JPS592003A - Protective layer for fiber type optical waveguide - Google Patents

Abstract

PURPOSE:To form protective layers which are vulnerable to bending on the operator's side by changing the length of stepped cylinders, the socket and spigot fitting length of the stepped cylinders, and the difference between the inside diameter in the large diameter cylindrical parts of the stepped cylinders and the outside diameter in the small diameter cylindrical parts thereof thereby making the min. radius of bending of the protective layers for an optical waveguide smaller. CONSTITUTION:The length L of stepped cylinders 8, the outside diameter D in large diameter cylindrical parts 11, the outside diameter (d) in small diameter cylindrical parts 12 and the socket and spigot fitting length l of the cylinders 8 among the protective layers for an optical fiber as well as the min. redius Rmin of bending of a fiber type optical waveguide for a laser knife and a laser working device have the relation shown by the equation. The protective layers vulnerable to bending on the operator's side of said optical waveguide are obtained by satisfying at least one among the three conditions, i.e., the lengths L, l are made smaller and the difference (D-d) in the diameter is made larger, to make the radius Rmin smaller from the incident end side of light toward the exit end side. Otherwise the outermost circumferential coverings are made gradually thinner toward the exit side. The protective layers which are vulnerable to bending and are easy to operate are thus formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a protective layer for a fiber-type optical waveguide that is easy to bend on the proximal side.

In laser scalpels and laser processing equipment, C02 laser,
・YAG laser, Ar laser, ruby laser, etc. are used depending on the application. Waveguides that guide light include optical fiber waveguides and mirror waveguides.

Those using optical fibers are easy to handle and convenient.

Since the C02 laser has a long wavelength, mirror waveguides are the mainstream, but fiber waveguides have also come into practical use. YAG lasers and the like can be transmitted with low loss through fiber waveguides.

FIG. 1 is a diagram showing the overall configuration of a laser device.

The laser oscillator 1 includes a CO□ laser, a YAG laser, and an Ar laser.
laser, ruby laser, etc. The power supply control section 2 drives the laser oscillator 1. The input optical system 3 focuses the laser beam and makes it enter the fiber optical waveguide 4 .

The laser light propagates through the fiber optical waveguide 4, is emitted from the hand beam 5, and is irradiated onto a target object (not shown).

Laser oscillator 1 of fiber optical waveguide 4, input optical system 3
The side closer to the handpiece 5 is called the input end side A, and the side closer to the handpiece 5 is called the output side B.

The fiber optical waveguide 4 must be freely bendable.

FIG. 2 is a partial cross-sectional view of a conventional fiber optical waveguide. This will explain the bendable configuration of the fiber optical waveguide.

An optical fiber 6 is housed in the center of the waveguide 4, and a Teflon tube 7 surrounds the optical fiber 6. On the outside of the Teflon tube 7, a large number of stepped cylinders 8 are continuous in the axial direction, overlapping each other. An O-ring 9 is fitted into the joint of the stepped cylinder 8.

Further outside the stepped cylinder 8.0 ring 9 is covered with a flexible covering 10.

The only rigid thing is the stepped cylinder 8.

In the conventional optical waveguide 4, such a structure was uniformly continuous from the input end side A to the output end side B. The large diameter cylindrical part and the small diameter cylindrical part of the stepped cylinder 8 have the same inner and outer diameters and lengths, and are used from the beginning to the end.

For this reason, conventional optical waveguides have the following drawbacks.

At the output end side B where the hand beef 5 is provided, the optical waveguide 4
is difficult to bend. Poor operability.

On the other hand, the incident end side A connected to the laser oscillator 1 has a cantilever structure and often remains bent. This is because the bending moment due to the weight of the waveguide 4 is often maximum at the input end side A.

The present inventor conjectures that the reason why the conventional fiber optical waveguide 4 uniformly employs the stepped cylinder 8 of the same size from the input end side A to the output end side B is probably due to the following reason. .

The central optical fiber 6 is of uniform construction and has a uniform diameter. Therefore, the allowable bending radius Rf of the optical fiber is uniform over the entire length of the optical waveguide 4.

The minimum bending radius Rmin of the optical fiber is determined by the dimensional difference between the outer cylinder and the inner cylinder of the stepped cylinder 8, the lengths of the overlapping parts, and the like.

Naturally, over the entire length of the optical waveguide, Rmin　　　　　　R(- Must.

Rf is constant over the entire length. Therefore, it seems better to set Rmin to a constant value over the entire length.

Making Rmin constant means that stepped cylinders 8 of the same size are arranged at the same intervals.

For this reason, conventionally a uniform waveguide has been adopted. However, there is a fallacy in this kind of thinking.

Even if the allowable bending radius Rr of the optical fiber is the same over the entire length of the optical waveguide, the bending moment M applied to the optical waveguide is not uniform as well.

In the free state, the fiber guide waveguide 4 hangs down and rests.

Let G be the vertical line passing through the center of hand beef 5.

Let X be the distance from the vertical line G to a point P on the optical waveguide.

The bending moment acting on the O fiber optical waveguide 4 is (i) where the distance between the vertical line G and the input end H of the waveguide is Xm.
When x=o, M=Q (ii)x=XmteM takes the maximum value MOrrax.

Maximum bending moment) Mmax is applied at the incident end (Xm)H. The optical waveguide 4 has a bending radius mi with respect to rrax. Suppose we take .

Naturally, for Rmin in equation (1), R”　　　＞　　　　Rmin　　　　(2) ln It is necessary that

Since the maximum bending moment l-Mmax is applied at the input end H, the waveguide bends most strongly at the input end. The bending radius of the waveguide increases as it moves away from the input end, and the bending radius becomes infinite near the handpiece (X=0).

Bending radius RITLi at the input end. satisfies the inequality (2). Since the optical waveguide may be strongly pulled downward, the minimum bending radius in such a group of states must be larger than Rmin.

It is desirable that the hand beef 5 move freely.

The movement of the hand beef in the axial direction and the movement in the direction perpendicular to the axis is accompanied by a change in the bending state at a portion away from the output end side B.

The change in the bending state near the incident end side A gives the amount of movement of the hand piece as a product of the distance to the hand piece.

Therefore, the movement of the hand beef in the axial direction and vertical direction is
It's relatively easy.

This suddenly becomes more difficult when attempting to cause the handpiece to change direction rather than move. When attempting to bend with a small radius of curvature, the operator must directly apply a bending moment to the hand beef 5 itself by hand.

The ratio of the curvature (reciprocal of the bending radius) to the bending moment is in this case the same over the entire length of the optical waveguide.

Therefore, when holding the hand beef 5 and trying to change the direction, the operator must apply a strong bending moment that is constantly applied to the incident end side A.

A desirable fiber optic waveguide does not have uniform bending rigidity; it is hard to bend at the input end side A, and is hard to bend at the output end side B.
It is easy to bend.

It is necessary to distinguish between having a large bending rigidity and having a large minimum bending radius Rmin.

The bending rigidity strongly depends on the wall thickness and diameter of the coating 10. 0
It also depends on the elasticity of the ring 9.

The minimum bending radius Rmin is determined by the shape and dimensions of the stepped cylinder 8.

The condition that it is difficult to bend at the input end A and easy to bend at the output end B relates to bending rigidity. It appears to be unrelated to the minimum bending radius Rmin.

First, it will be considered how the minimum bending radius Rmin is determined depending on the shape and dimensions of the stepped cylinder 8.

FIG. 3 is a cross-sectional view of the stepped cylinder 8.

The stepped cylinder 8 has a shape in which a large diameter cylinder part 11 and a small diameter cylinder part 12 are connected by an intermediate step part 13.

Into the large diameter cylindrical part 11, the small diameter cylindrical part 12 of the adjacent stepped cylinder
Insert. Let L be the inner diameter D of the large diameter cylindrical portion 11, the outer diameter d of the small diameter cylindrical portion 12, and the length of the stepped cylinder.

D) Since d, the combination of stepped cylinders 8 can be bent freely.

There is one more important factor.

This refers to how long the adjacent small-diameter cylindrical portion 12 is inserted into the large-diameter cylindrical portion 11. The overlapping portion of the two stepped cylinders, that is, the insertion length is assumed to be 4.

Figure 4 shows that the combination of stepped cylinders has a minimum bending radius Rmi.
FIG. 3 is a partially sectional plan view in a state bent at n.

From the center of curvature O, one repetition length (L
-n ) is assumed to be the angle θ.

The small diameter cylindrical portion 12 of the stepped cylinder 8 contacts the inner surface of the large diameter cylindrical portion 11 of the adjacent cylinder 8 from the front and back.

Let F be the contact point at the end of the large-diameter dark portion 11'. Small diameter cylinder part 1
Let the end point of 2 be E, and let C be the foot of the perpendicular line drawn from E to the surface of the large-diameter cylindrical portion 11. △Think about CFE.

At the 00th turn around the center of curvature, the stepped cylinder 8 is in a rotationally symmetrical position. The pitch angle is 0. Therefore, the angle between the cylinders 8 is also θ. Tsumashi, /EFC=θ (
3).

The side CF is approximately equal to the insertion length l.

The side EC is equal to I d (D-d).

These are all approximations assuming that θ is considerably smaller than 1.

Then D-d θ = − (4) becomes.

On the other hand, a cylinder 8 with a step chair 1 is placed on a circle with a minimum radius of curvature) jmin from the center of curvature O, and the length of one period of the cylinder is (
Since it is L-1, it is auspicious.

(4), (5) Yoshi, get.

The insertion length is 4 mm, less than L/2. This is because one stepped cylinder and two stepped cylinders apart do not overlap.

(Consider in the range 1<L/2.

(1) The smaller L is, the smaller the length L of the stepped cylinder,
Rmin is small.

(2) The smaller the insertion length l, the smaller the Rmi
n is small.

(3) The larger the diameter difference (D - d), the Rmin
is small.

There are two or three possible cases.

As already mentioned, the bending stiffness and the minimum bending radius Rmin
must be considered separately.

In order to easily change the direction of the handpiece 5 at hand, it is required that the bending rigidity at hand is small. This does not require that the minimum bending radius Rmin be small. Rmin is determined only by the shape and dimensions of the stepped cylinder 8.

However, the bending stiffness is related to the minimum bending radius Rmin through the O-ring 9.

What determines the bending rigidity is not only the wall thickness and diameter of the coating 10. It also depends on the elasticity of the O-ring 9 fitted between the adjacent large-diameter cylindrical portions 11 of the stepped cylinder 8.

One O-ring 9 is shown and explained in FIG. 4.

When the waveguide 4 curves, the inner O-ring 9a is compressed.

Bending moment 1. Since M is proportional to the amount of compression, an elastic force of the O-ring 9a corresponding to the bending moment M is generated.

Although the minimum bending radius Rmin is determined by the shape and dimensions of the stepped cylinder 8, the O-ring 9 functions as an important factor in determining the bending rigidity until the bending radius R changes from infinity to Rmin.

The force required to compress the O ring by unit length is O
This will be tentatively called the elastic modulus of the ring.

By appropriately changing the material and thickness of the O-ring, it is possible to manufacture an O-ring with an arbitrary elastic modulus.

If the elastic coefficient of the 0-ring can be arbitrarily given, conversely, what kind of distribution of the 0-ring should be given to the fiber optical waveguide? You can consider that.

FIG. 5 is a graph showing the bending moment M from the output side B to the input side A of the fiber guide waveguide 4.

In the free state, M is O at 8 points and increases monotonically until it reaches point A. It is shown by graph g0.

When you hold handpiece 5 and bend it downward, moment) M
is shown as a graph that moves upward as a whole.

If you hold the handpiece 5 and bend it upward, the moment) M will move downward as a whole. Shown by Graphsha.

The movement of the handpiece is not limited to movement within this vertical plane. However, the movement in the vertical plane causes a moment) M
There is no doubt that it is the largest. When bending in a direction away from the vertical plane, a large bending moment L is not required.

After all, when a fiber optical waveguide is hanging down due to gravity, it is sufficient to consider the dynamics of the fiber optical waveguide within the vertical plane that includes this.

Then, the moment M applied to the fiber optical waveguide is
Graph g for a free-form j river. It can be thought of as a group of graphs in which ``1'' is appropriately lowered.

Let S be the coordinates of the fiber optical waveguide measured from the output end side B.

The minimum bending radius Rmin (S) for eight points is predetermined.

Moment) M is a monotonically increasing function that increases in proportion to S.

When the moment l-M is increased over the entire length, the bending radius R(S) becomes smaller at each of the eight points.

When the moment M is further increased, the radius R(S) reaches the minimum bending radius for any bend of S. As the moment) M increases, the number of points at which the radius R(S) reaches the minimum bending radius Rmin(S) increases.

In this way, for the value of S, the minimum bending radius Rmin (
The time at which S) is reached generally differs.

However, in order for the handpine to operate most smoothly, the radius R(S) must be set to Rmin for all values of S at the same time.
It is desirable to converge to (S).

Bending stiffness I (is defined as 1M. K is a function of S. Output end side B (S = 0
) is small, and K is large at the incident end side A (S.sub.So).

FIG. 6 is a graph showing how the relationship between the bending radius R and the bending moment 1- is (i+J) at each point S of the optical waveguide.

As is clear from equation (7), this becomes an inversely proportional graph. The seed constant K is large at the input end side A, and smaller than the seed constant at the output end side B.

The left half of Fig. 6 shows the coordinate S, and graph groups g0, g+, g0 of S and moment M. shows.

For example, the coordinates are S=Q, S, and S. This is 0/2
Read the value of M corresponding to S from 0 and draw a straight line parallel to the horizontal axis on the graph. H at the point that cuts the corresponding inversely proportional graph
The value of gives the bending radius corresponding to the moment graph group.

Go, g+, and g+10 are shown on the lines connecting each R.

It is assumed that g++ is the state in which M (the maximum bending moment) is applied.

At this time, if R(S) simultaneously reaches the minimum bending radius Rmin(S) for all S, then Rmin(S)"
The line connecting them must be a straight line. Moreover, it must pass near the origin 0.

If gH(S) is strictly linear with respect to S, then Rm
The line connecting in(S) must be a straight line and must pass through the origin 0. This is called critical gravel.

g□-+(S) is close to stone gravel, but it is not always a straight line. Therefore, the straight line connecting Rmin (S) is ideally on the straight line OQ passing through the origin 0, and generally the straight line OQ
It can be said that it is close to.

Rmin(S) is on the straight line OQ, which means that Rmin(S) is on the straight line OQ.
in(S) is a linear function of S that is minimum when s=o and maximum when 5=50.

In other words, the requirement that "the minimum bending radius Rmin is small at the output end side B and large at the input end side A" is equivalent to the requirement that "the minimum bending radius Rmin is reached at the same time at each point S of the optical waveguide". When meeting these requirements, the bending rigidity is exactly the same as the requirement for ease of operation, which is that the bending rigidity is small at the output end side B and large at the input end side A.

The present invention was made based on this idea.

In order to achieve the purpose of making the fiber guided wavepath of the present invention easy to bend at the output end side B and hard to bend at the input end side A, the following four factors are varied.

(1) Step A: Change the insertion length l of the No. 1 cylinder. 1 is made shorter on the output end side B, and e is made longer on the input end side A. The insertion length can be changed stepwise or continuously.

FIG. 7 is a partially cutaway top view of a fiber optical waveguide showing such an embodiment.

Optical fiber 6 in the middle, Teflon tube 7 surrounding it
, a fiber optic waveguide consisting of a stepped cylinder 8, a cushioning material (for example, an O-ring) 9, and a coating 10, which are assembled in a plurality of stacked cylinders.

Only a portion of the output end side B and the input end side A are illustrated.

The insertion length e is short for B and long for A.

The candy factors D, d, and L are the same.

(2) Change the length of the stepped cylinder 8. L at output end side B
is made shorter, and L is made longer on the incident end side A. The change in L may be gradual or continuous.

FIG. 8 is a partially cutaway front view of a fiber optical waveguide showing such an embodiment.

In this example, not only L is changed, but l is also changed. As seen in equation (6), all that is required is to change e(L-1>).

(3) Inner diameter of the large-diameter cylindrical part and small-diameter cylindrical part d of the stepped cylinder
change the difference between

Output end [Large (D・-d) at 111B, input end side A
Then, reduce (D−d). The change in (Dd) may be gradual or continuous.

FIG. 9 is a partially cutaway front view of a fiber waveguide showing such an embodiment.

The above three examples are for changing Rmin in equation (6).

(4) Change the thickness of the cover [10].

The coating is thinner on the output end side B, and thicker on the input end side A.

FIG. 1O is a partially cutaway front view of a fiber waveguide showing such an embodiment.

This is different from the front lens example in that it is easy to bend the output end side and difficult to bend the input end side.

A plurality of changes in these four factors may be combined.

It is even better if the minimum bending radius Rmin(S) is a monotonically increasing function of S, as in the case of the front lens.

In the examples (1) to (3), the condition is imposed that the elastic modulus of the elastic material 9 is appropriately selected so that the elastic modulus becomes correspondingly small at the position where the minimum radius of curvature Rmin is small. It will be done.

Describe the effects.

(1) The output end side where the handpiece is located is easy to bend and has good operability.

(2) Since the optical waveguide does not curve slightly on the input end side and extends horizontally, the horizontal distance between the laser oscillator and the handpiece can be increased.

Particularly in surgery using a laser scalpel, the bed and the laser scalpel body (laser oscillator, power supply control section) can be separated.

Teflon tube 7, stepped cylinder 8, elastic material 9, coating 1
0 is called the protective layer of the optical fiber 6.

The effects (1) and (2) are both due to the fact that the inspection layer is not uniform and is difficult to bend on the incident end side and easy to bend on the output end side.

The present invention can be used for fiber type optical waveguides of laser scalpels and laser processing equipment.

[Brief explanation of drawings]

Figure 1 is an overall view of the laser device equipped with a fiber optical waveguide. FIG. 2 is a cross-sectional view of the fiber optical waveguide. FIG. 8 is a cross-sectional view of a stepped cylinder. FIG. 4 is a partially cutaway plan view showing a curved state of a set of stepped cylinders inserted into each other. @Figure 5 is a graph showing the change in bending moment (M) from the output side B to the input side A of the fiber optical waveguide. Coordinate S
indicates the length from point B. go is a free state, g0 is a state where the output end 1IllIB is twisted downward, g-
is a shape that lifts the output end side B upward! Show belly. FIG. 6 is a graph illustrating the relationship between the bending radius R and the bending moment M of the fiber optical waveguide, and between the position S on the fiber-optical waveguide and the bending moment M. The bending radius R and the bending moment M are inversely proportional to each other, and the product constant has a maximum value at the input end A (S=80) and a maximum at the output end B (S
=O), it is minimum, and at the middle point SO/2, it takes an intermediate value. OQ
is a critical straight line, which exists under the condition that the bending radius simultaneously converges to the minimum value Rmin(S) at all points S as the fiber leading wavepath is bent. FIG. 7 shows an example of the present invention, in which the insertion length l is changed, the output end side B and the input end side A of the fiber optical waveguide.
FIG. FIG. 8 is a partially cutaway front view of another embodiment in which the length L of the stepped cylinder and the insertion length l are changed to B and A depending on the case. Fig. 9 is related to the third embodiment, where the difference (D-d)k,8,A between the inner diameter of the large-diameter cylindrical part of the stepped cylinder and the outer diameter d of the small-diameter cylindrical part is changed. It is a partially cutaway front view. FIG. 10 is related to the fourth embodiment, and shows the thickness of the coating C, B, A
FIG. 1 ...... Laser oscillator 2 ......
...... Power control section 3 ...... Input optical system 4 ...... Fiber guiding waveguide 5
・・・・・・・・・ Handpiece 6 ・・・・・・・・・
・・・ Optical fiber 1 ・・・・・・ Teflon tube 8 ・・・
...... Stepped cylinder 9 ...... Ballistic material (0 linog) 10 ・
・・・・・・・・・ Covering 11 ・・・・・・
... Large diameter cylindrical part 12 ...... Small diameter cylindrical part 13 ...... Step part A ...
...... Input end side B ...... Output end side D ...... Inner diameter d of large diameter cylinder section ...
・・・・・・Outer diameter L of small diameter cylinder portion ・・・・・・・・・
Length l of stepped cylinder ・・・・・・・・・ Length of insertion between stepped cylinders Fig. 7 Fig. 8 Fig. 9 Fig. 10

Claims (4)

[Claims] (1) A tube surrounding an optical fiber, a large number of stepped cylinders having a large diameter cylinder part and a small diameter cylinder part on the outside of the tube, and adjacent stepped cylinders being connected by being inserted into each other; In the protective layer of a fiber-type optical waveguide consisting of a resilient material fitted between stepped cylinders and a coating covering the stepped cylinder and the resilient material, from the input end side A to the output end side B. A protective layer for a fiber-type optical waveguide, characterized by a small minimum bending radius Rmin or a thin coating. (2) A protective layer for a fiber-type optical waveguide according to claim (1), wherein the minimum bending radius Rmin is changed by changing the insertion length l between the stepped cylinders. (3) Claim No. 1 in which the minimum bending radius Rmin is changed by changing the length L of the stepped cylinder.
A protective layer for a fiber-type optical waveguide as described in Section 2. (4) The inner diameter of the large-diameter cylinder part and the outer diameter d of the small-diameter cylinder part of the stepped cylinder.
A protective layer for a fiber-type optical waveguide according to claim (1), wherein the minimum bending radius Rmin is changed by changing the difference (D-d) between the two.