JP3828089B2

JP3828089B2 - Position detection method and apparatus

Info

Publication number: JP3828089B2
Application number: JP2003108098A
Authority: JP
Inventors: 孝彦舟橋; 克人小尾
Original assignee: Wacom Co Ltd
Current assignee: Wacom Co Ltd
Priority date: 2003-04-11
Filing date: 2003-04-11
Publication date: 2006-09-27
Anticipated expiration: 2021-09-27
Also published as: JP2003271298A

Description

【０００１】
【発明の属する技術分野】
本発明は、電磁誘導または電磁結合を利用した位置指示器による指示位置の検出方法及びその装置の改良に関するものである。
【０００２】
【従来の技術】
この出願に先立ち、出願人は、多数のループコイルを位置検出方向に並設してなるセンス部と位置指示器との間で電波をやりとりすることにより、該位置指示器による指示位置の座標値を求める位置検出装置（以下、先願と称す。）を提案した（特許文献１参照）。
【０００３】
前記先願の内容を簡単に説明すると、多数のループコイルより一のループコイルを選択し、これに所定の周波数の交流信号を供給して電波を送信させ、該電波を位置指示器に設けた共振回路に受信させる。この際、該電波によるエネルギーを受けた共振回路から発生される電波を前記一のループコイルに受信させ、誘導電圧を発生させる。これを多数のループコイルについて順次、走査・選択して繰返し、各ループコイルに発生した誘導電圧の大きさに基づいて共振回路の位置、即ち指示位置の座標値を求める如くなしたものである。
【０００４】
ところで、この種の位置検出装置では指示位置の座標値の外、実際に入力すべき指示位置を特定した状態（ペンダウン状態）を表す情報や、ソフトウェアに応じて座標値以外のパラメータ、例えば線の太さ、指示位置あるいは指示領域の色相や濃度（明度）等を変化させるための情報を、前記指示位置の座標値とともに入力したいという要求がある。
【０００５】
そこで、前述した先願では、共振回路を構成するコイル及びコンデンサに手動のスイッチを介して他のコンデンサを接続することにより、該スイッチに対する操作に応じて共振周波数がわずかに変化するようになし、この共振周波数のわずかな変化量を位相角の変化量として検出し、前述した各種の情報（以下、これらを操作情報と称す。）となしていた。
【０００６】
【特許文献１】
特開昭６３−７０３２６号公報
【０００７】
【発明が解決しようとする課題】
図２は前記先願の位置検出装置における動作波形の一例を示すもので、図中、Ｔ₁ ，Ｔ₂ ，……Ｔ₆ は電波の送信期間、Ｒ₁ ，Ｒ₂ ，……Ｒ₆ は電波の受信期間、(イ) はセンス部側の送信電波、(ロ) ，(ロ)'は共振回路内の誘導電圧、(ハ) ，(ハ)'はセンス部側の受信信号、(ニ) ，(ニ)'は前記受信信号を整流し高周波成分を取り除いた信号（以下、受信誘導電圧と称す。）である。
【０００８】
ここでは、送信期間Ｔ₁ 及び受信期間Ｒ₁ に一のループコイルを選択し、送信期間Ｔ₂ 及び受信期間Ｒ₂ に該一のループコイルに隣接するループコイルを選択し、以下、同様に隣接するループコイルを一方向に順次走査・選択した場合であって、特に送信期間Ｔ₃ 及び受信期間Ｒ₃ に選択したループコイルの真上に位置指示器、即ち共振回路が存在する場合の例を示している。
【０００９】
ところで、一の送信期間中に一のループコイルから送信される電波によって共振回路内に発生した誘導電圧は、送信電波が停止する受信期間中に徐々に減少するが、次の送信期間に次のループコイルから電波が送信されるまでに全てが消滅するわけではなく、該次のループコイルによる電波の送受信に影響を及ぼす。
【００１０】
即ち、送信電波の周波数と共振回路の共振周波数とが一致している場合、図２中の(ロ) ，(ハ) に示すように、共振回路内の残留誘導電圧と次の送信期間における送信電波との位相がほぼ一致し、これらは互いに相加されることになるため、各受信期間Ｒ₁ ，Ｒ₂ ，……Ｒ₆ に対応して得られる受信誘導電圧(ニ) のレベルＶ₁ ，Ｖ₂ ，……Ｖ₆ は、全体的にループコイルの走査・選択の進行方向寄り（図２では右側）のレベルが前記影響がない場合に比べて大きくなる。
【００１１】
一方、前述したスイッチ等の操作により共振回路における共振周波数を変化させた場合、図２中の(ロ)'，(ハ)'に示すように、受信期間中の共振回路内の誘導電圧の位相がずれる（ここでは遅れる）ため、共振回路内の残留誘導電圧と次の送信期間における送信電波との位相は必ずしも一致せず、これらは互いに相殺し合うこともある。その結果、各受信期間Ｒ₁ ，Ｒ₂ ，……Ｒ₆ に対応して得られる受信誘導電圧(ニ)'のレベルＶ₁'，Ｖ₂'，……Ｖ₆'は、前記位相のずれの量（位相角の変化量）に応じて様々な変化を示すことになる。
【００１２】
位置指示器による指示位置の座標値は、通常、最もレベルの大きな受信誘導電圧を含む２〜４個の受信誘導電圧のレベルを所定の式に代入して演算処理することにより求められるため、前述した共振回路内の残留誘導電圧による受信誘導電圧のレベルの変化は指示位置の座標値に誤差をもたらすことになる。
【００１３】
特に、位置指示器が位置検出方向の端付近にあり、前記演算処理に用いられる受信誘導電圧を発生するループコイル以前に選択可能なループコイルが存在しないような場合、即ち共振回路内の残留誘導電圧がない場合は、前記同様な理由によって、位置指示器が位置検出方向の端付近以外にある場合、即ち共振回路内の残留誘導電圧がある場合に比べて、該演算処理に用いられる受信誘導電圧のレベルが低くなり、これによって指示位置の座標値に誤差が生ずるという問題があった。
【００１４】
なお、前述した残留誘導電圧による座標値のずれの問題は、共振回路内の残留誘導電圧に限らず、受信信号の検出回路内における残留誘導電圧、例えば受信信号より高周波成分を除去するフィルタにおける残留誘導電圧によっても引き起こされる問題であるから、先願のような共振回路を有する位置指示器を用いた位置検出装置に限らず、多数のループコイルを走査・選択し、その時に検出される誘導電圧から指示位置の座標値を求めるタイプの全ての位置検出装置において共通に生じ得る問題である。
【００１５】
本発明の目的は、座標検出範囲の周辺部において回路中に残留する誘導電圧による座標値の誤差を生じない位置検出方法及びその装置を提供することにある。
【００１６】
【課題を解決するための手段】
前記目的を達成するため、本発明では、位置検出方向に並設された多数のループコイルからなるセンス部と少なくともコイルを有する位置指示器との間で電波を送受信し、得られた誘導電圧から前記位置指示器による指示位置の座標値を求める位置検出方法であって、当初は前記多数のループコイルについて一のループコイルを切り替え選択して電波の送受信を繰り返し、得られた誘導電圧のうちで最大の誘導電圧から位置指示器が有効読み取り高さ内にあるか否かを判定し、判定の結果、位置指示器が有効読み取り高さ内にない場合は前記同様の動作を繰り返し、また、判定の結果、位置指示器が有効読み取り高さ内にある場合は前記多数のループコイルのうち最大の誘導電圧を検出した時のループコイルを中心とする所定の数のループコイルについて一のループコイルを位置検出方向の一端から他端に向けて順次切り替え選択して電波の送受信を繰り返し、得られた少なくとも２つの誘導電圧に基づいて前記位置指示器による指示位置の座標値を検出し、もしくは前記多数のループコイルのうち最大の誘導電圧を検出した時のループコイルを中心とする所定の数のループコイルについて一のループコイルを位置検出方向の他端から一端に向けて順次切り替え選択して電波の送受信を繰り返し、得られた少なくとも２つの誘導電圧に基づいて前記位置指示器による指示位置の座標値を検出する位置検出方法において、前記所定の数のループコイルを位置検出方向の一端から他端に向けて順次切り替え選択する際、選択可能なループコイルの数が前記所定の数に足りるか否かを、最大の誘導電圧を検出した時のループコイルが位置検出方向の一端からみて前記所定の数の１／２より少ない本数のループコイルに含まれるか否かより判定し、判定の結果、選択可能なループコイルの数が前記所定の数に足りない場合のみ該足りないループコイルが存在すると仮定した場合の位置と最大の誘導電圧を検出した時のループコイルを中心として対称位置にあるループコイルを位置検出方向の一端のループコイルを選択する以前に選択し、もしくは前記所定の数のループコイルを位置検出方向の他端から一端に向けて順次切り替え選択する際、選択可能なループコイルの数が前記所定の数に足りるか否かを、最大の誘導電圧を検出した時のループコイルが位置検出方向の他端からみて前記所定の数の１／２より少ない本数のループコイルに含まれるか否かより判定し、判定の結果、選択可能なループコイルの数が前記所定の数に足りない場合のみ該足りないループコイルが存在すると仮定した場合の位置と最大の誘導電圧を検出した時のループコイルを中心として対称位置にあるループコイルを位置検出方向の他端のループコイルを選択する以前に選択する位置検出方法及びその装置を提案する。
【００１７】
本発明によれば、位置指示器が位置検出方向の端付近にある場合でも、座標値算出の演算処理に用いる誘導電圧を検出する時に選択すべきループコイル以前に選択可能なループコイルを疑似的に存在するようにでき、これによって位置指示器が位置検出方向の端付近以外にある場合と同様な残留誘導電圧を生じせしめることができ、誤差の少ない座標値を求めることが可能となる。
【００１８】
【発明の実施の形態】
図１は本発明の第１の実施の形態のハードウェア構成を示すもので、基本的に前述した先願のものと同一であるが、これを簡略化した形で示す。図中、１は位置指示器、２はセンス部、３は選択回路、４は送受切替回路、５は発振器、６はレベル検出回路、７は位相検出回路、８は処理装置である。
【００１９】
位置指示器１は、コイル、コンデンサ及びスイッチを含み、スイッチをオフとした状態では所定の周波数ｆ₀ を共振周波数とし、また、スイッチをオンとした状態では該周波数ｆ₀ よりわずかに低い周波数、例えばｆ₁ を共振周波数とする共振回路を内蔵してなるものである。
【００２０】
センス部２は、位置検出方向（ここではＸ軸方向）に並設された多数、例えば４８本のループコイルＣ０，Ｃ１，Ｃ２，……Ｃ４７からなっている。選択回路３はセンス部２の４８本のループコイルより一のループコイルを選択するものであり、処理装置８からの選択情報に基づいて動作する。送受切替回路４は前記選択された一のループコイルを発振器５とレベル検出回路６及び位相検出回路７とに交互に接続するものであり、処理装置８からの切替信号に基づいて動作する。
【００２１】
発振器５は前記所定の周波数ｆ₀ の基準クロックを発生し、これを位相検出回路７、処理装置８並びに図示しない低域フィルタ及び電流ドライバを介して送受切替回路４へ供給する。レベル検出回路６は検波器及び前記周波数ｆ₀ より十分遮断周波数の低い低域フィルタよりなり、図示しない増幅器により増幅された受信信号中の周波数ｆ₀ 成分のエネルギーに応じたレベルを有する直流信号を出力する。位相検出回路７は位相検波器及び前記周波数ｆ₀ より十分遮断周波数の低い低域フィルタよりなり、図示しない増幅器により増幅された受信信号と前記基準クロックとの位相差に応じたレベルを有する直流信号を出力する。
【００２２】
処理装置８は周知のマイクロプロセッサ等より構成され、前記周波数ｆ₀ の基準クロックより送受切替信号を作成して送受切替回路４に供給するとともに、選択回路３を制御してセンス部２のループコイルを切替え、また、レベル検出回路６の出力レベルをアナログ／ディジタル（Ａ／Ｄ）変換し、所定の演算処理を実行して位置指示器１による指示位置の座標値を求め、これを後述する如く平均化し、さらにまた、位相検出回路７の出力レベルをアナログ／ディジタル（Ａ／Ｄ）変換し、位置指示器１におけるスイッチの状態を検出する。
【００２３】
図３は本実施の形態における処理の流れ図であり、以下、これに従って動作を説明する。
【００２４】
まず、処理装置８は選択回路３にセンス部２のうちのループコイルＣ０を選択する情報を送出するとともに、送受切替回路４に送信側を選択する信号を送出し、前記ループコイルＣ０に発振器５の基準クロックに基づく周波数ｆ₀ の正弦波信号を供給して周波数ｆ₀ の電波を発生させる。この時、センス部２上に位置指示器１が載置されていると前記電波はその共振回路を励振し、これに周波数ｆ₀ の誘導電圧を発生させる。
【００２５】
処理装置８は送受切替回路４に送信側を選択する信号を一定時間送出すると、受信側を選択する信号を送出し、ループコイルＣ０より発生する電波を消滅させる。この際、位置指示器１の共振回路に発生した誘導電圧はその損失に応じて徐々に減衰するとともに周波数ｆ₀ の電波を発信するが、該電波は前述したループコイルＣ０を逆に励振し、誘導電圧を発生させる。
【００２６】
処理装置８は送受切替回路４に受信側を選択する信号を一定時間送出すると、再び送信側を選択する信号を送出し、以下、前記同様な電波の送受信をループコイルＣ０について複数回、例えば合計４回繰返させる。次に、処理装置８は選択回路３に送出する情報を変更して選択するループコイルをＣ１に切替え、前記同様の電波の送受信を行い、以下、センス部２のループコイルＣ２〜Ｃ４７を順次走査・選択して前記同様の電波の送受信を行う（ステップＳ１）。
【００２７】
なお、この際、センス部２のループコイルＣ０〜Ｃ４７の全てを選択することなく、１つ置き、２つ置き、というように適当に間引いて選択しても良い。
【００２８】
前述した４回の受信期間中にセンス部２のループコイルに発生した誘導電圧はレベル検出回路６の帯域フィルタで平均化され、さらに検波されて直流信号に変換され処理装置８に送出される。前記直流信号のレベルは位置指示器１とループコイルとの間の距離に依存した値となるから、処理装置８はその最大値が予め設定した所定の閾値以上か否かを判別することにより位置指示器１がセンス部２の有効読取り高さ内にあるか否かを判定する（ステップＳ２）。
【００２９】
処理装置８は前記高さ内に位置指示器１があると判定した場合、前記得られた各ループコイル毎の信号より最大値が得られたループコイル（以下、ピークコイルと称す。）を抽出し（ステップＳ３）、位置指示器１が有効エリア内にあるか否か、ここではピークコイルが端のループコイルＣ０又はＣ４７に該当しないかどうかを調べる（ステップＳ４）。ここで、位置指示器１が有効エリア外であれば検出中止や特別な方法による位置検出等の別処理へ送る。なお、前記高さ内に位置指示器１がないと判定された場合には前記ステップＳ１，Ｓ２の処理を繰返す。
【００３０】
一方、位置指示器１が有効エリア内であれば、処理装置６は前記求めたピークコイル（ＰＣ）を中心とする所定の数、例えば７つのループコイルについて番号の小さい方から大きい方（順方向）へ順次走査・選択して前記同様の電波の送受信を行い（ステップＳ５）、さらに前記７つのループコイルについて番号の大きい方から小さい方（逆方向）へ順次走査・選択して前記同様の電波の送受信を行う（ステップＳ６）。図４はピークコイルがＣ３の場合にステップＳ５，６の処理によって得られる誘導電圧の一例を示すものである。
【００３１】
前述したピークコイルを中心としたループコイルの順方向及び逆方向の部分選択（セクタスキャン）が終了すると、処理装置８はこの際、レベル検出回路６より得られた誘導電圧より、順方向及び逆方向のセクタスキャン毎にレベルの大きい順に複数、例えば３つの誘導電圧（図４の例ではｅ２，ｅ３，ｅ４）をそれぞれ抽出し（ステップＳ７）、これらの信号に基づいて先願で述べているような周知の座標計算を実行し、位置指示器１による指示位置の座標値をループコイルの走査・選択方向別に求め、さらにこれらを平均化する（ステップＳ８）。
【００３２】
ここで、従来技術の項で述べたように、一のループコイルより送信される電波によって共振回路内に発生した誘導電圧は、次のループコイルより電波が送信されるまでに全て消滅せず残留し、次のループコイルによる電波の送受信に影響を及ぼすが、その影響は、ループコイルを順方向にスキャンした時と逆方向にスキャンした時とで反対方向に働くことになる。
【００３３】
前記共振回路内の残留誘導電圧は各ループコイルに対応する各誘導電圧値を変化させるが、その変化の方向も反対方向となるから、順方向セクタスキャン時の各誘導電圧と逆方向セクタスキャン時の各誘導電圧とは、図４に示すように、ちょうど対称的な形となる。
【００３４】
また、位置指示器１の共振回路におけるスイッチがオンとなり、その共振周波数がｆ₀からｆ₁へ変化し、共振回路内の残留誘導電圧の位相と次の送信電波の位相とが一致せず、これによって各ループコイルに対応する各誘導電圧値を変化させる場合も、順方向セクタスキャン時の各誘導電圧と逆方向セクタスキャン時の各誘導電圧とは、ちょうど対称的な形となる。
【００３５】
前述した各誘導電圧値の変化は指示位置の座標値の演算結果に影響をもたらし、座標値にずれを発生させるが、順方向セクタスキャン時の各誘導電圧に基づく座標値のずれと、逆方向セクタスキャン時の各誘導電圧に基づく座標値のずれとは反対方向となる。
【００３６】
本実施の形態では、前述したようにセクタスキャンを順方向及び逆方向の両方について行い、それぞれについて座標値を算出して平均化しているため、前述した座標値のずれがキャンセルされることになり、座標値を補正することなく、また、位置指示器の共振回路における共振周波数の変化に拘らず、常に正確な指示位置の座標値が検出可能となる。
【００３７】
なお、前述した共振回路における共振周波数の変化は位相検出回路７により位相の変化を表す直流信号として出力され、これより処理装置８によって位置指示器１におけるスイッチの状態が識別される（ステップＳ９）。
【００３８】
ところで、前記実施の形態ではピークコイルがループコイルＣ１に当たる場合、座標算出に必要な３つの信号、即ちｅ０，ｅ１，ｅ２は得られるが、図５に示すように、順方向セクタスキャンにおいてはループコイルＣ０以前に選択可能なループコイルが存在しないため、該ループコイルＣ０における信号ｅ０のレベルが、従来技術の項で述べたように本来のレベル（ループコイルＣ０以前に選択するループコイルが存在する場合のレベル）より低くなる。従って、このような順方向セクタスキャンによって得られた信号に基づく座標値は誤差を含むものとなる。なお、逆方向セクタスキャンにおいてはループコイルＣ０以前に選択可能なループコイルが存在する（ループコイルＣ１が該当）ため、問題はない。
【００３９】
図６は前述した点を改良した順方向セクタスキャンの処理フローを示すもので、ピークコイルがループコイルＣ１に当たる場合、ループコイルＣ０を選択する前にループコイルＣ４，Ｃ３を選択して電波の送受信を行うことにより、疑似的にループコイルＣ０以前に選択可能なループコイルが存在するようにして、図７に示すように信号ｅ３’，ｅ４’を発生させ、ループコイルＣ０における信号ｅ０のレベルを本来のレベルに近づけ、前述した誤差を少なくすることができる。
【００４０】
また、ループコイルＣ０を選択する以前にループコイルＣ４，Ｃ３を選択する場合、該ループコイルＣ４，Ｃ３より発生する電波の強度を制御してやることにより、さらに誤差を少なくすることができる。即ち、ピークコイルの両側のループコイル、ここではＣ０，Ｃ２における信号レベルを比較し、例えば図８に示すように、ループコイルＣ０における信号レベルが低ければ、ループコイルＣ０の前に選択するループコイルＣ４，Ｃ３に流す電流値を本来の値より下げ、また、ループコイルＣ０における信号レベルが高ければ、ループコイルＣ０の前に選択するループコイルＣ４，Ｃ３に流す電流値を本来の値より上げ、該ループコイルＣ４，Ｃ３から発生する電波の強度をより弱く又は強くすることにより、その際の信号レベルｅ３’，ｅ４’を、ループコイルＣ０以前に選択すべきループコイルが実際に存在する場合と同様なレベルとすることができ、これによって、ループコイルＣ０における信号ｅ０のレベルをさらに本来のレベルに近づけ、さらに誤差を少なくすることができる。なお、ループコイルＣ３，Ｃ４を選択する代わりに、ループコイルＣ０，Ｃ１等を選択するとともにその電流値を制御することにより、前述した信号ｅ３’，ｅ４’を発生させるようになしても良い。
【００４１】
また、ピークコイルがループコイルＣ２に当たる場合は、図６に示したように、ループコイルＣ０を選択する前にループコイルＣ５を選択して電波の送受信を行うことにより、前記同様に座標値の誤差を少なくすることができ、また、この場合もループコイルＣ５より発生する電波の強度を制御してやることにより、さらに座標値の誤差を少なくすることができる。なお、この場合もループコイルＣ５を選択する代わりに、ループコイルＣ０等を選択するとともにその電流値を制御するようになしても良い。
【００４２】
また、前記実施の形態ではピークコイルがループコイルＣ４５又はＣ４６に当たる場合であって逆方向セクタスキャンを行う場合にも前記同様な問題が発生する。図９はこの点を改良した逆方向セクタスキャンの処理フローを示すもので、基本的に図６のものと同様な処理を実行することにより、座標値の誤差を少なくする。なお、ループコイルＣ４７以前に選択すべきループコイルにおける電波の強度を制御してやることにより、座標値の誤差をより少なくすることができる点も同様である。
【００４３】
図１０は本発明の第２の実施の形態のハードウェア構成を示すもので、ここではＸ軸方向及びＹ軸方向の互いに直交する２方向の位置検出を行うようになした例を示す。図中、第１の実施の形態と同一構成部分は同一符号をもって表す。即ち、５は発振器、６はレベル検出回路、７は位相検出回路、１１はセンス部、１２，１３は選択回路、１４，１５は送受切替回路、１６，１７はＸＹ切替回路、１８は処理装置である。なお、図面を簡略化するため、制御ラインについては省略した。
【００４４】
センス部１１はＸ軸方向に並設された多数、例えば４８本のループコイルと、Ｙ軸方向に並設された多数、同じく４８本のループコイル（但し、いずれも図面では省略）とからなっている。選択回路１２はセンス部１１のＸ軸方向の４８本のループコイルより一のループコイルを選択するものであり、また、選択回路１３はセンス部１１のＹ軸方向の４８本のループコイルより一のループコイルを選択するものであり、いずれも処理装置１８からの選択情報に基づいて動作する。
【００４５】
送受切替回路１４は前記選択されたＸ軸方向の一のループコイルをＸＹ切替回路１６，１７を介して発振器５とレベル検出回路６及び位相検出回路７とに交互に接続するものであり、また、送受切替回路１５は前記選択されたＹ軸方向の一のループコイルをＸＹ切替回路１６，１７を介して発振器５とレベル検出回路６及び位相検出回路７とに交互に接続するものであり、処理装置１８からの切替信号に基づいて動作する。
【００４６】
ＸＹ切替回路１６は発振器５で発生する周波数ｆ₀ の基準クロックを図示しない低域フィルタ及び電流ドライバを介して送受切替回路１４及び１５に交互に切り替えて供給するもので、処理装置１８からのＸＹ切替信号に基づいて動作する。ＸＹ切替回路１７は選択回路１２及び１３でそれぞれ選択されたＸ軸方向及びＹ軸方向の一のループコイルを送受切替回路１４及び１５を介して交互にレベル検出回路６並びに位相検出回路７に切り替えて接続するもので、処理装置１８からのＸＹ切替信号に基づいて動作する。
【００４７】
処理装置１８は周知のマイクロプロセッサ等より構成され、前記周波数ｆ₀ の基準クロックより送受切替信号を作成して送受切替回路１４，１５に供給するとともに、選択回路１２，１３及びＸＹ切替回路１６，１７を制御してセンス部１１のループコイルを切替え、また、レベル検出回路６の出力レベルをアナログ／ディジタル（Ａ／Ｄ）変換し、所定の演算処理を実行して位置指示器（図示せず）による指示位置の座標値を求め、これを後述する如く平均化し、さらにまた、位相検出回路７の出力レベルをアナログ／ディジタル（Ａ／Ｄ）変換し、位置指示器におけるスイッチの状態を検出する。
【００４８】
図１１は本実施の形態における処理の流れ図であり、その動作はＸ軸方向のループコイルに対する動作とＹ軸方向のループコイルに対する動作とが交互に行われる点及びＸ軸方向及びＹ軸方向の指示位置の座標値を時系列的に偶数個平均化する、即ち移動平均を求める点を除いて基本的に第１の実施の形態の場合と同様である。従って、この実施の形態によれば、座標値を補正することなく、位置指示器の共振回路における共振周波数の変化に拘らず、常に正確なＸ軸方向及びＹ軸方向の指示位置の座標値が検出可能となる。
【００４９】
なお、この第２の実施の形態においても図６及び図９で説明したような改良したセクタスキャン処理を行わせることができ、センス部１１の周辺部における座標値のずれを少なくすることができる。
【００５０】
【発明の効果】
以上説明したように、本発明の請求項１及び２によれば、位置指示器が位置検出方向の端付近にある場合でも、座標値算出の演算処理に用いる誘導電圧を検出する時に選択すべきループコイル以前に選択可能なループコイルを疑似的に存在するようにでき、これによって位置指示器が位置検出方向の端付近以外にある場合と同様な残留誘導電圧を生じせしめることができ、誤差の少ない座標値を求めることが可能となる。
【００５１】
また、本発明の請求項３及び４によれば、位置指示器が位置検出方向の端付近にあって座標値算出の演算処理に用いられる誘導電圧を検出する時に選択すべきループコイル以前に選択可能なループコイルが存在しないような場合に、より誤差の少ない座標値を求めることができる。
【図面の簡単な説明】
【図１】本発明の第１の実施の形態のハードウェア構成図
【図２】従来の位置検出装置における動作波形の一例を示す波形図
【図３】第１の実施の形態のソフトウェア構成を示すフローチャート
【図４】順方向及び逆方向セクタスキャンにより得られた信号の一例を示す図
【図５】ピークコイルがループコイルＣ１の場合の図４と同様な図
【図６】改良後の順方向セクタスキャン処理のフローチャート
【図７】図６の処理フローを用いた場合の図５と同様な図
【図８】電波の強度制御を付加した場合の図７と同様な図
【図９】改良後の逆方向セクタスキャン処理のフローチャート
【図１０】本発明の第２の実施の形態のハードウェア構成図
【図１１】第２の実施の形態のソフトウェア構成を示すフローチャート
【符号の説明】
１…位置指示器、２，１１…センス部、３，１２，１３…選択回路、４，１４，１５…送受切替回路、５…発振器、６…レベル検出回路、７…位相検出回路、８，１８…処理装置、１６，１７…ＸＹ切替回路。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for detecting an indicated position by a position indicator using electromagnetic induction or electromagnetic coupling and an improvement of the apparatus.
[0002]
[Prior art]
Prior to this application, the applicant exchanged radio waves between a position indicator and a sense unit in which a large number of loop coils are arranged in the position detection direction, whereby the coordinate value of the indicated position by the position indicator is obtained. Has been proposed (refer to Patent Document 1).
[0003]
Briefly describing the contents of the prior application, one loop coil is selected from a large number of loop coils, and an AC signal having a predetermined frequency is supplied thereto to transmit a radio wave, and the radio wave is provided in a position indicator. The resonance circuit receives the signal. At this time, the one loop coil receives a radio wave generated from a resonance circuit that receives energy from the radio wave, and generates an induced voltage. This is repeated for a plurality of loop coils by sequentially scanning and selecting, and the position of the resonance circuit, that is, the coordinate value of the indicated position is obtained based on the magnitude of the induced voltage generated in each loop coil.
[0004]
By the way, in this type of position detection device, in addition to the coordinate value of the designated position, information indicating a state (pen down state) in which the designated position to be actually input is specified, and parameters other than the coordinate value according to the software, for example, the line There is a demand to input information for changing the thickness, the designated position or the hue or density (brightness) of the designated area together with the coordinate value of the designated position.
[0005]
Therefore, in the above-mentioned prior application, by connecting another capacitor via a manual switch to the coil and capacitor constituting the resonance circuit, the resonance frequency is changed slightly according to the operation on the switch, A slight change amount of the resonance frequency is detected as a change amount of the phase angle, and the various information described above (hereinafter referred to as operation information) is obtained.
[0006]
[Patent Document 1]
JP-A-63-70326
[0007]
[Problems to be solved by the invention]
FIG. 2 shows an example of operation waveforms in the position detection device of the prior application. ₁ , T ₂ , …… T ₆ Is the radio wave transmission period, R ₁ , R ₂ , …… R ₆ Is the radio wave reception period, (A) is the transmission radio wave on the sense unit side, (B) and (B) 'are the induced voltages in the resonance circuit, (C) and (C) are received signals on the sense unit side, D) and (d) ′ are signals obtained by rectifying the received signal and removing high-frequency components (hereinafter referred to as reception induced voltage).
[0008]
Here, the transmission period T ₁ And reception period R ₁ Select one loop coil for the transmission period T ₂ And reception period R ₂ A loop coil adjacent to the one loop coil is selected, and thereafter, similarly, the adjacent loop coils are sequentially scanned and selected in one direction, particularly in the transmission period T. _Three And reception period R _Three Fig. 6 shows an example in which a position indicator, that is, a resonance circuit exists just above the selected loop coil.
[0009]
By the way, the induced voltage generated in the resonance circuit by the radio wave transmitted from one loop coil during one transmission period gradually decreases during the reception period when the transmission radio wave is stopped. Not all the radio waves are lost before the radio wave is transmitted from the loop coil, but the transmission / reception of radio waves by the next loop coil is affected.
[0010]
That is, when the frequency of the transmission radio wave coincides with the resonance frequency of the resonance circuit, as shown in (b) and (c) of FIG. Since the phase with the radio wave substantially matches and these are added to each other, each reception period R ₁ , R ₂ , …… R ₆ Received induced voltage (d) level V obtained corresponding to ₁ , V ₂ , …… V ₆ As a whole, the level near the traveling direction of the scanning and selection of the loop coil (on the right side in FIG. 2) becomes larger than when there is no such influence.
[0011]
On the other hand, when the resonance frequency in the resonance circuit is changed by the operation of the above-described switch or the like, the phase of the induced voltage in the resonance circuit during the reception period as shown in (b) 'and (c)' in FIG. Therefore, the phase of the residual induced voltage in the resonance circuit and the transmitted radio wave in the next transmission period do not always match, and they may cancel each other. As a result, each reception period R ₁ , R ₂ , …… R ₆ Received induced voltage (d) 'level V obtained corresponding to ₁ ', V ₂ ', …… V ₆ 'Indicates various changes according to the amount of phase shift (phase angle change amount).
[0012]
Since the coordinate value of the indicated position by the position indicator is usually obtained by calculating by substituting the level of two to four received induced voltages including the highest received induced voltage into a predetermined formula, The change in the level of the received induced voltage due to the residual induced voltage in the resonant circuit causes an error in the coordinate value of the indicated position.
[0013]
In particular, when the position indicator is near the end in the position detection direction and there is no selectable loop coil before the loop coil that generates the reception induction voltage used in the calculation process, that is, the residual induction in the resonance circuit. When there is no voltage, for the same reason as described above, the reception induction used for the calculation processing is compared with the case where the position indicator is located near the end in the position detection direction, that is, when there is a residual induced voltage in the resonance circuit. There has been a problem that the voltage level is lowered, which causes an error in the coordinate value of the indicated position.
[0014]
Note that the above-described problem of the deviation of the coordinate value due to the residual induced voltage is not limited to the residual induced voltage in the resonance circuit, but the residual induced voltage in the detection circuit of the received signal, for example, the residual in the filter that removes high frequency components from the received signal. Since this problem is also caused by the induced voltage, it is not limited to the position detection device using the position indicator having the resonance circuit as in the previous application, and the induced voltage detected at that time by scanning and selecting a number of loop coils. This is a problem that can occur in common in all position detection devices of the type that obtains the coordinate value of the indicated position from the position.
[0015]
SUMMARY OF THE INVENTION An object of the present invention is to provide a position detection method and apparatus that do not cause an error in coordinate values due to an induced voltage remaining in a circuit in the periphery of a coordinate detection range.
[0016]
[Means for Solving the Problems]
In order to achieve the above-mentioned object, in the present invention, radio waves are transmitted and received between a sense unit composed of a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least the coil, and the obtained induced voltage is used. In the position detection method for obtaining the coordinate value of the position indicated by the position indicator, initially, one of the plurality of loop coils is switched and selected to repeat transmission and reception of radio waves. It is determined whether the position indicator is within the effective reading height from the maximum induced voltage. If the position indicator is not within the effective reading height as a result of the determination, the same operation is repeated, and the determination is made. As a result, when the position indicator is within the effective reading height, a predetermined number of loop coils centered on the loop coil when the maximum induced voltage is detected among the many loop coils. Toward the other one of the loop coils from one end of the position detection direction for Le In order Select next switching and repeat transmission / reception of radio waves, and detect the coordinate value of the indicated position by the position indicator based on the obtained at least two induced voltages Alternatively, one loop coil is sequentially switched from the other end to the one end in the position detection direction with respect to a predetermined number of loop coils centering on the loop coil when the maximum induced voltage is detected among the many loop coils. Select and repeat the transmission and reception of radio waves, and detect the coordinate value of the indicated position by the position indicator based on the obtained at least two induced voltages In the position detection method, the predetermined number of loop coils are directed from one end to the other end in the position detection direction. In order When the next switching is selected, whether or not the number of selectable loop coils is sufficient for the predetermined number is determined based on whether the loop coil when the maximum induced voltage is detected is in the position detection direction. End Accordingly, it is determined whether or not the number of loop coils is less than ½ of the predetermined number, and the determination is not sufficient only when the number of selectable loop coils is not sufficient for the predetermined number. If the position of the loop coil in the position detection direction is determined based on the assumption that the loop coil exists and the loop coil when the maximum induced voltage is detected, End Select before selecting loop coil Alternatively, when the predetermined number of loop coils are sequentially switched and selected from the other end to the one end in the position detection direction, it is determined whether or not the number of selectable loop coils is sufficient for the predetermined number. It is determined whether or not the loop coil at the time of detecting the voltage is included in the number of loop coils that is less than ½ of the predetermined number when viewed from the other end in the position detection direction. Only when the number of loop coils is less than the predetermined number, the position when the loop coil is assumed to be present and the position of the loop coil at the symmetrical position around the loop coil when the maximum induced voltage is detected Select before selecting the loop coil at the other end of Proposed position detection method and apparatus.
[0017]
According to the present invention, even when the position indicator is near the end in the position detection direction, the loop coil that can be selected before the loop coil to be selected when detecting the induced voltage used for the calculation processing of the coordinate value calculation is simulated. Thus, a residual induced voltage similar to that in the case where the position indicator is located near the end in the position detection direction can be generated, and a coordinate value with less error can be obtained.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows the hardware configuration of the first embodiment of the present invention, which is basically the same as that of the above-mentioned prior application, but is shown in a simplified form. In the figure, 1 is a position indicator, 2 is a sensing unit, 3 is a selection circuit, 4 is a transmission / reception switching circuit, 5 is an oscillator, 6 is a level detection circuit, 7 is a phase detection circuit, and 8 is a processing device.
[0019]
The position indicator 1 includes a coil, a capacitor, and a switch. When the switch is turned off, the position indicator 1 has a predetermined frequency f. ₀ Is the resonance frequency, and when the switch is on, the frequency f ₀ A slightly lower frequency, eg f ₁ A resonance circuit having a resonance frequency as a built-in is incorporated.
[0020]
The sense unit 2 includes a large number of, for example, 48 loop coils C0, C1, C2,... C47 arranged in parallel in the position detection direction (here, the X-axis direction). The selection circuit 3 selects one loop coil from the 48 loop coils of the sense unit 2, and operates based on selection information from the processing device 8. The transmission / reception switching circuit 4 alternately connects the selected one loop coil to the oscillator 5, the level detection circuit 6, and the phase detection circuit 7, and operates based on a switching signal from the processing device 8.
[0021]
The oscillator 5 has the predetermined frequency f. ₀ Is supplied to the transmission / reception switching circuit 4 via the phase detection circuit 7, the processing device 8, a low-pass filter and a current driver (not shown). The level detection circuit 6 includes a detector and the frequency f. ₀ A frequency f in a received signal which is composed of a low-pass filter having a sufficiently low cutoff frequency and is amplified by an amplifier (not shown). ₀ A DC signal having a level corresponding to the energy of the component is output. The phase detection circuit 7 includes a phase detector and the frequency f. ₀ It comprises a low-pass filter having a sufficiently low cutoff frequency, and outputs a DC signal having a level corresponding to the phase difference between the received signal amplified by an amplifier (not shown) and the reference clock.
[0022]
The processing device 8 is constituted by a known microprocessor or the like, and the frequency f ₀ The transmission / reception switching signal is generated from the reference clock and supplied to the transmission / reception switching circuit 4, the selection circuit 3 is controlled to switch the loop coil of the sensing unit 2, and the output level of the level detection circuit 6 is changed to analog / digital ( A / D) conversion, and a predetermined calculation process is executed to obtain the coordinate value of the indicated position by the position indicator 1, which is averaged as will be described later, and the output level of the phase detection circuit 7 is analog / digital. (A / D) Conversion is performed and the state of the switch in the position indicator 1 is detected.
[0023]
FIG. 3 is a flowchart of processing in the present embodiment, and the operation will be described below in accordance with this flowchart.
[0024]
First, the processing device 8 sends information for selecting the loop coil C0 of the sensing unit 2 to the selection circuit 3, and sends a signal for selecting the transmission side to the transmission / reception switching circuit 4, and the oscillator 5 is sent to the loop coil C0. F based on the reference clock of ₀ The sine wave signal of the frequency f ₀ Generate radio waves. At this time, if the position indicator 1 is placed on the sense unit 2, the radio wave excites the resonance circuit, and the frequency f ₀ Inductive voltage is generated.
[0025]
When the processing device 8 sends a signal for selecting the transmitting side to the transmission / reception switching circuit 4 for a certain period of time, the processing device 8 sends a signal for selecting the receiving side and extinguishes the radio wave generated from the loop coil C0. At this time, the induced voltage generated in the resonance circuit of the position indicator 1 is gradually attenuated according to the loss and the frequency f ₀ However, the radio wave excites the loop coil C0 described above to generate an induced voltage.
[0026]
When the processing device 8 sends a signal for selecting the receiving side to the transmission / reception switching circuit 4 for a certain period of time, the processing device 8 sends the signal for selecting the transmitting side again. Repeat 4 times. Next, the processing device 8 changes the information sent to the selection circuit 3 and switches the loop coil to be selected to C1, performs transmission / reception of the same radio wave, and subsequently sequentially scans the loop coils C2 to C47 of the sense unit 2. Select and perform transmission / reception of radio waves similar to the above (step S1).
[0027]
At this time, instead of selecting all of the loop coils C0 to C47 of the sense unit 2, the selection may be made by appropriately thinning out such as placing one or two.
[0028]
The induced voltage generated in the loop coil of the sensing unit 2 during the four reception periods described above is averaged by the band filter of the level detection circuit 6, further detected, converted into a DC signal, and sent to the processing device 8. Since the level of the DC signal is a value depending on the distance between the position indicator 1 and the loop coil, the processing device 8 determines the position by determining whether or not the maximum value is equal to or greater than a predetermined threshold value. It is determined whether or not the indicator 1 is within the effective reading height of the sense unit 2 (step S2).
[0029]
When it is determined that the position indicator 1 is within the height, the processing device 8 extracts a loop coil (hereinafter referred to as a peak coil) having a maximum value from the obtained signal for each loop coil. (Step S3), it is checked whether or not the position indicator 1 is in the effective area, and here whether or not the peak coil corresponds to the end loop coil C0 or C47 (Step S4). Here, if the position indicator 1 is outside the effective area, it is sent to another process such as detection stop or position detection by a special method. If it is determined that there is no position indicator 1 within the height, the processes of steps S1 and S2 are repeated.
[0030]
On the other hand, if the position indicator 1 is within the effective area, the processing device 6 has a predetermined number centered on the obtained peak coil (PC), for example, seven loop coils, from the smaller number to the larger number (forward direction). ) Are sequentially scanned and selected (step S5), and the seven loop coils are sequentially scanned and selected from the larger number to the smaller number (reverse direction), and the same radio waves are transmitted. Are transmitted and received (step S6). FIG. 4 shows an example of the induced voltage obtained by the processing in steps S5 and S6 when the peak coil is C3.
[0031]
When the above-described partial selection (sector scan) in the forward direction and the reverse direction of the loop coil with the peak coil as the center is completed, the processing device 8 at this time uses the induced voltage obtained from the level detection circuit 6 in the forward direction and the reverse direction. For each sector scan in the direction, a plurality of, for example, three induced voltages (e2, e3, e4 in the example of FIG. 4) are extracted in descending order (step S7) and described in the prior application based on these signals. Such well-known coordinate calculation is executed, the coordinate value of the position indicated by the position indicator 1 is obtained for each scanning / selecting direction of the loop coil, and these are averaged (step S8).
[0032]
Here, as described in the section of the prior art, the induced voltage generated in the resonance circuit by the radio wave transmitted from one loop coil does not completely disappear until the radio wave is transmitted from the next loop coil. However, the transmission / reception of radio waves by the next loop coil is affected, but the influence acts in the opposite direction when the loop coil is scanned in the forward direction and when scanned in the reverse direction.
[0033]
The residual induced voltage in the resonance circuit changes each induced voltage value corresponding to each loop coil, but the direction of the change is also opposite, so each induced voltage during forward sector scan and reverse sector scan As shown in FIG. 4, each induced voltage has a symmetrical shape.
[0034]
Further, the switch in the resonance circuit of the position indicator 1 is turned on, and the resonance frequency is f ₀ To f ₁ Even when the phase of the residual induced voltage in the resonance circuit and the phase of the next transmission radio wave do not match, and the induced voltage value corresponding to each loop coil is thereby changed, Each induced voltage and each induced voltage at the time of reverse sector scanning are just symmetrical.
[0035]
The change in each induced voltage value described above affects the calculation result of the coordinate value at the indicated position, causing a shift in the coordinate value, but the shift in the coordinate value based on each induced voltage during the forward sector scan and the reverse direction This is in the opposite direction to the shift of the coordinate value based on each induced voltage during the sector scan.
[0036]
In this embodiment, as described above, the sector scan is performed in both the forward direction and the reverse direction, and the coordinate values are calculated and averaged for each, so the above-described deviation of the coordinate values is cancelled. It is possible to always accurately detect the coordinate value of the indicated position without correcting the coordinate value and regardless of the change of the resonance frequency in the resonance circuit of the position indicator.
[0037]
The change in the resonance frequency in the above-described resonance circuit is output as a DC signal representing the change in phase by the phase detection circuit 7, and the state of the switch in the position indicator 1 is identified by the processing device 8 (step S9). .
[0038]
By the way, in the above embodiment, when the peak coil hits the loop coil C1, three signals necessary for coordinate calculation, ie, e0, e1, and e2 are obtained. However, as shown in FIG. Since there is no selectable loop coil before the coil C0, the level of the signal e0 in the loop coil C0 is the original level as described in the section of the prior art (there is a loop coil to be selected before the loop coil C0). The level). Therefore, the coordinate value based on the signal obtained by such forward sector scan includes an error. In the reverse sector scan, there is no problem because a selectable loop coil exists before the loop coil C0 (the loop coil C1 is applicable).
[0039]
FIG. 6 shows the process flow of forward sector scan with the above-described improvement. When the peak coil hits the loop coil C1, the loop coils C4 and C3 are selected before the loop coil C0 is selected, and transmission / reception of radio waves is performed. To generate signals e3 ′ and e4 ′ as shown in FIG. 7 so that there is a selectable loop coil before the loop coil C0, and the level of the signal e0 in the loop coil C0 is set. The above-mentioned error can be reduced by approaching the original level.
[0040]
Further, when selecting the loop coils C4 and C3 before selecting the loop coil C0, the error can be further reduced by controlling the intensity of the radio waves generated from the loop coils C4 and C3. That is, the signal levels in the loop coils on both sides of the peak coil, here C0 and C2, are compared. For example, as shown in FIG. 8, if the signal level in the loop coil C0 is low, the loop coil selected before the loop coil C0 is selected. Lower the current value flowing through C4 and C3 from the original value, and if the signal level in the loop coil C0 is high, increase the current value flowing through the loop coils C4 and C3 selected before the loop coil C0 from the original value, When the intensity of the radio waves generated from the loop coils C4 and C3 is made weaker or stronger, the signal levels e3 ′ and e4 ′ at that time are actually present before the loop coil C0. A similar level can be obtained, and thereby the level of the signal e0 in the loop coil C0 is further brought closer to the original level. , It is possible to further reduce the error. Instead of selecting the loop coils C3 and C4, the above-described signals e3 ′ and e4 ′ may be generated by selecting the loop coils C0 and C1 and controlling the current value thereof.
[0041]
Further, when the peak coil hits the loop coil C2, as shown in FIG. 6, by selecting the loop coil C5 and transmitting / receiving radio waves before selecting the loop coil C0, the error of the coordinate value is similar to the above. In this case, the error of the coordinate value can be further reduced by controlling the intensity of the radio wave generated from the loop coil C5. In this case, instead of selecting the loop coil C5, the loop coil C0 or the like may be selected and the current value thereof may be controlled.
[0042]
In the above embodiment, the same problem as described above also occurs when the peak coil hits the loop coil C45 or C46 and the reverse sector scan is performed. FIG. 9 shows a process flow of reverse sector scanning in which this point is improved. Basically, the same process as in FIG. 6 is executed to reduce the coordinate value error. The same is true in that the error of the coordinate value can be further reduced by controlling the intensity of the radio wave in the loop coil to be selected before the loop coil C47.
[0043]
FIG. 10 shows a hardware configuration according to the second embodiment of the present invention. Here, an example is shown in which position detection is performed in two directions orthogonal to each other in the X-axis direction and the Y-axis direction. In the figure, the same components as those of the first embodiment are denoted by the same reference numerals. That is, 5 is an oscillator, 6 is a level detection circuit, 7 is a phase detection circuit, 11 is a sense unit, 12 and 13 are selection circuits, 14 and 15 are transmission / reception switching circuits, 16 and 17 are XY switching circuits, and 18 is a processing device. It is. In order to simplify the drawing, control lines are omitted.
[0044]
The sense unit 11 includes a large number of, for example, 48 loop coils arranged in parallel in the X-axis direction, and a large number of 48 loop coils arranged in parallel in the Y-axis direction (all of which are omitted in the drawing). ing. The selection circuit 12 selects one loop coil from the 48 loop coils in the X-axis direction of the sense unit 11, and the selection circuit 13 selects one from the 48 loop coils in the Y-axis direction of the sense unit 11. Loop coils are selected, and both operate based on selection information from the processing device 18.
[0045]
The transmission / reception switching circuit 14 alternately connects the selected one loop coil in the X-axis direction to the oscillator 5, the level detection circuit 6 and the phase detection circuit 7 via the XY switching circuits 16, 17. The transmission / reception switching circuit 15 alternately connects the selected one loop coil in the Y-axis direction to the oscillator 5, the level detection circuit 6, and the phase detection circuit 7 via the XY switching circuits 16, 17. It operates based on a switching signal from the processing device 18.
[0046]
The XY switching circuit 16 has a frequency f generated by the oscillator 5. ₀ Is supplied to the transmission / reception switching circuits 14 and 15 alternately via a low-pass filter and a current driver (not shown), and operates based on the XY switching signal from the processing device 18. The XY switching circuit 17 switches one loop coil selected by the selection circuits 12 and 13 to the level detection circuit 6 and the phase detection circuit 7 alternately via the transmission / reception switching circuits 14 and 15. And operate based on an XY switching signal from the processing device 18.
[0047]
The processing device 18 is constituted by a known microprocessor or the like, and the frequency f ₀ The transmission / reception switching signal is generated from the reference clock and supplied to the transmission / reception switching circuits 14 and 15, and the selection circuits 12 and 13 and the XY switching circuits 16 and 17 are controlled to switch the loop coil of the sensing unit 11, and the level. The output level of the detection circuit 6 is subjected to analog / digital (A / D) conversion, predetermined calculation processing is executed to obtain the coordinate value of the indicated position by a position indicator (not shown), and this is averaged as described later. Furthermore, the output level of the phase detection circuit 7 is analog / digital (A / D) converted to detect the state of the switch in the position indicator.
[0048]
FIG. 11 is a flowchart of processing in the present embodiment, and the operation is that the operation for the X-axis direction loop coil and the operation for the Y-axis direction loop coil are alternately performed, and in the X-axis direction and the Y-axis direction. This is basically the same as the case of the first embodiment except that the coordinate values of the designated positions are averaged evenly in time series, that is, the moving average is obtained. Therefore, according to this embodiment, the coordinate values of the indicated positions in the X-axis direction and the Y-axis direction are always accurate regardless of the change in the resonance frequency in the resonance circuit of the position indicator without correcting the coordinate values. It can be detected.
[0049]
In the second embodiment as well, the improved sector scan processing described with reference to FIGS. 6 and 9 can be performed, and the deviation of the coordinate values in the peripheral portion of the sense unit 11 can be reduced. .
[0050]
【The invention's effect】
As described above, according to the first and second aspects of the present invention, even when the position indicator is near the end in the position detection direction, it should be selected when detecting the induced voltage used for the calculation processing of the coordinate value calculation. A loop coil that can be selected before the loop coil can exist in a pseudo manner, and this can cause a residual induced voltage similar to that in the case where the position indicator is not near the end in the position detection direction. A small number of coordinate values can be obtained.
[0051]
According to claims 3 and 4 of the present invention, the position indicator is located near the end in the position detection direction and is selected before the loop coil to be selected when detecting the induced voltage used for the calculation processing of the coordinate value calculation. When there is no possible loop coil, a coordinate value with less error can be obtained.
[Brief description of the drawings]
FIG. 1 is a hardware configuration diagram of a first embodiment of the present invention;
FIG. 2 is a waveform diagram showing an example of operation waveforms in a conventional position detection device.
FIG. 3 is a flowchart illustrating a software configuration according to the first embodiment.
FIG. 4 is a diagram illustrating an example of signals obtained by forward and backward sector scans.
FIG. 5 is a view similar to FIG. 4 when the peak coil is the loop coil C1.
FIG. 6 is a flowchart of forward sector scan processing after improvement.
7 is a view similar to FIG. 5 when the processing flow of FIG. 6 is used.
FIG. 8 is a view similar to FIG. 7 when radio wave intensity control is added.
FIG. 9 is a flowchart of reverse sector scan processing after improvement.
FIG. 10 is a hardware configuration diagram of the second embodiment of the present invention;
FIG. 11 is a flowchart illustrating a software configuration according to the second embodiment;
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Position indicator, 2,11 ... Sense part, 3, 12, 13 ... Selection circuit, 4, 14, 15 ... Transmission / reception switching circuit, 5 ... Oscillator, 6 ... Level detection circuit, 7 ... Phase detection circuit, 8, 18 ... Processing device, 16, 17 ... XY switching circuit.

Claims

A radio wave is transmitted and received between a sense unit composed of a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil, and the coordinate value of the indicated position by the position indicator is obtained from the obtained induced voltage. A position detection method to be obtained,
Initially, one loop coil is switched and selected for the multiple loop coils, and radio wave transmission / reception is repeated. Whether or not the position indicator is within the effective reading height from the maximum induced voltage among the obtained induced voltages. If the position indicator is not within the effective reading height as a result of the determination, the same operation is repeated.If the position indicator is within the effective reading height as a result of the determination, for a given number of loop coils around the loop coil at the time of detecting the maximum of the induced voltage of the loop coil of the radio wave by selecting sequential switching toward the other one of the loop coils from one end of the position detection direction repeating transmission and reception, to detect the coordinates of the position indicated by the position indicator based upon at least two induction voltages thus obtained, or the maximum induction of the multiple loop coils For a predetermined number of loop coils centered on the loop coil at the time of detecting the voltage, one loop coil is sequentially switched and selected from the other end to the other end in the position detection direction to repeat transmission and reception of radio waves, and at least obtained In the position detection method for detecting the coordinate value of the position indicated by the position indicator based on two induced voltages ,
When selecting sequential switching toward the other loop coils of said predetermined number from one end of the position detecting direction, whether the number of selectable loop coil sufficient to the predetermined number, the maximum of the induced voltage loop coils when detected is determined from whether included Te one end of the position detecting direction Lami the loop coil of the small number than 1/2 of the predetermined number, the determination result, the selectable loop coil Only when the number is less than the predetermined number, the position when it is assumed that there is an insufficient loop coil and the loop coil at the symmetrical position around the loop coil when the maximum induced voltage is detected are moved in the position detection direction. previously selected for selecting loop coils one end, or the predetermined number of loop coils from the other end of the position detection direction when sequentially switching selection towards one end, a selectable loop coil Whether the loop coil when the maximum induced voltage is detected is included in the number of loop coils less than ½ of the predetermined number when viewed from the other end in the position detection direction. It is determined whether or not, and as a result of the determination, only when the number of selectable loop coils is insufficient for the predetermined number, the position when the insufficient loop coil is assumed to exist and the maximum induced voltage are detected. A position detection method comprising: selecting a loop coil at a symmetrical position about a loop coil before selecting a loop coil at the other end in the position detection direction .

A radio wave is transmitted and received between a sense unit composed of a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil, and the coordinate value of the indicated position by the position indicator is obtained from the obtained induced voltage. A position detection device to be obtained,
Initially, one loop coil is switched and selected for the multiple loop coils, and radio wave transmission / reception is repeated. Whether or not the position indicator is within the effective reading height from the maximum induced voltage among the obtained induced voltages. If the position indicator is not within the effective reading height as a result of the determination, the same operation is repeated.If the position indicator is within the effective reading height as a result of the determination, for a given number of loop coils around the loop coil at the time of detecting the maximum of the induced voltage of the loop coil of the radio wave by selecting sequential switching toward the other one of the loop coils from one end of the position detection direction repeating transmission and reception, to detect the coordinates of the position indicated by the position indicator based upon at least two induction voltages thus obtained, or the maximum induction of the multiple loop coils For a predetermined number of loop coils centered on the loop coil at the time of detecting the voltage, one loop coil is sequentially switched and selected from the other end to the other end in the position detection direction to repeat transmission and reception of radio waves, and at least obtained In the position detection device that detects the coordinate value of the position indicated by the position indicator based on two induced voltages ,
When selecting sequential switching toward the other loop coils of said predetermined number from one end of the position detecting direction, whether the number of selectable loop coil sufficient to the predetermined number, the maximum of the induced voltage loop coils when detected is determined from whether included Te one end of the position detecting direction Lami the loop coil of the small number than 1/2 of the predetermined number, the determination result, the selectable loop coil Only when the number is less than the predetermined number, the position when it is assumed that there is an insufficient loop coil and the loop coil at the symmetrical position around the loop coil when the maximum induced voltage is detected are moved in the position detection direction. previously selected for selecting loop coils one end, or the predetermined number of loop coils from the other end of the position detection direction when sequentially switching selection towards one end, a selectable loop coil Whether the loop coil when the maximum induced voltage is detected is included in the number of loop coils less than ½ of the predetermined number when viewed from the other end in the position detection direction. It is determined whether or not, and as a result of the determination, only when the number of selectable loop coils is insufficient for the predetermined number, the position when the insufficient loop coil is assumed to exist and the maximum induced voltage are detected. A position detection apparatus comprising: a selection unit that selects a loop coil at a symmetrical position with respect to the loop coil before selecting a loop coil at the other end in the position detection direction .

A radio wave is transmitted and received between a sense unit composed of a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil, and the coordinate value of the indicated position by the position indicator is obtained from the obtained induced voltage. A position detection method to be obtained,
Initially, one loop coil is switched and selected for the multiple loop coils, and radio wave transmission / reception is repeated. Whether or not the position indicator is within the effective reading height from the maximum induced voltage among the obtained induced voltages. If the position indicator is not within the effective reading height as a result of the determination, the same operation is repeated.If the position indicator is within the effective reading height as a result of the determination, for a given number of loop coils around the loop coil at the time of detecting the maximum of the induced voltage of the loop coil of the radio wave by selecting sequential switching toward the other one of the loop coils from one end of the position detection direction repeating transmission and reception, to detect the coordinates of the position indicated by the position indicator based upon at least two induction voltages thus obtained, or the maximum induction of the multiple loop coils For a predetermined number of loop coils centered on the loop coil at the time of detecting the voltage, one loop coil is sequentially switched and selected from the other end to the other end in the position detection direction to repeat transmission and reception of radio waves, and at least obtained In the position detection method for detecting the coordinate value of the position indicated by the position indicator based on two induced voltages ,
When selecting sequential switching toward the other loop coils of said predetermined number from one end of the position detecting direction, whether the number of selectable loop coil sufficient to the predetermined number, the maximum of the induced voltage loop coils when detected is determined from whether included Te one end of the position detecting direction Lami the loop coil of the small number than 1/2 of the predetermined number, the determination result, the selectable loop coil Only when the number is less than the predetermined number, the position when it is assumed that there is an insufficient loop coil and the loop coil at the symmetrical position around the loop coil when the maximum induced voltage is detected are moved in the position detection direction. previously selected for selecting loop coils one end, or the predetermined number of loop coils from the other end of the position detection direction when sequentially switching selection towards one end, a selectable loop coil Whether the loop coil when the maximum induced voltage is detected is included in the number of loop coils less than ½ of the predetermined number when viewed from the other end in the position detection direction. It is determined whether or not, and as a result of the determination, only when the number of selectable loop coils is insufficient for the predetermined number, the position when the insufficient loop coil is assumed to exist and the maximum induced voltage are detected. Select the loop coil at the symmetrical position around the loop coil before selecting the loop coil at the other end in the position detection direction ,
The radio wave transmission intensity when the loop coil at the symmetric position is selected is changed according to the level of the induced voltage when the loop coil on both sides of the loop coil is selected when the maximum induced voltage is detected. Position detection method.

A radio wave is transmitted and received between a sense unit composed of a large number of loop coils arranged in parallel in the position detection direction and a position indicator having at least a coil, and the coordinate value of the indicated position by the position indicator is obtained from the obtained induced voltage. A position detection device to be obtained,
Initially, one loop coil is switched and selected for the multiple loop coils, and radio wave transmission / reception is repeated. Whether or not the position indicator is within the effective reading height from the maximum induced voltage among the obtained induced voltages. If the position indicator is not within the effective reading height as a result of the determination, the same operation is repeated.If the position indicator is within the effective reading height as a result of the determination, for a given number of loop coils around the loop coil at the time of detecting the maximum of the induced voltage of the loop coil of the radio wave by selecting sequential switching toward the other one of the loop coils from one end of the position detection direction repeating transmission and reception, to detect the coordinates of the position indicated by the position indicator based upon at least two induction voltages thus obtained, or the maximum induction of the multiple loop coils For a predetermined number of loop coils centered on the loop coil at the time of detecting the voltage, one loop coil is sequentially switched and selected from the other end to the other end in the position detection direction to repeat transmission and reception of radio waves, and at least obtained In the position detection device that detects the coordinate value of the position indicated by the position indicator based on two induced voltages ,
When selecting sequential switching toward the other loop coils of said predetermined number from one end of the position detecting direction, whether the number of selectable loop coil sufficient to the predetermined number, the maximum of the induced voltage loop coils when detected is determined from whether included Te one end of the position detecting direction Lami the loop coil of the small number than 1/2 of the predetermined number, the determination result, the selectable loop coil Only when the number is less than the predetermined number, the position when it is assumed that there is an insufficient loop coil and the loop coil at the symmetrical position around the loop coil when the maximum induced voltage is detected are moved in the position detection direction. previously selected for selecting loop coils one end, or the predetermined number of loop coils from the other end of the position detection direction when sequentially switching selection towards one end, a selectable loop coil Whether the loop coil when the maximum induced voltage is detected is included in the number of loop coils less than ½ of the predetermined number when viewed from the other end in the position detection direction. It is determined whether or not, and as a result of the determination, only when the number of selectable loop coils is insufficient for the predetermined number, the position when the insufficient loop coil is assumed to exist and the maximum induced voltage are detected. A selection means for selecting a loop coil at a symmetrical position around the loop coil before selecting the loop coil at the other end in the position detection direction ;
Control means for changing the transmission intensity of the radio wave when the loop coil at the symmetric position is selected according to the level of the induced voltage when the loop coil on both sides of the loop coil is selected when the maximum induced voltage is detected; A position detection device comprising: