JP2007183251A - Photoelectric encoder - Google Patents

Photoelectric encoder Download PDF

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JP2007183251A
JP2007183251A JP2006326180A JP2006326180A JP2007183251A JP 2007183251 A JP2007183251 A JP 2007183251A JP 2006326180 A JP2006326180 A JP 2006326180A JP 2006326180 A JP2006326180 A JP 2006326180A JP 2007183251 A JP2007183251 A JP 2007183251A
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grating
measurement axis
photoelectric encoder
shift
light receiving
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JP5154072B2 (en
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Toru Yaku
亨 夜久
Tetsuo Kiriyama
哲郎 桐山
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Mitutoyo Corp
Mitsutoyo Kiko Co Ltd
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Mitsutoyo Kiko Co Ltd
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Abstract

<P>PROBLEM TO BE SOLVED: To heighten accuracy by removing a harmonic component without increasing manufacturing cost by devising a first grating pattern formed on a glass substrate having low manufacturing cost. <P>SOLUTION: In this three-grating type photoelectric encoder equipped with a second grating 20 formed on a scale and first and third gratings 22, 24 disposed on the detection part side, a part of at least the first grating 22 is shifted in the measuring axis direction by P/(2n) (P: a grating pitch, n: the order of a harmonic component required to be removed), to thereby remove the n-th order harmonic component. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

本発明は、スケール上に形成された第２格子と、検出部側に配設された第１、第３格子を備えた３格子型の光電式エンコーダに係る。特に、高調波を効果的に削減することが可能な光電式エンコーダに関する。   The present invention relates to a three-grating photoelectric encoder including a second grating formed on a scale, and first and third gratings arranged on the detection unit side. In particular, the present invention relates to a photoelectric encoder that can effectively reduce harmonics.

リニアエンコーダに利用されている、例えば特許文献１に記載されたような、いわゆる３格子原理では、３枚の光学格子（図１（Ａ）に示す透過型の場合は、メインスケールとしての第２格子２０とインデックススケールとしての第１、第３格子２２、２４、図１（Ｂ）（Ｃ）に示す反射型の場合は、共通化された第１（第３）格子２２を光が２回通過）が空間フィルタとなるので、正弦波に近い信号を検出でき、高精度の補間が可能である。図において、２６は光源、２８は、例えばコリメータレンズでなる光学系、３０は受光素子、３２は反射型で用いられるハーフミラー、３４は同じくミラー、３６は同じく集光レンズである。   In the so-called three-grating principle used in the linear encoder, for example, as described in Patent Document 1, three optical gratings (in the case of the transmission type shown in FIG. 1A, the second as the main scale). In the case of the reflection type shown in FIGS. 1B and 1C, the light is transmitted twice through the shared first (third) grating 22 in the case of the grating 20 and the first and third gratings 22 and 24 as index scales. Since (passing) becomes a spatial filter, a signal close to a sine wave can be detected, and highly accurate interpolation is possible. In the figure, reference numeral 26 denotes a light source, 28 denotes an optical system composed of, for example, a collimator lens, 30 denotes a light receiving element, 32 denotes a half mirror used in a reflection type, 34 denotes a mirror, and 36 denotes a condenser lens.

この３格子原理を反射型エンコーダとして活用する場合には、図１（Ｂ）（Ｃ）に示すように、スケール格子が第２格子２０となる。しかしながら、スケール上の光学格子は、スケールの場所によって線幅が変動してしまう。そのために、その部分では出力信号に高調波成分が重畳されてしまうという問題があった。   When this three-grid principle is utilized as a reflective encoder, the scale grating becomes the second grating 20 as shown in FIGS. However, the line width of the optical grating on the scale varies depending on the location of the scale. Therefore, there is a problem that the harmonic component is superimposed on the output signal in that portion.

そこで、特許文献２や特許文献３では、図２に示す如く、受光素子３０前面の第３格子２４と受光素子を組み合わせて受光素子アレイ３１とし、該受光素子アレイの平均化効果によって安定化する方法が提案されている。   Therefore, in Patent Document 2 and Patent Document 3, as shown in FIG. 2, the third grating 24 on the front surface of the light receiving element 30 and the light receiving element are combined to form a light receiving element array 31, which is stabilized by the averaging effect of the light receiving element array. A method has been proposed.

又、図２の構成において更に高調波を除去するために、受光素子アレイに位相差（特許文献４）や線幅変調（特許文献５）を与える方法も提案されている。   In order to further remove harmonics in the configuration of FIG. 2, a method of providing a phase difference (Patent Document 4) and a line width modulation (Patent Document 5) to the light receiving element array has also been proposed.

又、特許文献６には、３格子原理を用いた検出原理において、第１格子と第３格子の格子パターンに位相差を設ける方法が提案されている。   Patent Document 6 proposes a method of providing a phase difference between the grating patterns of the first grating and the third grating in the detection principle using the three-grid principle.

特開昭６３−３３６０４号公報（図１〜図３）JP 63-33604 A (FIGS. 1 to 3) 特開平９−１９６７０６号公報（図５）JP-A-9-196706 (FIG. 5) 特開２００４−２６４２９５号公報（図４）JP 2004-264295 A (FIG. 4) 特開平１０−１２２９０９号公報（図２）Japanese Patent Laid-Open No. 10-122909 (FIG. 2) 特開平８−１４５７２４号公報（図２）JP-A-8-145724 (FIG. 2) 特開平９−１１３２１３号公報（図３）JP-A-9-113213 (FIG. 3)

しかしながら、特許文献４や５に記載された、受光素子アレイに位相差や線幅変調を与える方法では、受光素子のパターンを変更する必要があるので、製造コストを上げてしまう。   However, in the methods described in Patent Documents 4 and 5 in which the phase difference or line width modulation is applied to the light receiving element array, it is necessary to change the pattern of the light receiving element, which increases the manufacturing cost.

又、特許文献６に記載された、第１格子と第３格子の格子パターンに位相差を設ける方法では、第３格子の代わりに受光素子アレイを用いると、同じ格子を２回通るため、偶数次の高調波しか除去できず、奇数次、特に、２次高調波より大きく一番問題な３次高調波を除去することができない。従って、第３格子の代わりに受光素子アレイを用いることができないという問題点を有していた。   In the method of providing a phase difference between the grating patterns of the first grating and the third grating described in Patent Document 6, if a light receiving element array is used instead of the third grating, the same grating is passed twice. Only the next harmonic can be removed, and the third harmonic, which is the most problematic than the odd harmonic, especially the second harmonic, cannot be removed. Therefore, there is a problem that the light receiving element array cannot be used in place of the third grating.

上記の問題点は反射型エンコーダに限らず透過型エンコーダでも同じである。   The above problem is not limited to the reflective encoder, but is the same for the transmissive encoder.

本発明は、前記従来の問題点を解決するべくなされたもので、第１格子パターンを工夫することにより、製造コストを上げずに高調波を除去して、高精度化することを課題とする。   The present invention has been made to solve the above-mentioned conventional problems, and it is an object to improve the accuracy by removing the harmonics without increasing the manufacturing cost by devising the first lattice pattern. .

本発明は、スケール上に形成された第２格子と、検出部側に配設された第１、第３格子を備えた３格子型の光電式エンコーダにおいて、少なくとも第１格子の一部分を、測定軸方向にＰ／（２ｎ）（Ｐ：格子ピッチ、ｎ：除去したい高調波の次数）だけシフトして、第ｎ次高調波を除去することにより、前記課題を解決したものである。   The present invention measures at least a part of the first grating in a three-grid photoelectric encoder including a second grating formed on a scale and first and third gratings arranged on the detection unit side. The above problem is solved by removing the nth harmonic by shifting in the axial direction by P / (2n) (P: lattice pitch, n: order of the harmonic to be removed).

又、前記第１格子を、測定軸と垂直な方向又は測定軸方向に分割してシフトするようにしたものである。   The first grating is divided and shifted in a direction perpendicular to the measurement axis or in the measurement axis direction.

又、前記第１格子の複数の部分を、それぞれ異なるシフト量でシフトするようにしたものである。   Further, the plurality of portions of the first lattice are shifted by different shift amounts.

又、前記シフト量を連続的に変化させて、格子パターンを正弦波状に変形させるようにしたものである。   Further, the shift amount is continuously changed to deform the lattice pattern into a sine wave shape.

又、前記第３格子の一部分も、測定軸方向にシフトするようにしたものである。   A part of the third grating is also shifted in the measurement axis direction.

本発明によれば、第１格子の一部分を、測定軸方向にＰ／（２ｎ）だけシフトさせることにより、受光素子アレイ面上で千渉縞を合成して、図３にｎ＝３の３次高調波の場合を例示する如く、第ｎ次高調波を削減することができる。   According to the present invention, a part of the first grating is shifted by P / (2n) in the direction of the measurement axis, thereby synthesizing the thousand fringes on the light receiving element array surface. As illustrated in the case of the second harmonic, the nth harmonic can be reduced.

又、第１格子を、測定軸と垂直な方向又は測定軸方向に分割してシフトすることにより、受光素子アレイ面上における干渉縞合成が平均化される。   Further, by dividing and shifting the first grating in the direction perpendicular to the measurement axis or in the measurement axis direction, the interference fringe synthesis on the light receiving element array surface is averaged.

又、前記第１格子の複数の部分を、それぞれ異なるシフト量でシフトすることにより、複数次の高調波を削減することができる。   Further, the plurality of harmonics can be reduced by shifting the plurality of portions of the first grating by different shift amounts.

又、前記シフト量を連続的に変化させて、格子パターンを正弦波状に変形させることにより、受光素子アレイ面上における干渉縞合成が平均化される。   Further, the interference fringe synthesis on the light receiving element array surface is averaged by continuously changing the shift amount and deforming the lattice pattern into a sine wave.

更に、前記第３格子の一部分も、測定軸方向にシフトすることにより、高調波を一層削減することができる。   Furthermore, harmonics can be further reduced by shifting a part of the third grating in the measurement axis direction.

以下図面を参照して、本発明の実施形態を詳細に説明する。   Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

反射型エンコーダに適用した本発明の第１実施形態は、図４に示す如く、例えば、受光素子アレイ３１を搭載する、製造コストが小さいガラス基板上に形成されている第１格子２２のパターンを測定軸と垂直な方向に２分割して、一方を、他方に対して測定軸方向にシフトして配置するようにしたものである。除去したい高調波の次数をｎとすると、対応するシフト量は、格子ピッチＰ÷（２×ｎ）となる。第３高調波を除去したいときには、シフト量はＰ／６である。   In the first embodiment of the present invention applied to the reflective encoder, as shown in FIG. 4, for example, the pattern of the first grating 22 formed on the glass substrate on which the light receiving element array 31 is mounted and the manufacturing cost is low. It is divided into two in a direction perpendicular to the measurement axis, and one is shifted from the other in the measurement axis direction. If the order of the harmonic to be removed is n, the corresponding shift amount is lattice pitch P ÷ (2 × n). When it is desired to remove the third harmonic, the shift amount is P / 6.

この第１実施形態において、光源から出た光は、第１格子２２を通過して、第２格子２０で反射して、受光素子アレイ３１の受光面上に干渉縞４０を生成する。   In the first embodiment, the light emitted from the light source passes through the first grating 22 and is reflected by the second grating 20 to generate interference fringes 40 on the light receiving surface of the light receiving element array 31.

これにより、第１格子２２と第２格子２０を通して生成されるｎ次の高調波の干渉縞４０が受光素子アレイ３１の受光面上で合成、相殺され、除去される。   As a result, the nth-order harmonic interference fringes 40 generated through the first grating 22 and the second grating 20 are combined, offset, and removed on the light receiving surface of the light receiving element array 31.

従って、受光素子アレイ３１上の第３格子２４（図２参照）のパターンには、特に高調波対策を施す必要が無くなる。なお、第３格子２４にも第１格子２２と同様の高調波対策を施して、例えば第１格子とは異なる次数の高調波を除去するように構成することも可能である。   Therefore, it is not necessary to take measures against harmonics in the pattern of the third grating 24 (see FIG. 2) on the light receiving element array 31. The third grating 24 may be configured so as to take the same harmonic countermeasures as the first grating 22 and remove, for example, higher-order harmonics different from the first grating.

次に、図５を参照して、本発明の第２実施形態を説明する。   Next, a second embodiment of the present invention will be described with reference to FIG.

本実施形態は、第１格子２２を測定軸と垂直な方向（図の上下方向）に多数分割して、シフト領域と非シフト領域を測定軸に対して垂直な方向に交互に配置したものである。なお、シフト領域の幅Ｗは、格子ピッチＰ以上とする。   In the present embodiment, the first grating 22 is divided into a large number in the direction perpendicular to the measurement axis (up and down direction in the figure), and the shift region and the non-shift region are alternately arranged in the direction perpendicular to the measurement axis. is there. Note that the width W of the shift region is greater than or equal to the lattice pitch P.

このようにして、シフト領域と非シフト領域を測定軸と垂直な方向に交互に配置することにより、受光素子アレイ上の干渉縞合成が平均化される。   In this way, the interference fringe synthesis on the light receiving element array is averaged by alternately arranging the shift regions and the non-shift regions in the direction perpendicular to the measurement axis.

次に、図６を参照して、本発明の第３実施形態を詳細に説明する。   Next, a third embodiment of the present invention will be described in detail with reference to FIG.

本実施形態は、第１格子２２のシフト領域を、例えば格子本数Ｎ毎に、測定軸方向（図の左右方向）に分割して配置したものである。   In the present embodiment, the shift region of the first grating 22 is divided and arranged in the measurement axis direction (left-right direction in the figure), for example, for every N grids.

このようにして、シフト領域と非シフト領域を測定軸方向に交互に配置することにより、受光素子アレイ上の干渉縞合成が平均化される。   In this way, the interference fringe synthesis on the light receiving element array is averaged by alternately arranging the shift regions and the non-shift regions in the measurement axis direction.

次に、図７を参照して本発明の第４実施形態を詳細に説明する。   Next, a fourth embodiment of the present invention will be described in detail with reference to FIG.

本実施形態は、第１格子２２を測定軸と垂直な方向に３以上（図では９）に分割すると共に、各領域でシフト量を個々に設定したものである。   In the present embodiment, the first grating 22 is divided into three or more (9 in the figure) in the direction perpendicular to the measurement axis, and the shift amount is individually set in each region.

例えば削減したい高調波としてｎ１次とｎ２次がある場合、少なくとも３つの領域を設けて、そのうちの１つの領域を基準領域とし、他の領域の光学格子シフト量を、それぞれＰ／（２ｎ１）とＰ／（２ｎ２）に設定する。 For example, if there are n 1 order and n 2 order as harmonics to be reduced by providing at least three regions, the one of the regions as a reference area, the optical grating shift amount of the other areas, respectively P / (2n 1 ) and P / (2n 2 ).

これにより、ｎ１次とｎ２次の複数の高調波を除去することができる。 Thus, it is possible to remove the n 1-th and n 2-order multiple harmonics.

次に、図８を参照して、本発明の第５実施形態を詳細に説明する。   Next, a fifth embodiment of the present invention will be described in detail with reference to FIG.

本実施形態は、第１格子２２の格子パターンを測定軸と垂直な方向に周期Ｌで正弦波状に変形させて、シフト量がＰ／（２ｎ）×（１＋sin２π（ｙ／Ｌ））／２になるように、連続的に変化させたものである。   In the present embodiment, the grating pattern of the first grating 22 is deformed into a sine wave shape with a period L in a direction perpendicular to the measurement axis, and the shift amount is P / (2n) × (1 + sin2π (y / L)) / 2. As shown, it is continuously changed.

本実施形態においては、シフト量が連続的に変化するので、例えばｎ＝２とした場合は、ｎ＝３以上の高調波も同時に削減される。   In the present embodiment, since the shift amount changes continuously, for example, when n = 2, harmonics of n = 3 or more are also reduced at the same time.

本発明の適用対象は、上記実施形態に示した反射型エンコーダに限定されず、図９に第６実施形態として示したように、透過型エンコーダにも適用できる。   The application target of the present invention is not limited to the reflective encoder shown in the above embodiment, and can be applied to a transmissive encoder as shown in FIG. 9 as the sixth embodiment.

この第６実施形態において、光源から出た光は、第１格子２２及び第２格子２０を順次透過して、受光素子アレイ３１の受光面上に干渉縞４０を生成する。   In the sixth embodiment, light emitted from the light source is sequentially transmitted through the first grating 22 and the second grating 20 to generate interference fringes 40 on the light receiving surface of the light receiving element array 31.

なお、前記実施形態においては、いずれも第３格子と受光素子が一体化された受光素子アレイが用いられていたが、別体であっても構わない。   In each of the above embodiments, the light receiving element array in which the third grating and the light receiving element are integrated is used, but it may be a separate body.

又、第１格子だけでなく、第３格子の一部分も、第１格子と同様に測定軸方向にシフトさせることで、第１格子と同じ、又は異なる次数の高調波を除去するように構成することもできる。   Further, not only the first grating but also a part of the third grating is configured to be shifted in the measurement axis direction in the same manner as the first grating so as to remove harmonics having the same or different orders as the first grating. You can also.

特許文献１に記載された３格子原理のエンコーダの基本的構成を示す図The figure which shows the basic composition of the encoder of the 3 grating | lattice principle described in patent document 1 特許文献２や３に記載された受光素子アレイを有する３格子原理の反射型エンコーダの例を示す断面図Sectional drawing which shows the example of the reflection type encoder of the 3 grating | lattice principle which has the light receiving element array described in patent document 2 or 3 本発明の効果を示す図The figure which shows the effect of this invention 本発明の第１実施形態の基本構成を示す（ａ）平面図及び（ｂ）側面図(A) Top view and (b) Side view showing the basic configuration of the first embodiment of the present invention 同じく第２実施形態の第１格子を示す平面図The top view which similarly shows the 1st grating | lattice of 2nd Embodiment. 同じく第３実施形態の第１格子を示す平面図The top view which similarly shows the 1st grating | lattice of 3rd Embodiment. 同じく第４実施携帯の第１格子を示す平面図The top view which similarly shows the 1st grating | lattice of 4th implementation mobile phone. 同じく第５実施形態の第１格子を示す平面図The top view which similarly shows the 1st grating | lattice of 5th Embodiment. 同じく第６実施形態の基本構成を示す斜視図The perspective view which similarly shows the basic composition of 6th Embodiment

符号の説明Explanation of symbols

２０…第２格子
２２…第１格子
２４…第３格子
２６…光源
３０…受光素子
３１…受光素子アレイ
４０…干渉縞 DESCRIPTION OF SYMBOLS 20 ... 2nd grating | lattice 22 ... 1st grating | lattice 24 ... 3rd grating | lattice 26 ... Light source 30 ... Light receiving element 31 ... Light receiving element array 40 ... Interference fringe

Claims (7)

スケール上に形成された第２格子と、検出部側に配設された第１、第３格子を備えた３格子型の光電式エンコーダにおいて、
少なくとも第１格子の一部分を、測定軸方向にＰ／（２ｎ）（Ｐ：格子ピッチ、ｎ：除去したい高調波の次数）だけシフトして、第ｎ次高調波を除去することを特徴とする光電式エンコーダ。 In a three-lattice photoelectric encoder including a second grating formed on the scale and first and third gratings disposed on the detection unit side,
At least a part of the first grating is shifted by P / (2n) (P: grating pitch, n: the order of the harmonic to be removed) in the measurement axis direction to remove the n-th harmonic. Photoelectric encoder. 前記第１格子を、測定軸と垂直な方向又は測定軸方向に分割してシフトすることを特徴とする請求項１に記載の光電式エンコーダ。   The photoelectric encoder according to claim 1, wherein the first grating is divided and shifted in a direction perpendicular to a measurement axis or a measurement axis direction. 前記第１格子を測定軸と垂直な方向に複数に分割して、シフト領域と非シフト領域を測定軸に対して垂直な方向に交互に配置することを特徴とする請求項２に記載の光電式エンコーダ。   3. The photoelectric device according to claim 2, wherein the first grating is divided into a plurality of parts in a direction perpendicular to the measurement axis, and shift regions and non-shift regions are alternately arranged in a direction perpendicular to the measurement axis. Type encoder. 前記第１格子のシフト領域を、所定の格子本数毎に、測定軸方向に複数に分割して、シフト領域と非シフト領域を測定軸方向に交互に配置することを特徴とする請求項２に記載の光電式エンコーダ。   The shift area of the first grating is divided into a plurality in the measurement axis direction every predetermined number of grids, and the shift areas and the non-shift areas are alternately arranged in the measurement axis direction. The described photoelectric encoder. 前記第１格子の複数の部分を、それぞれ異なるシフト量でシフトすることを特徴とする請求項２に記載の光電式エンコーダ。   The photoelectric encoder according to claim 2, wherein the plurality of portions of the first grating are shifted by different shift amounts. 前記シフト量を連続的に変化させて、格子パターンを正弦波状に変形させることを特徴とする請求項５に記載の光電式エンコーダ。   6. The photoelectric encoder according to claim 5, wherein the shift amount is continuously changed to deform the lattice pattern into a sine wave shape. 前記第３格子の一部分も、測定軸方向にシフトすることを特徴とする請求項１乃至６のいずれに記載の光電式エンコーダ。   The photoelectric encoder according to claim 1, wherein a part of the third grating is also shifted in the measurement axis direction.
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