JP2814732B2 - Inter-vehicle distance detection device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inter-vehicle distance detection apparatus, and more particularly to an apparatus for detecting an inter-vehicle distance to a preceding vehicle by a small CCD sensor having a wide detection range in a horizontal direction.

[Prior Art] Conventionally, various systems have been devised for the purpose of driving a vehicle safely, and there is also an automatic following system that measures the distance between vehicles and an automatic speed with respect to a preceding vehicle and safely follows the preceding vehicle. One of them. Such an automatic following system is particularly suitable when traveling on a motorway such as an expressway where the vehicle speed and traveling road are almost constant, and the driving vehicle can safely reach the destination without being bothered by accelerator operation or brake operation. It has the advantage of being able to run easily and easily.
It is necessary to detect control parameters such as the distance between the vehicle and the vehicle in front and the vehicle speed with high accuracy.

Therefore, conventionally, various devices for measuring the distance between the vehicle and the preceding vehicle with high accuracy, more generally, the distance to the object in front of the vehicle have been considered. One example is disclosed in
There is known a so-called phase difference method disclosed in a camera provided with an autofocus system in Japanese Patent No. 137216.

In this method, a lens, a separator lens and
Detection elements such as CCDs are sequentially arranged on the same optical axis,
The image of the subject is placed on the detector by a separator lens.
The images are formed as individual images. Then, the subject 2 to be imaged on the detection element according to the change in the distance between the lens and the subject.
The defocus amount is calculated by measuring the distance to the subject by using the change in the image formation interval of the individual images on the detection element. Then, when measuring the distance at a plurality of locations on the subject, each time the separator and the detection element are shifted from the optical axis, the location to be measured is imaged on the detection element.

Conventionally, ITJ Technical Report VoL.12.No.24, PP.1-6, ICS'88-
29, IPA '88 -32 (Jun, 1988), a method of measuring an inter-vehicle distance by stereo vision has also been proposed. According to this method, a vehicle ahead is photographed by two video cameras installed at positions separated by a predetermined distance, and the inter-vehicle distance to the vehicle ahead is calculated using the parallax of the two video cameras.

[Problems to be Solved by the Invention] However, there are some problems in such conventional technology. In the method disclosed in Japanese Patent Application Laid-Open No. 63-137216, it is possible to measure the distance at a plurality of locations of a subject by mechanically displacing the separator lens and the detection element from the optical axis as described above. In essence, it is a one-dimensional distance measurement that measures the distance of only one location of the front subject. Therefore, it is suitable for the distance measurement each time when it is used for the distance measurement of a vehicle whose luminance greatly changes depending on the structural position. There was a problem that the position had to be selected and sufficient distance measurement could not be performed.

Also, in a device that measures the distance using two video cameras, it is basically based on the principle of triangulation, so that the two video cameras must be installed so that their optical axes are parallel to each other. Must. If two video cameras are installed vertically in parallel at the front of the vehicle, for example, the captured image will be blurred due to the vibration of the vehicle during traveling, and accurate distance measurement cannot be performed. There was a problem.

Further, when the vehicle in front is an ordinary passenger car, the vehicle height is lower than that of a large vehicle such as a truck, so that the vertical camera has a narrower viewing angle with respect to the vehicle in front (for example, the vehicle height of the front vehicle is 1.4 m). , When the distance between vehicles is 50m, viewing angle
1.6 ゜) There was a problem that a sufficiently large ranging range could not be obtained.

Of course, it is conceivable that two video cameras are installed at a predetermined distance apart from each other on the left and right instead of up and down. In this case, however, it is necessary to extract the vertical component from the obtained image of the front vehicle, so that the vertical It becomes extremely difficult to extract a vehicle with a small change in the luminance in the direction, which causes a problem that high-precision distance measurement cannot be performed.

In view of such a conventional problem, the present applicant has previously proposed in Japanese Utility Model Application No. 1-150999 an inter-vehicle distance detecting apparatus using a plurality of pairs of fan-shaped anamorphic lenses arranged radially. However, this inter-vehicle distance detection device can basically measure only the inter-vehicle distance to the preceding vehicle in the same lane as the own vehicle. There is a problem that the device configuration must be individually arranged and the device configuration becomes large.

The present invention has been made in view of the above conventional problems,
Its purpose is small and has a wide detection range, especially in the horizontal direction,
An object of the present invention is to provide an inter-vehicle distance detecting device capable of measuring the inter-vehicle distance to a preceding vehicle with high accuracy.

Means for Solving the Problems In order to achieve the above object, an inter-vehicle distance detection device according to the present invention includes a plurality of vehicles that detect a vehicle in a vertical direction and a first oblique direction at a predetermined angle with respect to the vertical direction. A first CCD sensor having a sawtooth shape, and a plurality of sensors having a planar shape symmetrical with respect to the first CCD sensor with respect to a vertical direction and detecting a preceding vehicle in a vertical direction and a second oblique direction symmetric with the first oblique direction. Sawtooth
A first CCD sensor; and a calculating device for calculating an inter-vehicle distance to a preceding vehicle based on detection signals from the first and second CCD sensors.
Are arranged to be separated so that the oblique direction detection portions are located on the same straight line, and the plurality of second CCD sensors
Of the first CCD sensor are separated from each other so that the oblique portions of the first CCD sensor are located on the same straight line. It is characterized by.

[Operation] The inter-vehicle distance detection device of the present invention has such a configuration, and the first and second CCD sensors have a sawtooth shape to detect a forward vehicle in a vertical direction and a diagonal direction. Since the first CCD sensor and the second CCD sensor have their oblique and vertical detection parts separated and arranged on the same straight line, the front vehicle image causes parallax, and the distance to the preceding vehicle is measured using this parallax. .

Then, a plurality of detection ranges are formed by the plurality of vertical and oblique detection portions formed in a sawtooth shape of the first and second CCD sensors, and it is possible to widen the measurement range.

Hereinafter, a preferred embodiment of an inter-vehicle distance detecting device according to the present invention will be described with reference to the drawings.

FIG. 4 shows the first and second CCD sensors 10 used in this embodiment,
14 shows a plan view. As shown in FIG. 4A, the first CCD sensor 10 is formed on a silicon substrate 12 and has a sawtooth-shaped planar shape. As will be described later, the first CCD sensor 10 is mounted on the rear surface of the rearview mirror of the vehicle. The first CCD sensor 10 detects the front vehicle in the vertical direction by the vertical direction detection portions (10e to 10g), and detects the oblique direction detection portion (10e).
The vehicle ahead in the diagonal direction is detected by a to 10d). On the other hand,
As shown in FIG. 4 (B), the 2CCD sensor 14 has a plane shape symmetrical with respect to the first CCD sensor 10 in the vertical direction, and is similarly formed on a silicon substrate. And these two types
The CCD sensor measures not only the lane of the vehicle, but also the distance between the vehicle and the vehicle ahead in the adjacent lane.

FIG. 1 shows a first CCD sensor 10 and a second CCD in this embodiment.
FIG. 2 is a sectional view of the sensor 14 and FIG. These first and second CCD sensors 10 and 14 are connected to the rearview mirror 1 of the vehicle.
6 are arranged on the back surface so as to have the following positional relationship. That is, the two first CCD sensors 10 are spaced apart from each other by l1 so that the oblique direction detection portions 10a to 10e are on the same straight line, and the two second CCD sensors 14 also detect the oblique direction. The parts are spaced apart by l1 so that the parts are on the same straight line. Furthermore, the first CCD sensor 10 and the second CCD sensor
14 is arranged at a distance of l2 so that the vertical detection portions 10e to 10g are on the same straight line. A condensing lens 18 is disposed in front of the first and second CCD sensors 10 and 14 as shown in the sectional view of FIG.

As described above, in the present embodiment, two first CCD sensors 10 for detecting vehicles in the vertical direction and the first oblique direction and two second CCD sensors for detecting vehicles in the vertical direction and the second oblique direction.
The two CCD sensors 14 are disposed on the rear-view mirror with distances of 11 and 12, respectively, and the distance to the preceding vehicle is measured from the phase difference between the images of the preceding and following vehicles in the vertical and diagonal directions of these CCD sensors.

For this reason, in the present embodiment, as shown in FIG. 5, the detection signals from the two CCD sensors 10 and the two second CCD sensors 14 are converted into digital signals by the A / D converter 18,
It is configured to input to the electronic control unit ECU20 that performs arithmetic processing.

The ECU 20 has an interface I / F, a ROM for storing a predetermined program, a CPU for performing calculations in accordance with the program,
It incorporates RAM and the like that temporarily stores the calculation results, and calculates the distance to the vehicle ahead based on digital signals from each CCD sensor.

Hereinafter, the distance calculation operation performed by the ECU 20 will be described.

FIG. 3 shows a detection range of the inter-vehicle distance detection device in the present embodiment. As described above, two first CCDs
The sensor 10 is spaced apart by l1 so that the first oblique direction detection portions 10a to 10d are located on the same straight line with each other, and the two oblique direction detection portions 10a separated by l1 in FIG. A) A detection range 100a is formed, a detection range 100b is formed by two oblique direction detection sites 10b, a detection range 100c is formed by two oblique direction detection sites 10c, and two oblique direction detection sites A detection range 100d is formed by 10d.

Then, in each of the detection ranges, an oblique direction detection portion separated by l1 has a parallax corresponding to the inter-vehicle distance with respect to the preceding vehicle, and an image is formed.According to the parallax corresponding to the given known reference inter-vehicle distance, By comparing with the reference imaging position, the distance to the vehicle in front within the detection range can be calculated. That is, assuming that the length of each CCD bit constituting the first CCD sensor 10 is Δx, the focal length of the condenser lens 18 is f, and the bit shift amount due to parallax from the reference imaging position is n, the inter-vehicle distance D is D = f · l1 / (Δx · n).

On the other hand, the two second CCD sensors 14 also have their oblique direction detection portions 14.
a to 14d are arranged so as to be on the same straight line with each other, and these oblique direction detection parts form detection ranges 200a to 200d as shown in FIG. 3 (B). And
The inter-vehicle distance can be calculated from the phase difference of the preceding vehicle formed on each of the oblique direction detection sites, that is, the bit shift amount, according to the above-described equation.

Further, in the present embodiment, the first CCD sensor 10 and the second CCD sensor
The sensor 14 is spaced apart from the sensor 14 by l2 so that their vertical directions are on the same straight line, and as a result, as shown in FIG.
300c is formed. At this time, the first CCD sensor 10 and the second CCD
Since the vertical detection site of the sensor 14 is separated by l2, the relationship between the inter-vehicle distance D and the bit shift amount n is expressed by the following equation.

D = f · l2 / (Δx · n) FIG. 6 shows the relationship between the bit shift amount and the inter-vehicle distance at the separation lengths l1 and l2. Focusing on the region where the bit shift amount n is small, it is understood that the separation length l2 changes more steeply than the separation length l1. Therefore, for example, when the inter-vehicle distance is d0 or less, the separation length l2, that is, the first CCD sensor 10 and the second CCD
The detection signal from the sensor 14 is used, and in the case where the inter-vehicle distance is d0 or more, the separation distance l1, that is, the detection signal from the two first CCD sensors 10 or the two second CCD sensors 14 is used. It is possible to more accurately determine the inter-vehicle distance to the vehicle.

As described above, in the present embodiment, two first CCD sensors and two second CCD sensors are arranged on the rear surface of the rearview mirror of the vehicle, and the phase difference of the image is obtained based on the detection signal from each CCD sensor to determine the inter-vehicle distance. In addition to the fact that each CCD sensor is formed on a silicon substrate, it is possible to obtain an inter-vehicle distance detection device having a small detection area having a wide detection range in the horizontal direction, and the inter-vehicle distance to be measured. By appropriately selecting the CCD sensor according to the distance, the inter-vehicle distance can be calculated with high accuracy.

[Effects of the Invention] As described above, according to the inter-vehicle distance detection device according to the present invention, a plurality of detection ranges can be obtained in a small size, a wide detection range is provided in the horizontal direction, and the forward vehicle is accurately detected. There is an effect that distance measurement up to can be performed.

[Brief description of the drawings]

FIG. 1 shows a CC of an embodiment of an inter-vehicle distance detecting apparatus according to the present invention.
FIG. 2 is a sectional view of the same embodiment, FIG. 3 is an explanatory diagram showing a detection range in the same embodiment, FIG. 4 is a plan view of first and second CCD sensors in the same embodiment, FIG. 5 is a system configuration diagram in the embodiment, and FIG. 6 is a graph showing the relationship between the bit shift amount and the inter-vehicle distance in the embodiment. 10: First CCD sensor 14: Second CCD sensor 16: Rearview mirror 20: ECU

Claims (1)

(57) [Claims] 1. A plurality of sawtooth-like vehicles for detecting a vehicle in a vertical direction and a first oblique direction forming a predetermined angle with the vertical direction.
A first CCD sensor having a planar shape symmetrical with respect to the first CCD sensor in a vertical direction, and a second CCD symmetrical with the vertical direction and the first oblique direction;
A plurality of sawtooth-shaped second CCD sensors for detecting a forward vehicle in a diagonal direction, and a calculating device for calculating an inter-vehicle distance to a forward vehicle based on detection signals from the first and second CCD sensors. The first CCD sensors are spaced apart such that their first oblique direction detection sites are located on the same straight line, and the plurality of second CCD sensors are located so that their second oblique direction detection sites are located on the same straight line. And a vertical direction detection part is disposed so as to be located on the same straight line as the vertical direction detection part of the first CCD sensor.