Lighting system with light guiding body having trivalent cerium luminescent material

Abstract

A lighting system includes a plurality of light sources; an elongated luminescent body defining a length (L) and a height or diameter (H), and having a light input face, a light output face, and at least one side face bridging the height or diameter (H); a garnet type A.sub.3B.sub.5O.sub.12 luminescent material including trivalent cerium, provided in the elongated luminescent body with a height dependent concentration range defined by a minimum concentration y.sub.min=0.036*x.sup.−1 and a maximum concentration y.sub.max=0.17*x.sup.−1, where y is the trivalent cerium concentration in % relative to the A element, and x is the height (H) in mm; at least one heat transfer elements in thermal contact with the elongated luminescent body; and a reflector provided opposite the light sources on the elongated luminescent body. The garnet type A.sub.3B.sub.5O.sub.12 luminescent material converts at least part of light from the light sources into converted light.

Claims

1. A lighting system comprising: a plurality of light sources configured to provide light source light at a wavelength selected from the range of 360 nm-490 nm; an elongated luminescent body having a length (L), and a height or diameter (H), the elongated luminescent body having light guiding properties, and the elongated luminescent body comprising: at least three side faces over at least part of the length (L), including a radiation input face, and a radiation exit window (112) bridging at least part of the height or diameter (H); a garnet type A.sub.3B.sub.5O.sub.12 luminescent material including trivalent cerium, with a height dependent concentration selected from a concentration range defined by a minimum concentration y.sub.min=0.036*x.sup.−1 and a maximum concentration y.sub.max=0.17*x.sup.−1, wherein y is the trivalent cerium concentration in mole % relative to the A element, and wherein x is the height or diameter (H) in mm, wherein the garnet type A.sub.3B.sub.5O.sub.12 luminescent material is configured to convert at least part of the light sources light into converter light; one or more heat transfer elements in thermal contact with at least one of the side faces; and a reflector configured to reflect light sources light escaping from the elongated luminescent body back into the elongated luminescent body, wherein the elongated luminescent body is configured between the light source and the reflector.

2. The lighting system according to claim 1, wherein the minimum concentration y.sub.min=0.04*x.sup.−l.

3. The lighting system according to claim 1, wherein A comprises one or more of yttrium, gadolinium and lutetium, and wherein B comprises one or more of aluminum and gallium.

4. The lighting system (1000) according to claim 1, wherein A=Lu and wherein B=Al, or wherein A comprises Y and Lu, and wherein B=Al.

5. The lighting system according to claim 1, elongated luminescent body comprises a ceramic body or single crystal, and wherein the mean free path for the wavelength of interest is at least 0.5 times the length (L) of the elongated luminescent body, wherein the wavelength of interest is the wavelength at maximum emission of the converter light of the luminescent material.

6. The lighting system according to claim 1, wherein the one or more heat transfer elements are configured parallel to at least part of one or more of the side faces over at least part of the length (L) of the elongated luminescent body at a shortest distance (d1) from the respective one or more side faces with 1 μm≤d1≤100 μm.

7. The lighting system according to claim 1, wherein the reflector comprises a specular mirror or a diffuse reflector.

8. The lighting system according to claim 1, wherein the luminescent material has an excitation maximum λ.sub.xm, wherein the light sources are configured to provide the source light with an intensity maximum λ.sub.px, wherein λ.sub.xm−5 nm≤λ.sub.px≤λ.sub.xm+5 nm.

9. A projection system or a luminaire comprising the system according to claim 1.

10. The lighting system according to claim 1, wherein the one or more heat transfer elements comprise one or more heat transfer element faces directed to one or more side faces, wherein at least part of the one or more heat transfer element faces of the respective one or more heat transfer elements is in physical contact with the elongated luminescent body, and wherein the shortest distance (d1) according to claim 6 is an average distance.

11. The lighting system according to claim 10, wherein 2 μm≤d1≤50 μm, and wherein the one or more heat transfer elements comprise or are functionally coupled to a heat sink.

12. The lighting system according to claim 1, wherein the side faces comprise a first side face, comprising the radiation input face, and a second side face configured parallel to the first side face, wherein the side faces define the height (H), wherein the elongated luminescent body further comprises the radiation exit window bridging at least part of the height (H) between the first side face and the second side face, wherein the reflector is configured at the second side face and is configured to reflect light source light escaping from the elongated luminescent body via second face back into the elongated luminescent body.

13. The lighting system according to claim 12, wherein the one or more heat transfer elements are at least in thermal contact with all side faces other than the first side face, and wherein the one or more heat transfer elements are configured as a monolithic heat transfer element, which is configured in thermal contact with a support for the light source, wherein a heat transfer element face of the one or more heat transfer element directed to the second face comprises the reflector.

14. The lighting system according to claim 1, comprises a plurality of light sources, wherein the light sources have optical axes (O) configured perpendicular to one or more of the one or more side faces.

15. The lighting system according to claim 14, wherein the plurality of light sources is configured to provide the light source light to only one of the one or more side faces.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) 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:

(2) FIGS. 1a-1e schematically depict some aspects of the invention; and

(3) FIG. 2a schematically shows an embodiment of a cross section of configuration with single-sided illumination of luminescent rod. The inner sides of the cooling block(s) may be made reflective or covered by a mirror;

(4) FIG. 2b provides a schematic representation of single-sided concept;

(5) FIG. 3a shows the cerium concentration in cerium comprising A.sub.3B.sub.5O.sub.12 garnets vs. thickness for obtaining 90% (lowest curve) or 99% absorption (highest curve) as a function of thickness in a single-sided configuration. The Ce concentration is especially in the region between the two lines; and

(6) FIG. 3b schematically depicts some aspects of excitation, emission, and light source emission; the vertical dashed lines e.g. depicted e.g. the +/−10 nm range around the maximum of the excitation.

(7) The schematic drawings are not necessarily on scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(8) A light emitting device according to the invention may be used in applications including but not being limited to a lamp, a light module, a luminaire, a spot light, a flash light, a projector, a (digital) projection device, automotive lighting such as e.g. a headlight or a taillight of a motor vehicle, arena lighting, theater lighting and architectural lighting.

(9) Light sources which are part of the embodiments according to the invention as set forth below, may be adapted for, in operation, emitting light with a first spectral distribution. This light is subsequently coupled into a light guide or waveguide; here the light transmissive body. The light guide or waveguide may convert the light of the first spectral distribution to another spectral distribution and guides the light to an exit surface.

(10) An embodiment of the lighting system as defined herein is schematically depicted in FIG. 1a. FIG. 1a schematically depicts a lighting system 1000 comprising a plurality of solid state light sources 10 and a luminescent concentrator 5 comprising an elongated light transmissive body 100 having a first face 141 and a second face 142 defining a length L of the elongated light transmissive body 100. The elongated light transmissive body 100 comprising one or more radiation input faces 111, here by way of example two oppositely arranged faces, indicated with references 143 and 144 (which define e.g. the height H), which are herein also indicated as edge faces or edge sides 147. Further the light transmissive body 100 comprises a radiation exit window 112, wherein the second face 142 comprises the radiation exit window 112. The entire second face 142 may be used or configured as radiation exit window. The plurality of solid state light sources 10 are configured to provide (blue) light source light 11 to the one or more radiation input faces 111. As indicated above, they especially are configured to provide to at least one of the radiation input faces 111 a blue power W.sub.opt of in average at least 0.067 Watt/mm.sup.2. Reference BA indicates a body axis, which will in cuboid embodiments be substantially parallel to the edge sides 147. Reference 140 refers to side faces or edge faces in general.

(11) In embodiments herein, the radiation exit window 112, which may in embodiments be essentially identical to the second face 142 may be configured under an angle (or angles) with the one or more side faces 140 of essentially 90°.

(12) The elongated light transmissive body 100 may comprise a ceramic material 120 configured to wavelength convert at least part of the (blue) light source light 11 into converter light 101, such as at least one or more of green and red converter light 101. As indicated above the ceramic material 120 comprises an A.sub.3B.sub.5O.sub.12:Ce.sup.3+ ceramic material, wherein A comprises e.g. one or more of yttrium (Y), gadolinium (Gd) and lutetium (Lu), and wherein B comprises e.g. aluminum (Al). References 20 and 21 indicate an optical filter and a reflector, respectively. The former may reduce e.g. non-green light when green light is desired or may reduce non-red light when red light is desired. The latter may be used to reflect light back into the light transmissive body or waveguide, thereby improving the efficiency. Note that more reflectors than the schematically depicted reflector may be used. Note that the light transmissive body may also essentially consist of a single crystal, which may in embodiments also be A.sub.3B.sub.5O.sub.12:Ce.sup.3+.

(13) The light sources may in principle be any type of light source, but is in an embodiment a solid state light source such as a Light Emitting Diode (LED), a Laser Diode or Organic Light Emitting Diode (OLED), a plurality of LEDs or Laser Diodes or OLEDs or an array of LEDs or Laser Diodes or OLEDs, or a combination of any of these. The LED may in principle be an LED of any color, or a combination of these, but is in an embodiment a blue light source producing light source light in the UV and/or blue color-range which is defined as a wavelength range of between 380 nm and 490 nm. In another embodiment, the light source is an UV or violet light source, i.e. emitting in a wavelength range of below 420 nm. In case of a plurality or an array of LEDs or Laser Diodes or OLEDs, the LEDs or Laser Diodes or OLEDs may in principle be LEDs or Laser Diodes or OLEDs of two or more different colors, such as, but not limited to, UV, blue, green, yellow or red.

(14) The light sources 10 are configured to provide light source light 11, which is used as pump radiation 7. The luminescent material 120 converts the light source light into luminescent material light 8 (see also FIG. 1e). Light escaping at the light exit window is indicated as converter light 101, and will include luminescent material light 8. Note that due to reabsorption part of the luminescent material light 8 within the luminescent concentrator 5 may be reabsorbed. Hence, the spectral distribution may be redshifted relative e.g. a low doped system and/or a powder of the same material. The lighting system 1000 may be used as luminescent concentrator to pump another luminescent concentrator.

(15) FIGS. 1a-1b schematically depict similar embodiments of the lighting system. Further, the lighting system may include further optical elements, either separate from the waveguide and/or integrated in the waveguide, like e.g. a light concentrating element, such as a compound parabolic light concentrating element (CPC). The lighting systems 1 in FIG. 1b further comprise a collimator 24, such as a CPC.

(16) As shown in FIGS. 1a-1b and other Figures, the light guide has at least two ends, and extends in an axial direction between a first base surface (also indicated as first face 141) at one of the ends of the light guide and a second base surface (also indicated as second face 142) at another end of the light guide.

(17) FIG. 1c schematically depicts some embodiments of possible ceramic bodies or crystals as waveguides or luminescent concentrators. The faces are indicated with references 141-146. The first variant, a plate-like or beam-like light transmissive body has the faces 141-146. Light sources, which are not shown, may be arranged at one or more of the faces 143-146 (general indication of the edge faces is reference 147). The second variant is a tubular rod, with first and second faces 141 and 142, and a circumferential face 143. Light sources, not shown, may be arranged at one or more positions around the light transmissive body. Such light transmissive body will have a (substantially) circular or round cross-section. The third variant is substantially a combination of the two former variants, with two curved and two flat side faces. In the embodiment having a circular cross-section the number of side faces may be considered unlimited (∞).

(18) In the context of the present application, a lateral surface of the light guide should be understood as the outer surface or face of the light guide along the extension thereof. For example in case the light guide would be in form of a cylinder, with the first base surface at one of the ends of the light guide being constituted by the bottom surface of the cylinder and the second base surface at the other end of the light guide being constituted by the top surface of the cylinder, the lateral surface is the side surface of the cylinder. Herein, a lateral surface is also indicated with the term edge faces or side 140.

(19) The variants shown in FIG. 1c are not limitative. More shapes are possible; i.e. for instance referred to WO2006/054203, which is incorporated herein by reference. The ceramic bodies or crystals, which are used as light guides, generally may be rod shaped or bar shaped light guides comprising a height H, a width W, and a length L extending in mutually perpendicular directions and are in embodiments transparent, or transparent and luminescent. The light is guided generally in the length L direction. The height H is in embodiments <10 mm, in other embodiments <5 mm, in yet other embodiments <2 mm. The width W is in embodiments <10 mm, in other embodiments <5 mm, in yet embodiments <2 mm. The length L is in embodiments larger than the width W and the height H, in other embodiments at least 2 times the width W or 2 times the height H, in yet other embodiments at least 3 times the width W or 3 times the height H. Hence, the aspect ratio (of length/width) is especially larger than 1, such as equal to or larger than 2, such as at least 5, like even more especially in the range of 10-300, such as 10-100, like 10-60, like 10-20. Unless indicated otherwise, the term “aspect ratio” refers to the ratio length/width. FIG. 1c schematically depicts an embodiment with four long side faces, of which e.g. two or four may be irradiated with light source light.

(20) The aspect ratio of the height H:width W is typically 1:1 (for e.g. general light source applications) or 1:2, 1:3 or 1:4 (for e.g. special light source applications such as headlamps) or 4:3, 16:10, 16:9 or 256:135 (for e.g. display applications). The light guides generally comprise a light input surface and a light exit surface which are not arranged in parallel planes, and in embodiments the light input surface is perpendicular to the light exit surface. In order to achieve a high brightness, concentrated, light output, the area of light exit surface may be smaller than the area of the light input surface. The light exit surface can have any shape, but is in an embodiment shaped as a square, rectangle, round, oval, triangle, pentagon, or hexagon.

(21) Note that in all embodiments schematically depicted herein, the radiation exit window is especially configured perpendicular to the radiation input face(s). Hence, in embodiments the radiation exit window and radiation input face(s) are configured perpendicular. In yet other embodiments, the radiation exit window may be configured relative to one or more radiation input faces with an angle smaller or larger than 90°.

(22) Note that, in particular for embodiments using a laser light source to provide light source light, the radiation exit window might be configured opposite to the radiation input face(s), while the mirror or reflector 21 may consist of a mirror having a hole to allow the laser light to pass the mirror while converted light has a high probability to reflect at mirror or reflector 21. Alternatively or additionally, a mirror may comprise a dichroic mirror. Reflector 21 may especially be configured to reflect luminescent material light back into the elongated luminescent body 100.

(23) FIG. 1d very schematically depicts a projector or projector device 2 comprising the lighting system 1000 as defined herein. By way of example, here the projector 2 comprises at least two lighting systems 1000, wherein a first lighting system 1000a is configured to provide e.g. green light 101 and wherein a second lighting system 1000b is configured to provide e.g. red light 101. Light source 10 is e.g. configured to provide blue light. These light sources may be used to provide the projection (light) 3. Note that the additional light source 10, configured to provide light source light 11, is not necessarily the same light source as used for pumping the luminescent concentrator(s). Further, here the term “light source” may also refer to a plurality of different light sources. The projector device 2 is an example of a lighting system 1000, which lighting system is especially configured to provide lighting system light 1001, which will especially include lighting system light 101.

(24) High brightness light sources are interesting for various applications including spots, stage-lighting, headlamps and digital light projection.

(25) For this purpose, it is possible to make use of so-called luminescent concentrators where shorter wavelength light is converted to longer wavelengths in a highly transparent luminescent material. A rod of such a transparent luminescent material can be used and then it is illuminated by LEDs to produce longer wavelengths within the rod. Converted light which will stay in the luminescent material such as a doped garnet in the waveguide mode and can then be extracted from one of the surfaces leading to an intensity gain (FIG. 1e).

(26) High-brightness LED-based light source for beamer applications appear to be of relevance. For instance, the high brightness may be achieved by pumping a luminescent concentrator rod by a discrete set of external blue LEDs, whereupon the phosphor that is contained in the luminescent rod subsequently converts the blue photons into green or red photons. Due to the high refractive index of the luminescent rod host material (typically 1.8) the converted green or red photons are almost completely trapped inside the rod due to total internal reflection. At the exit facet of the rod the photons are extracted from the rod by means of some extraction optics, e.g. a compound parabolic concentrator (CPC), or a micro-refractive structure (micro-spheres or pyramidal structures). As a result the high luminescent power that is generated inside the rod can be extracted at a relatively small exit facet, giving rise to a high source brightness, enabling (1) smaller optical projection architectures and (2) lower cost of the various components because these can be made smaller (in particular the, relatively expensive, projection display panel).

(27) FIGS. 2a-2b schematically depict embodiments of a lighting system 1 comprising a light source 10 configured to provide light source light 11 and an elongated luminescent body 100 having a length L (see FIG. 2b).

(28) As indicated above, the elongated luminescent body 100 comprises (n) side faces 140, here 4, over at least part of the length. The (n) side faces 140 comprise a first side face 143, comprising a radiation input face 111, and a second side face 144 configured parallel to the first side face 143, wherein the side faces 143, 144 define a height h.

(29) As indicated above, the elongated luminescent body 100 further comprises a radiation exit window bridging at least part of the height h between the first side face 143 and the second side face 144 (see especially FIG. 1a). The luminescent body 100 comprises a garnet type A.sub.3B.sub.5O.sub.12 luminescent material 120 comprising trivalent cerium, wherein the garnet type A.sub.3B.sub.5O.sub.12 luminescent material 120 is configured to convert at least part of the light source light 11 into converter light 101.

(30) Further, the lighting system 1000 comprises one or more heat transfer elements 200 in thermal contact with one or more side faces 140 and a reflector 2100 configured at the second side face 144 and configured to reflect light source light 11 escaping from the elongated luminescent body 100 via second face 144 back into the elongated luminescent body 100.

(31) The one or more heat transfer elements 200 are especially configured parallel to at least part of one or more of the side faces 140 over at least part of the length of the elongated luminescent body 100 at a shortest distance (d1) from the respective one or more side faces 140. The shortest distance d1 is especially 1 μm≤d1≤100 μm.

(32) As shown in FIGS. 2a-2b, the one or more heat transfer elements 200 comprise one or more heat transfer element faces 201 directed to one or more side faces 140. As shown in these schematic drawings, the one or more heat transfer elements 200 are at least in thermal contact with all side faces 140 other than the first side face 143. Further, as also shown in these schematic drawings, the one or more heat transfer elements 200 may be configured as a monolithic heat transfer element 220. In embodiments, this monolithic heat transfer element 220 is configured in thermal contact with a support 240 for the light source 10.

(33) A heat transfer element face 201 of the one or more heat transfer element 200 directed to the second face 144 comprises the reflector 2100. Here, all faces 201 directed to the luminescent body 100 comprise such reflector 2100.

(34) FIG. 2b schematically depict another embodiment of the monolithic heat transfer element 220, including a slit 205 configured to host the luminescent body 100. The light sources 10 may be provided as LED bar. The monolithic heat transfer element 220 is used for cooling of the luminescent body 100.

(35) The optional intermediate plate, indicated with reference 250, may serve as a spacer to keep the luminescent body at the desired distance from the light sources and may also serve as a reflector for the light that escapes from the luminescent body side faces. As an alternative, the spacer could be integrated with the one or more heat transfer element 200, especially a top one or more heat transfer element 200 (such as a top cooling block).

(36) In FIGS. 2a-2b, the one or more heat transfer elements are configured within a circle section of at least 180°, here in fact about 270°.

(37) The availability of the reflector 2100, such as in embodiments comprised by or provided to a heat transfer element 200 may, especially when configured opposite of the light source 10 with the elongated luminescent body in between, reflect light source light that may have escaped from the elongated luminescent body 100 back therein. As the optical axis of the light source may especially be configured perpendicular to the side face of the elongated (in case of a rod with circular cross-section) or perpendicular to one of the side faces (in case of e.g. a rod with a rectangular cross-section), light source light may escape from an opposite (part of the) side face.

(38) As shown in FIG. 3a, the luminescent body has a height dependent concentration, which may especially be selected from a concentration range defined by a minimum concentration y.sub.min=0.036*x.sup.−1 and a maximum concentration y.sub.max=0.17*x.sup.−1, wherein y is the trivalent cerium concentration in % relative to the A element, and wherein x is the height or diameter in mm. Here, in FIG. 2c the embodiment is shown wherein the height dependent concentration is selected from a concentration range defined by a minimum concentration y.sub.min=0.036*x.sup.−1 and a maximum concentration y.sub.max=0.17*x.sup.−1.

(39) FIG. 3a especially relates to luminescent material comprising an A.sub.3B.sub.5O.sub.12:Ce.sup.3+ (garnet material), wherein A is especially selected from the group consisting of Sc, Y, Tb, Gd, and Lu (especially at least Y and/or Lu, and optionally Gd), wherein B is especially selected from the group consisting of Al and Ga (especially at least Al). For LuAG, YAG, YGdAG, and YGaAG the absorption coefficients at the respective excitation maxima around about 460 nm are essentially the same.

(40) FIG. 3b very schematically depicts an excitation spectrum, left curve, indicated with EX, with excitation maximum λ.sub.xm, and emission spectrum, right curve, indicated with EM. The light source emission, such as an emission of a LED is indicated with light source light 11, which has a maximum λ.sub.px. In specific embodiments, λ.sub.xm−5 nm≤λ.sub.px≤λ.sub.xm+5 nm. The maximum of the emission curve is the emission maximum. The wavelength at maximum emission is herein also indicated as “wavelength at maximum emission of the converter light of the luminescent material”. For the garnets, this maximum may e.g. be in the green-yellow wavelength range.

(41) Hence, as indicated above, the top of the excitation maximum only slightly varies for the different types of garnets, and all of LuAG, YAG, YGdAG, and YGaAG comply with the formula's as e.g. indicated in FIG. 3a.

(42) In the formula, x may also be the diameter in mm. In embodiments wherein the elongated luminescent body has a cross-sectional shape other than circular or rectangular (including square), or anyhow more in general, x may refer to the length through the elongated luminescent body along the optical axis of a light source. Especially, the optical axis of the light source is configured perpendicular to one of the one or more side faces. Hence, referring to FIGS. 1a and 2a, x refers to the height H. referring to FIG. 1c, in the top and bottom embodiment, x may also refer to the height H, assuming irradiation from below or from the top. In the middle embodiment, i.e. the embodiment wherein the cross-sectional shape is circular, x refers to the diameter D (or to the width or height, as these all are the same).

(43) Note that terms as height and width are essentially only labels. Would e.g. the elongated luminescent body 100 in FIG. 2a be configured differently, such as with light source 10 directed to a smaller side face (e.g. luminescent body rotated over 90°), the x may refer to the width. For instance, referring to FIG. 1c.

(44) In FIG. 2a, the three of the plurality of side faces 140 are in thermal contact with one or more heat transfer elements 200. Hence, at least 50% of the total area of the one or more side faces 140 may be in thermal contact with one or more heat transfer elements 200. This might also apply when the elongated luminescent body 100 has another shape, such as having a circular cross-section.

(45) The term “plurality” refers to two or more.

(46) 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%.

(47) The term “comprise” includes also embodiments wherein the term “comprises” means “consists of”.

(48) The term “and/or” 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”.

(49) 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.

(50) 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.

(51) 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.

(52) In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim.

(53) 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”.

(54) The article “a” or “an” preceding an element does not exclude the presence of a plurality of such elements.

(55) 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.

(56) 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.

(57) 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.

(58) 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.