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 the 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 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, spectroscopic, technical and scientific lighting fields. State of the art

[0004] From the second half of the 20th century, light-emitting diodes, commonly known 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 led to the development of LEDs emitting in different colours, including yellow, green and blue.

[0008] As time went on, the range of available colours expanded, notably with the appearance of white light sources based on this technology, and in parallel, LEDs became more energy efficient and more powerful.

[0009] Today, for example, intense white 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 called "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 supercontinuum lasers have a very broad emission range. However, they are expensive, have complex architectures, and their use is primarily limited to scientific applications. Furthermore, this technology necessarily produces pulsed light, which can have both advantages and disadvantages depending on the application.

[0011] Recently, a new technology, called Laser Excited Phosphors (LEP), has made it possible to obtain white light by combining a laser emitting in the blue or violet wavelength range with a phosphorescent component that converts part of the blue or violet light into yellow light, among other colors. This robust and economical technology is used by some car manufacturers to produce 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. Moreover, despite existing solutions, coupling the light produced by this technology with optical fibers remains complex.

[0012] US2020232610A1 describes a white light system coupled to an optical fiber and based on a laser. The white light system mainly comprises: - a laser device emitting at 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, produces a white light emission. The transmission fiber receives and then remotely transmits the white light produced to one or more passive luminaires.

[0014] Document US2014126200Al describes a white light source using a 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 makes it possible to create 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 containing phosphors, and whose attachment to the structure can complicate their implementation.

[0017] In order to meet the growing need for intense light sources which must in particular be compact, easy to use and economical, it is therefore 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 described above and proposes a broad-spectrum lighting system using a monochromatic laser and a component containing phosphors, which, when excited, emit light at 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 adhesives, for example.

[0019] Moreover, the present invention is advantageously compact, robust, economical, while having a high gloss.

[0020] In addition, the present invention includes an evolving technology that allows it to adapt according to lighting requirements (spectral band, power, etc.).

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

[0022] The present invention relates to a lighting system comprising a laser, a coupling lens, and an optical fiber. The lighting system is remarkable in that it includes a phosphor-doped component configured to generate secondary light from primary light emitted by the laser. The component is assembled at the optical fiber without glue. The component is either the core of the optical fiber or integrated into an optomechanical system for retaining the component at one end of the fiber. The optomechanical system comprises, for this purpose, a fiber port, two caps screwed onto the port, each cap having an opening for the passage of the fiber, the primary light, or the secondary light. A spring is positioned inside one of the caps to maintain the component under compression by screwing the cap onto the port.

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

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

[0025] According to another particular feature of the lighting system, the optomechanical system is positioned at the input of the optical fiber.

[0026] According to another particular feature of the lighting system, the optomechanical 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 from the spectral band ranging from 400 nm to 800 nm.

[0028] The fundamental concepts of the invention having been set forth above in their most elementary form, other details and features will become clearer upon reading the following description and with reference to the accompanying drawings. Presentation of the drawings

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

[0030] It is thus illustrated in:

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

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

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

[0034] [Fig.2C]: a cross-sectional view of the interior of a double-sheathed 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 cross-sectional view of the interior of a double-sheathed optical fiber, according to a particular embodiment of the invention where said fiber comprises two sheaths and the inner sheath 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 at one end of an optical fiber a component containing phosphorus;

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

[0040] It should be noted that certain technical elements well known to those skilled in the art are described here 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 limitation, alternative embodiments allowing the generation of lights in other spectral ranges.

[0043] For this purpose, the lighting system notably uses the technology known in English as Laser Excited Phosphors (LEP).

[0044] In the particular case of generating 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 upconversion and downconversion of photons (respectively upconversion and downconversion fluorescence), the phosphor emitting either at wavelengths higher or lower than that of the primary light.

[0047] Figure 1 represents a broad-spectrum lighting system 100 comprising mainly a monochromatic laser 10 emitting a primary light 101, for example in the blue or violet range, a coupling lens 102, and an optical fiber 11 from whose output a secondary light 13 is emitted. The optical fiber 11 has an output 114s which may include 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 consists of a diverging beam 10Id, 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 then also consists of the wavelength of the primary light 101.

[0052] Thus, the embodiment shown in [Fig.1] is particularly suited to applications in the fields of microscopy or endoscopy.

[0053] Advantageously, the use of optical fiber 11 first of all 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 systems used for automobile headlights), which is the length of said fiber.

[0054] Indeed, the optical fiber 11, by virtue of its length, makes it possible to adjust the interaction between the light emitted by the laser 10 and the phosphor contained in said fiber, 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 phosphors along the length of the optical fiber 10 is substantially homogeneous in order to facilitate the thermalization of said fiber. Indeed, the phosphors release heat when excited by the laser 10. Since the phosphors are distributed substantially homogeneously along the length of the optical fiber 11, the heat released by the phosphors is not concentrated but rather diffused, which facilitates the cooling of said fiber and protects the system 100 from thermal effects that degrade the conversion efficiency of the phosphors, such as the quenching phenomenon.

[0057] Finally, the architecture of system 100 shown in [Fig. 1] is advantageously compact. System 100 allows the secondary light 13 to be transmitted over long distances, and also allows the system to be interfaced with other optical elements using connectors with well-established standards and performance.

[0058] For example, laser sources now exist that guarantee an optical power on the order of a hundred watts. Commercially available phosphors, on the other hand, 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 represent respectively a cross-sectional view of a single-clad optical fiber 1 la and cross-sectional views of double-clad optical fibers 1 Ib-d.

[0061] The optical fiber 1a comprises a component 111a which contains the phosphors, and which corresponds to the core of said fiber, as well as an outer sheath 113a. Light propagates only in the component 11a of the optical fiber 1a, and said light is totally reflected at the interface between said component and the outer sheath 113a.

[0062] Optical fiber 1 IB, on the other hand, 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 inner cladding 112b and an outer cladding 113b, said inner cladding enveloping said core and said outer cladding enveloping said inner cladding.

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

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

[0065] In the example shown in [Fig. 2B], component 111b, corresponding to the core of optical fiber 11b, is positioned at the center of said fiber. In other embodiments, component 111b is offset in order to increase the conversion efficiency of primary light 101 into secondary light 13, in particular by exploiting certain propagation modes of the inner cladding 113b. The same applies to optical fiber types 1le and 1Id shown in [Fig. 2C] and [Fig. 2D].

[0066] Fig. 2C and Fig. 2D respectively represent a cross-sectional view of the optical fiber 11c which has an internal sheath 113c of straight section in the shape of D, and a cross-sectional view of the optical fiber 1 Id which has an internal sheath 112d of hexagonal 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 outer sheath 113c-d.

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

[0069] Figure 3 shows a schematic diagram of the architecture of a second embodiment of a broad-spectrum lighting system 200a comprising a laser 20 and a coupling lens 202, which converts a divergent light beam 20Id exiting said laser into a convergent beam 201c directed at the input of an optical fiber 31 comprising an optomechanical system 25 containing a phosphor-doped component, as shown in Figure 5. As before, a secondary light 23 is obtained at the output 214s of the optical fiber 21. The secondary light is preferably white, although this does not limit the invention. Indeed, 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 from the laser 20 is therefore produced in the optomechanical system 25 located at the entrance 214e of the optical fiber 21.

[0071] Fig. 4 represents a schematic of the architecture of a third embodiment of a broad spectrum lighting system 200b which includes the same elements as those of the system 200a, namely the laser 20, the coupling lens 202, the optical fiber 21. In contrast, 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 at either the input 214e or the output 214s of the optical fiber 21 and which allows a phosphorus-doped component 26 to be kept in contact with the optical fiber 21.

[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 opening 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 allow the secondary light 23 emitted by said component to pass through (system 200b).

[0077] Inside the first cap 252 is a spring 254 which applies pressure to the phosphorus-doped component 26 in order to hold it against the face located at the inlet 214e or outlet 214s of the optical fiber 21. The inner diameter of the spring 254 is sufficiently large in comparison to the width of the converging beam 201c or that of the secondary light 23.

[0078] The first cap 252 screwing 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 has an opening 2531 through which the optical fiber 21 is inserted. The optical fiber 21 is held in place when the second cap 253 is screwed onto the fiber port 251, a radial pressure then being applied to the surface of said fiber, sufficiently high to prevent any translational movement of said fiber within 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 allows the mechanical coupling between the phosphorus-doped component 26 and the optical fiber 21 to be adjusted and regulated.

[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 degrade this brightness. It is 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 phosphor 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 so as to allow the primary light 201 to pass through.

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

[0087] This cross-sectional view makes it easier to visualize the inside 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 allows the doped component 26 to be interchanged without having to modify or change the optical fiber 21, said component not being glued to said fiber.

[0089] Thus, in the event that component 26 is damaged due to high thermal stress, it is possible to replace said component. The same applies in the case where we want 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

Demands

1. Lighting system (100) comprising a laser (10), a coupling lens (102) and an optical fiber (1 la-d), said system being characterized in that it comprises a phosphor-doped component (11 la-d), in that it is configured to generate secondary light (13) from primary light (101) emitted by the laser (10), and in that the component (11 la-d) is assembled at the optical fiber (1 la-d) without glue, the component (11 la-d) being the core of the optical fiber (1 la-d) and in that the secondary light (13) generated is a polychromatic light composed of at least two wavelengths from the spectral band from 400 nm to 800 nm.

2. System (100) according to claim 1, wherein the optical fiber (lia) is a single-clad optical fiber.

3. System (100) according to claim 1, wherein the optical fiber (1 Ib-d) is a double-clad optical fiber.