Light melanopic activity indicator

Abstract

The invention provides a light indicator (100) for use in evaluating melanopsin active radiation in a flux of light, the light indicator (100) comprising a first light indicator element (110) comprising a first light reflective element (112) and a second light indicator element (120) comprising a second light reflective element (122), the light reflecting elements (112,122) having different wavelength dependencies of the spectral reflectivity, wherein the light reflecting elements (112,122) are selected to provide the same intensity of reflected light of two or more different types of light irradiating on the light indicator elements (110,120), wherein the two or more different types of light have different spectral power distributions in the visible wavelength range but having the same ratios of the melanopic flux and the luminous flux, wherein the ratio of the melanopic flux and the luminous flux of light is defined as $\begin{array}{cc}\mathrm{MEF}=1.22\frac{{.Math.}_{=380}^{780}\mathrm{SPD}\left(\right)m\left(\right)}{{.Math.}_{=380}^{780}\mathrm{SPD}\left(\right)V\left(\right)}& \left(\mathrm{Eq}.1\right)\end{array}$
wherein SPD() is the spectral power distribution of the light, m() is the melanopic sensitivity function, and the V() is the photopic sensitivity.

Claims

1. A light indicator for use in evaluating melanopsin active radiation of light, the light indicator comprising a first light indicator element comprising a first light reflective element and a second light indicator element comprising a second light reflective element, the light reflecting elements having different wavelength dependencies of the spectral reflectivity, wherein the light reflecting elements are selected to provide the same intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different spectral power distributions in the visible wavelength range but have the same ratios of the melanopic flux to the luminous flux, wherein the ratio of the melanopic flux to the luminous flux of light is defined as $\begin{array}{cc}\mathrm{MEF}=1.22\frac{{.Math.}_{=380}^{780}\mathrm{SPD}\left(\right)m\left(\right)}{{.Math.}_{=380}^{780}\mathrm{SPD}\left(\right)V\left(\right)}& \left(\mathrm{Eq}.1\right)\end{array}$ wherein SPD() is the spectral power distribution of the light, m() is the melanopic sensitivity function, and V() is the photopic sensitivity, and wherein the light reflecting elements are further selected to provide a different intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different ratios of the melanopic flux to the luminous flux.

2. The light indicator (100) according to claim 1, wherein the at least two light reflecting elements are selected to provide also the same color point of the reflected light of the two or more different types of light.

3. The light indicator according to claim 1, wherein the at least two light reflecting elements have different wavelength dependencies of the spectral reflectivity at least within the wavelength range of 380-550 nm.

4. The light indicator according to claim 1, wherein the at least two light reflecting elements have different wavelength dependencies of the spectral reflectivity at least within the wavelength ranges of 380-470 nm, 470-500 nm, and 500-550 nm.

5. The light indicator according to claim 1, wherein, the first light indicator element comprising a first sensing area, wherein the first light reflecting element being configured to reflect at least part of light illuminating the first sensing area having one or more wavelengths selected from the wavelength range of an absorption band of melanopsin in the visible wavelength range and configured to absorb at least part of light illuminating the first sensing area having one or more wavelengths in the visible wavelength range outside the wavelength range of the absorption band of melanopsin in the visible wavelength range; the second light indicator element comprising a second sensing area, wherein the second light reflecting element being configured to reflect at least part of light illuminating the second sensing area having one or more wavelengths selected from the wavelength range of an absorption band of melanopsin in the visible wavelength range and configured to absorb at least part of light illuminating the second sensing area having one or more wavelengths in the visible wavelength range outside the wavelength range of the absorption band of melanopsin in the visible wavelength range; wherein first light indicator element and the second light indicator element are chosen such that: (i) under illumination with first light with a predefined first spectral power distribution, including first spectral power in the wavelength range of an absorption band of melanopsin in the visible wavelength range, the intensities of the reflections of the first light from the first sensing area and the second sensing area are the same; (ii) under illumination with second light, including second spectral power in the wavelength range of an absorption band of melanopsin in the visible wavelength range, wherein the second spectral power is larger than the first spectral power, the intensity of the reflection of the second light from the first sensing area is larger than from the second sensing area; and (iii) under illumination with third light, including third spectral power in the wavelength range of an absorption band of melanopsin in the visible wavelength range, wherein the third spectral power is smaller than the first spectral power, the intensity of the reflection of the third light from the first sensing area is smaller than from the second sensing area.

6. The indicator according to claim 5, wherein (i) the first light reflecting element is (ia) configured to reflect at least part of light illuminating the first sensing area having one or more wavelengths selected from the wavelength range of 440-530 nm and (ib) configured to absorb at least part of light illuminating the first sensing area having one or more wavelengths in the visible wavelength range outside the wavelength range of 440-530 nm, (ii) the second light reflecting element is (iia) configured to reflect at least part of light illuminating the second sensing area having one or more wavelengths selected from the wavelength range of 440-530 nm and (iib) configured to absorb part of light illuminating the second sensing area having one or more wavelengths in the visible wavelength range outside the wavelength range of 440-530 nm.

7. The light indicator according to claim 5, wherein (i) a reflection of visible light at the first sensing area in the wavelength range of the absorption band of melanopsin is in average at least two times higher than in average the reflection at the other wavelengths in the visible wavelength range, and (ii) a reflection of visible light at the second sensing area in the wavelength ranges of 380-470 nm and 500-550 nm is in average at least two times higher than in average the reflection at the other wavelengths in the visible wavelength range.

8. The light indicator according to claim 1, wherein the first light reflecting element comprises a first pigment and wherein the second light reflecting element comprise a second pigment, wherein (i) the first light reflecting element comprises a light transmissive material, wherein the first pigment is embedded in the light transmissive material, and (ii) wherein the second light reflecting element comprises a light transmissive material, wherein the second pigment is embedded in the light transmissive material.

9. A kit of parts comprising: a light indicator for use in evaluating melanopsin active radiation of light, the light indicator comprising a first light indicator element comprising a first light reflective element and a second light indicator element comprising a second light reflective element, the light reflecting elements having different wavelength dependencies of the spectral reflectivity, wherein the light reflecting elements are selected to provide the same intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different spectral power distributions in the visible wavelength range but have the same ratios of the melanopic flux to the luminous flux, wherein the ratio of the melanopic flux to the luminous flux of light is defined as
MEF=1.22((=380){circumflex over ()}780SPD()m())/((=380){circumflex over ()}780SPD()V()) (Eq. 1) wherein SPD() is the spectral power distribution of the light, m() is the melanopic sensitivity function, and V() is the photopic sensitivity, and wherein the light reflecting elements are further selected to provide a different intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different ratios of the melanopic flux to the luminous flux; and reference information or a reference to such reference information which is available on one or more of the light indicator, a data carrier, and another tangible element, and wherein the reference information contains information allowing one or more of a qualitative analysis and a quantitative analysis of a ratio of the melanopic flux and the luminous flux of light on the light indicator elements, of the light indicator.

10. The kit of parts according to claim 9, wherein the reference information contains information instructing a user how to perform the one or more of the qualitative analysis and the quantitative analysis by using a camera, and wherein the other tangible element is selected from the group consisting of a manual of the light indicator, a package of the light indicator, a manual of a lighting device, and a package of a lighting device.

11. The kit of parts according to claim 9, wherein the tangible element is a portable device having a camera and wherein the reference information contains information instructing a user how to perform the one or more of the qualitative analysis and the quantitative analysis by using said camera.

12. A method of evaluating a melanopsin active radiation of light, using a light indicator, wherein the light indicator is for use in evaluating melanopsin active radiation of light, the light indicator comprising a first light indicator element comprising a first light reflective element and a second light indicator element comprising a second light reflective element, the light reflecting elements having different wavelength dependencies of the spectral reflectivity, wherein the light reflecting elements are selected to provide the same intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different spectral power distributions in the visible wavelength range but have the same ratios of the melanopic flux to the luminous flux, wherein the ratio of the melanopic flux to the luminous flux of light is defined as
MEF=1.22((=380){circumflex over ()}780SPD()m())/((=380){circumflex over ()}780SPD()V()) (Eq. 1) wherein SPD() is the spectral power distribution of the light, m() is the melanopic sensitivity function, and V() is the photopic sensitivity, and wherein the light reflecting elements are further selected to provide a different intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different ratios of the melanopic flux to the luminous flux, wherein the method comprises: illuminating the light indicator with light from a light source and evaluating on the basis of the intensities of light emanating from the first light indicator element and from the second light indicator element the ratio of the melanopic flux to the luminous flux of the light source.

13. The method according to claim 12, comprising evaluating with an optical sensor, wherein the optical sensor is an optical sensor of a portable device.

14. The method according to claim 13, wherein the optical sensor is an image capturing device and the method further comprising: taking an image of the light indicator when being illuminated by the light source, calculating the value of the melanopic DER from the intensities of light emanating from the first light indicator element (110) and the second light indicator element using the formula: $\begin{array}{cc}\mathrm{melanopic}\mathrm{DER}={k\left(\frac{m_1{R}_m+m_2{G}_m+m_3{B}_m}{p_1{R}_p+p_2{G}_p+p_3{B}_p}\right)}^n& \left(\mathrm{Eq}.9\right)\end{array}$ wherein: R.sub.m, G.sub.m, B.sub.m: mean R, G, B values for the first light reflective element, R.sub.p, G.sub.p, B.sub.p: mean R, G, B values for the second light reflective element, k, m.sub.1, m.sub.2, m.sub.3, p.sub.1, p.sub.2, p.sub.3, n: regression parameters.

15. A computer program product when running on a processor is capable of carrying out a method of evaluating a melanopsin active radiation of light, wherein the method comprises the steps of: taking an image of a light indicator when being illuminated with the light, wherein the light indicator is for use in evaluating melanopsin active radiation of light, the light indicator comprising a first light indicator element comprising a first light reflective element and a second light indicator element comprising a second light reflective element, the light reflecting elements having different wavelength dependencies of the spectral reflectivity, wherein the light reflecting elements are selected to provide the same intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different spectral power distributions in the visible wavelength range but have the same ratios of the melanopic flux to the luminous flux, wherein the ratio of the melanopic flux to the luminous flux of light is defined as
MEF=1.22((=380){circumflex over ()}780SPD()m())/((=380){circumflex over ()}780SPD()V()) (Eq. 1) wherein SPD() is the spectral power distribution of the light, m() is the melanopic sensitivity function, and V() is the photopic sensitivity, and wherein the light reflecting elements are further selected to provide a different intensity ratio of reflected light of two or more different types of light irradiating on the light indicator elements, wherein the two or more different types of light have different ratios of the melanopic flux to the luminous flux, calculating the value of the melanopic DER from the intensities of light emanating from the first light indicator element and the second light indicator element using the formula: $\begin{array}{cc}\mathrm{melanopic}\mathrm{DER}={k\left(\frac{m_1{R}_m+m_2{G}_m+m_3{B}_m}{p_1{R}_p+p_2{G}_p+p_3{B}_p}\right)}^n& \left(\mathrm{Eq}.9\right)\end{array}$ wherein: R.sub.m, G.sub.m, B.sub.m: mean R, G, B values for the first light reflective element, R.sub.p, G.sub.p, B.sub.p: mean R, G, B values for the second light reflective element, k, m.sub.1, m.sub.2, m.sub.3, p.sub.1, p.sub.2, p.sub.3, n: regression parameters.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the invention will now be described, by way of example only, with reference to the accompanying schematic drawings in which corresponding reference symbols indicate corresponding parts, and in which:

(2) FIG. 1 schematically depicts an example of execution, showing color renderings of two light reflecting patches in center-surround (top) and side-by-side (bottom) configuration. In the center-surround configuration, the central patch is Pantone 3272C. In the side-by-side configuration it is the left patch. The other patch (surround/right) has a theoretical reflectance spectrum resulting from colorimetric calculations. From left to right, the color renderings of the patches were obtained for an equal energy light spectrum (left: I and IV) having MEF=1, a light spectrum having MEF>1 (middle: II and V) and a light spectrum having MEF<1(right: III and VII); the MEF values of the light that is received on the theoretical patches are indicated and are 1, 5.1 and 0.47, respectively;

(3) FIG. 2a shows the spectral reflectance R1 of a Pantone 3272C color patch and R2 a theoretical patch resulting from colorimetric calculation as explained herebelow; on the x-axis the wavelength (nm) is indicated and on the y-axis the reflection;

(4) FIG. 2b shows normalized spectral power distributions of the illuminants used in the colorimetric calculations underlying the visualizations shown in FIG. 1. Equal energy EE is used as the reference illuminant, having MEF=1. The high MEF illuminant L1 and low MEF illuminant L2 have MEF=5.1 and MEF=0.47, respectively (these spectra can e.g. be obtained by combining different LEDs; on the x-axis the wavelength (nm) is indicated and on the y-axis the normalized spectral power distribution (in a.u.);

(5) FIG. 3 schematically depict some aspects;

(6) FIGS. 4a-4b also schematically depict some aspects and embodiments;

(7) FIG. 5a shows the normalized absorption spectrum of the melanopsin pigment, further corrected for the transmission of the lens and interocular media of the human eye; and

(8) FIG. 5b shows a normalized reflection spectrum of copper acetate.

(9) FIG. 6 shows a light indicator according to the invention.

(10) FIG. 7 shows the spectral reflectance R1 of a Sikkens K2.40.70 color patch; on the x-axis the wavelength (nm) is indicated and on the y-axis the reflection R.

(11) FIG. 8 shows the predicted melanopic DER (P on y-axis) versus the actual melanopic DER (A on x-axis) of various light spectra for mobile phone A (top) and mobile phone C (bottom).

(12) FIG. 9 shows a method of evaluating a melanopsin active radiation of light according to the invention.

(13) The schematic drawings are not necessarily to scale.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(14) Amongst others, the invention provides e.g. a visual indicator, consisting of multiple patches. The current invention proposes a system (e.g. in the form of two light reflecting color patches) that visually (or by use of a smartphone app) provides an estimate of the MEF. FIG. 1 schematically illustrates an embodiment of the principle, with two light reflecting patches in a center-surround (I, II, III) or side-by-side (IV, V, VI) configuration. One of the patches has a reflectance spectrum that resembles the absorbance spectrum of melanopsin. A physical example of such a reflectance spectrum is e.g. Pantone 3272C. The other patch is, may be designed to have an optimized reflectance spectrum (see further also below).

(15) Hence, FIG. 1 shows on the top row and the bottom row two embodiments of possible light indicators, each under three different lighting conditions, with a lighting condition wherein the MEF value (see also below) is in both cases the same, i.e. the value is 1; with a lighting condition wherein the MEF value is 5.1; and with a lighting condition wherein the MEF value is 0.47. As very schematically shown, the reflected intensities are the same for the two different patches of the two embodiments on the left. The reflected intensities are different for the two other types of light, especially such that the same patch that is brighter at a higher MEF value than a predefined MEF value, is also less bright when light is provided with a lower MEF value than the predefined MEF value.

(16) Hence, FIG. 1 schematically depicts two embodiments, and working examples, of a light indicator 100. The light indicator 100 can thus be used in evaluating a melanopsin active radiation in a flux of light. The light indicator 100 may comprise a first light indicator element 110 comprising a first light reflective element 112 and a second light indicator element 120 comprising a second light reflective element 122. The light reflecting elements 112,122 have different wavelength dependencies of the spectral reflectivity (see also below). At least two of the at least two light reflecting elements 112,122 are selected to provide the same intensity of reflected light of two or more different types of light having different spectral power distributions in the visible wavelength range but having the same spectral powers within the wavelength range of the absorption band of melanopsin.

(17) More in detail, FIG. 1 also schematically depict embodiments of the light indicator 100, especially for use in evaluating a melanopsin active radiation in a flux of light on an indicator sensing area 101 of the light indicator 100, wherein the light indicator 100 comprises a first light indicator element 110 comprising a first sensing area 111. The first light indicator element 110 comprises a first light reflecting element 112 configured to reflect at least part of light illuminating the first sensing area 111 having one or more wavelengths selected from the wavelength range of an absorption band of melanopsin in the visible wavelength range and configured to absorb at least part of light illuminating the first sensing area 111 having one or more wavelengths in the visible wavelength range outside the wavelength range of the absorption band of melanopsin in the visible wavelength range. The light indicator 100 further comprises a second light indicator element 120 comprising a second sensing area 121. The second light indicator element 120 comprises a second light reflecting element 122 configured to reflect at least part of light illuminating the second sensing area 121 having one or more wavelengths selected from the wavelength range of an absorption band of melanopsin in the visible wavelength range and configured to absorb at least part of light illuminating the second sensing area 121 having one or more wavelengths in the visible wavelength range outside the wavelength range of the absorption band of melanopsin in the visible wavelength range. As schematically depicted, the first sensing area 111 and the second sensing area 121 are configured adjacent to each other. Especially, the first light indicator element 110 and the second light indicator element 120 are chosen such that under illumination with first light with a predefined first spectral power distribution, including first spectral power in the wavelength range of an absorption band of melanopsin in the visible wavelength range, the intensities of the reflections of the first light from the first sensing area 111 and the second sensing area 121 are the same. Further, the first light indicator element 110 and the second light indicator element 120 are especially chosen such that under illumination with second light, including second spectral power in the wavelength range of an absorption band of melanopsin in the visible wavelength range, wherein the second spectral power is larger than the first spectral power, the intensity of the reflection of the second light from the first sensing area 111 is larger than from the second sensing area 121. Further, the first light indicator element 110 and the second light indicator element 120 are especially chosen such that under illumination with third light, including optionally third spectral power in the wavelength range of an absorption band of melanopsin in the visible wavelength range, wherein the optional third spectral power is smaller than the first spectral power, the intensity of the reflection of the third light from the first sensing area 111 is smaller than from the second sensing area 121.

(18) FIG. 1 also schematically depicts an embodiment wherein e.g. the first light reflecting element 112 comprises a first pigment 1212 and wherein the second light reflecting element 122 also comprises a (second) pigment 1222. Especially, the second pigment is different from the first pigment 1212, though in some embodiments they may also be the same.

(19) As shown in FIG. 1, in embodiments the at least two light reflecting elements 112,122 are selected to provide also the same color point of the reflected light of the two or more different types of light. This may especially be the case when the absorption of the pigments is relatively high outside the melatonin absorption band wavelength range, and the pigments essentially only have different reflection spectra within this melatonin absorption band wavelength range.

(20) Hence, amongst others the invention may provide a visual indicator, consisting of e.g. two light reflecting patches, where the reflectance spectrum of the first patch resembles the absorbance spectrum of melanopsin. The second patch may especially have a reflection spectrum, such that (i) under a reference illuminant the two patches are visually indistinguishable, (ii) the first patch may appear lighter under an illuminant having a higher MEF than the MEF of the reference illuminant, and (iii) the first patch may appear darker under an illuminant having a lower MEF than the MEF of the reference illuminant. Note that this may in embodiments also be the other way around. In the instructions, the user can be instructed how to interpret the visual indicator. Hence, instructions may be provided that allows the user (after visual inspection of the patches) to get an indication of the potential melanopic activity of the illumination being tested. For example: when the central patch appears lighter than the surround this means that the light has a higher melanopic activity than daylight). Alternatively, a smartphone based app may signal the melanopic activity by analysis of an image of the patches captured by the smartphone camera. See further also below.

(21) Hence, in embodiments the invention may provide two patches. Overall dimensions of the visual indicator may be no larger than a few cm.sup.2. The reflectance curve of one patch, see FIG. 5b, may resemble the melanopsin pigment absorbance (illustrated in FIG. 5a) as closely as possible. For instance, the spectral reflectance of copper acetate is virtually identical to the absorbance of the melanopsin pigment, making it an ideal candidate to use in the present invention. The color Pantone 3272C (e.g. printed on a support, such as paper) may be a commercially available alternative. The measured reflectance of this Pantone color (R1 in FIG. 2a) was used in the colorimetric calculations to optimize the theoretical reflectance of the second patch, underlying the visualizations shown in FIG. 1. In FIGS. 2a and 2b the reflectance spectra of the two patches and the spectral power distributions of the illuminants used for creating FIG. 1 are shown (FIG. 1 is a schematically depiction of a color picture).

(22) As shown in FIG. 2a, the two light reflecting elements have different wavelength dependencies of the spectral reflectivity at least within the wavelength range of 380-550 nm. The light reflecting elements 112,122 (see FIG. 1) have different wavelength dependencies of the spectral reflectivity at least within the wavelength ranges of 380-470 nm, 470-500 nm, and 500-550 nm.

(23) Hence, the first light reflecting element is especially configured to reflect at least part of light illuminating the first sensing area having one or more wavelengths selected from the wavelength range of 440-530 nm. Further, the first light reflecting element may be configured to absorb at least part of light illuminating the first sensing area having one or more wavelengths in the visible wavelength range outside the wavelength range of 440-530 nm.

(24) The second light reflecting element may be (optionally) configured to reflect at least part of light illuminating the second sensing area having one or more wavelengths selected from the wavelength range of 440-530 nm. Yet further, the second light reflecting element may be configured to absorb at least part of light illuminating the second sensing area 121 having one or more wavelengths in the visible wavelength range outside the wavelength range of 440-530 nm.

(25) Therefore, in embodiments the reflection of visible light at the first sensing area 111 (see FIG. 1) in the wavelength range of the absorption band of melanopsin may in average at least two times higher than in average the reflection at the other wavelengths in the visible wavelength range (see FIG. 2a), and a reflection of visible light at the second sensing area 121 (see FIG. 1) in the wavelength ranges of 380-470 nm and 500-550 nm may in average be at least two times higher than in average the reflection at the other wavelengths in the visible wavelength range (see FIG. 2a).

(26) Hence, in embodiments the first light reflecting element may have a reflection spectrum having a reflection band with a maximum having a wavelength selected from the wavelength range of 470-500 nm and having a full width half maximum selected from the range of 10-112 nm; the reflection in the reflection spectrum in the visible wavelength range outside the wavelength range of 440-530 nm may in average be at least two times smaller than the reflection at the maximum of the reflection band. Further, the second light reflecting element may have a reflection spectrum having reflections band with maxima having wavelengths selected from the wavelength ranges of 380-470 nm and 500-550, respectively, and may have a full width half maximum selected from the range of at least 10 nm. Further, the reflection in the reflection spectrum in the visible wavelength range outside these wavelength ranges may in average be at least two times smaller than the reflection at the largest maximum of the reflection bands.

(27) FIG. 2b, as indicated above, shows two different spectral power distributions which provide with the reflection spectra of FIG. 2a essentially the same spectral distribution of the reflection on the different patches 111 and 121 (herein also indicated as patches).

(28) Here, by way of example the spectral distribution of the reflection R2 and the spectral distribution of the two light sources are based on colorimetric calculations. In these calculations, the theoretical reflectance spectrum is optimized such that the two patches have exactly the same color under a chosen reference illuminant, and are maximally different under illumination having a higher and a lower MEF than the MEF of the reference illumination, respectively. The associated visual effect is that under high MEF illumination the Pantone 3272C patch appears lighter than the other patch, while under low MEF illumination the Pantone patch appears darker than the other patch.

(29) FIG. 2a also shows that in the range of about 530 to about 700 nm the difference between the reflectivities is equal to or less than about 25% pp. In the range of 380-440 nm the difference is larger than 25% pp. However, in average the reflectivities of the light reflecting elements are within a range of 20% (or 25% pp) of the total reflectivity, wherein no reflectivity is 0% and wherein total reflectivity is 100% (note that the drawing displays 1 instead of 100%).

(30) FIG. 3 schematically depicts with embodiment I an embodiment wherein the first light reflecting element 112 comprises a light transmissive material 125, wherein the first pigment 1212 is embedded in the light transmissive material 125, and wherein the second light reflecting element 122 comprises a light transmissive material 125, wherein the second pigment 1222 is embedded in the light transmissive material 125. These light reflecting elements 112 and 122 may be embedded in a support. In such embodiments, the light indicator receives light at the top side and the observer (or sensor) also observes (or senses) from the top side. In yet an alternative embodiment, shown with embodiment II, the light indicator may be used in transmissive mode. Whereas in embodiment I the evaluation may be done from the top side (in this drawing), in embodiment II this may be from the bottom side, i.e. the light indicator 100 is configured between the source and the observer (or sensor).

(31) Alternative embodiments may be applied wherein e.g. one or more of the first light indicator element 110 and the second light indicator element 120 comprise one or more of an interference filter, optical rejection filter, and a dielectric mirror. By using such optics, also spectral distributions can be tuned to desired wavelength ranges. For instance, two or more optical rejection filters may be applied in combination with a pigment. Such filters may be essentially transparent over the entire visible wavelength range, except for one or more discrete wavelength bands.

(32) FIGS. 4a-4b schematically depict embodiments of a kit of parts 1000 comprising such light indicator 100 and reference information 1400 on a carrier or a reference to such reference information 1400 on a carrier. The reference information 1400 may be (i) available on one or more of the light indicator 100, a data carrier 1410, see also FIG. 4a, and another tangible element 1420, see FIG. 4b, and/or (ii) which is accessible on the internet via a reference to an internet site, wherein the reference is available on one or more of the light indicator 100, a data carrier 1410 see also FIG. 4a as possible variant, and another tangible element 1420, and wherein the reference information 1400 contains information allowing one or more of a qualitative analysis and a quantitative analysis of a melanopsin active radiation in a flux of light on a first sensing area 111. Reference 1410 in FIG. 4a may e.g. be a USB stick with reference information 1400 or with a link to such reference information. Reference 1420 in FIG. 4b may e.g. be a package of a lamp. By using the light indicator 100 on the package, and the reference information 1400 on the package, one may evaluate the melanopsin active radiation flux at a location in a space where the lamp is configured.

(33) The light indicator 100 can be used in a method of evaluating a melanopsin active radiation in a flux of light, wherein the method comprises illuminating the light indicator 100 with light from a light source and evaluating on the basis of the (relative) intensities of light emanating from the first light indicator element 110 and from the second light indicator element 120 the flux of the light of the light source. The flux may be evaluated as being essentially the same, larger, or smaller than a flux of a reference light source at an identical distance from the light source of which the light is shed on the light indicator. Sensing may be done with the human eye. However, alternatively, the method may comprise evaluating with an optical sensor. The optical sensor may in embodiments be an optical sensor of a portable device, such as a smartphone.

(34) Alternatively, the reference information 1400 is avaible on or accessible by a portable device, for example a mobile phone, having a camera. The reference information 1400 contains information instructing a user how to perform the one or more of the qualitative analysis and the quantitative analysis by using said camera. The reference information may be avaible via a computer program product that is installed on or accessible by the portable device. The computer program product may comprise software that determines the value of the melanopic DER applying equation 9 based on data obtained from an image taken by the camera of the portable device of the light indicator 1000 when being illuminated by a light source.

(35) FIG. 5a shows the normalized absorption spectrum of the melanopsin first pigment in the human eye, corrected for the transmission of the lens and the interocular media, for a representative age and macular first pigment density;

(36) FIG. 5b shows a normalized reflection spectrum of copper acetate. As can be derived from the Figure, the similarity to the absorption spectrum of the melanopsin first pigment is very good. Hence, this first pigment may very well be applied in a comparative test as described herein.

(37) As indicated above, the current invention proposesamongst othersa system (e.g. in the form of a color checker chart) that provides an estimation of the relative amount of short wavelength energy (460-490 nm) in a given spectrum. The chosen wavelength range corresponds to the peak sensitivity of ipRGCs.

(38) However, the current invention is not limited to use with a color checker chart but could also be applied using a smart device, e.g. a smartphone or tablet. Here, the camera of the smart device acts as a sensor and provides an estimation of the amount of short wavelength energy in a given spectrum.

(39) The effectiveness of a given light spectrum in suppressing melatonin production can be expressed in terms of the melanopsin effectiveness factor (MEF). This factor is calculated by multiplying the spectral power distribution of the light emitted by a lighting system (SPD()) with the melanopic sensitivity function (mW) divided by the product of SPD (and the photopic sensitivity (VW), normalized by the areas under the curves of m() and V(), see equation 1 (and see also e.g. WO2016146688, which is herein incorporated by reference, especially FIG. 1 from this reference and the accompanying information):

(40) $\begin{array}{cc}\mathrm{MEF}=\left(\frac{{}_{}V\left(\right)d}{{}_{}m\left(\right)d}\right).Math.\left(\frac{{}_{}\mathrm{SPD}\left(\right)m\left(\right)d}{{}_{}\mathrm{SPD}\left(\right)V\left(\right)d}\right)& \left(\mathrm{Eq}.7\right)\end{array}$
This can be simplified to

(41) $\begin{array}{cc}\mathrm{MEF}=1.22\left(\frac{{}_{}\mathrm{SPD}\left(\right)m\left(\right)d}{{}_{}\mathrm{SPD}\left(\right)V\left(\right)d}\right)& \left(\mathrm{Eq}.8\right)\end{array}$
as

(42) $\begin{array}{cc}\mathrm{MEF}=1.22\frac{{.Math.}_{=380}^{780}\mathrm{SPD}\left(\right)m\left(\right)}{{.Math.}_{=380}^{780}\mathrm{SPD}\left(\right)V\left(\right)}& \left(\mathrm{Eq}.1\right)\end{array}$

(43) Hence, the above indicated summations are over the visible range of 380-780 nm. By definition, the MEF for an equi-energy light source MEFEE equals 1. Especially, an equi-energy light source has SPD(lambda)=constant (for instance 1) for all (visible) wavelengths.

(44) In an alternative embodiment, the value of the melanopic DER (daylight efficacy ratio) of particular light is calculated from an image taken from a light indicator that is illuminated with that particular light. FIG. 6 shows a light indicator 600 with a first light indicator element 610 comprising a first light reflective element 612, and a second light indicator element 620 comprising a second light reflective element 622. The first light reflective element 612 has a spectral reflectance that is substantially similar to or resembles s.sub.mel(), representing the action spectrum of ipRGCs due to their photopigment melanopsin. The second light reflective element 622 has a spectral reflectance that is substantially similar to or resembles V(), the photopic luminous efficiency function. In this embodiment, the first light reflective element 612 has a spectral reflectance of a Pantone 3272C color patch as shown in FIG. 2A. The normalized spectral reflectance of the second light reflective element 622 is shown in FIG. 7 and is that of Sikkens K2.40.70. The value of the melanopic DER is calculated using equation 9:

(45) $\begin{array}{cc}\mathrm{melanopic}\mathrm{DER}={k\left(\frac{m_1{R}_m+m_2{G}_m+m_3{B}_m}{p_1{R}_p+p_2{G}_p+p_3{B}_p}\right)}^n& \left(\mathrm{Eq}.9\right)\end{array}$
wherein: R.sub.m, G.sub.m, B.sub.m: mean R, G, B values for the first light reflective element, R.sub.p, G.sub.p, B.sub.p: mean R, G, B values for the second light reflective element, k, m.sub.1, m.sub.2, m.sub.3, p.sub.1, p.sub.2, p.sub.3, n: regression parameters, to be estimated.

(46) Using images in RAW or JPG format, for example, the values of the regression parameters were determined by using values of the melanopic DER calculated from the spectral power distribution of the light used to illuminate the light indicator 600 using equation 5. Images may be taken by using the camera of a mobile phone, for example. The table below shows the values of the regression parameters of equation 9 for three different mobile phones A, B and C. The table shows the estimated parameter values, percentage explained variance (adjusted R.sup.2), the mean absolute error (MAE) and mean percentage error (MPE) for the three different mobile phones, for the processing based on RAW images. For the regression based on the analysis of the RAW images, relatively high values for the adjusted R.sup.2 are obtained, resulting in a mean error of 2.6% for mobile phone A, a mean error of 2.3% for mobile phone B, and a mean error of 4.1% for mobile phone C.

(47) TABLE-US-00001 Mobile phone A Mobile phone B Mobile phone C m.sub.1 1.16 1.55 3.60 m.sub.2 0.77 0.88 0.70 m.sub.3 1.85 0.95 1.26 p.sub.1 0.93 1.31 1.88 p.sub.2 0.85 0.95 0.88 p.sub.3 1.06 0.62 1.15 k 1.52 1.12 1.74 n 2.75 2.49 3.31 adj R.sup.2 0.99 0.99 0.96 MAE 0.025 0.023 0.044 MPE 2.6 2.3 4.1

(48) FIG. 8 shows the predicted melanopic DER versus the actual melanopic DER of various light spectra for mobile phone A (top) and mobile phone C (bottom).

(49) FIG. 9 shows a method for evaluating a melanopsin active radiation light, by determining the melanopic DER value of said light, using a portable device, such as a mobile phone or any other device having a camera. In a first step 901, a light indicator 600 is provided. In a next step 902, the light indicator 600 is illuminated with the light from which the melanopsin active radiation is being evaluated. In a next step 903, an image is taken from the light indicator 600 using the camera of the portable device. In a next step 904, the value of the melanopic DER is calculated by the mobile phone using equation 9 and estimated values for the regression parameters. This calculation may be performed by using software installed on the portable device. The values of the regression parameters of equation 9 may be estimated by using a set of different light spectra for illuminating a light indicator 600, taking images of the light indicator 600 when being illuminated by various different light spectra using the camera of the mobile phone, and determining the melanopic DER of the various light spectra based on their respective spectral power distribution, as explained above.

(50) Below, a table for the melanopic and photopic human eye sensitivity functions is provided:

(51) TABLE-US-00002 Photopic Melanopic 380 0.000039 0.000918 381 4.28264E05 0.001033 382 4.69146E05 0.001163 383 5.15896E05 0.00131 384 5.71764E05 0.001477 385 0.000064 0.001667 386 7.23442E05 0.001883 387 8.22122E05 0.002129 388 9.35082E05 0.00241 389 0.000106136 0.002729 390 0.00012 0.003094 391 0.000134984 0.003512 392 0.000151492 0.003989 393 0.000170208 0.004536 394 0.000191816 0.005162 395 0.000217 0.00588 396 0.000246907 0.006705 397 0.00028124 0.007651 398 0.00031852 0.008739 399 0.000357267 0.009989 400 0.000396 0.011428 401 0.000433715 0.013104 402 0.000473024 0.015038 403 0.000517876 0.017268 404 0.000572219 0.019841 405 0.00064 0.022811 406 0.00072456 0.02624 407 0.0008255 0.0302 408 0.00094116 0.034773 409 0.00106988 0.040055 410 0.00121 0.046155 411 0.001362091 0.051431 412 0.001530752 0.057325 413 0.001720368 0.06391 414 0.001935323 0.071264 415 0.00218 0.079477 416 0.0024548 0.088645 417 0.002764 0.098878 418 0.0031178 0.110297 419 0.0035264 0.123034 420 0.004 0.137237 421 0.00454624 0.146047 422 0.00515932 0.155409 423 0.00582928 0.16535 424 0.00654616 0.175902 425 0.0073 0.187096 426 0.008086507 0.198964 427 0.00890872 0.21154 428 0.00976768 0.224858 429 0.01066443 0.238954 430 0.0116 0.253865 431 0.01257317 0.266176 432 0.01358272 0.279 433 0.01462968 0.29235 434 0.01571509 0.306239 435 0.01684 0.320679 436 0.01800736 0.335684 437 0.01921448 0.351265 438 0.02045392 0.367435 439 0.02171824 0.384205 440 0.023 0.401587 441 0.02429461 0.415459 442 0.02561024 0.429639 443 0.02695857 0.444126 444 0.02835125 0.458915 445 0.0298 0.474003 446 0.03131083 0.489382 447 0.03288368 0.505051 448 0.03452112 0.520999 449 0.03622571 0.537223 450 0.038 0.553715 451 0.03984667 0.56863 452 0.041768 0.583694 453 0.043766 0.598893 454 0.04584267 0.614217 455 0.048 0.629654 456 0.05024368 0.645191 457 0.05257304 0.660812 458 0.05498056 0.676507 459 0.05745872 0.692256 460 0.06 0.708048 461 0.06260197 0.723532 462 0.06527752 0.739008 463 0.06804208 0.75446 464 0.07091109 0.769869 465 0.0739 0.785216 466 0.077016 0.800481 467 0.0802664 0.815643 468 0.0836668 0.830679 469 0.0872328 0.845571 470 0.09098 0.86029 471 0.09491755 0.872405 472 0.09904584 0.88423 473 0.1033674 0.89574 474 0.1078846 0.906916 475 0.1126 0.917734 476 0.117532 0.928169 477 0.1226744 0.938197 478 0.1279928 0.947794 479 0.1334528 0.956938 480 0.13902 0.965604 481 0.1446764 0.971753 482 0.1504693 0.977347 483 0.1564619 0.98237 484 0.1627177 0.9868 485 0.1693 0.990622 486 0.1762431 0.993814 487 0.1835581 0.996364 488 0.1912735 0.998254 489 0.199418 0.999471 490 0.20802 1 491 0.2171199 0.999832 492 0.2267345 0.998957 493 0.2368571 0.997369 494 0.2474812 0.995059 495 0.2586 0.992021 496 0.2701849 0.988257 497 0.2822939 0.983766 498 0.2950505 0.978548 499 0.308578 0.972608 500 0.323 0.965951 501 0.3384021 0.958588 502 0.3546858 0.950526 503 0.3716986 0.941781 504 0.3892875 0.932367 505 0.4073 0.9223 506 0.4256299 0.911597 507 0.4443096 0.900281 508 0.4633944 0.888376 509 0.4829395 0.875903 510 0.503 0.862887 511 0.5235693 0.848186 512 0.544512 0.833038 513 0.56569 0.817476 514 0.5869653 0.80153 515 0.6082 0.785234 516 0.6293456 0.768617 517 0.6503068 0.751716 518 0.6708752 0.734563 519 0.6908424 0.71719 520 0.71 0.699628 521 0.7281852 0.681754 522 0.7454636 0.663768 523 0.7619694 0.645696 524 0.7778368 0.62757 525 0.7932 0.609422 526 0.8081104 0.59128 527 0.8224962 0.573171 528 0.8363068 0.555121 529 0.8494916 0.537159 530 0.862 0.519309 531 0.8738108 0.501594 532 0.8849624 0.484037 533 0.8954936 0.466662 534 0.9054432 0.449487 535 0.9148501 0.432534 536 0.9237348 0.41582 537 0.9320924 0.399364 538 0.9399226 0.383183 539 0.9472252 0.367292 540 0.954 0.351707 541 0.9602561 0.336519 542 0.9660074 0.321656 543 0.9712606 0.30713 544 0.9760225 0.292953 545 0.9803 0.279135 546 0.9840924 0.265686 547 0.9874182 0.252613 548 0.9903128 0.239924 549 0.9928116 0.227626 550 0.9949501 0.215722 551 0.9967108 0.204171 552 0.9980983 0.193028 553 0.999112 0.182295 554 0.9997482 0.171971 555 1 0.162056 556 0.9998567 0.152549 557 0.9993046 0.143447 558 0.9983255 0.134745 559 0.9968987 0.12644 560 0.995 0.118526 561 0.9926005 0.110943 562 0.9897426 0.103744 563 0.9864444 0.096917 564 0.9827241 0.090455 565 0.9786 0.084346 566 0.9740837 0.078579 567 0.9691712 0.073143 568 0.9638568 0.068026 569 0.9581349 0.063217 570 0.952 0.058701 571 0.9454504 0.054443 572 0.9384992 0.050457 573 0.9311628 0.046732 574 0.9234576 0.043253 575 0.9154 0.040009 576 0.9070064 0.036986 577 0.8982772 0.034174 578 0.8892048 0.031558 579 0.8797816 0.029129 580 0.87 0.026875 581 0.8598613 0.024784 582 0.849392 0.022848 583 0.838622 0.021055 584 0.8275813 0.019396 585 0.8163 0.017862 586 0.8047947 0.016446 587 0.793082 0.015137 588 0.781192 0.01393 589 0.7691547 0.012817 590 0.757 0.01179 591 0.7447541 0.010839 592 0.7324224 0.009964 593 0.7200036 0.009158 594 0.7074965 0.008416 595 0.6949 0.007734 596 0.6822192 0.007107 597 0.6694716 0.006531 598 0.6566744 0.006001 599 0.6438448 0.005514 600 0.631 0.005067 601 0.6181555 0.004655 602 0.6053144 0.004277 603 0.5924756 0.003929 604 0.5796379 0.00361 605 0.5668 0.003318 606 0.5539611 0.003049 607 0.5411372 0.002802 608 0.5283528 0.002576 609 0.5156323 0.002368 610 0.503 0.002177 611 0.4904688 0.002002 612 0.4780304 0.001841 613 0.4656776 0.001693 614 0.4534032 0.001558 615 0.4412 0.001433 616 0.42908 0.001319 617 0.417036 0.001214 618 0.405032 0.001117 619 0.393032 0.001029 620 0.381 0.000947 621 0.3689184 0.000872 622 0.3568272 0.000803 623 0.3447768 0.00074 624 0.3328176 0.000681 625 0.321 0.000628 626 0.3093381 0.000578 627 0.2978504 0.000533 628 0.2865936 0.000491 629 0.2756245 0.000453 630 0.265 0.000418 631 0.2547632 0.000386 632 0.2448896 0.000356 633 0.2353344 0.000328 634 0.2260528 0.000303 635 0.217 0.00028 636 0.2081616 0.000258 637 0.1995488 0.000239 638 0.1911552 0.000221 639 0.1829744 0.000204 640 0.175 0.000188 641 0.1672235 0.000174 642 0.1596464 0.000161 643 0.1522776 0.000149 644 0.1451259 0.000138 645 0.1382 0.000127 646 0.1315003 0.000118 647 0.1250248 0.000109 648 0.1187792 0.000101 649 0.1127691 0.000093 650 0.107 0.000087 651 0.1014762 0.00008 652 0.09618864 0.000074 653 0.09112296 0.000069 654 0.08626485 0.000064 655 0.0816 0.000059 656 0.07712064 0.000055 657 0.07282552 0.000051 658 0.06871008 0.000047 659 0.06476976 0.000044 660 0.061 0.000041 661 0.05739621 0.000038 662 0.05395504 0.000035 663 0.05067376 0.000033 664 0.04754965 0.00003 665 0.04458 0.000028 666 0.04175872 0.000026 667 0.03908496 0.000024 668 0.03656384 0.000023 669 0.03420048 0.000021 670 0.032 0.00002 671 0.02996261 0.000018 672 0.02807664 0.000017 673 0.02632936 0.000016 674 0.02470805 0.000015 675 0.0232 0.000014 676 0.02180077 0.000013 677 0.02050112 0.000012 678 0.01928108 0.000011 679 0.01812069 0.00001 680 0.017 0.00001 681 0.01590379 0.000009 682 0.01483718 0.000008 683 0.01381068 0.000008 684 0.01283478 0.000007 685 0.01192 0.000007 686 0.01106831 0.000006 687 0.01027339 0.000006 688 0.009533311 0.000005 689 0.008846157 0.000005 690 0.00821 0.000005 691 0.007623781 0.000004 692 0.007085424 0.000004 693 0.006591476 0.000004 694 0.006138485 0.000004 695 0.005723 0.000003 696 0.005343059 0.000003 697 0.004995796 0.000003 698 0.004676404 0.000003 699 0.004380075 0.000003 700 0.004102 0.000002 701 0.003838453 0.000002 702 0.003589099 0.000002 703 0.003354219 0.000002 704 0.003134093 0.000002 705 0.002929 0.000002 706 0.002738139 0.000002 707 0.002559876 0.000002 708 0.002393244 0.000001 709 0.002237275 0.000001 710 0.002091 0.000001 711 0.001953587 0.000001 712 0.00182458 0.000001 713 0.00170358 0.000001 714 0.001590187 0.000001 715 0.001484 0.000001 716 0.001384496 0.000001 717 0.001291268 0.000001 718 0.001204092 0.000001 719 0.001122744 0.000001 720 0.001047 0.000001 721 0.00097659 0.000001 722 0.000911109 0.000001 723 0.000850133 0.000001 724 0.000793238 0.000001 725 0.00074 0 726 0.000690083 0 727 0.00064331 0 728 0.000599496 0 729 0.000558455 0 730 0.00052 0 731 0.000483914 0 732 0.000450053 0 733 0.000418345 0 734 0.000388718 0 735 0.0003611 0 736 0.000335384 0 737 0.00031144 0 738 0.000289166 0 739 0.000268454 0 740 0.0002492 0 741 0.000231302 0 742 0.000214686 0 743 0.000199288 0 744 0.000185048 0 745 0.0001719 0 746 0.000159778 0 747 0.000148604 0 748 0.000138302 0 749 0.000128793 0 750 0.00012 0 751 0.00011186 0 752 0.000104322 0 753 9.73356E05 0 754 9.08459E05 0 755 0.0000848 0 756 7.91467E05 0 757 0.000073858 0 758 0.000068916 0 759 6.43027E05 0 760 0.00006 0 761 5.59819E05 0 762 5.22256E05 0 763 4.87184E05 0 764 4.54475E05 0 765 0.0000424 0 766 3.9561E05 0 767 3.69151E05 0 768 3.44487E05 0 769 3.21482E05 0 770 0.00003 0 771 2.79913E05 0 772 2.61136E05 0 773 2.43602E05 0 774 2.27246E05 0 775 0.0000212 0 776 1.97789E05 0 777 1.84529E05 0 778 1.72169E05 0 779 1.60646E05 0 780 0.00001499 0

(52) The term plurality refers to two or more.

(53) The term substantially herein, such as in substantially all light or in substantially consists, will be understood by the person skilled in the art. The term substantially may also include embodiments with entirely, completely, all, etc. Hence, in embodiments the adjective substantially may also be removed. Where applicable, the term substantially may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. The term comprise includes also embodiments wherein the term comprises means consists of. The term and/or especially relates to one or more of the items mentioned before and after and/or. For instance, a phrase item 1 and/or item 2 and similar phrases may relate to one or more of item 1 and item 2. The term comprising may in an embodiment refer to consisting of but may in another embodiment also refer to containing at least the defined species and optionally one or more other species.

(54) Furthermore, the terms first, second, third and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequential or chronological order. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

(55) The devices herein are amongst others described during operation. As will be clear to the person skilled in the art, the invention is not limited to methods of operation or devices in operation.

(56) It should be noted that the above-mentioned embodiments illustrate rather than limit the invention, and that those skilled in the art will be able to design many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. Use of the verb to comprise and its conjugations does not exclude the presence of elements or steps other than those stated in a claim. Unless the context clearly requires otherwise, throughout the description and the claims, the words comprise, comprising, and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of including, but not limited to. The article a or an preceding an element does not exclude the presence of a plurality of such elements. The invention may be implemented by means of hardware comprising several distinct elements, and by means of a suitably programmed computer. In the device claim enumerating several means, several of these means may be embodied by one and the same item of hardware. 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.

(57) The invention further applies to a device comprising one or more of the characterizing features described in the description and/or shown in the attached drawings. The invention further pertains to a method or process comprising one or more of the characterizing features described in the description and/or shown in the attached drawings.

(58) The various aspects discussed in this patent can be combined in order to provide additional advantages. Further, the person skilled in the art will understand that embodiments can be combined, and that also more than two embodiments can be combined. Furthermore, some of the features can form the basis for one or more divisional applications.