Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2001-11-27
2003-11-18
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By partial reflection at beam splitting or combining surface
C359S633000
Reexamination Certificate
active
06650483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical element and an optical system using the same and, more particularly, to an optical system element suitable for, e.g., a video camera, still video camera, copying machine, and the like, and an optical system using the same.
The present invention also relates to an optical device which is used in, e.g., a silver halide camera, video camera, electronic still camera, or the like, and comprises an optical element formed integrally with a plurality of refracting surfaces and a plurality of reflecting surfaces.
2. Description of Related Art
Conventionally, as a photographing optical system, some components of which are built by reflecting surfaces, a so-called mirror optical system (reflection optical system), as shown in
FIG. 12
, is known.
FIG. 12
is schematic view showing principal part of a mirror optical system made up of one concave mirror and one convex mirror. In the mirror optical system shown in
FIG. 12
, an object light beam
104
coming from an object is reflected by a concave mirror
101
, and propagates as a converging beam toward the object side. The light beam is reflected by a convex mirror
102
, and thereafter, is refracted by a lens
110
, thus forming an image on an image surface
103
.
This mirror optical system is based on an arrangement of a so-called Cassegrainian reflecting telescope, and aims at shortening the total length of the optical system by folding the optical path of a telescope lens system with a large total lens length made up of a refraction lens using two reflecting mirrors.
In an objective lens system, such a telescope system, a large number of methods for shortening the total lengths of optical systems using a plurality of reflecting mirrors are known in addition to the Cassegrainian type for the same purpose as above.
In this manner, a compact mirror optical system is conventionally obtained by efficiently folding the optical path using a reflecting mirror in place of a lens of a photographing lens with a large total lens length.
However, in general, mirror optical systems such as a Cassegrainian reflecting telescope and the like suffer a problem that some object light rays are eclipsed by the convex mirror
102
. This problem is caused by the presence of the convex mirror
102
in the passage region of the object light beam
104
.
In order to solve this problem, there has also been proposed a mirror optical system that uses a decentered reflecting mirror to avoid the passage region of the object light beam
104
from being shielded by other portions of the optical system, i.e., to separate main rays of the light beam from an optical axis
105
.
FIG. 13
is a schematic view showing principal part of a mirror optical system disclosed in U.S. Pat. No. 3,674,334. This optical solves the problem of eclipse using portions of reflecting mirrors which are rotationally symmetrical about the optical axis.
The mirror optical system shown in
FIG. 13
includes a concave mirror
111
, a convex mirror
113
, and a concave mirror
112
in the passage order of a light beam, and these mirrors are originally rotationally symmetrical about an optical axis
114
, as indicated by two-dashed chain lines in FIG.
13
. Of these mirrors, only the upper side of the concave mirror
111
, the lower side of the convex mirror
113
, and the lower side of the concave mirror
112
with respect to the optical axis
114
on the plane of the drawing are used, thus constituting an optical system that separates main rays
116
of an object light beam
115
from the optical axis
114
and avoids the object light beam
115
from being eclipsed.
FIG. 14
is a schematic view showing principal part of a mirror optical system disclosed in U.S. Pat. No. 5,063,586. The mirror optical system shown in
FIG. 14
solves the above problem by decentering the central axis itself of each reflecting mirror. In
FIG. 14
, if an axis perpendicular to an object surface
121
is defined to be an optical axis
127
, central coordinates and central axes (an axis that connects the center of the reflecting surface and the center of curvature of that surface)
122
a
,
123
a
,
124
a
, and
125
a
of a convex mirror
122
, a concave mirror
123
, a convex mirror
124
, and a concave mirror
125
in the passage order of a light beam are decentered from the optical axis
127
. In this mirror optical system, by appropriately setting the decentering amounts and the radii of curvature of the individual surfaces at that time, an object light beam
128
can be prevented from being eclipsed by these reflecting mirrors, and an object image is efficiently formed on an imaging surface
126
.
Also, U.S. Pat. Nos. 4,737,021 and 4,265,510 disclose an arrangement for avoiding eclipse using portions of reflecting mirrors which are rotationally symmetrical about the optical axis, and an arrangement for avoiding eclipse by decentering the central axis itself of each reflecting mirror from the optical axis.
As described above, by decentering the reflecting mirrors that build the mirror optical system, an object light beam can be avoided from being eclipsed. However, since the individual reflecting mirrors must be set to have different decentering amounts, a structure that attaches these reflecting mirrors is complicated, and it becomes very difficult to assure high alignment precision.
As one method of solving this problem, for example, a mirror system may be formed as a block to avoid assembly errors of optical parts upon assembly.
As conventional blocks having a large number of reflecting surfaces, for example, optical prisms such as a pentagonal roof prism, a Porro prism, and the like, which are used in a finder system or the like, a color separation prism that separates a light beam coming from a photographing lens into three, i.e., red, green, and blue color light beams and forms object images based on the individual color light beams on the surfaces of corresponding image sensing elements, and the like are known.
In these prisms, since a plurality of reflecting surfaces are integrally formed, the relative positional relationship among the reflecting surfaces is accurately determined, and the positions of the reflecting surfaces need not be adjusted.
However, the principal function of such prisms is to reverse an image by changing the traveling directions of light rays, and each reflecting surface is defined by a plane.
In contrast to this, an optical system in which reflecting surfaces of a prism have curvatures is also known.
FIG. 15
is a schematic view showing principal part of an observation optical system disclosed in U.S. Pat. No. 4,775,217. This observation optical system allows an observer to observe the landscape of the outer field and also to observe an image displayed on an information display member overlapping the landscape.
In this observation optical system, a display light beam
145
originating from an image displayed on an information display member
141
is reflected by a surface
142
, and propagates toward the object side. The light beam is then incident on a half mirror surface
143
defined by a concave surface. The light beam is reflected by the half mirror surface
143
, and becomes a nearly collimated light beam by the refractive power of the concave surface
143
. After the light beam is refracted by and transmitted through a surface
142
, it forms an enlarged virtual image of the displayed image and enters the pupil
144
of the observer, thus making the observer to see the displayed image.
On the other hand, an object light beam
146
from an object is incident on and refracted by a surface
147
which is nearly parallel to the reflecting surface
142
, and reaches the half mirror surface
143
as the concave surface. Since a semi-transparent film is deposited on the concave surface
143
, some light components of the object light beam
146
are transmitted through the concave surface
142
, are refracted by and transmitted through the surface
142
, and then enter the pupil
144
of th
Iida Seiji
Kawano Kenji
Sekita Makoto
Uehara Tsukasa
Canon Kabushiki Kaisha
Mack Ricky
Morgan & Finnegan , LLP
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