GB2504460A

GB2504460A - Colour mixing luminaire

Info

Publication number: GB2504460A
Application number: GB1210387.5A
Authority: GB
Inventors: James Albert Powell
Original assignee: MICHAEL COLIN EDWARDS; Lumonics Ltd
Current assignee: MICHAEL COLIN EDWARDS; Lumonics Ltd
Priority date: 2012-06-12
Filing date: 2012-06-12
Publication date: 2014-02-05
Also published as: GB201210387D0

Abstract

A method whereby the chromaticity of primary colours used for additive colour mixing in an LED based luminaire can be defined and selected electronically. A technique is described whereby the user of the luminaire is able to select and store within the luminaire the exact chromaticity produced in relation to any of the primary colours that are typically used by the luminaire when generating coloured light by additive mixing of the primary colours. By allowing the user of the luminaire control over the exact colour coordinates of the primaries used for colour mixing, it is possible to precisely match the colour output of the luminaire to that of other manufacturers or products based on different colour mixing and light source technologies.

Description

DESCRIPTION OF THE BACKGROUND ART

A colour mixing luminaire is a common product used within the lighting industry to gellerate light of a specified colour with typical applications involving the illumination of stages, TV studios, and architecture. The uses of high powered light emitting diodes (LEDs) are now commonplace as the light source within such fixtures, in a colour mixing luminaire, different coloured light sources are used and mixed together to produce the desired colour. Typically a remote lighting desk will be used to send control signals to the luminaire to control the relevant amounts of each colour to be mixed. A typical colour mixing LED luminaire will contain at least two different colours of LEDs with three or more different colours being the norm. A common fixture will contain LEDs of the three primaly colours, red, green and blue. By varying the intensities of each of these primary colour sources, a wide range of resultant colours can be produced. In this example, three channels of control would be used on a lighting dcsk, cach channcl controlling the intensity of each of the thrce primary LED colours in the fixture.

Unfortunately, there is an inherent problem with LEDs regarding colour consistency. Due to manufacturing tolerances there are variations in emitted wavelength between different LEDs of the same colour. For example, a particular manufacturer's green LED may have a typical wavelength of 530nm. In practice the delivered LED may have a wavelength of anywhere between 520nm to 540nm. Manufacturers use a technique called binning to narrow down the range of wavelengths delivered on a specific rcel of LEDs, but large yariations can still exist between different reels.

This variation in wavclcngth produccd by cffcctively thc same colour LED gives rise to problems when trying to produce consistent colour output between different LED luminaires.

Two identical fixtures connected to a lighting desk without any colour conection will in practice produce a different colour when for instance the blue channel is raised on the control desk. This problem obviously magnifies when colour mixing takes place and colour variations in each of the primaries being mixed gives rise to an unpredictable resultant colour.

As a solution to this variation in LED wavelength, it is now common practice to introduce a form of colour correction within the driving electronics of the LEDs. This correction automatically mixes in proportions of thc other LEDs in the luminaire to producc consistcnt colour. At the factory, a manufacturcr will fix a refcrcnce for cach of the LED colours used in the luminaire and then some form of software algorithm with be used to mix the LED colours to produce the reference colour. In practice, when using the luminaire, when for instance the red channel is increased on the lighting desk, the software in the luminaire will automatically add in a small amount to blue and green to create the "reference" red for the manufacturer.

This technique is now common within LED fixtures to allow a manufacturer to produce luminaircs that produce consist colour bctwccn fixtures. Onc cxamplc is US patent 7893633 that dcscribes a mcthod to achicyc this fixturc calibration.

However, there is still a problem with these calibration techniques. The calibrated colours for each of the primaries are decided by the manufacturer of a specific luminaire and will be typically drivcn by the LED type used. This means for example that a particular manufacturer will offer consistency of red, green and blue output from their range of luminaires. This consistency may be valid across their entire product portfolio or just a particular LED product range. Another manufacturer of LED products may also offer a similar guarantee of consistency across their product range. However, there is no guarantee what so ever that products will bc consistcnt between manufacturcrs. For examplc, say therc is a lighting rig with tcn LED products from manufacturer (a) and tcn LED products from manufacturer (b). If the lighting desk commands all products to output blue at thll, although all the blues will be the same for manufacturer (a) and all the same for manufacturer (b), there is no guarantee that the two manufacturer's products will match and the lighting rig will produce two different blue colours. The same is thus valid for any colours produced by the different manufacturer's products.

This problem is also valid when flying to mix products based on LEDs with traditional light sourccs. It is highly likely that thc primary colours produced by the fixturcs will diffcr. An exampic is when trying to match LED products with for instancc moving hcad luminaircs whose colour system is based on RUB or CMY dichroic colour filters.

This patent introduces a method to solve this problem and presents a novel method whereby in an LED bascd luminaire, the opcrator has the ability to define the cxact colour produccd as a primary. This means that the red, green, blue or any other primary colour control can be matched to any other product, whether it is based on LEDs or any other traditional light source.

DESCRIPTION OF THE INVENTION

The invention described herein presents a method by which the user of a luminaire based on LED technology is able to select the exact chromaticity of the primary colours used for colour mixing. This facility and technique is not available on any LED based colour mixing lighting fixtures to date.

Figure 1 shows an instancc of the CIE 1931 chromaticity diagram which allows diffcrcnt colours to be plotted in a graph like format. All producible colours in the visible spectrum are contained within the ellipse. Greens appear in the area around "1", blues in area "2" and reds in area "3". Each producible colour can be defined by an "x" and "y" colour or chromaticity coordinate.

For a typical LED colour mixing luminaire based on red, green and blue LEDs, as explained previously there will be a yariation in the colour of the LEDs and hence the chromatic.ity coordinates will also vary. As an example, these variations are show as x on the diagram.

This patent allows the operator of the product to define exactly the colour coordinate of light produccd for cach of the primary control chanucis within thc fixturc. AJthough rcd green and blue primaries have been discussed so far, this technique applies equally well to any colour or multiples of colour primaries present in the fixture. It is now common to see amber and white primary channels present in a fixture.

As an example, it might be desired that to match other fixtures on a lighting rig, when the red control channel is raised on the lighting desk, the fixture produces light of CIE coordinate (0.60, 0.40), when the green channel is raised, the colour coordinate is (0.20,0.65) and for bluc (0.20, 0.20). It follows that if colour mixing takes place, it will bc thesc primary coordinates that wifl bc mixcd togethcr in proportions rclating to thc lcvds of the individual control channels, not the arbitrary colours of the LEDs present in the fixture.

In order to achieve this control, the product must contain a calibrated intelligent light engine that has knowledge of the LEDs prcsent in the system and in real time can calculate how to drive the LEDs in the product to create the desired colour. There must also be a way for the user to input the required values to be used at the primary colours of the mixing system Figure 2 illustrates how a typical product can be implemented.

At the heart of the product is a digital controller (1) which may be a microcontroller or FPGA device. This controller processes control commands either from the communications port (4) or user interface (3) which is local to the luminaire. This user interface typically takes the form of a graphic or character LCD display. The controller generates the required control commands for the LED drivers (5) which provide the required power to the LEDs present in the system. (6) to (9). Non volatile memory (2) is present that is used for storing calibration data and user settings for the luminaire.

In this implementation the controller can be calibrated and programmed to produce the correct drive signals to the LEDs to create the required chromaticity of light from the LED array depending on the primary control signals being received through the communications port.

A menu option can be made available in the user interface to allow the user to enter or select thc requircd chromaticity of thc luminaire's primary colours.

The entry of each of the requircd primary colour chromaticities could be made by inputting the exact x andy CIE values or by selecting from a list of pre-defined values.

The number of primary control channels within the fixture may not necessarily equate to the number of different coloured LEDs in the fixture. For example, the user may be presented with three primary control channels, red, green and blue. However these primary colours may well be produced by combining the light output from a plurality of different LEDs colours within the fixture, for example including amber, white and cyan in addition to red green and blue. It is the role of the digital controller to calculate how to mix the different LEDs together with software algorithms to produce the require colour.

It is also within the scope of this patent that these defined primary colour ehromaticities can be utilised by other functions present within the lighting fixture such as effects generators, local control or other methods of colour selection such as HSI (Hue Saturation & Intensity) in addition to being directly driven by discrete channels on a lighting desk through the communications port.

The method described above explains how a single fixture can be configured to produce a set of desired primary colours using the user interface on the product. In most instances, multiple fixtures are used together and it would not be desirable if every single fixture on a lighting rig had to have its primary colours set independently.

A solution is to set one fixture using the method defined above and then for this first unit to transmit its primary colour settings to other units within the network using its communication port. I-knee it is to be covered within the scope of the patent, the transmission of primary colour data between fixtures networked within a lighting system. This network could be any used networking topology such as wired or wireless systems.

This transmission of primary colour data between fixtures could take place automatically transparent to the user or could be instigated manually once the primaries of the initial unit on the network have been set, for example by executing an "upload colour settings to all networked fixtures" option in the user interface of the luminaiit.

Claims

CLAIMS1. An intelligent colour mixing luminaire consisting of at least two different coloured light sources whereby each independent colour has its intensity controlled remotely via an electronic circuit.
2. An intelligent colour mixing luminaire according to claim 1, in which the light sources arc light emitting diodes LEDs
3. An intelligent colour mixing luminaire according to claim 1, in which the controlling circuit is a microprocessor or equivalent device with a communication port to allow the luminaire to be remotely controlled and programmed.
4. An intelligent colour mixing luminaire according to claim 3, whereby the light sources and controlling circuitry are calibrated with reference to an internationally recognised colour coordinate system.
5. An intelligent colour mixing luminairc according to claim 4 where it is possible for the user to exactly define the colour coordinate of each of the primary colours the luminaire is configured to produce.
6. An intelligent colour mixing luminaire according to claim 5 where the selection of primary colour coordinates is made through a user interface local to the luminaire.
7. An intelligent colour mixing luminaire according to claim 5 where thc scttings of thc primary colour colour coordinates can bc transmitted eithcr automatically or manually to other lummaires 011 the same iletwork using the communication port on the luminaire.
8. An intelligent colour mixing luminaire according to claim 5 whereby entered primary colour coordinates are used to define colours produced by internal effects engines or other colour mixing algorithms within the fixture.