JP2688988B2 - Optical measuring device - Google Patents
Optical measuring deviceInfo
- Publication number
- JP2688988B2 JP2688988B2 JP15829689A JP15829689A JP2688988B2 JP 2688988 B2 JP2688988 B2 JP 2688988B2 JP 15829689 A JP15829689 A JP 15829689A JP 15829689 A JP15829689 A JP 15829689A JP 2688988 B2 JP2688988 B2 JP 2688988B2
- Authority
- JP
- Japan
- Prior art keywords
- light
- amplitude grating
- order diffracted
- diffracted light
- fourier transform
- 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 - Fee Related
Links
Landscapes
- Length Measuring Devices By Optical Means (AREA)
- Optical Transform (AREA)
Description
【発明の詳細な説明】 （産業上の利用分野） 光学式エンコーダのように光を使った測長、測角等の
測定装置に関する。DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a measuring device such as an optical encoder that uses light to measure length and angle.
（従来の技術） 従来の光学式エンコーダは、光源に対向させて移動可
能に配置され、光透過部と非透過部の長さの比が1:1と
された振幅格子を有し、光源の光がこの振幅格子を透過
後、例えば反射鏡等によって再度振幅格子を透過するこ
とによって、振幅格子の２倍のピッチ（１波長が振幅格
子１ピッチの半分）の正弦波を生ぜしめ、この正弦波を
用いて測長又は、測角を行うようになっている。(Prior Art) A conventional optical encoder is movably arranged so as to face a light source, has an amplitude grating in which a length ratio of a light transmitting portion and a non-transmitting portion is 1: 1, and After the light passes through the amplitude grating, the light is again transmitted through the amplitude grating by, for example, a reflecting mirror, so that a sine wave having a pitch twice that of the amplitude grating (one wavelength is half the pitch of the amplitude grating) is generated. The length or angle is measured using waves.
（発明が解決しようとする課題） 従来の光学式エンコーダによれば、その構造が複雑
で、コスト高であると云う課題があった。(Problems to be Solved by the Invention) According to the conventional optical encoder, there is a problem that the structure is complicated and the cost is high.
本発明は、測定精度は従来のものと同様にして、この
ような課題を解決することをその目的とするものであ
る。An object of the present invention is to solve such a problem by making the measurement accuracy similar to the conventional one.
（課題を解決するための手段） 本発明は、上記の目的を達成するために、光源に対し
て一定距離を保って移動するように配置され、光透過部
と非透過部の長さの比が2:1とされた振幅格子と、該振
幅格子を透過した光を光学的にフーリェ変換する第１の
レンズと、前記光学的フーリェ変換により生ずる回折光
のうち、２次回折光だけを選択する選択フィルタと、選
択された２次回折光を逆フーリェ変換する第２のレンズ
と、光学的に逆フーリェ変換された光を受光する受光器
とを備えたことを特徴とする。(Means for Solving the Problem) In order to achieve the above-mentioned object, the present invention is arranged so as to move with a constant distance with respect to a light source, and has a ratio of the lengths of a light transmitting portion and a non-transmitting portion. Of 2: 1 is selected, only the second-order diffracted light is selected from the diffracted light generated by the optical Fourier transform, and the first lens for optically Fourier-converting the light transmitted through the amplitude grating. It is characterized in that it is provided with a selection filter, a second lens for performing inverse Fourier transform on the selected second-order diffracted light, and a light receiver for receiving the light that has been optically subjected to inverse Fourier transform.
（作 用） 振幅格子のパターンの関数ｆ（ｘ）は、 で表わされる。(Operation) The function f (x) of the amplitude grating pattern is Is represented by
但し、x;原点からの距離 前記振幅格子の光透過部l1と非透過部l2の長さの比
は、2:1であり、第１図に示すように、光透過部l1の中
心をＹ軸とし、光透過部l1の振幅を１とすると、振幅格
子のパターンの関数ｆ（ｘ）はＹ軸に対称であるから、
前記（２）式は、 となり、（３）式は bn＝０ …（５） となる。However, x; a light transmitting portion l 1 of the distance the amplitude grating from the origin ratio of the length of the non-transmissive portion l 2 is 2: 1, as shown in FIG. 1, the light transmitting portion l 1 When the center is the Y axis and the amplitude of the light transmitting portion l 1 is 1, the function f (x) of the pattern of the amplitude grating is symmetric with respect to the Y axis.
Equation (2) is Therefore, the equation (3) becomes bn = 0 (5).
（４）（５）（６）式を（１）式に代入すると、 振幅格子を通過した光を光学的にフーリェ変換する第
１のレンズに入射させたとき、その焦点距離に設けられ
たフィルタ面に結像する像関係すなわち、像平面上の点
像の複素振幅は、次のフーリェ変換された式で与えられ
る。 Substituting equations (4), (5) and (6) into equation (1), When the light that has passed through the amplitude grating is made incident on the first lens that performs optical Fourier transform, the image relation that is imaged on the filter surface provided at the focal length, that is, the complex amplitude of the point image on the image plane is , Given by the following Fourier transformed formula:
（１′）と（７）式から （７′）式の右辺第２項のterm Bにおいて、 であるから、 ｎ＝０すなわち０次の回折光は、 （７′）式の右辺の第２項のterm B＝０ （７′）式の右辺の第１項のterm Aは であるから、 で表わされる。 From equations (1 ') and (7) In term B of the second term on the right side of equation (7 ′), Because n = 0, that is, the 0th-order diffracted light, term B = 0 in the second term on the right side of equation (7 ′) is term A in the first term on the right side of equation (7 ′) Because Is represented by
１次の回折光は（８）式においてｎ＝１を代入する
と、 ２次の回折光は、（８）式においてｎ＝２を代入する
と、 ３次の回折光は、（８）式においてｎ＝３を代入する
と、 そこで、選択フィルタで２次の回折光のみを選択し、
これを逆フーリェ変換する第２のレンズで逆フーリェ変
換をする。For the first-order diffracted light, substituting n = 1 in the equation (8), For the second-order diffracted light, substituting n = 2 in the equation (8), For the 3rd-order diffracted light, substituting n = 3 in the equation (8), Therefore, select only the second-order diffracted light with the selection filter,
Inverse Fourier transform is performed by the second lens that performs inverse Fourier transform.
点像の強度は振幅の２乗に比例することが知られてい
るから、 ２次回折光の強度分布I2は （９）式から である。 Since it is known that the intensity of the point image is proportional to the square of the amplitude, the intensity distribution I 2 of the second-order diffracted light can be calculated from equation (9). It is.
（９）式から明らかなようにフーリェ変換レンズを経
ることにより振幅格子のパターンに比べて２倍のピッチ
の明暗のパターンが生ずる。As is clear from the equation (9), a bright and dark pattern having a pitch twice as large as that of the amplitude grating pattern is generated through the Fourier transform lens.
かくて逆フーリェ変換する第２のレンズから出射した
光を受光器で受光すれば、振幅格子の動きに対して変化
する光の波数は従来のものと同じく振幅格子のピッチＰ
の２倍となる。Thus, if the light emitted from the second lens that performs the inverse Fourier transform is received by the light receiver, the wave number of the light that changes with the movement of the amplitude grating is the same as the conventional one.
Is twice as large as
（実施例） 以下本発明の実施例を図面につき説明する。Embodiment An embodiment of the present invention will be described below with reference to the drawings.
第２図は本発明の１実施例の説明図である。同図にお
いて、１は回転軸２に固着された回転円盤で、その周縁
部には、回転円盤１の回転方向の長さの比が2:1の関係
にある光透過部３例えば透孔と非透過部４が一定ピッチ
Ｐで全周に亘って配設されていて振幅格子５が形成され
ており、その回転円盤１は、例えばレーザ・ダイオード
から成る光源６に対して一定距離を保って移動するよう
になっている。FIG. 2 is an explanatory diagram of one embodiment of the present invention. In the figure, reference numeral 1 denotes a rotary disc fixed to a rotary shaft 2, and a peripheral portion of the rotary disc 1 has a light transmitting portion 3 having a relationship of a length ratio of 2: 1 in the rotating direction, such as a transparent hole. A non-transmissive part 4 is arranged at a constant pitch P over the entire circumference to form an amplitude grating 5, and the rotating disk 1 is kept at a constant distance from a light source 6 composed of, for example, a laser diode. It is designed to move.
前記光源６から射出されたレーザ光（可干渉性の光）
は集光レンズ７で平行光線になり、その平行光線は前記
振幅格子５を介してフーリェ変換用凸レンズ８に入射す
るようになっている。このフーリェ変換用凸レンズから
その焦点距離f8だけ離れた位置には２次回折光を選択す
る選択フィルタ９が配設され、この選択フィルタ９の近
傍に、選択フィルタ９を通過した２次回折光を後述の逆
フーリェ変換用凸レンズ11に伝達するために用いるエレ
クタレンズ10が配設される。また、逆フーリェ変換用凸
レンズ11はその焦点距離f11だけ前記選択フィルタ９か
ら離れた位置に配設され、逆フーリェ変換用凸レンズ11
からその焦点距離f11だけ離れた位置に受光器12が配設
される。Laser light emitted from the light source 6 (coherent light)
Is converted into parallel rays by the condenser lens 7, and the parallel rays are incident on the Fourier transform convex lens 8 through the amplitude grating 5. A selection filter 9 for selecting the second-order diffracted light is disposed at a position separated from the Fourier transform convex lens by the focal length f 8, and the second-order diffracted light that has passed through the selection filter 9 will be described in the vicinity of the selection filter 9. An erector lens (10) used for transmitting to the inverse Fourier transform convex lens (11) is arranged. The inverse Fourier transform convex lens 11 is arranged at a position separated from the selection filter 9 by the focal length f 11 thereof, and the inverse Fourier transform convex lens 11 is provided.
A photodetector 12 is arranged at a position away from the focal length f 11 by.
光源６から射出されたレーザ光は回転円盤１の振幅格
子を通過すると、主として０次、１次及び２次の回折光
から成る明暗パターンに形成され、フーリェ変換用凸レ
ンズ８を通過すると各次数の回折光に分離され、選択フ
ィルタ９において結像される。そして選択フィルタ９に
より２次回折光のみ選択される。この２次回折光はエレ
クタレンズ10を経て逆フーリェ変換用凸レンズ11により
第３図示のように、受光器12に前記振幅格子５のピッチ
Ｐの２倍のピッチの明暗パターンとなって入射する。When the laser light emitted from the light source 6 passes through the amplitude grating of the rotating disk 1, it is formed into a bright-dark pattern mainly composed of 0th-order, 1st-order and 2nd-order diffracted light. It is separated into diffracted light and imaged on the selection filter 9. Then, the selection filter 9 selects only the second-order diffracted light. The second-order diffracted light passes through the erector lens 10 and enters the light receiver 12 in a light-dark pattern having a pitch twice the pitch P of the amplitude grating 5, as shown in FIG.
かくて回転円盤１が回転すると、その回転角に応じた
波数を有する電気信号が受光器12から出力する。回転円
盤１の回転角は、従来のものと同じように受光器12から
出力する電気信号を波数をカウントすることによって測
定する。Thus, when the rotating disk 1 rotates, an electric signal having a wave number corresponding to the rotation angle is output from the light receiver 12. The rotation angle of the rotating disk 1 is measured by counting the wave number of the electric signal output from the light receiver 12 as in the conventional case.
（発明の効果） 本発明は上述の構成を有するから、従来のものと同様
な測定精度が得られると共に光学系が簡素で安価な測定
装置が得られる効果を有する。(Advantages of the Invention) Since the present invention has the above-mentioned configuration, it has the effects that the same measurement accuracy as that of the conventional one can be obtained, and that the measurement device having a simple optical system and inexpensive can be obtained.
第１図は本発明の原理説明図、第２図は本発明の１実施
例の構成を示す概略図、第３図は振幅格子と受光器に入
射する明暗パターンとの関係を示す図である。 １……回転円盤、２……回転軸 ３……光透過部、４……非透過部 ５……振幅格子、６……光源 ８……フーリェ変換用凸レンズ ９……選択フィルタ 11……逆フーリェ変換用凸レンズ 12……受光器FIG. 1 is a diagram for explaining the principle of the present invention, FIG. 2 is a schematic diagram showing the configuration of one embodiment of the present invention, and FIG. 3 is a diagram showing the relationship between the amplitude grating and the light-dark pattern incident on the light receiver. . 1 ... Rotating disk, 2 ... Rotating axis 3 ... Light transmitting part, 4 ... Non-transmissive part 5 ... Amplitude grating, 6 ... Light source 8 ... Fourier transform convex lens 9 ... Selection filter 11 ... Inverse Convex lens for Fourier transform 12 …… Receiver
Claims (1)
うに配置され、光透過部と非透過部の長さの比が2:1と
された振幅格子と、該振幅格子を透過した光を光学的に
フーリェ変換する第１のレンズと、前記光学的フーリェ
変換により生ずる回折光のうち、２次回折光だけを選択
する選択フィルタと、選択された２次回折光を逆フーリ
ェ変換する第２のレンズと、光学的に逆フーリェ変換さ
れた光を受光する受光器とを備えたことを特徴とする光
学式測定装置。1. An amplitude grating, which is arranged so as to move a certain distance from a light source, and has a length ratio of a light transmitting portion and a non-transmitting portion of 2: 1, and transmitted through the amplitude grating. A first lens for optically Fourier transforming light, a selection filter for selecting only second-order diffracted light among diffracted light generated by the optical Fourier transform, and a second filter for inverse Fourier transforming selected second-order diffracted light. And an optical receiver for receiving light that has been optically inversely Fourier transformed.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15829689A JP2688988B2 (en) | 1989-06-22 | 1989-06-22 | Optical measuring device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP15829689A JP2688988B2 (en) | 1989-06-22 | 1989-06-22 | Optical measuring device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0324417A JPH0324417A (en) | 1991-02-01 |
| JP2688988B2 true JP2688988B2 (en) | 1997-12-10 |
Family
ID=15668512
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP15829689A Expired - Fee Related JP2688988B2 (en) | 1989-06-22 | 1989-06-22 | Optical measuring device |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP2688988B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5891921B2 (en) * | 2012-04-16 | 2016-03-23 | 富士通株式会社 | Displacement measuring device, displacement measuring method, and displacement measuring program |
-
1989
- 1989-06-22 JP JP15829689A patent/JP2688988B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0324417A (en) | 1991-02-01 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| R250 | Receipt of annual fees |
Free format text: JAPANESE INTERMEDIATE CODE: R250 |
|
| LAPS | Cancellation because of no payment of annual fees |