Optical Filters and Method of Manufacturing the Same

Abstract

The selective filtering of light by polarization interference may be used to enhance vision and/or protect eyes from harmful light rays. For example, such filtering may be used in sunglasses, color corrective eyewear or protective eyewear. The selective filtering of incident light may provide any desired spectral transmission (including visible light and light not visible to the eye) and is performed by a pair of polarizing elements that sandwich a retarder stack. The filtering structure may be formed by multi-layer polarizing structures and may be formed by fabricating sheet laminates that are die cut to form inexpensive laminates. The laminates may be flat or curved in one (e.g., wrap-around) or more dimensions.

1 . An optical filter comprising: 
 an input polarizing element;    an output polarizing element; and    a retarder stack between the input polarizing element and the output polarizing element, the retarder stack comprising N≧2 retarder films;    wherein the input polarizing element, the output polarizing element, and the retarder stack are collectively designed to comprise an FIR filter, and thereby are operable to generate at least N+1 spatially offset light pulses in response to a linearly polarized light impulse input, the FIR filter operable to substantially filter at least one band of light,    wherein the optical filter is curved.    
   
   
       2 . An optical filter according to  claim 1 , wherein the curvature of the optical filter is in a first dimension.  
   
   
       3 . An optical filter according to  claim 2 , wherein the curvature of the optical filter is in a second dimension.  
   
   
       4 . An optical filter according to  claim 2 , wherein the curvature of the optical filter in the first dimension is obtained by laminating the output polarizing element, the retarder stack and the input polarizing element using a rotating drum.  
   
   
       5 . An optical filter according to  claim 4 , wherein the rotating drum has a radius selected to achieve a predetermined curvature of the optical filter.  
   
   
       6 . An optical filter according to  claim 3 , wherein the curvature of the optical filter in the first and second dimensions is obtained by casting.  
   
   
       7 . An optical filter according to  claim 6 , wherein the casting comprises forming a laminated sheet over a mold, the mold comprising a predetermined curvature in the first and second dimensions, the laminated sheet comprising the input polarizing element, the retarder stack, and the output polarizing element.  
   
   
       8 . An optical filter according to  claim 6 , wherein the optical filter is cast between two substrates.  
   
   
       9 . An optical filter according to  claim 6 , wherein the curvature of the optical filter provides a lens.  
   
   
       10 . An optical filter according to  claim 9 , wherein the lens is die cut from sheet stock.  
   
   
       11 . An optical filter according to  claim 10 , wherein the lens is mounted in a frame.  
   
   
       12 . An optical filter according to  claim 1 , 
 wherein the optical filter is configured for human vision; and    the input polarizing element, the output polarizing element, and the retarder stack are adapted to be positioned at least partially in a human's field of view.    
   
   
       13 . An optical filter according to  claim 1 , wherein 
 the optical filter is configured for animal vision; and    the input polarizing element, the output polarizing element, and the retarder stack are adapted to be positioned at least partially in an animal's field of view.    
   
   
       14 . An optical filter according to  claim 1 , wherein the at least one band of light is an inter-primary band of light.  
   
   
       15 . An optical filter according to  claim 1 , wherein the at least one band of light has a wavelength that is smaller than or equal to about 400 nm.  
   
   
       16 . An optical filter according to  claim 1 , wherein the at least one band of light has a wavelength that is greater than or equal to about 700 nm.  
   
   
       17 . An optical filter according to  claim 1 , wherein the at least one band of light has a wavelength of about 500 nm.  
   
   
       18 . An optical filter according to  claim 1 , wherein the at least one band of light has a wavelength of about 580 nm.  
   
   
       19 . An optical filter according to  claim 1 , wherein the FIR filter is operable to filter at least two inter-primary bands of light.  
   
   
       20 . An optical filter according to  claim 1 , wherein the input polarizing element, the output polarizing element, and the retarder stack filter light so as to maintain a color neutral appearance.  
   
   
       21 . An optical filter according to  claim 1 , wherein the optical filter is one of a pair of sunglasses, a canopy for a helmet, or a visor.  
   
   
       22 . A method for manufacturing an optical filter, the method comprising: 
 providing a flat stock comprising: 
 an input polarizing element,  
 an output polarizing element, and  
 a retarder stack between the input polarizing element and the output polarizing element, the retarder stack comprising N≧2 retarder films; and  
   forming the flat stock to provide curvature to the optical filter,    wherein the input polarizing element, the output polarizing element, and the retarder stack are collectively designed to comprise an FIR filter, and thereby are operable to generate at least N+1 spatially offset light pulses in response to a linearly polarized light impulse input, the FIR filter operable to substantially filter at least one band of light.    
   
   
       23 . A method for manufacturing an optical filter according to  claim 22 , the method further comprising: 
 generating the flat stock by laminating the input polarization filter to a first side of the retarder stack, and laminating the output polarization filter to a second side of the retarder stack.    
   
   
       24 . A method for manufacturing an optical filter according to  claim 22 , wherein the curvature of the optical filter is in a first dimension.  
   
   
       25 . A method for manufacturing an optical filter according to  claim 24 , wherein the curvature of the optical filter is in a second dimension.  
   
   
       26 . A method for manufacturing an optical filter according to  claim 22 , further comprising forming the flatstock by laminating the output polarizing element, the retarder stack and the input polarizing element using a rotating drum.  
   
   
       27 . A method for manufacturing an optical filter according to  claim 26 , wherein the rotating drum has a radius selected to achieve a predetermined curvature of the optical filter.  
   
   
       28 . A method for manufacturing an optical filter according to  claim 25 , wherein the curvature of the optical filter in the first and second dimensions is obtained by casting.  
   
   
       29 . A method for manufacturing an optical filter according to  claim 28 , wherein the casting comprises casting between two substrates.  
   
   
       30 . A method for manufacturing an optical filter according to  claim 22 , wherein the curvature of the optical filter comprises a lens.  
   
   
       31 . A method for manufacturing an optical filter according to  claim 30 , wherein the lens is die cut from a sheet stock.  
   
   
       33 . A method for manufacturing an optical filter according to  claim 30 , wherein the lens is mounted in a frame.