JP3961884B2

JP3961884B2 - Multi-axis photoelectric sensor

Info

Publication number: JP3961884B2
Application number: JP2002160072A
Authority: JP
Inventors: 慎司今井; 徹和氣; 宏昇永井
Original assignee: サンクス株式会社
Priority date: 2002-05-31
Filing date: 2002-05-31
Publication date: 2007-08-22
Anticipated expiration: 2022-05-31
Also published as: JP2004007233A

Description

【０００１】
【発明の属する技術分野】
本発明は、安定入光判定機能を備えた多光軸センサに関する。
【０００２】
【従来の技術】
従来、この種の多光軸光電センサとして、例えば上下方向に一列に配置された複数の投光素子のそれぞれに対向して配置された複数の受光素子からの受光信号を順次１つのコンパレータを介して検出部に伝送することにより物体検出判定動作を行うようにしたものである。
【０００３】
ところで、このような多光軸光電センサでは、投受光素子の素子劣化、それらの前面に配された光学レンズの汚れや光軸のずれ等によって、入光状態における受光素子での受光レベルが低下してしまう不安定入光状態となり、安定した物体検出判定が行えなくなることがある。そこで、例えば各受光素子からの受光信号を、別途設けたコンパレータにて前記物体検出判定用の閾値より高く、正常時の入光状態における受光レベルよりやや低いレベルを安定入光判定用の閾値として比較することで、安定入光か不安定入光かの判定を行う安定入光判定機能を備えたものがある。
【０００４】
【発明が解決しようとする課題】
ところが、この種の多光軸光電センサにおいては、前記複数の受光素子から１つのコンパレータまでの距離は当然それぞれ異なり、その間に配される信号線の長さもそれぞれ異なる。更には、近年、光軸数は益々増加傾向にあり、しかも小型化の要請にも対応すべく前記信号線も極細化の傾向にあるため、受光信号は、その細くて長い信号線を伝送することによりノイズの影響を受け易い。従って、コンパレータに入力される各受光素子からの受光信号レベルが不安定となって、各光軸について安定した物体検出判定及び安定入光判定が行えなくなるといった問題があった。
なお、このような問題は、物体検出判定に比べて、正常時のおける受光レベルと閾値との余裕度が小さい安定入光判定において特に誤判定となる可能性が高い。
【０００５】
本発明は、上記事情に鑑みてなされたもので、その目的は、ノイズ等による影響を抑制し、安定した物体検出判定及び安定入光判定が可能な多光軸光電センサを提供するところにある。
【０００６】
【課題を解決するための手段】
上記目的を達成するため、請求項１の発明に係る多光軸光電センサは、複数の投光素子と、それら複数の投光素子のそれぞれと対をなす複数の受光素子と、複数の受光素子のそれぞれに対応して設けられ、各受光素子からの受光信号レベルを予め設定された基準レベルと比較し、その比較結果に応じた出力信号を出力する複数の比較手段と、複数の投光素子を所定の発光タイミングで順次投光させると共に、各受光素子からの受光信号と基準レベルとの比較結果に応じた出力信号を、それぞれに対応する各投光素子の発光タイミングに同期して順次取り込む投受光動作を行う投受光制御手段と、投受光制御手段に取り込まれた出力信号に基づいて判定動作を行う判定手段と物体検出判定モードと安定入光判定モードとの間で切替可能なモード切替手段と、モード切替手段による切替動作に基づいて投受光動作における投光素子の投光量を変える投光量変更手段とを備えて、モード切替手段が物体検出判定モードに設定されているとき、投光量変更手段は、各投光素子を物体検出レベルで投光させるよう動作し、判定手段は出力信号に基づき物体検出判定動作を行い、安定入光判定モードに設定されているときは、投光量変更手段は、各投光素子を物体検出判定レベルより低いレベルの安定入力判定レベルで投光させるよう動作し、判定手段は、出力信号に基づき安定入光判定動作を行うところに特徴を有する。
【０００７】
請求項２の発明は、請求項１に記載の多光軸光電センサにおいて、判定手段は、安定入光判定モードに設定されているとき、各受光素子からの受光信号レベルが基準レベル以上であるとの比較結果に基づく出力信号を、全ての比較手段から受けたことを条件に、安定入光状態であるとの判断に応じた安定入光判定動作を行うところに特徴を有する。
【０００８】
請求項３の発明は、請求項１又は請求項２に記載の多光軸光電センサにおいて、投受光制御手段により全ての投受光素子について一巡するまで投受光動作を行うスキャン動作を繰り返すよう構成され、モード切替手段は、常には物体検出判定モードに設定し、スキャン動作が所定回数繰り返されたことを条件に、次の１回分のスキャン動作の間、安定入光判定モードに切り換えるところに特徴を有する。
【０００９】
【発明の作用及び効果】
＜請求項１の発明＞
請求項１の構成によれば、比較手段を各受光素子に対応して複数設けて、各比較手段での比較結果に応じた出力信号を、各投光素子の投光タイミングに同期して順次受光制御手段に取り込む構成とした。ここで、受光素子から出力される受光信号は受光素子での受光量に応じたアナログ的信号であるのに対して、比較手段から出力される出力信号は大小比較に基づくデジタル的信号なので、出力信号は、受光信号に比べて耐ノイズ性が高い。従って、例えば、各比較手段を対応する受光素子に近接配置し、前記出力信号を受光制御手段側に送るよう構成することが可能となる。このように構成すれば、たとえ光軸が極めて多く、しかも小型化により各受光素子及び受光制御手段間に配される伝送用信号線が極めて細いものであってもノイズによる影響を抑制でき、もって安定した物体検出判定及び安定入光判定を行うことができる。
【００１０】
更に、物体検出判定時と安定入光判定時とで投光素子の投光動作における投光量を変える構成としたので、各比較手段において１つの基準レベルに基づき前記物体検出判定及び安定入光判定を行うことができる。従って、比較手段について、例えば物体検出用及び安定入光判定用の２つのコンパレータを設けることなく１つのコンパレータで簡単な構成にすることができ、上記構成に伴うセンサの大型化を最小限に抑制することができる。
【００１１】
＜請求項２の発明＞
複数の光軸のうち１つでも不安定入光状態となっていると、物体物体検出判定に支障が生じる。そこで、請求項２の構成では、判定手段は、全ての光軸について受光信号レベルが前記基準レベル以上であるとの判断結果に基づく出力信号が出力された場合にのみ安定入光であるとの判断に基づく判定動作を行う構成とした。逆に言えば、各光軸のうち１つでも受光信号レベルが基準レベルより低いとの比較結果に基づく出力信号が出力された場合には、不安定入光であると判断するのである。
【００１２】
このような構成であれば、各光軸毎に表示手段を設けることなく、安定入光か不安定入光かを１つの表示手段で表示させることができ、もってセンサの大型化を回避することができる。
【００１３】
＜請求項３の発明＞
１回のスキャン動作内で物体検出判定動作及び安定入光判定動作を混在させて投光素子の投光量を随時変更する構成も考えられるが、複雑な制御が必要となるばかりでなく、特に高速性を要するセンサにおいては物体検出精度を低下させるおそれもある。そこで、請求項３の構成によれば、繰り返されるスキャン動作において、常には物体検出判定を行い、複数回に１回の割合で投光素子の投光量を下げて安定入光判定を行うよう構成した。即ち、スキャン動作単位毎に、モード切替を切り換えて投光量を変更させる構成として、１スキャン内に物体検出判定動作及び安定入光判定動作が混在しないようにしたので、複雑な制御を要することなく安定した物体検出判定及び安定入光判定を行うことが可能になる。
【００１４】
【発明の実施の形態】
本発明の一実施形態について図１ないし図４を参照しつつ説明する。
本発明に係る多光軸光電センサは、Ｎ個の投光素子Ｔ（例えばＬＥＤ）が一列に配列された投光器１０と、それらのＮ個の投光素子Ｔのそれぞれと対をなすＮ個の受光素子Ｊ（例えばフォトダイオード）が配列された受光器３０とを所定の検出エリアを挟んで対向配置された構成をなす。
【００１５】
図１には、電気的構成図が示してある。なお、同図では、Ｎ個の投光素子Ｔ及び受光素子Ｊのうち後述する駆動電流切替手段１９に一番近い投光素子Ｔ1 及び受光素子Ｊ1 、次に近い２番目の投光素子Ｔ2 及び受光素子Ｊ2 、Ｎ−１番目の投光素子ＴN-1 及び受光素子ＪN-1 と、Ｎ番目の投光素子ＴN 及び受光素子ＪN のみ示してあり、３〜Ｎ−２番目の投光素子Ｔ及び受光素子Ｊとそれらに対応する構成（スイッチング回路１１、駆動回路１３及びＡＮＤ回路１４）は省略してある。また、以下の説明で使用される文字Ｋは、上記の投光素子及び受光素子の任意の順位（１〜Ｎ）を示したものであり、かつ後述するシフトレジスタ１７，３５のカウント数にも対応付けられている。
【００１６】
まず、投光器１０において、各投光素子Ｔは、アノード側が各光軸毎に設けられた図示しない定電圧電源回路に接続され、カソード側がスイッチング回路１１を介して共通接続線１６に接続されている。なお、各投光素子Ｔの定電圧電源回路の入力側は共通接続線１６との間に、投光器１０の配列方向の一端側（本実施形態では投光素子Ｔ1 側）に位置する図示しない直流電源が接続されている。また、共通接続線１６には、抵抗２０とスイッチ２１とを並列接続してなる駆動電流切替手段１９（本発明の投光量変更手段に相当）が設けられている。各スイッチング回路１１を構成するＮＰＮトランジスタのベースには駆動回路１３が接続されており、この駆動回路１３からの信号に基づいてスイッチング回路１１がオン動作することで投光素子Ｔに駆動電流が流れて点灯することになる。
【００１７】
これらの駆動回路１３は、ＡＮＤ回路１４とシフトレジスタ１７とを備えてなる選択回路を介して投光側ＣＰＵ１８に接続され、投光側ＣＰＵ１８からのパルス信号に同期して投光素子Ｔの配列方向（例えば１番目の投光素子Ｔ1 からＮ番目の投光素子ＴN に向う方向）に沿って１つずつ順番に駆動信号が与えられて順次に駆動する。より詳しくは、シフトレジスタ１７は、入力端子側が投光側ＣＰＵ１８に接続されると共に、複数の出力端子側がＮ個のＡＮＤ回路１４の一方の入力端子にそれぞれ接続されている。そして、これらＮ個のＡＮＤ回路１４の他方の入力端子が投光側ＣＰＵ１８に接続されると共に、出力端子が各駆動回路１３に接続されている。
【００１８】
投光側ＣＰＵ１８は、後述する受光側ＣＰＵからの同期信号Ｄ１或いは同期信号Ｄ２に基づいてシフトレジスタ１７にスタートパルスＳを与える。それと共に、前記駆動電流変更手段のスイッチ２１に信号を与えてオンオフ動作を行わせる。これにより、スイッチ２１がオンしている場合とオフしている場合とでは前記抵抗２０分だけ各投光素子Ｔに流れる駆動電流を低下させることができる。本実施形態ではこのことを利用して、投光側ＣＰＵ１８は、受光側ＣＰＵ３４から与えられるパルス幅の異なる前記同期信号Ｄ１と同期信号Ｄ２とを識別し、同期信号Ｄ１を受けたときには、スイッチ２１をオン動作させて各投光素子Ｔを物体検出レベルで投光させる一方で、同期信号Ｄ２を受けたときには、スイッチ２１をオフ動作させて各投光素子Ｔを前記物体検出レベルより低い安定入光判定レベルで投光させるよう動作する（図２参照）。
【００１９】
次に、受光器３０において、各受光素子Ｊは、受光回路３１、本発明の比較手段に相当するコンパレータ３３とスイッチ素子３２とを介して受光側ＣＰＵ３４に共通接続されている。受光素子Ｊから出力された受光信号は、受光回路にて積分処理され、コンパレータ３３にて所定の基準レベル（図２参照）と比較される。そしてこの比較結果に応じた出力信号が比較手段から出力されてスイッチ素子３２の入力に与えられる。この出力信号は、例えば、受光素子Ｊからの受光信号レベルが前記基準レベルより高いときはハイレベルとなり、低いときにはローレベルとなる、いわゆるデジタル的な信号である。
【００２０】
各スイッチ素子３２の制御端子は、受光側ＣＰＵ３４からのスタートパルスＳに基づいて動作するシフトレジスタ３５の出力側に接続されている。受光側ＣＰＵ３４は、上記の投光側ＣＰＵ１８に同期信号Ｄ１，Ｄ２を与えると共に、シフトレジスタ３５にスタートパルスＳを与えて、シフトレジスタ３５の起動により投光器１０側と同様の所定時間間隔で、かつ同様の配列方向に沿って順にスイッチ素子３２に駆動信号を与えて順次に各受光素子Ｊに対応するコンパレータ３３からの出力信号を有効化させる。このような構成により同一光軸同士の投光素子Ｔ及び受光素子Ｊが順に投受光動作を行うことになり、もって各光軸間の相互干渉を防止することができる。
【００２１】
次に、本発明のモード切替手段、投受光制御手段及び判定手段として機能する投光側ＣＰＵ１８及び受光側ＣＰＵ３４の制御内容について図３及び図４に示すフローチャートを参照しつつ説明する。
【００２２】
＜受光側ＣＰＵ３４の制御内容＞
多光軸光電センサに電源を投入すると、ステップＳ１にてスキャン回数を初期値「１」にセットし、ステップＳ２においてスキャン回数が「５」回かどうかのチェックが行われる。５回でない場合には（ステップＳ２で「ＮＯ」）、同期信号Ｄ１を出力すると共に、シフトレジスタ３５のカウント数Ｋを初期値「１」にセットする（ステップＳ３，Ｓ４）。これにより受光素子Ｊ1 に対応するコンパレータ３３からの出力信号が有効化されることになる。
【００２３】
そして、所定の受光タイミングでそのときの出力信号レベルを読込んで（ステップＳ５，Ｓ６）、ステップＳ７にてその出力信号レベルがハイレベルかどうかを判定する。ここで、ローレベルであれば物体検出信号を出力回路３６に出力し（ステップＳ８）、ハイレベルであるときにはそのままステップ９にてシフトレジスタ３５のカウント数Ｋと、光軸数Ｎとの比較動作を行う。以上のステップＳ５〜Ｓ８までの動作を各光軸毎に繰り返し（ステップＳ１０）、全光軸について一巡したときに（ステップＳ９にて「ＹＥＳ」）、スキャン回数Ｍを１加算して（ステップＳ１１）、再びステップＳ２でのスキャン回数のチェックが行われる。
【００２４】
一方、スキャン回数が５回になったときには（ステップＳ２で「ＹＥＳ」）、前記同期信号Ｄ１とパルス幅の異なる同期信号Ｄ２を投光側ＣＰＵ１８に出力すると共に、やはりシフトレジスタ３５のカウント数Ｋを初期値「１」にセットして受光素子Ｊ1 に対応するコンパレータ３３からの出力信号が有効化される（ステップＳ１２，Ｓ１３）。そして、所定の受光タイミングでそのときの出力信号レベルを読込んで（ステップＳ１４，Ｓ１５）、ステップＳ１６にてその出力信号レベルがハイレベルかどうかを判定する。
【００２５】
ここで、ローレベルであれば入光光軸数Ｘに１加算して（ステップＳ１７）、ハイレベルであるときにはそのままステップＳ１８にてシフトレジスタ３５のカウント数Ｋと、光軸数Ｎとの比較動作を行う。以上のステップＳ１４〜Ｓ１７までの動作を各光軸毎に繰り返し（ステップＳ１９）、全光軸について一巡したときに（ステップＳ１８にて「ＹＥＳ」）、入光光軸数Ｘが全光軸数Ｎと一致するかどうかをステップＳ２０にて判定する。ここで、一致するときには（ステップＳ２０で「ＹＥＳ」）出力回路３６に安定入光信号を出力し（ステップＳ２１）、一致しないときには（ステップＳ２０で「ＮＯ」）出力回路３６に不安定入光信号を出力する。そして、例えば、これらの出力信号に応じて表示態様で図示しない表示灯が点灯動作を行う（請求項２の発明に相当）。
【００２６】
＜投光側ＣＰＵ１８の制御内容＞
投光側ＣＰＵ１８は、ステップＳ３１にて受光側ＣＰＵ３４からの同期信号Ｄ１，Ｄ２を待つ待機状態となり、同期信号Ｄ１を受けたときには（ステップＳ３１で「ＹＥＳ」、ステップＳ３２で駆動電流変更手段のスイッチ２１をオン動作させて、ステップＳ３３でシフトレジスタ１７のカウント数Ｋを初期値「１」にセットする。次いで、所定の投光タイミング（上記受光タイミングに同期したタイミング）で投光信号Ｅを出力しシフトレジスタ１７のカウント数Ｋを１加算する（ステップＳ３４〜Ｓ３５）。この動作を最後の光軸Ｎまで順次行って１回のスキャン動作が終了する（ステップＳ３７で「ＹＥＳ」）。従って、このスキャン動作では各投光素子Ｔは物体検出レベルで順次投光することになる。
【００２７】
一方、同期信号Ｄ２を受けたときには（ステップＳ３８で「ＹＥＳ」）、ステップＳ３９で駆動電流変更手段のスイッチ２１をオフ動作させるところが、同期信号Ｄ１を受けたときと異なる。従って、このスキャン動作では各投光素子Ｔは物体検出レベルより低い安定入光判定レベルで順次投光することになる。
【００２８】
以上のような投光側ＣＰＵ１８及び受光側ＣＰＵ３４の制御により、前記投受光タイミングで各光軸毎に順次投受光が行われるスキャン動作が繰り返される。また、受光側ＣＰＵ３４は、常には投光側ＣＰＵ１８に同期信号Ｄ１を与え、前記スキャン動作の５回に１回の割合で同期信号Ｄ２を与えるよう動作すると共に、コンパレータ３３からの出力信号に対して物体検出判定から安定入光判定に切り換えて判定動作を行う。これにより投光側ＣＰＵ１８は、スキャン動作の５回に１回の割合で投光素子Ｔの投光レベルを、物体検出判定レベルから安定入光判定レベルに切り換えて投光動作をさせることになる。即ち、本実施形態の多光軸光電センサは、４回連続して物体検出用のスキャン動作を行った後に、１回安定入光用のスキャン動作を行う一連の動作を繰り返すことになる（請求項３の構成に相当）。
【００２９】
そして、上記物体検出判定時には、図２に示すように、各投光素子Ｔが物体検出レベルで投光し、受光素子Ｊからの受光信号は、検出エリアに物体がないときは入光状態となって基準レベルを大きく上回る高いレベルを示し、コンパレータ３３からハイレベルの出力信号が出力される。これに対して、物体があるときは遮光状態となって基準レベルを大きく下回る低いレベルを示し、ローレベルの出力信号が出力されることになる。従って、この出力信号レベルに基づいて物体検出を行うことが可能となる。
【００３０】
一方、安定入光判定時には、図２に示すように、各投光素子Ｔが物体検出レベルより低い安定入光判定レベルで投光する。これに伴って受光素子Ｊでの受光量も前記物体検出判定時に比べて低下する。そして、物体がないときにおける受光素子Ｊからの受光信号は、正常時は基準レベルをやや上回るレベルとなるのに対し、素子劣化等による不安定入光となったときには基準レベルを下回るよう基準レベルが調整されている。従って、コンパレータ３３からの出力信号は、安定入光時はハイレベルとなって、不安定入光時にはローレベルとなり、これにより出力信号レベルに基づいて安定入光か不安定入光かの判定が可能となる。
【００３１】
このように本実施形態では、各受光素子Ｊ毎にコンパレータ３３を設けて、そこからのデジタル的信号（ハイレベル、ローレベル）である出力信号を、信号線を介して受光側ＣＰＵ３４に伝送する構成とした。従って、アナログ的信号である受光信号を伝送する場合に比べて耐ノイズ性が高く、安定した物体検出判定及び安定入光判定を行うことができる。
【００３２】
また、物体検出判定時と安定入光判定時とで投光素子Ｔの投光動作における投光量を変える構成としたので、各コンパレータ３３において１つの基準レベルに基づき物体検出判定及び安定入光判定を行うことができ、１つのコンパレータで簡単な構成してセンサの大型化を最小限に抑制することができる。
【００３３】
＜他の実施形態＞
本発明は、前記実施形態に限定されるものではなく、例えば、以下に説明するような実施形態も本発明の技術的範囲に含まれ、さらに、下記以外にも要旨を逸脱しない範囲内で種々変更して実施することができる。
（１）上記実施形態とは異なり、受光器３０側の各スイッチ素子３２をコンパレータ３３の入力側に設けて、受光素子Ｊからの受光信号を有効化させる構成であっても良い。
【００３４】
（２）上記実施形態では、モード切替手段により切替動作を受光側ＣＰＵ３４の制御により自動で切り換える構成としたが、例えばモード切替スイッチを設けて作業者による切替操作でモードを切り換える構成であっても良い。
【００３５】
（３）上記実施形態では、投光量変更手段は、駆動電流切替手段１９で構成したが、これに限らず、例えば各投光素子に駆動電流を流すための駆動信号のデューティ比を変える構成でも良い。このような構成であっても投受光動作における各投光素子からの投光量が変わり、それに伴って各受光素子側で積分処理される受光信号レベルを変更することができ、上記第１実施形態と同様の作用効果を得ることができるからである。
【００３６】
（４）上記実施形態では、各受光素子Ｊのコンパレータ３３からの出力信号が全て安定入光であるとのハイレベルであった場合にのみ安定入光状態であるとの判定を行う構成としたが、これに限らず、各受光素子Ｊに対応するコンパレータ３３からの出力信号に基づき各光軸毎に安定入光か不安定入光かの判定を行う構成であっても良い（請求項１の発明に含まれる構成）。
【図面の簡単な説明】
【図１】本発明の一実施形態に係る多光軸光電センサの電気的構成図
【図２】物体検出判定及び安定入光判定時における投受光レベルの関係図
【図３】受光側ＣＰＵの制御内容を示すフローチャート
【図４】投光側ＣＰＵの制御内容を示すフローチャート
【符号の説明】
１１…スイッチング回路
１３…駆動回路
１４…ＡＮＤ回路
１７，３５…シフトレジスタ
１８…投光側ＣＰＵ
１９…駆動電流切替手段（投光量変更手段）
３２…スイッチ素子
３３…コンパレータ
３４…受光側ＣＰＵ
Ｊ（ＪN〜1）…受光素子
Ｔ（ＴN〜1）…投光素子[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-optical axis sensor having a stable light incident determination function.
[0002]
[Prior art]
Conventionally, as this type of multi-optical axis photoelectric sensor, for example, light reception signals from a plurality of light receiving elements arranged facing each of a plurality of light projecting elements arranged in a line in the vertical direction are sequentially passed through one comparator. Then, an object detection determination operation is performed by transmitting to the detection unit.
[0003]
By the way, in such a multi-optical axis photoelectric sensor, the light receiving level at the light receiving element in the light incident state is lowered due to element deterioration of the light projecting / receiving elements, contamination of the optical lens arranged in front of them, deviation of the optical axis, and the like. May result in an unstable light incident state, which may prevent stable object detection determination. Therefore, for example, a light reception signal from each light receiving element is set to a threshold that is higher than the threshold for object detection determination by a separately provided comparator and slightly lower than the light reception level in the normal light incident state. Some of them have a stable incident light judging function for judging whether the incident light is stable or unstable by comparing.
[0004]
[Problems to be solved by the invention]
However, in this type of multi-optical axis photoelectric sensor, the distances from the plurality of light receiving elements to one comparator are naturally different, and the lengths of signal lines arranged therebetween are also different. Furthermore, in recent years, the number of optical axes has been increasing more and more, and the signal lines are also becoming extremely thin in order to meet the demand for miniaturization. Therefore, the light reception signal transmits the thin and long signal lines. Therefore, it is easily affected by noise. Therefore, there is a problem that the level of the received light signal from each light receiving element input to the comparator becomes unstable, and stable object detection determination and stable light incident determination cannot be performed for each optical axis.
Note that such a problem is particularly likely to be an erroneous determination in a stable incident light determination in which the margin between the light reception level and the threshold value in the normal state is small compared to the object detection determination.
[0005]
The present invention has been made in view of the above circumstances, and an object thereof is to provide a multi-optical axis photoelectric sensor capable of suppressing the influence of noise or the like and performing stable object detection determination and stable light input determination. .
[0006]
[Means for Solving the Problems]
To achieve the above object, a multi-optical axis photoelectric sensor according to the invention of claim 1 includes a plurality of light projecting elements, a plurality of light receiving elements paired with each of the plurality of light projecting elements, and a plurality of light receiving elements. A plurality of comparing means provided corresponding to each of the light receiving elements, comparing the light receiving signal level from each light receiving element with a preset reference level, and outputting an output signal according to the comparison result, and a plurality of light projecting elements Are sequentially projected at a predetermined light emission timing, and an output signal corresponding to the comparison result between the light reception signal from each light receiving element and the reference level is sequentially captured in synchronization with the light emission timing of each corresponding light projecting element. A mode that can be switched between a light projecting / receiving control unit that performs a light projecting / receiving operation, a determination unit that performs a determination operation based on an output signal captured by the light projecting / receiving control unit, and an object detection determination mode and a stable light incident determination mode And a light emission amount changing means for changing the light emission amount of the light projecting element in the light projection / reception operation based on the switching operation by the mode switching means, and when the mode switching means is set to the object detection determination mode, The light quantity change means operates to project each light projecting element at the object detection level, and the judgment means performs an object detection judgment operation based on the output signal. When the stable light incident judgment mode is set, The changing unit operates to cause each light projecting element to project light at a stable input determination level that is lower than the object detection determination level, and the determination unit is characterized by performing a stable light incident determination operation based on an output signal.
[0007]
According to a second aspect of the present invention, in the multi-optical axis photoelectric sensor according to the first aspect, the light receiving signal level from each light receiving element is equal to or higher than a reference level when the determining means is set to the stable light incident determining mode. It is characterized in that a stable light incident determination operation is performed in accordance with the determination that the light is in a stable light input condition on the condition that the output signal based on the comparison result is received from all the comparison means.
[0008]
According to a third aspect of the present invention, in the multi-optical axis photoelectric sensor according to the first or second aspect of the present invention, the scanning operation for performing the light projecting / receiving operation is repeated until all the light projecting / receiving elements are made a round by the light projecting / receiving control means. The mode switching means is characterized in that it is always set to the object detection determination mode and switches to the stable light incident determination mode during the next one scanning operation on condition that the scanning operation has been repeated a predetermined number of times. Have.
[0009]
[Action and effect of the invention]
<Invention of Claim 1>
According to the configuration of the first aspect, a plurality of comparison units are provided corresponding to the respective light receiving elements, and output signals corresponding to the comparison results of the respective comparison units are sequentially synchronized with the light projection timings of the respective light projection elements. It was set as the structure taken in to a light reception control means. Here, the light reception signal output from the light receiving element is an analog signal corresponding to the amount of light received by the light receiving element, whereas the output signal output from the comparison means is a digital signal based on a magnitude comparison, so output The signal is more resistant to noise than the received light signal. Therefore, for example, it is possible to arrange each comparison means close to the corresponding light receiving element and send the output signal to the light reception control means side. With this configuration, even if the number of optical axes is very large and the transmission signal lines arranged between the light receiving elements and the light receiving control means are extremely thin, the influence of noise can be suppressed. Stable object detection determination and stable light incident determination can be performed.
[0010]
Further, since the light emission amount in the light projecting operation of the light projecting element is changed between the object detection determination and the stable light input determination, the object detection determination and the stable light input determination are made based on one reference level in each comparison unit. It can be performed. Therefore, the comparator can be configured simply with one comparator without providing two comparators for object detection and stable light incident determination, for example, and the increase in size of the sensor associated with the above configuration is minimized. can do.
[0011]
<Invention of Claim 2>
If even one of the plurality of optical axes is in an unstable light incident state, it will hinder the object / object detection determination. Therefore, in the configuration of claim 2, the determination means is that the light is stably incident only when the output signal based on the determination result that the light reception signal level is equal to or higher than the reference level is output for all the optical axes. The determination operation based on the determination is performed. In other words, if an output signal based on the comparison result that the received light signal level is lower than the reference level is output even in one of the optical axes, it is determined that the incident light is unstable.
[0012]
With such a configuration, it is possible to display a stable or unstable incident light with one display means without providing a display means for each optical axis, thereby avoiding an increase in the size of the sensor. Can do.
[0013]
<Invention of Claim 3>
Although a configuration in which the object detection determination operation and the stable light input determination operation are mixed in one scan operation to change the light emission amount of the light projecting element as needed is considered, not only complicated control is required, but also particularly high speed In a sensor that requires high performance, the object detection accuracy may be reduced. Therefore, according to the configuration of the third aspect, in the repeated scanning operation, the object detection determination is always performed, and the light incident amount of the light projecting element is decreased at a rate of once every plural times to perform the stable light input determination. did. That is, as the configuration for switching the mode switching and changing the light emission amount for each scan operation unit, the object detection determination operation and the stable light incident determination operation are not mixed in one scan, so that complicated control is not required. It is possible to perform stable object detection determination and stable light incident determination.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
An embodiment of the present invention will be described with reference to FIGS.
The multi-optical axis photoelectric sensor according to the present invention includes a projector 10 in which N light projecting elements T (for example, LEDs) are arranged in a row, and N pieces of light that form a pair with each of the N light projecting elements T. The light receiving element J (for example, a photodiode) is arranged so as to face the light receiving element 30 with a predetermined detection area in between.
[0015]
FIG. 1 shows an electrical configuration diagram. In the figure, of the N light projecting elements T and light receiving elements J, the light projecting elements T1 and J1 that are closest to the drive current switching means 19 described later, the second light projecting element T2 and Only the light receiving element J2, the (N-1) th light projecting element TN-1 and the light receiving element JN-1, and the Nth light projecting element TN and the light receiving element JN are shown. In addition, the light receiving elements J and the corresponding structures (the switching circuit 11, the drive circuit 13, and the AND circuit 14) are omitted. In addition, the letter K used in the following description indicates an arbitrary order (1 to N) of the light projecting element and the light receiving element, and the count number of the shift registers 17 and 35 to be described later. It is associated.
[0016]
First, in the projector 10, each of the light projecting elements T is connected to a constant voltage power supply circuit (not shown) provided for each optical axis on the anode side, and connected to the common connection line 16 via the switching circuit 11 on the cathode side. . The input side of the constant voltage power supply circuit of each light projecting element T is connected to the common connection line 16 and is located on one end side in the arrangement direction of the light projectors 10 (in the present embodiment, the light projecting element T1 side). The power supply is connected. The common connection line 16 is provided with drive current switching means 19 (corresponding to the light emission amount changing means of the present invention) formed by connecting a resistor 20 and a switch 21 in parallel. A drive circuit 13 is connected to the base of the NPN transistor constituting each switching circuit 11, and the drive current flows through the light projecting element T when the switching circuit 11 is turned on based on a signal from the drive circuit 13. Will light up.
[0017]
These drive circuits 13 are connected to the light projection side CPU 18 via a selection circuit including an AND circuit 14 and a shift register 17, and the arrangement of the light projection elements T is synchronized with a pulse signal from the light projection side CPU 18. A drive signal is given one by one along the direction (for example, the direction from the first light projecting element T1 to the Nth light projecting element TN) to drive sequentially. More specifically, the shift register 17 has an input terminal side connected to the light emitting side CPU 18 and a plurality of output terminal sides connected to one input terminal of each of the N AND circuits 14. The other input terminal of these N AND circuits 14 is connected to the light emitting side CPU 18, and the output terminal is connected to each drive circuit 13.
[0018]
The light emitting side CPU 18 gives a start pulse S to the shift register 17 based on a synchronizing signal D1 or a synchronizing signal D2 from the light receiving side CPU described later. At the same time, a signal is given to the switch 21 of the drive current changing means to perform an on / off operation. As a result, the drive current flowing through each light projecting element T can be reduced by the resistance 20 minutes when the switch 21 is on and when it is off. In the present embodiment, by utilizing this fact, the light emitting side CPU 18 identifies the synchronizing signal D1 and the synchronizing signal D2 having different pulse widths supplied from the light receiving side CPU 34, and when receiving the synchronizing signal D1, the switch 21 Is turned on so that each light projecting element T is projected at the object detection level, and when receiving the synchronization signal D2, the switch 21 is turned off so that each light projecting element T is stably input lower than the object detection level. It operates to project at the light determination level (see FIG. 2).
[0019]
Next, in the light receiver 30, each light receiving element J is commonly connected to the light receiving side CPU 34 via the light receiving circuit 31, the comparator 33 corresponding to the comparison means of the present invention, and the switch element 32. The light receiving signal output from the light receiving element J is integrated by the light receiving circuit, and compared with a predetermined reference level (see FIG. 2) by the comparator 33. An output signal corresponding to the comparison result is output from the comparison means and applied to the input of the switch element 32. This output signal is, for example, a so-called digital signal that is high when the level of the light receiving signal from the light receiving element J is higher than the reference level and low when it is low.
[0020]
The control terminal of each switch element 32 is connected to the output side of the shift register 35 that operates based on the start pulse S from the light receiving side CPU 34. The light receiving side CPU 34 gives the synchronizing signals D1 and D2 to the light emitting side CPU 18 and gives a start pulse S to the shift register 35, and at the same predetermined time interval as the light projector 10 side by the activation of the shift register 35, and A drive signal is sequentially given to the switch elements 32 along the same arrangement direction, and the output signals from the comparators 33 corresponding to the respective light receiving elements J are sequentially validated. With such a configuration, the light projecting element T and the light receiving element J having the same optical axis sequentially perform the light projecting / receiving operation, thereby preventing mutual interference between the optical axes.
[0021]
Next, the control contents of the light emitting side CPU 18 and the light receiving side CPU 34 that function as the mode switching means, the light projecting / receiving control means and the determining means of the present invention will be described with reference to the flowcharts shown in FIGS.
[0022]
<Control contents of light receiving side CPU 34>
When the multi-optical axis photoelectric sensor is turned on, the number of scans is set to an initial value “1” in step S1, and whether or not the number of scans is “5” is checked in step S2. If not five times (“NO” in step S2), the synchronization signal D1 is output and the count number K of the shift register 35 is set to the initial value “1” (steps S3 and S4). As a result, the output signal from the comparator 33 corresponding to the light receiving element J1 is validated.
[0023]
Then, the output signal level at that time is read at a predetermined light reception timing (steps S5 and S6), and it is determined in step S7 whether the output signal level is high. Here, if it is at the low level, an object detection signal is output to the output circuit 36 (step S8), and if it is at the high level, the comparison operation between the count number K of the shift register 35 and the number of optical axes N is performed in step 9 as it is. I do. The above operations from Step S5 to S8 are repeated for each optical axis (Step S10), and when all the optical axes have been completed ("YES" in Step S9), 1 is added to the number of scans M (Step S11). ) Again, the number of scans is checked in step S2.
[0024]
On the other hand, when the number of scans becomes 5 (“YES” in step S2), the synchronization signal D2 having a pulse width different from that of the synchronization signal D1 is output to the light-emission CPU 18 and the count number K of the shift register 35 is also used. Is set to the initial value “1”, and the output signal from the comparator 33 corresponding to the light receiving element J1 is validated (steps S12 and S13). Then, the output signal level at that time is read at a predetermined light reception timing (steps S14 and S15), and it is determined in step S16 whether the output signal level is high.
[0025]
Here, if the level is low, 1 is added to the number of incident optical axes X (step S17). If the level is high, the count number K of the shift register 35 is compared with the number of optical axes N in step S18. Perform the action. The above-described operations from step S14 to S17 are repeated for each optical axis (step S19), and when all the optical axes are made a round (“YES” in step S18), the number of incident optical axes X is the number of all optical axes. In step S20, it is determined whether or not N matches. Here, when they match (“YES” in step S20), a stable light input signal is output to the output circuit 36 (step S21), and when they do not match (“NO” in step S20), an unstable light input signal is output to the output circuit 36. Is output. For example, an indicator lamp (not shown) performs a lighting operation in accordance with these output signals (corresponding to the invention of claim 2).
[0026]
<Control contents of light-projecting side CPU 18>
The light emitting side CPU 18 waits for the synchronization signals D1 and D2 from the light receiving side CPU 34 in step S31, and when receiving the synchronization signal D1 (“YES” in step S31, the switch of the drive current changing means in step S32). In step S33, the count number K of the shift register 17 is set to the initial value “1.” Then, the light projection signal E is output at a predetermined light projection timing (timing synchronized with the light reception timing). Then, 1 is added to the count number K of the shift register 17 (steps S34 to S35) This operation is sequentially performed up to the last optical axis N and one scanning operation is completed (“YES” in step S37). In this scanning operation, each light projecting element T projects light sequentially at the object detection level.
[0027]
On the other hand, when the synchronization signal D2 is received ("YES" in step S38), the switch 21 of the drive current changing means is turned off in step S39, which is different from when the synchronization signal D1 is received. Therefore, in this scanning operation, each light projecting element T sequentially projects light at a stable incident light determination level lower than the object detection level.
[0028]
Under the control of the light projecting side CPU 18 and the light receiving side CPU 34 as described above, the scanning operation in which light is projected and received sequentially for each optical axis at the light projecting / receiving timing is repeated. The light receiving side CPU 34 always operates to provide the synchronizing signal D1 to the light emitting side CPU 18 and to provide the synchronizing signal D2 at a rate of once every five scanning operations, and to the output signal from the comparator 33. The determination operation is performed after switching from the object detection determination to the stable light incident determination. As a result, the light projection side CPU 18 performs the light projection operation by switching the light projection level of the light projecting element T from the object detection determination level to the stable light incident determination level at a rate of once every five scan operations. . In other words, the multi-optical axis photoelectric sensor of the present embodiment repeats a series of operations for performing a scan operation for stable incident light once after performing a scan operation for object detection four times in succession (claims). Corresponding to the configuration of item 3).
[0029]
At the time of the object detection determination, as shown in FIG. 2, each light projecting element T emits light at the object detection level, and the light reception signal from the light receiving element J is in the light incident state when there is no object in the detection area. Thus, a high level that greatly exceeds the reference level is indicated, and a high-level output signal is output from the comparator 33. On the other hand, when there is an object, it is in a light-shielding state, showing a low level that is significantly below the reference level, and a low-level output signal is output. Therefore, object detection can be performed based on this output signal level.
[0030]
On the other hand, at the time of stable light incident determination, as shown in FIG. 2, each light projecting element T emits light at a stable light incident determination level lower than the object detection level. Along with this, the amount of light received by the light receiving element J also decreases compared to the time of the object detection determination. The light reception signal from the light receiving element J when there is no object is slightly higher than the reference level when normal, whereas the reference level is lower than the reference level when unstable incident light is caused by element deterioration or the like. Has been adjusted. Therefore, the output signal from the comparator 33 is at a high level when the light is stably input and is at a low level when the light is unstable. Thus, it is determined whether the light is stable or unstable based on the output signal level. It becomes possible.
[0031]
As described above, in this embodiment, the comparator 33 is provided for each light receiving element J, and an output signal which is a digital signal (high level or low level) therefrom is transmitted to the light receiving side CPU 34 via the signal line. The configuration. Therefore, compared with the case where a light reception signal that is an analog signal is transmitted, noise resistance is high, and stable object detection determination and stable light input determination can be performed.
[0032]
Further, since the light emission amount in the light projecting operation of the light projecting element T is changed between the object detection determination and the stable light input determination, the object detection determination and the stable light input determination are performed in each comparator 33 based on one reference level. The size of the sensor can be minimized with a simple configuration with a single comparator.
[0033]
<Other embodiments>
The present invention is not limited to the above-described embodiment. For example, the embodiments described below are also included in the technical scope of the present invention, and various other than the following can be made without departing from the scope of the invention. It can be changed and implemented.
(1) Unlike the above embodiment, each switch element 32 on the light receiver 30 side may be provided on the input side of the comparator 33 to enable the light reception signal from the light receiving element J to be valid.
[0034]
(2) In the above embodiment, the switching operation is automatically switched by the mode switching means under the control of the light receiving side CPU 34. However, for example, a mode switching switch may be provided to switch the mode by a switching operation by an operator. good.
[0035]
(3) In the above embodiment, the light emission amount changing means is constituted by the drive current switching means 19, but the invention is not limited to this, and for example, it is also possible to change the duty ratio of the drive signal for flowing the drive current to each light projecting element. good. Even in such a configuration, the light projection amount from each light projecting element in the light projecting / receiving operation can be changed, and accordingly, the light receiving signal level integrated on each light receiving element side can be changed. This is because the same operational effects can be obtained.
[0036]
(4) In the above embodiment, it is determined that the stable light incident state is determined only when the output signals from the comparators 33 of the respective light receiving elements J are all at a high level as stable incident light. However, the present invention is not limited to this, and a configuration may be adopted in which it is determined whether the light is stable or unstable for each optical axis based on the output signal from the comparator 33 corresponding to each light receiving element J. Included in the invention).
[Brief description of the drawings]
FIG. 1 is an electrical configuration diagram of a multi-optical axis photoelectric sensor according to an embodiment of the present invention. FIG. 2 is a relationship diagram of light projecting and receiving levels at the time of object detection determination and stable light incident determination. Flowchart showing control contents [FIG. 4] Flowchart showing control contents of light emitting CPU [Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Switching circuit 13 ... Drive circuit 14 ... AND circuit 17, 35 ... Shift register 18 ... Light projection side CPU
19: Driving current switching means (light emission amount changing means)
32 ... Switch element 33 ... Comparator 34 ... Reception side CPU
J (JN to 1) ... Light receiving element T (TN to 1) ... Projecting element

Claims

A plurality of light emitting elements;
A plurality of light receiving elements paired with each of the plurality of light projecting elements;
A plurality of comparison means provided corresponding to each of the plurality of light receiving elements, comparing a light reception signal level from each of the light receiving elements with a preset reference level, and outputting an output signal according to the comparison result; ,
The plurality of light projecting elements are sequentially projected at a predetermined light emission timing, and the output signals corresponding to the comparison results between the light receiving signals from the respective light receiving elements and the reference level are respectively transmitted to the corresponding light projecting elements. Projection / reception control means for performing projection / reception operation that sequentially captures in synchronization with the light emission timing of the element;
A determination unit that performs a determination operation based on the output signal captured by the light projecting and receiving control unit;
Mode switching means capable of switching between an object detection determination mode and a stable incident light determination mode;
A light projection amount changing means for changing the light projection amount of the light projecting element in the light projecting and receiving operation based on the switching operation by the mode switching means,
When the mode switching unit is set to the object detection determination mode, the light projection amount changing unit operates to project each of the light projecting elements at an object detection level, and the determination unit is based on the output signal. Perform object detection judgment operation,
When the stable light incident determination mode is set, the light emission amount changing means operates to cause each of the light projecting elements to project light at a stable input determination level lower than the object detection determination level. The means performs a stable incident light determination operation based on the output signal.

When the determination means is set to the stable light incident determination mode, an output signal based on a comparison result that a light reception signal level from each light receiving element is equal to or higher than the reference level is output from all the comparison means. The multi-optical axis photoelectric sensor according to claim 1, wherein the stable incident light determining operation is performed in response to the determination that the light is in a stable incident state on condition that the light is received.

The light emitting / receiving control means is configured to repeat the scanning operation for performing the light emitting / receiving operation until all the light emitting / receiving elements make a round. The mode switching means is always set to the object detection determination mode, and the scanning operation is predetermined. 3. The multi-optical axis photoelectric sensor according to claim 1, wherein the multi-optical axis photoelectric sensor is switched to the stable incident light determination mode during a next scanning operation on condition that the number of repetitions is repeated.