JP2004187951A

JP2004187951A - Method and device for collecting data

Info

Publication number: JP2004187951A
Application number: JP2002360093A
Authority: JP
Inventors: Masanori Higuchi; 正法樋口
Original assignee: Kanazawa Institute of Technology (KIT)
Current assignee: Kanazawa Institute of Technology (KIT)
Priority date: 2002-12-12
Filing date: 2002-12-12
Publication date: 2004-07-08

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for collecting data by which data, from which power supply hum noise is removed, can be acquired even when such a measurement is performed that data collecting timing can be decided independently from a power supply cycle. <P>SOLUTION: In the data collecting method, data collection which is performed for a fixed period at the timing synchronous to the zero-crossing point of the positive slope of the power supply cycle at and after a basic trigger Btr and another data collection which is performed for a fixed period at the timing synchronous to the zero-crossing point of the negative slope of periodical noise at and after the next basic trigger Btr are repeated and obtained data are added to each other. Consequently, data collection can be repeated at an arbitrary timing and, the power supply hum noise can be suppressed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
本発明は、データ収集方法および装置に関し、さらに詳しくは、データ収集間隔が周期的ノイズの周期とは独立に決められる測定においても周期的ノイズを除去したデータを得ることが出来るデータ収集方法および装置、並びに、周期的ノイズの偶数次高調波をも除去したデータを得ることが出来るデータ収集方法および装置に関する。
【０００２】
【従来の技術】
従来、電源ハムノイズを除去するため、電源周期の整数倍のデータ収集時間に渡って第１のデータを収集し、それから電源周期の「１／２＋Ｎ」倍の時間後に第１のデータと同じデータ収集時間に渡って第２のデータを収集し、第１のデータと第２のデータを平均する技術が知られている（例えば、特許文献１参照）。
【０００３】
【特許文献１】
特開２００２−２５７８６８号公報
【０００４】
【発明が解決しようとする課題】
例えば、聴覚刺激により誘発される脳磁気反応を測定するために、聴覚刺激を与えるのと同期してデータ収集時間９００ｍｓ，サンプリング周期５ｋＨｚでデータを収集することを、データ収集間隔２秒間毎に、２６回繰り返し、得られたデータを加算する、ということが行われる。
このような刺激誘発反応測定では、データ収集間隔は電源周期とは独立に決められているが、前記従来技術では、１回目のデータ収集が行われた後、電源周期の「１／２＋Ｎ」倍の時間後に２回目のデータ収集が自動的に行われてしまい、データ収集間隔が整合しない。すなわち、電源ハムノイズを除去する前記従来技術は、データ収集間隔が電源周期とは独立に決められる測定に対して適用しにくい問題点があった。
【０００５】
また、前記従来技術は、電源周期の基本波および奇数次高調波に対しては有効であるが、偶数次高調波に対しては無力であるという問題点があった。
【０００６】
そこで、本発明の第１の目的は、データ収集間隔が周期的ノイズの周期とは独立に決められる測定においても周期的ノイズを除去したデータを得ることが出来るデータ収集方法および装置を提供することにある。
また、本発明の第２の目的は、周期的ノイズの偶数次高調波をも除去したデータを得ることが出来るデータ収集方法および装置を提供することにある。
【０００７】
【課題を解決するための手段】
第１の観点では、本発明は、ある基本トリガ以後の周期的ノイズの正または負のスロープのゼロクロス点に同期したタイミングでデータを一定期間収集し、前記基本トリガの次の基本トリガ以後の周期的ノイズの前回と逆向きのスロープのゼロクロス点に同期したタイミングでデータを一定期間収集することを繰り返し、得られたデータを加算することを特徴とするデータ収集方法を提供する。
上記第１の観点によるデータ収集方法では、基本トリガが発生されると、それ以後の周期的ノイズの正または負のスロープのゼロクロス点に同期したタイミングでデータを一定期間収集する。次の基本トリガが発生されると、それ以後の周期的ノイズの前回と逆向きのスロープのゼロクロス点に同期したタイミングでデータを一定期間収集する。この２回一組のデータ収集を繰り返し、得られたデータを加算するが、２回一組のデータ収集で収集したデータに含まれる周期的ノイズの基本波および奇数次高調波の極性が逆になるため、周期的ノイズの基本波および奇数次高調波をキャンセルできる。そして、基本トリガの発生間隔は、周期的ノイズの周期とは独立に決めることが出来る。また、基本トリガを任意の回数発生してもよい。なお、基本トリガの発生回数が偶数回でないと、１回分の周期的ノイズがキャンセルされないが、基本トリガの発生回数を多くすれば、１回分の周期的ノイズは無視できる。例えば、基本トリガの発生回数を２５回とすれば、被測定信号と周期的ノイズの比が２５：１になるため、周期的ノイズは実質的に無視できる。
【０００８】
第２の観点では、本発明は、Ｎを０以上の整数とするとき、ある基本トリガ以後の周期的ノイズの所定位相に同期したタイミングでデータを一定期間収集し、前記基本トリガの次の基本トリガ以後の前記所定位相と周期的ノイズの周期の「１／２＋Ｎ」倍の時間だけ異なる位相に同期したタイミングでデータを一定期間収集することを繰り返し、得られたデータを加算することを特徴とするデータ収集方法を提供する。
上記第２の観点によるデータ収集方法では、基本トリガが発生されると、それ以後の周期的ノイズの所定位相に同期したタイミングでデータを一定期間収集する。次の基本トリガが発生されると、それ以後の周期的ノイズの所定位相と周期的ノイズの周期の「１／２＋Ｎ」倍の時間だけ異なる位相に同期したタイミングでデータを一定期間収集する。この２回一組のデータ収集を繰り返し、得られたデータを加算するが、２回一組のデータ収集で収集したデータに含まれる周期的ノイズの基本波および奇数次高調波の極性が逆になるため、周期的ノイズの基本波および奇数次高調波をキャンセルできる。そして、基本トリガの発生間隔は、周期的ノイズの周期とは独立に決めることが出来る。また、基本トリガを任意の回数発生してもよい。なお、基本トリガの発生回数が偶数回でないと、１回分の周期的ノイズがキャンセルされないが、基本トリガの発生回数を多くすれば、１回分の周期的ノイズは無視できる。例えば、基本トリガの発生回数を２５回とすれば、被測定信号と周期的ノイズの比が２５：１になるため、周期的ノイズは実質的に無視できる。
【０００９】
第３の観点では、本発明は、ある基本トリガ以後の周期的ノイズの正または負のゼロクロス点に同期したタイミングでデータを一定期間収集し、前記基本トリガの後の１番目の基本トリガ以後の前記周期的ノイズの前回と同向きのゼロクロス点から周期的ノイズの周期の１／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集し、前記基本トリガの後の２番目の基本トリガ以後の前記周期的ノイズの前回と同向きのゼロクロス点から周期的ノイズの周期の２／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集し、前記基本トリガの後の３番目の基本トリガ以後の前記周期的ノイズの前回と同向きのゼロクロス点から周期的ノイズの周期の３／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集することを繰り返し、得られたデータを加算することを特徴とするデータ収集方法を提供する。
上記第３の観点によるデータ収集方法では、基本トリガが発生されると、それ以後の周期的ノイズの正または負のスロープのゼロクロス点に同期したタイミングでデータを一定期間収集する。次の基本トリガが発生されると、それ以後の周期的ノイズの最初と同向きのスロープのゼロクロス点から周期的ノイズの周期の１／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集する。また、次の基本トリガが発生されると、それ以後の周期的ノイズの最初と同向きのスロープのゼロクロス点から周期的ノイズの周期の２／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集する。さらに次の基本トリガが発生されると、それ以後の周期的ノイズの最初と同向きのスロープのゼロクロス点から周期的ノイズの周期の３／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集する。この４回一組のデータ収集を繰り返し、得られたデータを加算するが、４回一組のデータ収集で収集したデータに含まれる周期的ノイズの基本波および奇数次高調波および２次高調波の極性が逆になるため、周期的ノイズの基本波および奇数次高調波および２次高調波をキャンセルできる。そして、基本トリガの発生間隔は、周期的ノイズの周期とは独立に決めることが出来る。また、基本トリガを任意の回数発生してもよい。なお、基本トリガの発生回数が４の倍数回でないと、１回分〜３回分の周期的ノイズがキャンセルされないが、基本トリガの発生回数を多くすれば、１回分〜３回分の周期的ノイズは無視できる。例えば、基本トリガの発生回数を２５回〜２７回とすれば、被測定信号と周期的ノイズの比が２５：１〜２７：３になるため、周期的ノイズは実質的に無視できる。
【００１０】
第４の観点では、本発明は、Ｎを０以上の整数とし、Ｋを２以上の２のべき乗とし、ｉを１から「Ｋ−１」までの整数とするとき、ある基本トリガ以後の周期的ノイズの所定位相θ(０)に同期したタイミングでデータを一定期間収集し、前記基本トリガからｉ番目の基本トリガ以後の前記所定位相θ(０)と周期的ノイズの周期の「ｉ／Ｋ＋Ｎ」倍の時間だけ異なる位相θ(２・π・ｉ／Ｋ)に同期したタイミングでデータを一定期間収集することを繰り返し、得られたデータを加算することを特徴とするデータ収集方法を提供する。
上記第４の観点によるデータ収集方法では、基本トリガが発生されると、それ以後の周期的ノイズの所定位相θ(０)に同期したタイミングでデータを一定期間収集する。最初の基本トリガから１番目の基本トリガが発生されると、それ以後の周期的ノイズの所定位相θ(０)と周期的ノイズの周期の「１／Ｋ＋Ｎ」倍の時間だけ異なる位相θ１に同期したタイミングでデータを一定期間収集する。また、最初の基本トリガから２番目の基本トリガが発生されると、それ以後の周期的ノイズの所定位相θ(０)と周期的ノイズの周期の「２／Ｋ＋Ｎ」倍の時間だけ異なる位相θ２に同期したタイミングでデータを一定期間収集する。同様の処理を行って、最初の基本トリガから「Ｋ−１」番目の基本トリガが発生されると、それ以後の周期的ノイズの所定位相θ(０)と周期的ノイズの周期の「（Ｋ−１）／Ｋ＋Ｎ」倍の時間だけ異なる位相θ_Ｋ−１に同期したタイミングでデータを一定期間収集する。このＫ回一組のデータ収集を繰り返し、得られたデータを加算するが、Ｋ回一組のデータ収集で収集したデータに含まれる周期的ノイズの基本波および奇数次高調波および２(log2{Ｋ}−１)次高調波までの偶数時高調波の極性が逆になるため、周期的ノイズの基本波および奇数次高調波および２(log2{Ｋ}−１)次高調波までの偶数時高調波をキャンセルできる。なお、log2{}は、２を底とする対数とする。そして、基本トリガの発生間隔は、周期的ノイズの周期とは独立に決めることが出来る。また、基本トリガを任意の回数発生してもよい。なお、基本トリガの発生回数がＫの倍数回でないと、１回分〜「Ｋ−１」回分の周期的ノイズがキャンセルされないが、基本トリガの発生回数を多くすれば、１回分〜「Ｋ−１」回分の周期的ノイズは無視できる。例えば、Ｋ＝８とし、基本トリガの発生回数を２５回〜３１回とすれば、被測定信号と周期的ノイズの比が２５：１〜３１：７になるため、周期的ノイズは実質的に無視できる。
【００１１】
第５の観点では、本発明は、Ｎを０以上の整数とし、Ｋを４以上の２のべき乗とし、ｉを１から「Ｋ−１」までの整数とするとき、周期的ノイズの所定位相θ(０)に同期したタイミングでデータを一定期間収集し、前記所定位相と周期的ノイズの周期の「ｉ／Ｋ＋Ｎ」倍の時間だけ異なる位相θ(２・π・ｉ／Ｋ)に同期したタイミングでデータを一定期間収集し、得られたデータを加算することを特徴とするデータ収集方法を提供する。
上記第５の観点によるデータ収集方法では、周期的ノイズの所定位相θ(０)に同期したタイミングでデータを一定期間収集する。次に、所定位相θ(０)と周期的ノイズの周期の「１／Ｋ＋Ｎ」倍の時間だけ異なる位相θ１に同期したタイミングでデータを一定期間収集する。また、所定位相θ(０)と周期的ノイズの周期の「２／Ｋ＋Ｎ」倍の時間だけ異なる位相θ２に同期したタイミングでデータを一定期間収集する。同様の処理を行って、所定位相θ(０)と周期的ノイズの周期の「（Ｋ−１）／Ｋ＋Ｎ」倍の時間だけ異なる位相θ_Ｋ−１に同期したタイミングでデータを一定期間収集する。このＫ回一組のデータ収集を繰り返し、得られたデータを加算するが、Ｋ回一組のデータ収集で収集したデータに含まれる周期的ノイズの基本波および奇数次高調波および２(log2{Ｋ}−１)次高調波までの偶数時高調波の極性が逆になるため、周期的ノイズの基本波および奇数次高調波および２(log2{Ｋ}−１)次高調波までの偶数時高調波をキャンセルできる。なお、log2{}は、２を底とする対数とする。
【００１２】
第６の観点では、本発明は、基本トリガを発生する基本トリガ発生手段と、ある基本トリガ以後の周期的ノイズの正または負のスロープのゼロクロス点に同期したタイミングでデータを一定期間収集すると共に前記基本トリガの次の基本トリガ以後の周期的ノイズの前回と逆向きのスロープのゼロクロス点に同期したタイミングでデータを一定期間収集することを繰り返すデータ収集手段と、得られたデータを加算するデータ加算手段とを具備することを特徴とするデータ収集装置を提供する。
上記第６の観点によるデータ収集装置では、前記第１の観点によるデータ収集方法を好適に実施できる。
【００１３】
第７の観点では、本発明は、Ｎを０以上の整数とするとき、基本トリガを発生する基本トリガ発生手段と、ある基本トリガ以後の周期的ノイズの所定位相に同期したタイミングでデータを一定期間収集すると共に前記基本トリガの次の基本トリガ以後の前記所定位相と周期的ノイズの周期の「１／２＋Ｎ」倍の時間だけ異なる位相に同期したタイミングでデータを一定期間収集することを繰り返すデータ収集手段と、得られたデータを加算するデータ加算手段とを具備することを特徴とするデータ収集装置を提供する。
上記第７の観点によるデータ収集装置では、前記第２の観点によるデータ収集方法を好適に実施できる。
【００１４】
第８の観点では、本発明は、基本トリガを発生する基本トリガ発生手段と、ある基本トリガ以後の周期的ノイズの正または負のゼロクロス点に同期したタイミングでデータを一定期間収集し、前記基本トリガの後の１番目の基本トリガ以後の前記周期的ノイズの前回と同向きのゼロクロス点から周期的ノイズの周期の１／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集し、前記基本トリガの後の２番目の基本トリガ以後の前記周期的ノイズの前回と同向きのゼロクロス点から周期的ノイズの周期の２／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集し、前記基本トリガの後の３番目の基本トリガ以後の前記周期的ノイズの前回と同向きのゼロクロス点から周期的ノイズの周期の３／４倍の時間だけ遅れた位相に同期したタイミングでデータを一定期間収集することを繰り返すデータ収集手段と、得られたデータを加算するデータ加算手段とを具備したことを特徴とするデータ収集装置を提供する。
上記第８の観点によるデータ収集装置では、前記第３の観点によるデータ収集方法を好適に実施できる。
【００１５】
第９の観点では、本発明は、Ｎを０以上の整数とし、Ｋを２以上の２のべき乗とし、ｉを１から「Ｋ−１」までの整数とするとき、基本トリガを発生する基本トリガ発生手段と、ある基本トリガ以後の周期的ノイズの所定位相θ(０)に同期したタイミングでデータを一定期間収集すると共に前記基本トリガからｉ番目の基本トリガ以後の前記所定位相と周期的ノイズの周期の「ｉ／Ｋ＋Ｎ」倍の時間だけ異なる位相θ(２・π・ｉ／Ｋ)に同期したタイミングでデータを一定期間収集することを繰り返すデータ収集手段と、得られたデータを加算するデータ加算手段とを具備したことを特徴とするデータ収集装置を提供する。
上記第９の観点によるデータ収集装置では、前記第４の観点によるデータ収集方法を好適に実施できる。
【００１６】
第１０の観点では、本発明は、Ｎを０以上の整数とし、Ｋを４以上の２のべき乗とし、ｉを１から「Ｋ−１」までの整数とするとき、周期的ノイズの所定位相θ(０)に同期したタイミングでデータを一定期間収集すると共に前記所定位相と周期的ノイズの周期の「ｉ／Ｋ＋Ｎ」倍の時間だけ異なる位相θ(２・π・ｉ／Ｋ)に同期したタイミングでデータを一定期間収集するデータ収集手段と、得られたデータを加算するデータ加算手段とを具備したことを特徴とするデータ収集装置を提供する。
上記第１０の観点によるデータ収集装置では、前記第５の観点によるデータ収集方法を好適に実施できる。
【００１７】
【発明の実施の形態】
以下、図に示す実施の形態により本発明をさらに詳細に説明する。なお、これにより本発明が限定されるものではない。
【００１８】
−第１の実施形態−
図１は、第１の実施形態に係る脳磁気データ収集装置の構成図である
脳磁気データ収集装置１００は、コンピュータ１と、基本トリガＢtrを発生する基本トリガ発生部２と、電源波形を出力する電源波形出力部３と、基本トリガの入力以後の電源波形の所定位相θに同期したシンクロトリガＳtrを出力するシンクロトリガ発生部４と、シンクロトリガＳtrに応じて刺激を発生し被検体Ｈに与える刺激発生部５と、被検体Ｈの脳磁気を検出し脳磁気信号を出力する脳磁気検出部６と、脳磁気信号を増幅する信号増幅部７と、脳磁気信号をデジタル値に変換するＡＤ変換部８とを具備している。
【００１９】
コンピュータ１は、制御部１ａと、データ収集部１ｂと、データ加算部１ｃとを含んでいる。
制御部１ａは、基本トリガＢtrを例えば２秒間隔で２６回発生する指示を基本トリガ発生部２に与える。また、シンクロトリガＳtrに応じて、ＡＤ変換部８に制御信号を送る。
データ収集部は、シンクロトリガＳtrに応じてＡＤ変換部８から脳磁気信号のデジタル値Ｄ(j)を取り込む。例えば、データ収集時間９００ｍｓ，サンプリング周期５ｋＨｚとすると、１回のシンクロトリガＳtrでＤ(1)〜Ｄ(4500)の４５００個のデータを取り込む。
データ加算部１ｃは、シンクロトリガＳtr毎に取り込んだデータＤ(1)〜Ｄ(4500)を、サンプリング順ｊを合わせて加算し、測定データｄ(1)〜ｄ(4500)とする。例えば、２６回のデータＤ(1)〜Ｄ(4500)を加算するなら、ｍを回数として、
ｄ(j)＝_ｍ＝１Σ^２６Ｄ(j)
ｊ＝１，２，…，４５００
である。
【００２０】
図２は、第１の実施形態に係るシンクロトリガ発生部４の構成を示すブロック図である。
このシンクロトリガ発生部４は、基本トリガＢtrをカウントし「０」個または偶数個なら第０出力に「１」を出力し奇数個なら第１出力に「１」を出力するカウンタ４１と、電源波形の正スロープのゼロクロス点（電圧が負から正に変わる点）で「１」になり電源波形の１／２周期後に「０」に戻る第０フェーズ信号θ(０)を出力すると共に電源波形の負スロープのゼロクロス点（電圧が正から負に変わる点）で「１」になり電源波形の１／２周期後に「０」に戻る第１フェーズ信号θ(π)を出力するフェーズ信号発生部４２と、第０フェーズ信号θ(０)の立上りでカウンタ４１の第０出力の値を読み込んで保持する第０ラッチ４３０と、第１フェーズ信号θ(π)の立上りでカウンタ４１の第１出力の値を読み込んで保持する第１ラッチ４３１と、第０ラッチ４３０の出力ａ０の立上りで短い時間幅のパルスｂ０を出力する第０ワンショット回路４４０と、第１ラッチ４３１の出力ａ１の立上りで短い時間幅のパルスｂ１を出力する第１ワンショット回路４４１と、第０ワンショット回路４４０の出力ｂ０および第１ワンショット回路４４１の出力ｂ１の論理和を出力するＯＲ回路４５と、基本トリガＢtrが「０」個の時は「０」であり基本トリガＢtrが「１」個でも来ると「１」になるマスク信号Ｍを出力するマスク用ラッチ４６と、ＯＲ回路４５の出力およびマスク信号Ｍの論理積をシンクロトリガＳtrとして出力するＡＮＤ回路４７とを具備している。
【００２１】
図３は、第１の実施形態に係る脳磁気データ収集装置１００の動作を示すタイムチャートである。
電源波形は、５０Ｈｚまたは６０Ｈｚの正弦波である。
第０フェーズ信号θ(０)は、電源波形の電圧が負から正に変わるゼロクロス点で「１」になり、電源波形の１／２周期後に「０」に戻る。
第１フェーズ信号θ(π)は、電源波形の電圧が正から負に変わるゼロクロス点で「１」になり、電源波形の１／２周期後に「０」に戻る。
【００２２】
基本トリガＢtrは、電源周期の数倍の間隔で発生されるように図示しているが、これは図示の都合上であり、実際には秒オーダーの間隔（電源周期の１００倍以上の間隔）で発生される。
【００２３】
カウンタ４１の第０出力は、基本トリガＢtrが「０」個または偶数個なら「１」となり、奇数個なら「０」となる。
カウンタ４１の第１出力は、基本トリガＢtrが奇数個なら「１」となり、「０」個または偶数個なら「０」となる。
【００２４】
第０ラッチ４３０の出力ａ０は、電源投入後最初に電源波形の電圧が負から正に変わるゼロクロス点で「１」になり、１個目の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で「０」に戻る。また、偶数個目の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で「１」になり、次の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で「０」に戻る。
第１ラッチ４３１の出力ａ１は、奇数個目の基本トリガＢtr以後最初に電源波形の電圧が正から負に変わるゼロクロス点で「１」になり、次の基本トリガＢtr以後最初に電源波形の電圧が正から負に変わるゼロクロス点で「０」に戻る。
【００２５】
第０ワンショット回路４４０の出力パルスｂ０は、電源投入後最初に電源波形の電圧が負から正に変わるゼロクロス点および偶数個目の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で出力される。
第１ワンショット回路４４１の出力パルスｂ１は、奇数個目の基本トリガＢtr以後最初に電源波形の電圧が正から負に変わるゼロクロス点で出力される。
【００２６】
マスク信号Ｍは、基本トリガＢtrが来る前は「０」であり、１個目の基本トリガＢtrが来ると「１」になる。
【００２７】
シンクロトリガＳtrは、奇数個目の基本トリガＢtr以後最初に電源波形の電圧が正から負に変わるゼロクロス点および偶数個目の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で出力される。
【００２８】
データ収集期間の開始タイミングは、シンクロトリガＳtrの立上りである。
データ収集期間の長さは、電源周期の２倍であるように図示しているが、これは図示の都合上であり、実際には数百ミリ秒オーダーの間隔（電源周期の１０倍以上の長さ）であり、且つ、電源周期とは独立に決めてよい。
データ収集期間に、数百マイクロ秒オーダーのサンプリング間隔でデータＤ(j)を収集する。
【００２９】
電源ハムノイズ（基本波）は、データ収集期間に対応する電源波形であるが、図３から判るように、奇数番目のデータ収集期間に含まれる波形と偶数番目のデータ収集期間に含まれる波形とは、極性が逆で、大きさが等しくなっている。
このため、データ加算部１ｃで、奇数番目のデータ収集期間と偶数番目のデータ収集期間とに取り込んだデータＤ(j)を、サンプリング順ｊを合わせて加算すれば、電源ハムノイズ（基本波）はキャンセルされる。
【００３０】
第１の実施形態に係る脳磁気データ収集装置１００によれば、電源周期とは独立に基本トリガＢtrを発生させても、電源ハムノイズの基本波を除去した脳磁気データを得ることが出来る。
なお、電源ハムノイズの奇数次高調波は、基本波と同様に奇数番目のデータ収集期間に含まれる波形と偶数番目のデータ収集期間に含まれる波形とが逆極性で大きさが等しくなるため、加算により除去される。
【００３１】
一方、電源ハムノイズの偶数次高調波は、奇数番目のデータ収集期間に含まれる波形と偶数番目のデータ収集期間に含まれる波形とが同極性で大きさが等しくなるため、加算しても除去されない。例えば、図４に示すように、電源ハムノイズの２次高調波は、奇数番目のデータ収集期間に含まれる波形と偶数番目のデータ収集期間に含まれる波形とが同極性で大きさが等しい。このため、加算してもキャンセルされない。但し、電源ハムノイズの偶数次高調波は、基本波に比べて大きさが小さいため、それほど問題にならない場合が多い。
【００３２】
−第２の実施形態−
第２の実施形態の脳磁気データ収集装置は、第１の実施形態の脳磁気データ収集装置１００のシンクロトリガ発生部４として、図５に示すシンクロトリガ発生部４を用いた構成である。
【００３３】
カウンタ４１は、基本トリガＢtrをカウントし、「０」個または「４で割った余りが０になる個数番目」なら第０出力に「１」を出力し、「４で割った余りが１になる個数番目」なら第１出力に「１」を出力し、「４で割った余りが２になる個数番目」なら第２出力に「１」を出力し、「４で割った余りが３になる個数番目」なら第３出力に「１」を出力する。
【００３４】
フェーズ信号発生部４２は、電源波形の正スロープのゼロクロス点（電圧が負から正に変わる点）で「１」になり電源波形の１／２周期後に「０」に戻る第０フェーズ信号θ(０)と、第０フェーズ信号θ(０)を電源波形の１／４周期だけ遅延させた第１フェーズ信号θ(π／２)と、電源波形の負スロープのゼロクロス点（電圧が正から負に変わる点）で「１」になり電源波形の１／２周期後に「０」に戻る第２フェーズ信号θ(π)と、第２フェーズ信号θ(π)を電源波形の１／４周期だけ遅延させた第３フェーズ信号θ(３π／２)とを出力する。
【００３５】
第０ラッチ４３０は、第０フェーズ信号θ(０)の立上りでカウンタ４１の第０出力の値を読み込んで保持する。
第１ラッチ４３１は、第１フェーズ信号θ(π／２)の立上りでカウンタ４１の第１出力の値を読み込んで保持する。
第２ラッチ４３２は、第２フェーズ信号θ(π)の立上りでカウンタ４１の第２出力の値を読み込んで保持する。
第３ラッチ４３３は、第３フェーズ信号θ(３π／２)の立上りでカウンタ４１の第３出力の値を読み込んで保持する。
【００３６】
第０ワンショット回路４４０は、第０ラッチ４３０の出力ａ０の立上りで短い時間幅のパルスｂ０を出力する。
第１ワンショット回路４４１は、第１ラッチ４３１の出力ａ１の立上りで短い時間幅のパルスｂ１を出力する。
第２ワンショット回路４４２は、第２ラッチ４３２の出力ａ２の立上りで短い時間幅のパルスｂ２を出力する。
第３ワンショット回路４４３は、第３ラッチ４３３の出力ａ３の立上りで短い時間幅のパルスｂ３を出力する。
【００３７】
ＯＲ回路４５は、第０ワンショット回路４４０の出力ｂ０，第１ワンショット回路４４１の出力ｂ１，第２ワンショット回路４４２の出力ｂ２および第３ワンショット回路４４３の出力ｂ３の論理和を出力する。
【００３８】
マスク用ラッチ４６は、基本トリガＢtrが「０」個の時は「０」であり、基本トリガＢtrが「１」個でも来ると「１」になるマスク信号Ｍを出力する。
ＡＮＤ回路４７は、ＯＲ回路４５の出力およびマスク信号Ｍの論理積をシンクロトリガＳtrとして出力する。
【００３９】
図６および図７は、第２の実施形態に係る脳磁気データ収集装置の動作を示すタイムチャートである。
図６に示す電源波形は、５０Ｈｚまたは６０Ｈｚの正弦波である。
第０フェーズ信号θ(０)は、電源波形の電圧が負から正に変わるゼロクロス点で「１」になり、電源波形の１／２周期後に「０」に戻る。
第１フェーズ信号θ(π／２)は、第０フェーズ信号θ(０)を電源波形の１／４周期だけ遅延させた信号である。
第２フェーズ信号θ(π)は、第０フェーズ信号θ(０)を電源波形の２／４周期だけ遅延させた信号になっている。
第３フェーズ信号θ(３π／２)は、第０フェーズ信号θ(０)を電源波形の３／４周期だけ遅延させた信号になっている。
【００４０】
基本トリガＢtrは、電源周期の数倍の間隔で発生されるように図示しているが、これは図示の都合上であり、実際には秒オーダーの間隔（電源周期の１００倍以上の間隔）で発生される。
【００４１】
カウンタ４１の第０出力は、基本トリガＢtrが「０」個または「４で割った余りが０になる個数番目」なら「１」となり、他では「０」となる。
カウンタ４１の第１出力は、基本トリガＢtrが「４で割った余りが１になる個数番目」なら「１」となり、他では「０」となる。
カウンタ４１の第２出力は、基本トリガＢtrが「４で割った余りが２になる個数番目」なら「１」となり、他では「０」となる。
カウンタ４１の第３出力は、基本トリガＢtrが「４で割った余りが３になる個数番目」なら「１」となり、他では「０」となる。
【００４２】
第０ラッチ４３０の出力ａ０は、電源投入後最初に電源波形の電圧が負から正に変わるゼロクロス点で「１」になり、１個目の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で「０」に戻る。また、「４で割った余りが０になる個数番目」の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で「１」になり、次の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で「０」に戻る。
第１ラッチ４３１の出力ａ１は、「４で割った余りが１になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の１／４だけ遅延させた点」で「１」になり、次の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の１／４だけ遅延させた点」で「０」に戻る。
第２ラッチ４３２の出力ａ２は、「４で割った余りが２になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の２／４だけ遅延させた点」で「１」になり、次の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の２／４だけ遅延させた点」で「０」に戻る。
第３ラッチ４３３の出力ａ３は、「４で割った余りが３になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の３／４だけ遅延させた点」で「１」になり、次の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の３／４だけ遅延させた点」で「０」に戻る。
【００４３】
第０ワンショット回路４４０の出力パルスｂ０は、電源投入後最初に電源波形の電圧が負から正に変わるゼロクロス点および「４で割った余りが０になる個数番目」の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で出力される。
第１ワンショット回路４４１の出力パルスｂ１は、「４で割った余りが１になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の１／４だけ遅延させた点」で出力される。
第２ワンショット回路４４２の出力パルスｂ２は、「４で割った余りが２になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の２／４だけ遅延させた点」で出力される。
第３ワンショット回路４４３の出力パルスｂ３は、「４で割った余りが３になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の３／４だけ遅延させた点」で出力される。
【００４４】
図７に示すマスク信号Ｍは、基本トリガＢtrが来る前は「０」であり、１個目の基本トリガＢtrが来ると「１」になる。
【００４５】
シンクロトリガＳtrは、「４で割った余りが１になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の１／４だけ遅延させた点」、「４で割った余りが２になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の２／４だけ遅延させた点」、「４で割った余りが３になる個数番目」の基本トリガＢtr以後最初の「電源波形の電圧が負から正に変わるゼロクロス点を電源周期の３／４だけ遅延させた点」、および、「４で割った余りが０になる個数番目」の基本トリガＢtr以後最初に電源波形の電圧が負から正に変わるゼロクロス点で出力される。
【００４６】
データ収集期間の開始タイミングは、シンクロトリガＳtrの立上りである。
データ収集期間の長さは、電源周期の２倍であるように図示しているが、これは図示の都合上であり、実際には数百ミリ秒オーダーの間隔（電源周期の１０倍以上の長さ）であり、且つ、電源周期とは独立に決めてよい。
データ収集期間に、数百マイクロ秒オーダーのサンプリング間隔でデータＤ(j)を収集する。
【００４７】
電源ハムノイズの基本波は、データ収集期間に対応する電源波形であるが、図７から判るように、「４で割った余りが１になる個数番目」のデータ収集期間に含まれる波形と「４で割った余りが３になる個数番目」のデータ収集期間に含まれる波形とは、極性が逆で、大きさが等しくなっている。また、「４で割った余りが２になる個数番目」のデータ収集期間に含まれる波形と「４で割った余りが０になる個数番目」のデータ収集期間に含まれる波形とは、極性が逆で、大きさが等しくなっている。
このため、データ加算部１ｃで、「４で割った余りが１になる個数番目」のデータ収集期間と「４で割った余りが３になる個数番目」のデータ収集期間と「４で割った余りが２になる個数番目」のデータ収集期間と「４で割った余りが０になる個数番目」のデータ収集期間とに取り込んだデータＤ(j)を、サンプリング順ｊを合わせて加算すれば、電源ハムノイズの基本波はキャンセルされる。
【００４８】
電源ハムノイズの２次高調波は、データ収集期間に対応する電源波形の２次高調波であるが、図７から判るように、奇数番目のデータ収集期間に含まれる波形と偶数番目のデータ収集期間に含まれる波形とは、極性が逆で、大きさが等しくなっている。
このため、データ加算部１ｃで、「４で割った余りが１になる個数番目」のデータ収集期間と「４で割った余りが３になる個数番目」のデータ収集期間と「４で割った余りが２になる個数番目」のデータ収集期間と「４で割った余りが０になる個数番目」のデータ収集期間とに取り込んだデータＤ(j)を、サンプリング順ｊを合わせて加算すれば、電源ハムノイズの２次高調波はキャンセルされる。
【００４９】
第２の実施形態に係る脳磁気データ収集装置によれば、電源周期とは独立に基本トリガＢtrを発生させても、電源ハムノイズの基本波および２次高調波を除去した脳磁気データを得ることが出来る。
なお、電源ハムノイズの奇数次高調波は、基本波と同様に「４で割った余りが１になる個数番目」のデータ収集期間に含まれる波形と「４で割った余りが３になる個数番目」のデータ収集期間に含まれる波形とが逆極性で大きさが等しくなり、また、「４で割った余りが２になる個数番目」のデータ収集期間に含まれる波形と「４で割った余りが０になる個数番目」のデータ収集期間に含まれる波形とが逆極性で大きさが等しくなるため、加算により除去される。
【００５０】
一方、電源ハムノイズの４次以上の偶数次高調波は、除去されない。但し、電源ハムノイズの４次以上の偶数次高調波は、基本波に比べて大きさがずっと小さいため、問題にならない場合が多い。
【００５１】
−第３の実施形態−
第３の実施形態は、第１および第２の実施形態を一般的に拡張したものである。
すなわち、Ｎを０以上の整数とし、Ｋを４以上の２のべき乗とし、ｉを１から「Ｋ−１」までの整数とするとき、電源周期の所定位相θ(０)に同期したタイミングでデータを一定期間収集し、所定位相θ(０)と周期的ノイズの周期の「ｉ／Ｋ＋Ｎ」倍の時間だけ異なる位相θ(２・π・ｉ／Ｋ)に同期したタイミングでデータを一定期間収集し、得られたデータを加算する構成とする。
【００５２】
第３の実施形態に係る脳磁気データ収集装置によれば、電源ハムノイズの基本波および奇数次高調波および２(log2{Ｋ}−１)次高調波までの偶数時高調波をキャンセルできる。なお、log2{}は、２を底とする対数とする。
【００５３】
なお、Ｎ＝０，Ｋ＝４，電源波形の電圧が負から正に変わるゼロクロス点を所定位相θ(０)とすると、第２の実施形態となる。
【００５４】
−第４の実施形態−
刺激誘発反応測定以外の測定に対しても本発明を適用することが出来る。この場合、刺激発生部５を省略すればよい。
【００５５】
−第５の実施形態−
電源ハムノイズ以外の周期的ノイズ（例えばコンピュータのクロックノイズ）に対しても本発明を適用することが出来る。
【００５６】
【発明の効果】
本発明のデータ収集方法および装置によれば、データ収集間隔が周期的ノイズの周期とは独立に決められる測定においても周期的ノイズを除去したデータを得ることが出来る。また、周期的ノイズの偶数次高調波をも除去したデータを得ることが出来る。
【図面の簡単な説明】
【図１】第１の実施形態に係る脳磁気データ収集装置を示す構成図である。
【図２】第１の実施形態に係るシンクロトリガ発生部を示すブロック図である。
【図３】第１の実施形態に係る脳磁気データ収集装置の動作を示すタイミングチャートである。
【図４】第１の実施形態に係る脳磁気データ収集装置のデータ収集期間と交流電源の２次高調波の関係を示すタイミングチャートである。
【図５】第２の実施形態に係るシンクロトリガ発生部を示すブロック図である。
【図６】第２の実施形態に係る脳磁気データ収集装置の動作を示すタイミングチャートである。
【図７】図６の続きのタイミングチャートである。
【符号の説明】
１コンピュータ
１ａ制御部
１ｂデータ収集部
１ｃデータ加算部
２基本トリガ発生器
３電源波形出力部
４シンクロトリガ発生部
５刺激発生装置
６脳磁気検出部
７信号増幅部
８ＡＤ変換部
１００脳磁気データ収集装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a data collection method and apparatus, and more particularly, to a data collection method and apparatus capable of obtaining data from which periodic noise has been removed even in a measurement in which the data collection interval is determined independently of the period of the periodic noise. And a data collection method and apparatus capable of obtaining data from which even-order harmonics of periodic noise have been removed.
[0002]
[Prior art]
Conventionally, in order to remove power hum noise, first data is collected over a data collection time that is an integral multiple of the power supply cycle, and then the same data collection as the first data is performed after "1/2 + N" times the power supply cycle. A technique is known in which second data is collected over time and the first data and the second data are averaged (for example, see Patent Document 1).
[0003]
[Patent Document 1]
JP 2002-257868 A
[0004]
[Problems to be solved by the invention]
For example, in order to measure a brain magnetic response induced by an auditory stimulus, collecting data at a data collection time of 900 ms and a sampling cycle of 5 kHz in synchronization with the application of the auditory stimulus is performed at every data collection interval of 2 seconds. The obtained data is added 26 times, and the obtained data is added.
In such a stimulus-evoked response measurement, the data collection interval is determined independently of the power supply cycle. However, in the above-described conventional technique, after the first data collection is performed, “１／ + N” times the power supply cycle. After the time, the second data collection is automatically performed, and the data collection intervals do not match. That is, the conventional technique for removing the power supply hum noise has a problem that it is difficult to apply to the measurement in which the data collection interval is determined independently of the power supply cycle.
[0005]
Further, the above-mentioned prior art is effective for fundamental waves and odd-order harmonics of a power supply cycle, but has a problem in that it is ineffective for even-order harmonics.
[0006]
Therefore, a first object of the present invention is to provide a data collection method and apparatus capable of obtaining data from which periodic noise has been removed even in a measurement in which the data collection interval is determined independently of the period of the periodic noise. It is in.
It is a second object of the present invention to provide a data collection method and apparatus capable of obtaining data from which even-order harmonics of periodic noise have been removed.
[0007]
[Means for Solving the Problems]
According to a first aspect, the present invention provides a method for collecting data for a certain period of time at a timing synchronized with a zero-cross point of a positive or negative slope of a periodic noise after a certain basic trigger; A data collection method characterized by repeatedly collecting data for a certain period of time at a timing synchronized with a zero cross point of a slope opposite to the previous slope of a target noise, and adding the obtained data.
In the data collection method according to the first aspect, when a basic trigger is generated, data is collected for a certain period of time at a timing synchronized with the zero cross point of the positive or negative slope of the periodic noise thereafter. When the next basic trigger is generated, data is collected for a certain period of time at a timing synchronized with the zero cross point of the slope in the opposite direction to the previous periodic noise. The set of data collection is repeated twice, and the obtained data is added. The polarity of the fundamental noise and the odd-order harmonic of the periodic noise included in the data collected by the set of data collection twice is reversed. Therefore, the fundamental wave and the odd-order harmonic of the periodic noise can be canceled. Then, the generation interval of the basic trigger can be determined independently of the period of the periodic noise. Further, the basic trigger may be generated any number of times. If the number of times of generation of the basic trigger is not even, the periodic noise of one time is not canceled, but if the number of times of generation of the basic trigger is increased, the periodic noise of one time can be ignored. For example, if the number of occurrences of the basic trigger is 25, the ratio between the signal under measurement and the periodic noise is 25: 1, so that the periodic noise can be substantially ignored.
[0008]
In a second aspect, when N is an integer of 0 or more, the present invention collects data for a certain period at a timing synchronized with a predetermined phase of periodic noise after a certain basic trigger, Collecting data for a certain period of time at a timing synchronized with a phase different from the predetermined phase by a period of "1/2 + N" times the period of the periodic noise after the trigger, and adding the obtained data; Provide a data collection method.
In the data collection method according to the second aspect, when a basic trigger is generated, data is collected for a predetermined period at a timing synchronized with a predetermined phase of the subsequent periodic noise. When the next basic trigger is generated, data is collected for a predetermined period at a timing synchronized with a phase different from that by a predetermined phase of the subsequent periodic noise and a time that is "1/2 + N" times the period of the periodic noise. The set of data collection is repeated twice, and the obtained data is added. The polarity of the fundamental noise and the odd-order harmonic of the periodic noise included in the data collected by the set of data collection twice is reversed. Therefore, the fundamental wave and the odd-order harmonic of the periodic noise can be canceled. Then, the generation interval of the basic trigger can be determined independently of the period of the periodic noise. Further, the basic trigger may be generated any number of times. If the number of times of generation of the basic trigger is not even, the periodic noise of one time is not canceled, but if the number of times of generation of the basic trigger is increased, the periodic noise of one time can be ignored. For example, if the number of occurrences of the basic trigger is 25, the ratio between the signal under measurement and the periodic noise is 25: 1, so that the periodic noise can be substantially ignored.
[0009]
In a third aspect, the present invention provides a method in which data is collected for a certain period of time at a timing synchronized with the positive or negative zero-cross point of periodic noise after a certain basic trigger, and after the first basic trigger after the basic trigger. Data is collected for a certain period of time at a timing synchronized with a phase delayed by a quarter of the period of the periodic noise from the zero-cross point in the same direction as the previous period of the periodic noise, and the second data after the basic trigger is collected. Data is collected for a certain period of time at a timing synchronized with a phase delayed by 2/4 times the period of the periodic noise from the zero crossing point in the same direction as the previous time of the periodic noise after the basic trigger, and after the basic trigger, At the timing synchronized with the phase delayed by 3/4 times the period of the periodic noise from the zero-cross point in the same direction as the previous period of the periodic noise after the third basic trigger. Repeatedly for a certain period of time collecting data, adding the resulting data to provide a data collection method according to claim.
In the data collection method according to the third aspect, when the basic trigger is generated, data is collected for a certain period of time at a timing synchronized with the zero cross point of the positive or negative slope of the periodic noise thereafter. When the next basic trigger is generated, data is synchronized with the phase that is delayed from the zero-cross point of the slope in the same direction as the beginning of the subsequent periodic noise by a time that is 1/4 of the period of the periodic noise. Collect for a certain period. Further, when the next basic trigger is generated, at the timing synchronized with the phase delayed by 2/4 times the period of the periodic noise from the zero cross point of the slope in the same direction as the beginning of the subsequent periodic noise. Collect data for a period of time. When the next basic trigger is further generated, the data is synchronized with a phase delayed from the zero-cross point of the slope in the same direction as the beginning of the subsequent periodic noise by a time that is 3/4 times the period of the periodic noise. For a period of time. This set of four data collections is repeated, and the obtained data is added. The fundamental, odd-order harmonics, and second-order harmonics of the periodic noise included in the data collected by the four sets of data collection are repeated. Are reversed, the fundamental wave, the odd-order harmonic, and the second harmonic of the periodic noise can be canceled. Then, the generation interval of the basic trigger can be determined independently of the period of the periodic noise. Further, the basic trigger may be generated any number of times. If the number of occurrences of the basic trigger is not a multiple of 4, the periodic noise for one to three times is not canceled, but if the number of occurrences of the basic trigger is increased, the periodic noise for one to three times is ignored. it can. For example, if the number of occurrences of the basic trigger is 25 to 27, the ratio between the signal to be measured and the periodic noise becomes 25: 1 to 27: 3, so that the periodic noise can be substantially ignored.
[0010]
In a fourth aspect, the present invention provides a method for controlling the period after a certain basic trigger, where N is an integer of 0 or more, K is a power of 2 or more, and i is an integer from 1 to “K−1”. Data is collected for a certain period of time at a timing synchronized with a predetermined phase θ (0) of the periodic noise, and the predetermined phase θ (0) after the i-th basic trigger from the basic trigger and “i / K + N” of the period of the periodic noise. A data collection method characterized by repeatedly collecting data for a certain period of time at a timing synchronized with a phase θ (2 · π · i / K) that is different by a time “times” and adding the obtained data. .
In the data collection method according to the fourth aspect, when a basic trigger is generated, data is collected for a certain period at a timing synchronized with a predetermined phase θ (0) of the subsequent periodic noise. When the first basic trigger is generated from the first basic trigger, it is synchronized with a predetermined phase θ (0) of the subsequent periodic noise and a phase θ1 which is different by a period of “1 / K + N” times the period of the periodic noise. Data is collected for a certain period at the specified timing. Further, when the second basic trigger is generated from the first basic trigger, a phase θ2 different from the predetermined phase θ (0) of the subsequent periodic noise by a time “2 / K + N” times the period of the periodic noise is used. Data is collected for a certain period at the timing synchronized with. When the same process is performed and the “K−1” -th basic trigger is generated from the first basic trigger, the predetermined phase θ (0) of the periodic noise and “(K −1) / K + N ”times different phases θ _K-1 Data is collected for a certain period at the timing synchronized with. This set of data collection is repeated K times and the obtained data is added. The fundamental and odd harmonics of periodic noise and 2 (log2 { K} -1) Even-numbered harmonics up to the 2nd (log2 {K} -1) -order harmonic, because the polarity of the even-numbered harmonics up to the 1st-order harmonic is reversed. Harmonics can be canceled. Note that log2 {} is a logarithm having a base of 2. Then, the generation interval of the basic trigger can be determined independently of the period of the periodic noise. Further, the basic trigger may be generated any number of times. If the number of occurrences of the basic trigger is not a multiple of K, the periodic noise of one to “K−1” times is not canceled. However, if the number of occurrences of the basic trigger is increased, the number of occurrences of one to “K−1” is reduced. The "periodic noise" is negligible. For example, if K = 8 and the number of occurrences of the basic trigger is 25 to 31, the ratio between the signal under measurement and the periodic noise is 25: 1 to 31: 7, so that the periodic noise is substantially reduced. I can ignore it.
[0011]
According to a fifth aspect, the present invention provides a method for determining a predetermined phase of periodic noise when N is an integer of 0 or more, K is a power of 2 of 4 or more, and i is an integer from 1 to “K−1”. Data is collected for a certain period of time at a timing synchronized with θ (0), and is synchronized with a phase θ (2 · π · i / K) different from the predetermined phase by a time “i / K + N” times the period of the periodic noise. A data collection method is provided in which data is collected for a predetermined period at a timing and the obtained data is added.
In the data collection method according to the fifth aspect, data is collected for a fixed period at a timing synchronized with the predetermined phase θ (0) of the periodic noise. Next, data is collected for a certain period at a timing synchronized with a phase θ1 different from the predetermined phase θ (0) by “1 / K + N” times the period of the periodic noise. Further, data is collected for a certain period at a timing synchronized with a phase θ2 different from the predetermined phase θ (0) by “2 / K + N” times the period of the periodic noise. By performing the same processing, a phase θ different from the predetermined phase θ (0) by a time “(K−1) / K + N” times the period of the periodic noise. _K-1 Data is collected for a certain period at the timing synchronized with. This set of data collection is repeated K times and the obtained data is added. The fundamental and odd harmonics of periodic noise and 2 (log2 { K} -1) Even-numbered harmonics up to the 2nd (log2 {K} -1) -order harmonic, because the polarity of the even-numbered harmonics up to the 1st-order harmonic is reversed. Harmonics can be canceled. Note that log2 {} is a logarithm having a base of 2.
[0012]
According to a sixth aspect, the present invention provides a basic trigger generating means for generating a basic trigger, collecting data for a certain period at a timing synchronized with a zero cross point of a positive or negative slope of periodic noise after a certain basic trigger, and Data collection means for repeating data collection for a certain period of time at a timing synchronized with a zero-cross point of a slope in a direction opposite to that of the previous periodic noise after the basic trigger, and data for adding the obtained data A data collection device comprising an adding unit is provided.
In the data collection device according to the sixth aspect, the data collection method according to the first aspect can be suitably implemented.
[0013]
According to a seventh aspect of the present invention, when N is an integer equal to or greater than 0, a basic trigger generating means for generating a basic trigger, and data is kept constant at a timing synchronized with a predetermined phase of periodic noise after a certain basic trigger. Data that is collected during a period and repeatedly collects data for a predetermined period at a timing synchronized with a phase different from the predetermined phase by a period of “１／ + N” times the period of the periodic noise after the basic trigger following the basic trigger. There is provided a data collecting apparatus comprising a collecting means and a data adding means for adding obtained data.
In the data collection device according to the seventh aspect, the data collection method according to the second aspect can be suitably implemented.
[0014]
According to an eighth aspect, the present invention provides a basic trigger generating means for generating a basic trigger, and collecting data for a certain period at a timing synchronized with a positive or negative zero-crossing point of periodic noise after a certain basic trigger, Data is collected for a certain period of time at a timing synchronized with a phase delayed by a quarter of the period of the periodic noise from the zero-cross point in the same direction as the previous period of the periodic noise after the first basic trigger after the trigger. Then, at a timing synchronized with a phase delayed by 2/4 times the period of the periodic noise from a zero-cross point in the same direction as the previous period of the periodic noise after the second basic trigger after the basic trigger. From the zero-cross point in the same direction as the previous period of the periodic noise after the third basic trigger after the basic trigger, and ３ times the period of the periodic noise. Providing a data acquisition means for repeating for a certain period of time to collect data at a timing synchronized with the delayed phase between the data collecting device, characterized by comprising a data adding means for adding the resulting data.
The data collection device according to the eighth aspect can suitably implement the data collection method according to the third aspect.
[0015]
In a ninth aspect, the present invention provides a basic method for generating a basic trigger when N is an integer equal to or greater than 0, K is an integer power greater than or equal to 2 and i is an integer from 1 to “K−1”. A trigger generating means for collecting data for a predetermined period at a timing synchronized with a predetermined phase θ (0) of the periodic noise after a certain basic trigger, and the predetermined phase and the periodic noise after the i-th basic trigger from the basic trigger; Data collecting means that repeats collecting data for a certain period at a timing synchronized with a phase θ (2 · π · i / K) that is different by a time “i / K + N” times the cycle of A data collection device comprising a data addition means is provided.
In the data collection device according to the ninth aspect, the data collection method according to the fourth aspect can be suitably implemented.
[0016]
In a tenth aspect, the present invention provides a method for generating a predetermined phase of periodic noise when N is an integer of 0 or more, K is a power of 2 of 4 or more, and i is an integer from 1 to “K−1”. Data is collected for a fixed period at a timing synchronized with θ (0), and is synchronized with a phase θ (2 · π · i / K) that is different from the predetermined phase by a period of “i / K + N” times the period of the periodic noise. There is provided a data collection device comprising: a data collection unit that collects data at a timing for a predetermined period; and a data addition unit that adds obtained data.
In the data collection device according to the tenth aspect, the data collection method according to the fifth aspect can be suitably implemented.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in more detail with reference to the embodiments shown in the drawings. Note that the present invention is not limited by this.
[0018]
-1st Embodiment-
FIG. 1 is a configuration diagram of the brain magnetic data collection device according to the first embodiment.
The brain magnetic data collecting apparatus 100 includes a computer 1, a basic trigger generating unit 2 for generating a basic trigger Btr, a power supply waveform output unit 3 for outputting a power supply waveform, and a predetermined phase θ of the power supply waveform after the input of the basic trigger. A synchro trigger generator 4 for outputting a synchronized synchro trigger Str, a stimulus generator 5 for generating a stimulus according to the synchro trigger Str and applying the stimulus to the subject H, and detecting a brain magnetism of the subject H and outputting a brain magnetic signal A brain magnetic detector 6, a signal amplifier 7 for amplifying brain magnetic signals, and an AD converter 8 for converting brain magnetic signals into digital values.
[0019]
The computer 1 includes a control unit 1a, a data collection unit 1b, and a data addition unit 1c.
The control unit 1a gives an instruction to the basic trigger generation unit 2 to generate the basic trigger Btr 26 times at intervals of, for example, two seconds. Also, it sends a control signal to the AD converter 8 in response to the synchro trigger Str.
The data collection unit captures the digital value D (j) of the brain magnetic signal from the AD conversion unit 8 according to the synchro trigger Str. For example, assuming that the data collection time is 900 ms and the sampling period is 5 kHz, 4,500 data D (1) to D (4500) are fetched by one synchronization trigger Str.
The data adder 1c adds the data D (1) to D (4500) fetched for each synchro trigger Str with the sampling order j and adds them to the measurement data d (1) to d (4500). For example, if data D (1) to D (4500) are added 26 times, m is the number of times, and
d (j) = _{m = 1} Σ ²⁶ D (j)
j = 1, 2,..., 4500
It is.
[0020]
FIG. 2 is a block diagram illustrating a configuration of the synchro trigger generator 4 according to the first embodiment.
The synchro trigger generation unit 4 counts the basic trigger Btr, outputs “1” to the 0th output if the number is “0” or even, and outputs “1” to the first output if the number is odd, and a power supply A zero phase signal θ (0) is output at the zero crossing point of the positive slope of the waveform (the point at which the voltage changes from negative to positive) and returns to “0” after １／ cycle of the power supply waveform, and the power supply waveform is output. A phase signal generator that outputs a first phase signal θ (π) that becomes “1” at a zero crossing point (a point where the voltage changes from positive to negative) of the negative slope and returns to “0” after a half cycle of the power supply waveform 42, a 0th latch 430 that reads and holds the value of the 0th output of the counter 41 at the rise of the 0th phase signal θ (0), and the 1st output of the counter 41 at the rise of the first phase signal θ (π). A first latch 431 for reading and holding the value of A zero one-shot circuit 440 that outputs a pulse b0 having a short time width at the rising edge of the output a0 of the zero latch 430, and a first one-shot circuit that outputs a pulse b1 having a short time width at the rising edge of the output a1 of the first latch 431 441, an OR circuit 45 that outputs the logical sum of the output b0 of the 0th one-shot circuit 440 and the output b1 of the first one-shot circuit 441, and “0” when the number of basic triggers Btr is “0”. A mask latch 46 that outputs a mask signal M that becomes “1” when the number of triggers Btr reaches “1”, and an AND circuit 47 that outputs the logical product of the output of the OR circuit 45 and the mask signal M as a synchro trigger Str. Is provided.
[0021]
FIG. 3 is a time chart showing the operation of the brain magnetic data collection device 100 according to the first embodiment.
The power supply waveform is a 50 Hz or 60 Hz sine wave.
The 0th phase signal θ (0) becomes “1” at the zero crossing point where the voltage of the power supply waveform changes from negative to positive, and returns to “0” after １／ cycle of the power supply waveform.
The first phase signal θ (π) becomes “1” at a zero crossing point where the voltage of the power supply waveform changes from positive to negative, and returns to “0” after １／ cycle of the power supply waveform.
[0022]
Although the basic trigger Btr is illustrated as being generated at intervals of several times the power supply cycle, this is for convenience of illustration and is actually an interval on the order of seconds (an interval of 100 times or more the power supply cycle). Generated in
[0023]
The 0th output of the counter 41 is “1” if the number of basic triggers Btr is “0” or even, and is “0” if the number of basic triggers Btr is odd.
The first output of the counter 41 is "1" if the number of basic triggers Btr is odd, and is "0" if the number of basic triggers Btr is "0" or even.
[0024]
The output a0 of the 0th latch 430 becomes “1” at the zero crossing point where the voltage of the power supply waveform changes from negative to positive after the power is turned on, and the voltage of the power supply waveform changes from negative first after the first basic trigger Btr. It returns to "0" at the zero crossing point that changes to positive. In addition, the voltage of the power supply waveform becomes “1” at the zero crossing point where the voltage of the power supply waveform changes from negative to positive first after the even-numbered basic trigger Btr, and the zero crossing where the voltage of the power supply waveform changes from negative to positive first after the next basic trigger Btr. Return to "0" at the point.
The output a1 of the first latch 431 becomes "1" at the zero crossing point where the voltage of the power supply waveform changes from positive to negative after the odd-numbered basic trigger Btr, and the voltage of the power supply waveform first after the next basic trigger Btr. Returns to “0” at the zero crossing point at which the value changes from positive to negative.
[0025]
The output pulse b0 of the zeroth one-shot circuit 440 is such that the voltage of the power supply waveform changes from negative to positive first after the zero cross point where the voltage of the power supply waveform changes from negative to positive after power-on and the even-numbered basic trigger Btr. Output at the zero crossing point.
The output pulse b1 of the first one-shot circuit 441 is output at the zero cross point where the voltage of the power supply waveform changes from positive to negative after the odd-numbered basic trigger Btr.
[0026]
The mask signal M is “0” before the basic trigger Btr comes, and becomes “1” when the first basic trigger Btr comes.
[0027]
The synchro trigger Str is a zero-cross point where the voltage of the power supply waveform changes from positive to negative first after the odd-numbered basic trigger Btr and a zero-cross point where the voltage of the power supply waveform changes first from negative to positive after the even-numbered basic trigger Btr Is output.
[0028]
The start timing of the data collection period is the rising of the synchro trigger Str.
Although the length of the data collection period is illustrated as being twice as long as the power supply cycle, this is for convenience of illustration, and in practice, the interval is on the order of several hundred milliseconds (more than 10 times the power supply cycle). Length) and may be determined independently of the power supply cycle.
During the data collection period, data D (j) is collected at sampling intervals on the order of several hundred microseconds.
[0029]
The power supply hum noise (fundamental wave) is a power supply waveform corresponding to the data collection period. As can be seen from FIG. 3, the waveform included in the odd-numbered data collection period and the waveform included in the even-numbered data collection period are different from each other. , The polarities are opposite and the magnitudes are equal.
Therefore, if the data addition unit 1c adds the data D (j) taken in the odd-numbered data collection period and the even-numbered data collection period together with the sampling order j, the power supply hum noise (fundamental wave) can be reduced. Canceled.
[0030]
According to the brain magnetic data collection apparatus 100 according to the first embodiment, even when the basic trigger Btr is generated independently of the power cycle, brain magnetic data from which the fundamental wave of the power hum noise is removed can be obtained.
Note that the odd-order harmonics of the power supply hum noise have the same polarity as the waveforms included in the odd-numbered data collection periods and the waveforms included in the even-numbered data collection periods in the same manner as the fundamental wave. Is removed.
[0031]
On the other hand, the even-order harmonics of the power supply hum noise are not removed even if they are added because the waveform included in the odd-numbered data collection period and the waveform included in the even-numbered data collection period have the same polarity and the same magnitude. . For example, as shown in FIG. 4, in the second harmonic of the power hum noise, the waveform included in the odd-numbered data acquisition period and the waveform included in the even-numbered data acquisition period have the same polarity and the same magnitude. Therefore, the addition does not cancel. However, even-order harmonics of the power supply hum noise are smaller in magnitude than the fundamental wave, and thus often do not cause much problem.
[0032]
-2nd Embodiment-
The brain magnetic data collection device of the second embodiment has a configuration using the synchro trigger generation unit 4 shown in FIG. 5 as the synchronization trigger generation unit 4 of the brain magnetic data collection device 100 of the first embodiment.
[0033]
The counter 41 counts the basic trigger Btr, and outputs “1” to the 0th output if “0” or “the number at which the remainder after division by 4 becomes 0”, and “the remainder after division by 4 becomes 1”. If the number is "1", output "1" to the first output. If "the number becomes the remainder divided by 4 is 2", output "1" to the second output, and the remainder divided by 4 becomes 3. If the number is "the number", "1" is output to the third output.
[0034]
The phase signal generator 42 sets the zero-phase signal θ () to “1” at the zero-cross point of the positive slope of the power supply waveform (point at which the voltage changes from negative to positive) and returns to “0” after １／ cycle of the power supply waveform. 0), the first phase signal θ (π / 2) obtained by delaying the 0th phase signal θ (0) by １／ cycle of the power supply waveform, and the zero-crossing point of the negative slope of the power supply waveform (voltage from positive to negative). The second phase signal θ (π) which becomes “1” at the point where it changes to “0” after returning to “0” after 1/2 cycle of the power supply waveform, and the second phase signal θ (π) for only 1/4 cycle of the power supply waveform And outputs the delayed third phase signal θ (3π / 2).
[0035]
The zeroth latch 430 reads and holds the value of the zeroth output of the counter 41 at the rise of the zeroth phase signal θ (0).
The first latch 431 reads and holds the value of the first output of the counter 41 at the rise of the first phase signal θ (π / 2).
The second latch 432 reads and holds the value of the second output of the counter 41 at the rise of the second phase signal θ (π).
The third latch 433 reads and holds the value of the third output of the counter 41 at the rise of the third phase signal θ (3π / 2).
[0036]
The zeroth one-shot circuit 440 outputs a pulse b0 having a short time width at the rise of the output a0 of the zeroth latch 430.
The first one-shot circuit 441 outputs a pulse b1 having a short time width at the rise of the output a1 of the first latch 431.
The second one-shot circuit 442 outputs a pulse b2 having a short time width at the rise of the output a2 of the second latch 432.
The third one-shot circuit 443 outputs a pulse b3 having a short time width at the rise of the output a3 of the third latch 433.
[0037]
The OR circuit 45 outputs the logical sum of the output b0 of the zeroth one-shot circuit 440, the output b1 of the first one-shot circuit 441, the output b2 of the second one-shot circuit 442, and the output b3 of the third one-shot circuit 443. .
[0038]
The mask latch 46 outputs a mask signal M which is "0" when the number of basic triggers Btr is "0" and becomes "1" when the number of basic triggers Btr is "1".
The AND circuit 47 outputs the logical product of the output of the OR circuit 45 and the mask signal M as a synchro trigger Str.
[0039]
FIGS. 6 and 7 are time charts showing the operation of the brain magnetic data collection device according to the second embodiment.
The power supply waveform shown in FIG. 6 is a 50 Hz or 60 Hz sine wave.
The 0th phase signal θ (0) becomes “1” at the zero crossing point where the voltage of the power supply waveform changes from negative to positive, and returns to “0” after １／ cycle of the power supply waveform.
The first phase signal θ (π / 2) is a signal obtained by delaying the 0th phase signal θ (0) by １／ cycle of the power supply waveform.
The second phase signal θ (π) is a signal obtained by delaying the 0th phase signal θ (0) by ／ cycle of the power supply waveform.
The third phase signal θ (3π / 2) is a signal obtained by delaying the 0th phase signal θ (0) by 3/4 cycle of the power supply waveform.
[0040]
Although the basic trigger Btr is illustrated as being generated at intervals of several times the power supply cycle, this is for convenience of illustration and is actually an interval on the order of seconds (an interval of 100 times or more the power supply cycle). Generated in
[0041]
The 0th output of the counter 41 is “1” if the basic trigger Btr is “0” or “the number of times when the remainder after division by 4 becomes 0”, and becomes “0” otherwise.
The first output of the counter 41 is “1” when the basic trigger Btr is “the number of which the remainder after division by 4 becomes 1”, and becomes “0” otherwise.
The second output of the counter 41 is “1” when the basic trigger Btr is “the number of which the remainder after division by 4 becomes 2”, and becomes “0” otherwise.
The third output of the counter 41 is “1” when the basic trigger Btr is “the number of which the remainder after division by 4 becomes 3”, and becomes “0” otherwise.
[0042]
The output a0 of the 0th latch 430 becomes “1” at the zero crossing point where the voltage of the power supply waveform changes from negative to positive after the power is turned on, and the voltage of the power supply waveform changes from negative first after the first basic trigger Btr. It returns to "0" at the zero crossing point that changes to positive. In addition, the voltage of the power supply waveform becomes “1” at the zero crossing point where the voltage of the power supply waveform changes from negative to positive after the “basic trigger Btr of“ the number at which the remainder divided by 4 becomes 0 ”, and the power supply becomes the first after the next basic trigger Btr. It returns to "0" at the zero crossing point where the voltage of the waveform changes from negative to positive.
The output a1 of the first latch 431 determines the first zero-crossing point at which the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number whose remainder after division by 4 becomes 1” by だけ of the power supply cycle. It becomes "1" at the "delayed point" and becomes "0" at the first "point where the zero cross point at which the voltage of the power supply waveform changes from negative to positive is delayed by 1/4 of the power supply cycle" after the next basic trigger Btr. Return to
The output a2 of the second latch 432 determines the first zero-crossing point at which the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number whose remainder after division by 4 becomes 2” by 2/4 of the power supply cycle. "1" at the delayed point, and "0" at the first "zero-cross point at which the voltage of the power supply waveform changes from negative to positive after the next basic trigger Btr is delayed by 2/4 of the power supply cycle". Return to
The output a3 of the third latch 433 is such that the first zero-crossing point at which the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number of which the remainder divided by 4 becomes 3” is only ／ of the power supply cycle. It becomes "1" at the "delayed point" and becomes "0" at the first "point at which the zero-cross point at which the voltage of the power supply waveform changes from negative to positive is delayed by 3/4 of the power supply cycle" after the next basic trigger Btr. Return to
[0043]
The output pulse b0 of the zeroth one-shot circuit 440 is first after the power is turned on, after the zero-cross point at which the voltage of the power supply waveform changes from negative to positive and the “number-th where the remainder when divided by 4 becomes 0” is the first after the basic trigger Btr. It is output at the zero cross point where the voltage of the power supply waveform changes from negative to positive.
The output pulse b1 of the first one-shot circuit 441 is the first zero-cross point at which the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number of which the remainder after division by 4 becomes 1” is one power supply cycle. At a point delayed by / 4 ".
The output pulse b2 of the second one-shot circuit 442 is the first “zero-cross point at which the voltage of the power supply waveform changes from negative to positive” after the “number-th basic trigger Btr whose remainder after division by 4 becomes 2”. At a point delayed by / 4 ".
The output pulse b3 of the third one-shot circuit 443 is the first zero-crossing point at which the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number of which becomes the remainder when divided by 4 is 3”. At a point delayed by / 4 ".
[0044]
The mask signal M shown in FIG. 7 is “0” before the basic trigger Btr comes, and becomes “1” when the first basic trigger Btr comes.
[0045]
The synchro trigger Str is a point obtained by delaying the first zero-crossing point at which the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number of which the remainder after division by 4 becomes 1” by 1/4 of the power supply cycle. "The first number after the basic trigger Btr of" the number of which the remainder when divided by 4 becomes 2 "" The point at which the zero cross point at which the voltage of the power supply waveform changes from negative to positive is delayed by 2/4 of the power supply cycle "," The number "the number at which the remainder after division by 4 becomes 3" is the first "after the zero cross point at which the voltage of the power supply waveform changes from negative to positive is delayed by 3/4 of the power supply cycle", and "4. The power supply waveform voltage is output at the zero crossing point where the voltage of the power supply waveform changes from negative to positive after the basic trigger Btr of “the number of times when the remainder obtained by dividing by 0 becomes zero”.
[0046]
The start timing of the data collection period is the rising of the synchro trigger Str.
Although the length of the data collection period is illustrated as being twice as long as the power supply cycle, this is for convenience of illustration, and in practice, the interval is on the order of several hundred milliseconds (more than 10 times the power supply cycle). Length) and may be determined independently of the power supply cycle.
During the data collection period, data D (j) is collected at sampling intervals on the order of several hundred microseconds.
[0047]
The fundamental wave of the power supply hum noise is a power supply waveform corresponding to the data collection period. As can be seen from FIG. 7, the waveform included in the “number-th part whose remainder after division by 4 becomes 1” and “4 The waveforms included in the data collection period of “the number of which the remainder divided by 3 becomes 3” have the opposite polarity and the same magnitude. In addition, the waveform included in the “number-th period when the remainder divided by 4 becomes 2” and the waveform included in the “number-th period when the remainder divided by 4 becomes 0” have polarities. Conversely, the sizes are equal.
For this reason, the data addition unit 1c divides the data collection period of “the number of which the remainder divided by 4 becomes 1” and the data collection period of “the number of which the remainder divided by 4 becomes 3” by “4. The data D (j) captured in the data collection period of the "number-th where the remainder becomes 2" and the data collection period of the "number-th where the remainder divided by 4 becomes 0" are added together with the sampling order j. The fundamental wave of the power hum is canceled.
[0048]
The second harmonic of the power supply hum noise is the second harmonic of the power supply waveform corresponding to the data collection period. As can be seen from FIG. 7, the waveform included in the odd-numbered data collection period and the even-numbered data collection period Are opposite in polarity and equal in magnitude.
For this reason, the data addition unit 1c divides the data collection period of “the number of which the remainder divided by 4 becomes 1” and the data collection period of “the number of which the remainder divided by 4 becomes 3” by “4. The data D (j) captured in the data collection period of the "number-th where the remainder becomes 2" and the data collection period of the "number-th where the remainder divided by 4 becomes 0" are added together with the sampling order j. The second harmonic of the power supply hum noise is canceled.
[0049]
According to the brain magnetic data collection apparatus according to the second embodiment, even if the basic trigger Btr is generated independently of the power cycle, it is possible to obtain brain magnetic data from which the fundamental wave and the second harmonic of the power hum noise are removed. Can be done.
The odd-order harmonics of the power supply hum noise are the same as the fundamental wave, except that the waveform included in the data collection period of “the number of remainders divided by 4 becomes 1” and the “number of harmonics divided by 4 become 3” And the waveforms included in the data collection period of the “number-th where the remainder when divided by 4 becomes 2” and the “remainder divided by 4” Since the waveforms included in the data collection period of the “number-th time when becomes 0” have opposite polarities and the same magnitude, they are removed by addition.
[0050]
On the other hand, even-order harmonics of the fourth or higher order of the power supply hum noise are not removed. However, even-order harmonics of the fourth or higher order of the power supply hum noise are much smaller than the fundamental wave, and thus often do not cause a problem.
[0051]
-Third embodiment-
The third embodiment is a general extension of the first and second embodiments.
That is, when N is an integer greater than or equal to 0, K is a power of 2 greater than or equal to 4, and i is an integer from 1 to “K−1”, at a timing synchronized with a predetermined phase θ (0) of the power supply cycle. Data is collected for a certain period, and the data is collected for a certain period at a timing synchronized with a phase θ (2 · π · i / K) that is different from the predetermined phase θ (0) by a time “i / K + N” times the period of the periodic noise. It is configured to collect and add the obtained data.
[0052]
According to the brain magnetic data collection device according to the third embodiment, it is possible to cancel the fundamental wave of the power supply hum noise, the odd harmonics, and the even harmonics up to the 2 (log2 {K} −1) harmonic. Note that log2 {} is a logarithm having a base of 2.
[0053]
It is to be noted that, if N = 0, K = 4, and a zero-cross point at which the voltage of the power supply waveform changes from negative to positive is a predetermined phase θ (0), a second embodiment is obtained.
[0054]
-Fourth embodiment-
The present invention can be applied to measurements other than the stimulation-evoked response measurement. In this case, the stimulus generator 5 may be omitted.
[0055]
-Fifth embodiment-
The present invention can also be applied to periodic noise other than power supply hum noise (for example, computer clock noise).
[0056]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the data collection method and apparatus of this invention, the data from which the periodic noise was removed can be obtained also in the measurement whose data collection interval is determined independently of the period of the periodic noise. Further, data from which even-order harmonics of periodic noise have been removed can be obtained.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing a brain magnetic data collection device according to a first embodiment.
FIG. 2 is a block diagram illustrating a synchro trigger generation unit according to the first embodiment.
FIG. 3 is a timing chart showing the operation of the brain magnetic data collection device according to the first embodiment.
FIG. 4 is a timing chart showing a relationship between a data collection period of the brain magnetic data collection device according to the first embodiment and a second harmonic of an AC power supply.
FIG. 5 is a block diagram illustrating a synchro trigger generator according to a second embodiment.
FIG. 6 is a timing chart showing the operation of the brain magnetic data collection device according to the second embodiment.
FIG. 7 is a timing chart subsequent to FIG. 6;
[Explanation of symbols]
1 computer
1a Control unit
1b Data collection unit
1c Data adder
2 Basic trigger generator
3 Power supply waveform output section
4 Synchro trigger generator
5 Stimulus generator
6 Brain magnetic detector
7 Signal amplifier
8 AD converter
100 Brain magnetic data collection device

Claims

Data is collected for a certain period of time at a timing synchronized with the zero-cross point of the positive or negative slope of the periodic noise after a certain basic trigger, and the slope of the periodic noise after the basic trigger following the previous basic trigger has the opposite slope. A data collection method characterized by repeatedly collecting data for a certain period at a timing synchronized with a zero-cross point, and adding the obtained data.

When N is an integer of 0 or more, data is collected for a certain period at a timing synchronized with a predetermined phase θ (0) of periodic noise after a certain basic trigger, and the predetermined phase after the next basic trigger after the basic trigger is collected. It is necessary to repeatedly collect data for a certain period at a timing synchronized with a phase θ (π) that is different from θ (0) by a time “「 + N ”times the period of the periodic noise, and add the obtained data. Characteristic data collection method.

Data is collected for a certain period of time at a timing synchronized with the positive or negative zero-crossing point of the periodic noise after a certain basic trigger, and the same direction of the previous periodic noise after the first basic trigger as the previous one is obtained. Data is collected for a certain period of time at a timing synchronized with a phase delayed by a quarter of the period of the periodic noise from the zero-crossing point, and the previous period of the periodic noise after the second basic trigger after the basic trigger is collected. Data is collected for a certain period of time at a timing synchronized with a phase delayed by 2/4 times the period of the periodic noise from the zero cross point in the same direction as the above, and the period after the third basic trigger after the basic trigger Data is collected for a certain period of time at a timing synchronized with a phase delayed by 3/4 times the period of the periodic noise from the zero-cross point in the same direction as the previous time of the target noise Repeating, data collection method, which comprises adding the resulting data.

When N is an integer of 0 or more, K is a power of 2 or more, and i is an integer from 1 to “K−1”, a predetermined phase θ (0) of the periodic noise after a certain basic trigger is obtained. Data is collected for a certain period of time at the synchronized timing, and a phase θ (2) different from the predetermined phase θ (0) after the i-th basic trigger from the basic trigger by “i / K + N” times the period of the periodic noise. A data collection method characterized by repeatedly collecting data for a certain period at a timing synchronized with (π · i / K) and adding the obtained data.

When N is an integer greater than or equal to 0, K is a power of 2 greater than or equal to 4, and i is an integer from 1 to “K−1”, data is synchronized with a predetermined phase θ (0) of the periodic noise. Are collected for a certain period of time, and the data is collected for a certain period of time at a timing synchronized with a phase θ (2 · π · i / K) different from the predetermined phase θ (0) by “i / K + N” times the period of the periodic noise. A data collection method characterized by collecting and adding obtained data.

A basic trigger generating means for generating a basic trigger; collecting data for a certain period at a timing synchronized with a zero cross point of a positive or negative slope of a periodic noise after a certain basic trigger; and It is characterized by comprising a data collection unit that repeats collecting data for a certain period of time at a timing synchronized with a zero-cross point of a slope in a direction opposite to the previous period of the periodic noise, and a data addition unit that adds the obtained data. Data collection device.

When N is an integer of 0 or more, a basic trigger generating means for generating a basic trigger, data is collected for a certain period at a timing synchronized with a predetermined phase of periodic noise after a certain basic trigger, and the next Data collection means for repeatedly collecting data for a certain period of time at a timing synchronized with a phase different from that of the predetermined phase by a period of "1/2 + N" times the period of the periodic noise after the basic trigger, and adding the obtained data A data collection device, comprising:

A basic trigger generating means for generating a basic trigger; and collecting data for a certain period at a timing synchronized with a positive or negative zero-cross point of periodic noise after a certain basic trigger, and after a first basic trigger after the basic trigger The data is collected for a certain period of time at a timing synchronized with a phase delayed by a quarter of the period of the periodic noise from the zero-cross point in the same direction as the previous time of the periodic noise, and the second after the basic trigger The data is collected for a certain period of time at a timing synchronized with a phase delayed by 2/4 times the period of the periodic noise from the zero cross point in the same direction as the previous time of the periodic noise after the basic trigger. Synchronize with a phase delayed from the zero-cross point in the same direction as the previous time of the periodic noise after the third basic trigger by a time which is 3/4 times the period of the periodic noise. Data collection device, wherein the data collecting means for repeating for a certain period of time to collect data at a timing, by comprising the data adding means for adding the resulting data.

When N is an integer of 0 or more, K is a power of 2 or more, and i is an integer from 1 to “K−1”, a basic trigger generating means for generating a basic trigger; Data is collected for a fixed period at a timing synchronized with the predetermined phase θ (0) of the periodic noise, and the predetermined phase θ (0) after the i-th basic trigger from the basic trigger and “i / A data collection unit that repeats collecting data for a certain period at a timing synchronized with a phase θ (2 · π · i / K) that is different by a time of “K + N” times; and a data addition unit that adds the obtained data. A data collection device characterized by the following.

When N is an integer greater than or equal to 0, K is a power of 2 greater than or equal to 4, and i is an integer from 1 to “K−1”, data is synchronized with a predetermined phase θ (0) of the periodic noise. Is collected for a certain period of time, and data is synchronized for a certain period at a timing synchronized with a phase θ (2 · π · i / K) different from the predetermined phase θ (0) by “i / K + N” times the period of the periodic noise. A data collection device, comprising: a data collection unit for collecting; and a data addition unit for adding obtained data.