Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-08-25
2003-01-14
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C250S216000, C340S602000
Reexamination Certificate
active
06507015
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
This application is based upon and claims the benefit of Japanese Patent Applications No. 11-242096 filed on Aug. 27, 1999, the contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a raindrop sensor suitably used for a vehicle wiper automatic control device.
2. Description of the Related Art
A conventional raindrop sensor is shown in FIG.
4
. The raindrop sensor is attached to an interior wall of a vehicle windshield W to optically detect presence of raindrops. In the raindrop sensor, a light-emitting element
2
and a light-receiving element
3
are disposed at both sides in a longitudinal direction of a prism
1
. The prism
1
has a plano-convex lens
1
a
facing the light-emitting element
2
, a plano-convex lens
1
b
facing the light-receiving element
3
, and a prism body
1
c
provided between the lenses
1
a
and
1
b.
The plano-convex lens
1
a
changes light from the light-emitting element
2
to parallel rays that are to be incident on the prism body
1
c
. Light incident on the prism body
1
c
is reflected several times between an exterior wall of the windshield Wand the central portion upperwall of the prismbody
1
c
as indicated by arrows in
FIG. 4
, and then enters the plano-convex lens
1
b
. Light from the plano-convex lens
1
b
converges to be incident on the light-receiving element
3
. Incidentally, in
FIG. 4
, reference numeral
4
denotes a transparent adhesive layer.
In the raindrop sensor having the structure as described above, a light-emitting axis of the light-emitting element
2
and a light-receiving axis of the light-receiving element
3
must be respectively inclined at approximately 45 degrees with respect to the exterior wall of the windshield W to provide the optical path of light as described above. The light-emitting element
2
and the light-receiving element
3
are therefore provided on a wiring board
5
disposed above the prism
1
so that the light-emitting axis and the light-receiving axis have inclination of approximately 45 degrees with respect to the wiring board
5
. The prism body
1
c
has two inclined surfaces on which the convex lenses
1
a
and
1
b
are respectively disposed so that optical axes of the convex lenses
1
a
and
1
b
respectively correspond to the light-emitting axis and the light-receiving axis of the elements
2
and
3
.
In this connection, each of the inclined surfaces of the prism body
1
c
must have an area sufficient for holding each of the convex lenses
1
a
and
1
b
. This may result in unnecessary increase in height or length of the prism
1
. In addition, since the light-emitting element
2
and the light-receiving element
3
project downward from the wiring board
5
via leads, the wiring board
5
must be positioned at a much higher position than the prism
1
.
Further, when the raindrop sensor has several light-emitting elements to widen a detection region to improve detection accuracy, the raindrop sensor must have several light-receiving elements, a number of which corresponds to that of the light-emitting elements.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above problems. An object of the present invention is to provide a raindrop sensor constructed with a compact structure with a decreased number of parts and having a widened detection region.
According to the present invention, briefly, a raindrop sensor has first and second light-emitting elements and first a and second incoming radiation side plano-convex lens portions provided on a prismbody to face the first and second light-emitting elements. The raindrop sensor further has a light-receiving element and first and second outgoing radiation side plano-convex lens portions. The first and second outgoing radiation side plano-convex lens portions are provided by dividing one, plano-convex lens into two pieces so that each of the first and second outgoing radiation side plano-convex lens portions has a divided surface. The divided surface of the first outgoing radiation side plano-convex lens portion faces the divided surface of the second outgoing radiation side plano-convex lens portion.
Accordingly, when the raindrop sensor is attached to a windshield, light emitted by the first and second light-emitting elements is incident on a wide region of an exterior wall of the windshield after passing through the first and second incoming radiation side plano-convex lens portions, and is reflected by the exterior wall. Then, light enters the first and second outgoing radiation side plano-convex lens portions, and is refracted toward the divided surface by each of the first and second outgoing radiation side plano-convex lens portions. As a result, light from both the first and second outgoing radiation side plano-convex lens portions can enter the light-receiving element.
The number of the light-receiving elements can be decreased largely as compared to that of the light-emitting element(s). As a result, the number of parts for the raindrop sensor is reduced. Since the outgoing radiation side lens portions are provided by dividing the one plano-convex lens, the size of the prism body for holding the lens portions can be reduced in a vertical direction. As a result, a gap between the prism body and a wiring board holding the light-emitting and light-receiving elements can be reduced resulting in decreases in height and length of the raindrop sensor.
REFERENCES:
patent: 4701613 (1987-10-01), Watanabe et al.
patent: 5278425 (1994-01-01), Bendicks et al.
patent: 5323637 (1994-06-01), Bendicks et al.
patent: 5391891 (1995-02-01), Wiegleb et al.
patent: 5498866 (1996-03-01), Bendicks et al.
patent: 5572017 (1996-11-01), Veltum et al.
patent: 5661303 (1997-08-01), Teder
patent: 5898183 (1999-04-01), Teder
patent: 6232603 (2001-05-01), Nelson
patent: 6262407 (2001-07-01), Teder
patent: WO 98/57830 (1998-12-01), None
Maeno Satoru
Terakura Osamu
Allen Stephone B.
Denso Corporation
Nixon & Vanderhye PC
Spears Eric J
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