WO2024177102A1

WO2024177102A1 - Light diffusion device

Info

Publication number: WO2024177102A1
Application number: PCT/JP2024/006194
Authority: WO
Inventors: 英明長谷川; 淳一長谷川; 圭佑武; 喬介山内
Original assignee: 古河電気工業株式会社
Priority date: 2023-02-21
Filing date: 2024-02-21
Publication date: 2024-08-29

Abstract

A light diffusion device (1) according to the present invention is provided with an optical fiber (20) that comprises a core disposed on the radially central side and cladding positioned on the outer circumferential side of the core, and emits, from the leading end side (T) of the optical fiber (20), light that entered from the base end of the optical fiber (20). The optical fiber (20) has a light transmission unit (20a) for transmitting the light having entered from the base end toward the leading end (20TE) and has a light emission unit (20b) which has removed therefrom a portion positioned on the outer circumferential side of the cladding at the leading end side T and thereby emits light having transmitted through the light transmission unit (20a) from the outer circumferential surface. The light diffusion device comprises: a reflective element (24) that surrounds the outer circumferential surface of the light emission unit (20b) except for a region serving as a light emission port (23); and a heat-dissipating covering (25) which is in contact with the reflective element (24) at the leading end side (T) and which covers at least a portion of the light transmission unit (20a).

Description

Light Diffuser

The present invention relates to a light diffusion device for use in medical equipment.

A conventional light diffusion device is known that includes an optical fiber consisting of a core located at the center in the radial direction and a cladding located on the outer periphery of the core, and that emits laser light incident on the base end of the optical fiber from the tip end and the outer periphery on the tip side (see, for example, Patent Document 1). The optical fiber of the conventional light diffusion device has a light transmission section that transmits the laser light incident on the base end, and a light emission section at the tip side that emits the laser light transmitted through the light transmission section.

The optical diffusion device is used in photoimmunotherapy, a cancer treatment method, by inserting the tip of an optical fiber into the human body and irradiating laser light onto a drug that has been administered to the human body and has reached the cancer cells.

Special Publication No. 2012-506569

For example, when treating metastatic liver cancer, especially for small tumors, there is a demand to provide a cylindrical diffuser at the tip of an optical fiber, insert this into the affected area, and irradiate as little of the affected area as possible with limited irradiation. For this reason, there is a technology that provides a reflective element (shielding element) that surrounds the outer circumferential surface of the light emitting part, leaving only the area that will become the light exit port. Of the light emitted radially outward from the outer circumferential surface of the light emitting part, light that is directed toward areas other than the area that will become the light exit port is reflected by the reflective element and collected at the light exit port. As a result, it is limited to a specific area in the circumferential direction, so strong light can be irradiated only to the affected area.

However, providing a reflective element causes problems with heat generation at the light output section and its vicinity. If the light output section of the light diffusion device generates too much heat, there is a concern that the patient receiving the treatment may sense the heat or that it may affect healthy cells, so the practitioner must take measures such as reducing the amount of light and the exposure time during treatment. Therefore, from the perspective of making treatment more efficient, easier, and more accurate, there is a need for a light diffusion device that can reduce heat generation at the light output section and its vicinity.

One of the objectives of the present invention is to provide a light diffusion device that can suppress heat generation at the light exit section and its vicinity.

A light diffusing device according to one aspect of the present invention is a light diffusing device comprising an optical fiber having a core located at a radial center side and a clad located on an outer peripheral side of the core, the light diffusing device causing light incident on a base end of the optical fiber to exit from a tip end side of the optical fiber,
the optical fiber has a light transmitting section that transmits light incident from a base end portion toward a tip end portion, and a light emitting section that emits the light transmitted through the light transmitting section from an outer circumferential surface by removing a portion located on the outer circumferential side of the clad at the tip end side,
a reflecting element that surrounds an outer peripheral surface of the light emitting portion, leaving a region that serves as a light emitting opening;
a heat dissipation coating that contacts the reflecting element at a tip side and covers at least a part of the light transmitting portion;
Equipped with.

The thermal conductivity of the heat dissipation coating may be 80 W/m·K or more.

The length of the heat dissipation coating may be equal to or greater than the thermal diffusion length.

The heat dissipation coating may be metallic.

The outer circumferential surface of the light emitting portion may be cylindrical.

In the reflecting element, a region corresponding to the arc-shaped outer peripheral surface of the optical fiber with a predetermined central angle may be opened in a slit shape to serve as the light exit port.

The tip of the optical fiber may have an end face that is oblique to a plane perpendicular to the axis of the core.

The light reflectance of the reflective element may be 1% or more.

The reflective element may be metal.

The reflective element and the heat dissipation coating may be integrated.

The reflective element may be a reflective resin.

The reflective element may be ceramic.

The heat dissipation coating may extend to the area in the axial direction where the light emitting portion is located, within the area in the circumferential direction where the reflecting element is located, on the tip side, and may be in radial contact with the reflecting element.

The heat dissipation coating may be made of separate materials in the axial direction, with a region that covers at least a portion of the light transmission section and a region where the light emission section is present.

The unevenness of the surface of the reflecting element facing the light emitting portion may be less than the wavelength of the light being used.

The thermal conductivity of the heat dissipation coating may be 0.2 W/m·K or more.

The heat dissipation coating may be tubular.

According to one aspect of the present invention, it is possible to provide a light diffusion device that can suppress heat generation at the light emitting section and its vicinity.

1 is a schematic diagram of a light diffusing device according to a first embodiment which is an exemplary aspect of the present invention. 5 is a longitudinal sectional view of the light exit portion of an optical fiber in the light diffusing device according to the first embodiment and its vicinity, and is a sectional view taken along the CC section in FIGS. 3 and 4. FIG. 3 is a cross-sectional view of a portion of a light transmitting portion of an optical fiber in the light diffusing device according to the first embodiment, taken along the line BB in FIG. 2. 3 is a cross-sectional view of a portion of a light output portion of an optical fiber in the light diffusing device according to the first embodiment, taken along the line AA in FIG. 2. 1A-1C are cross-sectional views of optical fibers illustrating variations in cladding removal at the outer surface of the optical fiber. 11 is a vertical cross-sectional view of a light exit portion of an optical fiber in a light diffusing device according to a second embodiment and its vicinity. FIG. 11 is an enlarged vertical cross-sectional view of a light exit portion of an optical fiber in a light diffusing device according to a second embodiment. FIG. 13 is a vertical cross-sectional view of a light exit portion of an optical fiber in a light diffusing device according to a third embodiment and its vicinity. FIG. 9 is a cross-sectional view of a portion of a light exit portion of an optical fiber in a light diffusing device according to a third embodiment, taken along the line FF in FIG. 8 . 1 is a graph for explaining the maximum height of a profile curve, the curve of the graph being an example of a roughness curve. 13A and 13B are schematic diagrams showing modified examples of the reflecting element.

Below, three exemplary embodiments of the light diffusion device according to the present invention will be described in detail with reference to the drawings.

First Embodiment
Fig. 1 is a schematic diagram of a light diffusing device 1 according to a first embodiment, Fig. 2 is a longitudinal sectional view of a light emitting portion of an optical fiber in the light diffusing device 1 and its vicinity, Fig. 3 is a transverse sectional view of a portion of a light transmitting portion of an optical fiber in the light diffusing device 1, and Fig. 4 is a transverse sectional view of a portion of a light emitting portion of an optical fiber in the light diffusing device 1. The base end side of the optical fiber is indicated by an arrow B, and the tip side is indicated by an arrow T.

In detail, FIG. 2 is a cross-sectional view taken along the line CC in FIG. 3 and FIG. 4, FIG. 3 is a cross-sectional view taken along the line B-B in FIG. 2, and FIG. 4 is a cross-sectional view taken along the line A-A in FIG. 2.

The light diffusion device 1 of this embodiment is used in photoimmunotherapy, which is one of the cancer treatment methods. Photoimmunotherapy is a procedure for treating cancer by administering to the human body a drug consisting of an antibody that binds to cancer cells and a substance that reacts to light, and then irradiating the drug that has bound to the cancer cells with laser light to destroy the cancer cells.

The light diffusion device 1 is a device that emits light incident on the base end 20BE of the optical fiber 20 from the tip side T, and a laser oscillator 10 is connected to the base end 20BE on the base side B of the optical fiber 20 as a light source for generating laser light.

The laser oscillator 10 has a semiconductor laser, and generates laser light by passing electricity through the semiconductor laser to cause laser oscillation. The laser oscillator 10 generates red laser light having a wavelength of 630 nm or more and 700 nm or less.

The optical fiber 20 is made of a resin (plastic) member. As shown in Figures 3 to 5, the optical fiber 20 is a single-core optical fiber consisting of a core 21 located in the center in the radial direction and a cladding 22 located on the outer periphery of the core 21. The optical fiber 20 has a relative refractive index difference between the core 21 and the cladding 22 of 2% to 11%.

The optical fiber 20 has, for example, an outer diameter of 500 μm, an outer diameter of the core 21 of 480 μm, and a thickness of the cladding 22 of 10 μm. Here, it is preferable that the outer diameter of the cladding 22 of the optical fiber 20 is 102 μm or more and 1100 μm or less. It is also preferable that the outer diameter of the core 21 of the optical fiber 20 is 100 μm or more and 1000 μm or less. It is preferable that the thickness of the cladding 22 is 1 μm or more and 50 μm or less.

As shown in Figures 1 and 2, the optical fiber 20 has a light transmission section 20a that transmits the laser light incident from the base end 20BE toward the tip side T, and a light emission section 20b that causes the laser light transmitted through the light transmission section 20a to exit from the outer circumferential surface by removing a portion located on the outer circumferential side of the cladding 22 within a predetermined range in the extension direction of the tip side T.

As shown in Figures 2 and 3, at the tip side T of the optical fiber 20, a certain area of the light transmitting section 20a, except for the light emitting section 20b, is covered (coated) with a heat dissipating coating 25, and its outer periphery is further coated with a soft resin tube 26. In this embodiment, the tube 26 has a thickness of 0.1 mm, an outer diameter of 0.95 mm, and an inner diameter of 0.85 mm, but of course these sizes are not limited to these. It is also possible to use it without covering it with the tube 26 and leaving the heat dissipating coating 25 exposed.

In this embodiment, nylon is used as the material for the tube 26, but there are no particular limitations as long as it is a soft resin, and examples of the material that can be used in addition to nylon include polyvinyl chloride, vinylidene chloride, urethane resin, silicone resin, etc.

The light emitting portion 20b that is not covered by the tube 26 is formed within a range of, for example, 10 mm to 100 mm, preferably 20 mm to 40 mm, on the tip side T of the optical fiber 20. The outer peripheral surface of the light emitting portion 20b has a cylindrical outer peripheral surface shape. The light emitting portion 20b is formed by removing a portion of the outer peripheral side of the clad 22 by, for example, blasting or etching, leaving the inner peripheral side in the thickness direction of the clad 22.

When the radial size of the light emitting section 20b becomes smaller than the diameter Da of the light transmitting section 20a by more than the wavelength of the laser light due to the removal of the cladding 22 (i.e., the thickness of the removed cladding 22 becomes more than half the wavelength of the laser light), the change in the structure of the optical fiber 20 in the longitudinal direction, which is of the order of wavelength, changes the light intensity distribution in the cross section of the optical fiber 20, causing light to leak and laser light to be emitted from the outer peripheral surface.

In the light emitting portion 20b in this embodiment, as shown in Figure 4, the cladding 22 is removed from the entire circumference of the optical fiber 20. However, as shown in Figure 5, the cladding 22 may be removed only from the outer surface of a circular arc in a certain region of the optical fiber 20 in the circumferential direction (central angle of 180° in Figure 5). In this case, the laser light is emitted from the outer surface of the region where the cladding 22 has been removed.

As shown in Figures 2 and 4, the outer peripheral surface of the light emitting portion 20b is surrounded by a reflecting element 24, leaving only a small area. In detail, as shown in Figure 4, the area a corresponding to the arc-shaped outer peripheral surface of the optical fiber 20 with a predetermined central angle θ is opened in a slit shape, and this opening becomes the light emitting port 23. In this embodiment, the central angle θ is set to, for example, 45°. There are no particular limitations on this central angle θ, and it may be set appropriately depending on the purpose, desired performance, standards, etc., and is preferably selected from the range of 30° to 350°.

The reflecting element 24 is a member that reflects light that leaks in a direction (area other than the area a corresponding to the light exit port 23) other than the light exit direction of the light exit section 20b (directions within the range of the central angle θ) in the circumferential direction, and causes the light to exit from the light exit port 23.

The reflective element 24 has a light reflectance of 1% or more, preferably 30% or more, more preferably 50% or more, and more preferably 80% or more, and preferably close to 100%. In this embodiment, the reflective element 24 has a thickness of 0.1 mm, an outer diameter of 0.8 mm, and an inner diameter of 0.6 mm, but of course the dimensions are not limited to these.

It is desirable that the surface of the reflecting element 24 facing the light emitting portion 20b is as close to a mirror surface as possible in order to efficiently reflect the laser light. Specifically, it is preferable that the unevenness of the surface of the reflecting element 24 facing the light emitting portion 20b is equal to or less than the wavelength of the light being used (laser light transmitted within the optical fiber 20). Here, "unevenness" refers to the difference Rz between the peak of the maximum mountain and the bottom of the minimum valley of the unevenness as shown in Figure 10 (maximum height of the contour curve: see JIS B0601). Note that Figure 10 is a graph to explain the maximum height of the contour curve, and the curve in the graph is an example of a roughness curve.

The reflective element 24 desirably has high thermal conductivity in view of the heat dissipation requirements described below. Specifically, for example, the thermal conductivity is preferably 0.2 W/m·K or more, more preferably 2 W/m·K or more, and even more preferably 16 W/m·K or more.

The material of the reflective element 24 is not particularly limited as long as it has the desired light reflectance, but a material with high light reflectance is preferable. Specific examples of the material of the reflective element 24 include metals such as stainless steel, aluminum, gold, silver, copper, and nickel-titanium (Ni-Ti) alloy, fluororesins such as polytetrafluoroethylene (PTFE), resins containing barium sulfate, and reflective resins such as silicone resin, and ceramics such as alumina. Among these, from the viewpoints of light reflectance, cost, processability, and thermal conductivity, the reflective element 24 is preferably made of metal, and is particularly preferably made of stainless steel. In addition, the reflective element 24 does not have to be manufactured from a single material. For example, a stainless steel cylinder is processed, the inside is mirror-polished, and then coated with a metal having a high reflectance, such as gold or silver, can be given as an example.

In the light diffusion device 1 according to this embodiment, when the laser oscillator 10 is operated to cause laser light to be incident on the base end 20BE of the optical fiber 20, the laser light is transmitted through the light transmission section 20a and emitted from the light emission section 20b. The laser light emitted radially in all directions in the circumferential direction from the light emission section 20b of the optical fiber 20 is partially emitted directly and the rest is reflected by the reflecting element 24 and emitted from the light emission port 23. In other words, the laser light transmitted through the light transmission section 20a is collected within a certain range in the circumferential direction by the light emission section 20b and is emitted from the side of the optical fiber 20. Therefore, the transmitted laser light can be efficiently irradiated onto the target to be irradiated, such as cancer cells.

When laser light is emitted from the light exit port 23, heat is generated near the light emitting portion 20b of the optical fiber 20, and the temperature of the reflecting element 24, which is particularly close to the light emitting portion 20b, tends to rise. Therefore, the practitioner is required to appropriately control the intensity and irradiation time of the laser light during treatment so that the temperature near the light emitting portion 20b does not become, for example, 5°C higher than the body temperature of the patient.

On the other hand, in order to achieve a high effect from the treatment, it is desirable for the intensity of the laser light to be relatively high; specifically, for example, an output of about 400 mW/cm is desirable. Furthermore, the continuous irradiation time of the laser light is a maximum of 5 minutes. Therefore, it is more desirable for the temperature near the light emitting part 20b to be less than 50°C at an output of 400 mW/cm x continuous irradiation time of 5 minutes.

In this embodiment, therefore, a heat dissipation coating 25 is provided to suppress heat generation in the light emitting portion 20b and its vicinity. The heat dissipation coating 25 is provided at the tip side TE, in contact with the reflecting element 24 and covering a part of the light transmitting portion 20a, so heat from the reflecting element 24 can be released and heat generation in the light emitting portion 20b and its vicinity can be suppressed.

The heat dissipation coating 25 covers at least a portion of the light transmission section 20a. The heat dissipation coating 25 is flexible and tubular, into which the optical fiber 20 is inserted, and the outer periphery is further covered with the tube 26. That is, in the light diffusion device 1 of this embodiment, a certain region on the tip side T of the light transmission section 20a has a three-layer structure consisting of, in order from the center, the optical fiber 20, the heat dissipation coating 25, and the tube 26.

The heat dissipation coating 25 is in contact with the reflecting element 24 at the tip side T. There are no particular limitations on the manner of contact between the heat dissipation coating 25 and the reflecting element 24 as long as they are in physical contact. To ensure that the heat dissipation coating 25 and the reflecting element 24 are in contact, they may be fixed together with a fixing means such as adhesive, screws, or welding, or they may be molded into a shape that allows them to engage with each other and then engaged.

Furthermore, even if the heat dissipation coating 25 and the reflective element 24 are molded as a single unit and are physically indistinguishable from each other (integrated), if the part that functions as the reflective element 24 and the part that functions as the heat dissipation coating 25 are separate and the parts that perform each function are connected at some point, the connected part is included in the concept of "contact" in this invention.

The heat dissipation coating 25 comes into contact with the reflective element 24 and has the function of dissipating heat from the reflective element 24. For this reason, it is desirable for the heat dissipation coating 25 to have high thermal conductivity. Specifically, for example, the thermal conductivity of the heat dissipation coating 25 is preferably 80 W/m·K or more, more preferably 200 W/m·K or more, and even more preferably 350 W/m·K or more. Furthermore, it is desirable for the thermal conductivity of the reflective element 24 to be higher than that of the heat dissipation coating 25. In this embodiment, the heat dissipation coating 25 has a thickness of 0.1 mm, an outer diameter of 0.8 mm, and an inner diameter of 0.6 mm, but of course these sizes are not limited to these.

The material of the heat dissipation coating 25 may be any material having the above-mentioned thermal conductivity. Specifically, the material may be metals such as stainless steel, aluminum, gold, silver, copper, nickel-titanium (Ni-Ti) alloy, ceramics such as alumina, or resins such as silicone resin and polytetrafluoroethylene (PTFE) resin that have been processed to have heat dissipation properties. Examples of processing to have heat dissipation properties include processing in which metal particles or ceramic particles with high thermal conductivity (e.g. alumina particles) are dispersed in the material. Of these, it is particularly preferable that the material of the heat dissipation coating 25 is the same as that of the reflecting element 24. In addition, the torque coil used to regulate the position (twist) of the optical fiber in the rotational direction may also function as the heat dissipation coating 25.

In this embodiment, the longitudinal region of the light transmitting section 20a covered by the heat dissipation coating 25 depends on the thermal conductivity of the heat dissipation coating 25. For example, if the thermal conductivity of the heat dissipation coating 25 is about 80 W/m·K, heat can be efficiently removed if the heat dissipation coating heat is equal to or greater than the thermal diffusion length at which 1/e is reached. Also, for example, if the thermal conductivity of the heat dissipation coating 25 is 200 W/m·K or greater, the temperature near the light emitting section 20b can be kept at the desired temperature even if the length is about half the thermal diffusion length.

Here, the thermal diffusion length μ is a physical property defined as an index of how far temperature can be transmitted. The amplitude of a temperature wave emitted from a certain point diffuses while exponentially decaying, and the thermal diffusion length μ is the distance at which the amplitude of the temperature wave becomes 1/e. Specifically, the thermal diffusion length μ is defined as √(α/πf) (where α is a physical property called thermal diffusivity).

If the thermal conductivity of the heat dissipation coating 25 is less than 80 W/m·K, it is preferable for the heat dissipation coating 25 to extend to an area located outside the body during treatment, as this area will come into contact with the outside air temperature and the heat dissipation effect will be enhanced. Conversely, the heat dissipation coating 25 may cover the entire optical transmission section 20a up to the base end BE. More preferably, it is desirable to connect a heat sink for heat dissipation and actively dissipate heat from the heat sink.

The heat sink for heat dissipation can be connected to the end of the base end side B of the heat dissipation coating 25 or near it, or halfway along the longitudinal direction. By actively releasing heat from the heat sink, the heat dissipation effect can be further improved. Examples of such a heat sink include a metal member with multiple plate-shaped protrusions for heat dissipation, or a metal lump with a volume sufficient to absorb the generated heat.

The heat sink may be attached midway through the light transmission section 20a of the optical fiber 20, or may be disposed separately from the optical fiber 20. When the heat sink is attached midway through the light transmission section 20a of the optical fiber 20, the end of the base end side B of the heat dissipation coating 25 or its vicinity, or midway in the longitudinal direction (axial direction) may be connected to the heat sink. When the heat sink is disposed separately from the optical fiber 20, the heat dissipation coating 25 may be branched off from the light transmission section 20a of the optical fiber 20 and connected to the heat sink.

The tube 26 is not an essential component, so if there is no particular problem, the heat dissipation coating 25 may be exposed without the tube 26. However, in this embodiment, in order to protect the heat dissipation coating 25 and the optical fiber 20, the entire area of the optical fiber 20 that is located inside the body during treatment is covered in the longitudinal direction.

In this embodiment, the tip 20TE of the optical fiber 20 is left in the cut state, but a cap may be provided on the tip 20TE to prevent leakage of laser light from the tip 20TE and to protect the reflecting element 24 and the tip 20TE of the optical fiber 20. Examples of materials for the cap include resins such as polytetrafluoroethylene (PTFE) and metals such as aluminum.

In this embodiment, the outer diameter of the optical fiber 20 in the light transmission section 20a, the inner and outer diameters of the heat dissipation coating 25, and the inner diameter of the tube 26 do not match each other, and there is a difference in diameter between each layer. This difference in diameter is a margin to ensure flexibility in the light transmission section 20a of the optical fiber 20 and to absorb tolerances during manufacturing, and is not intended to intentionally create gaps between each layer.

For example, in Figures 2 to 4, gaps are depicted in some areas between the layers, but this does not mean that gaps are maintained over the entire area in the longitudinal direction, and the layers are in contact in many areas. On the other hand, in Figures 2 to 4, in areas where the layers are depicted as being in contact, there may in fact be gaps in some areas.

Second Embodiment
Fig. 6 is a vertical cross-sectional view of a light output portion of an optical fiber in the light diffusing device 2 according to the second embodiment and its vicinity, and Fig. 7 is an enlarged vertical cross-sectional view of the light output portion. Since the light diffusing device 2 according to the present embodiment has a configuration substantially similar to that of the light diffusing device 1 according to the first embodiment, please refer to Fig. 1 for an outline of the light diffusing device 2.

In addition, the D-D cross section in FIG. 6 is the same as FIG. 4, and the E-E cross section is the same as FIG. 3, so please refer to FIG. 3 and FIG. 4 for these cross sections. Note that the light diffusion device 2 according to the second embodiment has the same configuration as the light diffusion device 1 according to the first embodiment, except that the shape of the tip portion 20TE of the optical fiber 20 is unique to this embodiment. Therefore, the members having the same functions as the light diffusion device 1 according to the first embodiment are given the same reference numerals as in FIG. 1 to FIG. 6, and their description will be omitted.

As shown in Figures 6 and 7, in the light diffusion device 2 according to this embodiment, the tip 20TE of the optical fiber 20 has an end face 20s that is inclined with respect to a plane P perpendicular to the axis 21A of the core 21. In this case, the angle γ between the plane P and the end face 20s is set to be equal to or greater than the angle at which the laser light transmitted through the optical fiber 20 is totally reflected. Specifically, if the refractive index of the core 21 of the optical fiber 20 is ncore and the refractive index of air is nair, then γ = arcsin(nair/ncore), and if ncore = 1.465 and nair = 1.0, then γ = 43°.

In the light diffusing device 2 according to this embodiment, when the laser oscillator 10 is operated to cause laser light to be incident on the base end 20BE of the optical fiber 20, the laser light is transmitted through the light transmitting section 20a and emitted from the light emitting section 20b. In the light emitting section 20b, the tip end 20TE of the optical fiber 20 has an end face 20s that is inclined with respect to the plane P perpendicular to the axis 21A of the core 21 as described above, and theoretically undergoes total reflection. The totally reflected laser light travels in the direction of the arrow _L1 and is emitted from the light emitting port 23.

In reality, not all of the laser light is reflected, but a small amount leaks out from the end face 20s. The laser light leaking out from the end face 20s travels in the direction of the arrow _L2 and is reflected by the reflecting element 24. The laser light then travels in the direction of the arrow _L3 and is emitted from the light emitting port 23. That is, the laser light transmitted through the light transmitting section 20a is collected within a certain range in the circumferential direction by the light emitting section 20b, including not only the totally reflected laser light _L1 but also the laser light _L2 leaking out from the end face 20s, and is emitted from the side of the optical fiber 20. Therefore, the transmitted laser light can be efficiently irradiated onto the target to be irradiated, such as cancer cells.

When laser light is emitted from the light exit port 23, heat is generated near the light exit portion 20b of the optical fiber 20, as in the light diffusion device 1 of the first embodiment, and the temperature of the reflecting element 24, which is particularly close to the light exit portion 20b, tends to rise. However, in this embodiment, the tip side TE also has a heat dissipation coating 25 that contacts the reflecting element 24 and covers part of the light transmission portion 20a, so that heat from the reflecting element 24 can be released and heat generation in and near the light exit portion 20b can be suppressed.

Other modifications and the materials of each component are the same as in the first embodiment, so explanations will be omitted.

Third Embodiment
Fig. 8 is a vertical cross-sectional view of the light output portion of an optical fiber in a light diffusing device 3 according to the third embodiment and its vicinity, and Fig. 9 is a horizontal cross-sectional view of the portion of the light output portion of an optical fiber in the light diffusing device 3. In detail, Fig. 9 is a cross-sectional view taken along the line F-F in Fig. 8. Since the light diffusing device 3 according to this embodiment has a configuration substantially similar to that of the light diffusing device 1 according to the first embodiment, refer to Fig. 1 for an overview of the light diffusing device 3.

The cross section G-G in FIG. 8 is the same as that in FIG. 3, so please refer to FIG. 3 for this cross section. Note that the light diffusion device 3 according to the third embodiment has the same configuration as the light diffusion device 1 according to the first embodiment, except for the structure in the vicinity of the light emission portion 20b of the optical fiber 20 which is unique to this embodiment. Therefore, the members having the same functions as the light diffusion device 1 according to the first embodiment are given the same reference numerals as in FIGS. 1 to 6, and their description will be omitted.

8 and 9, in the light diffusion device 3 according to this embodiment, a reflective resin is used as the reflective element 27 (hereinafter, referred to as "reflective resin 27"). As described above, examples of the reflective resin 27 include fluororesins such as polytetrafluoroethylene (PTFE), resins containing barium sulfate, silicone resins, etc.

In addition, in this embodiment, the heat dissipation coating 25 is composed of separate members in the axial direction, a member (heat dissipation coating main body 25a) for the area covering part of the light transmission section 20a, and a member (heat dissipation metal 25b) for the area where the light emitting section 20b is present. In other words, if the heat dissipation coating main body 25a and the heat dissipation metal 25b are regarded as a single body that constitutes the heat dissipation coating 25, the heat dissipation coating 25 extends to the area where the light emitting section 20b is present in the axial direction 21A, within the range of the area where the reflecting element 24 is present in the circumferential direction, at the tip side TE, and is in radial contact with the reflective resin 27.

The reflective resin 27 has a larger specific heat than the metallic reflective element 24 in the first and second embodiments, so the heat dissipation effect is ensured by making radial contact with the heat dissipation metal 25b to increase the contact area.

The configuration of the heat dissipation coating body 25a is the same as the heat dissipation coating 25 in the first and second embodiments. The configuration of the heat dissipation metal 25b does not cover the entire circumference of the optical fiber 20, but is located only within the range of the area where the reflective resin (reflective element) 27 exists in the circumferential direction (range b in Figure 9).

The material for the heat dissipation metal 25b is preferably one with the characteristics described as the material for the heat dissipation coating 25 in the first embodiment, and specific examples are similar. It is preferable that the heat dissipation coating body 25a and the heat dissipation metal 25b are made of the same material.

There are no particular limitations on the form of contact between the heat dissipation metal 25b and the reflective resin 27, so long as they are in physical contact. To ensure that the heat dissipation metal 25b and the reflective resin 27 are in contact with each other, they may be fixed together with adhesive, screws, welding, or other fixing means, or they may be molded into a shape that allows them to engage with each other and then engaged.

There are no particular limitations on the form between the heat dissipating metal 25b and the heat dissipating coating body 25a, as long as they are in physical contact. To ensure that the heat dissipating metal 25b and the heat dissipating coating body 25a are in contact, they may be fixed together with adhesive, screws, welding, or other fixing means, or they may be molded into a shape that allows them to engage with each other and then engaged.

Furthermore, the heat dissipation metal 25b and the heat dissipation coating body 25a may be molded as a single unit, so that they are physically indistinguishable from each other. In this embodiment, whether they are integrated or separate, the heat dissipation metal 25b and the heat dissipation coating body 25a together constitute the heat dissipation coating 25.

In the light diffusion device 3 according to this embodiment, when the laser oscillator 10 is operated to cause laser light to be incident on the base end 20BE of the optical fiber 20, the laser light is transmitted through the light transmission section 20a and emitted from the light emission section 20b. The laser light emitted radially in all directions in the circumferential direction from the light emission section 20b of the optical fiber 20 is partially reflected directly and the rest is reflected by the reflective resin 27 and emitted from the light emission port 23. In other words, the laser light transmitted through the light transmission section 20a is collected within a certain range in the circumferential direction by the light emission section 20b and is emitted from the side of the optical fiber 20. Therefore, the transmitted laser light can be efficiently irradiated onto the target to be irradiated, such as cancer cells.

When laser light is emitted from the light exit port 23, heat is generated near the light exit portion 20b of the optical fiber 20, similar to the light diffusion device 1 according to the first embodiment, and the temperature of the reflective resin 27, which is particularly close to the light exit portion 20b, tends to rise. Furthermore, since the reflective resin 27 has a larger specific heat than metal, it is difficult to cool down once it becomes hot.

However, in this embodiment, the heat dissipation metal 25b contacts the reflective resin 27 in the radial direction, making it possible to increase the contact area and achieve a high heat dissipation effect. The heat dissipation metal 25b can also dissipate heat from the heat dissipation coating body 25a with which it is in contact, making it possible to suppress heat generation in and around the light emitting portion 20b.

The configuration of this embodiment is also suitable for the case where ceramics, which has a larger specific heat than metal, is used as the reflecting element 24 .
Other than that, the modified examples and the materials of the respective members are similar to those of the first embodiment, and therefore the description thereof will be omitted.

The above-described embodiment merely shows a representative example of the present invention, and the present invention is not limited to this embodiment. In other words, a person skilled in the art can implement the present invention by making various modifications in accordance with conventionally known knowledge without departing from the gist of the present invention. As long as such modifications still have the configuration of the light diffusion device of the present invention, they are of course included in the scope of the present invention.

For example, in the above embodiment, the shape of the light exit port is exemplified as a slit extending in the axial direction of the optical fiber (in a region corresponding to the arc-shaped outer circumferential surface of the optical fiber with a specified central angle), but is not limited to this. For example, multiple perforations may be provided on the exit side surface of the reflecting element, and the perforations may serve as the light exit port. The shape of the perforations is also arbitrary, and may be circular, rectangular, or some other shape.

Also, for example, as shown in FIG. 11, a long and thin elliptical opening 28 may be provided on the exit side surface of the reflecting element 24' to form a window structure, which may serve as the light exit port 23'. Note that FIG. 11 is a schematic diagram showing a modified example of the reflecting element. The shape of the opening of this window structure may also be appropriately selected, such as rectangular or polygonal.

The present invention will be described more specifically below with reference to examples and comparative examples.
A light diffusing device 1 and a laser oscillator 10 similar to those of the first embodiment shown in Figures 1 to 6 were prepared. Specific specifications and conditions of the examples and comparative examples are as follows. Specifications and conditions not described below are as described in the explanation of the first embodiment.

(Specifications and conditions of the examples and comparative examples)
Test environment temperature: Room temperature (22°C)
Axial length of light emitting portion 20b: 40 mm
Material of heat dissipation coating 25: SUS304
Material of the reflecting element 24: silicone resin, SUS304, aluminum, copper, silver Axial length of the heat dissipation coating 25 and the tube 26: 1 to 1000 mm
Total length of optical fiber 20: 1040 mm
State of the light emitting portion 20b when heated: held in air Room temperature during testing: 21° C.
Wavelength of laser light from laser oscillator 10: 690 nm
Laser light intensity of the laser oscillator 10: 550 mW

For the light diffusion devices of the examples and comparative examples with the conditions shown in Tables 1 to 3 below, under the above specifications and conditions, the outer surface of the reflecting element 24 was measured with an infrared thermometer while the laser oscillator 10 was operated to cause laser light to enter the base end 20BE of the optical fiber 20 and emit (laser irradiation) from the light emitting portion 20b. The laser irradiation was continued for 5 minutes from the start, and the temperature of the outer surface of the reflecting element 24 was monitored.

The evaluation criteria in Tables 1 to 3 are as follows.
⊚: The temperature of the light emitting part and its vicinity is less than 40°C. ◯: The temperature of the light emitting part and its vicinity is 40°C or higher and lower than 50°C. ×: The temperature of the light emitting part and its vicinity is 50°C or higher.

Table 1: Cases where there is no thermally conductive coating, and where the thermally conductive coating is made of silicone resin (not treated to have thermal conductivity)

As shown in Table 1 above, in Examples 1 to 4, where the heat dissipation coating material was silicone resin (thermal conductivity 0.15 W/mK), the lengths (L3) of the heat dissipation coating were 1 mm, 40 mm, 100 mm, and 1000 mm, and the temperatures at the light output section and its vicinity were 76.5°C, 76.5°C, 76.5°C, and 76.4°C, respectively, meaning that even if the length of the heat dissipation coating was made sufficiently longer than the thermal diffusion length, the temperature at the light output section and its vicinity could not be suppressed to the target level. However, in Examples 1 to 4, although the results were judged to be ×, the effect of suppressing temperature rise was confirmed compared to Comparative Example 1, where no heat dissipation coating was provided.

Table 2: When the material of the thermal insulating coating is SUS304

As shown in Table 2 above, in Examples 7 to 8, where the heat dissipation coating is made of SUS304 (thermal conductivity 84 W/mK), the temperature at the light emitting section and its vicinity was below 50°C when the length (L3) of the heat dissipation coating was at a level equal to or greater than the thermal diffusion length, and the temperature rise could be suppressed to below the desired temperature. In Examples 5 and 6, where the length (L3) of the heat dissipation coating is at a level less than the thermal diffusion length, the result was judged to be ×, but a suppression effect on the temperature rise was confirmed compared to Examples 1 to 4, which had the same or better conditions.

- Table 3: When the thermal insulation coating material is aluminum, copper, or silver

As shown in Table 3 above, in Examples 9-10 where the heat dissipation coating was aluminum (thermal conductivity 204 W/m·K), the temperature at the light output and its vicinity was 33.2°C when the heat dissipation coating length (L3) was 40 mm for a thermal diffusion length of 96 mm. Furthermore, when the heat dissipation coating length (L3) was 100 mm, which is greater than the diffusion length, the temperature at the light output and its vicinity was 22.0°C (the same temperature as room temperature), confirming a significant effect in suppressing temperature rise.

In addition, in Examples 11 and 12, where the heat dissipation coating was copper (thermal conductivity 386 W/mK), the temperature at the light emitting part and its vicinity was 31.4°C when the length (L3) of the heat dissipation coating was 40 mm for a thermal diffusion length of 106 mm. Furthermore, when the length (L3) of the heat dissipation coating was at the level of 100 mm, which is greater than the diffusion length, the temperature at the light emitting part and its vicinity was 22.0°C (the same temperature as room temperature), confirming a significant effect in suppressing temperature rise.

In addition, in Examples 13-14, where the heat dissipation coating was silver (thermal conductivity 418 W/mK), the temperature at the light emission section and its vicinity was 30.4°C when the heat dissipation coating length (L3) was 40 mm for a thermal diffusion length of 129 mm. Furthermore, when the heat dissipation coating length (L3) was 100 mm, which is greater than the diffusion length, the temperature was 22.0°C (the same temperature as room temperature), confirming a significant effect in suppressing temperature rise.

In Example 14, which was the same as Example 13 but also had a tip cap attached, the temperature at the light-emitting part and its vicinity dropped from 30.4°C to 26.9°C (-3.5°C), confirming a further effect in suppressing temperature rise.

As described above, it was confirmed that the light diffusion device of the embodiment, which is provided with a metallic heat dissipation coating 25 with heat dissipation properties, was able to reduce the temperature of the light emitting section and its vicinity by 35% or more compared to the comparative example.

1, 2, 3 Light diffusion device,
10 laser oscillator,
20 optical fiber,
20a optical transmission unit,
20b light emitting portion,
20BE base end,
20TE tip,
21 cores,
22 Clad,
22a uneven surface,
23, 23' light exit port,
24, 24' reflective element;
25 heat dissipation coating,
25a heat dissipating coating body (heat dissipating coating),
25b heat dissipating metal (heat dissipating coating),
26 tubes,
27 Reflective resin (reflective element),
28 Opening

Claims

A light diffusing device comprising an optical fiber having a core located at a radial center side and a clad located on an outer peripheral side of the core, the light diffusing device diffusing light incident on a base end of the optical fiber being emitted from a tip end side of the optical fiber,
the optical fiber has a light transmitting section that transmits light incident from a base end portion toward a tip end portion, and a light emitting section that emits the light transmitted through the light transmitting section from an outer circumferential surface by removing a portion located on the outer circumferential side of the clad at the tip end side,
a reflecting element that surrounds an outer peripheral surface of the light emitting portion, leaving a region that serves as a light emitting opening;
a heat dissipation coating that contacts the reflecting element at a tip side and covers at least a part of the light transmitting portion;
A light diffusing device comprising:
The light diffusion device of claim 1, wherein the thermal conductivity of the heat dissipation coating is 80 W/m·K or more.
The light diffusion device of claim 1, wherein the length of the heat dissipation coating is equal to or greater than the heat diffusion length.
The light diffusion device of claim 1, wherein the heat dissipation coating is metal.
The light diffusion device according to claim 1, wherein the outer peripheral surface of the light emitting portion has a cylindrical outer peripheral surface shape.
The light diffusion device according to claim 1, wherein the reflecting element has a slit-shaped opening in an area corresponding to the arc-shaped outer peripheral surface of the optical fiber at a predetermined central angle, forming the light exit port.
The light diffusion device of claim 1, wherein the tip of the optical fiber has an end face that is oblique with respect to a plane perpendicular to the axis of the core.
The light diffusion device of claim 1, wherein the light reflectance of the reflective element is 1% or more.
The light diffusion device of claim 1, wherein the reflective element is a metal.
The light diffusion device of claim 9, wherein the reflective element and the heat dissipation coating are integrated.
The light diffusion device of claim 1, wherein the reflective element is a reflective resin.
The light diffusion device of claim 1, wherein the reflective element is made of ceramics.
The light diffusion device according to claim 11 or 12, wherein the heat dissipation coating extends to the area in the axial direction where the light emitting portion is located, within the area in the circumferential direction where the reflecting element is located, at the tip side, and is in contact with the reflecting element in the radial direction.
The light diffusion device according to claim 13, wherein the heat dissipation coating is made of separate members in an area in the axial direction that covers at least a portion of the light transmission section and an area in which the light emission section is present.
The light diffusion device according to claim 1, wherein the unevenness of the surface of the reflecting element facing the light emitting portion is equal to or smaller than the wavelength of the light used.