Directional flat illuminators

Abstract

Disclosed is an optical valve or light valve for providing large area collimated illumination from localized light sources, and system and method thereof for 2D, 3D, and/or autosteroscopic displays. An optical valve may include a stepped structure, in which the steps include separated extraction features which may be optically hidden to light propagating in a first direction. Light propagating in a second direction may be refracted, diffracted, or reflected by the features to provide illumination beams exiting from the top surface of the optical valve. Such controlled illumination may provide for efficient, multi-user autostereoscopic displays as well as improved 2D display functionality.

1 . A method for guiding light by employing an optical valve, comprising:
 allowing light rays to propagate in a first direction through the optical valve, wherein the light rays propagate in the first direction with substantially low loss;   allowing the light rays to interact with an end surface of the optical valve; and   allowing the light rays to propagate in a second direction through the optical valve, wherein at least some of the light rays encounter at least one extraction feature and are extracted from the optical valve.   
     
     
         2 . The method for guiding light by employing the optical valve of  claim 1 , wherein the light rays enter the optical valve at a first end, wherein the end surface is located at a second end of the optical valve, and wherein the optical valve is thicker at the second end than at the first end of the optical valve. 
     
     
         3 . The method for guiding light by employing the optical valve of  claim 2 , wherein the light rays propagating in the first direction, propagate from the first end to the second end, further wherein the light rays propagating in the second direction propagate from the second end to the first end, wherein the second end is a reflecting surface. 
     
     
         4 . The method for guiding light by employing the optical valve of  claim 3 , wherein the second end is a curved surface. 
     
     
         5 . The method for guiding light by employing the optical valve of  claim 1 , wherein the light rays encountering the at least one extraction feature further comprises the light rays reflecting off the extraction feature. 
     
     
         6 . The method for guiding light by employing the optical valve of  claim 1 , further comprising allowing the light to substantially expand when propagating in the first direction. 
     
     
         7 . The method for guiding light by employing an optical valve of  claim 2 , wherein light is generated by illumination elements and the light enters at the first end of the optical valve, and wherein the illumination elements are LEDs. 
     
     
         8 . The method for guiding light by employing an optical valve of  claim 1 , further comprising providing a substantially uniform illumination across a display. 
     
     
         9 . A light valve for guiding light, comprising:
 a first light guiding surface, wherein the first light guiding surface is substantially planar; and   a second light guiding surface, opposite the first light guiding surface, further comprising a plurality of guiding features and a plurality of extraction features, wherein the extraction features and the guiding features are connected to and alternate with one another respectively, further wherein the plurality of extraction features allow light to pass with substantially low loss when the light is propagating in a first direction and allow light to reflect and exit the light valve when the light is propagating in a second direction.   
     
     
         10 . The light valve for guiding light of  claim 9 , further comprising a first end, wherein light enters the light valve at the first end, further comprising a second end, wherein light interacts with the second end and is redirected back toward the first end, wherein the light valve thickness at a first end is thinner than at a second end, and wherein the second end comprises a reflecting surface. 
     
     
         11 . The light valve for guiding light of  claim 10 , wherein the second end comprises a curved surface. 
     
     
         12 . The light valve for guiding light of  claim 9 , wherein the extraction features are optically hidden from light propagating in a first direction. 
     
     
         13 . The light valve for guiding light of  claim 10 , further comprising illumination elements for generating light to enter at the first end of the light valve, wherein the illumination elements comprise an array of illumination elements configured to provide light at the first end of the light valve. 
     
     
         14 . The light valve for guiding light of  claim 9 , wherein each of the plurality of extraction features are substantially elongated linear surfaces. 
     
     
         15 . The light valve for guiding light of  claim 9 , wherein each of the plurality of extraction features are substantially parallel to one another, wherein the guiding features are substantially planar and are separated by substantially the same distance. 
     
     
         16 . The light valve for guiding light of  claim 9 , wherein at least one of the plurality of extraction features is coated with a reflective coating. 
     
     
         17 . The light valve for guiding light of  claim 9 , wherein the plurality of extraction features have a tilt angle in the approximate range between 20 and 50 degrees to each of the plurality of guiding features. 
     
     
         18 . The light valve for guiding light of  claim 9 , wherein the guiding features are substantially planar to the first light guiding surface. 
     
     
         19 . The light valve for guiding light of  claim 10 , wherein the second end is a convex mirror. 
     
     
         20 . The light valve for guiding light of  claim 10 , wherein the second end is a cylindrical mirror, wherein the optical axis of the cylindrical mirror is substantially orthogonal to the surface normal of the first light guiding surface. 
     
     
         21 . The light valve for guiding light of  claim 9 , wherein each extraction feature has a surface normal direction to direct at least some of the light rays propagating in the second direction to be extracted in a direction outside the light valve, wherein at least some of the extracted light rays pass from the extraction feature, and exit from the light valve through the first light guiding surface. 
     
     
         22 . The light valve for guiding light of  claim 9 , wherein the plurality of extraction features further comprise:
 a first region wherein the extraction features of the first region have a first orientation; and   a second region wherein the extraction features of the second region have a second orientation, wherein the first orientation and the second orientations are different from one another.   
     
     
         23 . The light valve for guiding light of  claim 9 , further comprising a Fresnel lens. 
     
     
         24 . The light valve for guiding light of  claim 9 , further comprising a vertical diffuser. 
     
     
         25 . The light valve for guiding light of  claim 9 , wherein the extraction features are curved, wherein the extraction features substantially focus the principal rays of the optical system onto the viewing plane. 
     
     
         26 . A directional display system comprising:
 an illuminator array; and   an optical valve comprising:
 a first light guiding surface of the optical valve, wherein the first light guiding surface is substantially planar, and 
 a second light guiding surface of the optical valve, opposite the first light guiding surface, further comprising a plurality of guiding features and a plurality of extraction features, wherein the plurality of extraction features further comprise a first region and a second region, further wherein the extraction features of the first and second regions have respective orientations such that at least some of the light rays from a first illuminator are directed to a first viewing window outside of the optical valve and at least some of the light rays from a second illuminator are directed to a second viewing window different from the first viewing window outside of the optical valve, 
   wherein the illuminator array is configured to selectively provide light to the optical valve.   
     
     
         27 . The directional display system of  claim 26 , wherein the extraction features are configured such that light interacting with a second reflective end provides a real image of the illuminator array. 
     
     
         28 . The directional display system of  claim 26 , further comprising a lens to direct light from the illuminator elements to respective viewing windows. 
     
     
         29 . The directional display system of  claim 26 , wherein the plurality of extraction features further comprise:
 a first region wherein the extraction features of the first region have a first orientation; and   a second region wherein the extraction features of the second region have a second orientation, wherein the first orientation and the second orientations are different from one another.   
     
     
         30 . An observer-tracking autostereoscopic display, comprising:
 an optical valve;   an array of illumination elements operable to provide light to the optical valve; and   a sensor for detecting an observer in the proximity of viewing windows of the optical valve; and   an illuminator controller for determining a setting for the array of illumination elements, wherein the setting determines a first illumination phase for a first set of illuminator elements corresponding to a first viewing window, and the setting determines a second illumination phase for a second set of illuminator elements corresponding to a second viewing window;   wherein the illumination controller adjusts illumination elements depending on the position of an observer;   wherein the first illumination phase corresponds to a left eye image on a display, and the second illumination phase corresponds to a right eye image on the display.