Optical system including a reflecting polarizer for a rear projection picture display apparatus

• US 5,557,343 A
• Filed: 01/26/1995
• Issued: 09/17/1996
• Est. Priority Date: 01/28/1994
• Status: Expired

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Yamagishi, Shigekazu
• Primary Examiner(s): Metjahic, Safet
• Assistant Examiner(s): WEST, NINA NHYCHON
• Application Number:
  US08/378,795
• Time in Patent Office: 600 Days
• Field of Search: 348/781, 348/383, 348/782, 348/780, 348/832, 348/751, 348/739, 348/744, 348/756, 348/757
• US Class Current: 348/781
• CPC Class Codes: G03B 21/10 Projectors with built-in or built-on screen
• CPC Class Codes: H04N 5/7408 Direct viewing projectors, e.g. an image displayed on a video CRT or LCD display being projected on a screen
• CPC Class Codes: H04N 9/3141 Constructional details thereof details not peculiar to the presence of an electronic spatial light modulator G03B21/14

Abstract

An optical system for a rear projection picture display has reduced size while maintaining screen size. Two plane mirrors are provided along a light path between a picture display unit and a screen. The first plane mirror at a projection lens side is made of a reflecting polarizer and is located along a light path between the second plane mirror and the screen. The two plane mirrors are set in a relative angle so that the incident angle of the light traveling from the projection lens to the first plane mirror is large as compared with the incident angle of the light traveling from the second plane mirror to the first plane mirror. A polarizing plate is attached at the rear side of the screen.

Claims

1. An optical system for a rear projection picture display apparatus comprising:

a picture display unit for generating a picture corresponding to an input video signal;

a projection lens for magnifying and projecting said picture to produce a magnified picture;

a first plane mirror positioned between a second plane mirror and a screen, said first plane mirror having a plane of incidence for receiving and reflecting said magnified picture to produce a reflected magnified picture, wherein said magnified picture is comprised of P-polarized light oscillating in a direction parallel to the plane of incidence and S-polarized light oscillating in a direction perpendicular to the plane of incidence;

said second plane mirror for receiving and reflecting said reflected magnified picture to produce a further reflected magnified picture; and

said screen for displaying said further reflected magnified picture, said screen including a polarizing plate for absorbing light forming said further reflected magnified picture oscillating in a parallel direction relative to said incidence plane;

wherein a first incident angle of light forming said magnified picture relative to said first plane mirror is larger than a second incident angle of light forming said further reflected magnified picture relative to said second plane mirror.

5. An optical system for a rear projection picture display apparatus as recited in claim 1, wherein said picture display unit comprises a picture display device in which the oscillating direction of emitted light forming said picture is restricted to a designated direction.

2. An optical system for a rear projection picture display apparatus comprising:

a picture display unit for generating a picture corresponding to an input video signal;

a projection lens for magnifying and projecting said picture to produce a magnified picture;

a first plane mirror comprised of a reflecting polarizer for receiving and reflecting said magnified picture to produce a reflected magnified picture, said first plane mirror positioned between a second plane mirror and a screen;

said second plane mirror including a quarter-wave plate on the reflecting surface of said second plane mirror for receiving and rotating the polarizing direction of light forming said reflected magnified picture; and

said screen for displaying said rotated light from said reflected magnified picture.

3. An optical system for a rear projection picture display apparatus as recited in claim 2, further comprising:

means located between said picture display unit and said first plane mirror for eliminating light oscillating in a parallel direction to an incidence plane of said first plane mirror.

4. An optical system for a rear projection picture display apparatus as recited in claim 2, further comprising:

a polarizing plate included with said screen for absorbing light oscillating in a perpendicular direction to the incidence plane of said first plane mirror.

6. An optical system for a rear projection picture display apparatus as recited in claim 2, wherein said picture display unit comprises a picture display device in which the oscillating direction of emitted light forming said picture is restricted to a designated direction.