JPH02115701A - Laser interferometric length measuring meter - Google Patents
Laser interferometric length measuring meterInfo
- Publication number
- JPH02115701A JPH02115701A JP63268113A JP26811388A JPH02115701A JP H02115701 A JPH02115701 A JP H02115701A JP 63268113 A JP63268113 A JP 63268113A JP 26811388 A JP26811388 A JP 26811388A JP H02115701 A JPH02115701 A JP H02115701A
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- Prior art keywords
- light
- length measuring
- face
- reflected
- reference light
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- 238000005259 measurement Methods 0.000 claims abstract description 66
- 230000003287 optical effect Effects 0.000 claims abstract description 44
- 230000010287 polarization Effects 0.000 claims description 25
- 239000000463 material Substances 0.000 claims description 7
- 239000010453 quartz Substances 0.000 claims description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 4
- 238000006073 displacement reaction Methods 0.000 abstract description 5
- 239000011888 foil Substances 0.000 abstract 1
- 238000001514 detection method Methods 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 230000035945 sensitivity Effects 0.000 description 7
- 230000035559 beat frequency Effects 0.000 description 6
- 238000000034 method Methods 0.000 description 4
- 239000011521 glass Substances 0.000 description 3
- 230000000087 stabilizing effect Effects 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 210000003127 knee Anatomy 0.000 description 2
- 229910001220 stainless steel Inorganic materials 0.000 description 2
- 239000010935 stainless steel Substances 0.000 description 2
- 229910001374 Invar Inorganic materials 0.000 description 1
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000004378 air conditioning Methods 0.000 description 1
- 210000004556 brain Anatomy 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 230000010363 phase shift Effects 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- -1 stainless steel Chemical class 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
Landscapes
- Instruments For Measurement Of Length By Optical Means (AREA)
Abstract
Description
【発明の詳細な説明】
（産業上の利用分野）
この発明は、レーザー干渉測長計、特に、外乱の影響を
少なくした高精度のレーザー干渉測長計に関する。DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a laser interferometric length measuring meter, and particularly to a highly accurate laser interferometric length measuring meter that is less affected by disturbances.
（従来波Ｗｉ）
従来の干渉測長計は、０．１μｍ以下の測長分解能を得
るため、光源にガスレーザーや半導体レーザー等を用い
、そのビーム光を参照光と測長光に分けた後、被測長物
からの戻り光を再度参照光と一致させ、干渉縞やビート
を観測することによって測長（変位）情報を得ている。(Conventional wave Wi) In order to obtain a length measurement resolution of 0.1 μm or less, a conventional interferometric length meter uses a gas laser, semiconductor laser, etc. as a light source, and after dividing the beam light into a reference light and a length measurement light, Length measurement (displacement) information is obtained by matching the return light from the object to be measured with the reference light again and observing interference fringes and beats.
干渉計の構成は、いずれも第１０図に示すマイケルソン
型干渉計を基本としている。すなわち。The configurations of the interferometers are all based on the Michelson type interferometer shown in FIG. Namely.
光源２０からの光はビームスプリッタ−２１で参照光と
測長光に分けられ、測長光は測長物に取り付けられた移
動＃Ｉ２２で反射し、ビームスプリッタ−２１で固定鏡
２３からの反射光と合成され干渉縞を生じる。測長情報
の検出方法によって、戻り光により発生した干渉縞の動
きをカウントする干渉縞計数方式と、コヒーレントな複
数の波長を用いてビートを打たせ、被測定物の速度によ
って測長光の周波数がドツプラーシフトすることを利用
し、ビートの周波数変化を検出するヘテロダイン方式と
がある。The light from the light source 20 is divided into a reference light and a length measurement light by a beam splitter 21, the length measurement light is reflected by a moving #I22 attached to the length measurement object, and the beam splitter 21 separates the light reflected from a fixed mirror 23. are combined to produce interference fringes. The length measurement information is detected using an interference fringe counting method that counts the movement of interference fringes generated by the returned light, and a beat using multiple coherent wavelengths, which determines the frequency of the length measurement light based on the speed of the object being measured. There is a heterodyne method that uses the Doppler shift of the beat to detect changes in the beat frequency.
前者は第１１図に示す光学配置となっており、阿、 Ｊ
、 Ｄｏｖｈｓとに、 Ｌ Ｒａ１ｈａｌによる公知文
献ＰＲＥＣＩＳＩＯＮ ＥＮＧＩＮＥＥＲＩＮＧ Ｖｏ
ｌ、１． Ｎｏ、１（１９７９） ８５に検出信号処理
も含めて詳しく記載されている。すなわち、安定化レー
ザー２０からの直線偏光はλ／４板２４を通過して円偏
光となり、偏光ビームスプリッタ−２１によって参照光
と測長光に分けられる。測長光は移動＠２２で反射され
偏光ビームスプリッタ−２１に戻るが、λ／４板２板上
５過することにより偏光方向が直交するように変換され
、偏光ビームスプリッタ−２１で反射される。そして、
固定鏡２３で反射され、λ／４板２板上５過して偏光面
が変換され、偏光ビームスプリッタ−２１を透過した参
照光と合成される。ここでは参照光と測長光は偏光方向
が直交しているので干渉はしないが、偏光子２７．２９
によって共通偏光成分を抽出することによって干渉縞を
発生する。この干渉縞の動きを検出器２８．３０で検出
するが、移動鏡２２の移動方向を判別するため、偏光子
２７と２９は互いに直交する偏光を抽出するように配置
されている。２６はビームスプリッタ−である。The former has the optical arrangement shown in Figure 11, and A, J
, Dovhs, Publicly known literature PRECISION ENGINEERING Vo by L Rahal
l, 1. No. 1 (1979) 85, it is described in detail including detection signal processing. That is, the linearly polarized light from the stabilized laser 20 passes through the λ/4 plate 24 to become circularly polarized light, and is split into reference light and length measurement light by the polarizing beam splitter 21. The length measurement light is reflected by the movement @ 22 and returns to the polarizing beam splitter 21, but by passing through two λ/4 plates, the polarization direction is converted to be orthogonal, and then reflected by the polarizing beam splitter 21. . and,
It is reflected by the fixed mirror 23, passes over two λ/4 plates, has its polarization plane changed, and is combined with the reference light transmitted through the polarization beam splitter 21. Here, the polarization directions of the reference light and length measurement light are orthogonal, so they do not interfere, but the polarizer 27.29
Interference fringes are generated by extracting the common polarization component. The movement of the interference fringes is detected by detectors 28 and 30, and in order to determine the moving direction of the movable mirror 22, polarizers 27 and 29 are arranged so as to extract polarized light orthogonal to each other. 26 is a beam splitter.
後者は第１２図に示す様な光学配置となっており、 Ｌ
、Ｊ、ｖｕｅｒｚとＲ，Ｃ，Ｑｕｅｎｅｌｌｅによる公
知文献ＰＲＥ（ＪＳＩＯＮＥＮＧＩＮＥＥＲＩＮＧ Ｖ
ｏｌ、５． Ｎｏ、３ （１９８３） １１１に詳しい
、すなわち、互いに逆方向に回転する周波数ｆ□、ｆ２
の２つの円偏光を発生する２周波ゼーマンレーザー２０
’ からのビームは、λ／４板２４によって互いに直角
な偏光面を持つ直線偏光となる。ビームスプリッタ−３
４、偏光子３１を経て検出器３２では周波数ｆいｆ２の
ビート（ｆｌ−ｆ、）が検出される。移動鏡２２からの
反射光は、ドツプラー効果によって移動速度に応した周
波数変化Δｆを生じており、検出器３３で検出されるビ
ートは（ｆニーｆ２±Δｆ）となり、雨検出器からのビ
ート周波数を比較減算することによって物体の移動情報
を得ることが出来る。偏光ビームスプリッタ−３５によ
り、ｆ１光、ｆ２光は別々に検出器３６．３７で検出さ
れ、レーザー同調回路３８へ入力される。The latter has an optical arrangement as shown in Figure 12, and L
, J. Vuerz and R. C. Quenelle, PRE (JSION ENGINEERING V
ol, 5. No. 3 (1983) 111 in detail, that is, frequencies f□, f2 that rotate in opposite directions to each other.
A dual-frequency Zeeman laser 20 that generates two circularly polarized lights
The beams from ' are turned into linearly polarized light by the λ/4 plate 24 with planes of polarization perpendicular to each other. Beam splitter 3
4. The beat (fl-f,) of frequency f2 is detected by the detector 32 via the polarizer 31. The reflected light from the moving mirror 22 causes a frequency change Δf depending on the moving speed due to the Doppler effect, and the beat detected by the detector 33 is (f knee f2 ± Δf), which is the beat frequency from the rain detector. By comparing and subtracting, the movement information of the object can be obtained. By the polarizing beam splitter 35, the f1 light and the f2 light are detected separately by detectors 36 and 37, and are input to the laser tuning circuit 38.
いずれの例も、測長分解能は、電気的な処理も含めて、
０．０１μ■と極めて高く、この分解能を精度良く維持
するために、レーザー光源は、１０−’〜１０−８程度
の精度で周波数の安定化がなされている。In both examples, the length measurement resolution, including electrical processing, is
The resolution is extremely high as 0.01 μι, and in order to maintain this resolution with high accuracy, the frequency of the laser light source is stabilized with an accuracy of about 10-' to 10-8.
さらに、外乱に対する検出信号の安定化を図るために、
干渉縞計数方式の第１１図の例では、検出干渉縞の位相
を０°、９０° １８０°と３種類変えた信号をとり
出し、それぞれ差動出力をとる事により、９０ｍ位相の
異なる２つの安定した信号を得ている。これにより、検
出ビーム光の強度が９０％程度外乱で変化しても正確な
干渉縞の計数が実現されている。Furthermore, in order to stabilize the detection signal against disturbances,
In the example of the interference fringe counting method shown in Figure 11, by extracting signals with three different phases of the detected interference fringes: 0°, 90°, and 180°, and taking differential outputs for each, two signals with 90m different phases are obtained. I am getting a stable signal. This makes it possible to accurately count interference fringes even if the intensity of the detection beam changes by about 90% due to disturbance.
また、ヘテロダイン方式の外乱に対する検出信号の安定
化の例として、第１３図に示す様な差動型の光路を持っ
た干渉測長計を持つ公知例がある。Further, as an example of stabilizing the detection signal against disturbances using the heterodyne method, there is a known example having an interferometric length measuring meter having a differential optical path as shown in FIG.
偏光ビームスプリッタ２１とλ／４板２板上５より、測
長光はビームスプリッタ２１→移動コーナーキユーブ２
２→ビームスプリツタ２１→コーナーキユーブ４ｏ→移
動コーナーキユーブ２２→コーナーキユーブ４１→ビー
ムスプリツタ２１→コーナーキユーブ３９→ビームスプ
リツタ２１→出射の経路をたどり、参照光はビームスプ
リツタ２１→コーナーキユーブ３９→コーナーキユーフ
４１→反射鏡４２→コーナーキューブ４０→反射鏡４２
→出射の経路をたどる。これは周波数安定化レーザーの
ビームを測長光と参照光にわけ再度−致させる干渉測長
計内において、光路長を参照光と測長光ともに同じにす
る事により、温度変化等の外乱が両方に等しく影響する
ため、検出信号の安定性を大幅に向上する事ができる。From the polarizing beam splitter 21 and the λ/4 plate 2, the length measurement light is transmitted from the beam splitter 21 to the moving corner cube 2.
2 → Beam splitter 21 → Corner cube 4o → Moving corner cube 22 → Corner cube 41 → Beam splitter 21 → Corner cube 39 → Beam splitter 21 → Follow the output path, and the reference light passes through the beam splitter 21 → Corner cube 39 → Corner cube 41 → Reflector 42 → Corner cube 40 → Reflector 42
→Follow the exit route. This is achieved by making the optical path length the same for both the reference light and measurement light in the interferometric length meter, which divides the frequency-stabilized laser beam into length measurement light and reference light and re-aligns them. , the stability of the detection signal can be greatly improved.
しかし第１３図に示す様に、従来の差動型干渉測長計は
極めて複雑で大きな構造となっており、測長プリズム内
の光路長も極めて長く、これらは、外乱からの安定性を
高めるためにはマイナス要因として働く、シかも測長光
は被測長物との間を一往復するだけなので、干渉計とし
ての光学的な検出感度も二往復する第１４図に示すよう
な干渉計と比べて半分となり、精度が向上する割に有利
とは言えない、またコーナーキューブを用いているので
、測長光の温度安定性は、あまり良くない。However, as shown in Figure 13, conventional differential interferometers have extremely complex and large structures, and the optical path length within the measuring prism is extremely long. However, since the length measurement light only makes one round trip to the object to be measured, the optical detection sensitivity of the interferometer is also lower than that of an interferometer shown in Figure 14, which makes two round trips. This is not advantageous even though the accuracy is improved, and since a corner cube is used, the temperature stability of the length measurement light is not very good.
しかし、第１４図に示すものはプリズム内での光路長が
参照光と測長光とで異なっており、温度等の外乱の影響
が大きい。However, in the case shown in FIG. 14, the optical path length within the prism is different between the reference light and the length measurement light, and the influence of disturbances such as temperature is large.
また従来、干渉測長計を構成する多くの光学部品が、Ｂ
Ｋ−７の様な、あまり熱線膨張係数の小さくない硝材を
使用しており、またプリズムの固定枠等の機械部品もス
テンレス等の鋼と熱線膨張係数がたいして違わない材料
を使用している。そのため外乱を受は易く、また外乱を
少なくするためには極めて精密にコントロールされた高
価な測定環境を必要としたり、あるいは外乱の影響を全
く無視する等、レーザー干渉測長計の分解能を十分に活
かせるほど測定精度の向上に対して考慮がされていなか
った。In addition, conventionally, many of the optical components that make up the interferometer are B
A glass material such as K-7, which does not have a very small coefficient of linear thermal expansion, is used, and mechanical parts such as the fixing frame for the prism are made of materials whose coefficient of linear thermal expansion is not much different from that of steel, such as stainless steel. Therefore, it is susceptible to disturbances, and in order to reduce disturbances, it is necessary to have an extremely precisely controlled and expensive measurement environment, or to completely ignore the effects of disturbances, making it difficult to fully utilize the resolution of the laser interferometer. However, little consideration was given to improving measurement accuracy.
（この発明が解決しようとする問題点）この発明は従来
のレーザー干渉測長計において、この干渉計が本来持っ
ている分解能に見合った測定精度を、光学的な検出感度
をおとす事なく実現する事を目的としている。(Problems to be Solved by the Invention) This invention aims to achieve measurement accuracy commensurate with the inherent resolution of the interferometer in a conventional laser interferometer without compromising optical detection sensitivity. It is an object.
（問題を解決するための手段）
この発明のレーザー干渉測長計においは、測定光と参照
光の干渉測長系内の光路長さを等しくとり、差動型の光
路配置とした事を特徴とする。(Means for Solving the Problem) The laser interferometric length measuring meter of the present invention is characterized in that the optical path lengths of the measuring light and the reference light in the interferometric measuring system are made equal, and a differential optical path arrangement is used. do.
この様な光路配置は、測長光と参照光に偏光方向の異な
る複数の波長を用い、ヘテロダイン干渉計としてもよく
、また、測長光と参照光に偏光方向の異なる単一の波長
を用い、干渉縞計数型として構成しても良い。Such an optical path arrangement can be used as a heterodyne interferometer by using multiple wavelengths with different polarization directions for the length measurement light and reference light, or by using a single wavelength with different polarization directions for the length measurement light and reference light. , may be configured as an interference fringe counting type.
ここで言う干渉測長系とは、ビームスプリッタ−１参照
光の反射面を含み、一体に構成されている光学系部分を
意味する。The term "interferometric measurement system" as used herein refers to an optical system part that includes a reflection surface of the reference beam of the beam splitter 1 and is integrally configured.
（実施例）
光学系のアライメントの問題を除けば、温度安定性の高
い干渉測長計は第１図の様な簡単な構成で実現できる。(Example) Except for the problem of alignment of the optical system, an interferometric length measuring meter with high temperature stability can be realized with a simple configuration as shown in FIG.
干渉縞計数型もヘテロダイン型も干渉計内のビームスプ
リッタ−に偏光膜を用い、検出部に検光子（又は等価な
光学素子）を用いればほとんど共用できる場合が多く、
ビームスプリッタ−の偏光特性をなくすと、干渉縞計数
型専用となる。In most cases, both the interference fringe counting type and the heterodyne type can be used in common by using a polarizing film in the beam splitter in the interferometer and an analyzer (or equivalent optical element) in the detection section.
If the polarization characteristic of the beam splitter is eliminated, it becomes exclusive to the interference fringe counting type.
以下に第１図の実施例によって干渉縞計数型の測長原理
を説明する。今、干渉計の偏光ビームスプリッタ−とし
て直角プリズム１の垂直な２面をそれぞれ使用すると、
左から入射した円偏光の単一周波数レーザー光は、偏光
ビームスプリッタ−で参照光と測長光に分けられる。参
照光は紙面に垂直な偏光方向を持つ直線偏光で、ビーム
スブリット面での反射光である。測長光は偏光ビームス
ブリット面を透過後、測長物に取りつけられたコーナー
キューブあるいは直角プリズム２で反射し、再び干渉プ
リズム１内に入射する。偏光ビームスブリット面で再度
参照光と測長光が合成させられ、位相変位に変換され干
渉プリズムを出射する。このままでは参照光と測長光の
偏光方向が直交しているため、干渉は発生しないが、λ
／４位相板によって、両直線偏光を回転方向が反対とな
る円偏光にしたり、偏光子によって両方の共通偏光成分
を抽出することによって干渉縞を発生させる事ができる
。The principle of interference fringe counting type length measurement will be explained below using the embodiment shown in FIG. Now, if we use the two perpendicular surfaces of right-angle prism 1 as the polarizing beam splitter of the interferometer, we get
A circularly polarized single-frequency laser beam incident from the left is split into a reference beam and a length measurement beam by a polarizing beam splitter. The reference light is linearly polarized light with a polarization direction perpendicular to the plane of the paper, and is reflected light from the beam split surface. After the length measurement light passes through the polarized beam split surface, it is reflected by a corner cube or right angle prism 2 attached to the object to be measured, and enters the interference prism 1 again. The reference light and length measurement light are combined again on the polarized beam split surface, converted into a phase shift, and output from the interference prism. As it is, the polarization directions of the reference light and length measurement light are orthogonal, so no interference will occur, but λ
It is possible to generate interference fringes by converting both linearly polarized lights into circularly polarized lights with opposite rotation directions using a /4 phase plate, or by extracting a common polarized component of both using a polarizer.
測長物体が移動すると、その変位量に応じて干渉縞が移
動しこれを計数する事で変位量を知る事ができる。When the length-measuring object moves, the interference fringes move according to the amount of displacement, and by counting this, the amount of displacement can be determined.
ヘテロダイン型では、左から入射した互いに直交する直
線偏光で一方向が紙面に平行な２つの周波数ｆいｆ２の
レーザー光は、偏光ビームスプリッタ−で参照光と測長
光に分けられる。参照光は紙面に垂直な偏光方向を持つ
直線偏光で、かつ、一方の単一周波数ｆ２のビームでビ
ームスブリット面での反射光である。測長光は偏光ビー
ムスブリット面を透過後、測長物に取りつけられたコー
ナーキューブあるいは直角プリズム２で反射し、その移
動速度が周波数変位に変換され、再び干渉プリズム１内
に入射する。偏光ビームスブリット面で再度参照光と測
長光が合成させられ、干渉プリズムを出射する。このま
までは参照光（ｆ２）と測長光（ｆｌ）の偏光方向が直
交しているため。In the heterodyne type, two laser beams of frequencies f and f2, which are linearly polarized beams orthogonal to each other and whose one direction is parallel to the plane of the paper, are incident from the left and are split into a reference beam and a measurement beam by a polarizing beam splitter. The reference light is linearly polarized light with a polarization direction perpendicular to the plane of the paper, and one beam with a single frequency f2 is reflected light on the beam split surface. After the length measurement light passes through the polarized beam split surface, it is reflected by a corner cube or right angle prism 2 attached to the length measurement object, its moving speed is converted into a frequency displacement, and the light enters the interference prism 1 again. The reference light and length measurement light are combined again on the polarized beam split surface and exit the interference prism. This is because the polarization directions of the reference light (f2) and length measurement light (fl) are orthogonal as it is.
干渉ビートは発生しないが、λ／４位相板によって、両
直線偏光を回転方向が反対となる円偏光にしたり、偏光
子によって両方の共通偏光成分を抽出することによって
干渉縞ビートを発生させる事ができる。Interference beats do not occur, but interference fringe beats can be generated by converting both linearly polarized lights into circularly polarized lights with opposite rotation directions using a λ/4 phase plate, or by extracting the common polarization component of both using a polarizer. can.
測長物体が移動すると、その速度に応じて干渉縞ビート
周波数ｆ、、−ｆ２±Δｆが移動し、これを計数する事
で速度を知る事ができる。すなわち、干渉計に入射直前
の２つの周波数のビート周波数（ｆニーｆ２）をとり、
測長後のビート周波数（ｆｌ−ｆ２±Δｆ）と比較減算
する事で、物体の移動に伴うドツプラー効果のみによる
周波数変化（±Δｆ）を安定して取り出す事ができる。When the length-measuring object moves, the interference fringe beat frequencies f, -f2±Δf move according to its speed, and by counting this, the speed can be determined. That is, take the beat frequency (f knee f2) of the two frequencies immediately before entering the interferometer,
By comparing and subtracting the beat frequency (fl-f2±Δf) after length measurement, it is possible to stably extract the frequency change (±Δf) due only to the Doppler effect due to the movement of the object.
第１図の直角プリズムを２分すれば、第２図の様に偏光
ビームスプリッタ−プリズムを、２つ重ねても同一の効
果が得られる。If the right-angle prism shown in FIG. 1 is divided into two parts, the same effect can be obtained by stacking two polarizing beam splitter prisms as shown in FIG. 2.
この干渉測長計は単純な割に参照光と測長光の光路長が
プリズム内で同じになるため、安定性が高いが、前述し
たアライメントの難点の他に、測長光が一往復のため光
学的な測長感度があまり高くないという欠点もある。こ
れを解決するために、第３図の様に並列化するのが良い
。この光学系では、参照光と測長光は順次、ビームスプ
リッタ−１，１′ １”およびプリズム２．２′、２”
を通過し、検出精度を３倍に高める。Although this interferometric length meter is simple, it has high stability because the optical path lengths of the reference light and the length measurement light are the same inside the prism. Another disadvantage is that the optical length measurement sensitivity is not very high. To solve this problem, parallelization as shown in FIG. 3 is recommended. In this optical system, the reference light and the length measurement light are sequentially transmitted to the beam splitter 1, 1'1'' and the prism 2, 2', 2''.
, increasing detection accuracy by three times.
第４図は、′ｆ！４長物体からの測長光の反射をコーナ
ーキューブからプレーンミラーに変えた例である。参照
光は偏光ビームスブリット面３で反射後λ／４位相板４
を通り、コーナーキューブ５により反射し、再びλ／４
位相板４を通りλ／２のリタデーションを受け、直交す
る直線偏光となる。Figure 4 shows 'f! This is an example of changing the reflection of length measurement light from a four-length object from a corner cube to a plane mirror. The reference light is reflected by the polarized beam splitting surface 3 and then passes through the λ/4 phase plate 4
, is reflected by corner cube 5, and is again λ/4
The light passes through the phase plate 4 and receives retardation of λ/2, and becomes orthogonally linearly polarized light.
今度は偏光ビームスブリット面を透過し、干渉プリズム
外へ射出する。測長光もプレーンミラー６の反射の前後
でλ／４位相板を１往復し、最初と直行する直線偏光と
なり、偏光ビームスブリット面で反射し、参照光と一致
後干渉プリズムを射出する０図ではへテロダイン型で示
しであるが、干渉縞計数型にも用いる事ができる。This time, the polarized beam passes through the split surface and exits the interference prism. The length measurement light also makes one round trip through the λ/4 phase plate before and after reflection from the plane mirror 6, becomes linearly polarized light perpendicular to the initial direction, is reflected on the polarized beam split surface, and after matching with the reference light is emitted from the interference prism. Although a heterodyne type is shown here, it can also be used for an interference fringe counting type.
第５図はこれを２組組合せて測長光を４往復にし、光学
的測長感度を２倍にあげた例を示す。FIG. 5 shows an example in which two sets of these are combined to make the length measurement light go back and forth four times, thereby doubling the optical length measurement sensitivity.
第６図に最も実用的な実施例を示す、これも第１図の場
合と同様に、干渉縞計数型としてもヘテロダイン型とし
ても使用できる。以下に第１図と同様に干渉縞計数型（
ヘテロダイン型としたばあいを括弧内に示す、）の測長
原理を示す。The most practical embodiment is shown in FIG. 6, which, like the case in FIG. 1, can be used either as an interference fringe counting type or as a heterodyne type. Below, similar to Figure 1, the interference fringe counting type (
In the case of a heterodyne type, the length measurement principle of ) is shown in parentheses.
左側から入射した円偏光の単一周波数（互いに直交する
２つの周波数ｆ□、ｆ、の直線偏光で、方向が紙面に平
行な偏光°面を有する）レーザー光は、偏光ビームスブ
リット面７で参照光と測長光に分けられる。参照光は紙
面に垂直な偏光方向を持つ直線偏光（かつ一方の単一周
波数ｆ、）で偏光ビームスブリット面７での反射光であ
り、測長光は、偏光ビームスブリット面７の透過光であ
る。The single-frequency circularly polarized laser beam incident from the left side (linearly polarized light with two mutually orthogonal frequencies f□, f, with a polarization degree plane whose direction is parallel to the plane of the paper) is referenced at the polarized beam split plane 7. It is divided into light and length measurement light. The reference light is linearly polarized light with a polarization direction perpendicular to the plane of the paper (and one with a single frequency f) reflected by the polarized beam split surface 7, and the length measurement light is transmitted light from the polarized beam split surface 7. be.
参照光は反射後、偏光ビームスブリット面７の下方のλ
／４位相板８に入射する。λ／４位相板の裏面はＡＱ等
により反射コートが施されているので、参照光は一往復
してλ／２のリタデーションを受け、即ち最初と直交す
る方向（紙面に平行な方向）の直線偏光となって戻り、
再び偏光ビームスブリット面７に入射する。しかし最初
と偏光方向が直交するため、今度は参照光は偏光ビーム
スブリット面７を透過し、上部のコーナーキューブプリ
ズム８に入射する。After reflection, the reference light is λ below the polarized beam splitting plane 7.
/4 phase plate 8. Since the back side of the λ/4 phase plate is coated with a reflective coating made of AQ or the like, the reference light undergoes retardation of λ/2 in one round trip, that is, a straight line in the direction orthogonal to the initial direction (parallel to the paper surface). It returns as polarized light,
The polarized beam enters the splitting surface 7 again. However, since the polarization direction is perpendicular to the initial polarization direction, the reference light now passes through the polarized beam split surface 7 and enters the upper corner cube prism 8.
ここで偏光方向を１８０°変え再び偏光ビームスブリッ
ト面７に入射する。偏光方向が１８０゜変わっても偏光
ビームスブリット面７に対しては変わりなく透過するた
め、再度λ／４板８に入射し、前回と同様λ／２のリタ
デーションを発生し。Here, the polarization direction is changed by 180° and the beam enters the polarized beam splitting surface 7 again. Even if the polarization direction changes by 180 degrees, the beam still transmits through the polarized beam splitting surface 7, so it enters the λ/4 plate 8 again and generates a retardation of λ/2 as before.
紙面と直交する方向の直線偏光となって再び偏光ビーム
スブリット面７に戻る。今度は、偏光ビームスブリット
面７で反射し、干渉計外へ出射する。The light becomes linearly polarized in a direction perpendicular to the plane of the paper and returns to the polarized beam splitting surface 7 again. This time, it is reflected by the polarized beam splitting surface 7 and exits from the interferometer.
一方、測長光は偏光ビームスブリット面７を透過後λ／
４位相板９に入射し、円偏光となり、測長物体に取り付
けられたコーナーキューブ１０に入射する。コーナーキ
ューブ１０では上下左右が逆転し、偏光方向が１８０°
変わるが、位相変化はないので入射と同一方向の円偏光
となって戻る。On the other hand, the length measurement light passes through the polarized beam splitting surface 7 and then λ/
The light enters the four phase plate 9, becomes circularly polarized light, and enters the corner cube 10 attached to the length measuring object. In Corner Cube 10, the top, bottom, left, and right are reversed, and the polarization direction is 180°.
However, since there is no phase change, the light returns as circularly polarized light in the same direction as the incident direction.
さらにλ／４板９を透過すると結局最初の偏光方向と直
交する紙面に垂直な偏光方向の直線偏光となって偏光ビ
ームスブリット面７に入射する。すると今度はここで反
射して、上方のコーナーキューブ８を通り、再度偏光ビ
ームスブリット面７に入射し５反射する。When the light is further transmitted through the λ/4 plate 9, it becomes linearly polarized light with a polarization direction perpendicular to the plane of the paper, which is orthogonal to the initial polarization direction, and enters the polarized beam splitting surface 7. Then, it is reflected here, passes through the upper corner cube 8, enters the polarized beam split surface 7 again, and is reflected 5 times.
結局、最初と同一の光路を通り、λ／４板９を透過後、
測長物体上のコーナーキューブ１０へ入射する。但し、
この時の円偏光は最初の時とは逆廻りであり、戻り光は
再度λ／４板９を透過すると紙面に平行な偏光方向を持
つ直線偏光となり、偏光ビームスブリット面７を透過し
、参照光と合成され干渉計を出射する事となる。In the end, after passing through the same optical path as the beginning and passing through the λ/4 plate 9,
The light is incident on the corner cube 10 on the object to be measured. however,
The circularly polarized light at this time is in the opposite direction from the first time, and when the returned light passes through the λ/4 plate 9 again, it becomes linearly polarized light with a polarization direction parallel to the plane of the paper. It will be combined with light and emitted from the interferometer.
このままでは参照光（ｆ２）と測長光（ｆ工）は、お互
いに直交する直線偏光のため干渉縞（ビート）を発生し
ないが、図示しないλ／４位相板によって両直線偏光を
回転方向が逆となる円偏光としたり、偏光子により、両
方の共通偏光成分を抽出する事によって干渉縞（ビート
）を発生する事ができる。ヘテロダイン型では、第１図
の場合と同様に、干渉計に入射する直前の２つの周波数
のビート（ｆよ−ｆ、）をとって測長後のビート周波数
（ｆ、−ｆ２±Δｆ）と比較減算する事で物体の移動に
伴うドツプラー効果のみによる周波数変化（±Δｆ）を
安定して取り出す事ができる。In this state, the reference light (f2) and the measurement light (f) do not generate interference fringes (beats) because they are linearly polarized lights that are perpendicular to each other, but a λ/4 phase plate (not shown) changes the direction of rotation of both linearly polarized lights. Interference fringes (beats) can be generated by using opposite circularly polarized light or by extracting the common polarized component of both using a polarizer. In the case of the heterodyne type, as in the case of Fig. 1, the beat of the two frequencies just before entering the interferometer (f, -f,) is taken and compared with the beat frequency (f, -f2±Δf) after length measurement. By subtracting, it is possible to stably extract the frequency change (±Δf) due only to the Doppler effect due to the movement of the object.
第６図の実施例では参照光と測長光の光路が干渉計内で
全く同一で短く、シかも半分以上が全く同一の光路を通
るため極めて高い精度安定性を実現し、光学的な測長感
度も測長光が２往復するため高いというすぐれた特長を
有している。さらに全体がコンパクトであるということ
は、硝材よりも線膨張係数の高いステンレス等の金属で
できた枠部品を小さくできるということを意味し、測長
精度を安定化する上で非常に有利になっている。In the embodiment shown in Fig. 6, the optical paths of the reference light and length measurement light are exactly the same and short within the interferometer, and more than half of them pass through the same optical path, achieving extremely high accuracy and stability, and optical measurement. It also has the excellent feature of high long-range sensitivity because the length-measuring light makes two round trips. Furthermore, the overall compactness means that frame parts made of metals such as stainless steel, which have a higher coefficient of linear expansion than glass materials, can be made smaller, which is extremely advantageous in stabilizing length measurement accuracy. ing.
さらに測長精度を安定化するために、光学部品に石英を
使う事で、大きな効果をあげられる。Furthermore, to stabilize length measurement accuracy, using quartz for optical parts can have a great effect.
第７図は、測長物体にとりつけたコーナーキューブの温
度変化による光路長変化をなくすために。Figure 7 is for eliminating changes in optical path length due to temperature changes in the corner cube attached to the length-measuring object.
ブレーンミラー１１で置き換えた実施例を示す。An example in which a brain mirror 11 is used is shown.
第６図と若干干渉計内の測長光の光路が変わるが、光路
長は参照光も測長光も全く同一で、半分以上の光路を共
通とするため、第６図と同様の高い差動特性が維持され
る。しかもプレーンミラーにより測長光の温度高安定性
の他に１部品単価も下げるという理想的な光学系となっ
ている６第８図に第７図の実施例を並列に配置し、光学
的検出感度を２倍にした実施例を示す。片方の干渉計の
出射光をコーナーキューブや直角プリズム１２を用いて
光路を曲げ、もう一方の干渉計の入射光としたものであ
り、これにより４往復の測長光路を持つため、干渉縞１
カウント当たりλ／８の分解能を実現できる。Although the optical path of the length measurement light in the interferometer is slightly different from Figure 6, the optical path length is exactly the same for both the reference light and the length measurement light, and more than half of the optical paths are shared, so the difference is as high as in Figure 6. Dynamic characteristics are maintained. In addition, the plane mirror provides an ideal optical system that not only provides high temperature stability of the length measurement light but also reduces the cost of each component. An example in which the sensitivity is doubled is shown. The optical path of the emitted light from one interferometer is bent using a corner cube or a right-angle prism 12, and it becomes the incident light for the other interferometer.As a result, it has a length measurement optical path that makes four round trips, so interference fringes 1
A resolution of λ/8 per count can be achieved.
第９図は、１つの干渉計で第７図と同じ４往復の測長光
路を持つ実施例で、出射光を直角プリズム１２で少し横
にずらして再入射させたものである。同図（ａ）に平面
図を、同図（ｂ）に側面図を、同図（Ｃ）に斜視図を示
す、極めてコンパクトで部品数も単独な場合と比較し２
点増えるだけで第８図の実施例と同一の光学的検出感度
を得られる。しかもコンパクトなため外乱の影響を受け
にくい。FIG. 9 shows an embodiment in which one interferometer has a four-return length measurement optical path as in FIG. 7, in which the emitted light is slightly shifted laterally at the right-angle prism 12 and then re-entered. The figure (a) shows a plan view, the figure (b) shows a side view, and the figure (C) shows a perspective view, which is extremely compact and has only a single number of parts.
The same optical detection sensitivity as in the embodiment shown in FIG. 8 can be obtained by simply increasing the number of points. Moreover, because it is compact, it is less susceptible to external disturbances.
第５図ないし第９図の実施例における各光学素子は、そ
れぞれ偏光ビームスプリッタ−、コーナーキューブ、位
相板、あるいは位相板の裏面ミラーをそれぞれ別部品と
する等、分離して構成しても全く同一の効果をあげられ
る。但し、それらの固定する枠について、例えばインバ
ーの様な線膨張係数の小さい材料を選ばないと、せっか
くの精度の高安定性を下げる。Each of the optical elements in the embodiments shown in FIGS. 5 to 9 may be constructed separately, such as by using a polarizing beam splitter, a corner cube, a phase plate, or a rear mirror of a phase plate as separate components. The same effect can be achieved. However, if a material with a small coefficient of linear expansion, such as invar, is not selected for the frame to be fixed, the high precision and stability will be degraded.
また、各実施例の光学部品に線膨張係数の低い石英やＺ
ｅｒｏｄｕｒのような材料を用いると、さらに測長精
度の安定化を計ることが出来る９例えば第１図、第２図
、第３図、第６図に示す実施例において、測長光の光路
を構成するコーナーキューブ内部の幾何学的光路長を５
Ｏｎ＋＋＋＋とすると、通’ｌｌノ硝材（Ｂ Ｋ −７
１’ ａ ＝ ７．１ｘ１０−’）では、環境温度が１
℃変化すると０．３５μｍ程度の変化が生じる。これは
、測長分解能の実に数十倍に達する値で、測長精度を再
現性よく維持するには±０．０２℃以下に環境温度を制
御せねばならず、極めて高価で大規模な空調設備を必要
とする。In addition, the optical components of each example were made of quartz or Z, which has a low coefficient of linear expansion.
If a material such as erodur is used, the length measurement accuracy can be further stabilized.9 For example, in the embodiments shown in FIGS. The geometric optical path length inside the constituting corner cube is 5
If On + + + +, the glass material (B K -7
1'a = 7.1x10-'), the environmental temperature is 1
A change in temperature causes a change of about 0.35 μm. This is a value several tens of times higher than the length measurement resolution, and in order to maintain the length measurement accuracy with good reproducibility, the environmental temperature must be controlled to below ±0.02℃, which requires extremely expensive and large-scale air conditioning. Requires equipment.
しかし１石英（α＝４，３Ｘ１０−’）を用いれば、温
度１℃あたりの光路長変化が、０．０２μｍで前述の場
合の１／１５以下となり、従って測長環境の温度制御も
測長器本体の安定性に関しては、前者の１５倍程度、緩
くできる。However, if 1 quartz (α=4,3 Regarding the stability of the main body, it can be made about 15 times looser than the former.
（発明の効果）
この発明は、上記のように、プリズム等で構成される干
渉測長系内の光路長を、測定光と参照光とで等しくとる
ことにより、極めて簡単な構成で、温度変化等の外乱の
影響を極めて小さくすることが出来、レーザー干渉側長
針本来の精度を実現することが出来た。(Effects of the Invention) As described above, the present invention has an extremely simple configuration by making the optical path length in the interferometric measurement system composed of prisms etc. equal for the measurement light and the reference light, and allows temperature change. We were able to minimize the influence of disturbances such as these, and achieve the original accuracy of the long hand on the laser interference side.
第１図、第２図、第３図、第４図、第５図、第６図、第
７図、第８図、第９図はそれぞれこの発明のレーザー干
渉測長計の異なる実施例の光学配置図、第１０図、第１
１図、第１２図、第１３図、第１４図は従来公知のレー
ザー干渉測長計の光学配置図である。
１：直角プリズム
２．５．８．１０．１２．３９．４０．４１：コーナー
キューブ
３．７：偏光ビームスブリット面
４．９：λ／４位相板
６．１１ニブレーンミラー
２０：安定化レーザー
２１．３５：偏光ビームスプリッタ−
２２：移動鏡 ２３：固定鏡
２４．２５：λ／４板
２６．３４：ビームスプリッタ−
２７，２９，３１：偏光子1, 2, 3, 4, 5, 6, 7, 8, and 9 are optical diagrams of different embodiments of the laser interferometer of the present invention, respectively. Layout, Figure 10, 1st
1, 12, 13, and 14 are optical layout diagrams of conventionally known laser interferometric length measuring meters. 1: Right angle prism 2.5.8.10.12.39.40.41: Corner cube 3.7: Polarized beam split surface 4.9: λ/4 phase plate 6.11 Nibrane mirror 20: Stabilizing laser 21.35: Polarizing beam splitter 22: Moving mirror 23: Fixed mirror 24.25: λ/4 plate 26.34: Beam splitter 27, 29, 31: Polarizer
Claims (1)
長干渉系内の光路長を等しくとり、差動型の光路配置と
したことを特徴とするレーザー干渉測長計 ２ 請求項１において、測長光と参照光に偏光方向の異
なる複数の波長を用い、ヘテロダイン干渉計としたこと
を特徴とする干渉測長計 ３ 請求項１において、測長光と参照光に偏光方向の異
なる単一の波長を用い、干渉縞計数型としたことを特徴
とする干渉測長計 ４ 請求項１〜３のいずれかにおいて、測長光が被測長
物との間を複数回往復することを特徴とする干渉測長計 ５ 請求項１〜４のいずれかにおいて、測長プリズムの
素材を石英としたことを特徴とする干渉測長計[Claims] 1. A laser interferometric length measuring meter, characterized in that the optical path lengths of the measurement light and the reference light in the length measuring interference system are made equal, and a differential optical path arrangement is used.2. In claim 1, the interferometric length measuring meter 3 is characterized in that a plurality of wavelengths having different polarization directions are used for the length measurement light and the reference light to form a heterodyne interferometer. Interferometric length measuring meter 4 characterized in that it uses different single wavelengths and is of an interference fringe counting type.In any one of claims 1 to 3, the length measuring light travels back and forth between the length measuring object and the object to be measured a plurality of times. Characteristic interferometric length measuring meter 5 An interferometric length measuring meter according to any one of claims 1 to 4, characterized in that the material of the length measuring prism is quartz.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63268113A JPH02115701A (en) | 1988-10-26 | 1988-10-26 | Laser interferometric length measuring meter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63268113A JPH02115701A (en) | 1988-10-26 | 1988-10-26 | Laser interferometric length measuring meter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH02115701A true JPH02115701A (en) | 1990-04-27 |
Family
ID=17454070
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP63268113A Pending JPH02115701A (en) | 1988-10-26 | 1988-10-26 | Laser interferometric length measuring meter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH02115701A (en) |
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002333311A (en) * | 2001-05-10 | 2002-11-22 | Matsushita Electric Ind Co Ltd | Shape measuring apparatus and method |
| JP2003279309A (en) * | 2002-03-27 | 2003-10-02 | Pioneer Electronic Corp | Laser apparatus and method for measuring length |
| JP2009162629A (en) * | 2008-01-08 | 2009-07-23 | Sokkia Topcon Co Ltd | Interferometer |
| JP2009288071A (en) * | 2008-05-29 | 2009-12-10 | Mitsutoyo Corp | Optical path length multiplier |
| JP2010237203A (en) * | 2009-03-30 | 2010-10-21 | Nikon Corp | Optical unit, interference device, stage device, pattern forming device, and device manufacturing method |
| JP2011064674A (en) * | 2009-08-21 | 2011-03-31 | Canon Inc | Laser gauge interferometer, machining device using the same, and machining method of work piece |
| EP2369372A2 (en) | 2010-03-15 | 2011-09-28 | Mitutoyo Corporation | Laser reflector |
| JP2019523403A (en) * | 2016-07-29 | 2019-08-22 | シャンハイ マイクロ エレクトロニクス イクイプメント（グループ）カンパニー リミティド | Diffraction grating measuring device |
-
1988
- 1988-10-26 JP JP63268113A patent/JPH02115701A/en active Pending
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2002333311A (en) * | 2001-05-10 | 2002-11-22 | Matsushita Electric Ind Co Ltd | Shape measuring apparatus and method |
| JP2003279309A (en) * | 2002-03-27 | 2003-10-02 | Pioneer Electronic Corp | Laser apparatus and method for measuring length |
| JP2009162629A (en) * | 2008-01-08 | 2009-07-23 | Sokkia Topcon Co Ltd | Interferometer |
| JP2009288071A (en) * | 2008-05-29 | 2009-12-10 | Mitsutoyo Corp | Optical path length multiplier |
| JP2010237203A (en) * | 2009-03-30 | 2010-10-21 | Nikon Corp | Optical unit, interference device, stage device, pattern forming device, and device manufacturing method |
| JP2011064674A (en) * | 2009-08-21 | 2011-03-31 | Canon Inc | Laser gauge interferometer, machining device using the same, and machining method of work piece |
| EP2369372A2 (en) | 2010-03-15 | 2011-09-28 | Mitutoyo Corporation | Laser reflector |
| JP2019523403A (en) * | 2016-07-29 | 2019-08-22 | シャンハイ マイクロ エレクトロニクス イクイプメント（グループ）カンパニー リミティド | Diffraction grating measuring device |
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