Aligning a polarization device using a spatially variant polarization element

Abstract

An alignment apparatus for a polarization device includes a polarizer subassembly for polarizing a light beam, a rotary support for rotatably supporting the polarization device in a path of the light beam downstream of the polarizer subassembly, an analyzer subassembly downstream of the rotary support for receiving the light beam propagated through the polarization device, and a photodetector array disposed downstream of the analyzer subassembly and extending along the width dimension of the light beam for detecting the light beam propagated through the analyzer subassembly. At least one of the polarizer or analyzer subassemblies includes a spatially variant polarization element having a polarization property varying along the width dimension of the light beam.

What is claimed is: 
     
         1 . An alignment system for aligning a polarization device, the alignment system comprising:
 a light source for providing a first light beam having a width along a first axis;   a first spatially variant polarization element having a polarization property varying along the first axis for receiving and polarizing the first light beam; and   a first alignment apparatus comprising a first rotary support for rotatably supporting a first polarization component of the polarization device in a path of the first light beam and a first photodetector array disposed downstream of the first spatially variant polarization element, wherein the first photodetector array extends along the first axis for detecting the first light beam propagated through the first spatially variant polarization element.   
     
     
         2 . The alignment system of  claim 1 , wherein the light source is configured for providing a second light beam having a width along a second axis;
 the alignment system further comprising a second alignment apparatus comprising a second rotary support for rotatably supporting a second polarization component of the polarization device in a path of the second light beam, a second spatially variant polarization element having a polarization property varying along the first axis and disposed downstream of the second rotary support for receiving the second light beam propagated through the second polarization component, and a second photodetector array disposed downstream of the second spatially variant polarization element and extending along the second axis for detecting the second light beam propagated through the second spatially variant polarization element.   
     
     
         3 . The alignment system of  claim 2 , further comprising a translation stage for combining the first and second polarization components of the polarization device after aligning by the first and second alignment apparatuses, respectively. 
     
     
         4 . The alignment system of  claim 1 , wherein the polarization device comprises a reflective polarizer. 
     
     
         5 . The alignment system of  claim 1 , wherein the polarization device comprises a pancake lens. 
     
     
         6 . The alignment system of  claim 1 , wherein the first spatially variant polarization element comprises an array of polarizer segments, the array extending along the first axis, wherein a transmission axis direction of the polarizer segments varies from a polarizer segment to a polarizer segment of the array. 
     
     
         7 . The alignment system of  claim 1 , wherein the spatially variant polarization element comprises:
 an array of half-wave waveplate segments, the array extending along the first axis, wherein an optic axis direction of the half-wave waveplate segments of the array varies from a half-wave waveplate segment to a half-wave waveplate segment of the array; and   a linear polarizer downstream of the array.   
     
     
         8 . The alignment system of  claim 1 , wherein the spatially variant polarization element comprises:
 a half-wave optical retarder extending along the first axis and having an optic axis direction smoothly and monotonically varying along the first axis; and   a linear polarizer downstream of the half-wave optical retarder.   
     
     
         9 . The alignment system of  claim 1 , wherein the spatially variant polarization element comprises an array of optical retarders, the array extending along the first axis, wherein at least one of a retardation or an optic axis direction of the optical retarders of the array varies from an optical retarder to an optical retarder of the array. 
     
     
         10 . The alignment system of  claim 9 , wherein the retardation of the optical retarders of the array varies between 0.2 and 0.3 wavelengths of the light beam. 
     
     
         11 . The alignment system of  claim 1 , wherein the spatially variant polarization element comprises an optical retarder extending along the first axis and having at least one of an optical retardation or an optic axis direction smoothly and continuously varying along the first axis. 
     
     
         12 . A method for aligning a polarization device, the method comprising:
 polarizing a light beam having a width along a first axis by a polarizer subassembly;   rotatably supporting the polarization device in a path of the light beam by a rotary support;   receiving the light beam propagated through the polarization device at an analyzer subassembly; and   detecting the light beam propagated through the analyzer subassembly by a photodetector array disposed downstream of the analyzer subassembly and extending along the first axis;   wherein at least one of the polarizer or analyzer subassemblies comprises a spatially variant polarization element having a polarization property varying along the first axis.   
     
     
         13 . The method of  claim 12 , further comprising:
 obtaining an optical power distribution of the light beam detected by the photodetector array; and   obtaining a rotation angle of the polarization device to make the optical power distribution match a pre-determined optical power distribution.   
     
     
         14 . The method of  claim 13 , further comprising rotating the rotary support by the rotation angle. 
     
     
         15 . An alignment apparatus for a polarization device, the alignment apparatus comprising:
 a polarizer subassembly for polarizing a light beam having a width along a first axis;   a rotary support for rotatably supporting the polarization device in a path of the light beam downstream of the polarizer subassembly;   an analyzer subassembly downstream of the rotary support for receiving the light beam propagated through the polarization device; and   a photodetector array downstream of the analyzer subassembly, the photodetector array extending along the first axis for detecting the light beam propagated through the analyzer subassembly;   wherein the polarizer subassembly comprises a linear transmission polarizer, and wherein the analyzer subassembly comprises the spatially variant polarization element.   
     
     
         16 . The alignment apparatus of  claim 15 , wherein the polarizer subassembly further comprises a quarter-wave waveplate downstream of the linear transmission polarizer.