Luminaire and illumination system

Abstract

A luminaire and an illumination system are disclosed. In an embodiment a luminaire includes at least one light-emitting semiconductor chip having a main emission side and a reflector having a reflection side facing the main emission side, the reflection side being a freeform different from a circle, an ellipse, a parabola or a hyperbola when seen in cross-section, wherein a base line of the reflector runs through the main emission side and a local height of the reflection side is measured against the base line, wherein a local focal length of the reflection side is increased along the local height, concerning ray bundles coming in parallel with the base line from an exterior of the luminaire during operation, and wherein local heights do not have a common focal point.

Claims

1. A luminaire comprising: at least one light-emitting semiconductor chip having a main emission side; and a reflector having a reflection side facing the main emission side, the reflection side being a freeform different from a circle, an ellipse, a parabola or a hyperbola when seen in cross-section, wherein a base line of the luminaire runs through the main emission side and a local height of the reflection side is measured against the base line, wherein a local focal length of the reflection side is increased along the local height when ray bundles come in parallel with the base line from an exterior of the luminaire during operation, wherein local heights do not have a common focal point, wherein the following is true with a tolerance of at most 5% of a maximum focal length F for the local focal length fin dependence from the local height h: f(h)/F=−0.000029 (h/H)3+0.0031 (h/H)2−0.0017 (h/H)+0.23, and wherein H is a maximum height of the reflection side at the maximum focal length F.

2. The luminaire according to claim 1, wherein the reflection side has a shape of a modified parabola when seen in the cross-section so that a distance of focal points of the ray bundles toward the reflection side along the base line increases with increasing local height, and wherein the reflector comprises a metal foil.

3. The luminaire according to claim 2, wherein a first one of the focal points is located at a point of intersection between the base line and the main emission side, with a tolerance of at most 5% of the respective local focal length, and wherein the focal points assigned to greater local focal lengths than the local focal length of the first one of the focal points are located on a side of the base line remote from the reflection side and are located out of the main emission side.

4. The luminaire according to claim 2, wherein the focal points are located on a bended curve when seen in the cross-section, the bended curve being a parabola or a spiral line, and wherein a curvature radius of the bended curve increases in a direction away from the base line.

5. The luminaire according to claim 1, wherein an angle between the base line and a direction of maximum emission of the luminaire is at least 2° and at most 15°, and wherein the base line is in parallel with a mounting plane of the luminaire.

6. The luminaire according to claim 5, wherein the at least one light-emitting semiconductor chip comprises LEDs configured to independently generate red, green and blue light so that an emission color of the luminaire can be adjusted during operation, and wherein the luminaire in a plane which is parallel to the base line and also to the mounting plane and/or the at least one light-emitting semiconductor chip has a Lambertian emission characteristic.

7. The luminaire according to claim 1, wherein an angle between the base line and the main emission side is at least 30° and at most 60°, and wherein at most 40% of the main emission side are on a side of the base line remote from the reflection side.

8. The luminaire according to claim 1, further comprising a housing in which the reflector and the light-emitting semiconductor chip are located, wherein the housing encloses the reflector and the light-emitting semiconductor chip in a waterproof and gas tight manner.

9. The luminaire according to claim 8, wherein the housing comprises a plurality of the light-emitting semiconductor chips arranged along a straight line, and wherein a length of the housing along the straight line exceeds a height as well as a width of the housing by at least a factor of 100.

10. The luminaire according to claim 1, further comprising a cover sheet, wherein the luminaire is configured to emit light through the cover sheet, wherein the cover sheet is oriented perpendicular to the base line and touches the reflector on a side remote from the at least one light-emitting semiconductor chip.

11. The luminaire according to claim 1, wherein the reflector comprises a plurality of facets, the facets running perpendicular to the base line and the local heights and being separated from one another by a kink in each case, and wherein the reflection side deviates in individual facets from an averaged, fitted mean shape of the reflector by at most 2% of the maximum height of the reflection side.

12. An illumination system comprising: at least one luminaire according to claim 1, wherein the luminaire is arranged on a wall or a pillar of a building which has at least in part a glass front, wherein the luminaire is arranged to illuminate a part of the building that protrudes from the wall or the pillar, and wherein at most 2% of the light emitted by the luminaire enters the building so that glaring within the building is avoided.

13. The illumination system according to claim 12, wherein the luminaire is a sectional strip arranged on an exterior face of the wall or the pillar and facing the part of the building to be illuminated.

14. The illumination system according to claim 12, wherein the main emission side faces away from the wall or the pillar and faces away from the part of the building to be illuminated, and wherein light generated in the at least one light-emitting semiconductor chip is emitted from the luminaire after one reflection on the reflection side during operation.

15. A luminaire comprising: at least one light-emitting semiconductor chip having a main emission side; and a reflector having a reflection side facing the main emission side, the reflection side being a freeform different from a circle, an ellipse, a parabola or a hyperbola when seen in cross-section, wherein a base line of the luminaire runs through the main emission side and a local height of the reflection side is measured against the base line, wherein a local focal length of the reflection side is increased along the local height when ray bundles come in parallel with the base line from an exterior of the luminaire during operation, wherein local heights do not have a common focal point, wherein the reflection side has a shape of a modified parabola when seen in the cross-section so that a distance of focal points of the ray bundles toward the reflection side along the base line increases with increasing local height, wherein the reflector comprises a metal foil, wherein the focal points are located on a bended curve when seen in the cross-section, the bended curve being a parabola or a spiral line, and wherein a curvature radius of the bended curve is increased in a direction away from the base line.

16. The luminaire according to claim 15, further comprising a housing in which the reflector and the light-emitting semiconductor chip are located, wherein the housing encloses the reflector and the light-emitting semiconductor chip in a waterproof and gas tight manner.

17. The luminaire according to claim 16, wherein the housing comprises a plurality of the light-emitting semiconductor chips arranged along a straight line, and wherein a length of the housing along the straight line exceeds a height as well as a width of the housing by at least a factor of 100.

18. The luminaire according to claim 15, further comprising a cover sheet, wherein the luminaire is configured to emit light through the cover sheet, wherein the cover sheet is oriented perpendicular to the base line and touches the reflector on a side remote from the at least one light-emitting semiconductor chip.

19. An illumination system comprising: at least one luminaire comprising: at least one light-emitting semiconductor chip having a main emission side; a mounting plane; and a reflector having a reflection side facing the main emission side, the reflection side being a freeform different from a circle, an ellipse, a parabola or a hyperbola when seen in cross-section, wherein a base line of the luminaire runs through the main emission side and a local height of the reflection side is measured against the base line, wherein a local focal length of the reflection side is increased along the local height when ray bundles come in parallel with the base line from an exterior of the luminaire during operation, wherein local heights do not have a common focal point, wherein the luminaire is arranged on a wall or a pillar of a building which has at least in part a glass front, wherein the luminaire is arranged to illuminate a part of the building that protrudes from the wall or the pillar, wherein at most 2% of the light emitted by the luminaire enters the building so that glaring within the building is avoided, wherein the reflection side, when seen in the cross-section, has a shape of a modified parabola so that a distance of focal points of the ray bundles toward the reflection side along the base line increases with increasing local height, wherein the base line is in parallel with the mounting plane, wherein the luminaire is mounted on the building with the mounting plane so that the mounting plane is on a side of the luminaire facing the building, wherein an angle between the base line and a direction of maximum emission of the luminaire is at least 2° and at most 15°, the direction of the maximum emission points away from the mounting plane, and wherein the base line runs through the main emission side so that the base line and the main emission side have a point of intersection.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) A luminaire and an illumination system described herein are explained in greater detail below by way of exemplary embodiments with reference to the drawings. Elements which are the same in the individual figures are indicated with the same reference numerals. The relationships between the elements are not shown to scale, however, individual elements may be shown exaggeratedly large to assist in understanding.

(2) In the figures:

(3) FIGS. 1A-1C and 6A-6B show exemplary embodiments of luminaires;

(4) FIG. 2A-2B shows exemplary embodiments of illumination systems;

(5) FIGS. 3 to 5 show optical properties of luminaires; and

(6) FIGS. 7A-7B and 8 show modifications of illumination systems.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

(7) In FIGS. 1A and 1C sectional views, and in FIG. 1B a perspective view of an exemplary embodiment of a luminaire 1 are shown. The luminaire 1 comprises a plurality of light-emitting semiconductor chips 2 which are formed by LED chips. The light-emitting semiconductor chips 2 are arranged on a straight line L and can independently emit red, green and blue light or also other colored light like yellow or cyan or orange. In FIG. 1C, generated radiation R is shown schematically.

(8) The luminaire 1 further comprises a reflector 3. A reflection side 30 of the reflector 3 faces a main emission side 20 of the semiconductor chips 2. The reflection side 30 is approximately formed like a semi-parabola, wherein said modified parabola opens more strongly than a regular parabola. By means of the reflector a light emission pattern of the luminaire 1 is formed. All or nearly all light generated by the semiconductor chips 2 is emitted after just one reflection at the reflection side 30. No, or virtually no, light from the semiconductor chips 2 emit the luminaire 1 directly.

(9) As an option, the semiconductor chips 2 are located on a heatsink 46. The heatsink 46 as well as the semiconductor chips 2 and the reflector 3 are located in a housing 4. The housing 4 preferably is waterproof and gastight. The housing 4 comprises a cover sheet, for example, made of glass. The light generated in the semiconductor chips 2 is emitted from the luminaire 1 through the cover sheet 42.

(10) The housing 4 also has a mounting plane 45. In particular, the luminaire 1 is designed to be arranged on an external surface via the mounting plane 45. For this purpose, the housing 4 could comprise openings and/or recesses to ensure an easy mounting of the luminaire 1.

(11) Preferably, see FIG. 1B, the luminaire is formed as a sectional strip along a longitudinal axis A. Hence, the luminaire 1 has a length along the longitudinal axis A that is significantly larger than a width and a height of the luminaire.

(12) In FIGS. 2A and 2B, exemplary embodiments of an illumination system 10 comprising a luminaire 1 are shown in sectional views. In each case, the luminaire 1 is arranged on a building 50 with a wall 5. A direction M of maximum emission of the luminaire 1 is approximately parallel with the wall 5 on which the luminaire 1 is mounted. The wall 5 is purposefully not, or not significantly, illuminated by the luminaire 1.

(13) Further, there is a protrusion that forms a part 55 of the building 50 to be laminated. A radiation R generated by the luminaire is led to said part 55. Hence, in particular due to the reflector 3 only said part 55 is illuminated and it is avoided that persons in the building 50 are glared by the luminaire 1. An angle between said part 55 and the wall 5 can exceed 90°, and is by way of example around 135° as shown in FIG. 2.

(14) According to FIG. 2B, the luminaire 1 is in particular configured as described in connection with FIG. 1. Contrary to that, according to FIG. 2A a more complex luminaire 1 is used. The luminaire 1 of FIG. 2A comprises three subunits 1a, 1b, 1c that emit light in different directions. Such luminaires comprising more than one subunit can also be used in all of the other exemplary embodiments.

(15) FIG. 3 shows another exemplary embodiment of the luminaire 1 in a cross-section. Here, the emphasis is on the optics.

(16) There is a base line B that intercepts the main emission side 20 of the semiconductor chip 2. An angle between the main emission side 20 and the base line B is about 45°. From the base line B, a local height h and a maximum H of the reflection side 30 are measured. For different local heights h, the reflection side 30 shows different local focal lengths f. At the maximum height H, there is a maximum focal length F.

(17) The different local focal lengths f are illustrated in FIG. 3 with the help of parallel ray bundles R that come from an exterior of the luminaire 1. These different parallel ray bundles R are focused by the reflection side 30 into focal points P. One of said focal points P is on or very close to a point S of intersection between the base line B and the main emission side 20.

(18) When seen in cross-section, the focal points P are located on a bent curve 7. Said bent curve 7 begins approximately at the point S of intersection. A radius of curvature of said bent curve 7 increases towards focal points P that are associated with larger local focal lengths f. With increasing local focal length f, the associated focal point P moves away from the base line B. Further, at least some or all of the focal points P move away from the reflection side 30 when seen in projection on the base line B. That is, the larger the local focal length f, the more left-sided is the corresponding focal point P in FIG. 3.

(19) As an option, the reflector 3 comprises one or more mounting parts 33 that protrude from the reflection side 30. In the area of the mounting parts 33, the reflector 3 which is preferably made of a metal foil, can be fixed in the housing 4, for example, near the heatsink 46 and near the cover sheet 42, compare FIG. 1A.

(20) In FIG. 4, the local height h is drawn in arbitrary units against the normalized local focal length. Normalized means that the local focal length f is divided by the maximum focal length F. The normalized local focal length f/F follows a cubic equation. In the exemplary embodiment of FIGS. 3 and 4, the normalized local focal length f/F follows the following equation:
f(h)/F=−0.000028821233(h/H)3+0.003108357(h/H)2−0.00170994(h/H)+0.22830713.

(21) In FIG. 5, an emission characteristic of the luminaire 1 is provided. A luminous intensity I is drawn in arbitrary units against an angle of emission with respect to the mounting plane 45 and the base line B. The direction M of maximum emission is at an angle of about 8°.

(22) For comparison, an exemplary emission pattern of the semiconductor chip 2 is also indicated. The emission pattern of the semiconductor chip 2 is approximately Lambertian. By means of the reflector 3, the luminous intensity is strongly enhanced in the direction M of maximum emission. Thus, in a plane perpendicular to the mounting plane 45 there is only an emission into a small sector.

(23) FIG. 6A shows a cross-sectional view of a further exemplary embodiment of the luminaire 1, the respective reflector 3 can be seen in more detail in FIG. 6B in a perspective view. The housing 4 can correspond to the housing of FIG. 1.

(24) This type of reflector 3 is also based on a freeform reflector profile, but the reflection side 30 is divided into a plurality of facets 35. Borders between the facets 35 can be constituted by kinks. Preferably, the overall shape of the reflections side 30 is not strongly influenced by the partitioning into the facets 35. The individual facets 35 can be of convex shape so that a plurality of further focal points Q results in the exterior of the luminaire 1. A distance of the further focal points Q to the cover sheet 42 is, for example, between 50% and 500% of the maximum height H of the reflection side 30. However, preferably there is no common focal plane so that a distance of the further focal points Q towards the cover sheet 42 varies.

(25) As an option, as in all the other exemplary embodiments, the cover sheet 42 can be formed as a convex lens. Further, contrary to what is shown in FIG. 6B, there can be a plurality of different facets along the longitudinal axis A so that the reflection side 30 can have kinks or bends along the longitudinal axis A, too.

(26) This solution can resolve big color differences due to the light-emitting semiconductor chips 2 and can improve color uniformity of the resulting light spot. Otherwise, color uniformity may be impaired by the use of semiconductor chips 2 with different emission colors, for example, a mixture of red, green and blue emitting semiconductor chips 2, or may be impaired by non-uniformity of a luminescence conversion element (not shown) that is a part of the semiconductor chips 2. If the semiconductors chips 2 show good color uniformity, however, the freeform solution as presented in connection with FIG. 1 is preferred.

(27) In the sectional view in FIG. 7A and in the perspective view in FIG. 7B a modification 11 of an illumination system is illustrated. A lens 6 which is a lens with total internal reflective parts follows an LED chip 2. However, the light of the LED chip 2 is not perfectly parallelized so that a divergent bundle of rays R is present. Thus, a part of the rays R enters and runs through a glass face of the wall 5 of the building 50. Thus, glaring of persons within the building 50 can occur.

(28) The same is true for the modification 11 of FIG. 8. Here, the main emission side 20 points to the same side as the direction M of maximum emission. Thus, the bundle of rays R points toward the wall 5. For this reason, glaring of persons in the building 50 can also occur.

(29) These problems can be avoided or greatly reduced by the reflector 3 and the arrangement of the light-emitting semiconductor chip 2 as explained in connection with FIGS. 1 to 5. Further, the part 55 can be illuminated with good uniformity and homogeneity.

(30) The invention described is not restricted by the description given with reference to the exemplary embodiment. Rather, the invention encompasses any novel feature and any combination of features, including in particular any combination of features in the claims, even if this feature or this combination is not itself explicitly indicated in the claims or exemplary embodiments.