WO2011154756A2 - Method for constructing a lighting device with discrete light sources and thus obtained lighting device - Google Patents
Method for constructing a lighting device with discrete light sources and thus obtained lighting device Download PDFInfo
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- WO2011154756A2 WO2011154756A2 PCT/HU2011/000052 HU2011000052W WO2011154756A2 WO 2011154756 A2 WO2011154756 A2 WO 2011154756A2 HU 2011000052 W HU2011000052 W HU 2011000052W WO 2011154756 A2 WO2011154756 A2 WO 2011154756A2
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- light sources
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21V—FUNCTIONAL FEATURES OR DETAILS OF LIGHTING DEVICES OR SYSTEMS THEREOF; STRUCTURAL COMBINATIONS OF LIGHTING DEVICES WITH OTHER ARTICLES, NOT OTHERWISE PROVIDED FOR
- F21V19/00—Fastening of light sources or lamp holders
- F21V19/001—Fastening of light sources or lamp holders the light sources being semiconductors devices, e.g. LEDs
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21W—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO USES OR APPLICATIONS OF LIGHTING DEVICES OR SYSTEMS
- F21W2131/00—Use or application of lighting devices or systems not provided for in codes F21W2102/00-F21W2121/00
- F21W2131/10—Outdoor lighting
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21W—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO USES OR APPLICATIONS OF LIGHTING DEVICES OR SYSTEMS
- F21W2131/00—Use or application of lighting devices or systems not provided for in codes F21W2102/00-F21W2121/00
- F21W2131/10—Outdoor lighting
- F21W2131/103—Outdoor lighting of streets or roads
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F21—LIGHTING
- F21Y—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED
- F21Y2113/00—Combination of light sources
Abstract
The invention relates to a method for constructing a lighting device (100) with a light source configuration optimized with respect to one or more criteria in order to solve an arbitrarily defined illumination problem, in particular, a lighting device (100) comprising light emitting diodes as elementary light sources (10). The invention also relates to the lighting device (100) obtained by the method. In the method, a supporting panel (101) is prepared from a sheet material by metal forming, said supporting panel (101) conforms to the light source configuration optimized for the illumination problem, wherein said configuration is obtained by a previously executed two-step optimization process. Next, the elementary light sources (10) with light emission directions corresponding to the optimized configuration are mounted onto the supporting panel (101), and then said supporting panel (101) with the elementary light sources (10) is arranged in a region defined by the casing (1 1 1) and the base sheet, being translucent at least in a portion thereof, of the lighting device (100) so as to be capable of emitting light through the translucent portion of the base sheet.
Description
METHOD FOR CONSTRUCTING A LIGHTING DEVICE WITH DISCRETE LIGHT SOURCES AND
THUS OBTAINED LIGHTING DEVICE
The present invention relates to a method for constructing a lighting device with discrete elementary light sources, as well as the thus obtained lighting device. In particular, the in- vention relates to a method for constructing a lighting device with a light source configuration that is optimized with respect to one or more pre-set criteria in order to solve an arbitrarily defined illumination problem, wherein the discrete elementary light sources are preferentially light emitting diodes (LED). The invention also relates to the lighting device itself, in particular to a public lighting luminaire (street and/or road lamp) prepared by the method, as well as to a supporting panel forming part of said lighting device.
Nowadays, the extent of energy consumption and the dissipation of electric energy closely related to it represent a problem that is getting more and more alarming. This is extremely true if lighting is considered, wherein only a fraction of the consumed energy is used in the form of light - the remaining portion gets into the environment essentially as heat, that is, in most cases it can be practically considered as a loss as far as recycling is concerned. Besides this loss, the excessive and irrational lighting, including particularly the illumination of roads, squares, etc., i.e. public lighting, also causes damages in many cases in the form of e.g. the luminous pollution of the environment.
As a result of developments in the field of semiconductor technology, a broad range of light emitting diodes (LEDs) has become attainable by the time being: LEDs of various color, light power, energy consumption, lighting characteristics, etc. are commercially available today. Therefore, the usage of semiconducting light emitting diodes that consume much less energy but are capable of much more intensive light emission compared to traditional light sources, such as bulbs and fluorescent lamps, becomes more and more common nowadays. A further advantage of the so-called LED lighting devices is that due to the small physical dimensions of the LEDs used as light sources therein, extremely compact lighting devices can be constructed with one or more LEDs. Moreover, if appropriate conditions (such as e.g. temperature, moisture content or humidity) are maintained, the lifetime of LEDs is much longer than that of traditional light sources, which means that servic- ing and maintenance of LED lighting devices are required much rarely.
Both International Publication Pamphlet No. WO2008/141493 and Chinese Patent Publication No. 201014327 Y disclose a public LED luminaire comprising a fixed number of elementary light sources (ranging from 4 to 12) and a lamp shade which carries said light sources in a detachably mounted manner. The lamp shade is designed with an inner surface that - when viewed from the direction of light emission - is eudipleural as a whole. Furthermore, its circumferential edge defines a horizontal plane and the design of the inner surface of said lamp shade is symmetrical to the longitudinal axis thereof. Said inner surface is composed of flat plates joining together in angles therebetween and oriented to various directions, wherein the angles of said flat plates formed with said horizontal plane (and hence with each other) fall into various domains of angles chosen experimentally. The elementary light sources used in the lamp are LED groups, wherein each of said LED groups is arranged on a separate flat plane. A heat radiator, preferably a cooling fin is mounted detachably onto each plate on a side thereof which locates opposite to the LED groups. Said heat radiators can be mounted separately onto the individual plates, one by one. Due to the orientation of the individual plates, the light emission directions of said LED groups form different angles with one another. Consequently, the illumination of a road surface that is lit up can improve. The LED groups are basically uniform as to their optical and illumination properties. It is apparent from the illumination charts of a rectangular area to be lit up by the lamp at issue (see Figures 6, 8 and 10 of the cited WO publi- cation document) that varying the light emission directions of the LED groups within the chosen domains of angles, the ratio of the luminous intensities measured in the darkest and in the brightest regions of said area is at least 1 :3 if the domains of angles set experimentally are used. This means that uniform illumination of the whole area to be lit up cannot be achieved if such a lamp is exploited in which the elementary light sources are practically uniform as to their optical and illumination properties and the position of the elementary light sources in the lamp, as well as the light emitting directions thereof are determined without taking actually into account the peculiarities of the area to be illuminated.
Australian Patent No. 2008201673 Bl discloses a lighting device comprising a lamp shade with an inner surface and discrete elementary light sources. The elementary light sources r are arranged on locating faces of the inner surface of the lamp shade, said locating faces are provided by flat plates of the inner surface, wherein each flat plate is defined by a different tangent angle of said inner surface. The illuminating beam of an elementary light
source is always perpendicular to the locating face that carries the elementary light source, and thereby the angle and dimension of the illumination can be controlled. The elementary light sources are specifically provided by LEDs. According to the disclosure, the number of the locating faces and the magnitude of the tangent angles are determined with a view of the desired angle of illumination or the type of the lamp, however, the patent document cited contains no further pieces of information as to the practical realization and theoretical aspects of this.
U.S. Patent No. 6,250,774 Bl teaches a lighting device constructed with a given number of discrete light sources of different lighting characteristics, said light sources being prepared with LED chips, for the effective illumination of a section of a public road in zones (strips) parallel to one another. Depending on the light directing optics used for the beam shaping of light emitted by the LED chips, preferably, three LED light sources with different lighting characteristics are applied in the lighting device. When the road section is lit up, the illumination within a certain zone is always performed by LED light sources of the same lighting characteristics in such a way that the light spots of the individual light sources overlap one another. Consequently, when going away from a single lighting device, it will create brighter and darker regions in turn within a zone alone, and thus the illumination of the road section by said lighting device cannot be considered uniform at all.
EP Patent No. 1,916,468 Al discloses a LED lamp comprising a fixture and different types of LED lighting units with various light distribution characteristics (narrow direction angle, wide direction angle and intermediate direction angle) arranged in said fixture so as to obtain a desired illumination of a surface to be lit up by said lamp. Every LED lighting unit is formed with a fixed number of elementary LED light sources, e.g. three pieces each, with the same light distribution characteristics. Each elementary LED light source comprises a LED of a given power ensuring the illumination and a light distribution modifying optical lens of various shape arranged in the path of the light emitted by the LED. The elementary LED light sources can be used to illuminate a surface either alone or in combination with each other in the form of said LED lighting units through oval light spots generated by said elementary LED light sources. The cited published document illustrates through various examples (see Examples 2 and 3, as well as corresponding Figures 18 and 21) that luminosity and light distribution of the illuminated surface can be modified by the number of LED lighting units applied and by the distribution according to type of said lighting units.
In the examples shown, the ratio of the luminous intensities measured in the brightest and darkest regions of the surface to be illuminated is at least about 1 :2.5, that is, uniformity of the illumination of the surface can be questioned.
Light distribution modifying lenses of the elementary LED light sources are adapted to the illumination problem in the following manner: the surface to be lit up by a certain elementary light source is divided into domains and then a lighting characteristics to be attained in the domain is determined for each domain. Then the shape of the surface of the light distribution modifying lens is chosen in such a way that the light entering, passing through and exiting from the lens during its propagation refract so as to result in the desired lighting characteristics. If the shape of the entrance surface of the lens in the propagation direction of the light emitted by the LED, the distance of the illuminating LED from the entrance surface, as well as the refraction index of the optical medium of the lens are known, the shape mentioned above is determined by a highly computing intensive and hence time consuming technique with the application of ray tracing. International Publication Pamphlet No. WO2004/008022 A2 discloses a method for the uniform illumination of surfaces with reflecting behavior falling between perfectly diffuse and perfectly specular. According to the method, a lighting means is constructed which lights up said surface in every single illuminated point thereof under the same illumination angle. To this end, in particular, discrete light sources, preferably LEDs, are assembled into a two-dimensional illumination surface. Each elementary light source of said illumination surface emits light in the same direction, thus to illuminate the surface uniformly, discrete light sources with essentially identical optical and illumination properties are required. A further drawback of the present solution is that only those surfaces can be lit up with said lighting device uniformly at a time that have dimensions commensurate to those of the il- lumination surface itself This renders practically impossible the application of this type of lighting devices for everyday illumination, such as e.g. the illumination of streets and/or public roads.
International Publication Pamphlet No. WO2009/012314 Al teaches a luminaire to illuminate a target region in conformity with an illumination problem, said luminaire comprising one or more reflecting surfaces and LEDs, as light sources, arranged within a plane in a specific geometry, as well as a method for constructing such luminaire. By performing said
method, the shape of the one or more reflecting surfaces, as well as the number and (spatial) distribution of LEDs required to solve the illumination problem posed can be obtained.
According to the method, the shape of a region to be illuminated on the target plane is de- termined as a start. Then, the spatial position of a luminaire to be constructed is defined relative to the chosen region to be lit up. In this step, a distance d from the luminaire to the target plane is also determined. Next, the desired measure of illuminance is specified at given locations of the area to be illuminated in the form of e.g. the value of luminous intensity per unit area (being, in general, constant across the whole area to be illuminated) in lm units; this way the illumination problem to be solved is fully defined. Knowing the distance d and the desired measure of illuminance at various locations of the region to be illuminated, light intensity distribution curves characteristic of the luminaire to be constructed are determined. As a next step, by exploiting the formula of E = l*cos30/d2, a reverse calculation is performed to determine the light intensity that should be emanated by the luminaire in a given direction Θ (angle of incidence) so as to achieve just the desired illuminance in the region to be illuminated along the direction Θ. Then, the number of LEDs to be used in the luminaire, as well as their respective output powers are determined so that the luminous intensity of the luminaire constructed from these LEDs approximates as closely as possible the maximum luminous intensity required to obtain the desired light in- tensity distribution curves for the region to be illuminated. Next, the LEDs are arranged at least along a curve and then the shapes of the additional optical element(s) (in this case, the one or more reflecting surfaces which are necessary) are determined so that they direct light incident thereon to attain or to approximate as closely as possible the aimed illuminance. As a result of this step, one or more lines of LEDs are obtained, along which line(s) the illumination direction of the LEDs changes form LED to LED relatively evenly. Finally, by means of computer simulations/modeling, the shapes of the LED line(s) and the reflecting surface(s) are determined, by making use of which the light intensity distributions related to the region to be illuminated represent the best approximation for the light intensity distribution to be achieved. In order to simplify the task of design, in the above method for designing the luminaire, the determination of the LED configuration takes place with the assumption that the luminaire is of fixed geometry. That is, the optimization at issue is performed with a view to a physi-
cal constraint: according to the examples discussed, the LEDs must be positioned along curves that are closed and basically concentric, as well as lie in the same plane. This limits the applicability of said design method enormously when an arbitrary illumination problem is to be solved. Moreover, the known techniques determine the number and the required power of the elementary light sources to be used in the luminaire through a reverse calculation starting with the light intensity to be obtained on the illuminated surface. Hence, the thus obtained configuration of elementary light sources cannot be considered optimal.
It is also well-known that LEDs can be manufactured with a great fluctuation as to their nominal properties (such as e.g. illumination characteristics, power, etc.). Consequently, due to this fluctuation of LEDs, a design method not taking the actual properties (i.e. which are measured in advance) of the LEDs available for the construction of the lighting device into account, cannot provide e.g. a uniform illumination over the target region chosen.
A further drawback of LED lighting devices is that the total heat generation of the elementary LED lighting sources concentrated within a relatively small volume in said devices is relatively high and therefore it is essential to provide appropriate heating of the light sources. Considering this issue, public lamps are extremely problematic. In these, besides the thermal load due to the LEDs used, a further thermal load of seasonal periodicity appears as well: in order to avoid overheating and thus a significant decrease in their life time, the nominal operational temperature of the LEDs should be maintained even if high outer temperatures characteristic of summer nights and high inner temperatures within the lighting fixture are present. In light of this, such public LED lamps should preferentially be manufactured, in which the combined thermal load of the LEDs applied is as low as possible. To this end, hence, it would also be preferred to decrease/optimize the amount of heat generated by the LEDs used in operation if a specific illumination problem is to be solved. In view of the above, the object of the present invention is to provide a method for designing/producing a lighting device with elementary light sources that results in an elementary light source configuration as the solution of a given illumination problem for a certain starting set of elementary light sources with given illumination characteristics, wherein by means of the elementary light source configuration a lighting device optimized in terms of one or more criteria/features specified as part of the illumination problem can be con-
structed. A further object of the present invention is to provide a lighting device that is optimized with respect to one or more criteria/features specified.
In particular, the object of the present invention is to provide a public, i.e. a street and/or road lamp, by means of which e.g. the uniform illumination of specifically a rectangular region to be lit up can be accomplished - the illumination achieved by said lamp is, in particular, more uniform than those obtainable by the lighting devices used nowadays.
Here, and from now on, the term„elementary light source" refers to the combination of a suitable light emitting element, e.g. a LED chip arranged on a substrate and equipped with appropriate electronics required for its operation and a light guiding means, e.g. an optical lens, arranged in the path of light emitted by said light emitting element and performing beam shaping/directing of said light (and thus resulting in a real lighting characteristics). Furthermore, the term„elementary light source configuration" refers to a given number of elementary light sources, wherein said light sources are optionally distributed with respect to their lighting characteristics (or type) and each light source is characterized by a well- defined light emission direction. Here, the term„light emission direction" of a single elementary light source refers to the direction identical with the optical axis of a given light source in which light emanates from said light source. Here, and from now on, for the sake of simplicity, elementary light sources with rotation-symmetric light plumes are assumed, this assumption, however, represents no severe limitation for the inventive solution, as it is clear to a person skilled in the relevant field. The term„defining an illumination problem", without any further limitations, refers to e.g. selecting the geometrical shape of an area to be illuminated, specifying the strength and/or distribution of illumination of said area (or at least a portion thereof), determining a starting set of various elementary light sources that can be used to obtain said illumination, selecting the spatial position of the lighting device with the elementary light sources relative to the area to be illuminated, as well as specifying at least one such criterion/feature related to the illumination of the area to be illuminated with respect to which the lighting device to be constructed can be considered optimized. Such a criterion/feature might be e.g. the extent of deviation from the desired luminous intensity if the illuminance of an area to be illuminated is considered. Further crite- ria/features will be apparent from the teaching of the present specification. Solving the illumination problem" means the determination/finding, by means of preferably a computer,
an elementary light source configuration that is optimal with respect to the specified feature^).
These objectives, on the one hand, are achieved by providing a method of determining an elementary light source configuration for lighting devices that is optimal with respect to one or more pre-set criteria, in accordance with Claim 1. Possible further preferred variants of the method are defined by Claims 2 to 5. The above objectives, on the other hand, are achieved by providing a method for preparing a lighting device with elementary light sources arranged in an optimized configuration tailored to the illumination problem, in accordance with Claim 6. A preferred further variant of the method is set forth in Claim 7. Moreover, the above objectives are achieved by preparing a supporting panel according to Claim 8 for a lighting device constructed with elementary light sources. A possible further preferred embodiment of the supporting panel concerned is defined by Claim 9. Finally, the above objectives are achieved by constructing a lighting device in accordance with Claim 10. Possible further preferred embodiments of the lighting device are set forth by Claims 1 1 to 14.
In the method according to the invention, in a first step, an illumination problem with given parameters is specified, i.e. the shape and the dimensions of a surface to be illuminated (which is preferably, but not necessary, is an in-plane surface), the position of the lighting device relative to the surface to be illuminated, as well as e.g. the parameters of a desired illumination of the area to be illuminated (e.g. the average illuminance thereof, the allowed maximal deviation from this latter value, etc.) are fixed. Then, in a second step of the method, a set of elementary light sources that can be used when solving the illumination problem is specified. To this end, elementary light sources, preferentially elementary LED light sources, with previously measured lighting characteristics and of given optical operating power are used. Next, modeling of the illuminance to be obtained is performed by means of optimizing the total number, the distribution with respect to type and the light emission directions of the elementary light sources, i.e. the elementary light source configuration used in the lighting device (assumed to be a point-like one, for the sake of simplicity) constructed from the elementary light sources available. This latter operation is carried out in two steps:
(a) by performing a discrete optimization algorithm (preferably, a so-called genetic algorithm) at reference points defined on the surface to be illuminated, a set of elementary light sources consisting of the necessary number and type of the light sources to solve the illumination problem is determined, and e.g. an approximate, i.e.„rough" fixing of the light emitting directions of the chosen elementary light sources is performed; and
(b) a continuous optimization algorithm (preferably, a Monte-Carlo type, preferentially a 'simulated annealing' like algorithm) is performed at said reference points so as to determine the optimized light source configuration by improving, i.e. by„fine tuning" the light emission directions of the elementary light sources of the set determined in step (a).
Steps (a) and (b) are performed by iterating a target function constructed by means of the parameters characteristic of the illumination problem specified.
Due to a significant decrease in computational labor required, the determination of a light source configuration that is optimized with respect to one or more criteria and/or features by means of the above combination of discrete and continuous optimization algorithms is highly preferred when solving the illumination problem defined. Due to the step of discrete optimization, in particular, it becomes also possible to take different types of elementary light sources into account that facilitates the determination of an elementary light source configuration providing uniform illuminance of the whole area to be illuminated.
Next, in the step of practical realization of the lighting device, according to the invention, optimized/adapted to a pre-set illumination problem, a supporting panel for accommodating the individual light sources in accordance with the optimized light source configuration determined is produced by per se known metal forming process(es), the elementary light sources are arranged, and optionally also affixed, on said supporting panel in the optimized light source configuration, and the thus obtained supporting panel with elementary light sources is then installed into a lighting device. The supporting panel concerned, when viewed from the light emission direction, forms a concave enveloping surface that is built up of continuously connected light source seatings that receive and secure individual light sources along with maintaining their respective light emission directions determined.
The lighting device according to the invention, optimized with respect to one or more arbi- trarily chosen criteria is produced then by arranging the elementary light sources in accor-
dance with the previously determined optimal light source configuration within a lighting fixture, specifically on a suitably formed supporting panel.
The elementary light sources of the optimal light source configuration are located preferably in one or more lines within the lighting device according to the invention; more prefer- ably, they (and the light source seatings accommodating them) form a three-dimensional array, and their light emission directions are determined so as to optimize the solution of the illumination problem defined with respect to the one or more pre-set criteria and/or features. Hence, the light emission directions are not constant, in general, that is, they change from location to location (i.e. from light source to light source) on the supporting panel. The invention is discussed in more detail with reference to the attached drawings, wherein
— Figure 1 shows a schematic flow diagram of a preferred variant of the method for preparing a lighting device according to the invention;
— Figures 2A and 2B illustrate in perspective front and back elevational views, respectively, a light source used in the inventive method as elementary light source, said light source comprising specifically a LED, as well as an optics arranged in the path of light emitted by the LED, specifically a light transmitting optical lens;
— Figures 3A to 3F illustrate in-plane lighting characteristics (angle/lux) measured under laboratory conditions of some exemplary elementary LED light sources within the initial set of light sources differing from one another (e.g. in lighting characteristics, operating power, etc.) that can be used when the inventive method is accomplished;
— Figure 4A shows in perspective view the light emission directions of the elementary light sources within an optimal light source configuration obtained by the method according to the present invention for illuminating uniformly a surface portion (M) with a given shape (in particular, rectangular) and dimensions (a = 35 m; b = 10 m) from a point (P) located above said surface portion (d = 1 m) at a given height (D = 10 m) measured from the plane (S) of said surface portion (for the sake of simplicity and clarity, illustrated merely for one half of said surface portion with taking into account plane symmetry of the configuration);
— Figures 4B and 4C represent, in side elevational view and plan view, respectively, the light emission directions of Figure 4A;
Figure 5 shows in perspective view the optimal light source configuration characterized by the light emission directions illustrated in Figure 4, wherein the elementary light sources constituting the members of said configuration are fixed onto the supporting panel obtained by the method illustrated in Figure 1 (here, the elementary light sources denoted by different numbers exhibit lighting characteristics differing from one another);
Figure 6A and 6B illustrate, in side and front elevational views, respectively, a possible embodiment of fixing the elementary light sources mounted onto the supporting panel;
Figure 7 illustrates the exemplary supporting panel shown in Figure 5 when installed into a lighting fixture of an embodiment of the lighting device prepared by the method according to the invention without a heat dissipation casing;
Figure 8 shows the lighting fixture of Figure 7 after installing said heat dissipation casing;
Figure 9 illustrates in various elevational views an exemplary lighting device constructed with the configuration of elementary light sources of a given initial set of light sources, wherein said configuration is optimized for the illumination problem discussed in relation with Figure 4 (Figures 9 A and 9B: back and front perspective elevational views, respectively; Figure 9C: bottom elevational view);
Figure 10A is the luminance chart of a surface portion illuminated in harmony with the exemplary illumination problem shown in Figure 4, said illumination chart is for a light source configuration obtained by optimization performed with an initial set of light sources comprising three different types of elementary light sources;
Figure 10B is the contour luminance chart of a surface portion illuminated in accordance with Figure 10A, wherein the intersections of the light emission directions of the elementary light sources corresponding to the optimal configuration with the plane of the illuminated surface portion are also indicated (here, the symbols x, +, o refer to the first, second and third, respectively, type of elementary light source);
Figure 11A is the luminance chart of a surface portion illuminated in harmony with the exemplary illumination problem shown in Figure 4, said illumination chart is for a light source configuration obtained by optimization performed with an initial set of light sources comprising four different types of elementary light sources;
— Figure 11 B is the contour luminance chart of a surface portion illuminated in accordance with Figure 11 A, wherein the intersections of the light emission directions of the elementary light sources corresponding to the optimal configuration with the plane of the illuminated surface portion are also indicated (here, the symbols x, +, o, refer to the first, second, third and fourth, respectively, type of elementary light source);
— Figure 12A is the luminance chart of a surface portion illuminated in harmony with the exemplary illumination problem shown in Figure 4, said illumination chart is for a light source configuration obtained by optimization performed with an initial set of light sources comprising five different types of elementary light sources;
— Figure 12B is the contour luminance chart of a surface portion illuminated in accordance with Figure 12 A, wherein the intersections of the light emission directions of the elementary light sources corresponding to the optimal configuration with the plane of the illuminated surface portion are also indicated (here, the symbols x, +, o, Φ refer to the first, second, third and fourth, respectively, type of elementary light source; in this case, the fifth type of elementary light source did not appear within the optimal light source configuration);
— Figure 13A is the luminance chart of a surface portion illuminated in harmony with the exemplary illumination problem shown in Figure 4, said illumination chart is for a light source configuration obtained by optimization performed with an initial set of light sources comprising six different types of elementary light sources; and
— Figure 13B is the contour luminance chart of a surface portion illuminated in accordance with Figure 13 A, wherein the intersections of the light emission directions of the elementary light sources corresponding to the optimal configuration with the plane of the illuminated surface portion are also indicated (here, the symbols x, +, o, Φ refer to the first, second, third and fourth, respectively, type of elementary light source).
When performing the steps of an embodiment of the method according to the invention, illustrated in Figure 1, to find a light source configuration optimized with respect to one or more given criteria, for example uniform illuminance of the surface to be illuminated is kept in mind. In said method, the necessary number of elementary light sources and the lighting direction of each light source, as well as the distribution of elementary light sources with respect to type (i.e. the optical element species applied in combination with
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13 the light sources) are determined via performing optimizing routines carried out preferentially in a computerized manner so that the illumination strength in each portion of the surface to be illuminated falls into the pre-set range. Accordingly, as the input, there is a need for data unambiguously defining the illumination problem concerned. That is, it is neces- sary to provide the dimensions of the surface area (here, in particular, of a rectangular shape) to be illuminated, the orientation of said surface relative to the lighting device comprising the elementary light sources to be used for the illumination, as well as the extent of deviation of illuminance, that is yet acceptable, expressed in units of %, relative to e.g. the average illuminance of the surface. Taking all this into account, in the method according to the invention, the light source configuration that will be used later on to construct a lighting device optimized with respect to one or more given criteria, in particular, to design and prepare a supporting panel of said lighting device, is obtained by optimizing the target function defined by the relation /y, ,, .r . /y ) - .4i
Here, in relation (1), N stands for the total number of elementary light sources present in the optimal configuration, refers to the z'-th elementary light source (here / e {7, TV }) of said configuration that emits a beam of light directing to a point with coordinates (x„ yi) on a surface portion M to be illuminated via an optical element providing lighting characteristics (x, y) refers to an arbitrary location on the surface portion M to be illuminated, / denotes the overall illuminance on the surface portion M provided collectively by the elementary light sources (its definition in physical terms will be discussed below), and A represents the one or more pre-set criteria/features expressed in a quantified form, i.e. in the form of a given value (e.g. the average illuminance of the surface).
Contrary to the known techniques that perform calculations based on the simple light dis- tribution, in the method according to the invention instead of calculating the incoming luminous power at the surface based on a great number of samplings and characterizing the illumination strength on the surface to be illuminated by the thus obtained average value, reference points are defined on the surface to be illuminated relatively close to one another,
a fixed sampling is performed at these points and the thus obtained values are used for the characterization.
Accordingly, coordinates (x, y) of relation (1) are varied over the reference points defined on the surface to be illuminated as part of the illumination problem. Said reference points form a geometrical lattice, the grid points of which are the preferably equidistantly distributed reference points, while the edges of which are formed by the sections connecting the nearest (i.e. directly) neighboring reference points. In particular, in the case of the exemplary illumination problem illustrated in Figures 4A to 4C, to be discussed later in detail, the reference points form a lattice, wherein the distance of any two directly neighboring (i.e. along an edge) reference points is 1 meter. Naturally, the reference points can be taken at a different density or according to another configuration. For a person skilled in the relevant art, it is apparent that the optimization problem defined by the target function in accordance with relation (1) can be solved basically on any continuous two-dimensional lattices, although, the number of reference points (that is, the„density" of grid points) signifi- cantly influences the computational labor required by the search for the solution.
The illumination strength at the reference points is calculated by means of a well accepted principle of physics: if / denotes the luminous intensity of an individual elementary light source, r stands for its distance from the illuminated point and a represents its lighting direction (i.e. the angle made by the geometrical axis of the light beam emitted by said ele- mentary light source with vertical), then the illuminance in an arbitrary chosen reference point is given by the relation
E =— cos
(2)
The value of the overall illuminance generated in a reference point of the surface by the elementary light sources is obtained by summation. As elementary light sources of identic- al nature are used, the summation means a simple linear summation. The distance r between a light source and an irradiated reference point can be calculated by means of simple geometrical relations if the position of said light source and the angle a made by the illuminating light beam of the light source incident to the given reference point with the normal to the surface are known.
It can be assumed without loss of generality that the optical elements defining lighting characteristics Oi of the individual elementary light sources attribute a rotation-symmetric like illumination plume to the light sources. To perform the optimization, the elementary light sources are arranged virtually at a single point P in a given height above the surface to be illuminated (see Figure 4A). That is, the lighting device aimed is considered to be pointlike. When solving the illumination problem, an assumption is made according to which, as far as the optimal configuration of said elementary light sources is concerned, the positions occupied by the individual elementary light sources in the lighting device are irrelevant and merely the light emission directions provided by the optical elements applied are of importance. Or putting this another way, it is assumed that the locations of the elementary light sources in the lighting device exercise a non-essential influence on the illuminance of the surface to be illuminated. Grounding of this assumption is supported by the fact that, in general, the distances between the elementary light sources within the lighting device are significantly smaller than the distances between the elementary light sources and the sur- face to be illuminated. With a knowledge of the optimal light source configuration, for a lighting device of given shape/dimensions, in particular, on the supporting panel forming part of said lighting device, a skilled person in the art can easily determine (by taking some fundamental geometrical constraints into account, such as e.g. the avoidance of lapping elementary light sources to one another, the blocking due to the envelope of the lighting device, etc.) the positions needed to actually arrange said elementary light sources, that is, the positions of the light source seatings accommodating said elementary light sources.
Without limiting the concept of the method according to the present invention, as far as the practical implementation is concerned, an important simplification can be made according to which the optimal light source configuration is searched for as a configuration with ref- lectional symmetry about its longitudinal axis. Since, generally, the surface to be lit up by the lighting device itself has a symmetry about the actual position of the lighting device, this simplification is justified. Here, the term symmetric configuration" refers to the fact that if an elementary light source with a lighting characteristics o, lights into a point with coordinates („ yi) of the surface, then the elementary light source emitting a beam of light into the point with coordinates (2xi-xi,y,) of the surface is totally identical with it (here, XL is the x coordinate of the lighting device relative to the surface illuminated by it). Due to this, the computational labor significantly decreases as only half of the elementary light
sources must be determined. A result of this simplification is that the supporting panel which corresponds to the optimal light source configuration in the lighting device will be symmetric as well. This eases significantly the (automated) manufacturing of said supporting panel, too. It is also apparent for a skilled person in the art, however, that the method according to the present invention can also be accomplished without exploiting the above symmetry.
The determination of the optimal light source configuration takes place in two steps. At first, the optimal number of elementary light sources and the distribution with respect to lighting characteristics (that is, type) of the optimal numbered light sources are determined which forms the solution of a discrete first optimization problem. Orientations, i.e. light emission directions of the elementary light sources obtained in the first step are determined in the second step as the solution of a continuous second optimization problem. It can easily be seen that the solution of the first problem influences the second problem, and it is also apparent that the solution of the second problem is a must for the solution of the first problem, as a decision on whether or not a configuration of elementary light sources meets the one or more criteria set can be made only if at least the approximately correct light emission directions of the elementary light sources constituting said configuration are also known.
In accordance with the core feature of the inventive method, when the solution of the first problem is looked for, the light emission directions of the elementary light sources are already taken into account to a given extent. Nevertheless, no attempts will be made to find a complete solution to the first problem (that is, e.g. no reach of full convergence is required). However, the configuration obtained in the first step, naturally, approximates well the optimal configuration to be achieved in the second step. Consequently, as the input of the second problem the elementary light source configuration obtained in the first step is used, and the continuous optimization is performed on the configuration achieved in the first step. Thus, the inventive solution gives the elementary light source configuration optimized with respect to the one or more pre-set criteria by performing basically a two-step optimization procedure. Due to the complexity and large size of the problem, to perform the discrete optimization procedure of the first step, heuristic methods are made use of. Amongst these, the so-called
genetic algorithms proved to be the most advantageous. By the term genetic algorithms, a class of search techniques is referred to, by means of which an optimal value or an element with given properties can be looked for. The genetic algorithms are dedicated evolutionary algorithms, they borrow their mechanisms from evolutionary biology. In particular, the in- dividuals of the population are the members of the search space; the individuals of the population can be subjected to crossover with one another (recombination) and to mutation, thus new individuals can be reproduced from them. As it is known by a skilled person in the art, when performing a genetic algorithm, on the one hand, new individuals are created by the operators that correspond to recombination and mutation and, on the other hand, the individuals with worse target function values are filtered out and removed from the population (selection) by said operators.
When performing the discrete first optimization step of the method according to the invention, the search space is specifically generated in the form of two-dimensional arrays containing integer values. Each element of the arrays represents an elementary light source having a given light emission direction. Or to be more precise, the elements of the array correspond to the elementary light sources directed towards the reference points of the geometrical lattice defined on the surface to be illuminated. At the same time, the values of the array provide the type of the elementary light source emitting light towards the given reference point. In this embodiment a zero value means that no elementary light source emits light into the direction concerned.
In the case of said crossover, the good partial solution already found in the form of an individual of the population is combined with a further individual. This is effected, in particular, by copying a real partial block of the two-dimensional array into the place of a similar partial block of said further individual. By this operation, the good partial solutions are transmitted from individual to individual.
In the case of said mutation, the value located in a position of the array is altered in the position at issue. Performing this operation is practically equivalent with investigating whether or not a solution of a better target function value would be obtained if one elementary light source was switched on or switched off in a direction, or if the type of an elementary light source was changed. As a further possibility of mutation, an elementary light source already emitting light is transposed into another adjacent light emission direction.
By performing the continuous second optimization step of the method according to the invention, a correction/improvement of the configuration obtained in the first step takes place via the continuous optimizing procedure aiming at improving the light emission directions of the elementary light sources. In particular, in the second step, the objective is to improve the light source configuration via taking the distances within the geometrical lattice into account. To this end, those light emission directions have to be found which lead to an improvement of the value of the target function. This takes place basically in every case experimentally".
Therefore, this second step is completed by applying a well-known Monte Carlo type op- timization technique, the so-called simulated annealing technique, known by the skilled person in the art. This technique is based on the experience that through the continuous, uniform and slow cooling of bodies, their lattice structure gets into a state of optimal (minimum) energy. When the algorithm is executed, choosing of the next peak takes place randomly. If the target function value for the selected new searching point is worse than that of the actual point, the acceptance probability for the point concerned to be accepted as new point is inversely proportional to the difference of the two target function values. The probability of accepting a worse new point decreases with decreasing the temperature. The simulated annealing algorithm asymptotically converges to an optimal solution, provided that any point can be reached from any searching point within finite number of steps by the algorithm, as it holds in the present case.
In the first step of the method according to the invention, the size of the population was set to 5000, and the first step was considered completed (stopping condition) if the value of the target function changed only to a negligibly small extent thereafter; in particular, the value of the target function did not change significantly in 50 generations, or more precise- ly, its change remained below a given threshold value ει, wherein preferably the choice of Ei = 10"6 is used.
Similarly to the first step, the stopping condition for the optimization method completed for the x and y coordinates of the elementary light sources considered as variables (in order to improve the light emission directions) in the second step is bound to the amount of change of the target function value and of the variables concerned. In particular, the second step ends if said values remain below a threshold value ε2 after a fixed number of iterations
Δ; here, preferably the choices of ε2 = 10"6 and e.g. Δ = 500*(number of varying coordinates x, y of the elementary light sources) are used. It is noted as a reminder that the type of the elementary light sources does not change in this step any more.
By the two-step optimization method according to the present invention, a light source configuration optimized with respect to one or more given criteria can be derived as the solution of a well-defined illumination problem in a fully automated manner, if said method is carried out e.g. by a computer.
In comparison with the known techniques, an advantage of the above-discussed method according to the invention is that here the total impact, that is, the net illuminance, of all the elementary light sources is taken into account in every moment over the whole illuminated surface, wherein all types of used elementary light sources are present in said net illuminance with appropriate weights. A further advantage of the method according to the invention is that it is an optimization model which, in principle, is capable of finding the best solution of the model with one or more pre-set criteria features by an optimizing me- thod ready for optimum determination, while the known techniques attempt to determine elementary light sources to be built into the lighting device via carrying out a reverse calculation starting from the intensity values obtained on the surface to be illuminated. Of course, in extreme cases the time requirement for such an optimum searching method can be very high, thus in practice the objective is to reach a solution as good as possible within an acceptable amount of time. It is clear, nevertheless, that the„goodness" of the thus obtained solution merely depends on the available calculating capacity.
A practical embodiment of the above detailed method according to the invention will be illustrated for a given illumination problem in relation with Examples 1 to 4 discussed below in detail. To solve the illumination problem to be discussed, the method according to the invention was executed with the above choice of the parameters (sj; ε2, Δ) by personal computers having processors with a clock rate of 2 to 3 GHz and a memory of 4 GB. Under these circumstances, completion of the first step requires a computing time of about 5 hours, while reaching the condition of convergence in the second step requires a computing time of about 3 hours. Thus, the various light sources that are of importance as far as e.g. uniform illuminance is concerned can easily be handled in the first step for performing the
discrete optimization, and due to the discrete optimization step, the execution of the continuous optimization step becomes relatively fast too.
The optimal light source configuration obtained by the method according to the invention provides hence the number of elementary light sources that can be used to prepare the op- timized lighting device, the distribution of said elementary light sources with respect to type, as well as their light emission directions. Knowing the accurate position of the lighting device relative to the area to be illuminated, a one-to-one mapping exists between the thus obtained light emission directions of the individual elementary light sources and the intersection points of the lines directed through the lighting device, which is considered to be a point-like one, in parallel with said light emission directions with said area to be illuminated. Hence, the light emission directions can be uniquely defined by the intersection points indicated in the illuminated area, as it is shown in Figures 4A to 4C, and Figures 10B, 1 1B, 12B and 13B.
To prepare a lighting device 100 according to the invention (see Figure 9C), elementary light sources 10 (see e.g. Figures 2A and 2B) have to be installed into a lighting fixture of given outer dimensions in harmony with the optimal light source configuration. To this end, the light sources 10 have to be arranged and fixed, preferably in a replaceable manner, onto a supporting panel 101 , an embodiment of which is schematically illustrated in Figure 5, that conforms to the optimized light source configuration determined. Said supporting panel 101 is constituted by planar light source seatings 102, in particular light source seat- ings provided in the form of individual tiny plates of given size and shape, and filling elements 103 that connect said tiny plates into an integral and continuous member, i.e. the supporting panel; here the number of said tiny plates basically corresponds to that of the elementary light sources within the optimal light source configuration. The light source seatings 102 are formed so as to receive and firmly fix the light sources 10. Said fixing can take place in numerous detachable manners (via e.g. locking, by means of clamping with clips or strips, by keying-up in appropriately shaped and sized openings of said light source seatings, etc.) or non-detachable manners (by means of e.g. bonding into said openings) that are known to a person skilled in the art. In order to ensure subsequent maintenance and/or servicing that might become necessary, in this case the detachable types of fixings are considered to be preferred. After the proper type of light sources 10 have been fixed onto the light source seatings 102, they will exhibit such orientations that their light emis-
sion directions just correspond to the light emission directions of the optimal light source configuration. Or putting this another way, the normal vectors of said tiny plates forming the light source seatings 102 just point into the above defined intersection points (that is, said normal vectors are practically parallel with the light emission directions determined). The filling elements 103 connect the light source seatings 102 into the supporting panel 101 in such a manner that said light sources 10 mounted onto said supporting panel 101 do not hamper one another (via e.g. physical blocking by overlapping) when the area to be lit up is illuminated. Figures 6A and 6B schematically illustrate said elementary light sources 10 being mounted onto the support panel 101.
The optimal light source configuration is determined by the method according to the invention with the assumption that each elementary light source thereof is located in a single point. As far as illumination problems related to public lighting are concerned, due to the geometrical relationships, this assumption holds essentially in every case and thus constitutes no further restriction. In a lighting device to be constructed in harmony with the op- timal light source configuration, in practice, the elementary light sources 10 are generally arranged,„distributed" on the supporting panel 101 of certain dimensions. The basic form for the supporting panel 101 is determined empirically with a knowledge of the illumination problem. To enhance heat removal, the basic form is preferably provided by a concave surface. Said light source seatings 102 are„seated" onto this surface so that their normal vectors point into the intersection points concerned, and the elementary light sources 10 arranged on the seatings do not interfere with each other when the area to be lit is illuminated. To avoid luminous pollution, the preferably concave curvature of the basic form ensures that no concentrated light can exit from the lighting fixture in an angle to the horizontal (defined according to practice) less than 10°. For the mass production of the supporting panel 101 , a set of tools in conformity with the optimal light source configuration is prepared by making use of computer-aided tool designing techniques/softwares (e.g. CAD) known by a person skilled in the art. Having such a set of tools, the supporting panel 101 is preferably prepared from a sheet material by means of a metal-forming process, preferably by vacuum forming or deep-drawing. In the metal-forming process, the light source seatings 102 and the filling elements 103 connecting together said seatings are formed by applying the previously prepared set of tools. Then, said light source seatings 102 are equipped with mechanical means corresponding to
the previously decided way of fixing of the elementary light sources 10. Such a supporting panel 101 with light sources 10 is shown in Figure 5. Figures 6A and 6B illustrate in enlarged view the elementary light sources 10 arranged on and specifically mounted onto the supporting panel 101. Next, the supporting panel 101 with the elementary light sources 10 is attached to the base sheet 104 of the lighting device 100 in a way known to the skilled person in the art, as it is shown in Figure 7. The base sheet 104 does not hamper the illumination of the surface portion to be lit up, and is provided with a supporting bracket 106 that enables mounting of the lighting device 100 in various positions tilted from the horizontal position. To avoid the access of external pollution into the lighting device, the portion of said base sheet 104 transmitting the light of the elementary light sources 10 is provided in the form of a translucent sheet (see Figure 9C) that is preferably made of an UV -resistant material, such as e.g. polycarbonate. The base sheet 104 also provides room for a power-supply unit 1 10, as it can be seen in Figure 8, that supplies the light sources 10 with electric energy. Said pow- er-supply unit 1 10 is electrically connected with the light sources 10 via e.g. an appropriate wiring (not shown in the drawings).
As a next step of assembling the lighting device according to the invention, a heat dissipating casing 108 provided with ventilating openings 107 is arranged on and then attached to the supporting panel 101 with light sources 10. The preferentially concave (or hollow) in- ner surface of the heat dissipating casing 108 is in contact with the elementary light sources 10, preferably with their heat removal surfaces (to be discussed below), via a suitable heat conducting material (e.g. a foil or a paste) inserted therebetween. The objective of said heat dissipating casing 108 is to remove heat generated by the elementary light sources 10, and thus to maintain the prescribed operation temperature of said elementary light sources 10. The light sources 10, in case of need, can also be equipped with individual heat sinks on the outer surface of the heat dissipating casing 108. In a preferred embodiment, the heat dissipating casing 108 also serves for the pressing of elementary light sources 10 onto the supporting panel 101 , and hence it also arranges for the light sources 10 to remain firmly in their positions. On the convex (or raised) outer surface of the heat dissipating casing 108, there are provided supplementary cooling ribs 109 serving also as spacers. Besides heat removal, the objective of these cooling ribs 109 is to maintain a casing 1 1 1, shown in Figure 9A, of the lighting device spaced apart from the heat dissipating
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23 casing 108 to a given distance when said heat dissipating casing 108 has been installed, and hence to allow aeration of the lighting device 100. The aeration is facilitated by the ventilating openings 107 formed in the heat dissipating casing 108, and the ventilating openings 112 formed in and through the outer surface of the casing 1 1 1.
It is noted that the dissipation of heat generated by the elementary light sources 10 when the lighting device 100 is in operation takes place mostly via convection and thus it is of extreme importance to ensure appropriate aeration of the region located between the casing 111 and the heat dissipating casing 108. To enhance aeration, in a possible further preferred embodiment of the lighting device according to the invention (not shown in the drawings), said ventilating openings 1 12 of the casing 1 1 1 are provided in the form of projecting members, each with a ventilation channel that is about 20 to 30 mm in height and is contracting in cross-section upwards to an opening with a diameter of about 2 to 3 mm, in order to assist the aeration of said region under the casing 1 1 1 by exploiting the principle of chimney effect (that is, on a passive gravitational concept) in lack of external air motion. To maximize the chimney effect, the geometrical axis of the channel of each ventilating opening 1 12 forms an angle of at most 10° with the vertical. The necessary number of such ventilating elements is determined by the cooling demand of the lighting device; it can easily be calculated by a skilled person in the art. The remaining portion of the heat dissipation takes place through the casing 1 1 1 via radiation. It is noted that the ventilating elements concerned can be equally formed from the material of the casing 1 11 and as integral parts thereof, or in the form of separate elements that can be mounted onto the casing 1 1 1.
In general, the lighting device according to the invention is located not in a shady, but a sunny place. In strong sunshine, the above discussed cooling geometry significantly de- creases the internal temperature increase due to the warming up of the lighting device 100, and thus largely contributes to the behavior, according to which said light sources 10 can commence their operation and/or operate at the prescribed operational temperature or close to it after dark even in hot summer days. In harmony with this, the outer surface of the casing 1 1 1 is formed preferentially as a reflecting surface in order to decrease extreme warm- ing up. Moreover, the outer surface of the heat dissipation casing 108 is dark-colored to enhance the heat removal as much as possible via radiation.
For constructing the lighting device according to the invention in harmony with the above detailed teaching, a starting set of light sources comprised of any kinds of elementary light sources can be used. To prepare a compact, energy saving lighting device with relatively low cooling demands, i.e. a lighting device that is preferred as far as the practical applica- tions are concerned, the per se known compact elementary LED lighting sources 10 illustrated in Figures 2A and 2B can be made use of. The light sources 10 can be of identical or different power, and the illuminance provided by each of them separately, that is, the lighting characteristics of the light sources 10, can be the same or differ from one another. The lighting characteristics are defined essentially by the optical elements, preferably the lens or mirrors or any suitable combination of these elements, directing the light emanated by the light emitting member. Figures 3A to 3F show some typical exemplary lighting characteristics that are suitable for being used in the solution according to the present invention.
As it can be seen in Figures 2A and 2B, the LED lighting source 10 used in a possible em- bodiment of the optimized lighting device 100 comprises preferably a semiconducting based LED chip 12 of a given power arranged on a planar substrate 11 of given dimensions, an electronics 13 necessary for the operation of said chip, positive and negative connectors 14, 15 in electrical connection with said electronics 13 and a heat dissipation surface 16. Energizing of the light source 10 takes place via the connectors 14, 15. Operation of said LED chip 12, that is, its light emission is controlled by the electronics 13. The LED chip 12 can be considered basically as a point-like light source, and the light emitted by it (illumination cone of light) exits within a conical surface that broadens evenly along the axis perpendicular to the substrate 1 1.
In this embodiment of the light source 10, the heat dissipation surface 16 is preferably formed on the side of said substrate 1 1 facing opposite to the LED chip 12. The size of the heat dissipation surface 16 depends on the power of the LED chip 12. Its objective is to dissipate heat being generated during the operation of the LED chip 12 from said LED chip 12, and thereby to maintain it at about a constant operational temperature, as well as to avoid its degradation and decrease in life-time that can emerge due to excess thermal load. On the same side of the substrate 11 that carries the LED chip 12, a packaging 17 is provided mounted onto said substrate 1 1 for the mechanical protection of the LED chip 12. Said packaging 17, in its portion 18 located opposite to the LED chip 12, is permeable to
light at least at the emission wavelength of the LED chip 12. Besides transmitting the generally white light emitted by the LED chip 12, this portion 18 of the packaging 17 can also act as diffuser. Within the packaging 17, in the path of light emitted by the LED chip 12, there is provided a suitably fixed optical lens 19. The lighting characteristics of the light source 10 is basically determined by the combination of the transparent portion 18 of the packaging 17 and the lens 19. Putting this another way, an elementary light source 10 with desired lighting characteristics can be provided by selecting the optical properties of said lens 19 and portion 18 in accordance with given conditions.
Fixing of light sources 10 into the lighting fixture in a configuration determined by the me- thod according to the invention takes place through the substrates 1 1 in a suitable manner, as it will be discussed later in detail. For the sake of simpler handling, each substrate 1 1 is essentially of the same physical dimensions. When choosing the dimensions of the substrates 1 1 , two requirements are kept in mind: as the lighting device contains, in general, more than one elementary light sources 10, its compactness requires the application of the smallest possible substrate size on the one hand. In the assembled state of the lighting device, on the other hand, maintaining the operational temperature of the LED chips 12 on the substrates 1 1 requires a good heat dissipation capability which requires a heat transfer surface with relatively large sizes. Moreover, there is also a need for spaces between the light sources 10 that can be easily aerated by air; this latter requirement can readily be en- sured by increasing substrate size. To satisfy both requisites, the planar dimensions of the substrates 1 1 are several centimeters, preferably they range between 2 to 7 centimeters, more preferably between 4 to 6 centimeters. As far as the shape of said substrates 11 is concerned, there are no special requirements, and thus said substrates 1 1 can be of any planar form. However, as far as the simplicity of fixing of said substrates 1 1 into a lighting fixture is concerned, the substrates 11 will preferably be square or rectangular shaped, perhaps triangle shaped or regular hexagonal shaped. Optionally, the choice of shape of said substrates 1 1 may be influenced by the compact form of the lighting device. When this is also kept in mind, in order to achieve the best possible space filling, optionally, the substrates 1 1 for the light sources 10 used for the practical implementation of the lighting de- vice according to the invention can be of different shapes and/or dimensions.
In what follows, the method according to the invention and the optimized lighting device prepared by the method will be illustrated with several non-limiting examples. In the ex-
amples, various starting sets of elementary light sources will be used. These sets are constituted by elementary light sources, preferably LED light sources 10, that differ as to their lighting characteristics and/or power from one another, wherein the number of elementary light sources within the sets is also different. The illumination problem is, however, the same throughout the next examples. In particular, a rectangular shaped portion M, located in a plane S, with the length of a = 35 m and the width of b = 10 m of a public road is to be illuminated evenly with an illumination strength of about 6 lx by a single lighting device 100 according to the invention. Said lighting device 100 is arranged in a point P at a height of D = 10 m above the perpendicular bisector of the longer side a of said surface portion M, wherein said point P is located in a position that projects to a distance of d = 1 m from the side a above the surface portion M (that is, the orthogonal projection of the lighting device 100 within the plane S falls onto the perpendicular bisector of the longer side a of the surface portion M, inside of said surface portion M to be illuminated, at a distance of d = 1 m from said longer side a of said surface portion M). The optimal number and/or the mu- tual positions of the elementary LED light sources 10 forming the lighting device 100 that corresponds to this illumination problem is determined by the method according to the invention. It is, nevertheless, noted here that the method according to the invention is also apt for determining the optimal light source configuration for a lighting device that belongs to a surface portion differing from the surface portion M in shape and/or in size, has a differ- ent spatial location and/or is present in a different number, or provides a different illumination strength over the surface, as it is apparent in view of the present teaching to a person skilled in the relevant art.
EXAMPLES
In the next examples, the method according to the invention was specifically used to de- termine the construction of a public road lighting fixture optimized with respect to a given illumination problem. The starting sets of elementary light sources were composed of the elementary LED light sources having a compact design shown in Figure 2 for each example, however, taking various types of light sources into account as the basis from example to example. The individual lighting characteristics of the various elementary LED light sources used in the examples are shown in Figures 3A to 3F. In harmony with the above teaching, the optimization was performed with respect to the necessary number of elemen-
tary light sources and their light emission directions, as well as the distribution according to type of the necessary number of elementary light sources with various subsets selected from the above starting set of light sources. When carrying out the method according to the invention, a requirement was set against the optimized light source configuration to be reached (cf. the illumination problem), according to which the luminous intensity should be about 6 lux as uniformly as possible over the whole surface of the illuminated rectangular surface (i.e., here, the amount of deviation from the value of 6.0 lux was minimized). Naturally, lighting means optimized with respect to different illumination problems, as well as suitable for other applications can also be designed by means of the method accord- ing to the present invention. Moreover, the starting set of light sources can optionally be composed of elementary light sources being different (e.g. as to their power, lighting characteristics, etc.) from the above elementary light sources.
Example 1
In this example, a starting set of light sources consisting of three different types of light sources built with LED - having the same power (of 1 W) but different lighting characteristics (see Figures 3 A to 3C) - and used as the elementary light sources 10 was used to construct the supporting panel (see Figure 5), and then an optimized public road lighting luminaire forming a possible embodiment of the lighting device according to the present invention (see e.g. Figures 9A and 9B).
In figure 1 OA and 10B the perspective and the contour luminance charts, respectively, are illustrated for a light source configuration which is the most appropriate one with respect to the above requirement (i.e. optimal over the starting set) from amongst the light source configurations obtained by the method according to the invention. In this particular configuration the total number of elementary LED light sources is seventy-two, wherein twenty- six light sources contain a first type LED (1.) with the lighting characteristics illustrated in Figure 3A, twenty-eight light sources contain a second type LED (2.) with the lighting characteristics shown in Figure 3B, and eighteen light sources contain a third type LED (3.) with the lighting characteristics illustrated in Figure 3C. The supporting panel corresponding to the light source configuration at issue is shown in Figure 5, wherein different LED types are denoted by different numbers (indicated only in one half of the supporting panel, due to the axial symmetry of said supporting panel deriving from the method of construe-
tion). According to the results of the inventive method, the average illuminance is 5.9229 lux with the standard deviation of 0.4362 lux in the measurement points of the surface portion illuminated, while the minimum value is 4.33 lux and the maximum value is 7.75 lux; these values - taking the dimensions of the illuminated surface portion also into account - represent a highly uniform illuminance over the whole illuminated surface.
From the illuminance chart of Figure 10 it can also be seen that in the case of public lighting provided by the public road luminaire built with the exemplary, optimized LED configuration, at transitions between adjacent illumination regions (such as e.g. consecutive sections of a public road or a highway with the above given dimensions) joining to one anoth- er, the human eye will be exposed to essentially uniform luminous load, while the luminous pollution of the environment is practically zero.
Example 2
In this example, a starting set of light sources consisting of four different types of light sources built with LED - having the same power (of 1 W) but different lighting characte- ristics (see Figures 3 A to 3D) - was used to derive the elementary light source configuration for the optimized lighting device, shown in Figure 9, functioning as public road lighting luminaire.
In the optimal configuration obtained for the starting set of light sources concerned, the total number of elementary LED light sources to be used is sixty-two, wherein twenty light sources contain a first type LED (1.) with the lighting characteristics illustrated in Figure 3 A, twenty-four light sources contain a second type LED (2.) with the lighting characteristics shown in Figure 3B, eight light sources contain a third type LED (3.) with the lighting characteristics illustrated in Figure 3C and ten light sources contain a fourth type LED (4.) with the lighting characteristics illustrated in Figure 3D. The perspective and the contour luminance charts of the illuminated surface portion are shown in Figures 1 1A and 1 IB, respectively. According to the results of the inventive method, the average illuminance is 5.9730 lux with the standard deviation of 0.5214 lux in the measurement points of the surface portion, while the minimum value is 3.98 lux and the maximum value is 7.44 lux; these values - taking the dimensions of the illuminated surface portion also into account - represent a highly uniform illuminance over the whole illuminated surface.
Example 3
In this example, a starting set of light sources consisting of five different types of light sources built with LED - having different powers (1 W; 4 W) and lighting characteristics (1 W - see Figures 3 A to 3D; 4 W - see Figure 3E) - was used to derive the elementary light source configuration for the optimized lighting device, shown in Figure 9, functioning as public road lighting luminaire.
In the optimal configuration obtained over the above starting set of light sources, the total number of elementary LED light sources to be used is sixty-eight, wherein twenty-six light sources contain a first type LED (1.) with the lighting characteristics illustrated in Figure 3 A, twenty-six light sources contain a second type LED (2.) with the lighting characteristics shown in Figure 3B, twelve light sources contain a third type LED (3.) with the lighting characteristics illustrated in Figure 3C, four light sources contain a fourth type LED (4.) with the lighting characteristics illustrated in Figure 3D and zero light sources contains a fifth type LED (5.) with the lighting characteristics illustrated in Figure 3E. The perspec- tive and the contour luminance charts of the illuminated surface portion are shown in Figures 12A and 12B, respectively. According to the results of the inventive method, the average illuminance is 5.8833 lux with the standard deviation of 0.5323 lux in the measurement points of the surface portion, while the minimum value is 3.47 lux and the maximum value is 7.38 lux. Compared to the illuminance achieved by the configuration of Example 2, the present configuration provides a less uniform illuminance over the whole illuminated surface. Moreover, it can also be seen that the optimal configuration obtained by the method according to the invention requires the application of no fifth type elementary light sources.
The present example also shows that due to non-linearity of the algorithm used in the me- thod, the solution of a given illumination problem obtained as an optimal solution also depends on the initial conditions.
Example 4
In this example, a starting set of light sources consisting of six different types of light sources built with LED - having different powers (1 W; 4 W) and lighting characteristics (1 W - see Figures 3A to 3D; 4 W - see Figures 3E and 3F) - was used to derive the ele-
W
30 mentary light source configuration for the optimized lighting device, shown in Figure 9, functioning as public road lighting luminaire.
In the optimal configuration obtained over the above starting set of light sources, the total number of elementary LED light sources to be used is fifty-six, wherein fourteen light sources contain a first type LED (1.) with the lighting characteristics illustrated in Figure 3A, twenty light sources contain a second type LED (2.) with the lighting characteristics shown in Figure 3B, sixteen light sources contain a third type LED (3.) with the lighting characteristics illustrated in Figure 3C, four light sources contain a fourth type LED (4.) with the lighting characteristics illustrated in Figure 3D, zero light sources contains a fifth type LED (5.) with the lighting characteristics illustrated in Figure 3E and two light sources contain a sixth type LED (6.) with the lighting characteristics illustrated in Figure 3F. The perspective and the contour luminance charts of the illuminated surface portion are shown in Figures 13A and 13B, respectively. According to the results of the inventive method, the average illuminance is 5.9098 lux with the standard deviation of 0.4766 lux in the measurement points of the surface portion, while the minimum value is 4.27 lux and the maximum value is 7.72 lux. Compared to the illuminance achieved by the configuration of Example 2, the present configuration provides a less uniform illuminance over the whole illuminated surface. However, compared to the illuminance achieved by the configuration of Example 3, the present configuration provides a more uniform illuminance over the whole illuminated surface and also requires less elementary light sources. Moreover, it is also clear that the optimal configuration obtained by the method according to the invention requires the application of no fifth type elementary light sources.
Summary: the method according to the invention provides an optimal configuration of elementary light sources to be arranged within a lighting device adapted to a given illumi- nation problem (defined by the shape and/or the size of the surface to be illuminated, the number and/or the position(s) of luminaire(s) to be applied, etc.) to be solved for„arbitrary number" of elementary light sources (assigned into the same class or different classes by power, lighting characteristics, etc.), in particular LED light sources, with respect to one or more pre-set criteria (such as e.g. the average, as well as the lightest and/or strongest illu- minance of the surface to be illuminated, standard deviation of the illuminance, etc.). The method according to the invention also allows the study of mutual influences of more than one luminaires to one another, as well as the completion of optimization with respect to
such a criterion. Thus, the present method is suitable for the optimal solution of any illumination problems that might arise in practice.
The method according to the invention is also suitable for optimizing the light source configuration adapted to an illumination problem with respect to economic profitability criteria (for example, the total energy consumption at a given illuminance, the production cost per light source in case of mass production, etc.). In this case, if e.g. the price of the (various) elementary light sources available or to be used and the major parameters of mass production (e.g. the maximal number of pieces, the size of the lighting device, etc.) are provided as starting parameters, the optimization performed focuses not only on the optimal solution for the illumination problem, but it is also apt to take demands of the producer/user/operator into account too.
Moreover, according to the above examples, contiguous areas, such as e.g. public roads, can be illuminated highly uniformly in their entirety by employing the lighting devices according to the invention ensuring e.g. uniform illumination over the whole surface to be illuminated, with no need for the surface portions lit up by individual lighting devices to overlap one another. This renders the public lighting luminaries optimized by the inventive method highly preferred as, in comparison with the number of traditionally employed lu- minaires, fewer lighting devices according to the invention are required to evenly illuminate a road section of given length in its entirety, that results in significant savings.
Claims
1. Method of determining an elementary light source configuration being optimal with respect to one or more pre-set criteria for a lighting device with elementary light sources, characterized in that it comprises the steps of
defining an illumination problem characteristic of the application of the lighting device;
providing a set of elementary light sources (10) applicable in the lighting device (100) to solve the illumination problem;
performing a discrete optimization over the set of applicable elementary light sources along with satisfying the one or more criteria pre-set when the illumination problem has been defined so as to derive a light source configuration applicable in the lighting device via determining sufficient number and distribution as to type of the elementary light sources and setting an approximate -„rough" - light emission direction for each individual light source;
performing a continuous optimization over the light source configuration obtained by the discrete optimization along with satisfying the one or more pre-set criteria so as to determine the light emission directions of said elementary light sources precisely and to generate thereby an optimized elementary light source configuration representing a solution for the illumination problem defined.
2. The method according to Claim 1 , characterized in that the one or more pre-set criteria is/are chosen from the group comprising the extent of an average, the lowest and the highest illumination of a surface portion (M) to be illuminated defined as part of the illumination problem, the extent of deviation of illuminance from a prescribed luminous intensity and the standard deviation of the illuminance.
3. The method according to Claim 1 or 2, characterized in that said optimized elementary light source configuration is generated via optimizing a target function defined by 
A'€N..i:; wherein N stands for the total number of elementary light sources in the optimized configuration, /' refers to the z-th elementary light source (here z e {1, N }) of said configuration that emits a beam of light directing to a point with coordinates („ y,) on the surface portion (M) to be illuminated via an optical element providing lighting characteristics o„ (x, y) refers to an arbitrary location on the surface portion (M) to be illuminated, / denotes the overall illuminance on the surface portion (M) provided collectively by the elementary light sources, and A represents the one or more pre-set criteria expressed in a quantified form, and wherein the overall illuminance is a sum of the illuminances provided by the individual elementary light sources alone in accordance with the relation
E =— cos wherein / represents the luminous intensity of a single elementary light source, r is a distance between the elementary light source concerned and an illuminated point on the surface portion M, and a stands for the light emission direction of the elementary light source concerned.
4. The method according to any of Claims 1 to 3, characterized in that said discrete optimization is performed by making use of genetic algorithms.
5. The method according to any of Claims 1 to 4, characterized in that said continuous optimization is performed by a Monte Carlo type algorithm.
6. Method of constructing a lighting device with elementary light sources in an optimized configuration, comprising the steps of
preparing a supporting panel (101) from a sheet material by metal forming, said supporting panel (101) being formed with a shape conforming to the elementary light source configuration obtained via optimizing in consecutive discrete and continuous steps a target function defined by 
here N stands for the total number of elementary light sources in the optimized configuration, / refers to the j'-th elementary light source (here / e {/, ..., N }) of said configuration that emits a beam of light directing to a point with coordinates (xi} y,) on the surface portion (M) to be illuminated via an optical element providing lighting characteristics o„ (x, y) re- fers to an arbitrary location on the surface portion (M) to be illuminated, / denotes the overall illuminance on the surface portion (M) provided collectively by the elementary light sources, and A represents the one or more pre-set criteria expressed in a quantified form, and wherein the overall illuminance is a sum of the illuminances provided by the individual elementary light sources alone in accordance with the relation
/
E—— cos
r2
wherein / represents the luminous intensity of a single elementary light source, r is a distance between the elementary light source concerned and an illuminated point on the surface portion M, and a stands for the light emission direction of the elementary light source concerned;
mounting the elementary light sources (10) onto the supporting panel (101) with their light emission directions corresponding to the optimized elementary light source configuration;
arranging the thus obtained supporting panel (101) in a region defined by a casing (1 1 1) and a base sheet (104) of the lighting device (100), said base sheet (104) being trans- lucent at least in a portion thereof, so as to be capable of emitting light through the translucent portion of the base sheet (104).
7. The method according to Claim 6, characterized in that forming of the sheet material is performed by vacuum forming or deep-drawing.
8. Supporting panel for a lighting device constructed with elementary light sources, characterized in that said supporting panel (101) comprises planar light source seatings
(102) and filling elements (103) connecting said light source seatings (102) into an integral continuous member, wherein the number of light source seatings (102) corresponds to the number of elementary light sources (10) of an optimized elementary light source configuration obtained via optimizing in consecutive discrete and continuous steps a target func- tion defined by 
here N stands for the total number of elementary light sources in the optimized configuration, i refers to the z'-th elementary light source (here e {/, ..., N }) of said configuration that emits a beam of light directing to a point with coordinates (J„ yi) on the surface portion (M) to be illuminated via an optical element providing lighting characteristics (x, y) refers to an arbitrary location on the surface portion (M) to be illuminated, / denotes the overall illuminance on the surface portion (M) provided collectively by the elementary light sources, and A represents the one or more pre-set criteria expressed in a quantified form, and wherein the overall illuminance is a sum of the illuminances provided by the individual elementary light sources alone in accordance with the relation 
wherein / represents the luminous intensity of a single elementary light source, r is a distance between the elementary light source concerned and an illuminated point on the surface portion M, and a stands for the light emission direction of the elementary light source concerned, and wherein
each light source seating (102) exhibits a normal vector that points basically into a light emission direction of one and only one elementary light source (10) within the elementary light source configuration obtained by the optimization.
9. The supporting panel according to Claim 8, characterized in that the light source seatings (102) are located on an essentially concave surface when viewed from the light emission directions of the elementary light sources (10).
10. Lighting device comprising a region to accommodate elementary light sources, said region being defined by a casing and a base sheet of the lighting device, said base sheet being translucent at least in a portion thereof, and a power-supply unit to energize the elementary light sources via electrical connectors, characterized in that the elementary light sources (10) are arranged on a supporting panel (101) according to any of Claims 8 and 9, wherein said supporting panel (10) is fixed into the region defined by the casing (1 1 1) and the base sheet (104).
1 1. The lighting device according to Claim 10, characterized in that it comprises ventilating openings (112) to provide passive cooling of the elementary light sources (10), said ventilating openings (1 12) being formed in the casing (1 1 1) and connecting said region with a region located external to said casing (1 1 1).
12. The lighting device according to Claim 1 1 , characterized in that each of said ventilating openings (112) is provided by a member projecting from the casing (1 11) into the region located external to the casing (1 11) and having an internal channel contracting in cross-section in a direction away from said casing (1 1 1).
13. The lighting device according to Claim 1 1 or 12, characterized in that a geometrical axis of the channel of each ventilating opening (112) forms an angle of at most 10° with the vertical.
14. The lighting device according to any of Claims 1 1 to 13, characterized in that said ventilating openings (1 12) are formed from the material and as parts of the casing
(1 1 1).
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| HUP1000303 | 2010-06-09 | ||
| HU1000303A HU230914B1 (en) | 2010-06-09 | 2010-06-09 | Method for producing a light, containing optimized configuration of elementary lights, said light and carrier sheet |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| WO2011154756A2 true WO2011154756A2 (en) | 2011-12-15 |
| WO2011154756A3 WO2011154756A3 (en) | 2012-03-29 |
Family
ID=89989768
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/HU2011/000052 WO2011154756A2 (en) | 2010-06-09 | 2011-06-09 | Method for constructing a lighting device with discrete light sources and thus obtained lighting device |
Country Status (2)
| Country | Link |
|---|---|
| HU (1) | HU230914B1 (en) |
| WO (1) | WO2011154756A2 (en) |
Cited By (1)
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|---|---|---|---|---|
| WO2023118506A1 (en) * | 2021-12-22 | 2023-06-29 | Schreder S.A. | Computer-implemented method for designing an optical unit for a luminaire, and associated production method |
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Also Published As
| Publication number | Publication date |
|---|---|
| HU1000303D0 (en) | 2010-08-30 |
| WO2011154756A3 (en) | 2012-03-29 |
| HU230914B1 (en) | 2019-02-28 |
| HUP1000303A2 (en) | 2012-03-28 |
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