JPH11316122A - Image range finder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce dispersion in measured distances caused by-vibration of a vehicle or the like. SOLUTION: This image range finder for measuring a distance to a preceding vehicle traveling on a road is provided with two cameras for image-picking up the preceding vehicle to measure the distance to the preceding vehicle by trigometrical survey, a distance height calculating part for identifying respective observation points in observation faces of the two cameras with respect to a gage mark of the preceding vehicle to find a distance to the gage mark and the height of the gage mark from the road, and a height determining part for determining as the final distance a distance when the height of the gage mark provided by the distance.height determining part is within a prescribed range and for repeating setting for a renewal gage mark until it comes within the prescribed range when out of the prescribed range. Dispersion in manufacture, vibration of a vehicle and dispersion of distances measured resulting from reflected light from other object is reduced by this means.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image distance measuring apparatus for measuring a distance from a preceding vehicle by triangulation, and more particularly to a vibration of a vehicle, reflected light frequently incident from another object, and variation in pixel density detection. The present invention relates to an apparatus for reducing a variation in a distance measured due to the above.

[0002]

2. Description of the Related Art Two CCD (charge-coupled device) cameras arranged at regular intervals are used in the above image distance measuring apparatus.
The distance to the vehicle ahead is measured by using the principle of triangulation (stereo method). Reflected waves of sunlight from behind the preceding vehicle are input to these two CCD cameras, and the reference points to be measured in the preceding vehicle are detected as observation points of each image on the observation surface of the two cameras. . The distance from the coordinates of these two observation points to the reference point is obtained.

[0003] When the vehicle is a passenger car, the shape viewed from the rear is a substantially vertical portion near the rearmost number plate, and the rear portion is flattened forward from the vertical portion. Many winds have a sharp smell. If the vehicle is a truck, there is a vertical portion on the rearmost carrier shroud, which is flat from the vertical portion forward to a vertical portion in the cab.

[0004] Various indications are drawn on the road on which the vehicle travels, and further, there are patterns of road distortion and the like. If the display, the pattern, and the like are erroneously determined by the image ranging device as an image of the vehicle and an observation point corresponding to the reference point is set, a correct distance cannot be obtained. For this reason, the observation point corresponding to the reference point is set on the image so as to be located at a certain height or higher from the road.

[0005]

However, in the above image distance measuring apparatus, there is a variation in manufacturing the two CCD cameras, so that there is a problem that the distance measured with respect to the same reference point varies. is there. In the image distance measuring apparatus, light reflected from an object other than the vehicle may be temporarily input to only one of the two CCD cameras. As a result, the observation point on the observation surface of the one CCD camera temporarily shifts, which causes a shift in the distance from the preceding vehicle. If the frequency of input of reflected light from other objects is high, there is a problem that the distance to the vehicle in front varies.

Further, roads have irregularities, and vehicles generate vertical vibrations due to the irregularities of the roads. The vibrations of the own vehicle equipped with the image ranging device and the preceding vehicle whose distance is measured are different. Therefore, along with the vibration, the image behind the preceding vehicle also vibrates up and down on the observation surface of the two CCD cameras. For this reason, each time image data is captured, an observation point on the image must be determined. The vehicle has a certain length in the traveling direction.For example, when the vehicle is a passenger car, when the observation point is set to the vertical portion of the rearmost number plate or set to the rear window at the rear. Depending on the set position, a distance of about 1 m occurs in the distance measurement of the preceding vehicle. If the vehicle is a truck, the observation point is set at the last vertical part,
When set in the operator's cab, a variation of several meters occurs depending on the set position.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in view of the above problems, and provides an image distance measuring apparatus in which variations in the distance measured due to manufacturing variations, vehicle vibrations, and reflected light from other objects are reduced. The purpose is to do.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an object of the present invention is to provide an image ranging apparatus for measuring the distance of a preceding vehicle traveling on a road by measuring the distance to the preceding vehicle by triangulation. For this purpose, two cameras that image the preceding vehicle, and the distance to the reference point by identifying each observation point on the observation surface of the two cameras with respect to the reference point of the preceding vehicle, and the distance to obtain the height of the reference point from the road If the height of the reference point obtained by the height calculator and the distance / height calculator is within the first range, the distance at that time is regarded as the final distance, and if not, the first range is not included. And a height judging unit for repeating the setting of a new reference point until the image distance measuring apparatus is provided.

The height judging section takes the heights of the plurality of reference points in the first range in the horizontal direction of the vehicle, and determines the distance to the height of the highest one of the heights as the final distance. The height judging unit stores a plurality of the reference point heights in the first range in time series, obtains a reference point of a plurality of the reference point heights, and calculates a reference point height corresponding to the reference point height closest to the reference point. Let the distance be the final distance.

[0010] By this means, variations in the distance measured due to manufacturing variations, vehicle vibrations, and reflected light from other objects are reduced.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram for explaining the relationship between a vehicle equipped with the image ranging device according to the present invention and a preceding vehicle. As shown in the drawings (a) and (b), an image ranging device 1 is mounted in front of the vehicle, and the image ranging device 1 emits light reflected from, for example, the rear of a front passenger car or truck. input.

FIG. 2 is a view for explaining a schematic example of the image distance measuring apparatus of FIG. As shown in the figure, in the image distance measuring apparatus, two CCD cameras 11 and 12 are arranged at a certain height H at a certain interval d in front of the vehicle. The forward vehicle recognition units 13 and 14 recognize an image of the forward vehicle from the images obtained by the CCD cameras 11 and 12. CCD camera 1
For the edge features of the images obtained by
Time-series smoothing is performed, and a process of extracting an image having a small change on the screen by blurring an image of an object having a large change on the screen is performed. In this way, the range of recognizing the preceding vehicle and searching for both observation points for the reference point is
As described later, the processing is limited and simplified.

The observation search unit 15 includes a forward vehicle recognition unit 13,
In the search area provided for the image of the vehicle ahead recognized by the area 14, the range in which the density values of the pixels of the observation surface of the CCD cameras 11 and 12 within a certain size range coincide with each other will be described later. , Search and if there is a match,
The center coordinates of the coincident range are set as both observation points corresponding to the reference points.

The distance calculation unit 16 calculates the distance L to the reference point based on the coordinates (x, z) of the observation point obtained by the observation search unit 15.
Is determined as described later. The height calculation unit 17 calculates the height h of the reference point based on the coordinates (x, z) of the observation point obtained by the observation search unit 15 and the distance to the reference point obtained by the distance calculation unit 16, as described below. Ask to do.

The height judging section 18 judges whether the height h is within a certain range as described below. If the height of the h ₀ ≦ h ≦ h ₁ reference point is not in this range, the observation point is reset by the observation point search unit 15 in the z direction, and the height calculation unit 17 is set via the distance calculation unit 16. Find the height with The above processing is repeated until the above expression is satisfied.

If the above equation is satisfied, the final distance obtained by the distance calculation section 16 is output. FIG. 3 is a diagram illustrating an example of a search range of a preceding vehicle recognized by the preceding vehicle recognition units 13 and 14. As shown in the figure, the preceding vehicle is recognized within the white line of the vehicle equipped with the image ranging device. Since many edges appear behind the vehicle in front,
The vehicle is recognized as the preceding vehicle from the distribution state of the edge. A search area is set so as to surround this collection of edges.

FIG. 4 is a diagram showing an example for explaining search of both observation points with respect to a reference point by the observation search unit 15. As shown in (a) and (b) of FIG.
Density value search ranges A and B are set in the search areas 1 and 12, respectively. As shown in FIGS. 2A and 2B, each of the density value search ranges A and B is, for example, a size of 8 × 8 pixels, and one of the density value search ranges A is fixed. the concentration of each pixel by, a _11, a _12, ... with respect to a _88, the concentration of pixels of the other density value search range _{B, B 11, B 12,} ...
B ₈₈ . For the density values in both density value search ranges,
Δ is obtained by the following equation, and Δ = | A ₁₁ −B ₁₁ | + | A ₁₂ −B ₁₂ | +... + | A ₈₈ −B
₈₈ | changing the other density value search range B sequentially, in the case where Δ is minimized, positions A _P of both the observation point position of both concentrations search range for the gauge is determined as B _P. This Δ includes a manufacturing variation of the two CCD cameras 11 and 12. That is, the variation in the density detection of the pixels between the CCD cameras 11 and 12 is included.

FIG. 5 is a diagram for explaining an example of distance calculation processing and an example of height calculation processing in the distance calculation section 16 and the height calculation section 17. As shown in the figure, the convex lenses a and b of the CCD cameras 11 and 12 are arranged at a distance d and parallel to each other. An observation surface is provided at a position perpendicular to the axes of the convex lenses a and b and behind the convex lenses a and b by a focal distance f. The straight line connecting the convex lenses a and b is defined as the x-axis, the axis of the convex lens a is defined as the y-axis, and the axis perpendicular to the xy plane is defined as the z-axis. The coordinates of the convex lens a are (0, 0, H), the coordinates of the convex lens b are (d, 0, H), and the coordinates of the reference point P are (x, y, h). the coordinates of the point a _P and _{(-x a, -f, H +} z c), the coordinates of the observation point B _P for gage _{P (d + x b, -f} , H + z c).
Note that y represents the distance (L) to the preceding vehicle. The coordinates (x, y, h) of the reference point P are as follows.

X = x _a · d / (x _a −x _b ) y = x _a · f / (x _a −x _b ) h = H−linear ap · sin β Therefore, h = H − ｛(x ² + y ² ) / (1−sin ² α)｝ ^1/2 sin α = z _c / (z _c ² + f ² ) ^1/2 FIG. 6 is a diagram for explaining an example of the judgment processing by the height judgment unit 18. As shown in the figure, so that the height h of the target point P is limited to the range of the vertical portion of the rear of the vehicle, an upper limit h ₁ and the lower limit h ₀ in the height h is provided. This range of h is preferably, for example, an upper limit h ₁ = 50 with respect to the lower part of the vehicle.
cm, and the lower limit h ₀ is set to 30 cm.

Further, the range of h is set at the upper part of the vehicle.
And preferably, for example, the upper limit h ₁= 130cm, below
Limit h₀It may be set to be 110 cm. This
During the measurement period, the height of the
In the area of the rearmost vertical section of the
In the case of a rear window of the vehicle in front or a truck
Is fixed to the cab. For this reason, as described in the prior art
In this way, the mark on the vehicle ahead is
And set at different positions, for example,
In the case of a car, the rear vertical
Conversely, if the gauge moves frequently,
To prevent the distance variation (ΔL) from increasing
Becomes possible.

As shown in FIG. 6, the height of the reference point is h ₀ ≦ h ≦ h ₁ , and a plurality of reference points P ₁ , P
₂ ... to set the P _6. That is, the position A _{P1 of the} observation point,
When A _P2 ,... A _P3 are set at a constant height and at a constant interval in the horizontal direction, and the positions of the observation points B _P1 , B _P2 ,..., B _P6 are searched, B _P1 , B _P2 … B _P6
A _P1 , A _P2 ,... A _P6 are not uniquely determined, and a positional variation occurs. The heights for the plurality of altitudes P ₁ , P ₂ ... P ₆ set in this way vary according to the manufacturing variations of the CCD camera regarding pixel density detection.

FIGS. 7 and 8 are views for explaining an example of processing of the height of the reference point in order to suppress variations in the manufacture of the CCD camera. As shown in FIG. 7A, the height calculating unit 17
The heights of the plurality of gauge points P ₁ , P _2, ..., P ₆ are obtained, and the final distance is determined for the one having the greatest gauge height h among them. By doing so, statistical processing is performed on the pixels in place, so that even if there is a manufacturing variation for detecting the density values of the pixels of the two CCD cameras, the variation can be reduced. Will be possible.

[0023] As shown in FIG. 7 (b), the height calculation unit 17, and the final distance to the average value of the plurality of heights obtained for a plurality of P _1, P ₂ ... P ₆ determines May be. As described above, since statistical processing is performed, even if there is variation in detecting the density values of the pixels of the two CCD cameras, the variation can be reduced.

FIG. 7A is a modification example of FIG. 7A. As shown in FIG. 8A, the height calculation unit 17 sets the maximum value of the height of the reference point within a certain range with respect to the reference value. Alternatively, the final distance may be determined. In other words, the highest value in this example is determined excluding the highest value and the lowest value measured. Note that the reference value may be an average value of the measured heights of all the gauge points. The reference value is a median value (= (h ₀ + h ₁ )
/ 2). The certain range may be a standard deviation.

FIG. 8B is a modification of FIG. 7B. As shown in FIG. 8B, the height calculating section 17 calculates the average of the heights of the reference points within a certain range with respect to the reference value. The final distance may be determined. In other words, the average value in this example is determined excluding the measured maximum value and minimum value. Note that the reference value may be an average value of the measured heights of all the gauge points. The reference value is a median value (= (h ₀ + h ₁ ) /
2). The certain range may be a standard deviation.

FIG. 9 is a diagram showing an example of processing of a reference point height in order to suppress variations due to reflected light from objects other than the preceding vehicle. As shown in the figure, the height calculating unit 17 stores, for example, the heights of the reference points P obtained at time series t ₁ , t ₂ ,... T ₆ , and from these heights, by a predetermined method. , A reference value is determined, and a final distance is determined for a height having a height closest to the reference value. Even if there is variation in the density values of the pixels of the two CCD cameras due to the presence or absence of reflected light from other objects, statistical processing is performed in time series, so that the variation is reduced. It becomes possible.

The reference value may be obtained by a moving average of the heights of the reference points P obtained in time series as the predetermined method. Furthermore, although the height position is within a certain range from the reference value of the height of a certain reference point P, for example, a final distance may be obtained with respect to the highest value. Furthermore, a certain reference point P
Although it has a height position within a certain range from the height reference value, for example, a final distance may be obtained from an average value.

[0028]

As described above, according to the present invention, CC
Variations in the distance measured due to manufacturing variations of the D camera, vibrations of the vehicle, and reflected light from other objects are reduced.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between a vehicle equipped with an image ranging device according to the present invention and a preceding vehicle.

FIG. 2 is a diagram illustrating a schematic example of the image distance measuring apparatus of FIG. 1;

FIG. 3 is a diagram illustrating an example of a search range of a forward vehicle recognized by forward vehicle recognition units 13 and 14;

FIG. 4 is a diagram showing an example for explaining search of both observation points for a reference point by an observation search unit 15;

FIG. 5 is a diagram illustrating an example of a distance calculation process and an example of a height calculation process in a distance calculation unit 16 and a height calculation unit 17.

FIG. 6 is a diagram illustrating an example of a determination process performed by a height determination unit.

FIG. 7 is a diagram illustrating an example of processing of a reference point height in order to suppress manufacturing variations of a CCD camera.

FIG. 8 is a diagram illustrating an example of processing of the height of a reference point in order to suppress manufacturing variations of the CCD camera.

FIG. 9 is a diagram illustrating a processing example of a reference point height in order to suppress variations due to reflected light from an object other than a vehicle ahead.

[Explanation of symbols]

 11, 12: Camera 13, 14, Front vehicle recognition unit 15: Observation point search unit 16: Distance calculation unit 17: Height calculation unit 18: Height determination unit

Claims (13)

[Claims] 1. An image ranging apparatus for measuring the distance of a preceding vehicle traveling on a road, comprising: two cameras for inputting an image of the preceding vehicle to measure the distance to the preceding vehicle by triangulation; A distance / height calculation unit for identifying each observation point of the observation planes of the two cameras with respect to the reference point and calculating the height of the reference point from the road and the road, and the distance / height calculation unit The height of the obtained gauge is the first
If it is within the range, the distance at that time is the final distance, and the first
An image distance measuring apparatus, comprising: a height judging unit that repeats setting of a new reference point until the first range is reached if the range is not within the range. 2. The height judging section takes the heights of the plurality of reference points in a first range in the horizontal direction of the vehicle, and sets a distance to a height of the highest one of the heights as a final distance. The image distance measuring apparatus according to claim 1, wherein: 3. The height judging section takes the heights of the plurality of reference points in the first range in the horizontal direction of the vehicle, and sets a distance with respect to an average elevation height as a final distance. The image distance measuring apparatus according to claim 1, wherein 4. The height judging section obtains a reference point for the height of the plurality of gauge points, and calculates the highest value among the heights of the gauge points in a second range obtained by narrowing the first range from the reference points. The image distance measuring apparatus according to claim 2, wherein a distance with respect to the height of the altitude is set as a final distance. 5. The height judging unit obtains a reference point for the height of the plurality of reference points, and calculates an average of the heights of the reference points in a second range obtained by narrowing the first range from the reference points. The image distance measuring apparatus according to claim 3, wherein a distance with respect to the altitude is a final distance. 6. The image ranging apparatus according to claim 4, wherein the height determination unit sets the reference value as an average value of a plurality of the heights. 7. The height determining unit determines the reference value as the first value.
The center value of the range is set as the center value.
An image distance measuring device according to any one of the above. 8. The image ranging apparatus according to claim 4, wherein the second range is a standard deviation of heights of the plurality of gauge points. 9. The image ranging apparatus according to claim 1, wherein the first range is one of a certain range from an upper part of a front vehicle and a certain range from a lower part of the front vehicle. 10. The height judging section stores a plurality of the reference point heights in the first range in a time series, determines a reference point of a plurality of the reference point heights, and determines a reference point closest to the reference point. The image distance measuring apparatus according to claim 1, wherein a distance with respect to the altitude is a final distance. 11. The image ranging apparatus according to claim 11, wherein the height determination unit sets the reference value to an average value of the heights of the plurality of reference points in time series. 12. The height judging unit sets a distance to a height of a highest value among heights of reference points in a second range obtained by narrowing the first range from the reference value as a final distance. The image ranging apparatus according to claim 11, wherein: 13. The height determining unit sets a final distance as a distance from an average altitude of a reference point in a second range obtained by narrowing the first range from the reference value. The image ranging apparatus according to claim 11, wherein: