Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2002-04-18
2003-10-28
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S037000
Reexamination Certificate
active
06637889
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to projection type image display apparatus for color separating illumination light to illuminate a plurality of image display devices with the separated light components and combining image light components emanating from these image display devices for projective display.
2. Description of the Related Art
In recent years, a projection type image display apparatus with an improved brightness and a compact size is needed.
FIG. 4
shows the configuration of a conventional projection type image display apparatus. In
FIG. 4
, white illumination light emitted from an illumination light source
101
is reflected by a reflector
102
, passes through a fly eye lens A
103
, further reflected by a mirror M
101
, passes through a fly eye lens B
104
, a light polarization converting device
105
and a condenser lens
106
, and then incident on a dichroic mirror DM
101
.
In general, as the illumination light source, a halogen lamp, a metal halide lamp, an ultra-high pressure mercury lamp or the like is used.
The dichroic mirror DM
101
has a spectral transmittance shown in FIG.
5
(
a
), in which a light component in a wavelength range for blue is reflected and a light component in a wavelength range for green to red is transmitted. The light component in the wavelength range for green to red passing through the dichroic mirror DM
101
is incident on a dichroic mirror DM
102
. The dichroic mirror DM
102
has a spectral transmittance shown in FIG.
5
(
b
), in which a light component in a wavelength range for green is reflected and a light component in a wavelength range for red is transmitted.
The light component in the wavelength range for blue reflected by the dichroic mirror DM
101
is turned 90 degrees by a reflecting mirror M
102
, passes through a field lens
107
B, and incident on an image display device
108
B, where the light is modulated in accordance with a signal input to the image display device
108
B.
The light component in the wavelength range for green reflected by the dichroic mirror DM
102
passes through a field lens
107
G and is incident on an image display device
108
G, where the light is modulated in accordance with a signal input to the image display device
108
G.
The light component in the wavelength range for red transmitted through the dichroic mirror DM
102
passes through a trimming filter TR
0
having a spectral transmittance shown in FIG.
5
(
c
), a condenser lens
111
, a relay lens
112
, reflecting mirrors M
103
, M
104
and a field lens
107
R, and then is incident on an image display device
108
R, where the light is modulated.
The image light component for each color, modulated by the respective image display device
108
R,
108
B and
108
G as described above, is incident on a cross dichroic prism
109
. The light components in the wavelength ranges for blue and red are turned 90 degrees within the cross dichroic prism
109
, while the light component in the wavelength range for green is transmitted as it is through the cross dichroic prism
109
. Then, the light components of all the wavelength ranges emanate in combination.
The image light resulting from the color combination in the cross dichroic prism
109
is projected and displayed on a screen, not shown, by a projection lens
110
.
In the conventional projection type image display apparatus configured in this manner, the dichroic mirror DM
102
is disposed immediately before the image display device
108
G and is responsible for separating the optical path of the light component in the wavelength range for green from the optical path of the light component in the wavelength range for red and for bending the optical path of the light component in the wavelength range for green. The dichroic mirror DM
102
is arranged such that the optical axis of the light incident on the dichroic mirror DM
102
forms an angle of 45 degrees with the normal to the incident surface of the dichroic mirror DM
102
.
In the aforementioned configuration of the apparatus, however, the optical axis of the illumination light from the illumination light source
101
to the reflecting mirror M
101
is arranged in parallel with the optical axis of the projection lens
110
, and the condensing effect of the condenser lens
106
converges the luminous flux toward the image display device
108
R,
108
G and
108
B. Thus, when the apparatus is housed in an outer box
120
, the probability is that spaces S
1
, S
2
with little usefulness are created as shown by hatched portions in
FIG. 6
to increase the apparatus in size.
In addition, while the aforementioned image display apparatus employs the relay lens
112
, the reflecting mirrors M
103
, M
104
and the like to form the relay system for red light, it is contemplated that a relay system formed of combined concave mirrors is used instead of the above relay system. The concave mirrors, however, are likely to suffer from aberration if light is incident thereon at a large angle, thereby possibly causing loss of light quantity or failing to achieve favorable display images.
SUMMARY OF THE INVENTION
It is an object of the present invention to propose a projection type image display apparatus which has a higher degree of freedom in arranging a color separation optical system with respect to an image light combination/projection optical system to allow the whole apparatus to be compact in size.
To achieve the aforementioned object, the present invention provides an image display apparatus comprising:
a condensing optical system for changing illumination light from a light source to converging light;
a color separation optical system having a color separation optical member for reflecting a color light component in a specific wavelength range of the converging light and transmitting color light components in the other wavelength ranges;
a plurality of image display device illuminated by a plurality of color light components separated by the color separation optical system, respectively,
a color combination optical system for combining image light components of a plurality of colors emanating from the plurality of image display devices; and
a projection optical system for projecting image light components combined by said color combination optical system on a surface on which projection is performed,
wherein the optical axis of light incident on the color separation optical member forms an angle smaller than 45 degrees with the normal to a light incident surface of the color separation optical member.
The aforementioned invention further has a relay optical system disposed in an optical path with a length larger than the lengths of the other optical paths of a plurality of optical paths of color light components from the light source to the plurality of image display device, wherein the relay optical system includes a reflecting member having a concave-shaped reflecting surface. An angle which an optical axis of light incident on the reflecting member forms with the normal to the reflecting surface passing through the intersection of the optical axis and the reflecting surface of the reflecting member is smaller than 45 degrees.
In addition, in the present invention, an angle which an optical axis of light incident on the reflecting member forms with the normal to the reflecting surface passing through the intersection of the optical axis and the reflecting surface of the reflecting member is smaller than an angle which an optical axis of light incident on the color separation optical member forms with the normal to the light incident surface of the color separation optical member.
To achieve the aforementioned object, the present invention provides an image display apparatus comprising:
a condensing optical system for changing illumination light from a light source to converging light;
a color separation optical system having a color separation optical member for reflecting a color light component in a specific wavelength range of the converging light and transmitting color light components in th
Kodama Hiroyuki
Okuyama Atsushi
Canon Kabushiki Kaisha
Dowling William
Morgan & Finnegan , LLP
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