JP2000002529A - Vehicle distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correctly recognize a tracking object without recognizing white lines and characters on a road surface in error and precisely measure a distance to the tracking object in a vehicle distance measuring device that calculates the distance to the object by a principle of a trigonometrical survey using an amount of deviation from an optical axis of both images obtained by comparing a pair of image signals that are formed images on an image sensor. SOLUTION: Tracking windows longitudinal arranged that respectively include a plurality of small windows are set by a tracking window determining means 8, and distance calculating is done to every small window in each tracking window by a distance calculating means 10. A distance judging means 11 judges whether a plurality of small windows included in each tracking window are used for a present distance calculating based upon comparison of a previous calculating distance to an object with a present distance of a small window by the distance calculating means 10, and only tracking windows having gravity positions of small windows presently used that are higher than a set height are used for calculating distance to an object 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for triangulation by comparing a pair of image signals formed on an image sensor by a pair of optical systems and electrically detecting a shift amount of the two images from the optical axis. The present invention relates to a vehicle distance measurement device that measures a distance to a target object by executing a calculation based on a principle using the deviation amount.

[0002]

2. Description of the Related Art Such a vehicle distance measuring device is disclosed, for example, in Japanese Patent Application Laid-Open Nos. Hei 6-266825 and Hei 7-836.
55, etc.
In Japanese Patent No. 6825, a distance to an object is calculated for each of a plurality of set windows, and it is determined whether or not the object is a tracking object based on a difference between the distances obtained for each of the windows. In Japanese Unexamined Patent Publication No. Hei 7-83655, when the distances obtained for a plurality of windows arranged on a vertical line are substantially the same, it is determined that a three-dimensional object exists on that line, and a similar result is obtained by a predetermined number or more. It is determined that the preceding vehicle is detected when the vehicle is obtained on the vertical line.

[0003]

However, according to the technique disclosed in Japanese Patent Laid-Open Publication No. Hei 6-266825, white lines, characters, and the like existing on the road surface near the tracking target are accidentally substantially the same as the target. When the distance is obtained, the tracking performance of the preceding vehicle may be deteriorated. Further, in the technique disclosed in Japanese Patent Application Laid-Open No. 7-83655, the difference in image contrast disappears due to a part of a tracking target entering a shade or the like, and the distance output is reduced in some windows on a vertical line. If the distance cannot be obtained (or if the distance accuracy decreases and it cannot be determined that the distances are the same), the recognition performance of the preceding vehicle may deteriorate.

The present invention has been made in view of such circumstances, and accurately recognizes an object to be tracked without erroneously recognizing a white line or a character on a road surface and accurately determines a distance to the object to be tracked. It is an object of the present invention to provide a vehicle distance measuring device capable of measuring the distance in a vehicle.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention compares a pair of image signals formed on an image sensor by a pair of optical systems and calculates a shift amount of both images from the optical axis. Electrically detected, in a vehicle distance measuring device that measures the distance to the object by executing a calculation based on the principle of triangulation using the deviation amount, distributed over the entire field of view determined by the two optical systems Small window setting means for determining a plurality of small windows, and tracking window determining means for setting a plurality of tracking windows for distance measurement in a vertically elongated arrangement each including a plurality of the small windows in the field of view in order to track movement of an object. Distance calculating means for performing a calculation based on the principle of the triangulation for each small window in each tracking window, and a distance between the object and a plurality of small windows included in each tracking window. Distance determining means for determining, for each small window in the tracking window, whether or not to employ this time in the calculation; and in each tracking window based on the distribution of the small window employed in the distance determining means in each tracking window. The center of gravity of the small window is determined, and only the tracking window whose center of gravity is higher than the set height is used for the distance calculation to the object, and it is determined whether or not each tracking window can be used for the distance calculation. Tracking window determination means, and an object distance calculation for calculating a distance to an object based on a tracking window determined to be employable by the tracking window determination means among a plurality of tracking windows determined by the tracking window determination means. Means.

[0006] According to such a configuration, of the plurality of small windows included in the vertically long tracking window, the small window indicating a distance value far from the calculation distance to the previous object is set to the preceding object. Each tracking window can be provisionally determined based on the distribution of other small windows, excluding the small window temporarily determined not to capture the preceding target among the small windows in the tracking window. When the center of gravity of the small window distributed within the tracking window is obtained, the center of gravity of the tracking window including the small window corresponding to the white line or the character on the road surface is located at the lower position. Therefore, the tracking window whose center of gravity is located below the set height is not used in the distance calculation to the object, thereby avoiding erroneous recognition of white lines and characters on the road surface as the preceding object. Thus, the tracking target can be accurately recognized, and the distance to the tracking target can be accurately measured.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described based on embodiments of the present invention shown in the accompanying drawings.

FIGS. 1 to 7 show a first embodiment of the present invention. FIG. 1 is a block diagram showing the configuration of a distance measuring device, FIG. 2 is a diagram for explaining the principle of distance measurement, and FIG. Is a diagram showing the arrangement of small windows in the whole image, FIG. 4 is a diagram showing the arrangement of small windows and tracking windows in the whole image,
FIG. 5 is a diagram showing a determination result by the distance determination unit, FIG. 6 is a diagram for explaining a setting method of the set height, and FIG. 7 is a diagram showing a determination result by the tracking window determination unit.

First, in FIG. 1, a pair of upper and lower imaging means 1 is shown.
A and 1B are arranged, for example, on the rear side of a windshield in a vehicle cabin of the vehicle, and these imaging means 1A and 1B are provided.
The image signals of the object 4 such as the preceding vehicle obtained in the above are converted into digital signals by the individual A / D converters 5A and 5B, and are further stored in the individual image storage means 6A and 6B, respectively.

In FIG. 2, both imaging means 1A and 1B are
Optical systems 2A and 2B including lenses and their optical systems 2
A and 2B are respectively constituted by image sensors 3A and 3B disposed behind by a focal length f, and the two optical systems 2A and 2B are disposed at intervals above and below by a base line length BL.

According to such imaging means 1A and 1B,
An object 4 such as a preceding vehicle existing in front of the own vehicle is an optical system 2.
A and 2B form images on the image sensors 3A and 3B. The image sensors 3A and 3B are, for example, two-dimensional CCDs in which many pixels are dispersed in a two-dimensional plane.
And PD.

As shown in FIG. 3, a plurality of small windows w, w are distributed over the entire field of view by the small window setting means 7 as shown in FIG.
w ... are set. Each of the small windows w, w... May be distributed in a matrix with a constant size, or may be changed in size depending on the position. They may be arranged spatially overlapping.

As shown in FIG. 4, a plurality of tracking sections extending in a vertically long manner including a plurality of small windows w, w,..., Respectively, over the entire visual field determined by the two optical systems 2A, 2B, as shown in FIG. Are set to track the movement of the object 4 and measure the distance to the object 4. Among the image signals stored in the image storage means 6A and 6B, the windows W _P , W _P. Only the image signals of the plurality of tracking windows W _P , W _P ... Determined by the window determination means 8 are cut out. Thus to each tracking window W _P, W is _P ... lateral position of can be arbitrarily set, tracking performance and distance measurement accuracy in order to improve each tracking window W _P,
It is desirable to set the interval between W _P ... small.

Each tracking window W_P, W_P… Small win inside
For the image signals of w, w,.
Is performed. That is, the tracking window W_P, W_P...
For example, numbers from “0” to “i” are assigned in order from the left
With each tracking wind W _P, W_PSmall c contained in ...
India w, w ... from the bottom in order from "0" to "n"
When an address number is assigned, each tracking window W_P, W
_PPhase of the small windows w, w ... of the address numbers included in ...
.. Are executed by the correlation operation means 9, 9,.

The correlation calculation by the correlation calculation means 9 is a calculation for obtaining a shift amount n at a point where the correlation between the luminance data obtained from the two image sensors 3A and 3B is the best. That is, one of the images of the two image sensors 3A, 3B is shifted for each small window w, w.
The subtraction of the two image signals is performed by alternately shifting both the images of the two image sensors 3A and 3B, and the shift amount n when the two image data are most matched, that is, when the correlation value is the minimum. Are performed by the correlation operation means 9, 9,.... Thus, the shift amount n
Is a shift amount nA of the image signal obtained from the lower image sensor 3A from the optical axis of the optical system 2A, as shown in FIG.
And the shift amount nB of the image signal obtained from the upper image sensor 3B from the optical axis of the optical system 2B. In calculating the shift amount n,
Since the resolution is determined by the interval between the pixels in the image sensors 3A and 3B, the shift amount n may be corrected by performing interpolation between the intervals in order to improve the resolution.

The shift amount n obtained by the correlation operation in each of the correlation operation means 9, 9,... Is input to the distance operation means 10, 10,.
In, a distance calculation based on the principle of triangulation is performed. Thus, the operation distance dw for each small window w, w ...
Is obtained as dw = (BL × f) / n. At this time, the image sensor 3
A temperature sensing element may be arranged near A and 3B, and the distance dw may be corrected based on temperature information obtained by the temperature sensing element.

The distances dw obtained by the distance calculation means 10, 10 are input to the distance determination means 11, 11..., And the tracking windows W _P , W are obtained by the distance determination means 11, 11,. _It is determined whether a plurality of small windows w, w... Respectively included in _P ...

By the way, the distance to the object 4, which is calculated by the inter-vehicle distance calculating means 13 as the object distance computation means, the object distance D _p which is previously calculated by the inter-vehicle distance calculating means 13 Are stored in the output storage means 16, and each of the distance determination means 11, 11,...
_A determination process is performed based on _P. Output storage means 16
Subject distance D _P of the previous operation is stored in is inputted to the tracking window determining unit 8, the tracking window determining means 8, this tracking window W on the basis of the object distance D _P of previously calculated The position and the number of _P , W _P ... are determined.

In each of the distance judging means 11, 11 ..., when the distance dw of each small window w, w ... satisfies the following expression (D _P -α1) ≦ dw ≦ (D _P + α2), w is the preceding object 4
Is determined to be adopted in the calculation of the distance to the object 4 this time, and the small window w not satisfying the above expression is determined not to be used in the current distance calculation.

As a method of calculating α1 and α2 in the above equation, for example, one of the following three methods is used.

In the first method, α1 and α2 are determined based on the previously calculated distance D _{P. Since} the resolution of the distance measuring device is proportional to the square of the distance in principle, α1 = α1 when ^{_{a · D P 2 + b1 ...}} (1) where [alpha] 1 ≧ D _P is defined as _{α1 = D P α2 = a ·} D P 2 + b2 ... (2). Here, a is a constant determined by the base line length BL, the focal length f, the pixel pitch in the image sensors 3A and 3B, and the like. B1 is the measurement period ts
This is the maximum distance that the preceding vehicle can approach the own vehicle within (for example, 50 msec), and for example, when the maximum speed that the own vehicle can output is Vmax, it is, for example, (b1 = Vmax · ts).
Further, b2 is the maximum distance that the preceding vehicle can leave from the own vehicle within the measurement cycle, and the maximum speed that the preceding vehicle can output is Vtma.
x, for example, (b2 = Vtmax · ts)
It is.

In the second method, the data is stored in the output storage unit 16.
Object distance D of the previous calculation _PAnd before this calculation
Based on at least two distance outputs obtained at
Based on the calculated relative speed between the vehicle and the preceding vehicle,
α1 and α2 are determined.

Further, in the third method, the output storage means 16
B1 and b2 in the above equations (1) and (2) are calculated based on the object distance D _P of the previous calculation stored in the vehicle, the speed Vs of the own vehicle, and the maximum acceleration Gmax that the own vehicle can output.
It is determined as follows.

B1 = {Vs + (Gmax / 2) × ts} × ts b2 = {Vtmax−Vs− (Gmax / 2) × ts}
× ts According to the determination by the distance determining means 11, 11,..., As shown in FIG. 5, of the small windows w, w... Included in the tracking windows W _P , W _P. Only the windows w, w... Are determined to be employed this time in the calculation of the distance to the object 4.

.. Are input to the tracking window determining means 12, 12... Corresponding to the tracking windows W _P , W _P. , The tracking windows W _P , W of the small windows w, w... Adopted by the distance determination means 11, 11,.
Each tracking window W _P on the basis of the distribution of the in _P ... within, W _P ...
A small window w, the distance calculation only to the object 4 the tracking window W _P centroid position Inw _(i) is in a position higher than the set height DIF with determining the w ... center of gravity Inw _(i) in Each tracking window W _P , W
_It is determined whether _{P can be used for} the distance calculation.

The center-of-gravity position Inw _(i) is calculated in each tracking window determining means 12, 12,... Based on the following equation. Inw _(i) = (@ Wad _(i) / Nad _(i) ) / (wst
_(i) + end _(i) ) In the above equation, ΣWad _(i) is the i-th tracking window W
_{In P} , the small window w used for this distance calculation,
is the sum of w ... of the address number, Nad _(i) is the i-th of the tracking window W small window w is adopted in this time of the distance calculated in the _P, w ... is the total number of, wst _(i) is the i-th tracking window W is the address number of the small window w at the bottom of the in _P, wend _(i) is the top of the address number of small wind w of the i-th of the tracking window W _P.

In FIG. 5, when the center of gravity position Inw ₍₃₎ is calculated for the third tracking window W _P from the left, ΣWad ₍₃₎ is (4 + 5 + 6 + 7), and Nad _(i) Is 4, wst ₍₃₎ is 3, w
Since end ₍₃₎ is 8, Inw ₍₃₎ = {(4 + 5 + 6 + 7) / 4} / (3 + 8) = 0.5.

Further a set height DIF, as shown in Figure 6, the mounting height Hs of the distance measuring device to the vehicle, a set height Hw of the tracking window W _P determined based on the setting field
When, D _P used in distance determining means 11 ..., by the [alpha] 2,
It is calculated by the following equation: DIF = (Hs / Hw) × {α2 / (D _P + α2)}.

The tracking window determining means 12, 1
According to 2 ..., as shown in Figure 7, the tracking window W _P, W _P ... of their tracking window W _P, W _P
The center of gravity Inw _{(i) of the} small windows w, w ... included in ...
However, the tracking window W _P whose height is equal to or less than the set height DIF is not used for the distance calculation. That is, in FIG. 7 is not employed in the tracking window W _P on the left end the distance calculation.

Each of the tracking window determining means 12, 12,...
When the determination result is input to the following distance calculation means 13,
It is also input to the preceding vehicle direction estimating means 14 and
In the calculating means 13, each tracking window W_P, W_P...
The tail window determination means 12, 12,...
Tracking window W determined to be used_P, W_P...
Distance to the preceding vehicle, which is the object 4 based on the distance
The preceding vehicle direction estimating means 14 calculates
India W_P, W_P... the tracking window determination means 12,
Tracking c judged to be adopted for distance calculation by 12 ...
India W_P, W _PThe destination that is the object 4 based on the position of ...
The direction of the traveling train is estimated.

The output of the inter-vehicle distance calculating means 13 is input to the vehicle travel control device 15 and the output storage means 1
6 and the output of the preceding vehicle direction estimating means 14 is input to the vehicle traveling control device 15 and the output storing means 16
Is stored. Thus, the vehicle traveling control device 15 executes traveling control of the own vehicle based on the distance from the preceding vehicle and the direction of the preceding vehicle.

According to the first embodiment, of the plurality of small windows w, w... Respectively included in the plurality of vertically long tracking windows W _P , W _P. The small window w indicating the far distance value can be provisionally determined not to have captured the preceding object 4, and the small windows w, w in the tracking windows W _P , W _P ...
.. Among the tracking windows W _P , W _P ... Based on the distribution of other small windows w, w... Except for the small window w which is temporarily determined not to capture the preceding target object 4. When the position of the center of gravity of the windows w, w... Is obtained, a tracking window W including a small window w corresponding to a white line, a character, or the like on the road surface is obtained.
_{In P} , the position of the center of gravity is the lower position.

Therefore, the tracking window W _P whose center of gravity is located below the set height DIF is not used for the distance calculation to the object 4, so that white lines and characters on the road surface can be used as the preceding object 4. It is possible to avoid erroneously recognizing that the target object 4 is being tracked, and to accurately measure the distance to the tracking target object 4.

In the first embodiment, the distance calculation means 10, 10... Perform the distance calculation on the small windows w, w... In the tracking windows W _P , W _P. However, as in the second embodiment shown in FIG. 8, all the small windows w, w... Set by the small window setting means 7 are correlated by the correlation calculating means 9, 9 and the distance calculating means 10, 10,. distance in advance by performing operation, small window w contained in the tracking window W _P is determined by the tracking window determining unit 8, the w ..., may be performed distance determination and tracking window determination.

Although the embodiments of the present invention have been described in detail, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention described in the appended claims. It is possible to do.

[0036]

As described above, according to the present invention, it is possible to avoid erroneously recognizing a white line or a character on a road surface as a preceding target object, to accurately recognize a tracking target object, and to reach a tracking target object. Can be accurately measured.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a distance measuring device according to a first embodiment.

FIG. 2 is a diagram for explaining a principle of distance measurement.

FIG. 3 is a diagram showing an arrangement of small windows in an entire image.

FIG. 4 is a diagram showing an arrangement of a small window and a tracking window in an entire image.

FIG. 5 is a diagram illustrating a determination result by a distance determination unit.

FIG. 6 is a diagram illustrating a setting height setting technique.

FIG. 7 is a diagram showing a determination result by a tracking window determination unit.

FIG. 8 is a block diagram illustrating a configuration of a distance measuring device according to a second embodiment.

[Explanation of symbols]

2A, 2B: Optical system 3A, 3B: Image sensor 4: Target object 7: Small window setting unit 8: Tracking window determination unit 10: Distance calculation unit 11: Distance Judgment means 12: Tracking window judgment means 13: Inter-vehicle distance calculation means as object distance calculation means

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Akira Terauchi, Inventor 1-4-1, Chuo, Wako-shi, Saitama F-term in Honda R & D Co., Ltd. (Reference) 2F112 AC04 AC06 BA06 BA15 CA05 DA05 DA28 FA03 FA07 FA21 FA36 FA41 FA50

Claims (1)

[Claims] 1. A pair of optical systems (2A, 2B) compares a pair of image signals formed on an image sensor (3A, 3B) and electrically detects a shift amount of both images from an optical axis. In a vehicle distance measuring device for measuring the distance to the object (4) by executing an operation based on the principle of triangulation using the deviation amount, the entire visual field determined by the two optical systems (2A, 2B) A small window setting means (7) for determining a plurality of small windows distributed, and a plurality of tracking windows for distance measurement in a vertically long arrangement including a plurality of the small windows, respectively, for tracking the movement of the object (4). Tracking window determining means (8) defined in the field of view, distance calculating means (10) for executing an operation based on the principle of triangulation for each small window in each tracking window, and a plurality of small windows included in each tracking window. Wine Distance determining means (11) for determining, for each small window in the tracking window, whether or not the distance is to be used in the calculation of the distance to the object, and the small window employed by the distance determining means (11). The center of gravity of the small window in each tracking window is determined based on the distribution in each tracking window, and only the tracking window whose center of gravity is higher than the set height is used for distance calculation to the object (4). Tracking window determining means (12) for determining whether or not each tracking window can be used for distance calculation by adopting it;
Calculating the distance to the object (4) based on the tracking window determined to be employable by the tracking window determining means (12) among the plurality of tracking windows determined by the tracking window determining means (8). Object distance calculating means (1
3) A distance measuring device for a vehicle, comprising: