KR900005642B1 - Checking machine of dia-meter - Google Patents

Abstract

A monochromatic light beam (2) from a source (1) passes at right angles through the fibre under test (3). A pick-up lens (4) directs the image to a television camera (5). The image is porcessed using an image processing unit (7), a monitor (8), a host computer (9) and a printer (10). The stand (6) holding the fibre allows it to be completely rotated about its optical axis. The light is diffracted by the outer edge of the optical fibre to form diffraction fringes in a position of the luminance distribution corresp. to the outer edge of the fibre. The accurate outer diameter of the fibre can be obtained by calculating the distance between diffraction fringes.

Description

Optical fiber structure and device and method of outer diameter measurement

1 is a block diagram for a microscope which is a conventional device for measuring the internal structure and outer diameter of an optical fiber.

2 is a luminance distribution diagram of a monitor image obtained by the microscope shown in FIG.

3 is a block diagram of an apparatus for testing the structure of an optical fiber through a method for testing the structure according to the present invention.

4 is a cross sectional view of an optical fiber showing the entry of optical fiber backlight;

FIG. 5 is a diagram showing a monitor image of the optical fiber backlight shown in FIG. 4 on a TV camera. FIG.

FIG. 6 is a luminance distribution diagram of the straight line aa 'of the monitor image shown in FIG. 5 when white light is used as the irradiation light.

7 is a schematic diagram illustrating the lens effect.

8 is a relationship diagram of a correction factor for the lens effect at the distance between the center of the optical fiber and the viewing surface.

9 is a graph in which measurement data of a coating diameter according to the present invention is written.

10 is a graph in which measurement data of a core diameter according to the present invention is written.

11 is a graph in which eccentricity measurements of optical fibers are written.

12 is a flowchart showing the steps of outer diameter measurement of the optical fiber.

Figure 13a is a block diagram of a measuring device for measuring the outer diameter of an optical fiber as the method of the present invention.

FIG. 13B is a luminance distribution diagram of the B-B line of the monitor image shown in FIG. 13A. FIG.

14 is a graph comparing the values measured using a contact precision measuring instrument with those measured under an outer diameter measuring process of an optical fiber.

Fig. 15 is a schematic block diagram of a position detection device embodying the method of the present invention.

16 is a luminance distribution diagram of the image shown in FIG.

FIG. 17 is a relation diagram of the distance between P ₁ and P _{2 shown in} FIG. 16 to the distance between the position of the observation surface and the center position of the optical fiber.

18 is a block diagram of an optical welder according to the present invention.

19 is a view showing a measuring device using a cylindrical lens according to the present invention.

20 is a view of another measuring device using a cylindrical lens according to the present invention applied to the optical welder shown in FIG.

21 is a schematic diagram of a fiber bundle consisting of a plurality of optical fibers and a plurality of LEDs optically connected to the LEDs.

22A to C are diagrams illustrating a distortion effect of the magnification of an imaging system when an optical fiber without an eccentricity is inspected.

Fig. 23 is a diagram illustrating the positional shift of the light source.

FIG. 24 is a diagram illustrating a change in illumination distribution pattern due to the displacement of the light source of FIG. 23. FIG.

* Explanation of symbols for main parts of the drawings

1: light source 3: optical fiber

7: image processing device 9: upper CPU

10: printer 18: objective lens

27 band filter 28 pinhole plate

46: monochromatic light 47: cylindrical lens

50: sheath 51: core

The present invention relates to a structure of an optical fiber and a device light method for measuring the outer diameter, and more particularly, to an apparatus and a method for measuring the optical fiber structure and the outer diameter without cutting the inspected optical fiber.

The prior art has been used in the apparatus and method for measuring the internal structure and outer diameter of an optical fiber by cutting the inspected optical fiber and observing its cross section through a television camera or a microscope.

FIG. 1 shows a conventional arrangement for measuring the internal structure and outer diameter of an optical fiber by a microscope, in which light from the light source 1 is first converged by the scanning lens 2, and at one end of the optical fiber 3 Cause incidence

Thus, the light converged from the light source 1 propagates through the core of the optical fiber 3. However, since light in the coating of the optical fiber is emitted and absorbed by the coating, it is thinned while propagating through the coating. As a result, the light emitted to be observed from the exit corner 33 emits only the light propagating through the core. Therefore, it is used as dimming for the core.

On the other hand, the light from the light source 10 is incident on the exit edge 3a absorbed by the translucent mirror 9 and reflected from the cover of the exit edge 3a to be used as coating dimming.

The image pickup tube 4 is positioned at the rear of the optical fiber 3 exit edge (observed edge) 3a so that the edge 3a of the optical fiber is observed by the lens 8. The imaging tube 4 is connected to a monitor TV, which can magnify and display an image (luminance distribution) of the observed edge 3a of the optical fiber 3. The luminance distribution of the A-A 'line on the monitor TV is as shown in FIG.

The apparatus of the conventional method as described above has the following absurdity.

In the first position, the tested optical fiber was cut, and the cut cross section had structural parameters observed by the conventional cutting method, so that the tested optical fiber was reliably damaged.

Secondly, since only the cross section of the optical fiber is observed in the cross section cut by the conventional method, it is impossible to measure the structural parameters continuously along the optical axis of the optical fiber. For this reason, the total length of the optical fiber is not measured accurately since a change in the structure parameters locally generated in part of the optical fiber is rarely used for the measurand.

Third, even if a high technical level is required for the cutting operation, scratches and breakages generated during the cutting operation of the optical fiber allow the inclination of the cross section, thereby reducing the accurate measurement amount. As a result, structural parameters are rarely measured accurately.

Fourthly, the cross section of the inclined optical fiber shows the angle of association relative to the optical axis, and in this case, the difference in the observed magnification between the upper end and the lower end (or left and right) of the monitor TV 5 is corrected for the absolute value. Makes it difficult.

Fifthly, as shown in FIG. 2, portions (i) and (iv), which are the light intensity distributions at the edges of the optical fiber, are not formed completely at the forming step due to the characteristics of the image pickup tube, and are inclined to some extent. As a result, the measurand should be set in advance with the threshold level to recognize (i) (iv). However, since the luminous intensity distributions (i) and (iv) parts depend on the characteristics of the device and the illumination light (γ-characteristics, etc.), it is impossible to accurately measure the inner and outer diameters of the optical fiber.

In order to solve the above-mentioned problems inherent in the related art, there is provided an apparatus and method for measuring the structure parameters of an optical fiber simply and accurately, and an object of the present invention is to optically detect the structure of an optical fiber by detecting light transmitted through the optical fiber. A method of measuring, comprising: an imaging system having an imaging lens and a television camera connected to an image processing apparatus such that an optical axis connecting the light source to the imaging system is perpendicular to the tested optical fiber and passes through the center of the optical fiber; Adjusting the light source, rotating the light source and the imaging system or rotating the optical fiber around the optical axis in such a manner that the optical side connecting the light source to the imaging system is perpendicular to the axis of the optical fiber and passes through the measurement point of the optical fiber; The relative position of the sheath-core boundary and the outer sheath edge of the optical fiber at at least two rotation angles in The same steps as described above, correct the lens effect of the basic position data of the observation surface or the luminance distribution on the observation surface, and since the true eccentricity of the coating and the core diameter of the optical fiber is obtained at one or more measured angles, Obtaining the true position of the core-cladding boundary, inserting a sine wave function into the eccentricity, and adding the average process to the sheath and core diameter, the eccentricity of the sheath and core diameter and the structural parameters of the optical fiber. The non-circular shape of the coating which separates is obtained.

Another object of the present invention is to provide a method for optically measuring the outer diameter of an optical fiber by detecting diffracted light from an outer edge of the optical fiber, the method being parallel to the flow of monochromatic light, in a direction perpendicular to the optical axis of the optical fiber. Where the monochromatic light is irradiated on the side of the optical fiber, and the image obtained by irradiating the monochromatic light is projected and enlarged, the luminance distribution of the projected and enlarged image is measured, and the position corresponding to the outer edge of the optical fiber is precisely connected to obtain the optical fiber. Computing the distance between the diffraction stripes appearing in.

It is still another object of the present invention to provide an apparatus for optically testing the structure of an optical fiber, the apparatus comprising an optical system comprising a light source for irradiating sidewalls of the optical fiber with observation light and an imaging system for detecting observation light across the optical fiber. The measuring means and the optical fiber mounting member for mounting the optical fiber so as to be able to rotate relative to one of the optical fiber mounting member and the other of the optical measuring means while the axis of the optical fiber and the optical axis of the optical measuring means are perpendicular to each other.

The invention will be described in more detail hereinafter with reference to the accompanying drawings.

3 is a block diagram of an apparatus for inspecting an optical fiber structure through a method for inspecting a structure according to the present invention. Fig. 3 is a fiber setting with a light source 1, an inspected optical fiber 3, an imaging lens 4, a television camera 5 (TV camera, and a device for rotating the optical fiber 3 around an axis). An array of the stand 6, the image processing apparatus 7, the TV monitor 8, the upper CPU 9, and the printer 10 is shown: a light source 1, an optical fiber 3, and an imaging lens The optical axis 2 connecting the 4 and the TV camera 5 is arranged at a position perpendicular to the axis of the optical fiber 3.

4 is a cross-sectional view of an optical fiber showing the propagation of light across the optical fiber when light is incident on the sidewall of the optical fiber. Light incident on the sidewalls of the optical fiber is refracted by the pivot and penetrates the sheath. Some of the light propagating through the sheath is refracted by the core with a higher refractive index than the sheath and passes through the core. Thus, the light passing through the sheath and core is monitored by the TV camera.

In FIG. 4, the parts shown in B and C are shaded areas of the coating and the core through which light does not pass.

5 shows a monitor image of light traversing an optical fiber on a TV camera.

When monochromatic light is used as the incident light on the optical fiber, the light is diffracted by the outer edge of the optical fiber to form a diffraction stripe at the position of the luminance distribution corresponding to the outer edge of the optical fiber. The diffraction stripes thus formed are denoted by D as shown in FIG. The exact outer diameter of the optical fiber is obtained by calculating the distance between the diffraction stripes.

In the case where the optical fiber is shown at a given angle, definite structural parameters such as coating and core diameter and eccentricity can be obtained by the process data of the luminance distribution of the monitor image as shown in FIG.

When white light is used as incident light, diffraction stripes are not formed and therefore do not appear in the TV camera. FIG. 6 shows the luminance distribution on the line aa 'of the monitor image as shown in FIG. 5 when white light is used.

In Fig. 6, the positions P ₁ and P ₂ of the outer coating edges are obtained using the fixed slice level, and the coating center position M ₁ is obtained as the average point between P ₁ and P ₂ . The positions Q ₁ , Q ₂ on the core-coated boundary and the core center position M ₂ are obtained by processing luminance data between R ₁ and R ₂ of the luminance distribution. In this case, the eccentricity is distinguished by the difference between M ₁ and M ₂ . Furthermore, the positions Q ₁ , Q ₂ on the core-covered boundary and the core center position M ₂ vary depending on the position of the viewing plane, ie the relative position of the focal point (plane) of the imaging system due to the lens effect on the data of the optical fiber viewing plane. Becomes an optical fiber and it is necessary to correct the lens effect as described above.

7 shows a schematic diagram illustrating the lens effect. In Fig. 7, O, P and Z represent the radius of the central optical fiber of the optical fiber (cover) and the distance between the center of the optical fiber and the observation plane, respectively.

Since the focal position of the imaging system moves toward the center O, the monitor image of the TV camera is gradually enlarged. On the other hand, the monitor image is gradually reduced by moving the focus position toward the TV camera. Therefore, the observed luminance distribution changes with the distance Z. As a result, true structural parameters such as eccentricity, coating and core diameter of the optical fiber are not obtained accurately.

8 shows the relationship between the distance Z and the correction coefficient for the lens effect. If the above relationship is obtained before the measurement of the structural parameters of the optical fiber, the correction of the luminance distribution on the observation plane lying at any observation angle and position can predict the relationship between the position of the observation plane Z and the correction coefficient.

에 의해 얻어지는 명암비율(t)을 기초로 하여 보정된다. 예를 들면, 관측된 모든 관측면의 휘도분포 각각은 관측면 위치의 각각이 미리 조절된 후 측정되어서, 관측면은 위하여 얻어진 명암비율은 서로가 일정하게 같다.Another way to correct the lens effect is

Correction is made based on the contrast ratio t obtained by For example, each of the luminance distributions of all observed observation planes is measured after each of the observation plane positions is pre-adjusted, so that the contrast ratios obtained for the observation planes are constantly equal to each other.

9 to 11 show measurement results of eccentricity, coating and core diameter of a single mode optical fiber using the measuring device of FIG. 3 when the optical fiber is rotated 30 degrees by each time. In this measurement, eccentricity means the distance between the sheath and the core center.

9 shows the measured diameter of the coating. The average value of the coating diameters measured at each observation angle is the coating diameter of the optical fiber to be inspected. Further, at each observation angle, the distance δ between the maximum value and the minimum value of the cover diameter is divided by the average cover diameter to obtain the specific circularity ratio δ / D × 100 of the cover.

10 shows the measured core diameter. The average core diameter measured at each observation angle becomes the core diameter of the optical fiber to be inspected.

11 shows the measured eccentricity, and the result obtained by fitting the sine wave function to the eccentricity measured at each observation angle indicates a solid line. The amplitude A of the sine wave function becomes the eccentricity of the optical fiber, but the initial phase is applied as the direction angle θ of the optical fiber eccentricity.

The following table shows the reproducibility of the measurements obtained from the measuring device of FIG. 3 compared to those obtained through conventional methods. As used herein, the term reproducibility means that the dispersion of the measurements is very small. The reproducibility of the measured values is expressed as standard deviation of 20 repetitions. As is apparent from the following table in each item of coating diameter, core diameter, core / coating eccentricity and specific circularity of coating, the present invention shows the smaller standard difference of measured data by repeating the measurement, and the conventional method A clear experimental result is obtained by comparison with that obtained with.

As described above, the embodiments relate to the case where the structural parameters are obtained using light transmitted through the optical fiber. However, if a substantially parallel monochromatic light is used as incident light on the optical fiber, a diffraction pattern appears on the monitor image. By using the diffraction pattern, the outer diameter of the optical fiber and the position of the viewing surface can be measured accurately. In this case, the monochromatic light not only produces a diffraction pattern but also has an effect of producing a clear monitor image of an optical fiber.

The following description is about the outer diameter of the optical fiber using the diffraction pattern as described above.

12 is a flowchart showing the step of measuring the outer diameter of the optical fiber. 13A is a block diagram of a measuring device for measuring the outer diameter of an optical fiber as an application of the present invention. Fig. 13B shows the luminance distribution on the lines B to B 'of the diffractive image and the transmission image of monochromatic light.

With reference to Fig. 13B, a measuring apparatus for measuring the outer diameter of the optical fiber will be described as an application of the present invention.

Reference characteristics have been given for the components, and description thereof will be omitted. By arranging the light source 16 for detecting monochromatic light in a direction perpendicular to the optical axis of the optical fiber 13 to be inspected, the light beam is directed straight to the side wall of the optical fiber 13.

A light emitting diode (LED) having a high monochromatic characteristic can be used for the light source 16 and the lens 12, and the collimator lens can be used to parallelize the monochromatic light from the light source 16 and the optical fiber 13. Installed between). The light source 16 is thus arranged at the focal point of the lens 12. The imaging tube 14 is disposed in a position facing the side darkened by the optical fiber 13 together with the objective lens 18 between the optical fiber 13 and the imaging tube 14, and the enlarged diffraction image of the optical fiber 13 is located therein. Projected. The imaging tube 14 is connected to a monitor TV which shows an enlarged diffraction image. The observed and indicated planes are arranged to be between the plane P ₀ across the center of the optical fiber 13 and the objective lens 18. The light source 16, the lens 12, and the imaging tube 14 are arranged on the same straight line, but the optical axis of the optical fiber 13 is set vertically.

The inspection method of the optical fiber will be described with reference to FIGS. 12 and 13.

In the first step shown in FIG. 12, the monochromatic light emitted from the light source 16 is paralleled by the lens 12 and irradiated to the sidewall of the optical fiber 13. Therefore, the optical axis of parallel monochromatic light traverses perpendicular to the optical fiber 13.

In the second step, the image on the observed surface P ₁ of the optical fiber 13 resulting from the irradiation of the parallel monochromatic light is magnified by the objective lens 18 and projected onto the imaging tube 14. Since the monitor TV is connected to the image pickup tube 14, the image of the optical fiber enlarged in the third step is observed by the monitor TV 15. The magnification of the image is performed by the objective lens 18 of the image pickup tube 14, and an appropriate magnification is selected depending on the optical fiber size observed.

In the fourth step, the luminance distribution is obtained along the line B-B 'of the image of the optical fiber 13 appearing on the monitor TV 15. The arrangement provided was made as the case of this example, and the distribution is shown as shown in Figure 13b.

The important point is that since monochromatic light with high collimation with narrow spectral width is used, the diffraction pattern shown by (i) and (ii) appears in the portion corresponding to the outer edge of the optical fiber. Based on the luminance distribution, the distance X between the first peaks (iii) and (iv) was obtained. The relationship of X to the outer diameter Y of the optical fiber is linear and is expressed by the following equation of the first order.

In this case, a and b indicate the amount depending on the magnification of the observation system and the distance ΔX between P ₀ across the center of the optical fiber 13 and the observed P ₁ . The outer diameter Y of the optical fiber 13 can be obtained from the distance X between diffraction patterns in the fifth step by setting ΔX as a constant when the measurement is performed and obtaining a and b in advance.

Fig. 14 shows a comparison between the value measured under the optical fiber outer diameter measuring method and the value measured using a contact type precision measuring instrument.

In this experiment, various kinds of quartz fibers with an outer diameter of about 125 μm were sampled and used together with an imaging tube having a wavelength of 7.3 μm as a light source and an output of 10 μm and an objective lens with 60 magnification as a detector. As X and Y values, the average value of 12 data resulting from the measurement of the optical fiber every 30 degrees is used.

As is apparent from FIG. 14, the linear relationship between the quantities X and Y, i.e., the values measured according to the method of the present invention and the values measured using a precision measuring instrument, are very consistent.

Since the calibrating of the imaging tube was made using a microscale, a = 1 and b = 0 in Equation (1), and the reproducibility (standard deviation at N = 10) of the outer diameter measurement of the same optical fiber is the method according to the present invention. Became 0.01 μm.

Therefore, the outer diameter of the optical fiber can be measured accurately and reliably by the above method.

In addition, by moving the position of the luminance distribution on the monitor TV from the line B-B 'to the C-C', or by moving the optical fiber in the direction with respect to the optical axis of the optical fiber, the outer diameter of the outer end can be made easy. .

The following description is for the precise measurement of the position of the observation plane, using diffraction patterns.

Fig. 15 is a schematic block diagram showing the position of the detection apparatus for implementing the present invention. The apparatus shown in FIG. 15 is equipped with a light source 21 and a light emitting diode (LED) capable of emitting a white light source such as a halogen lamp or a high luminance light beam as a light source. The light rays emitted from the light source 21 are incident on the bandpass filter 27 for the passage of light rays of a specific wavelength. The light rays passing through the bandpass filter 27 pass through the small holes provided in the pinhole plate 28 and the optical fiber ( 22) Exclude the edge side. The side image of the optical fiber 22 is picked up by the TV camera 24 so that the optical axis connecting the light source 21 and the camera 24 is perpendicular to the perspective surface including the central axis of the optical fiber 22. Is set. The output of the TV camera 24 is connected to the input of the camera controller 25. The output of the camera controller 25 is connected to the input of the monitor TV 26.

Light rays emitted from a white light source 21 such as a halogen lamp pass through the bandpass filter 27 and pass through a small hole of the pinhole plate 28 that changes to a point where a corresponding light is irradiated in proportion to the monochromatic light. When using LED as a light source, it is not necessary to provide the pinhole plate 28 which has the bandpass filter 27 and a small hole.

While the point of irradiation of the rays is used to illuminate the side wall of the optical fiber 22 at the end, the TV camera 24 is used to image the side of the optical fiber 22. The image picked up in this way is displayed on the monitor TV 26 via the camera control device 25. The optical fiber is supported by the supporting means (not shown) in such a manner as to set the central axis of the supporting means perpendicular to the luminance measurement line AA 'on the TV monitor 26.

According to the present invention, an optical fiber having an outer diameter of 125 µm is generated by receiving a light beam from a set of light emitting diodes separated by 30 cm in order to observe a side view of the optical fiber by an ITV camera equipped with a 60-fold objective lens. FIG. 16 shows the luminance distribution of the image shown in FIG. In the luminance distribution of FIG. 16, the vertical axis represents luminance, while the horizontal axis represents position along the luminance measurement line AA ', and the origin corresponds to the upper end of the luminance measurement line AA'.

Such a peak position of the diffraction pattern is _{P 1, P 2, P 3} , ... , P _n and P ₁ ^* , P ₂ ^* , P ₃ ^* ,... , Is represented by P _n ^*, represented by P ₁ and P _2, P ₂ and _{P 3, ‥‥, P n-} 1 and the distance _{Z 1, Z 2, ‥‥‥,} Z n-1 , respectively between P _n And P ₁ ^* and P ₂ ^* , P ₂ ^* and P ₃ ^* ,. , The distance between P _n-1 and P _n ^* is Z ₁ ^* , Z ₂ ^* ,. , Z ^* _n-1 , Z ₁ , Z ₂ , ..., Z _n-1 , and Z ₁ ^* , Z _n , Z ₃ ,. , Z ^* _n-1 depends on the distance between the position P ₁ ^* of the observation plane and the center position P ₁ of the cylindrical object under test. Thus, if Z ₁ , Z ₂ ..., Z _n-1 and Z ₁ ^* , Z ₂ ^* ,. When the relationship between the positions of, Z _n-1 is obtained in advance, the distance δ is Z ₁ , Z ₂ .................. Z _n-1 and Z ₁ ^* , Z ₂ ^* ,. , Can be calculated from Z _n-1 . That is, the position of the observed plane can be detected precisely.

The relationship of the Z ₁ (distance between P ₁ and P ₂ ) of the diffraction pattern to be surely measured with respect to the distance δ can be measured and is shown in FIG. 17. As shown in FIG. 17, the relationship between Z ₁ and the distance δ is single, and its value, that is, the position of the observed face, can be detected accurately from the measurement of Z ₁ .

In this embodiment, the optical fiber placed on the precision stage is moved in the optical axis direction connecting the light source and the TV camera, and the distance δ is measured by reading the amount shifted from the linear scale which can be read at 0.1 μm.

This embodiment accurately measures the position of the observation plane by using diffraction patterns of monochromatic light paralleled from the light source. However, the present invention can apply not only monochromatic light in parallel, but also light and scattered light of an incandescent lamp.

When incandescent light rays or diffused light are used, the monitor image corresponding to the outer edge of the optical fiber becomes sharpest when the viewing surface is located at the center of the optical fiber. The viewing surface is pre-positioned at the position moved from the position by the use of the precision length measuring device for which the monitor image is sharpest and which determines the position of the viewing surface. When the method of determining the position of the observation surface according to the present invention is used for an optical fiber welder, more effect is produced for the optical fiber welder.

18 shows a block diagram of an optical fiber welder. In Fig. 18, a lens 31b for collimating (parallel rays of light) emitted from the light source 31a is disposed behind the light source 31a. The lens 31b may change into a shape having the shape of the light source 31a, and the distance traverses the light source 31a. In the case of a convex lens, the point of the light source may be located at the focal point of the lens front. However, such a lens can be omitted if the plane of the light source is considered instead of the point of the light source in view of the size of the object to which the light source is illuminated. Importantly, the luminous flux is collimated between the objects 33 and 34 being tested. The light collimated from the lens 31b is irradiated to the connection of the optical fibers 33 and 34 as the object to be tested, and then its luminance distribution is determined by an image analyzer installed behind the objects 33 and 34 to be tested. 35). The image of the object is taken by the image observing member 35a via the objective lens and observed by the monitor TV 35b. The luminance distribution between A-A 'of the image 33' of the object 33 and the B-B 'of the image 34' of the object 34 on the monitor TV 35b controls the controller. By comparison by the CPU, the relative position of the object 33 relative to the object 34 can be known. Usually, the axes of either object are adjusted to make the axes of both objects coincide with each other. Especially when the optical fibers are in contact, the above operation is useful for coinciding the core centers of both optical fibers. In the case, an important point must be attached in the scanning direction of the luminance distributions A-A 'and B-B', and the scanning of the luminance distribution is made perpendicular to the axis of the collimated light beam and the object.

When an optical fiber is observed from the side wall, the lens effect on the surface of the optical fiber generally creates an apparent eccentricity (apparent eccentric distance between the center of the core and the center of the outer diameter of the optical fiber) that is different from the real one. On the basis of the calculations taken from the measured apparent eccentricity, a correction factor dependent on the position of the viewing plane on the side of the optical fiber must be obtained in advance in order to obtain the true eccentricity, ie to determine the true center core position. . In other words, it is necessary to precisely determine the position of the observation plane in order to determine the true eccentricity rate, that is, to precisely contact the optical fiber.

In addition, by using the methods for determining the position of the observation plane as the above-described method, the accuracy of coinciding the axes during the process of contacting the optical fiber can be improved by the short time required for coinciding the axes. In addition, the accuracy of matching the improved axis reduces the connection loss of the optical fiber and increases the reliability of the optical communication.

In the above-described embodiment, the observation light from the light source is directly or through the aiming lens used on the sidewall of the optical fiber. However, the cylindrical lens is disposed between the optical fiber and the light source in order to increase the amount of light detected and to improve the signal-to-noise ratio and to increase the detection ratio.

19 shows a measuring mechanism equipped with a cylindrical lens to which, for example, an outer diameter measuring method of an optical fiber is applied. Cylindrical lenses may be used to collect light in a fixed direction so that scanning of the luminance distribution of the image appearing on the monitor TV may not be blocked. In such a case, for the measurement of the outer diameter of the optical fiber, since the scanning direction is limited perpendicular to the optical axis of the optical fiber, the cylindrical lens 47 is mounted in the same way as to collect light on the optical axis of the optical fiber. That is, as shown in FIG. 19, the longitudinal axis (vertical direction) in which the radius of curvature of the cylindrical lens is infinite is placed perpendicular to the optical axis of the optical fiber.

In the measurement process, high luminance data can be obtained without increasing the output of the monochromatic light 46 and consequently the accuracy of the measured outer diameter can be improved along with the reliability.

FIG. 20 shows another measuring instrument in which a cylindrical lens is used in an optical welder as shown in FIG.

The cylindrical lens 52 is arranged so that its longitudinal direction is perpendicular to the aimed light and the axial direction of the object to be tested, so that the aimed light is collected in the axial direction. This embodiment of the present invention is not limited to the use of a cylindrical lens as illustrated, as long as it can collect light in the aforementioned direction.

The core eccentricity of an outer diameter 125 μm single mode fiber is measured using the present invention and conventional luminance distribution detection method. The refresh rate of the measured eccentricity and the time required to obtain the data were compared with the test data type shown in the following table.

로 단축되었다.Depending on the light source, the LED with a wavelength of 0.73 μm and the optical fiber tested were positioned at the focal point of the cylindrical lens. As is apparent from the above table, the luminance detecting device as shown in FIG. 20 is compared with that shown in FIG. 18 using only the aiming light source, so that the time required for obtaining the data does not have to decrease the measurement accuracy.

Shortened to.

As described above, according to the present embodiment, the illumination on the object having the axis can converge with great brightness in the direction in which the scanning of the luminance distribution is not blocked, so that the structural parameters of each corner portion are the objects having the axes. This makes it possible to accurately detect the axes, in particular of the optical fibers. Cylindrical lenses also have the same effect on measuring devices that deform ordinary light, such as white light, from the aimed monochromatic light.

In the above embodiment, the TV camera is mounted on the imaging system, whereby the monitor image (luminance distribution) becomes useful for determining the structural parameters of the optical fiber. However, the present invention is not limited thereto.

CCD line sensors may be used in place of TV cameras. To increase the resolution of the imaging system and to the average of the measured data obtained in the longitudinal direction of the optical fiber, the CCD line sensor may be scanned dynamically in a direction perpendicular to the axis of the sensor.

In addition, a plurality of CCD line sensors are arranged in the longitudinal direction of the optical fiber to simultaneously measure the luminance distributions in the respective line sensors, calculate the respective eccentricities obtained by the respective line sensors, calculate their average value, The average eccentricity at the associated viewing angle is thus determined.

In the above embodiments, a fiber bundle composed of a plurality of LEDs and a plurality of optical fibers optically connected to the LEDs shown in FIG. 21 is used as a light source to make the brightness of the observation light harder and to increase the degree of freedom of the position of the light source. Let's do it. Also, in order to clean the measurement surroundings and prevent adverse effects such as dust, clean air may be sent to at least one space in which the light source, the optical fiber to be tested, and the objective lens are disposed.

As described above, in the structure and outer diameter measuring apparatus and method of the optical fiber according to the present invention, the optical fiber to be tested does not need to be cut because it is observed from its sidewall and its cross-sectional state does not affect the measured value. Therefore, the structure of the optical fiber can be tested accurately without being simply damaged.

In addition, since the optical fiber or optical axis of the imaging system is rotated for measurement purposes, the cover and core diameters and the eccentricity in the circumferential direction can be known, and the data are processed so that the real skin and core diameters, the cover eccentricity and non-circularity The rate can also be measured accurately. The method of harmonizing the sinusoidal function with respect to the eccentricity makes it possible to extract only the true eccentric component of the eccentricity measured at each rotation angle, so that the optical fiber is hardly subject to eccentricity or mechanical measurement error.

When the magnification of the imaging system differs in the vertical direction, for example, the measured eccentricity is influenced by the knitting of the magnification in the conventional test method as shown in Fig. 22A, and the optical fiber in which the amount corresponding to the above-described deformation is eventually tested. It is measured as the eccentricity rate for. 22A illustrates the sheath 50, the core 51, the center 52 common to the real core, the real sheath and the measured core and the center 53 of the sheath measured. In the method for investigating the structure of an optical fiber according to the present invention, the eccentricity of the optical fiber is obtained from the change of the eccentricity measured in the circumferential direction of the optical fiber and is hardly affected by the deformation. 22B and 22C show the results of deformation of the magnification of the imaging system at measurement angles of 0 ° and 180 ° as an example of testing an optical fiber without an eccentricity. In the test method of the present invention, the eccentricity of the optical fiber to be tested is determined to be zero because the measured eccentricity does not change even when the measurement angle is irradiated, and the presence of the deformation of the magnification of the imaging system is the eccentricity of the optical fiber in the circumferential direction. It will not affect the change, and its amplitude becomes zero when the sinusoidal function is harmonized. As a result, the eccentricity of the optical fiber tested is measured as zero.

When the optical axis connecting the light source and the imaging system are not perpendicular to the axis of the optical fiber, for example, when the position of the light source 63 changes from A to B as shown in FIG. 23, the optical fiber 64 and the objective lens ( The pattern of the luminance distribution observed by the television camera 66 via 65 changes as in FIG. There are luminance distributions in which the light source 63 of FIG. 23 is not moved at point A and luminance distributions in which the light source 63 is moved to point B, respectively. The structural parameters that can be obtained from the luminance distribution are affected by the moved point of the light source. In the apparatus for investigating the structure of the optical fiber according to the method of the present invention, the parameters are not affected by the movement of the light source because the optical axis connected to the light source and the imaging system lies perpendicular to the axis of the optical fiber.

In addition, the position detection method and apparatus according to the present invention can accurately detect the position of the observation plane of the optical fiber to be irradiated by measuring the distance between the flower pattern formed on the outer edge of the optical fiber using a point light source for actually emitting monochromatic light. have. As a result, the center point of the core is accurately measured by observing the side of the optical fiber. The position detection method according to the present invention can thus be useful in a wide range of uses, such as optical fiber welders.

Claims (17)

Optical measuring means comprising a light source for irradiating the sidewall of the optical fiber with observation light and an imaging system for detecting the observation light traversing the optical fiber, and while the axis of the optical fiber and the optical axis of the optical measuring means are perpendicular to each other And an optical fiber mounting member for mounting the optical fiber, wherein one of the optical fiber mounting member and the optical measuring means can rotate relative to the other. The method of claim 1. And the imaging system comprises a television camera for monitoring the image of the observation light and an image processing device for analyzing the luminance distribution of the image. The optical fiber structure measuring apparatus according to claim 1, wherein the optical measuring means comprises optical aiming means disposed between the light source and the optical fiber to aim the observation light at the light source. The structure measuring apparatus according to claim 1, wherein the observation light is made of monochromatic light. The optical fiber structure measuring apparatus according to claim 1, wherein the observation light comprises scattered light. The optical fiber structure measuring apparatus according to claim 1, wherein the optical measuring means comprises a cylindrical lens for converging the observation light in the axial direction of the optical fiber. The optical fiber structure measuring apparatus according to claim 1, wherein the imaging system comprises a charge coupled device (CCD) line sensor which is scanned dynamically in a direction perpendicular to the sensor axis. The apparatus of claim 1, wherein the light source comprises a fiber bundle having a plurality of light emitting diodes (LEDs) and a plurality of optical fibers optically connected to the LEDs. 4. The optical fiber structure measuring apparatus according to claim 3, wherein the light aiming means is composed of collimated lenses. The optical fiber structure measuring apparatus according to claim 4, wherein the light source comprises a light emitting diode (LED). Arranging optical measuring means comprising a light source for generating light, an image pickup system for detecting the light in such a manner that the axis of the optical fiber and the axis of the optical measuring means are perpendicular to each other; Irradiating with light in a direction perpendicular to the axis of the optical fiber; Measuring a luminance distribution of the light traversing the optical fiber; Correcting a lens effect on the luminance distribution of the light based on position data of an observation plane; And calculating structural parameters such as the eccentricity of the optical fiber, the coating diameter, the core diameter, the non-circularity of the coating, and the like based on the luminance distribution, which is also subject to the correction of the lens effect. Way. 12. The method of claim 11, further comprising: rotating one of the optical fiber and the optical detection means relative to the other while the axis and the optical axis lie perpendicular to each other; Measuring a luminance distribution subject to the correction of the lens effect over the observed viewing angle; And calculating structural parameters such as eccentricity, covering diameter, core diameter, non-circularity of skin, and the like at the measurement angle. Arranging an optical detecting means comprising a monochromatic light source for generating monochromatic light, an aiming means for aiming the monochromatic light, and an imaging system for detecting the monochromatic light in such a manner that the axis of the optical fiber and the optical axis of the optical measuring means are perpendicular to each other; Steps; Aiming the monochromatic light; Irradiating sidewalls of the optical fiber with the aimed monochromatic light in a direction perpendicular to the axis of the optical fiber; The luminance distribution has a diffraction pattern appearing at a position corresponding to the outer edge of the optical fiber, detecting the luminance distribution of the aimed monochromatic light across the optical fiber, and the outer diameter of the optical fiber and the position of the observation plane of the optical fiber. Comprising the step of calculating the distance between the diffraction pattern in order to obtain accurately, the outer diameter of the optical fiber and the position of the observation plane position measuring method. The method according to claim 11 or 13, wherein the method comprises converging the light of the light source in the axial direction of the optical fiber before irradiating the optical fiber with the light. How to measure the position of the plane. 14. The method according to claim 11 or 13, wherein the imaging system comprises the CCD line sensor which is scanned dynamically in the axial direction of the CCD line sensor or the position measurement of the outer diameter and the observation plane. A light source for generating diffused light and an imaging system for detecting diffused light arrange optical measuring means in such a manner that the axis of the optical fiber and the optical axis of the optical measuring means are perpendicular to each other, and the sidewall of the optical fiber is the optical fiber. Irradiates in a direction perpendicular to the axis of the optical fiber, focuses the imaging system at the center of the optical fiber, moves one of the imaging system and the optical fiber in the optical axis direction with respect to the other, and moves the movement distance in a precise range And measuring the position of the observation plane of the optical fiber accordingly by measuring with a measuring device of the optical fiber. 17. The structure of any of claims 1, 5, and 16, wherein the method further comprises the step of sending at least clean air to the location where the optical fiber and the optical measuring means are arranged. Method of positioning inspection or external light observation plane.

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