JPH11344333A - Distance measuring device for vehicle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure distance to an object stably without increasing the operation time and cost with a distance measuring device for vehicles provided with a distance operation means operating the distance to the object by an operation based on the triangulation principle using the shift quantity of a pair of images from a light axis. SOLUTION: A tracking window as a region of operation object in correlation operation with a correlation operation means 8 is varied to be small as the operation distance becomes large when the operation distance of the distance operation means 9 does not vary or varies to be larger, maintained the size of immediately before the operation distance is varying to be smaller when the operation distance becomes smaller at a speed below the access speed of a static object to self-vehicle, and varied to be larger as the operation distance is varying to be smaller when the operation distance becomes smaller at a speed over the access speed of the static object.

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 for a vehicle, and more particularly, to a pair of optical systems, a pair of image sensors for forming images from the optical systems, and a pair of image sensors formed on both image sensors. A correlation operation unit that compares the image signals of the paired images and calculates a shift amount from the optical axis of the two images, and a calculation based on the principle of triangulation using the shift amount obtained by the correlation calculation unit. The present invention relates to a vehicle distance measurement device including a distance calculation unit that calculates a distance to an object.

[0002]

2. Description of the Related Art Conventionally, such a distance measuring device is disclosed in, for example, Japanese Patent Application Laid-Open Nos. 4-262499 and 4-262.
In the related art, image tracking of an object such as a preceding vehicle is performed as follows. That is, the first window and the second window, which is a part of the first window, are located within the field of view determined by the pair of optical systems.
A window is determined, a displacement of an image signal is detected in each of the first and second windows, a distance calculation is performed, and the next position of the first window is changed based on distance information from the first and second windows, The sizes of the first and second windows are changed based on the distance information from the first window, and stable image tracking is performed so that the windows do not shift from the object.

[0003]

However, in the above conventional device, as shown in FIG. 8, in addition to an object 4 such as a preceding vehicle, a background such as a tree 20 and a road surface character 21 is displayed in a first window W1. If it is included, the calculation distance may include an error due to the influence of the background. If the entire background around the object 4 is detected in the second window in order to prevent the occurrence of an error due to the influence of the background, the second window must be arranged above, below, and to the left and right of the first window W1. However, there is a possibility that the calculation time will increase and the cost of the device will increase. Furthermore, when calculating the distance by the second window, the distance by the second window in the measurement cycle may include an error due to the background, and the first window W1 is determined based on the fact that the background is included. When the position of the first window W1 is changed, the distance output may be unstable until the position of the first window W1 is changed.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has been made in consideration of the above circumstances, and is intended to provide a vehicle distance capable of more stably measuring a distance to an object without causing an increase in calculation time and cost. It is an object to provide a measuring device.

[0005]

In order to achieve the above object, the present invention provides a pair of optical systems and a pair of image sensors for forming images from the optical systems, respectively.
Correlation calculating means for comparing the image signals of a pair of images formed on both image sensors to calculate a shift amount from the optical axis of both images, and triangulation using the shift amount obtained by the correlation calculating means A distance calculating device for calculating a distance to an object by a calculation based on the principle of the above, wherein a region to be calculated within a field of view determined by both optical systems in performing a correlation calculation by the correlation calculating device. A window determining means for determining a tracking window based on the calculated distance of the distance calculating means, wherein the window determining means increases the calculated distance when the calculated distance is changed to a constant or larger side. The size of the tracking window is changed so as to become smaller as the distance becomes smaller, and the calculated distance becomes smaller at a speed less than the speed at which the stationary object approaches the own vehicle. The size of the tracking window immediately before changing to the smaller side is held, and when the calculation distance decreases at a speed higher than the speed at which the stationary object approaches the own vehicle, the tracking window increases as the calculation distance decreases. It is characterized in that the size of is changed.

According to such a configuration, when the distance between the object and the vehicle is constant or when the object moves away from the vehicle, the size of the object occupied in the field of view determined by the two optical systems. Since the tracking window is determined to have a size corresponding to the size, it is possible to avoid as much as possible that the background around the target is subjected to the correlation calculation and the distance calculation. When the calculation distance is smaller than the speed at which the stationary object approaches the own vehicle, the size of the tracking window immediately before the target object changes to the side closer to the own vehicle is held in the visual field. Although the area occupied by the target object increases, the size of the tracking window becomes constant, and it is possible to avoid as much as possible that a stationary object such as a road surface character is subjected to the correlation calculation and the distance calculation. Further, a state in which the calculation distance decreases at a speed equal to or higher than the speed at which the stationary object approaches the own vehicle is a state in which the target object may be lost. In this state, the calculation distance increases as the calculation distance decreases. By changing the size of the tracking window, it becomes possible to capture the lost object again in the tracking window.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

FIGS. 1 to 7 show an 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 window arrangement, FIG. 4 is a diagram corresponding to FIG. 3 for explaining distance determination, FIG. 5 is a flowchart showing processing in the first window shape changing unit, and FIG. 6 is a flowchart in the second window shape changing unit. FIG. 7 is a flowchart showing the processing, and FIG. 7 is a flowchart showing the processing in the third window shape changing 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.

Image sensor 3 of both optical systems 2A and 2B
A, 3B, image storage means 6A,
A tracking window WP for cutting out a part of the image signal stored in 6B and making it a target of the distance calculation is determined by the window determination means 7 as shown in FIG. 3, and the image signal in the tracking window WP is determined. Are image storage means 6A, 6
B is input to the correlation calculation means 8.

In addition, as shown in FIG. 3, a plurality of calculation windows WC... Are provided in the visual field determined by the optical systems 2A and 2B.
The correlation calculation means 8 sets the two image sensors 3A and 3B for each calculation window WC in the tracking window WP, for example, WC1 to WC8 in FIG.
The calculation for obtaining the shift amount n at the point where the correlation of the luminance data obtained from the best match is performed.

That is, the correlation calculating means 8 shifts one of the images of the two image sensors 3A and 3B for each of the calculation windows WC1 to WC8, or
The subtraction of both image signals is performed by alternately shifting both of the 3B images, and the shift amount n when the two image data are most matched, that is, when the correlation value is the minimum.
Is obtained. Thus, the shift amount n is
As shown in FIG. 2, the shift amount nA of the image signal obtained from the lower image sensor 3A from the optical axis of the optical system 2A,
This is obtained as the sum of the image signal obtained from the upper image sensor 3B and the shift amount nB from the optical axis of the optical system 2B. In calculating the shift amount n, the resolution is determined by the interval between pixels in the image sensors 3A and 3B. Therefore, in order to improve the resolution, the shift amount n is corrected by performing interpolation between the intervals. You may.

The distance calculating means 9 includes an individual distance calculating unit 10
And a distance storage unit 11 and a distance determination unit 12.

The individual distance calculation unit 10 has a tracking window WP
The distance calculation based on the principle of the triangulation method is executed for each of the calculation windows WC1 to WC8 in the calculation window, and the distance D to the object 4 in each of the calculation windows WC1 to WC8 is calculated.
Is calculated by the individual distance calculator 10 based on the following equation (1): D = (BL × f) / n (1) On this occasion,
A temperature sensitive element is arranged near the image sensors 3A and 3B, and the distance DC is determined based on temperature information obtained from the temperature sensitive element.
May be corrected.

The distance storage unit 11 stores the distances D for each of the calculation windows WC1 to WC8 obtained by the individual distance conversion unit 10, and the distance determination unit 12 stores the distances D in the distance storage unit 11. Based on the distance D for each of the calculation windows WC1 to WC8, and the object 4 based on the following equation (2).
Is determined.

DC = (ΣD _i × F _i ) / ΣF _i (2) In the above equation (2), D _i is each of the calculation windows WC1 to WC1.
Is indicative of the distance D in the i-th calculation window of WC8, F _i is the adoption number flag indicating either whether to adopt the distance calculation to the object 4 for each calculation window WC1~WC8 There, D _i visual of this D _i and last time "1" when the absolute value of the difference between the temporary target distance is less than 2.5 m, in other cases is set to "0". That is, if a large amount of distance change (2.5 m or more) occurs as the arithmetic processing cycle elapses, it is not used for the distance calculation. For example, 8 of WC1 to WC8
First calculation window WC out of the calculation windows
1. If the operation distance in the fifth calculation window WC5 and the eighth calculation window WC8 is rejected as shown by the outline in FIG. 4, DC = (D ₂ + D ₃ + D ₄ The distance DC to the object 4 is calculated as + D ₆ + D ₇ ) / 5.

The distance DC obtained by the distance calculating means 9 is input to a vehicle running control device 13 for causing the own vehicle to run following an object 4 such as a preceding vehicle, and is transmitted to a window determining means 7. Is entered.

The window determining means 7 includes a first window shape changing unit 14, a second window shape changing unit 15, a third window shape changing unit 16, and a window change switching unit 17, and calculates a distance. Distance DC obtained by means 9
Any one of the tracking windows WP set by the window shape changing units 14 to 16 based on the distance is used as the window change switching unit 1 based on the distance DC obtained by the distance calculation unit 9.
7, the tracking window WP selected by the window change switching unit 17 is given to the correlation calculating unit 8.

The window change switching unit 17 determines whether or not the distance DC has been obtained by the distance calculating means 9 at the time of the previous calculation processing, and also determines whether or not the distance DC has changed to the invariable or large side. Then, which of the tracking windows WP of the window shape changing units 14 to 16 is to be adopted is determined, and the distance DC has not been obtained by the distance calculation means 9 in the previous calculation processing. Sometimes, the tracking window WP obtained by the first window shape changing unit 14 is used, and the distance DC is obtained by the distance calculating means 9 in the previous calculation processing. If it has changed to the unchanged or larger side, the tracking window WP obtained by the second window shape changing unit 15 is used, and the distance calculation means 9 is used in the previous calculation processing. When the distance DC were obtained had calculated distance DC is the distance DC at the current distance calculating means 9 is changed to decrease side third window shape changing portion 16
The tracking window WP obtained in the above is used.

The first window shape changing unit 14 sets the tracking window WP in accordance with the procedure shown in FIG. 5. First, in step S1, the object 4 is detected at every predetermined distance and temporarily. Determine the object detection distance. For example, the distance from the own vehicle is initially set to 5 m, and it is determined whether or not the object 4 exists at that distance. If not, the distance is sequentially increased to 10 m, 15 m, 20 m. The object 4 is searched, and a distance at which the object 4 is detected is determined as a temporary object detection distance.

In the next step S2, it is assumed that a vehicle having a predetermined size (for example, a width of 1.8 m and a height of 1.5 m) exists at the temporary object detection distance determined in step S1. Tracking window W according to the temporary object detection distance
Set P.

The second window shape changing unit 15 determines the tracking window WP in accordance with the procedure shown in FIG. 6, and resets the window holding flag FW to "0" in step S11. The window holding flag FW is used for processing in the third window shape changing unit 16, and is used for calculating the calculation distance DC by the distance conversion unit 9.
Is set to FW = 1 when the speed becomes larger than the approach speed of the stationary object to the own vehicle. Step S1
In 2, the vehicle has a previously calculated distance DC obtained by the distance calculation means 9, that is, a vehicle having a predetermined size (for example, a width of 1.8 m and a height of 1.5 m) at the previous object detection distance. The tracking window WP corresponding to the temporary object detection distance is set.

The tracking window WP set by the second window shape changing unit 15 is employed when the distance DC calculated by the distance calculating means 9 is changing to a constant or larger side. The size of the tracking window WP is changed so as to decrease as the distance increases.

The third window shape changing unit 16 sets the tracking window WP in accordance with the procedure shown in FIG. 7, and in step S21, determines whether or not the window setting distance DW has already been set. . Thus, the window setting distance DW is set by the processing in the third window shape changing unit 16, and in the first processing in the third window shape changing unit 16, the window setting distance DW is not set. In this case, the process proceeds from step S21 to step S22.

In step S22, the calculation distance DC of the distance calculation means 9 is determined as the window setting distance DW. In step S23, the window setting distance DW has a predetermined size (for example, a width of 1.8 m and a height of 1. Assuming that a vehicle of 5 m) exists, a tracking window WP corresponding to the window setting distance DW is set.

When it is determined in step S21 that the window setting distance DW has been set, the process proceeds from step S21 to step S24, in which it is determined whether the window holding flag FW is "1". . Since the window holding flag FW is reset in step S11 of the process in the second window shape changing unit 15, FW = 0 when executing the process of step S24 for the first time. The process proceeds to step S22.

On the other hand, when it is determined in step S24 that FW = 1, in step S25, (DW-DC)
Is smaller than K. DW is set as the calculated distance DC of the distance calculating means 9 in step S22, and DW is set in the process of step S25.
W is substantially the previous calculation distance, and (DW-DC)
Indicates the difference between the previous calculation distance and the current calculation distance, that is, the distance at which the object 4 approaches the own vehicle after one calculation processing cycle. The above K is
It is obtained by multiplying the traveling speed of the own vehicle by the time of one arithmetic processing cycle, and is the distance at which a stationary object approaches the own vehicle due to the elapse of one arithmetic processing cycle. Therefore, (DW-DC) <K is satisfied by the distance calculation means 9
Is determined to be smaller at a speed less than the speed at which the stationary object approaches the own vehicle, and when (DW-DC) <K, that is, the distance calculation unit 9 Is determined to be smaller at a speed lower than the speed at which the stationary object approaches the own vehicle, in step S25, the window set distance DW immediately before the calculated distance is changed to a smaller side is held. Then, it is assumed that a vehicle having a predetermined size (for example, a width of 1.8 m and a height of 1.5 m) exists at the window setting distance DW, and the tracking window W corresponding to the window setting distance DW.
Set P.

When it is determined in step S25 that DW-DC ≧ K, that is, it is determined that the calculated distance DC of the distance calculating means 9 is reduced at a speed higher than the speed at which the stationary object approaches the own vehicle. At this time, the process proceeds from step S25 to step S27. After setting the window holding flag FW to "1" in step S27, the process proceeds to step S22.

According to the setting of the tracking window WP by the third window shape changing unit 16, the distance calculating means 9
When the calculated distance DC decreases at a speed lower than the approach speed of the stationary object to the own vehicle, the size of the tracking window WP immediately before the calculated distance DC changes to the side where the calculated distance DC decreases is held,
When the calculation distance DC decreases at a speed higher than the speed at which the stationary object approaches the own vehicle, the size of the tracking window WP is changed so as to increase as the calculation distance DC decreases.

Next, the operation of this embodiment will be described. When the distance between the object 4 and the vehicle is constant or when the object 4 moves away from the vehicle, the pair of optical systems 2A and 2B are used. The tracking window WP is determined to have a size corresponding to the size occupied by the object 4 within the determined field of view. Therefore, it is possible to prevent the background around the object 4 from being subjected to the correlation calculation by the correlation calculation unit 8 and the distance calculation by the distance calculation unit 9 as much as possible.

When the distance DC calculated by the distance calculating means 9 is reduced at a speed lower than the speed at which the stationary object approaches the own vehicle, the tracking window WP immediately before the target object 4 changes to the side closer to the own vehicle. Hold the size. Therefore, despite the area occupied by the object 4 in the visual field increases, the size of the tracking window WP becomes constant, and a stationary object such as a road surface character can be correlated by the correlation calculation means 8 and calculated by the distance calculation means 9. Can be avoided as much as possible.

Further, a state in which the calculated distance DC of the distance calculating means 9 is reduced at a speed higher than the speed at which the stationary object approaches the own vehicle is a state in which the object 4 may be lost. By changing the size of the tracking window WP so that the tracking window WP increases as the calculation distance DC decreases, the lost object 4 can be relocated to the tracking window WP.
It is possible to capture within.

As described above, the tracking window WP is set by the window determining means 7 in accordance with the calculated distance DC of the distance calculating means 9, so that the calculation time and the cost are not increased and the operation is more stably performed. The distance to the object 4 can be measured.

Although the embodiments of the present invention have been described in detail above, 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.

[0037]

As described above, according to the present invention, it is possible to minimize the background around the object to be subjected to the correlation calculation and the distance calculation, and to lose the object when there is a possibility that the object may be lost. The captured object can be captured again in the tracking window, and the distance to the object can be measured more stably without increasing the calculation time or the cost.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a distance measuring device.

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

FIG. 3 is a view showing a window arrangement.

FIG. 4 is a diagram corresponding to FIG. 3 for explaining distance determination.

FIG. 5 is a flowchart showing a process in a first window shape changing unit.

FIG. 6 is a flowchart showing processing in a second window shape changing unit.

FIG. 7 is a flowchart showing processing in a third window shape changing unit.

FIG. 8 is a diagram showing a conventional window arrangement.

[Explanation of symbols]

 2A, 2B ... Optical system 3A, 3B ... Image sensor 4 ... Object 7 ... Window determination means 8 ... Correlation calculation means 9 ... Distance calculation means WP ... Tracking window

Claims (1)

[Claims] 1. A pair of optical systems (2A, 2B), a pair of image sensors (3A, 3B) for forming images from the optical systems (2A, 2B), respectively, and both image sensors (3A, 2B). 3B) Correlation calculating means (8) for comparing the image signals of a pair of images formed on the upper side and calculating the shift amount from the optical axis of both images, and the shift amount obtained by the correlation calculating means (8) And a distance calculating means (9) for calculating a distance to the object (4) by a calculation based on the principle of triangulation using the method for calculating a correlation by the correlation calculating means (8). Both optical systems (2A, 2B)
Includes a window determining means (7) for determining a tracking window (WP) which is an area to be calculated in the field of view based on the calculated distance of the distance calculating means (9), wherein the window determining means (7) When the operation distance is invariable or increases, the tracking window (WP) is set to decrease as the operation distance increases.
When the calculation distance decreases at a speed lower than the speed at which the stationary object approaches the own vehicle, the tracking window (WP) immediately before the calculation distance decreases.
When the calculation distance decreases at a speed equal to or higher than the speed at which the stationary object approaches the own vehicle, the tracking window (W) increases as the calculation distance decreases.
A distance measuring device for a vehicle, wherein the magnitude of P) is changed.