JP3627308B2

JP3627308B2 - Optical displacement measuring device

Info

Publication number: JP3627308B2
Application number: JP21933295A
Authority: JP
Inventors: 裕司高田
Original assignee: Matsushita Electric Works Ltd
Current assignee: Panasonic Electric Works Co Ltd
Priority date: 1995-08-28
Filing date: 1995-08-28
Publication date: 2005-03-09
Anticipated expiration: 2015-08-28
Also published as: JPH0961114A

Description

【０００１】
【発明の属する技術分野】
本発明は、物体までの距離や物体の変位を三角測量法を用いて非接触で測定する光学式変位測定装置に関するものである。
【０００２】
【従来の技術】
図９は、この種の光学式変位測定装置の従来例を示す回路ブロック図である。この光学式変位測定装置は、投光素子たるレーザダイオード１と、レーザダイオード１からの光を細く絞って投光スポットを形成する投光レンズ２とによって投光手段を構成し、この投光スポットを物体Ａの表面に照射し、物体Ａ表面での反射光を受光レンズ３に通して収束させ、投光スポットの像として形成された受光スポットの位置に応じて受光素子であるＰＳＤ（ＰｏｓｔｉｏｎＳｅｎｓｉｔｉｖｅＤｅｖｉｃｅ）４から出力される位置信号を用いて演算手段において三角測量法に基づく演算を行うことにより、物体Ａまでの距離や変位を測定するように構成されている。受光素子であるＰＳＤ４は、受光面に対する受光スポットの位置に応じて比率の決まる一対の位置信号（電流信号）を出力する。なお、各位置信号の信号値はＰＳＤ４における受光量に応じて増減する。いま、一対の位置信号の信号値がＩ_１，Ｉ_２であるときに、両信号を用いて変位に相当する値を求めるとすると、（Ｉ_１−Ｉ_２）／（Ｉ_１＋Ｉ_２）ないしこの形に類似した演算が必要になることが知られている。
【０００３】
図９に示した従来構成をさらに詳しく説明すると、レーザダイオード１は駆動回路５により発振器６の発振出力に同期して駆動されており、レーザダイオード１から照射される光ビームは発振器６の発振周期に同期して断続されている。ＰＳＤ４から出力される電流信号の位置信号は、それぞれ各別に電流電圧変換回路（Ｉ／Ｖ回路）７_１，７_２において電圧信号に変換され、さらに増幅器８_１，８_２において増幅され、各々同期検波回路９_１，９_２に入力される。同期検波回路９_１，９_２では、発振器６の発振出力から検波のタイミングを決定するタイミング回路１０の出力に応じて、増幅器８_１，８_２の出力が同期検波されて各位置信号の信号成分のみが検波される。この検波された各位置信号が積分回路から成るローパスフィルタ（以下、ＬＰＦと略す）１１_１，１１_２にて平滑され、ノイズ分が除去されて演算部１２の加算器１３及び減算器１４にそれぞれ入力される。さらに、これら加算器１３と減算器１４の出力が除算器１５に入力され、最終的に除算器１５の出力が演算部１２の出力となる。すなわち、上記演算部１２においては、ＬＰＦ１１_１，１１_２から出力される各位置信号（電圧信号）をＶ_１，Ｖ_２としたとき、（Ｖ_１−Ｖ_２）／（Ｖ_１＋Ｖ_２）という上述した変位を求めるための演算を行っているに他ならない。よって、この演算部１２の出力に基づいて物体Ａの変位を求めることができるのである。
【０００４】
図１０は他の従来構成を示しており、図９に示した従来構成とは演算部１２における除算器１５をなくし、代わりにＰＳＤ４での受光光量に対応してレーザダイオード１の発光出力をフィードバック制御するようになっている。つまり、加算器１３の出力が比較器１６において基準値Ｖ_ｒｅｆと比較され、両者の差に応じた出力が変調回路１７に出力されており、一方、変調回路１７は、比較器１６の出力に応じてタイミング回路１０の出力をパルス変調（パルス振幅変調）し、その変調出力を駆動回路５に与えることでレーザダイオード１の発光出力を可変するようになっている。ゆえに、変調回路１７によって比較器１６の出力（加算器１３の出力と基準値Ｖ_ｒｅｆとの差）を小さくするようにレーザダイオード１の発光光量が調整され、ＰＳＤ４の受光光量が略一定に保たれることになる。その結果、加算器１３からの加算出力（Ｖ_１＋Ｖ_２）は、回路のダイナミックレンジや応答特性を無視した理想系では一定であって、減算器１４からの減算出力（Ｖ_１−Ｖ_２）は、（Ｖ_１−Ｖ_２）／（Ｖ_１＋Ｖ_２）に比例することになり、除算器１５が必要で無くなるのである。
【０００５】
図１１は更に別の従来構成を示しており、図１０に示した従来構成とはフィードバック制御の方法が異なっている。つまり、図１１に示した従来構成では、電圧信号に変換された一対の位置信号を増幅する増幅器を可変増幅器１８_１，１８_２とし、加算器１３の加算出力（Ｖ_１＋Ｖ_２）と基準値Ｖ_ｒｅｆとを比較した比較器１６の出力により可変増幅器１８_１，１８_２の増幅度を可変し、加算器１３の加算出力（Ｖ_１＋Ｖ_２）が略一定に保たれるようにフィードバック制御しており、図１０に示した従来構成と同様に除算器１５が必要で無くなるのである。
【０００６】
【発明が解決しようとする課題】
ところが、上記各従来構成においては、何れもＰＳＤ４の一対の位置信号に対して各別にＩ／Ｖ回路７_１，７_２、増幅器８_１，８_２（あるいは可変増幅器１８_１，１８_２）、同期検波回路９_１，９_２及びＬＰＦ１１_１，１１_２が設けられており、全く同一の機能を有する回路を２系統用いなければならなかった。このように同一構成及び機能を有する回路群を２系統設けることにより、以下のような不具合が生じていた。
【０００７】
まず、実際の回路では構成部品のばらつきなどによって同一の２つの回路の間に増幅率の差（ゲイン誤差）を生じる場合がある。また、各回路が構成部品のばらつきなどによって固有の温度特性や周波数特性を有し、周囲温度の変化や経時変化に対して各別の増幅率を持つようになる場合がある。その結果、上記ゲイン誤差により測定精度が低下してしまうという不具合があった。
【０００８】
さらに、図１２（ａ）に示すような物体Ａの移動に対して、同一の２つの回路間に周波数特性の差が無いときには物体Ａの移動に対する応答特性に差は生じないが（図１２（ｂ）参照）、上述のように２つの回路が異なる周波数特性を有するようになった場合にはそれぞれが異なる応答特性を示すことになり、物体Ａの変位に対して過渡的誤差を生じてしまう（図１２（ｃ）参照）。また、同一の回路間で混入するノイズによるオフセットずれに差が生じ、測定精度を低下させるとともにオフセットずれの補正を行う場合には２つの系統毎に補正手段を設ける必要があり、それだけコストアップを招いてしまうという不具合があった。しかも、根本的に同一回路群を２系統設けることは、装置全体の小型化を妨げるだけでなく、コストダウンを困難にしてしまうという不具合があった。
【０００９】
本発明は上記事情に鑑みて為されたものであり、その目的とするところは、一対の位置信号を簡単な構成により高精度で処理可能とする光学式変位測定装置を提供することにある。
【００１０】
【課題を解決するための手段】
請求項１の発明は、上記目的を達成するために、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算するとともに求めた差と和の商を演算する演算手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の一周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたものであり、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになるから、少なくとも同期検波手段を一対の位置信号に対して共通に用いることができ、しかも、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるため、切換時に発生するノイズの影響を低減することができる。
【００１１】
請求項２の発明は、上記目的を達成するために、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算するとともに求めた差と和の商を演算する演算手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の複数周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたものであり、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになるから、少なくとも同期検波手段を一対の位置信号に対して共通に用いることができる。しかも、切換手段による切り換えを照射周期の複数周期毎に行うとともに、一対の位置信号を、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるため、切換時に発生するノイズの影響を低減することができる。
【００１２】
請求項３の発明は、上記目的を達成するために、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように投光手段の発光光量をフィードバック制御する光量制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の一周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたものであり、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになるから、少なくとも同期検波手段を一対の位置信号に対して共通に用いることができ、しかも、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるため、切換時に発生するノイズの影響を低減することができる。
【００１３】
請求項４の発明は、上記目的を達成するために、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように投光手段の発光光量をフィードバック制御する光量制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の複数周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたものであり、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになるから、少なくとも同期検波手段を一対の位置信号に対して共通に用いることができる。しかも、切換手段による切り換えを照射周期の複数周期毎に行うとともに、一対の位置信号を、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるため、切換時に発生するノイズの影響を低減することができる。
【００１４】
請求項５の発明は、上記目的を達成するために、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように各位置信号を増幅する可変増幅器の増幅度をフィードバック制御する増幅度制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の一周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたものであり、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになるから、少なくとも同期検波手段を一対の位置信号に対して共通に用いることができ、しかも、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるため、切換時に発生するノイズの影響を低減することができる。
【００１５】
請求項６の発明は、上記目的を達成するために、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように各位置信号を増幅する可変増幅器の増幅度をフィードバック制御する増幅度制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の複数周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたものであり、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになるから、少なくとも同期検波手段を一対の位置信号に対して共通に用いることができる。しかも、切換手段による切り換えを照射周期の複数周期毎に行うとともに、一対の位置信号を、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるため、切換時に発生するノイズの影響を低減することができる。
【００１７】
【発明の実施の形態】
（実施形態１）
図１は請求項１に係る発明の実施形態を示す回路ブロック図であり、図９に示した従来構成に比較してＰＳＤ４の一対の位置信号を格別に切り換える切換手段たるスイッチ回路１９_１，１９_２をＩ／Ｖ回路７の前段と同期検波回路９の後段とに設けることにより、Ｉ／Ｖ回路７、増幅器８及び同期検波回路９の回路群を１系統とした点が異なる。
【００１８】
Ｉ／Ｖ回路７の前段に設けられたスイッチ回路１９_１は、タイミング回路１０から出力され、駆動回路５を通じてレーザダイオード１を発光させる発振器６の原発振信号（変調信号）の１周期毎に反転する制御信号ｔ_１（図２（ｇ）参照）により切り換えられるものであり、Ｉ／Ｖ回路７に入力される位置信号を選択するようになっている。つまり、図２（ａ）（ｂ）に示すような位置信号の原信号（電流信号）Ｉ_１，Ｉ_２がスイッチ回路１９_１において選択されることにより、Ｉ／Ｖ回路７には図２（ｃ）に示すように一対の位置信号Ｉ_１，Ｉ_２が時系列的に混合されて入力される。ここで、各位置信号Ｉ_１，Ｉ_２が持つ直流成分ＤＣ_１，ＤＣ_２はスイッチ回路１９_１において混合されることで両者の電流値の差分ＤＣ_１−ＤＣ_２に変換される（図２（ｃ）参照）。Ｉ／Ｖ回路７では上記混合された位置信号を電圧信号に変換し、増幅器８へ出力する。増幅器８は入力された位置信号（電圧信号）を適当なレベルにまで増幅する（図２（ｄ）参照）。このとき、上記直流成分ＤＣ_１，ＤＣ_２がオフセット電圧Ｖ_ｄｃ１，Ｖ_ｄｃ２として増幅器８の出力信号Ｖａに含まれている。
【００１９】
増幅器８にて増幅された位置信号Ｖａは同期検波回路９に入力される。同期検波回路９は、タイミング回路１０から出力される検波タイミング信号ｔ_２（図２（ｅ）参照）によって位置信号Ｖａを同期検波し、信号Ｖｂを出力する（図２（ｆ）参照）。ここで、上記検波タイミング信号ｔ_２は変調信号（発振器６の原発振信号）の周期と一致させてある。
【００２０】
同期検波回路９にて検波された信号（位置信号）Ｖｂは、スイッチ回路１９_２によって出力される先のＬＰＦ１１_１，１１_２が選択され切り換えられるようになっている。すなわち、スイッチ回路１９_２はスイッチ回路１９_１と同様にタイミング回路１０からの制御信号ｔ_１により切り換えられるから、結局、スイッチ回路１９_１において混合された位置信号Ｉ_１，Ｉ_２が一対の脈流信号（位置信号）Ｖｄ_１，Ｖｄ_２に分離されることになる（図２（ｈ）（ｉ）参照）。ここで各位置信号Ｖｄ_１，Ｖｄ_２においては、増幅器８の出力Ｖａに含まれているオフセット電圧Ｖ_ｄｃ１，−Ｖ_ｄｃ２の逆極性電圧−Ｖ_ｄｃ１，Ｖ_ｄｃ２が同期検波回路９での同期検波時に生じている（図２（ｈ）（ｉ）参照）。しかしながら、後段のＬＰＦ１１_１，１１_２によって各脈流信号Ｖｄ_１，Ｖｄ_２から直流成分を取り出すことにより、これらオフセット分Ｖ_ｄｃ１，Ｖ_ｄｃ２をキャンセルすることができる。後は、図９に示す従来構成と同様に、ＬＰＦ１１_１，１１_２から出力される一対の位置信号に対して演算部１２にて加算、減算及び除算処理が行われ、物体Ａまでの距離や変位を示すアナログ信号が出力される。
【００２１】
上記構成によれば、図９に示した従来構成の不具合を回避することができる。すなわち、レーザダイオード１の変調信号（発振器６の原発振信号）の一周期毎に切り換わるスイッチ回路１９_１により、一対の位置信号Ｉ_１，Ｉ_２のうちで次段に出力される信号を切り換え、これによって両位置信号Ｉ_１，Ｉ_２を時系列的に混合するとともに、後段のスイッチ回路１９_２において上記変調信号の一周期毎に次段に出力される信号を選択し切り換えることで混合された信号を分離するようにしたため、Ｉ／Ｖ回路７、増幅器８及び同期検波回路９の回路群を１系統のみにすることができ、同一の回路群を２系統備える図９に示した従来構成に比較して、同一回路間の部品ばらつきや温度特性の違いによる増幅率の変動による測定誤差の発生を抑えることができるのである。また、一対の位置信号を一つの同期検波回路９にて同期検波することにより、それぞれの位置信号を各別に同期検波回路９_１，９_２を用いて同期検波する場合に比較して、オフセットによる誤差の発生を回避することができる。なお、このオフセット誤差は、上述のように同期検波回路９の前段（増幅器８より前段）で発生したものであれば、その原因が直流誤差による誤差であっても、また、混入ノイズによる誤差であってもほぼ完全にキャンセルすることができる。ここで、同期検波回路９の出力時に発生する僅かなオフセット誤差については、回路群が１系統であるために簡単な補正回路を設けることで取り除くことができる。さらに、周波数特性にも差が生じることがなく、レーザダイオード１の変調周波数の変化による測定誤差の発生や、位置信号の変化に対する過渡的な誤差の発生を防止することができる。
【００２２】
ところで、本実施形態ではスイッチ回路１９_１，１９_２の切換タイミング（制御信号ｔ_１の周期）は、図２（ｇ）に示すようにレーザダイオード１を発光させる変調信号（発振器６の原発振信号）の一周期毎としているが、例えば、図３（ｇ）に示すように、三周期毎としてもよい。このように、スイッチ回路１９_１、１９_２を上記変調信号の複数周期毎に切り換えるようにすれば、一周期毎に切り換える場合に比較して、スイッチ回路１９_１，１９_２の切換時に発生するノイズの位置信号への影響を抑制し、このようなノイズによる誤差の発生を防止することができる。
【００２３】
また、図４に示すように、位置信号を混合するためのスイッチ回路１９_１は、Ｉ／Ｖ回路７_１，７_２の次段に設けてもよい。このように、ＰＳＤ４から出力される電流信号から成る一対の位置信号を、一旦適当なレベルの電圧信号に変換してからスイッチ回路１９_１にて混合するようにすれば、スイッチ回路１９_１の切換時に発生するノイズの上記位置信号に対する影響を抑制し、このようなノイズによる誤差の発生を防止することができる。
【００２４】
（実施形態２）
図５は請求項４に係る発明の実施形態を示す回路ブロック図であり、図１０に示した従来構成に比較してＰＳＤ４の一対の位置信号を格別に切り換える切換手段たるスイッチ回路１９_１，１９_２をＩ／Ｖ回路７の前段と同期検波回路９の後段とに設けることにより、Ｉ／Ｖ回路７、増幅器８及び同期検波回路９の回路群を１系統とした点が異なる。なお、他の構成及び基本的な動作については図１０に示した従来構成と共通であり、また、スイッチ回路１９_１，１９_２の動作については実施形態１と同様であるから詳しい説明は省略する。
【００２５】
本実施形態においては、実施形態１と同様にＩ／Ｖ回路７の前段に設けられたスイッチ回路１９_１によってＰＳＤ４から出力された一対の位置信号Ｉ_１，Ｉ_２をレーザダイオード１の変調信号の一周期毎に時系列的に混合し、１系統の回路群（Ｉ／Ｖ回路７、増幅器８、同期検波回路９）にて信号処理した後、再度上記変調信号の一周期毎に切り換えられるスイッチ回路１９_２によって混合された位置信号を時系列的に分離し、ＬＰＦ１１_１，１１_２及び演算部１２において処理演算されることで物体Ａの距離あるいは変位情報を含むアナログ信号が出力されるのである。ここで、演算部１２の加算器１３の加算出力（Ｖ_１＋Ｖ_２）を略一定とするフィードバック系の動作については、図１０に示した従来構成と共通であるから説明は省略する。
【００２６】
上記構成によれば、図１０に示した従来構成の不具合を回避することができる。すなわち、レーザダイオード１の変調信号（発振器６の原発振信号）の一周期毎に切り換わるスイッチ回路１９_１により、一対の位置信号Ｉ_１，Ｉ_２のうちで次段に出力される信号を切り換え、これによって両位置信号Ｉ_１，Ｉ_２を時系列的に混合するとともに、後段のスイッチ回路１９_２において上記変調信号の一周期毎に次段に出力される信号を選択し切り換えることで混合された信号を分離するようにしたため、Ｉ／Ｖ回路７、増幅器８及び同期検波回路９の回路群を１系統のみにすることができ、同一の回路群を２系統備える図１０に示した従来構成に比較して、同一回路間の部品ばらつきや温度特性の違いによる増幅率の変動による測定誤差の発生を抑えることができるのである。また、一対の位置信号を一つの同期検波回路９にて同期検波することにより、それぞれの位置信号を各別に同期検波回路９_１，９_２を用いて同期検波する場合に比較して、オフセットによる誤差の発生を回避することができる。なお、このオフセット誤差は、同期検波回路９の前段（増幅器８より前段）で発生したものであれば、その原因が直流誤差による誤差であっても、また、混入ノイズによる誤差であってもほぼ完全にキャンセルすることができる。ここで、同期検波回路９の出力時に発生する僅かなオフセット誤差については、回路群が１系統であるために簡単な補正回路を設けることで取り除くことができる。さらに、周波数特性にも差が生じることがなく、レーザダイオード１の変調周波数の変化による測定誤差の発生や、位置信号の変化に対する過渡的な誤差の発生を防止することができる。
【００２７】
ところで、本実施形態ではスイッチ回路１９_１，１９_２の切換タイミング（制御信号ｔ_１の周期）は、図２（ｇ）に示すようにレーザダイオード１を発光させる変調信号（発振器６の原発振信号）の一周期毎としているが、例えば、図３（ｇ）に示すように、三周期毎としてもよい。このように、スイッチ回路１９_１，１９_２を上記変調信号の複数周期毎に切り換えるようにすれば、一周期毎に切り換える場合に比較して、スイッチ回路１９_１，１９_２の切換時に発生するノイズの位置信号への影響を抑制し、このようなノイズによる誤差の発生を防止することができる。
【００２８】
また、図６に示すように、位置信号を混合するためのスイッチ回路１９_１は、Ｉ／Ｖ回路７_１，７_２の次段に設けてもよい。このように、ＰＳＤ４から出力される電流信号から成る一対の位置信号を、一旦適当なレベルの電圧信号に変換してからスイッチ回路１９_１にて混合するようにすれば、スイッチ回路１９_１の切換時に発生するノイズの上記位置信号に対する影響を抑制し、このようなノイズによる誤差の発生を防止することができる。
【００２９】
（実施形態３）
図７は請求項７に係る発明の実施形態を示す回路ブロック図であり、図１１に示した従来構成に比較してＰＳＤ４の一対の位置信号を格別に切り換える切換手段たるスイッチ回路１９_１，１９_２をＩ／Ｖ回路７の前段と同期検波回路９の後段とに設けることにより、Ｉ／Ｖ回路７、可変増幅器１８及び同期検波回路９の回路群を１系統とした点が異なる。なお、他の構成及び基本的な動作については図１１に示した従来構成と共通であり、また、スイッチ回路１９_１，１９_２の動作については実施形態１と同様であるから詳しい説明は省略する。
【００３０】
本実施形態においては、実施形態１と同様にＩ／Ｖ回路７の前段に設けられたスイッチ回路１９_１によってＰＳＤ４から出力された一対の位置信号Ｉ_１，Ｉ_２をレーザダイオード１の変調信号の一周期毎に時系列的に混合し、１系統の回路群（Ｉ／Ｖ回路７、可変増幅器１８、同期検波回路９）にて信号処理した後、再度上記変調信号の一周期毎に切り換えられるスイッチ回路１９_２によって混合された位置信号を時系列的に分離し、ＬＰＦ１１_１，１１_２及び演算部１２において処理演算されることで物体Ａの距離あるいは変位情報を含むアナログ信号が出力されるのである。ここで、演算部１２の加算器１３の加算出力（Ｖ_１＋Ｖ_２）を略一定とするフィードバック系の制御動作（加算出力（Ｖ_１＋Ｖ_２）を略一定とするように可変増幅器１８の増幅度を調整する制御）については、図１１に示した従来構成と共通であるから説明は省略する。
【００３１】
上記構成によれば、図１１に示した従来構成の不具合を回避することができる。すなわち、レーザダイオード１の変調信号（発振器６の原発振信号）の一周期毎に切り換わるスイッチ回路１９_１により、一対の位置信号Ｉ_１，Ｉ_２のうちで次段に出力される信号を切り換え、これによって両位置信号Ｉ_１，Ｉ_２を時系列的に混合するとともに、後段のスイッチ回路１９_２において上記変調信号の一周期毎に次段に出力される信号を選択し切り換えることで混合された信号を分離するようにしたため、Ｉ／Ｖ回路７、可変増幅器１８及び同期検波回路９の回路群を１系統のみにすることができ、同一の回路群を２系統備える図１１に示した従来構成に比較して、同一回路間の部品ばらつきや温度特性の違いによる増幅率の変動による測定誤差の発生を抑えることができるのである。また、一対の位置信号を一つの同期検波回路９にて同期検波することにより、それぞれの位置信号を各別に同期検波回路９_１，９_２を用いて同期検波する場合に比較して、オフセットによる誤差の発生を回避することができる。なお、このオフセット誤差は、同期検波回路９の前段（可変増幅器１８より前段）で発生したものであれば、その原因が直流誤差による誤差であっても、また、混入ノイズによる誤差であってもほぼ完全にキャンセルすることができる。ここで、同期検波回路９の出力時に発生する僅かなオフセット誤差については、回路群が１系統であるために簡単な補正回路を設けることで取り除くことができる。さらに、周波数特性にも差が生じることがなく、レーザダイオード１の変調周波数の変化による測定誤差の発生や、位置信号の変化に対する過渡的な誤差の発生を防止することができる。
【００３２】
ところで、本実施形態ではスイッチ回路１９_１，１９_２の切換タイミング（制御信号ｔ_１の周期）は、図２（ｇ）に示すようにレーザダイオード１を発光させる変調信号（発振器６の原発振信号）の一周期毎としているが、例えば、図３（ｇ）に示すように、三周期毎としてもよい。このように、スイッチ回路１９_１，１９_２を上記変調信号の複数周期毎に切り換えるようにすれば、一周期毎に切り換える場合に比較して、スイッチ回路１９_１，１９_２の切換時に発生するノイズの位置信号への影響を抑制し、このようなノイズによる誤差の発生を防止することができる。
【００３３】
また、図８に示すように、位置信号を混合するためのスイッチ回路１９_１は、Ｉ／Ｖ回路７_１，７_２の次段に設けてもよい。このように、ＰＳＤ４から出力される電流信号から成る一対の位置信号を、一旦適当なレベルの電圧信号に変換してからスイッチ回路１９_１にて混合するようにすれば、スイッチ回路１９_１の切換時に発生するノイズの上記位置信号に対する影響を抑制し、このようなノイズによる誤差の発生を防止することができる。
【００３４】
【発明の効果】
請求項１の発明は、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算するとともに求めた差と和の商を演算する演算手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の一周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたので、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになり、少なくとも同期検波手段を一対の位置信号に対して共通に用いることで複数の同期検波手段を用いた場合の不具合を解消し、且つ構成の簡素化による小型化やコストダウンが図れ、一対の位置信号を簡単な構成により高精度で処理することができ、しかも、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるので、切換時に発生するノイズの影響を低減することができるという効果がある。
【００３５】
請求項２の発明は、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算するとともに求めた差と和の商を演算する演算手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の複数周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたので、一対の位置信号は投光スポットの照射周期の複数周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになり、少なくとも同期検波手段を一対の位置信号に対して共通に用いることで複数の同期検波手段を用いた場合の不具合を解消し、且つ構成の簡素化による小型化やコストダウンが図れ、一対の位置信号を簡単な構成により高精度で処理することができ、しかも、切換手段による切り換えを照射周期の複数周期毎に行うとともに、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるので、切換時に発生するノイズの影響を低減することができるという効果がある。
【００３６】
請求項３の発明は、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように投光手段の発光光量をフィードバック制御する光量制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の一周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたので、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになり、少なくとも同期検波手段を一対の位置信号に対して共通に用いることで複数の同期検波手段を用いた場合の不具合を解消し、且つ構成の簡素化による小型化やコストダウンが図れ、一対の位置信号を簡単な構成により高精度で処理することができ、しかも、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるので、切換時に発生するノイズの影響を低減することができるという効果がある。
【００３７】
請求項４の発明は、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように投光手段の発光光量をフィードバック制御する光量制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の複数周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたので、一対の位置信号は投光スポットの照射周期の複数周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになり、少なくとも同期検波手段を一対の位置信号に対して共通に用いることで複数の同期検波手段を用いた場合の不具合を解消し、且つ構成の簡素化による小型化やコストダウンが図れ、一対の位置信号を簡単な構成により高精度で処理することができ、しかも、切換手段による切り換えを照射周期の複数周期毎に行うとともに、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるので、切換時に発生するノイズの影響を低減することができるという効果がある。
【００３８】
請求項５の発明は、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように各位置信号を増幅する可変増幅器の増幅度をフィードバック制御する増幅度制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の一周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたので、一対の位置信号は投光スポットの照射周期の一周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになり、少なくとも同期検波手段を一対の位置信号に対して共通に用いることで複数の同期検波手段を用いた場合の不具合を解消し、且つ構成の簡素化による小型化やコストダウンが図れ、一対の位置信号を簡単な構成により高精度で処理することができ、しかも、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるので、切換時に発生するノイズの影響を低減することができるという効果がある。
【００３９】
請求項６の発明は、点状の投光スポットを物体の表面に周期的に照射する投光手段と、投光手段から照射された光の物体表面での反射光を受光光学系に通して収束させ投光スポットの像として形成された受光スポットの位置に対応して出力レベルの比率が決まる一対の位置信号を電流信号として出力する受光手段と、各位置信号を電圧信号に変換する電流電圧変換手段と、電圧信号に変換された各位置信号を投光手段による投光スポットの照射に同期して検波する同期検波手段と、同期検波手段にて検波された各位置信号の出力レベルの差及び和を演算する演算手段と、位置信号の出力レベルの和が略一定に保たれるように各位置信号を増幅する可変増幅器の増幅度をフィードバック制御する増幅度制御手段と、一対の位置信号のうちで少なくとも同期検波手段にて同期検波されて演算手段に出力される位置信号を上記照射周期の複数周期毎に各別に切り換える切換手段とを備え、該切換手段を電流電圧変換手段の後段に設けたので、一対の位置信号は投光スポットの照射周期の複数周期毎に交互に少なくとも同期検波手段へ入力され且つ演算手段へ出力されることになり、少なくとも同期検波手段を一対の位置信号に対して共通に用いることで複数の同期検波手段を用いた場合の不具合を解消し、且つ構成の簡素化による小型化やコストダウンが図れ、一対の位置信号を簡単な構成により高精度で処理することができ、しかも、切換手段による切り換えを照射周期の複数周期毎に行うとともに、一対の位置信号は、電流信号から成る位置信号の原信号を一旦電圧信号に変換した後で切換手段により切り換えるので、切換時に発生するノイズの影響を低減することができるという効果がある。
【図面の簡単な説明】
【図１】実施形態１を示す回路ブロック図である。
【図２】同上の動作を説明するためのタイミングチャートである。
【図３】同上の別の動作を説明するためのタイミングチャートである。
【図４】同上の別の構成を示す回路ブロック図である。
【図５】実施形態２を示す回路ブロック図である。
【図６】同上の別の構成を示す回路ブロック図である。
【図７】実施形態３を示す回路ブロック図である。
【図８】同上の別の構成を示す回路ブロック図である。
【図９】従来例を示す回路ブロック図である。
【図１０】他の従来例を示す回路ブロック図である。
【図１１】さらに別の従来例を示す回路ブロック図である。
【図１２】同上の動作を説明するための説明図である。
【符号の説明】
１レーザダイオード
４ＰＳＤ
６発振器
７電流電圧変換回路
８増幅器
９同期検波回路
１０タイミング回路
１１_１，１１_２ＬＰＦ
１２演算部
１９_１，１９_２スイッチ回路
Ａ物体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an optical displacement measuring apparatus that measures the distance to an object and the displacement of the object in a non-contact manner using a triangulation method.
[0002]
[Prior art]
FIG. 9 is a circuit block diagram showing a conventional example of this type of optical displacement measuring apparatus. This optical displacement measuring device comprises a light projecting means comprising a laser diode 1 as a light projecting element and a light projecting lens 2 that narrows the light from the laser diode 1 to form a light projecting spot. Is applied to the surface of the object A, and the reflected light on the surface of the object A is converged through the light receiving lens 3, and a PSD (Position Sensitive) which is a light receiving element according to the position of the light receiving spot formed as an image of the light projection spot. Device 4) is configured to measure the distance and displacement to object A by performing calculation based on the triangulation method in the calculation means using the position signal output from Device 4. The PSD 4 as a light receiving element outputs a pair of position signals (current signals) whose ratio is determined according to the position of the light receiving spot with respect to the light receiving surface. Note that the signal value of each position signal increases or decreases according to the amount of light received by the PSD 4. Now, the signal value of the pair of position signals is I ₁ , I ₂ When the value corresponding to the displacement is obtained using both signals, (I ₁ -I ₂ ) / (I ₁ + I ₂ It is known that an operation similar to this form is required.
[0003]
The conventional configuration shown in FIG. 9 will be described in more detail. The laser diode 1 is driven in synchronization with the oscillation output of the oscillator 6 by the drive circuit 5, and the light beam emitted from the laser diode 1 is the oscillation period of the oscillator 6. Is intermittently synchronized. The position signal of the current signal output from the PSD 4 is a current-voltage conversion circuit (I / V circuit) 7 for each. ₁ , 7 ₂ Is converted to a voltage signal, and the amplifier 8 ₁ , 8 ₂ Are respectively amplified in the synchronous detection circuit 9. ₁ , 9 ₂ Is input. Synchronous detection circuit 9 ₁ , 9 ₂ Then, according to the output of the timing circuit 10 that determines the detection timing from the oscillation output of the oscillator 6, the amplifier 8. ₁ , 8 ₂ Are synchronously detected, and only the signal component of each position signal is detected. Each detected position signal is a low-pass filter (hereinafter abbreviated as LPF) 11 formed of an integration circuit. ₁ , 11 ₂ And the noise component is removed and input to the adder 13 and the subtractor 14 of the arithmetic unit 12. Further, the outputs of the adder 13 and the subtracter 14 are input to the divider 15, and finally the output of the divider 15 becomes the output of the arithmetic unit 12. That is, in the arithmetic unit 12, the LPF 11 ₁ , 11 ₂ Each position signal (voltage signal) output from ₁ , V ₂ (V ₁ -V ₂ ) / (V ₁ + V ₂ The calculation for obtaining the above-described displacement is nothing but. Therefore, the displacement of the object A can be obtained based on the output of the calculation unit 12.
[0004]
FIG. 10 shows another conventional configuration. The conventional configuration shown in FIG. 9 eliminates the divider 15 in the arithmetic unit 12 and instead feeds back the light emission output of the laser diode 1 in accordance with the amount of light received by the PSD 4. It comes to control. That is, the output of the adder 13 is compared with the reference value V in the comparator 16. _ref And the output corresponding to the difference between the two is output to the modulation circuit 17, while the modulation circuit 17 performs pulse modulation (pulse amplitude modulation) on the output of the timing circuit 10 according to the output of the comparator 16. The modulation output is given to the drive circuit 5 so that the light emission output of the laser diode 1 can be varied. Therefore, the modulation circuit 17 outputs the output of the comparator 16 (the output of the adder 13 and the reference value V _ref The amount of light emitted by the laser diode 1 is adjusted so as to reduce the difference between the amount of light received by the PSD 4 and the amount of light received by the PSD 4 is kept substantially constant. As a result, the addition output (V ₁ + V ₂ ) Is constant in an ideal system ignoring the dynamic range and response characteristics of the circuit, and the subtraction output (V ₁ -V ₂ ) Is (V ₁ -V ₂ ) / (V ₁ + V ₂ Therefore, the divider 15 is not necessary.
[0005]
FIG. 11 shows still another conventional configuration, which differs from the conventional configuration shown in FIG. 10 in the feedback control method. In other words, in the conventional configuration shown in FIG. 11, the amplifier that amplifies the pair of position signals converted into voltage signals is the variable amplifier 18. ₁ , 18 ₂ And the addition output (V ₁ + V ₂ ) And reference value V _ref And the variable amplifier 18 by the output of the comparator 16 ₁ , 18 ₂ And the addition output of the adder 13 (V ₁ + V ₂ ) Is maintained to be substantially constant, and the divider 15 is not necessary as in the conventional configuration shown in FIG.
[0006]
[Problems to be solved by the invention]
However, in each of the above conventional configurations, the I / V circuit 7 is separately provided for each of the pair of position signals of the PSD 4. ₁ , 7 ₂ , Amplifier 8 ₁ , 8 ₂ (Or variable amplifier 18 ₁ , 18 ₂ ), Synchronous detection circuit 9 ₁ , 9 ₂ And LPF11 ₁ , 11 ₂ Therefore, two systems having exactly the same function had to be used. Thus, by providing two systems of circuit groups having the same configuration and function, the following problems have occurred.
[0007]
First, in an actual circuit, a difference in gain (gain error) may occur between the same two circuits due to variations in components. In addition, each circuit may have unique temperature characteristics and frequency characteristics due to variations in components and the like, and may have different amplification factors for changes in ambient temperature and changes over time. As a result, there is a problem that the measurement accuracy is lowered due to the gain error.
[0008]
Further, for the movement of the object A as shown in FIG. 12A, there is no difference in the response characteristics for the movement of the object A when there is no difference in frequency characteristics between the same two circuits (FIG. 12 ( b))) When the two circuits have different frequency characteristics as described above, each of them exhibits different response characteristics, and a transient error occurs with respect to the displacement of the object A. (See FIG. 12 (c)). In addition, there is a difference in offset deviation due to noise mixed between the same circuits, and it is necessary to provide a correction means for each of the two systems in order to reduce the measurement accuracy and correct the offset deviation. There was a problem of being invited. Moreover, providing two systems of the same circuit group fundamentally has the disadvantage that it not only prevents downsizing of the entire apparatus but also makes it difficult to reduce costs.
[0009]
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an optical displacement measuring apparatus that can process a pair of position signals with high accuracy with a simple configuration.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the invention according to claim 1, a light projecting means for periodically irradiating the surface of the object with a spot-like light projecting spot, and a reflection of the light irradiated from the light projecting means on the object surface. Light receiving means for outputting light as a current signal, a pair of position signals in which the ratio of the output level is determined corresponding to the position of the light receiving spot formed as an image of the light projecting spot by converging the light through the light receiving optical system, and each position signal Current-voltage conversion means for converting the signal into a voltage signal, synchronous detection means for detecting each position signal converted into the voltage signal in synchronization with irradiation of the light projection spot by the light projection means, and detection by the synchronous detection means Calculation means for calculating the difference and sum of the output levels of the position signals and calculating the quotient of the obtained difference and sum, and at least synchronous detection of the pair of position signals by the synchronous detection means and output to the calculation means Position signal above And a switching means for switching to each cycle of the irradiation period to each other The switching means is provided at the subsequent stage of the current-voltage conversion means. The pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one period of the irradiation period of the projection spot. Can be used in common for signals In addition, since the pair of position signals is converted by the switching means after once converting the original position signal consisting of the current signal into a voltage signal, it is possible to reduce the influence of noise generated at the time of switching. The
[0011]
In order to achieve the above object, a second aspect of the present invention provides a light projecting means for periodically irradiating a surface of an object with a spot-like light projecting spot, and a reflection of light irradiated from the light projecting means on the object surface. Light receiving means for outputting light as a current signal, a pair of position signals in which the ratio of the output level is determined corresponding to the position of the light receiving spot formed as an image of the light projecting spot by converging light through the light receiving optical system Current-voltage conversion means for converting the signal into a voltage signal, synchronous detection means for detecting each position signal converted into the voltage signal in synchronization with irradiation of the light projection spot by the light projection means, and detection by the synchronous detection means Calculation means for calculating the difference and sum of the output levels of the position signals and calculating the quotient of the obtained difference and sum, and at least synchronous detection of the pair of position signals by the synchronous detection means and output to the calculation means Position signal above And a switching means for switching to every plurality of cycles of the irradiation period to each other The switching means is provided at the subsequent stage of the current-voltage conversion means. The pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one period of the irradiation period of the projection spot. It can be used in common for signals. Moreover, switching by the switching means is performed for each of a plurality of irradiation periods. In addition, in order to switch the pair of position signals by the switching means after once converting the original signal of the position signal consisting of the current signal into a voltage signal, The influence of noise generated during switching can be reduced.
[0012]
The invention of claim 3 Up In order to achieve the above purpose, the light projecting means for periodically irradiating the surface of the object with a spot-like light projecting spot and the light reflected from the object surface of the light irradiated from the light projecting means are passed through the light receiving optical system. And a light receiving means for outputting a pair of position signals as current signals, the ratio of the output level of which is determined according to the position of the light receiving spot formed as an image of the projected light spot, and a current for converting each position signal into a voltage signal Voltage conversion means, synchronous detection means for detecting each position signal converted into a voltage signal in synchronization with the irradiation of the projection spot by the light projection means, and output level of each position signal detected by the synchronous detection means At least a synchronization between at least one of the pair of position signals, a calculation means for calculating the difference and the sum, a light quantity control means for feedback control of the emitted light quantity of the light projecting means so that the sum of the output levels of the position signals is kept substantially constant Wave detector The position signal is output to the synchronous detection has been operating means and a switching means for switching to another each in each period of the irradiation period at The switching means is provided at the subsequent stage of the current-voltage conversion means. The pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one period of the irradiation period of the projection spot. Can be used in common for signals In addition, since the pair of position signals is converted by the switching means after once converting the original position signal consisting of the current signal into a voltage signal, it is possible to reduce the influence of noise generated at the time of switching. The
[0013]
Claim 4 In order to achieve the above-mentioned object, the invention provides a light projecting means for periodically irradiating the surface of the object with a spot-like light projecting spot, and a light reflected from the object surface of the light irradiated from the light projecting means. Light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the light projection spot converged through an optical system, and each position signal as a voltage signal Current-voltage conversion means for converting to voltage, synchronous detection means for detecting each position signal converted into a voltage signal in synchronization with irradiation of the light projection spot by the light projection means, and each position signal detected by the synchronous detection means Calculating means for calculating the difference and sum of the output levels, a light quantity control means for performing feedback control of the emitted light quantity of the light projecting means so that the sum of the output levels of the position signals is kept substantially constant, and a pair of position signals At least at home The position signal is synchronously detected by the synchronous detection means is outputted to the computing means and a switching means for switching to another each in every plurality of cycles of the irradiation period The switching means is provided at the subsequent stage of the current-voltage conversion means. The pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one period of the irradiation period of the projection spot. It can be used in common for signals. Moreover, switching by the switching means is performed for each of a plurality of irradiation periods. In addition, in order to switch the pair of position signals by the switching means after once converting the original signal of the position signal consisting of the current signal into a voltage signal, The influence of noise generated during switching can be reduced.
[0014]
Contract Claim 5 In order to achieve the above-mentioned object, the invention provides a light projecting means for periodically irradiating the surface of the object with a spot-like light projecting spot, and a light reflected from the object surface of the light irradiated from the light projecting means. Light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the light projection spot converged through an optical system, and each position signal as a voltage signal Current-voltage conversion means for converting to voltage, synchronous detection means for detecting each position signal converted into a voltage signal in synchronization with irradiation of the light projection spot by the light projection means, and each position signal detected by the synchronous detection means So that the sum of the output level of the position signal and the calculating means for calculating the difference and sum of the output levels of the position signal are kept substantially constant. Amplification degree control means for feedback control of the amplification degree of the variable amplifier for amplifying each position signal; And switching means for switching the position signal that is synchronously detected by at least the synchronous detection means and output to the calculation means among the pair of position signals for each irradiation period. The switching means is provided at the subsequent stage of the current-voltage conversion means. The pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one period of the irradiation period of the projection spot. Can be used in common for signals In addition, since the pair of position signals is converted by the switching means after once converting the original position signal consisting of the current signal into a voltage signal, it is possible to reduce the influence of noise generated at the time of switching. The
[0015]
Claim 6 In order to achieve the above-mentioned object, the invention provides a light projecting means for periodically irradiating the surface of the object with a spot-like light projecting spot, and a light reflected from the object surface of the light irradiated from the light projecting means. Light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the light projection spot converged through an optical system, and each position signal as a voltage signal Current-voltage conversion means for converting to voltage, synchronous detection means for detecting each position signal converted into a voltage signal in synchronization with irradiation of the light projection spot by the light projection means, and each position signal detected by the synchronous detection means And a gain control means for feedback-controlling the gain of the variable amplifier that amplifies each position signal so that the sum of the output levels of the position signals is kept substantially constant. , A pair of places And a switching means for switching a position signal output to the synchronous detection has been operating means at least the synchronous detection means among the signals independently in every plurality of cycles of the irradiation period The switching means is provided at the subsequent stage of the current-voltage conversion means. The pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one period of the irradiation period of the projection spot. It can be used in common for signals. Moreover, switching by the switching means is performed for each of a plurality of irradiation periods. In addition, in order to switch the pair of position signals by the switching means after once converting the original signal of the position signal consisting of the current signal into a voltage signal, The influence of noise generated during switching can be reduced.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(Embodiment 1)
FIG. 1 is a circuit block diagram showing an embodiment of the invention according to claim 1, and a switch circuit 19 serving as a switching means for switching a pair of position signals of the PSD 4 in comparison with the conventional configuration shown in FIG. 9. ₁ , 19 ₂ Is provided in the previous stage of the I / V circuit 7 and the subsequent stage of the synchronous detection circuit 9, so that the circuit group of the I / V circuit 7, the amplifier 8 and the synchronous detection circuit 9 is one system.
[0018]
A switch circuit 19 provided in front of the I / V circuit 7 ₁ Is a control signal t output from the timing circuit 10 and inverted every cycle of the original oscillation signal (modulation signal) of the oscillator 6 that causes the laser diode 1 to emit light through the drive circuit 5. ₁ (See FIG. 2 (g)), and the position signal input to the I / V circuit 7 is selected. That is, the original signal (current signal) I of the position signal as shown in FIGS. ₁ , I ₂ The switch circuit 19 ₁ As shown in FIG. 2C, the I / V circuit 7 has a pair of position signals I. ₁ , I ₂ Are mixed and input in time series. Here, each position signal I ₁ , I ₂ DC component DC ₁ , DC ₂ Is a switch circuit 19 ₁ The difference DC between the two current values ₁ -DC ₂ (See FIG. 2C). The I / V circuit 7 converts the mixed position signal into a voltage signal and outputs it to the amplifier 8. The amplifier 8 amplifies the input position signal (voltage signal) to an appropriate level (see FIG. 2D). At this time, the DC component DC ₁ , DC ₂ Is the offset voltage V _dc1 , V _dc2 Is included in the output signal Va of the amplifier 8.
[0019]
The position signal Va amplified by the amplifier 8 is input to the synchronous detection circuit 9. The synchronous detection circuit 9 detects a detection timing signal t output from the timing circuit 10. ₂ (See FIG. 2 (e)), the position signal Va is synchronously detected and the signal Vb is output (see FIG. 2 (f)). Here, the detection timing signal t ₂ Is made to coincide with the period of the modulation signal (original oscillation signal of the oscillator 6).
[0020]
The signal (position signal) Vb detected by the synchronous detection circuit 9 is supplied from the switch circuit 19. ₂ LPF11 output by ₁ , 11 ₂ Is selected and switched. That is, the switch circuit 19 ₂ Is a switch circuit 19 ₁ Control signal t from timing circuit 10 in the same manner as ₁ As a result, the switch circuit 19 is eventually switched. ₁ Position signal I mixed in ₁ , I ₂ Is a pair of pulsating flow signals (position signals) Vd ₁ , Vd ₂ (See FIGS. 2 (h) and (i)). Where each position signal Vd ₁ , Vd ₂ , The offset voltage V included in the output Va of the amplifier 8 is _dc1 , -V _dc2 Reverse polarity voltage -V _dc1 , V _dc2 Is generated during synchronous detection in the synchronous detection circuit 9 (see FIGS. 2 (h) and (i)). However, the latter LPF11 ₁ , 11 ₂ By means of each pulsating flow signal Vd ₁ , Vd ₂ By taking out the DC component from _dc1 , V _dc2 Can be canceled. After that, the LPF 11 is similar to the conventional configuration shown in FIG. ₁ , 11 ₂ Are added, subtracted and divided by the calculation unit 12 to output an analog signal indicating the distance to the object A and the displacement.
[0021]
According to the above configuration, the problem of the conventional configuration shown in FIG. 9 can be avoided. That is, the switch circuit 19 that switches every period of the modulation signal of the laser diode 1 (the original oscillation signal of the oscillator 6). ₁ Thus, a pair of position signals I ₁ , I ₂ The signal output to the next stage is switched, so that both position signals I ₁ , I ₂ Are mixed in time series, and the switch circuit 19 in the subsequent stage is mixed. ₂ Since the mixed signal is separated by selecting and switching the signal output to the next stage for each period of the modulation signal in FIG. 1, the circuit group of the I / V circuit 7, the amplifier 8, and the synchronous detection circuit 9 is changed. Compared with the conventional configuration shown in FIG. 9 which can be only one system and has two identical circuit groups, generation of measurement errors due to variations in amplification factors due to component variations between the same circuits and differences in temperature characteristics Can be suppressed. Further, by synchronously detecting a pair of position signals by one synchronous detection circuit 9, each position signal is individually detected by the synchronous detection circuit 9 ₁ , 9 ₂ As compared with the case of performing synchronous detection using, it is possible to avoid occurrence of an error due to an offset. If the offset error is generated in the previous stage of the synchronous detection circuit 9 (before the amplifier 8) as described above, the cause of the offset error may be an error due to a DC error or an error due to mixed noise. You can cancel almost completely. Here, a slight offset error generated at the time of output of the synchronous detection circuit 9 can be removed by providing a simple correction circuit because the circuit group is one system. Furthermore, there is no difference in frequency characteristics, and it is possible to prevent the occurrence of measurement errors due to changes in the modulation frequency of the laser diode 1 and the occurrence of transient errors due to changes in position signals.
[0022]
By the way, in the present embodiment, the switch circuit 19 ₁ , 19 ₂ Switching timing (control signal t ₁ 2 (g), for each period of the modulation signal (the original oscillation signal of the oscillator 6) for causing the laser diode 1 to emit light as shown in FIG. 2 (g), for example, as shown in FIG. It may be every three cycles. Thus, the switch circuit 19 ₁ , 19 ₂ Is switched every plural cycles of the modulation signal, the switch circuit 19 is compared with the case where the modulation signal is switched every cycle. ₁ , 19 ₂ It is possible to suppress the influence of noise generated at the time of switching on the position signal, and to prevent the occurrence of errors due to such noise.
[0023]
Further, as shown in FIG. 4, a switch circuit 19 for mixing the position signals. ₁ I / V circuit 7 ₁ , 7 ₂ It may be provided in the next stage. As described above, the pair of position signals composed of the current signals output from the PSD 4 are once converted into voltage signals of appropriate levels, and then the switch circuit 19. ₁ If the mixing is performed at the switch circuit 19 ₁ The influence of the noise generated at the time of switching on the position signal can be suppressed, and the occurrence of an error due to such noise can be prevented.
[0024]
(Embodiment 2)
FIG. 5 is a circuit block diagram showing an embodiment of the invention according to claim 4. Compared with the conventional configuration shown in FIG. 10, a switch circuit 19 serving as switching means for switching a pair of position signals of PSD 4 exceptionally. ₁ , 19 ₂ Is provided in the previous stage of the I / V circuit 7 and the subsequent stage of the synchronous detection circuit 9, so that the circuit group of the I / V circuit 7, the amplifier 8 and the synchronous detection circuit 9 is one system. Other configurations and basic operations are the same as those of the conventional configuration shown in FIG. ₁ , 19 ₂ Since this operation is the same as that of the first embodiment, detailed description thereof is omitted.
[0025]
In the present embodiment, the switch circuit 19 provided in the preceding stage of the I / V circuit 7 as in the first embodiment. ₁ A pair of position signals I output from the PSD 4 by ₁ , I ₂ Are mixed in time series for each period of the modulation signal of the laser diode 1 and processed by one circuit group (I / V circuit 7, amplifier 8, synchronous detection circuit 9) and then the modulation signal again. Switch circuit 19 which is switched every one cycle ₂ The position signal mixed by the time is separated in time series, and the LPF 11 ₁ , 11 ₂ In addition, an analog signal including distance or displacement information of the object A is output by being processed and calculated in the calculation unit 12. Here, the addition output (V ₁ + V ₂ Since the operation of the feedback system in which) is substantially constant is the same as that of the conventional configuration shown in FIG.
[0026]
According to the above configuration, it is possible to avoid the problem of the conventional configuration shown in FIG. That is, the switch circuit 19 that switches every period of the modulation signal of the laser diode 1 (the original oscillation signal of the oscillator 6). ₁ Thus, a pair of position signals I ₁ , I ₂ The signal output to the next stage is switched, so that both position signals I ₁ , I ₂ Are mixed in time series, and the switch circuit 19 in the subsequent stage is mixed. ₂ Since the mixed signal is separated by selecting and switching the signal output to the next stage for each period of the modulation signal in FIG. 1, the circuit group of the I / V circuit 7, the amplifier 8, and the synchronous detection circuit 9 is changed. Compared to the conventional configuration shown in FIG. 10 that can be only one system and two systems with the same circuit group, generation of measurement errors due to variations in amplification factors due to component variations and temperature characteristics differences between the same circuits Can be suppressed. Further, by synchronously detecting a pair of position signals by one synchronous detection circuit 9, each position signal is individually detected by the synchronous detection circuit 9 ₁ , 9 ₂ As compared with the case of performing synchronous detection using, it is possible to avoid occurrence of an error due to an offset. If the offset error is generated in the previous stage of the synchronous detection circuit 9 (before the amplifier 8), the cause is almost equal to the error due to the DC error or the error due to the mixed noise. Can be canceled completely. Here, a slight offset error generated at the time of output of the synchronous detection circuit 9 can be removed by providing a simple correction circuit because the circuit group is one system. Furthermore, there is no difference in frequency characteristics, and it is possible to prevent the occurrence of measurement errors due to changes in the modulation frequency of the laser diode 1 and the occurrence of transient errors due to changes in position signals.
[0027]
By the way, in the present embodiment, the switch circuit 19 ₁ , 19 ₂ Switching timing (control signal t ₁ 2 (g), for each period of the modulation signal (the original oscillation signal of the oscillator 6) for causing the laser diode 1 to emit light as shown in FIG. 2 (g), for example, as shown in FIG. It may be every three cycles. Thus, the switch circuit 19 ₁ , 19 ₂ Is switched every plural cycles of the modulation signal, the switch circuit 19 is compared with the case where the modulation signal is switched every cycle. ₁ , 19 ₂ It is possible to suppress the influence of noise generated at the time of switching on the position signal, and to prevent the occurrence of errors due to such noise.
[0028]
Further, as shown in FIG. 6, a switch circuit 19 for mixing the position signals. ₁ I / V circuit 7 ₁ , 7 ₂ It may be provided in the next stage. As described above, the pair of position signals composed of the current signals output from the PSD 4 are once converted into voltage signals of appropriate levels, and then the switch circuit 19. ₁ If the mixing is performed at the switch circuit 19 ₁ The influence of the noise generated at the time of switching on the position signal can be suppressed, and the occurrence of an error due to such noise can be prevented.
[0029]
(Embodiment 3)
FIG. 7 is a circuit block diagram showing an embodiment of the invention according to claim 7. Compared with the conventional configuration shown in FIG. 11, a switch circuit 19 as switching means for switching a pair of position signals of the PSD 4 exceptionally. ₁ , 19 ₂ Is provided in the preceding stage of the I / V circuit 7 and the subsequent stage of the synchronous detection circuit 9, so that the circuit group of the I / V circuit 7, the variable amplifier 18 and the synchronous detection circuit 9 is made one system. Other configurations and basic operations are the same as those of the conventional configuration shown in FIG. ₁ , 19 ₂ Since this operation is the same as that of the first embodiment, detailed description thereof is omitted.
[0030]
In the present embodiment, the switch circuit 19 provided in the preceding stage of the I / V circuit 7 as in the first embodiment. ₁ A pair of position signals I output from the PSD 4 by ₁ , I ₂ Are mixed in a time series for each period of the modulation signal of the laser diode 1, and after signal processing by one circuit group (I / V circuit 7, variable amplifier 18, synchronous detection circuit 9), the modulation is performed again. Switch circuit 19 which is switched every one signal cycle ₂ The position signal mixed by the time is separated in time series, and the LPF 11 ₁ , 11 ₂ In addition, an analog signal including distance or displacement information of the object A is output by being processed and calculated in the calculation unit 12. Here, the addition output (V ₁ + V ₂ ) Of the feedback system (addition output (V ₁ + V ₂ The control for adjusting the degree of amplification of the variable amplifier 18 so as to be substantially constant) is the same as the conventional configuration shown in FIG.
[0031]
According to the above configuration, the problem of the conventional configuration shown in FIG. 11 can be avoided. That is, the switch circuit 19 that switches every period of the modulation signal of the laser diode 1 (the original oscillation signal of the oscillator 6). ₁ Thus, a pair of position signals I ₁ , I ₂ The signal output to the next stage is switched, so that both position signals I ₁ , I ₂ Are mixed in time series, and the switch circuit 19 in the subsequent stage is mixed. ₂ Since the mixed signal is separated by selecting and switching the signal output to the next stage for each period of the modulation signal in FIG. 1, the circuit group of the I / V circuit 7, the variable amplifier 18 and the synchronous detection circuit 9 Compared to the conventional configuration shown in FIG. 11 having two identical circuit groups, the measurement error caused by fluctuations in the amplification factor due to component variations between the same circuits and differences in temperature characteristics can be reduced. The occurrence can be suppressed. Further, by synchronously detecting a pair of position signals by one synchronous detection circuit 9, each position signal is individually detected by the synchronous detection circuit 9 ₁ , 9 ₂ As compared with the case of performing synchronous detection using, it is possible to avoid occurrence of an error due to an offset. If this offset error occurs in the previous stage of the synchronous detection circuit 9 (before the variable amplifier 18), the cause may be an error due to a DC error or an error due to mixed noise. You can cancel almost completely. Here, a slight offset error generated at the time of output of the synchronous detection circuit 9 can be removed by providing a simple correction circuit because the circuit group is one system. Furthermore, there is no difference in frequency characteristics, and it is possible to prevent the occurrence of measurement errors due to changes in the modulation frequency of the laser diode 1 and the occurrence of transient errors due to changes in position signals.
[0032]
By the way, in the present embodiment, the switch circuit 19 ₁ , 19 ₂ Switching timing (control signal t ₁ 2 (g), for each period of the modulation signal (the original oscillation signal of the oscillator 6) for causing the laser diode 1 to emit light as shown in FIG. 2 (g), for example, as shown in FIG. It may be every three cycles. Thus, the switch circuit 19 ₁ , 19 ₂ Is switched every plural cycles of the modulation signal, the switch circuit 19 is compared with the case where the modulation signal is switched every cycle. ₁ , 19 ₂ It is possible to suppress the influence of noise generated at the time of switching on the position signal, and to prevent the occurrence of errors due to such noise.
[0033]
Further, as shown in FIG. 8, a switch circuit 19 for mixing the position signals. ₁ I / V circuit 7 ₁ , 7 ₂ It may be provided in the next stage. As described above, the pair of position signals composed of the current signals output from the PSD 4 are once converted into voltage signals of appropriate levels, and then the switch circuit 19. ₁ If the mixing is performed at the switch circuit 19 ₁ The influence of the noise generated at the time of switching on the position signal can be suppressed, and the occurrence of an error due to such noise can be prevented.
[0034]
【The invention's effect】
According to the first aspect of the present invention, there is provided a light projecting means for periodically irradiating the surface of the object with a spot-like light projecting spot, and a light reflected from the object surface of the light irradiated from the light projecting means through the light receiving optical system. Light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the projected light spot, and a current voltage for converting each position signal into a voltage signal The difference between the output level of the position signal detected by the conversion means, the synchronous detection means for detecting each position signal converted into the voltage signal in synchronization with the irradiation of the projection spot by the light projection means, and the synchronous detection means And a calculating means for calculating the sum and a quotient of the obtained difference and the sum, and a position signal that is synchronously detected by at least the synchronous detecting means and is output to the calculating means among the pair of position signals. Separate for each cycle And a switching means for switching The switching means is provided at the subsequent stage of the current-voltage conversion means. Therefore, a pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one irradiation period of the projection spot, and at least the synchronous detection means is applied to the pair of position signals. By using them in common, the problems associated with using multiple synchronous detection means can be eliminated, and downsizing and cost reduction can be achieved by simplifying the configuration, and a pair of position signals can be processed with high accuracy with a simple configuration. Can In addition, since the pair of position signals is converted by the switching means after once converting the original position signal consisting of the current signal into a voltage signal, the influence of noise generated at the time of switching can be reduced. There is an effect that.
[0035]
According to a second aspect of the present invention, there is provided a light projecting means for periodically irradiating the surface of an object with a spot-like light projecting spot, and a light reflected from the object surface of the light irradiated from the light projecting means is passed through a light receiving optical system Light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the projected light spot, and a current voltage for converting each position signal into a voltage signal The difference between the output level of the position signal detected by the conversion means, the synchronous detection means for detecting each position signal converted into the voltage signal in synchronization with the irradiation of the projection spot by the light projection means, and the synchronous detection means And a calculating means for calculating the sum and a quotient of the obtained difference and the sum, and a position signal that is synchronously detected by at least the synchronous detecting means and is output to the calculating means among the pair of position signals. Each for multiple cycles And a switching means for switching the The switching means is provided at the subsequent stage of the current-voltage conversion means. Therefore, the pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means for each of the plurality of irradiation periods of the light projection spots, and at least the synchronous detection means is applied to the pair of position signals. By using them in common, the problems associated with using multiple synchronous detection means can be eliminated, and downsizing and cost reduction can be achieved by simplifying the configuration, and a pair of position signals can be processed with high accuracy with a simple configuration. In addition, switching by the switching means is performed at every plurality of irradiation cycles. At the same time, the pair of position signals are switched by the switching means after once converting the original position signal consisting of current signals into voltage signals. There is an effect that the influence of noise generated at the time of switching can be reduced.
[0036]
The invention of claim 3 point Light projecting means for periodically irradiating the surface of the object with a light-projecting spot, and the reflected light on the object surface of the light emitted from the light projecting means is converged through a light receiving optical system as an image of the light projecting spot Light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the formed light receiving spot, current-voltage converting means for converting each position signal to a voltage signal, and conversion to a voltage signal Synchronous detection means for detecting each position signal thus generated in synchronism with the irradiation of the projection spot by the light projection means, and calculation means for calculating the difference and sum of the output levels of the respective position signals detected by the synchronous detection means; , A light amount control means for feedback control of the light emission amount of the light projecting means so that the sum of the output levels of the position signals is kept substantially constant, and at least a synchronous detection means among the pair of position signals is calculated by synchronous detection hand The position signal output and a switching means for switching to another each in each period of the irradiation period The switching means is provided at the subsequent stage of the current-voltage conversion means. Therefore, a pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one irradiation period of the projection spot, and at least the synchronous detection means is applied to the pair of position signals. By using them in common, the problems associated with using multiple synchronous detection means can be eliminated, and downsizing and cost reduction can be achieved by simplifying the configuration, and a pair of position signals can be processed with high accuracy with a simple configuration. Can In addition, since the pair of position signals is converted by the switching means after once converting the original position signal consisting of the current signal into a voltage signal, the influence of noise generated at the time of switching can be reduced. There is an effect that.
[0037]
Claim 4 According to the present invention, light projecting means for periodically irradiating the surface of an object with a spot-like light projecting spot and light reflected from the object surface of the light irradiated from the light projecting means are converged and projected through a light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the light spot; and a current-voltage converting means for converting each position signal into a voltage signal; The synchronous detection means for detecting each position signal converted into the voltage signal in synchronization with the irradiation of the projection spot by the light projection means, and the difference and sum of the output levels of each position signal detected by the synchronous detection means A calculation means for calculating, a light quantity control means for feedback control of the emitted light quantity of the light projecting means so that the sum of the output levels of the position signals is kept substantially constant, and at least the synchronous detection means among the pair of position signals Synchronous detection It is a position signal which is output to the computing means and a switching means for switching to another each in every plurality of cycles of the irradiation period The switching means is provided at the subsequent stage of the current-voltage conversion means. Therefore, the pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means for each of the plurality of irradiation periods of the light projection spots, and at least the synchronous detection means is applied to the pair of position signals. By using them in common, the problems associated with using multiple synchronous detection means can be eliminated, and downsizing and cost reduction can be achieved by simplifying the configuration, and a pair of position signals can be processed with high accuracy with a simple configuration. In addition, switching by the switching means is performed at every plurality of irradiation cycles. At the same time, the pair of position signals are switched by the switching means after once converting the original position signal consisting of current signals into voltage signals. There is an effect that the influence of noise generated at the time of switching can be reduced.
[0038]
Contract Claim 5 According to the present invention, light projecting means for periodically irradiating the surface of an object with a spot-like light projecting spot, and light reflected from the object surface of the light projected from the light projecting means are converged and projected through a light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the light spot; and a current-voltage converting means for converting each position signal into a voltage signal; The synchronous detection means for detecting each position signal converted into a voltage signal in synchronization with the irradiation of the projection spot by the light projection means, and the difference and sum of the output levels of each position signal detected by the synchronous detection means The sum of the calculation means and the output level of the position signal is kept substantially constant Amplification degree control means for feedback control of the amplification degree of the variable amplifier for amplifying each position signal; And switching means for switching the position signal that is synchronously detected by at least the synchronous detection means and output to the calculation means among the pair of position signals for each irradiation period. The switching means is provided at the subsequent stage of the current-voltage conversion means. Therefore, a pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means every one irradiation period of the projection spot, and at least the synchronous detection means is applied to the pair of position signals. By using them in common, the problems associated with using multiple synchronous detection means can be eliminated, and downsizing and cost reduction can be achieved by simplifying the configuration, and a pair of position signals can be processed with high accuracy with a simple configuration. Can In addition, since the pair of position signals is converted by the switching means after once converting the original position signal consisting of the current signal into a voltage signal, the influence of noise generated at the time of switching can be reduced. There is an effect that.
[0039]
Claim 6 According to the present invention, light projecting means for periodically irradiating the surface of an object with a spot-like light projecting spot, and light reflected from the object surface of the light projected from the light projecting means are converged and projected through a light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as an image of the light spot; and a current-voltage converting means for converting each position signal into a voltage signal; The synchronous detection means for detecting each position signal converted into a voltage signal in synchronization with the irradiation of the projection spot by the light projection means, and the difference and sum of the output levels of each position signal detected by the synchronous detection means Among the pair of position signals, a calculation means for calculating, an amplification degree control means for feedback-controlling the amplification degree of the variable amplifier for amplifying each position signal so that the sum of the output levels of the position signals is kept substantially constant At least the same The position signal is output to the synchronous detection has been operating means at detecting means and a switching means for switching to another each in every plurality of cycles of the irradiation period The switching means is provided at the subsequent stage of the current-voltage conversion means. Therefore, the pair of position signals are alternately input to at least the synchronous detection means and output to the calculation means for each of the plurality of irradiation periods of the light projection spots, and at least the synchronous detection means is applied to the pair of position signals. By using them in common, the problems associated with using multiple synchronous detection means can be eliminated, and downsizing and cost reduction can be achieved by simplifying the configuration, and a pair of position signals can be processed with high accuracy with a simple configuration. In addition, switching by the switching means is performed at every plurality of irradiation cycles. At the same time, the pair of position signals are switched by the switching means after once converting the original position signal consisting of current signals into voltage signals. There is an effect that the influence of noise generated at the time of switching can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit block diagram showing a first embodiment.
FIG. 2 is a timing chart for explaining the operation described above.
FIG. 3 is a timing chart for explaining another operation of the above.
FIG. 4 is a circuit block diagram showing another configuration of the above.
FIG. 5 is a circuit block diagram showing a second embodiment.
FIG. 6 is a circuit block diagram showing another configuration of the above.
FIG. 7 is a circuit block diagram showing a third embodiment.
FIG. 8 is a circuit block diagram showing another configuration of the above.
FIG. 9 is a circuit block diagram showing a conventional example.
FIG. 10 is a circuit block diagram showing another conventional example.
FIG. 11 is a circuit block diagram showing still another conventional example.
FIG. 12 is an explanatory diagram for explaining the operation described above;
[Explanation of symbols]
1 Laser diode
4 PSD
6 Oscillator
7 Current-voltage conversion circuit
8 Amplifier
9 Synchronous detection circuit
10 Timing circuit
11 ₁ , 11 ₂ LPF
12 Calculation unit
19 ₁ , 19 ₂ Switch circuit
A object

Claims

An image of the projection spot by projecting a point-shaped projection spot periodically on the surface of the object and converging the reflected light from the projection surface of the object through the light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as a current signal, a current voltage converting means for converting each position signal into a voltage signal, and a voltage signal Calculate and calculate the difference and sum of the output levels of the respective position signals detected by the synchronous detection means and the synchronous detection means for detecting each converted position signal in synchronization with the irradiation of the projection spot by the light projection means. A calculation means for calculating a quotient of the difference and the sum, and a position signal that is synchronously detected by at least the synchronous detection means and output to the calculation means among the pair of position signals is switched separately for each cycle of the irradiation period. Switch Preparative comprising optical displacement measuring apparatus characterized in that a said changeover switching means downstream of the current-voltage conversion means.

An image of the projection spot by projecting a point-shaped projection spot periodically on the surface of the object and converging the reflected light from the projection surface of the object through the light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as a current signal, a current voltage converting means for converting each position signal into a voltage signal, and a voltage signal Calculate and calculate the difference and sum of the output levels of the respective position signals detected by the synchronous detection means and the synchronous detection means for detecting each converted position signal in synchronization with the irradiation of the projection spot by the light projection means. A calculation means for calculating the quotient of the difference and the sum, and a position signal that is synchronously detected by at least the synchronous detection means and is output to the calculation means among the pair of position signals is switched separately for each of a plurality of the irradiation periods. Switching And a stage, an optical displacement measuring apparatus characterized in that a said changeover switching means downstream of the current-voltage conversion means.

An image of the projection spot by projecting a point-shaped projection spot periodically on the surface of the object and converging the reflected light from the projection surface of the object through the light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as a current signal, a current voltage converting means for converting each position signal into a voltage signal, and a voltage signal Synchronous detection means for detecting each converted position signal in synchronization with the irradiation of the projection spot by the light projection means, and calculation means for calculating the difference and sum of the output levels of each position signal detected by the synchronous detection means And a light amount control means for feedback control of the light emission amount of the light projecting means so that the sum of the output levels of the position signals is kept substantially constant, and at least the synchronous detection means among the pair of position signals is synchronously detected. Calculation The position signal is output to stage a switching means for switching to another each in each period of the irradiation period, it said changeover switching means optical and displacement measuring apparatus you characterized in that disposed downstream of the current-voltage converting means .

An image of the projection spot by projecting a point-shaped projection spot periodically on the surface of the object and converging the reflected light from the projection surface of the object through the light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as a current signal, a current voltage converting means for converting each position signal into a voltage signal, and a voltage signal Synchronous detection means for detecting each converted position signal in synchronization with the irradiation of the projection spot by the light projection means, and calculation means for calculating the difference and sum of the output levels of each position signal detected by the synchronous detection means And a light amount control means for feedback control of the light emission amount of the light projecting means so that the sum of the output levels of the position signals is kept substantially constant, and at least the synchronous detection means among the pair of position signals is synchronously detected. Calculation The position signal is output to stage a switching means for switching to another each in every plurality of cycles of the irradiation period, the optical displacement measuring apparatus characterized in that a said changeover switching means downstream of the current-voltage conversion means.

An image of the projection spot by projecting a point-shaped projection spot periodically on the surface of the object and converging the reflected light from the projection surface of the object through the light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as a current signal, a current voltage converting means for converting each position signal into a voltage signal, and a voltage signal Synchronous detection means for detecting each converted position signal in synchronization with the irradiation of the projection spot by the light projection means, and calculation means for calculating the difference and sum of the output levels of each position signal detected by the synchronous detection means When the amplification controlling means for feedback controlling the gain of the variable amplifier in which the sum of the output levels of the position signal to amplify the position signal so as to keep substantially constant, at least synchronous detection means of the pair of position signals And a switching means for switching a position signal output to the synchronous detection has been operating means independently in every one period of the irradiation period Te, optical, characterized in that a said changeover switching means downstream of the current-voltage converting means Type displacement measuring device.

An image of the projection spot by projecting a point-shaped projection spot periodically on the surface of the object and converging the reflected light from the projection surface of the object through the light receiving optical system. A light receiving means for outputting as a current signal a pair of position signals whose output level ratio is determined corresponding to the position of the light receiving spot formed as a current signal, a current voltage converting means for converting each position signal into a voltage signal, and a voltage signal Synchronous detection means for detecting each converted position signal in synchronization with the irradiation of the projection spot by the light projection means, and calculation means for calculating the difference and sum of the output levels of each position signal detected by the synchronous detection means An amplification degree control means for feedback-controlling the amplification degree of the variable amplifier that amplifies each position signal so that the sum of the output levels of the position signals is kept substantially constant, and at least synchronous detection means among the pair of position signals You characterized in that the position signal output and a switching means for switching to another each in every plurality of cycles of the irradiation period was only set to said changeover switching means downstream of the current-voltage converting means to the synchronous detection has been calculating means Te optical and displacement measuring device.