Polarization conversion element, polarization illuminator, display using the same illuminator, and projector

Abstract

A polarizing conversion device in accordance with the invention includes a first optical element for condensing an incident beam and forming a plurality of intermediate beams spatially separated from one another, and a second optical element for spatially separating each intermediate beam into two polarized beams and aligning the polarization directions of the polarized beams, thereby obtaining the same type of polarized beams. In the second optical element, a shading plate is placed to prevent light from directly entering a section corresponding to a reflecting plane of a polarizing separation unit array. Since the ability of separating the intermediate beam into two polarized beams is thereby enhanced, it is possible to perform conversion into the same type of polarized beams polarized in the same direction, with high efficiency.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a polarizing conversion device and a polarizing illumination device for generating, from incident light beams as randomly polarized beams, illuminating beams that have a more uniform light intensity distribution in an illumination region than that of the incident beams and are polarized in almost the same direction. Furthermore, the present invention relates to a display apparatus and a projection display apparatusprojector using these devices.[0003]2. Description of Related Art[0004]A polarizing illumination device capable of efficiently generating the same type of polarized light beams is ideal as an illuminating device for use in a display apparatus, such as a liquid crystal apparatus, which employs a panel for modulating polarized light beams. Accordingly, an illuminating optical system has been proposed that converts random polarized light beams emitted from a light source into the ...

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Benefits of technology

[0034]By adopting the above structure, the projection display apparatusprojector of the present invention can effectively prevent a phenomenon in which other polarized beams polarized in a different direction mix into polarized beams of almost the same type polarized in the same direction. Therefore, when a polarizing plate is used to obtain a required polarized beam to be modulated by the modulating device, it is possible to prevent the increase in temperature of the polarizing plate caused by absorption of an unnecessary polarized beam, and to substantially simplify and reduce the size of a cooling device for cooling the polarizing plate. A liquid crystal device may be used as the modulating device.

[0035]According to the above structure, an incident beam is initially separated into a plurality of intermediate beams and the intermediate beams are finally superimposed on the modulating device. Therefore, even if the intensity distribution of the light emitted from the light source is very imbalanced in the cross section thereof, it is possible to obtain as illumination light polarized beams that are uniform in brightness and color. Consequently, it is possible to achieve a compact display apparatus capable of producing a display that is bright and uniform in brightness and color.

[0036]The projection display apparatusprojector fu...

Problems solved by technology

The optical system disclosed in Japanese Unexamined Patent Publication No. 7-294906 has, however, the following problems.

However, a real light source has a limited emission area.

Therefore, parallelism of the light beam emitted from the light source is not always good.

Consequently, it is impossible to excessively increase the refractive power of the small lens used for reducing the diameter of the beam.

For the above reasons, it is difficult to sufficiently reduce the diameter of the l...

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