Optical: systems and elements – Polarization without modulation – Polarizarion by dichroism
Reexamination Certificate
2000-02-25
2002-02-19
Spyrou, Cassandra (Department: 2872)
Optical: systems and elements
Polarization without modulation
Polarizarion by dichroism
C359S490020, C359S634000, C353S020000, C349S009000
Reexamination Certificate
active
06348997
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polarizing illumination device for uniformly illuminating a rectangular illumination area and the like by using polarized light beams polarized in the same direction, and to a projector using the polarizing illumination device. More particularly, the present invention relates to a structural technique for synthesizing light emitted from two light source sections while unifying the directions of polarization of the light.
2. Description of Related Art
A liquid crystal display device using a modulation device of a type that modulates a specific polarized light beam, such as a liquid crystal device, can utilize only one of two types of polarized light components included in light emitted from a light source. Therefore, there is a need to enhance light utilization efficiency in order to obtain a bright projection image. However, since a projector using only one light source has a limited ability to enhance light utilization efficiency, the amount of light has been increased by using a plurality of light sources as a way of obtaining a bright image.
However, when simply a plurality of light sources are arranged, the angle distribution of light for illuminating an illumination area is increased (the illumination angle is increased). Therefore, the amount of light in a given illumination angle is the same as that in the case where only one single light source is used. Consequently, in a projector in which the illumination angle is controlled by a projection system, the amount of light is not practically increased even when a plurality of light sources are used.
In addition, even if the amount of light is increased by using a plurality of light sources, when only one of two types of polarized light components, which are included in light emitted from the light sources, can be used, and half the light is wasted, which reduces the effectiveness by half.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a polarizing illumination device that is able to utilize both polarized light components by using a plurality of light sources, without increasing the illumination angle, and to provide a projector that is able to project a considerably bright projection image.
In order to achieve the above object, according to the present invention, there is provided a polarizing illumination device including:
a polarization separating optical element having a first polarization separating film for separating light incident from a first direction into two types of polarized light beams, emitting transmitted light in a third direction, and emitting reflected light in a fourth direction, and a second polarization separation film for separating light incident from a second direction into two types of polarized light beams, emitting reflected light in the fourth direction, and emitting transmitted light in a fifth direction;
a first light source section for allowing light to enter the polarization separating optical element from the first direction;
a second light source section for allowing light to enter the polarization separating optical element from the second direction;
a first condensing-and-reflecting optical element including a plurality of condensing-and-reflecting devices for approximately reversing the direction of travel of the light emitted in the third direction by the polarization separating optical element and forming a plurality of focal images;
a second condensing-and-reflecting optical element including a plurality of condensing-and-reflecting devices for approximately reversing the direction of travel of the light emitted in the fifth direction by the polarization separating optical element and forming a plurality of focal images;
a reflecting optical element for approximately reversing the direction of travel of the light emitted in the fourth direction by the polarization separating optical element;
a first polarization-state conversion optical element disposed between the polarization separating optical element and the first condensing-and-reflecting optical element;
a second polarization-state conversion optical element disposed between the polarization separating optical element and the second condensing-and-reflecting optical element;
a third polarization-state conversion optical element disposed between the polarization separating optical element and the reflecting optical element; and
a polarization conversion optical element for unifying the direction of polarization of the light emitted in a sixth direction from the polarization separating optical element;
wherein an approximately central axis of a luminous flux, which is reflected by the condensing-and-reflecting devices of the first condensing-and-reflecting optical element and enters the polarization conversion optical element, and an approximately central axis of a luminous flux, which is reflected by the condensing-and-reflecting devices of the second condensing-and-reflecting optical element and enters the polarization conversion optical element, are not parallel to each other, and do not overlap.
In the polarizing illumination device of the present invention, a randomly polarized light beam emitted from the first optical source section is allowed to enter from the first direction of the polarization separating optical element, and is separated into two types of polarized light beams by the first polarization separating film. On the other hand, a randomly polarized light beam emitted from the second light source section is allowed to enter from the second direction of the polarization separating optical element, and is separated into two types of polarized light beams by the second polarization separating film.
Of the thus-separated polarized light beams, the transmitted light, which is emitted in the third direction by the first polarization separating film, passes through the first polarization-state conversion optical element, is reflected by the first condensing-and-reflecting optical element, passes through the first polarization-state conversion optical element again, and travels toward the polarization separating optical element. In this case, this light is separated into a plurality of intermediate luminous fluxes by the first condensing-and-reflecting optical element, and passes through the first polarization-state conversion optical element two times, whereby it is converted into a polarized light beam whose direction of polarization is rotated about
90
degrees. Therefore, this light is reflected by the first polarization separating film, and is emitted in the sixth direction. The polarized light beam emitted in the sixth direction in this way is designated as a first polarized luminous flux.
In addition, the transmitted light, which is emitted in the fifth direction by the second polarization separating film, passes through the second polarization-state conversion optical element, is reflected by the second condensing-and-reflecting optical element, passes through the second polarization-state conversion optical element again, and travels toward the polarization separating optical element. In this case, this light is separated into a plurality of intermediate luminous fluxes by the second condensing-and-reflecting optical element, and passes through the second polarization-state conversion optical element two times, whereby it is converted into a polarized light beam whose direction of polarization is rotated about 90 degrees. Therefore, this light is reflected by the second polarization separating film, and is emitted in the sixth direction. The polarized light beam emitted in the sixth direction in this way is designated as a second polarized luminous flux.
The first and second polarized luminous fluxes each including a plurality of intermediate luminous fluxes form a plurality of focal images on the polarization conversion optical element or in the vicinity thereof. Here, approximately central axes of the first and second polarized luminous fluxes are not parallel to each other, and do not o
Cherry Euncha
Oliff & Berridg,e PLC
Seiko Epson Corporation
Spyrou Cassandra
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