JP2971692B2 - Image tracking type inter-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 an image tracking type inter-vehicle distance measuring apparatus for a vehicle using a pair of image sensors, and more particularly to an image tracking type inter-vehicle distance having improved reliability in window tracking and distance measurement. It relates to a measuring device.

[0002]

2. Description of the Related Art Conventionally, an image tracking type inter-vehicle distance measuring apparatus using a pair of image sensors is well known.
For example, reference can be made to JP-A-2-232511.

FIG . 7 is a block diagram showing an example of a general image tracking type inter-vehicle distance measuring apparatus. In the figure, reference numerals 1 and 2 denote lenses of a pair of video cameras for capturing an image in front of the host vehicle, and are disposed apart from each other by a base line length L.
Reference numerals 3 and 4 denote a pair of two-dimensional image sensors (hereinafter simply referred to as image sensors) disposed on the optical axis of each of the lenses 1 and 2, and are disposed at a focal distance f from the lenses 1 and 2. The lenses 1 and 2 and the image sensors 3 and 4 constitute a pair of optical systems.

Reference numeral 5 denotes a preceding vehicle, that is, an object located at an inter-vehicle distance R in front of the host vehicle, and an image of the object 5 is formed on the image sensors 3 and 4 via the lenses 1 and 2. 6 and 7 are AD converters for converting the image signals M1 and M2 obtained from the image sensors 3 and 4 into digital signals, and 8 and 9 are image signals M via the AD converters 6 and 7.
A memory storing 1 and M2, 8 'is a memory which is updated alternately at predetermined time intervals in cooperation with the memory 8. The memories 8 and 8 'correspond to a reference image at the time of window tracking (described later), and the memory 9 corresponds to a reference image.

[0005] Reference numeral 10 denotes a CPU comprising a microcomputer which takes in each image signal in the memories 8, 8 'and 9 and performs image calculation processing. The CPU 10 is based on window tracking means for the preceding vehicle 5 and based on the image signals M1 and M2. And a distance measuring means for measuring an inter-vehicle distance between the vehicle and the preceding vehicle 5. Reference numeral 11 denotes memories 8, 8 'and 9 under the control of the CPU 10.
This is a display device for displaying an image signal inside and displaying a message or the like from the CPU 10.

Reference numeral 12 denotes a window forming means for forming a tracking window (hereinafter simply referred to as a window) W with respect to the window tracking means in the CPU 10. Reference numeral 13 denotes a window setting switch manually operated by a driver. The means 12 and the switch 13 constitute a window setting means for setting a window W in the image signal M1 serving as a reference image.

Next, the operation of the conventional image tracking type inter-vehicle distance measuring apparatus will be described with reference to FIG. First,
The setting of the window W will be described.
It is assumed that the image signals M1 and M2 are displayed in advance under the control of the CPU 10, and the driver operates the switch 13 while watching the display device 11 to display the image of the preceding vehicle 5 to be tracked in the window. Select window W to enter W.

Hereinafter, the window tracking means in the CPU 10 is updated so that the window W automatically tracks the preceding vehicle 5. That is, the memories 8 and 8 'are updated alternately at predetermined time intervals in order to update the windows in time series. At this time, for example, when the reference image of the previous window is stored in the memory 8, the memory 8 'searches for an image having the highest correlation with the reference image in the memory 8 and obtains a new window.

Thereafter, the image signal M2 stored in the memory 9 is electrically superimposed on the reference image of the newly set window in the memory 8 'while sequentially shifting the image signal M2 as a reference image. By using the same method, an image having the highest correlation can be searched, and the displacement n can be substituted to obtain the inter-vehicle distance R. Note that the image signals M1 and M2, the distance measurement value of the inter-vehicle distance R, and the like are displayed on the display unit 14.

[0010]

As described above, in the conventional image tracking type inter-vehicle distance measuring apparatus, after the driver once sets the window W, the preceding vehicle 5 is automatically set by the window tracking means in the CPU 10. The distance between vehicles by tracking the image of
Therefore, when the preceding vehicle 5 is captured in the window area and travels while measuring the inter-vehicle distance R, the preceding vehicle 5 is not in the window area due to incorrect setting of the window W, or the leading vehicle 5 is Even if erroneous tracking occurs outside the window area, there is a problem in that erroneous image tracking may be continued and ranging with low reliability may be performed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and it is determined that a window is within an appropriate range, and an error is displayed when the window is out of the range, thereby preventing erroneous tracking. It is an object of the present invention to provide an image tracking type inter-vehicle distance measurement device that prevents continuation and improves the reliability of distance measurement.

[0012]

According to the present invention, there is provided an image-tracking type inter-vehicle distance measuring apparatus, comprising: a memory for storing image signals obtained from a pair of optical system image sensors; A CPU for performing processing,
A display device for displaying an image signal, a message from the CPU, etc., wherein the CPU measures window position on the screen of the window; Tracking availability determination means for determining whether or not the target to be tracked is captured in the window area based on the window position of the window area, and the tracking availability determination means does not capture the target to be tracked in the window area. When it is determined that an error has occurred, an error signal is generated to display a tracking impossible state on the display device.

[0013]

According to the present invention, a movable area with respect to an inter-vehicle distance between an own vehicle and an image tracking target, that is, a preceding vehicle, is assumed.
Estimates the window movable area on the screen when the preceding vehicle is caught in the window area determined by the inter-vehicle distance and the installation of the optical system, and the position on the screen of the measured distance window is the window movable area Is determined. If the window position is not in the window movable area and is in a position where the preceding vehicle cannot exist, it is determined that there is no preceding vehicle in the window area and an error is displayed,
Prompts the driver to reset the window. Thus, the window is reset through the window setting means.
In this way, by determining whether or not the preceding vehicle exists in the window based on the measured values of the window position and the inter-vehicle distance, it is possible to prevent the erroneous tracking from being continued and to continue to output the measured value, and to perform the tracking. And improve the reliability of distance measurement.

[0014]

【Example】

Embodiment 1 FIG. Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a functional configuration of a CPU 10 according to a first embodiment of the present invention, and numerals 8 to 12 are the same as those described above. The overall configuration of the first embodiment is as shown in FIG.

A window updating means 21 cooperates with the window setting means, ie, the window forming means 12 and the switch 13 (see FIG. 7).
A window W is set in the image signal M1 stored in the memory 8 using one of the two M1 as a reference image,
Each time the window is updated thereafter, a new image signal M1 'is stored alternately in each of the memories 8 and 8'.
That is, the window updating means 21 compares the image signal M1 'with the window W already set with the new image signal M1 output from the image sensor 3 (see FIG. 7) on the reference image side after a predetermined time. Update the window W.

Reference numeral 22 denotes a distance measuring means for measuring an inter-vehicle distance R between the host vehicle and the preceding vehicle 5 by triangulation based on the reference image (M1) and the reference image (M2) by the other image sensor 4, and 23 denotes a window. The window position measuring means 24 measures the position LW of the window W on the screen set by the updating means 21. The window position measuring means 24 calculates the distance Rd of the distance between the vehicles by the distance measuring means 22 and the current position LW of the window W on the screen. This is a tracking possibility determination unit that determines whether or not a target (preceding vehicle 5) to be tracked is captured based on the window area.

The tracking possibility determining means 24 estimates a movable area on an image when the preceding vehicle 5 is present based on the window position LW and the distance measurement value Rd of the following distance,
Means for comparing the movable area with the window position LW to determine whether or not the image in the window area captures the preceding vehicle 5, and determines that the target to be tracked is not captured in the window area. When the error signal E
Is generated to display the tracking impossible state on the display device 11.

FIGS. 2 and 3 are explanatory diagrams showing an example of a display screen of the display device 11. FIG. 2 shows a pair of video cameras arranged on the left and right or up and down of the camera on the reference image side at the time of tracking. FIG. 3 shows an example of a screen shot by the image sensor 3 during traveling, and FIG. 3 shows an example of a screen when erroneous tracking occurs.

In FIGS. 2 and 3, Wo is the width ± Hma.
a settable area of the window W defined by x and height ± Vmax, Wt is a movable area of the window W defined by width ± Hlim and height Vlim, Hw and Vw are two-dimensional coordinates of the window position LW, Y Is a road sign displayed on the screen. As an example of erroneous tracking in FIG. 3, here,
This shows a state in which the window W captures the road sign Y and erroneously tracks the road sign Y. The following description will be made based on the screens shown in FIGS.

FIGS. 4 and 5 are explanatory diagrams showing the operation of calculating the movable area Wt of the window W for each of the curve state and the gradient state of the traveling road. FIG. 4 shows a case where the window movable area + Hlim in the horizontal right direction is calculated when the curve radius of curvature of the road on which the vehicle is traveling is equal to or less than Rc and the left and right angles of view of the camera are 2 × θh. And a distance Rh2 from a point P on the lane of the radius Rc to the right.

FIG. 5 shows a case in which the vertical window movable area + Vlim is calculated when the gradient of the traveling road is not more than θs and the vertical angle of view of the camera is 2 × θv, at the distance Rd from the camera. A distance Rv1 from the upper end of the screen to the camera optical axis and a distance Rv2 from a point Q on the lane when the own vehicle descends at the gradient θs and the target vehicle climbs at the gradient θs. Note that the negative window movable areas -Vlim and -Hlim are calculated in the same manner.

The operation of the first embodiment of the present invention will be described below with reference to FIGS. First, the driver operates the switch 13 while watching the screen of the display device 11 to set the window W at the positions Hw and Vw as shown in FIG.
At this time, the settable area Wo of the window W on the screen
Is limited by the areas ± Hmax and ± Vmax, and the movable area Wt of the window W is limited by the areas ± Hlim and ± Vlim estimated from the distance measurement value Rd.

That is, in step S1, the switch 1
When the driver selects an image of the preceding vehicle 5 to be tracked through the window 3 and the window forming unit 12, the window W is set on the screen by the window updating unit 21.
Subsequently, in step S2, the distance L in the step S1 is determined by the distance measuring means 22 and the window position measuring means 23.
The object in the window W set to W, that is, the preceding vehicle 5
The inter-vehicle distance Rd is measured.

Next, in step S3, the tracking possibility determination means 24 determines the distance measurement value R obtained in step S2.
d, the window movable area Wt (Hlim
And Vlim) are calculated. First, the distances Rh1 and Rh2 in FIG. 4 are calculated as follows in order to calculate the horizontal rightward window movable area Hlim.

Rh1 = Rd × sin θh Rh2 = Rd ² / (2 × Rc)

Here, when Rh1 ≧ Rh2, the horizontal rightward movable area Hlim is calculated as follows.

Hlim = (Rh2 / Rh1) × Hmax

When Rh1 <Rh2, the movable area Hlim in the horizontal right direction is equal to the settable area Hmax and is calculated as follows.

Hlim = Hmax

Similarly, in order to calculate the vertical upward window movable area Vlim, distances Rvl and Rv2 in FIG. 5 are calculated as follows.

Rv1 = Rd × sin θv Rv2 = Rd ² / (2 × θs)

Here, when Rv1 ≧ Rv2, the vertically movable area Vlim is calculated as follows.

Vlim = (Rv2 / Rvl) × Vmax

When Rv1 <Rv2, the vertically movable area Vlim is equal to the settable area Vmax, and is calculated as follows.

Vlim = Vmax

The horizontal left direction (-Hlim) and the vertical downward direction (-Vlim) can be similarly calculated.

Next, in step S4, the tracking permission / prohibition means 24 changes the position LW of the window W set in step S1 to the window movable area Wt (± Hli).
m and ± Vlim).

If it is determined that there is no window W in the movable area Wt, an error signal E is generated to display on the display device 11 a state indicating that tracking is not possible, and the driver is returned to the window again. Prompt for settings. Therefore, returning to step S1, the driver sets the window W again. Further, by inputting the error signal E to the distance measuring means 22, useless distance measuring processing may be immediately stopped.

On the other hand, the window W is set in the movable area Wt.
If it is determined that there is a window update process, the process proceeds to step S5, a window update process is performed as usual, and the process returns to the distance measurement process of step S2.

As described above, in steps S3 and S4 by the tracking possibility determination means 24, the window position LW is determined based on the distance measurement value Rd and the movable area Wt to be tracked is determined.
In the case where an erroneous tracking occurs as shown in FIG. 3 by determining whether or not the position is within the movable area Wt, it is determined that the position LW (Hw and Vw) of the window W is outside the movable area Wt.
An error signal E can be generated. Accordingly, the tracking and the distance measurement are immediately stopped, and the window W is set again in step S1. Therefore, the distance measurement value Rd without reliability due to the erroneous tracking is not continuously output, and the distance measurement is not performed. The reliability of the value Rd is improved.

Embodiment 2 FIG. In the first embodiment, the setting of the window W is performed by the driver operating the switch 13. However, the setting of the window W may be freely determined according to the applied system. For example, a vehicle extraction filter as described in JP-A-3-45898 may be used, or as described in IPSJ Vol. 27, No. 7 (1986), the left-right symmetry of a vehicle may be used. You may pay attention to.

[0042]

As described above, according to the present invention, a pair of image sensors for capturing an image of the front of the host vehicle, a memory for storing image signals output by the pair of image sensors, and a display for displaying the image signals. A device, a window setting means for setting a window to an image signal stored in the memory using one of the pair of image signals as a reference image, and an image sensor on the reference image side after a predetermined time after the window-set image signal. Window update means for updating a window by comparing with a new image signal to be output, and measuring an inter-vehicle distance between the own vehicle and a preceding vehicle by triangulation based on a reference image and a reference image from the other image sensor. Distance measuring means, window position measuring means for measuring the position of the window on the screen, distance measurement and window position measurement by the distance measuring means Tracking availability determination means for determining whether or not the target to be tracked is captured in the window area based on the current window position from the step, and the tracking availability determination means determines the target to be tracked in the window area. When it is determined that the camera has not been caught, an error signal is generated and a tracking impossible state is displayed on the display device, and continuation of erroneous tracking is prevented by resetting the window. There is an effect that a high image tracking type inter-vehicle distance measuring device can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a functional configuration of a CPU according to a first embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an example of a display screen during traveling for explaining a window setting operation and a tracking operation according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a case where a window is erroneously tracked on the display screen of FIG. 2;

FIG. 4 is an explanatory diagram for calculating a horizontal rightward window movable area according to the first embodiment of the present invention;

FIG. 5 is an explanatory diagram for calculating a vertically movable window movable area according to the first embodiment of the present invention;

FIG. 6 is a flowchart illustrating a procedure of a processing operation of a CPU according to the first embodiment of the present invention.

FIG. 7 is a block diagram partially showing a side view of a general image tracking type inter-vehicle distance measuring apparatus.

[Explanation of symbols]

3, 4 image sensor, 5 preceding vehicle 8, 8 ', 9 memory 10 CPU 11 display device 12 window forming means (window setting means) 13 switch (window setting means) 14 display device 21 window updating means 22 distance measuring means 23 window Position measuring means 24 Tracking possibility determining means E Error signal M1, M1 ', M2 Image signal R Inter-vehicle distance Rd Inter-vehicle distance measured value W Window LW window position Wo Window settable area Wt Window movable area

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI G08G 1/04 H04N 7/18 G 1/16 G06F 15/62 380 H04N 7/18 15/70 350J

Claims (1)

(57) [Claims] 1. A pair of image sensors for capturing an image in front of a host vehicle, a memory for storing image signals output by the pair of image sensors, a display device for displaying the image signals, and a pair of image signals Window setting means for setting a window in the image signal stored in the memory using one of the image signals as a reference image, and a new image output from the image sensor on the reference image side after a predetermined time from the image signal in which the window is set Window updating means for updating the window by comparing the image signal with the image signal of the other vehicle; and distance measurement for measuring an inter-vehicle distance between the own vehicle and the preceding vehicle by triangulation based on the reference image and a reference image from the other image sensor. Means for measuring the position of the window on the screen. Tracking means, based on the distance measured by the distance measuring means and the current window position from the window position measuring means, and a tracking possibility determining means for determining whether or not a target to be tracked in the window area is captured. Wherein the tracking possibility determination means generates an error signal and causes the display device to display a tracking impossible state when it is determined that the tracking target is not captured in the window area. Image tracking type inter-vehicle distance measuring device.