Lighting apparatus

Abstract

Lighting apparatus 100, 200 comprising a plurality of light sources each arranged to generate a luminous flux in a predetermined spectral band, the apparatus comprising a first light source 102, 202 for generating a first luminous flux 102, 212, 510, 610, 710, 760, 810, 840 having a first peak intensity at a first wavelength in a range of 420nm to 450nm, a second light source 104, 204 for generating a second luminous flux 112, 114 520, 620, 720, 770, 820, 850 having a second peak intensity at a second wavelength in a range of 512 to 600nm, wherein the lighting apparatus 100, 200 does not emit a substantial luminous flux at wavelengths equal to or greater than 600nm. The apparatus may have a third light source 106, 206 for generating a third luminous flux 216 having a third peak intensity at a third wavelength of 530nm to 600nm. The second wavelength may be in the range of 512nm to 570nm. Less than 25% of the luminous flux emitted may have wavelengths equal to or greater than 600 nanometres. The apparatus may combine the luminous flux of each light source so the combined emitted luminous flux has a wavelength less than 550nm. The apparatus may be installed in the interior of a vehicle.

Description

TECHNICAL FIELD The present disclosure relates to a lighting apparatus. Aspects of the invention relate to a lighting apparatus for providing an efficient lighting function. In particular, but not exclusively, the disclosure relates to a lighting apparatus and a vehicle. BACKGROUND It is known to provide a lighting apparatus for providing illumination. Such a lighting apparatus may comprise one or more light sources, whereby each light source emits a light (‘luminous flux’) having a wavelength distribution determined by the design of each light source. A colour of the total luminous flux emitted by the lighting apparatus may be in accordance with a combination of luminous flux from each light source having a peak intensity, or by appropriate control of the wavelength distribution from one light source. One consideration for lighting apparatus is power consumption, with it generally being desired to reduce a power consumption of lighting apparatus. However, another consideration is providing a lighting apparatus facilitating visual perception such as the recognition of objects. Often reducing power consumption leads to lower visual perception i.e. an increased time to recognise an object. It is an aim of the present invention to address one or more of the disadvantages associated with the prior art. SUMMARY OF THE INVENTION Aspects and embodiments of the invention provide a lighting apparatus and a vehicle as claimed in the appended claims. According to an aspect of the present invention there is provided a lighting apparatus, the apparatus comprising a plurality of light sources each arranged to generate a luminous flux in a predetermined spectral band, the apparatus comprising a first light source for generating a first luminous flux having a first peak intensity at a first wavelength in a range of 420nm to 450nm, a second light source for generating a second luminous flux having a second peak intensity at a second wavelength less than 600nm. The lighting apparatus may not emit a substantial luminous flux at wavelengths equal to or greater than 600nm. Advantageously an increased proportion of photons from the lighting apparatus are emitted at wavelengths to which the human eye is most sensitive. Advantageously it has been appreciated that a coloured or non-white luminous flux may be useful. According to an aspect of the present invention there is provided a lighting apparatus, the apparatus comprising a plurality of light sources each arranged to generate a luminous flux in a predetermined spectral band, the apparatus comprising a first light source for generating a first luminous flux having a first peak intensity at a first wavelength in a range of 420nm to 450nm, a second light source for generating a second luminous flux having a second peak intensity at a second wavelength in a range of 512 to 600nm, wherein the lighting apparatus does not emit a substantial luminous flux at wavelengths equal to or greater than 600nm. Advantageously an increased proportion of photons from the lighting apparatus are emitted at wavelengths to which the human eye is most sensitive. Advantageously it has been appreciated that a coloured or non-white luminous flux may be useful. The lighting apparatus may comprise a third light source for generating a third luminous flux having a third peak intensity at a third wavelength in a range of 530 to 600nm. The second wavelength is optionally in a range of 512 to 570nm. Advantageously the combined luminous flux may be adapted to sensitive wavelengths of the human eye. The lighting apparatus of any preceding claim, wherein the lighting apparatus is arranged to emit a luminous flux, wherein less than 25% of the luminous flux has wavelengths equal to or greater than 600nm. Advantageously reduced luminous flux is output at wavelengths to which the human eye is less sensitive. The lighting apparatus is arranged to combine the luminous flux of each light source, such that a combined luminous flux emitted by the lighting apparatus has a wavelength of less than 550nm. Advantageously the combined luminous flux is output at wavelengths to which the human eye is most sensitive. The combined luminous flux emitted by the lighting apparatus optionally has a mean wavelength of less than 550nm. Advantageously the combined luminous flux is output at wavelengths to which the human eye is most sensitive. The combined luminous flux emitted by the lighting apparatus may have a predetermined wavelength distribution. Advantageously the combined luminous flux has a predetermined wavelength distribution. Each of the first and second light sources may provide a predetermined contribution to the combined luminous flux. Advantageously the combined luminous flux has a predetermined contribution from the first and second light sources. The lighting apparatus may be arranged to combine the luminous flux of each light source, such that any combined luminous flux emitted by the lighting apparatus has an RGB value comprising G and B values of at least 200. G and B values of 200 and above are indicative of a relatively large proportion of green and blue in the total luminous flux, to which the human eye is sensitive. The G and B values are optionally at least 220. Optionally the G value is at least 240. The G and B values are optionally around 255 and 220, respectively. Advantageously a significant proportion of the luminous flux is at wavelengths to which the human eye is particularly sensitive, thereby ensuring consumed power is used efficiently. The lighting apparatus may consist of two or three light sources. The lighting apparatus may consist of two light sources. Advantageously a light source with two light sources has a simple construction whilst producing an effective luminous flux. Advantageously a light source with three light sources may provide a luminous flux adapted for sensitive wavelengths of the human eye. The first wavelength is optionally in a range 440nm to 450nm. Advantageously the human eye is sensitive to wavelengths in the range 440nm to 450nm. The second wavelength is optionally in a range 512 to 570nm. Advantageously the human eye is sensitive to wavelengths in the range 512 to 570nm. The second wavelength may be in a range 540 to 545nm. The third wavelength may be in a range 555 to 580nm. Advantageously the human eye is sensitive to wavelengths in the range 555 to 580nm. The lighting apparatus may not comprise a light source arranged to generate a luminous flux having a peak intensity at a peak wavelength equal to or greater than 600nm. Advantageously the light source generates limited luminous flux at wavelengths to which the human eye is less sensitive. Advantageously it has been recognised that it is not necessary to generate a luminous flux having a significant component at wavelengths equal to or greater than 600nm, such as for controlling a colour of the combined luminous flux. Each light source may be arranged to generate a respective luminous flux in the predetermined spectral band having a generally gaussian distribution. Advantageously the generally gaussian distribution of each luminous flux allows for control of the wavelength of the combined luminous flux. The generally gaussian distribution may have a Full-Width at Half-Maximum of equal to or less than 60nm. Advantageously the respective luminous flux has a relatively precise wavelength distribution. Each light source may be arranged to generate a respective luminous flux in a predetermined spectral band of equal to or less than 60nm width. Advantageously the respective luminous flux has a confined wavelength distribution. According to an aspect of the present invention there is provided a vehicle comprising the lighting apparatus described above. The lighting apparatus may be used internally within the vehicle. Advantageously a power consumption of the lighting apparatus is effectively used. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and / or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and / or features of any embodiment can be combined in anyway and / or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and / or incorporate any feature of any other claim although not originally claimed in that manner. BRIEF DESCRIPTION OF THE DRAWINGS One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a schematic view of a lighting apparatus according to an embodiment of the invention; Figure 2 is a schematic view of a lighting apparatus according to another embodiment of the invention; Figure 3 shows a lighting apparatus according to an embodiment of the invention; Figure 4 illustrates spectral sensitivity of cones of the human eye; Figure 5 illustrates a wavelength distribution of a lighting apparatus according to an embodiment of the invention; Figure 6 illustrates a wavelength distribution of a lighting apparatus according to an embodiment of the invention; Figures 7(a) &(b) illustrate wavelength distributions of lighting apparatus according to embodiments of the invention in relation to the spectral sensitivity of cones of the human eye; Figures 8(a) &(b) illustrates wavelength distributions of lighting apparatus according to further embodiments of the invention; Figure 9 illustrates test results under varying illumination luminance; Figure 10 illustrates a wavelength distribution of a white light source; and Figure 11 shows a vehicle in accordance with an embodiment of the invention. DETAILED DESCRIPTION Figure 1 shows an example embodiment of the present invention, being a lighting apparatus 100 comprising a light source 102. The light source 102 converts an electrical power 122 into a luminous flux 112. The luminous flux 112 has a respective wavelength distribution. That is, a luminous flux 112 emitted by the light source 102 is in a predetermined wavelength or spectral band. In the embodiment of Figure 1 there is more than one light source 102, where each additional light source 104 also converts electrical power 124 into a respective luminous flux 114. Each of the plurality of light sources 102, 104, emits the luminous flux 112, 114 having a respective wavelength distribution. In some embodiments, each of the plurality of light sources 102,104 emits a luminous flux of a different wavelength distribution, such as having a peak intensity at different wavelengths. Irrespective of the number of light sources, the total electrical power is a sum of the electrical power 122,124, consumed by each of the respective light sources 102, 104. Also, a total luminous flux is a sum of each luminous flux 112, 114 generated by each respective light source 102,104. In embodiments of the invention, a combined luminous flux output by the lighting apparatus 100 having a wavelength equal to or less than 600nm is substantially confined to spectrally sensitive region(s) of at least one of the S-cone of the human eye, the M-cone of the human eye, or the L-cone of the human eye. In this way, the luminous flux output by the lighting apparatus is directed to one or more spectrally sensitive wavelength regions of the human eye. In the embodiment of Figure 1 the lighting apparatus 100 comprises two light sources 102, 104 i.e. a first light source 102 and a second light source 104 which, in use, emit a first luminous flux 112 and a second luminous flux 114. Figure 2 shows another example embodiment of the present invention, being a lighting apparatus 200 comprising a plurality of light sources 202, 204, 206. Each light source 202, 204, 206 converts electrical power 222, 224, 226 into a respective luminous flux 212, 214, 216. Each of the plurality of light sources 202, 204, 206 emits the luminous flux 212, 214, 216 having a respective wavelength distribution. A total luminous flux is a sum of each luminous flux 212, 214, 216 generated by each respective light source 202, 204, 206. The light sources 102,104, 202, 204, 206 may be light-emitting diode (LED) light sources, laser light sources, gas-discharge light sources, neon, xenon, or sodium-based light sources, although other light-emitting technologies may be used. Figure 3 shows an embodiment of the invention comprising a lighting apparatus 100, 200 in connection with Figure 1 or 2 as described above, used within an illumination lamp 300 which may further comprise one or both of a lens 302 and a reflector 304. The illumination lamp 300 may be used to illuminate a region, such as within a vehicle i.e. at least a portion of a vehicle’s interior, ora portion of an area within a building or an outside area such as a street light, floodlight or similar. The illumination lamp 300 may be used with a vehicle, such as a wheeled vehicle (including bicycles) in particular, although embodiments may be useful with other vehicles such as watercraft and aircraft, for example. Embodiments of the invention in the form of a lighting apparatus 100 comprising two light sources 102, 104 will now be described with reference to Figure 1 as an example. Historically, lighting apparatus have been developed such that, for a given electrical power, the emitted luminous flux is maximised, or conversely, for a required luminous flux the electrical power is minimised. However, embodiments of the present invention seek to optimise the usefulness to a viewer of the wavelength distribution emitted by the lighting apparatus. In particular, in embodiments of the invention, it is sought to emit an increased proportion of photons from the lighting apparatus at wavelengths to which the human eye is most sensitive, as will be explained. The present invention takes a broader, more holistic, view of the efficiency of such lighting apparatuses by recognising that the ultimate efficiency requirement for a lighting system is to provide the greatest sensory response of the human vision system for the least electrical power, rather than simply emitting more light for the least electrical power. In particular, the present inventors have reframed the problem of efficient lighting to include the sensory response of the human vision system. Therefore, the benefit of embodiments of the invention arises due to the selection of wavelength(s) of emitted luminous flux not according to colour requirements but rather corresponding to the discrete peak spectral sensitivities of the human eye. A combined luminous flux output by the lighting apparatus 100 having a wavelength equal to or less than 600nm is substantially confined to spectrally sensitive region(s) of at least one of the S-cone of the human eye, the M-cone of the human eye, or the L-cone of the human eye. In this way, the luminous flux output by the lighting apparatus is directed to one or more spectrally sensitive wavelength regions of the human eye. Furthermore, the lighting apparatus 100 does not emit a substantial luminous flux at wavelengths equal to or greater than 600nm. That is, the lighting apparatus does not emit a substantial luminous flux in ‘red’ wavelengths. The lighting apparatus does not comprise a light source which is arranged to generate a luminous flux having a peak intensity at a peak wavelength equal to or greater than 600nm. In some embodiments the lighting apparatus is arranged to generate 95% of its luminous flux between 400 and 600nm. That is, in some embodiments up to 5% of the luminous flux may be outside of the range 400 and 600nm. Up to 5% of the luminous flux may be above 600nm, or more particularly in some embodiments up to 2.5% of the luminous flux above 600nm. In some embodiments up to 2.5% of the luminous flux may be below 400nm. Figure 4 shows an example of the spectral sensitivity of the S-cone, M-cone and L-cone of the human eye. These data are available in published literature such as ‘The spectral sensitivities of the middle- and long-wavelength-sensitive cones derived from measurements in observers of known genotype’ by Andrew Stockman and Lindsay T. Sharpe and published in Vision Research vol 40, 2000, pp1711-1737. In Figure 4 the peak spectral sensitivity of each cone is labelled as 445nm (S), 540nm (M) and 565nm (L) although it will be understood by those skilled in the art that there is some variation in these sensitivities within the human population. It should be understood that these data account for the optical properties of the ocular structures such as the cornea, lens, aqueous humour and vitreous body. Embodiments of the present invention seek to align a wavelength distribution of emitted luminous flux with the peak spectral sensitivities of one or more of the cones. Figures 5-7 illustrate example wavelength distributions of the lighting apparatus 100. The first light source 102 emits the first luminous flux 112, 510 having a peak intensity at, in the example, around 450nm in the example of Figure 5. The second light source 104 emits the second luminous flux 114, 520 having a peak intensity at, in the example, around 527nm in the example of Figure 5. Whilst the first luminous flux 112, 510 has a peak intensity at around 450nm, it will be appreciated that the peak intensity may not necessarily be at this wavelength and may be in the range 420 to 480 nm or 440 to 450 nm whilst still generally corresponding to the peak spectral sensitivity of the S cone of the human eye, which is illustrated at 445nm in Figure 4. The first peak intensity 112, 510 may particularly be in a range of 420 to 450nm or442nm to 473nm. The range 442nm to 473nm, defines the band to which the S cone of the human eye is most sensitive. Beyond this band the S cone of the human eye responds with less than 25% of the reaction to the same illumination intensity. Whilst the second luminous flux 114, 520 has a peak intensity at around 527nm it will be appreciated that the peak intensity may not necessarily be at this wavelength and may be in the range 512 to 600 nm whilst still generally corresponding to the peak spectral sensitivity of one of the M or L cone of the human eye, such as at one of 540 or 565nm as shown in Figure 4. The range 512 to 600nm corresponds to at least an upper 25% response to the luminous flux stimulus of the M and L cones combined (recognising that the M and L curves overlap). The upper 25% response wavelength range of the M cone is 512 to 570nm and the L cone is 530 to 600nm. The second peak intensity 114, 520 may be in the range of 512 to 600nm or 512 to 570nm, or 530 to 600nm such as a range 540 to 545nm. The present inventors have appreciated that by maximising the radiant flux falling within the spectrally sensitive regions of the S-, M-, and L-cones of the human eye to that falling outside, the usefulness of energy consumed by the light source can be improved. Figures 6 &7 illustrate further example wavelength distributions of the example lighting apparatus 100. Referring to Figure 6, the first light source 102 emits the first luminous flux 112, 610 having a peak intensity at, in the example, around 452nm. The second light source 104 emits the second luminous flux 114, 620 having a peak intensity at, in the example, around 529nm. Figure 7 illustrates wavelength distributions for two example lighting apparatus according to embodiments of the invention in Figures 7(a) and (b) respectively. Referring to Figure 7(a) the first light source 102 emits the first luminous flux 112, 710 having a peak intensity at, in the example, around 467nm. The second light source 104 emits the second luminous flux 114, 720 having a peak intensity at, in the example, around 555nm. Figure 7(a) also illustrates the spectral sensitives of the S 730, M 740 and L 750 cones of the human eye. It can be appreciated that the first luminous flux 112, 710 is generally aligned with the spectral sensitivity of the S cone 730. However, the second luminous flux 114, 720 at around 555nm lies generally between the peak spectral sensitivities of the M and L cones the human eye. As can be appreciated, the spectral sensitivities of the M and L cones form a substantial or major portion overlap. Therefore, the second luminous flux 114, 720 may generally correspond to both M and L cones by being in the range 512 to 600 nm which represents the overlapping upper 25% sensitivity range of both the M and L cones. In the examples of Figure 7(a) the second luminous flux 114, 720 has a peak intensity at 555nm. It will be appreciated that in some practical embodiments, the peak intensity of a luminous flux may not always precisely correspond with the peak sensitivity of a cone of the human eye whilst still being within one or more of the aforementioned wavelength ranges. As illustrated in Figure 7(b), in other embodiments, the first light source 102 emits the first luminous flux 112, 760 having a peak intensity at, in the example, around 450nm which improves a correspondence with the S-cone of the human eye. The second light source 104 emits the second luminous flux 114, 770 having a peak intensity at, in the example, around 555nm. In the embodiment shown in Figure 2 comprising three light sources 202, 204, 206, the first light source 202 emits the first luminous flux 212 having a peak intensity in the range 442 to 473 nm such as around 445 or 450nm. The first luminous flux 212 therefore corresponds to the peak spectral sensitivity of the S cone of the human eye. The second and third light sources together emit luminous fluxes which generally correspond to the peak spectral sensitivities of the M and L cones of the human eye. The second and third luminous fluxes 214, 216 having peak intensities in the range 512 to 600 nm, in the range of 512 to 570nm or 530 to 600nm such a range 555 to 580nm. Figures 8(a) &(b) illustrate example wavelength distributions of lighting apparatus 200 having three light sources 202, 204, 206. In the examples of Figures 8(a) and 8(b) the first light source 202 emits the first luminous flux 810, 840 having a peak intensity at, in the example, around 445nm. The second light source 204 emits the second luminous flux 820, 850 having a peak intensity at, in the example, around 540nm. The third light source 204 emits the second luminous flux 830, 860 having a peak intensity at, in the example, around 565nm. The peak intensities of the three light sources 202, 204, 206 correspond to the peak sensitives of the S, M and L cones, respectively, of the human eye. It will be appreciated that with the range of wavelengths 420 to 450 nm generally corresponding to blue or indigo light, and with the range of wavelengths 512 to 590 nm generally corresponding to green and yellow, a mixture of luminous fluxes in these wavelengths ranges does not result in a white light. Especially since the lighting apparatus 100, 200 does not emit a substantial luminous flux at wavelengths equal to or greater than 600nm i.e. in the red wavelength range. Red is understood to be wavelengths of light between 620nm and 750nm, with wavelengths in the range 600 to less than 620nm being referred to as reddish orange, both herein referred to as ‘red’. A total luminous flux emitted by the lighting apparatus 100,200 according to an embodiment of the invention has a colour corresponding to an RGB value comprising G and B values of at least 200. It will be understood that RGB values represent colours with values in the range 0-255. Therefore the total luminous flux of a lighting apparatus 100, 200 according to an embodiment of the invention has green (G) and blue (B) values of at least 200 i.e. each in the range 200-255, indicative of a relatively large proportion of green and blue in the total luminous flux. In some embodiments, the G and B values are at least 220 and in some embodiments the G value is at least 240. The G and B values may in some embodiments be around 255 and 220 respectively. In one embodiment, the total luminous flux has a colour corresponding to RGB values of R=155, G=255 and B=220, with it being appreciated that this is an example. A close Pantone colour is 333c. As can be appreciated from Figure 5, in the example the first luminous flux 510 has a larger intensity than the second luminous flux 520. Similarly, in Figure 8(b), the first luminous flux 840 has a larger intensity than the second and third luminous fluxes 850, 860. Advantageously an intensity of wavelengths emitted around 555nm, or above 520nm i.e. in the range 530-580nm is relatively lower than most other wavelengths emitted in the examples of Figures 5 -7 to provide a balanced colour of luminous flux i.e. closer to white light, than for example a perceived green luminous flux. That is, if the emitted luminous flux at around 555nm was equal in intensity to that at around 450nm, the eye would perceive a greater green colour as the M and L cones of the eye overlap in the region of 555nm. However, it will be appreciated that this is not limiting. The relative intensities of the first and second luminous fluxes 510, 520, or the first, second and third luminous fluxes may be in any ratio or may be equal. Similarly, where there are three luminous fluxes, the intensities may be in any ratio and embodiments of the present invention are not limited in this respect. In some embodiments, each light source 102,104,202,204,206 is arranged to generate a respective luminous flux in its respective spectral band having a generally gaussian distribution. The generally gaussian distribution may have a Full-Width at Half-Maximum (FWHM) of equal to or less than 60nm. It will be appreciated that for some types of light source, particularly lasers, the FWHM may be substantially less than 60nm e.g., less than 40 or 20nm. It can be appreciated that the distributions of the luminous fluxes in Figure 8 are relatively narrow e.g. less than 20nm FWHM. It has been surprisingly discovered that, despite the non-white chromaticity of the total luminous flux, it is beneficial with respect to a light source emitting a generally white luminous flux in terms of a response time for the human eye to recognise objects. Tests were conducted with a subject being asked to recognise objects displayed on a display device and to, in response, press a button indicating the displayed object. The displayed object may be one of a plurality of symbols, with a keypad comprising corresponding labelled keys such that the subject is directed to press a key corresponding to the displayed symbol. The tests were conducted under varying lighting conditions, such as white light and lighting comprised of selected illumination wavelengths or wavelength ranges and luminance. An experiment was conducted to compare subject’s ability to recognise objects in the presence of white light illumination and an illumination spectrum as illustrated in Figure 5 with varying luminance levels. A computer system recorded a time of displaying an image of an object and receipt of a signal corresponding to a button press indicative of the object being recognised. Such a test may be referred to as a visual acuity test. During testing, various symbols of various sizes are displayed at varying illumination intensity or luminance. For a set luminance, the symbols are made progressively smaller until not a single one of the eight symbols in that size category were correctly identified by the subject. All symbols smaller than this were presumed incorrect without being exhaustively tested. The size of the symbol is then increased until all eight of the symbols within a size category were correctly identified. All symbols larger than this are presumed correct without exhaustive testing. All the size categories below the 100% correct and 100% incorrect are exhaustively tested. The number of correct symbols out of a predetermined number such as 120 is the score of the test subject. The test is repeated at five illumination intensity levels for each light spectrum tested to establish a trend in the data. Testing is conducted for both white light and wavelength distributions as illustrated above in Figures 5-7. Figure 9 illustrates an average variance in response time for a subject under varying illumination luminance. Reference number 910 is a curve fitted to experimental data points for white light illumination; 920 is a curve fitted to experimental data points for illumination with the spectra illustrated in Figure 5 and reference 930 illustrates a difference between 910 and 920. As can be appreciated, for all luminance values, the subject experiences a negative variance (is quicker to recognise an object) compared to white light of the same luminance. Therefore, it can be appreciated that illumination from a lighting apparatus according to an embodiment of the present invention surprisingly improves a speed of object recognition when compared to white light illumination. Figure 10 illustrates a wavelength distribution 1010 or spectra of a white light source used in the experiment described above. As indicated in Figure 9 the wavelength distribution 1010 comprises a broad spectrum of wavelengths in the region of 400 to 700nm. It will be appreciated that the white light source may emit a relatively small amount of light outside of the range 400 to 700nm which is not illustrated. As can be appreciated, the wavelength distribution includes a substantial contribution from wavelengths of red light i.e., above 600nm, leading to the white light nature of the illumination. Figure 11 illustrates a vehicle 1100 according to an embodiment of the present invention. The vehicle 1100 comprises a lighting apparatus 100, 200, 300 according to an embodiment of the invention as described above. The lighting apparatus 100, 200, 300 may be installed in an interior of the vehicle 1100 to provide interior lighting for persons seated within the vehicle 1100. It will be appreciated that various changes and modifications can be made to the present invention without departing from the scope of the present application.

Claims

1. A lighting apparatus, the apparatus comprising a plurality of light sources each arranged to generate a luminous flux in a predetermined spectral band, the apparatus comprising:a first light source for generating a first luminous flux having a first peak intensity at a first wavelength in a range of 420nm to 450nm;a second light source for generating a second luminous flux having a second peak intensity at a second wavelength in a range of 512 to 600nm;wherein the lighting apparatus does not emit a substantial luminous flux at wavelengths equal to or greater than 600nm.

2. The lighting apparatus of claim 1, comprising:a third light source for generating a third luminous flux having a third peak intensity at a third wavelength in a range of 530 to 600nm;wherein the second wavelength is in a range of 512 to 570nm.

3. The lighting apparatus of any preceding claim, wherein the lighting apparatus is arranged to emit a luminous flux, wherein less than 25% of the luminous flux has wavelengths equal to or greater than 600nm.

4. The lighting apparatus of any preceding claim, wherein the lighting apparatus is arranged to combine the luminous flux of each light source, such that a combined luminous flux emitted by the lighting apparatus has a wavelength of less than 550nm.

5. The lighting apparatus of any preceding claim wherein the lighting apparatus is arranged to combine the luminous flux of each light source, such that any combined luminous flux emitted by the lighting apparatus has an RGB value comprising G and B values of at least 200.

6. The lighting apparatus of claim 5, wherein the G and B values are at least 220; optionally the G value is at least 240.

7. The lighting apparatus of any preceding claim, consisting of two or three light sources.

8. The lighting apparatus of any preceding claim, wherein the first wavelength is in a range 440nm to 450nm.

9. The lighting apparatus of any preceding claim, wherein the second wavelength is in a range 512 to 570nm.

10. The lighting apparatus of claim 2 or any claim dependent thereon, wherein the second wavelength is in a range 540 to 545nm and the third wavelength is in a range 555 to 580nm.

11. The lighting apparatus of any preceding claim, wherein the lighting apparatus does not comprise a light source arranged to generate a luminous flux having a peak intensity at a peak wavelength equal to or greater than 600nm.

12. The lighting apparatus according to any preceding claim, wherein each light source is arranged to generate a respective luminous flux in the predetermined spectral band having a generally gaussian distribution.

13. The lighting apparatus according to claim 12, wherein the generally gaussian distribution has a Full-Width at Half-Maximum of equal to or less than 60nm.

14. The lighting apparatus according to any of claims 1 to 11, wherein each light source is arranged to generate a respective luminous flux in a predetermined spectral band of equal to or less than 60nm width.

15. A vehicle comprising the lighting apparatus of any of claims 1 to 14.12

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