U.S. patent application number 11/497427 was filed with the patent office on 2006-11-30 for projection system and optical path transfer device thereof.
Invention is credited to Sean Chang, Albert Lin.
Application Number | 20060266933 11/497427 |
Document ID | / |
Family ID | 34102236 |
Filed Date | 2006-11-30 |
United States Patent
Application |
20060266933 |
Kind Code |
A1 |
Chang; Sean ; et
al. |
November 30, 2006 |
Projection system and optical path transfer device thereof
Abstract
A projection system. The projection system has a light source, a
relay module, an optical path switching device and an optical path
transfer device. The light source emits a light beam, and the relay
module relays the light beam. The optical path switching device is
used to receive and switch the light beam and has at least one
active area. The optical path transfer device is disposed between
the relay module and the optical path switching device directing
the light beam toward the optical path switching device in a first
angle, and the optical path transfer device has an incident surface
tilted perpendicular to an incidence of the light beam.
Inventors: |
Chang; Sean; (Taoyuan Hsien,
TW) ; Lin; Albert; (Taoyuan Hsien, TW) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
34102236 |
Appl. No.: |
11/497427 |
Filed: |
August 2, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10901118 |
Jul 29, 2004 |
|
|
|
11497427 |
Aug 2, 2006 |
|
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Current U.S.
Class: |
250/216 ;
348/E5.139 |
Current CPC
Class: |
G02B 26/0833 20130101;
G02B 17/04 20130101; H04N 5/7416 20130101 |
Class at
Publication: |
250/216 |
International
Class: |
H01J 3/14 20060101
H01J003/14 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2003 |
TW |
92121044 |
Claims
1. An optical path transfer device for guiding a light beam toward
a light receiving device, the optical path transfer device
comprising: at least two parts for transferring the light beam,
each comprising an incident surface; and at least one air gap
formed between the at least two parts; wherein the incident surface
tilts in a direction perpendicular to an incidence of the light
beam.
2. The optical path transfer device as claimed in claim 1, wherein
the light beam is incident onto the light receiving device at a
first angle.
3. The optical path transfer device as claimed in claim 2, wherein
the incident surface forms a second angle with a normal of each
side surface of the at least two parts, variable corresponding to
the first angle.
4. The optical path transfer device as claimed in claim 1, wherein
the light receiving device comprises an optical path switching
device for receiving or switching the light beam.
5. The optical path transfer device as claimed in claim 4, wherein
the optical path switching device comprises a digital micromirror
device (DMD) or a liquid crystal on silicon (LCoS).
6. The optical path transfer device as claimed in claim 1, wherein
the at least two parts are prisms, glass, or a photoconductive
material with a refractive index larger than 1.
7. The optical path transfer device as claimed in claim 1, wherein
an illumination area of the light beam projected on the light
receiving device from the optical path transfer device is similar
to the active area in s size and shape.
8. The projection system as claimed in claim 1, wherein the optical
path transfer device is a total internal reflection prism (TIR
prism) or a reversed total internal reflection prism (reversed TIR
prism).
Description
[0001] This application is a Divisional of co-pending application
Ser. No. 10/901,118, filed on Jul. 29, 2004, which claims priority
under 35 U.S.C. .sctn.119(a) on Patent Application No(s). 092121044
filed in Taiwan, Republic of China on Jul. 31, 2003, the entire
contents of which are hereby incorporated by reference and for
which priority is claimed under 35 U.S.C. .sctn.120.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a projection system and an
optical path transfer device thereof, and particularly to a
projection system and an optical path transfer device thereof with
high illumination efficiency.
[0004] 2. Description of the Related Art
[0005] In a conventional optical projection display, a light beam
emitted from a light source is projected toward a digital
micromirror device (DMD). The DMD is formed with a plurality of
micromirrors selectively disposed in one of two predetermined tilt
angles, in which the light beam is guided and reformed for
projection as an image onto the display screen. Thus, each of the
pixels on the display can be selectively switched to either a
bright mode, in which the light beam passes through the projection
system, or a dark mode, in which the light beam does not pass
through the projection system.
[0006] FIG. 1 illustrates a conventional projection system 100.
FIG. 2A is a partial perspective view of the total internal
reflection prism (TIR prism) 112 and the DMD 114 in FIG. 1.
Further, a side view of the X-Y plane in FIG. 2A is shown in FIG.
2B, and a top view of the X-Z plane in FIG. 2A is shown in FIG.
2C.
[0007] The optical path of the projection system 100 is described
hereinafter with reference to FIG. 1. The light beam I, emitted
from the light source 102 and condensed by the reflector 104,
passes through the color wheel 106, the light tunnel 108, the relay
lens 110 and the total internal reflection prism (TIR prism) 112,
and is projected toward the DMD 114. With the switching of the DMD
114, the light beam I corresponding to the image signal passes
through the projection lens 116 and is projected toward the display
device 118 to display the image.
[0008] Generally, the projection lens 116 and the DMD 114 are
disposed in an on-axis configuration. Specifically, the light beam
I is directed toward the projection lens 116 along a direction
substantially parallel to the light axis of the projection lens
116. Accordingly, the light beam I reflected by the TIR prism 112
is projected toward the DMD 114 at a tilt angle .theta.. That is,
the light beam I is projected toward the DMD 114 in an off-axis
manner with the tilt angle .theta..
[0009] Configuration of the optical path can be further described
in detail with reference to FIG. 2A to FIG. 2C.
[0010] In FIG. 2A, the light beam I is projected perpendicularly
toward the TIR prism 112 on the incident surface 120 and is
reflected toward the DMD 114 in the off-axis manner. In view of the
X-Y plane as shown in FIG. 2B, the light beam I is incident on the
DMD 114 at a tilt angle .theta.. Further, in view of the X-Z plane
as shown in FIG. 2C, the light beam I in the TIR prism 112 is
directed in a direction parallel to two side surfaces 122 of the
TIR prism 112.
[0011] Since the light beam I from the TIR prism 112 is incident on
the DMD 114 at the tilt angle .theta., an illumination area 126 of
the light beam I on the DMD 114 is stretched and deformed as a
parallelogram. However, the illumination area 126 may exceed the
active area 206, generally in a rectangular shape, of the DMD 114.
Accordingly, luminosity waste occurs in the DMD 114, which reduces
the illumination efficiency of the projection system 100.
SUMMARY OF THE INVENTION
[0012] Accordingly, an object of the present invention is to
provide a projection system, in which the illumination area of the
light beam projected toward the optical path switching device is
fully enclosed by the active area thereof. Thus, the illumination
efficiency can be effectively enhanced.
[0013] The present invention discloses a projection system. The
projection system comprises a light source, a relay module, an
optical path switching device and an optical path transfer device.
The light source emits a light beam, relayed by the relay module.
The optical path switching device receives and switches the light
beam and comprises at least one active area. The optical path
transfer device is disposed between the relay module and the
optical path switching device, directing the light beam toward the
optical path switching device with a first angle, and the optical
path transfer device has an incident surface tilted in a direction
perpendicular to an incident direction of the light beam.
[0014] Further, the present invention discloses an optical path
transfer device for projecting a light beam toward a light
receiving device. The optical path transfer device has at least two
parts and at least one air gap. Each part transfers the light beam
and has an incident surface. The air gap is disposed between the at
least two parts. Further, the incident surface tilts perpendicular
to the incidence of the light beam.
[0015] In the present invention, the light receiving device
comprises an optical path switching device receiving or switching
the light beam. The optical path switching device can be a digital
micromirror device (DMD) or liquid crystal on silicon (LCOS).
Further, the light beam is incident perpendicularly toward the
incident surface, the incident surface forms a second angle with a
normal of each side surface of the optical path transfer device,
variable corresponding to the first angle.
[0016] The projection system of the present invention may further
comprise a reflector for focusing the light beam, a color wheel for
changing the color of the light beam, a light tunnel for uniformly
merging the light beam, a display device for displaying image
signals of the light beam from the optical path switching device,
or a projection lens disposed between the optical path switching
device and the displaying device for projecting the light beam.
Further, the relay module may comprise at least one lens to adjust
focus and projection distance of the light beam. Further, the
optical path transfer device can be a total internal reflection
prism (TIR prism) or a reversed total internal reflection prism
(reversed TIR prism).
[0017] In the present invention, an illumination area of the light
beam projected on the optical path switching device from the
optical path transfer device correlates in size and shape to the
active area.
[0018] With the tilt incident surface of the optical path transfer
device in the present invention, deformation of the illumination
area due to off-axis incidence in the conventional projection
system can be eliminated. Accordingly, the illumination area fully
overlaps the active area of the optical path switching device, i.e.
the entire light beam is projected on the active area. Thus,
illumination efficiency is significantly enhanced.
[0019] A detailed description is given in the following embodiments
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] The present invention can be more fully understood by
reading the subsequent detailed description and examples with
references made to the accompanying drawings which are given by way
of illustration only, and thus are not limitation of the present
invention, and wherein:
[0021] FIG. 1 is a schematic diagram of a conventional projection
system;
[0022] FIG. 2A is a partial perspective view of the TIR prism and
the DMD of FIG. 1;
[0023] FIG. 2B is a side view of the X-Y plane in FIG. 2A;
[0024] FIG. 2C is a top view of the X-Z plane in FIG. 2A;
[0025] FIG. 3 is a schematic diagram of an illumination area of the
light beam passing through the conventional TIR prism and incident
on the DMD;
[0026] FIG. 4A is a perspective view of one embodiment of the
optical path transfer device of the present invention;
[0027] FIG. 4B is a top view of the X-Z plane in FIG. 4A;
[0028] FIG. 5 is a schematic diagram of an illumination area of the
light beam passing through the optical path transfer device and
incident on the DMD according to the present invention;
[0029] FIG. 6A is a perspective view of another embodiment of the
optical path transfer device of the present invention; and
[0030] FIG. 6B is a side view of the X-Y plane in FIG. 6A.
DETAILED DESCRIPTION OF THE INVENTION
[0031] FIG. 4A is a perspective view of an embodiment of the
optical path transfer device 200 of the present invention. A top
view of the X-Z plane in FIG. 4A is shown in FIG. 4B. Referring to
both FIGS. 4A and 4B, the optical path transfer device 200 includes
at least two parts 200a and 200b, and an air gap 208 disposed
between these two parts 200a, 200b. The incident surface 202 of the
first part 200a tilts perpendicular to the incidence of the light
beam I, and an angle .alpha. is formed between the normal of the
incident surface 202 and the normal of the two side surfaces 204.
The optical path transfer device 200 alters the light beam in a
direction different from the incident direction thereof.
[0032] The optical path transfer device 200 can be a total internal
reflection prism (TIR prism) or a reversed total internal
reflection prism (reversed TIR prism). The first and second parts
200a and 200b can be prisms, made of glass or any other
photoconductive material with a refractive index larger than 1.
[0033] The refractive indices of the first and second parts 200a,
200b are significantly larger than that of the air gap 208.
Accordingly, when the light beam I passes through the interface
between the first and second parts 200a, 200b, total internal
reflection occurs due to the difference between the refractive
index and the incident angle, and the light beam I is projected
toward the optical path switching device 214.
[0034] Further referring to FIGS. 4A and 4B, the light beam I is
projected toward the optical path transfer device 200 on the
incident surface 202, and toward the optical path switching device
214 in the off-axis manner.
[0035] In view of the X-Y plane, the light beam I is projected
perpendicularly toward the incident surface 202, and toward the
optical path switching device 214 at a tilt angle .theta. (i.e. the
angle between the light beam I and the normal of the optical path
switching device 214). Further, in view of the X-Z plane as shown
in FIG. 4B, the light beam I incident toward the optical path
transfer device 200 forms an angle .alpha. with each side surface
204 of the optical path transfer device 200, and is directed
through the optical path transfer device 200 at the same angle
toward the projection lens 116 referred to in FIG. 1.
[0036] FIG. 5 is a schematic view of an illumination area 206 of
the light beam I passing through the optical path transfer device
200 of the present invention. The light beam I from the optical
path transfer device 200 is projected toward the optical path
switching device 214 at the tilt angle .theta., such that the
illumination area of the light beam I on the optical path switching
device 214 is stretched and deformed. However, the incident surface
202 of the optical path transfer device 200 is set to tilt at the
angle .alpha., such that the deformed illumination area is
pre-stretched to correspond to the final illumination area 206 on
the optical path switching device 214, substantially assuming a
rectangular shape, correlating in size and shape to the rectangular
active area 206 of the optical path switching device 214. Thus,
luminosity waste is reduced, and the illumination efficiency of the
projection system 200 is significantly enhanced.
[0037] Referring to FIG. 1 and FIG. 4A, the TIR prism 112 in FIG. 1
is replaced by the optical path transfer device 200 of the present
invention in FIG. 4A. The projection system 100 of the present
invention has a light source 102, a relay module 128, the optical
path switching device 214, the optical path transfer device 200,
and a display module 130. The incident surface 202 of the optical
path transfer device 200 forms an angle .alpha. with the normal of
the side surfaces 204.
[0038] The light source 102, which can be in the form of a point or
a line, emits a light beam I for the projection system 100.
Further, a reflector 104 can be provided for focusing the light
beam I to focus onto the relay module 128.
[0039] The relay module 128 is disposed between the light source
102 and the optical path transfer device 200 to relay and change
the projection distance of the light beam I. The relay module 128
can include a color wheel 106 changing color of the light beam I, a
light tunnel 108 uniformly merging the light beam I, and a relay
lens 110. The color wheel 106 also can be replaced by a polarizing
plate.
[0040] The light tunnel 108 receives light beam I from the light
source 102 for merging. The peripheral walls of the light tunnel
108 include reflective surfaces.
[0041] The relay lens 110 relays and adjusts the focus and
projection distance of the light beam I. Generally, the relay lens
110 includes a plurality of lenses of either the same or different
type.
[0042] The optical path transfer device 200 is disposed between the
relay module 128 and the optical path switching device 214,
directing light beam I toward the optical path switching device
214. The structure of the optical path transfer device 200 is
described in detail in the above paragraph.
[0043] The optical path switching device 214 has a plurality of
optical path switching elements (not shown) to respectively control
the direction of the light beam I. The optical path switching
device can be a digital micromirror device (DMD), a liquid crystal
on silicon (LCoS), or any other light-receiving device. Further, an
angle is formed between the light beam I and the normal of the
optical path switching device 214, including the above-mentioned
off-axis projection angle .theta..
[0044] The projection module 130 receives the light beam I from the
optical path switching device 214 and forms the image signal of the
light beam I. The projection module 130 can include a projection
lens 116 and a display device 118.
[0045] The projection lens 116 relays and adjusts the focus and the
projection distance of the light beam I. The projection lenses 116
can include a plurality of lens of either the same or different
type.
[0046] The display device 118 displays the image signals of the
light beam I from the optical path switching device 214. The
display device 118 can be an LCD screen, a projection screen, or
any other type of display.
[0047] In the projection system 100, the light beam I emitted from
the light source 102 passes through the optical path transfer
device 200 at a tilt angle .theta.. Further, the incident surface
202 and the optical path transfer device 200 form an angle .alpha..
Thus, the illumination area 206 on the optical path switching
device 214 is altered to substantially in a rectangular,
corresponding in size and shape to the rectangular active area of
the optical path switching device 214. Thus, luminosity waste is
reduced, and the illumination efficiency of the projection system
200 is significantly enhanced.
[0048] It should be mentioned that the optical path transfer device
of the embodiment includes, in its simplest form, two prisms and an
air gap, but additional elements can also be selected and used. An
embodiment of a reversed optical path transfer device 300 is shown
in FIG. 6A.
[0049] Referring to FIGS. 6A and 6B, the reversed optical path
transfer device 300 has three parts 300a, 300b and 300c. An angle
.alpha. is formed between the incident surface 302 of the first
part 300a and the normal of the two side surfaces 304. Thus, the
light beam I passes through the incident surface 302 at the tilt
angle .alpha. and is projected on the optical path switching device
314 at the angle .theta. to form the illumination area
corresponding in size and shape to the active area of the optical
path switching device 314.
[0050] A further embodiment is applied to the optical path transfer
device of the present invention. Referring to FIGS. 4A and 4B, when
the first angle .theta. is set to 22.degree. to 24.degree., the
second angle .alpha. between the incident surface 202 and the
normal of the side surfaces 204 is about 8.degree.. Thus, the
illumination area 206 of the light beam I projected on the optical
path switching device 314 correlates in size and shape (or even
overlaps) to the active area of the optical path switching device
214. The first angle .theta. can be variable corresponding to the
second angle .alpha.. Thus, luminosity waste is reduced, and the
illumination efficiency of the projection system 100 is
significantly enhanced.
[0051] With the tilt incident surface of the optical path transfer
device in the present invention, deformation of the illumination
area due to off-axis incidence in the conventional projection
system is eliminated. Accordingly, the illumination area fully
overlaps the active area of the optical path switching device, i.e.
the entire light beam is projected on the active area. Thus, the
illumination efficiency is significantly enhanced.
[0052] While the invention has been described by way of example and
in terms of the preferred embodiments, it is to be understood that
the invention is not limited to the disclosed embodiments. To the
contrary, it is intended to cover various modifications and similar
arrangements (as would be apparent to those skilled in the art).
Therefore, the scope of the appended claims should be accorded the
broadest interpretation so as to encompass all such modifications
and similar arrangements.
* * * * *