Liquid crystal reflective polarizer and pancake lens assembly having the same

Abstract

An illumination system is provided. The illumination system includes a light source assembly configured to output a first polarized light having a first handedness. The illumination system also includes a light guide plate configured to guide the first polarized light received from the light source assembly and output a second polarized light having a second handedness opposite to the first handedness. The light guide plate includes two wedges coupled to one other at a slanted surface between the two wedges and a reflective polarizer disposed at the slanted surface. The illumination system also includes a reflective sheet arranged at a first side surface of the light guide plate and configured to reflect the first polarized light as the second polarized light. The reflective polarizer includes a birefringent material having a chirality, and is configured to selectively transmit the first polarized light and reflect the second polarized light.

What is claimed is: 
     
         1 . An illumination system, comprising:
 a light source assembly configured to output a first polarized light having a first handedness;   a light guide plate configured to guide the first polarized light received from the light source assembly and output a second polarized light having a second handedness opposite to the first handedness, the light guide plate including two wedges coupled to one other at a slanted surface between the two wedges and a reflective polarizer disposed at the slanted surface; and   a reflective sheet arranged at a first side surface of the light guide plate and configured to reflect the first polarized light as the second polarized light,   wherein the reflective polarizer includes a birefringent material having a chirality, and is configured to selectively transmit the first polarized light and reflect the second polarized light.   
     
     
         2 . The illumination system of  claim 1 , wherein
 the light source assembly is coupled to the light guide plate at a second side surface of the light guide plate, and   the first side surface and the second side surface of the light guide plate are arranged opposite to one another.   
     
     
         3 . The illumination system of  claim 1 , wherein
 the light guide plate is configured to guide the first polarized light received from the light source assembly to the reflective sheet,   the reflective sheet is configured to reflect the first polarized light as the second polarized light,   the light guide plate is configured to guide the second polarized light received from the reflective sheet to the reflective polarizer, and   the reflective polarizer is configured to reflect the second polarized light to output from a light outputting surface of the light guide plate to illuminate a display panel.   
     
     
         4 . The illumination system of  claim 3 , wherein the light outputting surface is arranged between the first side surface and the second side surface of the light guide plate. 
     
     
         5 . The illumination system of  claim 3 , further comprising at least one of a diffuser sheet or a prism sheet disposed at the light outputting surface of the light guide plate. 
     
     
         6 . The illumination system of  claim 1 , wherein the reflective polarizer is a cholesteric liquid crystal (“CLC”) reflective polarizer. 
     
     
         7 . The illumination system of  claim 6 , wherein the light source assembly includes a narrowband monochromatic light source, and the CLC reflective polarizer is a narrowband CLC reflective polarizer with a constant helix pitch. 
     
     
         8 . The illumination system of  claim 6 , wherein the light source assembly includes a broadband light source, and the CLC reflective polarizer is a broadband CLC reflective polarizer with a gradient helix pitch. 
     
     
         9 . The illumination system of  claim 6 , wherein the light source assembly includes a plurality of narrowband monochromatic light sources for different colors, and the CLC reflective polarizer includes a plurality of CLC layers stacked together, the CLC layers having at least two different helix pitches. 
     
     
         10 . A system, comprising:
 a light guide plate including two wedges having slanted surfaces coupled to one other;   a reflective sheet coupled to the light guide plate and configured to reflect a first polarized light having a first handedness as a second polarized light having a second handedness opposite to the first handedness; and   a reflective polarizer disposed between the slanted surfaces and configured to selectively transmit the first polarized light and reflect the second polarized light,   wherein the light guide plate is configured to guide the first polarized light to the reflective sheet, and guide the second polarized light reflected from the reflective sheet to the reflective polarizer.   
     
     
         11 . The system of  claim 10 , wherein the reflective sheet is disposed at a first side surface of the light guide plate, and the system further comprises a light source assembly disposed at a second side surface of the light guide plate opposite to the first side surface, the light source assembly being configured to output the first polarized light. 
     
     
         12 . The system of  claim 11 , wherein the reflective polarizer is configured to reflect the second polarized light guided by the light guide plate toward a light outputting surface of the light guide plate, and the second polarized light is output from the light outputting surface to illuminate a display panel. 
     
     
         13 . The system of  claim 12 , wherein the light outputting surface is a surface connecting the first side surface and the second side surface of the light guide plate. 
     
     
         14 . The system of  claim 12 , wherein the light outputting surface is perpendicular to the first side surface and the second side surface of the light guide plate. 
     
     
         15 . The system of  claim 12 , wherein the side surface and the second side surface are parallel to one another. 
     
     
         16 . The system of  claim 12 , further comprising at least one of a diffuser sheet or a prism sheet disposed at the light outputting surface of the light guide plate. 
     
     
         17 . The system of  claim 10 , wherein the reflective polarizer is a cholesteric liquid crystal (“CLC”) reflective polarizer.