JP2635232B2 - Inter-vehicle distance detection 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 optical distance detecting apparatus using an image sensor, and more particularly to an inter-vehicle distance detecting apparatus for continuously measuring the inter-vehicle distance between a preceding vehicle and a host vehicle.

[0002]

2. Description of the Related Art FIG. 8 is a block diagram of an optical distance detecting apparatus using a conventional image sensor disclosed in, for example, Japanese Patent Publication Nos. 63-38085 and 63-46363. In the figures, reference numerals 1 and 2 denote left and right lenses as optical systems disposed apart from each other by a base line length L, reference numerals 3 and 4 denote image sensors disposed at focal lengths f of the lenses 1 and 2, respectively, and reference numeral 30 denotes an image sensor 3. , 4 is a signal processing device that calculates the distance to the object 31 using the image signals sent from the signal processing device.

Next, the principle of detecting the distance to an object will be described. Image sensors 3 through lenses 1 and 2, respectively
The image signal of the object 31 imaged on the object 4
0 is electrically superimposed while being sequentially shifted by 0, and the shift amount a when the two image signals match best.
The distance R to the object 31 is obtained from the following equation by the principle of triangulation.

R = f × L / a

On the other hand, a method of tracking an image of a preceding vehicle captured by an image sensor or the like is described in, for example, Japanese Patent Publication No. 60-333.
No. 52 discloses this. According to this, the target is image-tracked by the operator setting a tracking gate (window) surrounding the target to be tracked on the display screen while viewing the display screen.

[0006]

In the conventional distance detecting apparatus, the distance to the object is obtained by comparing the entire image taken by a pair of left and right or upper and lower optical systems, so that a background image signal is obtained. As a result, the S / N ratio deteriorates and accurate distance measurement cannot be performed. Also, when trying to measure the inter-vehicle distance with the preceding vehicle while the vehicle is actually mounted on the own vehicle and traveling, if another vehicle is traveling on the left or right side of the preceding vehicle, the inter-vehicle distance with any vehicle There is a problem that the driver does not know whether the vehicle is measuring the vehicle speed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has a configuration in which a conventional optical inter-vehicle distance detecting device and an image tracking device of a preceding vehicle are combined. With this setting, stable image tracking can be performed as long as it is within the field of view even if it moves, and the distance to the target can be measured continuously, and the inter-vehicle distance can be measured even when multiple preceding vehicles are running. It is an object of the present invention to obtain an inter-vehicle distance detection device capable of confirming the state of image tracking such as which vehicle is the preceding vehicle of the target.

[0008]

According to a first aspect of the present invention, an inter-vehicle distance detecting apparatus compares image signals formed on an image sensor by a pair of optical systems, which are substantially up and down or left and right. In the inter-vehicle distance detection device which electrically detects the vehicle and measures the distance to the preceding vehicle ahead of the own vehicle based on the principle of triangulation, the image of the preceding vehicle is tracked by the window on the image taken by one image sensor. and image tracking means, and binarizing means for obtaining a binary image obtained by extracting the edge components of the captured image, the binarization of
Window position correcting means for correcting the position of the upper Kiu guiding as determined by good symmetry binary image <br/> symmetry of the binary image within the window obtained by the processing means is located in the center And distance detecting means for detecting a shift between a pair of corresponding image signals using the image signal in the window as a reference signal and calculating an inter-vehicle distance between the host vehicle and the preceding vehicle.

According to a second aspect of the present invention, there is provided an inter-vehicle distance detecting apparatus for use in an on-vehicle distance detecting apparatus according to the first aspect. A video output means for displaying on a television or the like is provided.

[0010]

According to the first aspect of the present invention, an inter-vehicle distance detecting apparatus is provided.
Using the image signal in the window as a reference signal and detecting the deviation of the corresponding upper and lower image signals and calculating the inter-vehicle distance between the host vehicle and the preceding vehicle, the influence of the background image signal is reduced and accurate ranging can be performed. Further, the window position correcting means determines the symmetry using the binary image from which the edge component is extracted by the binarizing processing means, and the preceding vehicle image comes to the center of the window set by the image tracking means. So as to compensate for an appropriate position.

According to a second aspect of the present invention, the inter-vehicle distance detecting apparatus displays, on a vehicle-mounted television or the like, a state in which an image of a target preceding vehicle image is being tracked even when a plurality of preceding vehicles are running. Can be.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an inter-vehicle distance detecting apparatus according to an embodiment of the present invention. In FIG. 1, reference numerals 1 and 2 correspond to lenses constituting upper and lower optical systems, and reference numerals 3 and 4 correspond to lenses 1 and 2, respectively. The two-dimensional image sensor 5 disposed indicates a preceding vehicle to be followed. 6 is an analog / digital converter,
8, 9, 16 are memories, 10 is a microcomputer,
A display screen 11 displays an image captured by the lower image sensor 3 and is controlled by the microcomputer 10. Reference numeral 12 denotes an image tracking device for forming a window 17 for image-tracking the preceding vehicle image 5a on the display screen 11 as shown in FIG. 3, and for tracking the image of the preceding vehicle image 5a surrounded by the window 17. 1
Reference numeral 3 denotes an image tracking instruction switch operated by the driver. Reference numeral 14 denotes a binarization processing device for extracting an edge component of an image captured by the image sensor 3, and reference numeral 15 is set by the image tracking device 12 using the binary image obtained by the binarization processing device 14. This is a window position correction device that corrects the set position of the window 17.

Next, the operation will be described. For example, an image 5a of the preceding vehicle that should follow the image of the lower image sensor 3
As shown in FIG. 2, assuming that the vehicle enters the display screen 11 in which the window 17 is set, the driver drives the own vehicle, changes the relative position between the preceding vehicle 5 and the own vehicle, and The preceding vehicle image 5a moves to a position where it enters the window 17. Then, as shown in FIG.
When the driver operates the image tracking instruction switch 13 when the preceding vehicle image 5a enters the vehicle, the display screen 1 is thereafter displayed.
No matter how the preceding vehicle image 5a moves within the window 1, the window 17 moves accompanying it, and the image tracking action of the preceding vehicle image 5a by the window 17 is automatically performed. In addition,
The image tracking operation is the same as that of the conventional device disclosed in Japanese Patent Publication No. Sho 60-33352 or Japanese Patent Publication No. 1-35305, and a detailed description thereof will be omitted.

Thus, since the image tracking device 12 performs the image tracking by comparing the time-series images, the window 17 may deviate from the preceding vehicle image 5a due to accumulation of errors, and stable image tracking cannot be performed. By the way, if the object whose distance is to be measured is a car, the image seen from behind is
In general, many horizontal edge components are included, and the image is often left-right symmetric. Therefore, using such a feature, the symmetry is determined and the window setting position is corrected. First, as shown in FIG. 4, in an input image captured by the image sensor 3 and stored in the memory 8, an area 1 surrounded by a window 17 set by the image tracking device 12 is set.
The image signal of the neighborhood area 19 having a width of 8 pixels and the width of w pixels on the left and right sides thereof is read out, and the edge component is extracted by the binarization processing device 14. For example, the edge is enhanced using a differential filter or the like. The differential image is binarized at a certain threshold level. The differential binary image obtained by this processing is stored in the memory 16.

Next, the window position correcting device 15 determines the symmetry of the binary image stored in the memory 16. It is assumed that the memory 16 stores a binary image as shown in FIG. While shifting the size of the window corresponding to the window 17 on the memory 16, the symmetry is evaluated by performing an operation represented by the following equation on the image in the window. Here, S (i, j) is an image signal of a binary image and is 0 or 1. Also, m and n are the width and height of the window 17 respectively, and w is the width of the neighboring area 19 stored in the memory 16. Also, k = 0, 1,..., 2w.

[0016]

(Equation 1)

Since this arithmetic expression is for a binary image, it is folded left and right on the central axis of the area in the window to obtain the logical product of the overlapping portions. Then, the symmetry is best at the position k where the value of A _k is maximum in the above equation 2, and the value of k at that time is obtained. Here, assuming that the position of the upper left pixel of the window 17 set by the image tracking device 12 is (p, q) as shown in FIG. 6, the position of the upper left pixel is newly (p−w + k, q). A window 17a having a size of m × n is set, and an image in an area surrounded by the window 17a is set as a reference image in the distance calculation. The window setting position is corrected as described above.

Next, a method for detecting the distance between the host vehicle and the preceding vehicle will be described. First, the microcomputer 10
Reads the pixel signal in the window 17a after the set position correction, which tracks the preceding vehicle image 5a, from the memory 8 and uses it as a reference image signal for the following distance calculation. Then, the microcomputer 10 selects an area corresponding to the window 17a in the memory 9 in which the image signal of the upper image sensor 4 is stored, and compares the image signal of the memory 9 with the reference image signal by one pixel. While sequentially shifting, the sum of the absolute values of the differences between the signals of the upper and lower pixels is calculated. That is, the position of the image that is most consistent with the image in the window 17a is obtained while being sequentially shifted one pixel at a time. At this time, the area in the memory 9 involved in the calculation is the area 18 corresponding to the position of the window 17a as shown in FIG. As described above, the upper and lower pixels are compared, the shift amount of the pixel when the sum of the absolute values of the difference signals is minimum is a pixel, the pixel pitch is P, the base line length of the optical system is L, and the lens 1 , 2 as f, the distance R to the preceding vehicle can be obtained by the following equation.

R = f × L / a × P

In this way, the position of the window 17a for tracking the image of the preceding vehicle image 5a is set with the preceding vehicle image 5a at the center, and stable image tracking becomes possible. Even if the preceding vehicle 5 moves left and right, it can be tracked to accurately and continuously determine the inter-vehicle distance to the host vehicle.

[0021]

As described above, according to the present invention, an image sensor for capturing an image of a preceding vehicle by a pair of upper and lower optical systems, image tracking means for tracking an image of a preceding vehicle by a window, and this window Since the distance detecting means for calculating the distance to the object surrounded by is provided, the distance to the preceding vehicle can be accurately measured.

Further, since the symmetry is determined using the binary image from which the edge component has been extracted and the position of the window is corrected, it is possible to prevent the displacement of the position between the preceding vehicle image and the window. , And stable image tracking can be performed.

Further, even when a plurality of preceding vehicles are running, the image tracking of the target preceding vehicle image can be displayed on an on-vehicle television or the like by the video output means. It is possible to easily know the preceding vehicle that is following and detects the following distance.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an inter-vehicle distance detection device according to an embodiment of the present invention.

FIG. 2 is a diagram of a display screen showing a state in which a preceding vehicle image has entered the display screen.

FIG. 3 is a diagram of a display screen showing a state in which a preceding vehicle image has entered a window on the display screen.

FIG. 4 is a diagram of a display screen showing an image area to be subjected to a binarization process in one embodiment of the present invention.

FIG. 5 is a diagram showing a binary image in one embodiment of the present invention.

FIG. 6 is a diagram showing a state in which a set position of a window is corrected in one embodiment of the present invention.

FIG. 7 is a diagram illustrating an image area to be compared with a reference image in distance calculation according to an embodiment of the present invention.

FIG. 8 is a configuration diagram showing a conventional distance detection device.

[Explanation of symbols]

1 level, 2 lenses, 3 image sensors, 4 image sensors, 5 preceding vehicles, 8 memories, 9 memories, 10 microcomputers, 11 display screens (display means), 12 image tracking devices (image tracking means), 14 binarization Processing device (binary processing means), 15 window position correcting device (window position correcting means), 16
Memory, 17 windows.

Claims (2)

(57) [Claims] An image signal formed on an image sensor by a pair of upper and lower or left and right optical systems is substantially compared, a shift between the two images is electrically detected, and a shift in front of the host vehicle is detected based on the principle of triangulation. the inter-vehicle distance detecting device for measuring the distance to the preceding vehicle, and extracted image tracking means for image tracking the preceding vehicle image by windows on the captured by one of the image sensor image, the edge component of the captured image
And binarizing means for obtaining binary image, this binary processing hand
And window position correcting means for correcting the position of the upper Kiu guiding determine the symmetry of the window within the binary image obtained by the step as good binary image symmetry is located in the center, in the window An inter-vehicle distance detection device comprising: a distance detection unit that calculates a distance between a host vehicle and a preceding vehicle by detecting a shift between a pair of corresponding image signals using the image signal as a reference signal. 2. An image output means for displaying, on an on-vehicle television or the like, an image picked up by an up / down or left / right image sensor or a state of tracking an image of a preceding vehicle. 2. The inter-vehicle distance detection device according to 1.