Optical: systems and elements – Lens – With support
Reexamination Certificate
2002-08-12
2004-06-01
Mack, Ricky (Department: 2873)
Optical: systems and elements
Lens
With support
C359S631000
Reexamination Certificate
active
06744573
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention and Description of the Related Art
The present invention relates to an optical element for enlarging an image displayed on an image display element.
In general, to obtain a good optical performance in an optical device using an optical element such as a prism, or the like, it is necessary to position the optical element with respect to a cabinet and to other optical element and to fix it in the cabinet or to the other optical element accurately with a pinpoint accuracy.
The optical element is typically represented by an optical prism. Since the optical prism has the smaller number of flat surfaces acting as a reference, there are conventionally proposed various methods as a fixing method of it.
For example, an optical prism
1
as a prior example shown in
FIG. 1
is arranged such that flange portions
1
a
project from two confronting surfaces that do not contribute to the optical action of the optical prism
1
, screw insertion holes
1
b
are drilled through the flange portions
1
a
as well as positioning pins
1
c
project from the back surfaces of the flange portions
1
a.
In contrast, a cabinet
2
to which the optical prism
1
is fixed has joint surfaces
2
a
against which the flange portions
1
a
provided with the optical prism
1
are abutted, and then screw holes
2
b
are threaded into the joint surfaces
2
a
at the positions thereof corresponding to the screw insertion holes
1
b
, and further positioning recessed portions
2
c
, into which the positioning pins
1
c
are inserted, are drilled into the joint surfaces
2
a.
In assembly, the optical prism
1
is fixed to the cabinet
2
by abutting the back surfaces of the flange portions
1
a
, which project from both the side surfaces of the optical prism
1
, against the joint surfaces
2
a
formed on the cabinet
2
, by positioning the optical prism
1
with respect to the cabinet
2
by inserting the positioning pins
1
c
, which project from the back surfaces of the flange portions
1
a
, into the positioning recessed portions
2
c
drilled into the joint-surfaces
2
a
, and by driving screws
3
, which have been inserted through the screw insertion holes
1
b
, into the screw holes
2
b
drilled into the joint surfaces
2
a.
In this case, as shown in
FIGS. 2 and 3
, each flange portion
1
a
may be cut to shorten its size up to the position where the screw insertion hole
1
b
is halved, whereas a projecting portion
2
d
having a height slightly lower than the thickness of the flange portion
1
a
may be projected from the outside surface of each joint surface
2
a
of the cabinet
2
.
That is, in the arrangement shown in
FIGS. 2 and 3
, when the flange portions
1
a
projecting from both the sides of the optical prism
1
are inserted between the projecting portions
2
d
of the cabinet
2
, circular screw insertion holes are formed by the halved screw insertion holes
1
b
drilled through the flange portions
1
a
and halved screw insertion holes
2
e
formed on the inside surfaces of the projecting portions
2
d
, and the screws
3
having been inserted through the screw insertion holes are driven into the screw holes
2
b
drilled into the joint surfaces
2
a
of the cabinet
2
, thereby the optical prism
1
is fixed to the cabinet
2
.
As described above, since the flange portions
1
a
are formed in the halved state in
FIGS. 2 and 3
, it is possible to reduce the shape of the flange portions
1
a
as compared with the Free-Form-Surface prism
1
shown in FIG.
1
. Further, when the screws
3
are tightened, the heads thereof are abutted against the projecting portions
2
d
on the cabinet
2
side and the screws
3
are prevented from being more tightened, thereby the occurrence of internal stress to the optical prism
1
is suppressed so that the deformation of the optical prism
1
can be prevented.
Further, as shown in
FIG. 4
, there is also known a technology for fixing the optical prism
1
to the cabinet
2
by drilling screw holes
2
f
through the side surfaces of the cabinet
2
and by pressing the side surfaces of the optical prism
1
by the extreme ends of set screws
3
b
driven into the screw holes
2
f.
According to this prior example, the shape of the flange portions
1
a
can be more reduced because it is not necessary to drill insertion holes, through which tightening screws are inserted, through the flange portions
1
a
of the optical prism
1
. As a result, the reduction in size of the cabinet
2
for holding it can be realized, and thus a device can be reduced in size in its entirety.
In this case, as shown in
FIG. 5
, the extreme ends of the set screws
3
b
do not directly press the side surfaces of the optical prism
1
by attaching a sheet member
4
bent in a U-shape to the inner surface of the cabinet
2
and by pressing the side surfaces of the optical prism
1
by the set screws
3
b
through the side surfaces
4
a
of the sheet member
4
, thereby internal stress occurred to the optical prism
1
can be suppressed.
In contrast, as shown in
FIG. 6
, when the set screws
3
b
are arranged as pointed set screws
3
c
, V-shaped grooves
1
d
, into which the extreme ends of the pointed set screws
3
c
are inserted, are formed on the side surfaces of the optical prism
1
, and the pointed set screws
3
c
are driven into the screw holes
2
f
threaded into the cabinet
2
, the extreme ends of the pointed set screws
3
c
impinge on the slants of the V-shaped grooves
1
d
formed in the side surfaces of the optical prism
1
.
When the pointed set screws
3
c
are further driven, the optical prism
1
is pulled in an impinging surface direction and pressed as well as can be fixed to the cabinet
2
. Note that reference numeral
2
g
denotes pins that are inserted into guide holes drilled through the flange portions
1
a
and regulate the movement of the optical prism
1
in a width direction.
Further, as shown in
FIG. 7
, there is also known a technology for interposing elastic fixing members
5
such as spring between both the side surfaces of the optical prism
1
and the inner surfaces of the cabinet
2
.
According to this prior example, a fixing and pressing force is made constant to the optical prism
1
. Further, when the optical prism
1
is expanded or contracted by a temperature change, or the like, the deformation of the optical prism
1
is allowed by the elastic deformation of the elastic fixing members
5
, thereby the occurrence of internal stress is prevented, thereby the breakage of the optical prism
1
can be prevented before it occurs.
Further, an optical prism
11
as shown in
FIG. 8
is also known. This optical prism
11
is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 9-73005. The optical prism
11
shown in
FIG. 8
is used in an image observation device such as a head mount display (HMD), or the like for displaying an image displayed on a small image display element in enlargement. The optical prism
11
has a first light incident optical surface
11
a
composed of a flat surface or a curved surface, a second optical surface
11
b
composed of a flat surface or a curved surface for totally reflecting light beams incident in an element from the first optical surface
11
a
, a third optical surface
11
c
for reflecting at least a part of the light beams from the second optical surface
11
b
to the second optical surface
11
b
side, and optically positioning flange portions lid disposed to two side surfaces, which confront each other and do not execute an optical action, other than the first to third optical surfaces
11
a
-
11
c.
There is disclosed a technology for accurately holding the optical prism
11
without causing optical distortion by holding the optical prism
11
through the flange portions
11
d.
However, the conventional examples described above have the following problems.
In the optical prisms
1
and
11
shown in
FIGS. 1 and 8
, the flange portions
1
a
and
11
d
project from the side surfaces thereof, which increases the sizes o
Atsumi Motohiro
Ichikawa Hirotoshi
Maeda Yoshihiro
Miyairi Nobuo
Mack Ricky
Olympus Corporation
Ostrolenk Faber Gerb & Soffen, LLP
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