JP3586938B2 - In-vehicle distance measuring device - Google Patents

Description

【００４２】
【数２】

【００４３】
式▲２▼では、まず、直線▲２▼と道路とが成す角はα−θｙとなるため、直線▲２▼の傾きはｔａｎ（α−θｙ）となる。このため、直線▲２▼と同じ傾きで原点Ｃを通る直線▲２▼−１について、ｘの値がｋとなる場合のｙの値ａが算出される。このため、直線▲２▼については、式▲２▼で表される。
【００４４】
次いで、原点Ｃを通り撮像面１１と平行な直線▲３▼は次式▲３▼で表される。この直線▲３▼は、図５に示した監視スクリーン４である。
【００４５】
【数３】

【００４６】
直線▲３▼と直線▲１▼とが成す角は（１８０−θｙ）／２となるため、直線▲３▼の傾きは式▲３▼に示す通りとなる。
【００４７】
次いで、図８に示すように、測定対象範囲１を、基準間隔ｂでｎ個に分割する。ここでは、原点から計数してｊ番目のラインと、焦点位置（ｋ，ｈ）とを結ぶ直線▲４▼について説明する。まず、直線▲４▼と平行で原点Ｃを通る直線▲４▼−１は、次式▲４▼−１（４）によって表される。
【００４８】
【数４】

【００４９】
まず、直線▲２▼を表す式▲２▼を用いて測定対象範囲１の長さを表し、これをｎ個に分割すると、基準間隔ｂの長さが表される（式▲４▼−１（１））。さらに、原点Ｃからｊ番目のラインまでの長さｃは式▲４▼−１（２）で定義される。
【００５０】
直線▲４▼の傾きはｈ／（ｃ＋ｋ）で表されるため、▲４▼−１は式▲４▼−１（３）で表される。これを整理すると式▲４▼−１（４）となる。
【００５１】
この式▲４▼−１（４）により、ｘがｋであるときのｙの値ｄを表すことができるため、直線▲４▼は、次式▲４▼で表される。
【００５２】
【数５】

【００５３】
次に、図９に示すように、直線▲３▼と直線▲４▼との交点Ｂの座標を算出する。直線▲３▼と直線▲１▼との交点をＡとすると、長さＡＢと長さＡＣの比率は、監視エリアデータに定義する計算エリアの垂直方向の間隔の比率となる。
【００５４】
各交点ではｙの値が等しいため、連立方程式により各交点の座標を定義すると、まず、交点Ａについては式（５）で表され、交点Ｂについては式（６）で表される。
【００５５】
【数６】

【００５６】
さらに、長さＡＢは式（７）で、長さＡＣは式（８）で表される。
【００５７】
【数７】

【００５８】
計算エリア設定手段１５（垂直方向計算エリア位置設定機能２０）は、上述した各式により垂直方向の計算エリア１４ａの位置を求める。実際には、監視ライン１４ｂの数に応じて基準間隔ｂが定まり、さらに各監視ライン１４ｂ毎に式▲４▼を定義する。次いで、各ライン毎にＡＢとＡＣの比率を求め、この比率で監視ライン１４ｂの位置を求める。
【００５９】
ここでは監視エリアデータに定義される最上部の監視ラインの位置（原点）からの画素数により他の監視ラインの位置が定まるため、監視エリアデータの垂直方向の画素数が２５６［ドット］だとすると、計算エリア設定手段１５は、式（９）により原点からの画素数を求める。
【００６０】
【数８】

【００６１】
このように、計算エリア設定手段１５は、ＣＣＤセンサ１０，１２の設置高さ（ｈ）と、当該ＣＣＤセンサ１０，１２の視野角（θｙ）と、当該撮像手段の俯角（α−θｙ／２）とに基づいて、監視エリアデータに設定する複数の計算エリア１４ａの位置を算出する。本実施形態では、直線▲１▼と道路との交点を原点とした座標で、各直線を定義することにより算出したが、これと異なる手法であってもよい。
【００６２】
例えば、直線▲１▼と直線▲２▼の焦点位置から道路までの長さを求め、この各直線の長さの比率から求めるようにしても良い。
【００６３】
次に、計算エリア設定手段１５による監視ウインドウの設定例を図１０を参照して説明する。ここでは、測距を行う目的に応じて、自車の進行方向に対する左右方向の測定対象範囲の幅を定めている。以下この幅の半分をＷとする。左右方向の測定対象範囲は、車間距離（危険度）の測定であれば自車の進行車線のみが問題となるため、一般的な道路の１車線分の幅とする。また、ＣＣＤセンサ１０，１２など全体の処理能力に応じて、自車が進行している道路の進行方向の幅を測定対象範囲としてもよい。この場合、ナビゲーションシステムや、光ビーコン等による交通情報システムから自車が進行中の道路の幅を取得する。さらに、測定したい障害物の最大の大きさを予め定めておき、この認識対象とする最大の大きさの障害物から測定対象範囲を定めるようにしてもよい。
【００６４】
図１０に示す例では、ＣＣＤセンサ１０，１２の水平視野角をθｘとする。さらに、ＣＣＤセンサ１０，１２の中心から、撮像対象範囲２Ｗへの複数の直線を各監視ウインドウ１４ｃに対応する直線とする。ｘ座標はＣＣＤセンサ１０，１２の撮像方向の位置を示し、ｙ座標は撮像方向を前方とした時の左右方向の位置を示す。ＣＣＤセンサ１０，１２の視野角θｘに従って定まる監視ライン１４ｂの端部に対応した直線を直線（１０）とする。これを１番目の直線とし、道路上で自車の進行方向に基準間隔ｂの間隔を有する次の直線を、直線（１１）とする。このように、図８に示した場合と同様に、監視ウインドウ１４ｃの数に応じたｎ個の直線を考える。また、直線（１０）をｉ番目の直線とすると、直線（１１）はｉ＋１番目のとなる。まず、直線（１１）を定義すべく、直線（１０）と測定対象範囲２Ｗの外側との交点を考え、ｘ軸に直交して当該交点を含む直線をここでは仮にｙ軸とする。このｙ軸とｘ軸との交点を点Ｅとする。
【００６５】
直線（１１）は、ｉ番目のラインと測定対象範囲外側との交点と、焦点位置とを結ぶ直線である。まず、直線（１１）を２番目の直線として説明する。
【００６６】
直線（１０）は、次式（１０）で表される。
【００６７】
【数９】

【００６８】
従って、図１１に示すように、ＣＣＤカメラ１０，１２の中心から点Ｅまでのまでの距離が表わされる。さらに、直線（１１）が２番目の直線であれば点Ｅから図示する点Ｆまでの距離は距離ｂで表わされ、直線（１１）がｉ番目であれば距離ｉｂで示される。このように定義すると、図１１に示すように、直線（１１）の傾きはＷｉを用いずに表され、さらに、ｉ番目の直線（１１）は次式（１１）で表される。
【００６９】
【数１０】

【００７０】
式（１１）においてｘの値が０のときのｙの値（Ｗｉ）は、次式（１２）で表される。ｉ番目の各直線についてＷｉを求めると、各監視ウインドウ１４ｂの比率が算出される。
【００７１】
従って、監視エリアデータの水平方向の画素数が５１２［ドット］だとすると、ｉ番目のウインドウ位置は次式（１３）で求めることができる。
【００７２】
【数１２】

【００７３】
このように計算エリア設定手段１５（水平方向計算エリア位置設定機能）は、計算エリア１４ａの水平方向の位置を実空間での幅に応じて設定する。
【００７４】
図７乃至図１０を参照して説明した手法により計算エリアの位置を設定すると、図１２に示す如くとなる。この図１２示す例では、監視エリアデータの上部では監視ラインの間隔が狭く、一方、下端に近づくほど間隔が広くなる。このため、遠方の障害物は詳細な精度で測距を行うことができ、さらに、接近した障害物は大きい計算エリアで測距を行うため、接近して大きく撮像されていてもそのエッジを良好に得ることができる。このような計算エリアの設定は、左右のＣＣＤセンサ１０，１２から出力される監視エリアデータに対して同様の位置に設定される。
【００７５】
次に、測距結果のチェック手法について説明する。図１２に示した計算エリア１４ａの設定の手法では、監視ライン１４ｂ毎に撮像される実空間での道路上への距離が判明している。即ち、図８に示すｉ番目のラインと道路との交点が実空間でＣＣＤセンサ１０，１２から何［ｍ］であるかは高さｈの値などから算出される。障害物は必ず高さがあるため、実際の測距結果は、この監視ラインによって定まる道路面での距離よりも短いはずである。
【００７６】
このため、距離算出手段１８には、計算エリア１４ａ毎に定まるＣＣＤセンサの設置位置から当該計算エリアで撮像される道路の位置までの長さ情報に基づいて、当該距離算出手段１８による各計算エリア１４ａでの測距結果が長さ情報による長さよりも長い場合には、当該計算エリアでの測距結果をエラーとするエラー処理部１９が併設されている。
【００７７】
エラー処理部１９は、ノイズ等により測距が正確に行われなかった場合を有効に捕捉し、さらに、カメラの俯角などが左右でずれている場合などを発見することができる。
【００７８】
次に、距離が測定された障害物の実空間での高さを算出する手法を説明する。ここでは、距離算出手段１８は、計算エリア毎に定まる各測距結果に基づいて当該障害物の実空間での高さを算出する障害物高さ算出機能を備えている。障害物高さ算出機能は、上述した式▲４▼と、測距結果とにより当該障害物の高さを各計算エリア毎に算出する。
【００７９】
図１３は障害物の高さを算出する場合の座標を示す説明図である。図３では、高さをｚ座標とし、図７及び図１０に示したＣＣＤセンサの撮像方向をｘ座標、図１０に示した撮像方向に直交する方向をｙ座標とした。ここでは、図１２に示したｉ番目の監視ウインドウで、ｊ番目のラインで障害物をとらえ、測定値がＸ。である場合を例に説明する。このとき、ＣＣＤセンサ１０，１２が、その位置（ｋ，０，ｈ）から測定値Ｘの負の方向に向いているとすると、障害物のｘ座標は−Ｘとなる。もちろん、ｘ座標を式▲４▼から正確に算出してもよい。さらに、このＸを式▲４▼に代入したときのｙの値がｚ座標となる。これにより、当該障害物の実空間での位置が判明する。
【００８０】
さらに、測定値Ｘを式（１１）に代入したときのｙの値が図１３に示すｙ座標となる。従って、ｉ番目の監視ウインドウ、ｊ番目のラインで距離が測定された障害物の実座標は、次式（１４）で示される。このように、各計算エリア毎にその障害物の高さが判明すると、障害物の概略形状を実空間での座標として得ることができる。従って、この概略形状情報は、その障害物が何であるのかの判断材料として利用することができる。
【００８１】
【数１３】

【００８２】
次に、本実施形態による車載用距離測定装置を用いた車間距離警報装置について説明する。車間距離警報装置は、前方の車両を認識し、次いで、自車位置から認識した車両までの距離を算出し、さらに、自車の走行状態や前方車両までの距離に基づいて、自車の進行方向の危険度を判定して警報などの外部表示を行うものである。
【００８３】
図１４は車間距離警報装置の構成を示すブロック図である。車間距離警報装置は、２つのＣＣＤセンサ１０，１２と、上述した計算エリアを用いた障害物認識処理を行う制御手段３０（信号処理ＢＯＸ）とを備えている。
【００８４】
さらに、制御手段３０には、自車のハンドル舵角を捕捉して制御手段３０に出力するハンドル舵角センサ３８と、自車のブレーキの状態を捕捉して制御手段３０に出力するブレーキセンサ４０とを備えている。また、車速センサや、ウインカ信号を捕捉するセンサ等を併設するようにしても良い。
【００８５】
制御手段３０は、障害物の測距結果と、自車両の走行状態とに基づいて、当該障害物との車間距離について警報を行う。制御手段３０は、例えば、一定の距離以下で、ブレーキングしていなければ警報する等の判断を行う。
【００８６】
また、制御手段３０には、警報の出力を行うスピーカ３２と、警報のメッセージ等を出力する表示部３４と、各種設定が入力される入力部３６とが併設されている。
【００８７】
車間距離警報装置では、まず、ＣＣＤセンサ１０，１２からの監視エリアデータに基づいて、各計算エリア毎に測距を行う。この測距により障害物が発見された場合、ハンドル舵角センサ３８やブレーキセンサ４０からの出力に基づいて、車間距離の警報を行うか否かの判定を行う。
【００８８】
【発明の効果】
本発明は以上のように構成され機能するので、これによると、計算エリア設定手段が、計算エリアの垂直方向の位置を等間隔にではなく上側を狭い間隔で、下側を広い間隔で設定し、計算エリアデータ抽出手段は、遠い障害物については細かい間隔で、接近した障害物については粗い間隔で計算エリアデータを抽出するため、計算エリアデータには、対象物との距離にかかわらず一定の大きさの障害物のエッジ部分が撮像され、このため、距離算出手段は、測定対象範囲内にある障害物について満遍なく測距することができ、従って、画像処理の精度を上げることなく測距を詳細に行うことができる。このように、対象物との距離にかかわらず一定の精度で距離の測定を行うことのできる従来にない優れた車載用距離測定装置を提供することができる。
【図面の簡単な説明】
【図１】本発明の実施の形態の構成を示すブロック図である。
【図２】図１に示した計算エリア設定手段の構成を示すブロック図である。
【図３】図１に示したＣＣＤセンサにより撮像された画像データ（監視エリアデータ）に定義される計算エリアの一例を示す説明図で、図３（Ａ）は第１のＣＣＤセンサによる監視エリアデータを示す図で、図３（Ｂ）は第２のＣＣＤセンサによる監視エリアデータの一例を示す図である。
【図４】図１に示した比較手段の処理例を説明するための説明図で、図４（Ａ）は第１のＣＣＤセンサによる計算エリアデータの一例を示す図で、図４（Ｂ）は第２のＣＣＤセンサによる計算エリアデータの一例を示す図で、図４（Ｃ）は比較データの一例を示す図である。
【図５】測定対象範囲と計算エリアの位置とを側面から見た場合の関係を示す説明図である。
【図６】測定対象範囲と計算エリアの位置とを上面から見た場合の関係を示す説明図である。
【図７】計算エリアの垂直方向の位置を算出する処理を説明するための第１の説明図である。
【図８】監視エリウの垂直方向の位置を算出する処理を説明するための第２の説明図である。
【図９】計算エリアの垂直方向の位置を算出する処理を説明するための第３の説明図である。
【図１０】計算エリアの水平方向の位置を算出する処理を説明するための第１の説明図である。
【図１１】計算エリアの水平方向の位置を算出する処理を説明するための第２の説明図である。
【図１２】図１に示した計算エリア設定手段により計算エリアが設定された監視エリアデータの一例を示す説明図である。
【図１３】図１に示した距離算出手段により障害物の高さを算出する場合の座標を示す説明図である。
【図１４】図１に示した車載用距離測定装置を用いた車間距離警報装置の構成を示すブロック図である。
【符号の説明】
１０ 第１のＣＣＤセンサ（撮像手段）
１２ 第２のＣＣＤセンサ（撮像手段）
１４ 計算エリアデータ抽出手段
１５ 計算エリア設定手段
１６ 比較手段
１８ 距離算出手段
２０ 垂直方向計算エリア位置設定機能
２２ 水平方向計算エリア位置設定機能
【数１１】

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an in-vehicle distance measurement device, and more particularly to an in-vehicle distance measurement device that measures a distance to an obstacle in front of a host vehicle using a plurality of calculation areas set in image data.
[0002]
The in-vehicle distance measurement device is used for an in-vehicle rear-end collision warning device and an inter-vehicle distance sensor. In addition to automobiles, mobile objects can be used in general transportation equipment such as motorcycles and ships.
[0003]
[Prior art]
Conventionally, various types of rear-end collision warning devices and inter-vehicle distance sensors have been proposed.
[0004]
For example, there is a method in which stereo image processing is performed and matching is performed with 9 × 9 pixels for 480 × 512 pixels on the left and right sides. In addition, a dedicated ECU performs white line detection processing on the image captured by the imaging unit, and determines the target range by extracting the two right and left contours of the lane in which the vehicle is traveling. There is a method of detecting a hologram with a scanning laser radar.
[0005]
In this example, the white line recognition process recognizes the white line by performing a spatial differentiation process on the captured image to emphasize the edge of the gradation difference, and then extracting an outline.
[0006]
As a method of recognizing an image in front of the own vehicle by image processing, an edge portion having a large vertical gradation difference (luminance difference) is extracted from a captured image, and this is binarized and labeled. And performs recognition of a vehicle traveling ahead of the own vehicle from the characteristics of the label after the processing.
[0007]
Further, there has been proposed a method of dividing a captured image into a plurality of calculation areas and recognizing a vehicle ahead of a host vehicle based on a measurement result of each calculation area.
[0008]
[Problems to be solved by the invention]
However, in the method of recognizing the preceding vehicle using the plurality of calculation areas, a portion far in the imaging direction is roughly captured, so that it is necessary to reduce the calculation area in order to increase the accuracy of the distance measurement target. However, when the number of monitoring lines and the number of monitoring windows are increased, an extra processing time is required, and it is difficult to measure a distance in real time. As described above, in the method of measuring the distance to the vehicle in front using the plurality of calculation areas, there is an inconvenience that the improvement in recognition accuracy has a certain limit.
[0009]
[Object of the invention]
The present invention improves the inconvenience of the conventional example, and particularly, in a method of measuring the distance to the target object for each of a plurality of calculation areas in the image data, the distance with a constant accuracy regardless of the distance to the target object. It is an object of the present invention to provide an in-vehicle distance measuring device capable of measuring the distance.
[0010]
[Means for Solving the Problems]
Therefore, in the present invention, as first means, two image pickup means for picking up an image in front of the own vehicle, and a calculation for setting a plurality of calculation areas for image data (monitoring area data) picked up by these image pickup means. Area setting means, calculation area data extraction means for extracting image data of a plurality of calculation area portions set by the calculation area setting means, and calculation area data extracted by the calculation area data extraction means for each calculation area A comparison unit is provided for comparison, and a distance calculation unit for calculating a distance from the target obstacle for each comparison data based on the comparison data extracted by the comparison unit.
In addition, the calculation area setting unit sets the vertical interval of the calculation area between the upper end and the lower end of the measurement target range of the image data at intervals that are equal in the imaging direction in the real space where the image is captured by the imaging unit. A vertical calculation area position setting function (first area setting function) to be set is provided.
[0011]
In the first means, the calculation area setting means sets the vertical position of the calculation area not at regular intervals but at a narrow interval on the upper side and at a wide interval on the lower side. Therefore, the position at which the calculation area data is extracted is small for obstacles that are far away, and coarse for obstacles that approach it. For this reason, distance measurement is performed in accordance with the size at which the obstacle is imaged.
[0012]
As a second means, in addition to the items that specify the first means, the calculation area setting means sets the measurement area of the image data at intervals that are equal in the imaging direction in the real space imaged by the imaging means. A horizontal calculation area position setting function (second area setting function) for setting a horizontal interval of the calculation area between the left end and the right end is provided.
[0013]
As a third means, in addition to the items for specifying the first means, the calculation area setting means includes a setting height (h) of the imaging means, a viewing angle (θ) of the imaging means, and a depression angle of the imaging means. A function of calculating the position of the calculation area of the image data based on (α−θ / 2) is provided.
[0014]
As a fourth means, in addition to the matters specifying the third means, the distance calculating means is configured to provide the distance calculating means based on length information from the installation position of the imaging means determined for each calculation area to the position of the road imaged in the calculation area. If a distance measurement result in each calculation area by the distance calculation means is longer than the length information, an error processing unit which sets an error in the distance measurement result in the calculation area is provided.
[0015]
As a fifth means, in addition to the matters specifying the third means, the obstacle calculating means calculates the height of the obstacle in the real space based on each distance measurement result determined for each calculation area. It has a function to calculate the length.
[0016]
The present invention intends to achieve the above-mentioned object by each of these means.
[0017]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a vehicle-mounted distance measuring device according to the present invention. The in-vehicle distance measuring device includes two image capturing means (CCD sensors) 10 and 12 for capturing an image of the front of the vehicle and a plurality of calculations for image data (monitoring area data) captured by the CCD sensors 10 and 12. Calculation area setting means 15 for setting an area, calculation area data extraction means 14 for extracting image data of a plurality of calculation area parts set by the calculation area setting means 15, and calculation area data extraction means 14 Comparing means 16 for comparing the calculated calculation area data for each calculation area, and distance calculating means 18 for calculating the distance to the target obstacle for each comparison data based on the comparison data extracted by the comparison means 16. ing.
[0018]
The CCD cameras 10 and 12 as the imaging means include a first CCD camera 10 installed on the left side of the own vehicle and a second CCD camera 12 installed on the right side of the own vehicle. The two CCD cameras 10 and 12 are installed at positions separated by 70 [mm].
[0019]
As shown in FIG. 2, the calculation area setting unit 15 sets the distance between the upper end and the lower end of the measurement target range of the image data at intervals that are equal in the imaging direction in the real space where the images are captured by the CCD sensors 10 and 12. Is provided with a vertical calculation area position setting function 20 for setting a vertical interval between the calculation areas.
[0020]
Further, the calculation area setting means 15 similarly sets a horizontal interval of the calculation area between the left end and the right end in the measurement target range of the image data at intervals that are equally spaced in the imaging direction in the real space. A direction calculation area position setting function 22 is provided.
[0021]
This will be described in detail.
[0022]
In the present embodiment, the distance to an obstacle (e.g., a vehicle running ahead) in front of the host vehicle is measured using a multi-stage remote sensor. FIGS. 3 and 4 illustrate the principle of distance measurement using the multi-stage remote sensor. FIG.
[0023]
FIG. 3 is a diagram showing an example of image data (monitoring area data) from the first and second CCD sensors 10 and 12. Here, data captured by each CCD sensor is referred to as image data, and data corresponding to the measurement target range 1 in the image data is referred to as monitoring area data. The calculation area data extraction means 14 extracts calculation area data from each of the monitoring area data. In the example shown in FIG. 3, five monitoring lines 14b and five monitoring windows 14c for each monitoring line 14b are provided at regular intervals on the monitoring area data with respect to the monitoring area data 10a imaged by the first CCD sensor. Provided.
[0024]
Here, one monitoring window 14c of each monitoring line 14b is a calculation area 14a. In the example shown in FIG. 3, since the setting by the calculation area setting means 15 is not performed, the 25 calculation areas 14a are positioned at equal intervals on the monitoring area data.
[0025]
The calculation area data extraction means 14 extracts calculation area data from the monitoring area data for each calculation area. Here, since the image data is monochrome data of a plurality of gradations (luminance), the calculation area data is luminance data as shown in FIGS. 4A and 4B. Further, the difference of the hue of the color data may be compared.
[0026]
When the edge of the target object is imaged in the calculation area 14a, as shown in FIG. 4, the calculation area data differs depending on the installation positions of the CCD sensors 10 and 12.
[0027]
As shown in FIG. 4 (C), the comparing means 16 compares the calculated area data by the first CCD sensor 10 with the calculated area data by the second CCD sensor 12 for the corresponding calculation area 14a at the same position. I do. For example, by comparing the positions where the luminance becomes the maximum value, comparison data 16a as shown in FIG. 4C can be obtained for each calculation area.
[0028]
The distance calculation means 18 calculates the distance to the object based on the principle of triangulation based on the comparison data 16 shown in FIG. The same number of distance measurement results as the number of calculation areas in which the object is imaged is obtained.
[0029]
In the setting of the monitoring line and the monitoring window shown in FIG. 3, the distance is coarse for a distant object, and fine enough that an edge is not extracted well for a nearby object. In this embodiment, the calculation area data extracting means 14 is provided with a calculation area setting means 15 in order to solve this inconvenience.
[0030]
FIG. 5 is a side view showing the positional relationship at the time of measurement. The imaging range 2 for the road 5 is uniquely determined by the depression angles, the viewing angles, and the installation heights of the CCD sensors 10 and 12. Of the calculation area 14a defined in the monitoring area data, the area between the upper end and the lower end is the measurement target range 1 on the road.
[0031]
When this measurement target range 1 is divided at equal intervals in the imaging direction, the result is as shown in FIG. In the illustrated example, the image is divided into four places by five lines arranged at the reference interval 3. The intervals between the lines according to the reference interval in the measurement target range 1 are not equal on the imaging surfaces of the CCD sensors 10 and 12.
[0032]
Assuming that the monitoring screen 4 parallel to the imaging planes of the CCD sensors 10 and 12 is as shown in FIG. 5, on the monitoring screen 4, as shown in FIG.
[0033]
For this reason, if the calculation areas defined in the monitoring area data are set at equal intervals on the monitoring area data, it will be coarse for obstacles with a long measurement distance, while it will be coarse for obstacles with a short measurement distance. Is too fine.
[0034]
Such a relationship also occurs in the horizontal direction. FIG. 6 is a plan view showing a positional relationship at the time of measurement. FIG. 6 shows the state at the time of measurement, as viewed from directly above (right half). On the monitoring screen 4, the window positions are symmetrical and narrower toward the center of the window interval.
[0035]
The calculation area setting means 15 sets vertical and horizontal intervals of the calculation area 14a defined in the monitoring area data. That is, the calculation area 14a is set at the interval ratio on the monitoring screen 4 shown in FIGS. Hereinafter, an example of a calculation method of the interval ratio on the monitoring screen 4 by the calculation area setting means 15 will be described.
[0036]
7 to 9 are explanatory diagrams for explaining the process of calculating the vertical interval of the calculation area 14a by the calculation area setting means 15.
[0037]
As shown in FIG. 7, the viewing angle of the CCD sensors 10 and 12 is represented by θy, and the height of the CCD sensors 10 and 12 at the focal position is represented by h. Here, the viewing angle θy does not correspond to the maximum range of imaging but corresponds to the measurement target range 1 shown in FIG.
[0038]
Further, the intersection point of the straight line (1) passing through the position closest to the CCD sensors 10 and 12 and the focus position with respect to the road in the measurement target range 1 on the road is defined as the origin C. The angle between the road and the straight line {circle around (1)} is α. The depression angle of the CCD sensors 10 and 12 is α-θy / 2 [degrees]. The straight line {circle around (2)} is a straight line passing through the position farthest from the CCD sensors 10 and 12 in the measurement target range 1 on the road and the focal position.
[0039]
According to the definition shown in FIG. 7, the coordinates of the focal positions of the CCD sensors 10 and 12 are (k, h). Although this is simply shown here for the sake of explanation, an inverted image is actually projected on the imaging surface 11.
[0040]
In the coordinates shown in FIG. 7, the straight line (1) is represented by the following equation (1), and the straight line (2) is represented by the following equation (2).
[0041]
(Equation 1)

[0042]
(Equation 2)

[0043]
In the formula (2), first, the angle formed by the straight line (2) and the road is α-θy, and the inclination of the straight line (2) is tan (α-θy). For this reason, the value a of y when the value of x is k is calculated for the straight line {circle around (2)}-1 passing through the origin C with the same inclination as the straight line {circle around (2)}. Therefore, the straight line (2) is represented by the formula (2).
[0044]
Next, a straight line (3) passing through the origin C and parallel to the imaging surface 11 is expressed by the following equation (3). This straight line {circle around (3)} is the monitoring screen 4 shown in FIG.
[0045]
(Equation 3)

[0046]
Since the angle formed by the straight line (3) and the straight line (1) is (180−θy) / 2, the inclination of the straight line (3) is as shown in the equation (3).
[0047]
Next, as shown in FIG. 8, the measurement target range 1 is divided into n pieces at a reference interval b. Here, a straight line (4) connecting the j-th line counted from the origin and the focal position (k, h) will be described. First, a straight line (4) -1 parallel to the straight line (4) and passing through the origin C is represented by the following equation (4) -1 (4).
[0048]
(Equation 4)

[0049]
First, the length of the measurement target range 1 is expressed by using the equation (2) representing the straight line (2), and when this is divided into n pieces, the length of the reference interval b is expressed (equation (4) -1) (1)). Further, the length c from the origin C to the j-th line is defined by Expression (4) -1 (2).
[0050]
Since the slope of the straight line (4) is represented by h / (c + k), (4) -1 is represented by the formula (4) -1 (3). When this is rearranged, Equation (4) -1 (4) is obtained.
[0051]
Since the value d of y when x is k can be represented by the equation (4) -1 (4), the straight line (4) is represented by the following equation (4).
[0052]
(Equation 5)

[0053]
Next, as shown in FIG. 9, the coordinates of the intersection B between the straight line (3) and the straight line (4) are calculated. Assuming that the intersection of the straight line (3) and the straight line (1) is A, the ratio between the length AB and the length AC is the ratio of the vertical interval of the calculation area defined in the monitoring area data.
[0054]
Since the value of y is equal at each intersection, if the coordinates of each intersection are defined by simultaneous equations, first, the intersection A is expressed by Expression (5), and the intersection B is expressed by Expression (6).
[0055]
(Equation 6)

[0056]
Further, the length AB is expressed by Expression (7), and the length AC is expressed by Expression (8).
[0057]
(Equation 7)

[0058]
The calculation area setting means 15 (vertical direction calculation area position setting function 20) obtains the position of the calculation area 14a in the vertical direction according to the above-described equations. Actually, the reference interval b is determined according to the number of the monitoring lines 14b, and the equation (4) is defined for each monitoring line 14b. Next, the ratio between AB and AC is determined for each line, and the position of the monitoring line 14b is determined based on this ratio.
[0059]
Here, the position of another monitoring line is determined by the number of pixels from the position (origin) of the uppermost monitoring line defined in the monitoring area data. Therefore, if the number of pixels in the monitoring area data in the vertical direction is 256 [dots], The calculation area setting means 15 obtains the number of pixels from the origin by using equation (9).
[0060]
(Equation 8)

[0061]
As described above, the calculation area setting unit 15 determines the installation height (h) of the CCD sensors 10 and 12, the viewing angle (θy) of the CCD sensors 10 and 12, and the depression angle (α−θy / 2) of the imaging unit. ), The positions of the plurality of calculation areas 14a set in the monitoring area data are calculated. In the present embodiment, the calculation is performed by defining each straight line with coordinates having the origin at the intersection of the straight line (1) and the road. However, a different method may be used.
[0062]
For example, the length from the focal position of the straight line (1) to the road from the focal point of the straight line (2) may be obtained, and the length may be obtained from the ratio of the length of each straight line.
[0063]
Next, an example of setting a monitoring window by the calculation area setting means 15 will be described with reference to FIG. Here, the width of the measurement target range in the left-right direction with respect to the traveling direction of the own vehicle is determined according to the purpose of performing the distance measurement. Hereinafter, half of this width is W. The measurement range in the left-right direction is the width of one lane of a general road because only the traveling lane of the own vehicle is a problem when measuring the inter-vehicle distance (risk). Further, the width in the traveling direction of the road on which the vehicle is traveling may be set as the measurement target range according to the overall processing capability of the CCD sensors 10 and 12 and the like. In this case, the width of the road on which the vehicle is traveling is acquired from a navigation system or a traffic information system such as an optical beacon. Furthermore, the maximum size of the obstacle to be measured may be determined in advance, and the measurement target range may be determined from the maximum size obstacle to be recognized.
[0064]
In the example shown in FIG. 10, the horizontal viewing angles of the CCD sensors 10 and 12 are set to θx. Further, a plurality of straight lines from the centers of the CCD sensors 10 and 12 to the imaging target range 2W are set as straight lines corresponding to the respective monitoring windows 14c. The x-coordinate indicates the position of the CCD sensors 10 and 12 in the imaging direction, and the y-coordinate indicates the position in the left-right direction when the imaging direction is forward. A straight line corresponding to the end of the monitoring line 14b determined according to the viewing angle θx of the CCD sensors 10 and 12 is defined as a straight line (10). This is defined as a first straight line, and the next straight line having a reference interval b in the traveling direction of the vehicle on the road is defined as a straight line (11). Thus, as in the case shown in FIG. 8, n straight lines corresponding to the number of monitoring windows 14c are considered. If the straight line (10) is the i-th straight line, the straight line (11) is the (i + 1) -th straight line. First, in order to define the straight line (11), an intersection between the straight line (10) and the outside of the measurement target range 2W is considered, and a straight line orthogonal to the x-axis and including the intersection is temporarily set as the y-axis. The point of intersection between the y axis and the x axis is point E.
[0065]
The straight line (11) is a straight line connecting the intersection between the i-th line and the outside of the measurement target range and the focal position. First, the straight line (11) will be described as a second straight line.
[0066]
The straight line (10) is represented by the following equation (10).
[0067]
(Equation 9)

[0068]
Therefore, as shown in FIG. 11, the distance from the center of the CCD cameras 10 and 12 to the point E is represented. Further, if the straight line (11) is the second straight line, the distance from the point E to the illustrated point F is represented by the distance b, and if the straight line (11) is the i-th straight line, it is represented by the distance ib. With this definition, as shown in FIG. 11, the slope of the straight line (11) is expressed without using Wi, and the i-th straight line (11) is expressed by the following equation (11).
[0069]
(Equation 10)

[0070]
In Expression (11), the value of y (Wi) when the value of x is 0 is expressed by the following Expression (12). When Wi is obtained for each i-th straight line, the ratio of each monitoring window 14b is calculated.
[0071]
Therefore, if the number of pixels in the horizontal direction of the monitoring area data is 512 [dots], the i-th window position can be obtained by the following equation (13).
[0072]
(Equation 12)

[0073]
Thus, the calculation area setting means 15 (horizontal calculation area position setting function) sets the horizontal position of the calculation area 14a according to the width in the real space.
[0074]
When the position of the calculation area is set by the method described with reference to FIGS. 7 to 10, the result is as shown in FIG. In the example shown in FIG. 12, the interval between the monitoring lines is narrow at the upper part of the monitoring area data, while the interval becomes wider as approaching the lower end. For this reason, it is possible to measure the distance of a distant obstacle with detailed accuracy, and to measure the distance of an approaching obstacle in a large calculation area. Can be obtained. Such a calculation area is set at the same position with respect to the monitoring area data output from the left and right CCD sensors 10 and 12.
[0075]
Next, a method of checking the result of distance measurement will be described. In the method of setting the calculation area 14a shown in FIG. 12, the distance to the road in the real space imaged for each monitoring line 14b is known. That is, what [m] the intersection of the i-th line and the road shown in FIG. 8 is in the real space from the CCD sensors 10 and 12 is calculated from the value of the height h and the like. Since the obstacle always has a height, the actual distance measurement result should be shorter than the distance on the road surface determined by the monitoring line.
[0076]
For this reason, the distance calculation unit 18 calculates each calculation area by the distance calculation unit 18 based on the length information from the installation position of the CCD sensor determined for each calculation area 14a to the position of the road imaged in the calculation area. If the distance measurement result at 14a is longer than the length based on the length information, an error processing unit 19 that sets the distance measurement result at the calculation area as an error is provided.
[0077]
The error processing unit 19 can effectively capture a case where the distance measurement is not accurately performed due to noise or the like, and can further detect a case where the depression angle of the camera is shifted from side to side.
[0078]
Next, a method of calculating the height in the real space of the obstacle whose distance has been measured will be described. Here, the distance calculation means 18 has an obstacle height calculation function of calculating the height of the obstacle in the real space based on each distance measurement result determined for each calculation area. The obstacle height calculation function calculates the height of the obstacle for each calculation area based on the above formula (4) and the distance measurement result.
[0079]
FIG. 13 is an explanatory diagram showing coordinates when the height of an obstacle is calculated. In FIG. 3, the height is defined as the z coordinate, the imaging direction of the CCD sensor illustrated in FIGS. 7 and 10 is defined as the x coordinate, and the direction orthogonal to the imaging direction illustrated in FIG. 10 is defined as the y coordinate. Here, in the i-th monitoring window shown in FIG. 12, an obstacle is caught on the j-th line, and the measured value is X. An example will be described. At this time, if the CCD sensors 10 and 12 are oriented in the negative direction of the measured value X from the position (k, 0, h), the x coordinate of the obstacle is -X. Of course, the x coordinate may be accurately calculated from equation (4). Furthermore, the value of y when this X is substituted into equation (4) becomes the z coordinate. Thus, the position of the obstacle in the real space is determined.
[0080]
Further, the value of y when the measured value X is substituted into the equation (11) becomes the y coordinate shown in FIG. Accordingly, the actual coordinates of the obstacle whose distance is measured in the i-th monitoring window and the j-th line are expressed by the following equation (14). As described above, when the height of the obstacle is determined for each calculation area, the approximate shape of the obstacle can be obtained as coordinates in the real space. Therefore, the rough shape information can be used as a material for determining what the obstacle is.
[0081]
(Equation 13)

[0082]
Next, an inter-vehicle distance alarm device using the in-vehicle distance measurement device according to the present embodiment will be described. The inter-vehicle distance warning device recognizes a vehicle ahead, calculates a distance from the own vehicle position to the recognized vehicle, and further, based on a traveling state of the own vehicle and a distance to the preceding vehicle, advances the own vehicle. The danger degree in the direction is determined, and an external display such as an alarm is performed.
[0083]
FIG. 14 is a block diagram showing a configuration of the inter-vehicle distance warning device. The inter-vehicle distance warning device includes two CCD sensors 10 and 12 and a control unit 30 (signal processing BOX) that performs an obstacle recognition process using the above-described calculation area.
[0084]
Further, the control means 30 includes a steering angle sensor 38 which captures the steering angle of the steering wheel of the own vehicle and outputs it to the control means 30, and a brake sensor 40 which captures the state of the brake of the own vehicle and outputs it to the control means 30. And Further, a vehicle speed sensor, a sensor for capturing a turn signal, or the like may be provided in addition.
[0085]
The control unit 30 issues a warning about the inter-vehicle distance to the obstacle based on the distance measurement result of the obstacle and the traveling state of the own vehicle. The control means 30 makes a determination such as issuing an alarm if braking is not performed within a certain distance or less, for example.
[0086]
The control means 30 is provided with a speaker 32 for outputting an alarm, a display unit 34 for outputting an alarm message and the like, and an input unit 36 for inputting various settings.
[0087]
In the inter-vehicle distance warning device, first, distance measurement is performed for each calculation area based on monitoring area data from the CCD sensors 10 and 12. When an obstacle is found by this distance measurement, it is determined whether or not to issue an inter-vehicle distance warning based on outputs from the steering wheel angle sensor 38 and the brake sensor 40.
[0088]
【The invention's effect】
Since the present invention is configured and functions as described above, according to this, the calculation area setting means sets the vertical position of the calculation area not at regular intervals but at a narrow interval at the upper side and at a wide interval at the lower side. The calculation area data extraction means extracts calculation area data at fine intervals for distant obstacles and coarse intervals for approaching obstacles.Therefore, calculation area data has a constant value regardless of the distance to the target. An edge portion of an obstacle having a size is imaged, so that the distance calculating means can measure the distance evenly for the obstacle within the measurement target range, and thus can perform the distance measurement without increasing the accuracy of the image processing. Can be done in detail. As described above, it is possible to provide an unprecedented excellent in-vehicle distance measuring device capable of measuring a distance with a constant accuracy regardless of the distance to an object.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.
FIG. 2 is a block diagram showing a configuration of a calculation area setting unit shown in FIG.
FIG. 3 is an explanatory diagram showing an example of a calculation area defined in image data (monitoring area data) picked up by the CCD sensor shown in FIG. 1; FIG. 3A shows a monitoring area by a first CCD sensor; FIG. 3B is a diagram showing an example of data monitored by the second CCD sensor.
4A and 4B are explanatory diagrams for explaining a processing example of a comparing unit shown in FIG. 1; FIG. 4A is a diagram showing an example of calculation area data by a first CCD sensor; FIG. FIG. 4C is a diagram illustrating an example of calculation area data obtained by the second CCD sensor, and FIG. 4C is a diagram illustrating an example of comparison data.
FIG. 5 is an explanatory diagram showing a relationship when a measurement target range and a position of a calculation area are viewed from a side.
FIG. 6 is an explanatory diagram showing a relationship when a measurement target range and a position of a calculation area are viewed from above.
FIG. 7 is a first explanatory diagram for describing a process of calculating a vertical position of a calculation area.
FIG. 8 is a second explanatory diagram for explaining a process of calculating a vertical position of a monitoring eleu.
FIG. 9 is a third explanatory diagram illustrating a process of calculating a vertical position of a calculation area.
FIG. 10 is a first explanatory diagram illustrating a process of calculating a horizontal position of a calculation area.
FIG. 11 is a second explanatory diagram illustrating a process of calculating a horizontal position of a calculation area.
FIG. 12 is an explanatory diagram showing an example of monitoring area data in which a calculation area has been set by the calculation area setting means shown in FIG. 1;
FIG. 13 is an explanatory diagram showing coordinates when the height of an obstacle is calculated by the distance calculating means shown in FIG. 1;
FIG. 14 is a block diagram showing a configuration of an inter-vehicle distance warning device using the vehicle-mounted distance measuring device shown in FIG. 1;
[Explanation of symbols]
10 First CCD sensor (imaging means)
12. Second CCD sensor (imaging means)
14 Calculation area data extraction means
15 Calculation area setting means
16 Comparison means
18 Distance calculation means
20 Vertical calculation area position setting function
22 Horizontal calculation area position setting function
(Equation 11)

Claims (7)

Two image pickup means for picking up an image of the front of the vehicle, calculation area setting means for setting a plurality of calculation areas for image data picked up by these image pickup means, and a plurality of calculations set by the calculation area setting means Calculation area data extraction means for extracting image data of an area portion; comparison means for comparing the calculation area data extracted by the calculation area data extraction means for each calculation area; and comparison data extracted by the comparison means. Distance calculating means for calculating the distance to the target obstacle for each of the comparison data based on the
The calculation area setting unit sets a horizontal interval of a calculation area between a left end and a right end with respect to a measurement target range of the image data at intervals that are equal intervals in an imaging direction in a real space imaged by the imaging unit. A vehicle-mounted distance measuring device having a horizontal calculation area position setting function for setting a distance. The calculation area setting means sets an equal interval in an imaging direction in a real space imaged by the imaging means, and a vertical interval of a calculation area between an upper end and a lower end of a measurement target range of the image data. 2. The in- vehicle distance measuring device according to claim 1, further comprising a vertical calculation area position setting function for setting the distance. Two image pickup means for picking up an image of the front of the vehicle, calculation area setting means for setting a plurality of calculation areas for image data picked up by these image pickup means, and a plurality of calculations set by the calculation area setting means Calculation area data extraction means for extracting image data of an area portion; comparison means for comparing the calculation area data extracted by the calculation area data extraction means for each calculation area; and comparison data extracted by the comparison means. Distance calculating means for calculating the distance to the target obstacle for each of the comparison data based on the
The calculation area setting means, at intervals to be equally spaced about the imaging direction in the real space, which is a measuring object range on a road that is captured by the imaging means, between the upper and lower ends for the measurement target range of the image data An in-vehicle distance measuring device comprising a vertical calculation area position setting function for setting a vertical interval between calculation areas in the vertical direction. The calculation area setting unit sets a horizontal interval of a calculation area between a left end and a right end with respect to a measurement target range of the image data at intervals that are equal intervals in an imaging direction in a real space imaged by the imaging unit. 4. The in-vehicle distance measuring device according to claim 3, further comprising a horizontal calculation area position setting function for setting the distance. The calculation area setting unit calculates a position of a calculation area of the image data based on an installation height (h) of the imaging unit, a viewing angle (θ) of the imaging unit, and a depression angle of the imaging unit. The in-vehicle distance measuring device according to claim 2 , wherein the distance measuring device is provided with a function of performing the following. The distance calculating means determines a distance in each calculation area by the distance calculating means based on length information from an installation position of the imaging means determined for each calculation area to a position of a road imaged in the calculation area. 6. The in-vehicle distance measuring apparatus according to claim 5, further comprising an error processing unit that, when the result is longer than the length based on the length information, sets an error in the distance measurement result in the calculation area. Claim wherein the distance calculating means, characterized by comprising an obstacle height calculation function for calculating the height in the real space of the obstacle on the basis of the respective measurement result determined in the each calculation area 5 The in-vehicle distance measuring device according to the above.

Images