JP3772503B2 - Temperature detection device - Google Patents
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- JP3772503B2 JP3772503B2 JP35706697A JP35706697A JP3772503B2 JP 3772503 B2 JP3772503 B2 JP 3772503B2 JP 35706697 A JP35706697 A JP 35706697A JP 35706697 A JP35706697 A JP 35706697A JP 3772503 B2 JP3772503 B2 JP 3772503B2
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Description
【０００１】
【発明の属する技術分野】
本発明は非接触で対象物の温度を検出する温度検出装置に関し、特に赤外線の入光と遮光を制御する遮光板に関するものである。
【０００２】
【従来の技術】
従来より非接触で対象物の温度を検出する温度検出装置として焦電型赤外線検出器を用いたものにおいては、赤外線検出器に入射する赤外光の入光と遮光を切り替える遮光板が設けられている。この遮光板は例えば金属板のように赤外線を透過しない材料で構成し、その端部を直流モータや交流モータの回転軸に取り付け回転駆動させ、赤外線検出器に至る赤外光の入光と遮光を繰り返し断続させるという方法がある。即ち図６に示すように半
円弧状の遮光板１を直流または交流モータ２の回転軸に取り付けて矢印の方向に回転駆動することで赤外線検出器３に入射する赤外光を断続する。
【０００３】
またパルスモータを回転駆動源として所定周期でパルス印加し、所定角度を例えば正転と反転を繰り返すことで赤外光を断続させる方法もある。例えば特開平７−２８０６５２号公報に示す温度測定装置の例を図７を参照しながら説明する。チョッパ（遮光板）１はパルスモータと同様の原理による駆動源である水晶時計ムーブメント４により往復運動するように駆動され、赤外線検出器３に至る赤外光を断続する。水晶時計ムーブメント４は永久磁石５と、コア６とコイル７を含み、永久磁石５にはチョッパ１の端部を取り付けている。コイル７は第１および第２の入力端子８、９にパルス入力を受け取り、このパルス入力に応答して永久磁石５が回動し、チョッパ１が矢印に示すように往復運動する。
【０００４】
【発明が解決しようとする課題】
しかしながら、直流モータを駆動源として遮光板を回転させる上記従来例の場合には入光時間、遮光時間のばらつきにより、温度測定精度が低いという課題がある。直流モータは一般に電源電圧の変動等の原因で回転数が変動する。回転数が変動すれば入光、遮光の周期が変わり、この周期の変動により赤外線検出器の出力も変動して正確な温度検出ができない。回転数を安定させるためには、フォトインタラプタ等の回転数を検出する手段と電源電圧を調整する手段を設け、フィードバック制御を行うような複雑な制御回路が必要となる。
【０００５】
また交流モータを駆動源とした場合には、商用電源のように比較的安定した周波数のもとでは直流モータより回転数を安定させ易いが、商用電源のような交流電源を必要とするという課題がある。これは携帯型の放射温度計や放射体温計のように電池電源で構成する場合には直流電源しかなく、安定した周波数の交流電源を作るための複雑な回路が必要となり実現が困難である。
【０００６】
また水晶時計ムーブメントやパルスモータを駆動源とした場合にはマイクロプロセッサ等のデジタル信号を基に駆動するので、入光、遮光の周期は高い精度で断続できるが、遮光板が揺動しながら停止するために入光、遮光を精度よく切り替えることが困難であるという課題がある。即ちこれら駆動源は磁力による吸引力と反発力のバランスで停止し、磁力の極性を変えることで駆動するものであるから、停止の瞬間に遮光板は揺動しながら吸引力と反発力をバランスさせて停止するという特性がある。
【０００７】
図８にパルスモータの挙動の特性を示す。横軸は経過時間であり、（ａ）は駆動パルスで一定周期ｔ、デューティ５０％でＣＷ（時計方向）とＣＣＷ（反時計方向）のパルスを交互に出力している。（ｂ）がパルスモータの回転軸の回転角度で図のように停止位置に到達する時点でオーバーシュートを起こし、その後アンダーシュートを起こし、その振幅は小さくなりながら停止位置で安定する。
【０００８】
パルスモータや水晶時計ムーブメントは一般に図８に示すような挙動の特性を持つものであるために、これらを遮光板の駆動源として赤外光を断続すると、入光から遮光、または遮光から入光に切り替わる瞬間に非常に短い間隔で入光と遮光が切り替わる状況が発生し、そのために赤外線検出器の出力は不安定になり、温度検出の正確さを欠くという課題がある。この課題を回避するためには、揺動の最大位置であるΔθに対して十分大きい遮光板の形状にする方法があるが、この場合には温度検出装置自体も大型化してしまうという課題がある。
【０００９】
【課題を解決するための手段】
本発明は上記課題を解決するために、被測定物が放射する赤外線を検出する赤外線検出
器と、前記赤外線検出器に入射する赤外線を遮光する遮光板と、前記赤外線検出器と前記遮光板の間に設け、前記赤外線検出器の視野を限定する視野限定手段と、前記遮光板を駆動する直流モータと、前記遮光板の停止位置を決めるストッパと、前記直流モータを制御する制御手段と、前記赤外線検出器の出力を基に被測定物の温度を換算する温度換算手段とを有し、前記遮光板は前記赤外線検出器の遮光位置における視野より大きい構成とし、前記制御手段は前記直流モータの回転方向を交互に反転させて前記赤外線検出器に至る赤外線光路の入光と遮光を切り替える構成とした。
【００１０】
上記発明によれば、赤外線検出器が被測定物の放射する赤外線を検出し、赤外線検出器と遮光板の間に設けた視野限定手段により赤外線検出器の視野を限定し、遮光板は赤外線検出器の遮光位置における視野より大きい構成とし、直流モータで駆動する遮光板がストッパに衝突して赤外線検出器に至る赤外線光路の入光、遮光それぞれの状態で停止し、制御手段は直流モータを交互に反転させるよう駆動して入光と遮光を切り替え、赤外線検出器の出力を基に温度換算手段が被測定物の温度を換算する。そして、視野限定手段により赤外線検出器の視野を限定することにより、遮光板を小型にすることができ、ストッパにより遮光板の駆動による入光時間、遮光時間は安定し、遮光板の停止位置での揺動も起こさないので、遮光板は十分小型にしても入光と遮光の状態を安定して切り替えることができ、小型で精度の高い温度検出を行うことができる。そして、遮光板は赤外線検出器の遮光位置における視野より大きい構成とするので、赤外線検出器の入光と遮光の状態における出力の差が大きくなり、さらに温度検出の精度を向上させることができる。
【００１１】
【発明の実施の形態】
本発明は、被測定物が放射する赤外線を検出する赤外線検出器と、前記赤外線検出器に入射する赤外線を遮光する遮光板と、前記赤外線検出器と前記遮光板の間に設け、前記赤外線検出器の視野を限定する視野限定手段と、前記遮光板を駆動する直流モータと、前記遮光板の停止位置を決めるストッパと、前記直流モータを制御する制御手段と、前記赤外線検出器の出力を基に被測定物の温度を換算する温度換算手段とを有し、前記遮光板は前記赤外線検出器の遮光位置における視野より大きい構成とし、前記ストッパは、前記遮光板の遮光状態における停止位置から入光開始状態までの移動角度と、前記遮光板の入光状態における停止位置から遮光開始状態までの移動角度とが等しくなる位置に設け、前記制御手段は前記直流モータの回転方向を交互に反転させる信号を等間隔で出力して前記赤外線検出器に至る赤外線光路の入光と遮光を切り替え、前記温度換算手段は前記赤外線検出器の出力信号から離散フーリエ変換により前記直流モータの回転方向を交互に反転させる周波数と等しい周波数の信号成分を算出するフーリエ変換手段を有し、前記フーリエ変換手段の出力を基に被測定物の温度を換算する構成とした。
【００１２】
そして、赤外線検出器が被測定物の放射する赤外線を検出し、赤外線検出器と遮光板の間に設けた視野限定手段により赤外線検出器の視野を限定し、遮光板は赤外線検出器の遮光位置における視野より大きい構成とし、遮光板の遮光状態における停止位置から入光開始状態までの移動角度と、遮光板の入光状態における停止位置から遮光開始状態までの移動角度とが等しくなる位置にストッパを設け、制御手段は遮光版を駆動する直流モータの回転方向を交互に反転させる信号を等間隔で出力して、遮光板がストッパに衝突して赤外線検出器に至る赤外線光路の入光、遮光それぞれの状態で停止し、制御手段は直流モータを交互に反転させるよう駆動して入光と遮光を切り替え、温度換算手段は赤外線検出器の出力信号から離散フーリエ変換により直流モータの回転方向を交互に反転させる周波数と等しい周波数の信号成分を算出するフーリエ変換手段の出力を基に温度換算手段が被測定物の温度を換算する。そして、視野限定手段により赤外線検出器の視野を限定することにより、遮光板を小型にすることができ、ストッパにより遮光板の遮光状態における停止位置から入光開始状態までの移動角度と、遮光板の入光状態における停止位置から遮光開始状態までの移動角度とが等しくなり、制御手段は直流モータの回転方向を交互に反転させ
る信号を等間隔で出力するので、遮光板の停止位置での揺動も起こさないので、遮光板は十分小型にしても入光と遮光の状態を安定して切り替えることができ、小型で精度の高い温度検出を行うことができる。そして、遮光板は赤外線検出器の遮光位置における視野より大きい構成とするので、赤外線検出器の入光と遮光の状態における出力の差が大きくなり、さらに温度検出の精度を向上させることができる。そして、フーリエ変換手段が、離散フーリエ変換により直流モータの回転方向を交互に反転させる周波数と等しい周波数の信号成分を算出するので、信号以外のノイズ成分を除去でき、更に入光時間と遮光時間が等しいので離散フーリエ変換では除去しきれない高次の高調波ノイズ成分をほとんど発生させず、精度の高い温度検出を行うことができる。
【００１３】
また、視野限定手段は表面を少なくともその内面を低反射率としたものである。
【００１４】
そして、視野限定手段からの赤外線の反射を押さえることができ、視野限定手段で反射した赤外線が赤外線検出器に入射することがなくなるので、赤外線検出器の視野を確実に限定することができ、小型で精度の高い温度検出を行うことができる。
【００１５】
また、遮光板は円形形状とするものである。
そして、遮光板を円形形状としたので、遮光板を小型にすることができる。
【００１６】
【実施例】
（実施例１）
以下、本発明の実施例１を図１〜図３を参照しながら説明する。図１は本発明の温度検出装置を体温計に搭載した応用例の構成ブロック図である。また図２は遮光板部の要部拡大図である。また図３は動作を説明するタイミングチャート図である。
【００１７】
一般に表面温度を計測する体温計としては、鼓膜や口腔、肛門など外気に接触しにくい部分の温度を計測することでほぼ体温を計測できる。特に鼓膜は体温を制御する視床下部が近いこともあり、体温計測として適切な場所として知られている。図１において１０は温度を測定すべき被測定物で例えば鼓膜である。１１は耳孔に挿入するプローブで先端にいくに従って径を細くして耳孔に挿入しやすい形状としている。遮光板１は赤外線検出器３に対面する面を鏡面とし、継手１２を介して直流モータ２に取り付けられており、直流モータ２により継手１２がストッパ１３に衝突しながら往復回転駆動し、遮光板１は赤外線検出器３に至る赤外線の入光、遮光状態の切り替えを繰り返し断続する。赤外線検出器３は焦電型であり、感知する赤外線量の微分値に相関を持って出力が変化する。１４は遮光板１と赤外線検出器３の間に設けた視野限定手段で、赤外線が通過する小孔１５を持ち、少なくとも内面に黒色化塗装などの処理をして赤外線に対して低反射率とした筐体で構成している。
【００１８】
上記構成において、遮光板１が入光状態にある時、図1中の点線で光線を示す
ように、小孔１５を通過して赤外線検出器３に入射する赤外線は、プローブ１１の先端開口部を通過した赤外線のみであり、例えばプローブ１１の内面から放射され、小孔１５を通過した赤外線は視野限定手段１４の内面で吸収され赤外線検出器３には入射しない。従って、視野限定手段１４により赤外線検出器３に入射する赤外線の視野を限定し、さらに、視野限定手段１４の内面を低反射率にすることで、赤外線検出器の視野を確実に限定することができるので、遮光板１を小型にすることができる。
【００１９】
一方、遮光板１が遮光状態にある時は、赤外線検出器３自身が放射する赤外線が遮光板１の鏡面で反射され、視野限定手段１４の小孔１５を通過して赤外線検出器３に入光する。
【００２０】
ここで、視野限定手段１４の内面から放射される赤外線は遮光板１による入光と遮光の状態の変化にかかわらず赤外線検出器３に入射するので、赤外線検出器３の出力は視野限定手段１４の内面から放射される赤外線については相殺される。
【００２１】
従って、赤外線検出器３は、遮光板１の断続動作により鼓膜１０と赤外線検出器３の温度差に相関のある値を出力する。
【００２２】
また、赤外線検出器３の近傍には赤外線検出器３の温度を検知するための温度センサ１６を配設している。温度センサ１６は一般周知のサーミスタによるものである。赤外線検出器３の出力は増幅器１７で増幅し、増幅器１７で増幅した出力電圧と温度センサ１６の出力電圧はＡＤ変換器１８でデジタル化する。１９は温度換算手段でＡＤ変換器１８の出力を基に鼓膜１０の温度換算を行う。赤外線検出器３の出力は遮光板１の断続動作により交流波形となり、その振幅は鼓膜１０の温度と赤外線検出器３の温度の４乗の差に比例する。温度換算手段１９はこの関係に基づき鼓膜１０の温度換算を行い表示手段２０で表示する。
【００２３】
また、２１は直流モータ２の駆動制御を行う制御手段で、遮光状態から入光状態に切り替える正電力供給手段２２と、入光状態から遮光状態に切り替える負電力供給手段２３より成る。更に正電力供給手段２２は遮光板１を駆動する電力を供給する初期電力供給手段２２ａと、遮光板１をストッパ１３の位置に保持する電力を供給する減少電力供給手段２２ｂより成り、負電力供給手段２３も遮光板１を駆動する電力を供給する初期電力供給手段２３ａと、遮光板１をストッパ１３の位置に保持する電力を供給する減少電力供給手段２３ｂより成る。
【００２４】
次に、図２を用いて遮光板部の構成について詳しく説明する。図２において、遮光板１が遮光状態で停止している状態を実線で示し、入光状態で停止している状態を破線で示している。
【００２５】
赤外線を遮光する遮光板１は円形形状であり、継手１２によって直流モータ２のシャフト２４に固定されている。２５は視野限定手段１３によって限定された赤外線検出器の遮光位置における視野を表しており、遮光板１は視野２５より大きい構成とする。遮光板１を円形形状とすることにより、角がなくなり、小型にすることができる。また、遮光板１を視野２５より大きくすることにより、赤外線検出器３に入射する赤外線量の入光状態と遮光状態の差を大きくすることができる。即ち、赤外線検出器３の出力である交流波形の振幅が大きくなるため、Ｓ／Ｎが向上し、温度検出精度を向上させることができる。
【００２６】
また、ストッパ１３は、遮光板１が遮光状態で停止するときに継手１２が接する遮光停止部１３ａと、入光状態で停止するときに接する入光停止部１３ｂとからなっており、遮光停止部１３ａ及び入光停止部１３ｂは、遮光板１の遮光状態における停止位置から入光開始状態までの移動角度θ１と、遮光板の入光状態における停止位置から遮光開始状態までの移動角度θ２とが等しくなる位置に設ける。上記構成で直流モータ２が正転、反転を繰り返すと遮光板１はストッパ１３の入光停止部１３ａと遮光停止部１３ｂに衝突して停止し、遮光板１は停止時の揺動を起こさないので、遮光板は十分小型にしても入光と遮光の状態を安定して切り替えることができ、小型で精度の高い温度検出を行うことができる。
【００２７】
次に、図３を用いて制御手段２１の具体的動作を説明する。図３の直流モータ２への供給電圧を示す図において、ｔ１の期間は遮光板１を入光状態に駆動し入光状態で静止させる正電力供給期間で、正電力供給手段２２により電力供給する。ｔ２の期間は遮光板１を遮光状態に駆動し遮光状態で静止させる負電力供給期間で、負電力供給手段２３で電力供
給する。
【００２８】
正電力供給期間の中でｔ１ａは初期電力供給期間で、遮光板１を入光状態に駆動するために初期電力供給手段２２ａにより電力供給を行い、ｔ１ｂは減少電力供給期間で、遮光板１をストッパ１３の入光停止部１３ｂの位置に保持しておくために減少電力供給手段２２ｂにより間欠的に電力供給を行う。同様に負電力供給期間の中でｔ２ａは初期電力供給期間で、遮光板１を遮光状態に駆動するために初期電力供給手段２３ａにより電力供給を行い、ｔ２ｂは減少電力供給期間で、遮光板１を遮光停止部１３ａの位置に保持しておくために減少電力供給手段２３ｂにより間欠的に電力供給を行う。
【００２９】
正電力供給期間ｔ１と負電力供給期間ｔ２とは同じ時間であり、制御手段２１は直流モータ２の回転方向を等間隔で交互に反転させている。そして、遮光板１の駆動により、図３に示すように赤外線の入光と遮光とが繰り返される。ｔ１ｃは、図２で示したように遮光板１が遮光状態における停止位置から入光を開始するまでの移動角度θ１を移動する時間であり、ｔ１ｄは入光を開始してから完全に入光状態となるまでの移動角度θ０を移動する時間である。そして、ｔ１ｅは、さらにそこから移動してストッパ１３の遮光停止部１３ｂに衝突して停止している時間である。また同様に、ｔ２ｃは遮光板１が入光状態における停止位置から遮光を開始するまでの移動角度θ２を移動する時間であり、ｔ２ｄは遮光を開始してから完全に遮光状態となるまでの移動角度θ０を移動する時間である。そして、ｔ２ｅは、さらにそこから移動してストッパ１３の入光停止部１３ａに衝突して停止している時間である。今、移動角度θ１とθ２とが等しくなるようにストッパ１３を設けたことによりｔ１ｃとｔ２ｃが等しい。また、移動角度θ０を移動する時間であるｔ１ｄとｔ２ｄも等しく、さらに、ｔ１とｔ２が等しくなるよう制御しているので、赤外線の入光時間ｔ１ｆと遮光時間ｔ２ｆとを等しくすることができる。
【００３０】
従って赤外線検出器３の出力感度（振幅Ｖ）を大きく得ることができる。即ち、赤外線検出器３の出力が過渡的に変化する時間内においては入光と遮光の時間が等しくなければ出力感度は短い方の時間で規制される性質がある。従って、入光時間と遮光時間を等しくすることで、最も効率良く出力感度を得ることができ、精度の高い温度検出を行うことができる。
【００３１】
なお、上記構成において、屈折レンズや凹面鏡などの集光手段を用いても良く、その場合には視野限定手段１４の小孔１５を大きくしてもプローブ１１を赤外線検出器３の視野に入らないようにでき、赤外線検出器３に入射する有効な赤外線量を増大させ、更にＳ／Ｎを向上させ温度検出精度を高める効果がある。
【００３２】
また、減少電力供給手段２２ｂ、２３ｂは間欠的に電力供給を行うものとしたがこれは電力供給回路構成を簡単にできる効果があるが、本発明を拘束するものではない。例えば、一定電力で初期電力供給期間より少ない電力供給を行ってもよいし、ｔ１、ｔ２が十分短ければ電力供給を休止してもよい。それは遮光板１がストッパ１３の遮光停止部１３ａまたは入光停止部１３ｂからずれる要因として人の手の振動が考えられるが、ｔ１、ｔ２が十分短く例えば０．１秒未満のような時間であれば、人の手の振動周期の方が十分長いので遮光板１はほとんどずれないからである。
【００３３】
（実施例２）
本発明の実施例２を図４、図５を参照しながら説明する。図４は本発明の温度換算手段の構成ブロック図である。また図５は赤外線検出器の出力のサンプリングのタイミングチャート図である。なお、実施例１と同様の構成要素には同じ番号を付けた。
【００３４】
図４において、温度換算手段１９は、赤外線検出器３の出力信号から離散フーリエ変換
により直流モータ２の回転方向を交互に反転させる周波数と等しい周波数の信号成分を算出するフーリエ変換手段２６を有している。そして、フーリエ変換手段２６は正弦関数の値として定まる複数の定数値を記憶している正弦値記憶手段２７と、余弦関数の値として定まる複数の定数値を記憶している余弦値記憶手段２８と、赤外線検出器３の出力と正弦値記憶手段２７及び余弦値記憶手段２８の出力を基にフーリエ係数を算出するフーリエ係数算出手段２９と、フーリエ係数算出手段２９の出力を基に赤外線検出器３の出力の信号成分の振幅に比例する振幅相関値を算出する振幅算出手段３０を有している。
【００３５】
図５において、Ｖ１、Ｖ２、Ｖ３．．．Ｖｎは、赤外線検出器３、増幅器１７、ＡＤ変換器１８を介して時系列に温度換算手段１９に入力されるデジタル値を示し、遮光板１を入光状態に駆動し入光状態で静止させる正電力供給期間ｔ１と遮光板１を遮光状態に駆動し遮光状態で静止させる負電力供給期間ｔ２との合計時間である基本周期Ｔの間に、サンプリング周期ｔ０時間ごとにｎ回サンプリングして得られる値である。
【００３６】
ここで、正電力供給期間ｔ１と負電力供給期間ｔ２とは同じ時間であり、制御手段２１は直流モータ２の回転方向を等間隔で交互に反転させている。また、遮光板１の構成は実施例１の図２で示したように、遮光板１の遮光状態における停止位置から入光開始状態までの移動角度θ１と、遮光板１の入光状態における停止位置から遮光開始状態までの移動角度θ２とが等しくなる位置にストッパ１３を設けている。即ち、遮光板１による赤外線の入光と遮光の時間が等しくなる。
【００３７】
再び図４にもどって、温度換算手段１９の動作について説明する。
【００３８】
正弦値記憶手段２７は、（数１）の正弦関数により定まる複数の値ＫＳ１、ＫＳ２、ＫＳ３、．．．ＫＳｎを記憶している。
【００３９】
【数１】
【００４０】
また、余弦値記憶手段２８は、（数２）の余弦関数により定まる複数の値ＫC１、ＫC２、ＫC３、．．．ＫCｎを記憶している。
【００４１】
【数２】
【００４２】
ここで、ｎは先に示したサンプリングの回数ｎと同じ値である。
【００４３】
また、フーリエ係数算出手段２９は、（数３）で示されるように、時系列のデジタル値Ｖ１、Ｖ２、Ｖ３．．．Ｖｎと正弦値記憶手段２７に記憶されている値ＫＳ１、ＫＳ２、
ＫＳ３、．．．ＫＳｎとのそれぞれの積の和Ｖsinと、（数４
）で示されるように、時系列のデジタル値Ｖ１、Ｖ２、Ｖ３．．．Ｖｎと余弦値記憶手段２８に記憶されている値ＫC１、ＫC２、ＫC３、．．．ＫCｎとのそれぞれの積の和Ｖcosとを算出する。
【００４４】
【数３】
【００４５】
【数４】
【００４６】
そして、振幅算出手段３０が（数５）に基づき振幅相関値Ｖｆを算出する。
【００４７】
【数５】
【００４８】
このようにして、フーリエ変換手段２６は赤外線検出器３の出力信号から離散フーリエ変換により直流モータ２の回転方向を交互に反転させる周波数と等しい周波数の信号成分である振幅相関値Ｖｆを算出する。
【００４９】
この振幅相関値Ｖｆは赤外線検出器３の出力の信号成分の振幅Ｖに比例した値であり、鼓膜１０の温度と赤外線検出器３の温度の４乗の差に比例している。温度換算手段１９はこの関係に基づき鼓膜１０の温度換算を行う。
【００５０】
従って、フーリエ変換手段２６が、離散フーリエ変換により直流モータ２の回転方向を交互に反転させる周波数と等しい周波数の信号成分を算出することにより、基本周波数の整数倍の高調波のノイズ成分を除去することができる。
【００５１】
しかし、遮光板１による赤外線の入光と遮光の時間が等しくなければ、赤外線検出器３の出力波形には高次の高調波成分が多く含まれる。離散フーリエ変換で除去することができる高調波は、サンプリング周期ｔ０の２倍の周期の高調波、即ち、サンプリング周波数の２分の１の高調波までである。従って、高次の高調波成分を除去するにはサンプリング
周期ｔ０を十分に短くしなければならない。しかし、メモリや処理速度からサンプリング周期を短くするには限界があるため、高性能のアナログフィルタ回路が必要となる。
【００５２】
遮光板１による赤外線の入光と遮光の時間が等しければ、赤外線検出器３の出力波形含まれる高次の高調波成分が少ないので、実用的なサンプリング周期で十分高調波ノイズ成分を除去することができ、精度の高い温度検出を行うことができる。
【００５３】
なお、実施例２において、温度換算手段１９は遮光板１の入光、遮光の１周期Ｔの期間に得られるＶ１〜Ｖｎに基づき離散フーリエ変換の処理を行ったが、複数周期、即ちＴの整数倍の期間に得られる複数のＶ１〜Ｖｎに基づき、Ｖ１の合計値、Ｖ２の合計値、・・・Ｖｎの合計を求めて離散フーリエ変換の処理を行っても良く、そうすることでランダム性のノイズ成分が除去でき更に精度の高い温度検出が可能となる。
【００５４】
なお、実施例１及び実施例２では、本発明の温度検出装置を鼓膜の温度を非接触で計測する携帯型の体温計に搭載した応用例として説明を行ってきたが、これは本発明を限定するものでなく、例えば機器に組み込み非接触で温度を検出し制御する電子レンジやエアコンなどに応用してもよく同様の効果を得ることができる。
【００５５】
【発明の効果】
以上説明したように本発明の温度検出器は以下の効果を有する。
【００５６】
（１）視野限定手段により赤外線検出器の視野を限定することにより、遮光板を小型にすることができ、ストッパにより遮光板の駆動による入光時間、遮光時間は安定し、遮光板の停止位置での揺動も起こさないので、遮光板は十分小型にしても入光と遮光の状態を安定して切り替えることができ、小型で精度の高い温度検出を行うことができる。そして、遮光板は赤外線検出器の遮光位置における視野より大きい構成とするので、赤外線検出器の入光と遮光の状態における出力の差が大きくなり、さらに温度検出の精度を向上させることができる。
【００５７】
（２）視野限定手段は少なくともその内面を低反射率としたので、視野限定手段による赤外線の反射を押さえることができ、視野限定手段で反射した赤外線が赤外線検出器に入射することがなくなるので、赤外線検出器の視野を確実に限定することができ、小型で精度の高い温度検出を行うことができる。
【００５８】
（３）遮光板の遮光状態における停止位置から入光開始状態までの移動角度と、遮光板の入光状態における停止位置から遮光開始状態までの移動角度とが等しくなり、制御手段は直流モータの回転方向を交互に反転させる信号を等間隔で出力するので、遮光板の駆動による赤外線の入光時間と遮光時間とが等しくなり、
赤外線検出器の高出力を得ることができ、精度の高い温度検出を行うことができる。
【００５９】
（４）フーリエ変換手段が、離散フーリエ変換により直流モータの回転方向を交互に反転させる周波数と等しい周波数の信号成分を算出するので、信号以外のノイズ成分を除去でき、更に入光時間と遮光時間が等しいので離散フーリエ変換では除去しきれない高次の高調波ノイズ成分をほとんど発生させず、精度の高い温度検出を行うことができる。
【００６０】
（５）遮光板を円形形状としたので、遮光板を小型にすることができる。
【図面の簡単な説明】
【図１】 本発明の実施例１における温度検出装置の構成ブロック図
【図２】 同温度検出装置の遮光板部の要部拡大図
【図３】 同温度検出装置の動作を説明するタイミングチャート
【図４】 本発明の実施例２の温度検出装置の温度換算手段の構成ブロック図
【図５】 同温度検出装置の赤外線検出器の出力のサンプリングのタイミングチャート
【図６】 従来例の温度検出装置の構成図
【図７】 その他の従来例の温度検出装置の構成図
【図８】 その他の従来例の動作を説明するタイミングチャート
【符号の説明】
１ 遮光板
２ 直流モータ
３ 赤外線検出器
１０ 被測定物
１３ ストッパ
１４ 視野限定手段
１９ 温度換算手段
２１ 制御手段
２５ 視野
２６ フーリエ変換手段[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a temperature detection device that detects the temperature of an object in a non-contact manner, and more particularly to a light shielding plate that controls infrared light incident and light shielding.
[0002]
[Prior art]
Conventionally, in the case of using a pyroelectric infrared detector as a temperature detection device that detects the temperature of an object in a non-contact manner, a light shielding plate that switches between incident light and light shielding of infrared light incident on the infrared detector is provided. ing. This light-shielding plate is made of a material that does not transmit infrared light, such as a metal plate, and its end is attached to a rotating shaft of a DC motor or AC motor and rotated to drive infrared light incident on the infrared detector. There is a method of repeatedly interrupting. That is, as shown in FIG.
Infrared light incident on the infrared detector 3 is interrupted by attaching the arc-shaped light shielding plate 1 to the rotating shaft of the direct current or alternating current motor 2 and rotationally driving it in the direction of the arrow.
[0003]
There is also a method of intermittently irradiating infrared light by applying pulses at a predetermined cycle using a pulse motor as a rotation drive source and repeating forward rotation and reverse rotation at a predetermined angle, for example. For example, an example of a temperature measuring device disclosed in Japanese Patent Application Laid-Open No. 7-280652 will be described with reference to FIG. A chopper (light-shielding plate) 1 is driven to reciprocate by a quartz watch movement 4 which is a drive source based on the same principle as a pulse motor, and interrupts infrared light reaching the infrared detector 3. The quartz watch movement 4 includes a permanent magnet 5, a core 6 and a coil 7, and the end of the chopper 1 is attached to the permanent magnet 5. The coil 7 receives a pulse input at the first and second input terminals 8 and 9, the permanent magnet 5 rotates in response to the pulse input, and the chopper 1 reciprocates as indicated by arrows.
[0004]
[Problems to be solved by the invention]
However, in the case of the above conventional example in which the light shielding plate is rotated using a DC motor as a drive source, there is a problem that the temperature measurement accuracy is low due to variations in the light incident time and the light shielding time. In general, the rotational speed of a DC motor fluctuates due to fluctuations in power supply voltage. If the rotation speed fluctuates, the period of incident light and light shielding changes, and the fluctuation of this period also fluctuates the output of the infrared detector, making accurate temperature detection impossible. In order to stabilize the number of revolutions, a complicated control circuit is required which provides a means for detecting the number of revolutions such as a photo interrupter and a means for adjusting the power supply voltage and performs feedback control.
[0005]
When an AC motor is used as a drive source, the rotational speed is easier to stabilize than a DC motor under a relatively stable frequency like a commercial power source, but an AC power source such as a commercial power source is required. There is. This is difficult to achieve because it requires only a DC power source in the case of a battery power source such as a portable radiation thermometer or a radiation thermometer, and requires a complicated circuit for producing an AC power source with a stable frequency.
[0006]
When a quartz watch movement or pulse motor is used as the drive source, it is driven based on a digital signal from a microprocessor, etc., so the light incident and light shielding cycles can be interrupted with high accuracy, but the light shielding plate stops while swinging. Therefore, there is a problem that it is difficult to switch between incident light and light shielding with high accuracy. In other words, these driving sources are stopped by the balance between the attractive force and the repulsive force due to the magnetic force, and are driven by changing the polarity of the magnetic force. Therefore, at the moment of stopping, the shading plate swings to balance the attractive force and the repulsive force. It has the characteristic of letting it stop.
[0007]
FIG. 8 shows the characteristics of the behavior of the pulse motor. The abscissa is the elapsed time, and (a) is a drive pulse with CW (clockwise) and CCW (counterclockwise) pulses alternately output at a constant period t and a duty of 50%. When (b) reaches the stop position as shown in the figure at the rotation angle of the rotation shaft of the pulse motor, an overshoot occurs, and then an undershoot occurs, and the amplitude becomes stable while the amplitude decreases.
[0008]
Since pulse motors and quartz watch movements generally have behavioral behaviors as shown in FIG. 8, if these are used as a light source for the light shielding plate, and infrared light is interrupted, light is shielded from incident light, or light is incident from light shielding. At the moment of switching, there is a situation in which the incident light and the light shielding are switched at a very short interval. For this reason, there is a problem that the output of the infrared detector becomes unstable and the accuracy of temperature detection is lacking. In order to avoid this problem, there is a method of making the shape of the light shielding plate sufficiently large with respect to Δθ which is the maximum position of oscillation, but in this case, there is a problem that the temperature detection device itself is also increased in size. .
[0009]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention detects infrared rays emitted from the object to be measured.
, A light shielding plate for shielding infrared rays incident on the infrared detector, a visual field limiting means for limiting the visual field of the infrared detector provided between the infrared detector and the light shielding plate, and a direct current for driving the light shielding plate A motor, a stopper for determining the stop position of the light shielding plate, a control means for controlling the DC motor, and a temperature conversion means for converting the temperature of the object to be measured based on the output of the infrared detector, The light shielding plate is configured to be larger than the visual field at the light shielding position of the infrared detector, and the control means is configured to switch light incident and light blocked in the infrared optical path to the infrared detector by alternately reversing the rotation direction of the DC motor. did.
[0010]
According to the above invention, the infrared detector detects the infrared ray emitted from the object to be measured, limits the visual field of the infrared detector by the visual field limiting means provided between the infrared detector and the light shielding plate, and the light shielding plate is the infrared detector. The structure is larger than the field of view at the light shielding position, and the light shielding plate driven by the DC motor collides with the stopper and stops in the incident and light shielding states of the infrared light path leading to the infrared detector, and the control means inverts the DC motor alternately. The light conversion is switched between incident light and light shielding, and the temperature conversion means converts the temperature of the object to be measured based on the output of the infrared detector. By limiting the field of view of the infrared detector by the field limiting means, the light shielding plate can be made smaller, and the light incident time and the light shielding time due to the driving of the light shielding plate are stabilized by the stopper, and at the stop position of the light shielding plate. Therefore, even if the light shielding plate is sufficiently small, the state of incident light and light shielding can be stably switched, and the temperature detection can be performed with a small size and high accuracy. Since the light shielding plate is configured to be larger than the visual field at the light shielding position of the infrared detector, the difference in output between the incident light and the light shielding state of the infrared detector is increased, and the temperature detection accuracy can be further improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides an infrared detector that detects infrared rays emitted from the object to be measured, a light shielding plate that shields infrared rays incident on the infrared detector, and is provided between the infrared detector and the light shielding plate. Based on the output of the infrared ray detector, the visual field limiting means for limiting the visual field, a DC motor for driving the light shielding plate, a stopper for determining a stop position of the light shielding plate, a control means for controlling the DC motor, and the infrared detector. Temperature conversion means for converting the temperature of the measurement object, the light shielding plate is configured to be larger than the visual field at the light shielding position of the infrared detector,The stopper is provided at a position where the movement angle from the stop position in the light shielding state of the light shielding plate to the light entrance start state is equal to the movement angle from the stop position in the light entrance state of the light shielding plate to the light shielding start state,The control means alternately reverses the rotation direction of the DC motor.Output at regular intervals.Switch between entering and blocking the infrared light path leading to the infrared detectorThe temperature conversion means includes Fourier transform means for calculating a signal component having a frequency equal to a frequency for alternately reversing the rotation direction of the DC motor by discrete Fourier transform from the output signal of the infrared detector, and the Fourier transform means Convert the temperature of the object to be measured based on the output ofThe configuration is as follows.
[0012]
The infrared detector detects the infrared rays emitted from the object to be measured, limits the field of view of the infrared detector by the field-of-view limiting means provided between the infrared detector and the light shielding plate, and the light shielding plate has a field of view at the light shielding position of the infrared detector. A larger configuration,A stopper is provided at a position where the movement angle from the stop position of the light shielding plate in the light shielding state to the light entrance start state is equal to the movement angle from the stop position of the light shielding plate in the light entrance state to the light shielding start state. A signal that alternately reverses the direction of rotation of the DC motor that drives the plate is output at equal intervals,The light blocking plate collides with the stopper and stops in the incoming and outgoing states of the infrared light path leading to the infrared detector, and the control means drives the DC motor to alternately reverse to switch between incoming light and light shielding, and temperature conversion The temperature conversion means calculates the temperature of the object to be measured based on the output of the Fourier transform means that calculates a signal component having a frequency equal to the frequency at which the rotation direction of the DC motor is alternately reversed by discrete Fourier transform from the output signal of the infrared detector. Is converted. Then, by limiting the field of view of the infrared detector by the field limiting means, the light shielding plate can be reduced in size, and the light blocking plate can be reduced by the stopper.The movement angle from the stop position in the light shielding state to the light entrance start state is equal to the movement angle from the stop position in the light entrance state to the light shielding start state, and the control means alternately reverses the rotation direction of the DC motor. Let
Output signals at regular intervals.Since the light-shielding plate does not swing at the stop position, even if the light-shielding plate is sufficiently small, the light incident and light-shielding states can be switched stably, and the temperature detection can be performed with a small size and high accuracy. . Since the light shielding plate is configured to be larger than the visual field at the light shielding position of the infrared detector, the difference in output between the incident light and the light shielding state of the infrared detector is increased, and the temperature detection accuracy can be further improved.Since the Fourier transform means calculates a signal component having a frequency equal to the frequency at which the rotation direction of the DC motor is alternately reversed by discrete Fourier transform, noise components other than the signal can be removed, and the light incident time and the light shielding time are further reduced. Since they are equal, high-order harmonic noise components that cannot be removed by discrete Fourier transform are hardly generated, and highly accurate temperature detection can be performed.
[0013]
Further, the visual field limiting means has at least a low reflectance on the inner surface.
[0014]
And the reflection of the infrared rays from the field limiting means can be suppressed, and the infrared rays reflected by the field limiting means do not enter the infrared detector, so the field of view of the infrared detector can be surely limited, and the small size Thus, highly accurate temperature detection can be performed.
[0015]
The light shielding plate has a circular shape.
And since the light-shielding plate was made into circular shape, a light-shielding plate can be reduced in size.
[0016]
【Example】
(Example 1)
Embodiment 1 of the present invention will be described below with reference to FIGS. FIG. 1 is a configuration block diagram of an application example in which the temperature detection device of the present invention is mounted on a thermometer. FIG. 2 is an enlarged view of a main part of the light shielding plate. FIG. 3 is a timing chart for explaining the operation.
[0017]
In general, as a thermometer for measuring the surface temperature, it is possible to measure the body temperature almost by measuring the temperature of a part of the eardrum, oral cavity, anus and the like that is difficult to contact with outside air. In particular, the eardrum is close to the hypothalamus, which controls body temperature, and is known as an appropriate place for body temperature measurement. In FIG. 1, reference numeral 10 denotes an object to be measured for temperature, for example, an eardrum. Reference numeral 11 denotes a probe inserted into the ear canal, which has a diameter that decreases toward the tip and is easily inserted into the ear canal. The light shielding plate 1 has a mirror surface as a surface facing the infrared detector 3 and is attached to the DC motor 2 via a joint 12. The DC motor 2 drives the joint 12 to reciprocate while colliding with the stopper 13. Reference numeral 1 repeats intermittently the switching between the incident and blocking states of infrared rays reaching the infrared detector 3. The infrared detector 3 is a pyroelectric type, and its output changes in correlation with the differential value of the infrared amount to be sensed. 14 is a visual field limiting means provided between the light-shielding plate 1 and the infrared detector 3 and has a small hole 15 through which infrared rays pass. It is made up of a housing.
[0018]
In the above configuration, when the light shielding plate 1 is in the light incident state, a light beam is indicated by a dotted line in FIG.
As described above, the infrared ray that passes through the small hole 15 and enters the infrared detector 3 is only the infrared ray that has passed through the tip opening of the probe 11. For example, the infrared ray that is emitted from the inner surface of the probe 11 and passes through the small hole 15. Is absorbed by the inner surface of the field limiting means 14 and does not enter the infrared detector 3. Therefore, the field of view of the infrared detector can be surely limited by limiting the field of infrared rays incident on the infrared detector 3 by the field of view limiting means 14 and further reducing the reflectance of the inner surface of the field of view limiting means 14. Since it can do, the light-shielding plate 1 can be reduced in size.
[0019]
On the other hand, when the light-shielding plate 1 is in a light-shielded state, the infrared rays emitted from the infrared detector 3 itself are reflected by the mirror surface of the light-shielding plate 1 and enter the infrared detector 3 through the small hole 15 of the field limiting means 14. Shine.
[0020]
Here, since the infrared rays radiated from the inner surface of the visual field limiting means 14 are incident on the infrared detector 3 regardless of the change of the incident light and the light shielding state by the light shielding plate 1, the output of the infrared detector 3 is the visual field limiting means 14. It cancels out about the infrared rays radiated from the inner surface.
[0021]
Therefore, the infrared detector 3 outputs a value correlated with the temperature difference between the eardrum 10 and the infrared detector 3 by the intermittent operation of the light shielding plate 1.
[0022]
A temperature sensor 16 for detecting the temperature of the infrared detector 3 is disposed in the vicinity of the infrared detector 3. The temperature sensor 16 is a generally known thermistor. The output of the infrared detector 3 is amplified by the amplifier 17, and the output voltage amplified by the amplifier 17 and the output voltage of the temperature sensor 16 are digitized by the AD converter 18. Reference numeral 19 denotes a temperature conversion means for converting the temperature of the eardrum 10 based on the output of the AD converter 18. The output of the infrared detector 3 becomes an AC waveform due to the intermittent operation of the light shielding plate 1, and its amplitude is proportional to the difference between the temperature of the eardrum 10 and the temperature of the infrared detector 3 to the fourth power. Based on this relationship, the temperature conversion means 19 converts the temperature of the eardrum 10 and displays it on the display means 20.
[0023]
Reference numeral 21 denotes control means for controlling the driving of the DC motor 2, and comprises a positive power supply means 22 for switching from the light shielding state to the light incident state and a negative power supply means 23 for switching from the light incident state to the light shielding state. Further, the positive power supply means 22 includes an initial power supply means 22a for supplying power for driving the light shielding plate 1 and a reduced power supply means 22b for supplying power for holding the light shielding plate 1 at the position of the stopper 13, and supplies negative power. The means 23 also includes an initial power supply means 23 a for supplying power for driving the light shielding plate 1 and a reduced power supply means 23 b for supplying power for holding the light shielding plate 1 at the position of the stopper 13.
[0024]
Next, the configuration of the light shielding plate will be described in detail with reference to FIG. In FIG. 2, the state where the light shielding plate 1 is stopped in the light shielding state is indicated by a solid line, and the state where the light shielding plate 1 is stopped in the light incident state is indicated by a broken line.
[0025]
The light shielding plate 1 that shields infrared rays has a circular shape and is fixed to the shaft 24 of the DC motor 2 by a joint 12. Reference numeral 25 denotes a visual field at the light shielding position of the infrared detector defined by the visual field limiting means 13, and the light shielding plate 1 is configured to be larger than the visual field 25. By making the light-shielding plate 1 into a circular shape, there are no corners and the size can be reduced. Further, by making the light shielding plate 1 larger than the visual field 25, the difference between the incident state and the light shielding state of the amount of infrared rays incident on the infrared detector 3 can be increased. That is, since the amplitude of the AC waveform that is the output of the infrared detector 3 is increased, the S / N is improved and the temperature detection accuracy can be improved.
[0026]
The stopper 13 includes a light blocking stop portion 13a that contacts the joint 12 when the light blocking plate 1 stops in the light blocking state, and a light incident stop portion 13b that contacts when the light blocking plate 1 stops in the light incident state. The movement angle θ1 from the stop position of the light shielding plate 1 in the light shielding state to the light incident start state and the movement angle θ2 from the stop position of the light shielding plate in the light incident state to the light shielding start state Provide at the same position. When the DC motor 2 repeats normal rotation and reversal in the above configuration, the light shielding plate 1 collides with the light incident stop portion 13a and the light shielding stop portion 13b of the stopper 13 and stops, and the light shielding plate 1 does not swing when stopped. Therefore, even if the light shielding plate is sufficiently small, the state of incident light and light shielding can be stably switched, and the temperature detection can be performed with a small size and high accuracy.
[0027]
Next, the specific operation of the control means 21 will be described with reference to FIG. In the diagram showing the supply voltage to the DC motor 2 in FIG. 3, the period t1 is a positive power supply period in which the light-shielding plate 1 is driven in the light incident state and is stationary in the light incident state, and power is supplied by the positive power supply means 22. . The period t2 is a negative power supply period in which the light shielding plate 1 is driven to a light shielding state and is kept stationary in the light shielding state.
To pay.
[0028]
In the positive power supply period, t1a is an initial power supply period, and power is supplied by the initial power supply means 22a in order to drive the light-shielding plate 1 to a light incident state, and t1b is a reduced power supply period, and the light-shielding plate 1 is turned on. In order to keep the light incident stop portion 13b of the stopper 13 at the position, power is intermittently supplied by the reduced power supply means 22b. Similarly, in the negative power supply period, t2a is an initial power supply period, and power is supplied by the initial power supply means 23a to drive the light shielding plate 1 in a light shielding state, and t2b is a reduced power supply period, and the light shielding plate 1 Is held intermittently by the reduced power supply means 23b in order to hold the light at the position of the light shielding stop 13a.
[0029]
The positive power supply period t1 and the negative power supply period t2 are the same time, and the control means 21 reverses the rotation direction of the DC motor 2 alternately at equal intervals. Then, by driving the light shielding plate 1, infrared light incident and light shielding are repeated as shown in FIG. 3. As shown in FIG. 2, t1c is the time for the light shielding plate 1 to move the moving angle θ1 from the stop position in the light-shielded state until light entry starts, and t1d is completely light incident after the light entry is started. This is the time to move the movement angle θ0 until the state is reached. And t1e is the time when it further moves from there and collides with the light blocking stop part 13b of the stopper 13 and stops. Similarly, t2c is the time required for the light shielding plate 1 to move the moving angle θ2 from the stop position in the light incident state until the light shielding starts, and t2d is the movement from the start of the light shielding until the light shielding plate 1 is completely in the light shielding state. This is the time for moving the angle θ0. And t2e is the time when it further moves from there and collides with the light incident stop portion 13a of the stopper 13 and stops. Now, since the stopper 13 is provided so that the movement angles θ1 and θ2 are equal, t1c and t2c are equal. Further, t1d and t2d, which are times for moving the movement angle θ0, are also equal, and furthermore, t1 and t2 are controlled to be equal, so that the infrared light incident time t1f and the light shielding time t2f can be made equal.
[0030]
Therefore, the output sensitivity (amplitude V) of the infrared detector 3 can be increased. That is, within the time when the output of the infrared detector 3 changes transiently, the output sensitivity is restricted by the shorter time unless the incident light and light shielding times are equal. Therefore, by making the light incident time and the light shielding time equal, it is possible to obtain the output sensitivity most efficiently and to perform temperature detection with high accuracy.
[0031]
In the above configuration, condensing means such as a refractive lens or a concave mirror may be used. In this case, the probe 11 does not enter the field of view of the infrared detector 3 even if the small hole 15 of the field limiting unit 14 is enlarged. The effective infrared ray amount incident on the infrared detector 3 can be increased, the S / N can be improved, and the temperature detection accuracy can be improved.
[0032]
The reduced power supply means 22b and 23b intermittently supply power, but this has the effect of simplifying the power supply circuit configuration, but does not restrict the present invention. For example, power may be supplied at a constant power and less than the initial power supply period, or power supply may be suspended if t1 and t2 are sufficiently short. This is because the vibration of the human hand is considered as a factor causing the light shielding plate 1 to deviate from the light shielding stop portion 13a or the light incident stop portion 13b of the stopper 13, but t1 and t2 are sufficiently short, for example, less than 0.1 second. For example, the vibration period of the human hand is sufficiently long, so that the light shielding plate 1 hardly deviates.
[0033]
(Example 2)
A second embodiment of the present invention will be described with reference to FIGS. FIG. 4 is a block diagram of the temperature conversion means of the present invention. FIG. 5 is a timing chart for sampling the output of the infrared detector. In addition, the same number was attached | subjected to the component similar to Example 1. FIG.
[0034]
In FIG. 4, the temperature conversion means 19 performs discrete Fourier transform from the output signal of the infrared detector 3.
Thus, there is provided Fourier transform means 26 for calculating a signal component having a frequency equal to the frequency at which the rotation direction of the DC motor 2 is alternately reversed. The Fourier transform unit 26 stores a sine value storage unit 27 that stores a plurality of constant values determined as sine function values, and a cosine value storage unit 28 that stores a plurality of constant values determined as cosine function values. The Fourier coefficient calculation means 29 for calculating the Fourier coefficient based on the output of the infrared detector 3 and the outputs of the sine value storage means 27 and the cosine value storage means 28, and the infrared detector 3 based on the output of the Fourier coefficient calculation means 29 Amplitude calculating means 30 for calculating an amplitude correlation value proportional to the amplitude of the output signal component.
[0035]
In FIG. 5, V1, V2, V3. . . Vn indicates a digital value input to the temperature conversion means 19 in time series via the infrared detector 3, the amplifier 17, and the AD converter 18, and the light shielding plate 1 is driven into the light incident state to be stopped in the light incident state. It is obtained by sampling n times every sampling period t0 during the basic period T which is the total time of the positive power supply period t1 and the negative power supply period t2 in which the light shielding plate 1 is driven in the light shielding state and is kept stationary in the light shielding state. Value.
[0036]
Here, the positive power supply period t1 and the negative power supply period t2 are the same time, and the control means 21 reverses the rotation direction of the DC motor 2 alternately at equal intervals. Further, as shown in FIG. 2 of the first embodiment, the configuration of the light shielding plate 1 is the movement angle θ1 from the stop position of the light shielding plate 1 in the light shielding state to the light incident start state, and the stop of the light shielding plate 1 in the light incident state. The stopper 13 is provided at a position where the movement angle θ2 from the position to the light shielding start state becomes equal. That is, the incident time of infrared rays by the light shielding plate 1 is equal to the time of light shielding.
[0037]
Returning to FIG. 4 again, the operation of the temperature conversion means 19 will be described.
[0038]
The sine value storage means 27 includes a plurality of values KS1, KS2, KS3,. . . KSn is stored.
[0039]
[Expression 1]
[0040]
The cosine value storage means 28 has a plurality of values KC1, KC2, KC3,. . . KCn is stored.
[0041]
[Expression 2]
[0042]
Here, n is the same value as the number of samplings n shown above.
[0043]
In addition, the Fourier coefficient calculation means 29, as shown in (Equation 3), displays time-series digital values V1, V2, V3. . . Vn and the values KS1, KS2 stored in the sine value storage means 27,
KS3,. . . The sum Vsin of each product with KSn and (Equation 4
), The time-series digital values V1, V2, V3. . . Vn and the values KC1, KC2, KC3,. . . The sum Vcos of each product with KCn is calculated.
[0044]
[Equation 3]
[0045]
[Expression 4]
[0046]
Then, the amplitude calculating means 30 calculates the amplitude correlation value Vf based on (Equation 5).
[0047]
[Equation 5]
[0048]
In this way, the Fourier transform means 26 calculates an amplitude correlation value Vf that is a signal component having a frequency equal to the frequency at which the rotation direction of the DC motor 2 is alternately reversed by discrete Fourier transform from the output signal of the infrared detector 3.
[0049]
This amplitude correlation value Vf is a value proportional to the amplitude V of the signal component of the output of the infrared detector 3 and is proportional to the difference between the temperature of the eardrum 10 and the temperature of the infrared detector 3 to the fourth power. The temperature conversion means 19 converts the temperature of the eardrum 10 based on this relationship.
[0050]
Accordingly, the Fourier transform unit 26 calculates a signal component having a frequency equal to the frequency at which the rotation direction of the DC motor 2 is alternately reversed by discrete Fourier transform, thereby removing a noise component of a harmonic that is an integral multiple of the fundamental frequency. be able to.
[0051]
However, if the incident time of infrared rays by the light shielding plate 1 is not equal to the time for shielding, the output waveform of the infrared detector 3 contains many high-order harmonic components. The harmonics that can be removed by the discrete Fourier transform are harmonics having a period that is twice the sampling period t0, that is, harmonics that are half the sampling frequency. Therefore, sampling is required to remove higher-order harmonic components.
The period t0 must be made sufficiently short. However, since there is a limit to shortening the sampling cycle due to memory and processing speed, a high-performance analog filter circuit is required.
[0052]
If the incident time of the infrared rays by the light shielding plate 1 is equal to the time of the light shielding, the higher-order harmonic components included in the output waveform of the infrared detector 3 are small, so that the harmonic noise components should be sufficiently removed with a practical sampling period. Temperature detection with high accuracy.
[0053]
In the second embodiment, the temperature conversion means 19 performs discrete Fourier transform processing based on V1 to Vn obtained in the period of one period T of incident light and light shielding of the light-shielding plate 1. Based on a plurality of V1 to Vn obtained in an integral multiple period, the total value of V1, the total value of V2,..., Vn may be obtained to perform the discrete Fourier transform process. Noise components can be removed, and more accurate temperature detection is possible.
[0054]
In the first and second embodiments, the temperature detection device according to the present invention has been described as an application example in which the temperature of the eardrum is mounted on a portable thermometer that measures the temperature of the eardrum in a non-contact manner, but this limits the present invention. For example, it may be applied to a microwave oven or an air conditioner that is incorporated in a device and detects and controls the temperature without contact, and the same effect can be obtained.
[0055]
【The invention's effect】
As described above, the temperature detector of the present invention has the following effects.
[0056]
(1) By limiting the field of view of the infrared detector by the field limiting means, the light shielding plate can be reduced in size, and the light incident time and the light shielding time by driving the light shielding plate are stabilized by the stopper. Therefore, even if the light shielding plate is sufficiently small, it is possible to stably switch between the incident light state and the light shielding state, and it is possible to perform temperature detection with high accuracy and small size. Since the light shielding plate is configured to be larger than the visual field at the light shielding position of the infrared detector, the difference in output between the incident light and the light shielding state of the infrared detector is increased, and the temperature detection accuracy can be further improved.
[0057]
(2) Since at least the inner surface of the field limiting means has a low reflectance, it is possible to suppress the reflection of infrared rays by the field limiting means, and the infrared light reflected by the field limiting means will not enter the infrared detector. The field of view of the infrared detector can be surely limited, and a small and highly accurate temperature detection can be performed.
[0058]
(3) The movement angle from the stop position in the light shielding state of the light shielding plate to the light entrance start state is equal to the movement angle from the stop position in the light entrance state of the light shielding plate to the light shielding start state. Since the signals for alternately reversing the rotation direction are output at equal intervals, the incident time of infrared light by the driving of the light shielding plate is equal to the light shielding time,
High output of the infrared detector can be obtained, and highly accurate temperature detection can be performed.
[0059]
(4) Since the Fourier transform means calculates a signal component having a frequency equal to the frequency at which the rotation direction of the DC motor is alternately reversed by discrete Fourier transform, noise components other than the signal can be removed, and the incident time and light shielding time are further reduced. Therefore, almost no high-order harmonic noise components that cannot be removed by discrete Fourier transform are generated, and highly accurate temperature detection can be performed.
[0060]
(5) Since the light shielding plate has a circular shape, the light shielding plate can be reduced in size.
[Brief description of the drawings]
FIG. 1 is a block diagram illustrating a configuration of a temperature detection device according to a first embodiment of the present invention.
FIG. 2 is an enlarged view of a main part of a light shielding plate part of the temperature detecting device.
FIG. 3 is a timing chart for explaining the operation of the temperature detection device.
FIG. 4 is a block diagram showing the configuration of temperature conversion means of the temperature detection apparatus according to the second embodiment of the present invention.
FIG. 5 is a timing chart of sampling of the output of the infrared detector of the temperature detection device.
FIG. 6 is a block diagram of a conventional temperature detection device.
FIG. 7 is a configuration diagram of another conventional temperature detection device.
FIG. 8 is a timing chart for explaining the operation of another conventional example.
[Explanation of symbols]
1 Shading plate
2 DC motor
3 Infrared detector
10 DUT
13 Stopper
14 Field of view limiting means
19 Temperature conversion means
21 Control means
25 fields of view
26 Fourier transform means
Claims (3)
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35706697A JP3772503B2 (en) | 1997-12-25 | 1997-12-25 | Temperature detection device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP35706697A JP3772503B2 (en) | 1997-12-25 | 1997-12-25 | Temperature detection device |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH11183262A JPH11183262A (en) | 1999-07-09 |
| JP3772503B2 true JP3772503B2 (en) | 2006-05-10 |
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| JP35706697A Expired - Fee Related JP3772503B2 (en) | 1997-12-25 | 1997-12-25 | Temperature detection device |
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| JP (1) | JP3772503B2 (en) |
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| KR101446674B1 (en) * | 2013-07-01 | 2014-10-06 | 현대로템 주식회사 | Method and system for measuring temperature of rotor |
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1997
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