Patent ID: 12242096

DETAILED DESCRIPTION

Several embodiments of the invention with reference to the appended drawings are now explained. Whenever the shapes, relative positions and other aspects of the parts described in the embodiments are not explicitly defined, the scope of the invention is not limited only to the parts shown, which are meant merely for the purpose of illustration. Also, while numerous details are set forth, it is understood that some embodiments of the invention may be practiced without these details. In other instances, well-known structures, and techniques have not been shown in detail so as not to obscure the understanding of this description.

In this disclosure an optical fiber side-emitting light source is described whose overcoating structure is made of dissimilar materials that are designed and shaped in order to support the redirection and re-shaping of the light emerging from the side of an optical fiber that is embedded in the overcoating structure. The light source may be used as part of any illumination system.

In accordance with an embodiment of the invention and referring now toFIG.1a, a fiber-based side-emitting light source has an optical fiber6that may have a core and a cladding. Primary propagating light is produced by a light emitter such as a laser or a light emitting diode (LED) that is coupled to the fiber (not shown.) The primary light propagates along a center longitudinal axis2of the fiber6, in a downstream direction as shown, until it is scattered out of the fiber through a side of the fiber6, by a scattering zone (e.g., formed in a core of the fiber6.) The scattered radiation or out-coupled light takes place in a direction substantially transverse to the longitudinal axis2of the fiber6, either in a directional manner (forming a cone or lobe of light having a radial span of under) 360° or in an isotropic or omnidirectional manner (radiating at equal strength all around the fiber). Examples of scattering zones that can yield such a result can be found in international patent application no. PCT/IB2012/000617(WAVEGUIDE APPARATUS FOR ILLUMINATION SYSTEMS) filed 28 Mar. 2012. Other types of side-emitting optical fibers can alternatively be used. The fiber6may also have formed on it a layer of photoluminescent material to perform wavelength conversion upon the primary propagating light, to result in a side-emitted light that includes secondary light having a different wavelength than the primary light. The resulting side-emitted light may exhibit a broader spectrum as compared to the primary light, e.g., white light resulting from the combination of unabsorbed primary light and the secondary light. Alternatively, the photoluminescent material and the wavelength of the primary light may be selected such that very little primary light is left unabsorbed, resulting in the side-emitted light emerging from the fiber6being dominated by the secondary light, e.g., red or infrared.

Still referring toFIG.1a, there is a light transmissive part3that conforms to the side surface of the fiber6, and a reflective part4(also referred to as a reflective backing), both forming a single, composite overcoating structure (where the fiber6is “embedded” within the light transmissive part3of the composite overcoating structure.) The light transmissive part3may be made of a single, light transmissive, inactive (i.e., not photoluminescent, or not wavelength converting) material, e.g., polycarbonate, and may completely surround the side surface of the fiber6and may leave no air gaps between the fiber and the reflective part4, the latter conforming to the bottom surface of the light transmissive part3(as shown.) All of the light transmissive part3may be made of the same material, or it may be composed of layers of different materials.

The overcoating structure ofFIG.1amay alternatively be viewed as having a solid body (e.g., the light transmissive part3) that is made of an inactive, light transmissive material and is generally cylindrical (having a side surface that extends from a near end or face to a far end or face) but without rotational symmetry about an internal, longitudinal axis or spine of the body (e.g., the center longitudinal axis2. An external reflector (e.g., the reflective part4) has a curved, light reflective surface that conforms to and abuts a portion of the side surface of the solid body while leaving another portion of the solid body (e.g., the top layer or top surface7) uncovered for the illumination light to emerge therefrom after being reflected by the light reflective surface of the reflector.

The overcoating structure serves to shape a specific illumination scheme or pattern of radiation of the side-emitted light, and/or cases the integration of the light source into a system. It may also serve as an exoskeleton of the light source (where the light transmissive part3is made of a material that is more rigid than the fiber6.)

FIG.1bshows several aspects of an example composite overcoating structure. This is a section view in a transverse plane (transverse to the longitudinal axis2of the fiber6), withFIG.1cillustrating the side-emitted light emerging from the embedded fiber6. One aspect that is shown here is that the light transmissive part3has a flat or entirely horizontal top layer7(or top surface7), which is not covered by the reflective part4and through which the concentrated or redirected side-emitted light emerges, e.g., into air that surrounds the light source. This is facilitated by the “asymmetric shape” of the composite structure about the center longitudinal axis2, which refers to the fact that it lacks rotational symmetry about the center longitudinal axis2. However, as best illustrated inFIG.1c, the overcoating structure may have left-right reflection symmetry across a vertical, longitudinal plane5(in which the center longitudinal axis2lies.)

In the particular example ofFIGS.1b-1c, the light transmissive part3has a “parabolic” shape, and where the reflective part4is formed as a layer that covers and conforms to the bottom surface of the light transmissive part3, while the latter's top surface (or top layer)7is not covered, as shown; the light gathering function of the composite lighting structure is however not limited to this shape. Any alternative shape for the reflective part4(and its conforming, bottom surface of the light transmissive part3) that concentrates the light emerging from the side of the fiber6(e.g., as inFIG.1b) in a preferred direction may be possible, such as a U-shape (seeFIG.1a), a half or partial cylindrical shape, a half or partial elliptical shape, a hyperbolical shape, and a multi-segmented shape (composed of straight or curved line segments, similar or different, and that are joined end to end to form a longer curve.) In one embodiment, the entirety of the outer side surface of the light transmissive part3(having any one of the above shapes), or its complete side circumference, is divided into two, contiguous sections, namely the top surface or top layer7, and the rest which is referred to here as the bottom surface. The bottom surface may be curved and covered in its entirety by the reflective part4, but the top surface is not curved (flat) and is not covered at all by the reflective part4.

The asymmetrical shape of the composite overcoating serves to concentrate and redirect the side-emitted light (that is emerging from the fiber6) in a preferred outward transverse direction, which in the case of the examples here is directed outward through the top surface7(or top layer7) of the light transmissive part3.FIG.1bshows the interaction of the light that emerges from the side of optical fiber, with the overcoating, in a plane transverse to the longitudinal axis2of the fiber6. The longitudinal axis2of the optical fiber6in this example is substantially positioned on a vertical symmetry axis (lying in the vertical longitudinal plane5) of the parabolic shape, in the vicinity of the focus of the parabola (that is defined by the bottom surface). As seen in the perspective view ofFIG.1c, light emerging from the lengthwise segment9of the fiber6is redirected by the reflective part4in a transverse direction, and, especially due to the asymmetric shape of the reflective part4. In one embodiment, the redirected light emerges from the composite structure from only the top layer or surface7of the composite lighting structure (due to the entirety of the bottom surface being covered by the reflective part4).

FIG.2aandFIG.2bshow another composite structure in a section view in a longitudinal plan, but where the top layer7is mechanically structured into a “prismatic lens” (or simply, prismatic) structure10(although the light redirection and/or recycling function of the mechanical structure is not limited to a prismatic lens-see for exampleFIG.3aandFIG.4b. A goal here is to redirect and recycle the light that is emerging transversely from the fiber6and that reaches the top surface of the light transmissive part3, so as to become more collimated as it emerges outward, and along the length of the fiber6. The prismatic structure10may have any suitable combination of adjacently placed, prism cells or conical cells, each of which may be tilted relative to the vertical, e.g., a one-dimensional array of adjacently placed, tilted prism cells, or other types of prism cells that are arranged to form a prismatic lens that achieves a particular light beam redirection function. In this embodiment of the prismatic structure10, each individual prism cell is elongated in the transverse direction as seen inFIG.2c, and the prism cells are positioned or oriented side by side (not end to end) in the longitudinal direction as seen inFIG.2aand inFIG.2b. In other embodiments, the prism cells may not be elongated, e.g., they may be squares. The prismatic structure10may be made of a suitable light transmissive material, which may be different than that of the light transmissive part3which is joined directly below; it may be made as separate piece (of which the top surface or top layer7is a part) that is then joined to a flat top surface of the light transmissive part3.FIG.2bshows the interaction between light that emerges from the side of the optical fiber6and the composite overcoating, in a plan longitudinal to the fiber6. Light emerging from the fiber may be directly redirected by refraction at the air-prism interface which is indicated as (1) in the figure, and it may also be indirectly redirected, i.e. undergoing several reflections inside the composite lighting structure before leaving it, indicated as (2) in the figure.FIG.2cshows the composite structure ofFIG.2ain a section view in a transverse plane.

FIG.3ashows a section view in a transverse plane of a composite overcoating structure having a microlens array structure12at its top surface7.FIG.3bshows a section view in a vertical longitudinal plane, of the composite overcoating structure ofFIG.3a. In this embodiment, each individual microlens is elongated in the transverse direction as seen inFIG.3a, and the microlenses are positioned or oriented side by side (not end to end) in the longitudinal direction as seen inFIG.3b. The individual microlenses of the microlens structure12are said to “selectively” focus or homogenize the side-emitted light out of the overcoating structure, in contrast to the single continuous lens structure14shown inFIG.4aand inFIG.4bthat “totally” focuses the side-emitted light out of the overcoating. The microlens array structure12and the single continuous lens structure14may each be made of a suitable light transmissive material, which may be different than that of the light transmissive part3which is joined directly below; each may be made as separate piece (of which the top surface of top layer7is a part) that is then joined to a flat top surface of the light transmissive part3.

FIG.5andFIG.6show further aspects of an embodiment of the composite structure, where different examples of a bottom part of the composite structure are shown that can serve to more easily affix the light source as part of a larger system.FIG.5shows a polygon shaped or polygonal bottom part16, which on one side conforms to the outer face of the reflective part4while on the opposite side is polygon shaped (here, having a left corner joined by a straight section to a right corner, although other polygonal shapes are possible.) The polygonal shape enables use of the bottom part16as a keyed structure, to fit the light source into a mating, keyed receptacle of the system.FIG.6shows the combination of the structure ofFIG.5and several knobs17(two are visible), where the knobs17are affixed to the outer face of the polygonal bottom part16and extend outward therefrom. The knobs17can serve to affix the light source to a system. The knobs can be made of the same material as the polygonal bottom part16such that they form a single or integral part of the light source. Alternatively, the knobs17can be separately formed pieces that are bonded to or inserted into the polygonal bottom part16, e.g., prior to a polymerization process that yields the precise boundary of the outside face of the polygonal bottom part16.

While certain embodiments have been described above and shown in the accompanying drawings, it is to be understood that such embodiments are merely illustrative of and not restrictive on the broad invention, and that the invention is not limited to the specific constructions and arrangements shown and described, since various other modifications may occur to those of ordinary skill in the art. For example, whileFIGS.2a-2cshow the prismatic lens structure composed of elongated prism cells arranged side by side in a sequence that extends in the longitudinal plane, an alternative may be to orient the prism cells side by side in a sequence extending in the transverse plane. The description is thus to be regarded as illustrative instead of limiting.