JP3544576B2 - Optical encoder - Google Patents

Description

【００２３】
【数２】

となる。ここでビーム径とは光強度が最大ピークに対して１／２以上のビームの差し渡し寸法を意味する。
【００２４】
次に、多数の透過窓を透過した光の受光素子面でのパターンについて考える。スケール２の透過窓を通過した光ビームは図５に示すように広がるため、光ビームの重なりや干渉を考慮する必要がある。
【００２５】
以下では、スケール２から受光素子３までの距離Ｌが、領域Ｉ：Ｌ＜ωｏ ^２ ／λにある場合と、領域ＩＩ：Ｐｓ ωｏ ／λ＞Ｌ≧ωｏ ^２ ／λにある場合と、領域ＩＩＩ：Ｌ＞Ｐｓ ωｏ ／λにある場合とに分けて考える。
【００２６】
まず、Ｌが領域Ｉにある場合、すなわちＬ＜ωｏ ^２ ／λの場合、スケール２と受光素子３は非常に近くにあり、複数のビームは互いに干渉しない。従って、受光素子面上に現れるパターンは、（２）式で表される径を持つビームの重ね合わせとなり、図６（Ｄ）に示すようになる。
【００２７】
次に、Ｌが領域ＩＩにある場合、すなわちＰｓ ωｏ ／λ＞Ｌ≧ωｏ ^２ ／λの場合、複数のビームの互いの干渉は小さく、ほとんど無視できる。従って、受光素子面上に現れるパターンは、（１）式で表される径を持つビームの重ね合わせとなり、図６（Ｃ）に示すようになる。図中、破線は重ね合わせ前の各ビームの強度分布を示しており、実線はビームを重ね合わせた光の実際に観測される強度分布を示している。このため、Ｌ＝Ｐｓ ωｏ ／λの付近では、実際に観測される光の強度分布は図６（Ｂ）に示すようなほぼ平坦なものになる。この領域では複数のビームの互いの干渉は小さいが、完全に無視できるものではない。
【００２８】
最後に、Ｌが領域ＩＩＩにある場合、すなわちＬ＞Ｐｓ ωｏ ／λの場合、スケール２の複数の透過窓から射出した光ビームが互いに干渉するため、実際に観測されるビームの強度分布は、図６（Ａ）に示すようになる。図６（Ａ）において、最大ピークのｘ方向の間隔Δｘｄｉｆｆと、このピークの半値全幅ω’ｂ、およそ以下の式で表せる。
【００２９】
【数３】

【００３０】
【数４】

ここにおいて、ｍは、スケール上に照射されたレーザビームの有効領域（ほぼスケール上のビーム径と考えてよい）内にある透過窓（遮光部５の隙間）の数である。これはピッチの数にほぼ一致する。
【００３１】
なお、本明細書では、受光素子面における光ビームの幅は、単に透過や反射によるビーム径ωｂ を考える場合と、干渉パターンのピークの半値全幅ω’ｂを考える場合があるが、特に断らない限り、これらをともにビーム径ωｂ として扱う。
【００３２】
以上に説明したように、スケール２から受光素子３までの距離が領域Ｉないし領域ＩＩＩのいずれに属するかにより、受光素子面上には異なる明暗のパターンが生成される。いずれのパターンにおいても、スケール２がｘ軸方向に移動すると、受光素子面に生成される明暗パターンが同じ方向に同じ速度で移動するため、受光素子３の出力は、図３に示すように、正弦波形に似た周期的波形となり、この出力波形を調べることにより、スケール２の移動量が求められる。
【００３３】
スケール２から受光素子３までの距離Ｌが領域Ｉないし領域ＩＩＩのいずれにあるかで、図１内の諸寸法同士の関係が異なるので、これについて以下に説明する。
【００３４】
距離Ｌが領域Ｉにある場合、スケール２からの射出光同士は干渉しないので、スケール上でのビームは、スケールの１ピッチ以上をカバーしていればよい。すなわち、スケール面上における光ビーム照射領域のｘ軸方向のビーム径をＷｓ とし、Ｗｓ ＞Ｐｓ である。また、受光素子３の幅ωｐｄの開口部で、明暗パターンを検出するためには、その周期をＰｂ とし、ωｐｄ＜Ｐｂ であることが必要である。
【００３５】
距離Ｌが領域ＩＩにある場合、干渉パターンを利用しているわけではないので、領域Ｉと同様に、スケール上でのビームは、スケールの１ピッチ以上をカバーしていればよい。すなわち、スケール面上における光ビーム照射領域のスケール移動方向（ｘ軸方向）のビーム径（光ビームの強度がピーク値の１／２になるｘ軸方向の寸法）をＷｓ とし、Ｗｓ ＞Ｐｓ である。また、明暗パターンを検出するためには、その周期をＰｂ とし、ωｐｄ＜Ｐｂ であることが必要である。
【００３６】
距離Ｌが領域ＩＩＩにある場合、干渉パターンを利用しているため、スケール２からは二本以上のビームが射出される必要がある。すなわち、スケール面上における光ビーム照射領域のｘ軸方向のビーム径をＷｓ とし、Ｗｓ ≧２Ｐｓ である。また、明暗パターンを検出するためには、干渉パターンのピークの半値幅をωｂ とするとき、ωｐｄ≦ωｂ であることが必要である。
【００３７】
以上に述べたように、本実施例においては、スケール２と受光素子３の間隔Ｌに応じて三つの場合に分けられ、それぞれ一定の条件を満たすように各部の寸法を決めれば、スケール２の変位を検出することができる。
【００３８】
このように本実施例では、レンズや固定スケールを必要とせず、ビーム径がスケールピッチに対して大きい場合にも、スケールピッチによって決まる分解能を持ち、センサ構成や組み立てがシンプルで、小型、低コスト高精度な光学式エンコーダが得られる。
【００３９】
なお、受光素子における受光部位置の限定方法は、図１に示すように受光素子の受光面に開口部を設ける方法に限定されるものではなく、受光面を所定の大きさにする方法、あるいはＣＣＤ等の光位置検出機能を有するものでもよい。
【００４０】
また、図５の領域ＩＩＩにおいて、図６の（Ａ）のような干渉パターンによる測定を行なう場合は、スケール５を照射する光はコヒーレントな平面波を有するレーザ光であればよいから、光源は面発光レーザだけではなく、通常使用されている端面出射型の半導体レーザとコリメータレンズの組み合わせなどを用いることができる。
【００４１】
（第二実施例）
第二実施例の光学式エンコーダについて図７を参照しながら説明する。
図７に示すように、本実施例の光学式エンコーダは、第一実施例の光学式エンコーダに類似しており、唯一、受光領域４の表面の遮光膜５１に、幅ωｐｄの開口部が複数個、（第一実施例では一個だが）、等間隔で設けられている点で異なっている。複数の開口部のピッチＰｐｄは、受光素子面に生成される明暗パターンの周期Ｐｂ に一致している。
【００４２】
本実施例の動作原理、各寸法間の関係等は、すべて第一実施例と同じであり、その説明はここでは省略する。
本実施例によれば、第一実施例と同様な効果が得られるうえ、受光部を複数個設けたことにより第一実施例に比べて高出力を得ることができる。
【００４３】
なお、受光素子における受光部位置の限定方法は、図７に示すように受光素子の受光面に遮光窓を設ける方法に限定されるものではなく、受光面を所定の大きさに分割する方法、あるいはＣＣＤ等の光位置検出機能を有するものでもよい。
【００４４】
（第三実施例）
第三実施例の光学式エンコーダについて図８を参照しながら説明する。
図８に示すように、本実施例の光学式エンコーダは、第二実施例の光学式エンコーダに類似しているが、次に述べる二点で異なっている。第一に、スケール２と受光素子３がｘ軸を中心に回転した状態すなわち面発光レーザ１の射出光に対して傾いた状態で配置されている。第二に、スケール２と受光素子３に反射防止膜が設けられていない。
【００４５】
本実施例では、スケール２と受光素子３が面発光レーザ１の射出光に対して傾けて配置されているため、スケール２と受光素子３からの反射光は面発光レーザ１に戻らない。このような理由により本実施例ではスケール２と受光素子３の反射防止膜が省略されている。
【００４６】
本実施例では、スケール２と受光素子３に反射防止膜がなくても、面発光レーザの安定な動作が達成される。
本実施例の動作原理、各寸法間の関係等は、第二実施例と全く同じであり、その説明はここでは省略する。
【００４７】
次に、本実施例の変形例について図９を参照しながら説明する。本変形例は、本実施例の透過型の光学式エンコーダを、反射型に変形したものである。
図９に示すように、スケール２は面発光レーザ１の射出光に対して傾けて配置され、スケール２の透明基板７には、透過型におけるスケールの遮光部に代わる、等しい幅の複数の反射部５’ が等間隔で設けられている。スケール２による反射方向には、受光素子３が垂直に配置されている。受光素子３は、第二実施例と同じもの、すなわち、遮光膜５１に複数の開口部が形成され、遮光膜５１の表面に反射防止膜５２が形成されたものである。面発光レーザ１と受光素子３はベースに固定されている。
【００４８】
本変形例では、スケール２による反射光は面発光レーザ１に戻らないので、スケール２には反射防止膜が省略されているが、受光素子３により反射光は面発光レーザ１に戻るので、受光素子３には反射防止膜５２が設けられている。受光素子３をスケール２からの反射光の光軸に対して傾けて配置し、受光素子３による反射光が面発光レーザ１に戻らないようにすれば、反射防止膜は省略してもよい。
【００４９】
本実施例では、スケール２に（受光素子３を傾けた場合には加えて受光素子３にも）反射防止膜がなくても、面発光レーザの安定な動作が達成される。
本変形例も、その動作原理、各寸法間の関係等は、第二実施例と全く同じである。
【００５０】
（第四実施例）
第四実施例の光学式エンコーダについて図１０を参照しながら説明する。
図１０に示すように、本実施例の光学式エンコーダは、第三実施例（図８）の構成において、スケール２と受光素子３を面発光レーザ１の射出光に垂直な状態からｘ軸を中心に回転させて傾斜させる代わりに、ｚ軸を中心に回転させて傾斜させた構成となっている。このため、スケール２はｘ軸を斜めに横切る方向に移動する。
【００５１】
本実施例では、第三実施例と同様に、スケール２と受光素子３に反射防止膜がなくても、面発光レーザの安定な動作が達成される。
本実施例の動作原理、各寸法間の関係等は、第三実施例（すなわち第二実施例）と全く同じである。
【００５２】
次に、本実施例の変形例について図１１を参照しながら説明する。本変形例は、本実施例の透過型の光学式エンコーダを、反射型に変形したものである。
図１１に示すように、第三実施例の変形例（図９）構成において、スケール２を面発光レーザ１の射出光に垂直な状態からｘ軸を中心に回転させて傾斜させる代わりに、ｚ軸を中心に回転させて傾斜させた構成となっている。また、受光素子３は、スケール２からの反射光が垂直に入射するように配置されている。
【００５３】
本変形例では、第三実施例の変形例と同様に、スケール２に反射防止膜がなくても、面発光レーザの安定な動作が達成される。
本実施例の動作原理、各寸法間の関係等は、第三実施例の変形例（すなわち第二実施例）と全く同じである。受光素子３上に反射防止膜を省略するための配置についても第三実施例の変形例と同じである。
【００５４】
（第五実施例）
第五実施例の光学式エンコーダについて図１２を参照しながら説明する。
本実施例では、受光素子３は、面発光レーザ１の射出光の光軸から外れた位置に配置されている。受光素子３は、第三実施例のものと同様に、受光領域４を覆う遮光膜５１に複数の開口部が形成されたものである。面発光レーザ１と受光素子３の間には、入射光の向きを変える回折格子８を備えたスケール２がｘ軸方向に移動可能に配置されている。
【００５５】
スケール２は、図１４に示すように、ガラス基板７に形成した反射防止膜６の表面に、複数の回折格子８を等間隔で形成して作製される。このスケール２は、回折格子８の機能領域の幅をωｏ 、回折格子８の機能領域の１ピッチをＰｓ 、スケール面上における光ビーム照射領域のスケール移動方向のビーム径をＷｓ とすると、第一実施例において記した各条件が成立する。
【００５６】
別のスケール２を図１５に示す。このスケール２は、ガラス基板７の表面全体に回折格子８’ を形成し、この回折格子８’ の表面に等しい幅の遮光部５を等間隔で形成して作製される。これいより、等しい幅の複数の回折格子が等間隔で形成されたものと等価になり、図１４のスケールと同じ機能を果たす。このスケール２でも、図１４のスケール２と同様に、第一実施例において記した各条件が成立する。
【００５７】
図１２に示すように、面発光レーザ１から射出したレーザ光はスケール２に入射し、回折格子８に入射した光は回折される。回折格子８は入射光と反対側の一次回折光の回折強度が最大となるように設計されており、回折光は面発光レーザ１からの射出光に対して対して斜めになり、受光素子３に向かう。受光素子３に入射した光は、遮光膜５１に設けた開口部を通過した光が受光領域４に入射する。
【００５８】
本実施例の動作原理は、スケール２から回折光が射出される以外は、第二実施例と同様であり、図１２に記載した各寸法間の関係等は、基本的に第一実施例に記したものと同様であり、その説明は省略する。
【００５９】
本実施例では、受光素子３からの反射光は面発光レーザ１に戻らないので、受光素子３に反射防止膜がなくても、面発光レーザは安定に動作する。回折により光ビームを曲げているので、各光学素子（面発光レーザ１、スケール２、受光素子３）を平行に配置することができ、第三実施例や第四実施例に比べて、実装が容易かつ高精度に行える。
【００６０】
次に、本実施例の変形例について図１３を参照しながら説明する。本変形例は、本実施例の透過型の光学式エンコーダを、反射型に変形したものである。
図１３に示すように、受光素子３はスケール２に対して面発光レーザ１と同じ側にあり、これらは半導体基板１１の上に一体的に形成されている。また、スケール２の回折格子８は、入射光と同じ側の一次回折光の回折強度が最大となるように設計されている。
【００６１】
本変形例の動作原理、図１３に記載した各寸法間の関係等は、基本的に第一実施例に記したものと同様であり、ここでは説明を省略する。
本変形例によれば、本実施例と同じ効果が得られるとともに、面発光レーザ１と受光素子３が同一基板上に設けられているので、装置全体の構成が小型になり、実装も容易に行なえる。
【００６２】
なお、本実施例では、スケールからの回折光を利用して測定するものであるから、スケール５を照射する光はコヒーレントな平面波を有するレーザ光であればよいから、光源は面発光レーザだけではなく、端面出射型の半導体レーザとコリメータレンズの組み合わせなどを用いることができる。
【００６３】
（第六実施例）
これまでに説明した実施例の光学式エンコーダは、単にスケールの移動量のみを検出する機能を有するだけで、移動の向きを判別する機能は有していない。第六実施例は、前述の実施例の光学式エンコーダに改良を加えて、スケールの移動の向きを判別する機能を持たせるものである。
【００６４】
図１６に示すように、スケール２の遮光部は、移動方向（ｘ軸）に平行な中心線に対して、上側の遮光部５ａと下側の遮光部５ｂからなっている。上側の遮光部５ａと下側の遮光部５ｂは、ｘ軸方向に関して同一の周期構造を持ち、両者の位相はピッチＰｓ の四分の一ずれている。光ビーム照射領域は、上側の遮光部５ａと下側の遮光部５ｂの両方を同時に含むように設定される。また、受光素子は、上側の受光素子３ａと下側の受光素子３ｂからなり、上側の受光素子３ａはスケール２の上側部分すなわち遮光部５ａの隙間を透過したビームを受光し、下側の受光素子３ｂはスケール２の下側部分すなわち遮光部５ｂの隙間を透過したビームを受光する。勿論、スケール２と受光素子３ａと３ｂは、第一実施例に記した条件を満たしている。
【００６５】
このような構成により、スケール２の上側部分すなわち遮光部５ａの隙間を透過したビームは受光素子３ａの受光面上に、スケール２の下側部分すなわち遮光部５ｂの隙間を透過したビームが受光素子３ｂの受光面上に生成する明暗パターンに対して、ピッチＰｓ の四分の一ずれた明暗パターンを生成する。従って、スケール２が面発光レーザに対して移動するとき、上側の受光素子３ａと下側の受光素子３ｂとからは、互いの位相が９０度ずれた二つの正弦波信号が出力される。この二つの正弦波信号を比較することで、具体的にはどちらの正弦波信号の位相が９０度進んでいるかを調べることで、スケール２の移動の向きを判定することができる。
【００６６】
本実施例は、第一実施例ないし第五実施例のすべてに適応可能である。また、本実施例では遮光部５ａと遮光部５ｂのずれ量をピッチＰｓ の四分の一に選んだが、これはピッチＰｓ の二分の一以外であればいくつでもよく、いずれの場合にもスケールの移動方向を判断できる。
【００６７】
（第七実施例）
第七実施例について図１７を参照しながら説明する。本実施例は、第六実施例と同様に、第一実施例ないし第五実施例の光学式エンコーダに改良を加えて、スケールの移動の向きを判別する機能を持たせるものである。
【００６８】
図１７に示すように、受光素子は、上側の受光素子３ａと下側の受光素子３ｂからなり、上側の受光素子３ａの遮光膜５１ａと下側の受光素子３ｂの遮光膜５１ｂは、ｘ軸方向に関して同一の周期構造を持ち、両者の位相はピッチＰｐｄの四分の一ずれている。光ビーム照射領域は、スケール２からの光が二つの受光素子３に同時に入射するように設定されている。従って、上側の受光素子３ａはスケール２の上側部分を透過したビームを受光し、下側の受光素子３ｂはスケール２の下側部分を透過したビームを受光する。勿論、スケール２と受光素子３ａと３ｂは、第一実施例に記した条件を満たしている。
【００６９】
上側の受光素子３ａの遮光膜５１ａと下側の受光素子３ｂの遮光膜５１ｂは、その周期構造すなわち開口部の位置がｘ軸方向にピッチＰｐｄの四分の一ずれているため、上側の受光素子３ａと下側の受光素子３ｂとからは、互いの位相が９０度ずれた二つの正弦波信号が出力される。この二つの正弦波信号を比較することで、具体的にはどちらの正弦波信号の位相が９０度進んでいるかを調べることで、スケール２の移動の向きを判定することができる。
【００７０】
本実施例は、第一実施例ないし第五実施例のすべてに適応可能である。また、本実施例では遮光膜５１ａと遮光膜５１ｂのずれ量をピッチＰｐｄの四分の一に選んだが、これはピッチＰｐｄの二分の一以外であればいくつでもよく、いずれの場合にもスケールの移動の向きを判断できる。
【００７１】
以上、本発明のいくつかの実施例について説明したが、本発明は上述の実施例に何等限定されるものでない。本発明は以下の発明を含んでいる。
１．（第一実施例１〜第七実施例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するように形成されたスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダにおいて、
受光素子の受光領域または受光窓のスケール移動方向の寸法をωｐｄ、面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンのスケール移動方向の周期をＰｂ 、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ＜Ｐｂ かつ Ｗｓ ＞Ｐｓ
の関係を満たすことを特徴とする光学式エンコーダ。
【００７２】
（作用）面発光レーザからの出射ビームは非常にビーム放射角が小さいのでほぼ平行ビームでかつほぼ平面波であるとみなすことができる。以下、代表的な場合として、スケールに照射された光が透過して受光素子で検出される場合について説明する。スケール面上においてビーム直径Ｗｓ がＷｓ ＞Ｐｓ の関係を満たすことにより、スケール上において光ビームはスケールの１ピッチより大きなビーム径をもつ。また、ωｐｄ＜Ｐｂ なる関係があるため、受光素子は主として１ピッチ分の透過光を受光する。今、スケールが移動方向に変位したとすると、スケールを通過した光ビームもこの方向に動くので、受光素子からの出力が、変位に対して、周期Ｐｓ で三角波状または擬似的な正弦波状に変化することを利用してスケールの変位を検出することができる。
【００７３】
（効果）従来の光学式エンコーダのようにレンズや固定スケールを必要とせずに、スケール変位に対して周期Ｐｓ の三角波状または擬似的な正弦波状の信号を得ることができる。同時に、スケール面上における光ビームの径はスケールのピッチより十分大きくすることができ、スケールピッチがスケール面上における光ビームの径以下に制限されることがないため高分解能なエンコーダが実現できる。
【００７４】
２．（第二実施例２〜第七実施例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するように形成されたスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダにおいて、
受光素子の受光領域または受光窓が面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンとスケール移動方向に対して同じ間隔で複数形成され、
前記受光領域または受光窓のスケール移動方向の寸法をωｐｄ、前記受光面上における明暗パターンのスケール移動方向の周期をＰｂ 、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ＜Ｐｂ かつ Ｗｓ ＞Ｐｓ
の関係を満たすことを特徴とする光学式エンコーダ。
【００７５】
（作用）面発光レーザからの出射ビームは非常にビーム放射角が小さいのでほぼ平行ビームでかつほぼ平面波であるとみなすことができる。以下、代表的な場合として、スケールに照射された光が透過して受光素子で検出される場合について説明する。スケール面上においてビーム直径Ｗｓ がＷｓ ＞Ｐｓ の関係を満たすことにより、スケール上において光ビームはスケールの１ピッチより大きなビーム径をもつ。また、ωｐｄ＜Ｐｂ なる関係があるため、受光素子のひとつの受光窓または受光領域は主として１ピッチ分の透過光を受光する。今、スケールが移動方向に変位したとすると、スケールを通過した複数のビームもこの方向に動くので、受光素子からの出力が、スケール変位に対して、周期Ｐｓ で三角波状または擬似的な正弦波状に変化することを利用してスケールの変位を検出することができる。
【００７６】
（効果）従来の光学式エンコーダのようにレンズや固定スケールを必要とせずに、スケール変位に対して周期Ｐｓ の三角波状または擬似的な正弦波状の信号を得ることができる。同時に、スケール面上における光ビームの径はスケールのピッチより十分大きくすることができ、スケールピッチがスケール面上における光ビームの径以下に制限されることがないため高分解能なエンコーダが実現できる。この場合、第１項に比べて多くの受光窓を有し、たくさんの透過光（あるいは反射光、回折光）を受光するので、より強い出力信号が得られ、電子回路等による信号処理がより容易になる。
【００７７】
３．（第一実施例〜第七実施例に対応する）
（構成）第１項において、
受光素子がスケールの透過光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ とし、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｐｓ ωｏ ／λ＞Ｌ≧ωｏ ^２ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００７８】
（作用）第１項の作用と同じである。
（効果）第１項の効果に加え、Ｐｓ ωｏ ／λ＞Ｌ≧ωｏ ^２ ／λの構成要件を満たすことにより、受光素子面上での光強度分布が平坦となることを妨げるので、スケール変位に対する出力信号の強弱が適正値以上で得られる。
【００７９】
４．（第一実施例〜第七実施例に対応する）
（構成）第１項において、
受光素子がスケールの透過光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ とし、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｌ＜ωｏ ^２ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００８０】
（作用）第１項の作用と同じである。
（効果）第１項の効果に加え、Ｌ＜ωｏ ^２ ／λの構成要件を満たすことにより、受光素子面上での光強度分布が複数の光ビームの重ね合わせや干渉の効果に影響されず、スケール変位に対する出力信号の強弱が非常に強く得られる。また、このため、光ビームの重ね合わせによるビーム強度の平坦化による出力信号の劣化が殆どないので、スケールのピッチを非常に小さく設定できる。
【００８１】
５．（第二実施例〜第七実施例に対応する）
（構成）第２項において、
受光素子がスケールの透過光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ とし、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｐｓ ωｏ ／λ＞Ｌ≧ωｏ ^２ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００８２】
（作用）第３項の作用に加えて、複数の受光素子の受光領域または受光窓を有し、スケール上の各々の透過または反射領域からの光ビームを受光領域または受光窓で同時に検出する。
【００８３】
（効果）第３項の効果に加えて、スケール上の各々の透過または反射領域からの光ビームを受光領域または受光窓で同時に検出するので、受光強度が大きくなり信号処理が容易となる。
【００８４】
６．（第二実施例〜第七実施例に対応する）
（構成）第２項において、
受光素子がスケールの透過光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ とし、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｌ＜ωｏ ^２ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００８５】
（作用）第４項の作用に加えて、複数の受光素子の受光領域または受光窓を有し、スケール上の各々の透過または反射領域からの光ビームを受光領域または受光窓で同時に検出する。
【００８６】
（効果）第４項の効果に加えて、スケール上の各々の透過または反射領域からの光ビームを受光領域または受光窓で同時に検出するので、受光強度が大きくなり信号処理が容易となる。
【００８７】
７．（第一実施例〜第七実施例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するように形成されたスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの回折光を受光するための受光素子を有する光学式エンコーダで、
前記受光領域または受光窓のスケール移動方向の寸法をωｐｄ、前記レーザ光源からスケールに照射された光ビームの回折光による受光素子の受光面上における明暗パターンの光強度が最大ピークの１／２となるスケール移動方向の幅をωｂ とし、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ≦ωｂ かつ Ｗｓ ≧２Ｐｓ
の関係を満たす光学式エンコーダにおいて、
受光素子がスケールの透過・回折光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射・回折光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ 、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｌ＞Ｐｓ ωｏ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００８８】
（作用）面発光レーザからの出射ビームは非常にビーム放射角が小さいのでほぼ平行ビームでかつほぼ平面波であるとみなすことができる。以下、代表的な場合として、スケールに照射された光が透過して、さらに、回折することにより受光素子で検出される場合について説明する（反射して、回折する場合も同様）。スケール面上においてビーム直径Ｗｓ がＷｓ ≧２Ｐｓ の関係を満たすことにより、スケール上において光ビームはスケールの２ピッチ以上のビーム径をもつ。従って、受光素子にはスケールを通過した光が複数のビームになって照射されるが、ωｐｄ≦ωｂ なる関係があるため、受光素子は特定の次数の回折光を受光する。今、スケールが移動方向に変位したとすると、スケールからの回折光もこの方向に同じ変位量だけ動くので、受光素子からの出力が、変位に対して周期Ｐｓ で三角波状または擬似的な正弦波状に変化することを利用してスケールの変位を検出することができる。
【００８９】
（効果）従来の光学式エンコーダのようにレンズや固定スケールを必要とせずに、スケール変位に対して周期Ｐｓ の三角波状または擬似的な正弦波状の信号を得ることができる。同時に、スケール面上における光ビームの径はスケールのピッチより十分大きくすることができ、スケールピッチがスケール面上における光ビームの径以下に制限されることがないため高分解能なエンコーダが実現できる。さらに、領域Ｉや領域ＩＩでセンサを使用する場合はＬが大きくなると、スケールの変位に対して受光素子での出力信号の強弱の幅が小さくなるが、本構成では回折を用いるのでこのような問題はない。
【００９０】
８．（第二実施例〜第七実施例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するように形成されたスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの回折光を受光するための受光素子を有する光学式エンコーダで、
受光素子の受光領域または受光窓が面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンとスケール移動方向に対して同じ間隔で複数形成され、
前記受光領域または受光窓のスケール移動方向の寸法をωｐｄ、前記レーザ光源からスケールに照射された光ビームの回折光による受光素子の受光面上における明暗パターンの光強度が最大ピークの１／２となるスケール移動方向の幅をωｂ とし、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ≦ωｂ かつ Ｗｓ ≧２Ｐｓ
の関係を満たす光学式エンコーダにおいて、
受光素子がスケールの透過・回折光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射・回折光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ 、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｌ＞Ｐｓ ωｏ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００９１】
（作用）第７項の作用に加えて、複数の受光素子の受光領域または受光窓を有し、異なる次数の回折光を各々の受光領域または受光窓で同時に検出する。このとき、異なる次数の回折光は各々特定の回折角で回折するので、スケールの移動に対して受光面上で各回折次数の光ピークの位置は互いに同じ変位量だけ移動する。
【００９２】
（効果）第７項の効果に加えて、異なる次数の回折光を各々の受光領域または受光窓同時に検出するので、受光強度が大きくなり信号処理が容易となる。
９．（第一実施例の変形例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するように形成されたスケールと、このスケールの一部を照射するコリメータレンズと半導体レーザからなるレーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダで、
受光素子の受光領域または受光窓のスケール移動方向の寸法をωｐｄ、半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンの光強度が最大ピークの１／２となるスケール移動方向の幅をωｂ とし、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ≦ωｂ かつ Ｗｓ ≧２Ｐｓ
の関係を満たす光学式エンコーダにおいて、
受光素子がスケールからの透過・回折光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射・回折光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ とし、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｌ＞Ｐｓ ωｏ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００９３】
（作用）光源は面発光レーザの代わりに、端面出射型の半導体レーザを用い、出射ビームの拡がりをコリメートレンズで制御し、平行ビームに成形する。この他は第７項の作用と同じである。
【００９４】
（効果）第７項の効果に加えて、技術的に面発光レーザに比べてレーザの製造が容易で入手しやすい通常の半導体レーザを使うことができる。
１０．（第二実施例を第一実施例の変形例に適用した場合に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するように形成されたスケールと、このスケールの一部を照射するコリメータレンズと半導体レーザからなるレーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダで、
受光素子の受光領域または受光窓が面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンとスケール移動方向に対して同じ間隔で複数形成され、
前記受光領域または受光窓のスケール移動方向の寸法をωｐｄ、半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンの光強度が最大ピークの１／２となるスケール移動方向の幅をωｂ とし、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ≦ωｂ かつ Ｗｓ ≧２Ｐｓ
の関係を満たす光学式エンコーダにおいて、
受光素子がスケールからの透過・回折光を受光する場合はスケールの１ピッチあたりの透過部分のスケール移動方向の寸法をωｏ 、また、受光素子がスケールの反射・回折光を受光する場合はスケールの１ピッチあたりの反射部分のスケール移動方向の寸法をωｏ とし、スケールを形成した面と受光素子の受光面または遮光面の間の距離をＬ、レーザ光の波長をλとしたとき、
Ｌ＞Ｐｓ ωｏ ／λ
の関係を満たすことを特徴とする光学式エンコーダ。
【００９５】
（作用）第９項の作用に加えて、複数の受光素子の受光領域または受光窓を有し、異なる次数の回折光を各々の受光領域または受光窓同時に検出する。
（効果）第９項の効果に加えて、異なる次数の回折光を各々の受光領域または受光窓同時に検出するので、受光強度が大きくなり信号処理が容易となる。
【００９６】
１１．（第三実施例に対応する）
（構成）第１項ないし第１０項において、
スケールをスケールの移動方向を軸として回転させ、スケールの透過または反射面がレーザビームに対して垂直でない配置とすることを特徴とする光学式エンコーダ。
【００９７】
（作用）スケールを傾斜させることにより、スケールから面発光レーザに反射して帰還してくるレーザ光が抑制され、レーザ光の強度変化が抑えられる。この他は、第１項ないし第１０項の各々の作用と同じである。
【００９８】
（効果）スケールから面発光レーザに反射して帰還してくるレーザ光がある場合は、スケールと面発光レーザの距離により帰還する光の位相が変化し、これがレーザと相互作用し、レーザ光の強度変化を引き起こす。また、スケールが動くとスケールの反射率の高い部分と低い部分からの帰還光の割合がわずかに変化するのでこれによってもレーザ光の強度が変化する。スケールを傾斜させることにより、スケールから面発光レーザに反射して帰還してくるレーザ光が抑制され、レーザ光の強度変化が抑えられ、ひいては、センサ信号を安定にする効果がある。
【００９９】
１２．（第四実施例に対応する）
（構成）第１項ないし第１０項において、
スケールをスケールの移動方向に対する垂線とレーザビームの主軸を互いに傾斜させるように配置することを特徴とする光学式エンコーダ。
【０１００】
（作用）スケールを傾斜させることにより、スケールから面発光レーザに反射して帰還してくるレーザ光が抑制され、レーザ光の強度変化が抑えられる。この他は、第１項ないし第１０項の各々の作用と同じである。
【０１０１】
（効果）第１１項の場合は、レーザビームの主軸と垂直な面に対してスケールをスライドさせる場合にコンパクトな構成であるが、本構成では、レーザビームの主軸に対して傾斜した面でスケールをスライドさせる場合にコンパクトな構成となる。
【０１０２】
１３．（第五実施例に対応する）
（構成）光源に対して相対的に移動し、かつ、回折格子が機能する領域と機能しない領域を交互に形成したスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダにおいて、
受光素子の受光領域または受光窓のスケール移動方向の寸法をωｐｄ、面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンのスケール移動方向の周期をＰｂ 、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ＜Ｐｂ かつ Ｗｓ ＞Ｐｓ
の関係を満たすことを特徴とする光学式エンコーダ。
【０１０３】
（作用）レーザからスケールに照射された光の全部または一部が回折して受光素子に入射する。この他は、第１項または第２項の作用と同じである。
（効果）第１項または第２項の効果に加えて、受光素子に入射する回折光はスケールからの単なる反射光や透過光と向きが異なるため、受光素子の受光面からの反射光が半導体レーザに帰還しない。従って、受光素子の受光面をスケールの面と平行にした場合でも、受光面に反射防止膜などの反射防止対策を講じなくても、帰還する光によるレーザ出力の不安定化を抑制できる。
【０１０４】
１４．（第五実施例の変形例に対応する）
（構成）光源に対して相対的に移動し、かつ、回折格子が機能する領域と機能しない領域を交互に形成したスケールと、このスケールの一部を照射するコリメータレンズと半導体レーザよりなる光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダにおいて、
受光素子の受光領域または受光窓のスケール移動方向の寸法をωｐｄ、半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンのスケール移動方向の周期をＰｂ 、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ＜Ｐｂ かつ Ｗｓ ＞Ｐｓ
の関係を満たすことを特徴とする光学式エンコーダ。
【０１０５】
（作用）コリメータレンズを半導体レーザと組み合わせることにより、面発光半導体レーザの場合と同様に、平行度の高いビームを出射できる。その他は、第１３項の作用と同じである。
【０１０６】
（効果）第１３項の効果に加えて、光源である半導体レーザの入手が、面発光半導体レーザに比較して容易である。
１５．（第六実施例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するようにパターン形成されたスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダで、
受光素子の受光領域または受光窓が面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンとスケール移動方向に対して同じ間隔で複数形成され、
前記受光領域または受光窓のスケール移動方向の寸法をωｐｄ、前記受光面上における明暗パターンのスケール移動方向の周期をＰｂ 、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ＜Ｐｂ かつ Ｗｓ ＞Ｐｓ
の関係を満たす光学式エンコーダにおいて、
前記パターン形成されたスケールのパターンが、ビーム照射領域内で１／２周期以外の位相シフトを有して２組形成され、これらの各々の組からの反射または、透過、回折光を分離して検出できる受光素子を備えた光学式エンコーダ。
【０１０７】
（作用）面発光半導体レーザから出射した光が互いに異なる位相で形成されたスケール上のパターンに同時に照射され、スケール上の位相差をもった各々のパターンから反射または透過、回折した光が分離された受光素子に各々入射する。従って、スケールが移動すると、各々の受光素子からの出力は互いに相似形状だが、互いに一定の位相差をもって出力される。
【０１０８】
（効果）互いに分離された受光素子から位相差をもった信号波形が出力されるので、これらの位相の遅延の関係を調べることにより、スケールの移動の向きが判定できる。
【０１０９】
１６．（第七実施例に対応する）
（構成）光源に対して相対的に移動し、光の反射率または透過率が周期的に変化するようにパターン形成されたスケールと、このスケールの一部を照射する面発光半導体レーザ光源と前記スケールからの反射光、透過光または回折光を受光するための受光素子を有する光学式エンコーダで、
受光素子の受光領域または受光窓が面発光半導体レーザ光源からスケールに照射された光ビームの反射光、透過光または回折光による受光素子の受光面上における明暗パターンとスケール移動方向に対して同じ間隔で複数形成され、
前記受光領域または受光窓のスケール移動方向の寸法をωｐｄ、前記受光面上における明暗パターンのスケール移動方向の周期をＰｂ 、
前記スケールの反射率または透過率を変調させたスケール移動方向のピッチをＰｓ 、スケール面上において光ビーム強度がピーク値の１／２になるスケール移動方向のビーム径をＷｓ とすると、
ωｐｄ＜Ｐｂ かつ Ｗｓ ＞Ｐｓ
の関係を満たす光学式エンコーダにおいて、
前記複数形成された受光領域または受光窓のパターンが、ビーム受光領域内で１／２周期以外の位相シフトを有して２組形成され、これらの各々の組の受光量を分離して検出できる受光素子を備えた光学式エンコーダ。
【０１１０】
（作用）面発光半導体レーザから出射した光が互いに異なる位相で形成されたスケール上のパターンに同時に照射され、スケール上の位相差をもった各々のパターンから反射または透過、回折した光が、受光素子の受光面上で明暗のパターン示すが、この明暗パターンに対して、互いに位相シフトした受光窓または受光領域に入射し、更に、これらの位相シフトした受光窓または受光領域が分離されている。従って、スケールが移動すると、各々の受光素子からの出力は互いに相似形状だが、互いに一定の位相差をもって出力される。
【０１１１】
（効果）第１５項と同様なスケールの移動の向き判定可能な二つ以上の位相差信号を、受光窓に形成した受光領域または受光窓のパターンにより得ることができる。第１５項の場合はこの位相シフトパターンをスケール上に配置する必要があるが、この場合は面発光半導体レーザからのビームの照射領域内にこの位相シフトが配置されるように調整する必要があり、更に、各々のパターンからのビーム領域に合うように受光素子も空間的に分離する必要があり組立が難しい。これに対して、本項では、面発光半導体レーザとスケールの配置にこのような制約がなく、単にスケールからの反射または透過、回折光が受光素子の位相シフトパターンにかかるように配置するだけでよく、素子の組立が容易になる。
【０１１２】
【発明の効果】
本発明の光学式エンコーダによれば、従来の光学式エンコーダのようにレンズや固定スケールを必要とせずに、スケール変位に対して周期Ｐ_sの三角波状または擬似的な正弦波状の信号を得ることができる。同時に、スケール面上における光ビームの径はスケールのピッチより十分大きくすることができ、スケールピッチがスケール面上における光ビームの径以下に制限されることがないため高分解能なエンコーダが実現できる。
【図面の簡単な説明】
【図１】本発明の第一実施例の光学式エンコーダの構成を示す図である。
【図２】図１に示したスケールの正面図である。
【図３】図１の光学式エンコーダにおけるスケールの変位に対する受光素子の出力の特性を示すグラフである。
【図４】一つの透過窓を通過した光の広がり方を示す図である。
【図５】複数の透過窓を通過した光の重なり具合を示す図である。
【図６】図５において透過窓からの距離をＬとした場合に、様々な距離Ｌの面上に生成される明暗パターンを示す図である。
【図７】本発明の第二実施例の光学式エンコーダの構成を示す図である。
【図８】本発明の第三実施例の光学式エンコーダの構成を示す図である。
【図９】本発明の第三実施例の変形例である反射型の光学式エンコーダの構成を示す図である。
【図１０】本発明の第四実施例の光学式エンコーダの構成を示す図である。
【図１１】本発明の第四実施例の変形例である反射型の光学式エンコーダの構成を示す図である。
【図１２】本発明の第五実施例の光学式エンコーダの構成を示す図である。
【図１３】本発明の第五実施例の変形例である反射型の光学式エンコーダの構成を示す図である。
【図１４】第五実施例に使用されるスケールの構造を説明するための図である。
【図１５】第五実施例に使用される別のスケールの構造を説明するための図である。
【図１６】第一実施例ないし第五実施例に改良を加えてスケールの移動方向を判別する機能をもたせた第六実施例の光学式エンコーダにおいて、スケールと受光素子を光源側から見た図である。
【図１７】第一実施例ないし第五実施例に改良を加えてスケールの移動方向を判別する機能をもたせた第七実施例の光学式エンコーダにおいて、スケールと受光素子を光源側から見た図である。
【図１８】従来例の光学式エンコーダを説明するための図である。
【図１９】本発明者らが提案した光学式エンコーダを説明するための図である。
【符号の説明】
１…面発光レーザ、２…スケール、３…受光素子、５…遮光部、５１…遮光膜。[0001]
[Industrial applications]
The present invention relates to an optical encoder used for detecting displacement or rotation of an object.
[0002]
[Prior art]
As a typical conventional example of a high-resolution optical encoder, there is an encoder using two slits (or scales) (Nikkei Mechanical, 1988.7.25, p. 54). FIG. 18 shows the configuration.
[0003]
As shown in FIG. 18A, light emitted from a light source 100 is shaped into a parallel beam by a lens 13, passes through a fixed scale 22 and a movable scale 2, and is received by a light receiving element 3 (in this specification, the light receiving element is a light detecting element). Is regarded as synonymous with the container), the intensity of the transmitted light is detected. In the case where the scale is only the moving scale 2, as shown in FIG. 18B, the output of the light receiving element with respect to the displacement x is only slightly changed in the same cycle as the pitch of the scale. In the case where the scale is composed of the fixed scale 22 and the movable scale 2 as in the conventional example, when the movable scale 2 moves with respect to the fixed scale 22, a change in the overlap between the two scales causes a change in FIG. As shown in (C), the output of the light receiving element 3 changes in a shape close to a triangular wave or a sine wave (when the directions of the two scales are slightly inclined), and the change in the signal intensity becomes large. Therefore, by using two slits, the output signal has a large signal-to-noise ratio (S / N), and can be divided into displacements according to the waveform of the output signal, and the pitch of the scale The displacement of the moving scale smaller than の of the moving scale can be detected.
[0004]
[Problems to be solved by the invention]
In this conventional example, since it is necessary to spatially dispose and assemble the lens, the fixed slit, the light source, and the moving slit with very high accuracy, it is difficult to assemble the encoder, the size of the entire encoder is large, and the manufacturing cost is high. It has to be something.
[0005]
On the other hand, the present inventors have proposed an encoder using a vertical cavity surface emitting laser (also referred to as a surface emitting laser or a surface emitting semiconductor laser) in Japanese Patent Application No. 06-043656. FIG. 19 shows the configuration.
[0006]
As shown in FIG. 19A, a laser beam emitted from a surface emitting laser 1 is applied to a scale 2 which moves relative to the laser beam, and reflected light or transmitted light from this scale is detected by a photodetector 3 or a photodetector. The light enters the detector 3 'and the intensity is detected.
[0007]
When the diameter of the laser beam on the scale surface is very small compared to the pitch of the scale, an output signal of the light receiving element as shown in FIG. When the diameter of the laser beam is about の of the pitch of the scale, a light-receiving element output signal as shown in FIG. 19C is obtained for the displacement Δx of the scale. A signal having a shape close to a triangular wave or a sine wave as shown in FIG. 19C is obtained because the emission angle of the laser light is very small in the case of the surface emitting laser 1, and therefore, in the conventional example of FIG. This is because the irradiation area of the laser beam is limited to a small area without using the lens and the fixed slit.
[0008]
As described above, the encoder proposed by the present inventors uses a thin and sharp beam of a surface emitting laser, and does not require a lens or a fixed slit. As a result, a small, high-resolution encoder can be obtained at low cost.
[0009]
However, in this encoder, when the diameter of the laser beam on the scale surface is very small compared to the pitch of the scale, the output signal of the light receiving element has a shape close to a rectangular wave with respect to the displacement of the scale, and the pitch of the scale is reduced. It is difficult to detect a displacement smaller than 1/2. Further, when the diameter of the laser beam on the scale surface is larger than the pitch of the scale, the intensity of the output signal of the light receiving element becomes extremely small with respect to the displacement of the scale, so that it is difficult to detect the displacement. In such a case, even if a surface emitting laser is used, a lens is arranged between the surface emitting laser and the scale, and the beam diameter of the laser beam on the scale is set to about 1 to 1/2 times the pitch of the scale. There is a need to.
[0010]
It is an object of the present invention to provide an optical encoder that does not require a lens or a fixed scale, has a simple configuration and is easy to assemble, and has a small scale displacement with respect to the diameter of the light beam on the scale surface even if the pitch of the scale is small. Is to provide an optical encoder that can accurately detect the optical encoder. That is, an object of the present invention is to provide a small, inexpensive, and high-precision optical encoder.
[0011]
[Means for Solving the Problems]
A first optical encoder according to the present invention moves relative to a light source, and irradiates a scale formed so that the reflectance or transmittance of light periodically changes, and a part of the scale. It has a surface emitting semiconductor laser light source and a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale, and has a light receiving area of the light receiving element or a light receiving window having a dimension in the scale moving direction of ω._pdThe period in the scale moving direction of the light and dark pattern on the light receiving surface of the light receiving element due to the reflected light, transmitted light or diffracted light of the light beam emitted from the surface emitting semiconductor laser light source to the scale is P_b, The pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is P_s, The beam diameter in the scale movement direction at which the light beam intensity becomes の of the peak value on the scale surface is W_sThen ω_pd<P_b, And W_s> P_sWhen the light receiving element receives the transmitted light of the scale, the dimension of the transmitted portion per pitch of the scale in the scale moving direction is ω._oWhen the light receiving element receives the reflected light of the scale, the dimension of the reflecting portion per pitch of the scale in the scale moving direction is ω._oWhen the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ, P_sω_o/ Λ> L ≧ ω_o ^Two/ Λ is satisfied.
The second optical encoder according to the present invention moves relative to the light source and irradiates a scale formed so that the reflectance or transmittance of light changes periodically and a part of the scale. It has a surface emitting semiconductor laser light source and a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale, and has a light receiving area of the light receiving element or a light receiving window having a dimension in the scale moving direction of ω._pdThe period in the scale moving direction of the light and dark pattern on the light receiving surface of the light receiving element due to the reflected light, transmitted light or diffracted light of the light beam emitted from the surface emitting semiconductor laser light source to the scale is P_b, The pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is P_s, The beam diameter in the scale movement direction at which the light beam intensity becomes の of the peak value on the scale surface is W_sThen ω_pd<P_b, And W_s> P_sWhen the light receiving element receives the transmitted light of the scale, the dimension of the transmitted portion per pitch of the scale in the scale moving direction is ω._oWhen the light receiving element receives the reflected light of the scale, the dimension of the reflecting portion per pitch of the scale in the scale moving direction is ω._oWhen the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L and the wavelength of the laser beam is λ, L <ω_o ^Two/ Λ is satisfied.
[0012]
The third optical encoder according to the present invention moves relative to the light source, and irradiates a scale formed so that the reflectance or transmittance of light changes periodically and a part of the scale. A light emitting element having a surface emitting semiconductor laser light source and a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale, wherein a light receiving region or a light receiving window of the light receiving element is irradiated on the scale from the surface emitting semiconductor laser light source; A plurality of light and dark patterns on the light receiving surface of the light receiving element due to reflected light, transmitted light or diffracted light of the beam are formed at the same interval with respect to the scale moving direction, and the dimension of the light receiving area or the light receiving window in the scale moving direction is ω._pd, The period in the scale moving direction of the light and dark pattern on the light receiving surface is P_b, The pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is P_s, The beam diameter in the scale movement direction at which the light beam intensity becomes の of the peak value on the scale surface is W_sThen ω_pd<P_b, And W_s> P_sWhen the light receiving element receives the transmitted light of the scale, the dimension of the transmitted portion per pitch of the scale in the scale moving direction is ω._oWhen the light receiving element receives the reflected light of the scale, the dimension of the reflecting portion per pitch of the scale in the scale moving direction is ω._oWhen the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ, P_sω_o/ Λ> L ≧ ω_o ^Two/ Λ is satisfied.
A fourth optical encoder according to the present invention moves relative to a light source and irradiates a scale formed so that the reflectance or transmittance of light changes periodically and a part of the scale. A light emitting element having a surface emitting semiconductor laser light source and a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale, wherein a light receiving region or a light receiving window of the light receiving element is irradiated on the scale from the surface emitting semiconductor laser light source; A plurality of light and dark patterns on the light receiving surface of the light receiving element due to reflected light, transmitted light or diffracted light of the beam are formed at the same interval with respect to the scale moving direction, and the dimension of the light receiving area or the light receiving window in the scale moving direction is ω._pd, The period in the scale moving direction of the light and dark pattern on the light receiving surface is P_b, The pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is P_s, The beam diameter in the scale movement direction at which the light beam intensity becomes の of the peak value on the scale surface is W_sThen ω_pd<P_b, And W_s> P_sWhen the light receiving element receives the transmitted light of the scale, the dimension of the transmitted portion per pitch of the scale in the scale moving direction is ω._oWhen the light receiving element receives the reflected light of the scale, the dimension of the reflecting portion per pitch of the scale in the scale moving direction is ω._oWhen the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L and the wavelength of the laser beam is λ, L <ω_o ^Two/ Λ is satisfied.
[0014]
[Action]
In the optical encoder according to the present invention, the beam emitted from the surface emitting laser has a very small beam emission angle, and thus can be regarded as a substantially parallel beam and a substantially plane wave. Hereinafter, as a typical case, a case where light applied to a scale is transmitted and detected by a light receiving element will be described. Beam diameter W on scale surface_sIs W_s> P_sBy satisfying the relationship, the light beam on the scale has a beam diameter larger than one pitch of the scale. Also, ω_pd<P_bTherefore, one light receiving window or light receiving region of the light receiving element mainly receives transmitted light for one pitch. Now, assuming that the scale is displaced in the moving direction, the light beam passing through the scale also moves in this direction._s, The displacement of the scale can be detected by utilizing the change in a triangular waveform or a pseudo sine waveform.
[0017]
【Example】
Hereinafter, specific embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
The optical encoder according to the first embodiment will be described with reference to FIGS. FIG. 1 shows the configuration of the optical encoder of this embodiment.
[0018]
As shown in FIG. 1, the optical encoder includes a surface emitting semiconductor laser light source (hereinafter, simply referred to as a surface emitting laser) 1, a light receiving element 3 arranged to receive the emitted light, and a light emitting element x between them. The scale 2 is configured to be movable in the direction. The scale 2 has a transparent substrate 7, and light-shielding portions 5 having the same width are provided at equal intervals on the surface of the transparent substrate 7 on the light receiving element 3 side, as shown in FIG. 2. An anti-reflection film 6 is formed on the surface of the transparent substrate 7 on the side of the surface-emitting laser, as shown in FIG. A light-shielding film 51 is formed on the surface of the light-receiving region 4 of the light-receiving element 3, and the light-shielding film 51 has one opening. On the surface of the light shielding film 51, an antireflection film 52 is formed.
[0019]
The laser light emitted from the surface emitting laser 1 is incident on the scale 2, the light transmitted through the transmission window formed by the gap of the light shielding unit 5 irradiates the light receiving element 3, and the light passing through the opening provided in the light shielding film 51 is emitted. The light enters the light receiving region 4. The antireflection film 6 prevents the reflected light from the scale 2 from returning to the surface emitting laser 1, and the antireflection film 52 similarly prevents the reflected light from the light receiving element 3 from returning to the surface emitting laser 1. Thereby, the stable operation of the surface emitting laser is ensured.
[0020]
Here, the behavior of the light transmitted through the scale 2 will be described. The light emitted from the surface emitting laser has a very small beam divergence angle, and can be regarded as a substantially plane wave and parallel beam.
[0021]
As shown in FIGS. 1 and 2, the moving direction of the scale 2 is taken on the x-axis and the beam emitting direction is taken on the y-axis. , The distance from the scale 2 to the light receiving element 3 is L, the wavelength of light is λ, the beam width of the light beam traveling from one transmission window to the light receiving element in the scale moving direction (x-axis direction) on the light receiving element surface. Is ωb.
First, consider light transmitted through one transmission window. The light beam traveling from one transmission window to the light receiving element spreads as shown in FIG.
[0022]
(Equation 1)

[0023]
(Equation 2)

It becomes. Here, the beam diameter means a beam passing dimension of which the light intensity is 1/2 or more of the maximum peak.
[0024]
Next, a pattern on the light receiving element surface of light transmitted through a number of transmission windows will be considered. Since the light beam that has passed through the transmission window of the scale 2 spreads as shown in FIG. 5, it is necessary to consider overlapping and interference of the light beams.
[0025]
In the following, the distance L from the scale 2 to the light receiving element 3 is the area I: L <ωo²  / Λ and region II: Ps ωo / λ> L ≧ ωo²  / Λ and the case where it is in the region III: L> Psωo / λ are considered separately.
[0026]
First, when L is in the region I, that is, L <ωo²  In the case of / λ, the scale 2 and the light receiving element 3 are very close, and the plural beams do not interfere with each other. Accordingly, the pattern appearing on the light receiving element surface is a superposition of beams having the diameter represented by the expression (2), as shown in FIG.
[0027]
Next, when L is in the region II, that is, Psωo / λ> L ≧ ωo²  In the case of / λ, the interference between the beams is small and almost negligible. Therefore, the pattern appearing on the light receiving element surface is a superposition of beams having the diameter represented by the expression (1), and is as shown in FIG. 6C. In the figure, the broken line indicates the intensity distribution of each beam before superposition, and the solid line indicates the actually observed intensity distribution of the light obtained by superimposing the beams. Therefore, near L = Psωo / λ, the actually observed light intensity distribution becomes substantially flat as shown in FIG. 6B. In this region, the mutual interference of the beams is small but not completely negligible.
[0028]
Finally, when L is in the region III, that is, when L> Ps ωo / λ, the light beams emitted from the plurality of transmission windows of the scale 2 interfere with each other. The result is as shown in FIG. In FIG. 6A, the interval Δxdiff of the maximum peak in the x direction and the full width at half maximum ω′b of this peak can be approximately expressed by the following equation.
[0029]
(Equation 3)

[0030]
(Equation 4)

Here, m is the number of transmission windows (gap between the light shielding portions 5) in an effective area of the laser beam irradiated on the scale (which can be considered as a beam diameter on the scale). This corresponds approximately to the number of pitches.
[0031]
In the present specification, the width of the light beam on the light receiving element surface may be considered simply by considering the beam diameter ωb due to transmission or reflection or by considering the full width at half maximum ω′b of the peak of the interference pattern. As far as possible, these are both treated as the beam diameter ωb.
[0032]
As described above, different light and dark patterns are generated on the light receiving element surface depending on which of the regions I to III the distance from the scale 2 to the light receiving element 3 belongs to. In any of the patterns, when the scale 2 moves in the x-axis direction, the light-dark pattern generated on the light-receiving element surface moves in the same direction at the same speed, so that the output of the light-receiving element 3 becomes as shown in FIG. A periodic waveform similar to a sine waveform is obtained. By examining the output waveform, the amount of movement of the scale 2 can be obtained.
[0033]
The relationship between the various dimensions in FIG. 1 differs depending on whether the distance L from the scale 2 to the light receiving element 3 is in the region I or the region III. This will be described below.
[0034]
When the distance L is in the region I, the emitted lights from the scale 2 do not interfere with each other, so that the beam on the scale only needs to cover at least one pitch of the scale. That is, Ws is the beam diameter in the x-axis direction of the light beam irradiation area on the scale surface, and Ws> Ps. In addition, in order to detect a light and dark pattern at the opening of the light receiving element 3 having the width ωpd, it is necessary that the period be Pb and ωpd <Pb.
[0035]
When the distance L is in the area II, the interference pattern is not used, so that the beam on the scale needs to cover at least one pitch of the scale as in the case of the area I. That is, the beam diameter (dimension in the x-axis direction at which the intensity of the light beam becomes １ ／ of the peak value) in the scale movement direction (x-axis direction) of the light beam irradiation area on the scale surface is Ws, and Ws> Ps. is there. Further, in order to detect a light and dark pattern, it is necessary that the period be Pb and ωpd <Pb.
[0036]
When the distance L is in the region III, two or more beams need to be emitted from the scale 2 because the interference pattern is used. That is, the beam diameter in the x-axis direction of the light beam irradiation area on the scale surface is Ws, and Ws ≧ 2Ps. In addition, in order to detect a light and dark pattern, it is necessary that ωpd ≦ ωb when the half width of the peak of the interference pattern is ωb.
[0037]
As described above, in the present embodiment, there are three cases according to the distance L between the scale 2 and the light receiving element 3, and if the dimensions of the respective parts are determined so as to satisfy certain conditions, the scale 2 Displacement can be detected.
[0038]
As described above, this embodiment does not require a lens or a fixed scale, and has a resolution determined by the scale pitch even when the beam diameter is larger than the scale pitch, and the sensor configuration and assembly are simple, small, and low cost. A highly accurate optical encoder can be obtained.
[0039]
The method for limiting the position of the light receiving section in the light receiving element is not limited to the method of providing an opening in the light receiving surface of the light receiving element as shown in FIG. A device having a light position detecting function such as a CCD may be used.
[0040]
Further, in the case of performing the measurement by the interference pattern as shown in FIG. 6A in the region III of FIG. 5, since the light for irradiating the scale 5 may be a laser beam having a coherent plane wave, Not only a light emitting laser but also a combination of a commonly used edge emitting semiconductor laser and a collimator lens can be used.
[0041]
(Second embodiment)
An optical encoder according to a second embodiment will be described with reference to FIG.
As shown in FIG. 7, the optical encoder of the present embodiment is similar to the optical encoder of the first embodiment, and only the light-shielding film 51 on the surface of the light receiving region 4 has a plurality of openings of width ωpd. And (although one in the first embodiment) are provided at equal intervals. The pitch Ppd of the plurality of openings coincides with the period Pb of the light and dark pattern generated on the light receiving element surface.
[0042]
The operation principle of this embodiment, the relationship between the dimensions, and the like are all the same as those of the first embodiment, and a description thereof will be omitted here.
According to this embodiment, the same effects as those of the first embodiment can be obtained, and a higher output can be obtained as compared with the first embodiment by providing a plurality of light receiving portions.
[0043]
The method of limiting the position of the light receiving portion in the light receiving element is not limited to a method of providing a light shielding window on the light receiving surface of the light receiving element as shown in FIG. 7, but a method of dividing the light receiving surface into a predetermined size, Alternatively, a CCD or the like having a light position detecting function may be used.
[0044]
(Third embodiment)
An optical encoder according to a third embodiment will be described with reference to FIG.
As shown in FIG. 8, the optical encoder of this embodiment is similar to the optical encoder of the second embodiment, but differs in the following two points. First, the scale 2 and the light receiving element 3 are arranged in a state of being rotated about the x-axis, that is, in a state of being inclined with respect to the emission light of the surface emitting laser 1. Second, the scale 2 and the light receiving element 3 are not provided with an antireflection film.
[0045]
In this embodiment, since the scale 2 and the light receiving element 3 are arranged at an angle with respect to the emission light of the surface emitting laser 1, the reflected light from the scale 2 and the light receiving element 3 does not return to the surface emitting laser 1. For this reason, the antireflection films of the scale 2 and the light receiving element 3 are omitted in this embodiment.
[0046]
In this embodiment, a stable operation of the surface emitting laser can be achieved even if the scale 2 and the light receiving element 3 have no antireflection film.
The operation principle of this embodiment, the relationship between the dimensions, and the like are exactly the same as those of the second embodiment, and a description thereof will be omitted.
[0047]
Next, a modification of the present embodiment will be described with reference to FIG. In this modification, the transmission type optical encoder of this embodiment is modified to a reflection type.
As shown in FIG. 9, the scale 2 is arranged to be inclined with respect to the emission light of the surface emitting laser 1, and the transparent substrate 7 of the scale 2 has a plurality of reflections of the same width instead of the light-shielding portion of the transmission type scale. Parts 5 'are provided at equal intervals. The light receiving element 3 is arranged vertically in the direction of reflection by the scale 2. The light receiving element 3 is the same as that of the second embodiment, that is, a light shielding film 51 in which a plurality of openings are formed, and an antireflection film 52 is formed on the surface of the light shielding film 51. The surface emitting laser 1 and the light receiving element 3 are fixed to a base.
[0048]
In this modification, the reflection light from the scale 2 does not return to the surface-emitting laser 1, and therefore, the scale 2 does not include an anti-reflection film. The element 3 is provided with an antireflection film 52. The antireflection film may be omitted if the light receiving element 3 is arranged at an angle to the optical axis of the light reflected from the scale 2 so that the light reflected by the light receiving element 3 does not return to the surface emitting laser 1.
[0049]
In the present embodiment, stable operation of the surface emitting laser can be achieved even without the antireflection film on the scale 2 (and also on the light receiving element 3 when the light receiving element 3 is tilted).
In this modification, the operation principle, the relationship between the dimensions, and the like are exactly the same as those of the second embodiment.
[0050]
(Fourth embodiment)
An optical encoder according to a fourth embodiment will be described with reference to FIG.
As shown in FIG. 10, the optical encoder of the present embodiment is different from the configuration of the third embodiment (FIG. 8) in that the scale 2 and the light receiving element 3 are moved along the x-axis from a state perpendicular to the emission light of the surface emitting laser 1. Instead of being rotated about the center and tilted, it is configured to be rotated about the z-axis and tilted. Therefore, the scale 2 moves in a direction obliquely crossing the x-axis.
[0051]
In this embodiment, as in the third embodiment, a stable operation of the surface emitting laser can be achieved even if the scale 2 and the light receiving element 3 do not have the antireflection film.
The operation principle of this embodiment, the relationship between dimensions, and the like are exactly the same as those of the third embodiment (that is, the second embodiment).
[0052]
Next, a modification of the present embodiment will be described with reference to FIG. In this modification, the transmission type optical encoder of this embodiment is modified to a reflection type.
As shown in FIG. 11, in the configuration of the modification (FIG. 9) of the third embodiment, instead of rotating the scale 2 about the x-axis from a state perpendicular to the emission light of the surface emitting laser 1 and tilting it, z It is configured to be rotated and tilted about an axis. Further, the light receiving element 3 is arranged so that the reflected light from the scale 2 is incident vertically.
[0053]
In this modified example, as in the modified example of the third embodiment, stable operation of the surface emitting laser can be achieved even without the antireflection film on the scale 2.
The operation principle of this embodiment, the relationship between dimensions, and the like are exactly the same as those of the modification of the third embodiment (that is, the second embodiment). The arrangement for omitting the anti-reflection film on the light receiving element 3 is the same as that of the modification of the third embodiment.
[0054]
(Fifth embodiment)
An optical encoder according to a fifth embodiment will be described with reference to FIG.
In the present embodiment, the light receiving element 3 is disposed at a position off the optical axis of the light emitted from the surface emitting laser 1. The light receiving element 3 has a plurality of openings formed in a light shielding film 51 covering the light receiving area 4 as in the third embodiment. A scale 2 having a diffraction grating 8 for changing the direction of incident light is arranged between the surface emitting laser 1 and the light receiving element 3 so as to be movable in the x-axis direction.
[0055]
As shown in FIG. 14, the scale 2 is manufactured by forming a plurality of diffraction gratings 8 at equal intervals on the surface of an antireflection film 6 formed on a glass substrate 7. This scale 2 has the first width ωo of the function area of the diffraction grating 8, Ps the pitch of the function area of the diffraction grating 8, and Ws the beam diameter in the scale moving direction of the light beam irradiation area on the scale surface. Each condition described in the embodiment is satisfied.
[0056]
Another scale 2 is shown in FIG. The scale 2 is manufactured by forming a diffraction grating 8 ′ on the entire surface of a glass substrate 7 and forming light shielding portions 5 having the same width on the surface of the diffraction grating 8 ′ at equal intervals. This is equivalent to a structure in which a plurality of diffraction gratings having the same width are formed at equal intervals, and performs the same function as the scale of FIG. In the scale 2, similarly to the scale 2 in FIG. 14, each condition described in the first embodiment is satisfied.
[0057]
As shown in FIG. 12, the laser light emitted from the surface emitting laser 1 is incident on the scale 2, and the light incident on the diffraction grating 8 is diffracted. The diffraction grating 8 is designed so that the diffraction intensity of the first-order diffracted light on the side opposite to the incident light is maximized. The diffracted light is oblique to the light emitted from the surface emitting laser 1, and Head for. As for the light incident on the light receiving element 3, the light passing through the opening provided in the light shielding film 51 is incident on the light receiving region 4.
[0058]
The operation principle of this embodiment is the same as that of the second embodiment except that diffracted light is emitted from the scale 2. The relationship between the dimensions shown in FIG. 12 is basically the same as that of the first embodiment. This is the same as that described above, and the description thereof is omitted.
[0059]
In this embodiment, since the reflected light from the light receiving element 3 does not return to the surface emitting laser 1, even if the light receiving element 3 does not have an antireflection film, the surface emitting laser operates stably. Since the light beam is bent by diffraction, each optical element (the surface emitting laser 1, the scale 2, and the light receiving element 3) can be arranged in parallel, so that the mounting can be performed as compared with the third and fourth embodiments. Easy and highly accurate.
[0060]
Next, a modification of the present embodiment will be described with reference to FIG. In this modification, the transmission type optical encoder of this embodiment is modified to a reflection type.
As shown in FIG. 13, the light receiving element 3 is on the same side as the surface emitting laser 1 with respect to the scale 2, and these are integrally formed on the semiconductor substrate 11. The diffraction grating 8 of the scale 2 is designed so that the diffraction intensity of the first-order diffracted light on the same side as the incident light is maximized.
[0061]
The operation principle of this modification, the relationship between the dimensions described in FIG. 13, and the like are basically the same as those described in the first embodiment, and a description thereof will not be repeated.
According to this modification, the same effect as that of the present embodiment can be obtained, and the surface emitting laser 1 and the light receiving element 3 are provided on the same substrate. I can do it.
[0062]
In the present embodiment, since the measurement is performed using the diffracted light from the scale, the light for irradiating the scale 5 may be a laser light having a coherent plane wave. Instead, a combination of an edge-emitting semiconductor laser and a collimator lens can be used.
[0063]
(Sixth embodiment)
The optical encoders of the embodiments described so far only have a function of detecting only the amount of movement of the scale, and do not have a function of determining the direction of movement. In the sixth embodiment, the optical encoder of the above-described embodiment is improved to have a function of determining the direction of movement of the scale.
[0064]
As shown in FIG. 16, the light-shielding portion of the scale 2 includes an upper light-shielding portion 5a and a lower light-shielding portion 5b with respect to a center line parallel to the moving direction (x-axis). The upper light-shielding portion 5a and the lower light-shielding portion 5b have the same periodic structure in the x-axis direction, and their phases are shifted by a quarter of the pitch Ps. The light beam irradiation area is set so as to include both the upper light-shielding portion 5a and the lower light-shielding portion 5b at the same time. The light receiving element includes an upper light receiving element 3a and a lower light receiving element 3b. The upper light receiving element 3a receives a beam transmitted through an upper portion of the scale 2, that is, a gap between the light shielding portions 5a. The element 3b receives the beam transmitted through the lower portion of the scale 2, that is, the gap between the light shielding portions 5b. Of course, the scale 2 and the light receiving elements 3a and 3b satisfy the conditions described in the first embodiment.
[0065]
With such a configuration, the beam transmitted through the upper portion of the scale 2, that is, the gap between the light-shielding portions 5a, is placed on the light-receiving surface of the light receiving element 3a, and the beam transmitted through the lower portion of the scale 2, that is, the gap between the light-shielding portions 5b. With respect to the light and dark pattern generated on the light receiving surface 3b, a light and dark pattern shifted by a quarter of the pitch Ps is generated. Therefore, when the scale 2 moves with respect to the surface emitting laser, two sine wave signals whose phases are shifted from each other by 90 degrees are output from the upper light receiving element 3a and the lower light receiving element 3b. The direction of movement of the scale 2 can be determined by comparing the two sine wave signals, specifically, by checking which sine wave signal has a phase leading by 90 degrees.
[0066]
This embodiment is applicable to all of the first to fifth embodiments. Further, in this embodiment, the shift amount between the light-shielding portion 5a and the light-shielding portion 5b is selected to be one-fourth of the pitch Ps, but this may be any number other than one-half of the pitch Ps. Can be determined.
[0067]
(Seventh embodiment)
A seventh embodiment will be described with reference to FIG. In the present embodiment, similarly to the sixth embodiment, the optical encoder of the first to fifth embodiments is improved to have a function of determining the direction of movement of the scale.
[0068]
As shown in FIG. 17, the light receiving element is composed of an upper light receiving element 3a and a lower light receiving element 3b, and a light shielding film 51a of the upper light receiving element 3a and a light shielding film 51b of the lower light receiving element 3b have an x-axis. They have the same periodic structure in the direction, and their phases are shifted by a quarter of the pitch Ppd. The light beam irradiation area is set so that light from the scale 2 is simultaneously incident on the two light receiving elements 3. Therefore, the upper light receiving element 3a receives the beam transmitted through the upper part of the scale 2, and the lower light receiving element 3b receives the beam transmitted through the lower part of the scale 2. Of course, the scale 2 and the light receiving elements 3a and 3b satisfy the conditions described in the first embodiment.
[0069]
The light-shielding film 51a of the upper light-receiving element 3a and the light-shielding film 51b of the lower light-receiving element 3b have a periodic structure, that is, the position of the opening is shifted by a quarter of the pitch Ppd in the x-axis direction. From the element 3a and the lower light receiving element 3b, two sine wave signals whose phases are shifted from each other by 90 degrees are output. The direction of movement of the scale 2 can be determined by comparing the two sine wave signals, specifically, by checking which sine wave signal has a phase leading by 90 degrees.
[0070]
This embodiment is applicable to all of the first to fifth embodiments. Further, in the present embodiment, the shift amount between the light-shielding film 51a and the light-shielding film 51b is selected to be one-fourth of the pitch Ppd, but this may be any number other than one-half of the pitch Ppd. Can determine the direction of movement.
[0071]
Although several embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments. The present invention includes the following inventions.
1. (Corresponding to the first to seventh embodiments)
(Constitution) A scale which is relatively moved with respect to a light source and whose reflectance or transmittance periodically changes, a surface-emitting semiconductor laser light source for irradiating a part of the scale, and the scale In an optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from,
The size of the light receiving area of the light receiving element or the light receiving window in the scale moving direction is ωpd, and the light and dark pattern on the light receiving surface of the light receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface emitting semiconductor laser light source to the scale. The cycle in the scale movement direction is Pb,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd <Pb and Ws> Ps
An optical encoder characterized by satisfying the following relationship:
[0072]
(Effect) Since the beam emitted from the surface emitting laser has a very small beam emission angle, it can be regarded as a substantially parallel beam and a substantially plane wave. Hereinafter, as a typical case, a case where light applied to a scale is transmitted and detected by a light receiving element will be described. When the beam diameter Ws on the scale surface satisfies the relationship of Ws> Ps, the light beam on the scale has a beam diameter larger than one pitch of the scale. Further, since there is a relationship of ωpd <Pb, the light receiving element mainly receives transmitted light for one pitch. Now, if the scale is displaced in the moving direction, the light beam passing through the scale also moves in this direction, so that the output from the light receiving element changes in a triangular waveform or a pseudo sine waveform with a period Ps with respect to the displacement. The displacement of the scale can be detected by utilizing this.
[0073]
(Effect) A triangular or pseudo sine wave signal having a period Ps can be obtained for scale displacement without requiring a lens or a fixed scale unlike the conventional optical encoder. At the same time, the diameter of the light beam on the scale surface can be made sufficiently larger than the pitch of the scale, and a high-resolution encoder can be realized because the scale pitch is not limited to the diameter of the light beam on the scale surface.
[0074]
2. (Corresponding to the second to seventh embodiments)
(Constitution) A scale which is relatively moved with respect to a light source and whose reflectance or transmittance periodically changes, a surface-emitting semiconductor laser light source for irradiating a part of the scale, and the scale In an optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from,
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving surface of the light-receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ωpd, the period of the light and dark pattern on the light receiving surface in the scale moving direction is Pb,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd <Pb and Ws> Ps
An optical encoder characterized by satisfying the following relationship:
[0075]
(Effect) Since the beam emitted from the surface emitting laser has a very small beam emission angle, it can be regarded as a substantially parallel beam and a substantially plane wave. Hereinafter, as a typical case, a case where light applied to a scale is transmitted and detected by a light receiving element will be described. When the beam diameter Ws on the scale surface satisfies the relationship of Ws> Ps, the light beam on the scale has a beam diameter larger than one pitch of the scale. Further, since there is a relationship of ωpd <Pb, one light receiving window or light receiving area of the light receiving element mainly receives transmitted light for one pitch. Now, assuming that the scale is displaced in the moving direction, a plurality of beams passing through the scale also move in this direction, so that the output from the light receiving element has a triangular waveform or a pseudo sine waveform with a period Ps with respect to the scale displacement. The displacement of the scale can be detected using the change in the scale.
[0076]
(Effect) A triangular or pseudo sine wave signal with a period Ps can be obtained for scale displacement without requiring a lens or a fixed scale unlike the conventional optical encoder. At the same time, the diameter of the light beam on the scale surface can be made sufficiently larger than the pitch of the scale, and a high-resolution encoder can be realized because the scale pitch is not limited to the diameter of the light beam on the scale surface. In this case, since there are more light receiving windows and more light transmitted (or reflected light, diffracted light) than in the first term, a stronger output signal can be obtained, and signal processing by an electronic circuit or the like can be more easily performed. It will be easier.
[0077]
3. (Corresponding to the first to seventh embodiments)
(Structure) In paragraph 1,
When the light receiving element receives the transmitted light of the scale, the dimension of the transmitting portion per scale pitch in the scale moving direction is ωo. When the light receiving element receives the reflected light of the scale, the reflection per scale pitch is performed. When the dimension of the portion in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
Ps ωo / λ> L ≧ ωo²  / Λ
An optical encoder characterized by satisfying the following relationship:
[0078]
(Operation) This is the same as the operation of the first term.
(Effect) In addition to the effect of the first term, Ps ωo / λ> L ≧ ωo²  By satisfying the configuration requirement of / λ, it is prevented that the light intensity distribution on the light receiving element surface becomes flat, so that the intensity of the output signal with respect to the scale displacement can be obtained with an appropriate value or more.
[0079]
4. (Corresponding to the first to seventh embodiments)
(Structure) In paragraph 1,
When the light receiving element receives the transmitted light of the scale, the dimension of the transmitting portion per scale pitch in the scale moving direction is ωo. When the light receiving element receives the reflected light of the scale, the reflection per scale pitch is performed. When the dimension of the portion in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
L <ωo²  / Λ
An optical encoder characterized by satisfying the following relationship:
[0080]
(Operation) This is the same as the operation of the first term.
(Effect) In addition to the effect of the first term, L <ωo²  By satisfying the configuration requirement of / λ, the light intensity distribution on the light receiving element surface is not affected by the effect of superposition or interference of a plurality of light beams, and the intensity of the output signal with respect to the scale displacement can be obtained very strongly. Further, since the output signal is hardly degraded due to the flattening of the beam intensity due to the superposition of the light beams, the pitch of the scale can be set very small.
[0081]
5. (Corresponding to the second to seventh embodiments)
(Structure) In item 2,
When the light receiving element receives the transmitted light of the scale, the dimension of the transmitting portion per scale pitch in the scale moving direction is ωo. When the light receiving element receives the reflected light of the scale, the reflection per scale pitch is performed. When the dimension of the portion in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
Ps ωo / λ> L ≧ ωo²  / Λ
An optical encoder characterized by satisfying the following relationship:
[0082]
(Operation) In addition to the operation of the third term, the light receiving device has a light receiving area or a light receiving window of a plurality of light receiving elements, and simultaneously detects light beams from each transmission or reflection area on the scale in the light receiving area or the light receiving window.
[0083]
(Effect) In addition to the effect of the third item, since the light beams from the respective transmitting or reflecting areas on the scale are simultaneously detected in the light receiving area or the light receiving window, the light receiving intensity is increased and the signal processing is facilitated.
[0084]
6. (Corresponding to the second to seventh embodiments)
(Structure) In item 2,
When the light receiving element receives the transmitted light of the scale, the dimension of the transmitting portion per scale pitch in the scale moving direction is ωo. When the light receiving element receives the reflected light of the scale, the reflection per scale pitch is performed. When the dimension of the portion in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
L <ωo²  / Λ
An optical encoder characterized by satisfying the following relationship:
[0085]
(Operation) In addition to the operation of the fourth term, the light receiving area or the light receiving window of the plurality of light receiving elements is provided, and the light beams from the respective transmitting or reflecting areas on the scale are simultaneously detected by the light receiving area or the light receiving window.
[0086]
(Effect) In addition to the effect of the fourth item, since the light beams from the respective transmissive or reflective areas on the scale are simultaneously detected in the light receiving area or the light receiving window, the light receiving intensity is increased and the signal processing is facilitated.
[0087]
7. (Corresponding to the first to seventh embodiments)
(Constitution) A scale which is relatively moved with respect to a light source and whose reflectance or transmittance periodically changes, a surface-emitting semiconductor laser light source for irradiating a part of the scale, and the scale An optical encoder having a light receiving element for receiving diffracted light from
The size of the light receiving area or the light receiving window in the scale moving direction is ωpd, and the light intensity of the light and dark pattern on the light receiving surface of the light receiving element by the diffracted light of the light beam emitted from the laser light source to the scale is １ ／ of the maximum peak. Let ωb be the width in the scale movement direction
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd ≦ ωb and Ws ≧ 2Ps
In the optical encoder satisfying the relationship of
When the light receiving element receives the transmitted / diffracted light of the scale, the dimension of the transmitting portion per scale pitch in the scale moving direction is ωo, and when the light receiving element receives the reflected / diffracted light of the scale, it is 1 of the scale. When the dimension of the reflecting portion per pitch in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
L> Psωo / λ
An optical encoder characterized by satisfying the following relationship:
[0088]
(Effect) Since the beam emitted from the surface emitting laser has a very small beam emission angle, it can be regarded as a substantially parallel beam and a substantially plane wave. Hereinafter, as a typical case, a case where light irradiated on the scale is transmitted and further diffracted and detected by the light receiving element will be described (the same applies to the case where the light is reflected and diffracted). When the beam diameter Ws on the scale surface satisfies the relationship of Ws ≧ 2Ps, the light beam has a beam diameter of two pitches or more of the scale on the scale. Accordingly, the light receiving element is irradiated with light that has passed through the scale as a plurality of beams. However, since there is a relationship of ωpd ≦ ωb, the light receiving element receives the diffracted light of a specific order. If the scale is displaced in the movement direction, the diffracted light from the scale also moves by the same displacement amount in this direction, so that the output from the light receiving element has a triangular waveform or a pseudo sine waveform with a period Ps with respect to the displacement. The displacement of the scale can be detected using the change in the scale.
[0089]
(Effect) A triangular or pseudo sine wave signal having a period Ps can be obtained for scale displacement without requiring a lens or a fixed scale unlike the conventional optical encoder. At the same time, the diameter of the light beam on the scale surface can be made sufficiently larger than the pitch of the scale, and a high-resolution encoder can be realized because the scale pitch is not limited to the diameter of the light beam on the scale surface. Further, when the sensor is used in the region I or the region II, as L increases, the width of the intensity of the output signal at the light receiving element decreases with respect to the displacement of the scale. No problem.
[0090]
8. (Corresponding to the second to seventh embodiments)
(Constitution) A scale which is relatively moved with respect to a light source and whose reflectance or transmittance periodically changes, a surface-emitting semiconductor laser light source for irradiating a part of the scale, and the scale An optical encoder having a light receiving element for receiving diffracted light from
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving surface of the light-receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ωpd, and the light intensity of the light and dark pattern on the light receiving surface of the light receiving element by the diffracted light of the light beam emitted from the laser light source to the scale is １ ／ of the maximum peak. Let ωb be the width in the scale movement direction
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd ≦ ωb and Ws ≧ 2Ps
In the optical encoder satisfying the relationship of
When the light receiving element receives the transmitted / diffracted light of the scale, the dimension of the transmitting portion per scale pitch in the scale moving direction is ωo, and when the light receiving element receives the reflected / diffracted light of the scale, it is 1 of the scale. When the dimension of the reflecting portion per pitch in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
L> Psωo / λ
An optical encoder characterized by satisfying the following relationship:
[0091]
(Function) In addition to the function of the seventh item, the light receiving element has light receiving regions or light receiving windows of a plurality of light receiving elements, and diffracted lights of different orders are simultaneously detected in the respective light receiving regions or light receiving windows. At this time, since the diffracted lights of different orders are diffracted at specific diffraction angles, the positions of the light peaks of each diffraction order move by the same displacement amount on the light receiving surface with respect to the movement of the scale.
[0092]
(Effect) In addition to the effect of the seventh item, since the diffracted lights of different orders are simultaneously detected in the respective light receiving regions or the light receiving windows, the light receiving intensity is increased and the signal processing is facilitated.
9. (Corresponding to a modification of the first embodiment)
(Constitution) A scale which is relatively moved with respect to a light source and whose light reflectance or transmittance is periodically changed, and a laser comprising a collimator lens and a semiconductor laser for irradiating a part of the scale. An optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from the light source and the scale,
The size of the light receiving area of the light receiving element or the light receiving window in the scale moving direction is ωpd, and the light intensity of the light and dark pattern on the light receiving surface of the light receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the semiconductor laser light source to the scale Is ωb, the width in the scale movement direction at which becomes the half of the maximum peak,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd ≦ ωb and Ws ≧ 2Ps
In the optical encoder satisfying the relationship of
When the light receiving element receives the transmitted / diffracted light from the scale, the dimension in the scale moving direction of the transmission portion per pitch of the scale is ωo. When the dimension of the reflecting portion per scale in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
L> Psωo / λ
An optical encoder characterized by satisfying the following relationship:
[0093]
(Operation) Instead of the surface emitting laser, an edge emitting type semiconductor laser is used as the light source, and the spread of the emitted beam is controlled by a collimating lens to form a parallel beam. Other than the above, the operation is the same as that of the seventh term.
[0094]
(Effects) In addition to the effects described in the above item 7, it is possible to use an ordinary semiconductor laser which is technically easier to manufacture and easily available than a surface emitting laser.
10. (Corresponding to the case where the second embodiment is applied to a modification of the first embodiment)
(Constitution) A scale which is relatively moved with respect to a light source and whose light reflectance or transmittance is periodically changed, and a laser comprising a collimator lens and a semiconductor laser for irradiating a part of the scale. An optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from the light source and the scale,
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving surface of the light-receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ωpd, and the light intensity of the light and dark pattern on the light receiving surface of the light receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the semiconductor laser light source to the scale is maximum. Let ωb be the width in the scale movement direction that is の of the peak,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd ≦ ωb and Ws ≧ 2Ps
In the optical encoder satisfying the relationship of
When the light receiving element receives the transmitted / diffracted light from the scale, the dimension in the scale moving direction of the transmission portion per pitch of the scale is ωo. When the dimension of the reflecting portion per scale in the scale moving direction is ωo, the distance between the surface on which the scale is formed and the light receiving surface or light shielding surface of the light receiving element is L, and the wavelength of the laser light is λ,
L> Psωo / λ
An optical encoder characterized by satisfying the following relationship:
[0095]
(Function) In addition to the function of the ninth item, in addition to the light receiving area or the light receiving window of the plurality of light receiving elements, diffracted lights of different orders are simultaneously detected in the respective light receiving areas or the light receiving windows.
(Effect) In addition to the effect of the ninth item, since the diffracted lights of different orders are simultaneously detected in the respective light receiving regions or the light receiving windows, the light receiving intensity is increased and the signal processing is facilitated.
[0096]
11. (Corresponding to the third embodiment)
(Configuration) In the first to tenth aspects,
An optical encoder characterized in that a scale is rotated about a movement direction of the scale as an axis, and a transmission or reflection surface of the scale is arranged not perpendicular to the laser beam.
[0097]
(Function) By tilting the scale, the laser light reflected from the scale to the surface emitting laser and returned is suppressed, and the intensity change of the laser light is suppressed. Other than the above, the operation is the same as that of each of the first to tenth items.
[0098]
(Effect) When there is a laser beam reflected back from the scale to the surface emitting laser, the phase of the returning light changes depending on the distance between the scale and the surface emitting laser, which interacts with the laser, and Causes a change in intensity. In addition, when the scale moves, the ratio of the feedback light from the high and low reflectance portions of the scale slightly changes, so that the intensity of the laser light also changes. By tilting the scale, the laser light reflected from the scale to the surface emitting laser and returned is suppressed, and the intensity change of the laser light is suppressed, and the sensor signal is stabilized.
[0099]
12. (Corresponding to the fourth embodiment)
(Configuration) In the first to tenth aspects,
An optical encoder characterized in that a scale is arranged so that a perpendicular to a moving direction of the scale and a main axis of a laser beam are inclined with respect to each other.
[0100]
(Function) By tilting the scale, the laser light reflected from the scale to the surface emitting laser and returned is suppressed, and the intensity change of the laser light is suppressed. Other than the above, the operation is the same as that of each of the first to tenth items.
[0101]
(Effect) In the case of the eleventh paragraph, the configuration is compact when the scale is slid with respect to a plane perpendicular to the main axis of the laser beam. However, in this configuration, the scale is formed by a plane inclined with respect to the main axis of the laser beam. , The structure becomes compact.
[0102]
13. (Corresponding to the fifth embodiment)
(Structure) A scale which moves relatively to a light source and alternately forms a region in which a diffraction grating functions and a region in which a diffraction grating does not function, a surface emitting semiconductor laser light source which irradiates a part of the scale, and the scale In an optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light,
The size of the light receiving area of the light receiving element or the light receiving window in the scale moving direction is ωpd, and the light and dark pattern on the light receiving surface of the light receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface emitting semiconductor laser light source to the scale. The cycle in the scale movement direction is Pb,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd <Pb and Ws> Ps
An optical encoder characterized by satisfying the following relationship:
[0103]
(Operation) All or part of the light emitted from the laser to the scale is diffracted and enters the light receiving element. Otherwise, the operation is the same as that of the first or second term.
(Effect) In addition to the effects of the first and second items, since the direction of the diffracted light incident on the light receiving element is different from the direction of the mere reflected light or transmitted light from the scale, the reflected light from the light receiving surface of the light receiving element is a semiconductor. Does not return to laser. Therefore, even when the light receiving surface of the light receiving element is made parallel to the surface of the scale, it is possible to suppress instability of the laser output due to the returning light without taking anti-reflection measures such as an anti-reflection film on the light receiving surface.
[0104]
14． (Corresponding to a modification of the fifth embodiment)
(Construction) A scale which is relatively moved with respect to a light source and in which a region in which a diffraction grating functions and a region in which a diffraction grating does not function is formed alternately, and a light source comprising a collimator lens for irradiating a part of the scale and a semiconductor laser. In an optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale,
The size of the light receiving area of the light receiving element or the light receiving window in the scale moving direction is ωpd, and the scale movement of the light and dark pattern on the light receiving surface of the light receiving element due to reflected light, transmitted light, or diffracted light of the light beam emitted from the semiconductor laser light source to the scale. The period in the direction is Pb,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd <Pb and Ws> Ps
An optical encoder characterized by satisfying the following relationship:
[0105]
(Operation) By combining a collimator lens with a semiconductor laser, a beam with high parallelism can be emitted as in the case of a surface emitting semiconductor laser. Others are the same as the operation of the thirteenth item.
[0106]
(Effects) In addition to the effects described in the above item 13, it is easier to obtain a semiconductor laser as a light source than a surface emitting semiconductor laser.
15. (Corresponding to the sixth embodiment)
(Structure) A scale which is relatively moved with respect to a light source and is patterned so that the reflectance or transmittance of light periodically changes, a surface emitting semiconductor laser light source which irradiates a part of the scale, and An optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale,
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving surface of the light-receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ωpd, the period of the light and dark pattern on the light receiving surface in the scale moving direction is Pb,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd <Pb and Ws> Ps
In the optical encoder satisfying the relationship of
The patterned scale pattern is formed in two sets with a phase shift other than 周期 cycle in the beam irradiation area, and reflected or transmitted from each of these sets, and separated into diffracted light. An optical encoder with a light-receiving element that can be detected.
[0107]
(Function) Light emitted from a surface emitting semiconductor laser is simultaneously irradiated on patterns on a scale formed with different phases from each other, and reflected, transmitted, or diffracted light is separated from each pattern having a phase difference on the scale. Incident on the respective light receiving elements. Therefore, when the scale moves, the outputs from the respective light receiving elements have similar shapes but are output with a constant phase difference.
[0108]
(Effect) Since signal waveforms having a phase difference are output from the light receiving elements separated from each other, the direction of movement of the scale can be determined by examining the relationship between these phase delays.
[0109]
16. (Corresponding to the seventh embodiment)
(Structure) A scale which is relatively moved with respect to a light source and is patterned so that the reflectance or transmittance of light periodically changes, a surface emitting semiconductor laser light source which irradiates a part of the scale, and An optical encoder having a light receiving element for receiving reflected light, transmitted light or diffracted light from the scale,
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving surface of the light-receiving element due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ωpd, the period of the light and dark pattern on the light receiving surface in the scale moving direction is Pb,
Assuming that the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale is Ps, and the beam diameter in the scale moving direction at which the light beam intensity becomes の of the peak value on the scale surface is Ws.
ωpd <Pb and Ws> Ps
In the optical encoder satisfying the relationship of
Two sets of the plurality of light receiving areas or light receiving window patterns are formed in the beam light receiving area with a phase shift other than 1/2 cycle, and the light receiving amount of each of these sets can be detected separately. Optical encoder with light receiving element.
[0110]
(Function) Light emitted from a surface emitting semiconductor laser is simultaneously irradiated on patterns on a scale formed with phases different from each other, and light reflected, transmitted, or diffracted from each pattern having a phase difference on the scale is received. A light-dark pattern is shown on the light-receiving surface of the element. The light-dark pattern is incident on a light-receiving window or light-receiving region that is phase-shifted from each other, and the light-receiving window or light-receiving region that is phase-shifted is separated. Therefore, when the scale moves, the outputs from the respective light receiving elements have similar shapes but are output with a constant phase difference.
[0111]
(Effect) Two or more phase difference signals capable of judging the direction of movement of the scale similar to those in the fifteenth term can be obtained by the light receiving region or the light receiving window pattern formed in the light receiving window. In the case of the fifteenth term, it is necessary to arrange this phase shift pattern on the scale. In this case, it is necessary to adjust the phase shift pattern so as to be arranged within the irradiation area of the beam from the surface emitting semiconductor laser. Further, the light receiving elements need to be spatially separated so as to match the beam area from each pattern, which is difficult to assemble. On the other hand, in this section, there is no such restriction on the arrangement of the surface emitting semiconductor laser and the scale, and it is simply arranged so that reflection or transmission from the scale or diffracted light is applied to the phase shift pattern of the light receiving element. Well, the assembly of the element becomes easy.
[0112]
【The invention's effect】
According to the optical encoder of the present invention, the period P with respect to the scale displacement does not require a lens or a fixed scale unlike the conventional optical encoder._s, Or a pseudo sinusoidal signal can be obtained. At the same time, the diameter of the light beam on the scale surface can be made sufficiently larger than the pitch of the scale, and a high-resolution encoder can be realized because the scale pitch is not limited to the diameter of the light beam on the scale surface.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an optical encoder according to a first embodiment of the present invention.
FIG. 2 is a front view of the scale shown in FIG. 1;
FIG. 3 is a graph showing characteristics of output of a light receiving element with respect to displacement of a scale in the optical encoder of FIG. 1;
FIG. 4 is a diagram showing how light passing through one transmission window spreads.
FIG. 5 is a diagram showing how light passing through a plurality of transmission windows overlaps;
FIG. 6 is a diagram showing light and dark patterns generated on surfaces at various distances L when the distance from the transmission window is L in FIG. 5;
FIG. 7 is a diagram illustrating a configuration of an optical encoder according to a second embodiment of the present invention.
FIG. 8 is a diagram showing a configuration of an optical encoder according to a third embodiment of the present invention.
FIG. 9 is a diagram showing a configuration of a reflection type optical encoder which is a modification of the third embodiment of the present invention.
FIG. 10 is a diagram illustrating a configuration of an optical encoder according to a fourth embodiment of the present invention.
FIG. 11 is a diagram showing a configuration of a reflection type optical encoder which is a modification of the fourth embodiment of the present invention.
FIG. 12 is a diagram showing a configuration of an optical encoder according to a fifth embodiment of the present invention.
FIG. 13 is a diagram showing a configuration of a reflection type optical encoder which is a modification of the fifth embodiment of the present invention.
FIG. 14 is a view for explaining a structure of a scale used in a fifth embodiment.
FIG. 15 is a view for explaining the structure of another scale used in the fifth embodiment.
FIG. 16 is a view of the optical encoder of the sixth embodiment in which the function of determining the moving direction of the scale is added by improving the first to fifth embodiments and the scale and the light receiving element are viewed from the light source side. It is.
FIG. 17 is a view of the optical encoder of the seventh embodiment in which the function of determining the moving direction of the scale is added by improving the first to fifth embodiments and the scale and the light receiving element are viewed from the light source side. It is.
FIG. 18 is a diagram for explaining a conventional optical encoder.
FIG. 19 is a diagram illustrating an optical encoder proposed by the present inventors.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Surface emitting laser, 2 ... Scale, 3 ... Light receiving element, 5 ... Light shielding part, 51 ... Light shielding film.

Claims (4)

A scale that moves relative to the light source and is formed such that the reflectance or transmittance of light changes periodically; a surface-emitting semiconductor laser light source that irradiates a part of the scale; and a reflection from the scale. In an optical encoder having a light receiving element for receiving light, transmitted light or diffracted light,
The size of the light receiving area of the light receiving element or the light receiving window in the scale movement direction is ω _pd , and the light / dark pattern on the light receiving surface of the light receiving element due to reflected light, transmitted light or diffracted light of the light beam emitted from the surface emitting semiconductor laser light source to the scale scale moving direction of the cycle P _b, scale movement direction in which the light beam intensity is half of the peak value of the pitch of the scale movement direction of the reflectance or transmittance is modulated P _s, on the scale surface of the scale of Let W _{s be} the beam diameter of
ω _pd <P _b and W _s> P _s
When the light receiving element receives the transmitted light of the scale, the dimension of the transmission portion per scale pitch in the scale moving direction is ω _o , and when the light receiving element receives the reflected light of the scale, the scale 1 scale movement direction of the dimension of the reflecting portion per pitch and omega _o, when the distance between the light receiving surface or the light shielding surface of the formed surface and the light receiving element scales L, and the wavelength of the laser beam was λ of,
_{P s ω o / λ> L} ≧ ω o 2 / λ
An optical encoder characterized by satisfying the following relationship: A scale that moves relative to the light source and is formed such that the reflectance or transmittance of light changes periodically; a surface-emitting semiconductor laser light source that irradiates a part of the scale; and a reflection from the scale. In an optical encoder having a light receiving element for receiving light, transmitted light or diffracted light,
The size of the light receiving area of the light receiving element or the light receiving window in the scale movement direction is ω _pd , and the light / dark pattern on the light receiving surface of the light receiving element due to reflected light, transmitted light or diffracted light of the light beam emitted from the surface emitting semiconductor laser light source to the scale scale moving direction of the cycle P _b, scale movement direction in which the light beam intensity is half of the peak value of the pitch of the scale movement direction of the reflectance or transmittance is modulated P _s, on the scale surface of the scale of Let W _{s be} the beam diameter of
ω _pd <P _b and W _s> P _s
When the light receiving element receives the transmitted light of the scale, the dimension of the transmission portion per scale pitch in the scale moving direction is ω _o , and when the light receiving element receives the reflected light of the scale, the scale 1 scale movement direction of the dimension of the reflecting portion per pitch and omega _o, when the distance between the light receiving surface or the light shielding surface of the formed surface and the light receiving element scales L, and the wavelength of the laser beam was λ of,
L <ω _o ² / λ
An optical encoder characterized by satisfying the following relationship: A scale that moves relative to the light source and is formed such that the reflectance or transmittance of light changes periodically; a surface-emitting semiconductor laser light source that irradiates a part of the scale; and a reflection from the scale. In an optical encoder having a light receiving element for receiving light, transmitted light or diffracted light,
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving element's light-receiving surface due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ω _pd , the period of the light and dark pattern on the light receiving surface in the scale moving direction is P _b , the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale. Is P _s , and W _s is the beam diameter in the scale movement direction at which the light beam intensity on the scale surface becomes の of the peak value.
ω _pd <P _b and W _s> P _s
When the light receiving element receives the transmitted light of the scale, the dimension of the transmission portion per scale pitch in the scale moving direction is ω _o , and when the light receiving element receives the reflected light of the scale, the scale 1 scale movement direction of the dimension of the reflecting portion per pitch and omega _o, when the distance between the light receiving surface or the light shielding surface of the formed surface and the light receiving element scales L, and the wavelength of the laser beam was λ of,
_{P s ω o / λ> L} ≧ ω o 2 / λ
An optical encoder characterized by satisfying the following relationship: A scale that moves relative to the light source and is formed such that the reflectance or transmittance of light changes periodically; a surface-emitting semiconductor laser light source that irradiates a part of the scale; and a reflection from the scale. In an optical encoder having a light receiving element for receiving light, transmitted light or diffracted light,
The light-receiving area or light-receiving window of the light-receiving element has the same spacing as the light-dark pattern on the light-receiving element's light-receiving surface due to the reflected light, transmitted light, or diffracted light of the light beam emitted from the surface-emitting semiconductor laser light source to the scale and the scale movement direction Formed by
The size of the light receiving area or the light receiving window in the scale moving direction is ω _pd , the period of the light and dark pattern on the light receiving surface in the scale moving direction is P _b , the pitch in the scale moving direction obtained by modulating the reflectance or transmittance of the scale. Is P _s , and W _s is the beam diameter in the scale movement direction at which the light beam intensity on the scale surface becomes の of the peak value.
ω _pd <P _b and W _s> P _s
When the light receiving element receives the transmitted light of the scale, the dimension of the transmission portion per scale pitch in the scale moving direction is ω _o , and when the light receiving element receives the reflected light of the scale, the scale 1 scale movement direction of the dimension of the reflecting portion per pitch and omega _o, when the distance between the light receiving surface or the light shielding surface of the formed surface and the light receiving element scales L, and the wavelength of the laser beam was λ of,
L <ω _o ² / λ
An optical encoder characterized by satisfying the following relationship:

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