Optics: image projectors – Composite projected image – Multicolor picture
Reexamination Certificate
1998-04-09
2003-12-23
Dowling, William (Department: 2851)
Optics: image projectors
Composite projected image
Multicolor picture
C353S081000
Reexamination Certificate
active
06666557
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates in general to a reflection type projector, and more particularly, to a reflection type projector capable of increasing the intensity of light projected onto a screen.
2. Description of the Related Art
A projector projects a formed image onto a screen using an additional light source. The projector is usually classified as a projection type projector or a reflection type projector according to the way by which the image is formed.
FIG. 1
shows an optical system of a conventional reflection type projector. The conventional reflection type projector includes a light source
10
for emitting light, a color wheel
20
for selectively transmitting a certain color of light, a scrambler
30
for mixing rays of the input light having different degrees of intensity into a uniform beam, a condensing lens
32
, a collimating lens
34
, a polarization beam splitter
40
for changing an optical path of the light, a display device
50
for forming an image by selectively reflecting an input light, and a projection lens unit
60
for projecting an input light onto a screen (not shown).
The light source
10
is comprised of a lamp
11
, such as a metal haloid lamp or a xenon arc lamp, for generating light, and a reflection mirror
13
for reflecting the light emitted from the lamp
11
. The color wheel
20
installed along the optical path of the light between the light source
10
and the scrambler
30
is rotated by a driving motor
21
. The color wheel
20
is composed of color filters of red (R), green (G) and blue (B). The color wheel
20
rotates at a speed corresponding to the response speed of the display device. At any given time, one of the color filters R, G and B is disposed along the optical path of the light, according to the response speed of the display device
50
.
The scrambler
30
mixes the input light through diffused reflection to make uniform light. The condensing lens
32
converges the light passing through the scrambler
30
, which then diverges, to enlarge a transmission width of the light. The collimating lens
34
condenses the input divergent light to make parallel light beams.
The polarization beam splitter
40
is arranged in the optical path of the light between the collimating lens
34
and the display device
50
, and changes the optical path of an input light by selectively transmitting or reflecting the input light at a mirror surface
41
according to the polarization component thereof. That is, the light input from the light source
10
is selectively transmitted or reflected depending on the polarization component of the light.
In
FIG. 1
, the light transmitted from the polarization beam splitter
40
is used as an efficiency light. A ferroelectric liquid crystal display (FLCD) of a two-dimensional array structure exhibiting an excellent response speed is used as the display device
50
. The display device
50
has a multiplicity of reflection areas of a two-dimensional array structure, each area being independently driven to form an image by changing the polarization direction of the input light.
The light input to the display device
50
is reflected and re-enters the polarization beam splitter
40
. Here, the efficiency light re-entering the polarization beam splitter
40
has had its polarization direction changed to 90° by the display device
50
. Then, the beam is reflected from the mirror surface
41
of the polarization beam splitter
40
to proceed toward the projection lens unit
60
. The beam passes through the projection lens unit
60
and is projected onto a screen (not shown).
As described above, the conventional reflection type projector requires parallel beams of light to be input into the polarization beam splitter, to avoid deterioration of the transmission/reflection according to the polarization component. Thus, the width of the light input into the polarization beams splitter must be increased to make the parallel beam between the light source and the polarization beam splitter, which also requires a larger polarization beam splitter and projection lens unit, which are expensive.
In another reflection type projector employing an FLCD, instead of the polarization beam splitter, the angle of the light input into the FLCD is different from that reflected therefrom, to thereby change the path of the light. Here, the FLCD is smaller than the collimating lens. Therefore, the optical distance between the FLCD and the projection lens unit must be lengthened or the slope of the FLCD must be increased. When the optical distance is lengthened, the diameter of the projection lens unit is reduced. On the other hand, an increase in the slope of the FLCD complicates the arrangement of optical axes between the FLCD and the projection lens unit.
SUMMARY OF THE INVENTION
To solve the above problems, it is an objective of the present invention to provide a reflection type projector having a critical angle prism which changes the path of light, to thereby simplify the arrangement of optical axes without the use of a polarization beam splitter or the increase in optical length.
It is another objective of the present invention to provide a reflection type projector in which three colors are irradiated onto a screen to improve optical efficiency and increase the intensity of the light projected on the screen.
Accordingly, to achieve the above first objective, there is provided a reflection type projector including: a light source for generating and emitting light; an image generation unit having a multiplicity of pixels in a two-dimensional array structure, each of the pixels being independently driven, for forming and reflecting an image from the input light; a critical angle prism having a transmission/reflection surface disposed along an optical path of the light, to transmit the light input from the light source and reflect the light re-entering from the image forming unit; and a projection lens unit for enlarging and transmitting the light reflected from the transmission/reflection surface of the critical angle prism onto a screen.
To achieve the second objective, there is provided a reflection type projector including: a light source for generating and emitting light; a first dichroic mirror, disposed along an optical path, for transmitting and reflecting input light according to a wavelength to divide the transmitted and reflected light into two; a first optical path changing unit for changing the path of one light beam divided by the first dichroic mirror; a first image forming unit for generating an image from input light passing through the first optical path changing unit; a second dichroic mirror for transmitting and reflecting the light reflected from the first dichroic mirror according to wavelength; a second optical path changing unit for changing the path of the other light beam divided by the second dichroic mirror; a second image forming unit for generating an image from input light passing through the second optical path changing unit; a third optical path changing unit for changing the path of the light transmitting the second dichroic mirror: a third image forming unit for generating an image from input light passing through the third optical path changing unit; a dichroic beam splitter having first and second mirror surfaces for selectively transmitting and reflecting the input light passing through the first, second and third optical path changing units in one direction according to wavelength; and a projection lens unit for enlarging and transmitting the light input from the dichroic beam splitter onto a screen.
The above and other features of the invention including various and novel details of construction and combination of parts will now be more particularly described with reference to the accompanying drawings and pointed out in the claims. It will be understood that the particular reflection type projector embodying the invention is shown by way of illustration only and not as a limitation of the invention. The principles and features of thi
Dowling William
Samsung Electronics Co,. Ltd.
Sughrue & Mion, PLLC
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