WO2019186718A1

WO2019186718A1 - Optical fiber bundle, endoscope scope, and endoscope

Info

Publication number: WO2019186718A1
Application number: PCT/JP2018/012557
Authority: WO
Inventors: 英明高久
Original assignee: 株式会社住田光学ガラス
Priority date: 2018-03-27
Filing date: 2018-03-27
Publication date: 2019-10-03
Also published as: CN111758062B; CN111758062A

Abstract

An optical fiber bundle 1 has a configuration in which a plurality of optical fibers are bundled, wherein the plurality of optical fibers include at least two types of optical fibers 11, 12 having different numerical apertures NA.

Description

Optical fiber bundle, endoscope scope, and endoscope

The present invention relates to an optical fiber bundle, an endoscope scope, and an endoscope.

A general optical fiber bundle is formed by bundling a large number of optical fibers of the same material. Such an optical fiber bundle has a limit in the function and performance obtained.
For example, when such an optical fiber bundle is used as a light guide for observation in a tube, depending on the optical characteristics of each optical fiber constituting the optical fiber bundle, only the front side or the back side in the tube can be sufficiently observed. There is a problem that both the near side and the far side in the tube cannot be observed well. As a technique for solving this problem, the shape of the emission end face of the optical fiber bundle is processed into a non-flat shape such as a convex shape, a concave shape, a wave shape, etc. It is possible to adjust (for example, patent document 1, 2).

Japanese National Publication No. 52-010346 Japanese Unexamined Patent Publication No. 03-123311

However, the processing of the end face of the optical fiber bundle is not easy, and is particularly difficult when the optical fiber bundle has a small diameter. In addition, the light distribution characteristics cannot be greatly changed as required only by changing the end face shape of the optical fiber bundle.

Therefore, an object of the present invention made by paying attention to this point is to provide an optical fiber bundle, an endoscope scope, and an endoscope capable of easily and freely adjusting a light distribution characteristic.

The optical fiber bundle of the present invention is
In an optical fiber bundle having a configuration in which a plurality of optical fibers are bundled,
The plurality of optical fibers include two or more types of optical fibers having different numerical apertures NA.
According to the optical fiber bundle of the present invention, the light distribution characteristics can be adjusted easily and freely.

In the optical fiber bundle of the present invention,
The plurality of optical fibers are fixed only at both ends of the optical fiber bundle,
It is preferable that both end surfaces of the optical fiber bundle are optical polishing surfaces.
Such an optical fiber bundle is particularly suitable for being configured as a light guide.

In the optical fiber bundle of the present invention,
You may comprise as a light guide which transmits the light from a light source only in the direction which goes to the other side from the one side of the longitudinal direction of the said optical fiber bundle.

In the optical fiber bundle of the present invention,
The optical fiber bundle may be configured as a branched optical fiber bundle in which at least one of the one side and the other side in the longitudinal direction is branched.
Such an optical fiber bundle is particularly suitable for being configured as a light guide.

In the optical fiber bundle of the present invention,
It is preferable that the plurality of optical fibers include at least one type of optical fiber in which at least one of the core and the clad is made of multicomponent glass.
In this case, the light distribution characteristic can be adjusted more easily and freely.

In the optical fiber bundle of the present invention,
The optical fiber bundle is configured as a light guide, and it is preferable that the waveform representing the light distribution characteristic includes six or more inflection points.
In this case, it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance.

In the optical fiber bundle of the present invention,
The optical fiber bundle is configured as a light guide,
The plurality of optical fibers include a plurality of first optical fibers having a first numerical aperture NA1 and a plurality of second optical fibers having a second numerical aperture NA2 that is 0.15 or more larger than the first numerical aperture NA1. It is preferable.
In this case, it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance.

In the optical fiber bundle of the present invention,
The optical fiber bundle is configured as a light guide,
The plurality of optical fibers include a plurality of first optical fibers having a first numerical aperture NA1, and a plurality of second optical fibers having a second numerical aperture NA2 larger than the first numerical aperture NA1.
It is preferable that the ratio (FN2 / FN1) of the number FN2 of the second optical fibers to the number FN1 of the first optical fibers is 0.05 to 9.
In this case, it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance.

An endoscope scope according to the present invention includes the above-described optical fiber bundle.
According to the endoscope scope of the present invention, the light distribution characteristic can be adjusted easily and freely.

The endoscope of the present invention includes the endoscope scope described above.
According to the endoscope of the present invention, the light distribution characteristic can be adjusted easily and freely.

According to the present invention, it is possible to provide an optical fiber bundle, an endoscope scope, and an endoscope that can adjust light distribution characteristics easily and freely.

Fig.1 (a) is a partial cross section side view which shows the optical fiber bundle which concerns on one Embodiment of this invention roughly by a partial cross section, FIG.1 (b) is the optical fiber of Fig.1 (a). It is a cross-sectional view which shows the edge part of a bundle roughly. It is a transverse cross section showing roughly the modification of the optical fiber bundle concerning one embodiment of the present invention. It is a partial cross section side view which shows roughly the other modification of the optical fiber bundle which concerns on one Embodiment of this invention by a partial cross section. It is a figure for demonstrating the experimental method of an Example and a comparative example. It is a figure for demonstrating the waveform showing the light distribution characteristic obtained as an experimental result of an Example and a comparative example. It is a figure for demonstrating the waveform showing the light distribution characteristic. It is a figure showing roughly an example of an endoscope provided with an optical fiber bundle concerning one embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

The optical fiber bundle of the present invention has a configuration in which a plurality of optical fibers are bundled, and the plurality of optical fibers includes two or more types of optical fibers having different numerical apertures NA. The optical fiber bundle of the present invention can be used as a light guide, an image guide, or various optical fibers for sensors in various fields such as the industrial field and the medical field. It is suitable when used as a light guide or image guide (further, a light guide) used for an endoscope or a light guide for a microscope.

FIG. 1 shows an example of an optical fiber bundle 1 according to an embodiment of the present invention. Fig.1 (a) is a partial cross section side view which shows the optical fiber bundle 1 of this embodiment schematically by a partial cross section, and FIG.1 (b) is the optical fiber bundle 1 of Fig.1 (a). It is a cross-sectional view which shows the edge part 1A of one side roughly. In the example of FIG. 1, the other end 1B of the optical fiber bundle 1 and the end faces on both sides of the optical fiber bundle 1 also have the same configuration as the cross section shown in FIG. The optical fiber bundle 1 of this embodiment is configured as a light guide for transmitting light from a light source to a remote location.
The optical fiber bundle 1 has a configuration in which two types of

optical fibers

11 and 12 having different numerical apertures NA are bundled. In this specification, the

optical fibers

11 and 12 constituting the optical fiber bundle 1 may be collectively referred to as an “optical fiber group 10”. In this example, the optical fiber group 10 includes a plurality of first optical fibers 11 and a plurality of second optical fibers 12. The first optical fiber 11 and the second optical fiber 12 are single-core optical fibers composed of

cores

11a and 12a and clads 11b and 12b covering the outer peripheral surfaces thereof, respectively.
In the example of FIG. 1, the numerical aperture NA of the second optical fiber 12 (hereinafter also referred to as “second numerical aperture NA2”) is the numerical aperture NA of the first optical fiber 11 (hereinafter referred to as “first numerical aperture NA1”). It is also larger than.)
In the example of FIG. 1, the

cores

11a and 12a of the first optical fiber 11 and the second optical fiber 12 have a circular cross-sectional shape, and the

claddings

11b and 12b of the first optical fiber 11 and the second optical fiber 12 are It has a circular outer edge shape.

At both ends 1A and 1B of the optical fiber bundle 1, the

optical fibers

11 and 12 of the optical fiber group 10 are fixed in the

tubular sleeves

2A and 2B by a solidifying agent 40 such as an adhesive. The

sleeves

2A and 2B are made of metal, for example. End faces 10SA and 10SB on both sides of the optical fiber group 10 of the optical fiber bundle 1 are formed on the optically polished surface by a polishing process. The end faces 10SA and 10SB on both sides of the optical fiber group 10 are, for example, flat surfaces.
In an intermediate portion located between both

end portions

1A and 1B in the longitudinal direction of the optical fiber bundle 1, the optical fiber group 10 is not fixed by the solidifying agent 40 or the like but is simply bundled, and is a flexible exterior. Covered by a tube 3. Thereby, the optical fiber bundle 1 can be easily bent. The outer tube 3 is made of, for example, a resin tube or a bellows-like metal tube.
In the example of FIG. 1, the optical fiber bundle 1 can use either one side or the other side in the longitudinal direction as the incident side, but the light from the light source is changed from one side to the other side at a time. It is configured to transmit only in one direction, and is not configured to transmit light in both directions at once. In the example of FIG. 1, for example, one end 1 </ b> B of the optical fiber bundle 1 is used as the incident side, and is connected to a light source device (not shown), for example. The other end 1A of the optical fiber bundle 1 is used as the emission side.

Generally, the numerical aperture NA of the optical fiber, the refractive index of the core and n _1, the refractive index of the cladding and n _2, the external optical fiber air (refractive index 1) to,

It is calculated by the following formula. The refractive index n _{1 of} the core and the refractive index n ₂ of the clad are obtained, for example, by measuring using the “optical refractive index measuring method” in the Japan Optical Glass Industry Association Standard when the core and the clad are made of glass. It is done.
In equation (1), θ is the light receiving angle (also referred to as the aperture angle) of the optical fiber. As can be seen from the equation (1), when the difference between the refractive index n _{1 of the} core and the refractive index n _{2 of the} cladding is large, the numerical aperture NA increases, and the optical fiber receives light in a wide angular range, Light is emitted in a wide angle range. Conversely, the optical fiber, the difference between the refractive index n ₂ of the refractive index n ₁ and a cladding of the core is small, the numerical aperture NA is reduced, by receiving light in a narrow range of angles, the light in a narrow angular range It comes out.

The optical fiber bundle 1 of the present embodiment has a configuration in which two or more types (two types in the example of FIG. 1) of

optical fibers

11 and 12 having different numerical apertures NA are bundled. Different light distribution characteristics can be obtained as compared with the case where only the optical fibers are bundled.
That is, as described above, a conventional optical fiber bundle is a bundle of optical fibers made of the same material, that is, has a configuration in which only optical fibers having the same numerical aperture NA are bundled. . For example, when this conventional optical fiber bundle is used as a light guide and the inside of a tube is to be observed, when the amount of light is weak, only the front side of the tube is visible, and sufficient light does not reach the back side of the tube. When the amount of light is strong, it becomes difficult to observe both the front side and the back side in the tube simultaneously and satisfactorily, such as causing halation on the inner wall on the front side in the tube. As described above, it is very difficult to simultaneously illuminate points with different distances from the emission end face with good illuminance by using an optical fiber bundle in which only optical fibers having the same numerical aperture NA are bundled. In particular, this problem becomes more prominent as the inner diameter of the tube to be observed is thinner.
On the other hand, since the optical fiber bundle 1 of the present embodiment has a configuration in which two or more types of

optical fibers

11 and 12 having different numerical apertures NA are bundled, for example, when used as a light guide, light having a relatively large numerical aperture NA. The optical fiber 11 having a relatively small numerical aperture NA can satisfactorily illuminate an object that is far from the exit end face, while the fiber 12 can satisfactorily illuminate the object that is close to the exit end face. In other words, it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance. Therefore, for example, when the optical fiber bundle 1 of the present embodiment is used for observation inside the tube as a light guide, it is possible to simultaneously illuminate and observe the near side and the far side in the tube at the same time.
In the optical fiber bundle 1 of the present embodiment, the numerical aperture NA of each type of

optical fiber

11, 12 constituting the optical fiber bundle 1, the ratio of the number of each type of

optical fiber

11, 12, each type By adjusting the total number of the

optical fibers

11 and 12, etc., the light distribution characteristics can be adjusted freely and easily.

As in the example of FIG. 1, the optical fiber group 10 includes a plurality of first optical fibers 11 having a first numerical aperture NA1 and a plurality of second optical fibers 12 having a second numerical aperture NA2. The second numerical aperture NA2 of the second optical fiber 12 is preferably larger than the first numerical aperture NA1 of the first optical fiber 11 by 0.15 or more, more preferably by 0.2 or more, and further preferably by 0.55 or more. This configuration is particularly suitable when the optical fiber bundle 1 is configured as a light guide, and thereby it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance. For example, when the optical fiber bundle 1 is used as a light guide for observation inside the tube, both the near side and the far side in the tube can be observed more favorably.
As in the example of FIG. 1, the optical fiber group 10 includes a plurality of first optical fibers 11 having a first numerical aperture NA1, and a plurality of second optical apertures NA2 having a second numerical aperture NA2 larger than the first numerical aperture NA1. In the case of including two optical fibers 12, the ratio of the number FN2 of the second optical fibers 12 to the number FN1 of the first optical fibers 11 (FN2 / FN1) is preferably 0.05 to 9, and more preferably 0.1 to 5.5. It is preferably 0.25 to 4, more preferably. This configuration is particularly suitable when the optical fiber bundle 1 is configured as a light guide, and thereby it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance. For example, when the optical fiber bundle 1 is used as a light guide for observation inside the tube, both the near side and the far side in the tube can be observed more favorably.

In the optical fiber bundle 1, it is preferable that the waveform representing the light distribution characteristic includes six or more inflection points Q.
This configuration is particularly suitable when the optical fiber bundle 1 is configured as a light guide, and thereby it is possible to simultaneously illuminate points with different distances from the emission end face with good illuminance.
Here, the “waveform representing the light distribution characteristic” means that, as schematically shown in FIG. 6, the vertical axis represents the light intensity, and the horizontal axis represents the angle (°) from the exit end face 10SA of the optical fiber bundle 1. It refers to the waveform when. As a method of obtaining this waveform, for example, as will be described later with reference to FIGS. 4 and 5, FFP described in “Optical fiber structure parameter test method—optical characteristics” defined in JIS C 6825: 2009. There are methods that comply with the law. In this method, light (for example, white light) is incident on the incident end face 10SB of the optical fiber bundle 1 while the light source 330 is pressed. Then, the light receiving element 310 with the aperture member 320 having the pinhole 320a attached to the light receiving surface is emitted from the optical fiber bundle 1 along an arc path having a predetermined radius r centering on the output end surface 10SA of the optical fiber bundle 1. The direction perpendicular to the end face is set to 0 ° and moved over an angle range of 90 ° to −90 °, and during that time, the total amount of light transmitted through the optical fiber bundle 1 is measured. Thereby, a waveform representing the light distribution characteristic is obtained.
Further, the “inflection point Q” refers to a point where the secondary differential value of the waveform curve representing the light distribution characteristic is 0, and the sign of the secondary differential value is reversed before and after that.

Note that the optical fiber bundle 1 of the present embodiment is not limited to the example of FIG. 1, and various modifications are possible.
For example, the optical fiber bundle 1 may have a configuration in which three or more types of optical fibers having different numerical apertures NA are bundled.

Adjustment of the numerical aperture NA of each type of optical fiber constituting the optical fiber bundle 1 can be performed by adjusting the composition of each core and cladding of each type of optical fiber.
The core and clad of each type of optical fiber constituting the optical fiber bundle 1 may each be made of glass of any composition, such as multicomponent glass or quartz glass, or plastic. However, if the optical fiber bundle 1 includes at least one type of optical fiber in which at least one of the core and the clad is made of multicomponent glass, the numerical aperture NA of each optical fiber is greatly changed as necessary. Therefore, the light distribution characteristics can be adjusted more easily and freely. From the same viewpoint, it is further preferable that the core and the clad of each type of optical fiber constituting the optical fiber bundle 1 are each made of multicomponent glass.

In the example of FIG. 1, the

optical fibers

11 and 12 constituting the optical fiber bundle 1 have substantially the same outer diameter (and consequently cladding outer diameter) and core outer diameter, but this is not essential. For example, the outer diameter and core diameter of each type of optical fiber constituting the optical fiber bundle 1 may be different from each other. Or the outer diameter and core diameter of each optical fiber which comprises the optical fiber bundle 1 may mutually differ.
In the example of FIG. 1, the distance between the

optical fibers

11 and 12 constituting the optical fiber bundle 1 is substantially uniform when the cross sections or the end faces 10SA and 10SB of the

end portions

1A and 1B of the optical fiber bundle 1 are viewed. In addition, although the

optical fibers

11 and 12 of each type are randomly arranged, this is not essential. Any spacing may be selected between the

optical fibers

11 and 12 constituting the optical fiber bundle 1 and the arrangement of the various types of

optical fibers

11 and 12 may be selected.

In the example of FIG. 1, the

optical fibers

11 and 12 of the optical fiber group 10 are fixed by the solidifying agent 40 only at the

end portions

1A and 1B on both sides of the optical fiber bundle 1, but this is essential. is not.
For example, as in the modification schematically shown in FIG. 2, each light of the optical fiber group 10 is bonded by thermal fusion without using the solidifying agent 40 only at the ends 1 </ b> A and 1 </ b> B on both sides of the optical fiber bundle 1. The

fibers

11 and 12 may be fixed. In this case, as compared with the example of FIG. 1, the gap between the

optical fibers

11 and 12 can be eliminated. As a result, the core occupied area ratio of the optical fiber bundle 1 can be increased. As a result, the amount of light can be increased. The core occupied area ratio of the optical fiber bundle 1 is an optical fiber with respect to the cross-sectional area of the outer edge of the optical fiber group 10 (and thus the cross-sectional area of the inner peripheral surfaces of the

sleeves

2A and 2B) in the cross section of the optical fiber bundle 1. The total ratio of the areas of the

cores

11a and 12a of the

optical fibers

11 and 12 of the group 10 is indicated.
Moreover, the location where the

optical fibers

11 and 12 of the optical fiber bundle 1 are fixed by the solidifying agent 40 or heat fusion or the like is only one end portion of the optical fiber bundle 1 or a portion extending over the entire length of the optical fiber bundle 1. Any location may be used. However, when the

optical fibers

11 and 12 are fixed only at both ends of the optical fiber bundle 1 as in the example of FIG. 1, the intermediate portion of the optical fiber bundle 1 can be easily bent, so that it is used as a light guide. It is particularly suitable for the case.
As a method for fixing the end portion of the optical fiber group 10 to the inner peripheral surface of the sleeve 2A, any method such as fixing with a solidifying agent 40 or the like as shown in FIG. 2 or fixing by heat fusion may be used. .

In the example of FIGS. 1 and 2, the optical fiber group 10 has a substantially circular cross-sectional shape that is substantially the same as the cross-sectional shape of the inner peripheral surfaces of the

sleeves

2A and 2B over the entire length of the optical fiber bundle 1. This is not mandatory. The optical fiber group 10 may have an arbitrary cross-sectional shape at an arbitrary position in the longitudinal direction of the optical fiber bundle 1. For example, the shape of the optical fiber group 10 on the emission end face of the optical fiber bundle 1 may be generally an arbitrary shape such as a linear shape, a square shape, or an annular shape.

Further, the optical fiber bundle 1 is a branched type light in which at least one of one side and the other side in the longitudinal direction of the optical fiber bundle is branched, as in another modification schematically shown in FIG. It may be configured as a fiber bundle. Such a configuration is particularly suitable when the optical fiber bundle 1 is used as a light guide.
In the example of FIG. 3, only one side of the optical fiber bundle 1 is branched into two branched optical fiber bundles. More specifically, on one side of the optical fiber bundle 1, a branched optical fiber bundle having an optical fiber group 110 in which a plurality of types of

optical fibers

111 and 112 having different NAs (two types in the example in the figure) are bundled, A branched optical fiber bundle having an optical fiber group 210 in which a plurality of types of

optical fibers

211 and 212 with different NAs (two types in the example in the figure) are bundled is formed. At one

end

101A, 201A of each branched optical fiber bundle, the

optical fibers

111, 112 of the optical fiber group 110 and the

optical fibers

211, 212 of the optical fiber group 210 are respectively connected within the

sleeves

102A, 202A. It is fixed. These branched optical fiber bundles are coupled at an intermediate portion of the optical fiber bundle 1, and on the other side, the optical fiber group 10 in which the

optical fiber groups

110 and 210 of each branched optical fiber bundle are bundled together. Is configured. At the other end 1B of the optical fiber bundle 1, the

optical fibers

111, 112, 211, 212 of the optical fiber group 10 are fixed in the sleeve 2B. In the example of FIG. 3, when the end faces 110SA and 210SA of the branched optical fiber bundles of the optical fiber bundle 1 are used as the incident end faces, and the unbranched end face 10SB of the optical fiber bundle 1 is used as the outgoing end face as a light guide. For example, it is possible to emit a strong light amount in which the light amounts of a plurality of light sources are combined. On the other hand, in the example of FIG. 3, the end faces 110SA and 210SA of the branched optical fiber bundles of the optical fiber bundle 1 are used as emission end faces, and the unbranched end face 10SB of the optical fiber bundle 1 is used as an incident end face as a light guide. In this case, for example, the light can be distributed to a plurality of arbitrary locations with one light source.
In addition, both the one side and the other side of the longitudinal direction of the optical fiber bundle may be branched. Further, the number of branches may be three or more.
The configuration of the

optical fiber groups

110 and 210 of each branch optical fiber bundle may be the same as or different from each other. Each of the

optical fiber groups

110 and 210 of each branch optical fiber bundle may include a plurality of types of optical fibers having different NAs, or may include only one type of optical fiber having the same NA.

FIG. 7 shows an example of an endoscope including the optical fiber bundle 1 according to the above-described embodiment of the present invention (for example, the example of FIG. 1 or FIG. 2). The endoscope 50 of this example is an industrial or medical endoscope, and includes a scope (endoscope scope) 60, a light source 70, a control unit 80, and a display 90. The scope 60 includes an operation unit 61 and an insertion unit 62. A light guide 31 and an image guide 32 are provided inside the insertion portion 62 and the operation portion 61 of the scope 60. At the distal end of the insertion portion 62 of the scope 60, for example, an optical system (disposed further on the distal end side with respect to the emission end of the light guide 31, the incident end of the image guide 32, and the incident end of the image guide 32). For example, an objective lens) is arranged. The light guide 31 is configured to transmit light from the light source 70 and irradiate the object to be observed from the tip of the insertion portion 62. In this example, the light guide 31 is comprised from the optical fiber bundle 1 which concerns on one Embodiment of this invention. The image guide 32 is configured to transmit an image of the observation target image formed at the incident end thereof through, for example, an optical system (objective lens or the like). The image transmitted by the image guide 32 enters the control unit 80 via, for example, an eyepiece (not shown). The control unit 80 includes, for example, a photodetector, an ADC (analog-digital converter), a CPU, and a memory (RAM, ROM, etc.). The control unit 80 performs image processing or the like based on the image incident from the image guide 32 to generate an image signal, and displays an image of the observation target on the display 90 based on the generated image signal. The control unit 80 also controls the light source 70.
Note that, instead of / in addition to the light guide 31, the image guide 32 may also be configured from the optical fiber bundle 1 according to an embodiment of the present invention.
Further, the endoscope 50 shown in FIG. 7 is merely an example, and the endoscope 50 including the optical fiber bundle 1 according to the embodiment of the present invention may have a configuration different from that in FIG.

Examples 1 to 3 and Comparative Examples 1 and 2 of the optical fiber bundle according to the present invention were experimentally manufactured and evaluated by experiments, and will be described below with reference to FIGS. FIG. 4 is a diagram for explaining the experimental method. FIG. 5 is a diagram for explaining the experimental results.
The optical fiber bundles of Examples 1 to 3 are ride guides having a configuration similar to that described with reference to FIG. 1, and the optical fiber group 10 includes a plurality of first fibers having a first numerical aperture NA1. The optical fiber 11 and a plurality of second optical fibers 12 having a second numerical aperture NA2 are bundled in a randomly arranged state. The first numerical aperture NA1 was 0.13 (opening angle 2θ = 15 °), the second numerical aperture NA2 was 0.87 (opening angle 2θ = 120 °), and NA2−NA1 = 0.74. Here, θ is θ in the formula (1). In the optical fiber bundle of Comparative Example 1, the optical fiber group 10 was configured by bundling only the second optical fiber 12. In the optical fiber bundle of Comparative Example 2, the optical fiber group 10 was configured by bundling only the first optical fibers 11. In Examples 1 to 3 and Comparative Examples 1 and 2, only the ratio (FN1: FN2) of the number FN1 of the first optical fibers 11 and the number FN2 of the second optical fibers 12 is different as shown in FIG. Other configurations were the same. Specifically, in Comparative Example 1, FN1: FN2 = 0: 100 (that is, FN2 / FN1 = infinity), in Example 1, FN1: FN2 = 25: 75 (that is, FN2 / FN1 = 3), and in Example 2, FN1: FN2 = 50: 50 (ie, FN2 / FN1 = 1), FN1: FN2 = 75: 25 (ie, FN2 / FN1 = 0.33) in Example 3, and FN1: FN2 = 100: 0 in Comparative Example 2 FN2 / FN1 = 0).
In each example and comparative example, the outer diameter of each of the

optical fibers

11 and 12 was about 50 μm, and the outer diameter of the optical fiber group 10 was about 1 mm. In each example and comparative example, the filling ratio of the optical fibers 11 and 12 (the total cross-sectional area of the

optical fibers

11 and 12 with respect to the cross-sectional area of the optical fiber group 10 (and thus the cross-sectional area of the inner peripheral surfaces of the

sleeves

2A and 2B)) Ratio) was about 86%, and the total number of

optical fibers

11 and 12 was about 344. In each of the examples and comparative examples, the outer tube 3 is made of nylon net, the incident end side sleeve 2B is made of aluminum, and the emission end side sleeve 2A is made of stainless steel. Planar processing and optical polishing were performed on the end faces 10SB and 10SA on both sides of the optical fiber bundle 1.
In each of the examples and comparative examples, the cores and claddings of the

optical fibers

11 and 12 were each composed of multicomponent glass. The first numerical aperture NA1, when calculates the second numerical aperture NA2 by the formula (1), the refractive index n ₁ of the _core, the refractive index n ₂ of the cladding, the refractive index of the "optical in Japanese Optical Glass Industrial Standard It was obtained by measuring using the “measurement method”.

The light distribution characteristics of the optical fiber bundles of Examples 1 to 3 and Comparative Examples 1 and 2 were obtained by the experimental method described below. The experiment was performed by a method based on the FFP method described in “Optical Fiber Structural Parameter Test Method—Optical Properties” defined in JIS C 6825: 2009. More specifically, as shown in FIG. 4, white light was incident on the incident end face 10 </ b> SB of the optical fiber bundle 1 with the light source 330 pressed. As the light source 330, an LED for illumination (product code: CL-L230-C10N-A) manufactured by Citizen was used. Then, the light receiving element 310 having the aperture member 320 with the pinhole 320a attached to the light receiving surface is moved along the circular path having a radius r = 50 mm centered on the emission end surface 10SA of the optical fiber bundle 1. The direction perpendicular to the emission end face was set to 0 ° and moved over an angle range of 90 ° to −90 °, and during that time, the total amount of light transmitted through the optical fiber bundle 1 was measured. FIG. 5 shows a waveform representing the light distribution characteristics obtained as a result. The vertical axis of the graph represents the light intensity measured by the light receiving element 310, and the horizontal axis represents the angle (°) from the emission end face 10SA. Respectively. The numerical value on the vertical axis is a value obtained by normalizing the light intensity when the angle is 0 ° for each optical fiber bundle 1 as 1.

As shown in FIG. 5, the comparative example 1 comprised only from the 2nd optical fiber 12 with a large numerical aperture NA had strong light intensity over a wide angle range. When the inside of the tube was illuminated using the optical fiber bundle of Comparative Example 1, the illuminance on the near side as well as the back side in the tube was too strong, and as a result, the inside of the tube could not be sufficiently observed. On the other hand, Comparative Example 2 composed of only the first optical fiber 11 having a small numerical aperture NA had strong light intensity only in the vicinity of 0 °, and sufficient light intensity could not be obtained in the angular range outside it. When the inside of the tube was illuminated using the optical fiber bundle of Comparative Example 2, only the back side in the tube was illuminated, and the near side could not be observed sufficiently. On the other hand, in Examples 1 to 3, which are composed of the first optical fiber 11 and the second optical fiber 12 having different numerical apertures NA, a strong light intensity was obtained in the vicinity of 0 °, and on the outside In this angle range, a moderate light intensity that was neither too strong nor too weak was obtained. As a result, when the inside of the tube was illuminated using the optical fiber bundles of Examples 1 to 3, both the inside and the inside of the tube could be well illuminated and observed.
The waveforms representing the light distribution characteristics of Comparative Example 1 and Comparative Example 2 each had two inflection points Q. The waveforms representing the light distribution characteristics of Examples 1 to 3 each had six or more inflection points Q.

The optical fiber bundle of the present invention can be used in various fields such as an industrial field and a medical field, for example, as a light guide, an image guide, or an optical fiber for sensors. It can be suitably used as a light guide or an image guide (further speaking, a light guide) used for a light source or a light guide for a microscope.

DESCRIPTION OF SYMBOLS 1

Optical fiber bundle

1A, 1B, 101A,

201A End part

2A, 2B, 102A,

202A Sleeve

3, 103, 203

Outer tube

10, 110, 210 Optical fiber group 10SA, 10SB, 110SA,

210SA End face

11, 12, 111, 112, 211, 212

Optical fiber

11a,

12a Core

11b, 12b Clad 31 Light guide 32 Image guide 40 Solidifying agent 50 Endoscope 60 Scope (Scope for endoscope)
61 Operation part 62 Insertion part 70 Light source 80 Control part 90 Display 310 Light receiving element 320 Diaphragm member 320a Pinhole 330 Light source Q Inflection point

Claims

In an optical fiber bundle having a configuration in which a plurality of optical fibers are bundled,
The plurality of optical fibers includes an optical fiber bundle including two or more types of optical fibers having different numerical apertures NA.
The plurality of optical fibers are fixed only at both ends of the optical fiber bundle,
The optical fiber bundle according to claim 1, wherein both end faces of the optical fiber bundle are optically polished surfaces.
The optical fiber bundle according to claim 2, wherein the optical fiber bundle is configured as a light guide that transmits light from a light source only in a direction from one side of the longitudinal direction of the optical fiber bundle to the other side.
The optical fiber bundle according to claim 1, wherein the optical fiber bundle is configured as a branched optical fiber bundle in which at least one of one side and the other side in the longitudinal direction of the optical fiber bundle is branched.
The optical fiber bundle according to any one of claims 1 to 4, wherein the plurality of optical fibers include at least one type of optical fiber in which at least one of a core and a clad is made of multicomponent glass. .
The optical fiber bundle according to any one of claims 1 to 5, wherein the optical fiber bundle is configured as a light guide, and a waveform representing the light distribution characteristic includes six or more inflection points.
The optical fiber bundle is configured as a light guide,
The plurality of optical fibers include a plurality of first optical fibers having a first numerical aperture NA1 and a plurality of second optical fibers having a second numerical aperture NA2 that is 0.15 or more larger than the first numerical aperture NA1. The optical fiber bundle according to any one of claims 1 to 6.
The optical fiber bundle is configured as a light guide,
The plurality of optical fibers include a plurality of first optical fibers having a first numerical aperture NA1, and a plurality of second optical fibers having a second numerical aperture NA2 larger than the first numerical aperture NA1.
The optical fiber bundle according to any one of claims 1 to 7, wherein a ratio (FN2 / FN1) of the number FN2 of the second optical fibers to the number FN1 of the first optical fibers is 0.05 to 9.
An endoscope scope comprising the optical fiber bundle according to any one of claims 1 to 8.
An endoscope comprising the endoscope scope according to claim 9.