JP3874870B2 - Fiberscope and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an ultrafine fiberscope used for medical endoscopes and the like.
[0002]
[Prior art]
Conventionally, ultrafine fiberscopes with a diameter of several hundreds of μm have been used to observe the inside of piping in industrial facilities and blood vessels of human bodies. This type of ultrafine fiberscope has a configuration in which an eyepiece is attached to one end of an image fiber and an objective lens is attached to the other end.
In general, a quartz glass ultra-fine image fiber is used as the image fiber, and multicomponent glass such as a SELFOC (trade name) lens is used as the eyepiece and objective lens. These eyepiece and objective lens Was bonded to the image fiber by an adhesive such as an optical epoxy adhesive.
[0003]
[Problems to be solved by the invention]
However, in this fiberscope, since a very small lens is attached to an extremely small diameter image fiber, it takes much time to adjust the bonding position between the image fiber and the lens, and the manufacturing efficiency is low.
Further, since the adhesive used for bonding the lens has a low heat-resistant temperature, the fiberscope cannot be used at a high temperature, and its application is limited.
[0004]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fiberscope that can be used at high temperatures and has high manufacturing efficiency.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides a method for manufacturing a fiberscope having the following characteristics. Moreover, the fiberscope manufactured by these manufacturing methods is provided. That is,
The process of claim fiberscope according to 1 of the present invention, by heating plurality of pixels fibers, the leading edge of the welded image fiber in the jacket, the fiber structure by diffusion of the dopant included in the pixel fiber tip And a spherical portion forming step of forming a spherical portion that functions as a lens having a uniform composition .
Method for producing a fiberscope according to claim 2 of the present invention, the cutting plurality of pixels fibers, and heating and drawing step of forming the tapered portion by heating and drawing the middle of the welding in the jacketed image fiber, the tapered portion And a spherical surface forming step of forming a spherical surface portion by heating the tip of the tapered portion , and by the diffusion of dopant contained in the pixel fiber by the heating and stretching step and the spherical surface forming step. A spherical portion that functions as a lens having a uniform composition from which the fiber structure has disappeared is formed .
The method according to claim 3 fiberscope according to the present invention, plurality of pixels fibers, by heating the end portion of the welded image fiber in the jacket, by diffusing the dopant contained in the pixel fibers, fiber structures and having a dopant diffusion step but the loss has been composition uniform end and a spherical portion forming a spherical surface portion which functions as a lens in the tip to heat the tip of the end portion .
The method of manufacturing fiberscope according to claim 4 of the present invention, plurality of pixels fibers, heating the middle of the welded image fiber in the jacket, by diffusing the dopant contained in the pixel fibers, fiber structures heating and diffusion step of disappearance is composition to form a uniform spreading unit, the heating and drawing step of forming the tapered portion by heating and drawing said diffusion portion, and cutting the tapered portion, the distal end of the tapered portion and having a spherical portion forming a spherical surface portion which functions as a lens in the tip and.
According to a fifth aspect of the present invention, there is provided a fiberscope manufacturing method according to any one of the first to fourth aspects, wherein the pixel fiber includes a dopant contained only in the core or both the core and the clad. Features.
A fiberscope according to a sixth aspect of the present invention is manufactured by the method for manufacturing a fiberscope according to any one of the first to fifth aspects, and has a spherical portion functioning as a lens at a tip thereof.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
1 to 4 show an example of a method for manufacturing a fiberscope according to the present invention, in which image fibers in each manufacturing process are shown in cross-sectional views along the longitudinal direction thereof.
FIG. 1 shows a first example of the present invention, in which reference numeral 1 is an image fiber, 2 is an image circle, 4 is a jacket layer, and this image fiber 1 is inside a jacket tube made of, for example, quartz glass. A plurality of quartz glass fibers are bundled and inserted into a base material, and the base material is formed by heating and drawing from the end to a predetermined diameter. The plurality of glass fibers are drawn. As a result, although they are welded to each other, the individual fiber structures are maintained to form the pixels.
[0007]
The pixel fiber constituting the image fiber 1 is generally used as an optical fiber. A core having a high refractive index is provided at the center thereof, and a clad having a refractive index lower than that of the core is provided on the outer periphery of the core. It is provided and configured.
The core is preferably made of SiO ₂ containing germanium as a dopant, and the cladding is preferably made of SiO ₂ or SiO ₂ to which fluorine is added as a dopant. The SiO ₂ containing germanium is usually formed by adding germanium oxide.
[0008]
In order to fabricate a fiberscope using the image fiber 1, first, one end of the image fiber 1 is heated by discharge with a pair of discharge electrodes 6 and 6 as shown in FIG. 1.
Then, a dopant such as germanium contained in the core of the plurality of pixel fibers constituting the image fiber 1 diffuses into the clad, and a dopant such as fluorine contained in the clad diffuses to make the composition of the pixel fiber uniform, and the fiber structure Disappears and a diffusion portion having a uniform composition is formed. At the same time, the diffusion part and the jacket layer 4 are heated and rounded at the tip of the image fiber 1 to form a hemispherical spherical part 2c that functions as a lens.
[0009]
In this way, the tip of the image fiber 1 has a function as an objective lens by the spherical portion 2c and the diffusion portion (hereinafter sometimes referred to as an objective lens portion), and a fiber scope is formed.
The spherical curvature radius R of the objective lens part (spherical part 2c) is substantially determined by the outer diameter of the image fiber 1, but when the spherical part 2c is formed by discharge, the discharge intensity of the discharge electrodes 6 and 6; By suitably setting the heating conditions such as the discharge time, an objective lens portion having a desired R can be obtained with good reproducibility.
As a heating method of the image fiber 1, a method using a discharge as described above or a method using a heating source such as an oxyhydrogen flame can be mentioned. However, since the heating conditions can be easily adjusted, a method using a discharge is preferable.
[0010]
Since the objective lens portion of the fiberscope is composed of the image fiber 1, the image fiber 1 and the objective lens portion are always integrated, unlike the case where the objective lens is bonded with an adhesive. For this reason, the fiberscope can be used at a high temperature as long as the image fiber 1 can withstand.
In addition, since the tip of the image fiber 1 is processed into the objective lens portion, it is not necessary to adjust the bonding position between the objective lens and the image fiber as in the prior art, and the manufacturing efficiency is improved.
[0011]
FIG. 2 shows a second example of the present invention, and FIG. 3 is an enlarged view of a main part thereof. This 2nd example consists of a heating extending process and a spherical part formation process.
In the figure, reference numeral 10 denotes an image fiber, 12 denotes an image circle, and 14 denotes a jacket layer.
First, the middle of the image fiber 10 is disposed between the pair of discharge electrodes 6 and 6, the image fiber 10 is heated and stretched to form a tapered portion 12 b, and the tapered portion 12 b extends in the distal direction of the image fiber 10. The diameter of the image fiber 10 is reduced and the image fiber 10 is divided so as to be the tip of the image fiber 10 (heating and stretching step).
Further, when the tip of the tapered portion 12b is heated by the discharge electrodes 6 and 6, the tip is rounded to form a hemispherical spherical portion 12c covered with the jacket layer 14 (spherical portion forming step).
[0012]
Due to the heating performed in the heating drawing step and the spherical surface forming step, the composition of the plurality of pixel fibers constituting the image fiber 10 is made uniform by diffusion of a dopant such as germanium contained in the core or fluorine contained in the cladding. Thus, a diffusion portion having a uniform composition and disappearing fiber structure is formed.
In this way, the distal end of the image fiber 10 has a function as an objective lens (referred to as an objective lens portion) by the spherical portion 12c at the distal end of the tapered portion 12b and a diffusion portion having a uniform composition (called an objective lens portion), and a fiber scope is formed. Is done.
[0013]
In this example, the spherical radius of curvature R of the objective lens portion (spherical surface portion 12c) can be arbitrarily adjusted by adjusting the outer diameter of the distal end of the tapered portion 12b that becomes the distal end of the image fiber 10. In particular, since the spherical radius of curvature R can be obtained, for example, smaller than 1/2 of the outer diameter of the image fiber 10, it is suitable when the focal length is small and a large angle of view is required.
The length and outer diameter of the tapered portion 12b can be adjusted by setting the heating conditions, the stretching length, and the like in the heating and stretching step.
An objective lens having a desired radius R of the fiberscope has a desired reproducibility by adjusting the outer diameter of the tip of the tapered portion 12b and appropriately setting the heating conditions in the spherical portion forming step. Part can be obtained.
[0014]
Further, in the fiberscope of the first example shown in FIG. 1, the core of the pixel fiber in the vicinity of the outer periphery of the image fiber 1 is bent at the tip portion, so that the vignetting phenomenon occurs in the peripheral portion, and the image ratio (image diameter / The image circle diameter may be small.
The image diameter is a diameter in a range in which an image can be propagated, and the image circle diameter is a diameter in a range in which light propagates (hereinafter referred to as an image circle). The image ratio is represented by these ratios, and the larger this value, the more effectively the image circle is used for image propagation, and the more preferable characteristics as a fiberscope. In the second example, since the waveguide of light incident from the spherical surface portion 12c gradually spreads at the tapered portion 12b, the image ratio can be increased. In some cases, the image diameter and the image can be increased. In some cases, the circle diameter can be made equal.
[0015]
FIG. 4 shows the diffusion process in the third example of the present invention.
In the third example, first, the middle of the image fiber 10 is disposed between the pair of discharge electrodes 6 and 6, and the image fiber 10 is moved up and down to heat while adjusting the heating range. Then, germanium, fluorine and other dopants contained in the plurality of pixel fibers are diffused in the heated portion, the pixel fiber composition becomes uniform, and a diffusion portion 12a in which the fiber structure disappears is formed.
Next, in the same manner as in the second example, this diffusion portion 12a is heated and stretched to form a tapered portion, and a spherical portion functioning as a lens is formed at the tip thereof to obtain a fiberscope.
[0016]
What is obtained in the above-described second example is that the heating range of the image fiber 10 is narrow, and in reality, there is a possibility that a diffusion portion is formed only near the tip of the tapered portion 12b. In this case, the diffusion portion and the spherical portion 12c The length of the objective lens portion (lens length) consisting of the above may be short and cannot be arbitrarily adjusted. The lens length indicates the distance between the spherical surface portion 12c and the imaging surface formed on the diffusing portion.
On the other hand, the third example is more effective because the diffusion portion can be formed over a wide range and the lens length can be arbitrarily set.
[0017]
When combining the third example and the first example, after heating one end portion of the image fiber to form a diffusion portion at this end portion, as shown in FIG. A spherical portion is formed at the tip to form a fiber scope.
Alternatively, as shown in FIG. 4, after the diffusion process is performed by heating the middle of the image fiber, the diffusion part is cut by an arbitrary method so as to be the tip of the image fiber, and this diffusion is performed as shown in FIG. It is also possible to form a spherical portion by heating the tip of the image fiber consisting of a portion to form a fiberscope.
[0018]
<Examples of manufacturing conditions>
In the third example described above, the manufacturing conditions of the fiberscope in the case of heating by discharge in the method combining the second example will be specifically shown.
In this method, a fiberscope is manufactured through the diffusion process shown in FIG. 4 and the heating and stretching process and spherical surface forming process shown in FIGS.
An image fiber having an outer diameter of 100 to 1500 μm is preferably used. For example, if the outer diameter is 200 μm, the image circle diameter is about 180 μm, the number of pixels is about 1600 pixels, and the pixel fiber diameter is about 4.5 μm.
[0019]
The setting range of suitable conditions in each step is shown below.
In actual manufacturing, specific numerical values are set so that a desired fiberscope can be obtained from these ranges.
[0020]
(Diffusion process)
Discharge power (%) ^{* 1} : 30-120
One discharge time (second): 0.05-2
Number of discharges: 1-1000
Diffusion length (mm) ^{* 2} : 0.01 to 10
Diffusion span (mm) ^{* 3} : 0.01-1
(Heat stretching process)
Discharge power (%) ^{* 1} : 30-120
One discharge time (seconds): 0.1 to 30
Number of discharges: 1 to 100
Stretching length (mm) ^{* 4} : 0.5 to 10
(Spherical surface forming process)
Discharge power (%) ^{* 1} : 30-120
One discharge time (second): 0.01 to 10
Number of discharges: 1 to 100
[0021]
* 1 Discharge power: Value when the voltage is 500V or more and discharge current 20mA is 100% * 2 Diffusion length: Diffusion length * 3 Diffusion span: After one discharge, the discharge electrode is placed in the length direction of the image fiber * 4 Stretching length: The length of the image fiber that has been stretched in the heat-stretching process.
An example of the characteristics of a fiberscope manufactured by setting the conditions of each step from the above numerical range is shown below.
Angle of view average (deg.): 35
Working distance (mm): 6
Screen ratio (image diameter / image circle diameter): 0.75
The angle of view (average angle of view) is a viewing angle when viewing the entrance window with the center of the entrance pupil of an imaging system such as a lens as a viewpoint, and gives a standard of a viewing angle that can be imaged.
The working distance indicates an object distance at which an image is formed. Usually, this type of fiberscope has a working distance of about 3 mm or about 5 mm.
[0023]
【Example】
A fiberscope was manufactured by setting the conditions of each step shown in the above manufacturing condition example as follows.
At this time, an image fiber having an outer diameter of 200 μm, an image circle diameter of 180 μm, a number of pixels of 1600 pixels, a pixel fiber diameter of 4.5 μm, and a relative refractive index difference Δ of pixel fiber of 3% was used.
(Diffusion process)
Discharge power (%) ^{* 1} : 100
One discharge time (second): 0.5
Number of discharges: 6
Diffusion length (mm) ^{* 2} : 0.5
Diffusion span (mm) ^{* 3} : 0.1
(Heat stretching process)
Discharge power (%) ^{* 1} : 80
One discharge time (second): 3.0
Number of discharges: 1
Stretching length (mm) ^{* 4} : 3.5
(Spherical surface forming process)
Discharge power (%) ^{* 1} : 70
One discharge time (seconds): 1
Number of discharges: 1
[0024]
The characteristics of the obtained fiberscope are shown below.
Angle of view average (deg.): 36
Working distance (mm): 4
Screen ratio (image diameter / image circle diameter): 0.75
[0025]
Further, when the MTF value (modulation transfer function) was measured in order to evaluate the resolution of this fiberscope, it was 0.88 at a spatial frequency of 10 (lp / mm), and 0.8 at a spatial frequency of 20 (lp / mm). 65.
From the above results, it was confirmed that a practical fiberscope was obtained.
[0026]
【The invention's effect】
As described above, the fiberscope manufacturing method of the present invention heats the tip of the image fiber or the tip of the tapered portion formed at the end of the image fiber to form a spherical portion that functions as a lens, Since the dopant contained in the plurality of pixel fibers to be formed is diffused to form the objective lens unit, the following effects can be obtained.
That is, since it is not necessary to perform difficult adjustments such as positioning for bonding a minute objective lens to an ultrafine image fiber as in the prior art, manufacturing efficiency is high.
Further, since the objective lens portion is made of an image fiber, it is always integrated with the image fiber. For this reason, the fiberscope can be used at a high temperature as long as the image fiber can withstand.
Further, in the method of forming the spherical portion at the tip after forming the tapered portion, the spherical radius of curvature R of the objective lens portion can be arbitrarily adjusted, and the image ratio can be increased. Is obtained.
In addition, after forming the diffusion part by heating the image fiber in advance, the spherical part is formed at the tip thereof, or the spherical part is formed after forming the taper part at the diffusion part, thereby forming the lens of the objective lens part. The effect that the length can be arbitrarily adjusted is obtained.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a first example of the present invention.
FIG. 2 is an explanatory diagram showing a second example of the present invention.
FIG. 3 is an enlarged view showing a main part of the second example shown in FIG. 2;
FIG. 4 is an explanatory diagram showing a diffusion step in the third example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Image fiber, 2 ... Image circle, 2c ... Spherical surface part, 4 ... Jacket layer, 10 ... Image fiber, 12 ... Image circle, 12a ... Diffusion part, 12b ... Tapered part, 12c ... Spherical part, 14 ... Jacket layer

Claims (6)

Plurality of pixels fibers, by heating the tip of the welded image fiber in the jacket, the fiber structure by diffusion of the dopant included in the pixel fiber tip is lost, the spherical portion whose composition functions as a uniform lens A method of manufacturing a fiberscope, comprising the step of forming a spherical surface. And heating and drawing step for forming a tapered portion pixel fibers more, and heat stretching the middle of welded image fiber in the jacket, and cutting the tapered portion, the spherical portion by heating the tip of the tapered portion A spherical surface functioning as a lens having a uniform composition in which the fiber structure has been eliminated by diffusion of the dopant contained in the pixel fiber by the heating and stretching step and the spherical surface forming step. A method of manufacturing a fiberscope, comprising forming a portion. A dopant diffusion step in which a plurality of pixel fibers are heated in an end portion of an image fiber welded in a jacket to diffuse a dopant contained in the pixel fiber so that the fiber structure disappears and the composition has a uniform end portion. When manufacturing method of fiberscope characterized by having a spherical portion forming a spherical surface portion which functions as a lens to the tip by heating the tip of said end portion. A diffusion step in which a plurality of pixel fibers are heated in the middle of an image fiber welded in a jacket to diffuse a dopant contained in the pixel fibers to form a diffusion portion having a uniform composition in which the fiber structure has been eliminated ; spherical to form the heating and drawing step for forming a tapered portion heating and drawing to the diffusion portion, and cutting the tapered portion, the spherical portion that serves as a lens to the tip by heating the tip of the tapered portion method for producing a fiber scope and having a part forming step. 5. The fiberscope manufacturing method according to claim 1, wherein the pixel fiber includes a dopant that is contained only in the core or in both the core and the clad. 6. Produced by the production method of the fiberscope according to any one of claims 1 to 5, fiberscope characterized by having a spherical surface portion which functions as a lens on the tip.

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