JP3116086B2 - Object motion measurement method using photodetector - Google Patents
Object motion measurement method using photodetectorInfo
- Publication number
- JP3116086B2 JP3116086B2 JP09344339A JP34433997A JP3116086B2 JP 3116086 B2 JP3116086 B2 JP 3116086B2 JP 09344339 A JP09344339 A JP 09344339A JP 34433997 A JP34433997 A JP 34433997A JP 3116086 B2 JP3116086 B2 JP 3116086B2
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- JP
- Japan
- Prior art keywords
- photodetector
- element photodetector
- correlation
- array element
- single element
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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- Indicating Or Recording The Presence, Absence, Or Direction Of Movement (AREA)
- Image Analysis (AREA)
Description
【０００１】[0001]
【発明の属する技術分野】本発明は光学的に物体の速さ
や方向を求める方法に関するものである。The present invention relates to a method for optically determining the speed and direction of an object.
【０００２】[0002]
【従来の技術】従来、流体等の物体の運動の速度や方向
を測定する手段として、物体の運動をＣＣＤカメラ等の
撮像装置を用いて画像をとり、時間の異なる画面（フレ
ーム）相互の相関をとり、相関のピークの位置から速度
や方向を求める方法が用いられてきている。2. Description of the Related Art Conventionally, as means for measuring the speed and direction of movement of an object such as a fluid, images of the movement of the object are taken using an image pickup device such as a CCD camera, and the correlation between screens (frames) at different times. And a method of obtaining the velocity and direction from the position of the correlation peak has been used.
【０００３】[0003]
【発明が解決しようとする課題】しかしながら、一般の
テレビカメラでは露光時間がフレーム間隔の１／３０秒
とほぼ等しい値になっているので、１／３０秒以内に画
面を通過してしまうような高速の物体は測定できない。
一方、フレーム間隔を定格より短くした特殊な高速撮像
装置もあるが、高速のため画像データの蓄積や処理が大
変なうえに、装置が非常に高価になるという問題を有し
ていた。However, since the exposure time of a general television camera is almost equal to 1/30 second of the frame interval, the exposure time may pass through the screen within 1/30 second. High-speed objects cannot be measured.
On the other hand, there is a special high-speed image pickup apparatus in which the frame interval is shorter than the rated value. However, the high-speed image pickup and processing of image data are difficult, and the apparatus becomes very expensive.
【０００４】[0004]
【課題を解決するための手段】本発明は上記従来の欠点
に鑑み提案されたもので、ＣＣＤカメラ等のアレイ素子
光検出器と単素子光検出器で、ある遅延時間だけ時間を
ずらして、運動物体からの光を各々検出し、両者の光強
度の相関を計算して相関のピークの位置から物体の運動
の速度と方向を求める光検出器を用いた物体の運動測定
方法を提供するものである。SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional drawbacks, and has been proposed in which an array element photodetector such as a CCD camera and a single element photodetector are shifted in time by a certain delay time. Provide a method of measuring the motion of an object using a photodetector that detects light from a moving object, calculates the correlation between the light intensities of the two, and determines the speed and direction of the motion of the object from the position of the peak of the correlation. It is.
【０００５】また、本発明は、上記アレイ素子光検出器
と上記単素子光検出器の出力の相関を求める掛算で、上
記単素子光検出器の信号強度と（ある誤差以内で）等し
い信号強度をもつアレイ型素子光検出器の画素のみを残
し、他の画素の信号強度は０にして演算する光検出器を
用いた物体の運動測定方法を提供するものである。The present invention also provides a signal intensity equal to (within a certain error) the signal intensity of the single element photodetector by multiplying the correlation between the output of the array element photodetector and the output of the single element photodetector. The present invention is to provide a method for measuring the motion of an object using a photodetector which calculates only the pixels of the array-type element photodetector having the above, and sets the signal intensity of the other pixels to 0.
【０００６】[0006]
【発明の実施の形態】以下に本発明の実施形態を図面に
基づいて説明する。尚、簡単のため、本発明の原理は一
次元で説明する（現実には一般に二次元のアレイを用い
て二次元で信号処理を行うことが多い）。Embodiments of the present invention will be described below with reference to the drawings. For simplicity, the principle of the present invention will be described in one dimension (in reality, signal processing is generally performed in two dimensions using a two-dimensional array).
【０００７】従来の方法では、上記したように１台のア
レイ素子光検出器で物体の運動の状態の画像を撮り（図
１で、ビームスプリッタ４と単素子光検出器６は用いな
い）、時間がτだけ異なるｔとｔ＋τでのアレイ素子光
検出器の信号（画像）の相関をとり、相関のピークの位
置から物体の運動の速度を求める。（図２参照）（二次
元の場合、相関のピークの位置から運動の方向も同時に
求まる。）In the conventional method, as described above, an image of the state of motion of an object is taken by one array element photodetector (in FIG. 1, the beam splitter 4 and the single element photodetector 6 are not used). The correlation between the signals (images) of the array element photodetector at t and t + τ where the time differs by τ is obtained, and the speed of the motion of the object is obtained from the position of the correlation peak. (See FIG. 2) (In the case of two dimensions, the direction of the motion is also determined from the position of the correlation peak.)
【０００８】これに対して、本発明ではアレイ素子光検
出器と単素子光検出器を対として用いる（図１参照）。
この際、単素子光検出器の視野はピンホールの大きさで
決定する。ここでは、原理を簡単に説明するためアレイ
素子光検出器の画素のうちの１個相当の空間領域（視
野）で物体を見ることにする。On the other hand, in the present invention, an array element photodetector and a single element photodetector are used as a pair (see FIG. 1).
At this time, the field of view of the single-element photodetector is determined by the size of the pinhole. Here, in order to briefly explain the principle, an object is viewed in a spatial region (field of view) corresponding to one of the pixels of the array element photodetector.
【０００９】この２個の検出器で各々ｔ及びｔ＋τの時
間で光を検出し、両者の信号の掛算を行う。（図３参
照）The two detectors detect light at times t and t + τ, respectively, and multiply both signals. (See Fig. 3)
【００１０】運動物体の各部分からの放射光は一般にラ
ンダムであるので、アレイ素子光検出器で検出された各
画素の光強度はランダムとなる。従って、アレイ素子光
検出器の各素子と単素子光検出器の信号の掛算を複数回
のデータについて行えば相関を求めることができるとい
う原理である。Since the light emitted from each part of the moving object is generally random, the light intensity of each pixel detected by the array element photodetector is random. Therefore, the principle is that the correlation can be obtained by multiplying the data of each element of the array element photodetector and the signal of the single element photodetector for a plurality of times of data.
【００１１】統計的には、アレイ素子光検出器５の画素
数に等しい回数のデータによる掛算が、アレイ素子光検
出器５同志の１回のデータ相関計算に相当する。流体等
のような連続物体に対しては、測定時間が長くとれるの
でその分多くのデータを取得することによってより高精
度に相関を求めることができる。高速で動く物体に対し
ては、アレイ素子光検出器に高速シャッターをつけるな
どして露光時間を十分短くする必要がある。但し、フレ
ーム速度は定格でもかまわない。Statistically, multiplication by data of the number of times equal to the number of pixels of the array element photodetector 5 corresponds to one data correlation calculation between the array element photodetectors 5. For a continuous object such as a fluid or the like, the measurement time can be increased, so that more data can be acquired to obtain a correlation with higher accuracy. For an object that moves at high speed, it is necessary to shorten the exposure time sufficiently by, for example, attaching a high-speed shutter to the array element photodetector. However, the frame speed may be rated.
【００１２】簡単のため、ビームスプリッタ４の透過率
と反射率を等しくしてアレイ素子光検出器と単素子光検
出器には等しい光強度が入射するものとする。また、信
号はランダムと仮定する。ここでも一次元で考え、アレ
イ素子光検出器のｉ番目のフレームのｊ番の画素の信号
強度をＡｉｊ、ｉ番のフレームと同期した単素子光検出
器の強度をＢｉとする。For the sake of simplicity, it is assumed that the transmittance and the reflectance of the beam splitter 4 are equal, and the same light intensity is incident on the array element photodetector and the single element photodetector. Also assume that the signal is random. Again, one-dimensionally considered, let Aij be the signal intensity of the j-th pixel in the i-th frame of the array element photodetector, and Bi be the intensity of the single-element photodetector synchronized with the i-th frame.
【００１３】アレイ素子光検出器の各画素及び単素子光
検出器の信号強度の平均値をＡとし、平均値からのずれ
を各々△Ａｉｊ、△Ｂｉとすると、これらは下記の数式
で表される。Assuming that the average value of the signal intensities of each pixel of the array element photodetector and the single element photodetector is A and the deviations from the average values are △ Aij and △ Bi, respectively, these are expressed by the following equations. You.
【００１４】[0014]
【数１】 (Equation 1)
【００１５】Ｎ回のフレームデータに対する相関の平均
は下記の数式で表される。The average of the correlation for the N-time frame data is expressed by the following equation.
【００１６】[0016]
【数２】 (Equation 2)
【００１７】また、十分大きな回数のデータ（Ｎ→∞）
については下記の数式で表される。In addition, a sufficiently large number of data (N → ∞)
Is represented by the following equation.
【００１８】[0018]
【数３】 (Equation 3)
【００１９】アレイ素子光検出器の画素の強度と単素子
光検出器の強度が等しくない場合と等しい場合に対して
下記の数式のようになる。The following equation is obtained for the case where the intensity of the pixel of the array element photodetector is not equal to the intensity of the single element photodetector.
【００２０】[0020]
【数４】 (Equation 4)
【００２１】各々の場合に対して数式２のＮ回のフレー
ムデータの平均は、下記のようになる。For each case, the average of N frame data in Equation 2 is as follows.
【００２２】[0022]
【数５】 (Equation 5)
【００２３】[0023]
【数６】 (Equation 6)
【００２４】数式５、数式６から、単素子光検出器の強
度と等しい強度の画素の場所に相関のピークが現れる
（平均値に対してσ2 だけ大きくなる）ので、この画素
の位置より運動の速度が決定できる。これが従来の相関
計算法の原理である。例えば、光強度信号が０と１の間
で一様に分布する場合、Ａ2 ＝１／４、σ2 ＝１／１２
となる。From Equations (5) and (6), a correlation peak appears at a pixel location having an intensity equal to that of the single-element photodetector (increases by σ 2 with respect to the average value). Speed can be determined. This is the principle of the conventional correlation calculation method. For example, when the light intensity signal is uniformly distributed between 0 and 1, A 2 = 1/4 and σ 2 = 1/12
Becomes
【００２５】この際、一般にはガウス分布等が多いが、
この場合σの値はずっと小さくなる。At this time, generally, there are many Gaussian distributions and the like.
In this case, the value of σ is much smaller.
【００２６】本発明による相関の計算では、単素子光検
出器の強度と等しいアレイ素子光検出器の画素の値のみ
残し、他の画素の値を０とする。これは、物体が変形せ
ずに検出器の視野を通過するという条件では、単素子光
検出器の見る物体の部分と同じ部分をアレイ素子光検出
器の中の１画素が見ているはずであるので、この画素の
強度は単素子光検出器の強度と等しいので相関がある。
しかし、物体がランダムな形状故に他の部分は等しくな
く相関がない、という原理に基づいている。この場合、
数式５、数式６は下記のようになる。In the calculation of the correlation according to the present invention, only the value of the pixel of the array element photodetector equal to the intensity of the single element photodetector is left, and the values of the other pixels are set to 0. This means that under the condition that the object passes through the field of view of the detector without deformation, one pixel in the array element photodetector should see the same part as the part of the object viewed by the single element photodetector. As such, there is a correlation since the intensity of this pixel is equal to the intensity of the single element photodetector.
However, it is based on the principle that the other parts are unequal and uncorrelated due to the random shape of the object. in this case,
Equations 5 and 6 are as follows.
【００２７】[0027]
【数７】 (Equation 7)
【００２８】[0028]
【数８】 (Equation 8)
【００２９】現実にはアレイ素子光検出器の中の該当す
る１画素以外の画素でもたまたま強度が単素子光検出器
の強度と等しい場合もある（数式７が完全に０にならな
い）が統計的には０に近い値となる。従って相関のピー
クはＡ2 ＋σ2 となり（従来の方法ではσ2 ）、従来の
方法より大きな相関のピークを得ることができる。In reality, the intensity of a pixel other than the corresponding one pixel in the array element photodetector happens to be equal to the intensity of the single element photodetector (Equation 7 is not completely zero). Has a value close to 0. Therefore, the correlation peak is A 2 + σ 2 (σ 2 in the conventional method), and a larger correlation peak than in the conventional method can be obtained.
【００３０】 さらに注目すべきことは、従来の相関計
算法では、相関のピークを十分なコントラストで得るの
には非常に多くのフレーム回数が必要である。例えば、
物体からの光強度がガウス分布とした場合、１０００回
のフレームでもσ 2 はＡ 2 の０．３％程度である。これに
対し、本発明による方法では下記の数式の通りである。It should be further noted that the conventional correlation calculation method requires a very large number of frames to obtain a correlation peak with sufficient contrast. For example,
Assuming that the light intensity from the object has a Gaussian distribution, σ 2 is about 0.3% of A 2 even for 1000 frames. On the other hand, in the method according to the present invention, the following equation is used.
【００３１】[0031]
【数９】 (Equation 9)
【００３２】[0032]
【数１０】 (Equation 10)
【００３３】従って、相関のピーク値は０に対する有限
値となり、理想的な場合１個のフレーム回数（Ｎ＝１）
でも相関のピークが求まり、従来の計算法に比較して著
しく少ないフレーム回数でも求まることになる。Therefore, the peak value of the correlation becomes a finite value with respect to 0, and in an ideal case, the number of times of one frame (N = 1)
However, the peak of the correlation is obtained, and the number of frames can be obtained even with a significantly smaller number of frames compared to the conventional calculation method.
【００３４】ここでは、単素子光検出器側ではアレイ素
子光検出器の１画素相当の視野で物体からの光を検出す
るとして原理を説明した。実際には、測定対象物体の形
状や光学系の理由から複数画素相当の視野（ピンホール
の大きさにより決定する）で測定することもあるが、複
数画素分を１画素と考えれば原理的には変わらない。Here, the principle has been described assuming that the light from the object is detected in the field of view corresponding to one pixel of the array element photodetector on the single element photodetector side. Actually, measurement may be performed in a visual field equivalent to a plurality of pixels (determined by the size of a pinhole) due to the shape of an object to be measured or an optical system. Does not change.
【００３５】現実には、信号には雑音が含まれる。従っ
て単素子光検出器の信号にアレイ素子光検出器の画素の
信号が等しいか否かの判定をする際、等しいと判定する
際の誤差の範囲を設定する必要がある。この場合数式９
が０でなく有限値となり、その分相関のピーク値が小さ
くなるが、雑音があっても、本発明の相関計算方法が有
利なことは変わりない。In reality, the signal contains noise. Therefore, when it is determined whether or not the signal of the pixel of the array element photodetector is equal to the signal of the single element photodetector, it is necessary to set an error range for determining that the signal is equal. In this case, Equation 9
Becomes a finite value instead of 0, and the peak value of the correlation decreases accordingly. However, even if there is noise, the correlation calculation method of the present invention is still advantageous.
【００３６】以上、本発明を図面に記載された実施形態
に基づいて説明したが、本発明は上記した実施形態だけ
ではなく、特許請求の範囲に記載した構成を変更しない
限りどのようにでも実施することができる。As described above, the present invention has been described based on the embodiments described in the drawings. However, the present invention is not limited to the above-described embodiments, but can be implemented in any manner unless the configuration described in the claims is changed. can do.
【００３７】[0037]
【発明の効果】以上要するに、本発明によれば、ＣＣＤ
カメラ等のアレイ素子光検出器とフォトダイオードや光
電子増倍管等の単素子光検出器とを組合せ、ある一定の
時間ずらして（一方に対して他方を遅延させて）運動物
体からの光を検出し、両者の相関を求めて、物体の運動
速度や方向を決定するので、従来に比較して、画像の蓄
積・処理が容易で且つ装置も簡単である。In summary, according to the present invention, the CCD
Combining an array element photodetector such as a camera with a single element photodetector such as a photodiode or a photomultiplier tube, the light from a moving object is shifted by a certain time (one is delayed with respect to the other). Since the detection and the correlation between the two are detected to determine the motion speed and direction of the object, image storage and processing are easier and the device is simpler than in the conventional case.
【００３８】更に本発明では、相関のピークを求める
際、バイナリー的な特殊演算を行うことによって従来 フ
演算方法より著しく演算時間を短縮できることが可能に
なる等、多大な効果を奏する。Further, according to the present invention, when a correlation peak is obtained, a special operation in a binary manner is performed, so that the calculation time can be remarkably reduced as compared with the conventional calculation method.
【図１】本発明の一実施形態における光学系統図であ
る。FIG. 1 is an optical system diagram according to an embodiment of the present invention.
【図２】従来における素子の相関関係を示す概念図であ
る。FIG. 2 is a conceptual diagram showing a correlation between elements in the related art.
【図３】本発明における素子の相関関係を示す概念図で
ある。FIG. 3 is a conceptual diagram showing a correlation between elements in the present invention.
１ 運動物体 ２ 放射光 ３ 集光レンズ又は望遠鏡 ４ ビームスプリッタ ５ アレイ素子光検出器 ６ 単素子光検出器 ７ ピンホール DESCRIPTION OF SYMBOLS 1 Moving object 2 Synchrotron radiation 3 Condensing lens or telescope 4 Beam splitter 5 Array element photodetector 6 Single element photodetector 7 Pinhole
Claims (2)
単素子光検出器で、ある遅延時間だけ時間をずらして、
運動物体からの光を各々検出し、両者の光強度の相関を
計算して相関のピークの位置から物体の運動の速度と方
向を求めることを特徴とする光検出器を用いた物体の運
動測定方法。1. An array element photodetector such as a CCD camera and a single element photodetector are shifted in time by a certain delay time.
Motion measurement of an object using a photodetector, which detects light from a moving object, calculates the correlation between the light intensities of the two, and obtains the speed and direction of the motion of the object from the position of the peak of the correlation. Method.
検出器の出力の相関を求める掛算で、上記単素子光検出
器の信号強度と（ある誤差以内で）等しい信号強度をも
つアレイ型素子光検出器の画素のみを残し、他の画素の
信号強度は０にして演算することを特徴とする請求項１
に記載の光検出器を用いた物体の運動測定方法。2. An array type having a signal strength equal to (within a certain error) the signal strength of the single element photodetector by multiplication for obtaining the correlation between the output of the array element photodetector and the output of the single element photodetector. 2. The arithmetic operation according to claim 1, wherein only the pixels of the element photodetector are left, and the signal intensities of the other pixels are set to 0.
3. A method for measuring the motion of an object using the photodetector according to item 1.
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|---|---|---|---|
| JP09344339A JP3116086B2 (en) | 1997-11-28 | 1997-11-28 | Object motion measurement method using photodetector |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP09344339A JP3116086B2 (en) | 1997-11-28 | 1997-11-28 | Object motion measurement method using photodetector |
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| Publication Number | Publication Date |
|---|---|
| JPH11160336A JPH11160336A (en) | 1999-06-18 |
| JP3116086B2 true JP3116086B2 (en) | 2000-12-11 |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| KR20080089673A (en) * | 2005-01-04 | 2008-10-07 | 미쓰비시덴키 가부시키가이샤 | Mover position/speed detecting device |
-
1997
- 1997-11-28 JP JP09344339A patent/JP3116086B2/en not_active Expired - Lifetime
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| Publication number | Publication date |
|---|---|
| JPH11160336A (en) | 1999-06-18 |
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