Optics: image projectors – Color filter
Reexamination Certificate
2001-12-27
2003-11-11
Adams, Russell (Department: 2851)
Optics: image projectors
Color filter
C353S030000, C353S031000, C353S033000, C353S081000, C359S885000, C359S887000
Reexamination Certificate
active
06644815
ABSTRACT:
This application claims the benefit of the Korean Application No. P2000-85798 filed on Dec. 29, 2000, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a total reflection prism and a projector with the same.
2. Background of the Related Art
The projector enlarges, and projects a small picture by using a projection lens to a large sized screen, to display a large sized picture. The projector is provided with a color wheel for splitting a red color ‘R’, a green color ‘G’, and a blue color ‘B’ on time basis for reproducing colors. The color wheel is rotated by motor for splitting the colors in succession.
FIGS. 1 and 2
illustrate related art projectors.
Referring to
FIGS. 1 and 2
, the related art projector is provided with a lamp
1
, a reflection plate
2
, a color wheel
4
, a rod lens
6
, first lenses
7
and
8
, a mirror
10
, a second lens
12
, a prism
16
, a display
14
, and a projection lens
18
.
Beams of lights from the lamp
1
are focused onto the color wheel
4
by the reflection plate
2
, and the color wheel
4
transmits the red, green, and blue colors in succession as motor
5
rotates the color wheel. The beams split by the color wheel
4
are incident on the rod lens
6
, and the rod lens
6
makes the beams uniform for uniform distribution of the beams on a screen. The beams passed through the rod lens
6
proceeds to the mirror
10
through the first lenses
7
and
8
, and reflected at the mirror
10
toward the second lens
12
. The second lens
12
focuses the beams from the mirror
10
onto the prism
16
, and the prism
16
guides the beams from the second lens
12
to a display
14
, and, on the same time, supplies a picture beam from the display
14
toward the projection lens
18
. The display
14
produces a picture beam loaded with picture information by using the beams from the prism
16
. The prism
16
reflects the picture beam from the display
14
toward the projection lens
18
. To do this, as shown in
FIGS. 3A and 3B
, the prism
16
has a first reflection surface
20
for reflecting the beams from the second lens to the display for the first time, and a second reflection surface
22
for reflecting the picture beam from the display
14
to the projection lens
18
for the second time. Finally, the projection lens
18
enlarges the picture beam, and projects the picture beam to a screen at a distance in front of the projection lens
18
.
FIGS. 4A and 4B
illustrate related are the color wheel in FIG.
1
.
Referring to
FIGS. 4A
,
4
B and
5
, the related art color wheel
4
is provided with color filters
26
each for transmitting a beam of light with a wavelength of a relevant color among the white beams, a coupler
24
having the color filters
26
fitted thereto, and a motor
5
having the coupler
24
fitted thereto.
The color filter
26
is provided with a red color filter
26
R for transmitting red beams among the white beams, a green color filter
26
G for transmitting green beams among the white beams, and a blue color filter
26
B for transmitting blue beams among the white beams.
The color filter
26
is attached to the coupler
24
by an adhesive, and the coupler
24
is fastened to the motor
5
by holes
25
therein. That is, the color filter
26
splits colors in succession as the motor rotates the color filters
26
. It is preferable that the beam passes a boundary
27
of the color filters within the shortest time period when the beam transmits the color wheel
4
shown in
FIGS. 4A
,
4
B and
5
. For an example, when it is assumed that the motor rotates at 3600 rpm for displaying 60 fields per a second, a time period required for the beam to pass the boundary will be calculated. In this instance, it is assumed that the beam is rectangular with an 8 mm width, and a 6 mm height, and the color filter
26
has an inside radius of 30 mm, and an outside radius of 40 mm.
Equation (1) expresses an angle when the beam passes a surface of the color filter
26
, and the equation (2) expresses a time when the beam passes the boundary
27
of the color filter
26
.
θ
=
2
×
arctan
(
3
31
)
=
11.055
°
,
(
1
)
(where, 31 is a distance from a center of the color wheel
4
to the beam, and 3 is a half of the height of the beam).
t
=
1
60
×
11.055
120
=
1.54
μ
s
,
(
2
)
(Where, 120 is a value obtained by dividing 360° by 3, a number of boundaries
27
).
From equation (2), it can be known that the time period required for the beam to pass through the boundary
27
of the color filter
26
is 1.54 &mgr;s. As can be known from equations (1) and (2), for reducing the time period required for the beam to pass through the boundary
7
of the color filter
26
, it is necessary to make the inside radius of the color wheel
4
greater. However, the greater the inside diameter of the color wheel
4
, the larger and the heavier the projector become.
Moreover, the related art color wheel
4
can not be fitted overlapped with other optical system (various lenses), to require much space. Furthermore, the related art prism
16
makes two times of total reflection for transmission of the beams from the second lens
12
to the projection lens
18
, with a loss of luminance.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a total reflection prism and a projector with the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a total reflection prism and a projector with the same, which permits to fabricate a thinner projector, and enhance a luminance.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the total reflection mirror makes one time of total reflection of the beams of lights from an optical system to a projection lens.
In another aspect of the present invention, there is provided a projector with a total reflection prism including a light source for emitting beams of lights, a color wheel for receiving the beams from the light source, splitting color beams from the beams in succession, and transmitting the color beams, a transmission part for guiding the color beams to the prism, a display for producing a picture beam according to a video signal by using the color beams from the transmission part, a prism arranged between the transmission part and the display for guiding the color beams from the transmission part to the display, and reflecting the picture beam from the display, and a projection lens for enlarging, and projecting the picture beam.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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Adams Russell
Fleshner & Kim LLP
Koval Melissa J
LG Electronics Inc.
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