GB2522862A

GB2522862A - Controlling apparatus and method for controlling a lighting apparatus having at least two light sources

Info

Publication number: GB2522862A
Application number: GB1401994.7A
Authority: GB
Inventors: James Albert Powell
Original assignee: INNOVATION LED Ltd
Current assignee: INNOVATION LED Ltd
Priority date: 2014-02-05
Filing date: 2014-02-05
Publication date: 2015-08-12
Also published as: GB201401994D0

Abstract

A controlling apparatus 3 for a lighting apparatus 4 having at least two light sources 5, 7, 9, 11, each generating light of a different colour, includes means 17 for storing calibration data relating to measured wavelengths and maximum intensities of light generated by each source, a processor 13 to drive the sources and a user-operable control 19 comprising respective variable controls nominally associated with each of the sources to enable a user to vary the intensity of each source to obtain a desired output colour and intensity. A further user-operable control 21 enables a user to specify and store a primary colour for each variable control. When a colour is specified for a variable control which differs from the measured wavelength of the light source nominally associated with that control, the processor will drive the light sources in response to operation of the control to generate the specified colour, enabling the lighting apparatus to emulate a different lighting apparatus having light sources with different characteristics.

Description

CONTROLLING APPARATUS AND METHOD FOR CONTROLLING A

LIGHTING APPARATUS HAVING AT LEAST TWO LIGHT SOURCES

Technical Field of the Invention

The present invention relates to controlling apparatus and a method for controlling a lighting apparatus having at least two light sources.

Background to the Invention

Colour mixing luminaires are widely used in the commercial lighting industry to output light of a particular colour and intensity. Different coloured light may be required, for example, for lighting up stages, television studios and architecture. Increasing'y, luminaires comprising high powered light emitting diodes LEDs) are employed due to improved efficiencies over more traditional forms of lighting such as incandescent light sources.

A typical colour mixing LED luminaire contains at least red LEDs, blue LEDs and green LEDs. By varying the intensity ofthese three primary colours, it is possible for the luminaire to output a wide range of different colours. For example, by mixing red light and blue light a luminaire will output purple coloured light.

Figure 1 shows a CIE 193 colour space chromaticity diagram. The thU range of possible colours visible to the human eye is represented in Figure 1 by the area bounded by the horseshoe shape labelled V. Each colourwithin area V may be defined by an x and a y coordinate. Red light with a particular wavelength, for example, may be defined by the CuE coordinates (0.60, 0.40) whereas green light of a particular wavelength may be defined by the CIE coordinates (0.20, 0.65), Mixing red light having coordinates (0.60, 0.40) with green light having coordinates (0.60, 0.40) will produce a colour with coordinates somewhere along a line linking the two primary coordinates together. In this case, a colour appearing yellow/orange will be produced. It can be seen, therefore, that a desired colour with a particular wavelength within area V (and hence coordinate) can be achieved by mixing primaries having appropriate coordinates to achieve the desired coordinate and hence colour.

In practice, a luminaire cannot produce every colour within area V because it is limited by the number of primary colours its light sources can produce and the wavelengths ofthose light sources. With reference to Fig, 1, the range of colours that an ROB luminaire can produce is defined by the area CO which is commonly referred to as the colour gamut of the luminaire. The line GB shows ali colours producible by the luminaire in the absence of red, the line GR shows all colours producible by the luminaire in the absence of blue and the line RB shows all colours producible by the luminaire in the absence of green. Any colour within area CG may be produced by mixing an appropriate amount of red and/or green and/or blue. Since this luminaire has only three primary colours, the colour gamut available to the luminaire is triangular in shape. The colour gamut can, though, be increased by introducing other primary colours into the luminaire such as cyan.

A problem with these luminaires is that different LEDs are not always colour consistent. Due to manufacturing tolerances, LEDs ofthe same primary colour emit light of slightly different wavelengths and intensities. For example, a particular manufacturer's green LED may have a typical quoted wavelength of 530nm but, in practice, one LED may produce light of wavelength 540nm and another LED may produce light of wavelength 520nm. Manufacturers use a technique called binning to narrow down the range of wavelengths delivered on a specific reel of LEDs but large variations can still exist between different reels, This means that different luminaires can have slightly different colour gamuts due to slight variations in the wavelengths emitted by the primary colour LEDs, The result is that two supposedly identical luminaires connected to a lighting desk without any colour correction will produce a slightly different colour. These variations in emitted primary colours are magnified when combining the primaries to produce colour mixes which means that it is difficult to achieve consistent colours across a number of supposedly identical luminaires. The problem is compounded further when trying to match colour across luminaires from different manufacturers when greater primary colour variations are encountered, To try and achieve consistent colour throughout a range of luminaires, manufacturers use a colour correction technique within the driving electronics of the LLJJs. For example, a manufacturer may decide that its desired primary or "reference" red be specified at a wavelength of66onm with an x, y coordinate (0.60, 0.35). One of its luminaires in a range may have a red LED that emits light having a wavelength of 660nm. In this case, no correction is necessary. Another luminaire in the same range may have a red LED that emits light having a wavelength of 620nm with colour coordinate (0.65, 0.35). In this case, a correction is applied so that a small amount of Nue and a small amount of green is introduced into the mix to bring the output red light as close as possible to the desired colour coordinate of (0.60, 0.35). By repeating this process for each luminaire, a manufacturer can produce a range of fittings that each output consistent primary colours and that are therefore consistent when colour mixing.

A problem still exists with these calibration techniques due to the fact that each manufacturer may choose its own "reference" primary colours. If one manufacturer's reference red is different from another manufacturer's reference red, their respective luminaires will not match and so it will not be possible to achieve consistent colour mixing across different manufacturer fixtures. Thus, a lighting rig comprising ten fixtures from one manufacturer and ten fixtures from another manufacturer may produce inconsistent blue or any other colour for that matter.

It is an object of the present invention to overcome the above difficulties in producing consistent colour.

Summary of the Invention

According to a first aspect of the present invention, there is provided controlling apparatus for controlling a lighting apparatus having at least two light sources, each source generating light of a different colour, the controlling apparatus having means for storing a measured wavelength of light produced by each source, means for storing a measured maximum intensity which can be generated by each source, a processor arranged to drive the sources in order to obtain an overall light output of a desired intensity and colour within a colour gamut of the lighting apparatus, a user operable control comprising respective variable intensity controls, one control nominally associated with each of the at least two sources to enable a user to vary the intensity of each source in order to obtain a desired overall colour and intensity, a further user operable control enabling a user to specify a colour for each variable control, said specified colour being within the colour gamut of the apparatus, means for storing the specified colour, wherein the processor is arranged so that, when a colour is specified for a variable intensity control which differs from the measured wavelength of the light source nominally associated with that control, it will drive the light sources in response to operation of the control to generate the specified colour, thereby to enable the lighting apparatus to be adjusted to emulate a different lighting apparatus having light sources of the same colours but different wavelengths.

Advantageously, a lighting system comprising a controlling apparatus according to the invention can be calibrated so that the primary colours emitted by a lighting apparatus to which the controlling apparatus is connected are substantially the same as those of different lighting system having different primary colour light sources. Thus, the controlling apparatus can define a different primary colour for a lighting system in order to try and match the colour gamut of a different lighting system and thereby force the lighting apparatus to which the controlling apparatus is connected generate substantially the same overall colour output based on the same input commands.

The controlling apparatus may be arranged to specify colours according to an internationally recognised standard. The controlling apparatus may be arranged to specify colours as x and y coordinates in colour space.

The apparatus may further comprise a sensor to measure characteristics ofemitted IS light, wherein the measured characteristics are used to specify a colour for a variable intensity control. The apparatus may further comprise communication means to enable data relating to specified colours to be transmitted to and received from other devices.

The controlling apparatus may be arranged to specify a different primary colour for at least two different variable intensity controls. The controlling apparatus may be arranged to specify a red colour for one variable intensity control, a green colour for a second variable intensity control and a blue colour for a third variable intensity control.

The controlling apparatus may be arranged to specify a white colour temperature for a fourth variable control.

There may be a lighting system comprising a controlling apparatus according to the first aspect. The lighting system may further comprise a lighting apparatus comprising at least two light sources. The lighting apparatus may comprise a red light source, a green light source and a blue light source. The lighting apparatus may further comprise a white light source, The light sources may comprise one or more light emitting diodes.

In accordance with another aspect of the present invention, there is provided a method of controlling a lighting apparatus having at least two light sources comprising the steps of: I 0 a. providing a controlling apparatus according to the first aspect, b. connecting the controlling apparatus to the lighting apparatus; c. measuring a wavelength and intensity of each light source; and d. specifying a colour for one or more variable intensity controls that is substantially equivalent to a colour emitted by a different lighting apparatus.

The colour may be specified for one or more variable intensity controls by entering a colour space x and y coordinate. The lighting apparatus may have a red light source, a green light source and a blue light source and the method may include the additional step of specifying a colour for one or more of the three light sources so that light emitted by each light source is substantially the same as light emitted by the equivalent light sources of a different lighting apparatus.

According to another aspect of the present invention, there is provided a method of calibrating a network of lighting apparatus having at least two light sources comprising the steps of: a. providing a controlling apparatus according to the first aspect for each lighting apparatus; connecting a controlling apparatus to a respective lighting apparatus; c. using one controlling apparatus, specifying a colour for one or more variable intensity controls that is substantially equivalent to a colour emitted by a different lighting apparatus; and transmitting the specified colours to each other controlling apparatus so that each other controlling apparatus will cause each respective lighting apparatusto emit the same specified colours.

Detailed Description of the Invention

In order that the invention may be more clearly understood an embodiment IS thereof will now be described, by way of example only, with reference to the accompanying drawings, of which: Fig. I shows a CIE 1931 colour space chromaticity diagram which represents graphically the x, y coordinates of all possible colours visible to the human eye and the colour gamut of a typical RGB lighting apparatus; Fig. 2 shows schematically a lighting apparatus comprising a controlling apparatus according to the present invention; Fig. 3 shows the CIE 1931 colour space diagram of Fig. I and includes the colour gamut of a different RGB lighting apparatus; Fig. 4 shows an image of the user interface with the three available primary colour channels; and Fig. 5 shows an image of the user interface with the adjustable x and y coordinates of the green channel, With reference to the drawings there is shown a lighting system 1 comprising a controlling apparatus 3 and a lighting apparatus 4 having four light sources 5, 7, 9, 11.

Three of the light sources 3, 7, 9 are arranged to output light of a primary colour which may be one of red light, blue light or green light. Of course, it is envisaged that other primary colours could be used in addition to or as a replacement for red, green and blue.

For example, cyan and/or amber could be used in the lighting apparatus 4. The other light source 11 is arranged to output white light with a colour temperature of approximately 6500K in order to boostthe white light produced by the three primary colours combined, The three primary colour light sources 5, 7, 9 each comprise one or more light emitting diodes which are arranged to emit light at a particular wavelength, The white light source comprises one or more blue LEDs with a phosphor coating which is arranged to emit a broad range of spectra from greenish to reddish, with most of the output in the yellow spectrum. The broad spectrum of the white light source gives rise to improved colour rendering over a red, green, blue only arrangement, In this embodiment, each red light emitting diode is arranged to emit lightwith an average wavelength of approximately 625nm and a maximum intensity ofapproximately lOOlm, each green light emitting diode is arranged to emit light with an average wavelength of approximately S2Snm and a maximum intensity of approximately I 50lm and each blue light emitting diode is arranged to emit light with an average wavelength of approximately 450nm and a maximum intensity of approximately 700mW, Each ofthese wavelengths correspond to CIE coordinates of (0.60, 0.40) for the red LEDs, (0.20,0.65) for the green LEDs and (0.20, 0.20) for the blue LEDs, By varying the intensity of each ofthe primary colours based upon the known primary coordinates it is possible to cause the lighting apparatus 3 to emit an overall light having a particular Cifi x, y coordinate arid, hence, colour.

The controlling apparatus 3 comprises a programmable integrated circuit 13 for processing information relating to the desired colour outputs of the lighting apparatus 4.

The controlling apparatus 3 further comprises a communications port 15, a non-volatile memory 17 for storing calibration data and data relating to the characteristics ofthe light sources including wavelength and intensity data, a colour output control 19 for varying the intensity ofthe individual light sources and a primary colour control 21 for specifzing a particular colour as the reference colour for each of the primary light sources, each of which are connected to the circuit 13. The circuit 13 is connected to the light sources 5, 7, 9, 11 of the lighting apparatus 3 by respective light source drivers 23 which power the light sources to generate light of a particular intensity.

The communications port 15 has a DMX input/output, an Ethernet port to enable a wired Ethernet connection between devices, a USB port, a wireless transmitter and a wireless receiver. The wireless transmitter and receiver enables the controlling apparatus 3 to send and receive calibration data and intensity values wirelessly to corresponding controlling apparatus and other wireless enabled devices. l0

The colour output control 19 comprises a user interface having a di splay and an input means to enable a user to choose a specific desired overall output colour from a colour palette. The user interface also comprises a channel associated with each light source to enable a user to input discrete intensity values for each primary colour depending upon the desired overall output colour, Two channels are also provided for the white point. The first channel is for full intensity white which corresponds to each individual red, green and blue light sources being set to frill intensity. The second channel enables a user to dictate a particular desired white point which results in the colour output control 19 adjusting the intensity ofthe different primary colours and the white colour to achieve the desired white point CIE x, y coordinate, This enables the lighting apparatus 4 to produce a broad range of white temperatures from 2600K to 6400K.

I'he colour output control 19 is arranged to transmit the selected intensity values to the integrated circuit 13 where the transmitted data is used to generate control commands to instruct the drivers 23 to power the LEDs as appropriate in order to produce the required intensities for each light source to produce an overall desired output colour with a particular CIE x, y coordinate, The primary colour control 21 comprises a user interface having an LCD display and input means which are incorporated into the housing ofthe lighting apparatus 4, The primary colour control 21 further has three primary colour control channels, one associated with the red light source, one associated with the green light source and one associated with the blue light source, The primary colour control channels are arranged to generate control signals that relate to the intensity values entered using the input means and transmit those control signals to the circuit 13, With reference to Figs. 4 and 5, the user interface provides a user with the option of choosing which colour channel to Ii calibrate. When selected, a primary colour channel can be calibrated by adjusting the x and y CIE chromaticity values or by selecting from a list of pre-defined chromaticity values which correspond to industry standard primary colours such as Lee Filters L124 or [139.

Whilst three primary control channels are provided for the red, green and blue light sources, it is not always necessary to have a control channel assigned to every different light source. For example, the primary colour control 21 could have three primary colour control channels for red green and blue but the lighting apparatus could comprise additional primary colour light sources such as cyan and amber. In this case, the CIE x, y chromaticity coordinates could still be set for the green channel, the red channel and the blue channel but the circuit 13 may introduce some of the other primary colours into the mix in order to achieve a closer match to the desired output primary colour for green, red and blue.

Following manufacture, and typically conducted by the manufacturer, each ofthe primary colour light sources of the lighting apparatus 4 is independently set to full intensity. A calibrated colour meter is used to measure the average wavelength and maximum intensity of each of the primary light sources in turn and these measured values are stored in the non-volatile memory 17. Based upon these measurements it is possible to determine the CIE x, y chromaticity coordinate of each light source of the lighting apparatus 4 and therefore plot the colour gamut of the lighting apparatus on a chromaticity diagram as shown in Fig. I. The range of colours available to the lighting apparatus is therefore known. The controller is then supplied to an end user.

In use by the end user, if it is desired to match the colour output of the lighting apparatus 4 to another lighting apparatus having light sources with the same primary colours but different wavelengths and, hence, CIE x, y coordinates, a user must alternate between each light source of the other lighting apparatus and set them to iftll intensity, 1t for example, the red light source of the other lighting apparatus is set to full intensity, a user can access the user interface of the primary colour control 21 of the lighting apparatus 4 and using the input means begin to adjust the Cifi x, y coordinate for the red colour control channel. Adjusting the CIE x, y coordinate for the red channel introduces small amounts of blue and green as appropriate to shift the overall output colour of the lighting apparatus 4 and, thereby, shift the CIE x, y coordinate ofthe red control channel.

When the output colour appears to match the red output colour of the other lighting apparatus, the new CfE x,y coordinate for the red colour channel is set as the primary coordinate for red and saved in the non-volatile memory 17. The process is repeated for the blue and green colour channels until each ofthe primary colours is set to substantially I 5 match the primary output colours ofthe other lighting apparatus. An exaggerated shifting of the coordinates for the primary colours is shown in Fig. 3 as indicated by the arrows which shows the primary colours ofthe main lighting apparatus 4 being adjusted so as to match its colour gamut to that ofthe colour gamut CCI (shown with a broken line) ofthe other lighting apparatus.

When the lighting apparatus 4 has been calibrated and the calibration data saved and the colour gamut of the lighting apparatus 4 is approximately equal to the colour gamut of the other lighting apparatus, it will substantially reproduce the same overall output colour as the other lighting apparatus based upon the same input commands from a user via the colour output control 19. Colour consistency across different lighting apparatus can therefore be achieved.

If it is desired to calibrate a network of lighting systems I having controlling apparatus 3 according to the present invention, a first lighting system 1 is calibrated such that its primary colour coordinates substantially match those of a lighting system whose colour output it is intended to emulate. Once the primary coordinates have been set, the data relating to those coordinates is transmitted via the communications port 15 to each other lighting system in a network. The transmitted data is received by the receiver of each communications port 15 and stored in the respective memory 17. Equally, the data could be transmitted over a wired connection linking any two lighting systems where they are incorporated into a wired network as opposed to a wireless network. This enables a network of lighting systems to be quickly and easily calibrated to substantially colour match the colour output of a different lighting system.

It is envisaged that the controlling apparatus 3 could additionally comprise a light sensor positionable in path of light emitted from the lighting apparatus 4 so as to measure the wavelength and intensity of the emitted light. The light sensor could be aranged to provide a feedback loop whereby the measured values of the emitted light are used to determine the exact CIE x, y coordinates of the primary colours in real time, This measured data could be used to calibrate other corresponding lighting systems 1 comprising a controlling apparatus 3. For example, one lighting apparatus 1 could be set as the master and a number of other networked lighting apparatus could beset as slaves.

The slaves could be continuously calibrated according to real time measurements of the emitted light taken by the sensor on the master apparatus 1. The sensor could also be positionable so as to be directed toward the light emitted from a different lighting system to accurately obtain the wavelength and intensity data of the other lighting system in order to obtain accurate Cifi x, y coordinates of the emitted primary colours and adjust the primary colour channels of the master lighting system accordingly.

The above embodiment is described by way of example only. Many variations are possible without departing from the scope of the invention as defined in the appended claims.

Claims

ISCLAIMS1 Controlling apparatus for controlling a lighting apparatus having at least two light sources, each source generating light of a different colour, the controlling apparatus having means for storing a measured wavelength of light produced by each source, means for storing a measured maximum intensity which can be generated by each source, a processor arranged to drive the sources in order to obtain an overall light output of a desired intensity and colour within a colour gamut of the lighting apparatus, a user operable control comprising respective variable intensity controls, one control nominally associated with each of the at least two sources to enable a user to vary the intensity of each source in order to obtain a desired overall colour and intensity, a further user operable control enabling a user to specify a colour for each variable control, said specified colour being within the colour gamut of the apparatus, means for storing the specified colour, wherein the processor is arranged so that, when a colour is specified for a variable intensity control which differs from the measured wavelength of the light source nominally associated with that control, it will drive the light sources in response to generate the specified colour thereby to enable the lighting apparatus to be adjusted to substantially emulate a different lighting apparatus having light sources of different colours.
2. Apparatus as claimed in claim i,wherein the controlling apparatus is arranged to specify colours according to an internationally recognised standard.
3. Apparatus as claimed in claim 2, wherein the controlling apparatus is arranged to specify colours as x andy coordinates in colour space.
4. Apparatus as claimed in any preceding claim, further comprising a sensor to measure characteristics of emitted light, wherein the measured characteristics are used to specify a colour for a variable intensity control,
5. Apparatus as claimed in any preceding claim, further comprising communication means to enable data relating to specified colours to be transmitted to and received from other devices.
6. Apparatus as claimed in any preceding claim, wherein the controlling apparatus is arranged to specify a different primary colour for at least two different variable intensity controls,
7. Apparatus as claimed in claim 6, wherein the controlling apparatus is arranged to specify a red colour for one variable intensity control, a green colour for a second variable intensity control and a blue colour for a third variable intensity control.
8. Apparatus as claimed in claim 7, wherein the controlling apparatus is arranged to specify a white colour temperature for a fourth variable control,
9. A controlling apparatus as substantially hereinbefore described with reference to the accompanying drawings.0. A lighting system comprising a controlling apparatus as claimed in any preceding claim.11. A lighting system as claimed in claim 10, further comprising a lighting apparatus comprising at least two light sources, 12. A lighting system as claimed in claim 11, wherein the lighting apparatus comprises a red light source, a green light source and a blue light source, H. A lighting system as claimed in claim 12, wherein the lighting apparatus further comprises a white light source.N, A lighting system as claimed in any ofclaims 10 to 13, wherein the light sources comprise one or more light emitting diodes.15. A lighting system as substantiafly hereinbefore described with reference to the accompanying drawings, 16. A method of controlling a lighting apparatus having at least two light sources comprising the steps of: a. providing a controlling apparatus as claimed in any of claims 1 to 9, b, connecting the controlling apparatus to the lighting apparatus; c, measuring a wavelength and intensity of each light source; and d, specifying a colour for one or more variable intensity controls that is substantially equivalent to a colour emitted by a different lighting apparatus.IS 7, A method as claimed in claim 16, wherein a colour is specified for one or more variable intensity controls by entering a colour space x and y coordinate 18. A method as claimed in claim 16 or claim 17, wherein the lighting apparatus has a red light source, a green light source and a blue light source and the method includes the additional step of specifying a colour for one or more of the three light sources so that light emitted by each light source is substantially the same as light emitted by the equivalent light sources of a different lighting apparatus.19. A method of calibrating a network of lighting apparatus having at least two light sources comprising the steps of: a. providing a controlling apparatus as claimed in any of claims Ito 9 for each lighting apparatus; b. connecting a controlling apparatus to a respective lighting apparatus; c. using one controlling apparatus, specifying a colour for one or more variable intensity controls that is substantially equivalent to a colour emitted by a different lighting apparatus; and d. transmitting the specified colours to each other controlling apparatus so that each other controlling apparatus will cause each respective lighting apparatus to emit the same specified colours.