Hologram

Computer-generated hologram(CGH) : digitally generated hologram based on light diffraction simulation
- Hologram for virtual object represented by point cloud or mesh
- Numerical reconstruction for verification
- Optical reconstruction by SLM(Spatial Light Modulator) or holographic display
Popular CGH methods : basically numerical methods for light propagation
- Point-based raytracing method
- Fresnel/Fraunhofer diffraction method
- Angular spectrum method
Technical skills : Scalar diffraction theory, Fourier optics and Fourier transform, Fast Fourier transform(FFT)
Why hologram?
- Next-generation digital content which provides natural 3D experience without wearables

Surface details with texture image in polygon-based CGH(2019)

FFT-based fast calculation
Full texture techniques : arbitrary texture image and uv-coordinates

C++ CGH API
- User-friendly FFT and convolution
- Light propagation method : Fresnel/Fraunhofer transform, angular spectrum method
- CGH generation method : point-based raytracing, mesh-based angular spectrum
- All calculation methods support high-performance GPU computing(CUDA).

See a code example : here
Simple cgh generation/reconstruction GUI program based on the CGH api : snap-shot
CGH example result :

Point-based CGH : fringe pattern(left) and reconstruction result(right), #pts=144647

Mesh-based CGH : amplitude and phase(left) and reconstruction(right)

Interactive hologram using spherical angular spectrum
- Conference paper : Interactive computer-generated hologram using spherical angular spectrum, Digital holography and 3-D Imaging 2016

Cylindrical angular spectrum for point cloud and fast hologram generation
- Journal paper : Cylindrical angular spectrum using Fourier coefficients of point light source and its application to fast hologram calculation, Optics Express, 23(23) 29555-29564, 2015 (selected as cover image!)
  - Explicit formula for angular spectrum of a point light source
  - 360 hologram generation using cylindrical angular spectrum with occlusion culling
  - CUDA OptiX library for ray-tracing computations

Object distance extraction from CGH using frequency analysis
- Journal paper : Fast focus estimation using frequency analysis in digital holography, Optics Express 22(23) 28926-28933, 2014
  - Fast frequency-based focus distance calculation without numerical reconstructions

(a)(b) : Amplitude and phases of hologram, (c) numerical reconstruction at computed distance, the rightest is the density distribution of the intersection of local rays which predicts the exact focus distance

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