HK1148824A - Light guide and light irradiation device - Google Patents

Description

Light guide and light irradiation device

The present application is directed to the date of application: 2006, 10/13/application No.: 200610141147.8, title of the invention: light guides and light irradiation devices are filed as divisional applications.

Technical Field

The present invention relates to a light guide that transmits light and irradiates an object to be irradiated, and a light irradiation device having the light guide.

Background

Conventionally, a light guide is used as a mechanism for transmitting light emitted from a light emitting body such as a laser oscillator to an arbitrary position of an irradiation object.

Such a light guide is generally used when optical fiber lines are used as a single body or when a plurality of optical fiber lines are bundled as an optical fiber bundle, and is used separately depending on the required light amount and the characteristics of the light emitting body.

In the case of using an optical fiber bundle, it is necessary to bundle and cure the ends thereof, and a method of bonding the optical fiber wires with an organic or inorganic adhesive or low-melting glass is generally used.

However, in a device using a laser processing machine or a high output lamp, it is necessary to improve the heat resistance of the end portion thereof in order to receive strong light emitted from a light emitting body, and there is known a method of melting the optical fiber wires themselves by applying heat from the outside using a heating means such as high frequency heating or an oxyhydrogen burner, and welding them to each other.

Here, as a method of welding the ends of the optical fiber bundle by applying heat from the outside as described above, a method shown in patent document 1 is exemplified.

Patent document 1: JP-A-57-97503

This patent document 1 shows the following method: the method includes bundling ends of a plurality of quartz-based optical fibers, inserting the bundled ends into a glass tube, and then applying heat from the outer periphery of the glass tube to fuse the glass tube and the optical fibers, thereby reducing or eliminating a gap between the glass tube and the optical fibers.

Therefore, the light guide manufactured by the above method can form the light guide terminal portion in which the optical fibers are firmly adhered without using an adhesive having poor heat resistance, and can secure sufficient heat resistance of the terminal portion even for heat from a large light source or the like for the purpose of transmitting a large amount of light.

In addition, since the gap between the optical fiber lines in the end portion is reduced or eliminated, the occupancy of the core in the end face thereof is increased, and the light incidence efficiency with respect to the light source can be improved.

However, in the fusion spliced portion formed by the above method, since the gap between the optical fiber wires is reduced or eliminated by deforming the optical fiber wires themselves into a substantially hexagonal shape, the bundle diameter of the fusion spliced portion is reduced only by the proportion of the gap reduced or eliminated between the optical fiber wires as compared with the bundle diameter of the non-fusion spliced portion.

As a result, in the light guide end portion, the optical fiber arranged in the position close to the outer peripheral portion of the optical fiber bundle is inclined in the central axis direction of the optical fiber bundle from the portion not subjected to fusion splicing (the side far from the end of the optical fiber bundle) to the portion subjected to fusion splicing (the end side of the optical fiber bundle) at such an inclination that the optical fiber becomes more distant from the central axis of the optical fiber bundle and conversely, the optical fiber becomes smaller closer to the central axis of the optical fiber bundle and the central axis of the optical fiber becomes parallel to the central axis of the optical fiber bundle substantially on the central axis of the optical fiber bundle.

When the fusion-spliced portion of the light guide end is cut and polished on a plane a perpendicularly intersecting the central axis of the optical fiber bundle in the light guide end portion as shown in fig. 2, since the central axis 14 of the optical fiber line is not perpendicular to the end face 32 of each optical fiber line as shown in fig. 4, the light 50 perpendicularly incident on such an end face 32 cannot be transmitted along the central axis 14 of the optical fiber line after being incident on the end face 32, and is repeatedly totally reflected on the inner surface of the cladding 12 constituting the optical fiber line 10 and reaches the emission end face 36 of the optical fiber line.

As a result, the following problems occur: the light emitted from the emission end surface of the light guide includes light having an inclination angle with respect to the central axis of the optical fiber bundle, and the incident angle of the light incident on the incident end of the light guide cannot be maintained.

Disclosure of Invention

In view of the above-described circumstances, an object of the present invention is to provide a light guide having a fusion-spliced portion at an end portion of an optical fiber bundle, which can introduce light incident to the optical fiber bundle in parallel with a central axis of an optical fiber, and a light irradiation device having the light guide.

In order to achieve the above object, the present invention provides:

(1) a light guide comprising a bundle of optical fibers composed of a plurality of optical fibers and having at least an end portion on a light incident side thermally fused,

the central axis of each optical fiber located outside the central axis of the optical fiber bundle has an inclination angle with respect to the central axis of the optical fiber bundle at the end of the optical fiber bundle thermally fused,

the light incidence end surface of the optical fiber bundle is concave;

(2) the light guide according to the above (1), wherein the concave surface is a spherical surface;

(3) the light guide according to the above (1) or (2), wherein at least a part of the optical fiber line processes a light incident surface in such a manner that: an angle theta 2 formed by a light incident surface of the optical fiber line and a surface perpendicularly intersecting with light incident to the light incident surface satisfies the following expression,

θ2＝cot^-1(cotθ1-(n2/(n1sinθ1)))

where θ 1 is an angle formed by light incident on the light incident surface of the optical fiber and the central axis of the optical fiber, n1 is a refractive index of a core constituting the optical fiber, and n2 is a refractive index of a space outside the optical fiber;

(4) the light guide according to any one of the above (1) to (3), wherein the optical fiber wire is made of quartz, multicomponent glass, or plastic;

(5) a light irradiation device comprising a light emitter that emits light and a light guide that irradiates the light emitted from the light emitter to an object to be irradiated, wherein the light guide is the light guide according to any one of (1) to (4) above.

According to the present invention, it is possible to provide a light guide that cures an end portion of an optical fiber bundle by fusion splicing and can introduce light incident to the optical fiber bundle in parallel with a central axis of an optical fiber line, and a light irradiation device having the light guide.

Drawings

Fig. 1(a) is a sectional view showing a light guide distal end structure in a first embodiment of a light guide according to the present invention, and fig. 1(b) is a sectional view of an optical fiber.

Fig. 2 is a view showing a position a where cutting and polishing are performed to form a light incident end surface at a fusion spliced portion at the end of an optical fiber bundle.

Fig. 3 is a diagram showing the end of the light guide after cutting at position a.

Fig. 4 is a diagram showing incident light and outgoing light in an optical fiber before processing of a light incident surface.

Fig. 5 is a diagram showing a measuring device for measuring the inclination angle θ 1.

Fig. 6 is a diagram showing a light intensity distribution of the outgoing light.

Fig. 7 is a view showing a cross section of an optical fiber for explaining a method of calculating the tilt angle θ 2.

Fig. 8(a) is a diagram showing θ 1 and θ 2 at positions separated by a predetermined distance from the central axis of the optical fiber bundle, and fig. 8(b) is a diagram showing that the incident end face of the optical fiber bundle is processed to have an aspherical shape so as to satisfy the obtained θ 2.

Fig. 9 is a diagram showing a device for measuring the intensity distribution of outgoing light when laser light is incident on the light guide.

Fig. 10 is a graph showing the intensity distribution of the outgoing light when the laser light is incident on the light guide.

Fig. 11 is a diagram for explaining a configuration of a distal end portion of a light guide of the present invention.

Fig. 12 is a view showing an embodiment of a light irradiation device of the present invention.

The symbols in the drawings illustrate that:

1 light guide 2 optical fiber bundle 10 optical fiber 11 core 12 cladding

13 cladding layer 14 optical fiber central axis 15 light incident surface

16 straight line 20 sleeve 21 step part orthogonal to light incident surface

30 end face of light guide end 31 fusion-bonded part 32

33 central axis 34 of optical fiber bundle, 35 aspheric surface and 35 spherical surface

36 exit end face 101 light guide 101a light entrance end face

101b light output end face 110 laser oscillator 130 optical intensity meter

Detailed Description

Embodiments of the light guide and the light irradiation device according to the present invention will be described in detail below with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description thereof is omitted. The dimensional ratios in the drawings do not necessarily correspond to the dimensional ratios described in the specification by way of numerical values.

A feature of the light guide of the present invention is that,

comprises a fiber bundle composed of a plurality of optical fibers and having at least the end portion on the light incident side thermally fused,

the central axis of each optical fiber located outside the central axis of the optical fiber bundle has an inclination angle with respect to the central axis of the optical fiber bundle at the end of the optical fiber bundle thermally fused,

the light incident end surface of the optical fiber bundle is concave.

Fig. 1(a) is a cross-sectional view showing a structure of a light guide distal end portion in a first embodiment of the light guide of the present invention.

The light guide 1 is composed of an optical fiber bundle 2 composed of a plurality of optical fiber lines 10 and a sleeve 20, and has a light guide terminal portion 30 formed by thermally welding a terminal portion on a light incident side, then cutting the welded portion at a predetermined position, and further processing a cut surface into a concave shape described later.

In addition, the optical fiber line 10 includes: a core 11 having an outer diameter of 190 μm made of high purity silica as shown in FIG. 1 (b); a cladding 12 having an outer diameter of 200 μm and formed by fluorine doping quartz and a cladding 13 having an outer diameter of 220 μm and formed by an ultraviolet curable resin were used, and a quartz tube having an outer diameter of 12mm, an inner diameter of 10mm and a total length of 35mm, which had a thermal expansion coefficient and a softening temperature substantially equal to those of the quartz used for the optical fiber 10, was used for the sleeve 20.

Next, a method of forming the light incident end surface in the light guide of fig. 1 is explained.

As shown in fig. 2, about 2000 optical fibers 10 from which the coating layer 13 near the end portion was removed by solvent melting were inserted into the jacket 20 in a state where the tip thereof protruded by about 5mm, and then heated by an oxyhydrogen burner within a range of about 10mm from the tip of the jacket 20, whereby the optical fibers 10 were softened and fused to each other, and fused integrally with the jacket 20, thereby forming the light guide tip portion 30 having the gentle step portion 21 on the outer peripheral surface of the jacket 20.

Here, although the fusion-spliced portion 31 improves the firmness because the fusion-spliced portion is more densely fused between the optical fiber lines 10 in the region closer to the tip (right side in fig. 2), in such a region, the boundary line between the core 11 and the cladding 12 of the optical fiber line 10 may become unclear due to softening, and when light enters, the incident light may be diffusely reflected at the boundary surface between the core 11 and the cladding 12, thereby reducing the light transmission efficiency as the light guide.

Therefore, in the light guide terminal portion 30 formed by fusion splicing, it is necessary to cut a portion where the boundary line between the core 11 and the cladding 12 is not clear, the cutting being performed at a position closest to the step portion 21 in a range where the optical fiber wires 10 are fusion-spliced to each other in the sleeve 20.

In the light guide 1 shown in fig. 2, this position is set to a position a where the outer diameter of the sleeve 20 including the fusion-bonded portion 31 is about 11mm, and cutting is performed 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 in a state where the central axis 33 of the optical fiber bundle 2 has the inclination angle θ 1. The inclination angle θ 1 is larger as the optical fiber 10 arranged near the outer periphery of the optical fiber bundle 2 is closer to the light guide terminal portion 30; conversely, the closer to the central axis 33 of the optical fiber bundle 2, the smaller the central axis 14 of the optical fiber line in the vicinity of the central axis 33 is, the more parallel the central axis 33 of the optical fiber bundle 2 at the light guide terminal part 30 is.

As shown in fig. 4, when light 50 enters the cut surface 32 perpendicularly, the incident light 51 propagates while repeating total reflection at an inclination angle θ 1a equal to θ 1, which is an inclination angle between the central axis 14 of the optical fiber 10 and the incident light 50, and is further refracted at the exit end surface 36 to further widen an angle with the central axis 14 of the optical fiber, and is emitted at an angle θ 3.

As will be described later, in the present embodiment, the light guide 1 is formed by performing predetermined concave processing on the cut surface 32 of the light guide terminal portion 30, and thereby, an inclination angle θ 2 for compensating for the influence of the inclination angle θ 1 is provided on the incident end surface of the optical fiber 10, and the light incident on the optical fiber 10 is introduced in parallel to the central axis 14 of the optical fiber. The inclination angle θ 2 can be obtained from the inclination angle θ 1 of the central axis 14.

Here, a method of obtaining the inclination angle θ 1 and a method of deriving the inclination angle θ 2 from the obtained inclination angle θ 1 will be described.

Fig. 5 shows a device configuration for measuring the tilt angle θ 1.

The measuring device measures the angle θ 3 (corresponding to θ 3 in fig. 4) of the outgoing light 141 by inputting the laser beam 140 with the corrected beam diameter into the light guide 101 for measurement, and thereby obtains the inclination angle θ 1 at the light incident end surface.

The light guide 101 was cut at the position a in fig. 2 and polished flat after the incident end face 101a was welded in the above-described order, and the outer diameter of the optical fiber bundle at the incident end face was 9 mm.

The light output end surface 101b is bonded with an organic adhesive instead of heat bonding, and is subjected to surface polishing in the same manner as the light input end surface 101 a.

The radiation beam from the He-Cd laser oscillator 110 is corrected by a slit 120 to a laser beam 140 having a beam diameter of 0.5mm, and is incident on the incident end surface 101 a.

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

As shown in fig. 6, since the measured light intensity distribution has a shape having two peaks, the inclination angle θ 3 of the light emitted from the light-emitting end surface 101b of fig. 5 can be calculated from the distance D between the peaks by using equation 1.

θ3＝tan^-1(D/2)/L … … formula 1

(where D is the distance between two peaks in the measured light intensity distribution chart, and L is the distance from the emission end face to the face on which the light intensity meter 130 is provided.)

Next, the angle θ 1a and the inclination angle θ 1 of the light 51 propagating through the optical fiber as shown in fig. 4 are determined using the angle θ 3 determined above.

Here, as for the relationship between the light 51 before emission and the light 52 after emission at the light-emitting end face 36 of fig. 4, the following equation holds in accordance with snell's law:

n1sinθ1a＝n2sinθ3

(where n1 is the refractive index of the core, and n2 is the refractive index of the space outside the optical fiber 10), the angle θ 1a of the light 51 propagating inside the optical fiber can be expressed by the following formula:

θ1a＝sin^-1((n2/n1)×sinθ3)

as is apparent from fig. 4, the inclination angle θ 1 of the central axis 14 of the optical fiber 10 is equal to the angle θ 1a of the light 51 propagating in the optical fiber, and therefore the following equation holds:

θ1＝θ1a＝sin^-1((n2/n 1). times.sin theta.3) … … formula 2

As an example, if θ 1 is specifically determined based on the measurement results shown in fig. 6, the following is shown. Fig. 6 shows the light intensity distribution of the outgoing light when the incident position of the laser beam 140 is set to a position 4mm away from the center of the incident end surface 101a along the X1 axis.

In fig. 6, the horizontal axis represents the distance along the X2 axis, and the vertical axis represents the relative value of the light intensity.

As can be seen from fig. 6, the two peaks are located at a distance of 35mm apart, and by substituting the distance D between the peaks into 35mm and the distance L from the emission end surface to the light intensity meter 130 into 150mm in equation 1, the inclination angle θ 3 of the emitted light can be determined to be about 6.65 °.

Here, since the core refractive index n1 of the optical fiber 10 is about 1.5, the inclination angle θ 1 of the central axis 14 of the optical fiber is 4.43 ° as can be seen from equation 2.

The method of obtaining the inclination angle θ 1 of the optical fiber inclined by fusion splicing is described above, and the method of obtaining the inclination angle θ 2 of the light incident surface 15 for compensating for the influence of the inclination angle θ 1 on the output angle θ 3 is described below with reference to fig. 7.

Fig. 7 shows a propagation state of the optical fiber 10 and the incident light 51, in which the optical fiber 10 has a central axis 14 inclined at an angle θ 1 with respect to the light 50 incident on the light incident surface 15 (incident light parallel to the central axis of the optical fiber bundle) and the light incident surface 15 inclined at an angle θ 2 with respect to a surface 61 perpendicularly intersecting the light 50 incident on the light incident surface 15.

The broken line 16 is a straight line perpendicularly intersecting the light incident surface 15, and the light 50 before incidence at this intersection is incident at an angle of the incident angle θ 5 with respect to the broken line 16. If the light 51 after incidence is refracted at the light incidence surface 15 and propagated along the central axis 14 of the optical fiber line, the relationship between the light 50 before incidence and the light 51 after incidence satisfies equation 3 according to snell's law.

n1sin θ 4 ═ n2sin2 θ 05 … … formula 3

Where n1 is the refractive index of the core, and n2 is the refractive index of the space outside the optical fiber 10. In addition, since θ 4 is a refraction angle of the incident light 51 and is equal to a value obtained by subtracting the inclination angle θ 1 from the incident angle θ 5 of the light 50 before incidence, equation 3 can be converted into a relational expression of the incident angle θ 5 and θ 1, as shown in equation 4, that is:

n1sin (θ 5- θ 1) ═ n2sin θ 5 … … formula 4

Since the inclination angle θ 2 of the light incident surface 15 with respect to the surface 61 perpendicularly intersecting the light before incidence 50 is equal to the incident angle θ 5 of the light before incidence 50, θ 5 can be expressed by equation 5 instead of θ 2.

n1sin (θ 2- θ 1) ═ n2sin θ 2 … … formula 5

As a result, the inclination angle θ 2 can be obtained by the following equation:

θ2＝cot^-1(cot theta 1- (n2/(n1sin theta 1))) … … formula 6

By substituting the above-obtained θ 1 of 4.43 °, n1 of 1.5, and n2 of 1.0 into equation 6, it is possible to obtain θ 2 of 13.16 °, and it is known that by setting the inclination angle of the incident surface of the optical fiber at a position 4mm away from the center of the light incident end surface of the optical fiber bundle to 13.16 °, the light incident on the optical fiber at that position can be taken in along the central axis of the optical fiber.

In order to obtain θ 2 more easily, equation 6 may be simplified as appropriate by using a known approximation equation or the like when deriving equation 6.

Fig. 8(a) shows θ 1 and θ 2 when the incident position of the laser beam 140 in fig. 5 is set to be 1mm, 2mm, 3mm, and 4mm from the center of the incident end surface 101a along the X1 axis, respectively.

In fig. 8, θ 1 and θ 2 are shown at points 1mm apart from the central axis of the incident end surface 101a, but it is more preferable to increase the measurement positions from the center of the incident end surface 101a along the X1 axis and process the light incident surface of the optical fiber based on θ 2 obtained at each measurement point.

In the present embodiment, the light guide 1 is formed such that the inclination angle θ 2 is concentrically provided around the central axis 33 on the cut surface 32 of the welded light guide distal end portion 30, and the inclination angle increases as the central axis 33 approaches the outer peripheral portion, as shown in fig. 8 (b). In the light guide shown in fig. 8(b), θ 2 was measured at a plurality of positions along the X1 axis from the center of the incident end surface 101a except for points 1mm apart from the center axis of the incident end surface 101a, and the light incident surface of the optical fiber was processed based on θ 2 obtained at each measurement point.

As a device for performing such concave surface processing of the aspherical surface 34, a super high precision processing machine based on numerical control with a high degree of freedom of processing is used, but an ELID grinding method may be used in order to improve the mirror surface of the processed surface.

The processing shape of the welded portion 31 of the light guide 1 according to the present embodiment is described above, and the intensity distribution of the light emitted from the emission end face when the laser light is incident on the entire light incident end face of the light guide will be described with reference to fig. 9 and 10.

In the device shown in fig. 9, in order to make uniform laser light incident on the light incident end surface of the light guide, a beam expander 150 is provided instead of the slit 120 of the device shown in fig. 5, the laser light is incident on the entire light incident end surfaces 32 and 34 of the light guide 1, and the light intensity distribution at a position separated by 150mm from the light emitting end surface 36 of the light guide 1 is measured by a light intensity meter 120.

Fig. 10 shows the intensity distribution of the outgoing light from the light guide 1 measured by the above-described device, the solid line shows the intensity distribution of the outgoing light when the laser light is incident on the light guide whose light incident end surface is aspheric, and the broken line shows the intensity distribution of the outgoing light when the laser light is incident on the conventional light guide whose light incident end surface is not aspheric.

As can be seen by comparing the light intensity distribution of the light guide aspheric-processed on the light incident end surface shown by the solid line with the light intensity distribution of the light guide aspheric-processed on the light incident end surface shown by the broken line, the light guide aspheric-processed on the light incident end surface irradiates a relatively narrow range without diffusing the emitted light. Further, it is found that the light intensity of the irradiated central portion is about 4 times higher than that of the light guide without the aspherical surface processing.

As described above, according to the light guide of the present embodiment, the inclination angle θ 2 for compensating the influence of the inclination angle of the central axis of the optical fiber is concentrically provided on the cut surface of the welded light guide terminal portion with the central axis of the optical fiber bundle as the center, whereby the light incident in parallel with the central axis of the optical fiber bundle at the light guide terminal portion can be taken in parallel with the central axis of each optical fiber, and the diffusion of the light at the emission end face of the optical fiber bundle can be suppressed.

In the present embodiment, the light incident on the light incident surface of the optical fiber line is described using the light incident in parallel with the central axis of the optical fiber bundle, but the light incident on the light guide of the present invention is not necessarily limited to the light incident in parallel with the central axis of the optical fiber bundle, and the same effects can be obtained even in the case of the light having an inclination angle with respect to the central axis of the optical fiber bundle or the light having a plurality of angle components condensed on the light incident surface of the optical fiber line. In the case of using light having a plurality of angle components condensed on the light incident surface of the optical fiber, it is preferable to determine θ 2 by using the incident angle of the light at the center thereof or the light having the strongest intensity.

In the light guide of the present invention, the angle θ 2 formed by the light incident surface of the optical fiber and the surface that intersects the light incident on the light incident surface perpendicularly does not necessarily match equation 6, and the same effect can be obtained by setting the angle θ 2 to an angle similar to the value obtained by equation 6 as in the light guide described in the second embodiment of the invention described later.

Fig. 11 is a cross-sectional view showing a configuration of a distal end portion of a light guide in a second embodiment of the light guide of the present invention.

The light entrance end surface shape of the light guide in the present embodiment is obtained by processing the cut surface of the fused optical fiber bundle into a spherical surface shape 35 having a radius of 30mm similar to the aspherical surface 34 shown by the dotted line in fig. 11, and the optical fiber 10 and the sleeve 20 constituting the light guide are the same as those of the first embodiment.

By processing the light incident end surface of the light guide into such a shape, it is understood that the parallelism of the light introduced into the optical fiber with respect to the central axis 14 of each optical fiber is slightly lower than that of the light guide processed into an aspherical shape, and the peak value of the intensity distribution of the outgoing light when the laser light is incident on the light incident end surface of the optical fiber bundle is reduced by about 20% as shown by the chain line in fig. 10.

Further, by processing into a spherical shape, processing can be performed even by a method of polishing with a conventional polishing disk having a spherical shape, and therefore, processing cost can be suppressed.

In addition, in the light guides shown in the first and second embodiments, the optical fiber line made of quartz is used, but the light guide of the present invention can also be applied to a light guide using an optical fiber line made of multicomponent glass or plastic.

In the first and second embodiments, the laser oscillator is used as the light emitter that emits light, but the present invention is not limited to this, and a short arc lamp, a halogen lamp, or the like may be used as the light emitter in the light guide of the present invention.

Next, a light irradiation device of the present invention will be explained.

The light irradiation device of the present invention includes a light emitter that emits light, and a light guide that irradiates the light emitted from the light emitter to an object to be irradiated, and is characterized in that the light guide is the light guide of the present invention.

Fig. 12 is a view showing an embodiment of a light irradiation device of the present invention.

In the present embodiment, the light irradiation device includes: a laser oscillator 210 for oscillating a laser beam; a lens 220 for condensing the laser light; a light guide 230 that transmits the condensed light; a condenser lens 241 for condensing the light emitted from the light guide 230 on the irradiation target W; and a processing head 240 having the condensing lens 241.

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 device, since the laser light is condensed on the light incident end surface 230a of the light guide 230, a light guide in which the light incident end portion of the optical fiber bundle made of a quartz fiber line is fused is used as in the light guide of the first embodiment, and the light incident surface 230a of the light guide 230 is processed into an aspherical shape as shown in fig. 8.

In the case of using the light guide whose incident end surface is processed into an aspherical shape as described above, the light 250 emitted from the light guide has a smaller emission angle than the light guide whose incident end surface is not processed into an aspherical shape, and therefore, the condensing lens 241 may be a lens having a small diameter corresponding to the angle Φ, and the size of the processing head 240 may be made more compact.

In the light irradiation device according to the embodiment of the present invention, a laser oscillator is used as a light emitter that emits light, but the present invention is not limited thereto, and a short arc lamp, a halogen lamp, or the like may be used as the light emitter in the light irradiation device according to the present invention.

(availability in industry)

In the light guide of the present invention, the end portion of the optical fiber bundle is fused, and the light incident on the optical fiber bundle can be introduced in parallel to the central axis of the optical fiber line at the light guide end portion, and therefore, the light guide can be suitably used in a light irradiation device having the light guide.

Claims (3)

1. A light guide, characterized in that,

comprises a fiber bundle composed of a plurality of optical fibers and having at least the end portion on the light incident side thermally fused,

the central axis of each optical fiber located outside the central axis of the optical fiber bundle has an inclination angle with respect to the central axis of the optical fiber bundle at the end of the optical fiber bundle thermally fused,

the light incident end surface of the optical fiber bundle is concave, wherein,

at least a part of the optical fiber located outside the central axis of the optical fiber bundle is processed on the light incident end face in the following manner: an angle θ 2 formed by a light incident end surface of the optical fiber line and a surface perpendicularly intersecting with light incident on the light incident end surface satisfies the following expression:

θ2＝cot^-1(cotθ1-(n2/(n1sinθ1)))

where θ 1 is an inclination angle formed by light incident on the light incident end surface of the optical fiber and the central axis of the optical fiber, excluding zero degrees, n1 is a refractive index of a core constituting the optical fiber, n2 is a refractive index of a space outside the optical fiber,

the concave surface is spherical.

2. The light guide of claim 1, wherein the fiber optic strand is composed of quartz, multicomponent glass, or plastic.

3. A light irradiation device comprising a light emitting body that emits light and a light guide for irradiating the light emitted from the light emitting body to an object to be irradiated, wherein the light guide is the light guide according to claim 1 or 2.