Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1998-08-20
2001-07-31
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
C359S630000
Reexamination Certificate
active
06268963
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an optical system having a reflecting surface, and particularly to an optical system for forming the image of an object on the surface of an image pickup element such as silver halide film or a CCD by the use of an optical element provided with an incidence surface, an emergence surface and a plurality of reflecting surfaces on the surface of a transparent member. This optical system is suitable for a video camera, a still video camera and an image pickup apparatus such as a copying apparatus.
2. Related Background Art
There have heretofore been proposed various phototaking optical systems utilizing the reflecting surface of concave mirror, a convex mirror or the like.
FIG. 9
of the accompanying drawings is a schematic view of a so-called mirror optical system comprising a concave mirror and a convex mirror.
In the mirror optical system of
FIG. 9
, an object light beam
104
from an object is reflected by the concave mirror
101
, whereby it travels toward the object side while being converged, and impinges on the convex mirror
102
. The light beam
102
is further reflected by the convex mirror
102
, and hereafter it is imaged on an image plane
103
.
This mirror optical system has the same construction as that of a so-called Cassegrainian type reflection telescope, and the optical path of a telephoto lens system comprised of a refracting lens which is long in the full length of the optical system is folded by the use of a reflecting mirror, whereby the full length of the optical system can be shortened.
Besides the Cassegrainian type, there are known a number of mirror optical systems of which the full length is shortened by the use of a plurality of reflecting mirrors.
Generally, in a mirror optical system such as the Cassegrainian type reflection telescope, there is the problem that part of the object light beam
104
is eclipsed by the convex mirror
102
. This problem is attributable to the fact that the convex mirror
102
is in the passage area of the object light beam
104
.
In order to solve this problem, there has also been proposed a mirror phototaking optical system used with the principal ray of the object light beam
104
spaced apart from an optical axis
105
.
FIG. 10
of the accompanying drawings is a schematic view of a mirror optical system disclosed in U.S. Pat. No. 3,674,334, and the center axis itself of the reflecting surface of a reflecting mirror is made eccentric relative to an optical axis
114
and at the same time, the principal ray
116
of an object light beam
115
is spaced apart from the optical axis
114
to thereby solve the above-mentioned problem of eclipse.
The mirror optical system of
FIG. 10
has a concave mirror
111
, a convex mirror
113
and a concave mirror
112
in the order of passage of the light beam, but as indicated by dots-and-dash line, they originally are portions of reflecting mirrors rotation-symmetrical with respect to the optical axis
114
. Of these, only the upper portion of the concave mirror
111
relative to the optical axis
114
as viewed in
FIG. 10
, only the lower portion of the convex mirror
113
relative to the optical axis
114
as viewed in FIG.
10
and only the lower portion of the concave mirror
112
relative to the optical axis
114
as viewed in
FIG. 10
are used, whereby there is constructed an optical system in which the principal ray
116
of the object light beam
115
is spaced apart from the optical axis
114
and the eclipse of the object light beam
115
is eliminated.
FIG. 11
of the accompanying drawings is a schematic view of a mirror optical system disclosed in U.S. Pat. No. 5,063,586.
In
FIG. 11
, when an axis passing through the center of an object surface
121
perpendicular to the object surface
121
is defined as an optical axis
127
, the central coordinates and center axes of the reflecting surfaces of a convex mirror
122
, a concave mirror
123
, a convex mirror
124
and a concave mirror
125
arranged in the order of passage of a light beam (the axes linking the centers of the reflecting surfaces and the centers of curvature of the surfaces)
122
a
,
123
a
,
124
a
and
125
a
are eccentric relative to the optical axis
127
. In
FIG. 11
, the amount of eccentricity at this time and the radius of curvature of each surface are appropriately set to thereby prevent the eclipse of an object light beam
128
by each reflecting mirror and image the object light beam
128
efficiently on an imaging plane
126
.
U.S. Pat. No. 4,737,021 and U.S. Pat. No. 4,265,510 also disclose a construction in which as in the optical system of
FIG. 10
, eclipse is avoided by the use of a portion of a reflecting mirror rotation-symmetrical with respect to the optical axis, or a construction in which as in the optical system of
FIG. 11
, the center axis itself of a reflecting mirror is made eccentric relative to the optical axis to thereby avoid eclipse.
FIG. 12
of the accompanying drawings shows an a focal optical system for observation using four reflecting surfaces disclosed in U.S. Pat. No. 5,309,276. In
FIG. 12
, four mirrors
201
to
204
are disposed so that a light beam from an object, not shown, lying at the left as viewed in
FIG. 12
may be reflected by the first mirror
201
, the second mirror
202
, the third mirror
203
and the fourth mirror
204
in the named order, and may pass the front of the first mirror
201
twice, and then may emerge from the fourth mirror in a direction perpendicular to the direction of incidence of incident light
200
and may be imaged on an observer's pupil
205
.
These reflecting optical systems have required many constituent parts, and to obtain necessary optical performance, it has been necessary to assemble respective optical parts with good accuracy. Particularly, the accuracy of the relative position of the plurality of reflecting mirrors has been severe and therefore, the adjustment of the position and angle of each reflecting mirror has been requisite.
As a method for solving this problem, it has been proposed to construct, for example, a mirror system having a plurality of reflecting mirrors (surfaces) by a single element.
As an element having a plurality of reflecting surfaces, there is a pentagonal roof prism used, for example, in a finder system or the like, or an optical prism such as a porroprism.
In these prisms, the plurality of reflecting surfaces are formed integrally with one another and therefore, the relative positional relation among the reflecting surfaces is made accurate and the mutual positional adjustment of the reflecting surfaces becomes unnecessary. The main function of these prisms is to change the direction of travel of rays of light to thereby effect the reversal of an image, and each reflecting mirror is comprised of a flat surface.
In contrast, there is also known an optical system in which a reflecting surface (reflecting mirror) formed on a prism is endowed with a curvature (refracting power).
FIG. 13
is a schematic view of the essential portions of an observation optical system disclosed in U.S. Pat. No. 4,775,217. This observation optical system for observing therethrough a scene of the outside and a display image displayed on an information display member as they are made to overlap each other.
In this observation optical system, a light beam
145
emerging from the display image on the information display member
141
enters from the incidence surface
148
of a prism, is reflected by a surface
142
and travels toward the scene at the left as viewed in
FIG. 13
, and enters a concave surface
143
comprising a half mirror. The display light beam
145
is reflected by this concave half mirror
143
, and becomes a parallel light beam in which rays of light are substantially parallel to one another by the refracting power of the concave surface
143
, and is refracted by and transmitted through the surface
142
to thereby form the enlarged virtual image of the display image, and enters an observer's pupil
144
,
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
Mack Ricky
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