Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2001-01-18
2002-12-10
Epps, Georgia (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
06493146
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to image display apparatus and, more particularly, to image display apparatus suitably applicable to head-mounted displays or the like adapted to enable observation of an enlarged view of image information displayed on a reflective liquid-crystal display element as a display element through an optical element having properly set free-form surfaces.
2. Related Background Art
There are conventionally well-known image display apparatus of a head-mounted type (head-mounted displays) using the display element of a CRT, an LCD, or the like and constructed to enlarge an image displayed on such a display element through an optical system to permit observation of an enlarged view of the displayed image.
FIG. 10
is a schematic diagram of main part of a conventional image display device using a coaxial concave reflector. In the same figure light from the image displayed on the display element
61
is reflected by a half mirror
62
to be incident to the concave mirror
63
. The light reflected by the concave mirror
63
is guided through the half mirror
62
to an observer E. The image displayed on the display element
61
is focused as an enlarged virtual image by the concave mirror
63
. This permits the observer to observe the enlarged virtual image of the image displayed on the display element
61
.
For example, Japanese Patent Applications Laid-Open No. 07-333551, No. 08-50256, No. 08-160340, No. 08-179238, etc. describe proposals of the image display devices reduced in the thickness of the entire apparatus by using an LCD (liquid-crystal display) as a display means for displaying an image and a slim prism as an observation optical system.
FIG. 11
is a schematic diagram of main part of the image display device proposed in Japanese Patent Application Laid-Open No. 07-333551. In
FIG. 11
, the light emitted from the LCD
51
is made incident to an entrance surface
53
of the compact prism
52
. Then the light is folded between a total reflection surface
54
with curvature and a reflective surface
55
in the compact prism
52
and thereafter is guided out of the compact prism
52
through the surface
54
toward the observer E. This results in forming a virtual image of the image displayed on the display means (LCD)
51
so as to permit the observer E to observe the virtual image. The reflective surface
55
of the compact prism
52
is a decentered free-form surface comprised of a decentered rotationally asymmetric surface (a surface with optical powers differing depending upon azimuths, which is so called a free-form surface).
The type of the optical system illustrated in
FIG. 11
has such a feature that it is easier to decrease the thickness of the entire apparatus and increase the angle of view of the observation field than in the case of the type using the conventional coaxial concave mirror illustrated in FIG.
10
.
With the conventional image display devices such as the head-mounted displays, goggle-type displays, etc., there are particular demands for further decrease in the size and weight of the entire apparatus, because these devices are mounted on the head. Particularly, they are preferably constructed to be thin in the direction of the visual axis of the observer in view of the weight balance, the appearance, and so on. Another important subject is to widen the angle of observation view in order to give strong appeal to the observation of the image displayed on the display means.
In the image display device such as the thin head-mounted display (HMD) of the type illustrated in
FIG. 11
, if the display element is constructed of a reflective display element with a high aperture ratio advantageous in compactification, an illumination system
70
for illuminating the display element
74
will be needed, for example, between the reflective display element
74
and the entrance surface
53
of the compact prism
52
, as illustrated in FIG.
12
.
The illumination system
70
herein is composed, for example, of a light source
71
, a condenser lens
72
for condensing diverging light from the light source
71
, a prism
73
including a half mirror surface
73
a
which reflects the light from the condenser lens
72
to illuminate the display element
74
and which makes the angle of 45° with the display surface of the display element
74
, and so on. In the image display apparatus, the use of the reflective display element raises the necessity for the placement of the illumination system for illuminating it between the display element
74
and the compact prism
52
and, in turn, the need for increasing the space between the prism
52
and the display element
74
, as illustrated in
FIG. 12
, thus posing the problem of decrease in the angle of view or the like with failing to take advantage of the feature of this type.
SUMMARY OF THE INVENTION
An object of the present invention is to provide image display apparatus that can accomplish both compactness of apparatus and a wide angle of view by properly setting construction of the illumination optical system for illuminating the display means, a display optical system for guiding the light from the display means to the observer's eyes, for example, an optical means consisting of a prism body with refracting action, etc. for observation of the image information displayed on the reflective display means of the liquid-crystal display or the like in the image display apparatus of HMD or the like and that can realize observation of the image with excellent image quality without bringing about degradation of contrast, unevenness of contrast in the screen, etc. in the observation field.
An image display apparatus according to one aspect of the present invention is an image display apparatus for permitting an observer to observe image information displayed on display means, comprising: reflective display means; an illumination optical system having a reflective surface A for guiding light from light source means to the display means; and a display optical system for guiding light from the display means to an observation position of the observer, wherein when principal rays are defined as rays emerging from a display surface of the display means and impinging upon the center of an exit pupil and when a center-view-angle principal ray is defined as a ray emerging from the center of the display surface of the display means and passing the center of the exit pupil of the display optical system, the display optical system comprises a decentered reflective surface or a plurality of decentered optical systems decentered relative to the center-view-angle principal ray and having a power, wherein when illumination principal rays are defined as rays emerging from the light source means and guided onto the display surface by the illumination optical system to become the principal rays, an angle of incidence of each illumination principal ray onto the display surface and an angle of emergence of a corresponding principal ray from the display surface make a predetermined angle, and wherein when a center illumination principal ray is defined as a ray emerging from the light source means and guided to the center of the display surface by the illumination optical system to become the center-view-angle principal ray, when a coordinate system is so defined that a yz plane is set on a surface formed by incidence and emergence of the center illumination principal ray to and from the reflective surface A and that a z-axis is taken along a direction of a normal to the reflective surface A in the yz plane, a y-axis along a tangent direction thereto, and an x-axis along a direction normal to the yz plane, and when the illumination principal rays are projected onto the xz plane of the coordinate system, the illumination principal rays projected onto the xz plane are incident at respective angles of incidence approximately equal to each other to the reflective surface A.
In a further aspect of the present invention, said reflective surface A acts to totally reflect the li
Inoguchi Kazutaka
Takagi Akinari
Canon Kabushiki Kaisha
Epps Georgia
Fitzpatrick ,Cella, Harper & Scinto
Seyrafi Saeed
LandOfFree
Image display apparatus does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Image display apparatus, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Image display apparatus will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2920272