Television – Video display – Projection device
Reexamination Certificate
1998-03-23
2001-08-28
Hsia, Sherrie (Department: 2614)
Television
Video display
Projection device
C348S751000, C348S756000, C348S766000, C348S761000
Reexamination Certificate
active
06281949
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the invention
This invention relates to a picture display method and apparatus for displaying a picture by spatially modulating the light outgoing from a light source and projecting the modulated light.
2. Description of the Related Art
Among picture display apparatus used for the purpose of appreciating a picture, there is a projection type picture display apparatus in which the light outgoing from a light source is spatially modulated by a picture display light valve for projection on a screen. This projection type picture display apparatus is classified into a front side projection type in which the picture is projected from the front side, such as a screen, and a back side projection type in which the picture is projected from the back side of the screen. As this projection type picture display apparatus, there is known such apparatus in which a white light source, including a discharge type xenon lamp, a metal halide lamp or a heat light emission type halogen lamp, is used as a light source, and a liquid crystal light valve is used as a picture display light valve.
FIG. 1
shows an illustrative structure of a conventional projection type picture display device. This projection type picture display device includes a lamp
201
emitting a white light beam, a UV-IR cutting filter, not shown, for cutting the ultraviolet light (UV light) and infrared light (IR light) of the light radiated from the lamp
201
, and a lens
202
for condensing the light passed through the UV-IR cutting filter. This projection type picture display device also includes a red color separating mirror
203
reflecting only the red wavelength component of the light condensed by the lens
202
and transmitting other wavelength components, and a green color separating mirror
204
for reflecting only the green wavelength component passed through the red color separating mirror
203
and transmitting other wavelength components. The projection type picture display device also includes a blue color separating mirror
205
for reflecting only the blue wavelength component passed through the green color separating mirror
204
and transmitting other wavelength components. As the lamp
201
, a white light source, such as a xenon lamp, a metal halide lamp or a halogen lamp, is used. As the mirrors
203
to
205
, dichroic mirrors are used.
The projection type picture display device also includes a cubic-shaped synthesis prism
210
, arranged for causing the green light reflected by the green color separating mirror
204
to fall on a surface
210
G of the synthesis prism
210
, and a reflection mirror
206
for causing the red light reflected by the red color separating mirror
203
to fall on a surface
210
R of the synthesis prism perpendicular to the surface
210
G. The projection type picture display device also includes a reflection mirror
207
for reflecting the blue light reflected by the blue color separating mirror
205
so as to fall on a surface
210
B of the synthesis prism parallel to the surface
210
R of the synthesis prism
210
.
The projection type picture display device also includes a red picture display light valve
211
R arranged between the reflection mirror
206
and the surface
210
R of the synthesis prism
210
, and a green picture display light valve
211
G arranged between the green color separating mirror
204
and the surface
210
B of the synthesis prism
210
. The projection type picture display device also includes a blue picture display light valve
211
B arranged between the reflection mirror
207
and the surface
210
B of the synthesis prism
210
, and a projection lens
212
arranged facing a surface
210
A parallel to the surface
210
G of the synthesis prism
210
. The light valves
211
R,
211
G and
211
B may, for example, be rectangular in shape. The light valves
211
R,
211
G and
211
B are adapted for being driven on the basis of red picture signals, green picture signals and blue picture signals, respectively.
The projection type picture display device also includes a red field lens
212
R arranged between the reflection mirror
206
and the red picture display light valve
211
R, and a green field lens
212
G arranged between the green color separating mirror
204
and the green picture display light valve
211
G. The projection type picture display device also includes a blue field lens
212
B arranged between the reflection mirror
207
and the blue picture display light valve
211
B, and an optical path length adjustment lens
213
arranged between the blue color separating mirror
204
and the blue color reflection mirror
205
. The projection type picture display device also includes an optical path length adjustment lens
214
arranged between the blue color separating mirror
205
and the reflection mirror
207
.
The synthesis prism includes a reflecting mirror
210
r
for reflecting only the red light incident from the surface
210
R towards the surface
210
R, and a reflecting surface
210
B for reflecting only the blue light incident from the surface
210
B towards the surface
210
A.
The above-mentioned components of the projection type picture display apparatus are held by a suitable holder and installed in this state in a casing
214
.
In the projection type picture display apparatus, shown in
FIG. 1
, the white light radiated from the lamp
201
is freed by the UV-IR cutting filter of redundant wavelength light beams, that is the UV and IR light beams, and condensed by the lens
202
so as to fall on the red color separating mirror
203
. Of the light incident on the red color separating mirror
203
, the red light is reflected by the red color separating mirror
203
. The reflected red light is further reflected by the reflection mirror
206
to pass via red field lens
212
R through the red picture display light valve
211
R and is spatially modulated based on red picture signals so as to fall on the synthesis prism
210
.
Of the light incident on the red color separating mirror
203
, the light other than the red light is transmitted through the red color separating mirror
203
to fall on the green color separating mirror
204
. Of the light incident on the green color separating mirror
204
, the green light is reflected by the green color separating mirror
204
and transmitted via green field lens
212
G through the green picture display light valve
211
G and is spatially modulated based on red picture signals to fall on the synthesis prism
210
.
Of the light incident on the green color separating mirror
204
, the light other than the green light is transmitted through the green color separating mirror
204
to fall on the blue color separating mirror
205
. Of the light incident on the blue color separating mirror
205
, the blue light is reflected by the blue color separating mirror
205
, reflected by the reflection mirror
207
through the optical path length adjustment lens
214
and transmitted via blue field lens
212
B through the blue picture display light valve
211
B and is spatially modulated based on blue picture signals to fall on the synthesis prism
210
.
The light beams of respective colors, modulated by the light valves
211
R,
211
G and
211
B, are synthesized by the synthesis prism
210
so as to be then radiated from the surface
210
A to fall on the projection prism
212
. The light beams are then projected to an enlarged scale on a transmission or reflection projection type picture display apparatus type screen
213
.
The above-described conventional projection type picture display apparatus has a defect that, since the white light source (lamp), such as xenon lamp, metal halide lamp or halogen lamp, used as a light source, generally undergoes significant chronological changes, and is of short service life, the picture tends to become dark, while the lamp tends to be used up, such that the displayed picture tends to become dark or the lamp has to be exchanged during display of the picture.
On the other hand, the light beam radiated from the white light source used in the co
Akimoto Osamu
Hashimoto Shunichi
Matsui Takeshi
Tanaka Yoshinori
Yoshida Takuji
Frommer William S.
Frommer Lawrence & Haug LLP.
Hsia Sherrie
Smid Dennis M.
Sony Corporation
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