WO2013144907A1

WO2013144907A1 - System for limiting the diffusion of light

Info

Publication number: WO2013144907A1
Application number: PCT/IB2013/052510
Authority: WO
Inventors: Fabio FALCHI
Original assignee: Falchi Fabio
Priority date: 2012-03-29
Filing date: 2013-03-28
Publication date: 2013-10-03
Also published as: ITVR20120062A1

Abstract

A system (1) for limiting the diffusion of light emitted by a light source (3), comprising a plurality of identical refracting prisms (2, 102, 202, 302) which are superimposed at parallel and mutually opposite faces (10, 110, 210, 310) of the refracting prisms (2, 102, 202, 302). The refracting prisms (2, 102, 202, 302) have an entry face (11, 111, 211, 311), which extends transversely with respect to the parallel faces (10, 110, 210, 310) and is adapted to intercept at least part of the light emitted by the light source (3). Each one of the refracting prisms (2, 102, 202, 302) comprises an exit face (4, 104, 204, 304) for the light intercepted by the entry face (11, 111, 211, 311), where the exit face (4, 104, 204, 304) extends transversely with respect to the parallel faces (10, 110, 210, 310). All the exit faces (4, 104, 204, 304) of the refracting prisms (2, 102, 202, 302) are adapted to refract the intercepted light so as to direct it into a limited region (15) of space.

Description

SYSTEM FOR LIMITING THE DIFFUSION OF LIGHT

The present invention relates to a system for limiting the diffusion of light.

Light pollution is a problem that is currently very important worldwide. In particular, light pollution is any irradiation of light directed outside the areas to which it is functionally dedicated, and in particular toward the sky. Light pollution is, thus, caused by any type of light source, be it a streetlight, a luminous sign, a lighthouse, or the like.

As is known, light pollution causes environmental, economic and even scientific damage. The environmental damage includes alteration of the circadian rhythms of living beings, including humans; the economic damage relates to the waste of electricity to light areas that do not need lighting; and lastly the scientific damage relates to the difficulties encountered by astronomers when they study a night sky that is too bright, in that light pollution drastically limits the efficiency of telescopic optical viewing systems.

Nowadays, conventional methods used to reduce light pollution consist in switching off light sources at a certain time and/or limiting the emission of such light sources to some spectral bands only. In other cases, systems are known for reducing light pollution which consist in the use of opaque screens that intercept part of the light radiation of a light source, essentially creating an area of shadow, such as for example the hoods over ordinary streetlights.

Such conventional systems are not devoid of drawbacks, among which there is the fact that they are not particularly efficient, since they do not make it possible to increase energy savings for the same lighting directed at the area of effective interest.

Another drawback of such conventional systems consists in the fact that they cannot be easily applied to all types of light sources, such as for example luminous signs, or advertising screens. The aim of the present invention consists in the provision of a system for limiting the diffusion of light which solves the above drawbacks and overcomes other problems of the known art, by making it possible to reduce the light pollution emitted by various types of light sources.

Within this aim, an object of the present invention is to provide a system for limiting the diffusion of light which ensures an effective and efficient screening of the light from unwanted directions in apparatuses that by their nature have up to now been essentially unscreened, such as for example advertising signs or business signs for which nowadays systems would be prescribed for limiting light pollution, i.e. switching-off at a certain time and/or limitation of the total flow emitted in every direction.

Another object of the invention consists in the provision of a system for limiting the diffusion of light which ensures increased energy savings with respect to conventional systems.

Another object of the invention consists in the provision of a system for limiting the diffusion of light which is capable of offering the strongest guarantees of reliability and safety of use.

Another object of the invention consists in the provision of a system for limiting the diffusion of light which is easy to implement.

This aim and these and other objects which will become more apparent hereinafter are all achieved by a system for limiting the diffusion of light emitted by a light source, characterized in that it comprises a plurality of identical refracting prisms which are superimposed at parallel and mutually opposite faces of said refracting prisms, said refracting prisms having an entry face, which extends transversely with respect to said parallel faces and is adapted to intercept at least part of the light emitted by said light source, each one of said refracting prisms comprising an exit face for the light intercepted by said entry face, said exit face extending transversely with respect to said parallel faces, all the exit faces of said refracting prisms being adapted to refract said intercepted light so as to direct it into a limited region of space.

Further characteristics and advantages of the invention will become more apparent from the description of two preferred, but not exclusive, embodiments of the system for limiting the diffusion of light according to the invention, illustrated by way of non-limiting example with the help of the accompanying drawings wherein:

Figure 1 is a perspective view of a system for limiting the diffusion of light, according to the invention, applied, by way of example, to a luminous sign;

Figure 2 is a side view of the sign in Figure 1 , which shows the limited diffusion of the light, according to the invention;

Figure 3 is a side view of a portion of the system for limiting the diffusion of light according to a first embodiment, which shows in particular the refracting prisms;

Figure 4 is a side view of a portion of the system for limiting the diffusion of light, according to a second embodiment;

Figure 5 is a side view of a portion of the system for limiting the diffusion of light, according to a third embodiment;

Figure 6 is a side view of a portion of the system for limiting the diffusion of light, according to a fourth embodiment;

Figure 7 is a schematic side view of a refracting prism according to the first embodiment, shown in Figure 3, which shows the passage of light through a refracting prism, according to the laws of geometrical optics;

Figure 8 is a perspective view of a system for limiting the diffusion of light, according to the invention, applied, by way of example, to the lighting of a display window;

Figure 9 is a view from above of the system for limiting the diffusion of light shown in Figure 8.

With reference to the figures, the system for limiting the diffusion of light is generally designated by the reference numeral 1, where the light is emitted by a light source 3, such as for example a luminous sign, and is intercepted at least partially by a plurality of identical refracting prisms 2 which are superimposed at their parallel and mutually opposite faces 10.

The refracting prisms 2 have an entry face 11, which extends transversely with respect to the parallel faces 10 and is adapted to intercept at least part of the light emitted by the light source 3. Each one of the refracting prisms 2 comprises an exit face 4 for the light intercepted by the entry face 11. The exit face 4 extends transversely with respect to the parallel faces 10. All the exit faces 4 of the refracting prisms 2 are adapted to refract the intercepted light so as to direct it in a limited region 15 of surrounding space which is provided with a lower refractive index than that of the material of which the refracting prisms 2 are made. This space, in the preferred embodiments of the invention, is constituted substantially by air and the refractive index can thus be considered equal to 1 in the band of visible light.

The refracting prisms according to the invention can be obtained with normal techniques of manufacturing lenticular surfaces and can be deposited on a film, of suitable thickness, to be applied on the luminous surface for which it is desired to limit the phenomena of diffusion of light toward unwanted regions of the space.

Figure 1 shows the system 1 for limiting the diffusion of light applied to a luminous sign. The refracting prisms 2 are laterally adjacent and are superimposed onto each other so as to fully cover the luminous surface of the sign that represents the light source 3. Such refracting prisms 2, which are transparent, have, compared to visible light, a refractive index higher than 1, for example 1.5, and they can be made of glass or plastic, optionally doped. The refracting prisms 2 refract the light of the luminous sign so as to direct it to a limited region 15 of space with a refractive index substantially equal to 1 , as illustrated in Figure 2, thus allowing a person 16 to see the luminous sign and its content 17, while preventing the emission of light to unwanted regions, such as for example the region 18 of space over the horizon.

The interface region 20 between each pair of adjacent refracting prisms 2 is preferably opaque to visible light. Such a region is capable of absorbing light with an efficiency advantageously comprised between 90% and 99.99%.

Advantageously such an interface 20 is made of a material that is capable of completely absorbing light, for example a black screen, or which is subjected to a surface treatment that is capable of rendering it completely black or opaque.

Such a treatment can consist, for example, in painting with opaque black paint with an absorption efficiency of incident light which is generally higher than 96%, or in applying materials of the type of velvet, or of the type of carbon nanotubes, which have even higher efficiency levels.

Moreover an opaque surface 21 of the interface region 20 directed toward one of the refracting prisms 2 of a pair of adjacent refracting prisms 2 can be reflective.

Such a surface 21 is capable of reflecting visible light with a reflectivity comprised between 70% and 100% (total reflection) of incident light.

Advantageously such a surface 21 is made of a shiny material that is capable of completely reflecting light at least in the visible band, or that is subjected to a surface treatment capable of rendering it completely reflective.

Such a treatment can consist, for example, in painting with paints of the metalized grey type, which reflect at least 70% of incident light. An aluminizing treatment on plastic achieves a reflection higher than 85%, while adapted surface treatments based on metals, adapted to substrates both of glass and plastic, achieve reflections even higher than 95%. Alternatively it is possible to obtain total reflection by way of providing a thin layer of air between the prisms at the surface 21 of the interface region 20.

Between the light source 3 and the refracting prisms 2 which are laterally adjacent and superimposed there can be a transparent layer 30, for example the glass sheet that constitutes the display window of a shop, or the glass of a luminous sign, the bulb of a lightbulb, or the glass of a spotlight.

In order to cover the surface of interest of the light source 3, the system 1 for limiting the diffusion of light comprises a plurality of refracting prisms 2 which conveniently are superimposed and laterally adjacent. Such prisms 2 are superimposed on each other, with the opaque interface regions 20 alternating along a first direction, but are laterally adjacent, and continuous, along a second direction that is perpendicular to the first direction.

In particular, in the embodiment shown in Figures 1 and 2, where it is desired to direct the light exiting from the system 1 for limiting the diffusion of light in a substantially vertical direction, i.e., for example, to prevent the light from being diffused above the horizon of the light source, the prisms 2 are superimposed, with the opaque interface regions 20 alternating, in the vertical direction, and are laterally adjacent, and continuous, in the horizontal direction.

As illustrated in Figure 3, in a first embodiment of the invention, the refracting prisms 2 have a lateral section in the shape of a rectangular trapezium, where the parallel faces 10 arranged in the direction of overlapping of each refracting prism 2 define the bases of the trapezium and are substantially perpendicular to the entry face 11 of the light emitted by the source 3. The exit face 4 is inclined with respect to the parallel faces 10, and, with particular reference to the embodiment shown in Figure 3, it is inclined, and defines an acute angle with respect to the lower parallel face 10 of the prism 2, which, of the two parallel faces 10, is the one closest to the base of the space where the diffusion of visible light must be directed.

The operation of the system for limiting the diffusion of light is described below.

The explanation of the operation of the system for limiting the diffusion of light refers in particular to Figure 7, and draws on the laws of geometrical optics, which is the study of optical phenomena and assumes that light propagates in rectilinear rays, and in particular it draws on Snell's law, which describes the refraction of a light ray when passing between two media with different refractive indices.

Figure 7 shows a refracting prism 2 crossed by an incident ray i.

Considering the presence of the opaque interface region 20 between two refracting prisms 2, and optionally of the reflective surface 21 , i represents the light ray entering from the entry face 11 and incident on the exit face 4 having the minimum angle of incidence on the exit face 4.

The angle of incidence of a light ray on a surface is defined as the angle comprised between the light ray and the normal to the surface, while the angle of refraction is defined as the angle comprised between the refracted light ray exiting from such surface and the normal to that surface.

Considering the geometry of the refracting prism 2 shown in Figure 7, the light rays that can strike the exit face 4 with angles of incidence smaller than 6>, are in fact intercepted by the opaque interface regions 20. Any other ray entering from the entry face 11 , whether it directly strikes the exit face 4, or is reflected by the reflective surface 21 and thus strikes the exit face 4, will have an angle of incidence on the exit face 4 larger than 0,·.

By conveniently selecting the refractive index n of the material of which the refracting prism 2 is made, and the geometric dimensions of the prism itself, it is shown that the rays entering the refracting prisms 2 and exiting from the exit faces 4 of those prisms are directed to a desired and preset region of space downstream of the exit face 4 with respect to the direction of the light entering the prism.

For example, the refracting prism 2 the side view of which is shown in Figure 7 is made of a material with a refractive index n of 1.54, such as for example glass, and has the following dimensions (given per unit of thickness d of the prism):

a = 6.5;

b = 6.

As shown below, these dimensions are such that, in relation to the example refractive index n - 1.54 of the material of the prism, all light rays striking the exit face 4 will be refracted in directions that do not pass beyond the horizon line 40, therefore not flooding the region of space surrounding the prism above the horizon 40.

In particular, the angle comprised between the lower parallel face 10 and the exit face 4 of the prism 2 is S:

δ = arctan ( d) / (a - b )) [~ 63.4°];

The angle comprised between the lower parallel face 10 of the prism 2 and the ray i striking the exit face 4 of the prism 2 is a:

a = arctan ( d) / b ) [- 9.5°];

It follows from this that the angle of incidence < , is linked to the angles a and δ by the following relationship:

θ, = 90° - α - δ [~ 17.1°];

According to Snell's law, the angle of refraction 6_r, i.e. the angle comprised between the normal to the exit face 4 and the refracted ray r, is linked to the angle of incidence (9, and to the refractive index n by the following relationship:

6_r ~ arcsin (n * sin ( θι)) [~ 26.9°];

Considering that the normal 41 to the exit face 4 of the prism 2 forms an angle β with respect to the horizon 40 which is defined by the following relationship:

β = 90° - [- 26.6°];

it follows from this that the refracted ray r exiting from the exit face 4 of the prism 2 has a direction that does not vertically go beyond the horizon 40. The example illustrated makes it clear that it is possible to vary the parameters that define the geometry of the refracting prism 2, i.e. the lengths a, b and d, and its refractive index n so as to result in the directing of the rays exiting from the exit face 4 of the prism 2 exclusively in a desired and preset region. The same concept also applies to the further embodiments which are described below.

Figure 3, which illustrates the first embodiment of the invention, shows, by way of example, the path of some light rays 50-54 inside a refracting prism 2. In particular, note that the ray 50 passes through the prism 2 and is refracted at the exit face 4. The same applies to the ray 54. The ray 51 , however, strikes the opaque interface region 20, and is thus blocked. The ray 52 strikes the reflective surface 21 of the upper interface region 20 of the prism 2 in question, is reflected, and thus strikes the lower opaque interface region 20, where it is blocked. The ray 53 strikes the reflective surface 21 of the upper interface region 20 of the prism 2 in question, is reflected, strikes the exit face 4 and is thus refracted.

Figure 4 illustrates a second embodiment of the invention, in which the refracting prisms 102 have a lateral section in the shape of a parallelogram in which the entry face 111 and the exit face 104 are mutually parallel, but inclined with respect to the parallel faces 110. The interface region 120 between each of the refracting prisms 102 is opaque. The opaque interface regions 120 between each pair of prisms 102 are such that a ray entering at the entry face 111 and perpendicularly to the entry face is intercepted by the opaque interface region 120, or possibly by a reflective surface 121 of the interface region 120. Therefore the rays incident on the exit face 104 of the prism 102 are refracted upon exiting from the prism 102 in a direction that never goes above the horizon.

Figure 4 illustrates, by way of example, the path of some light rays 150-154 inside the refracting prism 102. Similarly to the case in Figure 3, the ray 150 passes through the prism 102 and is refracted at the exit face 104, and so is the ray 154. However, the ray 151 strikes the opaque interface region 120, and is thus blocked. The ray 152 strikes the reflective surface 121 of the upper interface region 120 of the prism 102 in question, is reflected, and thus strikes the lower opaque interface region 120, where it is blocked. The ray 153 strikes the reflective surface 121 of the upper interface region 120 of the prism 102 in question, is reflected, strikes the exit face 104 and is thus refracted.

Figure 5 illustrates a third embodiment according to the invention, in which the refracting prisms 202 have an entry face 211 which is inclined with respect to the parallel faces 210, and an exit face 204 which is curved and with its concavity directed toward the inside of the respective prism 202, having for example the shape of an arc of circumference. The interface regions 220 between each prism 202 are opaque. All incident rays that strike the exit face 204 are refracted upon exiting from the prism 202 in a direction that never goes above the horizon, thanks to the fact that the center of the arc of circumference that constitutes the face 204 lies on the line 232 that is perpendicular to the entry face 211 and passes through the point of intersection 233 between the lower interface region 220 of the prism 202 in question and the entry face 211. In this embodiment too, a surface 221 of the interface region 220 can be reflective.

Figure 5 illustrates, by way of example, the path of some light rays 250-254 inside the refracting prism 202. The ray 250 passes through the prism 202 and is refracted at the exit face 204, and so is the ray 254. However, the ray 251 strikes the opaque interface region 220, and is thus blocked. The ray 252 strikes the reflective surface 221 of the upper interface region 220 of the prism 202 in question, is reflected, and thus strikes the lower opaque interface region 220, where it is blocked. The ray 253 strikes the reflective surface 221 of the upper interface region 220 of the prism 202 in question, is reflected, strikes the exit face 204 and is thus refracted.

Figure 6 illustrates a fourth embodiment according to the invention, in which the refracting prisms 302 have an entry face 311 which is substantially perpendicular to the parallel faces 310, where the exit face 304 is curved with the concavity directed toward the inside of the respective prism 302, and is for example constituted by an arc of circumference. The entry face 311 has an opaque portion 331 which is such as to intercept light whose incident rays would be refracted in a direction such as to go above the horizon. In particular, if the parallel faces 310 of a prism 302 have the same dimensions, then the opaque portion 331 will cover all of the portion of the entry face 311 of the prism 302 that lies under the line 332 passing through the center of the arc of circumference that constitutes the face 304, such line 332 being perpendicular to the entry face 311. The interface regions 320 between each of the prisms 302 are opaque, and if possible a surface 321 of the interface region 320 is reflective.

Figure 6 illustrates, by way of example, the path of some light rays 350-355 inside the refracting prism 302. The ray 350 passes through the prism 302 and is refracted at the exit face 304, and so is the ray 354. However, the ray 351 strikes the opaque interface region 320, and is thus blocked. The ray 352 strikes the reflective surface 321 of the upper interface region 320 of the prism 302 in question, is reflected, and thus strikes the lower opaque interface region 320, where it is blocked. The ray 353 strikes the reflective surface 321 of the upper interface region 320 of the prism 302 in question, is reflected, strikes the exit face 304 and is thus refracted. The ray 355 is blocked by the opaque portion 331 in front of the entry face 311 before it enters the prism 302.

Advantageously, the system for limiting the diffusion of light can be applied to a luminous sign or other light source, or it can be provided as an integral part of a luminous sign or other light source, where it is for example provided integrally with the diffuser panel of a luminous sign.

Figures 8 and 9 illustrate the system 1 for limiting the diffusion of light applied to the lighting of a display window 80, where the refracting prisms are applied to the glass of the light sources 3, such as for example spotlights, of the lighting system of the display window 80. The system 1 for limiting the diffusion of light refracts the intercepted light of the light sources 3 so as to direct it into a limited region 81 of the surrounding space, inside the display window 80. In fact the light rays are contained within the glass 82 of the display window 80, illuminating the content of the display window 80, but avoiding dazzling a person 83 who, from outside the glass 82, looks into the display window 80.

The system for limiting the diffusion of light, conceived as a panel for application to a luminous sign, can be for example conceived in the shape of a cylinder or a hemisphere, in order to limit the diffusion of the light emitted by a spherical source, such as for example a conventional lightbulb.

In practice it has been found that the system for limiting the diffusion of light, according to the present invention, achieves the intended aim and objects by making it possible to limit the diffusion of light by directing it into a limited region of the surrounding space.

Another advantage of the system for limiting the diffusion of light, according to the invention, consists in the fact that it enables the drastic reduction of light pollution.

Another advantage of the system for limiting the diffusion of light, according to the invention, consists in the fact that it ensures greater efficiency of lighting than conventional systems for the reduction of light pollution. In fact, the system for limiting the diffusion of light, according to the invention, is capable of deviating light toward the desired region of space which, through conventional systems, such as opaque screens, would simply be blocked.

Another advantage of the invention consists in the fact that it can be adapted to different types of light source.

The system for limiting the diffusion of light thus conceived is susceptible of numerous modifications and variations all of which are within the scope of the appended claims.

Moreover, all the details may be substituted by other, technically equivalent elements.

In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements.

The disclosures in Italian Patent Application No. VR2012A000062 from which this application claims priority are incorporated herein by reference.

Where the technical features mentioned in any claim are followed by reference numerals and/or signs, those reference numerals and/or signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference numerals and/or signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference numerals and/or signs.

Claims

1. A system (1) for limiting the diffusion of light emitted by a light source (3), characterized in that it comprises a plurality of identical refracting prisms (2, 102, 202, 302) which are superimposed at parallel and mutually opposite faces (10, 110, 210, 310) of said refracting prisms (2, 102, 202, 302), said refracting prisms (2, 102, 202, 302) having an entry face (11 , 111 , 211, 311), which extends transversely with respect to said parallel faces (10, 110, 210, 310) and is adapted to intercept at least part of the light emitted by said light source (3), each one of said refracting prisms (2, 102, 202, 302) comprising an exit face (4, 104, 204, 304) for the light intercepted by said entry face (11 , 111 , 211 , 311), said exit face (4, 104, 204, 304) extending transversely with respect to said parallel faces (10, 110, 210, 310), all the exit faces (4, 104, 204, 304) of said refracting prisms (2, 102, 202, 302) being adapted to refract said intercepted light so as to direct it into a limited region (15) of space.

2. The system (1) for limiting the diffusion of light according to claim 1, characterized in that the region of interface (20, 120, 220, 320) between each pair of adjacent refracting prisms (2, 102, 202, 302) is opaque.

3. The system (1) for limiting the diffusion of light according to claim 2, characterized in that a surface (21, 121 , 221 , 321) of said opaque interface region (20, 120, 220, 320) directed toward one of the refracting prisms (2, 102, 202, 302) of said pair of refracting prisms (2, 102, 202, 302) is reflective.

4. The system (1) for limiting the diffusion of light according to one or more of the preceding claims, characterized in that said exit face (4, 104) is inclined with respect to said parallel and mutually opposite faces (10, 210) of said refracting prism (2, 102).

5. The system (1) for limiting the diffusion of light according to one or more of claims 1 to 3, characterized in that said exit face (204, 304) has at least one curved portion (234).

6. The system (1) for limiting the diffusion of light according to one or more of the preceding claims, characterized in that said entry face (311) comprises an opaque portion (331).

7. The system (1) for limiting the diffusion of light according to one or more of the preceding claims, characterized in that said light source (3) is a luminous sign or a backlit display window.

8. The system (1) for limiting the diffusion of light according to one or more of the preceding claims, characterized in that the rays of refracted light that exit from said exit face (4, 104, 204, 304) do not pass beyond the horizon line of the light source (40).

9. The system (1) for limiting the diffusion of light according to one or more of the preceding claims, wherein said refracting prisms (2, 102, 202, 302) are applied to a transparent film.

10. The system (1) for limiting the diffusion of light according to one or more of the preceding claims, wherein said refracting prisms (2, 102, 202,

302) are applied to a surface of the light source.