JPH09292305A - Apparatus for detecting defect of translucent long body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect the defects at a comparable signal sensitivity, from the inner side to the outer side of the vicinity of the center of a material under inspection, without generating problem points regarding the dynamic range for light-receiving intensity. SOLUTION: Parallel rays 3 are projected from the direction intersecting a moving optical fiber 2. Scattered light 4 from the optical fiber 2 is received with image sensors 5a and 5b. These image sensors 5a and 5b are arranged so as to have a light-receiving angle θ from the position, squarely facing a light projecting axis 3a of the parallel rays. The outputs of these image sensors 5a and 5b are processed in a signal processing part 6, and the distribution pattern of the scattered light intensity is obtained. The activity defects in the optical fiber 2 are judged by a judging part 7, based on the distribution pattern of the scattered light intensity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmissive elongated body defect detecting apparatus for detecting a cavity defect such as a bubble inside a translucent elongated body such as an optical fiber.

[0002]

2. Description of the Related Art Cavity defects such as air bubbles inside a light-transmissive elongated body, for example, an optical fiber, cause undesirable problems such as increased optical transmission loss, reduced mechanical strength, and failure of end face fusion. Be done. Therefore, this cavity defect is detected inline with an optical fiber drawing facility or the like.

As a device for detecting an internal defect of an optical fiber, for example, as disclosed in Japanese Patent Application Laid-Open No. 4-106448, a light beam such as a laser beam is radiated from the lateral direction with respect to the axis of the optical fiber, An optical fiber defect detection device has been proposed which detects a cavity defect such as a bubble by receiving forward scattered light from an optical fiber with an image sensor and detecting an abnormality in the intensity distribution pattern of the scattered light.

As shown in FIG. 5, this optical fiber defect detecting apparatus has an optical fiber (transparent long body) 2 which is running in an uncoated state immediately after drawing from an optical fiber preform 1.
Parallel light rays 3 are continuously emitted from the lateral direction, the forward scattered light 4 is received by a light receiving image sensor 5 such as a CCD line sensor or a photodiode array, and its output is processed by a signal processing unit 6, The scattered light intensity distribution pattern obtained from the signal processing unit 6 is determined by the determination unit 7 and the processing unit 6
The processing result of (1) is displayed on the monitor unit 8, an alarm is issued from the alarm unit 9 when an abnormality is determined, and the determination result is recorded by the recording unit 10.

In such an optical fiber defect detecting device,
When the output from the light-receiving image sensor 5 is processed by the signal processing unit 6, a scattered light intensity distribution pattern 11 as shown in the left part of FIG. 6 is obtained.

When the optical fiber 2 has a cavity defect such as a bubble whose refractive index is largely different from that of the surrounding area, a dimming concave portion due to the cavity defect appears in the scattered light intensity distribution pattern 11. The mutation due to the dimming concave portion is detected by the judgment unit 7 which judges the scattered light intensity distribution pattern 11 obtained from the signal processing unit 6. The content of this determination is output to the outside, an alarm is issued from the alarm unit 9, and the determination result is recorded in the recording unit 10.

Here, the radial position and scattered light distribution of the optical fiber 2 having a cavity defect will be described. Figure 7 shows an optical fiber with a diameter of about 125 μm (refractive index of the cladding: about
1.46) This is a trace of the optical path when a parallel ray 3 is incident on 2 from the uniaxial direction. Core 2 of optical fiber 2
From the center line 2b passing through a, d1 = 42 .mu.m, d2 =
The parallel rays 3 incident at a distance of 57 μm are t1
= 30 ° and t2 = 55 °.

Further, in the shaded area in FIG. 7, since the incident light does not enter, a dead zone 12 is obtained for measurement, and even if there is a cavity defect in this area, it cannot be detected. This dead zone 12
Can be eliminated by changing the angle of incidence of the light projecting section (and the light receiving section corresponding thereto) on the measurement plane to make the incident light multiaxial.

For example, when there is a cavity defect at point P in FIG. 7, in the scattered light intensity distribution pattern 11 in FIG. 8 (the scattered light intensity distribution pattern 11 has left and right tails as shown in FIG. 6). , The processing to be performed on each of the left and right sides is the same, and therefore, the scattered light pattern on one side is representatively shown.
A dimming concave portion such as P appears. Further, when there is a cavity defect at the point Q in FIG. 7, a dimming concave portion like Q appears in the scattered light intensity distribution pattern 11 in FIG. The reference line of the scattered light intensity distribution pattern 11 is shown by a broken line in FIG. 8, and the scattered light intensity distribution pattern 11 obtained by the measuring device in the drawing equipment is the vibration of the drawn optical fiber 2 and the like. Even in a normal state where there are no cavity defects due to various factors, the fluctuation is as shown in the R portion of FIG.

In the pattern processing, in order to identify the variation of the scattered light intensity distribution pattern 11 due to the cavity defect from the normal state, the displacement amount H from the reference line shown by the broken line in FIG. It is necessary to exceed the amount of noise in the scattered light intensity distribution pattern 11. There are two types of noise, one is due to sensor characteristics and the other is due to fluctuations in the scattered light state associated with the position of the image sensor 5 which is a light receiving element.

From the actual measurement, a threshold amount capable of distinguishing between the normal state and the defective state is obtained as a noise amount N which changes depending on the light receiving position, that is, the sensor position coordinate, and the sensor position coordinate x along the longitudinal direction of the image sensor 5. H /
FIG. 10 shows an example in which N, that is, the discrimination sensitivity evaluation value H / N is plotted. This figure corresponds to the case where there is a cavity defect on the line connecting the points P and Q in FIG. 8, and the identification sensitivity changes depending on the position of the cavity defect in the radial direction of the optical fiber 2, but the average of the cavity defects. When the inner diameter of the target cross section is 4 μm, the discrimination sensitivity evaluation value H / N falls below 1 outside the vicinity of the S position of the sensor position coordinate corresponding to the scattering angle of 30 °.

That is, with respect to the position where there is a cavity defect on the PQ line in FIG. 7, the dimming recess appears at the corresponding position on the sensor position coordinate x, depending on the depth dimension H and the noise dimension N of each dimming recess. The discrimination sensitivity evaluation value H / N can be experimentally obtained. At this time, the size of the light-reducing concave portion also changes depending on the cross-sectional inner diameter of the cavity defect. Therefore, as typical values used in the experiment, cases where the cross-sectional inner diameter of the cavity defect is 6 μm, 4 μm, and 2 μm are shown. Of course, the size of the light-reducing recess and the identification sensitivity change depending on the cross-sectional position of the cavity defect from the center of the optical fiber 2.
Here, an assumed line on the PQ line is assumed. The average cross-sectional inside diameter of the cavity defect found so far is 4 μm
In the example in which the cross-sectional inner diameter of the cavity defect is 4 μm, the discrimination sensitivity evaluation value H / N falls below 1 outside the sensor position coordinate x = S (the position where the scattering angle is about 30 °).
When the discrimination sensitivity evaluation value H / N is smaller than 1, it means that the detection of the mutation in the scattered light intensity distribution pattern 11 due to the cavity defect becomes unstable.

As described above, in the conventional transmissive long-body defect detecting device, the image sensor 5 is installed so as to face the uniaxial parallel light beam 3 (depending on the device to be manufactured, the light emitting / receiving light may be received). Sometimes the part is multi-axis, but pay attention to one of them.).

[0014]

Therefore, in the actual device, the following problems occur.

The light receiving intensity of the scattered light intensity distribution pattern 11 is a characteristic when the light receiving angle θ (the angle formed by the position directly facing the light projecting axis shown in FIG. 1 and the light receiving surface of the light receiving means) shown in FIG. 11 is 0 °. As shown, near the center, the inside is strong and the outside is weak. Therefore, although the defect located inside the vicinity of the center of the object to be detected can be detected relatively accurately, it is very difficult to detect the defect located outside the object to be detected. In order to detect a defect located outside the object to be detected as well as a defect located inside the center, that is, when the intensity of the parallel light beam 3 is increased while trying to receive the same amount of light as the inside near the center, The received light intensity inside becomes even stronger and exceeds the measurement range of the light receiving sensor.
Dynamic range issues arise. In other words,
If it is attempted not to cause the problem of the dynamic range, it is impossible to detect the defect located outside the detected object.

Further, in an actual device, the pattern change outside the scattered light intensity distribution pattern 11 becomes slow as shown in FIG. 9 (A), so that line disturbance and other various disturbance factors are caused. In some in-line measurement, it is difficult to detect the dimming recess. At this time, if the light intensity of the incident parallel rays 3 is increased, the variation amount is also increased.
The S / N ratio does not improve. In this case, in the scattered light intensity distribution pattern 11, when the intensity of the light received on the outer side becomes stronger, the intensity of the light received on the inner side also becomes stronger accordingly, so that the problem of the dynamic range becomes more serious. Therefore, with respect to the position of the cavity defect in the radial direction of the optical fiber 2, a dead zone 12a such as a hatched portion is newly generated in the originally detectable region shown in FIG. 7, and the cavity defect of this dead zone 12a is generated. I miss it. In order to eliminate the dead zone 12a, it is necessary to further increase the number of axes, but in order to realize the number of axes, a large number of detectors must be arranged, which is not practical.

It is an object of the present invention to detect a defect with the same signal sensitivity from the inner side to the outer side in the vicinity of the center of the object to be detected without causing the problem of the dynamic range of the received light intensity. An object is to provide a scale defect detecting device.

Another object of the present invention is to provide a light-transmissive long-body defect detecting device capable of installing a sensor at an arbitrary position and at an arbitrary angle.

Another object of the present invention is to provide a transmissive elongated body defect detecting apparatus capable of reducing the number of sensors used.

[0020]

SUMMARY OF THE INVENTION According to the present invention, a light beam is projected from a direction intersecting with a light-transmissive elongated member, scattered light from the light-transmissive elongated member is received by an image sensor, and its output is output. To improve the light-transmissive long-body defect detection device in which the determination unit determines the defect in the light-transmissive elongated body from the scattered light intensity distribution pattern by processing the Is.

In the translucent elongated body defect detection device according to the first aspect, the image sensor is arranged with a light receiving angle θ from a position directly facing the light projection axis of the light beam. .

As described above, when the image sensor is arranged with a light receiving angle θ from the position directly facing the light projection axis,
The light receiving intensity on the light emitting axis side of the image sensor is weakened, and the light receiving intensity on the side away from the light emitting axis is strengthened, which solves the problem of the dynamic range and is similar from the inside to the outside near the center of the object to be detected. Defects can be detected with signal sensitivity.

Further, in this case, the pattern change at the skirt of the scattered light intensity distribution pattern forming a mountain shape becomes apparent, and it is possible to detect the dimming concave portion at the skirt of the scattered light intensity distribution pattern. It can be done easily.

In the translucent long-body defect detecting device according to the second aspect, the image sensor is provided on both sides of the projection axis of the light beam with a light receiving angle θ from a position directly facing the projection axis. It is characterized by being arranged.

Thus, when the image sensors are arranged on both sides of the projection axis of the light beam so as to have a light receiving angle θ from the position directly facing the projection axis, the scattered light scattered on both sides of the projection axis is formed. Both can be reliably received.

In the transmissive elongated body defect detecting device according to the third aspect, the light receiving surface of the light guide member is arranged with a light receiving angle θ from a position directly facing the light projecting axis of the light beam, The light receiving output of the optical member is input to the image sensor.

When the light receiving surface of the light guide member is arranged with a light receiving angle θ from the position directly facing the light projecting axis in this way, the light receiving intensity of the light receiving surface on the light projecting axis side is weakened, and the light receiving surface is separated from the light projecting axis. The received light intensity on the remote side is strengthened, and the problem of dynamic range can be solved.

Also in this case, the pattern change at the skirt of the scattered light intensity distribution pattern forming a mountain shape becomes apparent, and it is easy to detect the dimming concave portion at the skirt of the scattered light intensity distribution pattern. Can be done.

Further, when the light receiving output is input to the image sensor by using the light guide member, there is an advantage that the image sensor can be installed at an arbitrary position and at an arbitrary angle.

In the transmissive elongated body defect detecting device according to the fourth aspect, the light guide member is provided on both sides of the light projecting axis of the light beam, and the light receiving surface of each of the light receiving surfaces is located directly opposite to the light projecting axis. It is characterized in that they are arranged with θ.

As described above, when the light guide members are arranged on both sides of the light projecting axis of the light beam so that each light receiving surface thereof has a light receiving angle θ from a position directly facing the light projecting axis, the light guiding members are arranged. Both of the scattered light scattered on both sides can be reliably received.

Further, even if the light guide members are arranged on both sides of the projection axis of the light beam, there is an advantage that only one image sensor can receive the output of these light guide members.

In the transmissive long-body defect detecting device according to the fifth aspect, the light receiving angle θ is set in the range of 30 ° to 60 °.

When the light receiving angle θ is set in the range of 30 ° to 60 ° in this way, the discrimination sensitivity evaluation value H / N exceeds 1, and the detection of the mutation in the scattered light intensity distribution pattern due to the cavity defect is detected. It can be done stably.

In the present invention, the light receiving angle θ means the angle formed by the light receiving surface of the light receiving means and the position directly facing the light projecting axis (the position orthogonal to the light projecting axis).

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first example of an embodiment of a transmissive elongated body defect detecting device according to the present invention. Parts corresponding to those in FIG. 5 described above are denoted by the same reference numerals.

In the transmissive elongated body defect detecting apparatus of this example, the output beam 14 from the beam source 13 such as a laser oscillator is shaped into a parallel light beam 3 by a beam shaper 15, and the parallel light beam 3 is converted into an optical fiber. Irradiation is performed on the uncoated optical fiber (transparent elongated body) 2 immediately after drawing from the base material 1 in a direction orthogonal to the lateral direction. In this way, when the parallel light beam 3 is applied to the optical fiber 2 in a direction orthogonal to the lateral direction, the forward scattered light 4 is scattered from the optical fiber 2 in the forward direction of the parallel light beam 3.

In the transmissive long-body defect detecting apparatus of this example, since the forward scattered light 4 is received, the first and second image sensors 5a and 5b are particularly arranged to project the parallel rays 3 from the projection axis. It is arranged on both sides of 3a such that the central portions are aligned on the same measurement surface with an angle θ from the position directly facing the projection axis 3a. In the present invention, this angle θ is referred to as the light receiving angle as described above. The first and second image sensors 5a and 5b are composed of, for example, a CCD line sensor, a photodiode array, or the like.

These first and second image sensors 5a,
The image output photoelectrically converted by 5b is processed by the signal processing unit 6, and the scattered light intensity distribution pattern obtained from the signal processing unit 6 is determined by the determination unit 7.

In this case, as shown in FIG. 5 described above, the processing result of the processing unit 6 is displayed on the monitor unit 8, and if an abnormality is determined, the alarm unit 9 issues an alarm and the determination result is recorded in the recording unit. It is also possible to adopt a structure in which recording is performed by 10.

In this way, the light-transmissive long-body defect detecting device is configured, and the first and second image sensors 5a and 5b are provided on both sides of the projection axis 3a of the parallel light beam 3 and directly on the projection axis 3a. When the light receiving angle θ is arranged at, for example, θ = 45 ° from the opposite position, the scattered light is greater in the case of the light receiving angle θ = 45 ° than in the case of the conventional light receiving angle θ = 0 ° as shown in FIG. The light intensity inside the intensity distribution pattern 11 is weak and the light intensity outside is strong. Therefore, the problem of the dynamic range due to the light intensity difference between the inside and outside of the scattered light intensity distribution pattern 11 is alleviated.

Further, by emphasizing the light intensity on the outer side (skirt) of the scattered light intensity distribution pattern 11, it is possible to improve the defect identification ability on the outer side of the scattered light intensity distribution pattern 11. That is, as in this example, the first and second image sensors 5a and 5b are arranged on both sides of the projection axis 3a of the parallel light beam 3 with a light receiving angle θ from a position directly facing the projection axis 3a. Then, as shown in FIG. 9B, the displacement amount H from the reference line shown by the broken line increases, and the defect recognition sensitivity is improved.

With respect to the sample having a cavity defect having a cross-sectional inner diameter of 2 μm on the line S1 in FIG. 7, a variation of the scattered light intensity distribution pattern 11 appears as a dimming concave portion at the site corresponding to the scattering angle t = 30 °, so that here An example in which the discrimination sensitivity evaluation value H / N of (1) is examined while changing the light receiving angle θ is shown as S1 in FIG. Similarly, a cavity defect having an inner diameter of 2 μm in cross section is S2 in FIG.
For the sample on the line, the variation of the scattered light intensity distribution pattern 11 appears as a dimming concave portion at the site corresponding to the scattering angle t = 45 °, so that the discrimination sensitivity evaluation value H / N
FIG. 2 shows an example of S2 which was investigated while changing the light receiving angle θ.

From FIG. 2, the light receiving angle θ is 30 ° to 60 °.
It is understood that the discrimination sensitivity evaluation value H / N exceeds 1 in the range of. Further, in this range, the sensitivity inside the scattered light intensity distribution pattern 11 is also smaller than the value shown in FIG. 10, but does not fall below 1.

As described above, when the discrimination sensitivity evaluation value H / N exceeds 1, it is possible to stably detect the mutation in the scattered light intensity distribution pattern 11 due to the cavity defect.

Therefore, the dead zone 1 shown by the hatched portion in FIG.
Even if there is a minute void defect having a cross-sectional inner diameter of about 1 to 2 μm at the location 2a, it can be detected without missing the void defect.

FIG. 3 shows a second example of the embodiment of the transparent long-body defect detecting device according to the present invention. The parts corresponding to those in FIG. 1 described above are denoted by the same reference numerals.

In the transmissive long-body defect detecting apparatus of this example, the first and second image sensors 5a and 5b face the projection axis 3a on both sides of the projection axis 3a of the parallel light beam 3. An angle θ is provided from the position, and the central portions are arranged in different measurement planes with respect to the fiber axis direction. Although not shown, other configurations are similar to those of the first example.

Even with such a structure, the same effect as in the first example can be obtained. Furthermore, by arranging so that the central portions are aligned on different measurement planes, the image sensor on the other side (5a for 5a, 5a for 5b)
There is also an advantage that reflected light from can be avoided.
Further, the light receiving angle θ of each sensor may be different.

FIG. 4 shows a third example of the embodiment of the transmissive elongated body defect detecting device according to the present invention. The parts corresponding to those in FIG. 1 described above are denoted by the same reference numerals.

In the transmissive long-body defect detection apparatus of this example, the light receiving surfaces 16a1 and 16b1 of the first and second light guide members 16a and 16b made of fiber fusion conduits or the like project the parallel light beam 3. On both sides of the axis 3a, the light receiving angle θ is provided from the position directly facing the light projecting axis 3a, and the central portions are arranged horizontally in the same measurement plane. The light receiving outputs of the first and second light guide members 16a and 16b are output to the output end 16 of the first and second light guide members 16a and 16b.
In the present example, a2 and 16b2 are arranged to face a common image sensor 5 to be input. Also in this example, the light receiving angle θ is set in the range of 30 ° to 60 °. Although not shown, other configurations are similar to those of the first example.

When the light receiving surfaces 16a1 and 16b1 of the light guide members 16a and 16b are arranged at a light receiving angle θ from the position directly facing the light projecting axis 3a, the light receiving surfaces 16a1 and 16b
The received light intensity on the side of the projection axis 3a of 16b1 is weakened, and the received light intensity on the side away from the projection axis 3a is strengthened, and the problem of the dynamic range can be solved as in the first example.

Also in this case, in the scattered light intensity distribution pattern 11 having a mountain shape obtained from the signal processing unit 6, the pattern change at the skirt becomes apparent, and the scattered light intensity distribution pattern 11 of the scattered light intensity distribution pattern 11 becomes It is possible to easily detect the dimming concave portion at the hem.

Further, by using the light guide members 16a and 16b,
If the received light output is input to the image sensor 5, there is an advantage that the image sensor 5 can be installed at any position and at any angle.

As in this example, the first and second light guide members 16
a and 16b together with the projection axis 3a of the parallel light beam 3 on both sides of different measurement planes with respect to the fiber axis direction, and their light receiving surfaces 16a1 and 16b1 from the position directly facing the projection axis 3a at the light receiving angle .theta. When each of them is arranged with the above, it is possible to surely receive both of the scattered light 4 scattered on both sides of the projection axis 3a.

Further, the first and second light guide members 16a, 16
Even if b is arranged on both sides of the projection axis 3a of the parallel light beam 3, there is an advantage that only one image sensor receives the outputs of the first and second light guide members 16a and 16b.

Also in this example, the light receiving angle θ is 30 ° to 60 °.
If the range is set to, the discrimination sensitivity evaluation value H / N exceeds 1, and it is possible to stably detect the mutation in the scattered light intensity distribution pattern 11 due to the cavity defect.

[0058]

In the light-transmitting elongated body defect detecting device according to the first aspect of the present invention, the image sensor is arranged with a light receiving angle θ from a position directly facing the light projection axis of the light beam.
The light receiving intensity on the light emitting axis side of the image sensor is weakened, and the light receiving intensity on the side remote from the light emitting axis is strengthened, which solves the problem of the dynamic range and is similar from the inside to the outside near the center of the detected part. Defects can be detected with signal sensitivity.

Further, according to the present invention, the pattern change at the skirt of the scattered light intensity distribution pattern forming a mountain shape becomes apparent, and the detection of the dimming concave portion at the skirt of the scattered light intensity distribution pattern is detected. Can be done easily.

In the transmissive long-body defect detecting device according to the second aspect, the image sensor is provided on both sides of the projection axis of the light beam with a light receiving angle θ from a position directly facing the projection axis. Since they are arranged, both the scattered light scattered on both sides of the projection axis can be reliably received.

In the transmissive long-body defect detecting device according to the third aspect, since the light receiving surface of the light guide member is arranged with a light receiving angle θ from a position directly facing the light projecting axis, The light receiving intensity on the light emitting surface side of the light receiving surface is weakened, and the light receiving intensity on the side away from the light emitting axis is strengthened, and the problem of the dynamic range can be solved.

Also in the present invention, the pattern change at the skirt of the scattered light intensity distribution pattern forming a mountain shape becomes apparent, and it is easy to detect the dimming concave portion at the skirt of the scattered light intensity distribution pattern. Can be done.

Further, when the light receiving output is input to the image sensor by using the light guide member, there is an advantage that the image sensor can be installed at an arbitrary position and at an arbitrary angle.

In the translucent elongated body defect detecting device according to the fourth aspect, the light guide members are disposed on both sides of the light projecting axis of the light beam, and the light receiving surfaces of the light receiving members are located at positions opposite to the light projecting axis. Since they are respectively arranged with θ, it is possible to reliably receive both of the scattered light scattered on both sides of the projection axis.

Further, even if the light guide members are arranged on both sides of the projection axis of the light beam, there is an advantage that only one image sensor receives the output of these light guide members.

In the transparent long-body defect detecting device according to the fifth aspect, since the light receiving angle θ is set in the range of 30 ° to 60 °, the discrimination sensitivity evaluation value H / N exceeds 1. Therefore, it is possible to stably detect the mutation in the scattered light intensity distribution pattern due to the cavity defect.

[Brief description of drawings]

FIG. 1 is a plan view showing a schematic configuration of a first example of an embodiment of a transparent long-body defect detecting device according to the present invention.

FIG. 2 is a characteristic diagram showing a relationship between a sensor installation angle and a discrimination sensitivity evaluation value H / N in the case of the configuration of the first example.

FIG. 3 is a side view showing a configuration of a main part of a second example of the embodiment of the transparent long-body defect detecting device according to the present invention.

FIG. 4 is a plan view showing a configuration of a main part of a third example of the embodiment of the transparent long-body defect detecting device according to the present invention.

FIG. 5 is a perspective view showing a schematic configuration of a conventional translucent long body defect detection device.

FIG. 6 is an explanatory diagram showing scattered light input to the image sensor of the translucent elongated body defect detection device shown in FIG. 5 and a scattered light intensity distribution pattern obtained based on the scattered light.

FIG. 7 is an explanatory diagram showing a relationship between parallel rays incident on an optical fiber and scattered light.

FIG. 8 is an explanatory diagram showing an example of a scattered light intensity distribution pattern when there is a cavity defect in the optical fiber.

9A and 9B are enlarged views of a Q portion in FIG. 8 in the case of the conventional example and the case of the present invention.

FIG. 10 is a characteristic diagram showing an example in which the discrimination sensitivity evaluation value H / N is plotted with respect to the sensor position coordinate x in the conventional example while changing the cross-sectional inner diameter of the cavity defect.

FIG. 11 is a characteristic diagram showing a relationship between sensor position coordinates x and light receiving intensity of the sensor when the light receiving angle of the sensor is changed.

FIG. 12 is an explanatory diagram showing a state of a dead zone when parallel rays are incident on an optical fiber.

[Explanation of symbols]

 1 Optical fiber base material 2 Optical fiber 2a Core 2b Center line 3 Parallel light beam 3a Projection axis 4 Forward scattered light 5 Image sensor 6 for receiving 6 Signal processing unit 7 Judgment unit 8 Monitor unit 9 Alarm unit 10 Recording unit 11 Scattered light intensity distribution Pattern 12, 12a Dead zone 13 Beam light source 14 Output beam 15 Beam shaper 16a, 16b First and second light guide members 16a1, 16b1 Light receiving surface 16a2, 16b2 Output end

Claims (5)

[Claims] 1. A light ray is projected from a direction intersecting with the translucent elongated body, scattered light from the translucent elongated body is received by an image sensor, and an output thereof is processed by a signal processing unit. In a transmissive long-body defect detection device for obtaining a scattered light intensity distribution pattern and determining a defect in the translucent long body from the scattered light intensity distribution pattern by a determination unit, the image sensor projects the light beam. A transparent long-body defect detecting device, which is arranged with a light receiving angle θ from a position directly facing the axis. 2. The transmission according to claim 1, wherein the image sensors are arranged on both sides of the projection axis with a light receiving angle θ from a position directly facing the projection axis. Optical long-body defect detection device. 3. A light beam is projected from a direction intersecting with the translucent elongated body, scattered light from the translucent elongated body is received by an image sensor, and the output thereof is processed by a signal processing unit. In a translucent long-body defect detection device for obtaining a scattered light intensity distribution pattern and determining a defect in the translucent long body from the scattered light intensity distribution pattern by a determination unit, a light-receiving surface of a light guide member is the light beam. Is arranged so as to have a light-receiving angle θ from a position directly facing the light-projecting axis, and the light-receiving output of the light-guiding member is input to the image sensor. Defect detection device. 4. The light guide member is arranged on both sides of the light projecting axis, with each light receiving surface having a light receiving angle θ from a position directly facing the light projecting axis. The transmissive elongated body defect detection device according to claim 3. 5. The transparent long-body defect detecting apparatus according to claim 1, 2, 3 or 4, wherein the light receiving angle θ is set in a range of 30 ° to 60 °.