Abstract
The invention relates to an illumination device comprising a plurality of LEDs (3) arranged on a carrier, an optical element disposed in a path of light emitted by at least one of said LEDs (3), and a driving unit for operating at least one of said LEDs (3). The driving unit in a first operation mode drives at a selected power a first selection of LEDs (13, FIG. 3A) to issue a first beam with a device light flux and with a first beam width, and drives in an at least one further operation mode at said selected power a further selection of LEDs (13, FIG. 3B), different in at least one LED from said first selection, to issue a further beam with said device light flux and with a further beam width wider than the first beam width. The LEDs of the further selection of the LEDs are evenly distributed over the carrier.
Claims
1. An illumination device comprising: a plurality of LEDs arranged on a carrier around a center thereof; an optical element disposed in a path of light emitted by at least one of said LEDs, an optical axis extending through said center and said optical element; and a driving unit for operating at least one of said LEDs, the driving unit in a first operation mode is configured to drive at a selected power P1 a first selection of LEDs L1 to issue a first beam with a first device light flux F1 and with a first beam width, and is configured to drive in an at least one further operation mode at a further selected power Pf a further selection of LEDs Lf, different in at least one LED from said first selection, to issue a further beam with a further device light flux, with 0.5*F1<=Ff<=1.5*F1, preferably with 0.8*F1<=Ff<=1.2*F1, and with a further beam width wider than the first beam width, wherein the LEDs Lf of the further selection of the LEDs are evenly distributed over the carrier in that shortest distances between each two neighboring LEDs of the LEDs Lf that are driven differ at the most by a factor three and wherein the first selection of LEDs has a first number N1 of LEDs and that the further selection of LEDs has a further number Nf of LEDs, wherein N1 is in the range of Nf±20%.
2. Illumination device as claimed in claim 1, characterized in that the LEDs arranged on the carrier numbers n and the LEDs to be operated simultaneously numbers k, wherein n is in the range of 30-2500 and k in in the range of 10<=k<=0.35*n.
3. Illumination device as claimed in claim 1, characterized in that each LED of the plurality of LEDs has essentially the same LED light flux when operated at the same (nominal) power.
4. Illumination device as claimed in claim 1, characterized in that at least one LED comprises a set of RGB LED dies.
5. Illumination devices as claimed in claim 1, characterized in that the optical element is a common, single lens having a lens axis coinciding with the optical axis.
6. Illumination devices as claimed in claim 1, characterized in that the LEDs of the first and further selection are all different LEDs.
7. Illumination devices as claimed in claim 1, characterized in that the LEDs of the first and further selection comprises as a shared subset of the same LEDs.
8. Illumination devices as claimed in claim 1, characterized in that in operation in first and further operation mode activated LEDs all are operated at same current.
9. Illumination devices as claimed in claim 1, characterized in that at least LEDs located adjacent to the center are activated for the illumination device to issue a relatively narrow beam.
10. Illumination device as claimed in claim 1, characterized in that the LEDs of the plurality of LEDs are arranged in a matrix, said matrix may comprise empty cells.
11. Illumination device as claimed in claim 1, characterized in that during operation a high frequency switching (100 Hz-100 MHz) of different but a same amount of activated LEDs is imposed by the driver.
12. Illumination device as claimed in claim 1, characterized in that the optical element can be slightly diffusing for smoothen the issued first and further beam.
13. A lighting system comprising at least two illumination devices according to claim 1 and a control unit for controlling the at least two illumination devices.
14. Method of operating an illumination device according to claim 1, the method comprising the steps of: driving a first selection of LEDs L1 at a selected first operation power P1 for issuing a first beam with a first beam width and generating a first device light flux F1; simultaneously switching off the first selection of LEDs and activating a further selection of LEDs Lf at a further selected operation power Pf for issuing a further beam generating a further device light flux Ff and with a further beam width different from the first beam width.
15. Method of operating an illumination device according to claim 14, the method comprising the further steps of: setting the dimming level of the illumination devices; and select a repetition of these steps to create an illumination cycle program.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] The invention will now be further elucidated by means of the schematic drawings, which are by no means intended to limit the scope of the invention but rather serve as illustration for the ample range of possibilities of the invention. In the drawings
[0032] FIGS. 1A-B show the principle of an illumination device providing an adaptable spot;
[0033] FIG. 2 shows top views of operation modes of a plurality of LEDs arranged in an array in an illumination device according to the prior art providing an adaptable spot;
[0034] FIGS. 3A-B show top views of operation modes of a plurality of LEDs arranged in an array in a first embodiment of an illumination device according to the invention providing an adaptable spot;
[0035] FIG. 4A-B show driver operation windows according to prior art and according to the invention;
[0036] FIGS. 5A-D show operation modes of a second embodiment illumination device according to the invention providing an adaptable spot;
[0037] FIG. 6 shows an LED array of a third embodiment illumination device according to the invention providing an adaptable spot;
[0038] FIG. 7 shows an LED array of a fourth embodiment illumination device according to the invention providing an adaptable spot;
[0039] FIG. 8 shows an embodiment of a system according to the invention; and
[0040] FIG. 9 shows a method according to the invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0041] FIGS. 1A-B show an illumination device 1 and the principle of operation of an illumination device with a pixelated light source providing an adaptable spot. The illumination device comprises as the pixelated light source a plurality of LEDs 3 arranged as an LED array on a carrier 5. The LEDs issue light over a path of light along 7 an optical axis 9 towards an optical element 11, in the figure a single lens positioned downstream from the LED array. The optical axis 9 extends through a center 10 of the carrier and through the transversely arranged optical element. In FIG. 1A only one LED 13 positioned on the optical axis in the center of the carrier is driven (i.e. is in operation to produce light) by driver 15. Light rays 17 issued by the LED towards the optical element are redirected via refraction to form a narrow beam 19 of device light. In FIG. 1B only two LEDs 13 positioned remote from the optical axis close to perimeter/edge of carrier are driven by driver 15. Light rays 17 issued by the LED towards the optical element are redirected via refraction to form a wide beam 20 of device light.
[0042] FIG. 2 shows top views of a plurality of LEDs 3 arranged in a matrix array. The plurality of LEDs functions as a pixelated light source. The figure further shows two operation modes of the pixelated light source of an illumination device according to the prior art. In the operation mode shown on the left in the figure, twelve only relatively centrally located LEDs 13 are driven at a relatively high current at hence at a relatively high power and provide a relatively narrow beam of relatively high intensity with a device light flux, while the other LEDs are switched off. In the operation mode shown on the right in the figure, essentially all LEDs 13 of the plurality of LEDs 3 are driven in a dimmed state, i.e. the prior art illumination device requiring a dimming circuitry to enable to operate the LEDs at a low current and hence at a relatively low power, and provide a relatively wide beam of a relatively low intensity, but with the same device light flux. Thus an adaptable spot with the same device light flux is obtained according to the prior art.
[0043] FIGS. 3A-B show top views of a plurality of LEDs 3, all having the same light output when operated at the same nominal power, arranged in a matrix array in the same arrangement as shown for the prior art illumination device shown in FIG. 2. The plurality of LEDs functions as a pixelated light source. The FIGS. 3A-B further shows two operation modes of the pixelated light source of a first embodiment of an illumination device according to the invention for providing an adaptable spot. In the operation mode shown in FIG. 3A, a first selection L1 21 of only twelve, relatively centrally located LEDs 13 are driven at nominal power and provide a relatively narrow beam of relatively high intensity with a device light flux F1. In the operation mode shown in FIG. 3B, a further selection Lf 23 of also only twelve LEDs 13 of the plurality of LEDs 3 are driven at nominal power. However, compared to the twelve driven LEDs of the first selection, the twelve driven LED of the further selection are at a mutually increased distance and are in more spread/distributed positions, in a rather evenly manner, on the LED array. This results in a relatively wide beam of a relatively low intensity but with the same device light flux, i.e. Ff=F1, as issued by the illumination device of FIG. 3A. Thus an adaptable spot with the same device light flux is obtained according to the invention. For the light beam as issued form the illumination device to appear uniform in the far field, in the embodiment shown in FIGS. 3A-B, the optical element is preferably slightly diffusing/scattering. The diffusive property of the optical element can, for example, be obtained by etching, sand-blasting at least one of the main surfaces of the optical element, or provide at least one of said main surfaces with a diffusing coating/sticker. In FIG. 3B it is further shown that the ignited LEDs 13 comprise outermost LEDs 13′ forming a perimeter 16 of an area of active LEDs. Said perimeter surrounds a sub-area which is in size about 80% of the total area occupied by all of the plurality of LEDs that are arranged on the carrier, said total area is indicated by circle 18. Within said sub-area the feature of said shortest distances between two closest LEDs of the active LEDs differing at the most by a factor three, is fulfilled.
[0044] FIG. 4A-B show driver operation windows according to prior art 61 and according to the invention 63. A typical method to drive a multiple LED's is by putting them in series and using a current source to drive the string. FIG. 4A shows the principle by which the boundaries of the operating window of drivers are obtained. Typically these drivers have an operating window which is on the high side limited by a maximum voltage Vmax, a maximum current Imax, and in a maximum power Pmax. On the low side the operating window has a minimum current Imin and a minimum voltage Vmin. The voltage on the LED string depends on the number of LED's in series and the forward voltage of the LED. The output current of the driver is set to a value to generate the right amount of flux. Setpoint 1 and Setpoint 2 indicate setpoints 69, 71 for about a maximum flux. Dimming is achieved by reducing the current through the LED string and is indicated by dimming arrows 65, 67. In FIG. 4B one can see the two modes of operation (narrow beam wide beam) of the known illumination device a shown in FIG. 2, plotted in one figure. “Setpoint 1” 71 is plotted at 36 Volt, 1 A for operating only twelve LEDs for obtaining the narrow spot, and a dimming range down to 0.1 A indicated by arrow 67. When switching to “Setpoint 2” 69 the string length increases from 12 to 52 operating LED's so the required voltage is 156V, hence the current should be 0.231 A to arrive at the same output flux of the known illumination device. If also in this case a dimming to 10% is needed, the current should be reduced to 0.0231 A. Hence, as shown, the driver window 61 for the known illumination devices, as indicated by the fine dotted line, must be very large in both the current and the voltage direction to support both operation modes. Contrary to the relatively large operation window required for the prior art illumination devices, the invention keeps the two modes inside the relatively small driver window 63 for the inventive illumination devices, indicated by the coarse dotted line, by using (more or less) equal amounts of LED's in both modes.
[0045] FIGS. 5A-D show operation modes of a second embodiment of an illumination device according to the invention providing an adaptable spot. In these FIGS. 5A-D four operation modes are shown which all result in the illumination device to issue practically the same wide light beam with the same intensity and the same device light flux. In FIG. 5A a first selection 21 of twelve driven LEDs 13 is made to generate the light beam, while in FIGS. 5B-C respectively a second selection 23, a third selection 25 and a fourth selection 27, all as further selections, of twelve driven LEDs are made to generate essentially the same light beam. In the FIGS. 5A-D only four different selections are shown. However, it is evident that a much larger number of selection of LEDs from the plurality/array of LEDs 3 is possible to create a wide variety of possible beams. In particular in the illumination device shown in FIG. 5A-D the number of possible selections in principle are:
[00002]
wherein n=52 and k=12, resulting in n!/((n!−k!)*k!)≠2*10{circumflex over ( )}11 possible selections. By a high frequency change, for example at a frequency of 10,000 Hz or 1 MHz, in the selection of wider spread LEDs in the source such that more LEDs are contributing to the beam profile and less smoothing is needed from the optical element.
[0046] FIG. 6 shows a top view of a plurality of LEDs 3 according to a third embodiment of an illumination device according to the invention providing an adaptable spot. In this embodiment the plurality of LEDs is arranged in a matrix, cell arrangement wherein quite a large number of cells are empty, i.e. LEDs are removed or never provided in these empty cells. Such an embodiment of the illumination device is interesting and feasible in the case the illumination device is used in only a (very) limited number of settings. As shown in the FIG. 6, the illumination device is designed to switch between two settings, i.e. the setting shown, which is a single type of wide beam as generated by a first selection 21 of evenly spread driven LEDs 13, and in the alternative narrow beam setting to be generated by a selection 23 of inactive/non-driven LEDs arranged relatively centrally around center 10 of the carrier 5. In the embodiments shown there is an overlap of three out of the twelve LEDs that are part of both the first and the second selection.
[0047] FIG. 7 shows a plurality of LEDs 3 arranged in an LED array of a fourth embodiment of an illumination device according to the invention providing a color adaptable spot. The fourth embodiment shown has four different colored LEDs 13, i.e. red LEDs 13a, green LEDs 13b, blue LEDs 13c and amber LEDs 13d. The plurality of LEDs comprises either a mixture of single colored LEDs of different color, for example single colored red, green, blue, and optionally amber and white LEDs, in a well-mixed arrangement, or the plurality of LEDs comprises at least one single LED, but preferably all LEDs, having differently colored LED dies, for example red 14a, green 14b, blue 14c, amber dies 14d, which is indicated in the figure for one LED. Well-mixed means that LEDs of a specific color has neighboring LEDs of only different colors, for example in an arrangement as shown in the FIG. 6. The dies and/or LEDs can be individually addressed and operated which enables the illumination device to provide color signals, for example a red signal in case of emergency or to issue a versatile variety in colored beam patterns.
[0048] FIG. 8 shows a lighting system 29 according to the invention comprising three illumination devices 1 according to the invention and a control unit 31 connected to the illumination devices. Each illumination device comprises a respective housing 30 accommodating a respective plurality of LEDs (not shown), a driver (not shown), a reflector 32 and a lens (not shown). The control unit can actualize a controlled cooperation of a plurality of illumination devices to create a static lighting setting or to create dynamic lighting scenes. Thereto the control unit can activate anyone of the illumination devices individually, which can result in that the illumination devices can operate solely, sequentially or simultaneously, dependent on what light setting or lighting scene is desired.
[0049] FIG. 9 shows a method according to the invention. The method shown comprises four steps, i.e.
[0050] First step 33 setting the dimming level of the illumination devices, please note that this step is optional;
[0051] Second step 35: driving a first selection of LEDs at a selected operation power for issuing a first beam with a first beam width and generating a device light flux;
[0052] Third step 37: simultaneously switching off the first selection of LEDs and activating a further selection of LEDs at said selected operation power for issuing a further beam generating said device light flux and with a further beam width different from the first beam width; and
[0053] Fourth step 39: select a repetition of these steps to create an illumination cycle program either to repeat from the first step or from the second step, please note that this is an optional step.
