Calibration system

Abstract

The invention relates to a calibration method for calibrating a position of at least two spots illuminating a performance environment with radiation, comprising: selecting a calibration location inside the performance environment; emitting a spot identifier from each of the at least two spots; receiving the emitted spot identifiers at the calibration location; determining a variable per spot using the received spot identifiers; and calculating the position of the at least two spots based on the respective variables characterized in that the spot identifiers uniquely identify the at least two spots in the performance environment.

Description

[0001] CALIBRATION SYSTEM

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a calibration system for a tracking system tracking a performer in a performance environment. More specifically, the invention relates to a calibration system using a calibration pod.

[0004] BACKGROUND OF THE INVENTION

[0005] To emphasize the visual presence of a performer, on stage spots or spot lamps may be used placing the performer in a light beam, while the background of the stage is not or less illuminated. As a performer typically moves across the stage, the beam of the spot may follow the performer. The spot following the performer across the stage is named a follow spot. A follow spot may be operated manually, semi-automatically or automatically. Calibration of the follow spot, especially in the semi-automatic and automatic cases, is essential.

[0006] AT526212 (A1) discloses a method for determining the position of a spotlight which is arranged above an underlying surface and creates an illuminated region on the underlying surface, wherein a light sensor is arranged on the underlying surface, wherein the light sensor is designed as a camera, wherein the camera comprises a wide-angle lens, preferably a fisheye lens, and wherein the light sensor comprises one to three position sensors, preferably ultra-wideband position sensors, which are designed to determine the position of the light sensor in a three-dimensional coordinate system, wherein the camera creates a recording of the spotlight, and wherein the position of the spotlight is at least approximately determined from the recording and the position of the light sensor.

[0007] GB2336906 (A) discloses that a beam from a spot light is directed at a predetermined position by locating a light sensor at the predetermined position, causing the spot light to scan the beam over an area which includes that predetermined position, monitoring output from the light sensor and monitoring the corresponding direction of the beam from the spotlight and in response to a signal from the light sensor indicating incidence of the light beam on the sensor, recording the direction of the beam from the spotlight. The method is used to calibrate master light control apparatus used for directing a spotlight at substantially any predetermined position on a surface such as a stage. Light sensing apparatus comprises a light sensor, an output for providing a trigger signal responsive to incidence on a light beam on a sensor and an output for identifying that apparatus or an output for providing a start signal to master lighting control apparatus to initiate is calibration.

[0008] Almost always multiple spotlights are used to light a stage. A disadvantage of the disclosures is that only one spotlight at the time can be calibrated. This disadvantage is exacerbated for larger stages where the spotlights may number over a hundred.

[0009] SUMMARY OF THE INVENTION

[0010] An object of the invention is to overcome one or more of the disadvantages mentioned above.

[0011] According to a first aspect of the invention, a calibration method for calibrating a position of at least two spots illuminating a performance environment with radiation, comprising: selecting a calibration location inside the performance environment; emitting a spot identifier from each of the at least two spots; receiving the emitted spot identifiers at the calibration location; determining a variable per spot using the received spot identifiers; and calculating the position of the at least two spots based on the respective variables; wherein the spot identifiers uniquely identify the at least two spots in the performance environment.

[0012] The spots are typically follow spots. Further, the spots have typically a pan and tilt value for orienting a part of the follow spot typically emitting radiation, such as a radiation or light beam, such that the radiation beam or the light beam is directable to a particular location in the performance environment. The performance environment typically comprises a stage. The particular location lights up with the radiation or the light beam is typically at some height above the stage, wherein the height above the stage correlates to the height of the performer on the stage.

[0013] The calibration method is for calibrating a position of at least two spots illuminating a performance environment with radiation, light, or light beam. Typically, the calibration method relates a pan tilt value for the follow spot to light up a particular location on the stage.

[0014] The calibration method comprises selecting a calibration location inside the performance environment. The calibration method typically comprises selecting multiple calibration locations for defining a calibration or reference plane. The multiple calibration locations are typically arranged to or located on a stage inside the performance environment, where the stage may be used as reference plane. In an alternative calibration method, the calibration method defines three axes as reference, wherein the origin of the axis and orientation of the axis may be selected based on the calibration locations.

[0015] The calibration method comprises emitting a spot identifier from each of the at least two spots. The spot identifier identifies, preferably uniquely identifies, the spot. The spot identifier is emitted in the form of light or radiation emitted from the spot. The spot identifier may be a code or pattern in the form of emitted light or radiation.

[0016] The calibration method comprises receiving the emitted spot identifiers at the calibration location. The reception is typically done with a camera able to view the at least two spots, preferably most or all the spots. The reception typically depends on the calibration location selected in the selecting step. As the identifiers identify a spot, and multiple emitted spot identifiers are received, it follows that the at least two spots are in view or in line of sight of the calibration location.

[0017] The calibration method comprises determining a variable per spot using the received spot identifiers for differentiating between the variables of the at least two spots. The variable may be a variable associated with the spot and / or associated with the reception at the calibration location.

[0018] The calibration method comprises calculating the position of the at least two spots based on the respective variables. This is the actual calibration based on the determined variable per spot. Typically, the calibration requires multiple calibration locations to be selected, wherein the variable per spot and per calibration location is determined. Through the use of emitting spot identifiers, receiving of the emitted spot identifiers is uncoupled over time providing the advantage that calibration of a specific spot is uncoupled over time. The calibration of the at least two spots can therefore overlap or partly overlap having the technical effect of decreasing the total calibration time of the at least two spots. According to another aspect of the invention, a calibration assembly for calibrating a position of at least two spots illuminating a performance environment with radiation, comprising: at least two spots arranged for emitting a spot identifier; a reception device arranged for receiving the emitted spot identifiers at a calibration location inside the performance environment; and a controller arranged for: obtaining the reception with the received identifiers from the reception device; determining a variable per spot in the reception using the spot identifiers; and calculating the position of the at least two spots based on the respective variables; wherein the spot identifiers uniquely identify the at least two spots in the performance environment. The calibration assembly provides the same advantages as described for the other aspects or embodiments of the invention. In an embodiment of the calibration assembly, the controller is advantageously further arranged for instructing the at least two spots to emit a spot identifier.

[0019] According to another aspect of the invention, a calibration device for calibrating a position of at least two spots illuminating a performance environment with radiation, comprising: a reception device arranged for receiving emitted spot identifiers of at least two spots at a calibration location inside the performance environment; and a controller arranged for: obtaining the reception with the received identifiers from the reception device; determining a variable per spot in the reception using the spot identifiers; and calculating the position of the at least two spots based on the respective variables; wherein the spot identifiers uniquely identify the at least two spots in the performance environment. The calibration device provides the same advantages as described for the other aspects or embodiments of the invention. In an embodiment of the calibration device, the controller is advantageously further arranged for instructing the at least two spots to emit a spot identifier.

[0020] According to another aspect of the invention, a computer implemented method for calibrating a position of at least two spots illuminating a performance environment with radiation and emitting a spot identifier from each of the at least two spots: obtaining a reception of a reception device arranged for receiving the emitted spot identifiers at a calibration location inside the performance environment; determining a variable per spot using the spot identifiers; and calculating the position of the at least two spots based on the respective variables; wherein the spot identifiers uniquely identify the at least two spots in the performance environment. The computer implemented method provides the same advantages as described for the other aspects or embodiments of the invention. In an embodiment of the computer implemented method, the method further comprises advantageously instructing the at least two spots to emit a spot identifier.

[0021] According to another aspect of the invention, a computer program product comprising instructions which, when the program is executed by a suitable processor, causing the processor to carry out the method of any of the claims or embodiments. The computer program product provides the same advantages as described for the other aspects or embodiments of the invention.

[0022] According to another aspect of the invention, a calibration method for calibrating a placement of a plurality of spots illuminating a performance environment with light: selecting a first, and a second location inside the performance environment; instructing at least one of the plurality of spots to emit at least one identification towards the performance environment; receiving at the first, and the second location inside the performance environment the at least one identification under a first, and a second reception angle, respectively, wherein instructing comprises placing, such as orienting, the at least one of the plurality of spots to emit the at least one identification such that the at least one identification is substantially optimally received at the first, and the second location with a first, and a second spot orientation of the at least one of the plurality of spots, respectively; and calculating the placement of the at least one of the plurality of spots emitting the at least one identification based on the first location, the second location, the first reception angle, the second reception angle, the first spot orientation, and the second spot orientation. This calibration method provides the same advantages as described for the other aspects or embodiments of the invention.

[0023] According to another aspect of the invention, a calibration method for calibrating a placement of a plurality of spots illuminating a performance environment with light: selecting a first, a second, and a third location inside the performance environment; instructing at least one of the plurality of spots to emit at least one identification; receiving at the first, the second, and the third location inside the performance environment the at least one identification under a first, a second, and a third reception angle, respectively, wherein instructing comprises orienting the at least one of the plurality of spots to emit the at least one identification such that the at least one identification is receivable at the first, the second, and the third location, respectively; and calculating the placement of the at least one of the plurality of spots emitting the at least one identification based on the first, the second, the third location, and the first, the second, and the third reception angle. Although mathematically the minimum number of reference locations is three, if a horizontal reference or calibration plane is selected, it may be assumed that the spots are not arranged below the calibration plane. This restriction advantageously allows to reduce the calibration locations to at least three. This calibration method further provides the same advantages as described for the other aspects or embodiments of the invention.

[0024] According to another aspect of the invention, a calibration method for calibrating a position of at least two spots illuminating a performance environment with radiation, comprising: selecting a calibration location inside the performance environment; emitting a spot identifier from each of the at least two spots; receiving the emitted spot identifiers at the calibration location; determining a variable per spot using the received spot identifiers; and calculating the position of the at least two spots based on the respective variables. This calibration method provides the same advantages as described for the other aspects or embodiments of the invention.

[0025] DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

[0026] In an embodiment of the calibration method, determining the variable comprises measuring the variable per spot, and associating the variable with the spot identifier. Measuring a variable per spot may comprises a spatial separated measurement of the variable per spot. As an example of a spatial separated measurement, using for the measurement a group of pixels at a specific or determined location in an image. The group of pixels and / or the pixel values may be related to a specific direction relative to and / or a specific distance from the calibration location. Measuring a variable per identified spot advantageously allows to contribute to the positioning of the spots in space.

[0027] In an embodiment of the calibration method, emitting comprises placing each spot of the at least two spots until the emitted identifiers are received at the calibration location. The emitted spot identifier from the spot is typically placement, such as orientation, sensitive. The placing of the spot is typically done with trial-and-error until the emitted identifier is received at the calibration location. As an example, depending on the placement of a spot and in case of multiple calibration locations, it might be that the emitted spot identifier cannot be received at every calibration location with the same placement, such as orientation, of the spot. The trial-and-error may be optimized with knowledge of the emission cone of the emitted spot identifier. Furthermore, the trial-and-error may be improved based on knowledge of the placement resulting in reception at other calibration locations, if present.

[0028] In a further embodiment of the calibration method, placing advantageously comprises orienting. Placing typically comprises positioning and orienting. The typical spot is able to rotate and thus orient along a Z-axis and a horizontal axis. This type of rotation is typically specified with a pan and tilt value. The spot may be a pan-tilt spot. In a further embodiment of the calibration method, orienting comprises providing a pan and / or a tilt setting for the spot.

[0029] In a further embodiment of the calibration method, the method comprises: after receiving the emitted spot identifier, repeatedly placing each spot of the at least two spots; after each placing of each spot emitting radiation from the respective spot; and receiving the emitted radiation resulting in a received radiation intensity; wherein the variable comprises a placement of each spot associated with a received radiation intensity. This embodiment allows to use the emitted radiation, typically a light cone, to advantageously be used to determine a relation between the placement of each spot and the calibration location. In a preferred embodiment, associating a placement of each spot with a received radiation intensity above an intensity threshold. As a light cone of a spot is typically having an even light intensity within the light cone, the middle of the light cone may be determined by using measurements above an intensity threshold and advantageously determining the middle of the light cone of all these measurements. Further, as the middle of the light cone is found, the placement of the spot is found wherein a centre line of the light cone of the spot is directly coinciding with the calibration location. In a preferred embodiment, the placement comprises orienting, or even is orienting. In a preferred embodiment, the placement comprises the pan and / or the tilt setting for preferably a pan-tilt spot.

[0030] In a further embodiment of the calibration method, calculating also comprises calculating the placement of a plurality of spots illuminating a performance environment with radiation. The inventive calibration method allows to calibrate a plurality of spots parallel in time or at least partly overlapping in time providing the advantage of significantly reducing the overall calibration time for all of the plurality of spots. A plurality of spots may be more than 10 spots, preferably 50 spots, more preferably 100 spots. The larger the plurality of spots, the larger the advantageous reduction in calibration time.

[0031] In a further embodiment of the calibration method, receiving comprises repeatedly receiving the emitted spot identifier for different placements for determining a range of placements for which the received radiation intensity is above the intensity threshold for advantageously determining from the measurements the placement of each spot where the centre line of the light cone of each spot coincides with the calibration location.

[0032] In a further embodiment of the calibration method, determining the range also comprises determining placements for which the received radiation intensity is below the intensity threshold for determining the boundary of the range. As the boundary or edge of the light cone emitted by a spot can be determined, the centre may advantageously be determinable from this boundary. In a further embodiment, the spots are placed in a pattern, such as a zig-zag pattern, until the emitted spot identifier is received. After the first reception a more refined placement pattern may be applied to the spot for determining the boundary. In a further embodiment of the calibration method, receiving comprises imaging and / or recording the environment; and determining the variable comprises: detecting per spot a detected spot position in the image and / or the recording showing the spot identifier; and assigning per spot a reception direction relative to the calibration location based on the detected position, wherein the variable advantageously comprises the reception direction.

[0033] In an embodiment of the calibration method, receiving comprises imaging and / or recording the environment with a camera, preferably an upward looking camera and / or omnidirectional camera arranged on a stage of the performance environment. Typically, the omnidirectional camera is having a field of view equal to a dome.

[0034] In an embodiment of the calibration method, the emitted spot identifiers are emitted simultaneously and / or overlapping in time for advantageously allowing calibration of multiple spot parallel in time or at least overlapping in time. In an embodiment of the calibration method, receiving at the calibration location is receiving multiple of the emitted identifiers simultaneously and / or overlapping in time for advantageously allowing calibration of multiple spots parallel in time or at least overlapping in time.

[0035] In an embodiment of the calibration method, the spot identifier advantageously comprises a light colour, a light spectrum, a wavelength range, or a set of wavelength ranges. In a further embodiment of the calibration method, the spot identifier comprises a change in the light colour, a light spectrum, a wavelength range, or a set of wavelength ranges overtime.

[0036] In an embodiment of the calibration method, the spot identifier comprises a change in radiation intensity over time. The change in radiation intensity over time may be an on / off switching of the spot. The change in radiation intensity overtime may be a gradual change in radiation intensity such as with a triangle wave pattern or a sinus wave pattern. The change in radiation intensity over time may be a pattern or a code. Typically, the pattern or the code comprises or is the emitted spot identifier.

[0037] In an embodiment of the calibration method, the steps of instructing and receiving are advantageously synchronised in time such that the spot identifier comprises emitting radiation at a particular moment in time. Synchronisation allows simpler spot identifiers to be emitted while still being identifiable, preferably uniquely identifiable, due to their separation in time and / or the known start in time.

[0038] In an embodiment of the calibration method, the spot identifiers uniquely identify the at least two spots in the performance environment. The spot identifier may be unique for this setup, stage, system, or calibration assembly. The spot identifier may be unique in the world. The spot identifier may be unique in a region. The spot identifier being unique advantageously simplifies the association of a particular received spot identifier with a spot. In an embodiment of the calibration method, the spot identifiers are advantageously usable for differentiating between the variables of the at least two spots. In an embodiment of the calibration method, emitting comprises instructing the at least two spots to emit the spot identifier. The spot can thereby advantageously be switched in a calibration mode emitting the spot identifier and the operational mode wherein the spot follows other commands.

[0039] In an embodiment of the calibration method, receiving the emitted spot identifiers comprises receiving the emitted spot identifiers at at least four distinct calibration locations; determining the variable comprises determining the variable per spot using the received spot identifiers for the at least four distinct calibration locations; and calculating the position of the at least two spots comprises calculating the position of the at least two spots based on the respective variables for the at least four distinct calibration locations. Four calibration locations are advantageously selected for determining the position of the at least two spots. The four calibration locations may be arranged in one plane, such as using the stage as a reference or calibration plane. The four calibration locations should not be arranged on a single line.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The invention will be apparent from and elucidated further with reference to the embodiments described by way of example in the following description and with reference to the accompanying drawings, in which:

[0042] Figure 1 schematically shows a performance environment;

[0043] Figure 2 schematically shows a controlled object;

[0044] Figure 3 schematically shows a tracking system according to the invention;

[0045] Figure 4 schematically shows a 2D view on the performance environment;

[0046] Figure 5 schematically shows a method for a tracking system;

[0047] Figure 6 schematically shows a method for a tracking system;

[0048] Figure 7 schematically shows a method for a tracking system;

[0049] Figure 8 schematically shows a method for a tracking system; and

[0050] Figure 9 schematically shows an embodiment of a computer program product, computer readable medium and / or non-transitory computer readable storage medium according to the invention.

[0051] The figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.

[0052] LIST OF REFERENCE NUMERALS

[0053] Figure 1 schematically shows a performance environment 10. The performance environment typically comprises a stage 11 . The stage is where the performer may walk on. Although a flat stage is shown, the stage may comprise elevations, stairs, lifts or other elements providing a static or dynamic height difference.

[0054] Dots in the figure identify different locations. The dotted lines provide an indication how the locations relative to the performance environment should be seen in 3D. At the front middle side of the stage is typically the reference point (R). The leading edge of the stage is typically used as reference direction as indicated. The X direction is parallel to the front of the public / the stage to the right for the public, the Y direction from the stage straight away from the public and straight into the stage, and Z direction straight up from the stage. Alternative directions and reference point may be used.

[0055] The exemplary performance environment comprises four spots 20, 21 , 22, 23 illuminating the performance environment, typically the performer and / or the stage. The performance environment further may comprise four calibration locations. The dotted lines show the distance along the X, Y, Z axis between one calibration location and one spot position. This is merely for providing a 3D reference to the figure. The different dashed lines show a direct line between a respective calibration location and a respective spot position. A variable may be the direction of a dashed line from a calibration location to a spot position. Based on the direction of the dashed line determined at the calibration location, the spot position is determinable. In the case of two dashed lines and knowledge of the orientation at the calibration location of the reception device, the spot position can be determined based on two directions of the dashed lines. Furthermore, in the case of only looking upward reception devices and no knowledge of the orientation of the reception device, the spot position can be determined based on three directions of the dashed lines. A spot position is typically the X,Y,Z position or location of a spot. A spot position is typically the 3D position or location of a spot. In special cases, a spot position may be the initial X,Y,Z or 3D position or location of a spot. A spot position therefore defines the origin of the light beam originating from a spot at the spot position. In a specific embodiment, the reception device also emits an identifier receivable by one or more reception devices arranged at other calibration locations. This arrangement allows calibration of the assembly without determining distances between and / or orientation at the calibration points.

[0056] When the reception device is arranged or located on the stage, the calibration location is typically at some height from the stage upwards. For example, when the reception device is an upward looking camera with a dome field of view, the calibration location may be at the image sensor of the camera.

[0057] Figure 2 schematically shows a controlled object 40. The controlled object may be a follow spot, a camera, or any other object of which the orientation may be controlled in the context of the performance environment.

[0058] In the current example, the orientation of one or more of the spots of Figure 1 may be shown. The spot has an illumination cone typically extending over a part of the stage. The spot identifier can typically be received by objects, such as a reception device positioned within the illumination cone. The spot identifier is typically emitted as part of the illumination cone. The controlled object is typically rotated around a centre point C. Relative to a horizontal plane H, the controlled object is rotated over an angle (p typically labelled as pan. Relative to a vertical axis V, the controlled object is rotated over an angle 0 typically labelled as tilt. The pan and tilt together provide an orientation of the controlled object. The combination of the location of the controlled object, such as the camera or follow spots in Figure 1 , with the orientation as shown in Figure 2 provides the attitude of the controlled object. The position of the controlled object may be C.

[0059] Figure 3 schematically shows a calibration method 300 for calibrating a position of at least two spots illuminating a performance environment with radiation. The method comprises the step of selecting 310 a calibration location inside the performance environment. The method further comprises emitting 315 a spot identifier from each of the at least two spots The method further comprises receiving 320 the emitted spot identifiers at the calibration location. The method further comprises determining 325 a variable per spot using the received spot identifiers. The method further comprises calculating 330 the position, specifically the spot position, of the at least two spots based on the respective variables. In specific cases the position may be the location of another reception device arranged or located at another calibration location.

[0060] The calibration may be performed with one calibration device arranging the calibration device to several calibration locations. Alternatively, several calibration devices may perform the calibration allowing parallel calibration or calibration overlapping in time further reducing the total calibration time. More calibration locations than four may be used from a practical point such as that not all spots may reach all calibration locations. Further, other numbers of calibration devices than one and four may be used.

[0061] The spot identifier may be a visual identification. The spot identifier may be a colour. The spot identifier may be switching on / off pattern. A placement is typically a pan and tilt value of a spot. A placement may be an orientation or an attitude. A placement may be a position, for example in an embodiment where the spot is arranged on rails. A placement may be a combination. The spot may be a follow spot, a pan-tilt spot, or PTZ spot. Typically, the combination for a spot of a spot position of the spot and a placement of the spot define where a light beam originating from the spot is arranged in the performance environment.

[0062] Figure 4 schematically shows an embodiment of a computer program product 1000, computer readable medium 1010 and / or non-transitory computer readable storage medium according to the invention comprising computer readable code 1020. The compounding system typically comprises a controller arranged for executing one or more of the methods as specified throughout the description and claims as typically coded in software.

[0063] Examples, embodiments or optional features, whether indicated as non-limiting or not, are not to be understood as limiting the invention as claimed. It should be noted that the figures are purely diagrammatic and not drawn to scale. In the figures, elements which correspond to elements already described may have the same reference numerals.

[0064] The term “substantially” herein, such as in “substantially all emission” or in “substantially consists”, will be understood by the person skilled in the art. The term “substantially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term “substantially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term “comprise” includes also embodiments wherein the term “comprises” means “consists of’.

[0065] The term "functionally" will be understood by, and be clear to, a person skilled in the art. The term “substantially” as well as “functionally” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective functionally may also be removed. When used, for instance in “functionally parallel”, a skilled person will understand that the adjective “functionally” includes the term substantially as explained above. Functionally in particular is to be understood to include a configuration of features that allows these features to function as if the adjective “functionally” was not present. The term “functionally” is intended to cover variations in the feature to which it refers, and which variations are such that in the functional use of the feature, possibly in combination with other features it relates to in the invention, that combination of features is able to operate or function. For instance, if an antenna is functionally coupled or functionally connected to a communication device, received electromagnetic signals that are receives by the antenna can be used by the communication device. The word “functionally” as for instance used in “functionally parallel” is used to cover exactly parallel, but also the embodiments that are covered by the word “substantially” explained above. For instance, “functionally parallel” relates to embodiments that in operation function as if the parts are for instance parallel. This covers embodiments for which it is clear to a skilled person that it operates within its intended field of use as if it were parallel.

[0066] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0067] The devices or apparatus herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation. 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. Use of the verb "to comprise" and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device or apparatus claims enumerating several means, several of these means may 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.

[0068] The invention further applies to an apparatus or device comprising one or more of the characterising features described in the description and / or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterising features described in the description and / or shown in the attached drawings.

[0069] The various aspects discussed in this patent can be combined in order to provide additional advantages. Furthermore, some of the features can form the basis for one or more divisional applications.

Claims

CLAIMS1 . Calibration method (300) for calibrating a position (20, 21 , 22, 23) of at least two spots illuminating a performance environment (10) with radiation, comprising:- selecting a calibration location (30, 31 , 32, 33) inside the performance environment;- emitting a spot identifier from each of the at least two spots;- receiving the emitted spot identifiers at the calibration location;- determining a variable per spot using the received spot identifiers; and- calculating the position of each of the at least two spots based on the respective variables; characterized in that the spot identifiers uniquely identify the at least two spots in the performance environment.

2. Calibration method according to the preceding claim, wherein determining the variable comprises measuring the variable per spot, and associating the variable with the spot identifier.

3. Calibration method according to any of the preceding claims, wherein emitting comprises placing each spot of the at least two spots until the emitted identifiers are received at the calibration location.

4. Calibration method according to the preceding claim, wherein placing comprises orienting.

5. Calibration method according to the preceding claim, wherein orienting comprises providing a pan and / or a tilt setting for the spot.

6. Calibration method according to any of the preceding claims 3-5, wherein the method comprises:- after receiving the emitted spot identifier, repeatedly placing each spot of the at least two spots;- after each placing of each spot emitting radiation from the respective spot; and- receiving the emitted radiation resulting in a received radiation intensity; wherein the variable comprises a placement of each spot associated with a received radiation intensity, preferably above an intensity threshold; wherein, when depending on claim 4, the placement comprises orienting; and wherein, when depending on claim 5, the placement comprises the pan and / or the tilt setting.

7. Calibration method according to the preceding claim, wherein calculating also comprises calculating the placement of a plurality of spots illuminating a performance environment with radiation.

8. Calibration method according to any of the preceding claims 6-7, wherein receiving comprises repeatedly receiving the emitted spot identifier for different placements for determining a range of placements for which the received radiation intensity is above the intensity threshold.

9. Calibration method according to the preceding claim, wherein determining the range also comprises determining placements for which the received radiation intensity is below the intensity threshold for determining the boundary of the range.

10. Calibration method according to any of the preceding claims, wherein receiving comprises imaging and / or recording the environment; and wherein determining the variable comprises:- detecting per spot a detected spot position in the image and / or the recording showing the spot identifier; and- assigning per spot a reception direction relative to the calibration location based on the detected position, wherein the variable comprises the reception direction.11 . Calibration method according to any of the preceding claims, wherein receiving comprises imaging and / or recording the environment with a camera, preferably an upward looking camera and / or omnidirectional camera arranged on a stage of the performance environment.

12. Calibration method according to any of the preceding claims, wherein the emitted spot identifiers are emitted simultaneously and / or overlapping in time.

13. Calibration method according to any of the preceding claims, wherein receiving at the calibration location is receiving multiple of the emitted identifiers simultaneously and / or overlapping in time.

14. Calibration method according to any of the preceding claims, wherein the spot identifier comprises a light colour, a light spectrum, a wavelength range, or a set of wavelength ranges.

15. Calibration method according to the preceding claim, wherein the spot identifier comprises a change in the light colour, a light spectrum, a wavelength range, or a set of wavelength ranges over time.

16. Calibration method according to any of the preceding claims, wherein the spot identifier comprises a change in radiation intensity over time, preferably a pattern or a code.

17. Calibration method according to any of the preceding claims, wherein the steps of instructing and receiving are synchronised in time such that the spot identifier comprises emitting radiation at a particular moment in time.

18. Calibration method according to any of the preceding claims, wherein the spot identifiers are usable for differentiating between the variables of the at least two spots.

19. Calibration method according to any of the preceding claims, wherein emitting comprises instructing the at least two spots to emit the spot identifier.

20. Calibration method according to any of the preceding claims, wherein receiving the emitted spot identifiers comprises receiving the emitted spot identifiers at at least four distinct calibration locations; wherein determining the variable comprises determining the variable per spot using the received spot identifiers for the at least four distinct calibration locations; and wherein calculating the position of the at least two spots comprises calculating the position of the at least two spots based on the respective variables for the at least four distinct calibration locations.21 . Calibration device for calibrating a position of at least two spots illuminating a performance environment with radiation, comprising:- a reception device arranged for receiving emitted spot identifiers of at least two spots at a calibration location inside the performance environment; and- a controller arranged for: obtaining the reception with the received identifiers from the reception device; determining a variable per spot in the reception using the spot identifiers; and calculating the position of the at least two spots based on the respective variables; characterized in that the spot identifiers uniquely identify the at least two spots in the performance environment.

22. Calibration device according to the preceding claim, wherein the controller is further arranged for instructing the at least two spots to emit a spot identifier.

23. Calibration device according to any of the preceding claims 21-22, comprising the at least two spots arranged for emitting the respective spot identifiers.

24. Computer implemented method for calibrating a position of at least two spots illuminating a performance environment with radiation and emitting a spot identifier from each of the at least two spots:- obtaining a reception of a reception device arranged for receiving the emitted spot identifiers at a calibration location inside the performance environment;- determining a variable per spot using the spot identifiers; and- calculating the position of the at least two spots based on the respective variables; characterized in that the spot identifiers uniquely identify the at least two spots in the performance environment.

25. Computer implemented method according to the preceding claim, further comprising instructing the at least two spots to emit a spot identifier.

26. Computer program product comprising instructions which, when the program is executed by a suitable processor, causing the processor to carry out the method of claims 24-25.

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