JPH04319643A - Method and device for measuring eccentricity of coating - Google Patents

Abstract

PURPOSE:To accurately measure the eccentricity of the coating of a coated linear body. CONSTITUTION:A coated optical fiber 100 composed of a glass section 100a and resin section 100b is irradiated from one side face to the other side face with the parallel P-polarized light of a laser beam 113 from a laser light source 111 through a shield plate 112 after the beam 113 is P-polarized through a polarizing plate 114. When the positions of the critical reflected light and non- transmitted light of the forward scattered light of the beam 113 are received and a pattern analysis is performed by means of an image sensor 121, the extent of the eccentricity of the resin section 100b can be accurately measured.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus 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. 9, 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. 1.
This will be explained with reference to 0. As shown in the figure, conventionally, the thickness unevenness is measured by irradiating the side surface of the 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 the sake of simplicity, the coated optical fiber 10 is made up of a glass portion 10a and a resin portion 10b. Part 1
The refractive index nr of 0b is approximately 1.48 to 1.51)
Therefore, the forward scattered light pattern 13 includes a central light beam 13a that has passed through the resin portion 10b-glass portion 10a-resin portion 10b, and a peripheral light beam 1 that has passed only through the resin portion 10b.
3b exists. Therefore, forward scattered light pattern 1
Unbalanced thickness can be detected based on the left and right symmetry of No. 3 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. 11 (FIG. 12(A)), or if the thickness deviation is too large, as shown in FIG. (Figure 1
2(B)), uneven thickness cannot be detected well. In other words, in the case of FIG. 12(A), since the thickness of the resin part 10b is too small, no light passes through the resin part 10b, and all of the light passes through both the resin part 10b and the glass part 10a. Uneven thickness cannot be detected. In addition, in the case of FIG. 12(B), since the resin portion 10b is thinner at the lower side in the figure,
Since there is no light that passes only through the resin portion 10b on the lower side of the figure, it can be determined that an uneven thickness has occurred, but it is not possible to detect the degree of uneven thickness.

[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 uneven thickness according to the present invention which solves the above-mentioned problems is to measure the thickness of a linear body from the side surface of the linear body, the surface of which is coated with at least one layer. A light beam from a light source is irradiated on one half side of the surface perpendicular to the longitudinal direction, and the position of the critical reflected light and non-transmitted light that has not passed through the linear body is detected, while the other half side is irradiated with a light beam from the light source. irradiate the light beam, detect the position of the critical reflected light and the non-transmitted light that did not pass through the linear body,
It is characterized by measuring the degree of uneven thickness.

The structure of the first thickness unevenness measuring device according to the present invention is that it is provided opposite to the side surface of a linear body whose surface is coated with at least one layer, and that is perpendicular to the longitudinal direction of the linear body. a light source unit that irradiates a light beam on one half side of the linear body while irradiating the other half side with a light beam within a plane, a critical reflection light of the light beam from this light source unit on the linear body, and the above-mentioned light beam; A light receiving unit that receives non-transmitted light that has not passed through the linear body and detects the light receiving position, and a processing unit that processes the detected light receiving position of the received light to determine the uneven thickness of the linear body. It is characterized by

A second method for measuring uneven thickness according to the present invention is as follows:
A polarized light beam from a light source is irradiated from the side surface of a linear body whose surface is coated with at least one layer to one half side of the surface perpendicular to the longitudinal direction of the linear body, and only the critical reflected light is detected. It is characterized by measuring the degree of uneven thickness.

The configuration of the second thickness unevenness measuring device according to the invention is as follows:
Light that is provided opposite to the side surface of a linear body whose surface is coated with at least one layer and irradiates a polarized light beam from the side surface of the linear body in a plane orthogonal to the longitudinal direction of the linear body. a beam light source section, a light receiving section that receives the critical reflected light of the polarized light beam on the linear body and detects the light receiving position, and a light receiving section that detects the light receiving position of the detected light and processes it and then outputs it to the linear body. It is characterized by comprising a processing section for obtaining uneven thickness.

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. As shown in the figure, a coated optical fiber 100 is an example of a linear object that is a test object.
consists of a glass part 100a and a resin part 100b, and a beam scanning part 110 and a light receiving part 120 are arranged on the side of the coated optical fiber 100. Here, the beam scanning unit 110 includes a laser light source 111 that is provided facing the side surface of the coated optical fiber 100 and irradiates laser light;
A shielding plate 112 is interposed between the laser light source and the linear body and blocks only one side of the linear body (the irradiation surface on the left side or the irradiation surface on the right side in the drawing), and the shielding plate 112 100
The laser beam 113 can irradiate only one half side of the plane perpendicular to the longitudinal direction. On the other hand, the light receiving unit 120 is disposed facing the side surface of the coated optical fiber 100 and receives and detects forward scattered light and critical reflected light of the coated optical fiber 100 as well as non-transmitted light that has not passed through the optical fiber 100. It is equipped with an image sensor 121 as a light receiver. The control unit 130 functions to estimate the thickness deviation by data processing the reception detection positions of the critical reflected light and non-transmitted light of the coated optical fiber 100 received by the light receiving unit. In the present invention, critical reflected light refers to forward scattered light that is reflected at the interface between the coating layer of a linear body such as an optical fiber and an air layer, and the interface between the coating layer and the glass part. scattered light.

Although the light source used in the present invention is not particularly limited, by using a polarized beam (P wave) that is polarized by a polarizing plate, it becomes easier to penetrate the linear body.
As a result, the intensity of the transmitted light is increased and the critical reflected light becomes clear, which is particularly preferable. In the device of FIG. 1, the light source section 12
A polarizing plate 114 is interposed between 0 and the shielding plate 112, and the light is P-polarized.

[0015] In the present invention, the image sensor refers to a solid-state image sensor, which receives light on an array of MOS transistors or CCD memory and converts the light into a potential signal by electronically scanning the output of each cell. Refers to equipment. Furthermore, in the present invention, a light receiver refers to an element that detects the reception of light and outputs an electrical signal in accordance with the light.

Note that in the light receiving section, the shielding plate 11
At the position corresponding to the part not blocked by 2,
Two image sensors 121 each serving as a light receiver are provided.

Next, the principle of thickness unevenness measurement will be explained with reference to FIGS. 2 and 3.

A laser beam 113 from a laser light source (not shown) in FIG.
The polarized light is directed toward the optical fiber 100. Of this P-polarized light, that which passes very close to the optical fiber is received as it is at P1 of the light receiving section. Further, the light that has entered the resin part 100b is reflected at the critical surface 100c between the resin part and the glass part to become critical reflected light, which is received at the position P2. Furthermore, the light that has entered the glass portion 100a is received at a position P3.

As a result, the received light intensity at each light receiving part becomes as shown in FIG. 3, and since the light P1 passes through the outside of the optical fiber 100, it remains bright at the intensity at the time of irradiation, but after that it becomes dark. Become. This is because the light entering the resin portion 100b is refracted and goes downward in FIG. 3. and P
2, the light is reflected at the critical surface 100c between the glass portion 100a and the resin portion 100b of the optical fiber 100 and becomes bright, so that the light receiving portion 121 detects the light receiving position P2.

On the other hand, as shown in FIG. 4, the other half side is similarly measured to detect the light receiving position and intensity. In this manner, the laser beam 113 irradiates parallel light onto one half side of the coated optical fiber 100 at a time, and the forward scattered light is received by the light receiving section 121, thereby detecting the positions of P1 and P2 at the light receiving section 121. The forward scattered light pattern shown in FIG. 5 is a pattern obtained by combining these detection results. When there is no uneven thickness, the following relationship (1) holds true. (P1 +P'1)=(P2 +P
'2) - (1) Then, when uneven thickness occurs, the value on the right side of equation (1) changes in size in proportion to the degree of uneven thickness. Based on this, eccentricity is detected.

FIG. 6 shows a case where the coated optical fiber 100 is irradiated with P-polarized light by the polarizing plate 114 over all sides and only the critical reflected light is received via the analyzer 122. There is. In other words, the light reflected from the critical surface is P
Since the wave becomes an S wave, by detecting only this S wave through the analyzer 122, a pattern shown in FIG. 7 is obtained, and the relationship of equation (2) below is established. (S1
+S'1)=(S2+S'2)-(2) When uneven thickness occurs, the value on the right side of equation (2) changes in size in proportion to the degree of uneven thickness. Based on this, eccentricity is detected.

FIG. 8 shows a device that detects only this critical reflected light. As shown in the figure, the overall configuration is almost the same as the measuring device shown in FIG. 1, but since only the critical reflected light is received, there is no interference, so the shielding plate 114 is unnecessary.
There is one light receiver, and the image sensor 121 receives light through an analyzer 122. Also, instead of using the analyzer 122, the image sensor 12 may be
1 may be used to receive light.

In this way, only the critical reflected light is detected by the analyzer 12.
By patterning the results of light received through the optical fiber 2, it is possible to determine the uneven thickness of the optical fiber.

[0024] For the sake of simplicity, the above explanation is based on the case where the coating is one layer, but even if the coating is multiple layers, the forward scattered light pattern can be measured and the unevenness in thickness can be determined in the same way.

Furthermore, if the uneven thickness is eccentric only in the direction in which the laser beam advances, the obtained forward scattered light pattern will be in a normal state. Thickness unevenness can be determined by scanning in a plurality of directions, for example, by measuring two axes of X and Y in the same manner as described above.

Furthermore, during measurement, by irradiating the laser beam through a liquid having a refractive index similar to that of the coating layer of the coated optical fiber, the light beam can be directed inward in the coating layer. Even if the coating is thin, it is possible to prevent the light from penetrating into the glass part, and it is possible to receive the scattered light that passes only through the resin part, making it easier to analyze the forward scattered light pattern.

[0027]

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

Thickness unevenness was determined using the thickness unevenness measuring device shown in FIG. The thickness unevenness of the single-layer coated optical fiber 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
(*Measured value before curing) b. Measurement position: Downstream side of the first layer coating resin curing furnace c. Measurement conditions Measurement area 2mmφ
Fiber movement max1000m/min
Measurement frequency: once/min or more d. Measurement method - Laser beam irradiation and critical reflected light pattern detection method of the fiber (method shown in Figures 2 and 4) - Simultaneous measurement of two XY axes e. Light source Laser light f. Light-receiving section image sensor The results of measurements and synthesis under the above conditions are shown in FIG. This makes it possible to determine in-line the degree of uneven thickness during wire drawing.

[0029]

[Effects of the Invention] As explained above, according to the present invention,
By scanning the coated linear body with a laser beam, changes in the forward scattered light pattern due to uneven thickness can be detected in-line.

[Brief explanation of drawings]

FIG. 1 is a conceptual diagram showing an example of a thickness unevenness device of the present invention.

FIG. 2 is a principle diagram for explaining thickness unevenness measurement according to the present invention.

FIG. 3 is a graph showing a forward scattered light pattern.

FIG. 4 is a principle diagram for explaining thickness unevenness measurement according to the present invention.

FIG. 5 is a graph showing a forward scattered light pattern.

FIG. 6 is a principle diagram for explaining thickness unevenness measurement according to the present invention.

FIG. 7 is a graph showing a forward scattered light pattern.

FIG. 8 is a conceptual diagram showing an example of the device of the present invention.

FIG. 9 is a conceptual diagram showing an example of an optical fiber manufacturing line.

FIG. 10 is a principle diagram for explaining thickness unevenness measurement according to the prior art.

FIG. 11 is an explanatory diagram for explaining the principle of thickness unevenness measurement according to the prior art.

FIG. 12 is an explanatory diagram showing a problem with thickness unevenness measurement according to the prior art.

[Explanation of symbols]

100 Coated optical fiber 100a Glass part 100b Resin part 110 Beam scanning section 111 Laser light source 112　Shielding plate 113 Laser beam 114 Polarizing plate 120 Light receiving section 121 Image sensor 122 Analyzer 130 Control section

Claims (7)

[Claims] Claim 1: A light beam from a light source is irradiated from a side surface of a linear body whose surface is coated with at least one layer to one half side of a surface perpendicular to the longitudinal direction of the linear body, and the critical reflection is performed. While detecting the position of the light and the non-transmitted light that did not pass through the linear body, the other half side is irradiated with a light beam from the light source, and the critical reflected light and the non-transmitted light that did not pass through the linear body are detected. A thickness unevenness measuring method characterized by detecting the position of transmitted light and measuring the degree of thickness unevenness. 2. The uneven thickness measuring method according to claim 1, wherein the light beam is a polarized light beam (P wave). 3. Provided opposite to the side surface of a linear body whose surface is coated with at least one layer, and which illuminates one half side of the linear body in a plane perpendicular to the longitudinal direction of the linear body. A light source unit that irradiates a beam while irradiating a light beam to the other half side, and a light source unit that irradiates the light beam from the light source unit with critical reflected light on the linear body and non-transmitted light that did not pass through the linear body. A thickness unevenness measuring device comprising: a light receiving section that receives light and detects the light receiving position; and a processing section that processes the detected light receiving positions of the received light to determine the thickness unevenness of the linear body. 4. A polarized light beam from a light source is irradiated from a side surface of a linear body whose surface is coated with at least one layer to one half side of a surface perpendicular to the longitudinal direction of the linear body,
A thickness unevenness measuring method characterized by detecting only the critical reflected light and measuring the degree of thickness unevenness. 5. Polarized light from the side surface of the linear body in a plane that is provided opposite to the side surface of the linear body whose surface is coated with at least one layer and that is perpendicular to the longitudinal direction of the linear body. A light beam light source unit that irradiates a beam (P wave), a light receiving unit that receives critical reflected light (S wave) of this polarized light beam on a linear body and detects the position of the received light, and a light receiving unit that receives the detected light beam. 1. A thickness unevenness measuring device comprising: a processing unit that detects a light receiving position and performs post-processing to determine the thickness unevenness of the linear body. 6. In the thickness unevenness measuring method according to claims 1, 2, and 4, when the light beam is irradiated, the refractive index of the coating layer that is coated on the linear body is similar to the refractive index of the coating layer. A method for measuring uneven thickness characterized by irradiating from the side of a linear body through a liquid. 7. In the thickness unevenness measuring method according to claims 1, 2, 4, and 6, when irradiating the light beam, irradiation is performed from at least two or more directions on the same surface perpendicular to the longitudinal direction of the linear body. A method for measuring uneven thickness.