JP2011194137A - Optical fiber unit and endoscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent optical fibers from being damaged due to movement of an optical fiber bundle or the optical fibers in a metal-made protective tube, and to enhance manufacturing suitability.SOLUTION: A light guide 34 includes: the bundle 40 of the optical fibers 40a; a cap 35 into which the distal end part of the optical fiber bundle 40 is fitted; a spiral tube 36 as the metal-made protective tube; and a heat contraction tube 37. The spiral tube 36 is arranged around the outer periphery of the optical fiber bundle 40 in the curved part 12 of an inserting part 3. The heat contraction tube 37 has a first part 37a for covering the outer peripheral part of the spiral tube 36; and a second part 37b extending rearward from the rear end of the spiral tube 36 and covering the optical fiber bundle 40. The heat contraction tube 37 is thermally shrunk in the radial direction, so that the inner diameter Dof the second part 37b is formed smaller than the inner diameter Dof the spiral tube 36 near the border between the first part 37a and the second part 37b.

Description

  The present invention relates to an optical fiber unit that is inserted into an insertion portion of an endoscope, and an endoscope including the same.

  An optical fiber unit such as a light guide that guides illumination light from the light source device is inserted through the insertion portion of the endoscope. This optical fiber unit includes an optical fiber bundle obtained by bundling a plurality of optical fibers. The individual optical fibers forming the optical fiber bundle are members that are vulnerable to compression, and may be broken by external compression or the like. Usually, in the insertion portion, in addition to the optical fiber unit, a treatment instrument insertion channel as a guide member for forceps and other treatment instruments is inserted, so that they are pressed against these other built-in objects. For this reason, the optical fiber must be protected from disconnection. In particular, since the bending portion constituting the insertion portion has a large bending angle, the optical fiber may be broken by another built-in object. When the optical fiber is broken, the amount of illumination light is reduced, or the broken portion is reflected in the endoscopic image as a black spot, and in some cases, observation becomes impossible.

  In order to solve the above problem, in the light guide or the image guide described in Patent Document 1, a silicon tube having elasticity is coated on the outer periphery of the optical fiber bundle in the bending portion, and the base end portion of this silicon tube, that is, the bending The vicinity of the boundary between the portion and the soft portion provided continuously with the bending portion is covered with a heat shrinkable tube. Thus, by covering the inside of the bending portion with the silicon tube, the pressure from other built-in objects is absorbed by the elastic force of the silicon tube.

  On the other hand, in Patent Document 2, the outer periphery of the optical fiber bundle in the bending portion is covered with a metal spiral tube, and the outer periphery of the spiral tube and the optical fiber bundle is covered with a silicon flexible tube. By protecting with a spiral tube, the optical fiber is prevented from being broken by compression from other built-in portions. In Patent Document 3, a mesh tube formed by braiding metal wires is coated on the outer periphery of an optical fiber bundle, the mesh tube is coated with a flexible tube made of synthetic resin, and the optical fiber bundle is meshed. An arrangement for protection by a tube is described.

  As described above, when the outer periphery of the optical fiber bundle is covered with a metal protective tube such as a spiral tube or a mesh tube, and the outer periphery of the metal protective tube is further covered with a flexible tube, the inner diameter of the flexible tube Use a metal protective tube with a large outer diameter, and cover the outer periphery of the optical fiber bundle with the diameter reduced by an operation such as twisting the metal protective tube. It is put on the outer periphery. By covering in this way, the metal protective tube is hard to be inserted into the inner surface of the flexible tube by its urging force, so that the metal protective tube and the flexible tube are in close contact, and the metal protective tube and the optical fiber bundle are Since there is a gap between them, the metal protective tube does not press the optical fiber bundle.

JP 2004-298449 A Japanese Patent No. 2978295 JP 2004-89265 A

  In recent years, endoscopes such as transnasal endoscopes in which the diameter of the insertion portion is made smaller than those of oral endoscopes and lower endoscopes have been developed, and the diameter of the insertion portion has been reduced. However, in the light guide or the image guide described in Patent Document 1, if the silicon tube is made thin in consideration of the reduction in the diameter of the insertion portion, the optical fiber is damaged without being able to absorb the pressure, and the pressure is reduced. On the other hand, when a silicon tube having a sufficient thickness is covered, it is an obstacle to reducing the diameter of the insertion portion.

  On the other hand, in the configurations of Patent Documents 2 and 3 described above, the optical fiber can be sufficiently protected even when a thin metal protective tube is used in consideration of the reduction in diameter. When the rigidity of the flexible tube covering the optical fiber is low, the optical fiber may be blown (moves greatly) in the insertion portion. At this time, the optical fiber is broken by receiving pressure from other built-in components. There is a risk that.

  In order to improve the rigidity of the optical fiber unit, the outer periphery of the metal protective tube is covered with the heat shrinkable tube described in Patent Document 1 instead of the flexible tube described in Patent Documents 2 and 3. However, in this case, the heat-shrinkable tube is more rigid than the flexible tube made of silicon, etc., so that the entire optical fiber bundle can be suppressed, but the optical fiber bundle should not be compressed. There is a need to have a gap between the spiral tube and the optical fiber bundle, and the optical fiber bundle moved in this gap may hit the inner peripheral edge of the rear end of the inner diameter of the metal protective tube, and the optical fiber may be broken.

  In addition, as described in Patent Documents 2 and 3, when a flexible tube is coated on the outer periphery of a metal protective tube, the metal protective tube bites into and adheres to the inner surface of the flexible tube. The process of coating in a state in which the diameter is reduced by twisting is troublesome and takes time, and the manufacturing suitability is not good.

  The present invention has been made in view of the above problems, and prevents the optical fiber bundle or the optical fiber from moving in the metal protective tube to break the optical fiber, and improves the manufacturing suitability. Objective.

  The optical fiber unit of the present invention is inserted into an insertion portion of an endoscope in which a bending portion that bends in order to change the direction of the distal end portion and a flexible soft portion are sequentially provided from the distal end side. An optical fiber bundle or optical fiber bundled, a metal protective tube disposed on an outer periphery of the optical fiber bundle or the optical fiber in the bending portion, and a first portion covering the outer periphery of the metal protective tube; A heat shrinkable tube extending rearward from a rear end of the metal protective tube and having a second portion covering the optical fiber bundle or the optical fiber, wherein the heat shrinkable tube is at least a first portion. In the vicinity of the boundary between the second portion and the second portion, the inner diameter of the second portion is smaller than the inner diameter of the metal protective tube.

  The metal protective tube is preferably a spiral tube formed by winding a strip. Alternatively, the metal protective tube is preferably a reticulated tube formed by braiding fine wires.

The minimum optical fibers bendable radius and R _M, when the rear end of the metal protective tube, the distance between the front end of the second portion of the heat shrinkable tube is L, it is L ≦ 2R _M Is preferred.

When the step between the inner peripheral radius of the metal protective tube and the inner peripheral radius of the heat-shrinkable tube in the second portion is d, the condition of L ≦ √ (d (4R _M −d)) is satisfied. Is preferred.

When the bending radius at which the heat-shrinkable tube is bent when the bending portion and the flexible portion are bent to have a minimum radius in the vicinity of the boundary between the first portion and the second portion is R _C , The tube preferably has kink resistance when bent so that the bending radius is equal to or greater than _RC . The kink resistance refers to a characteristic that does not cause kink (a state in which the heat-shrinkable tube is bent and not restored) even when the heat-shrinkable tube is bent to a predetermined bending radius. The heat shrinkable tube is preferably made of polyolefin or PTFE.

  The endoscope according to the present invention includes the insertion portion, an operation means for bending the bending portion, a main body operation portion provided on a proximal end side of the insertion portion and incorporating the operation means, and the optical And a fiber unit.

  According to the present invention, the inner diameter of the second portion of the heat shrinkable tube that extends backward from the rear end of the metal protective tube and covers the optical fiber bundle or optical fiber is smaller than the inner diameter of the metal protective tube. The movement of the optical fiber bundle or the optical fiber in the protective tube can be suppressed, and the optical fiber can be prevented from coming into contact with the inner peripheral edge of the metal protective tube. Therefore, breakage of the optical fiber can be prevented. In addition, since the metal protective tube can be easily covered with the heat-shrinkable tube, the manufacturing suitability is improved.

It is an external view of the endoscope of the present invention. It is a top view which shows the end surface of the front-end | tip part of an insertion part. It is principal part sectional drawing which shows the structure of an insertion part. It is principal part sectional drawing which shows the structure of the light guide as an optical fiber unit of this invention. It is explanatory drawing which shows an example of the state (A) in which an optical fiber bundle does not contact the inner periphery of a spiral tube, and the state (B) which contacts. It is explanatory drawing which shows another example in which an optical fiber bundle does not contact the inner periphery of a spiral tube. It is explanatory drawing which shows the state (A) in which the heat-shrinkable tube was bent to the minimum bending range, and the state (B) in which the heat-shrinkable tube was kinked.

  In FIG. 1, an endoscope 2 according to the present invention is connected to an insertion portion 3 to be inserted into a body cavity, an operation portion 5 connected to a proximal end portion of the insertion portion 3, and a processor device or a light source device. The connector part 6, the operation part 5, and the universal cord 7 which connects between the connector parts 6 are provided.

  The insertion portion 3 is formed in a tubular shape, and is composed of a distal end portion 11, a bending portion 12 connecting a plurality of bending pieces, and a flexible flexible portion 13 in order from the distal end. The operation unit 5 is provided with angle knobs 21 and 22 for bending the bending portion 12 in the vertical and horizontal directions to change the direction of the distal end portion 11, a forceps insertion port 23 through which the treatment tool is inserted, and the like.

  As shown in FIGS. 2 and 3, the end surface 11 a of the distal end portion 11 is circular, and an observation window 30, an illumination window 31, a forceps outlet 32, and an air / water supply nozzle 33 are provided. The observation window 30 is disposed at the upper center of the end surface 11a.

  Two illumination windows 31 are arranged at symmetrical positions with respect to the observation window 30. Behind the illumination window 31, an exit end of a light guide 34 for guiding illumination light from the light source device is disposed. The illumination window 31 irradiates the observation site in the body cavity with the illumination light guided by the light guide 34. The light guide 34 is fitted and attached to a hole 14b formed in the distal end portion 11 through a cylindrical base 35 fixed to the distal end.

  In the back of the observation window 30, a photographing optical system and a solid-state image sensor (not shown) such as a CCD are provided. The solid-state imaging device captures image light in the body cavity imaged by the imaging optical system through the observation window 30. An imaging signal obtained by the solid-state imaging device is sent to a processor device connected to the universal cord 7 via a signal line inserted through the insertion unit 3 and the operation unit 5 and displayed as an endoscopic image on a monitor. The The forceps outlet 32 is connected to a forceps channel 38 disposed in the insertion portion 3 and communicates with the forceps insertion port 23. The distal end of the treatment instrument inserted through the forceps insertion opening 23 is exposed from the forceps outlet 32.

  As shown in FIG. 4, a light guide 34 as an optical fiber unit of the present invention includes a bundle 40 of a plurality of optical fibers 40a, a base 35 into which a tip portion of the optical fiber bundle 40 is fitted, and a metal protective tube. As a helical tube 36 and a heat shrinkable tube 37. For example, a quartz optical fiber is used as the optical fiber 40a. The spiral tube 36 is formed by winding a strip made of metal such as stainless steel, and is disposed on the outer periphery of the optical fiber bundle 40 in the bending portion 12 of the insertion portion 3. The front end of the helical tube 36 is fixed to the outer periphery of the rear end of the base 35 with, for example, an adhesive or a spool.

  The heat-shrinkable tube 37 is a well-known heat-shrinkable tube that shrinks when heated, and is made of, for example, polyolefin or PTFE. The heat-shrinkable tube 37 has a length that continues from the rear end portion of the base 35 to a position in the soft portion 13. More specifically, the heat-shrinkable tube 37 includes a first portion 37a that covers the outer periphery of the helical tube 36, and a second portion 37b that extends rearward from the rear end of the helical tube 36 and covers the optical fiber bundle 40. Have.

  The heat shrinkable tube 37 is contracted (thinned) particularly in the diameter direction by heating. In the present invention, this property is used to improve manufacturing suitability. In other words, when the optical fiber bundle 40 is covered with the spiral tube 36 and the heat shrinkable tube 37, the heat shrinkable tube 37 before the heat shrinkage has a larger inner diameter than the outer diameter of the spiral tube 36. Therefore, in the coating process of the helical tube 36 and the heat shrinkable tube 37, it is not necessary to twist the helical tube 36 to reduce its diameter or to increase the diameter of the heat shrinkable tube 37, and the optical fiber is formed by the helical tube 36 in the normal state. The operation of covering the bundle 40 and further covering the outer periphery of the spiral tube 36 with the heat-shrinkable tube 37 before heat-shrinking can be easily performed. Then, after the covering step, the heat shrinkable tube 37 and the spiral tube 36 may be brought into close contact with each other by performing a heat shrinking step of heating and shrinking in the diameter direction. At this time, in order to prevent the optical fiber bundle 40 from being compressed, the heat shrinkable tube 37 is thermally contracted to such an extent that the spiral tube 36 and the optical fiber bundle 40 have a gap.

The heat shrinkable tube 37, by contracting the diameter direction and thermal shrinkage in the vicinity of the boundary between the first portion 37a and second portion 37b, the inner diameter _{D T} of the second portion 37b is, than the inner diameter _{D S} of the spiral tube 36 It is formed small. By forming the heat-shrinkable tube 37 in this manner, the movement of the optical fiber bundle 40 inside the spiral tube 36 is suppressed, and the optical fiber bundle 40 is prevented from contacting the inner peripheral edge 36a at the rear end of the spiral tube 36. Can do. Thereby, breakage of the optical fiber bundle 40 can be prevented.

As described above, the inner diameter D _T of the second portion 37b of the heat shrinkable tube 37, by less than the inside diameter D _S of the spiral tube 36, reducing the contact between the inner peripheral edge 36a and an optical fiber bundle 40 of the spiral tube 36 be able to. However, the optical fiber bundle 40 is repeatedly bent according to the bending of the bending portion 12. Furthermore, since the optical fiber bundle 40 includes a plurality of optical fibers 40a bundled together, the individual optical fibers 40a bend in various states. In the following, a condition in which the individual optical fibers 40a are not in contact with the inner peripheral edge 36a of the spiral tube 36 in a state where the optical fibers 40a may be bent will be described.

  The bending state of the optical fiber 40a shown in FIG. 5 includes a distal end side portion 41 positioned substantially parallel to the inner peripheral surface of the helical tube 36 and a proximal end portion 42 positioned substantially parallel to the inner peripheral surface of the second portion 37b. Between the two, a bent portion 43 is provided. The bent portion 43 is located near the rear end portion of the first portion 37a and the front end portion of the second portion 37b. The bent portion 43b bends from the outside to the inside, and bends from the inside to the outside. The second bent portion 43b is connected, and the optical fiber 40a has the distal end portion 41 positioned outside the proximal end portion 42. Thereby, the front end side portion 41 of the optical fiber 40a is easily brought into contact with the inner peripheral edge 36a of the spiral tube 36. Since the optical fiber 40a is a fragile member compared to the spiral tube 36, the optical fiber 40a is broken when it comes into contact with the inner peripheral edge 36a.

Therefore, in order to prevent the optical fiber 40a from coming into contact with the inner peripheral edge 36a of the helical tube 36 in such a bent state, the rear end 36b of the helical tube 36 and the second portion of the heat shrinkable tube 37 are used. What is necessary is just to narrow the space | interval L of the front end of 37b. Here, when the optical fiber 40a to the minimum radius a bendable and R _M, the bent portion 43 described above is two quarter arcs (first and second bent portions 43a, 43 b) so shape connecting the long in the axial direction It is is at least 2R _M. As described above, the bent portion 43 is bent in the vicinity of the rear end portion of the first portion 37a and the front end portion of the second portion 37b. Therefore, as shown in FIG. 5A, the rear end 36 b of the spiral tube 36 only needs to be positioned behind the front end of the bent portion 43. From the above, it conditions the inner circumferential edge 36a of the helical tube 36 does not contact the optical fiber 40a is a distance L ≦ 2R _M.

In order to the inner peripheral edge 36a of the spiral tube 36 as described above satisfies the distance L ≦ 2R _M is a condition that does not contact the optical fiber 40a, the characteristic of the optical fiber 40a (minimum possible bend radius), and the heat shrinkable tube 37 From the above characteristics (shrinkage rate before and after heating), the thickness of the heat-shrinkable tube, the heating conditions (temperature, time) in the heat-shrinking process, and the like may be appropriately determined. Alternatively, when performing the heat shrinking process, a jig for sandwiching the heat shrinkable tube 37 located behind the spiral tube 36 is used, and the heat shrinkable tube 37 is pressed toward the rear end of the spiral tube 36 by this jig. By doing so, the interval L may be narrowed.

If the above-described condition (L ≦ 2R _M ) is not satisfied, the spiral tube 36 has a rear end 36b located in front of the front end of the bent portion 43 as shown in FIG. There is a possibility that the inner peripheral edge 36a of the 36 will contact the tip end portion 41 of the optical fiber 40a and break.

FIG. 6 shows a bent state in which the inner peripheral edge 36a of the spiral tube 36 is more likely to come into contact with the optical fiber 40a under the above-described conditions (L ≦ 2R _M ). In the example shown in FIG. 6, the step d between the inner peripheral radius R _S of the spiral tube 36 and the inner peripheral radius R _T of the second portion 37 b of the heat shrinkable tube 37 is small. In this case, the bent portion 45 that connects the distal end side portion 41 and the proximal end portion 42 of the optical fiber 40a bends within the range of the step d of the inner peripheral radius. The positional deviation between the portion 41 and the base end side portion 42) is equal to the step d of the inner radius. Therefore, the bent portion 45 of the optical fiber 40a has a shape in which the first bent portion 45a and the second bent portion 45b having an arc shorter than the quarter arc are connected to each other at the contact points. In order to prevent the optical fiber 40a from coming into contact with the inner peripheral edge 36a of the spiral tube 36 in this bent state, the distance L between the rear end 36b of the spiral tube 36 and the front end of the second portion 37b of the heat shrinkable tube 37 is set. The bent portion 45 may be smaller than the length l in the axial direction.

The length l in the axial direction of the bending portion 45 is determined by the minimum bend radius R _M of the inner radius of the step d and the optical fibers 40a as described above. That is, assuming that the bending angle at which the first bent portion 45a and the second bent portion 45b can be bent in the step d of the inner peripheral radius is θ (θ ≦ 90 °), the step d = 2R _M (1 −cos θ), the length l in the axial direction of the bent portion 45 can be expressed as 2 = 2 R _M sin θ. When these are applied to the trigonometric formula sin ² θ + cos ² θ = 1, (1−d / 2R _M ) ² + (l / 2R _M ) ² = 1, and from this equation, l = √ (d (4R _M − d)). Since the rear end 36b of the spiral tube 36 only needs to be located behind the front end of the bent portion 45 (that is, the interval L ≦ the length l in the axial direction of the bent portion 45), the inner peripheral edge of the spiral tube 36 The condition in which 36a does not contact the optical fiber 40a is L ≦ √ (d (4R _M −d)).

Further, as a condition that the inner peripheral edge 36a of the spiral tube 36 and the optical fiber 40a are not in contact with each other, the kink resistance of the heat shrinkable tube 37 can be increased. The kink resistance indicates a characteristic in which kinks (a state in which the heat-shrinkable tube 37 is bent and not restored) are not generated even when the heat-shrinkable tube 37 is bent to a predetermined bending radius. In the present invention, as shown in FIG. 7A, when the curved portion 12 and the flexible portion 13 are curved so as to have a minimum radius in the vicinity of the boundary between the first portion 37a and the second portion 37b, the heat-shrinkable tube is used. 37 has a kink resistance that does not generate kink. Here, when the bending radius at which the heat-shrinkable tube 37 bends when the bending portion 12 and the flexible portion 13 are bent to have a minimum radius is _RC , the heat-shrinkable tube 37 has a bending radius _RC or more. In the case of bending, it is necessary to have kink resistance that does not generate kink.

If the heat shrinkable tube 37 is kinked at the bending radius _RC or more and cannot be restored to its original state, as shown in FIG. The kink generating portion 37c on the side closer to the side presses the optical fiber bundle 40. In particular, when a kink is generated at a position close to the helical tube 36 in the second portion 37b of the heat shrinkable tube 37, the kink generating portion 37c presses the optical fiber bundle 40 to the opposite side (the direction from the center of bending toward the outside). Therefore, the optical fiber bundle 40 may be pressed against the inner peripheral edge 36a of the spiral tube 36 and broken. Therefore, in order to prevent this, it is necessary to have the kink resistance described above. In order to have such kink resistance, the thickness of the heat-shrinkable tube, heating conditions, and the like may be appropriately determined from the characteristics of the heat-shrinkable tube and the bending radius _RC .

  As described above, when observing the inside of a patient's body cavity with the configured endoscope 2, the operator connects the endoscope 2, the processor device, and the light source device, and inserts the insertion portion 3 into the body cavity. Then, by appropriately manipulating the angle knobs 21 and 22 to perform a procedure such as bending the bending portion 12 and directing the distal end portion 11 in a desired direction, while illuminating the body cavity with illumination light from the light source device The endoscopic image in the body cavity by the solid-state imaging device is observed on the monitor.

When the insertion portion 3 is inserted into the body cavity or when the bending portion 12 is bent, built-in objects such as the light guide 34, the forceps channel 38, and the signal line come into contact with each other and are pressed against each other. In the bending portion 12, the compression force from a built-in object other than the light guide 34 is protected by the spiral tube 36, and therefore does not reach the optical fiber bundle 40 inside. On the other hand, by repeating the bending of the bending portion 12, the optical fiber bundle 40 tries to move inside the spiral tube 36 and the heat shrinkable tube 37. As described above, the inner diameter of the second portion 37b of the heat shrinkable tube 37 is increased. D _T is because it is smaller than the inner diameter D _S of the spiral tube 36, to suppress the movement of the optical fiber bundle 40 in the helical tube 36, it is possible to prevent breakage of the optical fiber bundle 40. Further, the individual optical fibers 40a constituting the optical fiber bundle 40 tend to bend in various states, but satisfy the above conditions (L ≦ 2R _M , L ≦ √ (d (4R _M −d)). The space L between the rear end 36b of the helical tube 36 and the front end of the second portion 37b of the heat shrinkable tube 37 is narrowed, and the heat shrinkable tube 37 has kink resistance at a bending radius _RC or more. Therefore, the contact between the inner peripheral edge 36a of the spiral tube 36 and the optical fiber 40a can be prevented, and the optical fiber 40a can be prevented from being broken.

  In the above embodiment, the spiral tube 36 is used as a metal protective tube that covers the optical fiber bundle 40. However, the present invention is not limited to this, and instead of the spiral tube 36 having the above configuration, for example, stainless steel is used. A net-like tube braided with fine metal wires such as tungsten may be used as a metal protective tube.

  Moreover, in the said embodiment, although nothing is interposed between the optical fiber bundle 40 and the spiral tube 36, the structure which covers the outer periphery of the optical fiber bundle 40 with the spiral tube 36 is shown, but this invention is not limited to this. Instead, the outer peripheral surface of the optical fiber bundle 40 may be covered with a flexible tube such as a silicon tube, and the spiral tube 36 may be arranged on the outer periphery of the optical fiber bundle 40 via the flexible tube. .

  In the above embodiment, an optical fiber unit including an optical fiber bundle in which a plurality of optical fibers are bundled is described as an example. However, the optical fiber unit is applied to an optical fiber unit made of a single optical fiber instead of the optical fiber bundle. May be. Alternatively, in the above embodiment, a quartz optical fiber is used as the optical fiber, but the present invention is not limited to this, and other optical fibers such as a plastic optical fiber may be used.

  In the above embodiment, an electronic endoscope for observing an image obtained by imaging a body cavity using a solid-state image sensor has been described as an example. However, the present invention is not limited to this, and an optical image guide is used. The present invention can also be applied to an endoscope that observes the inside of a body cavity. In this case, the optical fiber unit of the present invention is applied to the optical image guide, and the optical fiber bundle or the optical fiber constituting the optical image guide is covered with the metal protective tube and the heat shrinkable tube having the same configuration as the above embodiment. Is done.

DESCRIPTION OF SYMBOLS 2 Endoscope 3 Insertion part 5 Operation part 11 Tip part 12 Bending part 13 Soft part 34 Light guide (optical fiber unit)
36 spiral tube 36a inner peripheral edge 36b rear end 37 heat shrinkable tube 37a first part 37b second part 40 optical fiber bundle 40a optical fiber d step L interval R _C bending radius _RM minimum radius

Claims (8)

An optical fiber bundle or an optical fiber in which a bending portion and a flexible flexible portion that are bent to change the direction of the distal end portion are inserted into an insertion portion of an endoscope that is sequentially arranged from the distal end side, and optical fibers are bundled. Fiber,
A metal protective tube disposed on an outer periphery of the optical fiber bundle or the optical fiber in the curved portion;
A heat shrinkable tube having a first portion covering the outer periphery of the metal protective tube and a second portion extending backward from the rear end of the metal protective tube and covering the optical fiber bundle or the optical fiber. Has
The optical fiber unit, wherein the heat shrinkable tube has an inner diameter of the second portion smaller than an inner diameter of the metal protective tube at least near the boundary between the first portion and the second portion.   The optical fiber unit according to claim 1, wherein the metal protective tube is a spiral tube formed by winding a strip.   2. The optical fiber unit according to claim 1, wherein the metal protective tube is a mesh tube formed by braiding fine wires. The minimum optical fibers bendable radius and R _M, when the rear end of the metal protective tube, the distance between the front end of the second portion of the heat shrinkable tube is L, it is L ≦ 2R _M The optical fiber unit according to any one of claims 1 to 3. When the step between the inner peripheral radius of the metal protective tube and the inner peripheral radius of the heat-shrinkable tube in the second portion is d, the condition of L ≦ √ (d (4R _M −d)) is satisfied. The optical fiber unit according to claim 4. When the bending radius at which the heat-shrinkable tube is bent when the bending portion and the flexible portion are bent to have a minimum radius in the vicinity of the boundary between the first portion and the second portion is R _C , The optical fiber unit according to any one of claims 1 to 5, wherein the tube has kink resistance when bent so that a bending radius is equal to or greater than _RC .   The optical fiber unit according to any one of claims 1 to 6, wherein the heat shrinkable tube is made of polyolefin or PTFE.   The said insertion part, the operation means for bending the said bending part, the main body operation part provided in the base end side of the said insertion part, and the said operation means was integrated, The any one of Claim 1 thru | or 7 An endoscope comprising the optical fiber unit.

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