IMPROVED THERMAL MANAGEMENT IN LASER-BASED LIGHTING USING A TRUNCATED BALL LENS

Abstract

The invention provides a system (1000) comprising (i) a light emitting layer (100), (ii) a first lens (200), and a thermal conductor (300), wherein: —the light emitting layer (100) comprises luminescent material (150), wherein the luminescent material (150) is configured to generate luminescent material light (151) upon excitation with light source light (11) from a first light source (10) comprising a wavelength where the luminescent material (150) can be excited, wherein the light emitting layer (100) comprises a light receiving area (110) having a light receiving area size A.sub.1; —the first lens (200) comprises a truncated ball shaped lens (250) having a curved lens surface (215) having a radius R.sub.0 relative to a central point (O), and a planar lens surface (225) configured at a first distance d.sub.1 from the central point (O), wherein the planar lens surface (225) has a planar lens surface area size A.sub.2, wherein the first lens (200) comprises a lens material (205) having an index of refraction n at a predetermined wavelength λ.sub.1 selected from a wavelength in the UV, visible, and infrared, wherein d.sub.1=x*R.sub.0/n, wherein 0.9≤x≤1.1, wherein the planar lens surface area size A.sub.2 is larger than the light receiving area size A.sub.1, wherein the first lens (200) is configured to concentrate light received at the curved lens surface (215) to provide light emanating from the planar lens surface (225), wherein the planar lens surface (225) is directed to the light receiving area (110); and —the thermal conductor (300) is configured in thermal contact with one or more of the light emitting layer (100) and the first lens (200).

Claims

1. A system comprising (i) a light emitting layer, (ii) a first lens, and a thermal conductor, wherein: the light emitting layer comprises a luminescent material, wherein the luminescent material is configured to generate luminescent material light upon excitation with light source light from a first laser light source comprising a wavelength λ.sub.1 where the luminescent material can be excited, wherein the light emitting layer comprises a light receiving area having a light receiving area size A.sub.1; the first lens comprises a truncated ball shaped lens having a curved lens surface having a radius R.sub.0 relative to a central point, and a planar lens surface configured at a first distance d.sub.1 from the central point, wherein the planar lens surface has a planar lens surface area size A.sub.2, wherein the first lens comprises a lens material having an index of refraction n at a predetermined wavelength λ.sub.1 selected from a wavelength in the UV, visible, and infrared, wherein d.sub.1=x*R.sub.0/n, wherein 0.9≤x≤1.1, wherein the planar lens surface area size A.sub.2 is larger than the light receiving area size A.sub.1, wherein the first lens is configured to concentrate light received at the curved lens surface to provide light emanating from the planar lens surface, wherein the planar lens surface is directed to the light receiving area; and the thermal conductor is configured in thermal contact with one or more of the light emitting layer and the first lens, the system further comprising the first laser light source configured to generate the first light source light, wherein the curved lens surface is configured in a light receiving relationship with the first laser light source and further comprising a second light source configured to generate second light source light having a spectral power distribution different from or equal to the first light source light and different from the luminescent material light, wherein the system is configured to generate lighting system light comprising the luminescent material light and wherein in an operation mode of the system the lighting system light further comprises the second light source light.

2. The system according to claim 1, wherein the light receiving area is configured at an average second distance d.sub.2a selected from the range of 1-10 μm from the planar lens surface.

3. The system according to claim 1, wherein the light receiving area is configured at an average second distance d.sub.2a selected from the range of <1 μm from the planar lens surface.

4. The system according to claim 1, wherein the first lens has an external surface comprising the curved lens surface and the planar lens surface, wherein the first lens is configured such that rays of luminescent material light entering the first lens via the planar lens surface cannot directly reach a first external surface part of the external surface, wherein the thermal conductor is in thermal contact with the first lens via the first external surface part.

5. The system according to claim 1, wherein the first lens comprises a ball part comprising the curved lens surface and a cylindrical part comprising the planar lens surface, wherein the cylindrical part has cylindrical shape or a tapered cylindrical shape, wherein the thermal conductor is in thermal contact with the cylindrical part but not in physical contact with the planar lens surface.

6. The system according to claim 1, wherein the lens material has an index of refraction n at 589.3 nm selected from the range of 1.4-1.9, wherein the lens material comprises one or more of sapphire, MgO, CaF.sub.2, quartz, BaF.sub.2, M.sub.3A.sub.5O.sub.12 garnet, ALON, MgAl.sub.2O.sub.4, and MgF.sub.2, wherein the thermal conductor comprises a heat sink, wherein the light emitting layer comprises a ceramic body comprising the luminescent material, and wherein 1.2≤A.sub.2/A.sub.1≤9.

7. The system according to claim 1, wherein the light emitting layer comprises a non-light receiving face, wherein the non-light receiving face is not configured in a light receiving relationship with the first lens, wherein the thermal conductor is in physical contact with at least part of the non-light receiving face of the light emitting layer.

8. The system according to claim 1, further comprising a control system, configured to control the lighting system light by controlling the first laser light source and the second light source.

9. The system according to claim 1, wherein the first light source comprises plurality of solid state light sources which together are configured to generate the first light source light, and wherein the lens material comprises sapphire.

10. The system according to claim 1, further comprising a second lens, comprising an aspherical condenser lens, configured upstream from the first lens as seen from the first light source.

11. The system according to claim 1, further comprising dichroic beam splitter optics, wherein the first light source is configured to provide the first light source light along a first optical path in a first direction via the beam splitter optics to the curved lens surface of the first lens, and wherein the beam splitter optics are configured to direct luminescent material light received by the dichroic beam splitter optics along a second optical path not coinciding with the first optical path in a second direction.

12. The system according to claim 1, wherein the system is configured to provide in an operation mode white system light.

13. A lighting device comprising (i) the lighting system according to claim 1 and (ii) optionally further optics for shaping and/or modifying the system light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0089] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

[0090] FIGS. 1a-1d schematically depict some aspects and embodiments of the system and the first lens;

[0091] FIGS. 2a-2c schematically depict some embodiments and aspects, also in relation to an alternative solution (see FIG. 2b); and

[0092] FIGS. 3a-3e schematically depict some further embodiments (and aspects).

[0093] The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0094] FIG. 1a schematically depicts a system 1000 comprising (i) a light emitting layer 100, (ii) a first lens 200, and a thermal conductor 300. More precisely, part of the system is shown, as the lens is not fully depicted.

[0095] The light emitting layer 100 comprises luminescent material 150, wherein the luminescent material 150 is configured to generate luminescent material light 151 upon excitation with light source light 11 from a first light source (not shown), wherein the light source light comprises a wavelength where the luminescent material 150 can be excited. The light emitting layer 100 is embedded in a support but could also be provided on a support.

[0096] Here, the support is indicated with reference 300, as the support can have the function of a thermal conductor. The thermal conductor 300 is configured in thermal contact with one or more of the light emitting layer 100 and the first lens 200; here with essentially only the light emitting layer 100. The thermal conductor may include one or more fins 320, especially a plurality of fins 320. The thermal conductor comprises a thermally conductive material 301. The thermal conductor 300 may especially comprises a heat sink.

[0097] The light emitting layer 100 comprises a light receiving area 110 having a light receiving area size A.sub.1.

[0098] The first lens 200 comprises a truncated ball shaped lens 250. The first lens comprises a planar lens surface 225. The planar lens surface 225 is directed to the light receiving area 110. The planar lens surface 225 has a planar lens surface area size A.sub.2.

[0099] As schematically depicted, the planar lens surface area size A.sub.2 is larger than the light receiving area size A.sub.1 (see also FIG. 1b). The light receiving area 110 is configured at a second distance d.sub.2 selected from the range of 1-10 μm from the planar lens surface 225 (see further also FIG. 1c), though the light receiving area 110 and the planar lens surface 225 may also essentially have a zero distance over the overlapping areas.

[0100] The first lens 200 comprises a lens material 205 having an index of refraction n at a predetermined wavelength λ.sub.1 selected from a wavelength in the UV, visible, and infrared. The lens material 205 may e.g. comprises one or more of sapphire, MgO, CaF.sub.2, quartz, BaF.sub.2, A.sub.3B.sub.5O.sub.12 garnet (A e.g. one or more of Y, Gd, and Lu; B e.g. one or more of Al and Ga, especially at least or essentially only Al), ALON, MgAl.sub.2O.sub.4, and MgF.sub.2. For instance, in embodiments the lens material 205 may be sapphire.

[0101] Reference 230 indicates the external surface of the first lens. The external surface of the lens comprises amongst others the planar lens surface 225.

[0102] The light emitting layer 100 comprises a non-light receiving face 120, wherein the non-light receiving face 120 is not configured in a light receiving relationship with the first lens 200, wherein the thermal conductor 300 is in thermal contact, especially in physical contact with at least part of the non-light receiving face 120 of the light emitting layer 100. The non-light receiving face 120 may e.g. comprise an edge face and/or a bottom face.

[0103] FIG. 1a schematically depicts a cross-section, e.g. with the cross-sectional plane parallel to an optical axis OA of the first lens 200. FIG. 1b schematically depicts a cross-section perpendicular to the cross-section of FIG. 1a. Assuming a circular support and a circular light emitting layer 100, the two solid circles in the middle indicate these respectively, with the smaller solid circle indicating the light receiving area 110, with area size A.sub.1 (see detail on the left), and the larger solid circle indicating the support, which is here an embodiment of the thermal conductor 300. The dashed circle in the middle, is in fact not in the same plane, as the dashed circle indicates the planar lens surface 225 of the first lens, having a planar lens surface area A.sub.2 (see detail on the right). The planar lens surface area size A.sub.2 is especially larger than the light receiving area size A.sub.1. For instance, 1.2≤A.sub.2/A.sub.1≤9.

[0104] The planar lens surface 225 and the light emitting layer 100 may be configured at a second distance d.sub.2 from each other, may essentially entirely be in physical contact, or may have parts that have physical contact and parts that do not have physical contact. The latter embodiment may e.g. be achieved when one of the phases has some surface roughness. Here, by way of example, the light emitting layer 100, such as a ceramic body, has surface roughness. Therefore, the light receiving area 110 may be configured at an average second distance d.sub.2a selected from the range of 1-10 μm from the planar lens surface 225. As indicated above, however, the average distance may also be smaller: the light receiving area 110 may be configured at an average second distance d.sub.2a selected from the range of <1 μm from the planar lens surface 225.

[0105] FIG. 1d schematically depicts an embodiment of the truncated ball lens 250 as embodiment of the first lens 200. Here, R.sub.0 is the radius of the ball, and n is the index of refraction. Reference O indicates the center of the virtually non truncated ball, and is at a distance R.sub.0 of a curved lens surface 215 (i.e. the remaining part of the ball). Reference O.sub.1 indicates the center of the plan lens surface 225, which is configured at first distance d.sub.1 from the center O. Distance d.sub.1 is defined as d.sub.1=R.sub.0/n. However, there may be some deviation therefrom.

[0106] Hence, the first lens 200 comprises a truncated ball shaped lens 250 having a curved lens surface 215 having a radius R.sub.0 relative to a central point O, and a planar lens surface 225 configured at a first distance d.sub.1 from the central point O, wherein, wherein d.sub.1=x*R.sub.0/n, wherein 0.9≤x≤1.1

[0107] The focal length of the ball is indicated as R.sub.2 and is defined as R.sub.2=(n+1)*R.sub.0.

[0108] The focal point of the ball is indicated as z.sub.FP and is defined as z.sub.FP=d+R.sub.0-R.sub.2.

[0109] The radius entrance R.sub.in is defined as R.sub.in=R.sub.0/n*(SQRT(n.sup.2−1)).

[0110] Reference 230 indicates the external surface of the first lens, which comprises the planar lens surface 225 and the curved lens surface 215.

[0111] Reference OA indicates an optical axis (here of the first lens 200).

[0112] FIG. 2a schematically depicts an embodiments of the system 1000, wherein the system is also a lighting system, and wherein the (lighting) system 1000 is configured to generate lighting system light.

[0113] As schematically depicted, the first lens 200 is configured to concentrate first light source light 11 received at the curved lens surface 215 to provide (focused) first light source light 11 emanating from the planar lens surface 225, to the light receiving area 110 of the light emitting layer 100.

[0114] FIG. 2a therefor schematically depicts an embodiment and variants of the system 1000 comprising the light emitting layer 100, the first lens 200, and the thermal conductor 300.

[0115] The light emitting layer 100 comprises luminescent material 150, wherein the luminescent material 150 is configured to generate luminescent material light 151 upon excitation with light source light 11 from the first light source 10 comprising a wavelength where the luminescent material 150 can be excited. The light emitting layer 100 comprises the light receiving area 110 having a light receiving area size A.sub.1. The first lens 200 comprises the truncated ball shaped lens 250 having the curved lens surface 215 and the planar lens surface 225 as defined above. The planar lens surface 225 has a planar lens surface area size A.sub.2. The first lens 200 is configured to concentrate light received at the curved lens surface 215 to provide (focused) light emanating from the planar lens surface 225. As schematically shown, the planar lens surface 225 is directed to the light receiving area 110.

[0116] Especially, the system 1000 may be configured to generate lighting system light 1001, wherein the lighting system light 1001 comprises the luminescent material light 151.

[0117] The thermal conductor 300 is configured in thermal contact with one or more of the light emitting layer 100 and the first lens 200. Here, the thermal conductor in in thermal contact, or even in physical contact, with both the light emitting layer 100 and the first lens 200, see lens holder(s) 50.

[0118] Hence, the embodiment of the system 1000 schematically depicted in FIG. 2a further comprises the first light source 10 configured to generate the first light source light 11. As schematically depicted, the curved lens surface 215 is configured in a light receiving relationship with the first light source 10.

[0119] In embodiments, the first light source 10 comprises plurality of solid state light sources 14, such as lasers, which together are configured to generate the first light source light 11. A (fourth) beam shaping element 3200 may be used to shape the light source light 11 in the right beam shape. Reference 15 indicates a concentrator, which is here an elongated rod at which nose the light of the plurality of light source escapes as concentrated beam of the light of the plurality of solid state light sources 14, such as lasers.

[0120] In embodiments of the system 1000, the system may further comprise a second lens 1200, comprising an aspherical condenser lens 1250, configured upstream from the first lens 200 as seen from the first light source 10. Further, the system 1000 may in embodiments further comprise a third lens 2200 for further beam shaping of the lighting system light 1001, such as downstream of the beam splitter optics 400 (see further below). The third lens 2200 may be a relay lens to create a focus further on the optical system or a projection lens to focus on a screen far away.

[0121] In embodiments of the system 1000, the system 1000 may further comprise dichroic beam splitter optics 400. In such embodiments, the first light source 10 may (thus) be configured to provide the first light source light 11 of a first wavelength along a first optical path 51 in a first direction via the dichroic beam splitter optics 400 to the curved lens surface 215 of the first lens 200, and the dichroic beam splitter optics 400 may be configured to direct luminescent material light 151 of a second wavelength received by the beam splitter optics 400 along a second optical path 52 not coinciding with the first optical path 51 in a second direction. The second wavelength may be identical to the first wavelength.

[0122] Essentially all first light source light 11 may be converted and absorbed by the luminescent material 150. Hence, it may be desirable to add further light to the system light 1001 in addition to the luminescent material light 151. In this way, e.g. the color point of visible light may be tuned, and the color rendering index of visible light may be improved. In case of controllable light sources, such as with control system 30, the spectral properties of the system light 1001 may also be controlled.

[0123] Hence, in embodiments the system 1000 may further comprise a second light source 20 configured to generate second light source light 21 having a spectral power distribution equal to or different from the first light source light 11 and different from the luminescent material light 151. In an operation mode of the system 1000 the system light 1001 further comprises the second light source light 21. Hence, in an operation mode, the control system may impose on the system that the system light 1001 further comprises the second light source light 21. In a specific embodiment, the system 1000 is configured to provide in an operation mode white system light 1001. In such embodiments, the luminescent material 150 and the optional second light source 20 are configured to generate visible luminescent material light 151 and visible second light source light 21, respectively.

[0124] As schematically depicted in the embodiment of the system of FIG. 2a, the second light source 20 may be configured to provide the second light source light 210 along a third optical path 53 via the beam splitter optics 400 in the second direction. This third optical path may coincide with the second optical path downstream of the beam splitter optics 400.

[0125] FIG. 2a also shows an embodiment and variants a lighting device 1 comprising (i) the lighting system 1000 according to any one of the preceding claims and (ii) optionally further optics for shaping and/or modifying the system light 1001. The dashed line surrounding the elements of the system 1000 may e.g. be considered a housing of the lighting device 1. Reference 3 indicates an opening in the housing for escape of the lighting system light 1001 to the external of the device 1 (or system 1000).

[0126] A possible architecture for e.g. a laser-based lighting system (for instance for GOBO (“goes before optics” or “goes between optics”) applications), with a reflective phosphor may comprise a pump laser, a lens, a dichroic beam splitter 1, and a ceramic phosphor. For instance, light from one or more blue pump lasers may be mixed in a mix rod and collimated with a lens. After passing a dichroic beam splitter the pump light is focused onto the ceramic phosphor with e.g. a tandem of condenser lenses. The converted light is collected by the same condenser lenses and directed by the dichroic mirror towards the exit of the lighting system.

[0127] It appears, however, that lenses are not perfectly transparent and may absorb a little light. The power density of the blue pump light inside the second (smaller) condenser lens can be so high that fracture occurs due to thermally induced stresses and the limited thermal conductivity of the lens. Hence, thermally induced stresses in the condenser lens may occur which may lead to damage, fracture, or even explosion of the lens. Further, it also appears that the image quality of the converted light beam at a Gobo of the lighting system may not be sufficiently high due to spherical aberrations in the condenser lenses. Further, high quality aspherical condenser lenses may be relatively expensive.

[0128] Referring to FIGS. 2b and 2c, by using a condenser lens e.g. from sapphire an improved thermal management may be accomplished because of higher thermal conductivity of sapphire (˜34 W/mK versus ˜1 W/mK for glass) and less optical absorption. By applying a truncated ball lens as the second condenser lens a system without spherical aberration may be accomplished, for instance resulting in a better spot quality at the Gobo gate. The manufacturing of a truncated ball lens may be less complex than that of a high-quality aspherical lens. This may also improve reliability.

[0129] Referring to FIG. 2b, in an alternative solution, two condenser lenses may be applied. This combination of optics in FIG. 2b may lead to a relatively large aberration.

[0130] Referring to FIG. 2c (see also FIG. 2a), the second (small) condenser lens (from FIG. 2b) is replaced by a truncated ball lens made from sapphire (or other material listed herein). Especially, the ball lens is truncated at a position d=R.sub.0/n, where R.sub.0 is the radius and n the refractive index of the ball. Such solution may essentially have no spherical aberration.

[0131] The (air) gap between phosphor and lens may be relatively small, such as 1-10 μm. A smaller air gap favors an improved heat flow from the phosphor through the lens towards the sides. As can be seen from the figures there is ample room to mount the ball lens onto a further heat sink (not shown): the light only passes through the center part of the ball lens and not through the rim.

[0132] Optionally the shape of the ball lens can be adapted to improve heat conduction by shortening the path to the heat sink and to improve the contact area with the heat sink, as detailed in the following embodiments.

[0133] With the thermal conductivity of sapphire of 34.6 W/mK the estimate of thermal resistance of a 10 mm.sup.2 area and a typical sapphire thickness dS are R_th=3 dS [K/W], so for a 10 mm typical distance the resistance would be 30 K/W. Reducing the distance dS to a few mms is thus much worthwhile.

[0134] Optionally the truncated side of the ball lens in the area around the converter element is mounted in thermal contact with a heat sink, which is enabled by the fact that this surface is optically inactive. In this way a very short thermal path is realized with the minimum possible thermal resistance. Various thermal interface materials could be used, such as preferably phase change materials. A schematic drawing (cross section) is shown in FIG. 3a.

[0135] FIG. 3a schematically depicts an embodiment of thermo-mechanical interfacing of the truncated ball lens around the converter towards the heat sink.

[0136] It may be preferable to have the thermal and mechanical function integrated, as shown in FIG. 3a, but it is possible as well to separate these two functions and realize the mechanical alignment independently.

[0137] Reference 300 refers to the thermal conductor, which may comprise a heatsink 315. Further, the thermal conductor may also comprise thermally conductive intermediate material, such as a thermally conductive glue. The intermediate material for thermal coupling is indicated with reference 316.

[0138] Referring to FIGS. 3b-3e, the first lens 200 may comprise a ball part 210 comprising the curved lens surface 215, and a cylindrical part 220 comprising the planar lens surface 225, wherein the cylindrical part 220 has cylindrical shape or a tapered cylindrical shape, wherein the thermal conductor 300 is in thermal contact with the cylindrical part 220 but not in physical contact with the planar lens surface 225.

[0139] Optionally the shape of the ball lens is adapted in the optically non-active areas to enable suitable mounting and good thermal contact to transfer the heat generated inside the lens due to the absorption of light in the lens. One configuration is the combination of a half-sphere with a cylindrical part. This is depicted schematically in FIG. 3b. FIG. 3b schematically depicts a schematic cross section of a modified ball lens comprising a cylindrical section and a half-spherical section, enabling convenient mounting, alignment, and cooling of the lens. The embodiment of 3b of the truncated ball shaped lens may be a kind of ball elongated in a single direction (here downwards) and truncated. The longer the elongation, the longer d.sub.1 may be.

[0140] Optically non-active areas are indicated with the dashed lines and with reference 211. Hence, the first lens 200 has an external surface 230 comprising the curved lens surface 215 and the planar lens surface 225, wherein the first lens 200 is configured such that rays of luminescent material light 151 entering the first lens 200 via the planar lens surface 225 cannot directly reach a first external surface part 211 of the external surface 230, wherein the thermal conductor 300 is in thermal contact with the first lens 200 via the first external surface part 211. The first external surface part 211 may thus also be indicated as optically inactive or non-active areas. Note that in general the first external surface part 211 will be different from the curved lens surface 215 but may partially overlap with the planar lens surface 225. However, the first external surface part 211 may also not overlap with either of these; for instance, in embodiments the external surface 230 may be defined by essentially the curved lens surface 215, the planar lens surface 225, and the first external surface part 211 (or the optically non-active areas).

[0141] Another configuration is the combination of a spherical part and a conical part. The latter has the advantage of a further reduction of the thermal path and therefore reduction of the thermal resistance. See FIGS. 3c-3d for a schematic picture of these embodiments. FIGS. 3c-3d schematically depict various modified truncated ball lens shapes and mounting options. (3c): cone-shaped part in the optically inactive region of the ball lens for accurate mounting in a heat sink for the lens using a mechanical and thermal interconnect material enabling independent cooling from the converter; (3d): integrated version of the version as depicted in (3c). Version (3c) as shown in the figure enables independent cooling of the ball lens from the luminescent converter, as well as accurate and independent alignment. Version (3d) offers a very simple mounting and alignment of the ball lens relative to the luminescent converter.

[0142] Optionally the truncated ball lens is mounted in optical contact with the luminescent converter. This has the advantage of a somewhat enhanced coupling of blue light into the converter and a significantly enhanced light extraction from the converter, resulting in reduced thermal dissipation in the converter and thereby enabling an increased system efficiency, albeit at the cost of some etendue increase. An embodiment with this configuration is shown in FIG. 3e. FIG. 3e schematically depicts an embodiment of an integrated opto-thermo-mechanical mounting of a truncated ball shaped condenser lens with conical thermo-mechanical mounting section and direct optical interconnection between the truncated part of the ball lens and the luminescent converter by an optically transparent interconnect material 317.

[0143] A suitable optical material for this interconnect would be an optical silicone material that shows very low absorption in the typically (deep-) blue wavelength range of the pump laser. The conical section should be sufficiently small in this case to limit the optical losses that will arise in that area, as the light rays in the ball lens will spread over a significantly wider angular range (depending on the relative refractive indices of the lens and the optical interconnect).

[0144] Amongst others, the invention is applicable in particular for laser-pumped light sources, but optionally as well for high brightness (HB) LED-pumped light sources with a remote luminescent converter. Application areas are all areas where high brightness sources are requested, such as high flux/narrow beam spot lighting, entertainment/studio/stage lighting, and projection, etc.

[0145] The term “plurality” refers to two or more.

[0146] The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%.

[0147] The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”.

[0148] The term “and/of” especially relates to one or more of the items mentioned before and after “and/or”. For instance, a phrase “item 1 and/or item 2” and similar phrases may relate to one or more of item 1 and item 2. The term “comprising” may in an embodiment refer to “consisting of” but may in another embodiment also refer to “containing at least the defined species and optionally one or more other species”.

[0149] Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

[0150] The devices, apparatus, or systems may herein amongst others be described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation, or devices, apparatus, or systems in operation.

[0151] 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.

[0152] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

[0153] Use of the verb “to comprise” and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words “comprise”, “comprising”, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of “including, but not limited to”.

[0154] The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

[0155] The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In a device claim, or an apparatus claim, or a system 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.

[0156] The invention also provides a control system that may control the device, apparatus, or system, or that may execute the herein described method or process. Yet further, the invention also provides a computer program product, when running on a computer which is functionally coupled to or comprised by the device, apparatus, or system, controls one or more controllable elements of such device, apparatus, or system.

[0157] The invention further applies to a device, apparatus, or system comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

[0158] The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.