Optics: image projectors – Unitary plural refracting surfaces
Reexamination Certificate
2001-03-21
2002-12-31
Adams, Russell (Department: 2851)
Optics: image projectors
Unitary plural refracting surfaces
C362S268000, C362S255000, C355S122000
Reexamination Certificate
active
06499845
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical apparatus used as an illuminating apparatus for a display apparatus such as a liquid crystal projector and to a projection type display apparatus using the optical apparatus.
2. Description of the Related Art
A projector apparatus utilizing-a spatial light modulator (hereinafter abbreviated as SL
2
) such as a liquid crystal panel or a DMD of Texas Instruments of the U.S. is suitable for reducing size.
Below, an optical system of a projector making use of an SLM will be, explained.
FIG. 1
is a view of an example of the configuration of an optical system in a projector using an SLM.
The projector
1
, as shown in
FIG. 1
, comprises a light source
2
, a reflecting and condensing mirror
3
, an integrator optical system
4
, a condenser lens
5
, an SLM
6
, and a projecting lens
7
as main components.
In a projector using an SLM, since the SLM itself does not emit light, a separate light source is necessary. A discharge lamp is often used as the light source
2
from the viewpoint of the luminous efficiency etc.
The reflecting and condensing mirror
3
condenses light beams from the light source
2
, that is, a discharge lamp, and emits the result in approximately the same direction.
The integrator optical system
4
spatially equally illuminates the SLM
6
, that is, spatially uniformly distributes the light emitted from the reflecting and condensing mirror
3
in order to illuminate the SLM
6
with a uniform distribution of luminous intensity.
The reason of realizing this uniform illumination is for achieving a high quality image.
The integrator optical system
4
, as shown in
FIG. 2
, is comprised of a first multi-lens array (MLA)
4
A and a second multi-lens array
4
B both of which include a plurality of lens LNS arranged in an array.
The first MLA
4
A divides the light emitted from the reflecting and condensing mirror
3
into a plurality of images and lays out their images of the light source in the vicinity of light incident plane of the second MLA
4
B.
The second MLA
4
B guides the images of light source divided by the first MLA
4
A to the condenser lens
5
so that they can be incident as the illuminating light of the SLM
6
.
In a projector having an optical system of such a configuration, the light emitted from the light source
2
is condensed by the reflecting and condensing mirror
3
having a reflecting surface of a parabolic shape, becomes nearly parallel light, and is incident on the first MLA
4
A.
The light incident on the first MLA
4
A is incident on the second MLA
4
B arranged in the proximity of the focal distances of the lenses LNS of the first MLA
4
A.
The light emitted from the second MLA
4
B is condensed by the condenser lens
5
so that the images of the lenses of the first MLA
4
A are superposed and is incident on the SLM
6
as illuminating light.
By superposing the images of the lenses of the first MLA
4
A, even if the light incident on the first MLA
4
A is not spatially uniform, the condensed image becomes spatially uniform.
In addition, a video signal is applied to the SLM
6
. At the SLM
6
, the incident light is spatially modulated and emitted in accordance with the applied video signal. For example, if the SLM is a liquid crystal panel, the intensity modulation is carried out by using deflection. If a DMD is used, the intensity modulation is carried out by changing the angle of emission of the emitted light (deflection).
The light emitted from the SLM
6
passes through the projecting lens
7
and is projected on the screen
8
. An image of the SLM
6
is projected on the screen
8
by the projecting lens
7
, whereby the video signal applied to the SLM
6
is displayed.
Summarizing the problem to be solved by the invention, reducing the size of an apparatus is important from the point of view of reducing weight, the amount of material, and so on.
To reduce the size of a projector using an SLM, for example reduction of the size of the SLM panel may be mentioned. This results in reduced size of the optical system, reduced size of the projecting lens, etc. Many optical elements forming an optical system can be made smaller.
The discharge lamp that forms the light source
2
, however, cannot be made small easily. The reasons are as follows.
That is, a discharge lamp has a high pressure gas sealed in its interior. Further, its temperature is elevated in order for emitting light. Due to this, considering safety when the lamp is broken, it is necessary to give the lamp sufficient strength. Therefore it cannot be made small easily.
FIG. 3
is a schematic view of a discharge lamp that forms a light source
2
.
A high pressure gas is sealed in the interior of the glass
2
A at the center of the lamp. Electrodes
2
B and
2
C stick out from the portion sealing the high pressure gas. Light is emitted by passing a current through the electrodes
2
B and
2
C.
In addition,
FIG. 4
is a schematic view of the reflecting and condensing mirror
3
.
As shown in
FIG. 4
, the reflecting surface
3
of the reflecting and condensing mirror
3
is shaped as a parabolic surface. A mount
3
B for plugging in the discharge lamp is formed at its approximate center.
The discharge lamp is mounted to such a reflecting and condensing mirror
3
as shown in FIG.
5
.
To facilitate change of the discharge lamp, or considering safety when the discharge lamp is broken, the discharge lamp is integrated with the reflecting and condensing mirror
3
by the insertion mount
3
B. Further, a surface plate
3
C being a plane plate just for passing light is provided at the plane from which the light leaves the reflecting and condensing mirror
3
so as to prevent pieces of glass from flying out from the reflecting and condensing mirror
3
when the discharge lamp is broken.
As described above, since the discharge lamp cannot be made small, the reflecting and condensing mirror
3
has to be large.
For example, as shown in
FIG. 6
, even if the cross-section of the light emitted from the reflecting and condensing mirror
3
is small, the total length of the discharge lamp does not change, so the total length of the reflecting and condensing mirror
3
does not become shorter.
In this way, because the discharge lamp
2
and the reflecting and condensing mirror
3
cannot be made small and because the integrator optical system
4
is arranged on the outgoing optical path of the light from the reflecting and condensing mirror
3
and at a position apart from the discharge lamp
2
and the surface plate
3
before that, the optical path of the illuminating light coming from the discharge lamp
2
through the reflecting and condensing mirror
3
becomes longer, the illumination optical apparatus becomes large, and consequently there is a problem that reduction of size of the projector is difficult.
SUMMARY OF THE INVENTION
The present invention was made in consideration of the above situation and has as an object to provide an optical system able to realize reduced size and a projection type display apparatus using the same. to a first aspect of the present
According to a first aspect of the present invention, there is provided the optical apparatus comprising a light source, a reflecting and condensing mirror for reflecting and condensing a light beam from the light source, guiding the light beam to substantially the same direction, and emitting the light beam from a light emitting part, a first multi-lens array in which a plurality of lens are arranged, and which divides an incident light into a plurality of images, and lays out the light spots of the divided images at predetermined locations, and a second multi-lens array in which a plurality of lens corresponding to the plurality of light spots condensed by the first multi-lens array are arranged and which is arranged in the proximity of the focal distance of the first multi-lens array, wherein the first multi-lens array is arranged integrally at the light emitting part of the reflecting and condensing mirror so that the
Adams Russell
Esplin D. Ben
Frommer William S.
Santisi Leonard J.
Sony Corporation
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