CA1295476C - Method and apparatus of measuring outer diameter and structure of optical fiber - Google Patents
Method and apparatus of measuring outer diameter and structure of optical fiberInfo
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- CA1295476C CA1295476C CA000543994A CA543994A CA1295476C CA 1295476 C CA1295476 C CA 1295476C CA 000543994 A CA000543994 A CA 000543994A CA 543994 A CA543994 A CA 543994A CA 1295476 C CA1295476 C CA 1295476C
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Abstract
ABSTRACT OF THE INVENTION
A method and apparatus for examing the structure of an optical fiber such as eccentricity, clad and core diameters, nonroundness of clad and so on. The structure of the optical fiber can be accurately determined by irradiating the side wall of the optical fiber with a light such as a white light, a monochromatic light or the like in the direction perpendicular to the axis of the optical fiber, detecting an image of the, light transmitted through the optical fiber, and/or diffraction fringes formed by lights diffracted by the outer edge of the optical fiber to obtain a luminance distribution of the light traversing the optical fiber, and calculating the luminance distribution thereby to obtain accurate structural parameters of the optical fiber.
A method and apparatus for examing the structure of an optical fiber such as eccentricity, clad and core diameters, nonroundness of clad and so on. The structure of the optical fiber can be accurately determined by irradiating the side wall of the optical fiber with a light such as a white light, a monochromatic light or the like in the direction perpendicular to the axis of the optical fiber, detecting an image of the, light transmitted through the optical fiber, and/or diffraction fringes formed by lights diffracted by the outer edge of the optical fiber to obtain a luminance distribution of the light traversing the optical fiber, and calculating the luminance distribution thereby to obtain accurate structural parameters of the optical fiber.
Description
1~5476 ~ 1 --The present invention relates to a method and an apparatus of measuring the outer diameter and the structure of an optical fiber, and more particularly to a method and an apparatus of measuring the outer diameter and structure of an optical fiber without cutting the optical fiber being examined.
BRIEF DESCRIPTOIN OF THE DRAWINGS
Fig. 1 is a block diagram for a microscope of a conventional instrument for measuring the outer diamenter and the internal structure of an optical fiber;
Fig. 2 shows a luminace distribution of a monitored image obtained by the microscope as shown in Fig. l;
Fig. 3 is a blcok diagram of an apparatus for examining the structure of an optical fiber through the method of examining the structure thereof according to this invention;
Fig. 4 is a cross-sectional view of an optical fiber to show the advance of ligt traversing the optical fiber;
Fig. 5 shows a monitored image of the light traversing the optical fiber as shown in Fig. 4 on a TV
camera;
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12~?5~76 Fig. 6 shows a luminace distribution on a straight line aa~ of the monitored image as shown in Fig.5 in a case where a white light is used as an incident light;
Fig. 7 shows a schematic diagram for explaining the lens effect;
Fig. 8 shows the relationship o~ correction efficient for the lens effect with a distancè between the center of an optical fiber and an observing plane;
Fig. 9 shows a graph in which measured data of a clad diameter according to this invention are plotted;
Fig. 10 shows a graph in which measured data of a core diameter according to this invention are plotted;
Fig. 11 shows a graph in which measured eccentricities of an optical fiber are plotted;
Fig. 12 is a flowchart showing the steps of measuring the outer diameter of an optical fiber;
Fig. 13(A) is a block diagram of a mesuring instrument for measuring the outer diameter of an optical fiber as an application of the method of the present invention, and Fig. 13~B) is a luminance distribution on a line B-B' of the monitored image as shown in Fig. 13~A);
Fig. 14 is a graph showing a comparison between teh values measured under the process of measuring the outer diameter of an optical fiber and those measured using a contact type precision measuring instrument;
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12~5476 1 Fig. 15 is a schematic block diagram of a position detecting apparatus embodying the method of this invention;
Fig. 16 shows a luminace distribution of the image as shown in Fig. 15;
Fig. 17 shows a relationship of a distance between Pl and P2 as shown in Fig. 16 to the distance between the position of the observing plane and the center position of an optical fiber;
Fig. 18 is a block diagram of an optical fusion welding machine according to this invention;
Fig. 19 shows a measuring instrument employing a cylindrical lens according to this invention;
Fig. 20 shows another measuring instrument in which a cylindrical lens according to this invention is applied to the optical fusion welding machine as shown in Fig. 18;
Fig. 21 is a schematic diagram of a bundle fiber comprising plural LEDs and plural optical fibers optically connected to the LEDs;
Fig. 22~A) through 22(C) are diagram illustrating the effect of distortion of the magnifying power of pickup system when an optical fiber free from eccentricity is examined;
.... l .
lZ~5476 1 Fig. 23 is a diagram illustriating the position sh;fting of a light source;
Fig. 24 is a diagram illustrating changes in distribution patterns of illumination due to the position shifting of the light source of Fig. ~3.
Conventionally, there has been employed a method and apparatus of measuring the outer diameter and the internal structure of an optical fiber by cutting the optical fiber being examined and by observing the cross o section thereof through a microscope or television camera.
Fig. 1 shows a conventional arrangement for measuring the outer diameter and the internal structure of an optical fiber by means of a microscope, wherein light from a light source 1 is first converged by an injection lens 2 and caused to be incident on an end of an optical fiber 3.
The light from the light source 1 thus converged is propagated through the core of the optical fiber 3.
However, the light in a clad of the optical fibér is attenuated during the propagation thereof through the clad because it is radiated from and absorbed by the clad. As a result, a light emitted from an exit edge 3a to be observed originates in only the light propagating through the core, and therefore is used as an illuminating light for the core.
,, 129~ 6 l On the other hand, as a light from a light source 10 is incident on the exit edge 3a being observed by a half mirror 9 and is reflected from the clad of the exit edge 3a, it is used as an illuminating light for the clad.
In the rear of the exit edge (edge being observed) 3a of the optical fiber 3, a pickup tube 4 is located so that the edge 3a of the optical fiber can be observed with a lens 8. The pickup tube 4 is connected to a monitor TV
5, which is capable of magnifying and displaying an image (light-intensity distribution) of the edge 3a being observed of the optical fiber 3. The luminance distribution on a line A-A' on the monitor TV becomes such as shown in Fig. 2.
A conventional method apparatus as described above has the following disadvantages.
In the first place, an optical fiber being examined is cut and the cross section thereof is used to observe its structural parameters under the conventional cutting method and accordingly the optical fiber being examined is infallibly damaged;
Secondly, because only the section of an optical fiber can be observed at the cross section thereof through the conventional method, it is impossible to measure the structural parameters continuously along the optical axis i~ ,, , 129~;476 of the optical fiber. For the above reason, changes in the structural parameters produced locally in part of the optical fiber are hardly intended for measurements, whereby the total length of the optical fiber cannot be measured accurately;
Thirdly, although a high level of technique is required for the cutting operation, scratches and breakages produced during the cutting operation of an optical fiber allow the inclination of the cross section lo thereof, which results in the reduction of measurement accuracy. Consequently, the structural parameters are hardly measured accurately;
Fourthly, the section of the optical fiber thus inclined wears a tilt angle relative to the optical axis thereof and, in this case, the difference in observing magnification between the upper and lower portions ~or left- and right-hand sides) of the monitor TV 5 makes difficult the caliberation of absolute values; and Fifthly, as shown in Fig. 2, (i) and (iv) portions in the light-intensity distribution at the edge o the optical fiber are not completely in a step form due to the characteristics of the pickup tube and tilted to some extent. Consequently, measurement must be made by presetting the threshold level to recognize (i), (iv).
However, since the (i) and (iv) portions in the light-~i.
1~95476 intensity distribution are dependent on the ch,aracteristics (r-characteristic, etc. ) of the element for use and an illuminating light, it is hardly possible to accurately measure the outer diameter and internal S structure of the optical fiber.
SUMMARY OF THE INVENTION
In order to solve the aforesaid problems inherent in the prior art and provide a method and apparatus of simply measuring the structural parameters of an optical fiber with accuracy, an object of the present invention is to provide a method of optically measuring the structure of an optical fiber by detecting transmitted lights through the optical fibers, the method comprising the steps of arranging a light source and a pickup system which includes a pickup lens and a television camera and is connected to an image processing unit in such a manner that an optical axis connecting the light source to the pickup system is perpendicular to the longitudinal direction of an optical fiber being examined and passes through the center of the optical f iber; revolving the optical f iber around the axis thereof or revolving the light source and the pickup system in such a manner that the optical axis connecting the light source to the pickup system passes a measuring point on said optical fiber and , lZ95~76 1 is perpendicular to the ~axis of the optical fiber;
ildentifying the relative position of the outer clad edge of the optical fiber and that of a clad-core boundary at angles of at least two revolutions in the revolving operation; correcting the lens effect on luminance distribution on an observing plane on the basis of position data of the obsèrving plane and obtaining the true position of the core-clad boundary at the angle concerned whereby true eccentricity, clad and core diameters of the optical fiber are obtained at more than one angle measured; fitting a sine wave function to the eccentricity; and adding an averaging process to the clad and core diameters, so that the eccentricity, clad and core diameters and the nonroundness of the clad defining the structural parameters of the optical fiber are obtained.
Another object of the present invention is to provide a method of optically measuring the outer diameter of an optical fiber by detecting diffracted lights from the outer edge of the optical fiber, the method comprising the steps of paralleling the flux of monochromatic light and irradiating to the side of the optical fiber the monochromatic light in the direction perpendicular to the optical axis of the optical fiber; magnifying and ;, j !~-~ ,,;
, 129S~
l projecting an image obtained by irradiating the monochromatic light; measuring the luminance distribution of the image thus magnified and projected; and calculating the distance between diffraction fringes appearing in a place corresponding to the outer edge of the optical fiber to obtain the outer diameter of the optical fiber and precisely connect optical fibers.
Other object of the present invention is to provide an apparatus for optically examining the structure of an optical fiber comprising a .light source for irradiating the side wall of the optical fiber with an observing light and a pickup system for detecting the observing light traversing the optical fiber; and an optical fiber mounting menber for mounting the optical fiber thereon, one of the optical fiber mounting member and the optical measuring means being rotatable relatively to the other while the axis of the optical fiber and the optical axis of the optical measuring means are set to be perpendicular to each other.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be described hereinafter in more detail with reference to the accompanying drawings.
Fig. 3 is a block diagram of an apparatus for examining the structure of an optical fiber through the , . ~, ,,.,;, 10 ~9~
1 method of examining the structure thereof according to the present invention. There is shown in Fig. 3 an arrangement of a light source l; an optical fiber 3 being examined; a pick up lens 4 ; a television camera 5 ~TV
camera); a fiber setting stage 6 with a mechanism for`
revolving the optical fiber 3 around its axis; image processing unit 7; an TV monitor 8; a host CPU 9; and a printer 10. An optical axis 2 connecting the light source 1, the optical fiber 3, the pickup lens 4 and the TV
camera 5 is arranged in a position perpendicular to the axis of the optical fiber 3.
Fig. 4 is a cross-sectional view of an optical fiber to show advance of light traversing the optical fiber when the light is incident on a side wall of the optical fiber. The light incident on the side of the optical fiber is refracted by a clad and passed through the clad. A part of the light propagating in the clad is refracted by a- core having a higher refractive index than the clad and passed through the core.
The light thus passed through the clad and the core is monitored by the TV camera.
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1 In Fig. 4, portions designated by (B) and (C) are shadow regions in the clad and the core respectively where the beam of light is not passed .
Fig. 5 shows a monitored image of the light traversing the optical fiber on the TV camera.
If a substantially monochromatic light is employed as an incident light on the optical fiber, the light is diffracted b~ the outer edge of the optical fiber to form diffraction fringes in a position of the luminance distribution corresponding to the outer edge of the optical fiber. The diffraction fringes thus formed are designated by (D) as shown in Pig. 5. ~ehe accurate outer diameter o~ an optical iber can be obtained by calculating the distance between diffraction fringes.
Apparent structural parameters such as the clad and core diameters and the eccentricity when the optical fiber is viewed from a given angle are obtainable by processing data of the luminance distribution of a monitored - image as shown in F~g. 5.
When a white light is used as an incident light, diffraction fringes are not formed and therefore don~t emerge on the TV camera. Pig. 6 shows a luminace distribution on a straight line aar of a monitored image as shown in Fig. 5 when the white light is used. In Fig.
6, positions Pl, P2 of the outer clad edge are obtained .
1 using a fixed slice level and the clad center position Ml is obtained as the mid-point between Pl and P2. Positions Ql, Q2 on the core-clad boundary and the core center position M2 are obtained by processing the luminance data between Rl, R2 of the luminance distribution. In this case, eccentricity is defined by the difference between Ml and M2. Moreover, as the positions Ql, Q~ on the core-clad boundary and the core center position ~2 change with the position of an observing plane, i.e., the relative position of the focusing position (plane) of the pickup system to the optical fiber due to the lens effect on data of the observing plane of the opti~al fiber, it is necessary to correct the lens effect as described above.
Pig.7 shows a schematic diagram for explaing the lens effect.
In Fig. 7, O, R and Z represent the center of an optical fiber (a clad), a radius of the optical fiber and a distance between the center of the optical iber and an observing plane, respectively.
As the focusing position of the pickup system is shifted forward the center lO), a monitored image of the TV camera is gradually magnified. On the other hand, the monitored image is gradually reduced as the focuslng position is shifted forward the TV camera. Therefore, a luminance distribution to be observed is changed in i4~6 ^13 -1 accordance with the distance (Z). As a result, true structural parameters such as eccentricity, clad and core diameters of an optical fiber are not accurately obtained.
~ig. 8 shows the relationship of correction efficient for the lens efect with distance (Z). Once the above relationship is obtained before the measurement of the structural parameters of the optical fiber, the corxection of a luminance distribution on an observing plane located at an optional observing angle and an optional position can be performed with the relationship of the correction efficient with the position of ob~erving plane (Z).
Another method of correcting the lens effect is a correction on the basis of a bright-dark ratio ~t) which is obtained by the following equation: t = RIR2/P~2.
For example, each luminance distribution of all observing p~lanes to be observed is measurd after each position of the observing planes is beforehand adjusted so that the bright-dark ratios obtained for the observing planes are constantly equal to each other.
- Figs. 9 through 11 shows the results o the measuremen~ of the clad and core diameters and the eccentricity of the single mode optical fiber using the ZS measuring instrument of Fig. 3 when the optical fiber is " .
.
lf29S~
1 revolved by 30 degrees each time. In this measuremen~, the term of "eccentricity" means a distance between the centers of a clad and a core.
Fig. 9 shows the clad diameters measured. The mean value of the clad diameter measured at each observing angle becomes the clad diameter of the optical fiber being examined. Moreover, the difference (~) between the maximum and minimum values of the clad diameter at eacb observing angle is divided by the means clad diameter to obtain the nonroundness of the clad 8/D x 100.
Fig. 10 shows the core diameters measured. The mean ~ore diametex measured at each observing angle becomes the core diameter of the optical ~iber being examined.
Fig. ll shows the eccentricities measured, wherein the results obtained by fitting the sine wave function to the eccentricity measured at each observing angle are indicated by a continuous line. the amplltude A of the sine wave function becomes the eccentricity of the optical 20 flber, whereas the initial phase applies as a directlon angel ~ of the eccentrlcity of the optlcal flber.
The following table shows the reproducibility of the measured values obtained from the measuring instrument of Pig. 3 in comparison with those obtained through the 25 conventional process. The term " reproduclbility " used 1 in this application means that dispersion of the measuresd values is considerably small. The reproducibility of the measured values is indicated with a standard deviation by 20 times repetitions. As is obviou~ from the following table, in each of the items: clad and core diameters and core/clad eccentricity, and the nonroundness of the clad, this invention shows a smaller standard deviation of data measured in the repeating measurement and obtains reliable test results as compared with what is obtained 10 through the conventional process.
this invention prior art Clad diameter 0.1~ pm 0.2 pm Core diameter 0.12 pm 0.2 pm Eccentricity 0.08 ~m 0.16 ~m lS Nonroundness of clad 0.06 % 0.08 ~
The embodiments as described above relate to the cases where structural parameters are obtained by use of a light transmitted through an optical fiber. ~owever, if a s~bstantially parallel monochromatic light is used as an incident light on the optical fiber, diffraction fringes thereof appear in a monitored image. By use of the diEfraction fringes, the outer diameter of the optical fiber and a position of an observing plane can be . .
12g~4~,~
1 precisely measured. In this case, the monochromatic light not only makes the diffraction fringes, but also has an effect of making a monitored image of the optical fiber vivider.
The following description is made on the measurement of the outer diameter of an optical fiber by use of the diffraction fringes as described above.
Fig. 12 is a flowchart show:;ng the steps of measuring the outer diameter of an op~ical fiber. Fig.
13tA) is a block diagram of a measuring instrument for measuring the outer diameter of an optical fiber as an application of the present invention. Fig. 13(B) a luminance distribution on a line B-B' of a dif~raction image and a transmittance image of a monochromatic light.
Referring to Fig. 13(B), a description will be given of a measuring instrument for measuring the outer diameter of an optical fiber as an application of the present invention.
Like reference characters are given to like elements ann the description thereof will be omitted.
A light source 16 for emitting monochromatic light is arranged in the direction perpendicular to the optical axis of an optical fiber 13 being examined so that the light is directed to the sidewall of the optical fiber 13.
, 1`~9~ `6 1 A LED having highly monochromatic properties can be used as the light source 16 and as for a lens 12, a collimator lens is installed between the light source 16 and the optical fiber 13 in order to collimate the monochromatic light from the light source 16.
Accordingly, the light source 16 is disposed at the focal point of the lens 12. A pickup tube 14 is installed in a position facing the side shaded by the optical fiber 13 with an objective lens 18 therebetween and a magnified diffraction image of the optical fiber 13 is projected thereto. The pickup tube 14 is connected to a monitor TV
15, which displays the magnified diffraction image. The plane being observed and displayed is disposed so as to be in between a plane Po crossing the center of the optical fiber 13 and the objective lens 18. The light source 16, the lens 12 and the pic~up tube 14 are disposed on the same straightly line, whereas the optical axis of the optical fiber 13 is set perpendicular thereto.
The process of examining an optical fiber will subseguently be described on reference to Figs. 12 through 13.
At the first step shown in Fig. 12f the monochromatic light emitted from the light source 16 is collimated by the lens 12 and irradiated to the sidewall of the optical fiber 13. Accordingly, the optical axis of 1~954~6 1 the collimated monochromatic light perpendicularly crossesthat of the optical fiber 13.
At the second step, the image on the face Pl being observed of the optical fiber 13 resulting from the irradiation of the collimated monochromatic light is magnified by, e.g., the objective lens 18 and projected on the pickup tube 14. Since the monitor ~V 15 has been connected to the pickup tube 14, the image of the opticai fiber thus magnified at the third step ;s observed by the monitor TV 15. The magnification of the image is performed by the objective lens 18 of the pickup tube 14 and, depending on the size o~ the optical fiber being observed, a proper magniication is selected.
At the subsequent fourth step, the luminance distribution along the line B-B' of the image of the optical fiber 13 displayed on the monitor TV 15 is obtained. Provided an arrangement i5 made as in the case of this embodiment, the distribution looks as shown in Fig. 13~
The important point is that, because ~he monochromatic light having high collimation with a narrow spectrum width is employed, diffraction fringes shown by (i), (ii) appear in a portion corresponding to the outer edge of the optical fiber. Based on the luminancq distribution, the distance X between the first peaks - lZ954--~
1 (iii), (iv) is obtained. ~he relation of the X to the outer diameter Y of the optical fiber is linear and expressPd by the following equation of the first degree:
Y - aX + b (where a, b are constants) ...(1) In this case, a, b represent quantities dependent on the magnification of the observing system and the vertical distance ~X between the planes, namely, Po crossin~ the center of the optical fiber 13 and Pl being observed. The outer diameter Y of the optical fiber 13 can thus be ~o obtained from the distance X between the diffraction fringes at the fifth step by obtaininq the a, b beforehand while the ~X is set constant when the measurement is taken.
Fig. 14 shows a comparison between the values measured under the process of measuring the outer diameter of an optical fiber and those measured using a contact type precision measuring instrument.
.
In this experiment, several kinds of quartz fibers about 125 ~m in outer diameter were used as test samples, with an LED having a wavelength of 0.73 ~m and an output of 10 ~m as a light source and a pickup tube having an object lens of 60 magnifications as a detector. As X, Y
values, the mean value of twelve data resulting from the me2surement of the optical fibers every 30 is used.
12954 ~6 l As is obvious from Fig. 14, there is the liner relation between both X, Y, i.e., the values measured in accordance with the process embodying the present invention coincides with those measured by the precision measuring instrument to a considerable extent.
Since the calibration of the pickup tube has been made using a microæcale, a=l, b=0 in the equation (l) and the reproducibility (standard deviation at N=10) of the measured outer diameter of the same optical fiber became 0 O.Ol ~m in the process according to the present invention.
Accordingly, the outer diameter of the optical fiber can be measured by the above me1:hod with accuracy and reliability.
Furthermore, by shifting the position where the luminance distribution on the monitor TV from a line B-B' to C-C' or the optical fiber in the direction of to its optlcal axis, the outer diameter of the outer portion thereof can readily be made.
The following description is made on the precise measurement of a position of an observing plane by use of the diffraction fringes.
Fig. 15 is a schematic block diagram of a position detecting apparatus embodying the present invention. The apparatus shown in Fig. 15 is equipped with a light source 21 and, as the light source, a white light source such as ~9 5 l a halogen lamp or light-emitting diode tLED) capable of emitting light of high luminance. The light emitted from the light source 21 is incident on a band-pass filter 27 for allowing }ight of a particular wavelength to pass s therethrough. The light passed through the band-pass filter 27 is passed through the small hole provided in a pinhole plate 28 and eliminates the edge side of an optical fiber 22. The side image of the optical fiber 22 is picked up by a television camera 24, which is arranged so that the optical axis connecting the light source 21 and the camera 24 is set perpendicular to the plan including the central axis of the optical fiber 22. The output of the television camera 24 i5 connected to the input of a camera control unit 25. The output of the camera control unit 25 is connected to the input of a monitor television 26.
~ he light emitted from the white light source 21 ~such as a halogen lamp is passed through the band-pass filter 27 and then the small hole of the pinhole plate 8 to be converted into a point irradiating light relatively eguivalent to a monochromatic light. When a light-emitting diode is used as a light source, it is unnecessary to provide the band-pass filter 27 and the pinhole plate 28 having the small hole. While the point irradiating light is employed to illuminate the side wall 1~954 1 of the optical fiber 22 at an end thereof, the television camera 24 is employed to pick up the side image of the optical fiber 22. The image thus picked up is displayed via the camera control unit 25 on the monitor television 26. The optical fiber is held by the holding means tnot shown? in such a manner that its center axis is set perpendicular to the luminance measuring line AAl on the television monitor 26.
Based on the present invention, an optical fiber having 12~ ~m of the outer diameter thereof was caused to receive light from a light-emitting diode set 30 cm apart therefrom in order to observe the si.de image of the optical fiber by an ITV camera equipped with an object lens of 60 magnifications. Fig. 16 shows a. luminance distribution of the image as shown in Fig. 15. In the luminance distribution of Fig. 16, the vertical axis represents the luminance, while the horizontal axis shows the position along the luminance measuring line AA', wherein the origin corresponds to the upper end of the luminance measuring line AA'.
Given that the peak positions of diffraction fringes are designated by Pl, P2, P3 ..., Pn and.Pl*, P2*, P3* ~ Pn*, the distances between Pl and P2, P2 and P3~ Pn-l and Pn are respectively designated by zl, Z2, ..., Zn-l~ and further the distances between Pl* and.pz*, 1295~6 1 P2* and P3* ~ Pn-l* and Pn* are respectively designated by Zl*~ Z2*~ Zn-l*~ Zl, Z2~ Zn-l and Zl*, Z2* ~ Zn-l* are dependent of the distance between the position ~* of the observing plane and the center position P~of the cylindrical object being examined. Accordingly, if the relation between each position of Zl, Z2, --, Zn-l a~d Zl*, Z2*, --, Zn-l to the distance ~ is predeterminedly obtained, the distance ~ can be calculated from the measured Zl, Z2 ~ Zn-l and Zl* I Z2* r ~
10 Zn-l* ~ that is the position of the plane being observed becomes precisely detectable.
The relation of Zl ~distance between Pl, P2) where diffraction fringes are clearly observed to the distance 8 was measured and shown in Fig. 17. As shown in Fig. 17, the relation between Zl and the distance 8is unitary and it was proved that the value, i.e., the position of the plane being observed is detectable from the measured value of Zl accurately.
In this embodiment, the optical fiber mounted on a precision stage was moved in the direction of the optical axis connecting the light source and the television camera and the distance 8 was measured by reading the amount of the movement from a linear scale with 0.1 ~m reading.
~ he above embodiment measures precisely a position of an observing plane by use of the diffraction fringes of 12954 ~f~
1 the collimated monochromatic light from the ligh~ source.
~owever, this invention can adopt a collimat~d monochromatic light, but also a light of a naked light bulb or a diffused light.
In a case where the light of a naked light bulb or the diffused light is employed, a monitored image corresponding to the outer edge of an optical fiber becomes sharpest when an observing plane is located at the center of an optical fiber. The o~,serving plane is predeterminedly located at the position where the monitored image is sharpest, and is shifted from the position by use of a precise length measuring apparatus thereby to determine the position of the observing plane.
If the methods of determining the position of an ob~rving lS plane according to the invention are applied to an optical fiber fusion welding machine, they produce more effect on the optical fiber fusion welding machine~
Fig. 18 is a block diagram of the optical fusion welding machine. In Fig. 18, a lens 31b for collimating the flux of light emitted from a light source 31a is arranged in the rear of the light source 31a. The lens 31b may vary in shape with the shape of the light source 31a and the distance across the light source 31a. In the case of~ a convex lens, for instance, a point source of light may be installed at the focal point in front of the 12954 ~6 1 lens. However, such a lens can be omitted when the light source is considered a plane source of light, instead of the point source of light in view of the size of the object being illuminated. What is important is that the flux of light is collimated between the objects 33, 34 being examined. The light thus collimated from the lens ~lh is irradiated to the connections of optical fibers 33, 34 as objects being examined and then the luminance distribution thereof is detected by an image analyzer 35 installed in the rear of the objects 33, 34 being examined. The images of the objects are taken by an image observing elements 35a via an objective lens and observed by a monitor TV 35b. The luminance distribution between A-A' of the image 33' of the object 33 and that between B-B' of the image 34' of the object 34 on the monitor TV 35b are compared by a CPU through a controller, so that the relative position o~ the object 33 to the object 34 is recognized. Normally, the axis of either object is adjusted to make the axes of both objects coincide with each other. Particularly when optical fibers areconnected, the aforesaid operation is of use to mate the core centers of both optical fibers. In this caser importance should be attached to the scanning direction of the luminance distribution ~A-A', B-B') and the scanning of the luminance distribution is made in the direction l Z95476 1 perpendicular to the collimated light and the axis of the object.
When an optical fiber is observed from the sidewall thereof, the lens effect on the surface of the optical fiber gener.ally makes different the "apparent"
eccentricity ("appa~ent eccentric distance between the center of the core and tha~ of the outer diameter of the optical fiber~ from the true one. In order to obtain the true eccentricity based on the calculation dexived from the measured "apparent" eccentricity, that is, to determine the true center core posit.ion, a correction coefficient, which is dependent on the position of the obsexving plane of the image on the sidewall of the optical fiber, must be obtained beforehand. In other words, in order to détermine true exccentricity, that is, to to precisely connect optical fibers, it is prerequisite to accurately determine the position of the observing plane.
Accord~ngly, by utilizing the methods of dètermining the position of an observing plane as dascribed above, axis mating accuracy in the process of connecting optical fibers can be improved with the shortened time reguired fo~ mating axes. Moreover, the lmproved axis mating accuracy decreases optical fiber l connection loss but increases reliability of light communication.
In the above-described embodiments, an observing light from a light source is directly or through a collimating lens applied to the sidewall of an optical fiber. ~owever, a cylindrical lens may be disposed between the light source and the optical fiber in order to increase quantity of light to be detecte~, improve signal-to-n~ise ratio and increase a detecting rate.
lo Fig. l9 shows a measuring instrument employing a cylindrical lens, for example, to which the process of measuring the outer diameter of an optical fiber is applied. The cylindrical lens is used .Eor converging the light in a fixed direction so that the scanning of luminance distribution in the image displayed on the monitor TV may not be obstructed. Por the purpose of measuring the outer diameter of the optical fiber in that case, because the scanning direction is limited to what is perpendicular to the optical axis of the optical fiber, the cylindrical lens 47 is installed in such a manner as to converge the light in the optical axis of the optical fiber. That is, as shown in Fig. l9, a long axis (longitudinal direction) where the curvature radius of the cylindrical lens is made infinite is set perpendicular to the optical axis of the optical fiber.
lZ95~*6 1 Under the measuring process, high luminance data is made obtainable without increasing the output of the monochromatic light 46 and consequently the accuracy of the outer diameter measured can be improved with reliability. A picture tube 44 is connected to a TV monitor 45 to display the image.
Fig. 20 shows another measuring instrument in which a cylindrical lens is applied to the optical fusion welding machine as shown in Fig. 18.
As the cylindrical lens 52 is so arranged that its long axis direction is set perpendicular to a collimated light and the axial direction of an object being examined, the collimated light is converged in the axial direction.
This embodiment of the present invention is not limited to the use of the cylindrical lens as exemplified, provided what is capable of converging light in the aforesaid direction.
The eccentricity of the core of the single mode fiber 125 ~m in outer diameter was measured using a conventional luminance distribution detecting method and the one of the present invention. The reproducibility of the eccentricity measured and the time required for obtaining data were compared in the form of test data ~ shown in the following table :~
:
~;.... .
12~;476 -~ 29-1 , reprodL~ibility of tir~ r~red foreccentricity meas~x~ obtain~g data an~ m~: N-S
prior art 0.024 this invention 0.025 0.1 As the light source, an LED having a wavelength of 0.73 pm was used and optical fibers being examined were located at the focal point of a cylindrical lens. As is apparent from the above table, the luminance distribution detecting apparatus as shown in Fig. 20, as compared with the one as shown in Fig. 18 using only a cD~ ~ ted ~light sourcer proved that the time required for obtaining the data was 1/10 shortened without reduction in measurement accuracy.
As set forth above, according to the present embodiment, since illumination on the object having an axis can be converged with great ~uminance in the direction in which the scanning of luminance distribution is not obstructed , the structural parameters of e~ch edge ;~ portion become detectable with accuracy in matlng the axes ;of the objects having axes, particularly optical fibers.
~he cylindrical lens also has the same effect on a measuring apparatus adopting other ordinary light, for ~;~ example a white light, than a collimated monochromatic 25 ~ llght.
:
' ` ' ... ..
12~5i476 1 In the above embodiments, a TV camera is ernployed in an image pickup system and an image (luminance distribution) monitored by it is utilized for determining structural parameters of an optical fiber. ~owever, this invention is not limited thereto. A CCD line sensor may be used in place of the TV camera. In order to make a resolution of the image pickup system higher and to average measured data which are obtained in the longitudinal direction of the optical fiber, the CCD line-sensor may be mechanically scanned in the directionperpendicular to the axis of the sensor.
Further plural CCD line-sensors are disposed in the longitudinal direction of an optical fiber to sumultaneously measure luminance distributions on the respective l~ne-sensors, calculate respective eccentricities obtained by the respective line-sensors, and obtain an average value thereof, whereby an average eccentricity at an observing angle concerned is determined.
In the above embodiments, a bundle fiber comprising plural LEDs and plural optical fibers optically connected to the LEDs as shown in Fig. 21 may be used as a light source to make a luminance of observing light stronger and increase degree of freedom of the position of the light source. Further, to keep measurement . ,, . ~ . . . ~
12~S~t6 1 environment clean and prevent a bad influence of dust or the like, a clean air may be sent to at least a space where a light source, an optical fiber to be examined and an objective lens are disposed.
As described above, in the method and apparatus of measuring the outer diameter and the structure of an optical fiber according to the present invention, the optical fiber bein~ examined needs not cutting because it is observed from its sidewall and the state of the cross section thereof does not affect the measured values.
Accordingly, the structure of the optical fiber can simply be examined accurately without being damaged.
Moreover, since the optical fiber or the optical axis of the pickup system is revolved for measuring purposes, the clad and core diameters and the eccentricity in the circumferential direction can be make known and, by processing the data, the true clad and core diameters, the eccentricity and the nonroundness of the clad can also be measured with accuracy. The process of fitting the sine wave function with resp$ct to the ecaentriaity makes it possible to extract only the true eccentric components from the eccentricity measured at each angle of revolution, so that the optical fiber is hardly subject to electric or mechanical measurement errors.
~2~5 ~ ~6 1 When the magnifying power of the pickup system differs in the vertical direction, for instance, the eccentricity measured is affected by the distortion of the magnifying power in the conventional examining method as shown in Pig. 22A and consequently a quantity corresponding to the aforesaid distortion is measured as an eccentricity for an optical fiber being examined but free from eccentricity. Fig. 22A illustrates a clad 50, a core 51, the center 52 common to a true core, a true clad and the co~e being measured, and the center 53 of the clad being measured. In the process of exam;ning the structure of the opt~cal fiber according to the present invention, the eccentricity of the optical fiber is obtained from changes in the eccentricity measured in the circumferential direction of the optical fiber and hardly affected by the aforesaid distortion. In Figs. 22B, 22C, there is shown the effect of the distortion of the magnifying power of the pickup system at measuring angles of 0 and 180 as an example of examining an optical fiber free from eccentricity. In the examining process of the present invention, the eccentricity of the optical fi~er being examined is judged zero because the eccentricity measured will not change even if the observing angle is examined, the presence of the dis~ortion of the magnifying power of the pickup system wilI not affect the change of 12~5~76 1 the eccentricity in the circumferential direction of the optical fiber and, when the sine wave function is fitted, its amplitude becomes zero. In consequence, the eccentricity of the optical fiber being examined is measured as zero.
~ hen the optical axis connecting the light source and the pickup system is not perpendicular to the axis of the optical fiber, e.g., when the posit.ion of the light souxce 63 changes from A to B as shown in Fig. 23, a pattern of the luminance disstribution observed by a television camera 66 via an optical fiber 64 being examined and an objective lens 65 change; as shown in Fig.
24. In the luminance distribution with the light source 63 of Fig. 23 without being shifted in the position A and a luminance distribution with the light source 63 shifted in the position B, respesctively. The structural parameters obtainable from the luminance distribution include the influence of the shifted position of the light source. In the instrument for examining the structure oE
the optical fiber according to the method of the invention, the parameters are not affected by the shift of the li~ht source because the optical axis connecting the light source and the pickup system is set perpendicular to the axis of the optical fiber.
12~476 - 34 ~
1 Still furthermore, the position detecting method and apparatus according to the present invention can accurately detect the position of the observing plane of the optical fiber to be examined by measuring the distance between the diffraction fringes produced at the outer edge of the optical fiber using the point sourc for emitting substantially monochromatic light. Consequently, the center position of the core is measured accurately by observing the side image of the optical fiber. the position detecting method according to the present invention can thus be utilized in a wide range oE use, e.g., for optical fiber fusion welding ~achines.
..... .
BRIEF DESCRIPTOIN OF THE DRAWINGS
Fig. 1 is a block diagram for a microscope of a conventional instrument for measuring the outer diamenter and the internal structure of an optical fiber;
Fig. 2 shows a luminace distribution of a monitored image obtained by the microscope as shown in Fig. l;
Fig. 3 is a blcok diagram of an apparatus for examining the structure of an optical fiber through the method of examining the structure thereof according to this invention;
Fig. 4 is a cross-sectional view of an optical fiber to show the advance of ligt traversing the optical fiber;
Fig. 5 shows a monitored image of the light traversing the optical fiber as shown in Fig. 4 on a TV
camera;
, 1~ ~
;~, .: , ~,~ . . .
12~?5~76 Fig. 6 shows a luminace distribution on a straight line aa~ of the monitored image as shown in Fig.5 in a case where a white light is used as an incident light;
Fig. 7 shows a schematic diagram for explaining the lens effect;
Fig. 8 shows the relationship o~ correction efficient for the lens effect with a distancè between the center of an optical fiber and an observing plane;
Fig. 9 shows a graph in which measured data of a clad diameter according to this invention are plotted;
Fig. 10 shows a graph in which measured data of a core diameter according to this invention are plotted;
Fig. 11 shows a graph in which measured eccentricities of an optical fiber are plotted;
Fig. 12 is a flowchart showing the steps of measuring the outer diameter of an optical fiber;
Fig. 13(A) is a block diagram of a mesuring instrument for measuring the outer diameter of an optical fiber as an application of the method of the present invention, and Fig. 13~B) is a luminance distribution on a line B-B' of the monitored image as shown in Fig. 13~A);
Fig. 14 is a graph showing a comparison between teh values measured under the process of measuring the outer diameter of an optical fiber and those measured using a contact type precision measuring instrument;
::~
12~5476 1 Fig. 15 is a schematic block diagram of a position detecting apparatus embodying the method of this invention;
Fig. 16 shows a luminace distribution of the image as shown in Fig. 15;
Fig. 17 shows a relationship of a distance between Pl and P2 as shown in Fig. 16 to the distance between the position of the observing plane and the center position of an optical fiber;
Fig. 18 is a block diagram of an optical fusion welding machine according to this invention;
Fig. 19 shows a measuring instrument employing a cylindrical lens according to this invention;
Fig. 20 shows another measuring instrument in which a cylindrical lens according to this invention is applied to the optical fusion welding machine as shown in Fig. 18;
Fig. 21 is a schematic diagram of a bundle fiber comprising plural LEDs and plural optical fibers optically connected to the LEDs;
Fig. 22~A) through 22(C) are diagram illustrating the effect of distortion of the magnifying power of pickup system when an optical fiber free from eccentricity is examined;
.... l .
lZ~5476 1 Fig. 23 is a diagram illustriating the position sh;fting of a light source;
Fig. 24 is a diagram illustrating changes in distribution patterns of illumination due to the position shifting of the light source of Fig. ~3.
Conventionally, there has been employed a method and apparatus of measuring the outer diameter and the internal structure of an optical fiber by cutting the optical fiber being examined and by observing the cross o section thereof through a microscope or television camera.
Fig. 1 shows a conventional arrangement for measuring the outer diameter and the internal structure of an optical fiber by means of a microscope, wherein light from a light source 1 is first converged by an injection lens 2 and caused to be incident on an end of an optical fiber 3.
The light from the light source 1 thus converged is propagated through the core of the optical fiber 3.
However, the light in a clad of the optical fibér is attenuated during the propagation thereof through the clad because it is radiated from and absorbed by the clad. As a result, a light emitted from an exit edge 3a to be observed originates in only the light propagating through the core, and therefore is used as an illuminating light for the core.
,, 129~ 6 l On the other hand, as a light from a light source 10 is incident on the exit edge 3a being observed by a half mirror 9 and is reflected from the clad of the exit edge 3a, it is used as an illuminating light for the clad.
In the rear of the exit edge (edge being observed) 3a of the optical fiber 3, a pickup tube 4 is located so that the edge 3a of the optical fiber can be observed with a lens 8. The pickup tube 4 is connected to a monitor TV
5, which is capable of magnifying and displaying an image (light-intensity distribution) of the edge 3a being observed of the optical fiber 3. The luminance distribution on a line A-A' on the monitor TV becomes such as shown in Fig. 2.
A conventional method apparatus as described above has the following disadvantages.
In the first place, an optical fiber being examined is cut and the cross section thereof is used to observe its structural parameters under the conventional cutting method and accordingly the optical fiber being examined is infallibly damaged;
Secondly, because only the section of an optical fiber can be observed at the cross section thereof through the conventional method, it is impossible to measure the structural parameters continuously along the optical axis i~ ,, , 129~;476 of the optical fiber. For the above reason, changes in the structural parameters produced locally in part of the optical fiber are hardly intended for measurements, whereby the total length of the optical fiber cannot be measured accurately;
Thirdly, although a high level of technique is required for the cutting operation, scratches and breakages produced during the cutting operation of an optical fiber allow the inclination of the cross section lo thereof, which results in the reduction of measurement accuracy. Consequently, the structural parameters are hardly measured accurately;
Fourthly, the section of the optical fiber thus inclined wears a tilt angle relative to the optical axis thereof and, in this case, the difference in observing magnification between the upper and lower portions ~or left- and right-hand sides) of the monitor TV 5 makes difficult the caliberation of absolute values; and Fifthly, as shown in Fig. 2, (i) and (iv) portions in the light-intensity distribution at the edge o the optical fiber are not completely in a step form due to the characteristics of the pickup tube and tilted to some extent. Consequently, measurement must be made by presetting the threshold level to recognize (i), (iv).
However, since the (i) and (iv) portions in the light-~i.
1~95476 intensity distribution are dependent on the ch,aracteristics (r-characteristic, etc. ) of the element for use and an illuminating light, it is hardly possible to accurately measure the outer diameter and internal S structure of the optical fiber.
SUMMARY OF THE INVENTION
In order to solve the aforesaid problems inherent in the prior art and provide a method and apparatus of simply measuring the structural parameters of an optical fiber with accuracy, an object of the present invention is to provide a method of optically measuring the structure of an optical fiber by detecting transmitted lights through the optical fibers, the method comprising the steps of arranging a light source and a pickup system which includes a pickup lens and a television camera and is connected to an image processing unit in such a manner that an optical axis connecting the light source to the pickup system is perpendicular to the longitudinal direction of an optical fiber being examined and passes through the center of the optical f iber; revolving the optical f iber around the axis thereof or revolving the light source and the pickup system in such a manner that the optical axis connecting the light source to the pickup system passes a measuring point on said optical fiber and , lZ95~76 1 is perpendicular to the ~axis of the optical fiber;
ildentifying the relative position of the outer clad edge of the optical fiber and that of a clad-core boundary at angles of at least two revolutions in the revolving operation; correcting the lens effect on luminance distribution on an observing plane on the basis of position data of the obsèrving plane and obtaining the true position of the core-clad boundary at the angle concerned whereby true eccentricity, clad and core diameters of the optical fiber are obtained at more than one angle measured; fitting a sine wave function to the eccentricity; and adding an averaging process to the clad and core diameters, so that the eccentricity, clad and core diameters and the nonroundness of the clad defining the structural parameters of the optical fiber are obtained.
Another object of the present invention is to provide a method of optically measuring the outer diameter of an optical fiber by detecting diffracted lights from the outer edge of the optical fiber, the method comprising the steps of paralleling the flux of monochromatic light and irradiating to the side of the optical fiber the monochromatic light in the direction perpendicular to the optical axis of the optical fiber; magnifying and ;, j !~-~ ,,;
, 129S~
l projecting an image obtained by irradiating the monochromatic light; measuring the luminance distribution of the image thus magnified and projected; and calculating the distance between diffraction fringes appearing in a place corresponding to the outer edge of the optical fiber to obtain the outer diameter of the optical fiber and precisely connect optical fibers.
Other object of the present invention is to provide an apparatus for optically examining the structure of an optical fiber comprising a .light source for irradiating the side wall of the optical fiber with an observing light and a pickup system for detecting the observing light traversing the optical fiber; and an optical fiber mounting menber for mounting the optical fiber thereon, one of the optical fiber mounting member and the optical measuring means being rotatable relatively to the other while the axis of the optical fiber and the optical axis of the optical measuring means are set to be perpendicular to each other.
DETAILED DESCRIPTION OF THE INVENTION
The invention will be described hereinafter in more detail with reference to the accompanying drawings.
Fig. 3 is a block diagram of an apparatus for examining the structure of an optical fiber through the , . ~, ,,.,;, 10 ~9~
1 method of examining the structure thereof according to the present invention. There is shown in Fig. 3 an arrangement of a light source l; an optical fiber 3 being examined; a pick up lens 4 ; a television camera 5 ~TV
camera); a fiber setting stage 6 with a mechanism for`
revolving the optical fiber 3 around its axis; image processing unit 7; an TV monitor 8; a host CPU 9; and a printer 10. An optical axis 2 connecting the light source 1, the optical fiber 3, the pickup lens 4 and the TV
camera 5 is arranged in a position perpendicular to the axis of the optical fiber 3.
Fig. 4 is a cross-sectional view of an optical fiber to show advance of light traversing the optical fiber when the light is incident on a side wall of the optical fiber. The light incident on the side of the optical fiber is refracted by a clad and passed through the clad. A part of the light propagating in the clad is refracted by a- core having a higher refractive index than the clad and passed through the core.
The light thus passed through the clad and the core is monitored by the TV camera.
. . ,~
t,, . .
~ " ~
', , : ' , ' \ 12954'~-~
1 In Fig. 4, portions designated by (B) and (C) are shadow regions in the clad and the core respectively where the beam of light is not passed .
Fig. 5 shows a monitored image of the light traversing the optical fiber on the TV camera.
If a substantially monochromatic light is employed as an incident light on the optical fiber, the light is diffracted b~ the outer edge of the optical fiber to form diffraction fringes in a position of the luminance distribution corresponding to the outer edge of the optical fiber. The diffraction fringes thus formed are designated by (D) as shown in Pig. 5. ~ehe accurate outer diameter o~ an optical iber can be obtained by calculating the distance between diffraction fringes.
Apparent structural parameters such as the clad and core diameters and the eccentricity when the optical fiber is viewed from a given angle are obtainable by processing data of the luminance distribution of a monitored - image as shown in F~g. 5.
When a white light is used as an incident light, diffraction fringes are not formed and therefore don~t emerge on the TV camera. Pig. 6 shows a luminace distribution on a straight line aar of a monitored image as shown in Fig. 5 when the white light is used. In Fig.
6, positions Pl, P2 of the outer clad edge are obtained .
1 using a fixed slice level and the clad center position Ml is obtained as the mid-point between Pl and P2. Positions Ql, Q2 on the core-clad boundary and the core center position M2 are obtained by processing the luminance data between Rl, R2 of the luminance distribution. In this case, eccentricity is defined by the difference between Ml and M2. Moreover, as the positions Ql, Q~ on the core-clad boundary and the core center position ~2 change with the position of an observing plane, i.e., the relative position of the focusing position (plane) of the pickup system to the optical fiber due to the lens effect on data of the observing plane of the opti~al fiber, it is necessary to correct the lens effect as described above.
Pig.7 shows a schematic diagram for explaing the lens effect.
In Fig. 7, O, R and Z represent the center of an optical fiber (a clad), a radius of the optical fiber and a distance between the center of the optical iber and an observing plane, respectively.
As the focusing position of the pickup system is shifted forward the center lO), a monitored image of the TV camera is gradually magnified. On the other hand, the monitored image is gradually reduced as the focuslng position is shifted forward the TV camera. Therefore, a luminance distribution to be observed is changed in i4~6 ^13 -1 accordance with the distance (Z). As a result, true structural parameters such as eccentricity, clad and core diameters of an optical fiber are not accurately obtained.
~ig. 8 shows the relationship of correction efficient for the lens efect with distance (Z). Once the above relationship is obtained before the measurement of the structural parameters of the optical fiber, the corxection of a luminance distribution on an observing plane located at an optional observing angle and an optional position can be performed with the relationship of the correction efficient with the position of ob~erving plane (Z).
Another method of correcting the lens effect is a correction on the basis of a bright-dark ratio ~t) which is obtained by the following equation: t = RIR2/P~2.
For example, each luminance distribution of all observing p~lanes to be observed is measurd after each position of the observing planes is beforehand adjusted so that the bright-dark ratios obtained for the observing planes are constantly equal to each other.
- Figs. 9 through 11 shows the results o the measuremen~ of the clad and core diameters and the eccentricity of the single mode optical fiber using the ZS measuring instrument of Fig. 3 when the optical fiber is " .
.
lf29S~
1 revolved by 30 degrees each time. In this measuremen~, the term of "eccentricity" means a distance between the centers of a clad and a core.
Fig. 9 shows the clad diameters measured. The mean value of the clad diameter measured at each observing angle becomes the clad diameter of the optical fiber being examined. Moreover, the difference (~) between the maximum and minimum values of the clad diameter at eacb observing angle is divided by the means clad diameter to obtain the nonroundness of the clad 8/D x 100.
Fig. 10 shows the core diameters measured. The mean ~ore diametex measured at each observing angle becomes the core diameter of the optical ~iber being examined.
Fig. ll shows the eccentricities measured, wherein the results obtained by fitting the sine wave function to the eccentricity measured at each observing angle are indicated by a continuous line. the amplltude A of the sine wave function becomes the eccentricity of the optical 20 flber, whereas the initial phase applies as a directlon angel ~ of the eccentrlcity of the optlcal flber.
The following table shows the reproducibility of the measured values obtained from the measuring instrument of Pig. 3 in comparison with those obtained through the 25 conventional process. The term " reproduclbility " used 1 in this application means that dispersion of the measuresd values is considerably small. The reproducibility of the measured values is indicated with a standard deviation by 20 times repetitions. As is obviou~ from the following table, in each of the items: clad and core diameters and core/clad eccentricity, and the nonroundness of the clad, this invention shows a smaller standard deviation of data measured in the repeating measurement and obtains reliable test results as compared with what is obtained 10 through the conventional process.
this invention prior art Clad diameter 0.1~ pm 0.2 pm Core diameter 0.12 pm 0.2 pm Eccentricity 0.08 ~m 0.16 ~m lS Nonroundness of clad 0.06 % 0.08 ~
The embodiments as described above relate to the cases where structural parameters are obtained by use of a light transmitted through an optical fiber. ~owever, if a s~bstantially parallel monochromatic light is used as an incident light on the optical fiber, diffraction fringes thereof appear in a monitored image. By use of the diEfraction fringes, the outer diameter of the optical fiber and a position of an observing plane can be . .
12g~4~,~
1 precisely measured. In this case, the monochromatic light not only makes the diffraction fringes, but also has an effect of making a monitored image of the optical fiber vivider.
The following description is made on the measurement of the outer diameter of an optical fiber by use of the diffraction fringes as described above.
Fig. 12 is a flowchart show:;ng the steps of measuring the outer diameter of an op~ical fiber. Fig.
13tA) is a block diagram of a measuring instrument for measuring the outer diameter of an optical fiber as an application of the present invention. Fig. 13(B) a luminance distribution on a line B-B' of a dif~raction image and a transmittance image of a monochromatic light.
Referring to Fig. 13(B), a description will be given of a measuring instrument for measuring the outer diameter of an optical fiber as an application of the present invention.
Like reference characters are given to like elements ann the description thereof will be omitted.
A light source 16 for emitting monochromatic light is arranged in the direction perpendicular to the optical axis of an optical fiber 13 being examined so that the light is directed to the sidewall of the optical fiber 13.
, 1`~9~ `6 1 A LED having highly monochromatic properties can be used as the light source 16 and as for a lens 12, a collimator lens is installed between the light source 16 and the optical fiber 13 in order to collimate the monochromatic light from the light source 16.
Accordingly, the light source 16 is disposed at the focal point of the lens 12. A pickup tube 14 is installed in a position facing the side shaded by the optical fiber 13 with an objective lens 18 therebetween and a magnified diffraction image of the optical fiber 13 is projected thereto. The pickup tube 14 is connected to a monitor TV
15, which displays the magnified diffraction image. The plane being observed and displayed is disposed so as to be in between a plane Po crossing the center of the optical fiber 13 and the objective lens 18. The light source 16, the lens 12 and the pic~up tube 14 are disposed on the same straightly line, whereas the optical axis of the optical fiber 13 is set perpendicular thereto.
The process of examining an optical fiber will subseguently be described on reference to Figs. 12 through 13.
At the first step shown in Fig. 12f the monochromatic light emitted from the light source 16 is collimated by the lens 12 and irradiated to the sidewall of the optical fiber 13. Accordingly, the optical axis of 1~954~6 1 the collimated monochromatic light perpendicularly crossesthat of the optical fiber 13.
At the second step, the image on the face Pl being observed of the optical fiber 13 resulting from the irradiation of the collimated monochromatic light is magnified by, e.g., the objective lens 18 and projected on the pickup tube 14. Since the monitor ~V 15 has been connected to the pickup tube 14, the image of the opticai fiber thus magnified at the third step ;s observed by the monitor TV 15. The magnification of the image is performed by the objective lens 18 of the pickup tube 14 and, depending on the size o~ the optical fiber being observed, a proper magniication is selected.
At the subsequent fourth step, the luminance distribution along the line B-B' of the image of the optical fiber 13 displayed on the monitor TV 15 is obtained. Provided an arrangement i5 made as in the case of this embodiment, the distribution looks as shown in Fig. 13~
The important point is that, because ~he monochromatic light having high collimation with a narrow spectrum width is employed, diffraction fringes shown by (i), (ii) appear in a portion corresponding to the outer edge of the optical fiber. Based on the luminancq distribution, the distance X between the first peaks - lZ954--~
1 (iii), (iv) is obtained. ~he relation of the X to the outer diameter Y of the optical fiber is linear and expressPd by the following equation of the first degree:
Y - aX + b (where a, b are constants) ...(1) In this case, a, b represent quantities dependent on the magnification of the observing system and the vertical distance ~X between the planes, namely, Po crossin~ the center of the optical fiber 13 and Pl being observed. The outer diameter Y of the optical fiber 13 can thus be ~o obtained from the distance X between the diffraction fringes at the fifth step by obtaininq the a, b beforehand while the ~X is set constant when the measurement is taken.
Fig. 14 shows a comparison between the values measured under the process of measuring the outer diameter of an optical fiber and those measured using a contact type precision measuring instrument.
.
In this experiment, several kinds of quartz fibers about 125 ~m in outer diameter were used as test samples, with an LED having a wavelength of 0.73 ~m and an output of 10 ~m as a light source and a pickup tube having an object lens of 60 magnifications as a detector. As X, Y
values, the mean value of twelve data resulting from the me2surement of the optical fibers every 30 is used.
12954 ~6 l As is obvious from Fig. 14, there is the liner relation between both X, Y, i.e., the values measured in accordance with the process embodying the present invention coincides with those measured by the precision measuring instrument to a considerable extent.
Since the calibration of the pickup tube has been made using a microæcale, a=l, b=0 in the equation (l) and the reproducibility (standard deviation at N=10) of the measured outer diameter of the same optical fiber became 0 O.Ol ~m in the process according to the present invention.
Accordingly, the outer diameter of the optical fiber can be measured by the above me1:hod with accuracy and reliability.
Furthermore, by shifting the position where the luminance distribution on the monitor TV from a line B-B' to C-C' or the optical fiber in the direction of to its optlcal axis, the outer diameter of the outer portion thereof can readily be made.
The following description is made on the precise measurement of a position of an observing plane by use of the diffraction fringes.
Fig. 15 is a schematic block diagram of a position detecting apparatus embodying the present invention. The apparatus shown in Fig. 15 is equipped with a light source 21 and, as the light source, a white light source such as ~9 5 l a halogen lamp or light-emitting diode tLED) capable of emitting light of high luminance. The light emitted from the light source 21 is incident on a band-pass filter 27 for allowing }ight of a particular wavelength to pass s therethrough. The light passed through the band-pass filter 27 is passed through the small hole provided in a pinhole plate 28 and eliminates the edge side of an optical fiber 22. The side image of the optical fiber 22 is picked up by a television camera 24, which is arranged so that the optical axis connecting the light source 21 and the camera 24 is set perpendicular to the plan including the central axis of the optical fiber 22. The output of the television camera 24 i5 connected to the input of a camera control unit 25. The output of the camera control unit 25 is connected to the input of a monitor television 26.
~ he light emitted from the white light source 21 ~such as a halogen lamp is passed through the band-pass filter 27 and then the small hole of the pinhole plate 8 to be converted into a point irradiating light relatively eguivalent to a monochromatic light. When a light-emitting diode is used as a light source, it is unnecessary to provide the band-pass filter 27 and the pinhole plate 28 having the small hole. While the point irradiating light is employed to illuminate the side wall 1~954 1 of the optical fiber 22 at an end thereof, the television camera 24 is employed to pick up the side image of the optical fiber 22. The image thus picked up is displayed via the camera control unit 25 on the monitor television 26. The optical fiber is held by the holding means tnot shown? in such a manner that its center axis is set perpendicular to the luminance measuring line AAl on the television monitor 26.
Based on the present invention, an optical fiber having 12~ ~m of the outer diameter thereof was caused to receive light from a light-emitting diode set 30 cm apart therefrom in order to observe the si.de image of the optical fiber by an ITV camera equipped with an object lens of 60 magnifications. Fig. 16 shows a. luminance distribution of the image as shown in Fig. 15. In the luminance distribution of Fig. 16, the vertical axis represents the luminance, while the horizontal axis shows the position along the luminance measuring line AA', wherein the origin corresponds to the upper end of the luminance measuring line AA'.
Given that the peak positions of diffraction fringes are designated by Pl, P2, P3 ..., Pn and.Pl*, P2*, P3* ~ Pn*, the distances between Pl and P2, P2 and P3~ Pn-l and Pn are respectively designated by zl, Z2, ..., Zn-l~ and further the distances between Pl* and.pz*, 1295~6 1 P2* and P3* ~ Pn-l* and Pn* are respectively designated by Zl*~ Z2*~ Zn-l*~ Zl, Z2~ Zn-l and Zl*, Z2* ~ Zn-l* are dependent of the distance between the position ~* of the observing plane and the center position P~of the cylindrical object being examined. Accordingly, if the relation between each position of Zl, Z2, --, Zn-l a~d Zl*, Z2*, --, Zn-l to the distance ~ is predeterminedly obtained, the distance ~ can be calculated from the measured Zl, Z2 ~ Zn-l and Zl* I Z2* r ~
10 Zn-l* ~ that is the position of the plane being observed becomes precisely detectable.
The relation of Zl ~distance between Pl, P2) where diffraction fringes are clearly observed to the distance 8 was measured and shown in Fig. 17. As shown in Fig. 17, the relation between Zl and the distance 8is unitary and it was proved that the value, i.e., the position of the plane being observed is detectable from the measured value of Zl accurately.
In this embodiment, the optical fiber mounted on a precision stage was moved in the direction of the optical axis connecting the light source and the television camera and the distance 8 was measured by reading the amount of the movement from a linear scale with 0.1 ~m reading.
~ he above embodiment measures precisely a position of an observing plane by use of the diffraction fringes of 12954 ~f~
1 the collimated monochromatic light from the ligh~ source.
~owever, this invention can adopt a collimat~d monochromatic light, but also a light of a naked light bulb or a diffused light.
In a case where the light of a naked light bulb or the diffused light is employed, a monitored image corresponding to the outer edge of an optical fiber becomes sharpest when an observing plane is located at the center of an optical fiber. The o~,serving plane is predeterminedly located at the position where the monitored image is sharpest, and is shifted from the position by use of a precise length measuring apparatus thereby to determine the position of the observing plane.
If the methods of determining the position of an ob~rving lS plane according to the invention are applied to an optical fiber fusion welding machine, they produce more effect on the optical fiber fusion welding machine~
Fig. 18 is a block diagram of the optical fusion welding machine. In Fig. 18, a lens 31b for collimating the flux of light emitted from a light source 31a is arranged in the rear of the light source 31a. The lens 31b may vary in shape with the shape of the light source 31a and the distance across the light source 31a. In the case of~ a convex lens, for instance, a point source of light may be installed at the focal point in front of the 12954 ~6 1 lens. However, such a lens can be omitted when the light source is considered a plane source of light, instead of the point source of light in view of the size of the object being illuminated. What is important is that the flux of light is collimated between the objects 33, 34 being examined. The light thus collimated from the lens ~lh is irradiated to the connections of optical fibers 33, 34 as objects being examined and then the luminance distribution thereof is detected by an image analyzer 35 installed in the rear of the objects 33, 34 being examined. The images of the objects are taken by an image observing elements 35a via an objective lens and observed by a monitor TV 35b. The luminance distribution between A-A' of the image 33' of the object 33 and that between B-B' of the image 34' of the object 34 on the monitor TV 35b are compared by a CPU through a controller, so that the relative position o~ the object 33 to the object 34 is recognized. Normally, the axis of either object is adjusted to make the axes of both objects coincide with each other. Particularly when optical fibers areconnected, the aforesaid operation is of use to mate the core centers of both optical fibers. In this caser importance should be attached to the scanning direction of the luminance distribution ~A-A', B-B') and the scanning of the luminance distribution is made in the direction l Z95476 1 perpendicular to the collimated light and the axis of the object.
When an optical fiber is observed from the sidewall thereof, the lens effect on the surface of the optical fiber gener.ally makes different the "apparent"
eccentricity ("appa~ent eccentric distance between the center of the core and tha~ of the outer diameter of the optical fiber~ from the true one. In order to obtain the true eccentricity based on the calculation dexived from the measured "apparent" eccentricity, that is, to determine the true center core posit.ion, a correction coefficient, which is dependent on the position of the obsexving plane of the image on the sidewall of the optical fiber, must be obtained beforehand. In other words, in order to détermine true exccentricity, that is, to to precisely connect optical fibers, it is prerequisite to accurately determine the position of the observing plane.
Accord~ngly, by utilizing the methods of dètermining the position of an observing plane as dascribed above, axis mating accuracy in the process of connecting optical fibers can be improved with the shortened time reguired fo~ mating axes. Moreover, the lmproved axis mating accuracy decreases optical fiber l connection loss but increases reliability of light communication.
In the above-described embodiments, an observing light from a light source is directly or through a collimating lens applied to the sidewall of an optical fiber. ~owever, a cylindrical lens may be disposed between the light source and the optical fiber in order to increase quantity of light to be detecte~, improve signal-to-n~ise ratio and increase a detecting rate.
lo Fig. l9 shows a measuring instrument employing a cylindrical lens, for example, to which the process of measuring the outer diameter of an optical fiber is applied. The cylindrical lens is used .Eor converging the light in a fixed direction so that the scanning of luminance distribution in the image displayed on the monitor TV may not be obstructed. Por the purpose of measuring the outer diameter of the optical fiber in that case, because the scanning direction is limited to what is perpendicular to the optical axis of the optical fiber, the cylindrical lens 47 is installed in such a manner as to converge the light in the optical axis of the optical fiber. That is, as shown in Fig. l9, a long axis (longitudinal direction) where the curvature radius of the cylindrical lens is made infinite is set perpendicular to the optical axis of the optical fiber.
lZ95~*6 1 Under the measuring process, high luminance data is made obtainable without increasing the output of the monochromatic light 46 and consequently the accuracy of the outer diameter measured can be improved with reliability. A picture tube 44 is connected to a TV monitor 45 to display the image.
Fig. 20 shows another measuring instrument in which a cylindrical lens is applied to the optical fusion welding machine as shown in Fig. 18.
As the cylindrical lens 52 is so arranged that its long axis direction is set perpendicular to a collimated light and the axial direction of an object being examined, the collimated light is converged in the axial direction.
This embodiment of the present invention is not limited to the use of the cylindrical lens as exemplified, provided what is capable of converging light in the aforesaid direction.
The eccentricity of the core of the single mode fiber 125 ~m in outer diameter was measured using a conventional luminance distribution detecting method and the one of the present invention. The reproducibility of the eccentricity measured and the time required for obtaining data were compared in the form of test data ~ shown in the following table :~
:
~;.... .
12~;476 -~ 29-1 , reprodL~ibility of tir~ r~red foreccentricity meas~x~ obtain~g data an~ m~: N-S
prior art 0.024 this invention 0.025 0.1 As the light source, an LED having a wavelength of 0.73 pm was used and optical fibers being examined were located at the focal point of a cylindrical lens. As is apparent from the above table, the luminance distribution detecting apparatus as shown in Fig. 20, as compared with the one as shown in Fig. 18 using only a cD~ ~ ted ~light sourcer proved that the time required for obtaining the data was 1/10 shortened without reduction in measurement accuracy.
As set forth above, according to the present embodiment, since illumination on the object having an axis can be converged with great ~uminance in the direction in which the scanning of luminance distribution is not obstructed , the structural parameters of e~ch edge ;~ portion become detectable with accuracy in matlng the axes ;of the objects having axes, particularly optical fibers.
~he cylindrical lens also has the same effect on a measuring apparatus adopting other ordinary light, for ~;~ example a white light, than a collimated monochromatic 25 ~ llght.
:
' ` ' ... ..
12~5i476 1 In the above embodiments, a TV camera is ernployed in an image pickup system and an image (luminance distribution) monitored by it is utilized for determining structural parameters of an optical fiber. ~owever, this invention is not limited thereto. A CCD line sensor may be used in place of the TV camera. In order to make a resolution of the image pickup system higher and to average measured data which are obtained in the longitudinal direction of the optical fiber, the CCD line-sensor may be mechanically scanned in the directionperpendicular to the axis of the sensor.
Further plural CCD line-sensors are disposed in the longitudinal direction of an optical fiber to sumultaneously measure luminance distributions on the respective l~ne-sensors, calculate respective eccentricities obtained by the respective line-sensors, and obtain an average value thereof, whereby an average eccentricity at an observing angle concerned is determined.
In the above embodiments, a bundle fiber comprising plural LEDs and plural optical fibers optically connected to the LEDs as shown in Fig. 21 may be used as a light source to make a luminance of observing light stronger and increase degree of freedom of the position of the light source. Further, to keep measurement . ,, . ~ . . . ~
12~S~t6 1 environment clean and prevent a bad influence of dust or the like, a clean air may be sent to at least a space where a light source, an optical fiber to be examined and an objective lens are disposed.
As described above, in the method and apparatus of measuring the outer diameter and the structure of an optical fiber according to the present invention, the optical fiber bein~ examined needs not cutting because it is observed from its sidewall and the state of the cross section thereof does not affect the measured values.
Accordingly, the structure of the optical fiber can simply be examined accurately without being damaged.
Moreover, since the optical fiber or the optical axis of the pickup system is revolved for measuring purposes, the clad and core diameters and the eccentricity in the circumferential direction can be make known and, by processing the data, the true clad and core diameters, the eccentricity and the nonroundness of the clad can also be measured with accuracy. The process of fitting the sine wave function with resp$ct to the ecaentriaity makes it possible to extract only the true eccentric components from the eccentricity measured at each angle of revolution, so that the optical fiber is hardly subject to electric or mechanical measurement errors.
~2~5 ~ ~6 1 When the magnifying power of the pickup system differs in the vertical direction, for instance, the eccentricity measured is affected by the distortion of the magnifying power in the conventional examining method as shown in Pig. 22A and consequently a quantity corresponding to the aforesaid distortion is measured as an eccentricity for an optical fiber being examined but free from eccentricity. Fig. 22A illustrates a clad 50, a core 51, the center 52 common to a true core, a true clad and the co~e being measured, and the center 53 of the clad being measured. In the process of exam;ning the structure of the opt~cal fiber according to the present invention, the eccentricity of the optical fiber is obtained from changes in the eccentricity measured in the circumferential direction of the optical fiber and hardly affected by the aforesaid distortion. In Figs. 22B, 22C, there is shown the effect of the distortion of the magnifying power of the pickup system at measuring angles of 0 and 180 as an example of examining an optical fiber free from eccentricity. In the examining process of the present invention, the eccentricity of the optical fi~er being examined is judged zero because the eccentricity measured will not change even if the observing angle is examined, the presence of the dis~ortion of the magnifying power of the pickup system wilI not affect the change of 12~5~76 1 the eccentricity in the circumferential direction of the optical fiber and, when the sine wave function is fitted, its amplitude becomes zero. In consequence, the eccentricity of the optical fiber being examined is measured as zero.
~ hen the optical axis connecting the light source and the pickup system is not perpendicular to the axis of the optical fiber, e.g., when the posit.ion of the light souxce 63 changes from A to B as shown in Fig. 23, a pattern of the luminance disstribution observed by a television camera 66 via an optical fiber 64 being examined and an objective lens 65 change; as shown in Fig.
24. In the luminance distribution with the light source 63 of Fig. 23 without being shifted in the position A and a luminance distribution with the light source 63 shifted in the position B, respesctively. The structural parameters obtainable from the luminance distribution include the influence of the shifted position of the light source. In the instrument for examining the structure oE
the optical fiber according to the method of the invention, the parameters are not affected by the shift of the li~ht source because the optical axis connecting the light source and the pickup system is set perpendicular to the axis of the optical fiber.
12~476 - 34 ~
1 Still furthermore, the position detecting method and apparatus according to the present invention can accurately detect the position of the observing plane of the optical fiber to be examined by measuring the distance between the diffraction fringes produced at the outer edge of the optical fiber using the point sourc for emitting substantially monochromatic light. Consequently, the center position of the core is measured accurately by observing the side image of the optical fiber. the position detecting method according to the present invention can thus be utilized in a wide range oE use, e.g., for optical fiber fusion welding ~achines.
..... .
Claims (18)
1. An apparatus for examining the structure of an optical fiber having a core and a cladding surrounding said core, said core and said cladding having different refractive indices, said apparatus comprising:
optical measuring means comprising a light source for irradiating a side wall of said optical fiber with an observing light beam and a pickup system for detecting that part of said observing light beam which traverses said optical fiber;
means for mounting said optical fiber, one of said optical fiber mounting means and said optical measuring means being rotatable relatively to the other such that an axis of said optical fiber and the optical axis of said optical measuring means are set perpendicular to each other;
and means coupled to said pickup system for correcting a luminance distribution as detected by said pickup system for a lens effect due to the different refractive indices of said core and said cladding of the optical fiber under observation.
optical measuring means comprising a light source for irradiating a side wall of said optical fiber with an observing light beam and a pickup system for detecting that part of said observing light beam which traverses said optical fiber;
means for mounting said optical fiber, one of said optical fiber mounting means and said optical measuring means being rotatable relatively to the other such that an axis of said optical fiber and the optical axis of said optical measuring means are set perpendicular to each other;
and means coupled to said pickup system for correcting a luminance distribution as detected by said pickup system for a lens effect due to the different refractive indices of said core and said cladding of the optical fiber under observation.
2. An apparatus as claimed in claim 1, wherein said pickup system comprises a television camera for monitoring an image of said traversed light beam and an image processing unit for analyzing a luminance distribution of said image.
3. An apparatus as claimed in claim 1, wherein said optical measuring means further comprises light collimating means disposed in between said light source and said optical fiber for collinating said observing light beam from said light source.
4. An apparatus as claimed in claim 1, wherein said observing light beam comprises substantially monochromatic light.
5. An apparatus as claimed in claim 1, wherein said observing light beam comprises diffused light.
6. An apparatus as claimed in claim 1, wherein said optical measuring means further comprises a cylindrical lens for converging said observing light beam in the direction of the axis of said optical fiber.
7. An apparatus as claimed in claim 1, wherein said image pickup system comprises charge coupled device(CCD) line-sensors, said CCD line-sensors being mechanically scanned in a direction perpendicular to the axis thereof.
8. An apparatus as claimed in claim 1, wherein said light source comprises a fiber bundle having plural light emitting diodes(LED) and plural optical fibers optically connected to said LEDs.
9. An apparatus as claimed in claim 3, wherein said light collimating means comprises a collimator lens.
10. An apparatus as claimed in claim 4, wherein said light source comprises a light emitting diode(LED).
11. The apparatus as claimed in claim 1, wherein said means for correcting includes means for determining a relative position of said optical fiber and said pickup system with respect to the optical axis, and performs correction of the luminance distribution based on the relative position.
12. A method of examinig the structure of an optical fiber, said mehtod comprising the steps of:
arranging optical measuring means comprising a light source for generating light and a pickup system for detecting said light in such a manner that the axis of said optical fiber and the optical axis of said optical measuring means are perpendicular to each other;
irradiating the side wall of said optical fiber with said light in the direction perpendicular to said axis of said optical fiber;
measuring a luminance distribution of said light traversing said optical fiber;
correcting the lens effect on said luminance distri-bution of said light on the basis of position data of an observing plane; and calculating structural parameters such as eccentri-city, clad diameter, core diameter, nonroundness of said clad and so on of said optical fiber on the basis of said luminace distribution subjected to correction of the lens effect.
arranging optical measuring means comprising a light source for generating light and a pickup system for detecting said light in such a manner that the axis of said optical fiber and the optical axis of said optical measuring means are perpendicular to each other;
irradiating the side wall of said optical fiber with said light in the direction perpendicular to said axis of said optical fiber;
measuring a luminance distribution of said light traversing said optical fiber;
correcting the lens effect on said luminance distri-bution of said light on the basis of position data of an observing plane; and calculating structural parameters such as eccentri-city, clad diameter, core diameter, nonroundness of said clad and so on of said optical fiber on the basis of said luminace distribution subjected to correction of the lens effect.
13. A method as claimed in claim 12, said mehtod further comprising the steps of:
revolving one of said optical fiber and said optical detecting means relatively to the other while said axis and said optical axis are set to be perpendicular to each other;
measuring luminance distributions subjected to said correction of the lens effect over observing angles to be observed;
calculating structural parameters such as eccentrici-ties, clad diameters, core diameters, nonroundnesses of clad and so on of said optical fibers at said observing angles;
revolving one of said optical fiber and said optical detecting means relatively to the other while said axis and said optical axis are set to be perpendicular to each other;
measuring luminance distributions subjected to said correction of the lens effect over observing angles to be observed;
calculating structural parameters such as eccentrici-ties, clad diameters, core diameters, nonroundnesses of clad and so on of said optical fibers at said observing angles;
14. A method of measuring the outer diameter and the position of an observing plane of an optical fiber, said method comprising the steps of:
arranging optical detecting means comprising a monochromatic light source for generating substantially a monochromatic light, light collimating means for collimating said monochromatic light and a pickup system for detecting said monochromatic light in such a manner that the axis of said optical fiber and the optical axis of said optical measuring means are perpendicular to each other;
collimating said monochromatic light;
irradiating the side wall of said optical fiber with said collimated monochromatic light in the direction perpendicular to said axis of said optical fiber;
detecting a luminance distribution of said collimated monochromatic light traversing said optical fiber, said luminance distribution including diffraction fringes appearing in a place corresponding to the outer edge of said optical fiber; and calculating the distance between said diffraction fringes to accurately obtain the outer diameter of said optical fiber and the position of said observing plane of said optical fiber.
arranging optical detecting means comprising a monochromatic light source for generating substantially a monochromatic light, light collimating means for collimating said monochromatic light and a pickup system for detecting said monochromatic light in such a manner that the axis of said optical fiber and the optical axis of said optical measuring means are perpendicular to each other;
collimating said monochromatic light;
irradiating the side wall of said optical fiber with said collimated monochromatic light in the direction perpendicular to said axis of said optical fiber;
detecting a luminance distribution of said collimated monochromatic light traversing said optical fiber, said luminance distribution including diffraction fringes appearing in a place corresponding to the outer edge of said optical fiber; and calculating the distance between said diffraction fringes to accurately obtain the outer diameter of said optical fiber and the position of said observing plane of said optical fiber.
15. A method as claimed in any one of claims 12 and 14 said method further comprising the steps of:
converging said light from said light source in the direction of said axis of said optical fiber before irradiating said optical fiber with said light.
converging said light from said light source in the direction of said axis of said optical fiber before irradiating said optical fiber with said light.
16. A method as claimed in any one of claims 12 and 14 where said pickup system comprises CCD line sensors, said line sensors being mechanically scanned in the direction of the axis of said CCD line sensors.
17. A method of determing the position of an observing plane of an optical fiber, said method comprising the steps of:
arranging optical measuring means comprises a light source for generating a diffused light and pickup system for detecting said diffused light in such a manner that the axis of said optical fiber and the optical axis of said optical measuring means are perpendicular to each other;
irradiating the side wall of said optical fiber with said light in the direction perpendicular to said axis of said optical fiber;
locating the focus position of said pickup system at the center of said optical fiber;
shifting one of said pickup system and said optical fiber relatively to the other in the direction of said optical axis and measuring the shifting distance of said one with a precise range-measuring device thereby to determine the position of said observing plane of said optical fiber.
arranging optical measuring means comprises a light source for generating a diffused light and pickup system for detecting said diffused light in such a manner that the axis of said optical fiber and the optical axis of said optical measuring means are perpendicular to each other;
irradiating the side wall of said optical fiber with said light in the direction perpendicular to said axis of said optical fiber;
locating the focus position of said pickup system at the center of said optical fiber;
shifting one of said pickup system and said optical fiber relatively to the other in the direction of said optical axis and measuring the shifting distance of said one with a precise range-measuring device thereby to determine the position of said observing plane of said optical fiber.
18. A method as claimed in any one of claims 1, 5, and 17, said method further comprising the step of sending clean air at least to a place where said optical fiber and said optical measuring means are disposed.
Applications Claiming Priority (9)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP19153486 | 1986-08-15 | ||
| JP191534/86 | 1986-08-15 | ||
| JP17506/87 | 1987-01-28 | ||
| JP1750687A JPH0797064B2 (en) | 1986-08-15 | 1987-01-28 | Optical fiber structure measurement method |
| JP4851987A JPH083403B2 (en) | 1987-03-03 | 1987-03-03 | Position detection device |
| JP48519/87 | 1987-03-03 | ||
| JP11533387A JP2504771B2 (en) | 1987-05-12 | 1987-05-12 | Luminance distribution measuring device |
| JP115333/87 | 1987-05-12 | ||
| JP117488/87 | 1987-05-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1295476C true CA1295476C (en) | 1992-02-11 |
Family
ID=27456790
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000543994A Expired - Fee Related CA1295476C (en) | 1986-08-15 | 1987-08-07 | Method and apparatus of measuring outer diameter and structure of optical fiber |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1295476C (en) |
-
1987
- 1987-08-07 CA CA000543994A patent/CA1295476C/en not_active Expired - Fee Related
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