WO2015058984A1

WO2015058984A1 - Led-based lighting apparatus

Info

Publication number: WO2015058984A1
Application number: PCT/EP2014/071831
Authority: WO
Inventors: Thomas DEFLANDRE
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-10-21
Filing date: 2014-10-13
Publication date: 2015-04-30

Abstract

A LED-based lighting apparatus (10) comprises a plurality of individual modules (16) which comprise each a LED unit (30) and a beam modifier (32) combined with each other. Any of the modules produces light with an individual intensity distribution which exhibits a two-fold symmetry about an optical axis (A) of the module, and has a peak value along two emission directions separated from the optical axis. All modules are arranged within the apparatus so that their optical axes are parallel to a common direction (Z), and with respective orientations which are evenly rotated in a plane perpendicular to the common direction.

Description

LED-BASED LIGHTING APPARATUS

-- TECHNICAL FIELD OF THE INVENTION --

The invention relates to a LED-based lighting apparatus, especially for a luminaire, and more especially for office lighting applications.

-- BACKGROUND OF THE INVENTION --

The new trend for luminaires is using devices which are based on mid- power LEDs.

However, a large number of such LEDs are needed for producing the required luminous flux, which depends on the applications but usually ranges from 1000 to 3000 lumens, thereby resulting in large and cumbersome lighting devices which are not adapted to common luminaire designs.

Besides, for indoor applications such as lighting for offices, revolved light distributions are usually obtained by using revolution surfaces which are provided by lenses or reflectors.

However, a mid-power LED is generally a rectangular or elongated shape, which does not suit by its own for producing revolved light distributions.

Starting from this situation, one object of the present invention consists in providing a LED-based lighting apparatus having high efficiency, improved beam control and small size in order to match common luminaire designs, and possibly match already existing luminaire designs.

Another object is providing such LED-based lighting apparatuses which are low-cost and quick and easy to manufacture.

Still another object is providing such LED-based lighting apparatuses which meet the requirements prescribed in lighting standards, including one desired UGR value, UGR standing for "Unified Glare Rating" as defined by the CIE (International Commission on Illumination) and UGR values being recited in European standard EN 12464-1 for example, related to the Lighting of Workplaces.

-- SUMMARY OF THE INVENTION - For meeting these objects or others, the present invention proposes a

LED-based lighting apparatus which comprises at least N individual modules, N being an integer higher than 3. Each module comprises a LED unit and a beam modifier out of a translucent material, combined with each other so that the module produces light with an individual light intensity distribution exhibiting a two-fold symmetry about an optical axis of the module. The individual light intensity distribution also has a peak value along two emission directions which are separated from the optical axis and correspond to each other through the two-fold symmetry, and this peak value is higher than 1 .20 times a center value of the individual light intensity distribution existing at the optical axis of the module. In the invention apparatus, all individual modules are arranged so that their respective optical axes are parallel to a common direction, and with respective orientations measured in a plane perpendicular to the common direction so that the orientations of N-1 ones among the N modules, when measured in degrees from the orientation of a first one of the N modules other than the N-1 ones, are each in a respective one of the ranges [k-360/N - 10/N ; k-360/N + 10/N], k equalling successively the integers from unity to N-1 .

According to the invention, the individual modules are progressively and evenly rotated in a plane perpendicular to the common direction, so as to mix the features of the individual module beams all around the common direction. This beam feature mixing is efficient with regard to the maximum emission directions but also for the color variations possibly existing in the individual module beams.

These invention features provide LED-based lighting apparatuses with optimum layouts, enabling to obtain high efficiencies and total light beams which are continuously revolution -symmetric. In addition, these optimum layouts are small enough to fit in currently existing luminaire designs.

Possibly, the LED-based lighting apparatus may comprise several subsets of modules. Then the invention features apply within each one of the modules subsets, but replacing the module number N with that N_s of each subset separately. But the common direction is set for the whole apparatus. Preferably, the module number N_s may be different for at least two module subsets which are comprised in the LED-based lighting apparatus. Improved light features can thus be obtained. Most preferably, the module number N_s may be odd for at least one of the module subsets and even for at least another one.

In some embodiments of the invention, one might also implement one or more of the following optional improvements: all the modules comprised in the apparatus may be identical to each other; each module may produce light with a color varying when moving about the optical axis of this module, for at least one non-zero elevation value measured from this optical axis, and the light which is produced by the whole apparatus for the same non-zero elevation value but measured from the common direction is devoid of color variations when moving all around this common direction; each LED unit may have a lighting intensity which is comprised between 20 and 200 lumens; each beam modifier may be such that 95% of the light intensity which is produced by the corresponding LED unit, is within an emission cone with half-apex angle comprised between 25° and 40°; the modules may be arranged on concentric circles contained in the plane perpendicular to the common direction, and the respective orientations of the modules may vary in accordance with radius directions for the circles at the module locations. In such embodiments of the invention, the modules may be further arranged within a disk of less than 100 mm in diameter; at least three of the modules may be arranged along a straight line in the plane perpendicular to the common direction; the LED-based lighting apparatus may further comprise a planar substrate which supports the LED units of the modules. In such embodiments of the invention, the LED-based lighting apparatus may also comprise a cover piece out of the translucent material, which is retained parallel to the substrate and facing the LED units, and shaped so as to form the beam modifiers of the modules at locations respectively in line with the LED units.

Another object of the invention is a beam modifier out of a translucent material and which comprises a first face which is planar and a second face which is free-form with two-fold symmetry. A cross-section of the second face has a convex shape in a first meridian plane containing an optical axis of the beam modifier, and a cross-section of the second face has, in a second meridian plane containing the optical axis and perpendicular to the first meridian plane, a convex shape in a center portion of the cross-section and a concave shape in side portions of the cross-section. -- BRIEF DESCRIPTION OF THE DRAWINGS --

Other features and advantages of the invention will readily appear from the following description of several of its embodiments, provided as non-limiting examples, with reference to the accompanying drawings now listed:

Fig. 1 is a perspective view from upper side for an assembled LED-based lighting apparatus according to a first embodiment of the invention;

Fig. 2 is an exploded perspective view corresponding to Fig. 1 ;

Fig. 3 is an exploded perspective view from lower side for the apparatus of Fig. 1 ; Fig. 4 is an assembled perspective view corresponding to Fig. 3;

Figs. 5A and 5B are respectively a perspective view and a plan view from lower side for an example of a beam modifier of the apparatus of Fig. 1 ;

- Figs. 6A and 6B are respectively a perspective view and a plan view from lower side for another example of a beam modifier of the apparatus of Fig. 1 ;

Fig. 7 is a diagram showing light intensity distribution for an individual module of the apparatus of Fig. 1 ; - Fig. 8 is a diagram showing light intensity distribution for the whole apparatus of Fig. 1 ; and

Fig. 9 is a perspective view of part of a LED-based lighting apparatus according to another embodiment of the invention.

In these figures, same reference signs denote identical elements or elements with similar functions or operations.

-- DETAILED DESCRIPTION OF THE INVENTION --

Fig. 1 shows a LED-based lighting apparatus 10 according to a first embodiment of the invention, to be used for example in an office luminaire.

This LED-based lighting apparatus 10 may be comprised of a planar substrate 12, a cover piece 14 and a plurality of individual modules 16, as shown in Figure 3 described hereinafter.

The planar substrate 12 may itself comprise a printed circuit board (PCB) 18 having a disk shape. The PCB 18 is supplied with electrical tracks and possibly electronic components (not represented), and also with a power supply plug 23 (Fig. 3) in a manner which is known in the art and out of the invention core.

The PCB 18 may be disk-shaped with a diameter D less than 100 mm, for example substantially equal to 90 mm. The cover piece 14 is made of a translucent material and may comprise a support plate 20 having a disk shape which matches that of the PCB 18. For example, the cover piece 14 may be out of polycarbonate-based material. Possibly, the support plate 20 has same diameter value as the PCB 18.

The cover piece 14 is retained parallel to the substrate 12 so that the support plate 20 and the PCB 18 are superimposed on each other. Spacers 21 , as shown in Figure 2, may be provided for ensuring a parallel arrangement for the cover piece 14 relative to the substrate 12. Practically, the spacers 21 may be moulding-formed within the face of the support plate 204 which faces the PCB 18.

The substrate 12 and the cover piece 14 are intended to be attached to each other by fixation means, and advantageously also to the luminaire using the same fixation means. In the present embodiment and as best seen on Fig. 2, the fixation means may comprise first fixation holes 22 arranged on the periphery and at the center of the PCB 18, and second fixation holes 24 arranged on the periphery and at the center of the support plate 20, in line with the respective first fixation holes 22. The fixation holes 22, 24 are adapted to cooperate with complementary fixation members (not represented) provided on the luminaire, such as screw-nut assemblies, clipping means, etc.

In the present invention, the relative orientation of the substrate 12 and cover piece 14 is important. In order to mount the substrate 12 and the cover piece 14 in a unique position relative to each other, the LED-based lighting apparatus 10 may preferably further comprise alignment means.

In the present embodiment, these alignment means comprise pins 26 which are arranged on the periphery of the support plate 20 and projecting from this support plate 20 through the PCB 18. The pins 26 are adapted to be received in complementary notches 28 which are provided on the periphery of the PCB 18. With reference to Figs. 3 and 4, at least some or all of the individual modules 16 which are comprised in the LED-based lighting apparatus 10 are identical to each other.

Each module 16 comprises a LED unit 30 and a beam modifier 32. The LED unit 30 is a mid-power LED usually with rectangular shape, and having a lighting intensity which is comprised between 20 and 200 lumens. Such LED unit is commercially available and widely used for other applications, in particular for display back-lighting. It is low-cost and easy to implement on a PCB. The LED units 30 are arranged on the PCB 18 of the substrate 12, with suitable connections to the electrical tracks, and the cover piece 14 faces the LED units 30.

Advantageously, the cover piece 14 is shaped so as to form the beam modifiers 32 at locations respectively in line with the LED units 30. For example, the beam modifier shapes are provided within the face of the cover piece 14 which is opposite to the LED units 30. For cost savings, the cover piece 14 may be moulded directly with such beam modifier shapes. The other face of the cover piece 14, which faces directly the LED units 30, may be planar, but additional beam modifier profiles may also be formed within this other face.

A first example of a beam modifier 32A is illustrated on Figs. 5A and 5B and a second example of a beam modifier 32B is illustrated on Figs. 6A and 6B. In each case, the inner face 34 of the beam modifier 32A, 32B is planar, thus suitable for being located on the PCB 18 provided with the LED units 30. The outer face 36 of each beam modifier 32A, 32 B is free-form with two-fold symmetry. A cross-section of this outer face 36 is convex in a first meridian plane AX containing an optical axis A of the beam modifier 32A, 32B and extending along a length direction X of the beam modifier 32A, 32B. This first meridian plane AX is a symmetry plane for the beam modifier 32A, 32B. In a second meridian plane AY also containing the optical axis A but extending along a width direction Y of the beam modifier 32A, 32B, the outer face 36 is convex again in cross-section, but only in a center portion, and is concave in side portions of this cross-section. The second meridian plane AY is perpendicular to the first meridian plane AX and is also a symmetry plane for the beam modifier 32A, 32B. The size of the beam modifiers 32A, 32B along the X and Y directions is for example 10.83x1 1 .71 mm for beam modifier 32A and 13.56x7.78 mm for beam modifier 32B.

For each module 16, the LED unit 30 and the beam modifier 32 are combined with each other so that the module 16 produces light with an individual light intensity distribution exhibiting a two-fold symmetry about the optical axis A of this module 16. Two-fold symmetry means that the distribution is unchanged when the module 16 is rotated about its optical axis A by 360° (degrees) divided by two, i.e. 180°.

Fig. 7 illustrates the individual light intensity distribution of one of the modules 16 in a meridian plane containing the optical axis A and extending along the length of the LED unit 30 (curve L1 ), and in another meridian plane also containing the optical axis A but extending along the width of the LED unit 30 (curve L2). Therefore both meridian planes considered are perpendicular to each other. The angle values indicated around the diagram and denoted γ are elevation values of light emission directions measured from the optical axis A. The light intensity unit is arbitrary.

The individual light intensity distribution of the module 16 has a peak value PV along two emission directions E1 , E2 which are separated from the optical axis A by about 20°, and which correspond to each other through the two-fold symmetry. Hence, the module 16 produces a beam having, in a plane perpendicular to the optical axis A, a substantially oblong or elongated shape. Simultaneously, the peak value PV along both emission directions E1 , E2 is higher than 1 .20 times the center value CV of the individual light intensity distribution existing at the optical axis A of the module 16. Each beam modifier 32 is further arranged such that 95% of the light intensity which is produced by the corresponding LED unit 30, is within an emission cone with half-apex angle Y_opt comprised between 25° and 40°.

Each module 16 may produce light with a color feature which varies when moving about the optical axis A of this module 16, for at least one non- zero value of the elevation angle γ. The color distribution of a single module 16 may be thus substantially non uniform.

Referring back to Figs. 3 and 4, all the individual modules 16 are arranged within the LED-based lighting apparatus 10 so that their respective optical axes A are all parallel to a common direction Z. Then, the modules 16 of the apparatus 10 may be distributed within subsets so that, within one and same subset, the respective orientations of the modules measured in a plane perpendicular to the common direction Z, for example the plane of the PCB 18 or of the support plate 20, are evenly offset about the common direction Z. Put another way, when N is the module number in a subset, greater than 3, the orientations of N-1 ones among the N modules 16, when measured in degrees from the orientation of a first one of the N modules 16 used as a reference, are each in a respective one of the ranges [k-360/N - 10/N ; k-360/N + 10/N], k equalling successively the integers from unity to N-1 .

In the first invention embodiment of figures 1 to 6, all modules 16 are arranged on three concentric circles each perpendicular to the common direction Z, and the respective orientations of the modules 16 match the radius directions for these circles at the module locations. The modules 16 are thus all arranged within a disk less than 100 mm in diameter.

For example, as seen on Fig. 3, there are 33 modules 16 arranged on concentric circles respectively labelled C1 , C2, C3: 4 modules 16 being arranged on the inner circle C1 , 12 modules 16 being arranged on the intermediate circle C2, and 17 modules 16 being arranged on the outer circle C3. This embodiment is a merging of three invention special cases where N equals 4, 12 and 17 respectively. The light intensity distribution of the whole LED-based lighting apparatus 10 is illustrated on Fig. 8. This total distribution, which results from all the individual distributions of the modules 16, is almost revolution-symmetric around the common direction Z. It is thus more homogeneous when turning continuously about the common axis Z, as compared to the individual distribution of a single module 16 as shown on Fig. 7. The light intensity unit in Fig. 8 is candela/1000 lumens.

The light produced by the whole apparatus 10 for any non-zero elevation value is also devoid of color variations when moving around this common direction Z. The color distribution of the whole apparatus 10 is thus rotationally uniform.

Examples

The LED-based lighting apparatus described above may be adapted for arranging 44 LED units on the PCB, again 90 mm in diameter. Then the shortest pitch between two adjacent LED units may be 15 mm. In this manner, a total luminous flux of 2000 lumens is available, which suits for a luminaire to be used in an office.

Fig. 9 shows part of a LED-based lighting apparatus 1 10 according to a second embodiment of the invention.

The LED-based lighting apparatus 1 10 differs from the LED-based lighting apparatus 10 of Fig. 1 to 6 in that the modules are arranged along a straight line in the plane perpendicular to the common direction Z.

In this second embodiment, the PCB 1 18 is rectangular shaped and there are 16 modules (N = 16), all modules being arranged along the length direction of the PCB 18. The light intensity distribution of the whole apparatus 1 10 meets again continuous revolution symmetry around the common direction.

In other variants of the invention, the arrangement of the modules in the plane perpendicular to the common direction may be along a curved line, a square, a rectangle, etc. The invention thus provides a great variety of optimized layouts for LED-based lighting apparatuses, enabling to produce beams with high efficiency, symmetric over continuous revolution about the apparatus axis, and without color flaws. In addition, these layouts may be as small as possible to fit in currently existing luminaire sets. Generally, the invention is based on using "imperfect" beams at individual level, but combined so that the total beam as resulting from all the individual beams has the required features.

The invention can be implemented for any indoor lighting application as well as any outdoor lighting application. In particular, it suits for obtaining an UGR value of 19 recommended for offices, UGR standing for "Unified Glare Ratio" and being calculated according to the CIE prescription, by using the table-registered Guth coefficient values.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

C L A I M S

1 . A LED-based lighting apparatus (10, 1 10) comprising at least N individual modules (16), N being an integer higher than 3, each module (16) comprising a LED unit (30, 130) and a beam modifier (32) out of a translucent material, combined with each other so that the module (16) produces light with an individual light intensity distribution exhibiting a two-fold symmetry about an optical axis (A) of said module (16), the individual light intensity distribution having a peak value (PV) along two emission directions (E1 , E2) which are separated from the optical axis (A) and correspond to each other through the two-fold symmetry, and said peak value (PV) being higher than 1 .20 times a center value (CV) of the individual light intensity distribution existing at the optical axis (A) of the module (16), all individual modules (16) being arranged within the apparatus (10, 1 10) so that their respective optical axes (A) are parallel to a common direction (Z), wherein the N modules (16) are arranged with respective orientations measured in a plane perpendicular to the common direction (Z) so that the orientations of N-1 ones among said N modules (16), when measured in degrees from the orientation of a first one of said N modules (16) other than the N-1 ones, are each in a respective one of the ranges [k-360/N - 10/N ; k-360/N + 10/N], k equalling successively the integers from unity to N-1 .

2. A LED-based lighting apparatus (10) according to Claim 1 , comprising several subsets each of at least 4 individual modules (16), and wherein each module (16) of any one of the subsets comprises a LED unit

(30) and a beam modifier (32) out of a translucent material, combined with each other so that the module (16) produces light with an individual light intensity distribution exhibiting a two-fold symmetry about an optical axis (A) of said module (16), the individual light intensity distribution having a peak value (PV) along two emission directions (E1 , E2) which are separated from the optical axis (A) and correspond to each other through the two-fold symmetry, and said peak value (PV) being higher than 1 .20 times a center value (CV) of the individual light intensity distribution existing at the optical axis (A) of the module (16), all individual modules (16) of the LED-based lighting apparatus (10) are arranged so that their respective optical axes (A) are parallel to a common direction (Z), and for any one of the subsets, the modules (16) of said subset being N_s in number and are arranged with respective orientations measured in the plane perpendicular to the common direction (Z) so that the orientations of N_s-1 ones among said N_s modules (16), when measured in degrees from the orientation of a first one of said N_s modules (16) other than the N_s-1 ones, are each in a respective one of the ranges [k-360/N_s - 10/N_S ; k-360/N_s + 10/N_S], k equalling successively the integers from unity to N_s-1 .

3. A LED-based lighting apparatus (10) according to Claim 2, wherein the module number N_s is different for at least two module subsets comprised in said LED-based lighting apparatus (10).

4. A LED-based lighting apparatus (10) according to Claim 3, wherein the module number N_s is odd for at least one of the module subsets and even for at least another one of the module subsets.

5. A LED-based lighting apparatus (10) according to any one of Claims 1 to 4, wherein the modules (16) are arranged on concentric circles (C1 , C2,

C3) contained in the plane perpendicular to the common direction (Z), and the respective orientations of said modules (16) vary in accordance with radius directions for said circles at said modules locations.

6. A LED-based lighting apparatus (10) according to Claim 5, wherein the modules (16) are arranged within a disk of less than 100 mm in diameter.

7. A LED-based lighting apparatus (1 10) according to Claim 1 , wherein at least three of the modules are arranged along a straight line in the plane perpendicular to the common direction (Z).

8. A LED-based lighting apparatus (10, 1 10) according to any one of Claims 1 to 7, wherein all the modules (16) comprised in the apparatus (10, 1 10) are identical to each other.

9. A LED-based lighting apparatus (10, 1 10) according to any one of Claims 1 to 8, wherein each module (16) produces light with a color varying when moving about the optical axis (A) of said module (16), for at least one non-zero elevation value measured from said optical axis (A), and the light produced by the whole apparatus (10, 1 10) for the non-zero elevation value measured from the common direction (Z) is devoid of color variations when moving all around said common direction (Z).

10. A LED-based lighting apparatus (10, 1 10) according to any one of Claims 1 to 9, wherein each LED unit (30, 130) has a lighting intensity comprised between 20 and 200 lumens.

1 1 . A LED-based lighting apparatus (10, 1 10) according to any one of Claims 1 to 10, wherein each beam modifier (32) is such that 95% of the light intensity produced by the corresponding LED unit (30, 130), is within an emission cone with half-apex angle comprised between 25° and 40°.

12. A LED-based lighting apparatus (10, 1 10) according to any one of Claims 1 to 1 1 , further comprising a planar substrate (12, 1 12), and the LED units (30, 130) of the modules (16) are supported by said substrate (12, 1 12).

13. A LED-based lighting apparatus (10, 1 10) according to Claim 12, further comprising a cover piece (14) out of the translucent material, said cover piece (14) being retained parallel to the substrate (12, 1 12) and facing the LED units (30, 130), and said cover piece (14) being shaped so as to form the beam modifiers (32) of the modules (16) at locations respectively in line with said LED units (30, 130).

14. A beam modifier (32) out of a translucent material and comprising a first face (34) which is planar and a second face (36) which is free-form with two-fold symmetry, a cross-section of the second face (36) having a convex shape in a first meridian plane (AX) containing an optical axis (A) of the beam modifier (32), and a cross-section of the second face (36) having, in a second meridian plane (AY) containing the optical axis (A) and perpendicular to the first meridian plane (AX), a convex shape in a center portion thereof and a concave shape in side portions thereof.