JP2007108396A - Light guide and optical irradiation apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light guide capable of taking in light rays entering into an optical fiber bundle in a light guide terminal so as to be parallel to the center axis of primary coated optical fibers in the light guide having a fusion splicing part at the end of the optical fiber bundle. <P>SOLUTION: The light guide is characterized in that it includes the optical fiber bundle composed of a plurality of primary coated optical fibers and thermally fussion-spliced at least in the end part on the light entering end, that the center axis of each primary coated optical fiber situated on the outer side from the center axis of the optical fiber bundle is inclined to the center axis of the optical fiber bundle in the fusion-spliced optical fiber bundle end, and that the entering end face of the optical fiber bundle has a concave shape. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a light guide that transmits light and irradiates an irradiated object, and a light irradiation apparatus including the light guide.

  Conventionally, a light guide has been used as a means for transmitting light emitted from a light emitter such as a laser oscillator to an arbitrary position of an irradiated object.

  Such a light guide usually has a case where an optical fiber strand is used alone and a case where a plurality of optical fiber strands are bundled and used as an optical fiber bundle, depending on the amount of light required and the characteristics of the light emitter. It is used properly.

Of these, when using an optical fiber bundle, it is necessary to condense and solidify the ends, and generally a method of fixing each optical fiber strand with an organic or inorganic adhesive or low melting point glass Is used.

However, in a laser processing machine or an apparatus using a high-power lamp, it is necessary to increase the heat resistance of the end portion because strong light emitted from the light emitter is incident, such as high-frequency heating or an oxyhydrogen burner. There is known a method in which heat is applied from the outside by the above heating means to melt the optical fiber strands themselves and fuse them together.

  Here, as described above, as a method of fusing the ends of the optical fiber bundle by applying heat from the outside, a method disclosed in Patent Document 1 can be cited.

JP-A-57-97503

  This Patent Document 1 focuses the ends of a large number of silica-based optical fiber strands, inserts the converged ends into a glass tube, then applies heat from the outer periphery of the glass tube, A method is shown in which each optical fiber is fused and the gap between the glass tube and each optical fiber is reduced or eliminated.

  Therefore, the light guide manufactured by the above method can form a light guide terminal portion to which each optical fiber is firmly fixed without using a heat-sensitive adhesive, and a large-sized light transmission for large light transmission. Sufficient heat resistance of the terminal portion can be secured against heat from a light source or the like.

  In addition, since the gap between the optical fiber strands in the terminal portion is reduced or eliminated, the core occupancy at the end face is increased, and the light incident efficiency with respect to the light source can be increased.

  However, in the fused portion formed by the above-described method, the gap between the optical fiber strands is reduced or eliminated by the optical fiber strand itself being deformed into a substantially hexagonal shape. The diameter of the fiber bundle is reduced by the ratio of the reduction or erased gap between the optical fiber strands as compared to the diameter of the optical fiber bundle in the unfused portion.

  As a result, in the light guide terminal portion, the optical fiber arranged at a position close to the outer peripheral portion of the optical fiber bundle is a portion fused from an unfused portion (the side far from the end of the optical fiber bundle) ( The central axis of the optical fiber bundle is inclined in the direction of the central axis of the optical fiber bundle, and this inclination increases as the optical fiber strand moves away from the central axis of the optical fiber bundle. The closer to the central axis of the bundle, the smaller, and the central axis of the optical fiber strand and the central axis of the optical fiber bundle are substantially parallel on the central axis of the optical fiber bundle.

  As shown in FIG. 2, when the fused portion of the light guide terminal is cut and polished along a plane A perpendicular to the central axis of the optical fiber bundle in the light guide terminal portion, as shown in FIG. Since the center axis 14 of the fiber strand is not perpendicular to the end face 32 of each optical fiber strand, the light 50 incident on the end face 32 perpendicularly enters the end face 32 and then enters the optical fiber strand. Without being able to proceed along the central axis 14 of the optical fiber, the total reflection is repeated on the inner surface of the clad 12 constituting the optical fiber 10 to reach the output end face 36 of the optical fiber.

  As a result, the light emitted from the light guide emission end includes light having an inclination with respect to the central axis of the optical fiber bundle, and the incident angle of the light incident on the light guide incident end can be maintained. Had the problem of not being able to.

  Under such circumstances, the present invention captures light incident on an optical fiber bundle in parallel with the central axis of the optical fiber in a light guide having a fused portion at the end of the optical fiber bundle. It is an object of the present invention to provide a light guide capable of performing light irradiation and a light irradiation apparatus including the light guide.

To achieve the above object, the present invention provides:
(1) An optical fiber bundle comprising a plurality of optical fiber strands and at least an end portion on the light incident side is heat-sealed,
The central axis of each optical fiber positioned outside the central axis of the optical fiber bundle has an inclination with respect to the central axis of the optical fiber bundle at the end portion of the thermally fused optical fiber bundle,
The light guide characterized in that the shape of the light incident end face of the optical fiber bundle is a concave shape,
(2) The light guide according to (1), wherein the concave shape is a spherical shape,
(3) At least a part of the optical fiber strand has an angle θ2 formed by a light incident surface of the optical fiber strand and a surface perpendicular to the light incident on the light incident surface,
θ2 = cot ⁻¹ (cot θ1− (n2 / (n1sin θ1)))
[However, θ1 is the angle formed by the light incident on the light incident surface of the optical fiber and the central axis of the optical fiber, and n1 is the refractive index of the core constituting the optical fiber. Yes, n2 is the refractive index of the space outside the optical fiber. ]
The light guide according to (1) or (2), wherein the light incident surface is processed so as to satisfy
(4) The light guide according to any one of (1) to (3) above, wherein the optical fiber is made of quartz, multicomponent glass or plastic, and (5) a light emitter that emits light, A light guide for irradiating an irradiated object with light emitted from the light emitter, wherein the light guide is the light guide according to any one of (1) to (4) above. It consists of the light irradiation apparatus characterized by the above.

  According to the present invention, a light guide in which an end portion of an optical fiber bundle is solidified by fusion, the light guide capable of taking light incident on the optical fiber bundle in parallel with the central axis of the optical fiber strand. And the light irradiation apparatus containing this light guide can be provided.

  Hereinafter, embodiments of a light guide and a light irradiation apparatus according to the present invention will be described in detail with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. In addition, the dimensional ratios in the drawings do not necessarily match those described with numerical values in this specification.

The light guide of the present invention is
An optical fiber bundle comprising a plurality of optical fiber strands and at least an end portion on the light incident side is heat-sealed,
The central axis of each optical fiber positioned outside the central axis of the optical fiber bundle has an inclination with respect to the central axis of the optical fiber bundle at the end portion of the thermally fused optical fiber bundle,
The shape of the light incident end face of the optical fiber bundle is a concave shape.
Fig.1 (a) is sectional drawing which shows the terminal part structure of the light guide in the 1st embodiment of the light guide of this invention.

  The light guide 1 is composed of an optical fiber bundle 2 composed of a large number of optical fiber strands 10 and a sleeve 20, and after heat-welding the end portion on the light incident side, the fused portion is cut at a predetermined position. Furthermore, it has the light guide terminal part 30 which gave the concave surface process mentioned later with respect to a cut surface.

As shown in FIG. 1B, the optical fiber 10 is composed of a core 11 made of high-purity quartz having an outer diameter of 190 μm, a cladding layer 12 having an outer diameter of 200 μm, in which quartz is doped with fluorine, and an ultraviolet curable resin. On the other hand, the sleeve 20 has an outer diameter of 12 mm, an inner diameter of 10 mm, and an overall length that are approximately the same as those of the quartz used in the optical fiber 10, and the thermal expansion coefficient and softening temperature are substantially equal. A 35 mm quartz tube is used.

Next, a method for forming a light incident end face in the light guide of FIG. 1 will be described.
As shown in FIG. 2, after inserting about 2000 optical fiber strands 10 in which the coating layer 13 in the vicinity of the end portion of the sleeve 20 is dissolved and removed into the sleeve 20 with the tip protruding about 5 mm, the tip of the sleeve 20 is inserted. To about 10 mm with an oxyhydrogen burner, the optical fiber strands 10 are softened and fused to each other, and at the same time, the sleeve 20 is fused and integrated to form a gentle step on the outer peripheral surface of the sleeve 20. The light guide terminal part 30 having 21 is formed.

Here, the fusion part 31 is more robust in the region closer to the tip (right side in FIG. 2) because the optical fiber strands 10 are more closely fused to each other. Then, there is a possibility that the boundary between the core 11 and the clad 12 of the optical fiber 10 becomes soft and becomes unclear, and when light is incident, the incident light is diffusely reflected at the interface between the core 11 and the clad 12, There is a risk that light transmission efficiency as a guide may be reduced.

  For this reason, it is necessary for the light guide terminal portion 30 formed by fusion to cut and delete the portion where the boundary between the core 11 and the clad 12 becomes unclear, and this cutting position is the optical fiber inside the sleeve 20. This is performed at a position closest to the stepped portion 21 in a range where the strands 10 are fused to each other.

In the light guide 1 shown in FIG. 2, this position is set to a position A where the outer diameter including the sleeve 20 of the fused portion 31 is about 11 mm, and the light guide 1 is cut at this position.

As a result, as shown in FIG. 3, the central axis 14 of the optical fiber 10 is cut at the light guide terminal portion 30 with an inclination angle θ1 in the direction of the central axis 33 of the optical fiber bundle 2. In the light guide terminal portion 30, the inclination angle θ 1 is larger as the optical fiber 10 disposed near the outer periphery of the optical fiber bundle 2, and conversely decreases as it approaches the central axis 33 of the optical fiber bundle 2. The central axis 14 of the nearby optical fiber is substantially parallel to the central axis 33 of the optical fiber bundle 2 in the light guide terminal portion 30.

As shown in FIG. 4, when light 50 is incident perpendicularly to the cut surface 32, the incident light 51 is inclined by θ1a equal to θ1 which is the inclination between the central axis 14 of the optical fiber 10 and the incident light 50. It propagates while repeating total reflection at a certain angle, and at the exit end face 36, the angle with the central axis 14 of the optical fiber is further expanded by refraction, and exits at an angle θ3.

  As will be described later, in the present embodiment, the light guide 1 is subjected to a predetermined concave surface processing on the cut surface 32 of the light guide terminal portion 30, so that the incident end surface of the optical fiber 10 has the inclination angle θ <b> 1 described above. An inclination angle θ2 for compensating the influence is provided so that light incident on the optical fiber strand 10 can be taken in parallel to the central axis 14 of the optical fiber strand. It can be obtained from the inclination angle θ1.

Here, a method for obtaining the inclination angle θ1 and a method for deriving the inclination angle θ2 from the obtained inclination angle θ1 will be described.

FIG. 5 shows an apparatus configuration for measuring the tilt angle θ1.
This measuring apparatus enters a laser beam 140 having a shaped beam diameter into a light guide 101 to be measured, and measures the emission angle θ3 (corresponding to θ3 in FIG. 4) of the emitted light 141, thereby making the light incident. The inclination angle θ1 at the end face is obtained.

The light guide 101 is obtained by fusing the incident end face 101a in accordance with the above-described procedure, cutting it at the position A in FIG. 2 and performing surface polishing, and the outer diameter of the optical fiber bundle at the incident end face is 9 mm. It has become.
The light emitting end face 101b is fixed by an organic adhesive instead of heat fusion, and is subjected to planar polishing in the same manner as the light incident end face 101a.

A laser beam 140 obtained by shaping the radiated light from the He-Cd laser oscillator 110 into a beam diameter of 0.5 mm by the slit 120 is incident on the incident end face 101a.

The incident position of the laser beam 140 on the light incident end face 101a is obtained by moving the incident end face 101a by 1 mm along the X1 axis extending in the radial direction of the optical fiber bundle, and is emitted from the light emitting end face 101b at each incident position. The light intensity distribution is obtained by installing a light intensity meter 130 at a position 150 mm away from the light exit end face 101b and moving the light intensity meter 130 along the X2 axis perpendicular to the central axis of the light guide 101. It is measured.

As shown in FIG. 6, since the measured light intensity distribution has a shape having two peaks, the inclination angle θ3 of the light emitted from the light emitting end face 101b of FIG. Can be calculated.

θ3 = tan ⁻¹ (D / 2) / L Expression 1

(However, D is the distance between two peaks in the measured light intensity distribution diagram, and L is the distance from the exit end face to the face where the light intensity meter 130 is installed).

Next, the angle θ1a and the inclination angle θ1 of the light 51 propagating through the optical fiber shown in FIG. 4 are obtained from the angle θ3 obtained above.
Here, the relationship between the light 51 before emission and the light 52 after emission on the emission end face 36 in FIG.

n1sin θ1a = n2sin θ3

(Where n1 is the refractive index of the core and n2 is the refractive index of the space outside the optical fiber 10)
Therefore, the angle θ1a of the light 51 propagating in the optical fiber is

θ1a = sin ⁻¹ ((n2 / n1) × sin θ3)

It becomes.
In addition, the inclination angle θ1 of the central axis 14 of the optical fiber 10 is equal to the angle θ1a of the light 51 propagating in the optical fiber as shown in FIG.

θ1 = θ1a = sin ⁻¹ ((n2 / n1) × sin θ3) Equation 2

It becomes.

As an example, when θ1 is specifically obtained based on the measurement result shown in FIG. 6, it is as follows. FIG. 6 shows the light intensity distribution of the emitted light when the incident position of the laser beam 140 is 4 mm away from the center of the incident end face 101a along the X1 axis.
In FIG. 6, the horizontal axis indicates the distance along the X2 axis, and the vertical axis indicates the relative value of the light intensity.

  As shown in FIG. 6, the two peaks are located at a distance of 35 mm. By substituting the distance D between the peaks D = 35 mm and the distance L = 150 mm from the emission end face to the light intensity meter 130 into Equation 1. Thus, it can be determined that the inclination θ3 of the emitted light is about 6.65 °.

  Here, since the refractive index n1 of the core constituting the optical fiber strand 10 is about 1.5, the inclination angle θ1 of the central axis 14 of the optical fiber strand is 4.43 ° from Equation 2. I understand.

  The method for obtaining the inclination angle θ1 of the optical fiber strand inclined by the fusion has been described above. Next, referring to FIG. 7, the light incident surface for compensating the influence of the inclination θ1 on the emission angle θ3. A method for obtaining the inclination angle θ2 of 15 will be described.

  In FIG. 7, the central axis 14 has an inclination angle θ1 with respect to light 50 incident on the light incident surface 15 (light incident parallel to the central axis of the optical fiber bundle). The optical fiber strand 10 which has inclination | tilt angle (theta) 2 with respect to the surface 61 orthogonal to the light 50 which injects into the surface 15, and the propagation state of the light 51 after incidence are shown.

A broken line 16 is a straight line orthogonal to the light incident surface 15, and light 50 before incidence enters the intersection at an angle of incidence θ 5 with respect to the broken line 16. Assuming that the incident light 51 is refracted on the light incident surface 15 and propagates along the central axis 14 of the optical fiber, the relationship between the light 50 before incident and the light 51 after incident is Snell's law. Therefore, Expression 3 is satisfied.

n1sin θ4 = n2sin θ5 Equation 3

Here, n1 is the refractive index of the core, and n2 is the refractive index of the space outside the optical fiber 10. Further, θ4 is the refraction angle of the light 51 after incidence, and is equal to the value obtained by subtracting the inclination θ1 from the incidence angle θ5 of the light 50 before incidence.

n1sin (θ5-θ1) = n2sinθ5

Thus, the relational expression of the incident angles θ5 and θ1 can be substituted.
In addition, since the inclination angle θ2 that is the inclination of the light incident surface 15 with respect to the surface 61 perpendicular to the light 50 before incidence is equal to the incident angle θ5 of the light 50 before incidence, θ5 is replaced with θ2 and expressed by Equation 5. Can do.

n1sin (θ2−θ1) = n2sinθ2

As a result, the inclination angle θ2 is

θ2 = cot ⁻¹ (cot θ1− (n2 / (n1sin θ1))).

It can ask for.

By substituting the previously determined θ1 = 4.43 °, n1 = 1.5, and n2 = 1.0 into Equation 6, θ2 = 13.16 ° can be obtained, and the light incident on the optical fiber bundle By setting the inclination of the incident surface of the optical fiber strand at a position 4 mm away from the center of the end face to 13.16 °, the light incident on the optical fiber strand at the position is made the central axis of the optical fiber strand. You can see that it can be taken along.
In order to obtain θ2 more easily, when deriving the above equation 6, the equation 6 may be simplified as appropriate using a well-known approximate equation or the like and used.

FIG. 8A shows θ1 and θ2 when the incident position of the laser beam 140 in FIG. 5 is 1 mm, 2 mm, 3 mm, and 4 mm, respectively, along the X1 axis from the center of the incident end face 101a.
FIG. 8 shows θ1 and θ2 at points 1 mm apart from the central axis of the incident end face 101a, but the number of measurement points is increased along the X1 axis from the center of the incident end face 101a, and θ2 obtained at each measurement point. Accordingly, it is more preferable to process the light incident surface of the optical fiber.

  In the present embodiment, the light guide 1 is formed by providing a concentric inclination angle θ2 around the central axis 33 on the cut surface 32 of the fused light guide terminal portion 30 described above, and its shape is As shown in FIG. 8B, the aspherical surface 34 has a slope that increases from the central axis 33 toward the outer peripheral portion. In the light guide shown in FIG. 8 (b), θ2 is measured at a plurality of positions along the X1 axis from the center of the incident end face 101a in addition to the point 1 mm apart from the central axis of the incident end face 101a. The light incident surface of the optical fiber is processed according to θ2 obtained at the point.

  As an apparatus for processing such a concave surface of the aspherical surface 34, an ultra-precision processing machine with numerical control with a high degree of processing freedom is used, but ELID grinding may be used to increase the mirror surface of the processing surface. it can.

  The processing shape applied to the fused portion 31 of the light guide 1 according to the present embodiment has been described above. Next, the laser beam is emitted from the emission end face when the laser beam is incident on the entire light incident end face of the light guide. The intensity distribution of the emitted light will be described with reference to FIGS.

  The apparatus shown in FIG. 9 is provided with a beam expander 150 in place of the slit 120 of the apparatus of FIG. 5 so that uniform laser light is incident on the light incident end face of the light guide. Laser light was incident on the entire surface of the light incident end faces 32 and 34, and a light intensity distribution at a position 150 mm away from the light emitting end face 36 of the light guide 1 was measured using a light intensity meter 120.

  FIG. 10 shows the intensity distribution of the emitted light from the light guide 1 measured by the above apparatus, and the solid line indicates the emitted light when the laser light is incident on the light guide whose light incident end surface is aspherical. The broken line shows the intensity distribution of the emitted light when the laser light is incident on a conventional light guide that is not subjected to aspherical processing on the incident end face.

  Comparing the light intensity distribution of the light guide with aspherical processing on the light incident end surface, shown by the solid line, and the light intensity distribution of the light guide with non-spherical processing on the light incident end surface, shown by the broken line, It can be seen that the light guide with the aspherical surface on the incident end face irradiates a relatively narrow range without the emitted light being diffused. Also, it can be seen that the light intensity of the irradiated central portion is about four times higher than that of the light guide not subjected to aspherical processing.

As described above, according to the light guide of this embodiment, the inclination angle θ2 for compensating for the influence of the inclination of the central axis of the optical fiber is applied to the cut surface of the fused light guide terminal portion. By providing concentric circles around the central axis of the fiber bundle, it is possible to capture light incident parallel to the central axis of the optical fiber bundle at the light guide terminal portion in parallel to the central axis of each optical fiber. Therefore, it is possible to suppress the diffusion of light on the emission end face of the optical fiber bundle.
In the present embodiment, the incident light on the light incident surface of the optical fiber is described using light incident parallel to the central axis of the optical fiber bundle. However, the incident light in the light guide of the present invention is However, it is not necessarily limited to the light incident parallel to the central axis of the optical fiber bundle, but is condensed on the light incident surface of the optical fiber bundle or light inclined with respect to the central axis of the optical fiber bundle. Similar effects can be obtained even in the case of light including many angle components. When using light including many angle components collected on the light incident surface of the optical fiber, θ2 is set using the incident angle of the light at the center or the strongest light. It is preferable to obtain.
In the light guide of the present invention, the angle θ2 formed by the light incident surface of the optical fiber and the surface perpendicular to the light incident on the light incident surface does not necessarily match Equation 6, and a book described later. Similar effects can be obtained by setting the angle θ2 to an angle approximate to the value obtained by the expression 6 as in the light guide shown in the second embodiment of the invention.

FIG. 11 is a cross-sectional view showing the terminal structure of the light guide in the second embodiment of the light guide of the present invention.

  The light incident end face shape of the light guide in this embodiment is obtained by processing the cut surface after the optical fiber bundle fusion into a spherical shape 35 having a radius of 30 mm, which approximates the aspherical surface 34 indicated by a dotted line in FIG. The optical fiber strand 10 and the sleeve 20 constituting the light guide were the same as those shown in the first embodiment.

  By processing the light incident end face of the light guide into such a shape, the parallelism of the light taken into the optical fiber strand with respect to the central axis 14 of each optical fiber strand is a light guide processed into an aspheric shape. As for the intensity distribution of the emitted light when the laser light is incident on the light incident end face of the optical fiber bundle, the peak value is reduced by about 20% as shown by the one-dot chain line in FIG. Compared with the peak of the conventional light guide that is not subjected to spherical processing on the light incident end face shown by the broken line in FIG. 10, the emitted light is not diffused and the high light intensity is similar to the light guide that is subjected to aspherical processing. You can see that

  In addition, since the processing shape is spherical, processing can be performed even by using a polishing method using a conventional polishing dish having a spherical shape, so that the processing cost can be reduced.

In the light guides shown in the first embodiment and the second embodiment, optical fiber strands made of quartz are used, but the light guide of the present invention is light made of multicomponent glass or plastic. The present invention can also be applied to those using fiber strands.
In the first embodiment and the second embodiment, the laser oscillator is used as the light emitter that emits light. However, the present invention is not limited to this, and the light guide of the present invention is used as a light emitter. A short arc lamp or a halogen lamp can also be used.

Next, the light irradiation apparatus of the present invention will be described.
The light irradiation device of the present invention includes a light emitting body that emits light, and a light guide for irradiating an object to be irradiated with light emitted from the light emitting body, and the light guide is the light of the present invention. It is a guide.
FIG. 12 is a diagram showing an embodiment of the light irradiation apparatus of the present invention.
In this embodiment, the light irradiation device includes a laser oscillator 210 that oscillates laser light, a lens 220 that condenses the laser light, a light guide 230 that transmits the condensed light, and light emitted from the light guide 230. A condensing lens 241 for condensing the irradiation object W and a processing head unit 240 including the condensing lens 241 are configured.

As the laser oscillator 210, a Q-switched YAG laser that emits ultraviolet light using a flash lamp as an excitation light source is used.

In this light irradiation apparatus, since the laser light is focused on the light incident end face 230a of the light guide 230, similarly to the light guide in the first embodiment, the light of the optical fiber bundle made of the optical fiber made of quartz is used. A light guide in which the incident end is fused is used, and the light incident end face 230a of the light guide 230 is processed into an aspherical shape as shown in FIG.

In this way, when a light guide whose incident end face is processed into an aspherical shape is used, the light 250 emitted from the light guide is compared with a light guide whose incident end face is not subjected to aspherical processing. Since the emission angle is smaller, the condenser lens 241 can also be used with a small diameter corresponding to this angle φ, and the size of the processing head portion 240 can be made more compact.

The light irradiation device shown in this embodiment uses a laser oscillator as a light emitter that emits light. However, the light irradiation device of the present invention is not limited to this. A halogen lamp or the like can also be used.

The light guide of the present invention is obtained by fusing the ends of optical fiber bundles, and at the light guide terminal portion, the light incident on the optical fiber bundle can be taken in parallel to the central axis of the optical fiber strand. Since it is possible, it can be suitably used for a light irradiation apparatus including the light guide.

It is sectional drawing (a) which shows the terminal part structure of the light guide in the 1st embodiment of the light guide of this invention, and sectional drawing (b) of an optical fiber strand. It is a figure which shows the position A cut | disconnected and grind | polished in order to form a light-incidence end surface in the melt | fusion part of an optical fiber bundle terminal. It is a figure which shows the light guide terminal after cut | disconnecting in the position A. It is a figure which shows the incident light and outgoing light in the optical fiber strand before light-incidence surface processing. It is a figure which shows the measuring apparatus for measuring inclination | tilt angle (theta) 1. It is a figure which shows the light intensity distribution of emitted light. It is a figure which shows the cross section of the optical fiber strand for demonstrating the calculation method of inclination | tilt angle (theta) 2. The figure (a) showing each θ1 and θ2 at a position away from the central axis of the optical fiber bundle and the light incident end face of the optical fiber bundle processed into an aspherical shape so as to satisfy each obtained θ2 FIG. It is a figure which shows the apparatus for measuring the intensity distribution of the emitted light when a laser beam injects into a light guide. It is a figure which shows intensity distribution of the emitted light when a laser beam injects into a light guide. It is a figure for demonstrating the terminal part structure of the light guide of this invention. It is a figure which shows the embodiment of the light irradiation apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light guide 2 Optical fiber bundle 10 Optical fiber strand 11 Core 12 Clad layer 13 Cover layer 14 Center axis 15 of optical fiber strand Light incident surface 16 Straight line 20 orthogonal to light incident surface Sleeve 21 Step part 30 Light guide terminal part 31 Fused portion 32 End surface 33 Central axis 34 of optical fiber bundle Aspherical surface 35 Spherical surface 36 Emitting end surface 101 Light guide 101a Light incident end surface 101b Light emitting end surface 110 Laser oscillator 130 Light intensity meter

Claims (5)

An optical fiber bundle comprising a plurality of optical fiber strands and at least an end portion on the light incident side is heat-sealed,
The central axis of each optical fiber positioned outside the central axis of the optical fiber bundle has an inclination with respect to the central axis of the optical fiber bundle at the end portion of the thermally fused optical fiber bundle,
A light guide characterized in that the shape of the light incident end face of the optical fiber bundle is concave. The light guide according to claim 1, wherein the concave shape is a spherical shape. At least a part of the optical fiber strand has an angle θ2 formed by a light incident surface of the optical fiber strand and a surface perpendicular to the light incident on the light incident surface,
θ2 = cot ⁻¹ (cot θ1− (n2 / (n1sin θ1)))
[However, θ1 is the angle formed by the light incident on the light incident surface of the optical fiber and the central axis of the optical fiber, and n1 is the refractive index of the core constituting the optical fiber. Yes, n2 is the refractive index of the space outside the optical fiber. ]
The light guide according to claim 1, wherein the light incident surface is processed so as to satisfy the above. The light guide according to claim 1, wherein the optical fiber is made of quartz, multicomponent glass, or plastic. It is a light irradiation apparatus containing the light-emitting body which radiates | emits light, and the light guide for irradiating a to-be-irradiated object with the emitted light from this light-emitting body, Comprising: The said light guide is in any one of Claims 1-4. A light irradiation apparatus characterized by being a light guide.

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