ITVI20100214A1 - OPTICAL SYSTEM FOR THE HOMOGENEOUS DIFFUSION OF LIGHT EMITTED BY LIGHT SOURCES - Google Patents

Description

OPTICAL SYSTEM FOR THE HOMOGENEOUS DIFFUSION OF LIGHT

EMITTED BY LIGHT SOURCES

------

The present invention is part of the field of lighting technology, and in particular it refers to an optical system for the homogeneous diffusion of the light emitted by point light sources, in particular Light Emitting Diodes (LED).

More specifically, the invention relates to a luminaire for indoor lighting, which makes use of point light sources, such as LEDs, and guarantees a homogeneous diffusion of light, while maintaining high efficiency of the luminaire.

In recent years, LEDs have shown a high potential for application in the field of architecture, presenting countless advantages.

For example, in addition to being very economical and durable over time, their dimensions allow you to integrate a lighting system directly into the architecture, being able to eliminate the classic lighting source and positioning the light source only where it is needed.

The presence of light with the use of LEDs, in the absence of a visible lighting body, because it is embedded in an architectural detail, offers the architect countless possibilities to express their creative flair, creating different and suggestive light scenarios each time. .

The possibility of creating, with LEDs, a light of any color, or a white light of any color temperature, has allowed the application of these light sources to the lighting bodies, causing in itself a certain revolution in architecture. and in design.

Even these light sources, like all the others, are subject to specific regulations regarding lighting in indoor areas, to guarantee the degree of luminance necessary for the various activities. For example, in the specific field of lighting worktops in the presence of video terminals, the UNI EN 12464-1 standard analyzes the usual visual tasks, highlighting the needs for visual comfort and giving indications on the levels of illumination, uniformity and maximum degree of glare necessary for the different visual performances that involve the use of video terminals.

In order to obtain correct lighting, it is necessary to satisfy three fundamental needs, such as visual comfort (feeling of well-being), visual performance (carrying out the task even in difficult and protracted situations) and safety.

To meet these needs it is necessary to avoid too high or too low luminance contrasts, because an annoying glare prevents a correct vision of the visual task.

To meet the requirements defined in this standard, some devices currently on the market use lenses of suitable shape (Figure 1a) to obtain the desired distribution of illuminance on a reference surface. These devices have the drawback of presenting a luminance that is too high, as the observer sees the radiation coming from a small area corresponding to the virtual image of the LED.

In other known devices, shown in Figure 1b, specular reflectors are used, which partially deflect the radiation from the LEDs. These devices have the disadvantage of having an excessive luminance in any case, as the radiation appears to come from the LED itself for direct light, or from the virtual LED source (specular reflector) for the reflected light. Another solution, adopted in some devices illustrated in figure 1c, is to adopt sets of LEDs, shielded by diffusing filters. In this case, it is possible to use a sufficiently diffusing material to effectively lower the luminance, given the large surface of the screens, but the transmission efficiency is generally low.

Finally, a solution, like the one shown in figure 1d, involves the use of light guides, usually made of plexiglass, which work by exploiting the internal reflection through their suitably polished walls. A disadvantage of this last solution is the refraction of light through the walls, which determines a low efficiency of the lighting body.

Obviously, although it is possible to create a lighting device in compliance with the aforementioned regulations, adopting the last two solutions, the resulting low efficiency would eliminate the advantages attributable to the choice of LEDs as light sources. In fact, by decreasing the efficiency, it would be necessary to increase the number of diodes used and consequently the energy consumption, as well as the overall volume of the lighting body.

Therefore, in the state of the art, the lack of an optical LED system, capable of complying with the regulations and which, at the same time, also allows to take advantage of the characteristics of the LEDs that make them advantageous compared to other light sources.

The aim of the present invention is therefore that of overcoming the drawbacks of the known art, realizing an optical system for the homogeneous diffusion of the light emitted by point sources.

In particular, the primary purpose of the present invention is to devise an optical system for limiting glare due to direct or indirect light from LEDs, without thereby losing the efficiency of the lighting body obtained.

A further purpose of the invention is to create an optical system for the homogeneous diffusion of the light emitted by point sources, in which the light radiations from these sources undergo only one reflection, to avoid the efficiency losses that usually occur. with multiple reflections.

Furthermore, the aim of the invention is to provide an optical system for the homogeneous diffusion of the light emitted by point sources, in which these sources are not directly visible, nor indirectly reflected in a reflector.

Another object of the present invention is to indicate an optical system for the homogeneous diffusion of the light emitted by point sources, which guarantees sufficiently high and rationally distributed luminances, in relation to the illuminance deriving from ambient or external light, to allow perception of important areas, as well as details, and minimize any form of glare.

Finally, the object of the present invention is that of realizing an efficient optical system, which is simple and inexpensive to make, so as to be able to enter the market at a competitive price, offering advantageous energy savings.

In this general framework of research of obtaining the best aesthetic and technical characteristics for a lighting device, the present invention is inserted, aimed at achieving characteristics of elegance, efficiency and reliability in an optical system for the homogeneous diffusion of light. emitted from point sources, the structure of which thus presents aesthetic and functional advantages.

These and other purposes, according to the present invention, are achieved by realizing an optical system for the homogeneous diffusion of the light emitted by point light sources, according to the attached claim 1.

Further technical characteristics are contained in the subsequent dependent claims.

The present invention will now be described, for illustrative but not limitative purposes, according to an embodiment thereof, with particular reference to the attached figures, in which the operation of the system according to the invention is schematically shown. In particular,

figure 1a schematically shows a first optical system for the diffusion of the light emitted by a point source according to a first known solution;

figure 1b schematically shows a second optical system for the diffusion of the light emitted by a point source according to a second known solution;

figure 1c schematically shows a third optical system for the diffusion of the light emitted by a point source according to a third known solution;

figure 1d schematically shows a fourth optical system for the diffusion of the light emitted by a point source according to a fourth known solution;

figure 2 is a perspective view from below of an optical system according to the invention;

figure 3 is an axonometric section of the optical system of figure 2, in which the shielding element is not present;

figure 4 is a half sectional view of the primary optical system of figure 3, in which the schematic tracing of the rays is shown, in the ideal case of point source and totally specular reflector; And

figure 5 shows the tracing of the rays in the optical system of figure 2 with primary diffusing optics and shielding element.

With particular reference to figures 2, 3, 4 and 5 mentioned, the optical system, object of the invention, which can be used in part or in full, in one or more units, in the design of a reflector for lighting fixtures, is defines as follows. The optical system, indicated in the figures with the numerical reference 1, consists of a primary optic 2 and a shielding element 3.

The primary optic 2 consists of one or more sets of LEDs 4 and one or more reflecting surfaces 5 diffusing.

Now and in the following, we mean by â € œscattering surfaceâ € any surface with a diffuse reflectance component that is not zero, even in the presence of a specular component.

The shielding element 3 consists of an anti-glare grille with one or more slats 6.

The peculiarity of primary optic 2 consists in the fact that the radiation 7, coming out of it, is not the direct radiation 8 of the LEDs 4. The LEDs 4 are not directly visible and their radiation 8 is conveyed outside of the luminaire with 5 diffusing reflective surfaces. In this way, the direct radiations 8 of the LEDs 4 are distributed over a larger surface than the emission ones, ie those of the LEDs 4 themselves. The luminance resulting from this primary optic 2, therefore, is lower than that which would result in the case of direct light emission by the same group of LEDs 4. The consequent reduction of glare, necessary to satisfy the aforementioned legislation , a further reduction is added, due to the application of the shielding element 3, which consists of an anti-glare grille.

Another peculiarity consists in the shape of the diffusing reflecting surfaces 5 and in the position of the LEDs 4 with respect to them: the primary optic 2 is designed so that the radiations 8 coming from the LEDs undergo only one reflection, thus avoiding efficiency losses. that would occur with multiple reflections. To increase this efficiency, highly reflective materials are used to create the diffusing reflective surfaces 5.

In particular, in the embodiment described, the material used is satin-finished aluminum with very high reflectance; alternatively, it is possible to use plastic or metal materials, painted with a high reflectance white diffusing paint, obtaining in the latter case a better comfort, even if at the expense of efficiency.

With reference to figures 3 and 4, the primary optic 2 is made up of two parts 9 symmetrical with respect to a central plane 10. In each part 9 the reflector is obtained by the extrusion of an elliptical profile.

The LEDs 4 are arranged along a row 11 coinciding with the axis perpendicular to the plane of the ellipse, passing through one of the foci F1 of the ellipse itself. Figure 4 illustrates the tracing of rays 7, 8, in section, in the simplified case of a single point source with two-dimensional emission in the drawing plane and in the case of a specular reflector. In the ideal case of a specular reflector, the radiation 7 is conveyed by the reflecting surface 5 towards the outside of the primary optic 2, after having undergone a single reflection on it.

With this geometry, in fact, a virtual source 12 is obtained, corresponding to the axis passing through the other focus F2 of the ellipse. The cutting of part 9, in correspondence with the axis passing through the two foci F1, F2, prevents the radiation 7, coming from the virtual source 12, from meeting the reflecting surface 5 a second time.

Up to now, a particular embodiment of the primary optic included in the optical system according to the invention has been described, concerning the extrusion of an elliptical profile, but it is understood that the same result can be obtained through the formation of any profile, capable of conveying the radiations coming from a mono or two-dimensional LED source towards the outside, minimizing the number of interactions with the reflector. Of course, the profile can also be obtained by bending, molding, or any other technique available at the time of making the optical system, suitable for the type of material used.

The second focus F2 of the ellipse, in which the rays 7 are concentrated, coming from the ideal point source 12, after being reflected by the reflecting surface 5, can be placed in a different position from the one illustrated, provided that the requests above, to minimize the number of interactions with reflective surfaces 5.

To avoid seeing the image of the LEDs reflected in the reflecting surface 5, the internal surface of the primary optic 2 is made using a diffusing material rather than a specular one. This also allows to increase the emitting surface and consequently reduce the glare coming from the luminaire.

Once the profile of the primary optic 2 has been defined, the LEDs 4 are oriented in order to maximize the flux coming out of the luminaire.

With reference now to figures 2 and 5, as already mentioned, the shielding element 3 is a CPC (Compound Parabolic Concentrator) anti-glare grille, which reduces the angle of emission of the radiation by the primary optic 2 .

In order to comply with the aforementioned standard, the slats 6 of the grate are designed with an angle with a cutting value of 60 degrees. With angles greater than 65 ° with respect to the vertical, a luminance of less than 200 cd / m2 is obtained.

The use of a CPC grid for the screen element is not to be construed as limiting. The shielding element can also be made up, for example, of lamellae obtained from extruded circumferential arcs or planes.

The primary optic 2 and the shielding element 3 together form a single complete optical system 1 (or cell) that can be replicated according to the overall output flux required for the lighting fixture to which it is intended to be applied. In the embodiment described here, represented in Figure 2, two cells 1, symmetrical with respect to a plane, constitute an elementary module.

In an alternative embodiment of the invention, an elementary module can be composed of a single cell 1 or of any number of cells 1 arranged according to various symmetry criteria, or even by one of the two parts 9 of the primary optic 2, with an appropriate shielding element, if necessary.

Advantageously, by applying the optical unit according to the invention to a lighting body, it is possible to illuminate very large areas, while ensuring a substantially uniform illumination on the work surface.

A further advantage of the present invention is that of obtaining an indirect light emission, since the source used is invisible.

Another advantage of the present invention is that of being able to use a smaller number of light sources to obtain the level of illumination required by the standards, thanks to the high efficiency of the LED sources and thanks to the high efficiency of the optical system described.

The present invention has been described by way of illustration, but not of limitation, according to a preferred embodiment thereof, but it is to be understood that variations and / or modifications may be made by those skilled in the art without thereby departing from the relative scope of protection. , as defined by the appended claims.

Claims (8)

CLAIMS 1) Optical system (1) for the homogeneous diffusion of the light emitted by light sources, comprising at least one optic (9), or primary module, having one or more rows (11) of light sources (4), said system being characterized by the fact that - said optic or primary module (9) has a profile suitable for reflecting the rays (8) coming from said one or more rows (11) of light sources (4), and by the fact that - said one or more rows (11) of light sources (4) is arranged inside said profile, said profile presenting inside it reflecting surfaces (5) suitable to reflect said rays (8) along a non-intersecting direction said reflecting surfaces (5), without direct light emission from said reflecting surfaces (5). 2) Optical system (1) according to claim 1, characterized in that said light sources (4) comprise point light sources, in particular, for example, LEDs. 3) Optical system (1) according to claim 1 or 2, characterized in that said primary module (9) has at least an elliptical portion, with a first (F1) and a second (F2) focus, called one or more rows ( 11) of light sources (4) coinciding with the axis passing through said first focus (F1), or being close to it. 4) Optical system (1) according to one of claims 1-3, characterized in that said reflecting surfaces (5) are made using a diffusing or partially diffusing material. 5) Optical system (1) according to claim 4, characterized in that said diffusing material is high reflectance satin-finished aluminum. 6) Optical system (1) according to claim 4, characterized in that said diffusing material is a plastic or metallic material, painted with a high reflectance white diffusing paint. 7) Optical system (1) according to one of claims 1-6, characterized in that it comprises at least two primary modules (9), arranged in pairs symmetrically with respect to a vertical plane (10), parallel to said one or more rows (11) ) of light sources (4), or combined according to various symmetries. 8) Optical system (1) according to one of claims 1-7, characterized in that it further comprises a shielding element (3), formed by a CPC anti-glare grille, or with extruded circumferential arcs or planes.