JP2005222087A - Image fiber and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image fiber which has high resolution, is free from unequal brightness and is formed to decrease the crosstalks of transmitted light and a process for producing the image fiber and further, the image fiber having a large outside diameter and high flexibility and a process for producing the image fiber. <P>SOLUTION: This image fiber is composed by arranging in parallel a plurality of conduit type image fiber units in which a plurality of cores have a cladding in common, by forming the so-arranged conduit type image fiber units each integrally at their incident end and exiting end, and by separating each in the intermediate section. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention mainly relates to a high-quality, small-diameter image fiber applied to a medical endoscope or the like, and a manufacturing method thereof.

  In general, as a medical endoscope using this type of image fiber, one having a configuration as shown in FIG. 12, for example, is well known. That is, in the configuration of the endoscope apparatus 21 shown in FIG. 12, the object T to be observed illuminated by an illumination optical system (not shown) is an image fiber 23 configured by bundling a plurality of optical fibers through the objective lens group 22. The observation image (T) thus formed is transmitted through the image fiber 23 and emitted from the emission end surface 23b and observed through the eyepiece 24. .

  In addition, as such an image fiber, a flexible image fiber having a configuration in which each optical fiber constituting the image fiber is integrated at an incident end and an output end and separated at an intermediate portion, A conduit-type image fiber in which each core is integrally formed with a common cladding is known. FIG. 13 schematically shows a cross-sectional structure of the conduit type image fiber. The conduit type image fiber 25 includes a plurality of cores 27 arranged in a common clad 26 and spaced apart from each other. Composed.

  Furthermore, in the endoscope apparatus 21 using this type of image fiber, the outer diameter of the endoscope apparatus 21 has been increasingly reduced in recent years, and recently, for example, a diameter of 1 mm so that the inside of a blood vessel or the like can be observed. Research and development of endoscopes that have been reduced in diameter to the following have been made, and along with this, the image fiber 23 applied to the endoscope apparatus 21 has also become very thin.

  However, each individual optical fiber constituting the image fiber 23 of the endoscope apparatus 21 has an extremely small outer diameter of about several hundreds μm, a core diameter of several μm, and a number of pixels of about 2 to 3,000. With respect to the observed image T, satisfactory image quality is not always obtained.

  In the image fiber described below, the core radius a, the cladding thickness d, and the core interval P of the image fiber are based on the definitions shown in FIG.

  Of the image fibers shown in FIGS. 12 and 13, the flexible image fiber retains its flexibility even if the outer diameter of the flexible image fiber is increased. However, the diameter of each individual optical fiber is reduced. Then, it becomes easy to break, and since the clad becomes thin, light on the long wavelength side oozes out from the clad and is colored blue. As a result, the mutual interval between the optical fibers is reduced to about 10 μm. There is an inconvenience that it cannot be done.

  On the other hand, the latter conduit-type image fiber is often used for such an ultra-fine diameter endoscope apparatus. In this conduit type image fiber, since the cores share the clad, it is possible to reduce the distance between the optical fibers, but in this case as well, if the outer diameter exceeds about 500 μm, The flexibility is remarkably impaired, and there is a problem that the diameter cannot be increased while maintaining the flexibility.

  In the conduit-type image fiber 25 having the above-described configuration, since the common clad 26 is continuous in the optical axis direction, the interval between the cores 27 can be made smaller than that of the flexible-type image fiber. A part of the light transmitted through the core 27 leaks into the clad 26 from the boundary surface between the clad 26 and the core 27, and this leaked light component is mixed into another core 27, so-called phenomenon. It is known that crosstalk of transmitted light is likely to occur, and this crosstalk phenomenon is particularly caused when the thickness of the clad 26 is reduced to about several times the wavelength. When the interval is reduced to about 10 μm or less, the image quality is remarkably deteriorated.

  Recently, as for these ultrafine image fibers 23, a bright image, that is, an image fiber having a high occupation ratio (pixel density) of the core 27 is desired as the number of pixels increases. For this reason, it is necessary to reduce the diameter of each core 27 and to thin the clad 26 between the cores 27 to increase the core occupation ratio.

  However, if the thickness of the clad 26 between the cores 27 is less than several times the wavelength of light, crosstalk is likely to occur due to mode coupling between the optical fibers, and the image quality of the transmitted image is remarkably increased. This will result in a decrease. In order to prevent the image quality from being deteriorated due to the crosstalk, the thickness of the clad 26 must be increased. In this case, however, the occupation ratio of the core 27 per unit area in the cross section of the optical fiber bundle is reduced. As a result, a bright image cannot be obtained, and at the same time, the disadvantage that high pixels cannot be achieved remains.

  Thus, in order to reduce the crosstalk, it is necessary to increase the thickness of the clad 26. On the other hand, in order to increase the core occupation ratio, there is a conflicting problem that the clad 26 must be thinned. .

  By the way, in general, in this type of image fiber, when the propagation constant (β) of light propagating in the core is composed of different optical fibers, the propagation constant (β) of light propagating in the core is equal. It is known that the crosstalk is smaller than that of an optical fiber. In order to make the propagation constant (β) of light propagating in the core of this image fiber different, the normalized frequency (V ) Should be different.

但し、ｋ＝２π／λ（λはファイバ内を伝搬する光の波長）
ｎ₁,ｎ₂ は夫々コアとクラッドの屈折率である。 Here, it can be seen that the V value depends on the radius (a) of the core as shown in the following equation (1).

Where k = 2π / λ (λ is the wavelength of light propagating in the fiber)
n ₁ and n ₂ are the refractive indexes of the core and the clad, respectively.

The following equation (2) is a parameter generally called a fiber numerical aperture (NA).

  And as one of the measures against crosstalk in the image fiber paying attention to these points, for example, as disclosed in Japanese Patent Publication No. 3-81126 and Japanese Patent Publication No. 3-77796, etc. A so-called random image fiber is known in which a plurality of optical fiber elements having a core diameter are bundled together to form an image fiber.

  However, in the case of a conventional random image fiber, there are few types of optical fiber strands to be used, and in order to bundle them at random, strands having the same core diameter are often adjacent to each other. There was an undesirable problem that image quality deteriorated due to crosstalk between the core diameter strands.

In these image fibers, each core is also randomly arranged, so that the resolution of the transmitted image may be uneven in some parts, and the straight edges may appear bent. The image was difficult to see.
Further, an image fiber in which each core diameter is random and the arrangement thereof is hexagonally dense is disclosed in Japanese Patent Laid-Open No. 4-214042. However, in this image fiber, the core / cladding ratio is also disclosed. Since optical fibers with different (ratio between the outer diameter of the optical fiber and the core diameter) are randomly arranged, for example, when an observed object with uniform brightness is observed, the observed image itself has uneven brightness. There is a problem that occurs.

  Therefore, the present invention has been made to solve such a conventional problem, and the object of the present invention is to be able to reduce crosstalk of transmitted light with high resolution and no brightness unevenness. Another object of the present invention is to provide an image fiber having a large outer diameter and high flexibility and a method for manufacturing the same.

  In order to achieve the above object, according to the image fiber of the present invention, a plurality of conduit-type image fiber units in which a plurality of cores share a clad are arranged in parallel, and the conduit-type image fiber unit by the arrangement includes The incident end and the emission end are integrally formed, and the intermediate portion is separated from each other.

The image fiber according to the present invention is an image fiber having a plurality of types of cores and made of a clad shared by the cores, wherein at least 50% or more of the cores are arranged so as not to be adjacent to the same type of cores. The types of cores are at least three types of cores having different shapes, and the thickness d of the clad portion satisfies the following conditional expression.
0.8μm <d <1.8μm

  The image fiber according to the present invention is preferably characterized in that the conduit-type image fiber unit is an image fiber having a plurality of types of cores and comprising a clad shared with the cores.

  The image fiber according to the present invention is preferably characterized in that in the conduit type image fiber unit having the plurality of types of cores, the same type of cores are arranged so as not to be adjacent to each other.

  The image fiber according to the present invention is preferably characterized in that the outer diameter of the conduit type image fiber unit is 500 μm or less.

  The image fiber according to the present invention is preferably characterized in that the arrangement of the cores is substantially regular.

  According to the present invention, each optical fiber is composed of a plurality of types of optical fibers, and the cores having the same outer diameter are arranged so as not to be adjacent to each other, so that crosstalk can be suppressed and image quality deterioration can be prevented. In addition, there is an excellent feature that an image fiber having a small diameter and high resolution without unevenness of brightness can be provided, and a high resolution image fiber having a relatively large outer diameter and high flexibility can be obtained.

  Prior to the description of the embodiment of the present invention, the function and effect of the present invention will be described.

  Here, FIG. 15 is a view showing an end face configuration according to an example of a conventional random image fiber, and FIG. 16 is an end face explanatory view showing an enlarged detail of a main part in the same configuration.

  That is, the random image fiber shown in FIG. 15 is a bundle of a large number of optical fibers each of which is coated with a clad around each core having three different core diameters, and thermocompression-bonded, and It is formed to have a desired outer diameter by drawing and drawing, and the clads are fused and integrated with each other. Here, a so-called conduit-type image fiber is formed. .

That is, in this case, as shown in FIG. 16, first, the first cores 27a ₁ and 27a ₂ having the same small diameter are arranged adjacent to each other in the same region A. Further, the second cores 27b having the same large diameter are arranged adjacent to each other in the same region B, and the third cores 27c having the intermediate diameter are adjacent to each other in the region C. The regions A, B, and C themselves are adjacent to each other.
Therefore, in the random image fiber configured as described above, three types of optical fiber strands having different core thicknesses are included as a result.

Here, in the configuration of the random image fiber shown in FIGS. 15 and 16, light is individually incident on each of the adjacent first cores 27a ₁ and 27a ₂ in the same region A. The light output state at that time is shown in FIGS. 17 and 18, respectively.
In each of these cases, as shown in FIGS. 17 and 18, light is emitted from all the cores belonging to the same region A, here, all the cores having the same diameter. In other words, it can be seen that light leaks to neighboring cores having the same diameter due to crosstalk. On the other hand, almost no light is emitted from the respective cores belonging to the regions B and C other than the region A. As a result, crosstalk is caused between fibers having different core diameters. It is clear that there is no or a low level that is unrecognizable, if any.

FIG. 19 shows the light output state when light is incident on the third core 27b in the same region B.
Here again, just as in the state shown in FIGS. 17 and 18, light is emitted only from the adjacent cores of the same diameter, and it can be seen that the crosstalk between the cores of the same diameter is large. .

On the other hand, if the diameters and shapes of adjacent cores are different, the propagation constant (β) of light propagating through the cores is also different, so that the occurrence of crosstalk is extremely reduced.
FIG. 20 shows the light output state when light is incident on the adjacent cores having different core diameters, here, the light output state when light is incident on the fourth core 27c in the region C. As shown, in this case, light is emitted only from the corresponding core, and it can be seen that the occurrence of crosstalk is extremely small as compared with the states shown in FIGS.

  In other words, as is clear from the above results, the crosstalk between the cores with different outer diameters is extremely small, and as shown in FIG. 20, if the surroundings are all surrounded by cores with different outer diameters, In effect, crosstalk can be suppressed to an undetectable level.

  Thus, in order to obtain an image fiber having the above-described configuration, as shown in FIG. 21, a plurality of optical fiber strands 31A, 31B, and 31C of at least three types (in FIG. 21, simply A, It is necessary to regularly arrange the optical fiber strands 31A, 31B, and 31C in a hexagonal close-packed manner, but an ordinary method that has been conventionally performed is an image having several thousand pixels. It is extremely difficult to achieve such a hexagonal dense and regular arrangement in the fiber.

  In this case, in order to arrange the optical fiber strands 31A, 31B, and 31C in a regular hexagonal close-packed shape, the optical fiber strands having the same outer diameter and different core diameters are used. Therefore, when the respective core occupancy rates (the square of the core / cladding ratio) of the optical fiber strands 31A, 31B, and 31C are different, the regular arrangement of the optical fiber strands is disturbed. Since there is a possibility that the entire brightness unevenness will inevitably occur when an object to be observed having a uniform brightness is viewed, a regular arrangement of each optical fiber, that is, a hexagonal close-packed arrangement is used. Sufficient consideration is necessary.

  Here, in FIG. 22, uniform light is incident on the entire surface of an image fiber in which five types of optical fiber wires having different core / cladding ratios and the same outer diameter are irregularly bundled in a hexagonal close-packed shape. FIG. 6 is a diagram showing a light output state in the case where, as is apparent from FIG.

  In order to eliminate the overall brightness unevenness, first, as shown in FIG. 21, optical fiber strands are regularly arranged. Second, the cross-sectional shape of the core is different, and the core occupancy rate is It is conceivable to use the same optical fiber strands, and thirdly, to use a plurality of optical fiber strands having the same core occupation ratio and different outer diameters.

  In order to realize the second image fiber, for example, a plurality of optical fiber strands having the same outer diameter, different core shapes, and equal core cross-sectional areas are bundled and stretched by thermocompression bonding. When using such strands, an image fiber with a hexagonal close-packed regular core arrangement can be configured, so that the resolution of the transmitted image is uniform and a subject with uniform brightness is observed. It is possible to prevent brightness unevenness that occurs when

  Further, by using at least three kinds of optical fiber strands and arranging these optical fiber strands regularly so that the strands of the same diameter are not adjacent to each other, an image fiber with less crosstalk can be obtained.

Next, the third image fiber will be described. FIG. 26 shows a light output state when uniform light is incident on the entire surface of an image fiber formed by bundling five types of optical fiber wires having the same core / cladding ratio and the same outer diameter in a hexagonal close-packed shape. As is apparent from this figure, an overall average brightness output is obtained.
However, when such a third image fiber is manufactured by the conventional method, the arrangement must be irregular. Therefore, the respective optical fiber strands are arranged so that the strands having the same outer diameter are not adjacent to each other. A device is required for the arrangement means.

Here, first, a first method for arranging the optical fiber strands will be described.
After mixing a plurality of optical fiber strands having different outer diameters, they are arranged almost horizontally. At this time, the mixed optical fiber strands are randomly arranged. However, if the optical fiber strands having a large outer diameter are concentrated on a part, a relatively large gap is formed between the strands. When vibration is applied here, the position of the optical fiber moves and changes due to the vibration, and the optical fiber with a relatively small outer diameter enters the portion where the large gap is formed. For this reason, the optical fiber strands having a relatively large outer diameter and the optical fiber strands having a relatively small outer diameter are arranged at a substantially uniform density. As a result, the optical fiber strands having the same outer diameter are not adjacent to each other.

The bundle of optical fiber wires arranged by such a method is not concentrated on a part of the same outer diameter strand, so when inserted into a jacket pipe, heated and compressed, and drawn to create an image fiber, A good image fiber with little crosstalk can be obtained.
In this technique, the difference in the wire diameter between the closest optical fiber strands is sufficient if it is at least 2%, but considering the tolerance of structural accuracy, The difference in size is preferably in the range of 5 to 10%. In addition, by doing so, it is easy to make uniform by vibration, and it is possible to minimize the difficulty in viewing an image due to the difference in the outer diameter of the optical fiber.

Next, a second method for arranging the optical fiber strands will be described.
In general, this type of image fiber is manufactured by randomly inserting a plurality of optical fiber strands of various types of outer diameters into a jacket pipe and then crimping them at a high temperature and drawing them to a required thickness. However, when inserting a plurality of types of outer diameters and a large number of optical fiber strands into the jacket pipe, for example, each array assisting means such as a mesh frame portion or a mesh frame portion as shown in FIGS. By using 41 and 42, an expected wire arrangement can be obtained.

Alternatively, it may be performed by mechanical device means controlled by a computer. That is, as shown in FIG. 25, for example, in each frame portion of the former arrangement assisting means 41, each of the arrangement assisting means 41 and 42 is divided into A, B. , C, and D, each of the four types of optical fiber strands 43, and in each frame portion of the latter arrangement assisting means 42, are again A, B, C, D, and Each of the five types of optical fiber strands 43 shown as E is arranged in advance as appropriate, and each of the optical fiber strands 43 thus arranged is jacketed pipe 44. If inserted inside, it is possible to prevent the strands having the same outer diameter from adjoining each other, and even if the arrangement is slightly collapsed, regularity to the extent that there is no practical problem is sufficiently maintained. The arrangement of the optical fiber strands may be arbitrarily determined depending on the number of types of strands so that the same type of strands are not adjacent.
And after inserting each optical fiber strand 43 in the jacket pipe 44 in this way, the jacket pipe 44 and each optical fiber strand 43 are heated at high temperature, and the clad part of each optical fiber strand 43 is mutually fused. In addition, the desired image fiber 10 can be obtained by drawing the whole to a desired thickness.

In the method of arranging the first and second optical fiber strands, when optical fiber strands having different core diameters are used, crosstalk can be reduced if the core diameter difference is 0.5% or more. is there.
2. Description of the Related Art In recent years, the manufacturing technology of optical fiber strands has been remarkably advanced, and at present, optical fiber strands having a variation in outer diameter of about ± 1 μm can be manufactured. Since the optical fiber used for this type of image fiber usually has an outer diameter of about 300 μm and a core diameter of about 200 μm, the core diameter difference of 0.5% can be sufficiently achieved. . However, in consideration of variations in the manufacturing process, the core diameter difference is desirably 1% or more, preferably 2% or more.

  In addition, in both the first and second methods for arranging the above-mentioned optical fiber strands, it is sufficient that there are three or more types of optical fiber strands to be used. It is desirable to use five or more types of optical fiber strands. Although it is ideal to arrange all the thousands to tens of thousands of optical fiber strands so that the same core diameters do not adjoin each other 100%, it is actually difficult. However, if 50% or more of the cores are not adjacent to the core having the same outer diameter, image quality degradation due to crosstalk due to the remaining cores is slight, and there is no problem in image observation. If 80% or more of the cores are not adjacent to the core having the same diameter, there is no problem.

  Also, if the variation in the core diameter and the distance between the cores in the image fiber becomes large, it becomes difficult to see the image. Therefore, the ratio of the maximum core diameter to the minimum core diameter and the ratio of the maximum strand diameter to the minimum strand diameter is Therefore, it is necessary to make the increase 50% or less. In particular, in an image fiber having a small number of pixels (number of strands) (for example, 5000 pixels or less), it is desirable that the ratio be suppressed to an increase of 30% or less. This is because an image fiber having a small number of pixels originally has a coarser image than an image fiber having a large number of pixels, so that when the image fiber is enlarged, the core diameter of the image fiber becomes large and becomes conspicuous.

On the other hand, for each of the optical fiber strands, the core / cladding ratio (ratio of the strand outer diameter to the core diameter) is constant and the outer diameter is different when considering the manufacturing cost. Preferably there is.
This is because an optical fiber with a required outer diameter can be arbitrarily manufactured by using the same base material and changing the drawing speed as expected.

  In the above first and second methods, it is desirable that the refractive index of the jacket pipe used together is higher than the refractive index of the cladding. If the refractive index of the jacket pipe is lower than the refractive index of the cladding, there is a possibility that flare due to the incident light of the cladding occurs.

In order to prevent the same type of optical fiber from adjoining, three or more types of optical fiber may be used.
When using fiber optic strands with the same outer diameter, different core cross-sections, and equal core occupancy, there will be no disturbance in the arrangement due to the difference in the outer diameter of the fiber optic strands. When optical fiber strands with different diameters are used, the arrangement is disturbed (not hexagonally dense), so the possibility that the same type of optical fiber strands will be adjacent to each other increases and crosstalk occurs. There is a risk that. As a method for preventing such problems, first, the ratio of the outer diameter of the largest optical fiber to the outer diameter of the smallest optical fiber is increased by 10% or less, preferably 5% or less. Is mentioned. In this way, by suppressing the difference in the outer diameter of each optical fiber, it is possible to minimize the disturbance of the arrangement of the optical fiber strands and prevent the occurrence of crosstalk.

  As the second method, it is effective to increase the types of the optical fiber used. However, due to accuracy and tolerances in the manufacturing process, the difference in the outer diameter of the optical fiber is required to be at least 2%, preferably about 5 to 10%. In order to reduce the ratio of the maximum outer diameter of the optical fiber to the outer diameter of the strand by 50% or less, it is preferable to use 10 or less types of optical fibers to be used. In particular, in an image fiber having a small number of pixels (for example, 5000 pixels or less), as described above, the ratio of the outer diameter of the largest optical fiber to the outer diameter of the smallest optical fiber is 30. Since it is desirable to increase the percentage by weight, it is desirable that about 4 to 6 types of optical fiber are used.

Furthermore, it is desirable that the core / cladding ratio of the optical fiber used satisfies the following conditional expression.
0.7> core / cladding ratio> 0.4
If this core / cladding ratio value exceeds the upper limit of the above formula, the clad becomes thin and crosstalk is likely to occur, and if the core / cladding ratio value falls below the lower limit of the above formula, the core occupancy is reduced. It becomes less and the brightness is insufficient.

  When the type of optical fiber strand used is small and the ratio of the outer diameter of the largest optical fiber to the outer diameter of the smallest optical fiber exceeds 10%, each optical fiber in the jacket pipe The arrangement of the strands will be disturbed due to the difference in the outer diameter, but according to the arrangement method as described above, the disorder is only enough to fill the gap due to the difference in the outer diameter. It is unlikely that a plurality of strands (or outer diameters) are adjacent to each other or concentrated in one place as seen in FIG. 16, and a plurality of types of optical fiber elements having the same outer diameter. Even when a line is used, brightness unevenness as shown in FIG. 22 does not occur.

  Further, the inner cross-sectional shape of the jacket pipe is usually formed in a circular shape. However, if necessary, the inner cross-sectional shape of the jacket pipe is hexagonal, so that the arrangement of the optical fiber strands in the peripheral portion is disturbed. Can be minimized.

  Next, the transmission efficiency of light transmitted by the image fiber will be described.

  As mentioned earlier, in order to maintain high resolution after reducing the diameter of the image fiber, it is inevitably necessary to reduce the fiber spacing and the core diameter. If the core diameter is decreased, the propagation mode generally decreases, and the single mode is obtained when the V value is 2.405 or less.

  FIG. 2 shows each propagation mode (wavelength is 600 nm) that is excited when light is incident on an optical fiber having a numerical aperture (NA) of 0.495 through an F-number 1.4 objective optical system. A graph of the energy ratio is shown. In the figure, the horizontal axis represents the core diameter, and the vertical axis represents the energy ratio, which is an arbitrary scale.

As is apparent from FIG. 2, in the case of the multimode, not only the LP ₀₁ mode (A) but also the LP ₁₁ mode (B) and the LP ₂₁ mode (C) have a large proportion of energy to propagate. In order to propagate the LP ₁₁ mode (B), the core diameter is 1 μm or more, and in order to propagate the LP ₂₁ mode (C), the core diameter is 1.5 μm or more. If the value is less than 1, the propagation mode is reduced and the brightness is expected to deteriorate significantly as seen in the modes (d) and (e). The same can be said even if the F number of the incident light beam is changed.

Therefore, in order to ensure the required brightness, it is desirable that the LP ₁₁ mode (b) is propagated in the visible range (about 400 nm to 650 nm).
V> 2.405 (3)
It is necessary to satisfy the relationship.

Further, in order to sufficiently increase the transmission efficiency, it is desirable that the LP ₂₁ mode (c) can also propagate. At this time, the propagation condition of LP ₂₁ mode (C) is as follows:
V> 3.83 (4)
It is necessary to satisfy the relationship.

Here, in the random image fiber, since a plurality of optical fiber strands having different V values of light propagating in the core are bundled, the thickness of the center value is practically used. It is sufficient if the above expression (3) or (4) is satisfied.
Furthermore, it is extremely ideal if all types of optical fibers used satisfy the relationships of the above formulas (3) and (4).

の通りであればよい。 For example, in an image fiber used for a blood vessel endoscope that is actually put into practical use, its outer diameter is about 0.3 mm, and cores of about 2 to 3 μm are about 3000 with a core interval of about 4 μm. It is often filled in (about 3000 pixels).
Therefore, in this specification, in order to satisfy the relationship of the above formula (4), the NA of the image fiber is expressed by the following formula (5).

If it is as follows.

However, on the other hand, the image of about 3000 pixels has a relatively poor image quality, so an image fiber of about 10000 pixels is usually desired.
In order to realize 10000 pixels in the image fiber having the outer diameter of about 0.3 mm, the core diameter needs to be about 1 μm and the core interval needs to be about 2 μm, which satisfies the relationship of the above formula (4). In order to achieve this, an image fiber having a very high NA is required.

のようになる。 However, in reality, an optical fiber having a high NA such that the NA exceeds 0.7 causes a problem that the transmittance is deteriorated and the optical fiber is colored. Therefore, when the condition for satisfying the above equation (3) is obtained even if the brightness is slightly lowered, the following equation (6) is obtained.

become that way.

  Therefore, when the core diameter is 2 to 3 μm or less, the NA of the optical fiber needs to be 0.4 or more, and when the core diameter is 1 μm or less, the NA needs to be 0.498 or more. In addition, with regard to the thickness of the clad, the crosstalk increases as the thickness becomes thinner. On the other hand, if the thickness is too thick, the core occupancy ratio is reduced, and the brightness becomes insufficient. Will occur.

Therefore, in order to make both of these relationships compatible, the thickness (d) of the clad here is expressed by the following equation (7):
1.8μm>d> 0.8μm (7)
It is desirable to prescribe.

On the other hand, in order to define the NA in the relationship of the above formula (5) or (6), the glass material applied to the optical fiber is preferably a multicomponent system rather than a quartz system. In the case of a glass-based material, since it is difficult to make the refractive index of the clad about 1.5 or less, the refractive index (n ₁ ) of the core is expressed by the following formula (8)
n ₁ > 1.56 (8)
It is necessary to specify.

When the refractive index (n ₁ ) of the core exceeds 1.7, the optical fiber having a length of about 0.5 to 5 m has properties of the glass material used (generally, the high refractive index glass transmits on the short wavelength side). The light propagating in the optical fiber may be colored yellow.
Therefore, also here, the refractive index (n ₁ ) of the core is given by the following formula (9)
1.7> n ₁ (9)
On the other hand, the refractive index (n ₂ ) of the cladding is expressed by the following equation (10).
1.53> n ₂ > 1.48 (10)
If this relationship is satisfied, the clad can be formed from a multi-component glass material, and the condition of the above formula (4) can also be satisfied.

  Each of these relations also applies to the embodiment of the present invention described below.

  In addition, when optical fiber strands having different core diameters are bundled, the cutoff frequency of each propagation mode is different because the V values of light propagating through the core of each optical fiber strand are different from each other. Different. For this reason, the transmission efficiency of an optical fiber having a small core diameter is lowered. As a result, the brightness is disadvantageous, which may cause uneven brightness.

  In such a case, for example, as in the embodiment described below, the ratio of the number of optical fibers having a small core diameter and the ratio of the number of optical fibers having a large core diameter are respectively reduced to reduce the number of optical fibers having an intermediate diameter. By increasing the ratio, it is possible to easily reduce the reduction in transmission efficiency and brightness unevenness based on the cut-off phenomenon.

Further, as described above, it is known that the flexibility of the conduit-type image fiber is remarkably impaired by increasing the outer diameter thereof.
Therefore, in the present invention, a plurality of conduit-type image fiber units having an outer diameter of about 500 μm or less are bundled to maintain flexibility. That is, even if it is a conduit type image fiber, if the outer diameter is 500 μm or less, sufficient flexibility can be maintained.
Furthermore, in the case of a conduit-type image fiber, if the outer diameter becomes too thin, the glass layer (jacket layer) without the core portion tends to break and the proportion of the glass layer (jacket layer) increases. The outer diameter is preferably about 30 μm or more.

Next, the manufacturing method of the image fiber configured as described above will be described as follows.
That is, first, in the first manufacturing process, a plurality of prepared optical fiber strands are arranged in an acid-dissolved glass pipe, and in this state, the base material of the conduit-type image fiber unit is formed by thermocompression bonding. In addition, in the second manufacturing process, a plurality of conduit-type image fiber unit base materials obtained in this way are further bundled, heat-pressed again, and drawn and drawn to the required thickness. Get a fiber bundle.

  Next, in the third manufacturing step, the image fiber bundle is cut to a required length, and subsequently, in the fourth manufacturing step, the acid-dissolved glass in the middle portion other than both ends of the image fiber bundle is eluted, In this way, a high-resolution image fiber having the desired relatively large outer diameter and the required flexibility can be obtained.

  Here, in the case of the conduit-type image fiber unit, the acid-dissolved glass pipe portion occupying the outside does not contribute to image transmission, so that the portion is in a state of missing pixels. Therefore, the thinner the pipe is, the better. However, the pipe with such a small wall is generally poor in productivity, so the pipe with a relatively thick wall is used first. It is desirable to cut to a thickness of about 100 μm to 500 μm after one manufacturing process.

  Hereinafter, each specific example of the image fiber to which the present invention is applied and its manufacturing method will be described in detail with reference to the drawings and Tables 1-8.

  FIG. 1 is a schematic cross-sectional view schematically showing a schematic configuration of an image fiber according to first to eighth embodiments of the present invention.

Each example data according to the present invention shows its eight modes by using Table 1 to Table 8 below.
In each of the first to third embodiments, each of the optical fiber strands having the cores 11a, 11b, 11c, 11d, and 11e having the same five core / cladding ratios and different outer diameters in each aspect. After each of these optical fiber strands is inserted into the common jacket pipe 12 in the above-described predetermined arrangement state, the clad portion of each optical fiber strand is heated by heating it to a high temperature. The image fiber 10 having a required outer diameter was manufactured by fusing together and continuously drawing the whole to a predetermined thickness.

Therefore, in the required image fiber 10 manufactured in this way, the clad portions of the respective optical fiber strands are fused and integrated with each other, and are in the integrated clad 13, As described above, the cores 11a, 11b, 11c, 11d, and 11e having five different thicknesses in a predetermined regular arrangement are mixed.
In this case, the cores 11a, 11b, 11c, 11d, and 11e are not necessarily placed under a complete regular arrangement, but the cores having the same outer diameter are adjacent to each other. There is less risk of being smelled.
The jacket pipe 12 is left as a jacket layer 12a surrounding the outer peripheral portion of the integrated clad 13 after the drawing process, and the outer peripheral surface is further coated with a protective coating layer 14. Yes.

First Example Table 1 shows data of this example.

  The image fiber according to the data of the present example was prepared by mixing five types of optical fiber strands having different core diameters and clad diameters by 600, respectively, by the second method, after thermocompression bonding, and then drawing. It is obtained.

Therefore, each core diameter (after spinning) of the image fiber obtained in this manner had five different values, but the average core spacing by each type was 3.8 μm on average.
As a result, the brightness unevenness can be eliminated here.

  In addition, when predetermined light (NA = 0.495, λ = 650 nm) is incident on this image fiber, the V value becomes five different values, and the same type of cores are connected to each other. Since it is almost not adjacent, crosstalk can be reduced.

  As described above, the image fiber based on the data of the present embodiment can suppress the crosstalk and prevent the deterioration of the image quality, and at the same time, it is possible to obtain a configuration with a small diameter and high resolution with no brightness unevenness.

Second Embodiment Table 2 shows data of this embodiment.

  In the image fiber according to the data of the present example, since the fiber with the smallest core diameter (after spinning) is single mode (λ = 650 nm), the largest core (core diameter = 1.13 μm) and the smallest core ( The core diameter = 0.87 μm) is 15% of the total number, and the second largest core (core diameter = 1.07 μm) and the second smallest core (core diameter = 0.93 μm), respectively. 25%, and the remaining intermediate diameter core (core diameter = 1 μm) is configured as 20%, mixed by the first method, and after thermocompression bonding, wire drawing is performed. is there.

Here, when only the composition ratio of one fiber is increased, the significance of mixing different fibers is diminished, and therefore the difference in the composition ratio of each optical fiber is preferably randomized within a range of about 10%. .
Therefore, in the image fiber based on the data of the present embodiment obtained in this way, as in the case of the image fiber based on the data of the first embodiment, it is possible to suppress the crosstalk and prevent the deterioration of the image quality. In addition, a small-diameter and high-resolution image fiber without uneven brightness can be obtained.

Third Embodiment Table 3 shows data of this embodiment.

In the case of the image fiber based on the data of this example, all the cores (after spinning) are configured to be capable of LP ₁₁ mode transmission, and the number of each of the five types of optical fiber strands is the same ratio (600). By using the first method, it is possible to achieve almost the same effect as in the case of the image fiber based on the data of the first and second embodiments.

Fourth Example Table 4 shows data of this example.

  The image fiber according to the data of the present embodiment uses about 430 optical fiber strands having seven core / cladding ratios which are substantially equal and have different outer diameters, and is mixed by the first method. After thermocompression bonding, the wire was drawn and obtained. Although the schematic configuration of the image fiber of the present embodiment is not particularly illustrated, the feature thereof is the same as that of the image fiber described in each of the above embodiments. Further, the image fiber based on the data of this embodiment can obtain the same effects as those of the image fiber based on the data of the above embodiments.

Fifth Embodiment Table 5 shows data of this embodiment.

The image fiber based on the data of the present embodiment is shown in FIG. 3 by the second method using about 1000 optical fiber strands each having three core / cladding ratios which are substantially equal and each having a different outer diameter. After arranging regularly using such an arrangement means, after thermocompression bonding, a drawing process was performed. Although the schematic configuration of the image fiber of the present embodiment is not particularly illustrated, the feature is the same as that of the image fiber described in each of the above embodiments.
Therefore, the image fiber based on the data of the present embodiment can obtain the same effects as the image fiber based on the data of the above embodiments.

Sixth Embodiment Table 6 shows data of this embodiment.

In the image fiber according to the data of this example, about 1000 optical fiber strands are regularly arranged by the above-mentioned second method using the arrangement means as shown in FIG. Processed and obtained. The image fiber according to the data of the present embodiment is formed using optical fiber strands having different core / cladding ratios, but the arrangement of the strands is regular, so there is no brightness unevenness and crosstalk is also caused. Less good image fibers can be obtained.
Although the schematic configuration of the image fiber of the present embodiment is not particularly illustrated, the feature is the same as that of the image fiber described in each of the above embodiments.
Therefore, the image fiber based on the data of the present embodiment can obtain the same effects as the image fiber based on the data of the above embodiments.

Seventh Example Table 7 shows data of this example.

The image fiber according to the data of the present example is mixed by the first method using about 430 optical fiber strands having seven core / cladding ratios which are substantially equal and each having a different outer diameter. Then, after thermocompression bonding, the wire is drawn and obtained. Although the schematic configuration of the image fiber of the present embodiment is not particularly illustrated, the feature thereof is the same as that of the image fiber described in each of the above embodiments.
Further, the image fiber based on the data of this embodiment can obtain the same effects as those of the image fiber based on the data of the above embodiments.

Eighth Example Table 8 shows data of this example.

The image fiber based on the data of the present embodiment is mixed by the first method using about 1430 optical fiber strands having seven core / cladding ratios which are substantially equal and each having a different outer diameter. Then, after thermocompression bonding, the wire is drawn and obtained. Although the schematic configuration of the image fiber of the present embodiment is not particularly illustrated, the feature thereof is the same as that of the image fiber described in each of the above embodiments.
Further, the image fiber based on the data of this embodiment can obtain the same effects as those of the image fiber based on the data of the above embodiments.

  The image fibers shown in the first to eighth embodiments all use a clad having a refractive index of 1.5177 and a jacket pipe having a refractive index of 1.53. It is configured by coating a resin mixed with carbon on the outside.

Ninth Embodiment FIG. 4 is a partial sectional view showing the arrangement of cores in a conduit type image fiber to which this embodiment is applied.

In this embodiment, three types of cores having different core diameters are used, and each core having the same diameter is regularly arranged in a hexagonal close-packed shape so as not to be adjacent to each other. The outer diameter is about 300 μm and the length is about 3 m. The conduit type image fiber 110 having about 3000 pixels is targeted.
In this case, the core diameters of the three types of cores 111a, 111b, and 111c are 2.5 μm, 2.55 μm, and 2.6 μm, respectively, and the distance between the cores is 3.8 μm, which is the closest large diameter to the small diameter core. The core diameter difference between the cores is about 2%, the core diameter difference with respect to the minimum core diameter is 4%, and the refractive indexes of the cores 111a, 111b, 111c are 1.59, respectively. The refractive index of the clad 112 shared by 111a, 111b, and 111c is 1.5177.

  Thus, in the conduit type image fiber 110 of the present embodiment configured in the plurality of core arrays of the three types, the core diameters of the adjacent cores 111a, 111b, and 111c are different from each other. The propagation constants of the cores 111a, 111b, and 111c are also different, and crosstalk hardly occurs. As a result, the interval between the cores, and thus the outer diameter of the image fiber 110 itself can be reduced.

  Moreover, although the cross-sectional areas of the respective cores 111a, 111b, and 111c are different, the difference is slight, and in addition, the arrangement of the cores 111a, 111b, and 111c is in a hexagonal close-packed shape that is not adjacent to each other. If the sum of the areas of three pixels adjacent to each other here is one unit area, the ratio of the core cross-sectional area to each unit area becomes uniform over the entire transmission screen. As a result, there is no risk of uneven brightness even when an object to be observed having a uniform brightness is observed.

Tenth Embodiment FIG. 5 is a partial sectional view showing the arrangement of cores in a conduit type image fiber to which this embodiment is applied.

  In this embodiment, each of the optical fiber strands having the same outer diameter including three types of cores having different cross-sectional shapes and the same cross-sectional area, that is, in this case, the core 122a having a circular cross-section is included in the clad 123a. A plurality of optical fiber strands 121a, an optical fiber strand 121b in which a core 122b having an elliptical cross section is encapsulated in a clad 123b, and a plurality of optical fiber strands 121c in which a core 122c having a square cross section is encapsulated in a clad 123c are used. A conduit-type image fiber 120 that is regularly arranged in a hexagonal close-packed shape so that the optical fiber strands 121a, 121b, and 121c having the cores 122a, 122b, and 122c are not adjacent to each other, and after thermocompression bonding is drawn. In this case, the interval between cores is 3μm, and image transmission Core area occupied by 40%, the length, and the refractive index between the core and the cladding in is the same as the ninth embodiment.

  Thus, in the conduit type image fiber 120 of the present embodiment having the above-described configuration, the core shapes of the cores 122a, 122b, and 122c adjacent to each other are different, so that the crosstalk is similar to the case of the ninth embodiment. In addition, the interval between the cores, and hence the outer diameter of the image fiber 120 itself, can be reduced, and the cross-sectional areas of the cores 122a, 122b, and 122c are equal. Therefore, even if an object to be observed having a uniform brightness is observed, there is no possibility of uneven brightness.

Eleventh Embodiment FIG. 6 is a partial sectional view showing the arrangement of cores in a conduit type image fiber to which this embodiment is applied.

  In the present embodiment, the cores 131a having a core diameter of 3 μm and the cores 131b having a core diameter of 2.5 μm are alternately arranged regularly at a spacing of about 7 μm in a quadrilateral close-packed manner, and arranged on the opposite image. Conduit-type image fiber 130 in which each core 131c having a core diameter of about 1 μm is disposed between the cores 131a and 131a, 131b and 131b having the same core diameter and encapsulated in a common clad 132 is intended. In this case, the refractive index of the core is 1.62, the refractive index of the cladding is 1.49, and the length is about 2 m.

  Thus, in the conduit type image fiber 130 of the present embodiment having the above-described configuration, the core diameters of the adjacent cores 131a, 131b, and 131c are different from each other. The propagation constants in the cores 131a, 131b, and 131c are also different, so that crosstalk hardly occurs, and the interval between the cores, and thus the outer diameter of the image fiber 130 itself can be reduced. Further, although the cross-sectional areas of the cores 131a, 131b, and 131c are different from each other, since they are regularly arranged, the four adjacent pixels (one each of the cores 131a and 131b and 131c2 pixels) are arranged. When the sum of the areas is taken as one unit area, the ratio of the core cross-sectional area to each unit area becomes uniform over the entire area of the transmission screen, resulting in uneven brightness even when observing an object with uniform brightness. There is no fear.

Twelfth Embodiment and Thirteenth Embodiment FIGS. 7 and 8 show optical fiber elements in a glass pipe for explaining a method of manufacturing a conduit-type image fiber to which the twelfth and thirteenth embodiments of the present invention are applied. It is each fragmentary sectional view which shows the arrangement | sequence aspect of a line, respectively.

  The twelfth and thirteenth embodiments are cases where the conduit type image fibers 140 and 150 similar to the ninth and tenth embodiments are manufactured.

That is, in the case of the twelfth embodiment, the refractive index of the core is 1.59, the refractive index of the cladding is 1.5177, the core / cladding ratio is 2/3, and the outer diameter is 300 μm. By using three types of optical fiber strands 141a, 141b, 141c having different diameters of 306 μm and 312 μm and sequentially combining these optical fiber strands 141a, 141b, 141c, the same as expected. After the optical fiber strands of the core diameter are regularly arranged in a hexagonal close-packed shape without being adjacent to each other, a combination of about 1000 optical fiber strands 141a, 141b, 141c is installed in the jacket pipe. And including the jacket pipe, it is stretched until the outer diameter is about 300 μm while thermocompression bonding. The conduit image fiber 140 were prepared.
Even in the case of the thirteenth embodiment, three types of optical fiber strands 151a, 151b, 151c having different diameters are used and arranged in the same manner in the jacket pipe. The required conduit type image fiber 150 was manufactured by stretching by thermocompression bonding.
As the arrangement method, the above-described second method may be used in the case of the twelfth embodiment, and the first or second method may be used in the case of the thirteenth embodiment.

  Thus, in the conduit type image fibers 140 and 150 of the twelfth and thirteenth embodiments manufactured as described above, the optical fiber strands 141a, 141b, 141c, 151a, 151b, Since the optical fiber strands of the same core diameter with each of 151c are arranged so as not to be adjacent to each other, the occurrence of crosstalk is reduced together, and because of the regular arrangement, it is very easy to see, In addition, a high-resolution image fiber without uneven brightness was obtained.

14th embodiment Figure 9 is a partial sectional view showing a mode of arrangement of each core conduit image fiber unit used in this embodiment, FIG. 10 is for explaining the method of manufacturing an image fiber according to the present embodiment FIG. 11 is an explanatory view schematically showing the outline of the appearance of the completed image fiber. FIG. 11 is a partial sectional view showing the arrangement of the image fiber units in the glass pipe.

  In this embodiment, as in the ninth embodiment, three types of optical fiber strands 162a, 162b, 162c having different core diameters are used. First, as shown in FIG. 1.57, the jacket layer 164 made of an acid-melted glass pipe having a hexagonal cross-section has a hexagonal close-packed shape so that the clad 163 is shared and optical fibers of the same diameter are not adjacent to each other. After being regularly arranged, this is heat-pressed and drawn and drawn to obtain a conduit-type image fiber unit 161 having an outer diameter of about 200 μm. Subsequently, as shown in FIG. After bundling about 500 units 161 and heat-pressing again, the incident end and the exit end, that is, the intermediate portion 161b excluding both end portions 161a are attached. There are, eluted jacket layer 164 part consisting of acid dissolution glass pipe was produced image fiber 160.

  Thus, in the image fiber 160 of the present embodiment manufactured as described above, although the outer diameter of the obtained image fiber 160 is substantially as large as about 5 mm, Similar actions and effects can be obtained, and at the same time, a high resolution of about 100,000 pixels can be achieved with an interval of 3.8 μm between the cores with sufficient flexibility.

  As is apparent from the description of the above embodiments, the present invention is adapted to the configuration of the image fiber described in claims 1 and 3 and the method for manufacturing the image fiber described in claims 2 and 4. Further, the present invention extends to the configuration of each image fiber and the method for manufacturing the image fiber.

  (1) The image fiber according to claim 1, wherein at least 50% or more of the cores are arranged so as not to be adjacent to the same kind of cores.

  (2) The image fiber according to (1), wherein at least 80% or more of the cores are arranged so as not to be adjacent to the same type of core.

  (3) The plurality of types of cores have at least three different types of cross-sectional shapes, and the cross-sectional areas thereof are all equal. Image fiber.

  (4) The image fiber according to (1) or (2), wherein the plurality of types of cores include at least three types of cores having different diameters.

  (5) The image fiber according to (1) or (2) above, wherein the arrangement of the cores is substantially regular.

  (6) The image fiber according to (4), wherein a core diameter difference between cores having different diameters is 2% or more.

  (7) The image according to (4), wherein the core diameter difference of the maximum core diameter with respect to the minimum core diameter of the cores having different diameters of at least three types is 50% or less. Fiber.

  (8) The core diameter difference of the maximum core diameter with respect to the minimum core diameter of the at least three kinds of cores having different diameters is 30% increase or less, and the number of pixels is 5000 pixels or less. The image fiber according to (7) above, which is characterized.

  (9) The core diameter difference between the cores having different diameters of at least three types is 0.5% or more, and the core diameter difference of the maximum core diameter with respect to the minimum core diameter is 10% or less. The image fiber as described in (4) above, wherein

  (10) The image fiber according to (4) above, wherein there are 4 to 10 types of cores having different diameters.

  (11) The image according to (10), wherein there are 4 to 6 types of cores having different diameters, and the core diameter difference between the cores is 5 to 10%. Fiber.

(12) The image fiber according to claim 1 or (1), wherein the thickness d of the clad portion satisfies the following conditional expression.
1.8 μm>d> 0.8 μm

  (13) The plurality of types of optical fiber strands are optical fiber strands having different outer diameters, and the step of arranging the same type of optical fiber strands so as not to be adjacent to each other includes at least A step of horizontally arranging a plurality of types of optical fiber strands having different outer diameters and a step of vibrating the optical fiber strands to arrange the plurality of types of optical fiber strands at a substantially uniform density. The method for producing an image fiber according to claim 2, wherein:

  (14) The image fiber manufacturing method according to (2) or (13), wherein the plurality of types of optical fiber strands have substantially the same core / cladding ratio.

(15) The image fiber production according to (2) or (13), wherein the plurality of types of optical fiber strands are configured so that a core / cladding ratio satisfies the following conditional expression: Method.
0.7> core / cladding> 0.4

  (16) The method for producing an image fiber according to (2), wherein the plurality of types of optical fiber strands have the same core occupation ratio and different core cross-sectional shapes.

  (17) The method for producing an image fiber according to (2) or (13), wherein the plurality of types of optical fiber strands have at least three types of cores having different diameters.

  (18) The method for producing an image fiber according to (17), wherein the number of the cores having different diameters is 4 to 10 types.

  (19) The method for manufacturing an image fiber according to (17), wherein the plurality of types of optical fiber strands have at least five types of cores having different diameters.

  (20) The optical fiber strands having cores of at least three different diameters have substantially the same core / cladding ratio, an outer diameter difference of 0.5% or more, and a maximum outer diameter with respect to a minimum outer diameter. The method for producing an image fiber as described in (17) above, wherein the difference in outer diameter between the diameters is 10% or less.

  (21) The method for producing an image fiber according to the above (17), wherein the at least three types of optical fiber elements having cores having different diameters have an outer diameter difference of 2% or more.

  (22) The method for producing an image fiber according to the above (17), wherein each of the optical fiber strands is 4 to 6 types, and an outer diameter difference between the strands is 5 to 10%.

  (23) In the plurality of types of optical fiber strands, the ratio of the size of the optical fiber strand with the maximum outer diameter to the size of the optical fiber strand with the minimum outer diameter, and the size of the maximum core diameter with respect to the size of the minimum core diameter Both of the ratios are 50% or less. The method for producing an image fiber according to the above (17), wherein the ratio is less than 50%.

  (24) The ratio of the size of the optical fiber with the maximum outer diameter to the size of the optical fiber with the minimum outer diameter and the size of the maximum core diameter with respect to the size of the minimum core diameter in the plurality of types of optical fibers. The ratio of the height is 30% or less, and the number of strands is 5000 or less. The method for producing an image fiber according to (23), wherein the number of strands is 5000 or less.

  (25) The image fiber unit according to claim 3, wherein the conduit type image fiber unit is an image fiber unit having a plurality of types of cores and comprising a clad shared with the cores.

  (26) The image fiber as described in (25) above, wherein in the conduit type image fiber unit having a plurality of types of cores, the same type of cores are arranged so as not to be adjacent to each other.

  (27) The image fiber according to claim 3, wherein the conduit type image fiber unit has an outer diameter of 500 μm or less.

  (28) The image fiber according to (27), wherein the conduit type image fiber unit has an outer diameter of 30 μm or more.

  (29) The method according to claim 4, wherein the acid-dissolved glass layer of the conduit-type image fiber unit has a thickness of about 100 to 500 μm.

  (30) The method according to claim 4, wherein the conduit type image fiber unit includes at least cores having different diameters.

  (31) The conduit type image fiber unit is composed of at least three types of cores having different diameters and a clad shared with the cores, and the cores having the same diameter are arranged almost regularly so as not to be adjacent to each other. The method for producing an image fiber according to the above (30), wherein:

(32) The refractive index (n ₁ ) of the core of the image fiber or the optical fiber is configured to satisfy the following conditional expression: (2), (3), (4) or (1) And an image fiber manufacturing method thereof.
n ₁ > 1.56

(33) The image fiber according to (32) above and a method for manufacturing the image fiber, wherein the refractive index (n ₁ ) of the core satisfies the following conditional expression.
1.7> n ₁

It is a transverse cross section showing typically the section structure by an example of the image fiber concerning the present invention. It is a figure which shows the ratio of the energy of each propagation mode excited in the core of an optical fiber. It is explanatory drawing which shows an example of the arrangement | sequence means of three types of each optical fiber strand from which core / clad ratio differs, and an outer diameter are equal, and this arrangement | sequence. It is a fragmentary sectional view which shows the arrangement | sequence aspect of each core in the conduit type image fiber to which the 9th Example of this invention is applied. It is a fragmentary sectional view which shows the arrangement | sequence aspect of each core in the conduit type image fiber to which 10th Example of this invention is applied. It is a fragmentary sectional view which shows the arrangement | sequence aspect of each core in the conduit type image fiber to which 11th Example of this invention is applied. It is a fragmentary sectional view which shows the arrangement | sequence aspect of each core in the glass pipe for demonstrating the manufacturing method of the conduit type image fiber to which 12th Example of this invention is applied. It is a fragmentary sectional view which shows the arrangement | sequence aspect of each core in the glass pipe for demonstrating the manufacturing method of the conduit type image fiber to which 13th Example of this invention is applied. It is a fragmentary sectional view which shows the arrangement | sequence aspect of each core of the conduit type image fiber unit used for 14th Example of this invention. It is each fragmentary sectional view which shows the arrangement | sequence aspect of each image fiber unit in the glass pipe for demonstrating the manufacturing method of the image fiber to which the 14th Example is applied. It is explanatory drawing which shows typically the outline | summary of the external appearance form of the completed image fiber. It is an arrangement block diagram which shows typically an outline of a general medical endoscope. It is a cross-sectional schematic diagram which shows typically the outline | summary of the conventional image fiber applied to the medical endoscope. It is a figure which shows the definition of the core diameter of an image fiber, clad thickness, and a core space | interval. It is a figure which shows partially the outline | summary of the end surface structure by an example of the conventional random image fiber. FIG. 16 is an end surface explanatory view schematically showing an enlarged detail of a main part in the configuration shown in FIG. 15. It is a figure which shows the light output state when light injects into the core 1 of each adjacent core made into the same small diameter in the same area | region in the structure shown in FIG. It is a figure which shows the light output state when light injects into the core 2 of each adjacent core made into the same small diameter in the same area | region in the structure shown in FIG. It is a figure which shows the light output state when light injects into one core (core 3) of each adjacent core made into the same large diameter in the same area | region in the structure shown in FIG. It is a figure which shows the light output state when light injects into the core 4 made into the intermediate diameter independent in the same area | region in the structure shown in FIG. It is a cross-sectional schematic diagram which shows typically the structure by an example at the time of arranging three types of optical fiber strands regularly in hexagonal close-packed form. FIG. 6 is a diagram showing a light output state according to an example in which uniform light is incident on the entire surface of an image fiber formed by bundling five types of optical fiber strands having different core / cladding ratios and the same outer diameter in a hexagonal close-packed shape. is there. It is explanatory drawing which shows an example of the arrangement | sequence means of four types of each optical fiber strand from which core / clad ratio is the same, and differed in outer diameter, and this arrangement | sequence. It is explanatory drawing which shows an example of the arrangement | sequence means of 5 types of each optical fiber strand from which core / clad ratio is the same, and differed in outer diameter, and this arrangement | sequence. It is sectional explanatory drawing which shows typically the aspect at the time of inserting each optical fiber strand in a jacket pipe using the said each arrangement | sequence means. The figure which shows the light output state by an example at the time of making uniform light incident on the whole surface of the image fiber formed by bundling five types of optical fiber strands with the same core / cladding ratio and the same outer diameter in a hexagonal close-packed shape It is.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Image fiber 11a-11e Core 12, 12a Jacket pipe, jacket layer 13 Clad part 14 Coat layer 110 Conduit type image fiber 111a, 111b, 111c Core 112 Cladding 120 Conduit type image fiber 121a, 121b, 121c Optical fiber strand 122a, 122b , 122c Core 123a, 123b, 123c Clad 130 Conduit image fiber 131a, 131b, 131c Core 132 Clad 140 Conduit image fiber 141a, 141b, 141c Optical fiber strand 150 Conduit image fiber 151a, 151b, 151c Optical fiber strand 160 Image Fiber 161 Conduit type image fiber unit 16 a integrally been both ends (entrance end, exit end)
161b Separated intermediate parts 162a, 162b, 162c Optical fiber strand 163 Cladding 164 Jacket layer (acid molten glass pipe)

Claims (6)

  A plurality of conduit-type image fiber units in which a plurality of cores share a clad are arranged in parallel, and the conduit-type image fiber units according to the arrangement are integrally formed at the entrance end and the exit end, and An image fiber characterized by being separated from each other in the middle. In an image fiber having a plurality of types of cores and made of a clad shared by the cores, at least 50% or more of the cores are arranged so as not to be adjacent to the same type of cores, and the plurality of types of cores have at least three different shapes. An image fiber which is a kind of core and wherein the thickness d of the clad portion satisfies the following conditional expression.
0.8μm <d <1.8μm   2. The image fiber according to claim 1, wherein the conduit-type image fiber unit is an image fiber unit having a plurality of types of cores and comprising a clad shared with the cores.   The conduit fiber image fiber unit having the plurality of types of cores, wherein the same type of cores are arranged so as not to be adjacent to each other.   The image fiber according to claim 1, wherein the outer diameter of the conduit type image fiber unit is 500 μm or less.   The image fiber according to claim 2, wherein the arrangement of the cores is substantially regular.

Images