JP2020069379A - Medical laser light guide - Google Patents

Abstract

To suppress a decrease in uniformity of light intensity in a longitudinal direction of a light guide body in a medical laser light guide provided with a light reflection part at an end of the light guide body.SOLUTION: A medical laser light guide includes a light guide body which is tapered and has an end surface and a light reflection part having a light reflection surface opposite the end surface. The light guide body has: a base end part; a core which includes an end surface, whose diameter is D, whose refractive index is n, and which extends in a longitudinal direction of the light guide body; an end part which has a clad covering the core, whose numerical aperture is NA, and whose length in the longitudinal direction of the light guide body is L defined by an equation below or larger; and a light diffusion part which is positioned between the base end part and the end part in the longitudinal direction of the light guide body and diffuses light received at the base end part sideways from an outer peripheral surface. Average strength of light emitted from the outer peripheral surface of a part of end side length L of the end part is smaller than average strength of light emitted from the outer peripheral surface of the light diffusion part.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a medical laser light guide.

  Conventionally, there is known a medical laser light guide that laterally emits laser light from an optical fiber inserted in a living body such as a blood vessel. For example, Patent Documents 1 and 2 disclose the structure of a catheter (light scattering light guide) for photodynamic treatment.

JP, 2008-148951, A US Pat. No. 6,315,775 JP, 2005-208271, A

  The medical laser light guide is for treating the affected area by irradiating the affected area located on the side by emitting the laser light to the side while being inserted into the living body. In such a medical laser light guide, it is desired that the laser light be emitted only from the side and not be emitted to the front. This is to prevent damage to normal cells that are not affected. Therefore, for example, in the light-scattering light guide described in Patent Document 2, a mirror is provided at the tip of the light guide (light guide), and the light that is going to be emitted forward is directed to the light guide (light guide). Are returning.

  On the other hand, in the medical laser light guide, the distribution of the intensity of light emitted from the side of the light guide is required to be uniform in the longitudinal direction of the light guide. However, when a light reflecting part such as a mirror is provided at the tip of the light guide, if the light reflected by the light reflecting part is easily emitted laterally from the vicinity of the tip of the light guide, the distribution of the light intensity is disturbed, and the light intensity is disturbed. Uniformity is reduced.

  An object of the present invention is to prevent the uniformity of light intensity in the longitudinal direction of the light guide body from being deteriorated in the medical laser light guide including the light reflecting portion at the tip of the light guide body.

A medical laser light guide according to an aspect of the present invention includes an elongated light guide having a tip surface, and a light reflecting portion having a light reflecting surface facing the tip surface. The light guide body includes a base end portion, a distal end surface, a diameter D, a refractive index n, a core extending in the longitudinal direction of the light guide body, and a clad covering the core. The numerical aperture is NA. Is located between the base end portion and the distal end portion in the longitudinal direction of the light guide, and the distal end portion whose length in the longitudinal direction of the light guide body is L or more defined by the following mathematical formula. A light diffusing portion that diffuses the light received by the portion laterally from the outer peripheral surface. The average intensity of the light emitted from the outer peripheral surface of the tip end side length L of the tip portion is lower than the average intensity of the light emitted from the outer peripheral surface of the light diffusion portion.

  According to one aspect of the present invention, in the medical laser light guide including the light reflecting portion at the tip of the light guide, it is possible to prevent the uniformity of the light intensity in the longitudinal direction of the light guide from decreasing.

FIG. 1A is a side view showing the vicinity of the tip of the medical laser light guide 1A according to the present embodiment. 1B is a sectional view taken along the central axis of the medical laser light guide 1A shown in FIG. FIG. 2 is a view showing a cross section perpendicular to the central axis C of the light guide 2. 3A and 3B are cutaway perspective views showing an example of the light reflecting portion 3. FIG. 4 is a side view showing the light guide 2. FIG. 5A is a side view showing the light diffusion portion 22 of the present embodiment in a partially enlarged manner. FIG. 5B is an enlarged cross-sectional view of the light diffusion portion 22 along the optical axis direction (longitudinal direction D1). FIG. 6 is a diagram showing, as a comparative example, how light is emitted from a medical laser light guide in which the light guide does not have the tip portion 23. FIG. 7 shows how light is emitted from the medical laser light guide 1A of the present embodiment. FIG. 8 is a diagram schematically showing a cross section of the tip portion 23 and the light reflecting portion 3. 8A shows the case where the tip 23 is sufficiently long, and FIG. 8B shows the case where the tip 23 is short. FIG. 9 is a diagram schematically showing the cross-sectional structure of the tip portion 23. FIG. 10A is a perspective view showing a distal end portion of a medical laser light guide 1B according to a modification of the above embodiment. FIG. 10B is a sectional perspective view of the distal end portion of the medical laser light guide 1B. FIG. 11A is a side view showing a medical laser light guide 1C according to another modification of the above embodiment. FIG. 11B is a side view showing the light guide body 52 of the medical laser light guide 1C. FIG. 12 is a cross-sectional view showing the enlarged diameter portion 54 of the tip portion 53 of the light guide body 52. FIG. 13 is a cross-sectional view showing the enlarged diameter portion 54A of the tip portion 53A of the light guide body 52A made of a material different from that of the light guide body 52. FIG. 14 is a diagram showing an example of a method of forming the enlarged diameter portion 54A of FIG. FIG. 15 is a diagram showing another method of forming the expanded diameter portion 54A of FIG.

[Description of Embodiments of the Present Invention]
First, the contents of the embodiments of the present invention will be listed and described. A medical laser light guide according to an embodiment of the present invention includes a light guide having an elongated shape and a tip surface, and a light reflection portion having a light reflection surface facing the tip surface. The light guide body includes a base end portion, a front end surface, a diameter D, a refractive index n, a core extending in the longitudinal direction of the light guide body, and a clad covering the core. Is located between the base end portion and the distal end portion in the longitudinal direction of the light guide body, and the distal end portion whose length in the longitudinal direction of the light guide body is L or more defined by the following mathematical formula, A light diffusing portion that diffuses the light received by the portion laterally from the outer peripheral surface. The average intensity of light emitted from the outer peripheral surface of the tip end side length L portion is lower than the average intensity of light emitted from the outer peripheral surface of the light diffusion portion.

  In this medical laser light guide, light for treating the affected area (for example, visible light or near infrared light) is input from one end side of the base end portion of the light guide. This light propagates in the base end portion and reaches the light diffusion portion. In the light diffusing section, this light is emitted to the side of the outer peripheral surface while being diffused. In addition, a part of the light that has passed through the light diffusing portion without being emitted propagates through the tip portion to reach the light reflecting surface, is then reflected by the light reflecting surface, propagates through the tip portion again, and propagates through the light diffusing portion. Return to. Then, the part of the light is emitted to the side of the outer peripheral surface while being diffused.

  In this medical laser light guide, a tip having a length of L or more is interposed between the light diffusing portion and the light reflecting surface. The tip portion includes a tip surface that faces the light reflecting surface, and has a core that extends in the longitudinal direction of the light guide body and a clad that covers the core. Therefore, the light reflected by the light reflecting surface is again confined in the core of the tip portion. Further, the average intensity of light emitted from the outer peripheral surface of the portion having the length L on the front end side (the degree of light diffusion) is the average intensity of light emitted from the outer peripheral surface of the light diffusing portion (light diffusion). The light confined in the core of the tip propagates to the light diffusing section while being suppressed from being emitted from the outer circumferential surface of the tip, and diffuses laterally from the outer circumferential surface of the light diffusing section. While emitting. Therefore, the light reflected by the light reflecting portion is less likely to be emitted laterally from the vicinity of the tip of the light guide body, so that it is possible to effectively suppress deterioration of the uniformity of light intensity in the longitudinal direction of the light guide body.

  In the medical laser light guide described above, the light reflecting portion may have a columnar shape with the longitudinal direction of the light guide as the central axis direction. In this case, the heat capacity of the light reflecting portion becomes larger than that in the case where it is formed in a film shape on the tip end surface of the light guide. Therefore, it is possible to reduce the temperature rise of the light reflecting portion due to the absorption of light.

  In the above medical laser light guide, the outer peripheral surface of the light diffusing portion has one or both of concave and convex for light diffusion, and the outer peripheral surface of the tip portion is smooth (there is no scratch or concave reaching the core. State). For example, with such a structure, the average intensity (light diffusion degree) of light emitted from the outer peripheral surface of the portion having the length L on the tip side at the tip portion is calculated as the average of the light emitted from the outer peripheral surface of the light diffusing portion. It can be made lower than the intensity (degree of light diffusion).

  In the above medical laser light guide, the outer peripheral surface of the light diffusing portion may have a plurality of grooves. For example, with such a structure, it is possible to easily realize a light diffusing section that diffuses light laterally from the outer peripheral surface. In this case, the light diffusing section may have a core extending in the longitudinal direction of the light guide body and a clad covering the core, and the depths of the plurality of grooves may reach the core of the light diffusing section. This makes it possible to easily increase the average intensity of light emitted from the light diffusing unit (degree of light diffusion). Further, in this case, each of the plurality of grooves is along the circumferential direction of the light diffusion portion, the plurality of grooves are arranged in the longitudinal direction of the light guide, and the length of the tip portion in the longitudinal direction of the light guide is , May be longer than the minimum interval between the plurality of grooves. As a result, the light diffusion portion and the tip portion are clearly distinguished.

  In the medical laser light guide described above, the outer peripheral surface of the light diffusion portion may be a rough surface. For example, even with such a structure, it is possible to easily realize a light diffusing portion that diffuses light laterally from the outer peripheral surface.

  The above-mentioned medical laser light guide further includes a light-transmissive tube that accommodates the light guide and the light reflection part, the light guide is bent in the tube, and the tip end surface of the light guide is restored by the restoring force of the light guide. It may be pressed against the reflective surface. As a result, even when the medical laser light guide bends in the living body, the contact state between the tip surface of the light guide and the light reflecting surface of the light reflecting portion is easily maintained. Therefore, even if the medical laser light guide is bent, it is possible to effectively suppress deterioration of the uniformity of the light intensity in the longitudinal direction of the light guide.

  In the medical laser light guide described above, the material forming the light reflecting surface may include at least one of Ag, Ag alloy, Au, or Au alloy. These metals have high reflection characteristics with respect to light (especially red light near the wavelength of 664 nm). Therefore, it is possible to improve the light utilization efficiency, reduce the light absorption in the light reflecting portion, and suppress the temperature rise of the light reflecting portion.

  In the medical laser light guide described above, the light reflecting portion may include a metal body or a metal film having a light reflecting surface. Thereby, the light reflecting portion having the light reflecting surface can be easily manufactured.

  In the medical laser light guide described above, at least one of the light reflecting surface and the tip surface may be a mirror surface. As a result, it is possible to increase the reflectance with respect to the light that has passed through the light diffusing unit, improve the light utilization efficiency, reduce the light absorption in the light reflecting unit, and suppress the temperature rise of the light reflecting unit.

  In the medical laser light guide described above, the light reflecting portion may further have another light reflecting surface facing the outer peripheral surface of the tip portion. Thereby, a slight amount of scattered light generated near the tip of the light guide can be returned to the tip, so that it is possible to more effectively suppress deterioration of the uniformity of the light intensity in the longitudinal direction of the light guide. In this case, the light reflecting portion may have a tubular portion that covers at least a part of the outer peripheral surface of the tip portion and includes another light reflecting surface. Thereby, another light reflecting surface can be easily realized. In this case, the material forming the other light reflecting surface may include at least one of Ag, Ag alloy, Au, or Au alloy. These metals have high reflection characteristics with respect to light (especially red light near the wavelength of 664 nm). Therefore, it is possible to improve the light utilization efficiency, reduce the light absorption in the tubular portion, and suppress the temperature rise in the tubular portion.

[Details of Embodiment of Present Invention]
A specific example of the medical laser light guide according to the embodiment of the present invention will be described below with reference to the drawings. It should be noted that the present invention is not limited to these exemplifications, and is shown by the scope of the claims, and is intended to include meanings equivalent to the scope of the claims and all modifications within the scope. In the following description, the same reference numerals are given to the same elements in the description of the drawings, and overlapping description will be omitted.

  The medical laser light guide according to one embodiment of the present invention is used for photodynamic therapy (PDT). In PDT, a photosensitizer (sensitizer) is injected into the living body, and the target biological tissue is irradiated with light of a certain wavelength to generate active oxygen from the photosensitizer, which causes cancer or infectious disease. Treat the lesion. As the photosensitizer for cancer, for example, Rezaphyrin (registered trademark) manufactured by Meiji Seika Pharma is used. In order to irradiate the affected area with laser light, a medical laser light guide in which a lateral light irradiation section is provided at the tip of an optical fiber is used. Since the insertion of the medical laser light guide into the body does not require surgery, the burden on the patient is small. When irradiating the affected part of the organ of the organ deep inside the body with laser light, it is better to irradiate the light from the side surface of the medical laser light guide than to irradiate the light in front of the medical laser light guide.

  FIG. 1A is a side view showing the vicinity of the tip of the medical laser light guide 1A according to the present embodiment. 1B is a sectional view taken along the central axis of the medical laser light guide 1A shown in FIG. As shown in FIGS. 1A and 1B, the medical laser light guide 1A of the present embodiment includes a light guide body 2, a light reflecting portion 3, and a tube 4.

  The light guide 2 is an element for propagating the light for irradiating the affected area toward the distal end portion of the medical laser light guide 1A, and has an elongated shape with the light propagation direction being the longitudinal direction D1. FIG. 2 is a view showing a cross section perpendicular to the central axis C of the light guide 2. The light guide 2 is, for example, an optical fiber made of plastic or glass, and has a core 5 that guides light and a clad 6 that covers the periphery of the core 5. When the light guide 2 is made of plastic, the core 5 is made of acrylic (PMMA) or polycarbonate (PC), for example. The clad 6 is made of, for example, a resin containing fluorine. The refractive index of the core 5 is larger than that of the cladding 6. The diameter of the core 5 is in the range of 0.11 to 2.1 mm, for example, 0.5 mm. The outer diameter of the clad 6 is in the range of 0.1 to 2 mm, for example, 0.5 mm. The numerical aperture (NA) is in the range of 0.1 to 0.6, for example, and is 0.5. The wavelength of the light input to the light guide 2 is appropriately selected according to the excitation energy of the photosensitizer injected into the living body, and is, for example, in the range of 400 to 800 nm, and as the photosensitizer, Rezaphyrin (registered trademark) is used. ) Is used, it is 664 nm.

  The light reflecting portion 3 is arranged at the tip of the light guide 2 (one end on the side opposite to the base end through which light is input). 3A and 3B are cutaway perspective views showing an example of the light reflecting portion 3. As shown in these figures, the light reflecting portion 3 has a light reflecting surface 3a that faces the tip surface 2a of the light guide 2, and transmits light that has propagated through the light guide 2 and reaches the tip surface 2a. , Is reflected by the light reflecting surface 3a. The light reflecting portion 3 of the present embodiment has a columnar shape with the longitudinal direction D1 of the light guide 2 (that is, the optical axis direction) as the central axis direction. The light reflecting surface 3a is composed of a bottom surface of a cylinder. The light reflecting surface 3a is a smooth surface, and at least one of the light reflecting surface 3a and the tip surface 2a of the light guide 2 is a mirror surface. The mirror surface means a surface that is mirror-finished, for example, by polishing. Further, the mirror surface may be a surface that suppresses light scattering and returns the light to the original direction. The light reflecting portion 3 may include a metal body 31 having a light reflecting surface 3a as shown in FIG. 3 (a), or may be made of metal or non-metal as shown in FIG. 3 (b). The metal film 32 having the light reflecting surface 3a formed on one end surface of the support 33 may be included. The material forming the light reflecting surface 3a (that is, the material forming the metal body 31 or the metal film 32 described above) includes, for example, at least one metal selected from Ag, Ag alloy, Au, Au alloy, Al, and Al alloy. But it's okay. The diameter of the light reflecting portion 3 is, for example, in the range of 0.5 to 0.7 mm, and the length in the longitudinal direction D1 is, for example, in the range of 0.5 to 5 mm. The shorter the length of the light reflecting portion 3, the smaller the tip portion of the medical laser light guide 1A can be made. Further, as the length of the light reflecting portion 3 is longer, the heat capacity of the light reflecting portion 3 is larger, and the heat generation due to the absorption of light can be reduced. The method of forming the metal film 32 is, for example, vapor deposition, plating or the like.

  Referring back to FIG. The tube 4 accommodates the light guide body 2 and the light reflection section 3 therein in order to protect the light guide body 2 and the light reflection section 3. The tube 4 of the present embodiment has a main body portion 41 and a tip portion 42. The main body 41 is a cylindrical member made of a resin having a light transmitting property. In addition, having a light transmittance means having a transmittance of 80% or more in a wavelength range including a wavelength of light. When the wavelength of light is included in the visible light range, the main body 41 may be transparent. When the wavelength of light is in the red region such as 664 nm, for example, a polyurethane-based or nylon-based colorless transparent resin can be used as the material of the tube 4. The main body 41 has a uniform inner diameter and outer diameter in the axial direction (that is, the longitudinal direction D1 of the light guide 2). The inner diameter of the main body 41 is, for example, 0.5 to 1.7 mm, and the outer shape is, for example, 1.0 to 2.0 mm. The tip 42 has a hemispherical shape having the same outer diameter as the body 41, and is welded or bonded to the tip of the body 41. That is, the tip of the main body 41 is hermetically sealed by the circular end surface formed on the tip 42. The body 41 and the tip 42 may be integrally formed. A gap is provided between the inner side surface 41 a of the main body 41 and the light guide 2, and the gap is filled with air. Of course, the gap may be filled with a liquid or gel substance having a refractive index lower than that of the cladding 6 of the light guide 2 and transparent to the light wavelength. The outer peripheral surface 3b of the light reflecting portion 3 may be arranged at a distance from the inner side surface 41a of the main body 41, or may be in close contact with the inner side surface 41a of the main body 41. The light guide 2 is bent in the main body 41, and the tip surface 2a is pressed against the light reflection surface 3a by the restoring force of the light guide 2.

  FIG. 4 is a side view showing the light guide 2. As shown in FIG. 4, the light guide 2 has a base end portion 21, a light diffusion portion 22, and a tip end portion 23. The base end portion 21, the light diffusion portion 22, and the tip end portion 23 are arranged side by side in this order along the longitudinal direction D1 (optical axis direction) of the light guide 2. Specifically, the distal end portion 23 is provided at a position including the distal end surface 2a, and the light diffusion portion 22 is located between the distal end portion 23 and the proximal end portion 21 in the longitudinal direction D1 of the light guide 2. ing. The light to be applied to the living tissue is input from one end of the base end portion 21 on the side opposite to the light diffusion portion 22. Therefore, a light source (not shown) that outputs light to be applied to the living tissue can be optically connected to the one end of the base end portion 21. The intensity of the light emitted from the light diffusion portion 22 is within the range of 100 to 500 mW, for example.

  Since the base end portion 21, the light diffusion portion 22, and the tip end portion 23 are each a part of the light guide body 2, the core 5 extending in the longitudinal direction D1 of the light guide body 2 and the clad 6 that covers the core 5 (FIG. 2)). The core 5 and the clad 6 are required at the tip end portion 23, but the core 5 and the clad 6 are optional elements at the base end portion 21 and the light diffusion portion 22. The base end portion 21 and the light diffusing portion 22 may be configured by only a region having a single refractive index, for example. In addition, in the present embodiment, the base end portion 21, the light diffusing portion 22, and the tip end portion 23 are configured by a single member (one optical fiber), but these may be members separate from each other. .. In that case, those members are integrated by being fixed (for example, adhered) to each other.

  The light diffusion portion 22 is a portion that diffuses the light received from the base end portion 21 laterally from the outer peripheral surface 22a. There are various structures for diffusion, and for example, one or both of concaves and convexes for light diffusion are formed on the outer peripheral surface 22a of the light diffusion portion 22, or inside the light diffusion portion 22 for light diffusion. There is a method of filling fine pores (or a scattering material). FIG. 5A is a side view showing the light diffusion portion 22 of the present embodiment in a partially enlarged manner. FIG. 5B is an enlarged cross-sectional view of the light diffusion portion 22 along the optical axis direction (longitudinal direction D1). As shown in these figures, in the present embodiment, a plurality of recesses (grooves) 22b are formed in the outer peripheral surface 22a of the light diffusion portion 22. These grooves 22b are formed by, for example, laser processing or mechanical processing, and their cross-sectional shape is, for example, V-shaped. Further, the depth of these grooves 22b reaches the core 5 of the light diffusion portion 22. Each of the plurality of grooves 22b is arranged along the circumferential direction of the light diffusion portion 22, and the plurality of grooves 22b are arranged along the longitudinal direction D1 of the light guide 2. The extending direction of the groove 22b is not limited to this, and may extend, for example, along the longitudinal direction D1. Further, the unevenness for light diffusion is not limited to such a groove 22b, and for example, the outer peripheral surface 22a of the light diffusion portion 22 may be a rough surface. The rough surface refers to a surface that has been roughened such as sandblasting, chemical etching, and sanding.

  The light that has entered the light diffusing portion 22 from the base end portion 21 diffuses laterally from the outer peripheral surface 22a every time it advances toward the tip end surface 2a. Therefore, the light intensity gradually decreases as it approaches the end of the light diffusion portion 22 on the tip surface 2a side. However, in order to irradiate the affected area with light uniformly, it is preferable that the intensity distribution of the emitted light is uniform over the longitudinal direction D1 of the light guide 2. In order to solve this problem, in the present embodiment, the distance between the grooves 22b is gradually narrowed toward the end of the light diffusion portion 22 on the side of the tip surface 2a. In other words, the degree of diffusion of light from the outer peripheral surface 22a of the light diffusing portion 22 increases as it approaches the end of the light diffusing portion 22 on the side of the front end surface 2a.

  Referring back to FIG. The tip portion 23 is a portion that guides light (hereinafter, referred to as afterglow) that is left without being diffused laterally in the light diffusion portion 22. The tip portion 23 is located between the light diffusion portion 22 and the light reflection portion 3. As described above, the tip portion 23 includes the tip surface 2a of the light guide 2. In other words, the end surface of the tip portion 23 on the light reflecting portion 3 side constitutes the tip surface 2a of the light guide 2. The average intensity of light emitted from the outer peripheral surface 23a in the portion having the length L on the front end side of the distal end portion 23 (that is, a value obtained by dividing the total intensity of light emitted from the outer peripheral surface 23a by the length L. Light diffusion The degree is also the average intensity of light emitted from the outer peripheral surface 22a of the light diffusion portion 22 (a value obtained by dividing the total intensity of light emitted from the outer peripheral surface 22a by the length of the light diffusion portion 22). Less than). In the present embodiment, the tip portion 23 is a non-diffusing portion that hardly diffuses light. That is, the outer peripheral surface 23a of the tip portion 23 is not subjected to any uneven processing such as grooves and rough surfaces, and the outer peripheral surface 23a is smooth (smooth surface). In other words, the outer peripheral surface 23a is flat along the longitudinal direction D1. The length of the tip portion 23 in the longitudinal direction D1 is longer than the minimum interval between the plurality of grooves 22b formed in the light diffusion portion 22. The length of the tip portion 23 is, for example, 0.5 to 5 mm. As described above, in the present embodiment, the intervals between the plurality of grooves 22b are gradually narrowed toward the end of the light diffusion portion 22 on the side of the front end surface 2a. Therefore, the minimum distance between the plurality of grooves 22b refers to the distance between the two grooves 22b closest to the tip surface 2a.

  Referring back to FIGS. 1 (a) and 1 (b). The medical laser light guide 1A further includes an X-ray opaque marker 7. The X-ray opaque marker 7 includes a material that blocks X-rays (such as Pt), and is made of a material that blocks X-rays in one example. When the medical laser light guide 1A is inserted into a living body, the living body is irradiated with X-rays, and the position of the X-ray opaque marker 7 is visually confirmed in the obtained X-ray transmission image to thereby perform light diffusion. The current position of the section 22 can be easily known. The X-ray opaque marker 7 of the present embodiment has a ring shape extending along the longitudinal direction D1 (optical axis direction) of the light guide 2, and is fitted in a portion of the base end portion 21 near the light diffusion portion 22. Has been. The radiopaque marker 7 may be fixed to the base end portion 21 by adhesion, crimping, or the like. When the light reflecting portion 3 contains a metal material, the light reflecting portion 3 can also have the same function as the X-ray opaque marker 7. The constituent material of the X-ray opaque marker 7 includes an X-ray shielding material such as Pt or its alloy, Au or its alloy.

  In the medical laser light guide 1A, light (for example, infrared light) for treating an affected area is input from one end side of the base end portion 21 of the light guide 2. This light propagates in the base end portion 21 and reaches the light diffusion portion 22. In the light diffusion portion 22, this light is emitted to the side of the outer peripheral surface 22a while being diffused. The afterglow that has not passed through the light diffusing portion 22 propagates through the tip portion 23 to reach the light reflecting surface 3a, is then reflected by the light reflecting surface 3a, and propagates through the tip portion 23 again. Return to the light diffusion unit 22. Then, the afterglow is emitted to the side of the outer peripheral surface 22a while being diffused.

  The action and effect obtained by the medical laser light guide 1A according to the present embodiment described above will be described together with the problems of the comparative example. FIG. 6 shows, as a comparative example, how light is emitted from the side surface of the medical laser light guide in which the light guide does not have the distal end portion 23 (that is, the light guide includes only the base end portion 21 and the light diffusion portion 22). FIG. In the same figure, a graph G1 showing the distribution of light emission intensity (emitted light intensity) in the longitudinal direction D1 is also shown. Here, the emitted light intensity is, for example, at each position in the longitudinal direction of the medical laser light guide 1A, a core diameter of 0.5 mm with one end opposed to the surface of the tube 4 with a gap of 0.3 mm, It can be evaluated by the intensity of light obtained through a light guide having a numerical aperture of 0.5. When the light guide does not have the tip portion 23, the light reflected by the light reflecting portion 3 is likely to be emitted laterally from the vicinity of the tip of the light guide (arrow P1 in the figure). Specifically, when light is diffused laterally in the light diffusing section 22, the angular component of light is not restricted by the NA (numerical aperture) of the light guide 2. Therefore, much of the light reflected by the light reflecting surface 3a cannot return to the core 5 of the light guide 2. As a result, the intensity of the emitted light near the tip of the light guide 2 becomes large (portion E1 of the graph G1 in the figure), the distribution of the intensity of the emitted light is disturbed, and the uniformity deteriorates.

  FIG. 7 shows how light is emitted from the medical laser light guide 1A of the present embodiment. In the same figure, a graph G2 showing the distribution of the intensity of emitted light in the longitudinal direction D1 is also shown. In the medical laser light guide 1A of the present embodiment, the tip portion 23 is interposed between the light diffusion portion 22 and the light reflection surface 3a. The tip portion 23 includes a tip surface 2a facing the light reflecting surface 3a, a core 5 extending in the longitudinal direction D1, and a clad 6 (see FIG. 2) covering the core 5. In this case, the light passing through the tip portion 23 is restricted by the NA of the light guide 2. Therefore, it is difficult for light having a large angle component to reach the light reflecting surface 3a. Therefore, most of the light reflected by the light reflecting surface 3 a is re-confined in the core 5 of the tip portion 23. Further, the average intensity of light emitted from the outer peripheral surface 23a of the portion having the length L on the distal end side of the distal end portion 23 (light diffusion degree) is the average intensity of light emitted from the outer peripheral surface 22a of the light diffusion portion 22. Since it is lower than (light diffusion degree), the light re-confined in the core 5 of the tip portion 23 propagates to the light diffusion portion 22 while being prevented from being emitted from the outer peripheral surface 23a of the tip portion 23, The light is emitted from the outer peripheral surface 22a of 22 while being diffused laterally. Therefore, since the light reflected by the light reflecting portion 3 is less likely to be emitted laterally from the vicinity of the tip of the light guide body 2, the light intensity near the tip of the light guide body 2 becomes small (part E2 of the graph G2 in the figure). ), The uniformity of the light intensity in the longitudinal direction D1 of the light guide 2 can be effectively suppressed. The emitted light in the vicinity of the tip of the light guide body 2 is limited to that caused by minute irregularities on the tip surface 2a and the light reflection surface 3a, and its intensity is extremely small.

  As in the present embodiment, the light reflecting portion 3 may have a columnar shape and have a thickness with the longitudinal direction D1 of the light guide 2 as the central axis direction. For example, when a light reflection film is formed on the tip surface 2a of the light guide 2, since the heat capacity is extremely small, even if the absorption is only a few percent, extreme heat is generated, and the tip portion of the medical laser light guide has a high temperature. There is a risk of becoming. Then, if blood or the like adheres to the tip portion of the medical laser light guide that has reached a high temperature, there is a risk that the medical laser light guide will be burned out starting from that point. Since the light reflecting portion 3 has a cylindrical shape, the heat capacity of the light reflecting portion 3 becomes larger than that in the case where a light reflecting film is formed on the tip surface 2a of the light guide 2. Therefore, it is possible to reduce the temperature rise of the light reflecting portion 3 due to the absorption of light.

  As in the present embodiment, the outer peripheral surface 22a of the light diffusion portion 22 may have one or both of concave and convex for light diffusion, and the outer peripheral surface 23a of the tip portion 23 may be smooth. For example, with such a structure, the average intensity (light diffusion degree) of the light emitted from the outer peripheral surface 23a of the end portion 23 having the length L on the front end side is emitted from the outer peripheral surface 22a of the light diffusion portion 22. Can be made lower than the average intensity of light (the degree of light diffusion).

  As in the present embodiment, the outer peripheral surface 22a of the light diffusion portion 22 may have a plurality of grooves 22b. For example, with such a structure, the light diffusing section 22 that diffuses light laterally from the outer peripheral surface 22a can be easily realized. In this case, the light diffusion portion 22 has a core 5 extending in the longitudinal direction D1 of the light guide 2 and a clad 6 covering the core 5, and the depth of the plurality of grooves 22b reaches the core 5 of the light diffusion portion 22. May be. This makes it possible to easily increase the average intensity of light emitted from the light diffusing unit 22 (light diffusion degree). Further, in this case, each of the plurality of grooves 22b is along the circumferential direction of the light diffusion portion 22, the plurality of grooves 22b are arranged in the longitudinal direction D1, and the length of the tip portion 23 in the longitudinal direction D1 is plural. It may be longer than the minimum distance between the grooves 22b. Thereby, the light diffusion portion 22 and the tip portion 23 are clearly distinguished.

  As described above, the outer peripheral surface 22a of the light diffusion portion 22 may be a rough surface. For example, even with such a structure, the light diffusing unit 22 that diffuses light laterally from the outer peripheral surface 22a can be easily realized.

  When the gap between the front end surface 2a of the light guide 2 and the light reflection surface 3a changes, the lateral light intensity distribution changes. Therefore, it is desirable that the tip surface 2a and the light reflecting surface 3a are always in contact with each other. In the present embodiment, the light guide 2 is bent inside the tube 4, and the tip surface 2a is pressed against the light reflection surface 3a by the restoring force of the light guide 2. Thereby, even when the medical laser light guide 1A is bent in the living body, the contact state between the tip surface 2a of the light guide 2 and the light reflecting surface 3a of the light reflecting portion 3 is easily maintained. Therefore, even when the medical laser light guide 1A is bent, it is possible to suppress the formation of a gap between the tip surface 2a and the light reflecting surface 3a, and to reduce the light intensity in the longitudinal direction D1 of the light guide 2. It is possible to effectively suppress deterioration of uniformity.

  As in the present embodiment, the material forming the light reflecting surface 3a may include at least one of Ag, Ag alloy, Au, or Au alloy. These metals have high reflection characteristics with respect to light (especially red light near the wavelength of 664 nm). Therefore, it is possible to improve the light utilization efficiency, reduce the light absorption in the light reflecting portion 3, and suppress the temperature rise of the light reflecting portion 3.

  As in the present embodiment, the light reflecting portion 3 may include the metal body 31 having the light reflecting surface 3a or the metal film 32 having the light reflecting surface 3a. Thereby, the light reflecting portion 3 having the light reflecting surface 3a can be easily manufactured.

  As in the present embodiment, at least one of the light reflection surface 3a and the tip surface 2a of the light guide 2 may be a mirror surface. As a result, it is possible to increase the reflectance with respect to the light that has passed through the light diffusing unit 22, improve the light utilization efficiency, reduce the light absorption in the light reflecting unit 3, and suppress the temperature rise of the light reflecting unit 3. ..

  Here, the length of the tip portion 23 in the longitudinal direction D1 will be examined. FIG. 8 is a diagram schematically showing a cross section of the tip portion 23 and the light reflecting portion 3. 8A shows the case where the tip 23 is sufficiently long, and FIG. 8B shows the case where the tip 23 is short. In these figures, a graph G3 showing the distribution of outgoing light intensity of outgoing light (light toward the light reflecting portion 3) in the longitudinal direction D1 and returning light in the longitudinal direction D1 (reflected at the light reflecting portion 3). A graph G4 showing the distribution of the intensity of emitted light (light) is also shown.

  As shown in (a) of FIG. 8, when the light P2 propagating inside the core 5 of the light diffusing section 22 hits the groove 22b (see (b) of FIG. 5), the scattered light becomes diffused outgoing light P3. Then, the light is emitted from the outer peripheral surface 22a to the side of the light guide 2, but part of the scattered light is diffused toward the inside of the light guide 2. In the groove 22b near the tip portion 23, a part of the scattered light diffuses toward the inside of the tip portion 23 (lights P4 and P5 in the figure). Of these diffused lights, the light P4 that enters the interface with an incident angle smaller than the critical angle of the interface between the core 5 and the cladding 6 passes through the interface and is emitted to the side of the tip portion 23. On the other hand, the light P5 incident on the interface with an incident angle larger than the critical angle of the interface between the core 5 and the clad 6 is reflected at the interface, propagates inside the core 5, and reaches the light reflecting surface 3a. Therefore, even after the light P5 is reflected by the light reflecting surface 3a, the light P5 propagates toward the light diffusing portion 22 inside the tip portion 23 while being reflected at the interface between the core 5 and the clad 6.

  However, when the tip portion 23 is short as shown in FIG. 8B, the following phenomenon occurs. A part of the light P4 that has diffused in the groove 22b near the tip portion 23 and has proceeded to the inside of the tip portion 23 reaches the light reflecting surface 3a before reaching the interface between the core 5 and the clad 6. The light P4 is reflected by the light reflecting surface 3a, then enters the interface between the core 5 and the cladding 6 with an incident angle smaller than the critical angle, passes through the interface, and is directed to the side of the tip portion 23. Emit. Due to such a phenomenon, the outgoing light intensity of the backward light locally increases near the light reflecting surface 3a (part E3 of the graph G4). Since the increase in the outgoing light intensity of the backward light is suppressed as the tip portion 23 becomes longer, it is desirable to set the length of the tip portion 23 according to the required degree of suppression of the outgoing light intensity.

この数式（１）を変形すると、角度θに関する数式（２）が得られる。

数式（２）及び図９から、長さＬは下記の数式（３）のように表される。

Here, the length required for the tip portion 23 to prevent the above-mentioned light P4 from reaching the light reflecting surface 3a will be described. FIG. 9 is a diagram schematically showing the cross-sectional structure of the tip portion 23. The arrow A1 in the figure indicates a virtual optical path having an incident angle equal to the critical angle of the interface between the core 5 and the cladding 6 (in other words, corresponding to the numerical aperture NA of the tip 23). The tip of the arrow A1 reaches the boundary (point Q1) between the core 5 and the clad 6 on the tip surface 2a. Further, the angle formed by the arrow A1 and the interface between the core 5 and the clad 6 is θ, the intersection of the base end of the arrow A1 and the interface between the core 5 and the clad 6 is Q2, and the point Q2 and the tip surface 2a are Is L, the diameter of the core 5 is D, and the refractive index of the core 5 is n. At this time, the numerical aperture NA is represented by the following mathematical expression (1).

By transforming this equation (1), equation (2) regarding the angle θ is obtained.

From the formula (2) and FIG. 9, the length L is expressed as the following formula (3).

  The length of the tip portion 23 in the longitudinal direction D1 needs to be greater than or equal to this length L. Then, at least the average intensity (light diffusion degree) of the light emitted from the outer peripheral surface 23a of the length L on the front end side of the front end portion 23 is equal to that of the light emitted from the outer peripheral surface 22a of the light diffusion portion 22. It must be lower than the average intensity (degree of light diffusion). By satisfying this condition, the light reflected by the light reflecting portion 3 becomes difficult to be emitted laterally from the vicinity of the tip of the light guide 2. Therefore, it is possible to effectively suppress the deterioration of the uniformity of the light intensity in the longitudinal direction D1 of the light guide 2. In one example, NA = 0.5, core diameter D = 0.5 mm, and refractive index n = 1.49. In this case, L = 1.40 mm.

(Modification)
FIG. 10A is a perspective view showing a distal end portion of a medical laser light guide 1B according to a modification of the above embodiment. FIG. 10B is a sectional perspective view of the distal end portion of the medical laser light guide 1B. Note that the tube 4 is not shown in these figures. The medical laser light guide 1 </ b> B according to this modification includes a light reflecting portion 34 instead of the light reflecting portion 3. The light reflecting portion 34 has a cylindrical portion 35 and a tubular portion 36. The configuration of the cylindrical portion 35 is the same as the configuration of the light reflecting portion 3 of the above-described embodiment, including the point having the light reflecting surface 3a. The tubular portion 36 has a cylindrical shape having a central axis along the longitudinal direction D1, and is coaxially fitted to the outer peripheral surface of the columnar portion 35. The tubular portion 36 projects toward the light guide 2 side with respect to the light reflecting surface 3 a of the columnar portion 35 and covers at least a part of the outer peripheral surface 23 a of the tip portion 23.

  The inner side surface of the cylindrical portion 36 is a light reflecting surface 3c different from the light reflecting surface 3a. The light reflecting surface 3c faces the outer peripheral surface 23a of the tip portion 23 with a space therebetween. The light reflecting surface 3c may be in contact with the outer peripheral surface 23a. The light reflecting surface 3c can be made of the same material as the light reflecting surface 3a. That is, the material forming the light reflecting surface 3c may include at least one of Ag, Ag alloy, Au, or Au alloy. In one example, the tubular portion 36 may be constructed of these materials.

  As in this modification, the light reflecting portion 34 may further include a light reflecting surface 3c facing the outer peripheral surface 23a of the tip portion 23, in addition to the light reflecting surface 3a. As a result, a small amount of diffused light generated near the tip of the light guide 2 can be returned to the tip 23, so that the uniformity of the light intensity in the longitudinal direction D1 of the light guide 2 is more effectively reduced. Can be suppressed. In this case, the light reflecting portion 34 may have a tubular portion 36 that covers at least a part of the outer peripheral surface 23a of the tip portion 23 and includes the light reflecting surface 3c. Thereby, the light reflecting surface 3c can be easily realized. In this case, the material forming the light reflecting surface 3c may include at least one of Ag, Ag alloy, Au, or Au alloy. These metals have high reflection characteristics with respect to light (especially red light near the wavelength of 664 nm). Therefore, it is possible to improve the light utilization efficiency, reduce the light absorption in the tubular portion 36, and suppress the temperature rise of the tubular portion 36.

  FIG. 11A is a side view showing a medical laser light guide 1C according to another modification of the above embodiment. FIG. 11B is a side view showing the light guide body 52 from which the light reflecting portion 3 and the tube 4 are removed from the medical laser light guide 1C. The light guide body 52 has a tip portion 53 different from the tip portion 23 described above. The tip portion 53 has an enlarged diameter portion 54 whose diameter increases toward the light reflecting portion 3. The enlarged diameter portion 54 has, for example, a truncated cone shape. The enlarged diameter portion 54 has an inclined surface 54a that increases in diameter from the outer peripheral surface 53a of the tip portion 53 toward the light reflecting portion 3, and a tip surface 54b that contacts the light reflecting portion 3. The tip surface 54b is, for example, a mirror surface, and may be mirror-finished by polishing.

  FIG. 12 is an enlarged cross-sectional view of the tip portion 53 of the light guide body 52, the light reflecting portion 3 and the tube 4. As shown in FIG. 12, the light guide 52 is an optical fiber having a core 55 and a clad 56, for example. The core 55 may be made of glass, and the clad 56 may be made of plastic (resin). In this case, the light guide 52 is an HPCF (Hard Plastic Clad Fiber) in which the core 55 is glass and the clad 56 is plastic. For example, the inner surface 4a of the tube 4 is circular, the tip surface 54b is circular, and the radius R1 of the tip surface 54b is less than or equal to the radius R2 of the inner surface 4a of the tube 4. The radius R1 of the tip surface 54b may be smaller than the radius R2 of the inner surface 4a of the tube 4. In this case, the expanded diameter portion 54 can be inserted into the inner surface 4a of the tube 4 more easily.

  FIG. 13 is a cross-sectional view showing the tip portion 53A of the light guide body 52A made of a material different from that of FIG. 12, the light reflecting portion 3 and the tube 4. As shown in FIG. 13, for example, both the core 55A and the clad 56A of the light guide 52A are made of plastic. In this case, the light guide 52 may be a POF (Plastic Optical Fiber) in which both the core 55A and the clad 56A are made of plastic.

  Next, an example of a method of forming the enlarged diameter portion 54A on the tip portion 53A of the light guide body 52A will be described with reference to FIG. Since the method of forming the expanded diameter portion 54 on the tip portion 53 of the light guide body 52 can be the same as the method of forming the expanded diameter portion 54A, the description of the method of forming the expanded diameter portion 54 is omitted. To do. FIG. 14 is a cross-sectional view showing the light guide body 52A and the pressed member 61 against which the front end portion 53A of the light guide body 52A is pressed. The pressed member 61 has a flat surface 61a against which the tip portion 53A is pressed, and the flat surface 61a has a high temperature. When the front end portion 53A is pressed against the flat surface 61a of the pressed member 61 which has been heated to a high temperature, the clad 56A of the front end portion 53A is softened and deformed so as to spread outward in the radial direction of the light guide body 52A. In this way, the expanded diameter portion 54A is formed by deforming the clad 56A of the distal end portion 53A so as to expand outward in the radial direction of the light guide body 52A. Further, the flat surface 61a of the pressed member 61 may be a mirror surface. In this case, since the front end surface 54b of the expanded diameter portion 54A is a mirror surface, light scattering at the front end surface 54b is suppressed, and light loss can be suppressed. As a result, the utilization efficiency of light can be further improved.

  When the tip end portion 53A is pressed against the flat surface 61a of the pressed member 61 to form the enlarged diameter portion 54A, at least one of the pressing force of the tip end portion 53A to the flat surface 61a, the pressing time, and the temperature of the flat surface 61a. By controlling this, it is possible to adjust the inclination degree (spreading amount) of the inclined surface 54a of the expanded diameter portion 54A and the radius R1 of the tip end surface 54b. Therefore, since the radius R1 of the distal end surface 54b can be adjusted, it is possible to reduce the possibility that the expanded diameter portion 54A does not enter the inner surface 4a of the tube 4. As an example, when the light guide body 52 is an acrylic resin optical fiber, the expanded diameter portion 54A can be easily formed by pressing the tip portion 53A against the flat surface 61a in a state where the temperature of the flat surface 61a is 120 ° C. it can.

  FIG. 15 is a cross-sectional view showing the light guide body 52A, the pressed member 61, and the diameter enlargement suppressing member 62 that suppresses the enlargement of the enlarged diameter portion 54A. The diameter enlargement suppressing member 62 has, for example, a half-split structure, and is composed of a first half portion 62a and a second half portion 62b. The diameter enlargement suppressing member 62 has, for example, a cylindrical shape, and has a first inner peripheral surface 62c extending in the axial direction of the diameter enlargement suppressing member 62 and an axial end of the first inner peripheral surface 62c. It has a tapered surface 62d whose diameter increases toward the end surface 62e. When the end surface 62e of the diameter enlargement suppressing member 62 contacts the flat surface 61a of the pressed member 61, the tapered surface 62d of the diameter enlargement suppressing member 62 faces the flat surface 61a. Then, the resin of the light guide body 52A that has been melted by heat enters the space defined by the flat surface 61a and the tapered surface 62d to form the expanded diameter portion 54A. At this time, the tapered surface 62d of the diameter enlargement suppressing member 62 suppresses the diameter expansion of the diameter expansion portion 54A beyond a certain level.

  As described above, in the medical laser light guide 1C according to the modified example, the distal end portion 53A of the light guide body 52A has the expanded diameter portion 54A that expands in diameter toward the light reflection portion 3. As a result, the diameter of the tip surface 54b of the tip portion 53A facing the light reflecting portion 3 can be increased. Therefore, when the light guide body 52A is inserted into the tube 4, the position of the light guide body 52A in the tube 4 can be stabilized, and the tip end surface 54b of the tip end portion 53A facing the light reflecting portion 3 can be fixed. It is possible to make sure contact with the light reflecting portion 3.

  Specifically, in the case of a light guide having no expanded portion, the tip of the light guide may be bent due to the large distance between the inner surface 4a of the tube 4 and the outer surface of the light guide. In this case, it may happen that a part of the tip surface of the light guide does not come into contact with the light reflecting portion 3. In this case, the amount of light returning from the light reflecting portion 3 to the light guide changes, so that the amount of light radiated laterally from the light guide changes and the intensity profile of the light radiated laterally changes. May change. On the other hand, it is conceivable to increase the outer diameter of the light guide so as to reduce the distance between the inner surface 4a of the tube 4 and the inner surface 4a. However, in this case, there is a concern that the ring-shaped X-ray opaque marker 7 cannot be inserted into the light guide body, and it may be difficult to insert the light guide body into the inner surface 4a of the tube 4.

  On the other hand, in the above-mentioned medical laser light guide 1C, the tip portion 53A of the light guide body 52A is provided with the enlarged diameter portion 54A that increases in diameter toward the light reflecting portion 3, so that a ring to the light guide body 52A is formed. It is possible to easily insert the X-ray opaque marker 7 and the light guide body 52A into the inner surface 4a of the tube 4. Further, since the tip end portion 53A has the enlarged diameter portion 54A, it is possible to suppress a decrease in light from the light reflection portion 3 due to the tip end surface of the light guide not contacting the light reflection portion 3. Moreover, since the position of the light guide 52A in the tube 4 can be stabilized, the intensity profile of the light diffused from the light diffusion portion can be stabilized.

  The medical laser light guide 1C includes a light-transmitting tube 4 that accommodates the light guide 52A and the light reflecting portion 3, the expanded diameter portion 54A includes a tip surface 54b, and the radius R1 of the tip surface 54b is the tube 4. The radius R2 of the inner surface 4a may be less than or equal to R2. Thereby, since the radius R1 of the tip end surface 54b formed in the expanded diameter portion 54A is equal to or smaller than the radius R2 of the inner surface 4a of the tube 4, it is possible to easily insert the expanded diameter portion 54A into the tube 4.

  In the medical laser light guide 1C, the tip surface 54b may be a mirror surface. As a result, the reflectance of the light from the light reflecting portion 3 with which the tip surface 54b is in contact can be increased, and the light utilization efficiency can be increased.

  In the medical laser light guide 1C, the clad 56A may be made of plastic. Thus, by pressing the tip end portion 53A of the light guide body 52A in a high temperature state, the tip end portion 53A is melted and the expanded diameter portion 54A can be easily formed. That is, the tip of the light guide 52A can be easily processed.

  The medical laser light guide according to the present invention is not limited to the above-described embodiment, but various modifications can be made. For example, although the case where the light guided by the light guide is red light has been illustrated in the above embodiment, the light guided by the light guide may be visible light other than red light, infrared light, or the like. It may have other wavelengths. Further, in the above embodiment, the tip end surface of the light guide body is pressed against the light reflection surface of the light reflection portion due to the bending of the light guide body. And may be bonded to each other via an adhesive or the like that is transparent to the wavelength of light (for example, red region). Further, in the above-described embodiment, the case where the light reflecting portion has a cylindrical shape is illustrated, but the shape of the light reflecting portion is not limited to this. For example, the light reflecting portion may be a light reflecting film formed on the tip surface of the light guide. Further, in the above embodiment, the case where the outer peripheral surface of the tip end portion of the light guide is smooth is illustrated, but the outer peripheral surface of the tip end portion may be formed with unevenness that is smaller than that of the light diffusion portion. Further, in the above embodiment, the medical laser light guide 1C including the light guide body 52A having the plastic clad 56A has been described. However, the material of the light guide of the medical laser light guide may be a material other than plastic such as glass.

  1A, 1B, 1C ... Medical laser light guide, 2, 52, 52A ... Light guide, 2a ... Tip surface, 3 ... Light reflecting portion, 3a, 3c ... Light reflecting surface, 3b ... Outer peripheral surface, 4 ... Tube, 4a ... inner surface, 5, 55, 55A ... core, 6, 56, 56A ... cladding, 7 ... X-ray opaque marker, 21 ... base end portion, 22 ... light diffusing portion, 22a ... outer peripheral surface, 22b ... groove, 23 , 53, 53A ... Tip part, 23a ... Outer peripheral surface, 31 ... Metal body, 32 ... Metal film, 33 ... Supporting body, 34 ... Light reflecting part, 35 ... Cylindrical part, 36 ... Cylindrical part, 41 ... Main body part, 41a ... inner side surface, 42 ... tip part, C ... central axis line, D1 ... longitudinal direction.

Claims (18)

An elongated light guide having a tip surface,
A light reflecting portion having a light reflecting surface facing the tip surface,
Equipped with
The light guide is
The base end,
The light guide includes the tip surface, the diameter is D, the refractive index is n, the core extends in the longitudinal direction of the light guide, and the cladding covers the core, and the numerical aperture is NA. A tip having a length in the longitudinal direction of L equal to or greater than L defined by the following mathematical formula,

A light diffusing portion that is located between the base end portion and the tip end portion in the longitudinal direction of the light guide body, and diffuses light received at the base end portion laterally from the outer peripheral surface,
Have
The medical laser light guide, wherein the average intensity of light emitted from the outer peripheral surface of the portion having the length L on the distal end side of the distal end portion is lower than the average intensity of light emitted from the outer peripheral surface of the light diffusing portion.   The medical laser light guide according to claim 1, wherein the light reflecting portion has a columnar shape having a longitudinal direction of the light guide body as a central axis direction.   The medical laser light guide according to claim 1 or 2, wherein the outer peripheral surface of the light diffusing portion has one or both of concave and convex for light diffusion, and the outer peripheral surface of the tip portion is smooth.   The medical laser light guide according to claim 3, wherein the outer peripheral surface of the light diffusion portion has a plurality of grooves. The light diffusing section has a core extending in the longitudinal direction of the light guide, and a clad covering the core,
The medical laser light guide according to claim 4, wherein the depths of the plurality of grooves reach the core of the light diffusion portion. Each of the plurality of grooves is along the circumferential direction of the light diffusion portion, the plurality of grooves are arranged in the longitudinal direction of the light guide,
The medical laser light guide according to claim 4 or 5, wherein the length of the tip portion in the longitudinal direction of the light guide is longer than the minimum interval between the plurality of grooves.   The medical laser light guide according to claim 3, wherein an outer peripheral surface of the light diffusion portion is a rough surface. Further comprising a light-transmissive tube that houses the light guide and the light reflector,
8. The light guide body is bent inside the tube, and the tip end surface is pressed against the light reflection surface by the restoring force of the light guide body. Medical laser light guide.   The medical laser light guide according to claim 1, wherein the material forming the light reflecting surface includes at least one of Ag, Ag alloy, Au, or Au alloy.   The medical laser light guide according to claim 1, wherein the light reflecting portion includes a metal body or a metal film having the light reflecting surface.   The medical laser light guide according to any one of claims 1 to 10, wherein at least one of the light reflection surface and the tip surface is a mirror surface.   The medical laser light guide according to any one of claims 1 to 11, wherein the light reflecting portion further has another light reflecting surface facing the outer peripheral surface of the tip portion.   The medical laser light guide according to claim 12, wherein the light reflecting portion has a cylindrical portion that covers at least a part of an outer peripheral surface of the tip portion and includes the another light reflecting surface.   The medical laser light guide according to claim 13, wherein the material forming the other light reflecting surface includes at least one of Ag, Ag alloy, Au, or Au alloy. The tip end portion of the light guide body has an enlarged diameter portion that increases in diameter toward the light reflecting portion,
The medical laser light guide according to any one of claims 1 to 14. A light-transmissive tube that accommodates the light guide and the light reflector,
The enlarged diameter portion includes the tip end surface,
The radius of the tip surface is less than or equal to the radius of the inner surface of the tube,
The medical laser light guide according to claim 15. The tip surface is a mirror surface,
The medical laser light guide according to claim 16. The clad is made of plastic,
The medical laser light guide according to any one of claims 15 to 17.

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