JPH0755451Y2 - Inter-vehicle distance detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to an inter-vehicle distance detecting device, and more particularly to a device for accurately measuring an inter-vehicle distance to an adjacent vehicle by a single detecting device.

[Prior Art] Conventionally, various systems have been devised for the purpose of safe driving of a vehicle, and there is also an automatic tracking system that measures the inter-vehicle distance to the preceding vehicle and the automatic speed to safely follow the preceding vehicle. It is one of them. Such an automatic tracking system is particularly suitable for traveling on a motorway such as a highway where the vehicle speed and the traveling route are almost constant, and the driver can safely reach the destination without being bothered by the accelerator operation and the brake operation. Although it has the advantage that it can travel easily, in order to perform automatic follow-up driving safely and reliably in this way, it is necessary to accurately detect control parameters such as the distance to the vehicle ahead and the automatic speed. There must be.

Therefore, conventionally, various devices have been conceived for highly accurately measuring the inter-vehicle distance to the front vehicle, more generally, the distance to the front object. As one example thereof, Japanese Patent Laid-Open No. 63-13
The so-called phase difference method disclosed in the camera provided with the autofocus system of 7216 is known.

In this system, the lens, separator lens and CC
Detection elements such as D are sequentially arranged on the same optical axis, and the image of the subject is formed as two images on the detection element by the separator lens. Then, the distance to the object is measured by utilizing the fact that the image formation interval on the detection element of the two images of the object formed on the detection element changes as the distance between the lens and the object changes. , The defocus amount is calculated. Then, when performing distance measurement at a plurality of locations on the subject, the separator and the detection element are displaced from the optical axis each time, and the location to be measured is imaged on the detection element.

Also, in the past, ITJ Technical Report VoL.12.No.24, PP.1-6, ICS '880-2
As disclosed in 9, IBI A'88-32 (Jun, 1988), a method of measuring the distance between vehicles by stereo vision has been proposed. In this method, a front vehicle is photographed by two video cameras set at positions separated by a predetermined distance, and the inter-vehicle distance to the front vehicle is calculated by using the parallax of the two video cameras.

That is, as shown in FIG. 8 (A), first, the predetermined interval h
Two vehicle-mounted video cameras that are vertically separated from each other capture a front vehicle that is D away from the vehicle. Then, the obtained two images are converted into a black and white binary image to extract the horizontal component of the front vehicle.

Here, as shown in FIG. 8 (B), the points P in the three-dimensional space XYZ are projected on upper and lower two screens respectively, and P _H (x _H ,
y _H ), P _L (x _L , y _L ), there are two upper and lower screens XY
The distance D from the plane to the point P can be obtained from the following equation using the principle of triangulation from its geometrical relationship.

D = f · h / (γ · dv) dv = | x _L −x _H ｜ ……… (1) where D: distance f: focal length of video camera h: distance between two video cameras γ: screen The coefficient dv: parallax depending on the size of the, therefore, the focal length f of the two video cameras and the distance h between the video cameras are known, and the parallax of the horizontal component extracted from the images obtained by the two video cameras is By calculating dv, the distance D to the vehicle in front can be obtained based on the equation (1).

[Problems to be Solved by the Invention] However, there are some problems in such a conventional technique. In the method disclosed in Japanese Patent Laid-Open No. 63-137216, it is possible to perform distance measurement at a plurality of positions of a subject by mechanically shifting the separator lens and the detection element from the optical axis as described above. Essentially, it is a one-dimensional distance measurement in which the distance measurement is performed only at one location where there is a subject in front. Therefore, when it is used for distance measurement of a vehicle whose brightness changes greatly depending on the structural position, it is suitable for distance measurement each time. There was a problem that the distance had to be selected because the position had to be selected.

In addition, an apparatus for performing distance measurement using two video cameras is basically based on the principle of triangulation, so the optical axes of the two video cameras must be installed parallel to each other. I have to. When two video cameras are installed vertically parallel to each other, for example, on the front part of the own vehicle, the vibration of the vehicle causes a blur in the captured image, which prevents accurate distance measurement. There was a problem.

Furthermore, when the front vehicle is a normal passenger vehicle, its vehicle height is lower than that of a large vehicle such as a truck, and therefore the vertical viewing angle of the video camera with respect to the front vehicle is narrowed (for example, the vehicle height of the front vehicle is 1.4 m). , When the distance between vehicles is 50 m, the viewing angle is 1.6
It becomes °. ) There was a problem that the range could not be made large enough.

Of course, it is conceivable to install the two video cameras at a predetermined distance apart from each other in the horizontal direction instead of in the vertical direction, but in this case, the vertical direction component must be extracted from the obtained front vehicle image, and the vertical structure is required. Extraction is extremely difficult for a vehicle with a small change in luminance in the direction, which causes a problem that high-precision distance measurement cannot be performed.

The present invention has been made in view of the above-mentioned conventional problems, and an object thereof is to provide an inter-vehicle distance detecting device capable of highly accurately measuring an inter-vehicle distance to an adjacent vehicle such as a vehicle in front by a single detecting device. To do.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the inter-vehicle distance detecting device of the present invention includes a pair of fan-shaped anamorphic lenses arranged in the same plane so as to face each other in the same plane. An aspherical lens which is formed by radially arranging a plurality of adjacent pairs and forms an image of an adjacent vehicle with parallax by the pair of fan-shaped anamorphic lenses, and an adjacent vehicle image formed by the aspherical lens A solid-state image sensor for photoelectric conversion, and an arithmetic processing unit for calculating the distance to the adjacent vehicle based on the parallax of the adjacent vehicle image photoelectrically converted by the solid-state image sensor, and a plurality of pairs of radially arranged The fan-shaped anamorphic lens detects the distance to the adjacent vehicle.

[Operation] The inter-vehicle distance detecting device of the present invention has such a configuration, and is particularly characterized by the structure of the aspherical lens. That is,
The aspherical lens of the present invention is composed of a plurality of pairs of fan-shaped anamorphic lenses, and each pair of fan-shaped anamorphic lenses is arranged to face each other. As is well known, anamorphic lenses are lenses having different magnifications in different directions in the image plane, and therefore a pair of fan-shaped anamorphic lenses form an image of a point light source as a band-shaped image. , And the images are imaged without parallax due to the physical distances between the oppositely arranged elements.

Since a plurality of such pairs of fan-shaped anamorphic lenses are radially arranged, the image of the light source is formed as a band-shaped image radially spreading in a plurality of directions.

Since the aspherical lens of the present invention has such a characteristic, when the light source is an adjacent vehicle, the images at respective positions of the adjacent vehicle are located at predetermined positions in the strip-shaped image forming areas which are arranged to face each other. The image is formed in accordance with. Then, when the distance to the adjacent vehicle changes, the parallax changes according to the change in the distance, so that the image formation position shifts.

Therefore, the distance from each position of the adjacent vehicle can be calculated at the same time by photoelectrically converting the formed image of the adjacent vehicle by the solid-state image sensor and detecting the change in the image forming position by the arithmetic processing device. , It is possible to measure the distances of multiple adjacent vehicles with a single device.

[Embodiment] A preferred embodiment of an inter-vehicle distance detecting apparatus according to the present invention will be described below with reference to the drawings.

FIG. 4 is a configuration block diagram of this embodiment. The image information from the aspherical lens 10 is imaged on a CCD solid-state image pickup device 16 which is two-dimensionally arranged through a slit 12 and an infrared cut filter 14 for removing noise due to a heat source. Then, the image information photoelectrically converted by the CCD solid-state image pickup device 16 is sent to the arithmetic processing unit 18, and the calculation for calculating the inter-vehicle distance is performed.

FIG. 1 (A) is a plan view of the aspherical lens 10 as viewed from the optical axis direction, and is formed by arranging a plurality of pairs of fan-shaped anamorphic lenses 10a adjacent to each other in a radial pattern around the center thereof.

As described above, the anamorphic lens is a lens having different magnification in different directions in the image plane. For example, in the case of a cylindrical lens, the image of the point light source is a straight line parallel to the cylindrical mother ship. Becomes

A pair of fan-shaped anamorphic lenses 10 in this embodiment
a has a predetermined inclined surface formed in the bb section from the central portion toward the peripheral edge as shown in FIG. 1 (B), and is shown in the dd sectional view of FIG. 1 (D). As described above, the convex lens has no curvature in the radial direction and has a predetermined curvature in the circumferential direction perpendicular to the radius. The pair of fan-shaped anamorphic lenses 10a in the present embodiment has such a structure, and the radial direction and the direction perpendicular to the radial direction cause refraction as a lens, so that the image of the point light source is parallel to the radial direction. The image is formed as a strip-shaped area.

And such a pair of fan-shaped anamorphic lenses
As shown in FIG. 1 (A), 10a are arranged adjacent to each other in a plurality of pairs (6 pairs in this embodiment).
The image of the point light source is a pair of fan-shaped anamorphic lenses 10a.
It becomes a strip image in 6 directions that is extended in the radial direction of.

There are various conceivable methods for forming the aspherical lens of this embodiment. For example, polymethylmethacrylate (PMM
A) It is possible to perform integral molding using resin by injection molding.

Then, the image from this aspherical lens 10 enters the slit 12.

FIG. 2 is a plan view of the slit 12 as seen from the optical axis direction, in which a plurality of pairs of transmission holes 12a provided corresponding to the pair of fan-shaped anamorphic lenses 10a of the aspherical lens 10 are formed. The center axes of the pair of transmission holes 12a and the pair of fan-shaped anamorphic lenses 10a of the aspherical lens 10 are arranged so as to coincide with each other.

Therefore, as shown in FIG. 4, the light emitted from the light source AB is a pair of fan-shaped anamorphic lenses 10a of the aspherical lens 10.
The light is refracted by the image forming device and is imaged on the CCD solid-state image pickup device 16 as two images A′B ′ and A ″ B ″ each having a predetermined width. Therefore, when such an optical system is installed in, for example, the front grill part of a vehicle and its optical axis is aligned with the rear license plate of the front vehicle, as shown in FIG. A plurality of band-shaped images that radially spread in the direction will be obtained.

On the other hand, the CCD solid-state image sensor 16 has a plurality of Cs as shown in FIG.
Slit-shaped fan-shaped imaging area composed of arrayed CD pixels
The slits 1 are provided corresponding to the 12 transmission holes 12a.
The light transmitted through 2 is photoelectrically converted and input to the arithmetic processing unit 18.

The arithmetic processing unit 18 processes the electric signal from the CCD solid-state imaging device 16 as follows to calculate the inter-vehicle distance to the vehicle in front.

FIG. 6 shows the ee cross section of the CCD solid-state imaging device 16. As described above, the CCD solid-state image sensor 16 has a plurality of CCD elements arrayed to form a fan-shaped image pickup area 16a. Now, the CCD elements constituting the fan-shaped image pickup area 16a are sequentially a ₁ , a _{2 respectively.} ,… A _n are numbered. Similarly, for the other fan-shaped imaging area that is arranged oppositely, b ₁ , b
Number them as ₂ ,… b _n . Then, a plurality of CCD elements in each fan-shaped imaging area thus numbered are grouped and divided into k groups.

Here, when the inter-vehicle distance to the vehicle in front is D ₀ , the strip-shaped image formed in the fan-shaped imaging region 16a of the CCD solid-state imaging device 16 is the sixth image.
In the figure, a _{3 to} a _n-2 and b _{3 to} b _n-2 are assumed. When the distance to the vehicle ahead changes from this state to D ₁ (D ₁ > D ₀ ), the parallax of the image formed by the pair of fan-shaped anamorphic lenses 10a of the aspherical lens 10 decreases. , areas formed on the imaging region 16a of the CCD image sensor 16 is shifted to the central part a ₅ ~a _n, and b ₁ vary with _~b n~4. On the other hand, when the inter-vehicle distance to the vehicle in front changes with D ₂ (D ₂ <D ₀ ), the parallax increases, so the area imaged in the fan-shaped imaging area 16a of the CCD solid-state imaging device shifts in the edge direction, a
It varies from _{1 to} a _n-4 , and b _{4 to} b _n . In this way, the amount of change in each area is obtained because the images formed in the pair of imaging areas 16a of the CCD solid-state imaging device 16 that are arranged to face each other shift due to the change in parallax depending on the vehicle-to-vehicle distance from the vehicle in front. Can measure the distance to the vehicle ahead.

FIG. 7 is a plot of the distance thus calculated in each region. Since the rear license plate of the front vehicle is on the optical axis, the image is formed almost at the center in the imaging area 16a of the CCD solid-state image sensor 16, and the distance is gradually reduced from the number 1 to the number k / 2 in the center. A profile is shown which goes to the number k and then increases again toward the number k. Therefore, by obtaining the minimum value of the distance profile thus obtained, the inter-vehicle distance to the vehicle in front can be detected.

It is possible to detect not only the inter-vehicle distance to the front vehicle, but also the shape, relative speed, relative yaw rate, etc. of the front vehicle from the distance profile thus obtained.

That is, such a distance profile is obtained at every predetermined time, and the relative speed with respect to the vehicle in front can be measured by calculating the distance change within this predetermined time, and the lateral displacement of this distance profile within the predetermined time can be measured. The relative yaw rate can also be calculated by obtaining

Then, when calculating these values, the arithmetic processing unit of the present embodiment may be used, but it is also possible to use a neural network in which a plurality of formal neurons having a predetermined threshold value are combined. As is well known, a formal neuron is a multi-input-1 output non-linear element and outputs a pulse only when the weighted addition of each input exceeds a predetermined threshold value. Then, by appropriately setting the weighting coefficient and the threshold value of each input signal of this type neuron, a logic gate such as an AND gate, an OR gate, and a NOT gate can be configured. Therefore, a neural network formed by combining these formal neurons can perform various arithmetic processing by appropriately changing the combination, and the relative speed and the relative yaw rate are calculated by the neural network. Is also good.

[Advantages of the Invention] As described above, according to the inter-vehicle distance detecting device of the present invention, it is possible to measure the distance between a plurality of adjacent vehicles such as a front vehicle and the like with a single device. It is possible to detect the distance with high accuracy.

In addition, the inter-vehicle distance detecting device according to the present invention is capable of simultaneously measuring the distance between a plurality of adjacent vehicles, and thus can obtain the three-dimensional information of the adjacent vehicles. It is also possible to detect the relative speed and the relative yaw rate.

[Brief description of drawings]

FIG. 1 is an explanatory view of an aspherical lens in an embodiment of an inter-vehicle distance detecting device according to the present invention, FIG. 2 is a plan view of a slit in the embodiment, and FIG. 3 is a plane of a CCD solid-state image pickup device in the embodiment. 4 and 5 are configuration block diagrams of the same embodiment, FIG. 5 is an explanatory view showing a range-finding range in the same embodiment, FIG. 6 is a divided area explanatory view of a CCD solid-state image sensor in the same embodiment, and FIG. FIG. 8 is a distance profile diagram showing an inter-vehicle distance to a vehicle ahead in the embodiment, and FIG. 8 is an explanatory diagram of a conventional inter-vehicle distance detecting device. 10 ... Aspherical lens 12 ... Slit 14 ... Infrared cut filter 16 ... CCD solid-state image sensor 18 ... Arithmetic processing unit

Claims (1)

[Scope of utility model registration request] 1. A pair of fan-shaped anamorphic lenses, which are arranged so as to face each other in a straight line in the same plane, are radially arranged adjacent to each other in the plane, and the parallax is formed by the pair of fan-shaped anamorphic lenses. An aspherical lens for forming an image of an adjacent vehicle accompanied by a solid-state image sensor for photoelectrically converting an image of the adjacent vehicle formed by the aspherical lens, and an adjacent vehicle photoelectrically converted by the solid-state image sensor And an arithmetic processing unit that calculates the distance to the adjacent vehicle based on the parallax of the image, and the distance to the adjacent vehicle is detected by a plurality of pairs of fan-shaped anamorphic lenses radially arranged. Distance detection device.