JPS63264707A - Image scope for medical use - Google Patents

Abstract

PURPOSE:To transmit a clear and bright image even if an image scope of a small diameter is used, by specifying the space factor and refractive index distribution of the cores in the cross sections of the optical fibers used in the image fiber. CONSTITUTION:The image scope of this invention uses a multiple fiber 1 composed of >5,000 crystal-glass optical fibers 7, each of which has a crystal-glass clad layer 72 on a core 71 having a mean radius of r1 and which are welded to each other, as an image transmission path. When the refractive index value at the central part of the core 71 and that at the outermost part of the core 71 are respectively designated as n0 and n1, the refractive index distribution of the core 71 is such that the refractive index n2 at the location of 0.65r1 from the center of the core 71 has a value which satisfies inequality I. In addition, the space factor of the cores 71 of the optical fibers 7 in the multiple fiber 1 in the cross sections of the optical fibers is at least 10%. Therefore, the quantity of light led into the cores becomes larger and, as a result, images transmitted through this image scope become bright, and clear images can be obtained even if the diameter of the image scope is small.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a medical image scope suitable for precisely observing the inside of a human body or an animal, particularly the inside of organs such as the stomach, uterus, and bladder.

With the recent advances in medical technology, medical image scopes with excellent flexibility and mechanical strength, and as small a diameter as possible, have been developed for the purpose of directly observing the inside of the human body or animal in detail. requested.

BACKGROUND ART Conventionally, as endoscopes for the human body and animals, fiber scopes using bundles of multiple multi-component glass optical fibers as image transmitting bodies and so-called lens scopes having multiple optical lenses arranged in a subordinate manner are known.

Lens scopes are rigid, making it difficult to insert them into organs, and cannot be equipped with a swing mechanism, so the observable area is narrow.They are extremely expensive, and the diameter of the lens itself has become smaller. There are some drawbacks, such as limitations.

Conventionally, medical image scopes have been used that have multiple fibers, which are simply bundles of multiple multi-component glass optical fibers, as image transmission paths. In order to make this type of multiple fiber even thinner, it is necessary to use individual optical fibers that are smaller in diameter than they currently are, but multi-component glasses generally contain a large amount of impurities. However, it has poor drawability compared to quartz glass, and even the optical fibers currently in use are manufactured at a drawing rate close to the limit, making it extremely difficult to reduce the diameter any further.

Another method for manufacturing multiple fibers is to heat-draw a bundle of multiple optical fibers to fuse the optical fibers together and reduce their outer diameters. However, even with this method, the obtained multiple fibers suffer due to the above-mentioned contained impurities in the multicomponent glass.
It has the disadvantage of being easily broken.

On the other hand, silica glass has excellent drawability, so by drawing a required number of bundles of optical fiber base material consisting of a core and a crund layer as its basic structure,
It has the advantage that multiple fibers with small diameters, which cannot be manufactured using multi-component glass, can be easily manufactured.

When the core part of the optical fiber base material is made of silica glass containing dopants, the difference in refractive index with the cladding layer can be increased by changing the type of dopant, the amount of dopant, etc., and as a result, even with a thin cladding layer, Since the effect of preventing light leakage is increased, the drawing rate can be made thicker (and multiple fibers with even smaller diameters can be manufactured).

By the way, in order to manufacture the above-mentioned optical fiber base material in which the core portion is made of quartz glass containing a dopant, a core iron made of quartz glass containing a dopant is required.
Such core ronds have only been used in the past for manufacturing optical fibers for communications, not for the production of image scopes.Moreover, conventional core ronds have a refractive index distribution that is Curve 1 at 70
As shown in the figure, this is a type in which the refractive index decreases rapidly from the Rondo center toward the outer surface.

Therefore, when multiple fibers are manufactured using such a core rond, only the center portion of each fiber as a pixel is bright, and the distance from the center is rapidly darkened, and the resulting multiple fibers are different from small diameter multiple fibers. There was a problem in that the transmitted image became extremely difficult to see.

The present invention is a multiple fiber having a graded index type core, which overcomes the above problems, and therefore can transmit clear and bright images even with a small diameter. The present invention aims to provide a medical image scope having an image transmission path as an image transmission path.

That is, the present invention has as an image transmission path a multiple fiber structure in which more than 5,000 silica glass optical fibers each having a structure having a silica glass cladding layer on a core with an average radius r are fused together. , the refractive index distribution of the core is such that the refractive index value at the center of the core is no, and the refractive index value at the outermost part of the core is nl, then the refractive index at a position at an average radius of 0.65r+ from the central axis of the core is n8.
has a value satisfying the following formula (11), and each optical fiber in the multiple fibers has a core space factor of at least 10% in the cross section of the optical fiber. This is what I am trying to do.

n2 ≧n+ ”O-50(no n, )
The core of each optical fiber in the multiple fibers that functions as an image transmission path has a refractive index distribution of one kind of Gl shape, but there is refraction in the section from the center to a radius of 0.65r. Since the reduction in index is small and the refractive index is above a certain value, and the space factor in the cross section of the optical fiber is at least 10%, the section with a radius of at least 0.65r+ from the center is Of course, even areas slightly outside this range have sufficient brightness for practical use.

Furthermore, both the core and the ground layer are made of doped silica glass. For example, the core material is quartz glass doped with a dopant that increases the refractive index of pure silica glass such as germanium, and the ground layer material is pure silica glass such as fluorine or boron. (using quartz glass doped with a dopant that has the effect of lowering the refractive index of quartz glass), and the refractive index distribution of the core as satisfying the above formula (11), the refractive index difference between the core and the cladding layer is By increasing the size, the resolution of the transmitted image is improved.

For this reason, the multiple fiber used as an image transmission path in the present invention has a large amount of light introduced into the core, making the transmitted image brighter, and the resolution of the transmitted image is good. Clear images can be obtained even with Moreover, in the present invention, since the number of optical fibers included in the multiple fibers is more than 5000, it has sufficient resolution for transmitted images.

FIG. 1 is a sectional view of an example of the multiple fiber used in the present invention, and FIG. 2 is a partially enlarged sectional view of FIG. 1.

FIG. 3 is a sectional view of another example of multiple fibers used in the present invention, and FIG. 4 is a partially enlarged sectional view of FIG. 3.

FIG. 5 is a sectional view of still another example of multiple fibers used in the present invention, and FIG. 6 is a partially enlarged sectional view of FIG. 5.

FIG. 7 is a diagram showing the refractive index distribution in the core of each optical fiber constituting the multiple fiber.

FIG. 8 is a sectional view of a medical image scope according to an embodiment of the present invention.

In FIG. 8, 1 is a multiple fiber used as an image transmission body, 2 is an objective lens attached to the tip of the multiple fiber 1, 3 is a removable eyepiece attached to the rear end of the multiple fiber 1, and 31 is a detachable eyepiece attached to the rear end of the multiple fiber 1. An eyepiece lens 4 is installed in the eyepiece 3, and 4 is a light guide for illumination. At least a certain length of the tip of the light guide 4 is housed in a protective tube 5 that is installed alongside the multiple fibers 1 and protects the entire length of the multiple fibers, and the remaining rear part is branched and housed in a protective tube 6. There is. When the image scope requires heat resistance rather than flexibility, the protective tubes 5 and 6 are made of metal such as stainless steel, titanium, copper, etc. For example, flexible organic polymers such as nylon, polyethylene, polypropylene, and polyvinyl chloride are used. In addition to the light guide 4, inside the protection tube 5, a water/air supply pipe, forceps, a balloon, a tip swinging device, a laser fiber, an electric coagulator, or other devices are installed together with the multiple fiber 1 as necessary.

In FIGS. 1 and 6, 1 is a multiple fiber, and 7 is an optical fiber constituting the multiple fiber l. 8 is a skin layer provided on the outermost side of the multiple fiber 1, and 9 is a reinforcing layer made of, for example, a thermosetting organic polymer, a thermoplastic organic polymer, or a char of these organic polymers.

In the embodiment shown in FIGS. 1 and 2, each of the multiple optical fibers 7 is composed of a core 71 and a cladding layer 72 provided thereon, and is bonded to each other by fusion of adjacent cladding layers 72. are doing. In the embodiment shown in FIGS. 3 and 4, a second cladding layer is further provided on the first cladding layer 72.
cladding layer 73 and an adjacent second cladding layer 73
They are joined to each other by fusion. In the embodiment shown in FIGS. 5 and 6, a third cladding layer 74 is further provided on the second cladding layer 73, and adjacent third cladding layers 74 are bonded to each other by fusion bonding. .

2, 4, and 6, Df is the diameter of the optical fiber 7, DC is the diameter of the core 71 (core 71 has an average radius r), and T1 is the diameter of the first cladding. The thickness of the layer 72, T2 is the thickness of the second cladding N73, T,
represents the thickness of the third cladding layer 74, D represents the diameter of the multiple fiber, and T represents the thickness of the skin N8.

The multiple fiber 1 includes, for example, 50 fibers made of an optical fiber preform having a circular cross-section and the same cross-sectional configuration as the optical fiber 7.
Desired number greater than 00, e.g. 5500-300
,000, preferably 6,000 to 100,000 skin pipes made of natural quartz glass or synthetic quartz glass, preferably synthetic quartz glass (forming material of the skin layer 8 in FIG. 1, FIG. 3, or FIG. 5). ) can be filled in an aligned state and then drawn into a skin pipe to manufacture it. By fusing the optical fibers together during drawing, each optical fiber is deformed into a hexagonal cross section as shown in FIG. 2, FIG. 4, or FIG. 6, or into a shape in which the hexagonal shape is slightly or significantly distorted.

Unless otherwise specified below, as above, DC1T+
. shall indicate the value of the parallel portion as shown. The refractive index distribution of the core 71 will be explained in FIG. 7 assuming that the core has a circular cross-section with an average radius r, but when the core has a hexagonal or other non-disk cross-sectional shape, For each optical fiber 7 to which the description regarding a circle having an area equal to the cross section applies, it is essential that the space factor of the core 71 in the cross section of the optical fiber is at least 10%. If the core space factor is less than 10%, the amount of light transmitted through the core 71 is insufficient, making it difficult to transmit bright images. Note that if the core space factor is too large, the cladding layer becomes too thin, causing a blurring phenomenon in the transmitted image, making it difficult to obtain a clear image unless the flexibility of the multiple fiber is sacrificed. Therefore, the core space factor is preferably 70% or less, particularly 25 to 50%.

In FIG. 2, each of Dr and TI is 3 to 16
μm, about 0.5 to 5 μm, preferably 4 to 1 μm each
5 μs+, about 1 to 4 μm.

In FIG. 4, each of D, TI, and T2 is about 3 to 15 μm, 0.3 to 4 μm, and 0.01 to 2 μm, preferably 3 to 8 μm, 5 to 1.5 μm, respectively.
Approximately 0.03 to 0.6 μ end, especially 3.5 to 6 μm, respectively.
They are about 5 μm, 0.7 to 1.2 μm, and 0.05 to 0.4 μm. In FIG. 6, Dr, TI, Tz,
Each piece of T3 is 3~16μ, 0.01~1.2
μm, about 0.1-2.5 μm, 0.01-1.5 μm, preferably 3-8 μm, 0.02-0.7 μm, respectively
Proverb: 0.1 to 1.5 μm, 0.02 to 0.6 μm,
In particular, 3.5 to 5.6 μm and 0.05 to 0.44 μm, respectively.
11.0.2-1.3prg.

It is about 0.05 to 0.4 μm.

In FIG. 7, curve 2 is an example of the refractive index distribution curve in the core 71 of each optical fiber 7 constituting the multiple fiber 1 according to the embodiment of the present invention, and curve 1 is a typical communication Gl type optical fiber shown for reference. In 0 curve 2, which is an example of a refractive index distribution curve in a core iron used for fiber manufacturing, the refractive index no at the center r0 of the core 71 (usually has the maximum refractive index) and the refractive index at the outermost core r n+
(usually has the minimum refractive index), i.e. (no n1), is between 0.015 and 0.080, preferably between 0.02 and 0.050, especially between 0.02 and 0.0
It is 45.

In the refractive index distribution shown in curve 2, the refractive index decreases gradually in the section from the center ro of the core to the average radius r2, that is, 0.65r+, and the average radius of the core r!
The refractive index rapidly decreases in the section from the average radius r1, that is, to the outermost part of the core. In other words, the change in the refractive index is small in the section r0 to rl, and the refractive index n2 at the radius "3" is n, +Q, 50
(Δn) (For example, when Δn is 0.025, n+
+o, 65X O, 025= n + +0.012
It has a value of 5> or more. Therefore, although the refractive index distribution of the core 71 is a type of GI type, the decrease in the refractive index is small in the central part r, and the refractive index is higher than a certain value, so that Not only that section, but even a region slightly outside it has sufficient brightness for practical use.

For the reasons mentioned above, it is preferable that the change in refractive index at the outer part of the core 71 is rapid and the change in the refractive index at the central part of the core is slow. Therefore, the refractive index n! more preferably satisfies the following formula (2), particularly the following formula (3).

n, ≧nl +Q, 60 (nl - nl) ・
--・(21n, ≧nl +Q, 65 (no -n
l) ・・−(3) Furthermore, curve 2 is ro (=
Not only does the refractive index n of r, (=0.5r1) have the above value, but also the refractive index n4 of r, (-0,33rl) teeth,
It is preferable to have the values shown in the following formulas (4) to (9), respectively.

n, ≧nI10.55 (no −n, )...
・+41 Preferably, n, ≧n+ +Q, 75 (no nl)”
...(51 Especially, n3≧nl +Q, 85 (no −J)
...(6)n4 ≧n+ +0.60 (n6
n,) ...(71 preferably n4≧nl +Q0go (no nl) ...
...(8) Especially, n4≧nl10Q, 90 (no nl)...
...(In 91 curve 2, the average radius of the core is 0
．． Particularly preferred is one that satisfies the refractive index condition of nl +Q, 50 (Δn) at the position 7r, and also satisfies the above refractive index distribution condition.

The above refractive index distribution of the core can be achieved by using a dopant that increases the refractive index of silica glass, such as germanium or phosphorus, and adjusting the amount of dopant according to the above refractive index distribution using a VAD method, a CVD method, etc. can be achieved.

Preferred dopants are germanium or germanium as a main component.

In the present invention, the core 71 of each optical fiber 7 is
Although it may have only one cladding layer 72 as in the embodiment shown in the figure, as shown in FIGS. 4 and 6,
The outermost refractive index n+ (minimum refractive index) of the core 71 and the cladding layer may have two or three cladding layers with mutually different refractive indexes. The larger the difference in refractive index with 72, the more preferable it is, and it is more preferable to have two or more cladding layers.

In the embodiment shown in FIG. 2, the refractive index difference between the refractive index n1 of the outermost part of the core 71 and the cladding layer 72 is at least 0.004, preferably at least 0.006, in particular at least 0.010.

In the embodiment shown in FIG. 4, the first cladding layer 72 has a minimum refractive index value n at the outermost part of the core 71, which is at least 0.004 lower than that of the second cladding layer.
especially at least 0.006, more especially at least 0
．． 010 preferably has a low refractive index.

In the embodiment shown in FIG.
The second cladding layer N73 preferably has a lower refractive index than the third cladding layer 74.

That is, the first cladding N72 has a refractive index at least 0.004, in particular at least 0.006, lower than the minimum refractive index value n1 at the outermost part of the core 71, and at least 0.002, in particular at least 0.06, lower than the second cladding layer. 00
The second cladding layer 73 preferably has a refractive index of at least 0.00% lower than the third cladding layer 74.
4, especially at least o,oos, and more especially at least 0.010.

Cladding layer 72 in FIG. 2, first cladding layer 72 in FIG.
, the first cladding N72 and the second cladding layer 7 in FIG.
It is preferable that each of the elements 3 is made of quartz glass doped with a dopant containing fluorine and/or boron, or at least one thereof as a main component. Particularly preferably BCIs as dopant precursors
, BFs or a mixture thereof. On the other hand, the second cladding layer 73 in FIG. 2 and the third cladding layer 74 in FIG. 6 may be made of quartz glass doped with various dopants; Glass, such as pure silica glass, especially purity 99.99
It is preferable to use a material having a high purity of at least % by weight. In that case, there are also advantages as described below.

If the optical fibers existing within a radius of at least 80% from the center of the cross section of the multiple fiber 1 are fused to each other in a honeycomb structure as regular as possible (this radius of 80%
There may be some defective parts such as parts where the honeycomb structure has collapsed or dark spots within 0%, and the above honeycomb structure is not only a set of geometric hexagons but also a slightly deformed hexagon. ),
The above structure of the optical fiber 7 used in the present invention and the inclusion of more than 5000 optical fibers combine to provide a clearer transmitted image.

In terms of -II, the multiple fiber with such a structure is made of a glass material for the layer forming the outermost layer of the optical fiber 7 (the second cladding layer 73 in FIG. 4, the third cladding layer 1174 in FIG. 6, etc.). The drawing temperature is in the highest range compared to the glass material of the inner layer (the glass constituting the core 71 has a potency that may be equal to or slightly higher than the drawing temperature of the outermost glass material, for example, the above-mentioned pure silica glass is used) , is obtained by drawing the optical fiber preform bundle at the drawing temperature of the glass or a slightly higher temperature.In this way, even if the glass material of the inner layer exhibits high fluidity at the time of drawing, Since the glass material forming the outermost layer exhibits only the minimum fluidity necessary for drawing, it serves to prevent excessive flow (which would cause an irregular cross section of the optical fiber 7).

The above drawing temperature means that a tube with an inner diameter of 23 mm and an outer diameter of 26 mm manufactured using the quartz glass to be tested is heated and softened, and a reduced tube with an inner diameter of 2.3 fi and an outer diameter of 2.6 mm is drawn at a rate of 0.5 m/min.
It is defined as the lowest temperature at which the drawing tension is 500 g or less when drawing a wire.

In FIGS. 1, 3 and 5, the thickness of the skin layer 8 is preferably at least about 3 .mu.m, particularly from 5 to 20 .mu.m. Further, it is preferable that the thickness of the reinforcing layer 9 is at least about 5 microns, particularly 10 to 150 microns. Further, the outer diameter (Da''27s) of the skin layer 8 is about 0.2 to 3.0 mm, particularly about 0.4 to 2.51 mm.

Among the multiple fibers used as image transmission paths in the medical image scope of the present invention, the following (1) to (
Those satisfying the condition 2) are particularly preferable because the images are clear.

(1) having two or three crund layers as in the embodiment shown in FIG. 4 or FIG. 6; (2) the second cladding layer 73 in FIG. 4 or the third cladding layer in FIG. 6; Layer 74 is made of quartz glass, preferably pure quartz glass, with a drawing temperature of at least 1800° C., especially purity 99.0°C.
Must be made of high purity material with a purity higher than 1999.

Furthermore, if the multiple fibers satisfy the following conditions (3) to (5) in addition to the conditions (1) to (2) above, the image scope of the present invention using such multiple fibers as an image transmitter can be used to It is suitable as an endoscope for digestive organs such as the stomach and intestines.

(3) The number of optical fibers in the multiple fiber is 30,000 or less, preferably s, ooo to 25.0.
(4) The outer diameter (D, +2'r,) of the skin layer 8 should be 0.00. 2
(5) The outer diameter of the protective tube 5 in the image scope shown in Fig. 8 should be about 3 to 1.51 ion, especially about 4 to 7 ion. Furthermore, the outer diameter of the tip 5 to about 151 of the protection tube 5 should be about 1.8N or less.

Furthermore, if the multiple fibers satisfy the conditions (6) to (8) below in addition to the conditions fil to (2) above, the image scope of the present invention using such multiple fibers as an image transmission body can be used as a hysteroscope. , cystoscope, fetoscope,
It is suitable as an arthroscope or an endoscope for other organs, especially as an endoscope for precision observation in place of a conventionally used lens scope.

(6) The number of optical fibers in the multiple fibers is 10,000 to 200,000, preferably 30.0.
(7) The outer diameter (D@+27a) of the skin layer 8 should be 0.00 to 100,000. 8-2.0m
(8) The outer diameter of the protective tube 5 in the image scope shown in FIG. The outer diameter of the 5-15cm portion of the tip is 1.8
Should be approximately n or less.

Below, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

Examples 1 to 20, Comparative Examples 1 to 6 Table 1 shows the detailed structure of the optical fiber preform used in each Example and Comparative Example, and the predetermined number of optical fiber preforms (the structure of the multiple fiber in the same table). The structure of multiple fibers obtained by densely filling a pure silica glass tube with fibers (indicated in the column marked N) and drawing each pure silica glass tube at 2100°C, and the performance of each multiple fiber in terms of transmission image quality are shown. . Each refractive index shown in the table is a value for infrared rays with a wavelength of 0.90 μm at 20° C. Also nl
The value of is 1.453.

The transmission image quality was evaluated using the method described below.

Length 5 from multiple fibers of each example and comparative example
Collect a sample of m and attach lenses to each end to create an image scope (eyepiece magnification: 200
(20.5x objective lens magnification) and 5x from the objective lens.
I looked directly into a 30W fluorescent light located m away. Generally, the poorer the light confinement effect of each cladding layer in a multiple fiber, the more intense coloring appears to exist around the light emitting part of a fluorescent lamp. Therefore, we have assigned the following numbers according to the degree of coloring around the light emitting part of the fluorescent lamp.

Excellent: No coloration observed.

Good: Very faint red or green coloration is observed.

Fair: Quite strong coloring is observed.

[Margin below]

The medical image scope of the present invention has a clear transmission image even though the optical fibers included in the multiple fibers used therein are fused together, and the fused structure of the multiple fibers and the quartz Due to the excellent drawability of glass, it is possible to make the diameter smaller, so it can be used as an endoscope for digestive organs such as the esophagus, stomach, and intestines, or as a hysteroscope, cystoscope, dental mirror, fetoscope, otolaryngoscope, and ophthalmoscope. It is extremely useful as a brainscope, arthroscope, etc., especially as a replacement for conventionally used lens scopes.

[Brief explanation of drawings]

FIG. 1 is a sectional view of an example of multiple fibers used in the present invention, FIG. 2 is a partially enlarged sectional view of FIG. 1, and FIG. 3 is a sectional view of another example of multiple fibers used in the present invention. , FIG. 4 is a partially enlarged sectional view of FIG. 3, and FIG.
A sectional view of still another example of multiple fibers used in the present invention, FIG. 6 is a partially enlarged sectional view of FIG. 5. FIG. 7 is a diagram showing the refractive index distribution in the core of each optical fiber constituting the multiple fiber, and FIG. 8 is a sectional view of a medical image scope according to an embodiment of the present invention. 1...Multiple fibers 2...Objective lens 3...Removable eyepiece 4...Light guide for illumination 5...Protection tube 6...Protection tube 7. Optical fiber 71 constituting multiple fiber 1 Core 71 72 Cladding layer 72 Cladding layer 73 Cladding layer 74 Cladding layer 8 Skin layer 9 ...Reinforcement layer

Claims (1)

[Claims] 1. Multiple fibers having a structure in which more than 5000 silica glass-based optical fibers are fused together and have a cladding layer of silica glass on a core with an average radius r_1 are used as an image transmission path. If the refractive index distribution of the core is n_0 at the center of the core and n_1 at the outermost part of the core, the refractive index at a position at an average radius of 0.65r_1 from the central axis of the core is n_2. has a value satisfying the following formula, and each optical fiber in the multiple fibers has a core space factor of at least 10% in a cross section of the optical fiber. n_2≧n_1+0.50(n_0-n_1)2, the difference (Δn) between the refractive index n_0 (maximum refractive index) at the center of the core and the refractive index n_2 (minimum refractive index) at the outermost part of the core is 0.01
5 to 0.080. The medical image scope according to claim 1. 3. The medical image according to any one of claims 1 to 2, wherein the refractive index n_3 at a position at an average radius of 0.5r_1 from the central axis of the core has a value satisfying the following formula. scope. Claims 1 to 3, wherein n_3≧n_1+0.55(n_0-n_1)4, the refractive index n_4 at a position at an average radius of 0.33r_1 from the central axis of the core satisfies the following formula. A medical image scope as described in any of the above. n_4≧n_1+0.60(n_0-n_1)5, the core is made of quartz glass doped in graded index form with germanium or a dopant containing germanium as a main component, according to claim 1. medical image scope. 6. The medical image according to claim 1, wherein the optical fibers existing within a radius of at least 80% from the center of the cross section of the multiple fibers are fused to each other in a honeycomb structure as regular as possible. scope. 7. The cladding layer is at least two layers: a first cladding layer made of pure silica glass doped with fluorine and/or boron, and a second cladding layer made of silica glass, preferably pure silica glass, whose drawing temperature is at least 1800°C. A medical image scope according to claim 1 consisting of: