Lighting device, lighting system and use thereof

Abstract

A lighting device comprising a light source being configured to generate source light of a white light emission spectrum having a color correlated temperature (CCT) in a range of 2500-20000K and comprising a control unit being configured to control a lighting element for tuning of the source light with respect to a ratio between a first emission peak in a wavelength range of 460-490 nm and a second emission peak in a wavelength range of 430-460 nm. Thus a lighting device with a tunable/adjustable spectrum is provided that can switch between a first operation state of energy efficiency lighting with a blue peak in the second wavelength range of 430-460 nm, but with blue hazard risk, and a second operation state of less efficient but safe, healthy lighting with a biological stimulant having a blue peak in the first wavelength range of 460-490 nm.

Claims

1. Lighting device operable in a first and a second operation state for controlling exposure to blue light, said lighting device comprising: a light source comprising blue LEDs and dimmable green and red LEDs, said light source being configured to generate source light of a white light emission spectrum having a color correlated temperature (CCT) in a range of 2500-20000K; a control unit being configured to control a lighting element being at least one of a tunable light filter, switchable lighting element, dimmable lighting element for tuning of the source light with respect to a ratio between a blue light emission peak in a wavelength range of 460-490 nm and a second light emission peak in a wavelength range of 430-460 nm, said tuning further comprises an adaption in the emission intensity in the green to red part of the spectrum by controlling the dimmable green and red LEDs to compensate a shift in the CCT of the white emission spectrum caused by a tuning of the ratio between the first and second blue light emission peak upon a switch from the first to the second operation state, such that the CCT of the white emission spectrum is without change, wherein the control unit receives a measured spectral composition of an initial spectrum and calculates the CCT and wherein a follow-up light spectrum is adapted in emission intensity using only the dimmable green and red LEDs, to compensate for and/or reverse an effect on and/or the shift of the CCT caused by a difference in the second emission peak between the initial and follow-up spectrum.

2. Lighting device as claimed in claim 1, characterized in that the lighting element is at least one of a dimmable blue light emitting lighting element, a switchable blue light emitting lighting element, a tunable blue light filter.

3. The lighting device as claimed in claim 2, characterized in that the tunable light filter is tunable for a wavelength range of <460 nm, preferably for a wavelength range of 430-460 nm.

4. A kit of parts comprising the lighting device as claimed in claim 3, characterized in that the light source and the tunable light filter are mutually mechanically disconnected, and in that the lighting device is a personal wearable, wherein the personal wearable is selected from the group consisting of a cap, glasses, burka.

5. Lighting device as claimed in claim 1, characterized in that lighting element is at least one of a dimmable lighting element of the light source, a switchable lighting element of the light source and comprises a first lighting element issuing light having a first maximum emission peak in a wavelength range of 460-490 nm during operation, and a second lighting element issuing light having a second maximum emission peak in a wavelength range of 430-460 nm during operation.

6. The lighting device as claimed in claim 3, characterized in that the first lighting element comprises a first LED and in that the second lighting element comprises a second LED.

7. The lighting device as claimed in claim 1, characterized in that the first emission peak is in a wavelength range of 465-475 nm, and the second emission peak is in a wavelength range of 445-455 nm.

8. The lighting device as claimed in claim 1, characterized in that for the mutually tuned first and second emission peak of the white emission spectrum the following requirement is essentially fulfilled:
I.sub.1*R.sub.1+I.sub.2*R.sub.2≈constant, wherein I.sub.1 is the intensity of the emission spectrum at the first emission peak; R.sub.1 is the melatonin responsiveness at the first emission peak; I.sub.2 is the intensity of the emission spectrum at the second emission peak; R.sub.2 is the melatonin responsiveness at the second emission peak.

9. A lighting system as claimed in claim 1, wherein the control unit is configured to enable a user to switch from an energy efficient light setting to a healthier light setting by adjusting the ratio, wherein the healthier light setting reduces a risk of retinal damage in human eyes by lowering blue light in the generated source light.

10. A lighting system comprising: a lighting device as claimed in claim 1 comprising a kit of parts, a user carried device, and a sensor and/or clock configured to measure or sense sensor data during operation, said sensor data comprising a location of the user carried device, (ambient) spectral lighting conditions, and exposure time of the user carried device to the (ambient) spectral lighting conditions, the sensor is further configured to provide the control unit with a sensor signal based on the sensor data which sensor signal is processed by the control unit to tune both the ratio between the first and second emission peak and their absolute emission intensity during operation.

11. A lighting system as claimed in claim 10, characterized in that the control unit sets lighting conditions of the lighting system at or below a maximum illumination level of 2000 lux.

12. A lighting system as claimed in claim 10, characterized in that the user carried device is uploaded with personal user data, both said personal data and sensor data are processed by the control unit to adjust both the emission spectrum and intensity to the personal user during operation.

13. A lighting system as claimed in claim 10, characterized in that it further comprises a user interface for manual control of operation, wherein said user interface is selected from the group consisting of a smart phone, a remote control, a laptop, a tablet.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be further elucidated by means of the exemplary, non-limiting schematic drawings, in which:

(2) FIG. 1 shows a general view of a standing lighting device according to the invention;

(3) FIG. 2A-B show an example of a first respectively a second emission spectrum as issued by lighting devices according to the invention;

(4) FIG. 3 shows the overlap for the blue part of emission spectra of the lighting devices of FIG. 2A respectively FIG. 2B with the blue hazard function and the circadian rhythm response function;

(5) FIG. 4 shows a schematic drawing of an interactive lighting system with dose control of blue light involving blue hazard risk.

DETAILED DESCRIPTION

(6) FIG. 1 shows a lighting device 1, in the figure a desklight, comprising a light source 3 inside a housing 5 with reflector 7, but alternatively this reflector could be absent or be a diffuser, the housing being connected via a flexible joint pole 9 to a base 11. The base contains a control unit 13, an intensity adjustment knob 15 and a first control knob 17. The lighting device is connectable to mains via an electric cable 19. The light source comprises a plurality of LEDs 21 comprising at least a first 23 and a second lighting element 25. The embodiment shown in the figure further comprises as a third lighting element at least one green light emitting LED 22 and as a fourth lighting element at least one orange-red light emitting LED 24. Both the first and second lighting element can be a single LED or a plurality of LEDs. The lighting device by its light source issues a beam 31 of a, preferably white, spectrum which is tuned source light in intensity and/or in spectral composition (in particular of the ratio between the first and second emission peaks) via control knob 17. The intensity of light issued by the at least first lighting elements can be controlled by knob 17 independently from the second lighting elements and vice versa. The intensity of both the first and the second lighting elements can be adjusted by dimming or boosting or by turning on/off a fraction of the respective plurality of LEDs. The intensity of the beam 31 as issued from the lighting device is adjustable by knob 15, through a light exit window 33 of the reflector to the exterior. Additionally or alternatively, the reflector accommodates a tunable filter 27 for tuning of the spectral composition of the beam 31 issued by the lighting device, which is also shown in FIG. 1 and which is tunable by a second control knob 29. To accommodate for the fact that each eye is unique and reacts differently under different circumstances, a light that is tunable in spectrum and in intensity is thus provided. Hence, a lighting device, for example as shown in FIG. 1, is provided that is dimmable and enables different spectral emission resulting in tuning between efficient lighting and less efficient but safer, more healthier lighting.

(7) FIG. 2A-B shows an example of a first 41 respectively a second emission spectrum 43 as issued by the lighting device according to the invention. Both spectra are obtained by a respective LED comprising a combination of a LED blue pump and a phosphor. Blue light from the LED pump is partly transmitted through the phosphor and partly absorbed and converted into light of longer wavelengths, the combination of transmitted and converted light results in white light. The spectrum shown in FIG. 2A provides safer healthier and more stimulative light, and has one peak in the blue part of the spectrum with a first maximum 45 at about 470 nm due to use of a “470 nm LED blue pump”. The spectrum of FIG. 2B provides more efficient lighting than the spectrum of FIG. 2A, yet with more blue hazard risk, and has one peak in the blue part of the spectrum with a second maximum 47 at about 450 nm, due to the use of a “450 nm LED blue pump”. Both spectra have a correlated color temperature (CCT) of about 6500K, which corresponds to a daylight spectrum. To attain the same CCT, the shift from the first maximum to the second maximum is accounted for via slight modifications of the spectrum in the longer wavelength ranges, for example in that the peak 49 in the orange-red part of the spectrum is somewhat shifted towards the yellow wavelength range of the spectrum. Though the CCT of both spectra is the same, the spectra each have specific properties and effects which become apparent, for example, in the experienced prolonged attention and vitality of respondents.

(8) FIG. 3 shows the overlap for the blue part of emission spectra of the lighting devices of FIG. 2A respectively FIG. 2B with the blue hazard function and the circadian rhythm response function. All curves in FIG. 3 are shown on a scale normalized to 100% as function of the wavelength. As shown in FIG. 3 the blue hazard function 51 extends roughly from 400 nm to 500 nm with a maximum 53 at about 435 nm. The circadian rhythm response function 55 is even broader than the blue hazard function, and extends well beyond the 400 nm and 500 nm and having a relatively broad maximum 57 at about 465 nm. The energy efficient 450 nm blue pump spectrum has a practically 100% overlap with the blue hazard function, while the overlap of the less energy efficient 470 nm blue pump spectrum with the blue hazard function is significant less. Hence, the 470 nm blue pump spectrum is safer and healthier than the 450 nm blue pump spectrum but less energy efficient. Both the 450 nm blue pump and the 470 nm blue pump spectra show a significant overlap with the circadian rhythm response function, and both spectra can be effectively be used for control of the circadian rhythm, yet the 470 nm blue pump spectrum being slightly different in this respect than the 450 nm blue pump spectrum. To show the possibility to tune the spectrum from safe and healthier light to more efficient light while keeping the melatonin suppression essentially unaffected, FIG. 3 shows a case in which a first emission peaks at 480 nm and the second emission peaks at 445 nm, and respective intensities I.sub.1,2, respective melatonin responsiveness R.sub.1,2 and respective blue hazard responsiveness B.sub.1,2. It is shown that the comparison between the emission spectra essentially fulfills the following requirement:
I.sub.1*R.sub.1+I.sub.2*R.sub.2≈constant, wherein I.sub.1 is the intensity of the emission spectrum at the first emission peak; R.sub.1 is the melatonin responsiveness at the first emission peak; I.sub.2 is the intensity of the emission spectrum at the second emission peak; R.sub.2 is the melatonin responsiveness at the second emission peak.

(9) Yet the responsiveness to the blue hazard function at the first and second emission maxima differs by more than a factor two.

(10) FIG. 4 shows a schematic drawing of an interactive lighting system 100 with dose control of light involving blue hazard risk. Thereto the lighting system comprises a lighting device 1 according to the invention, a user carried device 110, and a sensor 120 and/or clock configured to measure or sense sensor data during operation. The lighting device comprises an integrated tunable filter 27, a light source (not shown) and a control unit 13, which in the figure is located elsewhere in the lighting system outside the lighting device. The sensor is configured to communicate with the control unit via a sensor signal 130 based on the sensor data which sensor signal is processed by the control unit to tune both the ratio between the first and second emission peak and their absolute emission intensity during operation.

(11) As location sensing can be used measurement of signal strength of e.g. Bluetooth signals or Wifi signals. The dose of blue hazard energy is the product of blue hazard energy multiplied with the time duration of the exposure. After initial calibrating of the lighting system it is known which dose is present in the room as function of the light settings. For a given maximum dose there is a maximal amount of exposure time.
In formula: Dosis=C∫.sub.λ1.sup.λ2B(λ)I(λ)dλ*Δt
with B(λ) the sensitivity curve for blue hazard radiation as function of wavelength and I(λ) the spectral power distribution of the emitted light; Δt is the exposure time of the emitted light.

(12) The tunable filter can be integrated in the LED-module or can be part of the luminaire (for example included in the light diffusor). In an alternative embodiment the tunable filter is not integrated in the luminaire, but remote from it. This could be for example an (aftermarket) panel or foil that can be applied to the luminaire or placed in front of it or be hung above a table. It even could be “attached” to the individual consumer, for example in glasses (e.g. Google glass) or perhaps in caps. Advantages of remote filters can be better personalization, with one set of luminaires even with multiple users present and that light can still be kept bright outside the areas where people are present.