Holographic display apparatus for providing expanded viewing window

Abstract

Provided is a holographic display apparatus capable of providing an expanded viewing window when reproducing a holographic image via an off-axis technique. The holographic display apparatus includes a spatial light modulator comprising a plurality of pixels arranged two-dimensionally; and an aperture enlargement film configured to enlarge a beam diameter of a light beam coming from each of the plurality of pixels of the spatial light modulator. The beam diameter of each light beam enlarged by the aperture enlargement film may be greater than the width of an aperture of each pixel of the spatial light modulator.

What is claimed is: 
     
         1 . An aperture enlargement film comprising:
 a light guide layer, and   a grating layer disposed on an upper surface of the light guide layer,   wherein the light guide layer and the grating layer are configured to transmit a 0th order diffracted light beam and a 1st order diffracted light beam among incident light beams,   wherein the grating layer is configured to transmit the 0th order diffracted light beam of a light beam vertically incident on the lower surface of the grating layer from the light guide layer in a direction perpendicular to an upper surface of the one grating layer, and is configured to reflect the 1st order diffracted light beam of the light beam incident on the lower surface of the grating layer from the light guide layer at an angle to propagate obliquely in the light guide layer,   wherein the grating layer transmits a portion of the 1st order diffracted light beam that is reflected by a lower surface of the light guide layer and obliquely incident on the one grating layer in the direction perpendicular to the upper surface of the one grating layer,   wherein a boundary of the transmitted 1st order diffracted light beam coincides with a boundary of the transmitted 0th order diffracted light beam or the transmitted 1st order diffracted light beam overlaps with the transmitted 0th order diffracted light beam based on a thickness of the light guide layer, and   wherein an intensity of the transmitted 0th order diffracted light beam is greater than the intensity of the transmitted 1st order diffracted light beam.   
     
     
         2 . The aperture enlargement film of  claim 1 , wherein an intensity distribution of the enlarged light beam decreases from a center of the enlarged light beam to a periphery of the enlarged light beam. 
     
     
         3 . The aperture enlargement film of  claim 1 , wherein a beam diameter of the enlarged light beam is greater than a beam diameter of each of the incident light beams. 
     
     
         4 . The aperture enlargement film of  claim 1 , wherein a thickness of the light guide layer ranges from 1 μm to 5 μm. 
     
     
         5 . The aperture enlargement film of  claim 1 , wherein the light guide layer is configured to obliquely propagate the second light beam from the one grating layer along an inside of the light guide layer based on total reflection. 
     
     
         6 . The aperture enlargement film of  claim 1 , further comprising a substrate configured to support the light guide layer and the one grating layer such that the light guide layer and the one grating layer do not bend, and
 wherein a refractive index of the light guide layer is greater than a refractive index of the substrate.   
     
     
         7 . The aperture enlargement film of  claim 1 , further comprising a Gaussian apodization filter array disposed to face the lower surface of the light guide layer. 
     
     
         8 . The aperture enlargement film of  claim 7 , wherein the Gaussian apodization filter array comprises a plurality of Gaussian apodization filters configured to convert an intensity distribution of a light beam into a curved Gaussian distribution. 
     
     
         9 . The aperture enlargement film of  claim 1 , further comprising a prism array disposed to face the lower surface of the light guide layer or disposed to face a light exiting surface of the aperture enlargement film. 
     
     
         10 . The aperture enlargement film of  claim 9 , wherein the prism array is divided into a plurality of unit regions that are two-dimensionally disposed, and
 wherein each of the plurality of unit regions comprises a plurality of prisms configured to propagate an incident light in different directions.   
     
     
         11 . An aperture enlargement film comprising:
 a light guide layer;   a first grating layer disposed on an upper surface of the light guide layer; and   a second grating layer disposed on an lower surface of the light guide layer,   wherein the second grating layer is configured to transmit a light beam incident on a lower surface of the second grating layer,   wherein the first grating layer is configured to transmit a 0th order diffracted light beam in a direction perpendicular to an upper surface of the first grating layer and obliquely reflect a 1st order diffracted light beam toward the light guide layer,   wherein the second grating layer is further configured to reflect a portion of the 1st order diffracted light beam incident on an upper surface of the second grating layer in a direction perpendicular to the upper surface of the second grating layer,   wherein the first grating layer is further configured to transmit the portion of the 1st order diffracted light beam from the second grating layer,   wherein a boundary of the transmitted 1st order diffracted light beam coincides with a boundary of the transmitted 0th order diffracted light beam or the transmitted 1st order diffracted light beam overlaps with the transmitted 0th order diffracted light beam based on a thickness of the light guide layer, and   wherein an intensity of the transmitted 0th order diffracted light beam is greater than the intensity of the transmitted 1st order diffracted light beam.   
     
     
         12 . The aperture enlargement film of  claim 11 , wherein the second grating layer is further configured to diffract the light beam incident on the lower surface of the second grating layer such that the diffracted light beam by the second grating layer obliquely travels with respect to the upper surface of the second grating layer. 
     
     
         13 . The aperture enlargement film of  claim 11 , wherein an intensity distribution of the enlarged light beam decreases from a center of the enlarged light beam to a periphery of the enlarged light beam. 
     
     
         14 . The aperture enlargement film of  claim 11  wherein a beam diameter of the enlarged light beam is greater than a beam diameter of each of the incident light beams. 
     
     
         15 . The aperture enlargement film of  claim 11 , wherein a thickness of the light guide layer ranges from 1 μm to 5 μm. 
     
     
         16 . The aperture enlargement film of  claim 11 , wherein the light guide layer is configured to obliquely propagate the 1st order diffracted light beam from the first grating layer along an inside of the light guide layer based on total reflection. 
     
     
         17 . The aperture enlargement film of  claim 11 , further comprising a Gaussian apodization filter array disposed to face the lower surface of the light guide layer. 
     
     
         18 . The aperture enlargement film of  claim 17 , wherein the Gaussian apodization filter array comprises a plurality of Gaussian apodization filters configured to convert an intensity distribution of a light beam into a curved Gaussian distribution. 
     
     
         19 . The aperture enlargement film of  claim 11 , further comprising a prism array disposed to face the lower surface of the light guide layer or disposed to face a light exiting surface of the aperture enlargement film. 
     
     
         20 . The aperture enlargement film of  claim 19 , wherein the prism array is divided into a plurality of unit regions that are two-dimensionally disposed, and
 wherein each of the plurality of unit regions comprises a plurality of prisms configured to propagate an incident light in different directions.