JPH0416177Y2

JPH0416177Y2 -

Info

Publication number: JPH0416177Y2
Application number: JP1982148014U
Authority: JP
Priority date: 1982-10-01
Filing date: 1982-10-01
Publication date: 1992-04-10
Also published as: JPS5953209U

Description

[Detailed explanation of the idea]

産業上の利用分野本考案は、特に100mm程度の変位をサブμｍの
精度で測定する光学式測長スケールに関する。背景技術とその問題点２本のコヒーレントなビーム（可干渉性光束、
光源としてはレザーを用い、２本のビームにする
には１本のビームをビーム・スプリツタによつて
２本に分ける方法が通常用いられる）を回折格子
に入射させた時、回折格子から出射するビームが
相互に干渉し、その位相差は回折格子の長さ方向
の移動に対し、格子常数１ピツチ毎に同じ位相差
が繰り返される。この位相差、実際には出射ビー
ムの光量の変化を検出すれば回折格子の位相情
報、すなわち移動量を検出することができる。な
お、回折格子としてはホログラムを使用してもよ
い。ホログラムは回折格子の一形態と考えられる
からである。この原理を具体的に実施した例が既
に米国特許第3738735号公報と実開昭57−81510号
公報に開示されている。前者はホログラムをスケ
ールとして使用した例であり、後者は反射型回折
格子を使用した例である。以上を総合すると第１表の通りである。これらの装置の光学系の構成は可成り複雑で、
製造に当つて組立て、調整が難しいという欠点が
あつた。考案の目的本考案の目的は、動作原理は前述の装置と同じ
であるが、光学系の構成を簡単にし、組立て、調
整が容易な光学式測長スケールを提供することで
ある。 INDUSTRIAL APPLICATION FIELD The present invention particularly relates to an optical length measuring scale that measures displacements of about 100 mm with sub-μm accuracy. Background technology and its problems Two coherent beams (coherent beams,
When a laser is used as a light source and a beam splitter is used to split one beam into two beams, the beam is incident on a diffraction grating, the light is emitted from the diffraction grating. The beams interfere with each other, and the same phase difference is repeated for each pitch of the grating constant as the diffraction grating moves in the length direction. By detecting this phase difference, in fact, a change in the amount of light of the emitted beam, it is possible to detect the phase information of the diffraction grating, that is, the amount of movement. Note that a hologram may be used as the diffraction grating. This is because a hologram can be considered a form of diffraction grating. Examples of concrete implementations of this principle have already been disclosed in U.S. Pat. No. 3,738,735 and U.S. Pat. The former is an example in which a hologram is used as a scale, and the latter is an example in which a reflection type diffraction grating is used. The above is summarized in Table 1. The optical system configuration of these devices is quite complex;
The disadvantage of manufacturing was that it was difficult to assemble and adjust. Purpose of the invention The purpose of the present invention is to provide an optical length measuring scale which has the same operating principle as the above-mentioned device, but has a simplified optical system configuration and is easy to assemble and adjust.

【表】考案の概要上記目的を達成するために、本考案による光学
式測長スケールは、レーザ発生装置と、該レーザ
発生装置から出る光ビームを二つに分割する手段
と、回折格子と、上記二つの光ビームの上記回折
格子によるそれぞれ＋１次および−１次の回折光
の透過光または反射光を上記回折格子に向つて送
り返す反射面と、上記＋１次および−１次の回折
光の透過光または反射光がつぎに回折格子に当る
前に１回通過するように設けられた偏光子と、上
記＋１次および−１次の回折光の透過光または反
射光が２度目に回折格子に当つた時のそれぞれ−
１次および＋１次の透過光または反射光から成る
光ビームが入射するように設けられた受光系とを
含むことを要旨とする。以下に、図面を参照しながら、実施例を用いて
本考案を一層詳細に説明するが、それらは例示に
過ぎず、本考案の枠を越えることなしにいろいろ
な変形や改良があり得ることは勿論である。本考案による装置は、光源からのコヒーレント
なビームがビーム・スプリツタまたはプリズムに
より２本のビームに分けられ、回折格子（スケー
ル）に入射し、それぞれの＋１次および−１次回
折光が反射鏡あるいはプリズムにより反射され、
再び回折格子に入射して回折され、それぞれの−
１次および＋１次回折光が半透鏡により一緒にな
つて干渉を起すように作用する。また、回折格子
が透過型であるか反射型であるかに注目すれば、
第１図は前者に属し、第２図は後者に属する。実施例第１図は透過型回折格子を使つた本考案による
光学式測長スケールの代表的な構成を示す図であ
る。 He−Neレーザ、半導体レーザ等の光源１から
出たコヒーレントな光はレンズ２を通してある広
がりをもつ光束となつて半透鏡３に入射（光軸は
半透鏡とＡで交わる）し、２本の光束ABおよび
ACに分けられる。２本の光束は回折格子４に入
射し、回折される。この時それぞれの＋１次およ
び−１次回折光BD，CEは先ず１回目の回折光が
反射鏡５，６で反射され、次に再び反射鏡５，６
で反射された２回目の回折光が往きと正反対
（180°）の方向に復り偏光子７，８を通つて再び
回折格子４に入射し、それが回折されて出射され
る。この２回目の回折光は第１回目の入射光の方
向と正反対になるから、再度半透鏡３を通して二
つの光束が干渉できるように各光学系要素を配置
する。かくして２回目の２本の回折光は相互に干渉し
合うが、その位相は回折格子の位置により変化
し、格子常数1/4ピツチ毎に同じ位相差が繰り返
される。この出射ビームの光量の変化を受光系９により
検出することによつて格子常数の移動量を検出す
ることができる。特に第１図は第１回目の回折光が回折格子面に
垂直に入射する場合を示し、それぞれの＋１次お
よび−１次回折光BD，CEが、何れも格子面に垂
直になるように各光学要素を配置する。そのため
の条件は光束AB，ACの回折格子に対する入射
角をα₁，β₁、空気中におかれたこの回折格子の格
子常数をｌ、光の波長をλとすれば、 α₁＝β₁ sinα₁＝λ／ｌであればよい。つぎに光束BD、CEは格子に平行におかれた反
射鏡５，６に垂直に入射し、反射されて往きと全
く同じ光路を復ることになる。復路の２光束は再
度半透鏡３に入射し、一緒になつて干渉し合うが
その位相は回折格子の位置により変化し、格子常
数の1/4ピツチ毎に同じ位相差が繰り返される。
この出射ビームの光量の変化を受光系９により検
出する。このような構成とすることにより反射鏡５と６
を一枚の反射鏡とし、しかも偏光子７と８も一枚
の偏光子とすることができるので、部品点数を非
常に少なくすることが可能で、調整も容易な安価
な測長装置が得られる。以上は透過型回折格子を用いる実施例である
が、反射型回折格子を用いることもできる。第１
図に対応するものを第２図に示す。これらの実施
の態様による装置の動作は透過が反射に変つてい
る点を除き、前述の実施の態様におけるものと全
く同じであるから詳細な説明は省略するが、穴開
き反射鏡及び穴開き偏光子を使用すれば第１図及
び第２図の場合でも５，６，７，８の部品を一枚
の反射鏡及び偏光子で構成できるので光学系が非
常に簡単になる。考案の効果以上説明した通り、本考案によれば、光学系の
構成を簡単にすることができ、したがつて製造の
際に組立て、調整が容易となる。[Table] Summary of the invention In order to achieve the above object, the optical length measurement scale according to the invention includes a laser generator, a means for splitting the light beam emitted from the laser generator into two, a diffraction grating, A reflecting surface that sends back the transmitted light or reflected light of the +1st order and -1st order diffracted light by the diffraction grating of the two light beams toward the diffraction grating, and the transmission of the +1st order and -1st order diffracted light. A polarizer is provided so that the light or reflected light passes through it once before hitting the diffraction grating, and the transmitted light or reflected light of the +1st order and -1st order diffracted light hits the diffraction grating a second time. Each time -
A light receiving system is provided so that a light beam consisting of first-order and +first-order transmitted light or reflected light is incident thereon. Hereinafter, the present invention will be explained in more detail using examples with reference to the drawings, but these are merely illustrative and it is understood that various modifications and improvements may be made without going beyond the scope of the present invention. Of course. In the device according to the present invention, a coherent beam from a light source is split into two beams by a beam splitter or prism, and the two beams are incident on a diffraction grating (scale). reflected by
It enters the diffraction grating again and is diffracted, and each -
The 1st-order and +1st-order diffracted lights are brought together by the semi-transparent mirror and act to cause interference. Also, if you pay attention to whether the diffraction grating is a transmission type or a reflection type,
Figure 1 belongs to the former, and Figure 2 belongs to the latter. Embodiment FIG. 1 is a diagram showing a typical configuration of an optical length measuring scale according to the present invention using a transmission type diffraction grating. Coherent light emitted from a light source 1 such as a He-Ne laser or a semiconductor laser passes through a lens 2, becomes a beam with a certain spread, enters a semi-transparent mirror 3 (the optical axis intersects with the semi-transparent mirror at A), and is transmitted into two light beams. Luminous flux AB and
It is divided into AC. The two beams enter the diffraction grating 4 and are diffracted. At this time, the +1st order and -1st order diffracted lights BD and CE are first reflected by the reflecting mirrors 5 and 6, and then again by the reflecting mirrors 5 and 6.
The second diffracted light reflected by the beam returns in the opposite direction (180°), passes through the polarizers 7 and 8, enters the diffraction grating 4 again, is diffracted, and is emitted. Since this second diffracted light is in the exact opposite direction to the first incident light, each optical system element is arranged so that the two light beams can interfere with each other through the semi-transparent mirror 3 again. Thus, the two second diffracted lights interfere with each other, but their phase changes depending on the position of the diffraction grating, and the same phase difference is repeated every 1/4 pitch of the grating constant. The amount of movement of the lattice constant can be detected by detecting the change in the amount of light of this emitted beam using the light receiving system 9. In particular, Figure 1 shows the case where the first diffracted light is incident perpendicularly to the diffraction grating surface. Place elements. The conditions for this are: α ₁ , β ₁ are the incident angles of the light beams AB and AC on the diffraction grating, l is the grating constant of this diffraction grating placed in air, and λ is the wavelength of the light, then α ₁ = β ₁ It is sufficient if sinα ₁ =λ/l. Next, the light beams BD and CE are perpendicularly incident on reflecting mirrors 5 and 6 placed parallel to the grating, and are reflected to return along exactly the same optical path as before. The two returning beams enter the semi-transparent mirror 3 again and interfere with each other, but their phase changes depending on the position of the diffraction grating, and the same phase difference is repeated every 1/4 pitch of the grating constant.
A light receiving system 9 detects a change in the amount of light of this emitted beam. With such a configuration, the reflecting mirrors 5 and 6
Since it is possible to use a single reflective mirror as well as polarizers 7 and 8 as a single polarizer, it is possible to significantly reduce the number of parts and obtain an inexpensive length measuring device that is easy to adjust. It will be done. Although the above example uses a transmission type diffraction grating, a reflection type diffraction grating can also be used. 1st
The corresponding one is shown in FIG. 2. The operation of the apparatus according to these embodiments is exactly the same as that in the above-mentioned embodiments, except that transmission is changed to reflection, so a detailed explanation will be omitted. If a mirror is used, components 5, 6, 7, and 8 can be constructed from a single reflecting mirror and polarizer even in the cases of FIGS. 1 and 2, making the optical system extremely simple. Effects of the Invention As explained above, according to the present invention, the configuration of the optical system can be simplified, and therefore assembly and adjustment during manufacturing can be facilitated.

[Brief explanation of the drawing]

第１図は透過型回折格子を用いた場合の本考案
実施例による光学式測長スケールを示す構成図、
第２図は反射型回折格子を用いた場合の本考案実
施例による光学式測長スケールを示す構成図であ
る。１……光源、２……レンズ、３……半透鏡、４
……回折格子、５，６……平面鏡、７，８……偏
光子、９……受光系。 FIG. 1 is a configuration diagram showing an optical length measurement scale according to an embodiment of the present invention when a transmission type diffraction grating is used;
FIG. 2 is a configuration diagram showing an optical length measuring scale according to an embodiment of the present invention when a reflection type diffraction grating is used. 1...Light source, 2...Lens, 3...Semi-transparent mirror, 4
... Diffraction grating, 5, 6 ... Plane mirror, 7, 8 ... Polarizer, 9 ... Light receiving system.

Claims

[Claims for Utility Model Registration] (1) A laser generator, a means for splitting a light beam emitted from the laser generator into two, a diffraction grating, and a +1st-order beam generated by the diffraction grating for each of the two light beams. and a reflecting surface that sends the transmitted light or reflected light of the -1st order diffracted light back toward the diffraction grating, and a reflective surface that sends the transmitted light or reflected light of the +1st order and -1st order diffracted light back to the diffraction grating before it next hits the diffraction grating. a polarizer provided to pass through once;
It is arranged so that when the transmitted light or reflected light of the +1st order and -1st order diffracted light hits the diffraction grating for the second time, a light beam consisting of the -1st order and +1st order transmitted light or reflected light, respectively, is incident. an optical length measuring scale configured such that transmitted light or reflected light of the +1st-order or -1st-order diffracted light enters the diffraction grating at an angle perpendicular to the diffraction grating. (2) The optical length measuring scale according to claim 1, wherein the reflecting surface is a plane mirror.