OPTICAL FILTER AND LIGHTING DEVICE TO REPRODUCE THE LIGHT OF THE SKY AND THE SUN COMPRISING THE SAME
20240069260 ยท 2024-02-29
Inventors
Cpc classification
International classification
Abstract
The present invention relates to an optical filter (100) comprising a substantially flat entry surface (101), a substantially flat exit surface (102) parallel to the entry surface, a plurality of channels (103) made of a material substantially transparent to light, wherein the channels (103) of the plurality of channels comprise an entry face (104), an exit face (105) and a lateral surface extending perimetrically between the entry face (104) and the exit face (105) over a length (L) of the channels (103), are arranged side by side and parallel to each other so as to define a plurality of interspaces between adjacent channels (103), have a channel axis (Y) incident to the entry (101) and exit (102) surface, and are arranged with the entry face (104) substantially overlapping the entry surface (101) and with the exit face (105) substantially overlapping the exit surface (102), at least one element of optically absorbing and/or non-transparent material (108, 109; 109) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light between adjacent channels (103) of the plurality of channels and so as to reduce the passage of light parallel to the channels and externally thereto, or at least a first element of optically absorbing material (108) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light between adjacent channels (103) of the plurality of channels (103) and at least a second element of optically non-transparent material (109; 109) configured and arranged with respect to channels (103) so as to reduce and/or substantially prevent the passage of light parallel to the channels (103) and externally thereto through interspaces between adjacent channels (103); wherein the channels (103) have a refractive index whose value decreases starting from a maximum refractive index (na) along a radially outward direction away from the channel axis (Y) passing through a centre of gravity of a section of the respective channel (103), so as to define a radial profile of refractive index of the channels, and wherein the radial profile of refractive index of the channels (103) is configured such that the light rays crossing any channel (103) of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face (104) of the channel exit the exit face (105) of the channel with substantially parallel directions.
Claims
1. Optical filter (100,100,100,100) comprising a substantially flat entry surface (101), a substantially flat exit surface (102) parallel to the entry surface, a plurality of channels (103) made of a material substantially transparent to light, wherein the channels (103) of the plurality of channels comprise an entry face (104), an exit face (105) and a lateral surface extending perimetrically between the entry face (104) and the exit face (105) over a length (L) of the channels (103), are arranged side by side and parallel to each other, so as to define a plurality of interspaces between adjacent channels (103), have a channel axis (Y) incident to the entry (101) and exit (102) surface, and are arranged with the entry face (104) substantially overlapping the entry surface (101) and with the exit face (105) substantially overlapping the exit surface (102), at least one element of optically absorbing and/or non-transparent material (108,109;109) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light between adjacent channels (103) of the plurality of channels and so as to reduce and/or substantially prevent the passage of light parallel to and externally to the channels, or at least one first element of optically absorbing material (108) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light between adjacent channels (103) of the plurality of channels (103), and at least one second element of optically non-transparent material (109;109) configured and arranged with respect to the channels (103) so as to reduce and/or substantially prevent the passage of light parallel to the channels (103) and externally thereto through the interspaces between adjacent channels (103); wherein the channels (103) have a refractive index whose value decreases starting from a maximum refractive index (n.sub.a) along a radially outward direction away from the channel axis (Y) passing through a centre of gravity of a section of the respective channel (103), so as to define a radial profile of refractive index of the channels, and wherein the radial profile of refractive index of the channels (103) is configured such that the light rays crossing any channel (103) of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face (104) of the channel exit the channel (103) with substantially parallel directions.
2. Optical filter (100,100) according to claim 1, wherein the radial profile of refractive index of the channels (103) is configured such that the light rays crossing any channel (103) of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face (104) of the channel exit the exit face (105) from the channel (103) with substantially parallel directions, and/or wherein said optical filter (100,100) has an image plane and an object plane, the object plane being placed at a distance (D) from the entry surface (101) and/or the image plane being placed at a distance (D) from the exit surface (102), the distance (D) being measured along the direction of the channel axis (Y) and being comprised between 0.5 D.sub.1 and 2 D.sub.1, preferably being comprised 0.7 D.sub.1 and 1.5 D.sub.1, more preferably being comprised between 0.8 D.sub.1 and 1.3 D.sub.1, with D.sub.1 being a nominal distance given by the relation:
3. Optical filter (100) according to claim 1, wherein the radial profile of refractive index of the channels (103) is configured such that, when the exit surface (102) is placed side-by-side to a reflecting surface, the light rays crossing any channel (103) of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face (104) of the channel exit the entry face (104) from the channel (103) with substantially parallel directions, and/or wherein said optical filter (100) has an image plane and an object plane, the object plane being placed at a distance (D) from the entry surface (101) and/or the image plane being placed at a distance (D) from the exit surface (102), the distance (D) being measured along the direction of the channel axis (Y) and being comprised between 0.5 D.sub.1 and 2 D.sub.1, preferably being comprised between 0.7 D.sub.1 and 1.5 D.sub.1, more preferably being comprised between 0.8 D.sub.1 and 1.3 D.sub.1, with D.sub.1 being a nominal distance given by the relation:
4. Optical filter (100) according to claim 1, wherein the channel axis (Y) is orthogonal to the entry surface (101) and to the exit surface (102), and wherein the filter (100) comprises a reflecting surface (810) positioned in an adjacent manner, preferably in contact, to the exit surface (102), wherein the radial profile of refractive index of the channels (103) is configured such that the light rays crossing any channel (103) of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face (104) of the channel exit the entry face (104) with substantially parallel directions, and/or wherein said optical filter (100) has an image plane and an object plane, the object plane being placed at a distance (D) from the entry surface (101) and/or the image plane being placed at a distance (D) from the exit surface (102), the distance (D) being measured along the direction of the channel axis (Y) and being comprised between 0.5 D.sub.1 and 2 D.sub.1, preferably being comprised between 0.7 D.sub.1 and 1.5 D.sub.1, more preferably being comprised between 0.8 D.sub.1 and 1.3 D.sub.1, with D.sub.1 being a nominal distance given by the relation:
5. Filter (100,100,100,100) according to any one of the preceding claims, wherein each channel (103) has a regular polygonal section.
6. Filter (100,100,100,100) according to any one of claims 1 to 4, wherein each channel (103) has a substantially elliptical section.
7. Filter (100,100,100,100) according to any one of claims 1 to 4, wherein each channel (103) has a non-polygonal concave or convex section.
8. Filter (100,100,100,100) according to any one of claims 1 to 4, wherein each channel (103) has an irregular polygonal section, preferably a convex irregular polygonal section.
9. Optical filter (100,100,100,100) according to any one of claims 1 to 4, wherein the channels (103) of the plurality of channels are cylindrical elements (103) having substantially identical conformation between them and having a substantially circular section with a diameter of the cylindrical elements.
10. Optical filter (100,100,100,100) according to claim 9, wherein the channels of the plurality of channels have channel axis (Y) perpendicular to the entry (101) and exit (102) surface.
11. Optical filter (100,100,100,100) according to claim 9 or 10, wherein the first element of optically absorbing material (108) comprises a cylindrical jacket (108) substantially covering the lateral surface of the cylindrical elements (103), wherein the cylindrical jacket (108) has a thickness significantly lower than the diameter of the cylindrical elements (103), for example a thickness 2 times, preferably 5 times, more preferably 10 times less, and comprises a layer of rigid material preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymer resin.
12. Optical filter (100,100,100,100) according to claim 11, wherein the layer of rigid material is covered on an outer lateral surface thereof by the second element of optically non-transparent material (109), preferably in the form of varnish or film or sheath made of an optically absorbing material; and/or the layer of rigid material is made of an optically absorbing material.
13. Optical filter (100,100,100,100) according to any one of claims 1-9, wherein the first element of optically absorbing material (108) comprises a jacket (108) substantially covering the lateral surface of the channels (103) and comprises a layer of rigid material, preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymer resin.
14. Optical filter (100,100,100,100) according to any one of claims 1-9 and 13, wherein the first element of optically absorbing material (108) comprises a sheath or a film or a varnish or a layer of rigid material made with a first optically absorbing material substantially covering the lateral surface of the channels (103), wherein the first optically absorbing material has a refractive index lower than, or equal to, or greater than the refractive index of the channels (103) in proximity to the lateral surface, or a refractive index that depends on the distance from the channel axis (Y), and/or wherein the absorption coefficient of the first optically absorbing material guarantees an absorption of at least 10%, preferably at least 25%, more preferably at least 40% of the visible light for a material thickness equal to 1/5, preferably 1/10 of a diameter of the entry face or of the exit face of the channels, or wherein the optical filter is configured so that it ensures an absorption of at least 70%, preferably at least 80%, more preferably at least 90%, even more preferably at least 95% of the visible light entering each channel at an angle close to the opening angle of the angular acceptance cone with respect to the direction of the axis of the channel.
15. Optical filter (100,100,100,100) according to any one of the preceding claims, wherein the second element of optically non-transparent material (109,109) comprises an element of absorbing or reflective material covering and/or constituting at least a portion of the entry surface and/or of the exit surface not comprising the portions overlapping the entry (104) and exit (105) faces of the channels (103); and/or a second optically absorbing material that at least partially fills the plurality of defined interspaces between adjacent channels; and/or a second optically absorbing material having absorption coefficient ensuring an absorption of at least 50%, preferably at least 80%, more preferably at least 90% of the visible light for a thickness equal to 1/5, preferably 1/10 of the length of the channels (103).
16. Optical filter (100,100,100,100) according to claim 15, wherein the second optically absorbing material coincides with the first optically absorbing material; or the first and the 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, e.g., lower by at least 5, preferably at least 10, more preferably at least 20 degrees Celsius; or the first optically absorbing material is a thermosetting resin and the second optically absorbing material is a thermoplastic resin, and where the curing temperature Ti of the first optically absorbing material is lower than the glass transition temperature Tg of the second material, or the first and/or the second optically absorbing material has a glass transition temperature (Tg) different from a glass transition temperature of the material of which the channels (103) of the plurality of channels (103) are made, e.g. different by at least 5, preferably at least 10, more preferably at least 20 degrees Celsius.
17. Filter (100,100,100,100) according to any one of the preceding claims, wherein said filter (100) comprises a plurality of channels (103) characterized by: a distribution of channels which are statistically equivalent to each other; and/or a distribution of channels with an averagely circular section; and/or a distribution of channels having section substantially not equal between them; and/or a distribution of channels having a substantially non-circular section.
18. Optical filter (100,100,100,100) comprising a substantially flat entry surface (101), a substantially flat exit surface (102) parallel to the entry surface, a plurality of channels (103) made of a material substantially transparent to light, wherein the channels (103) of the plurality of channels comprise an entry face (104), an exit face (105) and a lateral surface extending perimetrically between the entry face (104) and the exit face (105) over a length (L) of the channels (103), are arranged side by side and parallel to each other, so as to define a plurality of interspaces between adjacent channels (103), have a channel axis (Y) incident to the entry (101) and exit (102) surface, and are arranged with the entry face (104) substantially overlapping the entry surface (102) and with the exit face (105) substantially overlapping the exit surface (102), at least one element of optically absorbing or non-transparent material (108,109;109) configured and arranged with respect to the channels (103) so as to reduce the passage of light between adjacent channels (103) of the plurality of channels and so as to reduce the passage of light parallel to and externally to the channels, or at least one first element of optically absorbing material (108) configured and arranged with respect to the channels (103) so as to reduce the passage of light between adjacent channels (103) of the plurality of channels (103), and at least one second element of optically non-transparent material (109;109) configured and arranged with respect to the channels (103) so as to prevent the passage of light parallel to the channels (103) and externally thereto through the interspaces between adjacent channels (103); wherein the channels (103) have a refractive index whose value decreases starting from a maximum refractive index (n.sub.a) along a radially outward direction away from the channel axis (Y) passing through a centre of gravity of a section of the respective channel (103), so as to define a radial profile of refractive index of the channels, and/or wherein the radial profile of refractive index of the channels (103) is configured such that the optical filter (100,100,100,100) has an image plane and an object plane, at least one between the object plane and the image plane being placed at a distance (D) from the entry surface (101) and/or from the exit surface (102), the distance (D) being comprised between 0.5 D.sub.1 and 2 D.sub.1, with D.sub.1 being a nominal distance given by a relation comprised in the group consisting of:
19. Optical filter (100,100,100,100) according to claim 18, wherein the distance (D) from the entry surface (101) and/or from the exit surface (102) is comprised between 0.7 D.sub.1 and 1.5 D.sub.1, preferably between 0.8 D.sub.1 and 1.3 D.sub.1.
20. Optical filter (100,100,100,100) comprising a substantially flat entry surface (101), a substantially flat exit surface (102) parallel to the entry surface, a plurality of channels (103) made of a material substantially transparent to light, wherein the channels (103) of the plurality of channels comprise an entry face (104), an exit face (105) and a lateral surface extending perimetrically between the entry face (104) and the exit face (105) over a length (L) of the channels (103), are arranged side by side and parallel to each other, so as to define a plurality of interspaces between adjacent channels (103), have a channel axis (Y) incident to the entry (101) and exit (102) surface, and are arranged with the entry face (104) substantially overlapping the entry surface (102) and with the exit face (105) substantially overlapping the exit surface (102), at least one element of optically absorbing or non-transparent material (108,109;109) configured and arranged with respect to the channels (103) so as to reduce the passage of light between adjacent channels (103) of the plurality of channels and so as to reduce the passage of light parallel to and externally to the channels, or at least one first element of optically absorbing material (108) configured and arranged with respect to the channels (103) so as to reduce the passage of light between adjacent channels (103) of the plurality of channels (103), and at least one second element of optically non-transparent material (109;109) configured and arranged with respect to the channels (103) so as to prevent the passage of light parallel to the channels (103) and externally thereto through the interspaces between adjacent channels (103); wherein the channels (103) have a refractive index whose value decreases starting from a maximum refractive index (n.sub.a) along a radially outward direction away from the channel axis (Y) passing through a centre of gravity of a section of the respective channel (103), so as to define a radial profile of refractive index of the channels, and/or wherein the radial profile of refractive index of the channels (103) is configured such that each channel (103) of the plurality of channels behaves substantially as a converging lens having optical axis coincident with a channel axis and a focal length (f) in the medium satisfying the relation 0.5 f<f<2f, preferably 0.7 f<f<1.6f, more preferably 0.7 f<f<1.4f, even more preferably 0.9 f<f<1.2f, with fL, or f2L.
21. Optical filter (100,100,100,100) according to claim 20, wherein the focal length (f) in the medium is substantially equal to f, with fL, or f2L.
22. Chromatic effect light reflective unit (800) comprising: an optical filter (100) according to any one of claims 4 and 5-21 when dependent on claim 4; and a chromatic diffusion layer (310) comprising a rear surface positioned in an adjacent manner, preferably in contact, to the exit surface (102) and a front surface configured to be illuminated by incident light, wherein the chromatic diffusion layer (310) comprises a plurality of substantially transparent nanoelements dispersed in a substantially transparent matrix, the nanoelements and the matrix having different refractive indexes, and is configured such that the light reflective unit (800) produces a first direct light at a first CCT at polar angles lower than the cut-off angle (.sub.0) and a second diffused light at a second CCT at polar angles greater than the cut-off angle (.sub.0), with the second CCT equal to at least 1.2 times, preferably at least 1.3 times or more preferably at least 1.5 times the first CCT, when the incident light is the standard illuminator CIE E.
23. Chromatic effect transmission unit (900) comprising: an optical filter (100,100) according to any one of claims 1-3 and 5-21 when dependent on at least one of claims 1-3; and a chromatic diffusion layer (310) comprising a surface positioned adjacent, preferably in contact, to the entry surface (101) or to the exit surface (102) of the optical filter (100,100) and configured to be illuminated by incident light, wherein the chromatic diffusion layer (310) comprises a plurality of substantially transparent nanoelements dispersed in a substantially transparent matrix, the nanoelements and the matrix having different refractive indexes, and is configured such that the chromatic effect unit (900) produces a first direct light at a first CCT at polar angles lower than the cut-off angle (.sub.0) and a second diffused light at a second CCT at polar angles greater than the cut-off angle (.sub.0), with the second CCT equal to at least 1.2 times, preferably at least 1.3 times or more preferably at least 1.5 times the first CCT, when the incident light is the standard illuminator CIE E.
24. Lighting unit of artificial light (1000,1000) to reproduce the light of the sun comprising: a direct light source (200,700) configured to emit visible light in a non-isotropic manner; and an optical filter (100,100,100) according to any one of claims 1 to 21, positioned downstream of the direct light source so that the entry surface (101) of the optical filter is illuminated by the light emitted by the direct light source (200).
25. Lighting unit of artificial light (1000) according to claim 24 wherein, the direct light source (200) emits visible light having a first correlated colour temperature or CCT; comprises a visible light emitter (201), an optical system (202) for collimating the light emitted by the visible light emitter and a flat surface of emission (203) of the direct light; is configured to generate light (230) mainly along directions comprised within an emission cone (207) having a directrix of the emission cone (205) perpendicular to the flat surface of emission of the direct light and having an angular half-opening of direct light (206), defined as the half-width of the angular luminance profile of the direct light source on the flat emission surface, lower than 50 degrees, preferably lower than 30 degrees, more preferably lower than 10 degrees, wherein the half-width is measured at a height equal to 0.5 times the peak value and the angular luminance profile is averaged over the spatial coordinates and the azimuth coordinate, and wherein the lighting unit of artificial light (1000) comprises a diffused light source (300) configured to emit a diffused visible light having a second correlated colour temperature or CCT equal to at least 1.2 times, preferably at least 1.3 times, more preferably at least 1.5 times greater than the first CCT, even more preferably at least 1.8 times greater than a CCT of natural light and/or a CCT equal to 5600 Kelvin.
26. Lighting device (1000) to reproduce the light of the sky and the sun comprising: a direct light source (200) configured to emit visible light in a non-isotropic manner having a first correlated colour temperature or CCT, wherein the direct 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 surface of emission (203) of the direct light; is configured to generate a light (230) mainly along directions comprised within an emission cone (207) having a directrix of the emission cone (205) perpendicular to the flat surface of emission of the direct light and having an angular half-opening of direct light (206), defined as the half-width of the angular luminance profile of the direct light source on the flat emission surface, lower than 20 degrees, preferably lower than 15 degrees, more preferably lower than 8 degrees, wherein the half-width is measured at a height equal to 1/e.sup.2 times the peak value and the angular luminance profile is averaged over the spatial coordinates and the azimuth coordinate, an optical filter (100,100) according to any one of claims 1-3 and 5-21 when dependent on at least one of claims 1-3, positioned downstream of the direct light source so that the entry surface (101) of the optical filter is at least partially overlapping the flat surface of emission (203) of the direct light of the direct light source; and a diffused light source (300) configured to emit a diffused visible light having a second correlated colour temperature or CCT equal to at least 1.2 times, preferably 1.3 at least times, more preferably at least 1.5 times greater than the first CCT, and which comprises a diffuser panel (301) which is positioned downstream of the optical filter so as to intercept at least partially 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 producing a transmitted or reflected light (330) whose angular luminance profile substantially coincides with the angular luminance profile of the filtered light (130) emitted by the exit surface of the optical filter, configured to generate, on a diffused light emission surface (302), a diffused light component (303) characterized by a luminance having an angular profile characterized by an angular half-opening of diffused light (304), defined as half-width of the angular luminance profile at height 1/e.sup.2, at least 2 times, preferably at least 3 times, more preferably at least 4 times greater than a half-opening of an acceptance cone of the filter (120) and/or of an angular half-opening of filtered light (130), defined as half-width of the angular luminance profile at height 1/e.sup.2 of the filtered light (130).
27. Lighting device (1000) to reproduce the light of the sky and the sun according to claim 26, wherein the direct light source (200) is configured to produce on the flat emission surface a substantially spatially uniform cone illuminance, wherein the cone illuminance is the illuminance relative only to the contribution of the light impinging from directions comprised within the emission cone.
28. Lighting device (1000) to reproduce the light of the sky and the sun according to claim 27, wherein the angular half-opening of direct light (206) is greater than 1.5, preferably greater than 2.5, more preferably greater than 3 degrees.
29. Lighting unit of artificial light (1000) according to claim 24 wherein, the direct light source (700) emits visible light having a first correlated colour temperature or CCT; comprises a plurality of light sources (702) arranged on a substantially transparent surface (710), each light source (702) of the plurality of light sources being arranged and configured to generate a beam of light (704) with an angular source luminance profile having a peak along a same main direction (705); and wherein the lighting unit of artificial light (1000) comprises an optical filter (100) according to any one of claims 4 and 5-21 when dependent on claim 4, positioned such that a normal to the optical filter (100) is substantially parallel to the main direction (705), and is positioned in the space so that the light sources of the plurality of light sources (702) illuminate it substantially uniformly, and a diffused light source (300) interposed between the optical filter (100) and the direct light source (700) and configured to emit a diffused visible light having a second correlated colour temperature or CCT equal to at least 1.2 times, preferably at least 1.3 times, more preferably at least 1.5 times, even more preferably at least 1.8 times the first CCT and/or of a CCT equal to 5600 Kelvin.
30. Natural lighting unit (2000,2000,2000) to reproduce the light of the sun comprising: a receiving surface (2001) configured to receive natural light, and an optical filter (100,100,100) according to any one of claims 1-21 having the entry surface (101) or the second exit surface (102) at least partially overlapping the receiving surface (2001).
31. Natural lighting unit (2000,2000) according to claim 30 further comprising: a diffused light source (300) configured to emit diffused visible light having a correlated colour temperature or CCT at least 1.2 times, preferably at least 1.3 times, more preferably at least 1.5 times, even more preferably at least 1.8 times greater than a CCT of natural light and/or a CCT equal to 5600 Kelvin; or a chromatic diffusion layer (310) comprising a plurality of substantially transparent nanoelements dispersed in a substantially transparent matrix, the nanoelements and the matrix having different refractive indexes, and being configured such that the natural lighting unit (2000,2000) produces a first direct light at a first CCT at polar angles lower than the cut-off angle (.sub.0) and a second diffused light at a second CCT at polar angles greater than the cut-off angle (.sub.0), with the second CCT equal to at least 1.2 times, preferably at least 1.3 times or more preferably at least 1.5 times the first CCT, when the incident light is the standard illuminator CIE E.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0110] The accompanying drawings, which are incorporated herein and form part of the description, illustrate exemplary embodiments of the present invention and, together with the description, are intended to illustrate the principles of the present invention.
[0111] In the drawings:
[0112]
[0113]
[0114]
[0115]
[0116]
[0117]
[0118]
[0119]
[0120]
[0121]
[0122]
[0123]
[0124]
[0125]
[0126]
[0127]
[0128]
DETAILED DESCRIPTION
[0129] The following is 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, allowing the person skilled in the art to implement and use the present invention in numerous different situations and applications. Therefore, the exemplary embodiments are not intended, nor should they be considered, to limit the scope of patent protection. Rather, the scope of patent protection is defined by the attached claims.
[0130] For the illustration of the drawings, use is made in the following description of identical numerals or symbols to indicate construction elements with the same function. Moreover, for clarity of illustration, certain references may not be repeated in all drawings.
[0131] The use of for example, etc., or indicates non-exclusive alternatives without limitation unless otherwise indicated. The use of comprises and includes means comprises or includes, but not limited to, unless otherwise indicated.
[0132] Furthermore, the use of measures, values, shapes and geometric references (such as perpendicular and parallel) associated with terms such as approximately, almost, substantially or similar, is to be understood as without measurement errors or unless inaccuracies due to manufacturing tolerances and in any case less than a slight divergence from the values, measures, shapes or geometric references with which the term is associated.
[0133] Finally, terms such as first, second, upper, lower, main and secondary are generally used to distinguish components belonging to the same type, not necessarily implying an order or a priority of relationship or position.
[0134] With reference to the figures, some embodiments of an optical filter according to the present invention are schematically illustrated, indicated as a whole with 100, 100, 100,100. The optical filter 100, 100,100,100 comprises a substantially flat entry surface 101, a substantially flat exit surface 102 parallel to the entry surface, and a plurality of channels 103 made of a substantially light-transparent material extending between the entry surface 101 and the exit surface 102. Substantially flat is understood to mean at least locally flat, i.e. flat over an area having a diameter at least 10 times, preferably 30 times, more preferably 100 times the length of the channels. Substantially transparent material is understood to mean a substantially transparent solid material, such as glass, quartz, PMMA, polycarbonate, or other polymer resin. The channels 103 of the plurality of channels comprise an entry face 104, an exit face 105 and a lateral surface extending perimetrically between the entry face 104 and the exit face 105 over a length L of the channels 103. The channels are arranged side by side and parallel to each other, so as to define a plurality of interspaces between adjacent channels 103. Further, the channels 103 have a channel axis Y passing through a centre of gravity of a section of the channel 103 and incident on the entry 101 and exit 102 surface and are arranged with the entry face 104 substantially overlapping the entry surface 101 and with the exit face 105 substantially overlapping the exit surface 102. There is also provided at least one element of optically absorbing or non-transparent material 108,109 configured and arranged with respect to the channels 103 so as to reduce or substantially eliminate the passage of light between adjacent channels 103 of the plurality of channels and so as to reduce or substantially eliminate the passage of light parallel to the channels and externally thereto. Alternatively, there is provided a first element of optically absorbing material 108 configured and arranged with respect to the channels 103 so as to reduce or substantially eliminate the passage of light between adjacent channels 103 of the plurality of channels, and a second element of optically non-transparent material 109 configured and arranged with respect to channels 103 so as to prevent the passage of light parallel to the channels and externally thereto through the interspaces between adjacent channels 103. In particular, the channels 103 have a refractive index whose value decreases starting from a maximum refractive index n.sub.a along a radially outward direction away from the channel axis Y passing through the centre of gravity of section of the channel 103, so as to define a radial profile of refractive index of the channels.
[0135] In the context of this description and in the following claims, [0136] maximum refractive index n.sub.a is understood to mean a maximum refractive index that is substantially common to all channels; [0137] the expression channel is understood to mean a solid conforming to an extruded solid, that is a solid that extends along a longitudinal axis having a substantially constant section orthogonal to the longitudinal axis; and [0138] the expression axis of/of the channel, or longitudinal axis or longitudinal axis Y-Y are understood to equivalently indicate an axis of/of the channel.
[0139] According to the present invention, the radial profile of refractive index of the channels 103 is configured such that the light rays crossing any channel 103 of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face 104 of the channel exit the channel with substantially parallel directions. In an embodiment of the optical filter 100,100, 100,100, such as by way of non-limiting example any of the cases illustrated in the figures, the channels 103 are elements made of a material preferably selected from the group comprising glass, quartz, PMMA, polycarbonate, or other polymer resin.
[0140] In the exemplary and non-limiting embodiment of
[0141] With reference to the embodiment of
[0142] In a particular embodiment, such as, by way of non-limiting example, the cases illustrated in
[0143] In the context of the present description and in the following claims, the property of an optical filter 100,100 of being configured such that the light rays crossing any channel 103 of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face 104 of the channel exit an exit face 105 of the channel with substantially parallel directions is understood to be equivalently verified if said optical filter 100, 100 can be associated with an object plane in front of and parallel to an entry surface 101 and an image plane behind and parallel to an exit surface 102 such that a light source with linear shape and lying on the object plane along a source direction substantially orthogonal to the channel axis Y produces in the image plane an image of said source, i.e., it produces an illuminance profile characterized by a contrast along a direction orthogonal to the aforesaid source direction and/or by a peak illuminance value that are respectively greater than the contrast and/or the peak illuminance value obtained in any other plane behind the exit surface 102 and in front of the image plane, and wherein the object plane is placed at a distance D from the entry surface 101 and/or the image plane is placed at a distance D from the exit surface 102, wherein the distance D is comprised between 0.5 D.sub.1 and 2 D.sub.1, preferably comprised between 0.7 D.sub.1 and 1.5 D.sub.1, more preferably comprised between 0.8 D.sub.1 and 1.3 D.sub.1, with D.sub.1 being a nominal distance given by the following relation:
wherein: [0144] the nominal distance D.sub.1 is measured along the direction of the channel axis Y, L is the length of the channels 103 and n.sub.a is the maximum refractive index and where the terms in front and behind are to be understood with respect to a direction of propagation of the light generated by the light source with linear shape and crossing the multichannel filter 100.
[0145] In the context of the present description and in the following claims, the property of an optical filter 100,100 of being configured such that the light rays crossing any channel 103 of the plurality of channels and belonging to a beam of rays emerging from any point on an edge of an entry face 104 of the channel exit the channelin this case the exit face 105 of the channelwith substantially parallel directions is understood to be equivalently verified if each channel 103 of the plurality of channels of the optical filter 100,100 has a radial profile of refractive index such as to give the channel 103 the property of a converging lens having optical axis coincident with a channel axis and a focal length f in the medium substantially equal to the length of the channel L. Particularly, the aforesaid property of an optical filter 100,100 is understood to be verified if each channel 103 of the plurality of channels has a radial profile of refractive index such as to give the channel 103 the property of a converging lens having a focal length f in the medium satisfying the relation 0.5 L<f<2L, preferably 0.7 L<f<1.6L, more preferably 0.7 L<f<1,4L, even more preferably 0.9 L<f<1.2L, wherein L is the length of the channel.
[0146] With reference to the embodiment of
[0147] The cylindrical elements 103 have a lateral surface substantially covered under conditions of optical contact (without gaps) by a first element of optically absorbing material 108, for example in the form of a sheath, film or varnish, or layer of rigid material having a refractive index substantially equal to the refractive index of the material of which the cylindrical elements 103 are made. In particular, the first element of optically absorbing material 108 is arranged and configured to prevent the passage of light between adjacent cylindrical elements.
[0148] The interspaces between adjacent cylindrical elements 103 are at least partially filled by a second element made of optically absorbing material 109, which is different from or the same as the first material 108, so as to prevent the passage of light parallel to the cylindrical elements and externally thereto through the interspaces between adjacent cylindrical elements 103.
[0149] Advantageously, an optical filter 100 where each channel has a cylindrical conformation having a substantially circular section allows, e.g., in the case of a diffused lighting source, to produce an angular profile of luminous intensity independent of the azimuth angle, so that an optical filter comprising a plurality of such channels produces an angular luminance profile independent of the azimuth angle, as necessary in order to be able to reproduce the image of a round sun.
[0150] Note that if the axis of the channel Y is inclined with respect to the normal to the entry or exit surface by an angle (not illustrated) other than 0, the shape from the section of each channel may be obtained, for example, by projecting the entry face 104 or the exit face 105 of the channel onto the plane orthogonal to the axis of the channel Y, i.e., on the section plane.
[0151] A method for producing an optical filter 100 according to the invention provides for modifying the technology known in the field of optical fibers and used to produce the optical filters commonly referred to as fiber optics face plates by using as a preform element for the fiber spinning process a preform element of the type used for the production of GRIN fibers (GRade index optical fibers), e.g., a preform element of cylindrical section, wherein said preform element has a radial profile of refractive index equal to the average of the radial profiles of the refractive indexes of the channels 103 of the plurality of channels 103 of the optical filter 100, said average being carried out on all the channels and on all azimuth directions.
[0152] According to an alternative embodiment, such as those shown by way of non-limiting example in
[0153] In a further embodiment illustrated in
[0154] With reference to
[0155] where L is the length of the channels 103 of the plurality of channels. Preferably, the channel axis Y is substantially orthogonal to the entry surface 101 and to the exit surface 102.
[0156] For example, an optical filter 100 according to
[0157] With reference to
[0158] In particular, in this embodiment, the entry surface 101 acts both as entry and as exit of the light rays. Specifically, the reflecting surface 810 causes the light to pass twice through each channel 103 used in the optical filter 100, so that the path travelled by the light is equal to double the physical length L of the channels 103. In this case, the channels 103 of the plurality of channels 103 comprise an exit face 105 overlapping the exit surface 102 to which the reflecting surface 810 is coupled, and an entry face 104 acting as an entry and an exit of the light rays, and a lateral surface extending perimetrically between the entry face 104 and the exit face 105 over a length L of the channels 103.
[0159] In the optical filter 100 of
[0160] where L is the length of the channels 103.
[0161] With reference to
[0162] According to other embodiments, the optical filter according to the present invention has a plurality of channels characterized by a distribution of channels having substantially non-circular sections. In the context of the present description and in the appended claims, the expression distribution of substantially non-circular channels is intended to mean a plurality of channels such that an average over the plurality of channels of the ratio among the radii of the circumferences circumscribed and inscribed to the section of each channel has a value greater than 1.05, preferably greater than 1.2, more preferably greater than 1.3. Preferably, the average of the ratio among the radii of the circumferences circumscribed and inscribed to the section of each channel has a value lower than 3, preferably lower than 2.5, more preferably lower than 2. An example of distribution of channels having substantially non-circular sections is a distribution of channels having a substantially elliptical section.
[0163] In the context of the present description and in the appended claims, the expression inscribed circumferences is intended to mean a plurality of inscribed circumferences, wherein each circumference is inscribed in the section of a respective channel. In the context of the present description and in the appended claims, the expression circumscribed circumferences is intended to mean a plurality of circumscribed circumferences, wherein each circumference circumscribes the section of a respective channel.
[0164] According to different embodiments, the optical filter comprises a plurality of channels with a polygonal section. Advantageously, channels with a polygonal section allow a greater covering or tessellation of the plane than in the case of channels with a circular section, and therefore a greater overall section of channels capable of collecting the incident light and a possible greater transmission efficiency. In fact, this conformation allows to optimise the occupation of the surfaces of the filter by the sections of the channels, reducing any possible interspaces to a minimum. Preferably, the optical filter may comprise a plurality of channels having a regular polygonal section, for example with a triangular, square or hexagonal section. An example of a channel with a hexagonal section 103 and relative optical filter 100,100,100,100 are shown respectively in
[0165] According to other embodiments of the invention, the optical filter has a plurality of channels characterized by a distribution of channels having sections which are substantially not equal between them. In particular, in the context of the present description and in the appended claims, the expression distribution of channels having sections that are not substantially equal is intended to mean a plurality of channels such that each channel has a section having an effective radius of channel Re substantially different from the effective radius of channel Rc of at least another channel and/or has a shape substantially different from the shape of the section of at least another channel, where the effective radius of channel is defined as
and where A.sub.c is the area of the section of the channel.
[0166] By way of non-limiting example, a first embodiment characterized by a distribution of channels having sections that are not substantially equal has a standard deviation of the distribution of the effective radii R.sub.c having a value comprised between 2% and 50%, preferably between 3% and 30%, more preferably between 4% and 20% of the value of the average radius R, where average radius is intended to mean the average of the channel effective radii R<R.sub.c>.
[0167] By way of further non-limiting example, in a different embodiment characterized by a distribution of channels having sections that are not substantially equal the optical filter comprises a plurality of channels such that the distribution of the radii of the circumferences inscribed in each section of each channel has a standard deviation greater than 2%, preferably 4%, more preferably 6% of the average value over the same distribution, the sections being in the plane orthogonal to the longitudinal axis. Preferably, the standard deviation is lower than 70%, preferably lower than 50%, more preferably lower than 30% of the average value.
[0168] According to other embodiments of the invention, the optical filter has a plurality of channels characterized by a distribution of averagely circular channels. In particular, in the context of the present description and in the appended claims, the expression distribution of averagely circular channels means a distribution of channels having substantially randomly oriented sections in a section plane. More particularly, the expression distribution of averagely circular channels is understood to mean a distribution such that: the locus of the points {x,y} in the section plane satisfying the relation F(x, y)>CF.sub.max is essentially a circle, i.e., it is a surface delimited by a perimeter where a maximum distance of the perimeter from a centre and a minimum distance of the perimeter from the centre differ from each other in an amount lower than 30%, preferably lower than 20%, more preferably lower than 10% of an average distance of the perimeter from the centre, where the average is carried out over the perimeter of the channel and where C=0.5, preferably C=0.3, more preferably C=0.2, and where F(x, y) is a function obtained: [0169] by translating without rotating in the section plane (x,y) all the sections of the channels so that they are aligned vertically, i.e. along the coordinate y, and horizontally, i.e. along the coordinate x, to a centre, and [0170] by attributing F(x, y) a value equal to the number of translated sections comprising the point (x,y).
[0171] By way of non-limiting example, in an embodiment characterized by a distribution of channels having averagely circular sections, the angular profile of luminous intensity I(, ) of the optical filter 100,100,100,100 when illuminated by a diffused light (i.e., by a light with a substantially uniform luminance profile, i.e. independent of the position, and isotropic, i.e. substantially Lambertian), is substantially independent or weakly dependent on , where is the polar angle with respect to the direction of the channels and is the azimuth angle. For example, the angular profile of luminous intensity I(, ) of the light produced by any portion of the optical filter 100,100,100,100 when illuminated by a diffused light is substantially independent or weakly dependent on the azimuth angle , where said portion circumscribes a circle having a radius equal to 15 cm, preferably at least equal to 10 cm more preferably at least equal to 5 cm.
[0172] Particularly, the angular profile of luminous intensity I(, ) of the optical filter 100,100,100,100 illuminated by a diffused light is such that the region in the space of the angular coordinates (, ) outside of which I(, ) assumes a value lower than 50%, preferably lower than 70%, more preferably lower than 80% of the peak value is substantially a cone with a circular or elliptical base characterized by a minor axis of the ellipse having a length equal to at least 50%, preferably at least 60%, more preferably at least 70% of the major axis of the ellipse, or it is a cone wherein the difference between the maximum and minimum polar angles is lower than 30%, preferably lower than 20%, more preferably lower than 10% of the average polar angle, the average being carried out on the azimuth angles.
[0173] According to other embodiments of the invention, the optical filter has a plurality of channels characterized by a distribution of channels that are statistically equivalent to each other. In particular, in the context of the present description and in the appended claims, the expression plurality of statistically equivalent channels means that the probability that a channel has a certain characteristic, for example a section of a certain area, shape, or orientation in the section plane, is substantially the same for each channel of the plurality of channels, or that this distribution produces local average values, such as the average of the areas and/or of the shapes and/or of the orientation of the sections, which are substantially independent of the particular position in the section plane, the local average being understood to mean, for example, the average over a circular area with a radius equal to 15 cm, preferably equal to 10 cm, more preferably equal to 5 cm. By way of non-limiting example, an embodiment characterized by a distribution of channels that are statistically equivalent to each other has: [0174] a distribution of radii of the inscribed circumferences with standard deviation greater than 3%, preferably 5%, more preferably 7% of the average value on the optical filter 100,100,100,100, and [0175] a distribution of a local average of the radii of the plurality of inscribed circumferences with standard deviation of less than 5%, preferably 3%, more preferably 1% of the average value over the entire optical filter, said local average being carried out over an area of the optical filter comprised in a circle of radius less than 15 cm, preferably less than 10 cm, more preferably less than 5 cm.
[0176] Preferred embodiments of the optical filter according to the present invention may comprise a plurality of channels characterized by a distribution of channels presenting a combination of the characteristics discussed above, and in particular a distribution of channels [0177] (i) that are substantially non-circular, and/or [0178] (ii) having sections that are not substantially equal, and/or [0179] (iii) averagely circular, and/or [0180] (iv) statistically equivalent to each other.
[0181] Advantageously, a configuration of the filter which provides for a plurality of channels with substantially non-circular sections allows a better covering or tessellation than in the case of circular channels.
[0182] Advantageously, a configuration of the filter which provides for a plurality of channels having sections that are not substantially equal reduces the demand for high precision in the production phase, and thus production times and costs, and also favours a random arrangement and orientation of the sections of the channels, so as to allow the optical filter to produce an angular luminance profile that is substantially isotropic, i.e., independent of the azimuth coordinate, as required to produce an image of a circular sun.
[0183] Advantageously, a configuration of the filter which provides for a plurality of averagely circular channels further facilitates obtaining an optical filter capable of producing an angular luminance profile that is substantially independent of the azimuth coordinate.
[0184] Advantageously, a configuration of the filter that provides for a plurality of channels statistically equivalent to each other results in an invariance of the optical properties of the filter as perceived by an observer with respect to the specific position observed inside the filter, regardless of how much the properties of a single channel differ from those of another channel. Considering for example channels with average radius R<0.5 mm, R<0.2 mm, more preferably R<0.1 mm, characterized by a cut-off angle .sub.0>1, more preferably .sub.0>2, more preferably .sub.0>4, the number of channels participating in the formation of the image of the sun in the observer at a typical distance from the filter, i.e. at a distance of more than a few tens of centimetres, is greater than several hundreds, thousands or tens of thousands of units, i.e. sufficient to produce a perception of the average luminance in the observer at any point of the optical filter 100,100,100,100. In the context of the present description and in the appended claims with cut-off angle of the filter .sub.0 it is intended to indicate the average of the polar angle, measured with respect to the longitudinal axis, such that the angular luminance profile of the filter substantially cancels out (due to the presence of the first optically absorbing material interposed between adjacent channels), i.e. it assumes a value equal to 1/10, preferably 1/20, preferably equal to 1/30 of the peak value, e.g. in the case in which the filter is illuminated by a diffused light, i.e. by a light with a uniform and isotropic luminance profile, the average being evaluated with respect to the azimuth angle and over the whole surface of the filter. Alternatively, the cut-off angle of the filter .sub.0 is the average over the azimuth coordinate of the polar angle value so that the luminous intensity profile of the filter substantially cancels out when the filter is illuminated by a diffused light. In the context of the present description and in the following claims, the angle of .sub.0 coincides with the angle of the angular acceptance cone of the filter. In the context of the present description and in the appended claims, the cut-off angle of the filter .sub.0 is equivalently referred to as the acceptance angle .sub.0 or half-open angle of the acceptance cone .sub.0.
[0185] According to different embodiments, the optical filter comprises a plurality of channels with a non-polygonal section, for example with a non-polygonal concave section or a non-polygonal convex section. An optical filter 100,100,100,100 comprising a plurality of channels with a non-polygonal section is illustrated by way of non-exhaustive example in
[0186] According to further embodiments, the optical filter comprises a plurality of channels with a non-regular polygonal section, for example with a convex non-regular polygonal section. An optical 100,100,100,100 comprising a plurality of channels with a non-regular convex polygonal section is illustrated by way of non-exhaustive example in
[0187] Also in the case of the embodiments of
[0188] Advantageously, the optical filter comprises a plurality of channels with a non-regular polygonal section, characterized by a distribution of channels having sections that are not substantially equal, averagely circular, and statistically equivalent between them, allows the maximum coverage section or tessellation of the plane, and thus maximum transmission efficiency, while at the same time allowing for the production of an angular profile of average luminance substantially independent of the azimuth coordinate, since the orientation of the polygons is substantially random.
[0189] With reference to the examples cited, and more generally to the optical filter according to the present invention, the particular configurations relative to the plurality of channels can be obtained, for example, by creating a block or melt by heating at temperatures close to the transition temperature of a bundle of optical fibers and then cutting a slice of said block or melt of the desired thickness along a plane that is suitably oriented with respect to the longitudinal axis of the fibers or channels. By way of non-limiting example, such blocking or melt may be obtained starting from [0190] a combination between a plurality of GRIN optical fibers and a plurality of elements of a first and/or a second optically absorbing material, or from [0191] a combination between a plurality of optical fibers GRIN covered with a layer or clad of a first optically absorbing material and a plurality of elements of a first and/or of a second optically absorbing material, or from [0192] a plurality of GRIN optical fibers covered with a layer or clad of a first optically absorbing material
[0193] wherein, for example, said GRIN optical fibers covered with a layer or clad of a first material optically are in turn obtained by means of the drawing or extrusion technology of the optical fibers starting from a preform cylinder or prism having a core made of a transparent material and a coating or clad made of a first optically absorbing material and wherein the transparent core is in turn characterized by a refractive index profile whose value decreases starting from a maximum refractive index n.sub.a along a radially outward direction away from an axis of the preform cylinder or prism.
[0194] In particular, different distributions of the plurality of channels can be obtained by making the block or melt starting from different initial conditions, for example from different distributions of sections of the plurality of GRIN optical fibers and/or from different materials having different glass transition temperatures.
[0195] Hereinafter, first surface equivalently means the entry surface 101 and second surface equivalently means the exit surface 102 of the plurality of channels 103 of the optical filters 100, 100,100,100.
[0196] Referring to
[0197] The chromatic effect light reflective unit 800 of
[0198] In the context of the present description and of the subsequent claims, for the quantification of CCT values, in general and for those indicated above, reference is made to an incident illumination coming from a white light source, for example a standard illuminator CIE E, which within the visible spectrum radiates equal energy and has a constant spectral power distribution (SPD). Although this is a theoretical reference, the standard illuminator CIE E is particularly suitable in the event of diffusion variability as a function of the wavelengths, as it has a uniform spectral weight with respect to all wavelengths.
[0199] Note that the chromatic diffusion properties are related to a relative refractive index between the nanoelements and the host material. Accordingly, the nanoelements may refer to solid particles, e.g., the spherical nanoparticles and/or nanoclusters and/or nanocylinders and/or nanoelements having at least one nanometric dimension, where by nanometric dimension it is meant a dimension preferably on average lower than 300 nm, more preferably lower at 250 nm, even more preferably lower than 150 nm, as well as to optically equivalent nanometric elements in liquid or gaseous phase, such as generally inclusions in liquid or gaseous phase (for example nanodrops, nanovoids, nanoinclusions, nanobubbles, nanochannels etc.) which have nanometric dimensions and are incorporated into the host materials. Exemplary materials comprising gas-phase inclusions (nanovoids/nanopores) in a solid matrix include aerogels that are commonly formed by three-dimensional metal oxides (e.g. silica, alumina, iron oxide) or by an organic polymer (e.g. polyacrylates, polystyrene, polyurethanes and epoxides) that host solid pores (air/gas inclusions) with dimensions on the nanometer scale. By way of example, materials comprising liquid-phase inclusions include nanometer-sized liquid crystal (LC) phases often referred to as liquid phase that includes nanodrops which are confined to a matrix which may commonly have a polymeric nature. The chromatic diffusion layer 310 is made, for example, in the form of a bulk panel, coating, varnish, coating film or the like.
[0200] The chromatic effect transmission unit 900 of
[0201] In different embodiments not illustrated, instead of the chromatic diffusion layer 310 the light reflective unit 800 and/or the light transmission unit 900 comprise a diffused light generator 300 comprising a plurality of LED sources that are laterally coupled to a substantially planar and transparent light guide and configured to generate a diffused light having a CCT of a value equal to at least 1.2 times, preferably at least 1.3 times, more preferably at least 1.5 times, even more preferably at least 1.8 times the value of 5600 Kelvin.
[0202] According to a further aspect, the present invention provides a lighting unit or lighting device. In the context of this description and in the appended claims, the terms lighting unit and lighting device are to be regarded as equivalent.
[0203] Preferably, the lighting unit is an artificial light unit. With reference to
[0204] In other embodiments according to the invention, the direct light source 200 is configured to emit visible light having a variable CCT, for example a variable CCT in the range 1700-8000 degrees Kelvin.
[0205] An optical filter 100,100 according to the invention is placed downstream of the direct light source 200 with respect to the main direction 205. Preferably, the optical filter is oriented with respect to the direct light source 200 so as to have the longitudinal axis Y-Y substantially parallel to the main direction 205. In the embodiment of
[0206] In some embodiments of the invention, the diffused light source 300 is configured to produce a light having a direct component having a correlated colour temperature or CCT lower than at least 20% of the correlated colour temperature or CCT of the light produced by the direct light source 200. For example, the diffused light source 300 is a Rayleigh diffuser. In other embodiments of the invention, the diffused light source 300 is configured to transmit and/or be at least partially transparent to a light having a direct component having a CCT substantially identical to the CCT of the light produced by the direct light source 200. For example, the diffused light source 300 is a side-lit diffuser panel, i.e. lit laterally by a source other than the direct light source.
[0207] In some embodiments of the invention, the diffused light source 300 is further configured to produce a diffused light component characterized by an angular luminance profile characterized by a divergence at least 2 times, preferably 3 times, more preferably 4 times greater than the divergence of the direct component, and/or by a correlated colour temperature or CCT at least 1.2 times, preferably at least 1.3 times, more preferably at least 1.5 times, even more preferably at least 1.8 times greater than the first CCT, and/or a CCT equal to 5600 Kelvin.
[0208] In other embodiments of the invention, as for example shown in
[0209] In other embodiments of the invention, the emission cone 207 has half-opening of less than 20 degrees, preferably less than 15 degrees, more preferably less than 8 degrees.
[0210] In some embodiments of the invention, such as that shown by way of non-limiting example in
[0211] In some embodiments of the invention, the optical system 202 is further configured such that the main component of the light 230 produced by it generates a substantially uniform illuminance on a surface, for example, referring to
[0212] In some embodiments of the invention, as shown by way of non-limiting example in
[0213] In some embodiments of the invention, as shown by way of non-limiting example in
[0214] A different example of a lighting unit of artificial light 1000 to reproduce the light of the sun using an optical filter 100 according to the present invention, shown by way of example in
[0215] Each light source 702 of the plurality of light sources is arranged and configured to generate a beam of light 704 with an angular source luminance profile having a peak along a main direction 705 and an angular half-width at half height of the peak s_HWHM, where the main direction 705 and the angular half-width of source s_HWHM are common to all the light sources of the plurality of light sources 702, and the main direction 705 is inclined with respect to the normal to the support plane by an angle comprised between 0 and 80, preferably between 0 and 70, more preferably between 0 and 60.
[0216] The lighting unit of artificial light 1000 also comprises a chromatic effect light reflective unit 800 which integrates the optical filter 100 according to the present invention. The chromatic effect light reflective unit 800 is substantially planar and with normal substantially parallel to the main direction 705. In particular, the chromatic effect light reflective unit 800 is positioned in the space such that the light sources of the plurality of light sources 702 illuminate it substantially uniformly. For this purpose, for example, a minimum distance Dmin between each light source 702 and the chromatic effect light reflective unit 800 measured along the main direction 705 fulfils the relation: Dmin>0.5 ds tan(s_HWHM), preferably Dmin>ds tan(s_HWHM), more preferably Dmin>2 ds tan(s_HWHM).
[0217] The chromatic effect light reflective unit 800 comprises at least: [0218] an optical filter 100 provided with a reflecting surface 810 oriented towards the direct light source 700 and with a plurality of channels 103 arranged in a position adjacent to the reflecting surface 810, preferably in contact with the same 810; and [0219] a diffused light source 300 interposed between the optical filter 100 and the direct light source 700, in particular placed adjacent to the optical filter 100. In particular, the diffused light source 300 is preferably made according to what was previously described with reference to the embodiment of
[0220] The optical filter 100 is preferably sized such that the assembly consisting of the reflecting surface 810 and the plurality of channels 103 produces an angular acceptance cone with half-opening 120 substantially coincident with or greater than, for example 1.5, 2 or 3 times greater than, a half-opening s_HWHM of the emission cone 704 characterizing the light emitted by each of the light sources 702.
[0221] Advantageously, the lighting unit of artificial light 1000 thus configured allows an observer positioned in such a way that the direct light source 700 is interposed between the observer and the chromatic effect light reflective unit 800 and observing said unit through the substantially transparent surface 710 of the light source 700 to perceive, beyond this transparent surface 710, a uniform sky and a circular sun placed at infinite distancein other words, a sun whose image follows the movement of the observer, for example, moving with the same distance or moving at the same speed if the observer moves in a plane perpendicular to the main direction 705. This effect takes place irrespective of whether the direct light source 700 is realized through a plurality of light sources 702 distributed on the transparent surface 710.
[0222] As a further advantage, the lighting unit of artificial light 1000 thus configured produces the image of a round sun in sharp contrast to the sky even under conditions of a very bright outdoor environment because the light reflected from the reflecting surface at angles greater than the cut-off angle .sub.0 of the optical filter 100 is intercepted and substantially removed by this filter 100.
[0223] In the embodiment of
[0224] A second exemplary and non-limiting embodiment of the lighting unit of artificial light 1000 is illustrated in
[0225] According to a different aspect of the present invention, the lighting unit is a lighting unit of natural light 2000,2000,2000 that is a lighting unit configured to produce a light originating from a natural light and/or obtained by processing a natural light. Exemplary embodiments of lighting units of natural light 2000,2000, 2000 according to the present invention are illustrated in
[0226] In the context of the present invention, the term natural light means a light originally produced by the sun. By way of non-limiting example, natural light is, for example, the direct light of the sun and/or the light of the sun transmitted and/or reflected and/or diffused and/or refracted and/or diffracted by a natural and/or artificial element, such as the light of the sun diffused by clouds, or by fog or haze or by the sky or by the moon or by a wall.
[0227] Preferably, the lighting unit of natural light 2000, 2000, 2000 comprises a receiving surface 2001 configured to receive a natural light and an optical filter 100, 100,100,100 according to the present invention, this optical filter having the entry surface 101 and/or the exit surface 102 at least partially overlapping the receiving surface 2001.
[0228] Preferably, the lighting unit of natural light 2000, 2000 comprises a diffused light source 300 configured to emit a diffused visible light 2101 having a correlated colour temperature or CCT at least 1.2 times, preferably at least 1.3 times, more preferably at least 1.5 times, even more preferably at least 1.8 times greater than a CCT of the natural light and/or a CCT equal to 5600 Kelvin.
[0229] Preferably, the lighting unit of natural light 2000,2000,2000 comprises a receiving surface 2001 configured to receive a natural light and a chromatic effect light reflective 800 and/or light transmission 900 unit according to the present invention.
[0230] In an alternative embodiment illustrated in
[0231] In a different embodiment illustrated in
[0232] In a further embodiment illustrated in
[0233] Advantageously, the lighting unit of natural light 2000 comprising an optical filter 100 provided with a reflecting surface 810 which produces an infinity image of a circular sun with well-defined contours. For example, this occurs when it is illuminated by direct light of the sun striking the optical filter 100 from a direction belonging to the acceptance cone of the optical filter 100, or when it is illuminated by diffused natural light, contributing to the creation of a perception of infinite space. Advantageously, in the presence of direct light of the sun, it is possible to significantly reduce the glare effect of the sun, which effectively prevents the observer from seeing the sun directly, without compromising the view to infinity. For this purpose it is sufficient to size the cut-off angle 80 so that the reflected image of the sun is perceived under a solid angle much greater than the solid angle which subtends the image of the sun, corresponding to a flat angle at the vertex of the cone that subtends the image equal to 0.5. For example, for .sub.0=10, the luminance of the reflected sun is attenuated by at least 1600 times with respect to that of the natural sun, without substantially compromising contrast (as is the case with conventional diffusive reflecting surfaces).
[0234] Advantageously, the lighting unit of natural light 2000 comprising a chromatic effect light transmission unit 900 and, for example, a chromatic diffusion layer 310 of the Rayleigh type, produces an infinity image of a sun in sharp contrast to a cloudless sky. This happens, for example, when it is illuminated by diffused white light. For example, if used as a skylight or window, it is illuminated and produces the effect of a clear day with the sun in the sky when outside the sky is instead grey and overcast, cutting off light in most of the directions of origin of the direct light of the sun when outside the day is sunny.
[0235] Advantageously, the lighting unit of natural light 2000 comprising a chromatic effect light reflective unit 800 and, for example, a chromatic diffusion layer 310 of the Rayleigh type, produces an infinity image of a sun in sharp contrast to a cloudless sky. This happens, for example, when it is illuminated by diffused white light, similarly to the case of the lighting unit of natural light 2000 provided with a chromatic effect light transmission unit 900. For example, when used as an element of a building faade, it can be configured to generate the image of a blue and clear sky and of a warmer coloured sun standing out sharply on the horizon in contrast to the sky when the day is completely grey and the sky overcast. Advantageously, in the presence instead of direct lighting from the sun, i.e. on a clear day, the lighting unit of natural light 2000 provided with a chromatic light effect reflective unit 800 diffuses in all directions a light having a CCT greater than the CCT of the light of the sun, e.g. a light having a CCT 2, or 3 or 4 times greater than the CCT of the light of the sun, thus recreating a light surface similar to the sky, e.g. by recreating it on the illuminated faade.