IT202100000074A1 - OPTICAL FILTER, LIGHTING DEVICE SIMULATING THE NATURAL LIGHT OF THE SKY AND THE SUN EMPLOYING THE SAME AND MANUFACTURING PROCESS AS AN OPTICAL FILTER - Google Patents

Description

OPTICAL FILTER, LIGHTING DEVICE THAT SIMULATES LIGHT

NATURAL SKY AND SUN EMPLOYING THE SAME AND PROCESS AS

PRODUCTION OF AN OPTICAL FILTER

Technical field

[1] The present invention refers in general terms to a new optical filter and in particular to an optical filter configured to transform an incident light into a filtered light having an angular luminance profile characterized by a first substantially constant value for emission directions including inside a cone of angular acceptance and a second substantially zero value for emission directions outside the cone of angular acceptance. Such an optical filter proves to be particularly suitable for use in a device which allows the artificial reproduction of a light capable of recreating, in interior spaces, the experience of the natural light of the sky and the sun on a day with clear skies. The present invention also refers to a lighting device simulating natural light from the sky and the sun which employs such an optical filter as well as an optical filter manufacturing process.

State of art

[2] From the international patent application n. WO 2020/201938 of the same Applicant so? as from further experience gained by the Applicant, it can be seen that the main characteristics of natural light on a day with a clear sky that distinguish it from the artificial light of the lamps are connected to the capacity? Of:

(i) produce sharp shadows, thanks to the highly directional characteristic of sunlight, having a divergence of only 0.5 degrees,

(ii) produce blue shadows, being these illuminated by the light of the sky whose correlated color temperature ? CCT ? ? much higher than the correlated color temperature of sunlight,

(iii) produce luminous shadows, i.e. with a luminance typically no lower than 15-20% of the characteristic luminance of surfaces exposed to both sky and sun light,

(iv) produce an image of the sky and the sun perceived by the eye of the observer at infinite distance, and

(v) produce the image of a clear cloudless sky and a round sun in stark contrast to the sky.

[3] The industrial development of a device capable of producing daylight identical to natural light according to all five of the above characteristics is not ? never been obtained to date. Furthermore, the complexity intrinsic to the achievement of such an objective, would imply costs such as to make it difficult to commercialize any resulting product.

[4] In particular, in order to produce in the eye an image of the sun at an infinite distance (iv characteristic) ? It is necessary that the luminance profile of the light be spatially uniform across the viewing surface. This ? in fact the condition by which the two eyes, to see the same image, must be aligned in a parallel way, giving the brain the information of an object substantially at an infinite distance. Also, in order to ensure the image of a round sun in stark contrast to a cloudless sky (v characteristic) ? The angular profile of luminance from sunlight must have a constant value up to a maximum angle, and be substantially zero elsewhere. A standard bell-shaped (e.g. Gaussian) luminance angular profile with a ?fading? gradually in the sky, the eye in fact associates the presence of clouds or mist in the sky. As the Applicant has been able to directly verify, this feature is not appreciated by the market, as it compromises the capacity? of the device to evoke the experience of a day with clear skies.

[5] An optical filter theoretically capable of producing a spatially uniform luminance on a given surface, and at the same time of producing a constant angular profile of luminance within a cone of angular acceptance, ? the tandem micro-optical mixer, hereinafter pi? simply ?tandem mixer? considered by the Applicant in the device described in WO 2020/201938. This optical filter? composed of two identical arrays of lenses (or micro-lenses), one facing the other, and arranged at a distance equal to the common focal length. This optical filter produces in the far field, and therefore also on the retina in the case of infinity vision, the uniformly illuminated image of the lens aperture. There? provided that the lenses of the input matrix are in turn illuminated uniformly, which is not difficult to achieve in the case of small-sized lenses.

[6] However, the tandem mixer employed in WO 2020/201938 has some relevant problems in practice. First of all, it reproduces in the far field, in addition to the main image, also one or more? secondary or ghost images, of the same shape as the main image, also uniformly illuminated, although typically with lower illuminance than that of the main image. This circumstance occurs when the light entering the channels formed by the pairs of facing lenses also comes from directions outside the filter acceptance cone, delimited by the bundle of straight lines passing through the center of the entrance lens and the edge of the entrance lens. ?exit. Typically this happens, for example, when the light to be mixed includes, in addition to a main component having characteristics of high and controlled directionality, also a secondary or spurious component, also called ?stray light?, for example associated with the presence of imperfections in the optical system that produce uncontrolled phenomena of diffusion and/or multiple reflection of light, as often happens in the case of the use of Fresnel optics. Or, it occurs when the incoming light includes tails in the angular profile, as for example in the frequent case of a regular angular profile of the Gaussian type. In such circumstances, the unwanted phenomenon that occurs? due to interaction or ?cross talk? between adjacent channels, since these are not optically independent of each other. Specifically, the light entering through an entrance lens of a channel, coming from directions outside the acceptance cone, exits the exit lens of a different channel, producing a ghost image laterally to the main image, associated with a second profile of luminance identical to the first except for the fact that it occurs at a different exit angle.

[7] A second problem of the tandem mixer employed in the device described in WO 2020/201938 ? given by the fact that, in order to ensure maximum simplicity? constructive and maximum luminosity, the lens matrices that compose it are made up of square, rectangular or hexagonal lenses, or in any case of a shape such as to allow maximum compaction and therefore maximum coverage of the input and output surfaces. Consequently, the image they produce in the far field is not? circular but square, or rectangular, or hexagonal etc. In summary, a device that simply uses a tandem mixer as described in WO 2020/201938 would produce in the sky the main image of a square (or rectangular, or hexagonal) sun surrounded by ghost images identical to the main one except for the fact that they less intense.

[8] In order to eliminate the problem of subpictures, in WO 2020/201938 ? It was considered to introduce, downstream of the tandem mixer, a spatial filter obtained by means of a matrix of parallel absorbing channels, for example organized according to a honeycomb structure. This spatial filter has for? the defect of introducing a regular pattern in the luminance profile easily perceptible by the observer, to remove which the Applicant has proposed the introduction of a further filter, ie a low angle diffuser filter, downstream of it. Significantly, this low-angle diffuser also aims to mitigate the second mentioned tandem mixer problem, as it allows the image of an object positioned beyond the image to be blurred. of it, the more how much more the item ? away, thus transforming the images of squares, rectangles, hexagons, etc. into circles.

[9] Like this, yes ? given up on producing a starkly contrasting sun with the sky. In fact, both the absorbing channel spatial filter, due to the geometric cut it imposes on the light that propagates at greater angles, and the low angle diffusing filter, independently and therefore co-operatively, transform an angular profile of constant luminance, such as that produced by the tandem mixer, in a bell-shaped profile. In practice, the result produced by the device described in WO 2020/201938 ? that of producing an image of a strongly out of focus sun, with contours that gradually fade into the sky, as happens in nature in the presence of haze or thin clouds in the upper atmosphere.

Summary of the Invention

[10] Purpose of the present invention? therefore that of devising an optical filter capable of guaranteeing the generation of a light having an angular distribution with the same characteristic shape as the angular distribution of sunlight, i.e. an angular distribution characterized by a substantially constant value of luminance for directions within a certain solid angle, i.e. the subtended solid angle or cone of the image of the sun, and substantially zero elsewhere, this value being equal to 0.5 degrees in the case of the natural sun (or equal to 0.25 degrees if one considers the semi-aperture of the cone). All of that? regardless of the angular distribution of the incoming light, i.e. both in the presence of spurious light (stray light), whether it is characterized by the presence of a background (background) for all directions, or by an angular luminance profile with even intense peaks for directions external or very external to the cone subtended by the image of the sun, both in the presence of important tails in the angular profile at angles close to the opening angle of the angular acceptance cone, thus eliminating the undesired effect caused by standard optical components in the ?scope of enlightenment.

[11] Another purpose of the present invention ? that of designing an optical filter which, once used in a lighting device that simulates the natural light of the sky and the sun, is capable of generating an infinite image of a circular sun with well-defined contours.

[12] Still a purpose? that of designing an optical filter which, once used in a lighting device that simulates the natural light of the sky and the sun, makes the use of both spatial filters with absorbing channels and low-angle diffusing filters superfluous, allowing preserve the sharp contrast between the image of the sun and that of the sky.

[13] Not the last aim of the present invention? that of creating a lighting device that simulates the natural light of the sky and the sun capable of offering an infinite image of a circular sun with well-defined contours.

[14] Another purpose of the present invention? that of realizing a process for the production of an optical filter for use in lighting devices that simulate the natural light of the sky and the sun which can be performed in a simple and cost-effective manner.

[15] These and other objects of the present invention are achieved by means of an optical filter for lighting devices which simulate the natural light of the sky and the sun incorporating the characteristics of the attached claims, which form an integral part of the present description.

[16] In accordance with a first aspect thereof, the invention therefore relates to an optical filter configured to transform an incident light into a filtered light having an angular luminance profile characterized by a first substantially constant value for emission directions included within an angular acceptance cone and a second substantially zero value for emission directions outside the angular acceptance cone, wherein the optical filter comprises a substantially flat input surface, a substantially flat output surface and parallel to the d? entrance, a plurality? of cylindrical elements made of a material substantially transparent to light, a first element of optically absorbent material configured and arranged with respect to the cylindrical elements in such a way as to prevent the passage of light between adjacent cylindrical elements of the plurality of cylindrical elements, a second element of optically non-transparent material configured and arranged with respect to the cylindrical elements in such a way as to prevent the passage of light parallel to the cylindrical elements and externally thereto through the spaces between adjacent cylindrical elements, at least a plurality of first lenses with positive focal length equal to the length of the cylindrical elements, each first lens of the plurality? of first lenses being coupled to or defining the outlet face of a respective cylindrical element.

[17] The cylindrical elements of the plurality? of cylindrical elements have a substantially identical shape to each other and comprise a substantially circular inlet face having a diameter of the cylindrical elements, a substantially circular outlet face having the diameter of the cylindrical elements and a lateral surface which extends perimetrically between the inlet face and the outlet face for a length of the cylindrical elements.

[18] The cylindrical elements are arranged side by side and parallel to each other, in such a way as to define a plurality of gaps between adjacent cylindrical elements. Furthermore, the cylindrical elements have a cylinder axis perpendicular to the inlet and outlet surfaces and are arranged with the inlet face substantially overlapping the inlet surface and with the outlet face substantially overlapping the outlet surface.

[19] In the context of the present description and in the attached claims, a face (inlet or outlet) of a cylindrical element is said to be substantially superimposed, or hereinafter simply superimposed, on a surface (inlet or outlet) of the optical filter when at least one point of the face of the cylindrical element belongs to the surface, for example when the entire face belongs to the surface, in the case of a flat face, or when the perimeter of the face belongs to the surface, in the case of a curved face .

[20] The optical filter object of the present invention allows ghost images to be removed by producing a single clear image of the sun thanks to the first element of optically absorbing material positioned inside the filter upstream of the plurality of of prime lenses. This first element of optically absorbent material ? in fact configured and arranged in such a way as to remove the cross-talk between the channels at the origin, without operating an excessive geometric cut on the components that generate, externally to the filter, the light that propagates to the most? large within the cone of acceptance, and therefore without excessively reducing the illumination of the edge of the image of the sun which forms on the observer's retina.

[21] Furthermore, the optical filter object of the present invention ? capable of producing a circular image of the sun, making the use of a low angle diffuser filter superfluous.

[22] Both of these aspects advantageously prevent a blurring of the image of the sun.

[23] The essential role of the lenses placed at the outlet emerges considering a matrix of parallel and cylindrical absorbing channels without lenses at the entrance and at the outlet of the channels. In this case the rays which are not absorbed are (only) those which propagate along the axis of the channels, and which therefore contribute to forming the central portion of the image in the far field. On the contrary, as regards the rays which propagate in other directions, only a part of them ? transmitted by the matrix, this part being as much less as more? great ? the angle of the rays with respect to the axis, and reducing to zero for directions that cross the channel passing from an edge at the entrance to the opposite edge at the exit. Therefore the far-field image will not be? uniformly illuminated (or, equivalently, the angular luminance profile will not be constant), this image having on the contrary a bell-shaped illuminance profile, which fades and vanishes at the edge of the image, not being in this way able to offer a jump sharp in the luminance profile for the observer looking at the light emitted by the source. It should be noted that the introduction of a matrix of lenses positioned on the entrance openings and having a focal length equal to the length of the channels would not modify the result. In fact, an extreme point on the edge of the far field image is always illuminated only by the single beam that crosses the channel passing from one edge at the entrance to the opposite edge at the exit.

[24] On the contrary, in the case of a matrix of parallel and cylindrical absorbing channels in association with a matrix of circular aperture lenses, with a focal length equal to the length of the channels and positioned at the exit of the channels themselves, each lens produces in the field far away the image of the field present in its focal plane, i.e. the image of the circular entrance opening of the canal. Here the central point of the entrance opening will be? reproduced in the image by the rays belonging to a first cone, formed by all the rays which originate from this central point and which reach the exit aperture. Conversely, a dot on the edge of the far-field image will illuminated by the rays of a second cone formed by all the rays originating from a point on the edge of the entrance opening and reaching the same exit opening. This determines that the image of the entrance opening that is formed in the case of a matrix of lenses placed at the exit of the channels ? however clear, even in the presence of a not completely uniform illuminance (the second cone in fact has a slightly smaller angular aperture than the first). However, the image of the entrance? characterized by having a circular shape and an edge beyond which the illuminance vanishes discontinuously (in other words, the angular luminance profile exhibits a sharp transition from a finite field edge value to zero, for directions that pass from? inside to the outside of the acceptance cone, since the edge value is obtained not from a single ray, as in the case in the absence of lenses or of the lens matrix positioned at the input, but from a plurality of rays). Thus, it is possible to produce in the eye a sharp image of the sun in stark contrast to the surrounding sky.

[25] Advantageously, furthermore, the optical filter according to the present invention is simple and economically feasible. technology. In fact, the decision to use cylindrical channels with a substantially circular section, here moreover dictated by the need to produce a circular sun, allows at the same time to make production industrially scalable. In fact, it is extremely simple to optically isolate cylindrical channels with absorbent material, using for example well-established technologies such as that of optical fibres.

[26] In accordance with a second aspect thereof, the invention relates to a lighting device for reproducing the light of the sky and the sun comprising a direct light source configured to emit visible light in a non-isotropic manner and having a first correlated temperature of color or CCT, an optical filter as described above, positioned downstream of the direct light source in such a way that the inlet surface of the optical filter overlaps at least partially the flat emitting surface of the direct light source of the light source direct; and a diffuse light source configured to emit diffuse visible light having a second correlated color temperature or CCT of at least 1.2 times, preferably 1.3 times, more? preferably 1.5 times greater than the first CCT.

[27] The directed light source comprises a visible light emitter, an optical system for collimating the light emitted by the visible light emitter, and a flat direct light emitting surface. Furthermore, the direct light source? configured to generate light mainly along directions included within an emission cone having a directrix of the emission cone perpendicular to the flat emission surface of the direct light and having an angular half-aperture of direct light, defined as half-width of the angular profile luminance of the direct light source on the flat emission surface, less than 20 degrees, preferably less than 15 degrees, more? preferably less than 8 degrees, where the semi-width ? measured at a height equal to 1/e<2 > times the peak value and the angular profile of luminance ? mediated on the spatial coordinates and on the azimuth coordinate.

[28] The diffused light source comprises a diffuser panel positioned downstream of the optical filter so as to at least partially intercept a filtered light emitted by the outlet surface of the optical filter. The diffuser panel? further configured to transmit or reflect part of the filtered light emitted from the optical filter exit surface, producing transmitted or reflected light whose luminance angular profile substantially coincides with the luminance angular profile of the filtered light emitted from the optical filter exit surface . Again, the diffuser panel ? configured to generate, on a diffuse light emission surface, a diffuse light component characterized by a luminance having an angular profile characterized by an angular half-aperture of diffuse light, defined as half-width of the angular luminance profile at height 1/e <2>, at least 2 times, preferably 3 times, more? preferably 4 times greater than a semi-aperture of an acceptance cone of the optical filter and/or an angular semi-aperture of the filtered light, defined as a semi-width of the angular luminance profile at height 1/e<2 > of the light filtered.

[29] Advantageously, the lighting device for reproducing the light of the sky and the sun achieves the most technical effects? described above in relation to the optical filter according to the present invention.

[30] In accordance with a third aspect thereof, the invention relates to a method for producing an optical filter as described above, comprising the steps consisting of:

to. produce at least one optical fiber having

the. a core in transparent material, such as preferably air, glass, quartz, PMMA, polycarbonate, or other polymeric resin, the core having a diameter equal to the diameter of the cylindrical elements and

ii. a first coating at least partially made of a first optically absorbent material;

b. Get a plurality? of lengths of at least one optical fibre, wherein the lengths have a length substantially equal to the length of the cylindrical elements, each length constituting a cylindrical element covered on its lateral surface by a sheath, a film, a paint or a layer of rigid material made with the first coating of optically absorbent material;

c. Obtain at least one structure with side-by-side segments;

d. Arranging, with respect to the structure of adjacent sections, at least one element of optically non-transparent material configured and arranged with respect to the sections in such a way as to prevent the passage of light parallel to the sections and externally therefrom through gaps present between adjacent sections;

And. Deposit, paste, print, grow or place at least a plurality? of first lenses, each facing at least one outlet face of the cylindrical elements.

[31] Advantageously, the method for producing an optical filter achieves the most technical effects? described above in relation to the optical filter according to the present invention.

[32] This invention can have at least one of the preferred characteristics listed below, the latter in particular being combinable with one another as desired in order to satisfy specific application requirements.

[33] In a variant of the filter according to the invention, the optical filter additionally comprises a plurality of of second lenses with positive focal length equal to the length of the cylindrical elements, each second lens of the plurality? of second lenses being coupled to or defining the input face of a respective cylindrical element.

[34] The advantage given by the plurality? of second lenses? to produce an exactly constant angular profile of luminance inside the cone of acceptance of the optical filter, and to increase the luminosity? of the device.

[35] In a variant of the filter according to the invention, the material substantially transparent to light in which the cylindrical elements are made? a solid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin.

[36] Preferably, the first element of optically absorbing material comprises a sheath, a film, a paint or a layer of rigid material made with a first optically absorbing material which substantially covers the lateral surface of the cylindrical elements, having a lower refractive index, equal to or greater than the cylindrical elements.

[37] Preferably, the absorption coefficient of the first optically absorbing material guarantees an absorption of at least 50%, preferably 80%, plus? preferably 90% of the visible light for a material thickness equal to 1/5, preferably 1/10 of a diameter of the entrance face or of the exit face of the cylindrical elements.

[38] Advantageously it is so? possible to have the technology of optical fibers for the construction of the device.

[39] In a variant of the filter according to the invention, the first element of optically absorbing material comprises a plurality of of cells with a polygonal section, preferably hexagonal or square, arranged around the cylindrical elements.

[40] In a variant of the filter according to the invention, the material substantially transparent to light in which the cylindrical elements are made? a gaseous material, preferably air.

[41] Preferably, the first element of optically absorbent material and the second element of optically non-transparent material consist of an optically absorbent panel in which the cylindrical elements are formed.

[42] Like this ? possible to produce a particularly light optical filter.

[43] Alternatively, the first element of optically absorbing material ? a cylindrical jacket which substantially covers the lateral surface of the cylindrical elements, wherein the cylindrical jacket has a significantly smaller thickness than the diameter of the cylindrical elements, for example a thickness 2 times, preferably 5 times, more? preferably 10 times less, and wherein the cylindrical jacket comprises a layer of rigid material preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin, wherein the layer of rigid material is coated on its inner side surface with an optically absorbing layer, preferably a paint or film made of optically absorbing material; and/or the layer of rigid material? covered on one of its outer side surfaces by the second element of optically non-transparent material, preferably in the form of a paint or film or sheath of optically absorbent material; and/or the layer of rigid material? made of an optically absorbent material.

[44] Conveniently, this solution makes it possible to use hollow fiber technology, which allows for lightness and stiffness to be obtained at the same time. to the device.

[45] In a variant of the filter according to the invention, the second element of optically non-transparent material comprises a second optically absorbent material which at least partially fills the plurality of elements. of defined gaps between adjacent cylindrical elements.

[46] Preferably, the absorption coefficient of the second optically absorbing material guarantees an absorption of at least 50%, preferably 80%, plus? preferably 90% of the visible light for a thickness equal to 1/5, preferably 1/10 of the length of the cylindrical elements.

[47] Preferably, the first and second optically absorbent materials are the same material.

[48] Alternatively, the first and second optically absorbing materials are polymers and where the second optically absorbing material has a glass transition temperature Tg lower than a glass transition temperature of the first optically absorbing material, for example lower by at least 5, preferably 10, more? preferably 20 degrees Celsius.

[49] Advantageously, it turns out so? it is possible to obtain the filling of the interspaces between channels by the second material, suitably heated and under pressure, without deforming the first element of optically absorbent material.

[50] Preferably, the first optically absorbent material ? a thermosetting resin and the second optically absorbent material ? a thermoplastic resin and where the hardening temperature Ti of the first optically absorbing material? lower than the glass transition temperature Tg of the second material.

[51] This expedient advantageously allows to have a sheath of a first optically absorbent material having the necessary flexibility? to allow the management of the fiber, such as for example to manage the winding, before the process of creating the cylindrical elements, and to then give this first material the necessary rigidity, for example to facilitate the cutting process and in any case to give stability to the system, and in any case to ensure the thickness at the point of maximum proximity? of the cylindrical elements.

[52] Alternatively, the second element of optically non-transparent material comprises an element of absorbent or reflective material which covers and/or constitutes at least a portion of the input surface and/or of the output surface not including the portions superimposed on the input and output faces of the cylindrical elements.

[53] In a variant of the filter according to the invention, the average value of an interaxis between adjacent cylindrical elements ? less than 2 times, preferably 1.5 times, more? preferably 1.2 times the diameter of the cylindrical elements.

[54] Preferably, the diameter of the entry face or the exit face of the cylindrical elements ? less than 5mm, preferably 3mm, pi? preferably at 2mm.

[55] In a variant of the lighting device according to the invention, the optical filter is configured so as to have a half-aperture of an angular acceptance cone equal to the arctangent of the ratio between a half-diameter of the entry face or of the exit face of the cylindrical elements and the length of the cylindrical elements, greater than or equal to the half-aperture angle of direct light.

[56] Preferably, the angular semi-aperture of direct light ? greater than 1.5, preferably 2.5, more? preferably 3 degrees.

[57] Surprisingly, the Applicant recognized the possibility to give up producing sharp shadows, or rather the possibility? to agree to produce in the eye an image of the sun even more? larger than that of the real sun which has an angular semi-opening of 0.25 degrees, allowing in this way to greatly simplify the necessary technology, without compromising functionality? of the device.

The reason this can happen specifically concerns the ability? to faithfully reproduce in an internal environment the correct luminosity, and therefore the perceived color, of the scenes in the shade compared to those in the sun. ? in fact, precisely the characteristic of the shadows there? which determines the difference between natural and artificial light, making us perceive the difference between inside and outside. To this end, ? important to note that there? which in nature determines the luminosity? of the shadows ? the total luminous flux that comes from the sky, which in turn depends on the size of the solid angle from which the sky illuminates the scene. This ? the reason why, due to the limited opening of windows and skylights, the shadows produced inside by the real sun and sky are more? dark, and perceptually less colourful, and therefore less ?natural? of those we are used to seeing outdoors. In the new solution proposed, the correct balance between shadow and light of the outdoors is re-established thanks to the increased divergence of sunlight, compared to that of the sky, which instead is? reproduced naturally. This increase in the ratio between the divergences in fact results in an equal reduction in the ratio between the illuminances, which restores the natural ratio between the illuminance of the sky and the sun despite the limited aperture of the device. In other words, the effect on the shadows of an artificial window with increased sun divergence? analogous to that of a natural window with a larger opening, which has an obvious and significant impact on the commercial value of the product.

[58] In a variant of the lighting device according to the invention, the first source of direct light is configured to produce a substantially spatially uniform cone illuminance on the flat emission surface, where the cone illuminance ? the illuminance relating only to the contribution of the light incident from directions included within the emission cone [59] In a variant of the lighting device according to the invention, the diffuser panel is configured to generate, on a diffuse light emission surface, a diffuse light component characterized by a substantially spatially uniform luminance

[60] In another variant of the lighting device according to the invention, the first source of direct light is configured to guarantee variations of the cone illuminance on at least 90% of the first flat exit surface that are less than 100%, preferably 70% plus? preferably at 50% of the average value of the cone illuminance on the first surface.

[61] Conveniently, limiting the cone illuminance variations in turn limits the luminance variations of the optical filter and therefore the luminance variations that it can produce on the diffuser panel, the presence of which reduces the quality? perceived of the sky.

[62] In a variant of the lighting device according to the invention, the first source of direct light is configured to guarantee a substantially monotonic dependence of the cone illuminance value on the spatial coordinates on at least 90% of the direct light emission flat surface.

[63] Advantageously, a monotonic variation of the cone illuminance implies a monotonic variation of the luminance of the sky, which can? be not only acceptable but also welcome being an effect present in nature.

[64] In a variant of the lighting device according to the invention, the cone illuminance ? higher than? 80%, preferably 90%, more? preferably at 95% of the total illuminance produced by the direct light source on the flat surface of direct light emission.

[65] In a variant of the lighting device according to the invention, the visible light emitter ? linear type including a plurality? of LEDs arranged along a straight line perpendicular to a section plane orthogonal to the input surface and to the output surface of the optical filter.

[66] Preferably, the optical system for collimating the light emitted by the linear-type visible light emitter comprises a plurality of optical elements. of refractors and/or reflectors, such as lenses, TIR lenses, Fresnel lenses, reflectors, CPCs, etc., each coupled to each LED of the plurality? of LEDs, and configured to collimate the LED light to which ? coupled in a first collimation plane containing the straight line along which the LEDs are arranged, and to give the collimated light an angular luminance profile, for directions included in the first collimation plane, having an angular semi-aperture whose value is ? between 0.5 and 2, preferably between 0.7 and 1.5, more? preferably between 0.85 and 1.2 times the value from the angular half-aperture of direct light.

[67] Preferably, the optical system for collimating the light emitted by the linear type visible light emitter comprises a Fresnel mirror having a first flat non-reflecting surface and a second prismatic reflecting surface, wherein the Fresnel mirror is? positioned and configured in such a way that the first flat non-reflective surface ? perpendicular to the orthogonal section plane and the second prismatic reflecting surface collimates the light emitted by the visible light emitter in a second collimation plane parallel to the orthogonal section plane and, for directions included in the second collimation plane, gives the light so? collimated an angular profile of luminance having an angular semi-aperture whose value ? between 0.5 and 2, preferably between 0.7 and 1.5, more? preferably between 0.85 and 1.2 times the value from the angular half-aperture of direct light.

[68] Preferably, the filter ? configured to remove at least? 80%, preferably 90%, more? preferably at least 95% of the spurious light produced by the Fresnel mirror.

[69] Conveniently, collimating the light produced by the direct light source in two independent stages, on orthogonal collimation planes, allows collimating in the second plane to be achieved using a single optical element, instead of a single optical element. a plurality? of optical elements, with a significant reduction in costs.

[70] In a variant of the lighting device according to the invention, the diffused light source comprises a panel of transparent material comprising a dispersion of nano particles, the panel being configured to transform the filtered light into a transmitted component, having similar angular profile and CCT at least 1.1, preferably 1.2, preferably 1.3 times lower than the first CCT, and in a diffuse component with CCT equal to at least 1.2 times, preferably 1.3 times, more? preferably 1.5 times greater than the first CCT.

[71] In a variant of the lighting device according to the invention, the diffused light source comprises a nanostructured reflector configured to transform the filtered light into a reflected component, having a similar angular profile and CCT at least 1.1, preferably 1, 2, preferably 1.3 times lower than the first CCT, and in a diffuse component with CCT equal to at least 1.2 times, preferably 1.3 times, more? preferably 1.5 times greater than the first CCT.

[72] In a variant of the lighting device according to the invention, the diffused light source comprises a diffuser panel which diffuses the light produced by a second plurality of lights. of LEDs coupled to the sides of the panel.

[73] In a variant of the lighting device according to the invention, the diffused light source is configured in such a way that the average value of the divergence in half? height HWHM of the light transmitted or reflected by it is less than 1.5, preferably 1.3, more? preferably 1.2 times the average value of the divergence in half? HWHM height of the filtered light.

[74] In a variant of the method for producing an optical filter, the step of producing at least one optical fiber comprises producing at least a first bundle of optical fibers comprising a plurality of of optical fibers.

[75] Preferably, the step of producing at least one optical fiber comprises producing at least a second bundle of optical fibers which combines a plurality of of first beams, where the first beams have a hexagonal, triangular or square section.

[76] Advantageously, being able to have first and second beams of different sections offers the possibility? to take advantage of different methods? of transport and packaging of the components, as the first bundle pu? be sized to be wrapped in reels while the second, being able to have the dimensions up to several tens of cm in diameter, or rather the dimensions of the filter, cannot? be wrapped and needs to be managed in sections, even if much longer than the length of the cylindrical elements, where from a cut of the sections you get the plurality? of fiber optic pieces.

[77] Preferably, the first optically absorbent material ? a thermoplastic resin having a first glass transition temperature Tg1 and wherein the method comprises the step of heating the at least one first beam and/or the at least one second beam in an oven to a temperature higher than the first glass transition temperature Tg1, previously to the phase of obtaining a plurality? of clips.

[78] Preferably, the warm-up phase? made at a pressure lower than atmospheric pressure in order to remove the air present in the interspaces between the adjacent sections.

[79] In a variation of the method for producing an optical filter, the step of producing at least one optical fiber comprises producing at least one optical fiber having a second coating of polymer resin having a second glass transition temperature Tg2 coating the first coating and making in the second optically absorbing material and the step of arranging the at least one element of optically non-transparent material comprises heating the at least one first beam and/or the at least one second beam in an oven to a temperature higher than the second glass transition temperature Tg2.

[80] Preferably, the second glass transition temperature Tg2 ? lower than the first glass transition temperature Tg1, for example lower by at least 5, preferably 10, plus? preferably 20 degrees Celsius, and where the heating phase in the oven? carried out at a temperature higher than the second glass transition temperature Tg2 and lower than the first glass transition temperature Tg1, for example at an intermediate temperature between Tg2 and Tg1.

[81] In a variant of the method for producing an optical filter the first optically absorbing material ? a thermosetting resin having a curing temperature Ti and the second optically absorbent material ? a thermoplastic resin having a glass transition temperature Tg2 greater than Ti, where the heating phase in the oven is? carried out at a temperature higher than Tg2 and the pressure reduction phase by eliminating the air contained in the interspaces is started when the temperature has reached an intermediate value between Ti and Tg2.

[82] In a variant of the method for producing an optical filter, the step of obtaining at least one structure with side-by-side portions of the at least one optical fiber comprises cutting into slices the at least one first bundle of a plurality of optical fibers. of fibers, after the heating phase, and in carrying out a surface treatment of the slices so? obtained, in order to obtain the polishing quality? optics of the faces of the fiber segments.

[83] As an alternative to what has been illustrated above with reference to the optical filter, and in particular as an alternative to the use of converging lenses having a focal length in the material of which the cylindrical elements are made equal to the length of the cylindrical elements, positioned on or constituting the outlet faces of the cylindrical elements or, preferably, positioned on or constituting both the outlet and inlet faces of the cylindrical elements, the object of the present invention can be equivalently obtained by using other optical elements incorporated inside the cylindrical elements. Merely by way of example, the purpose of the present invention can be equivalently obtained through the use of cylindrical elements characterized by a radial profile of the refractive index, also called ?GRIN lenses? (GRaded Index Lenses), where the radial profile of the refractive index is such as to give the lens formed by the cylindrical element a focal length equal to the length of the cylindrical element.

[84] Therefore, in a very general way, as an alternative to the above, the optical filter according to the present invention comprises:

a substantially flat input surface, a substantially flat output surface and parallel to the input surface, a plurality? of cylindrical elements made of a material substantially transparent to light, a first element of optically absorbent material configured and arranged with respect to the cylindrical elements in such a way as to prevent the passage of light between adjacent cylindrical elements of the plurality of cylindrical elements, a second element of optically non-transparent material configured and arranged with respect to the cylindrical elements in such a way as to prevent the passage of light parallel to the cylindrical elements and externally thereto through the gaps between adjacent cylindrical elements, where the cylindrical elements of the plurality ? of cylindrical elements

(i) have a substantially identical shape to each other and comprise a substantially circular inlet face having a diameter of the cylindrical elements, a substantially circular outlet face having the diameter of the cylindrical elements and a lateral surface which extends perimetrically between the inlet face and the outlet face for a length of the cylindrical elements; (ii) are arranged side by side and parallel to each other, in such a way as to define a plurality? of gaps between adjacent cylindrical elements;

(iii) have a cylinder axis perpendicular to the inlet and outlet surfaces and are arranged with the inlet face substantially overlapping the inlet surface and with the outlet face substantially overlapping the outlet surface;

(iv) are configured in such a way that the light rays passing through any cylindrical element of the plurality? some cylindrical elements passing through any point on the edge of an entrance face of the cylindrical element exit the exit face of the cylindrical element with substantially parallel directions, or

(v) comprise at least one refractive and/or diffractive optical element configured to focus at least one beam of parallel rays entering from any output face of a cylindrical element onto the input face of the same cylindrical element, such refractive optical element and/or diffractive as it could be, for example, a plano-convex lens positioned on or constituting the outlet face of the cylindrical element and having a focal length in the middle equal to the length of the cylindrical element or a GRIN lens which constitutes the entire cylindrical element having focal point in the middle equal to the length of the cylindrical element.

Brief Description of the Drawings

[85] The accompanying drawings, which are incorporated herein and form part of the specification, illustrate exemplary embodiments of the present invention and, together with the description, are intended to illustrate the principles of the present invention.

In the drawings:

Figs.1a and 1b are respectively a schematic top and bottom perspective view of a first embodiment of an optical filter according to the present invention;

Figs. 2a and 2b are two details of optical fibers used to make the optical filter of Figs. 1a and 1b.

Fig. 3 ? a schematic perspective view of a second embodiment of an optical filter according to the present invention;

Fig. 4 ? a schematic perspective view of a third embodiment of an optical filter according to the present invention;

Figs. 5, 5a and 5b are respectively a perspective view of a fourth embodiment of an optical filter according to the present invention and of two details of the optical fibers used to make it;

the Fig.6 ? an exploded perspective schematic view of a fifth embodiment of an optical filter according to the present invention;

the Fig.7 ? a schematic perspective view of a lighting device for reproducing sky and sun light according to the present invention;

Fig. 8 ? a schematic perspective view of a first variant of light source used in the lighting device for reproducing the light of the sky and the sun according to the present invention;

Figs. 9 and 10 are schematic representations of the light entering and leaving the components of the lighting device for reproducing the light of the sky and the sun according to the present invention; And

Figure 11 ? a schematic representation of a lighting device for reproducing sky and sun light according to the present invention comprising a second light source variant.

Detailed Description

[86] What follows? a detailed description of exemplary embodiments of the present invention. The exemplary embodiments described herein and illustrated in the drawings are intended to convey the principles of the present invention, enabling the person skilled in the art to implement and use the present invention in a number of different situations and applications. Therefore, the exemplary embodiments are not intended, nor? should be considered as limiting the scope of patent protection. Rather, the scope of patent protection ? defined by the attached claims.

[87] In the following description, for the illustration of the figures, identical reference numbers or symbols are used to indicate constructive elements with the same function. Furthermore, for clarity of illustration, some references may not be repeated in all the figures.

[88] The use of ?a example?, ?etc.?, ?or? indicates non-exclusive alternatives without limitation unless otherwise indicated. The use of ?includes? and ?include? means ?includes or includes, but not limited to? unless otherwise indicated.

[89] Furthermore, the use of measures, values, shapes and geometric references (such as perpendicular and parallel) associated with terms such as ?about?, ?almost?, ?substantially? or similar, ? to be understood as ?unless there are measurement errors? or ?barring inaccuracies due to manufacturing tolerances? and in any case ?unless there is a slight divergence from the values, measures, shapes or geometric references? which term? associated.

[90] Finally, terms such as ?first?, ?second?, ?superior?, ?inferior?, ?main? and ?secondary? are generally used to distinguish components belonging to the same typology, not necessarily implying an order or a priority? of relationship or position.

[91] With reference to Figs. 1a and 1b ? schematically illustrated an optical filter according to a first embodiment of the present invention indicated as a whole with 100.

[92] The optical filter of Figs. 1a and 1b includes a plurality? of cylindrical elements 103 with substantially circular section identical to each other made of a solid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin. Each cylindrical element 103 has a flat input face 104, perpendicular to the axis of the cylinder, and an output face 105 flat and parallel to the input face 104. Both the input 104 and output 105 faces are substantially circular, have a diameter equal to a diameter of a cylindrical element, and have quality? optics, i.e. they are arranged in such a way as to transmit the light incident on them with minimum distortion.

[93] On the exit face 105 of each cylindrical element 103 ? positioned, glued, deposited or facing through a substrate a converging lens 107 having a diameter substantially equal to the diameter of the cylindrical element and focal in the middle equal to the length of the cylinder, or the exit face 105 of each cylindrical element 103 ? constituted by a converging lens 107 having a diameter substantially equal to the diameter of the cylindrical element and focal in the middle equal to the length of the cylinder.

The cylindrical elements 103 are arranged side by side and parallel to each other, in a condition of maximum packing according to a hexagonal pattern, and having the inlet face 104 positioned on the same flat inlet surface 101 of the filter 100 and the outlet face 105 positioned on the same flat outlet surface 102 of the filter and parallel to the inlet surface 101.

[94] The cylindrical elements 103 have a lateral surface substantially covered in conditions of optical contact (without gaps) by a first element of optically absorbent material 108, for example in the form of a sheath, film or paint, having a refractive index substantially equal to the ?refraction index of the solid material of which the cylindrical elements 103 are made. In particular, the first element of optically absorbing material 108 ? arranged and configured to prevent the passage of light between adjacent cylindrical elements.

[95] The interspaces between adjacent cylindrical elements 103 are at least partially filled by a second element in optically absorbent material 109, different or equal to the first material 108, so as to prevent the passage of light parallel to the cylindrical elements and externally to them through the gaps between adjacent cylindrical elements 103.

[96] Such an arrangement of the first optically absorbing material element 108 and the second optically absorbing material element 109 ? obtainable starting from technologies for the production of optical fibers, suitably adapted to the purpose as described below.

[97] A method for producing an optical filter 100 according to the invention first of all provides for a first step which consists in producing a homogeneous fiber 103 of a solid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin transparent, using established techniques such as, for example, drawing the fiber from a preform in a spinning tower or extrusion techniques. The fiber 103, once cut into lengths, will go? to form the cylindrical elements 103 of the optical filter 100 and for this reason it is produced with a diameter equal to the diameter of the cylindrical elements 103 to be manufactured. Note that the fiber cos? made, unlike conventional optical fibers, does not have the ability? to guide the light inside it, for which a different radial index profile is needed. Nevertheless, given the close analogy as regards the production method, we will use the terms ?fiber? and ?optical fiber? in the present context.

[98] In a second step, in line with the previous one, the fiber 103 is covered by a first coating 108 or ?coating? optical polymer in the form of a sheath, film or varnish by, for example, an extrusion, or varnish, or deposition process, suitably followed by a rapid polymerization stage, for example by a UV polymerization stage. The first coating will go? to constitute the first element of optically absorbent material 108 and for this purpose? made with a first optically absorbent material and of the thickness necessary to extinguish at least 50%, preferably 80%, plus? preferably 90% of the light that crosses it perpendicular to the surface, typically of the order of tens of microns. By optical coating we specifically mean a layer adhered and optically coupled to the fiber, i.e. one that does not cause light diffusion or reflection effects at the interface, so that the light that reaches the outer surface of the fiber passes through it and can therefore be absorbed . For this the first optically absorbent material? chosen with a refractive index substantially identical to the refractive index of the material which constitutes the fibre.

[99] In a third phase, the fiber cos? covered by the first coating 108 is further covered by a second coating 109, by means of techniques, for example, of extrusion. The second coating will go? to make the second element in optically absorbent material 109 and, for this purpose, ? made with a second optically absorbent material. Preferably, the second coating is made with a thermoplastic polymer with a glass transition temperature Tg lower than the glass transition temperature of the polymer constituting the first coating 108 or, optionally, the fiber 103. The second coating 109 has the dual purpose of protecting the fiber 103 in the various phases of the process and at the same time to supply the material necessary for filling the interspaces between the first coatings 108, for example in conditions of maximum packing (hexagonal). To this end, the thickness of the second coating 109 is chosen according to the diameter of the fiber 103 and the thickness of the first coating 108 so that it provides at least the volume of material necessary for the filling. The fiber what? doubly covered? schematically illustrated in Fig.2b. The production process of the 103 fiber will be able contain other phases as usual in the optical fiber production process, such as for example the winding of the double-coated fiber at the end of the line on a storage reel.

[100] The method of production of the filter provides for a fourth phase, in which the doubly coated fiber is cut into sections, with a length for example of the order of one metre, which are arranged parallel, for example horizontally, in a preform, for example with a hexagonal, square or rectangular section. The bundle of logs cos? obtained is then heated so as to obtain the softening or liquefaction of the second coating 109, the substantial contact of the fibers through their first coatings 108, the consequent filling of the interspaces by the second optically absorbent material 109 deriving from the softening or liquefaction of the second coating, and the subsequent gluing with the formation of a block of fiber sections 103 covered by the first coating 108 in conditions of substantial maximum packing and with the interspaces between the first coatings 108 filled by the material deriving from the second coating 109. Fig. 2a schematically shows the condition of gaps filled by the second optically absorbent material 109, where however the figure ? for simplicity? illustrative ? does not show the resulting thinning of the second coating 109.

[101] In a fifth step of the production method of the optical filter 100, the block of stubs is reduced into slices, so that each slice contains a plurality of of lengths of fiber having a thickness substantially equal to the length of the cylindrical elements 103 of the optical filter 100, for example by cutting with a diamond wire. In this way, a structure with side-by-side sections is obtained, in which the second element of optically absorbent material 109? arranged, with respect to the segments 103, in such a way as to prevent the passage of light parallel and externally thereto, filling the interspaces between the segments 103.

[102] The slices cos? obtained are then treated superficially, for example by means of mechanical, and/or chemical, and/or thermal, and/or optical processes, so as to obtain high-quality polishing. optics of the faces 104, 105 of the lengths of fibers, which constitute the cylindrical elements 103 of the optical filter 100. In addition, the phase could? provide for the removal of the first 108 and second 109 optically absorbent material from the faces 104,105 and from the bordering areas, for example by means of mechanical, and/or chemical, and/or thermal, and/or optical processes.

[103] In a sixth step of the production method of the optical filter 100, the lenses are deposited on the polished exit faces 105 of the fiber segments 103, for example by means of ink-jet printing technology of polymer on glass or polymer on polymer. The component what? made, suitably trimmed and/or framed where necessary, constitutes the homogenized optical filter, or constitutes a portion of it if the filter is made from a plurality of? of side by side elements.

[104] According to an alternative embodiment (not shown) the optical filter 100 comprises a plurality of? of identical cylindrical elements constituted by a full volume 103 of solid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other transparent polymeric resin, and circumscribed by a first element 108 of optically absorbing material made as a layer of rigid material. Preferably, the material of which ? formed the layer of rigid material ? obtained from a modification of the material of which the cylindrical elements 103 are made by adding components for the absorption of light. Preferably, the first element of optically absorbent rigid material 108 has a coefficient of absorption to visible light sufficient to prevent the passage of light between adjacent cylindrical elements 103. For example, the absorption coefficient of the layer of rigid material guarantees an absorption of at least 50%, preferably 80%, plus? preferably 90% of the visible light for a material thickness equal to 1/5, preferably 1/10 of the diameter of the solid cylindrical elements 103. Also in this case, ? also provided is a sheath which externally wraps the first element of optically absorbent rigid material, made of a second optically absorbent material, which thus constitutes the second element of optically non-transparent material 109. Preferably, the sheath 109 is made of a thermoplastic polymer having a glass transition temperature lower than the glass transition temperature of the other polymers possibly present in the cylindrical elements 103 and in the first element of rigid optically absorbing material. Also in this case, in correspondence with the outlet face 105 or in constituting the outlet face 105 of each solid cylindrical element 103 ? positioned, grown, deposited or glued a respective converging lens 107 with focal length in the middle equal to the length of the cylindrical elements 103.

[105] This alternative embodiment can? be obtained through the method for the production of the optical filter described below. A first step involves the production of a non-homogeneous fiber made with two forms of the same solid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin, of which the first form? optically transparent and the second form ? made optically absorbent by the addition of light absorbing components. Specifically, the step provides for the production of a fiber consisting of a homogeneous and transparent central core 103, with a diameter equal to the diameter of the cylindrical elements 103 of the optical filter 100, made with the transparent shape of the solid material, and of a cylindrical jacket 108, of thickness significantly less than the diameter of the cylindrical element 103, made with the optically absorbing shape of the solid material.

[106] For example, the inhomogeneous fiber is produced by drawing in a spinning tower from a preform cylinder consisting of a central preform core, made with the transparent shape of the solid material, and a cylindrical preform jacket, made with the optically absorbent shape of the solid material, where the ratio between the diameters of the central preform core and the cylindrical preform jacket ? equal to the ratio of the diameters of the central fiber core 103 to the cylindrical fiber jacket 108. Alternatively, the non-homogeneous fiber can be produced by coaxial extrusion of the first and second forms of the same solid material.

[107] In a second phase, the fiber cos? produced, comprising the core 103 and the jacket of optically absorbent material 108, is covered by a second coating 109, by means of techniques, for example, of extrusion, made with a second optically absorbent material 109 in this case of a thermoplastic polymer with a temperature of glass transition Tg lower than the glass transition temperature of the polymer (if any) present in the fiber. How already? explained with reference to the first embodiment, the second coating 109 has the dual purpose of protecting the fiber in the various stages of the process and at the same time supplying the material necessary for filling the interspaces between the jackets of optically absorbent material 108, for example under conditions of maximum packing (hexagonal). The subsequent stages of the process are similar, for example, to those described above.

[108] With reference to Fig. 3 ? shown is a second embodiment of the present invention in which the optical filter 100 additionally comprises a second plurality of of converging lenses 106, each arranged on the entrance face 104 or constituting the entrance face 104 of a cylindrical element 103. The second lenses 106 are positioned, glued, deposited or facing by means of a substrate on the entrance face 104 or constitute the entrance face 104, of the respective cylindrical element 103. The second lenses 106 have a diameter substantially equal to the diameter of the cylindrical element 103 and a focal length in the middle equal to the length of the cylindrical element 103.

[109] Furthermore, in the second embodiment illustrated in Fig. 3 does the optical filter 100 comprise a second element of optically absorbing or reflective material 109? made in the form of covering the inlet surface 101 of the filter for the portion not including the portions superimposed on the inlet faces 104 of the cylindrical elements 103. In particular, the second element of optically absorbing or reflecting material 109? ? made and arranged in such a way as to prevent the passage of light parallel to the cylindrical elements and external to them through the interspaces between adjacent cylindrical elements 103.

[110] Fig. 4 shows a third embodiment of the present invention in which the optical filter 100 is made up of an optically absorbent panel in which ? obtained a plurality? of cylindrical elements 103? empty. To each entrance face 104 and to each exit face 105 of the empty cylindrical elements 103? faces a converging lens 106,107 positioned in correspondence with the respective face 104,105 by means of a thin support substrate (not shown), for example a thin glass substrate or a transparent polymer placed in contact with the upper surface of the optically absorbent panel, where the lenses 106,107 are converging lenses with a focal length in air substantially equal to the length of the cylindrical elements 103?, or each entrance face 104 ? constituted by a converging lens 106, and each output face 105 ? consisting of a converging lens 107 having a focal length in air substantially equal to the length of the cylindrical elements 103?.

[111] In this embodiment, the body of the optically absorbing panel implements both the first element of optically absorbing material 108 configured and arranged in such a way as to prevent the passage of light between cylindrical elements 103? adjacent, is the second element of optically non-transparent material 109 configured and arranged in such a way as to prevent the passage of light parallel to the cylindrical elements and externally thereto through the spaces between cylindrical elements 103? adjacent.

[112] With reference to Fig. 5 ? shown is a fourth embodiment of the invention in which the optical filter 100 comprises a plurality of? of identical cylindrical elements consisting of an empty volume 103? circumscribed by a first element of optically absorbent material made in the form of a cylindrical jacket 110.

[113] As shown in detail in Figs.5a and 5b, the cylindrical jacket 110 comprises a layer of rigid material 110?, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin, having a significantly smaller thickness of the diameter of the cylindrical elements 103?. Preferably, the rigid material layer 110? ? optically absorbent and has a visible light absorption coefficient sufficient to prevent the passage of light parallel to the empty cylindrical elements 103? and externally thereto through the rigid material 110? of the cylindrical jacket 110. For example, the absorption coefficient of the rigid material layer 110? guarantees an absorption of at least 50%, preferably l?80%, plus? preferably 90% of the visible light for a material thickness equal to 1/5, preferably 1/10 of the length of the hollow cylindrical elements 103?.

[114] The cylindrical jacket 110 further comprises a layer 110?? made of an optically absorbent material adhering to the inner surface of the rigid material layer 110? and thus defining the lateral surface of the empty cylindrical elements 103?. The layer of optically absorbent material 110?? ? for example an opaque black paint or an opaque black film, able to prevent the passage of light between adjacent cylindrical elements and to minimize the reflection of the light which grazes the lateral surface of the empty cylindrical elements 103?.

[115] ? a sheath is also provided which externally wraps the cylindrical jacket 110. The sheath? made of a second optically absorbent material and thus constitutes the second element of optically non-transparent material 109. The sheath 109 is made of a second optically absorbent material. made of a thermoplastic polymer having a glass transition temperature lower than the glass transition temperature of the other polymers present in the cylindrical jacket 110. In this way, during the construction phase of the filter 100, the sheath 109 determines the bonding between adjacent cylindrical jackets 110, going to fill the interspaces between them 110. In this way, the sheath 109 prevents the passage of light parallel to the cylindrical elements 1032, externally to the cylindrical liners 110 which define them.

[116] Also in this case, in correspondence with the or to constitute the entrance face 104 and the exit face 105 of each empty cylindrical element 103? ? positioned, grown, deposited or glued a respective converging lens 106,107 with focal length in the middle equal to the length of the cylindrical elements 103?.

[117] In this case the optical filter production method provides for a first step which consists in producing a hollow fiber made of an optically absorbing solid material 110?. The hollow fiber comprises a hollow core which, once coated, will go? to constitute the empty cylindrical elements 103? of the optical filter 100 once the fiber sar? cut. The optically absorbent solid material 110? will I go instead to make the layer of rigid material 110? of the cylindrical jacket 110, and for this reason ? preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other transparent polymeric resin. The hollow fiber is produced by known techniques such as, for example, drawing the fiber from a preform in a spinning tower or extrusion techniques.

[118] A second phase of the production method of the optical filter 100 provides for covering the inner surface of the hollow fiber with a coating, film or matt black paint which will go? to form the optically absorbent layer 110?? of the cylindrical jacket 110. In a preferential form, the second phase is subsequent to the first, and is based, for example, on the use of painting techniques or thin film deposition. In another preferential form, the second phase ? contextual to the first, and is based, for example, on the use of coaxial extrusion techniques. The inside and outside diameter of the layer of rigid material 110? and the thickness of the optically absorbent layer 110?? are determined such that the empty cylindrical space having an outer surface corresponding to the inner surface of the optically absorbing layer 110?? has the diameter of the empty cylindrical elements 103? of the optical filter. The subsequent stages of the process are similar, for example, to the relative ones described above.

[119] Fig. 6 shows a fifth embodiment of the present invention in which the optical filter 100 comprises a plurality of? of empty cylindrical elements 103?, not delimited by a physical lateral surface, but defined by a plurality? of first 106 and second 107 lenses positioned by means of a substrate so as to define the input 104 and output 105 faces of the empty cylindrical elements 103? and the input 101 and output 102 surfaces of the filter 100. The first 106 and second 107 lenses are converging lenses having focal lengths in the middle substantially equal to the length of the cylindrical elements 103?. The filter 100 further comprises a plurality? of cells with a polygonal section, preferably hexagonal or square, arranged around the cylindrical elements 103 and made with a first optically absorbing material 108?. Filter 100 further includes a pair of covers 109? in a second absorbing or reflecting material placed respectively at the inlet 101 and outlet 102 surfaces of the filter so as not to overlap the inlet 104 and outlet 105 faces of the cylindrical elements 103?.

[120] With reference to Fig.7 ? illustrated a lighting device 1000 for reproducing the light of the sky and the sun using an optical filter 100 according to the present invention. The lighting device 1000 comprises a directed light source 200 configured to emit visible light non-isotropically, preferably along directions in a neighborhood of a principal direction 205, having a first correlated color temperature or CCT greater than 5000 degrees Kelvin.

[121] Downstream of the direct light source 200 with respect to the main direction 205 ? placed an optical filter 100 according to the invention. In the embodiment of Fig. 7 the optical filter 100 ? oriented perpendicular to the principal direction 205 and produces a filtered light having an angular profile of luminance characterized by a sharp discontinuity in the luminance value for emission directions that pass from inside the acceptance cone of the optical filter 100 - for which the luminance value ? substantially constant - outside the acceptance cone of the optical filter 100 - for which the luminance value ? essentially close to zero.

[122] The lighting device 1000 further comprises a diffused light source 300 positioned downstream of the optical filter 100 with respect to the main direction 205. The diffused light source 300 ? configured to transmit at least some of the filtered light out of the filter 100 and produce light having a direct component with a luminance angular profile substantially equal to the luminance angular profile of the filtered light, and a correlated color temperature or CCT lower by at least 20% of the correlated color temperature or CCT of the light produced by the direct light source 200. The diffused light source 300 ? further configured to produce a diffuse light component, characterized by a spatially uniform angular profile of luminance, by a divergence of at least 2 times, preferably 3 times, more? preferably 4 times greater than the divergence of the forward component, and a correlated color temperature or CCT at least 1.2 times, preferably 1.3 times, more? preferably 1.5 times greater than the first CCT.

[123] Fig. 8 shows a preferred embodiment of the illumination device of Fig. 7 in which the direct light source 200 comprises a visible light emitter 201, an optical system 202 for collimating the light emitted by the light emitter visible, and a flat emission surface 203 of the direct light. The optical system 202 produces a light 230 which comprises a main component substantially collimated around a main direction 205 along directions preferably included within an emission cone 207 having a directrix along the main direction 205 and a semi-aperture 206 of less than 20 degrees, preferably less at 15 degrees, more? preferably below 8 degrees. The light 230 produced by the optical system 202 also comprises a secondary or spurious component 230?, which propagates along directions external to the emission cone 207. The optical system 202 ? further configured in such a way that the main component of the light 230 produced by it generates a substantially uniform illuminance on the flat emission surface 203. In the embodiment of Fig. 8 the section of the optical system 202 orthogonal to the main direction 205 has an area significantly smaller than the area of the flat emission surface 203. Therefore the light produced by the optical system 202 reaches the flat emission surface 203 from different directions, ie the luminance of the light 230 produced by the optical system 202 on the flat emission surface 203 is not ? spatially uniform having an angular profile characterized by a peak for a direction that varies across the surface, moving away from the main direction 205 the more? how much more we move away from the center.

[124] As shown in Fig. 9, the optical filter 100 ? preferably sized, in terms of diameters and length of the cylindrical elements included therein, in order to obtain an acceptance cone with half-aperture 120 substantially coinciding with the half-aperture 206 of the emission cone 207 which characterizes the light 230 emitted by the? visible light emitter 201 and collimated by the optical system 202, as illustrated in Fig. 8. Unlike the optical system 202, the optical filter 100 emits from its output surface 102 a filtered light 130 with a substantially uniform luminance angular profile on the whole surface.

[125] Finally, Fig. 10 shows a preferred embodiment of the diffused light source 300 comprising a Rayleigh diffusing panel - as for example described in the international patent application n. WO 2009/156348 by the same Applicant. The Rayleigh diffuser panel preferably comprises a dispersion of nanoparticles in a polymeric matrix, where diameter of the nanoparticles, the number of nanoparticles per unit? of surface, the refractive index of the nanoparticles and of the matrix in which they are dispersed are such as to allow the Rayleigh diffuser panel to produce on an emission surface 302, a diffused light 303 characterized by a correlated color temperature or CCT equal at least 1.2 times, preferably 1.3 times, more? preferably 1.5 times greater than the first CCT, from a luminance profile with an angular semi-aperture of diffused light 304 of at least 60?, preferably of at least 70?, and an overall luminous flux equal to at least 10% of the overall luminous flux of the filtered light 130 incident on the diffuser panel of Rayleigh 301.

[126] With reference to Fig. 11 ? shown is a different embodiment of the lighting device 1000 for reproducing the light of the sky and the sun using the optical filter 100 according to the present invention. In particular, the lighting device of Fig. 11 comprises a direct light source 200 which comprises a visible light emitter 201 of the linear type, comprising a plurality of light sources. of LEDs 240 arranged along a straight line perpendicular to a section plane orthogonal to the input and output surface of the optical filter 100. Furthermore, the optical system 202 ? configured as a two-stage collimation system 202?, 202??. The first stage 202? collimation optical system 202 ? made up of a plurality of cylindrical lenses, each coupled to a respective LED 240 of the plurality of LEDs and configured to collimate the LED light to which ? coupled into a collimating foreground 242 containing the straight line along which the LEDs are arranged, thus giving the light collimated an angular luminance profile, for directions included in the first collimation plane, having an angular half-aperture 243 equal to or smaller than the half-aperture of the angular acceptance cone 120 of the optical filter 100. The second collimation stage 202??of the optical system 202 ? consisting of a Fresnel mirror, characterized by a flat surface and a prismatic reflecting surface 246. The Fresnel mirror 202?? ? positioned and configured in such a way as to collimate the light emitted by the visible light emitter 201 in a second collimation plane parallel to the orthogonal section plane, and to give the light thus collimated an angular luminance profile, for directions included in the second collimation plane, having an angular semi-aperture 247 equal to or smaller than the semi-aperture of the angular acceptance cone 120 of the optical filter 100.

Claims (10)

Claims 1. Optical filter (100) comprising - a substantially flat entrance surface (101), - an outlet surface (102) substantially flat and parallel to the inlet surface, - a plurality? of cylindrical elements (103,103?) made of a material substantially transparent to light, in which the cylindrical elements (103,103?) of the plurality of cylindrical elements have substantially identical conformation and comprise a substantially circular inlet face (104) having a diameter of the cylindrical elements, a substantially circular outlet face (105) having the diameter of the cylindrical elements and a lateral surface which extends perimetrically between the inlet face (104) and the outlet face (105) for a length of the cylindrical elements (103,103?), and are arranged side by side and parallel to each other, in such a way as to define a plurality? of gaps between adjacent cylindrical elements (103,103?), the cylindrical elements (103,103?) having a cylinder axis perpendicular to the inlet (101) and outlet (102) surfaces and being arranged with the inlet face (104) substantially overlapping the input surface (102) and with the output face (105) substantially overlapping the output surface (102), - a first element of optically absorbing material (108,108?,110) configured and arranged with respect to the cylindrical elements in such a way as to prevent the passage of light between adjacent cylindrical elements (103,103?) of the plurality of cylindrical elements, - a second element of optically non-transparent material (109) configured and arranged with respect to the cylindrical elements (103,103?) in such a way as to prevent the passage of light parallel to the cylindrical elements and externally to them through the spaces between cylindrical elements (103,103?) adjacent, e - a plurality? of first lenses (107) with positive focal length equal to the length of the cylindrical elements, each first lens (107) being coupled to or defining the output face (105) of a respective cylindrical element (103,103?). 2. Optical filter (100) according to claim 1, comprising a plurality of? of second lenses (106) with positive focal length equal to the length of the cylindrical elements, each second lens (106) being coupled or defining the entrance face (104) of a respective cylindrical element (103,103?). 3. Optical filter (100) according to claim 1 or 2, wherein the material substantially transparent to light of which the cylindrical elements (103, 103?) are made? a gaseous material, preferably air, or a solid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin. 4. Optical filter (100) according to any one of claims 1 to 3, wherein the first element of optically absorbing material comprises a cylindrical jacket (110) which substantially covers the lateral surface of the cylindrical elements (103,103?), wherein - the cylindrical jacket (110) has a thickness significantly smaller than the diameter of the cylindrical elements (103,103?), for example a thickness 2 times, preferably 5 times, more? preferably 10 times lower, e - the cylindrical jacket comprises a layer of rigid material (110?) preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymeric resin, in which ? the layer of rigid material (110?) ? covered on an inner side surface thereof by an optically absorbing layer (110??), preferably a paint or film made of optically absorbing material; and/or ? the layer of rigid material (110?) ? covered on one of its outer side surfaces by the second element of optically non-transparent material (109), preferably in the form of a paint or film or sheath of optically absorbent material; and/or ? the layer of rigid material (100?) ? made of an optically absorbent material. 5. Optical filter (100) according to any one of claims 1 to 3, wherein the first element of optically absorbing material (108) comprises a sheath or film or paint made of a first optically absorbing material which substantially covers the surface side of the cylindrical elements (103) having a refractive index less than, equal to or greater than the cylindrical elements; and/or wherein the first element of optically absorbent material (108?) comprises a plurality of? of cells with a polygonal section, preferably hexagonal or square, arranged around the cylindrical elements (103?). 6. Optical filter (100) according to any one of the preceding claims, wherein the second element of optically non-transparent material (109,109?) comprises - an element of absorbent or reflecting material which covers and/or constitutes at least a portion of the input surface and/or of the output surface not including the portions superimposed on the input (104) and output (105) faces of the cylindrical elements (103,103?); and/or - a second optically absorbent material which at least partially fills the plurality? of gaps defined between adjacent cylindrical elements; and/or - a second optically absorbent material having an absorption coefficient which guarantees an absorption of at least 50%, preferably 80%, plus? preferably 90% of the visible light for a thickness equal to 1/5, preferably 1/10 of the length of the cylindrical elements (103,103?). The optical filter (100) according to claims 5 and 6, wherein - the second optically absorbing material coincides with the first optically absorbing material; or - the first and second optically absorbing materials are polymers and wherein the second optically absorbing material has a glass transition temperature Tg lower than a glass transition temperature of the first optically absorbing material, for example lower by at least 5, preferably 10, plus? preferably 20 degrees Celsius; or - the first optically absorbent material? a thermosetting resin and the second optically absorbent material ? a thermoplastic resin and where the hardening temperature Ti of the first optically absorbing material? lower than the glass transition temperature Tg of the second material. 8. Lighting device (1000) for reproducing the light of the sky and the sun comprising: a directed light source (200) configured to emit non-isotropic visible light having a first correlated color temperature or CCT, wherein the directed light source - comprises a visible light emitter (201), an optical system (202) for collimating the light emitted by the visible light emitter and a flat emission surface (203) of the directed light; and - ? configured to generate light (230) mainly along directions included within an emission cone (207) having a directrix of the emission cone (205) perpendicular to the flat emission surface of the directed light and having an angular half-aperture of direct light (206), defined as half-width of the luminance angular profile of the direct light source on the flat emission surface, less than 20 degrees, preferably less than 15 degrees, plus? preferably less than 8 degrees, where the semi-width ? measured at a height equal to 1/e<2 > times the peak value and the angular profile of luminance ? mediated on the spatial coordinates and on the azimuth coordinate, an optical filter (100) according to any one of claims 1 to 7, positioned downstream of the direct light source in such a way that the input surface (101) of the optical filter overlaps at least partially the flat emission surface (203) of the directed light of the directed light source; And a diffuse light source (300) configured to emit diffuse visible light having a second correlated color temperature or CCT of at least 1.2 times, preferably 1.3 times, more? preferably 1.5 times greater than the first CCT, and which includes a diffuser panel (301) that is - positioned downstream of the optical filter in such a way as to at least partially intercept a filtered light (130) emitted by the exit surface of the optical filter, - configured to transmit or reflect part of the filtered light (130) emitted by the exit surface (102) of the optical filter by producing a transmitted or reflected light (330) whose luminance angular profile substantially coincides with the luminance angular profile of the filtered light (130) emitted from the output surface of the optical filter, - configured to generate, on a surface of emission (302) of the scattered light, a component of scattered light (303) characterized by a luminance having an angular profile characterized by an angular half-aperture of scattered light (304), defined as half-width of the luminance angular profile at height 1/e<2 >, at least 2 times, preferably 3 times, more? preferably 4 times greater than a half-aperture of a filter acceptance cone (120) and/or an angular half-aperture of filtered light (130), defined as half-width of the angular luminance profile at height 1/e <2 >of the filtered light (130). The illumination device (1000) for reproducing sky and sun light according to claim 8, wherein the direct light angular half-aperture (206) is ? greater than 1.5, preferably 2.5, more? preferably 3 degrees. 10. Method for producing an optical filter (100) according to any one of claims 1 to 8, comprising the steps consisting of: to. produce at least one optical fiber having the. a core in transparent material, such as preferably air, glass, quartz, PMMA, polycarbonate, or other polymeric resin, the core having a diameter equal to the diameter of the cylindrical elements (103,103?) and ii. a first coating (108,110) at least partially made of a first optically absorbent material; b. get a plurality? of lengths of the at least one optical fibre, wherein the lengths have a length substantially equal to the length of the cylindrical elements (103,103?), each length constituting a cylindrical element (103,103?) covered on its lateral surface by a sheath, a film, by a paint or by a layer of rigid material made with the first optically absorbing material (108,110); c. obtaining at least a structure with side-by-side segments; d. arrange, with respect to the structure of adjacent sections, at least one element of optically non-transparent material (109,109?) configured and arranged with respect to the sections in such a way as to prevent the passage of light parallel to the sections (103,103?,108,110) and externally to them through interspaces present between adjacent segments (103,103?,108,110); And And. deposit, paste, print, grow or place at least a plurality? of first lenses (107), each facing at least one outlet face (105) of the cylindrical elements (103, 103?).