WO2017182458A1

WO2017182458A1 - Lighting system with object localization function

Info

Publication number: WO2017182458A1
Application number: PCT/EP2017/059164
Authority: WO
Inventors: Hugo Jose KRAJNC; Berent Willem MEERBEEK
Original assignee: Philips Lighting Holding B.V.
Priority date: 2016-04-22
Filing date: 2017-04-18
Publication date: 2017-10-26

Abstract

A lighting system (1) arranged to illuminate at least part of an environment, the lighting system comprising: - a plurality of luminaires (4) arranged to emit light to illuminate part of the environment; - a sensor (3) configured to detect an entity (12) at a location in the environment (L1); - a lighting controller (10); and - an input device (6) controllable by a user (8) occupying the environment to generate a locate instruction (18) to the lighting controller; wherein in response to the locate instruction the lighting controller is configured: - to use the sensor to estimate a location of each of the luminaires relative to the location of the detected entity and the location of the user and - to use the estimated locations to control the luminaires to change their emitted light so as to render a visible path, to be followed by the user, from the location of the user (L1) to the location of the entity (L2).

Description

LIGHTING SYSTEM WITH OBJECT LOCALIZATION FUNCTION

TECHNICAL FIELD

The present invention relates to a lighting system comprising at least one luminaire arranged to illuminate an environment, wherein the lighting system has

functionality to assist a user in locating a target entity (object or person), which is at a location in the environment remote from his own location and unknown him initially.

BACKGROUND

"Connected lighting" refers to lighting systems in which illumination sources are controlled not by a traditional, manually-operated mechanical switch between the mains and each of the illumination sources (or not only by such a switch), but by a means of a more intelligent lighting controller which connects to the illumination sources of the system via a data connection with each illumination source. The connection may be based on wireless network technology, wired network technology, or any combination thereof e.g. based on one or more of ZigBee, Bluetooth, Wi-Fi, 3 GPP, LTE or other cellular technology or Ethernet, or any other suitable network protocol. Communications between the lighting controller and the illumination sources may be direct, or indirect in the sense that data is relayed via one or more other luminaires of the lighting system.

The terms "luminaire", "light source" and "illumination source" are used interchangeably, to refer to a device which emits not just any light, but specifically light that provides illumination, i.e. light on a scale suitable for contributing to the illuminating of an environment occupied by one or more humans (so that the human occupants can see within the physical space as a consequence). A basic luminaire may consist simply of a light bulb or bulbs (e.g. LED, a filament bulb or gas-discharge lamp) and any associated support structure. Other luminaires may also comprise, for example, an associated casing or housing though others may not. A luminaire can take the form of a traditional ceiling or wall mounted room luminaire, or free standing luminaire (such as a floor or table lamp); or it may take a less traditional form such as an LED-strip embedded in a surface or item of furniture, a wall washer, or any other form of illumination device adapted to provide illumination specifically. Components for communicating with the controller (e.g. dedicated circuity, FPGA, processors and accompanying software (e.g. firmware) as applicable) may be incorporated in a light bulb with a standard fitting, to allow easy retrofitting of connected lighting

functionality into existing, non-specialised lighting systems. However, this is not essential and in general these communication components can be incorporated at any suitable location in the lighting system to allow communication between the luminaires and the controller.

A connected lighting system generally needs some form of "commissioning", e.g. when the lighting system is first installed. In this simplest case, this may just be a case of adding luminaires or bulbs to the lighting network so that they can be controlled.

A lighting system may be equipped with positioning functionality, so that it can provide a location service to a user in the illuminated environment. The environment may, for example, be one in which more traditional location services (such as GPS) are unavailable or unreliable. This relies on having a certain infrastructure in place which provides an "absolute" position reference within the environment that can be transmitted to a user device. "Absolute" in this context refers to a representation in which the user device's location is represented as coordinates (e.g. (x,y) or (x,y,z)) relative to the physical structure of the environment itself, such that is possible to display the user device's location using a marker on a map of the environment, or otherwise convey its location relative to the physical structure of the environment itself to the user in a meaningful fashion.

For example, a unique luminaire identifier may be embedded in the light emitted by each of the luminaires, using a suitable form of modulation, in a manner that is imperceptible to a human eye but detectable to a user device, such as a smartphone or tablet using its built in camera, or a peripheral device (camera, photo sensor etc.). This is an example of visual light communication (VCL), also referred to herein as "coded light". A configuration step may be performed as part of the commissioning process, e.g. when the lighting system is first installed, in order to populate a "localization database", by associating the luminaire identifiers with the absolute (x,y) or (x,y,z) locations of the corresponding luminaires within the environment. Thereafter, the user device may be able to receive the luminaire identifier from, say, the closest one of the luminaires (or from multiple luminaires in its vicinity). The populated database can then be used to estimate the absolute (x,y) or (x,y,z) location of the user device within the environment, using the absolute location(s) associated with the luminaire identifier(s) in the commissioning database. SUMMARY

One application of positioning systems is to provide what is referred to herein as "asset tracking", where that term is used herein to refer to any mechanism which assists a user in locating a target entity (object or person) at a location remote from his own location and that is initially unknown to him.

For example, a user may wish to locate and reach a lost device i.e. a device whose location he does not know (e.g. because he has forgotten where he left it, or it has been moved without his knowledge). Asset tracking systems for locating lost devices are known in the art. For example, the iCloud and Android Device Manager services provide asset tracking for a lost iOS or Android device provided the lost device knows it location, and is connected to a Wi-Fi network such that it can communicate its location to the service in question. The user can then use a separate display device to access the lost device's location, which is displayed on a map at the separate display device.

There are a number of problems with these existing systems: (i) they require a user to have to hand a separate display device which has the necessary functionality to be able to display the lost device's location on a map; moreover, these systems are of limited use in locating a device within a certain environments, such as a large room (e.g. warehouse space) or building as (ii) unless structural details of the environment are known and can be displayed on the map, the map-based representation will be unintuitive and of limited use to the user and (iii) the device may not know its location to a sufficient degree of accuracy (e.g. for an indoor environment, GPS may not be available). A possible extension of these techniques to a lighting system equipped with the positioning functionality might be for the lost device to determine its absolute location within the environment using the positioning infrastructure of the lighting system in the manner described above. However, whilst this may allow the lost device to provide a more accurate location, it would do nothing to solve problems (i) and (ii). What is more, such an approach would rely on the use of absolute locations (in the above sense) within the environment, and would thus need a localization database to be populated in the manner described above. Populating the localization database is essentially a manual process. It adds to the complexity of the commissioning process, and is often time consuming and error prone in practice, particularly for lighting systems with a large number of luminaires.

The iCloud asset tracking service also allows the user to request that the lost device begins emitting a sound. However, this relies on the user being able to hear the sound, and his ability to do so is limited by their proximity to the device, background noise levels etc. It also relies on the device having a functional and unobstructed loudspeaker, and the necessary connectivity to be able to receive a signal to activate the sound when desired for the user (e.g. which will not be the case if the lost device has lost its Wi-Fi connection, or if its battery has run out).

The present invention relates to a lighting system comprising one or more luminaires and one or more sensors. The lighting system has positioning functionality such that it is able to detect an entity at a first location - that is unknown to a user who is at a (different) second location - using the at least one sensor, and guide the user from the first location to the second location. Advantageously, the luminaire(s) of the lighting system itself are used to guide the user, by visibly changing their illumination. This solves problems (i) and (ii) noted above. Moreover, this approach does not require knowledge of the absolute locations of the entity or the luminaire(s) within the environment - it can be implemented knowing only the location(s) of the luminaire(s) relative to the entity and (in some embodiments) relative to each other, if necessary; hence, advantageously, it is possible to implement the present invention without any localization database of the kind described above, or any other absolute location information (in the above sense).

A first aspect of the present invention is directed to a lighting system arranged to illuminate at least part of an environment, the lighting system comprising: a luminaire arranged to emit light to illuminate part of the environment; a sensor configured to detect an entity at a location in the environment; a lighting controller; and an input device controllable by a user occupying the environment to generate a locate instruction to the lighting controller; wherein the lighting controller is configured to use the sensor to estimate a location of the luminaire relative to the location of the detected entity and, in response to the locate instruction, use the estimated location to control the luminaire to cause a visible change in its emitted light so as to guide the user to the entity.

The entity may be an object (e.g. a wireless communication device) or a person, and for the avoidance of doubt it is noted that the term "asset tracking" applies to any such entity herein.

Note that the estimated "location relative to the entity" in this context does not necessarily mean a strict two-dimensional (x,y) or three-dimensional (x,y,z) position vector relative to the luminaire (though that is not excluded) - the location may be estimated quantitatively in one dimension, e.g. as a radial distance between the entity and the luminaire, or qualitatively. For example, the location of the entity relative to the luminaire may be estimated qualitatively by determining that the luminaire is the closest one of multiple luminaires to the entity.

The sensor may be associated with the luminaire. Herein, a sensor is said to be "associated" with a luminaire if it has a location in the environment relative to that luminaire that is known to the lighting controller; for example, if there are multiple sensors and the lighting controller knows which of these is closest to a given luminaire, then that sensor is said to be associated with that luminaire. For example, that sensor may be a component of that luminaire or otherwise collocated with that luminaire, as in the

embodiments described below.

The entity is preferably a wireless communications device, wherein the location of the luminaire relative to the location of the wireless device can for example be estimated by identifying the luminaire as being, say, the closest luminaire to the wireless device based on a signal strength (or other signal characteristic) of a wireless signal emitted by the device as detected at the associated sensor.

It is noted, however, that the sensor is not required to be associated with the luminaire in this sense. For example, in embodiments, the entity may be a wireless communications device configured to determine information about its own location relative to the luminaire, and convey this self-determined location to the lighting controller. As an example, the luminaires may have unique luminaire identifiers embedded in their emitted light, allowing the wireless communications device to identify the luminaire to which it is closest, and convey the identifier of the closest luminaire to the lighting controller as a message embedded in the wireless signal. In this case, the sensor just functions as a wireless receiver so that the lighting controller can receive this information from the wireless device. In this case, the spatial relationship between the sensor and the luminaire need not be known to the lighting controller. Note that, in this case, there is no need for the lighting controller to determine an absolute (x,y) or (x,y,z) position of the identified luminaire (though the possibility of it doing so is not excluded) - the identifier in and of itself is sufficient for the lighting controller to identify that luminaire as closest to the entity, and thereby determine its location relative to the entity. Accordingly, it is possible to implement the invention without a localization database of the kind described above or any other absolute location

information.

However, for the avoidance of doubt it is noted that embodiments of the present invention may nonetheless make use of absolute location information when available. For example, the lighting controller may be configured so that the user has the option of entering room information pertaining to the luminaire(s), but is not required to do so i.e. if the user chooses not to enter the room information, the asset tracking functionality is still provided by the lighting system (based on spatial proximity of the luminaire(s) to the entity); if and when the user chooses to enter such room information, the lighting controller may then use this to provide additional contextually relevant information (e.g. by identifying all of the luminaire(s) in the same room as the target entity, and controlling them accordingly).

The location of the entity relative to which the location of the luminaire is estimated may be a last known location of the entity at the time the locate instruction is received i.e. its location when it was last detectable by the sensor. This means that the invention can still be used even if, when the locate instruction is received, the device is no longer detectable (e.g. if it is a wireless device whose battery has run out, or which is now unable to communicate with the sensor for some other reason).

In embodiments, the luminaire may be one of a plurality of luminaires of the lighting system, wherein the lighting controller may be configured to estimate a respective location of each of the luminaires relative to the location of the entity.

The sensor may be one of a plurality of sensors of the lighting system, each of which is associated with a respective one of the luminaires.

The lighting controller may be configured to also estimate a location of the luminaire relative to the user, and to also use the estimated location of the luminaire relative to the user to control the luminaire to cause the visible change.

The lighting controller may be configured to control the luminaires to render a visible path, to be followed by the user, from the location of the user to the location of the entity.

The entity may be a wireless communication device, and the location of the luminaire relative to the location of the wireless communication device is estimated based on a wireless signal received at the sensor from the wireless communication device.

The lighting controller may be configured to estimate the location of the luminaire relative to the location of the entity by comparing a signal characteristic of the wireless signal as sensed at the luminaire's associated sensor with a corresponding signal characteristic of the wireless signal as sensed by at least one other of the sensors.

The controller may be configured to identify the location of the luminaire relative to the location of the entity by:

- identifying the luminaire as being a closest one of the luminaires to the entity, - identifying the luminaire as being a luminaire neighbouring the luminaire closest to the entity,

- identifying the luminaire as being one of a set of luminaires surrounding the entity,

- identifying the luminaire as being located in the same room as the entity, and/or

- estimating a distance between the entity and the luminaire, thereby estimating its location relative to the location of the entity.

The lighting controller may be configured to track changes in the location of the user relative to the location of the luminaire and/or changes in the location of the entity location relative to the location of the luminaire, and vary at least one characteristic of the emitted light based on the tracking to convey, to the user, the changes as he moves though the environment.

The location of the user relative to the luminaire changes, for example, if the luminaire is at a fixed location in the environment and the user moves to a different location in the environment. The location of the entity relative to the luminaire changes, for example, if the entity moves in the environment, or if the luminaire is moved in the environment.

For example, the luminaire may be a portable luminaire, and the lighting controller may be configured to track the location of the portable luminaire relative to the location of the entity as the user moves though the environment carrying it.

Alternatively, the changes in the location of the luminaire relative to the user may be tracked based on another device carried by the user, such as the input device (e.g. the luminaire may be fixed, and the user may move around carrying the input device)

The locate instruction may be received when the luminaire is in an initial lighting state, and the visible change is caused by the lighting controller controlling the luminaire to change to a new lighting state. The lighting controller may be configured, in response detecting that the user has located the entity, to return the luminaire to the initial lighting state.

The sensor may be configured to receive from the wireless device a found signal transmitted in response to the wireless communication device detecting the user, wherein the lighting controller may be configured to return the luminaire to the initial lighting state in response to the found signal.

A second aspect of the present invention is directed to a lighting controller for a lighting system, the lighting system comprising a luminaire arranged to emit light to illuminate part of an environment, the lighting controller comprising: a control interface configured to connect to the luminaire for controlling its emitted light; a sensor input configured to connect to a sensor for detecting an entity at a location in the environment; an input configured to receive from an input device a locate instruction generated by a user occupying the environment using the input device; and a controller configured to use the sensor to estimate a location of the luminaire relative to the location of the detected entity and, in response to the locate instruction, use the estimated location to control the luminaire to cause a visible change in its emitted light so as to guide the user to the entity.

A third aspect of the present invention is directed to a method of guiding a user through an environment from an initial location of the user to a location of an entity, wherein a luminaire is arranged to emit light to illuminate part of the environment, the method comprising implementing, by a lighting controller, the following steps: using a sensor to detect the entity and estimate a location of the luminaire relative to the location of the detected entity; receiving from an input device a locate instruction generated by the user at the initial location using the input device; and in response to the locate instruction, using the estimated location to control the luminaire to cause a visible change in its emitted light so as to guide the user from the initial location to the location of the entity.

In embodiments of the second and third aspect, any feature disclosed herein in relation to the first aspect may be implemented.

A fourth aspect of the present invention is directed to a computer program product comprising code stored on a computer readable storage medium and configured when executed to implement the method of the third aspect, or more generally any of the system (e.g. lighting controller)functionality disclosed herein.

BRIEF DESCRIPTION OF FIGURES

To aid understanding of the present invention, and to show how the same may be carried into effect, reference is made to the following figures in which:

Figure 1 shows a schematic block diagram of a lighting system;

Figure 2 shows a flow chart of a method of controlling a lighting system to guide a user from an initial location to a location of a target entity, the latter location being unknown to him initially;

Figure 3 A shows a first example application of the present invention, in an environment comprising multiple rooms;

Figure 3B shows a second example application of the present invention, in an environment comprising multiple rooms; Figure 3C shows a third example application of the present invention in an environment, which is a large open space such as a warehouse.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the following examples, a lighting system, comprising one or more luminaires, is configured to operate as an asset tracking system, such that it can provide visual feedback to a user related to the location of a desired missing object using different visual mechanisms. The same infrastructure that provides the location information, i.e. the luminaires, is used to generate visual feedback signals that allows the user to intuitively follow a certain path towards the searched for object without needing additional tooling or complex installation and localization during commissioning. Moreover, by providing visual feedback in this manner, the search process is rendered more intuitive and contextually relevant than other methods (e.g. absolute coordinates).

In these examples, the object is a wireless communications device (such as a smartphone or tablet device), or an RF ("radio frequency") tag attached to another object

(such as the user's keys or wallet), and is detected based on visual light communication or RF positioning techniques.

Figure 1 shows a block diagram of a lighting system 1 , which comprises a lighting controller 10 and a plurality of luminaires 4 arranged to illuminate an environment (2 in later figures). The lighting controller 10 comprises a control interface 15, via which it is connected to the luminaires 4, such that it can transmit and receive signals to/from the luminaires 4. In this manner, the luminaires 4 form a lighting network, which is accessible via the lighting controller 10. The lighting controller 10 comprises at least one processor (e.g. a CPU or CPUs), on which control code 16 is executed so as to implement a controller for controlling the luminaires 4, which implements the functionality described below. Three luminaires 4 are shown in figure 1, but this is purely exemplary. The techniques can be applied using a greater or a lesser number of luminaires (e.g. only a single luminaire, or a much larger number of luminaires in a large environment).

The processor 14 is shown connected to a user input device 6. A user 8, who is occupying the environment 2, can use the input device 6 to instigate a locate instruction 18 to the lighting controller 10, the effect of which will be described in due course. For now, suffice it to say that the locate instruction 18 causes the lighting controller 10 to assist the user 8 in locating a target entity 12 present elsewhere in the environment 2, which is identified by the locate instruction 18 and which the user 8 wishes to locate. The user input device 6 can take a number of different forms, but in all cases is a device that is physically separate from the target entity 12, and at a different location in the environment.

The environment 2 can be any physical space, for example a room, e.g. a large warehouse space or open-plan office, or multiple rooms of all or part of a building (which may or may or may not be spread over different levels) such that the first and second locations LI, L2 may be in different rooms - a room being any enclosed or partially enclosed space, which includes for example corridors, stairwells etc. - or outdoor environment, or a combination of indoor and outdoor spaces etc.

The target entity 12 is shown at a location in the environment (first location LI), which is different from an initial location of the user 8 in the environment (second location L2), and which is initially unknown to the user 8 i.e. the user 8 does not know where the target entity 12 is initially.

Each of the luminaires 4 comprises at least one lamp 5, and at least one sensor

3. The luminaire 4 is configured so that the lighting controller 10 can control one or more characteristics of light emitted by the lamp 5 (such as intensity and/or colour), so as to cause visible changes in the light emitted by the luminaire, by transmitting suitable control signals to the luminaire 4 via the control interface 15.

The sensor 3 of each luminaire 4 is able to detect the entity 12 when in range of the sensor 3, and to transmit sensor signals via the lighting network to the lighting controller 10 to convey information about the detected entity 12 to it, which the latter receives via the control interface 15. The conveyed information is such that the lighting controller 10 can determine (i.e. estimate) the location of at least one of the luminaires 4 relative to the location L2 of the entity 12, using either the sensor signals from one of the sensors 3 or by comparing the sensor signals from at least two of the sensors 3. As noted above, the lighting controller 10 need not be able to determine the absolute location of the entity 12 in the environment (though in some embodiments it may do so).

The sensor 3 can take a number of forms, for example it may comprise one or more of the following: a photo sensor; a camera (e.g. comprising at least one array of photosensors), such as a visible light and/or infrared camera; a wireless RF receiver (which may comprise components such as an RF antenna(s), signal amplifier(s), demodulator(s) etc.).

In the examples described below, the entity 12 is a wireless communication device, such as a user device (e.g. smartphone, tablet device, remote control, laptop or desktop computer) or RF tag that e.g. that is configured to attach to another object such as the user's keys or wallet. The wireless device 12 is arranged to emit a wireless signal 20 that is detectable by the sensor 3. The lamp 5 may be configured such that a unique luminaire identifier ID (unique within the lighting system 1) is embedded in its emitted light using visual light communication techniques, at least some of the time, though as will be apparent in view of the following, this is not essential in all embodiments. In this case, the wireless device 12 is able to receive the luminaire ID, for example using a photosensor or camera of the wireless device 12.

Communication between the luminaires 4 and the lighting controller 10 can be effected in a number of different ways. For example, data transmitted and received between the lighting controller 10 and one or more of the luminaires 4 may be relayed via one or more other of the luminaires 4, i.e. the lighting network may have a mesh topology. Alternatively, data may be communicated directly between the luminaires 4 and the lighting controller 10 (i.e. not relayed via other luminaires), i.e. the lighting network may have a star topology. In general, the lighting network can have any suitable network topology, e.g. based on any suitable combination of direct and indirect (i.e. relayed) connections. The data can be communicated between the lighting controller 10 wirelessly, for example using ZigBee, Wi- Fi or Bluetooth, via wired connections, such as Ethernet or DMX connections, or a combination of two or more such technologies (wired and/or wireless). The lighting controller 10 may comprise a gateway, which provides an interface between the lighting network (e.g. ZigBee network or DMX network) and at least one other network, e.g. TCP/IP network, such as a local network based on Wi-Fi connections, Ethernet connections or a combination of both; Bluetooth network etc. A gateway is sometimes referred to as a bridge in this context (or a DMX controller for a DMX network specifically). An example of a suitable bridge is the Phillips Hue Bridge. In this case, the input device 6 may be a device of the other network (such as a smartphone or table device), e.g. it may be connected to the local networks via a Wi-Fi or Ethernet connection such that it can communicate with the gateway, or it may have a direct Bluetooth connection to the gateway. Alternatively, the lighting system architecture may be such that no bridge is required. For example, the lighting controller 10 may comprise or be part of a user device (such as a smartphone, tablet, laptop or desktop computer, wearable computing device such as, an augmented or virtual reality headset, etc.), wherein the control code 16 is executed on a local processor or processors of the user device. The input device 6 may be a user interface of the user device, such as touch screen, microphone or camera device (e.g. for gesture recognition). In this case, the user device may be able to communicate directly with the luminaires 4 (e.g. via Wi-Fi to Ethernet) such that no gateway is needed. The at least one processor 14 may be a single processor, for example that is part of the bridge where applicable, or part of some other computer device of the lighting controller 10 (e.g. a user device, or server). Alternatively, the lighting controller 10 may comprise multiple processors (possibly distributed over multiple locations) each of which executes a respective portion of the control code 16 to implement a respective part of the functionality outlined below. "Code" in the context covers any form of software, such as firmware, higher level software or a combination of both. Alternatively, some or all some of the functionality of the lighting controller 10 may be implemented in dedicated hardware of the lighting controller such as an application specific integrated circuit(s) and/or using programmable hardware such as a FPGA(s). In general, the term "lighting controller" generally refers to any control apparatus implemented in hardware, software or a

combination of both that is capable of controlling one or more luminaires of a lighting system.

As will be apparent, the present techniques can be applied to a wide range of lighting system architectures, such that the lighting controller 10 and input device 6 can take numerous different forms. In all cases, however, it is noted that the target entity 12 is an entity that is physically separate from the input device 6 and the initial location L2 of the user 8, and at a different location LI from the user 8 and input device 6 that is initially unknown to the user 8.

Figure 2 shows a flow chart of method steps for guiding the user 12 from the second location L2, i.e. his initial location, to the first location LI, i.e. the unknown location of the target entity 12.

As step S2, the user 8 instigates the locate instruction 18 using the input device 6. The locate instruction 18 identified the target entity 12 that the user 8 wishes to locate. For example, the target entity 12 may be a phone.

For example, the environment 1 may be a house fitted with a home automation system which can decode voice commands (e.g. Apple's HomeKit or Amazon's Echo), and the input device 12 may be an audio input device of the home automation system that is connected to the lighting controller 10. In this case, the lighting controller 10 may comprise a bridge (e.g. Philips Hue Bridge) between the home automation system and the lighting network. In this case, when needing to find the phone, the user 2 can, for example, speak a command such as "please guide me to my phone" (or similar) to instigate the locate instruction 18. The home automation system would detect that as a request to track a specific asset (the phone) and would trigger the lighting controller 10 to guide the user 8 to the phone, in the manner described below.

The input device 6 may also be a general-purpose user device, such as a phone (e.g. smartphone), tablet device, laptop or desktop computer etc. In some of the examples below, the target entity 12 is a similar device - it goes without saying that whatever form the input device 6 and target entity 12 take, the input device 6 is not the target entity 12 to be located (e.g. the user can use his tablet device to instigate a locate instruction to locate his phone and vice versa).

As another example, the input device 6 may be a dedicated control unit of the lighting system 1 itself, which the user can use to instigate the locate instruction 18 to locate his phone, say, by actuating a predetermined sequence of buttons or other user input elements of the dedicated control unit. The dedicated control unit may for example be a remote control or wall panel, which can communicate with the lighting controller 10 by wireless or wired means.

Alternatively, the dedicated control unit may be a local interface of one of the luminaires 4. That is, it may be integrated in that luminaire. For example, one of the luminaires 4 may be a portable luminaire (such as the Philips Hue Go), and the user input device 6 may be a local interface of the portable luminaire. By pressing, say, a specific combination of buttons in the local interface of the luminaire, it can be triggered to instigate the locate instruction 18 to locate the target entity 12, e.g. another preselected device. This may be particularly useful where the preselected device is a remote control of the lighting system 1 i.e. when the user has misplaced the remote control and wants to find it.

Note that the lighting controller 10 can be configured such that multiple devices can function as the input device 6, such that the user 8 has the option of using one of a number of different user input device depending on what he has available. For example the user may have the choice of using one or a number of generic user device (e.g. smartphone, tablet, other computer device etc.) or a dedicated lighting system control unit (e.g. remote control, wall panel, local luminaire interface).

Thus, for example even if the user has lost the remote control of the lighting system and wished to locate it (i.e. the remote control is the target entity 12), and has left his smartphone at the office so he cannot control the lighting as desired, and does not have a home automation system that detects voice commands, here may still be at least one alternative user input device 6 available to him such as a wall panel or local interface of one of the luminaires 4, e.g. a portable luminaire. Different exemplary implementations in a home context are shown in figures 3A and 3B, which show plan views of a part of a user's home. In the examples, the target entity 12 is a wireless communication device, such as a phone (figure 3 A) or remote control of the lighting system itself (figure 3B), which emits a wireless signal 20 that is used by the lighting controller 1 to locate it.

The wireless signal 20 is referred to in a number of different examples, and take various form e.g. it may be an RF, infrared (IR) or coded light signal etc.

As another example, the user 8 may be a worker in a large warehouse (the environment 2 in this example) and desires to find its way to the closest available forklift, which is the target entity 12 in this example. This example is illustrated in figure 3C, which shows a perspective view of warehouse space occupied by the user 8 and a plurality of forklifts, one of which is the target entity 12. In this example, the user input device 6 is a specialized remote control, which the user 8 can carry with him and use to instigate a locate instruction 18 to locate a forklift in the warehouse space. In this example, each of the forklifts comprises a wireless transmitter, which emits a wireless signal 20 that is detectable to the sensors 3 in the luminaires 4 and can thus be used to locate it. The locate instruction 18 may be an instruction to find any forklift in the warehouse space. For example, the remote control 6 may have several buttons, one of which has the symbol of a forklift. When the user wants to find an available forklift, he presses that button to instigate the locate instruction 18, which is transmitted to the lighting controller 10 wirelessly (e.g. using RF, IR or coded light). For example, the remote control may comprise a coded light transmitter, which emits light in a specific identifying code of the remote control is embedded so that the remote control can be distinguished from the forklifts by the lighting controller 10. To locate a specific forklift, the wireless signals 20 emitted by the forklifts may carry a unique identifier of that forklift. To locate a specific forklift, the user 8 can input a matching forklift identifier using the remote control. The user 8 may wish to use the lighting system 1 to locate a fork lift, for example because they do not have a direct line of sight to it, or if they want to locate a specific forklift that it is difficult for him to distinguish from other forklifts at a distance. Alternatively, the instruction may cause any available forklift to be located, e.g. the wireless signals emitted by the forklifts may indicate whether or not they are currently available.

At step S4 of figure 2, the lighting controller 10 uses at least one of the sensor 3 located in the environment to determine a location of at least one of the luminaires 4 relative to the location L2 of the target entity 12 (referred to as the "relative location" of that luminaire below for conciseness). The luminaire(s) whose relative locations are determined in this manner are referred to as the "target" luminaires below for convenience. All of the luminaires 4 may be target luminaires in this sense, or only one or some may be target luminaires as will become apparent.

As noted, in all of the examples of figures 3A-3C, the target entity 12 is (or comprises) a wireless communication device configured to emit a wireless signal 20 that is detectable to at least one of the sensors 3 in range of the wireless device 12.

The wireless signal 20 may be an RF signal, IR signal or a coded light signal, such that it can be detected by the lighting controller 10 using one or more of the sensors 3 at which the wireless signal 20 is received. It carries an identifier of the wireless device 12, allowing the lighting controller 10 to identify the wireless device 12.

As noted above, the relative location of a target luminaire can be determined in qualitative terms. For example, the location of the target luminaire relative to the target entity 12 can be determined in qualitative terms simply by, say, identifying the target luminaire as being:

- the closest of the luminaires 4 to the target entity 12 or as being a neighbouring luminaire to the closest luminaire, and/or

- one of a set of the luminaires 4 that surrounds the entity 12.

In identifying the target luminaire as any one of these, the lighting controller 10 has determined its location relative to the entity. As another example, the determined relative location of the target luminaire can be a one-dimensional measure, such as a radial distance between the target entity 12 and the luminaire 4, expressed in any system of units (i.e. not limited to standard or even linear units of distance, such as metres, feet etc.). These forms of location estimation are preferred, as they do not require any information about the absolute locations of the luminaire(s) within the environment, and can thus be implemented without any form of localization database of the kind described above.

Nevertheless, the possibility of using some form of absolute location information is not excluded - for example, information which rooms fixed luminaire(s) are located in may be used to, say, identify which luminaire(s) are in the same room as the target entity 12 (in the context of an environment having multiple rooms). This information can be stored as part of the commissioning process, inputted later by the user, and/or to some extent it may be possible to detect when luminaires are in the same room as one another on the fly, based on (say) their usage. As indicated above, the lighting controller 10 may be configured to provide the user 8 with the option of providing room pertaining to the luminaires 4, but does not require him to do so i.e. the lighting system 1 is capable of providing the asset tracking functionality without such information (based on spatial proximity between the luminaire(s) and the entity), but if and when the user 8 makes chooses to input such room information (and/or the lighting controller 10 detects it itself), it can use it to provide additional contextually relevant guidance information.

In the case that the target entity cannot be detected when the locate instruction is received, assuming it has been detected previously then the relative location(s) can be determined based on the last known position of the target entity 12. To implement this, the lighting controller may electronically store information about previous detections of the target entity in memory for use at a later time when the locate instruction 18 is received.

The relative location of a target luminaire can be determined by the lighting controller 10 using one or more of a number of different positioning techniques, examples of which will now be described.

For example, in some cases, the wireless device 12 can determine information about which of the luminaires 4 is in its vicinity, and communicate this to the wireless controller 10 for use in determine the location of at least one of those luminaires relative to the wireless device 12. For example, as noted, each of the luminaires 4 may be configured to emit a unique luminaire identifier ("ID"), for example by embedding it into its emitted light as coded light signal, or alternatively in an RF or IR signal. Such a signal emitted by a luminaire and carrying an identifier of that luminaire is referred to as a "light source signal" herein.

In this case, the wireless device 12 may comprise its own local sensor device, such as a photo-sensor, camera or RF receiver, such that it is able to receive the luminaire IDs from one or more of the luminaires 4 closest to it. In this case, it can convey the detected luminaire ID(s) to the lighting controller 10 in the wireless signal 20, possibly with additional information such as a signal strength and/or other signal characteristic of the light source signal(s) as measured at the wireless device's local sensor. The lighting controller 10 is then able to use this information to determine a location of one of more of these luminaires relative to the wireless device 12. For example, in the simplest case, assuming it knows the signal strength of the light source signals when emitted from the luminaires 4 (corresponding to the intensity of the visible light for a coded light signal), it can determine which of the luminaires is the closest based on the signal strength as received at the wireless device 12. In some cases, the lighting controller 10 may also be configured to use more sophisticated triangulation techniques to determine the location of one or more of the luminaires 4 relative to the wireless device 4 more accurately, based on the light source signal information contained in the wireless signal 20.

Note that, in this case, there is no need to the lighting controller 10 to determine any absolute location of the luminaires 4 from the luminaire ID(s) received in the wireless signal 20, and thus no need for it to have access to a commissioning database. The relative location(s) of the luminaire(s) in question can be determined entirely from the received ID(s) and, where applicable, the locally-measured light source signal

characteristic(s). Rather, all the lighting controller 10 needs to know is which luminaires emit which luminaire IDs.

Note also that, in this case, there is no need for the sensor 3 that receives the wireless signal 20 to have any particular spatial relationship with the luminaires 4, nor is there any need for the lighting controller 10 to know anything about the spatial relationship between the sensor and the luminaires. It is also sufficient to have a single sensor (such as a Wi-Fi receiver) in the environment, provided it can receive the wireless signal 20 and convey it to the lighting controller 10. This is because, in this example, the location of the wireless device 12 is determined from the content of the wireless signal 20 embedded in the wireless signal 20 by the wireless device 12 itself. The sensor just operated to relay this information to the lighting controller 10. In a sense, this is closer to a form of device-centric positioning in so far as it is the target wireless device 12 itself that is collecting the information needed to locate it, although the possessing of this information to do so may be performed wholly or in part by the illumination controller 10.

Alternatively or in addition, the relative location of at least one of the luminaires 4 can be determined by the lighting controller 10 based on one or more signal characteristics of the wireless signal 20 as measured at the sensors 3 of the luminaires 4 in the lighting network. This is a form of network- centric positioning.

For example, the wireless signal 20 may be received at multiple ones of the luminaires 4 in the vicinity of the wireless device 12. By comparing respective signal strengths (i.e. intensities) of the wireless signal 20 as measures at their sensors 3, it is possible for the luminaire controller 10 to identify, say, which of those luminaires 4 is closest to the wireless device 12, as the one whose sensor is detecting the highest signal strength. In this case, the wireless signal 20 may for example be a simple beacon signal, with limited information content (e.g. only enough to identify the wireless device 12 to the lighting controller 10). One or more other signal characteristics, as an alternative or in addition to signal strength, such as phase angle, based on the Doppler effect, can be used. For example, the wireless device 12 can send a certain message embedded in its wireless signal 20 at a frequency fl ; one of the sensors 3 receives that message and measures the phase angle φΐ . The wireless device then then sends a copy of the message at a later time, but having a slightly different frequency f2 = fl+df; the same sensor 3 receives this new message and this time measures a phase angle of φ2. One or more of the values of φΐ and φ2, their ratio and/or their sign (or relative sign) can be used to determine information about the location of the sensor 3 relative to the device 12.

Another viable positioning technique is to compare reception rates of messages; for example, if the wireless device 12 sends a burst of messages over a short interval of time, the effective reception rate of these messages at one of the sensors 3, can be used to estimate a distance to the wireless device 12, for example based on an assumption that, in a non-free space environment, the longer the linear distances between two entities the higher the chances are that there are unwanted objects in the communication path between both. This may be less preferred, as it is not always reliable, but is nonetheless within the scope of the present disclosure.

Signal strength of the wireless signal 20, reception rate of data carried by the wireless signal 20 (e.g. message rejection rate), frequency and phase angle are all examples of signal characteristics as that term is used herein.

Generally, in determining the relative location of the target luminaire(s), the lighting controller 10 can make use a variety of location information sources, such as of specific RF technology on the lamps 4, on the target wireless device 12 to be located, or a mixture of both (e.g. Hue lamps with ZigBee-Bluetooth combination chips, smartphones with ZigBee radios inside, lamps and smartphones with Wi-Fi control, etc.).

As step S6, the lighting controller 10 may also determine a location of at least one of the target luminaire(s) relative to the location LI of the user 8, though as explained below this is not always necessary. That is, such that the luminaire controller 10 knows the location of that target luminaire relative to both the target entity 12 (i.e. to the first location LI) and relative to the user 8 (i.e. to the second location L2). Again, this can be a qualitative determination, for example the lighting controller 10 may determine that the target luminaire is:

- in the same room as the target entity 12 but in a different room to the user 8 (if the necessary information is available), and/or - is at a location on, near to, or adjacent a path though the environment 2 between the user 8 and the target entity 12; for example, a straight line path (which does not require any knowledge of the environment) or a more complex which it knows to be traversable by the user 8 (which may require the lighting controller 10 to have some knowledge of the environment 2, such as the approximate locations of any walls and doors relative to the luminaires 4)

- and in so doing determines is location relative to both the user and the entity.

Alternatively or in addition, the lighting controller 10 can assume that the location of the user 8 is the same as the location of the input device 6. For example, where the input device 6 is a hand-held or wall mounted device that needs to be operated manually, the lighting controller can assume that the location of the user 8 is the location of the input device 6; for a voice activated input device 6, the same assumption could still be made, particularly as in some cases it may not be necessary to know the user's location to a high level of accuracy (e.g. it may be enough for the lighting controller 10 to know whether a target luminaire is in the same room as the user).

Where the input device 6 is a local input device of the target luminaire itself, the lighting controller can assume that the target luminaire 4 and the user 8 are collocated, at least initially, i.e. at the same location initially.

Alternatively, the user 8 can be detected explicitly, e.g. using one or more of the sensors 3 in the vicinity of the user 8, which may for example comprise camera devices or other sensor components that can be used to detect the user 8.

At step S8, the lighting controller 10 controls at least one of the target luminaire(s) via the control interface 15 to cause a visible change in its emitted light, i.e. that is perceptible to a human eye, by changing one or more lighting setting of that luminaire - for example, an (overall) intensity setting (e.g. a dimming level or other illumination level, luminance etc.) and/or or one or more colour settings (e.g. RGB, XYZ, chrominance settings etc.). The visible change is such that it guides the user 8 from his initial location L2 to the location LI of the target entity 12 that he wishes to locate. That is, the visible change conveys guidance information to the user so that he knows at least approximately where he should go in the environment 2 in order to find the target entity 12, just from looking at the behaviour of the luminaires 4 that are visible to him. There are various ways in which this guidance information can be conveyed, some examples of which are described below.

In some cases, a single luminaire may be sufficient to guide the user. For example, this is particular the case is a home setting, since it is expected that the lighting infrastructure will not be as dense as in a warehouse, a single lamp feedback is sufficient. For example, in one of the simplest cases, the lighting controller 10 may increase the illumination level (i.e. brightness) of the luminaire closest to the position of the target entity 12 to maximum, thereby marking its location, which may in and of itself be sufficient to guide the user to the target entity 12. For example, if the target entity is a phone that has dropped behind a sofa in the same room as the user 8, the brightness of (say) a reading lamp next to the sofa can be increased to guide the user to the lost phone.

Alternatively or in addition, all other luminaires (other than the closest luminaire) in the same functional room as the target entity 12 can be dimmed, such that the location of the closest luminaire (and therefore the target entity 12) is clearly noticeable by providing additional contrast.

One or more of the target luminaires can also be controlled to render a dynamic illumination pattern in their emitted light, such as a blinking pattern (i.e. transition in between emitting and non-emitting states). Dynamic effects are useful for attracting the attention of the user.

Similarly, in a warehouse setting (figure 3C), one or more of the luminaires closest to and surrounding the target forklift (denoted 4C) may be controlled to distinguish the other luminaires. In a large open environment, such as a warehouse, it may be beneficial to use multiple luminaires to mark the location of the forklift 12, so that it is clearly visible.

Note that the above examples do not require the location of the target luminaire(s) relative to the user 8 to be determined, i.e. it does not require step S6 to be performed.

However, the information determined at step S6 can be used in other variations to further assist the user.

Figure 3 A shows another example, in which the lighting system 1 can guide the user 8 from his current location L2 to the location of the target entity L 1 by controlling multiple target luminaires to render a visible path from L2 to LI through the environment 2, which the user 8 can follow. This does require the locations of those luminaires to be determined relative to both the user 8 (i.e. to L2) and the target entity 12 (i.e. to LI), in so far as it requires the luminaires 4 that lie along that path to be identified (e.g. to brighten them or change their colour, say, to green) and/or the luminaires adjacent that path to be identified (e.g. to dim them or change their colour to, say, red).

Figure 3 A shows an environment 2 with multiple rooms. The user 8 wishes to locate his phone 12, which is initially in a different room from him. In this example, the user uses a wall panel 6 to instigate a locate instruction 18, which indicates to the lighting controller 10 that the user 8 wants to locate the phone 12. The phone 12 is shown emitting a wireless signal 20, which is detected by the sensor 3 of at least one of the luminaires 4 in its vicinity - at least luminaires 4j (which is a table lamp closest to the phone 12), 4i and 4g in this example - and which the lighting controller 10 can use to determine the location of those luminaires 41, 4j, 4g using one or more of the position techniques described above. As can be seen the luminaires 4g, 4i lie substantially along a path from L2 to LI that is traversable by the user 8, as do luminaires 4a, 4d, 4e and 4f. In order to determine that this is the case, the lighting controller 10 may need forms of information about the locations of the luminaires 4 relative to one another. This can for example be determined based on communications between the luminaires 4 themselves, e.g. in the case that the luminaires emit light source signals of the kind described above, it may be possible to determine their relative locations based detections by the sensors 3 of the luminaires of one another's light source signals. Alternatively, the relative locations can be recorded manually in a memory accessible to the lighting controller 10. In this example, it is also beneficial for the lighting controller 10 to have available information about the layout of the walls and doors within the environment 2. Again, it may be possible to determine this automatically to some extent using the sensors 3, and/or at least some of this information may be entered manually in a similar manner. The lighting controller controls luminaires 4a, 4d, 43, 4f, 4g and 4h to render a visible path from L2 to LI, for example by changing their emitted light to a particular colour (e.g. green, denoted by diagonal shading). To further assist the user, luminaires 4c, 4e and 4f may be changed to a different colour (e.g. red, denoted by hatching) to make it clear to the user that they do not lie along this path (otherwise the user 8 might inadvertently go up or down the corridor shown towards the middle of figure 3 A, instead of into the room shown on the right- hand side in which the phone is located 12). Similarly, luminaires such as 4b that are in a different room to the phone 12 may also be set to the different colour, so that the user 8 knows not to bother entering such room in his search. The closest luminaire to the target entity (4j) may be set to distinguish its emitted light from all other luminaires, denoted by dotted shading, so that as soon at that luminaire 4j becomes visible to the user 8, he knows exactly where his phone 12 is.

Another example is illustrated in figure 3B. In this case, the user 8 is guided though the environment 2 by a single luminaire, which is a portable luminaire 4P that he carries with him as a location guide. This portable luminaire 4P can be the luminaire whose local interface the user 8 uses to instigate the locate instruction 18. The portable luminaire 4P starts with a specific visual effect (e.g. dimmed cool white light) in response to the locate instruction 18, and will start increasing in brightness and getting warmer as the user carries it from room to room to find the target entity 12, which in this example is the remote controller for the lighting system 1 itself. For example, at least one illumination characteristic (e.g. colour and/or intensity) of the light emitted by the portable luminaire 4P varies as a function of the radial distance between the portable luminaire 4P and the target entity 12, so that the user 8 knows when he is moving closer to the target entity 12 and when he is moving further from it. By knowing which pattern to follow, the user 8 will know whether he is moving in the right direction or not. In some embodiments, the user 8 can select which pattern he wants to be rendered.

The radial distance is determined based on the wireless signal 20, e.g. based on a detection of that signal 20 at the portable luminaire 4P itself (which is particularly suitable where the wireless signal 20 is an RF signal that can pass through walls and other internal structure of the environment 2), and/or based on a detection of that wireless signal 20 by another of the luminaires - 4j in the example of figure 3B - which is conveyed to the lighting controller 10. This is possible if information is known about the relative positions of luminaires 4j, 4P as the portable luminaire 4P is moved though the environment, which can for example be determined based on measurements performed within the lighting system (e.g. using the sensors 3 of the luminaires 4). As another example, if the target device 12 is able to receive a light source signal from the portable luminaire 4P (e.g. an RF signal caring an identifier of the portable luminaire 4P), it can convey information about this to the lighting controller 10 in its own wireless signal 20, via one or more of the luminaires.

To provide additional guidance, the remote control 12 can also have a small speaker embedded in it such that as the user approaches it with the portable luminaire 4P a distinctive audio signal is emitted (e.g. volume increases with proximity).

In some contexts, it is beneficial for the lighting controller to track the user 8, in order to track changes in the location of one or more of the target luminaires relative to the user 8 (S10, figure 2). E.g. as the user 8 moves through an environment in which a target luminaire is stationary, the location of the target luminaire relative to the user 8 changes as the user 8 moves.

For example, returning to the warehouse example of figure 3C, the visual feedback can be provided by slowly varying the brightness of the luminaires along a path between the user 8 (i.e. location L2) and the target forklift (i.e. location LI), e.g. to render a pulsing runway effect differentiating the correct path from the wrong one, such that the user 8 can clearly see which way he should go. The user location can be tracked, for example, using the sensors 3 and/or by tracking changes in the location of the input device 6 (assuming that the user 8 carries it with him).

Alternatively, the tracking can be used to render a dynamic lighting effect wherein, say, a large area centred around the forklift 12 starts blinking, and as the user 8 gets closer and closer to its location LI, the area of blinking lights reduces (since the area he no longer needs guidance through he has already traversed). The blinking may be controlled to have a "swing" that becomes more extreme as the user approaches the target forklift 12 (since it will affect a smaller area and higher resolution is needed). This way the user is guided intuitively towards the goal by means of a coarse-to-fine visual feedback.

Similarly in the example of figure 3 A, the lighting of the luminaires can be varied as the user moves along the path, or if the user 8 starts going in the wrong direction, the luminaires 4 can be controlled to convey this to him (e.g. by blinking red).

Embodiments of the invention may also be used to provide a game system. A first player can put RF tokens on objects that he wants to hide, each of which is a target entity in its own right. A second player needs to find back these objects. The lighting controller 10 can detect the location of the objects with RF tokens. The lighting controller 10 can assist the second player by giving visual clues where to find the objects. For example, the lights at random time and in short intervals blink in certain colours to indicate where the objects are or the proximity of player 2 to the objects. This feedback might be provided by the fixed lighting infrastructure (e.g. Hue E27 bulbs) or by a handheld/portable light sources such as the Hue Go. As such, the user 8 is not necessarily guided to the target entity in the most direct fashion: in the context of a game, the guidance information conveyed by the lighting system may be intentionally somewhat oblique, but none the less sufficient to guide the user to the target entity 12 eventually provided he has his wits about him.

In this manner the lighting system 1 , however it is configured, complements the asset tracking functionality by means of clear and intuitive visual patterns that give immediate feedback to the user in both small and large areas where a more complex guiding tool might not be available, or is too complex or expensive to have.

Note that not all of the environment need be illuminated by the lighting system

- for example, the environment can comprise an indoor environment (e.g. house) and an outdoor environment (garden) which is not necessarily illuminated artificially. In this case, if the target entity 12 is in the garden, then a path might not be feasible to construct, but if the indoor luminaire closest to the garden location of the device (e.g. by a bedroom window) is lit at e.g. highest brightness, that guides the user to go out and e.g. look close to the bedroom window that looks into the garden. Of course, if there are one or more outdoor luminaires in the garden, these can also be used to guide the user 8.

Note that not all of the sensors 3 need to able to directly sense the target entity 12, any may for example receive a certain signal characteristic from one of the other luminaires 4 conveying information about the entity sensed by another of the sensors 3 - i.e. a form of "second hand" information from another luminaire. This data can also be coupled in a certain way to the visual path that is generated for the user, and/or a different visual pattern can be chosen to e.g. indicate that this specific luminaire is only partially seeing the entity, and therefore it's not as reliable for the user as other visual indications he might find around him.

At step SI 2, once the target entity 12 has been located by the user (or all of the target entities if there are multiple ones), i.e. once the user 8 has found it, the lighting system is returned to "normal" i.e. the lighting controller 10 reverts to the lighting settings from immediately before the located instruction 18 was received.

The lighting controller 10 may detect that the user has found the target entity 12 using one or more of the sensors 3 of the luminaires, which as noted may comprise cameras in some cases.

Alternatively, where the target entity 12 is a wireless communication device, such as a phone, the device 12 itself may detect the user 8, and convey this to the lighting controller 10 so that the latter knows that the user has found the device 12. For example, when the device 12 is picked up by the user, the device 12 may detect this using one or more of its on-board sensors (e.g. accelerometer).

In the warehouse example of figure 3C, once the user 8 has found the object of interest (forklift 12) and starts to use it, the lighting controller may detect a location change of the forklift 12 using the sensors 3, and automatically return the luminaires 4 to their initial settings in response. Alternatively, the user may instigate a stop instruction via the input device 6 (or by some other mechanism) to confirm that the entity has been found and as such the location/guiding mechanism can be stopped, i.e. to perform a manual stop.

It will be appreciated that the above embodiments have been described by way of example only. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. For example, whilst it has been noted that the present techniques do not require the lighting system to be commissioned, the application to a commissioned lighting system is not excluded. For example, where a commissioning database of the kind described above that provides absolute locations of the luminaires, the relative location of a luminaire to the entity may be determined by comparing an absolute location of the entity (e.g. (x,y) or (x,y,z)) with the absolute location of that luminaire.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single processor or other unit may fulfil the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A lighting system (1) arranged to illuminate at least part of an environment 2), the lighting system comprising:

a lighting controller (10); and

an input device (6) controllable by a user (8) occupying the environment to generate a locate instruction (18) to the lighting controller;

wherein the lighting controller (10) is configured to use the sensor estimate a location of each of the luminaires (4) relative to the location of the detected entity (12) and, in response to the locate instruction (18), use the estimated location to control the luminaires (4) to cause a visible change in its emitted light so as to guide the user (8) to the entity (12), wherein the lighting controller is configured to control the luminaires (4) to render a visible path, to be followed by the user, from the location of the user (LI) to the location of the entity (L2).

2. A lighting system according to claim 1, wherein the sensor (3) is one of a plurality of sensors of the lighting system, each of which is associated with a respective one of the luminaires (4).

3. A lighting system according to claim 1 or 2, wherein the lighting controller (10) is configured to also determine a location of the luminaire (4) relative to the user (8), and to also use the determined location of the luminaire (4) relative to the user (8) to control the luminaire to cause the visible change.

4. A lighting system according to any preceding claim, wherein the entity is a wireless communication device, and the location of the luminaire relative to the location of the wireless communication device is estimated based on a wireless signal (20) received at the sensor from the wireless communication device.

5. A lighting system according to claim 4 when dependent on claim 2, wherein the lighting controller is configured to estimate the location of the luminaire relative to the location of the entity by comparing a signal characteristic of the wireless signal as sensed at the luminaire's associated sensor with a corresponding signal characteristic of the wireless signal as sensed by at least one other of the sensors.

6. A lighting system according to claim 4, wherein the controller is configured to identify the location of the luminaire relative to the location of the entity by:

identifying the luminaire as being a closest one of the luminaires to the entity, and/or

identifying the luminaire as being a luminaire neighbouring the luminaire closest to the entity, and/or

identifying the luminaire as being one of a set of luminaires surrounding the entity, and/or

identifying the luminaire as being located in the same room as the entity, and/or

estimating a distance between the entity and the luminaire,

thereby estimating its location relative to the location of the entity.

7. A lighting system according to any preceding claim, wherein the lighting controller (10) is configured to track changes in the location of the user (8) relative to the location of luminaire (4) and/or changes in the location of the entity (12) relative to the location of the luminaire (4), and vary at least one characteristic of the emitted light based on the tracking to convey, to the user, the changes as he moves though the environment.

8. A lighting system according to claim 7, wherein the luminaire is a portable luminaire (4P), and the lighting controller is configured to track the location of the portable luminaire relative to the location of the entity as the user moves though the environment carrying it.

9. A lighting system according to any preceding claim, wherein the locate instruction (18) is received when the luminaire (4) is in an initial lighting state, and the visible change is caused by the lighting controller (10) controlling the luminaire to change to a new lighting state, and wherein the lighting controller is configured, in response detecting that the user has located the entity, to return the luminaire to the initial lighting state.

10. A lighting system according to claim 9 when dependent on claim 6, wherein the sensor (3) is configured to receive from the wireless device a found signal transmitted in response to the wireless communication device detecting the user, wherein the lighting controller is configured to return the luminaire to the initial lighting state in response to the found signal.

1 1. A lighting controller (10) for a lighting system, the lighting system comprising a plurality of luminaires arranged to emit light to illuminate part of an environment, the lighting controller comprising:

a control interface (15) configured to connect to the luminaire for controlling its emitted light;

a sensor input configured to connect to a sensor (3) for detecting an entity (12) at a location in the environment (LI);

an input configured to receive from an input device (6) a locate instruction generated by a user (8) occupying the environment using the input device; and

a controller (14) configured to use the sensor to estimate a location of each of the luminaires relative to the location of the detected entity and, in response to the locate instruction, use the estimated location to control the luminaire to cause a visible change in its emitted light so as to guide the user to the entity, wherein the lighting controller is configured to control the luminaires (4) to render a visible path, to be followed by the user, from the location of the user (LI) to the location of the entity (L2).

12. A method of guiding a user (8) through an environment (2) from an initial location of the user (LI) to a location of an entity (L2), wherein a plurality of luminaires (4) is arranged to emit light to illuminate part of the environment, the method comprising implementing, by a lighting controller (10), the following steps:

using a sensor (3) to detect the entity and estimate a location of each of the luminaires relative to the location of the detected entity; receiving from an input device a locate instruction (18) generated by the user at the initial location using the input device; and

in response to the locate instruction (18), using the estimated location to control the luminaire (4) to cause a visible change in its emitted light so as to guide the user (8) from the initial location (L2) to the location of the entity (LI) , wherein the lighting controller is configured to control the luminaires (4) to render a visible path, to be followed by the user, from the location of the user (LI) to the location of the entity (L2).

13. A computer program product comprising code stored on a computer readable storage medium and configured when executed to implement the method of claim 12.