JPH036418A - Inter-vehicle distance detector - Google Patents

Abstract

PURPOSE:To enable detection of an angle of projection of an optical system and a distance and thereby to detect precisely the distance of a preceding vehicle to a driver's own vehicle and the direction thereof by a method wherein the optical system of the driver's own vehicle is so rotated automatically as to follow the direction of advance of the preceding vehicle and a pulse light is projected, reflected by a reflector and sensed. CONSTITUTION:An optical system 4 is rotated so that a pulse light of a specified code projected from a projector 10 is reflected by a reflector 2 of a preceding vehicle and then detected by a light-sensing unit 11. An angle of the optical system 4 at the time when the reflected light from the reflector 2 of the preceding vehicle is detected is detected by a vehicle angle detecting circuit 28 and the direction of the preceding vehicle to a driver's own vehicle is measured therefrom. Next, positions whereat the reflected light from the preceding vehicle are imaged in photoelectric converters 15 and 17 inside a light-sensing optical system 7 at that time are detected by an imaging position calculating circuit 25 and the distance and direction of the preceding vehicle to the driver's own vehicle can be measured therefrom.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an inter-vehicle distance detection device for an automobile.

[Conventional technology]

Conventionally, the emitter and receiver were placed apart by a certain baseline length,
A distance measuring device that detects the distance to the object by emitting pulsed light from a projector toward the object and detecting the reflected light by a rotating receiver detects the angle of the receiver. It is widely known and is used in automatic focusing devices for cameras, etc.

FIG. 7 shows a diagram of the principle of the above device. In the figure, 10 and 11 are a light projector and a light receiver arranged with a baseline length apart;
Reference numeral 12 indicates a light projecting lens provided on the front surface of the light projector 10, 13 indicates a light receiving lens provided on the front surface of the light receiver 11, and 19 indicates an object to be measured located at a distance from the light receiving lens 13. Here, L can be determined as −θ.

[Problem to be solved by the invention]

However, in such a distance measuring device, the object to be measured must be on the optical axis of the projector 10. For example, in the case of a camera, this can be realized by moving the camera by the operator himself, but it can be realized by moving the camera himself. If the driver has to adjust the position of the floodlight 1o so that the preceding vehicle is on the optical axis of the floodlight 1o while driving, the burden on the driver will be large and this will impede safe driving. However, when the projector 10 is fixed, it is difficult for the conventional device to detect the inter-vehicle distance when the preceding vehicle turns a curve and changes its traveling direction.

This invention was made to solve the above-mentioned problems, and aims to provide an inter-vehicle distance detection device that can always detect the distance and direction to the preceding vehicle regardless of changes in the traveling direction of the preceding vehicle. purpose.

[Means to solve the problem]

The inter-vehicle distance detection device according to the present invention includes a light projector that projects pulsed light having a specific code in the direction of travel, and a light receiver that detects the reflected light of the pulsed light projected from the projector by a reflector at the rear of the preceding vehicle. A light emitting optical system consisting of a light emitting optical system, a light receiving optical system consisting of a condensing lens that condenses the reflected light, and a photoelectric converter placed on the imaging plane of the condensed light are arranged so that their respective optical axes are approximately coaxial. In the inter-vehicle distance detection device, which is composed of an optical system installed close to each other and separated by a predetermined baseline length so that it can be assumed that the a rotating means for rotating the drive system; an imaging position detecting means for detecting the imaging position on the photoelectric converter of the light receiving optical system; and a vehicle detecting the angle between the optical system and the vehicle axis of the own vehicle. and a shaft angle detection means, the drive system is rotated within a predetermined angle range by the rotation means, and the optical axis direction of the optical system is aligned with the reflector of the preceding vehicle by the output of the light receiver, and the above-mentioned at that time The inter-vehicle distance and direction to the preceding vehicle are measured based on the output of the imaging position detection means and the output of the vehicle axis angle detection means.

[For production]

The inter-vehicle distance detection device according to the present invention sends an electric signal to the drive system so that the pulsed light having a specific code projected from the light projector is reflected by the reflector of the preceding vehicle and then detected by the light receiver, and the rotating means The optical system is rotated by The angle of the optical system when the reflected light from the reflector of the preceding vehicle is detected is detected by the vehicle axis angle detection means to measure the direction of the preceding vehicle with respect to the own vehicle, and the reflected light from the preceding vehicle at that time is detected within the light receiving optical system. The position of the image formed on the photoelectric converter is detected by the image position detection means, and the distance between the preceding vehicle and the own vehicle is measured.

Therefore, in the automobile inter-vehicle distance detecting device according to the present invention, since the adjustment operation to align the optical axis of the optical system and the object to be measured, which was performed by the operator in the conventional distance measuring device, is automatically performed, the progress of the preceding vehicle is Even if the direction changes, the device rotates to follow the change and can always measure the distance and direction of the preceding vehicle relative to the own vehicle.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. 1st
The figure shows the configuration of the inter-vehicle distance detection device according to the present invention,
In the figure, 1 is the preceding vehicle, and 2a.

2b is a reflector provided at the rear of the preceding vehicle 1. Reference numeral 3 designates the host vehicle, 4 an optical system provided at the front center O of the host vehicle 3, and 5 a drive system for rotationally driving the optical system 4. 8 is a CPU, and 9 is a vehicle distance display device, which is installed near the instrument panel.

In the inter-vehicle distance detection device configured as described above, a pulse signal having a specific pulse code is emitted from the optical system 4 toward the reflectors 2a and 2b of the preceding vehicle 1, and the optical system 4 receives the reflected light. and the reflector 2a of the preceding vehicle 1
Lines PO and QO connecting 2b and 2b, and a line A representing the vehicle body width
' By measuring the angles θa and θb with the perpendicular 2 and the distances La and Lb between the lines PO and QO,
The angle between the line RO and the perpendicular l that connects the rear center R of the preceding vehicle 1 and the front center O of the own vehicle 3 is the vehicle axis angle θ indicating the direction of the preceding vehicle with respect to the own vehicle, and the distance between the line RO and the preceding vehicle is It is calculated as the inter-vehicle distance between the own vehicles.

FIG. 2 is a configuration diagram of the optical system 4 and its peripheral parts of the apparatus of the embodiment shown in FIG. The optical system 4 includes a light projector 10 that includes an LED 14 that emits a pulse signal having a specific pulse code and a light projecting lens 12, and a light receiver 11 that includes a photoelectric conversion element 15 that detects the amount of reflected light and a light receiving lens 13.
a light receiving optical system 7 including a photoelectric conversion element 17 that detects the imaging position of the reflected light focused on the focal plane of the condensing lens 16 arranged at a predetermined distance apart. It consists of The drive system 5 rotates the optical system 4.
It is composed of a C motor 31 and a potentiometer 32 that detects the position of the DC motor 31.

Next, the operation of the inter-vehicle distance detection device of the present invention will be explained.

A pulse signal from the light emitting circuit 22 synchronized with the timing circuit 21 in the control circuit 20 causes the LED 14 in the light projector 10 of the optical system 4 to emit light, and the direction of travel of the vehicle is determined through the light projecting lens 12 so as to form a predetermined solid angle. When a light beam is irradiated towards the vehicle and the irradiation range 18 includes the reflector 2 of the preceding vehicle 1 as shown in the figure, the light beam reflected by the reflector 2 will be reflected by the light receiver disposed approximately coaxially with the projector 10. 1
1, the reflected light beam is focused by the light receiving lens 13, the amount of light is photoelectrically converted by the photoelectric conversion element 15, and detected as a light amount signal by the light receiving circuit 23. The light rays that are diffusely reflected by parts other than the reflector 2 within the irradiation range reach the optical axis center of the condenser lens 16 and the photoelectric conversion element 17.
When the light enters the light-receiving optical system 7, which is arranged so that the centers of the effective light-receiving lengths of Detected. In the CPU 8, the vehicle angle θn at which the motor position signal detected by the potentiometer 32 is converted by the vehicle angle detection circuit 28 is a predetermined limit vehicle angle θmin.

If the range is within θmax (θmin<θmax),
The light amount λn subjected to noise processing in the hold circuit 24 to which the above-mentioned light amount signal and a pulse signal synchronized with the timing circuit 21 are inputted, and a hold circuit to which the above-mentioned imaging position signal and a pulse signal synchronized with the timing circuit 21 are inputted. 2
In step 6, the noise-processed imaging position Xn is measured, and in order to rotate the motor 31 based on the above light amount signal and position signal, a motor drive request signal is output to the motor drive circuit 27 to rotate the motor. Repeat the action.

Next, the angle θ of the reflected light in Figure 1 is determined according to the reflected light La and θb detection subrunon flowchart in Figure 3.
A and how to determine the distance La between the optical system 4 and the reflector 2a of the preceding vehicle 1 will be explained. Here, in order to simplify calculations, it is assumed that the angle A OA' is 180°, and the direction ω-1 represents a positive direction, and the direction ω-1 represents a negative direction.

First, in step 41, n=0 and the LED 14 emits pulsed light. Next, in step 42, the motor 31 is rotated by a predetermined angle Δθ in the direction ω, and in step 43, the angle θn indicating the current motor position is determined by the potentiometer 32.
seek. Subsequently, in step 44, the light amount λn from the photoelectric conversion element 15 and the imaging position Xn from the photoelectric conversion element 17 are determined. In step 45, it is determined whether the current motor drive direction is positive. If positive, the process proceeds to step 46; if negative, the process proceeds to step 47. Then, in step 46, the angle θn measured in step 43 is equal to the predetermined maximum angle θma.
If it is larger than x, the process advances to step 49; otherwise, n is incremented in step 48 and the process returns to step 42. Subsequently, in step 47, if the angle θn measured in step 43 is smaller than the predetermined minimum angle θmin, the process proceeds to step 49; otherwise, n is incremented in step 48, and the process returns to step 42.

Thus, in step 49, a predetermined light amount λ0 is compared with the maximum light amount λ of the light amounts λn measured during execution of steps 42 to 48, and if λ is larger, reflected light is detected. The process proceeds to step 51. If not, the process proceeds to step 53, where the undetectable flag is turned on, and then the process proceeds to step 54. Next, in step 51, the angle θa of the reflected light and the distance La between the optical system 4 and the reflector 2a of the preceding vehicle l are determined, and then the process proceeds to step 52. The angle θa of reflected light is the angle θ when the maximum amount of light is detected.
The distance La between the optical system 4 and the reflector 2a of the preceding vehicle 1 is La, Lb-F*D/(2*X), since the imaging position X=Xk is the optical path through which the reflected light passes.
・=−■. However, the focal length of the condensing lens 16 is F1, and the distance between the optical axes of the same lens is D. Further, in step 52, the undetectable flag is turned off and the process proceeds to step 54. In step 54, the LHD 14 is turned off, the direction of motor drive is multiplied by (-1) and reversed, and the process ends.

By performing similar processing for the reflector 2b, θb and Lb can be determined.

Next, the inter-vehicle distance detection routine shown in FIG. 4 will be explained.

First, in steps 61 and 62, the reflected light detection subroutine shown in FIG. 3 is executed to determine La and θa.

Find Lb and θb. Next, in step 63, if the undetectable flag is turned on, the process proceeds to step 65, where the display device 9 displays that the undetectable state is present, and the process ends. If not, the process proceeds to step 64, where the following distance and the angle θ of the vehicle axis are determined according to the principle described below, the results are displayed on the display device 9, and the process is completed.

In the triangle POQ of FIG. 1, the angle θC between the line QO and the line PO is the difference between θa and θb, which have already been determined, and the distance Lc of the line PQ can be obtained from 2 using the cosine theorem.

Further, using the distance Lc of the line PQ and the law of sine, the angle φa between the line PQ and the line PO can be obtained from equation 0.

Lc2=La"+Lb2-2*La*Lb*(@z (
l θ a−θ bll −−−・−■Lc10+
n(lθa−θbl)−Lb10+nφa”
” ”'■Here, let R be the midpoint of line PQ, and draw triangle F.
In the OR, the distance of the line RO can be obtained using the cosine law again using the following formula 0. Furthermore, using the law of sine, the angle 1 Δφ between the line RO and the line PO can be obtained from the same equation 0, and the perpendicular line! The angle θ between the line OR and the line OR can be obtained from the formula 0.

L2= (Lc/2) 2+La2- (Lc/2)NingLa*(B φ a ”'”' ■(
Lc/2)/m(Δφ)=L10Illφa
・・・・・・■θ=θa−Δφ
......■ In this example, the following distance IL and the angle θ of the vehicle axis detected at predetermined intervals based on the above principle are displayed on the following distance display device 16, and the predetermined dangerous distance is displayed on the following distance display device 16. A collision prevention system function has been added that notifies the driver with an audible alarm and a display if the distance is less than that, and an error message will be displayed if detection becomes impossible due to external light disturbance, etc.

Further, the inter-vehicle distance detection device of the present invention uses the reflected light La
, La obtained by executing the θa detection subroutine
From θa, Lb and θb, the reflector 2a of the preceding vehicle l
Since it is possible to know where points P and Q representing the positions of points P and 2b are located when viewed from the front center O of the own vehicle 3, the lines A and A' in FIG. Y axis, origin at O
From the following formula 0, the angle ψ(-
90° to 90°), the direction of the vehicle body of the preceding vehicle can be determined.

tllll(ψ) = (La*Iθa-1-b*cIr
bθb)/(La season nθa−Lb*6(Bθb)
−・・■However, (La * embroidery θBL−L, b”anθb)−
〇 If =9o6*(La*(yθa−Lb*(y
θb)/l (La*,, θa−Ll)”C116θ
b) Fig. 5 is a schematic diagram showing the relationship between the vehicle body direction of the preceding vehicle and the angle ψ. For example, even if the following distance and the vehicle axis angle θ are the same in the figure, the direction of the preceding vehicle's body is a
), it goes straight at ψ=0°, and in (b), it turns right at ψ〈0°,
becomes readable. Therefore, if the inter-vehicle distance detection device of this invention is used as a component of an automatic tracking control system,
Since information about the direction of the vehicle in front can be provided to the system's vehicle direction control, it is possible to control the vehicle's body in accordance with the movement of the vehicle in front.

Furthermore, the inter-vehicle distance detection device of the present invention can also have a function of determining the vehicle type of the preceding vehicle based on the distance Lc between the left and right reflectors of the preceding vehicle obtained from the above equation 0.

Figure 6 shows the distance L between the vehicle type and the left and right reflectors of the preceding vehicle.
FIG. 3 is a schematic diagram showing the relationship between (a) a large vehicle, Lc>Lx, and (b) a light vehicle, Lx.
If the predetermined values Lx and Ly are appropriately set so that <Lc<Ly holds true, it becomes possible to determine the vehicle type of the preceding vehicle based on Lc. In automatic tracking control systems, automatic tracking control is performed while checking the type of vehicle in front to be tracked, and if the detected vehicle type changes midway through, it is determined that there is an intervening vehicle and automatic tracking is stopped. If used as one, it is possible to improve the security of the system.

In the embodiment, the motor 31 in the drive system 5 is a DC motor, but other types such as a stepping motor may be used as long as it can perform absolute position control, and in a simpler system, the first Among the distances La and Lb between the reflectors 2a and 2b and the own vehicle in the figure, and the angles θa and θb between the reflectors 2a and 2b and the vehicle axis,
It is also possible to obtain La and θa or Lb and θb and use them as approximate values of the inter-vehicle distance and the angle of the vehicle axis.

[Effects of the Invention] As explained above, according to the present invention, the optical system of the own vehicle automatically rotates in accordance with changes in the direction of travel of the preceding vehicle, and aims at the reflector of the preceding vehicle. Pulsed light with a specific code is emitted, reflected by a reflector, and received. This allows the projection angle and distance of the optical system to be detected, and the effect of accurately detecting the distance and direction of the preceding vehicle relative to the own vehicle. There is.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an automobile inter-vehicle distance detection device according to an embodiment of the present invention, and FIG. 2 shows a driving optical system and its surroundings of the inter-vehicle distance detection device according to an embodiment of the invention shown in FIG. The schematic diagram, FIG. 3, shows the distance La between the reflector 2a and the host vehicle.
4 is a subroutine for detecting inter-vehicle distance, FIG. 5 is a schematic diagram showing the relationship between the vehicle body direction of the preceding vehicle and angle ψ, and FIG. 7 is a schematic diagram showing the relationship between the vehicle type and the distance Lc between the left and right reflectors of the preceding vehicle, and FIG. 7 is a principle diagram of a conventional distance measuring device. 5 1... Leading vehicle, 2.2a, 2b... Reflector,
3... Own vehicle, 4... Optical system, 5... Drive system, 6
... Light emitting optical system, 7... Light receiving optical system, 8... CP
U, 9... Inter-vehicle distance display device, 10... Floodlight, 1
DESCRIPTION OF SYMBOLS 1... Light receiver, 12... Light emitting lens, 13... Light receiving lens, 14... LED, 15.17... Photoelectric conversion element, 16... Condensing lens, 20... control circuit,
25... Imaging position calculation circuit, 28... Vehicle angle detection circuit, 31... DC motor, 32... Potentiometer. Note that the same reference numerals in the figures indicate the same or equivalent parts. 6

Claims (1)

[Claims] a light projection optical system consisting of a light projector that projects pulsed light with a specific code in the direction of travel; a light receiver that detects the reflected light of the pulsed light projected by the projector by a reflector at the rear of the preceding vehicle; and the reflected light. A condensing lens that condenses the condensed light and a light-receiving optical system consisting of a photoelectric converter placed on the imaging plane of the condensed light are placed in close proximity so that their respective optical axes can be considered to be substantially coaxial, and In an inter-vehicle distance detection device comprising an optical system installed at a predetermined baseline length apart, and a drive system that adjusts the angle formed between this optical system and the vehicle axis of the host vehicle,
A rotating means for rotating the drive system, an imaging position detection means for detecting an imaging position on the photoelectric converter of the light receiving optical system, and an angle formed by the optical system and the vehicle axis of the host vehicle. and vehicle axis angle detection means, the drive system is rotated within a predetermined angle range by the rotation means, and the optical axis direction of the optical system is aligned with the reflector of the preceding vehicle by the output of the light receiver, and the direction of the optical axis of the optical system is aligned with the reflector of the preceding vehicle. An inter-vehicle distance detecting device, characterized in that the inter-vehicle distance and direction to a preceding vehicle are measured by the output of the imaging position detecting means and the output of the vehicle axis angle detecting means.