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 ...

AI Technical Summary

Benefits of technology

[0011]It is therefore an object of the present invention to solve the above problems by substantially restricting the mixing of other polarized beams, which are polarized in a different direction, in a process of converting randomly polarized beams emitted from a light source into the same type of polarized beams.

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 light beam that is incident on the polarizing beam splitter, and, in actuality, a relatively large amount of light also directly enters the reflecting prism adjoining the polarizing beam splitter.

Thus, in the process in which the conventional optical system disclosed in Japanese Unexamined Patent Publication No. 7-294906 converts random light beams emitted from the light source into polarized beams of the same type, a relatively large number of polarized beams of another type inevitably mix.

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