Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
2003-08-29
2004-06-15
Mahoney, Christopher (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S081000
Reexamination Certificate
active
06749305
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to an optical module and its assembling method, and more specifically, to an optical module and its assembling method of a projecting apparatus.
2. Description of the Prior Art
A projecting apparatus for generating an image is disclosed in U.S. Pat. No. 6,089,719 “Projecting Apparatus For Displaying Electrical Images”. Please refer to
FIG. 1
showing the projecting apparatus
10
according to U.S. Pat. No. 6,089,719. To display an image on a screen
34
, a projecting apparatus
10
comprised of a light source device
22
, three modulating units
24
,
26
,
28
, a dichroic-polarization beam splitter prism
30
composed of four triangular prisms
36
of equal proportion, and a projecting lens
32
is used. The light source device
22
is used to generate three different-colored rays red, green, and blue with uniform illumination but different polarities. Each of the modulating units
24
,
26
,
28
modulates and changes the polarity of one of the single-colored polarized raysby means of reflection. The beam splitter prism
30
is used to first receive the polarized rays of red, green and blue, then guide the rays to their respective modulating units
24
,
26
,
28
for modulation, and finally converge the three modulated rays into an output beam all of which are accomplished via mirror planes, which transmit or reflect light based its polarity, plated onto the triangular prisms
36
of the beam splitter prism
30
. The projecting lens
32
is installed in front of the output face of the beam splitter prism
30
for projecting the output beam to a screen
34
.
Other projecting apparatus arealso disclosed in U.S. Pat. No. 6,247,814 “Projecting Apparatus For Displaying Electronic Images” and U.S. Pat. No. 6,364,488 “Projection Display Device For Displaying Electrically Encoded Images” thatincorporate the use of an L-shaped optical module to create an optical path of approximately the same length for the three monochrome rays red, green, and blue in order to reduce the optical design of the projecting apparatus. Please refer to
FIG. 2
showing the projecting apparatus
40
according to U.S. Pat. No. 6,247,814. The projecting apparatus
40
includes a light source
42
, three modulating units
44
,
46
,
48
, an L-shaped optical module
50
, an input lens set
52
and a projecting lens
54
.
The light source
42
is for generating monochrome rays in red, green and blue in the same polarity. The three modulating units
44
,
46
,
48
are for modulating a single-colored polarized ray and changing its polarity by manner of reflection. The L-shaped optical module
50
is for controlling the path of each single-colored polarized ray. The input lens set
52
is installed between the light source
42
and the inner side of the L-shaped optical module
50
. The projecting lens
54
is for projecting the beam output from the L-shaped optical module
50
to a screen
56
.
To elaborate further upon the L-shaped optical
50
, its makeup consists of three rectangular, transparent light-guide units, which are named respectively as a first, second, and third light-guide unit
60
,
62
,
64
. Each light-guide unit is composed of a mirror sandwiched between the diagonals of two triangular prisms
66
. The first and third light-guide units
60
,
64
have a polarization light beam splitter mirror
70
,
74
respectively while the second light-guide unit has a dichroic mirror
72
.
The arrangement of the light-guide units has the second light-guide unit
62
restingat the apexof the first and the third light-guide units
60
,
64
. This arrangement ideally causes the first and the third polarization beam splitter mirror
70
,
74
to be aligned along the same plane, and the second dichroic mirror
72
to be perpendicular to both the first and the third polarization beam splitter mirrors
70
,
74
. Light is input through the right angle that is located on the inside of the L-shaped optical module
50
and formed by of perpendicular sides
61
,
65
of the first and the third light-guide units
60
,
64
.
Please refer to
FIG. 3
now to follow how a projecting apparatus
40
operates. Generally, image signals wish to be displayedare input into the projecting apparatus
40
where images corresponding to the input signals are generated. For instance, the signal from the output port of a computers video card can be connected to the projecting apparatus
40
in order to display the operational mode of the computer. The three modulating units
44
,
46
,
48
of the projecting apparatus
40
each modulate their respective monochromatic beam according to received image signals. Then an image from each monochromatic beam (a red image
12
, a green image
14
and a blue image
16
) is outputted and brought together to create one image for users to see.
Continuing with the example of displaying a computer operational mode, the three images (red image
12
, the green image
14
and the blue image
16
) have equal resolutions (e.g. 800*600 or 1024*768) composed from a plurality of pixels
18
. This means that pixels
18
from each of the three images with the same coordinates all correspond to one another. Under ideal conditions, the angles at which the red image
12
, the green image
14
and the blue image
16
are projected onto the screen
56
are less than the maximum tolerance level, resulting in the overlap of pixels from the three images with the same coordinates at the same position.
For instance, if the projection angles of the red image
12
, the green image
14
and the blue image
16
on the screen
56
are each less than the maximum tolerance level, a pixel
20
R on the upper left corner of the red image
12
, a pixel
20
G on the upper left corner of the green image
14
, and a pixel
20
B on the upper left corner of the red image
16
will overlap one another and form a single pixel for users to see. However, if any of the projection angles of the red image
12
, the green image
14
and the blue image
16
onto the screen
56
is larger than the maximum tolerance level, the pixels of the images with larger than maximum tolerance levels will not be in-line thereby decreasing projection quality. Therefore, it is imperative that the projection angles of the red image
12
, the green image
14
and the blue image
16
on the screen
56
each be made less than the maximum tolerance level.
The part that has the biggest effect on whether the projection angles fall within tolerance levels is the L-shaped optical
50
more specifically the three light-guide units
60
,
62
,
64
. Reason being if the three light-guide units
60
,
62
,
64
are not in proper position with respect to one another, the light-guide units
60
,
62
,
64
will project their respective single-colored polarized rays at different angles resulting in image quality degradation. Therefore, the design of a conventional L-shaped optical module
50
usually incorporates a holder
80
(
FIG. 4
) to align and maintain the positions of the three light-guide units
60
,
62
,
64
so as to guarantee the paths of the single-colored polarized rays.
However, the current-conventional method for assembling the L-shaped optical module
50
is not ideal because it easily leads to misalignment of parts. As can be deduced from the above-given information, any small misalignment can cause any, two, or all of the three beams of red, blue and green to be projected at angles above the maximum tolerance. Pixels therefore do not overlap but lie on different positions on the screen, resultingin lower than expected image quality.
Under conventional methods the manufacturing of light-guide units
60
,
62
,
64
involves gluing a mirror between two prisms, the mirror of choice either a dichroic mirror
72
or a polarization beam splitter mirror
70
,
74
depending on the type of light-guide unit is being produced. The assembled light-guide units
60
,
62
,
64
in
FIG. 2
are then attached to the holder
80
as shown in FIG.
4
. Each light-guide unit
60
,
62
,
64
is
Chu Yun-Liang
Huang Kao-Chun
Liau Bun-Liou
Tsao Chung-Feng
Mahoney Christopher
Primax Display Corpration
Winston Hsu
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