Devices and methods for enhancing brightness of displays using angle conversion layers

Abstract

Various embodiments of the present invention relate to enhancing the brightness of displays that employ illumination systems. In some embodiments, the illumination systems include light guides, diffractive microstructure, and light-turning features. The diffractive microstructure may be configured to receive ambient light at a first angle and produce diffracted light at a second angle greater than the first angle and greater than the critical angle for of light guide. The light is thereby guided within the light guide. The light-turning features may be configured to turn the light guided within the light guide out of a light guide and onto, for example, a spatial light modulator at near normal incidence.

1 . A display system, comprising:
 an array of display elements; and   an angle conversion layer overlying the display elements,   wherein the angle conversion layer is configured to turn ambient light towards the array of display elements such that the turned light is reflected and propagates away from the display system at angles within a field of view of the display system, wherein the turned light is incident on the angle conversion layer at angles outside of the field of view of the display system.   
     
     
         2 . The system of  claim 1 , wherein the angle conversion layer includes a diffractive microstructure. 
     
     
         3 . The system of  claim 2 , wherein the angle conversion layer is a holographic turning layer and the diffractive microstructure includes holographic light turning features. 
     
     
         4 . The system of  claim 3 , wherein the holographic light turning features are part of a volume hologram. 
     
     
         5 . The system of  claim 2 , wherein the turned light is incident on the diffractive microstructure from a plurality of directions. 
     
     
         6 . The system of  claim 1 , wherein the field of view is within about ±60° of a normal to a first surface of the display. 
     
     
         7 . The system of  claim 6 , wherein the field of view is within about ±45° of the normal to the first surface of the display 
     
     
         8 . The system of  claim 1 , wherein the display elements are reflective display elements. 
     
     
         9 . The system of  claim 8 , wherein the display elements include interferometric modulators, each interferometric modulator including a surface for reflecting the turned light. 
     
     
         10 . The system of  claim 1 , further comprising:
 a processor that is configured to communicate with the display elements, the processor being configured to process image data; and   a memory system that is configured to communicate with the processor.   
     
     
         11 . The system of  claim 10 , further comprising:
 a driver circuit configured to send at least one signal to the display.   
     
     
         12 . The system of  claim 11 , further comprising:
 a controller configured to send at least a portion of the image data to the driver circuit.   
     
     
         13 . The system of  claim 10 , further comprising:
 an image source module configured to send the image data to the processor.   
     
     
         14 . The system of  claim 13 , wherein the image source module includes at least one of a receiver, transceiver, and transmitter. 
     
     
         15 . The system of  claim 10 , further comprising:
 an input device configured to receive input data and to communicate the input data to the processor.   
     
     
         16 . A display system, comprising:
 a plurality of display elements configured to transmit reflected incident light outward from an image-displaying side of the display system to form a displayed image; and   a means for turning light incident on the display system towards the plurality of display elements such that the turned light is reflected from the plurality of display means and the reflected turned light propagates away from the display system at angles within a field of view of the display system, wherein the reflected turned light is incident on the means for turning light at angles outside of the field of view of the display system.   
     
     
         17 . The system of  claim 16 , wherein the plurality of display elements is a plurality of interferometric modulators. 
     
     
         18 . The system of  claim 16 , wherein the means for turning light includes a diffractive microstructure. 
     
     
         19 . The system of  claim 18 , wherein the diffractive microstructure is a volume diffractive microstructure. 
     
     
         20 . The system of  claim 16 , wherein the means for turning light is a hologram. 
     
     
         21 . The system of  claim 16 , wherein the field of view is within about ±60° of a normal to a first surface of the display system. 
     
     
         22 . A method for manufacturing a display system, comprising:
 providing a reflective display having a reflective layer; and   providing an angle conversion layer on the display, the angle conversion layer including a diffractive microstructure configured to turn light incident on the display towards the reflective layer such that the turned light is reflected off the reflective layer and the reflected turned light propagates away from the display at angles within a field of view of the display, wherein the reflected turned light is incident on the angle conversion layer at angles outside of the field of view of the display.   
     
     
         23 . The method of  claim 22 , wherein providing the angle conversion layer includes providing a holographic layer. 
     
     
         24 . The method of  claim 22 , wherein providing the angle conversion layer includes attaching the angle conversion layer to the reflective display. 
     
     
         25 . The method of  claim 22 , wherein providing the reflective display includes forming a plurality of interferometric modulators, the interferometric modulators forming pixels of the display.