JPH0373822A - Instrument for measuring distribution of refractive index - Google Patents
Instrument for measuring distribution of refractive indexInfo
- Publication number
- JPH0373822A JPH0373822A JP9705689A JP9705689A JPH0373822A JP H0373822 A JPH0373822 A JP H0373822A JP 9705689 A JP9705689 A JP 9705689A JP 9705689 A JP9705689 A JP 9705689A JP H0373822 A JPH0373822 A JP H0373822A
- Authority
- JP
- Japan
- Prior art keywords
- image
- light
- refractive index
- image pickup
- pickup tube
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000009826 distribution Methods 0.000 title claims description 31
- 230000003287 optical effect Effects 0.000 claims abstract description 34
- 239000011521 glass Substances 0.000 claims abstract description 12
- 238000001514 detection method Methods 0.000 claims description 4
- 238000005259 measurement Methods 0.000 description 5
- 239000013307 optical fiber Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 230000000694 effects Effects 0.000 description 2
- 238000000034 method Methods 0.000 description 2
- 238000005253 cladding Methods 0.000 description 1
- 238000003384 imaging method Methods 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000000691 measurement method Methods 0.000 description 1
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
- G01N21/17—Systems in which incident light is modified in accordance with the properties of the material investigated
- G01N21/41—Refractivity; Phase-affecting properties, e.g. optical path length
- G01N21/412—Index profiling of optical fibres
Landscapes
- Physics & Mathematics (AREA)
- Health & Medical Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Chemical & Material Sciences (AREA)
- Analytical Chemistry (AREA)
- Biochemistry (AREA)
- General Health & Medical Sciences (AREA)
- General Physics & Mathematics (AREA)
- Immunology (AREA)
- Pathology (AREA)
- Investigating Or Analysing Materials By Optical Means (AREA)
Abstract
Description
本発明は、例えば光フアイバ用プリフォームやロッドレ
ンズに使用される円柱ガラスの屈折率分布の測定装置に
関するもので、特に異なる屈折率を有するプリフォーム
等の屈折率分布測定の簡易化、高精度化に役立つもので
ある。The present invention relates to a measuring device for measuring the refractive index distribution of cylindrical glass used, for example, in optical fiber preforms or rod lenses, and in particular, it simplifies and highly accurately measures the refractive index distribution of preforms having different refractive indexes. It is useful for
光フアイバ用プリフォーム（母材）やロッドレンズに使
用される円柱ガラスは、半径方向の屈折率がほぼ２乗分
布、軸方向の屈折率は均一になっている。これを線引き
して光ファイバが形成される。線引き前のプリフォーム
の屈折率分布を正確に測定することが良好な製品を得る
ために必要である。
屈折率分布の測定法としては、例えば特開昭６３−９５
３３６号公報に光フアイバ用のプリフォームの中心軸と
垂直方向から光線を入射させ、その出射角を求めてプリ
フォームの屈折率分布を測定する方法が開示されている
。第７図には同公報に開示された屈折率分布測定装置を
示しである。図に示すように光源５とレンズ６からなる
入射光学系から、セル２内のマツチングオイル３中に設
置されたプリフォームｌに入射され、プリフォームｌを
通って出射された出射光はレンズ２１を有する出射光学
系を通過してＴＶカメラ２２の観察面に投影される。こ
の投影像をＴＶカメラ２２取り出し、投影像の座標Ｘと
出射光学系の焦点距離ｆとから出射角φを
φ： ｔａｎ引（Ｘ／ｆ）
で求めている。そしてパルスモータによりプリフォーム
をｉ１２置した移動テーブル４を移動しながら求めた出
射角φを用いプリフォームｌの屈折率分布ｎ （ｒ）を
次式
で算出している。
あるいは出射光学系を通った出射光の像をスクリーン上
に形成し、スクリーン上の投影像をＴＶカメラ２２で観
察して出射角φを求めている。Cylindrical glass used for optical fiber preforms (base materials) and rod lenses has a refractive index in the radial direction that has a substantially square distribution, and a refractive index in the axial direction that is uniform. An optical fiber is formed by drawing this. Accurately measuring the refractive index distribution of the preform before drawing is necessary to obtain a good product. As a method for measuring refractive index distribution, for example, Japanese Patent Application Laid-Open No. 1983-1995
Japanese Patent Application No. 336 discloses a method in which a light beam is made incident in a direction perpendicular to the central axis of a preform for an optical fiber, and its exit angle is determined to measure the refractive index distribution of the preform. FIG. 7 shows a refractive index distribution measuring device disclosed in the publication. As shown in the figure, an incident optical system consisting of a light source 5 and a lens 6 enters the preform l installed in the matching oil 3 in the cell 2, and the output light that passes through the preform l is emitted from the lens. The light passes through an output optical system having 21 and is projected onto the viewing surface of the TV camera 22. This projected image is taken out by the TV camera 22, and the output angle φ is calculated from the coordinates X of the projected image and the focal length f of the output optical system as follows: φ: tan subtraction (X/f). Then, the refractive index distribution n (r) of the preform l is calculated using the following equation using the exit angle φ obtained while moving the moving table 4 on which the preform is placed i12 by a pulse motor. Alternatively, an image of the output light that has passed through the output optical system is formed on a screen, and the projected image on the screen is observed with the TV camera 22 to determine the output angle φ.
上記のように構成された従来の屈折率分布測定装置にお
いては、入射光学系とともに出射光学系と′ｒＶカメラ
を必要とし、装置が複雑になるという欠点があった。ま
た光学系が複雑になるため、測定に際し各光学系の光軸
を合せるための調整が容易でないという問題もあった。
さらに出射角φが大幅に異なるプリフォームを精度良く
測定する場合には、出射光学系の焦点距離を変えてやる
必要があり、１台の測定装置で出射角φが大幅に異なる
プリフォームの屈折率分布を高精度に測定することがで
きないという欠点もあった。
本発明は、これらの欠点を解消するためになされたもの
にであり、簡単な構成で出射角が大幅に異なる場合であ
っても高精度に屈折率分布を測定することができる屈折
率分布測定装置を得ることを目的とするものである。The conventional refractive index distribution measuring apparatus configured as described above has the disadvantage that it requires an output optical system and an 'rV camera in addition to an input optical system, making the apparatus complicated. Furthermore, since the optical system is complicated, there is also the problem that adjustment to align the optical axes of each optical system during measurement is not easy. Furthermore, in order to accurately measure preforms with significantly different exit angles φ, it is necessary to change the focal length of the exit optical system, and one measuring device can measure the refraction of preforms with significantly different exit angles φ. Another drawback was that the rate distribution could not be measured with high precision. The present invention has been made to eliminate these drawbacks, and is a refractive index distribution measurement method that can measure refractive index distribution with high precision even when the emission angles are significantly different with a simple configuration. The purpose is to obtain a device.
上記課題を解決するための本発明を適用する屈折率分布
の測定装置は、軸方向には均一な屈折率、径方向には屈
折率分布が変化する円柱ガラスの中心軸と垂直方向から
光を入射させ、その出射角を測定して同軸円柱ガラスの
径方向に対する屈折率分布を求める屈折率分布測定装置
において、円柱ガラスからの出射光を受光してその受光
像の電気信号を送り出す撮像管と、該撮像管を搭載し入
射光学系の光軸と同一方向に移動できる移動手段と、該
移動手段に取付けられ撮像管の移動距離を検出する距離
検出手段とを有している。A refractive index distribution measuring device to which the present invention is applied to solve the above problems receives light from a direction perpendicular to the central axis of a cylindrical glass whose refractive index is uniform in the axial direction and whose refractive index distribution changes in the radial direction. In a refractive index distribution measuring device that determines the refractive index distribution in the radial direction of a coaxial cylindrical glass by making the incident light and measuring its exit angle, there is an imaging tube that receives light emitted from the cylindrical glass and sends out an electrical signal of the received light image. , a moving means that mounts the image pickup tube and can move in the same direction as the optical axis of the input optical system, and a distance detection means that is attached to the moving means and detects the moving distance of the image pickup tube.
上記本発明の装置で、円柱ガラスの中心軸と垂直方向か
ら入射して出た出射光を、入射光学系の光軸と同一方向
に移動できる移動手段に搭載された撮像管で受光して出
射光の出射角を測定できる。また出射光の出射角を測定
するときに移動手段を入射光学系の光軸と同一方向に移
動することにより、撮像管の検知範囲を有効に利用する
ことができる。In the above-mentioned device of the present invention, the outgoing light that enters the cylindrical glass in a direction perpendicular to the central axis and comes out is received by the image pickup tube mounted on the moving means that can move in the same direction as the optical axis of the incoming optical system, and then outputted. It is possible to measure the emission angle of incident light. Further, by moving the moving means in the same direction as the optical axis of the input optical system when measuring the output angle of the output light, the detection range of the image pickup tube can be effectively utilized.
以下、本発明の実施例を詳細に説明する。
第１図、第２図は本発明の一実施例の概略構成を示し、
第１図は光フアイバ用のプリフォームｌの中心軸２と同
方向であるｙ軸方向から見た平面図、第２図はｙ軸と垂
直なＸ軸方向から見た側面図である。図において、２は
プリフォームｌを装着したセルであり、セル２内にはプ
リフォームｌの表面における急激な屈折率変化を除くた
めにマツチングオイル３が満たされている。４はセル２
が設置された移動テーブルであり、移動テーブル４はパ
ルスモータ（不図示）により駆動されプリフォームｌを
Ｘ軸とｙ軸方向に移動する。５は例えばＨｅ−Ｎｅレー
ザ発振器からなる光源、６は入射光学系であり、入射光
学系６は光源５からの入射光をプリフォームｌの中心で
最小になるように収斂している。７はプリフォームｌか
ら出射した出射光を受光して像の電気信号を送り出す撮
像管、８は撮像管７を搭載した移動テーブルであり、移
動テーブル８はパルスモータ９により入射光学系６の光
軸と同一方向に移動する。１０は移動テーブル８の移動
距離を検出する移動距離センサ、１１は撮像管７で得た
投影像の電気信号から出射角をもとめて屈折率分布を演
算する制御部である。
第３図は制御部１１の構成を示すブロック図である。図
において、１２は撮像管７で得た電気信号のデータを蓄
えるフレームメモリ、１３は中央処理装置であり、中央
処理装置１３はフレームメモリ１２に蓄えられたデータ
の直線近似等を行ない出射角φを演算するとともに、フ
レームメモリ１２のデータに応じてパルスモータ９を駆
動するモータ駆動手段１４に駆動信号を与える。１５は
表示部、記録部からなる出力手段である。
上記のように構成された屈折率分布測定装置によりプリ
フォームｌの屈折率分布を測定するとき以下のような動
作をする。
光源５から入射光学系６を通って送られた光はプリフォ
ームｌの中心軸と垂直方向から入射し、プリフォームｌ
により屈折されて出射する。この出射光は撮像管７で観
察され、その像の画像データがフレームメモリ１２に送
られ蓄えられる。このデータを中央処理袋ｆｉ１３に送
り、中央処理装置１３で出射光の像の座標値から出射角
φを演算して出力手段１５に送る。
この出射角φを演算するときに、中央処理装置１３は出
射光の像の座標値が撮像管７から外れずに、かつ最も大
きな値となるようにモータ駆動手段１４に駆動信号を与
えてパルスモータ９を駆動し、移動テーブル８を前後に
移動する。一方移動距離センサｌＯは移動テーブル８の
移動距離を検出して中央処理装置１３に送る。そこで中
央処理装置１３は像の最も大きい座標値と移動距離セン
サ１０から送られた移動テーブル８の移動距離を利用し
て高精度に出射角φを演算する。
ここでプリフォームｌを搭載した移動テーブル４を入射
光学系６の光軸に対して垂直方向に移動しながら、プリ
フォームｌに入射する光の位置を変えて出射角φの変化
を求める。
上記のようにして例えば第４図に示すようなコアの最大
屈折率ｎ１、クラッドの屈折率ｎ２のプリフォームｌの
入射位置ｒと出射角φの関係を測定した結果を第５図に
示す。そしてこの第５図に示す出射角φにより屈折率分
布ｎ （ｒｌを求めると第６図に示す特性を得ることが
できた。この測定を３０回繰り返して次式に示す比屈折
率差Δ
Δ：（ｎ＋−ｎ＊）Ｘ１００／ｎｔ
を求め、比屈折率差Δの標準偏差０を測定して、比屈折
率差Δで正規化した結果、
ＣＯ／Δ） ＝ｏ、ｏｏｔ
を得れことができた。
また屈折率分布が異なる種々のプリフォームｌを用い出
射角φを測定して、測定精度を調べた結果も上記精度と
全く同様な測定精度を得ることができた。Examples of the present invention will be described in detail below. 1 and 2 show a schematic configuration of an embodiment of the present invention,
FIG. 1 is a plan view as seen from the y-axis direction, which is the same direction as the central axis 2 of the preform l for optical fiber, and FIG. 2 is a side view as seen from the x-axis direction, which is perpendicular to the y-axis. In the figure, 2 is a cell in which a preform I is mounted, and the cell 2 is filled with matching oil 3 to eliminate sudden changes in refractive index on the surface of the preform I. 4 is cell 2
The moving table 4 is driven by a pulse motor (not shown) to move the preform 1 in the X-axis and y-axis directions. Reference numeral 5 indicates a light source consisting of, for example, a He--Ne laser oscillator, and 6 indicates an input optical system, which converges the incident light from the light source 5 so as to be minimized at the center of the preform l. Reference numeral 7 designates an image pickup tube that receives the output light emitted from the preform l and sends out an electric signal of an image, and 8 is a moving table on which the image pickup tube 7 is mounted. Move in the same direction as the axis. 10 is a moving distance sensor that detects the moving distance of the moving table 8, and 11 is a control unit that determines the exit angle from the electric signal of the projected image obtained by the image pickup tube 7 and calculates the refractive index distribution. FIG. 3 is a block diagram showing the configuration of the control section 11. In the figure, 12 is a frame memory that stores data of electrical signals obtained by the image pickup tube 7, and 13 is a central processing unit.The central processing unit 13 performs linear approximation of the data stored in the frame memory 12, At the same time, a drive signal is given to the motor drive means 14 that drives the pulse motor 9 according to the data in the frame memory 12. 15 is an output means consisting of a display section and a recording section. When measuring the refractive index distribution of the preform I using the refractive index distribution measuring device configured as described above, the following operations are performed. The light sent from the light source 5 through the input optical system 6 enters the preform l from a direction perpendicular to the central axis of the preform l.
The light is refracted and emitted. This emitted light is observed by the image pickup tube 7, and image data of the image is sent to the frame memory 12 and stored therein. This data is sent to the central processing unit fi13, where the central processing unit 13 calculates the emission angle φ from the coordinate values of the image of the emitted light and sends it to the output means 15. When calculating this emission angle φ, the central processing unit 13 supplies a drive signal to the motor drive means 14 and pulses it so that the coordinate value of the image of the emission light does not deviate from the image pickup tube 7 and becomes the largest value. The motor 9 is driven to move the moving table 8 back and forth. On the other hand, the moving distance sensor lO detects the moving distance of the moving table 8 and sends it to the central processing unit 13. Therefore, the central processing unit 13 uses the largest coordinate value of the image and the moving distance of the moving table 8 sent from the moving distance sensor 10 to calculate the exit angle φ with high precision. Here, while moving the movable table 4 on which the preform l is mounted in a direction perpendicular to the optical axis of the input optical system 6, the position of the light incident on the preform l is changed to find a change in the output angle φ. FIG. 5 shows the results of measuring the relationship between the incident position r and the output angle φ of the preform l having the maximum refractive index n1 of the core and the refractive index n2 of the cladding as shown in FIG. 4 as described above. Then, by calculating the refractive index distribution n (rl) using the output angle φ shown in FIG. 5, the characteristics shown in FIG. 6 could be obtained. This measurement was repeated 30 times and the relative refractive index difference Δ Δ :(n+-n*) was completed. Furthermore, the output angle φ was measured using various preforms l having different refractive index distributions, and the measurement accuracy was examined, and the measurement accuracy was found to be exactly the same as the above-mentioned accuracy.
以上説明したように、本発明の装置によれば、円柱ガラ
スの中心軸と垂直方向から入射して出た出射光を、入射
光学系の光軸と同一方向に移動できる移動手段に搭載さ
れた撮像管で受光して出射光の出射角を求めるようにし
たので、出射光系やＴＶカメラのレンズ等の光学系を必
要とせず測定装置の小型化を図ることができる。また測
定装置の光学系を簡略化することができるから、光学系
の光軸調整を簡単に行なうことができ、屈折率分布を容
易に測定することができる。
さらに出射光の出射角を求めるときに移動手段を入射光
学系の光軸と同一方向に移動することにより、撮像管の
検知範囲を有効に利用することができるから、１台の測
定装置で大幅に屈折率分布が異なる種々の同軸円柱ガラ
スの屈折率分布を高精度に測定することもできる。As explained above, according to the device of the present invention, the emitted light that enters the cylindrical glass from a direction perpendicular to the central axis and exits is mounted on a moving means that can move the emitted light in the same direction as the optical axis of the incident optical system. Since the emission angle of the emitted light is determined by receiving the light with the image pickup tube, it is possible to downsize the measuring device without requiring an optical system such as an emitting light system or a TV camera lens. Furthermore, since the optical system of the measuring device can be simplified, the optical axis of the optical system can be easily adjusted, and the refractive index distribution can be easily measured. Furthermore, by moving the moving means in the same direction as the optical axis of the input optical system when determining the exit angle of the output light, the detection range of the image pickup tube can be effectively used, so a single measurement device can significantly improve the It is also possible to measure the refractive index distributions of various coaxial cylindrical glasses with different refractive index distributions with high precision.
第１図は本発明を適用する装置の実施例の概略平面図、
第２図はその側面図、第３図は上記実施例の制御部を示
すブロック図、第４図はプリフォームの屈折率分布を示
す特性図、第５図は上記装置により測定した出射角特性
図、第６図はその出射角特性から得た屈折率分布特性図
、第７図は従来の装置例を示す構成図である。
１−・・プリフォーム ２・・・セル４・・・移動
テーブル ５・・・光源６・・・入射光学系
７・・・撮像管８・・・移動テーブル ９・・・
パルスモータ１０・・・移動距離センサ １１・・・制
御部１２・・・フレームメモリ １３・・・中央処理装
置第
１
図
第７図
第４図
半径「FIG. 1 is a schematic plan view of an embodiment of an apparatus to which the present invention is applied;
Fig. 2 is a side view thereof, Fig. 3 is a block diagram showing the control section of the above embodiment, Fig. 4 is a characteristic diagram showing the refractive index distribution of the preform, and Fig. 5 is the output angle characteristic measured by the above device. 6 are refractive index distribution characteristics obtained from the output angle characteristics, and FIG. 7 is a configuration diagram showing an example of a conventional device. 1-...Preform 2...Cell 4...Moving table 5...Light source 6...Incidence optical system
7... Image pickup tube 8... Moving table 9...
Pulse motor 10...Moving distance sensor 11...Control unit 12...Frame memory 13...Central processing unit 1 Fig. 7 Fig. 4 Radius
Claims (1)
変化する円柱ガラスの中心軸と垂直方向から光を入射さ
せ、その出射角を測定して同軸円柱ガラスの径方向に対
する屈折率分布を求める屈折率分布測定装置において、
円柱ガラスからの出射光を受光してその受光像の電気信
号を送り出す撮像管と、該撮像管を搭載し入射光学系の
光軸と同一方向に移動できる移動手段と、該移動手段に
取付けられ撮像管の移動距離を検出する距離検出手段と
を有することを特徴とする屈折率分布測定装置。1. Refraction in the radial direction of the coaxial cylindrical glass is determined by entering light from a direction perpendicular to the central axis of the cylindrical glass, which has a uniform refractive index in the axial direction and varying refractive index distribution in the radial direction, and measuring its exit angle. In a refractive index distribution measuring device for determining index distribution,
An image pickup tube that receives the light emitted from the cylindrical glass and sends out an electric signal of the received light image; a moving means on which the image pickup tube is mounted and can move in the same direction as the optical axis of the input optical system; 1. A refractive index distribution measuring device, comprising distance detection means for detecting a moving distance of an image pickup tube.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1097056A JPH07109381B2 (en) | 1989-04-17 | 1989-04-17 | Refractive index distribution measuring device |
| US07/509,909 US5078488A (en) | 1989-04-17 | 1990-04-16 | Method and apparatus for determining refractive index distribution |
| DE69013963T DE69013963T2 (en) | 1989-04-17 | 1990-04-17 | Method and device for determining the refractive index profile. |
| EP90107269A EP0393591B1 (en) | 1989-04-17 | 1990-04-17 | Method and apparatus for determining refractive index distribution |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1097056A JPH07109381B2 (en) | 1989-04-17 | 1989-04-17 | Refractive index distribution measuring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0373822A true JPH0373822A (en) | 1991-03-28 |
| JPH07109381B2 JPH07109381B2 (en) | 1995-11-22 |
Family
ID=14181998
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1097056A Expired - Lifetime JPH07109381B2 (en) | 1989-04-17 | 1989-04-17 | Refractive index distribution measuring device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH07109381B2 (en) |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6395336A (en) * | 1986-10-10 | 1988-04-26 | Fujikura Ltd | Measurement of refractive index distribution |
| JPH0198949A (en) * | 1987-10-12 | 1989-04-17 | Sumitomo Electric Ind Ltd | Refraction angle measuring instrument |
-
1989
- 1989-04-17 JP JP1097056A patent/JPH07109381B2/en not_active Expired - Lifetime
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6395336A (en) * | 1986-10-10 | 1988-04-26 | Fujikura Ltd | Measurement of refractive index distribution |
| JPH0198949A (en) * | 1987-10-12 | 1989-04-17 | Sumitomo Electric Ind Ltd | Refraction angle measuring instrument |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH07109381B2 (en) | 1995-11-22 |
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