WO2011042157A1 - Asymmetrical reflector element for reflecting light emitted by one led unit, reflector comprising at least one reflector element, and lighting unit - Google Patents

Abstract

The invention relates to an asymmetrical reflector element for reflecting light emitted by one LED unit in order to illuminate a predetermined illumination area comprising a first opening at a first end of the reflector element, defining a light inlet area and a second opening at the opposite second side thereof; and a lateral area for reflecting the light emitted by the LED unit, said lateral area extending from the first end to the opposite second end; wherein the lateral area is formed such that a line extending from at least one position of the inlet area in a right angle towards the second opening crosses the lateral area.

Description

Asymmetrical reflector element for reflecting light emitted by one LED unit, reflector comprising at least one reflector element, and lighting unit

The present invention relates to an asymmetrical reflector element for reflecting light emitted by one LED unit, a reflector comprising at least one asymmetrical reflector element and a lighting unit.

For providing illumination on streets, railway stations, harbors, parking places, in rooms or other interior or exterior scenarios, currently different systems are discussed. In regard to effectiveness, one aspect is the use of LEDs (Light Emitting Diodes), which ensures a reduction of power consumption in respect to usual lighting means. One aspect thereof is to create an isotropic illumination from the anisotropic emission of the LED, because a spot like illumination is not satisfying for a number of purposes, such as illumination of a larger area, avoiding of dazzling persons e.g. in traffic situation etc. Most types of LED, however, exhibit a dominant emission direction at a radiation angle of zero degrees and subordinate emission directions at radiation angles unequal to zero, see also Fig. 1.

Therefore, lenses are used in order to bundle the light of one LED. In the case of more LEDs by the use of a lens a uniform angle of radiation of the several LEDs may be created. However, lenses absorb part of the light, such that the light yield decreases. Further, their material subject to degradation, so that the light yield might be further reduced.

Another approach is therefore to use reflectors, in order to avoid these disadvantages.

It is one object of the invention to provide a possibility for an effective illumination by reflecting the light of a light source with an anisotropic emission. This object is solved by what is disclosed in the independent claims. Advantageous embodiments are described by the dependent claims.

Preferred embodiments are an asymmetrical reflector element comprising a first opening at one end of the reflector element, which defines a light inlet area for the light to be reflected into the reflector element. Further, the asymmetrical reflector element comprises a second opening at its opposite end. Further it comprises a lateral area, at which the light emitted by the emitter having an anisotropic radiation behavior or an anisotropic light source, is reflected. The lateral area extends from the first opening to the second opening and is formed such that a line extending from at least one position of the inlet area in a right angle towards the second opening, i.e. a surface normal, crosses the lateral area.

The anisotropic light source may be in particular a unit with one or more LEDs, OLEDs (organic light emitting diodes).

This has the advantage that light emitted by the anisotropic light source, e.g. a LED unit in a radiation angle of zero degrees can be reflected and thus directed into a desired direction in order to illuminate a predetermined illumination area. Most of the LEDs show an emission characteristic with a dominant emission direction at a radiation angle of 0 degrees, see also Fig. 1 , thus that the dominant beam is reflected.

The LED unit may comprise one or more LEDs. By the tailored reflection element the light of an individual LED unit or anisotropic light source may be directed individually. Thus the effectivity of the reflection is increased in comparison to setups, where a number of different LED units or anisotropic light sources are reflected by the same common reflector element, because then the reflector element either cannot be optimized in regard to every single LED unit or anisotropic light source , or its production is very elaborate and therefore costly. Due to this lower efficiency of the common reflector element, then the LED units or anisotropic light sources have to be operated thus that their luminous intensity is higher in order that a predetermined luminous intensity at an area to be illuminated can be achieved. This has the drawback of higher energy consumption. For the embodiments described in the following reference is made to an LED unit as an example of an anisotropic light source. However instead of the LED unit any other anisotropic light source or emitter having an anisotropic emission behavior might be used. In particular, the LED unit might also use one or more OLEDs. According to an advantageous embodiment, the asymmetrical reflector element is adapted for reflecting light emitted by an emitter with an anisotropic radiation behavior, thus that a dominant emission direction and at least a first subordinate emission direction and at least a second subordinate emission direction is established. A lateral area extending from the first opening to the second opening is formed such that a beam of light emitted by the LED unit in its dominant emission direction can be reflected towards a point of the illumination area. As a point particularly a certain predefined part of the illumination area, e.g. a spot, is considered. The illumination area may be for example a part of a floor, a street or a wall. Further, a beam of light emitted by the LED unit in the at least first subordinate emission direction and the second subordinate emission direction can be reflected towards a common point of the illumination area. Thus a high intensity can be achieved also in subordinate emission direction. By further directing two or more light beams from a subordinate emission direction towards a common point, not only a spot illuminated by the light in the main emission direction can be achieved, but a wider area. These two embodiments allow predefining an illumination area, which is illuminated with an illumination profile determined by the reflector element. Particularly, by illumination profile, the spatial dependency of the luminous intensity on an area to be illuminated is considered. In particular by using an asymmetrical reflector element according to the embodiments a uniform illumination on an area to be illuminated, e.g. a part of a street or floor, can be achieved even if using an anisotropic light source.

The LED unit is for this description considered as a point source of light if its dimensions can be considered as small, compared to the reflector element dimensions. For embodiments where this should not be the case, a convolution with the geometry of the LED unit is done in order to optimize the reflector element's shape.

According to an advantageous embodiment, at least a part of the lateral area is formed as having a continuous curvature along the vertical direction from the first opening to the second opening. This allows to direct a light emitted in dominant or subordinate emission direction to a desired illumination area and to establish the desired illumination profile. The illumination profile is particularly the distribution of intensity in the illumination area. Further, discontinuities can be avoided, if there is no edge in a non vertical direction. By having a continuous curvature further the manufacturing of the reflector element may be facilitated.

Particularly, the curvature of a part of a lateral area is negative. This means that the first derivate is decreasing. This allows directing the light emitted by the LED unit in its dominant and subordinate emission direction to an illumination area situated far off the axis of the reflector element. Thus a lighting unit with a reflector element needs not to be positioned directly above the area to be illuminated. Further a dazzling of persons in reduced, because the light can be directed only to the points, where illumination is required. Further, the LED unit has not to be tilted such, that its main emission direction is towards the illumination area far which also would increase a dazzling which is to be avoided particularly where traffic is involved. The lateral area is particularly formed as an at least partially tubular element. As a tubular element in particular a geometric element is considered, which extends from a base area to a corresponding top area, which need not to be parallel or plain. This tubular element may be formed such that at least one edge along the direction from the first opening to the second opening is formed. Thus, distinct side walls can be formed. This allows an easy manufacturing and compact arranging of individual reflector elements in order to form a reflector. In regard to the illumination area the shape of the illuminated area and its illumination profile can be defined. The side walls may be formed such that a surface normal, i.e. a line protruding perpendicularly from the surface, extending from at least one position of the inlet area crosses a first side wall of the lateral areal. The second side wall is formed such that a surface normal from any position of the inlet area does not cross the second side wall. This allows a strong asymmetric reflection of the light in order to illuminate illumination areas situated far off the axis of the reflector element.

According to an advantageous embodiment, the first opening is positioned at least partially in a base area, from which the lateral area extends. By having a base area, the manufacturing may be simplified, as the side walls can be extended from this base area. Further, in the case of a plane base area the reflector elements may be positioned more safely and accurate on a PCB (printed circuit board), on which the LED unit is arranged.

Alternatively or additionally, at least a part of the first opening is confined by a light inlet area border from which the lateral area extends directly. This allows a compact setup of the reflector element, as no additional space for a base area is required. Thus compact reflectors with a plurality of reflection elements can be made, thus that also the corresponding lamps can be made relatively small or compact with a large number of reflection elements for a corresponding number of LED units

According to an advantageous embodiment at least parts of the lateral area of the reflector element are made of transparent material. On the back side of the lateral area, a reflection layer is deposited. By back side of the lateral area, the outer side of the reflector element is meant. This has the following advantage: If no special precautions are taken, a coating provided on a surface is not really plain, that means that elevations and depressions are formed, e.g. due to irregularities of the substrate on which the coating is deposited or due to an unequal deposition rate. A further aspect is here that the thickness of the coating may vary due to the shape of the surface on which the coating is to be deposited. For the asymmetrical reflector element it is very difficult to establish a uniform coating along the overhang of the at least first side wall. By depositing the reflective coating on the back side of the reflector element, material can be deposited uniformly on the region of the overhang. Further, an evenly reflection surface is established, because this surface is defined by the outer side of the reflector element.

In order to minimize losses due to absorption in the transparent lateral area, the lateral area is made of material with low absorption in the frequency regime of light emitted by the LED unit. Alternatively or additionally, the lateral area is designed very thin. Thin is understood in this context as to be seen in relation to dimensions necessary for the manufacture and/or in regard to the absorption length of the light emitted by the LED unit.

For an advantageous embodiment acrylic is used, which is durable and cheap. According to an advantageous embodiment, a reflector is formed which comprises at least a first asymmetrical reflector element, which is to be used with a first anisotropic light source, e.g. an LED unit. The lateral area of the at least first reflector element is formed such that light emitted by the first anisotropic light source or LED unit is reflected in order to illuminate a predetermined illumination area. According to an advantageous embodiment, the reflector comprises at least a second reflector element for use with a second light source. This light source might be an anisotropic light source, such as an LED unit or an isotropic light source, such as e.g. a halogen lamp. The lateral area of the second reflector element is formed such that light emitted by the second light source is reflected to illuminate a second predetermined illumination area.

The use of an essentially isotropic light source is in particular intended together with symmetrical reflector elements.

According to an advantageous embodiment, the first predetermined illumination different from the second predetermined illumination area. Thus, the region of illumination can be increased. According to another advantageous embodiment, the first predetermined illumination area is essentially identical to the second predetermined illumination area. This allows increasing the luminous intensity on this illumination area.

According to a further advantageous embodiment, the reflector comprises a plurality of reflector elements of which all illuminate the same predetermined illumination area.

According to a further embodiment, the reflector comprises a plurality of reflector elements of which all illuminate different illumination areas.

According to another advantageous embodiment, the reflector comprises a plurality of reflector elements of which some illuminate the same illumination area and some illuminate a different illumination area.

According to an advantageous embodiment the at least one asymmetrical reflector element and at least one symmetrical reflector element are assembled symmetrically. This has the advantage that the detector can be used with a lighting unit, the light of which seems to be the same regardless if looked at from the left or right side. Thus a uniform illumination can be provided.

According to a further aspect of the invention, a lighting unit is provided with at least one reflector having at least one reflector element. Further, the lighting unit comprises at least one anisotropic light source, in particular an LED unit, the light of which is reflected by the at least one reflector element and a control unit for controlling the light intensity of the at least one anisotropic light source in order to achieve a predetermined illumination. The illumination is particularly predetermined in regard to the overall area which is illuminated, the intensity of the illumination, the spatial dependency, the time behavior of the illumination and in the case of more LED units as anisotropic light sources, individual light intensity of each or a group of LED units.

In particular, the illuminated area can be assembled by one or more illumination areas of an individual reflector element. According to a further advantageous embodiment the reflector comprises at least a second reflector element. Further, at least a second light source is used, the light of which is reflected by this at least second reflector element. The second light source might be an essentially isotropic light source or an anisotropic light source such as an LED unit. The control unit is adapted such that the light intensity of the at least one anisotropic light source and the at least second light source can be controlled separately, in order to achieve a predetermined illumination. In the case of a plurality of first and second light sources, an embodiment is provided, where the light intensity for each individual is controlled separately. According to a further embodiment all of first and second light sources are LED units. According to another embodiment the intensity of each first and second light source is controlled jointly. According to another embodiment, the light intensity for a group of LED units, each made of at least one LED, is controlled jointly.

According to a further embodiment, at least one of the first anisotropic light source, e.g. an LED unit, and/or the second light source is at least partially put through, i.e. emerged through, the first opening of at least one reflector element. This allows an easy positioning of the light source, e.g. the LED unit, in regard to the reflector element.

According to another embodiment, the light source, e.g. the LED unit is positioned behind the opening, i.e. it does not reach through the opening. Then the light of the LED radiates through the opening. This allows a definition of the emissive area of the LED unit by adapting the light inlet area. Further, incorrectness in manufacturing can be accounted for in the case of a number of LED units and a reflector having a plurality of reflector elements, because the position of the LED unit in regard to the light inlet opening can be shifted slightly.

In particular the light sources of a lighting unit are arranged symmetrically in regard to their position and/or type as well as the arrangement of at least an asymmetrical reflector element and a further reflector element. By type is meant e.g. that the same blue colored LED units are used on the left side of a lamp unit as on the mirrored position on the right side. According to another embodiment, a lighting unit is provided with at least one interface configured for coupling one or more electronic components to the control unit of the lighting unit.

In particular, an electronic component is an ambient sensor comprising a movement detector for detecting a movement within a predetermined range of the lighting unit and/or a temperature sensor for controlling the temperature of the lighting unit and/or a detector for measuring the light intensity of the anisotropic light source and/or of the second light source at a predetermined position and/or a detector for measuring the distance of the lighting unit to the illuminated area and/or a metering device for measuring a current provided to the lighting unit and/or a power consumption of the lighting unit.

According to another embodiment, an electronic component is a transmission unit configured for wireless and/or wired transmission of data. The transmission unit is further configured for establishing a data connection to another lighting unit and/or a server unit to communicate data to and from said another lighting unit and/or to and from the server unit.

According to a further advantageous embodiment the lighting unit includes a cover removably coupled to the lighting unit, the cover being located externally to and in front of at least a part of the at least one reflector. In particular, the cover comprises a glass cover and/or a prismatic cover and/or a colored filter to achieve the predetermined illumination.

Further aspects and advantages of the invention are described in relation to

accompanying drawings of which show

Figure 1 : a schematic drawing of a reflector for an isotropically emitting light source; Figure 2a: a schematic drawing of the relative luminous intensity of an LED versus the radiation angle;

Figure 2b: the radiation angle for light emitted by an LED;

Figure 2c: an LED unit comprising several LEDs; Figure 3a: a perspective view of an asymmetrical reflector element according to the invention;

Figure 3b: a schematic drawing of a reflector element and the illuminated area;

Figure 3 c: a schematic drawing of a light beam emitted in the dominant emission

direction and a light beam formed by the superposition of two light beams emitted in subordinate emission directions;

Figure 4: a reflector made of a plurality of reflector elements;

Figure 5: an embodiment of a reflector having three distinct reflector elements;

Figure 6a: a lighting unit according to the state of the art, which allows to illuminate areas far off its optical axis but dazzles persons; Figure 6b: an asymmetrical reflector element with an LED unit for lighting an

illumination area far off its optical axis;

Figure 7: an asymmetrical reflector element with a lateral area made of transparenet material coated at the outside of the reflector element in order to establish a reflection layer;

Figure 8: a photograph showing lighting units using a reflector as depicted in Figure 4; Figure 9: a cross sectional view of a lighting unit; Figure 10: a schematic drawing of the setup of a lighting unit; and Figure 1 1 : a schematic drawing of a lighting network.

In Figure 1 a reflector 10 for an isotropically emitting light source 1 1 is depicted. Due to the essentially isotropic emission, the construction of the reflector 10 is fully determined by the position and characteristic of the desired light cone.

In the following, an LED is described as an example of a light source with anisotropic emission characteristics. The reflector element, a reflector with at least one reflector element and a lighting unit using such a reflector can be used with any other anisotropic light source, such as e.g. OLEDs (organic light emitting diodes). A light emitting diode (LED) has an anisotropic emission characteristic. As shown in

Figure 2, the relative luminous intensity decreases with an increasing radiation angle. The radiation angle a (see Figure 2b) is determined as the angle between a perpendicular line starting from the LED 25 and the direction of emission of light. Most of the light yield stems from a cone determined by a radiation angle of about 30° for most of the types of LEDs 25. The light emission is in a zero radiation angle is dominant. Therefore this emission direction is denoted as dominant emission direction. The light intensity in radiation angles different from zero is smaller that that in the dominant emission direction. These directions are therefore denoted as subordinate emission directions.

In Figure 2c an LED unit 26 is depicted which comprises several LEDs 25. Such an LED unit 26 is considered as an electrical component comprising one or more LEDs 25 which are controlled jointly and provided in one component. The LEDs 25 of Fig. 2c are a layer structure of approximately rectangular or squared form. The individual LEDs 25 are connected electrically such, that the LED unit 26 can be controlled as a whole.Thus the LED unit 26 comprises either one LED 25 or at least two individual LEDs 25. What type LED unit 26 is chosen depends on the purpose of the illumination and also the commercial availability. In the descriptions here, the LED 25 or LED unit 26 is considered as a point source, i.e. that all radiation is emitted from one point. This simplification is justified for

embodiments, where the dimensions of the LED 25 or the LED unit 26 are small in comparison to the dimensions of the reflector element 1. If the spatial extensions of the LED unit 26 or the LED 25 are such that this assumption does not hold, then for calculating the shape of the reflector element, a convolution with the geometrical shape of the LED 25 or the LED unit 26 has to be done.

As illustrated in Figure 2c the LED unit 26 further comprises a filter 27 for providing the desired light temperature of the LEDs. In the case of white LEDs a colored filter 27 is coupled to the LED unit 26 to provide the desired light color in the illuminated area. The filter 27 can be removed from the LED unit 26, so that the illumination can be changed after installation of the LED unit 26. Such a filter will be further discussed below with respect to Figure 9.

In Figure 3 a reflector element 1 is depicted which allows to reflect the light emitted by an anisotropic light source, e.g. an LED unit 26 to a predetermined illumination area 8. This is shown schematically in Figure 3b.

The asymmetric reflector element 1 of Figure 3a has a first opening 2 at a first end of the reflector element 1. In the vicinity of the first opening 2 the LED unit 26 is

accommodated. The LED unit 26 may comprise one or more LEDs 25. The LED unit 26 can be either positioned behind the opening, thus, that at least a part of its light is radiated through the first opening 2. Alternatively, the LED unit 26 may be put through the first opening 2. From the first opening 2 a lateral area 3 is extending towards a second end of the reflector element 1 which has a second opening 7. The lateral area 3 may extend directly from the border of the first opening 2 or from a base area, in which the first opening 2 is situated. The shape of the second opening 7 determines essentially the shape of the illumination area 8 which is to be illuminated from light reflected in the reflector element 1. The second opening 7 is confined by a rim 4.

The reflector element 1 is asymmetric in regard to an axis 27 extending from the first opening 2 towards the second opening 7. In the embodiment depicted in Figure 3a the second opening 7, which constitutes a light outlet opening of the reflector is basically of rectangular form. Thus, the lateral area 3 comprises four side walls 3a, 3b, 3c, 3d. The corners between at least some of the sidewalls may be sharp, that means that a fold or rebate is established, or rounded, that means that the first derivative of a curve describing the transition between one sidewall and the other is continuous.

In Fig. 3 a there is a rounded corner between side wall 3a and side wall 3b. Further there are sharp corners between the other side walls 3a and side wall 3d, side wall 3d and side wall 3c and side wall 3c and side wall 3 b.

Alternatively the reflector element 1 may comprise only rounded corners or only sharp corners or a first number of rounded corners and a second number of sharp corners.

According to another, not depicted embodiment, the reflector element has no corners but takes particularly the form of a circular or elliptical cylinder.

The side wall 3a is formed such that a perpendicular line 5 extending from the light inlet area defined by the opening 2 crosses the side wall 3a. Thus, light emitted in the main emission direction of the LED unit 26, i.e. along the axis 27 is reflected at this side wall 3a.

The form of the side wall 3a is that of a continuous curve, that means it is not formed of distinct facets. In other words, the first derivative of a function describing the shape of the side wall 3a in a direction from the first opening 2 to the second opening 7 is continuous. Particularly, the shape of the side wall 3a has a continuously decreasing curvature, thus that the first derivative is monotonically decreasing. By the continuous form the manufacturing process may be facilitated, the reflection efficiency can be high, as no light is lost in edges or interspaces or gaps between individual facets. By having a decreasing curvature the light can be directed far off the reflector's optical axis.

The side wall 3 c is formed such, that a perpendicular line from any point of the light inlet area defined by the first opening 2 does not cross the side wall 3 c. By such a form of the side wall 3 c in connection with the form of the side wall 3 multiple reflections can be avoided. Multiple reflections can lead to a decrease of the light yield due to reflection losses.

This asymmetrical reflector element 1 enables the illumination of an illumination area situated far off an optical axis of the reflector element 1. Thus, the reflector element 1 does not need to be positioned above the area to be illuminated, the illumination area 8, which provides a larger degree of freedom in where to put illumination devices or lighting units using the asymmetrical reflector element 1.

One further advantage is that the reflector element 1 does not have to be inclined in order to illuminate the illumination area far off its optical axis. Inclining a reflector element 1 with a light source would lead to a dazzling of persons entering the cone of light defined by a lighting unit comprising a reflector with at least one reflector element 1 through which the light of at least one LED unit 26 is reflected.

This will be described in more detail in regard with Figures 6a and 6b. In Figure 4 a reflector 20 comprising a plurality of reflector elements is depicted in order to achieve a desired illumination of an illumination area 8. On the left side 21 there is a plurality of asymmetric reflector elements 1 , which reflect the light essentially in a same direction leftwards. In the middle, there is a group of symmetrical reflector elements 22, which do not deflect the light in a direction off the axis of the symmetrical reflector element 22. On the right side 23 there is a further group of asymmetric reflector elements 1 , which reflect the light essentially in a same direction rightwards. This reflector element used for a lighting unit, the light of which can be seen only from the side to which the light is reflected. Thus, a dazzling is reduced, which is especially important for illumination of traffic zones. This is depicted in Figure 8.

Further, due to the symmetrical arrangement of the light emission from a lighting unit using such a reflector seems to be the same if observed from the left or right side. Thus a uniform illumination can be provided.

A reflector 20 may comprise at least one group with at least one asymmetric reflector element 1. The number of groups with different reflection behavior depends on the illumination purpose. Further the asymmetric reflector elements 1 or symmetric reflector elements 22 of one group may be positioned in coherent or incoherent areas.

The groups of reflector elements 1 which show the same asymmetric form illuminate an illumination area essentially not below the lighting unit. The reflector elements 22 of symmetric shape provide an illumination below the lighting unit.

In Figure 5 a reflector element 20 is depicted, which has only one asymmetric reflector element 1 directing the light to the left, one asymmetric reflector element 1 directing the light to the right and one symmetrical reflector element 22 which does not change the direction of light emission.

According to further embodiments a reflector 20 is provided having only one

asymmetrical reflector element 1. A further embodiment comprises more different types of asymmetrical reflector elements 1 , thus that illumination is not provided only towards the left side or the right side or directly down from the lighting unit, but also in a plurality of other directions.

In Figure 6a a lighting unit according to the prior art is depicted. In order to provide illumination far off the optical axis 37 of the lamp, the areas on which the light sources are positioned are inclined in regard to the perpendicular of the optical axis 37. However, persons might be dazzled by the parallel beams of light emitted from light sources on these inclined areas.

In contrast, the illumination scenario is shown in Figure 6b taking the example of one asymmetric reflector element 1 reflecting the light of one LED unit 26. Due to the special asymmetric shape, the light can be directed far off the optical axis 37 without dazzling a person in this area.

In Figure 7 an asymmetrical reflector element 1 is depicted in a cross sectional view. Parts of the first side wall 3a and a second side wall 3c are made of transparent material so that the light emitted by the LED unit 26, which is positioned on a PCB board 70, can go through side walls 3a, 3c until it is reflected at a reflection layer 71 , which is deposited on the back side of at least parts of the lateral area 3.

In Figure 7 the light beam 72 emitted in the dominant direction is reflected only once. This ensures that also the intensity losses due to reflection are kept low. Alternatively, in order to direct light to illumination area 8 at special positions in regard to an

asymmetrical reflector element 1 , a twofold or more fold or multiple reflection can be desired.

In Figure 8 a plurality of lighting units 80 are depicted. From the view from the left side, which is taken for Figure 8, only light reflected through the asymmetrical reflector elements 1 reflecting light towards the left can be seen. This further reduces a dazzling or unnecessary illumination of further areas. The reflector 20 used for the lighting unit 80 in Figure 8 is that of Figure 4. In addition to the symmetrical arrangement of the

asymmetrical reflector elements 1 and symmetrical reflector elements 22, further the arrangement of the type of LED units 26 is symmetrical.

According to an exemplary embodiment the temperature color of the LED units 26 emitting through the symmetrical reflector elements 22 is yellow and their power is twice that of the LEDs in the middle. For the asymmetrical reflector elements on the right hand and/ or left hand side LED units 26 with a blue temperature color are used. This provides a suitable illumination for railway stations or other traffic scenarios. As an example only, if the lighting unit 80 is used for the illumination of a street or a railway station, LED units 26 can be used which emit light with a high blue fraction, i.e. cool light, such as corresponding to a temperature range above circa 3,500 . This has the advantage that insects are less attracted by this cool light than it would be the case with warmer light.

In accordance with an embodiment an amber colored LED, that is a color between yellow and orange, is positioned in the indirect illumination lighting element or in the LED units 26. The amber colored LED can be part of a multicolor LED. As amber is the

predominant color of the human skin, by using amber the achieved illumination may be defined as comfortable and showing people in an approximately natural light.

Further, in accordance with an embodiment of the invention the lighting unit comprises a primary and a secondary illumination direction. While the primary illumination direction is specified by the LED units 26 and the reflector 20, the secondary illumination direction may vary. Such a secondary illumination can be achieved by at least one indirect illumination lighting element that is positioned on the back side of the housing of the lighting unit 80. The indirect illumination lighting element is formed in such a way that a major part of the emitted light illuminates an item surrounding the lighting unit 80, such as a ceiling or a wall. Advantageously the emitted light hits surrounding items in a predetermined angle, preferably perpendicular, to influence the way the light is reflected. In an embodiment such a lighting unit is installed in a tunnel. If the indirect illumination lighting elements illuminate the wall and/or ceiling of the tunnel, an evenly distributed illumination effect is achieved. When entering the tunnel the human eye can adapt faster to such an illumination than to single lighting units with direct illumination. In detail, the contrast between the light of the primary illumination direction and the usually dark background of the tunnel walls and ceiling is reduced by the secondary illumination direction. As a consequence security can be enhanced by a lighting unit having an indirect illumination according to the invention. The indirect illumination lighting element may be positioned at one or various distinct positions or be distributed over the whole back side of the housing. The design of the indirect illumination lighting element depends on the desired illumination, e.g.

brightness, the size and also the form of the illuminated item. Further, the housing of the lighting unit 80 provides for openings for emitting the light of the indirect illumination lighting element. In an advantageous embodiment the housing of the lighting unit 80 has at least one reflector element, such as the reflector element 1 , positioned on the back, i.e. the opposite side of the reflector 20. Thus, the angle and cone of the emitting light can be specified to achieve the desired indirect illumination. On the back side of the lighting units cooling ribs 81 are formed. This allows for reducing the temperature in the internal space of the lighting unit. According to an embodiment, the cooling ribs of the lighting unit are made of aluminum for improving the cooling effect due to the thermal conductivity of aluminum. In accordance with a further embodiment the complete housing of the lighting unit is made of aluminum. This allows for a more simple construction and manufacturing of the housing, as well as for an enhanced temperature management of the lighting unit.

In Figure 9 a cross sectional view of a lighting unit 80 is depicted. The reflector 20 with asymmetrical reflector elements 1 and symmetrical reflector element is positioned above LED units 26, which are arranged on a PCB 70. A control unit 90 is positioned on an opposite side of the PCB 70 for controlling the light of the individual LED units 26.

According to an embodiment the LED units 26 are controlled alone or jointly in a group of at least two LED units 26. For an advantageous embodiment all LED units deflecting light in essentially the same direction are controlled jointly.

In accordance with another embodiment the lighting unit is mounted to a pole or mast. The lighting unit can also be mounted to a wall. In any case, the height at which the lighting unit is affixed may vary. The control unit 90 is further configured for controlling the light intensity of one or more LEDs 25 or LED units 26 dependent on the height of the lighting unit. Thus, the control unit can be employed to adjust the light intensity based on the distance of the lighting unit from the area to be illuminated. For this purpose, the height can be input during installation of the lighting unit. Additionally or alternatively the height can be measured by a sensor attached to the lighting unit which will be explained in more detail below. According to another embodiment the LEDs 25 or LED units 26 are controlled by adjusting the electric current provided to each LED. Conventional lighting units are controlled by using different voltages. In order to react on desired changes of the provided voltage, the lighting unit of the present invention provides for adjusting the electric current supplied to the LEDs 25 and/or LED units 26. As an example, the control unit detects a change in the voltage and thereupon modifies the current provided to the LEDs 25 and/or LED units 26.

Thus, by the asymmetrical reflector element the possibility is provided to create an illumination by an anisotropic light source also on areas to be illuminated which are situated far off an axis of the reflector element. This is done by deflecting the light beams in various radiation angles towards the illumination area by a lateral area forming at least partly an overhang.

In order to have a high light yield, the beam in the dominant emission direction is deflected towards a first point of the illumination area 8 and at least two beams in subordinate emission directions are superimposed on the illumination area 8 in order to yield a high light intensity also at this points or positions of the illumination area 8. Thus the illumination profile of this illumination area can be determined by a superposition of light beams. Further, the problem of dazzling can be strongly reduced in contrast to lighting systems where the light sources are positioned on an inclined area.

A reflector 20 can be made comprising one or more of these asymmetrical reflector elementsl . A lighting unit 80 comprises at least one reflector 20, at least one LED unit 26 and a control unit. According to a further embodiment the reflector 20 is removably coupled to the housing of the lighting unit. In this case, the housing would provide for fastening elements to hold the reflector at the correct position with respect to the LED units 26. This has the advantage that the desired illumination of a lighting unit can be easily changed after installation of the lighting unit. For example, if another area has to be illuminated or if the shape and size of the illumination area has to be changed, the reflector 20 can be exchanged by a new reflector having different reflector elements 1 , i.e. reflector elements 1 of a different shape and/or form. It is also within the scope of the invention to install a new reflector 20 which does not provide a reflector element 1 for each LED 25 to achieve a desired illumination. In this case, the control unit 90 is reconfigured so that the LEDs 25 where a corresponding reflector element 1 is missing are not provided with a current, i.e. that these LEDs will not be used.

Further, a cover (not shown) can be mounted to the lighting unit externally to and in front of the reflector 20. Such a cover or attachment may be made of glass, an acrylic sheet or any other transparent and light and weather resistant material. Preferably the cover is coupled to the housing of the lighting unit in a similar manner as the reflector 20. Thus, the cover can also be exchanged easily by a new one. If the same fastening elements are used for the cover and the reflector 20, it can be assured that it fully covers, and thus protects, the reflector elements 1. The cover can be of any type, such as a simple protective glass or a filter for creating a predetermined light temperature or color. Such covers are a float glass or other tempered security glass with a thickness of 4mm. According to other embodiments, the glass has a different thickness, such as 2mm, 6mm or even more. Further, in order to achieve a predefined light temperature, a cold white glass can be installed which provides an efficient illumination. The preferred color is 4300 , while according to another embodiment a color of 3500 is achieved. Alternatively, the cover may be a warm white glass to have a color of preferably 7500K. According to other embodiments, the installed glass may achieve a higher or lower light color value. Additionally or alternatively, the cover is a prismatic glass to direct the light in a predetermined direction, a plasma glass or a diffusing cover, also referred to as a diffuser, to further reduce glare and to provide a uniform light. A diffuser has the advantage that the light distribution is symmetric in regard to the lighting unit. As an example only, the illuminated area is a circle or ellipse having a center underneath the lighting unit. Thus, an area behind the pole to which the lighting unit is mounted can also be illuminated.

Additionally or alternatively, the cover has one or more lenses to direct light to a predetermined area.

Thus, by installing a particular reflector and by employing a particular cover any kind of illumination can be created and every desired illumination is possible. An advantage of the invention is the reduced energy consumption due to an efficient light distribution within the desired illuminated area. By installing a specific reflector the light can be directed to the desired illuminated area. When further installing one of the above discussed cover, the properties of the light can be adapted to the desired lighting situation. These properties are light temperature, light color, direction of the light and also the size and shape of the illuminated area (e.g. using a diffuser).

According to another embodiment the cover only covers predefined reflector elements 1 and thus only predefined LEDs 25. Thus, different predetermined illumination areas can be created. Referring back to Figure 9 the lighting unit 80 comprises one or more interfaces to connect one or more electronic components to the lighting unit. The one or more interfaces are further coupled to the control unit to allow for data transfer and other communications between an electronic component and the control unit. An interface can be implemented as a standard bus interface installed on the PCB 70. As examples only, such a bus interface may be a serial bus, a parallel bus, a Peripheral Component

Interconnect (PCI) bus, Universal Serial Bus (USB) or the like. Additionally or alternatively some or all of the interfaces are integrated in the design of the PCB. Thus, the electronic component can also be integrated with the PCB.

In accordance with an embodiment of the invention the interface allows for coupling a sensor or a plurality of sensors to the control unit 90. For this purpose, the lighting unit 80 comprises an ambient sensor for measuring an ambient parameter. The control unit 90 is capable of controlling the LEDs 25, such as their brightness, based on the measured ambient parameter. This ambient sensor is particularly a movement detector for measuring a movement within a predetermined range of the lighting unit, e.g. within the light cone defined by the lighting unit 1. Based on the detected movement, the control unit can switch on or off specific LEDs 25 or groups of LEDs to illuminate areas where the movement occurs.

Alternatively or additionally, the ambient sensor is a light intensity measuring unit for measuring the light intensity of a single LED 25 or a group of LEDs. By comparison with a reference value for the light intensity a deviation to the reference value can be detennined and can be corrected. The deviation of the intensity from a reference value and a correction of the intensity is in particular controlled and managed by the control unit 90. If the measured deviation is within a certain range, e.g. 10 to 15%, the individual lighting unit 80 may compensate this by providing different driving parameters by the control unit 90 to the individual LED 25 or a group of LEDs. For higher deviations this deviation information is provided from the lighting unit to a master lighting unit which communicates this to a server unit in order to provide data for maintenance of a lighting network (slave and master units as well as a network will be explained further below).

Alternatively or additionally the ambient sensor may comprise a temperature sensor that is coupled to the control unit 90 via the one or more interfaces. The data thereof may be used for controlling the temperature within the lighting unit 80. Thus, for ensuring the desired brightness the lighting unit 80 can be cooled or the current provided to the LED 25 or LED units 26 may be adjusted. The temperature sensor may be placed in particular in the vicinity of the LED 25 or LED units 26 in order to ensure an accurate measurement of the relevant temperature. Thus, e.g. the temperature sensor may be placed on the PCB 70, on which also the LED 25 or LED units 26 are positioned. In a different embodiment, the temperature sensor is installed on the PCB 70 and is coupled with the control unit 90 via a direct bus connection, i.e. without an intermediate interface.

Alternatively or additionally the ambient sensor may comprise a height detector to measure the distance of the lighting unit to the ground and/or to the desired illuminated area. This measured distance can be used by the control unit 90 to adjust the light intensity based on the distance.

According to another embodiment the one or more interfaces are used to employ a wireless transmission unit for sending or receiving data. Via this wireless transmission unit a network of two or more lighting units can be established. In particular, a local wireless transmission unit operating in a range of less than 300 meters can be installed in the lighting units 80. An exemplary wireless transmission unit is a transmission unit which works in the regime around 2.4 GHz and uses an encryption of at least 128 bit. Such a transmission unit can include a module adapted to WLAN standards such as ZigBee and/or WiFi transmission and/or IEEE 802.1 1 transmissions and/or other alternatives, e.g. Bluetooth. This ensures that common wireless transmission units can be used which makes the production cheaper. Further, it ensures that the necessities for establishing a network of street lamps with a limited range between one street lamp and another street lamp are met. Alternatively, other frequency bands are used which are suitable in respect to range, interferences and allowed frequency bands.

In accordance with an embodiment some lighting units 80 function as master lighting units while one or more lighting units act as slave lighting units. The master lighting units include an additional module adapted to GPRS or UMTS or comparable transmission standards transmission for connecting the lighting unit 80 over longer distances. A master lighting unit is used for establishing a connection to a wide area access network and/or a remote control using the module for a long range connection. Thus, the wireless transmission unit comprises at least a module for establishing a connection in a short range, e.g. up to a few hundred meters, and optionally a module for a long range connection, e.g. a wireless telecommunications connection based on e.g. GPRS, UMTS or the like. Alternatively, two different transmission units are employed with the lighting unit via two interfaces.

According to a further embodiment, the transmission unit is adapted - alternatively or additionally - for wired transmission. Thus data between at least one slave lighting unit and at least one master lighting unit can also be transferred over power cables through power line technology, where they are available and where it is advantageous to use the prescribed fixed structures of the existing fixed network. By using power lines to which a lighting unit is connected anyway these lines can be used two-fold and no additional network infrastructure has to be provided.

Each lighting unit 80 has a unique identification number and has access to its neighboring units. A master lighting unit provides external control information to lighting units 80 which are therefore denoted as slave lighting units. The lighting units 80 transmit the information to the next neighboring units and so on. The transmission stops if specified or continues until the forwarded information arrives back at the master lighting unit.

Preferably, information or external control data are transmitted between neighbored lighting units 80 or between a neighbored master lighting unit and a lighting unit.

Alternatively or additionally, data are transmitted from the master lighting unit to each slave lighting unit. Any information is coded for one specific lighting unit 80 by its identification number or for all lighting units 80 in the local area network. Since some lighting units 80 may be in far distance from the master unit the information is being sent to the next two units and they forward the external control information as forwarded external control information to the next neighbors until the information is being received by the respectively addressed identification number. Alternatively, the process can start in the other direction.

Alternatively or additionally to transmitting data between only the nearest lighting units 80, i.e. the respective lighting units that have the smallest distance to each other, the data may be exchanged between all neighbored lighting units or at least a group of all the lighting units 80 which are positioned within the transmission range, wherein the lighting units to which a transmission takes place can be defined user or situation dependency.

A master lighting unit can access an access network via its transmission module or transmission unit for a long range connection by which data can be transferred to a server unit. Thus, overall control information for controlling the whole lighting network can be provided from a server unit via the access network to each or some, at least one, of the master lighting units. The master lighting units can alternatively be accessed by a local control master, such as a laptop, PC, PDA, etc. which is equipped with a transmission unit (e.g. a USB transmission unit). Both local control master and server can also initiate a communication process particularly via an SMS signal which can also be received by the master lighting unit.

A particular advantage of the described network of lighting units is that the control of the lighting network is realized via at least one master lighting unit instead of controlling each individual lighting unit 80 separately. Thus, the master lighting unit provides data of all related slave lighting units, so that the master lighting unit and the related slave lighting units form a single virtual light unit. The ability to control a multitude of such local networks through a global network combining all at least one local network into one global network acting as one entity being wirelessly connected through the web, or internet, and collectively managed by one central server is realized.

The lighting unit 80 further comprises a time registration device which measures or receives points of time. By using these points of time provided by the time registration device a time interval can be chosen by the control unit 90 and a light intensity corresponding to the chosen time interval can be adjusted. These points of time can be measured externally and received by use of the transmission unit. Particularly, the time registration device can be connected to the control unit 90 via the one or more interfaces. Alternatively, the time registration device may be contained in the control unit 90. The above described embodiments can be combined or some of their features may be combined. Particularly, several ambient detectors are used and the control of the light intensity considers the respective ambient detector signal.

Thus, particularly the present invention relates to a wireless connected network (a wireless local area network - WLAN - between lighting units on one geographic area) comprising at least one lighting unit acting as a master lighting unit and at least one lighting unit acting as a slave lighting unit collectively connected to a central server through the web (global area network - GAN) or to a master controlling unit being installed on a laptop or PC located particularly in less than 300 meters distance. The connection to the web or internet or other networks, e.g. private LANs etc, or to the master controlling unit is wireless. Each lighting unit is not further than 300 meters from each other.

This allows a high flexibility in positioning the individual lighting units 80 and master lighting units, because already predetermined fixed structures have not to be used. On the other hand an effective long range communication to the access network can be established which is resistant in regard to disturbances.

An advantage thereof is to provide an efficient long range communication via telecommunication technologies established in the area of the lighting network particularly in order to receive and/or send information to the access network and/or the server unit. Thus the access to the network via e.g. an internet connection in order to request or provide information, in particular to request internal control signals or measured ambient parameters or to provide overall control information, is realized with a high area coverage.

A further advantage of the network of lighting units is a comprehensive access network, such as a mobile WiFi or WiMAX access network. Such a network provides the implementation of additional services such as VoIP (voice over IP), connectivity for webcams, conferencing and other internet based services in addition to light services. According to an embodiment, an additional module is build in the lighting unit for connecting to metering devices, i.e. smart meters. This additional module provides for a data communication to and from a metering device and/or gate server for metering devices. Thus, the network of lighting units allows for reading meter data from meter devices within the range of the lighting units 80. In case of street lights the distance between a lighting unit and metering devices of nearby buildings is usually within the range of the employed transmission units. Therefore, a lighting unit establishes a wireless connection to at least one metering device to read the meter data. The lighting unit then transmits the meter data via the network of lighting units and the global access network to a computing device of, e.g. an energy provider. The meter device can be any of an electricity meter, water meter, gas meter, etc.

Claims

Claims

1. Asymmetrical reflector element (1 ) for reflecting light emitted by an emitter having an anisotropic radiation behavior (26) in order to illuminate a

predetermined illumination area (8) comprising

a first opening (2) at a first end of the reflector element (1 ), defining a light inlet area and a second opening (7) at the opposite second side thereof; and a lateral area (3) for reflecting the light, said lateral area (3) extending from the first end to the opposite second end; wherein

- the lateral area (3) is formed such that a line (5) extending from at least one position of the inlet area in a right angle towards the second opening (7) crosses the lateral area (3).

2. Asymmetrical reflector element (1) for reflecting light emitted by an emitter having an anisotropic radiation behavior with a dominant emission direction and at least a first subordinate emission direction and a second subordinate emission direction in order to illuminate a predetermined illumination area (8) comprising a first opening (2) at a first end of the reflector element (1), defining a light inlet area and a second opening (7) at the opposite second side thereof; and

- a lateral area (3) for reflecting the light, said lateral area (3) extending from the first end to the opposite second end;

wherein the lateral area (3) is formed such that light emitted in the dominant emission direction is reflectable towards a point of the illumination area (8) and light emitted in the at least first subordinate emission direction and second subordinate emission direction is reflectable towards a common point of the illumination area (8).

3. Reflector element (1) according to claim 1 or 2 wherein the asymmetry is

established in regard to an optical axis (37) of the reflector element (1).

4. Reflector element (1) according to any of the previous claims wherein the lateral area (3) is formed such that at least for a part of the lateral area (3) a continuous curvature is established in the direction from the first opening (2) to the second opening (7).

5. Reflector element (1 ) according to claim 4 wherein the curvature is negative.

6. Reflector element (1) according to any of the previous claims wherein the lateral area (3) is formed at least partially as a tubular element.

7. Reflector element (1) according to claim 6 wherein the tubular element has at least one edge along the direction from the first opening (2) to the second opening, thus that at least a first side wall (3a) and a second side wall (3c) are formed.

8. Reflector element (1) according to claim 7, wherein

a first line (5) extending in a right angle from at least one position of the inlet area crosses the at least first side wall (3a);

and a second line extending in a right angle from an arbitrary position of the inlet area does not cross the at least second side wall (3c).

9. Reflector element (1 ) according to any of the previous claims wherein the first opening (2) is positioned in a base area from which the lateral area (3) extends at least partially and/or the first opening (2) is confined by a light inlet area border (6) and the lateral area (3) extends at least partially from the light inlet area border (6).

10. Reflector element (1) according to any of the previous claims wherein at least parts of the lateral area (3) are made of transparent material, particularly acrylic, on which a reflection layer (71) is deposited on the back side of the lateral area (3) at the outer side of the reflector element (1).

1 1 . Reflector element (1) according to any of the previous claims wherein a unifomi illumination on the illumination area (8) is achieved by the light reflected towards the common point of the illumination area (8).

12. Reflector (20) comprising

at least a first asymmetrical reflector element (1) according to any of the previous claims for use with a first anisotropic light source (26),

wherein the lateral area (3) of the at least first reflector element (1) is formed such that light emitted by the first anisotropic light source (26) is reflected thus that a first predetermined illumination area (8) is illuminated.

13. Reflector (20) according to claim 12, comprising

at least a second reflector element (1 , 22) for use with a second light source (26, 1 1 ), wherein

by the second reflector element (1 , 22) the light emitted by the second light source (1 1 , 26) is reflected thus that a second predetermined illumination area (8) is illuminated.

14. Reflector (20) according to claim 13, wherein the first predetermined illumination area (8) is different from the second predetermined illumination area (8).

15. Reflector (20) according to claim 14, wherein the first predetermined illumination area (8) is the same as the second predetermined illumination area (8).

16. Lighting unit (80) for providing an illumination predetermined in regard to the illuminated area and/or intensity of the illumination comprising

at least one reflector (20) according to any of the previous claims 12 to 15 with at least one reflector element (1);

at least one anisotropic light source (26) for emitting light which is reflected by the at least one reflector element (1 ); a control unit (90) for controlling the light intensity of the at least one anisotropic light source (26) in order to achieve the predetermined illumination.

17. Lighting unit (80) for exterior or interior illumination according to the previous claim 16 wherein the reflector (20) has at least a second reflector element (1 , 22), comprising

at least a second light source (26,1 1 ) emitting light which is reflected by the at least second reflector element (1 , 22);

a control unit (90) for controlling the light intensity of the at least one anisotropic light source (26) and the at least second light source (26,1 1) separately in order to achieve the predetermined illumination.

18. Lighting unit (80) according to any of the claims 16 or 17, wherein

the control unit (90) is adapted such that the light intensity of an individual anisotropic or second light source (26,1 1) or a group of at least two anisotropic and/ or second light sources (26) is controlled separately such that by use of the reflector (20) the illumination is predetermined in regard to size and/or position of the illuminated area and/or intensity.

19. Lighting unit (80) according to any of the claims 16 to 18, wherein at least one of anisotropic light source (26) and light source (26) is at least partially put trough the first opening (2) of at least one reflector element (1 ) of the reflector (20).

20. Lighting unit (80) according to any of the claims 16 to 19, wherein at least one of anisotropic light source (26) and light source (26,1 1 ) is positioned behind the first opening (2) of at least one reflector element (1) so that its light radiates through the opening.

21. Lighting unit according to any of the claims 16 to 20, wherein at least the

anisotropic light source (26) is formed by an LED unit (26).

22. Lighting unit according to any of the claims 16 to 21 , comprising:

at least one interface configured for coupling one or more electronic components to the control unit (90) of the lighting unit.

23. Lighting unit according to claim 22, wherein an electronic component is an

ambient sensor comprising a movement detector for detecting a movement within a predetermined range of the lighting unit (80) and/or a temperature sensor for controlling the temperature of the lighting unit (80) and/or a detector for measuring the light intensity of the anisotropic light source (26) and/or of the second light source (26,1 1) at a predetermined position and/or a detector for measuring the distance of the lighting unit to the illuminated area and/or a metering device for measuring a current provided to the lighting unit (80) and/or a power consumption of the lighting unit (80).

24. Lighting unit according to claim 22 or 23, wherein an electronic component is a transmission unit configured for wireless and/or wired transmission of data, and wherein the transmission unit is further configured for establishing a data connection to another lighting unit and/or a server unit to communicate data to and from said another lighting unit and/or to and from the server unit.

25. Lighting unit according to any of the claims 16 to 24, comprising:

a cover removably coupled to the lighting unit, the cover being located externally to and in front of at least a part of the at least one reflector (20).

26. Lighting unit according to claim 25, wherein the cover comprises a glass cover and/or a prismatic cover and/or a colored filter to achieve the predetermined illumination.