JP3948965B2

JP3948965B2 - Multi-point thickness gauge

Info

Publication number: JP3948965B2
Application number: JP2002013937A
Authority: JP
Inventors: 武賀川
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2001-03-01
Filing date: 2002-01-23
Publication date: 2007-07-25
Anticipated expiration: 2022-01-23
Also published as: JP2002328016A; CN1378067A; CN1223827C; KR20020070824A; KR100491019B1; TWI272371B

Description

【０００１】
【発明の属する技術分野】
本発明は、放射線を用いて被測定物の厚さを非接触で測定する多点計測厚み計に関する。
【０００２】
【従来の技術】
近年、鉄鋼業における圧延の形状制御のニーズの高まりによって、より制御に適した板形状の測定器が求められている。従来、板幅方向の厚み測定は走査型厚み計などで行ってきているが、被測定物は板厚測定中も連続的に移動している場合が殆どであるため、そのままでは板形状を求めることは出来ない。従って多くの場合、走査型厚み計の他に、板中心を測定する厚み計を導入し、これによって得られたデータを基に補正を行って板形状を求めている。
【０００３】
多点計測厚み計について、図１５を参照して説明する。水平に配置された板状の被測定物４の板方向上下にやや距離をおいて対向するようにコ字型フレーム１の上側に検出部２、下側に発生器３を配置する。検出部２の出力信号は厚み演算器７に送られる。検出部２と発生器３はコ字型フレーム１に固定されている。検出部２内には円筒状の電離箱５が被測定物２の幅方向に複数個平行に配置され、これらが発生器３より出力される扇形状の放射線を感知するが、電離箱５の形状は円筒状であり、その中心部と端部では放射線に対する感度に大きな差がある。これについて、図１６〜図１８を用いて更に説明する。
【０００４】
図１６は、電離箱５と被測定物４の位置関係を表す斜視図である。発生器３から出力される扇形上の放射線を破線で表している。図１７は、電離箱５の真上から見た状態を示すＡＡ’矢視図である。電離箱５は、図１７に示すように、被測定物４に対し平行に配列している。電離箱５の端部は中心部に比べ感度が低いため、被測定物４のハイスポット（欠陥）の検出が困難である。
【０００５】
図１８に電離箱５を被測定物４に対し平行に配列した場合の感度分布を示す。図１８に示すように、電離箱５の感度が低いため精度良く板厚測定を出来なくなる不感帯が周期的に存在する事になり、幅方向の連続的な厚み値が得られなくなる。
【０００６】
また、エッジ部を高分解能・高精度で測定可能な装置のニーズも高まってきているが、従来の多点計測厚み計では電離箱と電離箱の間に存在する放射線に対する感度の低い領域（以後不感帯と呼ぶ）で精度の良い測定を行うことが出来ず、連続的なエッジ形状を得ることが困難である。
【０００７】
【発明が解決しようとする課題】
上述のように、多点計測厚み計においては、測定位置における板厚は電離箱の高さ方向で入射した放射線量の総和の平均をとって板厚に変換するが、電離箱は円筒状のため、中心部が最も放射線に対する感度が高く、端に近づくにつれその感度は低いという特性がある。
【０００８】
そのため、測定ポイントがちょうど不感帯であった場合、電離箱の高さ方向全域が不感帯ということになる。そのため、この位置において感度が著しく低くなり、被測定物の幅方向の板厚測定時に測定出来ない箇所が出て来る。
【０００９】
また、被測定物のエッジ部から任意の距離における位置の厚さ測定を行う場合において、幅計等の外部装置より被測定物の幅値を演算器に入力し、被測定物の蛇行量に合わせて多点計測厚み計を移動装置６により移動させ測定を行っているが、台車が目標位置に移動するまでは目標位置での測定が行えない。
【００１０】
一方、電離箱を隣接させて配列した場合、隣接する電離箱からの散乱線が電離箱に入射するためにエッジ部の精度低下、分解能低下など測定結果に悪影響を及ぼす恐れがある。
【００１１】
本発明は、以上の事情を考慮してなされたものであり、その目的は、測定位置による放射線に対する感度の差を減らし、より良い幅方向測定が可能となる多点計測厚み計を提供することである。
【００１２】
【課題を解決するための手段】
上記目的を達成するために、請求項１に係る発明は、放射線源と、被測定物を介して放射線源と対向する位置において被測定物の幅方向に複数個平行に配置された円筒状の電離箱を有し、放射線源から放射され被測定物を透過して入射された放射線のレベルに関連した出力信号を得る検出手段と、この検出手段の出力信号から被測定物の厚みを演算する演算手段とを備え、電離箱は、円筒の側面から放射線を入射する構造のものとし、電離箱を、入射される放射線の不感帯が無くなるように、被測定物の流れ方向に対し、時計方向若しくは反時計方向に任意の角度回転させて配列したことを特徴とする。
【００１３】
請求項１に係る発明によれば、従来の電離箱の配置で存在した不感帯の部分を無くすことが可能となり、被測定物の厚みの幅方向測定を連続的に精度良く行うことが出来る。
【００１４】
請求項２に係る発明は、請求項１に記載の多点計測厚み計において、演算手段が、被測定物の幅を測定する手段により測定された幅値が入力され、被測定物のエッジ位置、または中心位置を演算し、検出手段の出力信号から演算した厚みについての被測定物のエッジ位置、または中心位置からの位置を特定できるものであることを特徴とする。
【００１５】
請求項３に係る発明は、請求項１の多点計測厚み計において、前記演算手段が、被測定物のエッジを検出する手段からの出力信号が入力され、被測定物のエッジ位置を演算し、検出手段の出力信号から演算した厚みについての被測定物のエッジ位置からの位置を特定できるものであることを特徴とする。
【００１６】
請求項４に係る発明は、請求項１に記載の多点計測厚み計において、演算手段が、外部装置からの中心ずれ量が入力され、被測定物の中心位置を演算し、検出手段の出力信号から演算した厚みについての被測定物の中心位置からの位置を特定できるものであることを特徴とする。
【００１７】
請求項５に係る発明は、請求項１に記載の多点計測厚み計において、電離箱が、目標測定位置を含む所定範囲の位置に配列されているものとし、演算手段が、被測定物の幅を測定する手段、または被測定物のエッジを検出する手段、または外部装置からの出力信号が入力され、被測定物の蛇行量を求めるとともに、複数の測定位置の厚み値を基に測定位置間の厚み値を算出するための補間関数を求め、補間関数により目標測定位置から蛇行量ずれた位置の厚み値を演算するものであることを特徴とする。
【００１８】
請求項５に係る発明によれば、目標測定位置から被測定物がずれた場合でも連続的に厚みが測定できる。
【００１９】
請求項６に係る発明は、請求項１に記載の多点計測厚み計において、電離箱の全長と、電離箱側壁の肉厚に安全率を乗じて求めた不感帯の値とを用いて、被測定物の流れ方向に対し、不感帯が無くなるような電離箱の回転角度を決定したことを特徴とする。
【００２０】
請求項７に係る発明は、請求項１に記載の多点計測厚み計において、電離箱の全長と、電離箱内径および電離箱中心部に対するガス量比を用いて求めた不感帯の値とを用いて、被測定物の流れ方向に対し、不感帯が無くなるような電離箱の回転角度を決定したことを特徴とする。
【００２１】
請求項８に係る発明は、請求項１に記載の多点計測厚み計において、電離箱の全長と、電離箱外径およびガス充満係数を用いて求めた不感帯の値とを用いて、被測定物の流れ方向に対し、不感帯が無くなるような電離箱の回転角度を決定したことを特徴とする。
【００２２】
請求項９に係る発明は、請求項１乃至請求項８のいずれかに記載の多点計測厚み計において、隣接する２つの電離箱間にしきい板を挿入したことを特徴とする。
【００２３】
請求項９に係る発明によれば、隣接した電離箱から入射する散乱線の影響がなくなり、エッジ部の精度低下、分解能低下など測定結果に悪影響を及ぼす要因のない優れた測定を行うことが出来る。
【００２４】
【発明の実施の形態】
以下、図面を参照して本発明の実施の形態について説明する。なお、以下の図において、従来例を示す図を含めて、同符号は同一部分または対応部分を示す。
【００２５】
（第１の実施形態）
図１〜図４を参照して本発明の第１の実施形態について説明する。
【００２６】
図１において、板状の被測定物４の板厚を測定出来るように、多点計測厚み計移動装置６によるコ字型フレーム１の幅方向移動操作が行われる。コ字型フレーム１には、下側に発生器３、上側に検出部２が固定されている。また検出部２内には電離箱５が配列されている。
【００２７】
発生器３より出力される放射線は被測定物４を透過し、電離箱５に入射する。入射した放射線は電離箱５内に封入された気体を光電吸収、コンプトン散乱、電子対生成などの作用によって電離し、この際発生した電荷は電極間に加えられた電界によって電極に引き寄せられ、電極で再結合して中性の原子に戻る。この時流れ出た電流が検出部２の出力信号となり、Ａ／Ｄ変換された後に厚み演算器７に送られ、被測定物４の厚み値に変換される。
【００２８】
従来例においては、上述のように、電離箱５を被測定物４に対し平行に配列しているため不感帯が周期的に存在し、幅方向の連続的な厚み値が得られなかった。そこで、この実施形態においては、電離箱５の配列を変更し、不感帯を無くすようにしている。
【００２９】
図２は、この実施形態における電離箱５と被測定物４の位置関係を表す斜視図である。発生器３から出力される扇形上の放射線を破線で表している。図３は、電離箱５の真上から見た状態を示すＡＡ’矢視図である。電離箱５の配列を図３に示すように被測定物４に対し斜めに配列した構造とする。このように、電離箱５を、被測定物４の真上から見た平面上で、被測定物４の流れ方向に対し、時計方向若しくは反時計方向に任意の角度回転させた状態に配置にすることで、従来の電離箱の配置で存在した不感帯の部分を無くすことが可能となり、被測定物４の幅方向測定を連続的に精度良く行うことが出来る。
【００３０】
図４に、電離箱５を被測定物４の流れ方向に対し、時計方向もしくは反時計方向に回転させたこの実施形態における感度分布を示す。図より明らかなように、被測定物４の板幅方向について、一定以上の感度を得ることが可能となる。従って、被測定物４に局所的にハイスポット（欠陥）があった場合、これを容易に検出することができる。
【００３１】
（第２の実施形態）
図５は、本発明の第２の実施形態の構成を示す図である。この実施形態においては、厚み演算器７において、第１の実施形態の場合と同様に検出部２の出力信号から被測定物４の厚み値を演算するとともに、幅計８で測定された板幅値を厚み演算器７に入力し、被測定物４の板エッジ位置、または板中心位置を演算する。
【００３２】
従って、演算器７においては、検出部２の出力信号から演算した厚みについて、被測定物４の板エッジ位置、または板中心位置からの位置を特定することができる。
【００３３】
（第３の実施形態）
図６は、本発明の第３の実施形態の構成を示す図である。この実施形態においては、厚み演算器７において、第１の実施形態の場合と同様に検出部２の出力信号から被測定物４の厚み値を演算するとともに、エッジセンサー９で検出された信号を厚み演算器７に入力し、被測定物の板エッジ位置を演算する。
【００３４】
従って、演算器７においては、検出部２の出力信号から演算した厚みについて、被測定物の板エッジ位置からの位置を特定することができる。
【００３５】
（第４の実施形態）
図７は、本発明の第４の実施形態の構成を示す図である。この実施形態においては、厚み演算器７において、第１の実施形態の場合と同様に検出部２の出力信号から被測定物４の厚み値を演算するとともに、上位の計算機などの外部装置１０より板中心ずれ量を厚み演算器７に入力し、板中心位置を演算する。
【００３６】
従って、演算器７においては、検出部２の出力信号から演算した厚みについて、被測定物４の板中心位置からの位置を特定することができる。
【００３７】
（第５の実施形態）
図８〜図１０は、本発明の第５の実施形態を説明する図である。
【００３８】
図８は、第１の実施形態のような構成の多点計測厚み計を、被測定物４のエッジ部より任意の距離離れた目標位置の板厚を測定するために用いる場合の構成を示している。多点計測厚み計は被測定物４のエッジより任意の距離離れた目標位置を測定するため、この位置を中心とした所定範囲の位置に、板厚を測定出来るよう電離箱５を配列する。
【００３９】
厚み演算器７において、検出部２の出力信号から目標測定位置近傍の所定範囲の複数の測定位置における板厚値１１、１２、１３が求められ、また、幅計８、またはエッジセンサー９からの出力信号によりエッジ位置が求められると、図９に示すように、板厚値１１、１２、１３を、それぞれエッジ位置から測定位置までの距離に対応した位置にプロットし、これらの板厚測定結果を補間関数１４で結び、グラフ化することができる。目標測定位置が、実際の測定位置同士の間に位置する場合でも、補間関数１４より、エッジ位置から任意の距離１５離れた目標測定位置の板厚値１６を求めることができる。
【００４０】
また、被測定物４は通板されて来る際に幅方向に蛇行しながら来る場合が殆どである。幅計８、またはエッジセンサー９、または外部装置１０等からの板幅、またはエッジ位置、または中心ずれ量（蛇行量）などを表わす出力信号を厚み演算器７に入力し、被測定物４の蛇行量を演算する。そして、目標測定位置近傍の板厚測定結果を補間関数で結び、図１０に示すようにグラフ化する。即ち、目標測定位置での板厚値１７とその近傍の位置における板厚値１８、１９を補間関数２０で結ぶ。幅計８等より得たエッジ位置によって板ずれ量即ち蛇行量２１が算出された場合、補間関数２０より板厚値２２が求められる。この値を目標測定位置の板厚値とすることで、目標測定位置から被測定物４がずれた場合でも連続的に板厚が測定できるようになる。
【００４１】
（第６の実施形態）
図１１〜図１３は本発明の第６の実施形態を説明する図である。電離箱５の放射線に対する感度は電離箱５内のガス量に比例する。電離箱５端部ではガス量が少ないため感度が低下し、電離箱５の側壁部分では放射線に対する感度が無くなる。
【００４２】
この実施形態では、電離箱５が円筒の側面から放射線を入射する構造のものとし、図１１に示すように、被測定物の流れ方向に対し、この不感帯がなくなるような電離箱５の回転角度αを決定する。
【００４３】
まず、回転角度αを決定する第１の方法として、電離箱の全長と、電離箱側壁の肉厚に安全率を乗じて求めた不感帯の値とを用いて求めることができる。すなわち、電離箱５の全長を２Ｌとし、電離箱側壁の肉厚ｔに安全率γを乗じて求めた不感帯１１の値をＴ（＝ｔ・γ）とした場合、被測定物４の流れ方向に対し、不感帯がなくなるような電離箱５の回転角度αはα＝ｔａｎ^-1（Ｔ／Ｌ）として求められる。安全率γは任意の定数（例えば、２）とする。
【００４４】
次に、回転角度αを決定する第２の方法として、電離箱の全長と、電離箱内径および電離箱中心部に対するガス量比を用いて求めた不感帯の値とを用いて求めることができる。図１２に示すように、電離箱５の中心部Ｏに対しガス量比がｃとなる位置を不感帯１１との境界となる位置とし、中心部Ｏを通る水平線上のこの位置をＢとする。すなわち、位置Ｂは、電離箱内径を２ｒとしたとき、位置Ｂからその上方の内壁の位置Ｃまでの距離をｌ₁とすると、ｌ₁＝ｃ・ｒとなるような位置とする。また、図において、中心部Ｏの上方の内壁の位置をＡ、中心部Ｏから位置Ｂまでの距離をｔ”、位置Ｂからその水平方向の内壁の位置Ｄまでの距離をｔ’とし、ＯＡとＯＣのなす角度をβとする。
【００４５】
ここで、ｌ₁＝ｃ・ｒであるが、図より、ｌ₁＝ｒｃｏｓβとなるので、ｃ＝ｃｏｓβとなり、従って、電離箱中心部に対するガス量比ｃが与えられると、角度βを求めることができる。また、図より、ｔ”＝ｒｓｉｎβであるので、不感帯１１の値Ｔは次のようにして求めることができる。
【００４６】
【数１】

そして、このようにして求めた不感帯１１の値Ｔと電離箱５の全長２Ｌとから、被測定物４の流れ方向に対し、不感帯がなくなるような電離箱５の回転角度αをα＝ｔａｎ^-1（Ｔ／Ｌ）として求めることができる。なお、電離箱中心部に対するガス量比ｃは任意の定数（例えば、０．５）とすることができる。
【００４７】
また、第３の方法として、電離箱の全長と、電離箱外径およびガス充満係数（ガスが充満している有効径の係数）を用いて求めた不感帯の値とを用いて求めることができる。電離箱外径を２Ｒとしたとき、図１３に示すように、電離箱５の中心部Ｏを通る水平線上で、中心部Ｏからの距離が、電離箱外径の半分の値Ｒにガス充満係数ｃ’を乗じた値の位置Ｅを不感帯１１との境界とし、不感帯１１の値Ｔを次のようにして求める。
【００４８】
【数２】

そして、このようにして求めた不感帯１１の値Ｔと電離箱５の全長２Ｌとから、被測定物４の流れ方向に対し、不感帯がなくなるような電離箱５の回転角度αをα＝ｔａｎ^-1（Ｔ／Ｌ）として求めることができる。なお、ガス充満係数ｃ’は任意の定数（例えば、０．７〜０．８程度の値）とすることができる。
【００４９】
（第７の実施形態）
図１４は本発明の第７の実施形態を説明する図である。第１〜第６の実施形態のように、電離箱５を複数個隣接させて配列している場合、電離箱５には発生器３から放射された放射線１４以外に、隣接する電離箱５からの散乱線１３が入射するためエッジ部の精度低下、分解能低下など測定結果に悪影響を及ぼすことがある。
【００５０】
そこで、この実施形態では、このような散乱線１３の影響を低減させるため、隣接する電離箱５間にしきい板１２を配置している。
【００５１】
しきい板１２の厚みは散乱線を十分に吸収できる厚さとし、しきい板１２の長さ、高さについては、それぞれ電離箱５の長さ、高さと同等以上とする。
【００５２】
また、しきい板１２の材質は、ステンレス鋼（例えばＳＵＳ３０４）を用いることができるが、散乱線を吸収できる材質であればこの限りでない。例えば、タングステン、鉛などを用いることもできる。
【００５３】
また、線吸収係数の大きい材質のものほど、板厚を薄くすることが出来る。
【００５４】
なお、このように、しきい板１２を用いた場合、被測定物４の流れ方向に対し、不感帯がなくなるような電離箱５の回転角度α’は、しきい板１２の板厚をｔ₂としたとき、第６の実施形態の場合のＴの代わりに、（Ｔ＋０．５ｔ₂）を用いて、α’＝ｔａｎ^-1{（Ｔ＋０．５ｔ₂）／Ｌ}として求めることができる。
【００５５】
【発明の効果】
以上説明したように、本発明によれば、電離箱の配置を被測定物の流れ方向に対し、時計方向もしくは反時計方向に回転させることで、放射線感度の低い領域が減り、測定領域全体に渡って感度の変化が少ない多点計測厚み計を得ることが出来、被測定物に局所的にハイスポット（欠陥）がある場合に、これを容易に検出することができる。
【００５６】
また、入力された信号から蛇行量を求め、これを、各測定位置間を補間した関数に適用することで、被測定物の蛇行による目標測定位置のずれに対応でき、目標測定位置付近の測定を連続的に行うことが出来る。
【図面の簡単な説明】
【図１】本発明の第１の実施形態に係る多点計測厚み計の構成を示す正面図。
【図２】第１の実施形態における電離箱の配列を示す斜視図。
【図３】図２において電離箱の真上から見た状態を示すＡＡ’矢視図。
【図４】第１の実施形態における電離箱の幅方向についての感度分布を示す図。
【図５】本発明の第２の実施形態に係る多点計測厚み計の構成を示す図。
【図６】本発明の第３の実施形態に係る多点計測厚み計の構成を示す図。
【図７】本発明の第４の実施形態に係る多点計測厚み計の構成を示す図。
【図８】本発明の第５の実施形態に係る多点計測厚み計の構成を示す図。
【図９】第５の実施形態における目標測定位置が実際の測定位置同士の間にある場合に目標測定位置の板厚値を補間して求めるグラフを示す図。
【図１０】第５の実施形態における被測定物が蛇行した場合に目標測定位置の板厚値を補間して求めるグラフを示す図。
【図１１】本発明の第６の実施形態における電離箱の回転角度を決定する方法を説明するための図。
【図１２】本発明の第６の実施形態における電離箱内径、電離箱中心部に対するガス量比等を用いて電離箱の回転角度を決定する方法を説明するための図。
【図１３】本発明の第６の実施形態における電離箱外径、ガス充満係数等を用いて電離箱の回転角度を決定する方法を説明するための図。
【図１４】本発明の第７の実施形態に係る多点計測厚み計の主要部の構成を示す図。
【図１５】従来例の構成を示す正面図。
【図１６】従来例における電離箱の配列を示す斜視図。
【図１７】図１６において電離箱の真上から見た状態を示すＡＡ’矢視図。
【図１８】従来例における電離箱の幅方向についての感度分布を示す図。
【符号の説明】
１…コ字型フレーム
２…検出部
３…発生器
４…被測定物
５…電離箱
６…多点計測厚み計移動装置
７…厚み演算器
８…幅計
９…エッジセンサー
１０…外部装置
１１…不感帯
１２…しきい板
１３…散乱線
１４…放射線[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multi-point measurement thickness meter that measures the thickness of an object to be measured in a non-contact manner using radiation.
[0002]
[Prior art]
In recent years, due to the increasing need for shape control of rolling in the steel industry, a plate-shaped measuring device more suitable for control is required. Conventionally, thickness measurement in the plate width direction has been performed with a scanning thickness gauge, etc., but since the object to be measured is mostly moving continuously during plate thickness measurement, the plate shape is obtained as it is. I can't do that. Therefore, in many cases, a thickness meter for measuring the center of the plate is introduced in addition to the scanning thickness meter, and the plate shape is obtained by performing correction based on the data obtained thereby.
[0003]
The multipoint thickness gauge will be described with reference to FIG. The detection unit 2 is disposed on the upper side of the U-shaped frame 1 and the generator 3 is disposed on the lower side so as to face each other with a slight distance in the vertical direction of the plate-like object 4 to be measured. The output signal of the detection unit 2 is sent to the thickness calculator 7. The detector 2 and the generator 3 are fixed to the U-shaped frame 1. In the detector 2, a plurality of cylindrical ionization chambers 5 are arranged in parallel in the width direction of the object 2 to be measured, and these detect the fan-shaped radiation output from the generator 3. The shape is cylindrical, and there is a large difference in sensitivity to radiation at the center and at the end. This will be further described with reference to FIGS.
[0004]
FIG. 16 is a perspective view showing the positional relationship between the ionization chamber 5 and the DUT 4. The fan-shaped radiation output from the generator 3 is represented by a broken line. FIG. 17 is an AA ′ arrow view showing a state viewed from directly above the ionization chamber 5. As shown in FIG. 17, the ionization chambers 5 are arranged in parallel to the DUT 4. Since the end of the ionization chamber 5 is less sensitive than the center, it is difficult to detect a high spot (defect) of the DUT 4.
[0005]
FIG. 18 shows a sensitivity distribution when the ionization chambers 5 are arranged in parallel with the object to be measured 4. As shown in FIG. 18, since the sensitivity of the ionization chamber 5 is low, there is a dead zone in which the plate thickness cannot be measured accurately, and a continuous thickness value in the width direction cannot be obtained.
[0006]
In addition, there is an increasing need for devices that can measure the edge part with high resolution and high accuracy, but the conventional multipoint thickness gauge has a low sensitivity to radiation existing between the ionization chamber (hereinafter referred to as the ionization chamber). It is difficult to obtain an accurate measurement in a dead zone), and it is difficult to obtain a continuous edge shape.
[0007]
[Problems to be solved by the invention]
As described above, in the multi-point measurement thickness gauge, the plate thickness at the measurement position is converted to the plate thickness by taking the average of the total amount of radiation incident in the height direction of the ionization chamber, but the ionization chamber is cylindrical. Therefore, there is a characteristic that the central portion has the highest sensitivity to radiation and the sensitivity is low as it approaches the end.
[0008]
Therefore, when the measurement point is just a dead zone, the entire height direction of the ionization chamber is a dead zone. For this reason, the sensitivity is remarkably lowered at this position, and there are portions that cannot be measured when measuring the thickness of the object to be measured in the width direction.
[0009]
In addition, when measuring the thickness of the position at an arbitrary distance from the edge of the object to be measured, the width value of the object to be measured is input to the computing unit from an external device such as a width meter, and the meandering amount of the object to be measured is calculated. At the same time, the multipoint thickness gauge is moved by the moving device 6 for measurement, but measurement at the target position cannot be performed until the carriage moves to the target position.
[0010]
On the other hand, when ionization chambers are arranged adjacent to each other, scattered radiation from adjacent ionization chambers is incident on the ionization chamber, which may adversely affect measurement results such as a decrease in the accuracy of edge portions and a decrease in resolution.
[0011]
The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide a multipoint measurement thickness meter that can reduce the difference in sensitivity to radiation depending on the measurement position and can perform better width direction measurement. It is.
[0012]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1 is a cylindrical shape in which a plurality of radiation sources are arranged in parallel in the width direction of the object to be measured at positions facing the radiation source via the object to be measured. A detection means having an ionization chamber and obtaining an output signal related to the level of radiation emitted from a radiation source and transmitted through the measurement object, and the thickness of the measurement object is calculated from the output signal of the detection means The ionization chamber has a structure in which radiation is incident from the side surface of the cylinder , and the ionization chamber is clockwise or relative to the flow direction of the measurement object so that the dead zone of the incident radiation is eliminated. It is arranged by rotating at an arbitrary angle in the counterclockwise direction .
[0013]
According to the first aspect of the present invention, it is possible to eliminate the dead zone portion existing in the conventional ionization chamber arrangement, and it is possible to continuously and accurately measure the thickness direction of the object to be measured.
[0014]
The invention according to claim 2 is the multipoint thickness gauge according to claim 1, wherein the calculation means inputs the width value measured by the means for measuring the width of the measurement object, and the edge position of the measurement object Alternatively, the center position is calculated, and the edge position of the object to be measured or the position from the center position with respect to the thickness calculated from the output signal of the detection means can be specified.
[0015]
The invention according to claim 3 is the multipoint thickness gauge according to claim 1, wherein the calculation means receives an output signal from the means for detecting the edge of the object to be measured, and calculates the edge position of the object to be measured. The position calculated from the edge position of the measured object with respect to the thickness calculated from the output signal of the detection means can be specified.
[0016]
According to a fourth aspect of the present invention, in the multi-point measurement thickness gauge according to the first aspect, the calculation means receives the center deviation amount from the external device, calculates the center position of the object to be measured, and outputs the detection means. The position calculated from the center position of the object to be measured with respect to the thickness calculated from the signal can be specified.
[0017]
The invention according to claim 5 is the multipoint measurement thickness gauge according to claim 1, wherein the ionization chambers are arranged in a predetermined range of positions including the target measurement position, and the calculation means includes: A means for measuring the width, a means for detecting the edge of the object to be measured, or an output signal from an external device is inputted to obtain the meandering amount of the object to be measured, and a measurement position based on the thickness values of a plurality of measurement positions An interpolation function for calculating a thickness value between them is obtained, and a thickness value at a position shifted from the target measurement position by the meandering amount is calculated by the interpolation function.
[0018]
According to the invention which concerns on Claim 5, even when a to-be-measured object shift | deviates from a target measurement position, thickness can be measured continuously.
[0019]
The invention according to claim 6, using Te multipoint measuring thickness meter smell of claim 1, and the total length of the conductive away box, the value of the dead zone obtained by multiplying the safety factor to the thickness of the ion chamber sidewall The rotation angle of the ionization chamber is determined such that the dead zone disappears with respect to the flow direction of the object to be measured.
[0020]
Invention, Te multipoint measuring thickness meter smell of claim 1, and the total length of the conductive away box, and the dead band value was determined using gas amount ratio ionization chamber inside and an ionization chamber center according to claim 7 Is used to determine the rotation angle of the ionization chamber so that the dead zone disappears with respect to the flow direction of the object to be measured.
[0021]
The invention according to claim 8, using Te multipoint measuring thickness meter smell of claim 1, and the total length of the conductive away box, and a dead band of values obtained using the ionization chamber outside diameter and gas filling factor, The rotation angle of the ionization chamber is determined such that the dead zone disappears with respect to the flow direction of the object to be measured.
[0022]
The invention according to claim 9 is the multipoint measurement thickness gauge according to any one of claims 1 to 8, wherein a threshold plate is inserted between two adjacent ionization chambers.
[0023]
According to the ninth aspect of the present invention, the influence of the scattered radiation incident from the adjacent ionization chamber is eliminated, and excellent measurement can be performed without any factor that adversely affects the measurement result, such as a decrease in accuracy of the edge portion and a decrease in resolution. .
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In addition, in the following figures, including the figure which shows a prior art example, the same code | symbol shows the same part or a corresponding part.
[0025]
(First embodiment)
A first embodiment of the present invention will be described with reference to FIGS.
[0026]
In FIG. 1, the widthwise movement operation of the U-shaped frame 1 is performed by the multipoint measurement thickness gauge moving device 6 so that the plate thickness of the plate-like object 4 can be measured. In the U-shaped frame 1, a generator 3 is fixed on the lower side, and a detector 2 is fixed on the upper side. An ionization chamber 5 is arranged in the detection unit 2.
[0027]
The radiation output from the generator 3 passes through the object to be measured 4 and enters the ionization chamber 5. The incident radiation ionizes the gas sealed in the ionization chamber 5 by the action of photoelectric absorption, Compton scattering, electron pair generation, etc., and the generated charge is attracted to the electrodes by the electric field applied between the electrodes. To recombine back to neutral atoms. The current flowing out at this time becomes an output signal of the detection unit 2, and after A / D conversion, is sent to the thickness calculator 7 and converted into a thickness value of the DUT 4.
[0028]
In the conventional example, as described above, since the ionization chambers 5 are arranged in parallel to the object 4 to be measured, dead zones periodically exist, and a continuous thickness value in the width direction cannot be obtained. Therefore, in this embodiment, the arrangement of the ionization chambers 5 is changed to eliminate the dead zone.
[0029]
FIG. 2 is a perspective view showing the positional relationship between the ionization chamber 5 and the DUT 4 in this embodiment. The fan-shaped radiation output from the generator 3 is represented by a broken line. FIG. 3 is an AA ′ arrow view showing a state viewed from directly above the ionization chamber 5. The ionization chamber 5 is arranged obliquely with respect to the object 4 as shown in FIG. In this way, the ionization chamber 5 is arranged in a state where it is rotated at an arbitrary angle clockwise or counterclockwise with respect to the flow direction of the device under test 4 on a plane viewed from directly above the device under test 4. By doing so, it becomes possible to eliminate the dead zone part that has existed in the conventional ionization chamber arrangement, and the measurement of the measured object 4 in the width direction can be performed continuously and accurately.
[0030]
FIG. 4 shows the sensitivity distribution in this embodiment in which the ionization chamber 5 is rotated clockwise or counterclockwise with respect to the flow direction of the object 4 to be measured. As is apparent from the figure, it is possible to obtain a certain sensitivity or more in the plate width direction of the DUT 4. Therefore, if there is a local high spot (defect) in the DUT 4, it can be easily detected.
[0031]
(Second Embodiment)
FIG. 5 is a diagram showing the configuration of the second exemplary embodiment of the present invention. In this embodiment, the thickness calculator 7 calculates the thickness value of the DUT 4 from the output signal of the detector 2 as in the case of the first embodiment, and the width measured by the width meter 8. The value is input to the thickness calculator 7 and the plate edge position or the plate center position of the DUT 4 is calculated.
[0032]
Therefore, the calculator 7 can specify the position of the measured object 4 from the plate edge position or the plate center position with respect to the thickness calculated from the output signal of the detection unit 2.
[0033]
(Third embodiment)
FIG. 6 is a diagram showing the configuration of the third exemplary embodiment of the present invention. In this embodiment, the thickness calculator 7 calculates the thickness value of the DUT 4 from the output signal of the detector 2 as in the case of the first embodiment, and the signal detected by the edge sensor 9 is calculated. It inputs into the thickness calculator 7, and calculates the board edge position of a to-be-measured object.
[0034]
Therefore, the calculator 7 can specify the position of the object to be measured from the plate edge position with respect to the thickness calculated from the output signal of the detector 2.
[0035]
(Fourth embodiment)
FIG. 7 is a diagram showing the configuration of the fourth exemplary embodiment of the present invention. In this embodiment, the thickness calculator 7 calculates the thickness value of the device under test 4 from the output signal of the detector 2 as in the first embodiment, and from an external device 10 such as a host computer. The plate center deviation amount is input to the thickness calculator 7 to calculate the plate center position.
[0036]
Accordingly, the calculator 7 can specify the position of the DUT 4 from the plate center position with respect to the thickness calculated from the output signal of the detection unit 2.
[0037]
(Fifth embodiment)
8-10 is a figure explaining the 5th Embodiment of this invention.
[0038]
FIG. 8 shows a configuration in the case where the multi-point measurement thickness gauge having the configuration as in the first embodiment is used for measuring a plate thickness at a target position separated from the edge portion of the DUT 4 by an arbitrary distance. ing. Since the multipoint measurement thickness gauge measures a target position separated by an arbitrary distance from the edge of the object 4 to be measured, the ionization chamber 5 is arranged at a position within a predetermined range centered on this position so that the plate thickness can be measured.
[0039]
In the thickness calculator 7, the plate thickness values 11, 12, and 13 at a plurality of measurement positions in a predetermined range near the target measurement position are obtained from the output signal of the detection unit 2, and the width meter 8 or the edge sensor 9 When the edge position is obtained from the output signal, as shown in FIG. 9, the plate thickness values 11, 12, and 13 are plotted at positions corresponding to the distances from the edge position to the measurement position, and the plate thickness measurement results are obtained. Can be connected by the interpolation function 14 and graphed. Even when the target measurement position is located between the actual measurement positions, the thickness value 16 of the target measurement position at an arbitrary distance 15 from the edge position can be obtained from the interpolation function 14.
[0040]
Further, in many cases, the DUT 4 comes while meandering in the width direction. An output signal representing the plate width, edge position, or center shift amount (meandering amount) from the width gauge 8 or the edge sensor 9 or the external device 10 is input to the thickness calculator 7, and the measured object 4 is measured. Calculate the amount of meandering. Then, the plate thickness measurement results in the vicinity of the target measurement position are connected by an interpolation function, and are graphed as shown in FIG. That is, the plate thickness value 17 at the target measurement position and the plate thickness values 18 and 19 at the positions in the vicinity thereof are connected by the interpolation function 20. When the plate displacement amount, that is, the meandering amount 21 is calculated from the edge position obtained from the width gauge 8 or the like, the plate thickness value 22 is obtained from the interpolation function 20. By setting this value as the plate thickness value at the target measurement position, the plate thickness can be continuously measured even when the DUT 4 deviates from the target measurement position.
[0041]
(Sixth embodiment)
11 to 13 are views for explaining a sixth embodiment of the present invention. The sensitivity of the ionization chamber 5 to radiation is proportional to the amount of gas in the ionization chamber 5. Since the gas amount is small at the end of the ionization chamber 5, the sensitivity is lowered, and the sensitivity to radiation is lost at the side wall of the ionization chamber 5.
[0042]
In this embodiment, the ionization chamber 5 has a structure in which radiation is incident from the side surface of the cylinder. As shown in FIG. 11, the rotation angle of the ionization chamber 5 is such that the dead zone disappears with respect to the flow direction of the object to be measured. α is determined.
[0043]
First, as a first method for determining the rotation angle α, the rotation angle α can be obtained by using the total length of the ionization chamber and the dead zone value obtained by multiplying the wall thickness of the ionization chamber by the safety factor. That is, when the total length of the ionization chamber 5 is 2 L, and the value of the dead zone 11 obtained by multiplying the wall thickness t of the ionization chamber by the safety factor γ is T (= t · γ), the flow direction of the measurement object 4 On the other hand, the rotation angle α of the ionization chamber 5 that eliminates the dead zone is obtained as α = tan ⁻¹ (T / L). The safety factor γ is an arbitrary constant (for example, 2).
[0044]
Next, as a second method for determining the rotation angle α, it can be obtained by using the total length of the ionization chamber and the value of the dead zone obtained by using the gas chamber ratio with respect to the inner diameter of the ionization chamber and the center of the ionization chamber. As shown in FIG. 12, a position where the gas amount ratio is c with respect to the center portion O of the ionization chamber 5 is a position that becomes a boundary with the dead zone 11, and this position on a horizontal line passing through the center portion O is B. That is, the position B is, when the ionization chamber inner diameter and 2r, the distance from the position B to the position C of the inner wall of the upper When l _1, as the position such that l ₁ = c · r. In the figure, the position of the inner wall above the center O is A, the distance from the center O to the position B is t ″, the distance from the position B to the horizontal inner wall position D is t ′, and OA And the angle formed by OC and β.
[0045]
Here, l ₁ = c · r, but from the figure, since l ₁ = r cos β, c = cos β. Therefore, given the gas amount ratio c to the center of the ionization chamber, the angle β is obtained. Can do. Further, from the figure, since t ″ = rsinβ, the value T of the dead zone 11 can be obtained as follows.
[0046]
[Expression 1]

Then, from the value T of the dead zone 11 obtained in this way and the total length 2L of the ionization chamber 5, the rotation angle α of the ionization chamber 5 such that the dead zone disappears with respect to the flow direction of the object 4 to be measured is α = tan ^{−. 1} (T / L). Note that the gas amount ratio c to the center of the ionization chamber can be an arbitrary constant (for example, 0.5).
[0047]
Further, as a third method, the total length of the ionization chamber, the outside diameter of the ionization chamber and the gas filling coefficient (the coefficient of the effective diameter filled with gas) can be obtained using the value of the dead zone. . When the outer diameter of the ionization chamber is set to 2R, as shown in FIG. 13, the distance from the center O on the horizontal line passing through the center O of the ionization chamber 5 is filled with a gas value R that is half the outer diameter of the ionization chamber. The position E of the value multiplied by the coefficient c ′ is set as a boundary with the dead zone 11, and the value T of the dead zone 11 is obtained as follows.
[0048]
[Expression 2]

Then, from the value T of the dead zone 11 obtained in this way and the total length 2L of the ionization chamber 5, the rotation angle α of the ionization chamber 5 such that the dead zone disappears with respect to the flow direction of the object 4 to be measured is α = tan ^{−. 1} (T / L). The gas filling coefficient c ′ can be an arbitrary constant (for example, a value of about 0.7 to 0.8).
[0049]
(Seventh embodiment)
FIG. 14 is a diagram for explaining a seventh embodiment of the present invention. When a plurality of ionization chambers 5 are arranged adjacent to each other as in the first to sixth embodiments, in addition to the radiation 14 radiated from the generator 3, the ionization chambers 5 are adjacent to the ionization chambers 5. Since the scattered radiation 13 is incident, the measurement result may be adversely affected, such as a decrease in the accuracy of the edge portion and a decrease in resolution.
[0050]
Therefore, in this embodiment, the threshold plate 12 is disposed between the adjacent ionization chambers 5 in order to reduce the influence of the scattered radiation 13.
[0051]
The thickness of the threshold plate 12 is set to a thickness that can sufficiently absorb scattered radiation, and the length and height of the threshold plate 12 are equal to or greater than the length and height of the ionization chamber 5, respectively.
[0052]
The threshold plate 12 can be made of stainless steel (for example, SUS304), but is not limited to this as long as it can absorb scattered radiation. For example, tungsten, lead, or the like can be used.
[0053]
Further, the material having a larger linear absorption coefficient can reduce the plate thickness.
[0054]
As described above, when the threshold plate 12 is used, the rotation angle α ′ of the ionization chamber 5 that eliminates the dead zone with respect to the flow direction of the object 4 to be measured is the thickness t ₂ of the threshold plate 12. Then, instead of T in the case of the sixth embodiment, (T + 0.5t ₂ ) can be used to obtain α ′ = tan ⁻¹ {(T + 0.5t ₂ ) / L}.
[0055]
【The invention's effect】
As described above, according to the present invention, by rotating the arrangement of the ionization chamber clockwise or counterclockwise with respect to the flow direction of the object to be measured, the area with low radiation sensitivity is reduced, and the entire measurement area is reduced. A multi-point measurement thickness gauge with little change in sensitivity can be obtained, and when a high spot (defect) is locally present on the object to be measured, this can be easily detected.
[0056]
In addition, by calculating the meandering amount from the input signal and applying this to a function that interpolates between each measurement position, it is possible to cope with the deviation of the target measurement position due to the meandering of the object to be measured. Can be performed continuously.
[Brief description of the drawings]
FIG. 1 is a front view showing a configuration of a multipoint measurement thickness gauge according to a first embodiment of the present invention.
FIG. 2 is a perspective view showing an arrangement of ionization chambers in the first embodiment.
FIG. 3 is an AA ′ arrow view showing a state viewed from directly above the ionization chamber in FIG. 2;
FIG. 4 is a diagram showing a sensitivity distribution in the width direction of the ionization chamber in the first embodiment.
FIG. 5 is a diagram showing a configuration of a multipoint measurement thickness gauge according to a second embodiment of the present invention.
FIG. 6 is a diagram showing a configuration of a multipoint measurement thickness gauge according to a third embodiment of the present invention.
FIG. 7 is a diagram showing a configuration of a multipoint measurement thickness gauge according to a fourth embodiment of the present invention.
FIG. 8 is a diagram showing a configuration of a multipoint measurement thickness gauge according to a fifth embodiment of the present invention.
FIG. 9 is a graph showing a graph obtained by interpolating a plate thickness value at a target measurement position when the target measurement position is between actual measurement positions in the fifth embodiment.
FIG. 10 is a diagram showing a graph obtained by interpolating a plate thickness value at a target measurement position when an object to be measured meanders in the fifth embodiment.
FIG. 11 is a view for explaining a method for determining the rotation angle of an ionization chamber in a sixth embodiment of the present invention.
FIG. 12 is a diagram for explaining a method for determining the rotation angle of an ionization chamber using the inner diameter of the ionization chamber, the gas amount ratio with respect to the central portion of the ionization chamber, and the like in the sixth embodiment of the present invention.
FIG. 13 is a view for explaining a method for determining the rotation angle of an ionization chamber using the outer diameter of the ionization chamber, the gas filling coefficient, and the like in the sixth embodiment of the present invention.
FIG. 14 is a diagram showing a configuration of a main part of a multipoint measurement thickness gauge according to a seventh embodiment of the present invention.
FIG. 15 is a front view showing a configuration of a conventional example.
FIG. 16 is a perspective view showing an arrangement of ionization chambers in a conventional example.
FIG. 17 is an AA ′ arrow view showing a state viewed from directly above the ionization chamber in FIG. 16;
FIG. 18 is a diagram showing a sensitivity distribution in the width direction of an ionization chamber in a conventional example.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... U-shaped frame 2 ... Detection part 3 ... Generator 4 ... Object to be measured 5 ... Ionization chamber 6 ... Multi-point measurement thickness gauge moving device 7 ... Thickness calculator 8 ... Width meter 9 ... Edge sensor 10 ... External device 11 ... dead zone 12 ... threshold plate 13 ... scattered radiation 14 ... radiation

Claims

A radiation source, has a plurality parallel-arranged cylindrical ionization chamber in a width direction of the object to be measured at a position facing the radiation source through the object to be measured, the object to be emitted from the radiation source Detection means for obtaining an output signal related to the level of radiation incident through the measurement object, and calculation means for calculating the thickness of the measurement object from the output signal of the detection means, the ionization chamber, A structure in which radiation is incident from the side of a cylinder, and the ionization chamber is rotated at an arbitrary angle clockwise or counterclockwise with respect to the flow direction of the object to be measured so that the dead zone of the incident radiation is eliminated. Multi-point measuring thickness gauge characterized by being arranged.

The multi-point measurement thickness meter according to claim 1, wherein the calculation means receives a width value measured by a means for measuring the width of the measurement object, and calculates an edge position or a center position of the measurement object. A multi-point measuring thickness gauge characterized by being capable of calculating and determining the position from the edge position or the center position of the object to be measured for the thickness calculated from the output signal of the detection means.

2. The multi-point measurement thickness gauge according to claim 1, wherein the calculation means receives an output signal from a means for detecting an edge of the device under test, calculates an edge position of the device under test, and outputs the detection means. A multi-point measuring thickness gauge characterized by being capable of specifying a position from an edge position of the object to be measured with respect to a thickness calculated from a signal.

The multi-point measurement thickness meter according to claim 1, wherein the calculation means receives a center deviation amount from an external device, calculates a center position of the object to be measured, and calculates a thickness calculated from an output signal of the detection means. A multi-point thickness gage characterized in that the position from the center position of the object to be measured can be specified.

2. The multipoint measurement thickness gauge according to claim 1, wherein the ionization chambers are arranged at positions within a predetermined range including a target measurement position, and the calculation means measures the width of the object to be measured. Or a means for detecting the edge of the object to be measured, or an output signal from an external device is input to obtain the meandering amount of the object to be measured, and the thickness between the measurement positions based on the thickness values of a plurality of measurement positions An interpolating function for calculating a value is obtained, and a thickness value at a position shifted from the target measurement position by the meandering amount by the interpolating function is calculated.

Te multipoint measuring thickness meter smell of claim 1, and the total length of the front Symbol ionization chamber, wherein by using the value of the dead zone obtained by multiplying the safety factor to the thickness of the ionization chamber side wall, of the object to be measured A multi-point measuring thickness gauge, wherein a rotation angle of the ionization chamber is determined such that the dead zone disappears with respect to a flow direction.

Using Te multipoint measuring thickness meter smell of claim 1, and the total length of the front Symbol ionization chamber, and a dead zone value determined using a gas amount ratio to the inner diameter and the ionization chamber the center of the ionization chamber, A multi-point measurement thickness gauge, wherein a rotation angle of the ionization chamber is determined such that the dead zone disappears with respect to a flow direction of the measurement object.

Using Te multipoint measuring thickness meter smell of claim 1, and the total length of the front Symbol ionization chamber, and a dead band of values obtained by using the ionization chamber outside diameter and gas filling factor, the flow of the object to be measured A multipoint measurement thickness gauge, wherein a rotation angle of the ionization chamber is determined so that the dead zone disappears with respect to a direction.

The multipoint measurement thickness gauge according to any one of claims 1 to 8, wherein a threshold plate is inserted between two adjacent ionization chambers.