Computation of computer generated holograms

Abstract

A method of computing a computer generated hologram (CGH) for use in displaying a holographic image of a replay object. The method of generating a first computer generated hologram corresponding to the desired replay object (step 1 ); subdividing the first computer generated hologram into a plurality of blocks, each representing a sub CGH (step 2 ); for each block or sub CGH, calculating the corresponding replay sub-image hereafter called target wavefront data set (step 3 ); and generating for each target wavefront data set a second constrained modulation computer generated hologram wherein that second CGH is modulated within constrained values (step 5 ); and combining the plurality of second constrained modulation computer generated holograms to provide a third complete constrained modulation computer generated hologram (step 6 ).

1. A method of computing a computer generated hologram for use in displaying a holographic image of a replay object, the method comprisingthe steps of:
 calculating a plurality of target wavefront data sets , each representing a replayed block blocks of a single large a computer generated hologram corresponding to the desired a replay object; 
 generating a constrained modulation computer generated hologram holograms for each the plurality of target wavefront data set sets; and 
 combining the plurality of constrained modulation computer generated holograms to provide a complete, constrained modulation computer generated hologram. 
 
     
     
       2. A method of computing a computer generated hologram for use in displaying a holographic image, the method comprisingthe steps of:
 generating a first computer generated hologram corresponding to the desired a replay object; 
 subdividing the first computer generated hologram into a plurality of blocks; 
 for each block, generating a target wavefront data set, and sets corresponding to the plurality of blocks; 
 generating a second plurality of constrained modulation computer generated hologram for each holograms corresponding to the target wavefront data set sets; and 
 combining the plurality of second constrained modulation computer generated holograms to provide a third complete constrained modulation computer generated hologram. 
 
     
     
       3. A The method according to  claim 2 , wherein the step of generating a first the computer generated hologram corresponding to the replay object comprises using the a Coherent Ray Trace (CRT), Diffraction Specific (DS), or ping-pong algorithms algorithm to produce a full complex modulation or grey scale amplitude modulation computer generated hologram. 
     
     
       4. A The method according to  claim 2 , wherein the step of generating a target wavefront data set for each block of the first computer generated hologram sets comprises performing a Fourier Transform or an inverse Fourier Transform on each block the plurality of blocks to generate transformed data. 
     
     
       5. A The method according to  claim 4 , wherein the step of generating a the target wavefront data set sets comprises cropping the corresponding transformed data. 
     
     
       6. A The method according to  claim 2 , wherein the step of generating a second the plurality of constrained modulation computer generated hologram holograms comprises generating a binarised computer generated hologram. 
     
     
       7. A The method according to  claim 6 , wherein the step of generating a the binarised computer generated hologram uses the a Projection Onto Constraint Sets (POCS) or Direct Binary Search (DBS) algorithms algorithm. 
     
     
       8. A The method according to  claim 1 , wherein the processing steps applied to each wavefront data set are carried out constrained modulation computer generated holograms are generated in parallel with those applied to the other for the plurality of target wavefront data sets. 
     
     
       9. An A non-transitory electronic storage medium having stored thereon a computer generated hologram computed using the method of  claim 1 . 
     
     
       10. An apparatus comprising:
 a spatial light modulator (SLM);   optics configured to direct collimated light onto the SLM; and   a processor configured to:
 subdivide a computer generated hologram (CGH) into a plurality of sub-images; 
 calculate target wavefront data for each of the plurality of sub-images; 
 generate a plurality of constrained modulation CGH corresponding with the target wavefront data; and 
 write the plurality of constrained modulation CGH on the SLM. 
   
     
     
       11. The apparatus according to claim 10, wherein the processor is further configured to combine the plurality of constrained modulation CGH into a single CGH. 
     
     
       12. The apparatus according to claim 10, wherein the plurality of constrained modulation CGH is written on the SLM as a single CGH. 
     
     
       13. The apparatus according to claim 10, wherein the plurality of constrained modulation CGH comprises binarised data. 
     
     
       14. The apparatus according to claim 13, wherein the SLM operates using binary modulation. 
     
     
       15. The apparatus according to claim 10, wherein the target wavefront data comprises complex values including an amplitude and a phase component, and wherein the plurality of constrained modulation CGH comprises binarised data. 
     
     
       16. The apparatus according to claim 10, further comprising a viewing screen configured to reduce a viewing noise resulting from the generation of the constrained modulation CGH. 
     
     
       17. A non-transitory computer-readable medium having instructions stored thereon that, in response to execution by at least one device, cause the at least one device to perform operations comprising:
 subdividing a computer generated hologram (CGH) into a plurality of sub-holograms;   calculating corresponding replay sub-image data for the plurality of sub-holograms;   generating a plurality of constrained modulation holograms corresponding with the replay sub-image data; and   writing the plurality of constrained modulation holograms on a spatial light modulator.   
     
     
       18. The non-transitory computer-readable medium according to claim 17, wherein the operations further comprise cropping the plurality of sub-holograms to remove a surrounding area prior to calculating the replay sub-image data. 
     
     
       19. The non-transitory computer-readable medium according to claim 17, wherein the operations comprising calculating the corresponding replay sub-image data include performing an inverse Fourier Transform on one or more of the plurality of sub-holograms. 
     
     
       20. The non-transitory computer-readable medium according to claim 17, wherein the CGH comprises complex values including a real and an imaginary component. 
     
     
       21. The non-transitory computer-readable medium according to claim 17, wherein the spatial light modulator is a binary spatial light modulator. 
     
     
       22. The non-transitory computer-readable medium according to claim 17, wherein the operations comprising calculating the replay sub-image data include calculating the replay sub-image data in parallel. 
     
     
       23. An apparatus comprising:
 means for subdividing a computer generated hologram (CGH) into a plurality of sub-holograms;   means for calculating corresponding replay sub-image data for the plurality of sub-holograms;   means for generating a plurality of constrained modulation holograms corresponding with the replay sub-image data; and   means for sequentially writing the plurality of constrained modulation holograms on a spatial light modulator.   
     
     
       24. The apparatus according to claim 23, wherein the plurality of constrained modulation holograms are combined to form a single hologram. 
     
     
       25. The apparatus according to claim 23, wherein the means for calculating the replay sub-image data include means for calculating the replay sub-image data in parallel. 
     
     
       26. The apparatus according to claim 23, wherein the replay sub-image data comprises complex values including an amplitude and a phase component. 
     
     
       27. The apparatus according to claim 26, wherein the plurality of constrained modulation holograms comprises binarised data. 
     
     
       28. The apparatus according to claim 23, further comprising means for reducing a viewing noise resulting from the generation of the constrained modulation holograms.