Boaz Jessie Jackin

Fast calculation method for computer-generated cylindrical hologram based on wave propagation in spectral domain

A fast calculation method for computer generation of cylindrical holograms is proposed. The calculation method is based on wave propagation in spectral domain and in cylindrical co-ordinates, which is otherwise similar to the angular spectrum of plane waves in cartesian co-ordinates. The calculation requires only two FFT operations and hence is much faster. The theoretical background of the calculation method, sampling conditions and simulation results are presented. The generated cylindrical hologram has been tested for reconstruction in different view angles and also in plane surfaces.

Distributed calculation method for large-pixel-number holograms by decomposition of object and hologram planes.

A method has been proposed to reduce the communication overhead in computer-generated hologram (CGH) calculations on parallel and distributed computing devices. The method uses the shifting property of Fourier transform to decompose calculations, thereby avoiding data dependency and communication. This enables the full potential of parallel and distributed computing devices. The proposed method is verified by simulation and optical experiments and can achieve a 20 times speed improvement compared to conventional methods, while using large data sizes.

Fast calculation of spherical computer generated hologram using spherical wave spectrum method

A fast calculation method for computer generation of spherical holograms in proposed. This method is based on wave propagation defined in spectral domain and in spherical coordinates. The spherical wave spectrum and transfer function were derived from boundary value solutions to the scalar wave equation. It is a spectral propagation formula analogous to angular spectrum formula in cartesian coordinates. A numerical method to evaluate the derived formula is suggested, which uses only N(logN)2 operations for calculations on N sampling points. Simulation results are presented to verify the correctness of the proposed method. A spherical hologram for a spherical object was generated and reconstructed successfully using the proposed method.

360° reconstruction of a 3D object using cylindrical computer generated holography

Simulated reconstruction of a three-dimensional (3D) object in 360° from cylindrical hologram is proposed. The simulation is done using a fast calculation method, where wave propagation in spectral domain and in cylindrical coordinates is used to generate the cylindrical hologram of a 3D object. The same procedure is followed to reconstruct the object back. The reconstructions resembled the original object and could be seen from all 360°. The whole simulation process is done using open-source software.

Fast calculation method for computer-generated cylindrical holograms based on the three-dimensional Fourier spectrum

The relation between a three-dimensional (3D) object and its diffracted wavefront in the 3D Fourier space is discussed at first and then a rigorous diffraction formula onto cylindrical surfaces is derived. The azimuthal direction and the spatial frequency direction corresponding to height can be expressed with a one-dimensional (1D) convolution integral and a 1D inverse Fourier transform in the 3D Fourier space, respectively, and fast Fourier transforms are available for fast calculation. A numerical simulation of a diffracted wavefront on cylindrical surfaces is presented. An alternative optical experiment equivalent of the optical reconstruction from cylindrical holograms is also demonstrated.

Developmental and morphological studies in Japanese medaka with ultra-high resolution optical coherence tomography

We propose ultra-high resolution optical coherence tomography to study the morphological development of internal organs in medaka fish in the post-embryonic stages at micrometer resolution. Different stages of Japanese medaka were imaged after hatching in vivo with an axial resolution of 2.8 µm in tissue. Various morphological structures and organs identified in the OCT images were then compared with the histology. Due to the medakas close resemblance to vertebrates, including humans, these morphological features play an important role in morphogenesis and can be used to study diseases that also occur in humans.

Geometric phase shifting digital holography

A new phase shifting digital holographic technique using a purely geometric phase in Michelson interferometric geometry is proposed. The geometric phase in the system does not depend upon either optical path length or wavelength, unlike dynamic phase. The amount of geometric phase generated is controllable through a rotating wave plate. The new approach has unique features and major advantages in holographic measurement of transparent and reflecting three-dimensional (3D) objects. Experimental results on surface shape measurement and imaging of 3D objects are presented using the proposed method.

Overcoming the difficulty of large-scale CGH generation on multi-GPU cluster

The 3D holographic display has long been expected as a future human interface as it does not require users to wear special devices. However, its heavy computation requirement prevents the realization of such displays. A recent study says that objects and holograms with several giga-pixels should be processed in real time for the realization of high resolution and wide view angle. To this problem, first, we have adapted a conventional FFT algorithm to a GPU cluster environment in order to avoid heavy inter-node communications. Then, we have applied several single-node and multi-node optimization and parallelization techniques. The single-node optimizations include the change of the way of object decomposition, reduction of data transfer between CPU and GPU, kernel integration, stream processing, and utilization of multi-GPU within a node. The multi-node optimizations include distribution methods of object data from host node to the other nodes. The experimental results show that the intra-node optimizations attain 11.52 times speed-up from the original single node code. Further, multi-node optimizations using 8 nodes, 2 GPUs per node, attain the execution time of 4.28 sec. for generating 1.6 giga-pixel hologram from 3.2 giga-pixel object. It means 237.92 times speed-up of the sequential processing by CPU using a conventional FFT-based algorithm.

Data Distribution Method for Fast Giga-scale Hologram Generation on a Multi-GPU Cluster

The 3D holographic display has long been expected as a future human interface as it does not require users to wear special devices. However, in addition to the delay of display device technology, its heavy computation requirement prevents the realization of such displays. A recent study says that objects and holograms with several giga-pixels should be processed in real time for the realization of high resolution and wide view angle. To this problem, first, we have proposed a new data distribution method that utilizes a basic FFT-based O(N log N) computation but does not need any inter-node communications during the computation on a multi-GPU cluster. Then, we have implemented the method on a multi-GPU cluster, applying several single-node and multi-node optimization and parallelization techniques. The experimental results show that the intra-node optimizations attain 11.52 times speed-up from the original single node code. Further, multi-node optimizations using 8 nodes, 2 GPUs per node, attain the execution time of 4.28 sec. for generating 1.6 giga-pixel hologram from 3.2 giga-pixel object. It means 237.92 times speed-up of the sequential processing by CPU using a conventional FFT-based algorithm.

View synthesis from sparse camera array for pop-out rendering on hologram displays

A hologram of a scene can be digitally created by using a large set of images of that scene. Since capturing such a large amount is infeasible to accomplish, one may use view synthesis approaches to reduce the number of cameras and generate the missing views. We propose a view interpolation algorithm that creates views inside the scene, based on a sparse set of camera images. This allows the objects to pop out of the holographic display. We show that our approach outperforms existing view synthesis approaches and show the applicability on holographic stereograms.