JPH10239555A - Light guide bundle connecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light guide bundle connecting device capable of suppressing the increase of the diameter size of an endoscope side light guide bundle and keeping the optical coupling efficiency high when realizing a connecting structure separating the end faces of the light guide bundles on the light source side and endoscope side. SOLUTION: Both light guide bundles are separately arranged face to face to satisfy the relation Lx<=(R-S)/tanθ, where R is a radius o the light outgoing face of a light source side light guide bundle 100, S is radius of a light incidence face of an endoscope side light guide bundle 200, Lx is the interval between them, and θ is the opening angle of an optical fiber. Light transmission efficiency can be increased without providing an optical system between both light guide bundles 100, 200, and the structure can be simplified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light guide bundle used for transmitting illumination light in an endoscope or the like, and more particularly, to a light guide bundle for connecting two light guide bundles formed of optical fibers in a light transmission direction. Related to the device.

[0002]

2. Description of the Related Art In a recent endoscope, a plurality of optical fibers are bundled to illuminate an object 500 to be observed by an observation optical system 400 as shown in FIG. Endoscope-side light guide bundle 200 configured
A light source-side light guide bundle 100 that is detachably connected to the endoscope-side light guide bundle 200 at an end thereof and transmits light from the light source 600 to the endoscope-side light guide bundle 200; There is a separated configuration consisting of A connecting device 70 for connecting these two light guide bundles 100 and 200.
0, both light guide bundles 100, 20
A contact connection structure in which the end surfaces of the light guide bundles are directly contacted with each other and a separation connection structure in which the end surfaces of both light guide bundles are connected at an appropriate interval are proposed. When comparing these,
In the contact connection structure, the end faces of both light guide bundles are liable to be damaged due to mutual contact when the two light guide bundles are frequently attached and detached, and a foreign matter enters between the contact surfaces of both light guide bundles, and obstruction of light transmission. In this respect, it can be said that the separated connection structure is more excellent.

However, in the above-described separated connection structure, since the end faces of both light guide bundles are separated from each other, the light transmission efficiency is apt to be reduced, and the light emitted from the light source can be effectively irradiated on the object to be observed. The problem that it is difficult is easy to occur. This will be briefly described. FIG. 7A is a diagram for explaining a critical angle θ in an optical fiber. The optical fiber 101 is provided with a clad 103 on the outer periphery of a core 102 on the center side.
The light is transmitted through the core 102 while reflecting light at the interface between the core 102 and the clad 103 by using a critical angle based on the difference between the refractive indices of the clad 102 and the clad 103.
Therefore, in order to perform optical transmission while securing a critical angle at this interface, the incident angle θ of light incident on the end face of the optical fiber with respect to the optical axis of the optical fiber (hereinafter, this is referred to as an aperture angle) ) Has a limitation, and light incident on the end face at an angle larger than the opening angle θ is not effectively transmitted in the optical fiber.

Here, as shown in FIG. 7B, the radius of the thickness of the light source side light guide bundle 100, that is, the light exit end face is a circular surface having a radius R, and the thickness of the endoscope side light guide bundle 200 is changed. Of the light incident end face with the radius S
With a circular surface. Further, the distance between both end faces is Lx. The light emitted from the light emission surface of the light source side light guide bundle 100 is light having the maximum aperture angle θ due to the above-described relationship of the optical fiber aperture angle θ. Therefore, although not shown, in the state where both light guide bundles are in close contact with each other, that is, when Lx = 0, if R ≦ S, all of the light emitted from the light source side light guide bundle is the endoscope side light. The light is transmitted to the guide bundle, and its light transmission efficiency, that is, the light coupling efficiency between the two light guide bundles is close to 100%.

On the other hand, as shown in FIG.
0, that is, when the light entrance surface and the light exit surface of both light guide bundles are separated by an appropriate dimension without any consideration, the light from the light exit surface falls within the range of the opening angle θ. And a part of the light emitted from the light exit surface of the light source side light guide bundle 100 is not incident on the light incident surface of the endoscope side light guide bundle 200, The light that is not transmitted causes a loss in optical coupling efficiency, making it difficult to transmit 100%. It goes without saying that the same applies to the case where the area of the light exit surface is larger than the area of the light entrance surface. In this case, if the light incident surface of the endoscope-side light guide bundle 200 is made larger than the light exit surface of the light source-side light guide bundle 100 as shown in FIG. All light is incident on the light incident surface. However, in this case, the diameter of the endoscope-side light guide bundle 200 becomes extremely large with the increase in the distance Lx between both end surfaces, and the diameter of the endoscope section becomes large. It is unfavorable for downsizing the endoscope.

On the other hand, there is a structure in which both light guide bundles are optically connected to each other using an optical system such as a lens as disclosed in Japanese Patent Publication No. 61-15401 and Japanese Patent Application Laid-Open No. 2-114226. Proposed. In this way, by setting the magnification M of the optical system to the diameter dimension ratio of R and S, the area between the light exit surface and the light incident surface is made optically equal, and the optical coupling efficiency is improved. It is.

[0007]

However, simply making the areas of the light exit surface and the light entrance surface of both light guide bundles optically equal, the magnification m of the optical system becomes | m | <.
In the case of 1, the outgoing angle <the incident angle, the loss of optical coupling occurs, and the optical coupling efficiency is reduced. In the case of | m |> 1, the outgoing angle is greater than the incident angle, so that optical coupling loss occurs and the optical coupling efficiency is not reduced. That is, in an optical system for equalizing the optical areas of the light exit surface and the light incident surface, when | m | <1, R> S and | m |> 1
In the case of R, since R <S, as a result, in the case of R> S, the optical coupling efficiency is reduced, and the same result as when the above-described optical system is not used is obtained.

An object of the present invention is to realize a connection structure in which the end faces of the light guide bundles on the light source side and the endoscope side are separated from each other, and to suppress an increase in the diameter of the endoscope side light guide bundle. On the other hand, it is an object of the present invention to provide a light guide bundle connecting device capable of maintaining a high optical coupling efficiency.

[0009]

According to the present invention, there is provided a first light guide bundle for emitting light from a light source incident on one end from a light exit surface at the other end, and a first light guide bundle of the first light guide bundle. A second light guide bundle having a light incident surface facing the light exit surface and receiving the emitted light, wherein a radius of a light exit surface of the first light guide bundle is R, When the radius of the light incident surface of the second light guide bundle is S and the opening angle of the optical fiber constituting each light guide bundle is θ, the light exit surface and the light incident surface are aligned in the optical axis direction. It is configured such that the opposing interval dimension Lx arranged to oppose satisfies the relationship of 0 <Lx ≦ | R−S | / tan θ.

That is, in FIG. 1A, a first light guide bundle 1 whose one end (not shown) is connected to a light source.
The other end of the second light guide bundle 200 is coaxially opposed to the other end of the second light guide bundle 200, and the other end of the second light guide bundle 200 is connected to a photodetector.
The first and second light guide bundles 1
Each of 00 and 200 is configured as an optical fiber bundle in which a required number of optical fibers are bundled. Then, a predetermined amount of light from the light source is made incident on one end of the first light guide bundle 100, transmitted through the first light guide bundle 100, and transmitted from the other end to the second light guide bundle 200. , Is transmitted through the second light guide bundle 200, and emitted from the other end is detected by a photodetector and its light amount is measured. At this time, the first light guide bundle 1
00 and the second light guide bundle 2
00, the distance Lx facing one end of the end face to the end face is changed,
At that time, a change in the amount of light detected by the photodetector is measured.

Here, the first light guide bundle 10
The radius at the light exit surface of 0 is R, and the radius at the light entrance surface of the second light guide bundle 200 is S.
When R> S, here, R = 1.25 mm,
When S = 0.75 mm, the amount of light detected by the photodetector when the distance Lx between the opposing end faces of both light guide bundles 100 and 200 is gradually increased (separated) from 0 (close contact state). That is, the change in optical coupling efficiency is shown in FIG.
Shown in Here, the light guide bundle having an opening angle θ of 30 ° is used.

As can be seen from this figure, Lx is 0.866.
Below mm, the optical coupling efficiency is almost constant and there is no particular change, and when it becomes larger than this and the interval between both end faces increases, the optical transmission efficiency may deteriorate as a quadratic function. found. Similarly, a test was conducted on various combinations of light guide bundles having different R and S dimensions while maintaining the relationship of R> S. Found that the following relationship existed. Lx ≦ | R−S | / tan θ (1) where Lx> 0

On the other hand, the first light guide bundle 100
The radius R of the light exit surface at one end and the radius S of the light entrance surface at the other end of the second light guide bundle 200 are R <S.
The same test was performed for the case of (1). Here, contrary to the above test, R = 0.75 mm and S = 1.25 mm. The result is shown in FIG. Thus, even in this test, it was found that the optical transmission efficiency was almost constant when Lx was 0.866 mm or less, and that the optical coupling efficiency deteriorated as a quadratic function when the interval was larger than this. did. Also in this case, the following relationship exists. Lx ≦ | R−S | / tan θ (1 ′) where Lx> 0

As described above, the expressions (1) and (1 ') are completely the same. Therefore, regardless of the magnitude relation between R and S, the above equations hold. This allows
The distance between the opposing end faces of the first light guide bundle 100 and the second light guide bundle 200 is determined by the above (1).
By setting the interval to satisfy the relationship of the expression, it is possible to arrange the opposing surfaces of both light guide bundles apart while keeping the optical coupling efficiency high. Here, the values of the optical coupling rates on the vertical axes in FIGS. 2A and 2B are relative values, and it goes without saying that the absolute values of the optical coupling efficiencies in both figures are different. .

As a result, in the present invention, the distance between the opposing end faces of both light guide bundles can be changed within a range satisfying the expression (1), and the connecting device for connecting the two light guide bundles in a separated state. The degree of freedom of design can be increased. Further, even in a case where the separation distance between the two light guide bundles varies due to a manufacturing error in the connecting device, the connection can be performed with the most preferable optical coupling efficiency. This makes it easy to design and manufacture the coupling device.

Further, in the present invention, as shown in FIG. 1B, the light transmission property between the light exit surface of the first light guide bundle 100 and the light entrance surface of the second light guide bundle 200 is changed. A certain parallel plane plate 300 may be interposed. In this case, when the parallel flat plate 300 is a light-transmissive parallel flat plate having a higher light refractive index than air, the distance Lx between the opposed end faces of the light guide bundles 100 and 200 is used.
Is increased as compared with the case where only a gap is provided between the two. For example, in the figure, when a parallel plane plate 300 having a refractive index of n and a plate thickness of d is closely contacted with the light incident surface of the second light guide bundle 200, d (n-1) / n
Only the distance Lx between them can be increased. Therefore, the distance Lx ′ between the opposing surfaces of the two light guide bundles is Lx ′ = Lx + d (n−1) / n. Note that the separation plane Lx 'is exactly the same even when the plane-parallel plate 300 is arranged at an intermediate position between both end faces of the light guide bundles 100 and 200 as shown in FIG.

[0017]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 3 is a partially cutaway side view of a connecting device in which the present invention is applied to an endoscope-side light guide bundle of an endoscope as shown in FIG. 6 and a light source-side light guide bundle connecting device 700. FIG. It is the partial exploded perspective view.
In this embodiment, the light source side light guide bundle 100
In this example, the diameter R of the light exit surface is larger than the diameter S of the light guide bundle 200 of the endoscope, that is, the diameter S of the light entrance surface. End portions of the light guide bundles on the light source side and the inner mirror side are cylindrical holders 13 and 1 formed by bases 11 and 12, respectively.
4 are fixed. Here, the inner and outer diameters of the cap holders 13 and 14 of each light guide bundle are made equal by making the inner diameters of the caps 11 and 12 of each light guide bundle different.
14 can be of the same standard. These base holders 13 and 14 are inserted into the cylindrical connecting sleeve 15 from opposite sides, and are arranged concentrically in the connecting sleeve 15. Thereby, the optical axes of the respective light guide bundles 100 and 200 are matched.

A small hole 16 is provided on the outer periphery of the connecting sleeve 15 at a position corresponding to the base holder 13 on the light source side.
In the region corresponding to the base holder 14 on the endoscope side, guide grooves 17 in the cylindrical axis direction are formed so as to penetrate in the radial direction. Further, a gap adjusting sleeve 18 is covered on the outside of the connecting sleeve 15, and a first cam extending in a direction perpendicular to the cylinder axis at a position corresponding to the small hole 16 on the outer circumference of the gap adjusting sleeve 18. Groove 19
However, at positions corresponding to the guide grooves 17, second cam grooves 20 extending obliquely to the cylinder axis are formed so as to penetrate in the radial direction. Then, in the first cam groove 19, the first cam pin 21 is radially inserted through the small hole 16 of the connection sleeve 15, and the front end thereof is connected to the screw hole 13 a on the outer surface of the base holder 13. You. In the second cam groove 20, a second cam pin 22 is radially inserted through the guide groove 17 of the connection sleeve 17, and a tip end thereof is connected to a screw hole 14 a on an outer surface of the base holder 14. .

According to this configuration, the interval adjusting sleeve 18
Is rotated around the axis, the spacing adjustment sleeve 18 is rotated.
Since the first cam groove 19 is rotated along the first cam pin 21, its axial position is fixed at a fixed position with respect to the connection sleeve 15 and the base holder 13 on the light source side, that is, the light guide bundle 100 on the light source side. It is rotated while being kept. On the other hand, by the rotation of the space adjusting sleeve 18 around the axis, the second cam pin 22 is moved in the cylinder axis direction along the second cam groove 20 and along the guide groove 17 of the connecting sleeve 15. For this reason, the endoscope-side base holder 14 in which the second cam pins 22 are integrated, that is, the endoscope-side light guide bundle 2 supported by the end holder 14.
00 is moved in the cylinder axis direction. As a result, the rotation of the spacing adjusting sleeve 18 causes the connecting sleeve 1 to rotate.
5, the light source-side light guide bundle 100 is in a fixed state, but the endoscope-side light guide bundle 200 is moved in the cylinder axis direction, and both light guide bundles 100,
The distance of 200 in the optical axis direction will be changed. Therefore, based on the radius R of the light exit surface of the light source-side light guide bundle 100 and the radius S of the light incident surface of the endoscope-side light guide bundle 200, the distance Lx between both surfaces satisfies the above formula (1). By performing the adjustment so as to be changed within the range of the interval, the interval adjustment can be realized in a state where the optical coupling efficiency is high.

The endoscope-side light guide bundle 20
To replace the endoscope side light, for example, the second cam pin 22 is detached from the base holder 13 and the endoscope side light guide bundle 200 is pulled out from the coupling sleeve 15 together with the base holder 13 to be replaced. The guide holder of the guide bundle may be inserted into the connection holder, and the second cam pin may be fixed to the holder again. At the time of the replacement, the ends of both the ride guide bundles 100 and 200 are not in contact with each other, so that they do not come into contact with each other, interfere with each other, and are not damaged. Further, even if foreign matter enters the space between both light guide bundles, the light coupling efficiency hardly deteriorates due to the foreign matter as in the case of the close contact state. It is also possible to attach the connecting sleeve 15 and the interval adjusting sleeve 18 in a direction opposite to that in FIG. 4. In this case, the endoscope-side light guide bundle 20 is used.
0 is a fixed state, and the light source side light guide bundle 100 is moved.

In this embodiment, the two light guide bundles are separated from each other via a space. However, a configuration in which a parallel flat plate as shown in FIG. . For example, as shown in FIG. 5, a configuration may be adopted in which the parallel flat plate 300 is brought into close contact with the end surface of the endoscope-side light guide bundle 200 and held by the base holder 12. By providing such a parallel plane plate 300, it is possible to adjust the distance between the two light guide bundles 100 and 200 in the enlargement direction as described above. Even if it is inevitable to reduce the distance, the distance can be increased, and the manufacturing of the connecting device can be easily performed without being unnecessarily reduced in size. Further, when the light guide bundle is replaced by the parallel plane plate 300, especially when the replacement endoscope-side light guide bundle 200 is pulled out from the coupling sleeve 15, the end face of the light guide bundle which is the end face of the optical fiber is used. Can be prevented from being exposed to the outside, and the end face can be prevented from being damaged by impact or the like. At the same time, it is possible to prevent the end face of the endoscope-side light guide bundle from being exposed and contaminated by chemicals or gas, or the surface from being deteriorated.

The plane-parallel plate 300 may be in close contact with the end surface of the light source-side light guide bundle 100, or may be provided on each of the light guide bundles 100 and 200. This is preferably provided on the light guide bundle that is pulled out from the connection sleeve 15 for the above-described reason. Further, the light guide bundle may be held in the connection sleeve 15 at an intermediate position between the two light guide bundles. Furthermore, the parallel plane plate 300 may be configured to also serve as a filter or a density filter (ND filter) for limiting or transmitting light of a specific wavelength.

However, the adjustment range of the distance between the two light guide bundles 100 and 200 in the connecting device is (1)
If the distance is larger than the range that satisfies the expression, when the distance between the two light guide bundles is increased beyond this range, the optical coupling efficiency is reduced as shown in FIG.
By utilizing this in reverse, it is possible to adjust the illumination of the object to be observed in the endoscope. Therefore, it is not necessary to provide the above-described ND filter or the like for the purpose of reducing the illumination light amount, and the configuration can be simplified. In an actual configuration, a scale corresponding to the first or second guide pin 21 or 22 is provided on the peripheral surface of the gap adjusting sleeve 18, and the scale of the expression (1) and the decrease in the light amount are provided on the scale. If symbols, characters, and the like are attached, it is possible to easily adjust the interval and the amount of illumination light.

In the above-described embodiment, the case where the opening angles θ of the light guide bundles on the light source side and the endoscope side are the same is described. When the opening angle θr in the light source side light guide bundle and the opening angle θs in the endoscope side light guide bundle have a relationship of θr <θs,
That is, when the opening angle on the incident side is larger than the angle on the exit side, the present invention can be applied similarly. In this case, the above relational expression is as follows: 0 <Lx ≦ | R−S | / tan θr

Here, in the above-described embodiment, an example is shown in which the present invention is applied to an illumination optical system of an endoscope. The present invention can be similarly applied to any optical transmission device that performs transmission. In particular, the present invention can be applied not only to optical fiber optical devices other than endoscopes but also to the field of optical communication for transmitting optical signals, without interposing an optical system between both light guide bundles. Optical transmission with high optical coupling efficiency can be realized.

[0026]

As described above, according to the present invention, the radius R of the light exit surface of the first light guide bundle on the light source side and the light incidence of the second light guide bundle on which the emitted light is incident are described. By setting the distance between the light exit surface and the light entrance surface of both light guide bundles based on the radius S of the surface, an optical system with high light transmission efficiency can be obtained without disposing an optical system between both light guide bundles. Connection can be realized. As a result, a coupling device having a simple structure, easy design and manufacture, and high optical coupling efficiency can be realized. In addition, by interposing a plane-parallel plate between the two light guide bundles, the distance between the light emitting surface and the light incident surface can be increased while satisfying the above conditions, and the opposing dimensions of the two light guide bundles are reduced. As a result, it is possible to prevent the adjustment from becoming difficult, and at the same time, it is possible to physically and chemically protect the ends of the light guide bundle, thereby improving the reliability and life.

[Brief description of the drawings]

FIG. 1 is a schematic view of a light guide bundle at an opposite end face for explaining a basic configuration of the present invention.

FIG. 2 is a diagram showing a change characteristic of an optical coupling efficiency with respect to a change in an interval between end faces of light guide bundles arranged to face each other.

FIG. 3 is a partially cutaway side view of an embodiment of the connecting device of the present invention.

FIG. 4 is a partially exploded perspective view of the connecting device of FIG. 3;

FIG. 5 is a side view in which a part of a modification of the connecting device of the present invention is cut away.

FIG. 6 is a schematic configuration diagram of an endoscope to which the present invention is applied.

FIG. 7 is a schematic diagram for explaining a problem in a connecting portion of the light guide bundle.

[Explanation of symbols]

 11, 12 cap 13, 14 cap holder 15 connecting sleeve 16 small hole 17 guide groove 18 spacing adjusting sleeve 19 1st cam groove 20 2nd cam groove 21 1st cam pin 22 2nd cam pin 100 1st (light source side) light guide Bundle 200 Second (endoscope side) light guide bundle 300 Parallel plane plate 700 Connecting device

Claims (7)

[Claims] 1. A first light guide bundle for emitting light from a light source incident on one end from a light exit surface on the other end, and light incident on the light exit surface of the first light guide bundle. A second light guide bundle having a surface facing the second light guide bundle for receiving the emitted light, wherein a radius of a light exit surface of the first light guide bundle is R, and the second light guide bundle is a second light guide bundle. When the radius of the light incident surface of the light guide bundle is S and the opening angle of the optical fiber constituting each of the light guide bundles is θ, the light exit surface and the light incident surface are arranged to face each other in the optical axis direction. A light guide bundle connecting device, wherein the facing distance dimension Lx is configured to satisfy the following relational expression. 0 <Lx ≦ | R−S | / tan θ 2. The light guide bundle connection device according to claim 1, wherein a radius R of the light exit surface and a radius S of the light entrance surface have a relationship of R> S. 3. The light guide bundle connecting device according to claim 1, wherein a light-transmissive parallel flat plate is interposed between the light exit surface and the light entrance surface. 4. The light guide bundle connection device according to claim 3, wherein the plane-parallel plate is in close contact with at least one of the light exit surface and the light entrance surface. 5. The light guide bundle connection device according to claim 1, wherein a distance between the light exit surface and the light entrance surface is variable. 6. An optical axis direction such that an end of the first light guide bundle on the light exit surface side and an end of the second light guide bundle on the light incident surface side are aligned with each other. A cylindrical connecting sleeve which is held in a state of being opposed to the connecting sleeve, and which is rotatable in an axial direction at an outer peripheral position of the connecting sleeve, and has two cam grooves corresponding to the respective ride guide bundles. An interval adjusting sleeve, and a cam pin integrated with each of the ride guide bundles and engaged with each of the cam grooves of the interval adjusting sleeve. The light emitting surface and the light are emitted by rotating the interval adjusting sleeve. 6. The light guide bundle connecting device according to claim 5, wherein the distance between the incident surfaces can be changed. 7. The first light guide bundle is a light source side light guide bundle, the second light guide bundle is an endoscope side light guide bundle, and the first and second light guide bundles are separable. 7. The light guide bundle connection device according to claim 1, wherein the light guide bundle connection device is configured as an illumination system for an endoscope configured as described above.