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

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.

What is claimed:  
     
       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 minor 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 add 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 first plane mirror and all light transmitting in said further reflected magnified picture is transmitted toward said polarizing plate so that all of said light is projected onto said screen.  
     
     
       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 minor 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 all of 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.  
     
     
       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. 
     
     
       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.