Optical: systems and elements – Prism
Reexamination Certificate
1998-10-28
2001-05-01
Shafer, Ricky D. (Department: 2872)
Optical: systems and elements
Prism
C359S834000, C359S836000, C264S001100, C264S001900, C264S002200, C425S470000, C425S808000
Reexamination Certificate
active
06226135
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a reflector type prism having the function of reflecting an incoming beam in a direction that is the reverse of the incoming direction, and a reflector type prism forming die.
In the prior art, a light sensor
109
constituted of a light-emitting element
105
and a light-receiving element
107
and a reflector type prism
111
are employed to detect the number, the traveling speed and the like of bodies to be detected
103
, such as sheets of paper that are traveling on a conveyor
101
, as illustrated in FIG.
8
. The light sensor
109
and the reflector type prism
111
are positioned at opposing sides of the conveyor
101
, and face each other.
As illustrated in
FIG. 9
, the reflector type prism
111
has the function of reflecting a light beam A emitted by the light-emitting element
105
in a direction that is the reverse of its incoming direction to cause the light to strike the light-receiving element
107
as a light beam B. Consequently, the bodies to be detected
103
block the light beam A and the light beam B as they travel on the conveyor
101
. The blocking of the light beams A and B by a body to be detected
103
is detected by the light-receiving element
107
, so that the light sensor
109
can make decisions as to the presence/absence of a body to be detected
103
, its state and the like, based upon this information.
Since a high degree of accuracy is required in setting the optical axes of the light beams A and B, it is crucial that the positioning process for mounting the light sensor
109
and the reflector type prism
111
at specific mounting members be implemented with a high degree of precision. Thus, both a light-emitting surface
109
a
and a light-entering surface
109
b
of the light sensor
109
are formed as projecting portions so that the light sensor
109
can be mounted with ease and accuracy to one of the guides of the conveyor
101
, i.e., a guide
101
a
. Likewise, both alight-entering surface
111
a
and a light-emitting surface
111
b
of the reflector type prism
111
are formed as projecting portions so that the reflector type prism
111
can be mounted with ease and accuracy to another guide
101
b
of the conveyor
101
. It is to be noted that the reflector type prism
111
formed in the shape described above and having the function described above is constituted of a raw material such as an acrylic resin, a polycarbonate resin or the like and, as illustrated in
FIG. 10
, it is formed using a die
113
.
However, since the reflector type prism
111
shrinks to a certain degree during its formation using the die
113
, there is a concern that the light-entering surface
111
a
and the light-emitting surface
111
b
may be formed as concave surfaces relative to the direction of the light beams A and B, as illustrated in FIG.
11
. If the light-entering surface
111
a
and the light-emitting surface
111
b
form concave surfaces in this manner, the light beams A and B become scattered, and ultimately, the quantity of light in the light beam B reaching the light-receiving element
107
of the light sensor
109
becomes reduced. In particular, if the quantity of light in the light beam B is less than a specific value when the distance between the light sensor
109
and the reflector type prism
111
is great or when a high S/N ratio is required, the light-receiving element
107
may erroneously detect a body to be detected
103
, causing erroneous operation in various types of processing performed based upon a detection signal (not shown)output by the light sensor
109
.
In addition, the reflector type prism
111
is mounted at the conveyor
101
by inserting the projecting portion upon which the light-entering surface
111
a
is formed and the projecting portion upon which the light-emitting surface
111
b
is formed into through holes h
1
and h
2
, respectively, that are provided in the guide
101
b
for positioning, and then by securing the reflector type prism
111
with a separate mounting blade spring or the like (not shown). Thus, the structure through which the reflector type prism
111
is mounted to the guide
101
a
in the prior art is complicated, causing an increase in production cost and an increase in the number of work steps.
Furthermore, since the reflector type prism
111
in the prior art is colorless and transparent, a so-called random external light C unrelated to the light beam A may enter the reflector type prism
111
through a portion other than the light-entering surface
111
a
, as illustrated in
FIG. 8
, to reach the light-receiving element
107
. This presents a problem in that it may cause the light-receiving element
107
to operate erroneously, making accurate detection of the body to be detected by the light sensor
109
impossible.
SUMMARY OF THE INVENTION
A first object of the present invention, which has been completed by addressing the problems of the reflector type prism in the prior art described above, is to provide a new and improved reflector type prism with which a light beam emitted from the light-emitting surface of the reflector type prism is prevented from becoming scattered, to achieve stable detection of the light beam emitted from the reflector type prism by a light-receiving element, and to provide a reflector type prism forming die.
A second object of the present invention is to provide a new and improved reflector type prism that may be secured to a specific mounting member without having to provide a complicated mounting mechanism.
A third object of the present invention is to provide a new and improved reflector type prism that is capable of stably emitting a light beam that has entered it without being affected by a random external light.
In order to achieve the objects described above, in a first aspect of the present invention, a reflector type prism forming die for forming a reflector type prism which has the function of reflecting an incoming light beam in a direction that is the reverse of its incoming direction, is provided. This reflector type prism forming die is characterized in that either or both of a forming surface for forming a light-emitting surface of a reflector type prism and, a forming surface for forming a light-entering surface of the reflector type prism is formed as a concave surface.
This die makes it possible to form either or both of the light-emitting surface or the light-entering surface of the reflector type prism as a convex surface. In other words, even if shrinkage occurs during the formation of the reflector type prism, the light-emitting surface and/or the light-entering surface will not be formed as a concave surface so that an emitted light beam can be prevented from becoming scattered or attenuated. Consequently, with the reflector type prism formed by using the reflector type prism forming die according to the present invention, an emitted light, which may be received by, for instance, a light-receiving element, can be detected in a stable manner.
In addition, the reflector type prism may be constituted to have the function of reflecting an incoming light beam in a direction that is the reverse of its incoming direction. In this case, either or both of the prism's light-emitting surface and light-entering surface is formed as a convex surface.
Such a prism makes it possible to inhibit scattering and attenuation of a light beam that enters the reflector type prism and is emitted therefrom after being reflected. Consequently, a light emitted from the reflector type prism, which may be received by, a light-receiving element can be detected in a stable manner.
In addition, by forming the convex surface in the reflector type prism described above as a spherical surface, the scattering of a light beam emitted from the reflector type prism can be even more effectively prevented. By forming the convex surface as a nonspherical surface, spherical aberration of the emitted light beam can be avoided and, it becomes possible to adjust the focal length of the emitted light beam. Thus, with
Hagimoto Mitsuru
Masui Mayumi
OKI Electric Industry Co., Ltd.
Shafer Ricky D.
Wenderoth , Lind & Ponack, L.L.P.
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