Light emitting module, a lamp, a luminaire and a method of illuminating an object

Abstract

A light emitting module (100), a lamp and a luminaire are provided. The light emitting module is for illuminating an object and comprises a first light emitting module (102) and a second light emitting module (104). The first light emitting module emits first light (L1). The first light has a color point of white light. The second light emitting element emits a peak of blue light (L2). The peak of blue light has a peak wavelength in a range from 440 nanometer to 470 nanometer and has a spectral width that is smaller than 70 nanometers, the spectral width being expressed as a full width half maximum value.

Claims

1. A light emitting module for illuminating an object, the light emitting module comprising: a first light emitting element comprising a first light emitter and a first luminescent element, the first light emitting element configured to emit a first light having a color point of white light, the first light emitter configured to emit a first blue light that is at least partially converted by the first luminescent element to a light of another color, wherein the first light represents a combination of the at least partially converted first blue light and any unconverted first blue light; a second light emitting element configured to emit a peak of second blue light, the peak of second blue light having a peak wavelength in a range from 440 nanometer to 470 nanometer and having a spectral width that is smaller than 70 nanometers, the spectral width being expressed as a full width half maximum value, and the peak of second blue light being combined with the first light to form crispy white light having a light emission spectrum having more blue light in the range from 440 nanometer to 470 nanometer than the white light, such that when the light emitting module illuminates the object, an effect of using brighteners in the object is realized.

2. The light emitting module according to claim 1, wherein the color point of the first light is substantially on a black body line, the combination of the first light and the peak of second blue light has a combined color point, the first light emitting element emits a first amount of energy of first light, the second light emitting element emits a second amount of energy of the peak of second blue light, and a ratio between the first amount of energy and the second amount of energy is selected to obtain a coordinate for the combined color point in an area enclosed by the black body line and a line defined by y=0.328+0.13x, in the CIEXYZ color space, and optionally, the x-coordinate of the combined color point is in a range from 0.376 to 0.445.

3. The light emitting module according to claim 1, wherein the first light has at least one of the following characteristics: color temperature in a range from 2000 Kelvin to 4000 Kelvin, and a color rendering index in a range from 80 to 100.

4. The light emitting module according to claim 1, wherein the first light emitter being configured to emit the first blue light having a peak wavelength in a spectral range from 440 nanometer to 460 nanometer, wherein the emitted light of the another color distribution and an emitted non-absorbed portion of the first blue light together form the first light, and the second light emitting element comprising a second light emitter.

5. The light emitting module according to claim 1, wherein the second light emitting element comprises a second luminescent element, wherein the second luminescent element comprises luminescent material being configured to absorb light emitted by the second light emitter and to convert the absorbed light towards the peak of second blue light.

6. The light emitting module according to claim 1, wherein the second light emitting element comprising a solid state light emitter.

7. The light emitting module according to claim 1, wherein the first light emitter is a solid state light emitter.

8. The light emitting module according to claim 1, wherein the light emitting module is configured to allow a switching off and on of the emission of the peak of second blue light independently of the switching off and on of the emission of the first light.

9. The light emitting module according to claim 1 comprising a third luminescent element and a third light emitter, wherein the third luminescent element and the third light emitter together form the first light emitting element and together form the second light emitting element, the third light emitter being configured to emit second blue light, the third luminescent element comprising luminescent materials being configured to absorb a portion of the second blue light and convert the absorbed blue light towards a further color distribution, wherein the light emitting module is configured to emit a mix of the further color distribution and, optionally, a non-absorbed portion of the second blue light, and the light emitted by the light emitting module has a spectral distribution which comprises the peak of second blue light and forms the first light if the peak of second blue light is not taken into account, optionally, the second blue light having a peak wavelength in between 400 nanometer and 460 nanometer.

10. The light emitting module according to claim 9, wherein the third luminescent element comprises a particular luminescent material being configured to emit the peak of blue light.

11. The light emitting module according to claim 10, wherein the third luminescent element further comprises a mix of further luminescent materials, wherein the amounts of the further luminescent materials and the composition of the mix of the further luminescent materials is configured to convert the absorbed second blue light towards light that forms together with the optional non-absorbed portion of the second blue light the first light.

12. The light emitting module according to claim 11, wherein the mix of further luminescent materials comprises a plurality of different types of particles showing quantum confinement and having at least in one dimension a size in the nanometer range, each type of particles is configured to emit a different light emission when being excited, wherein the different types of particles are selected to obtain a combination of the different light emissions forming a substantially continuous spectral distribution from at least 470 nanometer to 700 nanometer.

13. A lamp comprising the light emitting module according to claim 1.

14. A luminaire comprising a light emitting module according to claim 1.

15. A method of illuminating an object, the method comprises: emitting first light having a color point of white light towards the object, emitting a peak of blue light towards the object, the peak of blue light has a peak wavelength in a range from 440 nanometer to 470 nanometer and has a spectral width that is smaller than 70 nanometers, the spectral width being expressed as a full width half maximum value, and the peak of blue light is combined with the white light to form crispy white light having a light emission spectrum having more blue light in the range from 440 nanometer to 470 nanometer than the white light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the drawings:

(2) FIG. 1a schematically shows an embodiment of a light emitting module,

(3) FIG. 1b schematically shows how in the light emitting module light emission spectra are combined to obtain a light emission spectrum for illuminating objects to obtain a crispy look,

(4) FIG. 2 schematically shows several embodiments of the light emitting modules,

(5) FIG. 3a schematically shows a further embodiment of a light emitting module,

(6) FIG. 3b schematically shows how in the light emitting module of the further embodiment light emission spectra are combined to obtain a light emission spectrum for illuminating objects to obtain a crispy look,

(7) FIG. 4a schematically shows an embodiment of a lamp,

(8) FIG. 4b schematically shows an embodiment of a luminaire,

(9) FIG. 5 schematically shows an embodiment of a method of illuminating an object, and

(10) FIGS. 6a and 6b schematically present in a CIEXYZ color space areas for a combined color point of the light emission of the light emitting module.

(11) It should be noted that items denoted by the same reference numerals in different Figures have the same structural features and the same functions, or are the same signals. Where the function and/or structure of such an item have been explained, there is no necessity for repeated explanation thereof in the detailed description.

(12) The Figures are purely diagrammatic and not drawn to scale. Particularly for clarity, some dimensions are exaggerated strongly.

DETAILED DESCRIPTION

(13) A first embodiment is shown in FIG. 1a. FIG. 1a schematically shows an embodiment of a light emitting module 100. The light emitting module 100 comprises a first light emitting element 102 that is capable of emitting first light L1. The first light L1 has a color point that is substantially on a black body line in a color space or close to the black body line. In other words, the first light L1 is white light. The color point of the white light is within 15 SDCM (Standard Deviation of Color Matching) from the black body line during operation of the light emitting element, even more especially within 10 SDCM, yet even more especially within 5 SDCM from the black body line. The light emitting module 100 further comprises a second light emitting element 104 that is configured to emit an peak of blue light L2. The peak of blue light L2 has a peak wavelength that is in a range from 440 nanometer to 470 nanometer and the peak has a spectral width that is smaller than 70 nanometer (when being expressed as a Full Width Half Maximum (FWHM) value). Optionally, the peak wavelength of the peak of blue light L1 is in a range from 445 to 465 nanometer. Optionally, the FWHM value is smaller than 60 nanometer, or smaller than 50 nanometer or even smaller than 40 nanometer. The light emitting module 100 emits a mix of white light L2 and the peak of blue light L2.

(14) FIG. 1b schematically shows how in the light emitting module 100 light emission spectra 152, 154 are combined to obtain a light emission spectrum 156 for illuminating objects to obtain a crispy look. The light emission spectrum 152 represents the light emission by the first light emitting element 102. The light emission spectrum 154 represents the light emission by the second light emitting element 104. As is seen, the light emission spectrum 154 is a relatively small peak of light which as a peak wavelength .sub.p which has a value in the range from 440 nanometer to 470 nanometer. The full width half maximum (FWHM) value of the peak (measured at half the maximum intensity I.sub.m/2 of the peak intensity I.sub.m) is smaller than 70 nanometer.

(15) An insight of the inventors is that when an emission spectrum of white light 152 is combined with the peak of blue light L2 (as shown in light emission spectrum 154), one can use light of the obtained light emission spectrum 156 to illuminate objects such that the objects look more crispy, more fresh, more appealing or, when it relates to a white object, it looks more white to the human naked eye. This effect of a more crispy or more white looking object is obtained without introducing brighteners in the objects.

(16) FIG. 2 presents several alternative embodiments of the light emitting module 100 of FIG. 1.

(17) Light emitting module 200 comprises a first light emitter 202 which is provided by a first luminescent element 203. The light that is generated by the combination of the first light emitter 202 and the first luminescent element 203 is the first light L1 (with a color point of white light). The first light emitter 202 may emit, for example, blue light that is partially of fully converted by luminescent material of the first luminescent element 203 towards light of one or more other colors. When not all blue light (that is emitted by the first light emitter 202) is converted towards light of another color, a remaining portion of the blue light emitted by the first light emitter 202 may also be emitted into an ambient of the light emitting module 200. The combination of this optional remaining portion of blue light and the light that is emitted by the luminescent material of the first luminescent element forms the first light L1 having a color point of white light. The light emitting module 200 further comprises a second light emitter 204 which is configured to emit the peak of blue light L2in other words, the second light emitter 204 directly emits the peak of blue light L2 without using any specific conversion of light. The first light emitter 202 and the second light emitter 204 may be provided on a support layer 209. The support layer 209 may be a good thermal conductor which conducts heat away from the first light emitter 202 and the second light emitter 204. Although the first luminescent element 203 is drawn in FIG. 2 as an element that is directly provided on top of the first light emitter 202, there may be (an air) gap present between the first luminescent element 203 and the first light emitter 202 (such that the first luminescent element 203 is arranged in a vicinity configuration or in a remote configuration depending on a width of the gap, which width may be, 0.1-0.5 mm or more than 1 cm, respectively).

(18) Light emitting module 210 is similar to the light emitting module 200, however, it comprises another second light emitter 214 which is provided with a second luminescent element 215. The another second light emitter 214 emits light towards the second luminescent element 215 and luminescent material provided in the second luminescent element 215 converts the light emitted by the another second light emitter 214 towards the peak of blue light L2. The light emitted by the second light emitter 214 may be Ultraviolet (UV) light, may be violet light or may be blue light with a peak wavelength below the peak wavelength of the peak of blue light L2. In an embodiment, the combination of the second luminescent element 215 and the second light emitter 214 is arranged such that no UV or no violet light is emitted into an ambient of the light emitting module 210.

(19) Light emitting module 220 is similar to light emitting module 200, however, instead of the support layer 209 is provided a box-shaped support member 221 which comprises at at least one side a light exit window 222. An inner surface 223 of the box-shaped support member 221 may be reflective white such that light which impinges on the inner surface 223 is well-reflected, not absorbed and is better mixed by the light emitting module 220.

(20) Light emitting module 230 is similar to light emitting module 220, however, an additional light diffusing element 236 is provided at the light exit window of the box-shaped support member 221. A diffusing element 236 may be a layer of glass or of a light transmitting synthetic material on which or in which scatting particles are provided. Diffusing the light results in a more homogeneous light output.

(21) Light emitting module 240 is similar to light emitting module 220, but another box-shaped support member 241 is provided which comprises a reflector for shaping a light beam emitted by the light emitting module 240 in a specific shape.

(22) Light emitting module 250 is similar to light emitting module 240 and comprises for each one of the light emitters 202, 204 separate power connectors 258, 259 for providing power separately to each one of the light emitters 202, 204. The power connectors 258, 259 are, for example provided at an outer surface of the light emitting module 250 that faces away form a light exit window of the light emitting module 250. The power connectors 258, 259 allow the separate driving of the first light emitter 202 and the second light emitter 204 and, thereby, one may, for example, implement that the second light emitter 204 can be switched off when the crispy look of the illuminated object is not required.

(23) The first light emitter 202, the second light emitter 204 and the another second light emitter 214 may be solid state light emitters. An example of a solid state light emitter is a Light Emitting Diodes. Other examples are an Organic Light Emitting Diode or a laser diode. The laser diode can be used to generate the peak of blue light L2. When a laser diode is used, the light emitting module comprises preferably a light diffusing element such as light diffusing element 236.

(24) It is further to be noticed that, in an embodiment, the first luminescent element 203 comprises a plurality of luminescent materials such that the combination of the light emitted by the plurality of luminescent materials (optionally combined with a remaining non-absorbed portion of the light emitted by the first light emitter 202) is the first light L1.

(25) In the above, one first light emitter 202 and one second light emitter 204 (or one another second light emitter 214) are drawn. The embodiments are not limited to such a low number of light emitters. The light emitting modules 200, 210, 220, 230, 240, 250 may comprises a plurality of first light emitters 202 each provided with a first luminescent element 203. The light emitting modules 200, 210, 220, 230, 240, 250 may comprise a plurality of second light emitters 204. The light emitting modules 200, 210, 220, 230, 240, 250 may comprises a plurality of another second light emitters 214 each provided with the second luminescent element 215. In an embodiment, a ratio between the number of first light emitters 202 and the number of second light emitters 204 (or, alternatively, the another second light emitters 214) is at least 1, or at least 2, or at least 3. In general, it is advantageous when more white light is emitted than the amount of light that is emitted in the peak of blue light, because otherwise it might result in illuminating an object with blue light instead of light that provides a crispy effect.

(26) The first luminescent element 203 and the second luminescent element 215 may comprise at least one of the follow types of luminescent materials: an inorganic phosphor, an organic phosphor, for example, based on perylene derivatives, or particles showing quantum confinement and have at least in one dimension a size in the nanometer range. Showing quantum confinement means that the particles have optical properties that depend on the size of the particles. Examples of such materials are quantum dots, quantum rods and quantum tetrapods. The first luminescent element 203 and the second luminescent element 215 may also comprise a mix of the above discussed materials.

(27) FIG. 3a schematically shows a further embodiment of a light emitting module 300. The light emitting module 300 comprises one type of a light emitter 302 which emits third light L3. Optionally, the third light L3 is blue light and has a peak wavelength in a range from 440 nanometer to 460 nanometer. In FIG. 3 it has been drawn that only a single third light emitter 302 is provided, but a plurality of third light emitters 302 may be provided to emit a larger amount of third light L3. The third light L3 is emitted towards a third luminescent element 304. The third luminescent element 304 comprises one specific luminescent material 308 that absorbs some of the third light L3 and converts the absorbed light towards the peak of blue light L2. The third luminescent element 304 further comprises a mix of other luminescent materials 306 which together emit (optionally, in combination with a non-absorbed portion of the third light L3) a light emission that corresponds to the first light L1 (and, thus, white light). In comparison with previous embodiment, a plurality of luminescent material 306, 308 generates the first light L1 and the peak of blue light L2. This is illustrated in FIG. 3b. FIG. 3b schematically shows how in the light emitting module 300 light emission spectra 352, 354 are combined to obtain a light emission spectrum 356 to obtain a crispy look of illuminated objects. For example, when the third luminescent element 304 comprises different types of Quantum Dots which all have a slightly different size (and/or are of different materials), they each may emit a slightly shifted peak of light and neighboring peaks of light may slightly overlap such that, about a continuous light emission is obtained (as shown in light emission spectrum 352). Another Quantum Dot may be added as well which has a specific size and a specific material that is configured to emit the peak of blue light as is shown in light emission spectrum 354. Together, the light emissions 352 and 354 result in the light emission spectrum 356. When an object is illuminated by the light emission spectrum 356, the object has a crispy, more fresh, more white appearance when seen through the human naked eye.

(28) The light emission spectrum 352 is an example of a spectrum which may be generated by the mix of other luminescent materials 306 (optionally, the light emission spectrum 352 also comprises a non-absorbed portion of the third light L3). As discussed above, such light emission spectrum 352 may be obtained by combining several slightly different Quantum Dots. As discussed above, Quantum Dots are particles showing quantum confinement and have at least in one dimension a size in the nanometer range, which means that the particles have optical properties that depend on the size of the particles. Thus, the mix of other luminescent materials 306 may comprises several Quantum dots of different sizes. It is to be noted that other particles that show quantum confinement are quantum rods of quantum tetrapods and that, instead of or in addition to Quantum Dots, these materials could be present in the mix of other luminescent materials 306. It is to be noted that, in other embodiments, other mixes of luminescent materials can be used to generate (optionally, together with an emitted non-absorbed portion of the third light L3) the first (white) light L1. For example, the mix of other luminescent materials 306 may also comprise one of: inorganic phosphors, or organic phosphors (such as, for example, perylene derivatives).

(29) Examples of luminescent materials comprises particles showing quantum confinement and have at least in one dimension a size in the nanometer range. This means, for example, that, if the particles are substantially spherical, their diameter is in the nanometer range. Or, this means, for example, if they are wire-shaped, that a size of a cross-section of the wire is in one direction in the nanometer range. A size in the nanometer range means that their size is at least smaller than 1 micrometer, thus, smaller than 500 nanometer, and larger or equal to 0.5 nanometer. In an embodiment, the size in one dimension is smaller than 50 nanometer. In another embodiment the size in one dimension is in the range from 2 to 30 nanometer. In embodiments of the invention the luminescent materials may comprise quantum dots. Quantum dots are small crystals of semiconducting material generally having a width or diameter of only a few nanometers. When excited by incident light, a quantum dot emits light of a color determined by the size and material of the crystal. Light of a particular color can, therefore, be produced by adapting the size of the dots. Most known quantum dots with emission in the visible range are based on cadmium selenide (CdSe) with shell such as cadmium sulfide (CdS) and zinc sulfide (ZnS). Cadmium free quantum dots such as indium phosphide (InP), and copper indium sulfide (CuInS.sub.2) and/or silver indium sulfide (AgInS.sub.2) can also be used. Quantum dots show very narrow emission band and thus they show saturated colors. Furthermore, the emission color can easily be tuned by adapting the size of the quantum dots. Any type of quantum dot known in the art may be used in the present invention, provided that it has the appropriate wavelength conversion characteristics. However, it may be preferred for reasons of environmental safety and concern to use cadmium-free quantum dots or at least quantum dots having a very low cadmium content.

(30) FIG. 4a schematically shows an embodiment of a lamp 400. The lamp 400 has, for example, a shape of a traditional incandescent lamp and is, as such, a retro-fit incandescent lamp. The lamp may comprise, for example, one or more light emitting modules (not shown) according to previously discussed embodiments of the light emitting modules.

(31) FIG. 4b schematically shows an embodiment of a luminaire 450. The luminaire 450 comprises, for example, one or more light emitting modules (not shown) according to previously discussed embodiments of the light emitting modules. In another embodiment, the luminaire 450 comprises one or more lamps (not shown) according to the embodiment of FIG. 4a.

(32) FIG. 5 schematically shows an embodiment of a method 500 of illuminating an object. The method 500 comprises the stages of: i) emitting 502 first light having a color point of white light, ii) emitting 504 an peak of blue light, the peak of blue light has a peak wavelength in a range from 440 nanometer to 470 nanometer and has a spectral width that is smaller than 70 nanometers when being expressed as a full width half maximum value.

(33) The lamp, the luminaire and the above discussed method of illuminating an object have similar embodiment with a similar effect as the embodiment of the light emitting module.

(34) FIGS. 6a and 6b schematically present in a CIEXYZ color space areas for a combined color point of the light emission of the light emitting module. In FIG. 6a a first chart 600 of the CIEXYZ color space is presented. In the CIEXYZ color space is drawn the black body line 602. The first light emitting element emits first light that has a color point on the black body line. The combination of the first light and the peak of blue light has a combined color point. Thus, the combined color point is the color point of the light emitting module as a whole. The first light emitting element emits a first amount of energy of first light, the second light emitting element emits a second amount of energy of the peak of blue light, and a ratio between the first amount of energy and the second amount of energy is selected to obtain a coordinate for the combined color point in the CIEXYZ color space in an area 604 enclosed by the black body line 602 and a line 606 defined by y=0.328+0.13x. Within area 604 the crispy effect is well visible to the human naked eye. The area 604 may be further limited such that the crispy effect is even better visible. This is shown in chart 650 of FIG. 6b. In FIG. 6b the area 654 in which the combined color point may be located is further limited by a first line 660 defined by x-coordinate 0.376 and a second line 662 defined by x-coordinate 0.445. Thus, the area 654 is an area in between the black body line, 602, the line 606 defined by y=0.328+0.13x, a line 660 defined by x=0.376 and a line 662 defined by x=0.445.

(35) It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims.

(36) In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb comprise and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. The article a or an preceding an element does not exclude the presence of a plurality of such elements. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.