JPH04299211A - Device for detecting intervehicle distance - Google Patents

Abstract

PURPOSE:To make it possible to detect accurately a change in relative position to a moving object. CONSTITUTION:A plurality of image sensors 1a, 1b which detect an image of a moving object and generate electric outputs being proportional to the light intensity of the detected image, and comparators 3a, 3b which compare the electric outputs generated in the image sensors with first reference values 2a, 2b respectively and deliver the electric outputs of voltages being larger than the first reference values 2a, 2b as pulse signals, are provided. Memory groups 4a, 4b which store the pulse signals outputted from the comparators 3a, 3b, sequentially in a time series, adders 5a, 5b which add up the output pulse signals of the memory groups, second comparators 7a, 7b which compare addition signal outputs delivered from the adders 5a, 5b with second reference values 6a, 6b and extract only electric outputs being larger than the second reference values 6a, 6b, and a distance signal generating circuit 8 which calculates the intervehicle distance between the vehicle and preceding vehicle on the basis of output signals of the second comparators 7a, 7b.

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 detection device for detecting the relative distance between a preceding vehicle and one's own vehicle in a non-contact manner.

0002

2. Description of the Related Art As a method of detecting the distance from an observation point to a target object, methods using ultrasonic waves or laser light are conventionally known. This measures the distance from an observation point to the target object without contact by projecting ultrasonic waves or laser light onto the target object and capturing the reflected waves from the target object.

However, the distance detection method described above that uses ultrasonic waves or laser light can only measure the distance from the observation point to the reflection point of the target object, and only the distance between the moving preceding vehicle and the own vehicle. When measuring the distance between vehicles, it is difficult to accurately measure the distance due to oscillation of the vehicle bodies, changes in relative position, and the like. Furthermore, in the case of ultrasonic waves, the beam width cannot be narrowed very much, so long-distance measurements are difficult.

[0004] As a device for solving such difficulties and detecting the distance between a moving object and a moving target object, for example, the invention ``absolute inter-vehicle distance detection method'' disclosed in the specification of Japanese Patent Application Laid-Open No. 63-26517 has been proposed. "It has been known. This inter-vehicle distance detection method includes an imaging device that captures an image of a moving target object, a means for performing spatial differential processing on the image of the target by this imaging device to detect a horizontal component, and a method that binarizes this 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 vertical significant region, The approach or distance of the object is determined by detecting the amount of change in the target object and the increase or decrease in this amount of change over time.

[0005]

[Problems to be Solved by the Invention] However, this conventionally known inter-vehicle distance detection method is difficult to identify a moving target object, and more specifically, to identify an image signal of a detected object input to an imaging device.
For example, in order to improve the identifiability of the image signal of the preceding vehicle, it is required to perform spatial differentiation processing (determining the density by the difference between the values of neighboring pixels), so when the own vehicle moves, the image signal of the preceding vehicle At the same time, surrounding background image signals also move on the imaging device.

[0006] Therefore, since the image signal of the preceding vehicle and the image signal of the background are extracted together, it becomes difficult to separate the two image signals. In addition, if the monitoring area is made smaller to eliminate the influence of background image signals, the relative positions of the vehicles may change due to curves in the driving route, lane changes, etc., and the vehicle being measured may move out of the monitoring area. Another drawback is that it cannot be detected.

Therefore, the present invention eliminates the drawbacks of the conventional inter-vehicle distance detection method described above, extracts an image of a moving object while clearly distinguishing it from the surrounding background image, and provides an accurate and easy-to-detect inter-vehicle distance. The present invention aims to provide a distance detection device.

[0008]

[Means for Solving the Problems] In order to achieve the above-mentioned problems, the inter-vehicle distance detecting device of the present invention includes an image detecting means that generates an electrical output according to the light intensity of an image signal, and an electric power generated in the image detecting means. A memory group consisting of a first comparison means that compares the electrical output with a first reference value, converts it into a binary value, and outputs it; and a plurality of memories that sequentially store the signals output from the first comparison means in chronological order. 4, an adding means for adding signal outputs from each of the plurality of memories constituting the memory group, and an integral output outputted from the adding means is compared with a voltage of a second reference value to be binarized and output. The present invention is characterized by comprising a second comparison means 7 and a distance calculation circuit that calculates the distance to the preceding vehicle based on the output of the second comparison means.

[0009]

According to the inter-vehicle distance detecting device of the present invention, an image signal of a running vehicle whose relative speed is relatively slow with respect to the own vehicle is output, so that the preceding vehicle can be accurately identified.

0010

DESCRIPTION OF THE PREFERRED EMBODIMENTS A vehicle distance detection device according to an embodiment of the present invention will be described below with reference to the drawings.

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

[0012] As shown in FIG. 5, the following distance detection in this embodiment is performed by using a pair of image sensors 1a and 1b installed on the own vehicle at a predetermined distance L, and a focal length f in front of each image sensor. Imaging lenses 22a, 22 arranged at
It is composed of b. Here, if the distance from the imaging lens to the preceding vehicle is D, and the difference between the imaging positions in the image sensors 1a and 1b is δ, then the inter-vehicle distance D is D=f・
L/δ...(1). Since the focal length f and the distance L between the image sensors are preset values, the inter-vehicle distance D can be calculated if the value of the difference δ between the imaging positions is known.

Therefore, the inter-vehicle distance detection device of this embodiment has the following features:
As shown in FIG. 1, the image signals of the preceding vehicle are extracted by each unit A and B from the signals of a pair of image sensors 1a and 1b placed a certain distance L apart on the vehicle, and the imaging position is The distance signal generating circuit 8 generates (1
) The following distance is calculated based on the formula. Note that all of these are controlled by a timing generation circuit 9.

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

However, since the configuration and function of each unit A and B are the same, only unit A provided on the right side of the vehicle will be described.

First, as shown in FIG. 1, the configuration includes an image sensor 1a in which a plurality of CCD elements are arranged in a line, and a low-pass filter (L.P.F.) that cuts noise in the output signal. a first comparator 3a that binarizes the signal by comparing it with a predetermined first reference value 2a; and a memory group 4a that stores the binarized signal in time series. It consists of an adder 5a that adds signals stored in time series, and a second comparator 7a that compares the added value with a predetermined second reference value 6a.

Next, the operation will be explained.

When input by 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 that are temporarily lined up are sequentially ( L.P.F) and is binarized by the first comparator 3a. (FIG. 6) This binarized signal is stored in the memory group 4a in time series. The details are shown in Figure 2.
As shown in FIG. 2, the input switch 10a-1 of 4a-1 in the memory group 4a is first turned on by the trigger pulse of the timing generation circuit 9. Then, the binarized signals are sequentially stored in the shift register 11a-1 by the clock from the timing generation circuit 9. The input switch 10a-1 is turned off by the next trigger pulse, the switch 12a-1 is turned on, and the contents of the shift register 11a-1 are circulated by the clock pulse without inputting new data. At the same time, 4a
-2 input switch 10a-2 is turned on, and the shift register 11a-2 is stored in the same manner as above.

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

[0020] This added value is calculated by the temporarily placed CCD.
It represents the frequency with which a signal equal to or higher than the first reference value 2a is input to one of the elements.

This added value and the second reference value 6a are compared by a second comparator 7a, and only those having a frequency equal to or higher than a predetermined value are extracted. (Figure 8) Here, image sensor 1
Among the signals input to a, a preceding vehicle with a low relative speed to the own vehicle constantly appears at a specific position, but objects such as trees, signs, etc. with a high relative speed to the own vehicle appear in the position where they appear on the image sensor 1a. changes, so it does not appear constantly at a specific location. From this, a signal appearing exceeding the second reference value 6a becomes a signal of the preceding vehicle.

As described above, when the signals of the preceding vehicle are obtained by each of 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, this distance signal generation circuit 8
, B, clock pulse signals are output to counters 16a, 16b based on F/Fs 17a, 17b output from the time when the signals d1, d2 of the preceding vehicle obtained from the signals d1 and d2 of the preceding vehicle are generated until the trigger pulse a of the timing generation circuit 9 is generated. (e1, e2) and output the output to D/A19a, 19
b is output as analog values f1 and f2. This value represents the position of the signal of the preceding vehicle on the image sensors 1a, 1b. The difference between these signals is converted into a differential amplifier 20.
-1 and 20-2, and by comparing them with the level comparator 21, a value corresponding to the difference δ in the imaging position in equation (1) is derived.

From this value, the inter-vehicle distance processing D is detected by the divider 22.

Although the present embodiment uses two sets of image sensors using CCD elements, the accuracy of inter-vehicle distance detection can be further improved by using two or more sets of image sensors.

[0025] Also, regarding image sensors, CCD
In addition to using elements, MOS transistors can also be used.

[0026]

[Effects of the Invention] As is clear from the above description, according to the inter-vehicle distance detection device of the present invention, changes in the position of background images such as signs and trees on the road whose relative speed is relatively fast with respect to the own vehicle can be realized. The resulting image signal is detected as a large number of pulse signals, but when integrated, they are averaged and are not extracted. On the other hand, the image signal of the preceding vehicle has a small change in position with respect to the host vehicle, so there is little change over several cycles, and if it is integrated, it can be detected as a pulse waveform, making it possible to easily determine an accurate inter-vehicle distance.

[Brief explanation of drawings]

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

FIG. 2 is a detailed diagram of a memory group of the inter-vehicle distance detection device shown in FIG. 1;

FIG. 3 is a detailed diagram of an adder of the inter-vehicle distance detection device shown in FIG. 1;

FIG. 4 is a detailed diagram of a distance signal generation circuit of the inter-vehicle distance detection device shown in FIG. 1;

FIG. 5 is a diagram showing the principle of detecting the distance between vehicles of the device shown in FIG. 1;

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

FIG. 7 is a binary signal diagram of each shift register configuring the memory group shown in FIG. 2;

FIG. 8 is a pulse signal diagram sent out from the second comparator 7a.

[FIG. 9] Timing generation circuit 9, second comparator 7
It is a diagram of signals output from D/A 19a, 19b.

[Explanation of symbols]

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

Claims (1)

[Claims] 1. An image detection means for generating an electrical output according to the light intensity of an image signal, and a first comparison for comparing the electrical output generated in the image detection means with a first reference value, converting it into a binary value, and outputting the binarized result. and a memory group consisting of a plurality of memory units for sequentially storing the signals output from the first comparing means in chronological order;
an adding means for adding signal outputs from each of the plurality of memories constituting the memory group; and a second means for comparing the integral output outputted from the adding means with a second reference value, converting it into a binary value, and outputting the resultant signal.
1. An inter-vehicle distance detection device comprising: a comparison means; and a distance calculation circuit that calculates a distance to a preceding vehicle based on the output of the second comparison means.