Optical: systems and elements – Prism – With reflecting surface
Reexamination Certificate
2001-08-06
2004-07-06
Cherry, Euncha (Department: 2872)
Optical: systems and elements
Prism
With reflecting surface
C359S837000
Reexamination Certificate
active
06760168
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a TIR (Total Internal Reflection) prism system for DMD(Digital Micromirror Device) and a projector adopting the same, and particularly, to a TIR prism system for DMD and a projector adopting the same which reduces the loss of incident light, and has a small size and light weight.
2. Description of the Background Art
A projector which is used frequently nowadays is a device for displaying an image using a display element such as an LCD (Liquid Crystal Display) element or a DMD (Digital Micromirror Device), and because it has a small size and light weight, it is distributed widely. Herein, the LCD element has a function of light valve display element, and the DMD has a function of light switch display element.
The DMD is a projection type display element developed by TI (Texas Instruments), US so as to control the light in a DLP (Digital Light Processing) system, and it is a microchip which is made such that a plurality of micromirrors (or micro aluminum mirrors) of 16 &mgr;m are planted on a silicon wafer with a 1 &mgr;m interval. And a thousand millions of micromirrors may be planted on the microchip.
The thousands millions of micromirrors planted on the microchip are able to display image on a screen by being controlled locations (two modes of on and off) so as to reflect the incident light within the angle of +10° through −10°. Herein, the strength of the light outputted from the DMD is subordinated by the outputting time of the light as a certain angle, and therefore if the outputting time of the light as a certain angle is long, the strength of the light becomes stronger.
General operating characteristics of the DMD will be described as follows.
FIG. 1
is a block diagram showing general operating characteristics of the projector using the DMD, as shown therein, the projector comprises a light source
9
such as a lamp, a DMD
10
receiving the light outputted from the light source
9
and reflecting the incident light as a certain angle according to a certain signal, a projection lens
11
throwing the light reflected from the DMD
10
on a certain screen
15
, and an absorption plate
13
for absorbing the light reflected from the DMD
10
at a certain angle but is not incident upon the projection lens
11
.
Herein, the DMD
10
includes a blackboard
1
, a plurality of electrodes
3
provided on the blackboard
1
, digital micromirrors
5
receiving the light outputted from the light source
9
and reflecting the light at a certain angle, and a supporting member
7
for supporting the digital micromirrors
5
.
The plurality of electrodes
3
generate an electrostatic field by a voltage signal inputted from outside so as to support movements of the supporting member
7
. Then the digital micromirrors
5
of tiny square shape of 16 &mgr;m attached on the supporting member
7
are rotated within the angle range of ±10°, and reflects the light inputted from the light source
9
to the projection lens
11
or to the absorption plate
13
in accordance with the rotating angle. The projection lens
11
receives the light reflected from the DMD
10
and projects the light to the screen
15
to display the image thereon.
The operation of the projector constructed as above will be described in more detail as follows.
The digital micromirrors
5
are slanted at a certain initial angle against the plane, when the light outputted from the light source
9
is projected to the micromirrors
5
, the digital micromirrors
5
does not reflect the light to the projection lens
11
, but reflects to the absorption plate
13
. Therefore, the screen
15
becomes black.
And, when a voltage signal is inputted to the plurality of electrodes
3
disposed on the blackboard
1
, the plurality of electrodes
3
generates the electrostatic field so as to rotate the supporting member
7
within a certain angle range of +10° through −10°. At that time, the digital micromirrors
5
attached on the supporting member
7
are rotated with the supporting member
7
, and therefore the light inputted into the digital micromirrors
5
is reflected to the projection lens
11
. When the light inputted into the projection lens
11
is reflected to the screen
15
through the projection lens
11
, the screen
15
becomes white.
Therefore, when the voltage signal from outer electric power source to the plurality of electrodes
3
, the electrodes
3
generate the electrostatic field so as to rotate the supporting member
7
within the angle of ±10°. Accordingly, the digital micromirrors
5
projects the light outputted from the light source
9
to the screen
15
. At that time, the digital micromirrors
5
are rotated at a high speed (on/off operations) according to the inputted motion image signal.
The projector using the DMD of operation characteristics can be divided into a projector of direct reflection type and a projector of TIR prism type, according to input/output type of the light to the DMD.
FIG. 2
is a perspective view showing a projector of direct reflection type for DMD according to the conventional art. As shown therein, the projector includes a light source
19
, a color wheel
17
for changing the color of the light outputted from the light source
19
to red, green, and blue and outputting the light, and a DMD
20
receiving the light outputted from the color wheel
17
and reflecting the light to a screen
23
. Herein, the DMD
20
is made as a chip and attached on a board
21
.
The projector like above displays image on the screen
23
by reflecting the light outputted from the light source
19
using DMD
20
. Herein, the color wheel
17
is a wheel having an element which changes the color of the light into red, green, and blue, and outputs it, and is rotated at a certain rotating speed.
However, the projector of direct reflection type is not able to reduce the size of an optical system, and therefore a projector using an optical system such as the TIR prism is developed.
FIG. 3A
is a plane view showing a projector using the TIR prism system for DMD according to the conventional art, and
FIG. 3B
is a perspective view of FIG.
3
A. As shown therein, the projector includes a light source
25
; a color Wheel
27
changing the color of the light inputted from the light source
25
into red, green, and blue, and outputting the changed color; a stick lens
29
receiving the light outputted from the color wheel
27
and outputting a light of a certain intensity; a first condensing lens
30
for collecting the light outputted from the stick lens
29
and reducing a diameter of the light; a mirror
31
for reflecting the light outputted from the first condensing lens
30
at a certain angle; a second condensing lens
32
for collecting the light outputted from the mirror
31
and outputting the light; a TIR prism system
33
receiving the light outputted from the second condensing lens
32
and outputting the light according to a certain image signal; a DMD
35
controlling the light proceeded inside the TIR prism system
33
; and a projection lens
37
receiving the light outputted from the TIR prism system
33
and outputting it to a certain screen
38
. Herein, the TIR prism system
33
for DMD
35
will be described in more detail.
FIG. 4A
is a perspective view showing the TIR prism system
33
shown in
FIG. 3
, and
FIG. 4B
is a side view of FIG.
4
A. As shown therein, the TIR prism system
35
includes an incident prism
33
-
1
receiving the light proceeded from the light source
25
on a certain position P
1
on a surface IS
5
and total projecting the light (IS
4
;P
2
and IS
2
;P
3
); and an outputting prism
33
-
2
coupled to the incident prism
33
-
1
at a certain angle, receiving the light transmitted (OS
4
; P
3
) from the incident prism
33
-
1
, total reflecting the light inside (OS
1
; P
4
and OS
4
;P
5
) without total reflecting when the light is inputted, and then outputting the light (OS
2
; P
6
). That is, the incident prism
33
-
1
and the outputtin
Cherry Euncha
Fleshner & Kim LLP
LG Electronics Inc.
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