Communications: electrical – Vehicle detectors – With camera
Reexamination Certificate
2000-02-28
2001-09-18
Trieu, Van T. (Department: 2632)
Communications: electrical
Vehicle detectors
With camera
C340S435000, C340S436000, C340S903000, C180S167000
Reexamination Certificate
active
06292111
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a vehicle-applied rear-and-side monitoring system and vehicle-applied rear-and-side monitoring and alarming system and more particularly, to a vehicle-applied rear-and-side monitoring system, which monitors a rear-and-side of a running vehicle, i.e. own vehicle, such as a motor vehicle by taking an image of a rear-and-side road view of the own vehicle by an image taking means such as a video camera and the like set on the own vehicle and by detecting a following vehicle being approaching the own vehicle from the rear-and-side with use of the taken road image, and to a vehicle-applied rear-and-side monitoring and alarming system, which alarms a driver when the above monitoring system have detected a danger.
2. Description of the Related Art
For example, Japanese Patent No. 2641562 (hereinafter JP '562), Japanese Patent Application Laid-open No. 6-107096 (hereinafter JP '096) and also Laid-open No. 7-50769 (hereinafter JP '769) disclose a vehicle-applied rear-and-side monitoring and alarming system, which correctly recognizes a neighboring traffic lane of a traffic lane on which an own vehicle is running, and which gives a driver of the own vehicle an alarm of dangerousness of a collision when the driver is going to change the lane in case that a following vehicle is running on the neighboring lane, thereby avoiding a collision with the following vehicle.
The above system recognizes a lane marking on the road so as to distinguish traffic lanes with use of a road image taken by a video camera and sets a monitoring area on the neighboring lane. This system is intended to reduce an image-processing amount for detecting the following vehicle in the neighboring lane, i.e. in the monitoring area, so that the following vehicle in the neighboring lane can be detected fast and surely.
JP '096 and JP '769 disclose the system applying an optical flow, which will be briefly described with reference to
FIGS. 13 and 14
.
FIG. 13
is a block diagram showing a prior art vehicle-applied rear-and-side monitoring and alarming system, wherein
10
indicates an image taking portion used as an image taking means and has a video camera
11
for example. And,
30
is a data processing portion use as an arithmetical unit, and
42
is a speaker use as an alarming means.
The image taking portion
10
is arranged at a required position on a rear side, e.g. over the trunk room, of the own vehicle for taking a rear-and-side road view of the vehicle. The data processing portion
30
has CPU
31
(i.e. a central processing unit) to operate according to a program, ROM
32
to keep the program for the CPU
31
and a preset value, and RAM
33
to temporary keep required data for calculation by the CPU
31
. The speaker
42
is arranged inside the own vehicle and raises a voice or an alarm sound on the basis of a signal from the CPU
31
of the data processing portion
30
so as to have the driver take notice of the danger.
FIGS. 14A-14C
are explanatory illustrations showing change of a rear-and-side road image taken by the image taking portion
10
.
FIG. 14A
is of at a time t, and
FIG. 14B
is of at a time t+&Dgr;t.
In these figures,
200
indicates a following vehicle running at the rear-and-side of the own vehicle,
300
indicates a road sign standing on one side of the road
500
, and
400
indicates a building neighboring the road
500
.
When the own vehicle is running straight on a plain road, the road sign
300
and the building
400
go away and therefore their images become small, as time goes by. That is, the road sign
300
and the building
400
in the image of
FIG. 14B
are smaller than those shown in FIG.
14
A.
Description is given below to an optical flow with reference to these figures.
There can be a plurality of subject points, for example, on the following vehicle
200
, the road sign
300
, and the building
400
such as
201
a,
202
a,
301
a,
302
a,
303
a,
401
a
and
402
a
at the time t in
FIG. 14A and 201
b,
202
b,
301
b,
302
b,
303
b,
401
b
and
402
b
at the time t+&Dgr;t in FIG.
14
B. Speed vectors connecting the corresponding subject points are obtained as optical flows such as
201
F,
202
F,
301
F,
302
F,
303
F,
401
F and
402
F shown in FIG.
14
C.
Here, the optical flow is acknowledged to be radially formed from an infinity point in the road image, which infinity point is defined as FOE (i.e. Focus of Expansion). In an image wherein the own vehicle is running straight, the FOE is positioned at the opposite point to the running direction of the vehicle.
Optical flows of objects being going away from the own vehicle become vectors to converge on the FOE, and optical flows of objects being approaching to the own vehicle become vectors to diverge from the FOE.
Accordingly, since the optical flows
201
F and
202
F of the following vehicle
200
are vectors in a diverging direction, the following vehicle is judged to be approaching to the own vehicle.
Length of the optical flow is in proportion to a distance per unit time, i.e. speed difference, between the own vehicle and the object and also in proportion to a distance itself between the own vehicle and the object. This will be described with reference to FIG.
15
.
FIG. 15
is a theoretical scheme showing an optical arrangement, wherein
11
a
indicates a lens of the video camera of the image taking portion
10
,
11
b
indicates an image plane of the video camera, f indicates a distance from the lens
11
a
to the image plane
11
b,
P(Xa,Ya,Za) indicates a point on the following vehicle, and p(xa,ya) on the image plane
11
b
indicates a corresponding point to the point P.
Based on the above scheme in
FIG. 15
, a following equation is obtained due to the similar triangles.
xa=f·Xa/Za
(1)
By differentiating the equation (1) an equation (2) is obtained.
Xa
′=(&Dgr;
xa/&Dgr;t·Za+xa·Za
′)/
f
(2)
The x component u of the optical flow is obtained as follows:
u=&Dgr;xa/&Dgr;t
(3)
Then, from the equation (3):
Za
=(
f·Xa′−xa·Za
′)/
u
(4)
Za′ in the equation (4) is a speed difference or a relative speed between the following vehicle
200
(
FIG. 14A
) and the own vehicle.
By replacing the relative speed Za′ with “−&agr;” the equation (4) is becomes:
Za
=(
f·Xa′+xa
·&agr;)/
u
(5)
Accordingly, the x component u of the optical flow can be given with the following equation (6).
u
=(
f·Xa′+xa
·&agr;)/
Za
(6)
Ya, i.e. the Y-axis of the point P, can be obtained similarly.
Accordingly, based on the equation (6), the smaller the above Z is, that is, the smaller the distance to the following vehicle
200
is, or the larger the above &agr; is, that is, the larger the relative speed is, the larger the x component of the optical flow is. This also applies to Y-direction.
Then, the smaller the distance to the following vehicle
200
is and further the larger the relative speed is, the longer the optical flow is, and then the optical flow diverges from the FOE. It can be understood that the longer the optical flow is, the bigger the danger with the following or adjoining vehicle is.
Accordingly, the data processing portion
30
judges that the object on the road exists near the own vehicle or is approaching thereto with a high speed when the optical flow is a vector in a diverging direction and simultaneously is large, and that degree of danger is high.
And, when degree of danger is judged high, the speaker
42
makes a driver know the situation.
Optical flows of objects on the image can be obtained similarly to the above, and thereby degree of danger with each of the objects can be judged. And, a driver can be given an alarm according to the degree of danger, thereby preventing a dangerous state or an actual trouble.
In the prior art, as shown in
FIG. 16
, the monitoring area is separated, by lane markings defining the own vehicle
Fujinami Kazutomo
Ishikawa Naoto
Okamoto Keiki
Armstrong Westerman Hattori McLeland & Naughton LLP
Trieu Van T.
Yazaki -Corporation
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