JP2917557B2 - 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 for detecting a relative distance between a preceding vehicle and a host vehicle in a non-contact manner.

[0002]

2. Description of the Related Art As a method for detecting a distance from an observation point to a target object, a method using an ultrasonic wave or a laser beam is conventionally known. In this method, an ultrasonic wave or a laser beam is projected onto a target object, a reflected wave from the target object is captured, and a distance from an observation point to the target object is measured in a non-contact manner.

However, what can be measured by the above-described distance detection method using an ultrasonic wave or a laser beam is the distance from the observation point to the reflection point of the target object, and the distance between the moving preceding vehicle and the moving vehicle. When measuring the distance between the vehicles, it is difficult to measure the distance accurately due to the fluctuation of the vehicle body or a change in the relative position. Further, in the case of ultrasonic waves, the beam width cannot be made very narrow, so that measurement at a long distance is difficult.

[0004] As an apparatus for solving such difficulties and detecting a distance to a moving target object, for example, the invention disclosed in Japanese Patent Application Laid-Open No. 63-26517 discloses an "absolute inter-vehicle distance detection system". "It has been known. This inter-vehicle distance detection method includes an imaging device for imaging a moving target object, a means for detecting a horizontal component by spatially differentiating an image of the target object with the imaging device, and binarizing the horizontal component. Means for determining a significant width in the vertical direction in the binarized image, and means for determining a significant width in the horizontal direction in the image of the significant region in the vertical direction. The approach or distance of the target object is obtained by detecting the target change amount and the increase or decrease of the temporal change amount.

[0005]

However, this conventional known inter-vehicle distance detection method is for identifying a moving target object, more specifically, an image signal of a detected object input to an image pickup device.
For example, in order to improve the discrimination of the image signal of the preceding vehicle, it is necessary to perform a spatial differentiation process (determining the density based on the difference between the values of neighboring pixels). At the same time, the surrounding background image signal also moves on the imaging device.

Therefore, since the image signal of the preceding vehicle and the image signal of the background are both extracted, it becomes difficult to separate the two image signals. In addition, if the monitoring area is made small to eliminate the influence of the background image signal, the vehicle to be measured goes out of the monitoring area if the relative position between the vehicles changes in the curve of the traveling route or the lane changes. There is also a drawback that detection becomes impossible.

In view of the foregoing, the present invention eliminates the above-described disadvantages of the conventional inter-vehicle distance detection method, and enables the image of a moving target object to be clearly distinguished and extracted from a surrounding background image, so that the inter-vehicle distance can be accurately and easily detected. An object of the present invention is to provide a distance detecting device.

[0008]

SUMMARY OF THE INVENTION In order to achieve the above object, an inter-vehicle distance detecting apparatus according to the present invention includes an image detecting means for generating an electric output corresponding to the light intensity of an image signal, and an image detecting means for generating an electric output. A first comparing means for comparing the electrical output with a first reference value to binarize and output, and a plurality of memories for sequentially and time-sequentially storing signals output from the first comparing means. a memory group consisting of, from each of a plurality of memory constituting the memory group, in sequence, adding means for adding signals outputted by the time series, the integrated output which is output from the adding means and the second reference value an image extraction unit consisting of a second comparative hand stage <br/> comparing to binarize the output has a plurality of systems, each of the preceding vehicle position corresponding to the outputs of the plurality of second comparison means
And a distance calculation circuit for calculating a distance to the preceding vehicle corresponding to the difference between the preceding vehicle positions .

[0009]

According to the inter-vehicle distance detecting device of the present invention, since the image signal of the traveling vehicle whose speed is relatively slow relative to the own vehicle is output, the preceding vehicle can be specified accurately.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An inter-vehicle distance detecting apparatus according to an embodiment of the present invention will be described below with reference to the drawings.

First, the principle of detecting an inter-vehicle distance in this embodiment will be described.

The inter-vehicle distance detection of this embodiment is performed by a set of image sensors 1a and 1b provided at a predetermined distance L from the host vehicle as shown in FIG. 5 and a focal distance f in front of each image sensor. Arranged imaging lenses 22a, 22b
It is performed by Here, assuming that the distance from the imaging lens 22b to the preceding vehicle is D, and the difference between the imaging positions of the image sensors 1a and 1b is δ, the inter-vehicle distance D is D = f · L / δ (1) . The focal length f and the image sensors 1a, 1b
Since the distance L between them is a preset value, if the value of the difference δ between the imaging positions is known, the inter-vehicle distance D can be calculated.

Therefore, the following distance detecting apparatus of this embodiment is
As shown in FIG. 1, each unit A and B extracts an image signal of a preceding vehicle from signals of a pair of image sensors 1a and 1b arranged at a fixed distance L on the vehicle, and forms an image forming position thereof. Based on the distance signal generation circuit 8
The following distance is calculated based on equation (1). Note that these components are entirely controlled by the timing generation circuit 9.

Next, means for extracting the image signal of the preceding vehicle in each of the units A and B will be described.

[0015] However, each of the units A, structure of B, effects are the same, will be described unit A which is provided on the right side toward the traveling direction of the vehicle.

First, as shown in FIG. 1, an image sensor 1a in which a plurality of CCD elements are temporarily arranged and a low-pass filter (LPF) for cutting noise in an output signal of the image sensor 1a. A first comparator 3a for comparing the signal with a predetermined first reference value 2a and binarizing the same, and a memory group 4a for storing the binarized signal in a time-series manner. It comprises an adder 5a for adding signals stored in time series, and a second comparator 7a for comparing the added value with a predetermined second reference value 6a.

Next, the operation will be described.

When the input from the image sensor 1a is started by a trigger pulse from the timing generation circuit 9, the outputs of the CCD elements of the image sensor 1a temporarily arranged from the timing generation circuit 9 based on the clock pulse are sequentially ( L.P.F., and is binarized by the first comparator 3a. (FIG. 6) The binarized signals are stored in the memory group 4a in time series. See Figure 2 for details.
As shown in (1), the trigger switch of the timing generation circuit 9 first turns on the input switch 10a-1 of the memory group 4a. Then, the binarized signal is sequentially stored in the shift register 11a-1 by the clock from the timing generation circuit 9. With the next trigger pulse, the input switch 10a-1 is turned off, the switch 12a-1 is turned on, and the contents of the shift register 11a-1 are circulated by the clock pulse without receiving new data. At the same time, 4
The input switch 10a-2 of a-2 is turned on, and the data is stored in the shift register 11a-2 in the same manner as described above.

In this way, the binarized value of the one-dimensional signal of the image sensor 1a is sequentially stored in the shift registers 11a-1 and 11a-2 of the memory group 4a. (FIG. 7) Thereafter, all the shift registers 11a-
When the signals are stored in the shift registers 11a and 11a-2 , the output switch 15a-1 is turned on by the trigger pulse, and the shift register 11 is sequentially sent to the adder 5a based on the clock pulse.
a-1 and 11a-2 are output. This adder 5
In a, as shown in FIG. 3, the input signal of the shift register is added by the operational amplifier via the input resistor.

This added value is calculated by a temporarily arranged CCD.
This indicates the frequency of input of a signal equal to or more than the first reference value 2a to one of the elements.

The added value and the second reference value 6a are compared by the second comparator 7a, and only those having a frequency equal to or higher than a predetermined value are extracted. (FIG. 8) Here, the image sensor 1
Among the signals input to a, the preceding vehicle having a lower relative speed with respect to the own vehicle constantly appears at a specific position, but the one having a higher relative speed with respect to the own vehicle such as a tree or a sign indicates the position appearing on the image sensor 1a. Does not always appear at a specific position. From this, a signal appearing beyond the second reference value 6a is a signal of the preceding vehicle.

As described above, when the signals of the preceding vehicle are obtained by the units A and B, the inter-vehicle distance is detected by the distance signal generating circuit 8 shown in FIG. As shown in FIG. 9, the distance signal generation circuit 8 outputs the signals from when the signals d1 and d2 of the preceding vehicle obtained from the units A and B are generated until the trigger pulse a of the timing generation circuit 9 is generated. Based on the F / Fs 17a and 17b, the clock pulse signal is counted by the counters 16a and 16b, and the output of (e1, e2) is output to the D / A 19a, 1
9b to output analog values f1 and f2. This value indicates the position of the signal of the preceding vehicle on the image sensors 1a and 1b. The difference between the signals is referred to as differential amplifier 2
The values are calculated by 0-1 and 20-2 and compared by the level comparator 21 to derive a value corresponding to the difference δ between the imaging positions in the above equation (1).

The inter-vehicle distance D is detected by the divider 22 from the value.

As described above, in this embodiment, two sets of image sensors using CCD elements are used. However, the accuracy of detecting the distance between vehicles can be further improved by using two or more sets of image sensors.

The image sensor is also a CCD.
In addition to using an element, a MOS transistor can be used.

[0026]

As is clear from the above description, according to the inter-vehicle distance detecting apparatus of the present invention, the position of a background image such as a sign or a tree on a road having a relatively high speed relative to the own vehicle is changed. However, the obtained image signal is detected as a large number of pulse signals, but is averaged and not extracted if integrated. On the contrary, the image signal of the preceding vehicle, since the position change with respect to the vehicle is small, little change over several cycles, can be detected as a pulse waveform by integrating, it is possible to easily obtain the exact distance between vehicles.

[Brief description of the drawings]

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

FIG. 2 is a detailed view of a memory group 4a of the inter-vehicle distance detection device shown in FIG.

FIG. 3 is a detailed view of an adder 5a of the following distance detecting apparatus shown in FIG.

FIG. 4 is a detailed diagram of a distance signal generation circuit 8 of the inter-vehicle distance detection device shown in FIG.

FIG. 5 is a diagram illustrating the principle of detecting the following distance of the following distance detecting apparatus shown in FIG. 1;

6 is an image sensor of the inter-vehicle distance detection device shown in FIG.
1a is a diagram showing an output signal of the output signal and a first comparator 3a for.

FIG. 7 is a binary signal diagram of each shift register 11a-1 and 11a- 2 included in the memory group 4a shown in FIG .

FIG. 8 is a diagram of a pulse signal transmitted from the second comparator 7a.

FIG. 9 is a timing generation circuit 9 and a second comparator 7
7A and 7B are diagrams of signals output from D / A 19a and 19b.

[Explanation of symbols]

 1a, 1b Image sensor 2a, 2b First reference voltage 5a, 5b Adder 8 Distance signal generating circuit 9 Timing generating circuit

Claims (1)

(57) [Claims] 1. An image detecting means for generating an electric output corresponding to the light intensity of an image signal, and a first comparison for binarizing and outputting the electric output generated by the image detecting means with a first reference value means, a signal output from the first comparison means, sequentially, and a memory group including a plurality of memories for storing in time series, from each of a plurality of memory constituting the memory group, in sequence, when
Adding means for adding signals outputted by the sequence, picture comprising a second comparison means for binarizing by comparing outputs the integrated output outputted from the addition means and the second reference value
It has a plurality of image extraction units, each of which corresponds to the output of a plurality of second comparing means.
An inter-vehicle distance detection device, comprising: a distance calculation circuit that calculates a vehicle position and calculates a distance to a preceding vehicle corresponding to the difference between the preceding vehicle positions .