The present invention relates in general to a lighting device, suitable for providing light for purposes of illumination and/or for ornamental or decorative purposes.
Lighting devices in general are known. They typically comprise one or more light-generating elements mounted in a housing, provided with shielding means. The light-generating elements may be of incandescent type, gas discharge type, LED type, etc. In the case of incandescent type, the actual light-generating element is the glowing wire, and the surrounding glass bulb is actually a shielding member. Apart from that, a lamp armature may comprise further shielding members, also indicated as “cap” or the like, which function to mechanically shield the light-generating element from damage, but which also function to prevent a direct view of the light-generating element. In many lighting devices, such shielding member receives the light from the light-generating element and distributes it into the surroundings, by reflection and/or scattering. As such, the shielding member may be termed a passive light source or secondary light source, the actual light-generating element being an active light source or primary light source.
It is an object of the invention to provide a lighting device of a new design. Particularly, the present invention aims to provide a lighting device which, when the lighting device is OFF, is substantially transparent.
According to an important aspect of the invention, the lighting device comprises a semi-transparent plate-shaped light source. The plate-shaped light source may be a primary light source, i.e. an actual light-generating element. The plate-shaped light source may alternatively be a secondary light source, provided with one or more primary light sources arranged adjacent one or more of its side edges, wherein the light from the primary light sources travels mainly parallel to the main surfaces of the plate-shaped light source until it is coupled out through at least one of the main surfaces. In both cases, the plate-shaped light source can be operated in an OFF state in which the plate-shaped light source is substantially transparent, or in an ON state in which the plate-shaped light source emits light having at least a component in a main direction substantially perpendicular to a main surface of the plate-shaped light source. It is noted that the light may be emitted in random directions.
In a preferred embodiment, the plate-shaped light source further comprises a reflective member disposed at one side, for reflecting a portion of the emitted light back through the plate-shaped light source. This would increase the illumination level at the other side of the plate-shaped light source.
According to the invention, the higher the reflectivity of the reflective member the better the light output of the plate-shaped light source. However, when the light source is OFF, it should preferably be completely transparent such as to be virtually invisible, but increased reflectivity typically involves reduced transmissivity. The invention further aims to reduce this problem. Specifically, the present invention aims to providing embodiments of the lighting device which have good performance in the illumination effect when the lighting device is ON and have good performance in transmitting light when the lighting device is OFF.
In a preferred embodiment, the plate-shaped light source is provided with a scattering layer, arranged to scatter a portion of the light which falls on the scattering layer. With scattering is meant that light is directed in random directions. Scattering also comprises diffuse reflection. In the case of the plate-shaped light source being a secondary light source, provided with one or more primary light sources arranged adjacent one or more of its side edges, the scattering layer may be optically coupled to the plate-shaped light source to assist in coupling out of light.
Further advantageous elaborations are mentioned in the dependent claims.
It is noted that the scattering layer does not only scatter light emitted by the plate-shaped light source but may also scatter a portion of the ambient light which falls on the scattering layer. In a particular embodiment of the lighting device according to the invention, the scattering layer is comprised in a scattering device further comprising electrical means for controlling the amount of scattering by the scattering layer. This embodiment of the lighting device according to the invention comprises a so-called active scattering layer. The amount of light scattering by the scattering layer is preferably related to a voltage difference across the scattering layer, which is created by electrodes at opposite sides of the scattering layer. Preferably the electrodes are highly transparent and may comprise indium tin oxide (ITO) but can occasionally also be indium zinc oxide (IZO) also known to those skilled in the field as a transparent electrode. Preferably the square resistance of the transparent electrodes is sufficiently low to minimize the required voltage between the two electrodes needed to switch between different states.
Preferably the scattering device is arranged to switch between a first state in which hardly any scattering of light takes place and a second state in which the scattering of light is relatively strong. Typically, the first state corresponds to the turned OFF state of the lighting device while the second state corresponds to the turned ON state of the lighting device. Preferably, a voltage difference across the scattering layer is minimal for the second state resulting in no energy consumption during the periods in which the lighting device is turned off.
In a particularly preferred embodiment, the scattering device is a switchable device and the reflective member is a switchable device, wherein the scattering device and the reflective member are switched simultaneously.
In another embodiment of the lighting device according to the invention, the scattering layer is a scattering polarizer, which is substantially transmissive for light having a first polarization direction and which is arranged to scatter the portion of the ambient light having a second polarization direction being orthogonal to the first direction. This embodiment of the lighting device according to the invention comprises a so-called passive scattering layer, meaning that the amount of scattering is predetermined and cannot be controlled during operation of the lighting device. A scattering polarizer is a material which has different behavior for respective polarization directions. The scattering polarizer is substantially transparent for light having a first polarization direction and is arranged to scatter light having a second polarization direction which is orthogonal with the first polarization direction. An example of the scattering polarizer is described in the PhD thesis of Henri Jagt, “Polymeric polarization optics for energy efficient liquid crystal display illumination”, 2001, Chapter 2 and in patent application WO01/90637.
In an embodiment of the lighting device according to the invention, the reflective layer is a semi transparent mirror.
In another embodiment of the lighting device according to the invention, the reflective layer is a polarizer which is substantially transparent for the display light having a first polarization direction. The reflective polarizer can be a stack of alternating birefringent and non-birefringent layers in a periodicity that enables Bragg reflection for the second polarization direction and provides transmission for the orthogonal, i.e. first polarization direction. An example of a reflective polarizer that is based on this principle is a polarizer film supplied by 3M company under the name of Vikuity™ Dual Brightness Enhancement Films (DBEF).
Another way of making reflective polarizers is based on cholesteric films as described in U.S. Pat. No. 5,506,704, U.S. Pat. No. 5,793,456, U.S. Pat. No. 5,948,831, U.S. Pat. No. 6,193,937 and in ‘Wide-band reflective polarizers from cholesteric polymer networks with a pitch gradient’, D. J Broer, J. Lub, G. N. Mol, Nature 378 (6556), 467-9 (1995). In combination with a quarter wave film this film provides the same optical function as DBEF.
Alternatively the reflective polarizer is based on the so-called wire grid principle where narrow periodic lines of a metal with a periodicity smaller than the wavelength of light are applied on a glass or plastic substrate.
These and other aspects, features and advantages of the present invention will be further explained by the following description of one or more preferred embodiments with reference to the drawings, in which same reference numerals indicate same or similar parts, and in which:
The Figures are diagrammatic and not drawn to scale.
In the following, first a description will be given of certain aspects of a scattering layer and a reflective member.
Thus, the viewer 204 is provided with:
light which originates from the object 104, which moves in the first direction towards the viewer 204; and/or
scattered light 206 which originates from the ambient light source 202 (direct and/or indirect) and the plate-shaped light source 950, and which is scattered by the scattering layer 102 and optionally reflected by the reflection layer 106.
The scattering layer 102 may be comprised in a scattering device 600 (see
In conjunction with the figures it is disclosed that several types of polarizers may be applied. With a polarizer is meant an optical element which filters a light ray depending on the polarization directions of the respective components of the light ray. Typically, a polarizer is substantially transmissive for components of the light ray having a first polarization direction while the polarizer is substantially influencing components of the light ray having a second polarization direction, which is orthogonal with the first polarization direction. Influencing in this context comprises scattering and absorbing.
Various polarizers may be used for the following functions:
in an embodiment of the lighting device according to the invention a polarizer is used as scattering layer 102;
in an embodiment of the lighting device according to the invention a polarizer is used as reflecting layer 106.
Because of the scattering and reflection of ambient light by the lighting device of the invention, the viewer 204 receives reflected ambient light. By applying an absorption polarizer 402, as optical absorption means 402, in front of the reflection layer 106 the reflection can be reduced. To achieve the required effect, the absorption polarizer 402 is arranged to absorb the components of the scattered ambient light 206 having the second polarization direction which would have been reflected by the reflective layer 106. Preferably, the reflective layer 106 is also based on a polarizer.
Preferably, the absorption polarizer 402 as described in connection with
A scattering polarizer 500 can be based on particles 504-510 embedded in a polymer matrix 502. Blending small particles 504-510 with a known polymer 502 like e.g. PEN or PET, followed by extrusion of this mixture to a foil and stretching this foil, makes the scattering polarizer 500. The stretching provides uniaxial orientation, making it transparent for the first polarization direction D1 whereas it is scattering for the orthogonal second polarization direction D2.
The principle of the scattering polarizer 500 is as follows. The small particles 504-510, depicted as white circles, correspond to a dispersed phase with reflective index nd in a uniaxialy oriented polymer matrix 502 with a first polymer reflective index no for light having a first polarization direction D1 and a second polymer reflective index ne for light having a second polarization direction D2. The refractive index nd of the particles 504-510 is matched to the first polymer refractive index no, whereas the second polymer refractive index ne>>nd.
The scattering polarizer 500 may be based on small particles embedded in a non-colored stretched foil. The particles may be e.g. core-shell particles (Rohm and Haas, Paraloid EXL 3647) having a diameter of 200 nm and consisting of a styrene-butadiene (S-BR) rubbery core and a poly(methylmethacrylate) (PMMA) shell. In order to add color, a dye or pigment can be added either to the particles 504-510 or to the polymer matrix 502. When the dye is added to the polymer matrix 502 also a dichroic dye can be selected that orient itself with the aligned polymer matrix 502 such that especially the polarization parallel to the stretching direction becomes colored, but the scattering polarizer 500 remains transmissive for first polarization direction D1.
Rather than using spherical particles the particles might have also other shapes, for instance elongated. In one embodiment the particles have a fiber-like shape obtained by melting and elongation of the initially spherical particles during the stretching process of the polymer matrix material.
As explained above, a scattering polarizer 500 may be applied as scattering layer 102 or as reflecting layer 106. Optionally, an embodiment of the lighting device according to the invention comprises a single scattering polarizer 500 which both fulfils the scattering and reflection function, i.e. the scattering layer 102 and the reflecting layer 106 are both realized by a single scattering polarizer 500.
a set of substantially flat substrates 602-604, e.g. based on glass, PMMA or some other substantially transparent material;
a scattering layer 102 being sandwiched by the set of electrical conductors 606-608.
The scattering layer 102 preferably comprises Polymer Dispersed Liquid Crystals (PDLC), Cholesteric Texture Liquid Crystals (CTLC), Liquid Crystal (LC) gels or polymer network Liquid Crystal (PNLC). By applying the appropriate voltage difference on the electrical conductors 606-608, i.e. across the scattering layer 102, the orientation of the liquid crystals can be modified, resulting in an increase or decrease of the amount of light scattering by the scattering layer 102.
To indicate the function of the scattering device 600 in the lighting device according to the invention, the direction of the light 210 originating from the object 104 behind the lighting device, the direction of the ambient light 208 and the direction of the light emitted by the plate-shaped light source 950 and scattered ambient light 206 are depicted.
In order to advantageously obtain a device as thin as possible, it is preferred that the distance between the reflecting layer 106 and the scattering layer 102 is as small as possible. The scattering device 600 as depicted in
If for ornamental design reasons it is desired to switch the scattering layer 102 partially, e.g. over a surface area corresponding to only a portion of the scattering device 600, the substrates 602-604 of the scattering device 600 may contain patterned electrodes. The patterned electrodes can be use to open and close the light scattering area in a discrete way. But it may also be used to open the lighting area only partially or to apply a gradient in illumination power.
The scattering device 600 may be configured to vary the size and/or dimensions of said partial surface area with time.
The operation of the light sources 702-704 may be simultaneous with the operation of the plate-shaped light source 950. The result is an increased amount of the light. Preferably, the scattering device 600 is also controlled simultaneously with the operation of the plate-shaped light source 950.
In
Preferably, multiple light sources 702-704 being arranged to generate light with mutually different colors are used.
In the above, the basic concept behind the present invention has been explained. In the following, some further preferred elaborations will be explained.
According to the present invention, the lighting device 900 comprises a substantially transparent, plate-shaped light source 950, arranged in parallel to the scattering layer 902 and preferably not optically coupled to the scattering layer 902. The plate-shaped light source 950 has a front surface 951 which in use will be directed to a viewing person 204, and a back surface 952. In the embodiment illustrated in
The operation is as follows. When the lighting device 900 is in its ornamental or illuminating state, the plate-shaped light source 950 is switched ON. In the case of the
It is noted that in the case of
The embodiment illustrated in
When the lighting device is OFF, the scattering layer 902 may be switched to a non-scattering state, so that the viewer 204 is not hindered by scattered light 962, 964. Light 914 from the object 104 will not be obstructed by the plate-shaped light source 950 because of its transparency.
It is noted that it is possible to omit the reflective member 906 entirely.
The plate-shaped light source 950 may be suitably implemented as a passive plate having scattering properties and being provided with one or more light sources arranged along its perimeter. Preferably, the plate-shaped light source 950 is switchable between two states, i.e. a scattering state and a non-scattering state, so that the scattering properties can be switched off in order to minimize disturbances when the screen 104 is ON.
However, it is also possible that the plate-shaped light source 950 is implemented as an active light source, actually generating light itself. By way of example, the plate-shaped light source 950 may be implemented using organic LEDs.
Preferably, the scattering layer 902 is a switchable layer having two states, i.e. a scattering state and a non-scattering state in which the layer 902 is substantially transparent.
Special ornamental effects will be described with reference to
In an ornamental mode, the entire lighting device 900 is producing scattered light 962 or 964 towards the viewer 204, i.e. both the peripheral part 972 and the central part 971. The backside of the peripheral part 972, i.e. the outer surface directed away from the viewer 204, may be provided with a black layer.
In another ornamental mode, the user may desire a white (or whitish) frame around a central transparent portion. To allow for such possibility, the central part 971 of the lighting device 900 is switched off but the peripheral part 972 of the lighting device 900 remains switched on. Particularly, light sources 967 arranged along the edges of the plate-shaped light source 950 remain switched on, and the central part 907 of the scattering layer 902 is switched to its non-scattering state while the peripheral part 908 of the scattering layer 902 is switched to its scattering state. If the plate-shaped light source 950 is an active light source, its central part 957 and peripheral part 958 are preferably capable of being switched on/off independently from each other, so that in this case the central part 957 is switched off while the peripheral part 958 is switched on.
It may be preferred that such white frame can have various sizes. Thus, the lighting device 900 preferably has multiple sections 981, 982, 983, 984, etc, as illustrated in
It is noted that it is possible to use the lighting device as a flat lamp.
It is noted that, basically, any plate-shaped transparent material with mutually parallel surfaces is suitable for use as a light guide plate.
The light source 1300 further comprises at least one active light generating element 1320, arranged at a predetermined location near the side face 1313 of the light guide plate body 1310. The active light generating element 1320 is advantageously implemented as a LED, but another embodiment, such as for instance a gas discharge tube, is also possible. If
For obtaining illumination properties, the light guide plate body 1310 should, as mentioned earlier, have scattering properties, i.e. light should be coupled out of at least one of the main surfaces 1311, 1312, in a direction having a component perpendicular to the main surfaces 1311, 1312. For providing suitable scattering properties, the present invention proposes that at least one of the main surfaces 1311, 1312 is provided with permanent unevennesses or obtrusions 1315. The obtrusions 1315 may be implemented as material portions projecting from the surface 1311 (haut relief) or as indentations recessed in the surface (bas relief).
Thus, the main surface with obtrusions is directed away from the scattering device 902. It is noted that in the above cases the scattering device 902 is preferably located close to, possibly even in contact with the plate-shaped light source 950, yet without being optically coupled, in situations where the combination of scattering protrusions and optically coupled would results in an outcoupling efficiency so high that it is difficult to achieve sufficient light intensity over the entire surface of the disguising device.
The obtrusions provide the scattering properties to the plate body 1310, or add to such properties. Thus, depending on the distribution over the corresponding surface 1311, 1312, said obtrusions improve the uniformity and efficiency of the lighting device 1302, 1301 in the situation when the light generating element 1320 is ON and the lighting device 1302, 1301 is in its ornamental state.
The obtrusions 1315 may be distributed evenly and uniformly over the corresponding surface 1311, 1312. However, it is also possible that the obtrusions 1315 are distributed according to a certain pattern to define a graphical image, for instance a photo. The obtrusions 1315 may be implemented as a dot pattern, wherein the density and/or size of the dots may vary over the surface 1311, 1312. An example of a suitable method for providing the obtrusions 1315 is sandblasting, wherein a mask may be used to provide the desired variation of density or other decoration preferences.
It is noted that Japanese patent application 1999-223805 to Nissha Printing Co Ltd, publication number 2001-052519, discloses the use of a light guide plate as a backlight for a display. The light guide plate comprises two non-parallel surfaces, one surface being provided with non-mirror projections having a diameter of less than 20 μm and having a cross-sectional shape according to a part of a circle. Adjacent the light guide plate, facing the projections, the device comprises a mirror plane. Light is inputted at a side of the plate, and partially outputted by the projections. Light outputted by a projection is reflected by the mirror, passes the width of the light guide plate and is finally outputted at the surface opposite the projections. Such device is not transparent in the OFF state, and is therefore not suitable as a transparent lighting device in accordance with the principles of the present invention.
In a specific experimental embodiment, the plate body 1310 was made from glass and the obtrusions were made by sandblasting in a dot pattern. The size of the dots (diameter of substantially circular dots) was varied, and the density of the dots was varied.
It was found that undesirable visibility in the OFF state increases with increasing dot size. In this respect, dot sizes larger than 0.4 mm were found to involve undesirable visibility, so that dot sizes smaller than 0.4 mm are preferred. In general, the preferred range of dot sizes is between 20 and 200 μm, which sizes can well be achieved using sandblasting. Dot sizes of approximately 0.1 mm were found to give very satisfying results. Smaller dot sizes may also give good results, and may even be preferred in view of reduced visibility, but it is more difficult to make predefined patterns in view of the necessity to use a mask.
Further, it was found that the dot density greatly influences the luminance of the plate-shaped light source 1300, and hence the illumination performance in the ON state. When a region of the plate body 1310 has higher dot density, more light is coupled out of the plate body 1310, so a higher local luminance and better illumination performance is achieved in that region. On the other hand, because more light is coupled out, less light remains beyond such region, so the luminance at larger distances from the light generating element 1320 may be reduced, reducing the illumination performance in the ON state. For a dot size of 0.1 mm, a dot density in the range between 5 and 500 dots/cm2 appeared to provide a suitable tradeoff.
In the above, lighting devices have been described comprising a combination of a reflective member and a scattering layer, wherein the scattering layer is provided with a plate-shaped light source. All in all, the combination of the scattering layer and the plate-shaped light source serves to provide a diffuse glare of light over the area of the lighting device. Both the scattering layer and the plate-shaped light source serve basically different purposes. Starting from the plate-shaped light source, which provides more or less diffuse light, the scattering layer serves to further scatter this light and make it even more diffuse and further increases luminance by scattering ambient light. However, with a suitable design it is possible that the illumination performance of the plate-shaped light source by itself is already sufficient so that the separate scattering layer may be omitted.
The above applies for an active plate-shaped light source, for instance implemented by using organic LEDs or by inorganic thin film electroluminescence layers, but also for a passive plate-shaped light source, such as described for instance with reference to
In
In
In
In the embodiments 1402, 1403, 1404, a light-generating element is always indicated at 1420. For the plate body 1410 and the obtrusions 1415, the same applies as what has been mentioned in relation to the plate body 1310 and the obtrusions 1315 of
In the
In the above, embodiments of a lighting device have been described, including a plate-shaped light source and a switchable scatterer (see for instance FIGS. 8 and 9A-B), wherein the plate-shaped light source is implemented as a light guide plate with at least one light-generating element arranged at a side. As has also been indicated above, there may be a problem that the luminance at larger distances from the light-generating element may be reduced. This problem is explained with reference to
L
OUT(i)=p·INT(i)
INT(i+1)=(1−p)·INT(i)
It should further be clear that LOUT(i) can thus graphically be represented as a logarithmic curve, as shown in
If p is relatively small, the decline of LOUT(i) over the extent of the light guide plate body 1310 may be small enough to be unnoticeable or acceptable. However, the surface light intensity of the plate-shaped light source may be relatively small. If p is increased, the surface light intensity of the plate-shaped light source at locations close to the light-generating element (small values of i) will be increased, but unavoidably the surface light intensity of the plate-shaped light source at locations remote from the light-generating element will be increased to a lesser extent, or will even be decreased, depending on the size of the light guide plate body 1310. Thus, the decline of LOUT(i) over the extent of the light guide plate body 1310 will increase.
Thus, although the dot size and dot density is uniform, the light output may be non-uniform, and this may be unacceptable. To a certain extent, this problem can be reduced by making the dot size and/or the dot density non-uniform such as to increase the outcoupling efficiency p as a function of the distance from the light-generating element. Alternatively and/or additionally, it is possible to arrange light-generating elements at opposite sides of the light guide plate body.
According to this aspect of the present invention, the switchable scatterer 1650 is subdivided into a plurality of longitudinal segments 1660, individual segments being identified by the index i, which ranges from 1 to N, N indicating the number of segments. The segments 1660 may mutually have the same width, but this is not essential. The longitudinal dimension of the segments 1660 is directed parallel to a light input side 1621, which is the side where the light generating element or elements 1620 is/are located. For increasing i, the distance from the light generating element(s) 1620 to the longitudinal segment 1660(i) is larger.
The scatterer segments 1660(i) are individually and independently switchable. The controller 1670 has scatterer control outputs 1671(1), 1671(2), . . . 1671(N) coupled to the respective scatterer segments 1660(1), 1660(2), . . . 1660(N). As shown, the controller 1670 may also have a control output 1672 coupled to the light generating element or elements 1620.
The controller 1670 drives the scatterer segments 1660(i) in a time-sequential manner. More particularly, the controller 1670 generates control signals Sc(i) at its respective control outputs 1671(i) for the respective scatterer segments 1660(i) in such a way that one specific scatterer segment 1660(j) is in a scattering state while all other scatterer segments 1660(i), i≠j, are in a non-scattering state. Further, the controller 1670 maintains this state for a predetermined segment maintenance duration τ(j), and then continues to a next state where the subsequent specific scatterer segment 1660(j+1) is in a scattering state while all other scatterer segments 1660(i), i≠j+1, are in a non-scattering state. This is continued until all scatterer segments have been switched briefly to their scattering state, and then the cycle is repeated. In other words, the scattering state is scanned over the scatterer. The cycle duration T can be defined as Στ(j).
The number of scatterer segments will be at least equal to two, and may in principle have any value as desired. In the drawing, the number of segments is shown to be equal to 8.
An advantage of this approach is that the amount of light coupled out of the light guide plate body (e.g. 1310 in
Of course, only the scatterer segment(s) which is/are in its/their scattering state has/have an illumination effect, while the other segments practically have no illumination effect. But this situation is momentarily, and lasts for the segment maintenance duration τ. At a time scale larger than the cycle duration T, all segments have partially been in an illumination state, and an illumination ratio can be defined as DR=τ(j)/T. If the cycle duration T is sufficiently short, for instance 10 ms or shorter, the sequential illumination or “scanning illumination” is hardly or not noticeable to the human eye. For each scatterer segment, the average output light amount can be written as DR·LOUT. An important aspect is that this average output light amount can basically be the same for all segments. This is illustrated in the two curves in the graph aligned with the scatterer 1650 in
The number of scatterer segments, or the width of the segments, can be selected to improve uniformity. Keeping the light intensity of the light-generating element 1620 constant, the decline per segment can be reduced by increasing the number of scatterer segments.
If the scatterer still suffers from loss of light for scatterer segments further away from the light generating element(s), it is possible to compensate this by having the segment maintenance duration τ(j) increase with increasing distance from the light generating element(s) (i.e. increasing j). It is also possible that the scattering segments do not merely allow for selecting a scattering state or a non-scattering state, but even allow for the efficiency p of the scattering to be controlled. In that case, loss of light can be compensated by having the controller control the segments such that the scattering efficiency p(j) increases with increasing distance from the light generating element(s) (i.e. for increasing j).
In the above explanation, it was assumed that the light intensity of the light-generating element(s) 1620 is constant with time. However, in the embodiment shown, the controller 1670 has a control output 1672 coupled to the light-generating element(s) 1620 for controlling the light intensity of the light-generating element(s) 1620. In that case, loss of light can be compensated by having the controller control the light-generating element(s) 1620 such that the light intensity is increased in proportion with increasing distance between the momentarily scattering segment 1660(j) and the light generating element(s) (i.e. for increasing j).
In the embodiment shown, the light-generating element(s) 1620 is/are arranged along one side 1621 of the lighting device 1600 only, and the scatterer 1650 is subdivided into a first plurality of individually controllable segments 1660 parallel to this one side, i.e. in a vertical direction in the figure. Light is assumed to propagate perpendicularly to this one side 1621 and said individually controllable segments 1660 only, i.e. in a horizontal direction in the figure. Uniformity can be improved by also having light-generating element(s) arranged along the opposite side 1622 of the lighting device 1600. Uniformity can be further improved if the scatterer 1650 is also subdivided into a second plurality of individually controllable segments perpendicular to the first plurality of segments, with second light-generating element(s) arranged along a third side 1623 perpendicular to the said one side 1621 of the lighting device 1600, and possibly further light-generating element(s) arranged along a fourth side 1624 opposite said third side 1623. For the time-sequential control of this second plurality of segments, the same applies as what has been mentioned in respect of the first plurality of segments, it being noted that the time-sequential control of this second plurality of segments may be entirely independent from the time-sequential control of said first plurality of segments.
The plate-shaped light source may have a planar shape, as shown in the drawings so far. However, this is not essential, and in fact it is foreseen that special ornamental effects are achieved if the plate-shaped light source has the shape of a curved plate. The curvature may be in one direction only, but may also be in two mutually perpendicular directions (to obtain a pillow-shape or saddle-shape).
The plate-shaped light source 1700 may, again, be an active light source.
In the lighting device 1702 of
Summarizing, the present invention provides a lighting device comprising a semi-transparent plate-shaped light source.
The transparent plate-shaped light source may be a passive plate-shaped light source comprising a transparent light guide plate body with two substantially parallel main surfaces, and wherein at least one of the main surfaces is provided with permanent obtrusions.
The obtrusions may be implemented as material portions projecting from the surface and/or as indentations recessed in the surface. The obtrusions may be arranged by sandblasting, preferably in a pattern of dots, wherein the dots may have sizes in the range between 20 and 200 μm, preferably approximately 100 μm, and wherein the dot density may be in the range between 5 and 500 dots/cm2.
While the invention has been illustrated and described in detail in the drawings and foregoing description, it should be clear to a person skilled in the art that such illustration and description are to be considered illustrative or exemplary and not restrictive. The invention is not limited to the disclosed embodiments; rather, several variations and modifications are possible within the protective scope of the invention as defined in the appending claims.
It is noted that the light sources 967 used in conjunction with the plate-shaped light source 950 may emit light of one color only, for instance white, but it is also possible that these light sources 967 emit light with variable color, so that it is possible to have the hiding light match the appearance of the wall; for instance, these light sources may be of RGB type.
Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope. Features described in relation to a particular embodiment can also be applied to other embodiments described.
Number | Date | Country | Kind |
---|---|---|---|
08155866.0 | May 2008 | EP | regional |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/IB2009/051707 | 4/27/2009 | WO | 00 | 11/1/2010 |