WO2011033330A1

WO2011033330A1 - Led based street lighting module

Info

Publication number: WO2011033330A1
Application number: PCT/HU2010/000100
Authority: WO
Inventors: László DOMJÁN; Gábor SZARVAS; Attila SÁGHY; Szabolcs Kautny; András MOLNÁR; Iván HOFFMAN
Original assignee: Eka Elektromos Készülékek És Anyagok Gyára Kft.; Optimal Optik Kft.
Priority date: 2009-09-17
Filing date: 2010-09-17
Publication date: 2011-03-24
Also published as: HU0900583D0; HUP0900583A2

Abstract

The invention is a LED based street lighting module (10) comprising LEDs (14, 14b, 14c, 14m) as light sources as well as mirrors for directing the light thereof. The street lighting module (10) according to the invention comprises an internal space (12), LEDs (14, 14c, 14d, 14m) in the internal space (12) positioned and oriented in accordance with a predetermined light distribution, as well as planar diverting mirrors (16a, 16b, 16c, 16d) forming a light diverting internal surface of the internal space (12). The invention is furthermore a modular street lighting luminaire arrangement realized by means of the street lighting module (10).

Description

LED BASED STREET LIGHTING MODULE

TECHNICAL FIELD

The present invention relates to a LED based street lighting module as well as to a modular street lighting luminaire arrangement made up of said street lighting modules configured for the purposes of public road vehicular traffic.

BACKGROUND ART

In order to realize the luminosity and/or illumination values stipulated by the street lighting standards (MSZ EN 13201), the street lighting luminaires are to produce a predetermined light distribution, e.g. a„bat wing" light distribution according to the polar diagram shown in Fig. 1. The light flux of the light source is normalized to 1000 Im in the figure. It is typical of the energy-efficient light distribution that the applied luminaire radiates in a lower angle perpendicular to the longitudinal direction of the road than in the direction of the longitudinal axis of the road. In this way, the main part of the light flux of the luminaire falls on the illuminable street surface, and not too much light reaches the regions near the street. The predetermined light distribution to be produced by the street lighting module, therefore, generally has a lengthwise direction along the direction of the street (the 0° - 180° direction in the figure) and a crosswise direction perpendicular to the street (the 90° - 270° direction in the figure).

On the one hand, the light escaping into the environment is a loss, while on the other hand it unnecessarily loads the illuminated natural objects, as well as causes possible disturbance to those living in the neighborhood. According to experience, the light distribution of a street lighting luminaire is good when the highest light density falls into the range exceeding 60 degrees - or in certain cases 72 - 73 degrees - from the vertical in the longitudinal direction of the road. At the same time, the light emitted above 80° shall be limited in order to avoid dazzling, and the luminaire is prohibited to emit any light above 90° for reasons of light pollution. In modern luminaires, this is achieved by means of a flat glass cover, because in this case not even the luminous flux reflected by the cap is being directed towards the sky. The conventional street lighting luminaires realizing a„bat wing" type of light distribution generally comprise one light source of high luminous power - with a light flux of up to thousands of lumens in some cases -, and a corresponding, in most cases specially formed (so-called 'freeform') optical system with mirrors or possibly lenses. The light sources are produced with various power ranges. Therefore, the natrium lamps, mercury lamps, metal-halogen lamps and compact fluorescent lamps etc. most widely used in public street lighting are available within the power range of 18 to 400 W.

Modern luminaires are arranged so that the relative positions of the light source with various power and the 'freeform' optics can be varied or shifted in fix positions along one or two axes, whereby the light distribution emitted by the luminaire is characteristically altered. Practically, by means of well-designed optics, modern luminaires are capable of radiating up to 5 - 10 different light distributions depending on the relative positioning of the light source and the optics. By altering the light distribution, the light flux leaving the luminaire can be effectively directed onto the illuminable, generally rectangular shape street surface. This is similar to the focusing of optical projection systems, where by moving the projection objective the image of an object is being focused, sharpened on the screen. By means of simple alteration of the light distribution, the luminaire is enabled to meet the requirements of evenness as stipulated by the public street lighting standards even in case of various pole heights, pole intervals and road widths, beside complying with the dazzling requirements. The luminaire families arranged in this way are capable of achieving levels of low luminosity (0,3 cd/m²) and low illumination (5 lux) prescribed for side streets with low traffic ranging to high luminosity (2 cd/m²) and high illumination (50 lux) levels prescribed for suburban sections of the motorway, as well as meeting all respective evenness requirements valid for various transportation situations in an economic, and energy-efficient manner.

The light flux of commercially available LEDs (Light Emitting Diodes) is significantly lower than the light flux of high power lamps. Therefore, a plurality (5 to 10 pieces) of high power LEDs - or in the case of higher luminosities it can range up to 50 high power LEDs - may be required to be integrated into one luminaire to attain the light power of state-of-the-art, high-power street lighting modules. Because of cooling problems, LEDs have to be placed at appropriate distances from each other, as the heat generated in the LEDs can only be conducted by way of thermal conduction. For this purpose, fixing elements and heat sinks of appropriate width and good thermal conductivity have to be arranged. In the case of conventional lamps, most of the thermal loss leaves through the window or through the cap in the form of infrared radiation. LEDs practically do not radiate in the infrared range, therefore, the thermal loss, which is in similar order of magnitude as the thermal loss of widely used state-of-the-art light sources, needs to be conducted from the LED chip to the surface of the luminaire, from where the heat will dissipate into the environment by way of heat transfer, heat conduction or heat radiation.

Because of the LED arrangement and of the need to arrange thermal conduction, none of the common street lighting mirrors or optical arrangements can be applied in LED luminaires. The sizes of current light sources exceed that of the LEDs', moreover they emit spatially continuous light. Public street lighting mirrors presently in use convert the light distribution of an extensive continuous light source to the bat-wing light distribution used typically in public street lighting. LED luminaires comprise numerous small-size light sources placed in offset positions for reasons of cooling. It is the task of the optical systems of the LED luminaires to unify and form with good efficiency the individual light distributions of the small- size, discrete light sources placed in offset positions, so as to provide the required light power together as well as the bat-wing light distribution optimal for the solution of public street lighting task.

A commonly used solution is to have a special 'freeform' lens fitted to each individual LED so as to form the light current of each individual LED into a bat- wing light distribution. The desired distribution is then maintained in the sum. While the light power of each LED is yet low, in order to achieve appropriate luminosity and illumination, matrices are made up of the LEDs and the special lenses including up to 10 to 20 LED+lens elements. The luminaires are then built from these matrices, which at the same time serve as the surface ensuring fixing and cooling. The luminaire in this way forms a closed, compact unit, the cooling is efficient, the 'freeform' lenses can be cheaply produced in large quantities. The lenses cover the LEDs, so there is no need for additional protection or cap. One such solution is by way of example disclosed in the product specification available on the webpage of http://www.osram- os.com/osram os/EN/News Center/Spotliqhts/Success Stories/ download/Flyer Starium Dragon 60.pdf .

US 6 250 774 B1 discloses a luminaire comprising numerous LEDs set in different directions and optics fixed thereto. The light distribution suitable for attaining public street lighting tasks is altered by way of directing the LEDs and by means of the optics' collimation angle.

It is, however, a disadvantage of the LED luminaires arranged with freeform lens as well as of the luminaires detailed in some embodiments of US 6 250 774 B1 that their light distribution can not be modified. The luminaire arranged in this way is optimized for one given lighting task. While in the case of LED modules with freeform lens the light distribution is 'frozen', an efficient solution cannot be provided with the module for a given lighting situation other than the arrangement having the geometry (pole interval, pole height, street width) assumed for the optimization. Another problem is that according to design experiences, the maximum angle of radiation of freeform lenses is approx. 60° only, which does not reach the ideal angle of 72° to 73°. The collimators with lenses used with LEDs have an efficiency of approx. 85 % only. Losses have partly geometric origin, however, the main reason is the fact that a good anti-reflection layer cannot be applied onto the complicated, high-curvature surfaces, or that the application of such anti-reflection layer can be achieved only at rather high costs. Thus, there will be light losses due to Fresnel reflection when the light enters and also when leaves the lens.

According to US 6 250 774 B1 , the LEDs are cemented onto the heat sink by means of a semi-spherical mounting element. Although, during the production, this allows for the tilting of the LEDs along two axes, but the thermal conduction is worse than in the case of a fixed mounting with a relatively great diameter. In the various disclosed embodiments, the light is required to pass through numerous beam-forming elements in order to configure the optimal light distribution, which considerably increases the loss as well as the light diffusion compared to a simple mirror system.

DESCRIPTION OF THE INVENTION

It is the object of the present invention to provide a LED based street lighting module and a modular street luminaire arrangement making use thereof, which are exempt of the deficiencies of prior art solutions. It has been our object to provide a street lighting module and arrangement simple to produce at low costs, easily adjustable to given application circumstances, efficient in achieving the required light distribution, as well as capable of providing efficient cooling. Yet another object has been to provide a solution that is simply controllable and diagnosable.

The objects according to the invention have been achieved by means of the street lighting module according to claim 1 as well as by means of the modular street luminaire arrangement according to claim 12. Preferred embodiments of the invention are defined in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary preferred embodiments of the invention will be described hereunder with reference to drawings, where

Fig. 1 is a diagram of an exemplary predetermined light distribution, the so- called bat wing distribution,

Fig. 2 is a schematic vertical section of the street lighting module according to the invention installed for street lighting,

Fig. 3 is a section of the planar diverting mirror optics arrangement of a simplified street lighting module,

Fig. 4 is a three-dimensional bottom view of a preferred street lighting module according to the invention,

Fig. 5 is another bottom view of the street lighting module according to Fig.

4,

Fig. 6 is a three-dimensional top view of the street lighting module according to Fig. 4, Fig. 7 is a section of the street lighting module according to the invention provided with a casing,

Figs. 8 and 9 are parts of the street lighting module according to the invention providing variable light distribution, in two three-dimensional views,

Figs. 10 to 12 are three-dimensional schematic views of the preferred street luminaire arrangements installed with the street lighting module according to the invention,

Fig. 13 is a schematic vertical section of a particularly preferred street lighting module according to the invention,

Figs. 14 and 15 are three-dimensional and side views of a preferred diverting mirror assembly.

MODES OF IMPLEMENTATION OF THE INVENTION

According to the invention, it has been recognized, that collimators with individual mirrors mounted onto LEDs have better efficiency than prior art collimators with lenses for the purposes of the given application. The commercially available collimators with mirror have an efficiency of 92% or more, as most of the 'light passing to the right direction' leaves the collimator with mirror freely, without any reflection, i.e. without any loss. In this case, the forming, directing of the light beam can be achieved by including a collimator of the appropriate angle and by adjusting the axis of the LED+mirror optical element to an appropriate angle.

It has further been recognized that for realizing the predetermined light distribution, by way of example the bat-wing light distribution, numerous mirrorless LEDs or - in given cases - LEDs+mirrors are to be adjusted to differing angles. Preferably, mirrorless LEDs radiate rotated around an axis parallel to the longitudinal axis of the road mainly, in a large spatial angle, but mainly in a plane perpendicular to the road. The preferably applied LEDs installed with mirror collimators radiate in a significantly lower angle, mostly in the longitudinal direction of the road, oriented mainly towards an edge point of the road opposite the adjacent pole. The LEDs directed towards said point are rotated around two axes. Precise orientation of the LEDs can be determined by means of computer optimization. By the design of the optical system, the LEDs are to be positioned so that the LEDs turned to different directions, as well as the LED+collimator elements should not cover each other's light. Therefore, the LED positions need to be optimized: the LEDs are to be offset relative to each other in the three directions of space. In the course of optimization, the optical effects (shading, reflection, light absorption, etc.) of the heat sinks serving for fixing the appropriately positioned and rotated LEDs shall be considered, as well. At the same time, for the sake of efficient thermal conduction, heat sinks and cooling elements of suitable width have to be used. The LEDs are preferably positioned symmetrically in the optical system to a plane perpendicular to the road.

The LED based street lighting module 10 according to the invention, therefore, comprises LEDs, 14c, 14d as light sources, as well as mirrors directing the respective lights thereof. In a way as seen in Figs. 2 and 3 especially, the street lighting module 10 according to the present invention comprises internal space 12, LEDs 14c, 14d positioned and oriented in the internal space 12 according to a predetermined light distribution, at least one of said LEDs 14c, 14d preferably being also fitted with collimator optics 24, as well as planar diverting mirrors 16a, 16b, 16c, 16d forming a light diverting internal surface of the internal space 12. The planar mirror shape is extraordinarily advantageous for reasons of simple production. In a way as described hereabove, the side LEDs 14c, 14d installed with collimator optics 24 are arranged radiating preferably in a lower angle, in the longitudinal direction of the road, oriented roughly in the direction of the edge point of the road opposite the adjacent pole. The additional middle LEDs 14m preferably without collimators, such as the one seen in Fig. 4, preferably radiate in a larger angle, essentially perpendicular to the road surface.

The LEDs 14c, 14d, 14m suitably positioned in space and rotated into given spatial directions, preferably installed in part with aspheric mirror optics are surrounded by a mirror system made up of planar diverting mirrors 16a-16d preferably on four or five sides, in a way shown in Figs. 2 to 5. One side of the optical system made up of planar diverting mirrors 16a-16d defines an optically open, rectangular light exit opening 11 , where the appropriately formed light beam leaves the street lighting module 10. The street lighting module 10 according to the invention preferably comprises two pairs of such diverting mirrors 16a, 16b, 16c, 16d that are arranged in opposite facing pairs 16a, 16b, 16c, 16d, and which diverting mirror pairs are arranged defining the internal space 12 expanding towards the light exit opening 11. According to the invention, naturally, the application of diverting mirrors of other than four pieces is just as well conceivable; in the shown embodiments, by way of example, a fifth plane can be arranged with a diverting mirror function for fixing LEDs 14c, 14d, 14m.

The planar diverting mirrors 16a-16d have complex functions: the mirrors on the one hand divert the light of the LEDs 14c, 14d, 14m installed without collimator optics into the direction of the illuminable road surface (pavements 20, carriageway 22), while on the other hand they prevent large-angle beams to leave the luminaire fixed onto the pole 18 comprising the street lighting module 10. This, on the one hand, increases the efficiency of the street lighting module 10, and reduces light being scattered into the vicinity of the road. So-called light pollution is on the other hand blocked, in other words, the street lighting module 10 does not emit any light in the direction of the sky.

According to one preferred embodiment, a section of the street lighting module 10 taken in a plane perpendicular to the longitudinal axis of the road in a way as shown in Fig. 2 resembles an angular housetop. As the pole 18 is on one side of the road, a front diverting mirror 16a is tilted at an angle lower than the horizontal and a back diverting mirror 16b is tilted at an angle higher than the horizontal, so that the light beam of the street lighting module 10 should appropriately illuminate the range of the road opposite the pole 18 and - if necessary - the pavement opposite the pole 18 as well. The angles of inclination of the front and back diverting mirrors 16a, 16b are preferably variable so as to allow that illumination and luminosity with good efficiency are produced in compliance with the required evenness in case of differing pole heights or varying road widths, as well.

Fig. 3 shows a section of a planar diverting mirror optical arrangement of a simplified LED based street lighting module 10 in a plane perpendicular to that of the road. The direct and reflected large-angle light rays leaving the street lighting module 10 can be clearly seen in the figure. Preferably, the street lighting module 10 further comprises one or more cooling element(s) 26 holding one or more LED(s) 14c, 14d for conducting the heat from the internal space 12. The cooling elements 26 are preferably heat sinks arranged in a way so as to minimize shading.

Figs. 4 and 5 show two spatial bottom views of an exemplary LED based street lighting module 10 realizing a bat wing light distribution. The street lighting module 10 is a planar mirror type optical system with six sides open on one side. The street lighting module 10 comprises 2x3 symmetrically positioned LEDs 14, 14c, 14d, 14m offset and rotated in the suitable direction. It can be seen in the figures, that the street lighting module 10 may comprise further LEDs 14 adjusted according to the given application in addition to the side LEDs 14c, 14d and middle LED 14m, as well. For the purpose of simplicity, the collimator optics 24 have not been shown in the figure. The LEDs 14, 14c, 14d, 14m are fixed onto cooling elements 26 and heat sinks of appropriate width and good thermal conductivity. The cooling elements 26 are thermally connected to a cooling rib 27, illustrated in more detail in Fig. 6, positioned on top of the street lighting module 10, and preferably are fixed thereto. The thermal loss of the LEDs 14, 14c, 14d, 14m is transferred into the environment by means of the cooling rib 27.

The street lighting module 10 as per the preferred embodiment shown in Figs. 4-6 comprises diverting mirrors 16a, 16b, 16c, 16d defining a rectangular light exit opening 11 , in one of said diverting mirror pairs the diverting mirrors 16c, 16d are arranged in parallel, while in the other pair the diverting mirrors 16a, 16b are arranged expanding towards the light exit, opening 11. This allows a simple structure, furthermore enables a modular street lighting arrangement to be produced when installed adjacently.

Fig. 7 shows another street lighting module 10 - arranged in a casing - 28 in a section perpendicular to a plane of the road taken in a plane parallel to the longitudinal axis of the road. The LEDs 14 are in part installed with collimator optics 24 with aspheric mirrors. ln a way as seen in Figs. 8 and 9, the front and back diverting mirrors 16a, 16b are preferably rotatable around the axis located along the upper side thereof, therefore the length - width ratio of the illuminated territory is variable by means of adjustment of the angles of the two rotatable diverting mirrors 16a, 16b: in the case of a lower pole 18 or a wider road the angle closed by the two diverting mirrors 16a, 16b is larger, whilst in the case of higher pole 18 or narrower road, the angle closed by the two diverting mirrors 16a, 16b is smaller. The diverting mirrors 16a, 16b arranged expanding towards the light exit opening 11 are, therefore, fixed in the street lighting module 10 by means of a joint 30 enabling adjustment of the angle closed by the diverting mirrors 16a, 16b. For the sake of simplicity, the side mirrors 16c, 16d are not shown on Figs. 8 and 9. It can be seen in the figures that the LEDs 14m are installed by way of printed circuit boards 32.

In a way as already mentioned above, the street lighting module 10 is preferably arranged symmetrically with respect to a vertical middle plane, comprising LEDs 14, 14c, 14d, 14m vertically and/or horizontally offset to each other within the internal space 12 positioned in an arrangement minimizing shading. The LEDs 14, 14c, 14d, 14m offset to each other are preferably rotated relative to each other as well along a horizontal and/or vertical axis, in order to provide the predetermined light distribution.

The open, planar light exit opening 11 or surface where light leaves the optical unit, is preferably covered by a covering plate 29 of a transparent material, such as a plane tempered glass plate or shatterproof plastic plate, so as to realize a cover exempt of light pollution and providing water and dust protection in accordance with IP66 requirements, what is a requirement in the case of modern luminaires. The covering plate 29 is preferably such a closing glass plate, which is provided with an antireflection layer on both sides for the sake of reducing reflection. In this way, the reflection of light incident on the surface of the glass plate is significantly decreased, by up to 10%, thereby increasing the light emitted into the critical direction, in other words, the bat wing light distribution will this way become more articulated, and the efficiency of the module increases. In accordance with the known Fresnel reflection laws, large-angle beams pass through the planar glass plate with a high reflection loss, only. By suitable collimation and direction of aspheric mirrors fixed onto the LEDs 14, 14c, 14d, 14m the loss caused by the Fresnel reflection on the closing planar glass plates can be compensated. By applying aspheric mirrors, high-intensity, large-angle beams can be produced in the case of planar glass closure as well. At the same time, the light rays reflected on the planar glass plate are partly directed by the planar mirror optical system onto the illuminable road surface, thereby increasing the efficiency of the street lighting module 10. It is the task of optical design to determine the shape of aspheric mirrors as well as the angle of planar mirrors in such a way that the bat wing light distribution is achieved as efficiently as possible at the least possible loss.

Figs. 10 to 12 show the schemes of the preferred street lighting luminaire arrangements installed with adjacently placed modules according to the invention. Fig. 10 shows a top view of an arrangement provided in a line parallel to the road. In this case the ..housetops" are lined up and the street lighting modules 10 connect each other via planar plates. This results a more compact arrangement, but reduces the efficiency of cooling in a small degree. Fig. 11 shows a side view of an arrangement realized in a line perpendicular to the road. The ..housetops" are positioned behind each other, the modules meet along respective lines. Fig. 12 shows a top view of a block type arrangement, wherein preferably the horizontal direction corresponds to the direction parallel to the road. The light exit openings 11 of the street lighting modules 10 in the shown arrangements preferably fall in one plane, which plane is parallel to the illuminable road surface.

The invention, therefore, relates to such an LED based optical module and luminaire family or arrangement made up of one or more street lighting modules, wherein the arrangement and orientation of the LEDs 14, 14c, 14d, 14m as well as, in certain cases, the collimator optics fixed onto the individual LEDs 14c, 14d and the optical system made up of the applied planar diverting mirrors 16a-16d substitute the light source of the street luminaires as well as the optical arrangement realizing the bat wing light distribution. The disclosed LED based module and luminaire family is competitive with the state-of-the-art street lighting modules in terms of variable light power and light distribution body. The power of the module can be varied by including less or more high-power LEDs into given LED positions of the given geometrical arrangement, or in certain positions not including any LEDs at all. Furthermore, the LED power is also selectable for the given application.

The bat wing light distribution is achieved by appropriate spatial positioning and orientation of the LEDs and by the help of mirrors. Optimally, a finite number of LEDs can be placed in one module, only. There are two factors influencing the number of LEDs within one module: on the one hand, owing to efficient heat conduction and covering, shading, the LEDs cannot be placed too close to each other, while on the other hand, the LEDs cannot be too far from the mirrors, as in that case the size of the mirror is to be enlarged proportionally or in case of smaller sized mirrors, the light beam would pass beside the mirror. These two aspects determine that a finite number of LEDs can be designed into one module. According to our planning experiences, the optimal number of LEDs ranges between four and twenty-five. The four to twenty-five LEDs in part, approx. two- four pieces, are provided collimator optics 24 with aspheric mirror, collecting the light radiated by the LED in an angle of approx. 80° - 90° to an angle of 20° - 30°. The collimated light largely contributes to forming the bat-wing light distribution. The axes of collimator optics point in the direction of the highest luminous power, thereby greatly increasing the light radiated into the critical direction. All remaining LEDs in the module radiate freely, without collimator optics.

As the number of LEDs within one optical module is limited according to the above mentioned details, in order to achieve higher luminosity or illumination values a plurality of modules need to be included in one luminaire or luminaire arrangement for one street lighting arrangement, by way of example as in Figs. 10 to 12.

Fig. 13 shows a simplified section of an especially preferred embodiment of the street lighting module 10 according to the invention in a vertical plane parallel to the longitudinal axis of the road. The predetermined light distribution applicable for illuminating the road has a longitudinal direction lengthwise the road as well as a cross direction crosswise the road. In a way as seen in the figures, the street lighting module 10 comprises two side diverting mirrors 16c, 16d, each arranged lengthwise on the two sides of the street lighting module 10, being essentially perpendicular to the longitudinal direction. At least one side LED 14c, 14d is arranged at each said side diverting mirror 16c, 16d - preferably at the upper part of the diverting mirror. The directions of the side LEDs 14c, 14d are tilted towards each other in such a way that the direction of the side LED 14c, 14d closes an angle of between 50° - 80° with the plane of the adjacent side diverting mirror 16c, 16d.

It is an essential feature of the illustrated embodiment that the side LEDs 14c, 14d being oriented closing a large angle with the vertical, radiating preferably in the direction of the longitudinal axis of the road and being offset to the two opposite sides of the street lighting module 10 radiate relatively far from each other, but turned towards each other. This solution results in a significant decrease in size. The direct light rays (solid line) and the reflected large angle light rays (dashed line) leaving the street lighting module can be clearly seen in the figure. It is the task of the side mirrors to limit the light rays departing with too large angle. This reduces the luminous power, which is the cause of dazzling, and makes illumination more even and smooth. While moving on the illuminated road and looking towards the opposite diverting mirror 16c, 16d - being essentially perpendicular to the longitudinal direction - the direct light of the opposite LED 14c, 14d and the reflected lights of the side LEDs 14c, 14d directed towards each other can be seen side-by-side, merged into each other. These together result in a more even and smooth illumination with less dazzling. According to the invention, the term 'essentially perpendicular' shall refer to an angle closing 90° +/- 2° with the longitudinal direction; according to our experiments said diverting mirror orientation, as well as an angle of 50° - 80° closed by the LEDs with the vertical line provide the evenness advantages as per the above.

The further two diverting mirrors 16a, 16b are arranged essentially parallel to the longitudinal direction and between the side diverting mirrors 16c, 16d, and define an internal space 12 expanding towards the rectangular light exit opening 11. ln Fig. 13, the directions of the middle LEDs 14m are preferably adjusted to an angle depending on road width and pole height in a plane perpendicular to the longitudinal direction, while the side LEDs 14c, 14d are preferably rotated around two axes (facing each other on the one hand, and also closing an angle of e.g. 5 - 20° with the longitudinal direction on the other hand). At the same time, the figure further demonstrates that due to size limitations only a finite number of LEDs 14, 14c, 14d, 14m can be included in the optical space being bordered by the planar mirrors. For reasons of shade reduction and efficient cooling, the LEDs 14, 14c, 14d, 14m fixed onto the heat sinks have to be placed at appropriate intervals from each other. The ratio of the H and V values indicated in Fig. 13 defines the angle of direct light rays leaving the internal space 12 in large angle. As mentioned above, in order to avoid dazzling, the quantity of light passing over 80° relative to the vertical axis of the module is to be limited, in other words the H / V < tg(80°) relationship is to be met. In order that the V size of the module not be too large, the H size is to be limited as well, which consequently limits the number of LEDs 14, 14c, 14d, 14m that can be built in the module. In the arrangement shown in the figure, H size is essentially determined by the number of LEDs 14, 14a, 14c, 14d, 14m to be fixed onto the middle heat sinks, and by the distance between them, in order to avoid shading of the heat sinks of the side LEDs 14c, 14d, H size should not be selected larger than the size thermally required. This solution results in a significantly smaller and more compact module, than in the case where side LEDs 14c, 14d are radiating outwardly from the optical space and heat sinks hung inwardly into the internal space 12.

The heat sinks included in the street lighting module 10, therefore, hold the LEDs 14, 14a, 14c, 14m in a position rotated along two axes and conduct the heat efficiently away from the internal space 12. In this arrangement, the heat sinks are directed outwardly from the internal space 12, thereby simplifying the configuration of the way of heat conduction. The side LEDs 14c, 14d are lighting inwardly into the internal space 12 and the heat sinks are directed outwardly from the internal space 12, thereby shading is minimized, a smaller and more compact module can be built. Heat sinks are preferably blocks with 5 to 15 cm² circle or square cross section, made of a material of good heat conductivity, preferably aluminum, and being 1 to 5 cm in height. The base plate of the heat sinks are fixed to the housing of the module or to the cooling rib, the loss heat of the LEDs 14, 14c, 14d, 14m is here transmitted. The LEDs 14, 14c, 14d, 14m are fixed onto the covering plate of the heat sink.

Typically, the base and the covering plates of the heat sinks are not parallel to each other, and one or both of the plates is not necessarily perpendicular to the axis of the heat sink. The surfaces (base and covering plates) tilted along one or two axes enable on the one hand the base plate to join appropriately the outer surfaces (lamp housing or cooling rib), on the other hand ensure the LEDs 14, 14c, 14d, 14m to be appropriately positioned and to radiate in the appropriate direction. The position of the heat sinks and the angle of the covering plate are determined by an optimization process carried out in the course of the optical design of the module. As the positions and the directing angle of the LEDs 14, 14c, 14d, 14m are defined by the size and arrangement of the heat sink as well as the angle of the covering plates, therefore, the geometrical parameters of the heat sinks bear essential influence on the light distribution body of the module. Depending on the type and module construction of the applied LEDs 14, 14c, 14d, 14m, 1 to 20 pieces of LEDs may connect to the cover plate of each heat sink.

The heat sinks are positioned in part in the internal space 12, transferring the heat through one or more diverting mirror(s) 16a, 16b, 16c, 16d bordering the internal space 12, through openings formed on the mirrors. The LEDs 14, 14c, 14d, 14m are advisably positioned close to the bordering plates of the internal space, the partly radiating facing each other side LEDs 14c, 14d are offset from each other at appropriate distances, so that neither the LEDs 14c, 14d nor the heat sinks would shade. Shading can be minimized by having the optical axis of the LEDs 14, 14c, 14d, 14m, which is perpendicular to the covering plate of the heat sink, directed inwardly into the internal space 12. In this case, the LEDs 14c, 14d partly radiating facing to each other are positioned relatively distant from each other on opposite sides of the internal space 12, which means that the radiation space is covered only in a very small cone angle. At the same time, the heat sinks belonging to the side LEDs 14c, 14d tilt outwardly, and do not cover the light of the upper LED row. For reasons of excessive increase of module sizes, it would be more disadvantageous if the heat sinks belonging to the side LEDs 14c, 14d tilted inwardly into the internal space 12; as in this case the distance of the middle LEDs 14m should be increased significantly from the side LEDs 14c, 14d so that the heat sinks shaded the light of the middle LEDs 14m to a small extent only.

The diverting mirrors 16a, 16b with adjustable angle are not necessarily fixed by means of joints, but any other type, by way of example self-holding, mirror system can be arranged just as well. In the embodiments shown in Figs. 14 and 15, small- size openings e.g. 1 to 2 x 4 to 8 mm in diameter, arranged exactly facing each other are positioned appropriately in the side diverting mirrors 16c, 16d. Plates 36 of 0,1 to 0,2 mm less in cross-section than the opening 34 are fixed therein, having diverting mirrors 16a, 16b installed thereon. In this case, therefore, two openings 34 per each side define the position of the movable diverting mirrors 16a, 16b. The diverting mirrors 16a, 16b can be fixed by selecting the appropriate fixing opening 34 pairs preferably in 2 to 4 positions within the self-holding optical system.

The invention, of course, is not limited to the above detailed preferred embodiments, but further modifications, variations are possible within the scope defined by the claims. The street lighting module may comprise additional elements, mirrors, and the predetermined light distribution may also be any required or specified light distribution other than the bat wing distribution.

Claims

1. A LED based street lighting module (10), comprising LEDs (14, 14c, 14d, 14m) as light sources and mirrors directing the light of the LEDs (14, 14c, 14d, 14m), c h a r a c t e r i z e d by comprising

an internal space (12),

LEDs (14, 14c, 14d, 14m) positioned and oriented in the internal space (12) in accordance with a predetermined light distribution, as well as

planar diverting mirrors (16a, 16b, 16c, 16d) forming a light diverting internal surface of the internal space (12).

2. The street lighting module according to claim 1 , characterized in that the predetermined light distribution has a longitudinal and a crosswise direction, and the street lighting module (10) comprises

two side diverting mirrors (16c, 16d) being essentially perpendicular to the longitudinal direction and being arranged longitudinally on the two sides of the street lighting module (10), respectively, as well as

at least one side LED (14c, 14d) arranged at each of the side diverting mirrors (16c, 16d), respectively, the direction of said side LEDs (14c, 14d) being tilted towards each other in such a way that the direction of the side LED (14c, 14d) close an angle of 50° to 80° with the plane of the adjacent side diverting mirror (16c, 16d).

3. The street lighting module according to claim 2, characterized by comprising two further diverting mirrors (16a, 16b) arranged essentially parallel to the longitudinal direction and between the side diverting mirrors (16c, 16d), said further diverting mirrors (16a, 16b) being arranged to define an internal space (12) expanding towards a rectangular light exit opening (11).

4. The street lighting module according to claim 3, characterized in that at least one diverting mirror (16a, 16b) of the further diverting mirrors (16a, 16b) is fixed by means of an angle adjustment enabling joint (30).

5. The street lighting module according to any of claims 2 to 4, characterized in that it is formed symmetrically to a plane perpendicular to the longitudinal direction, and comprising LEDs (14, 14b, 14c, 14m) positioned in the internal space (12) relatively offset to each other horizontally and/or vertically in an arrangement minimizing shading.

6. The street lighting module according to claim 5, characterized in that the LEDs (14, 14b, 14c, 14m) relatively offset to each other are rotated relative to each other along a vertical and/or a horizontal axis so as to provide the predetermined light distribution.

7. The street lighting module according to claim 1 , characterized in that it comprises one or more cooling element(s) (26) for transferring heat away from the internal space (12) and carrying one or more LEDs (14, 14c, 14d, 14m), said cooling elements (26) are preferably formed as heat sinks directed outwardly from the internal space (12) in an arrangement minimizing shading.

8. The street lighting module according to claim 1 , characterized in that at least one LED (14c, 14d) of the LEDs (14, 14c, 14d, 14m) is fitted with collimator optics (24), said collimator optics (24) preferably being optics with an aspheric mirror.

9. The street lighting module according to claim 1 , characterized in that the predetermined light distribution is a bat wing distribution.

10. The street lighting module according to claim 1 , characterized in that for the LEDs (14, 14c, 14d, 14m), there are LED places between four and twenty five formed in it, in which LED places LEDs (14, 14c, 14d, 14m) of a number and power appropriate for the given application are built into the street lighting module (10).

11. The street lighting module (12) according to any of claims 2 to 4, characterized in that the light exit opening (11) is covered by a covering plate (29) made of a transparent material, preferably a glass plate each side of which being provided with an antireflection layer.

12. A modular street lighting luminaire arrangement, c h a ra cte r i z e d in that it comprises street lighting modules (10) according to any of claims 1 to 11, arranged side-by-side.

13. The arrangement according to claim 12, characterized in that the light exit openings (11) of the street lighting modules (10) are arranged in one plane, said plane being parallel with an illuminable road surface.