Broad spectrum lighting system

Abstract

BROAD SPECTRUM LIGHTING SYSTEM Lighting system (100, 200a-b) comprising a laser (10, 20), a coupling lens (102, 202) and an optical fiber (11a-d, 21), said system comprising a phosphor-doped component (111a-d, 26) configured to generate secondary light (13, 23) from primary light (101, 201) emitted by the laser (10, 20), the component (111a-d, 26) being assembled to the optical fiber (11a-d) without glue, the component (111a-d, 26) being either the core of the optical fiber (11a-d) or integrated into an optomechanical system (25) for retaining said component at one end of said fiber, said optomechanical system comprising a fiber port (251), two caps (252,253) screwed onto said port, each of said caps comprising an opening (2521, 2531) for the passage of the fiber or the primary light (201) or the secondary light (23),a spring (254) being positioned inside one of said caps to maintain said component in compression by screwing said cap onto said port. Figure of the abstract: Figure 1,

Description

Title of invention: Broad spectrum lighting system Technical field

[0001] The present invention belongs to the technical field of lighting and light energy diffusion systems.

[0002] The invention relates more particularly to an intense, broad-spectrum light lighting system, comprising a monochromatic light source which exploits luminescence phenomena present in certain materials to produce polychromatic light, which may be white light, said light being guided by means of an optical fiber.

[0003] The invention finds direct application in various fields requiring intense light, such as the medical, spectroscopy, technical and scientific lighting fields. State of the art

[0004] From the second half of the 20th century, light-emitting diodes, commonly called by their English acronym LED (light-emitting diode), revolutionized lighting.

[0005] LEDs produce light when an electric current passes through a semiconductor junction. They have the properties of being very energy efficient, having a long lifespan (several thousand hours) and offering a wide range of colors.

[0006] The first visible semiconductor LEDs that were developed emitted in the red.

[0007] Subsequent research on semiconductors has made it possible to develop LEDs emitting in different colors, including yellow, green and blue.

[0008] Over time, the range of available colors has expanded, notably with the appearance of white light sources based on this technology, and at the same time, LEDs have become more energy efficient and more powerful.

[0009] Today, for example, white and intense light sources are used in many applications. However, these white light sources are difficult to implement and / or do not produce the desired intensity.

[0010] White laser technology (commonly referred to as a "supercontinuum laser") developed at the end of the 20th century uses a high-power pulsed laser source and exploits complex nonlinear optical phenomena present in photonic crystal fibers in particular to emit light having a spectrum very broad emission. On the other hand, supercontinuum lasers are expensive, have complex architectures and their use is mainly limited to scientific purposes. In addition, this technology necessarily induces pulsed light, which can have advantages but also disadvantages depending on the application.

[0011] Recently, a new technology, called Laser Excited Phosphors (LEP), makes it possible to obtain white lights by combining a laser emitting in the blue or violet wavelength, with a phosphorescent component which converts part of the blue or violet light into yellow light in particular. This robust and economical technology is used by certain car manufacturers to manufacture car headlights. However, this technology is not suitable for certain applications requiring an intense light source because it does not allow the light to be concentrated onto very small dimensions. In addition, and despite existing solutions, the coupling of the light produced by this technology with optical fibers remains complex.

[0012] Document US2020232610A1 describes a white light system coupled to an optical fiber and which is based on a laser. The white light system mainly comprises: - a laser device emitting in a first wavelength between 385 nm and 495 nm; - a phosphorescent element; - a transport fiber coupled to the phosphorescent element.

[0013] The phosphorescent element converts the laser emission with the first wavelength into a phosphorescent emission with a second wavelength which, when superimposed with the first wavelength, makes it possible to produce a white light emission. The transport fiber receives and then transmits the white light produced remotely to one or more passive luminaires.

[0014] Document US2014126200Al describes a white light source using a laser diode pumping one or more phosphors. As in the previous document, the laser diode emits light at a first wavelength which is converted into light of a second wavelength by the phosphors.

[0015] Combining light in the first wavelength with light of the second wavelength creates a highly directional white light.

[0016] Each of the white light sources described in these documents presents solutions in which it is necessary to add a component comprising phosphors, and the attachment of which to the structure can complicate their implementation.

[0017] In order to meet the growing need for intense light sources which must in particular to be compact, easy to use and economical, it is then necessary to continue the development of technologies combining the advantages of LEP technology with those provided by optical fibers. Presentation of the invention

[0018] The present invention aims to overcome all or part of the drawbacks presented above, and proposes a broad spectrum lighting system using a monochromatic laser as well as a component containing phosphors, which when excited emit light in wavelengths other than that of the monochromatic laser. In particular, the phosphors are directly integrated into the optical fiber or into a component whose coupling to an optical fiber is simplified and does not use glues for example.

[0019] Furthermore, the present invention is advantageously compact, robust, economical, while having high brilliance.

[0020] Furthermore, the present invention includes scalable technology that allows it to adapt according to light requirements (spectral band, power, etc.).

[0021] The present invention advantageously has several characteristics and in particular allows: - to concentrate the light produced at high intensity levels; - to efficiently couple white light into an optical fiber; - to collimate the light beam produced with very low divergence.

[0022] The present invention then relates to a lighting system comprising a laser, a coupling lens and an optical fiber. The lighting system is remarkable in that it comprises a phosphorus-doped component configured to generate a secondary light from a primary light emitted by the laser, the component is assembled at the optical fiber without glue, said component being either the core of the optical fiber, or integrated into an optomechanical system for holding said component at one of the ends of said fiber, said optomechanical system comprising for this purpose a fiber port, two caps screwed onto said port, each of said caps comprising an orifice for the passage of the fiber or the primary light or the secondary light, a spring being positioned inside one of said caps to hold said component in compression by screwing said cap onto said port.

[0023] According to a particular characteristic of the invention, the optical fiber of the lighting system is a single-clad optical fiber.

[0024] According to another particular characteristic of the invention, the optical fiber of the lighting system is a double-clad optical fiber.

[0025] According to another particular characteristic of the lighting system, the opto- mechanical is positioned at the entrance of the optical fiber.

[0026] According to another particular characteristic of the lighting system, the opto-mechanical system is positioned at the output of the optical fiber.

[0027] Advantageously, the secondary light produced by the lighting system is a polychromatic light composed of at least two wavelengths of the spectral band ranging from 400 nm to 800 nm.

[0028] The fundamental concepts of the invention having been set out above in their most elementary form, other details and characteristics will emerge more clearly on reading the description which follows and with reference to the appended drawings. Presentation of the drawings

[0029] The figures are given purely for illustrative purposes for a better understanding of the invention without limiting its scope. The various elements may be represented schematically and are not necessarily on the same scale. Throughout the figures, identical or equivalent elements bear the same numerical reference.

[0030] It is thus illustrated in:

[0031] [Fig-1]: a diagram of an architecture of a broad spectrum lighting system, according to a first embodiment of the invention;

[0032] [Fig.2A]: a sectional view of the interior of an optical fiber of the lighting system, according to a particular embodiment of the invention where said fiber only comprises one sheath;

[0033] [Fig.2B]: a sectional view of the interior of a double-clad optical fiber, according to a particular embodiment of the invention where said fiber comprises two sheaths;

[0034] [Fig.2C]: a sectional view of the interior of a double-clad optical fiber, according to a particular embodiment of the invention where said fiber comprises two sheaths and the inner sheath is D-shaped;

[0035] [Fig.2D]: a sectional view of the interior of a double-clad optical fiber, according to a particular embodiment of the invention where said fiber comprises two sheaths and the inner sheath of which is hexagonal in shape;

[0036] [Fig.3]: a diagram of the architecture of the broad spectrum lighting system, according to a second embodiment of the invention;

[0037] [Fig.4]: a diagram of the architecture of the broad spectrum lighting system, according to a third embodiment of the invention;

[0038] [Fig.5]: a perspective view of an optomechanical system holding a phosphorus-containing component at one end of an optical fiber;

[0039] [Fig.6]: a perspective section along a plane AA of the optomechanical system holding the component containing phosphorus. Detailed description of embodiments

[0040] It should be noted that certain technical elements well known to those skilled in the art are described herein to avoid any insufficiency or ambiguity in the understanding of the present invention.

[0041] In the embodiment described below, reference is made to a broad spectrum lighting system.

[0042] More particularly, the invention relates to a system generating white light, without this presenting a limit, alternative embodiments making it possible to generate lights in other spectral ranges.

[0043] To this end, the lighting system uses, in particular, the technology known in English as Laser Excited Phosphors (LEP).

[0044] In the particular case of the generation of white light, a blue or violet laser is used to excite phosphors contained in a component (generally a ceramic), the phosphors then producing emissions at other wavelengths.

[0045] The invention is not limited to the generation of white light, but on the contrary has the advantage of using laser sources across the entire available spectrum as primary light in order to generate secondary light at other wavelengths.

[0046] Thus, the present invention exploits both the upconversion and downconversion of photons (respectively upconversion and downconversion fluorescence in English), the phosphor then emitting either at wavelengths higher or lower than that of the primary light.

[0047] [Fig.l] represents a broad spectrum lighting system 100 mainly comprising a monochromatic laser 10 emitting a primary light 101 for example in blue or violet, a coupling lens 102, an optical fiber 11 at the output of which a secondary light 13 is emitted. The optical fiber 11 has an output 114s which may comprise a connector (not shown here), for example of the SMA (SubMiniature version A) or FC (Ferrule Connector) type, in order to couple the secondary light 13 to other compatible lighting or imaging devices.

[0048] In this particular embodiment, the primary light 101 is composed of a diverging beam 101d, which is converted into a converging beam 101c by means of the coupling lens 102. The converging beam 101c is introduced at an input 114e of the optical fiber 11.

[0049] In this first embodiment, the optical fiber 11 is doped with phosphors which, once excited by the primary light 101, emit the secondary light 13 at other wavelengths.

[0050] In a particular embodiment of the invention, the primary light 11 is entirely absorbed by the phosphors.

[0051] In another particular embodiment of the invention, only a portion of the primary light 101 is absorbed by the phosphors. The spectrum of the secondary light 13 is then also made up of the wavelength of the primary light 101.

[0052] Thus, the embodiment shown in [Fig.l] is particularly suitable for applications in the fields of microscopy or endoscopy.

[0053] Advantageously, the use of the optical fiber 11 firstly makes it possible to obtain superior brightness, but also to offer an additional degree of freedom compared to commercial lighting systems using a solid element doped with phosphors (in particular the systems used for automobile headlights), which is the length of said fiber.

[0054] Indeed, the optical fiber 11, due to its length, makes it possible to adjust the interaction between the light emitted by the laser 10 and the phosphorus contained in said fiber, and this according to the need.

[0055] The present invention is not limited by a particular concentration of phosphors in the optical fiber 11, said concentration being adapted to the intended application. The same applies to the distribution along the length of the optical fiber 11, which is homogeneous or concentrated depending on the intended application.

[0056] Preferably, the distribution of the phosphorus along the length of the optical fiber 10 is carried out in a substantially homogeneous manner in order to more easily thermalize said fiber. Indeed, the phosphors release heat when they are excited by the laser 10. The phosphors being distributed substantially homogeneously along the length of the optical fiber 11, the heat released by the phosphors is then not concentrated but on the contrary diffused, which facilitates the cooling of said fiber and makes it possible to preserve the system 100 from thermal effects which degrade the conversion efficiency of the phosphors, such as the quenching phenomenon.

[0057] Finally, the architecture of the system 100 shown in [Fig.l] is advantageously compact. The system 100 makes it possible to move the secondary light 13 over long distances, but also to interface said system with other optical elements by means of connectors with well-established standards and performances.

[0058] For example, there are currently laser sources that guarantee optical power of the order of a hundred Watts. Phosphors that are commercially available have a conversion capacity of between 200 and 300 lumens per Watt.

[0059] The present invention therefore makes it possible to obtain several tens of thousands of lumens, thus making an intense light source accessible to a large number of users and for different types of applications.

[0060] [Fig.2A], [Fig.2B], [Fig.2C] and [Fig.2D] respectively represent a cross-sectional view of a single-clad 11a optical fiber and cross-sectional views of double-clad 11b-d optical fibers.

[0061] The optical fiber 11a comprises a component 111a which contains the phosphors, and which corresponds to the core of said fiber, as well as an external cladding 113a. The light propagates only in the component 11a of the optical fiber 11a, and said light is totally reflected at the interface between said component and the external cladding 113a.

[0062] The optical fiber 1 IB is said to be double-clad and comprises a component 111b, which contains the phosphors, and which corresponds to the core of said fiber, an internal sheath 112b and an external sheath 113b, said internal sheath enveloping said core and said external sheath enveloping said internal sheath.

[0063] The refractive index of the inner cladding 112b is slightly lower than the refractive index of the fiber core, here the component 111b, allowing the transmission of the secondary light 13 between said cladding and said core. In addition, the inner cladding 112b has a numerical aperture greater than that of the core 111b in order to support a greater number of propagation modes, and facilitate the coupling of the convergent beam 103 with the fiber 11b.

[0064] The outer cladding 113b has a refractive index much lower than the refractive index of the inner cladding 112b, thus totally reflecting the light at the interface of the two claddings 112b and 113b.

[0065] In the example shown in [Fig.2B], the component 111b corresponding to the core of the optical fiber 11b is positioned at the center of said fiber. In other embodiments, the component 111b is eccentric in order to increase the conversion efficiency of the primary light 101 into secondary light 13, in particular by exploiting certain propagation modes of the internal cladding 113b. The same applies to the types of optical fibers 11c and 11d shown in [Fig.2C] and [Fig.2D].

[0066] [Fig.2C] and [Fig.2D] respectively represent a sectional view of the optical fiber 11c which comprises an internal sheath 113c of D-shaped cross-section, and a sectional view of the optical fiber 11d which comprises an internal sheath 112d of hexagonal cross-section.

[0067] The optical fibers 1 IC and 1 ID each comprise a component 11 Ic-d, doped with phosphors, which corresponds to the core of said fibers, as well as an external sheath 113c-d.

[0068] As for the optical fiber 1 IB, the refractive index of the internal claddings 112c-d is slightly lower than that of the refractive index of their core.

[0069] [Fig. 3] represents a diagram of the architecture of a second embodiment of a broad spectrum lighting system 200a which comprises a laser 20, a coupling lens 202, which makes it possible to convert an outgoing divergent light beam 20Id of said laser, into a convergent beam 201c directed at the input of an optical fiber 31 comprising an optomechanical system 25 in which there is a phosphorus-doped component, as shown in [Fig.5]. As previously, we obtain at the output 214s of the optical fiber 21 a secondary light 23. The secondary light is preferably white, without this presenting a limit to the invention. Indeed, and depending on the intended applications, it is possible to generate other spectral ranges for the secondary light 23.

[0070] In this particular embodiment of the invention, the emission of light at wavelengths other than that of the light coming from the laser 20 is therefore produced in the optomechanical system 25 located at the input 214e of the optical fiber 21.

[0071] [Fig.4] represents a diagram of the architecture of a third embodiment of a broad spectrum lighting system 200b which comprises the same elements as those of the system 200a, namely the laser 20, the coupling lens 202, the optical fiber 21. On the other hand, the optomechanical system 25 is in this embodiment positioned on the output 214s of the optical fiber 21.

[0072] In this particular embodiment of the invention, the secondary light 23 is therefore produced in the optomechanical system 25 located at the output 214s of the optical fiber 21.

[0073] [Fig. 5] represents a perspective view of the optomechanical system 25 which can be positioned either at the input 214e or at the output 214s of the optical fiber 21 and which makes it possible to maintain in contact with the optical fiber 21, a component 26 doped with phosphorus.

[0074] In a particular embodiment, the optomechanical system 25 mainly comprises a fiber port 251, onto which a first cap 252 and a second cap 253 are screwed respectively by means of the screw threads 2522 and 2532.

[0075] The first cap 252 has an orifice 2521 in its center.

[0076] The diameter D2521 of the orifice 2521 allows the primary light 101 to be focused on the phosphorus-doped component 26 (system 200a), or to let the secondary light 23 emitted by said component pass through (system 200b).

[0077] Inside the first cap 252 is a spring 254 for applying pressure to the phosphorus-doped component 26 to hold it against the face at the input 214e or output 214s of the optical fiber 21. The inner diameter of the spring 254 is sufficiently large compared to the width of the converging beam 201c or that of the secondary light 23.

[0078] The first cap 252 screws onto the fiber port 251, the compression force of the spring 254 on the component 26 is then adjusted.

[0079] The second cap 253 also includes an orifice 2531 through which the fiber optical fiber 21 is inserted. The optical fiber 21 is held when the second cap 253 is screwed onto the fiber port 251, a radial pressure then being applied to the surface of said fiber and this sufficiently high to prevent any translational movement of said fiber in said port.

[0080] The phosphorus-doped component 26 and the optical fiber 21 are then held together, without the use of glue or adhesive materials which would have limited the excitation power, the heat generated at the level of the component 26 being able to deteriorate the glue.

[0081] In addition, the use of the first cap 252 and the second cap 253 makes it possible to adjust and regulate the mechanical coupling between the phosphorus-doped component 26 and the optical fiber 21.

[0082] Due to the optical invariant, it is never possible to increase the brightness of a light source and an optical system can therefore only deteriorate this brightness. It is then by positioning the phosphorus-doped optical component 26 directly in contact with the optical fiber 21 that the coupling of the light emitted by the phosphorus is optimal.

[0083] Finally, the design is simplified by eliminating the use of lenses or mirrors, which therefore become unnecessary.

[0084] In the embodiment shown in [Fig.3], the primary light 201 excites the component 26 with an angle of incidence normal to its excitation surface s26.

[0085] In another embodiment, the phosphorus-doped component 26 is excited by the primary light 201 on one of its edges b26. The optomechanical system 25 is then designed in such a way as to allow the primary light 201 to pass through.

[0086] [Fig.6] represents a sectional view along a plane AA, and in perspective of the optomechanical system 25 represented in [Fig.5].

[0087] This sectional view makes it easier to visualize the interior of the optomechanical system 25, and how the phosphorus-doped component 26 and the optical fiber 21 are held.

[0088] Advantageously, the optomechanical system 25 makes it possible to interchange the doped component 26 without having to modify or change the optical fiber 21, said component not being bonded to said fiber.

[0089] Thus, in the case where the component 26 is damaged due to high thermal stresses, it is possible to replace said component. The same applies in the case where it is desired to obtain another secondary light 23 from the same primary light 201: the doped component 26 is simply replaced by another doped component having other properties (concentration, phosphors, etc.).

Claims

Claims

1. Lighting system (100, 200a-b) comprising a laser (10, 20), a coupling lens (102, 202) and an optical fiber (11a-d, 21), said system being characterized in that it comprises a component (11a-d, 26) doped with phosphorus, in that it is configured to generate a secondary light (13, 23) from a primary light (101, 201) emitted by the laser (10, 20), and in that the component (11a-d, 26) is assembled at the optical fiber (11a-d) without glue, the component (11a-d, 26) being either the core of the optical fiber (11a-d), or integrated in an optomechanical system (25) for holding said component at one of the ends of said fiber, said optomechanical system comprising for this purpose a fiber port (251), two caps (252, 253) screwed onto said port, each of said caps comprising an orifice (2521, 2531) for the passage of the fiber or the primary light (201) or the secondary light (23),a spring (254) being positioned inside one of said caps to hold said component in compression by screwing said cap onto said port.,

2. The system (100) of claim 1, wherein the optical fiber (11a) is a single-clad optical fiber.

3. The system (100) of claim 1, wherein the optical fiber (1 Ib-d) is a double-clad optical fiber.

4. The system (200a) of claim 1, wherein the optomechanical system (25) is positioned at the input (214e) of the optical fiber (21).

5. System (200b) according to claim 1, wherein the optomechanical system (25) is positioned at the output (214s) of the optical fiber (21).

6. System (100, 200) according to any one of the preceding claims, wherein the secondary light (13, 23) is a polychromatic light composed of at least two wavelengths of the spectral band ranging from 400 nm to 800 nm.

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