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Title:
LIGHTING APPARATUS, METHOD FOR FORMING THE SAME AND METHOD FOR CONTROLLING THE SAME
Document Type and Number:
WIPO Patent Application WO/2019/098942
Kind Code:
A1
Abstract:
According to embodiments of the present invention, a lighting apparatus is provided. The lighting apparatus includes a light collection arrangement adapted to collect sunlight incident on the light collection arrangement and focus the collected sunlight to provide a focused light, and a light guiding arrangement optically coupled to the light collection arrangement to receive the focused light, wherein the light guiding arrangement comprises an intensity tracking device configured to track an optical path of the focused light that is variable corresponding to a change in an optical path of the sunlight incident on the light collection arrangement for propagation of the focused light through the light guiding arrangement. According to further embodiments of the present invention, a method for forming a lighting apparatus and a method for controlling a lighting apparatus are also provided.

Inventors:
ABDOLVAND, Amir (50 Nanyang Avenue, Singapore 8, 639798, SG)
TJIN, Swee Chuan (50 Nanyang Avenue, Singapore 8, 639798, SG)
YOO, Seongwoo (50 Nanyang Avenue, Singapore 8, 639798, SG)
GOEL, Charu (50 Nanyang Avenue, Singapore 8, 639798, SG)
Application Number:
SG2018/050561
Publication Date:
May 23, 2019
Filing Date:
November 08, 2018
Export Citation:
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Assignee:
NANYANG TECHNOLOGICAL UNIVERSITY (50 Nanyang Avenue, Singapore 8, 639798, SG)
International Classes:
F21S11/00; F21S19/00
Domestic Patent References:
WO2009115085A22009-09-24
Foreign References:
US20160033100A12016-02-04
CN101672452A2010-03-17
CN104776393A2015-07-15
US6299317B12001-10-09
US20140174503A12014-06-26
US20130061911A12013-03-14
Attorney, Agent or Firm:
MCLAUGHLIN, Michael Gerard et al. (McLaughlin IP Pte. Ltd, 112 Robinson Road #14-01, Singapore 2, 059504, SG)
Download PDF:
Claims:
CLAIMS

1. A lighting apparatus comprising:

a light collection arrangement adapted to collect sunlight incident on the light collection arrangement and focus the collected sunlight to provide a focused light; and

a light guiding arrangement optically coupled to the light collection arrangement to receive the focused light,

wherein the light guiding arrangement comprises an intensity tracking device configured to track an optical path of the focused light that is variable corresponding to a change in an optical path of the sunlight incident on the light collection arrangement for propagation of the focused light through the light guiding arrangement.

2. The lighting apparatus as claimed in claim 1, wherein the intensity tracking device comprises a dual axis intensity tracking device.

3. The lighting apparatus as claimed in claim 1 or 2, wherein the light collection arrangement comprises a wide-field collection optics configured to collect the sunlight incident on the light collection arrangement and focus the collected sunlight.

4. The lighting apparatus as claimed in claim 3, wherein the wide-field collection optics is immovable.

5. The lighting apparatus as claimed in claim 3 or 4, wherein the wide-field collection optics comprises a spherical lens.

6. The lighting apparatus as claimed in claim 5, wherein the spherical lens comprises a solid core or a hollow core having a cavity filled with a transparent liquid.

7. The lighting apparatus as claimed in claim 6, wherein the spherical lens further comprises at least one spherical shell arranged concentrically with and surrounding the solid core or the hollow core.

8. The lighting apparatus as claimed in any one of claims 1 to 7, wherein the light guiding arrangement comprises at least one optical fiber coupled to the intensity tracking device to receive the focused light whose optical path is tracked for propagation through the at least one optical fiber.

9. The lighting apparatus as claimed in any one of claims 1 to 8, wherein the light guiding arrangement comprises a light pipe optically coupled to the light collection arrangement to receive the focused light, wherein a width of the light pipe decreases in a direction away from the light collection arrangement.

10. The lighting apparatus as claimed in any one of claims 1 to 9, further comprising a light source arrangement configured to generate an illumination light, the light guiding arrangement being optically coupled to the light source arrangement to receive at least a portion of the illumination light for propagation through the light guiding arrangement.

11. The lighting apparatus as claimed in any one of claims 1 to 10, further comprising a second light source arrangement configured to generate a second illumination light to illuminate a surrounding of the lighting apparatus. 12. The lighting apparatus as claimed in claim 11, wherein the second light source arrangement is arranged to have the second illumination light transmitted through the light collection arrangement to illuminate the surrounding of the lighting apparatus.

13. The lighting apparatus as claimed in any one of claims 1 to 12, further comprising a light sensor to detect ambient light level.

14. The lighting apparatus as claimed in any one of claims 1 to 13, wherein the lighting apparatus comprises a lamp post.

15. A method for forming a lighting apparatus comprising:

arranging a light guiding arrangement to be optically coupled to a light collection arrangement to receive a focused light from the light collection arrangement adapted to collect sunlight incident on the light collection arrangement and focus the collected sunlight to provide the focused light; and

arranging an intensity tracking device configured to track an optical path of the focused light that is variable corresponding to a change in an optical path of the sunlight incident on the light collection arrangement for propagation of the focused light through the light guiding arrangement.

16. A method for controlling a lighting apparatus comprising:

tracking an optical path of a focused light that is variable corresponding to a change in an optical path of sunlight incident on a light collection arrangement of the lighting apparatus for propagation of the focused light through a light guiding arrangement of the lighting apparatus optically coupled to the light collection arrangement, the focused light being provided by the light collection arrangement from the sunlight collected by the light collection arrangement and being received in the light guiding arrangement.

Description:
LIGHTING APPARATUS, METHOD FOR FORMING THE SAME AND

METHOD FOR CONTROLLING THE SAME

Cross-Reference To Related Application

[0001] This application claims the benefit of priority of Singapore patent application No. 10201709398P, filed 15 November 2017, the content of it being hereby incorporated by reference in its entirety for all purposes.

Technical Field

[0002] Various embodiments relate to a lighting apparatus, a method for forming a lighting apparatus, and a method for controlling a lighting apparatus.

Background

[0003] With limitations on the contemporary energy sources used for the generation of electricity, such as burning of natural gas or diesel fuel for powering the generators, as well as environmental consideration, efficient usage of sunlight as a natural, ready to use light source for indoor illumination is becoming more and more important.

[0004] The sun showers about 1000 W/m 2 of light energy during clear skies and most of it goes untapped by humans. In commercial buildings, about 20-50% of total energy consumption is due to artificial lighting. Natural sunlight has proven health benefits. It aids in the synthesis of Vitamin D, regulates circadian rhythms and thereby influences the mood and general feeling of well-being in people.

[0005] Because the position of the sun changes, in a predictable way, in the sky, known designs of such alternative light sources rely on tracking the sun path in the sky. However, this is inefficient and impractical in situations where the sky is cloudy most of the time. Indeed, this results in stray rather than direct illumination of the environment by sunlight; this is particularly problematic in tropical regions such as in Singapore as almost more than 50% of the times the sky is covered by clouds. Further, most commercial daylight harvesting systems include large solar concentrators (panels of Fresnel lenses or parabolic mirrors), which are aligned towards the sun with the help of solar intensity motorized trackers. These systems are bulky and require large outdoor space for installation of concentrator panels.

[0006] There is therefore need for a solution for the efficient collection and transmission of (stray) sunlight for indoor illumination.

Summary

[0007] The invention is defined in the independent claims. Further embodiments of the invention are defined in the dependent claims.

[0008] According to an embodiment, a lighting apparatus is provided. The lighting apparatus may include a light collection arrangement adapted to collect sunlight incident on the light collection arrangement and focus the collected sunlight to provide a focused light, and a light guiding arrangement optically coupled to the light collection arrangement to receive the focused light, wherein the light guiding arrangement comprises an intensity tracking device configured to track an optical path of the focused light that is variable corresponding to a change in an optical path of the sunlight incident on the light collection arrangement for propagation of the focused light through the light guiding arrangement.

[0009] According to an embodiment, a method for forming a lighting apparatus is provided. The method may include arranging a light guiding arrangement to be optically coupled to a light collection arrangement to receive a focused light from the light collection arrangement adapted to collect sunlight incident on the light collection arrangement and focus the collected sunlight to provide the focused light, and arranging an intensity tracking device configured to track an optical path of the focused light that is variable corresponding to a change in an optical path of the sunlight incident on the light collection arrangement for propagation of the focused light through the light guiding arrangement.

[0010] According to an embodiment, a method for controlling a lighting apparatus is provided. The method may include tracking an optical path of a focused light that is variable corresponding to a change in an optical path of sunlight incident on a light collection arrangement of the lighting apparatus for propagation of the focused light through a light guiding arrangement of the lighting apparatus optically coupled to the light collection arrangement, the focused light being provided by the light collection arrangement from the sunlight collected by the light collection arrangement and being received in the light guiding arrangement.

Brief Description of the Drawings

[0011] In the drawings, like reference characters generally refer to like parts throughout the different views. The drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. In the following description, various embodiments of the invention are described with reference to the following drawings, in which:

[0012] FIG. 1A shows a schematic block diagram of a lighting apparatus, according to various embodiments.

[0013] FIG. 1B shows schematic views of examples of wide-field collection optics.

[0014] FIG. 1C shows a flow chart illustrating a method for forming a lighting apparatus, according to various embodiments.

[0015] FIG. 1D shows a method for controlling a lighting apparatus, according to various embodiments.

[0016] FIG. 2 shows a schematic view of a ball lens.

[0017] FIGS. 3 A and 3B show schematic cross-sectional views of a lighting apparatus with a light pipe.

[0018] FIGS. 3C and 3D show schematic cross-sectional views of a lighting apparatus with a cleaved fiber bundle.

[0019] FIG. 3E shows a schematic view of a fiber bundle design with a cosine (or sine) profile.

[0020] FIGS. 4 to 6 show schematic views of respective lighting apparatus.

Detailed Description

[0021] The following detailed description refers to the accompanying drawings that show, by way of illustration, specific details and embodiments in which the invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention. Other embodiments may be utilized and structural, logical, and electrical changes may be made without departing from the scope of the invention. The various embodiments are not necessarily mutually exclusive, as some embodiments can be combined with one or more other embodiments to form new embodiments.

[0022] Embodiments described in the context of one of the methods or devices are analogously valid for the other methods or devices. Similarly, embodiments described in the context of a method are analogously valid for a device, and vice versa.

[0023] Features that are described in the context of an embodiment may correspondingly be applicable to the same or similar features in the other embodiments. Features that are described in the context of an embodiment may correspondingly be applicable to the other embodiments, even if not explicitly described in these other embodiments. Furthermore, additions and/or combinations and/or alternatives as described for a feature in the context of an embodiment may correspondingly be applicable to the same or similar feature in the other embodiments.

[0024] In the context of various embodiments, the phrase“at least substantially” may include “exactly” and a reasonable variance.

[0025] In the context of various embodiments, the term“about” as applied to a numeric value encompasses the exact value and a reasonable variance.

[0026] As used herein, the term“and/or” includes any and all combinations of one or more of the associated listed items.

[0027] Various embodiments may provide an FED (light-emitting diode)-compensated, non tracking sunlight collector and transmitter for indoor illumination. Here, the non-tracking sunlight collector may mean that the sunlight collector device or optics is static and not movable to track or follow the path of the sun in the sky.

[0028] Various embodiments may provide a design for a hybrid outdoor and indoor illumination device or apparatus, e.g., a lamp post. The apparatus may employ a combination of solar light and a built-in lamp, e.g., FED, to offer a constant illumination for indoor environment with a well-defined illuminance (Fux). The apparatus may also offer an adjustable degree of illumination for outdoor. The apparatus may use a fiber-optic platform for the delivery of the solar light for indoor applications. In contrast to known solar light collectors that use a sort of position tracking system to follow the path of the sun in the sky, the sunlight collector device or optics of the apparatus of various embodiments is static. The apparatus may use a wide-angle (or wide-field) collection optics and fiber-optics instrumentation (e.g., an optical fiber, fiber bundle, or light pipes) to efficiently (e.g., efficiencies more than 20%) collect and transmit sunlight for indoor illumination. The same optics may be used for outdoor illumination.

[0029] Various embodiments may provide a technique for the efficient collection and transmission of (stray) sunlight for indoor illumination without the need for the sunlight collector device or optics to be moved to track the sun path in the sky throughout the day. The apparatus of various embodiments may take advantage of the properties of optical elements with wide collection-angle, such as a ball lens, which may remain static and immovable. Such elements may collect the light entering them from various angles and concentrate it in or to a well-defined point (or region) which depends on their design and geometry. The concentrated sunlight may then be collected and transmitted by a fiber bundle to the point of interest.

[0030] There may be provided a lighting apparatus or system for collecting and directing sunlight into an indoor environment. The apparatus may include:

(a) a light guiding component (e.g., a light pipe) having an inlet opening at one end, an outlet opening at the opposing end, and a hollow portion extending from the inlet opening to the outlet opening;

(b) a wide-field collector (WFC), such as a ball lens or a monocentric lens, received partially in the inlet opening of the light guiding component;

(c) a plurality of optical fibers coupled to the outlet opening of the light guiding component;

(d) wherein the WFC is configured to collect and couple sunlight into the light guiding component;

(e) wherein the light guiding component is configured to couple the sunlight into the plurality of optical fibers;

(f) wherein the plurality of optical fibers are configured to direct the sunlight into an indoor environment.

[0031] The inner surface of the light guiding component may be reflective.

[0032] There may be provided a lighting apparatus or system for collecting and directing sunlight into an indoor environment. The apparatus may include:

(a) a plurality of optical fibers having an input end and an output end;

(b) a wide-field collector (WFC) placed on the input end of the optical fibers or arranged a distance from the input end of the optical fibers; (c) wherein the WFC is configured to collect and couple sunlight into the input end of the plurality of optical fibers;

(d) wherein the plurality of optical fibers are configured to direct the sunlight into an indoor environment.

[0033] The wide-field collector (WFC) as described herein may be or may include a ball lens. The ball lens may include a sphere made of glass or plastic, or a hollow sphere filled with transparent liquid (e.g., water, glycerine, etc).

[0034] The input end of each optical fiber may be cleaved at different angles to allow ease of coupling of the sunlight into the plurality of optical fibers from different angles.

[0035] The lighting apparatus as described herein may be a hybrid system, which may further include an artificial light source, such as a light-emitting diode (LED). The artificial light source may provide light if the illuminance in the indoor environment is insufficient. The artificial light source may also serve to provide light at night time both for indoor and outdoor environments.

[0036] Various embodiments may provide a daylight harvesting apparatus or system using ball lens and optical fiber. In one non-limiting example, there may be provided a lighting apparatus having a ball lens as a concentrator and a movable delivery fiber, that may serve as a daylight harvesting unit during the day and as an LED driven street lamp during the night. The lighting apparatus may be in the form of an efficient, sleek and highly aesthetic lamp post design.

[0037] FIG. 1A shows a schematic block diagram of a lighting apparatus 100, according to various embodiments. The lighting apparatus 100 includes a light collection arrangement 102 adapted to collect sunlight (as represented by the solid arrow 110) incident on the light collection arrangement 102 and focus the collected sunlight 110 to provide a focused light (as represented by the solid arrow 112), and a light guiding arrangement 104 optically coupled (as represented by the dashed line 114) to the light collection arrangement 102 to receive the focused light 112, wherein the light guiding arrangement 104 includes an intensity tracking device 106 configured to track an optical path of the focused light 112 that is variable corresponding to a change in an optical path of the sunlight 110 incident on the light collection arrangement 102 for propagation of the focused light 112 through the light guiding arrangement 104.

[0038] In other words, a lighting apparatus 100 for lighting or illumination of an area or space may be provided. The lighting apparatus 100 may include a light collection arrangement 102 that may collect or receive sunlight (or rays from the sun) 110. The light collection arrangement 102 may collect the sunlight 110 impinging on the light collection arrangement 102 and transmits the sunlight 110 through the light collection arrangement 102. This may mean that the light collection arrangement 102 or any light collection element or optics thereof may be optically (or light) transmissive (or transparent). The light collection arrangement 102 may focus the sunlight 110 as the sunlight 110 propagates through the light collection arrangement 102. This may mean that the light collection arrangement 102 or any light collection element or optics thereof may have focusing capability. As a result, a focused (sun)light 112 may be generated.

[0039] The lighting apparatus 100 may include a light guiding arrangement 104 that may receive the focused light 112. The light guiding arrangement 104 may include an (light) intensity tracking device 106 to track an optical path of the focused light 112 that may change or vary as a result of a change in (a direction of) an optical path of the sunlight 110 incident on the light collection arrangement 102 for propagation of the focused light 112 through the light guiding arrangement 104. Put in another way, the optical path of the focused light 112 may change as a result of a change in an incident angle of the sunlight 110 incident on the light collection arrangement 102. The sun moves along a path through the day, and as a result, the position of the sun relative to the light collection arrangement 102 changes through the day. As a result of the movement of the sun, the angle of incidence of the sunlight 110 on the light collection arrangement 102 changes, which in turn results in changes to the optical path of the focused light 112, which may be tracked by the intensity tracking device 106. It should be appreciated that the intensity tracking device 106 is movable to track the optical path of the focused light 112. As a non-limiting example, the intensity tracking device 106 may be movable along an arc.

[0040] In various embodiments, the intensity tracking device 106 may track a focal point or spot of the focused light 112 in or along the optical path of the focused light 112.

[0041] In various embodiments, the intensity tracking device 106 may include a photosensor. The intensity tracking device 106 may include a motor.

[0042] In various embodiments, the intensity tracking device 106 may include a dual axis intensity tracking device. This may mean that the intensity tracking device 106 may be movable along two axes.

[0043] The light collection arrangement 102 may include a wide-field collection optics (or wide- field collection optical element) configured to collect the sunlight 110 incident on the light collection arrangement 102 and focus the collected sunlight 110. The wide-field collection optics may collect the sunlight 110 over a wide incident angle. Some non-limiting examples of the wide wide-field collection optics are shown in FIG. 1B to be described further below.

[0044] In various embodiments, the wide-field collection optics may be immovable. This may mean that the wide-field collection optics may be fixed (or static) and not movable to track a path of the sun through the day. Accordingly, it should be appreciated that the lighting apparatus 100 may be free of sun tracker devices that are provided in known systems that, when used with their corresponding sun collectors, lead to re-orientation of the sunlight collectors to track or follow the sun through the day.

[0045] The wide-field collection optics may include a spherical (optical) lens, as illustrated in FIG. 1B for wide-field collection optics l30a, l30b, l30c. The spherical lens may be at least substantially transparent or transmissive. The spherical lens may be in the form of a ball lens. The spherical lens or the ball lens may collect the sunlight 110 and focus the collected sunlight 110.

[0046] The spherical lens may include a (completely) solid core 180 or a hollow core 181 having a cavity filled with a (optically) transparent liquid 182. The solid core 180 and/or the hollow core 181 may be made of glass or polymer or plastic. The transparent liquid 182 may be water, glycerine, etc. The solid core 180 may collect the sunlight 110 and focus the collected sunlight 110. The transparent liquid 182 may collect and focus the sunlight 110 in a manner similar to the solid core 180.

[0047] The spherical lens may further include at least one (optical) spherical shell (or shell element) 183 arranged concentrically with and surrounding the solid core 180 or the hollow core 181. In this way, the spherical lens may be a monocentric lens. The material of the at least one spherical shell 183 may be different from the material of the solid core 180 or the hollow core 181. The at least one spherical shell 183 may have a refractive index that is different from that of the solid core 180 or the hollow core 181. A plurality of spherical shells or spherical shell elements may be provided surrounding the solid core 180 or the hollow core 181, and arranged concentrically with the solid core 180 or the hollow core 181. Different spherical shells may be made of different materials and/or may have different refractive indices relative to each other.

[0048] In various embodiments, a spherical lens or a ball lens may be employed as it has the highest/maximum acceptance angle amongst solar collectors. Nevertheless, it should be appreciated that compound parabolic concentrators and/or parabolic dishes may be suitably employed as the wide-field collection optics.

[0049] In various embodiments, the light guiding arrangement 104 may include at least one optical fiber coupled to the intensity tracking device 106 to receive the focused light 112 whose optical path is tracked for propagation through the at least one optical fiber. The focused light 112 may propagate through (or within) the at least one optical fiber to be provided or guided to a desired location, for example, a remote area or space, e.g., an indoor space, an underground space, etc., that may be away from the lighting apparatus 100. A plurality of optical fibers may be employed, for example, in the form of a fiber bundle.

[0050] In various embodiments, the light guiding arrangement 104 may include a light pipe optically coupled to the light collection arrangement 102 to receive the focused light 112, wherein a width of the light pipe may decrease in a direction away from the light collection arrangement 102. For example, the light pipe may have an input end arranged proximal to the light collection arrangement 102 and an (opposite) output end, wherein the width of the light pipe decreases in a direction from the input end to the output end. As may be appreciated, the light pipe has a tapering structure. The light pipe may have a hollow structure. The light pipe may have a reflective inner surface, for example, made of or coated with a reflective material. The light pipe may reflect the focused light 112 propagating through and within the light pipe. Multiple reflections may occur.

[0051] The lighting apparatus 100 may further include a light source arrangement (e.g., having one or more light sources) configured to generate an illumination light, the light guiding arrangement 104 being optically coupled to the light source arrangement to receive at least a portion of the illumination light for propagation through the light guiding arrangement 104. Such an arrangement may be employed to provide illumination of indoor spaces. The light source arrangement may include one or more light emitting diodes (LEDs).

[0052] The lighting apparatus 100 may further include a second light source arrangement

(e.g., having one or more light sources) configured to generate a second illumination light to illuminate a (external) surrounding of the lighting apparatus 100. Such an arrangement may be employed to provide illumination of outdoor spaces. The second light source arrangement may include one or more light emitting diodes (LEDs). [0053] In various embodiments, the second light source arrangement may be arranged to have the second illumination light transmitted through the light collection arrangement 102 to illuminate the surrounding of the lighting apparatus 100.

[0054] It should be appreciated that the two light source arrangements may be employed in the lighting apparatus 100 to provide illumination of indoor spaces and outdoor spaces.

[0055] As described above, the lighting apparatus 100 may include a combination of a solar lighting arrangement and an artificial illumination lighting arrangement. The lighting apparatus 100 may, therefore, be a hybrid lighting apparatus.

[0056] In various embodiments, the light guiding arrangement 104 may be capable of receiving the focused light 112 and the illumination light, where it may not be necessary that the light guiding arrangement 104 receives both simultaneously at any one time, although this may be possible. For example, in one mode of operation (e.g., during daytime), the light guiding arrangement 104 may receive the focused light 112, and in another mode of operation (e.g., during nighttime), the light guiding arrangement 104 may receive the illumination light.

[0057] The lighting apparatus 100 may further include a light sensor to detect ambient (or outdoor) light level. The second light source arrangement maybe activated to generate the second illumination light in response to a detected ambient light level below a threshold level.

[0058] In the context of various embodiments, the lighting apparatus 100 may include or may be a (outdoor) lamp post.

[0059] FIG. 1C shows a flow chart 120 illustrating a method for forming a lighting apparatus, according to various embodiments.

[0060] At 122, a light guiding arrangement is arranged to be optically coupled to a light collection arrangement to receive a focused light from the light collection arrangement adapted to collect sunlight incident on the light collection arrangement and focus the collected sunlight to provide the focused light.

[0061] At 124, an intensity tracking device is arranged, which is configured to track an optical path of the focused light that is variable corresponding to a change in an optical path of the sunlight incident on the light collection arrangement for propagation of the focused light through the light guiding arrangement.

[0062] FIG. 1D shows a method 128 for controlling a lighting apparatus, according to various embodiments. An optical path of a focused light that is variable corresponding to a change in an optical path of sunlight incident on a light collection arrangement of the lighting apparatus is tracked for propagation of the focused light through a light guiding arrangement of the lighting apparatus optically coupled to the light collection arrangement, the focused light being provided by the light collection arrangement from the sunlight collected by the light collection arrangement and being received in the light guiding arrangement.

[0063] It should be appreciated that descriptions in the context of the light apparatus 100 may correspondingly be applicable in relation to the method for forming a light apparatus described in the context of the flow chart 120 and the method 128 for controlling a light apparatus.

[0064] Further, various embodiments may provide a method for controlling a lighting apparatus as described herein, the method including tracking the optical path of the focused light that is variable corresponding to the change in the optical path of the sunlight incident on the light collection arrangement.

[0065] The lighting apparatus, and its constituent elements, will now be described by way of the following non-limiting examples, and with reference to the corresponding figures.

[0066] Wide-field collector (WFC) or wide-field collection optics

[0067] The wide-field collector may be a free-form optics that may be optimised, e.g., through simulations, for a specific geographical position (e.g., sun path in the sky) and collection efficiency. Optimisation may be done, for example, via commercially available softwares such as Zemax, Comsol, etc. The WFC may also be a simple geometrical form, such as a ball lens, e.g., a sphere of glass, polymer, or a hollow sphere filled with a transparent liquid such as water, glycerine, or a monocentric lens design. The concentrated light by the WFC may be transported via a light pipe, e.g., an array of mirrors, a hollow tube with reflective inner side, a glass or polymer rod, or an optical fiber bundle. Further, an LED arrangement may be provided near the collector to provide illumination at night so that the same lighting apparatus may be used for night illumination.

[0068] Ball lens

[0069] A ball lens may be a sphere of a transparent, high refractive index medium (e.g., having a refractive index, N, higher than air), or a mixture of high refractive index media, in the form of concentric spheres (e.g., a monocentric lens). For example, a ball lens may be a transparent spherical ball of glass or a polymer (e.g., plastic, poly(methyl methacrylate) (PMMA), acrylic, etc.), or may be a spherical shell of glass or polymer filled with a liquid such as water, or glycerine. The surface(s) of the ball lens in direct contact with environment (e.g., outer air or the inner liquid) may be protected with one or more suitable coatings, including but not limited to, at least one of self-cleaning coating, anti-reflection coating, or UV (ultra-violet) protection coating. For a ball lens having an internal liquid, some amount of chemicals (e.g., propylene oxide) may be used in order to minimise or prevent growth of mould. The outer diameter of the ball lens may vary from about 1 mm to a few meters, depending on the applications.

[0070] FIG. 2 shows a schematic view of a ball lens 230, illustrating the geometry and focusing properties of the ball lens 230. The geometrical optics characteristics of the ball lens 230 may include the focal length,/, and the back focal length, bfl, which may be defined as follow:

f= RN/2(N-l) Equation (1), bfl =/- R = (2-N)R/2(N- 1 ) Equation (2), where N and R are respectively the refractive index and radius of the ball lens 230.

[0071] Collection of sunlight

[0072] FIGS. 3 A to 3E show various techniques for the collection part of the sunlight, that is, its concentration and transmission to the delivery part for indoor illumination. As non-limiting examples, a reflective concentrator, e.g., a light pipe with a reflective inner surface as shown in FIGS. 3A and 3B and which will be described further below, or a curved- or angled-cleaved fiber bundle as shown in FIGS. 3C and 3D and which will be described further below, may be employed. Both techniques or geometries may capture the sunlight collected by a wide-angle collection optics, e.g., a ball lens 330a, 330b, 330c, 330d (FIGS. 3A to 3D). Light from the sun may be collected and concentrated by a wide-field collection optics (such as the ball lens 330a, 330b, 330c, 330d), which may concentrate the sunlight in a specific, well-defined region in space. The geometry and the size of the concentration region may depend on the wide-angle collection optics, and the position and/or movement of the sun in the sky relative to the concentrator (i.e., the wide-angle collection optics; ball lens 330a, 330b, 330c, 330d). Each of the ball lens 330a, 330b, 330c, 330d may be spherical or may have a spherical surface, with a circular cross-section. [0073] Light Pipe

[0074] FIGS. 3 A and 3B show schematic cross-sectional views of a lighting apparatus 300a, 300b with a light pipe 332a, 332b, according to various embodiments. A ball lens 330a, 330b may be coupled or connected to the light pipe 332a, 332b, e.g., at an input region or end of the light pipe 332a, 332b. The light pipe 332a, 332b may have an opening at its input region to receive, at least partially, the ball lens 330a, 330b. The light pipe 332a, 332b may be hollow. The light pipe 332a, 332b may have a tapering structure or cross-section, with the corresponding dimension decreasing from its input region towards an output region or end of the light pipe 332a, 332b. A fiber bundle 334a, 334b, having a plurality of optical fibers, may be optically coupled to the light pipe 332a, 332b, for example, arranged at the output region of the light pipe 332a, 332b. The fiber bundle 334a, 334b may have a cross-sectional dimension (e.g., diameter), D.

[0075] The ball lens 330a, 330b may receive sunlight (illustrated as rays 336a, 336b) and transmit the sunlight 334a, 334b through the ball lens 330a, 330b. The ball lens 330a, 330b may focus or concentrate the sunlight 334a, 334b incident on and propagating through the ball lens 330a, 330b. The light pipe 332a, 332b may then channel the sunlight concentrated by the ball lens 330a, 330b to a smaller diameter suitable for coupling into an optical fiber or the fiber bundle 334a, 334b for onward transmission through the optical fibers, e.g., for indoor applications.

[0076] The design of the light pipe 332a, 332b may be as illustrated in FIG. 3B showing a cross- sectional view of the light pipe 332b as cut along a longitudinal axis or length of the light pipe 332b. Along the width of the light pipe 332a, 332b, in the direction perpendicular to its longitudinal axis, the light pipe 332a, 332b may have a square or circular cross-section. The sunlight focused by the wide-field collector, i.e., the ball lens 330a, 330b, may be transmitted, via multiple reflections in the light pipe 332a, 332b, to the fiber bundle 334a, 334b having a diameter, D, smaller than the diameter of the ball lens 330a, 330b. The light pipe 332a, 332b may be connected to the fiber bundle 334a, 334b which receives the concentrated sunlight and transfers the light to an intended location or destination, e.g., an indoor location. One or more parameters, such as the angle, Q, which is the minimum solar elevation angle of the sun’s rays that are intended to be guided through the light pipe 332a, 332b, the geometry of the wide-field collector, e.g., the radius, R, of the ball lens 330a, 330b, the tapering angle, O', of the light pipe 332a, 332b, and the diameter, D, of the final fiber bundle 334a, 334b, may define the geometry and/or the size of the light pipe 332a, 332b. As non-limiting examples, for a ball lens 330a, 330b having a radius, R, of about 15 cm, and a refractive index, N, of about 1.5, with Q = 20°, q' = 10°, and D = 5 cm, the length of the light pipe 332a, 332b is determined to be about 1.15 m.

[0077] As shown in FIG. 3A, the lighting appratus 300a may optionally include one or more light source arrangements that may generate a respective illumination light. The light source arrangement(s) may be arranged in the interior of the light pipe 332a towards the input region of the light pipe 332a. Each light source arrangement may include one or more light sources or lamps, e.g., LEDs, for compensating the sunlight for indoor applications when there may be insufficient sunlight, or for outdoor illumination during dark hours.

[0078] A light source arrangement having one or more light sources (e.g., LEDs) 338 may be arranged such that the corresponding output or illumination light may be directed to or faces the ball lens 330a for transmission through the ball lens 330a to the outside or ambient environment. Another light source arrangement having one or more light sources (e.g., LEDs) 340 may be arranged such that the corresponding output or illumination light may be directed towards the interior of or the output region of the light pipe 332a to be received by the fiber bundle 334a. While not shown in FIG. 3B, it should be appreciated that the lighting apparatus 300b may include similar light source arrangement(s).

[0079] Angled-cleaved fiber bundle

[0080] FIGS. 3C and 3D show schematic cross-sectional views of a lighting apparatus 300c, 300d with a cleaved fiber bundle 334c, 334d, illustrating two examples of geometries for the angled-cleaved fiber bundle 334c, 334d for the immediate collection of sunlight after the wide- field collection optics, which, as illustrated, may be a ball lens 330c, 330d. The cleaved fiber bundle 334c, 334d may be optically coupled to the ball lens 330c, 330d to receive (sun)light transmitted through (and focused by) the ball lens 330c, 330d. The ball lens 330c, 330d channels the sunlight (illustrated as rays 336c, 336d) directly into the fiber bundle 334c, 334d.

[0081] The ball lens 330c, 330d and the cleaved fiber bundle 334c, 334d may be supported by one or more support structures. The cleaved fiber bundle 334c, 334d may be arranged spaced apart from the ball lens 330c, 330d. Alternatively, the cleaved fiber bundle 334c, 334d may be directly connected to the ball lens 330c, 330d.

[0082] The cleaved fiber bundle 334c, 334d may have a plurality of optical fibers, where an end of one or more or all of the optical fibers facing the ball lens 330c, 330d may be cleaved at a respective angle. The individual fibers in the fiber bundle 334c, 334d may be cleaved so that they face the focused sunlight in a proper or suitable angle to encourage or ensure maximum coupling into the individual fibers. Different fibers may be cleaved at different angles. The cleaved fiber bundle 334c may be a straight fiber bundle having straight optical fibers, while the cleaved fiber bundle 334d may be a curved fiber bundle having curved optical fibers.

[0083] The ball lens 330c, 330d may receive sunlight 336c, 336d and transmit the sunlight 336c, 336d through the ball lens 330c, 330d. The ball lens 330c, 330d may focus or concentrate the sunlight 336c, 336d incident on and propagating through the ball lens 330c, 330d. Sunlight 336c, 336d received within an angle or received by the ball lens 330c, 330d may be transmitted and received by the cleaved fiber bundle 334c, 334d over an angle b. The cleaved fiber bundle 334c, 334d may then channel or couple the sunlight concentrated by the ball lens 330c, 330d for onward transmission through the optical fibers, e.g., for indoor applications.

[0084] The cleaved ends of the optical fibers of the fiber bundle 334c, 334d may be arranged to define a curve complimentary to the curvature of the ball lens 330c, 330d. For a ball lens or a monocentric lens, the corresponding fiber bundle may be part of a tapered circular cylindrical fiber bundle with a cosine (or sine profile) as shown in FIG. 3E illustrating an initial or original fiber bundle design 350 with a cosine (or sine) profile (traced by dashed lines 352). The profile of the angled-cleaved fiber bundle 334d may be obtained by cutting out a circular portion or cross-section from the initial bundle 350, as defined by the reference circle 354. The design or geometry of the angled-cleaved bundle may be optimised by changing the radius of the reference circle 354 and/or the position of the centre (indicated by dot 356) of the reference circle 354 with respect to the centre (indicated by line 358) of the symmetry of the initial fiber bundle 350. Subseqently, the wide-field collector such as the ball lens 330d may be placed directly on the cleaved fiber bundle 334d or placed a distance away from the fiber bundle 334d. It should be appreciated that a similar cutting technique may be employed for forming the straight fiber bundle 334c from an initial fiber bundle design with a straight or linear profile.

[0085] Hybrid design for indoor and outdoor applications

[0086] A hybrid design may be provided for the lighting appratus as described herein, that is, the possibility of providing illumination both for indoor, as well as outdoor applications during dark hours. The lighting apparatus may be equipped with light sources or lamps (for example, as part of the collection optics), such as a set of LEDs, suitably oriented so that the corresponding illumination light generated may be partially collected by the light pipe and/or the fiber bundle and may then be channelled through the delivery part for indoor applications. Part of the illumination light generated may also be channelled out of the light pipe and/or the fiber bundle and through the wide-field optics (e.g., a ball lens) for outdoor illumination·

[0087] As a non-limiting example based on the lighting apparatus 300a of FIG. 3A, the ball lens 330a may be illuminated from the inside by LEDs, e.g., LEDs 338. The glow may provide outdoor illumination. Moreover, to keep a substantially constant level of illumination for indoor applications, an indoor sensor may be provided to detect the illumination level provided by the sunlight and in case the illumination level drops below a desired value, a sensor driven electronic control system/mechanism (e.g., a micro-controller or a remote computer) may be employed to compensate the brightness by adjusting the brightness of the light sources (e.g., LEDs). For example, the indoor light sensor may send or transmit an electrical signal to the control system, which in turn may switch the compensating LEDs (e.g., LEDs 340) on if the indoor light levels drop beyond an acceptable level.

[0088] FIG. 4 shows a schematic view of a lighting apparatus 400, which may include a wide- field collection optics, e.g., a ball lens 430, and a fiber bundle 434 optically coupled to the ball lens 430. The ball lens 430 may be supported by or on a support structure 460, e.g., a metallic stand, installed on a surface or the ground. The support structure 460 may also help to encase and protect part of the fiber bundle 434. The lighting apparatus 400 may include a light pipe to optically couple light between the ball lens 430 and the fiber bundle 434. It should be appreciated that the lighting apparatus 400 may be in the form of a lamp post.

[0089] The fiber bundle 434 may include a plurality of optical fibers (represented by 435a, 435b, 435c for three optical fibers) for propagating and outputting light. Using the optical fiber 435a as a non-limiting example, the optical fiber 435a may output light (represented by dashed arrow 462a from one end 464a of the optical fiber 435a. One or more optical fibers 435a, 435b, 435c may be arranged to output light to a respective desired space or location.

[0090] The lighting apparatus 400 may collect sunlight (represented collectively by dashed ellipse 436) via the ball lens 430. As illustrated in FIG. 4, the ball lens 430 may receive sunlight 436 from the sun 470 as the sun 470 moves throughout the day along a path traced by the curved arrow line 472. Sunlight 436 received within an incident angle a may be collected and focused by the ball lens 430 for onward transmission to the desired locations. The acceptance angle (i.e., range of incident angles within which sunlight may be efficiently collected and transported by the lighting appratus 400), a, may be about 120°. The sunlight 436 that is collected may be channelled through the fiber bundle 434 for indoor applications.

[0091] The lighting apparatus 400 may include one or more light source arrangements, e.g., having one or more LEDs. The light source arrangement(s) may be as described in the context of the lighting apparatus 300a of FIG. 3 A. LEDs may be arranged to provide a LED band illumination to illuminate the outdoor or ambient environment when ambient light may be low, e.g., during dawn, dusk, night time, etc. As a non-limiting example, the lighting apparatus 400 may include LEDs arranged around the ball lens 430, or a LED band, to provide external illumination via illuminating the ball lens 430 towards the external environment. LEDs may also be arranged to provide illumination light to be coupled into the fiber bundle 434 for transmission to the desired locations when there may be insufficient sunlight level or when the sun has set, e.g., cloudy days, overcast days, night time, etc.

[0092] FIG. 5 shows a schematic view of a lighting apparatus 500, which may be in the form of a (outdoor) lamp post. The lighting apparatus 500 may include a wide-field collection optics such as a ball lens 530. As non-limiting examples, the ball lens 530 may be a solid ball lens, which may be made of glass or optically transparent plastic, or may be a hollow ball filled with an optically transparent liquid. A ball lens has a very high acceptance angle for incident solar radiation because of its spherical symmetry. Therefore, unlike known systems, the solar concentrator, in this case the ball lens 530, in the lighting apparatus 500 is stationary and need not be movably oriented to track the sun along the movement path of the sun.

[0093] The lighting apparatus 500 may include a casing 570 and a protective cover 572 to encase and/or support the ball lens 530. The casing 570 may be opaque. As a non-limiting example, the casing 570 may be a metal casing. The protective cover 572 may be at least substantially transparent, and may be a transparent protective dome.

[0094] The ball lens 530 effectively captures and focuses sunlight into a substantially compact spot at the focal point of the ball lens 530. The focal point, however, may move along an arc of a predetermined circular path when the sun moves from the east to the west during the day.

[0095] In order to track the position of the moving focused spot, the lighting apparatus 500 may include an intensity tracking device 574 (intensity tracker with a motor). The motion of the intensity tracking device 574 may be confined to a concave dish 576 under the ball lens 530. The concave dish 576 may also act to support the intensity tracking device 574. The radius and depth of the dish 576 may depend on the diameter and the refractive index of the ball lens 530 used. As a non-limiting example, the intensity tracking device 574 may be a dual axis intensity tracker- motor.

[0096] One or more optical fibers (or a fiber bundle) 534 may be coupled or attached to the intensity tracking device 574 (or the intensity tracker) so that the fiber(s) 534 may always be positioned to the focused spot or focal point of the ball lens 530. Depending on the output illumination requirement, a single fiber or a fiber bundle 534 with a fiber coupler attached at an (input) end of the fiber or fiber bundle 534 may be used. The fiber or fiber bundle 534 may pass through a support structure (or stem or stand) 560 of the lighting apparatus 500 that may be installed on a surface or the ground. Light may be outputted from another (or output) end of the fiber or fiber bundle 534 to illuminate a luminaire. Depending on the light requirements at the output, a single fiber 534 may provide the light to multiple levels underground.

[0097] It should be appreciated that movement of the focal point may not be limited to an arc. The focal point of the focused light may move along any path, depending on or defined by the wide-field collection optics (or its corresponding geometry) that is employed as part of the lighting apparatus, and a corresponding intensity tracker may be provided to track the focal point.

[0098] The lighting apparatus 500 may further include a plurality of light sources, for example, LEDs. One or more LEDs 538 may be provided to provide illumination light during night time to a surrounding of the lighting apparatus 500. The LEDs 538 may be sensor-driven LEDs for night time illumination. For example, one or more light sensors 578 may be provided such that, in response to the light sensor 578 detecting ambient (or outdoor) light level below a threshold level, the LEDs 538 may be activated to provide illumination light. The LEDs 538 may be arranged on the protective cover 572 or the casing 570, for example, on the outside of the protective cover 572. However, it should be appreciated that the LEDs 538 may be provided on the inside of the protective cover 572 to protect the LEDs from the external environment and weather elements. Further, it should be appreciated that the light sensor(s) 578 may be provided on any position or any part of the lighting apparatus 500, for example, on any part of the protective cover 572, the casing 570 or the support structure 560. [0099] The lighting apparatus 500 may include one or more LEDs 540 provided below the ball lens 530 to provide illumination light into the optical fiber 534 during times when there may be insufficient sunlight, for example, during overcast skies. The LEDs 540 may be driven by a photo-sensor placed at the output luminaire, i.e., at the desired location where light from the optical fiber 534 is to be outputted to.

[0100] The lighting apparatus 500 may provide one or more of the following:

• the light intensity tracking device 574 may be well concealed and protected behind the ball lens 530 and, therefore, may require lesser maintenance;

• the light intensity tracking device 574 may trace or track the focused beam through the ball lens 530, which may maximize light coupling efficiency to the fiber 534;

• the light output may be high enough to be transported to multiple levels underground, or may be split to light up multiple luminaires simultaneously;

• the design may be easily installed and maintained because its orientation does not change with the location;

• the design may be sleek and aesthetic and may offer a small footprint.

[0101] FIG. 6 shows a schematic view of a lighting apparatus 600. The lighting apparatus 600 may include a plurality of optical fibers, where each solid line (represented by 690a, 690b for two such lines) may be representative of a fiber arrangement of a single optical fiber or a plurality of optical fibers. One or more wide-field collectors, such as ball lens 630, may be optically coupled to or attached to each fiber arrangement 690a, 690b. Each ball lens 630 may be optically coupled to or attached to one or more optical fibers. The ball lens 630, which may be made from glass, plastic, etc., may collect the ambient light and channel it through the corresponding fiber arrangement 690a, 690b to a desired location, which may be a distant location. The same light collection and delivery optics of the lighting apparatus 600 may be used for providing partial outdoor illumination.

[0102] While the invention has been particularly shown and described with reference to specific embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. The scope of the invention is thus indicated by the appended claims and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced.