Optical unit, video display apparatus, and color switching method

• US 7,929,064 B2
• Filed: 07/11/2008
• Issued: 04/19/2011
• Est. Priority Date: 10/02/2000
• Status: Expired due to Fees

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Imahase, Taro, Ouchi, Satoshi, Kabuto, Nobuaki
• Primary Examiner(s): LEE, MICHAEL
• Application Number:
  US12/216,846
• Publication Number:
  US 20080278636A1
• Time in Patent Office: 1,012 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 converting the light beam to one of an S polarized light beam and a P polarized light beam;

an optical characteristics switching element for electrically and periodically converting polarization of the light beam outputted by said polarization converter with respect to each of a plurality of wavelength bands to control the wavelength bands for generating a plurality of color light beams;

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

an image forming optical system comprising a plurality of lenses; and

a projector for projecting the optical image formed by said video display element, wherein;

the plurality of color light beams are radiated to said video display element through said image forming optical system,

said optical characteristics element simultaneously outputs the plurality of color light beams and radiates the plurality of color light beams at different areas of said video display element, and

said plurality of color light beams sequentially move between said different areas.

2. A video display apparatus comprising:

a light source unit for radiating a light beam;

a polarization converter for converting the light beam to one of an S polarized light beam and a P polarized light beam;

an optical characteristics switching element for electrically and periodically converting polarization of the light beam outputted by said polarization converter with respect to each of a plurality of wavelength bands to control the wavelength bands for generating a plurality of color light beams;

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

an image forming optical system comprising a plurality of lenses; and

a projector for projecting the optical image formed by said video display element, wherein;

the plurality of color light beams are radiated to said video display element through said image forming optical system, and

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

the light beam reflected by said total reflection prism is incident on said projector.