ITUB20159346A1 - LIGHTING AND CORRESPONDENT PROCEDURE - Google Patents

Description

"Lighting device and corresponding procedure"

TEXT OF THE DESCRIPTION

Technical field

The description refers to the techniques for the generation of light radiation.

One or more embodiments can find application in the lighting engineering sector, for example in relation to lighting devices using electrically powered light radiation sources, for example solid state light radiation sources such as LED sources.

Technological background

The application, in the lighting engineering sector, of solid-state light radiation sources has made it possible to satisfy the need, felt by users, to have lighting sources whose chromatic characteristics can be varied (in short the "color") during application, for example during operation.

In this context it is possible, for example, to regulate ("tune") the light radiation by passing from saturated colors to unsaturated colors and / or to switch, for example. from red, green, orange, blue, magenta to white. This taking into account the fact that a greater degree of saturation of pure colors can be accompanied by a better perception of colors by the observer.

The choice of a particular color by the user can be seen as corresponding to the choice of an "objective" point within a colorimetric space, for example the colorimetric space known as CIE XYZ or CIE 1931, defined mathematically by the International Commission on Illumination (CIE) in 1931.

This choice can involve a compromise between different factors such as, for example, a saturated lighting color, a wide chromatic range, a reasonable value of the color rendering index (CRI) when working on white lenses ( e.g. along the Planckian curve).

We tried to respond to this need by using combinations of direct emission LEDs, such as:

- a red / amber colored source with an emission range from 605 nm to 660 nm wavelength,

a blue colored source with an emission range between 440 nm and 470 nm wavelength, e

a green color source, with an emission range from 500 nm to 550 nm wavelength.

This solution can allow to obtain a color temperature eg. of 3625 K also offering a wide range available, with saturated colors and a good appreciation by users. In addition, it is able to exploit a wide choice of direct emission LED sources available from different sources.

However, this solution has the drawback of demonstrating a low color rendering index (CRI) value in relation to white light in consideration of the narrow emission spectrum of the LEDs.

In addition, from the technological point of view, for example in InGaN-based sources, a drop in efficiency can be found in correspondence with the green wavelengths.

When aiming at producing a white light, the use of direct emission LEDs can also limit the overall flux also in relation to the possible exploitation of blue or red LEDs.

In this regard, it is possible to simply increase the number of LEDs in the green range or to increase the supply current (which can have negative reflections in terms of power load and efficiency).

It is also possible to think of including in the source a white LED capable of combining its radiation with those of the other three colored LEDs in order to maintain the same color point and increase the overall flux. A solution of this type is used, for example, in products sold under the trade name of OSTAR Stage by companies of the Applicants' group.

Another solution that can be proposed is the use of LEDs of the phosphor-converted type (sometimes called, with an expression perhaps not entirely proper, "conversion to phosphorus / s" or "conversion to phosphorus / s") in which, for example, a narrow band blue light is converted to a wider band light spectrum capable of providing radiation in the wavelength range from 500 nm to 700 nm. This solution proves to be more efficient and allows to achieve a higher CRI value at the point of white. However, it demonstrates a drawback linked to a narrower range, which results in a limitation of the vividness of the color as perceived by the observer.

Purpose and summary

One or more embodiments have the purpose of overcoming the drawbacks outlined above.

According to one or more embodiments, this object can be achieved thanks to a lighting device having the characteristics referred to in the following claims.

One or more embodiments can refer to a corresponding process.

The claims form an integral part of the technical teaching given in relation to one or more embodiments.

One or more embodiments offer the advantage of achieving an improved compromise between direct emission spectrum and spectrum (for example in green) deriving from the conversion with phosphors of the emission from LEDs, for example in the green range.

One or more embodiments allow to achieve a higher flux and a higher CRI value in the white points, optionally together with more saturated colors, if desired, through an area of chromatic range defined dynamically according to of the user's needs.

Brief description of the figures

One or more embodiments will now be described, purely by way of non-limiting example, with reference to the attached figures, in which:

Figure 1 illustrates the light emission characteristics of a light source,

Figure 2, comprising three portions indicated respectively with a), b), c), exemplifies possible characteristics of embodiments,

Figures 3 to 5 illustrate further characteristics of embodiments with reference to the CIE 1931 chromaticity diagram, and

Figures 6 and 7 illustrate possible embodiments of one or more embodiments.

Detailed description

Various specific details are illustrated in the following description, in order to provide an in-depth understanding of various embodiment examples. The embodiments can be obtained without one or more of the specific details, or with other processes, components, materials, etc. In other cases, known structures, materials or operations are not illustrated or described in detail so that the various aspects of the embodiments will not be made unclear.

A reference to "an embodiment" in the gain of the present disclosure is meant to indicate that a particular configuration, structure or feature described in relation to the embodiment is included in at least one embodiment. Thus, phrases such as "in one embodiment" which may be present at various points of the present disclosure do not necessarily refer to exactly the same embodiment. Furthermore, particular conformations, structures or features can be combined in any suitable way in one or more embodiments.

The references used herein are provided merely for convenience and therefore do not define the scope or scope of the embodiments.

In the remainder of this description, reference will be made repeatedly to the color space known as CIE XYZ (or CIE 1931).

The CIE XYZ space is a color space defined by the International Commission on Illumination (CIE) in 1931. Tools of possible application of this color space are the CIE 1931 chromaticity diagram (see for example Figures 3 to 5) as well as the function color of the CIE standard. The CIE XYZ or CIE 1931 space and the corresponding application and interpretation tools are to be considered widely known in the field of colorimetry, in particular by experts in the field to which the embodiments refer: this makes it unnecessary to provide here a corresponding detailed description.

One or more embodiments as exemplified here can be based on the combined use of three sources of light radiation having different chromatic emission characteristics.

In this regard it will be appreciated that each "source" considered here can comprise both a single emission device (for example a single LED) and a set of several emission devices (for example a set of LEDs having chromatic characteristics corresponding to each other).

In particular, in one or more embodiments it is possible to use, in combination:

- a first source of light radiation B and a second source of light radiation R, for example LEDs, which emit in the blue (first source B) and in the red (second source R) with direct emission, and

- a third second source of light radiation G, for example LED, which emits in the green through a conversion to phosphors (PC-green).

In one or more embodiments, a narrow band optical filter (e.g. the disk 14 or the lamina 16 which will be discussed below with reference to Figures 6 and 7) can be arranged in front of the LED G with emission at conversion to (by) phosphors, hereinafter referred to simply as PC, acronym for "phosphorconverted".

In one or more embodiments, the spectral transmission characteristics, i.e. the transfer function of the filter (which can be indicated with T_f), can be defined in such a way as to carry out a filtering action of the light of the source G, whose spectrum can be named S_pcg. In one or more embodiments, the filtering action expressed with T_f can be such as to reduce the spectrum S_pcg of the radiation emitted by the source G in the green band (PC-green) in such a way as to correspond to a point of more color. saturated in the CIE 1931 color space.

As an example, Figure 1 exemplifies (in a diagram in which the abscissa Wl / nm represents the wavelength in nm and the ordinate the intensity of emission expressed in Watt / nm x 10 <-1> the possible spectral combination of the radiation emitted by a red LED (direct emission), a blue LED (direct emission) and a green LED (emission subject to conversion to phosphors, i.e. Pti green) to obtain a correlated color temperature (Correlated Color Temperature or CCT) equal to 3625 K.

Figure 2 exemplifies the possible effect of a transfer function T_f of a filter associated with such a source in the green (PC-green), exemplifying:

- in the portion a) above, a possible trend of the S_pcg spectrum of the PC-green source (S_pcg) deriving from the conversion action through phosphors,

in portion b), in the center, the transfer function T_f of the filter, e

- in portion c), below, a possible trend of the convolution spectrum S_pcg * T_f (representative of the spectrum of the light passed through the filter). Figure 3 is a possible representation of the equivalent color points on the CIE 1931 chromaticity diagram.

In particular, points G and G 'are representative of the spectrum of the PC-green source respectively before filtering (portion a) of Figure 2) and after filtering (portion c) of Figure 2).

In one or more embodiments it is possible to use a filter T_f having a transfer function (transmission curve) with a fixed shape or profile (for example as represented in part b) of Figure 2), but with intervention intensity, instead that fixed, variable.

For example, in one or more embodiments it is possible to provide (for example according to the criteria exemplified below with reference to Figures 6 and 7) an intervention intensity of the filter capable of passing:

from a lower level R_0, corresponding in practice to the absence of filtering action, with total transmission of the PC-green radiation, ie with a diagram of portion c) of Figure 2 corresponding in fact to the diagram of portion a);

- to a higher value R_1, such as to cause the PC-green light radiation to present - after filtering a spectral trend resulting from the convolution expressed by the curve S_pcg * T_f as exemplified in portion c) of Figure 2.

All this with the possibility of varying the intervention intensity of the filter between R_0 and R_1, for example according to a function R_x (with x varying, for example in a linear way, between 0 and 1) so that the transmission curve functions filter transfer is expressible as T_f * R_x and the resulting filtered radiation is expressible as S_pcg * T_f * R_x.

In this way, in one or more embodiments it is possible to choose the value of x as a function of the chromatic characteristics of the radiation to be obtained.

The diagram of Figure 4 exemplifies, again with reference to the CIE 1931 chromaticity diagram, the possible effect deriving from the combination of a source in the red R (direct emission), a source in the blue B (direct emission) and a source in the green ( PC-green) subjected to the action of the filter T_f (for example with full intensity, that is R_1), with the "displacement" exemplified by the passage from point G to point G 'in Figure 3.

The representation of Figure 5 further exemplifies this concept by referring once again to a source in the red R and a source in the blue B both direct emission used in combination with a PC-green source (i.e. with phosphor conversion) subjected to filtering. according to the function T_f with a value of R_x that varies between the value x = 0 (point G) to the value x = l (point G ') through successive values of even x, for example a x = 0.25, x = 0, 50, x = 0.75 which gradually go towards more saturated colors, i.e. moving away from the central area and going towards the periphery of the CIE 1931 diagram

Naturally, the representation of a variation by steps and the choice of the entity of these steps is purely illustrative. One or more embodiments can in fact provide for a variation of x according to a continuous law and / or the adoption of variation steps with values other than those exemplified here.

One or more embodiments lend themselves to methods of use characterized by a high degree of flexibility.

For example, if during use it is desired to obtain a color point (CxCy) p within the area identified by points B, G and R (refer to Figure 5), it is possible to define and implement a certain combination of LED without taking into account the possible use of the T_f filter; in this way it is possible to increase the output in terms of flow and the achievable CRI value.

If you want to achieve a color point (CxCy) pal outside the area defined by the points R B G but included in the area defined by the points B G 'R (once again reference is made to Figure 5), it is possible to use the filter T_f by coupling it to the LED with green emission (PC-green) with the possibility of selectively increasing the value of x from 0 to 1 so as to increase the distance of the point (CxCy) compared to point G. This allows to increase the area of the available range of glove is required by modulating the effects induced by the use of the filter on the flow and on the CRI value.

Figures 6 and 7 exemplify possible implementations of one or more embodiments based on the use of a lighting device 10 comprising a substrate 12 on which light radiation sources, for example LEDs, with emission in the blue B and in the red R (direct emission) as well as a light radiation source with green emission G with conversion to phosphors (PC-green).

Figures 6 and 7 exemplify the possibility of implementing the optical filter capable of realizing the transfer function T_f with a selectively variable intensity value R_x (for example between R_0 and R_1 with x varying between x = 0 and x = 1).

For example, in one or more embodiments as exemplified in Figure 6, the filter can comprise a disc 14 of a material with optical characteristics corresponding to the transfer function T_f exemplified by portion b) of Figure 2 and comprising various areas (sectors ) 140, 141, 142, 143, 144 corresponding to different intensity values R_x, e.g. which vary according to the angular position of the disk 14 for example from a lower value x = G (sector 140) to a higher value x = 1 (sector 144) with a continuous variation or by steps as exemplified, for example, in Figure 5.

In one or more embodiments, the disc 14 can be made to rotate (e.g. by a motor M) so as to bring the sector 140, 141, 142, 143 or 144 corresponding to the value in front of the source PC-green G of R_x that you intend to use.

Figure 7 exemplifies the possibility of realizing the aforementioned filter in the form of a sheet or screen 16 of a material with optical characteristics corresponding to the transfer function T_f exemplified by portion b) of Figure 2 and comprising various areas 160, 161, 162, 163 , 164 corresponding to different intensity values R_x, e.g. which vary according to the position of the plate with respect to the source G eg. from a lower value x = 0 (zone 160) to a higher value x = l (zone 164) with a continuous or stepwise variation as exemplified, for example, in Figure 5.

In one or more embodiments, the foil or screen can be moved as exemplified by the double arrow of Figure 7 (e.g. by a motor not visible in the drawings or possibly with a manual action) so as to bring in front of the PC-green G source the zone 160, 161, 162, 163 or 164 corresponding to the R_x value that you intend to use.

Both in the case of the disk 14, or in the case of the lamina or screen 16, the aforementioned variation of the factor R_x can occur either continuously or in steps.

In one or more embodiments, both the disc 14 and / or the lamina or screen 16 can be made of a totally transparent material, for example glass, with the intensity value R_x differentiated from area to area of the disc 14 / plate 16 to example with a coating treatment of variable intensity (and therefore attenuation effect), thus being able to pass from a condition of complete transparency (R_0) to a position of maximum intensity of application of the filter transfer function (R_1) as a function of the position angle of the disk 14 or the relative position of the lamina 16 with respect to the source G.

One or more embodiments can adopt implementation variants of various nature with respect to the example illustrated above by way of example.

For example, it is possible to use instead of the source with blue emission (for example 440 -470 nm) a source that emits in cyan (for example 480 nm).

Similarly, in one or more embodiments, instead of a red emitting source (for example 605 nm at 660 nm) it is possible to use a source emitting orange (590 nm) or amber (605 nm) .

In one or more embodiments, the source here exemplified such as e.g. a direct emission red source can be replaced by a red source (or, for example, amber) with conversion to phosphors (i.e. PC type) with the possibility of applying to the radiation obtained with phosphor conversion a mechanism of filtering (shifting towards more saturated colors, from the central area to the periphery of the CIE 1931 diagram) such as that exemplified above with reference to the PC-green source, which can possibly be replaced with a direct emission green source.

In one or more embodiments, the aforementioned gamma extension mechanism by shifting towards more saturated colors by filtering (discrete by steps or dynamic continuously) can be applied to other chromatic components in addition to or alternatively to the source in the green. .

In one or more embodiments it is possible to regulate the intensity of the current of the source or sources subjected to this filtering action (think for simplicity of the source in the green G considered above) by increasing its value so as to compensate for the loss in level of luminous intensity induced by the action of the filter (for example of the disc 14 or of the screen 16).

For example (again referring for simplicity to the case of the source in the green PC-green considered extensively above, without this indication being intended as a limitation of the embodiments) it is possible to increase the intensity of the supply current, and hence the intensity of the light emission of the source as a function of the value x which varies for example from 0 to 1 according to the intensity of the filtering action.

This result can also be obtained, for example, with a PWM modulation of the intensity of the current fed to the source (for example PC-green), eg. intervening on the duty cycle by increasing it in order to compensate for the reduction in light intensity deriving from the greater filtering intensity.

In one or more embodiments, when multiple radiation sources are used comprising more than a single emission source (for example several LEDs with similar chromatic characteristics) this result can be achieved by activating a higher emission surface, by activating for example several LEDs. (e.g. green) or a larger surface of the light emission source (e.g. green) in order to compensate for the attenuation effect deriving from the filtering action.

Once again, it is recalled that the reference gui made to the PC-green source should not be understood in a limiting sense but related to the indications regarding possible alternatives for implementation previously given.

One or more embodiments can therefore provide a lighting device comprising:

- a first (eg. B), a second (eg. R) and a third (eg. G) electrically powered light radiation source with different emission fields ("ranges") (eg blue, red, green, etc ...) to produce a combined illumination radiation, where:

at least one (e.g. G) of said light radiation sources is a "phosphor converted" light radiation source, and

- said at least one light radiation source with phosphor conversion is coupled with a narrow band optical filter (e.g. 14, 16) which filters the light radiation of said light radiation source with phosphor conversion towards a point of more color saturated (i.e. going from the central area to the periphery) in the CIE 1931 color space.

In one or more embodiments, said optical filter can have a selectively variable filtering intensity (R_x).

In one or more embodiments, said optical filter can comprise a planar element (e.g. disk 14 or sheet / screen 16) comprising portions (e.g. 140, 141, 142, 143, 144 - Figure 6 or 160, 161 , 162, 163, 164 -Figure 7) with different filtering intensities (R_x), said planar element being capable of relative movement with respect to said at least one (e.g. G) of said light radiation sources to couple to said at least one light radiation source with conversion to phosphors different portions between said portions with different filtering intensities (R_x).

In one or more embodiments:

said first source of light radiation can be selected from a source of blue light radiation and a source of cyan light radiation, and / or

- said second source of light radiation can be selected from a source of red light radiation, a source of orange light radiation and a source of amber light radiation.

In one or more embodiments, said at least one light radiation source with conversion to phosphors may comprise a green, red or amber light radiation source.

In one or more embodiments, said at least one light radiation source with conversion to phosphors may comprise a green light radiation source.

In one or more embodiments, the light radiation sources (e.g. B, R) other than said at least one light radiation source with conversion to phosphors can be direct emission light radiation sources.

In one or more embodiments, a method of using a lighting device as exemplified above can comprise selectively adjusting the filtering intensity (for example R_x) of said optical filter, either continuously or in steps.

In one or more embodiments, a method of using a lighting device as exemplified above may comprise selectively varying the intensity of the light radiation emitted by said at least one light radiation source with conversion to phosphors to compensate for the adjustment of the filtering intensity of said optical filter.

In one or more embodiments, selectively varying the intensity of the light radiation emitted by said at least one (G) source of light radiation with conversion to phosphors (S_pcg) can take place in at least one way selected from:

vary the intensity of the current fed to said at least one light radiation source with conversion to phosphors,

- modulating in pulse width modulation (e.g. PWM) the power supply of said at least one light radiation source with conversion to phosphors, and / or

- varying the light radiation emission surface of said at least one light radiation source with conversion to phosphors.

Without prejudice to the basic principles, the construction details and the embodiments may vary, even significantly, with respect to what is illustrated here purely by way of non-limiting example without thereby departing from the scope of protection.

This scope of protection is defined by the attached claims.

Claims (11)

CLAIMS 1. Lighting device (10), comprising: - a first (B), a second (R) and a third (G) electrically powered light radiation source with different emission fields to produce a combined illumination radiation, in which: at least one (G) of said light radiation sources (B, R, G) comprises a light radiation source with conversion to phosphors, and - said at least one light radiation source with conversion to phosphors (G) is coupled with a narrow band optical filter (14; 16) which filters (T_f) the light radiation (S_pcg) of said at least one light radiation source with conversion phosphor to a more saturated color point in the CIE 1931 color space. Illumination device according to claim 1, wherein said optical filter (14, 16) has a selectively variable filtering intensity (R_x). 3. Lighting device according to claim 2, wherein said optical filter comprises a planar element (14; 16) comprising portions (140, 141, 142, 143, 144; 160, 161, 162, 163, 164) with intensity of different filtering (R_x), said planar element being capable of relative movement with respect to said at least one light radiation source with phosphor conversion (G) to couple to said at least one light radiation source with phosphor conversion different portions selected among said portions (140, 141, 142, 143, 144; 160, 161, 162, 163, 164) with different filtering intensities (R_x). Lighting device according to any one of the preceding claims, wherein said first light radiation source (B) is selected from a blue light radiation source and a cyan light radiation source. Lighting device according to any one of the preceding claims, wherein said second light radiation source (R) is selected from a red light radiation source, an orange light radiation source and an amber light radiation source. Lighting device according to any one of the preceding claims, wherein said at least one light radiation source with phosphor conversion comprises a green (G), red or amber light radiation source. Lighting device according to any one of the preceding claims, wherein said at least one light radiation source with phosphor conversion comprises a green light radiation source (G). Lighting device according to any one of the preceding claims, wherein the light radiation sources (B, R) other than said at least one phosphor conversion light radiation source (G) comprise direct emission light radiation sources. 9. Process of using a lighting device according to any one of the preceding claims, comprising selectively adjusting the filtering intensity (R_x) of said optical filter (14; 16), continuously or in steps. 10. Process according to claim 9, comprising selectively varying the intensity of the light radiation (S_pcg) emitted by said at least one light radiation source with conversion to phosphors (G) to compensate for the adjustment of the filtering intensity (R_x) of said optical filter (14; 16). 11. Process according to claim 10, comprising selectively varying the intensity of the light radiation emitted by said at least one light radiation source with conversion to phosphors (G) in at least one way selected from: vary the intensity of the current fed to said at least one light radiation source with conversion to phosphors (G), modulating in pulse width modulation the power supply of said at least one light radiation source with conversion to phosphors (G), and / or - varying the light radiation emission surface of said at least one light radiation source with conversion to phosphors (G).