Optics: image projectors – Polarizer or interference filter
Reexamination Certificate
2002-11-01
2004-03-02
Dowling, William (Department: 2851)
Optics: image projectors
Polarizer or interference filter
Reexamination Certificate
active
06698891
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polarizing unit to achieve illuminating light made up of, for example, linearly polarized light, a polarizing illumination device using a same polarizing/unit and a projection display device using a same polarizing/illumination.
The present application claims priorities of Japanese Patent Application Nos. 2001-337827 filed on Nov. 2, 2001 and 2002-207553 filed on Jul. 16, 2002, which are hereby incorporated by reference.
2. Description of the Related Art
In recent years, a step toward miniaturization and high definition proceeds and improvements of an optical system making up a projection display device is made. In particular, as a method for improving brightness of a projected image and uniformity of illumination of a screen both being a requirement for performing functions of a display device, an optical system configured by combining an integrated optical system made up of fly's eye lens with a polarized light converting optical system made up of a polarized light beam splitter array has become commercially practical and therefore an optical system using three pieces of liquid crystal display devices being currently on the market has the configuration described above.
In the optical system having the above configuration, by dividing light fed from a light source into a plurality of pieces of partial light using an integrated optical system made up of two pieces of fly's eye lens to form a plurality of light source images and by comparing the light source image to a secondary light source, and by superimposing light on the liquid crystal display devices, illuminating light having same distributions of intensity of light can be effectively obtained.
Moreover, by using the polarized light converting optical system made up of polarized beam splitter arrays and integrated optical systems in combination, illuminating light is superimposed on a liquid crystal panel after having divided light into a plurality of pieces of partial light and having converted polarized light, that is, after same polarization directions have been provided and, therefore, efficiency of using a light source is comparatively high.
However, in such the projection liquid crystal display device having configurations as described above, in ordinary cases, since sizes of the fly's eye lens and the polarized beam splitter array become larger than those of an image display portion of the liquid crystal display device serving as a surface to be illuminated, a diverging angle of incident light into the liquid crystal display device becomes large. When the diverging angle of incident light becomes large and, therefore, when parallelism of incident light into the liquid crystal panel is reduced, light cannot be applied effectively to the liquid crystal panel and, as a result, efficiency of using light is lowered. Moreover, in order to improve an aperture ratio of the liquid crystal panel, the liquid crystal display device having a microlens array is also commercially available, however, it is known that, in the projection liquid crystal display device, unless light having high parallelism is incident on the microlens, efficiency of using light transmitting through a pixel opening portion is reduced.
Conventional optical systems aimed at reducing a diverging angle of light being incident on a liquid crystal display device are disclosed in Japanese Patent Application Laid-open Nos. 2000-131647 and 2001-206464 in which an illumination unifying unit using a columnar integrated device (mainly, rod integrator) and a polarized light converting unit are combined. In the conventional optical systems, as a polarized light separating unit, an optical system in which a plurality of polarized light beam splitter arrays each having a polarized light separating film formed on a junction face between a rectangular prism and a wedge-type prism or a plurality of polarized light beam splitters are arranged in an array form.
However, since a device to obtain uniformity of illumination and a device to convert polarized light are independently arranged in both the conventional optical systems described above, physical space to house them is required. Since a polarized light beam splitter made of glass used, in particular, in the conventional optical system provided as the disclosed former example becomes relatively large, the conventional optical system is not suitable in realizing a small-sized projection display device. Moreover, the conventional optical system has a disadvantage in a point of costs. Since two rod integrators, one to be used for p-polarized light and another to be used for s-polarized light, each being separated by polarization, are required, the conventional optical system is not suitable in a point of making it lightweight and costs low. In the optical system provided in the disclosed latter example, since a necessary number of the rod integrators is one and polarized light converting process is performed using the polarized light beam splitter array, it is advantageous in point of weight and costs when compared with the optical system provided in the disclosed former example. However, since the optical device to be used for uniformity of illumination and the optical device to be used for polarized light conversion are independently placed, space for arrangement has to be secured and it lacks in a point of making the illuminating device compact.
SUMMARY OF THE INVENTION
In view of the above, it is a first object of the present invention to provide a polarizing unit which is capable of making compact an optical system made up of a columnar integrated device (mainly, rod integrator) and a polarized light converting optical system and of reducing a diverging angle of light being incident on a comparatively smaller liquid crystal panel. It is a second object of the present invention to provide a new type polarizing illumination device which is made small and lightweight when compared with a conventional polarizing illumination device and is capable of reducing a diverging angle of light being incident on a comparatively small liquid crystal panel by using the above polarizing unit. It is a third object of the present invention to achieve miniaturization of a single plate display device of a time-sharing type made up of an LCOS (Liquid Crystal On Silicon) and a projection display device made up of a microlens, by utilizing the above new type polarizing illumination device.
According to a first aspect of the present invention, there is provided a polarizing unit for receiving light fed from a light source and for emitting polarized-illuminating light to an subject to be illuminated, the polarizing unit comprising:
a polarized light converter (polarized light converting means) used to obtain a specified type of polarized light and, when polarized light is incident from a side of the subject to be illuminated, to convert a phase difference between two light components whose polarized directions orthogonal to each other and to emit the polarized light to a side of the subject to be illuminated;
a light guiding member (light guiding means) having a light incident end face formed on a side of the light source and a light outgoing end face formed on a side of the subject to be illuminated and used to have incident light travel in a straight line or have internal reflection occur to guide the light;
a polarized light separator (polarized light separating means) to separate a specified type of polarized light from an other specified type of polarized light and to transmit the separated polarized light; and
wherein the polarized light converter and the light guiding member are placed on a side of the light source in the polarized light separator.
With the above configuration, the polarized light converter, light guiding member, and polarized light separator can be formed in an integrated manner. As a result, the configuration contributes to miniaturization of the polarizing unit.
In the foregoing, a preferable mode is one wherei
Dowling William
NEC Viewtechnology Ltd.
Sughrue & Mion, PLLC
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