Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
1999-02-25
2001-08-21
Epps, Georgia (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
C359S563000, C359S566000, C359S707000, C359S833000
Reexamination Certificate
active
06278553
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 suitable for a silver halide camera, video camera, still video camera, or copying machine, which uses an optical element having a plurality of reflecting surfaces to form an object image on a predetermined plane and reduce the size of the entire optical system.
2. Related Background Art
Various photographing optical systems using the reflecting surfaces of concave mirrors or convex mirrors have been conventionally proposed.
FIG. 13
is a schematic view of a so-called mirror optical system (reflecting optical system) comprising one concave mirror and one convex mirror.
In the mirror optical system shown in
FIG. 13
, an object light beam
124
coming from an object is reflected by a concave mirror
121
, travels to the object side while being focused, and is reflected by a convex mirror
122
, thereby forming an image on an image plane
123
.
This mirror optical system is based on the arrangement of a so-called Cassegrain reflecting telescope. This system aims at shortening the total length of the optical system by deflecting the optical path of a telephoto lens system, which comprises refracting lenses and has a large total lens length, using two reflecting mirrors opposing each other.
For an object lens system of a telescope as well, a number of schemes for reducing the total length of the optical system using a plurality of reflecting mirrors are known in addition to the Cassegrain scheme for the same reason.
In this way, conventionally, a compact mirror optical system is obtained by using reflecting mirrors in place of photographing lenses with a large total lens length to efficiently deflect the optical path.
However, generally, in the mirror optical system such as a Cassegrain reflecting telescope, the object light beam is partially eclipsed by the convex mirror
122
. This problem is posed because the convex mirror
122
is inserted in the path of the object light beam
124
.
To solve this problem, a mirror optical system which prevents a portion of the optical system from blocking the path of the object light beam
124
, i.e., separates a principal ray
126
of the light beam from an optical axis
125
by decentering reflecting mirrors has also been proposed.
FIG. 14
is a schematic view of a mirror optical system disclosed in an U.S. Pat. No. 3,674,334. This system solves the problem of eclipse by separating the principal ray of an object light beam from the optical axis. The mirror optical system shown in
FIG. 14
comprises a concave mirror
131
, a convex mirror
132
, and a concave mirror
133
in the order the light beam passes through. These mirrors are originally rotationally symmetric with respect to an optical axis
134
, as is indicated by alternate long and two-dashed lines in
FIG. 14. A
principal ray
136
of an object light beam
135
is separated from the optical axis
134
by using only a portion of the concave mirror
131
above the optical axis
134
, only a portion of the convex mirror
132
below the optical axis
134
, and only a portion of the concave mirror
133
below the optical axis
134
, thereby constructing an optical system free from eclipse of the object light beam
135
.
FIG. 15
is a schematic view of a mirror optical system disclosed in U.S. Pat. No. 5,063,586. In the mirror optical system shown in
FIG. 15
, the central axes of reflecting mirrors are decentered from the optical axis to separate the principal ray of an object light beam from the optical axis, thereby solving the above problem.
Referring to
FIG. 15
, an axis perpendicular to an object surface
141
is defined as an optical axis
147
. The central coordinates and central axes (a central axis is formed by connecting the center of a reflecting surface to the center of curvature of the surface)
142
A,
143
A,
144
A, and
145
A of the reflecting surfaces of a convex mirror
142
, a concave mirror
143
, a convex mirror
144
, and a concave mirror
145
, which are located in the order the light beam passes through, are decentered from the optical axis
147
. In
FIG. 15
, by appropriately setting the decentering amounts and radii of curvature of the surfaces, the reflecting mirrors are prevented from eclipsing an object light beam
148
, so an object image is efficiently formed on an imaging plane
146
.
U.S. Pat. Nos. 4,737,021 or 4,265,510 also discloses an arrangement for avoiding eclipse partially using reflecting mirrors rotationally symmetric with respect to the optical axis or an arrangement for avoiding eclipse by decentering the central axes of reflecting mirrors from the optical axis.
As described above, when the reflecting mirrors constituting the mirror optical system are decentered, eclipse of the object light beam can be prevented. However, the reflecting mirrors must be set with different decentering amounts. This complicates the structure to which the reflecting mirrors are attached and also makes it difficult to ensure given attachment precision.
To solve this problem, a method of avoiding assembly errors of optical components in an assembly by forming the mirror system as one block has been proposed.
Conventionally, as a structure in which a number of reflecting surfaces form one block, there is an optical prism such as a pentagonal roof prism or Porro prism used in the viewfinder system of a camera, or an optical prism such as a color separation prism for separating a light beam from a photographing lens into, e.g., three color light components: red, green, and blue light components, and forming an object image based on each color light component on the surface of a corresponding image sensing element.
In these prisms, a plurality of reflecting surfaces are integrally formed, and have a precise relative positional relationship, so position adjustment of the reflecting surfaces is unnecessary. However, the main function of these prisms is to change the direction the light beam travels to invert the image, and each reflecting surface is flat.
On the other hand, an optical system using a prism whose reflecting surface has a curvature is also known.
FIG. 16
is a schematic view of an observation optical system disclosed in U.S. Pat. No. 4,775,217. This observation optical system observes the landscape and simultaneously observes an image displayed on an information display device overlapping the landscape.
In this observation optical system, a display light beam
165
emerging from an image displayed on an information display device
161
is reflected toward the object side by a surface
162
and enters a half mirror surface
163
formed from a concave surface. The display light beam
165
is reflected by the half mirror surface
163
and then converted into a nearly collimated light beam by the refracting power of the concave surface
163
. The display light beam
165
is refracted and transmitted through the surface
162
to form an enlarged virtual image of the displayed image, and simultaneously enters a pupil
164
of the observer to allow him/her to see the display image.
An object light beam
166
from the object enters a surface
167
almost parallel to the reflecting surface
162
, is refracted, and reaches the concave half mirror surface
163
. The half mirror surface
163
is coated with a semi-transparent film. Some components of the object light beam
166
pass through the concave surface
163
, are refracted and transmitted through the surface
162
, and enter the pupil
164
of the observer. With this arrangement, the observer sees the displayed image that overlaps the landscape.
FIG. 17
is a schematic view of an observation optical system disclosed in Japanese Laid-Open Pat. Application No. 2-297516. This observation optical system also serves to observe an external landscape and simultaneously observes an image displayed on an information display device overlapping the landscape.
In this observation optical system, a display light beam
174
emerging fr
Canon Kabushiki Kaisha
Epps Georgia
Fitzpatrick ,Cella, Harper & Scinto
Thompson Tim
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