Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
1998-09-16
2001-07-24
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
06266194
ABSTRACT:
This application is based on applications Nos. H9-253111 and H10-210643 filed in Japan, the contents of which are hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a picture display apparatus, and more particularly, to a picture display apparatus designed so as to be mounted on the viewer's head or face. The present invention further relates to a camera requiring no complicated picture conversion processing.
2. Description of the Prior Art
For a head mounted display (HMD), reduction in overall weight and protruding amount of the apparatus is important in order to improve the mountability of the apparatus. A factor that decides the overall weight of the apparatus is the optical system layout. Among the optical systems that have hitherto been disclosed, examples of optical systems that can be reduced in protruding amounts of apparatus are shown in
FIGS. 1 and 2
.
FIRST CONVENTIONAL EXAMPLE
FIG. 1
shows an optical system disclosed in Japanese Laid-open Patent Application No. H7-175009. This optical system projects an image surface
100
far away through a semitransparent reflecting surface
102
and a semitransparent reflecting surface
101
. According to this arrangement, the size of the optical system can be reduced by repetitively reflecting the light between the image surface
100
and a viewer's pupil position
103
, so that the amount of frontward protrusion of the HMD from the viewer's head can be reduced.
SECOND CONVENTIONAL EXAMPLE
FIG. 2
shows an optical system disclosed in U.S. Reissued Pat. No. 27356. This optical system projects an image surface
104
far away through a semitransparent concave mirror
105
and a semitransparent plane mirror
106
. According to this arrangement, like the first conventional example, the size of the optical system can be reduced by repetitively reflecting the light between the image surface
104
and a viewer's pupil position
107
.
For an HMD, in addition to reduction in overall weight and protruding amount of the apparatus, provision of a large angle of view is important. Provision of a large angle of view enables display of more realistic pictures. However, in the first conventional example, since plane images are viewed being enlarged, correction of optical aberrations such as field curvature and distortion is limited, so that the angle of view cannot be widened.
In the second conventional example, since the image surface is a curved surface having its center on the side opposite to the pupil position, the angle of view cannot be widened.
In both of the two conventional examples, the pictures projected onto the viewer's pupil are plane images. However, viewers view more realistic pictures by viewing spherical images than by viewing plane images.
Another problem will be described. A picture display apparatus for viewing pictures taken from life has been disclosed and in this apparatus, a necessary range of a picture is cut out from the shooting range and then the cut out picture is viewed. However, in case a picture is viewed with a position different from the shooting center as the viewing center, it is necessary to convert image data since faithful picture reproduction cannot be performed by using the video signals of the shot picture as they are. Therefore, for example, it is necessary to perform image processing and this increases the price of the apparatus.
A conventional camera for shooting plane images also has problems. Even if plane images are continuously shot, it is impossible to obtain a 360-degree picture in which these images connect neatly. In a case where plane images shot by this type of camera are viewed by being displayed on a display apparatus, when a picture is viewed with a position different from the shooting center as the viewing center, the positional relationship among the objects in the picture changes. This will be described with reference to
FIGS. 3
to
5
.
FIG. 3
is a schematic cross-sectional view of an optical system of a camera. Reference numeral
112
represents a taking lens. Point B
1
represents the principal point of the taking lens
112
. Reference numeral
111
represents an image shot surface comprising a plane. &agr;
11
represents the shooting range of the camera. When a picture including objects
108
,
109
and
110
is shot with the object
108
as the shooting center, the light rays from the objects are imaged on the image shot surface
111
as shown in the figure.
The angle between the straight lines connecting the objects and the principal point B
1
is &thgr;
111
between the objects
108
and
109
and is &thgr;
121
between the objects
109
and
110
. The distance between the objects shot on the image shot surface
111
is y
1
between objects
108
a
and
109
a
and is Y
2
between the objects
109
a
and
110
a
. The focal length of the taking lens
112
is f. Here, the relationship between Y
1
, Y
2
and &thgr;
111
, &thgr;
121
is represented by these expressions.
Y
1
=f tan&thgr;
111
(1)
Y
2
=f tan(&thgr;
111
+&thgr;
121
)−Y
1
(2)
Hereinafter, a picture viewed when a part of the shooting range &agr;
11
is viewed with a picture display apparatus will be described with reference to
FIGS. 4 and 5
.
FIGS. 4 and 5
are schematic cross-sectional views of the picture display apparatus. On a display device
113
, the picture on the image shot surface
111
which is horizontally and vertically flipped is displayed as it is. The viewer views the picture through an eyepiece
114
. Point B
2
represents the principal point of the taking lens. The focal length of the taking lens
114
is f same as that of the camera.
FIGS. 4 and 5
are schematic cross-sectional views of the optical system of the picture display apparatus when a range &bgr;
11
is viewed with the object
108
a
as the viewing center and when a range &bgr;
12
is viewed with the object
109
a
as the viewing center, respectively.
In
FIG. 4
, the viewer views objects
108
b
,
109
b
and
110
b
. At this time, the angle between the straight lines connecting the viewed objects and the principal point B
2
of the taking optical system
114
is &thgr;
112
between the objects
108
b
and
109
b
and is &thgr;
122
between the objects
109
b
and
110
b
. The relationship between &thgr;
112
, &thgr;
122
and y
1
, Y
2
is represented by these expressions.
&thgr;
112
=tan
−1
(y
1
/f) (3)
&thgr;
122
=tan
−1
{(y
1
+y
2
)/f}−&thgr;
112
(4)
Comparing the expressions (1) and (3) and the expressions (2) and (4), it is apparent that &thgr;
112
=&thgr;
111
and &thgr;
122
=&thgr;
121
.
In
FIG. 5
, the viewer views objects
108
c
,
109
c
and
110
c
. At this time, the angle between the straight lines connecting the objects and the principal point B
2
of the taking optical system
114
is &thgr;
113
between the objects
108
c
and
109
c
and is &thgr;
123
between the objects
109
c
and
110
c
. The relationship between &thgr;
113
, &thgr;
123
and Y
1
, Y
2
is represented by these expressions.
&thgr;
113
=tan
−1
(y
1
/f) (5)
&thgr;
123
=tan
−1
(y
2
/f) (6)
Comparing the expressions (1) and (5) and the expressions (2) and (6), it is apparent that &thgr;
113
=&thgr;
111
and &thgr;
123
≠&thgr;
121
. Thus, when a picture is viewed with a position different from the shooting center as the viewing center (this occurs when the shooting range is larger than the display screen), the picture viewed by the viewer is not faithful reproduction of the shot picture.
In order to display faithful reproduction of shot pictures with conventional display apparatuses, it is necessary to perform complicated image processing when pictures are displayed.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a picture display apparatus being lightweight, small in protruding amount and capable of inexpensively performing wide-angle displa
Sato Akira
Tanijiri Yasushi
Burns Doane , Swecker, Mathis LLP
Mack Ricky
Minolta Co. , Ltd.
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