GB2613785A

GB2613785A - Lighting apparatus for a vehicle

Info

Publication number: GB2613785A
Application number: GB2118036.9A
Authority: GB
Inventors: Louis Onley Ben; Widdowson Paul
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2021-12-14
Filing date: 2021-12-14
Publication date: 2023-06-21
Also published as: GB202118036D0

Abstract

Lighting apparatus 100 for a vehicle 500 comprising a predetermined spectral band, the apparatus 100 comprising a first light source 102 for generating a first luminous flux 122 having a first peak intensity at a first wavelength corresponding to a peak spectral sensitivity of any one of the S-cone, M-cone or L-cone of the human eye, a second light source 104 for generating a second luminous flux 114 having a second peak intensity at a second wavelength, wherein the lighting apparatus is arranged to combine the first and second luminous fluxes such that a combined luminous flux output by the lighting apparatus has a generally white chromaticity. The apparatus may comprise a third light source for generating a third luminous flux having a third peak intensity at a third wavelength corresponding to another one of S-cone, M-cone or L-cone of the human eye, the second peak intensity being 600-700nm. The apparatus may comprise a fourth light source for generating a luminous flux having a fourth peak intensity at a wavelength corresponding to the peak spectral sensitivity of the L-cone of the human eye. The apparatus may be used as a headlamp for a vehicle.

Description

LIGHTING APPARATUS FOR A VEHICLE

TECHNICAL FIELD

The present disclosure relates to a lighting apparatus. Aspects of the invention relate to a lighting apparatus for a vehicle and a vehicle. In particular, but not exclusively, the disclosure relates to a lighting apparatus for providing an efficient lighting function for a vehicle.

BACKGROUND

It is known to provide a lighting apparatus for a vehicle for illuminating regions proximal to the vehicle, such as in a travelling direction of the vehicle, and/or for signalling to other road users.

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. For example, 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. The required colour of the luminous flux is typically determined either by current legislation and/or according to a manufacturer's selection, which may include consideration of a brand preference. Such current legislation and manufacturer's brand preferences are historically defined at least partially according to subjective criteria such as the perceived colour or whiteness of the light, or the ability conferred for rendering colours of objects illuminated by the light, or simply the perceived quality of light and intended brand image.

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, a driving-beam headlamp, a passing-beam headlamp, a cornering lamp, a reversing lamp, registration plate lamp, a lighting system for a vehicle and a vehicle as claimed in the appended claims.

According to an aspect of the present invention there is provided a lighting apparatus comprising at least one light source 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 corresponding to a peak spectral sensitivity of any one of the S-cone of the human eye, or the M-cone of the human eye, or the L-cone of the human eye. Advantageously the lighting apparatus provides the luminous flux with increased efficiency through the sensitivity of the human eye to the generated luminous flux.

In some embodiments, the lighting apparatus comprises a second light source for generating a second luminous flux having a second peak intensity at a second wavelength. Optionally the lighting apparatus is arranged to combine the first and second luminous fluxes such that a combined luminous flux output by the lighting apparatus has a predetermined chromaticity.

According to another aspect of the present invention there is provided a lighting apparatus for a vehicle, 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 corresponding to a peak spectral sensitivity of any one of the S-cone of the human eye, or the M-cone of the human eye, or the L-cone of the human eye, a second light source for generating a second luminous flux having a second peak intensity at a second wavelength, wherein the lighting apparatus is arranged to combine the first and second luminous fluxes such that a combined luminous flux output by the lighting apparatus has a generally white chromaticity. Advantageously the white chromaticity allows the lighting apparatus to be useful with a vehicle and the correspondence of the peak intensity to the peak spectral sensitivity of one of the cones of the human eye provides improved efficiency. Advantageously the second luminous flux causes the first luminous flux to have the white chromaticity.

The lighting apparatus may comprise a third light source for generating a third luminous flux having a third peak intensity at a third wavelength corresponding to a peak spectral sensitivity of another one of: the S-cone of the human eye, or the M-cone of the human eye, or the L-cone of the human eye, wherein the second peak intensity is in the range of 600nm to 700nm Advantageously the third luminous flux provides additional luminous flux corresponding to the peak spectral sensitivity of another one of the cones of the human eye, thereby efficiently providing increased lighting power.

Optionally the first wavelength corresponds to the peak spectral sensitivity of the S-cone of the human eye. Advantageously the first luminous flux corresponds to the S-cone and allows for generation of the white chromaticity with the second luminous flux of a greater wavelength.

The third wavelength may correspond to the peak spectral sensitivity of the M-cone of the human eye. Advantageously the first luminous flux corresponds to the M-cone.

The apparatus may comprise a fourth light source for generating a fourth luminous flux having a fourth peak intensity at a fourth wavelength corresponding to the peak spectral sensitivity of the [-cone of the human eye. Advantageously the apparatus provides luminous flux corresponding to each of the S-, M-and [-cones of the human eye.

The third wavelength may be within a spectral waveband bounded by the peak spectral sensitivity of the M-cone of the human eye and the peak spectral sensitivity of the [-cone of the human eye. Advantageously the third luminous flux may lie between the peak sensitives of the M-and [-cones.

The first wavelength optionally corresponds to the peak spectral sensitivity of the S-cone of the human eye, and the second wavelength is in the range of 550nm to 600nm. Advantageously the white chromaticity is produced by the combination of the luminous fluxes.

The combined luminous flux output by the lighting apparatus having a wavelength equal to or less than 600nm is optionally substantially confined to a spectral sensitive region of at least one of: the S-cone of the human eye, the M-cone of the human eye, or the [-cone of the human eye. Advantageously the combined luminous flux is efficiently produced by being confined to the spectrally sensitive regions of the eye.

The combined luminous flux output by the lighting apparatus may have a generally white chromaticity within chromaticity boundaries: x = 0.31 (blue boundary) x = 0.50 (yellow boundary) y = 0.15 + 0.64x (green boundary) y = 0.05 + 0.75x (purple boundary) y = 0.44 (green boundary) y = 0.38 (red boundary). Advantageously the combined luminous flux has a white chromaticity meeting predetermined criteria for use with a vehicle.

The combined luminous flux output by the lighting apparatus optionally has a generally white chromaticity as defined by United Nations Regulation No. 48. Advantageously the combined luminous flux has a white chromaticity meeting predetermined criteria for use with a vehicle.

Each of the plurality of light sources may be arranged to generate the respective luminous flux in the predetermined spectral band having a generally gaussian distribution. Advantageously the gaussian distribution better matches a sensitivity of one or more cones of the human eye.

The generally gaussian distribution may have a Full-Width at Half-Maximum of equal to or less than 60nm. Each of the plurality of light sources may be arranged to generate the respective luminous flux in the predetermined spectral band of equal to or less than 60nm width. Advantageously the gaussian distribution is better confined to the sensitive region of one or more cones of the human eye.

Optionally at least one of the one or more light sources comprises a light-emitting diode (LED) light source. Advantageously the LED is an efficient light emitter.

Optionally at least one of the one or more light sources comprises a gas-discharge light source.

According yet another aspect of the invention, there is provided a driving-beam headlamp comprising the lighting apparatus as described above.

According to a further aspect of the invention, there is provided a passing-beam headlamp comprising the lighting apparatus as described above.

According to a still further aspect of the invention, there is provided a cornering lamp comprising the lighting apparatus as described above.

According to a still yet further aspect of the invention, there is provided a reversing lamp comprising the lighting apparatus as described above.

According to yet another aspect of the invention, there is provided a registration plate lamp or a load-space lamp or a cabin lamp comprising the lighting apparatus as described above.

According to another aspect of the invention, there is provided a lighting system for a vehicle comprising a plurality of lighting apparatus as described above.

According to a further aspect of the invention, there is provided a vehicle comprising the lighting apparatus as described above, the driving-beam headlamp as described above, the passing-beam headlamp as described above, the cornering lamp of claim as described above or the reversing lamp of claim as described above.

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 any way 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 shows a chromaticity diagram (PRIOR ART);

Figure 2 shows the spectral sensitivity of the S-cone, M-cone and L-cone of the human eye (PRIOR ART); Figure 3 is an illustration of a wavelength distribution of a lighting apparatus (PRIOR ART); Figure 4 is a schematic view of a lighting apparatus according to an embodiment of the invention; Figure 5 is a schematic view of a lighting apparatus according to another embodiment of the invention; Figure 6 is a schematic view of an illumination lamp comprising the invention; Figure 7 is an illustration of a wavelength distribution of a lighting apparatus according to an embodiment of the invention; Figure 8 is a schematic view of a lighting module comprising the invention; Figure 9 shows a lighting system comprising an embodiment of the present invention; and Figure 10 shows a vehicle comprising an embodiment of the invention.

DETAILED DESCRIPTION

Embodiments of the present invention relate to a lighting apparatus. In particular, but not exclusively, the disclosure relates to a lighting apparatus for providing an efficient lighting function for a vehicle 500, such as illustrated in Figure 10. However embodiments of the present invention may also be useful in other applications in which efficient lighting is required.

Prior art lighting apparatuses for vehicles are typically required to emit light (luminous flux') of a specific colour or whiteness. For example, Figure 1 shows a sample chromaticity diagram and paragraph 2.29.1 of E/ECE/324/Rev.1/Add.47/Rev.9 lists chromaticity coordinates (x,y) thus defining the current legislative boundaries of a white light for use in a vehicle lighting

system. See Table 1.

TABLE 1 -E/ECE/324/Rev.1/Add.47/Rev.9 paragraph 2.29.1 "White" means the chromaticity coordinates (x,y) of the light emitted that lie inside the chromaticity areas defined by the boundaries: x = 0.31 (blue boundary) x = 0.50 (yellow boundary) y = 0.15 + 0.64x (green boundary) y = 0.05 + 0.75x (purple boundary) y = 0.44 (green boundary) y = 0.38 (red boundary) Similarly, paragraphs 2.29.2, 2.29.3 and 2.29.4 of E/ECE/324/Rev.1/Add.47/Rev.9 provide current legal definitions of selective-yellow, amber and red emitted light. SAE Standard J1383 also requires that the colour of the emanating light produced by a headlamp shall be white as defined in SAE Standard J578. Such definitions are required because otherwise the definition of the colours, or of 'white', is ambiguous. It is also known that vehicle manufacturers further select chromaticity (within the allowable boundaries) which they believe communicate aesthetic properties of the light appropriate to their brand. For example, one manufacturer may prefer to have a blue 'tinge' to white light, whilst another a red 'tinge'.

The chromaticity of luminous flux is dependent on a wavelength distribution of light emitted. In the case of a lighting apparatus comprising multiple light sources each emitting different wavelengths of luminous flux, the chromaticity of the total luminous flux depends on the wavelength and the relative intensity emitted from each light source.

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, as will be explained. 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 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 such a lighting system is to provide the greatest sensory response of the human vision system for the least electrical power, rather than simply emit more light for the least electrical power. In particular, the inventors have reframed the problem of efficient lighting to include the sensory response of the human vision system. Therefore, the benefit 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.

Figure 2 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 2 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.

Figure 3(a) illustrates a wavelength distribution 310 of an example vehicle headlight and relative intensity of the spectral sensitivities 320 of the S-, M-, and L-cones of the human eye. Figure 3(b) illustrates the portion 330 of the radiant flux aligning most with the spectrally sensitive regions of the S-, M-, and [-cones showing the relative response to the radiant flux as perceived by a viewer. Figure 3(c) illustrates a portion 340 of the radiant flux with sub optimal alignment with the spectrally sensitive regions of the S-, M-, and L-cones such that the radiant flux is perceived less visible to the viewer than the same radiant flux more closely aligned to the peak sensitivity of the S-, M-, and [-cones. A combination of the portions of Figures 3(b) and (c) corresponds to the total luminous flux shown in Figure 3(a). As can be appreciated, a significant portion of the total luminous flux of Figure 3(a) aligns poorly with the spectrally sensitive regions of the S-, M-, and L-cones of the human eye, as shown in Figure 3(c) and therefore, is a less effective use of energy than the portion 330 of Figure 3(b). The present inventors have appreciated that by maximising the radiant flux falling within the spectrally sensitive regions of the S-, M-, and [-cones of the human eye to that falling outside, the usefulness of energy consumed by the light source can be improved, as will be explained.

Figure 4 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 alternative embodiments there may be more than one light source 102, as shown in Figure 5, where each additional light source 104, 106 also converts an electrical power 124, 126 into a respective luminous flux 114, 116. Each of the plurality of light sources 102, 104, 106 emits the luminous flux 112, 114, 116 having a respective wavelength distribution. In some embodiments, each of the plurality of light sources 102, 104, 106 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, 126 consumed by each of the respective light sources 102, 104, 106. Also, a total luminous flux is a sum of each luminous flux 112, 114, 116 generated by each respective light source 102, 104, 106. 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 [-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.

A light source 102 emits its luminous flux 112 over a range of wavelengths forming the wavelength distribution. Normally the wavelength distribution has a single peak intensity at one wavelength within the range. This wavelength may be referred to as a first wavelength corresponding to the first peak intensity of the first luminous flux 112 of the first light source 102. In embodiments of the invention, the or each light source 102, 104, 106 emits its respective luminous flux 112, 114, 116 having a peak intensity at a wavelength corresponding to a peak spectral sensitivity of one of: the S-cone of the human eye, or the M-cone of the human eye, or the [-cone of the human eye.

In this way, a usefulness of the luminous flux is maximised by corresponding to wavelengths to which the at least one cone of the human eye is most sensitive. The peak intensity may be at a wavelength corresponding to one of around 445nm, around 540nm, or around 565nm. In this sense, around may be understood to mean within ±5nm. The luminous flux may have a predetermined distribution, which may be generally symmetric with wavelength against relative intensity, such as a Gaussian distribution although other distributions may be envisaged.

The light source 102 may be a light-emitting diode (LED) light source or a gas-discharge light source, although other light-emitting technologies may be used.

When the peak intensity is at a wavelength corresponding to the peak spectral sensitivity of the S-cone, the first wavelength may therefore be in the range 420nm to 450nm and preferably in the range 440nm to 450nm.

In some embodiments of Figure 3, the peak intensity is at a wavelength corresponding to the peak spectral sensitivity of the M-cone of the human eye, in which case the wavelength may therefore be in the range 530nm to 545nm and preferably in the range 535nm to 545nm.

Alternatively, the peak intensity is at a wavelength corresponding to the peak spectral sensitivity of the L-cone of the human eye, in which case the wavelength would therefore be in the range 555nm to 580nm and preferably in the range 560nm to 570nm.

Figure 7(a) illustrates a wavelength distribution, denoted generally as 700, of luminous flux of light sources 100 according to embodiments of the present invention in relation to the spectral sensitivities of the S-, M-, and L-cones of the human eye denoted generally as 705.

Figure 7(b) illustrates a portion 740 of the luminous flux falling within the spectrally sensitive regions of the S-, M-, and [-cones, such that the luminous flux is most visible to a viewer, as explained below. Figure 7(c) illustrates a portion 750 of the luminous flux falling outside of the spectrally sensitive regions of the S-, M-, and L-cones such that the luminous flux is less visible to the viewer. A combination of the portions 740, 750 of Figures 7(b) and 7(c) corresponds to the total luminous flux shown in Figure 7(a).

In one embodiment of Figure 4, the apparatus 100 comprises the first light source 102 for generating the first luminous flux 112 having the first peak intensity at a first wavelength corresponding, in one embodiment, to a peak spectral sensitivity of the S-cone of the human eye. The first luminous flux 112 is shown in Figure 7 with reference numeral 710. Because the first wavelength corresponds to the peak spectral sensitivity of the S-cone of the human eye then the biological availability of the total luminous flux of the lighting apparatus 100 is maximised for a given consumption of total electrical power. The term 'biological availability' means the proportion of luminous flux which is utilizable by the human vision system.

Therefore, when biological availability is maximised in this way then for a given electrical power the visibility of the light is increased, and/or visual acuity within the visual field illuminated by the light is increased. Visual acuity includes any combination of object recognition, shape recognition, depth perception and colour perception in the visual field illuminated by the light. For a given total electrical power consumption which is the same as a prior art system the apparatus 100 then affords a greater biological availability of the luminous flux and thus improved vision for the vehicle 500 user and other road users.

As can be appreciated from Figures 7(a) and 7(b), the first luminous flux 112, 710 falls within the spectral sensitivity of the S-cone such that it is present in Figure 7(b) as portion 740 but not in Figure 7(b) as portion 750 and therefore the lighting apparatus 100 is highly efficient to the human eye. It will be noted that further luminous fluxes 720, 730 are shown in Figure 7 for the purpose of explaining other embodiments of the present invention. The, or each, luminous flux, such as the first luminous flux 112, 710 may have a generally gaussian distribution. The gaussian distribution may be of the relative intensity of light output by the light source 102, 104, 106 against the wavelength distribution. The generally gaussian distribution of each luminous flux may have a Full-Width at Half-Maximum of equal to or less than 60nm.

It will be appreciated that, with the peak wavelength at one of the above values or in one of the above ranges corresponding to the peak spectral sensitivity of one of the cones of the human eye, whilst being highly efficient, the luminous flux 112 may appear to be coloured e.g. to have a blue colour, for example. In order to address this, a light source 100 according to an embodiment of the invention comprises one or more further light sources 104, 106, which adjust the perceived colour or chromaticity of the total luminous flux output by the lighting apparatus 100 to the viewer.

An embodiment of the present invention comprises at least two light sources, such as light sources 102, 104 shown in Figure 5. Whilst Figure 5 shows three light sources 102, 104, 106 it will be appreciated that this is not limiting. Each of the light sources 102, 104, 106 may be a light-emitting diode (LED) light source or a gas-discharge light source, although other light-emitting technologies may be used. An embodiment of the present invention comprises a second light source 104 for generating a second luminous flux 114 having a second peak intensity at a second wavelength. The second light source 104 may be used to ensure that a combined luminous flux output by the lighting apparatus 100 has a predetermined chromaticity, such as a white chromaticity, as will be explained. In some embodiments, the second light source 104 may be referred to as a colour balance light source 104, in that the second luminous flux 114 is used for controlling the wavelength distribution of the total luminous flux output by the lighting apparatus 100.

Thus the second luminous flux 114 may be a colour balance luminous flux 114. In some embodiments, the second luminous flux 114 may have a peak intensity at a wavelength which does not correspond to the peak spectral sensitivity of one of one of the cones of the human eye. For example, the second peak intensity may be arranged to form the total luminous flux having a generally white chromaticity. In this sense, white chromaticity may be understood to mean with the boundaries above in Table 1. The second peak intensity may be in the range of 600nm to 700nm, such as luminous flux 720 illustrated in Figure 7. In some embodiments, the second peak intensity may be in the range 600 to 650nm or in the range 620nm to 640nm.

The lighting apparatus 100 is arranged to combine the first and second luminous fluxes 112, 114 such that the combined luminous flux output by the lighting apparatus 100 has a desired chromaticity. Although the second luminous flux 720 does not correspond to the spectrally sensitive region of one of the cones of the human eye, the presence of the second luminous flux 114 advantageously controls the colour of the total luminous flux of the lighting apparatus 100.

It will be noted that the numbering of light sources, such as second light source 104 and third light source 106 does not imply the presence of other light sources. For example, an embodiment of the present invention may be envisaged which comprises the first light source 102 and third light source 106 described below.

The colour balancing light source 104 may be used with only one other light source 102, or two other lights sources 102, 106 (see Figure 5), or three (or more) other lights sources (not shown). In other embodiments, depending on the relative intensity and wavelength of the colour balancing light source 104 in relation to the other lights source(s) 102, 106, then the total luminous flux of the lighting apparatus 100 may be nominally white, amber, or red.

In an embodiment of the invention the lighting apparatus 100 comprises a third light source 106 for generating a third luminous flux 116. The third luminous flux 116 may have a third peak intensity at a third wavelength corresponding to a peak spectral sensitivity of another, different from the first light source 102, one of: the S-cone of the human eye, or the M-cone of the human eye, or the [-cone of the human eye.

In an embodiment where the first light source 102 has a first luminous flux 112 having the first peak intensity at the first wavelength corresponding the peak spectral sensitivity of the S-cone of the human eye, the third light source 106 in some embodiments has a third luminous flux 116 where the third peak intensity is at the third wavelength corresponding to the peak spectral sensitivity of either the M-cone of the human eye or the [-cone of the human eye.

Referring to Figure 7(a), the third luminous flux 116 is indicated with reference 730. It will be recognised that the M-cone and the [-cone of the human eye have very similar i.e. adjacent wavelength sensitivity ranges. As such, in some embodiments, the peak intensity the third light source 106 may be broadly in the range of 500 to 600nm, 530 to 600nm or 550 to 600nm corresponding to a combined sensitivity of the M-and [-cones of the human eye. That is, the peak intensity of the third luminous flux 116 may be within a spectral waveband bounded by the peak spectral sensitivity of the M-cone of the human eye and the peak spectral sensitivity of the [-cone of the human eye. In one particular embodiment where the first wavelength of the first light source 102 corresponds to the peak spectral sensitivity of the S-cone of the human eye the peak intensity of the third luminous flux is in the range of 550nm to 600nm, such as around 580nm.

In the illustrated example, the third luminous flux 116, 730 generally corresponds to the spectral sensitivity of the M cone. That is, the peak intensity of the third luminous flux 116, 730 is at a wavelength in the range of 500-55nm. In particular, the third wavelength may be in the range of 525-550nm. The third wavelength may be around 540nm. In some embodiments where the third wavelength corresponds to the peak spectral sensitivity of the M-cone of the human eye, the lighting apparatus 100 may comprise a fourth light source (not shown) for generating a fourth luminous flux having a fourth peak intensity at a fourth wavelength corresponding to the peak spectral sensitivity of the [-cone of the human eye.

As can be appreciated from Figures 7(a) and 7(b), a majority of the combined luminous flux output by the first and third light sources 102, 106 i.e. the first luminous flux 112 and the third luminous flux 116 fall within the spectral sensitivities of the cones of the human eye, specifically the S-cone and the M-cone of the human eye, as evidenced by the majority of the luminous flux being present in Figure 7(b) rather than 7(c). Of course the luminous flux 114 of the colour balance light source 104 may not be in a spectrally sensitive wavelength region, as shown in Figure 7(c), but may be required to control the perceived colour of the luminous flux output by the lighting apparatus 100.

Figure 6 shows an embodiment of the invention comprising a lighting apparatus 100, as described above, used within an illumination lamp 200 which may further comprise one or both of a lens 202 and a reflector 204. The illumination lamp 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.

The illumination lamp 200 may be used for a lighting function for the illumination of the road and objects in a direction of vehicle movement. For example, the illumination lamp 200 may be used as a driving-beam ('main beam') headlamp, a passing-beam ('dipped beam') headlamp, a cornering lamp, a fog lamp or a reversing lamp. The illumination lamp 200 may also be used for lighting a part of the vehicle such as the registration plate, a portion of an interior of the vehicle, such as the load space or the passenger cabin. The illumination lamp may also be used for light-signalling to give other road users visual information on the presence, identification and/or the change of movement of the vehicle, such as a tail lamp, a stop lamp, a direction-indicator lamp, a front position lamp ('side light'), a rear position lamp (tail light'), a daytime running lamp, or a fog lamp.

Figure 8 shows a further embodiment of the invention which is a lighting module 300 which includes a plurality of illumination lamps 200 as described above with reference to Figure 6. The lighting module 300 further comprises one or both of a lighting apparatus 302 and a light source 304. The lighting module 300 may be a lighting module 300 for a vehicle, such as a headlight module. One of the illumination lamps 200 may form, for example, a driving beam and the other illumination lamp a passing-beam. The lighting apparatus 302 may be a daytime driving light (DRL) lighting apparatus e.g. formed by one or more light sources and a light guide to provide a shaped light source, e.g. curved or the like, to provide a visual impression for the DRL. The light source 304 may be, for example, a light source to provide a turn-indicator which may have a colour such as orange or amber to provide a flashing indication of the vehicle's intended direction of turn or manoeuvre. The light source 304 may thus be one or more LEDs or the like which may be coloured or associated with a coloured filter.

Figure 9 shows a lighting system 400 comprising two lighting modules 300, as described above, a power supply 402 and switching means 404. In some embodiments the lighting system may comprise and a controller 406. The components 402, 404, 406 are all interconnected by a wiring harness 410 which may comprise a communication bus such as [IN, CAN or Ethernet. Other communication bus types may be envisaged. In other embodiments the controller 406 may be combined with the power supply 402 and/or the switching means 404. The power supply is arranged to provide electrical power for the lighting modules 300. The switching means 404 and/or controller 406 is arranged to control which light emitters of each of said lighting modules 300 are illuminated.

Figure 10 shows a vehicle 500 comprising various example embodiments of the lighting apparatus 100 in a headlamp assembly 502, tail lamp cluster 504, direction indicator lamp 506, cabin lamp 508, load space lamp 510 and registration plate lamp 512. The headlamp assembly 502 may comprise a driving-beam headlamp, a passing-beam headlamp, a cornering lamp, a fog lamp and/or light-signalling lamps. The tail lamp cluster 504 may comprise a reversing lamp and/or light-signalling lamps.

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

CLAIMS1. A lighting apparatus for a vehicle, 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 corresponding to a peak spectral sensitivity of any one of: the S-cone of the human eye, or the M-cone of the human eye, or the [-cone of the human eye, a second light source for generating a second luminous flux having a second peak intensity at a second wavelength; wherein the lighting apparatus is arranged to combine the first and second luminous fluxes such that a combined luminous flux output by the lighting apparatus has a generally white chromaticity.
2. The lighting apparatus according to claim 1, comprising a third light source for generating a third luminous flux having a third peak intensity at a third wavelength corresponding to a peak spectral sensitivity of another one of: the S-cone of the human eye, or the M-cone of the human eye, or the [-cone of the human eye, wherein the second peak intensity is in the range of 600nm to 700nm.
3. The lighting apparatus according to claim 2, wherein the first wavelength corresponds to the peak spectral sensitivity of the S-cone of the human eye.
4. The lighting apparatus according to claim 2 or 3 wherein the third wavelength corresponds to the peak spectral sensitivity of the M-cone of the human eye, and the apparatus comprises a fourth light source for generating a fourth luminous flux having a fourth peak intensity at a fourth wavelength corresponding to the peak spectral sensitivity of the L-cone of the human eye.
5. The lighting apparatus according to claim 2, wherein the third wavelength is within a spectral waveband bounded by the peak spectral sensitivity of the M-cone of the human eye and the peak spectral sensitivity of the [-cone of the human eye. 7. 8. 9. 11.
The lighting apparatus according to claim 1 wherein: the first wavelength corresponds to the peak spectral sensitivity of the S-cone of the human eye, and the second wavelength is in the range of 550nm to 600nm.
The lighting apparatus of any preceding claim, wherein the combined luminous flux output by the lighting apparatus having a wavelength equal to or less than 600nm is substantially confined to a spectral sensitive region 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.
The lighting apparatus according to any preceding claim, wherein the combined luminous flux output by the lighting apparatus has a generally white chromaticity within chromaticity boundaries: x = 0.31 (blue boundary) x = 0.50 (yellow boundary) y = 0.15 + 0.64x (green boundary) y = 0.05 + 0.75x (purple boundary) y = 0.44 (green boundary) y = 0.38 (red boundary).
The lighting apparatus according to any preceding claim, wherein the combined luminous flux output by the lighting apparatus has a generally white chromaticity as defined by United Nations Regulation No. 48.
The lighting apparatus according to any preceding claim, wherein each of the plurality of light sources is arranged to generate the respective luminous flux in the predetermined spectral band having a generally gaussian distribution.
The lighting apparatus according to claim 10, wherein the generally gaussian distribution has a Full-Width at Half-Maximum of equal to or less than 60nm.
The lighting apparatus according to any of claims 1 to 10, wherein each of the plurality of light sources is arranged to generate the respective luminous flux in the predetermined spectral band of equal to or less than 60nm width.
13. The lighting apparatus of any preceding claim wherein at least one of the one or more light sources comprises a light-emitting diode light source.
14. The lighting apparatus of any preceding claim wherein at least one of the one or more light sources comprises a gas-discharge light source.
15. A vehicle comprising the lighting apparatus of any of claims 1 to 14.