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
06348996
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 lights 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, 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. Since a projector using only one light source has a limited ability to enhance light utilization efficiency, however, the amount of light has been increased by using a plurality of light sources as a way to obtain a bright image.
When simply a plurality of light sources are arranged, however, 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:
first and second light source sections;
a polarization-separating-and-synthesizing optical element having a first polarizing separation film for transmitting, of light emitted from the first light source section, a linear polarized light polarized in a direction parallel to an incident surface thereof and reflecting a linear polarized light polarized in a direction perpendicular to the incident surface, and a second polarizing separation film for transmitting, of light emitted from the second light source section, a linear polarized light polarized in a direction perpendicular to an incident surface thereof and reflecting a linear polarized light polarized in a direction parallel to the incident surface;
a first condensing-and-reflecting optical element including a plurality of condensing-and-reflecting devices for approximately reversing the direction of travel of the linear polarized light transmitted by the first polarizing separation film and forming focal images;
a second condensing-and-reflecting optical element including a plurality of condensing-and-reflecting devices for approximately reversing the directions of travel of the linear polarized lights reflected by the first polarizing separation film and the second polarizing separation film and forming focal images;
a third condensing-and-reflecting optical element including a plurality condensing-and-reflecting optical devices for approximately reversing the direction of travel of the linear polarized light transmitted by the second polarizing separation film and forming focal images;
a first polarization-state conversion optical element disposed between the polarization-separating-and-synthesizing optical element and the first condensing-and-reflecting optical element;
a second polarization-state conversion optical element disposed between the polarization-separating-and-synthesizing optical element and the second condensing-and-reflecting optical element;
a third polarization-state conversion optical element disposed between the polarization-separating-and-synthesizing optical element and the third condensing-and-reflecting optical element; and
a polarization conversion optical element for unifying the directions of travel of linear polarized lights synthesized by the polarization-separating-and-synthesizing 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 the third 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.
The construction of the polarizing illumination device of the present invention will be described more in detail as follows.
Firstly, of the light polarized in random directions (hereinafter, referred to as “randomly polarized light”) that is emitted from the first light source section, the linear polarized light polarized in the direction parallel to an incident surface thereof passes through the first polarization separation film, and the linear polarized light polarized in the direction perpendicular to the incident surface is reflected by the first polarizing separation film. On the other hand, of the polarized light emitted from the second light source section, the linear polarized light polarized in the direction perpendicular to the incident surface thereof passes through the second polarizing separation film, and the linear polarized light polarized in the direction parallel to the incident surface is reflected by the second polarizing separation film. Here, “incident surface” is a technical term used in the field of optics, and relates to a virtual plane including an approximately central axis of a luminous flux entering a film and a normal line to the film.
The linear polarized light, which passes through the first polarizing separation 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-and-synthesizing optical element. In this case, this light is divided by the first condensing-and-reflecting optical element into a plurality of intermediate luminous fluxes to pass through the first polarization-state conversion optical element two times, whereby it is converted into a linear polarized light polarized in a different direction by about 90 degrees. Therefore, when the light returns to the polarization-separating-and-synthesizing optical element, it is reflected by the first polarizing separation film, and travels toward the polarization conversion optical element. The polarized light that travels toward the polarization conversion optical element in this way is designated as a first polarized luminous flux.
The linear polarized lights, which are reflected by the first polarizing separation film and by the second polarizing separation film, pass through the second polarization-state conversion optical element, are reflected by the second condensing-and-reflecting optical element, pass through the second polarization-state conversion optical element again, and travel toward the polarization-separating-and-synthesizing optical element. In this case, each of the light is divided by the second condensing-and-reflecting optical element into a p
Cherry Euncha
Oliff & Berridg,e PLC
Seiko Epson Corporation
Spyrou Cassandra
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