NL1029231C2 - Street lighting arrangement for night-time lighting has solid-state light source in housing to generate light having dominant wavelength from predetermined wavelength region - Google Patents

Abstract

The arrangement has a supporting element and a lighting unit (1) supported by the element. The lighting unit comprises a housing (2) accommodating a solid-state light source (4) having LED (5) to generate light whose wavelength ranging from a predetermined wavelength region of 500-550 nm and the wavelength region of 560-610 nm. The lighting unit generates the light having a dominant wavelength from the predetermined region where the eye sensitivity of the human eye is dominated by rods. An independent claim is included for solid-state light source.

Description

Lighting device and solid-state light source

The invention relates to a lighting device for illuminating a surface comprising: a support element; - a lighting unit supported by the support element; wherein the lighting unit comprises a housing adapted to receive a solid-state light source suitable for generating light with wavelengths from at least one predetermined wavelength region, the housing being translucent on at least one side.

Such a lighting device is known from US patent application US2004 / 0105264 and makes it possible to illuminate a public space in a very efficient manner. In particular, such a lighting device is suitable for use as street lighting. As also described in US2004 / 0105264, light beams emitted by street lighting generally have a color that lies between blue white and yellow orange. This provides sufficient lighting with a pleasant appearance. A disadvantage of street lighting with such a color is, however, that the human eyes are not optimally accommodated for light of such a wavelength in a darkened environment. A human's eyes include so-called cones and rods. The cones are only active from a sufficiently large light intensity. They are individually connected to the brain via a nerve path and, moreover, able to perceive color. The rods, on the other hand, become much more active at low light intensity, cannot detect color and can connect to the brain in groups, so that a perception image from only rods has a lower resolution than an observation image from only cones. The cones are most sensitive to light with a wavelength of approximately 555 nm, i.e. yellowish light. On the other hand, with a low light intensity, as is the case with a completely darkened environment, the bars are active.

These are most sensitive to light with a smaller wavelength, namely 507 run ·

The present invention has for its object to provide a lighting device which, when illuminated at night with a public space such as a street, garden or parking space, provides a better perceptibility of said public space for the human eye. The aforementioned lighting device is therefore characterized in that the predetermined wavelength range comprises wavelengths of 480-550 nm and the minimum light power of the lighting device is 300 lumen.

5 By emitting light with a wavelength of 480-550 nm, namely "green" light, this increased sensitivity of the eyes is used. The sensitivity of the rods is even 2.5 times greater than the sensitivity of the cones around 555 nm.

In an embodiment of the lighting device according to the present invention, the lighting unit further comprises a light processing unit for processing the intensity and / or direction of light generated by the solid-state light source. This makes it possible to set up the lighting device as simply as possible, despite possibly limiting environmental factors.

The solid-state light source may comprise a plurality of Light Emitting Diodes (LEDs) 15, which preferably have an aperture angle of 30-70 °. In order to ensure that the luminance on the surface to be illuminated is as uniform as possible, the LEDs are preferably arranged so that the light source in use emits light at an angle of at least 20 ° with respect to that surface. In particular with an angle between 20-30 ° an optimum ratio between a horizontal and vertical light intensity can be achieved.

Furthermore, in all the aforementioned embodiments, the lighting unit may further comprise a power supply which can be connected to the solid-state light source. Due to the presence of the power supply, the lighting device is not dependent on the availability of an external electrical network.

The use of one dominant color in a lighting device makes color perception very difficult to impossible due to a lack of spectral bandwidth. As a result, there is less contrast and contours are less visible. This applies not only to the light emitted with the lighting device of US2004 / 0105264, but also to the "green light" from the previously described embodiments of the present invention. In order to ensure that the increased sensitivity to the "green light" is not accompanied by contrast loss and lack of color perception, in an embodiment of the invention, the at least one wavelength region comprises a first and a second wavelength region, the 1029231

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first wavelength range comprises wavelengths of 480-550 nm and the second wavelength range comprises wavelengths of 570-610 nm. Such an embodiment of the illumination device makes good observation possible in a darkened environment, whereby color detection also becomes possible due to the presence of light with wavelengths originating from the second wavelength region. The light perceived by the eyes, which comprises a combination of wavelengths from both wavelength regions, is therefore also perceived as "friendlier" and "softer" than "green light" only.

In a further embodiment, the solid-state light source of the lighting device comprises a number of first LEDs for emitting light with a wavelength located in the first wavelength region and a number of second LEDs for emitting light with a wavelength located in the second wavelength region. By dividing the light source into two groups of LEDs, each group being suitable for emitting light with a different wavelength, it is possible to illuminate 15 segments of the surface to be illuminated with different wavelength combinations adapted to local conditions.

The number of first LEDs is preferably 3-5 times greater than the number of second LEDs. It has been found that with such a ratio an optimum color perception is achieved without this being at the expense of an excessive loss of eye sensitivity to perception in the dark.

In one embodiment, the lighting device comprises a further light processing unit that can process light from the number of first LEDs and light from the number of second LEDs in mutually different ways.

In all embodiments of the present invention, the lighting device may further comprise a cover element with an opening, the cover element being placed around the lighting unit such that the opening coincides with the light-transmitting side of the housing of the lighting unit. The cover element can function as an additional protective means.

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The present invention further relates to a solid-state light source suitable for generating light with wavelengths from a predetermined wavelength range and a minimum light power wherein the solid-state light source is a multiple of Light

102923J

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Emitting diodes (LEDs) which are suitable for emitting light in the predetermined wavelength region, characterized in that the predetermined wavelength region comprises wavelengths of 480 - 550 nm and the minimum light power is 300 lumen.

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The present invention furthermore relates to a solid-state light source suitable for generating light with wavelengths located in a first wavelength region and wavelengths located in a second wavelength region, characterized in that the first wavelength region comprises wavelengths of 480 - 550 nm and it second wavelength range comprises wavelengths of 570-610 nm and the solid-state light source (4) has a total minimum light power of 300 lumen.

In one embodiment, the solid-state light source comprises a number of first LEDs for generating light with a wavelength located in the first wavelength region and a number of second LEDs for generating light with a wavelength located in the second wavelength region. By dividing the light source into two groups of LEDs, each group being suitable for generating light with a different wavelength, it is possible to generate light with a controlled local variation of wavelength combinations.

Preferably, the number of first LEDs is 3-5 times greater than the number of second LEDs. It has been found that at such a ratio an optimum color perception is achieved without this being at the expense of an excessive loss of eye sensitivity for dark perception.

The present invention will be further explained below by way of example with reference to the following figures. The figures are not intended to limit the scope of the invention, but merely to illustrate it. In addition: FIGURE 1 shows a lighting unit according to an embodiment of the invention; FIGURE 2a schematically shows a top view of a lighting device and the area illuminated by the lighting device according to a first embodiment of the invention; FIGURE 2b schematically shows a top view of a lighting device and the area illuminated by the lighting device according to a second embodiment of the invention; FIGURE 3 schematically shows a side view of a lighting device that illuminates a road surface according to an embodiment of the invention; FIGURES 4a and 4b show a top side view and a cross-section, respectively, of a lighting device according to another embodiment of the invention; FIGURE 5 schematically shows a side view of a cross-section of a lighting device according to yet another embodiment of the invention.

The present invention is discussed below with reference to an example with regard to street lighting, but is not limited thereto. However, the invention can be used to illuminate other spatial areas such as gardens and parking areas at night.

Figure 1 shows a lighting unit 1 according to the present invention.

The lighting unit 1, which is supported by a supporting element (not shown), comprises a housing 2 which is translucent on at least one side. In figure 1 this light transmittance is achieved by providing the housing 2 with a light transmitting element 3, but alternatives, such as leaving the housing open, making a hole in the housing on this at least one side or other known to the person skilled in the art measures are also possible. The lighting unit 1 further comprises a solid-state light source 4, for example, as in Figure 1, a plurality of Light Emitting Diodes (LEDs) 5. The light source 4 is connected to a power supply, for example, as in Figure 1 a power source 6. In Figure 1 shows the power supply in the housing, but it is, however, possible that it is located in the supporting element. In addition, the light source 4 can also be supplied by an external power supply, which is located outside the combination of supporting element and housing. Before going out through the light-transmitting side of the housing 2, the light generated by the light source 4 can pass through a light processing unit 7 as shown in Figure 1. This light processing unit 7 makes it possible, for example, to control the intensity and / or the direction of the light

1 n O Λ O O A

6 is produced by the light source 4. A majority of the plurality of LEDs 5 is arranged to emit light with a wavelength between 480 - 550 nm. The precise wavelength depends on which semiconductor materials, such as InGaAs, have been used and to what extent these materials are doped. The light emitted from "green" LEDs 5a, which are indicated in Figure 1 by a rectangle with a completely black top, is in the region of an extremely high sensitivity of the human eye under night-time conditions. However, since light with only one dominant wavelength is used, color perception is virtually impossible. Therefore, in addition to "green" LEDs 5a, the plurality of LEDs 5 preferably also includes "amber" LEDs 5b, i.e., LEDs that generate light with a wavelength of 570 - 610 nm. In figure 1, "amber" LEDs 5b are indicated by a rectangle with a shaded top. When used as road lighting, the combination of "green" and "amber" LEDs 5a, 5b allows a contrast-rich view, whereby relevant, colored objects and symbols, such as reflectors and colored road lines, are also visible. The minority of "amber" LEDs 5b in the light source 4 provide a reflection of, inter alia, yellow and red surfaces. In addition, the "amber" LEDs 5b soften the green character of the light.

It has been found that a plurality of LEDs 5 with 3-5 times as many "green" LEDs 5a as "amber" LEDs 5b provide optimum color perception without excessive loss of eye sensitivity to dark perception.

With the aid of the processing unit 7, for example, as in Figure 1, it can be achieved that the lighting unit 1 emits light with a different mixing color, i.e. a different composition of wavelengths, in individual light beams 8, 9.10 in different predetermined directions.

The light source 4 has at least a light power of 300 lumen. With this light output, the minimum requirements for street lighting can be met. It should be noted that these requirements, which can vary considerably per road type, are often linked to the amount of light that falls on a surface per square meter. This so-called light intensity, normally expressed in lux, is not only dependent on the light power of the light source 4, but also inversely quadratic proportional to the distance between the light source 4 and the surface to be illuminated. The normal average light intensity of street lighting is 5 lux in small residential streets and country roads up to 20 lux on highways and 30 lux on busy traffic points. Color perception requires a light intensity of at least 3 lux because the cones only become active in the human eye from such light intensity and these cones ensure color perception by humans.

The use of a solid-state light source 4, such as a multitude of LEDs 5, in applications such as road lighting makes it possible, in contrast to, for example, sodium lamps, to obtain optimum light distribution on the road surface with lenses. An LED light source is a point source. A lighting device 20 provided with such a point source illuminates a circle-symmetrical surface, as shown in Figure 2a, if exit is only possible in one direction. With the aid of a processing device 7, which comprises, for example, miniscule lenses, an arbitrary aperture angle can be obtained so that the light can be brought exactly where it is desired. As is known to those skilled in the art, such miniscule lenses can also be mounted on an LED itself. By a precise positioning of the lens relative to the light source of the LED, a certain opening angle of an LED can therefore also be obtained.

Figure 2b shows a top view of a lighting device 20 which illuminates four road sections with four LED (combination) s. As a result, the road surface 22 is illuminated in the direction of travel with so-called grazing light, so that the projection surfaces 23-26 of the four light beams are elliptical. In order not to lose too much light output, the opening angle of the LEDs is preferably between 30 ° and 70 °. In the aforementioned manner, the road surface can be illuminated over a larger surface with a sufficient light intensity, i.e. more than 5 to 30 lux, without an increase in energy consumption. Moreover, by illuminating the road surface at an angle, a greater uniformity of the luminance is achieved.

However, if the angle of incidence, i.e. the angle between the incident light with the surface to be illuminated (in the example above a road surface), falls below a critical angle of incidence, typically between 20 ° and 25 °, then the perception efficiency decreases. This is because when the angle of incidence becomes smaller, the horizontal light intensity drops and the vertical light intensity rises. As a result, in the presence of objects such as cars on the surface to be illuminated, a stronger shadow effect with dark zones occurs and horizontal elements become less visible as lines. Such a negative effect can be reduced by 1029231 8

light source 4 with a larger number of directed light sources of a smaller capacity. These light sources can then be directed such that they illuminate at least partially the same surface, such as the overlapping elliptic I

projection surfaces in Figure 2b.

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A division of the light to be emitted into individual light beams makes it possible to illuminate different road sections with light comprising different combinations of wavelengths. In order, for example, to be able to properly observe colored signage at the edge of a road at night without losing an optimum perception of contrast on the road itself, an orientation of light beams, as shown in Figure 3, is possible.

In Fig. 3, the lighting unit 1 of the lighting device 30 produces three different, slightly overlapping light beams 31, 32 and 33, each illuminating a different part of the road surface 34. Light beam 31 illuminates one side of the road surface 34, which is delimited by an abrupt elevation 36 of the roadside.

Light beam 33 illuminates, among other things, a road marking 35, for example a yellow stripe or a red reflector, which is mounted on or in the road. Optimal observation of the road marking 35 and the abrupt increase 36 at night requires a different optimization of the wavelength of the light incident on both objects. After all, the optimization for observation of the road marking 35 will be more focused on increasing the perceptibility of color, while the perceptibility of the abrupt increase 36 increases by including wavelengths in the light beam, which increases the eye sensitivity under nocturnal conditions.

Finally, the light beam 32 illuminates the center of the road surface 34. Because this beam 32 both the visibility of the road surface 34 and any vehicles present thereon, as well as the visibility of reflectors and the like on these vehicles | guarantee sufficiently, both aspects must be taken into account in optimization.

In an embodiment of the present invention, the light processing unit 7 and / or miniscule lenses mounted on the LEDs 5 ensure that each light beam 31-33 is produced by a different group of LEDs 5.

The group of LEDs, which is responsible for emitting light beam 32 and comprising both "amber" and "green" LEDs, is optimized for emitting 1029231-9 suitable light observation in combination with a sufficient eye sensitivity for night observation. The optimum achieved corresponds to a certain ratio between the number of "amber" LEDs and the number of "green" LEDs. Reducing the proportion of "amber" LEDs increases eye sensitivity.

5 Although increasing this share is unfavorable for this, it does promote color perception. The share of "amber" LEDs in the groups of LEDs that are responsible for generating bundles 31 and 33 is therefore lower and higher, respectively, than the share of "amber" LEDs responsible for generating bundle 32.

Other possibilities for obtaining a differentiation in wavelength on different segments of the road surface 34 are also possible. Thus, by limiting the aperture angle of the light rays originating from the "amber" LEDs, it is possible to illuminate the sides of a road surface 34 with a color sensation-sensitive wavelength than a central row portion of the road surface 34.

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In particular, because a solid-state light source, such as LED lighting, is less heavy and because of the simple processing possibilities that limit the energy loss, a more favorable arrangement and use of the lighting device is possible compared to lighting devices with conventional street lighting, such as sodium lamps.

It is thus possible to arrange the lighting units 1 at a low height, for example between 0.5 - 4 m. Due to the low height and the use of a lighting device with a solid-state light source such as LED lighting, a reduction in night-time light pollution is achieved.

In addition to a conventional post, a guardrail or a noise barrier can also serve as a supporting element. To prevent negative effects for the lighting unit 1 at a corresponding height, the lighting unit can be provided with one or more additional protection elements. In figures 4a and 4b, the lighting unit 1 is provided with a cover element 40 with a light-transmitting opening which coincides with the light-transmitting side of the lighting device 1.

With this cover element 40 it can be prevented that the lighting unit 1 is contaminated too much by passing traffic. Preferably, as schematically shown in the cross-section of Figure 4b, both the light-transmitting opening of the cover element 40 and the light-transmitting side of the lighting unit 1 are directed in a direction that forms a small angle with the direction of travel. This driving direction is indicated by an arrow in Figure 4a. The cover element 40 is connected with a fastening means 41 to a support element 42, for example a post of a guard rail, as shown in figures 4a, 4b and 5. An advantage of a low placement of the lighting units 1 is that there is a better concentration of the lighting unit 1. light on the road surface can be obtained. The low placement mainly results in a higher vertical light intensity. This is further enhanced by the fact that the light from the same direction as the vehicle driver is projected onto the road surface, whereby a large part of the reflections occurring on the road surface is reflected directly to the vehicle driver. The presence of the lighting units 1 at a relatively low height also offers the possibility of using the lighting units 1 for traffic signaling. For example, a series of lighting units 1 mounted on a guard rail could serve as a warning running light against the direction of travel, to signal an approaching traffic jam due to an accident or traffic jam.

The lighting unit 1 is preferably orientable, for example by making use of a fastening means 41 with a rotary coupling 43, as shown in the lighting device shown in Fig. 5, when connected to the supporting element 42.

Blinding can be prevented by directing the light. Moreover, with a correct orientation, a ratio between horizontal and vertical light intensity ideal for that environment can be obtained. A smaller angle between the light beam to be emitted and the road surface to be illuminated lowers the horizontal light intensity, which leads to a lower visibility of, for example, lines. On the other hand, the vertical light intensity is increased by such a change in angle, as a result of which objects, such as stones, will be more visible on the road surface.

The above description only describes a number of possible embodiments of the present invention. It is easy to see that many alternative embodiments of the invention can be devised, all of which fall within the scope of the invention. This is determined by the following claims.

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Claims (10)

A lighting device for illuminating a surface comprising: a support element; 5. a lighting unit (1) supported by the support element; the lighting unit (1) comprising a housing (2) adapted to receive a solid light source (4), the housing (2) being light-transmitting on at least one side, characterized in that the solid material light source (4) comprises a plurality of Light Emitting Diodes ((LEDs), the plurality of LEDs comprising: a plurality of first LEDs (5a) for emitting light with a wavelength in the range of 480-550 nm; and a plurality of second LEDs (5b) for emitting light with a wavelength in the range of 570-610 nm, wherein the number of first LEDs (5a) is 3-5 times greater than the number of second LEDs (5b). 2. Lighting device according to claim 1, characterized in that the lighting unit (1) further comprises a light processing unit (7) for processing the intensity and / or the direction of the light generated by the solid-state light source (4). Lighting device according to claim 1 or 2, characterized in that the LEDs (5) have an opening angle of 30-70 °. 4. Lighting device as claimed in any of the foregoing claims, characterized in that the LEDs (5) are arranged such that the light source (4), in use, emits light at an angle of at least 20 ° with respect to the surface to be illuminated. 5. Lighting device as claimed in claim 4, characterized in that the angle with respect to the surface to be illuminated is not greater than 30 °. 6. Lighting device as claimed in any of the foregoing claims, characterized in that the lighting unit (1) further comprises a power supply (6) connectable to the solid-state light source (4) for supplying the solid-state light source with an electrical supply. 7. Lighting device according to one of the preceding claims, characterized in that the lighting unit (1) further comprises a light processing unit (7) which has the light 1029231 from the number of first LEDs (5a) and the light from the number of second LEDs ( 5b) processed in different ways. 8. Lighting device as claimed in any of the foregoing claims, characterized in that the lighting unit (1) further comprises a cover element (40) with an opening which is arranged around the lighting unit (1) such that the opening coincides with the light-transmitting side of the housing (2) of the lighting unit (1). A solid-state light source (4) comprising a plurality of Light Emitting Diodes ((LEDs), the plurality of LEDs comprising: a plurality of first LEDs (5a) for emitting light with a wavelength located in the region 480- 550 nm, and a number of second LEDs (5b) for emitting light with a wavelength in the range of 570-610 nm, wherein the number of first LEDs (5a) is 3-5 times greater than the number of second LEDs (5b) ). The solid-state light source according to claim 9, which has a minimum light power of 300 lumens. 20 1029231