JP2004093205A - Optical movement detection device and transport system using the same - Google Patents

Abstract

An object of the present invention is to reduce the number of parts, reduce the size, and reduce the manufacturing cost.
Kind Code: A1 A delay time Δt between light receiving outputs of light receiving elements 17a and 17b when an object 19 moves is obtained, and a moving speed v and a moving amount d of the object 19 are determined using the delay time Δt. Seeking. In this device 11, a collimating lens 13, a beam splitter 14, an objective lens 15, and a light receiving lens 16 are provided, one by one. , And Lb, it is possible to reduce the number of parts, reduce the size, and reduce the manufacturing cost.
[Selection diagram] Fig. 1

Description

この様な相関計算は、演算処理回路１８で行われており、この演算処理回路１８の構成を図６に示す。この演算処理回路１８は、各受光素子１７ａ，１７ｂの受光出力の電流電圧変換を行って、それぞれの受光信号Ａ，Ｂを出力する各Ｉ−Ｖ変換部３１ａ，３１ｂと、各受光信号Ａ，Ｂを増幅する各信号増幅部３２ａ，３２ｂと、増幅された各受光信号Ａ，Ｂの波形を整形する各信号整形部３３ａ，３３ｂと、整形された各受光信号Ａ，Ｂを一定周期でサンプリング（標本化）して、各受光信号Ａ，Ｂのサンプリング値をそれぞれの標本列として記憶する各メモリ３４ａ，３４ｂと、各メモリ３４ａ，３４ｂ内の各受光信号Ａ，Ｂの標本列についての相関計算を行って、各受光素子１７ａ，１７ｂの受光出力間の遅延指数ｋを求める相関計算部３５と、この遅延指数ｋを用いて、被検出物１９の移動速度ｖを求め、移動速度ｖを積分することにより移動量ｄを求め、移動速度ｖ及び移動量ｄを出力する速度算出部及び表示部３６とを備えている。
【００２９】
各Ｉ−Ｖ変換部３１ａ，３１ｂから出力される各受光信号Ａ，Ｂは、例えば図７のグラフに示す様なものであり、受光信号Ｂが受光信号Ａよりも遅延時間Δｔだけ遅れる。これらの受光信号Ａ，Ｂは、各信号増幅部３２ａ，３２ｂ及び各信号整形部３３ａ，３３ｂを経て、各メモリ３４ａ，３４ｂにより一定のサンプリング周期ｔｓでサンプリングされて記憶される。これにより、標本列｛Ａ１，Ａ２，……，Ａｎ｝及び標本列｛Ｂ１，Ｂ２，……，Ｂｎ，……，Ｂｎ＋ｍ｝が各メモリ３４ａ，３４ｂに記憶される。ただし、Δｔ＜ｔｓ×ｍである。
【００３０】
相関計算部３５は、図８に示す様に標本列｛Ｂ１，Ｂ２，……，Ｂｎ，……，Ｂｎ＋ｍ｝からｎ個のサンプリング値を順次抽出して、その度に、標本列｛Ａ１，Ａ２，……，Ａｎ｝と標本列｛Ｂ１，Ｂ２，……，Ｂｎ｝の相関係数、標本列｛Ａ１，Ａ２，……，Ａｎ｝と標本列｛Ｂ２，Ｂ３，……，Ｂｎ，Ｂｎ＋１｝の相関係数、標本列｛Ａ１，Ａ２，……，Ａｎ｝と標本列｛Ｂ３，Ｂ４，……，Ｂｎ，Ｂｎ＋１，Ｂｎ＋２｝の相関係数を逐次求め、以降同様に標本列｛Ａ１，Ａ２，……，Ａｎ｝と標本列｛Ｂｍ＋１，……，Ｂｎ＋ｍ｝の相関係数まで求める。例えば、図９に示す様にｎ＝３００かつｍ＝１００であれば、標本列｛Ａ１，Ａ２，……，Ａ３００｝と標本列｛Ｂ１，Ｂ２，……，Ｂ３００｝の相関係数、標本列｛Ａ１，Ａ２，……，Ａ３００｝と標本列｛Ｂ２，Ｂ３，……，Ｂ３０１｝の相関係数、……、及び標本列｛Ａ１，Ａ２，……，Ａ３００｝と標本列｛Ｂ１０１，……，Ｂ４００｝の相関係数を逐次求める。そして、相関係数が最大になったときの受光信号Ａの標本列に対する受光信号Ｂの標本列のずれ（遅延時間Δｔ）を求める。このずれは、サンプリング周期×ｋ（ｋ：０，１，２，……、０≦ｋ≦ｍ）で表され、このｋが遅延指数として相関計算部３５から出力される。例えば、図７の各受光信号Ａ，Ｂについては、ｋ＝３となる。
【００３１】
速度算出部及び表示部３６は、この遅延指数ｋにサンプリング周期を掛けて、遅延時間Δｔを求め、更に被検出物１９上の各光ビームＬａ，Ｌｂのスポット中心間の距離Ｌ（既知）を遅延時間Δｔで割って、被検出物１９の移動速度ｖを求め（ｖ＝Ｌ／Δｔ）、この移動速度ｖを積分することにより移動量ｄを求め、これらの移動速度ｖや移動量ｄを出力したり表示する。
【００３２】
この様に本実施形態の光学式移動検出装置１１では、被検出物１９が移動したときの各受光素子１７ａ，１７ｂの受光出力間の遅延時間Δｔを求め、この遅延時間Δｔを用いて、被検出物１９の移動速度ｖ及び移動量ｄを求めている。
【００３３】
この装置１１では、コリメートレンズ１３、ビームスプリッタ１４、対物レンズ１５、及び受光レンズ１６をそれぞれ１つずつ設け、これらにより各発光素子１２ａ，１２ｂから各受光素子１７ａ，１７ｂへとそれぞれの光ビームＬａ，Ｌｂを共に導いているため、部品点数の減少、小型化、及び製造コストの低減を図ることができる。
【００３４】
尚、コリメートレンズ１３、対物レンズ１５、及び受光レンズ１６の代わりに、図１０に示す様に１枚のレンズ４１のみを用いても、光学式移動検出装置を実施することができる。また、図１１に示す様に１つの発光素子１２のみを設け、この発光素子１２からの光ビームを光学部品（ウォラストンプリズムやビームディスプレーサ等）４２により２分割して、一対の光ビームＬａ，Ｌｂを形成して用いても良い。更に、図１２に示す様に１つの発光素子１２のみを設け、この発光素子１２からの光ビームを回折格子４３により２分割し、±１次の回折光を一対の光ビームＬａ，Ｌｂとして用いても良い。回折格子４３を用いる場合は、厳密には、０次の回折光Ｌ０が生じることになるものの、回折格子４３の設計により、０次の回折光Ｌ０の強度を±１次の回折光である各光ビームＬａ，Ｌｂの強度よりも十分に小さくすることができるので、０次の回折光Ｌ０の影響を受けずに、各光ビームＬａ，Ｌｂを用いることができる。
【００３５】
ところで、演算処理回路１８の各信号整形部３３ａ，３３ｂは、例えばローパスフィルタ（ＬＰＦ）である。外乱光のノイズや信号ノイズ等の影響があって、図１３（ａ）に示す様な微小ノイズが受光信号に含まれるときには、ＬＰＦにより微小ノイズを低減して、図１３（ｂ）に示す様に受光信号を平滑化すれば良い。この結果として、相関計算の精度を上げることができる。あるいは、ＬＰＦによる平滑化の代わりに、図１４（ａ）に示す様な時々刻々と変化する受光信号のレベルをその前後の該受光信号のレベルを用いて平均化し、図１４（ｂ）に示す様な受光信号を生成しても良い。例えば、時点ｔ２の受光信号のレベルと前後の時点ｔ１及び時点ｔ３の受光信号のレベルの和を求めて、この和を３で割ることにより、時点ｔ２の受光信号のレベルを平均化し、更に以降の各時点　　　ｔ３，ｔ４，……でも同様の平均化を行う。更に、平均化の対象となる各受光信号の個数を増減しても構わない。また、各信号整形部３３ａ，３３ｂは、受光信号を微分して、この微分信号を出力するものであっても良い。この微分処理は、被検出物１９の表面の凹凸が小さく、図１５（ａ）に示す様に受光信号の変化が小さいときに有効である。この受光信号を微分すると、図１５（ｂ）に示す様な変化の大きな微分信号を得ることができ、各受光信号Ａ，Ｂの微分信号の相関係数も大きくなる。この結果として、各受光信号Ａ，Ｂ間の遅延時間を正確に導出して、被検出物１９の移動速度を正確に求めることができる。更に、図１６（ａ）に示す様に微小ノイズが受光信号に含まれ、かつ受光信号の変化が小さいときには、図１６（ｂ）に示す様にＬＰＦによる受光信号の平滑化あるいは受光信号の平均化を行い、かつ受光信号を微分してから、相関計算を行えば、ノイズの低減と遅延時間の精度向上を果たすことができる。
【００３６】
図１７は、本発明の搬送システムの一実施形態を示している。本実施形態の搬送システムでは、記録用紙Ｐを各搬送ローラ５１により搬送しつつ、記録用紙Ｐの移動速度ｖを図１の光学式移動検出装置１１により検出して、この移動速度ｖを光学式移動検出装置１１からローラ制御部５２へと出力しており、この移動速度ｖが一定となる様にローラ制御部５２により各搬送ローラ５１を回転駆動制御している。
【００３７】
図１８は、本発明の搬送システムの他の実施形態を示している。本実施形態の搬送システムでは、記録用紙Ｐを各搬送ローラ５１により搬送しつつ、記録用紙Ｐの移動速度ｖを図１の光学式移動検出装置１１により検出して、この移動速度ｖを処理装置５３に出力しており、この移動速度ｖを用いて、記録用紙Ｐが予め設定された位置に到達したタイミングを処理装置５３により判定し、記録用紙Ｐを該位置で処理装置５３により処理している。
【００３８】
この様な搬送システムは、プリンタや複写機等の画像形成装置に適用される。あるいは、他の被検出物を搬送する装置や機器にも適用することができる。
【００３９】
【発明の効果】
以上説明した様に本発明の光学式移動検出装置によれば、１つの光路形成手段と１つの光学手段だけで、発光手段からのそれぞれの光ビームのスポットを被検出物上に形成し、各光スポットからの反射光を各受光素子の受光面に集光させている。このため、部品点数の減少、小型化、及び製造コストの低減を図ることができる。
【００４０】
また、各受光出力をローパスフィルタにより平滑化して用いたり、各受光出力を平均化して用いているので、外乱光のノイズや信号ノイズ等の影響をほぼ排除することができ、各受光出力の相関係数を正確に導出して、被検出物の移動速度を正確に求めることができる。
【００４１】
また、各受光素子の受光出力の微分信号を求めて用いているので、被検出物の表面の凹凸が小さく、各受光素子の受光出力の変化が小さくても、各受光出力間の遅延時間を正確に導出して、被検出物の移動速度を正確に求めることができる。
【００４２】
一方、本発明の搬送システムによれば、本発明の光学式移動検出装置により被検出物の移動速度を求め、この被検出物の移動速度をフィードバックすることにより、この被検出物の移動速度を制御したり、この被検出物を予め設定された位置で処理している。
【図面の簡単な説明】
【図１】本発明の光学式移動検出装置の一実施形態を示す側面図である。
【図２】図１の装置における各発光素子の構成を示す図である。
【図３】図１の装置における各発光素子の他の構成を示す図である。
【図４】図１の装置における各受光素子の構成を示す図である。
【図５】図１の装置における各受光素子の他の構成を示す図である。
【図６】図１の装置における演算処理回路の構成を示すブロック図である。
【図７】図６の回路における各受光信号を示すグラフである。
【図８】図６の回路における相関計算部に入力される各標本列を示す図である。
【図９】図６の回路における相関計算部に入力される各標本列の一例を示す図である。
【図１０】図１の装置の変形例を示す図である。
【図１１】図１の装置の他の変形例を示す図である。
【図１２】図１の装置の別の変形例を示す図である。
【図１３】（ａ）はノイズを含む受光信号を示すグラフであり、（ｂ）はＬＰＦにより平滑化された受光信号を示すグラフである。
【図１４】（ａ）はノイズを含む受光信号を示すグラフであり、（ｂ）は平均化された受光信号を示すグラフである。
【図１５】（ａ）は変化が小さな受光信号を示すグラフであり、（ｂ）は受光信号の微分信号を示すグラフである。
【図１６】（ａ）はノイズを含みかつ変化が小さな受光信号を示すグラフであり、（ｂ）は平滑化又は平均化され受光信号の微分信号を示すグラフである。
【図１７】本発明の搬送システムの一実施形態を示す図である。
【図１８】本発明の搬送システムの他の実施形態を示す図である。
【図１９】従来の光学式移動検出装置を示す図である。
【図２０】図１９の装置における各測距センサの構成を示す図である。
【図２１】（ａ）及び（ｂ）は、図１９の装置における各測距センサの出力を示すグラフである。
【符号の説明】
１１　　光学式移動検出装置
１２，１２ａ，１２ｂ　　発光素子
１３　　コリメートレンズ
１４　　ビームスプリッタ
１５　　対物レンズ
１６　　受光レンズ
１７ａ，１７ｂ　　受光素子
１８　　演算処理回路
３１ａ，３１ｂ　　Ｉ−Ｖ変換部
３２ａ，３２ｂ　　信号増幅部
３３ａ，３３ｂ　　信号整形部
３４ａ，３４ｂ　　メモリ
３５　　相関計算部
３６　　速度算出部及び表示部
４１　　レンズ
４２　　光学部品
４３　　回折格子
５１　　搬送ローラ
５２　　ローラ制御部
５３　　処理装置[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an optical movement detection device for detecting the movement speed of an object without contact, and a transport system using the same.
[0002]
[Prior art]
This type of optical movement detection device is applied to, for example, an image forming apparatus such as a printer or a copying machine, and detects a moving speed and a moving amount of a recording sheet. FIG. 19 shows an example of a conventional optical movement detection device. This apparatus includes two distance measuring sensors 101 and 102 and an arithmetic processing circuit 103, and emits respective light beams L1 and L2 from each of the distance measuring sensors 101 and 102 to an object 104 to be detected. The light beams L1 and L2 are reflected by the object 104 to be incident on the distance measuring sensors 101 and 102, and the light receiving levels of the light beams L1 and L2 are detected by the distance measuring sensors 101 and 102. , L2 are input to the arithmetic processing circuit 103, and the arithmetic processing circuit 103 obtains the moving speed and the moving amount of the detected object 104.
[0003]
FIG. 20 shows the configuration of each of the distance measuring sensors 101 and 102. Each of the distance measuring sensors 101 and 102 includes a light-emitting element 111 for emitting a light beam, a light-receiving element 112 for receiving the light beam, and a light beam from the light-emitting element 111 for condensing the light beam spot. An output side lens 113 formed on the light receiving element 104 and a light receiving side lens 114 for condensing the light beam reflected by the object 104 on the light receiving surface of the light receiving element 112 are provided. It is output to the arithmetic processing circuit 103.
[0004]
Here, the illuminance of the spot of each light beam L1, L2 on the detection object 104 changes according to the respective distance between each of the distance measurement sensors 101, 102 and the detection object 104, and accordingly, each light receiving element The light receiving level of 112 changes, and each light receiving output changes. For this reason, if the surface of the detection object 104 has irregularities, the distance between each of the distance measuring sensors 101 and 102 and the detection object 104 changes with the movement of the detection object 104, and each light receiving element 112 Will also change. Since the distance measuring sensor 102 is positioned downstream of the distance measuring sensor 101 in the moving direction of the detection object 104, the light receiving output of each light receiving element 112 is, for example, as shown in FIGS. 21 (a) and 21 (b). As shown in the graph, the change in the light receiving output of the light receiving element 112 of the distance measuring sensor 102 is delayed by the delay time Δt from the change in the light receiving output of the light receiving element 112 of the distance measuring sensor 101. The arithmetic processing circuit 103 performs a correlation calculation on the light receiving output of each light receiving element 112 to obtain the delay time Δt, and obtains the moving speed and the moving amount of the detection object 104 using the delay time Δt.
[0005]
[Problems to be solved by the invention]
However, in the above-mentioned conventional optical movement detection device, since two distance measurement sensors are provided, there are problems that the number of components is large, miniaturization is difficult, and manufacturing cost is high. In addition, when the unevenness of the surface of the detection target is small and the surface is smooth, it is difficult to detect the moving speed and the movement amount of the detection target. Furthermore, it is easily affected by noise of disturbance light, signal noise, and the like, and the detection accuracy is easily lowered.
[0006]
As another device for detecting the moving speed of the object to be detected in a non-contact manner, there is a laser Doppler system (see Japanese Patent Application Laid-Open No. 8-292263). However, this type of device is large and It was expensive and could not be used easily.
[0007]
Therefore, the present invention has been made in view of the above-mentioned conventional problems, and it is possible to reduce the number of parts, reduce the size, and reduce the manufacturing cost, and even if the unevenness of the surface of the detected object is small. It is an object of the present invention to provide an optical movement detection device which has good detection accuracy and is not easily affected by noise, and a transport system using the same.
[0008]
[Means for Solving the Problems]
In order to solve the above-described problems, the present invention provides a light-emitting unit that emits a pair of light beams, a pair of light-receiving elements that receive each light beam, and that each light beam from the light-emitting unit is reflected by an object. Optical path forming means for forming an optical path for guiding the light beam together with each light receiving element, and condensing each light beam to form a respective light spot on the object to be detected, and reflecting light from each light spot to each light receiving element. Optical means for condensing light on the light receiving surface together, and the moving speed of the object to be detected is obtained based on the light receiving output of each light receiving element.
[0009]
According to the present invention having such a configuration, the optical path forming means forms an optical path in which each light beam from the light emitting means is reflected by the object to be detected and guided to each light receiving element. The optical means collects the respective light beams to form respective light spots on the object to be detected, and collects the reflected light from the respective light spots on the light receiving surfaces of the respective light receiving elements. That is, only one optical path forming unit and one optical unit form spots of respective light beams from the light emitting unit on the object to be detected, and the reflected light from each light spot is collected on the light receiving surface of each light receiving element. I'm shining. For this reason, the number of parts can be reduced, the size can be reduced, and the manufacturing cost can be reduced. The optical path forming means includes a beam splitter and a diffraction grating, and the optical means includes a collimating lens, an objective lens, and the like, or a combination thereof.
[0010]
Further, in the present invention, the received light output of each light receiving element is smoothed by a low-pass filter, and a delay time of one received light output with respect to the other received light output is obtained by a correlation calculation with respect to each smoothed light receiving output. The moving speed of the object to be detected is obtained using the time.
[0011]
By using each received light output smoothed by the low-pass filter in this way, it is possible to almost eliminate the influence of noise of disturbance light, signal noise, and the like, accurately derive the correlation coefficient of each received light output, and The moving speed of the detected object can be accurately obtained.
[0012]
Further, in the present invention, for each light receiving element, the light receiving output is averaged using the other light receiving outputs before and after, and the other light receiving outputs for one light receiving output are calculated by a correlation calculation on the averaged light receiving outputs of the light receiving elements. The output delay time is obtained, and the moving speed of the detected object is obtained using the output delay time.
[0013]
By using the light receiving outputs of the respective light receiving elements averaged in this way, the influence of disturbance light noise, signal noise, and the like can be almost eliminated, and the moving speed of the detected object can be accurately obtained. .
[0014]
Further, in the present invention, the light receiving output of each light receiving element is differentiated, a delay time of the other light receiving output with respect to one light receiving output is obtained by a correlation calculation with respect to the differential signal of each light receiving output, and this delay time is used. Thus, the moving speed of the detected object is obtained.
[0015]
It can be said that the differential signal of the light receiving output of each light receiving element emphasizes a change in the light receiving output of each light receiving element. For this reason, since the unevenness of the surface of the detection object is small, the change of the light receiving output of each light receiving element is small, and when the correlation coefficient of each light receiving output is small, the differential signal of the light receiving output of each light receiving element is obtained and used. For example, it is possible to accurately derive the delay time between the respective light receiving outputs, and to accurately determine the moving speed of the detected object.
[0016]
Further, in the present invention, the light receiving output of each light receiving element is smoothed by a low-pass filter, the smoothed light receiving output is differentiated, and a correlation calculation is performed on the smoothed differential signal of each light receiving output. The delay time of the other light receiving output with respect to the light receiving output is calculated, and the moving speed of the detection target is calculated using the delay time.
[0017]
By using the differential signal of the light receiving output of each light receiving element averaged in this way, it is possible to substantially eliminate the influence of disturbance light noise, signal noise, etc. By accurately deriving the correlation coefficient of the output, the moving speed of the detected object can be accurately obtained.
[0018]
Next, the transport system of the present invention obtains the moving speed of the detected object by the optical movement detecting device of the present invention, and feeds back the moving speed of the detected object to the conveying means for conveying the detected object. The moving speed of the object is controlled.
[0019]
Alternatively, the transport system of the present invention obtains the moving speed of the detected object by the optical movement detection device of the present invention, and feeds back the moving speed of the detected object to processing means for processing the detected object, The detected object is processed at a preset position.
[0020]
As described above, if the moving speed of the object to be detected is obtained by the optical movement detecting device of the present invention, an accurate moving speed can be obtained. Therefore, by feeding back the moving speed, it becomes possible to accurately control the moving speed and to process the detected object at a predetermined position.
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[0022]
FIG. 1 is a side view showing an embodiment of the optical movement detection device of the present invention. The optical movement detection device 11 of the present embodiment includes a pair of light emitting elements (for example, semiconductor lasers) 12a and 12b, a collimating lens 13, a beam splitter 14, an objective lens 15, a light receiving lens 16, and a pair of light receiving elements. 17a and 17b and an arithmetic processing circuit 18 are provided.
[0023]
Each light emitting element 12a, 12b emits a respective light beam La, Lb. These light beams La and Lb are collimated by a collimator lens 13, transmitted through a beam splitter 14, condensed by an objective lens 15, and irradiated onto an object 19 to be detected. As a result, spots of the light beams La and Lb are formed on the detection target 19. Further, these light beams La and Lb are reflected by the object 19, pass through the objective lens 15, are deflected by the beam splitter 14, are condensed by the light receiving lens 16, and enter the light receiving elements 17a and 17b. I do. Then, the light receiving outputs of the respective light receiving elements 17a and 17b are applied to the arithmetic processing circuit 18. The arithmetic processing circuit 18 obtains the moving speed and the moving amount of the detected object 19 based on the light receiving outputs of the light receiving elements 17a and 17b.
[0024]
Each of the light emitting elements 12a and 12b is preferably housed in one package 21 and integrated as shown in FIG. Instead of the light emitting elements 12a and 12b, a semiconductor laser chip 22 having two light emitting points 22a and 22b housed in a package 23 as shown in FIG. 3 may be used.
[0025]
A light shielding plate 24 as shown in FIG. 4 is provided in front of each light receiving element 17a, 17b, and each light beam La, Lb is transmitted through each pinhole 24a, 24b of the light shielding plate 24 to each light receiving element 17a. , 17b. Preferably, as shown in FIG. 5, each light receiving element 17a, 17b is housed in a package 25, a light shielding plate 24 is attached to the front surface of each light receiving element 17a, 17b, and each light receiving element 17a, 17b and the light shielding plate 24 are integrated. Become Each of the light receiving elements 17a and 17b may be a light receiving surface of one light receiving element (not shown).
[0026]
The pinholes 24a and 24b of the light shielding plate 24 are provided for preventing disturbance light from entering the light receiving surfaces of the light receiving elements 17a and 17b. Further, since the light beams La and Lb are narrowed down, the light in an extremely narrow area on the detection object 19 can be obtained without reducing the spots of the light beams La and Lb formed on the detection object 19. Only the light can enter the light receiving surfaces of the light receiving elements 17a and 17b. Accordingly, even if the distance between the optical movement detection device 11 and the object 19 fluctuates to some extent and the spot size of each of the light beams La and Lb fluctuates, the distance according to the unevenness of the surface of the object 19 is obtained. Light at each level enters the light receiving surfaces of the light receiving elements 17a and 17b. For example, if the diameter of the spot of each of the light beams La and Lb formed on the detection target 19 is about 10 to 100 μm, the diameter of each of the pinholes 24 a and 24 b of the light shielding plate 24 is set to about 10 to 50 μm.
[0027]
Now, in the optical movement detection device 11 having such a configuration, when the detection object 19 moves in the arrow direction D, the amount of light reflected from the spot of each of the light beams La and Lb is reduced due to unevenness of the surface of the detection object 19. Accordingly, the light receiving level of each of the light receiving elements 17a and 17b changes, and the respective light receiving outputs change. At this time, if the spot of the light beam La is located upstream of the spot of the light beam Lb in the moving direction of the object 19, the change in the light receiving output of the light receiving element 17b is longer than the change in the light receiving output of the light receiving element 17a by the delay time Δt. You will be late. At this time, assuming that the moving speed of the detection object 19 is v and the distance between the spot centers of the light beams La and Lb on the detection object 19 is L (known), v = L / Δt. The speed v can be determined. Further, the moving amount d can be obtained by integrating the moving speed v of the detection object 19.
[0028]
Here, correlation calculation is used to obtain the delay time Δt. Correlation calculation means that given two sample sequences {Xi | i = 1, 2,..., N} and {Yi | i = 1, 2,. That is, a correlation function ρ is obtained as a statistic for measuring the similarity. The correlation function ρ is obtained by setting the standard deviation of the sample sequence {Xi | i = 1, 2,..., N} to σx, the average to x bar, and the sample sequence {Yi | i = 1, 2,. If the standard deviation of｝ is σy and the average is y bar, it is expressed by the following equation (1). Here, −1 ≦ ρ ≦ 1.
(Equation 1)

Such a correlation calculation is performed by the arithmetic processing circuit 18, and the configuration of the arithmetic processing circuit 18 is shown in FIG. The arithmetic processing circuit 18 performs current-voltage conversion of the light receiving output of each light receiving element 17a, 17b, and outputs each light receiving signal A, B, each IV converter 31a, 31b, and each light receiving signal A, Each signal amplifying section 32a, 32b for amplifying B, each signal shaping section 33a, 33b for shaping the waveform of each amplified light receiving signal A, B, and sampling the shaped light receiving signal A, B at a constant period. (Sampling) and the correlation between the memories 34a and 34b for storing the sampled values of the light receiving signals A and B as respective sample columns and the sample columns of the light receiving signals A and B in the memories 34a and 34b. A calculation is performed to calculate a delay index k between the light receiving outputs of the respective light receiving elements 17a and 17b. Using the delay index k, a moving speed v of the object 19 is calculated. To integrate Ri obtains the movement amount d, and a velocity calculator, and a display unit 36 outputs the moving speed v and the movement amount d.
[0029]
Each light receiving signal A, B output from each of the IV converters 31a, 31b is, for example, as shown in the graph of FIG. 7, and the light receiving signal B is delayed from the light receiving signal A by a delay time Δt. These light receiving signals A and B pass through the respective signal amplifying sections 32a and 32b and the respective signal shaping sections 33a and 33b, and are sampled by the memories 34a and 34b at a fixed sampling period ts and stored. Thus, the sample sequences {A1, A2,..., An} and the sample sequences {B1, B2,..., Bn,..., Bn + m} are stored in the memories 34a and 34b. Here, Δt <ts × m.
[0030]
The correlation calculation unit 35 sequentially extracts n sample values from the sample sequence {B1, B2,..., Bn,..., Bn + m} as shown in FIG. A2,..., An} and the sample sequence {B1, B2,..., Bn}, the sample sequence {A1, A2,. .., An} and the sample sequence {B3, B4,..., Bn, Bn + 1, Bn + 2}. , An} and the sample sequence {Bm + 1,..., Bn + m}. For example, if n = 300 and m = 100 as shown in FIG. 9, the correlation coefficient between the sample sequence {A1, A2,..., A300} and the sample sequence {B1, B2,. , A300} and the sample sequence {B2, B3,..., B301}, the sample sequence {A1, A2,..., A300} and the sample sequence {B101} ,..., B400} are sequentially obtained. Then, the shift (delay time Δt) of the sample sequence of the light receiving signal B with respect to the sample sequence of the light receiving signal A when the correlation coefficient becomes maximum is obtained. This shift is represented by a sampling period × k (k: 0, 1, 2,..., 0 ≦ k ≦ m), and this k is output from the correlation calculator 35 as a delay index. For example, k = 3 for each of the light receiving signals A and B in FIG.
[0031]
The speed calculation unit and the display unit 36 multiply the delay index k by the sampling period to obtain the delay time Δt, and further calculate the distance L (known) between the spot centers of the light beams La and Lb on the detection object 19. By dividing by the delay time Δt, the moving speed v of the detected object 19 is obtained (v = L / Δt), and by integrating this moving speed v, the moving amount d is obtained. Output and display.
[0032]
As described above, in the optical movement detection device 11 of the present embodiment, the delay time Δt between the light receiving outputs of the respective light receiving elements 17a and 17b when the detection target 19 moves is obtained, and the delay time Δt is used by using the delay time Δt. The moving speed v and the moving amount d of the detection object 19 are obtained.
[0033]
In this device 11, a collimating lens 13, a beam splitter 14, an objective lens 15, and a light receiving lens 16 are provided one by one, and the light beams La from each light emitting element 12a, 12b to each light receiving element 17a, 17b are respectively provided. , Lb, it is possible to reduce the number of parts, reduce the size, and reduce the manufacturing cost.
[0034]
Note that the optical movement detection device can be implemented by using only one lens 41 as shown in FIG. 10 instead of the collimating lens 13, the objective lens 15, and the light receiving lens 16. Also, as shown in FIG. 11, only one light emitting element 12 is provided, and a light beam from this light emitting element 12 is divided into two by an optical component (Wollaston prism, beam displacer, etc.) 42, and a pair of light beams La, Lb may be formed and used. Further, as shown in FIG. 12, only one light emitting element 12 is provided, a light beam from this light emitting element 12 is divided into two by a diffraction grating 43, and ± 1st-order diffracted light is used as a pair of light beams La and Lb. May be. When the diffraction grating 43 is used, strictly speaking, although the 0th-order diffracted light L0 is generated, the intensity of the 0th-order diffracted light L0 is ± 1st-order diffracted light by the design of the diffraction grating 43. Since the intensities of the light beams La and Lb can be made sufficiently smaller, the light beams La and Lb can be used without being affected by the zero-order diffracted light L0.
[0035]
By the way, each of the signal shaping units 33a and 33b of the arithmetic processing circuit 18 is, for example, a low-pass filter (LPF). When the received light signal includes minute noise as shown in FIG. 13A due to the influence of disturbance light noise, signal noise, or the like, the minute noise is reduced by the LPF to obtain a signal as shown in FIG. The received light signal may be smoothed. As a result, the accuracy of the correlation calculation can be improved. Alternatively, instead of the smoothing by the LPF, the level of the light receiving signal that changes every moment as shown in FIG. 14A is averaged using the levels of the light receiving signals before and after the average, and the result is shown in FIG. 14B. Such a light receiving signal may be generated. For example, the level of the light receiving signal at time t2 is obtained by summing the level of the light receiving signal at time t2 and the levels of the light receiving signals at time points t1 and t3 before and after, and dividing this sum by 3 to average the level of the light receiving signal at time t2. The same averaging is performed at time points t3, t4,. Further, the number of light receiving signals to be averaged may be increased or decreased. Further, each of the signal shaping units 33a and 33b may differentiate the light receiving signal and output the differentiated signal. This differential processing is effective when the irregularities on the surface of the detection object 19 are small and the change in the light receiving signal is small as shown in FIG. By differentiating the received light signal, a differentiated signal having a large change as shown in FIG. 15B can be obtained, and the correlation coefficient between the differentiated signals of the received light signals A and B also increases. As a result, the delay time between the light receiving signals A and B can be accurately derived, and the moving speed of the detection object 19 can be accurately obtained. Further, when a small noise is included in the received light signal as shown in FIG. 16A and the change of the received light signal is small, smoothing of the received light signal by the LPF or averaging of the received light signal is performed as shown in FIG. If the correlation calculation is performed after the light reception signal is differentiated and the received light signal is differentiated, noise can be reduced and delay time accuracy can be improved.
[0036]
FIG. 17 shows an embodiment of the transport system of the present invention. In the transport system according to the present embodiment, the moving speed v of the recording paper P is detected by the optical movement detection device 11 in FIG. The movement detection device 11 outputs a signal to the roller control unit 52, and the roller control unit 52 controls the rotation of each transport roller 51 so that the movement speed v is constant.
[0037]
FIG. 18 shows another embodiment of the transport system of the present invention. In the transport system of the present embodiment, the moving speed v of the recording paper P is detected by the optical movement detecting device 11 in FIG. The moving speed v is used to determine the timing at which the recording sheet P arrives at a preset position by the processing device 53, and the recording sheet P is processed at the position by the processing device 53. I have.
[0038]
Such a transport system is applied to an image forming apparatus such as a printer or a copying machine. Alternatively, the present invention can be applied to a device or an apparatus for transporting another object to be detected.
[0039]
【The invention's effect】
As described above, according to the optical movement detection device of the present invention, the spot of each light beam from the light emitting means is formed on the object by only one optical path forming means and one optical means. Light reflected from the light spot is focused on the light receiving surface of each light receiving element. For this reason, the number of parts can be reduced, the size can be reduced, and the manufacturing cost can be reduced.
[0040]
In addition, since each received light output is smoothed by a low-pass filter, and each received light output is averaged, the influence of disturbance light noise and signal noise can be almost eliminated. By accurately deriving the relation number, the moving speed of the detected object can be accurately obtained.
[0041]
In addition, since the differential signal of the light receiving output of each light receiving element is obtained and used, the delay time between each light receiving output can be reduced even if the unevenness of the surface of the detection object is small and the change of the light receiving output of each light receiving element is small. With accurate derivation, the moving speed of the detected object can be accurately obtained.
[0042]
On the other hand, according to the transport system of the present invention, the moving speed of the detected object is obtained by the optical movement detection device of the present invention, and the moving speed of the detected object is fed back by feeding back the moving speed of the detected object. The object is controlled or processed at a preset position.
[Brief description of the drawings]
FIG. 1 is a side view showing an embodiment of an optical movement detection device according to the present invention.
FIG. 2 is a diagram showing a configuration of each light emitting element in the device of FIG.
FIG. 3 is a diagram showing another configuration of each light emitting element in the device of FIG.
FIG. 4 is a diagram showing a configuration of each light receiving element in the apparatus of FIG.
FIG. 5 is a diagram showing another configuration of each light receiving element in the apparatus of FIG.
FIG. 6 is a block diagram illustrating a configuration of an arithmetic processing circuit in the device of FIG. 1;
FIG. 7 is a graph showing each light receiving signal in the circuit of FIG. 6;
FIG. 8 is a diagram showing each sample sequence input to a correlation calculator in the circuit of FIG. 6;
FIG. 9 is a diagram illustrating an example of each sample sequence input to a correlation calculator in the circuit of FIG. 6;
FIG. 10 is a diagram showing a modified example of the device of FIG. 1;
FIG. 11 is a view showing another modification of the apparatus shown in FIG. 1;
FIG. 12 is a diagram showing another modified example of the device of FIG. 1;
13A is a graph showing a received light signal including noise, and FIG. 13B is a graph showing a received light signal smoothed by an LPF.
14A is a graph showing a light receiving signal including noise, and FIG. 14B is a graph showing an averaged light receiving signal.
15A is a graph showing a light receiving signal having a small change, and FIG. 15B is a graph showing a differential signal of the light receiving signal.
16A is a graph showing a received light signal including noise and having a small change, and FIG. 16B is a graph showing a differential signal of the received light signal which has been smoothed or averaged.
FIG. 17 is a diagram showing one embodiment of a transport system of the present invention.
FIG. 18 is a view showing another embodiment of the transport system of the present invention.
FIG. 19 is a diagram showing a conventional optical movement detection device.
20 is a diagram showing a configuration of each distance measuring sensor in the apparatus of FIG.
FIGS. 21 (a) and (b) are graphs showing the output of each distance measuring sensor in the apparatus of FIG.
[Explanation of symbols]
11 Optical movement detection device 12, 12a, 12b Light emitting element 13 Collimating lens 14 Beam splitter 15 Objective lens 16 Light receiving lens 17a, 17b Light receiving element 18 Arithmetic processing circuits 31a, 31b IV converters 32a, 32b Signal amplifier 33a, 33b Signal shaping units 34a, 34b Memory 35 Correlation calculating unit 36 Speed calculating unit and display unit 41 Lens 42 Optical component 43 Diffraction grating 51 Transport roller 52 Roller control unit 53 Processing device

Claims (7)

Light emitting means for emitting a pair of light beams,
A pair of light receiving elements for receiving each light beam,
Optical path forming means for forming an optical path for reflecting each light beam from the light emitting means on the object to be detected and guiding the light beam to each light receiving element,
Optical means for condensing each light beam and forming each light spot together on the object to be detected, and condensing the reflected light from each light spot together on the light receiving surface of each light receiving element,
An optical movement detection device that obtains a movement speed of an object based on a light receiving output of each light receiving element. The light-receiving output of each light-receiving element is smoothed by a low-pass filter, a delay time of the other light-receiving output with respect to one light-receiving output is obtained by a correlation calculation for each of the smoothed light-receiving outputs, and the detected time is used by using the delay time. 2. The optical movement detection device according to claim 1, wherein the movement speed of the object is obtained. For each light-receiving element, the light-receiving output is averaged using the other light-receiving outputs before and after, and the correlation calculation for the averaged light-receiving output of each light-receiving element is used to determine the delay time of one light-receiving output to the other light-receiving output, 2. The optical movement detection device according to claim 1, wherein the movement speed of the object is determined using the delay time. The light receiving output of each light receiving element is differentiated, a delay time of the other light receiving output with respect to one light receiving output is obtained by a correlation calculation with respect to the differential signal of each light receiving output, and the movement of the object is determined using the delay time. The optical movement detection device according to claim 1, wherein the speed is obtained. The light-receiving output of each light-receiving element is smoothed by a low-pass filter, the smoothed light-receiving output is differentiated, and the other light-receiving output for one light-receiving output is calculated by a correlation calculation on the smoothed differential signal of each light-receiving output. 2. The optical movement detection device according to claim 1, wherein a delay time of the output is obtained, and the movement speed of the object is obtained using the delay time. The moving speed of the detected object is obtained by the optical movement detecting device according to claim 1, and the moving speed of the detected object is fed back to the conveying means for conveying the detected object, thereby moving the detected object. A transport system characterized by controlling the speed. The moving speed of the detected object is obtained by the optical movement detecting device according to claim 1, and the moving speed of the detected object is fed back to the processing means for processing the detected object, whereby the detected object is previously determined. A transport system characterized by processing at a set position.

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