U.S. patent application number 09/751499 was filed with the patent office on 2002-07-04 for projection display with color separation/synthesizing prism unit.
This patent application is currently assigned to PROKIA TECHNOLOGY CO., LTD.. Invention is credited to Chan, Sheng-Hsiung, Chuang, Fu-Ming.
Application Number | 20020085289 09/751499 |
Document ID | / |
Family ID | 25022252 |
Filed Date | 2002-07-04 |
United States Patent
Application |
20020085289 |
Kind Code |
A1 |
Chuang, Fu-Ming ; et
al. |
July 4, 2002 |
PROJECTION DISPLAY WITH COLOR SEPARATION/SYNTHESIZING PRISM
UNIT
Abstract
A projection display includes a light source for generating a
beam output that contains first, second and third color components,
a color separation/synthesizing prism unit having a color
separation part for separating the beam output from the light
source into the first, second and third color components that exit
the prism unit in three different directions, and first, second and
third light modulators for modulating the first, second and third
color components that exit from the color separation part. The
prism unit further has a color synthesizing part that receives the
modulated first, second and third color components from the light
modulators and that synthesizes the modulated first, second and
third color components so as to form an output beam. A projection
lens receives the output beam from the color synthesizing part, and
is used to project a color image. The first, second and third color
components have equal optical path lengths measured from the light
source to the respective light modulator. The first, second and
third color components further have equal optical path lengths
measured from the respective light modulator to the projection
lens.
Inventors: |
Chuang, Fu-Ming; (Hsin-Chu
Hsien, TW) ; Chan, Sheng-Hsiung; (Hsin-Chu Hsien,
TW) |
Correspondence
Address: |
MERCHANT & GOULD
3200 IDS Center
80 South 8th Street
Minneapolis
MN
55402-2215
US
|
Assignee: |
PROKIA TECHNOLOGY CO., LTD.
|
Family ID: |
25022252 |
Appl. No.: |
09/751499 |
Filed: |
December 29, 2000 |
Current U.S.
Class: |
359/634 ;
359/625 |
Current CPC
Class: |
G02B 27/145
20130101 |
Class at
Publication: |
359/634 ;
359/625 |
International
Class: |
G02B 027/14; G02B
027/10 |
Claims
We claim:
1. A projection display comprising: a light source for generating a
beam output that contains first, second and third color components;
a color separation/synthesizing prism unit having a color
separation part for separating the beam output from said light
source into the first, second and third color components that exit
said prism unit in three different directions; first, second and
third light modulator means, disposed adjacent to said prism unit,
for modulating the first, second and third color components that
exit from said color separation part of said prism unit; said prism
unit further having a color synthesizing part that receives the
modulated first, second and third color components from said first,
second and third light modulator means and that synthesizes the
modulated first, second and third color components so as to form an
output beam; and a projection lens for receiving the output beam
from said color synthesizing part of said prism unit, and for
projecting a color image; wherein the first, second and third color
components have equal optical path lengths measured from said light
source to the respective one of said first, second and third light
modulator means; and wherein the first, second and third color
components have equal optical path lengths measured from the
respective one of said first, second and third light modulator
means to said projection lens.
2. The projection display of claim 1, wherein said prism unit
includes first, second and third prisms.
3. The projection display of claim 2, wherein the first, second and
third color components exit said color separation part of said
prism unit at said first, second and third prisms,
respectively.
4. The projection display of claim 3, wherein said color separation
part is a lower part of said first, second and third prisms, and
said color synthesizing part is an upper part of said first, second
and third prisms.
5. The projection display of claim 1, wherein each of said first,
second and third light modulator means includes a transmissive
light valve.
6. The projection display of claim 5, wherein said color
synthesizing part is vertically disposed relative to said color
separation part of said prism unit.
7. The projection display of claim 6, wherein each of said first,
second and third light modulator means further includes: a first
mirror for reflecting the respective one of the first, second and
third color components from said color separation part of said
prism unit vertically; and a second mirror spaced apart vertically
from said first mirror, said light valve being disposed between
said second mirror and said color synthesizing part of said prism
unit, said second mirror reflecting the respective one of the
first, second and third color components from said first mirror to
said light valve.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The invention relates to a projection display, more
particularly to a single-lens type projection display with a color
separation/synthesizing prism unit.
[0003] 2. Description of the Related Art
[0004] In a conventional projection display, white light is
separated into first, second and third color components that are
subsequently and respectively modulated by a corresponding light
valve. The modulated color components are then synthesized to form
an output beam prior to reception by a projection lens for
projecting a color image on a display screen.
[0005] U.S. Pat. No. 5,644,432 discloses a three-prism color
separator for use with three reflective light valves. As shown in
FIG. 1, according to this patent, white light 10 from a polarizing
cube 11 is separated into red, green and blue color components by
an optical beam splitter 12 that includes first, second and third
prisms 121, 122, 123. The three color components are directed by
the three prisms 121, 122, 123 to three reflective light valves
131, 132, 133 for light modulation. Thereafter, the light-modulated
color components retrace their paths through the three prisms 121,
122, 123 so as to be synthesized to form an output beam that is to
be received by a projection lens (not shown) via the polarizing
cube 11 for projecting a color image.
[0006] FIG. 2 illustrates another conventional projection display
2. The projection display 2 includes a light source 21 and a light
filter 22 downstream of the light source 21 for removing
ultra-violet rays and infra-red rays from a light beam generated by
the light source 21 to obtain a white beam output. First and second
beam splitters 231, 232 split the white beam output from the light
filter 22 into first, second and third color components 201, 202,
203, such as red, green and blue color components. The first and
second color components 201, 202 from the second beam splitter 232
are modulated by first and second transmissive light valves 251,
252, respectively. The third color component 203 from the first
beam splitter 231 is reflected by a mirror 241 prior to modulation
by a third transmissive light valve 253. After modulation, the
three color components 201, 202, 203 are synthesized using two beam
splitters 233, 234 and a mirror 242 prior to reception by a
projection lens 26 for projecting an image on a display screen (not
shown). Particularly, the first color component 201 is reflected
once by the mirror 242 before passing through the beam splitter
233. The second color component 202 is reflected once by each of
the beam splitters 234, 233. The third color component 203 passes
through the beam splitter 234 before being reflected by the other
beam splitter 233.
[0007] Because the three color components 201, 202, 203 either pass
through or are reflected by the beam splitters 234, 233 and the
mirror 242 in different ways during color synthesizing, minor
differences inherent in the different optical paths can result in
image distortion.
SUMMARY OF THE INVENTION
[0008] Therefore, the main object of the present invention is to
provide a single-lens type projection display which utilizes a
color separation/synthesizing prism unit to ensure uniformity of
the optical path lengths for the different color components during
color separation and color synthesizing to minimize the occurrence
of image distortion.
[0009] Another object of the present invention is to provide a
single-lens type projection display with a color
separation/synthesizing prism unit and which has light modulators
that use transmissive light valves.
[0010] According to this invention, a projection display
comprises:
[0011] a light source for generating a beam output that contains
first, second and third color components;
[0012] a color separation/synthesizing prism unit having a color
separation part for separating the beam output from the light
source into the first, second and third color components that exit
the prism unit in three different directions;
[0013] first, second and third light modulator means, disposed
adjacent to the prism unit, for modulating the first, second and
third color components that exit from the color separation part of
the prism unit;
[0014] the prism unit further having a color synthesizing part that
receives the modulated first, second and third color components
from the first, second and third light modulator means and that
synthesizes the modulated first, second and third color components
so as to form an output beam; and
[0015] a projection lens for receiving the output beam from the
color synthesizing part of the prism unit, and for projecting a
color image.
[0016] The first, second and third color components have equal
optical path lengths measured from the light source to the
respective one of the first, second and third light modulator
means. The first, second and third color components further have
equal optical path lengths measured from the respective one of the
first, second and third light modulator means to the projection
lens.
[0017] Preferably, the prism unit includes first, second and third
prisms, and the first, second and third color components exit the
color separation part of the prism unit at the first, second and
third prisms, respectively.
[0018] In the preferred embodiment, the color synthesizing part is
vertically disposed relative to the color separation part of the
prism unit. Each of the first, second and third light modulator
means includes a transmissive light valve, a first mirror for
reflecting the respective one of the first, second and third color
components from the color separation part of the prism unit
vertically, and a second mirror spaced apart vertically from the
first mirror. The light valve is disposed between the second mirror
and the color synthesizing part of the prism unit. The second
mirror reflects the respective one of the first, second and third
color components from the first mirror to the light valve.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] Other features and advantages of the present invention will
become apparent in the following detailed description of the
preferred embodiment with reference to the accompanying drawings,
of which:
[0020] FIG. 1 illustrates a conventional projection display
disclosed in U.S. Pat. No. 5,644,432;
[0021] FIG. 2 illustrates another conventional projection display
that utilizes transmissive light valves;
[0022] FIG. 3 is a schematic view showing the preferred embodiment
of a single-lens type projection display according to this
invention;
[0023] FIG. 4 is a perspective view of the preferred
embodiment;
[0024] FIG. 5 is a schematic view illustrating a color separation
operation of the preferred embodiment; and
[0025] FIG. 6 is a schematic view illustrating a color synthesizing
operation of the preferred embodiment.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0026] Referring to FIG. 3, the preferred embodiment of a
projection display 3 according to the present invention is shown to
comprise a color separation/synthesizing prism unit 4. A white beam
output 30 from a light source 36 passes through a focusing lens 31
before reaching a lower color separation part 401 of the prism unit
4. The color separation part 401 separates the white beam output 30
into first, second and third color components 301, 302, 303, such
as red, green and blue color components. After exiting the color
separation part 401 in three different directions, the first,
second and third color components 301, 302, 303 are processed by a
corresponding light modulator that includes first and second
mirrors 321, 331, 322, 332, 323, 333 and a transmissive light valve
341, 342, 343. Particularly, the first mirror 321, 322, 323 is
disposed inclinedly to reflect the respective one of the first,
second and third color components 301, 302, 303 from the color
separation part 401 vertically upward. The second mirror 331, 332,
333 is spaced apart vertically from the corresponding first mirror
321, 322, 323. The light valve 341, 343, 343 is disposed between
the corresponding second mirror 331, 332, 333 and the prism unit 4.
The second mirror 331, 332, 333 is disposed inclinedly to reflect
the respective one of the first, second and third color components
301, 302, 303 to the corresponding light valve 341, 342, 343. The
modulated first, second and third color components 301, 302, 303
from the light valves 341, 342, 343 enter an upper color
synthesizing part 402, which is vertically disposed relative to the
color separation part 401, of the prism unit 4. The color
synthesizing part 402 synthesizes the light-modulated color
components so as to form an output beam that is provided to a
projection lens 35 for projecting a color image on a display screen
(not shown).
[0027] Referring to FIGS. 4 to 6, the prism unit 4 includes first,
second and third prisms 411, 412, 413. A lower part of the first,
second and third prisms 411, 412, 413 serves as the color
separation part 401 of the prism unit 4. An upper part of the
first, second and third prisms 411, 412, 413 serves as the color
synthesizing part 402 of the prism unit 4. The first, second and
third prisms 411, 412, 413 are configured so as to ensure that the
color components 301, 302, 303 have equal optical path lengths
measured from the light source 36 to the respective one of the
light valves 341, 342, 343, and that the color components 301, 302,
303 have equal optical path lengths measured from the respective
one of the light valves 341, 342, 343 to the projection lens 35. A
three-prism color separation arrangement having identical optical
path lengths for three color components into and out of three
prisms has been disclosed in U.S. Pat. No. 5,644,432 described
beforehand. With reference to FIGS. 4 and 5, at the color
separation part 401 of the prism unit 4, the first color component
301 is reflected by a first surface 415 to a second surface 414 of
the first prism 411, and is further reflected by the second surface
414 so as to exit the first prism 411 at a third surface 416 of the
latter. The second and third color components 302, 303 pass through
the first surface 415 of the first prism 411, a clearance 410
formed between the first and second prisms 411, 412, and enter the
second prism 412 via a first surface 417 of the latter. The second
color component 302 is reflected by a second surface 418 back to
the first surface 417 of the second prism 412, and is further
reflected by the first surface 417 so as to exit the second prism
412 at a third surface 419 of the latter. The third color component
303 passes through the second surface 418 of the second prism 412,
enters the third prism 413, and is reflected by a first surface 420
of the third prism 413 so as to exit the third prism 413 at a
second surface 421 of the same. As such, the first, second and
third color components 301, 302, 303 exit the color separation part
401 of the prism unit 4 at the first, second and third prisms 411,
412, 413, respectively.
[0028] With reference to FIGS. 4 and 6, after being reflected by
the first and second mirrors 321, 331, 322, 332, 323, 333 and
modulated by the light valve 341, 342, 343 of the corresponding
light modulator, the light-modulated first, second and third color
components 301, 302, 303 enter the upper part of the first, second
and third prisms 411, 412, 413 in three different directions for
color synthesizing. Since the paths traveled by the three color
components 301, 302, 303 through the first, second and third prisms
411, 412, 413 during color synthesizing are simply the opposite of
those traveled by the three color components 301, 302,303 through
the first, second and third prisms 411, 412, 413 during color
separation, a detailed description of the same will be dispensed
with herein for the sake of brevity. The color-synthesized output
beam from the prism unit 4 is subsequently provided to the
projection lens 35 for projecting a color image on the display
screen (not shown).
[0029] Because the three color components 301, 302, 303 are
separated and then synthesized using the same prism unit 4,
differences in the optical paths of the color components 301, 302,
303 during color separation and color synthesizing can be minimized
to avoid the occurrence of image distortion.
[0030] While the present invention has been described in connection
with what is considered the most practical and preferred
embodiment, it is understood that this invention is not limited to
the disclosed embodiment but is intended to cover various
arrangements included within the spirit and scope of the broadest
interpretation so as to encompass all such modifications and
equivalent arrangements.
* * * * *