Optical: systems and elements – Single channel simultaneously to or from plural channels – By partial reflection at beam splitting or combining surface
Reexamination Certificate
2000-02-28
2002-11-12
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
C359S631000, C359S633000, C359S637000
Reexamination Certificate
active
06480337
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display apparatus, which is suitably applicable, for example, to head-mounted displays, goggle type displays, etc. designed so as to observe an enlarged image of image information displayed on a reflective liquid-crystal display element as a display element through an optical element having a free curved surface properly set.
2. Related Background Art
A variety of proposals have been made heretofore for the head-mounted image observing apparatus (image display apparatus), which are so called head-mounted displays, in such structure as to permit an observer to observe an enlarged virtual image of the image information displayed on the image display device of liquid crystal or the like, for example, by use of an optical element having an entrance surface, a plurality of reflective surfaces, and an exit surface in surfaces of a transparent material.
For example, Japanese Patent Application Laid-Open Nos. 7-333551, 8-50256, 8-160340, 8-179238 and 8-234137, etc. suggest the image observation apparatus the overall scale of which is decreased by using an LCD (liquid crystal display) as a display means for displaying the image information and using a compact prism as an observation optical system.
FIG. 1
is a schematic diagram of the major part of the image observation apparatus suggested in Japanese Patent Application Laid-Open No. 7-333551. In
FIG. 1
, light emitted from the LCD
51
is made incident to the entrance surface
53
of compact prism
52
. Then the light is folded between a totally reflecting surface
54
with curvature, formed in the compact prism
52
, and a reflecting surface
55
and thereafter the light is made to emerge from the compact prism
52
to be guided to the observer E. This results in forming a virtual image of the image information displayed on the display means (LCD)
51
and thus permits the observer E to observe the virtual image. The reflecting surface
55
of the compact prism
52
is comprised of an eccentric, free, curved surface, which is a decentered, rotationally asymmetric surface (a surface with different optical powers depending upon azimuths; a so-called free curved surface).
FIG. 2
is a schematic diagram of the major part of the image observation apparatus using a conventional, coaxial, concave mirror. In the same figure the light from the image information displayed on the display device
61
is reflected by a half mirror
62
and then is made incident to the concave mirror
63
. The light reflected by the concave mirror
63
is guided through the half mirror
62
to the observer E. The image information displayed on the display device
61
is formed as an enlarged virtual image by the concave mirror
63
. This permits the observer to observe the enlarged virtual image of the image information displayed on the display device
61
.
The optical system of the type illustrated in
FIG. 1
has such a feature that it is easier to decrease the overall scale of the apparatus and to increase the field of view than in the type using the conventional, coaxial, concave mirror illustrated in FIG.
2
.
There are particular desires for the decrease in the scale and weight of the whole apparatus, because the image observation devices such as the head-mounted displays, the goggle type displays, and the like are mounted on the head. Another important issue is to widen the field of view in order to provide the observation of image information displayed on the display means with strong appeal.
In the case of the image observation apparatus such as the head-mounted displays (HMD), the goggle type displays, and the like of the type as illustrated in
FIG. 1
, where the display device is constructed of a reflective display device (for example, a reflective, ferroelectric, liquid crystal display device), which has a high aperture ratio and which is advantageous in the decrease of scale, it is necessary to interpose an illumination system
70
for illuminating the display device
51
between the display device
51
and the entrance surface
53
of the compact prism
52
, as illustrated in FIG.
3
.
Here the illumination system
70
, for example, has a light source
71
, a condenser lens
72
for condensing the light from the light source
71
and converting it into parallel light, a prism
73
including a half mirror surface
73
a
for reflecting the light from the condenser lens
72
to illuminate the display device
51
, and so on. In the image observation apparatus the use of the reflective display element requires the placement of the illumination system for illuminating it between the display device
51
and the compact prism
52
and thus requires increase in the space between the prism
52
and the display device
51
, as illustrated in FIG.
3
. Therefore, there arise problems that the feature of this type is not taken advantage of and that it is difficult to decrease the size and weight and to increase the field of view.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an image display apparatus that permits the observer to observe the image information in a wide field of view and with good image quality while achieving the compactification of the whole apparatus, by properly setting an optical system from light source means to display means (an illumination optical system) and an optical system for guiding the light from the display means to the observer's eye (a display optical system), in observing the image information displayed on the display means such as a liquid crystal display or the like.
Another object of the present invention is to provide an image display apparatus suitably applicable as a head-mounted display that permits the observer to observe the image information displayed on the liquid crystal display in good order while achieving the compactification of the whole apparatus, by such structure that when the image information displayed on the liquid crystal display is observed using, for example, the reflective liquid crystal display as image display means and using, for example, an optical element having integrally formed surfaces of an entrance surface to which light from the liquid crystal display element is made incident, a decentered, curved, reflecting surface for reflecting the light entering the entrance surface, and an exit surface from which the light from the curved, reflecting surface is made to emerge, as display optical system, an illumination device for illuminating the liquid crystal display is properly set in accordance with the feature of the enlarging display system.
An image display apparatus according to one aspect of the present invention is an image display apparatus comprising: reflective display means; an illumination optical system for making light from light source means obliquely incident to a display surface of the display means; and a display optical system for guiding light from the display means to an observer to permit the observer to observe image information displayed on the display means, wherein a principal ray emerging from a central part of the display means is emergent obliquely from the display means, the display optical system comprises a decentered, rotationally asymmetric, reflecting surface, the illumination optical system and the display optical system share at least one optical element, and at least one surface of the optical element(s) shared is a curved surface.
An image display apparatus according to one aspect of the present invention is an image display apparatus comprising: a reflective display device; an illumination optical system for guiding light from light source means to the display device; and a display optical system for guiding the light reflected by the display device to the eye of an observer to allow the observer to observe an image, wherein at least one surface of the display optical system is a decentered, rotationally asymmetric, reflecting surface, a principal ray of display light at a center of a field of view from the display device is emer
Inoguchi Kazutaka
Morishima Hideki
Takagi Akinari
Yamazaki Shoichi
Epps Georgia
Fitzpatrick ,Cella, Harper & Scinto
Mixed Reality Systems Laboratory Inc.
Thompson Tim
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