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Technical Field

The present description relates to the control of lighting sources.

One or more embodiments may be applied to the control of lighting sources employing electrically powered light radiation generators such as solid-state light radiation generators, e.g. LED generators.

Technological Background

Lighting systems or installations may employ a plurality of lighting sources (e.g. electrically powered lighting sources) either of one model or of different models, which are adapted to cooperate in implementing a lighting action.

Given that the overall perceivable lighting effect originates from the light emission of a plurality of lighting sources, the coherence or consistency of the light output from the various sources may therefore be a key feature. Moreover, the overall lighting effect may be perceived not only by a human observer, but also by devices (e.g. electronic devices) of various nature, which are adapted to detect the light radiation: this may be the case e.g. of the cameras included in smartphones or other mobile devices, which may be used to take photographs or film videos which may then be transmitted and broadcast, or of one or more sensors used to detect or map the light intensity on a surface.

The coherence or consistency of the light emission is an issue intrinsic to the technology of light radiation sources, such as e.g. LED sources. For example, the manufacturing processes of LED light radiation generators have intrinsic tolerances as regards e.g. flux, colour coordinates, forward voltage, thermal resistance, the position of a given chip in the respective package: all these factors may determine a possible variation of the light emission.

This situation may be particularly critical in the lighting applications wherein the lighting quality plays a key role. For example, reference may be made to general lighting environments such as points of sale, indoor and outdoor home installations, as well as medical or entertainment applications.

Particular attention should be paid to those applications which envisage a mixing action of the light radiation generated by LEDs of different colours, e.g. in order to achieve a tuning effect on the colour of the resulting radiation: as a matter of fact, the coloured LEDs which are employed in such applications may exhibit, as regards the previously listed parameters, larger variations than white LEDs, e.g. as regards colour coordinates and flux.

The problems stated in the foregoing may appear either at "Oh lifetime" of the source, i.e. at the first activation thereof, or else, often more evidently, during the lifetime of the light radiation source .

The lighting sources such as LED sources undergo aging processes which lead to performance deterioration, as regards both flux and colour. This phenomenon may appear in a differentiated fashion on the basis of the operating conditions (specifically as a function of temperature) , with the light radiation sources included in a given lighting system being operated differently, so that the aging may have different intensities from source to source.

The aging effects may be due to a certain intrinsic variability, so that two sources which are used exactly at the same conditions may exhibit mutually different aging phenomena (e.g. the colour coordinate and flux shift being different from source to source) .

A further level of complexity may emerge when a new source is installed in a system including other sources which have already been operating for some time: in said conditions, the differences in colour and flux of the emitted light radiation may be even more evident and may be clearly perceived by an observer.

These problems may be mitigated to some extent by installing, into a given system, lighting sources including LEDs which all belong to a narrow "binning" range. This approach may require a strict selection by the LED suppliers (which may have a negative impact on the cost) and, at any rate, may only alleviate the problem on newly installed sources, without an appreciable effect on the phenomena originating from aging .

Object and Summary

One or more embodiments aim at facing the previously outlined problems.

According to one or more embodiments, said object may be achieved thanks to a method having the features set forth in the claims that follow.

One or more embodiments may also refer to a corresponding lighting system, as well as a corresponding computer program product loadable in the memory of at least one processing device, and including software code portions to execute the method steps when the product is run on at least one computer. As used herein, the reference to said computer program product is intended to be equivalent to the reference to computer-readable media, containing instructions to control the processing system in order to coordinate the implementation of the method according to the present specification. The reference to "at least one processing device" highlights the possibility of implementing one or more embodiments in a modular and/or distributed fashion.

The claims are an integral part of the technical teaching provided herein with reference to the embodiments .

One or more embodiments may tackle and solve the problems outlined in the foregoing by managing the flux value and the colour coordinates of a (e.g. LED) lighting source within each fixture of the overall installation or system, by carrying out a corresponding compensation action.

Brief Description of the Figures

One or more embodiments will now be described, by way of non-limiting example only, with reference to the annexed Figures, wherein:

Figures 1 and 2 are illustrative diagrams of aspects related to the use of lighting sources,

- Figure 3 shows the aspects introduced by Figures

1 and 2 with reference to a CIE1931 colour space,

Figure 4 shows, again with reference to a CIE1931 colour space, some features of a method according to embodiments,

- Figure 5 exemplifies possible particular features of one or more embodiments,

- Figure 6 shows, in dashed lines, some aspects illustrated with reference to Figures 3 to 5,

Figure 7 and Figure 8 further exemplify application approaches of embodiments,

- Figure 9 is a block diagram of a system adapted to operate according to one or more embodiments, and

Figure 10 is a flowchart exemplifying embodiments .

Detailed Description In the following description, various specific details are given to provide a thorough understanding of various exemplary embodiments. The embodiments may be practiced without one or several specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials or operations are not shown or described in detail in order to avoid obscuring the various aspects of the embodiments .

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the possible appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring exactly to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

The headings provided herein are for convenience only, and therefore do not interpret the extent of protection or scope of the embodiments.

One or more embodiments may derive from the observation that the problems outlined in the introduction of the present specification may originate from the fact that the possibility of reaching a given target colour point is linked to the respective gamut. Said gamut may be different for each lighting source, because of the intrinsic variability due e.g. to the manufacturing technologies of the respective light radiation generators, e.g. LED generators.

One way to visually depict the intrinsic variations of the behaviour of a light radiation source, such as a LED source, involves the mapping in a colour space, such as e.g. the CIE1931 colour space, wherein the chromatic behaviour of a light radiation source may be represented as a gamut, such as gamuts gl and g2 shown by way of example in Figure 1.

As it is known, the CIE XYZ space (conventionally denoted as CIE1931) is a colour space which was mathematically defined by the "Commission Internationale de l'Eclairage" (CIE) in 1931. This colour space derives from test results combined in the specifications of the CIE RGB colour space, from which CIE XYZ was derived.

Both gamuts gl and g2 of Figure 1 (for simplicity we will refer to two gamuts only, the respective differences whereof are deliberately emphasized for simplicity of explanation and comprehension) may correspond to one and the same model of LED source, e.g. a coloured LED source. Even though said sources may be virtually identical in all their aspects and even though they may theoretically operate with the same operating conditions, it is possible to observe differences between the two sources e.g. as regards the variation of the intrinsic colour and/or flux.

Assuming that both sources are regulated in a virtually identical fashion in order to produce a light radiation having a colour corresponding to a given point C in a colour space (e.g. CIE1931 colour space), the intrinsic variations due to the LED manufacturing process, which may lead to both sources having different gamuts (i.e. gl and g2 ) , may originate emissions with different colour features. Specifically, the "target" colour point C may be contained in only one of the gamuts, as exemplified by point C2=C in Figure 1: the point is only included in gamut g2, but not in gamut gl .

As a matter of fact, the difference between the two gamuts gl, g2 is such that both gamuts have a certain portion in common (practically a superposition or intersection area between both gamuts) and one or more portions which are included in only one of the gamuts and not in the other: this may be the case of the portion of gamut g2 wherein point C2=C is located, the latter being included in gamut g2 but being outside gamut gl .

In such situations, when both lighting sources are driven (as known in itself) so as to emit light radiation corresponding to the target point C, a situation may arise wherein:

- the source the gamut whereof (gamut gl, in the presently considered example) contains the target point C2=C actually emits light radiation of the desired colour,

- the other source, the gamut whereof (gamut gl, in the presently considered example) does not contain the target point C, is not adapted to emit light radiation exactly corresponding to the target point, and it emits light radiation at a point CI which may be very near, but may not exactly correspond to, the target point C2=C.

The overall result is that the lighting effect deriving from both light radiation sources lacks uniformity, because the light radiations emitted from the two sources are different from each other.

Figure 2, including two portions respectively denoted as a) and b) , further shows the previously described mechanism with reference to a colour point representation based on the HWS (Hue-Saturation-Value) system.

This system may be described as a system of polar coordinates, wherein hue is represented by the angular coordinate while the radial coordinate represents saturation (see for example the saturation level S=100% in portion a) on the left in Figure 2 and the lowest saturation level, S=k in portion b) on the right in the same Figure 2), an additional parameter being represented by the dimming value.

Assuming that:

the two sources considered herein by way of example are driven with the same input as regards hue and saturation (the dimming value is not particularly relevant in the presently considered instance) ,

- the centre of the HSV system corresponds to the point denoted as D in Figure 2,

it may be seen that, due the different boundary conditions deriving from the difference between gamuts gl, g2, the conversion of the hue and saturation value for reaching a given target point may be different for the two sources, as exemplified by the two points CI and C2 in portion b) of Figure 2: this corresponds to the situation, already examined in the foregoing, wherein both sources, albeit having the same input, emit light radiations of different colours.

It will be appreciated that the reference to the HSV system is merely exemplary, as the same considerations apply with reference to other coordinate representation systems, such as the RGB or CMY systems.

One or more embodiments may envisage identifying a gamut in common to the various lighting sources in a given lighting system or installation, and to "overwrite" said common gamut onto the single specific gamuts of each light radiation source.

In one or more embodiments, said method may be based on the availability of photometric data of the lighting sources (e.g. of the light radiation generators, e.g. LED generators) included in the system. It is therefore possible to perform, on the various sources or fixtures, a calibrating action which may be compared to what is already envisaged in the conventional manufacturing processes of lighting sources or fixtures which include a plurality of radiation generators, e.g. LED generators.

Such a calibration process may envisage:

- activating each (type of) LED in the lighting source,

- measuring the photometric parameters of the related emitted radiation (light spectrum, which is adapted to contain all the useful information in terms of gamut and flux) , and

storing the corresponding parameters into a local memory (e.g. an EEPROM memory) adapted to be associated to a given source or fixture.

Figure 3 is a representation, in the CIE1931 colour space, of a situation similar in principle to what has been previously exemplified with reference to Figures 1 and 2, i.e. the presence of two lighting sources or fixtures (each including a given number of light radiation generators, e.g. LED generators) having respective gamuts gl, g2 adapted to be represented, in the CIE1931 colour space, by respective polygonal lines Al, Bl, CI, Dl, El and respectively A2, B2, C2, D2 and E2.

For the reasons outlined in the foregoing, also in the case of two lighting sources or fixtures which are virtually identical, the respective gamuts are so to say similar or close to each other, but not coincident: this fact is exemplified in Figure 3, which shows that the polygonal lines representing both gamuts gl and g2 extend between pair of vertexes A1-A2, B1-B2, C1-C2, D1-D2 and E1-E2 which, although being adjacent, do not exactly coincide with each other. Once again it will be appreciated that, although the present discussion refers for simplicity to two sources having two gamuts gl, g2, what is presently being described and shown may generally extend to any number n of sources having gamuts gl, g2, ... gn.

Figures 4, 6 and Figure 6 (the latter in a simplified representation) exemplify the possibility of identifying (e.g. according to the procedure described in the following) an "intersection" area G_int between the gamuts gl and g2, including the portion of the CIE1931 colour space in common between gamuts gl and g2, i.e. the set of points which are present both in gamut gl and in gamut g2.

Once again it will be noted that the observations outlined with reference to two gamuts gl, g2 may generally be extended to virtually any number of different gamuts. Specifically, given any number n of different gamuts, the problem is posed of calculating the intersection area among a plurality of polygonal areas (in the same number as the considered lighting sources) .

Said problem may be solved by resorting to different processing solutions, e.g. by taking into account elements as accuracy, time and complexity.

In one or more embodiments, the identification of the intersection gamut G_int may be achieved according to the criterion exemplified in Figures 4 to 6, i.e. by locating the intersection points between the lines of the sides of the polygons which describe the various gamuts (i.e. gl and g2, in the presently considered example) .

This approach may substantially involve:

- identifying the intersection points between the lines of the sides of the polygon which describes each gamut, i.e. the vertexes of said polygon, e.g. Al, Bl, CI, Dl, El for the first gamut gl and A2, B2, C2, D2, E2 for the second gamut g2,

- identifying the intersection points between the lines of the sides of the polygons which describe different gamuts, i.e. between the sides Al-Bl, Bl-Cl, Cl-Dl, Dl-El and El-Al of the polygon describing the first gamut gl and the sides A2-B2, B2-C2, C2-D2, D2-E2 and E2-A2 of the polygon describing the second gamut g2,

- employing said intersection points in order to define vertexes 01, 02, 03, 04, 05, 06 of a (new) polygon describing the intersection gamut G_int .

One or more vertexes of the polygon describing the intersection gamut may therefore correspond to the vertexes of one of the original gamuts, e.g., in Figures 4 and 6, the vertex 03 in the intersection gamut G_int corresponding to the vertex Bl of gamut gl, corresponding to the intersection between the sides Al- Bl and Bl-Cl belonging to the same gamut 1.

As exemplified in Figure 5, some intersection points between lines (e.g. intersection point 0L between the lines denoted as Line 1 and Line 2) of the sides of the polygons of gamuts gl, g2 may be located outside the colour space; such points are therefore destined to be discarded as "outliers".

What has been exemplified in Figures 4 to 6 with reference to two gamuts gl, g2, which are different but substantially similar to each other, may also be applied to gamuts that totally differ from each other as regards shape and/or size, such as gamuts g2 and g3 (the latter having vertexes A3, B3, C3) exemplified in Figures 7 and 8, therefore originating e.g. an intersection gamut G_int having vertexes 01, 02, 03, 04.

One or more embodiments may be implemented in a lighting system as exemplified in Figure 9, including a set of lighting sources SI, S2, Sn.

In the diagram of Figure 9, reference 1000 denotes a processing device 1000 adapted to calculate the information identifying the intersection gamut G_int and to provide it to a control device 1002 (of a type known in itself) which, on the basis of such information, is adapted to activate the set of lighting sources SI, S2, Sn, while controlling them in such a way that the radiation emitted thereby corresponds to a common target point C which may be reached by all sources, because it is included in the intersection gamut G_int .

Devices 1000 and 1002 may both be included in a control panel of a professional lighting module.

As further discussed in the following, in some embodiments device 1000 (which is adapted to act onto photometric data which are exemplified herein by a repository DB) may be located remotely of device 1002 and/or it may be a mobile/portable device, the information about the intersection gamut G_int being transmitted from the remote device to device 1002.

One or more embodiments may adopt the procedure exemplified in the flowchart of Figure 10.

In this flowchart, after START, in a step 101 the sources (fixtures) are chosen which shall be involved in the calibration process, while in the steps denoted as 102 and 103 photometric data may be obtained for each selected source.

Such data may include e.g. data about flux and colour coordinates (Cx, Cy) of the radiation emitted by the radiation generators (e.g. LED generators) of the source. A reference to colour coordinates Cx, Cy - according the current denomination for the CIE 1931 colour space) is not to be construed as limiting, because the presently exemplified procedure may also be applied to different colour spaces.

Block 103 exemplifies the condition wherein, if said photometric data are not available in advance or are available in advance only for some sources and not for others, the data repository (DB in Figure 9) includes or is completed by photometric data which are collected (according to known criteria) so to say "on site": for example, if they are not collected during the manufacturing process of the sources, said data may be collected by using a portable photometric detector.

Step 104 corresponds to identifying, from said photometric data, a first gamut (e.g. gamut gl of Figures 3 and 4, identified by respective vertexes (Cx_i, Cy_i) such as e.g. the vertexes denoted as Al, Bl, CI, Dl, El.

Block 105 represents the calculation (performed according to known criteria) of the equation representing, on the colorimetric plane, the sides of the polygon corresponding to said gamut (e.g. the sides Al-Bl, Bl-Cl, Cl-Dl, Dl-El, El-Al) .

Blocks 106 and 106a exemplify that the operations of blocks 104 and 105 are iteratively repeated until said calculation has been carried out for all sides of a given gamut and for all the gamuts/sources being considered (negative result in step 106: there are still sides to be calculated; negative result in step 106a: there are still gamuts to be examined) .

Once the operations of blocks 104 and 105 have been performed for all the sides of each gamut and for all the gamuts (when steps 106 and 106 yield positive results in cascade) , a step 107 locates the intersection points of the sides of the considered gamuts, in all possible combinations, i.e. (as stated in the foregoing) the intersections between the lines of sides belonging to different gamuts, as well as the intersections between the lines of sides belonging to the same gamut (in practice, the vertexes of each polygon describing one of the initial gamuts) .

In performing said operation, various preliminary considerations may be taken into account as regards the position of the sides and the mutual proximity of the sides, so as to reduce the number of combinations to be examined .

For example, step 108 exemplifies that one or more intersection points may be negligible, e.g. such as:

- i) the points located outside the CIE1931 colour region (as in the case of Figure 5) , although they have non-negative Cx and Cy values;

- ii) the points having negative Cx (or Cy) , because they are too far below or too far left of the coloured region;

iii) the points having Cx (or Cy) > = 0.85, because they are too far right or too far above.

The points corresponding to cases ii) and iii) may be located immediately, and they may be discarded from the beginning in order to reduce the number of cases to verify.

The existence of said conditions may be verified in step 108, so that, if the point is of no interest (negative result of step 108), it may be excluded from the calculation (step 108a), thus reducing the number of combinations to be considered.

In other words, step 108 of Figure 10 exemplifies a verification step performed starting from the first intersection point (generally denoted as Cx_k, Cy_k) obtained in block 107, in order to verify whether said element belongs to the gamut of all the considered sources: if said condition is verified (positive result in step 108), the point is stored as a vertex of the intersection gamut common to the various sources, in order to proceed with the processing. If this is not the case (negative result in step 108), the considered point is discarded, as shown in block 108a.

It will be appreciated that the presently outlined procedure aims at verifying if a given point (Cx_k, Cy_k) belongs to the original polygon of a source (fixture), e.g. because it is included therein or is located on the perimeter thereof. The procedure may be repeated on the same point for the same number n of times as the number of the fixtures selected at the beginning, while changing the polygon (the gamut) every time, but the verification always regards one point with reference to a polygon.

For example, in the case of point 03 in Figure 4, when it is verified that Bl belongs to gamut gl, then it is located on the perimeter; when it is verified that Bl belongs to gamut g2, this means that it is located inside the perimeter.

After verifying that a point belongs to all gamuts, it is possible to deduce that it corresponds e.g. to a vertex of the intersection gamut, and so it is possible to state that such a point, being located on the perimeter of the gamut, belongs to the related polygon .

In order to implement said procedure in practice, techniques of the state of the art may be resorted to which are known as Ray Casting Algorithm, Winding Number Algorithm or others. The choice of one of such solutions may depend e.g. on the desired accuracy and on processing time and complexity requirements which must be taken into account.

Step 109 exemplifies the verification whether the processing described in step 108 (storing a given point or discarding the same) has been performed for all points obtained in step 107 (negative result in step 109: there are still points to be verified; positive result in step 109: all points have been verified) .

The result which may be obtained with such a procedure, exemplified in block 110, may be represented as an array of points in a given colour plane (e.g. CIE 1931, to keep to the same simplified example), which identify the vertexes of the intersection gamut G_int . For example, such vertexes are adapted to be ordered e.g. clockwise or anticlockwise, so as to obtain an ordered table (which for example may represent the information which, in the diagram of Figure 9, device 1000 provides to device 1002) .

The sequence of actions represented by blocks 104 to 110 explained in the foregoing corresponds in practice to the solution of the problem of calculating the intersection area among a plurality of polygonal areas (in the same number as the considered sources: once again, it must be remembered that the reference to only two sources having gamuts gl and g2 is merely exemplary), the possibility being given, e.g. as a function of different accuracy, time or complexity requirements, of resorting to different processing solutions .

Block 111 exemplifies the optional possibility of further improving the identification of the calculated intersection area or gamut G_int by taking into account the shift of the LED characteristics, due e.g. to temperature, aging or other variable parameters, which may cause a variation of the LED parameters, so as to obtain, at the end of said operation, a resulting gamut G_int which is common to all considered sources or fixtures SI, S2, ... , Sn, which is also compensated with respect to the previously mentioned shift phenomena . It will appreciated that the action exemplified in block 111 is optional and not mandatory.

In one or more embodiments, the possibility is therefore offered of applying the intersection gamut G_int (which may compensated or not compensated, according to the application and usage needs) to the various sources SI, S2, .., Sn of the system or installation. This enables establishing the target colour C in such a way that it is included within the intersection gamut G_int which is common to all light radiation sources, the consequent possibility being offered - to all sources SI, S2, Sn of the system or installation which are subjected to the "calibration" action described in the foregoing - of producing such a colour while avoiding the lack of precision exemplified by the distance between points CI and C2 in Figure 1.

In one or more embodiments the target colour, if it is not available as colour coordinates in the same space wherein the source calibration action has been carried out, may be converted starting from a set of specified input values in different systems (e.g. RGB, CMY o HSV) with an optional previous conversion to the colour space employed.

At any rate, as previously stated, what has been said by way of example with reference to the CIE1931 colour space may be applied in the same way to different colour spaces, wherein it is possible to apply the criterion of identifying an intersection gamut (G_int) which is common to the various sources of a given system or installation.

Block 112 exemplifies the optional possibility, in one or more embodiments, of performing a further regulation/calibration on the consistency of the light radiation, with reference to the intensity of the luminous flux, due to the fact that, for example, the human eye may perceive colours which are actually identical as if they were different colours, if they have a different intensity level.

Block 112 exemplifies e.g. the optional possibility, after obtaining the colour ratio for each source of fixture so as to achieve the target colour, of calculating the total flux of the resulting colour. For example, after obtaining (also) the information about the flux of the LEDs installed in the sources or fixtures, it is possible to define a light intensity threshold (F_lim) as the value which (also) the least efficient LED may achieve by being driven to the maximum value or, in the case of a LED with performances exceeding the expected level, by dimming the light input thereof.

The step denoted as 113 exemplifies the possibility of regulating the light radiation so as to reach said threshold level, in order to achieve a desired brightness uniformity.

One or more embodiments as exemplified herein enable achieving advantages of various nature.

For example, it is not necessary to limit (with reference to gamut and flux) to a theoretical worst case, with compromises, all the sources included in a given production batch, in order to limit the problem of the consistency of the emitted light radiation: in one or more embodiments, all the sources or fixtures may be used individually at their whole potential, while being optionally limited according to the needs established by the intersection gamut G_int (only) when it is desired to achieve a consistency among a plurality of sources.

Moreover, within a system or installation, it is possible to calibrate (only) a group of sources, in order to produce one consistent light output as a function of the same input data.

The calibration process described in the foregoing may be implemented so to say in a volatile fashion: as a function of different application or usage needs, a given source may be used alternatively in various groups of sources, including new sets of sources (other than the one they originally belonged to) .

As an alternative, the calibration process may be adapted to be permanent, e.g. when a given group of light sources is destined to be used together in a virtually constant way.

The group of sources may be chosen in different ways at different times, so as to implement a calibration compensation (e.g. as regards both G_int and F_lim) only for a given group of selected sources, without acting on sources which have not been chosen and which may be used at their full potential (both in terms of flux and in terms of colour gamut achievable) . When a source is used singularly, the gamut G_int practically corresponds to the intrinsic gamut, without limitations on the performances of said source, which may therefore be used at its full potential (100% of the colour gamut and 100% of the light output) .

In the presence of uncontrolled aging (in terms of colour and flux, as may occur for sources such as LED sources) the presently exemplified calibration procedure enables (e.g. in step 103 of Figure 10) measuring the colour and flux characteristics (Cx, Cy) at a given instant, and correctly calculating the intersection gamut G_int which represents the state of the radiation sources at a given instant.

If an aging model is implemented in the sources, starting from the intersection gamut G_int calculated at a given instant (e.g. at Oh lifetime of the sources), it is possible to estimate (e.g. at step 111 in Figure 10) a possible expected shift of G_int over time, so as to implement a compensation of the deterioration of the radiation generators without the need of periodically repeating the system calibration in the previously described fashion.

One or more embodiments may therefore concern a method of operating a plurality of lighting sources (e.g. SI, S2,..., Sn) activatable (e.g. 1002) to emit light radiation at colour points in respective light radiation emission gamuts (e.g. gl, g2 ; g2, g3) in a colour space, the method including:

- calculating (e.g. 1000; 104-111) an intersection gamut (e.g. G_int) of the respective light radiation emission gamuts of the lighting sources in said plurality of lighting sources, the intersection gamut including colour points in said colour space common to the light radiation emission gamuts of the lighting sources in said plurality of lighting sources, and

- activating the lighting sources in said plurality of lighting sources to emit light radiation of a common target colour point (e.g. C) in said colour space, said common target colour point being included (e.g. as a vertex) in said intersection gamut.

In one or more embodiments, wherein the lighting sources in said plurality of lighting sources may have respective light emission flux values, a method may include :

- detecting said respective light emission flux values,

- calculating, as a function of said respective light emission flux values detected, a light flux threshold value (e.g. F_lim) reachable by all the lighting sources in said plurality of lighting sources, - activating the lighting sources in said plurality of lighting sources to emit light radiation at said light flux threshold value.

In one or more embodiments, wherein said respective light radiation emission gamuts may include polygons in said colour space, said polygons having sides extending between polygon vertexes (e.g. Al, Bl, CI, Dl, El; A2, B2, C2, D2, E2; A3, B3, C3) calculating said intersection gamut may include:

- locating intersections between the lines of the sides of the polygons of said respective emission gamuts (as stated in the foregoing, either of the same gamuts, by locating the vertexes thereof, or of different gamuts) of the light radiation, and

including said intersections in the vertexes (e.g. 01, 02, 03, 04, 05, 06) of said intersection gamut .

One or more embodiments may include:

providing a repository (e.g. DB) of light radiation emission gamut data for lighting sources in said plurality of lighting sources, and

calculating said intersection gamut as a function of light radiation emission gamut data retrieved in said repository.

One or more embodiments may include:

- obtaining via photometric measurement light radiation emission gamut data for lighting sources in said plurality of lighting sources, and

calculating said intersection gamut as a function of light radiation emission gamut data obtained via said photometric measurement.

One or more embodiments may include applying to said intersection gamut compensation over time as a function of the variation of the light radiation emission parameters of said lighting sources.

In one or more embodiments, said colour space may be the CIE1931 colour space.

One or more embodiments may concern a lighting system including a plurality of lighting sources activatable (e.g. 1002) to emit light radiation at colour points in respective light radiation emission gamuts in a colour space, the system being adapted to include a control unit (e.g. 1002) configured for activating said lighting sources to emit light radiation at colour points in said respective light radiation emission gamuts in said colour space, the control unit being adapted to be configured for receiving (e.g. 1000) data representative of an intersection gamut of the respective light radiation emission gamuts of the lighting sources in said plurality of lighting sources, said intersection gamut (G_int) including colour points in said colour space common to the light radiation emission gamuts of the lighting sources in said plurality of lighting sources), the control unit being adapted to be configured for activating the lighting sources in said plurality of lighting sources to emit light radiation of a common target colour point in said colour space, said common target colour point being included in said intersection gamut.

One or more embodiments may include a processing unit (e.g. 1000) configured for calculating said intersection gamut of said respective light radiation emission gamuts of the lighting sources in said plurality of lighting sources, said intersection gamut including colour points in said colour space common to the light radiation emission gamuts of the lighting sources in said plurality of lighting sources.

In one or more embodiments, said lighting sources may include solid-state light radiation generators, optionally LED generators. One or more embodiments may include a computer program product loadable in the memory of at least one processing unit (e.g. 1000) and including software code portions for calculating said intersection gamut in the method according to one or more embodiments.

Without prejudice to the basic principles, the implementation details and the embodiments may vary, even appreciably, with respect to what has been described herein by way of non-limiting example only, without departing from the extent of protection.

The extent of protection is determined by the annexed claims.

LIST OF REFERENCE SIGNS

Lighting sources SI, S2,.„, Sn Emission gamuts gl, g2, g3 Intersection gamut G_int

Colour points CI, C2 Target colour point C Light flux threshold F_lim Polygon Al, Bl, CI, Dl, El Polygon A2, B2, C2, D2, E2 Polygon A3, B3, C3

Intersection gamut vertexes 01, 02, 03, 04, 05, 06 Center of HSV system D Collection of gamut data DB Processing unit 1000

Control unit 1002 Calculation 104 - 111