JPH095073A - Inter-vehicle distance detector - Google Patents

Abstract

PURPOSE: To precisely detect inter-vehicle distance to a preceding vehicle by a light receiving element arranged one-dimensionally on a straight line by forming an optical image of the rear face of the preceding vehicle on image forming faces of a pair of lenses and computing the inter-vehicle distance on the basis of a difference between distribution positions of the detected light intensity on both of the detection screens. CONSTITUTION: An optical image on the rear face of a preceding vehicle is formed on image formation faces of a pair of lenses A, 3B. By computing means 51, 61A, the inter-vehicle distance is computed from difference between a detected light intensity distribution for the preceding vehicle rear face image formed through a lens 3A on one detection screen 4A and a detected light intensity distribution for the preceding vehicle rear face image formed through the lens 3A on the other detection screen 4B. As to the computed inter-vehicle distance to the preceding vehicle, an image formation position on the image formation face matching with the computed inter-vehicle distance is found from a geometrical optics correspondence between the image formation position, in which the image of the preceding vehicle rear face is formed on the image formation face previously stored in a memory 62, and the inter-vehicle distance, and the detection screen is changed to this position.

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.

[0002]

2. Description of the Related Art An inter-vehicle distance detecting device is used to detect a distance to a preceding vehicle and maintain an appropriate inter-vehicle distance in automatic traveling or the like, and a device for detecting a distance by parallax is used. The principle will be described in the case of detecting the distance to the object T having the brightness distribution as shown in FIG. The distance detection unit 91 in the distance detection device is shown in FIG.
A pair of lenses 9 arranged with a constant base line length as shown in FIG.
3A and 93B are provided, and a plurality of light receiving elements are provided in the left and right directions on the rear image forming surface to form a light receiving screen 92. Light receiving screen 9
No. 2 has a single light-receiving element provided in the vertical direction in order to reduce the cost and the amount of calculation. An object T at a distance X in front of the lens is imaged on the left side portion of the light receiving screen 92 by the left lens 93A, and the detected light intensity distribution of the light receiving screen 92 is as shown in FIG. 7B, for example. Also,
The image formation of the object T by the right lens 93B is shown in FIG.
As shown in FIG. 8B, the detected light intensity distribution occurs on the right side of the light receiving screen 92 and becomes as shown in FIG. 8B. After all, the detected light intensity distribution on the light receiving screen 92 formed by the image formation of the left and right lenses 93A and 93B has the same shape as shown in FIG. 9, and is shifted by n pixels in the left and right direction. If the pixel pitch is Ep, the difference between the detected light intensity distribution positions is Ep.n.

In FIG. 10, the image forming point on the light receiving screen 92 by the left lens 93A of the point L at the distance X in front of the optical axis of the left lens 93A is PA, and the right lens 93B.
Let PB be the image forming point of the triangle E, and P∞ be the image forming point of the right lens 93B at a point at infinity.
From the similarity of F, X = Bf / y. f is each lens 93
Since the focal lengths of A and 93B and the distance B between PA and P∞ are lens intervals (base line length), these are known and PB
, P∞ is known, the distance X can be calculated by the above equation. Here, the distance between PA and PB is determined by the two lenses 93A,
Since it is the shift of the image forming position due to 93B, it is equal to the above Ep.n. Therefore, y = EP.multidot.B, and the distance X can be known from the difference Ep.n in the detected light intensity distribution position.

[0004]

FIG. 11 shows a distance detecting unit 91 in which light receiving elements are linearly arranged in the direction of the base line of the lens, and is attached to a vehicle 94. Preceding vehicle 9
6. A pair of lenses 93A are provided on the upper side of the interior of the windshield 95 of the vehicle so as to look down slightly on the rear surface.
93B are arranged side by side, and the inter-vehicle distance is detected from the detected light intensity distribution on the rear surface of the preceding vehicle obtained through the pair of lenses 93A and 93B. FIG. 12A shows that the distance detection device detects the inter-vehicle distance to the preceding vehicle 96. In the figure, the shaded area is the visual field range where an image is formed on the light receiving element. FIG. 12B is a diagram of the preceding vehicle 96 as viewed from the rear, and shows the above visual field range by a frame. The field of view has a slightly downward fan shape. When the preceding vehicle 96 is at the position (a) (FIG. 12 (A)), there are a license plate 97 and a tail lamp 98, which are arranged on the rear surface of the preceding vehicle 96 and have a distinct design, within the visual field range (FIG. 12). Therefore, the contrast of the detected light intensity distribution is clear and the detection accuracy of the inter-vehicle distance is good. However, the preceding vehicle 9
6 is at a position (b) farther than the position (a) (see FIG. 11).
In (A), the field of view moves downward, and there are only bumpers 99 and the like within the field of view (FIG. 12B), the contrast of the detected light intensity distribution decreases, and the detection accuracy of the inter-vehicle distance decreases. When the position of the preceding vehicle becomes further away, the preceding vehicle 96 moves out of the visual field range (FIG. 12 (B)), making it impossible to detect the inter-vehicle distance. As described above, the above-described inter-vehicle distance detecting device has a problem that the inter-vehicle distance cannot be satisfactorily detected from a short distance to a long distance.

Of course, if the distance detecting unit 91 is provided at the same height as the license plate 97 and the tail lamp 98 so that the visual field range is horizontal, the above problem does not occur.
For that purpose, the installation location must be the front part of the vehicle body. Then, it is necessary to incorporate the distance detecting unit 91 into the design of the vehicle body in advance, or the cost is increased due to the environment resistance measures such as waterproofing, which is not practical. Therefore, it is an object of the present invention to provide an inter-vehicle distance detecting device capable of accurately detecting an inter-vehicle distance from a preceding vehicle by a light receiving element which is one-dimensionally arranged on a straight line.

[0006]

As shown in FIGS. 1 (A) and 1 (B), a vehicle-interval distance detecting apparatus of the present invention includes a pair of lenses 3A provided in front of the vehicle with a constant base line length. 3B
And a pair of detection screens 4A composed of a plurality of light receiving elements linearly arranged in the baseline length direction on the image forming planes of the pair of lenses 3A and 3B, and the rear surface of the preceding vehicle is imaged through the lenses 3A and 3B. 4B and the distribution position of the detected light intensity on the rear surface of the preceding vehicle which is imaged through one lens 3A in one detection screen 4A, and the detected light intensity of the rear surface of the preceding vehicle which is imaged through the other lens 3B on the other detection screen 4B. Calculation means 51, 61A for calculating the inter-vehicle distance from the difference with the distribution position
And further includes the pair of lenses 3A and 3B and the pair of detection screens 4A and 4B.
B is arranged vertically, the position of the pair of detection screens is variable in association with the base line length direction, and the image formation position and the inter-vehicle distance in which the rear surface of the preceding vehicle forms an image in advance on the image formation surface. Storage means 62 storing the geometrical-optical correspondence with
And a detection screen control means 61B for changing the detection screen to the image forming position on the image forming surface corresponding to the inter-vehicle distance detected in the past from the above correspondence.

Detection screens 4A, 4B with variable position
Is composed of a large number of light receiving elements linearly arranged in the base line length direction, and a part of the plurality of light receiving elements is detected on the detection screen 4A,
4B, and is composed of a light receiving element group 2 in which the light receiving elements forming the detection screens 4A and 4B are variable.

The light receiving element group 2 is a line CCD 2.

[0009]

In the inter-vehicle distance detecting device of the present invention, the optical image of the rear surface of the preceding vehicle formed by the pair of lenses 3A and 3B is formed on the image forming planes of the pair of lenses 3A and 3B, and the calculating means 51 and 61A are provided.
Is the distribution position of the detected light intensity on the rear surface of the preceding vehicle which is imaged through one lens 3A in one detection screen 4A, and the distribution position of the detected light intensity of the rear surface of the preceding vehicle which is imaged through the other lens 3B on the other detection screen 4B. The inter-vehicle distance is calculated from the difference between. The calculated distance with respect to the preceding vehicle is calculated by the detection screen control means 61B from the geometrical optical correspondence relationship between the inter-vehicle distance and the image formation position where the rear surface of the preceding vehicle forms an image on the image formation surface, which is stored in the storage means 62 in advance. The image forming position on the image forming surface corresponding to the vehicle-to-vehicle distance is determined, and the detection screen is changed to that position. When the next inter-vehicle distance is detected, the image formation position on the rear surface of the preceding vehicle and the detection screens 4A and 4B show the detection accuracy in the previous detection, and the change in the actual inter-vehicle distance in the time from the previous detection to the next detection. Match within the range.

Detection screens 4A, 4B with variable position
Is composed of a large number of light receiving elements linearly arranged in the baseline length direction, and a part of the plurality of light receiving elements is detected on the detection screen 4A,
4B, and when the light receiving elements constituting the detection screens 4A and 4B are made variable, the light receiving elements which are the detection screens 4A and 4B are variable in the light receiving element group 2. The position of the detection screen can be easily changed from.

When the light receiving element group 2 is the line CCD 2, the device is light and small.

[0012]

【Example】

(Embodiment 1) As shown in FIG. 1 (A), an inter-vehicle distance detecting apparatus of the present invention comprises a line CCD module 1 and an ECU 6 for transmitting and receiving commands and data to and from the line CCD module 1. As shown in FIG. 1 (B), the line CCD module 1 has a casing 11 attached to the upper edge of the interior of a vehicle windshield 71. A pair of lenses 3A and 3B are vertically provided on the front wall surface of the casing 11 with a constant base line length (lens interval), and a CCD, which is a light receiving element, is linearly formed on the image forming surface of the lenses 3A and 3B. 170 line CCDs 2 are arranged so that the CCD arrangement direction coincides with the base line length direction of the lenses 3A and 3B.

Each CCD of the line CCD 2 is numbered for the sake of convenience, and when the ECU 6 sends a CCD number which is a detection screen designating command, the CC with the number is attached.
The 36 CCDs centering on D constitute one detection screen 4A, and the 36 CCDs centering on the CCD separated by the lens baseline length constitute the other detection screen 4B.

An electronic board 5 is housed in the rear part of the casing 11 so that the detected luminous intensity detected by each CCD of the line CCD 2 is inputted. The electronic board 5 has a front stage portion 51 of a calculating means for calculating the distance to the preceding vehicle from the difference in the positions of the detected light intensity distributions on the detection screens 4A and 4B.
Etc. are incorporated.

The ECU 6 has a general microcomputer configuration. The CPU 61 constituting the ECU 6 is configured to perform serial communication with the line CCD module 1 via the shift registers 63 and 64. The line CCD module 1, the shift registers 63 and 64, and the oscillation circuit 65
Are synchronized with clock pulses.

The output of the front stage section 51 of the arithmetic means is transmitted by serial communication to the rear stage section 61A of the arithmetic means which constitutes the CPU 61 via the shift register 64, and the detection screen control means which constitutes the CPU 61. 6
1B transmits the CCD number which is the above-mentioned detection screen designating command via the shift register 63. The latter part 61A of the calculating means and the detection screen control means 61B are executed by running a program for detecting the inter-vehicle distance on the CPU 61.

The memory 62, which is a storage means, stores the geometrical-optical correspondence between the position where the rear surface of the preceding vehicle forms an image on the image forming surfaces of the pair of lenses 3A and 3B and the inter-vehicle distance.

2A and 2B are optical path diagrams when the rear surface of the preceding vehicle is imaged on the line CCD 2 by the lens 3A. FIG. 2A shows the case where the preceding vehicle is at a long distance. Here, (B) is a case where the preceding vehicle is in a short distance. Since the optical image of the preceding vehicle is inverted through the lens, the image forming position is at the central portion 21 of the line CCD 2 when the preceding vehicle is at a long distance, and the optical image forming position of the preceding vehicle is when the preceding vehicle is at a short distance. It is above the line CCD 2. If the preceding vehicle is at a middle distance, the optical image forming position of the preceding vehicle is located at the central portion 21 of the line CCD 2 and above the line CCD 2.
The image forming position between the two is determined uniquely geometrically and the CCD positioned at the center of the optical image on the rear surface of the preceding vehicle is also determined. The correspondence between the inter-vehicle distance and the number given to the CCD as an index showing the image formation position where the rear surface of the preceding vehicle forms an image is shown by the ground height at the place where the line CCD module 1 is attached and the line CCD module 1 A function g (D) for associating the inter-vehicle distance with the CCD number is stored in the memory by formulating using the mounting angle and the like. Since one detection screen is composed of 36 CCDs, the 17 CCDs at the top of the line CCD 2 do not correspond to the inter-vehicle distance.

In the memory 62, in addition to the function g (D), there are functions used in the program and the post-stage portion 61A of the calculating means, which are line CCD modules transmitted from the line CCD module 1. Distance d between 1 and the preceding vehicle
A function f (d) for converting the vehicle distance into an inter-vehicle distance projected on a horizontal plane is stored.

The operation of the inter-vehicle distance detecting device is shown in FIG.
The operation of the CPU 61 will be described with reference to the flowchart of FIG. First, variables D and P are defined. D is an inter-vehicle distance, P is a CCD which is sent to the line CCD module 1 as a detection screen designating command and designates the detection screen 4A.
Is the number. Upper limit values Dmax and P for P and D, respectively
Pmax is set (step 101). Next, the defined variables are initialized. Let D be Dmax and P be Pmax
(Step 102).

P is a line CCD module for serial communication.
When it is transmitted to the module 2 (step 103), in the line CCD module 2, the CCD whose CCD number is P is the center 3
The position of the detected luminous intensity distribution of one detection screen 4A composed of 6 CCDs and the 36 CCs centered on the CCDs at the positions separated by the same length as the baseline length between the two lenses 3A and 3B.
The line CCD module 1 and the rear surface of the preceding vehicle from the position difference of the detected light intensity distribution of the one detection screen 4B composed of D
And the distance d between and is calculated. The calculated d is serially received by the CPU 61 via the shift register 64 (step 104), and the CPU 61 calculates the inter-vehicle distance D from the above d by the function f (d) (step 105). The calculated inter-vehicle distance D is compared with Dmax (step 106), and if D is smaller than Dmax, it is determined that the inter-vehicle distance is normally detected,
From the inter-vehicle distance D, P in the next inter-vehicle distance detection cycle is obtained by the function g (D) (step 107), and the inter-vehicle distance D is output (step 108).

After that, the routine returns to step 103, and steps 103 to 108 are repeated as an inter-vehicle distance detection cycle. At that time, in step 103, the line CC
Since the P transmitted to the D module 1 is always the P obtained in step 107 of the preceding intervehicular distance detection cycle, the detection screens 4A and 4B are located at the positions where the rear surface of the preceding vehicle is imaged in the previous intervehicular distance detection cycle. become. Therefore, the detection screen is changed following the change in the inter-vehicle distance within the range of the detection accuracy in the previous detection and the change in the actual inter-vehicle distance in the time from the previous detection to the next detection.

If D is larger than Dmax in step 106, it is judged that the detection of the inter-vehicle distance is abnormal, and the process returns to step 102. The variables are initialized again and the inter-vehicle distance detection cycle is performed again.

(Embodiment 2) Another embodiment of the present invention will be described. The difference from the inter-vehicle distance detection device described in the first embodiment is CP
Since it is only the operation of U61, the difference will be mainly described by the flowchart of FIG. 4 showing the operation of the CPU 61.

First, variables D, Dave, Buf (N) and P are defined. D is an inter-vehicle distance, Dave is an average value of the inter-vehicle distance D in N consecutive inter-vehicle distance detection cycles, and Buf (N) is detected in each inter-vehicle distance detection cycle in N consecutive inter-vehicle distance detection cycles. This is a buffer for temporarily storing the distance D between vehicles, and P is the number of the CCD that is the center of the detection screen. The upper limit value Dmax of the inter-vehicle distance and the upper limit value Pmax of P are set (step 10).
1). Next, the defined variables are initialized. D to D
max, P is Pmax, and the counter i of the buffer is
Is set to 1 (step 102).

In steps 103 to 106, the inter-vehicle distance D is obtained as in the first embodiment. If the inter-vehicle distance D is smaller than Dmax in step 106, D is stored in Buf (i) (step 203) and the counter i is incremented by 1 (step 20).
4). i is compared with N and if smaller than N, step 10
Return to 3, and repeat steps 103 to 204 with the same P as before. The counter i is incremented while repeating steps 103 to 204, and when steps 103 to 204 are repeated N times, the inter-vehicle distance D detected by the inter-vehicle distance detection for N times is stored in N Buf (i). At this time, the counter i is N
Since it is +1 step 205 to step 20
6, the average value of N Buf (i) is calculated, and D
Set as ave (step 206). From the average inter-vehicle distance Dave, P in the next inter-vehicle distance detection cycle is obtained by the function g (Dave) (step 107), and the inter-vehicle distance Dave is output (step 108).

Here, the counter i is initialized again (i = 1).
(Step 208) and returns to step 103. Then, the first inter-vehicle distance detection cycle in the next N inter-vehicle distance detection cycles starts.

If D is larger than Dmax in step 106, it is judged that the detection of the inter-vehicle distance is abnormal, and the process returns to step 202. The variables are initialized again and the inter-vehicle distance detection cycle is performed again.

In this embodiment, the inter-vehicle distance detected in N times of inter-vehicle distance detection cycles is averaged to obtain the inter-vehicle distance, so that the detection error can be suppressed. Moreover, when a detection abnormality occurs during the N inter-vehicle distance detection cycles, the counter i is initialized in step 202. Therefore, if all N consecutive inter-vehicle distance detection cycles are not normally performed, the average inter-vehicle distance is reduced. Do not proceed to step 206 for seeking. Therefore, the reliability of the inter-vehicle distance output in step 108 is further improved. And such an inter-vehicle distance D
Since P is obtained based on the above, the detection screens 4A and 4B and the image formation positions on the rear surface of the preceding vehicle can be further matched.

Although the number of CCDs constituting the detection screen is 36 in each of the above embodiments, the number of CCDs is not limited to this, and the cycle of the inter-vehicle distance detection cycle and the CPU 61 are not limited to this.
It may be increased or decreased as appropriate in consideration of the processing speed and the like. G (D) stored in the memory need not be a formalized one,
A table in which P and D have a one-to-one correspondence may be used. Although P is determined only by the inter-vehicle distance, it may be determined according to the contrast of the detected light intensity distribution.
Further, the number N of times the vehicle-to-vehicle distance is continuously performed may be appropriately set according to a detection error or the like to be suppressed.

[0031]

As described above, according to the inter-vehicle distance detecting apparatus of the present invention, as shown in FIG. 5, it is possible to determine whether the position of the preceding vehicle 8 is the short distance (a) or the long distance (b). However, the rear surface of the preceding vehicle 8 is within the visual field range of the light receiving element (indicated by an arrow), and the position of the detection screen is changed even if the inter-vehicle distance to the preceding vehicle 8 changes, and the rear surface of the preceding vehicle 8 is always detected. Since it is included in the visual field range (indicated by diagonal lines in the drawing), the inter-vehicle distance to the preceding vehicle can always be detected accurately.

[Brief description of drawings]

FIG. 1A is a block diagram of an inter-vehicle distance detecting device of the present invention, and FIG. 1B is a perspective view showing a part of a mounting mode of the inter-vehicle distance detecting device of the present invention.

FIG. 2A is an optical path diagram showing one state of the inter-vehicle distance detecting device of the present invention, and FIG. 2B is an optical path diagram showing another state of the inter-vehicle distance detecting device of the present invention.

FIG. 3 is a flow chart showing the operation of the inter-vehicle distance detecting device of the present invention.
It is a chart.

FIG. 4 is a flowchart showing the operation of another inter-vehicle distance detecting device of the present invention.

FIG. 5 is a diagram showing effects of the inter-vehicle distance detecting device of the present invention.

FIG. 6 is a diagram illustrating an operating principle common to the present invention and a conventional inter-vehicle distance detecting device.

FIG. 7A is another diagram for explaining the operating principle common to the present invention and the conventional inter-vehicle distance detecting device, and FIG. 7B is a graph for explaining the operating principle.

FIG. 8 (A) is still another diagram for explaining the operation principle, and FIG. 8 (B) is another graph for explaining the operation principle.

FIG. 9 is yet another graph explaining the above-mentioned operation principle.

FIG. 10 is still another view for explaining the above-mentioned operation principle.

FIG. 11 is a perspective view showing a mounting mode of a part of a conventional inter-vehicle distance detecting device.

FIG. 12A is a diagram illustrating a problem of a conventional inter-vehicle distance detecting device, and FIG. 12B is another diagram illustrating a problem of a conventional inter-vehicle distance detecting device.

[Explanation of symbols]

 1 line CCD module 2 line CCD (light receiving element group) 3A, 3B lens 4A, 4B detection screen 51 front stage part of calculation means (calculation means) 61A rear stage part of calculation means (calculation means) 61B detection screen control means 62 memory (Memory means) 8 preceding vehicle

Claims (3)

[Claims] 1. A pair of lenses provided with a fixed base line length toward the front of the vehicle, and linearly arranged in the base line length direction on an image forming surface of the pair of lenses, and a rear face of a preceding vehicle is passed through the lenses. A pair of detection screens formed by a plurality of light receiving elements that form an image, a distribution position of the detected light intensity on the rear surface of the preceding vehicle that forms an image through one lens in one detection screen, and an image that forms on the other detection screen through the other lens In an inter-vehicle distance detecting device, which comprises a calculating means for calculating an inter-vehicle distance from a difference between a detected light intensity distribution position on the rear surface of a preceding vehicle, the pair of lenses and a detection screen are arranged so that the pair of lenses are located above and below. The two detection screens are interlocked with each other in the longitudinal direction of the base line to change the position, and the geometrical-optical correspondence relationship between the inter-vehicle distance and the imaging position at which the rear surface of the preceding vehicle forms an image on the imaging surface in advance. Vehicle-to-vehicle distance detection provided with stored memory means and detection screen control means for determining an image-forming position on the image-forming surface corresponding to a vehicle-to-vehicle distance previously detected from the correspondence and changing the detection screen to that position. apparatus. 2. The inter-vehicle distance detecting device according to claim 1, wherein the detection screen whose position is variable is composed of a large number of light receiving elements linearly arranged in the base line length direction, and a part of the plurality of light receiving elements is arranged. An inter-vehicle distance detection device that does not serve as a detection screen and includes a light receiving element group in which the light receiving elements forming the detection screen are variable. 3. An inter-vehicle distance detecting device according to claim 2, wherein the light receiving element group is a line CCD.