the lighting devices 4.1, 4.2, 4.3,... into an ON state for emitting light, an OFF state for not emitting light and further taking into account the time of motion detection, an ambient light level, a required light level when a dimming function is available for at least some of the lighting devices 4.1, 4.2, 4.3.

The plurality of lighting devices 4.1, 4.2, 4.3 is distributed in the surveillance space 9 for illumination purposes. At least some of the lighting devices 4.1, 4.2, 4.3 have a VLC communication capability. In particular the lighting devices 4.1, 4.2, 4.3 with the VLC capability radiate modulated light 3 which includes a positioning signal and a downlink signal to a mobile surveillance device 2. The downlink signal may in one embodiment comprise data defining a surveillance task for the mobile surveillance device 2. A surveillance task may comprise an area or location of the surveillance space 9 which is to be monitored or more closely examined.

The mobile surveillance unit 2 is capable of autonomously moving in the surveillance space 9. The mobile surveillance device 2 may be a ground vehicle, an aerial vehicle or a unit which moves along rails, for example rails mounted below a ceiling of a large office area filled with cubicles. The mobile surveillance device according to a preferred embodiment is a fully or partially autonomously operating aerial vehicle with a hover flight capability, for example a helicopter drone, a quadrocopter drone or a ducted fan aerial vehicle.

The mobile surveillance device 2 carries a sensor unit as a payload which may be fixedly or interchangeably installed on the mobile surveillance device 2. The sensor unit may comprise one or more imaging devices, for example a camera or a video camera. The one or more imaging devices may acquire a still image or preferably a video in the optical spectrum or in the ultraviolet or infrared spectrum. The sensor unit may additionally or alternatively include for example one or more highly sensitive motion detection sensors, one or more acoustic sensors such as directional or omni-directional microphones, one or more smoke detectors, temperature sensors, accelerometer, magnetometer relative (barometric) pressure sensor.

The accelerometer enables the mobile surveillance device 2 to determine a viewing point and an optical sensor viewing angle. In addition to support fulfilling the surveillance task the accelerometer may provide data for stabilizing the mobile surveillance device 2. The magnetometer may also assist stabilizing the mobile surveillance device 2 in addition to aid determining the actual direction for navigation of the mobile surveillance device 2 in the surveillance space 9. The relative pressure sensor (barometric sensor) enables the mobile surveillance device to determine a travel altitude of the mobile surveillance device 2 relative to a floor level or a ceiling level of building in at least a coarse scale. The mobile surveillance device 2 may use one of the above mentioned sensing technologies to determine a travel altitude relative to a floor level and a ceiling level. An additional relative barometric pressure sensor would allow the mobile surveillance device 2 to determine the travel altitude on a coarser scale, for example on which level the mobile surveillance device 2 is travelling at in a building. The relative barometric pressure sensor could contribute to determine navigation paths in large areas, in areas with high ceiling heights, in airports and stadiums .

The cited sensor technologies of the sensor unit support fulfilling the surveillance task as well as support navigation of the mobile surveillance device 2 in the surveillance space 9. The cited and further sensor technologies may assist the mobile surveillance device 2 to navigate into a coverage area of the at least one lighting device 4 and hence into a zone in which communication using VLC is possible. This may be of particular importance if the mobile surveillance device 2 left the coverage area of the lighting device 4 accidentally.

It is particularly advantageous if the surveillance unit of the mobile surveillance device 2 includes an optical sensor unit which has night vision capability. The optical sensor unit operates for example in the infrared spectrum and acquires image information of a scene which is illuminated by infrared light. The infrared light is emitted by infrared lighting means either forming part of the sensor unit of the mobile surveillance device 2 or advantageously be integrated with one or more of the lighting devices 4.1, 4.2, 4.3.

The plurality of lighting devices 4.1, 4.2, 4.3 is further linked via a lighting interface 15 with a lighting control unit 19 which provides the necessary power to the lighting devices 4.1, 4.2, 4.3 as well as provides a bi-directional data exchange capability for monitoring and controlling each of the lighting devices 4.1, 4.2, 4.3. A PIR motion detector interface 26 provides a data link capability as well as a power supply between the lighting control unit 19 and the PIR motion detector unit 6. The PIR motion detector interface 26, the lighting interface 15 and an interface between the lighting devices 4.1, 4.2, 4.3 and the PIR motion detector unit 6 may be based on a technical interface standard for network based systems for controlling lighting in building automation such as the digital addressable lighting interface (DALI™) . A VLC control unit 17 provides the lighting control unit 19 with a communication capability employing visible light communication (VLC) . The VLC control interface 18 between the VLC control unit 17 and the lighting control unit 19 is a bidirectional interface which receives on the one hand surveillance data acquired by the mobile surveillance device 2, transmitted via VLC communication to a VLC receiver portion of the communication unit in at least one of the lighting devices

4.1, 4.2, 4.3, further on via the lighting device interface 15 to the lighting control unit 19. The surveillance data is then transferred to the surveillance control unit 15 for evaluation via the VLC surveillance interface 16. The VLC control unit 17 provides to the lighting control unit 19 via the VLC control interface 18, positional information forming the basis for the position signal emitted by the individual lighting devices 4.1,

4.2, 4.3 which supports navigation of the mobile surveillance device 2 in the surveillance space 9. This position signal to be emitted by the individual lighting devices 4.1, 4.2, 4.3 and information on the respective location of the individual lighting devices 4.1, 4.2, 4.3 in the surveillance space 9 forms the basis for determining the position of the mobile surveillance device 2 in the surveillance space 9. The information including the location the individual lighting devices 4.1, 4.2, 4.3 is to be provided by the data storage unit 23 to the VLC control unit 17 via the VLC data base interface 22.

The VLC control unit 17 of an embodiment can also use information including the location of the individual lighting devices 4.1, 4.2, 4.3 to control the transmission of mobile surveillance device control data via the lighting devices 4.1, 4.2, 4.3 in a targeted manner. Hence, for example only a lighting device 4.1, 4.2, 4.3 in whose illumination area the mobile surveillance device 2 is actually moving may radiate via VLC communication surveillance control data to the mobile surveillance device 2. The surveillance control unit 13 provides a core control capability for the autonomous surveillance system 1. The surveillance control unit 13 receives motion detection reports from the PIR motion detector units 6, status reports from one or more mobile surveillance devices 2, surveillance data from one or more mobile surveillance devices 2. The surveillance control unit 15 is adapted to access the data storage unit 23 via the data storage interface 1 . In particular the surveillance control unit 15 may record (store) and retrieve (read) data from the data storage unit 23.

Data stored in the data storage unit 23 may comprise map data of the surveillance space 9, for example a floor plan, furniture locations, spatial data relating to the lighting system such as positions of the lighting devices 4.1, 4.2, 4.3, respective illumination areas of the individual lighting devices 4.1, 4.2, 4.3, location and coverage areas of the individual PIR motion detector units 6. The stored data in the data storage unit 23 may include time related data such as office hours, timetables of security requirements applicable to the surveillance space 9, external light conditions such as daylight or night. Data in the data storage unit 23 may include status information of the mobile surveillance device 2 such as availability, current location, remaining range due to energy storage reserve, capabilities of the sensor unit. The data storage unit 14 may also include data on surveillance missions such as predefined surveillance missions, for example regular patrolling schedules or predefined tasks for responding to a specific motion detection report or specific motion report pattern being received by the surveillance control unit 15. A mobile surveillance device base unit 28 is configured to provide shelter for the mobile surveillance device 2 when not moving and/or reloading its energy storage unit. The mobile surveillance device base unit 28 may include a connector for reloading the energy storage unit of the mobile surveillance device 2 and thus be connected to the mains power supply. The mobile surveillance device base unit 28 may be situated within the surveillance space 9 at a suitable location for moving within a short reaction time to possible surveillance positions 5.2. The mobile surveillance device base unit 28 may be equipped with a surveillance control interface 13 to the surveillance control unit 15 and may also have a mobile surveillance device interface 25 for directly communicating with the mobile surveillance device 2. The mobile surveillance device interface 25 may be implemented via a wired connection, a wireless link or integrated with the VLC communication interface between the mobile communication unit of the mobile surveillance device 2 and the communication unit of the lighting device 4.1, 4.2, 4.3.

The mobile surveillance device 2 according to an embodiment is an aerial vehicle, preferably with a capability to hover a certain time in a surveillance position 5.2. The mobile surveillance device 2 may for example be a micro aerial vehicle in form of a quadrocopter and designed to operate autonomously or semi-autonomously in the surveillance space 9. The mobile surveillance device 2 carries a payload specific to its surveillance mission. The payload includes a sensor unit which preferably may comprise one or more cameras or other sensors (detectors ) .

Furthermore the payload includes a mobile navigation unit which is adapted to control the motion of the mobile surveillance device 2 from one location in the surveillance space 9 to another location in the surveillance space 9. The mobile navigation unit is adapted to determine (calculate) the position of the mobile surveillance device 2 in the surveillance space 9 based on received light signals emitted from the VLC capable lighting devices 4.1, 4.2, 4.3. The received light signals may be in the visual light spectrum or alternatively in the infrared or ultraviolet range of the electromagnetic frequency spectrum. Furthermore the mobile navigation unit determines a direction of movement in the three dimensions of the surveillance space 9, a movement speed or (movement speed profile) suitable to perform a specific surveillance task. Determining the position of the mobile surveillance device 2 may be performed by triangulation when evaluating the received light signals from different lighting devices 4.1, 4.2, 4.3 which emit respectively coded VLC IR or UV signals.

The surveillance control unit 15 is configured to determine and to adapt a surveillance task. This surveillance task can be triggered for example by a motion detection report received via the lighting system from the PIR motion detection sensor 6. The surveillance control unit 15 accesses the data storage device 23 for acquiring the corresponding location information of the PIR motion sensor 6 data including information on availability and current location of the mobile surveillance device 2. The surveillance control unit 15 instructs a navigation unit 20 via a navigation interface 21 to determine a route to a suitable monitoring position 5.2. The navigation unit 20 may also read map data of the surveillance space 9 from the data storage unit 23 and further relevant data such as location data and envisaged further movement paths of other mobile surveillance devices 2 operating in the same surveillance space 9. Moreover information on areas to which access is temporally or for an unlimited time restricted to an autonomously operating mobile surveillance device 2 may be taken into account for determining a movement path for the mobile surveillance device 2. The navigation unit 20 returns via the navigation interface 21 navigation data to the surveillance control unit 15. The surveillance control unit 15 generates the surveillance task information including the received navigation data from the navigation unit and communicates the generated surveillance task information to the mobile surveillance device 2.

The generated surveillance task may preferably be communicated to the mobile surveillance device 2 by using the VLC communication link between the communication unit of the lighting device 4.1, 4.2, 4.3 and the mobile communication unit of the mobile surveillance device 2. The description of the preferred embodiment focuses on investigating a detected intrusion into a building representing the surveillance space 9. However it is to be understood that this represents only one out of plurality of applications of the claimed autonomous surveillance system 1 which employs mobile surveillance devices 2 in combination with a system backbone linked via lighting devices 4, 4.1, 4.2, 4.3 for communication and positioning purposes.