JP2827682B2 - 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 inter-vehicle distance detecting device which optically detects an inter-vehicle distance using an image sensor and measures a distance to a vehicle traveling in front of or behind the vehicle.

[0002]

2. Description of the Related Art FIG. 7 shows Japanese Patent Publication No. 63-38085,
FIG. 8 is a configuration diagram of an optical distance detecting device using a conventional image sensor disclosed in Japanese Patent Publication No. 63-46363 and the like, and has two left and right optical systems as shown in FIG. In the figure, reference numerals 1 and 2 denote left and right lenses arranged at a distance of a base line L, 3 and 4 denote image sensors disposed at a position of a focal length f of the lenses 1 and 2, and 51 denotes a sensor from the image sensors 3 and 4 This is a signal processing device that calculates the distance to the object 52 using the obtained image signal.

Next, the principle of detecting the distance to an object will be described. When the image signals of the object 52 formed on the respective image sensors 3 and 4 through the lenses 1 and 2 are electrically superimposed while being sequentially shifted in the signal processing device 51, and the two image signals match best. The distance R from the shift amount a to the object 52 is calculated by the following equation (A) based on the principle of triangulation. R = (f × L) / a (A)

On the other hand, a method of tracking an image of a preceding vehicle captured by an image sensor or the like is disclosed in Japanese Patent Publication No. 60-33352. According to this publication, the target is image-tracked by an operator setting a tracking gate (hereinafter referred to as a window) surrounding a target to be tracked on the display screen while viewing the display screen.

[0005]

Since the conventional distance detecting device is constructed as described above, the distance to the object is determined by comparing images taken by a pair of right and left optical systems. If you try to measure the distance between the vehicle and the preceding vehicle while the vehicle is running with these components mounted on your own vehicle, if another vehicle is running on the left or right side of the preceding vehicle, There was a problem that the driver did not know whether it was measuring.

[0006] When starting the image tracking of the preceding vehicle,
Setting a window for image tracking using a joystick, trackball, or the like while the driver is watching the display screen while driving the vehicle has a problem in that there is a risk of being careless in the forward direction.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and once a target is determined, the distance to the target is continuously measured as long as the target moves within a field of view. It is possible to obtain an inter-vehicle distance detection device that can identify the target preceding vehicle whose inter-vehicle distance is measured even when a plurality of preceding vehicles are running, and further, performs image tracking of the preceding vehicle. It is an object of the present invention to provide an inter-vehicle distance detection device that can automatically set a tracking window without looking at a display screen.

[0008]

An inter-vehicle distance detecting apparatus according to the present invention compares an image signal formed on an image sensor by a pair of upper and lower optical systems and electrically detects a shift between the two images. A distance measuring means for measuring a distance to a vehicle traveling in front of or behind the own vehicle based on the principle of triangulation, and a vehicle monitoring band set at a predetermined position on a screen, and one of upper and lower image sensors A display screen that displays an image captured by the above, a left-right symmetry in an arbitrary region in the vehicle monitoring band is determined, a region with good symmetry is selected, and an image in the selected region is used as a reference. Detecting a shift between corresponding upper and lower images and calculating a distance to an object captured in the area, the degree of change of the calculated distance information indicates that a preceding vehicle image exists in the area. To estimate It is provided with a and Yuta.

When the existence of the traveling vehicle is estimated and the position of the traveling vehicle image is determined on the display screen, a window of a predetermined size is automatically surrounded by the traveling vehicle image in accordance with the distance to the traveling vehicle. , A means for image-tracking a running vehicle image by the window, and a microcomputer for detecting a distance to the running vehicle captured by the window.

[0010]

According to the present invention, the distance between a vehicle traveling in front of or behind the subject vehicle is measured based on the principle of triangulation by comparing image signals formed on a pair of image sensors of the distance measuring means. Under the control of the computer, an image captured by one of the upper and lower image sensors is displayed on a display screen, an area having good symmetry in the vehicle monitoring band on the display screen is searched, and the area is searched for the image of the preceding vehicle. As a candidate for the existence position, the distance to the object captured in these areas is detected. The presence of the preceding vehicle image can be estimated based on the degree of change in the detected distance information.

Further, the microcomputer according to the present invention, when estimating the position of the image of the preceding vehicle on the display screen, automatically sets a window having a size corresponding to the distance to the preceding vehicle by a window setting means. The distance between the vehicle and the preceding vehicle is continuously detected by the microcomputer while the image is tracked by the means for tracking the image of the image of the preceding vehicle through this window.

[0012]

【Example】

Embodiment 1 FIG. An embodiment of the present invention will be described below with reference to the drawings. In FIG. 1, reference numerals 1 and 2 designate upper and lower optical systems and lenses arranged at a distance of a base line L, and reference numerals 3 and 4 designate two-dimensional image sensors arranged corresponding to the lenses 1 and 2, respectively. Indicates a preceding vehicle to be followed.

Reference numerals 6 and 7 denote analog / digital converters for converting the output signals of the image sensors 3 and 4 into digital signals.
8 and 9 are memories for storing the outputs of the analog / digital converters 6 and 7, 10 is a microcomputer, 11 is
Is a display screen for displaying an image captured by the upper image sensor 4, and is controlled by a microcomputer. Reference numeral 12 denotes a monitoring band setting device for specifying a vehicle monitoring band for monitoring a preceding vehicle on the display screen 11. Reference numeral 13 denotes an image tracking instruction switch operated by the driver.

Next, the operation will be described. For example, when the driver operates the image tracking instruction switch 13, as shown in FIG. 2 by the monitoring band setting device 12, the display screen 11 on which the image ahead of the vehicle captured by the upper image sensor 4 is displayed. Vehicle monitoring band 14 at a predetermined position
Is set. Then, as shown in FIG. 3, when the preceding vehicle image 5a enters the image, it can be captured in the vehicle monitoring band 14.

By the way, an image of an automobile viewed from the front or the rear is generally symmetrical in many cases. Therefore, utilizing such a feature, a symmetric image in the vehicle monitoring band 14 is searched for. First, as shown in FIG. 3, a gate 15 having a predetermined size for judging left-right symmetry is prepared, and the gate 15 is shifted while moving the gate 15 in an area where the vehicle monitoring band 14 is set on the memory. The following equation (1) is performed on the image signal to evaluate the symmetry.

[0016]

(Equation 1)

However, in this (Equation 1), S (i, j)
Is an image signal in the vehicle monitoring band 14, for example, 25
It is assumed that shades are represented by six gradations. m is the width of the gate 15 n is the height of the gate 15 W is the width of the vehicle monitoring band. This means that the symmetry is best at the position _where the value of A _k is minimum in the above equation. In practice, however, there are some other vehicles with good symmetry on the road besides the preceding vehicle. For example, a road sign image 16 is one of them.

Therefore, the result of the operation of the above equation (1) has some minimum values. In FIG.
At the position 15a surrounding the image 5a of the preceding vehicle and at the position 15b surrounding the image 16 of the road sign. The positions having the minimum values are candidates for the position of the preceding vehicle.

As described above, there are several candidates for the preceding vehicle. Next, the distances to the objects existing at the positions 15a and 15b surrounding the images of the preceding vehicles that are candidates are measured. First, the microcomputer 10 is connected to the gate 1
The pixel signals in 5 are read from the memory 9 and used as reference image signals for distance calculation. The gate 1 is stored in the memory 8 in which the image signal of the lower image sensor 3 is stored.
The microcomputer 10 selects a region corresponding to the position 5 and sequentially calculates the sum of the absolute values of the signal differences between the upper and lower pixels while sequentially shifting the image signal of the memory 8 by one pixel with respect to the reference image signal. To go.

That is, the position of the image that is most matched with the image in the gate 15 is obtained while sequentially shifting one pixel at a time. At this time, the area in the memory 8 involved in the operation is:
As shown in FIG. 4, the area 17 corresponds to the position of the position 15a surrounding the image of the preceding vehicle.

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 n pixels, the pixel pitch is P, and the base line length of the optical system is L. If the focal length of the lenses 1 and 2 is f, the distance R to the preceding vehicle can be obtained by the following equation (B). R = (f × L) / (n × P) (B)

As described above, position 1 surrounding the image of the preceding vehicle
The distance to the object within 5a can be measured.

In the same manner, the distance to the object being captured is measured at the position 15b surrounding the image of the road sign capturing other than the preceding vehicle. At this time, as shown in FIG. 4, the image is compared in the area 18 corresponding to the position 15b, and the distance to the object is measured.

Next, the temporal change of each distance information measured as described above is calculated by the microcomputer 1.
Monitored by 0. The inter-vehicle distance between the host vehicle and the preceding vehicle does not change abruptly, but the distance to the road sign installed on the road changes abruptly in the direction in which the relative distance becomes shorter. Then, the gate position 15a where the temporal change of the distance information is small is selected from the surrounding positions 15a and 15b of the preceding vehicle candidate image, and the position of the preceding vehicle image is specified.

Next, as shown in FIG. 5, an image tracking window 19 is set by the monitoring band setting device 12 at the position 15a specified on the display screen 11 as described above. The window 19 has a predetermined size according to the distance information to the preceding vehicle. That is, the preceding vehicle image 5a is determined according to the distance to the preceding vehicle.
When the distance measurement value is relatively large, a small window 19 is set. When the distance measurement value is small, a large window 19 is set.

When the window 19 surrounding the preceding vehicle image 5a is set as described above, the image tracking operation of the preceding vehicle image 5a by this window 19 is started. This image tracking action is the same as that of the conventional apparatus disclosed in Japanese Patent Publication No. 60-33352 or Japanese Patent Publication No. 1-35305, and a detailed description thereof will be omitted.

Next, the inter-vehicle distance between the preceding vehicle 5 captured by the window 19 and the host vehicle is detected. This inter-vehicle distance is obtained by using the image signal in the window 19 that tracks the preceding vehicle image 5a as a reference image signal for the inter-vehicle distance calculation, and comparing the upper and lower image signals in the same manner as described in the above equation (A). It is detected by the principle of triangulation. Then, no matter how the preceding vehicle image 5a moves within the display screen 11, the window 19 is displayed.
Tracks the preceding vehicle image 5a and continuously detects the inter-vehicle distance between the preceding vehicle 5 and the own vehicle.

FIG. 6 is a flowchart showing the above operation procedure. The operation procedure will be described with reference to the flowchart of FIG. First, when the driver operates the image tracking instruction switch 13 in a state where the preceding vehicle appears in front of the own vehicle (step 101), the microcomputer 10 to which the operation signal has been input controls the monitor band setting device 12 to display. The vehicle monitoring band 14 is set at a predetermined position on the screen 11.
Is set (step 102). Then, the gate 15 selects the positions 15a and 15b surrounding the image region having good left-right symmetry in the vehicle monitoring band 14, and extracts the preceding vehicle candidate (step 103).

Next, the distance to the object in the positions 15a and 15b surrounding the image area selected as the preceding vehicle candidate is measured (step 104). The position 15a surrounding the image region where the measured distance information has little temporal change is selected, and the presence of the preceding vehicle is specified (step 105).

Further, the vehicle monitoring band 14 which has been displayed so far is deleted (step 106), and a window 19 having a size corresponding to the inter-vehicle distance is provided at a position 15a surrounding the image area in which the presence of the preceding vehicle is specified. Then, the image tracking of the preceding vehicle image 5a by the window 19 is started (step 107). Thereafter, the inter-vehicle distance between the preceding vehicle and the host vehicle captured by the window 19 is continuously detected (step 108).

In the above-described embodiment, a case has been described in which the inter-vehicle distance to the preceding vehicle is detected. However, a monitoring system for a rear vehicle that detects the inter-vehicle distance to a following vehicle traveling behind the host vehicle may be used. The invention is not limited to the above embodiment.

[0032]

As described above, according to the present invention, a vehicle monitoring band is provided at a predetermined position on a display screen that displays an image captured by an image sensor that captures a vehicle traveling in front of or behind a host vehicle. Since an image area with good left-right symmetry in this vehicle monitoring band is selected and the distance to the object captured in the selected image area is detected, the detected distance information changes. The presence of the preceding vehicle can be estimated from the degree.

Further, since a means for newly setting a window surrounding the preceding vehicle image at the specified position of the preceding vehicle image is provided, a window for tracking the image of the preceding vehicle image can be automatically set. Since the image of the target preceding vehicle is displayed on the display screen, the driver can easily know the preceding vehicle that is detecting the distance between the host vehicle and the own vehicle,
Even if the driver does not look at the window for image tracking, it can be automatically set and safe driving is possible.

[Brief description of the drawings]

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

FIG. 2 is an explanatory diagram showing a state in which a vehicle monitoring band is set on a display screen in the embodiment.

FIG. 3 is an explanatory diagram showing a state in which a preceding vehicle image is included in a display screen on which a vehicle monitoring band is set.

FIG. 4 is an explanatory diagram showing, as a reference image, an image of a region having good left-right symmetry displayed on the display screen, and an image region to be compared with this image.

FIG. 5 is an explanatory diagram showing a state in which a window is set in a preceding vehicle image displayed on the display screen.

FIG. 6 is a flowchart showing an operation procedure according to the embodiment.

FIG. 7 is a diagram illustrating a configuration of a conventional distance detection device.

[Explanation of symbols]

 Reference Signs List 1 lens 2 lens 3 image sensor 4 image sensor 5 preceding vehicle 6 analog / digital converter 7 analog / digital converter 8 memory 9 memory 10 microcomputer 11 display screen 12 monitoring band setting device 14 vehicle monitoring band 15 for left / right symmetry determination Gate of 17 17 Comparison area for distance measurement 18 Comparison area for distance measurement 19 Window

Claims (2)

(57) [Claims] An image signal formed on an image sensor is compared by a pair of optical systems, and a shift between the two images is detected electrically. Distance measuring means for measuring the distance to the vehicle traveling, a display screen for displaying an image captured by one of the upper and lower image sensors having a vehicle monitoring band at a predetermined position in advance, and The image signal of an arbitrary area is read from the image, the left-right symmetry of the image in the area is determined, the area having good symmetry is selected, and the corresponding upper and lower images are determined based on the image in the selected area. The distance between the subject vehicle and the object captured in the area is calculated by detecting the deviation of the vehicle, and based on the degree of change of the distance information obtained from the calculation result, is there any vehicle traveling in the area? How And a microcomputer for estimating the distance. 2. When the existence of a traveling vehicle is estimated and the position of the traveling vehicle image is determined on the display screen, a window having a predetermined size is automatically surrounded by the traveling vehicle image according to the distance to the traveling vehicle. Means for setting the distance, means for tracking the image of the running vehicle by the window, means for detecting the distance to the running vehicle captured by the window, and a microcomputer. 2. The inter-vehicle distance detection device according to 1.