JPH0996527A - Distance-measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a distance-measuring device for accurately measuring the distance to an object even if an obstacle other than the object or smear, etc., exists or occurs near the object. SOLUTION: The distance DIST to an object 20 being present at a distance- measuring point P (m, n) and a direction ANGL are repeatedly calculated at a certain interval by obtaining the phase difference from an image signal obtained by a pair of sensors 12L and 12R arranged corresponding to a plurality of lines m which are aligned in the horizontal direction and a plurality of ranging-finding points P (m, n) which are set in a grid shape of a plurality of windows which are aligned in the vertical direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for measuring a distance, in particular, an object located in front of an own vehicle such as a preceding vehicle.

[0002]

2. Description of the Related Art Development of a technique for improving safety when a vehicle is traveling is in progress. For example, in order to avoid a rear-end collision accident, the distance to an object that obstructs traveling is measured to determine a predetermined distance. There is a technique (for example, Japanese Examined Patent Publication No. 3-44005) that warns the driver when the vehicle is closer than the distance and controls the vehicle such that the traveling speed is automatically reduced.

As a device for measuring the distance mounted on such a device, a pair of left and right cameras using an image sensor such as a charge coupled device (CCD) is provided in front of the vehicle, and the images on the images of the respective cameras are displayed. There is known a technique for obtaining a distance by a so-called stereo method based on the principle of triangulation for calculating the displacement of an object position (for example, Japanese Patent Laid-Open No. 7-43149), but the amount of data is large and the processing method becomes complicated. There is a problem, and there is also a problem that an expensive device with high performance is required for an arithmetic unit for processing this. Therefore, the applicant of the present application calculates the phase difference from the image signals obtained by the pair of sensors arranged corresponding to the plurality of distance measuring points set in a grid pattern, and calculates the phase difference from the distance measuring points. A distance distribution is obtained, a correlation between the distance measuring points is obtained from the distance distribution, and a determination value of a detection area including a two-dimensional area defined by at least three of the distance measuring points is calculated using the correlation. , When the determination value is smaller than a set value, it is determined that an object exists in the detection area, and the distance to the object is obtained using the distance distribution of the distance measuring points that define the detection area. Proposed a distance measuring device (Japanese Patent Application No. 7-155272).

Further, the inventor of the present invention uses a pair of sensors arranged corresponding to a plurality of distance measuring points set in a grid pattern of a plurality of lines arranged in the horizontal direction and a plurality of windows arranged in the vertical direction. The phase difference is calculated from the obtained image signal to obtain the measurement distance at the distance measurement point, and the distance measurement point is located at each apex of the detection area formed of a two-dimensional area defined by at least three of the distance measurement points. The absolute value of the difference between the measured distances between the two is calculated, and when all of the calculated values are smaller than a reference value, the detected area is extracted as a box in which an object exists, and the distance measuring points constituting this box are extracted. Proposed a distance measuring device for obtaining the distance to the object using the measured distance of
Patent application “reference number P950825N03” filed on August 25, 2014).

According to these distance measuring devices previously submitted, the object is captured by using the detection area consisting of a two-dimensional area. There may be a case where an accurate distance cannot be measured because the detection area that catches an object decreases.

In order to solve such a problem, the inventor of the present invention determines a reference value composed of a reference distance of an object and a reference line which is one of the lines closer to the center of the object than the previous value. Then, the measurement distances of the distance measuring points on the reference line are measured, and those within a certain range with respect to the reference distance are extracted, and the distances are within a certain range with respect to the extracted distance measuring point. We proposed a distance measuring device that selects objects in the horizontal direction and measures the distance and direction from a set of extracted and selected distance measuring points.

[0007]

However, in the distance measuring device described above, when a white line (obstacle) formed of, for example, a pedestrian crossing or a road sign exists near the object,
Since it is determined that the distance measurement points are within a certain range with respect to the extracted distance measurement points and the distance measurement points are selected in the horizontal direction more than the object to be actually measured (the white line is recognized as an object), the extraction Also, there is a problem in that the set of selected distance measuring points becomes large and accurate distance and direction cannot be measured. Further, when the above-described sensor (line sensor, CCD, etc.) is used, an excessive amount of light is accumulated in a certain portion, the overflowed portion reaches the charge transfer portion, and the columns have the same brightness. Since it becomes data (smear), when this data occurs in the vicinity of the object to be actually measured like the obstacle described above, the same problem as the obstacle described above may occur. The present invention focuses on the above problems, and provides a distance measuring device that accurately measures a distance to an object even when an obstacle or a smear other than the object exists or occurs near the object.

[0008]

In order to solve the above problems, the present invention provides a plurality of distance measuring points set in a grid pattern of a plurality of lines arranged in the horizontal direction and a plurality of windows arranged in the vertical direction. In the distance measuring device in which the distance and the direction to the object existing at the distance measuring point are repeatedly calculated at fixed intervals by obtaining the phase difference from the image signals obtained by the pair of sensors arranged correspondingly, the previous value A reference distance of the object, an object width of the object, and a reference value consisting of the center of the object or a reference line which is one of the lines close to the center, and determines the reference value of the distance measuring point on the reference line. Extracting those that are within a certain range with respect to the reference distance together with measuring the measurement distance,
In order to select one that is within a certain range with respect to the measured distance of the extracted distance measuring point, the measuring distance of the distance measuring point in the detection area slightly larger than the object width is set horizontally with respect to the reference line. Direction sequentially,
The distance and the direction are calculated from the set of the distance measuring points extracted and selected.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A plurality of horizontal lines m
And a phase difference from image signals obtained by a pair of sensors 12L and 12R arranged corresponding to a plurality of distance measurement points P (m, n) set in a grid pattern of a plurality of windows n arranged in the vertical direction. In the distance measuring device in which the distance DIST and the direction ANGL to the object 20 present at the distance measuring point P (m, n) are repeatedly calculated at regular intervals, the reference distance Ds of the object 20 from the previous value and the object 20
Of the object width w and a reference line mS that is one of the lines at or near the center of the object 20 is determined, and the distance measurement point P (m, n) on the reference line mS is determined.
Measurement distance D (m, n) of each of the measurement distances D and the measurement distances D (m, n) of the extracted distance measurement points P (m, n) are extracted. ，
In order to choose those that are within a certain range for n),
The measurement distance D (m, n) of the distance measuring point P (m, n) within the detection area (w + α) slightly larger than the object width w is sequentially detected in the horizontal direction with respect to the reference line mS, and the extraction and selection are performed. By calculating the distance DIST and the direction ANGL from the set of distance measurement points, even when there is an obstacle other than the object near the object 20, a detection area (slightly larger than the object width w in the horizontal direction from the reference line mS ( Distance measuring point P (m, corresponding to the object width w + α)
Since the object 20 is captured at (n), a distance measuring point P (m, n) that may capture an obstacle other than the object 20.
It is possible to improve the measurement accuracy as compared with the conventional method.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described based on the embodiments described in the accompanying drawings on the assumption that the present invention is applied as a device for measuring a distance to an object located in front of a vehicle.

FIG. 1 is a block diagram showing the configuration of the embodiment, and 10 is a plurality of distance measuring points P set in a grid pattern.
Distance measurement unit (camera) for obtaining an image signal including an object (vehicle) 20 located in front of the own vehicle corresponding to (m, n)
And a pair of left and right lenses 11L and 11R as sensors
Image sensors 12L and 12R composed of CCDs having a vertical direction that coincides with the base line direction of the image sensors 12L and 12R are arranged.
The signals are amplified by L and 13R, converted into digital converted signals by sampling at a predetermined period by AD converters 14L and 14R, and stored in memories 15L and 15R, respectively. The image signals stored in the memories 15L and 15R are distance measuring units. 10 is output to the microcomputer 30 connected to the subsequent stage, and the distance DIST to the object 20 and the direction ANGL
Is calculated.

FIG. 2 is a distance measuring point P measured by the image sensors 12L and 12R of the distance measuring unit 10 shown in FIG.
It is a figure explaining the arrangement of (m, n), and in this embodiment,
A total of 112 distance measuring points P (1,1), with 16 horizontal lines and 7 vertical windows
P (16, 7) is set, and these distance measuring points P
(1,1) to P (16,7) are grids regularly arranged in lines and windows, and distance measuring points P (m, n) to P
The angle between lines at (m + 1, n) is 0.56 degrees, and the angle between windows at distance measuring points P (m, n) to P (m, n + 1) is 0.
It is 97 degrees. In addition, "m" of the distance measuring point P (m, n) is the order from the left side of the line, "n" is the order from the lower side of the window, and the position of m = 8.5 is the center m of the vehicle.
It is set to be 0. Image sensor 12
L and 12R are scanned by the drive pulse signal and sequentially read for each distance measuring point P (m, n). For example, distance measuring points P (1,1) to P (1,7) with m = 1. The distance measuring points P (2,1) to P (2,7) for m = 2 and the distance measuring points P (3,1) to P (3,3 for m = 3 are read out one by one from the lower end of the window. Final m = 16 as in 7)
When the distance measuring points P (16,1) to P (16,7) are completed, a series of scanning of the distance measuring points P (m, n) is repeated at regular intervals (several tens to hundreds of milliseconds). Done,
The distance DIST to the object 20 and the direction A at the end of each scan
NGL is calculated.

FIG. 3 is a flow chart for explaining the processing in the microcomputer 30. The image sensor 12 shown in FIG.
The image signals of the distance measuring points P (m, n) obtained from L and 12R are output to the microcomputer 30 and the measuring distances D (m of the distance measuring points P (m, n) based on the principle of triangulation. , N) is measured and the object 20
The procedure for calculating the distance DIST and the direction ANGL is shown. In the present embodiment, FIG. 4 when the object 20 moves from the position of FIG. 4A to the position of FIG. 4B after the next scanning.
Distance DIST and direction ANG of object 20 in (b)
A case of calculating L will be described. FIG. 4 (b)
The broken line indicates the position of the object 20 after the previous scan, that is, in FIG.
This is the position of the object 20 in (a).

First, the distance DIST and the direction ANGL of the object 20 calculated in the previous scan shown in FIG. 4A.
From the “previous value”, the reference distance Ds of the object 20
And the object width w and the reference line mS at the center or near the center are determined (step 10 in FIG. 3).
0). This step 100 will be additionally described later. Here, in the previous scan shown in FIG. 4 (a), the object 20 is located at a point 30 meters in front of the own vehicle and its center is line m = 8 (m = 8.5 which is the center of the own vehicle). Assuming that the position is on the left side of the line), the previous value "distance DIST = 30 meters" and "direction ANGL =-"
0.28 degrees (positive indicates right side, negative indicates left side) ", the reference distance Ds = 30 meters and the reference line mS = 8 m are determined. Further, the object width w is one distance measuring point P due to the principle of triangulation.
The detection width per (m, n) is 30 × tan 0.56 ≒ 0.3
It is assumed that the line width is about 5 lines (1.7 m / 0.3 m) when the object width of an ordinary car is 1.7 m.

Next, in the current scan shown in FIG. 4B, the measurement distance D of the distance measuring points P (8,1) to P (8,7) at the line m = 8 which is the reference line mS.
The measurement of (8,1) to D (8,7) is performed, respectively, and the determination formula shown in Formula 1 below is used to determine the satisfactory distance measurement points Pn (m, n) (see FIG. 3). Step two
00), FIG. 5 shows the result of this step 200, and the distance measuring points P (8,3), P (8,4) and P (8,5) indicated by the circles are the judgment formulas shown in Formula 1. Satisfied, also ×
Others marked are not satisfied. still,
The judgment value D1 can be arbitrarily set in consideration of the measurement error. For example, the reference value Ds is formed by a relative value obtained by multiplying the reference distance Ds by a constant ratio a as shown in Expression 1, and is also expressed by Expression 2. As described above, the absolute value of the difference between the measured distance D (m, n) and the reference distance Ds is a relative value obtained by multiplying the reference distance Ds by a certain ratio a and a constant value with respect to the reference distance Ds. The determination value D1 may be a value obtained by adding the value b.
In particular, when the object 20 is a short distance, the reference value Ds is multiplied by a fixed ratio a, and the determination value D1 consisting only of a relative value becomes small (see Formula 1), and when the measurement error of the device is large,
The absolute value of the difference between the measurement distance D (m, n) and the reference distance Ds becomes large and the distance measurement point P (m, n) cannot be extracted, that is, the object 20 cannot be captured, but the absolute value b By taking into account (see Equation 2), such a problem can be prevented.

[0016]

[Equation 1]

In Equation 1, assuming that a = 10%, the distance measuring points P (8,3), P (8,4) and P (8,
5) Measuring distances D (8,3), P (8,4) and P
(8,5) was in the range of 27 to 33 meters.

[0018]

[Equation 2]

In Equation 2, assuming that a = 10% and b = 1 m, distance measuring points P (8,3), P (8,
4) and P (8,5) measured distances D (8,3), D
(8,4) and D (8,5) were in the range of 26 to 34 meters. The absolute value b is the reference distance Ds.
You may set so that it may change in steps according to.

Next, the extracted distance measuring points Pn (m,
n) the distance measuring points P (8,3), P (8,4) and P (8,3), the measurement distances D (8,3),
Let D (8,4) and D (8,5) be the respective window reference distances Dn (m, n), and sequentially within the detection area (w + α) that is slightly larger than the object width w obtained from the previous value in the horizontal direction. The determination is performed according to the determination formula shown in Formula 3 below, and a distance measuring point P (m, n) that satisfies the determination formula shown in Formula 3 is selected (step 300 in FIG. 3). According to an experiment conducted by the inventor of the present invention, the detection area of the present embodiment is such that when the width of the object 20 to be detected is 1.7 m, each distance measuring point P (m,
n), the object 20 when the scanning time for scanning is 0.2 seconds
In consideration of the movement of 20% in the horizontal direction, it is preferable to add at least one line (one line = 0.3 m) to the left and right of the object width w as the detection area. Then, the width obtained by adding two lines (+ α) to the left and right of the object width w is set as the detection area. FIG. 6 shows this step 30
The result is 0, and the distance measuring points P (4,3) to P (8,3), P (4,4) in the detection area are indicated by circles.
4) to P (8,4) and P (5,5) to P (8,5)
Indicates that the selection is made by satisfying Expression 3, and the others marked with X are not selected by not satisfying. The determination distance D2 can be arbitrarily set in consideration of the measurement error. For example, as shown in Equation 3, the distance measurement point P (m, which is located on the reference line mS and extracted in step 200 is determined. n) measurement distance D (m, n)
As the window reference distance Dn (m, n) in each window n (n = 3 to 5 in this embodiment) in which the extracted distance measuring point Pn (m, n) exists, the window reference distance Dn ( It may be a relative value obtained by multiplying m, n) by a fixed ratio c. Further, c in the equation 3 can be appropriately selected, and for example, about 10% is desirable.

[0021]

(Equation 3)

In this way, the distance measuring points P extracted
For (8,3), P (8,4) and P (8,5),
The measurement distances D (8,3), D (8,4) and D (8,
5) respectively as the window reference distance Dn (m, n), the judgment is performed in the horizontal direction sequentially by the judgment formula shown in the following Expression 3, and the distance measuring point P to the end in the detection area is determined.
The detection is repeated up to (m, n), and the determination is not performed for the distance measuring points P (m, n) outside the detection area.
That is, for example, when the window n = 5, the distance measuring point P
(3,5) and P (13,5) are outside the detection area, and the distance measurement points P (3,5) to P (1,5) and P
Since the judgment is not performed for (13, 5) to P (16, 5) (the blank distance measurement points P (m, n) in FIG. 6 indicate that the judgment is not performed), other than the object 20 Even if another obstacle or the like exists near the object 20, the number of distance measuring points P (m, n) that may detect the other obstacle or the like is reduced, and the object 20 is more accurate than the conventional one. Distance of DIST
And the direction ANGL can be measured.
Further, since the detection range is limited, the load on the microcomputer 30 can be reduced.

Then, as shown in FIG. 7, the distance measuring points P (4,3) to P (8,3), P selected and selected.
(4,4) to P (8,4) and P (5,5) to P (8,
From the set Q of 5), it is determined that the object 20 exists at this position, and the distance DIST and the direction ANGL are calculated. still,
As a method of calculating the distance DIST, as in this embodiment,
Extracted and selected distance measuring points P (4, 3) to P
(8,3), P (4,4) to P (8,4) and P (5,5
5) to P (8,5) measurement distances D (4,3) to D (8,
3), D (4,4) to D (8,4) and D (5,5) to
The average value of D (8,5) is calculated, or the measured distance D
(4,3) to D (8,3), D (4,4) to D (8,
4) and D (5,5) to D (8,5) can be obtained by selecting an average value excluding the maximum value and the minimum value or appropriately selected. As the method of calculating the direction ANGL, the extracted and selected distance measuring points P (4,3) to P (8,3),
P (4,4) to P (8,4) and P (5,5) to P
Line (mL = 4) of the leftmost distance measuring point in (8, 5)
The intermediate line mC = 6 between the line mR = 8 and the line mR = 8 at the rightmost distance measuring point is calculated, and the calculation can be performed by the calculation formula shown in the following Expression 4. In the equation 4, m0
Is the line at the center of the vehicle (= 8.5), K is the angle between the distance measuring points P (m, n) to P (m + 1, n) (= 0.56 degrees), and if this value is negative, The center of the object 20 is located in front of the vehicle on the left side, and in the case of positive, the center of the object 20 is located on the right side of the vehicle. In the present embodiment, the direction ANGL = −1.
It will be 40 degrees. By the above processing, the distance DIST and the direction AN of the object 20 in the current scan shown in FIG.
GL is calculated.

[0024]

[Equation 4]

The determined distance DIST and the direction ANG
L becomes the “previous value” after the next scanning, and is used when determining the “reference value” that is the reference distance Ds of the object 20 and the reference line mS at the center or near the center (FIG. 3).
Step 100). When the intermediate line mC becomes a fraction, for example, 7.5, the reference line mS is set in advance so that either the near line m = 7 or m = 8 is selected. Further, the reference line mS which is one of the “reference values” is obtained from the direction ANGL which is the “previous value”, but the process is easier if the intermediate line mC is used as it is.

Then, it is judged whether or not to continue or end these measurements and calculations (step 500 in FIG. 3).

The distance DIST to at least the object 20 thus obtained is, as shown in FIG. 1, the ECU of the vehicle.
It can be sent to the (engine control unit) or the meter side and used as information to give the driver attention or control such as automatically lowering the traveling speed, as in the conventional technique.

The distance measuring device determines the reference line mS which is one of the reference values, and measures the measuring distance D (m, n) of the distance measuring point P (m, n) on the reference line mS. After extracting those within a certain range, within a certain range within the detection area (w + α) that is slightly larger than the object width w obtained from the previous value in the horizontal direction with respect to the extracted distance measurement point on the reference line mS. To calculate the distance DIST and the direction ANGL from the set Q of the extracted and selected distance measuring points P (m, n). The object 20 is detected by the detection area set from the previous value. Even if another obstacle, smear, or the like exists or occurs in the vicinity of the object 20 by being caught, the object 2
The number of distance measuring points P (m, n) that may catch other obstacles, smears, and the like decreases with 0, the distance DIST to the object 20 and the direction ANGL can be measured more accurately than before, and the detection area is Since it is limited, the load on the microcomputer 30 can be reduced.

The reference value of step 100 in FIG. 3 when the distance DIST and the direction ANGL of the object 20 calculated in the previous scanning does not exist, such as when starting or when the object 20 is lost, is " The previous value cannot be used. Therefore, for example, the above-mentioned August 1995
First, by the method disclosed in the distance measuring device of the patent application “reference number P950825N03” filed on March 25, first, the distance DIS of the object 20
T and the direction ANGL are obtained, and this is used as a "previous value" to obtain a "reference value", or a predetermined line such as m = 8 and a distance measuring point P (8, n) on this line. The "reference value" is determined by an appropriate method such as using the average value of the measurement distances D (8, n) of as the "reference value".

Further, the distance measuring point P in the detection area
Although the method of selecting the measurement distance D (m, n) at (m, n) is not described in detail, for example, the reference line D
The distance measuring point P (m, n) located at the lower end of either the left or right line m centering on s is sequentially scanned upward, and the scanning is performed alternately with respect to the reference line Ds until the detection area is reached. The selection method can be set as appropriate.

Further, the detection area (w + α) of the present embodiment is set as a detection area having a width of two lines added to the left and right of the object width w, but at least one line or more is set as the object width w. The width added to the left and right of the object can be used as the detection area, and can be appropriately changed in consideration of the object width of the object to be detected.

[0032]

The present invention can be obtained by a pair of sensors arranged corresponding to a plurality of distance measuring points set in a grid pattern of a plurality of lines arranged in the horizontal direction and a plurality of windows arranged in the vertical direction. In the distance measuring device in which the calculation of the distance and the direction to the object existing at the distance measuring point by obtaining the phase difference from the image signal is repeatedly performed at a constant interval, the reference distance of the object from the previous value, and the object A reference value composed of an object width and a reference line which is one of the lines at or near the center of the object is determined, and the measurement distances of the distance measurement points on the reference line are measured and the reference distance is determined. In order to select an object within a certain range with respect to the measured distance of the extracted distance measuring point, a value slightly larger than the object width The measured distances of the distance measuring points in the detection area are sequentially detected in the horizontal direction with respect to the reference line, and the distance and the direction are calculated from the set of the distance measuring points extracted and selected, and the previous value. By detecting the object by the detection area set by the above, even if another obstacle or smear or the like exists or occurs in the vicinity of the object, distance measurement that may catch the obstacle or smear or the like together with the object Point P (m,
n) is reduced, and the distance to the object can be measured more accurately than before. Further, since the detection area is limited, the load on the microcomputer can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an exemplary embodiment of the present invention.

FIG. 2 is a diagram for explaining an array of distance measuring points in the above-described embodiment.

FIG. 3 is a flowchart illustrating processing in the above embodiment.

FIG. 4A is a diagram for explaining the measurement according to the above-described embodiment, in which FIG. 4A shows after the previous scan and FIG. 4B shows after the current scan.

5A and 5B are views for explaining the distance measurement point extraction processing of FIG.

FIG. 6 is a diagram illustrating the edge detection process of FIG.

FIG. 7 is a diagram illustrating the distance and direction calculation process of FIG.

[Explanation of symbols]

 10 distance measuring unit 20 object (vehicle) 30 microcomputer Ds reference distance (reference value) mS reference line (reference value) w object width w + α detection area

Claims (1)

[Claims] 1. From an image signal obtained by a pair of sensors arranged corresponding to a plurality of distance measuring points set in a grid pattern of a plurality of lines arranged in a horizontal direction and a plurality of windows arranged in a vertical direction. In the distance measuring device in which the calculation of the distance and the direction to the object existing at the distance measuring point by obtaining the phase difference is repeatedly performed at a constant interval, the reference distance of the object from the previous value, and the object width of the object, A reference value consisting of the center of the object or a reference line that is one of the lines near the center is determined, and the measurement distances of the distance measurement points on the reference line are measured and fixed with respect to the reference distance. In order to extract those within a certain range and to select those within a certain range with respect to the measured distance of the extracted distance measuring points, a detection area slightly larger than the object width A distance measuring device, wherein the measured distances of the distance measuring points in the horizontal direction are sequentially detected in the horizontal direction with respect to the reference line, and the distance and direction are calculated from a set of the distance measuring points extracted and selected.