Optics: image projectors – Unitary plural refracting surfaces
Reexamination Certificate
2000-02-10
2001-06-19
Dowling, William (Department: 2851)
Optics: image projectors
Unitary plural refracting surfaces
C353S119000, C353S020000
Reexamination Certificate
active
06247817
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
The invention relates to a projection-type display apparatus which modulates light emitted from a light source in accordance with image signals using modulation devices such as liquid crystal light valves or the like, and performs enlarged projection of the light flux following modulation upon a screen via a projecting lens. More particularly, the invention relates to a structure for a projection-type display apparatus of such a type whereby the image formation range of the modulating devices can be illuminated in an appropriate manner.
2. Description of Related Art
A conventional projection-type display apparatus which forms modulated light flux in accordance with image signals using liquid crystal light valves and performs enlarged projection of the modulated light flux on a screen is disclosed in Japanese Unexamined Patent Publication No. 3-111806. The projection-type display apparatus disclosed in this Patent Publication is, as shown in
FIG. 14
, provided with an integrator optical system
923
. The integrator optical system
923
has two lens plates
921
and
922
for uniform illumination of the image formation range of the liquid crystal light valve
925
. The liquid crystal light valve
951
serves as the modulation device of the light emitted from the light source.
In
FIG. 14
, the single light flux emitted from the light source lamp unit
8
is separated into a plurality of intermediate light fluxes by lenses
921
a
of the first lens plate
921
. The light flux is superimposed on the liquid crystal light valve
951
via lenses
922
a
of the second lens plate
922
.
Regarding projection-type display apparatuses of the type illustrated in
FIG. 14
, problems occur when the image formation range of the liquid crystal light valve
951
cannot be illuminated accurately. These problems include a reduction in the brightness of the image projected on the projection surface, or the creation of shadows at the edge of the projected image. Accordingly, as illustrated in
FIG. 15
, a certain margin M is secured around the image formation area A of the liquid crystal light valve
925
, depending on various factors including the positioning precision of the liquid crystal light valve
951
and the lens plates
921
and
922
of the integrator optical system
923
, the margin of error of the focal distance and so forth of the lenses
921
a
and
922
a
of each of the lens plates, and the positioning precision and the like of other optical components disposed on the optical path. In other words, the image formation area A of the liquid crystal light valve
951
is sized to be distinctly smaller than the illumination range B of light emitted by the light source, so that even in the event that the illumination range B is shifted vertically or horizontally due to the positioning precision of the above-described components, the image formation range A does not extend beyond the illumination range B. This structure avoids problems such as the reduction of the brightness of the image projected on the projection surface, or the creation of shadows at the edge of the projected image. Thus, simply increasing the margin M is sufficient to deal with a wide margin of error in positioning of the above-described components.
On the other hand, in order to increase the brightness of the projected image, it is necessary to increase the usage efficiency of the light which is illuminating the liquid crystal light valve
925
. However, the problem occurs that when the margin M is increased to deal with a wide margin of error in positioning of the above-described components, the usage efficiency of the separated light decreases, and the projected image becomes dark. Accordingly, from this perspective, it is desirable that the margin formed around the display range of the liquid crystal light valve be as narrow as possible. However, if the margin is made to be narrow, the illumination range misses the image formation range of the liquid crystal light valve, as described above, so that shadows may be formed at the edge of the projected image.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a projection-type display apparatus wherein the margin formed around the image forming range of the liquid crystal light valve is small, and at the same time, capable of increasing the brightness of the projected image without forming shadows at the edge of the projected image.
In order to solve the above-described problems, a first projection-type display apparatus in accordance with the invention includes a light source; a modulating device for modulating light flux emitted from the light source in accordance with image signals; and a projecting device for performing enlarged projection of the light flux modulated by the modulating device upon a projection surface; wherein an integrator optical system having a first lens plate and a second lens plate that include a plurality of lenses arrayed in matrix-form is placed in the optical path between the light source and the modulating device; and wherein at least one of the first and second lens plates is arranged so that an attachment position thereof is adjustable in a direction intersecting the optical axis.
According to the structure described above, the invention is capable of increasing the usage efficiency of the light which is illuminating the modulating device, and the projected image can be made to be brighter. Also, fine adjustment of the illumination area of the modulation device can be performed so that the image forming range is positioned within the illumination area, which avoids problems such as the reduction of the brightness of the image projected upon the projection surface, or the creation of shadows at the edge of the projected image, even if the margin formed around the image forming range of the modulation device is made to be small.
In other words, subsequent to mounting the various components of the optical system, the image forming range of the modulation device is illuminated using the integrator optical system, and in the event that the illumination range is not within the image forming range of the modulation device, the attachment position of the first lens plate or the second lens plate of the integrator optical system is subjected to fine adjustment, so that the image forming range of the modulation device can be brought to be completely within the illumination range. Accordingly, the margin formed around the image forming range of the modulation device can be reduced and still handle the offset between the illumination range and the image formation range caused by the margin of error in the positioning of optical parts.
Further, the reflecting device for bending the optical path is sometimes provided on the optical path extending from the light source to the modulation device of projection-type apparatuses. In such cases, any margin of error in the attachment angle of the reflecting device may cause the illumination range to be offset from the image formation range of the modulating device. Accordingly, it is desirable that the attachment angle of the reflecting device mounted to his position also be adjustable relative to the incident optical axis.
Also, the above-described first embodiment of the projection-type display apparatus can similarly be applied to projection-type display apparatuses capable of protecting color images. In other words, the invention can similarly be applied to a projection-type display apparatus that includes a color separating optical system for separating the light emitted from the light source into light flux of each color, a plurality of the modulating devices for modulating the light flux of each color separated by the color separating optical system, and a color synthesizing system for synthesizing the light flux of each color modulated by the plurality of the modulating devices, wherein the modulated light flux synthesized by the color synthesizing system is projected on a projecting surface via the projecting device.
With
Haba Shinji
Hashizume Toshiaki
Iechika Hisashi
Ogawa Yasunori
Yajima Akitaka
Dowling William
Oliff & Berridg,e PLC
Seiko Epson Corporation
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