Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2002-05-29
2003-09-16
Adams, Russell (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S020000, C353S052000, C349S009000, C359S246000, C359S249000, C359S259000, C359S490020
Reexamination Certificate
active
06619803
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projector apparatus for displaying an enlarged computer image or video image.
2. Related Background Art
In recent years, image display apparatuses such as liquid crystal projectors are required to improve brightness.
FIG. 15
shows the arrangement of a conventional projecting image display apparatus (projector apparatus).
Referring to
FIG. 15
, white light emitted from a light source section
101
of an ultrahigh-pressure mercury-vapor lamp is reflected by a reflector
102
and transmitted through fly-eye lenses
103
and
104
. The direction of polarization is aligned through a PS conversion element
105
by a mirror which separates light into p-polarized light and s-polarized light and a &lgr;/2-plate which changes the polarization direction. The light that emerges from the PS conversion element
105
passes through a condenser lens
106
and the like. After that, a red-band light component is transmitted through a dichroic mirror DM
101
. Green- and blue-band light components are reflected by the dichroic mirror DM
101
. The blue-band light component is transmitted through a dichroic mirror DM
102
. The green-band light component is reflected by the dichroic mirror DM
102
. With this arrangement, the illumination light is separated into the light components in the red, green, and blue bands.
Each color light component becomes incident on a corresponding one of liquid crystal display elements
109
R,
109
G, and
109
B and is modulated. These color light components are synthesized by a dichroic prism
111
and enlarged and projected onto a projection surface by a projecting lens
112
.
Each dolor band will be described in more detail. The red-band light component transmitted through the dichroic mirror DM
101
is changed in its optical path by 90° by a reflecting mirror M
101
, passes through a field lens
107
R, becomes incident on an incident-side polarizing plate
108
RI and liquid crystal display element
109
R, and is modulated here.
The modulated red-band light component strikes an exit-side polarizing plate
110
RO and dichroic prism
111
in this order. The optical path is changed by 90° by the dichroic prism
111
. Then, the light component becomes incident on the projecting lens
112
. The dichroic prism
111
is formed by bonding four prisms with adhesive such that it has an almost cross-shaped wavelength selection reflecting layer.
On the other hand, the green- and blue-band light components reflected and changed in their operation paths by 90° by the dichroic mirror DM
101
become incident on the dichroic mirror DM
102
. The dichroic mirror DM
102
has a characteristic for reflecting a green-band light component G. Hence, the green-band light component is reflected and changed in its optical path by 90° by the dichroic mirror DM
102
, transmitted through a field lens
107
G, becomes incident on an incident-side polarizing plate
108
GI and liquid crystal display element
109
G, and is modulated here.
The modulated green-band light component strikes an exit-side polarizing plate
110
GO and dichroic prism
111
in this order, passes through the dichroic prism
111
, and becomes incident on the projecting lens
112
.
The blue-band light component transmitted through the dichroic mirror DM
102
passes through a condenser lens
113
, relay lens
114
, reflecting mirrors M
102
and M
103
, and field lens
107
B, becomes incident on an incident-side polarizing plate
108
BI and liquid crystal display element
109
B, and is modulated here.
The modulated blue-band light component strikes an exit-side polarizing plate
110
BO and dichroic prism
111
in this order, is changed in its optical path by 90° by the dichroic prism
111
, and becomes incident on the projecting lens
112
.
The light components in the respective color bands, which are incident on the projecting lens
112
in the above-described manner, are projected onto the projection surface and displayed as an enlarged image.
In the above-described conventional projecting image display apparatus, a polarizing plate is normally formed by bonding a film-shaped polarizer b to transparent substrate a, as shown in
FIG. 16
, such that a predetermined polarizing characteristic can be exhibited. Both the incident-side polarizing plates and the exit-side polarizing plates are formed by bonding predetermined polarizers to transparent substrates, which have identical shapes independently of colors, for the respective color bands.
An incident-side polarizing plate absorbs light having a rotating polarization axis and converts the light into heat to align the polarization direction of light that becomes incident on a liquid crystal display element. In an exit-side polarizing plate, when the display color is black, the polarization axis of the polarizing plate is perpendicular to the amplitude of light emerging from a liquid crystal display element. Since all light components are absorbed and converted into heat, the heat load is very high.
If the aperture ratio of a liquid crystal display element is low, and the light amount of a lamp to be used is small, transparent substrates, e.g., glass substrates (the heat conductivity is about 1.2 W/(m·K)) having identical shapes suffice, as in the prior art.
Recently, 1.3 inches liquid crystal display elements have an aperture ratio of 60% even though the number of pixels is about 770,000. Some liquid crystal display elements improve the brightness of a projected image by increasing the power consumption of a lamp. Liquid crystal display elements themselves are also becoming compact.
The heat load changes for each color band and also depending on whether the polarizing plate is on the incident side or exit side. For example, when color purity of at least one of a plurality of color bands should be changed, the heat load on the incident- or exit-side polarizing plate of a specific color band increases. For this reason, the heat load on some incident- or exit-side polarizing plates increases, resulting in degradation in performance of the polarizing plate.
To solve the problem of heat load on a polarizing plate, sapphire whose heat conductivity (42 W/(m·K)) is about 40 times higher than that of a transparent glass substrate is used as a substrate to which a polarizer is bonded, as is proposed in Japanese Patent Application Laid-Open No. 11-231277.
However, sapphire is expensive. Use of sapphire is preferably avoided as much as possible from the viewpoint of cost. Especially, a 3-plate projecting image display apparatus as shown in
FIG. 15
uses a total of six polarizing plates on the incident and exit sides. Since a plurality of sapphire substrates are normally required, the cost largely increases.
In addition, to increase the cooling efficiency by a cooling fan, the power consumption of the cooling fan increases, or noise becomes large.
SUMMARY OF THE INVENTION
The present invention has been made to solve the above problems, and has as its object to provide a projector apparatus which can reduce cost while reliably preventing any degradation in image quality due to heat by effectively transmitting heat of a polarizing plate to a transparent substrate in correspondence with the heat load on the polarizer and efficiently radiating the heat by the transparent substrate.
In order to achieve the above object, according to the present invention, there is provided a projector apparatus comprising:
a color separation optical system which separates illumination light into a plurality of color light components;
a plurality of image forming panels illuminated with the plurality of color light components, respectively;
a color synthesis optical system which synthesizes the light components from the plurality of image forming panels illuminated;
a projecting optical system which projects light from the color synthesis optical system; and
transparent substrates each arranged on at least one of incident and exit surface sides of the plurality of image forming panels, each of the transparent substrates holdi
Adams Russell
Canon Kabushiki Kaisha
Koval Melissa J
Morgan & Finnegan , LLP
LandOfFree
Color projector apparatus having means for preventing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color projector apparatus having means for preventing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color projector apparatus having means for preventing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3008286