JP3564878B2

JP3564878B2 - Biological signal detection device

Info

Publication number: JP3564878B2
Application number: JP17472396A
Authority: JP
Inventors: 拓生嶋田; 志郎竹下; 美幸河合
Original assignee: Panasonic Corp; Matsushita Electric Industrial Co Ltd
Current assignee: Panasonic Corp; Panasonic Holdings Corp
Priority date: 1996-07-04
Filing date: 1996-07-04
Publication date: 2004-09-15
Anticipated expiration: 2016-07-04
Also published as: JPH1014889A

Description

【０００１】
【発明の属する技術分野】
本発明は体重、心拍数、呼吸数、体動などの生体信号を無侵襲・無拘束に検出または表示・記録・報知する装置に関する。
【０００２】
【従来の技術】
従来のこの種の生体信号検出装置は、例えば特開昭６２−１６４４３５号公報に記載されているものが一般的であった。この装置は図１９に示されているように、ベッド１上にＦＥＴ２を用いて構成したピアス型発振回路３のホットライン側に電極４が接続され、またアースライン側に電極４と直交した電極５が接続されるもので、水晶振動子６を用いた発振回路における付加的な容量による発振周波数の変化を検出する構成となっている。さらに生体の変移に基づく周波数の変化の包絡線を検出・検波器７で抽出した後、フィルタ８でノイズ等の不要な周波数信号を除去し、記録装置９に記録したり、生体の動きが停止した時に警報を発生するものであった。
【０００３】
他の従来例としては、特開昭６３−２３８５０２号公報に記載されているようなものがある。この装置は図２０に示されているように感圧導電ゴム１０の両面に電極１１、１２を配設し、電極１１、電極１２を静電容量測定装置１３および抵抗測定装置１４に接続するものであった。つまりこれは感圧導電ゴム１０が可変コンデンサと可変抵抗からなる素子であるとみなしたものである。
【０００４】
【発明が解決しようとする課題】
しかしながら従来の生体信号検出装置では、生体に近接する電極構成や検出方式にまつわる様々な課題を有していた。
【０００５】
電極間に生じた静電容量の変化しか検出してないので、直流ないし直流に近い低周波信号が生体の動きに基づくものかどうか判別しにくい。
【０００６】
また出力信号が温湿度環境に非常に左右されやすい。
【０００７】
また電極３、４がリード線の形状なので、寝具上で簡単に位置ずれを起こしてしまい、静電容量の変化から生体の動きを再現性よく検出できない。
【０００８】
また寝具の折り目や電極の交差点で、断線しやすく、商用電源を用いている場合、万一生体と接触すると感電する危険性がある。
【０００９】
また電極３、４の機械的強度を持たせようとすれば、リード線径を相当太くしなければいけないが、そうするとベッド上の就寝者（生体）の寝心地感を損なうばかりか、電極交差点に集中して体圧がかかり、床ずれを起こす危険性がある。
【００１０】
また現在ベッド上に生体が存在しているのかいないのかがはっきりしない。特にベッド上から生体が離れた場合とベッド上で生体が死亡した場合との見分けがつかない。
【００１１】
また体重を検出することができない。
【００１２】
また電極の配置構成が複雑なので、量産化時に性能ばらつきが生じやすい。
【００１３】
電極は等間隔で離散的にしか配置されてないので、寝姿勢により信号検出性能に差が生じる。
【００１４】
出力信号の基線が動揺しやすく使用前に必ず信号レベルの初期化を必要とするという課題を有していた。
【００１５】
あるいは電極がリード線の場合、アンテナとなって外来電磁波ノイズを非常に受けやすいという課題を有していた。位置ずれも起こしやすく、生体以外の外来振動ノイズの影響を受けやすいという課題も有していた。
【００１６】
生体信号を検出するセンサ構成のうち、一般に静電容量型センサは温度特性が悪く、直流に近い低周波域で信号が変動する。また感圧特性を持つ導電ゴムやカーボンの感圧型センサは、クリープ特性などを有し、応答速度が遅い。つまり絶対圧の測定精度が悪く、動的な高周波信号を捉えることが出来ない。感圧型センサとしてひずみ抵抗素子を用いる方法もあるが、設置条件や温度などの環境によって出力信号が大きく左右される。結果的にこれまで生体信号センサは、使用者自らが測定開始の都度ゼロ点調節やゲイン調節をするか、センサの設置環境を安定させるための保護装置を別途設けるか、オンオフスイッチとしてのみ使うなどの制約を受けるという課題を有していた。
【００１７】
体圧によって再現性よく安定した抵抗値を出力させようと思うと低インピーダンスな導電体を用いなければならない。抵抗要素とコンデンサ要素の並列接続を考えた場合、その合成インピーダンスは抵抗値が小さい場合はほとんど抵抗値そのものになってしまうので、同じ素子で静電容量素子を併用しても、体動の測定は精度よく測定できないことになる。
【００１８】
【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、第１の電極と生体間に形成される第１の静電容量と、第２の電極と前記生体間に形成される第２の静電容量との直列接続静電容量に基づき生体の振動信号を測定する体動測定手段と、第１または第２の電極と第３の電極により生体の自重に伴う体圧信号を測定する体圧測定手段とを備え、さらに体動測定手段および体圧測定手段の出力によって生体の体重、心拍数、呼吸数、活動量、生命状態などの特徴量を算出する算出手段を備えたものである。
【００１９】
上記発明によれば、共用化した電極を用いた一体型センサによって、生体振動に基づく動的信号を静電容量や発生電荷の変化で捉え、同時に生体の自重つまり体圧に基づく静的信号を抵抗値や電圧値のレベルとして捉えることになる。共用化した第１または第２の電極は信号の基準電圧点（または面）であり、回路構成の簡素化が図れるとともに外来電磁波・振動ノイズを受けにくくなる。この生体信号検出装置では、生体の体動と体圧を同時に測定しているので、不在時に生体信号を算出するといった誤判定をなくすことができる。体圧測定手段と体動測定手段の片方からだけでは精度よく得られなかった体重、心拍、呼吸、活動量、生命状態等各種の生体信号を高精度に得ることができる。また寝具やカーペット、浴槽、便座など生体が接する生活用品に組み込むことで生体自身に何ら違和感を与えることなく健康状態の判定を行える。設置環境に対する制約が少ないので、新築住宅のみならず既築住宅の設備に後から簡単に取り付けることも可能である。
【００２０】
【発明の実施の形態】
本発明は、第１の電極と生体間に形成される第１の静電容量と、第２の電極と生体間に形成される第２の静電容量との直列接続静電容量に基づき生体の振動信号を測定する体動測定手段と、第１または第２の電極と第３の電極間の間に感圧素子より生体の自重に伴う体圧信号を測定する体圧測定手段とを備え、さらに体動測定手段および体圧測定手段の出力によって生体の体重、心拍数、呼吸数、活動量、生命状態などの特徴量を算出する算出手段を備えたものである。
【００２１】
そして同一の電極を用いて、生体の体動および体圧を測定しているので、構成の簡素化が図れるとともに外来電磁波ノイズを受けにくくなる。また不在時に生体信号を算出するといった誤判定をなくすことができる。体圧測定手段と体動測定手段の両者の出力から生体の健康状態を判定するので、片方からだけでは精度よく得られなかった体重、心拍、呼吸、活動量、生命状態等各種の特徴量を高精度に得ることができる。
【００２２】
また第１の電極と第２の電極の間に圧電体を形成し、生体の振動によって発生した電荷を測定する体動測定手段と、第１または第２の電極と第３の電極の間の感圧素子により生体の自重に伴う体圧信号を測定する体圧測定手段とを備え、さらに体動測定手段および体圧測定手段の出力によって生体の体重、心拍数、呼吸数、活動量、生命状態などの特徴量を算出する算出手段を備えたものである。
【００２３】
そして圧電体に加えられたひずみに対応した電荷を測定することで生体が発生する振動レベルを定量的に検出できる。圧電体は高インピーダンス材料であり、生体への悪影響は一切ない。万一圧電体が生体に触れても、感電等の恐れはない。当然、生体にとって無拘束、無意識的な測定が可能である。
【００２４】
また第１、第２、第３の電極は少なくとも３層の導電層と各導電層に接続され、第１の導電層と第２の導電層間または第２の導電層と第３の導電層間に生体の体動または体圧を測定するための第１または第２検知媒体層を形成したものである。
【００２５】
そして体動を測定するための電極と体圧を測定するための第１または第２の電極が面状体の導電層に接続されているので外来電磁波ノイズの影響を受けにくくなる。各導電層上のどの位置も等電圧なので生体が導電層上のどこにいても検出性能は同じである。検知媒体層は面状なので生体の動きによる位置ずれは起きにくく、断線や故障の危険性も少ない。生体に違和感を与えることもない。さらに電極の配置構成が単純なので、量産化時に性能ばらつきが生じにくい。
【００２６】
また第１の検知媒体層は生体の体動を測定し、第２の検知媒体層は生体の体圧を測定し、第１、第２の検知媒体層を密着させ、第１の検知媒体層の両側面に接続された電極の一方と第２の検知媒体層の両側面に接続された電極の一方を共通化したものである。
【００２７】
そして構造がより簡単になり、同じ位置の生体の体動と体圧を同時に検出することができる。
【００２８】
また第１、第２導電層および検知媒体層はそれぞれ可撓性を有し、一体成形した面状体のセンサシートを構成してなるものである。
【００２９】
そしてこのセンサシートは可撓性を有しているので、寝具やカーペット、浴槽、便座など生体が接する生活用品に容易に組み込むことが可能である。そして生体自身に何ら違和感を与えることなく無意識のうちに健康状態の判定を行える。加工もしやすく、設置環境に対する制約が少ないので、新築住宅のみならず既築住宅の設備に後から簡単に取り付けることができる。特に測定対象となる生体が、寝たきり高齢者、痴呆高齢者、身体障害者あるいは乳幼児やペット動物などの場合にも、その生体の自然な生活動作を何ら邪魔することなく長期間の生体信号検出が連続的に実施できる。
【００３０】
またセンサシートは、複数の通気孔を有することを特徴とするものである。
【００３１】
そして通気孔を有することで、センサシートを寝具などに埋設した場合でも生体の発汗・呼吸などの代謝を妨げることはない。
【００３２】
また通気孔の内側に防水膜を密着させたことを特徴とするものである。
【００３３】
そして防水膜を構成することによって、通気孔からセンサシート内部に水分が浸透し、体動や体圧の検出感度が経時劣化しにくくなり、高寿命化を図ることができる。
【００３４】
また複数の体圧測定手段の出力に応じて当該体動測定手段の出力を合成する合成手段を備えたものである。
【００３５】
これによりセンサシート上に生体が乗っているエリアの出力信号だけを生体の体動信号として抽出し、合成するので不要な振動信号が除去される。つまりＳ／Ｎ比が飛躍的に向上する。
【００３６】
また第１の導電層と第２の導電層間には圧力によって厚みが変化する弾性絶縁層を備えたものである。
【００３７】
そして生体が第１および第２の導電層上に乗ると、安静状態でも発生する生体振動によって弾性絶縁層の厚みが時間変化する。第１および第２の導電層の面積や弾性絶縁層の比誘電率は一定なので、第１の導電層と第２の導電層間で測定できる静電容量は生体の体動に対応した値となる。
【００３８】
また第２の導電層と第３の導電層間は圧力によって電気的に接続する多孔つき弾性絶縁層を備えたものである。
【００３９】
そして生体が第２および第３の導電層上に乗ると、第２の導電層と第３の導電層間の抵抗値は低インピーダンス（導通）となる。逆に生体が第２および第３の導電層上から離れると、第２の導電層と第３の導電層間の抵抗値は高インピーダンス（断線）となる。これにより生体の自重に見合う圧力がかかっているかどうかで体圧の有無を判定できる。
【００４０】
また第２の導電層と第３の導電層間は導電ゴム、導電カーボンなど圧力によって抵抗値が変化する感圧抵抗層を備えたものである。
【００４１】
そして感圧抵抗層により生体の体圧は２値化されたオンオフ信号ではなく、体重に対応した連続値として得ることができる。
【００４２】
また体圧測定手段の出力信号または出力変化速度が所定値以下の場合、体動測定手段の出力を初期化する体動信号校正手段を備えたものである。
【００４３】
そして体動信号校正手段により、生体が不在の場合でも経時変化や温湿度環境によって変動する体動測定手段の出力が安定し、より精度よく生体の体動信号を測定できる。
【００４４】
また体圧測定手段の出力信号が所定値以下の継続時間を計時するタイマー手段と、タイマー手段により継続時間が所定時間以上経過した場合、体圧測定手段の出力を初期化する体圧信号校正手段を備えたものである。
【００４５】
そして体圧信号校正手段により、あらかじめ生体が不在の場合にも存在する残差圧力分を自動的に差し引いておくことで生体の真の体圧信号を測定できる。
【００４６】
また体動測定手段および体圧測定手段の出力信号を周波数領域で合成する信号合成手段と、信号合成手段の出力から体重、心拍数、呼吸数、活動量などの生体信号を算出する算出手段を備えたものである。
【００４７】
そこで所定周波数以上で高精度な出力特性を持つ体動測定手段の出力と、直流または直流に近い低周波域で高精度な出力特性を持つ体圧測定手段の出力を周波数領域で合成することによって生体信号の算出誤差を低減することができる。
【００４８】
また信号合成手段は、所定周波数における体圧測定手段のパワー値に基づき体動測定手段の出力信号のパワースペクトルを補正あるいは所定周波数における体動測定手段のパワー値に基づき体圧測定手段のパワースペクトルを補正するものである。
【００４９】
そこで生体の活動や心拍動、呼吸運動など生体振動の加速度（または変位、速度）レベルが各周波数ごとのパワー値として精度よく検出できる。
【００５０】
以下本発明の第１の実施例について図面を用いて説明する。
【００５１】
（実施例１）
図１は本発明の実施例１の生体信号検出装置のブロック図である。また図２は同装置の外観図である。図３は同装置の要部断面図である。図４は同装置のセンサ入力回路図である。
【００５２】
図１において１５は生体であり、１６は生体１５が接するセンサシート、１７は信号処理装置である。センサシート１６には第１の電極１８、第２の電極１９、第３の電極２０が取りつけられている。生体１５がこのセンサシート１６の上に乗った場合、生体１５と第１の電極１８との間に静電容量Ｃ００が形成されまた生体１５と第２の電極との間に静電容量Ｃ０１が形成される。つまり第１の電極１８と第２の電極１９との間には生体１５の存在に伴う合成静電容量Ｃ０が発生する。さらに生体１５が存在しなくても第１の電極１８と第２の電極１９との間に静電容量Ｃ０２が形成されている場合、合成静電容量Ｃ０は、
【００５３】
【数１】

【００５４】
となる。
【００５５】
また第２の電極１９と第３の電極２０との間に感圧スイッチＳＷ０を埋設し、生体１５がこのセンサシート１６上に乗ればＯＮ、離れればＯＦＦするように構成してある。信号処理装置１７は、体動測定手段２１、体圧測定手段２２および算出手段２３からなる。センサシート１６に接続された第１の電極１８および第２の電極１９は体動測定手段２１に接続され、第２の電極１９と第３の電極２０は体圧測定手段２２に接続されている。体動測定手段２１は静電容量Ｃ０の時間変化から生体１５の振動信号を測定し、体圧測定手段２２は生体１５の体圧有無を判定する。体動測定手段２１および体圧測定手段２２は、算出手段２３に接続されている。算出手段２３は、体圧測定手段２２の出力からセンサシート１６上に体圧があると判定した場合、体動測定手段２１の出力に基づく振動加速度の実効値を生体１５の活動量として算出するものである。
【００５６】
図２、図３を用いてセンサシート１６の構成を説明する。第１の電極１８、第２の電極１９、第３の電極２０はそれぞれ第１の導電層２４、第２の導電層２６、第３の導電層２８に接続されている。第１の導電層２４と第２の導電層２６の間には誘電性を有するゴム、ウレタンなどの弾性絶縁層２５が挿入されている。また第２の導電層２６と第３の導電層２８の間には絶縁スペーサー２７がドット状に配置されている。絶縁スペーサー２７が配置されてない箇所は空隙部を形成している。第２の導電層２６と第３の導電層２８の間は、例えば１０００［Ｎ／ｍ^２］以上といった所定圧力がかかっていないときは電気的に絶縁されているが、所定圧力がかかっているときは電気的に導通する感圧スイッチ構成である。センサシート１６中の第１の導電層２４、弾性絶縁層２５、第２の導電層２６、絶縁スペーサー２７、第３の導電層２８は一体に形成され可撓性を有している。また厚みは２ｍｍ程度であり、寝具等の下にこのセンサシート１６を敷いておくだけで、生体１５に何ら悪影響を与えることなく無意識のまま生体信号を検出することができる。また既存のいろいろなタイプのベッドに後から取りつけることも可能である。
【００５７】
次に図４を用いて信号処理装置１７の中にあるセンサシート１６の入力回路構成を説明する。体動測定手段２１と体圧測定手段２２の共通電極である第２の電極１９には基準電圧としてＥ０を供給している。体動測定手段２１にはオペアンプＯＰ１、固定抵抗器Ｒ１、コンデンサＣ１が設けられている。生体１５の体動により合成静電容量Ｃ０（ｔ）が変化すると、第１の電極１８と第２の電極１９間に発生する電荷Ｑ（ｔ）は、
【００５８】
【数２】

【００５９】
という時間関数となるので流れる電流Ｉ（ｔ）は、
【００６０】
【数３】

【００６１】
ここでＶ１（ｔ）はオペアンプＯＰ１の出力電圧である。ゆえに、
【００６２】
【数４】

【００６３】
であるが、Ｒ１が非常に大きければ、左辺第２項は無視できるので、
【００６４】
【数５】

【００６５】
のように変形できる。つまり静電容量Ｃ０（ｔ）に比例した電圧出力Ｖ１（ｔ）を得ることになる。このオペアンプＯＰ１には、増幅部２１ａ、Ａ／Ｄ変換部２１ｂが接続されており、電圧出力Ｖ１（ｔ）の信号を増幅部２１ａでアナログ増幅後、Ａ／Ｄ変換部２１ｂでデジタル値に変換される。一方体圧測定手段２２において、第２の電極１９と第３の電極２０間には体圧の有無によってオンオフする感圧スイッチはＳＷ０が、固定抵抗器Ｒ２と直列接続されている。つまり第２の電極１９は常時Ｅ０［Ｖ］であるのに対し第３の電極２０は感圧スイッチＳＷ０オンでほぼＥ０［Ｖ］に、感圧スイッチＳＷ１オフでほぼ０［Ｖ］になる。これを固定抵抗器Ｒ３とＲ４で分割された比較電圧Ｅ０・Ｒ４／（Ｒ３＋Ｒ４）と比較して第３の電極２０における電圧の方が高ければロー、低ければハイとなるようにコンパレーターＯＰ２が接続されている。コンパレーターＯＰ２の出力は計数部２２ａ、体圧有無判定部２２ｃに接続され、所定時間分のハイまたはローの総数で体圧の有無を判定する。クロック２２ｂは計数部２２ａおよびＡ／Ｄ変換部２１ｂに接続され、例えば１０ｍｓごとに発生するパルスによって体圧信号の計数および体動信号のＡ／Ｄ変換を同時に行う基準クロックを生成している。
【００６６】
尚、ここでは説明簡単化のため基準電圧Ｅ０や入力信号に重畳するノイズを除去したり、インピーダンス変換や閾値変換により入力信号を安定化する回路構成は図示しなかった。静電容量Ｃ０（ｔ）を測定するには従来例のように発振回路を構成して測定しても構わない。生体１５の存在する時の静電容量Ｃ０（ｔ）の変化を測定するために体圧のない時のＣ０の値を保持しておき、体圧がある時の静電容量Ｃ０（ｔ）との偏差だけを差動増幅する構成を備えてもよい。また基準電圧Ｅ０を交流電圧源としてもよい。直流に近い低周波信号を検出しないよう、ハイパスフィルターを構成したり、直流分をカットして交流信号だけを増幅する構成を備えてもよい。さらに第１の導電層２４、弾性絶縁層２５、第２の導電層２６、絶縁スペーサー２７、第３の導電層２８をフィルム状シートとして説明したが、例えばこれを可撓性の同軸ケーブル状に一体成形し、検出したい領域に配置しても構わない。
【００６７】
（実施例２）
図５は、本発明の実施例２の生体信号検出装置の要部断面図である。図６は同装置のセンサ入力回路図である。実施例１と同じ機能を有する構成要素は同一番号を付与し、説明を省略する。図５において実施例１と異なる点は、第２の導電層２６と第３の導電層２８の間に絶縁スペーサー２７ではなく導電性ゴムなどの均一の厚みを持った感圧抵抗層２９が挿入されている点にある。図６において感圧抵抗層２９は体圧によって抵抗値が連続的に変化する可変抵抗Ｒ０で表せる。第３の電極２０には、
【００６８】
【数６】

【００６９】
なる体圧に応じた電圧Ｖ２が生じている。２２ｄは第２のＡ／Ｄ変換部であり、クロック２２ｂで与えられる１０ｍｓごとのパルスによってアナログ電圧信号をデジタル化する。
【００７０】
尚、生体１５の体圧を測定するのに、感圧抵抗層２９の代わりに可撓性を持った空気袋を設けこの空気の圧力をダイヤフラム式の圧力センサで測定してもよい。
【００７１】
（実施例３）
図７は、本発明の実施例３の生体信号検出装置の要部断面図である。図７において実施例２と異なる点は、センサシート１６上面をＰＥＴフィルム等の防水材３０でコーティングしていることと、第２の電極２６や第３の電極２８をセンサシート１６全体に敷き詰めるのではなく両端部に配置したことにある。
【００７２】
これによりセンサシート１６の腐食等による性能劣化がなくなるとともに構成の簡素化が図れる。
【００７３】
（実施例４）
図８は、本発明の実施例４の生体信号検出装置の要部断面図である。図８において実施例３と異なる点は、センサシート１６全体をＰＥＴフィルム等の防水材３０でコーティングしていることと、多数の通気孔３１を設けたことにある。これによりセンサシート１６両側面の通気が図れるとともに各導電層の腐食がなくなる。センサシート１６を寝具などに埋設した場合でも生体１５の発汗・呼吸などの代謝を妨げることはない。
【００７４】
（実施例５）
図９は、本発明の実施例５の生体信号検出装置の要部構造図である。図１０は同装置のブロック図である。図９において実施例４と異なる点は、センサシート１６中に２次元アレイ状に独立配置した１８枚のエリア別センサシート（１６ａ、１６ｂ、１６ｃ、・・・）を設けたことにある。ここで第２の電極１９（１９ａ、１９ｂ、１９ｃ）は全て等しい基準電圧Ｅ０に接続してある。各エリア別センサシートの感圧抵抗層２９の出力は等価的に可変抵抗Ｒ０（Ｒ０１、Ｒ０２、Ｒ０３、・・・）で表せるがこの出力に応じ各体圧スイッチ３２（３２ａ、３２ｂ、３２ｃ、・・・）で所定圧力以上が検出できれば、体動を測定するための合成静電容量Ｃ０（Ｃ０１、Ｃ０２、Ｃ０３、・・・）の出力信号を取り出す第１の電極１８（１８ａ、１８ｂ、１８ｃ、・・・）を接続し、そうでなければ接続しない構成である。各体圧スイッチ３２（３２ａ、３２ｂ、３２ｃ、・・・）の出力は体重測定手段３３で加算され、生体１５の体重に相当するデジタル値として算出手段２３に伝えられる。一方、第１の電極１８（１８ａ、１８ｂ、１８ｃ、・・・）のうち体圧スイッチ３２によって接続されたもののみ体動測定手段２１に並列接続されて入力される。つまり体動測定手段２１に接続される静電容量Ｃ０ａｃｔは、
【００７５】
【数７】

【００７６】
【数８】

【００７７】
で表せる。生体１５がセンサシート１６に乗っても寝姿勢や寝位置により、個々のエリア別センサシート（１６ａ、１６ｂ、１６ｃ、・・・）全て均等に体圧や体動が加わる訳ではない。また生体１５の形状自体にも凹凸があり、一般に体圧がかかっているエリアから体動が有効に検出できる。なぜなら体圧がかかっていないエリアは生体１５とセンサシート１６の距離が離れているので、体動による静電容量の変化もわずかである。体動測定手段２１で生体１５の体動をするのに全ての第１の電極を接続してしまうと、元々の合成静電容量Ｃ０が大きいために同じ体動でもＣ０の変化の比率が相対的に小さくなる。これに対し、体圧がかかっているエリアのみの合成静電容量Ｃａｃｔの変化を体動として検出すれば体動信号の分解能ひいてはＳ／Ｎ比を向上させることができる。
【００７８】
尚、ここでは縦６行横３列としたが、空間分解能はこれに限るものではない。また１次元配列にしても構わない。
【００７９】
（実施例６）
図１１は、本発明の実施例６の生体信号検出装置のブロック図である。図１２は圧電体の出力周波数特性図である。図１１において実施例５と異なる点は、第１の導電層２４と第２の導電層２６の間に誘電性を有するゴム、ウレタンなどの弾性絶縁層２５が挿入されているのではなく、ポリフッ化ビニリデンなどのフィルム状の圧電体層が挿入されている点にある。圧電体層は加えられた歪みに応じ電気的分極（電荷）を発生する素子で、機械振動といった動的運動を測定するために用いられる。図１１が図１０と異なるのは第１の電極１８（１８ａ、１８ｂ、１８ｃ、・・・）と第２の電極１９（１９ａ、１９ｂ、１９ｃ、・・・）の間にコンデンサではなく圧電体層を等価的に示した振動発振子Ｘ０１、Ｘ０２、Ｘ０３、・・・を備えた点と、体圧のかかっているエリアの圧電体層の出力を合成後、信号増幅する増幅手段３４を備えた点にある。増幅手段３４は出力インピーダンスが高い圧電体の信号を有効に取り出すためＦＥＴでインピーダンス変換し、また増幅後の出力電圧が飽和しないように自動増幅率制御（ＡＧＣ）機構を備え、常に最適なダイナミックレンジが得られるようになっている。圧電体は一定温度以下では安定した出力特性を持つが、図１２に示すように材質、形状、検出回路の入力インピーダンスなどの影響で直流に近い低周波成分の出力ゲインが低下する微分型の特性を持った素子である。尚、増幅手段３４には微小振動検出に有利なチャージアンプを用いてもよい。
【００８０】
上記構成により体圧のかかってないエリアに生じた外来の振動ノイズ（例えば自動車、電車あるいは無感地震、風など）を除外することができるので体動信号のＳ／Ｎ比を向上させることができる。
【００８１】
（実施例７）
図１３は、本発明の実施例７の生体信号検出装置のブロック図である。図１４は感圧抵抗層２９の抵抗値と体圧、増幅率を示すグラフである。図１３において実施例６と異なる点は、各エリアごとに体圧の大きさを測定する体圧測定手段３５ａ、３５ｂ、３５ｃ、・・・を設け、各エリアごとの体圧の大きさに応じ連続的に増幅率を変える増幅手段３６ａ、３６ｂ、３６ｃ、・・・を設けている点である。感圧抵抗層２９の抵抗値Ｒ０ｉ［Ω］（ｉ＝１〜１８）は素子の特性に応じ、図１４（ａ）のように体圧Ｐｉ［Ｎ／ｍ^２］に変換され、さらに図１４（ｂ）のように増幅率Ｇｉに非線形変換される。さらに各増幅手段３６ａ、３６ｂ、３６ｃ、・・・には絶対値化手段３７ａ、３７ｂ、３７ｃ、・・・が接続される。体動測定手段には絶対値化された信号が加算される。
【００８２】
上記構成により全てのエリアの圧電体層からの信号は、実施例５のように所定体圧以上なら接続、未満なら断線というのではなく、体圧に応じたなめらかで連続的な体圧の関数としてエリアごとに重みづけされているので、生体１５がほんの少し移動しただけで出力信号が不連続に大きく変化してしまう不都合がなくなる。
【００８３】
また各エリアごとの体動信号を一旦絶対値化してから合成しているので、信号を大きくすることができる。生体１５が安静にしている場合、心拍動、血流などによる周期的な生体振動が生体表面から生じているが、生体部位別に時間差つまり位相ずれがあり、単純に合成すると信号同士が打ち消しあう場合があるがこのような絶対値化手段３７ａ、３７ｂ、３７ｃ、・・・を設けることで得られる信号のＳ／Ｎ比を大きく保つことができる。
【００８４】
（実施例８）
図１５は、本発明の実施例８の生体信号検出装置のブロック図である。図１５が実施例１と異なる点は、体圧測定手段２２の出力が体動信号校正手段３８とタイマー手段３９に接続され、さらにタイマー手段３９が体圧信号校正手段４０を介して体圧測定手段２２にあるいは体動信号校正３８が体動測定手段２１に接続されている点である。体動信号校正手段３８は、例えば体圧測定手段２２からの出力が１０００［Ｎ／ｍ^２］以下であれば生体１５が存在しないと見なし、体動測定手段２１からの出力が最も小さくなるようにバイアスをかけてゼロ点調整する。同様にタイマー手段３９では、例えば体圧測定手段２２からの出力が１０００［Ｎ／ｍ^２］以下であれば生体１５が存在しないと見なし、同一体圧の継続時間を計時する。この状態が例えば１０分間継続すれば、体圧信号校正手段４０によって体圧測定手段２２の出力が０．０［Ｎ／ｍ^２］になるようにバイアスをかけてゼロ点調節する。タイマー手段３９は、１０分間以内に体圧の値が変動すれば、計時をクリアするし、体圧が１０００［Ｎ／ｍ^２］以上では計時自体を禁止する構成である。体圧測定手段２２のセンサ感度にも依存するが、生体１５は生命活動をしている限り完全に静止しているとは考えられない。よって体圧測定手段２２の出力をゼロ点調整する体圧信号校正手段４０を設けることで、はじめからセンサシート１６上に乗っていた敷き布団、枕などの不要物の重量をキャンセルすることができる。感圧抵抗素子のクリープ特性などにより同一重量でも出力抵抗値が異なっている場合でも、体圧信号を不在状態から在状態に変化した時の差として確実に捉えることができる。これは生体１５の体重などを精度よく測定するのに好都合である。また体動測定手段２１の出力をゼロ点調整する体動信号校正手段３８を設けることで、生体１５が存在しないのに継続的に発生している暗振動や温湿度環境の変化等によって生じる基線の同様を自動的に打ち消すことができる。これにより生体１５が不在から在に変わった瞬間から生体１５の体動信号だけを有効に検出してくることが可能になる。
【００８５】
（実施例９）
図１６は、本発明の実施例９の生体信号検出装置のブロック図である。図１７は生体１５がセンサシート１６上に安静仰臥位でいる場合に得られるパワースペクトル、図１８は体動測定手段２１と体圧測定手段２２の合成比を示した図である。図１６が実施例１と異なる点は、体動測定手段２１の出力が第１の周波数変換手段４１で周波数軸上のパワースペクトルとして、また体圧測定手段２２の出力が第２の周波数変換手段４２で周波数軸上のパワースペクトルとして表現され、両者がパワースペクトル合成手段４３で１つのパワースペクトルとして合成される点である。パワースペクトル合成手段４３は心拍数算出手段４４、呼吸数算出手段４５、活動量算出手段４６に接続され、さらに体圧測定手段２２に接続された体重測定手段３３とともに表示手段４７に接続されている。表示手段４７では現在の生体１５の心拍数、呼吸数、活動量、体重を表示・蓄積する。第１の周波数変換手段４１や第２の周波数変換手段４２からは図１７に示すようなパワースペクトルのグラフを得ることができるが、直流または低周波で高精度な信号を得られる第１の周波数変換手段４１のパワースペクトルと所定周波数より高周波域で高精度な信号を得られる第２の周波数変換手段４２のパワースペクトルは図１８に示すような合成比で１つのパワースペクトルにまとめる構成である。図１７において０．２Ｈｚ近傍のピークｆｒｅｓｐは呼吸周波数、１Ｈｚ近傍のピークｆｈｒは心拍周波数を示している。また活動量は０．１Ｈｚから１０Ｈｚにおけるパワー積算値（面積）で定義するものとする。心拍数算出手段４４や呼吸数算出手段４５で心拍数や呼吸数を算出するには、それぞれ所定周波数帯（例えば心拍数は０．５Ｈｚ〜２．０Ｈｚ、呼吸数は０．０５Ｈｚ〜０．４Ｈｚ）におけるピーク点を発見することで心拍数や呼吸数に換算する。さらに表示手段４７には異常報知手段４８が接続されている。生体１５の体圧がある状態で、生命活動が停止または活動量が所定レベル以下になった場合や、心拍数や呼吸数が所定範囲を逸脱した場合に警報音を発して緊急事態を報知する構成である。異常報知手段４８はタイマーと組み合わせ長期的なトレンド変化から体調や健康状態の異変を判定し、警告を発するようにしてもよい。心拍数や呼吸数の値だけでなく、心拍動や呼吸運動の強さを当該ピーク周波数点におけるパワー値として蓄積・表示してもよい。また心拍数、呼吸数の算出に関して、心拍動や呼吸運動に伴う波形は理想的な正弦波ではないため基本周波数の高調波が立つことが多い。誤算出を防ぐためにさらにケプストラム変換して、基本波だけを抽出してもよいしピーク点の候補の中から２倍周波数点を削除する方法を用いてもよい。ここで第１の周波数変換手段４１ないし第２の周波数変換手段４２は、例えばサンプリング周波数２００Ｈｚでサンプリングされた１分間分の時系列信号を５秒毎に順次ずらしながら周波数変換するものである。安静状態の時は、心拍数や呼吸数が２倍以上や１／２以下に急変することは考えにくいので心拍数や呼吸数の算出周波数帯（可動範囲）を前回の算出結果に基づいて、適応的に規定してもよい。比較的急峻なパルス状のＲ波成分を含む心拍動と呼吸運動を分離するためにはあらかじめフィルターをかけておいてもよい。周波数軸状で合成した後に時間軸状に戻してから心拍数や呼吸数、活動量などを算出してもよい。
【００８６】
また２つのパワースペクトラムを合成するには特定周波数例えば１Ｈｚにおけるパワー値の平均値を基準点とし、それ以上の周波数帯は第１の周波数変換手段４１のパワースペクトル、それ未満の周波数帯は第２の周波数変換手段４２のパワースペクトルを元にスライドあるいは線形変換によって合成してもよい。
【００８７】
これにより同一のセンサシート１６に内蔵された２種類のセンサの利点を活かしあった生体信号検出が可能になり、温湿度環境や暗振動、電磁波などの外来ノイズに対する影響を低減することができる。
【００８８】
【発明の効果】
以上の説明から明らかなように本発明の生体信号検出装置によれば、次の効果が得られる。
【００８９】
（１）体動測定と体圧測定のための電極を共用化しているので、構成の簡素化が図れるとともに外来電磁波・振動ノイズを受けにくくなる。また２種類のセンサ出力結果から生体信号を検出しているので不在時に生体信号を算出するといった誤判定をなくし、体重、心拍、呼吸、活動量、生命状態等各種の生体信号を高精度に得ることができる。
【００９０】
（２）体動測定に圧電体を用いているので生体への悪影響は一切なく、無意識的な測定が可能である。万一圧電体が生体に触れても、感電等の恐れはない。当然、生体にとって無拘束、無意識的な測定が可能である。
【００９１】
（３）各電極が面状体の導電層に接続されているので、生体が導電層上のどこにいても検出性能は同じである。生体の動きによる位置ずれは起きにくく、故障の危険性も少ない。電極の配置構成が単純なので、量産化時に性能ばらつきが生じにくい。
【００９２】
（４）導電層なしで２種類の検知媒体層を密着させて検出しているので、構造がより簡単になり、同じ位置の生体の体動と体圧を同時に検出することができる。
【００９３】
（５）可撓性のセンサシートを設けたので、寝具やカーペット、浴槽、便座など生体が接する生活用品に容易に組み込むことが可能である。加工もしやすく、設置環境に対する制約が少ないので、新築住宅のみならず既築住宅の設備に後から簡単に取り付けることができる。特に測定対象となる生体が、寝たきり高齢者、痴呆高齢者、身体障害者あるいは乳幼児やペット動物などの場合にも、その生体の自然な生活動作を何ら邪魔することなく長期間の生体信号検出が連続的に実施できる。
【００９４】
（６）複数の通気孔を有するので、センサシートを寝具などに埋設した場合でも生体の発汗・呼吸などの代謝を妨げることはない。
【００９５】
（７）防水膜を設けたので、検出感度が経時劣化しにくくなり、高寿命化を図ることができる。
【００９６】
（８）複数のセンサシートを設け、生体が存在するエリアの有効な生体信号を選択的に取り出せるので、不要な振動信号が除去され、Ｓ／Ｎ比が飛躍的に向上する。
【００９７】
（９）弾性絶縁体により、生体の体動に対応した静電容量を得ることができる。
【００９８】
（１０）多孔つき弾性絶縁体により、生体の自重に見合う体圧の有無を判定できる。
【００９９】
（１１）感圧抵抗層により、生体の体圧は体重に対応した連続値として得ることができる。
【０１００】
（１２）体動信号校正手段により、経時変化や温湿度環境に対しても精度よく測定できる。
【０１０１】
（１３）体圧信号校正手段により、生体の真の体圧信号を測定できる。
【０１０２】
（１４）体動測定手段の出力と体圧測定手段の出力を周波数領域で合成することにより、生体信号の算出誤差を低減することができる。
【０１０３】
（１５）体動測定手段のパワースペクトルおよび体圧測定手段のパワースペクトルを補正することにより、生体の周期的振動が各周波数ごとのパワー値として精度よく検出できる。
【図面の簡単な説明】
【図１】本発明の実施例１の生体信号検出装置のブロック図
【図２】同実施例の生体信号検出装置の外観図
【図３】同実施例の生体信号検出装置の要部断面図
【図４】同実施例の生体信号検出装置のセンサ入力回路図
【図５】本発明の実施例２の生体信号検出装置の要部断面図
【図６】同実施例の生体信号検出装置のセンサ入力回路図
【図７】本発明の実施例３の生体信号検出装置の要部断面図
【図８】本発明の実施例４の生体信号検出装置の要部断面図
【図９】本発明の実施例５の生体信号検出装置の要部構造図
【図１０】同実施例の生体信号検出装置のブロック図
【図１１】本発明の実施例６の生体信号検出装置のブロック図
【図１２】同実施例の圧電体の出力周波数特性図
【図１３】本発明の実施例７の生体信号検出装置のブロック図
【図１４】（ａ）同実施例において感圧抵抗層２９の抵抗値と体圧を示すグラフ
（ｂ）同実施例において感圧抵抗層２９の増幅率と体圧を示すグラフ
【図１５】本発明の実施例８の生体信号検出装置のブロック図
【図１６】本発明の実施例９の生体信号検出装置のブロック図
【図１７】同実施例の生体信号のパワースペクトルを示す図
【図１８】体動測定手段２１と体圧測定手段２２の合成比を示した図
【図１９】従来の静電容量型の生体信号検出装置を示す図
【図２０】従来の静電容量型と感圧型を併用した他の生体信号検出装置を示す図
【符号の説明】
１５生体
１６センサシート
１７信号処理装置
１８第１の電極
１９第２の電極
２０第３の電極
２１体動測定手段
２２体圧測定手段
２３算出手段
２４第１の導電層
２５弾性絶縁層
２６第２の導電層
２７絶縁スペーサー
２８第３の導電層
２９感圧抵抗層
３０防水材
３１通気孔
３２体圧スイッチ
３３体重測定手段
３５体圧測定手段
３８体動信号校正手段
３９タイマー手段
４０体圧信号校正手段
４１第１の周波数変換手段
４２第２の周波数変換手段
４３パワースペクトル合成手段
４４心拍数算出手段
４５呼吸数算出手段
４６活動量算出手段[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an apparatus for detecting, displaying, recording, and reporting biological signals such as weight, heart rate, respiratory rate, and body movement without invasion and without restriction.
[0002]
[Prior art]
2. Description of the Related Art A conventional biological signal detection device of this type is generally described in, for example, Japanese Patent Application Laid-Open No. 62-164435. In this device, as shown in FIG. 19, an electrode 4 is connected to a hot line side of a pierce type oscillation circuit 3 formed by using an FET 2 on a bed 1, and an electrode orthogonal to the electrode 4 is provided to an earth line side. 5 is connected, and is configured to detect a change in oscillation frequency due to an additional capacitance in an oscillation circuit using the crystal resonator 6. Further, after detecting and detecting the envelope of the frequency change based on the change of the living body by the detector / detector 7, the filter 8 removes unnecessary frequency signals such as noise and records the same on the recording device 9 or stops the movement of the living body. When it did, an alarm was issued.
[0003]
As another conventional example, there is one described in JP-A-63-238502. This device has electrodes 11 and 12 arranged on both sides of a pressure-sensitive conductive rubber 10 as shown in FIG. 20, and connects the electrodes 11 and 12 to a capacitance measuring device 13 and a resistance measuring device 14. Met. That is, it is assumed that the pressure-sensitive conductive rubber 10 is an element including a variable capacitor and a variable resistor.
[0004]
[Problems to be solved by the invention]
However, the conventional biological signal detection device has various problems related to an electrode configuration and a detection method close to a living body.
[0005]
Since only the change in the capacitance generated between the electrodes is detected, it is difficult to determine whether the direct current or a low frequency signal close to the direct current is based on the movement of the living body.
[0006]
Also, the output signal is very susceptible to temperature and humidity environments.
[0007]
Further, since the

electrodes

3 and 4 are in the form of lead wires, the

electrodes

3 and 4 easily displace on the bedding, and the movement of the living body cannot be detected with good reproducibility from the change in capacitance.
[0008]
In addition, bedding folds and intersections of electrodes are apt to be broken, and there is a danger of electric shock if a commercial power supply is used in case of contact with a living body.
[0009]
Further, in order to provide the

electrodes

3 and 4 with mechanical strength, the lead wire diameter must be considerably increased. However, this not only impairs the comfort of a sleeping person (living body) on the bed, but also concentrates on the electrode intersection. There is a danger of bed sores caused by body pressure.
[0010]
It is not clear whether a living body is present on the bed or not. In particular, it is difficult to distinguish between a case where the living body has left the bed and a case where the living body has died on the bed.
[0011]
Also, the weight cannot be detected.
[0012]
In addition, since the arrangement of the electrodes is complicated, performance variations are likely to occur during mass production.
[0013]
Since the electrodes are only discretely arranged at equal intervals, a difference occurs in signal detection performance depending on the sleeping posture.
[0014]
There has been a problem that the baseline of the output signal is likely to fluctuate and the signal level must be initialized before use.
[0015]
Alternatively, when the electrode is a lead wire, it has a problem that it becomes an antenna and is very susceptible to external electromagnetic noise. There is also a problem that the position is easily shifted, and is easily affected by external vibration noise other than the living body.
[0016]
Of the sensor configuration for detecting a biological signal, the capacitance type sensor generally has poor temperature characteristics, and the signal fluctuates in a low frequency range near DC. A pressure-sensitive sensor made of conductive rubber or carbon having pressure-sensitive characteristics has creep characteristics and the like, and has a low response speed. In other words, the measurement accuracy of the absolute pressure is poor, and a dynamic high-frequency signal cannot be captured. Although there is a method of using a strain resistance element as a pressure-sensitive sensor, an output signal largely depends on an environment such as an installation condition and a temperature. As a result, until now, the biosignal sensor has to be zero-adjusted or gain-adjusted every time the measurement is started by the user himself, a separate protective device is provided to stabilize the sensor installation environment, or only used as an on / off switch. Subject to the restrictions of
[0017]
In order to output a stable resistance value with good reproducibility depending on body pressure, a low-impedance conductor must be used. When considering the parallel connection of a resistor element and a capacitor element, the combined impedance is almost the same as the resistance value when the resistance value is small. Cannot be measured accurately.
[0018]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention relates to a first capacitance formed between a first electrode and a living body, and a second capacitance formed between a second electrode and the living body. Body movement measuring means for measuring a vibration signal of the living body based on the series-connected capacitance; and body pressure measuring means for measuring a body pressure signal associated with the weight of the living body with the first or second electrode and the third electrode. And calculating means for calculating characteristic quantities such as body weight, heart rate, respiratory rate, activity amount, and life state of the living body based on outputs of the body movement measuring means and the body pressure measuring means.
[0019]
According to the above invention, a dynamic signal based on biological vibration is captured by a change in capacitance or generated charge by an integrated sensor using a shared electrode, and at the same time, a static signal based on the body's own weight, that is, body pressure is detected. It can be understood as the level of the resistance value or the voltage value. The shared first or second electrode is a signal reference voltage point (or plane), which simplifies the circuit configuration and makes it less susceptible to external electromagnetic waves and vibration noise. In this biological signal detection device, since the body movement and the body pressure of the living body are measured at the same time, it is possible to eliminate the erroneous determination that the biological signal is calculated in the absence. Various biological signals, such as weight, heart rate, respiration, activity, and life status, which could not be obtained with high accuracy from only one of the body pressure measurement unit and the body movement measurement unit, can be obtained with high accuracy. In addition, by incorporating it into daily necessities, such as bedding, carpets, bathtubs, and toilet seats, which are in contact with the living body, it is possible to determine the health state without giving the living body any uncomfortable feeling. Since there are few restrictions on the installation environment, it is possible to easily install the equipment not only in a new house but also in an existing house.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention relates to a living body based on a series connection capacitance of a first capacitance formed between a first electrode and a living body and a second capacitance formed between the second electrode and the living body. Body movement measuring means for measuring a vibration signal of the body, and body pressure measuring means for measuring a body pressure signal accompanying the weight of the living body from the pressure-sensitive element between the first or second electrode and the third electrode. And the output of the body movement measuring means and the body pressure measuring means Weight, heart rate, respiratory rate, activity, life status, etc. It is provided with a calculating means for calculating the characteristic amount.
[0021]
Since the body movement and the body pressure of the living body are measured using the same electrode, the structure can be simplified and external electromagnetic noise is less likely to be received. In addition, it is possible to eliminate erroneous determination such as calculating a biological signal when absent. Since the health status of the living body is determined from the outputs of both the body pressure measuring means and the body motion measuring means, various characteristic quantities such as weight, heart rate, respiration, activity, life status, etc. It can be obtained with high accuracy.
[0022]
A body movement measuring means for forming a piezoelectric body between the first electrode and the second electrode and measuring an electric charge generated by vibration of a living body; Body pressure measuring means for measuring a body pressure signal associated with the weight of the living body by the pressure-sensitive element, and further comprising a body movement measuring means and an output of the body pressure measuring means, Weight, heart rate, respiratory rate, activity, life status, etc. It is provided with a calculating means for calculating the characteristic amount.
[0023]
Then, by measuring the electric charge corresponding to the strain applied to the piezoelectric body, the vibration level generated by the living body can be quantitatively detected. The piezoelectric body is a high impedance material, and has no adverse effect on the living body. Even if the piezoelectric body touches the living body, there is no risk of electric shock or the like. Naturally, it is possible to perform unrestricted and unconscious measurement for the living body.
[0024]
The first, second, and third electrodes are connected to at least three conductive layers and each conductive layer, and are provided between the first conductive layer and the second conductive layer or between the second conductive layer and the third conductive layer. A first or second detection medium layer for measuring body movement or body pressure of a living body is formed.
[0025]
Further, since the electrode for measuring body movement and the first or second electrode for measuring body pressure are connected to the conductive layer of the planar body, they are less susceptible to external electromagnetic noise. Since any position on each conductive layer has the same voltage, the detection performance is the same regardless of where the living body is on the conductive layer. Since the detection medium layer is planar, displacement of the detection medium layer due to movement of the living body is unlikely to occur, and there is little risk of disconnection or failure. There is no discomfort to the living body. Furthermore, since the arrangement of the electrodes is simple, performance variations hardly occur during mass production.
[0026]
The first sensing medium layer measures body movement of the living body, the second sensing medium layer measures body pressure of the living body, and the first and second sensing medium layers are brought into close contact with each other. And one of the electrodes connected to both sides of the second sensing medium layer.
[0027]
Then, the structure becomes simpler, and the body movement and the body pressure of the living body at the same position can be simultaneously detected.
[0028]
Further, the first and second conductive layers and the detection medium layer each have flexibility and constitute a planar sensor sheet formed integrally.
[0029]
Since the sensor sheet has flexibility, the sensor sheet can be easily incorporated into daily necessities such as bedding, a carpet, a bathtub, a toilet seat, and the like, which come into contact with a living body. And it is possible to judge the health state unconsciously without giving any unnatural feeling to the living body itself. Since it is easy to process and there are few restrictions on the installation environment, it can be easily attached later to not only new housing but also existing housing equipment. Especially when the living body to be measured is a bedridden elderly person, a demented elderly person, a disabled person or an infant or a pet animal, a long-term biological signal detection can be performed without disturbing the natural living operation of the living body at all. Can be performed continuously.
[0030]
The sensor sheet has a plurality of ventilation holes.
[0031]
By having the ventilation holes, even when the sensor sheet is embedded in bedding or the like, metabolism such as sweating and respiration of the living body is not hindered.
[0032]
In addition, a waterproof film is adhered to the inside of the ventilation hole.
[0033]
By forming the waterproof film, moisture permeates into the inside of the sensor sheet from the ventilation holes, and the detection sensitivity of body movement and body pressure hardly deteriorates with time, and the life can be extended.
[0034]
The apparatus further includes a synthesizing means for synthesizing the outputs of the body movement measuring means in accordance with the outputs of the plurality of body pressure measuring means.
[0035]
Thereby, only the output signal of the area where the living body is on the sensor sheet is extracted as the body movement signal of the living body and synthesized, so that unnecessary vibration signals are removed. That is, the S / N ratio is dramatically improved.
[0036]
Further, an elastic insulating layer whose thickness changes by pressure is provided between the first conductive layer and the second conductive layer.
[0037]
Then, when the living body rides on the first and second conductive layers, the thickness of the elastic insulating layer changes with time due to the biological vibration generated even in a resting state. Since the area of the first and second conductive layers and the relative dielectric constant of the elastic insulating layer are constant, the capacitance that can be measured between the first and second conductive layers is a value corresponding to the body movement of the living body. .
[0038]
The second conductive layer and the third conductive layer are provided with a porous elastic insulating layer that is electrically connected by pressure.
[0039]
When the living body rides on the second and third conductive layers, the resistance between the second and third conductive layers becomes low impedance (conduction). Conversely, when the living body separates from the second and third conductive layers, the resistance between the second and third conductive layers becomes high impedance (disconnection). Thus, the presence or absence of body pressure can be determined based on whether or not a pressure corresponding to the weight of the living body is applied.
[0040]
Further, between the second conductive layer and the third conductive layer, there is provided a pressure-sensitive resistance layer such as conductive rubber or conductive carbon whose resistance value changes according to pressure.
[0041]
Then, the body pressure of the living body can be obtained as a continuous value corresponding to the weight instead of the binarized on / off signal by the pressure-sensitive resistance layer.
[0042]
In addition, when the output signal or the output change rate of the body pressure measuring means is equal to or less than a predetermined value, the apparatus is provided with a body movement signal calibrating means for initializing the output of the body movement measuring means.
[0043]
The body movement signal calibrating means stabilizes the output of the body movement measuring means which fluctuates due to a temporal change or a temperature and humidity environment even when the living body is absent, so that the body movement signal of the living body can be measured more accurately.
[0044]
A timer means for measuring the duration of the output signal of the body pressure measuring means which is equal to or less than a predetermined value; and a body pressure signal calibrating means for initializing the output of the body pressure measuring means when the duration time exceeds the predetermined time by the timer means. It is provided with.
[0045]
Then, the body pressure signal calibrating means can automatically measure the residual pressure existing even when the living body is absent, thereby measuring the true body pressure signal of the living body.
[0046]
A signal synthesizing unit that synthesizes output signals of the body motion measuring unit and the body pressure measuring unit in a frequency domain; It is provided.
[0047]
Therefore, by combining in a frequency domain the output of the body motion measuring means having a high-precision output characteristic at a predetermined frequency or more and the output of the body pressure measuring means having a high-precision output characteristic in a low-frequency region close to DC or DC. The calculation error of the biological signal can be reduced.
[0048]
The signal synthesizing means corrects the power spectrum of the output signal of the body motion measuring means based on the power value of the body pressure measuring means at a predetermined frequency or the power spectrum of the body pressure measuring means based on the power value of the body motion measuring means at the predetermined frequency. Is to be corrected.
[0049]
Therefore, the acceleration (or displacement, speed) level of the biological vibration such as the activity of the living body, the heartbeat, and the respiratory movement can be accurately detected as the power value for each frequency.
[0050]
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings.
[0051]
(Example 1)
FIG. 1 is a block diagram of a biological signal detection device according to a first embodiment of the present invention. FIG. 2 is an external view of the apparatus. FIG. 3 is a sectional view of a main part of the apparatus. FIG. 4 is a sensor input circuit diagram of the device.
[0052]
In FIG. 1, reference numeral 15 denotes a living body, 16 denotes a sensor sheet with which the living body 15 contacts, and 17 denotes a signal processing device. A first electrode 18, a second electrode 19, and a third electrode 20 are attached to the sensor sheet 16. When the living body 15 rides on the sensor sheet 16, a capacitance C00 is formed between the living body 15 and the first electrode 18, and a capacitance C01 is formed between the living body 15 and the second electrode. It is formed. That is, a combined capacitance C0 is generated between the first electrode 18 and the second electrode 19 due to the presence of the living body 15. Furthermore, when the capacitance C02 is formed between the first electrode 18 and the second electrode 19 even when the living body 15 does not exist, the combined capacitance C0 is
[0053]
(Equation 1)

[0054]
It becomes.
[0055]
A pressure-sensitive switch SW0 is buried between the second electrode 19 and the third electrode 20, and is turned on when the living body 15 is on the sensor sheet 16 and turned off when the living body 15 is separated. The signal processing device 17 includes a body movement measuring unit 21, a body pressure measuring unit 22, and a calculating unit 23. The first electrode 18 and the second electrode 19 connected to the sensor sheet 16 are connected to a body movement measuring unit 21, and the second electrode 19 and the third electrode 20 are connected to a body pressure measuring unit 22. . The body movement measuring unit 21 measures the vibration signal of the living body 15 from the time change of the capacitance C0, and the body pressure measuring unit 22 determines the presence or absence of the body pressure of the living body 15. The body movement measuring means 21 and the body pressure measuring means 22 are connected to the calculating means 23. When the calculating unit 23 determines from the output of the body pressure measuring unit 22 that there is a body pressure on the sensor sheet 16, the calculating unit 23 calculates the effective value of the vibration acceleration based on the output of the body motion measuring unit 21 as the activity amount of the living body 15. Things.
[0056]
The configuration of the sensor sheet 16 will be described with reference to FIGS. The first electrode 18, the second electrode 19, and the third electrode 20 are connected to a first conductive layer 24, a second conductive layer 26, and a third conductive layer 28, respectively. An elastic insulating layer 25 made of rubber, urethane, or the like having a dielectric property is inserted between the first conductive layer 24 and the second conductive layer 26. Further, an insulating spacer 27 is arranged between the second conductive layer 26 and the third conductive layer 28 in a dot shape. A portion where the insulating spacer 27 is not disposed forms a gap. Between the second conductive layer 26 and the third conductive layer 28, for example, 1000 [N / m ² The pressure-sensitive switch is electrically insulated when the predetermined pressure is not applied as described above, but is electrically conductive when the predetermined pressure is applied. The first conductive layer 24, the elastic insulating layer 25, the second conductive layer 26, the insulating spacer 27, and the third conductive layer 28 in the sensor sheet 16 are formed integrally and have flexibility. The thickness is about 2 mm, and the biological signal can be detected unconsciously without any adverse effect on the living body 15 only by laying the sensor sheet 16 under bedding or the like. It can also be retrofitted to existing various types of beds.
[0057]
Next, the input circuit configuration of the sensor sheet 16 in the signal processing device 17 will be described with reference to FIG. E0 is supplied as a reference voltage to the second electrode 19, which is a common electrode of the body movement measuring means 21 and the body pressure measuring means 22. The body movement measuring means 21 is provided with an operational amplifier OP1, a fixed resistor R1, and a capacitor C1. When the combined capacitance C0 (t) changes due to the body movement of the living body 15, the charge Q (t) generated between the first electrode 18 and the second electrode 19 becomes
[0058]
(Equation 2)

[0059]
The current I (t) flowing since
[0060]
(Equation 3)

[0061]
Here, V1 (t) is the output voltage of the operational amplifier OP1. therefore,
[0062]
(Equation 4)

[0063]
However, if R1 is very large, the second term on the left side can be ignored.
[0064]
(Equation 5)

[0065]
Can be transformed as follows. That is, a voltage output V1 (t) proportional to the capacitance C0 (t) is obtained. An amplifier 21a and an A / D converter 21b are connected to the operational amplifier OP1. The signal of the voltage output V1 (t) is analog-amplified by the amplifier 21a and then converted to a digital value by the A / D converter 21b. Is done. On the other hand, in the body pressure measuring means 22, a pressure sensitive switch SW0 that is turned on and off depending on the presence or absence of body pressure is connected between the second electrode 19 and the third electrode 20 in series with the fixed resistor R2. That is, the second electrode 19 is always at E0 [V], while the third electrode 20 is at almost E0 [V] when the pressure-sensitive switch SW0 is turned on, and is almost 0 [V] when the pressure-sensitive switch SW1 is turned off. This is compared with the comparison voltage E0 · R4 / (R3 + R4) divided by the fixed resistors R3 and R4, and the comparator OP2 determines that the voltage at the third electrode 20 is low if it is higher, and high if it is low. It is connected. The output of the comparator OP2 is connected to the counting unit 22a and the body pressure presence / absence determination unit 22c, and determines the presence / absence of body pressure based on the total number of high or low for a predetermined time. The clock 22b is connected to the counting unit 22a and the A / D conversion unit 21b, and generates a reference clock for simultaneously counting the body pressure signal and performing A / D conversion of the body motion signal by a pulse generated every 10 ms, for example.
[0066]
Here, for simplicity of explanation, a circuit configuration for removing noise superimposed on the reference voltage E0 or the input signal or stabilizing the input signal by impedance conversion or threshold value conversion is not shown. In order to measure the capacitance C0 (t), an oscillation circuit may be configured as in the conventional example to measure the capacitance C0 (t). In order to measure a change in the capacitance C0 (t) when the living body 15 is present, the value of C0 when there is no body pressure is held, and the capacitance C0 (t) when there is body pressure. May be provided for differentially amplifying only the deviation of. Further, the reference voltage E0 may be used as an AC voltage source. A high-pass filter may be configured so that a low-frequency signal close to DC is not detected, or a configuration may be provided in which DC components are cut to amplify only AC signals. Further, the first conductive layer 24, the elastic insulating layer 25, the second conductive layer 26, the insulating spacer 27, and the third conductive layer 28 have been described as a film-like sheet. It may be integrally formed and arranged in a region to be detected.
[0067]
(Example 2)
FIG. 5 is a sectional view of a main part of a biological signal detection device according to a second embodiment of the present invention. FIG. 6 is a sensor input circuit diagram of the device. Components having the same functions as those in the first embodiment are given the same reference numerals, and description thereof is omitted. 5 is different from the first embodiment in that a pressure-sensitive resistance layer 29 having a uniform thickness such as conductive rubber is inserted between the second conductive layer 26 and the third conductive layer 28 instead of the insulating spacer 27. It is in that being. In FIG. 6, the pressure-sensitive resistance layer 29 can be represented by a variable resistor R0 whose resistance value changes continuously according to body pressure. The third electrode 20 has
[0068]
(Equation 6)

[0069]
A voltage V2 corresponding to the body pressure is generated. Reference numeral 22d denotes a second A / D converter, which digitizes the analog voltage signal by a pulse every 10 ms given by the clock 22b.
[0070]
In order to measure the body pressure of the living body 15, a flexible air bag may be provided instead of the pressure-sensitive resistance layer 29, and the pressure of this air may be measured by a diaphragm-type pressure sensor.
[0071]
(Example 3)
FIG. 7 is a sectional view of a main part of a biological signal detection device according to a third embodiment of the present invention. FIG. 7 is different from Example 2 in that the upper surface of the sensor sheet 16 is coated with a waterproof material 30 such as a PET film, and the second electrode 26 and the third electrode 28 are spread over the entire sensor sheet 16. Rather than being placed at both ends.
[0072]
This eliminates performance degradation due to corrosion of the sensor sheet 16 and simplifies the configuration.
[0073]
(Example 4)
FIG. 8 is a sectional view of a main part of a biological signal detecting device according to a fourth embodiment of the present invention. 8 differs from Example 3 in that the entire sensor sheet 16 is coated with a waterproof material 30 such as a PET film, and that a large number of air holes 31 are provided. Thereby, ventilation of both sides of the sensor sheet 16 can be achieved, and corrosion of each conductive layer is eliminated. Even when the sensor sheet 16 is embedded in bedding or the like, the metabolism of the living body 15 such as sweating and respiration is not hindered.
[0074]
(Example 5)
FIG. 9 is a structural diagram of a main part of a biological signal detection device according to a fifth embodiment of the present invention. FIG. 10 is a block diagram of the same device. 9 differs from the fourth embodiment in that 18 sensor sheets (16a, 16b, 16c,...) Are provided in the sensor sheet 16 and arranged independently in a two-dimensional array. Here, the second electrodes 19 (19a, 19b, 19c) are all connected to the same reference voltage E0. The output of the pressure-sensitive resistance layer 29 of each area-specific sensor sheet can be equivalently represented by a variable resistor R0 (R01, R02, R03,...), And each of the body pressure switches 32 (32a, 32b, 32c, ..), A first electrode 18 (18a, 18b,...) For extracting an output signal of a combined capacitance C0 (C01, C02, C03,...) For measuring body movement. 18c,...) Are connected, otherwise they are not connected. The outputs of the body pressure switches 32 (32a, 32b, 32c,...) Are added by the weight measuring means 33 and transmitted to the calculating means 23 as digital values corresponding to the weight of the living body 15. On the other hand, only the first electrodes 18 (18a, 18b, 18c,...) Connected by the body pressure switch 32 are connected in parallel to the body movement measuring means 21 and input. That is, the capacitance C0act connected to the body movement measuring means 21 is
[0075]
(Equation 7)

[0076]
(Equation 8)

[0077]
Can be represented by Even when the living body 15 rides on the sensor sheet 16, the body pressure and body movement are not evenly applied to all the individual sensor sheets (16 a, 16 b, 16 c,...) Depending on the sleeping posture and the sleeping position. In addition, the shape of the living body 15 itself has irregularities, and body movement can generally be effectively detected from an area where body pressure is applied. Because the distance between the living body 15 and the sensor sheet 16 is large in the area where the body pressure is not applied, the change in the capacitance due to the body movement is also small. If all of the first electrodes are connected to move the living body 15 by the body movement measuring means 21, the original combined capacitance C0 is large, so that the change ratio of C0 is relatively small even for the same body movement. Becomes smaller. On the other hand, if the change in the combined electrostatic capacity Cact only in the area where the body pressure is applied is detected as the body movement, the resolution of the body movement signal and thus the S / N ratio can be improved.
[0078]
Here, the vertical resolution is 6 rows and 3 columns, but the spatial resolution is not limited to this. Also, it may be a one-dimensional array.
[0079]
(Example 6)
FIG. 11 is a block diagram of the biological signal detection device according to the sixth embodiment of the present invention. FIG. 12 is an output frequency characteristic diagram of the piezoelectric body. 11 is different from the fifth embodiment in that an elastic insulating layer 25 made of rubber, urethane or the like having a dielectric property is not inserted between the first conductive layer 24 and the second conductive layer 26. The point is that a film-like piezoelectric layer such as vinylidene fluoride is inserted. The piezoelectric layer is an element that generates electric polarization (charge) according to applied strain, and is used for measuring dynamic motion such as mechanical vibration. FIG. 11 differs from FIG. 10 in that a piezoelectric body is provided between the first electrode 18 (18a, 18b, 18c,...) And the second electrode 19 (19a, 19b, 19c,. .. And amplifying means 34 for amplifying a signal after synthesizing the output of the piezoelectric layer in the area where the body pressure is applied, with a point having vibration oscillators X01, X02, X03,... It is in the point. The amplifying means 34 converts the impedance of the piezoelectric body with a FET in order to effectively extract the signal of the piezoelectric body having a high output impedance, and has an automatic gain control (AGC) mechanism so that the output voltage after the amplification is not saturated. Is obtained. A piezoelectric material has stable output characteristics at a certain temperature or lower, but as shown in FIG. 12, a differential type characteristic in which the output gain of a low-frequency component close to DC decreases due to the influence of the material, shape, input impedance of a detection circuit, and the like. It is an element having. Note that a charge amplifier that is advantageous for detecting minute vibrations may be used as the amplifying unit 34.
[0080]
With the above configuration, extraneous vibration noise (for example, automobile, train, insensitive earthquake, wind, etc.) generated in an area where body pressure is not applied can be excluded, so that the S / N ratio of a body motion signal can be improved. it can.
[0081]
(Example 7)
FIG. 13 is a block diagram of a biological signal detection device according to a seventh embodiment of the present invention. FIG. 14 is a graph showing the resistance value of the pressure-sensitive resistance layer 29, the body pressure, and the amplification factor. 13 is different from the sixth embodiment in that the body pressure measuring means 35a, 35b, 35c,... For measuring the body pressure for each area are provided, and according to the body pressure for each area. The point is that amplification means 36a, 36b, 36c,... For continuously changing the amplification rate are provided. The resistance value R0i [Ω] (i = 1 to 18) of the pressure-sensitive resistance layer 29 depends on the characteristics of the element, and the body pressure Pi [N / m] as shown in FIG. ² ], And nonlinearly converted to an amplification factor Gi as shown in FIG. Further, absolute value converting means 37a, 37b, 37c,... Are connected to the respective amplifying means 36a, 36b, 36c,. The absolute value signal is added to the body motion measuring means.
[0082]
According to the above configuration, the signals from the piezoelectric layers in all areas are not connected if the predetermined body pressure is higher than the predetermined body pressure as in the fifth embodiment, and are not disconnected if the pressure is lower than the predetermined body pressure, and are functions of a smooth and continuous body pressure according to the body pressure. Since the weight is weighted for each area, the inconvenience that the output signal greatly changes discontinuously even if the living body 15 moves only slightly is eliminated.
[0083]
Further, since the body motion signal for each area is once converted into an absolute value and then synthesized, the signal can be increased. When the living body 15 is at rest, periodic biological vibrations due to heart beat, blood flow, etc. are generated from the surface of the living body, but there is a time difference, that is, a phase shift for each living body part, and the signals cancel each other when simply combined. However, by providing such absolute value converting means 37a, 37b, 37c,..., The S / N ratio of a signal obtained can be kept large.
[0084]
(Example 8)
FIG. 15 is a block diagram of the biological signal detection device according to the eighth embodiment of the present invention. FIG. 15 differs from the first embodiment in that the output of the body pressure measuring means 22 is connected to a body movement signal calibrating means 38 and a timer means 39, and the timer means 39 is further connected to the body pressure signal calibrating means 40 to measure the body pressure. The point is that the means 22 or the body motion signal calibration 38 is connected to the body motion measuring means 21. The body motion signal calibrating unit 38 outputs, for example, 1000 [N / m] from the body pressure measuring unit 22. ² ], It is considered that the living body 15 does not exist, and the zero point adjustment is performed by applying a bias so that the output from the body movement measuring means 21 is minimized. Similarly, in the timer means 39, for example, the output from the body pressure measuring means 22 is 1000 [N / m ² ] If it is less than or equal to, it is considered that the living body 15 does not exist, and the duration of the same body pressure is measured. If this state continues for, for example, 10 minutes, the output of the body pressure measuring unit 22 is set to 0.0 [N / m] by the body pressure signal calibrating unit 40. ² ] And adjust the zero point by applying a bias. If the body pressure value fluctuates within 10 minutes, the timer means 39 clears the time measurement, and the body pressure becomes 1000 [N / m]. ² In the above description, the clocking itself is prohibited. Although it depends on the sensor sensitivity of the body pressure measuring means 22, it is not considered that the living body 15 is completely stationary as long as it is alive. Therefore, by providing the body pressure signal calibrating means 40 for zero-adjusting the output of the body pressure measuring means 22, it is possible to cancel the weight of unneeded objects such as mattresses and pillows on the sensor sheet 16 from the beginning. Even when the output resistance value is different even if the weight is the same due to the creep characteristic of the pressure-sensitive resistance element or the like, the body pressure signal can be reliably recognized as the difference when the state changes from the absence state to the presence state. This is convenient for accurately measuring the weight of the living body 15 and the like. Further, by providing the body motion signal calibrating means 38 for zero-adjusting the output of the body motion measuring means 21, the baseline generated by the dark vibration and the change in the temperature and humidity environment continuously occurring even when the living body 15 does not exist. Can be canceled automatically. This makes it possible to effectively detect only the body motion signal of the living body 15 from the moment the living body 15 changes from absent to present.
[0085]
(Example 9)
FIG. 16 is a block diagram of a biological signal detection device according to Embodiment 9 of the present invention. FIG. 17 is a power spectrum obtained when the living body 15 is in a resting supine position on the sensor sheet 16, and FIG. 18 is a diagram showing a combined ratio of the body movement measuring unit 21 and the body pressure measuring unit 22. FIG. 16 is different from the first embodiment in that the output of the body movement measuring means 21 is a power spectrum on the frequency axis by the first frequency converting means 41, and the output of the body pressure measuring means 22 is the second frequency converting means. 42 is represented as a power spectrum on the frequency axis, and both are combined as one power spectrum by the power spectrum combining means 43. The power spectrum synthesizing unit 43 is connected to the heart rate calculating unit 44, the respiratory rate calculating unit 45, and the activity calculating unit 46, and further connected to the display unit 47 together with the weight measuring unit 33 connected to the body pressure measuring unit 22. . The display means 47 displays and accumulates the current heart rate, respiratory rate, activity amount, and weight of the living body 15. A power spectrum graph as shown in FIG. 17 can be obtained from the first frequency conversion means 41 and the second frequency conversion means 42. The power spectrum of the conversion means 41 and the power spectrum of the second frequency conversion means 42 capable of obtaining a signal with high accuracy in a higher frequency range than a predetermined frequency are combined into one power spectrum with a combination ratio as shown in FIG. In FIG. 17, a peak fresp near 0.2 Hz indicates a respiration frequency, and a peak fhr near 1 Hz indicates a heartbeat frequency. The amount of activity is defined as a power integrated value (area) from 0.1 Hz to 10 Hz. To calculate the heart rate and the respiratory rate by the heart rate calculating means 44 and the respiratory rate calculating means 45, respectively, a predetermined frequency band (for example, the heart rate is 0.5 Hz to 2.0 Hz, and the respiratory rate is 0.05 Hz to 0.4 Hz) ) Is converted into a heart rate or a respiratory rate by finding a peak point. Further, an abnormality notification means 48 is connected to the display means 47. In a state where the body pressure of the living body 15 is present, when the life activity is stopped or the amount of activity falls below a predetermined level, or when the heart rate or respiratory rate deviates from a predetermined range, an alarm is sounded to notify an emergency. Configuration. The abnormality notifying means 48 may be combined with a timer to determine a change in physical condition or health condition from a long-term trend change, and issue a warning. In addition to the values of the heart rate and the respiratory rate, the intensity of the heart beat and the respiratory movement may be accumulated and displayed as the power value at the peak frequency point. Regarding the calculation of the heart rate and the respiratory rate, the waveform accompanying the heartbeat and the respiratory movement is not an ideal sine wave, and therefore a harmonic of the fundamental frequency often stands. In order to prevent erroneous calculation, cepstrum conversion may be further performed to extract only the fundamental wave, or a method of deleting the double frequency point from the peak point candidates may be used. Here, the first frequency conversion means 41 and the second frequency conversion means 42 perform frequency conversion while sequentially shifting the time-series signal for one minute sampled at a sampling frequency of 200 Hz, for example, every five seconds. In the resting state, it is unlikely that the heart rate or respiratory rate suddenly changes more than twice or less than 1/2, so the calculation frequency band (movable range) of the heart rate or respiratory rate is based on the previous calculation result. It may be defined adaptively. In order to separate a heartbeat and a respiratory motion including a relatively steep pulsed R-wave component, a filter may be applied in advance. The heart rate, the respiratory rate, the amount of activity, and the like may be calculated after returning to the time axis after the synthesis in the frequency axis.
[0086]
To combine the two power spectra, the average value of the power values at a specific frequency, for example, 1 Hz, is used as a reference point. The frequency band above that is the power spectrum of the first frequency conversion means 41, and the frequency band below it is the second. May be synthesized by sliding or linear conversion based on the power spectrum of the frequency conversion means 42.
[0087]
As a result, biological signal detection utilizing the advantages of the two types of sensors built in the same sensor sheet 16 can be performed, and the influence on external noise such as temperature and humidity environments, dark vibration, and electromagnetic waves can be reduced.
[0088]
【The invention's effect】
As is clear from the above description, according to the biological signal detection device of the present invention, the following effects can be obtained.
[0089]
(1) Since the electrodes for body movement measurement and body pressure measurement are shared, the structure can be simplified and external electromagnetic waves and vibration noise are less likely to be received. In addition, since the biological signal is detected from the two kinds of sensor output results, erroneous determination of calculating the biological signal when absent is eliminated, and various biological signals such as weight, heart rate, respiration, activity amount, and life status are obtained with high accuracy. be able to.
[0090]
(2) Since the piezoelectric body is used for body motion measurement, there is no adverse effect on the living body, and unconscious measurement is possible. Even if the piezoelectric body touches the living body, there is no risk of electric shock or the like. Naturally, it is possible to perform unrestricted and unconscious measurement for the living body.
[0091]
(3) Since each electrode is connected to the planar conductive layer, the detection performance is the same regardless of where the living body is on the conductive layer. Displacement due to movement of a living body is unlikely to occur, and there is little risk of breakdown. Since the arrangement of the electrodes is simple, there is little variation in performance during mass production.
[0092]
(4) Since the detection is performed by closely contacting the two types of detection medium layers without the conductive layer, the structure becomes simpler, and the body movement and the body pressure of the living body at the same position can be simultaneously detected.
[0093]
(5) Since the flexible sensor sheet is provided, it can be easily incorporated into daily necessities such as bedding, a carpet, a bathtub, a toilet seat and the like, which come into contact with a living body. Since it is easy to process and there are few restrictions on the installation environment, it can be easily attached later to not only new housing but also existing housing equipment. Especially when the living body to be measured is a bedridden elderly person, a demented elderly person, a disabled person or an infant or a pet animal, a long-term biological signal detection can be performed without disturbing the natural living operation of the living body at all. Can be performed continuously.
[0094]
(6) Since a plurality of ventilation holes are provided, even when the sensor sheet is embedded in bedding or the like, metabolism such as sweating and respiration of a living body is not hindered.
[0095]
(7) Since the waterproof film is provided, the detection sensitivity hardly deteriorates with time, and the life can be extended.
[0096]
(8) Since a plurality of sensor sheets are provided and an effective biological signal in an area where a living body exists can be selectively extracted, unnecessary vibration signals are removed, and the S / N ratio is dramatically improved.
[0097]
(9) Capacitance corresponding to body movement can be obtained by the elastic insulator.
[0098]
(10) It is possible to determine the presence or absence of a body pressure corresponding to the weight of the living body by using the elastic insulator with the porosity.
[0099]
(11) With the pressure-sensitive resistance layer, the body pressure of the living body can be obtained as a continuous value corresponding to the weight.
[0100]
(12) The body movement signal calibrating means can accurately measure even a change over time or a temperature and humidity environment.
[0101]
(13) The true body pressure signal of the living body can be measured by the body pressure signal calibrating means.
[0102]
(14) By combining the output of the body motion measuring means and the output of the body pressure measuring means in the frequency domain, it is possible to reduce the calculation error of the biological signal.
[0103]
(15) By correcting the power spectrum of the body movement measuring means and the power spectrum of the body pressure measuring means, the periodic vibration of the living body can be accurately detected as a power value for each frequency.
[Brief description of the drawings]
FIG. 1 is a block diagram of a biological signal detection device according to a first embodiment of the present invention.
FIG. 2 is an external view of the biological signal detection device of the embodiment.
FIG. 3 is a sectional view of a main part of the biological signal detecting device of the embodiment.
FIG. 4 is a sensor input circuit diagram of the biological signal detection device of the embodiment.
FIG. 5 is a sectional view of a main part of a biological signal detection device according to a second embodiment of the present invention.
FIG. 6 is a sensor input circuit diagram of the biological signal detection device of the embodiment.
FIG. 7 is a sectional view of a main part of a biological signal detection device according to a third embodiment of the present invention.
FIG. 8 is a sectional view of a main part of a biological signal detection device according to a fourth embodiment of the present invention.
FIG. 9 is a structural diagram of a main part of a biological signal detection device according to a fifth embodiment of the present invention.
FIG. 10 is a block diagram of the biological signal detection device of the embodiment.
FIG. 11 is a block diagram of a biological signal detection device according to a sixth embodiment of the present invention.
FIG. 12 is an output frequency characteristic diagram of the piezoelectric body of the embodiment.
FIG. 13 is a block diagram of a biological signal detection device according to a seventh embodiment of the present invention.
FIG. 14A is a graph showing the resistance value and the body pressure of the pressure-sensitive resistance layer 29 in the example.
(B) A graph showing the amplification factor and the body pressure of the pressure-sensitive resistance layer 29 in the same example.
FIG. 15 is a block diagram of a biological signal detection device according to an eighth embodiment of the present invention.
FIG. 16 is a block diagram of a biological signal detection device according to a ninth embodiment of the present invention.
FIG. 17 is a view showing a power spectrum of a biological signal of the embodiment.
FIG. 18 is a diagram showing a combined ratio of a body movement measuring unit 21 and a body pressure measuring unit 22.
FIG. 19 is a diagram showing a conventional capacitance-type biological signal detection device.
FIG. 20 is a diagram showing another conventional biological signal detection device using both a capacitance type and a pressure-sensitive type.
[Explanation of symbols]
15 living body
16 Sensor sheet
17 Signal processing device
18 First electrode
19 Second electrode
20 Third electrode
21 Body movement measuring means
22 Body pressure measuring means
23 Calculation means
24 First conductive layer
25 Elastic insulation layer
26 Second conductive layer
27 Insulation spacer
28 Third conductive layer
29 Pressure-sensitive resistance layer
30 Waterproof material
31 Vent
32 body pressure switch
33 Weight measurement means
35 Body pressure measuring means
38 Body motion signal calibration means
39 timer means
40 Body pressure signal calibration means
41 first frequency conversion means
42 Second frequency conversion means
43 Power spectrum synthesis means
44 Heart rate calculation means
45 Respiration rate calculation means
46 Activity amount calculation means

Claims

Vibration of the living body based on a series connection capacitance of a first capacitance formed between the first electrode and the living body and a second capacitance formed between the second electrode and the living body. A body movement measuring unit for measuring a signal; and a body pressure measuring unit for measuring a body pressure associated with the weight of the living body by a pressure-sensitive element between the first or second electrode and the third electrode. A biological signal detection device including a calculating unit that calculates a characteristic amount such as a weight, a heart rate, a respiratory rate, an activity amount, and a life state of the living body based on outputs of the body motion measuring unit and the body pressure measuring unit.

A body movement measuring means for forming a piezoelectric body between the first electrode and the second electrode and measuring an electric charge generated by vibration of a living body; Body pressure measuring means for measuring a body pressure signal associated with the weight of the living body by a pressure-sensitive element, further comprising the body movement measuring means and the output of the body pressure measuring means, the weight of the living body, heart rate, respiratory rate, A biological signal detection device including a calculation unit that calculates a feature amount such as an activity amount and a life state .

The first, second, and third electrodes are connected to at least three conductive layers and each of the conductive layers, and are provided between the first conductive layer and the second conductive layer or between the second conductive layer and the third conductive layer. 3. The biological signal detecting device according to claim 1, wherein a first or second sensing medium layer for measuring body movement or body pressure of a living body is formed.

The first sensing medium layer measures the body movement of the living body, the second sensing medium layer measures the body pressure of the living body, and the first and second sensing medium layers are brought into close contact with each other. 4. The biological signal detecting device according to claim 3, wherein one of the electrodes connected to both sides of the layer and one of the electrodes connected to both sides of the second sensing medium layer are shared.

The biological signal detecting device according to claim 3 or 4, wherein the first and second conductive layers and the sensing medium layer each have flexibility and constitute an integrally formed planar sensor sheet.

The biological signal detecting device according to claim 5, wherein the sensor sheet has a plurality of ventilation holes.

7. The biological signal detection device according to claim 6, wherein a waterproof film is adhered inside the ventilation hole.

6. The biological signal detecting device according to claim 5, further comprising a synthesizing unit that synthesizes outputs of the body motion measuring units in accordance with outputs of the plurality of body pressure measuring units.

4. The biological signal detecting device according to claim 3, further comprising an elastic insulating layer whose thickness changes with pressure between the first conductive layer and the second conductive layer.

4. The biological signal detection device according to claim 3, further comprising a porous elastic insulating layer electrically connected by pressure between the second conductive layer and the third conductive layer.

4. The biological signal detection device according to claim 3, further comprising a pressure-sensitive resistance layer between the second conductive layer and the third conductive layer, the resistance of which changes with pressure, such as conductive rubber or conductive carbon.

The biological signal according to any one of claims 1 to 11, further comprising a body movement signal calibrating unit that initializes an output of the body movement measuring unit when an output signal or an output change rate of the body pressure measuring unit is equal to or less than a predetermined value. Detection device.

Timer means for measuring the duration of the output signal of the body pressure measurement means being equal to or less than a predetermined value, and a body pressure signal for initializing the output of the body pressure measurement means when the duration time exceeds a predetermined time by the timer means. 13. The biological signal detection device according to claim 1, further comprising a calibration unit.

14. A signal synthesizing unit for synthesizing output signals of the body motion measuring unit and the body pressure measuring unit in a frequency domain, and a calculating unit for calculating an output characteristic amount of the signal synthesizing unit. Biological signal detection device.

The signal synthesizing means corrects the power spectrum of the output signal of the body motion measuring means based on the power value of the body pressure measuring means at a predetermined frequency or corrects the power spectrum of the body pressure measuring means based on the power value of the body motion measuring means at a predetermined frequency. The biological signal detection device according to claim 14, wherein