WO2017063888A1

WO2017063888A1 - Area lighting system and operating method

Info

Publication number: WO2017063888A1
Application number: PCT/EP2016/073130
Authority: WO
Inventors: Bart Andre Salters
Original assignee: Philips Lighting Holding B.V.
Priority date: 2015-10-13
Filing date: 2016-09-28
Publication date: 2017-04-20

Abstract

An area lighting system is disclosed that comprises a plurality of luminaires for illuminating respective portions of the area; a sensor arrangement adapted to determine a solar illumination characteristic in a particular solar position; and a controller for individually controlling said luminaires. The controller is responsive to the sensor arrangement and is adapted to access predetermined information predicting sunlit regions and/or shaded regions in said area caused by structural features in between the sun and the area exposed to solar illumination in different solar positions to identify the sunlit regions and/or shaded regions in said area for the determined solar illumination characteristic in the particular solar position; identify a subset of the plurality of luminaires arranged to illuminate the identified sunlit regions or shaded regions; and control an illumination of luminaires in said subset to reduce the contrast between the sunlit regions and shaded regions. A method of operating such an area lighting system is also disclosed.

Description

Area lighting system and operating method

FIELD OF THE INVENTION

The present invention relates to an area lighting system, comprising a plurality of luminaires for illuminating respective portions of the area and a controller for individually controlling said luminaires.

The present invention further relates to a method of operating such an area lighting system.

BACKGROUND OF THE INVENTION

Large area lighting systems and in particular arena lighting systems typically comprise a plurality of luminaires arranged around a large area such as a building facade, work area, parking area or sports pitch in case of an arena lighting system in order to generate a desirable illumination pattern onto the large area. This may be an illumination pattern designed to illuminate certain parts of the large area, for example display areas on a shop floor, driving lanes through a parking area, and so on, or may be an illumination pattern designed to homogeneously illuminate the large area, for example homogeneously illuminate the sports activity area of a sports arena such as a pitch or pool.

In many large area lighting applications, it is important that the desired illumination of any particular part of the large area is achieved from multiple viewing angles, for example to eliminate or at least reduce the generation of shadows on the large area. To this end, luminaires may be positioned in such a manner that such particular parts of the large area are illuminated from multiple angles, thereby reducing the formation of shadows in such areas. An example of such a multiple angled illumination approach is disclosed in US 2015/0077995 Al . This is for instance also desirable when the large area is captured by cameras, which may be surveillance cameras or, in case of sports arenas, may be television cameras to capture the activity on the large area, such that the camera images captured by the cameras are of high quality and allow for proper surveillance or watching of activity taking place on the large area. Where shadows exist on the large area, it is more difficult to generate images of high quality, particularly when the cameras track movement over the large area from an illuminated region into a shaded region or vice versa, which sudden change in contrast can lead to image overexposure or underexposure. This at least temporary loss of image quality (the loss of image quality may be compensated for by adjusting contrast levels of the camera) should therefore be avoided. In fact, some governing bodies such as FIFA issue strict guidelines about sports area illumination including shadow reduction such that sports events on the large area can be covered in a satisfactory manner by television broadcast.

Although appropriate large area illumination by correct positioning of luminaires can be readily achieved during night-time where the large area is entirely illuminated by the large area lighting system, this is less straightforward during daytime where illumination is typically (at least partially) provided by natural light, i.e. sunlight. This can cause the generation of shadows on the large area due to the presence of structural elements associated with the large area in between the large area and the sun, such as structural elements that form part of a sports arena such as (roofs of) stands, sports arena roof structures, and so on. This particularly is a problem at certain parts of the day such as late afternoon, where the positioning of such structural elements between the sun and the large area can cast large shadows on the large area. This may hinder high-quality image capturing of the large area or even hinder sportsmen or athletes in their activities due to variable lighting conditions on a sports area such as a pitch, field, track, pool or the like.

SUMMARY OF THE INVENTION

The present invention seeks to provide an area lighting system that can reduce the generation of shadows during daytime.

The present invention further seeks to provide a method of operating such an area lighting system.

According to an aspect, there is provided an area lighting system, comprising: a plurality of luminaires for illuminating respective portions of the area; a sensor arrangement adapted to determine a solar illumination characteristic in a particular solar position; and a controller for individually controlling said luminaires; said controller being responsive to the sensor arrangement and being adapted to access predetermined information predicting shaded regions in said area caused by structural features in between the sun and the area exposed to solar illumination in different solar positions to identify sunlit regions and/or the shaded regions in said area for the determined solar illumination characteristic in the particular solar position; identify a subset of the plurality of luminaires arranged to illuminate the identified sunlit regions or shaded regions; and control an illumination of luminaires in said subset to reduce the contrast between said sunlit regions and shaded regions.

The present invention is based on the insight that the fixed relationship between the position of the sun in the sky, i.e. its solar position, and the fixed structural elements around the area makes it possible to predict which regions of the area have shadows cast thereupon by the fixed structural elements in between the sun in its solar position and the area, with the remaining regions of the area, i.e. the complement of the shaded regions, being sunlit regions as a consequence. The predictability of the shaded regions of the area allows for these regions to be selectively illuminated by on the fly selection of luminaires of the area lighting system aiming at such predicted sunlit and/or shaded regions when a illumination characteristic indicative of shadow formation on the area is detected. In this manner, contrast between regions of the area illuminated by the sun and regions of the area cast in shadows can be almost instantaneously reduced, e.g within a second, such that it becomes easier to follow movement across the area either by a spectator or by a camera, and, in case of image capturing by a camera, allows for the generation of better quality images in the sense that transfers between high-contrast regions of the area can be avoided, thus avoiding sudden overexposure or underexposure of the images captured by the camera.

Such selective illumination may comprise reducing illumination levels of luminaires aimed at sunlit regions, e.g. dim or switch off such luminaires. This for instance may be advantageous in scenarios where the area illumination system is engaged during daylight hours. Alternatively, such selective illumination may comprise increasing illumination levels of luminaires aimed at shaded regions, e.g. reduced dimming or switch on such luminaires. This for instance may be advantageous in scenarios where the area illumination system is disengaged during daylight hours.

Said controlling an illumination of luminaires in said subset may comprise for example: an illumination level of luminaires, e.g. by dimming of switching on/off; intensity of luminous output; luminous flux; a color point of a luminous output; lighting colors;

orientation adjustment or adjustment of the aim of the luminaire; control luminous output of different spectral compositions.

In an embodiment, the sensor arrangement comprises a light intensity sensor, and wherein the controller is further adapted to obtain a point in time indicative of the particular solar position, e.g. the date and time of the solar position. This has the advantage that a relatively simple light intensity sensor may be used, which when correlated with a particular date and time at which a particular light intensity is measured, allows for an accurate determination of the solar position of the sun, which in turn allows for an accurate prediction of the shadows generated on the area by the structural elements in between the sun and the area such that upon detection of a particular illumination characteristic at a particular point in time, the appropriate set of luminaires for illuminating the predicted sunlit regions and/or shaded regions of the area can be achieved on the fly in order to reduce the contrast between the sunlit and shaded regions of the area.

In an alternative embodiment, the sensor arrangement comprises a light sensor arranged to identify the particular solar position. In this embodiment, the light sensor for instance may be able to adjust its orientation in order to focus on the sun in a particular solar position and may include an orientation sensor for detecting the actual orientation of the light sensor when focused on the sun such that the solar position can be derived from the orientation information provided by the orientation sensor.

The predetermined information predicting shaded regions in said area caused by structural features in the vicinity of the area exposed to solar illumination in different solar positions may be comprised in an algorithm for identifying the shaded regions in said area as a function of a determined natural solar illumination characteristic in a particular solar position, and wherein the controller is adapted to execute said algorithm using the determined illumination characteristic as an algorithm input. The algorithm for instance may be adapted to predict or retrieve previously predicted shaded regions or alternatively may be adapted to retrieve or calculate sets of luminaires targeting previously predicted shaded regions. As explained above, the predetermined shaded region information may be used to derive (predetermined) sunlit region information, as this is typically the complement of the shaded region information.

The area lighting system may comprise a data storage device storing the predetermined information, wherein the controller is adapted to access the predetermined information in the data storage device.

The predetermined information may further comprise identification information for the respective subsets of luminaires to be engaged for different solar positions to reduce the contrast between said sunlit regions and shaded regions caused by structural features exposed to solar illuminationin different solar positions, the controller being adapted to identify a subset of the plurality of luminaires arranged to illuminate the sunlit regions and/or shaded regions from the predetermined information. In this

embodiment, the set of luminaires to be engaged as a function of a particular solar position in order to compensate for shading on the area is also predetermined such that upon detection of a illumination characteristic indicative of the occurrence of such shading, this shading can be compensated for substantially instantaneously by simply selecting the appropriate set of luminaires to be engaged.

Alternatively, the area lighting system may further comprise a light plan stored in a further data storage device, wherein the controller is adapted to retrieve the subset of the plurality of luminaires from said light plan, for instance by identifying the luminaires arranged to aim the luminous outputs at a shaded region or sunlit region. The further data storage device may be the same as or may be different to the data storage device.

In an embodiment, the controller is adapted to adjust a dimming level of at least some of the luminaires in said subset to reduce the shading in the identified shaded regions. In this embodiment, rather than simply switching a selected luminaire on, the intensity of its luminous output may be controlled as a function of the detected illumination characteristic in order to achieve improved matching between the lighting levels generated by the sun and lighting levels generated by the selected luminaires, thus minimizing contrast between sunlit regions and luminaire-illuminated regions of the area.

In an embodiment, the controller is adapted to set a color point of a luminous output of at least some of the luminaires in said subset to reduce the contrast between the identified sunlit regions and shaded regions. In this embodiment, rather than simply switching a selected luminaire on, the colour of its luminous output may be controlled as a function of the detected illumination characteristic in order to achieve improved matching between the lighting colours generated by the sun and lighting colours generated by the selected luminaires, thus minimizing contrast between sunlit and luminaire-illuminated regions of the area. This is based on the realization that at different times of the day and/or different times of year the colour of the sunlight may be different, for instance because of the different angles under which the sunlight enters the Earth's atmosphere relative to the geographical location of the area.

The controller may be further adapted to readjust the luminaires in said subset in response to the sensor arrangement no longer detecting the illumination characteristic. This therefore ensures that as soon as substantial shadowed generation no longer takes place, for example because the sun has set or has been obscured by clouds, the luminaires previously controlled to reduce the contrast between sunlit regions and shaded regions of the area are reset to their original settings to ensure that the area remains illuminated as intended, e.g. substantially homogeneously illuminated. In a preferred embodiment, each luminaire comprises at least one solid state lighting element such as a light emitting diode. Solid state lighting elements can be switched to full power, dimmed or switched off relatively instantaneously and as such are particularly suitable to instantaneously illuminate regions of the area that suddenly become shadowed due to the presence of structural elements between the sun and the area, thus minimizing the duration of the large contrast between solar-illuminated and shaded regions on the area. Such solid state lighting elements can routinely be switched with switching frequencies well in excess of 1 Hz and are therefore particularly suitable for application in embodiments of the area lighting system of the present invention.

The area lighting system may be an arena lighting system although the invention is not limited to arena lighting systems as previously explained.

According to another aspect, there is provided a method of operating an area lighting system comprising a plurality of luminaires for illuminating respective portions of the area, the method comprising determining a solar illumination characteristic in a particular solar position; accessing predetermined information predicting shaded regions in said area caused by structural features in between the sun and the area exposed to solar illumination in different solar positions to identify the sunlit regions and/or shaded regions in said area for the determined solar illumination characteristic in the particular solar position; identifying a subset of the plurality of luminaires arranged to illuminate the identified sunlit regions or shaded regions; and controlling an illumination of luminaires in said subset to reduce the contrast between said identified sunlit and shaded regions.

This method ensures that shadow formation on the area due to the presence of structural elements between the sun illuminating the area and the area is compensated for, thereby reducing the contrast between solar-illuminated regions and shaded regions of the area, which facilitates better viewing and image-capturing conditions as previously explained.

In an embodiment, controlling the illumination of luminaires in said subset to reduce the contrast between said identified sunlit regions and shaded regions comprises increasing the luminous output of an identified subset of the plurality of luminaires arranged to illuminate the identified shaded regions. This is a particularly effective way of reducing such contrast.

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the invention are described in more detail and by way of non- limiting examples with reference to the accompanying drawings, wherein:

FIG. 1 schematically depicts shadows cast on an area by the sun in a solar position;

FIG. 2 schematically depicts shadows cast on an area by the sun in another solar position;

FIG. 3 schematically depicts a method of predicting shaded regions on an area according to an embodiment

FIG. 4 schematically depicts an area lighting system according to an embodiment;

FIG. 5 schematically depicts an area including aspects of an area lighting system according to an embodiment; and

FIG. 6 schematically depicts a method of operating an area lighting system according to an embodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

FIG. 1 schematically depicts an area 20 illuminated during daylight hours by the sun 30. The area 20 may be any area that can be illuminated during daylight hours by the sun 30, such as for example a sports area such as a pitch, track, swimming pool, and so on in case of the area forming part of a sports arena 10, e.g. a stadium or the like, although it should be understood that embodiments of the present invention may equally be applied to different types of areas 20, e.g. indoor floor areas that can receive daylight through one or more windows, building facades, outdoor areas such as parking lots, and so on where for whatever reason a particular type of illumination of the area 20 may be desirable, such as an illumination pattern having minimal contrast between different regions of the area 20, e.g. a (substantially) homogeneous illumination pattern.

Such areas 20 typically have structural elements 12 in their vicinity that can cast shadows in regions 22 of the area 20 due to the fact that these structural elements 12 are in the light path between the sun 30 and the area 20 when the area 20 is directly lit by the sun 30, i.e. no clouds obscure the sun 30. Such structural elements 12 may form part of a structure associated with the area 20, for example parts of a sports arena 10 such as a roof structure, elevations such as spectator stands or other buildings, and so on. Other examples of such structural elements 12 may include erected structures such as walls, ceilings, lamp posts, masts, adjacent buildings, and so on that can cast shadows in regions 22 of the area 20. In the context of the present application, a shaded region 22 of the area 20 is a region that cannot be directly illuminated by the sun 30 due to the presence of a structural element in the light path between the sun 30 and the shaded region 22. In contrast, a sunlit region 24 is a region that is directly illuminated by the sun 30. On a sunny day, the area 20 typically consists of sunlit regions 24 and shaded regions 22, with the sunlit regions 24 complementing the shaded regions 22 when defining the illumination pattern of the area 20. For the avoidance of doubt, although reference is made to such regions in plural, it should be understood that each of the sunlit regions 24 and shaded regions 22 may be a single region.

As is well-known per se, the sun 30 travels through the sky along a trajectory commonly referred to as the sun path, which refers to the apparent significant seasonal-and- hourly positional changes of the sun caused by the rotation of the Earth. This causes the shaded regions 22 and sunlit regions 24 of the area 20 to change as a function of the position of the sun 30 along its sun path. This is schematically depicted in FIG. 2, which depicts the sun 30 in a different position compared to its position in FIG. 1, causing shaded regions 22' in different regions of the area 20 compared to the positioning of shaded regions 22 in FIG. 1. This is because the sun 30 illuminates the structural elements 12 from a different angle and/or because other structural elements 12 block part of the area 20 from being illuminated by the sun 30, thus causing shaded regions 22' on the area. Sun paths at any latitude and any time of the year can be determined from basic geometry. The Earth's axis of rotation tilts about 23.5 degrees, relative to the plane of Earth's solar system orbit around the sun 30. As the Earth orbits the sun, this creates the 47-degree peak-to-peak solar altitude angle difference, and the hemisphere-specific difference between summer and winter.

Embodiments of the present invention are based on the insight that the positioning of shaded regions on the area 20 can be predetermined as they are a function of solar position, i.e. the position of the sun 30 along a particular sun path and the position of fixed structural elements 12 around the area 20. In other words, for a given solar position, the positioning of the shaded regions on the area 20 will always be the same as long as the same fixed structural elements 12 interfere with the sunlight projected towards the area 20.

Consequently, for a given solar position, the area 20 will exhibit shaded regions in specific locations on the area 20, which facilitates targeted illumination of these particular shaded regions during illumination characteristics in which the area 20 is directly lit by the sun 30, causing significant contrast between directly sun-lit regions and shaded regions of the area 20. This may cause problems in observing movement across the area 20, either by observers or by cameras having limited dynamic capabilities, where following movement across the area 20 may cause underexposure or overexposure of a captured image, which is undesirable. This is particularly problematic during certain times of day where the sun 30 is relatively close to the horizon, which may cause long and potentially harsh shadows to be cast on the area 20 by the structural elements 12 surrounding it.

To this end, embodiments of the present invention provide data specifying shaded regions on the area 20 as a function of solar position and/or complementary data specifying sunlit regions 24 on the area 20. Such shaded regions and/or sunlit regions may be directly linked to solar position or may be indirectly linked to solar position, for instance by being linked to a particular date and time for which the solar position can be accurately predicted as previously explained. Such a data may be generated in any suitable manner, for example by measuring the positioning of shaded regions on the area 20 at certain points in time, e.g. by one or more cameras up serving the entire area 20 and calculating the positioning of the shaded regions by evaluation of the illumination patterns observed by the one or more cameras. Sunlit regions may be determined in a similar manner, for instance as the complement of the determined shaded regions. All data identifying shaded regions and/or sunlit regions as a function of a particular solar position may be determined in this manner, i.e. experimentally, or at least part of the data may be extrapolated by simulation from experimentally determined data points. Alternatively, all data may be extrapolated by simulation, for example by using a model accurately positioning and dimensioning the structural elements 12 relative to the area 20 and using well-known algorithms to predict solar positions at a particular date and time to simulate, i.e. predict, the shaded regions generated by the sun 30 in a particular solar position.

An example embodiment of a method 60 for creating a dataset of predetermined shaded regions of the area 20 as a function of solar position and fixed structural elements 12 is schematically depicted by the flowchart of FIG. 3. The method 60 starts in step 61 after which the method proceeds to step 62 in which a particular solar position, i.e. the position of the sun 30 along a particular sun path, is determined, for example by association of the solar position with a particular date and time or by determining the solar position relative to the area 20, which for example may be achieved using a movable light sensor such as a camera including an orientation sensor, which light sensor may be adapted to track the sky in order to locate the sun 30, with the orientation sensor facilitating the determination of the orientation of the light sensor associated with the identified location of the sun 30 in the sky.

In step 63, the shaded regions of the area 20 that are cast upon the area 20 by structural elements 12 with the sun 30 in the determined solar position are determined or predicted, e.g. measured or simulated as previously explained and added to the dataset in step 64, which dataset may be stored in a suitable data storage medium in step 65. The shaded regions of the area 20 that are cast upon the area 20 by structural elements 12 with the sun 30 in the determined solar position may be determined or predicted based on the geographic location and positioning of the area 20 relative to the relevant sun paths as will be readily understood by the skilled person.

In some embodiments of the present invention, the dataset may be integrated in an algorithm that can be executed by a controller of an area lighting system, whereas in some other embodiments of the present invention the dataset may be stored in the form as a database, look up table or the like where the shaded regions of the area 20 or information associated with such shaded regions, such as a set of luminaires to be engaged, which set of luminaires are aimed at the shaded regions on the area 20 when the sun 30 is in a particular solar position. Such a dataset for instance may be accessed by a controller of the area lighting system, for example when executing particular control instructions, e.g. in the form of a computer program or algorithm, where the controller may be adapted to access the dataset in order to retrieve the data identifying the predetermined or predicted shaded regions for a particular solar position.

It may be checked in step 66 if further data, e.g. shaded regions on the area 20 for further solar positions needs determining or predicting, which if this is the case may cause the method 60 to revert back to step 62, or which if this is not the case may cause the method 60 to terminate in step 67. It will be readily understood that predetermined information regarding time-dependent positioning of sunlit regions on the area 20 may be derived simultaneously or analogously.

The thus obtained predetermined information or data may be used to accurately predict future shaded regions of the area 20 and to configure and control an area lighting system for illuminating the area 20 such that during certain (future) illumination characteristics, typically illumination characteristics that cause the generation of shaded regions on the area 20 with the sun 30 in a particular solar position, the area lighting system may be controlled to increase the illumination of the shaded regions of the area 20 only, thereby reducing contrast between the shaded regions and the sunlit regions of the area 20. Alternatively, the area lighting system may be controlled to decrease the illumination of sunlit regions of the area 20 only to reduce contrast between the shaded regions and sunlit regions of the area 20. In yet another embodiment, illumination of shaded regions may be increased and illumination of sunlit regions may be decreased to reduce such contrast. In the context of the present application, increasing illumination of the luminaire includes switching on the luminaire as well as reducing a dimming level of the luminaire, whereas decreasing illumination of the luminaire includes switching of the luminaire as well as increasing a dimming level of the luminaire.

FIG. 4 schematically depicts an area lighting system 100 according to an embodiment and FIG. 5 schematically depicts the luminaires 1 10 of such an area lighting system 100 positioned around an area 20, here a sports area of an arena 10, e.g. a stadium, by way of non-limiting example. The illumination system 100 comprises a plurality of luminaires 1 10 for mounting relative to the area 20 such that the luminaires 1 10 can be aimed at selected regions of the area 20 in order to generate a predefined illumination pattern, such as a (substantially) homogeneous illumination of the area 20. For example, in case of a sports arena 10, the luminaires 1 10 may be mounted around the area 20, i.e. around the sports area such as a field, pitch, track, pool or the like, in order to achieve the predefined illumination pattern. For example, the luminaires 1 10 may be mounted in dedicated mounting frames to be positioned in selected positions of the sports arena, e.g. in proximity corners of the area 20, in which case each mounting frame may include a mast for elevating the mounting frame to a desired height in order to achieve pitch illumination under suitable illumination angles. A particularly common arrangement is where the luminaires 1 10 are mounted on the stands and seating areas around the area 20, wherein the luminaires 1 10 may be mounted on different tiers of the spectator areas to achieve pitch illumination under a range of illumination angles. This for instance is advantageous when trying to achieve uniform or homogeneous illumination of a pitch region under different viewing angles, e.g. from different camera positions for capturing sports action on the area 20 for broadcasting purposes, where the illumination requirements may be more easily achieved when illuminating a pitch region from multiple illumination angles.

However, it will be understood that where the area lighting system 100 is arranged to illuminate a different type of area 20 as previously explained, the luminaires 1 10 may be mounted in different relative positions with respect to the area 20 to be illuminated; for instance, in case of the area 20 being the facade of the building, the luminaires 1 10 may be mounted opposite the area 20, in case of the area 20 being a floor area of a commercial building or parking lot, the luminaires 1 10 may be mounted above the area 20, and so on.

The luminaires 1 10 or their mounting may comprise an orientation adjustment mechanism that allows for the adjustment of the aim of a luminaire 1 10, such that the luminaire 1 10 can be aimed at a different part of the area 20. For example, the luminaire 1 10 may be mounted using a suitable mounting point or jig configured to be adjustable in order to change the orientation of the luminaire 1 10. This adjustment in some embodiments is a two dimensional adjustment. Suitable adjustments can be any of the following: an orientation around a horizontal axis (a tilt adjustment); an orientation around a vertical axis (a pan adjustment); and an orientation around the optical axis of the luminaire (a roll adjustment). The orientation adjustment mechanism may be manually adjustable. In at least some embodiments, the orientation adjustment mechanism may be electronically controllable, in which case the adjustment mechanism for instance may comprise an electromotor or the like to automatically adjust the orientation of the luminaire 1 10 in accordance with a control signal provided to the electronically controllable orientation adjustment mechanism.

The luminaires 1 10 may be any suitable type of luminaire. Suitable luminaires 1 10 typically are luminaires that can reach full flux relatively quickly, e.g. within 10 seconds or less, preferably within 1 second or less such that sudden changes in the illumination characteristics affecting the illumination of the area 20, e.g. the sun 30 appearing from behind a cloud, thus suddenly causing the formation of shaded regions on the area 20, can be rapidly compensated. In a particularly preferred embodiment, each luminaire 1 10 comprises at least one solid state light source such as a LED or LED package, i.e. a LED-based luminaire such as a LED-based flood light or the like, as such solid state light sources can substantially instantaneously reach full flux when being switched on. In at least some embodiments, the luminaires 1 10 may be dimmable and/or may be capable of generating a luminous output of different colours, for example by comprising a plurality of individually controllable solid state lighting elements such as LEDs configured to generate luminous outputs of different spectral compositions, e.g. luminous outputs of different colours or colour temperatures such as white light having different colour temperatures, e.g. cool light or warm white light.

The area lighting system 100 further comprises a controller 120 adapted to control the plurality of luminaires 1 10, with the controller 120 at least in some embodiments being adapted to control individual luminaires 1 10. The controller 120 may be adapted to simply switch on and off selected luminaires 1 10 although in at least some embodiments the controller 120 may be further adapted to adjust the luminous flux of selected luminaires 1 10, i.e. to set a dimming level of selected luminaires 1 10 and/or to adjust the spectral

composition of the luminous output of selected luminaires 1 10 as previously explained. The controller 120 may comprise a processor 121 for executing computer-readable program instructions that cause the controller 120 to control the luminaires 1 10 as explained above. The processor 121 may be a generic processor, such as a processor of a computer

implementing the controller 120 or may be a dedicated or application-specific processor, e.g. an ASIC, specifically designed to control the luminaires 1 10.

The area lighting system 100 further comprises a data storage device 130 storing the dataset of predetermined or predicted shaded regions and/or sunlit regions on the area 20 as a function of solar position and the fixed structural elements 12 as explained in more detail above. The data storage device 130 may be any suitable type of data storage device, such as any suitable type of memory, a magnetic or optical disk or disk array, and so on, which data storage device 130 may be integral to or physically separate from the controller 120. In some embodiments, the area lighting system 100 may not comprise the data storage device 130 but instead may be communicatively coupled to a remote data storage device 130, e.g. via a wired or wireless network such as a LAN, WAN, the Internet, and so on. For example, the remote data storage device 130 may form part of a remote data storage architecture such as a web server or a cloud storage architecture although other suitable remote implementations of the remote data storage device 130 will be immediately apparent to the skilled person.

In at least some embodiments, the dataset of predetermined or predicted shaded regions and/or sunlit regions on the area 20 as a function of a particular solar position and fixed structural elements 12 may form part of a computer program or algorithm for execution by the controller 120 or alternatively may be accessible by such a computer program or algorithm when executed by the controller 120. In the latter embodiment, the computer program or algorithm to be executed by the controller 120 may be stored in any suitable location, e.g. on the data storage device 130 or on a separate data storage device, such as a data storage device, e.g. a memory, optical disk, solid state disk or magnetic disk, internal to the controller 120 by way of non-limiting example.

The lighting system 100 further comprises a sensor arrangement 150 adapted to determine a solar illumination characteristic 30 in a particular solar position, which sensor arrangement 150 is communicatively coupled to the controller 120 and provides the controller 120 with an input for the computer program or algorithm to retrieve the appropriate information relating to shaded regions on the area 20 for the sensed solar illumination characteristic 30 in the particular solar position.

In an embodiment, the sensor arrangement 150 comprises a light intensity sensor adapted to detect the light intensity of the daylight generated by the sun 30, which light intensity when exceeding a predefined threshold, may be indicative of the area 20 being directly exposed to sunlight, thereby implying that the area 20 comprises shaded regions caused by shadows cast on the area 20 by the fixed structural elements 12 in between the area 20 and the sun 30 in a particular solar position. In this embodiment, the controller 120 may be adapted to determine the particular solar position by retrieving the actual date and time at which the illumination characteristic is determined by the light intensity sensor, which actual date and time can be used to determine or retrieve the particular solar position, i.e. the actual solar position and to retrieve the appropriate data from the dataset stored in the data storage device 130, that is, the data belonging to the retrieved particular solar position in case the data in the dataset is categorized as a function of solar positions.

Alternatively, the data in the dataset may be categorized as a function of particular dates and times, i.e. by implicit reference to particular solar positions, in which case the controller 120 may simply retrieve the appropriate data using the determined date and time. The controller 120 may determine the actual date and time in any suitable manner. For example, the controller 120 may incorporate a timing device such as a clock for determining the actual date and time or alternatively may be communicatively coupled to an external timing device such as an external clock for retrieving the actual date and time from the external timing device. The external timing device may form part of the sensor arrangement 150 or may be separate thereof.

In an alternative embodiment, the sensor arrangement 150 comprises a movable or adjustable light sensor such as a movable or adjustable camera that can track the sky to focus on the sun 30 in its actual solar position. In this embodiment, the sensor arrangement 150 typically further comprises an orientation sensor integral to or coupled to the movable or adjustable light sensor for determining the orientation of the movable or adjustable light sensor in its orientation when focusing on the sun 30 in its actual solar position, which orientation data may be provided to the controller 120 such that the controller 120 can retrieve the appropriate shading data from the dataset stored in data storage device 130 from the received orientation data. In this embodiment, each data entry in the dataset corresponding to a particular solar position may be identified by a particular instance of the orientation data such that the controller 120 may retrieve the appropriate shading and/or sunlit data from the dataset stored in data storage device 130 by matching the received orientation data with the orientation data stored in the dataset.

The sensor arrangement 150 optionally further comprises a light intensity sensor, wherein the movable or adjustable light sensor is adapted to search for the actual solar position only when the light intensity measured by the light intensity sensor exceeds a predetermined threshold, which may be indicative of the formation of shaded regions on the area 20 by the sun 30 in its actual solar position. This has the advantage that the movable or adjustable light sensor is not required to constantly track the sky, thereby avoiding unnecessary tracking of the sky, e.g. under cloudy conditions.

The sensor arrangement 150 preferably is positioned relative to the area 20, e.g. in or on the arena 10, such that the sensor arrangement 150 or at least the light intensity sensor and/or the movable or adjustable light sensor is not obscured by a fixed structural element 12 in any of the solar positions the sun 30 may adopt, such that an accurate determination of a illumination characteristic indicative of the formation of shaded regions on the area 20 can be achieved.

The luminaires 100 may be positioned and aimed in accordance with a light plan, which may be stored in a data storage device 140 accessible to the controller 120. Such a light plan for instance may include positional information and aiming information for each luminaire 1 10, e.g. a list or table of luminaires installed relative to the area 20, e.g. within a stadium or building, the type of luminaire, the mounting or placement location of the luminaires 1 10, which may be specified relative to a known reference point such as the center point or spot of a stadium, the desired orientation of the luminaire, and the desired aiming point of the luminaire 1 10, which may be specified relative to the known reference point for instance.

The data storage device 140 may be any suitable type of data storage device, such as any suitable type of memory, a magnetic or optical disk or disk array, and so on, which data storage device 140 may be integral to or physically separate from the controller 120. In some embodiments, the area lighting system 100 may not comprise the data storage device 140 but instead may be communicatively coupled to a remote data storage device 140, e.g. via a wired or wireless network such as a LAN, WAN, the Internet, and so on. For example, the remote data storage device 140 may form part of a remote data storage architecture such as a web server or a cloud storage architecture although other suitable remote implementations of the remote data storage device 140 will be immediately apparent to the skilled person. The data storage devices 130 and 140 may be or may form part of one and the same data storage device or may be distinct data storage devices.

In an embodiment, the dataset identifying information related to sunlit regions and/or shaded regions on the area 20 generated by the fixed structural elements 12 in between the area 20 and the sun 30 in a particular solar position may simply identify regions of the area 20 that are shaded when the sun 30 is in a particular solar position, which particular solar position may be explicitly determined or may be implied by a particular date and time as previously explained. In this embodiment, the controller 120 may be adapted to analyze the light plan to identify and select the luminaires 1 10 that are aimed at the identified sunlit regions and/or shaded regions.

In an alternative embodiment, the dataset identifying information related to sunlit regions and/or shaded regions on the area 20 generated by the fixed structural elements 12 in between the area 20 and the sun 30 in a particular solar position may include

predetermined subsets of luminaires 1 10 aimed at the sunlit regions and/or shaded regions, e.g. from a prior evaluation of the light plan, such that upon detection of a illumination characteristic indicative of the generation of shaded regions on the area 20 by the sun 30 in a particular solar position, it is not necessary for the controller 120 to evaluate the light plan to identify the appropriate subset of luminaires 1 10 to be controlled but instead the controller 120 can simply retrieve the appropriate subset of luminaires 1 10 to be controlled to reduce contrast between the sunlit regions and shaded regions from the dataset stored in the data storage device 130, which may improve the reaction speed of the area lighting system 100 to the sudden occurrence of a particular illumination characteristic indicative of the generation of shaded regions on the area 20.

An example embodiment of a method 80 of operating such an area lighting system 100 is schematically depicted by the flowchart of FIG. 6. After starting in step 81, e.g. by initializing the controller 120 and sensor arrangement 150 of the lighting system 100, the method 80 proceeds to step 82 in which the predetermined predicted shaded regions on the area 20 generated by fixed structural elements 12 as a function of a particular solar position and/or the complementary sunlit regions are made available, e.g. by enabling communication between the controller 120 and the data storage device 130. This allows the controller 120 to control the luminaires 1 10 that are aimed at the regions of the area 20 that are shaded and/or the luminaires 1 10 that are aimed at the regions of the area 20 that are sunlit when the sun 30 is in a particular solar position. Next, the actual natural illumination characteristics on or around the area 20, e.g. within or outside an arena 10, are monitored in step 83 using the sensor arrangement 150. The sensor output of the sensor arrangement 150 is provided to the controller 120, which decides in step 84 if the actual natural illumination characteristic sensed by the sensor arrangement 150 is indicative of the generation of shadows in predetermined or predicted regions of the area 20, e.g. by detection of a light intensity above a particular threshold or by detection of the sun in the sky, which may include the provision of orientation information regarding the orientation of a light sensor focusing on the sun 30 in its solar position such that this solar position can be derived from the orientation information as previously explained.

In case the controller 120 determines that the detected natural illumination characteristics are indicative of the presence of shaded regions on the area 20, the method 80 proceeds to step 85 in which the controller 120 identifies the information relating to the relevant shaded regions and/or complementary sunlit regions from the dataset stored in data storage device 130, which may be information identifying the shaded regions and/or sunlit regions or may be information identifying the luminaires 1 10 aimed at the predetermined or predicted shaded regions and/or sunlit regions as previously explained, which information is used by the controller 1 10 to select the subset of luminaires 1 10 aimed at these shaded regions and/or sunlit regions in step 86, e.g. by evaluating a light plan or by retrieving previously identified subset of luminaires 1 10 from the dataset in the data storage device 130 as previously explained, after which the controller 120 controls the selected subset of luminaires 1 10 such that the area lighting system 100 reduces the contrast between such sunlit regions and shaded regions, for instance only or more brightly illuminates the regions shaded by the fixed structural elements 12 with the sun 30 in its particular solar position. This may be achieved by reducing the luminous output of luminaires aimed at the sunlit regions, e.g. dimming or switching off such luminaires, and/or may be achieved by increasing the luminous output of luminaires aimed at shaded regions, e.g. reduce the dimming or switching on such luminaires.

The controller 120 may be adapted to simply switch on (or off) the selected subset of luminaires 1 10 or may be adapted to tune the luminous output of at least some of the selected luminaires 1 10 to the detected natural illumination characteristic. For example, the intensity or brightness of the sunlight of the sun in a particular solar position may vary depending on atmospheric conditions, e.g. thin clouds, smog, and so on, in which case the controller 120 may be adapted to adjust a dimming level of at least some of the selected luminaires 1 10 in order to match the luminous flux, i.e. the luminous output intensity, produced by the selected luminaires 1 10 to the detected natural illumination characteristic to minimize contrast between regions of the area 20 that are illuminated by the sun 30 and shaded regions of the area 20.

The controller 120 may be additionally or alternatively adapted to match the spectral composition of the luminous output of at least some of the selected luminaires 1 10 to the spectral composition of the sunlight, which may be detected by a sensor arrangement 150 including a spectral analyzer or alternatively which may be predefined based on a particular solar position or date and time indicative of a particular solar position, as the spectral composition of sunlight typically is a function of solar position. For example, each luminaire 1 10 may comprise a plurality of solid state lighting elements arranged to produce luminous outputs of different spectral compositions, where the controller 120 may be adapted to control individual solid state lighting elements of such a plurality, e.g. by switching on/off and/or adjusting dimming levels of individual solid state lighting elements in order to match the spectral composition of the luminous output of the luminaires 1 10 to the spectral composition of the sunlight. This has the advantage that the regions of the area 20 directly illuminated by the sun 30 (and a subset of the luminaires 1 10) and the shaded regions of the area 20 illuminated by selected luminaires 1 10 have a similar appearance, which reduces contrast between these regions and may improve aesthetic appearance of the overall illumination of the area 20.

In an embodiment, the area lighting system 100 may be adapted to continuously monitor the actual natural illumination characteristics with the sensor arrangement 150 such that the controller 120 may readjust the selected luminaires 1 10 as soon as the monitored natural illumination characteristic is indicative of shaded regions no longer being present on the area 20, for example because the sun 30 has disappeared behind clouds such that the area 20 is no longer directly illuminated by the sun 30. Such

readjustment for instance may reset the selected luminaires 1 10 to the original settings, e.g. the settings prior to the detection of the natural illumination characteristic triggering the contrast-lowering illumination of selected regions of the area 20. To this end, the method 80 may decide in step 88 that continued monitoring of the actual natural light conditions or solar positions is required, which causes the method 80 to revert back to step 83 to continue monitoring of the actual natural illumination characteristic or solar position.

In an embodiment, the controller 120 may be adapted to periodically adjust the selected set of luminaires 1 10 based on the actual solar path of the sun 30 such that changes in the sunlit and shaded regions on the area 20 caused by the sun 30 travelling along its actual solar path are matched by changes to the illumination pattern produced by the area lighting system 100, i.e. the illumination pattern produced by the area lighting system 100 is adjusted by adjusting the selection of luminaires 1 10 in order to dynamically, i.e. periodically, compensate for changes to the locations of the sunlit and shaded regions on the area 20 caused by the changes in the solar position of the sun 30.

The controller 120 may continue to monitor the actual natural illumination characteristic and/or periodically adjust the selection of luminaires 1 10 to compensate for changes in the solar position until it is decided in step 88 that it is no longer necessary to compensate shaded regions on the area 20, for example because the sun has set and the area 20 needs to be entirely illuminated by the area lighting system 100, i.e. by all luminaires 1 10, or because there no longer is a need to observe the area 20, for example because a sports event has finished, a shop or parking lot comprising such an area has closed, and so on. If it is decided in step 88 that is no longer necessary to compensate shaded regions on the area 20, the method 80 may terminate in step 89.

It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. 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.

Claims

CLAIMS:

1. An area lighting system ( 100), comprising:

a plurality of luminaires (1 10) for illuminating respective portions of an area

(20);

a sensor arrangement (150) adapted to determine a solar illumination characteristic (30) in a particular solar position; and

a controller (120) for individually controlling said luminaires; said controller being responsive to the sensor arrangement and being adapted to:

access predetermined information predicting shaded regions (22, 22') in said area caused by structural features (12) in between the sun and the area exposed to solar illumination in different solar positions to identify the shaded regions and/or sunlit regions in said area for the determined solar illumination characteristic in the particular solar position;

identify a subset of the plurality of luminaires arranged to illuminate the identified shaded regions or sunlit regions; and

control an illumination of luminaires in said subset to reduce the contrast between sunlit regions and shaded regions.

2. The area lighting system (100) of claim 1, wherein said area is a sports area, building facade, work area, parking area or indoor floor area that can receive daylight.

3. The area lighting system (100) of claim 1 or 2, wherein the sensor arrangement (150) comprises a light intensity sensor, and wherein the controller (120) is further adapted to obtain a point in time indicative of the particular solar position.

4. The area lighting system (100) of claim 1 or 2, wherein the sensor arrangement (150) comprises a light sensor arranged to identify the particular solar position.

5. The area lighting system (100) of any of claims 1-4, wherein the

predetermined information predicting shaded regions (22, 22') in said area (20) caused by structural features (12) in the vicinity of the area exposed to solar illumination (30) in different solar positions is comprised in an algorithm for identifying the shaded regions in said area as a function of a determined natural solar illumination characteristic in a particular solar position, and wherein the controller (120) is adapted to execute said algorithm using the determined illumination characteristic as an algorithm input.

6. The area lighting system (100) of any of claims 1 -5, wherein the area lighting system comprises a data storage device (130) storing the predetermined information, wherein the controller (120) is adapted to access the predetermined information in the data storage device.

7. The area lighting system (100) of any of claims 1 -6, wherein the

predetermined information further comprises identification information for the respective subsets of luminaires (1 10) to be engaged for different solar positions to reduce the contrast between predicted sunlit regions and shaded regions (22, 22') caused by structural features (12) exposed to solar illumination (30) in different solar positions, the controller (120) being adapted to identify a subset of the plurality of luminaires arranged to illuminate the predicted shaded regions and/or sunlit regions from the predetermined information.

8. The area lighting system (100) of any of claims 1 -6, further comprising a light plan stored in a further data storage device (140), wherein the controller (120) is adapted to retrieve the subset of the plurality of luminaires from said light plan.

9. The area lighting system (100) of any of claims 1-8, wherein the controller (120) is adapted to adjust a dimming level of at least some of the luminaires (1 10) in said subset to reduce the contrast between the identified sunlit regions and shaded regions (22, 22').

10. The area lighting system (100) of any of claims 1-9, wherein the controller (120) is adapted to set a color point of a luminous output of at least some of the luminaires (100) in said subset to reduce the contrast between the identified sunlit regions and shaded regions (22, 22').

1 1. The area lighting system (100) of any of claims 1-10, wherein the controller

(120) is further adapted to readjust the luminous output of the luminaires (1 10) in said subset in response to the sensor arrangement (150) no longer detecting the illumination

characteristic.

12. The area lighting system (100) of any of claims 1-1 1, wherein each luminaire (1 10) comprises at least one solid state lighting element such as a light emitting diode.

13. The area lighting system (100) of any of claims 1-12, wherein the area lighting system is an arena lighting system.

14. A method (80) of operating an area lighting system (100) comprising a plurality of luminaires (1 10) for illuminating respective portions of an area (20), the method comprising:

determining (83) a solar illumination characteristic (30) in a particular solar position;

accessing (85) predetermined information predicting shaded regions (22, 22') in said area caused by structural features (12) in between the sun and the area exposed to solar illumination in different solar positions to identify the sunlit regions and/or shaded regions in said area for the determined solar illumination characteristic in the particular solar position;

identifying (86) a subset of the plurality of luminaires arranged to illuminate the identified sunlit regions or shaded regions; and

controlling (87) an illumination of luminaires in said subset to reduce the contrast between said identified sunlit regions and shaded regions.

15. The method (80) of claim 14, wherein controlling (87) the illumination of luminaires in said subset to reduce the contrast between said identified sunlit regions and shaded regions comprises increasing the luminous output of an identified subset of the plurality of luminaires (1 10) arranged to illuminate the identified shaded regions (22,22').