Patent Description:
Passenger aircraft, such as commercial air planes, which comprise a passenger cabin with passenger seats, are usually equipped with general passenger cabin lights for illuminating the passenger cabin.

The general passenger cabin lights may in particular include elongated interior aircraft lights, which extend along a longitudinal direction of the passenger cabin, for example along a wall, along a ceiling, along a hand rail, or along a floor of the passenger cabin. Elongated interior aircraft lights may further by employed in other locations within the passenger cabin, such as galleys, washrooms and/or toilets.

Such elongated interior aircraft lights may include a plurality of elongated light modules, which are arranged next to each other for forming the respective elongated interior aircraft light. Each of the elongated light modules may comprise a plurality of light sources, which may be configured for emitting light of different colors. In this way, colored illumination of the aircraft cabin may be made possible.

In such a configuration, there is a risk that the light, which is emitted by the light sources of the elongated light modules, results in the formation of unpleasant or disturbing spots at the interfaces or gaps between adjacent light modules. Said unpleasant or disturbing spots may, for example, include an over-pronunciation of one color and/or a mixed color that becomes very prominent along a long section of an otherwise homogeneous light distribution, which is generated by the elongated interior aircraft light.

<CIT> discloses a lighting system of an aircraft cabin includes a plurality of light units disposed at a plurality of locations within the aircraft cabin, wherein each of the plurality of light units includes at least one infrared light source, with an emission of infrared light across the aircraft cabin resulting from an operation of the at least one infrared light source of the plurality of light units.

<CIT> discloses a light for an interior of a vehicle that contains at least two light modules, wherein in an installed state the light modules are mounted on a supporting structure in the vehicle, and the light modules are disposed in series along a profile line, and wherein in the installed state, each two adjacent light modules are attached to each other in regions in a fixed relative mutual position. All light modules that are mutually attached to each other together form a light strip, the light strip is attached with exactly one first region to the supporting structure in a fixed relative position to the supporting structure, and at least one second region of the light strip is movably supported on the supporting structure in a variable relative positionto the supporting structure.

It would therefore be beneficial to provide elongated light modules, comprising a plurality of light sources which are configured for emitting light of different colors, wherein the elongated light modules are configured such that the risk of forming unpleasant or disturbing spots at the interfaces or gaps between adjacent light modules is reduced, when the elongated light modules are arranged next to each other for forming an elongated interior aircraft light. It would further be beneficial to provide an according elongated interior aircraft light and according methods for providing such light modules and such elongated interior aircraft lights.

The invention is defined by a light module according to claim <NUM> and by a method according to claim <NUM>. Further embodiments are set out in the dependent claims.

Exemplary embodiments of the invention include a light module for an elongated interior aircraft light that comprises a plurality of light sources. The plurality of light sources are configured for emitting light of different colors and they are arranged next to each other forming an array of light sources, which extends along a longitudinal direction between a first end and a second end. The plurality of light sources include a first light source, which is arranged at the first end of the array of light sources, and a second light source, which is arranged at the second end of the array of light sources. The first and second light sources are selected in such a way from the plurality of light sources that a difference of the illuminating properties between the first and second light sources is the smallest difference that is possible between all potential pairs of light sources, which may be formed / combined from the plurality of light sources. The difference of the illuminating properties, which is minimized by an appropriate selection of the first and second light sources, is a function of the difference in chromaticity and/or in hue and/or in saturation and/or in intensity between the respective light sources.

Exemplary embodiments of the invention further include a method of arranging a plurality of light sources, which are configured for emitting light of different colors, as an array of light sources in a light module, wherein the array of light sources extends along a longitudinal direction between a first end and an opposing second end. The method includes selecting a first light source and a second light source from the plurality of light sources, so that a difference of the illuminating properties between the first and second light sources is the smallest difference that is possible between all potential pairs of light sources, which may be formed / combined from the plurality of light sources. The method further includes arranging the first light source at the first end of the array of light sources and arranging the second light source at the second end of the array of light sources. The difference of the illuminating properties, which is minimized by an appropriate selection of the first and second light sources, is a function of the difference in chromaticity and/or in hue and/or in saturation and/or in intensity between the respective light sources.

Exemplary embodiments of the invention further include an elongated interior aircraft light, comprising a plurality of light modules according to an exemplary embodiment of the invention. All light modules are assembled from the same types of light sources and comprise the same combination of light sources with respect to the colors, which are emitted by the light sources. In such an elongated interior aircraft light, the light modules are arranged next to each other for forming an array of light modules extending in the longitudinal direction. The plurality of light modules are oriented in such a way with respect to each other that, for each pair of neighboring light modules, the second light source of a first light module of the respective pair of light modules is arranged next to the first light source of a second light module of the respective pair of light modules.

Exemplary embodiments of the invention further include an aircraft, in particular a passenger aircraft, which is equipped with at least one elongated interior aircraft light according to an exemplary embodiment of the invention.

Elongated light modules according to exemplary embodiments of the invention may be combined for providing an elongated interior aircraft light, in which the risk of forming unpleasant or disturbing spots at the interfaces or gaps between adjacent light modules is considerably reduced, since light sources having highly similar illuminating properties may be arranged at said interfaces or gaps of such an elongated interior aircraft light. Despite imperfect color mixing at the interfaces or gaps between adjacent light modules, a highly even illumination of target surfaces and/or a highly pleasant / non-disturbing light output may be achieved.

In an embodiment, the difference of the illuminating properties, which determines the arrangement of the light sources within the light modules, is defined as a weighted sum of the difference in chromaticity and/or in hue and/or in saturation and/or in intensity between the respective light sources. The weighted sum may take into account any subset or all of the difference in chromaticity, the difference in hue, the difference in saturation, and the difference in intensity.

For reducing the risk of generating unpleasant or disturbing spots at the interfaces or gaps between adjacent light modules, it has been found particularly beneficial to minimize the difference in chromaticity between the first and second light sources.

With minimizing the difference between the first and second light sources in another one of the listed dimensions or in a combined metric for some or all of the listed dimensions, beneficial results in reducing the risk of generating unpleasant or disturbing spots at the interfaces or gaps between adjacent light modules may also be achieved.

In an embodiment, the difference of the illuminating properties is defined as the distance between the chromaticities in the CIE1976 color space. The CIE1976 color space provides a good indication of the perception of the different colors by the human eye. Two chromaticities, which have a small distance from each other in the CIE1976 color space, are perceived as similar by the human eye.

It may therefore be beneficial to use the distances between the chromaticities in the CIE1976 color space for determining that pair of light sources from a plurality of light sources, which emit light of different colors, whose color outputs are perceived as most similar among all potential pairs of light sources, which may be formed from said plurality of light sources.

If the chromaticities of the light sources are given in a different color space, for example in the CIE1931 color space, which is often used by the suppliers of light sources, the chromaticities may be converted into the CIE1976 color space, before the distances between the chromaticities of the light sources are determined.

In an embodiment, the light module further comprises a third light source, which is arranged next or adjacent to the first light source. The third light source is selected from the remainder of the plurality of light sources, i.e. from the plurality of light sources without the first and second light sources, as they have already been assigned to their positions within the light module. The third light source may in particular be selected so that the difference of the illuminating properties between the first and third light sources is the largest difference of the illuminating properties that is possible for all pairs of light sources, which may be formed from the first light source and a respective one of the remainder of the plurality of light sources.

The first and third light sources may be arranged at a small distance from each other, e.g. at a distance which is smaller than <NUM>. The first and third light sources may even be arranged abutting each other. When the first and third light sources are arranged at such a small distance from each other, there is a large overlap of the light emissions, which are emitted by the two light sources. This overlap results in an efficient blending of the light emissions having different colors, which are emitted by the first and third light sources. This efficient blending results in a homogeneous illumination, even if the difference between the illuminating properties, in particular between the chromaticities, of the two light sources is large.

In an embodiment, the light module further comprises a fourth light source, which is arranged next or adjacent to the second light source. The fourth source is selected from the remainder of the plurality of light sources, i.e. from the plurality of light sources without the first, second, and third light sources, as they have already been assigned to their positions within the light module. The fourth light source may be selected so that the difference of the illuminating properties between the second and fourth light sources is the largest difference that is possible for all pairs of light sources, which may be formed from the second light source and a respective one of the remainder of the plurality of light sources.

The second and fourth light sources are may be arranged at a small distance from each other, e.g. at a distance which is smaller than <NUM>. The second and fourth light sources may even be arranged abutting each other. When the second and fourth light sources are arranged at such a small distance from each other, there is a large overlap of the light emissions, which are emitted by the two light sources. This overlap results in an efficient blending of the light emissions having different colors, which are emitted by the second and fourth sources. This efficient blending results in a homogeneous illumination, even if the difference between the illuminating properties, in particular between the chromaticities, of the two light sources is large.

In an embodiment, the light module further comprises a fifth light source, which is arranged next or adjacent to the third light source. The fifth light source is selected from the remainder of the plurality of light sources, i.e. from the plurality of light sources without the first, second, third, and fourth light sources, as they have already been assigned to their positions within the light module. The fifth light source may be selected so that the difference of the illuminating properties between the third and fifth light sources is the largest difference that is possible for all pairs of light sources, which may be formed from the third light source and a respective one of the remainder of the plurality of light sources.

The third and fifth light sources may be arranged at a small distance from each other, e.g. at a distance which is smaller than <NUM>. The third and fifth light sources may even be arranged abutting each other. When the third and fifth light sources are arranged at such a small distance from each other, there is a large overlap of the light emissions, which are emitted by the two light sources. This overlap results in an efficient blending of the light emissions having different colors, which are emitted by the third and fifth sources. This efficient blending results in a homogeneous illumination, even if the difference between the illuminating properties, in particular between the chromaticities, of the two light sources is large.

In an embodiment, the light module further comprises a sixth light source, which is arranged next or adjacent to the fourth light source. The sixth fourth source is selected from the remainder of the plurality of light sources, i.e. from the plurality of light sources without the first, second, third, fourth, and fifth light sources, as they have already been assigned to their positions within the light module. The sixth light source may be selected so that the difference of the illuminating properties between the fourth and sixth light sources is the largest difference that is possible for all pairs of light sources, which may be formed from the fourth light source and a respective one of the remainder of the plurality of light sources.

The fourth and sixth light sources may be arranged at a small distance from each other, e.g. at a distance which is smaller than <NUM>. The fourth and sixth light sources may even be arranged abutting each other. When the fourth and sixth light sources are arranged at such a small distance from each other, there is a large overlap of the light emissions, which are emitted by the two light sources. This overlap results in an efficient blending of the light emissions having different colors, which are emitted by the fourth and sixth sources. This efficient blending results in a homogeneous illumination, even if the difference between the illuminating properties, in particular between the chromaticities, of the two light sources is large.

In an embodiment, the plurality of light sources include at least one white light source, which is configured for emitting white light. White light may be defined as a region within a color space, in particular as a region within the CIE1976 color space.

White light may, for example, be defined as the region within the CIE1976 color space which is centered at the point u'=<NUM> and v'=<NUM> of the CIE1976 color space. The region, which defines the white light, may have a radius in the range of between <NUM> and <NUM> in the CIE1976 color space.

According to the invention, said at lest one white light source is disregarded when the light sources are successively selected for forming pairs of light sources having the smallest or largest difference between their illuminating properties, as it has been described before. Instead, the at least one white light source may be assigned to the last free position(s) on the light module, after all other light sources from the plurality of light sources have been assigned to their respective positions within the light module.

The white light, which is emitted by a white light source, may have a much larger intensity than the light, which is emitted by other light sources, which are configured for emitting colored light, such as red, blue, cyan, amber or green light.

In consequence, the chromaticity of light, which is emitted by a white light source, is not really comparable with the chromaticity of light, which is emitted by such other light sources. It is therefore beneficial to exclude a white light source from said comparison and to assign said at least one white light source to the last free position(s) within the light module, after all other light sources from the plurality of light sources have been assigned to their respective positions within the light module.

In an embodiment, the plurality of light sources are LEDs, or each of the plurality of light sources comprises at least one LED. LEDs provide reliable and efficient light sources, which are available at low costs. The light sources may further comprise optical elements, such as reflectors or lenses, for forming the light output provided by the light sources. It is also possible that the light module comprises one or more optical elements, such as reflectors or lenses, which affect(s) the light output of multiple or all of the plurality of light sources.

In an embodiment, the light module comprises six light sources. Light modules comprising six light sources, which are configured for emitting light of different colors, have been found as well suited for providing a wide variety of differently colored illuminations.

In an embodiment, the light sources, when listed in an order, which corresponds to the sequence of the light sources in the array of light sources, are configured to emit light having the following colors: amber, blue, cyan, white, green, orange.

In an embodiment, the light sources, when listed in an order, which corresponds to the sequence of the light sources in the array of light sources, are configured to emit light having the following colors: red, blue, green, white, cyan, amber.

In an embodiment, the light sources, when listed in an order, which corresponds to the sequence of the light sources in the array of light sources, are configured to emit light having the following colors: green, blue, amber, white, red, cyan.

Light modules, in which the light sources are arranged in one of the above mentioned sequences, are well suited for providing elongated interior aircraft lights, which are able to provide a wide variety of differently colored illuminations, wherein the risk of generating unpleasant or disturbing spots at the interfaces or gaps between adjacent light modules is considerably reduced.

The above mentioned sequences are, however, only exemplary. The principles of arranging the light sources within the light modules, which have been described before, may result in different sequences of the light sources, if other light sources, which emit light of other chromaticities, are used.

Further exemplary embodiments of the invention are described in the following with respect to the accompanying drawings, wherein:.

<FIG> depicts a schematic side view of an aircraft <NUM>, in particular of an air plane, in accordance with an exemplary embodiment of the invention. In the exemplary embodiment shown in <FIG>, the aircraft <NUM> is a large passenger air plane, comprising a cockpit <NUM> and a passenger cabin <NUM>. The aircraft <NUM> may be a commercial passenger air plane, a private air plane, or a military aircraft. It is also possible that the aircraft is a rotorcraft, such as a helicopter.

<FIG> shows a schematic longitudinal cross-sectional view of a section of the passenger cabin <NUM> of the aircraft <NUM>, which is shown in <FIG>.

Four seats <NUM>, which are also referred to as passenger seats <NUM>, are visible in <FIG>. The passenger seats <NUM> comprise arm rests <NUM> and are mounted to a floor <NUM> of the passenger cabin <NUM>. Each of the depicted passenger seats <NUM> belongs to a different seat row 80a-80d. The seat rows 80a-80d are spaced apart from each other along the longitudinal direction LD of the passenger cabin <NUM>.

For each of the seat rows 80a-80d, a window 108a-108d is provided, which allows the passengers to view the outside of the aircraft <NUM>. Further, a plurality of overhead baggage compartments <NUM>, which provide storage space for the passengers' baggage, are provided above the passenger seats <NUM>.

Each seat row 80a-80d may include a plurality of passenger seats <NUM>, for example three passenger seats <NUM>, which are arranged next to each other along a lateral direction T, which is orthogonal to the longitudinal direction LD. The additional passenger seats, i.e. the middle seat and the window seat, of each seat row 80a-80d are not visible in <FIG>, as they are arranged behind and therefore hidden by the depicted aisle seats <NUM>. The hidden passenger seats are visible in <FIG>, which will be discussed in detail further below.

An aircraft overhead passenger service unit (PSU) 109a-109d is provided above each of the seat rows 80a-80d, respectively.

One or more elongated interior aircraft lights in accordance with exemplary embodiments of the invention may be arranged in the depicted section of the passenger cabin <NUM>. In particular, there may be one or more aircraft passenger cabin lights, which are examples of elongated interior aircraft lights in accordance with exemplary embodiments of the invention and which are not visible in <FIG>. The aircraft passenger cabin lights may extend in the longitudinal direction LD behind the aircraft overhead passenger service units 109a-109d and/or behind / above the overhead baggage compartments <NUM>. An example of such an elongated interior aircraft light is shown in <FIG>.

<FIG> depicts a schematic partial cross-sectional view of the passenger cabin <NUM> in a plane which is oriented in a lateral direction, i.e. in a plane which is orthogonal to the plane of the longitudinal cross-sectional view depicted in <FIG>.

<FIG> shows a single seat row 80a comprising three passenger seats <NUM>, which are arranged next to each other along the lateral direction T.

An overhead baggage compartment <NUM> and a passenger service unit 109a are installed above the seat row 80a.

An aircraft passenger cabin light <NUM>, which is an an example of an elongated interior aircraft light in accordance with an exemplary embodiment of the invention, is installed above the passenger seats <NUM>. The exemplary aircraft passenger cabin light <NUM> of <FIG> is configured for providing general cabin wall illumination.

The aircraft passenger cabin light <NUM> is arranged at or next to a side wall <NUM> of the passenger cabin <NUM> and extends along the longitudinal direction LD of the passenger cabin <NUM>, i.e. it extends orthogonal to the drawing plane of <FIG>. The exemplary aircraft passenger cabin light <NUM> may extend along a plurality of seat rows 80a along the longitudinal direction LD or may have an extension that is comparable to a single seat row spacing.

In the following, the details of an elongated interior aircraft light <NUM> according to an exemplary embodiment of the invention will be discussed.

<FIG> depicts a schematic view of an elongated interior aircraft light <NUM> according to an exemplary embodiment of the invention.

The elongated interior aircraft light <NUM> comprises three elongated light modules <NUM>, <NUM>, <NUM>, which are arranged next to each other forming an array of elongated light modules <NUM>, <NUM>, <NUM>.

In the exemplary embodiment depicted in <FIG>, the light modules <NUM>, <NUM>, <NUM> are arranged along a straight line A. In alternative embodiments, which are not explicitly shown in the figures, the light modules <NUM>, <NUM>, <NUM> may be arranged on a curved line or in a another configuration, in which the light modules <NUM>, <NUM>, <NUM> are arranged next to each other forming an elongated interior aircraft light <NUM>.

The number of three light modules <NUM>, <NUM>, <NUM>, as depicted in <FIG>, is exemplary as well. In further embodiments, which are not explicitly shown in the figures, the elongated interior aircraft light <NUM> may comprise only two or more than the depicted three light modules <NUM>, <NUM>, <NUM>. The elongated interior aircraft light <NUM> may in particular comprise between ten and twenty or even more light modules.

The elongated interior aircraft light <NUM> may extend along a single seat row 80a-80d or along a plurality of seat rows 80a-80d. It is possible that a plurality of like elongated interior aircraft lights are arranged in a row-like arrangement and that the plurality of elongated interior aircraft lights jointly extend along all seat rows within the passenger cabin <NUM>.

Although it is not explicitly shown in the figures, elongated interior aircraft lights according to exemplary embodiments of the invention may also be installed in other parts of the aircraft <NUM>, such as galleys, washrooms and/or toilets.

Each light module <NUM>, <NUM>, <NUM> may have a length L in the range of between <NUM> and <NUM>, in particular a length L in the range of between <NUM> and <NUM>, more particularly a length L of <NUM>.

Each light module <NUM>, <NUM>, <NUM> may have a width W in the range of between <NUM> and <NUM>, in particular a width W of between <NUM> and <NUM>.

Gaps <NUM> may be formed between adjacent light modules <NUM>, <NUM>, <NUM>. The gaps <NUM> may have an extension d of between <NUM> and <NUM>, in particular an extension d of between <NUM> and <NUM>. The extensions of the gaps <NUM> are defined as the spacing between adjacent light modules in a longitudinal direction LD.

Each of the light modules <NUM>, <NUM>, <NUM> comprises a plurality of light sources <NUM>-<NUM>, in particular six light sources <NUM>-<NUM>, which are arranged as an array of light sources <NUM>-<NUM>, extending along a longitudinal direction LD.

In the exemplary embodiment depicted in <FIG>, the light sources <NUM>-<NUM> are arranged on the straight line A. In alternative embodiments, which are not explicitly shown in the figures, the light sources <NUM>-<NUM> may be arranged on curved lines or on zig-zag lines, as long as the array of light sources <NUM>-<NUM> extends predominantly in the longitudinal direction LD.

The number of six light sources <NUM>-<NUM> is exemplary as well. In further embodiments, which are not explicitly shown in the figures, each light module <NUM>, <NUM>, <NUM> may comprise more or less than six light sources <NUM>-<NUM>, respectively.

The light sources <NUM>-<NUM> may be LEDs, or each of the light sources <NUM>-<NUM> may comprise at least one LED, respectively.

The light sources <NUM>-<NUM> may further comprise optical elements, such as reflectors or lenses, which are not shown in <FIG>.

According to an exemplary embodiment of the invention, the light sources <NUM>-<NUM> have different illuminating properties. The light sources <NUM>-<NUM> are in particular configured for emitting light of different colors. Using light sources <NUM>-<NUM>, which are configured for illuminating light of different colors, allows for selectively adjusting the color of the light, which is emitted by each light module <NUM>, <NUM>, <NUM>, by selectively switching and/or dimming the individual light sources <NUM>-<NUM> of each light module <NUM>, <NUM>, <NUM>. This may allow for selectively changing the illumination of the passenger cabin <NUM>, in which the elongated interior aircraft light <NUM> is installed.

Using light sources <NUM>-<NUM>, which emit light having different colors, may, however, result in the formation of unpleasant or disturbing spots due to the interfaces or gaps <NUM> between adjacent light modules <NUM>, <NUM>, <NUM>. These unpleasant or disturbing spots may include over-pronunciations of a single color or a mixed color that becomes prominent along a section of otherwise homogeneous illumination of the passenger cabin <NUM> provided by the light modules <NUM>, <NUM>, <NUM>. In the example of a wall illumination light, the imperfect mixing of colors, which may result from the gaps <NUM> between adjacent light modules, may generate spots or regions of uneven and potentially unpleasant / disturbing illumination of the cabin wall. The uneven illumination may catch an observer's attention and may distract the passengers and/ or cabin crew from their tasks during the flight, potentially even in emergency situations.

It is therefore beneficial to arrange the light sources <NUM>-<NUM> within each of the light modules <NUM>, <NUM>, <NUM> in a sequence, which reduces or even minimizes the risk of generating such unpleasant or disturbing spots / regions in the light output due to the interfaces or gaps <NUM> between adjacent light modules <NUM>, <NUM>, <NUM>.

In the exemplary embodiment depicted in <FIG>, each of the light modules <NUM>, <NUM>, <NUM> comprises a first light source <NUM>, which is arranged close to a first end 41a, 42a, 43a of the respective light module <NUM>, <NUM>, <NUM>, and a second light source <NUM>, which is arranged close to a second end 41b, 42b, 43b of the respective light module <NUM>, <NUM>, <NUM>. In the drawing plane of <FIG>, the first ends 41a, 42a, 43a of the light modules <NUM>, <NUM>, <NUM> are oriented to the left side, and the second ends 41b, 42b, 43b of the light modules <NUM>, <NUM>, <NUM> are oriented to the right side, respectively. In an alternative configuration, which is not explicitly shown in the figures, the first ends 41a, 42a, 43a of the light modules <NUM>, <NUM>, <NUM> may be oriented to the right side, and the second ends 41b, 42b, 43b of the light modules <NUM>, <NUM>, <NUM> may be oriented to the left side, respectively.

In the exemplary embodiment depicted in <FIG>, each of the light modules <NUM>, <NUM>, <NUM> has exactly six light sources <NUM>-<NUM>. The six light sources <NUM>-<NUM> form a predefined set of light sources <NUM>-<NUM>. The predefined set of light sources <NUM>-<NUM> may have been chosen in accordance with any sort of suitable criteria. For example, it is possible that the predefined set of light sources <NUM>-<NUM> has been put together, in order to enable a particular range of colors via the color mixing of the specific six light sources <NUM>-<NUM>.

According to exemplary embodiments of the invention, the plurality of light sources <NUM>-<NUM> are not arranged in an arbitrary manner. Rather, in exemplary embodiments of the invention, the plurality of light sources or at least some of the plurality of light sources may be arranged in an elaborate sequence / order. From a design point of view, the six light sources <NUM>-<NUM> form a reservoir of light sources that may be arranged in a desired sequence / order. The six light sources <NUM>-<NUM> can therefore also be seen and referred to as a stock of light sources that is available for designing and manufacturing a light module.

In the exemplary embodiment of <FIG>, each of the light modules <NUM>, <NUM>, <NUM> is formed from the same predefined set of light sources <NUM>-<NUM>. In other words, similar stocks of light sources <NUM>-<NUM>, i.e. stocks of light sources <NUM>-<NUM>, in which each stock comprises the same types of light sources <NUM>-<NUM>, are used for the light modules <NUM>, <NUM>, <NUM> of an elongated interior aircraft light <NUM> according to an exemplary embodiment of the invention. With respect to the illuminating properties, such as the colors or the chromaticities of the light, which is emitted by the light sources <NUM>-<NUM>, each of the light modules <NUM>, <NUM>, <NUM> comprises the same combination of light sources <NUM>-<NUM>, and the different light sources <NUM>-<NUM> are arranged in the same order in each of the light modules <NUM>, <NUM>, <NUM>.

The sequence / order of the light sources <NUM>-<NUM> within each of the light modules <NUM>, <NUM>, <NUM> is set based on the illuminating properties of the plurality of light sources <NUM>-<NUM>. The illuminating properties, which are considered for setting the order of the light sources <NUM>-<NUM>, may include the chromaticity and/or the hue and/or the saturation and/or the intensity of the light, which is emitted by the light sources <NUM>-<NUM>, when they are operated.

According to an embodiment of the invention, the first and second light sources <NUM>, <NUM>, which are arranged at the first and second ends 41a, 42a, 43a, 41b, 42b, 43b of the light modules <NUM>, <NUM>, <NUM>, are selected from the stock of light sources <NUM>-<NUM>, which are used for the respective light module <NUM>, <NUM>, <NUM>, so that a difference of the illuminating properties between the first and second light sources <NUM>, <NUM> is the smallest difference that is possible between all potential pairs of light sources <NUM>-<NUM> in the stock of light sources <NUM>-<NUM>.

The difference of the illuminating properties may for example be defined as a weighted sum of the difference(s) of chromaticity and/or hue and/or saturation and/ or intensity between the respective light sources.

The difference of the illuminating properties may also be defined as the distance between the chromaticities between the respective light sources in a predefined color space, in particular in the CIE1976 color space.

<FIG> depicts a diagram of the CIE1976 color space, in which the coordinates u', v' of the chromaticities of light, which is emitted by the light sources <NUM>-<NUM> of first and second exemplary selections of six different light sources, are plotted. As is known to a skilled person familiar with the CIE1976 diagram, the numbers <NUM>, <NUM>,. , <NUM>, <NUM>, listed along the c-shaped left line around the area containing the different chromaticities, denote the wavelengths of the respective colors, given in nm.

In <FIG>, the coordinates u', v' of the chromaticities of light, which is emitted by the light sources <NUM>-<NUM> of a first exemplary selection of the six different light sources <NUM>-<NUM>, are plotted as dots in the CIE1976 color space.

<FIG> depicts a table, which comprises the coordinates u', v' of the chromaticities of the light, which is emitted by the light sources <NUM>-<NUM> of the first exemplary selection of six different light sources, in the CIE1976 color space.

The six different light sources <NUM>-<NUM> are configured for emitting light of six different colors, in particular "Blue", "Cyan", "Green", "Amber", "Red", and "White".

<FIG> depicts a table, in which each entry indicates a distance in the CIE1976 color space between the chromaticities of the light, which is emitted by a pair of light sources, as it is defined by the row and column of the respective entry. The table comprises fifteen entries, one entry for every possible pair of light sources, which may be formed from the exemplary first selection of six different light sources <NUM>-<NUM>.

In the following steps, the light source that is configured for emitting "White" light is not considered, as it emits light having a much higher intensity than the other light sources. Therefore, its light emission is not directly comparable to the other light sources.

"White light" may be defined as a region of chromaticities within a color space, in particular within a region within the CIE1976 color space, more in particular as a region around the point u'=<NUM> and v'=<NUM> in the CIE1976 color space. The region, which defines the "white light", may have a radius in the range of between <NUM> to <NUM> in the CIE1976 color space, as may be appreciated in See <FIG>.

The table, which is depicted in <FIG>, shows that, when the light source, which is configured for emitting "White" light, is excluded, the distance of <NUM> between the chromaticities between the light source, which is configured for emitting "Red" light, and the light source, which is configured for emitting "Amber" light, is the smallest distance among all possible pairs of light sources <NUM>-<NUM>.

The light source emitting "Red" light is selected as the first light source <NUM>, and the light source emitting "Amber" light is selected as the second light source <NUM>, at is is depicted in <FIG>. Alternatively, the light source emitting "Amber" light could be selected as the first light source <NUM>, and the light source emitting "Red" light could be selected as the second light source <NUM>.

In a next step, a third light source <NUM>, which is to be arranged next to the first light source <NUM>, is selected from the remainder of the stock of light sources, i.e. from the plurality of light sources except for the "White" light source and except for the "Red" and "Amber" light sources, which have already been selected as the first and second light sources <NUM>, <NUM>.

The third light source <NUM> is selected from the remainder of the stock of light sources so that the difference of the illuminating properties between the first light source <NUM> and the third light source <NUM> is the largest difference that is possible for all potential pairs of light sources that may be formed from the first light source <NUM>, i.e. the "Red" light source, and the remaining light sources, i.e. the "Blue", "Cyan", and "Green" light sources.

<FIG> shows that the largest possible difference, having a value of <NUM>, is present, when the light source emitting "Blue" light is selected as the third light source <NUM>. Thus, the light source emitting "Blue" light is selected as the third light source <NUM> and arranged next to the first ("Red") light source <NUM>, as it is depicted in <FIG>.

In a next step, a fourth light source <NUM>, which is to be arranged next to the second light source <NUM>, is selected from the remainder of the stock of light sources, i.e. from the plurality of light sources except for the "White" light source and except for the "Red", "Amber", and "Blue" light sources, which have already been selected as the first, second, and third light sources <NUM>, <NUM>, <NUM>.

The fourth light source <NUM> is selected from the remainder of the stock of light sources so that the difference of the illuminating properties between the second light source <NUM> and the fourth light source <NUM> is the largest difference that is possible for all potential pairs of light sources that may be formed from the second light source <NUM>, i.e. the "Amber" light source, and the remaining light sources, i.e. the "Cyan" and "Green" light sources.

<FIG> shows that the largest possible difference, having a value of <NUM>, is present when the light source emitting "Cyan" light is selected as the fourth light source <NUM>. Thus, the light source emitting "Cyan" light is selected as the fourth light source <NUM> and arranged next to the second ("Amber") light source <NUM>, as it is depicted in <FIG>.

In a next step, a fifth light source <NUM>, which is to be arranged next to the third light source <NUM>, is selected from the remainder of the stock of light sources, i.e. from the plurality of light sources except for the "White" light source and except for the "Red", "Amber", "Blue" and "Cyan" light sources, which have already been selected as the first, second, third, and fourth light sources <NUM>-<NUM>.

The fifth light source <NUM> is selected from the remainder of the stock of light sources so that the difference of the illuminating properties between the third light source <NUM> and the fifth light source <NUM> is the largest difference that is possible for all potential pairs of light sources <NUM>-<NUM> that may be formed from the third light source <NUM>, i.e. the "Blue" light source, and the remaining light sources.

With the "White" light source being disregarded for the selection process, only the "Green" light source is left, as can be seen in the table of <FIG>, and above described selection - by default - leads to the "Green" light source being selected as the fifth light source <NUM>. The "Green" light source is arranged next to the third ("Blue") light source <NUM>, as it is depicted in <FIG>.

If the light module comprises more than six light sources, the steps, which have been described with respect to <FIG>, may be repeated for all additional light sources, which are comprised in the stock of light sources, until no light source or only the "White" light source(s) is/are left.

In the exemplary embodiment having the first exemplary selection of six light sources <NUM>-<NUM>, as introduced above, the light source emitting "White" light is arranged at the last free position within the light module <NUM>, <NUM>, <NUM>. In the embodiment shown in <FIG>, the light source emitting "White" light is arranged as the sixth light source <NUM> in the final empty position between the fourth ("Cyan") light source <NUM> and fifth ("Green") light source <NUM>.

<FIG> depicts a schematic view of an elongated interior aircraft light <NUM> in accordance with an exemplary embodiment of the invention, the elongated interior aircraft light <NUM> comprising three light modules <NUM>, <NUM>, <NUM>. In each light module <NUM>, <NUM>, <NUM>, the six light sources <NUM>-<NUM> are arranged in the order, which has been described above with reference to <FIG>.

In each of the light modules <NUM>, <NUM>, <NUM>, the six light sources <NUM>-<NUM> are arranged in a sequence comprising from left to right: the first light source <NUM> emitting "Red" light, the third light source <NUM> emitting "Blue" light, the fifth light source <NUM> emitting "Green" light, the sixth light source <NUM> emitting "White" light, the fourth light source <NUM> emitting "Cyan" light, and the second light source <NUM> emitting "Amber" light.

In an elongated interior aircraft light <NUM>, as it is depicted in <FIG>, the risk of generating an uneven illumination and/or unpleasant or disturbing spots / regions in the light output due to the interfaces or gaps <NUM> between adjacent light modules <NUM>, <NUM>, <NUM> is considerably reduced, since light sources <NUM>, <NUM>, which emit light of similar chromaticities, i.e. chromaticities, which are located close to each other in the CIE1976 color space, are employed as the first and second light sources <NUM>, <NUM> on both sides of the interfaces or gaps <NUM>.

<FIG> depicts a table comprising the coordinates u', v' of the chromaticities of the light, which is emitted by the light sources <NUM>-<NUM> of the second exemplary selection of six different light sources <NUM>-<NUM>, in the CIE1976 color space.

In <FIG>, the coordinates u', v' of the chromaticities of light, which is emitted by the light sources <NUM>-<NUM> of the second exemplary selection of the six different light sources <NUM>-<NUM>, are plotted as squares in the CIE1976 color space.

Again, the six light sources <NUM>-<NUM> are configured for illuminating light of six different colors, namely "Blue", "Cyan", "Green", "Amber", "Red", and "White". The colors are defined by their respective coordinates u', v' in the CIE1976 color space.

Although the names of the colors are identical to the names of the colors of the first example, which is depicted in <FIG>, it is noted that the coordinates u', v' of the light, which is emitted by the light sources <NUM>-<NUM> of the second exemplary selection, differ from the coordinates u', v' of the light, which is emitted by the light sources <NUM>-<NUM> of the first exemplary selection.

The first and second exemplary selections of light sources <NUM>-<NUM> may, for example, represent light sources, in particular LEDs <NUM>-<NUM>, which are provided by two different manufactures and which therefore emit light of different chromaticities.

Due to the different chromaticities, which are represented by different coordinates u', v' in the CIE1976 color space, the order, in which the light sources <NUM>-<NUM> are arranged in the light modules <NUM>, <NUM>, <NUM> is different, when the same procedure, as it has been described before with respect to <FIG>, is applied to the light sources <NUM>-<NUM> of the second exemplary selection according to <FIG>.

<FIG> depicts a table, in which each entry indicates a distance in the CIE1976 color space between the chromaticities of the light, which is emitted by a pair of light sources, as it is defined by the row and column of the respective entry. The table comprises fifteen entries, one entry for every possible pair of light sources, which may be formed from the second exemplary selection of six different light sources <NUM>-<NUM>.

Again, the light source that is configured for emitting "White" light is not considered in the following steps, as it emits "White" light, which has a much higher intensity than the other light sources.

The table depicted in <FIG> shows that, when the light source emitting "White" light is excluded, the distance between the chromaticities between the light source emitting "Green" light and the light source emitting "Cyan" light, having a value of <NUM>, is the lowest among all possible pairs of light sources <NUM>-<NUM>.

The light source emitting "Green" light is selected as the first light source <NUM>, and the light source emitting "Cyan" light is selected as the second light source <NUM>, see <FIG>. Alternatively, the light source emitting "Cyan" light could be selected as the first light source <NUM>, and the light source emitting "Green" light could be selected as the second light source <NUM>.

In the following step, a third light source <NUM>, which is to be arranged next to the first light source <NUM>, is selected from the remainder of the stock of light sources, i.e. from the second exemplary selection of light sources <NUM>-<NUM> except for the light sources emitting "White" light, "Green" light and "Cyan" light, which have already been selected.

The third light source <NUM> is selected from the remainder of the stock of light sources so that the difference of the illuminating properties between the first light source <NUM> and the third light source <NUM> is the largest difference that is possible for all potential pairs of light sources that may be formed from the first light source <NUM>, i.e. the "Green" light source, and the remainder of the stock of light sources, i.e. the "Blue", "Amber", and "Red" light sources.

In the present case, the light source emitting "Blue" light is selected as the third light source <NUM>.

In a next step, a fourth light source <NUM>, which is arranged next to the second light source <NUM>, is selected from the remainder of the stock of light sources, i.e. from the second exemplary selection of light sources <NUM>-<NUM> except for the light sources emitting "White" light, "Green" light, "Cyan" light and "Blue" light.

The fourth light source <NUM> is selected from the remainder of the stock of light sources so that the difference of the illuminating properties between the second light source <NUM> and the fourth light source <NUM> is the largest difference that is possible for all potential pairs of light sources that may be formed from the second light source <NUM>, i.e. the "Cyan" light source, and the remainder of the stock of light sources, i.e. the "Amber" and "Red" light sources.

In the present case, the light source emitting "Red" light is selected as the fourth light source <NUM>.

In a next step, a fifth light source <NUM>, which is arranged next to the third light source <NUM>, is selected from the remainder of the stock of light sources, i.e. from the second exemplary selection of light sources <NUM>-<NUM> except for the light sources emitting "White" light, "Green" light, "Cyan" light, "Blue" light and "Red" light.

The fifth light source <NUM> is selected from the remainder of the stock of light sources so that the difference of the illuminating properties between the third light source <NUM> and the fifth light source <NUM> is the largest difference that is possible for all potential pairs of light sources that may be formed from the third light source <NUM>, i.e. the "Blue" light source, and the remainder of the stock of light sources.

In the present case, the light source emitting "Amber" light is - by default - selected as the fifth light source <NUM>.

If the light module comprises more than six light sources, the previous steps of selecting the next light sources, i.e. the steps of selecting the third and ensuing light sources, may be repeated for all additional light sources, which are comprised in the stock of light sources <NUM>-<NUM>, until no light source or only the light source(s) emitting "White" light is/are left.

If only the light source(s) emitting "White" light is/are left, this light source / these light sources is/are arranged within the last empty position(s) of the light module <NUM>, <NUM>, <NUM>. In the embodiment depicted in <FIG>, the light source emitting "White" light is arranged as the sixth light source <NUM> between the fourth ("Red") light source <NUM> and the fifth ("Amber") light source <NUM>.

The described procedure results in an elongated interior aircraft light <NUM> with the configuration of the light modules <NUM>, <NUM>, <NUM> that is depicted in <FIG>.

In each of the light modules <NUM>, <NUM>, <NUM>, the six light sources <NUM>-<NUM> are arranged in a sequence, which comprises from left to right: the first light source <NUM> emitting "Green" light, the third light source <NUM> emitting "Blue" light, the fifth light source <NUM> emitting "Amber" light, the sixth light source <NUM> emitting "White" light, the fourth light source <NUM> emitting "Red" light, and the second light source <NUM> emitting "Cyan" light.

Claim 1:
Light module (<NUM>, <NUM>, <NUM>) for an elongated interior aircraft light (<NUM>), the light module (<NUM>, <NUM>, <NUM>) comprising:
a plurality of light sources (<NUM>-<NUM>), each of which configured for emitting light having different illuminating properties and arranged next to each other, forming an array of light sources (<NUM>-<NUM>) extending as a sequence of light sources (<NUM>-<NUM>) along a longitudinal direction, LD, between a first end (41a, 42a, 43a) of the light module and a second end (41b, 42b,
43b) of the light module;
wherein the plurality of light sources (<NUM>-<NUM>) include a first light source (<NUM>),
which is arranged at the first end (41a, 42a, 43a) of the light module, and a second light source (<NUM>), which is arranged at the second end (41b, 42b, 43b) of the light module, and a white light source;
characterized in that a difference in illuminating properties between the first and second light sources (<NUM>-<NUM>) is the smallest possible from all potential pairs of light sources (<NUM>-<NUM>) formed from the plurality of light sources (<NUM>-<NUM>), disregarding the white light source (<NUM>);
wherein the difference in the illuminating properties is a function of the difference in chromaticity and/or in hue and/or in saturation and/or in intensity between the respective light sources (<NUM>-<NUM>).