JPH09133525A - Distance measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform distance measurement with high precision by precisely correcting a deviation of an optical axis. SOLUTION: The image signals in front of a vehicle outputted from a pair of left and right image pickup devices 1A and 1B are inputted to a distance calculator 3 through A/D converters 2A and 2B. With the distance calculator 3, correlation calculation is performed based on the brightness information of the left and right image, and the distance to an object is measured based on parallax found by the correlation calculation. And, with the distance calculator 3, parallax distribution of the whole screen is formed, and, with an infinite- point in the image as a reference object, and with a point whose parallax is near zero as a normal value of parallax (parallax=0), a parallax correction value (deviation of parallax) is calculated based on variation degree of parallax distribution near the normal value. The parallax correlation correction value is used for a correction value of distance measurement. At this time, a point where parallax distribution is suddenly lowered in a range where parallax moved from a positive value to a negative value, is recognized as the parallax corresponding to the infinite-point, at this time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device, and more particularly to a device mounted on a vehicle for measuring the distance between the vehicle and an obstacle.

[0002]

2. Description of the Related Art A so-called stereoscopic method, in which two left and right image pickup devices are used as a distance measuring device, and two images obtained by the image pickup devices are made to correspond to the same object and the distance to the object is measured. A device utilizing is proposed. In such a stereoscopic method, the positional deviation (parallax) between two luminance information groups is obtained by using the luminance information from two different viewpoints, and the distance between the two viewpoints, the angle of view, and the number of luminance information measured in advance. Etc., the distance to the object is measured. The details will be described below.

FIG. 17 is a plan view showing a schematic structure of an optical system of a conventional distance measuring device based on a general stereoscopic method. The object M shown in FIG. 17A is an object to be measured. The distance measuring device is provided with two lenses 11 and 12 facing the object M in order to form two viewpoints, and these optical axes S1 and S2 are behind these two lenses 11 and 12, respectively. Matching image pickup devices 13 and 14 are provided. The optical axes S1 and S2 have a positional relationship parallel to each other. The image pickup devices 13 and 14 are, for example, CCDs (Charge C
oupled Device).

Here, "De" in the figure is the lens 11, 1.
2 is the distance between the object M, “f” is the focal length of the lenses 11 and 12, and “Z1” and “Z2” are points at which the object M is focused on the imaging elements 13 and 14 via the lenses 11 and 12, respectively. And the optical axes S1 and S2, "P" is the optical axes S1 and S2
It is the pitch between. In addition, FIG.
(A) One of the image pickup devices is moved so that the optical axes of both are overlapped. As shown in FIG. 17 (b),
The triangle ABC and the triangle ADE are similar to each other,
The ratio of (Z1 + Z2) to P is the same as the ratio of f to De. By using the formula, (Z1 + Z2): P = f: De, and by transforming this, the following formula is obtained.

De = Pf / (Z1 + Z2) In the above equation, since the pitch P and the focal length f of the lenses 11 and 12 are known, the distance De to the object M can be calculated by obtaining (Z1 + Z2). become. here,
In order to obtain (Z1 + Z2), the brightness values of the objects in the left and right images are compared while being shifted little by little, and the shift amount that most matches is set as the corresponding value. That is, this shift amount is (Z1
+ Z2), and this shift amount (Z1 + Z2) is called parallax.

If "Z1 + Z2" in the above equation is replaced with "δK0", the following equation is obtained. De = P · f / (δ · K0) where “δ” is the parallax represented by the number of pixels. Also,
"K0" is the length per unit pixel number of the image pickup devices 13 and 14, and this is a known value. Therefore,
If "δ" is known, the parallax on the screen can be obtained.

[0007]

However, in the above distance measuring apparatus, the optical axes S1 and S2 in FIG. 17 are deviated from the initial setting state due to environmental factors such as changes with time and temperature, and the distance measuring accuracy is improved. There is a problem of decrease. That is, when the optical axes S1 and S2 cannot be kept parallel, it causes a distance measurement error. In the conventional device, there is generally one that mechanically corrects the deviation of the optical axis using a calibration device or the like, but the correction is not one that can sufficiently cope with the above-mentioned aging and environmental factors, This issue has been a matter of concern.

The present invention has been made in view of the above problems, and an object of the present invention is to accurately correct a deviation of an optical axis and perform a highly accurate distance measurement. To provide.

[0009]

First of all, the distance measuring device of the present invention is provided with a pair of image pickup means which are provided at a constant interval and which obtains an image of an object, and a parallax in the direction of separation between the image pickup means. Distance measuring means for determining the distance to the object. Further, in addition to the above configuration, a standard value of parallax corresponding to the reference object is stored in advance, and deviation calculating means for calculating a deviation between the parallax at that time and the standard value of the parallax with respect to the reference object, And a distance correction unit that corrects the distance calculated by the distance measurement unit using the deviation calculated by the deviation calculation unit as a correction amount.

In short, in the stereoscopic method in the distance measuring apparatus of the present invention, the optical axes of the pair of image pickup means are set in parallel and the distance to the object is measured based on these optical axes. If the optical axis deviates from the initial setting due to a change or a temperature factor, the accuracy of distance measurement deteriorates. Therefore, in the present invention, as described above, the deviation between the standard value of parallax and the parallax at each time (for example, an error calculated and updated at every predetermined time) is calculated. This deviation corresponds to the amount of deviation of the optical axis. In such a case, by correcting the distance measurement value using the parallax deviation as a correction value, it is possible to eliminate the distance measurement error due to the deviation of the optical axis of the imaging means, and prevent the measurement accuracy from decreasing.

According to the invention of claim 2, in the invention of claim 1, the parallax distribution calculating means obtains the parallax distribution of the image obtained by the image pickup means. Also,
The deviation calculating means uses the point at infinity in the image as the reference object and the point at which the parallax is near zero as the standard value of the parallax,
The deviation of the parallax is calculated from the degree of change of the parallax distribution near the standard value. In this case, for example, as described in claim 3, the point where the parallax distribution sharply decreases in the region where the parallax shifts from a positive value to a negative value is regarded as the parallax corresponding to the point at infinity at that time. May be. Note that the point at infinity in the present specification is a viewpoint that generally exists most when the vehicle is traveling, and corresponds to a viewpoint excluding a vehicle traveling in front of the own vehicle and a three-dimensional obstacle on the road. .

That is, the most parallax corresponding to the point at infinity exists in the image obtained outdoors, and if the mutual optical axes of the image pickup means are kept parallel to each other, the parallax corresponding to this point at infinity is It becomes zero. Further, theoretically, the parallax is not distributed on the negative side of the parallax (= zero) corresponding to the point at infinity. Therefore, the deviation of the parallax corresponding to the deviation amount of the optical axis can be obtained from the degree of change of the parallax distribution near the parallax zero, and the deviation of the optical axis of the image pickup means can be accurately corrected to obtain a highly accurate distance. Measurement can be performed.

According to a fourth aspect of the present invention, in the second or third aspect of the invention, the parallax distribution calculation means sets a specific range including a point where the parallax is zero as a calculation range of the parallax distribution. In this case, the deviation (correction value) of the parallax is calculated only in the area corresponding to the point at infinity, and the calculation load required to eliminate the deviation of the optical axis can be significantly reduced.

According to a fifth aspect of the present invention, in the first aspect of the invention, the deviation calculating means sets an object whose distance in the image is known as a reference object to an object whose distance is already known. The parallax deviation is calculated from the standard value of the corresponding parallax and the parallax at each time corresponding to the same object. In this case, by obtaining the deviation (correction value) of the parallax with reference to an object whose distance is known, the deviation of the optical axis can be accurately corrected, and highly accurate distance measurement can be performed, as in the above claims. .

With respect to the invention described in claim 5, as described in claim 6, if an object whose distance is known is made a part of the own vehicle, the object whose distance is known can be easily set. it can. In this case, the known distance does not deviate from the true distance. In addition, as described in claim 7, the deviation calculation means significantly reduces the calculation load by performing the parallax calculation in a specific range including the standard value of the parallax corresponding to the object whose distance is known. You can

Further, in the invention described in claim 8, in the invention described in claim 1, the first means of the deviation calculating means uses the point at infinity in the image as a reference object and the parallax is near zero. The point that becomes is the standard value of the parallax, and the deviation of the parallax is calculated from the degree of change of the parallax distribution in the vicinity of the standard value. The second means uses the object whose distance in the image is known as a reference object, and the parallax deviation from the standard value of the parallax corresponding to the object whose distance is known and the parallax at that time corresponding to the same object. To calculate. The updating means updates the parallax deviation by selectively using at least one of the deviation calculated by the first means and the deviation calculated by the second means.

More specifically, in the invention described in claim 9, the updating means is the one before the updating among the deviation calculated by the first means and the deviation calculated by the second means. The deviation is updated with the value closer to the deviation. Moreover, in the invention described in claim 10, the updating means is:
The deviation is updated with an intermediate value between the deviation calculated by the first means and the deviation calculated by the second means.

That is, in the invention described in claims 8 to 10, a more accurate correction value is obtained by selectively using two deviations calculated by two different means,
The accuracy of distance measurement can be improved.

According to the eleventh aspect of the present invention, in the first aspect,
In the invention described in any one of 10, the deviation calculating means calculates the deviation between the parallax at that time with respect to the reference object and the standard value of the parallax to less than one pixel of the image by using interpolation calculation. In this case, more accurate correction calculation can be performed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of this embodiment. In the figure, an imaging device 1A as an imaging means,
1B has the pair of left and right lenses and the image pickup device described in FIG. 17, and outputs an image signal in front of the host vehicle. A / D converters 2A and 2B are connected to the image pickup apparatuses 1A and 1B, and the A / D converters 2A and 2B convert the image signals into luminance values of 256 gradations, for example. A / D converters 2A, 2
A distance calculator 3 mainly composed of a microcomputer is connected to B. The distance calculator 3 performs a correlation calculation from the brightness information of the left and right images, and detects the parallax from the minimum value of the correlation values calculated by the calculation.
And a distance calculation unit 5 that calculates the distance to the target object from the parallax detected by the parallax detection unit 4, and a determination unit 6 that determines whether the distance to the target object is in a dangerous area for the host vehicle.
And Further, the determination unit 6 is connected with a measured distance or a distance or warning indicator 7 for displaying a warning or the like for an obstacle.

In FIG. 1, the distance calculator 3 is shown for each functional block, but in actuality, the processing of each block is collectively executed by the arithmetic processing by the microcomputer. In this embodiment, the distance calculator 3 constitutes distance measuring means, deviation calculating means, distance correcting means, and parallax distribution calculating means.

FIG. 2 shows an image obtained by either the left or right image pickup device in the distance measuring device mounted on the vehicle. Speaking of such an image, the distance calculator 3
For example, the correlation value V (i) is calculated by shifting a small area (B1 in FIG. 2) composed of vertical 8 pixels × horizontal 8 pixels by 1 in the direction in which parallax occurs.

More specifically, the arrangement of the brightness values of the left and right two-dimensional images is treated as a sequence, and these are treated as "am, n", "bm,
Then, the correlation value V (i) is calculated by the following equation as "n".

[0025]

(Equation 1) However, "i" is the offset amount, "n" is the pixel number of the image,
"W" is the size of the region (8 in this case). In the present embodiment, the correlation value V (i) is calculated by shifting the data of the left image by one pixel with respect to the data of the right image, that is, increasing “i” by one. According to the calculation result of the correlation value V (i), the shift amount i of the point where the correlation value V (i) becomes the minimum value is obtained as the parallax. The parallax is obtained on the entire screen, and the parallax distribution is stored in the memory 8.

On the other hand, when the parallelism of the optical axes (S1, S2 in FIG. 17) in the pair of left and right image pickup devices 1A, 1B is deviated, the parallax obtained as described above is erroneous, and the distance is measured. Accuracy deteriorates. Therefore, in the present embodiment, (a) the image obtained outdoors has the most objects considered to be infinity points, and (b) if the optical axes maintain parallelism, it is considered to be infinity points. The parallax that can be obtained is “0”. (C) Similarly, if the optical axes maintain parallelism, theoretically the parallax does not become negative, so the parallax distribution on the negative side becomes sharp. Focusing on the decrease, the correction amount of the parallax due to the shift of the optical axis is calculated, and the distance is measured using the correction amount.

Next, the distance measuring procedure in this embodiment will be described with reference to FIGS. FIG. 3 is a schematic flow chart showing distance measurement and obstacle judgment processing, and this processing is executed by the distance calculator 3 at predetermined time intervals (for example, every 0.2 seconds). In addition, FIG. 4 is a schematic flow chart showing the calculation process of the parallax correction amount.
It is executed by interruption every time.

When the processing of FIG. 3 is started, first, at step 101, the distribution of parallax is obtained over the entire screen, and at step 102, the parallax distribution is stored in the memory 8 in the distance calculator 3.

In step 103, the parallax correction value FA for performing parallax correction due to the deviation of the optical axis is read. Here, the parallax correction value FA is obtained by the interrupt process shown in FIG. 4, and the interrupt process will be described. That is, in FIG. 4, in step 201, a parallax histogram is created from the parallax distribution information, and then in step 2
In 02, the parallax to be corrected is obtained from the histogram.

This will be specifically described with reference to the histograms of FIGS. Note that FIG. 5 shows a histogram in a state where the optical axis is not displaced, and FIG. 6 shows a histogram in a state where the optical axis is displaced. That is, in the state where the optical axis is not displaced, the frequency at the point G (parallax = 0) is the highest as shown in FIG. 5, and sharply decreases on the negative side.
This point G corresponds to the parallax at the point at infinity (standard value of parallax). Further, when the optical axis is displaced, the parallax histogram is generally shifted to the negative side as shown in FIG. 6, for example. When the optical axis is deviated, the point H in FIG. 6 corresponds to the parallax at the point at infinity. The difference in parallax between these points G and H is the “parallax correction value F”.
A ".

When the parallax correction value FA is calculated by interpolation calculation, the following procedure is followed. That is, as shown in FIG. 7, at points I and J before and after the point H where the frequency is maximum near the parallax = 0, the frequency is I <J, and therefore the straight line L1 passing between the points H and I is used. pull. Next, a straight line L2 that is symmetric to the straight line L1 and passes through the point J is drawn, and these straight lines L
Find the intersection K of 1 and L2. The point K thus obtained corresponds to the parallax by interpolation, and the deviation of the parallax between the point K and the point G becomes the “parallax correction value FA”.

After the parallax correction value FA is obtained as described above, in step 203 of FIG. 4, the parallax correction value FA is updated as the current value, and this processing ends. Further, returning to the processing of FIG. 3, in step 104, based on the difference images obtained from the image pickup devices 1A and 1B, three-dimensional objects such as vehicles and telephone poles in front of the own vehicle and plane information such as road markings are obtained. Then, the three-dimensional object is identified as an obstacle, and the distance to the obstacle is calculated using the following equation.

De = Pf / {(δ + FA) K0} Here, as described above, "δ" is the parallax represented by the number of pixels, and "K0" is the length per unit number of pixels of the image sensor. That's it.

In step 105, the relative speed to the obstacle is calculated by comparing the distance measured last time and the distance measured this time, and in the following step 106, the vehicle speed of the host vehicle is obtained. After that, in step 107, the degree of danger of the current traveling state is judged from the distance to the obstacle (inter-vehicle distance), the relative speed, and the speed of the own vehicle (own vehicle speed), and the following step 1
At 08, it is judged from the judged degree of danger whether or not the current driving is dangerous. This determination of the degree of risk is performed based on the relationship shown in FIG. 8, for example, and if the warning area is in the range shown in FIG. If it is determined that the vehicle is dangerous, an alarm is issued in step 109.

As described above in detail, in the present embodiment, the point at infinity in the image is used as the reference object, and the point where the parallax is near zero is set as the standard value (parallax = 0) of the parallax, and the vicinity of the standard value is set. The parallax correction value FA from the degree of change of the parallax distribution in
The (parallax deviation) is calculated (processing in FIG. 4).
In this case, the point where the parallax distribution sharply decreases in the region where the parallax shifts from a positive value to a negative value is regarded as the parallax corresponding to the infinity point at that time.

That is, the most parallax corresponding to the point at infinity exists in the image obtained outdoors, and if the mutual optical axes of the image pickup means are kept parallel, the parallax corresponding to this point at infinity will not occur. It becomes zero. Further, normally, the parallax is not distributed on the negative side of the parallax (= 0) corresponding to the point at infinity.
Therefore, the parallax correction value FA corresponding to the amount of deviation of the optical axis can be obtained from the degree of change of the parallax distribution in the vicinity of zero parallax, and the deviation of the optical axis due to environmental factors such as temporal change and temperature can be accurately calculated. It is possible to correct and perform highly accurate distance measurement.

Further, in this embodiment, the parallax correction value FA is calculated to less than one pixel of the image by using the interpolation calculation. As a result, more accurate correction calculation can be performed. The present embodiment corresponds to the invention described in claims 1 to 3.

(Second Embodiment) Next, a second embodiment embodying the invention described in claims 5 to 7 will be described with reference to FIG.
~ It demonstrates using FIG. However, in the configuration and the like of this embodiment, the description of the same components as those of the above-described first embodiment will be omitted. And, below, the first
The following description focuses on the differences from the first embodiment.

FIG. 9 is a side view showing the front portion of the vehicle. In FIG. 9, the optical section 21 of the image pickup device is installed on the ceiling of the passenger compartment. Also, the hood 2 of your vehicle
An emblem 23 having a shape such as a symbol mark of a vehicle maker is attached to a tip of the vehicle 2. In such a case, the distance between the optical unit 21 and the emblem 23 is constant as long as the respective positions are fixed.

FIG. 10 shows an image of one of the image pickup devices of the distance measuring device mounted on the vehicle. In the image of FIG.
The hood 22 and the emblem 23 of the vehicle are shown in the lower center of the screen, and a region (hereinafter referred to as window Wz) partitioned by a predetermined address is set around the emblem 23. The parallax with respect to the emblem 23 in the window Wz is calculated based on the correlation value with respect to the amount of shift between the left and right screen images.

Next, the distance measuring procedure in this embodiment will be described with reference to FIGS. FIG. 11 is a schematic flow chart showing distance measurement and obstacle judgment processing. This processing is performed by the distance calculator 3 at predetermined time intervals (for example, every 0.2 seconds).
Is executed. In addition, FIG. 12 is a schematic flow chart showing the calculation process of the parallax correction amount, and this process is executed by the distance calculator 3 by, for example, interruption when the ignition key is turned on.

Now, when the processing of FIG. 11 starts, first in step 301, the distribution of parallax is taken over the entire screen,
In the following step 302, an obstacle in front of the host vehicle is extracted from the entire parallax distribution. That is, the imaging devices 1A and 1
Based on the difference image obtained from B, a three-dimensional object such as a vehicle or a utility pole in front of the own vehicle and plane information such as a road sign are identified, and the three-dimensional object is extracted as an obstacle.

Thereafter, in step 303, the parallax correction value FB for performing parallax correction due to the shift of the optical axis is read, and the distance De to the obstacle is calculated from the following equation using the parallax correction value FB.

De = Pf / {(δ + FB) K0} Here, the parallax correction value FB is the deviation of the parallax corresponding to the same object with the emblem 23 existing in the window Wz as the reference object. Required. Hereinafter, the parallax correction value FB will be described with reference to interrupt processing for calculating the correction value FB (flow in FIG. 12) and graphs (FIGS. 13 to 15) showing the correction value FB more specifically.

That is, FIG. 13 is a graph showing the correlation value V (i) when the optical axis is not displaced, and FIG. 14 is the correlation value V (i) when the optical axis is displaced. It is a graph. Note that FIGS. 13 and 14 correspond to graphs when the correlation value V (i) is obtained by shifting either the left or right image by two pixels. That is, in the state where there is no deviation of the optical axis, FIG.
As shown in, the correlation value V (i) becomes minimum at the point M (i = 96), and the parallax at this point M corresponds to the standard value of the parallax. On the other hand, when the optical axis is displaced, the parallax that minimizes the correlation value V (i) shifts from the point M (i = 96) to the point N (i = 94) as shown in FIG. At this time, the shift amount of the parallax between the points M and N becomes the “parallax correction value FB” in units of 2 pixels.

On the other hand, when interpolation calculation is used, the following procedure is followed. That is, as shown in FIG. 15, at the points O and P before and after the point N, the frequency is O> P, so a straight line L3 passing through the points N and O is drawn. Next, a straight line L4, which is symmetric to the straight line L3 and passes through the point P, is drawn, and the parallax at the intersection Q of these straight lines L3 and L4 is an interpolated value (i≈94.7).
And The shift amount of the parallax between the point Q and the point M calculated in this way becomes the “parallax correction value FB” in units of less than 2 pixels.

Further, explaining the processing of FIG. 12, in step 401, for a specific area (window Wz of FIG. 10) on the screen, the standard value of the parallax corresponding to the emblem 23 in the area (FIG. 13). Read point M). In step 402, the parallax (point Q in FIG. 15) corresponding to the emblem 23 in the specific area is obtained for the specific area by interpolation calculation. Then, in step 403, the deviation between the parallax obtained by the interpolation and the standard value of the parallax is calculated as the parallax correction value FB.
Is updated as the current value of, and this processing ends.

Returning to the processing of FIG. 11, step 30
In 4, the relative speed with respect to the obstacle is calculated from the comparison between the distance measured last time and the distance measured this time. In step 305, the vehicle speed of the host vehicle is calculated. Then, in step 306, the degree of danger is calculated from the distance to the obstacle (inter-vehicle distance), the relative speed, and the speed of the host vehicle (host vehicle speed). For the determination of the degree of risk, for example, the relationship shown in FIG. 8 is used. In the following step 307, it is determined whether or not the driving is dangerous. If it is determined that the vehicle is dangerous, step 308
Then an alarm is issued.

As described above in detail, in the present embodiment, the standard value of the parallax corresponding to the emblem 23 and the parallax corresponding to the emblem 23 are set with the object (emblem 23) whose distance in the image is known as the reference object. Then, the deviation of the parallax is calculated, and the deviation is set as the parallax correction value FB (processing of FIG. 12). In this case, like the first embodiment, the deviation of the optical axis can be accurately corrected, and the distance measurement can be performed with high accuracy.

Further, in this embodiment, since the emblem 23 which is a part of the own vehicle is used as the reference object (object whose distance is known), the object can be easily set. In addition, the true parallax (true distance) corresponding to the emblem 23
Can be set easily.

Further, in this embodiment, the emblem 23
Set the window Wz so that it surrounds
Since the parallax calculation is performed on the specific area corresponding to z, the calculation load for calculating the correction value can be significantly reduced.

(Third Embodiment) Next, a third embodiment of the present invention as defined in claims 8 and 9 will be described. However, in the configuration and the like of this embodiment, the description of the same components as those of the above-described first and second embodiments will be omitted. Then, the differences from the first and second embodiments will be mainly described below.

FIG. 16 is a schematic flow chart showing the distance measurement and obstacle judgment processing in this embodiment. This processing is executed by the distance calculator 3 at predetermined time intervals (for example, every 0.2 seconds).

When the processing of FIG. 16 starts, first in step 501, the distribution of parallax is taken over the entire screen,
In the following step 502, the parallax distribution is stored in the memory 8 in the distance calculator 3. In step 503, the parallax correction value FA obtained from the parallax distribution at the point at infinity is read. The parallax correction value FA corresponds to the value obtained by the interrupt process of FIG. 4 in the first embodiment.

Further, in step 504, the parallax correction value FB obtained from the parallax deviation corresponding to the specific area is read. This parallax correction value FB corresponds to the value obtained by the interrupt processing of FIG. 12 in the second embodiment.

After that, in step 505, which of the parallax correction values FA and FB is a valid correction value is selected. In this case, which is appropriate is determined according to the difference between the correction value and the previous value, and the value having the smaller difference from the previous value, that is, the value closer to the previous value is updated as this time. . That is, a value having a large difference from the previous value is treated as an error value.

Thereafter, in step 506, the image pickup apparatus 1
Based on the difference image obtained from A and 1B, a three-dimensional object such as a vehicle or a telephone pole in front of the own vehicle and plane information such as a road marking are identified, and the three-dimensional object is regarded as an obstacle, and the obstacle is concerned. Calculate the distance to. After that, step 507
In steps 511 to 511, the degree of danger is determined from the relative speed with respect to the obstacle, the speed of the host vehicle, and the distance from the obstacle. Since this process is equivalent to steps 105 to 109 of FIG. 3 and steps 304 to 308 of FIG. 11, description thereof will be omitted.

As described above in detail, in this embodiment, the parallax correction value FA is obtained from the parallax distribution corresponding to the point at infinity in the image, and the parallax correction value is calculated from the deviation of the parallax corresponding to the emblem 23 whose distance is known. FB is calculated, and both correction values F
The distance correction is performed by using the correction value that is judged to be proper of A and FB. More specifically, the value closer to the previous correction value is used. According to the above configuration, by using the two correction values selectively, a more accurate correction value can be obtained, and the accuracy of distance measurement can be improved.

The present invention can be embodied in the following modes other than the above embodiment. (1) In the first embodiment, the calculation process is performed so as to obtain the parallax distribution of the entire screen, but the calculation range of the parallax distribution may be limited to a specific range including a point where the parallax is zero. . In this case, the deviation (correction value) of the parallax is calculated only in the area corresponding to the point at infinity, and the calculation load required to eliminate the deviation of the optical axis can be significantly reduced. The present embodiment corresponds to the invention described in claim 4. In particular, if the specific range for obtaining the parallax distribution is halved on the screen, there will be many objects located far away within the specific range (excluding vehicles in front and signs), and the point at infinity. Is easy and reliable.

(2) In the second embodiment, the process of selecting an appropriate value from the parallax correction values FA and FB may be changed as follows. For example, the intermediate value of the parallax correction values FA and FB is updated as the correction value at that time, and the distance is corrected by the updated correction value. This embodiment is claim 1.
0 corresponds to the invention described in 0.

(3) In each of the above-described embodiments, the degree of danger of the current running state is determined from the inter-vehicle distance, the relative speed, and the speed of the host vehicle, but this is determined from the inter-vehicle distance and the speed of the host vehicle. May be changed to

(4) In the second and third embodiments, the emblem 2 of the own vehicle is used as an object (reference object) whose distance is known.
However, this may be changed. For example, the pattern on the hood of the host vehicle, the parting line, or the like may be changed. Further, it is also possible to set two or more reference objects and selectively use them to improve the correction accuracy.

(5) In each of the above embodiments, the distance calculator 3
Is configured by a microcomputer and the parallax distribution and distance are measured by software processing, but this may be configured by hardware such as an electric circuit.

(6) In each of the above embodiments, the parallax calculation is performed for the two-dimensional area of the image, but it may be changed so as to be performed for the one-dimensional area.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a distance measuring device according to an embodiment of the invention.

FIG. 2 is a diagram showing an image of either the left or right imaging device.

FIG. 3 is a flowchart showing an outline of distance measurement and obstacle judgment processing according to the first embodiment.

FIG. 4 is a flowchart showing interrupt processing for correction.

FIG. 5 is a histogram showing a parallax distribution in a state where the optical axis is not displaced.

FIG. 6 is a histogram showing a parallax distribution in a state where the optical axis is displaced.

FIG. 7 is a histogram showing a parallax distribution for explaining interpolation calculation.

FIG. 8 is a map used to determine whether or not the traveling state is in an alarm area.

FIG. 9 is a diagram showing a configuration of a front portion of a host vehicle in the second embodiment.

FIG. 10 is a diagram showing a video image of either the left or right imaging device according to the second embodiment.

FIG. 11 is a flowchart showing an outline of distance measurement and obstacle determination processing according to the second embodiment.

FIG. 12 is a flowchart showing an interrupt process for correction.

FIG. 13 is a graph showing a relationship between a parallax and a correlation value in a state where the optical axis is not displaced.

FIG. 14 is a graph showing a relationship between a parallax and a correlation value when there is a shift of an optical axis.

FIG. 15 is a graph for explaining interpolation calculation.

FIG. 16 is a flowchart showing an outline of distance measurement and obstacle judgment processing according to the third embodiment.

FIG. 17 is a diagram showing a configuration of a distance measuring device based on a general stereoscopic method.

[Description of Reference Signs] 1A, 1B ... Imaging device as imaging means, 3 ... Distance measuring means, deviation calculating means (first means, second means, updating means), distance correcting means, parallax distribution calculating means Distance calculator.

Claims (11)

[Claims] 1. A distance measuring device comprising a pair of image pickup means provided at regular intervals to obtain an image of an object and a distance measuring means for obtaining a distance to the object from a parallax in a separation direction of each image pickup means. In, the standard value of the parallax corresponding to the reference object is stored in advance, the deviation calculation means for calculating the deviation between the parallax at that time and the standard value of the parallax with respect to the reference object, and the deviation calculation means A distance measuring device, comprising: a distance correcting unit that corrects the distance calculated by the distance measuring unit using the calculated deviation as a correction amount. 2. A parallax distribution calculating means for obtaining a parallax distribution of an image obtained by the image pickup means, wherein the deviation calculating means uses a point at infinity in the image as a reference object and has a parallax near zero. The distance measuring device according to claim 1, wherein the parallax deviation is calculated from the degree of change of the parallax distribution in the vicinity of the standard value, with the parallax being a standard value. 3. The distance measuring device according to claim 2, wherein the deviation calculating unit determines a point where the parallax distribution sharply decreases in a region where the parallax shifts from a positive value to a negative value, at that time point of infinity. Distance measuring device that is regarded as parallax corresponding to. 4. The distance measuring device according to claim 2 or 3, wherein the parallax distribution calculating means sets a specific range including a point where the parallax is zero as a calculation range of the parallax distribution. 5. The deviation calculating means uses an object whose distance in the image is known as a reference object, and calculates the standard value of the parallax corresponding to the object whose distance is known and the parallax at each time corresponding to the same object. The distance measuring device according to claim 1, wherein the deviation of parallax is calculated. 6. The distance measuring device according to claim 5, wherein the object of which the distance is known is a part of a vehicle equipped with the image pickup means. 7. The distance measuring device according to claim 5, wherein the deviation calculating means performs a parallax calculation in a specific range including a standard value of parallax corresponding to an object whose distance is known. . 8. A parallax distribution calculating means for obtaining a parallax distribution of an image obtained by the image pickup means, wherein the deviation calculating means uses an infinite point in the image as a reference object and has a parallax near zero. As a standard value of the parallax, a first means for calculating the deviation of the parallax from the degree of change of the parallax distribution in the vicinity of the standard value, and an object whose distance in the image is known as a reference object, the distance is known. Second means for calculating the deviation of the parallax from the standard value of the parallax corresponding to the object and the current parallax corresponding to the same object; and the deviation calculated by the first means and the second means. The distance measuring device according to claim 1, further comprising an updating unit that updates the deviation of the parallax by selectively using at least one of the calculated deviations. 9. The distance measuring device according to claim 8, wherein the updating means is a deviation before updating, of the deviation calculated by the first means and the deviation calculated by the second means. Distance measurement device that updates the deviation with a value closer to. 10. The distance measuring device according to claim 8, wherein the updating means updates the deviation with an intermediate value between the deviation calculated by the first means and the deviation calculated by the second means. Distance measuring device. 11. The deviation calculation means calculates a deviation between a parallax at that time with respect to the reference object and a standard value of the parallax,
The distance measuring device according to any one of claims 1 to 10, which calculates less than one pixel of an image using interpolation calculation.