WO2021105029A1

WO2021105029A1 - Lighting device with near-metameric device flicking

Info

Publication number: WO2021105029A1
Application number: PCT/EP2020/083001
Authority: WO
Inventors: Maurice Alexander Hugo Donners
Original assignee: Signify Holding B.V.
Priority date: 2019-11-26
Filing date: 2020-11-23
Publication date: 2021-06-03

Abstract

The invention is directed to a lighting device (100) that comprises a lighting unit (102) configured to emit light having two predetermined different spectral power distributions (S1, S2), each having respective u' and v' chromaticity coordinates in a CIELUV color space, and wherein a difference between the u' and v' chromaticity coordinates smaller than 0.05. Further the two different spectral power distributions are configured to cause a difference in response of at least one photoreceptor type of a target animal species of at least 30%. It also comprises a lighting-control unit (104) configured to control operation of the lighting unit by switching between the at least two spectral power distributions with a flickering frequency (fF) value. The lighting device thus causes a perceivable and uncomfortable flicker effect to the target animal species which is not perceivable by an average human eye.

Description

LIGHTING DEVICE WITH NEAR-METAMERIC DEVICE FLICKING

FIELD OF THE INVENTION

The invention is directed to a lighting device, a method for operating a lighting device and to a computer program.

BACKGROUND OF THE INVENTION

US 2017/0006848 A1 discloses an insect control system having a light source arrangement that comprises one or more light sources with tunable spectrum, polarization, intensity and or flickering pattern. The system enables a particular type of insect to be attracted or repelled in a particular time period.

To control insect behavior, one embodiment disclosed in US 2017/0006848 A1 employs a “blind-choice” strategy intended to influence the distribution of insects in an environment by offering them lighting choices with different spectra that are distinguishable to them but not to humans. The insects are lured from one position to another based on phototaxis, i.e. movement in response to a light stimulus, either towards the light source (positive phototaxis) or away from it (negative phototaxis).

SUMMARY OF THE INVENTION

It would be beneficial to further reduce the attractiveness of a light source to a target species.

The present invention is based on the recognition that most animal species, including humans tend to react negatively to light flickering. Flicker is defined by the CIE as the “impression of unsteadiness of vision perception induced by a light stimulus whose luminance or spectral distribution fluctuating with time for a static observer in a static environment” (CIE, technical note 006:2016).

Thus, according to a first aspect of the present invention, a lighting device is disclosed. The lighting device comprises a lighting unit configured to emit light having a controllable spectral power distribution being selectable between at least two different predetermined spectral power distributions having respective u’, v’ chromaticity coordinates in a CIELUV color space. Further, a difference between the u’ and v’ chromaticity coordinates of any two of the spectral power distributions of the lighting unit is smaller than 0.05 for each coordinate. Also, any two of the spectral power distributions of the lighting unit are suitably configured to cause a difference in response of at least one photoreceptor type of a target animal species other than a human being of at least 30%. The lighting device further comprises a lighting-control unit configured to control operation of the lighting unit by switching selection of a respective one of the at least two different predetermined spectral power distributions of the emitted light with a flickering frequency value assuming (approaching) a value between 0.5 and 100 Hz.

In colorimetry, the CIE 1976 L*, u*, v* color space, commonly known by its abbreviation CIELUV, is a color space adopted by CIE in 1976, as a simple-to-compute transformation of the 1931 CIE XYZ color space, but which attempted perceptual uniformity. It is extensively used for applications such as computer graphics which deal with colored lights.

The lighting device of the first aspect is thus configured to produce flickering effect by emitting light with at least two different spectral power distributions at a flickering frequency value between 0.5 and 500 Hz. In the lighting device of the first aspect, the spectral power distributions are advantageously chosen so that a person with average eyesight does not notice a substantial flicker-induced change in the perceived colors, as defined by the difference between the u’, v’ chromaticity coordinates in the CIELUV color space. This difference refers to the individual differences between respective u’ coordinates of the spectral power distributions and differences between respective v’ coordinates of the spectral power distributions and not to differences between the u’ and the v’ coordinate of a spectral power distribution. Further, and since other animal species have different types of photodetectors, the spectral power distributions are advantageously chosen so that a given target animal species perceives a flicker, i.e., that the spectral power distributions of the lighting unit cause a difference in response of at least one photoreceptor type of the target animal species of at least 30%.

The invention is thus based on the known fact that some animal species have photoreceptors whose spectral sensitivity differs from those of human cone cells. A photoreceptor cell is a specialized type of neuroepithelial cell found in the retina that is capable of visual phototransduction. The biological importance of photoreceptors is that they convert visible electromagnetic radiation into electrical signals that can stimulate biological processes. To be more specific, photoreceptor proteins in the cell absorb photons, triggering a change in the cell's membrane potential. According to the present invention, and for at least a given target species, the difference in the response of at least one photoreceptor type results in members of the target species that have an average eyesight perceiving a substantial change in the perceived light response with the predetermined flickering frequency value between 0.5 and 500Hz. This causes discomfort and acts as a repellent for that particular target animal species. However, the change between the predetermined different spectral power distributions at the flickering frequency, even at the low values within the given range, is not sensed by the average human eye and a human with an average sight would not perceive a disturbing flickering, due to the similarity of the u’, v’ coordinates of the spectral power distributions. In other words, the lighting unit of the first aspect of the invention is configured to, alternatively, and with the flickering frequency value, emit light having at least two predetermined different spectral power distributions that result in a near-metameric match for a human with average eyesight and in a non-metameric match for at least one target animal species other than human beings. A metameric match occurs when two lights with different spectral properties such as different wavelengths or amplitudes, are perceptually identical to each other for a given species and is not a solely a property of the light source, but depends also on the type of photoreceptors involved in light sensing.

In the following, embodiments of the first aspect of the invention will be disclosed.

In an embodiment, the spectral power distributions of the lighting unit are configured to cause a difference of at least 30% in the response of at least one photoreceptor type of a target insect species, a target bird species or a target rodent species. Each of these species has a different combination of photoreceptors and thus perceive colors in a respective different manner. By selecting the spectral power distributions of the lighting unit in accordance with the respective photoreceptors of the target species, the flicker-induced change in the perceived colors can be tailored to a given species. For instance, the perception of brightness and chromaticity is dominated in insects by R7 and R8 type photoreceptors, while motion sensitivity seems to be governed by Rl-6 photoreceptors.

In different alternative embodiments, the spectral power distributions of the lighting unit are configured to cause a difference of at least 80%, and more preferably of at least 95% in the response of at least one photoreceptor type of the target animal species, thus increasing the perceived flickering effect.

In a preferred embodiment, the lighting device comprises a lighting unit configured to emit light having exactly two predetermined different spectral power distributions. In alternative embodiments, the lighting unit is configured to emit light having three or more different predetermined spectral power distributions. In this case, any two of the spectral power distributions have respective u’ and v’ chromaticity coordinates in a CIELUV color space differing less than 0.05 from the respective u’ or v’ coordinates of the rest of the spectral power distributions.

In a preferred embodiment the difference between the CRI values of any two of the spectral power distributions of the lighting unit is smaller than 25, preferably smaller than 5. In this particular embodiment the spectral power distributions are more equally accurate when rendering different colors and the flickering is even less perceivable by the average human eye. Additionally, in another embodiment, at least two predetermined different spectral power distributions have a respective CRI value above 80, thus providing a high accuracy in rendering different colors. Alternatively, in other embodiments wherein high accuracy in rendering color is not a priority, such as for instance in street lighting, the CRI value of the spectral power distributions is between 25 and 80, which a difference between them not exceeding 20% of the smaller CRI value, preferably not exceeding 5% of the smaller CRI value.

In another embodiment, which can be combined with any of the technical features of the embodiments previously described, the lighting control unit is configured to switch between the at least two spectral power distributions at a flickering frequency assuming a value between 1 Hz and 20 Hz, preferably at a flickering frequency value between 2 Hz and 10 Hz. According to Jeavons, P.M. and Harding, G.F.A. Photosensitive epilepsy: a review of the literature and a study of 460 patients. Heinemann, London (1975), low frequency flicker is perceived as irritating and uncomfortable by most humans and it can induce headaches, migraine attacks or even epilepsy attacks in some. The maximum sensitivity is found around 10 to 15 Hz, with sensitivity between 1 and 65 Hz. However, such a low frequency flickering effect will not be perceived by an average human eye due to the near-metameric match of the spectral power distributions, whereas the flickering will be perceived by members of the target animal species.

In an embodiment, the lighting-control unit is configured to control operation of the lighting unit by switching between selection of a respective one of the at least two predetermined different spectral power distributions with a predetermined flickering frequency (fp) value assuming a value between 0.5 and 500 Hz, preferably between 1 and 20 Hz and more preferably between 2 and 10 Hz. In another embodiment, the lighting-control unit is configured to vary the flickering frequency with time according to a predetermined frequency variation algorithm, such that at any given time, the current flickering frequency value is between 0.5 and 500 Hz, preferably between 1 and 20 Hz and more preferably between 2 and 10 Hz. In a particular embodiment, the predetermined frequency variation algorithm is configured to vary the flickering frequency randomly or pseudo-randomly either in frequency value, or switching times or both.

In an embodiment of a lighting device of the first aspect, which can be combined with any of the technical features of the previous embodiments, the at least two different spectral power distributions have a respective correlated color temperature value between 2000 and 5000 K, and wherein a difference between the correlated color temperature value of any two of the spectral power distributions of the lighting unit is smaller than 5%. Decreasing difference between correlated color temperatures results in better near-metameric matches.

Color temperature is defined, for a light source, as the temperature of an ideal black-body radiator that radiates light of a color comparable to that of the light source. The color temperature of the electromagnetic radiation emitted from an ideal black body is defined as its surface temperature in kelvins. This permits the definition of a standard by which light sources are compared. To the extent that a hot surface emits thermal radiation but is not an ideal black-body radiator, the color temperature of the light is not the actual temperature of the surface. Many other light sources, such as fluorescent lamps, or light emitting diodes (LED’s) emit light primarily by processes other than thermal radiation. This means that the emitted radiation does not follow the form of a black-body spectrum. These sources are assigned what is known as a correlated color temperature (CCT). CCT is the color temperature of a black-body radiator which to human color perception most closely matches the light from the lamp. Because such an approximation is not required for incandescent light, the CCT for an incandescent light is simply its unadjusted temperature, derived from comparison to a black-body radiator.

Alternatively, or additionally, in another embodiment of the lighting device of the first aspect, a difference in luminous flux between any two of the spectral power distributions of the lighting unit is smaller than 20%, preferably smaller than 5% and more preferably smaller than 1%. Decreasing differences in the luminous flux results in better near-metameric matches for the average human eye.

In an embodiment of the lighting device of the first aspect, the difference between the u’ chromaticity coordinate and between the v’ chromaticity coordinate of any two of the spectral power distributions of the lighting unit is smaller than 0.0025. Particularly, in a preferred embodiment the spectral power distributions have respective u’ and v’ chromaticity coordinates in a CIELUV color space, and any two of the at least two spectral power distributions have a difference in the u’ chromaticity coordinate of at most 0.0022 and a difference in the v’ chromaticity coordinate of at most 0.0011.

In another embodiment, additionally, a respective color point of the spectral power distributions lies, in the CIELUV color space, below a Planckian locus of the CIELUV color space. In physics and color science, the Planckian locus or black body line is the path or locus that the color of an incandescent black body would take in a particular chromaticity space as the blackbody temperature changes.

This is particularly advantageous in embodiments wherein both spectral power distributions have a comparable amount of power in the near ultraviolet wavelength region, i.e., between 300 and 400 nm or in the UV-A wavelength region, i.e., between 315 and 400 nm. This prevents obtrusive or uncomfortable color changes in objects which contain optical whiteners which are subject to fluorescence when illuminated by a UV-A light, or black light.

Regarding the implementation of the lighting device, in a preferred embodiment, the lighting unit comprises a plurality of light emitting diodes, each configured to emit light having a respective LED-spectral power distribution. In this embodiment, a respective combination of light emitting diodes is configured to emit light with only one of the at least two predetermined different spectral power distributions. For instance, in an embodiment, the light emitting diodes have a respective LED-spectral power distribution which has power peaks at 406 nm, or 460 nm, or 475 nm, or 530 nm, or 545 nm, or 588 nm, or 615 nm, or 625 nm, or 632 nm, or 665 nm.

According to a second aspect of the invention, a method for operating a lighting device is disclosed. The method comprises selecting and emitting light having at least two predetermined different spectral power, each of the at least two predetermined different spectral power distributions having respective u’ and v’ chromaticity coordinates in a CIELUV color space, wherein a difference between the u’ and v’ chromaticity coordinates of any two of the spectral power distributions of the lighting unit is smaller than 0.05, and wherein any two of the spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type of the target animal species of at least 30%, and switching between at least two spectral power distributions of the emitted light with a flickering frequency value assuming a value between 0.5 and 500 Hz.

The method of the second aspect thus shares the advantages of the lighting device of the first aspect or of any of its embodiments. In an embodiment of the method of the second aspect, the flickering frequency value is lower than 100 Hz. In an alternative embodiment the flickering frequency value is between 1 and 20 Hz and more preferably between 2 and 10 Hz.

Alternatively, or additionally, in another embodiment of the method, the at least two predetermined different spectral power distributions of the emitted light have a respective CRI value above 80 and wherein a difference between the CRI values of any two of the spectral power distributions of the lighting unit is smaller than 5.

Alternatively, or additionally, in another embodiment of the method, the at least two spectral power distributions have a correlated color temperature value between 2000 and 5000 K, and wherein a difference between the correlated color temperature value of any two of the spectral power distributions of the lighting unit is smaller than 5%.

Alternatively, or additionally, in another embodiment of the method, a difference in luminous flux between any two of the spectral power distributions of the lighting unit is smaller than 1%.

Alternatively, or additionally, in another embodiment of the method, the spectral power distributions have respective u’ and v’ chromaticity coordinates in a CIELUV color space, and wherein any two of the at least two spectral power distributions have a difference in the u’ chromaticity coordinate of at most 0.0022 and a difference in the v’ chromaticity coordinate of at most 0.0011.

Alternatively, or additionally, in another embodiment of the method, any two of the predetermined different spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type of a target animal species of at least 80%, and more preferably of at least 95%.

According to a third aspect of the present invention, a computer program is disclosed. The computer program comprises instructions which, when the program is executed by a computer, cause the computer to carry out the method of the second aspect of the invention.

Different embodiments of the computer program of the third aspect are advantageously configured to carry out different embodiments of the method of the second aspect.

It shall be understood that the lighting device claim 1, method of claim 11 and the computer program of claim 13, have similar and/or identical preferred embodiments, in particular, as defined in the dependent claims. It shall be understood that a preferred embodiment of the present invention can also be any combination of the dependent claims or above embodiments with the respective independent claim.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

Fig. 1 shows the spectral sensitivities (S) of the cone cells S, L and M an average human eye,

Fig. 2 shows the spectral sensitivities (S) of typical insect photoreceptors Rl- 6, R7p, R7y, R8p and R8y,

Fig. 3 shows a schematic block diagram of an embodiment of a lighting device,

Fig. 4 shows the spectral power distributions (SP) as a function of the wavelength (l) of an embodiment of a lighting device,

Fig. 5 shows the spectral power distributions (SP) as a function of the wavelength (l) of another embodiment of a lighting device,

Fig. 6 shows the spectral power distributions (SP) as a function of the wavelength (l) of another embodiment of a lighting device, and

Fig. 7 shows a flow diagram of an embodiment of a method for operating a lighting device.

DETAILED DESCRIPTION OF EMBODIMENTS

Fig. 1 shows the spectral sensitivities of an average human eye. The average human eye with normal vision has three kinds of photoreceptor cells that sense light, called cone cells. The three type of cone cells have respective spectral sensitivity curves with peaks in short "S" (420-440nm), middle "M" (530-540nm), and long "L" (560-580nm) wavelength ranges. The L, M and S cone cells underlie human color perception in conditions of medium and high brightness. Weighting a total light power spectrum by the individual spectral sensitivities of the three kinds of cone cells renders three effective values of stimulus. These three values compose a tristimulus specification of the objective color of the light spectrum. The three parameters, denoted "S", "M", and "L", are indicated using a 3-dimensional space denominated the "LMS color space", which is one of many color spaces devised to quantify human color vision.

A color space is a three-dimensional space, and as such, any color is specified by a set of three numbers which specify the color and brightness of a particular homogeneous visual stimulus. A color space maps a range of physically produced colors to an objective description of color sensations registered in the human eye, typically in terms of tristimulus values, but not usually in the LMS color space defined by the spectral sensitivities of the cone cells. The tristimulus values associated with a color space can be conceptualized as amounts of three primary colors in a tri-chromatic, additive color model. Most wavelengths stimulate two or all three kinds of cone cells because the spectral sensitivity curves of the three kinds overlap. Certain tristimulus values are thus physically impossible, for example LMS tristimulus values that are non-zero for the M component and zero for both the L and S components.

Typically, colors to be adapted chromatically will be specified in a color space other than LMS. Human color perception is typically modeled using a CIE (Commission Internationale de TEclairage) color space. One of these CIE color spaces is the CIE 1931 color space where the defines its set of resulting tristimulus values are denoted by "X", "Y", and "Z". The CIE 1931 color space, also referred to as CIE XYZ color space, encompasses all color sensations that are visible to a person with average eyesight and therefore is a device-invariant representation of color. The relationship between the XYZ and LMS color spaces is linear, so the transition is representable by a transformation matrix. The CIE XYZ color space serves as a standard reference against which many other color spaces are defined. The XYZ tristimulus values are thus analogous to, but different from, the LMS cone responses of the human eye.

A color rendering index value, also referred to as CRI value, is a measurement of a light source's accuracy in rendering different colors when compared to a reference light source, according to standards based on average human perception. It generally ranges from 0 for a source like a low-pressure sodium vapor lamp, which is monochromatic, to 100, for a source like an incandescent light bulb, which emits essentially blackbody radiation. The higher the CRI value, the better the visual perception of colors is.

The CIE recommends the procedure of measuring and specifying color rendering properties of light sources based on a test color sample method. The method of measuring and specifying color rendering properties of light sources recommended by the CIE is based on resultant color shifts of test objects, and is referred to as the "Test-color Method". It is the fundamental method for appraisal of color rendering properties of light sources, and is recommended for type testing as well as for testing individual lamps.

To apply the recommended Test-color Method the resultant color shifts for suitably chosen test-color samples are calculated. A set of eight test-color samples is specified by their spectral radiance factors for calculating the color rendering index CRI-Ra. These samples cover the hue circle, are moderate in saturation, and are approximately the same in lightness. Data for six additional test-color samples representing a strong red, yellow, green and blue as well as complexion and foliage colors are also supplied. From the color shifts, color rendering Indices, CRI-Ra values are inferred.

Color perception varies for other animal species. For instance, the pineal and parapineal glands are photoreceptive in non-mammalian vertebrates, but not in mammals. Birds have photoactive cerebrospinal fluid (CSF)-contacting neurons within the paraventricular organ that respond to light in the absence of input from the eyes or neurotransmitters. Invertebrate photoreceptors in organisms such as insects and molluscs are different in both their morphological organization and their underlying biochemical pathways

The compound eyes of arthropods like insects, crustaceans and millipedes are composed of units called ommatidia. An ommatidium contains a cluster of photoreceptor cells surrounded by support cells and pigment cells. Ommatidia are typically hexagonal in cross-section and approximately ten times longer than wide. At the outer surface, there is a cornea, below which is a pseudocone that acts to further focus the light.

Depending on the species, the inner 90% of the ommatidium contains 6 to 9 long and thin photoreceptor cells often abbreviated as "R cells" in literature and often numbered R1 through R9.

Fig. 2 shows the spectral sensitivities of typical insect photoreceptors, which include rhabdomers Rl-6, R7y, R7p R8y and R8p.

As it can be seen by comparing the spectral sensitivities of human and insect eyes, color perception is different for both animal species. For insects, the perception of brightness and chromaticity is dominated by R7 and R8 rhabdomers, while motion sensitivity seems to be governed by Rl-6 rhabdomers humans. Other differences are present between the spectral sensitivities of human and that of other animal species such as birds or rodents.

Fig. 3 shows a schematic diagram of an embodiment of a lighting device 100. The lighting device comprises a lighting unit 102 that includes two light emitting units 104 and 106, each configured to emit light having a respective predetermined different spectral power distributions Si, S2. Each of the spectral power distributions have respective u’ and v’ chromaticity coordinates in a CIELUV color space. CRI. Further, a difference between the u’ and v’ chromaticity coordinates of the two of the spectral power distributions Si and S2 of the lighting unit is smaller than 0.05, and preferably smaller than 0.0025, and wherein any two of the spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type of a target animal species of at least 30%.

The lighting device 100 also comprises a lighting-control unit 104 which is configured to control operation of the lighting unit by switching between selection of a respective one of the at least two different spectral power distributions Si and S2 of the emitted light with a flickering frequency f_F value that assumes a value between 0.5 and 500Hz, preferably a value between 2 and 10 Hz. In alternative lighting devices the flickering frequency varies between a plurality of flickering frequency values, all with the specified frequency range. The variation is controlled by a frequency variation algorithm, which, in a variant includes a random or a pseudo-random variation of either the switching time, the flickering frequency value or both. Figure 3 shows a particular operation state of the lighting device in which the light emitting unit 106 is emitting light with a spectral power distribution Si as indicated by the solid arrows, whereas light emitting unit 108, which is configured to emit light with a spectral power distribution S2, is currently not emitting light, as indicated by the discontinuous arrows.

The following examples and tables, show different alternatives for the spectral power distributions SI and S2, achieved by combining light emitted by a plurality of light emitting diodes, each configured to emit light having a respective LED-spectral power distribution. In particular, and as an example, the LED-spectral power distributions of the light emitting diodes have power peaks at 406 nm, or 460 nm, or 475 nm, or 530 nm, or 545 nm, or 588 nm, or 615 nm, or 625 nm, or 632 nm, or 665 nm. Thus, the lighting unit contains a plurality of LED which are divided into two groups, which are synchronously controlled by the lighting control unit so as to be sequentially and alternatively be turned on and off at the predetermined flickering frequency value. Advantageously, this predetermined flickering frequency value is a low frequency value between 2 and 10 Hz.

In the following, several non-limiting examples will be presented. Each example is characterized and explained based on two tables. The first of the two tables includes spectral information regarding two different settings, Si and S2, that correspond to two different spectral power distributions. The second of the two tables includes the corresponding tristimulus values in the LMS color space, denoted by "S", "M", and "L", for each spectral power distribution, also referred to as “setting”, as well as the respective difference. Correspondingly, and as an example, the tables include stimulus values for Rl-6, R7y, R7p, R8y and R8p rhabdomers of some insects. Additionally, the tables also include, for each seting Si and S2, a respective CRI value and its difference, a respective CIE 1976 L*, u*, v* u’ and v’ chromaticity coordinates as well as t their respective difference and a corresponding chromatic difference value Au , and a respective correlated color temperature value in Kelvin. The tables include relative peak spectral power amount of the respective LED light source, i.e., the relative peak height of each LED spectrum in the spectral power distribution. Example 1

Table 1.1 shows spectral information regarding two different setings, Si and S2.

The corresponding spectral power distributions for both setings are shown in

Fig. 4.

Table 1.2 shows the relevant colorimetry parameters associated to the settings of Table 1.1, as well as the response of said setings on different photoreceptor types.

In this particular example 1, there is a modulation depth or change in response on the R7y of almost 34%. However, there is no perceptible color difference for the human eye, as it can be deduced from the value of the chromatic difference. The difference in the CRI values in this particular example is 23.01.

Example 2.

Table 2.1 shows spectral information regarding the two different settings, Si and S2 of example 2.

The corresponding spectral power distributions for both settings are shown in

Fig. 5.

Table 2.2 shows the relevant colorimetry parameters associated to the settings of Table 2.1, as well as the response of said settings on different photoreceptor types.

In this particular example 2, there is a difference in R7y and R7p stimulation of 99% and 72% respectively. However, there is no perceptible color difference for the human eye, as it can be deduced from the value of the chromatic difference. The difference in the CRI values in this particular example is 0.15 and there is near constant color rending above 60. In this example, only the LEDs with the three shortest wavelengths have to be modulated by the lighting control unit, whereas the green and the red LEDs can remain constantly on under operation. Example 3.

Table 3.1 shows spectral information regarding the two different settings, Si and S2 of example 3.

Table 3.2 shows the relevant colorimetry parameters associated to the settings of Table 3.1, as well as the response of said settings on different photoreceptor types.

This particular example 3, which is similar to example 2, the lighting level of the 475 nm LED, radiating in a blue wavelength region, is also kept constant and does not need to be modulated. Should the 460 nm LED also be kept constant, this would result in a perceivable color difference between both settings.

Example 4.

Table 4.1 shows spectral information regarding the two different settings, Si and S2 of example 4.

Table 4.2 shows the relevant colorimetry parameters associated to the settings of Table 4.1, as well as the response of said settings on different photoreceptor types.

This particular example 4, is advantageously configured to generate a perceived flicker in the Rl-6 channel, which is the most sensitive channel for motion. Example 5.

Table 5.1 shows spectral information regarding the two different settings, Si and S2 of example 5.

The corresponding spectral power distributions for both settings are shown in Fig. 6.

Table 5.2 shows the relevant colorimetry parameters associated to the settings of Table 5.1, as well as the response of said settings on different photoreceptor types.

This particular example 5 is advantageously configured to prevent obtrusive or uncomfortable color changes in objects containing optical whiteners. In the example, both setings or spectral power distributions, contain a comparable amount of short-wavelength- radiation to activate optical whiteners and also have a color point below the black body line, or Planckian locus.

In alternative examples of the lighting device, light sources other than LED are used, as long as they are suitable to be operated at the flickering frequency, i.e. they have a suitable response time.

The use of the lighting device 100, or any of its alternatives, is particularly advantageous in application where insects or any other target animal species has to be repelled. Non-limiting examples include home and hospitality lighting, including outdoor bar and restaurant lighting, public lighting in parks, road and streets, retail and industry, particularly when related to food products, and any other application where hygiene plays an important role, such as in healthcare facilities.

Fig. 7 shows a flow diagram of an embodiment of a method 200 for operating a lighting device. The method 200 comprises, in a step 202, selecting and emiting light having one of at least two predetermined different spectral power distributions, each of the at least two predetermined different spectral power distributions having respective u’ and v’ chromaticity coordinates in a CIELUV color space, wherein a difference between the u’ and v’ chromaticity coordinates values of any two of the spectral power distributions is smaller than 0.05, and wherein any two of the spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type of a target animal species of at least 30%. The method also comprises, in a step 204, switching between at least two spectral power distributions of the emited light with a flickering frequency value assuming a value between 0.5 and 100Hz. In summary, the invention is directed to a lighting device that comprises a lighting unit configured to emit light having two predetermined different spectral power distributions having respective u’ and v’ chromaticity coordinates in a CIELUV color space and a difference between u’ and v’ chromaticity coordinates smaller than 0.05, and wherein any two of the spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type of a target animal species of at least 30%. It also comprises a lighting-control unit configured to control operation of the lighting unit by switching between the at least two spectral power distributions with a flickering frequency value. The lighting device thus causes a perceivable and uncomfortable flicker effect to the target animal species which is not perceivable by an average human eye.

Also it is particularly advantageous in regions and seasons in which insects or other animal species act as vector for human or livestock diseases.

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.

A single unit or device may fulfill the functions of several items recited in the claims. 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.

A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium, supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A lighting device (100), comprising: a lighting unit (102) configured to emit light having a controllable spectral power distribution, the spectral power distribution being selectable between at least two different predetermined spectral power distributions (Si, S2) having respective u’ and v’ chromaticity coordinates in a CIELUV color space, wherein a difference between u’ and v’ chromaticity coordinates of any two of the spectral power distributions of the lighting unit is smaller than 0.05, and wherein any two of the different predetermined spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type (R1-R8) of a target animal species of at least 30%; and a lighting-control unit (104) configured to control operation of the lighting unit by switching between selection of a respective one of the at least two predetermined different spectral power distributions with a flickering frequency (fp) value between 0.5 and 500 Hz.

2. The lighting device of claim 1, wherein the lighting control unit is configured to perform the switching with the flickering frequency value between 2 Hz and 10 Hz.

3. The lighting device of claim 1 or 2, wherein the at least two different predetermined spectral power distributions have a respective CRI value above 80 and wherein a difference between the CRI values of any two of the different predetermined spectral power distributions of the lighting unit is smaller than 5.

4. The lighting device of any one of the preceding claims, wherein the at least two spectral power distributions each have a correlated color temperature value between 2000 and 5000 K, and wherein a difference between the correlated color temperature value of any two of the predetermined different spectral power distributions of the lighting unit is smaller than 5%.

5. The lighting device of any one of the preceding claims, wherein a difference in luminous flux between any two of the predetermined different spectral power distributions of the lighting unit is smaller than 1%.

6. The lighting device of any one of the preceding claims, wherein the spectral power distributions have respective u’ and v’ chromaticity coordinates in a CIELUV color space, and wherein any two of the at least two predetermined different spectral power distributions have a difference in the u’ chromaticity coordinate of at most 0.0022 and a difference in the v’ chromaticity coordinate of at most 0.0011.

7. The lighting device of claim 6, wherein a respective color point of the predetermined different spectral power distributions lies, in the CIELUV color space, below a Planckian locus, also referred to as black body line, of the CIELUV color space.

8. The lighting device of any one of the preceding claims, wherein the lighting unit comprises a plurality of light emitting diodes, each configured to emit light having a respective LED-spectral power distribution, and wherein a respective combination (106, 108) of light emitting diodes is configured to emit light with only one of the at least two predetermined different spectral power distributions.

9. The lighting device of claim 8, wherein the LED-spectral power distributions of the light emitting diodes have power peaks at 406 nm, or 460 nm, or 475 nm, or 530 nm, or 545 nm, or 588 nm, or 615 nm, or 625 nm, or 632 nm, or 665 nm.

10. Use of a lighting device according to any one of the preceding claims, wherein the target animal species is an insect species, a rodent species or a bird species.

11. Method (200) for operating a lighting device, comprising selecting and emitting (202) light having one of at least two predetermined different spectral power distributions, each of the at least two predetermined different spectral power distributions having respective u’ and v’ chromaticity coordinates in a CIELUV color space, wherein a difference between the u’ and v’ chromaticity coordinates of any two of the spectral power distributions is smaller than 0.05, and wherein any two of the spectral power distributions of the lighting unit are configured to cause a difference in response of at least one photoreceptor type of a target animal species of at least 30%; and switching (204) between at least two spectral power distributions of the emitted light with a flickering frequency value between 0.5 and 100 Hz.

12. The method of claim 11, wherein the predetermined flickering frequency value is between 1 and 20 Hz.

13. Computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the method of claim 11 or 12.