JPH0414293B2 - - Google Patents
Info
- Publication number
- JPH0414293B2 JPH0414293B2 JP1494984A JP1494984A JPH0414293B2 JP H0414293 B2 JPH0414293 B2 JP H0414293B2 JP 1494984 A JP1494984 A JP 1494984A JP 1494984 A JP1494984 A JP 1494984A JP H0414293 B2 JPH0414293 B2 JP H0414293B2
- Authority
- JP
- Japan
- Prior art keywords
- refractive index
- sample
- measurement
- samples
- standard
- 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.)
- Expired
Links
- 238000005259 measurement Methods 0.000 claims description 37
- 238000000034 method Methods 0.000 claims description 15
- 239000002131 composite material Substances 0.000 claims description 10
- 239000000463 material Substances 0.000 claims description 4
- 238000005498 polishing Methods 0.000 claims description 4
- 239000011521 glass Substances 0.000 description 8
- 230000006866 deterioration Effects 0.000 description 4
- 239000005304 optical glass Substances 0.000 description 4
- 238000000691 measurement method Methods 0.000 description 3
- 230000005856 abnormality Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000000835 fiber Substances 0.000 description 2
- 230000003287 optical effect Effects 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 235000007173 Abies balsamea Nutrition 0.000 description 1
- 239000004857 Balsam Substances 0.000 description 1
- 244000018716 Impatiens biflora Species 0.000 description 1
- 230000002159 abnormal effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000009499 grossing Methods 0.000 description 1
- 235000021440 light beer Nutrition 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 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)
Description
【発明の詳細な説明】
〔発明の技術分野〕
本発明は、自己集束型とフアイバ，レンズのよ
うに屈折率が少なくとも一方向に変化する光学部
材の屈折率分布プロフイールを測定する場合に好
適な屈折率分布測定方法に関する。[Detailed Description of the Invention] [Technical Field of the Invention] The present invention is suitable for measuring the refractive index distribution profile of an optical member whose refractive index changes in at least one direction, such as a self-focusing type, fiber, or lens. This invention relates to a method for measuring refractive index distribution.
上記のような屈折率分布を知る方法として、測
定面に垂直に光線を入射させその反射率の絶対値
を測定し、
反射率Ｒ＝（ｎ−１）2／（ｎ＋１）2 ……(1)
の関係式から光線入射点での屈折率ｎを求める方
法が知られている。
As a way to know the refractive index distribution as described above, a light beam is incident perpendicularly to the measurement surface and the absolute value of the reflectance is measured, and the reflectance R=(n-1) 2 /(n+1) 2 ...(1) ) A method of determining the refractive index n at the point of incidence of the light beam is known.
一般に光学ガラスは水を用いて研磨すると内部
とは屈折率の異なる表面層が出来ることが知られ
ており、前述のように表面反射率の絶対値を測定
する従来方法では、いかに高性能な装置を用いて
精度よく試料表面反射率を測定したとしても、そ
こから得られる屈折率は現実の値とは違つたもの
になるという問題がある。 It is generally known that when optical glass is polished with water, a surface layer with a refractive index different from that of the interior is created. Even if the sample surface reflectance is measured with high precision using a method, there is a problem that the refractive index obtained therefrom will be different from the actual value.
また試料表面の加工による傷あるいは付着異物
による局部的な屈折率の異常に関しても、それが
試料内で実際に異常分布があるのかあるいは外部
要因に拠るものなのかの区別が極めて難しい。 Furthermore, with respect to local refractive index abnormalities due to scratches or attached foreign matter on the sample surface, it is extremely difficult to distinguish whether there is actually an abnormal distribution within the sample or whether it is due to external factors.
さらに、反射光測定装置へ反射光ビールを導く
光学系における減衰も測定精度に悪影響を及ぼ
す。そして測定試料の材質がガラス以外であつて
も上記とほぼ同様の問題がある。 Furthermore, attenuation in the optical system that guides the reflected light beer to the reflected light measuring device also has a negative effect on measurement accuracy. Even when the material of the measurement sample is other than glass, there are almost the same problems as above.
本発明の主な目的は上述の問題点を解決し、測
定試料表面の変質等の外部要因による影響をほと
んど受けることなく屈折率分布を正確に測定し得
る反射率検出方法による測定方法を提供すること
にある。
The main purpose of the present invention is to solve the above-mentioned problems and provide a measurement method using a reflectance detection method that can accurately measure refractive index distribution without being influenced by external factors such as deterioration of the surface of a measurement sample. There is a particular thing.
本発明に従つた方法では、屈折率を予め他の方
法で測定してある屈折率一様な標準試料を屈折率
未知の測定試料に並列して一体固着した後、この
一体化した複合試料体に対して研磨等の測定面平
滑化加工を施し、前記測定面に光ビームを投射し
て前記両試料の反射率を共に測定する。そして上
記の標準試料の測定反射率と既知の屈折率の値お
よび測定試料における反射率測定結果をもとに、
光ビーム投射点での試料屈折率を算出する。自己
集束型のフアイバあるいはレンズの屈折率分布プ
ロフイールを求めるに当つては、上記測定試料の
最大屈折率および最小屈折率に近い二種の標準試
料ガラスを用意し、測定試料とこれら標準試料と
を直線上に配列して光ビームを全試料にわたつて
走査して各試料面上の反射率を連続的に測定して
屈折率分布プロフイールを求める方法が好適であ
る。
In the method according to the present invention, a standard sample with a uniform refractive index whose refractive index has been previously measured by another method is fixed in parallel with a measurement sample of unknown refractive index, and then this integrated composite sample is A measurement surface smoothing process such as polishing is performed on the sample, and a light beam is projected onto the measurement surface to measure the reflectance of both samples. Based on the measured reflectance of the standard sample mentioned above, the known refractive index value, and the reflectance measurement results of the measured sample,
Calculate the sample refractive index at the light beam projection point. In order to obtain the refractive index distribution profile of a self-focusing fiber or lens, prepare two types of standard glass samples that have the maximum and minimum refractive indices of the measurement sample, and compare the measurement sample and these standard samples. It is preferable to use a method in which the refractive index distribution profile is obtained by arranging the light beams in a straight line, scanning the light beam over the entire sample, and continuously measuring the reflectance on each sample surface.
本発明において、測定試料に並列固着する標準
試料は勿論三種以上であつてもよい。 In the present invention, there may of course be three or more types of standard samples fixed to the measurement sample in parallel.
本発明方法によれば、測定試料の測定面に研磨
加工を施すことによつて屈折率が本体と異なる表
面層ができたとしても、同様の表面変質は測定試
料とともに同時加工される標準試料の表面にも同
程度に発生し、したがつて両試料の反射率測定結
果と標準試料の既知屈折率をもとにして測定試料
の未知屈折率ｎを反射率と屈折率の関係式例えば
後述式から算出すれば、上記の試料表面変質によ
る変化分は両試料間で相殺されて真に近い屈折率
の値を求めることができる。また研磨加工で生じ
る傷あるいは反射率測定時に試料表面に付着する
異物も、標準試料と測定試料とを一体化した複合
試料体として取り扱うため、確率的に両試料にほ
ぼ同等の状態で発生し、したがつて両試料の相体
的な屈折率分布プロフイールから上記外部要因に
基づく局所的な屈折率異常も試料本体の分布から
容易に分離排除することができる。また、好適実
施例のように標準試料として測定試料の最大屈折
率および最大屈折率に近いものを用いれば、測定
試料ガラスの平均的な耐候性と、両標準試料ガラ
スの耐候性の平均値がほぼ等しくなるので三者の
反射率から屈折率を求める際にガラス表面変質の
影響を三者間でほぼ完全に相殺できるという利点
がある。
According to the method of the present invention, even if a surface layer with a refractive index different from that of the main body is created by polishing the measurement surface of the measurement sample, similar surface deterioration will not occur on the standard sample that is processed simultaneously with the measurement sample. It occurs to the same extent on the surface, and therefore, based on the reflectance measurement results of both samples and the known refractive index of the standard sample, the unknown refractive index n of the measurement sample can be calculated using the relational formula between reflectance and refractive index, for example, the formula described below. By calculating from , the change due to the sample surface deterioration described above is canceled out between both samples, and it is possible to obtain a refractive index value that is close to the true value. In addition, scratches caused by polishing or foreign matter that adheres to the sample surface during reflectance measurement are handled as a composite sample that integrates the standard sample and measurement sample, so they are likely to occur in almost the same condition on both samples. Therefore, from the relative refractive index distribution profiles of both samples, local refractive index abnormalities caused by the above-mentioned external factors can be easily separated and excluded from the distribution of the sample body. In addition, if the maximum refractive index and the maximum refractive index of the measurement sample are used as the standard sample as in the preferred embodiment, the average weather resistance of the measurement sample glass and the average value of the weather resistance of both standard sample glasses can be adjusted. Since they are almost equal, there is an advantage that when determining the refractive index from the reflectance of the three, the influence of glass surface deterioration can be almost completely canceled out among the three.
以下本発明を図面に示した実施例に基づき詳細
に説明する。
The present invention will be described in detail below based on embodiments shown in the drawings.
図において１は屈折率測定試料の一例として円
柱状の自己集束型ガラスレンズを示す。自己集束
型レンズは周知のように中心軸上の屈折率が最大
で外周に向けて半径方向にパラボリツクに屈折率
が減少する屈折率分布を有する透明円柱体からな
る。この測定試料１の半径方向の屈折率分布プロ
フイールを以下のようにして測定する。 In the figure, reference numeral 1 indicates a cylindrical self-focusing glass lens as an example of a refractive index measurement sample. As is well known, a self-focusing lens is composed of a transparent cylindrical body having a refractive index distribution in which the refractive index is maximum on the central axis and decreases parabolically in the radial direction toward the outer periphery. The radial refractive index distribution profile of this measurement sample 1 is measured as follows.
まず、上記測定試料１の両側に隣接して、屈折
率が一様であつて屈折率を予め周知方法で正確に
測定してある二種の標準試料ガラス片２，３を一
例に配置し、これら三者１，２，３をヤトイガラ
ス材４およびバルサム等の接合材５を用いて一体
に固着して複合試料体６をつくる。そして、この
複合試料体６の一面６Ａを平滑に研磨加工してこ
の面を屈折率測定面とする。ここで標準試料２，
３としては互いに屈折率の異なる、望ましくは標
準試料１の最大屈折率に近い光学ガラス片と最小
屈折率に近い光学ガラス片を用いる。 First, adjacent to both sides of the measurement sample 1, two types of standard sample glass pieces 2 and 3, each having a uniform refractive index and whose refractive index has been accurately measured in advance by a well-known method, are placed as an example. These three members 1, 2, and 3 are fixed together using a Yatoi glass material 4 and a bonding material 5 such as balsam to form a composite sample body 6. Then, one surface 6A of this composite sample body 6 is polished to a smooth surface, and this surface is used as a refractive index measurement surface. Here, standard sample 2,
3, an optical glass piece having a different refractive index from each other, preferably an optical glass piece close to the maximum refractive index of the standard sample 1 and an optical glass piece close to the minimum refractive index of the standard sample 1, are used.
第２図は、上記の複合試料体６中の試料１，
２，３の表面反射率を連続的に測定する装置を示
す。 FIG. 2 shows sample 1 in the above composite sample body 6,
This figure shows an apparatus for continuously measuring the surface reflectance of 2 and 3 surfaces.
複合試料体６は基台７上の微動ステージ８に取
り付けられ、試料体６の測定面６Ａには第１図中
の矢印９方向に走査する光ビーム１０が光源１１
から投射される。すなわち、光源としてのHe−
Neレーザ１１から出たビーム１０は偏向ビーム
スプリツタ１２と1/4波長板１３を通過し、対物
レンズ１４によつて試料表面に集光投射される。
集光投射されたビーム１０は試料表面で反射した
後再び対物レンズ１４を通り、1/4波長板１３を
往復で２回通過することによつて偏波面が90゜回
転し、偏向ビームスプリツタ１２で光源光に対し
て直角方向に反射される。この反射ビーム１５は
受光検出子１６例えばフオトダイオードに入射
し、検出子１６に接続されたパワーメーター１７
で受光強度が検出される。 The composite sample body 6 is mounted on a fine movement stage 8 on a base 7, and a light beam 10 scanning in the direction of arrow 9 in FIG.
projected from. In other words, He− as a light source
A beam 10 emitted from the Ne laser 11 passes through a polarized beam splitter 12 and a quarter-wave plate 13, and is condensed and projected onto the sample surface by an objective lens 14.
The condensed and projected beam 10 is reflected from the sample surface, passes through the objective lens 14 again, and passes through the 1/4 wavelength plate 13 twice in a round trip, thereby rotating the plane of polarization by 90 degrees and passing through the polarizing beam splitter. 12, the light is reflected in a direction perpendicular to the source light. This reflected beam 15 enters a photodetector 16, for example, a photodiode, and a power meter 17 connected to the detector 16
The received light intensity is detected.
さらにパワーメーター１７はステツプモーター
１８とともにコンピユータ１９で制御されてお
り、コンピユータ１９の制御によつてあらかじめ
指定された量だけ複合試料体６は基台７とともに
移動し、移動の都度反射光強度をパワーメーター
１７から読みとる。両標準試料２，３および測定
試料１の測定面を全幅にわたり走査し終えたなら
ば、後述の式に基づいてビーム投射各位置につい
ての屈折率を計算し出力する。このとき必要な微
調整は試料６に入射するビーム１０が入射面に対
して垂直になるように微動ステージ８を調節する
こと及び試料１，２，３が軸対称屈折率分布を持
つとき、その中心軸をビームが通るように同じく
微動ステージ８を調節することのみである。 Further, the power meter 17 is controlled by a computer 19 together with a step motor 18, and the composite sample 6 moves together with the base 7 by a predetermined amount under the control of the computer 19, and the intensity of the reflected light is changed to a power source each time it moves. Read from meter 17. After scanning the entire width of the measurement surfaces of both standard samples 2 and 3 and measurement sample 1, the refractive index for each beam projection position is calculated and output based on the formula described later. The fine adjustment required at this time is to adjust the fine movement stage 8 so that the beam 10 incident on the sample 6 is perpendicular to the incident plane, and when the samples 1, 2, and 3 have an axisymmetric refractive index distribution. All that is required is to similarly adjust the fine movement stage 8 so that the beam passes through the central axis.
次に上記装置の測定原理について述べる。標準
試料２，３からの反射光の強度をそれぞれV2，
V3として反射率をそれぞれR2，R3とすると被験
試料からの反射光強度Ｖ，反射率Ｒの間には、
Ｒ−R2／R3−R2＝Ｖ−V2／V3−V2＝Ｘ……
(2)
の関係がある。ここでＸは標準試料の反射率差に
対する測定試料と一方の標準試料の間の反射率差
の比である。 Next, the measurement principle of the above device will be described. The intensity of the reflected light from standard samples 2 and 3 is expressed as V 2 and
Assuming that V 3 is the reflectance and R 2 is R 3 , the relationship between the intensity of reflected light from the test sample V and the reflectance R is R-R 2 /R 3 -R 2 =V-V 2 /V 3 - V2 =X...
There is a relationship (2). Here, X is the ratio of the reflectance difference between the measurement sample and one standard sample to the reflectance difference of the standard sample.
前述の(1)式および上記(2)式より、
Ｒ＝XR3＋（１−Ｘ）R2＝Ｘ（n3−１／n3
＋１）2＋（１−Ｘ）（n2−１／n2＋１）２……(3)
の関係が成立する。 From the above equation (1) and the above equation (2), R=XR 3 + (1-X) R 2 = X(n 3 -1/n 3
+1) 2 + (1-X) (n 2 -1/n 2 +1) 2...(3) holds true.
Ｘは(2)式より反射光の強度で表現でき、また屈
折率n2，n3は周知の屈折率測定方法で測定でき
る。そこで(3)式を(1)式の逆関数に代入すると、
の関係が得られ、この式から求める屈折率ｎが得
られる。 X can be expressed by the intensity of reflected light from equation (2), and the refractive indices n 2 and n 3 can be measured by a well-known refractive index measurement method. So, by substituting equation (3) into the inverse function of equation (1), we get The following relationship is obtained, and the refractive index n can be obtained from this equation.
また、測定試料１の中心軸から半径方向ｒの距
離での屈折率ｎ（ｒ）が、
n2（ｒ）＝no2〔１−（gr）2＋h4（gr）4
＋h6（gr）6＋h8（gr）8〕……(5)
ただし、noは中心軸上屈折率，ｈ，ｇは分布定
数で表わされるとき、上述測定方法で得られた屈
折率分布曲線に最小二乗法を適用することによつ
て(5)式における各分布定数を直ちに算出すること
ができる。 Also, the refractive index n(r) at the distance r in the radial direction from the central axis of the measurement sample 1 is n 2 (r) = no 2 [1-(gr) 2 +h 4 (gr) 4
+h 6 (gr) 6 +h 8 (gr) 8 ]...(5) Where, no is the refractive index on the central axis, h and g are distribution constants, and the refractive index distribution curve obtained by the above measurement method By applying the least squares method to , each distribution constant in equation (5) can be immediately calculated.
以上に述べた方法によつて求めた自己集束型レ
ンズの屈折率分布の例を第３図のグラフに示す。
第３図のグラフで両端近くにあるほぼ直線的な分
布を示す部分２２，２３は標準試料２，３の屈折
率であり、パラボリツクな分布を示す部分２１は
レンズすなわち測定試料１の屈折率分布である。 An example of the refractive index distribution of a self-focusing lens obtained by the method described above is shown in the graph of FIG.
In the graph of FIG. 3, portions 22 and 23 showing a nearly linear distribution near both ends are the refractive index of the standard samples 2 and 3, and a portion 21 showing a parabolic distribution is the refractive index distribution of the lens, that is, the measurement sample 1. It is.
図面は本発明の実施例を示し、第１図は測定試
料と標準試料を一体固着した複合試料体を示す斜
視図、第２図は試料表面の反射率を測定する装置
の例を示す平面図、第３図は本発明方法で測定し
た自己集束型レンズおよび標準試料の屈折率分布
を示すグラフである。
１……測定試料、２，３……標準試料、６……
複合試料体、１０……光ビーム、１５……反射ビ
ーム、１６……受光検出子、１７……パワーメー
ター。
The drawings show an embodiment of the present invention, and FIG. 1 is a perspective view showing a composite sample body in which a measurement sample and a standard sample are fixed together, and FIG. 2 is a plan view showing an example of an apparatus for measuring the reflectance of a sample surface. , FIG. 3 is a graph showing the refractive index distribution of a self-focusing lens and a standard sample measured by the method of the present invention. 1...Measurement sample, 2, 3...Standard sample, 6...
Composite sample body, 10... light beam, 15... reflected beam, 16... light receiving detector, 17... power meter.
Claims (1)
料を屈折率未知の測定試料に並列して一体固着し
た後、この一体化した複合試料体に対して研磨等
の測定面平滑化加工を施し、前記測定面に光ビー
ムを投射して前記両試料の反射率を共に測定する
ことを特徴とする屈折率分布の測定方法。 ２ 特許請求の範囲第１項において、標準試料と
して測定試料の最大屈折率および最小屈折率に近
い一様な屈折率をもつ二種の材料を使用する屈折
率分布の測定方法。 ３ 特許請求の範囲第２項において、測定試料に
隣接してそれぞれ標準試料を一直線上に配置し、
光ビームを前記三種試料にわたり連続的に走査し
て各点での反射光量を検出することにより屈折率
分布プロフイールを求める屈折率分布の測定方
法。[Claims] 1. After at least one standard sample with a known refractive index is fixed together with a measurement sample of unknown refractive index in parallel, the measurement surface of the integrated composite sample is smoothed by polishing, etc. A method for measuring refractive index distribution, characterized in that the reflectance of both the samples is measured by projecting a light beam onto the measurement surface. 2. A method for measuring refractive index distribution according to claim 1, which uses two materials having uniform refractive indexes close to the maximum and minimum refractive indices of the measurement sample as standard samples. 3 In claim 2, each standard sample is arranged in a straight line adjacent to the measurement sample,
A method for measuring refractive index distribution in which a refractive index distribution profile is determined by continuously scanning a light beam over the three types of samples and detecting the amount of reflected light at each point.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1494984A JPS60158338A (en) | 1984-01-30 | 1984-01-30 | Measuring method of distribution of refractive index |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP1494984A JPS60158338A (en) | 1984-01-30 | 1984-01-30 | Measuring method of distribution of refractive index |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS60158338A JPS60158338A (en) | 1985-08-19 |
| JPH0414293B2 true JPH0414293B2 (en) | 1992-03-12 |
Family
ID=11875225
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP1494984A Granted JPS60158338A (en) | 1984-01-30 | 1984-01-30 | Measuring method of distribution of refractive index |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS60158338A (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP6269183B2 (en) * | 2014-03-07 | 2018-01-31 | 株式会社リコー | Refractive index measuring device |
-
1984
- 1984-01-30 JP JP1494984A patent/JPS60158338A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS60158338A (en) | 1985-08-19 |
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