JP3354449B2 - Vehicle distance measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring apparatus for a vehicle, and more particularly, to a method for comparing a pair of images formed on an image sensor by a pair of optical systems and measuring a shift amount of both images from an optical axis. The present invention relates to a vehicle distance measuring device that detects a distance to a target object by performing an operation based on the principle of triangulation using the deviation amount.

[0002]

2. Description of the Related Art Conventionally, such a distance measuring device has been already known, for example, from Japanese Patent Publication No. 3-72930. In this device, an image sensor composed of a plurality of line sensors is used. If the obtained distance is almost the same value, the distance obtained by the central line sensor is adopted as the distance to the object, and the previous distance value is maintained during a curve running or a long distance. I have.

[0003]

However, in the above-described conventional apparatus, the distance to the object when the vehicle is suddenly accelerated or decelerated is different from the previous distance value, making it difficult to recognize the object.
There is a possibility that a background distance that is close to the previous distance value may be erroneously recognized as an object.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is intended for a vehicle for accurately recognizing an object without erroneously recognizing a background other than a preceding vehicle and obtaining an accurate measurement distance. An object of the present invention is to provide a distance measuring device.

[0005]

According to a first aspect of the present invention, a pair of images formed on an image sensor by a pair of optical systems are compared with each other, and the distance between the optical axes of the two images is measured. In the vehicle distance measuring device that electrically detects the deviation amount and executes a calculation based on the principle of triangulation by using the deviation amount to measure the distance to the object, the distance based on the principle of triangulation is used. the calculated distance D _W is the distance D _P measured last time, the first set value that is determined based on the distance D _P measured last time [alpha] 1, the second set value that is determined based on the distance D _P the previously measured α2 Then, (D _P -α
When the value satisfies 1 ≦ D _W ≦ D _P + α2), a distance output evaluation unit that evaluates the distance D _W calculated this time as the current measurement distance is provided.

According to the configuration of the first aspect of the present invention, the present calculated distance value D _W is equal to or larger than the previous measured distance D _P by a first set value α1 or more, and when than D _P is greater value or less by the second set value [alpha] 2, the current calculated distance value D _W as the distance to the object
And the first and second set values α1, α
2 is determined based on the previous measurement distance D _P , so that a distance substantially matching the distance to the object estimated based on the previous measurement distance D _P can be determined as the distance to the object, and the curve It is possible to accurately measure the distance to the target object without erroneously recognizing a background or the like other than the preceding vehicle even when traveling.

[0007] The invention according to claim 2 provides the above-described claim 1.
In addition to the configuration of the invention, wherein the first and second setting value [alpha] 1, characterized in that α2 is defined as a quadratic function of the distance D _P previously measured, according to the configuration of the invention of claim 2, wherein If the resolution of this type of distance measuring device is
Based on the fact that it is proportional to the power, both set values α1 and α2 are relatively large for a long distance, and both set values α1 and α2 are relatively small for a short distance. The distance to the target object can be measured with the corresponding accuracy.

According to a third aspect of the present invention, in addition to the configuration of the first aspect of the present invention, there is further provided a relative speed calculating means for obtaining a relative speed with respect to the object based on a change in a past measured distance. 2 Set value α2 is the distance D _P measured last time,
The present invention is characterized in that it is determined based on the relative speed obtained by the relative speed calculating means, and according to the configuration of the invention as set forth in claim 3, the change tendency of the relative speed of the object and the own vehicle is taken into consideration. As a result, the second set value α2 is determined, and the setting accuracy in the direction away from the vehicle within the range defined as the distance to the object can be improved, and the distance to the object can be measured more accurately. .

The invention according to a fourth aspect of the present invention further includes, in addition to the configuration of the third aspect of the present invention, an own vehicle speed detecting means for detecting the speed of the own vehicle, wherein the first set value α1 is determined by a previous measurement. The distance is determined based on the determined distance D _P and the own vehicle speed obtained by the own vehicle speed detecting means. According to the configuration of the invention as set forth in claim 4, the own vehicle speed is taken into consideration. As a result, the first set value α1 is determined, so that the setting accuracy on the side close to the own vehicle in the range defined as the distance to the object can be improved, and the distance to the object can be measured more accurately. it can.

[0010]

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 6 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. FIG. 4 is a diagram showing the arrangement of windows with respect to the image area, FIG. 4 is a diagram for explaining the differential waveform shaping by the correlation calculation means, FIG. 5 is a diagram for explaining the correlation calculation by the correlation calculation means, and FIG. FIG. 4 is a diagram for describing an interpolation calculation by a calculation unit.

First, referring to FIG.
A and 1B are arranged, for example, on the rear side of a windshield in a vehicle interior of a vehicle, and these imaging means 1A and 1B are provided.
The image signals of the object 4 such as the preceding vehicle obtained by the above are converted into digital signals by the individual A / D converters 6A and 6B, and stored in the individual image storage means 7A and 7B, respectively.

In FIG. 2, both imaging means 1A and 1B are
Optical systems 2A and 2B including lenses and their optical systems 2
The two optical systems 2A and 2B are arranged at an interval vertically above and below the base line 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 an image on the image sensors 3A and 3B. The image sensors 3A and 3B include, for example, a plurality of vertically extending line CCDs as shown in FIG.
.. Are one-dimensional image sensors arranged at intervals from one another.

The image stored in the image storage means 7A, 7B
In the image signal, the window determined by the window determination means 8
Only the image signal of the image (shaded portion in FIG. 3) is cut out.
You. Of each line cut out from the image storage means 7A, 7B.
The image signal is processed by the correlation operation means 9. _One, 9_Two… 9_nTo each
Input and their correlation operation means 9_One~ 9_nAt
Image signals for each combination of windows W, W that correspond to each other
The signal correlation operation is executed.

In performing the correlation calculation, each correlation calculation is performed in order to avoid a decrease in the degree of correlation coincidence due to inferior image contrast at sunset or in the shade, and thus a decrease in distance measurement accuracy. in section 9 ₁ to 9 _n, as shown in Figure 4, by forming the luminance waveform reading the luminance of the image signal from the window W, then differential waveform by subtracting the luminance of the plurality of pixels for example 9 every other pixel in the vertical Is molded.

In the correlation calculation by each of the correlation calculation means 9 _{1 to} 9 _n , for example, one of the differentiated luminance data of the windows W, W corresponding to each other in the two image sensors 3A, 3B is fixed, and the other is fixed. The subtraction is performed while shifting one by one. That is, as shown in FIG. 5A, the luminance data of the image sensor 3B is fixed, and the luminance data of the image sensor 3A is subtracted from the luminance data of the image sensor 3B while shifting the luminance data one by one up and down. As a result, as shown in FIG. 5B, a shift amount corresponding to the correlation value is obtained, and the shift amount when the correlation value is the smallest is set as a value corresponding to the shift amount of the image signal from the optical axis. Desired.

Further, in each of the correlation calculating means 9 _{1 to} 9 _n , since there is an interval between the pixels of the line CCDs 5, 5,... In the two image sensors 3A, 3B, interpolation is performed between the pixels. An interpolation operation is performed to improve the resolution of the image sensors 3A and 3B. In this interpolation operation, as shown in FIG. 6, three points of a first point P1 which is a minimum correlation value and second and third points P2 and P3 which are correlation values close to the minimum correlation value are used. A straight line L passing through the first point P1 and one of the second and third points P2 and P3 P3
1 and the second and third points P at the same inclination as the straight line L1.
The intersection of the line P2 with the straight line L2 passing through the other P2 is obtained as an interpolation value, and this interpolation value is used as the shift amount n '. As shown by a chain line, an intersection of a straight line passing through the first point P1 and the second point P2 and a straight line passing through the third point P3 is also obtained, and this intersection has a correlation value larger than the minimum correlation value. Therefore, it is not adopted as an interpolation value.

[0019] In this way, after the shift amount n of the interpolated 'is obtained, the distance calculation unit 10 ₁ to 10 _n corresponding to each correlation operation unit 9 ₁ to 9 _n, the principle of the triangulation method The distance calculation based on each is performed. That is, the distance D _W to the object 4 for each combination of the windows W, W is obtained as D _W = (BL × f) / n ′. The image sensor 3
The distance _DW may be corrected based on temperature information obtained by a temperature-sensitive element arranged near A and 3B.

[0020] In this way, the distance D _W obtained by the distance calculating means 10 ₁ to 10 _n for each line are input to the distance output evaluation unit 11 ₁ to 11 _n, the calculated distance D _W until the object 4 whether or not capable of outputting the distance is evaluated respectively by the distance output evaluation unit 11 ₁ to 11 _n. Only Thus it was the object 4 Distance output evaluated to be outputted as the distance to the means 11 ₁ to 11 _n in evaluated the calculated distance D _W is input to the inter-vehicle distance calculating means 12, in該車distance calculating means 12 Then, processing such as averaging the calculated distance _DW that can be output as the distance to the object 4 is performed, and the distance to the object 4 such as a preceding vehicle is output from the inter-vehicle distance calculating means 12. Moreover the distance output from the inter-vehicle distance computing means 12 is temporarily stored in the inter-vehicle distance storage unit 14, the distance which has been stored in the inter-vehicle distance storage unit 14 when the distance output evaluation at each distance output evaluation unit 11 ₁ to 11 _n each distance output evaluating means as a previous measurement distance D _P 1
Is input to the 1 ₁ to 11 _n.

The combination of the windows W, W for which the distances D _W evaluated as being output as distances to the object 4 by the respective distance output evaluation means 11 _{1 to} 11 _n are calculated, is the preceding vehicle direction estimation means. 13, and the preceding vehicle direction estimating means 13 detects an object 4 such as a preceding vehicle based on the position of the window W which can be recognized as the preceding vehicle.
Is estimated, and the estimation result is reflected in the next window determination by the window determination means 8.

In each of the distance output evaluation means 11 _{1 to} 11 _n ,
This computed distance D _W is the previous measurement distance D _P obtained from the inter-vehicle distance storage unit 14, a first set value α1 determined based on previous measurement distance D _P, is determined based on the previous measurement distance D _P When the following inequality expression using the second set value α2 is satisfied, the distance D _W calculated this time when the value satisfies the following inequality D _P −α 1 ≦ D _W ≦ D _P + α 2 is evaluated as the current measurement distance.

Here, the first and second set values α1, α2
Is α1 = a · D _P ² + b1 (when α1 ≧ D _P , α1 =
D _P ) α2 = a · D _P ² + b2, where a is a constant determined by the base line length BL, the focal length f, the pixel pitch in each of the line CCDs 5, 5,. The b1 is the maximum distance that the object 4 can approach such as a preceding vehicle within the measurement period t _s in the distance measuring apparatus for the vehicle, the maximum speed that can be generated by the vehicle when the V _max for example, (b1 = V _max × t _s ). Further b2 is the maximum distance that the object such as a preceding vehicle on year measurement period t _s 4 may approach, the maximum speed can be generated by the preceding vehicle when the V _tmax example, (b2 = V _tmax
× t _s ).

As described above, the current calculated distance value D _W is equal to or larger than the previous measured distance D _P by a value smaller by the first set value α 1 and larger than the previous measured distance D _P by the second set value α 2. when it is less than or equal to the value, the current calculated distance value D _W is the distance output evaluating means as the distance to the object 11 ₁ to 11
By adopting _n , it is possible to determine, as the distance to the object 4, a distance substantially matching the distance to the object 4 estimated based on the previous measured distance D _P. Therefore, even when traveling on a curve or the like, it is possible to obtain an accurate measurement distance to the object 4 without erroneously recognizing a background or the like other than the object 4.

[0025] Moreover the first and second setting value [alpha] 1, [alpha] 2 are those defined as a quadratic function of the distance D _P measured last time, but the resolution of this kind of distance measuring apparatus is proportional to the square of the distance Therefore, in the case of a long distance, both the set values α1 and α2 are relatively large, and in the case of a short distance, both the set values α1 and α2 are relatively small. The distance to the object 4 can be measured.

FIG. 7 shows a second embodiment of the present invention, the relative velocity to the object 4 based on past at least twice the value of the measured distance D _P which is stored in the inter-vehicle distance storage means 14 V _C is calculated by the relative velocity calculation means 15,
A previously measured distance D _P from the inter-vehicle distance storage unit 14, and the relative velocity V _C calculated by the relative velocity calculation means 15 is input to each distance output evaluation unit 11 ₁ to 11 _n.

Thus, each of the distance output evaluation means 11 _{1 to} 11 _n
Then, when the distance D _W calculated this time is a value that satisfies the same inequality (D _P −α1 ≦ D _W ≦ D _P + α 2) as described above, the distance D _W calculated this time is evaluated as the current measurement distance. although being, this time, the first and second setting value [alpha] 1, [alpha] 2, when the ^{_{α1 = a · D P 2 +}} b1 (α1 ≧ D P, α1 =
_{D P) α2 = a · D} P 2 + has been defined as V _C · t _s + b3, V _C · t _s are those showing a distance that may vary within the measurement period t _s based on the relative velocity V _C It is. Also, b3 indicates the maximum distance that the object 4 such as the preceding vehicle can be separated from by the maximum change of the relative speed V _C that can change within the previous measurement period t _s . G _max, the maximum deceleration can be generated by the object 4 is taken as G _tmax, it is _{b3 = (G max + G tmax} ) × t s 2/2.

According to the second embodiment, the second set value α is set in consideration of the changing tendency of the relative speed V _C of the object 4 and the host vehicle.
2 is determined, and the setting accuracy in the direction away from the own vehicle in the range defined as the distance to the object 4 is improved, so that the distance to the object 4 can be measured more accurately.

FIG. 8 shows a third embodiment of the present invention. The speed of the host vehicle is detected by the host vehicle speed detecting means 16, and the host vehicle speed V _S detected by the host vehicle speed detecting means 16 is used. When,
A previously measured distance D _P from the inter-vehicle distance storage unit 14, and the relative velocity V _C calculated by the relative velocity calculation means 15 is input to each distance output evaluation unit 11 ₁ to 11 _n.

In each of the distance output evaluation means 11 _{1 to} 11 _n ,
The distance D _W calculated this time is equal to the inequality (D _P −
When the value satisfies α1 ≦ D _W ≦ D _P + α2), the distance D _W calculated this time is evaluated as the current measurement distance. At this time, the first and second set values α 1 and α
2, when ^{_{α1 = a · D P 2 +}} V S · t s (1α ≧ D P,
α1 = D _P ) α2 = a · D _P ² + V _C · t _s + b 3, where V _S · t _s is the object of the preceding vehicle or the like within the measurement cycle t _s based on the own vehicle speed V _S. It indicates the maximum distance that the object 4 can approach the own vehicle.

According to the third embodiment, since the first set value α1 is determined in consideration of the own vehicle speed V _S , the range set as the distance to the object 4 on the side close to the own vehicle is set. The accuracy is improved, and the second set value α2 is added in consideration of the relative speed V _C.
Is determined, the distance to the object 4 can be measured more accurately.

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.

For example, each of the image sensors 3A and 3B has a two-dimensional C in which a large number of pixels are dispersed in a two-dimensional plane.
It may be a CD or PD.

[0034]

As described above, according to the first aspect of the present invention, it is possible to determine, as the distance to the object, a distance substantially matching the distance to the object estimated based on the previous measured distance. Even when traveling on a curve or the like, the distance to the object can be accurately measured without erroneously recognizing the background other than the object.

According to the second aspect of the present invention, it is possible to measure a distance to an object with an accuracy corresponding to the distance.

According to the third aspect of the present invention, it is possible to improve the accuracy of setting the range defined as the distance to the object in the direction away from the vehicle, and more accurately measure the distance to the object.

Further, according to the present invention, it is possible to improve the setting accuracy on the side close to the own vehicle in the range defined as the distance to the object, and to more accurately measure the distance to the object. Can be.

[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 the principle of distance measurement.

FIG. 3 is a diagram showing an arrangement of windows with respect to an image area.

FIG. 4 is a diagram for explaining a differential waveform shaping by a correlation calculating unit.

FIG. 5 is a diagram for explaining a correlation calculation by a correlation calculation unit.

FIG. 6 is a diagram for explaining an interpolation calculation by a correlation calculation unit.

FIG. 7 is a block diagram illustrating a configuration of a distance measuring device according to a second embodiment.

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

[Explanation of symbols]

2A, 2B: Optical system 3A, 3B: Image sensor 4: Target object 11 _{1 to} 11 _n: Distance output evaluation means 15: Relative speed calculation means 16: Own vehicle speed detection means

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Kazuto Chisaka 1-4-1 Chuo, Wako-shi, Saitama Pref. Honda Technical Research Institute Co., Ltd. (56) References JP-A-9-68423 (JP, A) JP-A-9-79849 (JP, A) JP-A-7-149192 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01C 3/06 G01B 11/00 G06T 1/00 280 G08G 1/16 B60R 21/00 620

Claims (4)

(57) [Claims] 1. A pair of images formed on an image sensor (3A, 3B) by a pair of optical systems (2A, 2B) are compared to electrically detect a shift amount of both images from an optical axis, In a vehicle distance measuring device that measures the distance to the object (4) by executing a calculation based on the principle of triangulation using the deviation amount, the distance D _W calculated this time based on the principle of triangulation is: When the previously measured distance is D _P , the first set value determined based on the previously measured distance D _P is α1, and the second set value determined based on the previously measured distance D _P is α 2, D _P The distance output evaluation means (11 _{1) which} evaluates the currently calculated distance D _W as the current measured distance when the value satisfies −α1 ≦ D _W ≦ D _P + α2.
To 11 _n ). 2. The method according to claim 1, wherein the first and second set values α1, α2 are
Last measured distance D _PTo be defined as a quadratic function of
The vehicle distance measuring device according to claim 1, wherein: 3. A relative speed calculating means (15) for obtaining a relative speed with respect to an object (4) based on a change in a measured distance in the past.
And the second set value α2 is the distance D _P measured last time.
2. The vehicle distance measuring device according to claim 1, wherein the distance is determined based on the relative speed obtained by the relative speed calculating means. 4. A comprising a vehicle speed detecting means for detecting the speed of the vehicle (16), the first set value α1 is, the distance D _P measured last time, obtained by the vehicle speed detecting means (16) The vehicle speed is determined based on the own vehicle speed.
The distance measuring device for a vehicle according to the above.