Projection apparatus

Optics: image projectors – Composite projected image – Multicolor picture

Reexamination Certificate

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Reexamination Certificate

active

06280036

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a projection apparatus and, more particularly, to a projection liquid crystal projector for enlarging and projecting, on a screen or the like, image information displayed on an optical modulation device such as a color liquid crystal panel.
2. Related Background Art
A variety of conventional color liquid crystal projectors have been proposed as optical modulation devices to display image information on liquid crystal panels and enlarge and project the image information on screens.
FIGS. 9 and 10
show a projection liquid crystal projector described in Japanese Utility Model Publication No. 5-950.
Referring to
FIGS. 9 and 10
, a case
1
is divided into two chambers through side walls
4
and
5
. A light source
9
is arranged in a rear-side chamber
2
, and a liquid crystal display drive unit is arranged in a front-side chamber
3
. Openings
6
and
7
are formed at the central portions of the side walls
4
and
5
. Transparent plates
6
a
and
7
a
made of heat-resistant glass are fitted in the openings
6
and
7
. A plurality of vent holes
8
are formed in the outer surface of the case between the side walls
4
and
5
.
The light source
9
is located at a position opposing the openings
6
and
7
of the side walls
4
and
5
and comprises a lamp
10
and a reflecting mirror
11
. The lamp
10
is connected to a power circuit board
12
having a power transformer
13
and a transformer coil
14
through lead wires
15
. A polarizing separation prism
16
is arranged in front of the light source
9
to separate light reflected by the reflecting mirror
11
into S- and P-polarized light components. The P-polarized light component passes through the polarizing separation prism
16
and enters a liquid crystal panel
19
of a liquid crystal display drive unit in the front-side chamber
3
. The S-polarized light component is guided to the side surface of the polarizing separation prism
16
and emerges from an exit port
17
.
Heat dissipation slits
18
are formed in the upper, lower, and side surfaces of the rear-side chamber
2
containing the light source
9
. Heat from the lamp
10
is dissipated through the heat dissipation slits
18
and the exit port
17
.
A display panel cooler
20
through which the P-polarized light component pass is located at a position opposing the opening
7
in the front-side chamber
3
which accommodates the liquid crystal display drive unit. The P-polarized light component of the beam from the lamp
10
in the light source
9
passes through the display panel cooler
20
and is incident on the liquid crystal panel
19
. The liquid crystal panel
19
is connected to a main circuit board
23
through a panel drive circuit board
24
made of a flexible board. A Fresnel lens
21
is spaced apart from the front surface of the liquid crystal panel
19
. A projection lens
22
for projecting the beam focused by the Fresnel lens
21
is hold on the front surface side of the case
1
at a position in front of the Fresnel lens
21
. Heat dissipation slits
25
are formed in the front and upper surfaces of the front-side chamber
3
incorporating the above components, as in the rear-side chamber
2
.
An open space is formed between the liquid crystal panel
19
and the Fresnel lens
21
in the conventional liquid crystal projector described above. The heat dissipation slits
25
formed in the case
1
prevent dust from entering into the apparatus. Since the drive voltage generates static electricity on the surface of the liquid crystal panel
19
driven by the panel drive circuit board
24
, the dust is attracted to the surface of the liquid crystal panel
19
. As a result, an image enlarged and projected by the projection lens
22
through the Fresnel lens
21
contains an enlarged image of dust, so a high-quality image cannot be obtained.
The heat dissipation slits
18
are also formed in the rear-side chamber
2
for the light source
9
as in the heat dissipation slits
18
, and dust enters through the heat dissipation slits
18
. The dust attaches to the reflecting mirror
11
, the polarizing separation prism
16
, and the like to greatly decrease the brightness of the projector.
SUMMARY OF THE INVENTION
The present invention has been made in consideration of the conventional problems described above, and has as its object to provide a projection apparatus capable of displaying an image by eliminating or reducing the influence of dust.
In order to achieve the above object, there is provided a projection apparatus for projecting image information on a display surface such as a screen, comprising a dust preventive structure (prevention from attaching a foreign substance) of dusting main apparatus members such as an optical modulation device.
According to an aspect of the present invention, there is provided a projection apparatus comprising a display device, a projection optical system for projecting, on a display surface, an image obtained by the display device, and preventive means for preventing a foreign substance from attaching to a surface of the display device.
This projection apparatus is a single-plate monochrome or three-plate full-color image projection apparatus in which the projection optical system comprises a field lens and a projection lens in the order named from the display. device side, and the preventive means comprises sealing means for sealing a space formed between the field lens and the display device.
The present invention discloses the following arrangement. The preventive means comprises the field lens, a lens barrel for holding the field lens, and a seal ring.
The present invention discloses the following arrangements. The display device comprises three liquid crystal panels for forming red, green, and blue images. The projection optical system comprises a projection lens and three field lenses located in front of one of the three liquid crystal panels. The projection lens is one lens system shared by three pairs of liquid crystal panels and field lenses. The preventive means has sealing structures for sealing the spaces between the field lenses and the display device. Each sealing structure comprises the field lens, a lens barrel for holding the field lens, and a seal ring.
The present invention further comprises an illumination optical system for supplying red, green, and blue beams which illuminate the three liquid crystal panels. The illumination optical system comprises a trimming filter for each of red, green, and blue.
The present invention discloses the following arrangement. The trimming filter is located to seal the space between the field lens and itself.
According to another aspect of the present invention, there is provided a projection apparatus in which color separation means color-separates a beam from light source means into a plurality of color beams, lens means focuses the color-separated beams, first deflection means is arranged near-the focal position to irradiate optical modulation devices with the focused beams through field lenses, and second deflection means and a projection optical system project image information based on each optical modulation device to a desired position, wherein dusting structures are respectively arranged between the optical modulation devices corresponding to the plurality of color beams and the field lens opposing the optical modulation devices. Dust can be prevented from attaching to the optical modulation devices, and therefore a high-quality image free from the influence of dust can be projected.
According to still another aspect of the present invention, there is provided a projection apparatus in which color separation means color-separates a beam from light source means into a plurality of color beams, lens means focuses the color-separated beams, first deflection means is arranged near the focal position to irradiate optical modulation devices with the focused beams through field lenses, and second deflection means and a projection optical system project image information

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