Patent Application
20250164681
The invention relates to a lamp or a luminaire comprising a laser-based optical system, or an optical system configured to guide laser light, the optical system comprising a plurality of optical fibers, each optical fiber of the plurality of optical fibers comprising a longitudinal axis, a first end forming a light entry facet, a second end, a first section and a second section.
In laser-based lighting, it is well known that light can be transported and delivered by optical fibers. At the end of the fibers, lenses or reflectors are required for beam shaping and color mixing. These elements add considerably to the size of the lighting system.
Commercially available fiber combiners, where a fixed number of input fibers is fused together into one, are known in the art. The number of fibers is fixed, e.g., to three or four, and cannot be changed. If it is desired to combine more or less fibers, a new combiner needs to be installed.
WO 97/34175 A1 discloses a fiber optic probe assembly for low light spectrographic analysis which improves response to subtle light-matter interactions of high analytical importance and reduces sensitivity to otherwise dominant effects. This fiber optic probe assembly comprises a central fiber having a flat end face at its distal end and a plurality of fibers surrounding the central fiber and having a shaped end face at their distal ends. The plurality of fibers are parallel to the central fiber at their distal ends and the shaped end faces provide an internally reflective surface for steering the fields of view associated with the plurality of fibers toward the central fiber. The fibers also incorporate filters, cross-talk inhibitors and other features that provide a high performance probe in a robust package. Design variations provide side viewing, viewing through a common aperture, viewing along a common axis, and other features.
JP-A-S56119108 discloses the use of a laser light source and an optical fiber bundle for printing in order to increase the speed of printing.
Kosterin, Andrey, e.a., Tapered fiber bundles for combining high-power diode lasers, Applied Optics, vol. 43, No. 19, July 2004, discloses the use of tapered fiber bundles to combine the output power of several semiconductor lasers into an optical fiber in order to increase the brightness.
US-B1-9063289 discloses tapered couplers that include a plurality of optical fibers in order to increase the brightness. The tapering is the result of fibers fused in a fused and tapered region.
US-A1-2021/0263217 discloses an optical coupler array for coupling a plurality of fibers to an optical device for telecommunication in order to improve optical coupling between a set of isolated fibers.
CN-B_109621098 discloses a system for measuring space light radiation using an optical fiber transmission bundle.
It is desired to provide a laser-based optical system being more compact and comprising a smaller number of optical components.
It is an object of the present invention to overcome this problem, and to provide a lamp or a luminaire comprising a laser-based optical system being more compact and comprising a smaller number of optical components.
According to a first aspect of the invention, this and other objects are achieved by means of a lamp or a luminaire comprising an optical system configured to guide laser light, the optical system comprising a plurality of optical fibers, each optical fiber of the plurality of optical fibers comprising a longitudinal axis, a first end forming a light entry facet, a second end, a first section and a second section, the first section extending in a direction (substantially) parallel with the longitudinal axis from the first end to the second section, and the second section extending in a direction (substantially) parallel with the longitudinal axis from the first section to the second end, the first section comprising a first cross-section, the first cross-section comprising a first cross-sectional area being (substantially) constant in a direction parallel with the longitudinal axis, at least one of the second end and at least a part of an outer surface of the second section forming a light exit facet, and the second section comprising a second cross-section, the second cross-section comprising a second cross-sectional area, the second cross-sectional area decreasing in a direction parallel with the longitudinal extension from the first section towards the second end, where the plurality of optical fibers are arranged in an array of optical fibers, the array comprising n*m optical fibers, n and m being integers, and at least one of n and m being two or more.
The second section of each optical fiber is thus in essence tapered or conical. When using optical fibers of the type described above, and particularly when arranging such optical fibers in an array of optical fibers, the array comprising n*m optical fibers, wherein n and m are integers, and wherein at least one of n and m is two or more, the obtained fiber bundle does not need to be fused because the second ends have a reduced size which already fit in a small area.
Thereby it becomes possible to easily replace a defect fiber by another one and to easily add or remove a fiber from the bundle, both of which is not possible with a conventional fused combiner. It further becomes possible to combine different angular emissions from different fibers, for instance to compensate for angular color differences, or for aesthetic reasons.
In other words, such an optical system offers greater customization possibilities for the luminaire maker. Furthermore, such an optical system is much simpler to dismantle and separate for recycling purposes and is therefore more apt for a cyclic economy.
Furthermore, using optical fibers of the type described above and arranging them in an array, provides for an optical system configured to guide laser light with which separate optical elements, such as lenses or reflectors, required for beam shaping and color mixing is no longer necessary. Thus, such an optical system is more compact and requires a smaller number of optical components since no optical elements apart from the tapered optical fibers are necessary.
In an embodiment, at least one of n and m is at least three, at least six or at least nine.
In principle, the integers n and m may be chosen to be any desired integer. Thereby, laser-based optical systems with any desired number of optical fibers in the array of optical fibers may be obtained. Thereby a wide degree of freedom in design and construction of the laser-based optical system is enabled.
In an embodiment, at least a part of an outer surface of the second section adjacent to the second end forms at least a part of the light exit facet.
Thereby, not only an improved color mixing, but also an improved exit beam broadening is achieved.
In an embodiment, the second section comprises a tapering angle, β, defined as the angle between a longitudinal center axis of the second section and an outer surface of the second section, where the tapering angle, β, is less than 2 degrees.
In an embodiment, the second section extends over between 65% and 90% of the total longitudinal extension of the at least one optical fiber.
In an embodiment, the cross-sectional area at the second end is less than 10% of the cross-sectional area at the first end.
Thereby, tapered optical fibers with a pointed or sharp second end is achieved. Such optical fibers provide for an optical system configured to guide laser light with which a high degree of broadening of the exit light beam and/or complex far field light patterns or intensity patterns may be obtained.
In an embodiment, the second section comprises a tapering angle, β, defined as the angle between a longitudinal center axis of the second section and an outer surface of the second section, where the tapering angle, β, is between 2 and 6 degrees.
In an embodiment, the second section extends over between 35% and 65% of the total longitudinal extension of the at least one optical fiber.
In an embodiment, the cross-sectional area at the second end is less than 25% of the cross-sectional area at the first end.
Thereby, tapered optical fibers with a second end having a small surface area is achieved. Such optical fibers provide for an optical system configured to guide laser light with which the degree of broadening of the exit light beam obtained is high while the obtained far field light patterns or intensity patterns are less complex.
In an embodiment, the second section comprises a tapering angle, β, defined as the angle between a longitudinal center axis of the second section and the periphery of a circle circumscribing an outer surface of the second section, where the tapering angle, β, is between 6 degrees and 15 degrees.
In an embodiment, the second section extends over between 1% and 35% of the total longitudinal extension of the at least one optical fiber.
In an embodiment, the cross-sectional area at the second end is less than 50% of the cross-sectional area at the first end.
Thereby, tapered optical fibers with a second end having a small surface area is achieved. Such optical fibers provide for an optical system configured to guide laser light with which the exit light beam is only broadened to a relatively limited degree while the obtained far field light patterns or intensity patterns are homogenous and well defined.
Thus, it is generally possible, by adjusting the geometrical parameters of the optical fibers, and in particular the tapering angle, β, to obtain a far field light pattern or intensity pattern suitable and desired for a specific purpose.
In an embodiment, the second end is any one of blunt and pointed or point-shaped.
In an embodiment, the second section is any one of tapered, conical and frustoconical.
A blunt second end or a frustoconical second section enables obtaining far field light patterns or intensity patterns which are homogenous and well defined.
A pointed or point-shaped second end or a tapered or conical second section enables obtaining far field light patterns or intensity patterns of more complex structures as well as a further broadening of the light beam.
In an embodiment, the first section is configured to mix light propagating therethrough.
Thereby, improved color mixing is obtained without the need for any additional optical components.
In an embodiment, the second section is configured to broaden the angular spread of the light propagating therethrough. The second section is also configured to out-couple the light propagating therethrough.
Thereby, improved exit beam broadening is obtained without the need for any additional optical components.
In an embodiment, the optical fibers of the array of optical fibers all comprise a cross-section of the same shape.
In an embodiment, at least one optical fiber of the array of optical fibers comprises a cross-section having a first shape, and the remaining optical fibers of the array of optical fibers comprise a cross-section having a second shape being different from the first shape.
Thereby, a further parameter suitable for adjusting the geometrical parameters of the optical fibers, and in particular the tapering angle, β, to obtain a far field light pattern or intensity pattern suitable and desired for a specific purpose is provided.
In an embodiment, the cross-sectional shape of each optical fiber of the array of optical fibers perpendicular to the longitudinal extension is any one of square, rectangular, octagonal, circular and hexagonal.
Optical fibers with a cross-sectional shape being square rectangular, octagonal, or hexagonal have the advantage that the tapered ends may be stacked very densely, without any gaps. This in turn provides for an even more compact laser-based optical device.
Optical fibers with a cross-sectional shape being circular have the advantage of being particularly simple to manufacture, while still providing for a compact laser-based optical device.
In an embodiment, at least one optical fiber of the array of optical fibers further comprises a mirror or a rotatable mirror arranged at the light exit facet.
In an embodiment, the array of optical fibers further comprises a monolithic mirror element arranged at the light exit facets of the optical fibers of the array of optical fibers.
Providing, a mirror, a rotatable mirror or a monolithic mirror element provides the advantage of enabling to redirect the light exiting the optical fiber or fibers.
In an embodiment, the laser-based optical system further comprises a plurality of laser light sources, each being configured to, in operation, emit a beam of laser light, at least two laser light sources of the plurality of laser light source being arranged to emit the respective beams of laser light in a direction towards the first end of the same optical fiber of the plurality of optical fibers.
Thereby, the total light output of the laser-based optical system is increased and/or the mixing of laser light of different wavelengths is improved.
The lamp or the luminaire further comprises at least one laser light source configured to, in operation, emit a beam of laser light, the at least one laser light source being arranged to emit the beam of laser light in a direction towards the first end of at least one optical fiber of the plurality of optical fibers.
The term “laser light source” especially refers to a laser. Such laser may especially be configured to generate laser light source light having one or more wavelengths in the UV, visible, or infrared, especially having a wavelength selected from the spectral wavelength range of 200-2000 nm, such as 300-1500 nm. The term “laser” especially refers to a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.
Especially, in embodiments the term “laser” may refer to a solid-state laser. In specific embodiments, the terms “laser” or “laser light source”, or similar terms, refer to a laser diode (or diode laser).
In embodiments, the terms “laser light source” or “solid state laser” may refer to one or more of cerium doped lithium strontium (or calcium) aluminum fluoride (Ce:LiSAF, Ce:LiCAF), chromium doped chrysoberyl (alexandrite) laser, chromium ZnSe (Cr:ZnSe) laser, divalent samarium doped calcium fluoride (Sm:CaF2) laser, Er:YAG laser, erbium doped and erbium-ytterbium codoped glass lasers, F-Center laser, holmium YAG (Ho:YAG) laser, Nd:YAG laser, NdCrYAG laser, neodymium doped yttrium calcium oxoborate Nd:YCa4O(BO3)3 or Nd:YCOB, neodymium doped yttrium orthovanadate (Nd:YVO4) laser, neodymium glass (Nd:glass) laser, neodymium YLF (Nd:YLF) solid-state laser, promethium 147 doped phosphate glass (147Pm3+:glass) solid-state laser, ruby laser (Al2O3:Cr3+), thulium YAG (Tm:YAG) laser, titanium sapphire (Ti:sapphire; Al2O3:Ti3+) laser, trivalent uranium doped calcium fluoride (U:CaF2) solid-state laser, Ytterbium doped glass laser (rod, plate/chip, and fiber), Ytterbium YAG (Yb:YAG) laser, Yb2O3 (glass or ceramics) laser, etc.
In embodiments, the terms “laser light source” or “solid state laser” may refer to one or more of a semiconductor laser diode, such as GaN, InGaN, AlGaInP, AlGaAs, InGaAsP, lead salt, vertical cavity surface emitting laser (VCSEL), quantum cascade laser, hybrid silicon laser, etc.
In an embodiment, the optical system further comprises an optical fiber arranged to guide the beam of laser light from the at least one laser light source to the first end of at least one optical fiber of the plurality of optical fibers.
Thereby, the amount of light lost between the at least one laser light source and the optical fiber is minimized or eliminated altogether.
The lamp or the luminaire further comprises a controller configured for controlling or individually controlling one more laser light source of the at least one laser light source.
In an embodiment, the lamp or the luminaire comprises a plurality of laser light sources (19), each being configured to, in operation, emit a beam of laser light, at least two laser light sources of the plurality of laser light source being arranged to emit the respective beams of laser light in a direction towards the first end of the same optical fiber of the plurality of optical fibers.
In an embodiment, the controller is configured for individually controlling each of the plurality of laser light sources.
It is noted that the invention relates to all possible combinations of features recited in the claims.
This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.
As illustrated in the figures, the sizes of layers and regions are exaggerated for illustrative purposes and, thus, are provided to illustrate the general structures of embodiments of the present invention. Like reference numerals refer to like elements throughout.
The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which currently preferred embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and fully convey the scope of the invention to the skilled person.
Generally, and irrespective of the embodiment, the laser-based optical system 1 comprises a plurality of optical fibers 3-11. The plurality of optical fibers 3-11 are arranged in an array 2 of optical fibers. The array 2 generally comprises n*m optical fibers, n and m being integers, and at least one of n and m being two or more. In the embodiment shown in
Referring to
The first end 12 forms a light entry facet for coupling laser light 20a, 20b, 20c from a laser light source 19 into each the optical fibers 3-11. For simplicity the laser light sources 19 and the laser light 20a, 20b, 20c is not shown in
The first section 13 extends in a direction parallel with the longitudinal axis L from the first end 12 or light entry facet to the second section 14. The first section 13 is configured to mix laser light coupled into the fiber and propagating through the first section 13. The first section 13 comprises a first cross-section. As shown on
The second section 14 extends in a direction parallel with the longitudinal axis L from the first section 12 to the second end 15. The first section 13 and the second section 14 extend in extension of each other. The second section 14 is configured to broaden the angular spread of the mixed light, that is light having propagated through the first section 13, propagating through the second section 14. The second section 14 is further configured to couple out light propagating through the second section 14, especially at or through the second end 15. The second section 14 comprises a second cross-section. As shown on
At least one of the second end 15 and at least a part 17 (
By way of an example, the geometrical construction of each of the optical fibers 3-11 may also be described as follows. Each of the optical fibers 3-11 have a first end 12 or entrance facet. For instance, the first end 12 measures 1×1 mm. The first end 12 is arranged at a position Z=0 mm. A first section 13 with a straight un-tapered cross section extends from Z=0 mm to a position Z=Z_cone mm corresponding in the Figures to the transition 16 between the first section 13 and the second section 14. The first section 13 acts as a mixing portion to homogenize laser light that is injected at Z=0 mm. Then at Z=Z_cone the tapering second section 14 starts and extends until a position Z=Z_end. The second end 15 is arranged at the position Z_end. The total length of the optical fiber may for instance be 20 mm, such that Z_end is 20 mm. At the position Z_end the cross section of each optical fiber has dimensions (X_end, Y_end).
For instance, when the total length of the optical fiber is 20 mm, that is Z_end=20 mm, and Z_cone=2 mm, the second section 14 of the optical fiber is long and sharp with the second end 15 being a pointed end. This is the case for the embodiment shown in
If instead Z_cone=18 mm, the second section 14 of the optical fiber is short and the second end 15 may be either of a blunt end (cf. the laser-based optical systems 101 and 102 according to the third and fourth embodiments shown in
Finally, if instead Z_cone=10 mm, the second section 14 of the optical fiber is of a medium length and the second end 15 may be either of a blunt end (cf. the laser-based optical system 100 according to the second embodiment shown in
Generally, the length of the second section 14 as well as whether the second end 15 is blunt or sharp may be chosen to fit with a desired use or purpose of the resulting laser-based optical system 1, 100, 101, 102.
Referring to
The laser-based optical system may further comprise at least one laser light source 19 (cf.
Turning now to
The first section 13 comprises a length 21. The second section 13 comprises a length 22. The optical fiber 3 comprises a total length 23 being the sum of the length 21 of the first section 13 and the length 22 of the second section 14. The second section 14 may for instance extend over between 1% and 35% of the total length 23 of the optical fiber 3, between 35% and 65% of the total length 23 of the one optical fiber 3, or between 65% and 90% of the total length 23 of the optical fiber 3. Also, the cross-sectional area of the optical fiber 3 at the second end 15 may be less than 50%, less than 25% or less than 10% of the cross-sectional area of the optical fiber 3 at the first end 12.
Laser-based optical systems according to the invention may be used for lighting applications such as, but not limited to, laser-based lighting in retail spots, downlights, decorative lighting and pixelated lighting.
Turning now to
In each of the simulations nine laser light beams, three red, three green and three blue, or 3×(RGB), were transported via standard optical fibers (not shown) and subsequently coupled into a laser-based optical system according to the invention comprising an array of 3*3 fibers with a square cross-sectional shape. For each simulation result, the light pattern at a distance of 50 mm from the second end (left) as well as the far field intensity distribution (right) is shown.
White light results from combining the said 9 laser light beams. Each of the lasers provide a circular beam with a beam angle of 18°. The resulting output white light beam can be broadened or made square by the choice of the fiber geometry and especially the tapering angle, β. Broadening to approx. ±25°, ±350 or ±55° can for instance be obtained as shown in
In each of the simulations, nine laser light beams, three red, three green and three blue, or 3×(RGB), were transported via standard optical fibers (not shown) and subsequently coupled into a laser-based optical system according to the invention comprising an array of 3*3 fibers. For each simulation result, the light pattern at a distance of 50 mm from the second end (left) as well as the far field intensity distribution (right) is shown.
It may be seen that an optical fiber with a circular cross-sectional shape (top row in
An optical fiber with a hexagonal cross-sectional shape (middle row in
An optical fiber with a square cross-sectional shape (bottom row in
The light entry facet or first end 12 of each optical fiber comprises a size of 1×1 mm. The size of the second end 15, or exit facet, of each optical fiber is 0.6×0.6 mm. The three optical fibers are placed with a center to center distance of 1.1 mm. The entrance laser light beam comprises a beam angle of 18°. A mixing section, corresponding to the respective first sections 13 of the respective optical fibers, ensures light homogeneity over the cross-section of the respective optical fiber-cf.
In this example the laser-based optical system used further comprises a turning mirror 18 provided to redirect the light. Each optical fiber was provided with a turning mirror 18 arranged adjacent to the second end 15. Alternatively, the turning mirrors 18 may be combined into one monolithic mirror element 24.
Because the size of the second end 15, or light exit facet, of each optical fiber is as small as mentioned above, and the fibers are placed as closely as also mentioned above, the color mixing obtained in the far field is very good, as illustrated in
Table 1 below shows the obtained broadened beam width expressed as the Full Width at Half Maximum (FWHM) and Full Width at 10% of the Maximum (FW10M), respectively, for three different sizes of the second end 15, or exit facet, of each optical fiber of a laser-based optical system according to the invention and comprising an array of 1*3 fibers as shown in
The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims.
The terms “substantially” or “essentially” herein, and similar terms, will be understood by the person skilled in the art. The terms “substantially” or “essentially” may also include embodiments with “entirely”, “completely”, “all”, etc. Hence, in embodiments the adjective substantially or essentially may also be removed. Where applicable, the term “substantially” or the term “essentially” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. Moreover, the terms “about” and “approximately” may also relate to 90% or higher, such as 95% or higher, especially 99% or higher, even more especially 99.5% or higher, including 100%. For numerical values it is to be understood that the terms “substantially”, “essentially”, “about”, and “approximately” may also relate to the range of 90%-110%, such as 95%-105%, especially 99%-101% of the values(s) it refers to.
Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.
| Number | Date | Country | Kind |
|---|---|---|---|
| 22180064.2 | Jun 2022 | EP | regional |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2023/066377 | 6/19/2023 | WO |
