WO2012062347A1

WO2012062347A1 - Linear illumination device having leds

Info

Publication number: WO2012062347A1
Application number: PCT/EP2010/066988
Authority: WO
Inventors: Stefan Hadrath; Julius Muschaweck
Original assignee: Osram Ag
Priority date: 2010-11-08
Filing date: 2010-11-08
Publication date: 2012-05-18

Abstract

The invention relates to a linear illumination device, in particular a linear LED lamp (1), which is characterized in that the housing (2) has a plurality of cells (15) lined up in a row along the longitudinal axis, wherein each cell is assigned a primary light source (10) and a reflector, wherein each light source is arranged opposite the reflector (7), by means of which indirect lighting is achieved, and wherein the reflector is a paraboloid.

Description

Linear lighting device with LEDs

Technical area

The invention is based on a linear illumination device with LEDs according to the preamble of claim 1. It relates in particular to a linear LED lamp or a lighting device with a linear LED structure, for example a linear LED light.

State of the art

From WO 2007/054889 a linear LED lamp is vorbe ^¬ known, in which linearly arranged LEDs with a parabolic reflector, which is constructed as a trough reflector cooperate.

SUMMARY OF THE INVENTION An object of the present invention is to provide a li ^¬-linear lighting apparatus with LEDs, which collimates the light from the LEDs in a small angle as possible ^¬ area. A further object is to provide a li ^¬-linear lighting device having LEDs as possible ene ger emission characteristics. Another object is to provide such a linear lighting ^¬ device with LEDs with the lowest possible height.

These objects are achieved by the characterizing features of claim 1.

Particularly advantageous embodiments can be found in the dependent claims. According to the invention, a linear illumination device with LEDs is provided, which has a narrow luminous intensity distribution. These may be very high Achslicht ^¬ strength from 10,000 to 15,000 cd be achieved. In the following, for the sake of simplicity, without being meant to be limiting, it is usually referred to as a linear LED lamp.

The linear LED lamp has a good color rendering of at least Ra = 80, typically Ra = 85 to 93 and is characterized by particularly homogeneous color mixing. Moreover, it shows a high luminous flux of 1000 to 1300 Im, depending on the current applied to the LEDs.

The basic concept is the use of LED arrays, each with a reflector assigned. These together form men a basic cell of which then several are aneinanderge ^¬ lined up.

Good color reproduction is only possible through color mixing with several LEDs of different colors. The difficulty lies in achieving a good color mixture together with a narrow emission characteristic and at the same time the highest possible optical efficiency without the dimensions of the linear LED lamp becoming disproportionately large.

For this reason, the number of LEDs per cell is preferably limited to one to three, in particular two or three, be ^¬ , with preferably two to three groups of LEDs per cell are available. In the prior art, either white or different colored LEDs are arranged linearly, each with its own optics, thus creating a linear LED array. Übli ^¬ cherweise be converted white LED fluorescent blue LEDs, so-called. LUKO LEDs used. These have a weak emission in the red areas of the spectrum ^¬ rich and therefore a poor color reproduction. Using different colored LEDs, so much better color reproduction is possible, but this has the disadvantage that undesirable color shadows in the near field thaw ^¬ chen. The same thing happens when objects enter the visual beam.

Often, the LEDs emit directly to it, so that a high glare occurs. This must be avoided by indirect lighting.

Neither a linear LED lamp with a narrow radiation characteristic in the vertical and horizontal direction nor a linear LED lamp with a high axis light intensity of at least 10,000 cd are known to date. According to the invention, the linear LED lamp has a linear array of a plurality of semiconductor components, i.allg. Is this to chip LEDs or laser diodes ^¬, on which have a certain distance from each other. For the sake of simplicity, the following is always spoken of LEDs.

The individual LED or each array is its own cell, preferably associated with a parabolic reflector. A typical number is 2 to 5 LEDs in an array. The LED array with the reflectors is housed in a channel-like housing with a short transverse dimension. introduced. The individual reflectors are preferably rotationally symmetrical. However, this symmetry may be attenuated in terms of a mere axis symmetry or, in particular, towards the edges in one direction, possibly even in both the longitudinal and transverse directions. The more undisturbed the rotational symmetry, the higher the optical efficiency of the lamp.

Groups of at are preferred for the LED arrays least two different types of LEDs used ^¬ example, three LEDs, which emit red, green and blue, or two LEDs as a combination of white LEDs certain color temperature with further color LEDs.

A preferred approach is a group of white LEDs with relatively poor color rendering, along with a group of red LEDs, to improve the redness of the white LEDs, see, for example, US 6,234,648, US 7,736,017 or US 6,577,073 or US 7,213,940 . A konkre ^¬ tes example, groups of blue and green emitting LEDs, especially green emitting white, mint-colored LEDs, together with groups of red emitting LEDs.

A preferred concept is to use a first group of dominant wavelength LEDs LI and a second group of LEDs of dominant wavelength L2, where L2> L1.

A particularly narrow emission with a low overall height is achieved when the LEDs are as close as possible at ^¬ each other and arranged as close to the focal point of the reflector pre- vents ^¬ Re. Specifically, the first group may consist of two LEDs, between which one LED of the two th group is queued, this array is angeord ^¬ net that the LED of the second group at least near ^¬ approximately, preferably directly, sits at the focus of zugeord ^¬ Neten reflector. This ensures that the light from the LEDs leaves the lamp or luminaire with very low FWHM. Typical is a FWHM of at most 25 °.

The linear array illuminates the reflector indi ^¬ rect, best, by facing in the focus of the low point or apex of the reflector. In the apex of the reflector, a scattering means may preferably be provided to prevent radiation from the LEDs, in particular from the centrally arranged LED, being reflected back toward the light source or array. Since the array is arranged linearly, the scattering means may also preferably extend along the straight line of the linear array. In particular, the scattering means is a conical pin projecting at the foot of the reflector in the direction of the light source or he is a projecting triangular oa. In particular, to optimize the scattering, the reflector may also be shaped like an involute.

Preferably, the light exit surface of the reflector is provided with a further transparent or translucent scattering means in order to further improve the color mixing of the different groups of LEDs without color shadows. Particularly suitable are so-called microlens arrays, as are basically known from WO 2009/065389, for example. In this case, a microlens array is used, which is constructed plate-like, with a structure that as Microlens array acts, not only on a surface, but on both sides, front and back, the plate is present. Only in this way an effective Farbmi ^¬ research is achievable. Advantageously, the arrangement of the individual lenses is not regular, but randomly distributed, so randomized.

Furthermore, it is advantageous to connect a heat sink to the LED array so that it causes no significant additional shading, especially directly behind the LED array. the Kühlkö ^¬ ^¬ arranged per linear continuous from LED array to LED array is particularly preferred.

The lighting device according to the invention with LEDs, especially a linear LED lamp, has the following advantages:

- Low losses of light by a cell-like construction with ^¬ On assignment of a reflector for each LED array, optionally additionally improved by the Re ^¬ Flektor assigned spreading agent such as a triangular rod;

- glare-free by indirect lighting with back ^¬ radiating arrangement;

- Good heat dissipation through a massive, especially continuous heat sink;

- Very good color rendering of at least Ra = 80 by using differently colored LEDs in at least two groups in one array; - Improved color mixing and beam shaping through a microlens array;

- Narrow and defined emission characteristics;

- raising blurred transition between the lit and dark area by randomized Anord ^¬ voltage of the individual lenses in the microlens array;

- Very high axle luminous intensity between 10000 and 15000 cd;

Very high optical efficiency of typically 75% to 80%;

- Nevertheless, very compact design with small width of the housing and low height.

This arrangement allows, in contrast to the prior art, to collimate the light of the LEDs in a very small angular range. The primary optics used here are a substantially rotationally symmetrical reflector assigned to the LED array, in the lowest point of which, the apex, in particular a scattering means can be attached. In addition, there is excellent color mixing, as the exiting light passes through a microlens array. This achieves color mixing in both near field and far field.

Preferably LEDs are used with a large beam angle of 130 to 160 °, typically a value of about 150 °, which correspond at least approximately to a Lambertian radiator. This allows the reflector to be well illuminated so that better performance is achieved. Essential features of the invention in the form of a nume ^¬ tured list are:

A linear illumination device comprising LEDs having a housing defining a longitudinal axis, a bottom portion and an opposite light exit aperture, wherein a primary light source having at least one LED is disposed in the region of the focus of a reflector and away from the light exit aperture, thereby providing an indirect light source Lighting is achieved, characterized in that in the housing several ^¬ re cells are lined up along the longitudinal axis, each cell is associated with a primary light source and a reflector, wherein the reflector is a paraboloid. 2. Linear illumination device according to claim 1, characterized in that the primary light source is arranged so that it covers the focus of the reflector.

3. A linear illumination device according to claim 1, by DA in that the primary light source is an LED array having at least two, in particular three, LEDs, which include at least two groups of LEDs ^¬ showing different emission.

4. Linear lighting device according to claim 1, character- ized in that an LED sits in the focus of Re ^¬ reflector. Linear illumination device according to claim 1, characterized in that the LEDs have a large beam angle from ^¬ 130 to 160 °.

Linear lighting device according to claim 1, characterized in that a scattering means is arranged in the Schei tel of the reflector, and the Streumit tel, in particular along the longitudinal axis he stretches. Linear illumination device according to claim 6, characterized in that the scattering means is a cone or triangular rod.

Linear illumination device according to claim 1, characterized in that a Homogenisierungsmit ^¬ tel is arranged in the region of the light ^exit opening, in particular a two-sided microlens array with spherical lenses, preferably an array with randomized arrangement of the individual lenses.

Linear illumination device according to claim 1, characterized in that the primary light sources are arranged on a strip, in particular directly realized as a board, along the longitudinal axis.

Linear lighting device according to claim 10, characterized in that on the board a solid heat sink is mounted, which is in thermal contact with the primary light sources. Brief description of the drawings

In the following, the invention will be explained in more detail with reference to several embodiments. The figures show:

Figure 1 shows an embodiment of a linear LED lamp;

Figure 2 is a second view of the embodiment of Figure 1;

Figure 3 is a detail view of a cell of the linear

Led lamp ;

Figure 4 shows an embodiment of a beam path with and without triangular bar;

Figure 5 embodiments of a Mi krol insen array

(Figures 5a to 5e);

FIG. 6 shows color distributions without a microlens array;

FIG. 7 shows color distributions with microlens array;

8 shows the light distribution curve for a linear

LED lamp with triangular rod and microlens array.

Preferred embodiment of the invention

An embodiment of a linear LED lamp shown in FIG 1 and 2. The linear LED lamp 1 has a approximately qua ^¬ derförmiges housing 2 with four side walls 3 and 4, a bottom plate opposite the bottom plate 4, the light ^¬ outlet opening 5. Centrally in The outlet opening extends along a strip 8, a system of several LED arrays 6. Each LED array is assigned its own parabolic reflector 7. Following the concept of indirect illumination, each LED array 6 is at the apex 10 directed the associated reflector, so pointing away from the Öff ^¬ tion.

The parabolic reflector is preferably a rotation paraboloid of the type z = x ² / a ² , but in particular it can also be an elliptical paraboloid of the type z = x ² / a ² + y ² / b ² .

The LED array 6 are made according to Figure 2b from egg ^¬ ner first set 10 of LEDs, the greenish white, preferably aquamarine, and emit a second set 11 of LEDs that emit red, preferably amber respectively. Pro LED array 6 a centrally located LED 11 of the two ^¬ th group by a respective LED 10 of the first group surrounded on each side along the strip. All three LEDs are lined up linearly along the strip 8, wherein the LEDs are soldered to metal core boards 13 on a running along the bar continuous aluminum block as a heat sink 12th

A total of seven LED groups are strung together in cells 15 with seven reflectors. The boards 13 have a white anodized surface to reflect scattered radiation.

Figure 3 shows a cell 15 in detail, in different views Figure 3a to 3c. On the longitudinal bar 8 sits an LED array 6 with three LEDs. The strip consists of the metal core board 13 and the heat sink 12. The light of the LEDs is directed to the reflector 7 and is reflected from there in the direction of the outlet opening. As a scattering means for almost perpendicular reflected back light of the LEDs, especially the central LED, a triangular bar 16 is arranged in the apex of the reflector, which slightly deflects the light of the LEDs 10, 11 standing vertically above it. In the outlet opening sits as a homogenizing microlens array 17, see Figure 3b. The parabolic reflector is of the rotational paraboloid type with z = 1 / 2R * y ² . The central LED sits in the focus of the parabolic reflector. The focus is on R / 2. For example, R = 36 mm. The reflector is made of polished aluminum. The cell is about 70 to 90 mm wide (y-direction), resulting in a height of 20 to 30 mm (z-direction).

The reflector can be cut off in the x direction, see FIG. 3b. The relative dimensions are preferably selected such that the cell defines the opening with diameter F of the reflector in the y-direction, while in the x-direction the reflector constitutes at least 80%, preferably at least 90% of F. If too much of the contour of the reflector is cut off in one direction, the optical efficiency drops. The relative dimensions should be chosen so that - where x and y directions can be reversed - that the optical efficiency reaches at least 75%.

Figure 4 illustrates the effect of the triangle. In Figure 4a, the beam path is shown without triangular. In this case, the central beams (Sl), especially the central LED, are reflected by the reflector 7 so that they are reflected back to the LEDs 10, 11 themselves, the board 13 or at least the heat sink 12 back. They are either absorbed, which leads to the heating of the LEDs, or so unfavorably reflected that they act as disturbing scattered radiation. In contrast, a large part of the non-central radiation (S2) leaves the reflector with a small beam spread, as the LEDs are in focus or near it.

Figure 4b shows the beam path with triangular bar 16. The ^¬ should be as highly reflective as possible, for example, it is a rod made of highly polished aluminum. The central rays Sl are now deflected by the triangular rod 16 and deflected to the contour of the reflector 7. In this way, they contribute specifically to the total luminous flux of the system, even if they do not have the slight inclination of the regularly reflected without deflection (S2). To achieve a high Reflect the trihedral ensure ivity 16 and to improve the homogeneity, the triangular rod 16 may, in particular with specularly hochreflek ^¬ animal forming ESR film, for example, the Fa. 3M be covered.

FIG. 5 shows the surface of two microlens arrays 17 as a detail. In FIG. 5a, the microlens array 17 is provided with a strict hexagonal arrangement, ie small spherical lenses with a typical radius of 1 mm (typically a range of 0.8 to 1.3 mm) with a typical spacing dx of 0.3 mm (typical range for dy is 0.2 to 0.4 mm) and typical horizontal distance dy of 0.75 mm (ty ^¬ pischer range of 0.6 to 0.9 mm).

The lens radius determines in the case of a double-sided microlens array, the thickness of the microlens array and thus the distance of the lenses on the front and back of the microlens array from each other. The distances of the Peri ^¬ odizität dx and dy in two directions determine the radiation characteristics from ^¬. For example, a narrow distance dx makes the narrow light distribution of 10 ° in one direction (see FIG. 8) and the wider distance dy the wider light distribution of 24 ° in the other direction. The design of the individual element of the microlens array depending on it can in particular hexagonal, square or circular rather ^¬ be determined the shape of the illuminated area excluded that here an elongated hexagon (He- xagon) is. With such a regular structure, however, the illuminated area is relatively sharply delimited from the unlit.

FIG. 5b shows a preferred microlens array 17 with a randomized hexagonal arrangement. That is, only the average of dy and dx is sized as shown above. But the centers of each microlens statistically scatter their hexagonal origins. Instead of the single ^¬ NEN lenses arranged to be applied according to the described structure, strictly, the center is s (normally as shown in the middle) with individual microlenses once a bit arranged one direction, one slightly offset in the other direction toward the center of the element. The verscho ^¬ bene center of the single microlens 20 is designated here by way of example with a cross. The centers are too ^mature and arbitrarily distributed, this is schematically in FIG. 5b.

Figure 5c, d, e explains the hexagonal randomized Reali ^¬ tion of the individual microlenses. The starting point is FIG. 5c. There is a section of a regular ^¬ moderately structured microlens array is shown with a central micro lens 60, the center of MZ is shown centrally and hexagonal regularly arranged around it further microlenses MX. The respective Ba sisfläche a microlens is obtained here from the loading ^¬ trachtung of the connecting lines 61 between two central In this regular condition, a base surface of the single microlens 60, which is a hexagon along the center perpendicular 62, is formed.

FIG. 5 d shows the conditions in a randomized arrangement of the midpoints. The midpoints MZ and MX are taken as starting points, but the actual midpoints MZT and MXT are randomly distributed and taken a little different. Taking the Verbin ^¬ dung distance MX-MZ as a length scale, the Ab ^¬ deviation of randomized center MXT from the ideal center MX should be preferably 5 to 20% of the corresponding distance MX-MZ, wherein the deviation in any direction relative to the track MX -MZ can be done. The new centers of MXT define about their new connecting lines to MZT new center perpendicular 161, the area of each microlens centrally shown here, 160 is not a regular hexagon more, but either an irregular hexagon as concrete Darge ^¬ represents, or even just a pentagon, Square or triangle. The microlenses in their entirety thus form irregular ^¬ moderately shaped polygons of up hexagons, see fi gure ^¬ 5e. The front and back of the microlens array are preferably randomized in the same manner.

This makes it possible to achieve a flowing, blurred transition from the illuminated to the unlit surface.

In the case of a desired asymmetrical emission characteristic, either a hexagonal basic structure as explained above is advantageous for the microlens array, or alternatively a rectangular basic structure, or a basic structure derived therefrom. In the case of a symmetrical emission characteristic, a circular, elliptical or oval basic structure is advantageous, or a basic structure derived therefrom. The basic structure is randomized in a second step, as described above erläu ^¬ tert.

FIG. 6 shows the color distribution at a distance of one meter for a further exemplary embodiment of an LED light source. The LED arrays are composed of three LEDs that emit red, green and blue. FIG. 6 shows the color distribution for a structure without a microlens array. The different location of the three LEDs rela ^¬ tively to the focus of the reflector, which is a paraboloid of revolution, leads to a tendency Farbseparation on the opposite side. That is, when the blue LED left of the focus, the red center and green LEDs are to the right of focus angeord ^¬ net that leads Derge ^¬ Stalt in the far field for color separation that left side rather green fringes, centrally rather red fringing and right sides rather blue fringing on ^¬ occur, see Figure 6.

The color distribution in the vicinity is clearly inhomogeneous, with small illumination.

In an improved embodiment, microlens arrays are arranged in the outlet opening, following the principle as described in FIG. Such an array, in which convex lens parts are arranged on the front and back of the microlens array, mixes the outgoing radiation and homogenizes it. The color distribution is homogeneous from about 1 m distance, with large illumination, see Figure 7. Figure 8 shows the light distribution curve for a mintfar- ben and amber LED group as in Figure 4 beschrie ^¬ ben. These groups provide a warm white light color with color temperature of 3200 K. As explained above, the different radiation of 10 ° or 24 ° in the ^¬ spatial directions x and y does not come from the differently arranged LEDs, but only by the arrangement, quasi The lattice structure of the individual microlenses on the microlens array 17. If these are arranged, for example, circularly equidistant in the dx and dy directions, the surface is illuminated approximately and the Ab ^¬ radiation is the same in both directions. Here, however, she is desired as a hexagon.

Claims

claims

A linear illumination device comprising a housing defining a longitudinal axis, a bottom portion and an opposite light exit aperture, wherein a primary light source having at least one LED is disposed in the region of the focus of a reflector and away from the light exit aperture, thereby providing indirect illumination is characterized in that in the housing several ^¬ re cells are lined up along the longitudinal axis, each cell is a primary light source and a

Reflector is assigned, wherein the reflector is a paraboloid.

2. Linear illumination device according to claim 1, characterized in that the primary light source is arranged so that it covers the focus of the reflector.

3. A linear illumination device according to claim 1, characterized in that the primary light source is an LED array having at least two, in particular three, LEDs, which include at least two groups of LEDs ^¬ showing different emission.

4. Linear illumination device according to claim 1, characterized in that an LED sits in the focus of Re ^¬ reflector.

5. Linear lighting device according to claim 1, characterized in that the LEDs have a large beam angle from ^¬ 130 to 160 °. Linear illumination device according to claim 1, characterized in that a scattering means in the Schei ^¬ tel of the reflector is arranged, and the Streumit ^¬ tel, in particular along the longitudinal axis he ^¬ stretches.

Linear illumination device according to claim 6, characterized in that the scattering means is a cone or triangular rod.

Linear illumination device according to claim 1, characterized in that the primary light sources are arranged on a bar along the longitudinal axis.

Linear lighting device according to claim 1, characterized in that the strip is associated with a mas ^¬ sive heat sink, which is in thermal contact with the primary ^¬ ren light sources.