JP3200927B2 - Method and apparatus for measuring coating state - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Since it is extremely difficult to use an optical fiber as it is as an optical transmission medium due to material problems, it has been conventionally applied to a resin coating immediately after drawing an optical fiber to form a coated optical fiber. Immediately after the initial strength is maintained, and it is designed to withstand long-term use.

That is, as shown in FIG. 36, an optical fiber 3 formed by drawing the tip of an optical fiber preform 1 while heating and melting it by a heating furnace 2 generally includes a first pressing die 4A, By being sequentially inserted through the first curing furnace 5A, the second pressure die 4B, and the second curing furnace 5B, the coated optical fiber 6 having the outer surface coated with two layers of resin is formed into a capping optical fiber 6. It is wound on a winder 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 a silicone resin, a urethane resin, or an epoxy resin, or an ultraviolet curable resin such as an epoxy acrylate, urethane acrylate, or polyester acrylate. And other polymer materials such as radiation-curable resins.

Incidentally, in such a coated optical fiber 6, it is important that the resin coating applied around the optical fiber 1 is concentric in order to improve the transmission characteristics and mechanical characteristics. . On the other hand, if the linear velocity is increased to improve the productivity of the optical fiber, the temperature of the optical fiber 1 rises and the resin flow in the pressing dies 4A and 4B becomes uneven, possibly resulting in uneven thickness of the resin coating. There is a problem that it easily occurs. In addition, uneven thickness also occurs when dust enters 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 to control the linear velocity to be reduced or the drawing to be stopped according to the occurrence of the thickness deviation.

Here, an example of a conventional method for measuring uneven thickness is shown in FIG.
This will be described with reference to FIG. As shown in the figure, conventionally, a side surface of a coated optical fiber 10 to be drawn is irradiated with a laser beam 12 from a laser light source 11, and a thickness variation is measured by detecting a forward scattered light pattern 13 thereof. (See JP-A-60-238737). FIG. 38 shows the principle of such a method. As shown in the figure, assuming that the coated optical fiber 10 is composed of a glass portion 10a and a resin portion 10b for simplicity, the difference in the refractive index between the two (normally, the refractive index _ng of the glass portion 10a = 1.46, Resin part 1
From 0b the refractive index n _r = about 1.48 to 1.51 of), the forward scattered light pattern 13, the light flux of the central portion which has passed through the resin portion 10b- glass portion 10a- resin portion 10b 1
3a and the luminous flux 13 in the peripheral portion that has passed only through the resin portion 10b
b exists. Therefore, the forward scattered light pattern 13
Can be detected by the left-right symmetry and the ratio of the right and left light receiving powers.

[0006]

However, in the above-described method, on the left and right sides of the forward scattered light pattern 13, the light passing through both the resin portion 10b and the glass portion 10a and the light passing only through the resin portion 10b are compared. Cannot be detected unless they are clearly distinguished. For example, as shown in the figure, when the coating diameter is small and the thickness of the resin portion 10b is small (FIG. 39), or when the thickness is too large (FIG. 40). Cannot detect the uneven thickness well. That is, in the case of FIG. 39, since the thickness of the resin portion 10b is too small,
There is no light passing through 0b, and all light passes through both the resin portion 10b and the glass portion 10a, so that uneven thickness cannot be detected. Also, in the case of FIG. 40, the resin portion 10b becomes thinner on the lower side in the figure, so that the resin
Since there is no light passing only through 0b, it can be determined that the thickness is uneven, but it is not possible to detect how much the thickness is uneven.

Therefore, in the field of optical fiber production, in order to manufacture high-performance optical fibers with good productivity,
There is a demand for a technique capable of accurately measuring the coating thickness and uneven thickness of a coated optical fiber in-line. Further, such a technique is applicable to various fields.

[0008]

According to a first aspect of the present invention, there is provided a method for measuring a coated state, comprising the steps of: forming a side surface of a cylindrical linear body having at least one coated surface; The measurement light is irradiated from a direction that is not parallel to the longitudinal axis of the cylindrical linear body, and the surface reflected light reflected in at least one specific direction on the coating surface of the cylindrical linear body, and the coating and Detect the surface reflected light and the boundary surface reflected light reflected in a direction parallel to the boundary surface with the columnar linear body main body or the boundary surface of each layer of the coating, and determine the distance between these surface reflected light and the boundary surface reflected light. In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from the amount of displacement of the reflected light that is a distance in a direction orthogonal to the specific direction, the measuring light to be irradiated is substantially parallel light. At the same time, the image of the reflection point on the surface and boundary Observation is performed using an imaging optical system provided, and an image of a reflection point on a surface and a boundary surface is observed using an imaging optical system equipped with an imaging device to measure the amount of displacement of reflected light and irradiate. The measuring light to be measured is slit light perpendicular to the longitudinal axis of the columnar linear body. According to a second aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on its surface from a direction not parallel to the longitudinal axis of the cylindrical linear body. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from the amount of positional deviation of the reflected light that is a distance in a direction orthogonal to the specific direction between the surface reflected light and the boundary surface reflected light, The measurement light to be irradiated is substantially parallel light, and the images of the reflection points on the surface and the boundary surface are observed using an imaging optical system including an imaging device, and the images of the reflection points on the surface and the boundary surface are observed. Is measured using an imaging optical system having an imaging device to measure the amount of displacement of the reflected light, and the measurement light to be irradiated is pulsed light, and the imaging device is synchronized with the irradiation timing of the pulsed light. By driving, the amount of displacement of the reflected light is measured. According to a third aspect of the present invention, in the first aspect, the measurement light to be irradiated is pulsed light, and the imaging element is driven in synchronization with the irradiation timing of the pulsed light to measure the amount of displacement of the reflected light. It is characterized by doing. According to a fourth aspect of the present invention, the side surface of the cylindrical linear body having at least one coating on its surface is irradiated with measurement light from a direction not parallel to the longitudinal axis of the cylindrical linear body. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from the amount of positional deviation of the reflected light that is a distance in a direction orthogonal to the specific direction between the surface reflected light and the boundary surface reflected light, The measurement light to be irradiated is laser scanning light,
The method is characterized in that the position of the reflected light is measured by observing the images of the reflection points on the surface and the boundary surface using an imaging optical system having an imaging device. The invention according to claim 5 irradiates the measurement light from a direction not parallel to the longitudinal axis of the cylindrical linear body on the side surface of the cylindrical linear body having at least one coating on the surface. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
The reflected light position shift amount which is a distance between the surface reflected light and the boundary surface reflected light in a direction orthogonal to the specific direction, and the distance between the incident light providing the surface reflected light and the incident light providing the boundary surface reflected light. In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from both the incident light position shift amount which is the distance in the direction orthogonal to the incident direction, the measurement light to be irradiated is laser scanning light. In addition, the method is characterized in that the reflected light position shift amount is measured by observing the images of the reflection points on the surface and the boundary surface using an imaging optical system having an imaging element. According to a sixth aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on its surface from a direction not parallel to the longitudinal axis of the cylindrical linear body. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from the amount of positional deviation of the reflected light that is a distance in a direction orthogonal to the specific direction between the surface reflected light and the boundary surface reflected light, The measurement light to be irradiated is substantially parallel light, and the images of the reflection points on the surface and the boundary surface are observed using an imaging optical system including an imaging device, and the images of the reflection points on the surface and the boundary surface are observed. The reflected light position shift amount is measured by observing using an imaging optical system having an imaging device, and a part or the whole of the imaging optical system is formed in a cross section perpendicular to the longitudinal direction of the columnar linear body. The in-focus position of the imaging optical system is changed along the longitudinal direction of the columnar linear body by inclining in a direction that is not parallel to the cylindrical linear body. According to a seventh aspect of the present invention, in any one of the second to fifth aspects, a part or the whole of the imaging optical system is oriented in a direction not parallel to a cross section perpendicular to the longitudinal direction of the columnar linear body. By inclining, the focus position of the imaging optical system is changed along the longitudinal direction of the columnar linear body. [8] The invention according to claim 8 is to irradiate the side surface of the cylindrical linear body having at least one layer of coating on its surface with measurement light from a direction not parallel to the longitudinal axis of the cylindrical linear body. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
The coating thickness and uneven thickness of the columnar linear body are determined from the amount of incident light displacement which is a distance in a direction perpendicular to the incident direction between the incident light that gives the surface reflected light and the incident light that gives the boundary surface reflected light. In the estimated coating state measurement method, the measuring light to be irradiated is the laser scanning light, the reflected light from the surface and the boundary surface is guided to the light receiving element, and the amount of displacement of the incident light is measured from the time change of the light receiving element output. A method for measuring a coated state. [9] The invention of claim 9 irradiates the measurement light from a direction not parallel to the longitudinal axis of the cylindrical linear body, the side surface of which is coated with at least one layer on the surface. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from the amount of positional deviation of the reflected light that is a distance in a direction orthogonal to the specific direction between the surface reflected light and the boundary surface reflected light, The measurement light to be irradiated is laser scanning light,
The image of the reflection point on the surface and the boundary surface is generated by incident light which is made of a semiconductor having position signal electrodes at both ends on the light incident surface side and having the bottom surface as a reference electrode, and which is incident on the light incident surface. A photocurrent divided into a magnitude inversely proportional to the distance between the incident position and each of the position signal electrodes forms an image on a PSD element, which is a semiconductor device for position detection, which is output from each position detection electrode, and is detected by the PSD element. The amount of displacement of the reflected light is measured from the change in the position of the center of gravity of the light. According to a tenth aspect of the present invention, the side surface of the cylindrical linear body having at least one coating on the surface is irradiated with measurement light from a direction not parallel to the longitudinal axis of the cylindrical linear body. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
The reflected light position shift amount which is a distance between the surface reflected light and the boundary surface reflected light in a direction orthogonal to the specific direction, and the distance between the incident light providing the surface reflected light and the incident light providing the boundary surface reflected light. In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from both the incident light position shift amount which is the distance in the direction orthogonal to the incident direction, the measurement light to be irradiated is laser scanning light. In addition, an image of the reflection point on the surface and the boundary surface is generated by incident light which is made of a semiconductor having position signal electrodes at both ends on the light incident surface side and having a bottom surface as a reference electrode, and incident on the light incident surface. Then, an image is formed on a PSD element which is a semiconductor device for position detection, in which a photocurrent divided into a magnitude inversely proportional to the distance between the incident position and each of the position signal electrodes is output from each position detection electrode.
The amount of displacement of the reflected light is measured from the change in the position of the center of gravity of the light detected by the element. [11] The invention of claim 11 irradiates measurement light from a direction which is not parallel to the longitudinal axis of the cylindrical linear body having at least one coating on the surface. The surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light at the boundary between the coating and the columnar linear body or at the boundary of each layer of the coating. Detects the boundary surface reflected light reflected in the parallel direction,
The reflected light position shift amount which is a distance between the surface reflected light and the boundary surface reflected light in a direction orthogonal to the specific direction, and the distance between the incident light providing the surface reflected light and the incident light providing the boundary surface reflected light. In the coating state measuring method for estimating the coating thickness and uneven thickness of the cylindrical linear body from both the incident light position shift amount which is the distance in the direction orthogonal to the incident direction, the measurement light to be irradiated is laser scanning light. In addition, an image of the reflection point on the surface and the boundary surface is generated by incident light which is made of a semiconductor having position signal electrodes at both ends on the light incident surface side and having a bottom surface as a reference electrode, and incident on the light incident surface. Then, an image is formed on a PSD element which is a semiconductor device for position detection, in which a photocurrent divided into a magnitude inversely proportional to the distance between the incident position and each of the position signal electrodes is output from each position detection electrode.
The method is characterized in that the amount of displacement of the reflected light is measured from the change in the position of the center of gravity of the light and the change in the light intensity detected by the element, and at the same time the amount of displacement of the incident light is measured. According to a twelfth aspect of the present invention, in any one of the first to eleventh aspects, the light receiving numerical aperture of the observation optical system is limited to increase the depth of focus and to limit the angle range of the reflected light reaching the light receiver. Thereby, surface reflected light and boundary surface reflected light in a specific direction are detected. According to a thirteenth aspect of the present invention, in the twelfth aspect, the observation optical system includes a lens system having an optical axis coincident with a specific direction and converging parallel light to one point on a focal plane, and a lens system on the focal plane of the lens system. The light passing through the pinholes or slits arranged in the specific direction is detected as surface reflected light and boundary surface reflected light in the specific direction. [14] The invention of claim 14 is the method according to any one of claims 1 to 13, wherein the measuring light to be irradiated is linearly polarized light polarized in a direction perpendicular to the longitudinal direction of the cylindrical linear body, or a cylindrical line. The light detector detects only a polarization component in a direction perpendicular to the longitudinal direction of the columnar linear body in the reflected light from the linear body. [15] The invention according to [15], in any one of [1] to [14], wherein the reflection direction of light incident on the coating surface of the cylindrical linear body at a Brewster angle in the measurement light is a specific direction. And detecting boundary surface reflected light. [16] The invention according to claim 16 is the method according to any one of claims 1 to 15, wherein a refractive index matching agent is provided around the cylindrical linear body, and the reflectance of the cylindrical linear body on the coating surface, It is characterized in that the difference from the reflectance at the boundary surface with the cylindrical linear body or at the boundary surface of each layer of the coating is reduced. The invention of claim 17 irradiates the measurement light from a direction which is not parallel to the longitudinal axis of the cylindrical linear body, the side surface of which is coated with at least one layer on the surface. A light irradiator, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. A control unit for determining the coating thickness and uneven thickness of the cylindrical linear body from a coating state measuring device,
The light irradiation unit includes a parallel light source that emits substantially parallel light, the light detection unit includes an imaging optical system that includes an imaging element as a light detection element, and the light detection unit includes an imaging element as a light detection element And a slit generating means for generating light having a slit shape in which the light irradiating section extends in a direction perpendicular to the longitudinal axis of the columnar linear body, and through the slit generating means. It is characterized by irradiating measurement light. The invention of claim 18 irradiates the measurement light from a direction which is not parallel to the longitudinal axis of the cylindrical linear body, the side surface of which is coated with at least one layer on the surface. A light irradiator, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. A control unit for determining the coating thickness and uneven thickness of the cylindrical linear body from a coating state measuring device,
The light irradiation unit includes a parallel light source that emits substantially parallel light, the light detection unit includes an imaging optical system that includes an imaging element as a light detection element, and the light detection unit includes an imaging element as a light detection element Wherein the light irradiating unit includes a pulse light source, and a synchronization circuit that synchronizes the irradiation timing of the pulse light source with the imaging timing of the image sensor of the light detecting unit. According to a nineteenth aspect, in the seventeenth aspect, the light irradiation unit includes a pulse light source, and further includes a synchronization circuit that synchronizes the irradiation timing of the pulse light source with the imaging timing of the imaging element of the light detection unit. It is characterized by. According to a twentieth aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on the surface from a direction not parallel to the longitudinal axis of the cylindrical linear body. A light irradiator, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. A control unit for determining the coating thickness and uneven thickness of the cylindrical linear body from a coating state measuring device,
The light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit includes an image sensor as a light detection element. According to a twenty-first aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on the surface from a direction that is not parallel to the longitudinal axis of the cylindrical linear body. A light irradiating section, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body main body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. From the incident light beam that gives the surface reflected light and the incident light position shift amount that is the distance between the incident light beam that gives the boundary surface reflected light and the direction perpendicular to the incident direction. A control unit for obtaining thickness and uneven thickness; In the apparatus, the light irradiation unit is provided with a laser light source and laser beam scanning mechanism, the light detection unit is characterized by comprising an imaging element as a light-detecting element. According to a twenty-second aspect of the present invention, the measurement light is emitted from a direction not parallel to the longitudinal axis of the cylindrical linear body, the side surface of which is coated with at least one layer on the surface. A light irradiator, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. A control unit for determining the coating thickness and uneven thickness of the cylindrical linear body from a coating state measuring device,
The light irradiation unit includes a parallel light source that emits substantially parallel light, the light detection unit includes an imaging optical system that includes an imaging element as a light detection element, and the light detection unit includes an imaging element as a light detection element And the photodetector inclines a part or the whole of the imaging optical system in a direction that is not parallel to a cross section perpendicular to the longitudinal direction of the columnar linear body. The focus position changes along the longitudinal direction of the body. According to a twenty-third aspect of the present invention, in any one of the eighteenth to twenty-first aspects, the photodetector is arranged so that a part or the whole of the imaging optical system is parallel to a cross section perpendicular to the longitudinal direction of the cylindrical linear body. The in-focus position changes along the longitudinal direction of the columnar linear body by inclining in a direction other than the above. According to a twenty-fourth aspect of the present invention, the measurement light is emitted from a direction not parallel to the longitudinal axis of the cylindrical linear body on the side surface of the cylindrical linear body having at least one coating on the surface. A light irradiating section, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body main body or a boundary surface of each layer of the coating. A light detection unit that detects boundary surface reflected light reflected in a direction parallel to the surface reflected light, and a direction orthogonal to the incident direction between the incident light that provides the surface reflected light and the incident light that provides the boundary surface reflected light A control unit for calculating the coating thickness and uneven thickness of the cylindrical linear body from the incident light position shift amount that is the distance of the coating state measuring device, wherein the light irradiation unit includes a laser light source and a laser light scanning mechanism. And the light detection unit reflects from the surface and boundary A light receiving element for receiving, wherein the control unit is provided with a circuit for determining the temporal change rate of more incident light position displacement amount of the laser beam scanning of the output from the light receiving element. According to a twenty-fifth aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on the surface from a direction that is not parallel to the longitudinal axis of the cylindrical linear body. A light irradiator, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. A control unit for determining the coating thickness and uneven thickness of the cylindrical linear body from a coating state measuring device,
The light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit has position signal electrodes at both ends on the light incident surface side as elements for receiving light reflected from the surface and the boundary surface, and has a bottom surface side. A reference current is used as a reference electrode, and a photocurrent generated by incident light incident on the light incident surface and divided into a magnitude inversely proportional to the distance between the incident position and each of the position signal electrodes is output from each position detection electrode. A covering state measuring device, comprising: a PSD element which is a semiconductor device for position detection to be performed; and a control unit including a circuit for calculating a reflected light shift amount from a change in a position of a center of gravity of light detected by the PSD element. According to a twenty-sixth aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on the surface from a direction not parallel to the longitudinal axis of the cylindrical linear body. A light irradiating section, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body main body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. From the incident light beam that gives the surface reflected light and the incident light position shift amount that is the distance between the incident light beam that gives the boundary surface reflected light and the direction perpendicular to the incident direction. A control unit for obtaining thickness and uneven thickness; In the device, the light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit has position signal electrodes at both ends on the light incident surface side as elements for receiving reflected light from the surface and the boundary surface. In addition, each position is detected by a light current which is made of a semiconductor having a bottom surface as a reference electrode and which is generated by incident light incident on the light incident surface and divided into a magnitude inversely proportional to the incident position and the distance to each of the position signal electrodes. A covering state measurement, comprising: a PSD element which is a semiconductor device for position detection output from an electrode; and a control unit including a circuit for obtaining a deviation amount of reflected light from a change in a position of a center of gravity of light detected by the PSD element. apparatus. According to a twenty-seventh aspect of the present invention, the measurement light is applied to a side surface of the cylindrical linear body having at least one coating on the surface from a direction that is not parallel to the longitudinal axis of the cylindrical linear body. A light irradiating section, surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and a boundary surface between the coating and the columnar linear body main body or a boundary surface of each layer of the coating. A light detection unit that detects surface reflection light and a boundary surface reflection light reflected in a direction parallel to the surface reflection light, and a reflection light position shift amount that is a distance between the surface reflection light and the boundary surface reflection light in a direction orthogonal to the specific direction. From the incident light beam that gives the surface reflected light and the incident light position shift amount that is the distance between the incident light beam that gives the boundary surface reflected light and the direction perpendicular to the incident direction. A control unit for obtaining thickness and uneven thickness; In the device, the light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit has position signal electrodes at both ends on the light incident surface side as elements for receiving reflected light from the surface and the boundary surface. In addition, each position is detected by a light current which is made of a semiconductor having a bottom surface as a reference electrode and which is generated by incident light incident on the light incident surface and divided into a magnitude inversely proportional to the incident position and the distance to each of the position signal electrodes. A PSD element, which is a semiconductor device for position detection output from the electrode, wherein the control unit obtains the amount of reflected light deviation from the change in the barycentric position of the light detected by the PSD element and simultaneously detects the amount of incident light positional deviation from the change in light intensity A covering state measuring device comprising a circuit for determining [28] The invention of claim 28 is characterized in that, in any one of claims 17 to 27, the light detection unit includes a stop for limiting the light receiving numerical aperture of the observation optical system. According to a twenty-ninth aspect of the present invention, in the twenty-eighth aspect, the stop for limiting the light receiving numerical aperture of the observation optical system has an optical axis coincident with a specific direction and focuses parallel light to one point on a focal plane. It is a pinhole or a slit arranged on the focal plane of the system. [30] The invention according to [30] includes the polarizer according to any one of [17] to [29], wherein the light irradiation unit converts the light from the light source into linearly polarized light in a direction perpendicular to the longitudinal direction of the cylindrical linear body. Alternatively, the light detection unit detects only a polarized light component in a direction perpendicular to the longitudinal direction of the cylindrical linear body in the reflected light from the cylindrical linear body. [31] The invention according to claim 31 is the method according to any one of claims 17 to 30, wherein the optical axis of the light irradiating section and the optical axis of the light detecting section are determined by measuring the coating surface of the cylindrical linear body at the reflection point of the measurement light. It is characterized by making a Brewster angle with respect to the line. [32] The invention as set forth in [32], wherein in any one of claims 17 to 31, a refractive index matching agent is provided around the cylindrical linear body, and the reflectance of the cylindrical linear body on the coating surface is; The difference between the reflectance at the interface between the coating and the columnar linear body or the interface between the layers of the coating is reduced.

On the other hand, the coating state measuring device according to the present invention
A light irradiating unit that irradiates measurement light from a direction that is not parallel to a longitudinal axis of the cylindrical linear body with respect to a side surface of the cylindrical linear body having at least one coating on its surface; Surface reflected light reflected in at least one specific direction on the coating surface of the body, and reflected in a direction parallel to the surface reflected light on a boundary surface between the coating and the cylindrical linear body or a boundary surface of each layer of the coating. A light detection unit that detects the reflected light reflected from the boundary surface;
A control unit for determining the coating thickness and uneven thickness of the cylindrical linear body from the amount of displacement of the reflected light, which is the distance between the surface reflected light and the boundary surface reflected light in the direction orthogonal to the specific direction. A light irradiating unit that irradiates a measurement light from a direction not parallel to a longitudinal axis of the cylindrical linear body with respect to a side surface of the cylindrical linear body having at least one coating on the surface. Surface reflected light reflected in at least one specific direction on the coating surface of the columnar linear body, and the surface reflected light on the boundary between the coating and the columnar linear body or the boundary of each layer of the coating. And a light detection unit that detects boundary surface reflected light reflected in a direction parallel to the direction, and a distance in a direction orthogonal to the incident direction between the incident light that provides the surface reflected light and the incident light that provides the boundary surface reflected light. From a certain amount of incident light position shift, the coating thickness of the cylindrical linear body A control unit for seeking uneven thickness, and further comprising, on the longitudinal axis of the cylindrical linear body, with respect to the side surface of the cylindrical linear body having at least one coating on the surface. A light irradiating unit that irradiates measurement light from a direction that is not parallel, surface reflected light reflected in at least one specific direction on the coating surface of the cylindrical linear body, and a boundary surface between the coating and the cylindrical linear body main body Or, a light detection unit that detects the boundary surface reflected light reflected in a direction parallel to the surface reflected light at the boundary surface of each layer of the coating, and a direction orthogonal to the specific direction between the surface reflected light and the boundary surface reflected light And the incident light position shift amount, which is the distance between the incident light beam that provides the surface reflected light and the incident light beam that provides the boundary surface reflected light, in the direction perpendicular to the incident direction. The coating thickness and uneven thickness of the cylindrical linear body from That the control unit, characterized by comprising and.

The present invention will be described below with reference to the drawings.

As shown in FIG. 34, a coated optical fiber 100 as an example of a linear body as an object is a glass part 100.
a and the resin portion 100b, and the measuring light is irradiated from the side of the coated optical fiber 100. The light A is the surface reflected light and the boundary surface reflection light in a specific direction, to measure B, these light A, to measure the reflected light position displacement amount d ₂ is the distance B. Further, it required by these lights A, the incident light A corresponding to B ', B' also the incident light position displacement amount d ₁ is the distance between measuring. In FIG. 34, for simplicity, it is assumed that the lights A, B, A ', and B' are in a plane orthogonal to the longitudinal axis of the coated optical fiber 100, and the specific direction is orthogonal to the irradiation direction.

Here, an example of a method of estimating the covering state based on the distances d ₁ and d ₂ will be described with reference to FIG. Here, the radius r ₁ of the glass part 100a of the coated optical fiber 100 and the radius r _{1 of} the resin part 100b
_2, the refractive index n ₁ of the surrounding of the coated optical fiber 100, the refractive index n ₂ of the resin portion 100b is assumed to be known. When the center of the circle of radius r ₂ representing the surface of the resin portion 100b and the xy coordinates of the origin (C _2), the coordinates of the reflection point P ₀ of the light A is below the number 1
And the incident point P of the light B 'on the resin portion 100b.
_1, and the coordinate emission point P ₂ from the resin portion 100b of the light B is represented by each number 2 and number 3.

[0013]

(Equation 1)

[0014]

(Equation 2)

[0015]

(Equation 3)

[0016] On the other hand, the incident angle theta ₁ to the resin portion 100b of the light B 'has the coordinates _{P 1 (P 1x, P 1y} ) expressed by the number 4 using also emission angle theta ₃ of the light B is P ₂ of the coordinate (P _2x,
P _2y ) and is represented by _Equation 5. Further, P ₁ and P ₂
The relationship of refraction at is expressed by Equations 6 and 7, respectively.

[0017]

(Equation 4)

[0018]

(Equation 5)

[0019]

(Equation 6)

[0020]

(Equation 7)

Further, the coordinates of the reflection point P ₃ on the boundary surface between the resin portion 100b and the glass portion 100a of the light B '(P _3x,
The condition satisfying P _3y ) is expressed by _Expressions 8 and 9.

[0022]

(Equation 8)

[0023]

(Equation 9)

Here, tan (π−θ ₁ + θ ₂ ) = T ₁ ,
Solving with tan (θ ₃ −θ ₄ ) = T _{2 gives} P _3x , P _3y
Is represented by Equations 10 and 11, respectively.

[0025]

(Equation 10)

[0026]

[Equation 11]

Then, the center coordinate C _{1 of the} glass part 100a.
Since in the position of r ₁ from P ₃ with bisector of the angle between the incident light and the outgoing light at the reflection point P _3, the number 10, number 1
From 1, the coordinates (C _1x , C _1y ) are expressed by _Equation 12.

[0028]

(Equation 12)

That is, C ₁ (C _1x , C _1y ) represents a deviation (amount of eccentricity) of the center of the glass portion 100a from the center C ₂ of the resin portion 100b. And the coating state such as the thickness deviation direction. For the sake of simplicity, it is assumed that the light A, B, which is a single layer of reflected light, is orthogonal to the light A ', B', which is incident light. The state of the coating can be similarly determined by measuring the reflected light.

In addition, a conventional optical fiber production line
The outer diameter r of the resin portion 100b depends on the type._TwoChanges
Then n₁, N_TwoMay also change, but in this case
Described above from a plurality of directions around the coated optical fiber 100.
By performing similar measurements in the same way,
You can know the meat. That is, as shown in FIG.
In addition, d₁, D_TwoAt the same time as measuring
And the surface reflected light corresponding to the light C 'and D'
Lights C and D, which are reflected light at the boundary surface, are received, and light C 'and D'
Distance d_ThreeAnd the distance d between the lights C and D_FourMeasure the following procedure
The coated state is measured with. d₁, D_TwoThan P₀, P₁, P_TwoCalculate the coordinates of
Then d_Three, D_FourThan P _Four, P_Five, P₆Calculate the coordinates of
You. P₀, P_FourFrom the coordinates of the outer diameter r of the resin portion 100b_TwoWhen
Center C_TwoIs calculated. P_Three, P₇, C₁Coordinate of n₁, N_TwoTo
Shown as a function with unknowns. P_Three, P₇For each of₁Around
Radius r₁A conditional expression that is located on the circumference of
You. P_Three, P₇, C₁Coordinates and P_Three, P₇To
Solve the conditional expression for the coordinate C₁(X, y) is calculated. C₁, C_TwoIs estimated from the coordinates of.

Although the above is an example of estimating the covering state based on a pair of d ₁ and d ₂ , it can be estimated from either d ₁ or d ₂ . Further, a plurality of incident light position shift amounts d ₁ obtained by irradiating measurement light from one direction and detecting reflected lights in a plurality of specific directions,
Or more it can also estimate the covering state from the reflected light position displacement amount d _2. Furthermore, by irradiating measurement light from a plurality of directions and detecting reflected light in a plurality of specific directions to obtain a plurality of sets of d ₁ and d ₂ , it is possible to more accurately estimate the covering state.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to embodiments.

FIG. 1 conceptually shows a coating state measuring apparatus according to a first embodiment for carrying out the method of the present invention. As shown in the figure, a coated optical fiber 100 as an example of a linear body as an object includes a glass portion 100a and a resin portion 10a.
0b, a parallel light irradiating section 110 for outputting substantially parallel light and a reflected light receiving section 120 are arranged beside the coated optical fiber 100. Here, the parallel light irradiating unit 110 is provided to face the side surface of the coated optical fiber 100, and the collimating lens 111 whose optical axis is orthogonal to the longitudinal direction of the coated optical fiber 100, and is provided behind the collimating lens 111. With a light source 112,
The parallel light can be applied to the side surface of the coated optical fiber 100. On the other hand, the reflected light receiving unit 120
A condensing lens 121 disposed opposite to the side surface of the coated optical fiber 100 and having an optical axis orthogonal to the longitudinal direction of the coated optical fiber 100 and the optical axis of the collimating lens 111.
A pinhole member 122 having a slit 122a at a focal position behind the condenser lens 121, and a collimating lens 123 provided behind the pinhole member 122 and having the pinhole member 122a at the focal position.
And an image sensor 124 provided behind the collimating lens 123 to receive and detect the light passing through the pinhole 122a and the collimating lens 123, and to detect only reflected light parallel to the optical axis of the condenser lens 121. The image sensor 124 can receive light. The controller 130 processes the data from the image sensor 124 to determine the amount of displacement of the reflected light. The device shown in FIG. 1 uses a condenser lens 121 and a pinhole member 122 to selectively receive surface reflected light and boundary surface reflected light in a specific direction,
The coating condition can be measured with very simple equipment. In the present invention, an image sensor refers to a solid-state imaging device, and is a device that receives light on an array of MOS transistors and CCD memories and electronically scans the output of each cell to convert the light into an electric signal. . Further, a member having a slit may be used instead of the pinhole member 122.

Next, the principle of uneven thickness measurement performed by the apparatus shown in FIG. 1 will be described. When the parallel light is irradiated from the parallel light irradiating section 110, first, the light A which is the surface reflected light reflected on the surface of the resin section 100b of the coated optical fiber 100 and the resin section 100
The light B, which is the boundary light reflected at the boundary between the glass part 100a and the glass part 100a, is selectively received by the image sensor 124, and the other reflected light is not received. Therefore, light A
And the distance d between light A and light B from the position where light B was received.
₂ can be detected. Further, in order to measure the covering state, light A ′ which is incident light corresponding to light A and light B is used.
It is also necessary to detect the distance d ₁ between the light B ′ and the light B ′, which can be determined, for example, by reversing the light and measuring similarly. Note that the method of estimating the covering state based on these d ₁ and d ₂ is as described above, and the description is omitted here.

The apparatus shown in FIG. 2 can measure the amount of displacement of the incident light (the distance d ₂ between the lights A 'and B') simultaneously with the amount of the displacement of the reflected light (the distance d ₂ between the lights A and B). The second parallel light irradiating unit 150 is coupled to the reflected light receiving unit 120 via a beam splitter 141, and the beam splitter 14 is connected to the parallel light irradiating unit 110.
2, the second reflected light receiving section 160 is coupled. Here, the second parallel light irradiating unit 150 converts the parallel light that goes backward to the above-mentioned reflected light (light A, B) into the coated optical fiber 1.
The collimator lens 151 irradiates the light to the beam splitter 142 and includes a collimator lens 151 facing the beam splitter 142 and a light source 152 disposed behind the collimator lens 151. On the other hand, the second reflected light receiving unit 160 receives the reflected light that goes backwards from the incident light (lights A ′ and B ′) described above, and the condensing lens 1 facing the beam splitter 142.
61 and the pinhole 16 at the focal point of the condenser lens 161.
2a, a pinhole member 162 having a pinhole 162a
Is a focal position, and has a collimating lens 163 that makes reflected light passing through the pinhole 162a parallel light, and an image sensor 164 that receives light passing through the pinhole 112a and the collimating lens 163. In addition,
The control section may be configured in accordance with the apparatus shown in FIG.

The method of estimating the coating state with this uneven thickness measuring apparatus is the same as that described with reference to the apparatus shown in FIG. light a which is a light ', B' light a, distance d ₂ B a reflected light with distance d ₁ can be measured simultaneously. That is, as shown in FIGS. 3 and 4, d ₁ and d ₂ can be calculated from the positional relationship between the output peaks detected by the image sensor 124 and the image sensor 164. Therefore, by using these d ₁ and d ₂ , the covering state can be estimated by the method described above.

Here, the coated optical fiber actually causing uneven thickness is used.
Fiber (r₁= 125/2 µm, r _Two= 170 / 2μ
For m), d₁, D_TwoThe example which measured is shown. (Measurement Example 1) d₁= 10 μm, d_Two= 20 μm,
C₁Are (−1.732294, −7.66861)
2). In addition, the covering state of this example is illustrated.
Then, it becomes as shown in FIG. (Measurement Example 2) d₁= 20 μm, d_Two= 0 μm, and C
₁Is (-473.828, 7.53631)
Was asked. It should be noted that the covering state of this example is illustrated.
It looks like 6. (Measurement Example 3) d₁= −10 μm, d_Two= 30 μm
C₁Are (14.0952, -10.384)
7). In addition, the covering state of this example is illustrated.
Then, it becomes as shown in FIG.

Further, in the apparatus shown in FIG.
Although the collimating lens 124 is provided between the image sensor 22 and the image sensor 124, this is not always necessary.
Also, by providing two or more sets of the above-described devices,
Outer diameter r ₂ of resin part 100b, refractive index n of resin part 100b
_The uneven thickness can be measured even if the refractive index n ₁ and the surrounding refractive index n ₁ are unknown.
Further, the reflectance on the surface of the resin part 100b and the resin part 1
If the difference between the reflectance at the interface between the glass fiber 100b and the glass part 100a is large and it is difficult to detect the reflectance with the light receiver, a reflectance matching agent is disposed around the coated optical fiber 100 to reflect the above-mentioned surface reflection. It is preferable to reduce the difference between the reflectance and the reflectance of the interface.

The apparatus shown in FIG. 1 uses the condenser lens 121 and the pinhole member 122 in order to selectively receive only the surface reflected light and the boundary surface reflected light in a specific direction. Instead, a detection system including a light receiving lens and an image sensor may be used.

FIG. 8 shows an example in which a detection system including a light receiving lens 125 and a CCD image sensor 126 is used. Observation of the light received by the CCD image sensor 126 in this case on a television monitor is as shown in FIG. In FIG.
B, C, and D indicate reflected lights, and correspond to the reflected lights in A to D in FIG. Therefore, the distance between B and C is the above-described reflected light position shift amount d ₂ .

In FIG. 1 or FIG. 8, a wide slit light in a direction intersecting the longitudinal axis of the coated optical fiber 100 can be used instead of the parallel light as the measuring light. Note that the slit light is generated by slit generating means such as a slit member, a cylindrical lens, or a prism. FIG. 11 shows the measurement results when slit light is irradiated instead of parallel light in FIG. A in this case
To D correspond to the reflected lights A to D in FIG.

Further, in these cases, the irradiation of the parallel light or the slit light may be performed from a direction inclined with respect to a plane orthogonal to the longitudinal axis of the coated optical fiber 100.
FIG. 12 and FIG. 13 show this state.

In the case of FIG. 12, since the imaging optical system is inclined with respect to the cross section perpendicular to the longitudinal direction of the coated optical fiber 100, the focus position of the imaging optical system extends over the longitudinal direction of the coated optical fiber 100. Will change. Therefore, even when the coated optical fiber 100 is being drawn and is slightly moving, there is an effect that focusing is performed at any position in the vertical direction on the television monitor as shown in FIG.

Further, when the slit light is emitted from an inclined position as shown in FIG. 13, a measurement result as shown in FIG. 14 is obtained. That is, in this case, the distance between the reflected lights B and C is larger than in the case of FIG.

8, 12, and 13, the depth of focus is increased by limiting the light receiving numerical aperture of the observation optical system, and
Limiting the angle range of the reflected light reaching the CD image sensor 126 facilitates detection of the reflected light to be measured. More specifically, as shown in FIG.
An aperture member 127 may be provided between the image sensor 126 and the D image sensor 126.

When the stop member 127 is provided as shown in FIG. 15, for example, surrounding light indicated by a broken line among the reflected light on the surface of the cylindrical coated optical fiber 100 is removed, and a predetermined range including necessary reflected light is removed. There is an advantage that the reflected light can be received and observation becomes easy. Also, the aperture member 1
27, the depth of focus becomes deeper, so that the surface of the coated optical fiber 100 and the glass portion 100a and the resin portion 100
It becomes easy to focus on both the boundary with b, and the observation becomes easy even if the position of the coated optical fiber 100 is unstable.

FIG. 16 conceptually shows an example of another coating state measuring apparatus using slit light. As shown in the figure,
Coated optical fiber 10 as an example of a cylindrical shape as a subject
Reference numeral 0 denotes a glass part 100a and a resin part 100b, and a slit light irradiating part 210 and a reflected light receiving part 220 are arranged on the side of the coated optical fiber 100.
Here, the slit light irradiation unit 210 has a laser light source or a diode as a light source,
The slit light is applied in a strobe shape to the side surface of the coated optical fiber 100 along a plane that is inclined with respect to the plane perpendicular to the longitudinal direction of FIG. Further, the reflected light receiving section 220 is arranged in a plane including the center of the slit light irradiating section 210 and the central axis of the coated optical fiber 100 to receive the reflected light of the slit light. It has an image sensor. The data processing unit 230 that processes the data from the slit light irradiation unit 210 and the reflected light receiving unit 220 to estimate the covering state includes an image memory 231 that reads out and stores the image data from the reflected light receiving unit 220. , This image memory 231
And a CPU 232 that receives the image data from the camera and the strobe synchronization signal from the slit light irradiation unit 210 and processes the data to estimate the covering state.

Next, the principle of the coating state measurement performed by the apparatus shown in FIG. 16 will be described.

As shown in FIG. 17, the light L ₀ of the slit light directed toward the center of the coated optical fiber 100 is incident on each φ _1.
When there is no unevenness, the resin portion 100
a light L ₁ reflected by the b surface, a light L ₂ reflected by the boundary surface between the resin portion 100b and the glass portion 100a is obtained. At this time, the distance S between the light L ₁ and the light L ₂ and the thickness D have a relationship shown in Expression 13 when the refractive index of the resin portion 100b is n _1. To obtain the thickness D.

[0050]

(Equation 13)

However, when the thickness deviation occurs, the light L ₂ becomes the light L
18 and 19, the light L ₀ ′ which is not reflected in parallel to the light ₁ and is displaced in the direction in which the glass portion 100a is decentered is P ₁ as shown in FIGS.
After entering the resin part 100b toward the center of the glass portion 100a, the reflected light is reflected by the P ₂ of the glass portion 100a is emitted in a direction parallel to the light L ₁ from P _3. At this time, the incident angle in a plane orthogonal to the central axis of the light L ₀ ′ is θ ₁ ,
Assuming that the emission angle θ ₂ , the distance between P ₁ and P ₂ in the same plane is k, and the distance between light L ₀ and light L ₀ ′ is d, the coordinates of P ₁ and P ₂ shown in FIG. 14, represented by Equation 15.
Note that the outer diameter of the resin portion 100b (the radius) and r _2.

[0052]

[Equation 14]

[0053]

(Equation 15)

Further, in a plane including P ₁ and P ₂ and parallel to the central axis, the incident angle and refraction angle of the light L ₀ ′ at P ₁ are φ ₁ and φ ₂ , respectively, and the reflected light L _Two
Assuming that the distance between the light and the reflected light L ₂ ′ is h, h is expressed by Expression 16, and k is expressed by Expression 17 from Expression 16. In addition,
The radius of the glass portion 100a and r _1.

[0055]

(Equation 16)

[0056]

[Equation 17]

Here, the glass portion 100a in FIG.
Radial (r center C ₁ of the glass portion 100a from P _1
1 + k), the coordinates (C _1x,
C _1y ) is represented by _Expression 18. That is, by detecting h and d with the device shown in FIG. 16, the covering state can be estimated.

[0058]

(Equation 18)

In order to obtain h and d using the apparatus shown in FIG.
What is necessary is just to process the data of the reflected light obtained from the image sensor of the reflected light receiving unit 220 by adding a correction considering the refraction and the like in the resin unit 100b. Note that, for the sake of simplicity, the above description has been made with a single-layer coating.

The state of coating was measured by a thickness measuring apparatus shown in FIG. That is, the slit light is emitted from the slit light irradiating section 210 in a strobe shape, and the reflected light is received by the reflected light receiving section 220, and the data read into the image memory 131 by the CPU 132 is processed to obtain d and h. Thus, the covering state is estimated.

FIG. 20 shows what is actually observed.
Two arc-shaped reflectors R_A,R_BIt is. Where anti
Shooting part R_AIs composed of light reflected on the surface of the resin portion 100b
And the central spot P_ATo P₀Matches with
Conceivable. Also, the reflection part R _BIn the glass part 100a
The reflected light appears on the surface of the resin portion 100b.
Ri, spot P_BIs observed. And this
Pot P_BCorrection of refraction etc. in the resin part 100b at the position
By adding P_ThreeThe position of
This spot P_BPosition P_ThreePosition of
It can be. In this case, P_AAnd P_BUp and down
The direction distance corresponds to h ′ shown in FIG. _AAnd P_BWith
The distance in the left-right direction corresponds to d in FIG. Therefore,
By using these h ′ (h) and d,
Can estimate the covering state.

By providing two or more sets of the above-described devices, the outer diameter r ₂ of the resin portion 100b and the resin portion 100
Even if the refractive index n _{1 of} b and the surrounding refractive index n ₀ are unknown, uneven thickness can be measured. If the difference between the reflectance at the surface of the resin part 100b and the reflectance at the interface between the resin part 100b and the glass part 100a is large and it is difficult for the reflected light receiving part to detect it, the coated optical fiber 100 It is preferable that a difference in reflectance between the above-described surface and the boundary surface is reduced by disposing a reflectance matching agent around the periphery.

In the apparatus shown in FIG. 16, the data processing section 230 processes data in synchronization with the stroboscopic irradiation of the slit light irradiation section 210.
Even when the position of the coated optical fiber 100 varies in the direction intersecting the longitudinal axis, the effect can be obtained that the operation can be surely performed. It goes without saying that such a technique can be applied to all the devices of the other embodiments.

Next, an embodiment using laser scanning light as the measuring light will be described. FIG. 21 conceptually shows an example of a coating state measuring apparatus using laser scanning light. As shown in the figure, a coated optical fiber 100 as an example of a linear body as an object is composed of a glass part 100a and a resin part 100b, and a laser light scanning part is provided beside the coated optical fiber 100. 310 and a reflected light receiving unit 320 are provided. Here, the laser beam scanning unit 310 is provided to face the side surface of the coated optical fiber 100, and the collimating lens 311 whose optical axis is orthogonal to the longitudinal direction of the coated optical fiber 100.
A rotating mirror 312 provided at the focal position of the collimating lens 311 and passing through the focal position and rotating about an axis parallel to the longitudinal direction of the coated optical fiber 100; And a laser light source 313 that irradiates the laser light in a plane perpendicular to the longitudinal direction of the coated optical fiber 100. On the other hand, the reflected light receiving unit 320
Is a condensing lens 3 disposed opposite to the side surface of the coated optical fiber 100 and having an optical axis orthogonal to the longitudinal direction of the coated optical fiber 100 and the optical axis of the collimating lens 311.
21, a slit member 322 having a slit 322a at a focal position behind the condenser lens 321, and a light receiving and detecting light passing through the slit 322a provided behind the slit member 322, such as a photodiode. And the light receiver 323 can receive only reflected light parallel to the optical axis of the condenser lens 321. The control unit 330 functions to estimate the covering state by processing data from the laser beam scanning unit 310 and the reflected light receiving unit 320. That is, the control unit 330 sends a mirror drive signal to the rotating mirror 312 and outputs a synchronization signal thereof, a rotating mirror driver 331, an amplifier 332 that amplifies and outputs an output signal of the light receiver 323, and a rotating mirror driver 331. A / D is applied to the synchronization signal of
A / D converter 333 for conversion, and A / D converter 33
And a CPU 334 for processing a signal from the optical receiver 3 and detecting a scanning position when the light receiver 323 receives reflected light. The apparatus shown in FIG. 21 includes a condensing lens 32 for selectively receiving surface reflected light and boundary surface reflected light in a specific direction.
1 and the slit member 322, and the method of the present invention can be realized with very simple equipment. In the present invention, the light receiving device refers to an element that detects light reception and outputs an electric signal corresponding to the light. The beam diameter of the laser beam used in the present invention may be appropriately selected depending on the required resolution, but is preferably set to be at least smaller than the minimum value of the coating to be measured. Further, it goes without saying that a member having a pinhole may be used instead of the slit member 322.

Next, the thickness deviation measurement performed by the apparatus shown in FIG.
The principle will be described. The laser is driven by the rotation of the rotating mirror 312.
Laser light from the laser light source 313 from right to left in the figure.
When scanning, first, the resin portion 10 of the coated optical fiber 100
The light A which is the surface reflected light reflected on the surface
23, and then the resin portion 100b and the glass portion 1
Light B, which is the boundary surface reflected light reflected at the boundary surface with 00a,
The light is received by the light receiver 323, and other reflected light is not received.
No. Therefore, the output when light A and light B are received and
With the synchronization signal from the rotating mirror driver 331, the light
Between light A 'and light B' which are incident light corresponding to A and light B
Distance d in the scanning direction ₁Can be detected. Also,
In order to measure the coating state, if necessary, light A and light B
Distance d between_TwoAlso need to be detected
Can be similarly measured by reversing the above. Or light A
And the light B is separated into two, and one of them is detected by its light receiving position.
Other detection means such as an image sensor.
It can be obtained by detecting sometimes. further,
The above surface reflected light and boundary surface reflected light shall be detected.
Have position signal electrodes at both ends on the light incident surface side
And a semiconductor whose bottom side is the reference electrode
Generated by the incident light incident on the surface,
Divided into sizes inversely proportional to the distance to each position signal electrode
Position detection semiconductor that outputs the photocurrent from each position detection electrode
Body device (PSD; Position Sensitive)
e Device) and the above reference of both position signal electrodes
From the relationship between the output of the sum of potentials to the electrodes and time,
Light emission amount d ₁And the above of each position signal electrode
Incident position calculated from the magnitude of the potential with respect to the reference electrode
From the reflected light deviation d_TwoCan ask for
You.

FIG. 22 shows a coating state measurement according to another embodiment.
1 schematically shows the configuration of the device. Note that FIG.
The same reference numerals are given to members that have the same action as
Description is omitted. The device shown in FIG.
Quantity (distance d between light A 'and B') ₁) And reflected light position
Displacement (distance d between light A and B)_Two) Can be measured
The reflected light receiving section 320 has a beam splitter
The second laser beam scanning unit 350 is connected via the
The laser beam scanning unit 310 has a beam splitter
The second reflected light receiving unit 360 is coupled via the litter 342
Have been. Here, the second laser beam scanning unit 350
Coated with laser light that goes back to the above-mentioned reflected light (lights A and B)
The optical fiber 100 is scanned, and the beam split
A collimating lens 351 facing the
A rotating mirror arranged at the focal position of the collimating lens 351
352 and irradiate the rotating mirror 352 with laser light.
And a laser light source 353. Meanwhile, the second reflection
The light receiving unit 360 receives the incident light (light A ′, B ′) described above.
It receives reflected light that goes backwards, and
A condenser lens 361 opposed to the condenser 342;
Part having a slit 362a at the focal point of the slit 361
Material 362 and the rear of the slit member 362
Light receiver 363 for receiving light passing through slit 362a
With The control unit is based on the device shown in FIG.
What is necessary is just to comprise.

The method of estimating the coating state by the coating state measuring apparatus is the same as that described with reference to the apparatus shown in FIG. 21, and thus the description is omitted here. light a which is a light ', B' light a, distance d ₂ B a reflected light with distance d ₁ can be measured simultaneously. That is, as shown in FIGS. 23 and 24, d ₁ and d ₂ can be calculated from the relationship between the time between the output peaks detected by the light receivers 323 and 363 and the scanning synchronization signal. Therefore, by using these d ₁ and d ₂ , the covering state can be estimated by the method described above.

By providing two or more sets of the above-described devices, the outer diameter r ₂ of the resin portion 100b and the resin portion 100
refractive index n ₂ and the refractive index n ₁ of the surrounding b can be measured even covering state unknown. Further, when the difference between the reflectance on the surface of the resin portion 100b and the reflectance on the boundary surface between the resin portion 100b and the glass portion 100a is large and it is difficult to detect the reflectance with the light receiver, the area around the coated optical fiber 100 It is preferable to reduce the difference between the reflectance of the surface and the reflectance of the boundary surface by disposing a reflectance matching agent on the surface.

FIG. 25 conceptually shows an example of another coating state measuring apparatus using laser scanning light. As shown in the figure, a laser beam scanning unit 410 and a reflected light receiving unit 420 are arranged on the side of a coated optical fiber 100 as an example of a linear body as an object. Here, the laser beam scanning unit 41
Reference numeral 0 denotes a collimating lens 411 provided to face the side surface of the coated optical fiber 100 and having an optical axis orthogonal to the longitudinal direction of the coated optical fiber 100, provided at a focal position of the collimating lens 411, passing through the focal position and A rotating mirror 412 that rotates about an axis parallel to the longitudinal direction of the coated optical fiber 100 and a laser light source 413 that irradiates a laser beam to the center of rotation of the rotating mirror 412 are provided. The laser beam can be scanned in a plane perpendicular to the longitudinal direction of the laser beam. On the other hand, the condensing lens 421 is disposed opposite to the side surface of the coated optical fiber 100 and has a light axis orthogonal to the longitudinal direction of the coated optical fiber 100 and the optical axis of the collimating lens 411. A slit member 4 having a slit 422a at a focal position behind the condenser lens 421.
22 and a semiconductor device for position detection (PSD; Position Sens) which is provided behind the slit member 422 and receives and detects light passing through the slit 422a.
active device 423, and only the reflected light parallel to the optical axis of the condenser lens 421 is transmitted to the PSD 42.
3 can receive light. Then, the control unit 43
0 denotes the laser beam scanning unit 410 and the reflected light receiving unit 42
By processing the data from 0, it functions to estimate the covering state. That is, the control unit 430 sends a mirror driving signal to the rotating mirror 412 and outputs a synchronizing signal of the rotating mirror driver 431, a PSD driver 432 that processes an output signal of the PSD 423, and a synchronizing signal from the rotating mirror driver 431. PSD driver 4
A / D converter 43 for A / D-converting the output signal from 32
And a CPU that processes the signal from the A / D converter 433 to detect the amount of incident light positional deviation and the amount of reflected light positional deviation.
434. The apparatus shown in FIG. 25 uses a condenser lens 421 and a slit member 422 in order to selectively receive surface reflected light and boundary surface reflected light in a specific direction. Can be realized. Needless to say, a member having a pinhole may be used instead of the slit member 422.

Here, the PSD 423 used in this embodiment is
The configuration will be described with reference to FIG. As shown in the figure
The PSD 423 is provided on the surface of the flat silicon substrate 501.
A P-type semiconductor layer 502 and an N-type semiconductor layer 503 on the back surface.
And position signal electrodes 504 and 505 are provided at both ends on the front side.
In addition, the back side is a reference electrode 506.
Since the PSD 423 has such a configuration, the surface
A light spot L enters between the side position signal electrodes 504 and 505.
When emitted, a charge proportional to the light energy is generated at the incident position.
And this charge becomes the photocurrent I₁, I_TwoAnd both positions
The signal is output from the signal electrodes 504 and 505. At this time, light
Current I₁, I_TwoIs the incident position of the light spot L and the position signal
The size is inversely proportional to the distance (resistance value) between the poles 504 and 505
The current I₁, I_TwoTo the reference electrode 5
V with reference to 06₁, V_TwoIf you take out as
Calculation signal (V₁-V_Two) / (V₁+ V_Two)
You can ask. That is, for light A and light B
Position deviation amount d of reflected light from the incident position_TwoCan ask for
Wear. The PSD 423 usually has a light spot
It is used to find the incident position of L.
Is the sum signal (V₁+ V_Two) And time are monitored,
The light A and the light B are converted to PSD by this and the scanning synchronization signal.
423 to find the scanning position when receiving light
You. Therefore, this results in the incident light corresponding to light A, B
The distance d between the light beams A 'and B'₁Can ask for
You. Thus, in the present invention, the division signal
By extracting the sum signal at the same time as the signal in relation to time.
And the displacement d of the reflected light position_TwoAnd the incident light displacement d ₁
Can be detected simultaneously.

Next, the coating state measurement performed by the apparatus shown in FIG.
The constant principle will be described. With the rotation drive of the rotating mirror 412,
The laser beam from the laser light source 413 is directed from right to left in the figure.
First, the resin portion of the coated optical fiber 100
Light A, which is surface reflected light reflected on the surface of 100b, is received
Is received by the container 423, and then the resin portion 100b and glass
Light that is reflected light at the boundary surface reflected at the boundary surface with the portion 100a
B is received by the PSD 423, and other reflected light is received.
Not. Therefore, the output when light A and light B are received
Force and the synchronization signal from the rotating mirror driver 431.
And light A ′ and light which are incident light corresponding to light A and light B, respectively.
Distance d in the scanning direction between B ' ₁And the distance between light A and light B
d_TwoCan be detected.

The coating condition was determined by the coating condition measuring device shown in FIG. That is, the laser light from the laser light source 413 is scanned by rotating the rotating mirror 412 according to the mirror driving signal from the rotating mirror driver 431, and the PS
In the D driver 432, the sum signal (V ₁ + V ₂ ) and the division signal (V ₁ −V ₂ ) /
(V ₁ + V ₂ ) is obtained. Then, in the CPU 434,
The sum signal (V ₁ + V ₂ ) is monitored in relation to time with reference to the synchronization signal, and at the same time, the division signal (V ₁ −V ₂ ) / (V ₁ + V ₂ ) when the output forms a peak is obtained. Ask. The output state at this time is shown in FIG. Then, in the figure, d ₁ can be obtained from the peak position of the sum signal output, and d ₂ can be obtained from the divided signal at the peak. Therefore, by using these d ₁ and d ₂ , the covering state can be estimated by the method described above.

In the apparatus shown in FIG. 25, the reflected light passing through the slit 422a of the slit member 422 is directly received by the PSD 423.
If a collimating lens whose focal point coincides with the slit 422a is provided between the
3, which is more preferable. By providing two or more sets of the above-described devices,
Even if the outer diameter r _{2 of} 0b, the refractive index n ₂ of the resin portion 100b, and the refractive index n _{1 of the} surroundings are unknown, uneven thickness can be measured. Furthermore, the difference between the reflectance on the surface of the resin part 100b and the reflectance on the interface between the resin part 100b and the glass part 100a is large,
If it is difficult to detect by the PSD, the coated optical fiber 100
It is preferable that a difference in reflectance between the above-described surface and the boundary surface is reduced by disposing a reflectance matching agent around the periphery.

FIG. 28 conceptually shows another coating state measuring apparatus using laser beam scanning. As shown in the figure, a laser beam scanning unit 610 and a reflected light receiving unit 620 are arranged on the side of a coated optical fiber 100 as an example of a linear body as an object. Here, the laser beam scanning unit 61
Reference numeral 0 denotes a collimating lens 611 which is provided to face the side surface of the coated optical fiber 100 and whose optical axis is orthogonal to the longitudinal direction of the coated optical fiber 100, is provided at the focal position of the collimating lens 611, passes through the focal position A rotating mirror 612 that rotates about an axis parallel to the longitudinal direction of the coated optical fiber 100, and a laser light source 613 that irradiates a laser beam to the center of rotation of the rotating mirror 612. Laser light can be scanned in a plane perpendicular to the longitudinal direction of the laser beam. On the other hand, the condensing lens 621 disposed opposite to the side surface of the coated optical fiber 100 and having an optical axis orthogonal to the longitudinal direction of the coated optical fiber 100 and the optical axis of the collimating lens 611. A beam splitter 622 disposed behind the condenser lens 621, and a slit member 623 having slits 623a and 624a at the focal position of the light split by the beam splitter 622, respectively.
624, a one-dimensional image sensor 625 provided behind the slit members 623, 624 to receive and detect light passing through the slits 623a, 624a, and a light receiver 626 such as a photodiode, for example. The one-dimensional image sensor 625 and the light receiver 626 can receive only reflected light parallel to the optical axis of the lens 621. Here, the one-dimensional image sensor 625 outputs the position information in the vertical direction in the figure that receives the reflected light, and the light receiver 626 outputs an electric signal when receiving the reflected light. . The control unit 630 functions to estimate the covering state by processing data from the laser light scanning unit 610 and the reflected light receiving unit 620. That is, the control unit 630 controls the rotation mirror 612
Rotating mirror driver 631 that sends a mirror driving signal to the mirror and outputs a synchronization signal of the mirror driving signal;
A one-dimensional image processing device 632 that receives a synchronization signal from the first one and periodically reads and processes information from the one-dimensional image sensor 625, and outputs a synchronization signal from the rotating mirror driver 631 and an output signal from the light receiver 623 to A / A. A / D converter 633 for performing D conversion, and one-dimensional image processing device 632
And a CPU 6 that processes signals from the A / D converter 633
34. Here, the image sensor is a solid-state imaging device, and is a device that converts light into an electric signal by receiving light on an array of MOS transistors or CCD memories and electronically scanning the output of each cell. The light receiver here refers to an element that detects light reception and outputs an electrical signal in accordance with the light. Further, it goes without saying that a member having a pinhole may be used instead of the slit members 623 and 624.

Next, the principle of the coating state measurement performed by the apparatus shown in FIG. 28 will be described. When the laser light from the laser light source 613 is scanned from right to left in the figure by rotating the rotating mirror 612, first, the light A, which is the surface reflected light reflected on the surface of the resin portion 100b of the coated optical fiber 100, is primary. Received by the original image sensor 625 and the light receiver 626,
Next, light B, which is reflected light at the boundary surface between the resin portion 100b and the glass portion 100a, is received by the one-dimensional image sensor 625 and the light receiver 626, and other reflected light is not received. Therefore, the distance d ₂ in the direction orthogonal to the reflection direction of the light A and the light B from the light receiving position of the light A and the light B of the one-dimensional image sensor 625 can be detected. In addition, based on the output when the light receiver 626 receives the light A and the light B and the synchronization signal from the rotating mirror driver 631, the light A ′ which is the incident light corresponding to the light A and the light B is obtained.
And the distance d ₁ in the scanning direction between the light B ′ and the light B ′.

An example of measuring the incident light position shift amount d ₁ and the reflected light position shift amount d ₂ using the apparatus shown in FIG. 28 will be specifically described. FIG. 29 is a timing chart showing the thickness deviation measurement according to the present embodiment. As shown in the figure, in this embodiment, the laser light from the laser light source 613 reciprocates toward the side surface of the coated optical fiber 100 by reciprocatingly rotating the rotating mirror 612 in response to the mirror driving signal from the rotating mirror driver 631. Scanning is performed, and light A and B, which are reflected light at that time, are detected by the one-dimensional image sensor 625 and the light receiver 626. The rotating mirror driver 631 outputs a synchronization signal every time the scanning direction is changed. In the one-dimensional image sensor 625, the charge is accumulated during one scan (one forward pass or one return pass), and at the same time when the scanning direction is switched (synchronous signal output), the one-dimensional image processing device 632 transmits the received light signal. To read. This output signal can be obtained from the relationship between the light receiving intensity of each pixel and the pixel address, for example, as shown in FIG. 30, and d ₂ can be obtained from the positional relationship between the output of light A and the output of light B. . On the other hand, the light receiver 626 outputs a signal to the A / D converter 633 when receiving the reflected light.
The / D converter 633 performs A / D conversion for a certain period of time after the synchronization signal is output (until a short time before the next synchronization signal is output) and outputs a signal. It is possible to know the time between the reception of the light A and the light B. That is, an output peak as shown in FIG. 31 can be obtained, and the distance d ₁ between the incident light A ′ and light B ′ can be obtained from the time between the two peaks. By using d ₁ and d ₂ obtained in this way, the covering state can be estimated by the above-described method.

The various embodiments have been described above.
Next, a method for improving the accuracy of the coating state measurement in each of the embodiments will be described.

In the above-described method for measuring the coating state, there is a problem that the measurement is difficult because the amount of reflected light at the boundary surface is small compared to the reflected light at the surface. An analyzer may be provided to detect only the polarization component in the direction perpendicular to the longitudinal direction of the columnar linear body. This is because, in such a polarized light component, the light quantity of the boundary surface reflected light is relatively improved as compared with the surface reflected light. When the light source of the measurement light outputs polarized laser light, it goes without saying that the above-described polarizer and analyzer are not necessary.

The first coating in a coated optical fiber in which a first coating layer having a diameter of 180 μm and a refractive index of 1.497 and a second coating layer having a diameter of 250 μm and a refractive index of 1.51 are provided around the glass part. FIG. 32 shows the relationship between the ratio of the amount of reflected light at the interface between the layer and the second coating layer / the amount of reflected light at the surface and the polarization direction. The angle between the incident light and the observed reflected light was 90 degrees.
As is clear from the figure, in the vicinity of the polarization direction (90 degrees) perpendicular to the longitudinal direction of the coated optical fiber, the boundary surface reflected light amount is relatively improved with respect to the surface reflected light amount. Therefore, detection of such a polarization component ensures measurement of the boundary surface reflected light. This effect also occurs at the interface between the coating layer and the glass part, and depends on the difference in refractive index at the interface.
Therefore, the above-described effect is improved at the interface between the coating layer and the glass portion, which generally has a larger refractive index difference than the above-described example.

Instead of using a polarizer or an analyzer as described above, the direction of reflection of the measurement light incident on the coated surface of the cylindrical linear body at a Brewster angle is defined as a specific direction. When the reflected light and the boundary surface reflected light are detected, an effect is obtained that the boundary surface reflected light is easily detected as in the case described above. Further, in this case, if the measurement light is linearly polarized light perpendicular to the longitudinal direction of the coated optical fiber as described above, the effect becomes more remarkable.

The Brewster angle of a coated optical fiber in which a first coating layer having a diameter of 180 μm and a refractive index of 1.497 and a second coating layer having a diameter of 250 μm and a refractive index of 1.51 are provided around the glass part. θ (θ = tan ^-1 (1.51) =
(56.49 degrees), the surface reflected light and the boundary reflected light are observed from the direction in which the reflected light of the incident light can be observed, and the ratio of the boundary reflected light amount / surface reflected light amount when the polarization direction of the measurement light is changed. Are shown in FIG. As shown in the figure, when measurement light having a polarization direction perpendicular to the longitudinal direction of the coated optical fiber is used and incident at a Brewster angle θ, the amount of reflected light at the boundary surface further increases relatively, It can be seen that the reflected light is more easily detected.

[0082]

As described above, according to the present invention,
By measuring the reflected light in a specific direction on the coating surface and the reflected light in a specific direction at the interface between the coating and the linear body, the coating state can be continuously and accurately measured. The state of the optical fiber coating can be measured in-line in the production line.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a coating state measuring device according to one embodiment.

FIG. 2 is a conceptual diagram showing a coating state measuring device according to another embodiment.

FIG. 3 is an explanatory diagram showing an output peak of a light receiver of the device of FIG. 2;

FIG. 4 is an explanatory diagram showing an output peak of a light receiver of the apparatus of FIG.

FIG. 5 is an explanatory diagram showing a measurement example of a covering state.

FIG. 6 is an explanatory diagram showing a measurement example of a covering state.

FIG. 7 is an explanatory diagram showing a measurement example of a covering state.

FIG. 8 is a configuration diagram showing another example of the detection system.

FIG. 9 is an explanatory diagram showing an observation example of a television monitor.

FIG. 10 is an explanatory diagram showing a reflection state of measurement light.

FIG. 11 is an explanatory diagram showing an observation example of a television monitor.

FIG. 12 is an explanatory diagram showing measurement by oblique incidence of parallel light.

FIG. 13 is an explanatory diagram showing measurement by oblique incidence of slit light.

FIG. 14 is an explanatory diagram showing the measurement results of FIG.

FIG. 15 is an explanatory diagram illustrating an example of a diaphragm member.

FIG. 16 is a configuration diagram showing a coating state measuring device by slit light irradiation.

FIG. 17 is an explanatory view showing measurement by the apparatus of FIG.

FIG. 18 is an explanatory diagram showing a measurement by the device of FIG.

FIG. 19 is an explanatory diagram showing measurement by the device of FIG.

FIG. 20 is an explanatory view showing measurement by the device of FIG.

FIG. 21 is a configuration diagram showing a coating state measuring device by laser beam scanning.

FIG. 22 is a configuration diagram showing a coating state measuring device by laser beam scanning.

FIG. 23 is an explanatory diagram showing measurement results of the device of FIG. 22.

FIG. 24 is an explanatory diagram showing measurement results of the device of FIG. 22.

FIG. 25 is a configuration diagram showing a coating state measuring device by laser beam scanning.

FIG. 26 is a configuration diagram showing a PSD.

FIG. 27 is an explanatory diagram showing the measurement results of FIG. 25.

FIG. 28 is a configuration diagram showing a coating state measuring device by laser beam scanning.

FIG. 29 is a timing chart according to one embodiment of the apparatus of FIG. 28;

FIG. 30 is an explanatory diagram showing measurement results of the device of FIG. 28.

FIG. 31 is an explanatory diagram showing measurement results of the device in FIG. 28.

FIG. 32 is a graph showing a relationship between a boundary surface reflected light amount / surface light reflected light amount and a polarization direction.

FIG. 33 is a graph showing the relationship when the incident direction of the measurement light in FIG. 32 is the Brewster angle.

FIG. 34 is an explanatory diagram for explaining the principle of the present invention.

FIG. 35 is an explanatory diagram for explaining the principle of the present invention.

FIG. 36 is a conceptual diagram showing an example of an optical fiber production line.

FIG. 37 is a principle diagram for explaining uneven thickness measurement according to the related art.

FIG. 38 is an explanatory diagram for explaining the principle of uneven thickness measurement according to the related art.

FIG. 39 is an explanatory diagram showing a problem of uneven thickness measurement according to the related art.

FIG. 40 is an explanatory diagram showing a problem of uneven thickness measurement according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 100 Coated optical fiber 100a Glass part 100b Resin part 110 Parallel light irradiation part 111 Collimating lens 112 Light source 120 Reflected light receiving part 121 Condensing lens 122 Pinhole member 124 Image sensor 130 Control part 210 Slit light irradiated part 220 Reflected light receiving part 230 Data processing unit 310 Laser light scanning unit 311 Collimating lens 312 Rotating mirror 313 Laser light source 320 Reflected light receiving unit 321 Condensing lens 322 Slit member 323 Light receiving unit 330 Control unit 410 Laser light scanning unit 411 Collimating lens 412 Rotating mirror 413 Laser light source 420 Reflected light receiving section 421 Condensing lens 422 Slit member 423 PSD 430 Control section 610 Laser beam scanning section 611 Collimating lens 612 Rotating mirror 613 Laser light source 20 reflected light receiving unit 621 a condenser lens 622 beam splitter 623, 624 slit member 625 one-dimensional image sensor 626 receiving 630 the control unit

──────────────────────────────────────────────────続 き Continued on the front page (31) Priority claim number Japanese Patent Application No. 3-95441 (32) Priority date April 25, 1991 (1991. 4.25) (33) Priority claim country Japan (JP) (31) Priority claim number Japanese Patent Application No. 3-95442 (32) Priority date April 25, 1991 (1991. 4.25) (33) Priority claim country Japan (JP) (56) References JP JP-A-53-140054 (JP, A) JP-A-63-196106 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G01M 11/00-11 / 08

Claims (32)

(57) [Claims] 1. A coating comprising at least one coating on a surface.
Length of the cylindrical linear body with respect to the side surface of the cylindrical linear body
Irradiate the measuring light from a direction that is not parallel to the hand direction axis, and
Reflected in at least one specific direction on the coated surface of the linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
Parallel to the above surface reflected light at the boundary surface of the surface or each layer of the coating
Boundary light reflected in various directions
The direction perpendicular to that particular direction between the reflected light and the reflected light at the interface
Of the columnar linear body from the amount of displacement of the reflected light
In the coating condition measuring method for estimating the coating thickness and uneven thickness, the measuring light to be irradiated is substantially parallel light,
Imaging optics with image sensor for image of reflection point on boundary surface
Observation using the system and reflection points on surfaces and interfaces
Image of the object is observed using an imaging optical system equipped with an image sensor
A method for measuring the amount of displacement of the reflected light, and irradiating the measurement light with slit light perpendicular to the longitudinal axis of the cylindrical linear body. 2. A method for irradiating a side surface of a cylindrical linear body having at least one layer of coating on its surface with measurement light from a direction not parallel to a longitudinal axis of the cylindrical linear body. Surface reflected light reflected in at least one specific direction on the coating surface of the linear body, and in a direction parallel to the surface reflected light at a boundary surface between the coating and the columnar linear body or a boundary surface of each layer of the coating. The reflected thickness of the columnar linear body is determined by detecting the reflected light reflected on the boundary surface and the positional deviation between the surface reflected light and the boundary surface reflected light in the direction orthogonal to the specific direction. In the covering state measuring method for estimating the meat, the measuring light to be irradiated is substantially parallel light, and the images of the reflection points on the surface and the boundary surface are observed using an imaging optical system having an imaging device. Image sensor for reflecting points on the surface and boundary The reflected light position displacement amount measured by observing using an imaging optical system for, and, by driving the imaging device in synchronization with the irradiation timing of the pulsed light with the measurement light irradiated is a pulse light, A method for measuring a covering state, comprising measuring a displacement amount of a reflected light. 3. The method according to claim 1, wherein the measuring light to be irradiated is pulsed light, and the amount of displacement of the reflected light is measured by driving the image sensor in synchronization with the irradiation timing of the pulsed light. Method for measuring the state of coating. 4. A coating comprising at least one coating on the surface.
Length of the cylindrical linear body with respect to the side surface of the cylindrical linear body
Irradiate the measuring light from a direction that is not parallel to the hand direction axis, and
Reflected in at least one specific direction on the coated surface of the linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
Parallel to the above surface reflected light at the boundary surface of the surface or each layer of the coating
Boundary light reflected in various directions
The direction perpendicular to that particular direction between the reflected light and the reflected light at the interface
Of the columnar linear body from the amount of displacement of the reflected light
In the coating state measuring method for estimating the coating thickness and uneven thickness, the measuring light to be irradiated is laser scanning light, and the images of the reflection points on the surface and the boundary surface are observed using an imaging optical system having an imaging device. Measuring the amount of displacement of the reflected light. 5. A coating comprising at least one coating on the surface.
Length of the cylindrical linear body with respect to the side surface of the cylindrical linear body
Irradiate the measuring light from a direction that is not parallel to the hand direction axis, and
Reflected in at least one specific direction on the coated surface of the linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
Parallel to the above surface reflected light at the boundary surface of the surface or each layer of the coating
Boundary light reflected in various directions
The direction perpendicular to that particular direction between the reflected light and the reflected light at the interface
The amount of displacement of the reflected light, which is the distance between
Between the incident light and the incident light that gives the interface reflected light.
Incident light position shift, which is the distance in the direction perpendicular to the incident direction
Estimate the coating thickness and uneven thickness of the cylindrical linear body from both
In the coating state measurement method, the measurement light to be irradiated is laser scanning light, and the position of the reflected light is shifted by observing the images of the reflection points on the surface and the boundary surface using an imaging optical system having an imaging device. A method for measuring a coated state, comprising measuring an amount. 6. A coating comprising at least one coating on the surface.
Length of the cylindrical linear body with respect to the side surface of the cylindrical linear body
Irradiate the measuring light from a direction that is not parallel to the hand direction axis, and
Reflected in at least one specific direction on the coated surface of the linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
Parallel to the above surface reflected light at the boundary surface of the surface or each layer of the coating
Boundary light reflected in various directions
The direction perpendicular to that particular direction between the reflected light and the reflected light at the interface
Of the columnar linear body from the amount of displacement of the reflected light
In the coating condition measuring method for estimating the coating thickness and uneven thickness, the measuring light to be irradiated is substantially parallel light,
Imaging optics with image sensor for image of reflection point on boundary surface
Observation using the system and reflection points on surfaces and interfaces
Image of the object is observed using an imaging optical system equipped with an image sensor
By measuring the amount of displacement of the reflected light, and by tilting a part or the whole of the imaging optical system in a direction that is not parallel to a cross section perpendicular to the longitudinal direction of the cylindrical linear body, A covering state measuring method, wherein a focus position of an imaging optical system is changed along a longitudinal direction of a shape. 7. The method according to claim 2, wherein
By tilting a part or the whole of the imaging optical system in a direction that is not parallel to a cross section perpendicular to the longitudinal direction of the columnar linear body, A covering state measuring method, wherein a focus position of the object is changed. 8. A coating comprising at least one coating on the surface.
Length of the cylindrical linear body with respect to the side surface of the cylindrical linear body
Irradiate the measuring light from a direction that is not parallel to the hand direction axis, and
Reflected in at least one specific direction on the coated surface of the linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
Parallel to the above surface reflected light at the boundary surface of the surface or each layer of the coating
And the boundary surface reflected light reflected in various directions is detected.
Between the incident light that gives the light and the incident light that gives the reflected light at the interface
The incident light position, which is the distance in the direction perpendicular to its incident direction
Estimating the coating thickness and uneven thickness of the cylindrical linear body from the amount of deviation
In the coating state measurement method, the measuring light to be irradiated is laser scanning light, the reflected light from the surface and the boundary surface is guided to the light receiving element, and the amount of displacement of the incident light is measured from the time change of the light receiving element output. A coating state measuring method characterized by the above-mentioned. 9. A coating comprising at least one coating on the surface.
Length of the cylindrical linear body with respect to the side surface of the cylindrical linear body
Irradiate the measuring light from a direction that is not parallel to the hand direction axis, and
Reflected in at least one specific direction on the coated surface of the linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
Parallel to the above surface reflected light at the boundary surface of the surface or each layer of the coating
Boundary light reflected in various directions
The direction perpendicular to that particular direction between the reflected light and the reflected light at the interface
Of the columnar linear body from the amount of displacement of the reflected light
In the coating state measuring method for estimating the coating thickness and uneven thickness, the measuring light to be irradiated is laser scanning light, and the images of the reflection points on the surface and the boundary surface are respectively positioned at both ends on the light incident surface side by position signal electrodes. And a photocurrent generated by incident light incident on the light incident surface and divided into a magnitude inversely proportional to the distance between the incident position and each of the position signal electrodes. A coating state measurement characterized in that an image is formed on a PSD element which is a semiconductor device for position detection outputted from a position detection electrode, and a reflected light position shift amount is measured from a change in a position of a center of gravity of light detected by the PSD element. Method. 10. A coating comprising at least one coating on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Irradiate the measuring light from a direction not parallel to the longitudinal axis, and
At least one specific direction on the coated surface of the columnar linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
At the interface or at the interface of each layer of the coating,
And the boundary surface reflected light reflected in the
Orthogonal to its specific direction between surface reflected light and interface reflected light
The reflected light position shift amount, which is the distance in the direction, and the surface reflected light
Between the incident light to be applied and the incident light to be applied to the interface reflected light.
Incident light displacement, which is the distance in the direction perpendicular to the incident direction
Estimate the coating thickness and uneven thickness of the cylindrical linear body from both
In the coating state measuring method, the measuring light to be irradiated is laser scanning light, and the images of the reflection points on the surface and the boundary surface have position signal electrodes at both ends on the light incident surface side, respectively, and the bottom surface side is referenced. A position which is made of a semiconductor used as an electrode and which is generated by incident light incident on the light incident surface and outputs from each position detecting electrode a photocurrent divided into a magnitude inversely proportional to the incident position and the distance to each of the position signal electrodes. A coating state measuring method, wherein an image is formed on a PSD element which is a semiconductor device for detection, and the amount of displacement of reflected light is measured from a change in the position of the center of gravity of light detected by the PSD element. 11. A coating comprising at least one coating on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Irradiate the measuring light from a direction not parallel to the longitudinal axis, and
At least one specific direction on the coated surface of the columnar linear body
Surface reflected light and the boundary between the coating and the cylindrical linear body.
At the interface or at the interface of each layer of the coating,
And the boundary surface reflected light reflected in the
Orthogonal to its specific direction between surface reflected light and interface reflected light
The reflected light position shift amount, which is the distance in the direction, and the surface reflected light
Between the incident light to be applied and the incident light to be applied to the interface reflected light.
Incident light displacement, which is the distance in the direction perpendicular to the incident direction
Estimate the coating thickness and uneven thickness of the cylindrical linear body from both
In the coating state measuring method, the measuring light to be irradiated is laser scanning light, and the images of the reflection points on the surface and the boundary surface are provided with position signal electrodes at both ends on the light incident surface side and the bottom surface side is referenced. A position which is made of a semiconductor used as an electrode and which is generated by incident light incident on the light incident surface and outputs from each position detecting electrode a photocurrent divided into a magnitude inversely proportional to the incident position and the distance to each position signal electrode. An image is formed on a PSD element, which is a semiconductor device for detection, and the amount of displacement of reflected light is measured from the change in the position of the center of gravity and the change in light intensity detected by the PSD element, and at the same time the amount of displacement of incident light is measured. A method for measuring a coating state, comprising: 12. A specific direction by limiting the light-receiving numerical aperture of the observation optical system to increase the depth of focus and restricting the angle range of reflected light reaching the light-receiving device. 1. A method for measuring a coating state, comprising detecting surface reflected light and boundary surface reflected light. 13. The observation optical system according to claim 12, wherein:
The optical axis coincides with a specific direction and parallel light is
And detecting light passing through a lens system converging on a point and a pinhole or slit disposed on a focal plane of the lens system as surface reflected light and boundary surface reflected light in the specific direction. To measure the coating condition. 14. The method according to claim 1, wherein the measurement light to be applied is linearly polarized light polarized in a direction perpendicular to the longitudinal direction of the columnar linear body, or is a linear linear body. A method for measuring a covering state, wherein a photodetector detects only a polarization component in a direction perpendicular to a longitudinal direction of a cylindrical linear body in reflected light. 15. The surface reflected light and boundary surface reflection according to any one of claims 1 to 14, wherein the direction of reflection of the measurement light that is incident on the coated surface of the cylindrical linear body at a Brewster angle is a specific direction. A method for measuring a coating state, comprising detecting light. 16. The columnar linear body according to claim 1, wherein a refractive index matching agent is provided around the cylindrical linear body, the reflectance of the cylindrical linear body on the coating surface, and the coating and the cylindrical linear body. A method for measuring a coating state, wherein a difference between a reflectance at a boundary surface with a body or a boundary surface of each layer of a coating is reduced. 17. A coating comprising at least one coating on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
Surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
From the amount of displacement of the reflected light, which is the distance in the orthogonal direction,
A control unit for determining the coating thickness and uneven thickness of the linear body, wherein the light irradiation unit includes a parallel light source that emits substantially parallel light.
And the light detection section has an image sensor as a light detection element.
An image pickup optical system, and the light detection unit is a light detection element.
An imaging optical system having an imaging element as, and the light irradiation unit includes a slit generating means for generating light having a slit shape extending in a direction perpendicular to the longitudinal axis of the cylindrical linear body, the slit produced A coating state measuring device, which irradiates measurement light through a means. 18. A coating comprising at least one coating on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
Surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
From the amount of displacement of the reflected light, which is the distance in the orthogonal direction,
A control unit for determining the coating thickness and uneven thickness of the linear body , the light irradiation unit includes a parallel light source that emits substantially parallel light, and the light detection unit detects light. An image pickup optical system having an image pickup element as an element, the light detection unit includes an image pickup optical system having an image pickup element as a light detection element, and the light irradiation unit includes a pulse light source, and irradiation timing of the pulse light source And a synchronization circuit for synchronizing the imaging timing of the imaging element of the light detection unit with the imaging state of the imaging device. 19. The light emitting device according to claim 17, wherein the light irradiation unit includes a pulse light source, and a synchronization circuit that synchronizes the irradiation timing of the pulse light source with the imaging timing of the image sensor of the light detection unit. Coating condition measuring device. 20. A coating comprising at least one layer on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
Surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
From the amount of displacement of the reflected light, which is the distance in the orthogonal direction,
A control unit for determining the coating thickness and uneven thickness of the linear body.
A covering state measuring device, wherein the light irradiating unit includes a laser light source and a laser beam scanning mechanism, and the light detecting unit includes an imaging element as a light detecting element. 21. A coating comprising at least one layer on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
The above surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
The amount of displacement of the reflected light, which is the distance in the orthogonal direction,
An incident light beam that provides reflected light and an input light beam that provides the boundary surface reflected light
The distance between the rays in the direction perpendicular to the direction of incidence.
The coating thickness of the cylindrical linear body and the
And a control unit for determining uneven thickness, wherein the light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit includes an imaging element as a light detection element. Characteristic coating condition measuring device. 22. A coating comprising at least one coating on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
Surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
From the amount of displacement of the reflected light, which is the distance in the orthogonal direction,
A control unit for determining the coating thickness and uneven thickness of the linear body.
In the covering state measuring device, the light irradiation unit includes a parallel light source that emits substantially parallel light, the light detection unit includes an imaging optical system that includes an imaging element as a light detection element, and the light detection unit includes light. An imaging optical system having an imaging element as a detection element is provided, and the light detection unit tilts a part or the whole of the imaging optical system in a direction not parallel to a cross section perpendicular to the longitudinal direction of the cylindrical linear body. An in-focus position changing along a longitudinal direction of the columnar linear body; 23. The method according to claim 18, wherein
In the meantime, the light detection unit inclines a part or the whole of the imaging optical system in a direction that is not parallel to a cross section perpendicular to the longitudinal direction of the columnar linear body, thereby extending along the longitudinal direction of the columnar linear body. Wherein the focus position changes. 24. A coating comprising at least one layer on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
The above surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
An output part, and the incident light that gives the surface reflected light and the boundary light that gives the interface reflected light.
Is the distance in the direction perpendicular to the direction of incidence between the incident light
From the incident light position shift amount, the coating thickness and uneven thickness of the cylindrical linear body
A light irradiation unit includes a laser light source and a laser light scanning mechanism, and a light detection unit includes a light receiving element that receives light reflected from a surface and a boundary surface. A control unit comprising: a circuit for obtaining a shift amount of the incident light from the time change of the output from the light receiving element and the speed of the laser beam scanning. 25. A coating comprising at least one layer on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
Surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
From the amount of displacement of the reflected light, which is the distance in the orthogonal direction,
A control unit for determining the coating thickness and uneven thickness of the linear body.
In the coating state measuring device, the light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit serves as a device for receiving light reflected from the surface and the boundary surface, and has position signals at both ends on the light incident surface side. A photocurrent which is made of a semiconductor having electrodes and a bottom electrode serving as a reference electrode and which is generated by incident light incident on the light incident surface and divided into a magnitude inversely proportional to the distance between the incident position and each of the position signal electrodes. A PSD device which is a semiconductor device for position detection that outputs from each position detection electrode is provided, and a control unit is provided with a circuit for calculating a reflected light deviation amount from a change in a position of a center of gravity of light detected by the PSD device. Coating condition measuring device. 26. A coating comprising at least one layer on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
Table surface reflected light at the boundary surface of the boundary surface or coating of each layer
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
The amount of displacement of the reflected light, which is the distance in the orthogonal direction,
An incident light beam that provides reflected light and an input light beam that provides the boundary surface reflected light
The distance between the rays in the direction perpendicular to the direction of incidence.
The coating thickness of the cylindrical linear body and the
And a control unit for determining unevenness and thickness, wherein the light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit receives reflected light from the surface and the boundary surface. And a position signal electrode at both ends on the light incident surface side, and a semiconductor made of a base electrode on the bottom side, which is generated by incident light incident on the light incident surface, and is provided between the incident position and each of the position signal electrodes. A PSD element which is a semiconductor device for position detection that outputs a photocurrent divided into a magnitude inversely proportional to the distance from each position detection electrode, and the control unit detects a shift in reflected light from a change in the position of the center of gravity of light detected by the PSD element. A coating state measuring device comprising a circuit for determining an amount. 27. A coating comprising at least one layer on the surface.
Of the cylindrical linear body with respect to the side surface of the applied cylindrical linear body.
Illumination that irradiates measuring light from a direction that is not parallel to the longitudinal axis
Projection part , at least one specific direction on the coating surface of the cylindrical linear body
The surface reflected light reflected on the, the coating and the columnar linear body body
The above surface reflected light at the interface of
Photodetection to detect the boundary surface reflected light reflected in the direction parallel to
In the specific direction between the surface reflected light and the interface reflected light.
The amount of displacement of the reflected light, which is the distance in the orthogonal direction,
An incident light beam that provides reflected light and an input light beam that provides the boundary surface reflected light
The distance between the rays in the direction perpendicular to the direction of incidence.
The coating thickness of the cylindrical linear body and the
And a control unit for determining unevenness and thickness, wherein the light irradiation unit includes a laser light source and a laser light scanning mechanism, and the light detection unit receives reflected light from the surface and the boundary surface. And a position signal electrode at both ends on the light incident surface side, and a semiconductor made of a base electrode on the bottom side, which is generated by incident light incident on the light incident surface, and is provided between the incident position and each of the position signal electrodes. A position detecting semiconductor device for outputting a photocurrent divided into a magnitude inversely proportional to the distance from each position detecting electrode; and a control unit for controlling a reflected light shift due to a change in the optical barycentric position detected by the PSD element. A covering state measuring device comprising a circuit for obtaining an amount of displacement of incident light from a change in light intensity at the same time as obtaining an amount. 28. The method according to claim 17, wherein
A covering state measuring device, wherein the light detecting section includes a stop for limiting a light receiving numerical aperture of the observation optical system. 29. The focal plane of a lens system according to claim 28, wherein a stop for limiting the light-receiving numerical aperture of the observation optical system has an optical axis coincident with a specific direction and focuses parallel light to one point on the focal plane. A coating state measuring device characterized by being a pinhole or a slit arranged on the upper side. 30. The method according to claim 17, wherein
The light irradiation unit includes a polarizer that converts light from the light source into linearly polarized light in a direction perpendicular to the longitudinal direction of the columnar linear body, or the light detection unit includes light reflected from the columnar linear body. A coating state measuring device characterized in that it detects only a polarized light component in a direction perpendicular to a longitudinal direction of a cylindrical linear body. 31. The method according to claim 17, wherein
A coating state measuring device, wherein the optical axis of the light irradiating section and the optical axis of the light detecting section make a Brewster angle with respect to the normal of the coating surface of the cylindrical linear body at the reflection point of the measurement light. 32. In any one of claims 17 to 31,
A refractive index matching agent is provided around the cylindrical linear body, the reflectance of the cylindrical linear body on the coating surface, the boundary surface between the coating and the cylindrical linear body, or the boundary surface of each layer of the coating. A coating state measuring device characterized in that the difference between the reflectance and the reflectance at the surface is reduced.