Optics: image projectors – Cabinet encloses projector and one side of screen – Reflector between lamp and screen
Reexamination Certificate
2003-08-13
2004-11-30
Gray, David (Department: 2851)
Optics: image projectors
Cabinet encloses projector and one side of screen
Reflector between lamp and screen
C353S074000, C353S098000
Reexamination Certificate
active
06824274
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an image display device by which an optical image signal based on image information is projected onto a display means to display an image, and a method for adjusting optical elements of in the image display device into alignment.
2. Description of the Prior Art
FIG. 95
is a diagrammatic representation of a conventional image display device. Reference numeral
1
denotes a luminous element for emitting light;
2
denotes a parabolic reflector for reflecting the light from the luminous element
1
mostly into parallel rays of light; and
3
denotes a condenser lens for gathering the light reflected by the parabolic reflector
2
. The luminous element
1
, the parabolic reflector
2
and the condenser lens
3
constitute an illumination light source system.
Reference numeral
4
denotes a light valve for spatially intensity-modulating the light gathered by condenser lens
3
based on image information;
5
denotes a projecting optical lens for projecting the light intensity-modulated by the light valve onto a screen; and
6
denotes the screen for displaying, as an image, the light projected thereon by the projecting optical lens
5
. The arrows indicate optical paths.
Next, the operation of the prior art example will be described below.
Light emitted from the luminous element
1
is reflected by the parabolic reflector
2
and focused through the condenser lens
3
onto the light valve
4
. The light valve
4
spatially intensity-modulates the focused light based on image information. The intensity-modulated light is projected by the projecting optical lens
5
onto the screen
6
from behind (from the left-hand side in
FIG. 95
) and displayed thereon. A user of the image display device visually identifies the image from the front (from the right-hand side in FIG.
95
).
The depth dimension of the image display device of
FIG. 95
corresponds to the distance from the illumination light source system composed of the luminous element
1
, the parabolic reflector
2
and the condenser lens
3
to the screen
6
. It is preferable to minimize the depth dimension of the image display device if the image size displayable is the same. For such a reason, the conventional image display device of
FIG. 95
uses a wide-angle projecting optical lens
5
to display an image on the screen so that the depth dimension of the display device is minimized to provide a flat device configuration.
Since the projecting optical lens
5
has a limitation of increasing its angle of field, however, it is customary in the art, with a view to reducing the depth dimension, to place a plane mirror at an angle of 45° to the horizontal to bend the optical path from the projecting optical lens
5
, projecting an image onto the screen
6
as depicted in FIG.
96
.
In the image display device of
FIG. 96
, the illumination light source system, the light valve
4
and the projecting optical lens
5
are disposed in the direction of height of the device (in the vertical direction in
FIG. 96
) to reduce the depth dimension of the device. The depth dimension of the image display device in this case corresponds to the distance from the plane mirror
7
to the screen
6
. With the plane mirror
7
tilted more than 45° from the horizon, the depth dimension of the image display device can be further reduced; in this instance, however, the light valve
4
and the illumination light source system interfere with the projected light, and the light is shaded or eclipsed accordingly, resulting in the light path getting out of the screen
6
.
In Japanese Patent Application Laid-Open Gazette 6-11767 there is disclosed an image display device of the type wherein light is reflected by a convex mirror is used in place of the plane mirror
7
in
FIG. 96
to display a magnified image on the screen
6
, but the image displayed on the screen
6
is distorted.
The conventional device configurations described above impose limitations on the reduction of the depth dimension of the device and permit no further reduction.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an image display device that provides an enlarged display of distortion-free images and permits further reduction of its depth dimension than in the prior art.
Another object of the present invention is to provide a method of adjusting optical elements of the image display device into alignment.
According to an aspect of the present invention, there is provided an image display device which comprises projecting optical means composed of a reflecting part for reflecting the optical image signal, and a refracting optical part for correcting for a distortion if the reflecting part has the distortion and for projecting the optical image signal onto the reflecting part, and wherein display means receives the optical image signal through the projecting optical means.
According to another aspect of the present invention, there is provided an image display device which comprises projecting optical means composed of a reflecting part having a reflecting surface for reflecting the optical image signal, and a refracting optical part having a refracting surface for projecting the optical image signal onto the reflecting part, and wherein the display means receives the optical image signal through the projecting optical means and at least one of the reflecting surface and the refracting surface is aspherical.
According to another aspect of the present invention, the transmitting means comprises: an illumination light source part for emitting illumination light; and a reflecting type image information providing part for receiving the illumination light emitted from the illumination light source part and for providing image information to the illumination light and reflecting the illumination light as the optical image signal.
According to another aspect of the present invention, the reflecting part has a rotationally symmetric aspherical surface for reflecting the optical image signal transmitted from the transmitting means.
According to another aspect of the present invention, the reflecting part is a convex mirror of negative power.
According to another aspect of the present invention, the reflecting part is a Fresnel mirror of negative power.
According to another aspect of the present invention, the reflecting part has a reflecting surface that is formed by a low dispersive medium and a high dispersive medium stacked in the direction in which to transmit the optical image signal sent from the transmitting means, has a negative power and reflects the optical image signal having passed through the low and high dispersive media.
According to another aspect of the present invention, the reflecting part has a reflecting surface formed so that its convex curvature is large around an optical axis and becomes smaller toward the periphery of the reflecting surface.
According to another aspect of the present invention, the reflecting part has an odd-order aspherical reflecting surface obtained by adding odd-order terms to a polynomial composed of even-order terms.
According to another aspect of the present invention, the refracting optical part has odd-order aspherical refracting surfaces obtained by adding odd-order terms to a polynomial composed of even-order terms.
According to another aspect of the present invention, the reflecting part or refracting optical part reflects or refracts the optical image signal by the reflecting or refracting surface except around the optical axis of the reflecting or refracting part.
According to another aspect of the present invention, the refracting optical part is provided with a curvature-of-field correcting means for canceling a curvature of field of the reflecting part.
According to another aspect of the present invention, the refracting optical part is provided with positive lenses of positive power, negative lenses of negative power having a refractive index lower than that of the positive lens, and a Petzval's sum correc
Shikama Shinsuke
Suzuki Hiroshi
Suzuki Jiro
Teramoto Kohei
Cruz Magda
Gray David
Mitsubishi Denki & Kabushiki Kaisha
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