WO2021259816A1

WO2021259816A1 - A lighting system

Info

Publication number: WO2021259816A1
Application number: PCT/EP2021/066727
Authority: WO
Inventors: Di LOU; Weixi ZHOU; Bo PAN; Huajie LUO
Original assignee: Signify Holding B.V.
Priority date: 2020-06-23
Filing date: 2021-06-21
Publication date: 2021-12-30

Abstract

A lighting system (2) comprising a plurality of light sources (31-3n) adapted for, in operation and in combination, providing an illumination of a space (1), a control system (4) adapted for controlling the plurality of light sources (31-3n) by sending a control signal to one or more light sources of the plurality of light sources (31-3n), a detection system (5) configured to perform detection of one or more parameters related to a target (7) in the space (1) in real time, the one or more parameters including a position of the target (7) in the space (1), and a data processing unit (6) configured to perform a series of steps intended to control a modelling factor, Mt, at the position of the target (7) according to a current light distribution, the modelling factor being defined as Mt = Ecylt/Eht, where Ecylt is the cylindrical illuminance at the position of the target (7) and Eht is the horizontal illuminance at the position of the target (7), and thus to control either of the horizontal illuminance and the cylindrical illuminance at the position of the target (7), the control system (4) further being configured to individually control each light source of the plurality of light sources (31-3n) based on the required change of light output of each light source of the plurality of light sources (31-3n) received from the data processing unit (6).

Description

A lighting system

FIELD OF THE INVENTION

The invention relates to a lighting system comprising a plurality of light sources adapted for, in operation and in combination, providing an illumination of a space, each light source of the plurality of light sources being adapted for, in operation, providing two or more light distributions, each of the two or more light distributions being configured to provide a different contribution to a horizontal illuminance, Eh, and a cylindrical illuminance, Ecyl, of the illumination of the space, a control system adapted for controlling the plurality of light sources by sending a control signal to one or more light sources of the plurality of light sources, a detection system configured to perform detection of one or more parameters related to a target in the space in real time, the one or more parameters including a position of the target in the space, and a data processing unit.

BACKGROUND OF THE INVENTION

In current indoor lighting design for professional spaces, such as offices, the horizontal illuminance on a plane (usually the working plane) is very often used as a basic characteristic for evaluating the lighting effect and service parameters of a lighting installation or system. The most important assets within an office are the people, so to strike the right balance it is desired to light not just the task at hand, but also the space and the faces of people, so that said people can feel comfortable and communicate well with each other. Therefore, a good illumination of faces is important for communication purposes in offices.

Face to face communication is increasingly important in the modem workplace. Lighting needs to create an environment where people feel comfortable, look good and can better perceive each other’s facial expression, mood and body language. Thus, lighting should support human interaction in spaces where good visual communication is important. Such spaces include for example open plan offices, meeting rooms, break-out areas and video conference rooms.

Furthermore, the current indoor lighting solutions for professional spaces are mainly focused on tasks or targets which are usually placed on desks. The illumination on desks is the number one parameter that should meet the standards. The next focus for lighting design is discomfort glare, with the aim of mitigating discomfort risks when people look at the luminous surface of the lighting fixtures.

However, there are very little attention paid to the illumination on people, which largely impact people’s facial appearance (how a person looks), people’s visual communication (how do people look while talking to each other), and the overall appreciation level of the indoor space (how nice does this room look and/or feel).

Normally, if a person is asked about the illumination on people, the answer received, when translated into lighting parameters usually leads to a value of vertical illuminance, or a value of the ratio of horizontal to vertical illuminance.

For instance, US 2014/301077 A1 discloses a method for illuminating a space using a plurality of LED illumination modules, wherein the plurality of LED illumination modules adjusts a mutual distribution ratio between a vertical illuminance and a horizontal illuminance, which is greater than the vertical illuminance, according to a limitation of a radiation angle at one point within the space having the constant volume for the whole of the space simultaneously. The efficiency of illumination may be increased, and the electric energy consumption reduced, by lowering the vertical illuminance compared to the horizontal illuminance.

However, a value of vertical illuminance, or a value of the ratio of horizontal to vertical illuminance is too general to be useful, as, even if it is valid, it only describes the brightness part of the illumination. Particularly, for typical indoor lighting applications, brighter illumination is not always equal to better illumination.

Cylindrical illuminance and modelling are two indexes that are important for a good perception of faces. The cylindrical illuminance is the mean value of vertical illuminance rotating around a certain measuring point and is aimed at guaranteeing an optimum luminance of all solid objects, and especially people’s faces. Horizontal illuminance, vertical illuminance and cylindrical luminance is illustrated schematically in Figs. 1A, IB and 1C, respectively. Horizontal illuminance is the illuminance of a horizontal plane in a space or room. Vertical illuminance is the illuminance of a vertical plane in a space or room.

In a space where an optimum visual communication is required, such as in offices, classrooms and meeting rooms, the mean cylindrical illuminance, taken at 1.2 m or 1.6 m from the measuring point, must not be lower than 150 lux, as required in lighting standard EN 12464-1. Modelling is the balance between diffuse and directional light. The modelling factor is the ratio of cylindrical to horizontal illuminance in the same measuring point. It is an important quality feature. For normal indoor luminaires for office use, no matter how the light is dimmed, its brightness changes, but its relative light distribution is unchanged. This means that for a designated point in space the horizontal illuminance is changing as the light is dimmed, while the cylindrical illuminance is also changing, accordingly. The modelling factor is kept constant.

For uniform luminaire arrangement, a modelling factor between 0.3 and 0.6 is recommended in lighting standard EN12464-1 as being adequate.

Although the said lighting standard recommends a threshold and reasonable range for these two lighting parameters, the situation in real application scenarios is generally very complex. People in the space are often moving or have different orientations, postures and activities in different areas. Also, every space and workplace is unique and will require the lighting of tasks, spaces and faces to be considered and balanced differently. There is consequently a desire to improve the facial lighting effects in such complex environments.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome this problem, and to provide a lighting system with which either of the horizontal and the cylindrical luminance may be controlled, and with which the facial lighting effects in complex environments are improved.

A further object of the present invention is to provide a lighting system with which the modelling factor may be varied.

According to a first aspect of the invention, this and other objects are achieved by means of a lighting system comprising: a plurality of light sources adapted for, in operation and in combination, providing an illumination of a space, each light source of the plurality of light sources being adapted for, in operation, providing two or more light distributions, each of the two or more light distributions being configured to provide a different contribution to a horizontal illuminance, Eh, and a cylindrical illuminance, Ecyl, of the illumination of the space and a modeling factor, M, of the space, the modelling factor being defined as M = Ecyl/Eh, a control system adapted for individually controlling each light source of the plurality of light sources by sending a control signal to one or more light sources of the plurality of light sources, a detection system configured to perform detection of one or more parameters related to a target in the space in real time, the one or more parameters including a position of the target in the space, and a data processing unit configured to: a) calculate a modelling factor, Mt, at the position of the target according to a current light distribution, the modelling factor being defined as Mt =

Ecylt/Eht, where Ecylt is the cylindrical illuminance at the position of the target and Eht is the horizontal illuminance at the position of the target, b) compare the calculated modelling factor, Mt, with a predetermined modelling factor value, Mp, c) if the calculated modelling factor, Mt, and the predetermined modelling factor, Mp, value are not equal, calculate the difference between the calculated modelling factor and the predetermined modelling factor value, d) based on the calculated difference, varying the modelling factor, Mt, at the position of the target by causing the control unit (4) to vary the contribution to either of the horizontal illuminance, Eht, and the cylindrical illuminance, Ecylt, at the position of the target of each light source of the plurality of light sources (31-3n) in such a way that either of the the horizontal illuminance, Eht, and the cylindrical illuminance, Ecylt, at the position of the target is varied.

By providing a lighting system with a data processing unit configured to perform the above-mentioned steps a) to d) and with a control system configured to individually control each light source of the plurality of light sources based on the required change of light output of each light source of the plurality of light sources received from the data processing unit, a lighting system is provided with which the modelling factor at the position of a target may be controlled.

Furthermore, by controlling either of the horizontal illuminance and the cylindrical illuminance of the target, it also becomes possible to control - and vary - the modelling factor.

Thereby a lighting system is provided with which the facial lighting effects in complex environments are improved considerably.

In an embodiment, the control unit is in step d) caused to vary the contribution to the horizontal illuminance, Eht, at the position of the target of each light source of the plurality of light sources in such a way that the modelling factor, Mt, at the position of the target is varying according to the relation Mt = 0.73 - 0.30 * (Eht/700). The inventors have shown experimentally, by a series of perception experiments, that varying the modelling factor according to the above relation provides for an optimized improvement of facial lighting effects in complex environments.

In an embodiment, the above-described step d) comprises the steps of: based on the calculated difference, calculating a required change of horizontal illuminance, dEht, at the position of the target, based on the spatial layout of the space, the arrangement of the plurality of light sources and the position of the target, calculating a weight of each light source of the plurality of light sources on the calculated required change of horizontal illuminance, dEht, at the position of the target, based on the calculated weight of each light source of the plurality of light sources on the calculated required change of horizontal illuminance, dEht, at the position of the target position, calculate the required change of light output of each light source of the plurality of light sources for achieving the predetermined modelling value, and transmit the calculated required change of light output of each light source of the plurality of light sources to the control system, the control system further being configured to individually control each light source of the plurality of light sources based on the required change of light output of each light source of the plurality of light sources received from the data processing unit.

By controlling the horizontal illuminance of the target in this way, it becomes possible to control - and vary - the modelling factor in a particularly straight-forward manner.

This in turn provides for a particularly simple lighting system with which the facial lighting effects in complex environments are improved considerably.

In an embodiment the data processing unit is further configured to: based on the calculated difference and the horizontal illuminance,

Eht, at the position of the target, calculate a required change of cylindrical illuminance, dEcylt, at the position of the target, based on the spatial layout of the space, the arrangement of the plurality of light sources and the position of the target, calculate a weight of each light source of the plurality of light sources on the calculated required change of cylindrical illuminance, dEcylt, and on the horizontal illuminance, Eht, at the position of the target, based on the calculated weight of each light source of the plurality of light sources on the calculated required change of cylindrical illuminance, dEcylt, and on the horizontal illuminance, Eht, at the position of the target position, calculate the required change of light output of each light source of the plurality of light sources for achieving the predetermined modelling value, and transmit the calculated required change of light output of each light source of the plurality of light sources to the control system, the control system further being configured to individually control each light source of the plurality of light sources based on the required change of light output of each light source of the plurality of light sources received from the data processing unit.

By controlling the cylindrical illuminance of the target in this way, it becomes possible to control - and vary - the modelling factor in a particularly straight-forward manner.

This in turn provides for a particularly simple lighting system with which the facial lighting effects in complex environments are improved considerably irrespective of the direction of view of a person looking at the target.

In an embodiment, the detection system comprises sensors and/or cameras.

Thereby the position of the target as well as other relevant data regarding the target may be detected in a particularly simple and efficient manner, even in real time.

In an embodiment, the data processing device is configured to perform the step of repeating steps a) to g) in real time or with predetermined time intervals.

Thereby the illuminance of the target is continuously updated. Thereby a lighting system is provided with which the facial lighting effects in complex environments are not only improved but kept improved. Real time updating of the illumination of the target optimizes the facial lighting effects.

In an embodiment, the one or more parameters related to a target comprises one or more of a position of the target, an orientation of the target, an orientation of a face of the target, and a height of the target.

These parameters all provides valuable data for use in optimizing the illuminance of the target. The position, orientation, and orientation of a face are especially important for updating and controlling the cylindrical illuminance of the target. The height of the target is also important for optimizing the horizontal illuminance of the target.

In an embodiment the control system is configured to transform the required change of light output of each light source of the plurality of light sources received from the data processing unit into a control signal for a specific one of the light sources of the plurality of light sources and transmit the control signal to the said specific one of the light sources of the plurality of light sources.

Thereby, particularly efficient control of the individual light sources is provided for.

In an embodiment the control system is configured to individually control each light source of the plurality of light sources based on the required change of light output of each light source of the plurality of light sources received from the data processing unit by tuning the ratio between the cylindrical illuminance and the horizontal illuminance at the position of the target.

Thereby a lighting system is provided with which the facial lighting effects in complex environments are improved in a particularly efficient and straight forward manner.

In an embodiment each light source of the plurality of light sources is adapted for automatically adjusting the ratio between the cylindrical illuminance and the horizontal illuminance at the position of the target in reaction to a signal received from the control system.

Thereby a lighting system is provided which is especially adaptive and straight forward to control.

In an embodiment the predetermined modelling factor value, Mp, is in the range of 0.3 to 0.6.

Such predetermined modelling factor values have been shown to provide especially good results for the facial lighting effects in complex environments to be improved.

In an embodiment the data processing unit is further configured to calculate the modelling factor, Mt, at the target taking into account a relative dimming level, P, ranging from 0 to 100 % based on the formula Mt = a*P + b, where a is a negative value and b is a positive value, and where the values a and b depend on the practical lighting configuration in the space.

The inventors have by experimenting found that a constant modelling factor is not ideal for people’s facial appearance and the appreciation level. Rather, the modelling factor should be varied linearly according to the dimming level.

Thus, by calculating the modelling factor as described above, a lighting system is provided which may take into account dimming of the light and the effects thereof on the illuminance, especially the cylindrical illuminance, of the target, and with which the facial lighting effects in complex environments are therefore improved even further. In an embodiment at least one light source of the plurality of light sources is a troffer-like light source and comprises an array of LEDs and an array of lenses.

Such light sources are advantageous in uses of a lighting system according to the invention where horizontal illuminance is of improtance since most light energy is confined within an angular range of +/- 60 degrees, and since it provides a major contribution to the horizontal illuminance and a minor contribution to the cylindrical illuminance. This leads to a smaller modelling factor.

In an embodiment at least one light source of the plurality of light sources comprises a light emitting surface and reflecting layer arranged on a surface opposite to the light emitting surface.

Such light sources are advantageous in uses of a lighting system according to the invention where cylindrical illuminance is of improtance since some of the light energy is emitted at an angular range of more than 70 degrees, and since it provides a minor contribution to the horizontal illuminance and a major contribution to the cylindrical illuminance. This leads to a larger modelling factor.

The invention further relates to a lighting arrangement comprising a lighting system according to the invention and a memory unit, the memory unit comprising a set of instructions, which when executed by the data processing device of the lighting system causes the data processing device to perform at least steps a) to d).

The invention further relates to an open plan office, a meeting room, a break out area, a video conference room, a class room, a restaurant or a retail store room comprising a lighting system according to the invention.

The invention further relates to an open plan office, a meeting room, a break out area, a video conference room, a class room, a restaurant or a retail store room comprising a lighting arrangement according to the invention.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

Figs. 1A-1C is a schematic illustration of horizontal illuminance, Eh (Fig. 1A), vertical illuminance, Ev (Fig. IB), and cylindrical luminance, Ecyl (Fig. 1C), respectively. Fig. 2 shows a schematic top view of a lighting system according to the invention.

Fig. 3 is a flow diagram illustrating an embodiment the steps performed by a data processing unit of a light system according to the invention.

Fig. 4 is a schematic top view of a space in the form of a meeting room with a lighting system according to the invention and with several persons present.

Figs. 5 and 6 show schematic top views of two different exemplary light sources of a lighting system according to the invention.

Fig. 7 shows a table illustrating light distributions of the light sources according to Figs. 5 and 6 as well as of other light sources being combinations of the light sources according to Figs. 5 and 6.

Fig. 8 shows a graph illustrating the required modelling factor as a function of horizontal illuminance in a scenario using a lighting system according to the invention.

Fig. 9 shows a graph illustrating the required modelling factor as a function of dimming level in a scenario using a lighting system according to the invention and taking dimming into account.

DETAILED DESCRIPTION

The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.

Fig. 2 shows a schematic top view of a space 1 in which a lighting system 2 according to the invention is arranged. The lighting system 2 generally and irrespective of the embodiment comprises a plurality of light sources 31-3n adapted for, in operation and in combination, providing an illumination of the space 1, a control system 4 adapted for individually controlling the plurality of light sources 31-3n, a detection system 5 and a data processing unit 6.

The plurality of light sources 31-3n comprises n light sources, where n is an integer larger than one. The plurality of light sources 31-3n emit light, such as typically white light. The plurality of light sources 31-3n are adapted for, in operation and in combination, providing an illumination of the space 1. Each light source of the plurality of light sources 31-3n are adapted for, in operation, providing two or more light distributions. Each of the two or more light distributions provide a different contribution to a horizontal illuminance, Eh, and a cylindrical illuminance, Ecyl, of the illumination of the space 1.

The control system 4 is adapted for controlling the plurality of light sources 31-3n by sending a control signal to one or more light sources of the plurality of light sources 31-3n. The control system 4 is further configured to individually control each light source of the plurality of light sources 31-3n based on a required change of light output of each light source of the plurality of light sources 31-3n received from the data processing unit as described further below.

The detection system 5 is configured to perform detection of one or more parameters related to a target 7 in the space 1 in real time. In the context of the present invention the target 7 is typically a person or a group of persons but is not necessarily limited thereto. The one or more parameters related to the target 7 may comprise any one or more of a position of the target 7 in the space 1, an orientation of the target 7 in the space 1, an orientation of a face of the target 7 in the space 1, and a height of the target 7. The detection system 5 is further configured to transfer information relating to the detected one or more parameters to the data processing device 6. The detection system 5 may comprise sensors and/or cameras. Suitable sensors include, but are not limited to, position sensors, proximity sensors, image sensors and heat sensors.

The data processing unit 6 is generally configured to perform a series of steps. The data processing unit 6 may be configured to execute an optimization algorithm with a compensation module such as to perform the steps according to any of the below described embodiments.

Generally, and irrespective of the embodiment, the data processing unit 6 is configured to perform the following steps.

In a first step (cf. step 101 of Fig. 3) the data processing unit 6 calculates a modelling factor, Mt, at the position of the target according to a current light distribution, the modelling factor being defined as Mt = Ecylt/Eht, where Ecylt is the cylindrical illuminance at the position of the target and Eht is the horizontal illuminance at the position of the target.

In a second step (cf. step 102 of Fig. 3) the data processing unit 6 compares the calculated modelling factor, Mt, with a predetermined modelling factor value, Mp.

If the calculated modelling factor, Mt, and the predetermined modelling factor, Mp, value are not equal, the data processing unit 6 in a third step (cf. step 103 of Fig. 3) calculates the difference between the calculated modelling factor and the predetermined modelling factor value.

Based on the calculated difference, the data processing unit 6 in a fourth step varies the modelling factor, Mt, at the position of the target by causing the control unit 4 to vary the contribution to either of the horizontal illuminance, Eht, and the cylindrical illuminance, Ecylt, at the position of the target of each light source of the plurality of light sources 31-3n in such a way that either of the the horizontal illuminance, Eht, and the cylindrical illuminance, Ecylt, at the position of the target is varied. The variation of the modeling factor, Mt, thus obtained is illustrated by the slanted line on Fig. 8.

The above steps 101-103 are illustrated in the flow diagram of Fig. 3 together with an embodiment of the steps included in the above-mentioned fourth step and will be described below.

In a first step 101 the data processing unit 6 calculates a modelling factor, Mt, at the position of the target according to a current light setting or light distribution. The modelling factor is defined as Mt = Ecylt/Eht, where Ecylt is the cylindrical illuminance at the position of the target and Eht is the horizontal illuminance at the position of the target.

The cylindrical illuminance, Ecylt, at the position of the target and the horizontal illuminance, Eht, at the position of the target are calculated as the sum of the contributions of each of the light sources of the plurality of light sources 31-3n. Thus, if the contribution of the ith light source to the cylindrical illuminance, Ecylt, at the position of the target and the horizontal illuminance, Eht, at the position of the target is Ecylt(i) and Eht(i), respectively, the cylindrical illuminance at the position of the target may be expressed as:

Ecylt = X"i(Ecylt(i)) and the horizontal illuminance at the position of the target may be expressed as:

Eht = åⁿi(Eht(i)), where n is the number of light sources in the plurality of light sources 31-3n.

In a second step 102 the data processing unit 6 compares the calculated modelling factor, Mt, with a predetermined value, Mp, of the modelling factor, also denoted a predetermined modelling factor value. Typically, the predetermined modelling factor value is in the range of 0.3 to 0.6. In a third step 103, if the calculated modelling factor, Mt, and the predetermined modelling factor value, Mp, are not equal, the data processing unit 6 calculates the difference, DM, between the calculated modelling factor and the predetermined modelling factor value. The difference between the calculated modelling factor and the predetermined modelling factor value may be expressed as DM = Mt - Mp.

If the calculated modelling factor and the predetermined modelling factor value are equal (Mt = Mp), the data processing unit 6 proceeds to keeping the current light setting.

If the calculated modelling factor and the predetermined modelling factor value are not equal (Mt ¹ Mp), the data processing unit 6 proceeds to perform the above- mentioned fourth step. This may be done in two different ways, which are described below.

In one embodiment, the said fourth step includes the data processing unit 6 performing the following steps.

Based on the difference calculated in step 103, the data processing unit 6 calculates a required change of horizontal illuminance, dEht, at the position of the target.

Based on the spatial layout of the space, the arrangement of the plurality of light sources and the position of the target, the data processing unit 6 calculates a weight of each light source of the plurality of light sources on the calculated required change of horizontal illuminance, dEht, at the position of the target.

Based on the calculated weight of each light source of the plurality of light sources on the calculated required change of horizontal illuminance, dEht, at the position of the target position, the data processing unit 6 calculates the required change of light output of each light source of the plurality of light sources for achieving the predetermined modelling value.

Finally, the data processing unit 6 transmits the calculated required change of light output of each light source of the plurality of light sources to the control system - cf. step 107 of Fig. 3.

The control system 4 then individually control each light source of the plurality of light sources 31-3n based on the required change of light output of each light source of the plurality of light sources received from the data processing unit 6 - cf. step 108 of Fig. 3.

In another embodiment, which is illustrated on Fig. 3, the said fourth step includes the data processing unit 6 performing the following steps. In a step 104 the data processing unit 6 calculates the required change of the cylindrical illuminance, dEcylt, at the position of the target 7 based on the calculated difference obtained in step 103 and the current horizontal illuminance, Eht, at the position of the target 7.

In a step 105 the data processing unit 6 calculates a weight of each light source of the plurality of light sources 31-3n on the calculated required change of cylindrical illuminance, dEcylt, and on the horizontal illuminance, Eht, at the position of the target 7 based on the spatial layout of the space 1, the arrangement of the plurality of light sources 31- 3n and the position of the target 7,

In a step 106 the data processing unit 6 calculates the required change of light output of each light source of the plurality of light sources 31-3n for achieving the target modelling value based on the calculated weight of each light source of the plurality of light sources 31-3n on the calculated required change of cylindrical illuminance, dEcylt, and on the horizontal illuminance, Eht, at the position of the target 7 as obtained in step 105.

Finally, in a step 107, the data processing device 6 transmits the calculated required change of light output of each light source of the plurality of light sources 31-3n to the control system 4.

The control system 4 then (step 108 in Fig. 3) individually controls each light source of the plurality of light sources 31-3n based on the required change of light output of each light source of the plurality of light sources 31-3n received from the data processing unit 6

Referring again to Fig. 2, the system may further comprise a memory unit 8 comprising a set of instructions, which when executed by the data processing device 6 causes the data processing device 6 to perform the above-mentioned steps, such as to, in consequence thereof, also causing the control system 4 to perform above-mentioned step 108.

The control system 4 may be configured to transform the required change of light output of each light source of the plurality of light sources 31-3n received from the data processing unit 6 into a control signal for a specific one of the light sources of the plurality of light sources 31-3n and transmit the control signal to the said specific one of the light sources of the plurality of light sources 31-3n. The control system may also be configured to individually control each light source of the plurality of light sources 31-3n based on the required change of light output of each light source of the plurality of light sources 31-3n received from the data processing unit 6 by tuning the ratio between the cylindrical illuminance, Ecylt, and the horizontal illuminance, Eht, at the position of the target 7. Each light source of the plurality of light sources 31-3n is therefore adapted for automatically adjusting the ratio between the cylindrical illuminance, Ecylt, and the horizontal illuminance, Eht, i.e. the modelling factor, Mt, at the position of the target 7.

The data processing unit 6 may further be configured to calculate the modelling factor, Mt, at the position of the target 7 taking into account a relative dimming level, P, ranging from 0 to 100 % based on the formula Mt = a*P + b, where a is a negative value and b is a positive value, and where the values a and b depend on the practical lighting configuration in the space. The resulting variation of the modelling factor, Mt, is shown in Fig. 9.

The lighting system 2 is thus an intelligent lighting system 2 that can automatically adjust the light distribution for improving the appearance of a target 7, for instance the facial appearance of one or more targets 7, in the form of one or more persons in the space 1 with appropriate light quality according to the position of the target 7, activity and current light settings. Such a lighting system 2 is applicable not only for offices, e.g. open-plan offices and meeting rooms, but also for restaurants, retail applications and theaters, etc.

In the following, application of a lighting system 2 according to the invention in a meeting room is used to illustrate the working principle of the lighting system 2. In a specific meeting room 10 as illustrated schematically on Fig. 4, the room layout and light source arrangement in the room 10 are known. Information of the position of targets, here persons 71-75, in the room 10 is obtained by means of the detection system 5, e.g. using position sensors or cameras, and is transmitted to the control system 4 installed in the room 10. The detected data may also be used to analyze the potential activity of the person 71-75 and the light distribution adjustment may be varying according to the activity. The required light intensity and distribution varies from person to person. The ultimate goal is to optimize the facial illumination and provide a pleasant facial appearance for visual communication.

For example, and as illustrated on Fig. 4, when more than one person 71-75 is present in the meeting room 10, the distance between the persons 71-75 present could be analyzed on basis of the position of the individual persons.

If the distance between two or more given persons, such as the four persons 72-75 in Fig. 4, is less than a predetermined threshold value, illustrated as d2 on Fig. 4, these persons may be seen as one group 9. The modelling factor, Mt, of such a group 9 is the average of the modelling factor of each of the persons 72, 73, 74 and 75 belonging to the group 9. If the distance between two or more given persons, such as the person 71 and the persons 72-75 forming the group 9 in Fig. 4, is equal to or more than a predetermined threshold value, illustrated as dl on Fig. 4, they are seen as individual persons. The modelling factor, Mt, is then calculated for each person based on the position information of the person.

In the situation illustrated in Fig. 4, the person 71 may for instance be a speaker, while the group 9, consisting of several persons 72-75, may be the audience.

As is also mentioned above, the light sources 31-3n according to the invention may be any type of light source capable of providing at least two different light distributions. Two non-limiting examples are shown in Figs. 5 and 6.

Fig. 5 shows a troffer-like light source 300 comprisning an LED array and a lens array denoted 301 with a light guide 302, 303 arranged on each mutually opposite side of the arrays. This light source provides illumination in a directly downward direction. Most energy is confined within the angular range of +/- 60 degress. The light distribution of this type of light source is shown in the first row of the table in Fig. 7. This type of light source provides a major contribution to the horizontal illuminance, E_h, and a minor contribution to the cylindrical illuminance, E_cyi. This leads to a smaller modelling factor, M, of 0.45 as noted in the table in Fig. 7.

Fig. 6 shows a side-lit light guide 304 comprising an LED array and a lens array denoted 305 with a light guide 306, 307 arranged on each mutually opposite side of the arrays and a reflecting film (not visible) on the rear side, that is on the side opposite to a light emitting surface of the light source 304. With such a light source, some energy is radiating in an angular range above 70 degrees. The light distribution of this type of light source is shown in the last row of the table in Fig. 7. This type of light source provides a minor contribution to the horizontal illuminance, Eh, and a major contribution to the cylindrical illuminance, E_cyi. This leads to a larger modelling factor, M, of 0.59 as noted in the table in Fig. 7.

The remaining rows of the table in Fig. 7 shows light distributions and modelling factors of other feasible types of light sources. These are combinations of the two above-mentioned types of light sources also shown in Figs. 5 and 6. These have different modelling factors (cf. the second column of the table in Fig. 7), and they are obtained by changing the ratio of the abovementioned two light distributions (cf. the first column of the table in Fig. 7).

In the following examples illustrating the present invention and how it works will be described. Examnle 1

For a normal indoor luminaire for office use, no matter how you dim the light, its brightness changes, but its relative light distribution remains unchanged. This means that for a designated point in space the horizontal illuminance is changing as the light is dimmed, while the cylindrical illuminance is also changing, accordingly. The modelling factor is kept constant.

However, a constant modelling factor is not always preferred. It may in some practical applications be more preferred if the modelling factor varies when the horizontal illuminance changes. With a series of perception experiments, the inventors have identified that the required varying modelling factor is decreasing when the horizontal illuminance increases.

The results are shown in the graph in Fig. 8 illustrating the modelling factor, M, as a function of horizontal illuminance, Eh. As may be seen, when Eh = 300 lx, the preferred modelling factor is 0.60, meaning that the cylindrical illuminance E_cyi = 300 * 0.60 = 180 lx. When E_h = 1000 lx, the preferred modelling factor drops to 0.30, meaning that the cylindrical illuminance E_cyi = 1000 * 0.30 = 300 lx. When the horizontal illuminance, E_h, is between 300 and 1000 lx, the preferred modelling factor is decreasing following a linear manner, as:

E_h (0)

M « 0.73 — 0.30 —E- ’

700

According to the findings from the experiments, it has been shown that such a changing modelling factor is particularly good for optimizing people’s facial appearance and the appreciation level.

In comparison, for a normal luminaire, the actual modelling factor is a fixed value, as is illustrated by the horizontal line in Fig. 8.

Example 2 - varying modelling factor according to dimming level

In this example, the modelling factor, M, is varied according to the dimming level P such that the relationship between the modelling factor, M, and the dimming level, P, satisfies the following relation:

M = a P + b (1)

P is the relative dimming level, ranging from 0 to 100 %, corresponding to certain horizontal illuminance levels. Parameter a is a negative value and parameter b is a positive value. The specific values of a and b depend on the practical lighting configuration in an indoor space. The resulting modelling factor, M, as a function of dimming level, P, is illustrated in Fig. 9. It may be seen that when the illuminance level increases, the required modelling factor decreases.

It follows from equation (1), that when lights dim up, the modelling factor decreases and when lights dim down the modelling factor increases. It has been shown that in this way the facial appearance of people is constantly maintained at a high-level no matter how the total light level is changed.

The preferred modelling factor should thus change as the horizontal illuminance dims up or down. However, for a normal prior art luminaire, the actual modelling factor is a fixed value no matter how the light is dimmed, as is illustrated by the horizontal line in Fig. 8.

In practice, however, lighting design can never be 100 % accurate compared to theoretical numbers. Therefore, to achieve the preferred modelling factor shown as the slanted line in Fig. 8, an incremental change of the modeling factor is chosen.

For instance, when the light is dimmed up, every time the horizontal illuminance, Eh, increases by 100 lx, the preferred modelling factor, M, should decrease by between 0.04 and 0.045. Thereby, the preferred average cylindrical illuminance range may be found by reverse calculation.

Similarly, when light is dimmed down, every time the horizontal illuminance, Eh, decreases by 100 lx, the preferred modelling factor, M should increase by between 0.04 and 0.045. Thereby, the preferred average cylindrical illuminance range may be found by reverse calculation.

The result is summarized in table 1 for a horizontal illuminance range of 300 -

1000 lx.

Table 1

Every light source of a system according to the invention may be configured such that its multi-channel (at least two channels) dimming levels are defined in order to achieve the preferred modelling factor, M, as showed in Figure 9.

Example 3 - Detailed Calculations

In this example the calculations and considerations behind Example 1 above are described in more detail. Each light source of the plurality of light sources of a system according to the invention comprises N types of light distributions, where N is an integer being larger than 1. Each type of light distribution will provide different contributions to the horizontal illuminance, Eh, and to the cylindrical illuminance, Ecyl.

Let us take N = 2 as an example. The first light distribution of a given light source will then contribute (E_hi, Mi) to the overall illumination, and the second light distribution of the light source will contribute (E_h2, M2), where Mi is not equal to M2. Then, by tuning the ratio between the two light distributions, the overall modelling factor is changeable in the range between Mi and M2.

In more detail, suppose there are N types of light distributions for a given space dimension and a fixed lighting installation layout. When fully powered, the i^th light distribution will contribute a horizontal illuminance of E_h,i, and a cylindrical illuminance of E_cyi. . Thus the i^th modeling factor is: M,- = Ecyl, i

(2) Eh, I

The total horizontal illuminance and the total cylidrical illuminance both reach their maximum values:

N

E h,max =y (3) i= l¾ and

When partially powered by a coefficient of Xi e [0,1], its contributions to the horizontal and cylindrical illuminance become xiEh_,i and xiE_cyy, respectively, while its modeling factor remain unchanged, it is still Mi.

The total horizontal illuminance and the total cylidrical illuminance are changed to

and

Thus, the resultant modeling factor is

Now, let P denote the total dimming level. By taking equations (3) and (5), we can represent P in the following formula h,max (8)

Taking equations get E h, ,max (9)

The contribution of the i^th light distribution for the total horizontal illuminance can now be rewritten as

Taking equations (2) and (10), we can reduce equations (8) and (9) to the following equations ⁽n⁾ (12)

Finally, with equations r any total dimming level P, one may find the dimming values [xi ... XN] for all the concerned light distributions, so that the total modelling factor achieves the required value of M as showed in Fig. 8. In this way an optimal representation of people’s facial appearance may be obtained. Each light source of the plurality of light sources of a system according to the invention comprises N types of light distributions, where N is an integer being larger than 1. Each type of light distribution will provide different contributions to the horizontal illuminance, Eh, and to the cylindrical illuminance, Ecyl.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

CLAIMS:

1. A lighting system (2) comprising: a plurality of light sources (31-3n) adapted for, in operation and in combination, providing an illumination of a space (1), each light source of the plurality of light sources being adapted for, in operation, providing two or more light distributions, each of the two or more light distributions being configured to provide a different contribution to a horizontal illuminance, Eh, and a cylindrical illuminance, Ecyl, of the illumination of the space and a modelling factor of the illumination of the space, the modelling factor being defined as M = Ecyl/Eh, a control system (4) configured to individually control each light source of the plurality of light sources (31-3n) by sending a control signal to one or more light sources of the plurality of light sources, a detection system (5) configured to perform detection of one or more parameters related to a target (7) in the space (1) in real time, the one or more parameters including a position of the target in the space, and a data processing unit (6) configured to: a) calculate a modelling factor, Mt, at the position of the target according to a current light distribution, the modelling factor being defined as Mt =

Ecylt/Eht, where Ecylt is the cylindrical illuminance at the position of the target and Eht is the horizontal illuminance at the position of the target, b) compare the calculated modelling factor, Mt, with a predetermined modelling factor value, Mp, c) if the calculated modelling factor, Mt, and the predetermined modelling factor, Mp, value are not equal, calculate the difference between the calculated modelling factor and the predetermined modelling factor value, d) based on the calculated difference, varying the modelling factor, Mt, at the position of the target by causing the control unit (4) to vary the contribution to either of the horizontal illuminance, Eht, and the cylindrical illuminance, Ecylt, at the position of the target of each light source of the plurality of light sources (31-3n) in such a way that either of the horizontal illuminance, Eht, and the cylindrical illuminance, Ecylt, at the position of the target is varied, wherein step d) comprises the steps of: based on the calculated difference, calculating a required change of horizontal illuminance, dEht, at the position of the target or a required change of the cylindrical illuminance, Ecylt, at the position of the target, based on the spatial layout of the space, the arrangement of the plurality of light sources and the position of the target, calculating a weight of each light source of the plurality of light sources on the calculated required change of horizontal illuminance, dEht, at the position of the target or required change of cylindrical illuminance, Ecylt, at the position of the target, based on the calculated weight of each light source of the plurality of light sources on the calculated required change of horizontal illuminance, dEht, at the position of the target position or required change of cylindrical illuminance, Ecylt, at the position of the target, calculate the required change of light output of each light source of the plurality of light sources for achieving the predetermined modelling value, and transmit the calculated required change of light output of each light source of the plurality of light sources to the control system, the control system (4) further being configured to individually control each light source of the plurality of light sources (31-3n) based on the required change of light output of each light source of the plurality of light sources received from the data processing unit (6).

2. A lighting system according to any one of the preceding claims, wherein the control unit (4) in step d) is caused to vary the contribution to the horizontal illuminance, Eht, at the position of the target (7) of each light source of the plurality of light sources (31-3n) in such a way that the modelling factor, Mt, at the position of the target is varying according to the relation Mt = 0.73 - 0.30 * (Eht/700).

3. A lighting system according to claim 1, wherein step d) comprises the steps of: based on the calculated difference and the horizontal illuminance,

Eht, at the position of the target, calculate a required change of cylindrical illuminance, dEcylt, at the position of the target, based on the spatial layout of the space, the arrangement of the plurality of light sources and the position of the target, calculate a weight of each light source of the plurality of light sources on the calculated required change of cylindrical illuminance, dEcylt, and on the horizontal illuminance, Eht, at the position of the target, based on the calculated weight of each light source of the plurality of light sources on the calculated required change of cylindrical illuminance, dEcylt, and on the horizontal illuminance, Eht, at the position of the target position, calculate the required change of light output of each light source of the plurality of light sources for achieving the predetermined modelling value, and transmit the calculated required change of light output of each light source of the plurality of light sources to the control system, the control system (4) further being configured to individually control each light source of the plurality of light sources (31-3n) based on the required change of light output of each light source of the plurality of light sources received from the data processing unit (6).

4. A lighting system according to any one of the preceding claims, wherein the detection system (5) comprises sensors and/or cameras.

5. A lighting system according to any one of the preceding claims, wherein the data processing device (6) is configured to perform the step of repeating steps a) to h) in real time or with predetermined time intervals.

6. A lighting system according to any one of the preceding claims, wherein the one or more parameters related to a target (7) comprises one or more of a position, an orientation, an orientation of a face, and a height of the target.

7. A lighting system according to any one of the preceding claims, wherein the control system (4) is configured to transform the required change of light output of each light source of the plurality of light sources (31-3n) received from the data processing unit (6) into a control signal for a specific one of the light sources of the plurality of light sources and transmit the control signal to the said specific one of the light sources of the plurality of light sources (31-3n).

8. A lighting system according to any one of the preceding claims, wherein the control system (4) is configured to individually control each light source of the plurality of light sources (31-3n) based on the required change of light output of each light source of the plurality of light sources received from the data processing unit (6) by tuning the ratio between the cylindrical illuminance and the horizontal illuminance at the position of the target (7).

9. A lighting system according to any one of the preceding claims, wherein each light source of the plurality of light sources (31-3n) is adapted for automatically adjusting the ratio between the cylindrical illuminance and the horizontal illuminance at the position of the target (7) in reaction to a signal received from the control system (4).

10. A lighting system according to any one of the preceding claims, wherein the predetermined modelling factor value, Mp, is in the range of 0.3 to 0.6.

11. A lighting system according to any one of the preceding claims, wherein the data processing unit (6) is further configured to calculate the modelling factor, Mt, at the target taking into account a relative dimming level, P, ranging from 0 to 100 % based on the formula Mt = a*P + b, where a is a negative value and b is a positive value, and where the values a and b depend on the practical lighting configuration in the space (1).

12. A lighting system according to any one of the preceding claims, wherein the light sources of the plurality of light sources (31-3n) comprises any one or more of: a light source comprising an array of LEDs and an array of lenses, and a light source comprising a light emitting surface and reflecting layer arranged on a surface opposite to the light emitting surface.

13. A lighting arrangement comprising a lighting system (2) according to any one of the above claims and a memory unit (8), the memory unit comprising a set of instructions, which when executed by the data processing device (6) of the lighting system causes the data processing device to perform at least steps a) to d).

14. An open plan office, a meeting room, a break-out area, a video conference room, a class room, a restaurant or a retail store room comprising a lighting system (2) according to any one of claims 1-12 or a lighting arrangement according to claim 13.