Optical: systems and elements – Glare or unwanted light reduction – Directional or angular discrimination
Reexamination Certificate
2002-01-29
2004-09-07
Dunn, Drew A. (Department: 2872)
Optical: systems and elements
Glare or unwanted light reduction
Directional or angular discrimination
C359S834000, C359S601000
Reexamination Certificate
active
06786609
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for watching around a vehicle by photographing surrounding scenes at a driver's dead angle in such a condition that does not offer unobstructed view to a driver ahead or behind the vehicle and on the right or left side of the vehicle so as to display the scenes to the driver.
FIG. 13
is a block diagram of a conventional apparatus for watching around a vehicle. This apparatus for watching around a vehicle
1
comprises an imaging device
11
disposed on the outer side of the vehicle and used for picking up scenes in the two opposed directions around the vehicle, an image inversion processing portion
12
for subjecting image signals supplied from the imaging device
11
to image inversion processing, and a display portion
15
that is set inside the vehicle chamber and used for displaying the image signals obtained from the image inversion processing portion
12
.
The imaging device
11
has a shade casing
3
provided with a pair of right and left transmission window portions
2
R and
2
L formed of transparent glass in either side of the casing
3
, which contains a prism
4
in the form of an isosceles triangle in section with its vertical angle
5
directed to the front part of the casing (the upper part of the casing
3
in FIG.
13
), the right and left sides
8
R and
8
L of the prism
4
corresponding to the equal sides of the isosceles triangle being directed to the respective right and left transmission window portions
2
R and
2
L, and an imaging element
10
disposed to the rear of the prism
4
and used for converting rays of light
18
R and
18
L into image signals, the rays of light being incident on the respective sides
8
R and
8
L of the prism
4
and subjected to an optical path change within the prism
4
and guided via an imaging lens
9
onto an imaging plane.
The imaging device
11
is fitted to a front bumper, for example, so that its front part (the front part of the casing
3
) is directed ahead and that the transmission window portions
2
R and
2
L are respectively directed right and left. In this condition, the ray of light
18
L corresponding to the left side scene is as shown in
FIG. 13
passed through the transmission window portion
2
L and the side
8
L of the prism
4
, directly incident on the side
8
R of the prism
4
, reflected from the interior of the side
8
R of the prism
4
, emitted from the rear side
8
B of the prism
4
and formed into an image through the imaging lens
9
, which image is guided to the left half
10
L of the imaging plane of the imaging element
10
. In consideration of the ray of light
18
R corresponding to the right side scene from the standpoint of bilateral symmetry, the ray of light is guided to the right half
10
R of the imaging plane of the imaging element
10
likewise. Then both rays of light are converted by the imaging element
10
into image signals.
The right and left side scenes are picked up and the signals of the images thus picked up are subjected to the image inversion processing in the image inversion processing portion
12
before being supplied to the display portion
15
as shown in FIG.
13
. In the display portion
15
, the left side scene taken in from the transmission window portion
2
L is displayed as the left half of the image on the left half
15
L of a screen, whereas the right side scene taken in from the transmission window portion
2
R is displayed as the right half of the image on the right half
15
R of the screen.
In an apparatus
1
for watching around a vehicle, however, when a ray of light
21
a
emitted from a headlamp
21
is passed through the transmission window portion
2
R and the side
8
R of the prism
4
and directly incident on the rear side
8
B of the prism
4
and totally reflected from the rear side
8
B of the prism
4
while an oncoming vehicle with its headlamp
21
turned on is approaching, for example, the ray of light
21
a
is emitted to the side
8
L of the prism
4
and incident on the transmission window portion
2
L. At this time, though most of the ray of light
21
a
(96.1%) incident on the transmission window portion
2
L is passed through the transmission window portion
2
L and emitted outside, the remaining ray of light (3.2%) is incident on the side
8
L of the prism
4
as reflected light
21
b.
The reflected light
21
b
is passed through the side
8
L of the prism
4
, directly incident on the side
8
R of the prism
4
, reflected from the interior of the side
8
R of the prism
4
, emitted from the rear side
8
B of the prism
4
and guided via the imaging lens
9
to the left half
10
L of the imaging plane of the imaging element
10
. Consequently, the reflected light
21
b
is subjected to image processing on the left half
10
L of the imaging plane of the imaging element
10
after being synthesized with the ray of light
18
L corresponding to the left side scene.
In this case, an image
21
B deriving from the light
21
b
reflected from the transmission window portion
2
L with the ray of light
21
a
emitted from the headlamp
21
and taken in from the transmission window portion
2
R being passed therethrough is superposed on an image
22
L of the left side scene taken in from the transmission window portion
2
L on the left half
15
L of the screen whereby to indicate an error.
In this manner, in the conventional apparatus
1
for watching around a vehicle, part of the scene taken in from one side of the transmission window portions
2
R and
2
L falls on the other side of the screens
15
R and
15
L of the display portion
15
, thus causing an error in displaying, and the problem is that the visibility of a driver is deteriorated.
<First Proposal as an Example>
Therefore, the present applicant has made a first proposal by ways of example as shown in
FIG. 14
(the Japanese Patent Application No. 2000-139754). Under the first proposal, in order to prevent part of the scene taken in from the left transmission window portion
2
L from falling on the right half
15
R of the screen in the display portion
15
and thus causing an error in displaying or to prevent part of the scene taken in from the right transmission window portion
2
R from falling on the left half
15
L of the screen therein and thus causing an error in displaying likewise, the angles of the transmission window portions
2
R and
2
L with the rear side
8
B of the prism
4
have properly been set. Consequently, even though there is produced reflected light
21
b
that may be incident on the imaging element
10
as light is reflected from the interiors of the transmission window portions
2
R and
2
L, the reflected light
21
b
can be prevented from being emitted from the rear side
8
B of the prism
4
after being totally reflected from the rear side
8
B of the prism
4
.
Since any unnecessary ray of light is prevented from being emitted from the rear side
8
B of the prism
4
, the ray of light can be prevented from falling on the screens
15
R and
15
L of the display portion
15
. The visibility of the driver can also be improved accordingly.
<Second Proposal as an Example>
Further, the present applicant has also made a second proposal by ways of example as shown in
FIG. 15
(the Japanese Patent Application No. 2000-231289). Under the second proposal, a shading portion
3
a
for cutting off light substantially laterally crossing a field in front of the prism
4
is provided between the vertical angle portion
5
of the prism
4
and the front end wall
28
of the casing
3
A. With this arrangement, even though an ray of light from outside is incident ahead of the vertical angle portion
5
of the prism
4
so as to cross the field in front of the prism
4
, the light is cut off by the shading portion
3
a
, so that a phantom image is made preventable from falling on the screen as a result of the fact that the light crossing the field in front of the prism
4
is reflected from the interiors of the transmission window portions
2
R and
2
L and enters the prism
4
.
Autonetworks Technologies Ltd.
Dunn Drew A.
Oliff & Berridg,e PLC
Pritchett Joshua L
LandOfFree
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