Optical unit, video display apparatus, and color switching method

• US 7,474,360 B2
• Filed: 09/12/2005
• Issued: 01/06/2009
• Est. Priority Date: 10/02/2000
• Status: Expired due to Fees

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ouchi, Satoshi, Kabuto, Nobuaki, Imahase, Taro
• Primary Examiner(s): LEE, MICHAEL
• Application Number:
  US11/222,787
• Publication Number:
  US 20060012722A1
• Time in Patent Office: 1,212 Days
• Field of Search: 348/742, 348/743, 348/771, 349/96, 349/97, 349/117, 353/31, 353/122
• US Class Current: 348/742
• CPC Class Codes: G02B 27/283 used for beam splitting or combining
• CPC Class Codes: G03B 21/006 using LCD's
• CPC Class Codes: G03B 21/2073 Polarisers in the lamp house peculiar to electronic spatial light modulators H04N9/3197
• CPC Class Codes: G03B 33/08 Sequential recording or projection G03B33/02, G03B33/04, G03B33/06 take precedence
• CPC Class Codes: H04N 9/3117 by using a sequential colour filter producing two or more colours simultaneously, e.g. by creating scrolling colour bands

Abstract

A projection-type video display apparatus has a polarizing beam splitter for matching light, which is outputted by a light source unit, to one of S polarizing light and P polarizing light, an optical characteristics switching element for electrically and periodically switching a wavelength band of light outputted by the polarizing beam splitter, a video display element, as a light valve element, for forming an optical image from light outputted by the light source unit, in accordance with a video signal, and a radiating unit for radiating a plurality of color light, which are sequentially outputted by the optical characteristics switching element, to the video display element, wherein light outputted by the video display element is incident on a projecting lens, and a light path from the light source unit to the projecting lens is U-shaped. Consequently, the projection-type video display apparatus becomes compact and has improved contrast.

Claims

1. A video display apparatus, comprising:

a light source unit for radiating a light beam;

a polarization converter for matching the light beam, which is outputted by said light source unit, to one of a S polarized light beam and a P polarized light beam;

an optical characteristics switching element for separating a polarized light beam, which is outputted by said polarizing converter, into a plurality of color light beams, condensing the plurality of color light beams at different positions, and sequentially moving the plurality of color light beams between the different positions; and

a video display element, as light valve element, for forming an optical image with said plurality of color light beams, in accordance with a video signal; and

wherein said plurality of color light beams outputted by said optical characteristics switching element are radiated at different areas of said video display element, and said plurality of color light sequentially move between said different areas of said video display element.

2. An apparatus according to claim 1, further comprising:

an image forming optical system,

wherein said optical characteristics switching element comprises a hologram-type optical characteristics switching element using a diffracted light beam, and condenses said plurality of color lights beams at different positions of said image farming optical system.

3. An apparatus according to claim 1, further comprising:

an image forming optical system for forming an image of the plurality of color light beams outputted by said optical characteristics switching elements to said video display element,

wherein said optical characteristics switching element comprises a plurality of reflection-type optical characteristics switching elements for outputting and switching a color light beam sequentially, and an image forming lens, and the plurality of color light beams respectively outputted by said plurality of reflection-type optical characteristics switching elements are condensed at difference positions of said image forming lens.

5. An apparatus according to claim 1,

wherein said optical characteristics switching element is a reflection-type optical characteristics switching element comprising a total reflection prism by which the light beam outputted by said polarization converter is reflected, and

wherein the light beam reflected by said total reflection prism is transmitted through said video display element via said image forming optical system and is incident on said projector.

6. An apparatus according to claim 3, wherein said image forming lens is an aspherical lens.

4. A video display apparatus, comprising:

a light source unit for radiating a light beam;

a first polarizing beam splitter for matching the light beam, to one of a S polarized light beam and a P polarized light beam;

a first optical characteristics switching element of a transmission-type, for sequentially outputting a plurality of a first polarized light beam outputted by said first polarizing beam splitter;

a second polarizing beam splitter for reflecting the first polarized light beam outputted by said first optical characteristics switching element and transmitting a second light beam and a third light beam each having the other polarized light;

a second optical characteristics switching element for converting a polarizing axis of said second light beam;

a third polarizing beam splitter for reflecting said second light beam outputted by said second optical characteristics switching element and transmitting said third light beam;

a reflecting mirror for reflecting said third light beam which is transmitted through said third polarizing beam splitter;

a video display element, as light valve element, for forming an optical image, in accordance with a video signal; and

an image forming optical system which comprises an image forming lens,

wherein said first light beam reflected to said second polarizing beam splitter, said second light beam reflected to said third polarizing beam splitter, and said third light beam reflected to said reflecting mirror are radiated at different positions of said image forming lens.

7. An apparatus according to claim 4,

wherein said optical characteristics switching element is a reflection-type optical characteristics switching element comprising a total reflection prism by which the light beam outputted by said polarization converter is reflected, and

wherein the light beam reflected by said total reflection prism is transmitted through said video display element via said image forming optical system and is incident on said projector.

8. An apparatus according to claim 4, wherein said image forming lens is an aspherical lens.