FIELD OF THE INVENTION

The present invention relates to a projection system for aiding the installation of a large area lighting system in accordance with a light plan including an aiming target defined relative to a reference feature associated with the large area.

The present invention further relates to a large area lighting system including such a projection system.

The present invention yet further relates to a method of generating an aiming target to aid the installation of a large area lighting system in accordance with a light plan including said aiming target defined relative to a reference feature associated with the large area.

BACKGROUND OF THE INVENTION

Many high-end lighting applications require a plurality of luminaires aimed at an area of given size, i.e. a large area, to generate a predefined illumination pattern on the area. Examples of such applications include arena lighting systems for illuminating sports arenas, e.g. field, pitch or stadium lighting, facade lighting, shop floor lighting, parking lot lighting and so on. The desired predefined illumination pattern may be a uniform or homogenous lighting pattern.

A light designer may be employed to create a so-called light plan for the area to be illuminated, in which the light designer determines the mounting positions of the luminaires relative to the area to be illuminated and the aiming information for the luminaires, e.g. in which orientation the luminaires are to be mounted such that the luminaires can cooperate to generate the predefined illumination pattern. The light plan may contain, for each luminaire, information such as the type of luminaire, the mounting location and orientation of the luminaire, and the aiming location or point relative to a fixed reference point associated with the large area, e.g. relative to the centre of the area to be illuminated. For example, a football stadium may have a light plan or design where the large area lighting system contains more than 100 luminaires each mounted on part of the stadium and with a desired aiming location or point on the pitch to attempt to provide a suitable lighting effect. The light designer may create such a light plan remotely, e.g. by employing illumination simulations for the area to be illuminated, which simulations may yield the light plan to be implemented.

Such a light plan is typically used by a lighting system installer to install the luminaires in their relative positions and to aim the luminaires in accordance with the provided aiming information. This however is not without problems. For example, the installer may have difficulty in correctly aiming the luminaires, for instance because of a lack of a clear reference on the area to aim at. From the luminaire location, the installer has a clear overview of the field but it is very difficult to accurately determine the aiming location in the field.

To improve the accuracy of the alignment procedure, the installer can use a grid created by manually putting visual markers on the area to be illuminated at the required coordinates and a laser pointer aligned with the luminaire optical axis. In such a way the alignment is a matter of aiming the laser spot at the requested visually interpolated locations on the grid. However, the placement of the visual markers on the area is an elaborate task and the alignment itself based on the laser spot is prone to errors. Moreover, such a procedure is less suitable for inclined or vertical areas, e.g. facades, or areas with non-solid surfaces to be illuminated, e.g. swimming pools.

US 8,717,552 Bl discloses methods and apparatuses that can be utilized for accurate pre-aiming and installation of devices. The devices are pre-set to an aiming orientation relative to a universal reference plane. The reference plane is then correlated to a feature of a pole, tower, or other structure that will be used to elevate or suspend the devices. A position sensing subsystem is utilized to inform a worker when each device is correctly angularly oriented to the reference plane. The worker simply moves the mounting structure for the device to the correct three-dimensional angular orientation, uses the position sensor to confirm the correct orientation to within a highly accurate margin of error, and either locks the device in that orientation or marks the orientation. The pole, tower, or other elevating structure is preliminarily erected at its pre-designed location and pre-designed rotational orientation with the pre-aimed devices. However, this solution is not particularly flexible as it requires the pre-aiming of the devices, which may be undesirable if for whatever reason the device cannot be installed in its intended location. In addition, errors in the device pre-aiming or installation of a device intended for a particular location in a different location leads to an inaccurate implementation of a light plan, which may be difficult to redress on-site due to the absence of on-site aiming of the devices. SUMMARY OF THE INVENTION

The present invention seeks to provide a projection system for projecting a grid of visual markers, said grid of visual markers being used for aiming a luminaire of a large area lighting system in accordance with a light plan, wherein the light plan includes an aiming target defined relative to a reference feature associated with the large area that facilitates accurate on-site luminaire aiming without requiring physical aiming markers.

The present invention further seeks to provide a large area lighting system including such a projection system.

The present invention yet further seeks to provide a method of projecting a grid of visual markers for aiming a luminaire of a large area lighting system in accordance with a light plan including said aiming target defined relative to a reference feature associated with the large area that can be actioned without requiring physical aiming markers.

According to an aspect, there is provided a projection system for projecting a grid of visual markers, said grid of visual markers being used for aiming a luminaire of a large area lighting system in accordance with a light plan, wherein the light plan includes an aiming target defined relative to a reference feature associated with the large area, the projection system comprising

a projection unit adapted to (i) project a visual marker in a projection location of the large area and, defined relative to said visual marker in said projection location, (ii) project a grid of visual markers onto the large area, said grid including the visual marker in said projection location;

a position and orientation detector arrangement adapted to detect the position and orientation of the projection unit and provide orientation data; and a controller responsive to the position and orientation detector arrangement and adapted to access a data storage device wherein the light plan is stored; retrieve, from the light plan stored in the data storage device, the aiming target defined relative to the reference feature; identify the position and orientation of the projection unit relative to the reference feature from the orientation data; and control the projection unit in accordance with its identified relative position and orientation such that the projection location coincides with the aiming target.

The provision of such a projection system obviates the need for physical markers to be placed on the large area to be illuminated due to the fact that the physical markers are replaced by the visual markers projected by the projection system. Such visual markers can be accurately projected onto the large area are to be illuminated due to the retrieval of the relevant aiming information from the light plan. Consequently, the projection system according to embodiments of the present invention facilitates accurate on-site implementation of a light plan without requiring physical markers to be placed onto the large area.

In an embodiment, the position and orientation detector arrangement comprises a camera mounted on the projection unit and at least one orientation sensor; and the controller is adapted to identify the position and orientation of the projection unit relative to the reference feature by identification of the reference feature in an image provided by the camera and from orientation information derived from the sensor data provided by the at least one orientation sensor.

As mentioned before, the projection unit may be adapted to project a grid of visual markers onto the large area, said grid including the visual marker in said projection location. This for instance may facilitate a light plan installer to accurately aim a luminaire of the large area lighting system by aiming the luminous output of the luminaire at the designated visual marker for that luminaire.

Alternatively, the controller may be further responsive to a visual marker selection signal and is adapted to select a visual marker from a plurality of visual markers of said light plan for projection by the projection unit in response to the visual marker selection signal. This facilitates (semi-) automatic aiming of the respective luminaires of the large area lighting system due to the fact that a particular luminaire may cause the generation of its visual marker by the projection system in response to the visual marker selection signal generated by the luminaire (or its controller). For example, the luminaire may comprise an optical sensor such as a camera positioned along its aiming direction such that the projected visual marker may be aligned with the aiming direction by aligning the luminaire with the visual marker using the optical sensor.

In an embodiment, the projection unit comprises an orientation adjustment mechanism and the controller is adapted to control the orientation adjustment mechanism in accordance with the identified relative orientation of the projection unit such that the projection location coincides with the aiming target. This facilitates fully automatic alignment of the projection unit in accordance with the light plan.

According to another aspect, there is provided a large area lighting system comprising a plurality of luminaires and the projection system according to any of the embodiments, the large area lighting system further comprising at least one camera for observing illumination of at least a part of the large area, wherein each luminaire is mounted on a luminaire orientation adjustment mechanism and associated with an aiming controller adapted to control the luminaire orientation adjustment mechanism in response to visual feedback provided by the at least one camera; and the aiming controller is adapted to align the luminous output of an associated luminaire with a visual marker projected by the projection unit. This therefore provides a large area lighting system that can be aimed whilst requiring minimal intervention of a lighting system installer due to the fact that the provided visual feedback allows for the automatic alignment of the luminous output of each luminaire with its target visual marker projected by the projection system.

Each luminaire may comprise a camera for observing illumination of at least a part of the large area by said luminaire in order to achieve a particularly accurate alignment of the luminous profile produced by the luminaire with its intended aiming target as identified by the visual marker projected by the projection system.

The large area lighting system may be further adapted to generate a visual marker selection signal for the controller of the projection unit to trigger the projection of a visual marker at the aiming target of a particular luminaire of the large area lighting system. This further automates the aiming of such a large area lighting system as the generation of the relevant visual markers with the projection system may be triggered by the large area lighting system during the aiming of the respective luminaires of that system.

For example, each luminaire may be adapted to generate a visual marker selection signal for the controller of the projection unit to trigger the projection of a visual marker at the aiming target of said luminaire.

According to yet another aspect, there is provided a method of projecting a grid of visual markers for aiming a luminaire of a large area lighting system in accordance with a light plan, wherein the light plan includes said aiming target defined relative to a reference feature associated with the large area, the method comprising providing a projection unit adapted to project a visual marker in a projection location of the large area; detecting the position and orientation of the projection unit; retrieving, by accessing a data storage device wherein the light plan is stored, the aiming target defined relative to the reference feature from the light plan; identifying the position and orientation of the projection unit relative to the reference feature; controlling the projection unit in accordance with the identified relative position and orientation of the projection unit such that the projection location coincides with the aiming target and projecting the visual marker in the projection location comprising projecting, defined relative to said visual marker in said projection location, a grid of visual markers onto the large area, said grid including the visual marker in said projection location. This method therefore facilitates accurate on-site aiming of the luminaires of a large area lighting system without the requirement for the positioning of physical markers on the large area.

This for instance may assist a lighting system installer to identify the correct visual marker at which a luminaire should be aimed from its grid position.

Alternatively, the visual marker may form part of a plurality of visual markers, the method further comprising receiving a visual marker selection signal; selecting a visual marker of said plurality in accordance with the visual marker selection signal; and projecting the selected visual marker onto the large area with the projection unit. This further minimizes the need for manual intervention by the lighting system installer and may in some

embodiments facilitate fully automated aiming of the respective luminaires of the large area lighting system.

Identifying the position and orientation of the projection unit relative to the reference feature may comprise capturing an image of at least a part of the large area with a camera; identifying the reference feature in said image; obtaining orientation information of the projection unit with at least one orientation sensor; and calculating the orientation of the projection unit relative to the reference feature from the identified reference feature within said image and the obtained orientation information such that the projection unit may be correctly positioned automatically.

Calculating the position and orientation of the projection unit relative to the reference feature from the identified reference feature within said image may comprise calculating at least one of said position and orientation from at least one of the size and location of the reference feature within said image.

In an embodiment, the method further comprises aiming a luminaire at a virtual image generated with the projection unit.

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 a large area including a large area lighting system;

FIG. 2 schematically depicts a prior art alignment technique for such a large area lighting system;

FIG. 3 schematically depicts a projection system according to an embodiment; FIG. 4 schematically depicts a grid of visual markers generated by a projection system according to an embodiment;

FIG. 5 schematically depicts a projection system according to another embodiment;

FIG. 6 is a flowchart of an aiming target generation method according to an embodiment;

FIG. 7 is a flowchart of an aiming target generation method according to another embodiment; and

FIG. 8 schematically depicts a large area including a large 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.

Where reference is made to a virtual image, this should be understood to mean a virtual representation of an aiming target in the form of an image, e.g. a light spot, light pattern or the like.

Embodiments of the present invention relate to a lighting system for illuminating an area of given size, i.e. an area having known dimensions. Such an area will be also referred to as a large area. The lighting system is typically to be arranged to generate a predefined illumination pattern onto the area of given size. In at least some embodiments, the predefined illumination pattern is a homogeneous or uniform illumination pattern. In at least some other embodiments, the predefined illumination pattern is a non-homogeneous or non- uniform illumination pattern. In the context of the present application, a homogeneous or uniform illumination pattern is an illumination pattern in which across the area to be illuminated variations in the illumination intensity produced by the luminaires of the system are below a predefined threshold. By way of non-limiting example, the peak intensity in any region of the area to be illuminated is no more than three times the minimum intensity in any (other) region of the area to be illuminated. It should be understood that other ratios or other definitions expressing a uniform or homogeneous illumination of the area of given size are equally feasible.

In at least some embodiments, the area to be illuminated is an area on which a sport is practiced, such as a pitch, pool, velodrome or any other suitable area. The area to be illuminated may form part of a sports arena, in which the area to be illuminated typically is surrounded by a spectator area, e.g. seating areas, stands, and so on. However, it is emphasized that the present invention is not limited to the illumination of sports arenas; it is equally feasible that the area of given size to be illuminated is another type of large area such as a facade of a building, where for example facade illumination may be desirable for aesthetic reasons, a floor area of a commercial building such as a shop floor, a warehouse floor or the floor area of a parking lot, where the lighting system may be used to generate a predefined illumination pattern for functional reasons, e.g. to facilitate the commercial activities performed on the area of given size in a desirable, e.g. safe, manner.

Moreover, it should be understood that embodiments of the present invention may be deployed in large areas under construction, e.g. a sports arena in which a lighting system is installed prior to installation of the pitch or track, in which the projection of virtual markers facilitates the installation of the lighting system even in scenarios where the placement of physical markers is (yet) unfeasible. It should further be understood that where reference is made to an area of a given size, e.g. a large area, such an area may be a 2-D area or a 3-D area, e.g. in the case of a cycling track of a velodrome or the like.

FIG. 1 schematically depicts a lighting system 100 for generating a predefined illumination pattern on an area 10 of a given size, here a pitch of a sports arena by way of non-limiting example. The lighting system 100 comprises a plurality of luminaires 1 10 for mounting relative to the area 10 such that the luminaires 1 10 can be aimed at the area 10 in order to generate the predefined illumination pattern. For example, in case of a sports arena, the luminaires 1 10 may be mounted around the area 10, i.e. around the pitch, 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 to corners of the area 10, 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 alternative arrangement is where the luminaires 1 10 are mounted on the stands and seating areas around the area 10, 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 10 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 lighting system 100 is arranged to illuminate a different type of area 10 as previously explained, the luminaires 1 10 may be mounted in different relative positions with respect to the area 10 to be illuminated; for instance, in case of the area 10 being the facade of the building, the luminaires 110 may be mounted opposite the area 10, in case of the area 10 being a floor area of a commercial building or parking lot, the luminaires 1 10 may be mounted above the area 10, and so on.

The luminaires 1 10 or their mounting typically 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 10. 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 two or three 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, e.g. a LED-based luminaire such as a LED-based flood light or the like.

Each of the luminaires 1 10 may be manually aimed at a marker 20 on the area 10, as schematically depicted in FIG. 2. A grid of physical markers 20 may be laid out on the area 10, with a lighting system installer aiming each luminaire 1 10 at an appropriate physical marker 20 in order to realize a predefined light plan containing aiming instructions for each of the luminaires 1 10. Although not specifically shown, alternative aiming solutions that are well-known per se may include the placement of a few physical objects in specific locations on the area 10, in which the respective aims of a plurality of luminaires 1 10 are defined relative to the same physical object, e.g. by defining different offsets for the respective luminaires 1 10 relative to this physical object. As explained above, the positioning of such physical markers 20 is cumbersome (i.e. time-consuming) and prone to human error.

Moreover, not all areas 10 are suited to the temporary placement of such physical markers 20; for example, water surfaces or inclined surfaces may preclude the placement of such physical markers 20 in a manner that ensures that such physical markers are retained in the appropriate location long enough for the aiming exercise to be completed.

The lighting system 100 optionally may further comprise a plurality of cameras 120, wherein each camera is associated with a luminaire 1 10 such that the camera 120 is arranged to capture an image of an illuminated part of the area 10 including the contribution to the illumination in the part of the area 10, i.e. the contribution to the overall illumination pattern on the area 10, generated by its associated luminaire 120. The cameras 120 may be arranged such that there exists a defined relationship between a field of view of the camera 120 and the optical axis of the associated luminaire 1 10. For example, the defined relationship between the field of view of the camera 120 and the optical axis of the luminaire 1 10 may be that the field of view of the camera 120 includes the optical axis of the luminaire such that the centre of the image captured by the camera 120 is the aiming spot or point of the associated luminaire 1 10.

Each camera 120 may be mounted on an associated luminaire 1 10, wherein the field of view of the camera 120 may be aligned with a direction in which the associated luminaire 1 10 generates its contribution to the overall illumination pattern on the area 10. The luminous output of such luminaires 1 10 may be automatically aligned with their target physical marker 20 by identifying the target physical marker 20 in an image captured with the camera 120 and aligning the field of view of the camera 120 with the target physical marker 20. Other solutions exist in which multiple luminaires 1 10 share a camera 120, e.g. the camera 120 may be mounted in a mounting frame for a plurality of luminaires 1 10 or the camera 120 may be an overview camera mounted over the area 10.

The lighting system 100 further comprises a control unit 127 communicatively coupled to the plurality of cameras 120 via communicative coupling 125, which may be any suitable coupling such as a wired or wireless coupling, which may include dedicated couplings between each camera 120 and the control unit 130 and/or may include a coupling shared between the cameras 120 and a control unit 130, such as a bus architecture or the like. The luminaires 1 10 are typically positioned and aimed in accordance with a light plan, which may be stored in a data storage device 129 accessible to the control unit 127. 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 10, e.g. within a stadium or building, the type of luminaire, the mounting or placement location of the luminaires, which may be specified relative to a known reference point such as the centre point or spot of a stadium, the desired orientation of the luminaire, and the desired aiming point of the luminaire, which may be specified relative to the known reference point. Such a light plan is typically designed with the purpose to generate a particular luminous

distribution, i.e. the predefined illumination pattern, over the area 10. For example, the light plan gives an installer of the lighting system 100 installation guidance as where to position the individual luminaires 1 10 and how to aim the individual luminaires 1 10 towards a particular region of the area 10.

As explained above, for such lighting systems 100, the positioning of the physical markers 20 relative to a fixed reference point associated with the large area 10 in order to assist the installer or the automatic aiming of the lighting system 100 in correctly aiming the respective luminaires 1 10 at the appropriate aiming targets on the large area 10 is rather cumbersome, i.e. time-consuming and prone to errors. FIG. 3 schematically depicts a projection system 200 according to an embodiment that is adapted to project one or more visual markers 30 onto the large area 10 as schematically depicted in FIG. 4.

In the context of the present invention, such visual markers 30 are light shapes or patterns that augment the reality of the view of the large area 10, i.e. that act as virtual markers on the large area 10. Such visual markers 30 may be generated with the light of any suitable spectral composition, for example visible light, (near-) infrared light, ultraviolet light or combinations thereof. In addition, not all visual markers 30 have to be generated with the same luminous intensity; for example, selected visual markers 30 may be shown at a different intensity to the other visual markers, e.g. to highlight of the selected visual markers 30 such that an installer or an automated aiming system may more easily identify the selected visual marker 30. The visual markers 30 may correspond to aiming targets for the luminaires 110 of the lighting system 100 as defined in the light plan for the lighting system 100. Such aiming targets may each be defined relative to a reference feature 12 associated with the large area 10, here the centre spot of a sports pitch by way of non-limiting example. Alternatively, a subset of the aiming targets, e.g. a single aiming target, may be defined relative to the reference feature 12 and act as one or more reference aiming targets, with the position of the remaining aiming targets being defined relative to a reference aiming target.

As will be explained in further detail below, the projection system 200 may be arranged to project a grid of visual markers 30 in which all visual markers 30 are visible at the same time or alternatively may be arranged to only project a subset of the visual markers 30, e.g. a single visual marker 30 such that a particular luminaire 1 10 of the lighting system 100 intended to be aimed at the projected visual marker 30 may be readily aimed at the projected visual marker 30 without having to identify the correct visual marker from a plurality of projected visual markers 30. In such an embodiment, the lighting system 100, e.g. the controller 127 or the luminaire 1 10, may generate a visual marker selection signal to which the projection system 200 is responsive.

The projection system 200 typically comprises a projection unit 210 a projection unit adapted to project a visual marker 30 in a projection location of the large area 10. Any suitable projection unit may be used for this purpose. The projection system 200 further comprises a position and orientation detector arrangement adapted to detect the position and orientation of the projection unit 210 relative to the large area 10.

In the context of the present application, the position and orientation of the projection unit 210 relative to the large area 10 may be defined in terms of rotation and translation (e.g. expressed in x, y, z, Rx, Ry, Rz coordinates) of the projection unit 210 relative to the large area 10.

In FIG. 4, the position and orientation detector arrangement comprises a camera or visor 220 that is arranged along the aiming direction of the projection unit 210 such that the camera 220 may capture an image of at least a part of the large area 1 10 onto which the projection unit 210 is to project one or more visual markers 30 as explained above. In an embodiment, the camera 220 may be adapted to capture an image of part of the large area 1 10 including the reference feature relative to which the aiming targets of the light plan associated with the installation of the luminaires 1 10 are defined. The camera 220 may be any suitable camera or imaging means configured to capture an image and pass the image to the controller 230, which will be explained in more detail below. For example, in some embodiments the camera 220 comprises lenses or optics to enable an adjustment of the field of view of the camera such as a zooming operation. The camera 220 is not limited to a visible wavelength camera; any suitable type of camera, such as passive and active imaging devices, e.g. lidar devices, infra-red cameras, time-of-flight cameras, and so on, may be contemplated. The position and orientation detector arrangement further comprises one or more orientation sensors 240 to determine tilt of the projection unit 210 such as an accelerometer or the like, which for example may be positioned in a defined reference plane of the projection unit 210, e.g. a plane perpendicular to an optical axis of the projection unit 210.

The projection system 200 further comprises a controller 230 responsive to the orientation detector of the projection system 200, e.g. the camera 220 in FIG. 4. For example, the controller 230 may comprise a processor 231 adapted to process an image received from the camera 220, e.g. by implementing a suitable feature recognition algorithm in order to identify the reference feature relative to which the aiming targets of the luminaires 1 10 are defined in the light plan of the lighting system 100. The processor 231 may be adapted to determine the position and orientation of the projection unit 210 by processing an image provided by the camera 220 and orientation sensor data provided by the one or more orientation sensors 240 to determine the aiming direction of the projection unit 210 around a horizontal axis orientation by analysing the orientation sensor data and to determine the aiming direction of the projection unit 210 around a vertical axis orientation (a pan orientation) based on the analysis of the image.

The controller 230 may further comprise a data storage device 233 in which the light plan is stored, with the processor 231 being communicatively coupled to the data storage device 233. Any suitable data storage device may be used for this purpose, e.g. a memory device, a hard disk, an optical disk and so on. Alternatively, the data storage device 233 does not form an integral part of the controller 230 but may instead be accessible by the processor 231 over a wired or wireless network, e.g. a short-range network such as a Bluetooth or Wi-Fi network, a mobile communications network, the Internet, and so on, in which case the data storage device 233 may be a network attached storage device, a storage area network device, a cloud storage architecture, and so on.

The controller 230 is typically adapted to retrieve an aiming target defined relative to the reference feature 12 from the light plan in the data storage device 233, e.g. a reference aiming target, and to identify the orientation of the projection unit 210 relative to the reference feature 12 from orientation data provided by the orientation detector, e.g. an image including the reference feature captured by the camera 220. For example, the processor 231 may deploy image processing algorithms facilitating the recognition of the reference feature 12 in the image provided by the camera 220 and the relative location of the reference feature 12 in the image. The relative location information may be used by the processor 231 in combination with the orientation sensor data to derive the relative position and orientation of the projection unit 210 in respect of the reference feature 12, and to the large area 10 by association (due to the fixed position of the reference feature 12 relative to the large area 10).

For example, the processor 231 may be configured to analyse the image to determine a feature, i.e. the reference feature 12 such as a fixture associated with the large area 10, e.g. the centre spot of a sports pitch or the like. The determination of the visual indicator can be based on any known parameter such as colour, shape or size. For example the image can be colour filtered to identify the visual indicator having a specific colour, or the image can be processed to determine a specific shape. Having determined the feature within the image, the processor 231 may be configured to determine the position of the reference feature 12 within the image. For example, the position of the reference feature within the image may be determined based on the number of pixel rows (vertical offset) ΔΓ and the number of pixel columns (horizontal offset) Ac from the centre of the image (or another suitable reference point of the image). The processor 231 may be further adapted to estimate a distance from the reference feature 12 by calculating the size of the reference feature 12 in the captured image, e.g. by counting the number of image pixels belonging to the reference feature 12, and by deriving a distance between the projection unit 210 and the reference feature 12 from this calculated size and a known actual size of the reference feature 12.

In some embodiments the processor 231 may be configured to use the offset (the number of rows of pixels and columns of pixels) from the reference point of the image, e.g. the centre of the image, to define a vector line originating at the position on the image plane through the optical axis ending at the reference feature. This vector may in some embodiments be used to derive an estimation of the rotation angles around the row and column direction with respect to the optical axis, or in other words to determine an estimate of the orientation(s) of the projection unit 210 in case of the projection unit 210 being positioned in a predefined location, based on the relative location of the projection unit 210, the reference feature 12, and the 'distance' between the aiming target defined relative to the reference feature 12 in the light plan.

In this manner, the orientation of the projection unit in the predefined location or position may be accurately determined and controlled with the position and orientation detector arrangement to ensure that the one or more visual markers 30 are generated in the correct location(s) on the large area 10. Alternatively, the processor 231 may be adapted to calculate the direction into which the one or more visual markers 30 have to be projected with the projection unit 210 based on the determined position and orientation of the projection unit 210 and the aiming information in the light plan to ensure that the one or more visual markers 30 are generated in the correct location(s) on the large area 10.

In some embodiments, the projection system 200, e.g. the projection unit 210 further comprises a range or distance sensor 222 configured to determine a range or distance between the projection unit 210 or camera 220 and the reference feature 12. The term range or distance sensor is defined as any suitable means for determining the range or distance from the projection unit 210 or camera 220 to a defined location, e.g. the reference feature 12. The distance or range sensor output may be used as a complimentary way to determine the orientation angle of the projection unit 210 or camera 220. For example the range or distance sensor can in some embodiments be used to determine a distance to an aiming spot, e.g. the reference feature 12.

The controller 230, e.g. the processor 231, may subsequently control the projection unit 210 in accordance with its identified relative position and orientation in respect of the reference feature 12 such that the projection location of a visual marker 30 coincides with the aiming target that is defined relative to the reference feature 12. In this manner, the visual marker 30 may be used as the aiming target for a luminaire 1 10 of the lighting system 100 to be aimed at this target. The controller 230 may control the projection direction in which the projection unit 210 project the visual marker 30 to ensure that the visual marker coincides with the aiming target defined relative to the reference feature 12.

In some embodiments, the projection unit 210 may comprise a projection unit orientation adjustment mechanism 215, such as a suitable mounting point or jig configured to be adjustable in order to change the orientation of the projection unit 210. The controller 230 may be adapted to control the orientation adjustment mechanism 215 in accordance with the identified orientation of the projection unit 210 relative to the reference feature 12 such that the projection location of the visual marker 30 coincides with the aiming target defined relative to the reference feature 12 as previously explained.

In some embodiments, the controller 230 may be adapted to control the projection unit 210 by combined control of the aiming direction of the projection unit 210 and the projection unit orientation adjustment mechanism 215.

FIG. 5 schematically depicts an alternative embodiment of such a projection system 200, in which the position and orientation detector arrangement of the projection unit 210 is realized by an orientation sensor arrangement including one or more orientation sensors 240, such as accelerometers, gyroscopes, Hall sensors or the like. In an embodiment, the positioning of the projection unit 210 in a specific location relative to the reference feature 12 associated with the large area 10 may be predefined, in which case the controller 230 may be adapted to align the actual orientation of the projection unit 210 as determined from the sensor signals provided by the orientation sensor arrangement 240 with the predefined orientation of the projection unit 210, e.g. as defined in the light plan stored in the data storage device 233.

In an embodiment, the one or more orientation sensors 240 may include one or more range sensors, e.g. a range sensor matrix, which may be implemented by a line scan laser scanner that scans around the horizontal axis. With a 2-dimensional laser scanner or a time-of-flight camera it is possible to measure the orientation of the ground plane, i.e. the large area 10, by surface fitting. Also, the range sensor matrix may be used to detect a 3-D reference feature 12 based on its 3-D shape properties. In other words, the array/matrix of range sensing elements may be operated as an image generator, where the generated image includes depth or distance information, which for instance may (also) be used to determine the position of the projection unit 210.. The range or distance between the projection unit 210 and the reference feature 12 may be (indirectly) determined by using such an image. For example, the controller 230 may be adapted to size the reference feature 12 within the image as previously explained and compare its determined size to its actual or known size. As the properties of the optical system are typically known, this distance can be derived from the scale of the reference feature 12 (magnification factor) in the captured image.

In embodiments, the projection unit 210 may comprise a 3-D range camera, e.g. implemented by camera 220 or a range sensor arrangement 240, which may provide 3-D images from which the processor 231 can determine the actual 3-D layout of the large area 10 to be illuminated. This for example is desirable where the actual 3-D layout of the large area 10 differs from its final layout, e.g. in the case of a pitch or track yet to be installed. In such a scenario, where the aiming information for the respective luminaires 1 10 may be defined relative to the final 3-D layout in the light plan, the processor 231 may be adapted to calculate a difference between the actual 3-D layout of the large area 10 and its final layout and convert the aiming information in the light plan in accordance with the determined difference between the actual 3-D layout and the final 3-D layout such that the one or more virtual images 30 are projected in the correct locations on the actual 3-D layout. This facilitates installation of the lighting system 100 prior to completion of the area to be illuminated by the luminaires 1 10 of this lighting system.

The projection system 200 may be operated in a number of ways to implement a method 300 of generating an aiming target to aid the installation of the large area lighting system 100 in accordance with a light plan including said aiming target defined relative to the reference feature 12 associated with the large area 10, a flow chart of which is shown in FIG. 6. The method 300 starts in 301 with the provision of the projection system 200 after which the projection system 200 is installed in a projection location relative to the large area 10 in 203. As explained above, in several embodiments of the present invention the projection system 200 may be positioned in any suitable projection location relative to the large area 10 from where the reference feature 12 can be detected with the projection system 200, i.e. with the position and orientation detector arrangement of the projection system 200, and where the position and orientation of the projection unit 210 may be determined from the data provided with the position and orientation detector arrangement, e.g. an image generated with the camera 220, orientation data provided with one or more orientation sensors 240, with a range sensor matrix, and so on, as explained in more detail above. Alternatively, the projection system 200 may be positioned within a predefined location relative to the large area 10, in which embodiments the predefined location may be utilized to determine the orientation and position of the projection unit 210 relative to the reference feature 12, e.g. using one or more orientation sensors 240 as explained in more detail above.

Next, the light plan associated with the luminaires 1 10 of the lighting system 100 may be consulted in 305 to identify the reference feature 12 relative to which at least some of the aiming targets of the luminaires 1 10 are defined. In an embodiment, this may involve retrieving an identification of the reference feature 12 and an offset of a particular aiming target for one of the luminaires 1 10 defined relative to this reference feature. Where the light plan defined the respective aiming targets relative to a finalized area 10, the method 300 may further comprise determining a difference (in topology) between the actual area and the finalized area, e.g. by capturing a 3-D image of the actual area and comparing it against a model of the finalized area, and adjusting the aiming targets based on the determined difference between the actual area and the finalized area such that the adjusted aiming targets may be aimed on the actual area such that upon finalizing the area the luminaires 110 are aimed at their intended aiming targets on the finalized area 10.

In 307, the position and orientation of the projection unit 210 relative to the reference feature 12 is determined using the position and orientation detector arrangement of the projection unit 210 as explained in more detail above. This for example may include determining a further offset or displacement of the aim, e.g. optical axis, of the projection unit relative to the reference feature 12, e.g. a displacement in a two-dimensional plane relative to the location of the reference feature 12 in that plane.

In 309, the orientation or aim of the projection unit 210 is adjusted such that a visual marker 30 corresponding to the aiming target of the luminaire 1 10 that is defined in the light plan relative to the reference feature 12 coincides with this aiming target, i.e. is projected onto the aiming target, e.g. by altering the aim of the projection unit 210 and/or by adjusting the orientation of the projection unit 210 with the projection unit orientation adjustment mechanism 215 as explained in more detail above.

Upon achieving this alignment, the projection unit 210 projects the grid of visual markers 30 onto the large area 10 in 31 1 such that the various luminaires 110 of the lighting system 100 may be aimed at the appropriate visual marker 30 of this grid, i.e. at their respective aiming targets as specified in the light plan that coincide with one of the visual markers 30 or are offset by a defined amount relative to a particular visual marker 30.

In an embodiment, the projection of the visual markers 30 may be supplemented by the projection of a target marker 33 on a particular one of the visual markers 30, i.e. the target visual marker 30 for a particular luminaire 1 10, and an actual aim marker 31 for the luminaire 1 10 as shown in FIG. 4. Alternatively, the aim marker 33 may be omitted, in which case the actual aim marker 31 may be aligned with the visual marker 30. Such an actual aim marker 31 for example may be generated by a collimated light source optically aligned with the luminaire 1 10 to be aimed at the virtual image 30, e.g. a laser or the like having its optical axis aligned with the optical axis of the luminaire 1 10 to which the laser is attached.

The target marker 33 for example may be generated by an augmented reality device such as a visor or other head-mountable computing device comprising a display device onto which the markers 31, 33 may be displayed. This for example may be realized by generation of the relevant visual marker 30 having a non-overlapping spectral composition with the luminous output of the luminaire 1 10 to be aimed at the visual marker 30, e.g. a near-infrared visual marker 30, in which case the augmented reality device may include an infrared camera directed at the area 10 onto which the visual marker 30 is projected, such that an image captured with the infrared camera including the target marker 33, i.e. the near- infrared visual marker 30 in the image, may overlay the actual view of an installer to provide the augmented reality. In this manner, the installer may aim the collimated light source or the luminaire 1 10 itself onto the target marker 33 using the augmented reality device, e.g. a head- mountable device such as a visor or smart glasses or a display device such as a tablet device or the like, to augment the view of the installer of the lighting system 100 of the large area 10 The installer of the large area lighting system 100 may align the actual aim marker 31 with the target marker 33 as indicated by the arrow in FIG. 4 by adjustment of the orientation of the luminaire 1 10 to be aimed at the visual marker 30 coinciding with the target marker 33 in order to correctly align the luminous output of the luminaire 1 10 with the aiming target of the luminaire as specified in the light plan. This has the advantage that the luminaire 1 10 may be directly aimed at the visual marker 30, i.e. during projection of the visual marker 30. However, it should be understood that alternative embodiments, e.g. embodiments in which a visual marker 30 is used to position a light measurement device on the area 10 in the location of the visual marker 30, after which the projection unit 210 is switched off and the luminaire 1 10 is correctly aimed using the light measurement device, e.g. by maximizing the luminous flux incident on the light measurement device.

In 313, it is checked if the installer has aimed all luminaires 1 10 of the large area lighting system 100 at the respective visual markers 30 in accordance with the light plan. As long as this aiming exercise is not yet complete, the method 300 reverts back to 31 1 in which the projection of the grid of visual markers 30 by the projection unit 210 is continued. Once the aiming exercise has been completed, the method 300 terminates in 315.

FIG. 7 is a flowchart of an alternative embodiment of the method 300 in which at least part of the luminaire aiming has been automated. Up to and including step 309, this alternative embodiment of the method 300 is identical to the embodiment described with the aid of the flowchart in FIG. 6, such that steps 301, 303, 305, 307 and 309 are not described again for the sake of brevity. Upon completion of step 309 in which the projection unit 210 is aligned with the reference feature 12 as previously explained, the method 300 proceeds to 317 in which the projection system 200 receives a visual marker selection signal from the lighting system 100, e.g. from the controller 127 or from a luminaire 1 10. For example, the light plan may specify an order in which the luminaires 1 10 are to be aimed at the respective aiming targets, in which case the controller 127 or a luminaire 1 10 to be aimed may generate the visual marker selection signal to configure the projection system 200 to generate the visual marker 30 corresponding to the visual marker selection signal. For example, the visual marker selection signal may comprise an identifier of the visual marker 30, e.g. a grid location derived from the grid of aiming targets for the luminaires 1 10, a light plan entry identifier, and so on, which facilitates the identification of the appropriate visual marker 30 to be projected by the projection system 200.

Upon this identification, the method proceeds to 319 in which the visual marker 30 selected by the visual marker selection signal is projected onto the large area 10 in its intended location such that the installer may aim the appropriate luminaire 1 10 at the projected visual marker 30. Alternatively, the appropriate luminaire 1 10 may be

automatically aimed at the projected visual marker 30, which for example may be achieved with a camera 120 associated with the appropriate luminaire 1 10 as previously explained. It is subsequently checked in 313 if all luminaires 1 10 have been aimed at their respective aiming targets on the large area 10. As long as this is not the case, the method 300 reverts back to 317 in which the visual marker selection signal for the next luminaire 1 10 to be aimed is generated and received by the projection system 200 and the corresponding visual marker 30 is projected onto the large area 10. Once all luminaires 1 10 have been aimed in this manner, the method 300 terminates in 315.

In the above embodiment of the method 300, each visual marker selection signal triggers the projection of a single visual marker 30 onto the large area 10. However, it should be understood that this is by way of non-limiting example only. It is for instance equally feasible for the visual marker selection signal to cause a change in appearance of the visual marker 30 identified by the visual marker selection signal in a grid of projected visual markers 30. For example, the visual marker selection signal may cause a change in colour and/or a change in intensity of the selected visual marker 30 such that the selected visual marker 30 in the grid of visual markers 30 is clearly distinguished from the other visual markers 30 in the grid.

Further embodiments include the projection of a subset of visual markers 30 from the total set of visual markers on to the large area 10 in response to such a visual marker selection signal, which subset typically includes more than one visual marker 30 but less than the total number of visual markers 30, such that multiple luminaires 1 10 may be aimed concurrently to reduce the total installation time of the lighting system 100.

FIG. 8 schematically depicts an embodiment of a large area lighting system 100 including the projection system 200. The large area lighting system 100 may be a large area lighting system as described in detail with the aid of FIG. 1 such that the large area lighting system 100 will not be described in detail again for the sake of brevity only.

In an embodiment, each luminaire 1 10 is mounted on a luminaire orientation adjustment mechanism as previously explained and associated with an aiming controller 127 adapted to control the luminaire orientation adjustment mechanism in response to visual feedback provided by the at least one camera 120. The aiming controller 127 may be adapted to align the luminous output of an associated luminaire 1 10 with a visual marker projected by the projection unit in accordance with a light plan, which may be stored in a data storage device 129 as previously explained. The at least one camera 120 may be a camera arranged to capture a view of at least a part of the large area 10, which typically is the part including the aiming target of the luminaire 110, e.g. a camera 120 positioned above or opposite the large area 10. Alternatively, each luminaire 1 10 may comprise a camera 120 for observing illumination of at least a part of the large area 10 by this luminaire. Such a camera 120 for example may be mounted on the luminaire 1 10 such that the optical axis of the camera 120 coincides or is aligned with the optical axis of the luminaire 1 10. Preferably, the large area lighting system 100 is further adapted to generate visual marker selection signals for the controller 230 of the projection unit 210 to trigger the projection of a visual marker 30 at the aiming target of a particular luminaire 1 10 of the large area lighting system 100 as explained above. In this manner, the respective luminaires 1 10 of the large area lighting system 100 may be aimed in a largely automated manner without requiring significant intervention from an installer of the large area lighting system 100. As previously explained, the various visual marker selection signals may be generated by the aiming controller 127 or by the individual luminaires 1 10, in which case the aiming controller 127 may be adapted to route the visual marker selection signals generated by the individual luminaires 1 10 to the projection system 200.

The projection system 200 in some embodiments forms a temporary part of the large area lighting system 100. For example, in a scenario where the large area lighting system 100 only needs to be aimed once, the projection system 200 may be positioned on site and coupled to the large area lighting system 100 to facilitate the aiming of the respective luminaires 1 10 as explained above, with the projection system 200 being removed from the site upon completion of this aiming task. In some alternative embodiments, the projection system 200 may form a permanent part of the large area lighting system 100. This is for example useful in scenarios where the large area lighting system 100 is configured to implement a plurality of light plans, e.g. different light plans for different types of events to be hosted on the large area 10, different light plans for different lighting scenes to be displayed on the large area 10, etcetera. In such scenarios, the luminaires 1 10 of the large area lighting system 100 may require periodic re-aiming, in which case it may be beneficial to have the projection system 200 permanently installed at the side of the large area 10.

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.