EP1575338A1

EP1575338A1 - A lighting device with changeable color temperature and a method for varying the emission temperature of the light

Info

Publication number: EP1575338A1
Application number: EP04425158A
Authority: EP
Inventors: Piero Magnaghi
Original assignee: Individual
Current assignee: Individual
Priority date: 2004-03-09
Filing date: 2004-03-09
Publication date: 2005-09-14

Abstract

A device and a method for varying the color temperature of the light emitted by a lighting device are described. The independent control of the emission power of a plurality of light sources each one having different color temperatures from the others is provided.

Description

The present invention relates to a variable color temperature lighting device and a method for varying the light emission temperature of a lighting device.
Various types of lighting device are currently distributed on the market, such as for example neon bulbs or tubes, each one able to emit white light with a preset color temperature (shade). A same product, for example a neon tube with given electrical and dimensional characteristics, is therefore proposed in different versions, each one with its own color temperature in order to satisfy the different lighting requirements.
Generally, the bulbs or the tubes currently distributed cover a temperature range that varies approximately between 2500 and 7000 K (degrees Kelvin) and are thus also distinguished as "warm light", "cold light" lighting devices, etc., and this is to allow the most suitable choice to each particular application.
It has in fact been found that the human eye perceives reality in a different way according to the shade of the light. For example, in canteens or refrigerator units for displaying foodstuffs cold light bulbs should not be used because such shades make the food uninviting.
In the same way, if one considers for example the lighting of a kitchen, a warm light makes food more attractive, but particularly cold light makes it possible to easily detect any sign of grease on the shiny surfaces used.
If one considers for example the lighting in an area in the vicinity of a mirror, warm light (for example close to sunlight) makes the appearance of the person in front of the mirror more pleasing, but at the same time cold light, although worsening the appearance, will make it possible to detect more easily any details and defects in the make up.
In the prior art lighting devices with preset color temperatures are installed according to the characteristics one intends to enhance and/or conceal, thus compromising however other characteristics useful in given circumstances.
The need is therefore felt for providing a lighting device that allows to adapt the color temperature of the emitted light.
This being stated, the object of the present invention is to propose a novel lighting device that allows a user to vary the color temperature of the white light at will according to the particular requirements that may arise in an installation site.
Another object of the present invention is that of providing a device that allows to vary in a particularly simple way the color temperature of the white light.
These objects are achieved by the present invention, which relates to a variable color temperature lighting device, characterised by comprising a plurality of luminous sources each one having a different color temperature to the others and means for controlling in an independent way the emission power of each of the luminous sources.
The possibility of being able to regulate the color temperature allows numerous application possibilities. Besides it can also allow manufacturers and dealers to maintain in stock a lighting device suitable to all the possible applications, with considerable savings from the point of view of the costs.
The luminous sources preferably include at least three LEDs, of which at least one consists of a white light LED. More preferably, all the luminous sources consist of white light LEDS with different color temperatures.
The device according to the invention preferably includes optical means of mixing the beams of light emitted by the luminous sources. Particularly, the optical means include at least one lens for each of the luminous sources.
According to a particular aspect of the present invention, the luminous sources and the optical mixing means are enclosed inside a single enclosure to form an interchangeable module. The model as a whole can be advantageously provided with a standard type connection element to allow the installation of the device according to the invention with the systems or attachments used on the market.
The means for controlling in an independent way the emission power of each of the luminous sources are preferably commanded from a single command point.
Advantageously similar control means can be for example those described in patent application no. MI2003-A001987 filed in the name of the same Applicant and that is incorporated herein by reference. In any case, the control means suitable to the present invention preferably allow to change the color temperature of the light in a continuous, automatic way or in any case programmable with dedicated software, acting preferably through a single control member, such as a button or similar.
According to anther aspect of the invention, a method is provided for varying the color temperature of the light emitted by a lighting device, characterised in that it provides the independent control of the intensity power of a plurality of luminous sources each one having a different color temperature to the others.
Further characteristics and advantages of the present invention will appear from the following description of a non-limiting example, with reference to the appended schematic drawings, wherein:

Figure 1 is a diagram of a device according to the present invention; and
Figure 2 is a schematic view of a possible embodiment of an interchangeable module for the lighting device according to the present invention.

A lighting device according to the present invention is depicted in Figure 1 and comprises a control unit 10 that receives electrical energy through a power cable 11. The power supply may be provided in alternating current, withdrawn for example from the mains and optionally reduced upstream of the device 10, or it may be provided in direct current, using for example a battery or means for rectifying (and optionally reducing) the mains voltage.
The unit 10 is arranged and/or programmed to control in an independent way the emission power of each of the luminous sources connected thereto, preferably by acting through a single command point, such as, for example, a button 13 represented in Figure 1.
As luminous sources with different color temperatures at least three LEDs 20a, 20b, 20c are preferably used, mounted on a connection plate 21 to which the conductors 12 coming out of the unit 10 are joined.
The LEDs 20a, 20b and 20c are preferably LEDs able to emit white light with different color temperatures, and are selected with color temperatures such as to cover the whole range of temperatures desired. For example, the LED 20a is selected with a color temperature equal to the maximum value of the range, the LED 20b is selected with a color temperature equal to the minimum value of the range and the LED 20c is selected with a color temperature intermediate to the two extremes.
In a practical embodiment of the device according to the present invention LEDs of the Lambertian type identified by the trade name Luxeon Warm White and distributed by Lumileds Lighting were used. A first of the LEDs had a color temperature equal to 8000 K, a second LED had a color temperature equal to 2850 K and a third LED had a color temperature equal to 4000 K. Therefore by varying the luminous intensity of each of the LEDs in an independent way it was possible to make a lighting device able to emit light with color temperatures from 2850 K to 8000 K, thus substantially covering all the color temperatures supplied by bulbs and/or tubes currently on the market.
The device advantageously comprises optical means for mixing the beams of light emitted by the luminous sources. Particularly, for each of the LEDs 20a, 20b, 20c a respective lens 30a, 30b, 30c is provided. The lenses 30a-30c, of which the upper caps alone are represented for clarity in Figure 1, arranged on a support 31, allow to generate a single luminous beam with the desired temperature characteristics.
By varying in an independent manner the emission intensity of each of the LEDs a white light can be obtained in which the emission of one or more of the LEDs present in the device prevails, thereby obtaining a light having a color temperature prevalently determined by the LED that is commanded with emission intensity higher than the others.
Figure 2 schematically represents a possible embodiment of an interchangeable module 40 suitable to be used in a device according to the present invention.
The module 40 comprises an enclosure 41 housing the LEDs 20a, 20b, 20c therein, mounted on the connection plate 21, as are the lenses 30a, 30b, 30c with the relative support 31.
Lenses of the Lambertian type FHS series with luminous beam angles of approximately 40-45° ("wide beam" type version) distributed by the Fraen Corporation were used in the practical embodiment of the device.
The module 40 advantageously comprises a standard type connection element 42, for example an MR11 or MR16 type connection element in order to allow the installation of the module 40 with attachments particularly widespread on the market.
In order to vary the color temperature of the white light emitted by the device according to the present invention one can use, for example, a control unit 10 with microprocessor programmed to make available functions substantially similar to those described for patent application no. MI2003-A001987 filed in the name of the same Applicant.
For example, a pressure exerted for a short time on the button 13 may allow the switching on and off of the luminous sources, with the possibility of storing the setting of the color temperature emitted at the time of switching off.
In order to vary the color temperature of the white light emitted by the LEDs one can exert and maintain pressure on the control button 13 until a white light is obtained having the desired temperature characteristics. As soon as the pressure on the button 13 is released the desired color temperature is maintained.
Various modifications can be made to the embodiments represented herein without departing from the scope of protection of this invention. For example, more than three LEDs may also be used, or the connection element 42 may be of a different type to those described and/or represented.

Claims

A variable color temperature lighting device, characterised by comprising a plurality of luminous sources each one having a different color temperature from the others and means for controlling in an independent way the emission power of each of said luminous sources.
A device according to claim 1, wherein said luminous sources include at least three LEDs
A device according to claim 1 or 2, wherein at least one of said luminous sources is constituted by a white light LED.
A device according to claim 1 or 2, wherein said luminous sources consist of white light LEDS with different color temperatures.
A device according to claim 1, wherein optical means for mixing the beams of light emitted by said luminous sources are further provided.
A device according to claim 5, wherein said optical mixing means include at least one lens for each of said luminous sources.
A device according to any of the previous claims, wherein at least said luminous sources and at least said optical mixing means are enclosed in a single enclosure to form an interchangeable module.
A device according to claim 7, wherein said interchangeable module is provided with a standard connection element.
A device according to claim 1, wherein said means for controlling in an independent way the emission power of each of said luminous sources are commanded from a single command point.
A device according to any of the previous claims, wherein the color of the light of which the temperature is varied is the white color.
A method for varying the color temperature of the light emitted by a lighting device, characterised by providing the independent control of the emission power of a plurality of luminous sources each one having a different color temperature to the others.
A method according to claim 11, wherein said luminous sources include at least three LEDs.
A method according to claim 11 or 12, wherein at least one of said luminous sources is constituted by a white light LED.
A method according to claim 11 or 12, wherein said luminous sources are constituted by white light LEDs with different color temperatures.
A method according to claim 11, wherein optical means for mixing the beams of light emitted by said luminous sources are further provided.
A method according to claim 15, wherein said optical means for mixing include at least one lens for each of said luminous sources.
A method according to claim 11, wherein the independent control of the emission power of each of said luminous sources is performed from a single command point.
A method according to any of claims 11 to 17, wherein the temperature of the color white is varied.