Computer-GeneratedComputer-GeneratedHolography (CGH) as aHolography (CGH) as a

Generic Display TechnologyGeneric Display Technology

Niall Emmerson

Leo Walsh

Jon Etxezarreta

AdvantagesAdvantages

High Optical EfficiencyHigh Optical Efficiency

Ease of tilingEase of tiling holographic displays can be built from multiple holographic displays can be built from multiple SLM'sSLM's without loss of clarity without loss of clarity

Tolerance of Pixel DefectsTolerance of Pixel Defects

Wide colour gamutWide colour gamut use of lasers mean a wider range of colours perceivable by the human eyeuse of lasers mean a wider range of colours perceivable by the human eye

Advantages cont.Advantages cont.

Full depth cuesFull depth cues

High system volume and Image resolutionHigh system volume and Image resolution

Artefact-free binary modulationArtefact-free binary modulation

Aberration, distortion and conformal correctionAberration, distortion and conformal correction

ChallengesChallengesImage width and field of viewImage width and field of view

Image resolutionImage resolution -NCGH = 2NI-NCGH = 2NI

Image qualityImage quality -C -C ∝∝ nxlog[Q]nylog[Q]log(1+S/N) nxlog[Q]nylog[Q]log(1+S/N)

Laser speckleLaser speckle

Algorithms for CGH designAlgorithms for CGH design

Ping-pong algorithmPing-pong algorithm

-- Introduces an obscuration operator, shows hidden-line-removal effects on 3D imagesIntroduces an obscuration operator, shows hidden-line-removal effects on 3D images

-- Easy to codeEasy to code

-- Can only generate images of self-luminous objectsCan only generate images of self-luminous objects

-- Computationally inefficientComputationally inefficient

Interference-based algorithmInterference-based algorithm

-- Implement a 3D scalar diffraction integral, generates high quality imagesImplement a 3D scalar diffraction integral, generates high quality images

-- Can reproduce all human visual depth.Can reproduce all human visual depth.

-- Currently are the benchmark for image qualityCurrently are the benchmark for image quality

-- Problem: high computational loadsProblem: high computational loads

-- CGH require huge amount of pixels CGH require huge amount of pixels crucial the choice of the algorithm crucial the choice of the algorithmUsed to calculate the holographic fringe patternsUsed to calculate the holographic fringe patterns

-- Allow tradeoffs in image quality with computational speed.Allow tradeoffs in image quality with computational speed.

-- They count the hologram spatially (They count the hologram spatially (hogelshogels) and spectrally () and spectrally (hogelhogel vectors), vectors),can vary the computational loads.can vary the computational loads.

-- The algorithms can pre-compute much of the CGH calculation.The algorithms can pre-compute much of the CGH calculation.

-- CL= CL= hogelshogels x image points x (diffraction-table lookup entries) x rows x image points x (diffraction-table lookup entries) x rows

-- High definition TV= 100 x 1024 x 4096 x 1024 = 424 High definition TV= 100 x 1024 x 4096 x 1024 = 424 gigagiga MACsMACs

-- Optimisations can significantly REDUCE the computational loadOptimisations can significantly REDUCE the computational load

Diffraction-specific algorithmsDiffraction-specific algorithms

Computational loadsComputational loads

-- Large size computational loads Large size computational loads appropriate architecture appropriate architecture

-- Candidate architectures include supercomputersCandidate architectures include supercomputers

-- Intel IA-32 systems offer the most cost-effective and high-performance clusterIntel IA-32 systems offer the most cost-effective and high-performance cluster

-- Pixel prioritisationPixel prioritisation

-- Dynamic level of detailDynamic level of detail

-- Wireframe mode forWireframe mode forinteractioninteraction

-increasing the frame rate-increasing the frame rate

-enabling computation at same frame-enabling computation at same frame

rate with lower quality (reducing cost)rate with lower quality (reducing cost)

-- Users should be able to run their applications without modification.Users should be able to run their applications without modification.

Hardware architecturesHardware architectures

OptimizationsOptimizations

TO ACCELERATE CGH COMPUTATION

TO BE COMMERCIALLY SUCCESFUL:

By

Optical Hardware ConsiderationsOptical Hardware Considerations

SLM TechnologiesSLM Technologies−− HolovideoHolovideo

36 million pixels36 million pixels 10 thousand million pixels required for10 thousand million pixels required for

holographic workstationholographic workstation

−− QinetiQ Active TilingQinetiQ Active Tiling Uses both EASLM and OASLMUses both EASLM and OASLM EASLM output tiled onto OASLMEASLM output tiled onto OASLM Shutters used to build up picture on writeShutters used to build up picture on write

side of OASLM. Shutters side of OASLM. Shutters synchronisedsynchronised with withEASLM.EASLM.

Optical Hardware ConsiderationsOptical Hardware Considerations

Active Tiling is modular Active Tiling is modular –– can be stacked to can be stacked toallow for required number of pixelsallow for required number of pixels

Suitable for cluster computingSuitable for cluster computing Pixel areal density of more than 2.2×10Pixel areal density of more than 2.2×1066

pixels cmpixels cm-2-2

−− Pixel count in excess of to 1Pixel count in excess of to 1××101099

Experimental ResultsExperimental Results

This example shows 3This example shows 3××8 thousand million8 thousand millionpixels pixels –– full-colour, full-parallax full-colour, full-parallax

Standard computer graphics techniques canStandard computer graphics techniques canbe appliedbe applied

Large number of pixels requiredLarge number of pixels required Additional computationAdditional computation

−− High costHigh cost

ConclusionsConclusions

Paper was confusing with frequent use ofPaper was confusing with frequent use oftechnical terms specific to the field oftechnical terms specific to the field ofholography.holography.

Due to high cost Due to high cost –– both computational and both computational andmonetary monetary –– makes CGH unsuitable for makes CGH unsuitable forvirtual environments at the present time.virtual environments at the present time.