JPH04319641A - Eccentricity of coating measuring method - Google Patents

Abstract

PURPOSE:To accurately measure the eccentricity of the coating of a coated linear body. CONSTITUTION:The refraction of a laser beam 44 is suppressed at the time of making the beam 44 incident to a resin section 10b coated with a coated optical fiber 10 by irradiating the side face of a coated optical fiber 10 with the beam 44 through a liquid 49 having a refractive index which is close to that of the section 10b. Therefore, even when the thickness of the section 10b is thin, the eccentricity of coating of the section 10b can be discriminated by detecting a forward scattered light pattern.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for measuring uneven thickness (degree of uneven thickness, direction of uneven thickness) of a coating applied to a linear body.

0002

[Prior Art] Because it is extremely difficult to use optical fiber as it is as an optical transmission medium due to material problems, conventionally, optical fibers are coated with resin immediately after being drawn to produce coated optical fibers. We aim to maintain the initial strength immediately after use, and to ensure that it can withstand long-term use.

That is, as shown in FIG. 7, an optical fiber 3 formed by drawing the tip of an optical fiber preform 1 while heating and melting it in a heating furnace 2 is generally formed by a first pressure die 4A, By being sequentially inserted into the first curing furnace 5A, the second pressure die 4B, and the second curing furnace 5B, it becomes a coated optical fiber 6 whose outer surface is coated with two layers of resin. It is adapted to be wound up by a winding machine 8 via a stun 7. Here, the resin coating material used for the coated optical fiber 6 is, for example, a thermosetting resin such as silicone resin, urethane resin, or epoxy resin, or an ultraviolet curing resin such as epoxy acrylate, urethane acrylate, or polyester acrylate. , and other polymeric materials such as radiation-curable resins.

By the way, in such a coated optical fiber 6, in order to improve its transmission characteristics and mechanical characteristics, it is important that the resin coating applied around the optical fiber 1 is concentric. . On the other hand, when the linear speed is increased to improve the productivity of optical fibers, the temperature of the optical fiber 1 rises and the flow of resin in the pressure dies 4A and 4B becomes uneven, resulting in uneven thickness of the resin coating. There is a problem in that it is easy to occur. In addition, uneven thickness occurs when dust gets mixed into the resin. Therefore, in the optical fiber drawing line,
It is necessary to measure the thickness deviation of the coated optical fiber 6 in-line, and perform control such as reducing the drawing speed or stopping the drawing depending on the occurrence of the thickness deviation.

[0005] Here, an example of the conventional thickness unevenness measurement method is shown in FIG.
This will be explained with reference to. As shown in the figure, conventionally, thickness unevenness is measured by irradiating the side surface of a coated optical fiber 10 to be drawn with a laser beam 12 from a laser light source 11 and detecting the forward scattered light pattern 13. (Refer to Japanese Patent Application Laid-Open No. 60-238737). The principle of such a method is shown in FIG. As shown in the figure, for simplicity, the coated optical fiber 10 has a glass portion 10a and a resin portion 1.
0b, the difference in refractive index between the two (usually,
Refractive index ng of glass portion 10a = 1.46, resin portion 10
(refractive index nr of b is approximately 1.48 to 1.51), the forward scattered light pattern 13 includes a central portion of the light beam 1 that has passed through the resin portion 10b-glass portion 10a-resin portion 10b.
3a and the peripheral light beam 13 that has passed only through the resin portion 10b.
b exists. Therefore, the forward scattered light pattern 13
Unbalanced thickness can be detected based on the symmetry of the left and right sides and the ratio of the left and right received light powers.

[0006]

However, in the method described above, on the left and right sides of the forward scattered light pattern 13, the light that has passed through both the resin portion 10b and the glass portion 10a and the light that has passed only the resin portion 10b are separated. For example, if the coating diameter is small and the thickness of the resin part 10b is small as shown in FIG. 10 (FIG. 8(A)), or if the thickness deviation is too large, as shown in FIG. (Figure 8 (
In B)), uneven thickness cannot be detected well. That is, in the case of FIG. 8(A), since the thickness of the resin part 10b is too small, there is no light that passes only through the resin part 10b, and all of the light passes through both the resin part 10b and the glass part 10a. Because of this, uneven thickness cannot be detected. In addition, in the case of FIG. 8(B), since the resin part 10b is thinner at the lower side in the figure, there is no light that passes only through the resin part 10b at the lower side in the figure, so uneven thickness occurs. Although it can be determined that there is a difference in thickness, it is not possible to detect the degree of unevenness.

[0007] Therefore, in the field of optical fiber production, in order to manufacture high-performance optical fibers with high productivity, there is a desire for a technology that can accurately measure the uneven thickness of coated optical fibers in-line. Moreover, such technology is applicable to various fields.

[0008]

[Means for Solving the Problems] A first method for measuring thickness unevenness according to the present invention which achieves the above-mentioned object is to apply a coating consisting of at least one layer to the surface of a drawn linear body, and then apply a coating to the surface of the drawn linear body. irradiating a laser beam from the side of the linear body through a liquid having a refractive index similar to that of the outermost coating layer, detecting the forward scattered light pattern, and measuring the degree of uneven thickness. It is characterized by

[0009] Furthermore, in the second method for measuring uneven thickness according to the present invention, after drawing an optical fiber preform and providing a coating layer on the surface of the drawn linear body, the linear body is drawn in a drawing pass line. A laser beam is irradiated from the side of the linear body through a liquid having a refractive index similar to that of a coating layer coated on the body, and the scattering pattern is measured to measure the degree of uneven thickness. do.

Furthermore, in the third method for measuring uneven thickness according to the present invention, an optical fiber base material is drawn, an nth coating layer is provided on the surface of the drawn linear body, and then an n+1th coating layer is formed on the surface of the drawn linear body. Inside the die for coating the eyes, a laser beam is irradiated from the side of the linear body through the coating resin liquid of the n+1 layer, and the scattering pattern is measured to measure the degree of uneven thickness. Features.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below with reference to the drawings.

FIG. 1 conceptually shows an example of a thickness unevenness measuring device for carrying out the method of the present invention. FIG. 3 conceptually shows an example in which a thickness unevenness measuring device is installed in an optical fiber manufacturing line.

As shown in these drawings, a coated optical fiber 10, which is an example of a linear object to be inspected, is composed of a glass portion 10a and a resin portion 10b as a coating layer, and is manufactured as shown in FIG. After the line is drawn,
A covering layer is provided.

In the production line shown in FIG. 3, a thickness unevenness measuring device is incorporated in the second pressure die 4B that applies the second layer of resin. That is, as shown in FIG. 3, the optical fiber 3 whose tip end of the optical fiber preform 1 is drawn by the heating path 2 passes through the first pressure die 4A and the first curing furnace 5A, and then is heated to the first hardening furnace 5A. A resin portion 10b is formed on the surface of the glass portion 10a. Next, in order to coat the resin part of the second layer, it will be guided to the second pressure die 4B and the second curing furnace 5B, but here the fiber introduction side of the second pressure die 4B It is determined whether there is an uneven thickness in the coating of the first resin portion 10b.

This thickness unevenness measuring device will be explained with reference to FIG. As shown in FIG. 1, the thickness unevenness measuring device includes a die body 40 of the second pressurizing die 4B, which is integrated with a measurement resin reservoir 42 on the fiber inlet side that communicates with a coating resin reservoir 41. An entrance window 45 through which a laser beam 44 from a laser light source 43 enters is provided on one side of the measurement resin reservoir 42.
An exit window 47 is provided on the side surface facing the coated optical fiber 10, through which the forward scattered light 46 of the laser beam 44 irradiated onto the coated optical fiber 10 exits. The forward scattered light 46 from the exit window 47 is received by the light receiver 48.

Therefore, a liquid 49 whose refractive index is similar to that of the resin portion 10b (ie, the second layer resin) is stored on the outer periphery of the coated optical fiber 10, and the liquid 49 is The laser beam 44 from the laser light source 43 is irradiated from the side surface of the coated optical fiber 10, which is a linear body, and the forward scattered light 46 is detected by the receiver 48, thereby obtaining a forward scattered light pattern and detecting the state of uneven thickness. can be confirmed.

By irradiating the laser beam from the side surface of the linear body through the liquid having a refractive index close to that of the coating layer of the linear body, the laser beam reaches the coating layer more easily than in the past. Inward refraction when incident is suppressed,
The amount of information of the forward scattered light pattern increases. As a result, when the coating layer of the linear object is extremely thin, the disadvantage that all the beams pass through the glass part as described in the prior art and uneven thickness cannot be detected is solved, and the forward scattered light pattern in the resin part is eliminated. can be detected.

Furthermore, if the liquid whose refractive index is close to that of the coating layer is larger than the refractive index of the coating layer, the forward scattered light pattern will be wider, pattern analysis will be easier, and uneven thickness will be easily corrected. It becomes possible to detect.

Furthermore, since the state of uneven thickness is measured in the die for the second layer onwards, the passing position of the linear body inside the die is analyzed by the forward scattered light pattern, and the second layer coating is measured. The situation can be predicted in advance.

FIG. 2 shows an example of measurement of the scattered light pattern, and it can be seen that if the peak or shape is symmetrical, the line is in a normal drawing state with no uneven thickness.

[0021] Furthermore, the direction in which the laser beam is irradiated is set in at least two directions (X direction, Y direction) within the same plane with respect to the linear body.
By irradiating from the above directions, it is possible to measure accurately in all eccentric directions.

FIG. 4 shows a state in which the thickness unevenness measuring device is installed in the pass line of wire drawing, and shows the linear body 6A coated with the first layer after passing through the first hardening furnace 5A. , a laser beam 44 from a laser light source 43 is irradiated through a liquid 49 stored in a liquid coating means 50 having a refractive index similar to that of the coating layer, and a forward scattered light pattern is detected by a light receiver 48. I'm trying to analyze it. Liquid application means 5
After passing through the optical fiber 10 and measuring the uneven thickness, the liquid 49 applied to the surface of the optical fiber 10 is wiped off by a liquid removing means 51, and then guided to the second pressurizing die 4B.

[0023]

EXAMPLES The present invention will be explained below based on examples.

Thickness unevenness was determined using the thickness unevenness measuring device shown in FIGS. 1 and 3. The thickness unevenness of the coated optical fiber with the two-layer coating shown below was determined. a. Measurement target Glass part nD 25=1.4
583 φ=125 μm First layer covering part nD 25=1.480* φ=180
μm Second layer covering part nD 25=1.4
90*φ=250μm
(*Measured value before curing)
b. Measurement position: Inside the second layer coating resin pressure die c. Measurement conditions Measurement area 2mmφ
Fiber movement max1000m/min
Measurement frequency: 1 time/min or more d. Measurement method - Laser beam scanning fiber transmitted light forward scattering pattern detection method (shown in Figure 2) - Simultaneous measurement of two XY axes e. Light source Laser light f. Light receiving part PSD The results measured under the above conditions are shown in FIG. This makes it possible to determine in-line the degree of uneven thickness during wire drawing.

[0025]

[Effects of the Invention] As explained above, according to the present invention,
By irradiating a linear body with a laser beam through a liquid having a refractive index similar to the refractive index of the coating layer of the coated linear body, changes in the forward scattered light pattern due to uneven thickness can be easily detected in-line. Can be done.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an example of an apparatus for implementing the method of the present invention.

FIG. 2 is a graph showing a forward scattered light pattern.

FIG. 3 is a conceptual diagram showing an example of an optical fiber manufacturing line equipped with a thickness unevenness measuring device.

FIG. 4 is a conceptual diagram showing another example of an optical fiber manufacturing line equipped with a thickness unevenness measuring device.

FIG. 5 is a conceptual diagram showing an example of an optical fiber manufacturing line.

FIG. 6 is a principle diagram for explaining thickness unevenness measurement according to the prior art.

FIG. 7 is an explanatory diagram for explaining the principle of thickness unevenness measurement according to the prior art.

FIG. 8 is an explanatory diagram showing a problem with thickness unevenness measurement according to the prior art.

[Explanation of symbols]

1 Optical fiber base material 2 Heating furnace 3 Optical fiber 4A First pressure die 4B Second pressure die 5A First hardening furnace 5B Second hardening furnace 6 Coated optical fiber 10 Coated optical fiber 10a Glass part 10b Resin part 40 Die body 41 Coating resin reservoir 42 Resin reservoir for measurement 43 Laser light source 44 Laser beam 45 Entrance window 46 Forward scattered light 47 Exit window 48 Photo receiver 49 Liquid 50 Liquid application means 51 Liquid removal means

Claims (4)

[Claims] Claim 1: After coating the surface of a drawn linear body with at least one layer, the line is coated with a liquid having a refractive index close to that of the outermost coating layer of the linear body. A method for measuring uneven thickness, characterized by irradiating a laser beam from the side of a shaped body, detecting the forward scattered light pattern, and measuring the degree of uneven thickness. 2. After drawing the optical fiber base material and providing a coating layer on the surface of the drawn linear body, in the drawing pass line, a refractive index that approximates the refractive index of the coating layer coated on the linear body is obtained. 1. A method for measuring thickness unevenness, characterized in that a laser beam is irradiated from the side surface of the linear body through a liquid having a certain ratio, and a scattering pattern is measured to measure the degree of thickness unevenness. 3. After drawing the optical fiber preform and providing the nth coating layer on the surface of the drawn linear body, the nth
Inside the die to apply the +1st layer coating, a laser beam is irradiated from the side of the linear body through the n+1st layer coating resin liquid, and the scattering pattern is measured to determine the degree of uneven thickness. A method for measuring uneven thickness. 4. In the thickness unevenness measuring method according to claims 1 to 3, the method of irradiating the laser beam is to irradiate the linear body from two or more directions within the same plane, and to detect each forward scattered light pattern. A method for measuring uneven thickness, which is characterized by detecting and measuring the degree of uneven thickness.