JP3821458B2

JP3821458B2 - Object information detection device by optical scanning

Info

Publication number: JP3821458B2
Application number: JP06402498A
Authority: JP
Inventors: 耕太橋口; 俊行岸; 文彦中沢
Original assignee: Fujitsu Ltd; Fujitsu General Ltd
Current assignee: Fujitsu Ltd; Fujitsu General Ltd
Priority date: 1998-02-27
Filing date: 1998-02-27
Publication date: 2006-09-13
Anticipated expiration: 2018-02-27
Also published as: JPH11248854A

Description

【０００１】
【発明の属する技術分野】
本発明は、発光部からの光を回転可能なスキャンミラーで反射させて再帰性反射体に照射し、この再帰性反射体で反射した光をスキャンミラーの反射を介して受光部で受光し、受光エネルギーをしきい値と比較することによって、スキャンミラーと再帰性反射体の間に形成された光走査範囲内の対象物情報（例えば対象物が有るか否かの情報）を検出する装置に関するものである。
【０００２】
【従来の技術】
上述した光走査による対象物情報検出装置には、図１１に示すようなものが考えられている。すなわち、光学フィルタなどの基板１０の一方の側面の中央部分に光走査ユニット１１を配置し、基板１０の一面の光走査ユニット１１の取付け部を除く３方辺に再帰性反射体１２が取り付けられている。
光走査ユニット１１は、図１２に示すように、ユニット支持板３１の固定部（図示省略）が前記基板１０に接着剤などで固着され、この固定部と一体の略Ｌ字形の支持部１３の上にユニット本体１４が載せられ角度調整自在に取り付けられている。
【０００３】
ユニット本体１４は、下面に前記支持部１３に遊嵌する略Ｌ字形のＬ字溝１５が形成され、内部には、半導体レーザ装置などの発光素子１６と、受光素子１７が収納され、上面には、発光素子１６から出力したレーザ光（以下、単に光と記述する）１８を屈折させる屈折プリズム１９と、この屈折させた光１８を透過させるハーフミラー２０を具備したプリズム２１と、スキャンミラー２２とが設けられ、このスキャンミラー２２はパルスモータ２３により回転自在に設けられている。
【０００４】
そして、発光素子１６から出力した光１８が屈折プリズム１９で屈折し、ハーフミラー２０及びプリズム２１を透過してスキャンミラー２２で反射し再帰性反射体１２に照射する。この再帰性反射体１２では、入射光と略同一光路を戻りスキャンミラー２２で反射し、プリズム２１のハーフミラー２０で反射屈折して受光素子１７で受光される。パルスモータ２３によるスキャンミラー２２の回転により光１８は角度θ（例えば約１８０°）だけ走査される。この光走査範囲内に対象物２４ａ、２４ｂが有ると対象物２４ａ、２４ｂによって光１８が遮断されるので、走査角度θや受光素子１７の受光エネルギーを監視することによって対象物２４ａ、２４ｂの有無が検出される。
【０００５】
図１１において２５は上述の光走査にとって障害となる障害物を表し、この障害物２５は、発光素子１６からの光１８を再帰性反射体１２や対象物２４ａ、２４ｂ以外で反射させて受光素子１７に受光させたり、不要な外来光を受光素子１７に受光させる物体を総称し、装置の筐体であったり、装置の周囲に有る物体であったりする。
【０００６】
図１２の受光素子１７の受光エネルギーを監視するための電気回路としては、図１３に示すような回路が考えられる。すなわち、電流・電圧変換回路２６によって受光素子１７の受光エネルギーに相当した電流が電圧に変換され、この電圧が比較器２７の＋側に入力し、比較器２７の−側に基準電圧源２８からの基準電圧が入力し、この比較器２７の比較出力のレベルがＨレベルかＬレベルかをＭＰＵ（マイクロプロセッサユニット）２９で判断して、対象物２４ａ、２４ｂの有無を検出する。図中のＳは、受光素子１７が受光した光のうちの信号成分（再帰性反射体１２や対象物２４ａ、２４ｂで反射した光）を表し、Ｎは雑音成分（障害物２５で反射した光や外来光）を表す。
【０００７】
【発明が解決しようとする課題】
しかしながら、図１３に示した回路では、比較器２７によって受光素子１７の受光エネルギーに相当した電圧を基準電圧源２８の基準電圧と比較し、比較出力に基づいて対象物２４ａ、２４ｂの有無を検出していたので、正しい対象物情報が得られないという問題点があった。すなわち、走査角度θによって受光素子１７の受光エネルギーに差がでてくること、近傍の障害物２５からの乱反射等による雑音でＳＮ比が悪くなること等の理由によって正しい対象物情報が得られないという問題点があった。
また、対象物情報を判断する回路の応答速度によっては正しい対象物情報が得られないという問題点があった。
【０００８】
例えば、図１１に示すように光走査範囲内に２つの対象物２４ａ、２４ｂがある場合、走査角度θと受光エネルギーの関係が図１４に示すようになり、一方の対象物２４ｂの存在は検出できるが他方の対象物２４ａの存在を検出できないという問題点があった。すなわち、走査角度θが０（＝０°）、π（＝１８０°）のときに受光素子１７は発光素子１６からの光１８の殆どを受光するので受光エネルギーが最大となり、再帰性反射体１２は入射角が直角に近いほど反射エネルギーが大きいので再帰性反射体１２の両端部と中央部に相当する走査角度θで受光エネルギーが大きくなり、さらに雑音によって受光エネルギーのＤＣ（直流）レベルが上がる。
このように受光素子１７の受光エネルギーＪＥが図１４に示すように走査角度θに応じて変化するのに対して、スライスレベルＳＬが一定なので、一方の対象物２４ｂの存在は検出できるが他方の対象物２４ａの存在を検出できないという問題点があった。図１４中において、スライスレベルＳＬは比較器２７の−入力側に入力する基準電圧に相当した光エネルギーの値を表し、Ａは受光エネルギーＪＥの特性曲線のうちの対象物２４ａに対応した部分を表し、Ｂは受光エネルギーＪＥの特性曲線のうちの対象物２４ｂに対応した部分を表す。
【０００９】
本発明は、上述の問題点に鑑みなされたもので、走査角度θや雑音に起因する誤った対象物情報の検出を防止し、対象物が光走査範囲内の何処にあっても正しい対象物情報を得ることのできる光走査による対象物情報検出装置を提供することを目的とする。
【００１０】
【課題を解決するための手段】
請求項１の発明は、発光部からの光を回転可能なスキャンミラーで反射させて再帰性反射体に照射し、この再帰性反射体で反射した光を前記スキャンミラーの反射を介して受光部で受光し、受光エネルギーをしきい値と比較することによって、前記スキャンミラーと前記再帰性反射体の間に形成された光走査範囲内の対象物情報を検出する装置において、前記受光部の受光エネルギーに応じて前記しきい値を変化させるしきい値可変手段を設けてなり、このしきい値可変手段は、受光部の受光エネルギーに相当した信号をディジタル信号に変換するＡ／Ｄ変換回路と、このＡ／Ｄ変換回路の出力信号の一定期間の平均値を求める平均値算出回路と、この平均値算出回路で求めた平均値から前記Ａ／Ｄ変換回路の出力信号に応じて異なる定数を減算する定数減算回路と、この定数減算回路の演算値をアナログ信号に変換ししきい値として出力するＤ／Ａ変換回路とからなり、前記定数減算回路は、平均値算出回路で求めた平均値から相異なる定数Ｋ１、Ｋ２（Ｋ１＜Ｋ２）を減算する第１、第２減算器と、Ａ／Ｄ変換回路の出力信号と前記第１、第２減算器の一方の演算値とを比較する比較器と、この比較器の比較出力に応じて前記第１、第２減算器の演算値の一方を選択して出力するセレクタとからなることを特徴とする。
【００１１】
走査角度θによって受光部の受光エネルギーに差がでてきたり、近傍の障害物からの乱反射等による雑音で受光部の受光エネルギーが一定レベルもち上がっても、しきい値可変手段によって受光エネルギーと比較するしきい値が受光部の受光エネルギーに応じて変化するので、走査角度θや雑音に起因する誤った対象物情報の検出を防止することができる。
【００１２】
請求項２の発明は、発光部からの光を回転可能なスキャンミラーで反射させて再帰性反射体に照射し、この再帰性反射体で反射した光を前記スキャンミラーの反射を介して受光部で受光し、受光エネルギーをしきい値と比較することによって、前記スキャンミラーと前記再帰性反射体の間に形成された光走査範囲内の対象物情報を検出する装置において、前記受光部の受光エネルギーに応じて前記しきい値を変化させるしきい値可変手段を設け、受光エネルギーに相当した信号を一定期間遅延させしきい値と比較する信号として出力する遅延手段を設け、前記しきい値可変手段は、受光部の受光エネルギーに相当した信号をディジタル信号に変換するＡ／Ｄ変換回路と、このＡ／Ｄ変換回路の出力信号の一定期間の平均値を求める平均値算出回路と、この平均値算出回路で求めた平均値から一定の定数を減算する減算回路と、この減算回路の演算値をアナログ信号に変換ししきい値として出力するＤ／Ａ変換回路とからなることを特徴とする。
【００２３】
【発明の実施の形態】
以下、本発明に係る光走査による対象物情報検出装置の一実施形態例を図１を用いて説明する。
図１において図１３と同一部分は同一符号とする。図１において、１２は再帰性反射体、１６は発光素子、１７は受光素子、１８は前記発光素子１６からの光、２４ａ、２４ｂは情報検出対象としての対象物、２５は光走査にとって障害となる障害物、２６は前記受光素子１７の受光エネルギーに相当した電流を電圧に変換して出力する電流・電圧変換回路、２７は比較器、２９はＭＰＵを表し、Ｓは前記受光素子１７が受光した光のうちの信号成分を表し、Ｎは雑音成分を表す。
【００２４】
３０はしきい値可変手段で、このしきい値可変手段３０は、前記電流・電圧変換回路２６の出力電圧を分圧する分圧回路３２と、この分圧回路３２に結合され積分値をしきい値として出力する積分回路３４とからなり、前記分圧回路３２は抵抗３６、３８で構成され、前記積分回路３４は前記抵抗３６とコンデンサ４０で構成されている。
【００２５】
つぎに、図１の作用を図２を併用して説明する。
電流・電圧変換回路２６は、受光素子１７の受光エネルギーに相当した電流を電圧に変換し、この電圧を比較器２７の＋入力側に出力する。このため、比較器２７の＋入力側に入力する電圧に相当した受光エネルギーＪＥは、図１４の場合と同様に、図２に示すような特性曲線となる。すなわち、この受光エネルギーＪＥは、走査角度θが０、πのときに受光エネルギーが最大となり、π／２のときに受光エネルギーが大きくなり、さらに雑音によって受光エネルギーのＤＣレベルが上がっている。図２中においてＡは受光エネルギーＪＥの特性曲線のうちの対象物２４ａに対応した部分を表し、Ｂは受光エネルギーＪＥの特性曲線のうちの対象物２４ｂに対応した部分を表す。
【００２６】
しきい値可変手段３０は、その分圧回路３２が電流・電圧変換回路２６の出力電圧を抵抗３６、３８の値に応じて分圧し、積分回路３４が抵抗３６とコンデンサ４０による積分値をしきい値として比較器２７の−入力側に入力する。このため、比較器２７の−入力側への入力電圧に相当した光エネルギーであるスライスレベルＳＬａは、図２中に点線で示すように、、受光エネルギーＪＥの特性曲線を一定レベル下げた値となり、Ａ、Ｂの下端点より高いレベルとなる。
したがって、対象物２４ａ、２４ｂの何れに対しても、比較器２７の出力側に検出信号が現われ、ＭＰＵ２９によって対象物２４ａ、２４ｂが有ることを判別できる。すなわち、走査角度θや雑音に起因する誤った対象物情報の検出を防止することができる。
【００２７】
図１の実施形態例では、しきい値可変手段を分圧回路と積分回路で構成した場合について説明したが、本発明はこれに限るものでなく、受光素子の受光エネルギーに応じてしきい値を変化させるものであればよい。
例えば、図３に示すように、しきい値可変手段３０ａを、電流・電圧変換回路２６の出力電圧Ｅｓをその周波数の２倍以上の標本化周波数で標本化してディジタルの電圧Ｖｓに変換するＡ／Ｄ（アナログ／ディジタル）変換回路４２と、このＡ／Ｄ変換回路４２の出力電圧Ｖｓの一定期間（例えば３標本化周期）の平均値Ｖｓａを求める平均値算出回路４４と、この平均値算出回路４４で求めた平均値ＶｓａからＡ／Ｄ変換回路４２の出力電圧Ｖｓに応じて異なる定数を減算する定数減算回路４６と、この定数減算回路４６の演算値をアナログの電圧Ｅｒに変換ししきい値として出力するＤ／Ａ（ディジタル／アナログ）変換回路４８とで構成した場合についても利用することができる。
【００２８】
前記平均値算出回路４４は、３段に結合されたシフトレジスタ５０₁、５０₂、５０₃、加算器５２及び除算器５４からなり、前記シフトレジスタ５０₁、５０₂、５０₃は前記Ａ／Ｄ変換回路４２の出力電圧Ｖｓを順次１標本化クロック分遅延させ、前記加算器５２は、前記Ａ／Ｄ変換回路４２の出力電圧Ｖｓと前記シフトレジスタ５０₁、５０₂、５０₃のそれぞれから出力する電圧とを加算し、前記除算器５４は前記加算器５２で求めた加算値を４（シフトレジスタの段数＋１）で割った平均値Ｖｓａを出力する。
【００２９】
前記定数減算回路４６は、前記除算器５４から出力した平均値Ｖｓａから相異なる定数Ｋ１、Ｋ２（Ｋ１＜Ｋ２）を減算する第１、第２減算器５６、５８と、前記Ａ／Ｄ変換回路４２の出力電圧Ｖｓと前記第１減算器５６の演算値（Ｖｓａ−Ｋ１）とを比較する比較器６０と、この比較器６０の比較出力に応じて前記第１、第２減算器５６、５８の演算値の一方を選択して出力するセレクタ６２とで構成されている。なお、比較器６０は、Ａ／Ｄ変換回路４２の出力電圧Ｖｓと第２減算器５８の演算値（Ｖｓａ−Ｋ２）とを比較し、その比較出力でセレクタ６２の切り替えを制御するようにしてもよい。
【００３０】
つぎに、図３の場合の作用を図４を併用して説明する。
（イ）電流・電圧変換回路２６の出力電圧Ｅｓがなだらかに変化している場合には、第１減算器５６の演算値（Ｖｓａ−Ｋ１）がＡ／Ｄ変換回路４２の出力電圧Ｖｓより小さい（Ｖｓａ−Ｋ１＜Ｖｓ）ので、比較器６０の出力信号がＬレベルとなりセレクタ６２の可動片は実線で示すように第１減算器５６の演算値（Ｖｓａ−Ｋ１）を選択する。このため、Ｄ／Ａ変換回路４８は、（Ｖｓａ−Ｋ１）をアナログ信号に変換した電圧Ｅｒを比較器２７の−入力側に出力する。
【００３１】
（ロ）受光素子１７からの信号Ｓの強弱によってＳ／Ｎ比が極端に変化し、電流・電圧変換回路２６の出力電圧Ｅｓが図４に示すようになだらかに変化している途中で急激に変化した場合、セレクタ６２が第１減算器５６の演算値（Ｖｓａ−Ｋ１）を選択し続けていると、平均値算出回路４４の平均化処理によって比較器２７の−入力側に入力する電圧Ｅｒと＋入力側に入力する電圧Ｅｓとの間に部分的な逆転現象（Ｅｒ＞Ｅｓ）が生じるが、この逆転現象が生じる直前に比較器６０の出力信号がＬレベルからＨレベルに変化しセレクタ６２の可動片が点線で示すように第２減算器５８を選択するので、電圧Ｅｒが部分的に２点鎖線で示すように補正され、逆転現象による誤った対象物情報の検出を防止している。
すなわち、定数減算回路４６が無く、代わりに第１減算器５６が平均値算出回路４４で求めた平均値Ｖｓａから定数Ｋ１を減算した値（Ｖｓａ−Ｋ１）をＤ／Ａ変換回路４８へ出力するだけの構成とした場合には、Ｄ／Ａ変換回路４８の出力電圧Ｅｒが図４に×印で示すような値となり、部分的に逆転現象が生じる。しかし、図３の実施形態例では、定数減算回路４６が有り、逆転現象が生じる直前にセレクタ６２が第２減算器５８を選択して（Ｖｓａ−Ｋ２）をＤ／Ａ変換回路４８へ出力するので、Ｄ／Ａ変換回路４８から出力するＥｒは、その一部が図４に○印及び２点鎖線で示すように補正され、逆転現象による誤った対象物情報の検出を防止している。
【００３２】
図３に示した実施形態例では、定数減算回路４６を第１、第２減算器５６、５８、比較器６０及びセレクタ６２で構成し、平均値算出回路４４で求めた平均値ＶｓａからＡ／Ｄ変換回路４２の出力電圧Ｖｓに応じて異なる定数Ｋ１、Ｋ２を減算し、この減算で求めた演算値をＤ／Ａ変換回路４８へ出力し、さらに電流・電圧変換回路２６の出力電圧Ｅｓを比較器２７の＋入力側に直接入力するようにしたが、本発明はこれに限るものでなく、定数減算回路４６を無くして代わりに第１減算器５６（又は第２減算器５８）のみを設け、図３に２点鎖線で示すように電流・電圧変換回路２６の出力側と比較器２７の＋入力側との間に遅延回路６４を設けた場合についても利用することができる。
この場合、信号の強弱によってＳ／Ｎ比が極端に変化し、電流・電圧変換回路２６の出力電圧Ｅｓが図５に実線で示すように急激な増加から急激な減少に変化しても、逆転現象（Ｅｒ＞Ｅｓ）が生じるのを防止し、誤った対象物情報の検出を防止できる。すなわち、図３の実施形態例において、定数減算回路４６を無くし、代わりに第１減算器５６のみを設けただけでは、比較器２７の−入力側に入力するＥｒが図５に点線で示すようになり、Ｅｓがピークを過ぎて減少に転じた直後に逆転現象（Ｅｒ＞Ｅｓ）が生じるが、遅延回路６４によって出力電圧Ｅｓを一定期間遅延させた補正電圧Ｅｓｄ（図５に１点鎖線で示す）が比較器２７の＋入力側に入力するので、逆転現象が生じるのを防止し、誤った対象物情報の検出を防止している。
【００３３】
図６は本発明の他の実施形態例を示すもので、図１と同一部分は同一符号とし説明を省略する。図６において、１６は発光素子、１７は受光素子、１８は前記発光素子１６からの光、２６は電流・電圧変換回路、２７は比較器、２８は基準電圧源、４２はＡ／Ｄ変換回路、６６は各種の制御処理を行うＭＰＵ、６８は標準電圧値Ｖｒを置数する標準電圧値レジスタ、７０は積分処理メモリ、７２はＤ／Ａ変換回路、７４は電圧・電流変換回路、７６は警告を報知するための報知部（例えば警告ランプや警告ブザー）である。
【００３４】
前記ＭＰＵ６６は、以下の▲１▼〜▲５▼に記述する各機能を達成するためのプログラムを格納したＲＯＭ（リード・オンリ・メモリ）（図示省略）を具備するとともに、前記発光素子１６側へ出力する制御信号を一時的に置数するレジスタ７８及び設定された極限値を置数する極限値レジスタ８０を具備している。
▲１▼Ａ／Ｄ変換回路４２の出力電圧Ｖｓの一定期間（例えば３標本化期間）における平均値Ｖｓａを求める平均値演算機能。
▲２▼前記▲１▼の平均値演算手段で求めた平均値Ｖｓａを標準電圧値レジスタ６８の標準電圧値Ｖｒと比較し、Ｖｓａ＜Ｖｒのときに発光素子１６の発光エネルギを上げるための制御信号をレジスタ７８を介して発光素子１６側へ出力し、Ｖｓａ＞Ｖｒのときに発光素子１６の発光エネルギを下げるための制御信号をレジスタ７８を介して発光素子１６側へ出力する発光部制御機能。
▲３▼前記▲２▼の平均値演算機能で求めた平均値Ｖｓａが、受光素子１７の受光エネルギーが途切れたときに相当して予め設定された下限設定値Ｖｂ以下か否かを判別する下限判別機能。
▲４▼前記▲３▼の下限判別機能により平均値Ｖｓａが下限設定値Ｖｂ以下と判別されたときに、レジスタ７８の現在の置数値と直前の置数値との積分値を演算し、この積分値を積分処理メモリ７０に記憶するとともに、レジスタ７８を介して発光素子１６側へ出力する積分処理機能。
▲５▼レジスタ７８に置数された制御信号と極限値レジスタ８０に置数された極限値Ｖｕとを比較し、制御信号が極限値Ｖｕ以上のときに発光素子１６の発光エネルギーが極限になったことを報知するための信号を報知部７６へ出力する報知部制御機能。
【００３５】
前記Ｄ／Ａ変換回路７２は、前記ＭＰＵ６６内のレジスタ７８に置数された制御値をアナログの電圧に変換して出力し、前記電圧・電流変換回路７４は、前記Ｄ／Ａ変換回路７２から出力した電圧を電流に変換して前記発光素子１６へ出力する。
【００３６】
つぎに、図６の作用を図７及び図８を併用して説明する。
（イ）電流・電圧変換回路２６は、受光素子１７の受光エネルギーに相当した電流を電圧Ｅｓに変換し、この電圧Ｅｓを比較器２７の＋入力側に出力する。Ａ／Ｄ変換回路４２は、電流・電圧変換回路２６の出力電圧Ｅｓをディジタルの電圧Ｖｓに変換し、この電圧ＶｓをＭＰＵ６６へ出力する。
【００３７】
（ロ）ＭＰＵ６６は、その平均値演算機能▲１▼によって、一定期間（例えば３標本化期間）における入力電圧Ｖｓについての平均値Ｖｓａを演算し、発光部制御機能▲２▼によって、平均値Ｖｓａを標準電圧値Ｖｒと比較し、Ｖｓａ＜Ｖｒのときに発光素子１６の発光エネルギを上げるための制御信号をレジスタ７８を介して発光素子１６側へ出力し、Ｖｓａ＞Ｖｒのときに発光素子１６の発光エネルギを下げるための制御信号をレジスタ７８を介して発光素子１６側へ出力する。このＭＰＵ６６のレジスタ７８から出力した制御信号はＤ／Ａ変換回路７２でアナログの電圧に変換され、電圧・電流変換回路７４で電流に変換されて発光素子１６に供給される。このため、発光素子１６の発光エネルギーＨＥは、図７に示すように走査角度θに対して変化し、受光素子１７の受光エネルギーＪＥａは、図８に示すように光走査範囲内の走査角度θに対して一定となるとともに、対象物２４ａ、２４ｂに対応したＡ、Ｂの下端点より高いレベルとなる。したがって、対象物２４ａ、２４ｂの何れに対しても、比較器２７の出力側に検出信号が現われ、て対象物２４ａ、２４ｂが有ることを判別できる。すなわち、走査角度θや雑音に起因する誤った対象物情報の検出を防止することができる。
さらに、受光エネルギーの平均値（平均値Ｖｓａに相当するエネルギー）が一定となるように発光素子１７の発光エネルギーを制御しているので、対象物２４ａ、２４ｂによって遮られた光エネルギーのＤＣ値（ノイズ成分）が上がらないように制御することができる。
また、図６の場合では、図７に示すように、発光素子１６の発光エネルギーＨＥが従来例のＨＥｃより小さくなるので、エネルギーを節約できる。
【００３８】
（ハ）対象物２４ａ、２４ｂによって受光素子１７の受光エネルギーＪＥが途切れた場合、ＭＰＵ６６が、その下限判別機能▲３▼の判別信号に基づく積分処理機能▲４▼によって、レジスタ７８に置数する現在の制御信号と直前まで置数していた制御信号との積分値を演算し、この積分値を積分処理メモリ７０に記憶するとともにレジスタ７８を介してＤ／Ａ変換回路７２へ出力するので、発光素子１６の発光エネルギーが急激に上昇するのを防止している。
【００３９】
（ニ）受光エネルギーの平均値に相当した平均値Ｖｓａを標準電圧値Ｖｒと比較し、比較出力で発光素子１６の発光エネルギーを制御するフィードバック制御としたので、受光素子１７の感度や発光素子１６の発光効率が経年変化である程度劣化しても、又はスキャンミラー２２や再帰性反射体１２が埃等である程度汚れても、対象物２４ａ、２４ｂが有るか否かの情報を正しく検出することができる。
【００４０】
（ホ）本発明による対象物情報検出装置を複数連携して使用する場合には、各装置の標準電圧値レジスタの標準電圧値Ｖｒを共用することによって、同品質の検出感度（受信感度）を維持することができる。
すなわち、標準電圧値Ｖｒを共用することによって各装置の受光素子の受光エネルギーを一定に保つことが可能となり、各装置の発光素子の発光効率のバラツキや受光素子の感度のバラツキが制御されるので、発光素子の発光効率や受光素子の感度のバラツキに起因する対象物情報の検出誤差を防止できる。
例えば、一方の装置の標準電圧値Ｖｒ₁が他方の装置の標準電圧値Ｖｒ₂より小さいため、発光素子の発光効率や受光素子の感度のバラツキによって、図９に実線で示すように、標準電圧値をＶｒ₁とした一方の装置の受光エネルギーＪＥ₁のレベルの一部にスライスレベルＳＬとの間で逆転現象が生じた場合には、同図に１点鎖線で示すような逆転現象が生じない他方の装置の受光エネルギーＪＥ₂に対応したＶｒ₂を共通の標準電圧値として共用すれば、発光素子の発光効率や受光素子の感度のバラツキに起因する対象物情報の検出誤差を防止できる。この場合、必要に応じてスライスレベルＳＬを逆転現象が生じない範囲で上げることによって、装置の検出感度を同一に保つことができる。
【００４１】
（ヘ）受光素子１７の感度や発光素子１６の発光効率が経年変化によって限度以上劣化し、又はスキャンミラー２２や再帰性反射体１２が埃等である限度以上汚れて、レジスタに７８に置数された制御信号が極限レジスタ８０に置数された極限値Ｖｕ以上になると、ＭＰＵ６６は、その報知部制御機能▲５▼によって報知部７６へ報知信号を出力し、警告ランプや警告ブザーを作動して特性劣化や汚れが限度以上に達していることを報知する。
【００４２】
図６の実施形態例では、積分処理メモリ７０を設け、平均値が下限設定値以下と判別されたときに、ＭＰＵ６６の積分処理機能▲４▼によってレジスタ７８に置数する現在の制御信号と直前まで置数していた制御信号との積分値を演算し、この積分値を積分処理メモリ７０に記憶するとともにレジスタ７８を介してＤ／Ａ変換回路７２へ出力することによって、対象物２４ａ、２４ｂで受光素子１７の受光エネルギーＪＥが途切れても発光素子１６の発光エネルギーが急激に上昇しないようにしたが、本発明はこれに限るものでなく、積分処理メモリ７０を省略するとともに、積分処理機能▲４▼の代わりに置数値保持機能▲６▼をＭＰＵ６６に付加することによって、対象物２４ａ、２４ｂによって受光素子１７の受光エネルギーＪＥが途切れても発光素子１６の発光エネルギーが急激に上昇しないようにしてもよい。この置数値保持機能▲６▼は、平均値が下限設定値以下と判別されたときに、レジスタ７８の置数値を更新せずに直前の置数値を保持する機能を表す。
【００４３】
図６の実施形態例では、報知部７６を設けるとともに、ＭＰＵ６６に報知部制御機能▲５▼を設けることによって、レジスタ７８に置数された制御信号と極限値レジスタ８０に置数された極限値Ｖｕとを比較し、制御信号が極限値Ｖｕ以上のときに報知部７６の警告ランプや警告ブザーを作動し、受光素子１７の感度や発光素子１６の発光効率が経年変化によって限度以上劣化し、又はスキャンミラー２２や再帰性反射体１２が埃等である限度以上汚れてていることを報知するようにしたが、本発明はこれに限るものでなく、例えば図１０に示すように、報知部制御機能▲５▼を省略したＭＰＵ６６ａを設け、報知部７６の代わりに可視光発光手段８２を設けるようにしてもよい。
この可視光発光手段８２は直列接続されたツエナーダイオード８４と発光ダイオード８６からなり、Ｄ／Ａ変換回路７２から電圧・電流変換回路７４へ出力するアナログの制御電圧を分岐して取り出し、この制御電圧をツエナーダイオード８４を介して発光ダイオード８６へ供給し、制御電圧が予め設定された極限値を越えたときに発光ダイオード８６から可視光を発光し、受光素子１７の感度や発光素子１６の発光効率が経年変化によって限度以上劣化し、又はスキャンミラー２２や再帰性反射体１２が埃等で限度以上汚れてていることを報知するようにしてもよい。
【００４４】
図６の実施形態例では、極限値設定手段及び報知手段、又は可視光発光手段を設けることによて、受光素子１７の感度や発光素子１６の発光効率が経年変化によって限度以上劣化し、又はスキャンミラー２２や再帰性反射体１２が埃等である限度以上汚れてていることを報知するようにしたが、本発明はこれに限るものでなく、極限値設定手段及び報知手段、及び可視光発光手段を省略した場合についても利用することができる。
【００４５】
図６の実施形態例では、発光部制御手段が制御信号を一時的に置数するレジスタを具備し、平均値演算手段で求めた平均値が下限設定値以下か否かを判別する下限判別手段を設け、この下限判別手段で平均値が下限設定値以下と判別されたときにレジスタの置数値と直前の置数値との積分値を発光部へ出力する制御信号とする積分処理手段、又は下限判別手段で平均値が下限設定値以下と判別されたときにレジスタの置数値を更新せずに直前の置数値を保持する置数値保持手段を設けた場合について説明したが、本発明はこれに限るものでなく、レジスタ及び下限判別手段を省略するとともに、積分処理手段及び置数値保持手段を省略した場合についても利用することができる。
【００４６】
図６の実施形態例では、発光エネルギー制御手段は、受光素子の受光エネルギーに相当した信号をディジタル信号に変換するＡ／Ｄ変換回路と、このＡ／Ｄ変換回路の出力信号の一定期間における平均値を求める平均値演算手段と、この平均値演算手段で求めた平均値を標準値と比較し、平均値が標準値より小さいときは発光エネルギを上げるための制御信号を発光素子へ出力し、平均値が標準値より大きいときは発光エネルギを下げるための制御信号を発光素子へ出力する発光部制御手段とで構成された場合について説明したが、本発明はこれに限るものでなく、受光素子の受光エネルギーが一定となるように発光素子の発光エネルギーを制御するものであればよい。
【００４７】
【発明の効果】
請求項１の発明は、発光部からの光を回転可能なスキャンミラーで反射させて再帰性反射体に照射し、この再帰性反射体で反射した光をスキャンミラーの反射を介して受光部で受光し、受光エネルギーをしきい値と比較することによって、スキャンミラーと再帰性反射体の間に形成された光走査範囲内の対象物情報を検出する装置において、受光部の受光エネルギーに応じてしきい値を変化させるしきい値可変手段を設け、走査角度θによって受光部の受光エネルギーに差がでてきたり、近傍の障害物からの乱反射等による雑音によって受光部の受光エネルギーが一定レベルもち上がっても、しきい値可変手段によって受光エネルギーと比較するしきい値が受光部の受光エネルギーに応じて変化するようにしたので、走査角度θや雑音に起因する誤った対象物情報の検出を防止し、対象物が光走査範囲内の何処にあっても正しい対象物情報を得ることができる。
【００４９】
加えて、しきい値可変手段を、受光部の受光エネルギーに相当した信号をディジタル信号に変換するＡ／Ｄ変換回路と、このＡ／Ｄ変換回路の出力信号の一定期間の平均値を求める平均値算出回路と、この平均値算出回路で求めた平均値からＡ／Ｄ変換回路の出力信号に応じて異なる定数を減算する定数減算回路と、この定数減算回路の演算値をアナログ信号に変換ししきい値として出力するＤ／Ａ変換回路とで構成したので、しきい値可変手段の構成を簡単にすることができる。
【００５０】
さらに、定数減算回路を、平均値算出回路で求めた平均値から相異なる定数Ｋ１、Ｋ２（Ｋ１＜Ｋ２）を減算する第１、第２減算器と、Ａ／Ｄ変換回路の出力信号と第１、第２減算器の一方の演算値とを比較する比較器と、この比較器の比較出力に応じて第１、第２減算器の演算値の一方を選択して出力するセレクタとで構成したので、信号の強弱でＳ／Ｎ比が極端に変化し、受光エネルギーがなだらかに変化する途中で急激に変化した場合でも、逆転現象に起因する誤った対象物情報の検出をしないようにすることができる。
【００５１】
請求項２の発明は、受光エネルギーに相当した信号を一定期間遅延させしきい値と比較する信号として出力する遅延手段を設け、しきい値可変手段を、受光部の受光エネルギーに相当した信号をディジタル信号に変換するＡ／Ｄ変換回路と、このＡ／Ｄ変換回路の出力信号の一定期間の平均値を求める平均値算出回路と、この平均値算出回路で求めた平均値から一定の定数を減算する減算回路と、この減算回路の演算値をアナログ信号に変換ししきい値として出力するＤ／Ａ変換回路とで構成したので、信号の強弱でＳ／Ｎ比が極端に変化し、受光エネルギーが急激な増加から急激な減少へ変化した場合でも、逆転現象に起因する誤った対象物情報の検出をしないようにすることができる。
【図面の簡単な説明】
【図１】本発明に係る光走査による対象物情報検出装置の一実施形態例を示すブロック図である。
【図２】図１の作用を説明する受光エネルギーの特性図である。
【図３】図１のしきい値可変手段の他の実施形態例を示すブロック図である。
【図４】図３の作用を説明する受光エネルギーの特性図である。
【図５】図３において、定数減算回路４６を単なる減算器で置き換えるとともに、遅延回路６４を挿入した実施形態例の作用を説明する受光エネルギーの特性図である。
【図６】本発明に係る光走査による対象物情報検出装置の他の実施形態例を示すブロック図である。
【図７】図６中の発光素子の発光エネルギーの特性図である。
【図８】図６中の受光素子の受光エネルギーの特性図である。
【図９】図６に係る装置を２個連携して使用する場合の標準電圧値レジスタに置数する標準電圧値を共用する場合を説明する受光エネルギーの特性図である。
【図１０】図６の実施形態例において、一部を省略し、一部を変更し、一部を付加した実施形態例の要部を示すブロック図である。
【図１１】本発明を利用した光走査による対象物情報検出装置の平面図である。
【図１２】図１１中の光走査ユニットの取付け状態を示す側面図である。
【図１３】図１１の装置に用いる電気回路の従来例を示すブロック図である。
【図１４】図１３の作用を説明する受光エネルギー特性図である。
【符号の説明】
１１…光走査ユニット、１２…再帰性反射体、１６…発光素子、１７…受光素子、１８…発光素子１６から出力した光、２４ａ、２４ｂ…対象物、２５…障害物、２６…電流・電圧変換回路、２７…比較器、２９…ＭＰＵ（マイクロプロセッサ）、３０、３０ａ…しきい値可変手段、３２…分圧回路、３４…積分回路、３６、３８…抵抗、４０…コンデンサ、４２…Ａ／Ｄ変換回路、４４…平均値算出回路、４６…定数減算回路、４８、７２…Ｄ／Ａ変換回路、５０1〜５０3…シフトレジスタ、５２…加算器、５４…除算器、５６、５８…減算器、６０…比較器、６２…セレクタ、６４…遅延回路、６６、６６ａ…ＭＰＵ（発光エネルギー制御手段の要部を構成するマイクロプロセッサ）、６８…標準電圧値レジスタ、７０…積分処理メモリ、７４…電圧・電流変換回路、７６…報知部、７８…レジスタ、８０…極限値レジスタ、８２…可視光発光手段、８４…ツエナーダイオード、８６…発光ダイオード、Ａ…受光エネルギーＪＥの特性曲線のうちの対象物２４ａに対応した部分、Ｂ…受光エネルギーＪＥの特性曲線のうちの対象物２４ｂに対応した部分、ＪＥ、ＪＥａ、ＪＥ1、ＪＥ2…受光エネルギー、Ｋ１、Ｋ２…定数、ＳＬ、ＳＬａ…スライスレベル。[0001]
BACKGROUND OF THE INVENTION
The present invention reflects the light from the light emitting unit with a rotatable scan mirror and irradiates the retroreflector. The light reflected by the retroreflector is received by the light receiving unit through the reflection of the scan mirror, The present invention relates to an apparatus for detecting object information (for example, information on whether or not an object exists) within an optical scanning range formed between a scan mirror and a retroreflector by comparing received light energy with a threshold value. Is.
[0002]
[Prior art]
As the object information detection apparatus based on the optical scanning described above, the one shown in FIG. 11 is considered. That is, the optical scanning unit 11 is arranged at the center of one side surface of the substrate 10 such as an optical filter, and the retroreflector 12 is attached to three sides excluding the attachment portion of the optical scanning unit 11 on one surface of the substrate 10. ing.
In the optical scanning unit 11, as shown in FIG. 12, a fixing portion (not shown) of the unit support plate 31 is fixed to the substrate 10 with an adhesive or the like, and the substantially L-shaped supporting portion 13 integral with the fixing portion is provided. The unit main body 14 is placed on the top and attached so as to be adjustable in angle.
[0003]
The unit main body 14 is formed with a substantially L-shaped L-shaped groove 15 which is loosely fitted to the support portion 13 on the lower surface. A light emitting element 16 such as a semiconductor laser device and a light receiving element 17 are housed inside the unit main body 14. Includes a refraction prism 19 that refracts laser light (hereinafter simply referred to as light) 18 output from the light emitting element 16, a prism 21 that includes a half mirror 20 that transmits the refracted light 18, and a scan mirror 22. The scan mirror 22 is rotatably provided by a pulse motor 23.
[0004]
The light 18 output from the light emitting element 16 is refracted by the refraction prism 19, passes through the half mirror 20 and the prism 21, is reflected by the scan mirror 22, and irradiates the retroreflector 12. In the retroreflector 12, the optical path that is substantially the same as the incident light is reflected by the return scan mirror 22, is reflected and refracted by the half mirror 20 of the prism 21, and is received by the light receiving element 17. The light 18 is scanned by an angle θ (for example, about 180 °) by the rotation of the scan mirror 22 by the pulse motor 23. If the objects 24a and 24b are within the optical scanning range, the light 18 is blocked by the objects 24a and 24b. Therefore, the presence or absence of the objects 24a and 24b is monitored by monitoring the scanning angle θ and the light receiving energy of the light receiving element 17. Is detected.
[0005]
In FIG. 11, reference numeral 25 denotes an obstacle that obstructs the above-described optical scanning. The obstacle 25 reflects the light 18 from the light emitting element 16 except the retroreflector 12 and the objects 24a and 24b to receive the light. Objects that cause the light receiving element 17 to receive light or receive unnecessary extraneous light to the light receiving element 17 are collectively referred to as a casing of the apparatus or an object around the apparatus.
[0006]
As an electric circuit for monitoring the light reception energy of the light receiving element 17 in FIG. 12, a circuit as shown in FIG. 13 can be considered. That is, a current corresponding to the light reception energy of the light receiving element 17 is converted into a voltage by the current / voltage conversion circuit 26, and this voltage is input to the + side of the comparator 27, and from the reference voltage source 28 to the − side of the comparator 27. The MPU (microprocessor unit) 29 determines whether the comparison output level of the comparator 27 is H level or L level, and detects the presence or absence of the objects 24a, 24b. In the figure, S represents a signal component (light reflected by the retroreflector 12 and the objects 24a and 24b) in the light received by the light receiving element 17, and N represents a noise component (light reflected by the obstacle 25). Or extraneous light).
[0007]
[Problems to be solved by the invention]
However, in the circuit shown in FIG. 13, the comparator 27 compares the voltage corresponding to the light receiving energy of the light receiving element 17 with the reference voltage of the reference voltage source 28, and detects the presence or absence of the objects 24a and 24b based on the comparison output. Therefore, there was a problem that correct object information could not be obtained. That is, correct object information cannot be obtained due to a difference in the light receiving energy of the light receiving element 17 depending on the scanning angle θ, or a signal-to-noise ratio deteriorated due to noise caused by irregular reflection from an obstacle 25 nearby. There was a problem.
In addition, there is a problem that correct object information cannot be obtained depending on the response speed of the circuit for determining the object information.
[0008]
For example, as shown in FIG. 11, when there are two objects 24a and 24b within the optical scanning range, the relationship between the scanning angle θ and the received light energy is as shown in FIG. 14, and the presence of one object 24b is detected. However, there is a problem that the presence of the other object 24a cannot be detected. That is, when the scanning angle θ is 0 (= 0 °) and π (= 180 °), the light receiving element 17 receives most of the light 18 from the light emitting element 16, so that the light receiving energy is maximized, and the retroreflector 12. Since the reflected energy increases as the incident angle is closer to a right angle, the received light energy increases at the scanning angle θ corresponding to both ends and the center of the retroreflector 12, and the DC (direct current) level of the received energy increases due to noise. .
As shown in FIG. 14, the light receiving energy JE of the light receiving element 17 changes in accordance with the scanning angle θ as shown in FIG. 14, whereas the slice level SL is constant. Therefore, the presence of one object 24b can be detected, but the other There was a problem that the presence of the object 24a could not be detected. In FIG. 14, the slice level SL represents the value of light energy corresponding to the reference voltage input to the negative input side of the comparator 27, and A represents the portion corresponding to the object 24a in the characteristic curve of the received light energy JE. B represents a portion corresponding to the object 24b in the characteristic curve of the received light energy JE.
[0009]
The present invention has been made in view of the above-mentioned problems, prevents detection of erroneous object information due to the scanning angle θ and noise, and correct the object regardless of where the object is in the optical scanning range. An object of the present invention is to provide an object information detection apparatus by optical scanning that can obtain information.
[0010]
[Means for Solving the Problems]
According to the first aspect of the present invention, the light from the light emitting unit is reflected by a rotatable scan mirror and applied to the retroreflector, and the light reflected by the retroreflector is received through the reflection of the scan mirror. In the apparatus for detecting object information within an optical scanning range formed between the scan mirror and the retroreflector by comparing the received light energy with a threshold value, the light receiving unit receives the light. Ri Na provided threshold changing means for changing the threshold depending on the energy, the threshold varying means, a / D conversion circuit for converting a corresponding signal to the receiving energy of the light receiving unit into a digital signal An average value calculation circuit for obtaining an average value of output signals of the A / D conversion circuit over a certain period, and constants that differ from the average value obtained by the average value calculation circuit according to the output signal of the A / D conversion circuit The A constant subtraction circuit for calculating, and a D / A conversion circuit for converting an operation value of the constant subtraction circuit into an analog signal and outputting it as a threshold value. The constant subtraction circuit is an average value obtained by an average value calculation circuit. The first and second subtracters for subtracting different constants K1 and K2 (K1 <K2) from the output signal of the A / D conversion circuit and one operation value of the first and second subtractors are compared. It comprises a comparator and a selector that selects and outputs one of the operation values of the first and second subtracters according to the comparison output of the comparator .
[0011]
Even if there is a difference in the light receiving energy of the light receiving unit depending on the scanning angle θ, or the light receiving energy of the light receiving unit rises to a certain level due to noise due to irregular reflection from nearby obstacles, it is compared with the light receiving energy by the threshold variable means Since the threshold value to be changed changes according to the light reception energy of the light receiving unit, it is possible to prevent detection of erroneous object information due to the scanning angle θ or noise.
[0012]
According to a second aspect of the present invention, the light from the light emitting unit is reflected by a rotatable scan mirror and applied to the retroreflector, and the light reflected by the retroreflector is received through the reflection of the scan mirror. In the apparatus for detecting object information within an optical scanning range formed between the scan mirror and the retroreflector by comparing the received light energy with a threshold value, the light receiving unit receives the light. Threshold variable means for changing the threshold value according to energy is provided, delay means for delaying a signal corresponding to the received light energy for a certain period and outputting it as a signal to be compared with the threshold value is provided, and the threshold value variable The means includes an A / D conversion circuit that converts a signal corresponding to the light reception energy of the light receiving unit into a digital signal, and an average value calculation for obtaining an average value of the output signal of the A / D conversion circuit over a certain period. And a subtracting circuit for subtracting a constant from the average value obtained by the average value calculating circuit, and a D / A conversion circuit for converting the operation value of the subtracting circuit into an analog signal and outputting it as a threshold value. It is characterized by that.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of an object information detection apparatus by optical scanning according to the present invention will be described with reference to FIG.
In FIG. 1, the same parts as those in FIG. In FIG. 1, 12 is a retroreflector, 16 is a light emitting element, 17 is a light receiving element, 18 is light from the light emitting element 16, 24a and 24b are objects as information detection targets, and 25 is an obstacle to optical scanning. 26 is a current / voltage conversion circuit that converts a current corresponding to the light receiving energy of the light receiving element 17 into a voltage and outputs the voltage, 27 is a comparator, 29 is an MPU, and S is the light receiving element 17 receiving light. N represents a noise component.
[0024]
Reference numeral 30 denotes a threshold variable means. The threshold variable means 30 is coupled to a voltage dividing circuit 32 that divides the output voltage of the current / voltage conversion circuit 26 and to the voltage dividing circuit 32 to set an integral value. The voltage dividing circuit 32 is composed of resistors 36 and 38, and the integrating circuit 34 is composed of the resistor 36 and a capacitor 40.
[0025]
Next, the operation of FIG. 1 will be described with reference to FIG.
The current / voltage conversion circuit 26 converts a current corresponding to the light reception energy of the light receiving element 17 into a voltage, and outputs this voltage to the + input side of the comparator 27. For this reason, the received light energy JE corresponding to the voltage input to the + input side of the comparator 27 becomes a characteristic curve as shown in FIG. 2, as in FIG. That is, the received light energy JE is maximum when the scanning angle θ is 0 and π, the received light energy is increased when π / 2, and the DC level of the received light energy is increased due to noise. 2, A represents a portion corresponding to the object 24a in the characteristic curve of the received light energy JE, and B represents a portion corresponding to the object 24b in the characteristic curve of the received light energy JE.
[0026]
In the threshold variable means 30, the voltage dividing circuit 32 divides the output voltage of the current / voltage conversion circuit 26 in accordance with the values of the resistors 36 and 38, and the integrating circuit 34 calculates an integrated value by the resistor 36 and the capacitor 40. The threshold value is input to the negative input side of the comparator 27. For this reason, the slice level SLa, which is light energy corresponding to the input voltage to the negative input side of the comparator 27, is a value obtained by lowering the characteristic curve of the received light energy JE by a certain level, as indicated by a dotted line in FIG. , A and B are higher than the lower end point.
Therefore, a detection signal appears on the output side of the comparator 27 for both the objects 24a and 24b, and the MPU 29 can determine whether the objects 24a and 24b are present. That is, it is possible to prevent detection of erroneous object information due to the scanning angle θ or noise.
[0027]
In the embodiment shown in FIG. 1, the case where the threshold variable means is constituted by a voltage dividing circuit and an integrating circuit has been described. However, the present invention is not limited to this, and the threshold is changed according to the light receiving energy of the light receiving element. As long as it changes the value.
For example, as shown in FIG. 3, the threshold value changing means 30a converts the output voltage Es of the current / voltage conversion circuit 26 into a digital voltage Vs by sampling it at a sampling frequency more than twice that frequency. / D (analog / digital) conversion circuit 42, an average value calculation circuit 44 for obtaining an average value Vsa of the output voltage Vs of the A / D conversion circuit 42 for a certain period (eg, three sampling periods), and calculation of the average value A constant subtraction circuit 46 that subtracts a different constant according to the output voltage Vs of the A / D conversion circuit 42 from the average value Vsa obtained by the circuit 44, and an operation value of the constant subtraction circuit 46 is converted into an analog voltage Er. The present invention can also be used in the case of a D / A (digital / analog) conversion circuit 48 that outputs a threshold value.
[0028]
The average value calculation circuit 44 includes shift registers 50 ₁ , 50 ₂ , 50 ₃ , an adder 52 and a divider 54 coupled in three stages, and the shift registers 50 ₁ , 50 ₂ , 50 ₃ are connected to the A / A. The output voltage Vs of the D conversion circuit 42 is sequentially delayed by one sampling clock, and the adder 52 receives the output voltage Vs of the A / D conversion circuit 42 and each of the shift registers 50 ₁ , 50 ₂ , and 50 ₃ . The voltage to be output is added, and the divider 54 outputs an average value Vsa obtained by dividing the addition value obtained by the adder 52 by 4 (the number of shift register stages + 1).
[0029]
The constant subtraction circuit 46 includes first and second subtractors 56 and 58 for subtracting different constants K1 and K2 (K1 <K2) from the average value Vsa output from the divider 54, and the A / D conversion circuit. 42, the comparator 60 for comparing the output voltage Vs of 42 and the operation value (Vsa-K1) of the first subtractor 56, and the first and second subtractors 56, 58 according to the comparison output of the comparator 60. And a selector 62 that selects and outputs one of the calculated values. The comparator 60 compares the output voltage Vs of the A / D conversion circuit 42 with the operation value (Vsa−K2) of the second subtractor 58, and controls the switching of the selector 62 by the comparison output. Also good.
[0030]
Next, the operation in the case of FIG. 3 will be described with reference to FIG.
(A) When the output voltage Es of the current / voltage conversion circuit 26 changes gently, the calculated value (Vsa−K1) of the first subtractor 56 is smaller than the output voltage Vs of the A / D conversion circuit 42. Since (Vsa−K1 <Vs), the output signal of the comparator 60 becomes L level, and the movable piece of the selector 62 selects the operation value (Vsa−K1) of the first subtractor 56 as shown by the solid line. Therefore, the D / A conversion circuit 48 outputs the voltage Er obtained by converting (Vsa−K1) into an analog signal to the −input side of the comparator 27.
[0031]
(B) The S / N ratio changes drastically due to the strength of the signal S from the light receiving element 17, and the output voltage Es of the current / voltage conversion circuit 26 changes rapidly as shown in FIG. If the selector 62 continues to select the operation value (Vsa−K1) of the first subtractor 56, the voltage Er input to the −input side of the comparator 27 by the averaging process of the average value calculation circuit 44. And a voltage Es input to the + input side cause a partial reversal phenomenon (Er> Es). Just before this reversal phenomenon occurs, the output signal of the comparator 60 changes from L level to H level and the selector Since the second subtractor 58 is selected so that the movable piece 62 is indicated by a dotted line, the voltage Er is partially corrected to be indicated by a two-dot chain line to prevent detection of erroneous object information due to a reverse phenomenon. Yes.
That is, there is no constant subtraction circuit 46, and instead, the first subtractor 56 outputs a value (Vsa-K1) obtained by subtracting the constant K1 from the average value Vsa obtained by the average value calculation circuit 44 to the D / A conversion circuit 48. In the case of only the configuration, the output voltage Er of the D / A conversion circuit 48 becomes a value as indicated by a cross in FIG. 4, and a reverse phenomenon occurs partially. However, in the embodiment shown in FIG. 3, the constant subtraction circuit 46 is provided, and the selector 62 selects the second subtractor 58 and outputs (Vsa−K2) to the D / A conversion circuit 48 immediately before the reverse phenomenon occurs. Therefore, a part of Er output from the D / A conversion circuit 48 is corrected as indicated by a circle and a two-dot chain line in FIG. 4 to prevent erroneous object information from being detected due to a reverse phenomenon.
[0032]
In the embodiment shown in FIG. 3, the constant subtraction circuit 46 includes first and second subtractors 56 and 58, a comparator 60 and a selector 62, and the average value Vsa obtained by the average value calculation circuit 44 is converted to A / Different constants K1 and K2 are subtracted according to the output voltage Vs of the D conversion circuit 42, the calculated value obtained by this subtraction is output to the D / A conversion circuit 48, and the output voltage Es of the current / voltage conversion circuit 26 is further output. However, the present invention is not limited to this, and the constant subtraction circuit 46 is eliminated and only the first subtractor 56 (or the second subtractor 58) is used instead. It is also possible to use a case where a delay circuit 64 is provided between the output side of the current / voltage conversion circuit 26 and the + input side of the comparator 27 as shown by a two-dot chain line in FIG.
In this case, the S / N ratio changes drastically due to the strength of the signal, and even if the output voltage Es of the current / voltage conversion circuit 26 changes from a sudden increase to a sudden decrease as shown by the solid line in FIG. The phenomenon (Er> Es) can be prevented from occurring, and erroneous object information can be prevented from being detected. That is, in the embodiment of FIG. 3, if the constant subtracting circuit 46 is eliminated and only the first subtractor 56 is provided instead, the Er input to the negative input side of the comparator 27 is indicated by a dotted line in FIG. The reversal phenomenon (Er> Es) occurs immediately after the Es reaches a decrease after the peak, but the correction voltage Esd (indicated by a one-dot chain line in FIG. 5) obtained by delaying the output voltage Es by the delay circuit 64 for a certain period. ) Is input to the + input side of the comparator 27, so that the reverse phenomenon is prevented and erroneous object information is prevented from being detected.
[0033]
FIG. 6 shows another embodiment of the present invention. The same parts as those in FIG. In FIG. 6, 16 is a light emitting element, 17 is a light receiving element, 18 is light from the light emitting element 16, 26 is a current / voltage conversion circuit, 27 is a comparator, 28 is a reference voltage source, and 42 is an A / D conversion circuit. , 66 is an MPU for performing various control processes, 68 is a standard voltage value register for storing a standard voltage value Vr, 70 is an integration processing memory, 72 is a D / A conversion circuit, 74 is a voltage / current conversion circuit, and 76 is A notification unit (for example, a warning lamp or a warning buzzer) for reporting a warning.
[0034]
The MPU 66 includes a ROM (Read Only Memory) (not shown) that stores programs for achieving the functions described in (1) to (5) below, and to the light emitting element 16 side. A register 78 for temporarily storing a control signal to be output and a limit value register 80 for storing a set limit value are provided.
(1) An average value calculation function for obtaining an average value Vsa of the output voltage Vs of the A / D conversion circuit 42 over a certain period (for example, three sampling periods).
(2) Control for increasing the light emission energy of the light-emitting element 16 when Vsa <Vr by comparing the average value Vsa obtained by the average value calculation means of (1) with the standard voltage value Vr of the standard voltage value register 68 A light emitting unit control function that outputs a signal to the light emitting element 16 side via the register 78 and outputs a control signal for reducing the light emission energy of the light emitting element 16 to the light emitting element 16 side via the register 78 when Vsa> Vr. .
(3) Lower limit for determining whether or not the average value Vsa obtained by the average value calculation function of (2) is equal to or lower than a preset lower limit set value Vb corresponding to when the light receiving energy of the light receiving element 17 is interrupted. Discriminating function.
(4) When the average value Vsa is determined to be less than or equal to the lower limit set value Vb by the lower limit determination function of (3), the integration value between the current value of the register 78 and the previous value is calculated, and this integration is performed. An integration processing function for storing the value in the integration processing memory 70 and outputting the value to the light emitting element 16 side through the register 78.
(5) The control signal placed in the register 78 is compared with the limit value Vu placed in the limit value register 80, and when the control signal is equal to or greater than the limit value Vu, the light emission energy of the light emitting element 16 becomes the limit. An informing unit control function for outputting a signal for informing that to the informing unit 76.
[0035]
The D / A conversion circuit 72 converts the control value set in the register 78 in the MPU 66 into an analog voltage and outputs the analog voltage. The voltage / current conversion circuit 74 is supplied from the D / A conversion circuit 72. The output voltage is converted into a current and output to the light emitting element 16.
[0036]
Next, the operation of FIG. 6 will be described with reference to FIGS.
(A) The current / voltage conversion circuit 26 converts a current corresponding to the light reception energy of the light receiving element 17 into a voltage Es and outputs the voltage Es to the + input side of the comparator 27. The A / D conversion circuit 42 converts the output voltage Es of the current / voltage conversion circuit 26 into a digital voltage Vs, and outputs this voltage Vs to the MPU 66.
[0037]
(B) The MPU 66 calculates the average value Vsa for the input voltage Vs in a certain period (for example, three sampling periods) by the average value calculation function (1), and the average value Vsa by the light emitting unit control function (2). Is compared with the standard voltage value Vr, and when Vsa <Vr, a control signal for increasing the light emission energy of the light emitting element 16 is output to the light emitting element 16 side through the register 78, and when Vsa> Vr, the light emitting element 16 is output. A control signal for lowering the light emission energy is output to the light emitting element 16 side through the register 78. The control signal output from the register 78 of the MPU 66 is converted into an analog voltage by the D / A conversion circuit 72, converted into a current by the voltage / current conversion circuit 74, and supplied to the light emitting element 16. Therefore, the light emission energy HE of the light emitting element 16 changes with respect to the scanning angle θ as shown in FIG. 7, and the light reception energy JEa of the light receiving element 17 is changed to a scanning angle θ within the optical scanning range as shown in FIG. And a level higher than the lower end points of A and B corresponding to the objects 24a and 24b. Therefore, for any of the objects 24a and 24b, a detection signal appears on the output side of the comparator 27, and it can be determined that the objects 24a and 24b are present. That is, it is possible to prevent detection of erroneous object information due to the scanning angle θ or noise.
Furthermore, since the light emission energy of the light emitting element 17 is controlled so that the average value of received light energy (energy corresponding to the average value Vsa) is constant, the DC value of light energy blocked by the objects 24a and 24b ( The noise component) can be controlled so as not to increase.
In the case of FIG. 6, as shown in FIG. 7, the light emission energy HE of the light emitting element 16 becomes smaller than the HEc of the conventional example, so that energy can be saved.
[0038]
(C) When the light reception energy JE of the light receiving element 17 is interrupted by the objects 24a and 24b, the MPU 66 sets the number in the register 78 by the integration processing function (4) based on the determination signal of the lower limit determination function (3). Since the integral value between the current control signal and the control signal that has been placed just before is calculated, this integral value is stored in the integral processing memory 70 and output to the D / A conversion circuit 72 via the register 78. The light emission energy of the light emitting element 16 is prevented from rising rapidly.
[0039]
(D) Since the average value Vsa corresponding to the average value of the light reception energy is compared with the standard voltage value Vr and the feedback control is performed to control the light emission energy of the light emitting element 16 by the comparison output, the sensitivity of the light receiving element 17 and the light emitting element 16 Even if the light emission efficiency of the light source deteriorates to some extent due to secular change, or even if the scan mirror 22 or the retroreflector 12 is stained to some extent by dust or the like, it is possible to correctly detect information on whether or not the objects 24a and 24b are present. it can.
[0040]
(E) When a plurality of object information detection apparatuses according to the present invention are used in cooperation, the standard voltage value Vr of the standard voltage value register of each apparatus is shared, so that the detection sensitivity (reception sensitivity) of the same quality can be obtained. Can be maintained.
That is, by sharing the standard voltage value Vr, it becomes possible to keep the light receiving energy of the light receiving element of each device constant, and the variation in the light emitting efficiency of the light emitting element and the sensitivity of the light receiving element in each device is controlled. Thus, it is possible to prevent detection errors of object information due to variations in light emission efficiency of light emitting elements and sensitivity of light receiving elements.
For example, since the standard voltage value Vr ₁ of one device is smaller than the standard voltage value Vr ₂ of the other device, the standard voltage value as shown by the solid line in FIG. 9 varies depending on the light emission efficiency of the light emitting element and the sensitivity of the light receiving element. When a reverse phenomenon occurs between the slice level SL and a part of the level of the received light energy JE ₁ of _one apparatus with the value Vr ₁ , the reverse phenomenon as shown by a one-dot chain line in the figure occurs. If Vr ₂ corresponding to the light reception energy JE ₂ of the other device that is not used is shared as a common standard voltage value, it is possible to prevent detection error of object information due to variations in light emission efficiency of the light emitting element and sensitivity of the light receiving element. In this case, the detection sensitivity of the apparatus can be kept the same by raising the slice level SL within a range where the reverse phenomenon does not occur as necessary.
[0041]
(F) The sensitivity of the light-receiving element 17 and the light-emitting efficiency of the light-emitting element 16 are deteriorated more than the limit due to secular change, or the scan mirror 22 and the retroreflector 12 are more than the limit of dust and the like, and the number of registers 78 is set. When the control signal thus set reaches or exceeds the limit value Vu entered in the limit register 80, the MPU 66 outputs a notification signal to the notification unit 76 by its notification unit control function (5), and activates a warning lamp and a warning buzzer. Informs that the characteristic deterioration and dirt have exceeded the limit.
[0042]
In the embodiment of FIG. 6, the integration processing memory 70 is provided, and when the average value is determined to be equal to or lower than the lower limit set value, the current control signal placed in the register 78 by the integration processing function (4) of the MPU 66 By calculating the integral value with the control signal that has been placed up to and including the integral value in the integration processing memory 70 and outputting it to the D / A conversion circuit 72 via the register 78, the objects 24a, 24b are obtained. However, the light emission energy of the light emitting element 16 is not increased suddenly even if the light reception energy JE of the light receiving element 17 is interrupted. However, the present invention is not limited to this, and the integration processing memory 70 is omitted and the integration processing function is omitted. By adding a numeric value holding function (6) to the MPU 66 instead of (4), the light receiving energy JE of the light receiving element 17 is interrupted by the objects 24a and 24b. May be luminous energy of the light emitting element 16 is not rapidly increased even if. This numeric value holding function (6) represents a function of holding the previous numeric value without updating the numeric value of the register 78 when the average value is determined to be equal to or lower than the lower limit set value.
[0043]
In the embodiment shown in FIG. 6, the notification unit 76 is provided, and the MPU 66 is provided with the notification unit control function (5), whereby the control signal placed in the register 78 and the limit value placed in the limit value register 80 are provided. Compared with Vu, when the control signal is equal to or higher than the limit value Vu, the warning lamp or warning buzzer of the notification unit 76 is activated, and the sensitivity of the light receiving element 17 and the light emission efficiency of the light emitting element 16 are deteriorated over the limit due to secular change, Alternatively, it is notified that the scan mirror 22 and the retroreflector 12 are dirty beyond the limit such as dust, but the present invention is not limited to this. For example, as shown in FIG. The MPU 66a omitting the control function (5) may be provided, and the visible light emitting means 82 may be provided instead of the notification unit 76.
The visible light emitting means 82 includes a Zener diode 84 and a light emitting diode 86 connected in series. The analog control voltage output from the D / A conversion circuit 72 to the voltage / current conversion circuit 74 is branched and extracted. Is supplied to the light-emitting diode 86 via the Zener diode 84, and visible light is emitted from the light-emitting diode 86 when the control voltage exceeds a preset limit value, and the sensitivity of the light-receiving element 17 and the light-emitting efficiency of the light-emitting element 16 are emitted. However, it may be notified that the deterioration has exceeded the limit due to secular change, or that the scan mirror 22 and the retroreflector 12 are dirty with dust or the like exceeding the limit.
[0044]
In the embodiment example of FIG. 6, by providing the limit value setting means and the notification means or the visible light emitting means, the sensitivity of the light receiving element 17 and the light emitting efficiency of the light emitting element 16 are deteriorated more than the limit due to secular change, or Although notification is given that the scan mirror 22 and the retroreflector 12 are dirty beyond the limit of dust or the like, the present invention is not limited to this, and the limit value setting means, the notification means, and the visible light It can also be used when the light emitting means is omitted.
[0045]
In the embodiment of FIG. 6, the light emitting unit control means includes a register for temporarily storing the control signal, and the lower limit determination means for determining whether or not the average value obtained by the average value calculation means is less than or equal to the lower limit set value. Integration processing means that uses the integral value of the register value of the register and the immediately preceding value as a control signal to be output to the light emitting unit when the lower limit determination means determines that the average value is less than or equal to the lower limit set value, or the lower limit Although the description has been given of the case where there is provided a numeric value holding means for holding the previous numeric value without updating the numeric value of the register when the average value is determined to be equal to or lower than the lower limit set value by the discrimination means, the present invention is based on this. The present invention is not limited, and the present invention can also be used when the register and the lower limit determination unit are omitted, and the integration processing unit and the numeric value holding unit are omitted.
[0046]
In the embodiment of FIG. 6, the light emission energy control means includes an A / D conversion circuit that converts a signal corresponding to the light reception energy of the light receiving element into a digital signal, and an average of output signals of the A / D conversion circuit over a certain period. An average value calculating means for obtaining a value and an average value obtained by the average value calculating means are compared with a standard value, and when the average value is smaller than the standard value, a control signal for increasing the light emission energy is output to the light emitting element, The case where the average value is larger than the standard value has been described with the light emitting unit control means for outputting a control signal for reducing the light emission energy to the light emitting element, but the present invention is not limited to this, and the light receiving element Any light-emitting element may be used as long as the light-emitting energy of the light-emitting element is controlled to be constant.
[0047]
【The invention's effect】
According to the first aspect of the present invention, the light from the light emitting unit is reflected by a rotatable scan mirror and irradiated to the retroreflector, and the light reflected by the retroreflector is reflected by the scan mirror at the light receiving unit. In an apparatus for detecting object information within an optical scanning range formed between a scan mirror and a retroreflector by receiving light and comparing the received light energy with a threshold value, according to the received light energy of the light receiving unit A threshold variable means is provided to change the threshold value, and the light reception energy of the light receiving unit varies depending on the scanning angle θ, or the light receiving energy of the light receiving unit has a certain level due to noise due to irregular reflection from nearby obstacles. Even if the threshold value rises, the threshold value comparison means changes the threshold value to be compared with the received light energy according to the received light energy of the light receiving unit. Detection of incorrect object information can be prevented, and correct object information can be obtained wherever the object is in the optical scanning range.
[0049]
In addition, the threshold variable means includes an A / D conversion circuit that converts a signal corresponding to the light reception energy of the light receiving unit into a digital signal, and an average for obtaining an average value of the output signal of the A / D conversion circuit over a certain period. A value calculating circuit, a constant subtracting circuit that subtracts different constants from the average value obtained by the average value calculating circuit according to the output signal of the A / D conversion circuit, and an arithmetic value of the constant subtracting circuit is converted into an analog signal. Since it is configured with the D / A conversion circuit that outputs the threshold value, the configuration of the threshold variable means can be simplified.
[0050]
Further, the constant subtracting circuit includes first and second subtractors for subtracting different constants K1 and K2 (K1 <K2) from the average value obtained by the average value calculating circuit, and the output signal of the A / D conversion circuit and the first 1 and a comparator for comparing one of the operation values of the second subtractor, and a selector for selecting and outputting one of the operation values of the first and second subtractors according to the comparison output of the comparator. Therefore, even if the S / N ratio changes drastically due to the strength of the signal and the received light energy changes suddenly in the middle, the erroneous object information caused by the reverse phenomenon is not detected. be able to.
[0051]
The invention of claim 2, the delay means for outputting a signal to be compared with a threshold by a predetermined period of time delay corresponding signal to the light receiving energy provided, signals the threshold changing means, corresponding to the light receiving energy of the light receiving portion A / D conversion circuit for converting the signal into a digital signal, an average value calculation circuit for obtaining an average value of output signals of the A / D conversion circuit over a certain period, and a constant from the average value obtained by the average value calculation circuit And a D / A conversion circuit that converts the operation value of the subtraction circuit into an analog signal and outputs it as a threshold value, so that the S / N ratio changes extremely depending on the strength of the signal, Even when the received light energy changes from a rapid increase to a rapid decrease, it is possible to prevent detection of erroneous object information due to the reverse phenomenon.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an embodiment of an object information detection apparatus by optical scanning according to the present invention.
FIG. 2 is a characteristic diagram of received light energy for explaining the operation of FIG. 1;
FIG. 3 is a block diagram showing another embodiment of the threshold variable means in FIG. 1;
4 is a characteristic diagram of received light energy for explaining the operation of FIG. 3; FIG.
FIG. 5 is a characteristic diagram of received light energy for explaining the operation of the embodiment in which the constant subtracting circuit 46 is replaced with a simple subtracter and the delay circuit 64 is inserted in FIG. 3;
FIG. 6 is a block diagram showing another embodiment of the object information detecting apparatus by optical scanning according to the present invention.
7 is a characteristic diagram of light emission energy of the light emitting element in FIG. 6. FIG.
FIG. 8 is a characteristic diagram of received light energy of the light receiving element in FIG. 6;
FIG. 9 is a characteristic diagram of received light energy for explaining a case where a standard voltage value set in a standard voltage value register is shared when two devices according to FIG. 6 are used in cooperation.
FIG. 10 is a block diagram illustrating a main part of the embodiment in which a part is omitted, a part is changed, and a part is added in the embodiment in FIG. 6;
FIG. 11 is a plan view of an object information detection apparatus by optical scanning using the present invention.
12 is a side view showing a mounting state of the optical scanning unit in FIG. 11. FIG.
13 is a block diagram showing a conventional example of an electric circuit used in the apparatus of FIG.
FIG. 14 is a light reception energy characteristic diagram for explaining the operation of FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 11 ... Optical scanning unit, 12 ... Retroreflector, 16 ... Light emitting element, 17 ... Light receiving element, 18 ... Light output from the light emitting element 16, 24a, 24b ... Object, 25 ... Obstacle, 26 ... Current / voltage Conversion circuit 27 ... Comparator 29 ... MPU (microprocessor) 30, 30a ... Threshold variable means 32 ... Voltage dividing circuit 34 ... Integration circuit 36,38 ... Resistance 40 ... Capacitor 42 ... A / D conversion circuit 44 ... Average value calculation circuit 46 ... Constant subtraction circuit 48, 72 ... D / A conversion circuit 501-503 ... Shift register 52 ... Adder 54 ... Divisor 56, 58 ... Subtraction , 60 ... comparator, 62 ... selector, 64 ... delay circuit, 66, 66a ... MPU (microprocessor constituting the main part of the emission energy control means), 68 ... standard voltage value register, 7 ... Integral processing memory 74 ... Voltage / current conversion circuit 76 ... Notification unit 78 ... Register 80 ... Limit register 82 ... Visible light emitting means 84 ... Zener diode 86 ... Light emitting diode A ... Light receiving energy JE Of the characteristic curve corresponding to the object 24a, B... Part of the characteristic curve of the received light energy JE corresponding to the object 24b, JE, JEa, JE1, JE2... Received light energy, K1, K2. SL, SLa ... slice level.

Claims

The light from the light emitting part is reflected by a rotatable scan mirror and irradiated on the retroreflector, and the light reflected by the retroreflector is received by the light receiving part through the reflection of the scan mirror, and the received light energy is received. In an apparatus for detecting object information within an optical scanning range formed between the scan mirror and the retroreflector by comparing with a threshold value, the threshold is determined according to the light reception energy of the light receiving unit. Ri Na provided threshold changing means for changing the value, the threshold changing means includes an a / D converter circuit for converting a corresponding signal to the receiving energy of the light receiving unit into a digital signal, the a / D converter An average value calculation circuit for obtaining an average value of the output signal of the circuit for a certain period, and a constant subtraction circuit for subtracting different constants from the average value obtained by the average value calculation circuit according to the output signal of the A / D conversion circuit. And a D / A conversion circuit that converts an operation value of the constant subtraction circuit into an analog signal and outputs the analog signal as a threshold value. The constant subtraction circuit has a constant K1 different from the average value obtained by the average value calculation circuit. , K2 (K1 <K2) for subtracting, a comparator for comparing the output signal of the A / D converter circuit with one operation value of the first and second subtractors, An object information detecting apparatus by optical scanning, comprising: a selector that selects and outputs one of the operation values of the first and second subtracters according to the comparison output of the comparator .

The light from the light emitting part is reflected by a rotatable scan mirror and irradiated on the retroreflector, and the light reflected by the retroreflector is received by the light receiving part through the reflection of the scan mirror, and the received light energy is received. In an apparatus for detecting object information within an optical scanning range formed between the scan mirror and the retroreflector by comparing with a threshold value, the threshold is determined according to the light reception energy of the light receiving unit. provided a threshold changing means for changing the value, the delay means for outputting a corresponding signal to the light receiving energy as a signal to be compared with a predetermined period delaying threshold provided, the threshold value varying means, the light receiving portion An A / D conversion circuit that converts a signal corresponding to the received light energy into a digital signal, an average value calculation circuit that calculates an average value of output signals of the A / D conversion circuit over a certain period, and the average value An optical circuit comprising: a subtracting circuit that subtracts a constant from an average value obtained by an output circuit; and a D / A conversion circuit that converts an operation value of the subtracting circuit into an analog signal and outputs the analog signal as a threshold value. Object information detection apparatus by scanning.