WO2017063845A1

WO2017063845A1 - A lighting system and lighting control method

Info

Publication number: WO2017063845A1
Application number: PCT/EP2016/072637
Authority: WO
Inventors: Ruslan Akhmedovich Sepkhanov
Original assignee: Philips Lighting Holding B.V.
Priority date: 2015-10-12
Filing date: 2016-09-23
Publication date: 2017-04-20

Abstract

A lighting system comprises a lighting arrangement and a controller for controlling the lighting arrangement. The controller is adapted to adjust dynamically and automatically the polarization direction of the light output from the lighting arrangement, thereby to implement a sparkle effect when the light output illuminates an object. This system makes use of a dynamically varying polarization direction in order to create a dynamic sparkle effect on an object or scene to be illuminated. This is of interest for example for retail lighting applications, for example for illumination or fashion products such as jewelry or watches.

Description

A lighting system and lighting control method

FIELD OF THE INVENTION

The invention relates to a lighting system and lighting control method, in particular for creating a dynamic lighting effect on an object or scene illuminated by the lighting system.

BACKGROUND OF THE INVENTION

There have been significant improvements in the performance of LEDs in recent years, in particular the achievable light output, the available heat dissipation solutions, and the cost per unit.

There is now an increasing interest in new functionality within lighting devices and systems. The functions for example improve the quality of the light output, provide static or dynamic lighting effects, or provide lighting specific conditions which are better tailored to the functional needs of the user.

One lighting effect which is of interest is a so called sparkle effect. A sparkle is a glare effect, which is seen as aesthetically pleasing. An observed object is seen as sparkly when it has small areas of higher luminance than the surrounding area. The sparkle effect may be static or dynamic. If the areas change over time, a dynamic effect is produced. This may be more aesthetically pleasing.

A sparkle effect may relate to the appearance of an object when illuminated by a luminaire, or it may relate to the appearance of the luminaire itself. This invention relates in particular to lighting systems for producing a sparkle effect in the appearance of an illuminated object.

The dynamic aspect is a very important feature of a sparkly appearance. A dynamic effect may be produced by having areas of higher luminance which spatially move, or by controlling the luminance at a particular area so that it does not stay constant over time. This dynamic sparkle effect can often be observed in nature, for example when sunlight is reflected from moving objects, such as a water surface.

Creating a dynamic sparkle effect using a luminaire has two advantages. First, an object is perceived as being brought to life, because its sparkle changes over time. Second, the total illuminance of the object may be controlled to stay the same, while only the reflection from specular reflecting surfaces changes, providing the dynamics.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a lighting system comprising:

a lighting arrangement; and

a controller for controlling the lighting arrangement,

wherein the controller is configured to autonomously vary over time the polarization of the light output from the lighting arrangement via at least one of:

independent control of a first and second light unit configured to issue light of mutually different polarization,

control of an orientation or electric state of a polarizer,

thereby to implement a sparkle effect when the light output illuminates an object.

This system makes use of a dynamically varying polarization in order to create a sparkle effect on an object or scene to be illuminated. Varying polarization may mean a varying direction of the linear polarization or a change from un-polarized light to linear polarized light or a combination of varying polarization direction and un-polarized light. This is of interest for example for retail lighting applications, for example for illumination of sparking objects such as glass vessels, or fashion products such as jewelry or watches. More generally, the invention relates to a system for creating a dynamic effect to enhance the aesthetic appearance of a lighting space or illuminated object or objects within a lighting space. A polarizer in this respect can be, for example, an electrically controlled liquid crystal cell, a light source issuing light of a specific polarization, a polarizing filter or polarizing reflector. With respect to independent control of a first and second light unit configured to issue light of mutually different polarization, the controller is adapted to control, for example, the respective light output intensity, color, direction and/or top beam angle, of the first and second lighting unit. Said independent control equally applies to different lighting

arrangements.

To enable the controller to vary autonomously over time, i.e. as time proceeds, said polarization direction, the controller is configured or pre-programmed to execute a predetermined sequence in said polarization direction, or is configured or pre-programmed to generate in real time a random or pseudo-random sequence in said polarization direction of the light outputted from the lighting arrangement. Hence, the polarization direction may vary following a predetermined sequence which has previously been randomly or pseudo randomly generated, or else a random or pseudo random sequence may be generated in real time. Preferably, the controller is, for example, adapted to autonomously vary over time the polarization direction of light outputted from the lighting arrangement in a random or pseudo random way. The aim is to create a natural sparkle effect, for example without any perceivable repetition. Thus, a repetitive sequence may be used provided the period of repetition of the sequence is long enough not to be noticed by a user, for example more than 10 seconds, or more than 30 seconds, or even more preferred more than 10 minutes.

In a first set of examples, the lighting arrangement may comprise at least a first light unit with a linearly polarized output with a first polarization direction and a second light unit with a linearly polarized output with a second polarization direction different to the first polarization direction, wherein the controller is adapted to control independently the light output from the first and second light units.

This provides a simple way to adjust the effective polarization of the lighting arrangement output, based on the combination of different polarization components, wherein the combination varies over time. The polarization can be changed to un-polarized light, linearly polarized light with the polarizations direction identical to one of the light units or to partially polarized light. The un-polarized light is produced when the light outputs of the two lighting units are equal if the units have orthogonal polarization directions. There may be a single pair of light units, or else the lighting arrangement may comprise an array of pairs of light units.

The controller is for example adapted to control the light output from the first and second light units (or each pair if there are multiple pairs) such that the combined light output is constant. In this way, the luminance of a diffuse reflecting object (which will not sparkle) remains constant. An object will sparkle if it has specular reflecting facets, and ideally multiple facets which are oriented in different directions (by "orientation" is meant the direction of the vector normal to the plane of such a facet). Thus, illuminated objects can be made to sparkle while maintaining uniform illumination of non-sparkling objects, such as a fabric base on which an item of jewelry is seated for display purposes.

The first and second polarization directions may be orthogonal. In this way, the units may be controlled to implement various polarizations ranging from un-polarized light (when the light outputs of the units are equal) through partially polarized light to linearly polarized light with the polarization direction coinciding with the polarization direction of one of the units.

There may be more than two different light units in each arrangement each with a different output polarization direction.

In a second set of examples, the lighting arrangement comprises at least a first light unit and a linear polarizer at a light output of the first light unit, wherein the controller is adapted to control the polarization orientation of said linear polarizer. In this way, a single light unit is controlled to have a time- varying output polarization direction. In this case, the desired light output polarization is not fixed to the polarization directions of the light units as in the previous example (from slightly different locations) but is achieved from a single light unit, that may implement any polarization direction.

There may be a single light unit with the controlled output polarization direction, but equally there may be an array of such light units.

The linear polarizer may comprise a mechanical drive mechanism such as a motor or it may comprise an electrically controlled linear polarizer, i.e. with a direction of linear polarization which is controlled by an electrical input signal, with no physical mechanical rotation of components. Electrically controlled linear polarization may for example be implemented using a twisted nematic liquid crystal cell.

An array of lighting arrangements may be provided, wherein the linear polarization direction and light output for each lighting arrangement in the array is synchronized. The array is synchronized in a way that identical units emit identically polarized light. An array may be formed using any of the different examples of individual lighting arrangement.

The lighting system may further comprise a second lighting arrangement (in addition to a controlled first lighting arrangement or a set of controlled lighting arrangements in an array), wherein the second lighting arrangement has an un-polarized light output, and wherein the controller is adapted to control the light output intensity of the lighting arrangement and the second lighting arrangement to maintain a constant cumulative light output. In this way, some of the light output intensity is generated in a more efficient manner by being un-polarized.

Examples in accordance with another aspect of the invention provide a method of controlling a lighting arrangement, comprising: varying autonomously over time the polarization direction of the light output from the lighting arrangement, thereby to implement a sparkle effect when the light output illuminates an object.

The method may comprise adjusting the polarization direction of linear polarization and/or varying a ratio of un-polarized light and linear polarized light.

The polarization direction and/or ratio may be adjusted in a random or pseudo random way. The polarization direction and/or ratio may for example be adjusted to a value set in real time using a random or pseudo random process or it may be adjusted to follow a predetermined sequence, which has the characteristics of a pseudo random sequence but is previously fixed.

The light output may be controlled from at least a first light unit with a linearly polarized output with a first polarization direction and a second light unit with a linearly polarized output with a second polarization direction different to the first polarization direction. The light output from the first and second light units may then be controlled such that the combined light output is constant. The first and second polarization directions may for example be orthogonal.

The method may instead comprise controlling the orientation of a linear polarizer at the light output of at least the first light unit. This may be a mechanical control or an electrical control.

BRIEF DESCRIPTION OF THE DRAWINGS

Examples of the invention will now be described in detail with reference to the accompanying drawings, in which:

Figs. 1 A-C show a first set of examples of a lighting system;

Figs. 2A-B show a second set of examples of a lighting system;

Fig. 3 shows a third example of a lighting system also showing a controller; Fig. 4 shows a fourth example of a lighting system also showing a controller; Fig. 5 shows a fifth example of a lighting system also showing a controller; Fig. 6 shows a sixth example of a lighting system also showing a controller; Fig. 7 shows an example of an application for the lighting system; and

Fig. 8 shows in generic form a computer which may be used to implement the controller used in the lighting system. DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention provides a lighting system comprising a lighting arrangement and a controller for controlling the lighting arrangement. The controller is adapted to adjust dynamically and automatically the polarization direction of the light output from the lighting arrangement, thereby to implement a sparkle effect when the light output illuminates an object. This system makes use of a dynamically varying polarization direction in order to create a sparkle effect of an object or scene to be illuminated. This is of interest for example for retail lighting applications, for example for illumination or fashion products such as jewelry or watches.

A sparkle effect can arise in nature when light encounters a boundary between two media with different refractive indices. At such a boundary, some of the light is reflected. The fraction that is reflected is described by the Fresnel equations, and is dependent upon the polarization of the incoming light and the angle between the surface normal and the light propagation direction (i.e. the angle of incidence). For a moving surface (like a wave in the sea) a sparkle effect can be seen because the angle of incidence is dynamically changing, giving rise to changes in the fraction of light that is reflected and therefore a dynamic change in perceived brightness.

The Fresnel equations predict that light with a polarization in the same plane as the incident ray and the surface normal will not be reflected if the angle of incidence is:

where nl is the refractive index of the initial medium through which the light propagates and n2 is the index of the other medium. This is Brewster's law, and the angle defined is Brewster's angle. At this angle, if the incident light is un-polarized, the reflected light will be polarized.

The reflected light intensity from a surface thus depends on the relative orientation of the polarization direction and the reflective surface (wherein the orientation of a reflective surface is defined by its normal direction). The reflectivity reaches zero for Brewster's angle.

The invention is based on providing a dynamically changing polarization direction, which results in facets of an object dynamically lighting up and darkening. While some facets are becoming dark, others light up. A random or pseudo random character of the polarization change may be employed to correspond to a random or pseudo random temporal pattern from bright and dark facets.

The appearance of diffusely reflecting objects is unchanged, because the reflectivity is polarization independent.

A first set of examples of a system is shown in Figure 1.

Figure 1A shows two light units 10, 12 with orthogonal linear polarization directions 14, 16. This may be achieved by placing a linear polarizer at the exit window of the light unit, with a particular orientation. The light source of each light unit may thus initially generate a non-polarized light output. The light units are controlled so that their combined light output is constant, while the relative luminous power varies over time. This time variation may be random or pseudo random, or it may change following a

predetermined pattern which appears to be random to the user. The right part of Figure 1A shows the different polarizations at the outputs of the light units 10,12. The polarization is in the plane perpendicular to the direction of light propagation, with one polarization direction shown into and out of the page, and the other shown within the plane of the page.

Figure IB shows one light unit 10 with a linearly polarized output in combination with a second light unit 11 which has an un-polarized output.

Figure 1C shows a single light unit 10 with a first output portion 10a with a linearly polarized output (in direction 14) and a second output portion 10b with an un- polarized output.

Each light unit (or the different parts of the single light unit in Figure 1C) has an associated driver, and the drivers are independently controllable. The light source of each light unit may comprise an LED or an array of LEDs, and the driver then comprises a regulated current driver. It may operate based on an AC mains signal, in which case the driver comprises a rectifier and regulated current source, or it may operate based on a DC input voltage, such as a low voltage (12V or 20V for example) DC bus. Other types of light source may be used, and the invention does not require any particular characteristics of the initial light. It may be un-polarized or it may already be polarized.

By having the light units in close proximity, they approximate a single light source, with a polarization at their output which is derived from the combination of their individual outputs. The polarization may be changed between un-polarized light, partially polarized light and linearly polarized light with the polarization orientation equal to the orientation of one of the units. When this light is incident on an object, specular reflection on facets of the object create a sparkle effect in the manner as explained above.

By maintaining the total luminous power of the lighting device constant, a constant illumination intensity is provided. This means that the illuminated objects, which do not have a specular reflecting surface or surfaces, will be perceived to have a constant luminance.

In the example of Figure 1A, there are two light units with orthogonal polarization directions. It is equally possible to include more than two light units each with their own polarization direction.

For example, there may be four units, with 45 degrees between the different orientations. When there are two units with orthogonal polarization emitting incoherent light. When they are both turned on, the resulting light will be un-polarized. Adding additional orientations gives extra freedom in highlighting possible facets of objects that otherwise would have stayed un-highlighted when using only two specific orientations.

As mentioned above, in the example of Figure IB, one light unit has an un- polarized light output and the other has the controlled polarized light output or linearly polarized light output with fixed polarization direction. The light output of the two light units may then be changed keeping the cumulative value constant. In the case of the linearly polarized first light unit 10 with fixed polarization direction, there is less chance of activating many facets of the object, than in the case of two polarized units. However, the efficiency is expected to be higher, because one of the two lighting units has no polarizer.

The units can then be placed next to each other as shown in Figure 1 or they can be placed one inside the other as in the example of Figure 1C, with inner part being polarized or vice versa. An un-polarized light unit (or set of un-polarized light units) may be added to any number of the polarization-controlled light units.

Figure 2 shows a second set of examples. Figure 2A shows single light unit 20. At the output of the light unit there is a linear polarizer 22. The linear polarizer 22 is mechanically rotatable as shown by arrow 24. As in the example of Figure 1, this rotation may be random or pseudo random, or it may follow a fixed sequence.

The rotation may be controlled by a motor that mechanically rotates the polarizer. It is also possible to rotate only in one direction with randomly varied speed. The light unit may remain on during the rotation.

Instead of a mechanically varying linear polarizer, the orientation adjustment may be by electronic means. A liquid crystal arrangement may for example be used as a polarization switch. The polarization switch then comprises a twisted nematic liquid crystal cell in combination with a polarizer (if the initial light of the source output is un-polarized). The liquid crystal cell provides a switch between two linear polarizations so that the output polarization direction may be controlled.

Figure 2B shows an example in which the light unit 20 of Figure 2A is combined with light unit 11 with un-polarized output.

A lighting system may be implemented with one of the lighting unit arrangements as shown in Figures 1A to 1C or with one of the lighting unit arrangements as shown in Figures 2 A and 2B.. However, a lighting system may instead be formed as an array of such arrangements. In both cases, the array is for example synchronized so that all light units of the array with identical initial polarization change their polarization direction and intensity in the same way, so that their polarization direction and intensity stay identical.

A controller is used to control the lighting arrangement.

Figure 3 shows a controller 30 which electrically controls a polarization switch 32 which optically processes the output of a single light unit 34. This for example comprises a liquid crystal cell arrangement as discussed briefly above, and the example of Figure 3 is thus an implementation of the liquid crystal cell example.

Figure 4 shows a controller 40 which electrically controls the light output for two light units 42, 44 of the lighting arrangement 46. As explained above, the overall light output may be kept constant.

Figure 5 shows a controller 50 which electrically controls a motor 52 which mechanically rotates a polarizer 54 mounted over a light output face of a light unit 56.

Figure 6 shows that the controller 60 may control an array 62 of light units using any of the approaches explained above.

In all cases above, the controller implements a varying output polarization. The light output is either linearly polarized, with a time varying direction of polarization or is partly polarized with a time varying polarization direction and degree of polarization. The polarization direction is in the plane perpendicular to the propagation direction of the light output. This is shown in Figure 1.

The time variation is intended to generate a dynamic sparkle effect. The time variation may be discrete or continuous. The desired rate of change of polarization angle will depend on the application.

For example, for a very subtle effect a cumulative change of 10 degrees per minute may suffice. For a more dramatic effect, a cumulative change of 10 degrees per 1/24 of a second may for example be appropriate. Thus, the angle may change at a rate of between 10 degrees per minute and 15000 degrees per minute.

The polarization effect is preferably perceived as random. If users start noticing a fixed pattern, the effect may be perceived as boring. Any random sequence or sequence that is perceived as random may be used. This may for example be generated by a Markov chain process.

The sequence is preferably pseudo random, so that a user perceives the effect as random in the short term and also does not perceive a repetition over a longer time. For example the pattern may repeat (to make the generation or storage of the pseudo random sequence easier) as long as the repetition period is more than 10 seconds, more preferably more than 30 seconds, or more preferably more than 1 minute, or even more preferably more than 10 minutes. For all implementations of the controller, there may be a memory for storing a sequence of polarization directions or a sequence of lighting control signals which will generate such a sequence of polarization directions. Alternatively, a pseudo random sequence generator may be incorporated into the controller for generating in real time the next control signal to be applied to the lighting arrangement.

The light output from individual light units may be mixed by an output diffuser which preserves the incident polarization. For example, surface diffusers partly preserve linear polarization. An array of synchronized spatially mixed small light units may for example all be provided behind a diffuser.

As explained above, the system may adjust the polarization to a random or pseudo random value. A pseudo random sequence is to be understood as a sequence that appears to be random but is not. Pseudo random sequences typically exhibit statistical randomness while being generated by an entirely deterministic causal process.

The sequence may start from the same initial seed value each time the system is turned on. Alternatively, it may continue from where it left off last time the system was used, by generating the next values in a deterministic way from the historical values. In either case, the process is easier to produce than a genuinely random one.

It is also possible to generate truly random numbers, but this requires precise, accurate, and repeatable system measurements of a non-deterministic process.

The system of this invention requires only a level of randomness which appears random to the user in the sense that no cyclic repetition or ordered progression of the lighting effect is perceived. A pseudo random sequence is adequate for this purpose, and the same sequence may be used each time the lighting system is turned on. The sequence may repeat after a period of time likely to be longer than a user will be admiring the sparkle effect or longer than a person can recall the pattern, for example more than 10 minutes.

The invention is of interest for any lighting application wherein a sparkle effect is of interest, for example retail lighting, such as for fashion items, jewels, watches etc.

Figure 7 shows an example. The lighting arrangement is provided in a cabinet

72 for displaying jewelry, such as a diamond 74. The diamond is placed on a diffusely reflecting or absorbing material such as a cushion 76 to provide a contrast between the sparkle effect of the diamond and the background lighting. However, the lighting of the cushion is perceived by the customer as static as it essentially reflects diffuse light and therefore has constant luminance.

The light units may all be of the same color, for example white. However, color lighting effects may also be incorporated into the system. If desired, dynamic light effects may also be produced even for the objects which do not sparkle.

The invention is not limited to the display of fashion items, but may be used to illuminate any object where a dynamic lighting effect is desired, for aesthetic reasons.

As described above, the system makes use of a controller for controlling the light units or else controlling a linear polarizer. Figure 8 illustrates an example of a computer 80 which may be used to implement the controller in the examples above. Various operations discussed above may utilize the capabilities of the computer 80.

The computer 80 includes, but is not limited to, PCs, workstations, laptops,

PDAs, palm devices, servers, storages, and the like. Generally, in terms of hardware architecture, the computer 80 may include one or more processors 81, memory 82, and one or more I/O devices 87 that are communicatively coupled via a local interface (not shown). The local interface can be, for example but not limited to, one or more buses or other wired or wireless connections, as is known in the art. The local interface may have additional elements, such as controllers, buffers (caches), drivers, repeaters, and receivers, to enable communications. Further, the local interface may include address, control, and/or data connections to enable appropriate communications among the aforementioned components.

The processor 81 is a hardware device for executing software that can be stored in the memory 82. The processor 81 can be virtually any custom made or

commercially available processor, a central processing unit (CPU), a digital signal processor (DSP), or an auxiliary processor among several processors associated with the computer 80, and the processor 81 may be a semiconductor based microprocessor (in the form of a microchip) or a microprocessor. The memory 82 can include any one or combination of volatile memory elements (e.g., random access memory (RAM), such as dynamic random access memory (DRAM), static random access memory (SRAM), etc.) and non-volatile memory elements (e.g., ROM, erasable programmable read only memory (EPROM), electronically erasable programmable read only memory (EEPROM), programmable read only memory (PROM), tape, compact disc read only memory (CD-ROM), disk, diskette, cartridge, cassette or the like, etc.). Moreover, the memory 82 may incorporate electronic, magnetic, optical, and/or other types of storage media. Note that the memory 82 can have a distributed architecture, where various components are situated remote from one another, but can be accessed by the processor 81.

The software in the memory 82 may include one or more separate programs, each of which comprises an ordered listing of executable instructions for implementing logical functions. The software in the memory 82 includes a suitable operating system (O/S) 85, compiler 84, source code 83, and one or more applications 86 in accordance with exemplary embodiments. As illustrated, the application 86 comprises numerous functional components for implementing the features and operations of the exemplary embodiments. The application 86 of the computer 80 may represent various applications, computational units, logic, functional units, processes, operations, virtual entities, and/or modules in accordance with exemplary embodiments, but the application 86 is not meant to be a limitation.

The operating system 85 controls the execution of other computer programs, and provides scheduling, input-output control, file and data management, memory management, and communication control and related services. It is contemplated that the application 86 for implementing exemplary embodiments may be applicable on all commercially available operating systems.

Application 86 may be a source program, executable program (object code), script, or any other entity comprising a set of instructions to be performed. When a source program, then the program is usually translated via a compiler (such as the compiler 84), assembler, interpreter, or the like, which may or may not be included within the memory 82, so as to operate properly in connection with the O/S 85. Furthermore, the application 86 can be written as an object oriented programming language, which has classes of data and methods, or a procedure programming language, which has routines, subroutines, and/or functions, for example but not limited to, C, C++, C#, Pascal, BASIC, API calls, HTML, XHTML, XML, ASP scripts, JavaScript, FORTRAN, COBOL, Perl, Java, ADA, .NET, and the like.

The I/O devices 87 may include input devices such as, for example but not limited to, a mouse, keyboard, scanner, microphone, camera, etc. They are for receiving control commands from the user, for example to switch on or off the lighting, or to switch between sparkle and non-sparkle lighting.

Furthermore, the I/O devices 87 may also include output devices. Finally, the I/O devices 87 may further include devices that communicate both inputs and outputs, for instance but not limited to, a network interface controller (NIC) or modulator/demodulator (for accessing remote devices, other files, devices, systems, or a network), a radio frequency (RF) or other transceiver, a telephonic interface, a bridge, a router, etc. The I/O devices 87 also include components for communicating over various networks, such as the Internet or intranet.

If the computer 80 is a PC, workstation, intelligent device or the like, the software in the memory 82 may further include a basic input output system (BIOS) (omitted for simplicity). The BIOS is a set of essential software routines that initialize and test hardware at startup, start the O/S 85, and support the transfer of data among the hardware devices. The BIOS is stored in some type of read-only-memory, such as ROM, PROM, EPROM, EEPROM or the like, so that the BIOS can be executed when the computer 80 is activated.

When the computer 80 is in operation, the processor 81 is configured to execute software stored within the memory 82, to communicate data to and from the memory 82, and to generally control operations of the computer 80 pursuant to the software. The application 86 and the O/S 850 are read, in whole or in part, by the processor 81, perhaps buffered within the processor 81 , and then executed.

When the application 86 is implemented in software it should be noted that the application 86 can be stored on virtually any computer readable medium for use by or in connection with any computer related system or method. In the context of this document, a computer readable medium may be an electronic, magnetic, optical, or other physical device or means that can contain or store a computer program for use by or in connection with a computer related system or method.

The application 86 can be embodied in any computer-readable medium for use by or in connection with an instruction execution system, apparatus, or device, such as a computer-based system, processor-containing system, or other system that can fetch the instructions from the instruction execution system, apparatus, or device and execute the instructions. In the context of this document, a "computer-readable medium" can be any means that can store, communicate, propagate, or transport the program for use by or in connection with the instruction execution system, apparatus, or device. The computer readable medium can be, for example but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, device, or propagation medium.

The light-emitting module may e.g. comprise a light source being adapted to emit un-polarized light, and a polarizer arranged to receive the emitted light and to generate polarized light having a desired direction of polarization. Additionally, or alternatively, the light-emitting module may e.g. comprise a light source emitting polarized light having a selected direction of polarization.

In the context of the present application, the light unit may be substantially any device or element that is capable of emitting radiation in any region or combination of regions of the electromagnetic spectrum, for example the visible region, the infrared region, and/or the ultraviolet region, when activated e.g. by applying a potential difference across it or passing a current through it. Therefore a light source can have monochromatic, quasi- monochromatic, polychromatic or broadband spectral emission characteristics. Examples of light sources include semiconductor light-emitting diodes (LEDs) or lasers, organic, or polymer/polymeric light-emitting diodes (such as OLEDs), RGB LEDs, optically pumped phosphor coated LEDs, optically pumped nano-crystal LEDs, RGB laser combinations, white broadband lasers, laser pumped phosphors, or any other similar devices as known to a person skilled in the art.

Other variations to the disclosed embodiments can be understood and effected by those skilled in the art 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. Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A lighting system comprising:

a lighting arrangement (10,12; 20); and

a controller (30;40;50;60) for controlling the lighting arrangement,

independent control of the light output of a first and second light unit configured to issue light of mutually different polarization,

control of an orientation or electric state of a polarizer,

thereby to implement a dynamic sparkle effect when the light output illuminates an object.

2. A system as claimed in claim 1, wherein varying the polarization comprises varying the polarization direction of linear polarization and/or varying a ratio of un-polarized light and linearly polarized light.

3. A lighting system as claimed in claim 1 or 2, wherein the controller is adapted to vary the polarization in a random or pseudo random way.

4. A lighting system as claimed in any preceding claim, wherein the first light unit (10) has a linearly polarized output with a first polarization direction and the second light unit (12) has a linearly polarized output with a second polarization direction different to the first polarization direction, for example orthogonal to the first polarization direction.

5. A lighting system as claimed in claim 4, wherein the lighting arrangement comprises a set of more than two light units, each with different polarization direction.

6. A lighting system as claimed in claim 4 or 5, wherein the controller is adapted to control the light output from the light units of the lighting arrangement such that the combined light output is constant.

7. A lighting system as claimed in claim 1, 2 or 3, wherein the lighting arrangement comprises at least said first light unit and a linear polarizer at a light output of the first light unit, wherein the controller is adapted to control the linear polarizer, wherein the linear polarizer comprises:

a mechanical drive mechanism; or

a linear polarizer with an electrically controlled polarization direction.

8. A lighting system as claimed in claim 7, wherein the linear polarizer comprises an electrically controlled liquid crystal cell.

9. A lighting system as claimed in any preceding claim, comprising an array of lighting arrangements, wherein the polarization and light output for each lighting

arrangement in the array is synchronized.

10. A lighting system as claimed in any preceding claim, further comprising a second lighting arrangement, wherein the second lighting arrangement has an un-polarized light output, and wherein the controller is adapted to control the light output intensity of the lighting arrangement and the second lighting arrangement to maintain a constant cumulative light output.

11. A method of controlling a lighting arrangement, comprising:

varying autonomously over time the polarization of the light output from the lighting arrangement, thereby to implement a sparkle effect when the light output illuminates an object.

12. A method as claimed in claim 11, comprising adjusting the polarization direction of linear polarization and/or varying a ratio of un-polarized light and linearly polarized light.

13. A method as claimed in claim 13, wherein the polarization direction and/or the ratio of un-polarized light and linearly polarized light is adjusted in a random or pseudo random way.

14. A method as claimed in claim 11, 12 or 13, comprising:

controlling independently the light output from at least a first light unit with a linearly polarized output with a first polarization direction and a second light unit with a linearly polarized output with a second polarization direction different to the first polarization direction and optionally controlling the light output from the first and second light units such that the combined light output is constant; or

controlling the polarization direction of a linear polarizer at the light output of at least a first light unit.

15. A computer program comprising code means which is adapted, when run on a computer, to implement the method of any of claims 11 to 14.