JP2010072485A - Optical fiber bundle and optical irradiation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical fiber bundle and an optical irradiation device which enhances optical coupling efficiency to a light source, and in which sufficient light output is obtained. <P>SOLUTION: The optical fiber bundle 1 includes a main part section 3 in which a plurality of optical fibers 2 are bundled, and, a tapered section 4 which is disposed at the front end of the main part section 3 and turns to the incident end of the light. The tapered section 4 is formed by being integrated with the optical fibers 2, and is formed to a partially conical shape of an external diameter smaller toward the front end side, In the front end portion 3a of the main part section 3, the ratio of the sectional area of the core to the total sectional area is 0.85 to 1.00. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical fiber bundle and a light irradiation apparatus using the same.

In recent years, as an ultraviolet irradiation device used for curing an ultraviolet curable resin, an LED type ultraviolet irradiation device having low power consumption and excellent durability has been developed in place of the conventional lamp type ultraviolet irradiation device.
In an optical fiber bundle used as a light propagation path in this type of light irradiation device, an attempt is made to increase the light incident efficiency by optimizing the ratio of the core diameter to the optical fiber diameter (for example, Patent Documents). 1 and 2).
JP 2006-72025 A JP 2004-131340 A

In applications such as curing UV curable resins, high power density is required in addition to the amount of UV light, so there is a need to improve the optical coupling efficiency with the light source so that a large amount of light can be taken into a thinner optical fiber bundle. Has been.
As shown in Patent Document 1 and Patent Document 2, simply increasing the core area ratio of the cross section of the optical fiber bundle improves the optical coupling efficiency between the parallel light beam and the optical fiber bundle.
However, the optical fiber bundle has a limit in improving the optical coupling efficiency with a light source having a large light distribution angle, such as an LED, even if the core area is increased.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical fiber bundle and a light irradiation device that can increase the optical coupling efficiency with a light source having a large light distribution angle and obtain a sufficient light output.

The invention according to claim 1 of the present invention includes a main body portion in which a plurality of optical fibers are bundled, and a tapered portion that is provided at a front end of the main body portion and serves as an incident end of light. The optical fiber is integrally formed, has a partial conical shape whose outer diameter decreases toward the distal end side, and the distal end portion of the main body portion provided with the tapered portion has a cross-sectional area of the core with respect to a total sectional area. The ratio is 0.85 to 1.00.
According to a second aspect of the present invention, in the first aspect, the tapered portion is obtained by inserting the optical fiber from which the cladding has been removed through a glass tube and fusing them together. Is an optical fiber bundle characterized by
The invention according to claim 3 of the present invention is the optical fiber bundle according to claim 2, wherein the glass tube is made of fluorine-added quartz glass.
An invention according to a fourth aspect of the present invention includes the optical fiber bundle according to any one of the first to third aspects, and a light source that makes light incident on the optical fiber bundle from a tapered portion. It is the light irradiation apparatus characterized.

  According to the present invention, the ratio of the cross-sectional area of the core at the tip portion of the main body is 0.85 to 1.00. As a result, it is possible to increase the optical coupling efficiency with the light source and obtain a sufficient light output.

Hereinafter, an embodiment of an optical fiber bundle of the present invention will be described with reference to the drawings.
FIG. 1 is a side view schematically showing a light irradiation apparatus using the first embodiment of the optical fiber bundle according to the present invention. FIG. 2 is a view showing a part of the cross section taken along the line A1-A1 in FIG.
As shown in FIGS. 1 and 2, the light irradiation device includes a light source 5 and an optical fiber bundle 1 having an incident end on which light from the light source 5 is incident. The light can enter the optical fiber bundle 1 from the end, and can be emitted from the output end (not shown).
As the light source 5, a light emitting element that emits ultraviolet light, visible light, or the like, such as an LED, can be used.

The optical fiber bundle 1 includes a main body portion 3 configured by bundling a plurality of optical fibers 2 and a tapered portion 4 formed at the tip thereof.
As shown in FIG. 3, the optical fiber 2 has a core 2a made of quartz glass or the like, and a clad 2b covering the periphery of the core 2a. Specifically, for example, the core 2a has a diameter of 190 μm and the cladding 2b has a diameter of 200 μm, and the core 2a has a diameter of 200 μm and the cladding 2b has a diameter of 230 μm.
As shown in FIG. 2, the tip portion 3 a of the main body 3 is configured by bundling a plurality of optical fibers 2.

As shown in FIG. 1, the tapered portion 4 serves as an incident end of light from the light source 5, and a plurality of optical fibers 2 are integrated to form a partial conical shape whose outer diameter decreases toward the tip. It is the part (integrated part) made. The tapered portion 4 in the illustrated example has a truncated cone shape.
The tip surface 4a of the taper portion 4 is formed flat. The tip surface 4a may be a curved surface.

The tapered portion 4 can be formed by inserting and melting the tip portion of the optical fiber 2 from which the clad 2b has been removed through a glass tube (not shown). The glass tube may be made of pure quartz glass or may be made of fluorine-added quartz glass. The clad 2b can be removed by hydrofluoric acid treatment or the like.
Specifically, for example, the tip portion of the optical fiber 2 from which the clad 2b has been removed is inserted into a glass tube, set on a glass lathe (not shown), and heated by a burner while rotating around an axis. When the glass tube and the core 2a begin to soften, the glass tube is stretched to integrate the cores 2a and the core 2a with the glass tube.
The tapered portion 4 can be formed by cutting a predetermined position of the stretched portion and polishing the end face.
The tapered portion 4 can also be formed by putting the tip portion of the optical fiber 2 from which the clad 2b has been removed into a taper-shaped mold, melting it into a tapered shape, and polishing the end surfaces and side surfaces.

  As shown in FIG. 1, a part of light 5 a (for example, ultraviolet light or visible light) from a light source 5 such as an LED is incident on the tapered portion 4 after the propagation direction is bent at the tip surface 4 a of the tapered portion 4. Then, the light is reflected by the tapered surface 4b and enters the tip portion 3a of the main body 3. By the reflection on the tapered surface 4b, the incident angle on the tip portion 3a can be made smaller than the incident angle on the tip surface 4a.

FIG. 4 is a side view schematically showing a second embodiment of the optical fiber bundle according to the present invention. FIG. 5 is a view showing a part of the cross section taken along the line A2-A2 in FIG. In the following description, the same reference numerals are given to the above-described configurations, and description thereof is omitted. The same applies to other embodiments.
In the optical fiber bundle 11, the tip portion 13a of the main body 13 is configured by bundling a plurality of optical fibers 2 from which the cladding 2b is removed. That is, as shown in FIG. 5, the tip portion 13a is formed by bundling a plurality of cores 2a.

FIG. 6 is a side view schematically showing a third embodiment of the optical fiber bundle according to the present invention. FIG. 7 is a view showing a cross section taken along the line A3-A3 in FIG.
In the optical fiber bundle 21, the distal end portion 23 a of the main body portion 23 is configured by integrating a plurality of optical fibers 2 from which the cladding 2 b is removed. That is, as shown in FIG. 7, the tip portion 23a is obtained by melting and integrating a plurality of cores 2a.

FIG. 8 is a side view schematically showing a fourth embodiment of an optical fiber bundle according to the present invention. FIG. 9 is a view showing a cross section of the optical fiber bundle 31 taken along the line A4-A4 in FIG.
In the optical fiber bundle 31, the distal end portion 33 a of the main body portion 33 includes a core 32 a in which the core 2 a is integrated and a clad portion 32 b that covers the periphery thereof. The core 32a has the same configuration as the tip portion 23a shown in FIG.
The tapered portion 34 formed at the distal end of the distal end portion 33a includes a tapered portion main body 34a having the same configuration as the tapered portion 4 (see FIG. 6 and the like) and a clad portion 34b covering the periphery thereof.
The optical fiber bundle 31 can be formed by inserting the optical fiber 2 from which the cladding 2b has been removed into a glass tube, melting it, and molding it. This glass tube becomes the clad portions 32b and 34b, and is preferably made of fluorine-added quartz glass.

In the optical fiber bundle of the present invention, the ratio of the cross-sectional areas of the cores 2a and 32a to the total cross-sectional areas at the tip portions 3a, 13a, 23a, and 33a shown in FIGS. 1, 4, 6, and 8 is 0.85 to 1. 0.00 (preferably 0.90 to 1.00).
By setting the cross-sectional area ratio of the core 2a within this range, the light 5a from the light source 5 can be efficiently incident on the tip portions 3a, 13a, 23a, and 33a. For this reason, the optical coupling efficiency with the light source 5 is increased, and sufficient light output is obtained.
When the cross-sectional area ratio of the core 2a is less than 0.85, the optical coupling efficiency decreases, and a sufficient light output cannot be obtained particularly in the transmission of ultraviolet light in which the power density is important.

This cross-sectional area ratio is obtained as follows.
In the optical fiber bundle 1 of the first embodiment shown in FIGS. 1 and 2, the optical fiber 2 has a configuration in which the optical fibers 2 are bundled so as to have a hexagonal close-packed structure (see FIG. 2). The ratio of the cross-sectional area of the core 2a to the area of the hexagonal region formed by the center point 2c of the core 2a of the six optical fibers 2B surrounding the fiber 2A (hereinafter referred to as the core area ratio) is the diameter of the optical fiber 2 the d, indicated the diameter of the core 2a in the formula (1) shown below when the _{d c.}

As shown in the equation (1), the core area ratio is determined only by the ratio of the diameter of the optical fiber 2 and the diameter of the core 2a (d _c / d). As shown in FIG. 2 increases with the ratio of the diameter of the core 2a to the core 2a (d _c / d), and when d _c = d, π / 2√3, that is, about 0.91.
For example, in the optical fiber bundle 1 shown in FIGS. 1 and 2, when the diameter of the optical fiber 2 is 200 μm and the diameter of the core 2a is 190 μm, the core area ratio is about 0.82. When the diameter of the optical fiber 2 is 230 μm and the diameter of the core 2 a is 200 μm, the core area ratio is about 0.67.

In the optical fiber bundle 11 shown in FIGS. 4 and 5, the tip end portion 13a is composed only of the core 2a, so the core area ratio is about 0.91. This core area ratio is 1.11 times that of the optical fiber bundle 1 from which the clad 2b is not removed (see FIGS. 1 and 2; optical fiber diameter 200 μm, core diameter 190 μm). Compared with the case where the optical fiber diameter is 230 μm and the core diameter is 200 μm, it is 1.32 times.
Since the optical output is a value corresponding to the core area ratio, the optical output of the optical fiber bundle 11 (see FIGS. 4 and 5) is 1.11 respectively compared to the optical fiber bundle 1 (see FIGS. 1 and 2). Double (when the optical fiber diameter is 200 μm and the core diameter is 190 μm) and 1.32 times (when the optical fiber diameter is 230 μm and the core diameter is 200 μm).

In the optical fiber bundle 21 shown in FIGS. 6 and 7, the tip portion 23a is formed by melting and integrating the core 2a, so the core area ratio is 1.00. This core area ratio is 1.22 times that of the optical fiber bundle 1 from which the clad 2b is not removed (see FIGS. 1 and 2; optical fiber diameter 200 μm, core diameter 190 μm). Compared with the case where the optical fiber diameter is 230 μm and the core diameter is 200 μm, it is 1.46 times.
Since the optical output is a value corresponding to the core area ratio, the optical output of the optical fiber bundle 21 (see FIGS. 6 and 7) is 1.22 respectively compared to the optical fiber bundle 1 (see FIGS. 1 and 2). Double (when the optical fiber diameter is 200 μm and the core diameter is 190 μm) and 1.46 times (when the optical fiber diameter is 230 μm and the core diameter is 200 μm).

In the optical fiber bundle 31 shown in FIGS. 8 and 9, the tip portion 33a has a core area ratio smaller than 1.00 because the cladding portion 32b is provided around the core 32a in which the core 2a is integrated. Become. That is, the core area ratio is 0.85 or more and less than 1.00. If a glass tube having a sufficiently small thickness is used as the glass tube to be the clad portion 32b, the core area ratio becomes a value close to 1.00.
2, 5, 7, and 9 have the same shape as the tip surfaces of the tip portions 3 a, 13 a, 23 a, and 33 a of the main body portions 3, 13, 23, and 33.

According to the optical fiber bundle of the present invention, the optical coupling efficiency with the light source can be increased.
For example, in the optical fiber bundle 1 shown in FIG. 1, since the light 5a from the light source 5 is reflected by the tapered surface 4b, the radiation angle of the light 5a can be reduced, so that the optical coupling efficiency with the light source 5 is increased. it can.
Similarly, in the optical fiber bundles 11, 21, and 31 (see FIGS. 4 to 9), the light emission angle can be reduced by reflecting the light from the light source 5 on the tapered surface 4b. The optical coupling efficiency with 5 can be increased.
If the optical coupling efficiency between the light source and the optical fiber bundle is too low, the power density is also lowered. In particular, in the transmission of ultraviolet light, the light output necessary for curing the ultraviolet effect resin cannot be obtained.
On the other hand, in the optical fiber bundles 1, 11, 21, and 31, the optical coupling efficiency with the light source 5 can be increased. The optical coupling efficiency can be, for example, 36% or more (preferably 40% or more). Therefore, the power density of ultraviolet light or the like is improved, and efficient light transmission can be realized.

(1) When the diameter of the optical fiber bundle is constant <Examples 1 to 4>
The clad 2b at the tip of the optical fiber 2 (core diameter 190 μm, clad diameter 200 μm) is removed by hydrofluoric acid treatment, this portion is filled in a glass tube, melted by heating and integrated to form a tapered portion 4 and light. Fiber bundles 1 and 11 were obtained. The tip portions 3a and 13a of the main body portions 3 and 13 were formed by removing part or all of the clad 2b by hydrofluoric acid treatment.
In each example, the removal rate of the clad 2b was changed so that the tip portions 3a and 13a have an optical fiber diameter in the range of 190 to 196 μm in increments of 2 μm. (Shown as “fiber diameter” in Table 1)
A glass tube made of pure quartz glass was used.
The tapered portion 4 had a maximum diameter of 4.0 mm, a minimum diameter of 2.2 mm, and an axial length of 6.0 mm.
The number of optical fibers 2 packed in the glass tube was increased or decreased according to the removal ratio of the clad 2b. (Indicated in Table 1 as “number of fibers”)

The optical coupling efficiency of each optical fiber bundle was measured as follows.
As shown in FIG. 11, the light of the light source 5 is incident on the optical fiber bundles 1 and 11 with the tapered portion 4 as the incident end, and the output of the light passing through the optical fiber bundles 1 and 11 is output by the power meter 6 (detector). It was measured. As the light source 5, an LED (wavelength 365 nm, emitter size 1 mm × 1 mm) emitting ultraviolet light was used. The display unit 7 displays the detected value.
The distance between the tip surface 4a of the tapered portion 4 and the light source 5 was 1.5 mm.
For comparison, as shown in FIG. 12, light output measurement was performed without using an optical fiber bundle.
The ratio of the light output when using the optical fiber bundle to the light output when there is no optical fiber bundle was calculated as the optical coupling efficiency. The results are shown in Table 1.

<Example 5>
As shown in FIG. 8, an optical fiber bundle 31 was manufactured using a glass tube made of fluorine-added quartz glass. A glass tube having a thickness of 0.06 mm was used. Other conditions were the same as in Example 4. The optical coupling efficiency of the optical fiber bundle 31 was measured. The results are shown in Table 1.

<Example 6>
As shown in FIG. 6, the entire cladding 2b at the tip of the optical fiber 2 is removed by hydrofluoric acid treatment, put into a tapered mold and melted by heating to form the tapered portion 4, and the cladding 2b is removed. The optical fiber 2 was melted and integrated to form the tip portion 23a, and the optical fiber bundle 21 was produced. Other conditions were the same as in Example 4. The optical coupling efficiency of the optical fiber bundle 21 was measured. The results are shown in Table 1.

<Comparative Example 1>
An optical fiber bundle was produced in the same manner as in Example 1 except that the clad 2b was not removed. The optical coupling efficiency of this optical fiber bundle was measured. The results are shown in Table 1.

(2) When the number of optical fiber bundles is constant <Examples 7 to 10>
Optical fiber bundles 1 and 11 were produced with the number of optical fibers 2 being constant (320). In each Example, the glass tube in which the optical fiber 2 was packed used the thing from which a diameter differs according to the number of the optical fibers 2 (shown as "bundle diameter" in Table 2). Other conditions were the same as in Examples 1 to 4. The optical coupling efficiencies of these optical fiber bundles 1 and 11 were measured. The results are shown in Table 2.

<Example 11>
As shown in FIG. 8, an optical fiber bundle 31 was manufactured using a glass tube made of fluorine-added quartz glass. A glass tube having a thickness of 0.06 mm was used. Other conditions were the same as in Example 10. The optical coupling efficiency of the optical fiber bundle 21 was measured. The results are shown in Table 2.

<Example 12>
In accordance with Example 6, the optical fiber bundle 21 shown in FIG. The optical coupling efficiency of the optical fiber bundle 21 was measured. The results are shown in Table 2.

<Comparative example 2>
An optical fiber bundle was produced in the same manner as in Example 7 except that the clad 2b was not removed. The optical coupling efficiency of this optical fiber bundle was measured. The results are shown in Table 2.

  From Table 1 and Table 2, it can be seen that excellent optical coupling efficiency was obtained in Examples in which the core area ratio of the tip portion of the main body was 0.85 to 1.00.

It is a side view which shows typically the light irradiation apparatus using 1st Embodiment of the optical fiber bundle of this invention. It is a figure which shows a part of A1-A1 arrow cross section of the optical fiber bundle shown in FIG. It is a figure which shows the optical fiber which can be used for the optical fiber bundle shown in FIG. 1, (a) is a perspective view, (b) is sectional drawing. It is a side view which shows typically 2nd Embodiment of the optical fiber bundle of this invention. It is a figure which shows a part of A2-A2 arrow cross section of the optical fiber bundle shown in FIG. It is a side view which shows typically 3rd Embodiment of the optical fiber bundle of this invention. It is a figure which shows the A3-A3 arrow cross section of the optical fiber bundle shown in FIG. It is a side view which shows typically 4th Embodiment of the optical fiber bundle of this invention. It is a figure which shows the A4-A4 arrow cross section of the optical fiber bundle shown in FIG. It is a figure which shows the relationship between the core diameter and core area ratio in the optical fiber bundle which took the 6-way fine structure. It is a schematic block diagram which shows the test apparatus used for the measurement of optical coupling efficiency. It is a schematic block diagram which shows the test apparatus used for the measurement of optical coupling efficiency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 11, 21, 31 ... Optical fiber bundle, 2 ... Optical fiber, 2a, 32a ... Core, 2b ... Cladding, 4 ... Tapered part, 4a ... Tip surface, 5 ···light source.

Claims (4)

A main body portion in which a plurality of optical fibers are bundled, and a tapered portion that is provided at the tip of the main body portion and serves as an incident end of light,
The tapered portion is formed by integrating the optical fiber, and has a partial conical shape in which the outer diameter decreases toward the tip side.
The tip portion of the main body provided with the tapered portion has a ratio of the cross-sectional area of the core to the total cross-sectional area of 0.85 to 1.00.   2. The optical fiber bundle according to claim 1, wherein the tapered portion is obtained by inserting the optical fiber from which the cladding is removed through a glass tube and fusing them together. 3.   The optical fiber bundle according to claim 2, wherein the glass tube is made of fluorine-added quartz glass.   A light irradiation apparatus comprising: the optical fiber bundle according to any one of claims 1 to 3; and a light source that makes light incident on the optical fiber bundle from a tapered portion.

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