Optical system for projection display

Details Optical system for projection display Optical system for projection display

2003-08-21

2004-12-28

Nguyen, Judy (Department: 2851)

Optics: image projectors

Reflector

C353S037000

Reexamination Certificate

active

06834967

ABSTRACT:

BACKGROUND OF INVENTION
1. Field of the Invention
The present invention relates to an optical system and, more particularly, to an optical system for use in a projection display.
2. Description of the Prior Art
The development of electro-optical technology is tending to visualize information, and the key factor of determining projection-type imaging quality usually depends on the quality of an optical system of a projection display. Considering the production cost, how to produce a portable projection display with high clarity for promoting the market competition is always the focus of research and development in the electro-optical industry.
Referring to
FIG. 1
, an optical system
10
of a conventional projection display includes a light source
11
for producing a white light beam. The light beam is reflected by a reflector
12
and converges onto a color-generating device
13
, such as a color wheel. The color-generating device
13
comprising a series of red, green, and blue filters sequentially converts the color of the light beam into red, green, and blue primaries when the light beam passes through it. A first condenser lens
141
and a second condenser lens
142
after the color-generating device
13
are used for converging and transmitting the light beam. The light beam is reflected upward by a first mirror
151
for passing through a third condenser lens
143
, and then reflected by a second mirror
152
for passing through a fourth condenser lens
144
to impinge onto a digital micro-mirror device (DMD)
16
. The DMD
16
has a two-dimensional array of micro-mirrors. Each micro-mirror with the tilt angles about ±12 degree varies the angle of reflection of the light beam reflected therefrom and thereby causes on/off state. When the micro-minor switches to on-state, the light beam is reflected to enter a projection lens
17
for projecting on a screen (not shown). When the micro-mirror switches to off-state, the light beam is reflected away from the projection lens
17
to avoid projecting on the screen. Therefore, the necessary light beam can be properly selected to be projected on the screen.
As shown in
FIG. 2
, the third condenser lens
143
of the conventional optical system
10
is generally as close as possible to the optical axis between the DMD
16
and the projection lens
17
, so as to form a more compact optical system
10
. However, parts of the light beam from the third condenser lens
143
to the second mirror
152
will very possibly be obstructed by the projection lens
17
relatively. Thus, this obstruction causes a mechanical and optical interference such that the illumination efficiency of the projection display is degraded. To avoid the obstruction in the conventional projection display, the projection lens
17
moves toward the screen
18
to a position
17
′, or the third condenser lens
143
moves outward to a position
143
Therefore, all above-mentioned adjustments elongate the light path of the optical system
10
and result in a bulky projection display.
In addition, the light beam in the conventional optical system
10
passes through three condenser lens
141
,
142
, and
143
as well as two mirrors
151
and
152
to impinge onto the DMD
16
. The conventional optical system
10
needs excessive components and results in not only a complex optical structure but increasing the production cost, elongating the light path, and enlarging the bulk of the optical system
10
. Therefore, there are many defects in the conventional projection display needed to be improved.
SUMMARY OF INVENTION
An objective of the present invention is to provide an optical system that has a total reflection lens for avoiding the interference to raise the projection efficiency and image quality.
Another objective of the present invention is to provide an optical system that reduces some optical components to simplify and compact the whole projection display.
To achieve the above objectives, the optical system of the present invention disposes a total reflection lens between a light valve and a projection lens. When a white light beam from a light source passes through a color wheel, the color of the light beam is sequentially converted into red, green, and blue primaries, and uniformed by an integrator. Then, the light beam impinges into the total reflection lens and is reflected to the light valve therefrom. The light valve reflects the light beam into a projection lens to be projected on a screen. Therefore, this invention increases the projection efficiency and reduces the volume and components of the optical system.


REFERENCES:
patent: 6343862 (2002-02-01), Sawai et al.
patent: 6433942 (2002-08-01), Memezawa et al.
patent: 2002/0067469 (2002-06-01), Eguchi et al.
patent: 2003/0030914 (2003-02-01), Park

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